SSG-24 (Rev. 1) Safety in the Utilization and Modification of Research Reactors

Sekce Odstavec Text
Main 1.1. Requirements for the safety of research reactors, with particular emphasis on their design and operation, are established in IAEA Safety Standards Series No. SSR‑3, Safety of Research Reactors [1]. This Safety Guide provides recommendations on the utilization and modification of research reactors. This Safety Guide was developed in parallel with several other Safety Guides on the safety of research reactors, as follows:

  • IAEA Safety Standards Series No. SSG‑20 (Rev. 1), Safety Assessment for Research Reactors and Preparation of the Safety Analysis Report [2];

  • IAEA Safety Standards Series No. SSG‑80, Commissioning of Research Reactors [3];

  • IAEA Safety Standards Series No. SSG‑81, Maintenance, Periodic Testing and Inspection of Research Reactors [4];

  • IAEA Safety Standards Series No. SSG‑82, Core Management and Fuel Handling for Research Reactors [5];

  • IAEA Safety Standards Series No. SSG‑83, Operational Limits and Conditions and Operating Procedures for Research Reactors [6];

  • IAEA Safety Standards Series No. SSG‑84, The Operating Organization and the Recruitment, Training and Qualification of Personnel for Research Reactors [7];

  • IAEA Safety Standards Series No. SSG‑85, Radiation Protection and Radioactive Waste Management in the Design and Operation of Research Reactors [8];

  • IAEA Safety Standards Series No. SSG‑10 (Rev. 1), Ageing Management for Research Reactors [9];

  • IAEA Safety Standards Series No. SSG‑37 (Rev. 1), Instrumentation and Control Systems and Software Important to Safety for Research Reactors [10];

  • IAEA Safety Standards Series No. SSG‑22 (Rev. 1), Use of a Graded Approach in the Application of the Safety Requirements for Research Reactors [11].

Main 1.2. The terms used in this Safety Guide are to be understood as defined and explained in the IAEA Safety Glossary [12].
Main 1.3. This Safety Guide supersedes IAEA Safety Standards Series No. SSG‑24, Safety in the Utilization and Modification of Research Reactors1.
Main 1.4. The objective of this Safety Guide is to provide recommendations regarding the utilization and modification of research reactors to meet the relevant requirements of SSR‑3 [1].
Main 1.5. The recommendations provided in this Safety Guide are intended for operating organizations of research reactors and regulatory bodies, and also for external users of research reactors (i.e. experimenters), technical support organizations and other persons involved in utilization and modification projects.
Main 1.6. This Safety Guide is primarily intended for use for heterogeneous, thermal spectrum research reactors having a power rating of up to several tens of megawatts. Research reactors of higher power, specialized reactors (e.g. homogeneous reactors, fast spectrum reactors) and reactors having specialized facilities (e.g. hot or cold neutron sources, high pressure and high temperature loops) may need additional guidance. For such research reactors, the recommendations provided in IAEA Safety Standards Series No. SSG‑71, Modifications to Nuclear Power Plants [13], might be more suitable.
Main 1.7. Research reactors with low hazard potential having a power rating of up to several tens of kilowatts, and critical assemblies and subcritical assemblies might need less comprehensive modification and utilization programmes than those outlined here. While all recommendations in this Safety Guide are to be considered, some might not be applicable to those research reactors with low hazard potential (see paras 2.15–2.17 and Requirement 12 of SSR‑3 [1], and SSG‑22 (Rev. 1) [11]). However, in all cases, the preparation and implementation of a project for utilization or modification should follow the logical sequence outlined in this Safety Guide. In small projects, the individual stages may be very simple but none of the stages should be omitted.
Main 1.8. In this Safety Guide, subcritical assemblies are mentioned separately only if a specific recommendation is not relevant for, or is applicable only to, subcritical assemblies.
Main 1.9. This Safety Guide does not cover experiments in prototype power reactors or experiments performed in operating or decommissioned nuclear power plants.
Main 1.10. This Safety Guide also addresses other aspects of experiments and modifications, such as commissioning and provisions for radiation protection. Detailed recommendations on these matters are provided in SSG‑80 [3] and SSG‑85 [8].
Main 1.11. In the context of this Safety Guide, ‘utilization’ is the use of the research reactor or of an experiment or an experimental device during reactor operation. The experiment or experimental device might be situated in the reactor core, the reactor reflector, the shielding or the experimental facilities2 connected to the reactor, or might be located outside the biological shielding or outside the reactor building.
Main 1.12. In the context of this Safety Guide, a ‘modification’ is a deliberate change3 in, or an addition to, an existing reactor, a structure, system, component or item of software important to safety, or an experiment or experimental device. A modification may also involve a change in safety systems, safety related items, safety documentation (including operational limits and conditions and operating procedures) and operating conditions for the research reactor and for experiments. Organizational changes are considered modifications because such changes can affect safety.
Main 1.13. Modifications to structures, systems and components with relevance to nuclear security4 aspects will also be subject to confidentiality requirements. Recommendations on nuclear security matters are not provided in this Safety Guide; however, recommendations on managing the interface between nuclear safety and security in modification projects are provided.
Main 1.14. In the case of modifications that concern only changes to documentation, the recommendations presented in Section 6 are not fully applicable. For such modifications, the additional guidance provided in SSG‑20 (Rev. 1) [2] should be considered and followed, as applicable.
Main 1.15. Section 2 provides recommendations on the management system for the utilization and modification of a research reactor, including organizational changes. Categorization of the experiment or modification provides a basis for selecting the review and approval route; recommendations on these topics are provided in Section 3. Recommendations on the design of experiments or modifications are provided in Section 4. Sections 5–7 provide recommendations on the activities that should be considered in the various phases of a typical utilization or modification project. Section 8 covers additional recommendations for the operational safety of experiments, and Section 9 provides recommendations on the handling, dismantling, post‑irradiation examination and disposal of experimental devices. Section 10 provides recommendations on the safety of out‑of‑core experimental devices and modifications. Section 11 deals with safety related aspects of organizational changes. Annex I provides an example of a checklist for categorization of an experiment or modification. Annex II presents information on the content of the safety analysis report for an experiment at a research reactor. Annex III provides examples of modifications that could affect the safety and nuclear security interface, and Annex IV gives examples of safety focused questions and nuclear security focused questions for use in assessing the implications of a modification. Annex V provides examples of reasons for a modification at a research reactor.
Main 2.1. Requirements for the management system are established in SSR‑3 [1] and IAEA Safety Standards Series No. GSR Part 2, Leadership and Management for Safety [14]. Requirement 4 of SSR‑3 [1] states:

  • Management responsibility includes the support and commitment of management necessary to achieve the objectives of the operating organization.

  • Resource management includes measures necessary to ensure that the resources essential to the implementation of strategy and the achievement of the objectives of the operating organization are identified and made available.

  • Process implementation includes the activities and tasks necessary to achieve the goals of the organization.

  • Measurement and assessment provide an indication of the effectiveness of management processes and work performance compared with objectives or benchmarks. It is through measurement and assessment that opportunities for improvement are identified.

Main 2.2. Processes for utilization and modifications should be established as part of the management system. These processes should include the design, review, assessment and approval, fabrication, testing and implementation of a utilization or modification project. Relevant procedures describing the processes should be put into effect by the operating organization early in the utilization or modification project. The management system should cover all structures, systems and components and processes important to safety, and should include a means of establishing controls over utilization and modification activities, thereby providing confidence that these activities are performed safely in accordance with established requirements. The management system should also include provisions to ensure that utilization and modification activities are planned, performed and controlled in a manner that ensures effective communication and clear assignment of responsibilities. In establishing the management system, a graded approach based on the relative importance to safety of each item or process is required to be applied (see Requirement 7 of GSR Part 2 [14]).
Main 2.3. The objective of the management system is to ensure that the research reactor meets the requirements for safety as derived from the following:

  • National laws and regulations;

  • Regulatory requirements;

  • Design requirements and assumptions;

  • The safety analysis report;

  • Operational limits and conditions;

  • The administrative requirements established by the management of the research reactor.

Main 2.4. The management system should support the development, implementation and enhancement of a strong safety culture in all aspects of modification projects and the utilization programme.
Main 2.5. It is the responsibility of management to ensure that the procedures for utilization and modification describe how these activities are to be assessed, managed, authorized and performed in order to ensure that the objectives of the experiment or modification are met and that safe operation of the research reactor and its safe utilization are ensured. The documentation of the management system for utilization and modification should include descriptions of the organizational structure, functional responsibilities, levels of authority and interfaces for those assessing, managing, authorizing, performing, controlling and supervising these activities. It should also cover other management measures, including planning and scheduling of activities, resource allocation and human factors.
Main 2.6. The operating organization has responsibility for preparing and issuing specifications and procedures for the utilization and modification of the research reactor. The reactor manager5 should be an active participant in the implementation and evaluation of utilization and modification activities. The detailed responsibilities of the reactor manager are set out in paras 2.23 and 2.24, and the detailed responsibilities of the project manager are set out in paras 2.18–2.22.
Main 2.7. The operating organization should provide adequate resources to execute the utilization or modification as follows:

  • By determining the required competences and providing periodic training, where appropriate, to ensure that the personnel of the operating organization are competent to perform their assigned work;

  • By supervising external personnel (including suppliers) who perform safety related activities and ensuring that these personnel are adequately trained and qualified.

Main 2.8. Personnel who are not directly working for the research reactor and personnel of contracting organizations who are involved in the utilization or modification project should be appropriately trained and qualified for the work they are to perform. Such external personnel should perform their activities under the same controls, and to the same work standards, as reactor personnel. Reactor supervisors should review the work of these external personnel during preparation for work, at the job site during performance of the work, and during acceptance testing and inspection.
Main 2.9. The management system of the operating organization should be extended to include suppliers. The operating organization should ensure that the suppliers, manufacturers and designers have an effective management system in place. The operating organization should ensure, through audits, that the assigned activities are carried out in compliance with the management system.
Main 2.10. The equipment, tools, materials, hardware and software necessary to conduct the work in a safe manner and to ensure that the requirements are met should be determined, provided, checked and verified, and maintained.
Main 2.11. Activities relating to the utilization or modification of a research reactor should be performed and recorded in accordance with approved procedures and instructions.
Main 2.12. For successful implementation of a utilization or modification project, consideration should be given to the following aspects:

  • Planning and prioritization of work;

  • Meeting all relevant regulatory requirements and demonstrating that the overall level of safety will not be reduced;

  • Meeting the requirements derived from the operational limits and conditions;

  • Evaluating the feedback of operating experience from similar utilization or modification projects;

  • Addressing the maintenance requirements for the experiment or the modified system or component;

  • Ensuring the availability of qualified personnel with suitable skills;

  • Establishing appropriate operating procedures, including those for assessing and correcting non‑conforming items;

  • Performing and documenting the required inspections and tests, including those required for commissioning an experiment or modification;

  • Performing and documenting the required training and instruction.
Main 2.13. The management system should include measures to control records essential to the performance and verification of utilization and modification activities, including the justification and safety assessment of such activities, through a system for the identification, approval, review, filing, retrieval and disposal of records.
Main 2.14. Documents such as the procedures, specifications and drawings for utilization and modification projects, including the operating procedures, should be controlled. In particular, measures should be established for their preparation, identification, review, updating and validation as required, as well as their approval, issue, distribution, revision and archiving.
Main 2.15. Measures should be established for assessment, review and verification to determine whether and to ensure that utilization and modification activities have been accomplished as specified in the design. Such measures should include the following:

  • Review of the design and the design procedures;

  • Verification of the implementation of activities by inspection and witnessing;

  • Review and verification of records, results and reports relating to the design, the implementation of projects and the operation of the research reactor, including those on the status of non‑conformances and corrective actions;

  • Audits of the relevant processes, procedures and documentation;

  • Follow‑up of the adequacy and timeliness of corrective actions.

Main 2.16. Effective implementation of the management system for the utilization and modification of a research reactor should be assessed by qualified personnel who are not directly involved in performing these activities.
Main 2.17. The operating organization should evaluate the results of such independent assessments and should determine and take the necessary actions to implement recommendations and suggestions for improvement. The operational safety of experiments should be subjected to periodic review by the reactor safety committee.
Main 2.18. The operating organization should assign a person, normally a dedicated project manager with understanding of the research reactor and the applicable regulatory framework, to be responsible for implementing the objectives of a utilization or modification project. These responsibilities should include development of a project definition, determination of measures to ensure adherence to established safety criteria, evaluation of options, and management of detailed design, project implementation, commissioning and decommissioning, if relevant.
Main 2.19. The project manager should be responsible for determining the impact of a project on the existing safety analysis report and on the operational limits and conditions. This involves making proposals for the categorization of the experiment or modification and providing the safety documentation in order to enable the operating organization to submit the project for review and approval, as necessary, by the safety committee or the regulatory body. The advice of external specialists and consultants may be sought to support the project manager in performing these duties.
Main 2.20. The project manager should ensure that any contractor or supplier involved in the preparation or implementation of a utilization or modification project is made aware of and complies with the appropriate requirements and regulations.
Main 2.21. The project manager should be responsible for ensuring that adequate precautions are in place to provide protection against radiation risks and other hazards that might arise during or as a result of the project.
Main 2.22. Possible interactions between different utilization or modification projects that are being implemented or proposed should be considered and analysed by the project manager.
Main 2.23. The reactor manager has direct responsibility for the safety aspects of reactor operation. In this respect, the reactor manager should ensure that any proposal for utilization or modification of the reactor has been demonstrated to be safe and that additional review and approval, if required, has been carried out by an appropriate body6 before implementation of the project commences.
Main 2.24. The reactor manager should be responsible for ensuring that the scheduling of the implementation of the utilization or modification project does not affect safety.
Main 3.1. All utilization and modification projects, including organizational changes, should be subjected to a screening process to determine their implications for safety and the related safety category of the experiment or modification. The screening process should be documented, and the selection of the safety category should be justified.
Main 3.2. The safety category of the experiment or modification should provide the basis for determining the detail and the extent of the safety analysis and the review to be performed. The safety category should also provide the basis for the review and approval route to be followed for the utilization or modification project. A checklist could facilitate the categorization process. An example of such a checklist is provided in Annex I.
Main 3.3. For modification projects, the safety class of the relevant structures, systems and components (as required in accordance with Requirement 16 of SSR‑3 [1]) should be used as a first step in the safety categorization in order to determine the safety impact of the modification. This is described in paras 3.7–3.34.
Main 3.4. For utilization projects, the relevant experimental facilities and devices are also required to be classified on the basis of their safety function and their safety significance (see Requirement 16 of SSR‑3 [1]). This safety class should also be used as a first step in the safety categorization of the utilization project. In developing a safety categorization system for a utilization project, the potential impact on the main safety functions and the potential for challenging safety functions should be considered. In addition, at a minimum, the following aspects should be taken into account:

  • Criticality aspects;

  • Reactivity aspects;

  • In‑core and out‑of‑core irradiation;

  • Experiments within or outside the biological shielding or containment;

  • Physical conditions and behaviour of components;

  • Chemical conditions and behaviour of components;

  • Heat generation and thermal characteristics;

  • Mechanical and thermal stresses and behaviour of components;

  • The potential for a significant dose to site personnel;

  • The potential for a significant dose to members of the public off the site.

Main 3.5. The review and approval route for a utilization project should be based on the safety category determined for the experiment. In determining the safety category, the nature of the experiment — that is, whether it is a new experiment, a repeated experiment7 or isotope production — should be taken into account (see also paras 3.29 and 3.30 for recommendations relating to repeated experiments).
Main 3.6. The proposed categorization process for utilization and modification projects, including the proposed review and approval routes, should be submitted to the safety committee for review; following approval by the reactor manager, the proposal should be submitted to the regulatory body for review and approval, in accordance with the regulatory requirements.
Main 3.7. A detailed and comprehensive safety analysis should be carried out for experiments or modifications with a potential effect on safety. The results of the detailed safety analysis should indicate the extent of their safety significance (see paras 3.11–3.34). The results of the safety analysis for each experiment should be incorporated in the safety analysis report of the research reactor or described in a separate document (i.e. the safety analysis report for the experiment). An example of the content of the safety analysis report for an experiment is presented in Annex II.
Main 3.8. Modifications and new experiments should be subjected to the categorization process described in this Safety Guide.
Main 3.9. For repeated experiments, it should be demonstrated that they can use safety analyses approved earlier that were performed according to the requirements of the management system.
Main 3.10. In determining the potential effect on safety, the consequences of each experiment or modification for the reactor itself and the interactions with other systems should be taken into account.
Main 3.11. The safety significance of each experiment or modification, as defined in the following, and the potential for design errors or incorrect implementation of a project should be taken into account in determining the safety category of the utilization or modification project, the safety analyses to be performed and the documentation to be prepared:

  • Major effect on safety: experiments or modifications that could affect the design function or the ability of structures, systems or components to perform their intended safety function as described in the safety analysis; that are beyond the licence conditions or beyond the existing (i.e. approved) safety analysis8; or that could introduce hazards that have not been previously addressed.

  • Significant effect on safety: experiments or modifications that are within the approved licence conditions and safety analysis; that necessitate a change of the operational limits and conditions but not of the remaining chapters of the safety analysis report; that could significantly reduce the margin to criticality; or that necessitate a change of the operating procedures. Recommendations on operational limits and conditions for research reactors are provided in SSG‑83 [6].

  • Minor effect on safety: experiments or modifications that are within the approved licence conditions, safety analysis and operational limits and conditions; that still have significant safety margins and no effect on the safety system settings; and that do not necessitate a change in the operating procedures.

  • No effect on safety: experiments or modifications that present no hazard and have no impact on safety.

Main 3.12. The categorization process for experiments and modifications with an effect on safety should be documented in detail, together with the justification for the proposed safety category.
Experiments or modifications with a major effect on safety 3.13. Experiments or modifications with a major effect on safety should be subjected to safety analysis and to the same design, construction and commissioning procedures applied for the research reactor itself, in order to ensure that such experiments or modifications meet the same requirements as the existing structures, systems and components or existing experimental facilities.
Experiments or modifications with a major effect on safety 3.14. An assessment of radiation exposure of site personnel expected during or as a result of the project should be prepared. Measures to reduce exposures based on the principle of optimization of protection and safety should be determined for all facility states (i.e. normal operation, anticipated operational occurrences and accident conditions), and any potentially necessary mitigation measures should be identified. Recommendations on applying the principle of optimization of protection and safety are provided in SSG‑85 [8].
Experiments or modifications with a major effect on safety 3.15. The safety documentation for the project should cover the responsibilities and duties of the operating personnel, the experimenters and others involved in the project.
Experiments or modifications with a major effect on safety 3.16. A list of all new or modified items important to safety and their safety class should be included in the safety documentation. Information required for accident analysis and for determining mitigation measures under accident conditions should also be defined.
Experiments or modifications with a major effect on safety 3.17. The safety documentation for the project should be reviewed by the reactor manager with respect to safety, operability and compatibility with other experiments in or at the research reactor and with reactor systems.
Experiments or modifications with a major effect on safety 3.18. Experiments and modifications with a major effect on safety should be reviewed by the safety committee. After the review by the safety committee, the experiment or modification should be submitted to the regulatory body for review and approval in accordance with the same procedures applied for the research reactor itself.
Experiments or modifications with a major effect on safety 3.19. If the experiment or modification will affect the authorization for operation of the research reactor or the documentation for the authorization, an appropriate ‘re‑licensing’ process or a process for amendment of the authorization should be applied.
Experiments or modifications with a major effect on safety 3.20. The operating procedures, including emergency procedures, should be reviewed to ascertain whether they need to be revised as a result of the experiment or modification, and if necessary should be revised, reviewed and made subject to approval as appropriate.
Experiments or modifications with a significant effect on safety 3.21. The safety documentation for experiments or modifications with a significant effect on safety — including complex experiments, experimental facilities and modifications — should include a comprehensive and detailed description of the experiment or modification and its design and construction.
Experiments or modifications with a significant effect on safety 3.22. The safety analysis should cover all facility states (i.e. normal operation, anticipated operational conditions and accident conditions). The analysis should demonstrate that the licence conditions and the original safety limits would not be affected and that the radiological consequences of the experiment or modification are within the accepted limits.
Experiments or modifications with a significant effect on safety 3.23. An assessment of radiation exposure of the site personnel expected during or as a result of the project should be prepared. Measures to reduce radiation exposures based on the principle of optimization of protection and safety should be described for all facility states, and any potentially necessary mitigation measures should be identified.
Experiments or modifications with a significant effect on safety 3.24. The safety documentation for the project should cover the responsibilities and duties of the operating personnel, the experimenters and others involved in the project.
Experiments or modifications with a significant effect on safety 3.25. A list of all new or modified items important to safety and their safety class should be included in the safety documentation. Information required for accident analysis and for determining mitigation measures under accident conditions should also be defined.
Experiments or modifications with a significant effect on safety 3.26. The safety documentation for the project should be reviewed and made subject to approval by the reactor manager with respect to safety, operability and compatibility with other experiments in the reactor and with reactor systems.
Experiments or modifications with a significant effect on safety 3.27. Experiments and modifications with a significant effect on safety should be reviewed by the safety committee before submission to the regulatory body for review and approval in accordance with the regulatory requirements.
Experiments or modifications with a significant effect on safety 3.28. The operating procedures, including emergency procedures, should be reviewed as to whether they need to be revised as a result of the utilization or modification, and if necessary should be revised, reviewed and made subject to approval as appropriate.
Experiments or modifications with a minor effect on safety 3.29. Many experiments and modifications are considered to have a minor effect on safety. Such modifications include small modifications to structures, systems or components. Research reactors are, by their nature, often used for repeated sample irradiations or for repeated experiments with minor changes. Criteria should be defined for repeated experiments, isotope production or modifications with only minor changes from the original design, for which approval by the reactor manager would be sufficient without the need for resubmission to the safety committee or to the regulatory body. The recommendations provided in Sections 5–7 should be applied using a graded approach.
Experiments or modifications with a minor effect on safety 3.30. Clear criteria should define which irradiation can be regarded as a repeated experiment. The type and quantity of the samples for isotope production or activation analyses should be defined, and the irradiation facility and the irradiation position (i.e. the maximum allowable neutron flux) should be specified. The information and documentation to be prepared in support of a request to conduct an irradiation experiment and the review and approval route should also be specified. This proposed method of application to conduct an experiment or implement a modification with a minor effect on safety should be submitted to the safety committee for review.
Experiments or modifications with a minor effect on safety 3.31. Records of experiments and modifications with a minor effect on safety approved by the reactor manager should be periodically reviewed by the safety committee to ensure that there are no disagreements in the interpretation of the criteria for approval and that there has been no change in the original safety category of the experiment or modification because of, for example, ageing.
Experiments or modifications with no effect on safety 3.32. Careful consideration should be given to any proposed change before categorizing it as an experiment or modification with no effect on safety. Such consideration should be based on a description of the experiment or modification together with an assessment of its implications, and these should be submitted to the reactor manager for approval.
Experiments or modifications with no effect on safety 3.33. Records of all such approvals should be retained, together with the related documentation.
Experiments or modifications with no effect on safety 3.34. The safety committee should periodically review the records of experiments and modifications with no effect on safety, to ensure that there are no disagreements in the interpretation of the criteria for approval.
Experiments or modifications with no effect on safety 3.35. The operating organization should ensure that the interface between nuclear safety and nuclear security is duly taken into account and is managed within the context of an experiment or modification. As part of the integrated management system described in Section 2, all experiments or modifications should be designed and carried out with due attention to nuclear security matters. Annex III provides examples of modifications for which there could be an interface between safety and nuclear security. Further information on the interface between safety and nuclear security is provided in Ref. [18].
Experiments or modifications with no effect on safety 3.36. Modifications of systems for protection of the site and research reactor against sabotage and unauthorized removal of nuclear material and other radioactive material should be carried out in accordance with the requirements of the relevant national security authorities and the guidance provided in IAEA Nuclear Security Series publications (see Refs [19–27]). Guidance on the security aspects of modifications to instrumentation and control systems and software important to safety for research reactors is provided in IAEA Nuclear Security Series No. 17‑T (Rev. 1), Computer Security Techniques for Nuclear Facilities [19].
Experiments or modifications with no effect on safety 3.37. Modifications carried out on any equipment, including structures, systems and components important to safety, and on nuclear security systems should be screened and assessed for potential impacts on safety and nuclear security. The results might need to be described in a separate document and be kept confidential.
Experiments or modifications with no effect on safety 3.38. Nuclear security measures might need to be established to allow access to the site or research reactor for external workers and personnel. To allow this access, prior trustworthiness checks and other measures might be necessary and appropriate time should be allocated to perform these checks and measures. The importance of these checks and measures should not be underestimated, as they aim to counter insider threats, which are a major concern, in particular in nuclear research. Further guidance is provided in IAEA Nuclear Security Series No. 8‑G (Rev. 1), Preventive and Protective Measures Against Insider Threats [22].
Experiments or modifications with no effect on safety 3.39. The reactor manager should ensure that the organization responsible for providing nuclear security at the research reactor is involved in the modification project. The reactor manager should also ensure effective communication and coordination to ensure that safety measures and nuclear security measures do not compromise one another and that potential issues relating to the interface between safety and nuclear security are addressed. This should be done for all phases of the implementation of an experiment or modification.
Experiments or modifications with no effect on safety 3.40. The proposed experiment or modification should be reviewed to assess potential adverse impacts on the safety and nuclear security of the research reactor. When reviewing a modification, consideration should also be given to possibilities to enhance safety and nuclear security by design in conjunction with elements such as the following:

  • The physical layout of the research reactor;

  • The nuclear security layers in the research reactor surrounding potential theft or sabotage targets, including access controlled points;

  • The configuration and purpose of structures, systems and components important to safety and systems and equipment important to nuclear security at the research reactor;

  • Requirements of the management system and quality assurance procedures;

  • Operating procedures of the research reactor;

  • The nuclear security plan and procedures;

  • The operating programme of the research reactor;

  • The safety analysis and the operational limits and conditions;

  • Licence conditions and the authorization process;

  • Emergency plans and contingency plans;

  • Programmes for radiation protection and waste management;

  • Engineering;

  • Maintenance;

  • Work management (including control and planning);

  • Training and qualification of personnel;

  • Fire protection;

  • Environmental protection;

  • Health and safety with respect to all occupational hazards and risks (including chemical safety).

Experiments or modifications with no effect on safety 4.1. The design of an experiment or modification should demonstrate the following:

  • The experiment or modification can fulfil the task for which it is intended.

  • The experiment or modification can be installed and operated without compromising the safety of the research reactor.

  • The experiment or modification can be removed or decommissioned without compromising the safety of the research reactor.

  • In all operational states, the radiation exposure of site personnel and members of the public will remain within dose limits and, moreover, that the principle of optimization of protection is applied.

  • Any equipment can be safely stored during its lifetime and safely disposed of after decommissioning.

  • The amount of radioactive waste is limited to the extent possible, for example by means of the appropriate selection of materials.

Experiments or modifications with no effect on safety 4.2. The design of an experiment or modification should be such as to minimize additional demands on the reactor shutdown system. In the case of experiments, consideration should be given to providing the means for placing the experiment in a safe condition without the need for activation of the reactor shutdown system.
Experiments or modifications with no effect on safety 4.3. In addition to reactor operations such as startup, steady state or transient operation and shutdown, other reactor conditions should be considered in terms of their effects on the experiment or modification. These conditions include unscheduled shutdown followed by immediate restart, maintenance, extended shutdown, refuelling, low power operation, changes in core configuration, and failure of electrical power and other services. The operational states and accident conditions considered in the design of the research reactor should also be considered in terms of their effects on the experiment or modification. Similarly, the effects of all states of the experiment or modification on the reactor should be considered.
Experiments or modifications with no effect on safety 4.4. The design requirements for a utilization or modification project should be defined early in the project and should be selected on the basis of the safety significance of the project.
Experiments or modifications with no effect on safety 4.5. The operating organization’s safety policy regarding modifications should be subjected to continuous improvement and should be regularly reviewed. For each modification, adverse effects challenging the protection of the barriers to radioactive release, the independence of the levels of the defence in depth, and the reliability of each level should be avoided. The influence of human and organizational factors on one, several or all barriers and levels of defence in depth should be considered in the design of experiments and modifications.
Experiments or modifications with no effect on safety 4.6. Modifications aiming to continuously improve nuclear safety such as modifications to the design of safety features for design extension conditions, including non‑permanent equipment, should be performed in accordance with approved procedures for modifications and the safety assessment for the modification.
Experiments or modifications with no effect on safety 4.7. The interfaces between safety and nuclear security should be considered in the design process. These interfaces should be considered in such a way that the impacts of safety measures on nuclear security and the impacts of nuclear security measures on safety are taken into account from the design stage and do not compromise one another.
Reactivity 4.8. If an experimental device or modified system, or its failure, could lead to an increase in the reactivity of the reactor core, the experiment or modification should be designed so as to limit the positive reactivity effects to those effects that can safely be accommodated by the reactor control system and the reactor shutdown system.
Reactivity 4.9. If any modification of the reactor control system or the reactor shutdown system is necessary to accommodate an increase in the reactivity of the reactor core, then this modification should be treated as a separate modification with a major effect on safety and should be implemented before the originally proposed experiment or modification is implemented.
Reactivity 4.10. The reactivity worth of an experiment or modification should be determined for all situations (e.g. insertion of the experiment into the reactor core, removal of the experiment, potential failure modes). A calculated, or otherwise determined, reactivity worth should be checked, usually by measurement, by carrying out a critical experiment or by an equivalent method.
Reactivity 4.11. For subcritical assemblies, any potential for criticality because of the reactivity worth of an experiment should be considered among the design extension conditions, and such conditions should be assessed to identify whether the existing safety provisions remain effective or additional safety features for design extension conditions need to be implemented to prevent or mitigate the consequences of such an event.
Radiation protection 4.12. An experiment or modification should not significantly affect the radiation protection programme for the research reactor. The original design of the research reactor, including experimental devices, will typically have been based on a combination of shielding, ventilation, filtration and decay to reduce radioactive releases, with associated monitoring for radiation and airborne radioactive substances, for all operational states and for accident conditions. If an experiment or modification would affect the radiation protection measures, then additional measures should be taken to reduce the exposure of site personnel and the public during the installation of the project and the operation, handling and dismantling of the experiment or the implementation of the modification project to levels as low as reasonably achievable in accordance with the principle of optimization of protection and safety. Such measures might include the removal of sources that generate high radiation fields, the provision of additional shielding, the provision of remote handling devices and measures for controlling or mitigating the consequences of accident conditions. Requirements for radiation protection are established in IAEA Safety Standards Series No. GSR Part 3, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards [28].
Radiation protection 4.13. If the failure of an experimental device or modified system could lead to the degradation of either the original system of barriers or the additional system of barriers to the release of radioactive substances, the effects of such an accident should be considered in the design of the experiment or modification.
Radiation protection 4.14. The potential for an uncontrolled release of radioactive substances should be limited, and the amounts of such material released should be minimized by measures such as the use of delay tanks, inert purge gases, filters or recirculation. This applies for all stages of the project (including installation, construction, commissioning, operation and decommissioning); for all facility states (i.e. normal operation, anticipated operational occurrences and accident conditions); and for removal, storage and shipment of experimental devices or modified systems.
Safety devices 4.15. Whenever possible, experiments and modifications should be designed considering the use of inherent safety features, passive systems and fail‑safe design.
Safety devices 4.16. If safety devices are interconnected with the reactor protection system, they should be designed so as to maintain the quality and effectiveness of the reactor protection system. The potential for detrimental interactions with the reactor protection system should be assessed and should be demonstrated to be acceptable.
Safety devices 4.17. If an experiment might pose a hazard to the research reactor or to personnel, the protection and control system of the experiment should be connected to the reactor systems, so that the reactor power level would be reduced or the reactor would be shut down in the event of the failure of the experimental device. The method of effecting this connection should receive special attention and the connection should be classified and qualified as a safety system. Separate annunciators or other devices should be provided in the control room to notify the operating personnel whenever a safety action is initiated when a safety system setting of the experiment is reached. The reactor systems should not be used to control the experiment, nor to provide an indication of the progress of the experiment.
Safety devices 4.18. If a safety device is to be used only to protect the experiment itself or if the experimental device can be permitted to fail without causing a hazard to the research reactor or to personnel, then the safety device may be assigned a lower safety class. Such safety devices should not be connected to the reactor control system or the reactor protection system.
Safety devices 4.19. Annunciators should operate at an alarm level below the safety limit of the experiment parameters to allow operating personnel to take predefined actions to correct the situation.
Heat generation and cooling 4.20. Special consideration should be given to the possibility of an experiment or modification affecting the capability for heat removal from the reactor core.
Heat generation and cooling 4.21. A dominant cause of failure for many irradiation experiments is related to either excessive heat generation or insufficient cooling. Thus, adequate heat removal under all conditions considered in the design of the experiment and of the research reactor itself should be one of the main aspects addressed in the safety analysis for the experiment. In addition, the effect of the presence or absence of an experimental device on the power distribution in the reactor core should be carefully addressed, as this might influence the safety margins of the research reactor. Particular attention should be given to the calculation of the power distribution in the experimental device, in which all material compositions and the neutron and gamma heat deposition should be taken into account. Such calculations should be performed for all operational states. Adequate cooling should be provided to keep the temperature within acceptable limits. To avoid excessively high temperatures in all circumstances, means to place the experiment in a safe configuration should be provided. Means to reduce the reactor power or to shut down the reactor, as described in paras 4.8–4.10 and 4.17, should be analysed and ensured.
Heat generation and cooling 4.22. In addition to the above considerations, particular consideration should be given to the irradiation of fissile material or moderating material with respect to the potential for inadvertent criticality and to cooling provisions during and after irradiation to prevent overheating of the target material.
Pressure 4.23. Possible effects on the reactor of high or low pressure in an experimental device or modified system should be assessed and appropriate means to keep the pressure within acceptable limits should be ensured.
Pressure 4.24. Special precautions should be taken in the design of experiments for irradiating material, including their enclosures. Such material can readily decompose or otherwise change state, or its chemical reactivity might be enhanced, producing an overpressure or generating gases that might be flammable and/or explosive. It should be ensured that pressures within the enclosures and chemical concentrations of the target material do not adversely affect the safety of the reactor, personnel or the experiment.
Selection of materials 4.25. In the design of experiments, the selection of materials should take into account material compatibility; corrosion; changes of material properties due to irradiation (e.g. creep, embrittlement, radiolytic decomposition, activation), including transmutation of material; differential thermal expansion; ageing effects; and ease of decontamination, dismantling and final disposition.
Selection of materials 4.26. In the design of experiments, particular consideration should be given to the selection of materials for irradiation. For example :

  • Materials such as copper and cadmium should not be used without cladding.

  • Irradiation of materials whose corrosive properties might become enhanced as a result of irradiation (e.g. mercury, rhenium, magnesium) should be used with particular consideration to their properties.

  • Plastics and other organic or synthetic compounds will disintegrate under irradiation.

  • Cadmium, beryllium, silver, cobalt, boron compounds (e.g. B4C) and alloys containing these materials should be used with extreme caution owing to their neutronic properties.

  • Chemical compounds that decompose upon irradiation and produce off‑gases should be used with caution.

  • Explosive chemicals and materials should be used with extreme caution and in limited quantities.

  • Galvanic effects, in particular those due to interactions between water and aluminium, should also be considered.

  • The use of mercury should be excluded in research reactors with aluminium components owing to the extremely corrosive interactions between these elements.

Selection of materials 4.27. In the design of experiments, particular consideration should be given to certain activated corrosion products (such as silver) as they tend to plate‑out (i.e. form a coating) on cooling circuit surfaces, thus creating contamination and the potential for radiation exposure during handling and maintenance.
Selection of materials 4.28. In the design of experiments, particular consideration should be given to the provision of additional barriers to contain toxic material that could pose a hazard if released; for example, beryllium is particularly toxic if ingested.
Neutron flux perturbations 4.29. Consideration should be given to the effects of interactions of neutrons from an experiment or a modified system with core components, fuel or other experiments. Perturbations in the neutron flux should be evaluated, especially in the vicinity of devices that are important to safety (e.g. neutron detectors). Where experiments can be inserted, withdrawn or otherwise relocated while the reactor is at power, the effects on the power distribution in fuel assemblies and on the controllability of reactivity changes should be carefully assessed.
Protection against external and internal hazards 4.30. At each stage of the project, the design of the experiment or modification should include measures to withstand or mitigate the effects of the external and internal events (e.g. earthquakes, floods, fires, explosions) that have been taken into account for the research reactor. Experiments and modifications should be designed so that, in case of external events exceeding the design basis external events, the design has a sufficient margin to avoid event sequences leading to unacceptable radiological releases. The design should be reviewed by the appropriate experts and the implementation of any recommendations made should be documented.
Protection against external and internal hazards 4.31. If temporary equipment is to be used in the construction and installation stages of an experiment or modification, the proper measures should be taken to protect the structures, systems and components of the research reactor as well as the temporary equipment against external and internal hazards, for example by anchoring them or providing fire protection measures.
Mechanical interaction of experiments and the reactor 4.32. The possible vibration of experimental devices or modified components owing to coolant flow should be considered. Particular consideration should be given to avoiding vibrations at resonance frequency.
Testability and ageing management 4.33. In the design of an experiment or modification, particular consideration should be given to the proper testability of the experiment or modification during commissioning and during operation. If necessary to execute a commissioning programme successfully, special measuring and testing provisions should be made available to ensure the accessibility of the modified system or experiment for measurements.
Testability and ageing management 4.34. Particular consideration should be given to providing appropriate features to support the same degree of ageing management and in‑service inspection as for the original system, taking into consideration the lifetime of the utilization or modification project.
Testability and ageing management 5.1. Sections 5, 6 and 7 provide detailed recommendations for the various phases of a typical utilization or modification project. These recommendations should be followed for a project with a major effect on safety. For projects with lesser safety implications, the recommendations should be applied using a graded approach. Figure 1 shows a flow chart for a project with a major effect on safety and the relationship between the operating organization and the regulatory body throughout the execution of the project. Other organizations (e.g. a design organization, subcontractors) could also be involved in the utilization or modification project. For the design of a modification, the operating organization should consult the designer to the extent possible. However, the overall responsibility remains with the operating organization.
Testability and ageing management 5.2. The extent of the involvement of the safety committee and the regulatory body should depend on the safety category of the experiment or modification; recommendations for determining the safety category are provided in Section 3. Further recommendations on the interactions between the operating organization and the regulatory body are provided in GSG‑13 [17].
Testability and ageing management 5.3. The implementation of projects with a significant effect on safety or a minor effect on safety should follow the same steps but using a graded approach, especially regarding the extent and detail of the safety analysis, the documentation to be prepared, and the review and approval route to be followed.
Testability and ageing management 5.4. Each phase of the project should be clearly defined and should be understood by all persons involved. In particular, the transition points between phases should be formally acknowledged and recorded.
Testability and ageing management 5.5. Early in the project, the need to develop a mock‑up should be considered in order to facilitate the development of procedures for the implementation of the project and operating procedures, the training of operating personnel, and workability within a confined space, or to ensure the feasibility of the utilization or modification project.
Testability and ageing management 5.6. The need for an experiment or modification can arise from different groups of persons, such as the reactor management, the regulatory body, experimenters or equipment suppliers. Modifications may be necessary for the continuous improvement of nuclear safety involving changes to safety systems, safety related items, operational limits and conditions, procedures, documentation or operating conditions for the reactor as well as for experiments. Modifications may also be necessary to adapt the research reactor to the changing needs of science and research (e.g. high neutron flux density, new irradiation facility, modified or new experimental facilities). Whatever the reason for an experiment or a modification, the general concept should be discussed by the reactor management and the regulatory body early in the project. It might also be appropriate to include other groups, such as the safety committee, experimenters, equipment suppliers and independent consultants.
Testability and ageing management 5.7. Experiments and modifications at research reactors might also arise from a variety of considerations (see Annex V).
Testability and ageing management 5.8. The project definition stage involves the development of the specific objectives and the scope of the proposed experiment or modification and thus provides the starting point for the technical design. Limiting conditions, safety criteria and quality requirements with regard to the implementation of the project should also be developed at this stage.
Testability and ageing management 5.9. General organizational and administrative arrangements for the subsequent project steps should also be dealt with at the project definition stage.
Categorization of the experiment or modification and selection of safety codes and standards 5.10. The process of categorization of the experiment or modification, as described in Section 3, should be applied at this stage in order to determine the safety implications of the project and the review and approval route to be applied.
Categorization of the experiment or modification and selection of safety codes and standards 5.11. The applicability of relevant existing safety codes and national and international standards to the structures, systems and components should be evaluated, and in some cases, the development of some additional codes and standards might be necessary (see Requirement 13 of SSR‑3 [1]).
Data collection 5.12. The use of relevant technical data and information on performance and material properties and process characteristics as input in the design stage is essential to ensure the quality and safety of experiments and modifications. Considerations such as those provided in paras 4.20–4.28 should also form part of such design inputs.
Data collection 5.13. The existing documentation for the research reactor, component or software, including all modifications, should be provided to establish a pre‑design database. This documentation should be reviewed to verify that it is up to date. This might necessitate inspection of the equipment affected by the experiment or modification and an evaluation of the operating and maintenance history of this equipment to verify that the documentation is up to date and that the existing equipment is capable of performing its intended function.
Data collection 5.14. The establishment of the pre‑design database might also necessitate specific measurements or tests to be carried out on relevant reactor systems in order to complete or update the information. Verification of historical data might be necessary, and the data should be carefully authenticated. Historical information about repeated failures or generic common cause failures should also be collected.
Data collection 5.15. The inclusion of information on similar experiments or modifications carried out at other research reactors can provide an important contribution to the pre‑design database. Operating experience, including information on ageing effects, should also be collected.
Pre‑design appraisal 5.16. The design process is usually an iterative process. For each experiment or modification, several technical options should be evaluated. This appraisal will provide the basis for the subsequent evaluation of the safety and the technical and financial feasibility of the experiment or modification, and for justification of the chosen option. The appraisal of options should cover not only the hardware for the experiment or modification (i.e. equipment and materials) but also the implementation and operational aspects, including surveillance requirements, as well as decommissioning and disposal aspects. Consideration of these aspects should include an assessment of the effect of the experiment or modification on the research reactor under normal operation, anticipated operational occurrences and accident conditions, the required radiation protection measures and the projected volume of radioactive waste that will be generated, and will support an assessment of the safety, effectiveness and costs of the project. A technical description and a preliminary safety analysis should be provided for each option. The review scheme used for carrying out comparisons between the available options and for selection of the optimum solution should be documented. Reasons for the rejection of other options should also be documented.
Pre‑design appraisal 5.17. Depending on the safety category of the experiment or modification, the pre‑design appraisal should be discussed with the regulatory body and, if applicable, the safety codes and design standards that have been selected for the project should be submitted to the regulatory body for assessment and review. The associated time schedule should also be discussed with the regulatory body at the pre‑design stage.
Pre‑design appraisal 5.18. On the basis of the pre‑design appraisal, the operating organization should decide whether or not to execute the experiment or modification.
Pre‑design appraisal 5.19. At the design stage, the selected option should be developed into a fully documented and justified design for the experiment or modification. Thus, project plans, specifications, design assessments, safety analyses, detailed drawings for the manufacture and installation of the experiment or modification and all associated documentation should be prepared at this stage. Requirements for commissioning and post‑implementation safety evaluation and surveillance should also be determined at the design stage (see paras 7.2 and 7.5).
Pre‑design appraisal 5.20. Management system criteria for design control and continuous improvement should be established and implemented, covering all aspects of the design, including inspection and testing methods, and construction. Measures should be established and documented to ensure that the applicable codes, standards and regulatory requirements are correctly incorporated into the design documents for items important to safety. Measures should also be provided for verification of the adequacy of the design. This verification should be performed by qualified individuals other than those who developed the original design. Further recommendations are provided in Section 2.
Pre‑design appraisal 5.21. Detailed safety analysis should be carried out to the extent necessary for the potential hazards. The analyses should be capable of demonstrating that the design is safe and, in particular, of showing the following: — Any new system or component complies with all relevant safety standards and will function safely in all operational states.

  • New systems will not adversely affect the safety characteristics of other items important to safety under any operational states, nor will they affect the safety relevant characteristics of the research reactor.

  • The experiment or modification can be carried out without significantly increasing the dose to site personnel or members of the public; this should be determined in accordance with the principle of optimization of protection and with consideration of the risk of an accident.

  • The experiment or modification can be carried out without adversely affecting the safety of reactor operation.

  • Any new hazards introduced by the experiment or modification can be safely managed at any stage of the project.

Pre‑design appraisal 5.22. The following should be demonstrated and documented:

  • The introduction of the new system would not adversely affect any consequences, in terms of radiological hazards or other hazards, for any operational states.

  • The failure of the new system would not result in any new event scenario with significantly increased risks (different failure modes may have to be considered).
Pre‑design appraisal 5.23. The technical and operational implications of the proposed modified system or experiment should be evaluated for each of the accident sequences considered in the safety analysis report for the research reactor. The implications of the experiment or modification for the management of potential accidents and their consequences should be analysed.
Pre‑design appraisal 5.24. Furthermore, each credible failure mode of the modified system should be considered as a postulated initiating event for a new event scenario, and its consequences should be analysed by appropriate evaluation methods. Care should be taken to include in the assessment not only direct effects on the research reactor, but also the effect on items important to safety, such as systems for accident prevention and for mitigation of the consequences of accidents.
Pre‑design appraisal 5.25. At the end of this analysis, an updated version of the research reactor safety documentation should be produced, which may include an update of the safety analysis report and the operational limits and conditions.
Pre‑design appraisal 5.26. The safety documentation should be written and maintained according to the requirements established in SSR‑3 [1] and the recommendations provided in SSG‑20 (Rev. 1) [2]. Attention should be paid to the review and updating, as necessary, of the documentation covering the design, operational limits and conditions, and operating procedures and of other safety documentation to be used as a basis for approval for normal operation of the experiment or modified research reactor.
Pre‑design appraisal 5.27. Testing of experimental devices and equipment prior to their installation in the research reactor should be considered. Tests should be planned as part of the design and the commissioning of the experiment or modification.
Pre‑design appraisal 5.28. The output from the design stage should also include the following:

  • A statement of the objectives to be met.

  • Details of the structure of the organization established for the project and the responsibilities of the parties involved.

  • A description of the activities, techniques and procedures to be employed, including those for the implementation programme.

  • A safety evaluation of the specific procedures and techniques to be used.

  • A description of the expected state of the research reactor at the various phases of the project.

  • The necessary design calculations, drawings and specifications for the complete project.

  • The training programme designed to enable site personnel to cope with anticipated operational occurrences during the implementation of the project. (Site personnel should also be informed about the special safety considerations and provisions that apply during the various stages of the project.)

  • Documentation, such as procedures for the modified state of the research reactor, including any new or temporary emergency procedures and the associated training programme.

  • A plan for commissioning to verify that the design objectives have been achieved.

  • An outline of the preliminary decommissioning plan.

  • A special surveillance programme, including ageing management and in‑service inspection requirements, if necessary (see para. 7.5). Such surveillance should be used to demonstrate the continued safety of the research reactor systems.

  • An overview of spare parts important to safety that will need to be available before implementation of the utilization or modification project.

Pre‑design appraisal 5.29. For ageing management, the relevant recommendations in SSG‑10 (Rev. 1) [9] should be followed.
Pre‑design appraisal 5.30. For decommissioning, dismantling and removal of major reactor components, the relevant recommendations in IAEA Safety Standards Series No. SSG‑47, Decommissioning of Nuclear Power Plants, Research Reactors and Other Nuclear Fuel Cycle Facilities [29], should be followed.
Pre‑design appraisal 5.31. The need for approval of the experiment, approval of the design and approval for construction of the modification, or the need for formal authorization as referred to in paras 3.18 and 3.19, should be considered at this stage.
Pre‑design appraisal 6.1. This section covers the fabrication, installation and commissioning stages of the implementation phase of the utilization or modification project. For some projects, not all of the recommendations provided are relevant, for example in cases where the project involves only a modification to procedures.
Pre‑design appraisal 6.2. Irregularities encountered at a particular stage should be dealt with immediately, rather than at a subsequent stage.
Pre‑design appraisal 6.3. If the outcome of a certain stage could place a constraint on a subsequent stage, procedures should be put in place to ensure that such constraints will be satisfied.
Pre‑design appraisal 6.4. For the fabrication stage of the project, measures should be established for the control of procurement of materials; for the development, revision and use of documents and drawings; for the processing of materials; and for the inspection of such activities.
Pre‑design appraisal 6.5. New components or existing components that have to be modified are generally fabricated or modified by suppliers in accordance with the detailed specifications that have been established in the design phase. Before selecting a supplier, the project manager should ensure that the supplier has the necessary experience for the work and is aware of all of the particular constraints of the project, including management system criteria (see para. 5.20). Preliminary visits to potential suppliers should be conducted to verify this.
Pre‑design appraisal 6.6. The project manager should also ensure that the suppliers involved have an appropriate management system.
Pre‑design appraisal 6.7. During fabrication, technical audits and quality audits should be conducted to verify all aspects of fabrication, and to identify any deviations from specifications, quality control, the schedule or deadlines. After discussion with the regulatory body, the operating organization should define which inspections will be conducted during fabrication to verify that it is in compliance with applicable requirements, codes and standards. In particular, regulatory inspections should be conducted during fabrication for equipment that cannot be thoroughly inspected during installation.
Pre‑design appraisal 6.8. Revision of the safety documentation, as mentioned in para. 5.26, should be carried out as appropriate to include the as‑built description of the experiment or modification. The project manager should be responsible for such revisions. The time schedule for the revision of the documentation should be made subject to approval by the reactor manager, in accordance with regulatory requirements.
Pre‑design appraisal 6.9. If the safety documentation has been revised, the documentation should be approved and distributed in accordance with the approved procedures on the basis of the safety significance of the experiment or modification. This could require the involvement of the safety committee and review and approval by the regulatory body, as appropriate. Obsolete safety documentation should be removed from service and archived.
Pre‑design appraisal 6.10. Measures should be established for the control of the installation of equipment, and any potential hazards — for example, radiation, chemical and industrial hazards — should be taken into consideration.
Pre‑design appraisal 6.11. The modification or the installation of the experiment should not commence until all approvals have been obtained and the relevant site personnel involved in the installation have been trained satisfactorily.
Pre‑design appraisal 6.12. The schedule for the installation of the experiment or for the modification should be prepared in consultation with the reactor manager, to ensure that the research reactor is placed in a safe state before commencing the activity.
Management 6.13. Management of the installation stage of the project should cover at least the following:

  • Clear identification of all responsibilities, including those relating to management system procedures and radiation protection;

  • Frequent meetings to provide information about progress and exchange information with all site personnel (i.e. technical and operating personnel and radiation protection personnel) and interested parties involved in or affected by the project;

  • Coordination with security personnel at the research reactor to identify any additional security measures or any potential impacts on existing security measures during or after the installation;

  • Clear procedures with respect to the control (i.e. reporting, assessment and disposition) of deviations from approved methods and specifications or from expected behaviour;

  • Clear procedures to ensure that no foreign objects (e.g. assembly or installation tools, equipment) are left in the area around the modification;

  • Measurement and registration of all characteristics of the system as‑built, which is necessary for updating relevant technical documents, drawings and procedures;

  • Training of, and provision of information to, operating personnel and external personnel with respect to the modification or the conduct of the experiment, methods to be used, safety aspects and safe working practices;

  • Contingencies in the project plans to accommodate unforeseen events and operational deviations that might necessitate a revision of the working practices and the project planning.
Safety aspects 6.14. The designer should carry out a sufficiently detailed safety evaluation of the installation process. This evaluation should be based on a detailed installation plan that describes activities, methods, hazards and temporary provisions, and the technical or administrative measures or precautions that should be implemented to minimize risk during the installation activities.
Safety aspects 6.15. If temporary equipment has to be installed, the external and internal events that have been taken into account for the research reactor should be taken into account for the design and installation of temporary equipment (see also para. 4.31).
Safety aspects 6.16. Specific safety topics that should be considered for the installation stage are those relating to the following:

  • Identification of the hazards and the steps to be taken to control the hazards in order to minimize the risk to personnel, the research reactor and its systems, and the environment;

  • Management of radioactive waste, including transport, decontamination and dismantling aspects, as applicable;

  • External exposure to radiation;

  • Provisions required to prevent the spread of contamination and internal exposure to radiation;

  • Emergency preparedness and response, the safety requirements for which are established in IAEA Safety Standards Series No. GSR Part 7, Preparedness and Response for a Nuclear or Radiological Emergency [30];

  • Safe storage of the fuel, radioactive material and other radiation sources and chemicals during the modification period;

  • Industrial hazards such as high voltage, vacuum, working in high places or confined spaces, fire, local flooding and the use of chemicals and of potentially dangerous tools.

Safety aspects 6.17. All temporary adaptations (e.g. connections, procedures, arrangements) necessary for the implementation of an experiment or modification should be documented and should be made subject to approval by the reactor manager before they are applied.
Safety aspects 6.18. Special temporary safety provisions or procedures should be drafted as required, made subject to approval and exercised (see para. 5.28) in cases where potentially hazardous situations have been identified in connection with the installation of the experiment or the modification at the research reactor. These temporary procedures should be formally withdrawn once the installation is completed (see also para. 6.23).
Safety aspects 6.19. The commissioning of an approved utilization or modification project, which may include pre‑installation testing of experimental devices and equipment, as described in para. 5.27, should be aimed at demonstrating the functionality and safety of the project. Additional recommendations for the commissioning process and for the various stages of commissioning for large modifications are provided in SSG‑80 [3].
Safety aspects 6.20. The reactor manager should be given the responsibility to ensure that a review of the commissioning plan is conducted in accordance with established procedures.
Safety aspects 6.21. The safety of an experiment or modification that is to be implemented should be verified through a commissioning programme involving tests, checks, measurements and evaluations prior to and during implementation of the experiment or modification. Requirement 73 of SSR‑3 [1] is also applicable to the commissioning of an experiment or modification. After discussion with the regulatory body, the operating organization should define appropriate witness points and hold points for inspecting the commissioning of the experiment or modification project.
Safety aspects 6.22. The adequacy of the commissioning programme for each experiment or modification should be reviewed with respect to the following objectives:

  • Determination (by measurement under realistic conditions encountered in normal operation and in anticipated operational occurrences to the extent possible) of all reactor characteristics relevant to safety with respect to the modified system;

  • Demonstration that the structures, systems and components of the research reactor that have not been modified (in particular all items important to safety) will not be compromised;

  • Verification (on the basis of measured data) of the relevant safety parameters and proper performance of all safety functions;

  • Provision of additional information and data from commissioning, in order to update the safety documentation, the technical documentation and the operating procedures;

  • Provision of opportunities and time for the familiarization and training of operating and maintenance personnel;

  • Adjustment of the reactor systems affected by the experiment or modification for optimum performance.

Safety aspects 6.23. Special temporary safety provisions or procedures should be developed and exercised whenever necessary throughout the commissioning process.
Safety aspects 6.24. The completion of the commissioning process should include a check to confirm that all temporary adaptations (e.g. connections, procedures, arrangements) necessary for implementation have been removed or cancelled and that the research reactor has been returned to full operational status.
Safety aspects 6.25. The operating organization should submit the commissioning results to the regulatory body for formal approval and permission for operation of the experiment or with the modified system as required in the licence conditions.
Safety aspects 7.1. The basis for final approval of the experiment or modification for routine operation should be the successful completion of all stages of commissioning and the verification of all information and experience against the requirements as specified in the design. The results of the commissioning tests and the as‑built drawings and documentation should be reviewed in accordance with existing procedures, to demonstrate that the experiment or modification has been built in a manner that conforms to the approved specifications and ensures safe operation.
Safety aspects 7.2. A final commissioning report should be produced in which the results of commissioning are presented and assessed. The report should be subject to approval in accordance with established procedure.
Safety aspects 7.3. Revision of the safety documentation and the safety analysis report, as mentioned in para. 5.26, should be carried out as appropriate to include the as‑built description of the utilization or modification and to take into account the results of the commissioning process. The project manager should be responsible for such revisions. The time schedule for the revision of the documentation should be made subject to approval by the reactor manager, in accordance with the regulatory requirements.
Safety aspects 7.4. If the safety documentation has been revised, the documentation should be approved and distributed in accordance with the approved procedures on the basis of the safety significance of the experiment or modification. This could require the involvement of the safety committee and review and approval by the regulatory body, as appropriate. Obsolete safety documentation should be removed from service and archived.
Safety aspects 7.5. The justification for certain experiments or modifications might be dependent on technical or material characteristics that might be affected in long term reactor operation by irradiation embrittlement, corrosion or other ageing effects. In cases where such effects cannot be predicted with sufficient accuracy from previous experience or by analysis, a safety surveillance programme should be defined for monitoring the behaviour of the relevant characteristics. Any special surveillance requirements determined at the design stage (see paras 5.16 and 5.28) should be implemented.
Safety aspects 8.1. Although the recommendations provided in the following paragraphs are, in principle, applicable for both experiments and modifications, for major modification and utilization projects the recommendations for a new research reactor should be followed where applicable (see Refs [2, 3, 6–9, 11]).
Safety aspects 8.2. Experiments at research reactors can present significant radiological hazards for the persons conducting the experiment, for operating personnel, and in some cases for other site personnel and members of the public. In addition to the design, which should be such as to minimize radiological hazards and which is supported by the commissioning process, the experimenters and persons involved in the operation of the experiment should be trained and should follow approved procedures for the performance of their tasks.
Safety aspects 8.3. Every experiment should be performed using approved operating procedures that describe the responsibilities of those involved in the experiment and that include operating instructions for the experiment.
Safety aspects 8.4. In addition to general training in radiation protection, specific training should be provided for all experiments. Such specific training should cover the following:

  • Operating procedures for the experiment;

  • Rules and instructions for radiation protection associated with the performance of the experiment;

  • Emergency plans and procedures.

Safety aspects 8.5. Areas where there can be significant radiation levels during operation of the research reactor and during reactor shutdown — such as areas close to open beam tubes, reactor loops or irradiated materials — should be determined before reactor startup. Such areas should be classified as radiation protection zones in accordance with their hazard potential (see Requirement 34 of SSR‑3 [1] and GSR Part 3 [28]). After reactor startup, a survey of alpha, gamma and neutron radiation should be made, covering the area around the experiment in particular. The actual radiation fields should be measured, displayed and, where appropriate, recorded. Where necessary, such areas should be cordoned off or physically secured to prevent inadvertent or unauthorized access, and appropriate radiation warning signs should be exhibited.
Safety aspects 8.6. In addition to the information in the safety analysis report, experimenters should prepare the following for the operating personnel: a detailed description of the experimental device; a list of credible possible hazards posed by the experiment; the boundary conditions for operation of the experiment; and a list of all connections to the reactor protection system that might cause the research reactor to shut down.
Safety aspects 8.7. The reactor manager should be made responsible for the coordination necessary (e.g. to take into account the reactor shutdown periods needed for maintenance) for the conduct of experiments.
Safety aspects 8.8. For every experiment, the operating personnel and experimenters should have available the necessary information for the safe performance of the experiment, and the information that may be needed in the event of a safety related problem or operating difficulties. The information should include any operational limits and conditions for the experiment, such as maximum temperatures and pressures. The actions to be taken in the event that these limits are approached or exceeded should be clearly stated in written instructions. These actions should be provided mainly in the form of operating procedures and emergency procedures. A tabulation of the expected radiation levels or other hazards associated with the experiment should be provided, along with a list of the personnel allowed to run the experiment and those persons associated with the experiment who can be called upon for advice if difficulties arise. This information should be regularly reviewed and updated.
Safety aspects 8.9. The limiting conditions for safe operation for the reactor and for the experiment, as well as the procedures for handling and operation of the experiment, should be subject to approval by the reactor manager. Particular consideration should be given to the approval of limiting conditions for safe operation and the procedures relating to the startup of the reactor or the experiment, and to the response of operating personnel to anticipated operational occurrences and design basis accidents.
Safety aspects 8.10. Records should be kept of material, samples, equipment and devices inserted into the reactor core, and such items should be retrieved and accounted for at the end of their irradiation. These records should also include the measured or estimated activity of each item.
Safety aspects 8.11. To ensure safe operation of experimental devices, the experimenters and the operating personnel will need to work together closely. Special arrangements should be considered for startup of the research reactor or the experimental device, such as any special handling necessary by the operating personnel or the experimenters, or operation outside the normal schedule of either the experimental device or the research reactor. Procedures should be prepared, made subject to approval and implemented to ensure adequate communication between the experimenters and operating personnel. The following aspects should be considered for these procedures:

  • The need to announce, through a public address system, that the reactor is starting up or that the experiment will commence;

  • The need for the reactor manager to check the safe conduct of all experiments and the locations of all experimenters;

  • The use of warning lights, other visible signs or audible indications in experimental areas to indicate that the reactor is operating;

  • The use of dedicated communication provisions;

  • Contact details of persons who can be contacted after working hours if special actions are required.
Safety aspects 8.12. The activities of the experimenters and the operating personnel should also be coordinated during routine operation. If an experiment involves operations that might influence reactor parameters (e.g. displacement of a fuel test rig), a method of direct vocal communication between the experimenters and the operating personnel should be available at all times, and the actual status of the experiment should always be known to the operating personnel. These provisions should be put in place in addition to design provisions.
Safety aspects 8.13. The operating instructions should clearly define the tasks and responsibilities of the operating personnel and the experimenters, so as to avoid conflicts of interest between the progress of experiments and the safe conduct of the experiments or safe operation of the research reactor. These responsibilities should be reviewed by the safety committee and made subject to approval by the reactor manager.
Safety aspects 8.14. For some experiments, it might be necessary to change the operating conditions in some manner, such as changing the experimental set‑up, the safety system setting of the experiment or the operating sequence agreed to when the experiment was originally approved. Such proposed changes should be treated as a modification, and the recommendations provided in this Safety Guide should be followed.
Safety aspects 8.15. The reactor manager has direct responsibility for the safety of the reactor operation. Accordingly, the reactor manager or a designated member of the reactor manager’s staff should be given the authority to assume control of any necessary operation of the experimental equipment to ensure the safety of the research reactor and personnel, including stopping any experiment that the reactor manager considers hazardous and placing the experiment in a safe condition. Paragraphs 2.23 and 2.24 provide further recommendations on the responsibilities of the reactor manager.
Safety aspects 8.16. Experimenters should promptly report any deviation from normal operation of their experiment directly to the operating personnel.
Safety aspects 8.17. The reactor manager should enforce any safety rule or any limitations on experiments, if necessary, to ensure the safe operation of both the experiment and the research reactor and to ensure the safety of operating personnel and experimenters.
Safety aspects 8.18. Within the approved procedures and within the approved operational limits for their experiment, the experimenters should assume responsibility for the safe operation of the equipment of their experiment.
Safety aspects 8.19. The responsibilities of the operating personnel and the experimenters should be clearly defined and made subject to approval by the reactor manager.
Safety aspects 9.1. The handling, dismantling and disposal of experimental devices or other irradiated equipment that needs storage and eventual disposal should be carried out in accordance with approved procedures.
Safety aspects 9.2. The procedures should take into account the safety evaluation of all operations connected with the handling, dismantling, post‑irradiation examination, transport and storage or disposal of irradiated equipment. The activity and contamination of irradiated equipment should be evaluated in advance, under both of the following assumptions:

  • The most probable course of the experiment;

  • The worst possible combination of equipment failures and malfunctions due to organizational and human causes.

Safety aspects 9.3. Radiological hazards should be assessed for all relevant conditions. The radiation protection measures (e.g. shielding, cleaning of air, decontamination procedures, use of moveable provisions such as shielding and ventilation provisions to facilitate handling operations) should be demonstrated to be adequate to deal with the worst possible situation.
Safety aspects 9.4. The equipment for the handling, dismantling and safe storage or disposal of irradiated materials and devices should be procured and tested in advance.
Safety aspects 9.5. The operations should be planned such that the exposures of personnel are as low as reasonably achievable and the amounts of radioactive substances released are minimized. Measures necessary to prevent contamination of equipment and personnel should be developed and put in place.
Safety aspects 9.6. If the irradiated equipment can give rise to airborne contamination, a handling process to prevent this should be developed and put in place (e.g. by keeping the equipment in leaktight containers, by providing a system of negative pressures and filters). Criteria for items important to safety (e.g. redundancy; the single failure criterion, which ensures that no single failure or single maintenance action or any other single human action could disable a safety function) should be used in planning such a process. The requirements relating to such criteria are established in SSR‑3 [1].
Safety aspects 9.7. Decontamination schemes should be developed for all surfaces that might be contaminated by the experiment. The safe storage or disposal of decontaminants used should be ensured.
Training 9.8. All documentation describing the sequence of operations and the instructions for operating the equipment should be known to the operating personnel and should be available during the handling, dismantling, post‑irradiation examination and storage of the irradiated equipment or components until their release from regulatory control, further use or disposal.
Training 9.9. The personnel performing the handling, dismantling, post‑irradiation examination and storage of experimental devices should be given the necessary training in all aspects of these operations — including, if necessary, exercises using mock‑ups — before work with irradiated objects is commenced. A method for determining the effectiveness of training should be put in place.
Storage 9.10. If the irradiated equipment of the dismantled experiment, experimental facility or system is to be stored on the site, the volume and the characteristics of the materials to be stored, including their measured or estimated activities, should be evaluated and the safe storage of such equipment should be demonstrated.
Storage 10.1. Out‑of‑core experimental devices or modifications (installations) include two groups: (i) those installations that utilize the radiation produced by the reactor core but are located outside the reactor (biological) shielding (e.g. a neutron spectrometer); and (ii) those installations that are at or near the reactor core and do not utilize the radiation produced by the reactor core, but that constitute a potential hazard (e.g. a cryostat containing liquid nitrogen, cold neutron sources containing hydrogen or deuterium).
Storage 10.2. Both groups of installations should be subjected to the categorization process as described in paras 3.7–3.34.
Storage 10.3. For out‑of‑core installations that constitute a potential hazard, in addition to an analysis of ‘conventional’ safety (e.g. fire, explosion, chemical hazards), analyses should be performed to identify the potential hazards and determine the safety provisions to be implemented to reduce the hazards to the extent possible.
Storage 10.4. In addition to the review by the safety committee, if appropriate, the safety analysis should be reviewed in accordance with management system procedures by appropriate specialists (e.g. specialists in the field of occupational hazards, chemical hazards and electrical hazards).
Storage 10.5. The proposal for an out‑of‑core installation — including the safety analysis for its implementation — should be subject to approval by the reactor manager. Depending on its safety significance (i.e. major, significant, minor or no effect on safety), the proposal should be submitted to the safety committee and to the regulatory body for review and approval of the analysis, as appropriate.
Storage 11.1. The operating organization should set up its organizational structure for the safe operation of the research reactor before the commencement of operation.
Storage 11.2. Paragraph 7.11 of SSR‑3 [1] states:
Storage 11.3. Changes to the operating organization should be carefully evaluated. Frequent modifications to the organizational structure that might affect the stability of the organization should be avoided. Whenever organizational restructuring is undertaken at any level, the modified structure should be such as to ensure that all the responsibilities of the operating organization as defined in SSR‑3 [1] continue to be carried out.
Storage 11.4. If there are safety implications arising from an organizational change, an independent internal review should also be conducted to verify that the provisions for the management of safety, including the provisions for adequate control and supervision, will not be compromised. Proposed organizational changes should be reviewed by the safety committee before submission to the regulatory body for review and assessment, if necessary.
Storage 11.5. Special attention should be paid to the review, and revision as necessary, of the training programme for all site personnel and designated external personnel to ensure in advance that they have an understanding of the new tasks and functions that will follow the organizational changes. In particular, it should be ensured that adequate provisions have been made to maintain trained and qualified personnel in all areas important to safety, and that the new organizational structure has been documented with clear and well understood roles, responsibilities and interfaces. All needs for retraining should be identified by, for example, carrying out an analysis of training needs for any new roles and planning the retraining of personnel where necessary.
Storage 11.6. During periods of organizational change, the adequacy of safety arrangements should be maintained. Proposed organizational changes should be clearly defined and their safety implications should be assessed. Organizational changes should be properly planned well in advance.
Storage 11.7. An acceptable level of safety should be maintained throughout the implementation of organizational changes, starting from the existing organizational structure until new organizational arrangements have become fully established. The possible need for additional resources to cope with any increased workload during the implementation of organizational changes should be considered.
Storage 11.8. The involvement of personnel in any restructuring process should be considered at an early stage, to avoid undue uncertainty and concern with regard to the planned organizational changes.
Storage 11.9. Large organizational changes should be implemented stepwise, if appropriate. The implementation of each step should be monitored to assess the achievement of the objective of the change.

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Safety of Research Reactors, IAEA Safety Standards Series No. SSR‑3, IAEA, Vienna (2016).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Assessment for Research Reactors and Preparation of the Safety Analysis Report, IAEA Safety Standards Series No. SSG‑20 (Rev. 1), IAEA, Vienna (2022).

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  • INTERNATIONAL ATOMIC ENERGY AGENCY, Maintenance, Periodic Testing and Inspection of Research Reactors, IAEA Safety Standards Series No. SSG‑81, IAEA, Vienna (in preparation).

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  • INTERNATIONAL ATOMIC ENERGY AGENCY, Operational Limits and Conditions and Operating Procedures for Research Reactors, IAEA Safety Standards Series No. SSG‑83, IAEA, Vienna (in preparation).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, The Operating Organization and the Recruitment, Training and Qualification of Personnel for Research Reactors, IAEA Safety Standards Series No. SSG‑84, IAEA, Vienna (in preparation).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Radiation Protection and Radioactive Waste Management in the Design and Operation of Research Reactors, IAEA Safety Standards Series No. SSG‑85, IAEA, Vienna (in preparation).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Ageing Management for Research Reactors, IAEA Safety Standards Series No. SSG‑10 (Rev. 1), IAEA, Vienna (in preparation).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Instrumentation and Control Systems and Software Important to Safety for Research Reactors, IAEA Safety Standards Series No. SSG‑37 (Rev. 1), IAEA Vienna (in preparation).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Use of a Graded Approach in the Application of the Safety Requirements for Research Reactors, IAEA Safety Standards Series No. SSG‑22 (Rev. 1), IAEA, Vienna (in preparation).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, IAEA Safety Glossary: Terminology Used in Nuclear Safety and Radiation Protection, 2018 Edition, IAEA, Vienna (2019).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Modifications to Nuclear Power Plants, IAEA Safety Standards Series No. SSG‑71, IAEA, Vienna (in preparation).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Leadership and Management for Safety, IAEA Safety Standards Series No. GSR Part 2, IAEA, Vienna (2016).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Application of the Management System for Facilities and Activities, IAEA Safety Standards Series No. GS‑G‑3.1, IAEA, Vienna (2006).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, The Management System for Nuclear Installations, IAEA Safety Standards Series No. GS‑G‑3.5, IAEA, Vienna (2009).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Functions and Processes of the Regulatory Body for Safety, IAEA Safety Standards Series No. GSG‑13, IAEA, Vienna (2018).

  • INTERNATIONAL NUCLEAR SAFETY ADVISORY GROUP, The Interface Between Safety and Security at Nuclear Power Plants, INSAG‑24, IAEA, Vienna (2010).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, Computer Security Techniques for Nuclear Facilities, IAEA Nuclear Security Series No. 17‑T (Rev. 1), IAEA, Vienna (2021).

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  • INTERNATIONAL ATOMIC ENERGY AGENCY, Preventive and Protective Measures Against Insider Threats, IAEA Nuclear Security Series No. 8‑G (Rev. 1), IAEA, Vienna (2020).

  • INTERNATIONAL ATOMIC ENERGY AGENCY, National Nuclear Security Threat Assessment, Design Basis Threats and Representative Threat Statements, IAEA Nuclear Security Series No. 10‑G (Rev. 1), IAEA, Vienna (2021).

  • The Convention on the Physical Protection of Nuclear Material, INFCIRC/274/Rev.1, IAEA, Vienna (1980).

  • Amendment to the Convention on the Physical Protection of Nuclear Material, INFCIRC/274/Rev.1/Mod.1 (Corrected), IAEA, Vienna (2021).

  • 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).

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  • 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).

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Storage I–1. This annex provides an example of a checklist for categorization of an experiment or modification at a research reactor.
Storage II–1. The following list of topics sets out the minimum content necessary for the safety analysis report for an experiment. The topics are to be addressed using a graded approach based on the safety category of the experiment, as defined in Section 3. The topics that are not relevant for the safety analysis report of the utilization project can be indicated with the remark ‘not applicable’. The list of topics may be modified depending on the type and purpose of the research reactor.
Storage II–2. The layout of the safety analysis report is such that the main chapters contain only technical descriptions, summaries of calculation and analysis methods used, the main results and conclusions. Evaluations with detailed descriptions and calculations may be incorporated in the appendices if necessary.
Storage II–3. Furthermore, the safety analysis report for the utilization project will include figures, sketches and/or flow diagrams indicating overall dimensions, masses, temperatures and pressures. All computer codes used have to be verified, validated and benchmarked for their specific application and valid references have to be given. A summary has to be provided at the beginning of the safety analysis report.
Storage Chapter 1: Introduction

  • Purpose of the utilization project;

  • General nature of the irradiation target;

  • General nature of the irradiation facility;

  • If applicable, reference to earlier experiments or periodic review of the safety analysis report for the utilization project.

Storage Chapter 2: Experimental requirements

  • Nuclear conditions (e.g. fluence, radiation heating, linear power);

  • Process conditions (e.g. target environment, temperature distribution, pressure characteristics);

  • On‑line measurements;

  • Off‑line measuring or inspection possibilities.

Storage Chapter 3: Irradiation target

  • Detailed description (e.g. materials, composition, dimensions, special features);

  • Codes and standards applied;

  • Thermal and mechanical characteristics;

  • Design drawing;

  • Fabrication method and quality control procedures applied.1
Storage Chapter 4: Irradiation facility

  • A functional description of the experimental facility and all in‑core and out‑of‑core components (e.g. thermocouples, heaters);

  • Sketches showing vertical and horizontal cross‑sections;

  • A detailed assembly drawing (including a parts list, a list of materials used and material specifications).

  • A description of the radiation shielding, including calculations (considering optimization of protection and justification), shielding material, thickness, dose rates, sketches and drawings;

  • A description of the procedures for installation and maintenance of the radiation shielding;

  • Verification of the installation and effectiveness of the radiation shielding;

  • A description of procedures for disassembling the radiation shielding after completion of the experiments.

  • A functional description of all components, classified into subsystems, such as the cooling system and the gas supply and circulation system;

  • A flow sheet and block schemes of external systems;

  • Functional characteristics and design requirements of major components (e.g. pumps, valves).

  • A general description of the different groups of instrumentation.

  • The design of the safety instrumentation;

  • Connections or possible interference with the reactor protection system, and interlock instrumentation;

  • Connections with the experiment;

  • Components and diagrams.

  • The objective of the process instrumentation;

  • Components and diagrams.

  • The objective of the scientific instrumentation;

  • Components and diagrams.

  • Instrumentation not covered by the previous categories.

  • A functional description of data acquisition and evaluation systems;

  • Block schemes illustrating the entire set‑up.

Storage Chapter 5: Characteristics of the experiment2

  • Specification of anticipated fluence values.

  • A description of (or reference to) measurements and/or calculations made to verify fluence characteristics at the following points:

    (a) Prior to irradiation;

    (b) During irradiation (dosimetry).

  • Reference to or a summary of calculated and applied nuclear data.

  • Criticality aspects;

  • The total reactivity worth of the experiment;

  • The reactivity effect of the in‑core experimental facility for non‑fixed experiments;

  • The reactivity effect associated with voids that can be filled with water in case of leakage;

  • Reactivity effects from the movement of the experimental facility;

  • The effect on the reactivity worth of the control systems and safety systems.

  • The irradiation target (if fissionable, all noble gases, halogens, actinides and other dangerous nuclides are to be specified);

  • Gases or liquids that could escape as a result of failure of the means of confinement;

  • Structural parts of the in‑pile assembly.

  • Calculation of the decrease in activity owing to decay of the major activity contributors at the end of irradiation and 10 h, 10 d and 100 d after the end of irradiation.

  • Calculation of specific heating rates (due to nuclear fission and radiation heating) of all in‑core materials.

  • Calculation of the following:

    • The radial and axial heat flux density and the temperature distribution;

    • The temperature increase of the coolant.

  • Calculation of temperature control margin that can be achieved by the available control systems (heaters, mixed gas systems).

  • Calculation of the margins to the thermohydraulic critical phenomena under the worst possible operating conditions (i.e. maximum power, minimum cooling), applying all relevant uncertainty (hot spot) factors. A justification of the correlations used has to be provided.

  • Transient behaviour;

  • Containment lids;

  • Cryogenic material behaviour;

  • Standard gas supply pressures.

Storage Chapter 6: Fabrication, assembly and commissioning of equipment
Storage Chapter 7: Operation, maintenance and periodic testing
Storage Chapter 8: Handling, dismantling, transport and disposal
Storage Chapter 9: Post‑irradiation examination
Storage Chapter 10: Safety analysis

  • Target failure;

  • Failure of (some) means of confinement;

  • Cooling (system) failure;

  • Electrical power failure;

  • Failures of instruments;

  • Failures of services (e.g. electricity supply);

  • Failures of (other) components;

  • Operating errors;

  • Handling errors;

  • Applicable internal and external events.
Storage III–1. The following list is non‑exhaustive and provides some examples of modifications that could potentially result in an adverse impact on the safety or nuclear security of a research reactor if not adequately reviewed or properly managed by the operating organization:

  • Modifications that could cause a loss of power to systems relied on for safety or nuclear security.

  • Modifications resulting in the installation or removal of a barrier that could adversely impact safety, nuclear security, emergency response or contingency response.

  • Modifications involving the placement of heavy equipment, materials or any temporary structures that could do any of the following:

    • Obstruct functions relating to the detection of, assessment of or response to any malicious act;

    • Aid or otherwise provide advantage to an adversary in the completion of a malicious act;

    • Increase the response times of security personnel to a malicious act or the response times of those involved in an emergency response;

    • Prevent access of operating personnel to items important to safety or prevent timely completion of manual actions by operating personnel credited in safety analyses;

    • Prevent the access of mobile emergency equipment (e.g. fire trucks, ambulances) in case of an emergency.

  • Modifications involving the installation of a chemical or hazardous material plant or storage facility adjacent to or intersecting with any of the following:

    • A security central alarm station or other security post;

    • A protected response position;

    • An access route to be used in emergency response or contingency response;

    • Items important to safety;

    • Equipment important to nuclear security.

  • Construction activities associated with a modification that remove or degrade physical barriers, thus allowing established access control measures to be bypassed.

  • Modifications to potential theft or sabotage targets by adding, removing or relocating nuclear or radioactive material or equipment important to safety.

Storage IV–1. The following are examples of safety focused questions on proposed modifications to the nuclear security system, and of security focused questions on proposed modifications important to safety, for use in assessing a modification to a research reactor.
Safety focused questions

  • Could the proposed modification result in an increase in the frequency of occurrence of an accident previously evaluated in the safety analysis for the research reactor?

  • Could the proposed modification result in an increase in the likelihood of occurrence of a malfunction or failure of a structure, system or component important to safety previously evaluated in the safety analysis for the research reactor?

  • Could the proposed modification result in an increase in the consequences of an accident previously evaluated in the safety analysis for the research reactor?

  • Could the proposed modification result in an increase in the consequences of a malfunction of a structure, system or component important to safety previously evaluated in the safety analysis for the research reactor?

  • Could the proposed modification create a possibility for an accident to occur of a different type than any previously evaluated in the safety analysis for the research reactor?

  • Could the proposed modification create a possibility for a malfunction of a structure, system or component important to safety with a result that is different than any result previously evaluated in the safety analysis for the research reactor?

  • Could the proposed modification result in a design basis limit for a fission product barrier being exceeded or altered (e.g. changes to security measures aimed at preventing sabotage to the fuel cladding, reactor tank, pressure vessel or confinement structures)?

  • Could the proposed modification result in a departure from the method of evaluation used in establishing the design bases or in the safety analysis for the research reactor?

  • Could the proposed modification increase the risk of exposure of site personnel and the public?

  • Could the proposed modification obstruct operations personnel or obstruct emergency workers from carrying out actions for which credit is given in the safety assessment?

  • Could the proposed modification result in or lead to non‑compliance with the regulatory requirements for safety?
Nuclear security focused questions

  • Could the proposed modification decrease a nuclear security system’s reliability or its availability to perform its intended functions?

  • Could the proposed modification increase the likelihood of malfunction or failure of nuclear security equipment or systems?

  • Could the proposed modification decrease the effectiveness of the nuclear security plan for the site or research reactor or invalidate the protective strategy for the site or research reactor (e.g. communications, timelines and access routes for contingency response, equipment and systems for nuclear security, measures against potential insider threats or protected response positions)?

  • Could the proposed modification interfere with the detection or assessment of unauthorized access (i.e. interior and exterior sensors, zones of detection and fields of view of the sensors or of the security cameras, alarm communications, access control systems)?

  • Could the proposed modification increase the response times of security personnel, for example because of the installation of artificial or natural vehicle barriers, channelling barriers or vehicle access control points?

  • Could the proposed modification decrease delay times for adversaries, for example because of the installation of artificial or natural vehicle barriers, channelling barriers, vehicle access control points, access delay systems, or exterior or interior delay barriers?

  • Could the proposed modification increase the number of theft and sabotage targets, change their configurations, or create a new theft or sabotage target that was not included in the previous evaluations?

  • Could the proposed modification result in or lead to non‑compliance with the regulatory requirements for nuclear security?
Nuclear security focused questions V–1. Routine reviews of operation (including modifications to hardware and procedures, significant events, operating experience, management and personnel competence) and special reviews following events of major safety significance are the primary means of safety verification. In addition, systematic safety reassessment, also known as periodic safety review, is performed to assess the cumulative effects of ageing of systems, structures and components, modifications to the research reactor, operating experience, technical developments and siting aspects. Such reviews include an assessment of the design and operation of the reactor against current safety standards and practices in order to take into account advances in knowledge, and they have the objective of ensuring a high level and continuous improvement of safety throughout the operating lifetime of the research reactor. They are complementary to routine and special safety reviews and do not replace them. Such reviews could indicate that a modification of the existing reactor systems or procedures is necessary to meet current safety standards.
Nuclear security focused questions V–2. Operating experience from other research reactors, nuclear installations or other industrial facilities using similar structures, systems, components or processes could be applicable to the design or operation of the research reactor. In addition to operating experience assessed during periodic safety reviews, there may be a need to make modifications on a shorter timescale in response to emergent safety considerations.
Nuclear security focused questions V–3. Ageing of structures, systems and components or of an experimental facility, obsolescence of equipment, problems relating to spare parts, or experience from maintenance and operation might call for modification of reactor systems and operating procedures. Another incentive for modification might be the availability of new materials or improved components.
Nuclear security focused questions V–4. Reactor systems or reactor operating conditions might be upgraded in response to the need for improved irradiation conditions, more experimental capacity or improved reactor availability.
Nuclear security focused questions V–5. A major reason for modifications is the need to cater for new experiments or to extend existing experiments. Such modifications can entail new hazards.
Nuclear security focused questions V–6. The need for a modification might also arise from considerations of reactor economy, fuel availability, human factors or nuclear security at the reactor.
Nuclear security focused questions V–7. The relevance of these or other considerations for a particular research reactor will depend strongly on the reactor type, and its age and utilization, and on national safety criteria.