From the Viewpoint of Maintenance, the Probabilistic Integrity Evaluation of Reactor Pressure Vessel
阮 小勇 Xiaoyong RUAN 中筋 俊樹 Toshiki NAKASUJI 森下 和功 Kazunori MORISHITA
Computational Fluid Dynamics Finite Element Method Pressurized Thermal Shocks Probabilistic Integrity Evaluation Reactor Pressure Vessel
The structural integrity of a reactor pressure vessel (RPV) is important part of nuclear power plant safety. 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. In the present study, optimization of RPV maintenance is considered, where two different attempts are made to investigate the RPV integrity during PTS loading by employing the deterministic and probabilistic methodologies. For the deterministic integrity evaluation, 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 evaluation, a more accurate distribution of SIF on the RPV is calculated. By comparing the distribution thus obtained with the fracture toughness included as a part of the master curve, the dependence of fracture probabilities on the position inside the RPV is obtained. Using the distribution of fracture probabilities in RPV, the priority of the inspection and maintenance is discussed.