Thermal interactions between molten uranium dioxide and water: an experimental study using thermite generated uranium dioxide

Results are reported of an experimental investigation of thermal interaction involving molten uranium dioxide and water; materials of particular interest in LWR safety studies. Quantities of 0.5 kg of thermite generated molten uranium dioxide were released under water within a closed pressure vessel. Spontaneous and triggered MFCI were observed which for the small fraction of molten material involved (-6%) gave efficiencies of the order of 6% of the optimum Hicks Menzies value but with a maximum of 13%. Yields and efficiencies decreased with increasing coolant subcooling, and the yield of triggered interactions decreased with increasing delay of triggering. A characteristic time for heat transfer, also a function of subcooling, was of the order of 0.8 ms. 4 refs