Risk-Based Inservice Testing Dev of Gdlns Light Water Reactor Nuclear Pwr Plnt Comp: Volume 2 Pt 2

This ASME research report is the second in a series entitled, RISK-BASED INSERVICE TESTING DEVELOPMENT OF GUIDELINES, which describes a general risk-based process that can be used to develop inservice testing guidelines for any plant or facility. This document, VOLUME 2, is the first specific application and is directed at the inservice testing of light water reactor (LWR) nuclear power plant components, particularly for pumps and valves. Integrated risk-based operation, maintenance, and regulation at nuclear power plants offer the potential to make plants safer, lower operating costs, and optimize resources for both plant operators and the regulatory authority. Risk-based inservice testing (IST) programs will help achieve these benefits by basing test requirements on the failure modes of a component and its associated risk rather than on a prescriptive set of general requirements that were developed using implicit risk insights. The new risk based testing strategy is structured to improve testing for the more safety significant components and to reduce unnecessary testing requirements for the less safety significant components. Thus this approach is not an attempt to simply reduce costs by relaxing safety standards. Whereas the current programs based on the prescriptive requirements demand an inordinate amount of resources throughout plant organizations, implementation of risk based IST programs will allow plant operators a degree of flexibility in concentrating their resources on the more safety significant components and their inherent failure modes. In addition, developing a more sound technical basis for the testing selected for each component is less arbitrary and should lead to an enhanced professional technical understanding between plant operators and the regulatory authority. The recommended process for applying risk based methods to the IST of pumps and valves in nuclear power plant systems is centered on three major areas: ranking of component importance into two IST component groups, development of risk based IST programs for the two groups – implementation of the risk-based IST program, including an assessment of the predicted effect of a revised program on safety, and a feedback of the IST program results into the above steps of the risk based process. The research work that is reported in this document provides a starting point to implement risk based inservice testing in the nuclear industry. Several organizations will have to work closely together to achieve this goal. This close coordination of organizations involved in IST will significantly reduce the burden on industry and regulators while maintaining a high level of safety. This application should be integrated with the other risk based and performance based iniatives in order to further enhance these potentially significant benefits.