Development of Probabilistic Fracture Mechanics Code for Primary System Pipes and Application for RI-ISI

Recently, the use of risk information in regulatory decision as well as operation and maintenance of nuclear power plant has been gradually increased. Application of risk information to optimize the inservice inspection of nuclear piping system has been one of such an attempt in Korea. An accurate evaluation of the risk, or failure probability for each pipe subcomponent is essential to the application of the risk-informed inservice inspection. For this purpose, a probabilistic fracture mechanics code based on Monte Carlo simulation techniques was developed to handle various flaw shapes and orientations in nuclear piping system. Then, the failure probabilities of various subcomponents of the main coolant loop in a pressurized water reactor were calculated, and the relative risk ranking was determined using the plant’s data. Also, the effects of in-service inspection and frequency on the risk were investigated. Finally, the application of the probabilistic fracture mechanics methods to the risk-informed inservice inspection of nuclear piping system was discussed.