低温と積雪の重畳事象に対する確率論的リスク評価手法の開発

抄録

The objective of this study is to develop probabilistic risk assessment (PRA) methodology for combination event of low temperature and snow by focusing attention on decay heat removal system (DHRS) of sodium-cooled fast reactor. For this combination event, annual excess probability depending on the hazard intensity was statistically estimated based on the meteorological data. Event tree was developed by considering the impact of low temperature and snow on DHRS: e.g., plug at the air intake of ultimate heat sink and of emergency diegel generator due to accumulated snow, failure of air intake filter due to deposited snow, possibility of freezing of cooling circuits. Recovery actions (i.e., snow removal and filter replacement) were considered in the event tree. Quantification of the event tree showed that dominant core damage sequence is loss of access route for snow removal against the combination event at daily snowfall of 3m/day continued during 24h.