Thermal fragmentation of molten alumina in sodium

Experiments have been performed to study the thermal fragmentation of molten alumina drops in sodium. For the first time film boiling of oxide drops in sodium was achieved. With some drops undergoing film boiling the fragmentation was triggered by an externally applied pressure wave. In these experiments, the trigger was followed promptly by a strong reaction pressure if and only if a temperature threshold was exceeded. In agreement with similar experiments in which other materials were studied, this threshold was an interfacial temperature close to the homogeneous nucleation temperature of the vapourising liquid. The paper discusses these results and possible consequences for largescale vapour explosions. (orig.)