Effects of Age on Nuclear Power Plant Containment Cooling Systems

摘要

A study was performed to assess the effects of aging on the performance and availability of containment cooling systems in U.S. commercial nuclear power plants. The effects of age were characterized for the containment cooling system by reviewing and analyzing failure data from national databases, as well as plant-specific data. The predominant failure causes and aging mechanisms were identified, along with the components that failed most frequently. Current inspection, surveillance, and monitoring practices were also examined. A containment cooling system unavailability analysis was performed to examine the potential effects of aging by increasing failure rates for selected components. A commonly found containment spray system design and a commonly found fan cooler system design were modeled. Parametric failure rates for those components in each system that could be subject to aging were accounted for in the model to simulate the time-dependent effects of aging degradaton, assuming no provisions are made to properly manage it. System unavailability as a function of increasing component failure rates was then calculated.