Abstract During the core disruptive accident (CDA) of sodium-cooled fast reactor (SFR), the molten fuel and steel are solidified into debris particles, which form debris bed in the lower plenum. When the boiling occurs inside debris bed, the flow of coolant and vapor makes the debris particles relocated and the bed flattened, which called debris bed relocation. Because the thickness of debris bed has great influence on the cooling ability of fuel debris in low plenum, it’s very necessary to evaluate the transient changes of the shape and thickness in relocation behavior for CDA simulation analysis. To simulate relocation behavior, a large number of debris bed relocation experiments were carried out by improved bottom gas-injection experimental method in this paper. The effects of different experimental factors on the relocation process were studied from the experiments. The experimental data were also used to further evaluate a semi-empirical onset model for predicting relocation.

中文翻译：

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改进型底部注气实验法研究碎屑床重定位行为

摘要 在钠冷快堆（SFR）堆芯破裂事故（CDA）中，熔融燃料和钢凝固成碎片颗粒，在下腔室形成碎片床。当碎屑床内部发生沸腾时，冷却剂和蒸汽的流动使碎屑颗粒重新定位，床层变平，称为碎屑床重新定位。由于碎片床层的厚度对低压力通风室中燃料碎片的冷却能力影响很大，因此在CDA模拟分析中评估重定位行为中的形状和厚度的瞬态变化是非常必要的。为了模拟搬迁行为，本文采用改进的底部注气实验方法进行了大量碎屑床搬迁实验。从实验中研究了不同实验因素对搬迁过程的影响。实验数据还用于进一步评估用于预测搬迁的半经验发作模型。