Thermal and Hydrodynamic Fragmentation of a Single Molten Stainless Steel Droplet Penetrating Sodium Pool

In order to characterize the relationship between the hydrodynamic effect and the thermal effect in fragmentation of the molten core structural material with the interaction of sodium, the present study focuses on the fragmentation of a single molten stainless steel (304SS) droplet of 5 g with a high range of ambient Weber number (Wea) from 199 to 586. The fine fragmentation of the single molten stainless steel droplet with high Wea was clearly observed even at the instantaneous contact interface temperatures (Ti) between the droplet and sodium well below its melting point. The fragment size distributions with the high Wea tend to be less than those with the low Wea from 56 to 95 obtained in the previous experiment by the authors under the low Ti condition. As Wea increases, the hydrodynamic effect in fragmentation becomes predominant even under the low Ti condition. Under the high Wea or the high Ti condition separately, the size distributions of the present single metal droplet and the jet reported by Schins' group with 1000-fold difference in mass show almost the same level. The relatively larger size distributions of the single metal droplet only arise under the both low Wea and low Ti conditions. (author)