Studies relevant to in-vessel steam explosions

Arguments are given that the probability of vessel failure, owing to a steam explosion, from mixing of molten core material with water in the lower plenum, is very low. Also, experiments in a water-filled shock tube to examine the mechanism of rapid mixing of falling liquid metal drops with the surrounding water after passage of a pressure shock wave are described. A new mixing mechanism is proposed, consisting of entrainment of liquid into the drop, owing to vorticity production resulting from intermittent boundary layer separation at the trailing edge of the drop. (orig.)