Abstract
Nuclear power plants use lots of valves in different applications. Each valve type has specific tasks to perform. The vast majority of safety related valves are monitored during plant operation to ensure they are operable and can be relied upon to do their design functions. Unfortunately, check valves do not fall in the category of valves that can be readily monitored because of how they are designed; usually with all operating components internal to the pressure boundary. Since they are not easily monitored externally, plant operators typically disassemble and inspect them to assess the internal conditions and determine what actions to take, which can be either repair, replace, or use as found. However, not all check valves get inspected for a number of reasons resulting in some valves running to failure. In this paper, the authors present actions the nuclear industry has used to comply with ASME OM Code requirements (8) on check valves and US NRC regulatory activities in this area. The paper also covers the role the nuclear industry and other organizations have played to improve check valve reliability.
