Development of failure mitigation technologies for improving resilience of nuclear structures, 7; Effectiveness evaluation technology of the measures for improving resilience at ultra-high temperatures

Onoda, Yuichi ; Nishino, Hiroyuki  ; Kurisaka, Kenichi ; Yamano, Hidemasa   ; Demachi, Kazuyuki*

In order to evaluate the effectiveness of the measures for improving resilience at ultra-high temperatures, a concept of evaluation focusing on core damage frequency was proposed. Assuming loss of heat removal systems event after reactor shutdown which may result in core damage in sodium-cooled fast reactors, the measures for improving resilience which enable to recover the safety functions at ultra-high temperatures are identified: one is to retain the primary coolant using failure mitigation technology, and the other is to add a heat removal system that can be used under ultra-high temperature conditions. The core damage frequencies were calculated preliminarily and their reduction effect was estimated by comparing them before and after the introduction of the measures for improving resilience.