Fragmentation of a Single Molten Metal Droplet Penetrating Sodium Pool II Stainless Steel and the Relationship with Copper Droplet

Abstract

The present paper reports the fragmentation characteristics of a single molten stainless steel (304SS) droplet (1, 3, and 5 g) at initial temperatures from 1,470 to 1,820°C, which penetrated a sodium pool at initial temperatures from 295 to 337°C. The fine fragmentation of a single molten stainless steel droplet with a fivefold difference in mass is clearly confirmed in a range of instantaneous contact interface temperatures (Ti ) higher than approximately 1,000°C, which is supercooled well below its melting point of 1,427°C. A steep change from fine to coarse fragmentation of the droplet with both the same and different masses is found at Ti < 1,000°C. The present data also fairly agree with those obtained by Schins' group and Armstrong et al. in the molten stainless steel experiments of 2.5- and 4-kg jets and 9.1 to 29.1 g of streamlets and droplets, respectively. It is also found that at Ti > 1,000°C, the present dimensionless mass median diameters (Dm =D0 ), normalized by the diameter (D 0) of the droplet before touching the sodium pool surface, are in the same range with those of copper droplets with the different thermophysical properties, which were reported in the present authors' first paper.