Abstract During a severe accident in a nuclear reactor, the molten core may relocate in the lower head of the reactor vessel or in the reactor pit in case of vessel failure. In both cases, if water is present, it may lead to the so-called “fuel-coolant interaction”. When the melt jet enters into a water pool, it undergoes fragmentation and simultaneously initiates the rapid vapor generation due to high heat transfer. In the worst case, it could lead to steam explosion that may threat the integrity of the vessel or of the containment. The phenomenology of FCI phenomena depends on the nature of jet interaction with water: fragmentation/breakup, droplet deformation, vapor film destabilization. Many correlations have been developed to model these phenomena demonstrating the need for corium physical properties data. Nevertheless, experimental data about corium thermophysical properties are scarce, due to the difficulty to manage high temperature measurement. In order to assess the sensitivity of FCI scenarii to the corium thermophysical properties, French 900 MW PWR calculations have been performed using the MC3D code. Ten thermophysical properties (density, solidus-line temperature, liquidus-line temperature, solid heat capacity, liquid heat capacity, surface tension, emissivity, thermal conductivity, melting specific heat) were varied following the Morris statistic methodology. The sensitivity of the main calculation outputs (pressure peak, mass of fragment, steam production) has been quantified. The aim of the paper is to assess the impact of corium thermophysical properties on fuel-coolant interaction. In the first part, the phenomenology of FCI, together with the main correlations introducing the corium thermophysical properties, are presented. The main assumption of the calculation scenario is also given. The second part is devoted to the presentation of the Morris methodology and the definition of property variation range according to the literature or to model prediction. The results of MC3D calculations are presented in the fourth part. It exhibits the important role played by the corium surface tension on the progression of the FCI.

中文翻译：

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真皮热物理特性对燃料-冷却剂相互作用的影响

摘要 核反应堆发生严重事故时，当容器发生故障时，熔融堆芯可能会在反应堆容器的下封头或反应堆坑内重新定位。在这两种情况下，如果存在水，可能会导致所谓的“燃料-冷却剂相互作用”。当熔体射流进入水池时，它会发生碎裂，同时由于高热传递而开始快速产生蒸汽。在最坏的情况下，它可能导致蒸汽爆炸，从而威胁容器或安全壳的完整性。FCI 现象的现象取决于射流与水相互作用的性质：破碎/破碎、液滴变形、蒸气膜不稳定。已经开发了许多相关性来模拟这些现象，证明需要真皮物理特性数据。尽管如此，由于难以管理高温测量，关于真皮热物理特性的实验数据很少。为了评估 FCI 方案对真皮热物理特性的敏感性，法国 900 MW PWR 计算已使用 MC3D 代码进行。十种热物理性质（密度、固相线温度、液相线温度、固体热容、液体热容、表面张力、发射率、热导率、熔化比热）按照莫里斯统计方法变化。主要计算输出（压力峰值、碎片质量、蒸汽产量）的灵敏度已被量化。该论文的目的是评估真皮热物理特性对燃料-冷却剂相互作用的影响。在第一部分，FCI 的现象学，连同介绍真皮热物理特性的主要相关性，都被呈现出来。还给出了计算场景的主要假设。第二部分致力于根据文献或模型预测介绍莫里斯方法和定义属性变化范围。MC3D 计算的结果在第四部分给出。它展示了真皮表面张力对 FCI 进展所起的重要作用。MC3D 计算的结果在第四部分给出。它展示了真皮表面张力对 FCI 进展所起的重要作用。MC3D 计算的结果在第四部分给出。它展示了真皮表面张力对 FCI 进展所起的重要作用。