[en] Three areas which are relevant to the basic mechanisms of vapor explosions have been addressed, both experimentally and theortically: the destabilization of film boiling by a pressure shock wave; the basic fragmentation and mixing mechanisms once liquid-liquid contact has been achieved; the necessary conditions for a supercritical Board-Hall thermal detonation. It has been shown that shock waves of only a few bars overpressure can produce liquid-solid contacts for periods of a millisecond or more, with accompanying very high heat transfer rates, in a nickel-Freon system. The results are in agreement with a theoretical analysis demonstrating when contact is or is not established. Mixing time constants have been measured for tin-water interactions in a shock tube configuration. The predominant mode of interaction appears to be by multiple expansions and a contraction, which implies that in large scales the final contraction might give rise to a vigorous explosion. However this is not considered to be likely in the LMFBR because of the spontaneous nucleation requirement. Supercritical propagating plane detonations have been shown to be limited to a very narrow range of initial conditions, which would be very difficult to achieve in practice