Monitoring method development for safety component on standby state

Abstract

Although failure probabilities of several components have been dramatically reduced so far, it is still difficult to meet the required reliability in the safety-critical applications such as Nuclear Power Plant (NPP). Most of the components of which successful operation on demand is a crucial factor of safety are in standby states. Generally it is very difficult to detect the failure of standby components since their operation status cannot be observed. Periodic testing is currently the only mean to cope with this uncertainty. In this paper, a concept of a monitoring method for standby safety components is proposed in order to guarantee their integrity The proposed method basically operates the target component for the final decision of failure. However, for this approach, we should solve some problems: the time for component operation in certain signal, the independence from the other working parts during the operation for diagnosis, and the surveillance test interval. To solve these problems, the proposed method is composed with direct and indirect inspection methods. Furthermore, to show the effectiveness of proposed monitoring method, sensitivity analysis according to the surveillance test interval was conducted.