Experimental investigation on the moving characteristics of molten metal droplets impacting coolant

This paper reports the results of an experimental investigation on the moving characteristics of molten metal droplets impacting coolant free surface. A visualization experimental facility of molten fuel coolant interactions (MFCI) is designed and set up in the present study. The lead–bismuth (Pb–Bi) alloys are employed as the metal materials. An automatic control circuit is designed and applied to control the release of the molten droplets. High-speed camera is employed to record the movement of the molten metal droplets falling down and into a coolant pool. Based on the analysis of the experimental data, a so-called “J-region” of the droplet’s velocity–time curves was found and the melt droplet enters the “J-region” when it impacts the free water surface. In the “J-region”, the velocity of the melt droplet decreases rapidly and suddenly at first, and then increases again. The droplet gradually reaches a comparatively steady velocity when it leaves the “J-region”. The present study provides essential information for further study on the fragmentation behavior of high-temperature molten droplets in coolant.