Effect of pressurized thermal shock on the failure of base-cladding composite wall with different thickness ratios in thermal-mechanical coupling field

In the thermal-mechanical couplin-g field caused by pressurized thermal shock (PTS), crack propagation in nuclear reactor pressure vessel (RPV) is easy to occur in the base wall covered by cladding material. Especially when the temperature of base material is lower than the nil-ductile transition temperature, brittle fracture could occur. Considering that cladding has good thermal insulation effect under thermal shock, the finite element models of the cracked RPVs with different thickness ratios of base wall to the total vessel wall are established. Combined with the specified damage model, extended finite element method is used to analyze the structural integrity. The obtained allowable internal pressure is compared with the peak internal pressure during the PTS transient. Then the effects of the vessel diameter and nozzle diameter on the structural failure are studied. The results show that their influence on the bearing capacity of the structure is far less than that of the thickness ratios of base wall. The research results may provide an important reference for the design and optimization of RPV under high temperature, high pressure and PTS conditions.