SSG-15 (Rev. 1) Storage of Spent Nuclear Fuel

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Sekce	Odstavec	Text
Main	1.1.	Spent nuclear fuel is generated from the operation of nuclear reactors of all types and needs to be safely and securely managed following its removal from the reactor core. Spent fuel¹ is considered waste in some circumstances or a potential future energy resource in others and, as such, management options might involve direct disposal (as part of what is generally known as the ‘once through fuel cycle’) or reprocessing (as part of what is generally known as the ‘closed fuel cycle’). Either management option will involve a number of steps, which will necessarily include storage of the spent fuel for some period of time. This time period for storage can differ, depending on the management strategy adopted, from a few months to several decades. The time period for storage will be a significant factor in determining the storage arrangements adopted. The final management option might not have been determined at the time of design of the storage facility, leading to some uncertainty in the storage period that will be necessary, a factor that needs to be considered in the adoption of a storage option and the design of the facility. Storage options include wet storage in some form of storage pool, or dry storage in a facility or in storage casks built for this purpose. Storage casks can be located in a designated area on a site or in a designated storage building. A number of different designs for both wet and dry storage have been developed and used in different States.
Main	1.2.	Irrespective of the consideration of spent fuel (either waste or an energy resource), the requirements for the storage of spent fuel are the same as those for the storage of radioactive waste, which are established in IAEA Safety Standards Series No. GSR Part 5, Predisposal Management of Radioactive Waste [1].
Main	1.3.	The safety of a spent fuel storage facility, and of the spent fuel stored within it, is ensured by appropriate confinement of the radionuclides involved, maintaining subcriticality, heat removal, radiation shielding and retrievability of the spent fuel or spent fuel packages. These functions are ensured by the proper siting, design, construction and commissioning of the storage facility, and its proper management and safe operation. At the design stage, due consideration also needs to be given to the future decommissioning of the facility.
Main	1.4.	Spent fuel is generated continually by operating nuclear reactors. It is stored in the reactor fuel storage pool for a period of time for cooling and then may be transferred to a designated wet or dry storage facility, where it will await reprocessing or disposal (if it is considered to be radioactive waste). The spent fuel storage pools of some reactors have sufficient capacity to accommodate all the spent fuel that will be generated during the lifetime of the reactor.
Main	1.5.	The basic safety aspects for the storage of spent fuel are applicable to the storage of spent fuel from research reactors as well as from power reactors. For research reactors, an approach should be adopted that takes into account the differences between the fuel types (e.g. the lower heat generation of research reactor fuel, its higher enrichment level and cladding materials that are less corrosion resistant) when determining the measures to be taken to ensure confinement, heat removal, criticality control, radiation shielding and retrievability.
Main	1.6.	Many spent fuel storage facilities at reactors were intended to serve for a limited period of time (a few years) as a place to keep spent fuel between unloading from the reactor and its subsequent storage, reprocessing or disposal. In view of the time being taken to develop disposal facilities and the limited reprocessing programmes that have been developed, storage periods are being extended from years to decades. This change in approach to the management of spent fuel has been accompanied by other developments, for example increases in enrichment, increases of burnup, use of advanced fuel design and mixed oxide fuel, re‑racking, use of burnup credit and, in some cases, extension of storage periods beyond the original design lifetime of the storage facility. Nevertheless, storage cannot be considered the ultimate solution for the management of spent fuel, which requires a defined end point such as reprocessing or disposal in order to ensure safety. The design lifetime of a nuclear installation is generally of the order of decades, and experience with the storage of spent fuel of up to around 50 years has accrued. While design lifetimes of up to 100 years have been considered and adopted for certain spent fuel storage facilities, in view of the rate of industrial and institutional change, periods beyond around 50 years are deemed to be ‘long term’ in the context of this Safety Guide (see also Annex I).
Main	1.7.	The present publication supersedes the 2012 edition of SSG‑15². This Safety Guide complements IAEA Safety Standards Series No. WS‑G‑6.1, Storage of Radioactive Waste [2], and can be read in conjunction with it.
Main	1.7A.	The terms used in this Safety Guide are to be understood as defined and explained in the IAEA Safety Glossary [3].
Main	1.8.	The objective of this Safety Guide is to provide guidance and recommendations on the design, commissioning, operation and assessment of safety for the different types of spent nuclear fuel storage facility (wet and dry), by considering different types of spent nuclear fuel from nuclear reactors, including research reactors, and different storage periods, including storage beyond the original design lifetime of the storage facility. This Safety Guide presents guidance and recommendations on how to meet the requirements established in GSR Part 5 [1] and IAEA Safety Standards Series Nos SSR‑4, Safety of Nuclear Fuel Cycle Facilities [4], GSR Part 2, Leadership and Management for Safety [5], GSR Part 4 (Rev. 1), Safety Assessment for Facilities and Activities [6], and SSR‑2/1 (Rev. 1), Safety of Nuclear Power Plants: Design [7].
Main	1.9.	This Safety Guide covers spent nuclear fuel storage facilities that are either collocated with other nuclear facilities (e.g. nuclear power plant, research reactor, reprocessing plant) or located on their own site. However, it is not specifically intended to cover the storage of spent nuclear fuel as long as it remains a part of the operational activities of a nuclear reactor or a spent fuel reprocessing facility, which are addressed in IAEA Safety Standards Series Nos SSG‑40, Predisposal Management of Radioactive Waste from Nuclear Power Plants and Research Reactors [8], and SSG‑41, Predisposal Management of Radioactive Waste from Nuclear Fuel Cycle Facilities [9], respectively.
Main	1.10.	The scope of this Safety Guide includes the storage of spent nuclear fuel from water moderated reactors and can, with due consideration, also be applied to the storage of other types of nuclear fuel, such as spent nuclear fuel from gas cooled reactors and research reactors, and to the storage of spent fuel assembly components and degraded or failed nuclear fuel³ that might be placed in canisters.
Main	1.11.	This Safety Guide does not provide recommendations on the physical protection of nuclear material and nuclear facilities. Recommendations and guidelines on physical protection arrangements at nuclear facilities, including risk assessment, threat definition, design, maintenance and implementation of physical protection systems, evaluation of effectiveness and inspection of physical protection systems, are provided in Ref. [10] and in supporting publications in the IAEA Nuclear Security Series. This Safety Guide considers physical protection and accounting for and control of nuclear material only to highlight potential implications for safety.
Main	1.12.	Section 2 of this Safety Guide addresses the application of the fundamental safety objective and the fundamental safety principles to the storage of spent nuclear fuel. The roles and responsibilities of those involved in the storage of spent nuclear fuel are set out in Section 3. Section 4 provides recommendations on the management system necessary for safety. Section 5 provides recommendations on safety assessment and Section 6 provides recommendations on safety considerations in respect of design, construction, operation and decommissioning of spent fuel storage facilities, including considerations for long term storage. Appendix I addresses considerations specific to wet and dry storage of spent nuclear fuel and Appendix II addresses considerations in respect of spent fuel with particular characteristics. Annex I provides explanations of the concepts of short term and long term storage. Annex II summarizes operational and safety considerations for wet and dry storage facilities. Annex III provides an example of the sections that could be included in the operating procedures for a spent fuel storage facility. Annexes IV–VI provide listings of events for consideration in a safety assessment for a spent fuel storage facility.
Main	1.13.	For convenience, the text of each safety requirement that is applicable to the storage of spent nuclear fuel is reproduced in this Safety Guide, followed by the related recommendations.
Main	2.1.	National requirements for radiation protection are required to be established, in accordance with the fundamental safety objective and fundamental safety principles set out in IAEA Safety Standards Series No. SF‑1, Fundamental Safety Principles [11], and in compliance with IAEA Safety Standards Series No. GSR Part 3, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards [12]. In particular, doses to people as a consequence of the storage of spent fuel are required to be kept within specified dose limits and radiation protection is required to be optimized within dose constraints.
Main	2.2.	If several nuclear installations (e.g. nuclear power plants, spent fuel storage facilities, reprocessing facilities) are located at the same site, the dose constraints for public exposure should take into account all sources of exposure that could be associated with activities at the site. Particularly in such cases, the regulatory body should require the operating organization(s) of the nuclear installation(s) on the site to develop constraints, subject to regulatory approval. Alternatively, the regulatory body may establish the dose constraints. Requirements on dose constraints are established in GSR Part 3 [12] and recommendations are provided in IAEA Safety Standards Series No. GSG‑8, Radiation Protection of the Public and the Environment [13].
Main	2.3.	The design of a spent fuel storage facility and the storage of spent fuel must be such that the workers, the public and the environment, present and future, will be protected from harmful effects of radiation exposure from all sources of ionizing radiation associated with current activities with spent fuel at the site [11], with sufficient margins for foreseeable future activities at the site that might also give rise to exposure.
Main	2.4.	Discharges to the environment from spent fuel storage facilities should be controlled in accordance with the conditions imposed by the regulatory body and should be included when estimating doses to workers and to the public. Recommendations on discharge limits are provided in IAEA Safety Standards Series No. GSG‑9, Regulatory Control of Radioactive Discharges to the Environment [14].
Main	2.5.	The adequacy of control measures taken to limit the radiation exposure of workers and the public should be verified by monitoring and surveillance, both inside and outside the facility.
Main	2.6.	At each step in the management of spent fuel, a safety culture that encourages a questioning and learning attitude towards protection and safety and that discourages complacency should be fostered and maintained [5, 15, 16].
Main		Requirement 1 of GSR Part 5 [1]: Legal and regulatory framework
Main	3.1.	Storage of spent fuel should be undertaken within an appropriate national legal and regulatory framework that provides for a clear allocation of responsibilities [17], including responsibilities for meeting international obligations and for verifying compliance with these obligations, and which ensures the effective regulatory control of the facilities and activities concerned. The national legal framework should also ensure compliance with other relevant national and international legal instruments, such as the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management [18].
Main	3.2.	The management of spent fuel may entail the transfer of spent fuel from one operating organization to another and various interdependences exist between the various steps in the management of spent fuel. The legal framework should include provision to ensure a clear allocation of responsibility for safety throughout the entire process, in particular with regard to the storage of spent fuel and its transfer between operating organizations. Continuity of responsibility for safety should be ensured by means of a system of authorization by the regulatory body. For transfers between States, authorizations from the respective national regulatory bodies are required [18, 19].
Main	3.3.	The responsibilities of the regulatory body⁴, the operating organization and, where appropriate, the spent fuel owner in respect of spent fuel management should be clearly specified in the legal and regulatory framework and should be functionally separate.
Main	3.4.	A mechanism for providing adequate financial resources should be established to cover any future costs, in particular the costs associated with spent fuel storage and decommissioning of the storage facility as well as the costs of managing radioactive waste. The financial mechanism should be established before licensing of the storage facility and its operation and should be updated as necessary. Consideration should also be given to provision of the necessary financial resources in the event of a premature shutdown of the spent fuel storage facility.
Main		Requirement 2 of GSR Part 5 [1]: National policy and strategy on radioactive waste management
Main	3.5.	The government is responsible for establishing a national policy and corresponding strategy for the management of spent fuel and for providing the legal and regulatory framework necessary to implement the policy and strategy. The national policy and strategy should cover all types of spent fuel and spent fuel storage facility in the State, with account taken of the interdependences between the various stages of spent fuel management, the time periods involved and the options available [17].
Main	3.6.	The government is responsible for establishing a regulatory body independent of the owners of the spent fuel or the operating organizations managing the spent fuel, with adequate authority, power, staffing and financial resources to discharge its assigned responsibilities [17].
Main	3.7.	The government should consult interested parties (i.e. those who are involved in or are affected by spent fuel management activities) on matters relating to the development of the national policy and strategy for the management of spent fuel.
Main	3.8.	In the event that circumstances change and storage is required beyond the period originally envisaged in the national strategy for the management of spent fuel, a re‑evaluation of the national strategy should be carried out.
Main		Requirement 3 of GSR Part 5 [1]: Responsibilities of the regulatory body
Main	3.9.	The regulatory body should provide guidance to operating organizations on how to meet requirements relating to the safe storage of spent fuel, which should include, but is not limited to: the application of a management system for the handling and storage of spent fuel; development of operational limits and conditions; performance of the safety assessment; development and use of quantifiable performance indicators; and documentation and use of the safety case⁵.
Main	3.10.	Since spent fuel might be stored for long periods of time prior to its retrieval for reprocessing or disposal, the regulatory body should verify that the operating organization is providing the necessary personnel and the technical and financial resources for the lifetime of the spent fuel storage facility, to the extent that such confirmation is within the statutory obligations of the regulatory body.
Main	3.11.	The regulatory review of the decommissioning plans for spent fuel storage facilities should follow a graded approach, particularly considering the current stage in the lifetime of the storage facility. The initial decommissioning plan should be conceptual and should be reviewed by the regulatory body for its overall completeness rather than for specific decommissioning arrangements, but it should include specifically how financial and human resources and the availability of the necessary information from the design, construction and operational stages will be ensured when decommissioning takes place. The decommissioning plan should be updated regularly by the licensee and updates should be reviewed by the regulatory body. If a facility is to be shut down and no longer to be used for its intended purpose, a final decommissioning plan is required to be submitted to the regulatory body for review and approval [20].
Main	3.12.	3.12. General recommendations for regulatory inspection and enforcement actions relating to spent fuel storage facilities are provided in IAEA Safety Standards Series No. GSG‑13, Functions and Processes of the Regulatory Body for Safety [21]. The regulatory body should periodically verify that the key aspects of the operation of the storage facility meet the requirements of the national legal system and facility licence conditions, such as those relating to keeping records on inventories and material transfers, compliance with acceptance criteria for storage, maintenance, inspection, testing and surveillance, operational limits and conditions, physical protection of nuclear material and arrangements for on‑site emergency preparedness and response. Such verification might be carried out, for example, by routine inspections of the spent fuel storage facility and the operating organization, and by review and assessment of the safety case. In addition, verification should include observing and evaluating some exercises of the operating organization, in accordance with para. 6.30 of IAEA Safety Standards Series No. GSR Part 7, Preparedness and Response for a Nuclear or Radiological Emergency [22]. The regulatory body should verify that the necessary records are prepared and that they are maintained for an appropriate period of time. Recommendations on the records to be retained are provided in GSG‑13 [21].
Main	3.13.	The regulatory body should set up appropriate means of informing interested parties, such as people living in the vicinity, the general public, the media and others, about the safety aspects (including health and environmental aspects) of the spent fuel storage facility and about regulatory processes, and should consult these parties, as appropriate, in an open and inclusive manner. The need for confidentiality (e.g. for security reasons) should be respected. Further recommendations are provided in IAEA Safety Standards Series No. GSG‑6, Communication and Consultation with Interested Parties by the Regulatory Body [23].
Main	3.14.	The regulatory body should consider the licensing strategy to be adopted, for example: A licence issued for the entire lifetime of the storage system and/or the facility, which encompasses the whole anticipated operating period, including periodic review of safety assessments, as elaborated in Section 5; or A licence issued for a specified time period with the possibility for renewal after expiry.
Main	3.15.	If the regulatory body comprises more than one authority, effective arrangements should be made to ensure that regulatory responsibilities and functions are clearly defined and coordinated in order to avoid any omissions or unnecessary duplication and to prevent conflicting requirements being placed on the operating organization. The main regulatory functions of review and assessment and inspection and enforcement should be organized in such a manner as to achieve consistency and to enable the necessary feedback and exchange of information.
Main		Requirement 4 of GSR Part 5 [1]: Responsibilities of the operator⁶
Main	3.16.	The operating organization is responsible for the safety of all activities associated with the storage of spent fuel (including activities undertaken by contractors) and for the specification and implementation of the programmes and procedures necessary to ensure safety. The operating organization should maintain a high level of safety culture and should demonstrate safety. In some instances, the operating organization might be the owner of the spent fuel and in other cases the owner might be a separate organization. In the latter instance, particular consideration should be given to interdependences among the spent fuel management steps, including for any activity carried out prior to receipt of the spent fuel at a storage facility, such as its characterization or packaging, or the subsequent transport of the spent fuel from the facility, to ensure that conditions for safety will be met.
Main	3.17.	The responsibilities of the operating organization of a spent fuel storage facility typically include the following: Application to the regulatory body for permission to site, design, construct, commission, operate, modify or decommission a spent fuel storage facility; Conduct of appropriate safety assessment and environmental assessment in support of the application for a licence; Operation of the spent fuel storage facility in accordance with the requirements of the safety case, the licence conditions and the applicable regulations; Development and application of acceptance criteria for the storage of spent fuel, as approved by the regulatory body; Provision of periodic reports as required by the regulatory body (e.g. information on the actual inventory of spent fuel, any transfers of spent fuel into and out of the facility, any events that have occurred at the facility and which have to be reported to the regulatory body) and communication with interested parties and the general public.
Main	3.18.	Prior to authorization of a spent fuel storage facility, the operating organization should provide the regulatory body with a safety case that demonstrates the safety of the proposed activities and also demonstrates that the proposed activities at the facility will be in compliance with the safety requirements and criteria set out in national laws and regulations. As part of the safety case, the operating organization should use the safety assessment to establish specific operational limits and conditions for approval by the regulatory body. The operating organization may wish to set an operational target level within these specified limits to assist in avoiding any breach of approved limits and conditions (see para. 6.106).
Main	3.19.	At an early stage in the lifetime of a spent fuel storage facility, the operating organization should prepare the initial plan for its eventual decommissioning. For new facilities, features that will facilitate decommissioning should be taken into consideration at the design stage. Such features should be included in the decommissioning plan, together with information on arrangements regarding how the availability of the necessary human and financial resources and information will be ensured, for presentation in the safety case. The operating organization should regularly update the decommissioning plan and submit updates to the regulatory body for review and approval. If a facility is to be shut down and is no longer to be used for its intended purpose, the operating organization is required to submit a final decommissioning plan to the regulatory body for review and approval within a period agreed with the regulatory body [20].
Main	3.20.	For existing facilities without a decommissioning plan, the licensee should prepare such a plan as soon as possible and submit it to the regulatory body for review and approval. Subsequent updates are to be made in accordance with the requirements on decommissioning established in IAEA Safety Standards Series No. GSR Part 6, Decommissioning of Facilities [20], and recommendations provided in IAEA Safety Standards Series No. SSG‑47, Decommissioning of Nuclear Power Plants, Research Reactors and Other Nuclear Fuel Cycle Facilities [24].
Main	3.21.	The operating organization should establish the requirements for training and qualification of its staff and contractors, including for initial training and periodic refresher training [4]. The operating organization should ensure that all concerned staff members understand the nature of the spent fuel, its potential hazards and the relevant operating and safety procedures pertaining to it. Supervisory staff should be competent to perform their activities and should therefore be selected, trained, qualified and authorized for that purpose. A radiation protection officer should be appointed to oversee the application of radiation protection requirements.
Main	3.22.	The operating organization should carry out pre‑operational tests and commissioning tests to demonstrate compliance of the storage facility and storage activities with the requirements of the safety assessment and with the requirements established by the regulatory body.
Main	3.23.	The operating organization should ensure that discharges of radioactive material and other potentially hazardous material to the environment are in accordance with the conditions of the licence. Discharges should be documented.
Main	3.24.	The operating organization should prepare plans and implement programmes for personnel monitoring, area monitoring and environmental monitoring.
Main	3.25.	The operating organization should establish procedures on how to analyse the need for and how to implement modifications to the spent fuel storage facility, storage conditions and the spent fuel to be stored. As part of the procedures, the potential consequences of such modifications and of the works performed to implement them should be evaluated, including consequences for the safety of other facilities and also for the retrieval, transport, reprocessing and disposal of spent fuel. The procedures should be commensurate with the significance of the proposed modifications for safety.
Main	3.26.	The operating organization is required to allocate and maintain appropriate financial resources to undertake all necessary tasks throughout the lifetime of the facility, including its decommissioning [17].
Main	3.27.	The operating organization should develop and maintain a record keeping system on data relating to the spent fuel and the storage system, which should include the radioactive inventory, location and characteristics of the spent fuel, information on the ownership and origin of the spent fuel, and information about its characterization. An unequivocal identification system should be established, with markings that will last for the duration of the storage period. Such records should be preserved and updated to enable the implementation of the spent fuel management strategy, whether disposal or reprocessing.
Main	3.28.	The operating organization is required to prepare an emergency plan and the necessary procedures and analytical tools for on‑site emergency preparedness and effective response [22]. The operating organization is required to coordinate this emergency plan with those of all other bodies that have responsibilities in a nuclear or radiological emergency, including public authorities, and submit it to the regulatory body for approval [22]. Account is required to be taken, in the content, features and extent of the emergency plan, of the results of the hazard assessment and any lessons identified from operating experience and from past emergencies, including conventional emergencies [22, 25]. The operating organization should demonstrate to the regulatory body, as part of the safety case, that the emergency arrangements provide for sufficient assurance of an effective on‑site emergency response and that they are in place [26].
Main		Requirement 6 of GSR Part 5 [1]: Interdependences
Main	3.29.	There should be clear and unequivocal ownership of the spent fuel stored in the facility. The responsibilities of the spent fuel owner and the responsibilities of the operating organization, if they differ, should be clearly defined and documented. The spent fuel owner (namely, a body having legal title to the spent fuel, including financial liabilities) should be responsible for the overall strategy for the management of its spent fuel. In determining the overall strategy, the spent fuel owner should take into account interdependences between all stages of spent fuel management, the options available and the overall national spent fuel management strategy.
Main	3.30.	Information about any changes in ownership of the spent fuel or changes in the relationship between the owner and the operating organization of a spent fuel storage facility should be provided to the regulatory body.
Main		Requirement 21 of GSR Part 5 [1]: System of accounting for and control of nuclear material
Main	3.31.	The operating organization will be required to establish, maintain and implement a system for nuclear material accounting and control as an integrated part of the State system of accounting for and control of nuclear material⁷ [10].
Main	3.31A.	In addition, physical protection systems for deterrence and detection of the intrusion of unauthorized persons and for protection against sabotage from within and outside the facility are required to be designed and installed during the construction and operation of the spent fuel storage facility.
Main	3.31B.	Paragraph 1.10 of SF‑1 [11] requires that safety measures and security measures “be designed and implemented in an integrated manner so that security measures do not compromise safety and safety measures do not compromise security.” The operating organization should demonstrate to the regulatory body that security provisions, including physical protection systems, and safety measures at the facility are managed in such a way as to achieve this.
Main		Requirement 7 of GSR Part 5 [1]:
Main	4.1.	The requirements on the management system for all stages in the lifetime of a spent fuel storage facility are established in GSR Part 2 [5]. Recommendations on the management system for the storage of spent fuel are provided in IAEA Safety Standards Series No. GS‑G‑3.3, The Management System for the Processing, Handling and Storage of Radioactive Waste [28].
Main	4.2.	An integrated management system is required to be established, implemented, assessed and continually improved by the operating organization [5] and applied to all stages of the storage of spent fuel. The management system is required to be aligned with the goals of the operating organization and to contribute to their achievement [5]. The management system should address the siting, design, commissioning, operation, maintenance and decommissioning of the spent fuel storage facility. The management system is required to be designed to ensure that the safety of the spent fuel and of the spent fuel storage facility is maintained, and that the quality of the records and of subsidiary information of spent fuel inventories is preserved, with account taken of the length of the storage period and the consecutive management steps, for example reprocessing or disposal [5]. The management system should also contain provisions to ensure that the fulfilment of its goals can be demonstrated.
Main	4.3.	The long term nature of spent fuel management operations means that particular consideration should be given to establishing and maintaining confidence that the performance of the spent fuel storage facilities and activities will meet the safety requirements throughout the lifetime of the facility to the end of its decommissioning (e.g. by creation of the funding arrangements that will be necessary to manage the spent fuel in the long term).
Main	4.4.	National and international policies and principles for spent fuel management that currently constitute an accepted management arrangement can evolve over the lifetime of the facility. Policy decisions (e.g. regarding spent fuel reprocessing) and technological innovations and advances (e.g. in partitioning and transmutation) can lead to fundamental changes in the overall spent fuel management strategy. However, the operating organization retains its responsibility for safety at all times, and continuous commitment by the organization remains a prerequisite of ensuring safety and the protection of human health and the environment.
Main	4.5.	For the plans, goals and objectives associated with the strategy for achieving an integrated approach to safety, interaction with all interested parties should be considered, as well as long term aspects such as: Provision of adequate resources (the adequacy of resources for maintenance of facilities and equipment may need to be periodically reviewed over operational periods that may extend over decades); Preservation of technology and knowledge and transfer of such knowledge to people or organizations joining the spent fuel management programme in the future; Retention or transfer of ownership of spent fuel and spent fuel management facilities; Succession planning for the technical and managerial human resources of the spent fuel management programme or the operating organization; Continuation of arrangements for interacting with interested parties.
Main	4.6.	Spent fuel management activities will require financial and human resources and the necessary infrastructure at the site where the spent fuel storage facility is located. Senior management is required to make arrangements to provide adequate resources for spent fuel management activities, to satisfy the demands imposed by safety, health, environmental, security, quality, human and organizational factors, and societal and economic aspects of the full range of activities involved in the management of spent fuel and the potentially long duration of such activities [5].
Main	4.7.	Arrangements for the funding of future spent fuel management activities should be specified, and responsibilities, mechanisms and schedules for providing the funds should be established in due time. The generator of the spent fuel should establish an appropriate funding mechanism.
Main	4.8.	The management system for spent fuel management should include provisions to deal with funding related challenges, such as the following: For various reasons (e.g. bankruptcy, cessation of business), it might not be feasible to obtain the necessary funds from the spent fuel generator, especially if funds were not set aside at the time the benefits were received from the activity, or if ownership of the spent fuel has been transferred to another party. If funds are to come from public sources, their allocation will compete with other demands for public funding, and it may be difficult to gain access to adequate funds on a timely basis. It might be difficult to make realistic estimates of costs for spent fuel management activities that are still in the planning stage and for which no experience has been accumulated. It might be difficult to estimate anticipated costs for activities that will only begin in the long term, because they will depend strongly on assumptions made about future inflation rates, interest rates and technological developments. It might be difficult to determine appropriate risk and contingency factors to be built into estimates of future costs, owing to the uncertainties associated with future changes in societal demands, political imperatives, public opinion and the nature of unplanned events that may need resources for dealing with them. If several organizations are involved in spent fuel management activities, the necessary financial arrangements might be complex and might vary over the lifetime of the facility. It might be problematic to establish an adequate degree of confidence in all the arrangements so that the necessary continuity of funding throughout the entire series of activities is ensured.
Main	4.9.	Accumulated experience, including lessons identified from incidents and events, should be reviewed periodically and should be used in revising training programmes and in reaching future decisions.
Main	4.10.	In the design of facilities for long term spent fuel management, consideration should be given to the incorporation of measures that will facilitate operation, maintenance of equipment and eventual decommissioning of the facility. For long term spent fuel management activities, future infrastructural requirements should be specified and plans should be made to ensure that these will be met. In such planning, consideration should be given to the continuing need for support services, spare parts for equipment that might eventually cease to be manufactured, and equipment upgrades to meet new regulations and operational improvements, and to the evolution and inevitable obsolescence of software. Consideration should also be given to the need to develop monitoring programmes and inspection techniques for use during extended periods of storage.
Main	4.11.	Consideration should be given to the possible need to relocate spent fuel casks if problems arise after they have been placed in storage. The availability of any specialized equipment that may be necessary over a long time period while spent fuel is in storage or that may be necessary in the future should be assessed.
Main	4.12.	Records concerning spent fuel and its storage that need to be retained for an extended period should be stored in a manner that minimizes the likelihood and consequences of loss, damage or deterioration due to unpredictable events such as fire, flooding or other natural or human induced events (both internal and external to the facility). Storage arrangements for records should meet the requirements prescribed by the national authorities or the regulatory body, and the status of the records should be periodically assessed. If records are inadvertently destroyed, the status of surviving records should be examined and the importance of their retention and their necessary retention periods should be re‑evaluated.
Main	4.13.	The management system should be reassessed whenever the relationship between the owner of the spent fuel and the operating organization of the facility changes (e.g. public organizations are privatized, new organizations are created, existing organizations are combined or restructured, responsibilities are transferred between organizations, operating organizations undergo internal reorganization of the management structure, or resources are reallocated).
Main		Requirement 13 of GSR Part 5 [1]: Preparation of the safety case and supporting safety assessment
Main	5.1.	In demonstrating the safety of the spent fuel storage facility and related activities, a safety case should be developed as development of the facility progresses and the supporting safety assessment should be carried out in a structured and systematic manner. Proposed facilities, processes, operations and activities should be examined to determine whether they can be implemented safely and whether they meet all requirements with regard to safety. If storage casks are to be used, one or separate safety cases and/or safety assessments might be prepared for the storage casks, for the storage building or facility and for the subsequent transport arrangements if the cask will be used eventually for transport as well as for storage. This will depend on the national regulatory approach. However, irrespective of the approach taken, the interdependences between spent nuclear fuel management operations, activities and collocated facilities should be taken into consideration to ensure that an integrated approach to safety is adopted and that safety is optimized. The safety case and supporting safety assessment should provide the primary input to the licensing documentation that is used to demonstrate compliance with regulatory requirements [6].
Main	5.2.	The various stages in the lifetime of the spent fuel storage facility (i.e. siting, design, construction, commissioning, operation, decommissioning) should be taken into account in the safety case. The safety case should be periodically reviewed in accordance with regulatory requirements and should be revised as necessary.
Main	5.3.	The prime responsibility for safety throughout the lifetime of a facility lies with the operating organization [11]. This includes responsibility for both ensuring the safety of the facility and demonstrating its safety in the safety case.
Main	5.4.	Long term storage (see para. 1.6 and Annex I) might involve a period of time that exceeds the normal design lifetime of civil structures, including short term storage facilities, and this will have implications for the selection of construction materials, operating methods, and quality assurance and quality control requirements. Specific issues that should be given particular consideration in the safety case for a facility for long term storage of spent fuel include the anticipated lifetime of the facility, the importance of passive safety features, retrievability and the management system. Consideration should also be given to the provision of support services when the spent fuel storage facility remains in operation after other facilities at the site have been closed, in particular for storage facilities at reactor sites.
Main	5.5.	The rationale for the selection of the assessment time frame should be explained and justified. Depending on the purpose of the assessment and other components of assessment context [26], for ease of modelling or presentation it might be convenient to divide the overall time frame of the safety assessment into shorter ‘time windows’ with various end points.
Main	5.6.	In determining the assessment time frame, account should be taken of the characteristics of the particular storage facility or activity, the site and the spent fuel to be stored. Other factors that should be considered include the following: For most long term storage systems (including storage casks, engineered constructions and the surrounding environment), potential health and environmental impacts might increase for a period of time after commissioning of the facility. In the long term, and depending on the nature of the facility, potential impacts might decrease, in particular through decay of the radionuclide inventory of the spent fuel. The safety assessment calculations should consider the maximum, or peak, dose or risk associated with the facility or activity. A further consideration that might influence decisions on assessment time frames is the return period of natural external hazards, such as extreme meteorological events or earthquakes. Several factors that can significantly affect the results of the safety assessment might change with time, including external hazards from human activities such as the construction of other facilities nearby, natural events such as changes in water levels, and changes in the availability of support facilities and infrastructure due to shutdown and decommissioning of collocated facilities. Potential changes such as these should be considered in the safety assessment. As a means to assess the possible evolution of the long term storage, one or more scenarios postulated to reflect different evolution paths may be considered in the safety assessment. Assessment time windows may be defined, as appropriate, to reflect potential changes at the storage facility. The location, habits and characteristics of the representative person considered in radiological impact assessment might change over time. The representative person will generally be a hypothetical construct and not an actual member of the population. Nevertheless, individuals and populations in the future should be afforded at least the same level of protection as that required currently. The habits and characteristics assumed for the representative person should be chosen on the basis of reasonably conservative and plausible assumptions, considering current lifestyles as well as the available site or regional environmental conditions.
Main	5.7.	The operating organization should demonstrate in the safety case that, to the extent possible, passive safety features are applied. In the assessment of long term safety, the degradation of passive barriers over time should be taken into account.
Main	5.8.	The complementary performance of the different elements providing safety functions should be evaluated. Each element should be independent of the others, to the extent possible, to ensure that they are complementary and cannot fail through a single failure mode. The safety case should explain and justify the functions provided by each element and should identify the time periods over which they are expected to perform their various safety functions and also the alternative or additional safety functions that will be in place if a barrier does not fully perform.
Main	5.9.	As in the case of disposal of radioactive waste, the environment might also offer additional protective functions (e.g. underlying clay layers that would provide a sorption capacity for contaminants in the event of any leakages from the facility). Such aspects should be taken into account during the siting of the facility and should be considered in the safety case.
Main	5.10.	Storage is, by definition, an interim measure, but it can last for several decades. The intention in storing spent fuel is that it can be retrieved for reprocessing or processing and/or disposal at a later time. In the safety case, a plan for the safe handling of the spent fuel, following the period of storage, should be considered, and the potential effects of degradation of the spent fuel, and of any elements providing confinement, on the ability to retrieve and handle the spent fuel should be assessed (see also Section 6).
Main	5.11.	The possibility of inadvertent human intrusion normally would not be considered relevant when assessing the safety of a storage facility because the facility will need continued surveillance and maintenance not only during but also after the spent fuel emplacement stage. Prevention of intentional human intrusion needs adequate security arrangements (see Ref. [10]), which should be addressed in the safety case (see also paras 3.31A and 3.31B).
Main	5.12.	As storage is an interim measure, the safety case should describe the provisions for the regular monitoring, inspection and maintenance of the storage facility to ensure its continued integrity over the anticipated lifetime of the facility.
Main	5.13.	Because of the long time frames potentially involved, a plan for adequate record keeping over the expected time frame for storage should be considered in the safety case.
Main	5.14.	Periodically, the safety case should be reviewed to assess the continuing adequacy of the storage capacity; account should be taken of the predicted spent fuel arising, the expected lifetime of the storage facility and the availability of reprocessing or disposal options (see para. 5.26).
Main	5.15.	It may be necessary to reassess the anticipated challenges of decommissioning of the spent fuel storage facility after operating experience has been gained.
Main	5.16.	The requirement to perform safety assessment derives from national programme requirements and the recognition that the safety assessment can contribute directly to safety, as it is through the safety assessment that appropriate measures are identified that can be put in place to protect workers, the public and the environment. Safety assessment is undertaken in conjunction with the planning and design of a proposed facility or activity rather than being a separate activity. The results of the safety assessment can be used to determine any necessary changes in the plans or design so that compliance with all requirements is ensured. The results are also used to establish controls and limitations on the design, construction and operation of the facility.
Main	5.17.	Safety assessment is typically an iterative process used to ensure that a spent fuel storage facility can be operated safely and it should be commenced early in the design process. Generally, in the control of radiation risks, reliance should be placed principally on design features rather than on operating procedures.
Main	5.18.	Postulated initiating events that might influence the design of the spent fuel storage facility and the integrity and safety of the spent fuel should be identified. The primary causes of postulated initiating events might be credible equipment failure and operator error or natural or human induced events (both internal and external to the facility). In identifying the relevant postulated initiating events, generic lists of such events should be consulted (see Annexes IV–VI). Such lists should not be relied on solely, since site specific environmental conditions and phenomena and the design and operation of the facility will also influence the decision as to which postulated initiating events need to be evaluated in the safety assessment.
Main	5.19.	Safety assessment should cover the storage facility and the type of spent fuel to be stored and the storage arrangements. In this regard, the types, quantities, initial enrichment, burnup, integrity, heat production, storage mode (wet or dry storage) and physical and chemical characteristics of the spent fuel are basic aspects that need to be included in the safety assessment of the spent fuel storage facility.
Main	5.20.	Safety assessment for a spent fuel storage facility should cover the expected operational period of the facility. If the spent fuel is to be stored for long periods of time, events of lower likelihood would need to be evaluated in the safety assessment compared with the case of storage for a shorter duration. Similarly, processes that might not be relevant for a shorter duration of storage might become significant for a longer duration of storage (e.g. generation of gas, general corrosion, stress corrosion, radiation or hydride induced embrittlement of cladding material, natural processes such as a vermin infestation or a possible change in nuclear reactivity over a long time).
Main	5.21.	A specific safety case and supporting assessment for a spent fuel storage facility should generally include aspects such as: A description of the site and facility (including the maximum expected inventory of spent fuel and its acceptance criteria, the storage facility and its characteristics, structures, systems and components, including the characteristics of items important to the safety of the spent fuel storage facility, in accordance with the requirements of its licence) and a specification of applicable regulations and guidance. A description of spent fuel handling and storage activities and any other operations at the facility. Systematic identification of hazards that could lead to anticipated operational occurrences and possibly to accident conditions (see Annexes IV–VI). In the identification of hazards, consideration should be given to possible combinations of related events and hazards (e.g. earthquake and tsunami, fire and building collapse) that might occur and their consequential effects. In considering scenarios involving combinations of hazards, account should be taken of the likelihood of their simultaneous or consecutive occurrence and their causality. A graded approach should be taken to addressing combinations of hazards in the safety case and the safety assessment. An evaluation of scenarios, including screening of combinations of scenarios, that might result in a release of radioactive material, to identify those combinations of scenarios warranting consideration in the design basis of the facility. Combinations of scenarios that are of low likelihood but have high potential consequences that are above the design basis threshold should also be considered. Assessment of the probabilities and potential consequences of releases of radioactive material identified in the hazard evaluation by quantitative analyses, and comparison of the results of the assessment with safety criteria established by the regulatory body [6]. Arrangements for ageing management. Establishment of operational limits and conditions and administrative controls based on the safety assessment. If necessary, the design of the spent fuel storage facility should be modified and the safety assessment should be updated. Such controls should include acceptance criteria for spent fuel casks, including canisters containing failed fuel. Documentation of safety analyses and the safety assessment for inclusion in the licensing documentation for the facility. The commissioning programme. Organizational control of operations. Procedures and operational manuals for activities with significant safety implications, including procedures for response to the malfunction of equipment. The programme for periodic maintenance, inspection and testing. The expected values for subcriticality, heat removal capacity and radiation doses within and at the boundary of the spent fuel storage facility. Monitoring programmes, including a programme for verification of the integrity of the shielding, a programme for surveillance of the condition of stored spent fuel and a programme for surveillance of stored spent fuel assemblies, if appropriate. A programme for feedback of operating experience and its inclusion in manuals, guidelines and training. The training programme for staff. Safety implications of aspects of accounting for and control of nuclear material. Arrangements for management of the interface between safety and nuclear security. The on‑site emergency plan. The management system. Provisions for occupational radiation protection. Provisions for the management of radioactive waste and for decommissioning. Whenever the safety of the facility depends on human actions, including actions to be taken in accidents, assessment of these human actions.
Main	5.21A.	In the case of collocation of spent fuel storage facilities with other facilities, consideration should be given in the safety assessment to the potential hazards presented by each facility or activity to the others, and the effects of external events on all facilities and activities, including the possibility of concurrent events affecting different facilities and activities [6]. Where it is anticipated that facilities on the site will share resources (human resources or material resources) in accident conditions, evaluation of such scenarios in the safety assessment should demonstrate that the required safety functions can be fulfilled at each facility.
Main	5.22.	Key hazards should be identified in the safety assessment so that the required safety functions and safety systems can be identified and a level of confidence can be established in the parameters supporting the safety assessment that is commensurate with the safety significance of the safety functions and safety systems (e.g. by sensitivity analysis).
Main	5.23.	The safety assessment should include an assessment of hazards in operational states and accident conditions. It should provide an assessment of doses at the site boundary and of the potential for exposure in areas within the site to which there is to be unrestricted access. In normal operation, there should be no mechanism that could cause a rapid increase in reactivity in the stored spent fuel, and thus relatively few credible accident scenarios for such a sudden increase in reactivity followed by a release of radioactive material.
Main	5.24.	As appropriate, limits on authorized discharges should be established for the spent fuel storage facility, in accordance with the recommendations provided in GSG‑9 [14].
Main	5.25.	If the initial safety assessment yields results that are close to or that exceed the limiting performance objectives, it may be necessary to carry out a more rigorous evaluation of the suitability of any generic data sources that may have been used, and/or an inventory reduction or additional safety systems and controls may be necessary.
Main		Requirement 16 of GSR Part 5 [1]: Periodic safety reviews
Main	5.26.	The safety case and supporting safety assessment, including the management system for their implementation, should be periodically reviewed in accordance with regulatory requirements. The review of the management system should include aspects of safety culture. In addition, the safety case and supporting safety assessment should be reviewed and updated: When there is any significant change to the facility or to its radionuclide inventory that might affect safety. When changes occur in the site characteristics that might impact the storage facility (e.g. industrial development or changes in the surrounding population). When significant changes in knowledge and understanding occur (e.g. from research data or from feedback of operating experience). When there is an emerging safety issue due to a regulatory concern or an incident. Periodically, at predefined periods, as specified by the regulatory body. Some States specify that periodic safety review be carried out at least once every ten years.
Main	5.27.	Safety should be reassessed in the case of significant, unexpected deviations in storage conditions, for example if those properties of the spent fuel that are relevant to safety begin to deviate from those taken as a basis in the safety assessment.
Main	5.28.	For storage beyond the original design lifetime, a re‑evaluation should be performed of the initial design (and of the current design if it is significantly different), operations, maintenance, ageing management, safety assessment and any other aspect of the spent fuel storage facility relating to safety. If, during the design lifetime, an extension to the storage period is foreseen, a precautionary approach should be applied, in particular through validation of the adequacy of the design assumptions for the extended period envisaged.
Main		Requirement 15 of GSR Part 5 [1]: Documentation of the safety case and supporting safety assessment
Main	5.29.	In documenting the safety case, particular consideration should be given to ensuring that the level of detail and the supporting assessment are commensurate with the importance to safety of the particular system or component and its complexity, and that an independent reviewer will be able to reach a conclusion on the adequacy of the assessment and the arguments employed, both in their extent and in their depth. Assumptions used in the safety case are required to be justified in the documentation [1], as should be the use of generic information.
Main		Requirement 11 of GSR Part 5 [1]: Storage of radioactive waste
Main	6.1.	Spent fuel storage facilities should provide for the safe, stable and secure storage of spent fuel before it is reprocessed or disposed of. The design features and the operation of the facility should be such as to provide confinement of radioactive material to ensure that radiation protection of workers, members of the public and the environment is optimized within the dose constraints in accordance with the requirements established in GSR Part 3 [12] and to maintain subcriticality, to ensure removal of decay heat and to ensure retrievability of the spent fuel. These safety functions should be maintained during normal operation, anticipated operational occurrences and accident conditions.
Main	6.2.	Various types of wet and dry storage facility are currently in operation or under consideration in various States. Spent fuel is stored in essentially one of three different modes: Wet storage in pools at, or remote from, a reactor site. The spent fuel is stored in standard storage racks or in compact storage racks in which closer spacing of the fuel assemblies or fuel elements is allowed in order to increase the storage capacity. Dry storage in either storage casks or dual purpose (i.e. storage and transport) casks at, or remote from, a reactor site. Casks are modular in nature. Such systems are sealed systems designed to prevent the release of radioactive material during storage. They provide shielding and confinement of the spent fuel by physical barriers, which can include a metal or concrete body and metal liner or a metal canister and lids. They are usually cylindrical in shape, circular in cross‑section, with the long axis arranged either vertically or horizontally. The fuel position is maintained by means of a storage basket which might or might not be an integral part of the cask. Heat is removed from the stored fuel by conduction, radiation and forced or natural air convection to the surrounding environment. Casks might be enclosed in buildings or stored in an open area. Dry storage in vault type storage facilities. A vault is a massive, radiation shielded facility in which spent fuel is stored. A vault can be either above or below ground level; it might be a reinforced concrete structure containing an array of storage cavities. The spent fuel is appropriately contained in order to prevent unacceptable releases of radioactive material. Shielding is provided by the structure surrounding the stored material. Primary heat removal is achieved by forced or natural air convection over the exterior of the storage cavities. This air is released to the atmosphere either directly or via appropriate filtration, depending on the system design. Some systems also use a secondary cooling circuit.
Main	6.3.	Although designs of spent fuel storage facilities may differ, in general they should consist of relatively simple, preferably passive, inherently safe systems intended to provide adequate safety over the design lifetime of the facility, which might span several decades. The lifetime of a spent fuel storage facility should be appropriate for the envisaged storage period. The design should also contain features to ensure that associated handling and storage operations are relatively straightforward.
Main	6.4.	The storage facility should be designed to fulfil the main safety functions; that is, maintaining subcriticality, removal of heat, confinement of radioactive material and shielding from radiation and, in addition, retrievability of the fuel or spent fuel packages. The design should at least, if possible, include the following features: Systems for the removal of heat from the spent fuel should be driven, if possible, by the energy generated by the spent fuel itself (e.g. natural convection). A multibarrier approach should be adopted in ensuring confinement, with account taken of all elements, including the fuel matrix, the fuel cladding, the storage casks, the storage vaults and any building structures that can be demonstrated to be reliable and competent. Safety systems should be designed to achieve their safety functions with minimum need for monitoring. Safety systems should be designed to function with minimum human intervention. If the performance of safety systems depends on actions carried out by personnel, those human interactions with the facility or activity should be addressed in the safety assessment. The storage building, or the cask in the case of dry storage, should be resistant to the hazards taken into consideration in the safety assessment. Access should be provided for response to incidents. The spent fuel storage facility should be such that retrieval of the spent fuel or spent fuel package for inspection or reworking is possible. The spent fuel and the storage system should be sufficiently resistant to degradation. The storage environment should not adversely affect the properties of the spent fuel, spent fuel package or storage system. The spent fuel storage system should allow for inspections. The spent fuel storage system should be designed to avoid or minimize the generation of secondary waste streams.
Main	6.5.	This paragraph was deleted.
Design Process	6.6.	In the design process, appropriate analytical methods, procedures and tools should be used in conjunction with suitably selected input data and assumptions covering all operational states and accident conditions that are credible, with account taken of natural phenomena. Only verified and validated methods should be used for predicting the safety of operational states or the consequences of accidents. The input data selected should be conservative but still realistic. If possible, the degree of conservatism should be quantified. Where uncertainties in input data, analyses or predictions are unavoidable, appropriate allowances should be made to compensate for such uncertainties. The sensitivity of the assessment results to uncertainties should be evaluated.
Design Process	6.7.	As part of the overall process leading to an acceptable design, the design evolution and the supporting rationale should be clearly and adequately documented and kept readily available for future reference. The supporting documentation should be presented as a safety case [6].
Design Process	6.8.	In order to prevent cliff edge effects, the design should provide for an adequate margin against levels of external hazard selected for the design basis. It should be demonstrated in the safety case that all credible hazards and scenarios have been adequately analysed and appropriately addressed in the design. The safety case should describe the performance assessment models and methodologies used and the conclusions reached. Thus, for any design proposed, it should be demonstrated in the safety case that the spent fuel storage facility can, within the bounds of existing technologies, be safely constructed, commissioned, operated and decommissioned in accordance with the design specifications and the requirements of the regulatory body.
Design Process	6.9.	Items important to safety, including structures, systems and components, should be identified and classified in accordance with their importance to safety. Procedures should be established to ensure that the items important to safety will have appropriate functional and performance characteristics to perform their safety functions for the lifetime of the facility or for a defined replacement interval. Procedures relating to the control of design modifications in subsequent stages of the lifetime of the facility should also be defined. Such modifications might be necessary to take into account the findings of the safety case and periodic reassessment in the circumstances indicated in para. 5.26.
Design Process	6.10.	For dry storage facilities, the design should provide for arrangements to handle potential problems with the integrity of the spent fuel and of the storage system at the end of the original design lifetime of the storage facility in advance of any need for inspection of the content of the casks or assessment of the integrity of the spent fuel or storage casks. Such inspection might also be necessary to assess the integrity of the casks and the spent fuel, including a survey of the casks for leaktightness, to demonstrate that the storage period may be extended if an extension to the storage period in dry storage casks is under consideration. Careful consideration should be given to the approach to be adopted in determining the integrity of the spent fuel and storage system in order to prevent unnecessary occupational exposure and to prevent accidental release of radioactive material. For example, consideration should be given to whether to open the cask and remove the contents, or to inspect the contents in situ.
Design Process	6.11.	For storage beyond the original design lifetime, consideration should be given to mitigation of the consequences of potential changes in the storage facility and the stored spent fuel. Changes in the storage facility might be caused by radiation, heat generation and chemical or galvanic reactions. Changes in the stored spent fuel and storage cask might include the following: The generation of gases that might cause hazards, by chemical and radiolytic effects (e.g. the generation of hydrogen gas by radiolysis) and buildup of overpressure; The generation of combustible or corrosive substances; The corrosion of metals; The degradation of the spent fuel confinement system.
Siting	6.12.	Requirements for site evaluation are established in IAEA Safety Standards Series No. SSR‑1, Site Evaluation for Nuclear Installations [29]. The associated Safety Guides [30–35] contain criteria and methods that could be used in a graded approach in the siting of spent fuel storage facilities.
Defence in depth	6.13.	The concept of defence in depth is applied to all safety activities, whether organizational, behavioural or design related, to ensure that if a failure were to occur, it would be detected and compensated for or corrected by appropriate measures [4]. Defence in depth is required to be applied in the siting of a spent fuel storage facility and in its design, as well as when considering subcriticality, heat removal, confinement and radiation protection issues [4].
Defence in depth	6.14.	Application of the concept of defence in depth in the design of spent fuel storage should entail provision of a series of levels of defence (e.g. inherent features, equipment, procedures) aimed at preventing accidents and ensuring appropriate protection and mitigation of consequences in the event that prevention fails [4].
Defence in depth	6.15.	The facility should have a reserve storage capacity, which should be included in the design or should be otherwise available, for example in order to allow for reshuffling of spent fuel casks or unpackaged spent fuel elements for inspection, retrieval or maintenance work. The reserve capacity should be such that the largest type of storage cask can be unloaded or, in the case of a modular storage facility, that at least one module can be unloaded.
Structural integrity	6.16.	In order for safety systems and safety related items to perform properly, the components of the spent fuel storage facility should maintain their structural integrity in all operational states and accident conditions. Therefore, the integrity of the components and their related systems should be demonstrated by means of a structural evaluation. This should take account of relevant loading conditions (e.g. stress, temperature, corrosive environment, radiation levels), and should consider creep, fatigue, thermal stresses, corrosion and changes in material properties with time (e.g. concrete shrinkage).
Structural integrity	6.17.	To prevent deviations from normal operation, and to prevent system failures, careful attention should be paid to the selection of appropriate design codes and materials, and to control of fabrication of components and of construction of the spent fuel storage facility. In order to detect and terminate deviations from normal operational states, specific systems should be provided as determined in the safety case.
Structural integrity	6.18.	The integrity of the spent fuel and the geometries required to maintain subcriticality and heat removal, and the confinement barriers for the spent fuel, should be maintained throughout the lifetime of the facility and should be verified using appropriate methods, including both prospective analysis and ongoing surveillance.
Structural integrity	6.19.	The allowable stresses for given loading conditions should comply with the applicable codes and standards. If no such standards apply, justification should be provided for the allowable stress levels selected.
Structural integrity	6.20.	Structural materials and welding methods should be selected on the basis of accepted codes and standards. Consideration should be given to potential cumulative effects of radiation on materials likely to be subjected to significant radiation fields. In addition, potential thermal effects on material degradation should also be considered.
Structural integrity	6.21.	The materials of items important to safety, including those structures and components in direct contact with the spent fuel, should be compatible with the spent fuel, should be such as to minimize chemical and galvanic reactions, which might degrade the integrity of the spent fuel during its storage, and should not contaminate the spent fuel with substances that might significantly degrade the integrity of the spent fuel during its storage.
Structural integrity	6.22.	Detailed consideration should be given to the effects of the storage environment on the spent fuel and the structures, systems and components important to safety. In particular, the potential for oxidation of exposed uranium dioxide (UO₂) to triuranium octaoxide (U₃O₈), with consequent increase in volume and particulate formation, should be considered. In addition, any effects of changes in the storage environment (e.g. wet to dry or dry to wet) should be assessed.
Structural integrity	6.23.	As determined during the design stage, attaining adequate reliability might necessitate the use of durable construction materials, redundancy of key components, a specific level of reliability of supporting services (e.g. electrical power supply), effective monitoring plans and efficient maintenance programmes (i.e. programmes compatible with normal facility operations).
Structural integrity	6.24.	The construction materials used should allow for easy decontamination of surfaces. The compatibility of decontamination materials with the operating environment should be considered for all operational states and accident conditions. The integrity of systems that are connected to spent fuel storage systems, such as the heat removal system, is also important. Tube failures and leaks in the spent fuel storage system should be prevented, as these could provide a path for chemical species detrimental to either fuel or confinement integrity, such as chloride ions, to enter a spent fuel storage pond.
Structural and mechanical loads	6.25.	A full description of the structural and mechanical aspects of the design of a storage facility should be provided in sufficient detail to justify the basic design. Typical items for consideration should include the following: Determination of structural and mechanical loads due to the fuel, fuel storage casks and various components of the spent fuel storage facility for operational states and accident conditions; An evaluation of the foundations of the spent fuel storage facility; A full structural evaluation of the safety systems of the spent fuel storage facility; Evaluations of supporting features such as cranes, transfer vehicles and protective buildings.
Structural and mechanical loads	6.26.	Consideration should be given to all situations in which handling mechanisms could malfunction, thereby leaving fuel elements or casks inadequately shielded or irrecoverable. Consideration should also be given to the possibility of casks becoming wedged and immovable within the spent fuel storage facility. In addition to the issue of shielding in such circumstances, consideration should be given to whether handling equipment and systems can enable recovery from such situations or whether they could be damaged by the application of excessive stresses.
Thermal loads and processes	6.27.	In view of the decay heat generated by spent fuel, all thermal loads and processes should be given appropriate consideration in the design. Typical items for consideration should include the following: Thermally induced stresses; Internally and externally generated pressures; Heat transfer requirements; Evaporation and water make-up requirements; The effect of temperature on subcriticality.
Time dependent material processes	6.28.	The anticipated lifetime of the storage facility will be a determining factor for aspects such as corrosion, creep, fatigue, shrinkage, radiation induced changes and associated radiation fields. In the design of the storage facility, consideration should be given to the impact of such processes.
Subcriticality	6.29.	In accordance with Requirement 38 of SSR‑4 [4], the design of a spent fuel storage facility is required to ensure an adequate margin of subcriticality under operational states and conditions that are referred to as credible abnormal conditions.
Subcriticality	6.30.	The subcriticality of spent fuel might be ensured or influenced by a number of design factors and precautions. The physical layout and arrangement of the spent fuel storage facility should be designed in such a way as to ensure, through geometrically safe configurations, that subcriticality will be maintained in all operational states and for credible abnormal conditions.
Subcriticality	6.31.	Where spent fuel cannot be maintained subcritical by means of safe geometrical configurations alone, additional means such as fixed neutron absorbers and/or the use of a burnup credit (see Appendix II, paras II.7–II.9) should be applied. If fixed neutron absorbers are used, it should be ensured by means of proper design and fabrication that the absorbers will not become separated or displaced in operational states or in accident conditions. Consideration should also be given to the effects of burnup, ageing, corrosion and handling on the fixed neutron absorbers.
Subcriticality	6.32.	Subcriticality can be influenced by internal and external hazards that have the potential to reconfigure the pre‑existing spent fuel assembly array in such a way as to increase the potential for criticality. Consideration should also be given to routine fuel movements that could bring the fuel being moved into close proximity with stored fuel or in which fuel could be dropped and fall onto stored fuel. For operational states and credible abnormal conditions, the sequences of events leading to such abnormal fuel configurations should be evaluated. The possible consequences of such occurrences should be evaluated using reliable data and verified and validated methodologies. Appropriate mitigating measures should be put in place to ensure that subcriticality will be maintained under all such conditions.
Subcriticality	6.33.	An adequate margin of subcriticality in the effective neutron multiplication factor k_eff that is acceptable to the regulatory body should be maintained for operational states and credible abnormal conditions.⁸ to avoid criticality accidents. For a dry storage facility, the minimum margin should be maintained even in the event of water flooding of the locations where the spent fuel is stored, unless flooding is precluded by location or design. The potential for rearrangement or compaction of fuel pins should also be considered in demonstrating the required subcriticality margin. For a wet storage facility, the minimum margin should be maintained even in the event of water boiling after a loss of cooling (i.e. the storage environment could be more reactive under water vapour conditions than under water) or in case of a water leak.
Subcriticality	6.34.	The most appropriate approach to estimating the required multiplication factors will depend on a number of factors, including the spent fuel properties, as well as the circumstances being addressed (e.g. normal operation or accident conditions). In determining subcriticality, a conservative estimate should be made of the effective neutron multiplication factor, with account taken of the following: If the initial enrichment of fissile material within a fuel assembly or between fuel assemblies is variable, appropriate consideration of this variability in the modelling should be used. Alternatively, the highest enrichment may be used to provide a conservative characterization of the fuel assembly. Where uncertainties exist in any data relating to the fuel (e.g. in terms of design, geometries or nuclear data), conservative values for the data should be determined and should be used in all subcriticality calculations. If necessary, a sensitivity analysis should be performed to quantify the effects of such uncertainties. Any geometric deformations of the fuel and storage equipment that could be caused by any postulated initiating events should be taken into account. Optimum moderation and reflection should be assumed for operational states and accident conditions to provide a pessimistic assessment of criticality. It should be ensured that the system will remain subcritical for all credible water densities. The highest nuclear reactivity might be reached at some intermediate density, for example, if water in the pool begins to boil owing to failure of the heat removal system or during drying of a cask. Flooding should be assumed in dry storage situations, unless precluded by location or design features. For certain accident conditions, such as a fuel handling accident, limited credit for soluble boron may be allowed. The inventory of the spent fuel storage facility should be assumed to be at the maximum capacity of the design. Credit should not be claimed for neutron absorbing parts or components of the spent fuel storage facility unless they are permanently installed, their neutron absorbing capabilities can be determined and it has been demonstrated that they would not be degraded by any postulated initiating events. Consideration of reactivity changes of the fuel assembly may be included, although no allowance for the presence of burnable absorbers should be made unless on the basis of a justification acceptable to the regulatory body, which should include consideration of the reduction of neutron absorption capability with burnup. If burnable absorbers are taken into account, the representative fuel should be assumed to correspond to the highest nuclear reactivity. All fuel should be assumed to be at a burnup and enrichment value that results in maximum nuclear reactivity (i.e. fresh fuel assumption), unless credit for burnup is assumed on the basis of an adequate justification. Such justification should include an appropriate measurement or evaluation that directly or indirectly confirms the calculated values for the content of fissile material or depletion level. For application of burnup credit in long term storage, possible changes in the nuclide composition of the spent fuel with storage time should be taken into account. Assumptions of neutronic decoupling for different storage areas should be substantiated by appropriate calculations.
Subcriticality	6.35.	The infinite multiplication factor⁹ may be used as a conservative estimate of k_eff.
Subcriticality	6.36.	The determination of subcriticality for other kinds of fuel may involve special considerations. The composition of spent fuel might vary over a large range, and it might not be easy to specify appropriate conservative conditions. For example, boiling water reactor fuel with burnable poison might have increased reactivity due to the burning of poison. Also, uranium–thorium mixed oxide fuel or fuel from research reactors might have very specific properties that need to be considered.
Heat removal	6.37.	Spent fuel storage facilities should be designed with heat removal systems that are capable of reliably cooling the stored spent fuel when the fuel is initially received at the facility. The heat removal capability should be such that the temperature of all spent fuel does not exceed the maximum allowable temperature and that the temperature of other safety related components in the facility should also not exceed their maximum allowable temperatures in normal operation, anticipated operational occurrences and accident conditions, including design basis accidents and, as far as practicable, design extension conditions¹⁰, such as: Multiple failures leading to the sustained loss of the forced cooling system; Combinations of failures selected on the basis of probabilistic risk assessments (e.g. combinations of anticipated operational occurrences or postulated accidents with a common cause failure affecting the system designed for mitigating the event of concern).
Heat removal	6.38.	In the design of heat removal systems for a spent fuel storage facility, appropriate provision should be made for maintaining fuel temperatures within acceptable limits during the handling and transfer of spent fuel.
Heat removal	6.39.	The heat removal system should be designed for adequate removal of the heat likely to be generated by the maximum inventory of spent fuel anticipated during operation. In determining the necessary heat removal capability of the facility, the post‑irradiation cooling interval and the burnup of the fuel to be stored should be taken into consideration. Heat removal systems should be designed to include an additional margin of heat removal capability to take account of any processes foreseen to degrade or impair the system over time. In the design of the heat removal system, consideration should also be given to the maximum heat capacity of the facility.
Heat removal	6.40.	In the case of modular facilities such as vaults, the fact that the heat produced from the decay of spent fuel fission products decreases with time can be taken into account in the design. For example, natural cooling might be adequate later in a facility’s lifetime, even if forced cooling is initially necessary. An analysis should be performed to determine how long forced cooling will be necessary, with due consideration given to maintaining operability of the forced cooling system and the potential effects of its failure.
Heat removal	6.41.	The use of redundant and/or diverse heat removal systems may be appropriate, depending on the type of storage system used. The reliability of the heat removal systems should be considered in the design process. The design should include provisions to monitor and ensure the effectiveness of the cooling systems in operational states and accident conditions. In wet storage facilities, monitoring of cooling systems could be done by monitoring the temperature and the level of the water. In dry storage vault facilities, such monitoring could be done by monitoring the temperature and flow rate of the coolant gas. Consideration should be given to the potential for the spent fuel to overheat over an extended period. For such cases, the design of wet storage facilities should include features to enable the use of non‑permanent equipment to provide water for the long term cooling of the spent fuel.
Confinement of radioactive material	6.42.	In the design of spent fuel storage and handling systems, adequate and appropriate measures should be provided for containing radioactive material so as to prevent any uncontrolled release of radionuclides to the environment. The spent fuel cladding should be protected during storage against degradation in operational states and accident conditions and, later, during retrieval of the spent fuel. Confinement should be ensured by at least two independent static barriers. As necessary, and as far as possible, the effectiveness of the spent fuel storage confinement system should be monitored to determine whether corrective action is necessary to maintain safe storage conditions.
Confinement of radioactive material	6.43.	Ventilation and off‑gas systems should be provided where necessary to ensure the collection of airborne radioactive particulate material in operational states and accident conditions. In the design of the air supply system for the facility, consideration should be given to the potential for the presence of corrosive gases such as chlorine or sulphur dioxide in the external environment, which could be detrimental to the integrity of the spent fuel cladding or other safety related components.
Radiation protection	6.44.	The design of the spent fuel storage facility should be such as to avoid high radiation fields on the site and to provide for radiation protection of workers and the public and protection of the environment in accordance with the requirements of national legislation, the requirements established in GSR Part 3 [12] and the recommendations provided in IAEA Safety Standards Series No. NS‑G‑1.13, Radiation Protection Aspects of Design for Nuclear Power Plants [36].
Radiation protection	6.45.	In order to meet these requirements and recommendations in the design of spent fuel handling systems in a storage facility: Appropriate ventilation, including efficient, appropriately qualified and designed air filtration systems and provision for their periodic checking, should, as necessary, be included in the design to maintain the concentrations of airborne radioactive material and the related exposure of workers and the public at acceptable levels. Provision should be made for the monitoring of radioactive effluents. Measures for spent fuel handling should be designed to avoid a buildup of contamination to unacceptable levels and to provide for remedial measures if such a buildup occurs. Handling of spent fuel and casks should be carried out in an environment in which important parameters (e.g. temperature, concentration of impurities, intensity of radiation) are controlled. Areas in which spent fuel and casks are to be handled or stored should be provided with suitable radiation monitoring systems for the protection of workers. The storage facility should not contain any operation room to which access is gained solely through the storage area. Water monitoring and filtration should be provided for wet storage facilities.
Radiation protection	6.46.	Shielding should be provided to meet the recommendations in NS‑G‑1.13 [36]. To meet these recommendations, the following provisions should be included: In determining the source term for analysis for shielding design, consideration should be given to the bounding conditions for enrichment, burnup and cooling times for gamma and neutron radiation, the inventory at the maximum design capacity of the spent fuel storage facility, the effects of axial burnup on gamma and neutron sources, and the activation of non‑fuel hardware. Suitable shielding should be provided for operational states and accident conditions. The design of a wet storage facility should include provisions to prevent unacceptable loss of liquid shielding during accident conditions, such as design features to enable the use of non‑permanent equipment to retain minimum water levels for shielding. In dry storage facilities in which water is used for neutron shielding, alternate neutron shielding should be provided if water could be lost. Penetrations through shielding barriers (e.g. penetrations associated with cooling systems, penetrations provided for loading and unloading) should be designed to avoid localized high gamma and neutron radiation fields from both the penetration and direct irradiation from the fuel. In the analysis for shielding design, equipment for handling spent fuel should be assumed to contain the maximum amount of spent fuel. Handling equipment should be designed to prevent the inadvertent placing or lifting of spent fuel into insufficiently shielded positions. Consideration should be given to the radiological impact of deposits of activation products.
Layout	6.47.	Design aspects associated with the layout of a spent fuel storage facility are set out in the following: Handling and storage areas for spent fuel should be secured against unauthorized access and unauthorized removal of fuel. The area used for storage should not be part of an access route to other operating areas. Transport routes for handling spent fuel on the facility site and within the facility should be arranged to be as direct and as short as practicable, so as to avoid the need for complex or unnecessary moving and handling operations. The need to move heavy objects over stored spent fuel and items important to safety should be minimized by the layout. The layout should be such that all spent fuel handling operations, the storage of spent fuel and the access of authorized personnel are optimized. The layout should be such as to provide for the decontamination of surfaces of spent fuel elements (removal of deposits of radioactive material) and appropriate maintenance and repair of spent fuel handling equipment and storage casks. Sufficient space should be provided to permit inspection of spent fuel and inspection and maintenance of components, including spent fuel handling equipment. The layout should facilitate access to any stored fuel without the need to move or handle other stored fuel. Division of the storage area into sectors should enable different storage configurations and be such as to facilitate access to any stored fuel and to avoid application of the ‘first in last out’ concept. Retrieval of spent fuel and spent fuel packages, as well as the possible need for spent fuel encapsulation or conditioning, should be addressed in the layout of the facility. Sufficient space should be provided to allow for movement of the spent fuel and storage casks and the transfer of these from one item of handling equipment to another. Sufficient space should be provided for the safe handling of shipping and storage casks. This may be achieved by using a separate cask loading and unloading area or by including a dedicated space within the spent fuel storage facility. Sufficient space should be provided for the storage and use of the tools and equipment necessary for the repair and testing of storage components. Space for the receipt of other radioactive parts of fuel assemblies may also be necessary. Appropriate arrangements for confinement of radioactive material and for the safe storage of degraded or failed fuel should be provided. The layout should provide for an easy exit by personnel in an emergency. Penetrations should be designed in such a way as to prevent the ingress of foreign material (e.g. rain, inorganic solutions, organic materials) that could reduce subcriticality margins, impair heat transfer or increase corrosion and degradation of the storage facility in ways that might reduce the effectiveness of the main safety functions or prevent inspection or repair. The floor area on which any transport vehicle with a heavy spent fuel cask might move or be parked should be designed with adequate floor loading margins. Such areas should be clearly marked to avoid overloading a floor area designed to accept a lower floor loading.
Handling	6.48.	Spent fuel handling and transfer equipment and systems include the following: Fuel handling machines; Fuel transfer equipment; Fuel lifting devices; Fuel assembly dismantling devices; Handling devices for all operations associated with the transport of casks or inspection of spent fuel or casks; Provision for the safe handling of degraded or failed fuel or canisters and casks.
Handling	6.49.	Handling equipment should be designed to minimize the probability and consequence of accidents and other incidents, and to minimize the potential for damaging spent fuel, spent fuel assemblies and storage or transport casks. Consideration should be given to the following: Equipment should not have sharp edges or corners that could damage the surfaces of spent fuel assemblies. Equipment should be provided with positive latching mechanisms to prevent accidental unlatching of the equipment. Equipment should be designed to take account of radiation protection aspects and to facilitate maintenance. Speed limitations should be specified for equipment for moving spent fuel. Systems should be so designed that spent fuel cannot be dropped in the event of loss of power. Consideration should be given to the consequences of a single failure and, where appropriate, redundant load paths should be provided. Where it is necessary to ensure that spent fuel assemblies can be readily placed in a safe location, fuel handling equipment should be designed to permit manual operation in an emergency. Equipment should be designed to ensure that the magnitude and direction of any forces that are applied to spent fuel assemblies are within acceptable limits. Equipment should be provided with suitable interlocks or physical limitations to prevent dangerous or incompatible operations, such as to prevent movement in some circumstances (e.g. to avoid incorrect placement of spent fuel or, in the case of wet storage, where the equipment is very close to the pool walls), and also to prevent the lifting of spent fuel assemblies or other components over spent fuel and to heights greater than necessary, the accidental release of loads and the application of incorrect forces. Controls and tools should be ergonomically designed and user friendly. The possibility for tools to be mistaken should be avoided by design. Environmental conditions (e.g. noise, brightness, humidity, temperature) in working areas should provide for optimal conditions of work.
Handling	6.50.	Where operating personnel will need information on the non-visible state of the equipment or components in order to verify the safety of a planned operation, as stated in the safety case, provision should be made in the design for effectively transmitting such information to the operating personnel, through appropriately located indicator systems or by alternative means.
Handling	6.51.	In the design of spent fuel handling equipment, provision should be made for the related use of portable manual tools or portable power operated tools, provided that the planned use of such tools is consistent with the design objectives and that such use does not compromise the safety of the spent fuel handling operations.
Handling	6.52.	To minimize the probability of an accidental drop of any load, equipment for transferring spent fuel to a spent fuel storage facility should be designed to ensure that the equipment is capable of withstanding conditions of normal operation, anticipated operational occurrences and accident conditions. Equipment should be designed, and operational limits and conditions should be established such that, in the event of an accidental drop of a load, the confinement system or the shielding of fuel casks will not be damaged in a manner that could result in unacceptable radiation exposure of workers or the public. In addition, the design and the operational limits and conditions should be such that an accidental drop will neither prevent fuel retrieval nor cause significant damage to the spent fuel or spent fuel storage facility.
Handling	6.53.	Assumptions made that are critical to operational safety should be documented at the design stage to facilitate the subsequent development of operating procedures. Justification should be provided, through detailed analyses using appropriate techniques, in support of these assumptions and conclusions concerning the operational safety of the spent fuel storage facility.
Handling	6.54.	In order to ensure safe operation, spent fuel handling and storage systems should include the following: Measures to limit radioactive releases and radiation exposure of workers and the public in operational states and accident conditions in accordance with the principle of optimization of protection established in SF‑1 [11] and to meet the limits established by the regulatory body, with particular consideration being given to the use of remote techniques in areas of high radiation fields in order to reduce occupational exposure; Measures to prevent anticipated operational occurrences and design basis accidents from developing into severe accidents; Provision for ease of operation and maintenance of essential equipment (in particular, items important to safety); Provision for ready retrieval of spent fuel from storage through equipment and procedures.
Handling	6.55.	In the design and assessment of lifting and handling equipment, consideration should be given to categories of dropped loads such as casks or lids, spent fuel and spent fuel storage racks.
Handling	6.56.	The dropping of spent fuel during transfer from the cask to the storage rack (or vice versa in the case of cask loading for dry storage) could result in impacts that should be avoided, such as: Partial defects in the spent fuel cladding, leading to leaks and resulting in contamination of the pool by fission products; Deformation (e.g. bending) or damage of the spent fuel, which could lead to difficulties in its subsequent handling; An increased potential for a criticality accident if spent fuel with low burnup were to impact alongside a storage basket or other spent fuel in the storage racks; Radiation exposure of workers due to the release of fission products.
Ventilation systems	6.57.	Ventilation systems for the spent fuel storage facility should be designed and operated to maintain a safe and comfortable working environment during normal operation and to limit the potential for release of radioactive material in operational states and accident conditions, including design basis accidents and design extension conditions. In the design, consideration should be given to the potential for pressure buildup in the facility during an accident and the provision of a means to prevent concentration levels of hydrogen gas that could give rise to disruptive explosions.
Ventilation systems	6.58.	Ventilation systems should be designed in such a way as to control the accumulation of flammable or explosive gases (e.g. hydrogen gas formed by radiolysis). Consideration should also be given to the potential for the drawing in of hazardous gases from external sources.
Ventilation systems	6.59.	Ventilation systems should be designed to satisfy the recommendations provided in IAEA Safety Standards Series No. SSG‑64, Protection against Internal Hazards in the Design of Nuclear Power Plants [37]. The operation of ventilation systems should be compatible with requirements for fire protection.
Communications	6.60.	Adequate and diverse means of communication should be included in the design to meet the requirements for operation of the spent fuel storage facility and for emergency preparedness and response.
Instrumentation and control	6.61.	Instrumentation should be provided to detect conditions that could result in a loss of residual heat removal capability and excessive radiation levels. This instrumentation should provide appropriate alarms and indications at a protected location that would result in timely initiation of corrective actions by local operating personnel and operating personnel in main control rooms, and automatic initiation of protective actions when needed. The indicating range and design of the specified instrumentation should allow for monitoring of conditions during accidents, including design basis accidents and design extension conditions considered in the safety case. When practicable, control and protection functions should be designed to be mutually independent and not compromised by any corrective actions. Where independence is not feasible, detailed justification should be provided for the use of shared and interrelated systems. Account should be taken of ergonomic factors in the design of alarms and indications to the operating personnel. Control and monitoring equipment should be calibrated for its intended use.
Fire protection	6.62.	The operation of the fuel handling and storage areas should be carried out in accordance with the fire protection recommendations provided in SSG‑64 [37]. Fire protection measures should be implemented in such a way as to limit risks to personnel and the risk of damage to items important to safety, spent fuel storage areas, spent fuel handling systems and support systems.
Fire protection	6.63.	Fire protection systems of appropriate capacity and capability should be provided.
Fire protection	6.64.	Fire protection measures should include the limitation and control of amounts of combustible materials in fuel handling and storage areas (e.g. combustible packing materials, piping systems carrying combustible materials). The spent fuel storage area should be operated in such a way as to ensure that the use of fire suppression measures cannot cause unintended criticality.
Radioactive waste management	6.65.	The systems of the spent fuel storage facility should be designed and operated so as: To avoid or minimize the potential for generating radioactive waste; To provide safe and adequate means for handling radioactive waste.
Radioactive waste management	6.66.	The methods employed for processing radioactive waste should be compatible with the requirements of the receiving waste facility.
Lighting	6.67.	Provision should be made for adequate and reliable lighting in support of normal operation, anticipated operational occurrences and accident conditions and to facilitate inspection of spent fuel storage areas.
Lighting	6.68.	For wet storage in pools, the pool area should be provided with the necessary lighting equipment, including underwater lighting near work areas and provision for the replacement of underwater lamps.
Lighting	6.69.	Materials used in underwater lighting should be compatible with the environment in which they are used and, in particular, should not undergo unacceptable corrosion or lead to any unacceptable contamination of the pool water.
Monitoring	6.70.	Area monitoring should include measurements of radiation dose rates and airborne radionuclides. In controlled areas, fixed, continuously operating instruments with local alarms and unambiguous readouts should be installed to provide information on radiation dose rates. Such instruments should have characteristics and ranges that are sufficient to cover potential radiation levels, during normal operation, anticipated operational occurrences and accident conditions, including design basis accidents and design extension conditions.
Monitoring	6.71.	Instrumentation for detecting external contamination on workers should be provided at exits from locations where there is a potential for such contamination. Instruments for area monitoring and personnel monitoring should be demonstrated to be fit for purpose and should comply with appropriate manufacturing standards. The possible use of this instrumentation should be considered when developing provisions for the decontamination of equipment, components and personnel.
Monitoring	6.72.	For wet storage facilities, the water level in the spent fuel storage pool should be monitored and provisions to identify the potential for water leakage during both operational states and accident conditions should be provided.
Emergency preparedness	6.73.	Hazards should be identified and potential consequences of an emergency should be assessed to provide a basis for establishing on‑site as well as off‑site emergency arrangements associated with the storage of spent fuel. As such, the hazard assessment should be provided to off‑site authorities to inform their emergency planning, either by the operating organization or the regulatory body. A graded approach to emergency preparedness and response will need to be applied, in accordance with the results of the hazard assessment in line with GSR Part 7 [22] and GS‑G‑2.1 [25].
Emergency preparedness	6.73A.	While the responsibility for on-site emergency preparedness and response remains with the operating organization (see para. 3.28), the responsibility for off‑site emergency arrangements, including the development and implementation of emergency plans and procedures and the provision of emergency services, will be with the relevant off‑site response organizations [22, 25]. On‑site emergency arrangements should include, but are not limited to: Procuring and periodic testing of equipment to mitigate the consequences of accidents; Periodic training for personnel and procedures to deploy the mitigation equipment; Lists of persons and organizations to be alerted in the event of an emergency; Procedures and other arrangements to implement mitigatory actions, including operating procedures in abnormal conditions and in the event of an emergency; Procedures and other arrangements to ensure effective and uninterrupted communication in the event of an emergency; Procedures and other arrangements to ensure the safety of personnel in the event of an emergency; Procedures and other arrangements for the classification of emergencies and for the use of operational criteria in the event of an emergency; Periodic exercises to test emergency arrangements in place, including arrangements for coordination with off‑site response organizations; Periodic review and, as appropriate, updates to the emergency plan and procedures on the basis of lessons identified from exercises, operating experience and relevant changes to assessed hazards; Design and construction of emergency response facilities in accordance with the hazard assessment.
Emergency preparedness	6.74.	On‑site emergency procedures should be well documented, made available to the personnel concerned and kept up to date.
Support systems	6.75.	In addition to the design features of a spent fuel storage facility considered above, a number of other support systems may be necessary to ensure the operation and safety of spent fuel storage facilities (e.g. an emergency power supply). It should be ensured that such support systems are available.
Support systems	6.76.	Where the safety of spent fuel storage is dependent upon the supply of utilities (e.g. systems for compressed air or water), adequate sources should be reliably available.
Support systems		Requirement 18 of GSR Part 5 [1]: Construction and commissioning of the facilities
General	6.77.	Commissioning involves a logical progression of tasks intended to demonstrate the correct functioning of features specifically incorporated into the design to provide for safe storage of spent fuel. In addition, in commissioning, operating procedures are verified and the readiness of staff to operate the spent fuel storage facility is demonstrated. The operating procedures should cover normal operation, anticipated operational occurrences and accident conditions.
General	6.78.	The basis for commissioning should be established at an early stage in the design process as an intrinsic part of the project to facilitate its effective implementation. Commissioning plans should be reviewed and, where appropriate, made subject to approval by the regulatory body. The responsibilities of the various groups typically involved in commissioning should be clearly established. Arrangements should be established to cover: Specification of tests to be carried out (test objectives, safety criteria to be met); Provision and approval of documentation; Responsibilities; Safety during testing; Control of test work; Recording and review of test results; Interaction with the regulatory body; Management of equipment providing temporary commissioning aids and its removal before commencement of operation (and after completion of tests).
General	6.79.	Arrangements for testing should include the following: Regulatory requirements; Progression through the stages of commissioning; Reporting of results and approval for operation; Retention of records.
General	6.80.	For modular storage systems, most of the commissioning will have been completed on the loading of the first storage module. Some of the commissioning processes might become part of regular operation as new modules are brought into service. However, a change in module design may require some of the commissioning steps to be repeated for the new design.
General	6.81.	Some commissioning steps might continue during the operation of a spent fuel storage facility (e.g. commissioning of new spent fuel storage casks or dual purpose casks or commissioning of new equipment necessary for new designs of spent fuel). Commissioning activities during the operation of the facility should be anticipated to the extent possible already during the design stage (e.g. the need for installation of additional heat removal systems).
Commissioning stages	6.82.	Commissioning will usually be completed in several stages: Completion of construction; Equipment testing; Demonstration of performance; Non-active commissioning; Active commissioning.
Commissioning stages	6.83.	In the stage of completion of construction, the spent fuel storage facility should undergo detailed physical inspection to confirm compliance with the detailed design. Factors such as physical dimensions and levels of background radiation should be determined. A systematic check against design drawings and project documentation should be carried out to establish the as‑built status of the facility. (In addition to providing information to facilitate operation of the facility, this check can also be important when considering possible future modifications and ultimate decommissioning of the facility.)
Commissioning stages	6.84.	In the equipment testing stage, the equipment and systems of the spent fuel storage facility should be energized and aspects such as controls, directions of rotation, directions of flow, currents and interlocks should be tested. Activities such as load testing of casks and spent fuel assembly lifting equipment should also be carried out, and the safe control of equipment should be demonstrated in these tests. If necessary, it should also be demonstrated that the physical interaction between items of equipment is limited.
Commissioning stages	6.85.	In the performance demonstration stage, after individual items of equipment have been tested, a range of tests should be performed to demonstrate the safe interaction of all equipment and the overall operational capability and capacity of the spent fuel storage facility. At this stage, the safety and effectiveness of all instructions and procedures should be demonstrated. This should include demonstration of satisfactory training of operating personnel for both normal operation and anticipated operational occurrences. The ability of personnel to conduct maintenance work safely and effectively should also be demonstrated.
Commissioning stages	6.86.	The non‑active commissioning stage should provide a formal demonstration that the facility personnel, equipment and procedures function in the manner intended, especially those identified in the safety case as important to the safety of facility operation. All safety features that can be tested without the presence of spent fuel should be checked before the spent fuel storage facility is put into operation.
Commissioning stages	6.87.	Once non‑active commissioning has been satisfactorily accomplished, the active commissioning stage is commenced with the introduction of radioactive material into the spent fuel storage facility. All tests and any resulting amendments should be completed before the introduction of radioactive material. The introduction of radioactive material effectively marks the start of the operation of the facility and, hence, from this stage the relevant safety requirements for facility operation apply [1, 4, 7]. Active commissioning should involve a range of tests to demonstrate that the design criteria for radiation protection have been met.
Commissioning stages	6.88.	Upon completion of commissioning, a final commissioning report should be prepared. This should detail all testing carried out and should provide evidence of its successful completion. The report should demonstrate to the regulatory body that its requirements have been met and may provide the basis for the subsequent licensing of the spent fuel storage facility for full operation. In addition, any changes to the facility or to procedures implemented during commissioning should be documented in an appropriate way in the final commissioning report.
Commissioning stages		Requirement 9 of GSR Part 5 [1]: Characterization and classification of radioactive waste
General	6.89.	Spent fuel storage facilities are required to be operated in accordance with written procedures prepared by the operating organization. These documents and their updates should be prepared in cooperation with the organizations responsible for the design of the spent fuel storage facility. However, the operating organization is responsible for ensuring that the procedures are prepared, reviewed, approved and issued appropriately. These procedures should take into account human factors associated with handling operations and should, as a minimum, be such as to ensure compliance with the operational limits and conditions for the spent fuel storage facility and, more generally, with the safety assessment.
General	6.90.	Instructions and procedures should be prepared for normal operation of the spent fuel storage facility, anticipated operational occurrences and accident conditions, including design basis accidents and design extension conditions. Instructions and procedures should be prepared so that the designated responsible person can readily perform each action in the proper sequence. Responsibilities for approval of any deviations from operating procedures that may be necessary for operational reasons should be clearly specified.
General	6.91.	Adequate arrangements should be made for the review and approval of operating procedures, the systematic evaluation of operating experience, including that of other facilities, and the taking of corrective actions in a timely and appropriate manner to prevent and counteract developments adverse to safety. Provision should be made for controlling the distribution of operating procedures, in order to guarantee that operating personnel have access to only the latest approved edition.
General	6.92.	The maintenance and modification of any item of equipment, process or document of the spent fuel storage facility should be subject to specified procedures. These procedures should be subject to authorization before they are implemented. The procedures should describe the categorization of the modification in accordance with its safety significance. Depending on the safety categorization, each modification will be subject to varying levels of review and approval by management of the facility and the regulatory body.
General	6.93.	The maintenance or modification of any item of equipment should be appropriately recorded and documented together with its commissioning test results. The documents should be revised immediately after completion of the maintenance or modification.
Operational aspects	6.94.	The operating organization should ensure that operating procedures relating to the maintaining of subcriticality are subjected to rigorous review and compared with the safety requirements of the design. This might include confirmatory analysis and review by the regulatory body. Some of the factors that should be considered in this review include: The types of spent fuel to be stored; Spent fuel geometries necessary to ensure subcriticality; Spent fuel container types (if used); Handling operations for the spent fuel; The potential for abnormal operation; Spent fuel parameters (e.g. initial enrichment, final enrichment, burnup); Dependence of subcriticality on neutron absorbers.
Operational aspects	6.95.	Cladding failure can result in the release of isotopes such as ⁸⁵Kr, ¹³⁴Cs and ¹³⁷Cs, which are characteristic fission products detected following cladding failures in spent fuel that has been cooled for long periods. Cladding failure might be more probable when the spent fuel and spent fuel cladding are subjected to high temperatures, and when chemical conditions in the medium surrounding the spent fuel promote cladding corrosion. The operating organization should ensure that adequate monitoring of environmental conditions within the facility (e.g. composition of the pool water and atmosphere in the storage area and moisture or water on spent fuel cladding) is undertaken to prevent and provide notice of such undesirable conditions. Procedures should be provided for detecting and dealing with degraded and failed fuel.
Operational aspects	6.96.	In addition, the operating organization should ensure that procedures exist for the receipt, handling and storage of spent fuel with failed cladding, and that these procedures identify the safety measures to be taken for managing these situations or should ensure that such fuel is not accepted at the spent fuel storage facility. In cases where such fuel is accepted, in addition to confinement considerations there might be implications for criticality, which should be fully assessed. Where appropriate, the receipt, handling and storage of such fuel should be made subject to specific procedures.
Operational aspects	6.97.	Operating procedures should be developed for confinement systems in the spent fuel storage facility (e.g. closure seals on storage casks and canisters, and ventilation and filtration systems) to provide for their monitoring. The monitoring should be such that the operating organization will be able to determine when corrective actions are necessary to maintain safe storage conditions.
Operational aspects	6.98.	There are various safety related events that should be taken into account in the development of normal and emergency operating procedures and accident management programmes. Although many of these events would be addressed either as anticipated operational occurrences or as design basis accidents, some of these events, or some combinations of events, could also lead to severe accidents, which might be considered within design extension conditions while others might go beyond these. While the probability of such events, or combinations of events, occurring is very low, operating procedures and accident management programmes should be prepared by the operating organization. Events to be considered in the preparation of operating procedures and accident management programmes include the following: Crane failure with a water filled and loaded cask, suspended outside the pool; Loss of safety related facility process systems such as supplies of electricity, process water, compressed air and ventilation; Explosions due to the buildup of radiolytic gases; Fires leading to the damage of items important to safety (to reduce the risk of fire, the amount of combustible material or waste should be controlled, as should be the amount of other flammable materials, see para. 6.64); Extreme weather conditions, which could alter operating characteristics or impair pool or cask heat removal systems; Other natural events such as earthquakes or extreme meteorological events; External human induced events (e.g. airplane crashes)¹¹; Failure of access control systems leading to inadvertent access that could compromise safety¹².
Operational aspects	6.99.	In addition to providing operating procedures for normal operation and emergency operating procedures as described above, the operating organization should also develop an on‑site emergency plan in accordance with the requirements established in GSR Part 7 [22] (see para. 3.28 of this Safety Guide).
Operational aspects	6.100.	Operating experience and events at the facility and reported by operating organizations of similar facilities should be collected, screened and analysed in a systematic way. Conclusions should be drawn and implemented by means of an appropriate feedback procedure. Any new standards, regulations or regulatory guidance should also be reviewed to check their applicability for safety at the facility.
Operational aspects	6.101.	The integrity of stored spent fuel should be monitored during the operation of a spent fuel storage facility. When spent fuel is stored in sealed casks, the means for accounting for and control of nuclear material or for verifying the related sealing operations will be available. Such means should not impair the integrity of the spent fuel.
Operational aspects	6.102.	Operational limits and conditions for a spent fuel storage facility should be developed on the basis of the following: Design specifications and operating parameters and the results of commissioning tests; The sensitivity of items important to safety and the consequences of events following the failure of items, the occurrence of specific events or variations in operating parameters; The accuracy and calibration of instrumentation equipment for measuring safety related operating parameters; Consideration of the technical specifications for each item important to safety and the need to ensure that such items continue to function in the event of any specified fault occurring or recurring; The need for items important to safety to be available to ensure safety in operational states including maintenance; Specification of the equipment that should be available to enable a full and proper response to postulated initiating events or design basis accidents; The minimum staffing levels that need to be available to operate the spent fuel storage facility safely.
Operational aspects	6.103.	Operational limits and conditions form an important part of the basis on which operation is authorized and as such should be incorporated into the technical and administrative arrangements that are binding on the operating organization and operating personnel. Operational limits and conditions for spent fuel storage facilities, which result from the need to meet legal and regulatory requirements, should be developed by the operating organization and should be subject to approval by the regulatory body as part of the licence conditions. The operating organization might set an administrative margin as an operational target to remain within the approved limits and conditions.
Operational aspects	6.104.	The aim of operational limits and conditions should be to manage and control the hazards associated with the facility. Operational limits and conditions should be directed towards: Preventing situations that might lead to the unplanned exposure of workers and the public to radiation; Mitigating the consequences of any such events, if they were to occur.
Operational aspects	6.105.	Personnel directly responsible for the operation of the spent fuel storage facility should be thoroughly familiar with the facility’s operating procedures and the operational limits and conditions to ensure compliance with their provisions. Systems and procedures should be developed in accordance with the approved management system and operating personnel should be able to demonstrate compliance with the operational limits and conditions.
Operational aspects	6.106.	Operational limits and conditions should be kept under review and may also have to be revised as necessary in accordance with the national regulatory framework for the following reasons: In the light of operating experience; Following modifications made to the spent fuel storage facility and the type of spent fuel; As part of the process of periodically reviewing the safety case (including as part of periodic safety review) for the spent fuel storage facility; If there are changes in legal or regulatory conditions.
Maintenance, inspection and testing	6.107.	A management system (see also Section 4) covering operation and maintenance, and including approved procedures, should be established for controlling the following: Maintenance and inspection of the lifting attachments on the casks and of the lifting apparatus (e.g. slings, beams, chains, hooks); Maintenance of cranes and spent fuel grabs at the facility; Periodic load testing of cranes and other attachments; Maintenance, inspection and testing of other safety related equipment.
Maintenance, inspection and testing	6.108.	Operation of a spent fuel storage facility should include an appropriate programme of maintenance, inspection and testing of items important to safety (i.e. structures, systems and components). Safe access should be provided to all structures, systems and components and areas requiring periodic maintenance, inspection and testing. Such access should be adequate for the safe operation of all necessary tools and equipment and for the installation of spare parts.
Maintenance, inspection and testing	6.109.	Before the operation of any spent fuel storage facility commences, the operating organization should prepare a programme for maintenance, inspection and testing. In the programme, starting dates for all inspections should be specified and these should be re‑evaluated in the light of results from commissioning tests. The safety case for the spent fuel storage facility will form a basis for preparation of the programme in terms of the items (i.e. structures, systems and components) that should be included and the periodicity of planned activities for each item.
Maintenance, inspection and testing	6.110.	Provision should be made for maintenance of hot cell components, if a hot cell exists. This maintenance work can be done either in the cell or externally, whatever the preferred option might be.
Maintenance, inspection and testing	6.111.	The programme of periodic maintenance, inspection and testing should be subject to periodic review, with account taken of operating experience. All such activities should be covered in an integrated manner by the management system, with account taken of manufacturers’ recommendations.
Maintenance, inspection and testing	6.112.	The standard and frequency of activities for periodic maintenance, inspection and tests should be such that the level of reliability and effectiveness is ensured and remains in accordance with the design assumptions and intent so that a consistently high level of safety is maintained throughout the lifetime of the spent fuel storage facility.
Maintenance, inspection and testing	6.113.	Equally, the reliability and effectiveness of any component should not be significantly affected by the frequency of testing, which might result in premature wear and failure or induced maintenance errors, or which could cause unavailability to an unacceptable degree if the component is inoperative during maintenance and testing.
Maintenance, inspection and testing	6.114.	If maintenance, inspection or testing of the spent fuel storage facility can be carried out only while certain equipment is in a shutdown state, the maintenance schedule should be drawn up accordingly.
Maintenance, inspection and testing	6.115.	The maintenance, inspection and testing programme should take into account the structures, systems and components that are affected by the operational limits and conditions, as well as any regulatory requirements. Examples of structures, systems and components that might be included in a maintenance, inspection and testing programme are provided in Table 2.
Maintenance, inspection and testing	6.116.	Suitably qualified and experienced operating personnel should be deployed in the approval and implementation of the maintenance, inspection and testing programme and in the approval of associated working procedures and acceptance criteria.
Operational radiation protection	6.117.	An operational radiation protection programme should be put in place that ensures that areas of the facility are designated according to the radiation levels and that access control is in place in accordance with the level of designation. The operational radiation protection programme should cover the monitoring of radiation levels in the facility and should include provision to ensure that personnel working in the facility are provided with appropriate dosimetry. A programme of work planning should also be put in place to ensure that radiation exposures are kept as low as reasonably achievable.
Characterization and acceptance of spent nuclear fuel		Requirement 12 of GSR Part 5 [1]: Radioactive waste acceptance criteria
Characterization and acceptance of spent nuclear fuel	6.118.	Acceptance criteria should be developed for the spent fuel storage facility and the spent fuel, with account taken of all relevant operational limits and conditions and future demands for reprocessing or disposal, including retrieval of the spent fuel. Before spent fuel is transferred to a storage facility, acceptance should be given by the operating organization of the facility and the regulatory body. Contingency plans should be developed and made available to cover how to deal safely with spent fuel that does not comply with acceptance criteria.
Characterization and acceptance of spent nuclear fuel	6.119.	The operating organization of a spent fuel storage facility should be given detailed information concerning the characteristics of the spent fuel received for storage. This information should be supplied by the nuclear facility that generated the spent fuel (i.e. nuclear power plant or research reactor). The minimum information that should be provided is the following: Design of the fuel, including scale drawings; Construction materials, the radionuclide inventory, including the initial masses of the fissile content, the burnup and the cooling time of the fuel; Fuel identification numbers (e.g. serial numbers on fuel assemblies); Fuel history (e.g. burnup, reactor power rating during irradiation, decay heat, dates of loading and discharge from the reactor); Details of conditions that could affect fuel handling or storage (e.g. damage to fuel cladding or structural damage); Confirmation that the fuel can be correctly handled upon receipt at the spent fuel storage facility; Specific instructions for storage (e.g. for degraded or failed fuel); Surface contamination level and dose rate for the fuel assemblies.
Characterization and acceptance of spent nuclear fuel	6.120.	Upon receipt, spent fuel casks should be checked to determine gamma and neutron radiation levels, leakage and surface contamination and to ensure that the casks are consistent with the accompanying documentation. Characterization of the spent fuel, for example by means of process control and process monitoring, should be applied as part of the management system for the facility.
Characterization and acceptance of spent nuclear fuel	6.121.	In addition, information concerning the fuel transport cask should also be transmitted by the consignor of the spent fuel to the operating organization of the spent fuel storage facility. This information should include the following: Type of cask and appropriate information on its design, and the arrangement of fuel and internal components inside the cask cavity; Radiological survey data of the cask before shipment; Cask identification (e.g. serial number) and certification of compliance with current transport regulations [19]; Requirements and procedures for cask handling and sealing; Results of the most recent inspection of the cask.
Characterization and acceptance of spent nuclear fuel	6.122.	In cask handling, consideration should be given to carrying out the following operations to ensure safety: Before a cask is loaded with spent fuel: decontamination, as required. In loading and unloading of a cask, under both wet and dry conditions: sampling of the internal gas before the closure lid is removed and examination of the spent fuel, as appropriate. After a cask has been emptied: decontamination, as required, and routine cask maintenance and recertification operations.
Characterization and acceptance of spent nuclear fuel	6.123.	For facilities receiving spent fuel from a number of sites, the operating organization of the spent fuel storage facility should ensure that each consignor provides data on the characteristics of the spent fuel in a clearly understandable form that allows the operating organization to demonstrate that subcritical conditions will be maintained in the handling and storage of the spent fuel. The operating organization should also ensure that the data provided are supported by an approved management system and have been verified, as appropriate.
Characterization and acceptance of spent nuclear fuel	6.124.	Loss of confinement has the potential for both exposing workers to radiation and releasing radioactive material to the environment. Mechanisms by which loss of confinement might occur should be understood by the operating organization and its personnel and should be addressed, as appropriate, in operating procedures.
Fuel integrity	6.125.	The integrity of spent fuel might become degraded and lead to a release of radioactive material to the storage facility environment. There are a number of causes for the degradation of fuel, including: Manufacturing defects, such as defects due to incomplete welds or leaking end plugs; Embrittlement of the cladding material due to interaction with hydrogen or to high irradiation; General corrosion of the cladding as a result of improper chemical composition of the cooling water; Mechanical damage, for example as a consequence of stress corrosion or handling accidents; Unrevealed failures that arose during irradiation in the reactor; Loss of cooling or overheating in the reactor core resulting in damage to the fuel.
Fuel integrity	6.126.	Usually, spent fuel with decreased integrity should be canned to maintain the quality of the storage environment and/or to satisfy licensing requirements. Sealable casks or containers of approved design should be made readily available for the canning of leaking or damaged fuel assemblies.
Fuel integrity	6.127.	Spent fuel assemblies that have become damaged as a result of mechanical events should be kept separate from intact fuel, and appropriate monitoring should be provided to detect any failure of the outer confinement. Consideration should be given to technical contingency arrangements with a high degree of reliability for dealing with spent fuel that is not retrievable by normal means or that cannot be transported easily.
Fuel integrity	6.128.	For storage of spent fuel that has been characterized as degraded or failed, consideration should be given in the design to the condition of the fuel. This might include additional engineered methods for the safe handling of damaged fuel during loading and unloading (e.g. instrument tube tie rods for assemblies where stress corrosion cracking of the top nozzle is of concern), the canning of damaged fuel assemblies to maintain spent fuel configuration and to ensure criticality control, and additional measures to ensure the robustness of confinement since, the primary physical barrier of the confinement system for degraded fuel (i.e. the spent fuel cladding) cannot be relied upon for control of the spent fuel material. Stored degraded spent fuel should be monitored, and to carry out monitoring appropriately, the following should be ensured: Appropriate design of the storage in order to facilitate monitoring; Monitoring of the efficiency of the confinement as close as possible to each physical confinement barrier; Periodic checking of the state of the stored spent fuel (e.g. by sampling, by destructive testing, by placing corrosion test pieces in the storage location, by using reference objects).
Record of documents	6.129.	Operational data of a spent fuel storage facility should be collected and maintained in accordance with the recommendations relating to the management system provided in Section 4.
Record of documents	6.130.	Records of maintenance, inspection and testing should be retained, in order to provide a basis on which to review and justify the programme of maintenance, inspection and testing, and should be made subject to periodic examination to establish whether structures, systems and components have the required reliability.
Record of documents	6.131.	Since the storage time could span more than one human generation, transfer of information from one generation to the next is important. Therefore, accurate records of all relevant information should be maintained. This should include updated information on the spent fuel storage facility itself and on the stored spent fuel, and also supporting data such as monitoring results and records of unplanned events.
Record of documents	6.132.	These records should be duplicated and stored in separate locations. It should be ensured that the information is stored on media that remain accessible during and after the envisaged storage period.
Retrieval of spent fuel	6.133.	The storage facility should be operated in such a way as to allow retrieval of spent fuel or spent fuel packages at the end of the anticipated storage period and at the end of the lifetime of the storage facility.
Retrieval of spent fuel	6.134.	If spent fuel or a spent fuel package cannot be retrieved from storage with normal operating procedures, special operating procedures should be developed to ensure safe retrieval of spent fuel or the spent fuel package.
Retrieval of spent fuel	6.135.	A spent fuel storage facility should be considered to be an operating facility until all the spent fuel or spent fuel packages have been removed.
Transport after storage	6.136.	After storage, and before subsequent transport, the integrity of the spent fuel and the storage and/or transport casks and the associated documentation should be examined. The following issues should be addressed: Ownership and responsibility for the safe retention of records; The inspection and surveillance regime applied; Control of the storage environment; Nuclear safety issues, such as any degradation of the spent fuel itself, of the spent fuel support structure and of the neutron shielding materials.
Transport after storage	6.137.	The safety functions of the storage and/or transport casks should be assessed periodically to demonstrate compliance with current safety standards and the approval requirements and conditions of the transport licence [19]. Possible degradation of casks should be assessed and consideration should be given to the following: Spent fuel and fuel support structure; The confinement system: seals and restraining systems such as lid bolts; Packaging components: corrosion effects and radiation effects; Impact limiters: compatibility of the attachment and performance; Shielding materials: changes in density and composition; Design features incorporated to ensure subcriticality; Conventional safety issues, by means of periodic inspection of handling equipment.
Storage beyond the original design lifetime	6.138.	If storage of spent fuel is envisaged beyond the original design lifetime of the facility, the nuclear reactivity of the fuel should be reassessed and taken into account in the decision making, as necessary. In this case, an appropriately wide safety margin or additional safety provisions should be applied.
Storage beyond the original design lifetime	6.139.	It is essential that the operating organization develop expertise to manage difficulties that might arise from the effects of storage beyond the original design lifetime.
Storage beyond the original design lifetime	6.140.	Paragraph 3.29 of SF‑1 [11] states that “Radioactive waste must be managed in such a way as to avoid imposing an undue burden on future generations”. What constitutes an ‘undue burden’ will depend to a large extent on national circumstances. Aspects to be taken into account, particularly if long term storage of spent fuel is anticipated to span many generations, are the following: Providing adequate financial resources to ensure safe management of the spent fuel over this storage period; Maintaining of regulatory control; Transferring and maintaining knowledge and technical capability; Continuing education of specialists in spent fuel management, even if electricity generation by nuclear power ceases to be part of the national energy strategy.
Storage beyond the original design lifetime	6.141.	Safe operation of a spent fuel storage facility should be ensured for its entire lifetime. This is generally longer than the average lifetime of a commercial company. Consequently, in the event that the operating organization ceases to exist, for example after several decades, transfer of ownership of the spent fuel and the spent fuel storage facility to a government institute might be considered.
Storage beyond the original design lifetime	6.142.	For storage of spent fuel, a safety assessment should be carried out and the safety case developed prior to licensing of the facility. For long term storage, a reassessment of the safety case may become necessary, for example in the event of degradation of the facility or any of its components or structures important for the confinement of the fuel. Special attention should be paid to lining degradation for wet storage. The regulatory body should take such failure scenarios into account when determining the duration of the operating licence for the spent fuel storage facility.
Storage beyond the original design lifetime	6.143.	A monitoring programme should be established in order to be able to detect any deficiencies at an early stage. This monitoring programme should specify the parameters to be monitored, the frequency of monitoring, reference levels for actions, as well as the specific actions to be taken.
Storage beyond the original design lifetime	6.144.	Prolonged irradiation of cladding material, gaskets or other materials relevant to ensuring the confinement of the spent fuel might result in degradation of safety functions. An ageing management programme should be established to deal with ageing related degradation. The programme should specify the monitoring necessary for early detection of any deficiency.
Storage beyond the original design lifetime	6.145.	A mechanism for incorporating changes based on new findings from research and development, especially findings relating to ageing and degradation of materials due to storage beyond the original design lifetime, should be established.
Storage beyond the original design lifetime	6.146.	The longer the envisaged storage period, the greater the uncertainties in the assumptions made about safety parameters. In order to provide the operational or regulatory decisions with a scientific basis, research and development projects should be undertaken that are aimed at reducing these uncertainties, if they are of specific importance. For example, accelerated irradiation experiments on materials used in the spent fuel storage or long time sealing tests with intentionally aggressive media could provide useful information on the sensitivity of storage and sealing materials to ageing effects.
Storage beyond the original design lifetime		Requirement 20 of GSR Part 5 [1]: Shutdown and decommissioning of facilities
Storage beyond the original design lifetime	6.147.	Decommissioning of nuclear facilities comprises the following: Preparation and approval of the decommissioning plan; The actual conduct of decommissioning; The management of waste resulting from decommissioning activities; Release of the site for unrestricted or restricted use.
Storage beyond the original design lifetime	6.148.	An initial version of the decommissioning plan should be prepared during the design of the spent fuel storage facility in accordance with requirements and recommendations on decommissioning [20, 24].
Storage beyond the original design lifetime	6.149.	During the operation of the spent fuel storage facility, the initial decommissioning plan should be periodically reviewed and updated and should be made more comprehensive with respect to: Technological developments in decommissioning; Possible human induced accidents and other incidents and natural events; Modifications to systems and structures affecting the decommissioning plan; Amendments to regulations and changes in government policy; Cost estimates and financial provisions.
Storage beyond the original design lifetime	6.150.	A comprehensive decommissioning strategy should be developed for sites that also have other facilities to ensure that interdependences are taken into account in the planning for individual facilities [20].
Storage beyond the original design lifetime	6.151.	A final decommissioning plan is required to be submitted to the regulatory body for approval within a period defined by the regulatory body [20].
Storage beyond the original design lifetime	6.152.	Even when the bulk of the residual process material has been removed, a significant amount of contaminated material might remain. The expeditious removal of this material should be considered, as it would reduce the need for monitoring and surveillance. Other activities associated with decommissioning may be conducted concurrently with the removal of this material, but the potential for adverse interaction between concurrent activities should be identified and assessed.
Storage beyond the original design lifetime	6.153.	Dismantling and decontamination techniques are required to be chosen such that generation of waste and airborne contamination are minimized and protection of workers and the public is optimized [20].
Storage beyond the original design lifetime	6.154.	Before a site is released, for example for unrestricted use, it should be monitored and, if necessary, cleaned up [38]. A final survey should be performed to demonstrate that the end point criteria, as established by the regulatory body, have been met.
Storage beyond the original design lifetime	I.1.	In addition to the general safety considerations for the design and operation of spent fuel storage facilities set out in Section 6, there are specific safety considerations for the design and operation of wet and dry storage facilities. These include unique characteristics, specific to wet or dry storage facilities, that maintain design parameters within acceptable limits and that satisfy regulatory requirements.
Subcriticality	I.2.	For facilities for which the safety assessment takes into consideration and makes allowance for the boiling of pool water during abnormal operating conditions, specific allowances should be provided in the design evaluations for the change in water moderator density in such conditions. For water storage pools, subcriticality should be demonstrated for all credible water densities, including events for which boiling of pool water cannot be excluded in the safety assessment.
Subcriticality	I.3.	Criticality safety of pool storage should not rely on the use of soluble neutron poison. If this is not possible or if the operating organization chooses to use a soluble neutron poison such as borated water for criticality control, the design of the facility should include engineering features to preclude an increase in the reactivity of stored fuel caused by inadvertent dilution of the pool water by the addition of non-borated water.
Heat removal	I.4.	Heat removal systems for wet storage facilities should be designed to ensure the safe operation of the facility. The primary objective of heat removal systems should be to ensure that no temperature limit, as set to protect structures, systems, components and the fuel from damage, will be exceeded in operational states and accident conditions.
Confinement of radioactive material	I.5.	Wet pool storage facilities should be designed to include features that prevent or limit the release of radioactive material to the environment. Such features could include mechanisms to maintain subatmospheric pressures inside the storage building, to provide for filtration of potential venting pathways and to prevent ingress and egress of pool water, and can be used to minimize the number, size and location of building penetrations.
Radiation protection	I.6.	Where pool water is used to provide radiation shielding for the protection of workers and the public, the water level should be maintained so as to provide the required degree of shielding. For that reason, the design of a wet storage facility should include provision for an adequate and appropriately accessible supply of water, from redundant and diverse sources and of a quality acceptable for use in the facility.
Radiation protection	I.7.	Water storage pools should not be designed with penetrations below the minimum water level required for adequate shielding and cooling of stored spent fuel.
Radiation protection	I.8.	The design should not allow the permanent installation of piping or other equipment that could inadvertently lower (e.g. by acting as a siphon) the pool water level below the minimum required level.
Radiation protection	I.9.	The design of wet storage facilities should include provisions for the effective control of radioactive material released into the pool water and for the capability to purify the pool water. The controlled removal of dissolved and suspended radioactive material might be necessary to limit radiation fields at the surface of the pool. Permanent or temporary equipment should be provided for the periodic, or as necessary, cleaning and removal of radioactive deposits and sludges from pool liner surfaces.
Radiation protection	I.10.	The system for providing make-up water to the pool should be designed to provide water at a rate exceeding the maximum rate of water removal possible as a consequence of losses during operation, including removal of water via the pool water removal system. Conversely, the pool water removal system should have a capacity less than that of the pool water make-up system. Furthermore, mixing spent fuels in the same zone with different limits or a different control mode for criticality should be avoided.
Radiation protection	I.11.	Where water pools are to be connected by sluice ways, the design of the sluice pathways should afford confinement of water and detection, collection and removal of leakages. Sluice gates should be designed to withstand anticipated water pressures, including those resulting from accident conditions and the effects of internal hazards and external hazards.
Radiation protection	I.12.	Indications and alarms should be provided to alert facility personnel of any unintended decrease in water level and when the minimum water level is reached. Water level monitoring provisions and the pool water make‑up system should be assessed for their performance in accident conditions including design extension conditions.
Structure and layout	I.13.	The storage pool and other components important to the retention of cooling water should be designed to withstand conditions in both operational states and accident conditions, including impacts from collisions or dropped loads, without significant leakage of water. Furthermore, the storage pool should be designed to provide for the detection of leakages and the implementation of appropriate repairs or remedial actions, as necessary. The means for sampling groundwater at the facility should be provided (e.g. boreholes located around the facility).
Structure and layout	I.14.	When credit is given for burnup in the criticality safety analysis, the possibility of fuel assemblies being misplaced should be minimized by means of appropriate interlocks and administrative processes. For these cases, the fuel handling equipment should be appropriately designed.
Structure and layout	I.15.	If stacking is proposed for a wet storage facility, the mechanical stability of the spent fuel and any fuel rack or basket should be designed to withstand, without unacceptable structural deformation, the mass of a full stack. Static, impact and seismic loads should also be considered in the design of spent fuel and fuel racks or baskets.
Structure and layout	I.16.	The facility should be designed in such a way as to prevent overfilling of the storage pool. The civil structures supporting the pool should be designed for loads associated with a pool completely filled with spent fuel assemblies, including inserts (e.g. control rods, burnable poison absorbers, thimble plugs).
Materials	I.17.	The materials of the following facility systems should be compatible with the pool water and each other, or should be effectively protected against undue degradation: The spent fuel confinement structures, systems and components; Storage racks or casks; Cooling water structures, systems and components; Pool water make-up structures, systems and components; Handling systems.
Materials	I.18.	The chemical composition of the pool water should be consistent with the protection of the spent fuel cladding, pool structure and handling equipment. The clarity of pool water necessary for pool operation should be maintained.
Handling	I.19.	The design of handling systems and equipment should preclude the need for lubricants or other fluids or substances that could degrade the quality or otherwise affect the purity of the pool water. If lubricants are necessary, design measures should be provided to prevent their leakage and escape into the pool water. Substances should be used that are fully compatible with the spent fuel, the equipment and the storage structures (e.g. water may be used).
Handling	I.20.	Hollow handling tools intended for use under water should be designed so that they fill with water upon submergence (to maintain the water shielding effect) and drain upon removal.
Handling	I.21.	Fuel should be handled by equipment that minimizes the potential for a drop or other handling accident. Over‑raising of spent fuel or other components should be prevented by design features. Fuel damage should be prevented by incorporation of dedicated interlocks to inhibit lateral motion during hoist operations and to inhibit hoist motion in the event that hoist overload is detected. Design features to prevent dropped fuel should include the use of single‑failure‑proof handling systems and positive locking mechanisms on the grapples or hooks used for the fuel assembly.
Handling	I.22.	There are several pool management features that contribute to the safe operation of wet storage facilities. These include operations that maintain design parameters and minimize corrosion of pool structures, systems and components, and promote radiation protection, such as those shown in Table II–1 of Annex II. The integrity of the spent fuel and the geometry necessary to maintain subcriticality and for heat removal and its related confinement barriers should be maintained throughout the lifetime of the facility and should be verified using appropriate methods with a high degree of reliability. Operator errors should be avoided by application of the ‘four eyes principle’ or by the use of checklists.
Subcriticality	I.23.	Where soluble boron is used for criticality control, operational controls should be implemented to maintain water conditions in accordance with specified values of temperature, pH, redox, activity and other applicable chemical and physical characteristics so as to prevent boron dilution.
Radiation protection	I.24.	Operational controls should include proper maintenance of underwater lighting and water clarity, which are important for radiation protection of workers performing duties in and around the pool. The ability to perform activities that rely upon visual examination and/or inspection without need for repetition and in minimal time will result in reductions in the exposure of workers.
Heat removal	I.25.	The possible effects of very low or very high temperatures on the heat removal (cooling) systems should be taken into account in the design of the facility. Issues relating to possible damage of heat removal systems should also be considered in the operational limits and in the development of administrative procedures.
Heat removal	I.26.	Operating procedures should be such that the pool heat removal system is monitored to ensure that operating conditions remain within the design specifications, and to ensure functioning of this system. Impairment or damage to pool heat removal system should be responded to in a timely manner so as to return the system to the intended operating conditions. Furthermore, operating procedures should be such that the time when this system is unavailable due to routine maintenance and/or repair is minimized.
Heat removal	I.27.	Heat transfer considerations might increase in importance if spent fuel is placed in high density storage.
Confinement	I.28.	Operational controls should be implemented to avoid a decrease in the pool water level. A decrease in the pool water level could result, inter alia, in: Increased radiation fields and doses to operating personnel; Impaired fuel cooling if the reduction in water level interrupts or reduces water flow to the heat exchangers of the pool cooling system; Increased water temperature and, consequently, increased release of radioactive material into the water owing to corrosion of spent fuel and spent fuel cladding.
Confinement	I.29.	For wet storage facilities below ground level, operational controls should be implemented to avoid, minimize and manage the potential for in-leakage of water which might result in: Dilution of boron in a moderated pool environment and the potential for a reduction in the margin to criticality where soluble boron is used for criticality control; Corrosion and other degradation effects of materials important to safety.
Confinement	I.30.	The operating organization should undertake suitable routine monitoring of the parameters necessary to enable remedial action to be taken on a timely basis. Alarms should be put in place to alert facility personnel of any unintended decrease in water level and of when the minimum water level is reached. Samples of groundwater from boreholes located around the facility should be periodically collected and activity levels should be monitored.
Shielding	I.31.	Operational controls that avoid and minimize the potential for a loss of shielding during facility activities should be implemented. Loss of shielding can result in high radiation exposure. Operational controls should address and set limits to preclude: The hoisting of spent fuel higher than design limits during handling operations in the storage pool; Inadequate depth of pool water; Improper use of pool tools (e.g. empty rather than flooded).
Dropping of loads	I.32.	Operational controls should be implemented to ensure that events, such as a cask drop, do not result in undue challenges to the storage facility safety systems. Areas of prime concern in this regard include, inter alia: The zones between the entrance airlock to the cask handling area and the cask preparation area and the unloading area at the pool; The unloading area at the pool. Damage of the spent fuel element or assembly and resulting contamination of the pool; Damage of the pool structure and possible leakage of water; A criticality accident if several spent fuel assemblies are displaced from the rack, and if there is deformation of the spent fuel array or unacceptably close proximity of spent fuel assemblies or arrays in adjacent racks; A release of gaseous fission products.
Dropping of loads	I.33.	Operational controls and engineered safety features should be implemented to preclude the drop of a spent fuel element or assembly onto a pool storage rack or onto the pool bottom during transfer.
Subcriticality	I.34.	Fuel baskets and containers for spent fuel storage should be designed in such a way as to ensure that the spent fuel will remain in a configuration that has been determined to be subcritical during loading, transfer, storage and retrieval.
Subcriticality	I.35.	Dry storage facilities should be designed either to exclude the possibility of ingress of water or other moderating medium or in such a way that consequences likely to result from the redistribution or the introduction of a moderator as a consequence of an internal or external event can be accommodated.
Heat removal	I.36.	The storage facility should be constructed in a location for which there has been due consideration of climate change and associated potential increase in ambient temperatures and/or the level of naturally occurring bodies of water adjacent to the facility, and should be maintained in a manner that permits adequate heat dissipation. Design features should include provision to maintain cooling during adverse weather conditions, including high winds that might affect the performance of natural circulation design elements of a dry storage cask and the forced circulation and ventilation systems of a storage facility. Damage to the storage facility might occur in extreme cold weather conditions and extremely high or low rates of dissipation of decay heat. Damage might also result from high rates of temperature change that exceed the design limits. Such issues relating to heat removal should be considered in the specification of operational limits and in the development of administrative procedures. Sandstorms, volcanic fly ash re‑settled by the wind and landslides can all hinder the cooling of dry storage systems, for instance by stopping the airflow through the system. Sand or volcanic fly ash can move inside the facility and accumulate there. Furthermore, some materials, such as wet volcanic fly ash or mud from a landslide, can become hard and rocky after they dry out. All these scenarios can hinder the decay heat removal for a time period that depends on the features of the deposited or consolidated material.
Heat removal	I.37.	To the maximum extent practicable, cooling systems for dry storage should be passive and should need minimal maintenance. Maximization of the passive design features for heat removal will minimize the need for monitoring and operational considerations. Passive systems rely on natural convection, conduction and radiant heat transfer. If forced circulation of coolants is used, it should be demonstrated to be sufficiently reliable during operational states and accident conditions, with no adverse effects on structures, systems and components important to safety.
Heat removal	I.38.	Where the integrity of spent fuel relies on a cask’s internal gas medium, the design of the associated spent fuel storage cask should ensure the medium is maintained for the design life or should make provision for the monitoring and maintaining of both the presence and the quality of the medium for the time period demonstrated as necessary by the safety case.
Confinement of radioactive material	I.39.	The storage facility and dry storage casks should be designed to facilitate monitoring of the spent fuel confinement system and detection of confinement failures. If continuous monitoring is not provided, periodic verification by observation or measurement should be carried out to ensure that the confinement systems are performing satisfactorily. For dry storage casks, this should include monitoring of seal integrity for bolted closure designs.
Confinement of radioactive material	I.40.	The storage facility should be designed in such a way as to incorporate confinement barriers to prevent the release of radionuclides. This could include liners or canisters as an integral part of the dry storage system.
Radiation protection	I.41.	Spent fuel loading and unloading operations should be carried out using equipment and methods that limit ‘sky shine’ and reflection of radiation to workers and the public.
Radiation protection	I.42.	The dry storage facility should be monitored in order to detect increases in gamma and neutron fields that may indicate a degradation of confinement systems or shielding.
Radiation protection	I.43.	Dry storage areas with a significant potential for generating or accumulating unacceptable concentrations of airborne radionuclides should be either maintained at subatmospheric pressures to prevent the spread of airborne radionuclides to other areas of the spent fuel storage facility, or ventilated and filtered in order to maintain concentrations of airborne radionuclides at acceptable levels. For open dry storage facilities that do not use an overstructure or building, radiation monitoring should be, as a minimum, provided at the site boundary to detect any abnormal levels of airborne radionuclides.
Structure and layout	I.44.	Storage casks equipped with liners should be designed to prevent the accumulation of water between the liner and the body of the cask. Storage vaults and silos should be provided with features to facilitate drainage or it should be demonstrated that the potential for water accumulation is not of concern, i.e. that decay heat generated by the stored fuel is sufficient to evaporate and drive off any accumulated water.
Structure and layout	I.45.	If stacking is proposed for a dry fuel storage facility, the mechanical stability of the spent fuel and any cask or basket should be designed to withstand, without unacceptable structural deformation, the mass of a full stack. Static, impact and seismic loads should be considered in the design of spent fuel and casks or baskets.
Structure and layout	I.46.	Ease of access should be considered in the design to facilitate the transfer of spent fuel to or from storage positions in normal operation or during recovery operations after anticipated operational occurrences or accident conditions.
Structure and layout	I.47.	Casks should be designed in such a way as to provide stability and prevent them from tipping over.
Structure and layout	I.48.	The dry storage system area should be planned and the storage system itself effectively sealed such that unacceptable leakage of radionuclides and/or inert gases is prevented and ingress of water (moderator) and/or air is prevented.
Structure and layout	I.49.	The foundations of the dry storage area should be capable of withstanding the weight of the loaded spent fuel casks and the handling equipment without excessive settling and degradation.
Structure and layout	I.50.	The design of an open dry storage facility should be such as to provide for appropriate collection, monitoring and processing of surface runoff water.
Structure and layout	I.51.	Inclusion of a hot cell in the design of a dry storage facility should be considered to allow for unloading casks and subsequent repackaging of the fuel or repairs.
Structure and layout	I.52.	If a hot cell or other capabilities for unloading or repairs are not available, casks should be designed for maintenance or repair. Alternatively, they may be designed and maintained in order to enable their transport to a location where such facilities are available.
Materials	I.53.	The storage system, particularly the storage cask, should be constructed of suitable materials, using appropriate design codes and standards and construction methods, to maintain shielding and confinement functions under the storage and loading and unloading conditions expected throughout its design lifetime, unless adequate maintenance and/or replacement methods during operation can be demonstrated. These loading and unloading conditions include exposure to the atmosphere, internal and external humidity, fission products, temperature variations, internal buildup of gas and high radiation fields.
Materials	I.54.	Industry codes and standards used should be acceptable to the regulatory body. If codes and standards are not yet accepted by the regulatory body, sufficient justification for their use should be provided.
Materials	I.55.	The dry storage system, including any closures, especially cask closures, should be constructed of materials that provide chemical and radiological stability and appropriate resistance to mechanical and thermal impacts.
Materials	I.56.	The fuel storage container atmosphere should be adequately dried in order to attain and maintain the gaseous environment required to protect the integrity of the spent fuel. Drying of the fuel storage container atmosphere also ensures that any water entrained inside damaged fuel rods is adequately evacuated. This reduces the potential for additional fuel damage or degradation during the drying activity, where higher fuel temperatures might be experienced, and in subsequent storage. Maintaining of the required internal environment in the storage container is also key to ensuring continued functionality of the confinement, particularly the seal(s). For this reason, and to ensure retrievability of the fuel, the condition of the spent fuel should be correctly characterized and analysed and/or inspected if necessary prior to its loading into a storage container.
Handling	I.57.	The design of casks intended to be portable should include provision for lifting and handling that minimizes the potential for a drop accident. This should include the use of single‑failure‑proof cranes and positive locking mechanisms on lifting yokes. Lifting and handling mechanisms should be able to withstand anticipated loadings and usage during the design lifetime of the casks.
Handling	I.58.	For dry storage facilities incorporating canisters for which shielding is necessary, consideration should be given to the need for on‑site handling and for off‑site transport.
Handling	I.59.	For multipurpose casks intended for storage, transport and potential disposal after storage, the means for appropriate handling at the end of the storage period should be considered in the design.
Handling	I.60.	To limit corrosion, radiolysis phenomena and criticality issues, spent fuel should be dried to the greatest extent possible prior to being put in dry storage.
Handling	I.61.	There are several elements in the management of a dry storage facility that contribute to its safe operation. Some of the key elements are listed in Table II–2 of Annex II. Since dry storage facilities are by design principally passive, there are fewer specific operational considerations than for wet storage facilities.
Subcriticality	I.62.	In most cases, it can be shown by deterministic arguments that dry storage facilities remain subcritical. The effect of possible water ingress to areas where fuel might be present, for example, as a result of climate change and an associated increase in the levels of naturally occurring bodies of water adjacent to the facility, should be analysed. This can be done either deterministically or using a probabilistic analysis based on consideration of external environmental events or human induced accidents combined with an induced breach in the confinement barriers. In addition, if spent fuel is either loaded or unloaded from a dry storage cask in a pool environment, then subcriticality should be evaluated assuming credible optimum moderation.
Heat removal	I.63.	Heat is removed from spent fuel casks and/or the spent fuel storage facility by conduction, radiation and natural or, in some cases, forced convection. Operational controls should consist of verification that there are no impairments to the flow of the cooling medium. The internal cooling medium for casks is typically an inert gas, whereas the external cooling medium for dry storage is typically air. If forced circulation is necessary for heat removal, additional operational controls and maintenance will be required on air moving systems. Maximization of the passive design features for heat removal will minimize the need for operational considerations.
Heat removal	I.64.	Operating temperatures should be monitored to ensure the dissipation of spent fuel decay heat to the environment in order to maintain the integrity of materials important to safety.
Heat removal	I.65.	For casks relying upon a gas medium for internal convective cooling, the quality and/or density of the gas should be monitored and maintained if maintenance of the gas medium is not ensured by the design.
Confinement	I.66.	For double seal systems for dry storage casks, monitoring should be implemented to detect any loss of effectiveness of any of the seals and thereby prevent releases of radioactive material to the environment. For single seal systems and ventilation systems, releases of radioactive material (e.g. ⁸⁵Kr, ¹³⁴Cs and ¹³⁷Cs) should be monitored.
Confinement	I.67.	For dry cask storage systems with welded closure lids, monitoring might not be necessary.
Shielding	I.68.	Operational controls should be implemented to avoid a loss of shielding in spent fuel storage. A loss of shielding can lead to high radiation exposure. Specifically, operational controls should address the potential for, inter alia, the following: Handling errors when closing or sealing dry storage casks or containers; Improper operation or failure of protective interlocks on shielding cells; Melting of neutron shielding material due to high temperatures.
Dropping of loads	I.69.	Operational controls should be implemented that avoid the dropping of spent fuel during transfer from the cask to the storage rack (or vice versa in the case of cask loading for dry storage). A drop of spent fuel could result, inter alia, in the following: Partial defects in the spent fuel cladding, leading to leaks and, in the case of cask loading in a storage pool, resulting in contamination of the storage pool water by fission products; Deformation (e.g. bending) or damage of the spent fuel, which could lead to difficulties in its subsequent handling; An increased potential for the occurrence of a criticality accident if new spent fuel or spent fuel with low burnup were to be inadvertently dropped in the vicinity of other spent fuel in the pool storage racks; Radiation exposure of workers due to the release of volatile radionuclides.
Dropping of loads	I.70.	Processes should be established to evaluate the effect of any dropped fuel on the integrity of the cladding of the dropped fuel and on any other structure or component impacted by the drop. The results of the evaluation should be used in the future management of the dropped fuel.
Dropping of loads	II.1.	There are numerous types of fuel element that have to be considered for storage. They differ by the type of fuel, the enrichment in ²³⁵U for fresh uranium fuel, the cladding material and the geometry. After irradiation in a reactor, there will be large differences in heat generation, in gamma and neutron dose rates and in criticality safety requirements. In selecting a storage mode, due consideration should be given to the specific properties of the respective fuel.
Dropping of loads	II.2.	Fuel made from a mixture of uranium and recycled plutonium oxide (mixed oxide fuel) is increasingly being utilized in light water reactors. Although the fuel rods and fuel assemblies are essentially identical in structure and in form to analogous uranium oxide fuels, they differ from the latter in their radionuclide inventory and in their substantially higher decay heat generation and higher neutron radiation rates. These properties can significantly reduce the number of spent mixed oxide fuel assemblies that can be loaded into a dry storage cask, when cooling times are short. To facilitate the most efficient storage of mixed oxide fuel and to reduce the number of dry storage casks necessary, the operating organization of a spent fuel storage facility should optimize the cooling time, to allow sufficient reduction in the decay heat generation rate, before the spent mixed oxide fuel is loaded into a dry storage system.
Dropping of loads	II.3.	Protection against criticality accidents constitutes an important design requirement. In the analysis of nuclear reactivity, special consideration is required to be given to the nuclide vector of plutonium as well as to the specification of an enveloping plutonium and uranium ratio.
Dropping of loads	II.4.	Spent mixed oxide fuel might be loaded among uranium fuel assemblies. In such cases, the mixed oxide assemblies should be placed only at specific positions to allow for the effective dissipation of heat and to provide for adequate radiation shielding.
Dropping of loads	II.5.	Compared with uranium fuel, the increased heat generation, the high alpha activity and the higher buildup of gaseous fission products of spent mixed oxide fuel will impose additional stress on the cladding material. Therefore, for each type of cladding, the cladding integrity should be demonstrated before storage takes place, irrespective of whether wet or dry storage is used.
Dropping of loads	II.6.	Most safety measures necessary for the storage of mixed oxide fuel are also applicable to the storage of high burnup fuel (a high burnup can be defined as a level higher than 55 GW·d/t uranium for light water reactors).
Dropping of loads	II.7.	The use of burnup credit in the safety assessment means that credit is given for the reduction in spent fuel reactivity as a result of fission. It differs from the more conservative ‘fresh fuel’ assumption and, consequently, can be considered a more realistic approach. A decision to take credit for burnup should be fully justified with accurate experimental data, approved calculation methods and validated and verified benchmarked computer codes in accordance with international standards. This applies to both inventory determination calculations and criticality calculations. A licence application for the storage of spent fuel with the inclusion of burnup credit should be supported by an adequate safety assessment that demonstrates that the required safety level will be achieved.
Dropping of loads	II.8.	Approval to consider burnup credit in the safety assessment should be granted only if based on engineered safety features and operational controls. Operational controls provide defence in depth and contribute to maintaining subcritical conditions. The minimum required burnup value should be verified by independent measurement.
Dropping of loads	II.9.	Approval to consider burnup credit in the safety assessment should be granted in an incremental manner. Priority should be given to consideration of simple cases before considering more complex cases, such as spent fuel with mixed enrichments. This would allow for the accumulation of the necessary experience with fuel that can easily be characterized, such as standard pressurized water reactor fuel.
Dropping of loads	II.10.	The basic safety aspects for the storage of spent fuel from power reactors are applicable to the storage of spent fuel from research reactors. A proper graded approach, which takes the differences between the fuel types into account, should be applied. Issues relating specifically to the storage of research reactor fuel, for example, lower heat generation, higher enrichment and the use of cladding materials that are less corrosion resistant, should be given particular consideration.
Dropping of loads	II.11.	Fuel composition, cladding material and shapes and sizes of fuel assemblies differ significantly in research reactors. In a research reactor, different fuel elements can be loaded into the research reactor and thus a variety of spent fuel is generated. This might comprise, for example, fuel assemblies with different cladding materials (e.g. aluminium, stainless steel, zirconium) or with different fuel compositions. In certain research reactors, reconstitution of an irradiated fuel assembly (e.g. by replacement of pins) is carried out.
Dropping of loads	II.12.	In addition to the recommendations provided in this Safety Guide, it is essential that all aspects relating to the specific fuel assemblies used in a research reactor are taken into consideration.
Dropping of loads	II.13.	A detailed assessment of all fuel assemblies, including reconstituted assemblies, should be carried out for storage. Proper provision in the design should be made for storage of research reactor fuel assemblies in accordance with their shape, size, cladding type and fuel composition. Provision for the safe storage of any separated pins resulting from the reconstitution of fuel should also be made in the design.
Dropping of loads	II.14.	Owing to the higher enrichment of fuel used in research reactors, the potential for inadvertent criticality might be higher. Therefore, the design of a spent fuel storage facility should incorporate features that will add additional subcriticality margins in storage, as noted in paras 6.32 and 6.33.
Dropping of loads	II.15.	The compatibility of the cladding of the research reactor fuel with wet storage conditions should be assessed in order to ensure the integrity of the fuel cladding.
Dropping of loads	II.16.	Since aluminium and its alloys, which are widely used as cladding materials for research reactor fuel, have relatively less corrosion resistance, meticulous control of pool water composition is necessary to ensure the integrity of the fuel cladding. In view of this, it might be considered preferable in the longer term to store spent research reactor fuel in a dry storage environment.
Dropping of loads	II.17.	Spent research reactor fuel should be dried to the greatest extent possible prior to transferring it to dry storage. This may require placement in a suitably designed canister and specific treatment before it is transferred. The dry storage facility should be designed to ensure that the environment surrounding the fuel will inhibit corrosion and thus eliminate the possible release of airborne or water‑borne radionuclides. INTERNATIONAL ATOMIC ENERGY AGENCY, Predisposal Management of Radioactive Waste, IAEA Safety Standards Series No. GSR Part 5, IAEA, Vienna (2009). INTERNATIONAL ATOMIC ENERGY AGENCY, Storage of Radioactive Waste, IAEA Safety Standards Series No. WS-G-6.1, IAEA, Vienna (2006). INTERNATIONAL ATOMIC ENERGY AGENCY, IAEA Safety Glossary: Terminology Used in Nuclear Safety and Radiation Protection, 2018 Edition, IAEA, Vienna (2019). INTERNATIONAL ATOMIC ENERGY AGENCY, Safety of Nuclear Fuel Cycle Facilities, IAEA Safety Standards Series No. SSR-4, IAEA, Vienna (2017). INTERNATIONAL ATOMIC ENERGY AGENCY, Leadership and Management for Safety, IAEA Safety Standards Series No. GSR Part 2, IAEA, Vienna (2016). INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Assessment for Facilities and Activities, IAEA Safety Standards Series No. GSR Part 4 (Rev. 1), IAEA, Vienna (2016). INTERNATIONAL ATOMIC ENERGY AGENCY, Safety of Nuclear Power Plants: Design, IAEA Safety Standards Series No. SSR-2/1 (Rev. 1), IAEA, Vienna (2016). INTERNATIONAL ATOMIC ENERGY AGENCY, Predisposal Management of Radioactive Waste from Nuclear Power Plants and Research Reactors, IAEA Safety Standards Series No. SSG-40, IAEA, Vienna (2016). INTERNATIONAL ATOMIC ENERGY AGENCY, Predisposal Management of Radioactive Waste from Nuclear Fuel Cycle Facilities, IAEA Safety Standards Series No. SSG-41, IAEA, Vienna (2016). INTERNATIONAL ATOMIC ENERGY AGENCY, Nuclear Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities (INFCIRC/225/Revision 5), IAEA Nuclear Security Series No. 13, IAEA, Vienna (2011). EUROPEAN ATOMIC ENERGY COMMUNITY, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, IAEA, Vienna (2006). EUROPEAN COMMISSION, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, IAEA Safety Standards Series No. GSR Part 3, IAEA, Vienna (2014). INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONS ENVIRONMENT PROGRAMME, Radiation Protection of the Public and the Environment, IAEA Safety Standards Series No. GSG-8, IAEA, Vienna (2018). INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONS ENVIRONMENT PROGRAMME, Regulatory Control of Radioactive Discharges to the Environment, IAEA Safety Standards Series No. GSG-9, IAEA, Vienna (2018). INTERNATIONAL NUCLEAR SAFETY ADVISORY GROUP, Safety Culture, INSAG-4, IAEA, Vienna (1991). INTERNATIONAL NUCLEAR SAFETY ADVISORY GROUP, Key Practical Issues in Strengthening Safety Culture, INSAG-15, IAEA, Vienna (2002). INTERNATIONAL ATOMIC ENERGY AGENCY, Governmental, Legal and Regulatory Framework for Safety, IAEA Safety Standards Series No. GSR Part 1 (Rev. 1), IAEA, Vienna (2016). Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management, INFCIRC/546, IAEA, Vienna (1997). INTERNATIONAL ATOMIC ENERGY AGENCY, Regulations for the Safe Transport of Radioactive Material, 2018 Edition, IAEA Safety Standards Series No. SSR‑6 (Rev. 1), IAEA, Vienna (2018). INTERNATIONAL ATOMIC ENERGY AGENCY, Decommissioning of Facilities, IAEA Safety Standards Series No. GSR Part 6, IAEA, Vienna (2014). INTERNATIONAL ATOMIC ENERGY AGENCY, Functions and Processes of the Regulatory Body for Safety, IAEA Safety Standards Series No. GSG-13, IAEA, Vienna (2018). FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL CIVIL AVIATION ORGANIZATION, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, INTERPOL, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, PREPARATORY COMMISSION FOR THE COMPREHENSIVE NUCLEAR TEST BAN TREATY ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, UNITED NATIONS OFFICE FOR THE COORDINATION OF HUMANITARIAN AFFAIRS, WORLD HEALTH ORGANIZATION, WORLD METEOROLOGICAL ORGANIZATION, Preparedness and Response for a Nuclear or Radiological Emergency, IAEA Safety Standards Series No. GSR Part 7, IAEA, Vienna (2015). INTERNATIONAL ATOMIC ENERGY AGENCY, Communication and Consultation with Interested Parties by the Regulatory Body, IAEA Safety Standards Series No. GSG-6, IAEA, Vienna (2017). INTERNATIONAL ATOMIC ENERGY AGENCY, Decommissioning of Nuclear Power Plants, Research Reactors and Other Nuclear Fuel Cycle Facilities, IAEA Safety Standards Series No. SSG-47, IAEA, Vienna (2018). FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR OFFICE, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS OFFICE FOR THE COORDINATION OF HUMANITARIAN AFFAIRS, WORLD HEALTH ORGANIZATION, Arrangements for Preparedness for a Nuclear or Radiological Emergency, IAEA Safety Standards Series No. GS-G-2.1, IAEA, Vienna (2007). INTERNATIONAL ATOMIC ENERGY AGENCY, The Safety Case and Safety Assessment for the Predisposal Management of Radioactive Waste, IAEA Safety Standards Series No. GSG-3, IAEA, Vienna (2013). The Structure and Content of Agreements between the Agency and States required in Connection with the Treaty on the Non-Proliferation of Nuclear Weapons, INFCIRC/153(Corrected), IAEA, Vienna (1972). INTERNATIONAL ATOMIC ENERGY AGENCY, The Management System for the Processing, Handling and Storage of Radioactive Waste, IAEA Safety Standards Series No. GS-G-3.3, IAEA, Vienna (2008). (A revision of this publication is in preparation.) INTERNATIONAL ATOMIC ENERGY AGENCY, Site Evaluation for Nuclear Installations, IAEA Safety Standards Series No. SSR-1, IAEA, Vienna (2019). INTERNATIONAL ATOMIC ENERGY AGENCY, External Human Induced Events in Site Evaluation for Nuclear Power Plants, IAEA Safety Standards Series No. NS‑G‑3.1, IAEA, Vienna (2002). INTERNATIONAL ATOMIC ENERGY AGENCY, Dispersion of Radioactive Material in Air and Water and Consideration of Population Distribution in Site Evaluation for Nuclear Power Plants, IAEA Safety Standards Series No. NS-G-3.2, IAEA, Vienna (2002). INTERNATIONAL ATOMIC ENERGY AGENCY, Seismic Hazards in Site Evaluation for Nuclear Installations, IAEA Safety Standards Series No. SSG-9, IAEA, Vienna (2010). INTERNATIONAL ATOMIC ENERGY AGENCY, WORLD METEOROLOGICAL ORGANIZATION, Meteorological and Hydrological Hazards in Site Evaluation for Nuclear Installations, IAEA Safety Standards Series No. SSG-18, IAEA, Vienna (2011). INTERNATIONAL ATOMIC ENERGY AGENCY, Geotechnical Aspects of Site Evaluation and Foundations for Nuclear Power Plants, IAEA Safety Standards Series No. NS-G-3.6, IAEA, Vienna (2004). INTERNATIONAL ATOMIC ENERGY AGENCY, Volcanic Hazards in Site Evaluation for Nuclear Installations, IAEA Safety Standards Series No. SSG-21, IAEA, Vienna (2012). INTERNATIONAL ATOMIC ENERGY AGENCY, Radiation Protection Aspects of Design for Nuclear Power Plants, IAEA Safety Standards Series No. NS-G-1.13, IAEA, Vienna (2005). INTERNATIONAL ATOMIC ENERGY AGENCY, Protection against Internal Hazards in the Design of Nuclear Power Plants, IAEA Safety Standards Series No. SSG‑ 64, IAEA, Vienna (in preparation). INTERNATIONAL ATOMIC ENERGY AGENCY, Release of Sites from Regulatory Control on Termination of Practices, IAEA Safety Standards Series No. WS-G-5.1, IAEA, Vienna (2006).
Dropping of loads	I-1.	Short term storage (conventional storage) is defined in this Safety Guide as storage that can last up to approximately 50 years, since this period is representative with respect to: The typical design lifetime for conventional storage structures and facilities; The period over which one can be reasonably confident that the operating organization will have sufficient funds to continue operating; The period covering conventional regulatory experience; The time to produce an adequate quantity of material to make it economical to process (for interim or buffer storage); The period over which wastes are held to allow treatment and conditioning plants to be developed, for example a fuel encapsulation plant (for interim storage); The time needed to decide whether the material is a resource or a waste and to allow the development of the necessary processing techniques (for strategic or interim storage).
Dropping of loads	I-2.	To satisfy safety considerations, a short term storage concept needs to include an end point that will be reached within a time period of approximately 50 years. If this is not possible, it is more appropriate to compare the safety considerations against the safety considerations for a long term waste storage facility.
Dropping of loads	I-3.	Long term storage is considered in this Safety Guide to be storage beyond approximately 50 years, and with a defined end point. The storage end point is important since it determines the basis for the design lifetime of the facility, packaging requirements and financial guarantees, and the planning basis for subsequent disposal facilities. Long term storage is not expected to last more than approximately 100 years. This time frame is based on technical experience with civil construction. However, it is a fact that many existing industrial and civil analogues have lifetimes of 100–150 years and more. Archaeological analogues can be found with lifetimes of 1000–2000 years. Societal acceptance of longer design lifetimes, which is based on experience with existing industrial operations and facilities, is also an important factor to consider. The 100 year period is judged to be adequate to allow enough time to determine future fuel management steps.
Dropping of loads	III-1.	An example of the sections that could be included in the operating procedures for a spent fuel storage facility is as follows: Descriptive title, with revision number, date and approval status; Purpose of the procedure; Initial conditions required before the procedure can be used; Precautions and limitations that must be observed; Limitations and action levels on parameters being controlled (e.g. pool water composition) and corrective measures to return parameters to within a normal range; Procedures providing detailed, step by step operating instructions; Acceptance criteria, where applicable, for judging the success or failure of activities; Checklists for complex procedures (either included or referenced); References used in developing the procedure; Testing to verify radiation dose levels and heat removal performance after spent fuel loading; Monitoring of bore wells around the facility; Monitoring of stack discharge.
Dropping of loads	IV-1.	In making use of this list, it is to be recognized that the initiating events included would not necessarily be applicable to all facilities and to all sites: The meteorology and climatology of the site and region: Precipitation (averages and extremes, including frequency, duration and intensity): Rain, hail, snow and ice; Snow cover and ice cover (including the potential for blocking inlets or outlets); Drought. Wind (averages and extremes, including frequency, duration and intensity): Tornadoes, hurricanes and cyclones. Rate and duration of the input of direct solar radiation (insolation, averages and extremes). Temperature (averages and extremes, including frequency and duration): Permafrost and the cyclic freezing and thawing of soil. Barometric pressure (averages and extremes, including frequency and duration). Humidity (averages and extremes, including frequency and duration): Fog and frost. Lightning (frequency and intensity). The hydrology and hydrogeology of the site and region: Surface runoff (averages and extremes, including frequency, duration and intensity): Flooding (frequency, duration and intensity); Erosion (rate). Groundwater conditions (averages and extremes, including frequency and duration). Wave action (averages and extremes, including frequency, duration and intensity): High tides, storm surges and tsunami; Flooding (frequency, duration and intensity); Shore erosion (rate). The geology of the site and the region: Lithology and stratigraphy: The geotechnical characteristics of site materials. Seismicity: Faults and zones of weakness; Earthquakes (frequency and intensity). Vulcanology: Volcanic debris and ash. Historical mining and quarrying: Ground subsidence. The geomorphology and topography of the site: Stability of natural material: Slope failures, landslides and subsidence; Avalanches. Surface erosion. The effects of the terrain (topography) on weather conditions or on the consequences of extreme weather. The terrestrial and aquatic flora and fauna of the site (in terms of their effects on the facility): Vegetation (terrestrial and aquatic): The blocking of inlets and outlets; Damage to structures. Rodents, birds and other wildlife: Direct damage due to burrowing or chewing; Accumulation of nesting debris or guano; The potential for: Naturally occurring fires and explosions at the site; Methane gas or natural toxic gas (from marshland or landfill sites); Dust storms or sandstorms (including the possible blocking of inlets and outlets). Precipitation (averages and extremes, including frequency, duration and intensity): Rain, hail, snow and ice; Snow cover and ice cover (including the potential for blocking inlets or outlets); Drought. Wind (averages and extremes, including frequency, duration and intensity): Tornadoes, hurricanes and cyclones. Rate and duration of the input of direct solar radiation (insolation, averages and extremes). Temperature (averages and extremes, including frequency and duration): Permafrost and the cyclic freezing and thawing of soil. Barometric pressure (averages and extremes, including frequency and duration). Humidity (averages and extremes, including frequency and duration): Fog and frost. Lightning (frequency and intensity). Rain, hail, snow and ice; Snow cover and ice cover (including the potential for blocking inlets or outlets); Drought. Tornadoes, hurricanes and cyclones. Permafrost and the cyclic freezing and thawing of soil. Fog and frost. Surface runoff (averages and extremes, including frequency, duration and intensity): Flooding (frequency, duration and intensity); Erosion (rate). Groundwater conditions (averages and extremes, including frequency and duration). Wave action (averages and extremes, including frequency, duration and intensity): High tides, storm surges and tsunami; Flooding (frequency, duration and intensity); Shore erosion (rate). Flooding (frequency, duration and intensity); Erosion (rate). High tides, storm surges and tsunami; Flooding (frequency, duration and intensity); Shore erosion (rate). Lithology and stratigraphy: The geotechnical characteristics of site materials. Seismicity: Faults and zones of weakness; Earthquakes (frequency and intensity). Vulcanology: Volcanic debris and ash. Historical mining and quarrying: Ground subsidence. The geotechnical characteristics of site materials. Faults and zones of weakness; Earthquakes (frequency and intensity). Volcanic debris and ash. Ground subsidence. Stability of natural material: Slope failures, landslides and subsidence; Avalanches. Surface erosion. The effects of the terrain (topography) on weather conditions or on the consequences of extreme weather. Slope failures, landslides and subsidence; Avalanches. Vegetation (terrestrial and aquatic): The blocking of inlets and outlets; Damage to structures. Rodents, birds and other wildlife: Direct damage due to burrowing or chewing; Accumulation of nesting debris or guano; The blocking of inlets and outlets; Damage to structures. Direct damage due to burrowing or chewing; Accumulation of nesting debris or guano; Naturally occurring fires and explosions at the site; Methane gas or natural toxic gas (from marshland or landfill sites); Dust storms or sandstorms (including the possible blocking of inlets and outlets).
Dropping of loads	V-1.	In making use of this list it is to be recognized that the initiating eventsincluded would not necessarily be applicable to all facilities and all sites: Explosion: Solid substance; Gas, dust or aerosol cloud. Fire: Solid substance; Liquid substance; Gas, dust or aerosol cloud. Aircraft crash. Missiles generated as a result of structural or mechanical failure in nearby installations. Flooding: The structural failure of a dam; The blockage of a river. Ground subsidence or collapse due to tunnelling or mining. Ground vibration. The release of any corrosive, toxic or radioactive substance: Liquid; Gas, dust or aerosol cloud. Geographic and demographic data: Population density and expected changes over the lifetime of the facility; Industrial and military installations and related activities and the effects on the facility of accidents at such installations; Traffic; Transport infrastructure (highways, airports and flight paths, railway lines, rivers and canals, pipelines and the potential for impacts or accidents involving hazardous material). Power supply and the potential loss of power. Civil strife: Terrorism, sabotage and perimeter incursions; The failure of infrastructure; Civil disorder; Strikes and blockades; Health issues (e.g. endemic diseases or epidemics). Solid substance; Gas, dust or aerosol cloud. Solid substance; Liquid substance; Gas, dust or aerosol cloud. The structural failure of a dam; The blockage of a river. Liquid; Gas, dust or aerosol cloud. Population density and expected changes over the lifetime of the facility; Industrial and military installations and related activities and the effects on the facility of accidents at such installations; Traffic; Transport infrastructure (highways, airports and flight paths, railway lines, rivers and canals, pipelines and the potential for impacts or accidents involving hazardous material). Terrorism, sabotage and perimeter incursions; The failure of infrastructure; Civil disorder; Strikes and blockades; Health issues (e.g. endemic diseases or epidemics).
Dropping of loads	VI-1.	In making use of this list it is to be recognized that the initiating events included would not necessarily be applicable to all facilities and all sites: The acceptance (inadvertent or otherwise) of incoming spent fuel, spent fuel containers, process chemicals and conditioning agents that do not meet the specifications (acceptance criteria) included in the design basis. The processing of spent fuel that meets acceptance criteria but which is subsequently processed in an inappropriate way for the particular type of spent fuel (either inadvertently or otherwise). A criticality accident due to the inappropriate accumulation of fissile material, change of geometrical configuration, introduction of moderating material, removal of neutron absorbing material or various combinations of these. Explosion due to the evolution of explosive gas mixtures as a result of: Radiolysis. Off-gassing or volatilization. Chemical reactions from inappropriate mixing or contact with: Different spent fuel streams; Spent fuel and conditioning agents; Spent fuel cask material and conditioning agents; Process chemicals; Spent fuel, spent fuel casks, conditioning agents, process chemicals and the prevailing conditions of the working environment or storage environment. The inclusion of items such as bottles of compressed gas in the input to incinerators or compactors. Fire due to: Spontaneous combustion; Local hot spots generated by malfunctions of structures, systems or components. Sparks from machinery, equipment or electrical circuits. Sparks from human activities, such as welding or smoking. Explosions. Gross incompatibilities between the components of a process system and the materials introduced into the system. The degradation of process materials (chemicals, additives or binders) due to improper handling or storage. The failure to take account of the non-radiological hazards presented by the spent fuel (physical, chemical or pathogenic). The generation of a toxic atmosphere by chemical reactions due to inappropriate mixing or contact of various reagents and materials. Dropping of spent fuel elements or other loads due to mishandling or equipment failure, with consequences for the dropped spent fuel elements and possibly for other spent fuel elements or to the structures, systems and components of the facility. Collisions of vehicles or suspended loads with structures, systems and components of the facility or with spent fuel elements, spent fuel casks and pipes. Failures of structures, systems and components due to: A loss of structural integrity or mechanical integrity; Vibrations originating within the facility; Pressure imbalances (pressure surges or pressure collapses); Internal corrosion or erosion or the chemical effects of the working environment or storage environment. The generation of missiles and flying debris due to explosion of pressurized components or gross failure of rotating equipment. The malfunctioning of heating or cooling equipment, leading to unintended temperature excursions in process systems or storage systems. The malfunctioning of process control equipment. The malfunctioning of equipment that maintains the ambient conditions in the facility, such as the ventilation system or the dewatering system. The malfunctioning of monitoring or alarm systems so that an adverse condition goes unnoticed. Incorrect settings (errors or unauthorized changes) on monitors, alarms or control equipment. The failure of emergency equipment, such as the fire suppression system, pressure relief valves and ducts, to function when called upon. The failure of the power supply, either the main system or a subsystem. The malfunctioning of key equipment for handling spent fuel, such as transfer cranes or conveyors. The malfunctioning of structures, systems and components that control releases to the environment, such as filters or valves. The failure properly to inspect, test and maintain structures, systems and components. Incorrect operator action due to inaccurate or incomplete information. Incorrect operator action in spite of having accurate and complete information. Sabotage by employees. The failure of systems and components, such as incinerator linings, compactor hydraulics or cutting machinery, that poses a risk of significant additional radiation exposure of personnel called on to assist in effecting repairs or replacements. Encounter of an unanticipated radiation source in decommissioning (e.g. different in nature or amount) and with immediate recognition of the changed circumstances. Removal or weakening of a structure or component in decommissioning without realization of the possible effects on the structural integrity of other structures and components. Radiolysis. Off-gassing or volatilization. Chemical reactions from inappropriate mixing or contact with: Different spent fuel streams; Spent fuel and conditioning agents; Spent fuel cask material and conditioning agents; Process chemicals; Spent fuel, spent fuel casks, conditioning agents, process chemicals and the prevailing conditions of the working environment or storage environment. The inclusion of items such as bottles of compressed gas in the input to incinerators or compactors. Different spent fuel streams; Spent fuel and conditioning agents; Spent fuel cask material and conditioning agents; Process chemicals; Spent fuel, spent fuel casks, conditioning agents, process chemicals and the prevailing conditions of the working environment or storage environment. Spontaneous combustion; Local hot spots generated by malfunctions of structures, systems or components. Sparks from machinery, equipment or electrical circuits. Sparks from human activities, such as welding or smoking. Explosions. A loss of structural integrity or mechanical integrity; Vibrations originating within the facility; Pressure imbalances (pressure surges or pressure collapses); Internal corrosion or erosion or the chemical effects of the working environment or storage environment.

Sekce

Odstavec

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1.1.

Spent nuclear fuel is generated from the operation of nuclear reactors of all types and needs to be safely and securely managed following its removal from the reactor core. Spent fuel¹ is considered waste in some circumstances or a potential future energy resource in others and, as such, management options might involve direct disposal (as part of what is generally known as the ‘once through fuel cycle’) or reprocessing (as part of what is generally known as the ‘closed fuel cycle’). Either management option will involve a number of steps, which will necessarily include storage of the spent fuel for some period of time. This time period for storage can differ, depending on the management strategy adopted, from a few months to several decades. The time period for storage will be a significant factor in determining the storage arrangements adopted. The final management option might not have been determined at the time of design of the storage facility, leading to some uncertainty in the storage period that will be necessary, a factor that needs to be considered in the adoption of a storage option and the design of the facility. Storage options include wet storage in some form of storage pool, or dry storage in a facility or in storage casks built for this purpose. Storage casks can be located in a designated area on a site or in a designated storage building. A number of different designs for both wet and dry storage have been developed and used in different States.

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1.2.

Irrespective of the consideration of spent fuel (either waste or an energy resource), the requirements for the storage of spent fuel are the same as those for the storage of radioactive waste, which are established in IAEA Safety Standards Series No. GSR Part 5, Predisposal Management of Radioactive Waste [1].

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1.3.

The safety of a spent fuel storage facility, and of the spent fuel stored within it, is ensured by appropriate confinement of the radionuclides involved, maintaining subcriticality, heat removal, radiation shielding and retrievability of the spent fuel or spent fuel packages. These functions are ensured by the proper siting, design, construction and commissioning of the storage facility, and its proper management and safe operation. At the design stage, due consideration also needs to be given to the future decommissioning of the facility.

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1.4.

Spent fuel is generated continually by operating nuclear reactors. It is stored in the reactor fuel storage pool for a period of time for cooling and then may be transferred to a designated wet or dry storage facility, where it will await reprocessing or disposal (if it is considered to be radioactive waste). The spent fuel storage pools of some reactors have sufficient capacity to accommodate all the spent fuel that will be generated during the lifetime of the reactor.

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1.5.

The basic safety aspects for the storage of spent fuel are applicable to the storage of spent fuel from research reactors as well as from power reactors. For research reactors, an approach should be adopted that takes into account the differences between the fuel types (e.g. the lower heat generation of research reactor fuel, its higher enrichment level and cladding materials that are less corrosion resistant) when determining the measures to be taken to ensure confinement, heat removal, criticality control, radiation shielding and retrievability.

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1.6.

Many spent fuel storage facilities at reactors were intended to serve for a limited period of time (a few years) as a place to keep spent fuel between unloading from the reactor and its subsequent storage, reprocessing or disposal. In view of the time being taken to develop disposal facilities and the limited reprocessing programmes that have been developed, storage periods are being extended from years to decades. This change in approach to the management of spent fuel has been accompanied by other developments, for example increases in enrichment, increases of burnup, use of advanced fuel design and mixed oxide fuel, re‑racking, use of burnup credit and, in some cases, extension of storage periods beyond the original design lifetime of the storage facility. Nevertheless, storage cannot be considered the ultimate solution for the management of spent fuel, which requires a defined end point such as reprocessing or disposal in order to ensure safety. The design lifetime of a nuclear installation is generally of the order of decades, and experience with the storage of spent fuel of up to around 50 years has accrued. While design lifetimes of up to 100 years have been considered and adopted for certain spent fuel storage facilities, in view of the rate of industrial and institutional change, periods beyond around 50 years are deemed to be ‘long term’ in the context of this Safety Guide (see also Annex I).

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1.7.

The present publication supersedes the 2012 edition of SSG‑15². This Safety Guide complements IAEA Safety Standards Series No. WS‑G‑6.1, Storage of Radioactive Waste [2], and can be read in conjunction with it.

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1.7A.

The terms used in this Safety Guide are to be understood as defined and explained in the IAEA Safety Glossary [3].

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1.8.

The objective of this Safety Guide is to provide guidance and recommendations on the design, commissioning, operation and assessment of safety for the different types of spent nuclear fuel storage facility (wet and dry), by considering different types of spent nuclear fuel from nuclear reactors, including research reactors, and different storage periods, including storage beyond the original design lifetime of the storage facility. This Safety Guide presents guidance and recommendations on how to meet the requirements established in GSR Part 5 [1] and IAEA Safety Standards Series Nos SSR‑4, Safety of Nuclear Fuel Cycle Facilities [4], GSR Part 2, Leadership and Management for Safety [5], GSR Part 4 (Rev. 1), Safety Assessment for Facilities and Activities [6], and SSR‑2/1 (Rev. 1), Safety of Nuclear Power Plants: Design [7].

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1.9.

This Safety Guide covers spent nuclear fuel storage facilities that are either collocated with other nuclear facilities (e.g. nuclear power plant, research reactor, reprocessing plant) or located on their own site. However, it is not specifically intended to cover the storage of spent nuclear fuel as long as it remains a part of the operational activities of a nuclear reactor or a spent fuel reprocessing facility, which are addressed in IAEA Safety Standards Series Nos SSG‑40, Predisposal Management of Radioactive Waste from Nuclear Power Plants and Research Reactors [8], and SSG‑41, Predisposal Management of Radioactive Waste from Nuclear Fuel Cycle Facilities [9], respectively.

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1.10.

The scope of this Safety Guide includes the storage of spent nuclear fuel from water moderated reactors and can, with due consideration, also be applied to the storage of other types of nuclear fuel, such as spent nuclear fuel from gas cooled reactors and research reactors, and to the storage of spent fuel assembly components and degraded or failed nuclear fuel³ that might be placed in canisters.

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1.11.

This Safety Guide does not provide recommendations on the physical protection of nuclear material and nuclear facilities. Recommendations and guidelines on physical protection arrangements at nuclear facilities, including risk assessment, threat definition, design, maintenance and implementation of physical protection systems, evaluation of effectiveness and inspection of physical protection systems, are provided in Ref. [10] and in supporting publications in the IAEA Nuclear Security Series. This Safety Guide considers physical protection and accounting for and control of nuclear material only to highlight potential implications for safety.

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1.12.

Section 2 of this Safety Guide addresses the application of the fundamental safety objective and the fundamental safety principles to the storage of spent nuclear fuel. The roles and responsibilities of those involved in the storage of spent nuclear fuel are set out in Section 3. Section 4 provides recommendations on the management system necessary for safety. Section 5 provides recommendations on safety assessment and Section 6 provides recommendations on safety considerations in respect of design, construction, operation and decommissioning of spent fuel storage facilities, including considerations for long term storage. Appendix I addresses considerations specific to wet and dry storage of spent nuclear fuel and Appendix II addresses considerations in respect of spent fuel with particular characteristics. Annex I provides explanations of the concepts of short term and long term storage. Annex II summarizes operational and safety considerations for wet and dry storage facilities. Annex III provides an example of the sections that could be included in the operating procedures for a spent fuel storage facility. Annexes IV–VI provide listings of events for consideration in a safety assessment for a spent fuel storage facility.

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1.13.

For convenience, the text of each safety requirement that is applicable to the storage of spent nuclear fuel is reproduced in this Safety Guide, followed by the related recommendations.

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2.1.

National requirements for radiation protection are required to be established, in accordance with the fundamental safety objective and fundamental safety principles set out in IAEA Safety Standards Series No. SF‑1, Fundamental Safety Principles [11], and in compliance with IAEA Safety Standards Series No. GSR Part 3, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards [12]. In particular, doses to people as a consequence of the storage of spent fuel are required to be kept within specified dose limits and radiation protection is required to be optimized within dose constraints.

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2.2.

If several nuclear installations (e.g. nuclear power plants, spent fuel storage facilities, reprocessing facilities) are located at the same site, the dose constraints for public exposure should take into account all sources of exposure that could be associated with activities at the site. Particularly in such cases, the regulatory body should require the operating organization(s) of the nuclear installation(s) on the site to develop constraints, subject to regulatory approval. Alternatively, the regulatory body may establish the dose constraints. Requirements on dose constraints are established in GSR Part 3 [12] and recommendations are provided in IAEA Safety Standards Series No. GSG‑8, Radiation Protection of the Public and the Environment [13].

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2.3.

The design of a spent fuel storage facility and the storage of spent fuel must be such that the workers, the public and the environment, present and future, will be protected from harmful effects of radiation exposure from all sources of ionizing radiation associated with current activities with spent fuel at the site [11], with sufficient margins for foreseeable future activities at the site that might also give rise to exposure.

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2.4.

Discharges to the environment from spent fuel storage facilities should be controlled in accordance with the conditions imposed by the regulatory body and should be included when estimating doses to workers and to the public. Recommendations on discharge limits are provided in IAEA Safety Standards Series No. GSG‑9, Regulatory Control of Radioactive Discharges to the Environment [14].

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2.5.

The adequacy of control measures taken to limit the radiation exposure of workers and the public should be verified by monitoring and surveillance, both inside and outside the facility.

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2.6.

At each step in the management of spent fuel, a safety culture that encourages a questioning and learning attitude towards protection and safety and that discourages complacency should be fostered and maintained [5, 15, 16].

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Requirement 1 of GSR Part 5 [1]: Legal and regulatory framework

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3.1.

Storage of spent fuel should be undertaken within an appropriate national legal and regulatory framework that provides for a clear allocation of responsibilities [17], including responsibilities for meeting international obligations and for verifying compliance with these obligations, and which ensures the effective regulatory control of the facilities and activities concerned. The national legal framework should also ensure compliance with other relevant national and international legal instruments, such as the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management [18].

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3.2.

The management of spent fuel may entail the transfer of spent fuel from one operating organization to another and various interdependences exist between the various steps in the management of spent fuel. The legal framework should include provision to ensure a clear allocation of responsibility for safety throughout the entire process, in particular with regard to the storage of spent fuel and its transfer between operating organizations. Continuity of responsibility for safety should be ensured by means of a system of authorization by the regulatory body. For transfers between States, authorizations from the respective national regulatory bodies are required [18, 19].

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3.3.

The responsibilities of the regulatory body⁴, the operating organization and, where appropriate, the spent fuel owner in respect of spent fuel management should be clearly specified in the legal and regulatory framework and should be functionally separate.

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3.4.

A mechanism for providing adequate financial resources should be established to cover any future costs, in particular the costs associated with spent fuel storage and decommissioning of the storage facility as well as the costs of managing radioactive waste. The financial mechanism should be established before licensing of the storage facility and its operation and should be updated as necessary. Consideration should also be given to provision of the necessary financial resources in the event of a premature shutdown of the spent fuel storage facility.

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Requirement 2 of GSR Part 5 [1]: National policy and strategy on radioactive waste management

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3.5.

The government is responsible for establishing a national policy and corresponding strategy for the management of spent fuel and for providing the legal and regulatory framework necessary to implement the policy and strategy. The national policy and strategy should cover all types of spent fuel and spent fuel storage facility in the State, with account taken of the interdependences between the various stages of spent fuel management, the time periods involved and the options available [17].

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3.6.

The government is responsible for establishing a regulatory body independent of the owners of the spent fuel or the operating organizations managing the spent fuel, with adequate authority, power, staffing and financial resources to discharge its assigned responsibilities [17].

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3.7.

The government should consult interested parties (i.e. those who are involved in or are affected by spent fuel management activities) on matters relating to the development of the national policy and strategy for the management of spent fuel.

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3.8.

In the event that circumstances change and storage is required beyond the period originally envisaged in the national strategy for the management of spent fuel, a re‑evaluation of the national strategy should be carried out.

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Requirement 3 of GSR Part 5 [1]: Responsibilities of the regulatory body

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3.9.

The regulatory body should provide guidance to operating organizations on how to meet requirements relating to the safe storage of spent fuel, which should include, but is not limited to: the application of a management system for the handling and storage of spent fuel; development of operational limits and conditions; performance of the safety assessment; development and use of quantifiable performance indicators; and documentation and use of the safety case⁵.

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3.10.

Since spent fuel might be stored for long periods of time prior to its retrieval for reprocessing or disposal, the regulatory body should verify that the operating organization is providing the necessary personnel and the technical and financial resources for the lifetime of the spent fuel storage facility, to the extent that such confirmation is within the statutory obligations of the regulatory body.

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3.11.

The regulatory review of the decommissioning plans for spent fuel storage facilities should follow a graded approach, particularly considering the current stage in the lifetime of the storage facility. The initial decommissioning plan should be conceptual and should be reviewed by the regulatory body for its overall completeness rather than for specific decommissioning arrangements, but it should include specifically how financial and human resources and the availability of the necessary information from the design, construction and operational stages will be ensured when decommissioning takes place. The decommissioning plan should be updated regularly by the licensee and updates should be reviewed by the regulatory body. If a facility is to be shut down and no longer to be used for its intended purpose, a final decommissioning plan is required to be submitted to the regulatory body for review and approval [20].

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3.12.

3.12. General recommendations for regulatory inspection and enforcement actions relating to spent fuel storage facilities are provided in IAEA Safety Standards Series No. GSG‑13, Functions and Processes of the Regulatory Body for Safety [21]. The regulatory body should periodically verify that the key aspects of the operation of the storage facility meet the requirements of the national legal system and facility licence conditions, such as those relating to keeping records on inventories and material transfers, compliance with acceptance criteria for storage, maintenance, inspection, testing and surveillance, operational limits and conditions, physical protection of nuclear material and arrangements for on‑site emergency preparedness and response. Such verification might be carried out, for example, by routine inspections of the spent fuel storage facility and the operating organization, and by review and assessment of the safety case. In addition, verification should include observing and evaluating some exercises of the operating organization, in accordance with para. 6.30 of IAEA Safety Standards Series No. GSR Part 7, Preparedness and Response for a Nuclear or Radiological Emergency [22]. The regulatory body should verify that the necessary records are prepared and that they are maintained for an appropriate period of time. Recommendations on the records to be retained are provided in GSG‑13 [21].

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3.13.

The regulatory body should set up appropriate means of informing interested parties, such as people living in the vicinity, the general public, the media and others, about the safety aspects (including health and environmental aspects) of the spent fuel storage facility and about regulatory processes, and should consult these parties, as appropriate, in an open and inclusive manner. The need for confidentiality (e.g. for security reasons) should be respected. Further recommendations are provided in IAEA Safety Standards Series No. GSG‑6, Communication and Consultation with Interested Parties by the Regulatory Body [23].

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3.14.

The regulatory body should consider the licensing strategy to be adopted, for example:

A licence issued for the entire lifetime of the storage system and/or the facility, which encompasses the whole anticipated operating period, including periodic review of safety assessments, as elaborated in Section 5; or
A licence issued for a specified time period with the possibility for renewal after expiry.

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3.15.

If the regulatory body comprises more than one authority, effective arrangements should be made to ensure that regulatory responsibilities and functions are clearly defined and coordinated in order to avoid any omissions or unnecessary duplication and to prevent conflicting requirements being placed on the operating organization. The main regulatory functions of review and assessment and inspection and enforcement should be organized in such a manner as to achieve consistency and to enable the necessary feedback and exchange of information.

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Requirement 4 of GSR Part 5 [1]: Responsibilities of the operator⁶

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3.16.

The operating organization is responsible for the safety of all activities associated with the storage of spent fuel (including activities undertaken by contractors) and for the specification and implementation of the programmes and procedures necessary to ensure safety. The operating organization should maintain a high level of safety culture and should demonstrate safety. In some instances, the operating organization might be the owner of the spent fuel and in other cases the owner might be a separate organization. In the latter instance, particular consideration should be given to interdependences among the spent fuel management steps, including for any activity carried out prior to receipt of the spent fuel at a storage facility, such as its characterization or packaging, or the subsequent transport of the spent fuel from the facility, to ensure that conditions for safety will be met.

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3.17.

The responsibilities of the operating organization of a spent fuel storage facility typically include the following:

Application to the regulatory body for permission to site, design, construct, commission, operate, modify or decommission a spent fuel storage facility;
Conduct of appropriate safety assessment and environmental assessment in support of the application for a licence;
Operation of the spent fuel storage facility in accordance with the requirements of the safety case, the licence conditions and the applicable regulations;
Development and application of acceptance criteria for the storage of spent fuel, as approved by the regulatory body;
Provision of periodic reports as required by the regulatory body (e.g. information on the actual inventory of spent fuel, any transfers of spent fuel into and out of the facility, any events that have occurred at the facility and which have to be reported to the regulatory body) and communication with interested parties and the general public.

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3.18.

Prior to authorization of a spent fuel storage facility, the operating organization should provide the regulatory body with a safety case that demonstrates the safety of the proposed activities and also demonstrates that the proposed activities at the facility will be in compliance with the safety requirements and criteria set out in national laws and regulations. As part of the safety case, the operating organization should use the safety assessment to establish specific operational limits and conditions for approval by the regulatory body. The operating organization may wish to set an operational target level within these specified limits to assist in avoiding any breach of approved limits and conditions (see para. 6.106).

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3.19.

At an early stage in the lifetime of a spent fuel storage facility, the operating organization should prepare the initial plan for its eventual decommissioning. For new facilities, features that will facilitate decommissioning should be taken into consideration at the design stage. Such features should be included in the decommissioning plan, together with information on arrangements regarding how the availability of the necessary human and financial resources and information will be ensured, for presentation in the safety case. The operating organization should regularly update the decommissioning plan and submit updates to the regulatory body for review and approval. If a facility is to be shut down and is no longer to be used for its intended purpose, the operating organization is required to submit a final decommissioning plan to the regulatory body for review and approval within a period agreed with the regulatory body [20].

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3.20.

For existing facilities without a decommissioning plan, the licensee should prepare such a plan as soon as possible and submit it to the regulatory body for review and approval. Subsequent updates are to be made in accordance with the requirements on decommissioning established in IAEA Safety Standards Series No. GSR Part 6, Decommissioning of Facilities [20], and recommendations provided in IAEA Safety Standards Series No. SSG‑47, Decommissioning of Nuclear Power Plants, Research Reactors and Other Nuclear Fuel Cycle Facilities [24].

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3.21.

The operating organization should establish the requirements for training and qualification of its staff and contractors, including for initial training and periodic refresher training [4]. The operating organization should ensure that all concerned staff members understand the nature of the spent fuel, its potential hazards and the relevant operating and safety procedures pertaining to it. Supervisory staff should be competent to perform their activities and should therefore be selected, trained, qualified and authorized for that purpose. A radiation protection officer should be appointed to oversee the application of radiation protection requirements.

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3.22.

The operating organization should carry out pre‑operational tests and commissioning tests to demonstrate compliance of the storage facility and storage activities with the requirements of the safety assessment and with the requirements established by the regulatory body.

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3.23.

The operating organization should ensure that discharges of radioactive material and other potentially hazardous material to the environment are in accordance with the conditions of the licence. Discharges should be documented.

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3.24.

The operating organization should prepare plans and implement programmes for personnel monitoring, area monitoring and environmental monitoring.

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3.25.

The operating organization should establish procedures on how to analyse the need for and how to implement modifications to the spent fuel storage facility, storage conditions and the spent fuel to be stored. As part of the procedures, the potential consequences of such modifications and of the works performed to implement them should be evaluated, including consequences for the safety of other facilities and also for the retrieval, transport, reprocessing and disposal of spent fuel. The procedures should be commensurate with the significance of the proposed modifications for safety.

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3.26.

The operating organization is required to allocate and maintain appropriate financial resources to undertake all necessary tasks throughout the lifetime of the facility, including its decommissioning [17].

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3.27.

The operating organization should develop and maintain a record keeping system on data relating to the spent fuel and the storage system, which should include the radioactive inventory, location and characteristics of the spent fuel, information on the ownership and origin of the spent fuel, and information about its characterization. An unequivocal identification system should be established, with markings that will last for the duration of the storage period. Such records should be preserved and updated to enable the implementation of the spent fuel management strategy, whether disposal or reprocessing.

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3.28.

The operating organization is required to prepare an emergency plan and the necessary procedures and analytical tools for on‑site emergency preparedness and effective response [22]. The operating organization is required to coordinate this emergency plan with those of all other bodies that have responsibilities in a nuclear or radiological emergency, including public authorities, and submit it to the regulatory body for approval [22]. Account is required to be taken, in the content, features and extent of the emergency plan, of the results of the hazard assessment and any lessons identified from operating experience and from past emergencies, including conventional emergencies [22, 25]. The operating organization should demonstrate to the regulatory body, as part of the safety case, that the emergency arrangements provide for sufficient assurance of an effective on‑site emergency response and that they are in place [26].

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Requirement 6 of GSR Part 5 [1]: Interdependences

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3.29.

There should be clear and unequivocal ownership of the spent fuel stored in the facility. The responsibilities of the spent fuel owner and the responsibilities of the operating organization, if they differ, should be clearly defined and documented. The spent fuel owner (namely, a body having legal title to the spent fuel, including financial liabilities) should be responsible for the overall strategy for the management of its spent fuel. In determining the overall strategy, the spent fuel owner should take into account interdependences between all stages of spent fuel management, the options available and the overall national spent fuel management strategy.

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3.30.

Information about any changes in ownership of the spent fuel or changes in the relationship between the owner and the operating organization of a spent fuel storage facility should be provided to the regulatory body.

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Requirement 21 of GSR Part 5 [1]: System of accounting for and control of nuclear material

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3.31.

The operating organization will be required to establish, maintain and implement a system for nuclear material accounting and control as an integrated part of the State system of accounting for and control of nuclear material⁷ [10].

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3.31A.

In addition, physical protection systems for deterrence and detection of the intrusion of unauthorized persons and for protection against sabotage from within and outside the facility are required to be designed and installed during the construction and operation of the spent fuel storage facility.

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3.31B.

Paragraph 1.10 of SF‑1 [11] requires that safety measures and security measures “be designed and implemented in an integrated manner so that security measures do not compromise safety and safety measures do not compromise security.” The operating organization should demonstrate to the regulatory body that security provisions, including physical protection systems, and safety measures at the facility are managed in such a way as to achieve this.

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Requirement 7 of GSR Part 5 [1]:

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4.1.

The requirements on the management system for all stages in the lifetime of a spent fuel storage facility are established in GSR Part 2 [5]. Recommendations on the management system for the storage of spent fuel are provided in IAEA Safety Standards Series No. GS‑G‑3.3, The Management System for the Processing, Handling and Storage of Radioactive Waste [28].

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4.2.

An integrated management system is required to be established, implemented, assessed and continually improved by the operating organization [5] and applied to all stages of the storage of spent fuel. The management system is required to be aligned with the goals of the operating organization and to contribute to their achievement [5]. The management system should address the siting, design, commissioning, operation, maintenance and decommissioning of the spent fuel storage facility. The management system is required to be designed to ensure that the safety of the spent fuel and of the spent fuel storage facility is maintained, and that the quality of the records and of subsidiary information of spent fuel inventories is preserved, with account taken of the length of the storage period and the consecutive management steps, for example reprocessing or disposal [5]. The management system should also contain provisions to ensure that the fulfilment of its goals can be demonstrated.

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4.3.

The long term nature of spent fuel management operations means that particular consideration should be given to establishing and maintaining confidence that the performance of the spent fuel storage facilities and activities will meet the safety requirements throughout the lifetime of the facility to the end of its decommissioning (e.g. by creation of the funding arrangements that will be necessary to manage the spent fuel in the long term).

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4.4.

National and international policies and principles for spent fuel management that currently constitute an accepted management arrangement can evolve over the lifetime of the facility. Policy decisions (e.g. regarding spent fuel reprocessing) and technological innovations and advances (e.g. in partitioning and transmutation) can lead to fundamental changes in the overall spent fuel management strategy. However, the operating organization retains its responsibility for safety at all times, and continuous commitment by the organization remains a prerequisite of ensuring safety and the protection of human health and the environment.

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4.5.

For the plans, goals and objectives associated with the strategy for achieving an integrated approach to safety, interaction with all interested parties should be considered, as well as long term aspects such as:

Provision of adequate resources (the adequacy of resources for maintenance of facilities and equipment may need to be periodically reviewed over operational periods that may extend over decades);
Preservation of technology and knowledge and transfer of such knowledge to people or organizations joining the spent fuel management programme in the future;
Retention or transfer of ownership of spent fuel and spent fuel management facilities;
Succession planning for the technical and managerial human resources of the spent fuel management programme or the operating organization;
Continuation of arrangements for interacting with interested parties.

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4.6.

Spent fuel management activities will require financial and human resources and the necessary infrastructure at the site where the spent fuel storage facility is located. Senior management is required to make arrangements to provide adequate resources for spent fuel management activities, to satisfy the demands imposed by safety, health, environmental, security, quality, human and organizational factors, and societal and economic aspects of the full range of activities involved in the management of spent fuel and the potentially long duration of such activities [5].

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4.7.

Arrangements for the funding of future spent fuel management activities should be specified, and responsibilities, mechanisms and schedules for providing the funds should be established in due time. The generator of the spent fuel should establish an appropriate funding mechanism.

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4.8.

The management system for spent fuel management should include provisions to deal with funding related challenges, such as the following:

For various reasons (e.g. bankruptcy, cessation of business), it might not be feasible to obtain the necessary funds from the spent fuel generator, especially if funds were not set aside at the time the benefits were received from the activity, or if ownership of the spent fuel has been transferred to another party.
If funds are to come from public sources, their allocation will compete with other demands for public funding, and it may be difficult to gain access to adequate funds on a timely basis.
It might be difficult to make realistic estimates of costs for spent fuel management activities that are still in the planning stage and for which no experience has been accumulated.
It might be difficult to estimate anticipated costs for activities that will only begin in the long term, because they will depend strongly on assumptions made about future inflation rates, interest rates and technological developments.
It might be difficult to determine appropriate risk and contingency factors to be built into estimates of future costs, owing to the uncertainties associated with future changes in societal demands, political imperatives, public opinion and the nature of unplanned events that may need resources for dealing with them.
If several organizations are involved in spent fuel management activities, the necessary financial arrangements might be complex and might vary over the lifetime of the facility. It might be problematic to establish an adequate degree of confidence in all the arrangements so that the necessary continuity of funding throughout the entire series of activities is ensured.

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4.9.

Accumulated experience, including lessons identified from incidents and events, should be reviewed periodically and should be used in revising training programmes and in reaching future decisions.

Main

4.10.

In the design of facilities for long term spent fuel management, consideration should be given to the incorporation of measures that will facilitate operation, maintenance of equipment and eventual decommissioning of the facility. For long term spent fuel management activities, future infrastructural requirements should be specified and plans should be made to ensure that these will be met. In such planning, consideration should be given to the continuing need for support services, spare parts for equipment that might eventually cease to be manufactured, and equipment upgrades to meet new regulations and operational improvements, and to the evolution and inevitable obsolescence of software. Consideration should also be given to the need to develop monitoring programmes and inspection techniques for use during extended periods of storage.

Main

4.11.

Consideration should be given to the possible need to relocate spent fuel casks if problems arise after they have been placed in storage. The availability of any specialized equipment that may be necessary over a long time period while spent fuel is in storage or that may be necessary in the future should be assessed.

Main

4.12.

Records concerning spent fuel and its storage that need to be retained for an extended period should be stored in a manner that minimizes the likelihood and consequences of loss, damage or deterioration due to unpredictable events such as fire, flooding or other natural or human induced events (both internal and external to the facility). Storage arrangements for records should meet the requirements prescribed by the national authorities or the regulatory body, and the status of the records should be periodically assessed. If records are inadvertently destroyed, the status of surviving records should be examined and the importance of their retention and their necessary retention periods should be re‑evaluated.

Main

4.13.

The management system should be reassessed whenever the relationship between the owner of the spent fuel and the operating organization of the facility changes (e.g. public organizations are privatized, new organizations are created, existing organizations are combined or restructured, responsibilities are transferred between organizations, operating organizations undergo internal reorganization of the management structure, or resources are reallocated).

Main

Requirement 13 of GSR Part 5 [1]: Preparation of the safety case and supporting safety assessment

Main

5.1.

In demonstrating the safety of the spent fuel storage facility and related activities, a safety case should be developed as development of the facility progresses and the supporting safety assessment should be carried out in a structured and systematic manner. Proposed facilities, processes, operations and activities should be examined to determine whether they can be implemented safely and whether they meet all requirements with regard to safety. If storage casks are to be used, one or separate safety cases and/or safety assessments might be prepared for the storage casks, for the storage building or facility and for the subsequent transport arrangements if the cask will be used eventually for transport as well as for storage. This will depend on the national regulatory approach. However, irrespective of the approach taken, the interdependences between spent nuclear fuel management operations, activities and collocated facilities should be taken into consideration to ensure that an integrated approach to safety is adopted and that safety is optimized. The safety case and supporting safety assessment should provide the primary input to the licensing documentation that is used to demonstrate compliance with regulatory requirements [6].

Main

5.2.

The various stages in the lifetime of the spent fuel storage facility (i.e. siting, design, construction, commissioning, operation, decommissioning) should be taken into account in the safety case. The safety case should be periodically reviewed in accordance with regulatory requirements and should be revised as necessary.

Main

5.3.

The prime responsibility for safety throughout the lifetime of a facility lies with the operating organization [11]. This includes responsibility for both ensuring the safety of the facility and demonstrating its safety in the safety case.

Main

5.4.

Long term storage (see para. 1.6 and Annex I) might involve a period of time that exceeds the normal design lifetime of civil structures, including short term storage facilities, and this will have implications for the selection of construction materials, operating methods, and quality assurance and quality control requirements. Specific issues that should be given particular consideration in the safety case for a facility for long term storage of spent fuel include the anticipated lifetime of the facility, the importance of passive safety features, retrievability and the management system. Consideration should also be given to the provision of support services when the spent fuel storage facility remains in operation after other facilities at the site have been closed, in particular for storage facilities at reactor sites.

Main

5.5.

The rationale for the selection of the assessment time frame should be explained and justified. Depending on the purpose of the assessment and other components of assessment context [26], for ease of modelling or presentation it might be convenient to divide the overall time frame of the safety assessment into shorter ‘time windows’ with various end points.

Main

5.6.

In determining the assessment time frame, account should be taken of the characteristics of the particular storage facility or activity, the site and the spent fuel to be stored. Other factors that should be considered include the following:

For most long term storage systems (including storage casks, engineered constructions and the surrounding environment), potential health and environmental impacts might increase for a period of time after commissioning of the facility. In the long term, and depending on the nature of the facility, potential impacts might decrease, in particular through decay of the radionuclide inventory of the spent fuel. The safety assessment calculations should consider the maximum, or peak, dose or risk associated with the facility or activity.
A further consideration that might influence decisions on assessment time frames is the return period of natural external hazards, such as extreme meteorological events or earthquakes.
Several factors that can significantly affect the results of the safety assessment might change with time, including external hazards from human activities such as the construction of other facilities nearby, natural events such as changes in water levels, and changes in the availability of support facilities and infrastructure due to shutdown and decommissioning of collocated facilities. Potential changes such as these should be considered in the safety assessment. As a means to assess the possible evolution of the long term storage, one or more scenarios postulated to reflect different evolution paths may be considered in the safety assessment. Assessment time windows may be defined, as appropriate, to reflect potential changes at the storage facility.
The location, habits and characteristics of the representative person considered in radiological impact assessment might change over time. The representative person will generally be a hypothetical construct and not an actual member of the population. Nevertheless, individuals and populations in the future should be afforded at least the same level of protection as that required currently. The habits and characteristics assumed for the representative person should be chosen on the basis of reasonably conservative and plausible assumptions, considering current lifestyles as well as the available site or regional environmental conditions.

Main

5.7.

The operating organization should demonstrate in the safety case that, to the extent possible, passive safety features are applied. In the assessment of long term safety, the degradation of passive barriers over time should be taken into account.

Main

5.8.

The complementary performance of the different elements providing safety functions should be evaluated. Each element should be independent of the others, to the extent possible, to ensure that they are complementary and cannot fail through a single failure mode. The safety case should explain and justify the functions provided by each element and should identify the time periods over which they are expected to perform their various safety functions and also the alternative or additional safety functions that will be in place if a barrier does not fully perform.

Main

5.9.

As in the case of disposal of radioactive waste, the environment might also offer additional protective functions (e.g. underlying clay layers that would provide a sorption capacity for contaminants in the event of any leakages from the facility). Such aspects should be taken into account during the siting of the facility and should be considered in the safety case.

Main

5.10.

Storage is, by definition, an interim measure, but it can last for several decades. The intention in storing spent fuel is that it can be retrieved for reprocessing or processing and/or disposal at a later time. In the safety case, a plan for the safe handling of the spent fuel, following the period of storage, should be considered, and the potential effects of degradation of the spent fuel, and of any elements providing confinement, on the ability to retrieve and handle the spent fuel should be assessed (see also Section 6).

Main

5.11.

The possibility of inadvertent human intrusion normally would not be considered relevant when assessing the safety of a storage facility because the facility will need continued surveillance and maintenance not only during but also after the spent fuel emplacement stage. Prevention of intentional human intrusion needs adequate security arrangements (see Ref. [10]), which should be addressed in the safety case (see also paras 3.31A and 3.31B).

Main

5.12.

As storage is an interim measure, the safety case should describe the provisions for the regular monitoring, inspection and maintenance of the storage facility to ensure its continued integrity over the anticipated lifetime of the facility.

Main

5.13.

Because of the long time frames potentially involved, a plan for adequate record keeping over the expected time frame for storage should be considered in the safety case.

Main

5.14.

Periodically, the safety case should be reviewed to assess the continuing adequacy of the storage capacity; account should be taken of the predicted spent fuel arising, the expected lifetime of the storage facility and the availability of reprocessing or disposal options (see para. 5.26).

Main

5.15.

It may be necessary to reassess the anticipated challenges of decommissioning of the spent fuel storage facility after operating experience has been gained.

Main

5.16.

The requirement to perform safety assessment derives from national programme requirements and the recognition that the safety assessment can contribute directly to safety, as it is through the safety assessment that appropriate measures are identified that can be put in place to protect workers, the public and the environment. Safety assessment is undertaken in conjunction with the planning and design of a proposed facility or activity rather than being a separate activity. The results of the safety assessment can be used to determine any necessary changes in the plans or design so that compliance with all requirements is ensured. The results are also used to establish controls and limitations on the design, construction and operation of the facility.

Main

5.17.

Safety assessment is typically an iterative process used to ensure that a spent fuel storage facility can be operated safely and it should be commenced early in the design process. Generally, in the control of radiation risks, reliance should be placed principally on design features rather than on operating procedures.

Main

5.18.

Postulated initiating events that might influence the design of the spent fuel storage facility and the integrity and safety of the spent fuel should be identified. The primary causes of postulated initiating events might be credible equipment failure and operator error or natural or human induced events (both internal and external to the facility). In identifying the relevant postulated initiating events, generic lists of such events should be consulted (see Annexes IV–VI). Such lists should not be relied on solely, since site specific environmental conditions and phenomena and the design and operation of the facility will also influence the decision as to which postulated initiating events need to be evaluated in the safety assessment.

Main

5.19.

Safety assessment should cover the storage facility and the type of spent fuel to be stored and the storage arrangements. In this regard, the types, quantities, initial enrichment, burnup, integrity, heat production, storage mode (wet or dry storage) and physical and chemical characteristics of the spent fuel are basic aspects that need to be included in the safety assessment of the spent fuel storage facility.

Main

5.20.

Safety assessment for a spent fuel storage facility should cover the expected operational period of the facility. If the spent fuel is to be stored for long periods of time, events of lower likelihood would need to be evaluated in the safety assessment compared with the case of storage for a shorter duration. Similarly, processes that might not be relevant for a shorter duration of storage might become significant for a longer duration of storage (e.g. generation of gas, general corrosion, stress corrosion, radiation or hydride induced embrittlement of cladding material, natural processes such as a vermin infestation or a possible change in nuclear reactivity over a long time).

Main

5.21.

A specific safety case and supporting assessment for a spent fuel storage facility should generally include aspects such as:

A description of the site and facility (including the maximum expected inventory of spent fuel and its acceptance criteria, the storage facility and its characteristics, structures, systems and components, including the characteristics of items important to the safety of the spent fuel storage facility, in accordance with the requirements of its licence) and a specification of applicable regulations and guidance.
A description of spent fuel handling and storage activities and any other operations at the facility.
Systematic identification of hazards that could lead to anticipated operational occurrences and possibly to accident conditions (see Annexes IV–VI). In the identification of hazards, consideration should be given to possible combinations of related events and hazards (e.g. earthquake and tsunami, fire and building collapse) that might occur and their consequential effects. In considering scenarios involving combinations of hazards, account should be taken of the likelihood of their simultaneous or consecutive occurrence and their causality. A graded approach should be taken to addressing combinations of hazards in the safety case and the safety assessment.
An evaluation of scenarios, including screening of combinations of scenarios, that might result in a release of radioactive material, to identify those combinations of scenarios warranting consideration in the design basis of the facility. Combinations of scenarios that are of low likelihood but have high potential consequences that are above the design basis threshold should also be considered.
Assessment of the probabilities and potential consequences of releases of radioactive material identified in the hazard evaluation by quantitative analyses, and comparison of the results of the assessment with safety criteria established by the regulatory body [6].
Arrangements for ageing management.
Establishment of operational limits and conditions and administrative controls based on the safety assessment. If necessary, the design of the spent fuel storage facility should be modified and the safety assessment should be updated. Such controls should include acceptance criteria for spent fuel casks, including canisters containing failed fuel.
Documentation of safety analyses and the safety assessment for inclusion in the licensing documentation for the facility.
The commissioning programme.
Organizational control of operations.
Procedures and operational manuals for activities with significant safety implications, including procedures for response to the malfunction of equipment.
The programme for periodic maintenance, inspection and testing.
The expected values for subcriticality, heat removal capacity and radiation doses within and at the boundary of the spent fuel storage facility.
Monitoring programmes, including a programme for verification of the integrity of the shielding, a programme for surveillance of the condition of stored spent fuel and a programme for surveillance of stored spent fuel assemblies, if appropriate.
A programme for feedback of operating experience and its inclusion in manuals, guidelines and training.
The training programme for staff.
Safety implications of aspects of accounting for and control of nuclear material.
Arrangements for management of the interface between safety and nuclear security.
The on‑site emergency plan.
The management system.
Provisions for occupational radiation protection.
Provisions for the management of radioactive waste and for decommissioning.
Whenever the safety of the facility depends on human actions, including actions to be taken in accidents, assessment of these human actions.

Main

5.21A.

In the case of collocation of spent fuel storage facilities with other facilities, consideration should be given in the safety assessment to the potential hazards presented by each facility or activity to the others, and the effects of external events on all facilities and activities, including the possibility of concurrent events affecting different facilities and activities [6]. Where it is anticipated that facilities on the site will share resources (human resources or material resources) in accident conditions, evaluation of such scenarios in the safety assessment should demonstrate that the required safety functions can be fulfilled at each facility.

Main

5.22.

Key hazards should be identified in the safety assessment so that the required safety functions and safety systems can be identified and a level of confidence can be established in the parameters supporting the safety assessment that is commensurate with the safety significance of the safety functions and safety systems (e.g. by sensitivity analysis).

Main

5.23.

The safety assessment should include an assessment of hazards in operational states and accident conditions. It should provide an assessment of doses at the site boundary and of the potential for exposure in areas within the site to which there is to be unrestricted access. In normal operation, there should be no mechanism that could cause a rapid increase in reactivity in the stored spent fuel, and thus relatively few credible accident scenarios for such a sudden increase in reactivity followed by a release of radioactive material.

Main

5.24.

As appropriate, limits on authorized discharges should be established for the spent fuel storage facility, in accordance with the recommendations provided in GSG‑9 [14].

Main

5.25.

If the initial safety assessment yields results that are close to or that exceed the limiting performance objectives, it may be necessary to carry out a more rigorous evaluation of the suitability of any generic data sources that may have been used, and/or an inventory reduction or additional safety systems and controls may be necessary.

Main

Requirement 16 of GSR Part 5 [1]: Periodic safety reviews

Main

5.26.

The safety case and supporting safety assessment, including the management system for their implementation, should be periodically reviewed in accordance with regulatory requirements. The review of the management system should include aspects of safety culture. In addition, the safety case and supporting safety assessment should be reviewed and updated:

When there is any significant change to the facility or to its radionuclide inventory that might affect safety.
When changes occur in the site characteristics that might impact the storage facility (e.g. industrial development or changes in the surrounding population).
When significant changes in knowledge and understanding occur (e.g. from research data or from feedback of operating experience).
When there is an emerging safety issue due to a regulatory concern or an incident.
Periodically, at predefined periods, as specified by the regulatory body. Some States specify that periodic safety review be carried out at least once every ten years.

Main

5.27.

Safety should be reassessed in the case of significant, unexpected deviations in storage conditions, for example if those properties of the spent fuel that are relevant to safety begin to deviate from those taken as a basis in the safety assessment.

Main

5.28.

For storage beyond the original design lifetime, a re‑evaluation should be performed of the initial design (and of the current design if it is significantly different), operations, maintenance, ageing management, safety assessment and any other aspect of the spent fuel storage facility relating to safety. If, during the design lifetime, an extension to the storage period is foreseen, a precautionary approach should be applied, in particular through validation of the adequacy of the design assumptions for the extended period envisaged.

Main

Requirement 15 of GSR Part 5 [1]: Documentation of the safety case and supporting safety assessment

Main

5.29.

In documenting the safety case, particular consideration should be given to ensuring that the level of detail and the supporting assessment are commensurate with the importance to safety of the particular system or component and its complexity, and that an independent reviewer will be able to reach a conclusion on the adequacy of the assessment and the arguments employed, both in their extent and in their depth. Assumptions used in the safety case are required to be justified in the documentation [1], as should be the use of generic information.

Main

Requirement 11 of GSR Part 5 [1]: Storage of radioactive waste

Main

6.1.

Spent fuel storage facilities should provide for the safe, stable and secure storage of spent fuel before it is reprocessed or disposed of. The design features and the operation of the facility should be such as to provide confinement of radioactive material to ensure that radiation protection of workers, members of the public and the environment is optimized within the dose constraints in accordance with the requirements established in GSR Part 3 [12] and to maintain subcriticality, to ensure removal of decay heat and to ensure retrievability of the spent fuel. These safety functions should be maintained during normal operation, anticipated operational occurrences and accident conditions.

Main

6.2.

Various types of wet and dry storage facility are currently in operation or under consideration in various States. Spent fuel is stored in essentially one of three different modes:

Wet storage in pools at, or remote from, a reactor site. The spent fuel is stored in standard storage racks or in compact storage racks in which closer spacing of the fuel assemblies or fuel elements is allowed in order to increase the storage capacity.
Dry storage in either storage casks or dual purpose (i.e. storage and transport) casks at, or remote from, a reactor site. Casks are modular in nature. Such systems are sealed systems designed to prevent the release of radioactive material during storage. They provide shielding and confinement of the spent fuel by physical barriers, which can include a metal or concrete body and metal liner or a metal canister and lids. They are usually cylindrical in shape, circular in cross‑section, with the long axis arranged either vertically or horizontally. The fuel position is maintained by means of a storage basket which might or might not be an integral part of the cask. Heat is removed from the stored fuel by conduction, radiation and forced or natural air convection to the surrounding environment. Casks might be enclosed in buildings or stored in an open area.
Dry storage in vault type storage facilities. A vault is a massive, radiation shielded facility in which spent fuel is stored. A vault can be either above or below ground level; it might be a reinforced concrete structure containing an array of storage cavities. The spent fuel is appropriately contained in order to prevent unacceptable releases of radioactive material. Shielding is provided by the structure surrounding the stored material. Primary heat removal is achieved by forced or natural air convection over the exterior of the storage cavities. This air is released to the atmosphere either directly or via appropriate filtration, depending on the system design. Some systems also use a secondary cooling circuit.

Main

6.3.

Although designs of spent fuel storage facilities may differ, in general they should consist of relatively simple, preferably passive, inherently safe systems intended to provide adequate safety over the design lifetime of the facility, which might span several decades. The lifetime of a spent fuel storage facility should be appropriate for the envisaged storage period. The design should also contain features to ensure that associated handling and storage operations are relatively straightforward.

Main

6.4.

The storage facility should be designed to fulfil the main safety functions; that is, maintaining subcriticality, removal of heat, confinement of radioactive material and shielding from radiation and, in addition, retrievability of the fuel or spent fuel packages. The design should at least, if possible, include the following features:

Systems for the removal of heat from the spent fuel should be driven, if possible, by the energy generated by the spent fuel itself (e.g. natural convection).
A multibarrier approach should be adopted in ensuring confinement, with account taken of all elements, including the fuel matrix, the fuel cladding, the storage casks, the storage vaults and any building structures that can be demonstrated to be reliable and competent.
Safety systems should be designed to achieve their safety functions with minimum need for monitoring.
Safety systems should be designed to function with minimum human intervention. If the performance of safety systems depends on actions carried out by personnel, those human interactions with the facility or activity should be addressed in the safety assessment.
The storage building, or the cask in the case of dry storage, should be resistant to the hazards taken into consideration in the safety assessment.
Access should be provided for response to incidents.
The spent fuel storage facility should be such that retrieval of the spent fuel or spent fuel package for inspection or reworking is possible.
The spent fuel and the storage system should be sufficiently resistant to degradation.
The storage environment should not adversely affect the properties of the spent fuel, spent fuel package or storage system.
The spent fuel storage system should allow for inspections.
The spent fuel storage system should be designed to avoid or minimize the generation of secondary waste streams.

Main

6.5.

This paragraph was deleted.

Design Process

6.6.

In the design process, appropriate analytical methods, procedures and tools should be used in conjunction with suitably selected input data and assumptions covering all operational states and accident conditions that are credible, with account taken of natural phenomena. Only verified and validated methods should be used for predicting the safety of operational states or the consequences of accidents. The input data selected should be conservative but still realistic. If possible, the degree of conservatism should be quantified. Where uncertainties in input data, analyses or predictions are unavoidable, appropriate allowances should be made to compensate for such uncertainties. The sensitivity of the assessment results to uncertainties should be evaluated.

Design Process

6.7.

As part of the overall process leading to an acceptable design, the design evolution and the supporting rationale should be clearly and adequately documented and kept readily available for future reference. The supporting documentation should be presented as a safety case [6].

Design Process

6.8.

In order to prevent cliff edge effects, the design should provide for an adequate margin against levels of external hazard selected for the design basis. It should be demonstrated in the safety case that all credible hazards and scenarios have been adequately analysed and appropriately addressed in the design. The safety case should describe the performance assessment models and methodologies used and the conclusions reached. Thus, for any design proposed, it should be demonstrated in the safety case that the spent fuel storage facility can, within the bounds of existing technologies, be safely constructed, commissioned, operated and decommissioned in accordance with the design specifications and the requirements of the regulatory body.

Design Process

6.9.

Items important to safety, including structures, systems and components, should be identified and classified in accordance with their importance to safety. Procedures should be established to ensure that the items important to safety will have appropriate functional and performance characteristics to perform their safety functions for the lifetime of the facility or for a defined replacement interval. Procedures relating to the control of design modifications in subsequent stages of the lifetime of the facility should also be defined. Such modifications might be necessary to take into account the findings of the safety case and periodic reassessment in the circumstances indicated in para. 5.26.

Design Process

6.10.

For dry storage facilities, the design should provide for arrangements to handle potential problems with the integrity of the spent fuel and of the storage system at the end of the original design lifetime of the storage facility in advance of any need for inspection of the content of the casks or assessment of the integrity of the spent fuel or storage casks. Such inspection might also be necessary to assess the integrity of the casks and the spent fuel, including a survey of the casks for leaktightness, to demonstrate that the storage period may be extended if an extension to the storage period in dry storage casks is under consideration. Careful consideration should be given to the approach to be adopted in determining the integrity of the spent fuel and storage system in order to prevent unnecessary occupational exposure and to prevent accidental release of radioactive material. For example, consideration should be given to whether to open the cask and remove the contents, or to inspect the contents in situ.

Design Process

6.11.

For storage beyond the original design lifetime, consideration should be given to mitigation of the consequences of potential changes in the storage facility and the stored spent fuel. Changes in the storage facility might be caused by radiation, heat generation and chemical or galvanic reactions. Changes in the stored spent fuel and storage cask might include the following:

The generation of gases that might cause hazards, by chemical and radiolytic effects (e.g. the generation of hydrogen gas by radiolysis) and buildup of overpressure;
The generation of combustible or corrosive substances;
The corrosion of metals;
The degradation of the spent fuel confinement system.

Siting

6.12.

Requirements for site evaluation are established in IAEA Safety Standards Series No. SSR‑1, Site Evaluation for Nuclear Installations [29]. The associated Safety Guides [30–35] contain criteria and methods that could be used in a graded approach in the siting of spent fuel storage facilities.

Defence in depth

6.13.

The concept of defence in depth is applied to all safety activities, whether organizational, behavioural or design related, to ensure that if a failure were to occur, it would be detected and compensated for or corrected by appropriate measures [4]. Defence in depth is required to be applied in the siting of a spent fuel storage facility and in its design, as well as when considering subcriticality, heat removal, confinement and radiation protection issues [4].

Defence in depth

6.14.

Application of the concept of defence in depth in the design of spent fuel storage should entail provision of a series of levels of defence (e.g. inherent features, equipment, procedures) aimed at preventing accidents and ensuring appropriate protection and mitigation of consequences in the event that prevention fails [4].

Defence in depth

6.15.

The facility should have a reserve storage capacity, which should be included in the design or should be otherwise available, for example in order to allow for reshuffling of spent fuel casks or unpackaged spent fuel elements for inspection, retrieval or maintenance work. The reserve capacity should be such that the largest type of storage cask can be unloaded or, in the case of a modular storage facility, that at least one module can be unloaded.

Structural integrity

6.16.

In order for safety systems and safety related items to perform properly, the components of the spent fuel storage facility should maintain their structural integrity in all operational states and accident conditions. Therefore, the integrity of the components and their related systems should be demonstrated by means of a structural evaluation. This should take account of relevant loading conditions (e.g. stress, temperature, corrosive environment, radiation levels), and should consider creep, fatigue, thermal stresses, corrosion and changes in material properties with time (e.g. concrete shrinkage).

Structural integrity

6.17.

To prevent deviations from normal operation, and to prevent system failures, careful attention should be paid to the selection of appropriate design codes and materials, and to control of fabrication of components and of construction of the spent fuel storage facility. In order to detect and terminate deviations from normal operational states, specific systems should be provided as determined in the safety case.

Structural integrity

6.18.

The integrity of the spent fuel and the geometries required to maintain subcriticality and heat removal, and the confinement barriers for the spent fuel, should be maintained throughout the lifetime of the facility and should be verified using appropriate methods, including both prospective analysis and ongoing surveillance.

Structural integrity

6.19.

The allowable stresses for given loading conditions should comply with the applicable codes and standards. If no such standards apply, justification should be provided for the allowable stress levels selected.

Structural integrity

6.20.

Structural materials and welding methods should be selected on the basis of accepted codes and standards. Consideration should be given to potential cumulative effects of radiation on materials likely to be subjected to significant radiation fields. In addition, potential thermal effects on material degradation should also be considered.

Structural integrity

6.21.

The materials of items important to safety, including those structures and components in direct contact with the spent fuel, should be compatible with the spent fuel, should be such as to minimize chemical and galvanic reactions, which might degrade the integrity of the spent fuel during its storage, and should not contaminate the spent fuel with substances that might significantly degrade the integrity of the spent fuel during its storage.

Structural integrity

6.22.

Detailed consideration should be given to the effects of the storage environment on the spent fuel and the structures, systems and components important to safety. In particular, the potential for oxidation of exposed uranium dioxide (UO₂) to triuranium octaoxide (U₃O₈), with consequent increase in volume and particulate formation, should be considered. In addition, any effects of changes in the storage environment (e.g. wet to dry or dry to wet) should be assessed.

Structural integrity

6.23.

As determined during the design stage, attaining adequate reliability might necessitate the use of durable construction materials, redundancy of key components, a specific level of reliability of supporting services (e.g. electrical power supply), effective monitoring plans and efficient maintenance programmes (i.e. programmes compatible with normal facility operations).

Structural integrity

6.24.

The construction materials used should allow for easy decontamination of surfaces. The compatibility of decontamination materials with the operating environment should be considered for all operational states and accident conditions. The integrity of systems that are connected to spent fuel storage systems, such as the heat removal system, is also important. Tube failures and leaks in the spent fuel storage system should be prevented, as these could provide a path for chemical species detrimental to either fuel or confinement integrity, such as chloride ions, to enter a spent fuel storage pond.

Structural and mechanical loads

6.25.

A full description of the structural and mechanical aspects of the design of a storage facility should be provided in sufficient detail to justify the basic design. Typical items for consideration should include the following:

Determination of structural and mechanical loads due to the fuel, fuel storage casks and various components of the spent fuel storage facility for operational states and accident conditions;
An evaluation of the foundations of the spent fuel storage facility;
A full structural evaluation of the safety systems of the spent fuel storage facility;
Evaluations of supporting features such as cranes, transfer vehicles and protective buildings.

Structural and mechanical loads

6.26.

Consideration should be given to all situations in which handling mechanisms could malfunction, thereby leaving fuel elements or casks inadequately shielded or irrecoverable. Consideration should also be given to the possibility of casks becoming wedged and immovable within the spent fuel storage facility. In addition to the issue of shielding in such circumstances, consideration should be given to whether handling equipment and systems can enable recovery from such situations or whether they could be damaged by the application of excessive stresses.

Thermal loads and processes

6.27.

In view of the decay heat generated by spent fuel, all thermal loads and processes should be given appropriate consideration in the design. Typical items for consideration should include the following:

Thermally induced stresses;
Internally and externally generated pressures;
Heat transfer requirements;
Evaporation and water make-up requirements;
The effect of temperature on subcriticality.

Time dependent material processes

6.28.

The anticipated lifetime of the storage facility will be a determining factor for aspects such as corrosion, creep, fatigue, shrinkage, radiation induced changes and associated radiation fields. In the design of the storage facility, consideration should be given to the impact of such processes.

Subcriticality

6.29.

In accordance with Requirement 38 of SSR‑4 [4], the design of a spent fuel storage facility is required to ensure an adequate margin of subcriticality under operational states and conditions that are referred to as credible abnormal conditions.

Subcriticality

6.30.

The subcriticality of spent fuel might be ensured or influenced by a number of design factors and precautions. The physical layout and arrangement of the spent fuel storage facility should be designed in such a way as to ensure, through geometrically safe configurations, that subcriticality will be maintained in all operational states and for credible abnormal conditions.

Subcriticality

6.31.

Where spent fuel cannot be maintained subcritical by means of safe geometrical configurations alone, additional means such as fixed neutron absorbers and/or the use of a burnup credit (see Appendix II, paras II.7–II.9) should be applied. If fixed neutron absorbers are used, it should be ensured by means of proper design and fabrication that the absorbers will not become separated or displaced in operational states or in accident conditions. Consideration should also be given to the effects of burnup, ageing, corrosion and handling on the fixed neutron absorbers.

Subcriticality

6.32.

Subcriticality can be influenced by internal and external hazards that have the potential to reconfigure the pre‑existing spent fuel assembly array in such a way as to increase the potential for criticality. Consideration should also be given to routine fuel movements that could bring the fuel being moved into close proximity with stored fuel or in which fuel could be dropped and fall onto stored fuel. For operational states and credible abnormal conditions, the sequences of events leading to such abnormal fuel configurations should be evaluated. The possible consequences of such occurrences should be evaluated using reliable data and verified and validated methodologies. Appropriate mitigating measures should be put in place to ensure that subcriticality will be maintained under all such conditions.

Subcriticality

6.33.

An adequate margin of subcriticality in the effective neutron multiplication factor k_eff that is acceptable to the regulatory body should be maintained for operational states and credible abnormal conditions.⁸ to avoid criticality accidents. For a dry storage facility, the minimum margin should be maintained even in the event of water flooding of the locations where the spent fuel is stored, unless flooding is precluded by location or design. The potential for rearrangement or compaction of fuel pins should also be considered in demonstrating the required subcriticality margin. For a wet storage facility, the minimum margin should be maintained even in the event of water boiling after a loss of cooling (i.e. the storage environment could be more reactive under water vapour conditions than under water) or in case of a water leak.

Subcriticality

6.34.

The most appropriate approach to estimating the required multiplication factors will depend on a number of factors, including the spent fuel properties, as well as the circumstances being addressed (e.g. normal operation or accident conditions). In determining subcriticality, a conservative estimate should be made of the effective neutron multiplication factor, with account taken of the following:

If the initial enrichment of fissile material within a fuel assembly or between fuel assemblies is variable, appropriate consideration of this variability in the modelling should be used. Alternatively, the highest enrichment may be used to provide a conservative characterization of the fuel assembly.
Where uncertainties exist in any data relating to the fuel (e.g. in terms of design, geometries or nuclear data), conservative values for the data should be determined and should be used in all subcriticality calculations. If necessary, a sensitivity analysis should be performed to quantify the effects of such uncertainties.
Any geometric deformations of the fuel and storage equipment that could be caused by any postulated initiating events should be taken into account.
Optimum moderation and reflection should be assumed for operational states and accident conditions to provide a pessimistic assessment of criticality. It should be ensured that the system will remain subcritical for all credible water densities. The highest nuclear reactivity might be reached at some intermediate density, for example, if water in the pool begins to boil owing to failure of the heat removal system or during drying of a cask. Flooding should be assumed in dry storage situations, unless precluded by location or design features.
For certain accident conditions, such as a fuel handling accident, limited credit for soluble boron may be allowed.
The inventory of the spent fuel storage facility should be assumed to be at the maximum capacity of the design.
Credit should not be claimed for neutron absorbing parts or components of the spent fuel storage facility unless they are permanently installed, their neutron absorbing capabilities can be determined and it has been demonstrated that they would not be degraded by any postulated initiating events.
Consideration of reactivity changes of the fuel assembly may be included, although no allowance for the presence of burnable absorbers should be made unless on the basis of a justification acceptable to the regulatory body, which should include consideration of the reduction of neutron absorption capability with burnup. If burnable absorbers are taken into account, the representative fuel should be assumed to correspond to the highest nuclear reactivity.
All fuel should be assumed to be at a burnup and enrichment value that results in maximum nuclear reactivity (i.e. fresh fuel assumption), unless credit for burnup is assumed on the basis of an adequate justification. Such justification should include an appropriate measurement or evaluation that directly or indirectly confirms the calculated values for the content of fissile material or depletion level. For application of burnup credit in long term storage, possible changes in the nuclide composition of the spent fuel with storage time should be taken into account.
Assumptions of neutronic decoupling for different storage areas should be substantiated by appropriate calculations.

Subcriticality

6.35.

The infinite multiplication factor⁹ may be used as a conservative estimate of k_eff.

Subcriticality

6.36.

The determination of subcriticality for other kinds of fuel may involve special considerations. The composition of spent fuel might vary over a large range, and it might not be easy to specify appropriate conservative conditions. For example, boiling water reactor fuel with burnable poison might have increased reactivity due to the burning of poison. Also, uranium–thorium mixed oxide fuel or fuel from research reactors might have very specific properties that need to be considered.

Heat removal

6.37.

Spent fuel storage facilities should be designed with heat removal systems that are capable of reliably cooling the stored spent fuel when the fuel is initially received at the facility. The heat removal capability should be such that the temperature of all spent fuel does not exceed the maximum allowable temperature and that the temperature of other safety related components in the facility should also not exceed their maximum allowable temperatures in normal operation, anticipated operational occurrences and accident conditions, including design basis accidents and, as far as practicable, design extension conditions¹⁰, such as:

Multiple failures leading to the sustained loss of the forced cooling system;
Combinations of failures selected on the basis of probabilistic risk assessments (e.g. combinations of anticipated operational occurrences or postulated accidents with a common cause failure affecting the system designed for mitigating the event of concern).

Heat removal

6.38.

In the design of heat removal systems for a spent fuel storage facility, appropriate provision should be made for maintaining fuel temperatures within acceptable limits during the handling and transfer of spent fuel.

Heat removal

6.39.

The heat removal system should be designed for adequate removal of the heat likely to be generated by the maximum inventory of spent fuel anticipated during operation. In determining the necessary heat removal capability of the facility, the post‑irradiation cooling interval and the burnup of the fuel to be stored should be taken into consideration. Heat removal systems should be designed to include an additional margin of heat removal capability to take account of any processes foreseen to degrade or impair the system over time. In the design of the heat removal system, consideration should also be given to the maximum heat capacity of the facility.

Heat removal

6.40.

In the case of modular facilities such as vaults, the fact that the heat produced from the decay of spent fuel fission products decreases with time can be taken into account in the design. For example, natural cooling might be adequate later in a facility’s lifetime, even if forced cooling is initially necessary. An analysis should be performed to determine how long forced cooling will be necessary, with due consideration given to maintaining operability of the forced cooling system and the potential effects of its failure.

Heat removal

6.41.

The use of redundant and/or diverse heat removal systems may be appropriate, depending on the type of storage system used. The reliability of the heat removal systems should be considered in the design process. The design should include provisions to monitor and ensure the effectiveness of the cooling systems in operational states and accident conditions. In wet storage facilities, monitoring of cooling systems could be done by monitoring the temperature and the level of the water. In dry storage vault facilities, such monitoring could be done by monitoring the temperature and flow rate of the coolant gas. Consideration should be given to the potential for the spent fuel to overheat over an extended period. For such cases, the design of wet storage facilities should include features to enable the use of non‑permanent equipment to provide water for the long term cooling of the spent fuel.

Confinement of radioactive material

6.42.

In the design of spent fuel storage and handling systems, adequate and appropriate measures should be provided for containing radioactive material so as to prevent any uncontrolled release of radionuclides to the environment. The spent fuel cladding should be protected during storage against degradation in operational states and accident conditions and, later, during retrieval of the spent fuel. Confinement should be ensured by at least two independent static barriers. As necessary, and as far as possible, the effectiveness of the spent fuel storage confinement system should be monitored to determine whether corrective action is necessary to maintain safe storage conditions.

Confinement of radioactive material

6.43.

Ventilation and off‑gas systems should be provided where necessary to ensure the collection of airborne radioactive particulate material in operational states and accident conditions. In the design of the air supply system for the facility, consideration should be given to the potential for the presence of corrosive gases such as chlorine or sulphur dioxide in the external environment, which could be detrimental to the integrity of the spent fuel cladding or other safety related components.

Radiation protection

6.44.

The design of the spent fuel storage facility should be such as to avoid high radiation fields on the site and to provide for radiation protection of workers and the public and protection of the environment in accordance with the requirements of national legislation, the requirements established in GSR Part 3 [12] and the recommendations provided in IAEA Safety Standards Series No. NS‑G‑1.13, Radiation Protection Aspects of Design for Nuclear Power Plants [36].

Radiation protection

6.45.

In order to meet these requirements and recommendations in the design of spent fuel handling systems in a storage facility:

Appropriate ventilation, including efficient, appropriately qualified and designed air filtration systems and provision for their periodic checking, should, as necessary, be included in the design to maintain the concentrations of airborne radioactive material and the related exposure of workers and the public at acceptable levels.
Provision should be made for the monitoring of radioactive effluents.
Measures for spent fuel handling should be designed to avoid a buildup of contamination to unacceptable levels and to provide for remedial measures if such a buildup occurs.
Handling of spent fuel and casks should be carried out in an environment in which important parameters (e.g. temperature, concentration of impurities, intensity of radiation) are controlled.
Areas in which spent fuel and casks are to be handled or stored should be provided with suitable radiation monitoring systems for the protection of workers.
The storage facility should not contain any operation room to which access is gained solely through the storage area.
Water monitoring and filtration should be provided for wet storage facilities.

Radiation protection

6.46.

Shielding should be provided to meet the recommendations in NS‑G‑1.13 [36]. To meet these recommendations, the following provisions should be included:

In determining the source term for analysis for shielding design, consideration should be given to the bounding conditions for enrichment, burnup and cooling times for gamma and neutron radiation, the inventory at the maximum design capacity of the spent fuel storage facility, the effects of axial burnup on gamma and neutron sources, and the activation of non‑fuel hardware.
Suitable shielding should be provided for operational states and accident conditions. The design of a wet storage facility should include provisions to prevent unacceptable loss of liquid shielding during accident conditions, such as design features to enable the use of non‑permanent equipment to retain minimum water levels for shielding. In dry storage facilities in which water is used for neutron shielding, alternate neutron shielding should be provided if water could be lost.
Penetrations through shielding barriers (e.g. penetrations associated with cooling systems, penetrations provided for loading and unloading) should be designed to avoid localized high gamma and neutron radiation fields from both the penetration and direct irradiation from the fuel.
In the analysis for shielding design, equipment for handling spent fuel should be assumed to contain the maximum amount of spent fuel.
Handling equipment should be designed to prevent the inadvertent placing or lifting of spent fuel into insufficiently shielded positions.
Consideration should be given to the radiological impact of deposits of activation products.

Layout

6.47.

Design aspects associated with the layout of a spent fuel storage facility are set out in the following:

Handling and storage areas for spent fuel should be secured against unauthorized access and unauthorized removal of fuel.
The area used for storage should not be part of an access route to other operating areas.
Transport routes for handling spent fuel on the facility site and within the facility should be arranged to be as direct and as short as practicable, so as to avoid the need for complex or unnecessary moving and handling operations.
The need to move heavy objects over stored spent fuel and items important to safety should be minimized by the layout.
The layout should be such that all spent fuel handling operations, the storage of spent fuel and the access of authorized personnel are optimized.
The layout should be such as to provide for the decontamination of surfaces of spent fuel elements (removal of deposits of radioactive material) and appropriate maintenance and repair of spent fuel handling equipment and storage casks.
Sufficient space should be provided to permit inspection of spent fuel and inspection and maintenance of components, including spent fuel handling equipment.
The layout should facilitate access to any stored fuel without the need to move or handle other stored fuel.
Division of the storage area into sectors should enable different storage configurations and be such as to facilitate access to any stored fuel and to avoid application of the ‘first in last out’ concept.
Retrieval of spent fuel and spent fuel packages, as well as the possible need for spent fuel encapsulation or conditioning, should be addressed in the layout of the facility.
Sufficient space should be provided to allow for movement of the spent fuel and storage casks and the transfer of these from one item of handling equipment to another.
Sufficient space should be provided for the safe handling of shipping and storage casks. This may be achieved by using a separate cask loading and unloading area or by including a dedicated space within the spent fuel storage facility.
Sufficient space should be provided for the storage and use of the tools and equipment necessary for the repair and testing of storage components. Space for the receipt of other radioactive parts of fuel assemblies may also be necessary.
Appropriate arrangements for confinement of radioactive material and for the safe storage of degraded or failed fuel should be provided.
The layout should provide for an easy exit by personnel in an emergency.
Penetrations should be designed in such a way as to prevent the ingress of foreign material (e.g. rain, inorganic solutions, organic materials) that could reduce subcriticality margins, impair heat transfer or increase corrosion and degradation of the storage facility in ways that might reduce the effectiveness of the main safety functions or prevent inspection or repair.
The floor area on which any transport vehicle with a heavy spent fuel cask might move or be parked should be designed with adequate floor loading margins. Such areas should be clearly marked to avoid overloading a floor area designed to accept a lower floor loading.

Handling

6.48.

Spent fuel handling and transfer equipment and systems include the following:

Fuel handling machines;
Fuel transfer equipment;
Fuel lifting devices;
Fuel assembly dismantling devices;
Handling devices for all operations associated with the transport of casks or inspection of spent fuel or casks;
Provision for the safe handling of degraded or failed fuel or canisters and casks.

Handling

6.49.

Handling equipment should be designed to minimize the probability and consequence of accidents and other incidents, and to minimize the potential for damaging spent fuel, spent fuel assemblies and storage or transport casks. Consideration should be given to the following:

Equipment should not have sharp edges or corners that could damage the surfaces of spent fuel assemblies.
Equipment should be provided with positive latching mechanisms to prevent accidental unlatching of the equipment.
Equipment should be designed to take account of radiation protection aspects and to facilitate maintenance.
Speed limitations should be specified for equipment for moving spent fuel.
Systems should be so designed that spent fuel cannot be dropped in the event of loss of power. Consideration should be given to the consequences of a single failure and, where appropriate, redundant load paths should be provided.
Where it is necessary to ensure that spent fuel assemblies can be readily placed in a safe location, fuel handling equipment should be designed to permit manual operation in an emergency.
Equipment should be designed to ensure that the magnitude and direction of any forces that are applied to spent fuel assemblies are within acceptable limits.
Equipment should be provided with suitable interlocks or physical limitations to prevent dangerous or incompatible operations, such as to prevent movement in some circumstances (e.g. to avoid incorrect placement of spent fuel or, in the case of wet storage, where the equipment is very close to the pool walls), and also to prevent the lifting of spent fuel assemblies or other components over spent fuel and to heights greater than necessary, the accidental release of loads and the application of incorrect forces.
Controls and tools should be ergonomically designed and user friendly.
The possibility for tools to be mistaken should be avoided by design.
Environmental conditions (e.g. noise, brightness, humidity, temperature) in working areas should provide for optimal conditions of work.

Handling

6.50.

Where operating personnel will need information on the non-visible state of the equipment or components in order to verify the safety of a planned operation, as stated in the safety case, provision should be made in the design for effectively transmitting such information to the operating personnel, through appropriately located indicator systems or by alternative means.

Handling

6.51.

In the design of spent fuel handling equipment, provision should be made for the related use of portable manual tools or portable power operated tools, provided that the planned use of such tools is consistent with the design objectives and that such use does not compromise the safety of the spent fuel handling operations.

Handling

6.52.

To minimize the probability of an accidental drop of any load, equipment for transferring spent fuel to a spent fuel storage facility should be designed to ensure that the equipment is capable of withstanding conditions of normal operation, anticipated operational occurrences and accident conditions. Equipment should be designed, and operational limits and conditions should be established such that, in the event of an accidental drop of a load, the confinement system or the shielding of fuel casks will not be damaged in a manner that could result in unacceptable radiation exposure of workers or the public. In addition, the design and the operational limits and conditions should be such that an accidental drop will neither prevent fuel retrieval nor cause significant damage to the spent fuel or spent fuel storage facility.

Handling

6.53.

Assumptions made that are critical to operational safety should be documented at the design stage to facilitate the subsequent development of operating procedures. Justification should be provided, through detailed analyses using appropriate techniques, in support of these assumptions and conclusions concerning the operational safety of the spent fuel storage facility.

Handling

6.54.

In order to ensure safe operation, spent fuel handling and storage systems should include the following:

Measures to limit radioactive releases and radiation exposure of workers and the public in operational states and accident conditions in accordance with the principle of optimization of protection established in SF‑1 [11] and to meet the limits established by the regulatory body, with particular consideration being given to the use of remote techniques in areas of high radiation fields in order to reduce occupational exposure;
Measures to prevent anticipated operational occurrences and design basis accidents from developing into severe accidents;
Provision for ease of operation and maintenance of essential equipment (in particular, items important to safety);
Provision for ready retrieval of spent fuel from storage through equipment and procedures.

Handling

6.55.

In the design and assessment of lifting and handling equipment, consideration should be given to categories of dropped loads such as casks or lids, spent fuel and spent fuel storage racks.

Handling

6.56.

The dropping of spent fuel during transfer from the cask to the storage rack (or vice versa in the case of cask loading for dry storage) could result in impacts that should be avoided, such as:

Partial defects in the spent fuel cladding, leading to leaks and resulting in contamination of the pool by fission products;
Deformation (e.g. bending) or damage of the spent fuel, which could lead to difficulties in its subsequent handling;
An increased potential for a criticality accident if spent fuel with low burnup were to impact alongside a storage basket or other spent fuel in the storage racks;
Radiation exposure of workers due to the release of fission products.

Ventilation systems

6.57.

Ventilation systems for the spent fuel storage facility should be designed and operated to maintain a safe and comfortable working environment during normal operation and to limit the potential for release of radioactive material in operational states and accident conditions, including design basis accidents and design extension conditions. In the design, consideration should be given to the potential for pressure buildup in the facility during an accident and the provision of a means to prevent concentration levels of hydrogen gas that could give rise to disruptive explosions.

Ventilation systems

6.58.

Ventilation systems should be designed in such a way as to control the accumulation of flammable or explosive gases (e.g. hydrogen gas formed by radiolysis). Consideration should also be given to the potential for the drawing in of hazardous gases from external sources.

Ventilation systems

6.59.

Ventilation systems should be designed to satisfy the recommendations provided in IAEA Safety Standards Series No. SSG‑64, Protection against Internal Hazards in the Design of Nuclear Power Plants [37]. The operation of ventilation systems should be compatible with requirements for fire protection.

Communications

6.60.

Adequate and diverse means of communication should be included in the design to meet the requirements for operation of the spent fuel storage facility and for emergency preparedness and response.

Instrumentation and control

6.61.

Instrumentation should be provided to detect conditions that could result in a loss of residual heat removal capability and excessive radiation levels. This instrumentation should provide appropriate alarms and indications at a protected location that would result in timely initiation of corrective actions by local operating personnel and operating personnel in main control rooms, and automatic initiation of protective actions when needed. The indicating range and design of the specified instrumentation should allow for monitoring of conditions during accidents, including design basis accidents and design extension conditions considered in the safety case. When practicable, control and protection functions should be designed to be mutually independent and not compromised by any corrective actions. Where independence is not feasible, detailed justification should be provided for the use of shared and interrelated systems. Account should be taken of ergonomic factors in the design of alarms and indications to the operating personnel. Control and monitoring equipment should be calibrated for its intended use.

Fire protection

6.62.

The operation of the fuel handling and storage areas should be carried out in accordance with the fire protection recommendations provided in SSG‑64 [37]. Fire protection measures should be implemented in such a way as to limit risks to personnel and the risk of damage to items important to safety, spent fuel storage areas, spent fuel handling systems and support systems.

Fire protection

6.63.

Fire protection systems of appropriate capacity and capability should be provided.

Fire protection

6.64.

Fire protection measures should include the limitation and control of amounts of combustible materials in fuel handling and storage areas (e.g. combustible packing materials, piping systems carrying combustible materials). The spent fuel storage area should be operated in such a way as to ensure that the use of fire suppression measures cannot cause unintended criticality.

Radioactive waste management

6.65.

The systems of the spent fuel storage facility should be designed and operated so as:

To avoid or minimize the potential for generating radioactive waste;
To provide safe and adequate means for handling radioactive waste.

Radioactive waste management

6.66.

The methods employed for processing radioactive waste should be compatible with the requirements of the receiving waste facility.

Lighting

6.67.

Provision should be made for adequate and reliable lighting in support of normal operation, anticipated operational occurrences and accident conditions and to facilitate inspection of spent fuel storage areas.

Lighting

6.68.

For wet storage in pools, the pool area should be provided with the necessary lighting equipment, including underwater lighting near work areas and provision for the replacement of underwater lamps.

Lighting

6.69.

Materials used in underwater lighting should be compatible with the environment in which they are used and, in particular, should not undergo unacceptable corrosion or lead to any unacceptable contamination of the pool water.

Monitoring

6.70.

Area monitoring should include measurements of radiation dose rates and airborne radionuclides. In controlled areas, fixed, continuously operating instruments with local alarms and unambiguous readouts should be installed to provide information on radiation dose rates. Such instruments should have characteristics and ranges that are sufficient to cover potential radiation levels, during normal operation, anticipated operational occurrences and accident conditions, including design basis accidents and design extension conditions.

Monitoring

6.71.

Instrumentation for detecting external contamination on workers should be provided at exits from locations where there is a potential for such contamination. Instruments for area monitoring and personnel monitoring should be demonstrated to be fit for purpose and should comply with appropriate manufacturing standards. The possible use of this instrumentation should be considered when developing provisions for the decontamination of equipment, components and personnel.

Monitoring

6.72.

For wet storage facilities, the water level in the spent fuel storage pool should be monitored and provisions to identify the potential for water leakage during both operational states and accident conditions should be provided.

Emergency preparedness

6.73.

Hazards should be identified and potential consequences of an emergency should be assessed to provide a basis for establishing on‑site as well as off‑site emergency arrangements associated with the storage of spent fuel. As such, the hazard assessment should be provided to off‑site authorities to inform their emergency planning, either by the operating organization or the regulatory body. A graded approach to emergency preparedness and response will need to be applied, in accordance with the results of the hazard assessment in line with GSR Part 7 [22] and GS‑G‑2.1 [25].

Emergency preparedness

6.73A.

While the responsibility for on-site emergency preparedness and response remains with the operating organization (see para. 3.28), the responsibility for off‑site emergency arrangements, including the development and implementation of emergency plans and procedures and the provision of emergency services, will be with the relevant off‑site response organizations [22, 25]. On‑site emergency arrangements should include, but are not limited to:

Procuring and periodic testing of equipment to mitigate the consequences of accidents;
Periodic training for personnel and procedures to deploy the mitigation equipment;
Lists of persons and organizations to be alerted in the event of an emergency;
Procedures and other arrangements to implement mitigatory actions, including operating procedures in abnormal conditions and in the event of an emergency;
Procedures and other arrangements to ensure effective and uninterrupted communication in the event of an emergency;
Procedures and other arrangements to ensure the safety of personnel in the event of an emergency;
Procedures and other arrangements for the classification of emergencies and for the use of operational criteria in the event of an emergency;
Periodic exercises to test emergency arrangements in place, including arrangements for coordination with off‑site response organizations;
Periodic review and, as appropriate, updates to the emergency plan and procedures on the basis of lessons identified from exercises, operating experience and relevant changes to assessed hazards;
Design and construction of emergency response facilities in accordance with the hazard assessment.

Emergency preparedness

6.74.

On‑site emergency procedures should be well documented, made available to the personnel concerned and kept up to date.

Support systems

6.75.

In addition to the design features of a spent fuel storage facility considered above, a number of other support systems may be necessary to ensure the operation and safety of spent fuel storage facilities (e.g. an emergency power supply). It should be ensured that such support systems are available.

Support systems

6.76.

Where the safety of spent fuel storage is dependent upon the supply of utilities (e.g. systems for compressed air or water), adequate sources should be reliably available.

Support systems

Requirement 18 of GSR Part 5 [1]: Construction and commissioning of the facilities

General

6.77.

Commissioning involves a logical progression of tasks intended to demonstrate the correct functioning of features specifically incorporated into the design to provide for safe storage of spent fuel. In addition, in commissioning, operating procedures are verified and the readiness of staff to operate the spent fuel storage facility is demonstrated. The operating procedures should cover normal operation, anticipated operational occurrences and accident conditions.

General

6.78.

The basis for commissioning should be established at an early stage in the design process as an intrinsic part of the project to facilitate its effective implementation. Commissioning plans should be reviewed and, where appropriate, made subject to approval by the regulatory body. The responsibilities of the various groups typically involved in commissioning should be clearly established. Arrangements should be established to cover:

Specification of tests to be carried out (test objectives, safety criteria to be met);
Provision and approval of documentation;
Responsibilities;
Safety during testing;
Control of test work;
Recording and review of test results;
Interaction with the regulatory body;
Management of equipment providing temporary commissioning aids and its removal before commencement of operation (and after completion of tests).

General

6.79.

Arrangements for testing should include the following:

Regulatory requirements;
Progression through the stages of commissioning;
Reporting of results and approval for operation;
Retention of records.

General

6.80.

For modular storage systems, most of the commissioning will have been completed on the loading of the first storage module. Some of the commissioning processes might become part of regular operation as new modules are brought into service. However, a change in module design may require some of the commissioning steps to be repeated for the new design.

General

6.81.

Some commissioning steps might continue during the operation of a spent fuel storage facility (e.g. commissioning of new spent fuel storage casks or dual purpose casks or commissioning of new equipment necessary for new designs of spent fuel). Commissioning activities during the operation of the facility should be anticipated to the extent possible already during the design stage (e.g. the need for installation of additional heat removal systems).

Commissioning stages

6.82.

Commissioning will usually be completed in several stages:

Completion of construction;
Equipment testing;
Demonstration of performance;
Non-active commissioning;
Active commissioning.

Commissioning stages

6.83.

In the stage of completion of construction, the spent fuel storage facility should undergo detailed physical inspection to confirm compliance with the detailed design. Factors such as physical dimensions and levels of background radiation should be determined. A systematic check against design drawings and project documentation should be carried out to establish the as‑built status of the facility. (In addition to providing information to facilitate operation of the facility, this check can also be important when considering possible future modifications and ultimate decommissioning of the facility.)

Commissioning stages

6.84.

In the equipment testing stage, the equipment and systems of the spent fuel storage facility should be energized and aspects such as controls, directions of rotation, directions of flow, currents and interlocks should be tested. Activities such as load testing of casks and spent fuel assembly lifting equipment should also be carried out, and the safe control of equipment should be demonstrated in these tests. If necessary, it should also be demonstrated that the physical interaction between items of equipment is limited.

Commissioning stages

6.85.

In the performance demonstration stage, after individual items of equipment have been tested, a range of tests should be performed to demonstrate the safe interaction of all equipment and the overall operational capability and capacity of the spent fuel storage facility. At this stage, the safety and effectiveness of all instructions and procedures should be demonstrated. This should include demonstration of satisfactory training of operating personnel for both normal operation and anticipated operational occurrences. The ability of personnel to conduct maintenance work safely and effectively should also be demonstrated.

Commissioning stages

6.86.

The non‑active commissioning stage should provide a formal demonstration that the facility personnel, equipment and procedures function in the manner intended, especially those identified in the safety case as important to the safety of facility operation. All safety features that can be tested without the presence of spent fuel should be checked before the spent fuel storage facility is put into operation.

Commissioning stages

6.87.

Once non‑active commissioning has been satisfactorily accomplished, the active commissioning stage is commenced with the introduction of radioactive material into the spent fuel storage facility. All tests and any resulting amendments should be completed before the introduction of radioactive material. The introduction of radioactive material effectively marks the start of the operation of the facility and, hence, from this stage the relevant safety requirements for facility operation apply [1, 4, 7]. Active commissioning should involve a range of tests to demonstrate that the design criteria for radiation protection have been met.

Commissioning stages

6.88.

Upon completion of commissioning, a final commissioning report should be prepared. This should detail all testing carried out and should provide evidence of its successful completion. The report should demonstrate to the regulatory body that its requirements have been met and may provide the basis for the subsequent licensing of the spent fuel storage facility for full operation. In addition, any changes to the facility or to procedures implemented during commissioning should be documented in an appropriate way in the final commissioning report.

Commissioning stages

Requirement 9 of GSR Part 5 [1]: Characterization and classification of radioactive waste

General

6.89.

Spent fuel storage facilities are required to be operated in accordance with written procedures prepared by the operating organization. These documents and their updates should be prepared in cooperation with the organizations responsible for the design of the spent fuel storage facility. However, the operating organization is responsible for ensuring that the procedures are prepared, reviewed, approved and issued appropriately. These procedures should take into account human factors associated with handling operations and should, as a minimum, be such as to ensure compliance with the operational limits and conditions for the spent fuel storage facility and, more generally, with the safety assessment.

General

6.90.

Instructions and procedures should be prepared for normal operation of the spent fuel storage facility, anticipated operational occurrences and accident conditions, including design basis accidents and design extension conditions. Instructions and procedures should be prepared so that the designated responsible person can readily perform each action in the proper sequence. Responsibilities for approval of any deviations from operating procedures that may be necessary for operational reasons should be clearly specified.

General

6.91.

Adequate arrangements should be made for the review and approval of operating procedures, the systematic evaluation of operating experience, including that of other facilities, and the taking of corrective actions in a timely and appropriate manner to prevent and counteract developments adverse to safety. Provision should be made for controlling the distribution of operating procedures, in order to guarantee that operating personnel have access to only the latest approved edition.

General

6.92.

The maintenance and modification of any item of equipment, process or document of the spent fuel storage facility should be subject to specified procedures. These procedures should be subject to authorization before they are implemented. The procedures should describe the categorization of the modification in accordance with its safety significance. Depending on the safety categorization, each modification will be subject to varying levels of review and approval by management of the facility and the regulatory body.

General

6.93.

The maintenance or modification of any item of equipment should be appropriately recorded and documented together with its commissioning test results. The documents should be revised immediately after completion of the maintenance or modification.

Operational aspects

6.94.

The operating organization should ensure that operating procedures relating to the maintaining of subcriticality are subjected to rigorous review and compared with the safety requirements of the design. This might include confirmatory analysis and review by the regulatory body. Some of the factors that should be considered in this review include:

The types of spent fuel to be stored;
Spent fuel geometries necessary to ensure subcriticality;
Spent fuel container types (if used);
Handling operations for the spent fuel;
The potential for abnormal operation;
Spent fuel parameters (e.g. initial enrichment, final enrichment, burnup);
Dependence of subcriticality on neutron absorbers.

Operational aspects

6.95.

Cladding failure can result in the release of isotopes such as ⁸⁵Kr, ¹³⁴Cs and ¹³⁷Cs, which are characteristic fission products detected following cladding failures in spent fuel that has been cooled for long periods. Cladding failure might be more probable when the spent fuel and spent fuel cladding are subjected to high temperatures, and when chemical conditions in the medium surrounding the spent fuel promote cladding corrosion. The operating organization should ensure that adequate monitoring of environmental conditions within the facility (e.g. composition of the pool water and atmosphere in the storage area and moisture or water on spent fuel cladding) is undertaken to prevent and provide notice of such undesirable conditions. Procedures should be provided for detecting and dealing with degraded and failed fuel.

Operational aspects

6.96.

In addition, the operating organization should ensure that procedures exist for the receipt, handling and storage of spent fuel with failed cladding, and that these procedures identify the safety measures to be taken for managing these situations or should ensure that such fuel is not accepted at the spent fuel storage facility. In cases where such fuel is accepted, in addition to confinement considerations there might be implications for criticality, which should be fully assessed. Where appropriate, the receipt, handling and storage of such fuel should be made subject to specific procedures.

Operational aspects

6.97.

Operating procedures should be developed for confinement systems in the spent fuel storage facility (e.g. closure seals on storage casks and canisters, and ventilation and filtration systems) to provide for their monitoring. The monitoring should be such that the operating organization will be able to determine when corrective actions are necessary to maintain safe storage conditions.

Operational aspects

6.98.

There are various safety related events that should be taken into account in the development of normal and emergency operating procedures and accident management programmes. Although many of these events would be addressed either as anticipated operational occurrences or as design basis accidents, some of these events, or some combinations of events, could also lead to severe accidents, which might be considered within design extension conditions while others might go beyond these. While the probability of such events, or combinations of events, occurring is very low, operating procedures and accident management programmes should be prepared by the operating organization. Events to be considered in the preparation of operating procedures and accident management programmes include the following:

Crane failure with a water filled and loaded cask, suspended outside the pool;
Loss of safety related facility process systems such as supplies of electricity, process water, compressed air and ventilation;
Explosions due to the buildup of radiolytic gases;
Fires leading to the damage of items important to safety (to reduce the risk of fire, the amount of combustible material or waste should be controlled, as should be the amount of other flammable materials, see para. 6.64);
Extreme weather conditions, which could alter operating characteristics or impair pool or cask heat removal systems;
Other natural events such as earthquakes or extreme meteorological events;
External human induced events (e.g. airplane crashes)¹¹;
Failure of access control systems leading to inadvertent access that could compromise safety¹².

Operational aspects

6.99.

In addition to providing operating procedures for normal operation and emergency operating procedures as described above, the operating organization should also develop an on‑site emergency plan in accordance with the requirements established in GSR Part 7 [22] (see para. 3.28 of this Safety Guide).

Operational aspects

6.100.

Operating experience and events at the facility and reported by operating organizations of similar facilities should be collected, screened and analysed in a systematic way. Conclusions should be drawn and implemented by means of an appropriate feedback procedure. Any new standards, regulations or regulatory guidance should also be reviewed to check their applicability for safety at the facility.

Operational aspects

6.101.

The integrity of stored spent fuel should be monitored during the operation of a spent fuel storage facility. When spent fuel is stored in sealed casks, the means for accounting for and control of nuclear material or for verifying the related sealing operations will be available. Such means should not impair the integrity of the spent fuel.

Operational aspects

6.102.

Operational limits and conditions for a spent fuel storage facility should be developed on the basis of the following:

Design specifications and operating parameters and the results of commissioning tests;
The sensitivity of items important to safety and the consequences of events following the failure of items, the occurrence of specific events or variations in operating parameters;
The accuracy and calibration of instrumentation equipment for measuring safety related operating parameters;
Consideration of the technical specifications for each item important to safety and the need to ensure that such items continue to function in the event of any specified fault occurring or recurring;
The need for items important to safety to be available to ensure safety in operational states including maintenance;
Specification of the equipment that should be available to enable a full and proper response to postulated initiating events or design basis accidents;
The minimum staffing levels that need to be available to operate the spent fuel storage facility safely.

Operational aspects

6.103.

Operational limits and conditions form an important part of the basis on which operation is authorized and as such should be incorporated into the technical and administrative arrangements that are binding on the operating organization and operating personnel. Operational limits and conditions for spent fuel storage facilities, which result from the need to meet legal and regulatory requirements, should be developed by the operating organization and should be subject to approval by the regulatory body as part of the licence conditions. The operating organization might set an administrative margin as an operational target to remain within the approved limits and conditions.

Operational aspects

6.104.

The aim of operational limits and conditions should be to manage and control the hazards associated with the facility. Operational limits and conditions should be directed towards:

Preventing situations that might lead to the unplanned exposure of workers and the public to radiation;
Mitigating the consequences of any such events, if they were to occur.

Operational aspects

6.105.

Personnel directly responsible for the operation of the spent fuel storage facility should be thoroughly familiar with the facility’s operating procedures and the operational limits and conditions to ensure compliance with their provisions. Systems and procedures should be developed in accordance with the approved management system and operating personnel should be able to demonstrate compliance with the operational limits and conditions.

Operational aspects

6.106.

Operational limits and conditions should be kept under review and may also have to be revised as necessary in accordance with the national regulatory framework for the following reasons:

In the light of operating experience;
Following modifications made to the spent fuel storage facility and the type of spent fuel;
As part of the process of periodically reviewing the safety case (including as part of periodic safety review) for the spent fuel storage facility;
If there are changes in legal or regulatory conditions.

Maintenance, inspection and testing

6.107.

A management system (see also Section 4) covering operation and maintenance, and including approved procedures, should be established for controlling the following:

Maintenance and inspection of the lifting attachments on the casks and of the lifting apparatus (e.g. slings, beams, chains, hooks);
Maintenance of cranes and spent fuel grabs at the facility;
Periodic load testing of cranes and other attachments;
Maintenance, inspection and testing of other safety related equipment.

Maintenance, inspection and testing

6.108.

Operation of a spent fuel storage facility should include an appropriate programme of maintenance, inspection and testing of items important to safety (i.e. structures, systems and components). Safe access should be provided to all structures, systems and components and areas requiring periodic maintenance, inspection and testing. Such access should be adequate for the safe operation of all necessary tools and equipment and for the installation of spare parts.

Maintenance, inspection and testing

6.109.

Before the operation of any spent fuel storage facility commences, the operating organization should prepare a programme for maintenance, inspection and testing. In the programme, starting dates for all inspections should be specified and these should be re‑evaluated in the light of results from commissioning tests. The safety case for the spent fuel storage facility will form a basis for preparation of the programme in terms of the items (i.e. structures, systems and components) that should be included and the periodicity of planned activities for each item.

Maintenance, inspection and testing

6.110.

Provision should be made for maintenance of hot cell components, if a hot cell exists. This maintenance work can be done either in the cell or externally, whatever the preferred option might be.

Maintenance, inspection and testing

6.111.

The programme of periodic maintenance, inspection and testing should be subject to periodic review, with account taken of operating experience. All such activities should be covered in an integrated manner by the management system, with account taken of manufacturers’ recommendations.

Maintenance, inspection and testing

6.112.

The standard and frequency of activities for periodic maintenance, inspection and tests should be such that the level of reliability and effectiveness is ensured and remains in accordance with the design assumptions and intent so that a consistently high level of safety is maintained throughout the lifetime of the spent fuel storage facility.

Maintenance, inspection and testing

6.113.

Equally, the reliability and effectiveness of any component should not be significantly affected by the frequency of testing, which might result in premature wear and failure or induced maintenance errors, or which could cause unavailability to an unacceptable degree if the component is inoperative during maintenance and testing.

Maintenance, inspection and testing

6.114.

If maintenance, inspection or testing of the spent fuel storage facility can be carried out only while certain equipment is in a shutdown state, the maintenance schedule should be drawn up accordingly.

Maintenance, inspection and testing

6.115.

The maintenance, inspection and testing programme should take into account the structures, systems and components that are affected by the operational limits and conditions, as well as any regulatory requirements. Examples of structures, systems and components that might be included in a maintenance, inspection and testing programme are provided in Table 2.

Maintenance, inspection and testing

6.116.

Suitably qualified and experienced operating personnel should be deployed in the approval and implementation of the maintenance, inspection and testing programme and in the approval of associated working procedures and acceptance criteria.

Operational radiation protection

6.117.

An operational radiation protection programme should be put in place that ensures that areas of the facility are designated according to the radiation levels and that access control is in place in accordance with the level of designation. The operational radiation protection programme should cover the monitoring of radiation levels in the facility and should include provision to ensure that personnel working in the facility are provided with appropriate dosimetry. A programme of work planning should also be put in place to ensure that radiation exposures are kept as low as reasonably achievable.

Characterization and acceptance of spent nuclear fuel

Requirement 12 of GSR Part 5 [1]: Radioactive waste acceptance criteria

Characterization and acceptance of spent nuclear fuel

6.118.

Acceptance criteria should be developed for the spent fuel storage facility and the spent fuel, with account taken of all relevant operational limits and conditions and future demands for reprocessing or disposal, including retrieval of the spent fuel. Before spent fuel is transferred to a storage facility, acceptance should be given by the operating organization of the facility and the regulatory body. Contingency plans should be developed and made available to cover how to deal safely with spent fuel that does not comply with acceptance criteria.

Characterization and acceptance of spent nuclear fuel

6.119.

The operating organization of a spent fuel storage facility should be given detailed information concerning the characteristics of the spent fuel received for storage. This information should be supplied by the nuclear facility that generated the spent fuel (i.e. nuclear power plant or research reactor). The minimum information that should be provided is the following:

Design of the fuel, including scale drawings;
Construction materials, the radionuclide inventory, including the initial masses of the fissile content, the burnup and the cooling time of the fuel;
Fuel identification numbers (e.g. serial numbers on fuel assemblies);
Fuel history (e.g. burnup, reactor power rating during irradiation, decay heat, dates of loading and discharge from the reactor);
Details of conditions that could affect fuel handling or storage (e.g. damage to fuel cladding or structural damage);
Confirmation that the fuel can be correctly handled upon receipt at the spent fuel storage facility;
Specific instructions for storage (e.g. for degraded or failed fuel);
Surface contamination level and dose rate for the fuel assemblies.

Characterization and acceptance of spent nuclear fuel

6.120.

Upon receipt, spent fuel casks should be checked to determine gamma and neutron radiation levels, leakage and surface contamination and to ensure that the casks are consistent with the accompanying documentation. Characterization of the spent fuel, for example by means of process control and process monitoring, should be applied as part of the management system for the facility.

Characterization and acceptance of spent nuclear fuel

6.121.

In addition, information concerning the fuel transport cask should also be transmitted by the consignor of the spent fuel to the operating organization of the spent fuel storage facility. This information should include the following:

Type of cask and appropriate information on its design, and the arrangement of fuel and internal components inside the cask cavity;
Radiological survey data of the cask before shipment;
Cask identification (e.g. serial number) and certification of compliance with current transport regulations [19];
Requirements and procedures for cask handling and sealing;
Results of the most recent inspection of the cask.

Characterization and acceptance of spent nuclear fuel

6.122.

In cask handling, consideration should be given to carrying out the following operations to ensure safety:

Before a cask is loaded with spent fuel: decontamination, as required.
In loading and unloading of a cask, under both wet and dry conditions: sampling of the internal gas before the closure lid is removed and examination of the spent fuel, as appropriate.
After a cask has been emptied: decontamination, as required, and routine cask maintenance and recertification operations.

Characterization and acceptance of spent nuclear fuel

6.123.

For facilities receiving spent fuel from a number of sites, the operating organization of the spent fuel storage facility should ensure that each consignor provides data on the characteristics of the spent fuel in a clearly understandable form that allows the operating organization to demonstrate that subcritical conditions will be maintained in the handling and storage of the spent fuel. The operating organization should also ensure that the data provided are supported by an approved management system and have been verified, as appropriate.

Characterization and acceptance of spent nuclear fuel

6.124.

Loss of confinement has the potential for both exposing workers to radiation and releasing radioactive material to the environment. Mechanisms by which loss of confinement might occur should be understood by the operating organization and its personnel and should be addressed, as appropriate, in operating procedures.

Fuel integrity

6.125.

The integrity of spent fuel might become degraded and lead to a release of radioactive material to the storage facility environment. There are a number of causes for the degradation of fuel, including:

Manufacturing defects, such as defects due to incomplete welds or leaking end plugs;
Embrittlement of the cladding material due to interaction with hydrogen or to high irradiation;
General corrosion of the cladding as a result of improper chemical composition of the cooling water;
Mechanical damage, for example as a consequence of stress corrosion or handling accidents;
Unrevealed failures that arose during irradiation in the reactor;
Loss of cooling or overheating in the reactor core resulting in damage to the fuel.

Fuel integrity

6.126.

Usually, spent fuel with decreased integrity should be canned to maintain the quality of the storage environment and/or to satisfy licensing requirements. Sealable casks or containers of approved design should be made readily available for the canning of leaking or damaged fuel assemblies.

Fuel integrity

6.127.

Spent fuel assemblies that have become damaged as a result of mechanical events should be kept separate from intact fuel, and appropriate monitoring should be provided to detect any failure of the outer confinement. Consideration should be given to technical contingency arrangements with a high degree of reliability for dealing with spent fuel that is not retrievable by normal means or that cannot be transported easily.

Fuel integrity

6.128.

For storage of spent fuel that has been characterized as degraded or failed, consideration should be given in the design to the condition of the fuel. This might include additional engineered methods for the safe handling of damaged fuel during loading and unloading (e.g. instrument tube tie rods for assemblies where stress corrosion cracking of the top nozzle is of concern), the canning of damaged fuel assemblies to maintain spent fuel configuration and to ensure criticality control, and additional measures to ensure the robustness of confinement since, the primary physical barrier of the confinement system for degraded fuel (i.e. the spent fuel cladding) cannot be relied upon for control of the spent fuel material. Stored degraded spent fuel should be monitored, and to carry out monitoring appropriately, the following should be ensured:

Appropriate design of the storage in order to facilitate monitoring;
Monitoring of the efficiency of the confinement as close as possible to each physical confinement barrier;
Periodic checking of the state of the stored spent fuel (e.g. by sampling, by destructive testing, by placing corrosion test pieces in the storage location, by using reference objects).

Record of documents

6.129.

Operational data of a spent fuel storage facility should be collected and maintained in accordance with the recommendations relating to the management system provided in Section 4.

Record of documents

6.130.

Records of maintenance, inspection and testing should be retained, in order to provide a basis on which to review and justify the programme of maintenance, inspection and testing, and should be made subject to periodic examination to establish whether structures, systems and components have the required reliability.

Record of documents

6.131.

Since the storage time could span more than one human generation, transfer of information from one generation to the next is important. Therefore, accurate records of all relevant information should be maintained. This should include updated information on the spent fuel storage facility itself and on the stored spent fuel, and also supporting data such as monitoring results and records of unplanned events.

Record of documents

6.132.

These records should be duplicated and stored in separate locations. It should be ensured that the information is stored on media that remain accessible during and after the envisaged storage period.

Retrieval of spent fuel

6.133.

The storage facility should be operated in such a way as to allow retrieval of spent fuel or spent fuel packages at the end of the anticipated storage period and at the end of the lifetime of the storage facility.

Retrieval of spent fuel

6.134.

If spent fuel or a spent fuel package cannot be retrieved from storage with normal operating procedures, special operating procedures should be developed to ensure safe retrieval of spent fuel or the spent fuel package.

Retrieval of spent fuel

6.135.

A spent fuel storage facility should be considered to be an operating facility until all the spent fuel or spent fuel packages have been removed.

Transport after storage

6.136.

After storage, and before subsequent transport, the integrity of the spent fuel and the storage and/or transport casks and the associated documentation should be examined. The following issues should be addressed:

Ownership and responsibility for the safe retention of records;
The inspection and surveillance regime applied;
Control of the storage environment;
Nuclear safety issues, such as any degradation of the spent fuel itself, of the spent fuel support structure and of the neutron shielding materials.

Transport after storage

6.137.

The safety functions of the storage and/or transport casks should be assessed periodically to demonstrate compliance with current safety standards and the approval requirements and conditions of the transport licence [19]. Possible degradation of casks should be assessed and consideration should be given to the following:

Spent fuel and fuel support structure;
The confinement system: seals and restraining systems such as lid bolts;
Packaging components: corrosion effects and radiation effects;
Impact limiters: compatibility of the attachment and performance;
Shielding materials: changes in density and composition;
Design features incorporated to ensure subcriticality;
Conventional safety issues, by means of periodic inspection of handling equipment.