Abstract
During a severe accident in a nuclear reactor, an ex-vessel steam explosion may occur when the molten core come into contact with the liquid coolant, the crucial factor in the fuel-coolant interaction is the fragmentation of melt into small droplets, which rapidly increase the heat transfer to the coolant, and could lead to a steam explosion and formation of a pressure wave with a disastrous consequence for the surrounding components. In this research a numerical simulation of a steam explosion was performed using the VAPEX-D code which is being developed at the Department of NPP in “Moscow Power Engineering Institute” for the simulation of fuel-coolant interactions. Using the microinteractions concept, the propagation of thermal detonation waves was studied, and the characteristics of subcritical and supercritical waves were compared. A sharp increase in pressure is noted during the transition from subcritical mode to supercritical mode of propagation. A parametric study was performed where the volume fraction of corium was varied to determine the critical value at which the thermal detonation wave decayed. The study shows that increasing the melt volume fraction, will increase the maximum pressure and the velocity of the thermal detonation wave. While varying the initial void fraction showed that the thermal detonation wave can propagate in a very low melt volume fraction.
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