Multi-crack growth/coalescence simulation and its role in passive component leak-before-break concept

In order to demonstrate the role of multi-crack growth/coalescence in the leak-before-break concept, Monte Carlo method is applied to simulate multiple crack growth/coalescence behavior which are quite common to component vulnerable zone such as weld. For the multi-crack behavior simulation, typical component vulnerable zone is postulated to have randomly distributed initial cracks. The parameters such as crack number, crack location and crack length are all treated as random variables. The crack distribution parameters are assumed according to generic knowledge available. For single crack situation, the crack size with detectable leak and the critical crack size with unstable propagation are cited from literature. For the multi-crack situation, an equivalent crack-opening area is used to identify the detectable leak. The simulation results show that, for LBB concept related components, the existence of multiple cracks might lead to much shorter leak-free time and much shorter allowable response time compared with those in single crack situation. (orig.)