Sequence Analysis After Core Damage to Determine Safety Level of the AP1000:

Abstract

In safety analysis, one of important parameters is core damage as this occasion can cause fission products to release. In that regard, all possible sequences afterward must be analyzed in order to ensure that all events have been considered, because each sequence has different consequence. The objective of this research is to determine the probability of event sequences after core damage so safety level of AP1000 could be known. The AP1000 reactor is chosen as the research object because currently many units are under construction. In this research the accident sequences were analyzed by using event tree, and the probability of top event was calculated by fault tree analysis. Meanwhile, the failure rates of component or operator action were collected from IAEA documents and also published documents of the AP1000 from Westinghouse Inc. The analysis results show that probability of event sequences which causes fission product release is ranging from 10−2to 10−26 and the total probability is 3,48 x 10−2. Based on this analysis, it can be concluded that the AP1000 has high safety level because the probability of event sequences leading to fission product release is small. Moreover, if these results are joined with core damage probability then probability of fission product release would be less than 10−9.