Experiments on melt droplets falling into a water pool

This paper presents experimental data and analysis related to melt droplets falling into a water pool. A binary CaO-B2O3 melt mixture is used to study the influence of melt superheat and water subcooling on droplet deformation and fragmentation. For the conditions studied (We ≤ 1000), the surface tension of the melt droplet and the film boiling stability greatly affect the fragmentation behaviour. If the melt temperature is between the liquidus and solidus point (mushy zone) or if the film boiling is stable due to a relatively low subcooling, the droplet deformation and fragmentation are mitigated. This behaviour can be related to the effective Weber number (We) of the melt droplet upon entry into the water pool. Similar phenomena can be expected also for interactions of corium (UO2-ZrO2) and water, which are characterized by a potentially fast transformation of melt into the mushy zone and by particularly stable film boiling. (author)