IVR中熔融堆芯被牺牲性材料稀释后的传热计算

应用牺牲性材料的堆芯熔融物稀释方案是先进轻水堆中一种新型的严重事故缓解措施。严重事故发生时，掉落的堆芯熔融物被氧化物牺牲性材料（OSM）稀释，导致熔池结构发生翻转，因此计算翻转后熔融池的传热行为是进行牺牲性材料筛选和评价稀释方案可行性的重要研究内容。本文计算了容器内滞留（IVR）中熔融堆芯被Fe₃O₄、TiO₂和Al₂O₃3种候选OSM稀释后压力容器壁面的热流密度分布。研究发现，布置OSM后，上腔室结构在强烈热辐射的作用下会熔化掉落。随着OSM布置量的增大，压力容器壁面最大热流密度减小，当布置15 m³的OSM时，压力容器伸长约2 m，此时壁面最大热流密度较未布置时减小约45%，且当布置相同体积的OSM时，Fe₃O₄导致的壁面最大热流密度减小最多。此外，UO₂-ZrO₂-OSM三元混合物的熔点高低会对氧化物层表面是否结壳产生影响，从而影响壁面最大热流密度。

Heat Transfer Calculation of Core Melt Diluted by Oxide Sacrificial Material During In-vessel Retention

Diluting the core melt with oxide sacrificial material (OSM) during in-vessel retention (IVR) is a newly proposed severe-accident-management strategy of advanced LWRs. When severe accident occurs, the relocated core melt is diluted by OSM, resulting in the inverse stratification of melt pool configuration. Therefore, the researches on the calculations of heat transfer of melt pool are essential to optimize the component of OSM and evaluate the effectiveness of the strategy. The heat flux on the vessel outer surface after diluting the core melt with Fe₃O₄, TiO₂ and Al₂O₃ respectively was calculated. The results show that the structure of upper plenum will melt due to the intense heat radiation after OSM is used. The maximum heat flux on the vessel outer surface reduces with the increase of OSM. When the volume of the OSM ceramics reaches 15 m3, the reactor vessel length should be increased by approximately 2 m. In this case, the heat flux reduces about 45% compared to the reactors without OSM. Moreover, the reduction of heat flux is most pronounced as Fe₃O₄ is used. In addition, the melting point of UO₂-ZrO₂-OSM affects the appearance of a crust on the surface of the oxide mixture, which in turn influences the maximum heat flux on the vessel outer surface.