Three-dimensional nonlinear fracture analysis related to thermal shock

In order to improve the reliability of LWRs playing important role in the energy supply in Japan, the structural design to prevent the secondary damage under the new condition caused by an accident is necessary, and it must be confirmed that such primary accident cannot occur. The purpose of this study is to evaluate the soundness of a pressure vessel at the time of a loss of coolant accident in a LWR. The thermal impact due to the rapid temperature change of coolant is the problem in the thermo-hydraulic behavior of a pressure vessel. The injection of a large quantity of cold water from an emergency core cooling system after the loss of coolant causes severe thermal shock. In this study, prior to the analysis of thermal shock, the path integration as the parameter of nonlinear fracture mechanics was extended to three-dimensional field. The formulation was made by a new method with higher generality. The elastic and elastoplastic analyses of cracked test pieces were carried out. The experiment of thermal shock was performed on a pressure vessel steel with deteriorated quality. (Kako, I.)