Interaction of Drops falling into Volatile Liquids

Abstract

The incidence of explosive melt-coolant interactions (MCIs) has prompted widespread research in an attempt to explain their cause. The conditions under which such explosions may occur is the subject of the present work. Experiments have been performed both in the laboratory and in the field using different melts and usually water as the coolant. On the small scale, molten tin, lead, aluminium and copper metals have been dropped in small, reproducibly-sized quantities (=0.25 g), into perspex containers of water and occasionally different coolants. Other melts used have been molten sodium chloride and copper (I) iodide. In the field, larger amounts of melt (up to 5 kg) have been poured into mild steel containers of water. The melts have included copper, iron, nickel, magnox and sodium chloride. Photographic techniques were used to observe the MCIs and in addition, a hydrophone has monitored pressure fluctuations in the coolant on the small scale. The photographic techniques were three-fold: high speed photography, stroboscopically illuminated photography and short exposure, spark-illuminated photography. The effect of a pressure pulse within the coolant was also studied for both small and large melt masses. The result was very often an explosion under otherwise non-explosive conditions. Also, observation was made of a spark-induced steam bubble generated in water at different temperatures. This may help to throw light on the existence of a coolant critical temperature above which explosions fail to occur.