Research and development of safety approach and safety assessment for the next generation SFR

The preliminary safety assessments have been conducted on the Japan Sodium-cooled Fast Reactor during 2005-2010 as a part of the FaCT (Fast Reactor Cycle Technology Development) project. The main conclusions and achievements related to safety were that 1) the safety analyses results that the key safety-related parameters satisfy the design limits for the anticipated operational occurrences and design accidents; 2) passive reactor shutdown mechanism [i.e. Self-Actuated Shutdown System] for the prevention of severe accidents and an in-vessel retention concept for reactor core material retention for the mitigation of severe accidents were built-in the JSFR design, 3) the core damage frequency was assessed to be less than 10-5/site-year, and risk target for earthquakes was assessed to meet the design conditions as of 2007. In the light of TEPCO's Fukushima Dai-ichi NPP accidents, the next target safety-related R and D will be focused on acquiring safer and more robust SFR system: 1) In-detail Level-1 PRA on loss of heat sink type severe accidents, 2) Unreliability factor evaluations on passive safety mechanism/system, 3) Accident scenario initiated by external events, with due consideration on SFR system pro/con features, 4) Risk-informed approach to extreme external hazards by utilizing hazard curves for clarifying reasonable design margins and 5) Establishment of harmonized safety design approach/criteria based on fundamental SFR characteristics. (author)