Application of Probabilistic Fracture Mechanics Analysis on BWR Recirculation Piping Systems

In recent years, the probabilistic fracture mechanics (PFM) approach has been widely applied to estimate the fracture risk of nuclear power plant piping systems. In the paper, the probabilistic fracture mechanics code, PRO-LOCA, developed by the Probabilistic Analysis as a Regulatory Tool for Risk Informed Decision Guidance (PARTRIDGE) project, is employed to practically evaluate the fracture probability of the recirculation piping system welds in a Taiwan domestic boiling water reactor (BWR) nuclear power plant. To begin with, the models based on the real situation of the recirculation piping welds are built. Then, the probabilities of through-wall cracking, leak with different rates, and rupture on the welds considering both in-service inspection and leak detection are analyzed. Meanwhile, the effects of probability of detection curves of ISI on the piping are simulated. Further, the efficiencies of performing the induction heating stress improvement and weld overlay are also studied and discussed. The present work could provide a reference of operation, inspection and maintenance for BWR plants in Taiwan.