Technical Report. Overview of Knowledge Coverage for Geological Disposal. Bill Miller. AMEC Report Reference: Client Reference:

Transcription

1 Technical Report Overview of Knowledge Coverage for Geological Disposal Bill Miller AMEC Report Reference: Client Reference: ONR158 Issue Number: 1.1 Date of Report: 13th January 2015

2 DOCUMENT ISSUE RECORD (Engineering Documents) Document Title: Project Reference: Purpose of Issue: Security Class: Overview of Knowledge Coverage for Geological Disposal ONR158 Submission of final report to client prior to publication No classification Issue Description of Amendment Originator / Author 1.0 Final report Bill Miller Reviewers Approver Date Timo Saanio Peter Hufschmied Tim McEwen Bill Miller 19/12/ Minor amendments prior to publication Bill Miller William Turner Bill Miller 13/01/15 Previous issues of this document shall be destroyed or marked SUPERSEDED Amec Foster Wheeler UK Limited 2015 This report was prepared exclusively for ONR (the Company ) by Amec Foster Wheeler UK Limited ( AMEC ). This report must be read as a whole and is subject to, and limited by, (i) the information available at the time of preparation of the report; (ii) the data supplied by the Company and outside sources; (iii) the assumptions, methodology and procedures that have been agreed as the scope of work to be conducted by AMEC in connection with this report; (iv) the assumptions, conditions and qualifications set forth in this report; and (v) the terms and conditions of the agreement under which this report was prepared between the Company and AMEC, together with any subsequent amendments. To the extent permitted by law, this report shall not be used or relied upon by any person other than the Company without the express written consent of AMEC, and, absent any such consent, AMEC disclaims any liability or responsibility for the use of or reliance on this report or any information contained in this report by any third party. Office for Nuclear Regulation (ONR) Page i

3 Contacts For further information please contact the following: Contact Person Title Address Contact Number Bill Miller Repository Director AMEC The Renaissance Centre 601 Faraday Street Birchwood Park Warrington WA3 6GN United Kingdom TEL: +44(0) Office for Nuclear Regulation (ONR) Page ii

4 Contents 1 Introduction Background Objectives of this report Method of working UK context and open questions Inventory of wastes Ongoing waste conditioning and packaging operations Site selection Geological disposal concepts Co-disposal of wastes Retrievability and reversibility Significance The regulatory framework Health, safety and security regulation Environmental regulation Other regulations Significance Balancing risks during GDF implementation Significance Stages in the GDF programme Stages in the MRWS process An outline programme for the GDF and key activities Significance Main activities during the GDF programme stages Format of discussion and definitions Stage A: Programme planning and site selection Stage B: Surface investigations Stage C: Access shaft / tunnel construction Stage D: Phased underground excavations Stage E: Inactive and active commissioning Stage F: Phased waste emplacement Stage G: Closure and sealing Underpinning knowledge and understanding Significant projects and publications Office for Nuclear Regulation (ONR) Page iii

5 8 Knowledge coverage for geological disposal Organisational structure and planning Inventory and waste packaging Concept development and design optimisation Characterisation and monitoring of the site Construction, installation and testing Operations and waste emplacement Backfilling and closure Waste retrieval Safety cases and permitting References Appendix: Project workshop Office for Nuclear Regulation (ONR) Page iv

6 Executive Summary This contractor report may be used by the UK s nuclear and environmental regulators as one input when developing a Nuclear Research Needs (NRN) for the UK s planned geological disposal facility (GDF). Nonetheless, the information and opinions expressed in this report represent the views of the author and do not, necessarily, reflect the position of the regulators. The UK Government s Managing Radioactive Waste Safely (MRWS) policy sets out a staged approach to implementing the geological disposal of higher activity radioactive wastes (HAW). A volunteer siting process is underway that might lead to a GDF being constructed in any of the potentially available rock types and geological environments in the UK. The Radioactive Waste Management Directorate (RWMD) of the Nuclear Decommissioning Authority (NDA) has been identified by Government as the implementer for the GDF. The Office for Nuclear Regulation (ONR) is responsible for regulating the nuclear, radiological and industrial safety of the GDF during all stages of its implementation. In parallel, the relevant environment agency (depending on where the GDF may be sited) has responsibility to ensure protection of people and the environment. Jointly, the ONR and the relevant environment agency (the regulators ) will ensure safety and environmental protection by undertaking critical scrutiny and evaluation of the proposed GDF design, operational procedures and periodic safety assessments submitted by the implementer. This report is intended to support the regulators by reviewing the underpinning knowledge base relevant to geological disposal (e.g. technical publications, research studies, development work etc.) available internationally and in the UK. Note that it is not the intention of this report to undertake a detailed peer review of the research and other technical work performed by RWMD. To structure the review of the knowledge base, the main phases of the GDF implementation programme were considered, along with their associated key activities (e.g. excavation of disposal tunnels, emplacement of waste etc). Possible knowledge gaps and open questions were identified which might require further research and development (R&D) to support their understanding, assessment or mitigation. Although the review focussed on geological disposal, many (but not all) aspects of this study will also be relevant to proposals for near-surface and surface disposal facilities for certain types of low-level and short-lived radioactive wastes. The review identified a number of high-level issues that may be significant for the design and operation of the GDF, and consequently for its safety and environmental performance: 1. The GDF implementation programme is subject to many variables such as the choice of site, the inventory of wastes to be disposed, the design of the facility, its operation and closure methods, and the possible need for retrievability. Many of these variables are inter-dependent. For example, the design of the GDF cannot be decided until after the site has been chosen and a decision has been made on the wastes to be disposed. The large number of variables makes it difficult to plan for and design the GDF, and to account for all of the possible safety and environmental implications. It may not be feasible to progress far with implementation whilst keeping all variables open. Evaluating different options in the early stages of implementation will, however, provide useful information that can inform later decisions on which option is ultimately preferred. Office for Nuclear Regulation (ONR) Page v

7 2. Wastes continue to be generated during routine operations and decommissioning activities, and these wastes need to be conditioned and packaged to be made passively safe for interim storage. There is a risk that wastes packaged now may not be in a physical or chemical form that is optimal for disposal in the GDF, once a site and design are chosen. The RWMD Letter of Compliance (LoC) process is intended to mitigate this risk but it currently applies only to intermediate-level wastes. Several other waste types such as vitrified high-level wastes (HLW) and some potential waste materials (e.g. uranium and plutonium-bearing fissile materials) do not have LoCs. 3. Government has expressed a preference for a single GDF for disposal of both cementitious ILW, and vitrified HLW and spent fuels, in co-located but physically separated underground areas. No other national disposal programme plans to dispose of such a diverse range of waste types, with such a large total volume, in a single co-located facility. The closest comparison is with the planned French repository which is also intended to dispose of both HLW and ILW, but the UK ILW inventory is approximately five times greater than the French ILW inventory. There is, therefore, limited international experience of co-location to draw upon. Maintaining physical and chemical separation of the different waste types in a co-located facility is essential to avoid undesirable interactions and corrosion process occurring. This places important constraints on the requirements and suitability of the host rock. It is not yet known whether a suitable rock volume will be available within any volunteered site and, consequently, it remains a possibility that more than one geological disposal facility may need to be sited in the UK. 4. Deciding upon the disposal concept for the GDF is not a straightforward process, and many different safety, environmental, technical, financial and stakeholder issues will need to be taken into consideration. Optimisation of the GDF design and its operational practices will require appropriate balancing of full life-cycle operational safety (i.e. risk to site workers and current generations) against post-closure safety (i.e. risk to future generations), and against the other non-safety attributes. The process and methodology to be used for decision making and optimisation has yet to be agreed. This process will need to be transparent, auditable and acceptable to all key stakeholders, including the regulators and the local communities at the volunteer site. There has now been over five decades of detailed research into geological disposal. The bulk of this work has focussed on understanding and modelling the long-term evolution of disposal systems, and on assessing the post-closure consequences of radionuclide releases and exposures to people. Reviewing the underpinning knowledge, it is apparent that, at a high level, there is relevant knowledge applicable to all of the stages and activities anticipated in the GDF programme. Certain topics are very well researched and understood internationally, and it might be argued that no further fundamental research is required on aspects such as: HLW and spent fuel long-term stability, and radionuclide release processes in chemically reducing, low groundwater flow geological systems; packaging concepts for solid, chemically and physically inert wastes; long-term behaviour and containment properties afforded by compressed bentonite as a buffer material; and radionuclide release and transport modelling, and associated dose/risk consequence analysis for environmental safety cases. Much of the available knowledge comes from overseas HLW and spent fuel disposal programmes that have already chosen sites and are nearing full implementation (e.g. Finland, Sweden, France). Office for Nuclear Regulation (ONR) Page vi

8 This knowledge can be translated to disposal in the UK, provided allowances are made for any key differences in waste materials and the geological conditions at any volunteered site etc. Less emphasis has typically been given to research into methods for the construction and operation of geological disposal facilities, or to aspects of nuclear safeguards and security. This is despite the obvious hazards associated with handling large and heavy radioactive waste packages in confined spaces underground. This situation is now changing with several international collaborative projects ongoing in underground research laboratories that involve testing and demonstrating the equipment and methods that may be used for construction and operations, such as full-scale waste emplacement trials. The UK participates in some of these projects but the implementation methods that may be applied in the GDF cannot be fully developed until after a site has been chosen, and a disposal system designed that is consistent with the characteristics of the host rock. This review identified a number of potential knowledge gaps and open questions that will need to be addressed as the GDF programme moves forward. Not all of these knowledge gaps need to be addressed now, but a plan should be developed to ensure that key information is available at the time it is needed, and at the appropriate level of detail. In some cases, this may mean work needs to start soon to obtain the information that will be needed during later stages of implementation, especially where long-term research or development of technology may be required. Some of these open questions relate to the high-level issues of waste inventory, disposal concept design and decision making processes, described earlier. Questions such as: How should wastes continue to be processed and packaged without foreclosing options, given uncertainty regarding the site, geology and design of the facility? What disposal concepts and engineering designs are suitable for UK wastes and geological environments (both established concepts and promising but less well developed alternatives)? How will decisions (on site, inventory, design etc.) be closed out and banked, to enable the programme to move forward through each stage of implementation in the light of new information as it is gathered? Many other questions relate to specific technical, engineering, design and operational aspects of the GDF during later stages of implementation, such as: How will the as built design be recorded and input to the nuclear and environmental safety cases? How can active and non-active areas of the GDF be separated from each other? What will be the procedure and techniques for managing any waste package that might have degraded or leaked? What wastes and disposal areas will need to be backfilled at the time of waste emplacement? None of the open questions identified in this report are show stoppers and none of them would mean that the GDF programme could not move forward to the next stages of implementation. Several of them will, however, need to be answered with sufficient detail before embarking on MRWS Stage 6 (Underground operations) which marks a fundamental change in the programme from performing largely desk-based studies, to undertaking practical construction and engineering activities. Questions such as: Office for Nuclear Regulation (ONR) Page vii

9 What are the factors affecting the choice of primary access route to the underground parts of the GDF (e.g. shaft or inclined tunnel)? What are the safety critical posts in the implementing organisation, and what competence does the implementer need to manage the design and construction of the access shaft / tunnel? What site characterisation and baseline monitoring information must be collected before shaft / tunnel construction can commence? What information is needed to determine whether the access needs to be designed to allow retrievability? Their inclusion in this report does not imply that these open questions have not, or cannot, be answered at this time. It will be through the continuing process of scrutiny, that the regulators may come to a view that these questions have, or have not, been answered to their satisfaction, at a level of detail appropriate to the current stage of the GDF implementation programme. It is stressed that it is not the intention of this report to peer review the work of RWMD, and the list of open questions in this report does not imply any deficiency in their technical and research programmes. Clarification for publication This report was written in 2013, and presents the findings of a study that was carried out in the period It is being published in 2015 and so may not fully reflect more recent developments in Government policy (MRWS), or the updated programmes and working arrangements of the organisations mentioned herein. Office for Nuclear Regulation (ONR) Page viii

10 1 Introduction 1.1 Background In 2001 the UK Government and devolved administrations initiated the Managing Radioactive Waste Safely (MRWS) programme with the aim of finding a practicable solution for the UK s higher activity radioactive wastes (HAW). As part of the MRWS programme, Government appointed the independent Committee on Radioactive Waste Management (CoRWM) and charged them with making recommendations for how HAW should be managed. In 2006, CoRWM published their findings and recommended that geological disposal, supported by an integral programme of safe and secure interim storage, was the best available approach for the long-term management of HAW (CoRWM, 2006). The Government 1 accepted this recommendation and it is now policy in England, Wales and Northern Ireland that HAW will be disposed of in a geological disposal facility (GDF) at some future time and at a site yet to be identified. The policy and regulatory framework underpinning geological disposal was set out in a White Paper (Defra et al., 2008) that specified that the Nuclear Decommissioning Authority (NDA) is the body responsible for planning and implementing a GDF, through its Radioactive Waste Management Directorate (RWMD). The policy in Scotland is that the long-term management of HAW should be in near-surface facilities located as near to the site where the waste is produced as possible (Scottish Government, 2011). The implementation of a GDF will be a complex undertaking that will need to address many conventional and radiological hazards to people and the environment during its design, construction and operation, and also into the very far-future after it has been closed. The Office for Nuclear Regulation (ONR) has a statutory duty to regulate nuclear, radiological and industrial safety on nuclear sites in the UK, and so has a primary interest in all safety relevant aspects of the GDF throughout all stages in its lifecycle. The 2008 White Paper makes clear that the GDF will require a Nuclear Site Licence under the Nuclear Installations Act In parallel, the relevant environment agency 2 will have responsibility to ensure protection of people and the environment during construction and operation of the GDF, and also into the far-future after the facility has been closed. Jointly, the ONR and the relevant environment agency will ensure safety and environmental protection by undertaking critical scrutiny and evaluation of the proposed GDF design, operational procedures and periodic safety assessments submitted by the implementer. Although the primary focus of the report is on geological disposal, many (but not all) aspects of this study are also likely to be relevant to near-surface and surface disposal facilities (such as those considered in the Scottish policy for management of HAW), provided consideration is given to possible consequences for safety and environmental performance due to the depth of the disposal facility. 1 In this report, the term Government refers to the UK Government unless the context indicates otherwise. 2 Environmental regulation is a devolved matter. Consequently, either the Environment Agency (EA), Natural Resources Wales (NRW) or the Northern Ireland Environment Agency (NIEA) will be the relevant environment agency for the GDF, depending on whether it is sited in England, Wales or Northern Ireland. For the purposes of this project, the EA has taken the lead on behalf of all the environment agencies. Office for Nuclear Regulation (ONR) Page 1

11 1.2 Objectives of this report This contractor report will be used by the regulators to underpin a Nuclear Research Needs (NRN) for the GDF. Nonetheless, the information and opinions expressed in this report represent the views of the author and do not, necessarily, reflect the position of the regulators. The purpose of this report is to take a high-level overview of the GDF implementation programme and its associated activities, and to consider the extent of the underpinning knowledge base (e.g. research studies, development work etc). This review will help to identify any outstanding aspects that may affect the safety and environmental performance of the GDF, and associated knowledge gaps, which might require further research and development (R&D) to support their understanding, assessment or mitigation. At this stage in the GDF programme, the primary aim is to ensure there is sufficient knowledge to move forward to the next steps of implementation and there are no obvious show stoppers. Not all knowledge gaps need to be addressed now, but a plan should be developed to ensure that key information is available at the time it is needed, and at the appropriate level of detail. In some cases, this may mean work needs to start soon to obtain the information that will be needed during later stages of implementation, especially where long-term R&D may be required. It is understood that certain design features and operational practices have implications in terms of nuclear, environmental and conventional safety and security. There may, consequently, be a tension when meeting the totality of regulatory requirements. An additional specific purpose of this report is to examine how operational safety may be appropriately balanced against post-closure safety through optimisation of the facility design and its operational practices. It is not the purpose of this report to review RWMD s implementation programme for the GDF nor is the aim to peer review RWMD s technical publications. Other reports have recently addressed those topics (e.g. CoRWM, 2012, 2013; ONR & EA, 2011, 2013). This report may, however, be used as one input to the regulators continuing process of scrutiny and evaluation of RWMD. Through the continuing process of scrutiny, the regulators may seek to establish whether the open questions raised in this report have been, or are planned to be, answered by RWMD at a level of detail appropriate to the current stage of the GDF implementation programme. These open questions may then be tracked through the issues management processes already established by both the regulators and RWMD. 1.3 Method of working To help structure the project and ensure the objectives were met, the work was undertaken in a number of steps, as shown in Figure 1.1. This method of working was adopted because it was considered sensible to discuss the questions associated with geological disposal in the context of the most important activities that will be undertaken by the implementer in each of the main stages of GDF implementation (construction, operation etc.), and then to consider what are the potential high-level safety and environmental implications of those activities. These implications are phrased as possible questions that the regulators may wish to ask as part of their scrutiny of the GDF programme. Office for Nuclear Regulation (ONR) Page 2

12 Step 1: Review the Government policy and regulatory framework Identify programme drivers, open issues with safety and environmental implications Sections 2 and 3 Step 2: Consider balancing operational and post-closure safety Consider available methods to optimise the design accounting for all key decision attributes Section 4 Step 3: Identify the key stages in the implementation programme Determine what are the most significant activities that will be undertaken in the programme Section 5 Step 4: Consider implications of activities and associated questions Develop a set of questions the regulators may wish to ask as part of scrutiny of the programme Section 6 Step 5: Identify the underpinning knowledge for key activities Review published international research, development work and collaborative projects Section 7 Step 6: Identify any potential gaps in knowledge and need for new R&D Align international knowledge to GDF programme activities and identify any potential gaps Section 8 Figure 1.1: The steps in the project leading to fulfilment of the project objectives, and the sections in the report in which each step is described. For example, during construction, an important activity will be the design and excavation of the primary access route for waste transport to the underground parts of the GDF (e.g. vertical shaft or inclined tunnel). This access has obvious safety implications for construction and removal of excavated rock, routine waste handling operations, and potential accident scenarios. Additionally, the access might provide a pathway for post-closure radionuclide releases in the far-future. The regulators may wish to ensure all factors are taken into account in its design and so might ask the question: What information is needed to make the decision on the choice of the primary access route and what is the decision making process? An important step in the project was to consider the status of current knowledge relevant to the most important activities. When identifying the knowledge base, consideration was given to the international context and the experience from those national disposal programmes that are at a more advanced stage of implementation than the UK (e.g. Finland, Sweden, France). No assumptions have been made for the likely host rock type or concept design for the GDF, and international knowledge relevant to all possible options has been Office for Nuclear Regulation (ONR) Page 3

13 gathered, including some disposal concepts that have not been considered in detail within previous phases of R&D into geological disposal in the UK. This helps to identify what relevant knowledge could be applied to the GDF programme, and also where there may be key knowledge gaps due to the unique nature of the UK s radioactive wastes and its disposal programme. Within the resource constraints of the project, it was not feasible to identify all published research etc. but a concerted effort was made to identify the most recent and applicable sources of information. Particular attention was paid to the outputs from large-scale international collaborative projects (e.g. those led by the EC and IAEA) because these tend to be planned specifically to support knowledge transfer. Reports published by the UK regulators or the UK implementing body (RWMD) were not included in this review. To help identify the most important activities and associated high-level questions, a workshop was held at the beginning of the project that involved experts drawn from the regulators (ONR and EA) plus the following independent experts to provide additional knowledge and ensure an international perspective to the review. John Whyatt from the Health and Safety Executive s Mines Inspectorate (UK) Tim McEwen from McEwen Consulting Ltd (UK) Timo Saanio from Saanio & Riekkola Oy (Finland) Peter Hufschmied from ExTechNa GmbH (Switzerland) In addition to participating in the workshop, these experts also peer reviewed a draft of this report. The Appendix provides a full list of the workshop participants, together with a summary of the main points and questions that arose during discussions. Office for Nuclear Regulation (ONR) Page 4

14 2 UK context and open questions 2.1 Inventory of wastes The UK has a wide array of radioactive wastes and materials that are likely to be sentenced for disposal in the GDF, the most significant being vitrified high-level waste (HLW) and a broad range of intermediate-level wastes (ILW) generated during routine plant operations and decommissioning. Collectively, HLW and ILW form the bulk of wastes that are defined as HAW. In addition, HAW may also include a small volume of low-level waste (LLW) that cannot be disposed to the national LLW repository (LLWR) due to high concentrations of certain long-lived radionuclides that exceed the LLWR nuclide-specific waste acceptance criteria. In addition to HAW, there are large volumes of other radioactive materials that are not currently classified as wastes but may, subject to changes in Government policy, be reclassified as wastes and be sentenced for disposal in the GDF. These include: spent nuclear fuels that are not subject to existing reprocessing contracts, such as those from any new power reactors that may be built in the UK; depleted, natural and low-enriched uranium (DNLEU) stockpiles, generated during fuel manufacture and processing; and stockpiles of plutonium and highly-enriched uranium, held for strategic purposes. The quantities of the HAW wastestreams and their anticipated future arisings are provided in the 2010 UK Radioactive Waste Inventory (DECC & NDA, 2011a), whilst quantities of the other radioactive materials not classed as wastes are reported separately (DECC & NDA, 2011b). Those documents report conditioned volumes making assumptions for how each waste stream will or may be processed. For planning purposes, Government set out in the 2008 White Paper a Baseline Inventory for wastes that may be disposed to the GDF and this is summarised in Table 2.1. Table 2.1: The Baseline Inventory expressed as total packaged quantities of radioactive wastes and materials potentially to be disposed of in the GDF. Baseline Inventory Material Packaged volume Radioactivity m3 % TBq % HLW 1, ,000, ILW 364, ,200, LLW 17, < 100 < 0.1 Spent fuel 11, ,000, Plutonium 3, ,000, Uranium 80, ,000 < 0.1 Totals 476, ,200, The large total conditioned waste volume, the diversity of individual waste streams and the times of their arising will place certain requirements on the design of the GDF Office for Nuclear Regulation (ONR) Page 5

15 and also requirements of the host site. These relate to aspects such as the minimum necessary excavated rock volume, the need to operate the GDF over many years, and a requirement to separate different wastes from each other, and to coordinate parallel construction and operation activities. 2.2 Ongoing waste conditioning and packaging operations To date, approximately 25,000 m 3 of the ILW identified in Table 2.1 (c. 7% of the total) has already been produced, conditioned and encapsulated into some 47,000 waste packages (DECC & NDA, 2011a). This was done against Letters of Comfort/ Compliance (LoCs) previously issued by Nirex on the assumption that these wastes would be disposed of using the Phased Geological Disposal Concept (PGRC) that was developed by Nirex during the 1980s and 1990s. ILW continues to be generated and packaged following the LoC process (under RWMD), and it is likely that a substantial additional volume of packaged waste will exist by the time construction of the GDF begins. Similarly, vitrified HLW is being produced at Sellafield without an LoC although discussions with RWMD, and other related developments, are in progress. There is, nonetheless, widespread international consensus on the suitability of vitrified wastes for geological disposal. Given that there is, as yet, no site or host rock selected and, therefore, no agreed design concept for the GDF, there is a risk that some or all of the existing packaged wastes might not be in a form that is optimal for disposal. The LoC process is intended as a pragmatic means to mitigate this risk, and allow ongoing ILW management to continue until such time as a site and concept for the GDF have been agreed. The LoC process involves RWMD undertaking comprehensive disposability assessments of the waste producers proposals for conditioning and packaging each ILW waste stream against RWMD s generic waste package specifications. 2.3 Site selection The UK Government takes the view that a site for the GDF should be selected using a step-wise approach based on voluntarism and partnership. Following publication of the 2008 White Paper there has been an open invitation to communities to express an interest and engage with Government in the siting process. At the time of writing, however, no community has yet made a formal Decision to Participate and so no preferred location for the GDF has been identified. The White Paper recognises that the design and layout of the GDF (both above and below ground) must be tailored to the geological characteristics of the chosen host site, and the inventory to be disposed. Given that the volunteer siting process does not exclude any areas of the country or geological environments, disposal might occur in any of the potentially available geological environments and rock types, including hard (crystalline) rocks, clay (argillaceous) rocks and salt formations. These rock types have significantly different physical, chemical and hydraulic characteristics and, consequently, the detailed design of the GDF cannot be determined until after a site has been chosen (NDA, 2008). In late 2013, Government consulted on proposals to amend the volunteer siting process. The proposed changes would affect some aspects of how volunteerism would work, and how land-use planning decisions may be made, but would not materially change any of the conclusions or recommendations in this report. Office for Nuclear Regulation (ONR) Page 6

16 2.4 Geological disposal concepts The UK Government s policy is for deep geological disposal. The 2008 White Paper does not specifically define deep but suggests that disposal might occur at a depth somewhere between 200 and 1000 m below the surface, depending on the geology at the site in question. The general intent of geological disposal is that the facility is constructed at a depth sufficient to isolate it from the dynamic natural process and man-made activities that occur at or near the ground surface. Similarly, the White Paper does not mandate any aspect of the GDF design, other than it should be based on the multi-barrier principle, comprised of both engineered and natural barriers. As illustration, the White Paper makes reference to a number of multi-barrier designs that have been developed internationally, including: the operating WIPP facility constructed in bedded salt in the USA for the disposal of transuranic bearing ILW; the KBS-3V design for spent fuel disposal that is being implemented in both Sweden and Finland; and the cementitious repository design for ILW that was proposed by Nirex in the 1980s and 1990s, before the current Government policy was initiated. These well developed disposal concepts are not, however, the only design concepts that could be adopted for the GDF. Several other alternative concepts (some less developed but potentially promising) are possible based around design features such as large caverns in which waste packages can be stacked; long tunnels in which waste packages can be emplaced horizontally; and very deep boreholes in which waste packages can be emplaced vertically. In very broad terms, these concepts are all based on an engineered barrier system (EBS) that comprises multiple barriers including (from the inside out) a solid waste form, a robust waste package, a buffer or backfill material, and then the host rock. In some advanced overseas disposal programmes, disposal concept designs and operational methods have been subject to practical testing using half-scale and fullscale mock-ups in underground research laboratories (URLs). In some cases, this practical experience has led to significant design changes and design variants to simplify waste emplacement operations. One such example is the development of supercontainer designs which, in simple terms, change the order of the barriers by including buffer materials inside the canister overpack. One supercontainer design has now been adopted as the preferred concept in the Belgian HLW/SF programme (ONDRAF/NIRAS, 2011) and other supercontainer designs have been investigated in France, Switzerland, Sweden and Finland. In some national programmes, certain wastes with short half-lives (that would be considered HAW in the UK) are considered for near-surface instead of geological disposal. This strategy is based on radioactive decay significantly reducing the radiological hazard during the likely period of institutional control (usually taken to be around 100 to 300 years). For example, in Belgium Category A wastes are planned to be disposed of in a near-surface vault-type facility at Mol-Dessel. Category A wastes are defined as short-lived LLW and ILW containing radionuclides with halflives < 30 years and trace amounts of long-lived radionuclides (Sumerling & Vermariën, 2007). Office for Nuclear Regulation (ONR) Page 7

17 International experience illustrates that designing a disposal facility is a complex task that requires consideration of many different (and sometimes opposing) aspects, and must take account of the need to balance the practical aspects of constructing and operating the facility against the requirement to ensure long-term safety. 2.5 Co-disposal of wastes Although the 2008 White Paper does not mandate the design of the GDF, it does express a preference for co-locating disposal facilities for different types of waste at the same site. This essentially means having separate disposal areas beneath ground but sharing the same access tunnels and surface facilities, provided the necessary safety, security and environmental requirements can be met. In broad terms, a colocated facility would have (as a minimum) two disposal areas, one for ILW/LLW, and a second for HLW/SF. Co-location introduces significant requirements for an acceptable site and host rock, such as the availability of a sufficiently large volume of suitable rock, the ability to achieve the necessary minimum physical separation distances between disposal areas and predictable groundwater flow patterns. A co-located disposal facility would need to be designed to ensure different disposal areas were physically, chemically and hydrogeologically separated, so far as is reasonably practicable, because some wastes are chemically incompatible with each other, in particular the vitrified HLW is susceptible to corrosion in the high-ph leachates that will arise from cemented ILW. In a volunteer siting process, it is possible that a community may set restrictions during discussions with Government and RWMD on what wastes they are prepared to accept in a GDF. This is similar to the role communities have in decisions regarding retrievability as described in the White Paper, and so might influence the need for colocated facilities. As an example, in Canada, Ontario Power Generation (OPG) has a hosting agreement with the Municipality of Kincardine near the Bruce nuclear power station which specifically states the planned geological repository would only be used for the disposal of L/ILW from OPG reactors and specifically would not accept spent fuel (Municipality of Kincardine, 2004). Until the chemical, physical and radiological inventory of the wastes to be disposed has been determined, it is not possible to define at any level of detail what are the minimum physical requirements of a site to support co-location. Consequently it remains an open question whether or not co-location will be achievable at a site chosen through the MRWS process. 2.6 Retrievability and reversibility Many stakeholders favour disposal designs that would enable wastes to be taken back out of a disposal facility. This is generally referred to as retrievability but there are variants on the retrieval concept, depending on whether or not the facility remains open or has been partially or fully closed at the time waste recovery is considered. CoRWM used the following terminology: reversibility: designed into the option to facilitate the recovery of material by reversing the original emplacement process; retrievability: designed into the option to facilitate the physical retrieval of waste through means other than reversing the process, such as ensuring Office for Nuclear Regulation (ONR) Page 8

18 access to the waste and having (or being able to have) the retrieval mechanism in place; recoverability: addressing retrievability by demonstrating that the waste is technically recoverable through mining or other means. The concept of retrievability is particularly important for the phased disposal concept, in which wastes are emplaced in the disposal facility but the facility is explicitly designed and planned to then be left open to allow futures generations the option to either retrieve the waste or to finally close and seal the facility. Although members of the public often have a preference for phased disposal, many technical experts (and CoRWM itself) take the opposite view on the basis that leaving a facility open, possibly for centuries after waste has been emplaced, increases the risks disproportionately to any gains. In the 2008 White Paper, Government expressed its view that the decision about whether or not to keep the GDF open for an extended period of time after waste emplacement, to allow for retrievability, can be made at a future time and in consultation between the regulators and the host community. In the meantime the planning, design and construction of the GDF is to be carried out in such a way that the option of extended retrievability is not excluded. This policy requirement introduces complexities in the GDF implementation programme, not least because the extent of retrievability that should be designed for has not been specified. Furthermore, the safety and environmental consequences of incorporating retrievability into the GDF design (and in different rock types) are not yet well established. From an engineering perspective, multiple options and requirements need to be designed and maintained until such time as the question of retrievability is finally decided, and options can be down-selected. It should be noted that retrievability is also a requirement in some other national disposal programmes (notably France and Switzerland) but, because this requirement is clearly defined at the outset, not so many options need to be carried forward. In these programmes, retrievability is often linked to the concept of monitoring. For example, in the Swiss concept of monitored long-term geological disposal there is a legal requirement to include an underground pilot facility containing a small number of waste packages that will be monitored to provide representative information on the functioning of the entire disposal facility (Nagra, 2009). 2.7 Significance There are a number of observations relevant to this project that arise from this discussion of the UK context. These are set out below, together with some related questions with safety and environmental implications that the regulators may wish to ask. 1. The GDF implementation programme is subject to many variables that relate to aspects such as the choice of site, the inventory, the engineered design, its operation and closure methods, and the potential need for retrievability. These variables are all coupled, to a certain extent, and therefore it may not be feasible to progress far with implementation whilst keeping all of them open. Evaluating different options in the early stages of implementation (e.g. as done by RWMD in the gdssc) will, however, provide useful information that can inform later decisions on which option is ultimately preferred. Office for Nuclear Regulation (ONR) Page 9

19 What is the minimum level of protection (e.g. containment and isolation) required for each of the main waste types, and what are the essential design requirements of the GDF necessary to provide that level of protection to ensure the safe disposal of each waste type? What are the additional design features that may be desirable or add value, and what is the process for deciding which of these features should be included in the GDF design? What are the key variables that affect GDF implementation and what weighting is placed on them during decision making? What safety or environmental factors, other than those related to geological and surface conditions, might cause a site to be considered or eliminated during the site selection process? 2. The fact that the inventory is not fixed in terms of either materials or quantities introduces large uncertainties that affect all subsequent GDF design and implementation activities. In particular, the dimensional requirements for a host site and volume of rock suitable for the disposal of all wastes may be restrictive. What are the potential safety and environmental implications of different inventory boundary conditions, and is it realistic and feasible to plan for a single GDF for all HAW? 3. The potential inclusion of certain fissile materials (e.g. plutonium stocks) in the inventory of materials to be disposed to the GDF increases the importance of safeguards and security considerations. Depending on how these materials may be conditioned and packaged will affect the effort required to ensure safeguards and security in the design and operation of the GDF. What measures would need to be taken to ensure all safeguards and security requirements are met if fissile materials are disposed in the GDF? 4. The need to continue to condition and package wastes as they arise raises the potential risk that they might not be optimal for disposal in the GDF. ILW has been (and will continue to be) conditioned and packaged using RWMD s LoC process. It is not known how different the actual GDF design and site characteristics will be from those assumed in current disposability assessments, and the consequences of those differences is also unknown. In any case, the GDF must be capable of disposing all of the legacy wastes currently in storage, and still being produced, which sets a requirement for a broad envelope for waste acceptance, and flexibility in its design and operation. How should wastes continue to be processed and packaged without foreclosing options, given uncertainty on the site, geology and design of the facility? 5. The many permutations of host rocks, generic disposal concepts and their design variants means that there may be several engineered designs that could be implemented at a volunteered site. It is likely that there will be differences in the level of knowledge and understanding of these alternatives. The down-selection of designs to a preferred option will need to be done carefully to avoid bias in favour of the better understood options. The process will also need to be transparent and be consistent with all regulatory and stakeholder expectations. Office for Nuclear Regulation (ONR) Page 10

20 What disposal concepts and engineering designs (both well established and promising but less well developed alternatives) are suitable for UK wastes and geological environments? What is the process for comparing and contrasting alternative disposal concepts to identify reference designs, and for justifying the exclusion of others? How will local communities be involved in the process for comparing and down-selecting options during the volunteer process? And what other aspects of the GDF can they influence (e.g. site selection, facility design, allowable inventory, retrievability etc)? 6. International experience from underground testing and demonstration projects suggests that disposal system designs may need to be significantly modified to simplify emplacement activities. This experience has shown that it is not until underground tests have been attempted that a real appreciation of the nature and scale of the practical difficulties can be gained. Potential modifications ideally should be identified as early as possible to minimise the knock-on consequences for other aspects of the implementation of the GDF, and for the implementation schedule. What demonstration studies are needed to assess the safety and practicability of proposed designs, and how will this feed into design optimisation? 7. Some national programmes plan to dispose of short-lived ILW in near-surface facilities separately from long-lived wastes in geological disposal facilities. Segregating and managing wastes in the UK by half-life rather than by total activity may allow for additional disposal strategies to be considered. Is deep geological disposal the only appropriate option for all HAW? What might be the potential safety and environmental implications of segregating and disposing of short-lived ILW in near-surface facilities? 8. The incompatibility between different wasteforms means that it is essential to ensure a high degree of physical, chemical and hydrogeological separation between co-located disposal areas and their wastes, and this places important constraints on the suitability of the host rock. This is particularly important because of the very large volumes of cementitious ILW in the UK inventory. It is not yet known whether a suitable rock volume will be available within any volunteered site and, consequently, it remains a possibility that more than one geological disposal facility may need to be sited in the UK. What are the minimum requirements to ensure physical, chemical and hydrogeological separation of co-located disposal facilities? And what are the risks if separation were to fail? What are the potential safety and environmental implications of operating a single co-located facility compared to two entirely separate facilities? 9. The fact that retrievability remains an open question that is not due to be closedout until a site has been chosen and there has been dialogue with the host community introduces large uncertainties that affect all subsequent GDF design and implementation activities. In particular, the extent of reversibility / retrievability Office for Nuclear Regulation (ONR) Page 11

21 that might need to be designed for has not been specified, meaning that there are likely to be significant differences between the expectations of some stakeholders in this regard. There is currently only limited understanding from underground tests and demonstration projects of the practical constraints on the extent to which retrievability may actually be possible. What are the potential safety and environmental implications of incorporating different extents of retrievability into the GDF design for each possible host rock? Are there wastes with a higher likelihood of being retrieved than others, for whatever reason, and how will this affect the design of the facility and the waste emplacement strategy? What are the likely safety and environmental consequences if retrievability were to be carried out for whatever reason? Would the need for retrievability rule out certain disposal concepts? For example, boreholes. 10. The GDF implementation programme will take many decades and, in this time, new technology will be developed and new knowledge is likely to be gained. It is important that all new information is taken into consideration but key decisions need to be banked to enable the programme to maintain momentum. How will decisions (on site, inventory, design etc.) be closed out and banked, to enable the programme to move forward through each stage of implementation in the light of new information as it is gathered? Office for Nuclear Regulation (ONR) Page 12

22 3 The regulatory framework The regulatory framework that applies to the development of the GDF has evolved somewhat since the publication of the 2008 White Paper. Under the current framework, the GDF will be regulated jointly by the ONR and either the Environment Agency (EA), Natural Resources Wales (NRW) or the Northern Ireland Environment Agency (NIEA), depending on whether it is sited in England, Wales or Northern Ireland. Note that the policy in Scotland is for the long-term management of HAW in near-surface facilities located as near to the site where the waste is produced as possible (Scottish Government, 2011). To date, the EA has taken the lead on developing understanding and guidance on geological disposal, in collaboration with the other environmental agencies. For simplicity during the remainder of this report, reference to the EA can be taken to mean the relevant environment agency for wherever the GDF is finally sited. In simple terms, the ONR has responsibility for regulating the GDF to ensure safety and security throughout all aspects of its design, construction and operational phases (including waste transport aspects). The EA will have parallel responsibility to ensure protection of people and the environment during construction and operation of the GDF, and also into the far-future after the facility has been closed. Neither regulator has any formal role in selecting a site for the GDF but they will help the siting process by advising and commenting on safety and environmental matters. RWMD is voluntarily submitting to regulatory scrutiny through a process by agreement with both ONR and EA. This scrutiny is intended to help RWMD to progress implementation and to develop the applications that will be necessary for licensing and permitting processes. The regulatory framework is broadly the same for both geological and near-surface disposal and so would apply if, for example, some short-lived wastes were considered for disposal in shallow disposal facilities. 3.1 Health, safety and security regulation The principle regulations that the ONR will apply to regulation of the GDF are: Nuclear Installations Act 1965 (NIA). Ionising Radiations Regulations 1999 (IRRs) Nuclear Industries Security Regulations 2003 (NISR) Health and Safety at Work Act 1974 (HSWA) Although disposal is not a prescribed activity in NIA, Government has indicated in the 2008 White Paper that the GDF will become a licensed facility. The point in the GDF development programme at which the site will become licensed has not yet been established but it is reasonable to expect that the GDF might become a licensed site before significant underground construction begins, in line with ONR guidance that A nuclear site licence must be granted to a developer before they may undertake Office for Nuclear Regulation (ONR) Page 13

23 construction work which could, if inadequately conceived or executed, affect nuclear safety when the plant is operational (ONR, 2012). Neither the standard Licence Conditions nor the Safety Assessment Principles (SAPs) were developed with the GDF in mind, and so these will need to be reviewed and modified as necessary to take account of the unique nature of the GDF and its operations. For the GDF (as with any other planned new nuclear facility) iterative nuclear safety cases will be required at key stages in its development. The number, timing and content of these nuclear safety cases have not yet been decided. For the purposes of this report, it is assumed that the following nuclear safety cases will need to be produced by the implementer and evaluated by the ONR as part of a staged licensing process: Preliminary Nuclear Safety Case, once a preferred site has been chosen and characterised, to be used as the basis for the application for the site licence; Pre-Construction Nuclear Safety Case (Access), to demonstrate that the GDF access (vertical shaft or inclined tunnel) is capable of being constructed and operated safely on the basis of a site-specific design; Pre-Construction Nuclear Safety Case (First phase), to demonstrate that the first phase of the disposal tunnels and vaults are capable of being constructed and operated safely on the basis of a site-specific design; Pre-Commissioning Nuclear Safety Case, once the first phase excavations are complete to demonstrate that the as-built GDF meets relevant safety criteria and can be operated safely; Pre-Operational Nuclear Safety Case, once active commissioning has been completed to demonstrate that all necessary pre-operational actions and modifications are completed, validated and implemented; Post-Operational (Pre-Closure) Nuclear Safety Case, after all wastes have been emplaced to demonstrate that the GDF can be backfilled, closed and sealed safely. Due to the GDF having separate (co-located) but differently designed disposal areas for the various wastes, plus the likelihood of the facility being developed in phases, most of these nuclear safety cases may need to be produced for each separate disposal area and each phase of development. One important objective of the iterative nuclear safety cases produced during the early stages of GDF design and implementation will be to demonstrate how concept and design options and alternatives are progressively reduced, and how the final asbuilt engineering design is chosen and optimised (e.g. to ensure the ALARA principle is upheld). Optimisation of design is one activity that will need carefully to balance operational safety with post-closure safety, as discussed in Section 4. Another important objective of these iterative nuclear safety cases is to identify all outstanding issues which need to be resolved (e.g. through further R&D), their importance and the work required to resolve them (with timescales). Later iterations will need to demonstrate that outstanding issues have been closed out by the further work. Office for Nuclear Regulation (ONR) Page 14

24 3.2 Environmental regulation The EA will regulate the GDF under the Radioactive Substances Regulation (RSR) framework largely using Schedule 23 of the Environmental Permitting Regulations 2010 (EPR) which sets out the requirements for the safe handling of radioactive substances, and for the disposal and discharges of radioactive wastes. Schedule 23 provides the necessary powers for the EA to grant an environmental permit for the GDF under a staged regulation process, beginning from the point that intrusive investigation work is planned to be carried out. As with nuclear safety cases, iterative environmental safety cases will be required at key stages during the development of the GDF. The number, timing and content of these environmental safety cases has not yet been decided but the EA has published specific guidance on the requirements for authorisation (the GRA ) for geological disposal (EA & NIEA, 2009; EA, 2012). This sets out the EA s preliminary expectations for environmental safety cases that would show how the GDF will protect people and the environment, and the following would be expected: Initial Site Evaluation, before any intrusive site investigations can commence to give a largely qualitative view on the feasibility of constructing the GDF at the site; Preliminary Environmental Safety Evaluation, after the site has been characterised to provide a preliminary assessment that the GDF will be safe before underground excavations can begin; Initial Environmental Safety Case, before the significant underground excavations begin to provide enough evidence to inform EA s decision on whether to grant a permit for disposal in principle; Pre-Operational Environmental Safety Case, before waste emplacement to provide a sound scientific and technical basis to inform EA s decision on whether to grant a permit for disposal; Post-Operational (Pre-Closure) Environmental Safety Case, after all wastes have been emplaced to demonstrate that the GDF can meet its post-closure safety requirements. In addition to Schedule 23 of the EPR, the EA will also regulate the GDF under several other parts of EPR and other applicable regulations where they may be relevant to the construction and operation of the facility, such as the Conservation (Natural Habitats) Regulations 1994 and the Water Resources Act Since these are not primarily concerned with safety, they are not discussed further here but the GRA provides a summary of the other sets of legislation that will apply. 3.3 Other regulations The development of the GDF will be subject to other regulation, in addition to those described above to ensure health, safety and environmental protection. In particular, any proposal to develop a GDF at a particular site will be subject to land use planning regulation and the associated requirements for Strategic Environmental Assessment (SEA) and Environmental Impact Assessment (EIA). Office for Nuclear Regulation (ONR) Page 15

25 These regulations fall outwith the responsibilities of the ONR and environment agencies, and so are not discussed any further in this report, although it is worth noting that the environment agencies have responsibilities as statutory consultees under SEA and EIA legislation. 3.4 Significance There are a number of observations relevant to this project that arise from this summary of the regulatory framework. These are set out below, together with some related questions with safety and environmental implications that the regulators may wish to ask. Note that some of these questions will need to be considered by the regulators themselves, and would not be directed at the implementer. 1. The point at which the GDF will become a licensed facility has not been decided. This introduces a level of uncertainty that affects planning and preparations for performing regulatory oversight and scrutiny of the safety relevant aspects of its design and operation. Licence Condition 14 implies that licensing should occur early in the implementation process, before any significant decisions are made concerning the design of the GDF. In practice this is likely to mean before any access shafts or tunnels as constructed. The ongoing joint ONR and EA scrutiny programme can influence RWMD s plans now and before licensing. What is the regulatory process to be applied during the pre-construction phases of the GDF programme, and at what point should a site licence be granted? 2. Clear decisions will also be required in terms of deciding what is actually licensed, recognising that the GDF will effectively be an integration of engineered structures and the host geological environment. The physical boundaries of the GDF are, therefore, ambiguous in a way that is not the case for a conventional nuclear facility or site that is regulated under NIA. What will be the physical (3D) extent of the licensed site, and how does this relate to the above and below ground parts of the GDF? How is co-location defined in terms of site licensing? Should the entire disposal complex be licensed as a single facility or as two or more separate facilities? 3. The GDF may be regulated under existing sets of legislation that were never intended to be applied to geological disposal. Care will be required when developing guidance to explain how existing legislation will be applied to the GDF, and in developing licence conditions and safety assessment principles, to avoid difficulties in later stages of implementation. Similarly, the standard set of nuclear safety cases required for the development of a new nuclear facility (and their scope) should be evaluated to determine which of these is appropriate for the GDF. 4. Joint regulation implies that the regulators should integrate their requirements for safety and environmental cases, so that a single set of documents can be produced by RWMD to meet the expectations of both regulators. The environment agencies have published their requirements in the form of the GRA. ONR is currently in discussions with Government clearly to establish its regulatory vires in respect of the GDF, and determine what additional guidance is needed. Office for Nuclear Regulation (ONR) Page 16

26 What new (or modified) guidance is required to set out the safety principles and regulatory requirements that will be applied to each stage of the development of the GDF? 5. Although the ONR and the environment agencies will regulate the GDF under different sets of legislation, it is important to understand that there is no hierarchy of importance between them. All regulations will apply equally at all times to the GDF (at times and places when they are relevant) and, consequently, it is not the case that one regulation has primacy over another. This will necessitate the development of an optimal design for the GDF, and plan its operation, that ensures all requirements are met to protect the health and safety of people, and protection of the environment. Similarly, clear justifications will need to be made to explain how the GDF was optimised to ensure all regulatory requirements have been appropriately addressed and balanced. What is the process for design optimisation, and how are safety and environmental considerations taken into account in the process? 6. The GDF will need to be designed so as to be consistent with the characteristics of a volunteer site and its geology. This may have knock-on consequences for the safety and environmental performance of the GDF during its construction, operation and in the post-closure period. It may also mean that greater emphasis will be placed on the safety performance of the engineered barriers than the host rock. In simple terms, the GDF will need to be designed to work within the geological constraints imposed by whatever site is made available through the volunteer siting process. What isolation performance will be required from the EBS in different possible host rocks, and how will the EBS be designed to overcome possible inadequacies in the host rock isolation capacity? Office for Nuclear Regulation (ONR) Page 17

27 4 Balancing risks during GDF implementation Depending on the outcome of the volunteer siting process, a preferred site may need to be chosen from several different areas around the country, or from various locations within a single area. In either case, it is possible that there will be a number of geological environments and/or host rocks to be compared. In addition to identifying a preferred site, a reference disposal concept will need to be developed for the GDF excavations (tunnels, vaults, boreholes etc.) and the engineered barriers (canisters, backfills, seals etc.) that is consistent with the geology of the preferred site. Over time, as more information on the preferred site is obtained, the reference disposal concept will be progressively refined to develop a detailed system design which ultimately will need to be optimised. In simple terms, as shown in Figure 4.1, there will be a hierarchy of decision making events that starts with an optioneering case to evaluate potential sites and concepts, and leads on to a series of progressively more detailed safety cases that evaluate and balance the operational and post-closure safety of alternative system designs and operational methods. Figure 4.1: An illustrative example of how decision making for the GDF will need to be hierarchical and begin with sites and concepts, and move to detailed designs. Many of the optioneering and design decisions to be made for the GDF will have significant implications for the balance between operational and post-closure risks. Illustrative examples of some of these are given in Table 4.1. In this context, it is important to recognise that the overall operational safety of a GDF design concept is the sum of the risks associated with the totality of all of the design components and operating practices, over the full life-cycle of the GDF from initial shaft sinking or access tunnel excavation, through to final closure. It is evident from this, that certain design decisions may be made that could impose a real increase in occupational risks (both conventional and radiological) to present-day workers so as to achieve a reduction in the conditional (hypothetical) risk to people in Office for Nuclear Regulation (ONR) Page 18

28 the far future. In no case, however, would the GDF be allowed to be built if the risks to workers were considered by the regulators to be unacceptable in comparison with whatever limits are applicable at the time. Similarly, a GDF would not be built if the calculated post-closure doses and risk to people were deemed unacceptable. Nonetheless, it is probable that there will be some safety headroom due to robust engineering design and conservatism in the safety assessments. Optimisation of the GDF design may, consequently, allow some of the post-closure safety headroom to be reduced to achieve an increase in worker safety, or vice versa. This is consistent with the environmental regulators own guidance (the GRA) which makes clear that optimisation does not necessarily demand the choice of the option with the lowest possible radiological risk to the public (EA & NIEA, 2009). Table 4.1: Illustrative examples of design decisions that require careful balancing of operational and post-closure risks. Design aspect Primary access route design Geometry of disposal tunnels Waste package dimensions Potentially best option for post-closure safety Vertical shaft: Smallest volume of rock to be excavated, and potentially provides simplest design for sealing. Increased risk of conventional accidents during construction. High consequence if hoists fail during operations. Shortest flowpath to surface. Long, blind tunnels: Limits the potential for post-closure convective groundwater flow, and so reduce releases to the surface environment. Increases hazards to construction workers (e.g. rock collapse) and limits escape routes. Supercontainers: Provide postclosure durability and corrosion resistance. Large weight and dimensions make them difficult to handle in restricted underground space, especially if waste handling systems fail. Potentially best option for operational safety Inclined tunnel: Potentially more difficult to excavate and seal, depending on the rock type. More flexibility for waste handling, and lower consequence from mechanical failure during operations. Double entry tunnels: Increases the potential post-closure flowpath routes for released radionuclides. Offers greater flexibility during operations, and multiple escape routes for workers in case of accidents. Small containers: Potentially less overpack may mean shorter post-closure containment period. Lighter weight and smaller dimensions means waste handling systems can be simplified, and refurbishment made easier. Optimisation of the GDF design will require appropriate balancing of the full life-cycle operational safety (risk to site workers and current generations) against the postclosure safety (risk to future generations), and against the other non-safety attributes. As a minimum, this will require a method for balancing risks to workers and to members of the public, and risks to the current generation and to future generations. Assuming two different GDF design options and their associated operating practices (A and B in Figure 4.2), it might be that their respective distribution of risk to people is fundamentally different to each other. A similar assessment can be made for benefits arising from the GDF, and to the community to which they accrue. Office for Nuclear Regulation (ONR) Page 19

29 Figure 4.2: An illustration of how two different GDF concepts (A and B) might lead to skewed distributions of risks and benefits to certain populations. A balanced decision making process is, therefore, necessary to ensure decisions on GDF design and operations are not disproportionately skewed in favour of any one particular potentially impacted group of people. Although it is common for safetycritical industries to balance different risks in their decision making processes (e.g. optimisation in the nuclear sector), the disposal of long-lived wastes introduces particular complexities because of the potential for exposing populations in the very far future. In addition, concepts like BAT are usually applied in a much more technical context (e.g. to decide on a discharge abatement method for a permit under EPR) and do not typically take into consideration the much wider socio-economic factors that will apply to the GDF. At present, there is no agreed process for how design decisions and options selection for the GDF (at either a conceptual design or detailed engineering level) will be made. Whatever process is adopted, it will need to: take account of all important decision attributes including conventional and radiological risks to workers, and post-closure radiological risks to people, in addition to a range of other factors (e.g. technical viability, conventional environmental impacts, cost and affordability etc.); be understandable, transparent and auditable; be acceptable to both regulators, given that the GDF will be regulated under several sets of regulations with varying requirements; be acceptable to all other key stakeholders, including a local host community that reserves the right to withdraw from the siting process and to be involved in certain design decisions, including those related to retrievability; and balance risks to all potentially exposed groups and to the environment, in all stages of implementation (pre-construction, construction, operation and postclosure). In this decision making context, the term optimisation is often used but this has different meanings to different stakeholder groups which can lead to confusion. In engineering, optimisation usually refers to the refinement of a design to achieve particular goals, such as to meet a specific functional requirement (e.g. load, capacity, Office for Nuclear Regulation (ONR) Page 20

30 throughput, operating lifetime etc.) or to construct a system within a certain timeframe or below a certain cost target etc. In relation to radiological protection, optimisation of protection is one of the ICRP s basic principles and is directly linked to the ALARA principle. In terms of the GDF, however, there is the added complexity of deciding whether ALARA should apply equally to both current and future generations to reduce their respective risks (and, if so, how), as shown in Figure 4.2. For the GDF, both the engineering and radiological protection meanings of optimisation are relevant, and the decision making process applied to its design will need to take account of both. 4.1 Significance There are a number of aspects relevant to this project that arise from this discussion of balanced decision making. These are set out below, together with some related questions with safety and environmental implications that the regulators may wish to ask. 1. There is no agreed decision making process for down selecting GDF concepts and design alternatives. Existing MADA processes such as BAT/BPEO were not developed to be applied to facilities such as the GDF that have such wide ranging potential impacts in terms of space, time and exposed populations. What is the decision making process for comparing disposal concepts that will be applied to down select the preferred GDF concept design, once a site has been selected, and for justifying the exclusion of others? What are the key drivers / variables that affect decisions on the GDF design and implementation programme, and what weighting is placed on them during decision making? 2. Different GDF design alternatives are likely to place proportionately different burdens of risk on workers and members of the public, and on current and future generations. The ALARA principle does not make any clear distinction or recommendation concerning which potentially exposed population should be most protected when all groups cannot be equally protected. In the decision making process, what emphasis is placed on balancing risks to workers and the public, and current and future generations? What occupational risk target will be applied to conventional hazards during construction and operation of the GDF? 3. The terminology used for expressing the process of GDF design development is ambiguous, particularly in terms of the word optimisation that has different meanings to different stakeholders. What is the optimisation process, and how will engineering optimisation be integrated with radiological optimisation (ALARA)? Specifically how will proportionality be addressed in relation to ensuring exposures will be kept as low as reasonably achievable, economic and social factors taken into Office for Nuclear Regulation (ONR) Page 21

31 account, given that there may be significant differences in the costs and impacts to local communities associated with alternative GDF concepts? How does the application of conservatism differ in nuclear and environmental safety cases, and how does this affect optimisation and the balancing of risk to workers and future generations? Office for Nuclear Regulation (ONR) Page 22

32 5 Stages in the GDF programme 5.1 Stages in the MRWS process The 2008 White Paper set out, at a very high level, a staged process for the MRWS programme, as shown in Figure 5.1. This deliberately did not include any milestone dates or durations because of public and stakeholder considerations. Figure 5.1: The MRWS site selection stages. From Defra et al. (2008). The MRWS process is largely focussed on the front-end site selection activities. The bulk of the actual construction and operation activities associated with the GDF all occur within MRWS Stage 6 and, therefore, a more detailed programme is required against which research can be planned. To enable them to plan and prepare for their work, RWMD developed a preliminary implementation plan (NDA, 2010) that set-out the main phases they considered necessary, as shown in Figure 5.2. This preliminary plan includes an indicative timeline, although it should be noted that the dates given are simply planning assumptions and do not reflect any formal decisions made. Office for Nuclear Regulation (ONR) Page 23

33 Figure 5.2: Indicative timeline for the GDF implementation programme. All dates and durations shown are purely for preliminary planning purposes. From NDA (2010). One important aspect in RWMD s planning is that the construction and operation stages overlap each other because it is considered to be highly inefficient and potentially unsafe to excavate the entire GDF before first waste emplacement takes place. This pragmatic approach is consistent with the planning assumptions made for geological repositories in other countries, such as Finland, Sweden and the USA. 5.2 An outline programme for the GDF and key activities As with all large projects, the GDF development programme will be broken down into key stages, with associated project gates or decision points separating them. These decision points represent an opportunity for the GDF programme to be reviewed, and for all necessary safety cases and applications to be submitted to the regulators for the necessary formal authorisations and permits to operate in the next stage. It is not possible for the GDF development programme to be set out in detail at the present time because many important decisions have yet to be made, not least the choice of site and design of the facility. Nonetheless, the main stages in a generic programme are broadly known because they are independent of the site and design. Solely for the purposes of this project, an outline programme for the development of the GDF is set-out in Figure 5.3, starting from the point that a preferred site has been identified in Stage 4 of the MRWS volunteer siting process. This outline programme identifies the main stages in the programme, and the probable nuclear and environmental safety cases that will need to be submitted by the developer at each key decision point (see Section 3). It should be noted that this is a simplified and indicative programme solely for the purposes of this report. For simplicity, it is assumed in this report that each stage starts with its associated planning work but it should be understood that, in reality, there will be some overlap between stages because, for pragmatic reasons, some planning and preparation work for the next stage(s) will begin before the current stage is completed. So, for example, design and testing work on closure systems will be needed considerably in advance of reaching the closure stage. Similarly, the organisation structure and competences required by the implementer will need to be put in place before each stage commences to enable work to be planned efficiently. It should also be noted that this outline programme does not include an explicit stage for performing underground investigation before underground operations begin. This is because no such stage is included in the MRWS process (Figure 5.1) which represents Government policy. If it did, it would fall between Stages 5 and 6 of the MRWS process. Office for Nuclear Regulation (ONR) Page 24