Procedures, methods and computer codes for the probabilistic assessment of reactor pressure vessels subjected to pressurized thermal shocks

The reactor pressure vessel (RPV), as one of the most important safety barriers of light water reactors, is exposed to neutron irradiation at elevated temperatures, which results in embrittlement of the RPV steel. One potential challenge to the structural integrity of the RPV in a pressurized water reactor is posed by pressurized thermal shock (PTS). Therefore, the safety of the RPV with regard to neutron embrittlement has to be analyzed. In this paper, the procedure and method for the structural integrity analysis of RPV subjected to PTS are presented. FAVOR and PASCAL, two computer codes widely used for the probabilistic analysis of RPV subjected to PTS, are briefly reviewed and compared. By using FAVOR, a benchmark example is presented to show the procedure and method for the integrity analysis. The influence of warm prestressing (WPS), fracture toughness and constraint effect on the integrity analysis of RPV is discussed. The Master Curve method is more realistic than the ASME model to consider the analysis of fracture toughness and thus is recommended. In order to transfer the fracture toughness data from test specimen to the RPV, local approach provides a probabilistic method.