Understanding the spreading behavior of a molten core is important for predicting the progression of severe accidents and ensuring the smooth decommissioning of severe accident-experienced nuclear power plants. In the current study, molten-metal drop experiments were performed using tin and copper. These experiments were conducted to expand the fundamental knowledge on spreading and deposition behaviors to verify the analysis model. In the case of a nozzle diameter of 4 mm, the deposited metal was uniformly relocated; however, the center was extremely thin and Sn demonstrated a circular shape for a nozzle diameter of 10 mm, while Cu spread non-uniformly. The unevenness ratios for Cu were much higher than that of the Sn independent of the dropped height and the nozzle diameters. The effects of hydraulic and thermal dimensionless numbers on the deposition and spreading behaviors were analyzed. A correlation between the spreading and deposition behaviors and the dimensionless numbers of Re, We, Pe, Oh, and Bo was observed. In particular, the Oh and Bo numbers had significantly high correlation coefficients with the dimensionless spreading area, where effects of inertial force on the spreading process were relatively low. The experimental correlation of the dimensionless spreading area was proposed using the Re and Bo numbers. The prediction capability was improved, in which the predicted values were within 28% for the current experiments.

了解熔融堆芯的扩散行为对于预测严重事故的进展和确保经历过严重事故的核电厂顺利退役非常重要。在当前的研究中，使用锡和铜进行了熔融金属滴落实验。进行这些实验是为了扩展有关扩散和沉积行为的基础知识，以验证分析模型。在喷嘴直径为4mm的情况下，熔敷金属均匀重定位；然而，中心非常薄，当喷嘴直径为 10 mm 时，Sn 呈圆形，而 Cu 分布不均匀。与下落高度和喷嘴直径无关，Cu 的不均匀率远高于 Sn 的不均匀率。分析了水力和热无量纲数对沉积和铺展行为的影响。扩散和沉积行为与无量纲数之间的相关性Re、We、Pe、Oh和Bo被观察到。特别是Oh和Bo数与无量纲扩展区域的相关系数显着较高，其中惯性力对扩展过程的影响相对较低。使用Re和Bo数提出了无量纲扩展区域的实验相关性。预测能力得到提高，当前实验的预测值在 28% 以内。