Development of failure mitigation technologies for improving resilience of nuclear structures, 30; Effectiveness evaluation of the measures for improving resilience at ultra-high temperatures

Onoda, Yuichi ; Nishino, Hiroyuki ; Kurisaka, Kenichi ; Yamano, Hidemasa  

Focusing on the accident sequence leading to ultra-high temperatures due to loss of heat removal systems, the effectiveness of the measures for improving reactor structural resilience was evaluated for next-generation sodium-cooled fast reactors. Focusing on countermeasures to promote heat dissipation from the reactor vessel, the cooling performance of these measures was evaluated. In addition, we examined the uncertainty of accident progression and the success or failure of the measures for improving resilience, and evaluated the branch probability of the event tree. As a result, the reduction rate of the core damage frequency due to the assumed countermeasures was quantified.