SSG-1 (Rev. 1) Borehole Disposal Facilities for Disused Sealed Radioactive Sources

To contain the waste;

To isolate the waste from the accessible biosphere and to reduce substantially the likelihood of, and all possible consequences of, inadvertent human intrusion into the waste;

To inhibit, reduce and delay the migration of radionuclides at any time from the waste to the accessible biosphere;

To ensure that the amounts of radionuclides reaching the accessible biosphere due to any migration from the disposal facility are such that possible radiological consequences are acceptably low at all times.”

To establish and implement a decision making process for designating a disused sealed radioactive source as radioactive waste (see Ref. [8]).

To develop and maintain a comprehensive national inventory of radioactive waste (including disused sealed radioactive sources declared as radioactive waste).

To ensure that the preferred options for radioactive waste management are identified (see para. 3.5 of GSR Part 5 [3]).

To ensure that due consideration is given to interdependences between the various steps in waste management.

To ensure that the long term storage of disused sealed radioactive sources that have not been declared as radioactive waste is avoided.

To develop a disposal programme for disused sealed radioactive sources designated as radioactive waste that is compatible with the State’s overall radioactive waste management programme¹³ (see Ref. [8]).

To ensure that consideration is given to the national need for one or more radioactive waste disposal facilities and to the type(s) of facility that might be the most appropriate, depending on the inventory of disused sealed radioactive sources and other radioactive waste for disposal in the State.¹⁴

To ensure that safety is paramount among the factors considered when selecting appropriate types of disposal facility for disused sealed radioactive sources and other radioactive waste. Other factors that should be considered include the inventory of disused sealed radioactive sources and other radioactive waste for disposal in the State, the potential need for transport of radioactive material, and relevant socioeconomic factors.

To ensure that the resources devoted to safety by the licensee, and that the scope and stringency of regulations and their application, are commensurate with the magnitude of the radiation risks and their amenability to control (see para. 3.24 of SF‑1 [1]).¹⁵

Establishing or identifying legally responsible organizations for the development, commissioning, operation, closure and institutional control of borehole disposal facilities;

Setting clearly defined legal, technical and financial responsibilities for organizations that are to be involved in the development, commissioning, operation, closure and institutional control of borehole disposal facilities;

Ensuring the adequacy and security of financial provisions, for example by requiring the operating organizations of borehole disposal facilities to establish funds for facility closure and any subsequent controls for which they are responsible;

Defining the overall process for the development, commissioning, operation, closure and institutional control of borehole disposal facilities, including the legal and regulatory requirements at each step, and the processes for decision making and the involvement of interested parties;

Defining legal, technical and financial responsibilities and, if necessary, providing for any institutional arrangements that are envisaged after disposal facility closure, including monitoring and ensuring the nuclear security of the disposed waste;

Establishing a regulatory body with appropriate responsibilities for oversight of predisposal waste management facilities and borehole disposal facilities;

Ensuring that the necessary scientific and technical expertise (e.g. from national institutes for health, radiation protection, geology, hydrology and other relevant disciplines) is available to both the operating organization and the regulatory body.

Whether the operating organization has the necessary competences and resources (e.g. human, financial);

Whether the site is suitable;

Whether all aspects of the facility design and the limits and controls are adequate;

Whether the operating organization uses an appropriate safety management system;

Whether the safety assessments are adequate;

Whether there are additional requirements or conditions that should be imposed and, if these have already been imposed, whether they have been fulfilled.

In relation to justification, Requirement 10 of GSR Part 3 [2] states that “The government or the regulatory body shall ensure that only justified practices are authorized.” As indicated in para. 2.5 of GSR Part 5 [3], radioactive waste management is part of the ‘practice’ giving rise to the waste and as such does not require separate justification.

In relation to optimization, Requirement 11 of GSR Part 3 [2] states that “The government or the regulatory body shall establish and enforce requirements for the optimization of protection and safety, and registrants and licensees shall ensure that protection and safety is optimized.”

In relation to dose limits, Requirement 12 of GSR Part 3 [2] states that “The government or the regulatory body shall establish dose limits for occupational exposure and public exposure, and registrants and licensees shall apply these limits.”

In relation to dose and risk constraints, para. 3.120 of GSR Part 3 [2] states that “The government or the regulatory body shall establish or approve constraints on dose and constraints on risk to be used in the optimization of protection and safety for members of the public.” Dose and risk constraints are established at levels below those of the corresponding limits because exposures could be received from more than one source. Risk here refers to the risk of all cancers and the risk of hereditary effects.

An effective dose of 20 mSv per year averaged over five consecutive years (100 mSv in 5 years) and of 50 mSv in any single year;

……. “

An effective dose of 1 mSv in a year;

In special circumstances, a higher value of effective dose in a single year could apply, provided that the average effective dose over five consecutive years does not exceed 1 mSv per year”.

The dose limit for members of the public for doses from all planned exposure situations is an effective dose of 1 mSv in a year [2]. This and its risk equivalent are considered criteria that are not to be exceeded in the future (see para. 2.15(a) of SSR‑5 [4]).

To comply with this dose limit, a disposal facility (considered as a single source) is so designed that the calculated dose or risk to the representative person who might be exposed in the future as a result of possible natural processes affecting the disposal facility does not exceed a dose constraint of 0.3 mSv in a year or a risk constraint of the order of 10^‑5 per year (see para. 2.15(b) of SSR‑5 [4]).

In relation to the effects of inadvertent human intrusion after closure, if such intrusion is expected to lead to an annual dose of less than 1 mSv to those living around the site, then efforts to reduce the probability of intrusion or to limit its consequences are not warranted (see para. 2.15(c) of SSR‑5 [4]).

If human intrusion is expected to lead to a possible annual dose of more than 20 mSv (see table 8 of Ref. [33]¹⁶) to those living around the site, then alternative options for waste disposal are to be considered (para. 2.15(d) of SSR‑5 [4]).

If annual doses in the range 1–20 mSv (see table 8 of Ref. [33]) are indicated, then reasonable efforts are warranted at the stage of development of the facility to reduce the probability of intrusion or to limit its consequences by means of optimization of the facility’s design (see para. 2.15(b) of SSR‑5 [4]).

The International Commission on Radiological Protection considers that a dose rising towards 100 mSv will almost always justify protective action (see para. 241 of Ref. [33]).

The International Commission on Radiological Protection indicates that exposures above 100 mSv incurred either acutely or in a year would be justified only under extreme circumstances, either because the exposure is unavoidable or in exceptional situations such as the saving of life or the prevention of a serious disaster. No other individual or societal benefit would compensate for such high exposures (see para. 236 of Ref. [33]).

The radionuclide, and its half‑life and activity at a specified date;

The nature of radiation emitted and the dose rate at contact and 1 m distance;

The size of the unshielded source;

Whether the source is known to be leaking;

The physical and chemical form of the source;

The container materials and thickness.

Manufacturer;

Source type and model;

Serial number;

Date of manufacture;

Date of import;

Date of receipt by the operating organization of the borehole disposal facility;

Previous owners;

Name and type of device in which the source was used and the use to which it was put.

Provide the facilities and equipment necessary for these activities and develop and follow appropriate operating procedures;

Provide radiation shielding appropriate to the nature of the radioactive sources and radioactive waste to be processed;

Remove the sources from the devices in which they were used and place them in appropriate capsules for temporary storage;

Retrieve the sources from temporary storage and condition them for disposal;

Condition waste for borehole disposal and dispose of the waste packages.

Arrangements for above ground operations (e.g. waste handling and transport);

Provision of appropriate radiation shielding;

Control of working environments;

Design of predisposal waste management facilities and activities (e.g. waste processing);

Design of facilities and activities to avoid discharges;

Separation of facility construction activities (e.g. drilling) from waste emplacement operations;

Establishment and use of procedures for operating the disposal facility (e.g. waste emplacement procedures, borehole backfilling procedures);

Use of remote techniques as necessary (e.g. for waste handling and emplacement);

Reduction of the possibility of accidents and minimization of their potential consequences;

Minimization of the need for maintenance activities in radiation and contamination areas.

Whether due attention has been paid throughout the facility development process to the post‑closure safety implications of possible options, including those relating to the design and siting issues discussed in paras 6.14–6.21 and Appendix I, in particular the following:

Whether the assessed potential doses and risks fall below the relevant dose and risk criteria.

Whether the probability of events that might give rise to potential doses or risks above the relevant dose and risk criteria has been reasonably reduced by means of siting or design.

Whether the programmes for siting, design, construction, operation and closure have been conducted in accordance with a suitable management system to ensure the necessary level of quality in safety related aspects of the project (see GSG‑16 [26]).

Selecting a suitable site for the borehole disposal facility;

Designing the facility in such a way that it can accommodate the volume of waste to be disposed of (e.g. by choosing an appropriate number and diameter of boreholes);

Locating the disposal zone(s) appropriately within the geological environment, taking due account of the geology, hydrogeology and geochemistry;

Providing sufficient isolation of the waste to minimize the probability of inadvertent human intrusion;

Selecting appropriate borehole drilling techniques, in particular to avoid creating pathways for radionuclide migration along or close to the borehole walls.

What are the types and volumes of waste to be disposed of? What hazards are associated with the waste and how will these hazards evolve?

Where should the facility be sited?

How can the facility layout be designed to take advantage of the natural characteristics and barrier potential of the host environment?

How should predisposal waste management operations be performed?

How many boreholes should be constructed?

In what depth range should waste be disposed of?

What type of borehole casing should be used?

Within the chosen disposal concept, are there other options that could be considered (e.g. for waste conditioning, for waste emplacement) and what would be the safety implications of these options? For example, could alternative materials be used for the engineered barriers?

How can quality control be ensured throughout the management of the disused sealed radioactive sources and waste?

What monitoring might be needed?

What institutional controls should be put in place?

A generic design including the use of stainless steel and cement based engineered barriers (see Section 2);

Procedures for, and a demonstration of, operational safety;

A generic safety assessment (see Ref. [19]) — although this does not remove the need for a site specific assessment, the generic safety assessment does provide reasonable assurance that the disposal concept is capable of providing the necessary levels of safety in a wide range of environments.

Siting the borehole disposal facility at a location that has stable geological conditions, low potential for the abstraction of water and/or the extraction of minerals, oil, gas or other resources (thus a low probability of inadvertent human intrusion) and groundwater that is chemically compatible with the structures, systems and components of the facility.

Designing the borehole disposal facility in such a way that the waste is disposed of in solid waste forms that are chemically and physically stable, using waste packages and other structures, systems and components that are chemically and physically stable, ensuring that the waste, waste forms and structures, systems and components are compatible with each other and with the host rock; and in such a way that the waste is disposed of at depths deeper than the recommended minimum depth. The design should be consistent with the hazard posed by the waste and the degree of containment and isolation shown to be necessary in the safety case for the facility.

Keeping the operational period short (e.g. a few months to a year) and avoiding keeping a borehole open for an extended period; this should be achieved by drilling and constructing a borehole and emplacing waste and backfill only when sufficient waste has been collected to allow this sequence of activities to be conducted as a reasonably sized disposal campaign (e.g. sufficient waste to fill the disposal zone in a disposal borehole). The operating organization should provide sufficient storage capacity for waste before and between disposal campaigns. During predisposal management, waste is required to be processed into a safe and passive form for storage or disposal as soon as possible; the processing is required to be consistent with the type of waste, the possible need for its storage, the anticipated disposal option, and the limits, conditions and controls established in the safety case and in the assessment of environmental impacts (see paras 4.13 and 4.14 of GSR Part 5 [3]).

Closing the borehole disposal facility in such a way that does not involve subsequent maintenance of the structures, systems and components.

Implementing passive institutional controls, such as the archiving of records of the borehole disposal facility, controls on land ownership and restrictions on land use. Such passive institutional controls should be designed to reduce the possibility of future inadvertent human intrusion and provide additional assurance and confidence in the safety of the facility.

By showing that the safety assessment is as comprehensive as possible and is based on good science and engineering practice and high quality data;

By showing that the disposal system is safe and robust (i.e. its performance is not unduly sensitive to individual detrimental events or processes);

By providing evidence regarding the appropriateness and effectiveness of controls such as waste acceptance criteria (see paras 6.58–6.66);

By providing information to demonstrate the feasibility of, and build confidence in, the effectiveness and durability of the engineered components of the facility.

Host rocks with low permeability, where the rate of groundwater movement and the degree of radionuclide sorption onto the rocks together ensure that any radionuclides migrating from the waste will take many thousands of years to migrate to the biosphere;

Waste containers that are resistant to corrosion under the conditions in the disposal system, for example containers made of particular stainless steels for the disposal of different types of disused sealed radioactive source [17];

Waste in solid form that has low solubility and that releases radionuclides slowly under the relevant geochemical conditions;

Engineered barrier materials that retard radionuclide migration, for example a cement based backfill between the container and the borehole casing, which creates high pH conditions that limit solubility and promote sorption, thus providing containment.

Ordinary Portland cement for backfill when the surrounding groundwater or geology has high levels of sulphate, which is common in some types of clay;

Swelling clays (e.g. bentonite) for containment in highly saline environments or in groundwater with high levels of potassium.

Descriptions of the safety case context, the safety strategy and the disposal system;

Demonstrations of optimization and the management of uncertainty;

Evidence of independent review and the involvement of interested parties in the development of the safety case;

A statement of the limits, controls and conditions to be applied during facility development;

The management system and evidence that it has been applied to ensure the quality of safety related work and activities (see GSG-16 [26] and paras 4.60 and 4.61 of SSG‑23 [35]).

The legal and regulatory framework for the management of the waste, which may include international commitments (e.g. the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management [6] and the Code of Conduct on the Safety and Security of Radioactive Sources [7]) and national laws, regulations, policies and strategies on radioactive waste management, along with a description of their application to borehole disposal.

The purpose of the safety case at this stage within the context of the step by step approach to the development of the borehole disposal facility, possibly supplemented with specific supporting objectives (e.g. relating to proposed changes to operations).

The scope of the safety case at this stage, including the features, events and processes that are included in the safety case and those that are excluded, along with justifications for these decisions. The scope of the safety case might be influenced by aspects such as the site selection process, public engagement and acceptance, environmental and social impact assessment, operational and post‑closure time frames, and the application of a graded approach to safety case development.

The target audience for the safety case and how interested parties will be involved during the development of the safety case.

How the waste is to be contained and isolated from the biosphere using borehole disposal;

The inclusion of passive safety features in the borehole disposal system;

The robustness of the borehole disposal system;

The approach to management of uncertainties and interdependencies and the application of the graded approach.

The inventory of waste, how the inventory was derived and the level of confidence in the inventory;

The characteristics of the site and its surrounding environment;

The predisposal facilities and activities (e.g. hot cell or other facility for conditioning of waste);

The operating procedures;

The disposal facilities and activities (e.g. configuration and construction of waste packages and boreholes, commissioning activities, waste emplacement operations) and the closure activities;

The safety functions associated with the engineered and natural components of the borehole disposal system and how these are expected to be fulfilled over time.

Scenarios representing the expected evolution of the disposal system, including the disposal facility as designed and as constructed (in Ref. [19] and in Appendix II to this Safety Guide, these are termed ‘design scenarios’);

Scenarios including initial defects in engineered barriers (in Ref. [19] and in Appendix II to this Safety Guide, these are termed ‘defect scenarios’);

Scenarios that address uncertainties in, and possible changes to, environmental conditions (e.g. climate, hydrogeology, seismic activity);

Scenarios including radionuclide transport along a disposal borehole or in any zone of damaged rock adjacent to a disposal borehole;

Scenarios including radionuclide transport in groundwater to a water abstraction well and/or to other groundwater discharge points (e.g. a river);

Scenarios including radionuclide transport in groundwater and potential exposures via pathways that include irrigation of crops, watering of livestock and drinking water;

Scenarios including inadvertent human intrusion (in Ref. [19] and in Appendix II to this Safety Guide, these are termed ‘borehole disturbance scenarios’).

The construction of building foundations, cuttings for roads and railways, ‘cut and cover’ tunnels and standard tunnels;

Drilling (e.g. for natural resources, for research).

A single feature of the design or the site;

A single assumption made in the safety assessment;

A single safety function.

That the documents provide a complete record of the decisions and assumptions made in the development, commissioning, operation, closure and institutional control of the borehole disposal facility and a complete record of the models and data used in the safety assessments.

That information is presented in a traceable way so that independent, suitably qualified and experienced personnel could go back to the original sources of information supporting the various elements of the safety case, understand how these elements have been used in the safety case and, if necessary, reproduce the safety assessments.

That the reasoning for decisions taken (e.g. on the siting, design or operation of the facility) is recorded in a logical and clear way. The operating organization should document the arguments for and against the alternative options and should explain why one option was chosen over another.

That the short term storage of the sources always occurs in safe and secure conditions, with proper authorization and periodic inspections (see Ref. [8]);

That the short term storage of the sources occurs in a manner that does not preclude future management options (see Ref. [8]);

That the regulatory body sets an appropriate time limit for short term storage of the sources, contingent on availability of other management options (see Ref. [8]);

That consideration is given to centralized storage (see para. 5.3 of WS‑G‑6.1 [21] and para. 4.80 of SSG‑45 [22]).

If it is necessary to store the disused sealed radioactive sources temporarily before they can be conditioned for disposal, the operating organization should consider using IAEA standard source conditioning capsules. The capsules containing the sources should be stored inside containers that provide appropriate shielding to protect workers.

To condition disused sealed radioactive sources for borehole disposal, the operating organization should transfer the sources into disposal capsules, which should be sealed by welding, then placed and sealed inside a waste disposal container made of stainless steel with a cement based insert, as described in paras 2.15 and 2.16. Other containers and packaging may be used, but in all cases the operating organization should justify their use and demonstrate their performance in the safety case.

The geology and geological evolution of the area. This investigation should involve various surface based and underground activities such as geophysical and borehole drilling investigations and the collection of rock samples for examination and characterization. Investigatory drilling may help to establish drill penetration rates, determine the presence of resources and establish the geology at depth, including the presence of faults or other geological features that may influence the performance of the borehole disposal facility.

The geomorphology and geomorphological evolution of the area. This investigation should involve various studies to map and quantify the geomorphology and to investigate past, present and potential future erosive processes and land movements (e.g. landslips, faults, earthquakes, volcanism).

The hydrogeology and hydrogeological evolution of the area. This investigation should involve various studies to establish the groundwater conditions at the site, including the presence of perched water, the properties of the partially saturated or unsaturated zone, the depth to the water table, the piezometric surface and results from tests to determine hydraulic parameters (e.g. hydraulic head gradient, permeability, porosity, saturation).

The hydrology and hydrological evolution of surface water bodies in the area. This investigation should involve various studies to identify and establish the behaviour of surface water bodies in response to local meteorological conditions (e.g. precipitation), including studies of hydrological responses to adverse conditions (e.g. extreme rainfall, flooding).

The geochemistry and geological evolution of the disposal system. This investigation should involve various studies to identify the mineralogy and understand the geochemistry of the rocks and water in the disposal system. Particular attention should be focused on determining the chemical composition, redox potential and speciation of groundwater, as these parameters can strongly affect the mobility of radionuclides.

The meteorological conditions at present and their evolution, including the possible effects of future climate states on landform development and site conditions (e.g. Ref. [41]).

The ecology at and around the site. This investigation should include studies to collect data on fauna and flora.

Human populations and behaviours at and around the site. This investigation should involve studies to collect data on the size, locations and density of human populations; on human activities, including land uses (e.g. agriculture); and on human behaviours (e.g. where people obtain food and water from and consumption rates) that are needed for dose assessments in past, present and potential future conditions.

The inventory of waste, including the types, quantities and physical and chemical properties of the waste to be disposed of and the radionuclides present;

The geological conditions at the site (e.g. geological stability, groundwater flow, chemical compatibility of the rocks and groundwater with the engineered barriers) and how these affect considerations such as the number of boreholes, borehole dimensions, and number and depth of disposal zones;

The engineered barrier system;

Plans for operation of the borehole disposal facility, including waste emplacement and backfilling;

Plans for sealing of boreholes and closure of the borehole disposal facility;

Plans for the post‑closure period.

To assess whether a design has the potential to fulfil the relevant dose and risk criteria (if it does not, the design can be eliminated from further consideration);

To evaluate the performance of the disposal system and its components;

To inform decisions on the design and on optimization.

That the operating organization is applying its management system to ensure the safe operation of the borehole disposal facility;

That the operations do not compromise any safety functions on which the post‑closure safety of the borehole disposal facility depends;

That only waste that complies with the waste acceptance criteria is accepted for disposal in the borehole disposal facility (see paras 6.58–6.66).

A limitation to accept for disposal only solid disused sealed radioactive sources and low and intermediate level secondary radioactive waste generated during the management of the disused sealed radioactive sources;

A limitation to accept for disposal only waste forms with stable chemical and physical properties (e.g. no powders; no putrescible, reactive or explosive materials or waste);

Limits on the weight and size of waste packages;

Limits on the levels of surface contamination on a waste package;

Specifications for capsules and waste containers (e.g. materials, manufacturing and welding methods, testing protocols);

Specifications for backfill materials (e.g. materials, backfilling methods, testing protocols);

Limits on the heat output of a waste package;

Limits on the disposal of waste that might generate gas;

Limits on the total activity of each waste package, of the waste in each borehole and of the waste that can be disposed of in the entire disposal facility;

Limits on the radionuclide content of each waste package, of each borehole and of the entire disposal facility;

Controls on the mixing of different types of disused sealed radioactive sources and/or radionuclides within waste packages;

Limits on the fissile nuclide content of each waste package, of each borehole and of the entire disposal facility.

The protection of workers during disposal operations depends on the type of shielding available, which might in practice limit the activity of strong gamma emitters and neutron sources that can be accepted for processing and disposal.

Post‑closure safety considerations might limit the activity of long lived radionuclides that can be disposed of in the borehole disposal facility.

To avoid excessive temperature rises in the disposal borehole, heat generation should be kept below a few tens of watts per waste package, which might mean that the largest sources that can be accepted have activities of heat generating radionuclides of no more than several tens of GBq (see Ref. [16]).

The origin of the waste and the processes by which it was generated;

The physical and chemical forms and properties of the waste (e.g. of the materials used in waste conditioning and their radionuclide retention properties);

The activity concentration and total activity of radionuclides in the waste;

The mass, activity concentration and total activity of fissile nuclides in the waste;

The type of waste package;

The radiation level at the surface of the waste package;

The level of surface contamination on the waste package;

The mass and weight of the waste or waste package;

The date(s) of waste processing;

The methods, equipment and procedures used to describe and characterize the waste and to confirm compliance with established waste acceptance criteria.

Authorizations (e.g. licences, permits, amendments);

Commissioning records;

The safety case and safety assessments;

An environmental impact assessment;

Peer review reports;

Technical specifications and amendments;

Design options, concepts, documents, calculations and drawings;

Records of the facility actually constructed (‘as‑built’ records);

Approved design changes;

Procurement records for structures, systems and components;

Operating procedures;

Records of the implementation, review, updating and maintenance of emergency preparedness and response arrangements, including records of training, exercises, response to actual emergencies, lessons identified and corrective actions implemented;

Waste emplacement plans;

Records generated during facility operation, including records of emplaced waste packages;

Records of assessments, inspections and verifications of processes and activities;

Records of any non‑conformances and corrective actions;

Records of the training, experience and qualification of personnel;

Monitoring data;

Records of any incidents, including accidents, that have occurred;

Records of interactions between the operating organization and the regulatory body (e.g. meetings, inspections).

Be in accordance with applicable laws and regulatory requirements;

Be appropriate to the periods of facility development, commissioning, operation, closure and institutional control;

Include the collection and updating of information to help evaluate the behaviour of the disposal facility and its structures, systems and components, and the impact of the waste disposal system on the public and the environment;

Contribute to building confidence in the safety of the facility and to developing the safety case by providing measurements that can be used to demonstrate compliance and test assumptions;

Provide information that can be used to reassure interested parties, including the public, of the safety of the facility.

Operation of the site and the facility in accordance with the authorization;

Maintenance of signs, fences and guards at the authorized site, for example, to prevent unauthorized access and unintended radiation exposures;

Provision of nuclear security;

Monitoring and surveillance activities;

Remedial work that might become necessary.

Archiving of records of the disposal facility;

Controls on land ownership;

Restrictions on land use.

The location of the disposal facility;

Information on the geology, geochemistry and hydrology of the disposal facility site, including data derived from site characterization (see paras 6.14–6.21 and Appendix I);

Details of the design of the facility, including the locations and descriptions of the borehole(s) and the associated engineered structures, systems and components (e.g. borehole backfill, casing, seals) (see paras 6.22–6.26) and descriptions of the waste and waste packages, including the origins of the waste, the radionuclides present, the waste containers used and the depths of waste disposal;

Descriptions of the construction and operation of the facility, including dates and details such as measured water inflows to boreholes, and any non‑conformances and the actions taken to rectify them (see paras 6.38⁠–⁠6.48);

Records of any incidents, including accidents, that have occurred;

The safety case and safety assessments, including a description of the arrangements for the post‑closure period and the monitoring programme and monitoring results (paras 7.1–7.11);

Authorizations (i.e. permits and licences) issued by the regulatory body.

The adequacy of the collection and interpretation of site characterization data, and of the use of the data in safety assessment models;

The training of staff who will undertake predisposal management and disposal operations;

The capability of any contractor(s) employed (e.g.for borehole construction);

The proper management of waste emplacement and of events and incidents.

To assess whether the facility provides satisfactory protection from radiation for future generations and the environment, in accordance with the Fundamental Safety Principles [1] and the requirements established in GSR Part 3 [2] and SSR‑5 [4];

Where satisfactory protection is not provided, to assist in decision making on whether it is justified to take remedial action to upgrade the safety of the facility, for example by adding further physical and/or administrative protection or by retrieving the waste.

The geology and geological evolution of the site and the surrounding area. The site should be geologically stable. Some events and processes might bring disposed waste closer to the surface environment, result in a loss of isolation and cause people to be exposed to radiation. Such events and processes include erosion, tectonic uplift, glaciation and permafrost melting. Geological stability should be evaluated on the basis of evidence of relevant events and processes (e.g. recent or historic tectonic events and processes, faulting and seismicity, in situ stress, soil liquefaction, volcanism). Geological stability is generally consistent with an absence of features such as capable faults, diapirs, salt domes and volcanoes, and an absence of large in situ stress differentials. The geology of the site should include strata or horizons with characteristics that are suitable to be used as disposal zones and that have sufficient thicknesses to accommodate the waste and separate the disposed waste from any overlying or underlying zones with greater permeability.

The geomorphology and geomorphological evolution of the site and the surrounding area, and the events and processes that might affect facility operations. The site should be geomorphologically stable; this is generally consistent with an absence of features such as mountainous terrain with steep gradients or areas with active subsidence or landslip.

The hydrology and hydrogeological evolution. Information with which to evaluate hydrological and hydrogeological conditions should include, but not necessarily be limited to, rock permeability and porosity, groundwater flow rates and directions, hydraulic conductivity, hydraulic heads and gradients, and the presence of groundwater wells. Characteristics that tend to be favourable for siting a borehole disposal facility include rocks with low permeability, low hydraulic head gradients and low rates of groundwater flow at depth; these characteristics are generally consistent with low topography and the absence of aquifers and rocks with high permeability (e.g. karst). Events and processes that might affect borehole disposal facility operations include flooding, thus necessitating consideration of the climate and extreme weather conditions in the area of the facility. The generic safety assessment contained in Ref. [19] suggests that it is possible to develop safe borehole facilities for the disposal of disused sealed radioactive sources in either hydrologically unsaturated or saturated conditions, but it is recommended to avoid disposing of waste in a zone through which the level of the water table varies over time (see also para. I.39). The operating organization should ensure through appropriate facility design that disposed waste will be sufficiently isolated from any aquifers containing potable water that are present at the site (see para. 6.44).

The geochemistry and geochemical evolution. The information used to evaluate geochemical conditions should include, but not necessarily be limited to, rock types and mineralogy, and rock and groundwater compositions and ages. Characteristics that tend to be favourable for siting a borehole disposal facility include the presence of old groundwater, which tends to indicate low groundwater flows in the past, and groundwater whose geochemistry is and will remain generally unreactive to the rocks present and to the materials of the engineered barrier system. It should not be assumed, however, that a safe disposal facility cannot be developed at sites with other characteristics, such as the presence of saline groundwater; the suitability of these sites should be ascertained through safety assessment.

Inadvertent human intrusion. The operating organization should site borehole disposal facilities away from areas with mineral, oil, gas, geothermal, water or other resources in order to reduce the probability of inadvertent human intrusion.

Gathering information and evidence on the amount and rate of percolation of water through the unsaturated zone, on the basis of past and present groundwater levels and the characteristics of the groundwater in the underlying rocks, including details of groundwater chemistry, origin, age, flow and pressure;

Making an assessment of possible future movements of the water table and the probability of temporary saturation of the rock of the disposal zone, taking account of past and present hydrogeological conditions, possible future climatic conditions, and rates of erosion.

To help identify the key data and parameters that will need to be gathered and evaluated in order to develop a site specific assessment;

To help determine the extent of site characterization needed;

To serve as a basis for site specific assessment.

The design scenario. In this scenario it is assumed that the disposal facility has been constructed, operated and closed as designed and that it has evolved as expected during the post‑closure period.

The defect scenario. In this scenario it is assumed that not all of the components of the near field have performed as envisaged in the design scenario owing to either defective manufacturing of waste packages (e.g. welding defects) or defective implementation of the borehole disposal concept (e.g. improper emplacement of backfill). Several variants of the defect scenario are considered, all of which result in an earlier release of radionuclides from the near field.

The unexpected geological characteristics scenario. In this scenario it is assumed that the actual performance of the geosphere is worse than the expected performance (e.g. the geosphere has been subjected to an unexpected seismic event, resulting in the reactivation of high permeability fractures and/or modification of associated sorption properties).

The changing environmental conditions scenario. In this scenario it is assumed that the disposal system has been affected by climate change, resulting in modifications to certain geosphere characteristics (e.g. groundwater recharge rates) and biosphere characteristics (e.g. water demand, surface erosion rates).

The borehole disturbance scenario. In this scenario it is assumed that the drilling of a water abstraction borehole adjacent to the disposal borehole has resulted in an earlier exposure of humans to radionuclides (e.g. owing to the use of contaminated water from the abstraction borehole).

The stainless steel corrosion models and backfill degradation models developed as part of the generic safety assessment were incorporated into a borehole disposal concept scoping tool. The tool makes it possible to evaluate the containment provided by the disposal capsule and container in the post‑closure period and the chemical and physical degradation of the backfill. The tool also allows radionuclide transport and subsequent exposure of humans via the drinking water pathway to be evaluated using a conservative model that takes no account of the retardation of radionuclides during transport. The borehole disposal concept scoping tool was originally developed for disused sealed radioactive sources in Categories 3–5 but has been extended to allow consideration of sources in Categories 1 and 2.

The generic post‑closure safety assessment presented in Ref. [19] does not explicitly consider radiolysis, criticality or thermal processes because the effects of these processes are insignificant for the disposal of typical disused sealed radioactive sources in Categories 3–5. However, for the disposal of sources in Categories 1 and 2, the operating organization should assess the potential effects of radiolysis, criticality and thermal processes. Reference [17] addresses the potential impacts of the disposal of disused sealed radioactive sources in Categories 1 and 2 on the post‑closure safety of the borehole disposal concept. The study described in Ref. [17] is based on conservative assumptions and calculations; it is indicated in the study that, while there are no criticality issues, the disposal of some disused sealed radioactive sources in Categories 1 and 2 might result in high temperatures and high radiation fields that significantly reduce the expected lifetime of the waste disposal packages. Consequently, less conservative calculations have been performed to improve understanding of the thermal and radiation conditions in the borehole for representative disused sealed radioactive sources in Categories 1 and 2 and in Categories 3–5. The work described in Ref. [17] was supported by calculations using the CHEMSIMUL [50] and MicroShield [51] software and led to the development of various specifications for the disposal capsules and containers so that they could be used to contain disused sealed radioactive sources in Categories 1 and 2.

The rates of general and localized corrosion of stainless steel in cementitious environments have been analysed (e.g. Ref. [20]). This analysis also considered the potential effects of gamma radiation and galvanic corrosion between carbon and stainless steels in concrete, focusing on grades 304 and 316 austenitic stainless steel. This led to suggestions that, depending on the performance of the natural barriers at the site, super austenitic or super duplex stainless steel or a palladium‑containing titanium alloy may be used for the disposal capsules and containers for heat‑generating and gamma‑emitting disused sealed radioactive sources in Categories 1 and 2.

The work described in Ref. [17] highlights the need to integrate the mobile hot cell described in Ref. [24] into conditioning and disposal operations for disused sealed radioactive sources in Categories 1 and 2.

EUROPEAN ATOMIC ENERGY COMMUNITY, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Fundamental Safety Principles, IAEA Safety Standards Series No. SF‑1, IAEA, Vienna (2006). https://doi.org/10.61092/iaea.hmxn-vw0a

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). https://doi.org/10.61092/iaea.u2pu-60vm

INTERNATIONAL ATOMIC ENERGY AGENCY, Predisposal Management of Radioactive Waste, IAEA Safety Standards Series No. GSR Part 5, IAEA, Vienna (2009).

INTERNATIONAL ATOMIC ENERGY AGENCY, Disposal of Radioactive Waste, IAEA Safety Standards Series No. SSR‑5, IAEA, Vienna (2011).

INTERNATIONAL ATOMIC ENERGY AGENCY, IAEA Nuclear Safety and Security Glossary: Terminology Used in Nuclear Safety, Nuclear Security, Radiation Protection and Emergency Preparedness and Response, 2022 (Interim) Edition, IAEA, Vienna (2022). https://doi.org/10.61092/iaea.rrxi-t56z

Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management, INFCIRC/546, IAEA, Vienna (1997).

INTERNATIONAL ATOMIC ENERGY AGENCY, Code of Conduct on the Safety and Security of Radioactive Sources, IAEA, Vienna (2004)

INTERNATIONAL ATOMIC ENERGY AGENCY, Guidance on the Management of Disused Radioactive Sources, 2018 Edition, IAEA, Vienna (2018).

INTERNATIONAL ATOMIC ENERGY AGENCY, Near Surface Disposal Facilities for Radioactive Waste, IAEA Safety Standards Series No. SSG‑29, Vienna (2014).

INTERNATIONAL ATOMIC ENERGY AGENCY, Geological Disposal Facilities for Radioactive Waste, IAEA Safety Standards Series No. SSG‑14, Vienna (2011).

INTERNATIONAL ATOMIC ENERGY AGENCY, Classification of Radioactive Waste, IAEA Safety Standards Series No. GSG‑1, Vienna (2009).

INTERNATIONAL ATOMIC ENERGY AGENCY, Regulations for the Safe Transport of Radioactive Material, 2018 Edition, IAEA Safety Standards Series No. SSR‑6 (Rev. 1), IAEA, Vienna (2018). https://doi.org/10.61092/iaea.ur52-my9o

INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Assessment for Facilities and Activities, IAEA Safety Standards Series No. GSR Part 4 (Rev. 1), IAEA, Vienna (2016).

OECD NUCLEAR ENERGY AGENCY, Shallow Land Disposal of Radioactive Waste: Reference Levels for the Acceptance of Long‑Lived Radionuclides: A report by an NEA Expert Group, OECD, Paris (1987).

INTERNATIONAL ATOMIC ENERGY AGENCY, BOSS: Borehole Disposal of Disused Sealed Sources: A Technical Manual, IAEA‑TECDOC‑1644, IAEA, Vienna (2011).

INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident in Goiânia, IAEA, Vienna (1988).

LITTLE, R.H., BOND, A.E., EMERY, P., METCALFE, R., THATCHER, K.E., Extension of the IAEA’s GSA for the Borehole Disposal Concept to Include High Activity Sources, Rep.QRS‑1668A‑1, Quintessa, Henley (2016).

COCHRAN, J.R., et al., “International implementation of IAEA’s borehole disposal concept for sealed radioactive sources — 18545”, Proc. WM2018: Annual Waste Management Conference, Phoenix, 2018, Waste Management Symposia, Tempe (2018).

INTERNATIONAL ATOMIC ENERGY AGENCY, Generic Post‑closure Safety Assessment for Disposal of Disused Sealed Radioactive Sources in Narrow Diameter Boreholes, IAEA‑TECDOC‑1824, IAEA, Vienna (2017).

INTERNATIONAL ATOMIC ENERGY AGENCY, Application of the Graded Approach to Post‑closure Safety Assessment for the Disposal of Disused Sealed Radioactive Sources in Boreholes, IAEA‑TECDOC‑1928, IAEA, Vienna (2020).

INTERNATIONAL ATOMIC ENERGY AGENCY, Storage of Radioactive Waste, IAEA Safety Standards Series No. WS‑G‑6.1, IAEA, Vienna (2006).

INTERNATIONAL ATOMIC ENERGY AGENCY, Predisposal Management of Radioactive Waste from the Use of Radioactive Material in Medicine, Industry, Agriculture, Research and Education, IAEA Safety Standards Series No. SSG‑45, IAEA, Vienna (2019).

INTERNATIONAL ATOMIC ENERGY AGENCY, Categorization of Radioactive Sources, IAEA Safety Standards Series No. RS‑G‑1.9, IAEA, Vienna (2005).

LIEBENBERG, G.R., AL‑MUGHRABI, M., "The development of a mobile hot cell facility for the conditioning of spent high activity radioactive sources (SHARS)", Proc. WM2008: Waste Management Symposium 2008, Phoenix, 2008, Waste Management Symposia, Tempe (2018).

INTERNATIONAL ATOMIC ENERGY AGENCY, Leadership and Management for Safety, IAEA Safety Standards Series No. GSR Part 2, IAEA, Vienna (2016). https://doi.org/10.61092/iaea.cq1k-j5z3

INTERNATIONAL ATOMIC ENERGY AGENCY, Leadership, Management and Culture for Safety in Radioactive Waste Management, IAEA Safety Standards Series No. GSG‑16, IAEA, Vienna (2022).

INTERNATIONAL ATOMIC ENERGY AGENCY, Decommissioning of Facilities, IAEA Safety Standards Series No. GSR Part 6, IAEA, Vienna (2014).

INTERNATIONAL ATOMIC ENERGY AGENCY, Governmental, Legal and Regulatory Framework for Safety, IAEA Safety Standards Series No. GSR Part 1 (Rev. 1), IAEA, Vienna (2016).

INTERNATIONAL ATOMIC ENERGY AGENCY, Model Regulations for Borehole Disposal Facilities for Radioactive Waste, IAEA‑TECDOC‑1827, IAEA, Vienna (2017).

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

INTERNATIONAL ATOMIC ENERGY AGENCY, Communication and Consultation with Interested Parties by the Regulatory Body, IAEA Safety Standards Series No. GSG‑6, IAEA, Vienna (2017).

INTERNATIONAL ATOMIC ENERGY AGENCY, Organization, Management and Staffing of the Regulatory Body for Safety, IAEA Safety Standards Series No. GSG‑12, IAEA, Vienna (2018).

INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, The 2007 Recommendations of the International Commission on Radiological Protection, Publication 103, Elsevier, Oxford (2007).

INTERNATIONAL ATOMIC ENERGY AGENCY, The Safety Case and Safety Assessment for the Predisposal Management of Radioactive Waste, IAEA Safety Standards Series No. GSG‑3, IAEA, Vienna (2013).

INTERNATIONAL ATOMIC ENERGY AGENCY, The Safety Case and Safety Assessment for the Disposal of Radioactive Waste, IAEA Safety Standards Series No. SSG‑23, IAEA, Vienna (2012).

INTERNATIONAL ATOMIC ENERGY AGENCY, Methodology for Safety Assessment Applied to Predisposal Waste Management, IAEA‑TECDOC‑1777, IAEA, Vienna (2015).

INTERNATIONAL ATOMIC ENERGY AGENCY, Monitoring and Surveillance of Radioactive Waste Disposal Facilities, IAEA Safety Standards Series No. SSG‑31, IAEA, Vienna (2014).

INTERNATIONAL ATOMIC ENERGY AGENCY, Contents and Sample Arguments of a Safety Case for Near Surface Disposal of Radioactive Waste, IAEA‑TECDOC‑1814, IAEA, Vienna (2017).

KOZAK, M.W., Decision analysis for low level radioactive waste disposal safety assessments, Radioact. Waste Manag., 18 (1994) 209.

INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR OFFICE, Occupational Radiation Protection, IAEA Safety Standards Series No. GSG‑7, IAEA, Vienna (2018).

LINDBORG, T. et al., Climate change and landscape development in post‑closure safety assessment of solid radioactive waste disposal: Results of an initiative of the IAEA, J. Environ. Radioact. 183 (2018) 41–53, https://doi.org/10.1016/j.jenvrad.2017.12.006.

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). https://doi.org/10.61092/iaea.ko2c-dc4q

INTERNATIONAL ATOMIC ENERGY AGENCY, Nuclear Security Culture, IAEA Nuclear Security Series No. 7, IAEA, Vienna (2008).

INTERNATIONAL ATOMIC ENERGY AGENCY, Security of Radioactive Material in Use and Storage and of Associated Facilities, IAEA Nuclear Security Series No. 11‑G (Rev. 1), IAEA, Vienna (2019).

INTERNATIONAL ATOMIC ENERGY AGENCY, Nuclear Security Recommendations on Radioactive Material and Associated Facilities, IAEA Nuclear Security Series No. 14, IAEA, Vienna (2011).

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL CIVIL AVIATION ORGANIZATION, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANIZATION, INTERPOL, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, PREPARATORY COMMISSION FOR THE COMPREHENSIVE NUCLEAR‑TEST‑BAN TREATY ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, UNITED NATIONS OFFICE FOR THE COORDINATION OF HUMANITARIAN AFFAIRS, WORLD HEALTH ORGANIZATION, WORLD METEOROLOGICAL ORGANIZATION, Preparedness and Response for a Nuclear or Radiological Emergency, IAEA Safety Standards Series No. GSR Part 7, IAEA, Vienna (2015). https://doi.org/10.61092/iaea.3dbe-055p

INTERNATIONAL ATOMIC ENERGY AGENCY, Upgrading of Near Surface Repositories for Radioactive Waste, Technical Reports Series No. 433, IAEA, Vienna (2005).

INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Considerations in the Disposal of Disused Sealed Radioactive Sources in Borehole Facilities, IAEA‑TECDOC‑1368, IAEA, Vienna (2003).

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONS DEVELOPMENT PROGRAMME, UNITED NATIONS ENVIRONMENT PROGRAMME, UNITED NATIONS OFFICE FOR THE COORDINATION OF HUMANITARIAN AFFAIRS, Remediation Strategy and Process for Areas Affected by Past Activities or Events, IAEA Safety Standards Series No. GSG‑15, IAEA, Vienna (2022).

Kirkegaard, P., Bjergbakke, E., Olsen, J.V., CHEMSIMUL: A chemical kinetics software package, Danmarks Tekniske Universitet, Risø Nationallaboratoriet for Bæredygtig Energi, Denmark. Forskningscenter Risoe. Risoe‑R No. 1630(EN). Roskilde, Denmark, December 2008 https://backend.orbit.dtu.dk/ws/portalfiles/portal/6278806/ris‑r‑1630.pdf

GROVE ENGINEERING, INC., MicroShield Version 12, Grove Software Inc., Lynchburg, VA http://www.radiationsoftware.com