OUTAGE PRA METHODOLOGY FOR MULTI-UNIT CANDU GENERATING STATIONS

摘要

A Level 1 Internal Events Outage Probabilistic Risk Assessment (PRA) methodology was developed by AMEC NSS Ltd. for multi-unit Canadian Deuterium Uranium (CANDU) nuclear generation stations. The methodology was developed in cooperation with utilities, Ontario Power Generation and Bruce Power, owners and operators of multi-unit CANDU stations in Ontario, Canada. The methodology provides a generic framework that examines the plant operating states (POSs) where one unit is shutdown and placed in a guaranteed shutdown state (GSS) for outage maintenance while at least one adjacent unit is operating. The POS, initiating event, event tree, fault tree, reliability data and human reliability analyses methodologies are defined with the aim of determining the risk of core damage resulting from internal events occurring at the outage unit while in GSS. The scope of the analysis is limited to internal events, e.g. process and human interaction related events, for the outage unit in GSS and the adjacent units. Events originating in the adjacent units can be analyzed for their impact on the risk of core damage for the outage unit in GSS. The methodology is applicable to different CANDU designs and outage configurations, allowing each station to develop a comprehensive and detailed PRA for plant outage maintenance operation in GSS. This PRA can then be used to provide support for maintaining station Safety Goals, risk informed decision making and outage maintenance planning. This paper gives an overview of the methodology.