Results of LWR snubber aging research

Abstract

This report describes the aging research results and recommendations for snubbers used in commercial nuclear power plants. Snubbers are safety-related devices used to restrain undesirable dynamic loads at various piping and equipment locations in nuclear power plants (NPPs). Each snubber must accommodate a plant`s normal thermal movements and must be capable of restraining the maximum off-normal dynamic loads, such as a seismic event or a transient, postulated for its specific location. The effects of snubber aging and the factors that contribute to the degradation of their safety performance need to be better understood. Thus, Phase II of Nuclear Plant Aging Research was conducted to enhance the understanding of snubber aging and its consequences. Pacific Northwest Laboratory staff and their subcontractors, Lake Engineering and Wyle Laboratories, visited eight sites (encompassing thirteen plants) to conduct interviews with NPP staff and to collect data on snubber aging, testing, and maintenance. The Phase II research methodology, evaluation, results, conclusions, and recommendations are described in the report. Effective methods for service-life monitoring of snubbers are included in the recommendations.