Study on structural integrity of reactor pressure vessel with various ablation under core meltdown accident

Abstract

In-vessel retention is an important measure to alleviate the core meltdown accident in the third generation nuclear power plant. External Reactor Vessel Cooling(ERVC) is the key to the successful implementation of IVR. Due to the ablation caused by the molten pool in the lower head, the reactor pressure vessel(RPV) has various wall ablation and thinning, which poses a great threat to the integrity of the pressure boundary of the RPV. Based on the boiling water RPV as the research object, the model is established for the RPV with various ablation and local thinning by finite element method(FEM). The stress/strain response of the structure is calculated and analyzed under the core meltdown accident. The plastic and creep damage are assessed for the RPV in terms of its evolution and distribution with continuum damage mechanics(CDM). Due to the existence of internal pressure within the RPV, the effect of pressure on creep and plastic rupture is also studied within the required 72 h. According to the criterion of ductile exhaustion, the results show that the increase of internal pressure further reduces the load-bearing capacity of RPV.