(DRAFT Ver.3)
DISPOSAL FACILITIES FOR INTERMEDIATE
LEVEL RADIOACTVE WASTE
Drafted at
CS in Vienna, 15-19 September, 2014
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Table of Contents
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Introduction ............................................................................................................................................... 5
1.1
Background ........................................................................................................................................ 6
1.2
Objectives and scope ......................................................................................................................... 7
1.3
Structure ............................................................................................................................................ 7
Definitions and Timescales ........................................................................................................................ 8
2.1
Definitions associated with ILW classification ................................................................................... 8
2.2
Definitions and timescales associated with disposal options ........................................................... 8
Application of Safety Requirements and Guides to ILW disposal ........................................................... 10
3.1
Legal and Organizational Infrastructure .......................................................................................... 10
3.2
Safety Approach .............................................................................................................................. 10
3.3
Design Concepts for Safety .............................................................................................................. 11
3.4
Framework for disposal of radioactive ............................................................................................ 12
3.5
Demonstration of safety .................................................................................................................. 12
3.6
Assurance of safety.......................................................................................................................... 13
ILW characteristics................................................................................................................................... 14
4.1
Radionuclide content and activity concentration ........................................................................... 14
4.2
Waste volume and geometry .......................................................................................................... 14
4.3
Physical and chemical properties .................................................................................................... 15
4.4
Criticality .......................................................................................................................................... 15
4.5
Heat Generation .............................................................................................................................. 16
4.6
Chemotoxicity .................................................................................................................................. 16
4.7
Gas Generation ................................................................................................................................ 16
Preparing ILW for Disposal ...................................................................................................................... 17
5.1
Treatment ........................................................................................................................................ 17
5.2
Conditioning .................................................................................................................................... 17
5.3
Storage............................................................................................................................................. 18
5.4
Identification and compliance with waste acceptance criteria for disposal ................................... 18
Disposal Options ...................................................................................................................................... 19
6.1
Principal safety functions ................................................................................................................ 19
6.2
Available Disposal Options .............................................................................................................. 19
6.2.1
Near surface options ............................................................................................................... 20
6.2.1.1.
Landfill disposal ................................................................................................................... 20
6.2.1.2.
Trench disposal .................................................................................................................... 20
6.2.1.3.
Engineered vault .................................................................................................................. 20
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6.2.1.4.
6.2.2
Geological disposal options ..................................................................................................... 21
6.2.3
Disposal options ...................................................................................................................... 21
6.2.3.1.
Boreholes ............................................................................................................................. 21
6.2.3.2.
In-situ immobilization .......................................................................................................... 22
6.3
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Near surface underground disposal facilities ...................................................................... 21
Factors for the selection of a disposal option ................................................................................. 22
6.3.1
Safety related factors .............................................................................................................. 22
6.3.2
Waste volume related factors ................................................................................................. 23
6.3.3
Economic and technical resources .......................................................................................... 23
6.3.4
National policy and social aspects ........................................................................................... 23
Siting ........................................................................................................................................................ 24
7.1
Site natural properties ..................................................................................................................... 24
7.2
Site evolution ................................................................................................................................... 26
7.2.1
Precipitation and recharge ...................................................................................................... 26
7.2.2
Permafrost and glaciation ....................................................................................................... 26
7.2.3
Sea level change ...................................................................................................................... 27
7.2.4
Weathering .............................................................................................................................. 27
7.2.5
Uplift/erosion, faulting/folding and subsidence/sedimentation ............................................ 27
7.2.6
Impact of geodynamic evolution on the consideration of human intrusion .......................... 27
The likelihood of human intrusion may be impacted by site evolution processes including glaciation, sea
level change, and uplift/erosion. This issue needs to be considered over the timescale relevant for the
radiological content of the ILW, especially for near-surface disposal. ................................................... 27
7.2.7
8
Natural and social environment .............................................................................................. 28
Disposal Facility Design for ILW ............................................................................................................... 29
8.1
Design process ................................................................................................................................. 29
8.1.1
Requirements on the disposal facility ..................................................................................... 29
8.1.2
Design solution development .................................................................................................. 30
8.1.3
Verification of compliance ....................................................................................................... 30
8.2
Safety considerations for ILW disposal facility design..................................................................... 31
8.2.1
Construction phase .................................................................................................................. 31
8.2.2
Operational phase ................................................................................................................... 31
8.2.3
Post-closure phase................................................................................................................... 32
8.3
Design considerations for ILW ......................................................................................................... 33
8.3.1
Disposal volumes ..................................................................................................................... 33
8.3.2
Layout ...................................................................................................................................... 34
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8.3.3
Access ways ............................................................................................................................. 34
8.3.4
Operating systems ................................................................................................................... 34
8.3.5
Backfilling, capping and sealing ............................................................................................... 35
8.3.6
Monitoring and retrievability .................................................................................................. 36
8.3.7
Management of concurrent construction and operation ....................................................... 36
Safety Case Development........................................................................................................................ 37
9.1
Iterative Approach of the Safety Case ............................................................................................. 37
9.2
Demonstration of safety .................................................................................................................. 38
9.3
Aspects of safety assessment .......................................................................................................... 38
10
Institutional Control and Record Keeping ........................................................................................... 40
10.1
Institutional control ......................................................................................................................... 40
10.2
Record keeping ................................................................................................................................ 40
REFERENCE ...................................................................................................................................................... 41
APPENDIX I: National Examples ....................................................................................................................... 42
APPENDIX II: IAEA publications relevant to this document......................................................................... 43
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1
FOREWARD
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The IAEA safety standards have been developed in order to serve as the global reference for protecting
people and the environment from harmful effects of ionizing radiation, providing a robust framework of
fundamental principles, requirements and guidance to ensure safety.
In the field of disposal of radioactive waste, a specific Safety Requirement SSR-5 has been developed to
cover all disposal concepts. As supporting document of SSR-5, several Safety Guides have been developed,
such as Specific Safety Guide SSG-14 and SSG-29 for near surface disposal facilities and geological
disposal respectively.
Since 2008, it had been discussed on the needs on the development of additional safety guides or guidance
documents on the disposal of intermediate level waste (ILW).
In 2008, the Workshop on Intermediate Depth Disposal of Radioactive Waste: the Safety Basis and its
Realization was held in Korea. The workshop covered disposal of the broad range of wastes termed as ILW
under the recognition that disposal options for the broad range of materials in the middle of this spectrum
(ILW) have been developed at the national level but have not so far been the subject of as much attention
from the perspective of international activities. At the workshop, it was concluded that existing IAEA Safety
Standards for near surface disposal and geologic disposal provide the needed foundation for addressing ILW
disposal. The safety case for ILW disposal facilities would reflect a graded application of existing IAEA
Safety Standards to address issues such as the wastes included for disposal, the specificities of the natural
and engineered barriers, and operational considerations. However, conclusions of the workshop also
mentioned that additional guidance in existing IAEA draft guides may be needed to address ILW disposal.
This issue was followed by further discussion at several other IAEA meetings between 2011 and 2013. As a
result, it was decided to develop a Safety Report focusing on specific nature of ILW disposal as
supplemental document of existing Safety Standards, and this report was prepared by 5 consultancy meetings
and technical meetings in 2013 and 2014.
The IAEA officer responsible for this publication was Y. Kumano of the Division of Radiation, Transport
and Waste Safety.
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Introduction
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1.1
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Intermediate-level waste (ILW) is, from a disposal and safety case perspective, situated between low-level
waste which can be disposed of in a near surface facility and high-level waste that must be disposed in a
deep geological formation.
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Background
Guidance on near surface disposal facilities and geological disposal facilities are found in IAEA Specific
Safety Guide SSG-14 and SSG-29. While it is clear that near surface facilities are applicable to low-level
waste and geological disposal is required for high level waste and spent fuel that has been declared to be
waste, there is no specific guidance for ILW.
ILW is generated in a wide spectrum of activities, particularly:
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fuel production,
reprocessing of spent fuel,
reactor operation,
nuclear research,
decommissioning of nuclear facilities, and
medical and industrial applications.
It includes items such as:
 resins, filters, sludge and evaporator concentrates from operation of nuclear facilities,
 components from decommissioning or maintenance which may include some irradiated large items
such as core internals,
 residues from materials processing such as ore treatment,
 control rods and neutron monitoring devices,
 fuel debris and ends,
 concrete and rubble from demolition of buildings, and
 sealed sources from medical and industrial applications.
In consequence, particular feature of ILW is in its diversity, both in radionuclide contents and in physical and
chemical form.
ILW may be roughly categorized into two main groups. One group of ILW contains a relatively high
activity, but a low content of long lived radionuclides whereas the other group has a relatively high content
of long lived radionuclides, but with low to moderate activity. The volume of ILW is usually more
significant than HLW while the activity concentration is more significant than LLW. This justifies the
treatment of ILW as separate waste stream(s).
A particular challenge in ILW management is legacy or historic waste, held in some countries, which may
have limited characterisation. Some may have been conditioned previously but does not meet current Safety
Standards and therefore requires further treatment. Legacy waste often includes sealed sources.
Sometimes ILW is described as waste that needs to be disposed of in a facility at a depth of between a few
tens and a few hundreds of metres. However, it is not recommended to discuss an ILW disposal facility in
terms of depth only, but rather by considering many influencing properties of the site and engineered design
that can provide the required degree of containment and isolation [add reference to WS on ILW http://wwwns.iaea.org/downloads/rw/waste-safety/korea-workshop2008/korea-findings.pdf]. Therefore, ILW can be
divided into different waste streams for which different disposal options are appropriate.
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Whatever the type of waste and the depth of the disposal facility, an appropriate time scale needs to be
considered. It must be consistent with the characteristics of the waste, in particular the reduction of activity
with time as a function of the half-life of radionuclides, and with the natural evolution of the site.
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The design considerations for a disposal facility for ILW have many similar considerations to those for other
types of waste. Co-disposal of ILW with other types of waste, LLW or HLW, is considered in many
countries.
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The objective of this document is to provide a reference for the application of the IAEA Safety Standards to
the disposal of ILW.
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Chapter 2 provides definitions related to ILW and disposal options and discusses timescales.
Co-disposal may involve:
 disposal of ILW with other types of waste in the same disposal module,
 separate disposal modules at the same location with common infrastructure, such as access shafts or
drifts in the case of underground facilities, and
 separate disposal facilities for ILW and other waste at the same location.
In all cases, the selected design of the disposal facility which accommodates ILW needs to be tailored to the
characteristics of the waste, for instance the construction material used and the volume size of the cells or
pits and to the characteristics of the site.
Objectives and scope
This document examines requirements and guidance relevant to disposal of ILW either near-surface or deep
underground, and development of safety case. It demonstrates that the following IAEA Safety Standards
provide a comprehensive basis for the implementation of ILW disposal:
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IAEA Specific Safety Requirements SSR-5, Disposal of Radioactive Waste,
IAEA Specific Safety Guide SSG-14, Geological Disposal Facilities for Radioactive Waste,
IAEA Specific Safety Guide SSG-23, The Safety Case and the Safety Assessment for the Disposal
of Radioactive Waste, and
IAEA Specific Safety Guide SSG-29, Near Surface Disposal Facilities for Radioactive Waste.
Structure
Chapters 3, 4 and 5 are overview chapters providing information on application of Safety Standards, key
characteristics of ILW that need to be taken into account, and considerations in predisposal options including
packaging.
Chapters 5-10 provide detailed discussions on the application of Safety Standards; Chapter 5 discusses the
approach to the selection of disposal options for ILW; Chapter 7 describes consideration for siting of the
facility; Chapter 8 describes factors of ILW to be considered in the design of the facility including
operational and post-closure aspects; Chapter 9 describes the safety case; Chapter 10 describes the record
keeping and institutional control.
APPENDIX I give examples on the disposal of ILW provided by various Member States.
APPENDIX II provides an overview of other IAEA documents relevant to ILW.
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Definitions and Timescales
Definitions associated with ILW classification
While there are a number of IAEA definitions that are relevant to ILW disposal, there is no specific
definition for ILW in the IAEA Safety Glossary. Definitions are given in terms of radiological properties of
these wastes and intermediate-level waste is considered together with low-level waste as:
low and intermediate level waste (LILW). Radioactive waste with radiological characteristics between those
of exempt waste and high level waste. This may be long lived waste (LILW-LL) or short lived waste (LILWSL).
The following notes are provided:
 Typical characteristics of low and intermediate level waste are activity levels above clearance
levels and thermal power below about 2 kW/m3 [....].
 Many States subdivide this class in other ways, for example into low level waste (LLW) and
intermediate level waste (ILW) or medium level waste (MLW), often on the basis of waste
acceptance requirements for near surface repositories
The terms short lived and long lived waste are defined as:
short lived waste. Radioactive waste that does not contain significant levels of radionuclides with a half-life
greater than 30 years
long lived waste. Radioactive waste that contains significant levels of radionuclides with a half-life greater
than 30 years
It is however not clearly stated what is regarded as ”significant levels” in the IAEA Safety Glossary. This
needs to be determined in each Member States relating to the retention capability and the life-time of the
facility as discussed in the safety case. Different national approaches have been adopted to distinguish
between LLW, ILW, and HLW; therefore it is not appropriate to set a firm threshold in international
standards. Instead, constraints on radioactivity need to be reflected in the waste acceptance criteria (WAC)
associated with a specific site and design of a disposal facility.
The IAEA General Safety Guide GSG-1, Classification of Radioactive Waste, recognizes that ILW requires
a higher degree of containment than LLW, and an ILW disposal facility may need a specific design.
Although GSG-1 makes a direct association between ILW and intermediate depth disposal (see Figure 1 in
GSG-1 which is a conceptual illustration of the waste classification scheme), this document considers a
broader depth range from near-surface to deep geological depending on the specific characteristics of both
the ILW and the site.
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SSR-5 provides definitions of near-surface and geological disposal but does not list any specific
requirements for ILW.
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SSR-5 defines near surface disposal as disposal in a facility consisting of engineered trenches or vaults
constructed on the ground surface or up to a few tens of metres below ground level.
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SSR-5 suggests that near surface disposal may be designated as a disposal facility for low level radioactive
waste.
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Definitions and timescales associated with disposal options
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Geological disposal is defined in SSR-5 as disposal in a facility constructed in tunnels, vaults or silos in a
particular geological formation (e.g. in terms of its long term stability and its hydrogeological properties) at
least a few hundred metres below ground level.
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SSR-5 notes that a geological disposal facility could be designed to receive high level radioactive waste
(HLW), including spent fuel if it is to be treated as waste, and that with appropriate design, a geological
disposal facility could receive all types of radioactive waste.
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Available disposal options for ILW are referred to in Chapter 6.2.
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Regardless of the type of waste, disposal facility design and the depth, the safety case has to demonstrate
safety during an appropriate time-scale. It must be consistent with the characteristics of the waste, in
particular the reduction of activity with time as a function of the half-life of radionuclides, the natural
evolution of the site and the considered depth and design of the facility.
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Along with safety issues, the selection of appropriate disposal options for LLW and ILW may take into
account national societal factors. Therefore, some countries have chosen deep geological disposal for all
radioactive waste even when the safety criteria could be met through near surface disposal.
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On the surface, natural changes occur over shorter time scales than deep underground. Significant processes
leading to this evolution include erosion by wind, rain water, glacial activities, weathering and potential land
uplift, large-scale landslides, subsidence and post glaciation rebound as well as climate induced processes
like glaciation or permafrost. These phenomena may change the future boundary conditions of the system,
for example hydrographic system and hydrogeology, as well as the system itself for example through the
changing chemical, hydrological and temperature conditions. They will possibly progressively reduce the
thickness and/or performance of containment barriers interposed between the waste and the environment. In
an extreme situation the disposal facility and waste packages may be destroyed in the long term, leading to
loss of containment, direct access to waste and dispersion of residual activity. The affected depth with time
and the speed and consequence of these mechanisms are site dependent.
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Geologists can extrapolate the evolution of the deep geological environment for millions of years but
uncertainties increase with time. Uncertainties in the evolution of the site (that are relevant for the safety
case) can be assessed through scenarios and bounding cases. However, provisions are to be made in siting
geological disposal facilities to avoid excessive geodynamic disturbances that could affect the underground
facilities, the host rock and the long term safety functions. SSG-14 provides that
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“The site should be located in a geological and geographical setting where these geodynamic processes or
events will not be likely to lead to unacceptable releases of radionuclides. (…) Geodynamic effects such as
ground motion associated with earthquakes, land subsidence and uplift, volcanism and diapirism may also
induce changes in crustal conditions and processes. Such types of event, which in some cases can be
interrelated, may affect the overall disposal system through disturbances in the site integrity or modifications
of groundwater fluxes and pathways.”
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Reasonable margins are to be taken into account between the scientific capacity to predict the evolution of a
site, with adequate accuracy, and the relevant time-scale for the safety case. The radiological exposure of
man has to be acceptable at all times. Therefore one has to take into account loss of containment and
potential dispersion of waste at least at the end of the considered time-scale. As a consequence, the
acceptable content of long lived radionuclides is a function of the applicable time scale.
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Application of Safety Requirements and Guides to ILW
disposal
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SSR-5 provides requirements for the legal and regulatory framework, safety approach, design concepts for
safety, safety case and safety assessment and stepwise development that are applicable for all types of waste
including ILW. It sets out the safety objective and criteria for the protection of people and the environment
against radiation risks arising from disposal facilities. Applications of these requirements to near surface and
geological facilities are given by SSG-29 and SSG-14 respectively. Specific information on the application
of these documents to ILW is given below.
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The Requirements 1, 2 and 3 of SSR-5 address the national legal and organizational framework:
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SSR-5 addresses safety approach in requirements 4, 5 and 6:
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3
Legal and Organizational Infrastructure
The government is required to establish and maintain an appropriate governmental, legal and regulatory
framework for safety within which responsibilities shall be clearly allocated for disposal facilities for
radioactive waste to be sited, designed, constructed, operated and closed. This shall include: confirmation at
a national level of the need for disposal facilities of different types; specification of the steps in development
and licensing of facilities of different types; and clear allocation of responsibilities, securing of financial and
other resources, and provision of independent regulatory functions relating to a planned disposal facility.
The regulatory body shall establish regulatory requirements for the development of different types of
disposal facility for radioactive waste and shall set out the procedures for meeting the requirements for the
various stages of the licensing process. It shall also set conditions for the development, operation and
closure of each individual disposal facility and shall carry out such activities as are necessary to ensure that
the conditions are met.
The operator of a disposal facility for radioactive waste shall be responsible for its safety. The operator
shall carry out safety assessment and develop and maintain a safety case, and shall carry out all the
necessary activities for site selection and evaluation, design, construction, operation, closure and, if
necessary, surveillance after closure, in accordance with national strategy, in compliance with the
regulatory requirements and within the legal and regulatory infrastructure.
These requirements are fully applicable to any disposal facility which accommodates ILW. SSG-14 and
SSG-29 show the applicability to geological and near surface facilities respectively. In applying these
requirements to ILW it is important to reflect the necessary time scales of development and operation of the
disposal facility. In cases where long timeframes are involved, the possibility of a transfer of responsibilities
between different organizations needs to be considered and provisions need to be made to avoid any adverse
consequence on safety. In this respect, preservation of records is essential, including both characteristics and
inventories of the waste taking into account the diversity of ILW, and knowledge of development of the
facility.
In case of co-disposal, the responsibilities relevant for the different types of waste should be defined to
ensure that all aspects are clearly covered and that there are no conflicts.
Safety Approach
Throughout the process of development and operation of a disposal facility for radioactive waste, an
understanding of the relevance and the implications for safety of the available options for the facility shall be
developed by the operator. This is for the purpose of providing an optimized level of safety in the operational
stage and after closure.
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The operator shall evaluate the site and shall design, construct, operate and close the disposal facility in
such a way that safety is ensured by passive means to the fullest extent possible and the need for actions to
be taken after closure of the facility is minimized.
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SSR-5 addresses design concepts for safety in requirements 7, 8, 9, and 10:
The operator of a disposal facility shall develop an adequate understanding of the features of the facility and
its host environment and of the factors that influence its safety after closure over suitably long time periods,
so that a sufficient level of confidence in safety can be achieved.
In applying these requirements to ILW, it is important to reflect the considered ILW disposal options and the
time scale necessary for the development and operation of the disposal facility.
Consistent with SSG-14 and SSG-29, the safety approach includes all the ways in which the safety of people
and the environment is ensured throughout the lifetime of any disposal facility which accommodates ILW. It
may be useful for the government and the regulatory body to set out the national approach in a formal safety
strategy document that is produced at the start of the disposal programmes which include ILW and may be
updated periodically.
In case of co-disposal with either LLW or HLW, the specific characteristics of the waste to be co-disposed
have to be taken into account.
Design Concepts for Safety
The host environment shall be selected, the engineered barriers of the disposal facility shall be designed and
the facility shall be operated to ensure that safety is provided by means of multiple safety functions.
Containment and isolation of the waste shall be provided by means of a number of physical barriers of the
disposal system. The performance of these physical barriers shall be achieved by means of diverse physical
and chemical processes together with various operational controls. The capability of the individual barriers
and controls together with that of the overall disposal system to perform as assumed in the safety case shall
be demonstrated. The overall performance of the disposal system shall not be unduly dependent on a single
safety function.
The engineered barriers, including the waste form and packaging, shall be designed, and the host
environment shall be selected, so as to provide containment of the radionuclides associated with the waste.
Containment shall be provided until radioactive decay has significantly reduced the hazard posed by the
waste. In addition, in the case of heat generating waste, containment shall be provided while the waste is still
producing heat energy in amounts that could adversely affect the performance of the disposal system.
The disposal facility shall be sited, designed and operated to provide features that are aimed at isolation of
the radioactive waste from people and from the accessible biosphere. The features shall aim to provide
isolation for several hundreds of years for short lived waste and at least several thousand years for
intermediate and high level waste. In so doing, consideration shall be given to both the natural evolution of
the disposal system and events causing disturbance of the facility.
An appropriate level of surveillance and control shall be applied to protect and preserve the passive safety
features, to the extent that this is necessary, so that they can fulfil the functions that they are assigned in the
safety case for safety after closure.
With respect to safety functions, the choice of the design concept of ILW disposal facility needs to take into
account the diverse characteristics of waste to be emplaced. The half-lives and activities of key radionuclides
in the waste determine the required duration of containment and isolation to be considered by the design
including factors such as depth, geological settings, and engineered barriers. For ILW which contains lower
amounts of relatively long-lived radionuclides, near-surface disposal may be plausible. For ILW containing
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greater amount of radionuclides with intermediate or long half-life, the waste would need a greater duration
of containment and isolation.
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SSR-5 addresses step by step development and evaluation of disposal facilities in Requirement 11:
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SSR-5 addresses the concept and role of safety case and safety assessment in requirements 12, 13 and 14, as
well the steps of facility development, operation and closure in requirements 15-19. In addition, SSG-23
provides a comprehensive guidance on safety case and safety assessment that is applicable to any kind of
disposal of radioactive waste.
For the containment function, the design should take into account the nature of radionuclides contained in the
waste including the chemical stability of the waste and the mobility of any released radionuclides.
Surveillance and institutional controls should be consistent with the guidance in SSG-14 or SSG-29 as
appropriate to the selected disposal option.
Framework for disposal of radioactive
Disposal facilities for radioactive waste shall be developed, operated and closed in a series of steps. Each of
these steps shall be supported, as necessary, by iterative evaluations of the site, of the options for design,
construction, operation and management, and of the performance and safety of the disposal system.
The step by step iterative process seeks to maximize the value of information as it evolves over the series of
steps, for instance siting, design, construction, operation and closure.
While there may be many steps in the development, operation and closure of a disposal facility, the most
important ones occur at regulatory or governmental decision points for the approval of siting of an ILW
disposal facility (in some countries), the approval of construction, the approval to receive and emplace waste
(operations) and the approval to close the facility (closure).
For each step in the process, the operator should identify the decision that needs to be made and the
information that is necessary to make the decision. The operator should also identify the appropriate
interested parties and determine when and how to include them in the decision making process. Early
involvement of regulatory body and other relevant interested parties improves the quality of the decision
making and provides clarity for the direction of the project.
The step by step approach also allows opportunities for independent technical reviews, regulatory reviews,
and political and public involvement in the process.
Demonstration of safety
Those requirements and guidance are fully applicable to ILW disposal. The safety case needs to pay
particular attention to the aspects related to timescale and depth of the ILW disposal facility. Consideration
needs to be given to the specific characteristics of the waste, for example, quantity and mobility of long-lived
radionuclides, potential for gas generation, presence of potential complexants (See Chapter 4 for more
details). Particularly in the case of near surface disposal, WAC are more restrictive for the content of longlived radionuclides.
In the case of co-disposal with other types of waste, the safety case needs to consider all the waste types that
are disposed in the same location, especially with regards to radiological impacts to the human and the
environment. Potential for interactions between different disposal modules or waste packages also needs to
be considered and demonstrated that there is no significant detrimental interactions.
12 | P a g e
379
380
381
3.6
Assurance of safety
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
SSR-5 addresses WAC in requirement 20:
Waste packages and unpackaged waste accepted for emplacement in a disposal facility shall conform to
criteria that are fully consistent with, and are derived from, the safety case for the disposal facility in
operation and after closure.
Significant efforts are to be taken to define the WAC for ILW disposal facility considering the diversity of
the waste. The WAC for ILW disposal need to reflect the physical and chemical form of the conditioned
waste including the detailed description of the non-radiological contents to assure that they meet the
requirement of the safety case and the safety assessment.
Understanding of the evolution of the waste is also important in order to assess the potential for the physical
and chemical changes including formation of degradation products such as gases, complexing agents, and
those causing chemical disturbances.
Further consideration on the WAC specific to ILW disposal is addressed in Chapter 4.
Monitoring is addressed in Requirement 21 of SSR-5. In developing a monitoring programme for a nearsurface ILW disposal facility, consideration needs to be given to the higher radionuclide content in ILW,
compared with LLW. For geological disposal of ILW, the requirements on any monitoring programme need
to take into account any longer-lived radionuclides, particularly fission products, which may be relatively
mobile.
Requirement 22 of SSR-5 describes requirement on the institutional control as:
Plans shall be prepared for the period after closure to address institutional control and the arrangements for
maintaining the availability of information on the disposal facility. These plans shall be consistent with
passive safety features and shall form part of the safety case on which authorization to close the facility is
granted.
This requirement is particularly important for ILW which contains lower amounts of relatively long-lived
radionuclides disposed near surface.
Requirements 23 and 24 of SSR-5 address accounting and control of nuclear material, as well as
consideration on the security. Generally, those are not so significant to ILW compared with HLW. However,
some ILW may contain radionuclides that are subject to these requirements.
Requirement 25 of SSR-5 addresses the management systems that are important for any types of disposal
facilities.
423
13 | P a g e
ILW characteristics
424
4
425
426
A number of characteristics of ILW, including its non-radiological properties, need to be considered when
selecting treatment, conditioning and disposal options and approaches, in particular:
427

Radionuclide content and activity,
428

Waste volume,
429

Physical and chemical properties,
430

Criticality,
431

Heat generation,
432

Chemo toxicity, and
433

Gas generation.
434
435
436
4.1
Radionuclide content and activity concentration
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
The radionuclides in ILW and the evolution of activity with time are important attributes in determining the
extent of containment and duration of the containment period during which the waste must be isolated from
the environment.
455
4.2
456
457
458
459
460
461
462
463
464
465
466
467
468
469
The total amount of ILW (volume or mass) and the size of individual items need to be considered when
choosing an appropriate disposal option. The disposal option designed for accepting a few pieces of sealed
sources is likely to be different from a facility intended for the disposal of thousands of cubic metres from
the operation and decommissioning of nuclear power plants.
It is particularly important to have information on several main groups of radionuclides:




Uranium, plutonium and minor actinides such as americium
Mobile radionuclides, activation or fission products, especially those which are long-lived, Cl-36 and
I-129
Radionuclides with intermediate half-lives, such as C-14, Am-241, Ra-226
Radionuclides which have the ability to generate significant amounts of radiation and heat e.g. Co60.
ILW with a low content of long-lived radionuclides may be suitable for disposal near surface. That with a
high content of long-lived radionuclides needs longer containment and isolation, and therefore disposal at
greater depth is necessary.
Waste volume and geometry
In order to estimate the amount of waste, it is important to consider that both the waste that exists today and
that which will arise in future taking into account the on-going operation and decommissioning of existing
and/or planned facilities.
Particular consideration may need to be given to the range of sizes of ILW, in particular to the management
of large components. In some cases, segregation of waste according to size might contribute to optimize the
waste stream and the capacity of the disposal facility. Some large components may be cut down to facilitate
handling and improve packing efficiency. In other cases, some large components may be considered for
direct disposal without packaging, provided they meet the relevant WAC.
14 | P a g e
470
471
472
473
474
There may be opportunities to reduce the waste volume through selection of appropriate predisposal options
which will be discussed in Chapter 6.
475
4.3
Physical and chemical properties
476
477
ILW contains a wide range of materials as a function of its origin. The physical and chemical properties of
these materials influence the selection of appropriate disposal concepts:
478

Complexants present in some ILW may affect the mobility of contaminants;
479
480
481

Organic and some other types of materials may form complexants along with degradation processes. The
most well-known example is the alkaline degradation of cellulose to isosaccharinic acid (ISA) which can
increase the mobility of otherwise nearly insoluble radionuclides by many orders of magnitude;
482
483

Some organic materials such as PVC may also form corrosive species (For example HCl) as they degrade
under radiation or react in aqueous solutions, which impact the engineered barriers;
484

Nitrate may affect the redox conditions and therefore influence the mobility of contaminants;
485
486
487
488

Metals may react with water forming expansive corrosion products and sometimes generating heat; these
processes may degrade the functions of the engineered barriers. Some particular wastes, such as
bituminous wastes may also react with water and swell. Swelling can also be induced by radiolysis of
some waste;
489
490

ILW may generate gas by a number of material degradation mechanisms (see later section on gas
generation);
491

Graphite has the potential to combust, due to the stored Wigner energy; and
492
493

A number of materials may contain or produce particles of colloidal size, which might impact migration
of contaminants.
494
495
496
Some material types present in the ILW may also have positive effects for the containment of contaminants: for
example cements may contribute to the maintenance of a high pH environment in which corrosion of metals is
lower, and to the retention of contaminants.
497
498
499
500
501
502
The physical and chemical properties of ILW may be modified by treatment and /or conditioning and may
evolve during storage operations and with time after emplacement in the disposal facility. Liquid ILW is
generally processed to a solid form using techniques such as immobilization in cements. Other ILW may be
treated using processes such as incineration. Therefore it is important to consider the whole life cycle
including predisposal and disposal options when deciding the management route for the waste and verify that
the waste can meet the requirements of WAC for the anticipated disposal facility (see Chapter 8).
503
504
505
4.4
506
507
508
509
510
511
512
For ILW with significant amounts of fissile material, criticality needs to be taken into account when
considering its disposal. The distribution of fissile material within a single package and across the facility
needs to be assessed with respect to criticality safety particularly in the event that the waste is exposed to
water during or after disposal. The possible accumulation of fissile material within a package or elsewhere in
the disposal system during the post closure phase also needs to be considered.
15 | P a g e
Criticality
513
4.5
Heat Generation
514
515
516
517
518
519
520
The classification of waste as ILW requires that it needs no or only limited provision, for heat dissipation
during its storage and disposal. However, if the ILW contains significant amount of radionuclides such as
Co-60, Sr-90, Cs-137, Am-241 or Ag-108m, the heat generated may need to be considered in the design and
operation of the disposal facility, e.g. by ventilation during the operational period, arrangement of heatgenerating packages or disposal cells, or by limiting the inventory of heat-generating material in a package.
521
4.6
522
523
524
525
526
527
528
In addition to the radiological hazard, ILW may also contain chemically toxic components, such as heavy
metals and small organic complexing agents. These constituents may be persistent since their hazard
potential remains constant with time, i.e. no decay is expected. In addition to radiological requirements,
when disposing of ILW it is necessary to demonstrate compliance with relevant requirements, relating to
chemical toxicity for example, with respect to the maximum permitted concentrations of particular
chemically toxic materials in ground water or in drinking water. It should be noted that some elements such
as uranium present both a radiological and a chemotoxic hazard.
529
530
531
532
533
IAEA-TECDOC-1325 describes the issues associated with the management of chemically toxic materials in
LILW (add reference). It should be noted that waste conditioning may remove chemotoxic substances or
contribute to delaying or preventing their release to the environment.
534
4.7
535
ILW can generate gas by three main processes:
Chemotoxicity
Gas Generation
536

Metal corrosion,
537
538

Chemical or microbial degradation of organic components of the waste (cellulose, hydrocarbons),
and
539

Radioactive decay (radon).
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
Gas generation may also occur as a result of radiolysis, especially if the ILW contains significant amounts of
gamma emitters, but in general, this effect would be expected minor when compared with the processes
above.
If gas is produced in large amounts, it could lead to a build-up of pressure that may be sufficient to damage
the waste form or the surrounding barriers. Gas will tend to migrate by buoyancy and, where this occurs, it
could disturb the surrounding environment.
Some of the gases may themselves be radioactive, e.g. H-3, C-14 in carbon dioxide or methane, Rn-222.
Waste conditioning has the potential to affect gas generation. For example, cement-based material provides
an alkaline environment, in which the corrosion rate of many metallic materials is low and the associated gas
generation rate is also low. However, aluminium and magnesium in a cemented waste corrode readily in the
high pH environment that can accelerate the production of hydrogen gas. Therefore, other immobilization
approaches may therefore be preferred for these wastes.
16 | P a g e
Preparing ILW for Disposal
556
5
557
558
559
560
561
562
The proper selection of predisposal options including treatment, conditioning, and storage may make a
significant contribution to both operational and long term safety of a disposal system. All of these processes
may be particularly beneficial for ILW due to its diversity and volume. However, it is noted that once the
waste has been conditioned, the volume for disposal may be significantly greater than that of raw waste.
563
5.1
564
565
566
567
568
569
570
571
572
573
574
575
576
577
Treatment of ILW may be beneficial for safety and/or economy by changing the characteristics of the waste.
Treatment may result in volume reduction, removal of some radionuclides, and change in physical form and
chemical composition. For example, ILW may be incinerated to remove organic and combustible materials
and convert radionuclides into stable oxide forms. Large items may be cut into smaller pieces to optimize
packaging and disposal operations. Treatment may also contribute along with conditioning to control free
liquids in the waste.
578
5.2
579
580
581
582
583
584
585
586
587
588
Conditioning of ILW is important to produce a waste package suitable for handling, transport, storage and/or
disposal, and typically includes immobilization of the waste and packaging in metal or reinforced concrete
containers. Immobilization of ILW can increase its physical integrity and reduce potential for the
dissemination of contaminants. It contributes to minimize free liquids in the waste package to prevent
contamination and activity release in the case of any damage to the containers during handling and operation,
and to prevent corrosion. Conditioning also contributes to reduce residual void space which may affect the
stability of the waste package for both operational and post-closure phases against subsidence. Voidage can
facilitate the development of micro-environments within the waste package which may also be detrimental to
long-term containment.
589
590
591
592
593
594
In selecting an immobilization material, its chemical and physical compatibility with the waste and the
surrounding engineered and natural materials need to be considered. Cement is widely used as a fixing
material and offers a number of potential benefits, including neutralising acids present in or generated by the
waste and providing a chemical environment in which the corrosion rate of many metals is reduced.
However, other materials such as glass, ceramics, and polymers may be preferred for specific types of ILW.
Bitumen has also been used for certain waste.
595
596
597
598
599
600
601
602
603
604
605
Packaging waste in containers contributes to control of the gross weight of the waste package and facilitates
standardization of package dimensions and lifting mechanisms for handling, transportation and
emplacement. This is particularly useful for ILW due to its diversity. Containers can also be designed to
provide sufficient shielding and containment of contaminants during normal operations and in the event of an
incident such as fire or impact. For some wastes types, for example those containing bitumen, the container
may contribute to limit the increase of temperature of the waste in the case of a fire in the facility. ILW
containers are usually made from metal or reinforced concrete. Mild or stainless steels are commonly used,
although copper is occasionally considered for ILW. The choice will depend on both the characteristics of
the waste and the containment capacity of the host rock and other engineered barriers.
Treatment
If the hazard of the waste is reduced by treatment, it may enable the requirement on the containment system
provided by both engineered and natural barriers to less demanding. However, in evaluating treatment
options, the consequences of chemical or physical reactions during waste treatment need to be considered,
for example, radioactive gases (e.g. H-3 and C-14) may be released.
17 | P a g e
Conditioning
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
It is generally required for safety that the integrity of the waste package is maintained at least for the duration
of the operational period. During this period, the waste packages need to withstand any incidents during
handling and operation, such as fire or drop/impact events. The stability of the facility with respect to
subsidence needs to be considered as part of the assessment of the post-closure safety.
Disposal concepts for ILW typically involve the stacking of containers to optimise the disposal capacity.
Therefore, the waste package needs to have acceptable structural integrity and compressive strength to
ensure the stackability of waste packages.
Furthermore, in some disposal concepts, particularly for near surface disposal, the container has a role as a
barrier after closure delaying the release of radionuclides and therefore allowing short-lived radionuclides to
decay before there is any migration to the environment. In these cases, container lifetime is one component
used in the post-closure safety case.
For metallic containers, corrosion performance is an important indicator of container integrity and lifetime. It
is essential to establish underlying corrosion scenarios, considering swelling, gas generation and loss of
integrity, that contribute to container failure for the various types of material.
Carbonation rate degradation due to chemical and mechanical attack and corrosion of reinforcing metals
need to be considered in order to estimate the lifetime of concrete containers. On the other hand, polymercontainer materials (High Density Poly Ethylene (HDPE)) are not susceptible to corrosion; although creep,
embrittlement, and irradiation-induced degradation can affect their durability.
The safety functions of the waste package are provided by the combination of the form of the treated waste,
its immobilization and the container. There may be trade-off between the properties of the immobilized
waste and the requirements on the container. Moreover, if the containment performance of the waste package
is increased by conditioning options, it may enable the requirements on other engineered and natural barriers
to be less demanding.
633
634
635
5.3
Storage
636
637
638
639
640
641
642
Storage prior to disposal can offer benefits for the design and operation of disposal facilities for some types
of ILW. For example, thermal outputs at disposal can be reduced, especially from wastes with a high content
of Co-60. Storage may allow the quantities of radiolysis-induced gases and short-lived radionuclides such as
H-3 to be reduced prior to disposal. More generally, storage of ILW is essential where waste is being
generated and conditioned before an appropriate disposal facility is available.
643
644
5.4
645
646
647
648
649
650
651
652
653
654
655
656
657
Waste packages have to meet the WAC of the individual storage and disposal facilities, which can vary
widely in their design complexity. Further information on WAC can be found in IAEA TECDOC 1572.
Identification and compliance with waste acceptance criteria for
disposal
Quality control of waste packages is important to enhance the confidence that an adequate level of
performance can be achieved.
A key step in preparing ILW for disposal is the preparation of comprehensive documentation describing the
origin and characteristics of the waste as well as the history of its treatment and conditioning. In order to
ensure traceability, each individual waste package needs to be uniquely identified at every step up to its final
emplacement at the disposal facility. As the waste management may take place over several years or even
decades, appropriate measures to ensure maintenance of records over the required time frame is essential
including any arrangement related to the transfer of ownership or responsibility regarding waste
management.
18 | P a g e
Disposal Options
658
6
659
6.1
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
Containment and isolation are the principal safety functions of any disposal facility. The choice of disposal
option, concept and design of the disposal facility needs to ensure that these requirements are met during
operation and after closure of the facility.
690
6.2
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
An important factor in the management and disposal of ILW is the concentration of long lived radionuclides
in the waste stream. Disposal of radioactive waste with a limited concentration of long lived radioactivity can
be in facilities located near surface. Such facilities would be developed on sites with favourable
environmental and geological characteristics and may include engineered barriers or other features that
impede or limit the eventual release of radionuclides to acceptable rates and amounts.
Principal safety functions
Containment can be defined (IAEA Safety Glossary) as methods or structures that perform a confinement
function, namely preventing or controlling the release of radioactive substances and their dispersion in the
environment. Although related to confinement, containment is normally used to refer to methods or
structures that perform a confinement function, namely preventing or controlling the release of radioactive
substances and their dispersion in the environment. See confinement for a more extensive discussion.
Isolation means (SSR-5) retaining the waste and keeping its associated hazard away from the biosphere in a
disposal environment that provides substantial physical separation from the biosphere, making human
access to the waste difficult without special technical capabilities, and restricts the mobility of most of the
long lived radionuclides.
The disposal system needs to provide a combination of natural and engineered characteristics to support
efficient containment and isolation of the waste by maintaining package integrity, limiting the solubility of
radionuclides and the waste form, minimizing where possible groundwater inflow and/or providing a long
travel time for radionuclide transport from the disposal facility to the biosphere. In the long term, progressive
degradation of the engineered barrier system cannot be ruled out and, consequently, radionuclides may be
released into the geological environment where they may eventually migrate to the biosphere. Materials used
for backfilling or sealing should have properties that do not degrade unduly the safety functions of the
geological barriers.
As discussed in Chapter 2, timescales for isolation and containment of ILW are a function of the half-lives
and activities of the radionuclides contained in the waste to be disposed of. Containment performance of the
disposal facility needs to account for the properties of the contained radionuclides in relation to their
mobility potential.
Available Disposal Options
If the waste requires management for a period of the order of hundreds of thousands of years, it will require
disposal in a deep geological formation. Wastes with a management timescale of 10,000 to 100,000 years,
which is within a glaciation cycle, may be suitable for disposal at a shallower depth, with regard to
geodynamic evolution. Over these timescales, some radionuclides with intermediate half-lives such as C-14,
Am-241 and radium bearing waste containing low amount of uranium, will have been substantially
decreased. For wastes with higher amount of uranium, the ingrowth of Ra-226 needs to be considered.
Containment derives from a multi-barrier system that employs both engineered and natural barriers to
achieve the required safety. The role of the barriers, engineered and natural, in providing containment will
depend on the disposal option, the properties of the natural surface and underground environment and the
radiological inventory particularly with respect to half-lives and the mobilities of the radionuclides.
19 | P a g e
709
710
711
712
An overview of the various disposal options for ILW is given below. Additional information is available in
IAEA publication, NW-T-1.20 Disposal Approaches for Long Lived Low and Intermediate Level
Radioactive Waste.
713
6.2.1
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
As stated in SSR-5 and SSG-29, a near surface disposal is a facility consisting of engineered trenches or
vaults constructed on the ground surface or up to a few tens of meters below ground level. These near
surface disposal options present the greatest vulnerability to external phenomena which constraints the types
of wastes that can be disposed of.
731
6.2.1.1. Landfill disposal
732
733
734
735
736
737
738
739
A landfill disposal facility contains no complex engineered barriers or elaborate sealing. Therefore, adequate
WAC and quality control are needed to ensure that the radionuclide content, especially the content of long
lived activity, remains at levels compatible with the limited containment and isolation capabilities of the
design. Particular attention needs to be paid to surface phenomena that can reduce the degree of isolation and
containment of the waste, with particular reference to the extreme meteorological events, flooding and
erosion, phenomena related to hydrogeological instability. Surveillance and monitoring are required during
the period of institutional control.
740
6.2.1.2. Trench disposal
741
742
743
744
745
746
747
748
749
Trench disposal is an option usually used for waste with higher radioactive content than waste associated
with landfill disposal. The trench can be divided into individual compartments to increase radionuclide
containment and flexibility of operation and may be lined if required for mechanical stability or to enhance
containment. After filling, a waterproofing top cover is installed. Surveillance and monitoring are required
after closure during the period of institutional control. The WAC also will limit the type, concentration and
quantity of radionuclides allowed in waste packages, reflecting the limited retention capability of this type of
site. Particular attention is required to surface phenomena that can reduce the degree of isolation and
containment.
750
6.2.1.3. Engineered vault
751
752
753
754
755
756
757
758
An engineered surface disposal facility of the vault type provides more robust engineered barriers that aim to
reduce the amount of water that could contact the waste. These facilities are principally intended for the
disposal of short-lived waste with the activity of long lived isotopes being limited to low concentrations.
Near surface options
IAEA Technical Reports Series No. 412, Scientific and Technical Basis for the Near Surface Disposal of
Low and Intermediate Level Waste describes that near surface disposal options include two main types of
disposal system: (a) shallow facilities consisting of disposal units located either above (mounds, etc.) or
below (trenches, vaults, pits, etc.) the original ground surface; and (b) facilities where the waste is emplaced
at greater depths in rock cavities or boreholes. In the first case, the thickness of the cover over the waste is
typically a few metres, whereas in the second case, the layer of rock above the waste can be some tens of
metres thick. These depths can be contrasted with the case of geological disposal of long lived radioactive
wastes, where the wastes are emplaced at depths of hundreds of metres.
Advantages of near surface facilities are that they may be more economical to site, construct and operate, are
quicker to site and construct, and may result in an easier social acceptance than a geological option.
Engineered vault facilities are equipped with surface barriers (caps), vertical barriers (cut-off vaults) and subhorizontal barriers (floors). There are other containment technologies that may be applied, including
chemical barriers that retard migration of radionuclides without impeding the water movement. After the
waste is disposed of, the void spaces in vaults are usually filled with grout or some other backfill material.
20 | P a g e
759
760
761
762
763
The engineered barrier system may include drainage collectors to channel out infiltrating water.
Underground galleries may be installed to allow the functioning of the barriers to be checked. Additional
barriers might be constructed around the disposal vault to control the movement of water. Particular attention
is required to surface phenomena that can reduce the degree of isolation and containment.
764
6.2.1.4. Near surface underground disposal facilities
765
766
767
768
769
770
771
772
773
774
775
776
777
Near surface underground disposal facilities can be developed either in natural or excavated cavities in
various geological formations. The construction and operation of such facilities require access tunnels,
ramps or shafts. Isolation capability of the facility increases with depth. Contribution of the host formation to
containment depends upon its geological and hydrogeological properties. The engineered barriers also
contribute to containment.
778
6.2.2
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
ILW with higher contents of long-lived radionuclides is usually disposed of at depth in appropriate
geological formations. In principle, underground disposal facilities provide a higher level of isolation for
longer period than near-surface disposal facilities.
804
6.2.3
805
6.2.3.1. Boreholes
806
807
808
Disposal of ILW in boreholes drilled from the surface may be a suitable option where waste volumes and
diameter of waste packages are limited (e.g. disused sealed sources). The required depth of the borehole will
depend on the characteristics of the waste and local geological and environmental conditions. Sealing of the
There is a smooth transition between near surface underground disposal facilities and geological disposal
facilities with respect to containment and isolation as well as other issues such as construction, operation and
closure. Definitions for depth ranges of both near surface and geological disposal facilities vary from country
to country depending on national contexts. Consistently with SSR-5, it is not appropriate to set a firm
threshold at the international level. Instead, the definition needs to be established on the basis of the local
geological and geodynamic properties.
Geological disposal options
Human intrusion scenarios are a function of facility depth, as is the performance of isolation at any given
time. Depending upon the depth of the facility, intrusion by near surface human processes can be avoided.
A further characteristic of underground disposal is that the need for institutional control is much diminished in most cases, the land can be put to a range of uses, including agriculture, immediately after closure.
Containment provided by the host formation can be optimized by an appropriate location of the underground
facility within the host formation which includes depth taking into account geodynamic evolution.
Containment also relies on other factors such as the waste form and other engineered barriers for which
depth induced stresses must be taken into account.
ICRP Publication 122 on the Radiological Protection in Geological Disposal of Long-Lived Solid
Radioactive Waste indicates that “the goal of a geological disposal facility is to achieve the isolation and
containment of the waste and to protect humans and the environment for time-scales that are comparable
with geological changes. At great distance from the surface, such changes are particularly slow (…)”.
Depending on its characteristics, geological disposal of ILW can be carried out in various designs of
underground facilities. Disposal could be by emplacement in a facility constructed in caverns, vaults or silos.
It could include purpose built facilities and facilities developed in or from existing mines. It could also
include facilities developed by drift mining into mountainsides or hillsides.
Disposal options
21 | P a g e
809
810
811
812
boreholes after wastes have been emplaced is particularly important for the purposes of containment and
isolation. Further information on borehole disposal is given in IAEA Specific Safety Guide SSG-1, Borehole
Disposal Facilities for Radioactive Waste.
813
6.2.3.2. In-situ immobilization
814
815
816
817
818
819
A number of practices for in situ immobilization are available. They are not recommended practices in
situations in which the options mentioned above are available or could be reasonably implemented, but they
can constitute an acceptable practice for remediation purposes. This practice is out of the scope of this
document, and therefore it is not discussed further.
820
6.3
821
822
823
824
The selection of an appropriate disposal option for ILW must firstly be based on safety considerations. It
may also depend upon aspects that are related to waste inventory, economic considerations and social
acceptability reflecting the national context.
825
6.3.1
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
Appropriate disposal options will depend upon a number of safety related factors. Recognition of safety
related factors will primarily enable to identify appropriate options. Important factors include:
Factors for the selection of a disposal option






Safety related factors
Radiological characteristics of the waste (half-lives and activities)
The amount of mobile or potentially mobile radionuclides in the wastes
The physical and chemical form of the waste
The characteristics of the site and its surroundings (geological setting, hydrogeology and
environmental factors)
The timescale and degree of containment provided by the disposal option, including its evolution
The isolation potential provided by the disposal option (depth in particular)
Identification of appropriate disposal options may result from an analysis of all individual factors and an
assessment of the compatibility of each factor with the others. Safety-related factors will determine that,
while ILW with lesser amount of long-lived radionuclides are more appropriate for near surface facilities,
those with greater amounts of long-lived radionuclides are more appropriate for geological disposal.
A suitable combination of waste form and engineered barrier system may allow an increase in the specific
activity of long lived radionuclides that can be accepted for disposal at a given site.
Segregation of ILW streams with different characteristics may enable each disposal option to be tailored
more effectively. For example, a portion of ILW may be suitable for near-surface disposal and this may
enable the more expensive deep underground facilities to be utilised more effectively. The principle of
iterations addressed in Requirement 11 in SSR-5 (see Section 3.4) may also be applied to define appropriate
segregation.
Appropriately constructed geological disposal facilities render the highest possible degree of waste isolation,
and can therefore accept waste with high contents of long lived radioactivity. But the effort required to site
and construct a facility is high, so that its’ construction may not be justified for disposal of limited amounts
of long lived ILW, if a HLW facility is available and meets safety . In some cases, co-disposal of ILW with
HLW may be economically attractive and feasible.
22 | P a g e
856
6.3.2
Waste volume related factors
857
858
859
860
861
862
863
864
Where there are several appropriate disposal options for ILW with regard to safety, the waste volume may
influence the selection of one or several separate and dedicated ILW disposal facilities or, one or several
disposal facilities that allow co-location of ILW with low or high level radioactive waste types. Factors to be
considered here are waste inventory and potential interactions between co-located wastes.
865
6.3.3
866
867
868
869
870
871
872
873
874
875
876
Cost considerations in the development of an ILW management strategy are an important aspect in managing
national liabilities and resources, but must not preclude achieving an acceptable level of safety which
complies with national policy and lies within the country’s legal framework. Because skilled personnel are
needed to design, construct, operate and close a disposal facility, their availability could, in principle,
influence the choice of an option.
877
6.3.4
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
The national radioactive waste management policy of a Member State may prescribe or proscribe radioactive
waste disposal options for ILW. For example, near surface disposal of ILW might be acceptable for safety
and economic reasons, but national policy may require deep geologic disposal. Legislative aspects may also
constrain the siting procedure and programme development for ILW disposal.
IAEA technical report Series 412, Scientific and Technical Basis for the Near Surface Disposal of Low and
Intermediate Level Waste provides information on co-disposal of low and intermediate level radioactive
waste.
Economic and technical resources
Disposal facilities generally have high fixed costs that are independent of the volume of waste. Therefore,
significant economies may be achieved if a disposal facility is shared for different types of waste (colocation ILW with LLW or HLW). If it is decided to co-locate facilities, it should be confirmed that the
safety of any collocated facilities are not compromised.
National policy and social aspects
Stakeholder involvement is important to be taken into account in the decision making process. Public
acceptance is an important factor that may influence decisions.
The choice of disposal options and design of the facility need also to take account of any national
requirements with respect to reversibility or retrievability. In all cases, it has to be ensured that reversibility
and retrievability do not jeopardize the safety of the facility. Further information can be found in NEA 7085,
OECD 2012, Reversibility of Decisions and Retrievability of Radioactive Waste – Considerations for
National Geological Disposal Programmes).
893
23 | P a g e
Siting
894
7
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
Siting is a fundamentally important activity in the development of any disposal facilitiy, either near surface
or geological. In site selection, one or more preferred candidate sites are identified on the basis of
environmental and geological setting and with account taken of other factors. In addition to safety,
sociopolitical factors may also be an important consideration in any site selection process (e.g. social
acceptance, transport infrastructure, existing land use).
937
7.1
938
939
940
941
942
943
944
945
946
Natural properties of the site relevant to an ILW disposal facility that have an impact on containment are
listed in SSG-29 and SSG-14 for near-surface and geological disposal facilities respectively. They include:
Site selection for ILW disposal needs to take into account specific requirements related to these wastes in
terms of isolation and containment and related time scales as well as compatibility with volume and chemical
and physical properties of the waste. This concerns both current natural properites of the site and their
expected evolution over time. The consideration of the consistency of the site properties with the
requirements for safe disposal of the ILW may take into account potential trade-off between engineered and
natural barriers.
The main natural factors to be considered are common to both near-surface and geological disposal
facilities. However, depending upon the disposal options being considered, there may be differences in the
weighting of the factors being considered. For example, a near-surface disposal facility would consider that
the stability of the surface environment would have a greater impact on safety than that of a geological
disposal facility, which would be focused more upon the geological stability of the underground
environment.
Siting of any disposal faciity is usually carried out as a stepwise process, with the level of detail in the
understanding increasing as the process proceeds. This process is described in SSG-14 and SSG-29 as
follows:
”In the siting process for a radioactive waste disposal facility, four stages may be recognized:
(i) the conceptual and planning stage,
(ii) the area survey stage,
(iii) the site investigation stage, and
(iv) the stage of detailed site characterization leading to site confirmation for construction of
the disposal facility.”
The level of understanding which needs to be achieved in site characterisation is set out in Requirement 15
of SSR-5:
“The site for a disposal facility shall be characterized at a level of detail sufficient to support a general
understanding of both the characteristics of the site and how the site will evolve over time. This shall include
its present condition, its probable natural evolution and possible natural events, and also human plans and
actions in the vicinity that may affect the safety of the facility over the period of interest. It shall also include
a specific understanding of the impact on safety of features, events and processes associated with the site
and the facility.”
Site natural properties
 geology,
 hydrology and hydrogeology,
 geochemistry,
 tectonics and seismicity,
 geomechanical,
 thermal, and
24 | P a g e
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001

surface and meteorological processes (mainly for near-surface disposal).
To guarantee sufficient isolation, favourable characteristics for containment need to occur at a depth which
can provide the required separation from the biosphere and the absence of significant natural resources for
materials, energy or other potential uses of the space (e.g. for underground storage).
Avoidance of human intrusion may not just be depth dependent. For remote sites, the need to take active
measures to avoid human intrusion may be different for sites located near people provided a limited
timescale for the safety case is appropriate.
The size of the site must be sufficient to accommodate the volume of the waste to be emplaced. For colocation of ILW with either LLW or HLW, the site must be sufficient to accommodate the adequate spacing
of the different types of waste, to ensure that there would be no significant adverse reaction between them.
Geological disposal provides a higher level of isolation for ILW. Favourable geological contexts are ones in
which the migration of contaminants is strongly reduced due to the characteristics of the rock matrix (low
permeability, presence of minerals capable of capturing radionuclides, etc.) and the absence of preferential
paths of flow.
Some ILW contains a significant amount of long-lived and potentially mobile radionuclides, such as Cl-36 or
chemical contaminants such as nitrates or lead. For these wastes, the geometry of the host rock and presence
of features which will delay and/or mitigate the migration of mobile radionuclides and other contaminants
(for example volume of intact rock, frequency of conducting fractures, thickness of sedimentary layers as
host rock or in overburden) are particularly important. Similar features would also be help to compensate for
the presence of complexants and organic materials in the ILW.
Where colloids may be present in the ILW, the mobility of these particles in pores or natural fractures and
their ability to transport radionuclides needs to be investigated.
Sorption in the host rock can be a favourable attribute for the retention of some radionuclides in ILW, such
as aqueous 14C, radium and actinides. The presence of minerals such as iron oxide and clay phases is
therefore important.
Redox conditions may also be important for containment of some radionuclides, particularly the actinides.
For near-surface disposal, the impact of saturation/desaturation cycles along with climatic variation may
need to be taken into account.
The redox buffering capacity of the host rock may compensate for the presence of oxidising agents, such as
nitrates in the waste.
Geomechanical properties are important for construction and may dictate, for example, the maximum size of
vaults, their separation and the migration properties and extent of the damaged zone. The EDZ is
particularly to be considered for ILW with a high content of mobile radionuclides and/or producing particles
of colloidal size. The potential swelling of some waste and the expansion of corrosion products may also
require consideration with respect to the mechanical properties of the host rock.
A particular feature of some ILW is its potential to generate gas. The permeability of the host rock with
respect to gas and its ability to withstand gas pressure are therefore significant considerations in these cases.
Whilst less significant than for HLW, heat generation may still need to be considered for some ILW. The
thermal conductivity of the host rock and its response to an increase in temperature, for example THM
interactions in porous materials, may require consideration.
Although both near surface and geological disposal options have similar factors, depending upon the disposal
options being considered, there may be differences in the weighting of the factors considered. For example, a
25 | P a g e
1002
1003
1004
1005
1006
1007
1008
near-surface disposal facility would consider that the properties of the surface environment would have a
greater impact on safety than for a geological disposal facility, which would be focused more upon the
geological characteristics of the underground environment.
1009
7.2
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
In selecting a site for ILW, it is important to consider not just the current status of the site but also its
expected evolution over the time period for which isolation and containment of the waste will be required.
1024
7.2.1
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
One potential impact of climate change is alteration of the magnitude and/or distribution of precipitation. In
cases of significant precipitation or where groundwater is recharged via other mechanisms, the height of the
water table can increase. This may influence the hydraulic gradient and therefore the groundwater
movement, especially for near-surface disposal.
1039
7.2.2
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
Materials used during the construction of the disposal facility may be impacted by permafrost and/or
glaciation. If permafrost or glaciation occurs, there would be a reduction in hydraulic conductivity of the area
being impacted. Additionally, glaciation could have the effect of forcing the injection of oxic glacial (melt)
water deep into underground affecting geochemical conditions.
Specific site properties are required to be assessed in the safety case and safety assessment.
Site evolution
The future evolution of the site will be influenced by existing environmental processes, future climate
change and geologic processes. Future climate change may affect precipitation/recharge, permafrost,
glaciation, sea level change, weathering and erosion. As to geologic processes, significant uplift/subsidence,
unfavourable features such as active faults and active volcanoes should be avoided. However, indirect
effects from active faults, active volcanoes or other tectonic processes that may be occurring within the
region should be considered.
For a near surface disposal facility in particular, an understanding of existing environmental processes such
as erosion by rain or weathering are most important factors affecting the evolution of the site over the
relevant timescale of the next few hundreds to thousands of years. For geological disposal, the relevant
timescales are much longer and therefore future climate and geological processes become significant.
Precipitation and recharge
In situations where the water table level is low or decreasing, oxidizing or unsaturated conditions could
develop deeper into the underground environment, changing the redox conditions and therefore the mobility
of radionuclides.
Therefore, groundwater levels and their potential for change within the time period relevant for safety of the
ILW disposal needs to be considered when selecting the appropriate disposal option and designing the
facility, particularly for near-surface disposal of ILW with significant amounts of redox sensitive
radionuclides.
Permafrost and glaciation
The development of ice sheets may also significantly alter the stresses on the natural environment and
engineered barriers at the considered depth and/or erode or otherwise reshape the superficial geology to a
significant depth.
When determining the depth of the disposal facility, these factors will need to be considered. The depth of
the disposal facility may need to be increased in order to achieve a permafrost free environment and/or
reduce the likelihood of or consequences of other changes during the time period relevant for the safety of
the ILW disposal.
26 | P a g e
1053
1054
1055
1056
Surface facilities should be avoided if the required timeframe for isolation and containment extends beyond
the expected date of the next glaciation.
1057
7.2.3
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
Sea level change could alter the migration of radionuclides including the discharge environment where they
may return to the surface. This merits particular consideration in the case of long-lived ILW as the time
periods to be addressed for safety are very long.
1070
7.2.4
1071
1072
1073
1074
1075
Weathering of rock due to climate may alter the geology, hydrologic/hydrogeologic properties, existing
redox conditions, migration potential of the radionuclides and mechanical properties up to 100m from the
surface. It is particularly important when considering near-surface disposal of ILW where the time period to
be considered is relatively long.
1076
7.2.5
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
At some locations, uplift/erosion and the movement of faults/folds are important considerations in the long
term safety of a disposal facility. Uplift followed by erosion could reduce the geosphere/host rock thickness
and alter the hydrologic/hydrogeologic properties, affecting existing redox and geochemical conditions.
1089
7.2.6
1090
1091
1092
The likelihood of human intrusion may be impacted by site evolution processes including glaciation, sea
level change, and uplift/erosion. This issue needs to be considered over the timescale relevant for the
radiological content of the ILW, especially for near-surface disposal.
1093
1094
1095
1096
1097
As of 2014, currently, the IAEA organized an international project focusing on human intrusion for various
types of waste disposal facilities, which is called HIDRA Project (human intrusion in the context of disposal
of radioactive waste). HIDRA project is focused on various issues such as the difference and commonality of
human intrusion scenarios for geological and near-surface disposal facilities and approaches that have been
used for such assessments in different countries.”
Sea level change
In the case of sea level reduction, the hydraulic gradient could increase resulting in a decreased water table
impacting the existing redox environment, chemical composition of groundwater (including salinity), as well
as surface hydrology.
Sea level rise, from global warming for example, could decrease the hydraulic gradient, increasing the water
table resulting in associated changes to the chemical composition of groundwater.
Weathering
Uplift/erosion, faulting/folding and subsidence/sedimentation
On the other hand, subsidence/sedimentation could increase the disposal facility depth and generally work
favourably to safety, unless rock stress increases to a level that is detrimental to the disposal facility.
In mountainous areas, the possibility of a large-scale landslide and any associated impacts may need to be
evaluated.
Glaciation is an important cause of uplift and erosion (see Section 7.2.2).
Impact of geodynamic evolution on the consideration of human intrusion
27 | P a g e
1098
7.2.7
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
In addition to geological considerations, there are a number of other factors which need to be taken into
account in siting of any disposal facility, including ILW. The relevant factors apply to both near surface and
geological disposal and include:




Natural and social environment
existing and future land use;
proximity to population, especially urban centres
transport of waste, including ease of access to existing or new transportation networks;
protection of environmentally-significant sites
SSG-14 and SSG-29 provide detailed guidance on these considerations.
For ILW containing or generating gaseous radionuclides, control of environmental impacts of possible
releases of radioactive gases during the operational phase may need to be considered.
1114
28 | P a g e
Disposal Facility Design for ILW
1115
8
1116
8.1
1117
1118
1119
1120
1121
1122
1123
1124
1125
Design development in radioactive waste disposal is an iterative process involving regular testing of the
proposed solution for compliance with the requirements and feasibility of implementation with respect to
both technical and economic aspects. The principal requirements on the disposal facility relate to safety.
Therefore, the iterations are driven by the safety case.
1126
8.1.1
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
Developing disposal designs firstly requires a compilation of a comprehensive list of the functions and
requirements that are applicable to each stage of the facility lifecycle: construction, operation, closure and
post-closure. The external requirements to be considered in the design of a disposal facility arise from the
following sources:
Design process
Feedback from the design cycle is used to refine the requirements and optimise the solutions. In the early
stages of the development, the focus is more on clarifying and increasing details of the requirements. As the
design process becomes more mature, increased emphases is placed on detailing and optimising solutions.




Requirements on the disposal facility
international and national standards, regulations, and guidance,
waste inventory and characteristics,
constraints from the selected site, and
stakeholder expectations, especially those of a potential host community.
The requirements are progressively refined through the iterative process of design and safety case
development.
The overarching requirements for the design of a disposal facility are given in SSR-5, Requirement 16 which
states that:
“the disposal facility and its engineered barriers shall be designed to contain the waste with its associated
hazard, to be physically and chemically compatible with the host geological formation and/or surface
environment, and to provide safety features after closure that complement those features afforded by the host
environment. The facility and its engineered barriers shall be designed to provide safety during the
operational period. ”
The detail, whilst recognising that there is a wide range of design solutions, specifies requirements on the
engineered barrier system, which needs to:





make optimal use of the safety features offered by the host environment;
be designed so that it does not cause unacceptable long term disturbance of the site;
be protected by the site;
perform safety functions that complement the natural barriers; and
have a layout designed so that waste is emplaced in the most suitable locations.
SSG-14 and SSG-29 contain guidance for geological and near-surface facilities respectively, but list a
number of common requirements:



The design needs to take into account at an early stage the types and quantity of waste that will be
disposed at the site
In the course of the design of the facility, information about the waste needs to be used to support the
identification of a concept and the actual design
The design needs to provide safety during both the operational and post-closure periods
29 | P a g e
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193

The design needs to take account of any requirements for
o Monitoring
o Accounting and control of nuclear materials, if necessary
o Concurrent underground activities (such as excavation and nuclear operations)
o Any local requirement for retrievability and reversibility

The designs need to be developed in sufficient detail and accuracy to enable the effect of design
requirements to be appropriately evaluated in assessments of operational and post-closure safety. In
accordance with the stepwise approach to implementation, as the facility design evolves and
becomes progressively more detailed over the phases of facility development, safety assessments
need to be updated to evaluate the effects of design changes on compliance with regulatory criteria.
Implementation of this requirement places importance on effective record-keeping (see Chapter 10).

The design for safety in the post-closure period needs to meet the precepts of robustness, simplicity,
technical feasibility and passivity whilst that in the operational period will include both active and
passive systems.
The licencing of a disposal facility will require an initial inventory of the waste which is planned to be
disposed there, in terms of waste volume, waste types and physical and chemical content, including
radiological properties. It is good practice to design the ILW facility in a manner which is sufficiently
adaptable to incorporate a level of evolution in the disposal inventory, for example to respond to extensions
in lifetime of operating nuclear power plants. The amount of waste being produced and the date of delivery
to the facility will depend on a variety of factors, particularly for decommissioning waste. Therefore, it is
often difficult to define the duration of the operational time period early in the planning phase. When
extending the operational time period, the allowable extension must be assessed taking into account the
planned life time of the waste handling, maintenance and support devices.
1194
8.1.2
Design solution development
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
The selected disposal concept forms the foundation of the design considerations for an ILW facility. Concept
selection is therefore an early step of the iterative process of design development. The concept is selected to
provide the safety functions required for the specific waste type and form, site properties and their evolution,
repository depth. In more advanced stages, the design becomes progressively more detailed consistently with
the refined requirements derived from earlier iterations.
1205
8.1.3
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
The safety case and supporting safety assessment for a particular design will provide the demonstration of its
compliance with safety-related requirements. The safety case and assessment (see Chapter 0) need to be
supported by demonstration tests under appropriate conditions. For ILW, demonstration of an understanding
of any interaction between the engineered system and the surrounding environment is particularly important.
In addition to disposal volumes, design considerations need to address access ways, operating systems,
services and support facilities. Those parts of the facilities located on surface need to be properly interfaced
with the surrounding environment.
Verification of compliance
Best practice suggests a stepwise implementation process, with the safety case being developed in increasing
detail as knowledge of the engineered and natural systems matures and intermediate findings from the safety
case are used to refine and optimise the design in an iterative approach.
It will be important to demonstrate safety for the full range of ILW to be disposed in the various disposal
options being considered.
30 | P a g e
1219
8.2
Safety considerations for ILW disposal facility design
1220
8.2.1
1221
1222
1223
Safety considerations during construction of ILW facility are those related to non-nuclear industrial activities.
Construction regulations apply and mining regulations may also apply to the construction of underground
facilities depending on the national contexts.
1224
8.2.2
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
The main functions during the operational phase of the facility are to receive and emplace the waste, which
requires constructing disposal capacities and supporting the resulting open structures or underground caverns
as necessary until closure. A further function to be provided during operation is to backfill and cap or seal
the excavations to the standard required to comply with post-closure requirements. Monitoring of
performance is important to demonstrate that the facility is operating and evolving with time as planned.
Retrievability may also need to be considered if this is required by legislation or to meet stakeholder
expectations.
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
Operation of a disposal facility:
The disposal facility shall be operated in accordance with the conditions of the licence and the relevant
regulatory requirements so as to maintain safety during the operational period and in such a manner as to
preserve the safety functions assumed in the safety case that are important to safety after closure.
Construction phase
Operational phase
All of these operational functions need to be performed in a way which ensures conventional and
radiological safety and environmental protection consistently with Requirement 18 in SSR-5:
The design needs to include systems to comply with the relevant operational safety functions. Typical safety
functions for ILW during this phase are to:





limit the exposure of workers and the public to radiation,
contain radioactive materials in a robust manner,
dissipate gas produced from radiolysis and corrosion,
provide for criticality safety, and
dissipate heat, if any.
During operation of an ILW disposal facility, protection and safety has to be optimized so that the magnitude
of individual doses, the number of people exposed and the likelihood of incurring exposures are kept as low
as reasonably achievable, economic and social factors being taken into account. This applies to both workers
and the public. In addition to nuclear safety, protection against non-radiological hazards must also be
accommodated in the design.
Systems have to also be included to avoid, detect, and mitigate operational hazards such as fire, impact
accidents from e.g. drops, explosion and external aggressive events such as seismicity or flooding. Particular
consideration needs to be given on the hazards induced by potential interaction between different types of
activities performed at the same time, such as disposal vault construction and waste emplacement.
For surface facilities in particular, planning for and management of extreme weather events during operation
is important. Compared with similar LLW facilities, more consideration is required as the potential
consequences of a failure in the engineered system may be more significant.
For a disposal facility, as for any other operational nuclear facility or facility where radioactive material is
handled, used, stored or processed, an operational radiation protection programme, commensurate with the
radiological hazards, is required to be put in place to ensure that doses to workers during normal operations
are controlled and that the requirements for the limitation of radiation doses are met. In addition, emergency
plans are required to be put in place for dealing with accidents and other incidents, and for ensuring that any
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1279
1280
1281
1282
1283
1284
1285
1286
1287
consequent radiation doses are controlled to the extent possible, with due regard for the relevant emergency
action levels.
1288
8.2.3
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
In the post-closure phase, isolation and containment are provided through passive means. Multiple safety
functions are required to provide robustness in safety. The requirements on the various components in order
to achieve their contributions to post-closure safety depend strongly on the selected disposal option and on
the properties of the chosen site. Therefore, the safety functions of containment and, as necessary, isolation,
need to be broken down so that the contributions of the various components of the disposal system can be
designed appropriately.
Compared with HLW, gas production during operation from radiolysis or other means may be a significant
issue, where disposal of ILW is underground. Ventilation systems need to be able to dissipate gas effectively
to eliminate the possibility of explosion due to a local build-up of hydrogen gas. Approaches to ensure the
ongoing safety of the facility in the event of ventilation failure and during the closure process as ventilation
is removed also need to be developed.
Depending on the specific waste types, management of criticality during operation may be important. ILW
with a higher content of fissile material may be more suitable for underground disposal. Balancing the
competing demands of maximising the cavern size for ILW and managing for criticality safety needs to be
considered.
Whilst heat is not generally an issue for ILW, there may be cases where active management of the heat needs
to be factored into the design for protection of workers and equipment during operation in addition to the
consideration on heat conduction into the host rock. Where the design incorporates a cement-based backfill,
management of the heat generated during cement hydration also needs to be considered.
Post-closure phase
It is recommended to identify the features and processes which may contribute to containment in the various
parts of engineered and natural barrier systems, specifically:



factors which delay or reduce access of water to waste, such as container integrity and lifetime,
factors which reduce the release of radionuclides into water, e.g. chemical conditions provided by
materials in the engineered barrier system, and
factors which delay and limit migration of radionuclides, e.g. low advection and high sorption
provided by the engineered and natural barriers.
The weighting of the various factors and related requirements on the design will depend on the specific
properties of the ILW to be considered:




materials that comprise ILW (metal, concrete, bitumen, glass etc.) and their alteration processes
over timeframes relevant for safety (corrosion, dissolution, hydrolysis etc.),
major contained radionuclides (mobile fission/activation products or actinides etc.),
chemical form of contaminants (oxide, organic complex etc.), and
their physical form in the ILW (labile contamination, in immobilization matrix, in activated metal
etc.).
Therefore, consideration of these matters will enable waste-specific requirements for the post-closure safety
to be derived. In turn, it enables the disposal option and engineering solution to be optimised.
The large variety and the composition of the ILW bring the requirement to consider various constraints such
as chemical interactions between different waste types as well as between the waste and other engineered
materials.
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1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
Gas, heat and criticality management may continue to be important after closure. Under the anaerobic
conditions which will develop after closure, a build-up of gas may damage the engineered barriers and/or
alter the transport of radionuclides. Whilst not generally significant, thermal effects may be important for
some specific ILW types and may also impact the engineered barriers and the host rock. Management
options may include waste emplacement strategies which distribute the thermal loads across the disposal
volumes and provisions for sufficient heat conduction within the engineered barriers. For ILW with a
relatively higher concentration of fissile material, the possibility of an accumulation of this material
following degradation of the engineered structures needs to be considered in the design with respect to the
criticality safety.
1336
8.3
1337
8.3.1
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
The external volume and total number of waste packages is usually the most important determinant of the
size of the disposal facility. Other factors are the shape of the packages and their handling requirements. In
particular, the need for remote handling of packages may cause an increase in the excavated the size of the
disposal facility to provide space for handling equipment such as overhead cranes. Other related aspects such
as transportation may also influence the option to be selected.
1352
1353
1354
1355
1356
Because concepts based on large vaults are preferred for ILW, consideration also needs to be given to the
extent of residual voidage in the disposal system at closure and the way in which it will evolve or increase
further. Voidage may result in the establishment of a local chemical environment which may facilitate
corrosion or microbial activity with potential impact on safety. Large voids may cause structural instability
which, in turn, may lead to collapse of the engineered system.
1357
1358
1359
The facility also needs to be designed to account for gas generation during closure and beyond. It may be
possible to increase the robustness of the engineered system to contain gas or to make provision for
controlled release.
1360
1361
1362
1363
1364
1365
1366
1367
1368
The potential impact on the degradation of the waste package and on the dissolution and retention of
radionuclides needs to be considered when selecting materials used to construct the disposal cells and pits.
The differences of the waste properties and volumes, between ILW and HLW may lead to the use of
significantly different design and hence the materials used. On the other hand, materials used when designing
for LLW and ILW are often similar due large waste volumes considered and in some cases due to colocation. A long containment period provided by durable waste packages may not be practicable for lower
activity long-lived waste. The engineered materials need to be selected taking into account potential
chemical disturbances induced by the waste (e.g. nitrate resistant cement may be preferred for use with
nitrate-bearing wastes).
1369
1370
1371
1372
Cement-based materials are often used for structural stability and/or to provide an alkaline environment in
which the corrosion of many metallic elements is reduced. This is particularly relevant for ILW containing
activate metal pieces. It can also be favourable for the containment of actinides. This is particularly relevant
for ILW which contains significant amounts of actinides. However, fluids present in a cement-based
If a co-located facility is proposed, the design of the disposal facility and in particular the potentials of
separation of waste types needs to ensure that interactions do not have significant adverse effects on safety.
Design considerations for ILW
Disposal volumes
As the volume of ILW for disposal is often significant, designs are often based on disposal pits or vaults,
rather than individual deposition holes. The vaults are generally designed as large as possible to make
effective use of the space but with respect to criticality and with respect to dissipation of any heat generated
by the ILW for underground disposal facilities. The excavated size is limited by the in-situ stresses of the
host rock at the considered depth and also by the objective to limit mechanical disturbances to the host
formation, which may increase the permeability of the rock in the excavation damaged zone (EDZ). The
characteristics of the EDZ need to meet the requirements related to containment, e.g., the extent should be
limited compared with the thickness of the host formation.
33 | P a g e
1373
1374
1375
environment can react with other engineered components, especially those made of swelling clay, and with
the surrounding geological environment. Any potential detriments from these interactions must be
compensated for in the design. In some cases ‘low pH’ cements may be preferred.
1376
1377
1378
1379
1380
1381
1382
1383
When selecting materials for the engineered system for ILW, special consideration needs to be given to the
evolution of the engineered barrier system. The waste containers maintain integrity during operations but,
after closure, will gradually degrade and allow water to contact the waste. Corrosion products may interact
with the barrier materials and impact on their containment performance. Bentonite swelling capacity may be
reduced and cracks induced in cementitious materials. In cement-based systems, the cement may contribute
to containment by buffering the groundwater to an alkaline pH. The cement gradually dissolves in this
process and its composition evolves. Therefore it particularly impact to reflect the requirements for longterm performance in the design bases.
1384
1385
1386
1387
Structural stability of the excavated volumes has to be ensured during construction, waste emplacement, and
during any period of planned monitoring or easy1retrieval up to the time of backfilling or sealing. This
requirement may be more demanding for underground ILW facilities than for those for HLW as the
excavated caverns may need to be larger.
1388
1389
8.3.2
Layout
1390
1391
1392
1393
1394
1395
1396
1397
1398
The size of the individual cells, together with any access routes, determine the footprint of the facility and
needs to be adapted to the specific conditions at the selected site.
1399
1400
1401
Where ILW is being co-disposed with other waste types, the separation of the different wastes must be
sufficient to ensure that there are no significant detrimental interactions, particularly thermal or chemical
interactions. The layout may also be optimised with regard to the hydrogeological system as necessary.
It may be useful to include segregation of different waste streams which may interact, for example to
separate organics-containing wastes from radionuclides sensitive to complexing agents, such as plutonium.
Similarly nitrate-containing waste could be separated from those wastes which may be particularly sensitive
to the presence of oxidants. The relevant separation distances will need to be defined during the design
process, taking into consideration the migration properties of the host environments. Any requirement for
sealing materials in access tunnels to reinforce the separation would need to be decided at the design stage.
1402
1403
8.3.3
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
Access to an underground disposal facility may be by horizontal tunnels, inclined ramps and/or vertical
shafts. Selection of the location and design of the specific access way may be influenced by the
characteristics of the site, including relief and depth, presence of aquifers. Provisions in this location and the
design need to be made with respect to the long-term safety. The cross section of the access ways needs to
take into account the range of dimensions of waste packages that are planned to be accommodated during the
operation of the facility and any associated shielding and handling equipment. As a function of the specific
rock properties of the host rock and any overlying strata, reinforcement may need to be incorporated in the
design as required for the protection of workers during construction and for rock support during the
operational phase.
1414
8.3.4
1415
1416
1417
1418
1419
Waste inspection, handling and transfer equipment of the disposal facility need to take into account all the
different types of waste packages planned to be disposed of. Waste packages with higher surface dose rates
may need remote handling and/or shielding. This may be even more complicated for larger components.
Waste handling may be governed by national worker safety, transport and radiation protection regulations or
others.
1
Access ways
Operating systems
Level 2 on the NEA retrievability scale
34 | P a g e
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1421
1422
1423
1424
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1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
Some predisposal management activities, in particular conditioning, may be carried out at the disposal site or
at another installation, depending on the national strategy for radioactive waste management.
One main difference between HLW and ILW is the larger variety of waste types that need to be managed in
ILW disposal. This larger variety of waste types is also commonly found in LLW disposal. This variety of
waste types results in a potentially large variety of waste packages in terms of dimensions and shapes of the
packages, for instance, and also in terms of dose rates. Some packages may be suitable for direct handling,
whilst others must be managed remotely or with additional shielding. When designing handling equipment
and other parts of the disposal system, this has to be taken into account.
In addition, there may also be a desire to dispose of large components (e.g. pumps, steam generators, pipes)
to minimise dose to decommissioning workers or also for reasons of cost and time efficiency.
The disposal of large components may create operational issues, both logistically and radiologically. Large
components may need to be delivered at the disposal facility at a time when it is suitable for the waste
producers. Therefore temporary accommodation of the waste may need to be considered at the disposal site
prior to emplacement. The other issue that needs to be considered is the radiological issue during the
operational phase. These large components may need additional shielding and workers may have to operate
close to the component. Large components may also put other requirements on the disposal system, such as
the installation of a ramp as opposed to a shaft.
Electrical and mechanical installations need to be of a standard suitable for radiation-controlled
environments. Systems need to be included to limit and control hazardous substances such as explosive or
flammable materials. Selection of designs which contain inherent prevention of hazards such as fire can be
preferred especially for ILW that are sensitive to temperature (e.g. concerning bituminous waste).
Detection systems of a suitable sophistication to give early warnings of hazards such as fire or airborne
radioactivity need to be employed. Should a hazard occur, appropriate mitigation systems need to be
provided.
Ventilation systems need to manage any gas generated by the waste.
The operating lifetime of many facilities means that maintenance and refurbishment of the operating system
will be required and provision for this should be included in the design solution.
Whilst these design provisions are applicable in all facilities, they are of particular significance for some
ILW due to the waste types.
1459
8.3.5
Backfilling, capping and sealing
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
This comprises the backfill, seals and caps to be constructed during and after waste emplacement in order to
provide the required isolation and containment after the facility is closed. The requirements for this activity
are driven by the post-closure safety functions and will depend on the characteristics of the ILW being
disposed and on the disposal option and concept.
The re-use of excavated materials may be considered if they fulfil the safety function. In that case, some
protection of this material may need to be provided during storage in order to facilitate its reuse.
Particular attention may need to be given to the expected performance of the backfill around non-standard
waste packages particularly for large items.
Consideration also needs to be given on the sealing of any exploration boreholes in the vicinity of the
facility.
1473
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1474
8.3.6
Monitoring and retrievability
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
Requirements for monitoring and retrievability are influenced by national legislation and stakeholder
expectations. Monitoring and retrievability may be required to contribute to confidence building and to
decision-making during stepwise development of a facility.
1485
8.3.7
1486
1487
1488
On the surface, the construction zone can be separated by fences to limit unnecessary traffic between the two
zones of personnel, equipment and material. In an underground facility, separate access tunnels and
ventilation systems are desirable with limited and controlled connection between them.
ILW packages are typically less robust than HLW packages and contain more activity than LLW. Therefore,
monitoring of container evolution and integrity may be particularly relevant.
Some ILW packages may generate gas, which may be radioactive or non-radioactive. There may be a need to
monitor gases during the operational period.
Management of concurrent construction and operation
1489
36 | P a g e
Safety Case Development
1490
9
1491
1492
1493
1494
SSG-23 is fully applicable to the development of the safety case and safety assessment for ILW. Therefore,
this chapter only focuses on the aspects that are specific to the ILW.
1495
9.1
1496
SSG-23 states in paragraph 4.20 that;
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
“The safety case will be developed as the project progresses and will be used as a basis for decision making,
1509
1510
Among the issues addressed in this paragraph, the following needs particular consideration for specificity of
ILW disposal:
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
Iterative Approach of the Safety Case
for both regulatory decisions and other decisions relating to, for example, the design, supporting research
work or site characterization activities. The context for each revision of the safety case should be set out
clearly and should be updated as necessary and appropriate for subsequent revisions of the safety case.”
Paragraph 4.21 of SSG-23 states
“The purpose of each revision of the safety case will depend on a number of factors, such as the stage of
development of the disposal facility, and whether the safety case is to be submitted to the regulatory body as
part of a formal licensing procedure or to obtain directions from the regulatory body. For each revision of
the safety case, the operator should provide a clear description of its purpose, which, depending on the stage
of development of the facility”
-
Testing of initial ideas for safety concepts;
Optimization of the facility design;
Identification of safety related issues to be addressed by research and development
programmes;
Definition or revision of limits, controls and conditions such as WAC;
Assessment of the maximum inventory that can be disposed of (the ‘radiological capacity’ of
the facility).
A specificity of ILW disposal is that testing of safety concepts is important to underpin the selection of an
appropriate disposal options as such a wide range is available (see Chapter 5). Optimization of the facility
design is also particularly important, at the facility scale, to optimise the number, dimensions, and spacing of
vaults and, at the vault scale, to ensure efficient stacking of the variety of waste packages and to minimize
voidage.
Due to the diversity of the materials present in ILW and the wide range of treatment and imobilization
options, there are various specific issues that may need R&D to underpin safety. This includes:






Identification of complexing agents present in the waste or arising from degradation of materials and
their effects on the mobility of contaminants contained in the waste;
Characterisation of chemical and physical forms of contaminants within the waste and understanding
of the release mechanisms;
Understanding of release of chemically disturbing species and their effect on the engineered barriers
and on the mobility of contaminants, such as corrosive species or oxidising agents;
Gas generation and migration;
Swelling potential of some ILW (e.g. bituminous waste and reactive metal) and physical interactions
with surrounding materials;
Potential exothermic reactions within some ILW induced by internal or external energy (e.g.
bituminous and graphite waste);
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1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549




Colloid production and its migration;
Evolution of pH with time in cementitious material;
Evolution of materials and geometries within the vault for ILW with relatively high concentration of
fissile nuclides; and
Interactions between ILW specific engineered barrier(s) and the host rock.
It may be necessary to limit or control the quantities of some contaminants and the maximum inventory,
particularly for near surface disposal. These limits need to be derived from the safety case. Any requirements
of this type need to be captured in the WAC.
1550
9.2
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
The adoption of a graded approach in determining the scope, extent and level of detail of the safety case and
supporting assessment as described in Paragraph 4.25 of SSG-23 is particularly applicable to ILW disposal:
1569
9.3
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
Demonstration of safety
”A graded approach is required to be taken in determining the scope, extent and level of detail of the safety
case and supporting assessment. The graded approach adopted should be explained and justified, and
should be such that the scope, extent and level of detail of the safety case and supporting assessment are
commensurate with the level of risks posed by a facility or activity and the stage of facility development, e.g.
generic disposal concepts being considered prior to site selection might be considered in less detail than for
a specific site and disposal facility.
For ILW, the level of risk is a function of its content in long-lived and/or mobile radionuclides as well as the
activity level. These factors will also influence the timescales over which safety needs to be assessed.
In the case of co-disposal of ILW with other waste types, the scope, extent and level of detail of the safety
case and supporting assessment must reflect the potential of the most hazardous waste type and of the
potential interactions between the two waste types.
Aspects of safety assessment
as descibed in SSG-23, key elements of the safety assessment are the following:










Radiological impact assessment for the period after closure,
Site and engineering aspects,
Passive safety ,
Multiple safety functions,
Robustness,
Scientific and engineering principles,
Quality of the site characterization,
Operational safety aspects,
Non-radiological environmental impact, and
Management system.
With regards to those key elements, the large variety of ILW is important. The safety assessment needs to
take into account various processes which were described in previous sections that may affect some types of
ILW and needs to be tailored to specific characteristic of the individual vaults.
It should be noted that in the case of codisposal of other waste types with ILW, the safety case and safety
assessment must take into account any possible interactions between the wastes types.
38 | P a g e
1590
1591
1592
1593
1594
1595
1596
1597
Safety cannot rely on institutional control periods longer than a few hundred years. Human intrusion
scenarios must be considered in the safety case after the end of the institutional control period. The type of
intrusion scenario is depth dependent. This leads to the identification of limits for the acceptable residual
activity within the waste after the institutional control period. The institutional control has an influence only
on the initial amount of short lived radionuclides in the waste. The acceptable content in long lived
radionuclides is a function of the type of intrusion scenarios to be considered and therefore a function of
repository depth.
1598
39 | P a g e
Institutional Control and Record Keeping
1599
10
1600
10.1
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
SSR-5 Requirement 22 states:
1618
10.2
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
As for all other types of waste, the operator needs to retain all information relevant to the safety case and the
supporting safety assessments of the ILW disposal facility, the emplaced wastes, the facility design and the
records that demonstrate compliance with regulatory requirements. Such information and records have to be
retained by the operator unless or until such time as another organization assumes responsibility for the
facility, at which time the records should be transferred to the organization that assumes that responsibility.
Records should also include information associated with waste generation, processing and waste acceptance.
Institutional control
“Plans shall be prepared for the period after closure to address institutional control and the arrangements
for maintaining the availability of information on the disposal facility. These plans shall be consistent with
passive safety features and shall form part of the safety case on which authorization to close the facility is
granted.”
In applying this concept in ILW disposal, the requirements for control are a function of the depth of the
disposal facility, not of the type of the waste disposed. This is stated in paragraph 3.43 of SSR-5 as follows:
For near surface facilities, isolation has to be provided by the location and the design of the disposal facility
and by operational and institutional controls. For geological disposal of radioactive waste, isolation is
provided primarily by the host geological formation as a consequence of the depth of disposal.
There are a number of different national requirements on this issue.
Record keeping
Consideration should be given to the physical and electronic forms of the records to ensure that information
remains available and is archived appropriately for the benefit of future generations. The use of warning
signs or markers to warn of the presence of the disposal facility may also be considered. An important
consideration is that the location of where the records are archived may be lost to future generations, so that
care in determining the location of the archives must be taken.
Record keeping may include the posting of facility records in national and international archives accessible
to future generations and the transfer of responsibility for the facility to a successor organization. A suitable
mechanism may need to be developed for the transfer of responsibility from one generation to the next.
1635
1636
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REFERENCE
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APPENDIX I: National Examples
•
Analysis of common features and differing approaches may be added to Chapter 9 (to be
discussed at the plenary)
<NATIONAL EXAMPLES TO BE PREPARED BY PARTICIPANTS>
<Proposed new structure for national example>
1. National Waste Classification and Policy
- Describe national waste classification focusing on the results, no description on the process (give
reference of the process or other relevant materials
- Be consistent with the description in the main text
2. Approach to managing the ILW
- Provide overview of Existing or Planned Disposal facilities (options) for ILW, link to Chapter 3
of this annex
- Try to use terms consistent with the main text for disposal options
- Can be described with a schematic figure
- Also describe specific project schedule & current status (about 4-5 lines)
3. Details of Existing or Planned Disposal Facilities (maximum 1 page/site including figures)
3.1 Site A
3.1.1 Disposal option and timescales (about 4-5 lines)
use the term consistent with the main text, not the wording in the national context
Explain national example in relation to Chapter 3.2 Timescales
3.1.2 Waste characteristics and volume (about 4-5 lines)
3.1.3 Siting and safety function of natural barriers
3.1.4 Disposal facility design including EBS design
3.1.5 Facility specific considerations (e.g. institutional control, retrievability and reversibility)
3.2 Site B
3.2.1 Disposal option and timescales
3.2.2 Waste characteristics and volume
3.2.3 Siting and safety function of natural barriers
3.2.4 Disposal facility design including EBS design
3.2.5 Facility specific considerations
3.3 Site C
Reference
-Reference to waste classification
-Rference to safety case & supporting documents
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APPENDIX II: IAEA publications relevant to this document
The IAEA has published a number of Safety Standards and other technical documents relevant to ILW
disposal. The following are suggested for background information and additional technical details.
1. IAEA Safety Standard series
 IAEA General Safety Requirements, GSR Part4, Safety Assessment for Facilities and
Activities
 IAEA General Safety Guide GSG-1, Classification of Radioactive Waste
 IAEA General Safety Guide GSG-3, The Safety Case and Safety Assessment for the
Predisposal Management of Radioactive Waste
2. Other technical series documents

NW-T-1.20, Disposal Approaches for Long Lived Low and Intermediate Level Radioactive
Waste

Technical Report series TR-412, Scientific and Technical Basic for the Near Surface Disposal
of Low and Intermediate Level

TECDOC – 1572, Disposal Aspects of Low and Intermediate Level Decommissioning Waste

TECDOC – 1397, Long Term Behaviour of Low and \intermediate Level Waste Packages
Under Repository Conditions

TECDOC – 1325, Management of Low and Intermediate Level Radioactive Waste with
Regard to Their Chemical Toxicity

ISAM/ASAM report
There are also a number of publications published before 2000, which have not been included in the
list.
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