Investigation on Constraint Effect of a Reactor Pressure Vessel Subjected to Pressurized Thermal Shocks

The integrity of a reactor pressure vessel (RPV) related to pressurized thermal shocks (PTSs) has been extensively studied. This paper introduces the method of using fracture mechanics for the integrity analysis of a RPV subjected to PTS transients. A 3-D finite element (FE) model is used to perform thermal and fracture mechanics analyses by considering both elastic and elastic–plastic material models. The results show that the linear elastic analysis leads to a more conservative result than the elastic–plastic analysis. The variation of the T-stress and Q-stress (crack tip constraint loss) of a surface crack in a RPV subjected to PTSs is studied. A shallow crack is assumed in the RPV and the corresponding constraint effect on fracture toughness of the material is quantified by the K–T method. The safety margin of the RPV is larger based on the K–T approach than based only on the K approach. The J–Q method with the modified boundary layer formulation (MBL) is used for the crack tip constraint analysis by considering elastic–plastic material properties. For all transient times, the real stress is lower than that calculated from small scale yielding (SSY) due to the loss of crack tip constraint.