[en] Phil Metcalf (IAEA, Austria) gave an overview of the background, content, sources of information and schedule for the document that is proposed to be published jointly with the NEA currently known as the 'IAEA Safety Standards Series, Geological Disposal of Radioactive Waste, Draft Safety Requirements (DS-154)'. Discussion focused on the status of such a document, in respect of which the primacy of national laws and regulations was acknowledged by the speaker, as well as in the document, and on the safety case definition and description in the document

[en] Abe Van Luik (IGSC Chairman, US-DOE-YM) gave a quick overview of the status of the IGSC safety case brochure titled: 'The Nature and Purpose of the Post-closure Safety Case in Geological Disposal'. The need for IGSC member review, and the schedule for the review process, was explained. The objective was to have a document to present to the March 2004 RWMC meeting for its approval. In discussion it was noted that this document was in good agreement with the safety case content of the Safety Requirements document described by the preceding presenter. It accurately paraphrases the IAEA document's definition and expands on the idea of a safety case without contradiction of that document

[en] Vincent Nys (AVN, Belgium) presented the IAEA international projects ISAM/ASAM. ASAM (application of methodology developed under ISAM) began in 2002 as a follow-up of ISAM (project to develop methodology for near-surface disposals e.g. scenarios). One of the objectives of the working group of the ISAM project was to provide definitions, to look at the integration of the safety assessment and at the review procedure. The NEA international FEP's database was used and adapted to the near-surface context. The so-called 'design scenario' might be defined as the expected scenario according to functions. Building confidence in each stage is related to the confidence in the system, the scenarios process, and the assessment context. With regards to the on-going ASAM project, participants acknowledged that the safety case contains both a safety assessment and a confidence statement. Additionally, traceability and transparency are of importance. The management framework, e.g. clear regulatory framework and clear regulatory process (review procedure), is a key element for the success of a safety case. The use of what-if scenarios could be helpful for testing the robustness of the design. It was also noted that at each stage of a safety case, the implementers should always give alternatives and should argue the choice of the reference (reversibility of the process). IGSC members noted that the safety case of near-surface disposal facilities has much in common with the safety case for deep disposal facilities. Discussion suggested that the definition and achievement of 'optimization' are open issues in the post-closure safety context. Optimisation has a generally accepted meaning in the context of achieving safety in the operational phase

[en] Allan Hedin (SKB, Sweden) presented the current situation of the SKB programme. SR 97 was developed a few years ago and feedback of the international peer review was presented in a previous IGSC topical session. The primary function of the KBS-3 disposal concept is isolation, and the second function retention. Regarding the site investigation, two sites will be studied from 2002 to 2008. An application for the encapsulation plant will be submitted in 2006, supported, as regards long term safety of the deep repository in which the canisters are to be emplaced, by a safety assessment 'SR Can'. The SR Can report is planned by end 2005 and an interim report on methodology by summer 2004. The report will contain references to applicable regulations issued by SKI and SSI regarding long-term safety of deep repositories. The principal compliance criterion states that the annual risk for individuals should be less than 10-6. When developing the report, an audit of the NEA FEPs database will be used as a check list. One or more initial states of the system will be selected as the basis for the analysis, corresponding to a 'reference state' and 'deviating' states. Preliminary analyses are made in order to gain insight into the system evolution and to inform the subsequent choice of scenarios; a number of alternative scenarios will be identified. If evolution for a certain scenario implies canister ruptures, then a calculation of consequences will be performed. With respect to the handling of uncertainty, Allan Hedin noted that various approaches exist that may prove suitable for providing rigorous uncertainty analyses. During the discussion, it was acknowledged that one key step is to get feedback from the regulator on the selection of methodology for handling uncertainty before going forward. Regarding the initial state of the system, it was noted that the point in time for the initial state will depend on the component you are looking at. During the discussion the relevance was noted of having one report per aim, viz SR Can, to support the application for the encapsulation plant, and SR Site, to support a siting decision in 2008. The coupling between the biosphere and the other components was also noted as an issue in the discussion

[en] The session started with Abe Van Luik (IGSC Chair, US-DOE-YM, USA) who presented the feedback of the international peer review of the US-DOE Yucca Mountain TSPA (Total System Performance Assessment) supporting the successful designation of the site by the Congress and the President of the U.S. In particular, he listed key implications of the IRT (International Review team) recommendations on the forthcoming US-DOE documentation of its case for safety to be submitted to the regulator, the U.S. Nuclear Regulatory Commission, mainly: - The documentation submitted to the licensing authority should address technical aspects and compliance with regulatory criteria. - That documentation should reflect sound science and good engineering practice; it should present detailed and rigorous modelling. - In addition, it should present both quantitative and qualitative arguments, make a statement on why there can be confidence in the face of uncertainty, acknowledge remaining issues and provide the strategy to resolve them. - Demonstrating understanding is as important as demonstrating compliance. - There is a need to provide a clear explanation of the case made to the regulator for more general audiences to complement the large amount of technical documents that will be produced. The US-DOE response to these recommendations for the License Application, which is under preparation, is that the recommendations will be implemented to the maximum extent possible. In subsequent discussion, with respect to the License Application, it was acknowledged that detailed guidance from the U.S. regulator was very useful, and guidance of this type would be generally useful. At the current time, the words 'safety case' are not mentioned in U.S. regulations, but if one reads both the regulation and guidance documents it becomes evident that all aspects of a safety case need to be provided in the License Application and its accompanying documents

[en] Within the NEA, the IGSC (Integration Group for the Safety Case) has, as an essential role, to develop common views on such key aspects of the safety case. Therefore, since the inauguration of the IGSC in 2000, four meetings were organised with topical sessions to explore various of these key aspects. This is a report on the fifth such topical session, held as part of the 5. plenary meeting of the IGSC. The session was attended by 36 participants, representing waste management organisations and regulatory authorities from 16 NEA member countries, the IAEA and the European Commission. The purpose of this topical session was to provide support to the finalising of the IGSC safety case brochure by getting a description of the safety case content of the IAEA Draft Safety Requirements document and by getting an overview of progress that could be observed from national organisations on developing their cases for system safety and/or developing the required methodologies. The objective was that the IGSC safety case brochure should be supportive of the IAEA/NEA document, and be reflective of the experience of the IGSC member programmes and organisations. The topical session was mainly aimed at exchanging information on: - The safety case related content of the proposed IAEA/NEA document (currently titled: 'IAEA Safety Standards Series, Geological Disposal of Radioactive Waste, Draft Safety Requirements (DS-154)'). - National programmes where safety assessments have recently been completed, e.g. ONDRAF/NIRAS, Nagra and Andra. - Feedback from international peer reviews, e.g. the Andra Dossier 2001 Argile, the Belgian SAFIR 2 report, the SR 97 report and the US-DOE Yucca Mountain TSPA. - The evolution of some national assessment methods and approaches e.g. SKB and Nagra. - The content of the draft IGSC safety case brochure entitled: 'The Nature and Purpose of the Post-closure Safety Case in Geological Disposal'. This document presents the various presentations and exchanges that took place during the topical session. Part A of this document summarises the material presented and provides the main outcomes. The overheads presented are compiled without elaboration by the NEA Secretariat as Part B of the document, and Part C gives a list of participants. It is hoped that the document as a whole provides a synthesis of current issues in safety case development including key issues being identified in recently undertaken international peer reviews

[en] Juerg Schneider (Nagra, Switzerland) described the project on the Opalinus Clay (Project Entsorgungsnachweis, demonstration of disposal feasibility for SF/HLW/ILW in the Opalinus Clay of the Zuercher Weinland) for which the main objective is to demonstrate disposal feasibility and to provide input to the decision how to proceed. The report structure was described, the focus of the presentation being the report that aimed to provide a comprehensive assessment of long-term safety. The current situation was described in the presentation as follows: - The key need is to provide arguments for having proposed a good system for which there is sufficient understanding to allow a credible safety evaluation. - Alternative options exist, on which attention is maintained by a task-force. However, Nagra is confident in its results on Project Entsorgungsnachweis, given the knowledge base that currently exists, and has put forward a proposal, for consideration by the Swiss Government, to focus future work on the Opalinus Clay (OPA) of the Zuercher Weinland. - Making the safety case requires a proper integration of science, engineering and safety assessment. - Three key issues were identified in making a safety case: completeness, sufficient safety, and robustness to diminish the importance of uncertainties. - A safety case needs to be adequate to support a decision to proceed to the next stage in the programme, with multiple arguments including the existence of reserve FEP's. - The interacting functions of the relevant teams were viewed as a key component of the process of preparing a safety case: management; science; safety assessment; bias audit. During the discussion, the role of the bias team was recognised as being helpful to ensure completeness, as well as using the NEA FEP database as a check list. When speaking about sufficient safety, it should not imply predictive capability but rather that there is enough confidence in the current level of understanding to reliably bound the consequences, and that there is a continuing program for expanding and refining that understanding

[en] Arnaud Grevoz (Andra, France) presented the Andra Dossier 2001 Argile, which is an evaluation of knowledge and an interim report in anticipation of the Dossier 2005, and served as a test of methods to be applied to this dossier. The 'Dossier' consists of three main parts: a high-level synthesis, a more detailed one, and a series of reports. The Dossier 2001 Argile was not a safety case but some items of the safety case were already addressed. The Dossier 2001 Argile was submitted to an international peer review in 2002/2003. The main recommendations from the IRT were: - A clarification of the documentation is needed, mainly on information flow in the network of various levels of documents. - In view of communication to a wider audience, the synthesis could be improved e.g. using more illustrations. - The 'Dossier' did not always reflect the level of knowledge acquired. - New methodologies were presented and need to be further developed In particular, the AQS (Analyse Qualitative de Surete) corresponds to a failure mode analysis, but time-dependent phenomena were not taken into account. The IRT suggested less emphasis on the results of failure analysis, and more on the basis for analyses to allow the results to be placed into a coherent context. In view of the forthcoming 'Andra Dossier 2005', and with respect to the international peer review experience, Arnaud Grevoz described the main part of Andra's future work. The APSS (Analyse Phenomenologique des Situations de Stockage) will be updated. The safety analysis is being revised in more convincing and transparent ways to provide a clear exposition of the bases for arguments made in setting up the analyses and defining the models used for the analyses. The FEPs (Features, Events and Processes) date base will be utilised as a check list. In its future report, Andra intends to clarify terms such as pessimistic and conservative with a view to providing a more understandable document for wider readership. Some items where more development was needed were underlined, i.e. corrosion. Andra's research programme for 2002-2005 was judged adequate in this respect. For waste package source terms, Andra will integrate more the international experiences in particular on spent fuel. The gas issue that was not developed in the Dossier 2001 is one of the priorities that will be studied for the Dossier 2005. The safety strategy is a key part of the safety report; in particular safety margins and reserves could be used as arguments for building confidence in the robustness of a repository. One additional key point of the Dossier concerns the need to clarify the transposition of understanding to modelling. In conclusion, Arnaud Grevoz acknowledged the helpfulness of the international peer review to structure the new version of the Dossier 2005. He emphasised the international studies as a good input to build a high-level of argumentation and to inform the research programme

[en] Peter de Preter (ONDRAF/NIRAS, Belgium) presented the lessons learnt from the international peer review on SAFIR 2 of 2002 and the implications of the IRT's considerations for future work. He mentioned that the IRT, in accordance with its mandate, focused on the long-term safety (methodology and application), on the scientific basis of the safety assessments and on the management of uncertainties. During the peer review it was agreed that the mandate could be extended to the discussion of policy issues. The IRT noted that SAFIR 2 could be considered as a first integration exercise in attempting to combine the knowledge accumulated to date into an integrated safety case format. In the future, the two aims of recording the status of R and D and putting the R and D into a safety assessment/safety case would be addressed in separate documents. The results presented in SAFIR 2 confirmed that the main barrier was the Boom Clay, but the IRT considered that more credit could be taken for the Engineered Barrier System (EBS). Novel and innovative methods were established and the IRT encouraged ONDRAF/NIRAS to develop them e.g. safety functions, safety indicators. There is a need to better argue the geosphere stability and the engineered system capability. Peter de Preter mentioned that one of the difficulties during the preparation of the SAFIR 2 case was the lack of national guidance. The main lessons learnt from the peer review were: - Most recommendations were more or less expected, known weakness have been confirmed. - The international peer review provided the incentive for improved argumentation for the relevance of the system studied and justification of decisions. - Policy and regulations are necessary to have a clear framework and therefore the regulatory framework will be one of the priorities of the regulators. - There was a gap between the completion of the reviewed report (with results up till end 2000) and the timing of the review (2002) therefore the review process was exposed to new achievements and developments not reported in SAFIR 2. Peter de Preter then presented the main implications of the review on the future programme in view of making a safety case: - The future programme will focus on technical feasibility (construction and operation). One of the major problems concerned the level of the design, and the deliberations leading to choices being made. In response, ONDRAF/NIRAS has launched an integrated design group (with engineers, scientists and assessors), which will go through a complete design review with the aim of achieving more quality assurance and traceability of decisions and their bases. - The integration of the understanding of processes with recognition of the importance of a good interface between the different actors (engineers, scientists, assessors) which is viewed as a management issue at ONDRAF/NIRAS. Additionally, a good balance between realism and robustness is recommended: even if all understanding is not integrated in the modelling, it could be used as support for the argument for safety. - The uncertainty management, the strategic environmental assessment, and the involvement of stakeholders will be further developed in the future programme. - Some scenario analyses will be updated in the light of the experience of SAFIR 2. - The need for prioritising the work (uncertainty management to be reinforced) in respect of the stepwise decision-making process was recognised. In conclusion, Peter de Preter acknowledged that although such peer reviews require the implementer to mobilise resources, they are a very helpful exercise