Experimental investigation on the bursting of single molten droplet in coolant

An experiment facility for observing low-temperature molten tin alloy droplet into water was established to investigate mechanisms of vapor explosion occurring in severe accidents of a fission nuclear reactor. The vapor explosion behaviors of the molten material were observed by a high-speed video camera and the vapor explosion pressures were recorded by a pressure transducer mounted under the water surface. The results showed that the pressure reached a peak value when the molten metal temperature was 600°C-650°C, and the coolant temperature had an obvious decreasing effect on the droplet breakups. A model for single droplet fuel/coolant interaction is proposed. It considers that in the case of Rayleigh-Taylor instability, the coolant that jets from opposite direction penetrates into the fuel and the vapor explosion occurs because of the rapid evaporation. This model explained the effect of metal droplet temperature and coolant temperature on vapor explosion.