Aging and service wear of check valves used in engineered safety-feature systems of nuclear power plants. Volume 1. Operating experience and failure identification

This is the first in a series of three reports on check valves (CVs) to be published under the Nuclear Plant Aging Research Program, and it addresses the subject of Detection of Defects and Degradation Monitoring of Nuclear Plant Safety Equipment. The program is concerned with the evaluation and identification of practical and cost-effective methods for detecting, monitoring, and assessing the severity of time-dependent degradation (aging and service wear) of CVs in nuclear plants. These methods will allow degradation trends to be established prior to failure and allow guidance for effective maintenance to be developed. The topics of interest for this first report are failure modes and causes resulting from aging and service wear, manufacturer-recommended maintenance and surveillance practices, and measurable parameters (including functional indicators) for use in assessing operational readiness, establishing degradation trends, and detecting incipient failure. The results presented are based on information derived from operating experience records, nuclear industry reports, manufacturer-supplied information, and input from plant operators. Failure modes are identified for CVs. For each failure mode, failure causes are listed by subcomponent or subassembly, and parameters potentially useful for detecting degradation, which could lead to failure, are tabulated.