Evaluation of Shutdown Risk Using FT-FREE Risk Monitoring Function
In Japan, it is specified by law that most of systems of nuclear plant must be maintained periodically during refuelling outage. Shortening of shutdown length has been pursued for the purpose of improvement in operating ratio (shorter period of Japanese BWR shutdown: 30–40 days). In order to realize higher operating ratio, Japanese nuclear utilities need to make efforts of rational shutdown management considering risk with changing configuration. In 2002, TEPCO SYSTEMS Corp. improved FT-FREE  by addition of risk management function as a user-friendly tool for workers in nuclear power plant.
In this study, the authors organized problems and assumption associated with models of BWR5 plant configured in risk monitor, by comparing risk monitor with detailed shutdown PSA and verifying its accuracy.
KeywordsBinary Decision Diagram Probabilistic Risk Assessment Water Level Decrease Plant Configuration Probabilistic Safety Assessment
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