Small-scale Experiment on Subcooled Water Jet Injection into Molten Alloy by Using Fluid Temperature-Phase Coupled Measurement and Visualization

Abstract

The plunging water jet behavior into a pool of a molten lead-bismuth alloy is experimentally investigated. The mixing and interactions of fluids were detected by measuring the fluid temperature as well as the fluid phase distinction by the newly developed bifunctional probes. In general knowledge of fuel-coolant interactions, the film boiling of water is caused immediately after the first contact of high-temperature melt and water, but the vapor film is locally collapsed by some reasons and the direct contact is extensively propagating in some cases which may produce the explosive vapor generation. In the melt-injection mode previously investigated by numerous researchers, the triggering of explosive interactions is considered as a local rewetting caused by instabilities of the vapor film as the melt temperature decrease. In the coolant-injection mode discussed by the present study, on the other hand, the water temperature poured into bulk melt continues to rise for penetration, in general, that should be effective to stabilize the film boiling. The present experiments showed, however, that the explosive boiling occurred in a condition that both water and melt initial temperatures were high enough for maintaining stable film boiling on the melt-water interface that is clearly different manner of the melt injection mode. Such unstable phenomena are observed when the instantaneous interfacial contact temperature exceeds the homogeneous nucleation temperature of water and the amount of saturated water is accumulated in a melt pool.