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1 Unclassified NEA/SEN/SIN/WGRISK(2015)1 NEA/SEN/SIN/WGRISK(2015)1 Unclassified Organisation de Coopération et de Développement Économiques Organisation for Economic Co-operation and Development 02-Oct-2015 English text only NUCLEAR ENERGY AGENCY COMMITTEE ON THE SAFETY OF NUCLEAR INSTALLATIONS Working Group on Risk Assessment (WGRISK) Summary Record of the 16th Meeting of the Working Group on Risk Assessment 4-6th March 2015 OECD Conference Centre, Paris, France JT English text only Complete document available on OLIS in its original format This document and any map included herein are without prejudice to the status of or sovereignty over any territory, to the delimitation of international frontiers and boundaries and to the name of any territory, city or area.

2 16TH MEETING OF THE WORKING GROUP ON RISK ASSESSMENT OECD CONFERENCE CENTRE, PARIS-16, FRANCE 4-6TH MARCH Opening of the Meeting 1.1 Chairperson s welcome The Chair M. Roewekamp welcomed the members to the meeting and explained that the following apologies have been received: Milan Patrik Zoltan Kovacs - RELKO Ltd, Slovakia Dr P.V Varde BARC, India Alvio Bassanelli SOGIN, Italy Salvatore Massaiu - Institute for Energy Technology - OECD Halden Reactor Project, Norway Mirela Nitoi - Institute for Nuclear Research Pitesti, Romania In addition, the following changes in membership have between the 2014 and 2015 meetings Departing Members: None New Members: Finland Markus Porthin New EC member is potentially Roberto Passalacqua, EURATOM RTD Scientific Officer The Chair then requested that the head of the NEA Nuclear Safety Division to give an opening introduction. 2

3 1.2 NEA Head of Nuclear Safety Division Mr. Javier Reig, NEA Head of Nuclear Safety Division gave a welcome address that highlighted the work the NEA had pursued since the last meeting, including: New Director General has arrived. He has had a long history with NEA via the nuclear steering committee. As part of his new ideas for the NEA he has proposed to change the name of the agency and the structure of the safety Division. There will be two divisions, one of which will concentrate on soft nuclear safety issues like safety culture. CNRA has decided to issue a follow up report to Fukushima, March 2016, to reflect work NEA has learnt what NEA plans are and how the committees see the work moving forward. From a timescale perspective it has been decided that this will follow the publication of the IAEA report. There is a CNRA senior task group discussing safety culture of the regulatory body and a new working group on external events (WGEV) has been created and will initially be examining the effects of extreme wind. How to balance of probabilistic and deterministic decision making will be discussed at the next CNRA. They plan a 2hrs session and are seeking WGRISK input. This will generate additional work. NEA s nuclear development committee is carrying out study on the costs of a nuclear accident. It is a very sensitive topic and the NEA steering committee has asked them to focus on methodology and not on figures and numbers. There has been some discussion at CSNI and there is a difference of opinion between Europe and US approaches. WGRISK is likely to be given an opportunity, when the report is ready, to offer a viewpoint. Reference was made to the multi-unit sites and spent fuel pools work of WGRISK and the group was urged to ensure good cooperation between NEA and IAEA and the EC. In order to use WGRISK resources in the most open way and to make sure there is complementary effort rather than unnecessary duplication Mr Reig explained that there had been the annual meeting between NEA and IAEA to improve the interactions between the organisations and it was recognised that certain new developments may impact on issue including coordination. For instance the decision by the Russian Federation to join a number of CSNI and CNRA activities and the agreements with China and India to explore opportunities for mutual benefit will reduce the pressure of those countries asking IAEA to duplicate activities The chair thanked Mr Reig for the interesting news and the requests for involvement. She indicated the group would be covering SFPs in this meeting and will discuss a CAPS, for submission to CSNI, on PSA for multi-unit sites. She also pointed out that cooperation with IAEA and EC was embedded in the work of WGRISK and cooperation exists already due to the cross-cutting nature of the group s work 2. Adoption of the Agenda [NEA/SEN/SIN/WGRISK/A(2015)1] The agenda was reviewed and accepted with the following provisos: Adjustments will be made to optimise the schedule, and to support presenters availability, including the ASAMPSA-E and WGEV presentations. A technical discussion on SFP PSA on Thursday afternoon led by the chair was highlighted. 3

4 As there were no other changes the agenda was approved 3. Approval of the 15 th WGRISK Meeting Summary Record [NEA/SEN/SIN/WGRISK (2014)1] The Secretariat reported that the final version of the Summary Record had been distributed by to the group members. One set of additional comments had been received by the NEA Secretariat and it had been amended. No further comments were received and the Summary Record was accepted and approved for publishing on the CSNI website. The Secretariat reported that all actions had been completed except for the following four for which the Secretariat provided explanations: 13 Review and comments on the updated WGRISK Integrated Plan and future work Review and tabulation of recommendations from last 5-10 years of WGRISK reports and posting in ideas bank on webpage To be discussed at this meeting 14 Response to request on involvement in 3rd International Conference on Reliability, Safety and Hazard, ICRESH-15, Lulea, SWEDEN, 15-16th August 2015 Further details to be supplied to NEA Secretariat and then distributed to the group concerning the 3rd International Conference on Reliability, Safety and Hazard, ICRESH-15, SWEDEN, 15-16th August 2015 This was now a part of the ARMS ICRESH2015, 1-4 th June 2015 and less direct relevant to NEA although some members are attending 18 Proposed CAPS Application of Probabilistic Safety Assessment for Research Reactors Circulate CAPS presented by Dr Varde, BARC, India (ad-hoc expert) Application of Probabilistic Safety Assessment for Research Reactors with three questions: - Is there an active activity in your country? - Is there an active interest in this area? - Are you prepared to lead the CAPS? For response by 10th October 2014 to prepare result for WGRISK Bureau decision on value for continuation The Secretariat explained that he had circulated this but there had been no response. The decision had been made to add this to the ideas databank to be discussed later 20 Website Update of WGRISK Website NEA to progress the bringing of the WGRISK website up to date with information. Latest meeting first The Secretariat explained that progress had been made due to a new resource being made available. The update will be active elements first then older information. The work on collation of papers is also on hold although again a new resource may be able to take this forward. He added that some new publications 4

5 have been posted on web and that the Workshop papers - International Workshop on Fire PSA, May 2005, Puerto Vallarta, Mexico had been found. 4. The Use and Development of PSA in NEA Member Countries Individuals from the 22 NEA member countries, NEA non-member countries and economies represented in the meeting gave updates on their progress, changes and development in this area since the last meeting. The highlights were: Belgium The Belgian representative explained developments that had taken place since the last meeting in 2014 which significantly included: The preparation of flooding PSA models - It was reported that for the 5 Belgian reactors the DOEL3 flooding PSA has been completed and it was determined that flooding is a minor contributor to the global CDF per reactor year. Fire PSA models The analysis of the five reactors has again begun with DOEL 3 which has gone through a qualitative screening to choose Physical Analysis Units (PAU) that will feed into the detailed analysis. Canada There have also been upgrades of internal events models to improve the PSA s of the five reactors. The Canadian representative explained developments that had taken place since the last meeting in Guidance is being updated regarding use of PSA following a request from industry. As a result, a new industry standard is being developed for publication in It will incorporate inspection advice. CNSC are also developing new safety goals and there is a Level 3 PSA research project being launched to identify a best practice methodology. He also reported ongoing bilateral cooperation with U.S. NRC and multilateral cooperation with Finland and Sweden. Korea The Regulatory Body, KINS, has revised the text of the atomic laws for new reactor licensing. It is now agreed that the submission of PSA results is required as part of licensing application. These changes are now pending in the government. In addition, regulatory guidance is being developed to establish effective countermeasures against extreme external events including developing risk evaluation methodologies and an Integrated risk assessment technology for a multi-units site, For the utilities, KHNP, has carried out a number of PSAs for licensing applications and has two oversea projects: one is a PSA for NRC of an AP1000 and the other is for a PSA for UAE (United Arab Emirate) Braka NPPs. 5

6 United States Developments in the U.S. have occurred in five areas. Reactor Oversight, Accident Sequence Precursor, Licensing Initiatives, Fukushima Dai-ichi Near Term Task Force Activities and other activities. For the reactor oversight a number of tasks on improving modelling and approaches are being covered in the SPAR and SAPHIRE Programs as well as improvements in identifying precursor trends and categories. There is work ongoing on risk informed licensing including Categorizing SSCs according to Safety Significance. The post-fukushima Task near term task force has identified and progressed the areas of balancing defense-in-depth and risk, flooding and seismic re-evaluation, including a paper Integration of Mitigating Strategies For Beyond-design-basis External Events And The Re-evaluation of Flooding Hazards and order EA (March 12, 2012) -Mitigation Strategies for Beyond-Design Basis External Events. There are also a large number of smaller activities that have been initiated: Digital I&C, Integrated Site Level 3 PRA Project, Fire Testing and Modelling (including the OECD/NEA HEAF project), Human Reliability Analysis, improvements in the Risk Management Regulatory Framework and the creation of a new PRA Steering Committee to facilitate industry and public engagement on these issues. Finland Finland reported that there was no additional work on PSA during 2014 other than updating and refining of PSA models France The representative explained that work had been in progress on the updating and improvement of existing PSA studies with the intention of: Italy A. expanding the seismic PSA to include other external hazards as well as improving methods for screening hazards; B. developing methodological developments for EE/EH PSA; C. incorporating Ageing into PSA, The participant highlighted that although there had been no developments in PSA methodology within Italy, they had presented a number of PSA studies at the IEM8 (at IAEA) in February Japan The Japanese delegate explained that new regulatory requirements and regulations have been published in Japan based on international standards and are available to view on the website. Although some, of the documents, may be in Japanese. In addition, there was a nuclear risk centre founded within CRIEPI at the end of February2015. Hungary PAKS construction licence will need to be requested next year for the two proposed new reactors. The PSA framework and environment have been modified following the issuing of revised nuclear safety codes. 6

7 A PSA guideline as a framework document has been prepared to summarize overall recommendations on PSA development. Detailed guides on different areas of PSA are planned to be prepared, too. An update of the Level 2 PSA for low power and shutdown conditions for NPP Paks is ongoing and will include icing of power lines. A feasibility study on developing an integrated multi-unit PSA has been prepared and in the future development of specific regulatory guides on different PSA areas is envisaged. Poland The delegate reported that there had been no change in the progress of the NPP project. The contract for siting process has been stopped at the moment and this will be delayed until 201. Consequently, work concentrates on training and knowledge gathering including starting a project on Fire PSA and human reliability and the hosting of 2 conferences on PSA in Poland in Sweden It was reported that the recent elections have changed the political makeup and their parliament will discuss future of energy. The head of reactor safety at SSM, Lennart Carlsson, had been replaced by Mr Knochenhauer and the Swedish representative to WGRISK would be retiring soon. A number of new regulations were being issued on requirements for general safety, design, analysis and operation. Also projects had been initiated on Level 3 PSA, HRA and use of digital instrumentation. Switzerland A probabilistic seismic hazard analysis (PSHA) for all Swiss NPPs was submitted at the end of Concerning extreme weather conditions, a re-evaluation of the probabilistic hazard analysis was submitted to ENSI in All these studies are under review by ENSI. Furthermore, ENSI together with other federal offices is working on a comprehensive project in order to improve and harmonize the input to the external flood hazard analyses. A re-evaluation of the hydrogen hazard was conducted in For two plants it was decided to install passive recombiners (PAR) such that all Swiss NPPs will have passive measures (inertisation or PAR) against hydrogen. The various plant specific PSAs are regularly updated and applied according to the PSA regulatory guidelines. The refinements of the PSAs address various issues but mainly earthquake (in particular the fragility analysis) and internal fires. All hazard analyses were submitted in 2013 and those for extreme conditions were submitted to the regulator ENSI. Flooding is being examined as a joint effort with regulators to establish a consistent approach and work is ongoing on adding recombiners to reactors. Chinese Taipei Systematic analysis is being performed for all 4 plants within Chinese Taipei. The analysis includes not only tsunami but also internal flooding fire seismic and aircraft impact. These will be delivered in The exception is with volcano which is in planning. It was noted that seismic and tsunami in combination were analysed as well. Mexico 7

8 The representative explained that there was work on developing a safety assessment model for Spent Fuel Pools using MELCOR and an integral safety assessment for a reactor was being developed Slovak Republic Work has continued on updating existing PSA Level 1 and 2 analyses. The PSA response to internal and external hazards has been elaborated and updated regulatory guidance has been issued concerning the quality of the PSA Slovenia During the past year post-fukushima Dai-ichi upgrades have taken place on reactors including the installation of PARs and mobile equipment. This has resulted in the PSA delivering a substantial decrease in release frequencies The representative made the working group members aware of an external hazard termed Glaze ice which is ice hanging off power lines whose weight causes power lines to fail. The consequences were assessed and determined to be negligible. However, additional protection measures have been established. Czech republic The recent progress in Czech Republic was presented. There had been an update of the L1 PSA s for Dukovny and Temelin reactors and the importance of the involvement in the OECD NEA joint nuclear safety projects, FIRE, ICDE and OPDE (now CODAP) to assist these updates was highlighted. Incorporation of measures from post-fukushima National Action Plan the regulator plans in 2015 will be accompanied by updates of the Dukovany and Temelin Level 2 PSAs. Germany The activities in Germany that had progress since the 2014 meeting were presented and included extending PSA methods and data, impact of internal and external hazards (including systematically addressing event combinations) to both better cover safe shutdown phase and address post-fukushima issues more explicitly, aas well as to develop effective methods for explicitly including time dependencies including human response into PSA models (IDPSA). Guidance document for supplementing existing technical documents on PSA Methods and Data has been further improved and will be published in The extensions to the guidance cover: Methods for low power and shutdown PSA (including safe shutdown phase), Methods for Level 2 PSA, Methods for addressing external hazards in PSA. There is also continuing work on improving the PSA Data that is used for analysis: Generic CCF data, HRA reliability data, Technical reliability data for fire protection features. 8

9 At the conclusion of this topic the Chair congratulated everyone for their efforts to share the important international PSA developments that had occurred during Reports on Activities in the Area of PSA by other International Organisations 5.1 IAEA presentation (Abdallah Amri) Mr Amri gave an overview of not only the safety sections work but also the work of the wider IAEA of relevance to the WGRISK, in particular the Safety Assessment Section, Research Reactor Section and International Seismic Safety Centre. Within the Safety Assessment Section the development of guidance documents has focused on an update to TECDOC-1511 and the International Probabilistic Safety Assessment Review Team (IPSART) Guidelines as well as the creation of TECDOCs on Integrated Risk Informed Decision Making (IRIDM), Safety Goals for Nuclear Installations, Level 3 PSA Guidance (where there may be complementary efforts with the proposed CAPS on Level 3 PSA) and the Integration of DSA and PSA, The section is also involved in training on PSA & competence/capacity building activities and special projects to develop complementary safety assessment methods. The Research Reactor Section is developing a report on PSA for Research Reactors. He noted that the International Seismic Safety Centre has now become a focal point for protection against external hazards and is funded from regular IAEA budget and extra programmes. There are now 10 working areas, some of which are risk related, which are: WA1: Seismic Hazards; WA2: Seismic Design, Qualification and Safety Assessment; WA3: Seismic Experience Data; WA4: External Events Preparedness and Response; WA5: Tsunami Hazards; WA6: Volcano Hazards; WA7: Human Induced External Events; WA8: External Events Safety assessment of Multi-Unit Sites; WA9: Information and Notification System; WA10: Public Communication and Dissemination, and Capacity Building He focussed on one recent piece of their work on multi-unit PSA which is well summarized in a paper presented at PSAM 12 Technical Approach for Safety Assessment of Multi-Unit NPP Sites subject to External Events, which includes framework for site safety assessment, technical approach (interaction between units, risk metrics, screening of hazards, human reliability, infrastructure), an example based on loss of offsite power at a two-unit site. The ISSC is now drafting the related technical documents under the IAEA leadership of O. Coman, ISSC/NSNI/NS 5.2 EC presentation It was explained that the European Commission representative had not yet been officially appointed to the WGRISK meeting. It was believed that this would be Roberto Pasalacqua. The Secretariat was actioned to confirm this. 9

10 Number Description Owner Target Date 16.1 Contact Roberto Pasalacqua of EC to confirm intention to be EC member NEA End March European ASAMPSA_E project (Advanced Safety Assessment : Extended PSA) Emmanuel Raimond, IRSN As was reported in 2013 when it began this is an EC funded project having a large scope including the incorporation of internal and external hazards within an extended PSA. There are a large number of partners. Mr Raimond explained that at the meeting in May of 2014 and afterwards the project members explored the way forward for the project. It had been noted that funding is limited within each partner and the current phase focussed on the outcomes of a survey identifying the available and desired guidance to meet end user needs. This was synthesised into a key report to partners and a further 4 supporting reports. The latter were being readied for distribution. The project had developed a bibliography on regulatory requirements on implementation of DiD for NPP and the survey identified 64 recommendations which had been categorised as A, B, C. These have been fed into the phase 2 of the project which will examine applications of extended PSA and the relationship between decision making and PSA. For instance, the connection between risk metrics for extended PSA is being worked on and there are 6 groups examining external events earthquake, flooding, lightning, biological hazards, fire and aircraft crash. The Groups see value in sharing ideas with WGRISK on screening and are hoping to interact with WGRISK on this. It was highlighted that with the resources available the possibility of delivering the tasks within two years is challenging. An end date has not been defined yet but it is hoped to be mid There was some discussion between the members and Mr Emmanuel on the details of the programme and again there was support for continuing to monitor progress of this task and of discussions with the aim of achieving mutual benefit. 5.4 Report of the 17th Meeting of the PSAEA, 6-7th November 2014, Brussels Stanislas Mitaille, Tractabel, Belgium It was reported that 16 presentations were given by either utilities or regulatory bodies on the topic of experiences and national programs related to Risk-Based Precursor Analysis. 11 dedicated to risk based precursor analyses, 2 dedicated to use of risk information in France, 2 dedicated to the special topic of bypassed protections of safety equipment and 1 dedicated to PSA level 2 precursor analyses from Belgium: Of which, 3 were presented in detail to the WGRISK. The topics of these were: Unavailability of emergency Diesels due to flooding accident, Partial loss of outside power during mid-loop operation, Impact of opened internal airlock door on release categories: Level 2 PSA model. 10

11 Mr Mitaille reported that the PSAEA meeting concluded that it has been commonly agreed by all participants that the existing thresholds for the precursor categories were decided at the time that PSA scope was limited only to internal events and nowadays when the PSA scope becomes broader, the use of the absolute numbers does not reflect the importance of events in relation to PSA metrics. Also, it has been agreed that the what-if analyses are of greater importance than the thresholds considered for precursors categories. Therefore, it has been concluded that some reserve should be considered when making use of outdated established thresholds values. The presentation related to Level 2 PSA, for Belgium this was considered a first of a kind, it has been suggested to participants to present precursor analyses that concern PSA level 2 studies too. The Chair thanked him for the presentation of several events and a discussion took place around the three topics presented. 6. Report by the Secretariat 6.1 Update on the current WGRISK programme of work, actions taken by CSNI and CNRA and other recent developments in OECD/NEA The presentation by the NEA Secretariat, Mr Blundell, covered the following significant aspects: New NEA staff members including the new Director General, Mr. William D. Magwood, IV took up his duties as the new NEA Director-General on 1 st September Olli Nevander and Martin Kissane had joined to work within CSNI activities and and Young Joon Choi had joined to work with MDEP. Relevant Outcomes of the NEA Steering Committee A memorandum of understanding of cooperation has been signed between the NEA and NNSA (National Nuclear Safety Administration) of China, and NEA is encouraging engagement of China in CSNI/CNRA activities including WGRISK The NEA has observer status and is being considered as Technical Secretariat for the International Framework for Nuclear Energy Cooperation (IFNEC). Reshaping of the NEA Reshaping process is underway within NEA lead by Mr. Magwood that will result in changes to the NEA with a clear focus on safety. Two new streams of work on the human side of nuclear safety (human performance, organizational performance, safety culture, etc.) and the balance between deterministic and risk-based decision making will be started with the creation of a new division. More information will follow as the new division is defined in further detail. 11

12 Feedback from the CSNI on activities of interest to WGRISK The WGRISK FCAPS report International Workshop on PSA of Natural External Hazards Including Earthquake was approved and has been published as R(2014)9. Development of BPGs on failure modes taxonomy for reliability of digital I&C systems for PSA Report approved by December CSNI and published R(2014)16. 2 FCAPS from WGAMA Status Report on Hydrogen Risk Management and Related Computer Codes and OECD/NEA/CSNI Status Report on Filtered Containment Venting were also approved. The CNRA task group on external events (TGNEV)was converted to a new working group (WGEV) and would be expected to interact closely with WGRISK. A letter will be sent to CSNI members asking them to provide suggested topics for the NEA five-year follow-up report to Fukushima by the end of January Report is planned for end of December CSNI decided that the ROBELSYS task group should continue to pursue the rationale for a working group, including seeking input from the CNRA on objectives that are aimed at development of guidance or regulatory practice, and report back in June Preparations for development of a new CSNI Operating Plan have begun. A letter will be sent to CSNI members asking them to provide suggested topics for the NEA five-year follow-up report to Fukushima by the end of January Report is planned for end of December The work of other working groups of relevance to WGRISK;, Outcome of the actions from the previous Bureau and Annual Meetings; Progress on the four CAPS nearing completion: Report on Establishing desirable attributes of current HRA techniques in nuclear risk assessment (jointly with WGHOF, see WGHOF presentation) was nearing the completion of the publications process, the report on the International Workshop on Fire PRA in Member Countries Hosted by GRS in Garching in April 2014 was in 2 nd draft, an nitial draft has been produced on the report on Insights Provided by PSA Related to the Loss of Electrical Sources (presented later in the meeting), and a CAPS Human Reliability Analysis in External Events PSA survey of methods and practice had been approved by CSNI (presented later in the meeting). Updates on joint projects BSAF, HEAF, FIRE, ICDE, CODAP and CADAK, including the current task of investigating whether CODAP has come to a successful conclusion and should be closed. 12

13 Progress on website improvement: Progress has been made due to new resource, the active elements would be upgraded first then older information. Importantly, the Workshop papers - International Workshop on Fire PSA, May 2005, Puerto Vallarta, Mexico had been found and uploaded on the website. NEA had been approached by TEPCO to investigate working with WGRISK and these discussions were ongoing but would need further interaction. WGRISK is to report to CSNI in June The Secretariat discussed several comments on his report. It was pointed out to the meeting that the WGRISK Chair will report on the group at the next CSNI meeting in June Status report on Fire PRA in member countries [Task ] 7.1 Report on the status of the Task Task Group Leader Marina Röwekamp Marina Röwekamp gave an overview of the progress on the delivery of the task. She reminded the meeting that the workshop was hosted successfully by GRS on April 28-30, In total 59 participants from 17 countries, IAEA, and OECD/NEA covering 8 sessions with 32 expert presentations plus concluding summary discussion. The objectives and the report contents were presented in overview and it was explained that the current draft of the report would be circulated for comment in the week beginning the 9 th March 2015 for comment (it was agreed) by 4 th April and then onward submission to CSNI PRG and then CSNI approval on 4 th June The major workshop conclusions were that: Fire PRA has achieved a reasonable level of maturity. Internationally, Fire PRAs are performed within a consistent framework. Many Fire PRAs apply common methods, tools, and guidance. There seems be a common understanding of weaknesses, activities to reducing gaps are ongoing. The importance of treating uncertainties and developing basis and methods for treating them has been recognized. Despite the recognized weaknesses, the results of Fire PRA are being used to support riskinformed decision making to some extent. The report recommends that: WGRISK should continue to remain active in the Fire PRA area. Consideration be given to organization of a future workshop, perhaps focused on a specific aspect such as multiple hazards/events (including fire), fire HRA, multi-unit Fire PRA. 13

14 There should be consideration of the development of additional resource or focused guidance documents for member countries (e.g., condensed SOAR) based on member country experiences. There should be WGRISK participation in international comparison and harmonization activities. Decisions: 4 th April : deadline for Member Feedback on draft Fire PSA workshop report and 4 th June 2015 CSNI - submission of Fire PSA workshop report for approval 16.5 Fire PSA Workshop report Produce final draft, distribute, comment and prepare for submission to CSNI PRG for onward submission to CSNI for approval M. Roewekamp final draft NDA Distribute WGRISK members comment M. Roewekamp amend from comments NDA submit to PRG 10 th March th March th April th April th April Status report on the PSA insights relating to the loss of electrical sources [Task ]- Jeanne- Marie Lanore Jeanne-Marie Lanore gave an overview of the progress with the task and explained that there has been a task group meeting on the previous day on the draft report that had been drawn together in January. It was explained that the purpose of the Task Group meeting was to examine each chapter and by presentation of the draft text and discussion to determine the main findings and any missing information. This was followed by examination of the whole document to determine the preliminary conclusions and the contents of a complementary questionnaire to clarify or find the missing information. The WGRISK received an overview of progress of each chapter of the report and the next steps in the task which were: To make some improvements to the draft chapters, Distribute a complementary limited number of questions for clarification by the end of March with a request for responses for end of April 2015, Deliver a draft of the complete report including conclusions for mid-june for circulation to the core group, Distribute to the whole WGRISK in July for comments before mid-september The objective would be to present the completed report to the WGRISK Bureau meeting in October and to PRG and CSNI in November and December 2015 respectively. The presentation was completed by presenting some preliminary insights of the work. J.M. Lanore was complimented for her presentation and the strategy for delivery of the report to CSNI for approval was supported. Decision: Approval for Submission to CSNI PRG of report on the PSA insights relating to the loss of electrical sources 30th September

15 9. HRA in External Events PSA [Task ] HRA in EEPSA (V.N. Dang) NEA/SEN/SIN/WGRISK(2015)1 A short overview of the task was given by V.N. Dang. The Task had been approved by CSNI in December 2014 and the first meeting was to take place on Friday 6 th March The task would perform a survey of Human Reliability Analysis (HRA) methods and their applications in existing PSAs for external events, or being applied in or considered for PSAs of this scope. The members of the task group included Switzerland, Sweden, Korea, Czech Rep, Canada, France, Germany, Hungary, Japan, Mexico and the US. The kick-off meeting was to be Friday 6th March, where the team was to prepare a survey incl. sample response ready for distribution to the full working group in June 2015 with a response deadline of January The target was to present the final results in March 2017 at WGRISK18 and report approval from CSNI in June HRA in External Events PSA [Task ] HRA in EEPSA Ensure that the CAPS is distributed for awareness in WGHOF 16.7 Ensure all WGRISK 16 presentations and papers are uploaded on the WGRISK website and notify participants NEA 31 st March 2015 For next WGHOF meeting NEA 20 th March WGRISK participation to international conferences, workshops, etc WGRISK participation in External Conferences An overview of intended activities was then given and the following are the key WGRISK related activities although it is recognised that there will be presentations from individual countries within the WGRISK membership at these meetings and particularly ESREL. PSA 2015, Sun Valley, Idaho (USA), April, 2015: Recent and Future Activities of the OECD Working Group on Risk Assessment (WGRISK) ARMS-ICRESH15, Lulea, Sweden, June 1-4, 2015: Keynote Speech on WGRISK Activities and Perspectives ESREL 2015, Zürich, Switzerland, September 7-10, 2015: Recent and Future Activities of the OECD Nuclear Energy Agency Working Group on Risk Assessment (WGRISK) Distribute list of international conferences to WGRISK membership and load on website NEA 20 th March 2015 The Chair stressed the importance of having all of the WGRISK activities at major PSA conferences and requested the members to indicate whether there were any further conferences that they believe a WGRISK representation should be made. 15

16 The following conferences were then proposed: PSA Technical meeting in Brussels, PSAEA, October 28-30, 2015 at Electrabel (ENGIE), ESREL September 2015 in Zurich, PSAM October 2016 in Seoul. There were no further meetings proposed and thus the meeting was requested that if further opportunities arose in the future then the WGRISK Bureau should be informed via the Secretariat. The bureau would then manage the representation which would be requested from the WGRISK membership. 11. Outcome of Other International Meetings/Activities relevant to WGRISK 11.1 PSAM12 The Chair indicated that a paper was delivered at PSAM12 conference in Honolulu, Hawaii (USA), June 2014 entitled OECD WGRISK Challenges and Recent Tasks which was well received and a copy will be posted on the WGRISK webpage. 12. Cooperation with other NEA Working Groups, Task Groups or Expert Groups 12.1 WGEV Working Group on External Events Andrew White gave an overview of the development of the new working group on external events (WGEV) from the Task Group of Natural External Events (TGNEV) and its future work programme. The Task Group TGNEV recommended that the new Working Group on External Events (WGEV) take a phased approach to the initiation of its work scope. Specifically, TGNEV recommended, initially, WGEV focus on more frequent weather induced events and their ancillary hazards, before initiating work in the areas of earth, solar/space, and/or human-made induced events. TGNEV recognised and recommended that specialised skills will need to be represented on the sub working groups (e.g., Meteorologists, hydrologists, and dam safety specialist may be needed to supplement technical discussions and support methods development). The CSNI had approved the formation of the new working group and the group had chosen to follow a survey ti support a 2.5 day Severe Weather and Storm Surge Workshop in the fall of 2015 in Paris. The workshop will focus on the 4 major survey themes: Regulatory approaches (nuclear only), Hazard Assessment (nuclear and domestic) Lesson learned from events (nuclear and domestic) Research Activities (nuclear and domestic) He explained that the group would be seeking input from WGRISK representatives on the development of the integrated plan as the group are seeking to deliver a consolidate response. 16

17 16.20 WGRISK to feedback in a consolidated way on Integrated Plan of Working Group on External events (WGEV) WGRISK Bureau leading members response NEA/SEN/SIN/WGRISK(2015)1 Next Bureau meeting October 2016 The members were invited to ask questions regarding the group and its work and after this the Chair thanked Dr White for his interesting presentation and help at other points within the meeting. 13. WGRISK Discussion 2015 Spent Fuel Pool PSA This topical discussion was led by Marina Roewekamp. The purpose was to explore what are the ways that PSA practitioners are developing practices for implementing PSA around Spent Fuel Pools (SFP). Ultimately the working group would be asked to consider what follow up work could be followed Presentation 1 Spent Fuel Pool Risk Analysis for Dukovany NPP by Stanislav Husťák of ÚJV Řež, a. s (Czech Republic) The presentation covered the Living PSA for Dukovany NPP, the main principles of spent fuel pool (SFP) risk analysis, analyses for SFP Level 1 and Level 2 PSA followed by the Main results and conclusions. The scope of the analysis included plant operation with fuel in reactor as well as with the reactor core completely relocated to SFP (once every 4 years). The presentation explained the Long Time Window to Fuel Damage and how the modelling of loss of SFP cooling was achieved. The extension to Level 2 PSA was presented and the following conclusions drawn. For heavy load drops into open SFP there was a dominant FDF contributor; however, there is large uncertainty in determination of conditional probabilities of fuel damage. The contribution to the PSA outcome from loss of SFP cooling is negligible as there are many possibilities to makeup SFP to compensate evaporation. However the instantaneous risk cannot be neglected and depends on the actual occurrence of components out of service Human Reliability Analysis suggests that there is a large uncertainty in quantification of human error probabilities for such long time windows including uncertainty in quantification of dependency for redundant actions to avoid unrealistically low values.in terms of enhancement of SFP Analysis current activities include the incorporation of measures from Post Fukushima National Action Plan that ask for an update of SFP Level 1 analysis and significant update of external hazard analyses with impact on SFP Level 1 PSA as well as the development of Level 2 PSA for external hazards which will impact on the SFP Level 2 PSA as well 13.2 Presentation 2; Probabilistic Approach to Consider Spent Fuel Pools of German NPPs in Level 2 PSA by Thomas Steinrötter, GRS GmbH (Germany) Thomas Steinrötter presented the progress within a GRS R&D project regarding the extension of probabilistic analyses for spent fuel pools (SFP) supporting deterministic analyses of the accident progression inside the SFP. Its objectives are the development of a basic approach for consideration of SFP within Level 2 PSA, the quantification of the event trees. He explained that a full Level 2 PSA study has not been performed as there were no Level 1 PSA results available. The accident progression had been analysed for both PWR and BWR pools using donated plant data from the utilities of two reference plants. The results and characteristics of the analysis were presented. The lessons learned during deterministic severe accident analyses were presented as a back drop to the probabilistic approach. These included: 17

18 Very unlikely events, especially SBO with fully loaded and separated SFP only possible during repair work inside RPVEvaporation extends over several days leading to large value steam concentrations remaining inside SFP region and containment/reactor building which results in the impact of air oxidation being small for transients He concluded that for the probabilistic case, four different loadings of the SFPs have been considered in the severe accidents analyses for inside spent fuel pools of German PWRs and BWRs. The results of the SFP behaviour of a German PWR during long lasting failure of the SFP cooling have shown that: the postulated sequences are very unlikely events, leaks in the lower part of the SFP are considered as practically eliminated for German NPPs, In case of transients a lot of time is available for preventive SA measures, Oxidation under air atmosphere is less important for severe accidents starting from loss of SFP cooling, For German PWRs, it is very likely that SA sequences inside SFP run into filtered containment venting, For the BWRs, all scenarios will progress into an unfiltered release of radionuclides into environment, A first approach for a Level 2 event tree has been developed for PWR and BWR SFPs Presentation 3; Consideration of Spent Fuel Pools in the Swiss Probabilistic Safety Analyses by G. Schoen of Swiss Federal Nuclear Safety Inspectorate ENSI (Switzerland) Mr Schoen explained the legal and regulations within Switzerland that call for the use of PSA for spent fuel pools and when they must be applied. An overview was given of the status of the 4 plant specific PSA models, specifically shutdown state models. The challenges to the modelling were presented which included: Identifying a bounding case for the quantification of the various plant-specific operator actions, many thermo-hydraulic calculations have to be conducted to demonstrate the outcomes, Analysis of accidents involving SFP introduce phenomena and issues that require special attention, for example, low pressure boil-off and natural circulation of steam air mixture in fuel assemblies of differing vintage and age (radiological inventory and decay heat). The results of these analyses show amongst other things that dominating risk contributions are external events, fire and loss of RHR. In addition it is possible to assess the improvement from riskefficient back-fits, for example increasing SFP cooling system redundancy, and that Level 2 PSA for shutdown is an important technical basis for SAMG for shutdown state. 18

19 13.4 Presentation 4 Recent and Ongoing US NRC Spent Fuel Pool Research Activities by Kevin Coyne, U.S. NRC (USA) Dr Coyne described the U.S. approach to Spent Fuel Pool PSA including its history and the Key Results rom Recent NRC Research Study on the potential radiological consequences of a postulated beyonddesign-basis earthquake affecting the spent fuel pool for a U.S. Mark I boiling water reactor under both high-density and low-density loading conditions. A number of scenarios were examined and the key conclusions were presented which included that: No early fatalities were predicted for any of the scenarios studied. Implementation of protective actions may require significant land interdiction and displacement of individuals. Individual risks are dominated by long-term exposures to very lightly contaminated areas for which doses are small enough for the areas to be considered habitable- It was then explained that the key results from the associated regulatory decision were that: Expediting movement of spent fuel from the pool does not provide a substantial safety enhancement for the reference plant. The NRC continues to believe that spent fuel pools provide adequate protection of public health and safety and as a result expedited movement of fuel from the SFPs to dry cask storage is not being pursued as a new regulatory requirement. The presentation concluded with an overview of particular technical challenges remaining for SFP PSA include interfaces between unloading and loading the fuel. A number of technical clarification questions were then discussed by the members 13.5 Presentation 5 Development of PRA model for spent fuel pool by T Haruo Fujimoto of NRA (Japan) Following an introduction that related some of the work to the Fukushima Dai-ichi accident the presentation discussed the analysis for PRA model for SFP of BWR5 plant. The modelling covered a number of operational states of the SFP. The analysis presented was concentrated on two specific scenarios and explained in detail the construction of the fault trees and the subsequent analysis. The analysis showed that: A combined reactor and SFP PRA model is needed as a there are many interactions and interventions shared between the two and reactor and SFP are interconnected in some operating states. Human error and portable equipment can only be modelled when sufficient data on them is available. Detailed plant design information is required 19

20 13.6 Presentation 6 Spent Fuel Pool PSA for 1300 MWe NPPs by Nadia Juarez of EdF (France) The presentation covered EdF s work on PSA of SFPs to support the 3 rd Periodic Safety Review of the 1300 MW e reactors. It was explained that their analyses had covered two types of initiating events: Loss of cooling system, Loss of inventory, and two types of risk: Uncovering of fuel stored inside the pool, Uncovering of fuel under handling. The scope and the analysis were explained in detail. The outcomes showed that only a level 1 PSA was required as direct releases will occur when fuel is uncovered. The analysis was a simplified one only. The outcomes were that a number of improvements were made to the system including automatic stop of pumps and suction line automatic isolation were added. It was noted that several post Fukushima safety measures were still under investigation. WGRISK members asked a number of questions for clarification and understanding of the future anlysis plans for EdF 13.7 Summary of the Session Following the six presentations the Chair summarised that the meeting had heard some very different approaches, via studies and reporting of methodologies, across the three continents for dealing with the safety of spent fuel behaviour and the related safety analysis for different pool situations. It was recognised that there is still a need to address the options of delivering Level 2 PSAs and analyses examining external hazards. It was considered that it would be interesting to exchange further on the subject and perhaps look at providing a comparison between the methods, scopes and results. During the discussions around the presentations some key remarks had been made by member countries that suggested there was a need to develop some ideas to progress this subject further to get a more complete picture. Particularly, as the assumptions surrounding SFP hazards seem to vary according to country and initiator e.g. dropped loads versus seismic. The presentations consistently demonstrated that all envisaged scenarios are have a long time period and that this may drive the choice of techniques. It was important to emphasise the need to ensure that the models really reflect the actual situation. It was highlighted that WGAMA had just finished a report on Accident Analysis of spent fuel pools that had been approved at CSNI and presented a number of recommendations. This it was pointed out if shared within WGRISK would provide an opportunity to be aware of the challenges for spent fuel PSA and potentials for the future. 20

21 16.14 Send to members the number and title of the report by WGAMA on SFP LOCA NEA 31 st March WGRISK Planning 14.1 Overview of progress in existing work programme The Chair reviewed the current WGRISK programme of work and the operating framework given by the CSNI Operating Plan (particularly the CSNI Challenges and Technical Goals). It was noted that there had been no changes to direction or scope of work since the last meeting and that the only addition to the programme of work is a new task Review and comments on the updated WGRISK Integrated Plan and future work The Integrated Plan was reviewed and as with the existing work programme there were only updates to existing text and activities. The current integrated plan was approved for continued use with amendments related to the progress of the work to date Approval of WGRISK Integrated Plan and CSNI Interactions The integrated plan with amendments related to the progress of the work to date was approved for continued use until March 2016 and NEA was actioned to distribute it to the WGRISK membership and upload it onto the WGRISK website. Decision: Recognising that there was no change to the scope or direction of the WGRISK strategy or mandate the WGRISK Integrated Plan was approved to be raised to revision 15 with the minor additions and amendments presented at the meeting 16.9 Distribute the 15 th revision of the WGRISK Integrated Plan and load onto website and notify members NEA 31 st March 2015 It was noted by the Secretariat that the Operating Plans of CSNI Working Groups will change in 2016/7 and that there will need to be work by the WGRISK Bureau and members on the delivery of a revised operating plan for WGRISK during 2016 when the new CSNI plan is known. In addition the meeting was reminded that there would be Chair and Vice-Chair elections at the 2016 WGRISK annual meeting and in addition the WGRISK membership was encouraged to consider if they had an interest in joining the WGRISK Bureau. The meeting discussed the preparations for the WGRISK presentation to the June CSNI meeting that would be given by the Chair. It was agreed that the following would be incorporated in the presentation: Ongoing work, Request for approval of FIRE PSA Workshop Report, 21