EFFECTIVENESS EVALUATION METHODOLOGY OF THE MEASURES FOR IMPROVING RESILIENCE OF NUCLEAR STRUCTURES AT ULTRA-HIGH TEMPERATURE

抄録

The objective of this study is to develop an effectiveness evaluation methodology of the measures for improving resilience of nuclear structures at ultra-high temperature by using the failure mitigation technology. At the beginning, to identify the accident sequences having the potential to improve resilience, the characteristics of a next-generation loop-type sodium-cooled fast reactor (SFR) in Japan has been investigated by analyzing the event tree of level-1 and level-2 probabilistic risk assessment (PRA). As a result, an event of loss of heat removal systems (LOHRS) is identified. The effectiveness of the measures for improving resilience is evaluated by quantifying the reduction rate of core damage frequency (CDF) before and after the introduction of the measures for improving resilience for all the accident sequences leading to LOHRS. To examine applicability of the developed methodology, a trial evaluation has conducted for a next-generation loop-type SFR in Japan. Through the applicability examined, the method for the effectiveness evaluation was developed successfully. The refinement of the conditional success probability of the measures for improving resilience is the future work.