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 (T i ) 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 T i < 1;000C. 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 T i > 1;000 C, the present dimensionless mass median diameters (D m =D 0 ), 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.

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“…Nishimura et al (2010) carried out the FCI experiment in the form of a single molten copper jet penetrating into a sodium pool and analyzed the fragmentation characteristics from hydraulic and thermal perspectives. The processes of a single molten copper droplet (Nishimura et al, 2007;Zhang et al, 2009;Zhang and Sugiyama, 2010;Zhang and Sugiyama, 2012) and continuous copper droplets (Yang et al, 2018;Yang et al, 2019) interacting with liquid sodium have also been studied, and a thermal fragmentation mechanism of sodium entrainment was proposed and fragmentation due to a sodium microjet was presented.…”