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获取某压水堆核电厂相关参数,建立堆芯及维护结构三维模型,采用大空间自然对流换热和相邻八棒辐射换热模型,求解二维瞬态导热微分方程,计算事故发生后堆芯温度发展及熔融过程.研究表明:随着事故进程的发展,堆芯水位降低,堆芯温度升高,堆芯最高温度点逐渐下移.在事故进程560 s后,控制棒开始熔融;1200 s后,不锈钢棒开始熔融;燃料芯块在2700 s后开始熔融,7000 s后,堆芯熔融份额超50％.大部分堆芯节点熔融时,围桶结构仍未熔融.熔融物直接掉落,向下封头内发生初始迁移.蒸汽对流换热和辐射换热均能影响燃料棒熔融时刻,且蒸汽对流换热占主导地位,蒸汽的影响不能被忽略.辐射换热具有展平堆芯温度的作用.“,”Relevant parameters of a pressurized water reactor are obtained to establish the 3D geometric model and two-dimensional heat conduction differential equation.To calculate the temperature distribution and melting process,the natural convection heat transfer model and radiation heat transfer with neighbor 8-rod-cavity model are applied.The study shows that with the accident processes,the water level in the core decreases,but the temperature increases,and the point with the highest temperature in the core goes down gradually.After 560 seconds,the control rods begin to melt,and after 1200 seconds,the stainless steel rods begin to melt;the fuel rods begin to melt after 2700 seconds.About 7000 seconds later,the proportion of core melt is more than 50％.When most of the core nodes melted,the shroud didn\'t melt.The melt migrated directly down the lower plenum.Both the steam vapor and radiation can influence the melting time of the fuel rods,and the steam convection heat transfer is dominant.The effect of steam vapor cannot be neglected.Radiation heat transfer has the effect of flattening the temperature of the core.