Long-term Structural Integrity Analysis for Reactor Pressure Vessel under In-vessel Retention Condition

In-vessel retention (IVR) is one of appropriate severe accident mitigation strategies for generation Ⅲ nuclear power plant (NPP), and assurance of prevention against to thermal failure and structural failure of reactor pressure vessels (RPV) is the prerequisite of IVR. In the paper, the finite element model of RPV considering the lower head melting was established, the creep calculation was carried out after the temperature field analysis, and the stress-strain responses for different time were obtained. By means of choosing representative evaluation sections and applying the accumulative damage theory based on Larson-Miller parameter, the creep damage calculation and evaluation were conducted. The results show that the failure modes of creep rupture will not happen for RPV under IVR condition when a certain amount of internal pressure exist, and the long-term structural integrity can be ensured. The approach employed in this paper can be utilized in structural integrity evaluation of RPV under IVR for other new type NPPs.