Conceptual design for a large-scale Japan sodium-cooled fast reactor, 2; Safety design and evaluation in JSFR

Yamano, Hidemasa   ; Kubo, Shigenobu* ; Shimakawa, Yoshio*; Fujita, Kaoru  ; Suzuki, Toru; Kurisaka, Kenichi 

This paper describes safety requirements for Japan Sodium-cooled Fast Reactor (JSFR). Its specific design features are passive reactor shutdown system and re-criticality free concept against anticipated transient without scram (ATWS) accidents in design extension conditions (DECs). A fully passive decay heat removal system with natural circulation is also introduced for design-basis events (DBEs) and DECs. In this paper, the safety design accommodation in JSFR was validated by safety analyses for representative DBEs: primary pump seizure and long-term loss-of-offsite power accidents. The safety analysis also showed the effectiveness of the passive shutdown system against a typical ATWS accident. Severe accident analysis codes, validated by safety experiments, and phenomenological consideration led to the in-vessel retention without energetic recriticality. Moreover, a probabilistic safety assessment indicated to satisfy the risk target.