As a next-generation plant, a large-scale Japan sodium-cooled fast reactor (JSFR) adopts a number of innovative technologies in\r\norder to achieve economic competitiveness, enhanced reliability, and safety. This paper describes safety requirements for JSFR\r\nconformed to the defense-in-depth principle in IAEA. Specific design features of JSFR are a passive reactor shutdown system and\r\na recriticality-free concept against anticipated transients without scram (ATWS) in design extension conditions (DECs). A fully\r\npassive decay heat removal system with natural circulation is also introduced for design-basis events (DBEs) and DECs. In this\r\npaper, the safety design accommodation in JSFR was validated by safety analyses for representative DBEs: primary pump seizure\r\nand long-term loss-of-offsite power accidents. The safety analysis also showed the effectiveness of the passive shutdown system\r\nagainst a typical ATWS. Severe accident analysis supported by safety experiments and phenomenological consideration led to the\r\nfeasibility of in-vessel retention without energetic recriticality. Moreover, a probabilistic safety assessment indicated to satisfy the\r\nrisk target.
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