Operating experience and aging assessment of component cooling water systems in pressurized water reactors

An aging assessment of Component Cooling Water (CCW) systems in Pressurized Water Reactors (PWRs) was performed as part of the Nuclear Plant Aging Research (NPAR) program. The objective of the NPAR program are to provide a technical basis for the identification and evaluation of degradation caused by age in nuclear power plant applications. The information generated will be used to assess the impact of aging on plant safety and to develop effective mitigating actions. Aging in the CCW system was characterized using the aging and Life Extension Assessment Program (ALEAP) Systems Level Plan developed by Brookhaven National Laboratory. Failure data from various national data bases were reviewed and analyzed to identify predominant failure modes, causes and mechanisms in CCW systems. Time-dependent failure rates for major components were calculated to identify aging trends. Plant specific data were obtained and evaluated to supplement data base results. A computer program (PRAAGE) was developed and implemented to model a typical CCW system design and perform Probabilistic Risk Assessment (PRA) calculations. Time-dependent failure rates were input to the program to evaluate the effects of aging on component importance and system unavailability. Changes in component importance and system unavailability with age were observed and are discussed. 20 refs., 73 figs., 18 tabs