Reliability analysis of a BWR plant system at startup stage - analysis by the GO-FLOW methodology with consideration of loop structures and phased mission problem -

Abstract

A reliability analysis of a boiling water reactor (BWR) system at startup stage has been performed. This paper is a useful attempt at a reliability analysis of a phased mission system (PMS) with loop structures in a real engineering system. The system startup schedule has been set based on typical BWR system. During startup, phased mission problem occurs, and loop structures are formed in the system. The solution of Boolean expression for a reliability of loop structure has been explained. Reliability analysis has been performed by the GO-FLOW methodology; a brief explanation of the GO-FLOW has been given. The system has been modeled on a GO-FLOW chart. The loop structured parts have been modeled corresponding to the solution of the Boolean equations. The chart suggests a way to model logical loop relations in a diagram without loop structure. The PMS of a BWR system has been also modeled on the same GO-FLOW chart by using the phased mission operator. An exact analytical approach for loop structured system has been selected and both the logic of loop structures and the logic of PMS have been modeled on the same GO-FLOW chart. This allows PMS with loop structures to be easily solved. The mission success probabilities of the system have been obtained in a single computation by a single GO-FLOW chart. The proposed modeling method for logical loop structures and phased mission problem is useful in evaluating reliability and/or availability of large complex engineering systems.