Experimental investigation on pressure-buildup characteristics of a water lump immerged in a molten lead pool

Motivated to understand the pressure-buildup characteristics in a circumstance of a water droplet immerged inside a heavy liquid metal pool, which is a key phenomenon during a Steam Generator Tube Rupture accident of Lead-cooled Fast Reactor, many experiments have been conducted by injecting water lumps into a molten lead pool at Sun Yat-sen University. In order to deepen the understanding of the influence of melt material, this lead experiment was compared with a Lead-Bismuth-Eutectic (LBE) experiment in the literature. For both experiments, a steam explosion occurred in a small part of the experimental runs, which generally leads to strengthened pressure buildup. Regarding the non-explosion experimental cases, the impact of all parameters employed in lead experiments (i.e., water lump volume, water lump shape, molten pool depth, and temperature of water and melt) on the pressure buildup is non-negligible and similar to that in our previous experiments using LBE. Notably, limited pressure buildup with an increase in water lump volume was also observed. A slightly more violent pressure buildup tends to appear in the lead experiments than in the LBE experiments under the same experimental conditions, which may be due to the higher thermal conductivity of lead than of LBE. In a few experimental runs with a relatively low melt temperature close to the melting point of lead, local solidification of liquid lead was observed, restricting pressure buildup. For the lead and LBE experiments, the calculated melt kinetic energy conversion efficiency eta has a relatively small value (not exceeding 1.6%), and the eta values have an overall positive correlation with the impulse on the molten pool.