坩埚式堆芯捕集器熔融物长期冷却过程

堆芯捕集器是三代核电厂常用的严重事故后果缓解措施之一。在中国核电工程有限公司研发的新型堆芯捕集器中，设计者创新性地提出通过内置冷却管提高熔融物的冷却速率的设计方案。以江苏田湾核电厂堆芯捕集器设计为基础，采用FLUENT软件建立了相关数值模拟模型，研究了坩埚式堆芯捕集器中熔融物长期冷却过程，在此基础上探讨了内置冷却管对加快严重事故缓解进程的贡献。计算结果表明，坩埚式堆芯捕集器中氧化物层以由外向内的过程冷却，外部先形成的硬壳会阻碍衰变热的导出，增加了冷却全部熔融物所需的时间。通过增设内置冷却管可以为内部区域提供额外的冷源，从而提升熔融物的冷却速度，加快严重事故后果缓解进程。

Study on Long-term Cooling Process of Melt in Crucible Type Core Catcher

Core catcher is a commonly used measure to alleviate severe accident in third-generation nuclear power plants. In the research and design process of a new type domestic core catcher, the designers innovatively proposed a design scheme to improve the cooling rate of the corium by built-in cooling pipe. Based on the design of core catcher installed in Jiangsu Tianwan Nuclear Power Plant, a numerical simulation model is established by FLUENT software to study the long-term cooling process of molten material in the crucible type core catcher, and the contribution of built-in cooling pipe to accelerate the process of severe accident mitigation is also discussed. The calculation results show that the oxide in the crucible type core catcher will freeze from outside to inside, and the formed crust will keep the decay heat, thus increase the time required to cool all the corium. The built-in cooling pipe can provide additional cold source for the internal area, thus improving the cooling speed of the corium and accelerating the mitigation process of severe accident.