Monitoring method development for safety component on standby state

In the nuclear power plant, there are several safety components which are not in operation during normal plant condition but are expected to be operated in case of an emergency situation. Soundness of these components can be checked only by periodic testing which is usually performed with fixed interval since they are not in operation status during normal operation. In some extreme cases, it can be done only at the overhaul period. In addition, it is difficult to check internal elements without invasive decomposition inspection. When a demand for operation occurs to a certain component, the corresponding function is expected to be carried out with very high reliability. If the testing period is large, however, this periodic testing hardly guarantees the successful operation of safety components. In this study, a monitoring method checking the soundness of the components under the standby state was proposed to guarantee the successful functioning of the safety components. For this purpose, the concept of monitoring methods was described and applied to a motor operated valve (MOV). In addition, the effectiveness of the proposed monitoring method was shown by estimating the risk reducing effect