Nuclear Safety 2021 Long-Term Management and Actions for a Severe Accident in a Nuclear Power Plant Status Report NEA Nuclear Safety Long-Term Management and Actions for a Severe Accident in a Nuclear Power Plant Status Report © OECD 2021 NEA No. 7506 NUCLEAR ENERGY AGENCY ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENT ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENT The OECD is a unique forum where the governments of 37 democracies work together to address the economic, social and environmental challenges of globalisation. The OECD is also at the forefront of efforts to understand and to help governments respond to new developments and concerns, such as corporate governance, the information economy and the challenges of an ageing population. The Organisation provides a setting where governments can compare policy experiences, seek answers to common problems, identify good practice and work to co-ordinate domestic and international policies. The OECD member countries are: Australia, Austria, Belgium, Canada, Chile, Colombia, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Israel, Italy, Japan, Latvia, Lithuania, Luxembourg, Mexico, the Netherlands, New Zealand, Norway, Poland, Portugal, Korea, the Slovak Republic, Slovenia, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States. The European Commission takes part in the work of the OECD. OECD Publishing disseminates widely the results of the Organisation’s statistics gathering and research on economic, social and environmental issues, as well as the conventions, guidelines and standards agreed by its members. This work is published under the responsibility of the Secretary-General of the OECD. The opinions expressed and arguments employed herein do not necessarily reflect the official views of the member countries of the OECD or its Nuclear Energy Agency. NUCLEAR ENERGY AGENCY The OECD Nuclear Energy Agency (NEA) was established on 1 February 1958. Current NEA membership consists of 34 countries: Argentina, Australia, Austria, Belgium, Bulgaria, Canada, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Luxembourg, Mexico, the Netherlands, Norway, Poland, Portugal, Korea, Romania, Russia, the Slovak Republic, Slovenia, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States. The European Commission and the International Atomic Energy Agency also take part in the work of the Agency. The mission of the NEA is: – to assist its member countries in maintaining and further developing, through international co-operation, the scientific, technological and legal bases required for a safe, environmentally sound and economical use of nuclear energy for peaceful purposes; – to provide authoritative assessments and to forge common understandings on key issues as input to government decisions on nuclear energy policy and to broader OECD analyses in areas such as energy and the sustainable development of low-carbon economies. Specific areas of competence of the NEA include the safety and regulation of nuclear activities, radioactive waste management and decommissioning, radiological protection, nuclear science, economic and technical analyses of the nuclear fuel cycle, nuclear law and liability, and public information. The NEA Data Bank provides nuclear data and computer program services for participating countries. This document, as well as any [statistical] data and 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. Corrigenda to OECD publications may be found online at: www.oecd.org/about/publishing/corrigenda.htm. © OECD 2021 You can copy, download or print OECD content for your own use, and you can include excerpts from OECD publications, databases and multimedia products in your own documents, presentations, blogs, websites and teaching materials, provided that suitable acknowledgement of the OECD as source and copyright owner is given. All requests for public or commercial use and translation rights should be submitted to [email protected]. Requests for permission to photocopy portions of this material for public or commercial use shall be addressed directly to the Copyright Clearance Center (CCC) at [email protected] or the Centre français d'exploitation du droit de copie (CFC) [email protected]. Cover photos: Three Mile Island NPP, Chernobyl NPP (hujgcemj70, Creative Commons) and Fukushima Daiichi NPP (IAEA). TABLE OF CONTENTS Table of contents List of abbreviations and acronyms .................................................................................................... 9 Executive summary .............................................................................................................................. 11 Chapter 1. Introduction ........................................................................................................................ 13 1.1. Background ................................................................................................................................ 13 1.2. Objectives and scope ................................................................................................................ 13 1.3. Structure of the report ............................................................................................................. 14 Chapter 2. State of the art of long-term management and actions .............................................. 15 2.1. Feedback from Three Mile Island unit 2, Chernobyl and Fukushima Daiichi accidents .................................................................................................................................... 15 2.2. Status of long-term post-accident management and actions in NEA member countries .................................................................................................................................... 92 Chapter 3. Approach to long-term post-accident management and actions ........................... 101 3.1. Definition and scope .............................................................................................................. 101 -3.2. Long term controlled state functions and monitoring ...................................................... 103 3.3. Possible accident/plant damaged states classification for long-term management ........ 105 3.4. Methods and tools for risks and issues ranking for long-term management ................ 114 3.5. Action identification and ranking table exercise ............................................................... 134 Chapter 4. Summary of challenges and main issues for long-term management ................. 163 Regulatory and organisational aspects ........................................................................................ 163 Relation to the public during long-term management .............................................................. 164 Risk evaluation for long-term management................................................................................ 164 Radioprotection in long-term management ................................................................................ 165 Coolable configuration and confinement of radioactivity ......................................................... 165 Development and use of unique systems, equipment and instrumentation ......................... 166 Contaminated water treatment .................................................................................................... 167 Site clean-up, de-contamination and waste management ....................................................... 168 Fuel retrieval .................................................................................................................................... 168 Chapter 5. Recommendations for enhancing long-term post-accident management and for future research ................................................................................................. 171 5.1. Recommendations related to knowledge consolidation for cross-cutting issues ......... 171 5.2. Recommendations related to provisions development for cross-cutting issues ........... 174 5.3. Recommendations related to knowledge consolidation for specific long-term management ........................................................................................................................... 177 5.4. Recommendations related to provisions developments for specific long-term management and actions ...................................................................................................... 181 LONG-TERM MANAGEMENT AND ACTIONS FOR A SEVERE ACCIDENT IN A NUCLEAR POWER PLANT, NEA No. 7506, © OECD 2021 3 TABLE OF CONTENTS Appendix A. Questionnaire on long-term management and actions for a severe accident in a nuclear power plant ........................................................................... 183 Appendix B. Simplified application of SA-LT categorisation from level 2 probabilistic risk assessment release category figures of merit ............................................... 187 Appendix C. Fault tree analysis and event tree analysis ........................................................... 195 Appendix D. SA-LT management schematic guiding procedure ............................................... 197 References ….... ...................................................................................................................................