A simple correlation to estimate agglomerated debris formation based on experiments of melt jet-breakup using a metallic melt

The molten core (corium or melt) relocation in severe accidents in a light water reactor can cause agglomeration by the merging of melt particles with others, and form massive debris (agglomerated debris) when the particles that detach from a melt jet accumulate on the floor of the containment vessel. This paper presents a modification of a simple correlation to estimate the mass fraction of the agglomerated debris proposed in the previous study. The modification is based on experiments of melt jet-breakup using a metallic melt. The mass fraction of the agglomerated debris needs to be estimated because the agglomerated debris can severely affect the debris bed coolability. The present study focused on the effects of changes in the experimental conditions for melt jet injection (nozzle diameter and inlet velocity) on the mass fraction of the agglomerated debris to expand the experimental database of the previous study that focused only on the effects of changes in the melt and coolant temperatures, and coolant depth on the mass fraction of the agglomerated debris. The visualized observations using a high-speed camera and morphological investigation of recovered debris revealed the effects of changes in the nozzle diameter and inlet velocity on the mass fraction of the agglomerated debris. The extrapolation of the modified simple correlation revealed the mass fraction of the agglomerated debris under the anticipated reactor conditions.