Abstract In a Core Disruptive Accident (CDA) of Sodium-cooled Fast Reactor (SFR), by supposing rather pessimistic condition, a large molten fuel pool would be possibly formed that contains enough fuel with the potential to exceed prompt criticality due to fuel compactive motion. Local fuel-coolant interaction (FCI) in the molten pool is identified as one of the typical inducing factors that may result in such compactive motion. To understand the characteristics of this interaction, owing to the PMCI (Pressurization characteristics in Melt-Coolant Interaction) facility recently established at the Sun Yat-sen University, in our earlier publications two series of simulated experiments, i.e. Coolant-Injection (CI) experiments and Melt-Injection (MI) experiments, have been conducted, in which water and low-melting-point Bi-Sn-In alloy (60% Bi, 20% In and 20% Sn) were used respectively as the simulant materials for sodium and molten fuel. In this study, aimed at checking the generality of the experimental findings as well as achieving further enhanced understanding on this interaction, a large number of experiments are newly performed through delivering water into a simulated molten fuel pool comprised of Lead-Bismuth Eutectic (LBE) alloy (another low-melting-point alloy). Through detailed comparisons (with the CI-mode experiments using Bi-Sn-In alloy), it is found that a similar trend in the transient pressure and temperate history as well as the overall effect of experimental parameters (such as water quantity, melt and water temperature, water-lump shape and melt depth) on the pressurization characteristics can be reproduced for the new LBE experiments. Despite a much lower thermal diffusivity, for the LBE experiments it is confirmed that the most likely reason resulting in the limited pressurization as water volume increases should be also primarily owing to the isolation effect of vapor bubbles generated at the melt-water interface. Possibly due to the enhanced melt density which facilitates the penetration of melt through vapor bubbles, under the same parametric condition the pressurization in LBE experiments is generally much higher than that in Bi-Sn-In experiments. Compared to melt static pressure, the pressurization under different melt depths is supposed to be more influenced by the varied easiness of melt penetration. Current work provides a large amount of favorable experimental database and insight for promoted understanding on actual CDAs and improved verifications of SFR severe accident codes in China.

中文翻译：

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不同熔体熔池中局部燃料-冷却剂相互作用的实验研究

摘要 在钠冷快堆 (SFR) 的堆芯破裂事故 (CDA) 中，假设相当悲观的条件，可能会形成一个包含足够燃料的大型熔融燃料池，由于燃料的压实运动，有可能超过瞬时临界状态。 . 熔池中的局部燃料冷却剂相互作用 (FCI) 被认为是可能导致这种压实运动的典型诱导因素之一。为了了解这种相互作用的特征，由于最近在中山大学建立的 PMCI（熔体-冷却剂相互作用中的加压特性）设施，在我们早期的出版物中进行了两个系列的模拟实验，即冷却剂注入 (CI) 实验和熔体注射 (MI) 实验，其中水和低熔点 Bi-Sn-In 合金（60% Bi，20% In 和 20% Sn) 分别用作钠和熔融燃料的模拟材料。在这项研究中，为了检查实验结果的普遍性并进一步加深对这种相互作用的理解，通过将水送入由铅铋共晶 (LBE) 组成的模拟熔融燃料池，新进行了大量实验合金（另一种低熔点合金）。通过详细比较（与使用 Bi-Sn-In 合金的 CI 模式实验），发现瞬态压力和温度历史以及实验参数（如水量、熔体和水温、水团形状和熔体深度）对加压特性的影响可以为新的 LBE 实验重现。尽管热扩散率低得多，但对于 LBE 实验，已证实导致随着水量增加而受压受限的最可能原因也应该主要是由于在融水界面处产生的蒸汽气泡的隔离作用。可能是由于熔体密度的增加有利于熔体通过蒸汽泡的渗透，在相同的参数条件下，LBE 实验中的加压通常比 Bi-Sn-In 实验中的高得多。与熔体静压相比，不同熔体深度下的加压更受熔体渗透难易程度的影响。