Progress Report on the Molten UO Drop Experiment

Mizuta, H.; Hirabayashi, F.*; Yokozawa, Naoki; Fukushima, Y.*

A series of 30 experiments were performed to examine the fragmentation characteristics of Sodium-Fuel Interaction by dropping molten UO into sodium. In this experiment, annular UO pellets were heated by the center line heating of tungsten rod, and the molten UO droplets fell into the sodium tank. The fragmentations of the droplets on the surface of liquid sodium were photographed with high speed camera at 500-2000 pictures/sec. The Pressure and temperature of sodium tank were measured. The particle characteristics of the UO residue was examined on the particle size distribution, the particle surface condition, and the grain characteristic of the particles for the fragmentation mechanism. These examination indicates that the UO particles can be assumed to be spherical and to have the log-normal distribution function. The most pessimistic particle size distribution at present can be represented by the equation. Where f/supi(D)dD=weight percent of particles in size range D to D+