Developing a Safety Case for Borehole Disposal

1. Developing a safety case for borehole disposal Presenter Name School of Drafting Regulations for Borehole Disposal of DSRS 2016 Vienna, Austria

2. Content • What is a safety case? • What are the components of a safety case? • What are the purposes of a safety case? • Development of safety cases for the borehole disposal concept (BDC)

3. WHAT IS A SAFETY CASE? • The collection of arguments that aim to demonstrate the safety of a facility. • For a disposal facility it is the main part of a would-be operator’s submission to the regulatory body. • Aims to demonstrate to the regulator and the public that the facility is safe by showing that it meets the regulatory principles and requirements. • It may sit alongside, within or beneath an EIA. • Includes findings of a safety assessment and a statement of confidence in these findings. • May relate to a given stage of development. In such cases, the safety case should acknowledge the existence of any unresolved issues and should provide guidance for work to resolve these issues in future development stages.

4. Safety Case Requirements • The requirement for a safety case comes from the IAEA’s Specific Safety Requirements (SSR-5) on the Disposal of Radioactive Waste • SSR-5 Requirement 3 - Responsibilities of the Operator: • “The operator of a disposal facility for radioactive waste shall … develop and maintain a safety case, …”

5. Safety Case Requirements (cont.) • SSR-5 Requirement 12: Preparation, approval and use of the safety case • shall be prepared and updated by the operator at each stage of a disposal facility’s life cycle • shall be sufficiently detailed and comprehensive to provide necessary technical input for informing decisions necessary at each stage

6. Safety Case Requirements (cont.) • SSR-5 Requirement 13: Scope of the safety case • shall describe safety-relevant aspects of site, facility design, managerial control measures and regulatory controls • shall demonstrate the level of protection of people and the environment provided • shall provide assurance to regulatory body and other interested parties that safety requirements will be met

7. Safety Case Requirements (cont.) • SSR-5 Requirement 14: Documentation of the safety case • shall be documented to a level of detail and quality sufficient: • to inform and support the decisions to be made at each step • to allow for independent review of the safety case

8. SAFETY CASE COMPONENTS

9. Explanation of key terms • Safety case context is an agenda-setting phase where the basic safety objectives, principles and regulations are described • Safety strategy sets out the means whereby the safety objectives are to be achieved, introducing strategies such as isolation, containment, passivity, robustness, defense in depth and demonstrability • System description describes the borehole disposal facility including the disused sources, borehole design, site characteristics, safety functions

10. Explanations of key terms (cont.) • Assessments are made of the engineering, management systems and the impact of the borehole on operators, the public and the environment during construction, operation and post-closure • Iteration and design optimisation concerns the improvement of the borehole design, e.g. as a result of insights gained from safety assessment • Management of uncertainties recognises that uncertainty is inevitable and needs to be acknowledged and evaluated. This may lead to the identification of unresolved issues.

11. Explanations of key terms (cont.) • Limits, controls, and conditions need to be established so that the borehole can be operated safely, for example by establishing limits on the activity of sources that can be accepted for disposal in the borehole, and monitoring and surveillance requirements for the borehole • Integration of safety arguments is an activity that encompasses all safety relevant aspects such as multiple lines of reasoning, complementary indicators, independent review, future research to reduce uncertainties, etc.

12. Explanations of key terms (cont.) • Management system aims to provide a framework in which the work of the borehole developer is performed to appropriate levels of quality • Stakeholder and regulator involvement aims to ensure that appropriate responses are made to the concerns of all those who have an interest in the development of the borehole disposal facility

13. PURPOSES OF A SAFETY CASE • Overall purpose is to demonstrate, with an appropriate level of confidence given the programme stage, that the disposal programme is feasible and safe • Also acts as a decision making and communication tool

14. Decision making tool • Can be used to inform decisions on: • different potential sites for the borehole • prioritisation of site-specific data acquisition to address important areas of uncertainty • optimisation of borehole design, operation and closure at a specific site

15. Communication tool • Can be used to communicate safety related issues to all stakeholders (including waste producers, regulators, opinion formers and public) • Key input to licence application and approval process • Needs to be updated in light of stakeholder feedback and on-going work programmes undertaken by the borehole developer

16. Justification • Why the proposal is being made eg • national RW policy • arguments based on need for safety or security improvements • Why the proponent is putting forward this proposal – ie what is his authority? • How the site came to be chosen • What the proponent wants the Regulatory Body to do, what will happen next • Cite relevant legislation, regulations and policy

17. Background • Descriptions of • the facility • the wastes • the site • timescales • resources being utilized

18. OPERATIONAL SAFETY I • Some “off the shelf” components – Necsa documents • Detailed operational procedures • Calculation and analysis of operational doses • Where, when do operational doses occur? • Can they be easily reduced by adjusting the procedures and using different equipment (optimization)? • Will generally aim to ensure that routine doses to workers are kept to a fraction of the allowable limits (eg 10% of 20 mSv per annum) • Will usually define an operational alarm dose at which an investigation would be performed • Off site releases • Radiological protection plan • Staff training

19. OPERATIONAL SAFETY II • What could go wrong? HAZOP analysis • Off normal situations – accidents, component failures, unexpected circumstances, • Off site releases • Modification of procedures to mitigate against hazards arising from off-normal situations eg wrongly labeled sources • Detailed procedure for what to do when the unexpected happens • Staff training • Development of emergency procedures and plan

20. OPERATIONAL INFORMATION INCLUDED IN THE SAFETY CASE • Detailed description of the operations • Operational safety assessment • Normal operation • Off-normal operation • Demonstration of optimization • Waste Acceptance Criteria

21. TRANSPORT • Should be included in the Safety Case to show that transport safety has been addressed and that transport of DSRS to the site is feasible • Transport follows IAEA Regulations and should be relatively straightforward – not going to address it here

22. POST-CLOSURE SAFETY I • GSA provides a post-closure safety assessment for • A range of possible site conditions (actually hydrogeological conditions) • A reference inventory – said to be “typical” • A fixed borehole geometry • In other words it is generic with respect to siting, inventory and geometry • GSA also has • V conservative container lifetimes • No uncommon radionuclides • No assessment of the effects of radiolysis

23. POST-CLOSURE SAFETY II • GSA is probably sufficient for a preliminary assessment • Certainly provides useful insight into • Useful hydrogeological /climatic conditions • Radionuclides that are likely to be difficult to dispose of • Off-normal situations such as seismic events, poor quality control • Usually possible to make simple calculations to adjust the GSA to allow for different inventory, geometry and (less easily) container lifetimes • May be possible to interpolate for different hydrogeological conditions

24. POST-CLOSURE SAFETY III • But, even for the simplest cases, the safety case will almost certainly require a specially prepared assessment that is • Site-specific - appropriate values for • Geochemistry • Infiltration rate • Hydraulic conductivity • Water accessible porosity • Hydraulic gradient • Borehole geometry • Inventory specific • GSA still useful in that it will give confidence that the numerical model is OK

25. Management System • Management systems formally qualified to ISO 9001 (2000) or, at least, consistent with the requirements of ISO 9001 (2000) or similar • Provides confidence that work has been properly prioritised and controlled • Relies on documentation of procedures covering every aspect of the work including training • Is a formal requirement for the “constrained optimization” of post-closure safety • Subject of a separate talk • Peer review

26. UNDERSTANDING THE SITE I • Site characterisation • Aims to develop a description of the evolution of the geology of the site over tens of millions of years • Then becomes a small step to argue that evolution along the same path for another million years is a reasonable assumption • Helps if the site is tedious in geological terms • Because geochemistry derives from the geology it should be possible to apply the same kind of argument

27. UNDERSTANDING THE SITE II • In some circumstances it may not be necessary to develop a detailed understanding of the hydrogeology of the site eg • Unsaturated disposal • Short lived radionuclides • If the site is saturated AND if the radionuclides are long-lived it will probably be necessary to develop a detailed understanding of the hydrogeology so that the site can be faithfully modelled • This is a more difficult task • Explanations should be provided in terms of conventional (ie well attested) phenomena • Will be helpful to make comparisons with similar sites elsewhere • Information is usually available from many sources eg geological, hydrological institutes, prospecting drilling, geographical, meteorological information

28. NON-RADIOLOGICAL SAFETY Understanding of site: • Site characterisation • Description of the evolution of the site • Explanations in terms of well-known phenomena, similar sites elsewhere • Use of information from many sources

29. ENVIRONMENTAL SAFETY • Until recently, it was assumed (and asserted by ICRP) that if humans were protected the environment would be protected also - Therefore argued that there is no need to do a separate assessment of environmental safety • While this assertion is still widely held, the argument is often made that it has not been demonstrated • Much work being done to look at radiological effects on non-human biota. • Mostly focuses on population-level effects for most species and individual effects for endangered species

30. PUBLIC ACCEPTABILITY • In may countries the Regulatory Body will wish to be informed about • the extent to which the public has been informed about the proposed facility • the extent to which the public has been consulted about the proposed facility • Evidence that the public accepts the proposed facility • All this will be country-specific

31. NATURAL ANALOGUES I • Natural analogues aim to build confidence in post-closure safety by providing information about key processes over relevant timescales • Many examples • Natural and ancient man-made cements • Corrosion/ survivability of native copper and iron and ancient copper and iron objects • Egyptian glass (for vitrified wasteforms) • etc

32. GSA, site selection and characterization 32 NATURAL ANALOGUES II 1600 yrs old 305 yrs old

33. GSA, site selection and characterization 33 NATURAL ANALOGUES III

34. SAFETY CASES FOR THE BDC • A generic safety case summary was produced by the Nuclear Energy Corporation of South Africa (NECSA) in 2004 • The generic safety case was for a site-generic rather than site-specific disposal system and used synthesised site characteristics • No site-specific safety cases have yet been fully developed

35. NECSA Generic Safety Case • Included sections on: • Development philosophy (safety, quality management, design) • Disposal system description • Operational safety • Post-closure safety • Engineering substantiation (requirements, optimisation, evaluation) • Site selection • Commissioning and operations

36. IAEA TECDOC 1644 • Recommendations for a template for the preparation of a “safety report”to cover both: • Safety Case issues • Environmental Impact Assessment issues

37. Proposed Safety Report Template • General Information • Safety Strategy and Safety Case • Site Characteristics • Design and Construction of Borehole • Design and Construction of Waste Package Components • Design of Conditioning Facilities • Operation of Conditioning Facility • Operation of Disposal Borehole

38. Proposed Safety Report Template (cont.) • Site Closure Plan • Non-radiological Environmental Impacts of Operation • Occupational Radiation Protection • Exposure of the Public During Operations • Post-closure Safety of the Disposal Facility • Post-closure Control • Record Keeping • Final Statement • Annexes

39. SSG-23 Recommendations • IAEA’s Specific Safety Guide (SSG-23) makes suggestions on structure and content of a safety case • SSG-23 notes: “there are many possible ways of structuring and documenting the safety case”

40. SSG-23 Recommendations (cont.) • SSG-23 suggests that the following aspects of the safety case should be documented: • Executive summary • Introduction and context • Strategy for safety • Safety assessment • Synthesis and conclusions • Follow-up programmes and actions

41. SUMMARY • A safety case is a collection of arguments and evidence in support of the safety of a facility • Overall purpose is to demonstrate that the disposal programme is feasible and safe • Decision making and communication tool • A generic safety case developed by NECSA for the BDC • “There are many possible ways of structuring and documenting the safety case”

42. “A safety case is a collection of … in support of … . It includes findings of a … and a statement of … in these findings. It may relate to a given stage of development. In such cases, the safety case should acknowledge the existence of any … and should provide guidance for … in future development stages.” Self Assessment • Question 1: Insert the missing words • “A safety case is a collection of … in support of … . It includes findings of a … and a statement of … in these findings. It may relate to a given stage of development. In such cases, the safety case should acknowledge the existence of any … and should provide guidance for … in future development stages.” • Correct words (in order): arguments and evidence; the safety of a facility; safety assessment; confidence; unresolved issues; work to resolve these issues • Incorrect words: regulatory review; scenarios; calculations; government policy

43. Self Assessment • Question 2: Insert the missing components in the figure Missing components: Safety Case Context; System Description; Limits & Conditions; Integration of Safety Arguments; Management of Uncertainties; Stakeholders & Regulatory Involvement (see Slide 10); False components: Scenario Development; Quality Assurance; Purpose; Review

44. Self Assessment • Question 3: Which of the following statements are true? • The overall purpose of a safety case is to demonstrate that the disposal programme is feasible and safe (true) • The safety case is a key input to the licence application and approval process (true) • The safety case never needs to be updated (false) • A generic safety case has been produced for the BDC (true) • All safety cases have to follow the same structure (false)

45. Thank you!