One of the most critical issues for determining the life extension of a nuclear power plant is the structural integrity analysis of a reactor pressure vessel (RPV). This work, examines the specifics of thermal-mechanical analysis, for the lower plenum of the reactor pressure vessel of VVER-1000, during the late in-vessel phase of a severe accident. Thermal-hydraulics and structural models of ANSYS FLUENT17.2 are prepared to obtain both the radial, axial temperatures and the stress field across the vessel wall thickness. Boundary conditions obtained from the ASTEC code are applied as input to the ANSYS FLUENT simulation for corium behavior in lower plenum: 2D meshing of vessel lower plenum, two corium layers (oxide layer and metal layer).The variation of stress, strain and damage with time at the critical axial layer are investigated. The analysis identifies the worst crack orientation and location. The results show without external flooding of the vessel, a pure thermal failure (melt-through) is highly probable due to the high thermal loads imposed by the decay power. Applied external flooding of the vessel would help the stability of the vessel and the retention of the molten corium inside the reactor pressure vessel and can prevent the vessel failure.

确定核电厂寿命延长的最关键问题之一是反应堆压力容器 (RPV) 的结构完整性分析。这项工作检查了 VVER-1000 反应堆压力容器下部压力通风系统在严重事故的晚期容器阶段的热机械分析的细节。ANSYS FLUENT17.2 的热工水力和结构模型已准备好获得径向、轴向温度和跨容器壁厚的应力场。从 ASTEC 代码中获得的边界条件被用作 ANSYS FLUENT 模拟的输入，用于下腔室中的真皮行为：容器下腔室的二维网格划分，两个真皮层（氧化物层和金属层）。应力、应变和损伤的变化与研究了临界轴向层的时间。分析确定了最坏的裂纹方向和位置。结果表明，在容器没有外部溢流的情况下，由于衰变功率施加的高热负荷，纯热故障（熔穿）的可能性很大。应用容器的外部溢流将有助于容器的稳定性和反应堆压力容器内部的熔融真皮的保留，并且可以防止容器故障。