Effects of Aging and Service Wear on Main Steam Isolation Valves and Valve Operators

摘要

In recent years main steam isolation valve (MSIV) operating problems have resulted in significant operational transients (e.g., spurious reactor trips, steam generator dry out, excessive valve seat leakage), increased cost, and decreased plant availability. A key ingredient to an engineering-oriented reliability improvement effort is a thorough understanding of relevant historical experience. A detailed review of historical failure data available through the Institute of Nuclear Power Operation's Nuclear Plant Reliability Data System has been conducted for several types of MSIVs and valve operators for both boiling-water reactors and pressurized-water reactors. The focus of this review is on MSIV Failures modes, actuator failure modes, consequences of failure on plant operations method of failure detection, and major stressors affecting both valves and valve operators.