| Abstract: | This paper presents an analysis of risks associated with component outage configurations during power operation of a nuclear power plant and discusses approaches and strategies for developing a risk-based configuration control system. A configuration, as used here, is a set of component states. The objective of risk-based configuration control is to detect and control plant configurations using a risk perspective.The configuration contributions to core-melt frequency and core-melt probability are studied for two plants. Some equipment configurations can cause large core-melt frequency increases and there are a number of such configurations that are not currently controlled by technical specifications. However, the expected frequency of occurrences of the impacting configurations is small and the actual core-melt probability contributions are also generally small. Effective strategies and criteria for controlling configuration risks are presented. Such control strategies take into consideration the risks associated with configurations, the nature and characteristics of the configuration risks, and also the practical considerations such as adequate repair times and/or options to transfer to low risk configurations. Alternative types of criteria are discussed that are not overly restrictive to result in unnecessary plant shutdown, but rather motivate effective test and maintenance practices that control risk-significant configurations to allow continued operation with an adequate margin to meet challenges to safety. |
