Evaluation of the Integrity of Reactor Pressure Vessels in Nuclear Power Plants during Pressurized Thermal Shock Events

Abstract

The structural integrity of a reactor pressure vessel (RPV) is important for the safety of a nuclear power plant. Pressurized thermal shock (PTS) takes place when the emergency core cooling system (ECCS) is operated and the coolant water is injected into the RPV due to a loss-of-coolant accident (LOCA). With the neutron irradiation, PTS loading may lead a RPV to fracture. Therefore, it is necessary to evaluate the performance of RPV during PTS loading to keep the RPV's safety.
In the present study, the deterministic and probabilistic methods are made to investigate the RPV integrity during PTS loading. For the deterministic integrity assessment, 3D-CFD and finite element method (FEM) simulations are performed, and stress intensity factors (SIFs) are obtained as a function of crack position inside the RPV. As to the probabilistic integrity assessment, a more accurate distribution of SIF on the RPV is calculated. By comparing the distribution obtained with the fracture toughness included as a part of the master curve, the probabilistic integrity assessment method which can obtain the fracture probability on the RPV is finally investigated.