椭球形与球形下封头压力容器内熔融物滞留传热特性分析

严重事故下堆芯熔融物再分布于压力容器下封头，在衰变热作用下高温堆芯熔融物对压力容器壁面施加较大的热负荷，可能导致压力容器失效。针对压力容器内熔融物滞留下的传热过程，基于Fortran90语言开发了椭球形下封头压力容器内熔融物堆内滞留（IVR）分析程序IVRASA-ELLIP，计算具有椭球形下封头的压力容器在严重事故下稳态熔池的传热过程及IVR特性。利用IVRASA-ELLIP程序计算了VVER-1000压力容器内熔池的传热，分析具有椭球形下封头的压力容器各处的壁面热流密度、氧化物硬壳厚度和压力容器壁厚，并与运用IVRASA程序计算的AP1000稳态熔池传热结果进行对比分析。研究结果表明，在相同初始参数下椭球形下封头内的壁面热流密度较球形下封头内的小，与热流密度的变化趋势相对应，椭球形下封头内压力容器壁的消融量较球形下封头内的小，椭球形下封头内形成的氧化物硬壳厚度较球形下封头内的厚。

Heat Transfer Analysis of In-vessel Melt Retention in Ellipsoidal and Spherical Lower Heads

In the severe accident, the core melt with high temperature is redistributed in the pressure vessel and exerts a thermal load on the pressure vessel wall, which may lead to the failure of pressure vessel. Based on the Fortran90 language, in-vessel melt retention (IVR) analysis code IVRASA-ELLIP in severe accident of ellipsoidal lower head was developed, which was used to analyze the heat transfer and IVR of the pressure vessel with the ellipsoidal lower head under the severe accident. IVRASA-ELLIP was used to calculate the heat transfer of the VVER-1000, and the results of the wall heat flux, the oxide crust thickness and the wall thickness of the pressure vessel were obtained. The results of heat transfer of AP1000 were obtained through IVRASA code, which were compared with the results of VVER-1000. The results show that with the same initial parameters, the wall heat flux of the ellipsoidal lower head is smaller than that of the spherical lower head, the amount of ablation of the pressure vessel wall with the ellipsoidal lower head is smaller than that with the spherical lower head, and the oxide crust thickness in the pressure vessel with the ellipsoidal lower head is thicker than that with the spherical lower head.