Fragmentation of a Single Molten Metal Droplet Penetrating Sodium Pool: Comparisons of Thermal and Hydrodynamic Fragmentation

In order to characterize the relationship between hydrodynamic and thermal fragmentation of molten metallic fuels with the interaction of the coolant of sodium in the wide range of thermal and hydrodynamic conditions, the present paper focuses on a series of fragmentation experiments of a single molten copper droplets (1∼5 g) with wide ambient Weber number (102 ∼ 614) and superheat condition (15 ∼ 574 °C), which penetrated a sodium pool. The intensive fragmentations of single molten copper droplets were clearly observed even at the instantaneous contact interface temperatures (T_i) below the melting point besides higher T_i. The size distributions of molten droplet with high Weber number somewhat incline to be less than those with low Weber number in the same thermal condition. When approximately We_a>200, the effect of hydrodynamic fragmentation becomes predominant over that of thermal fragmentation in the low superheat condition. In the high Weber number or high superheating condition separately, the size distributions of the single metal droplet and jet reported by Schins’ group with different mass of thousand times can keep very similar. Moreover, the values of D_m/D₀ must be quite small. The relatively larger size distributions of the single metal droplet and the jet reported by Nishimura et al. will only arise in the both low Weber number and low superheating condition.