Spontaneous and triggered single metal drop in water thermal explosions

Physically-sound multi-fluid thermal hydraulic codes are needed for the work potential and probability of full-scale steam explosions postulated in various LWR severe-accident scenarios. A single fragmenting metal drop can serve in a cell model for local events occurring behind a detonation shock front. Single spherical drops of molten tin in water are spontaneously triggered and the subsequent explosion characterized by pressure transducers. The nature of the explosion was similar to triggered iron oxide drop explosions, with a sequence of bubble expansions and contractions occurring over an interaction period of less than eight milliseconds. Efficient steam explosions were attained with tin which contained similar thermal energy to the FeO/sub x/ experiments, though the tin mass was more than five times greater. Energy transfer rates were more than three times slower for the tin compared to the FeO/sub x/ 19600C runs. The time constant for energy transfer, tau, approached 10 milliseconds in the tin-water experiments. A multiphase, multiple-bubble model is presented for fragmentation af single drops of tin or iron oxide falling through water. Good agreement is shown with cycle times, maximum radii, and peak pressures of successive bubbles. Since both bubble dynamics and pressures are well-predicted likewise are the mechanical energies and thermal efficiencies