Probabilistic ageing and risk analysis tools for nuclear piping

Probabilistic fracture mechanics (PFM) is used to demonstrate the safety of nuclear power plant (NPP) components. With PFM, fracture mechanics methods and reliability theory are combined for assessing the reliability of cracked components. This paper describes PFM calculations for the leak-before-break (LBB) of piping using the pc-PRAISE and PRO-LOCA computer codes. The procedure, methods and computer codes for probabilistic piping assessment are briefly reviewed and compared. The codes consider the failure mechanisms of stress corrosion cracking (SCC) and fatigue for piping and operating conditions that are susceptible to cracking. Two benchmark cases are used to demonstrate the applicability of the computer codes and probabilistic methods in nuclear piping. Sensitivity calculations show that the predicted failure probabilities are sensitive to the operating pressure and temperature, in-service inspection interval and welding residual stress.