Large-scale reliability analysis by decomposition and integration

In this decade, the risk analysis for light water reactor nuclear power plants and other related facilities has become of remarkable importance. However, the plants or facilities to be analyzed are, in most cases, large-scale and complicated. Fault tree analysis for such a large-scale and complicated system often requires extremely time- and cost-consuming works. In this paper, a new method for the reliability analysis of the large-scale and complicated system (large-scale reliability analysis, hereinafter) is presented. The method enables the large-scale reliability analysis to be carried out practically and efficiently by decomposing the system into several subsystems and integrating the results obtained through reliability analyses for subsystems. For the demonstration of the methodology, a reliability analysis for a safety-related system of BWR nuclear power plants is provided. The merits of the method are confirmed by this application and the validity is shown by comparing the result with that of Interim Reliability Evaluation Program