Highlights From the Work of the NEA on Impacts of the Fukushima Accident. Javier Reig Head, Nuclear Safety Division

Transcription

1 Highlights From the Work of the NEA on Impacts of the Fukushima Accident Javier Reig Head, Nuclear Safety Division 1

2 Areas for NEA Post- Accident Activities 1 Accident Management and Progression a. TRANSITION: Review of on-site accident management programmes and procedures to address the transitional conduct of operations from normal to accident conditions to severe accident conditions, and to the implementation of protective measures under the emergency preparedness plans. This includes onsite and offsite decision-making processes. b. ACCIDENT PROGRESSION: Enhanced understanding of accident progression analyses methods and techniques. c. HUMAN PERFORMANCE: Human and organisational performance issues under accident response conditions. d. OFFSITE: Improvement of off-site emergency preparedness by sharing knowledge on core melt accident progression and source term quantification to improve off-site emergency procedures and technical tools. 2 Crisis or Emergency Communications (primary information exchange between CNRA and CRPPH) a. PUBLIC: Communication with the public, media and other stakeholders. b. REGULATORS: Communication with the regulators in other countries and with international organisations, such as the International Atomic Energy Agency (IAEA) and the Inter-Agency Committee on Radiological and Nuclear Emergencies (IACRNE). c. ONSITE OFFSITE: Crisis communications between onsite and offsite emergency response organisations. 3 Reassessment of Defence-in-Depth 4 Evaluating the methodologies for defining and assessing initiating internal and external events, including coupled, as well as methodologies defining the design basis criteria 5 Reassessment of Operating Experience and prior opportunities to identify or address conditions that could challenge nuclear safety. a. OP E: Evaluation of operating experience for events that may be precursors to future events that could challenge the safety of nuclear power plants given the insights from Fukushima. b. RESEARCH: Review and analysis of safety research relevant to the analysis of the accident. 6 Balancing deterministic and probabilistic approaches to regulatory decision making 7 Regulatory Infrastructure (non-cross committee that is planned and implemented following previously established processes) 8 Radiological Protection and Health Physics (non-cross committee activity that is planned and implemented following previously established processes) 9 Decontamination and recovery (onsite and offsite) (non-cross committee activity that is planned and implemented following previously established processes) 2

3 Activities Initiated Within CNRA The CNRA Task Group on Accident Management (TGAM) Defence-in-Depth (DiD) concept and Implementation (CNRA in conjunction with CSNI) Review of Precursor Events (WGOE) Nuclear Site Selection and Preparation (WGRNR) Crisis Communication (WGPC) 3

4 Defence-in-Depth (DiD) concept and Implementation (CNRA in conjunction with CSNI) NEA Member countries agree that the concept of DiD is sound, even if improvements may be discussed. However, NEA Member countries may have implemented the concept in different ways and to differing degrees particularly with respect to prevention and mitigation of severe accidents that could be initiated by rare external events including in combination. The level of attention needed in applying the DiD concept to external (and internal) hazards may need further consideration. CNRA and CSNI are holding a Joint Workshop for NEA Member countries on the Challenges and Enhancements to DiD in light of the Fukushima Daiichi Accident in June

5 Post Fukushima CSNI Work Following the process established through the Tri-Bureau, the CSNI has undertaken eight (8) activities to address technical issues from the Fukushima Daiichi NPS accident: Technical Opinion Paper on Filtered Containment Venting (WGAMA) Output: a comprehensive summary of the current status of the technology and venting strategies as well as developments required for possible improvements to filtration technologies Status Report on Hydrogen Generation, Transport and Management (WGAMA) Output: a comprehensive summary of hydrogen risk management technology and strategies 5

6 Post Fukushima CSNI Work - 2 Status Report on Spent Fuel Pool under Loss of Cooling Accident Conditions (WGAMA and WGFS) Output: a summary of spent fuel pool accident phenomenology and mitigation measures, and a guide for further research activities Metallic Component Margins under High Seismic Loads (MECOS) (WGIAGE) Output: a report documenting best practices for the analysis of ageing of passive metallic components (degradations, cracks or local thinning, reduced material properties, etc.) subjected to high seismic loads. Human Performance and Intervention under Extreme Conditions (WGHOF) Output: a summary of HOF challenges during extreme events, good HOF practises and knowledge gaps, and proposed HOF principles for human performance and interventions under extreme conditions 6

7 Post Fukushima CSNI Work - 3 Workshop on Natural External Events including Earthquake (WGRISK) Output: a report on commendable practices and experience gathered on PSA methodologies for natural external events. Workshop on the Robustness of Electrical Systems of NPPs in Light of the Fukushima Daiichi Accident (Task Group) Output: a report describing the technical basis of the provisions already taken or planned in each country after the Fukushima accident, regarding the sources, the distribution systems and the loads. International benchmarking project of fast-running software tools for the estimation of fission product releases during accidents at nuclear power plants (WGAMA) Output: a state-of-the-art report for simple tools to estimate fission product releases, including areas for improvement. 7

8 New Joint International Research Projects Since Fukushima there have been 3 new projects initiated that will also address, to varying degrees, lessons learned from Fukushima ATLAS - Advanced Thermal-hydraulic Test Loop for Accident Simulation Output: investigation of design extension conditions to identify major thermalhydraulic scenarios and provide guidance for accident management HYMERES - Hydrogen Mitigation Experiments for Reactor Safety Output: improved understanding of the hydrogen risk phenomenology in containment that can enhance its modelling in support of nuclear power plant safety assessments PKL phase 3 - PWR Transient Tests Under Postulated Accident Scenarios Output: address current safety issues related to beyond design basis accidents with significant core heat-up, i.e. station blackout scenarios or loss of coolant accidents in connection with failure of safety systems. Demonstrate the efficiency of long term initiated AM measures. 8

9 New Joint International Research Projects After Fukushima a new project was initiated following the proposal from Japan to improve severe accident codes and learn the evolution of the accident in the three units BSAF - Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station Project Output: Phase I will be a full-scope Severe Accident analysis for the first ~6 days of accident events. Modelling results from phase one will inform decommissioning processes and measurements, which in turn provide data for further phases of modelling and for improving severe accident codes and analysis Results will be useful for Japan to support planning of decommissioning activities and useful for other countries to improve the simulation of severe accident codes 9

10 Summary Focus on high priority issues where there are differences in approaches or implementation Mid to Long term activities Conceptual areas (Defence in Depth, Accident management) as well as technical areas (Containment response, Spent Fuel Pools) Status report to be discussed by CNRA next June. Contribution to IAEA report in