Safety design approach for external events in Japan Sodium-cooled Fast Reactor

Yamano, Hidemasa   ; Kubo, Shigenobu ; Tani, Akihiro*; Nishino, Hiroyuki  ; Sakai, Takaaki

This paper describes a safety design approach for external events in the design study of Japan Sodium-cooled Fast Reactor, in parallel to the approach for internal events which is conformed to the defence-in-depth principle in IAEA. An emphasis is the addition of new eventcategory that has to be considered in design, i.e., introduction of "design extension condition (DEC)." In this study, the DEC category was extended to the external events. In addition to seismic design, other external events such as tsunami, strong wind and abnormal temperature were addressed in this study. From a wide variety of external events consisting of natural hazards and human-induced ones, a screening method was developed in terms of sitting, consequence, frequency to select representative events. Design approaches for these events were categorized on the probabilistic, statistical and deterministic basis.