Melt pool configuration in the lower plenum of reactor pressure vessel (RPV) is the most controversial issue in the assessment methodology for severe accident strategy in-vessel retention (IVR). The generally accepted two-layer and three-layer melt pool configurations and a four-layer configuration which may form during the procedure of stable melt pool configuration formation were described. Heat transfer models of the three configurations were established, and effects of the three models to RPV integrity of reactors with different power levels were analyzed. The results show that RPV safety margin decreases as power level increases, and RPV failure is most likely to occur under the condition of a four-layer configuration.%严重事故缓解策略熔融物堆内滞留(IVR)有效性评价方法中,关于压力容器下封头内的熔池结构是最具争议的问题.本工作对目前国际上采用的稳定熔池2层和3层结构,以及在熔池形成过程中可能形成的4层结构进行了比较研究,建立了这3种结构下的熔池分层传热模型,并分析了3种结构在不同反应堆功率水平下对压力容器有效性的影响.结果表明,压力容器安全裕量随反应堆功率的升高而减小,在4层熔池结构下发生压力容器熔穿失效的可能性最大.
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