Study of water ingression models

It is important to understand the mechanisms of quenching molten corium material when estimating the safety of nuclear plants. The melt freezes creating an impermeable crust when water is injected on the top of the molten pool. The heat is carried away from the melt only by conduction through the crust and thus the cooling rate decreases as the crust grows. Cracking of the crust allows water to penetrate into the crust making conduction layer thinner and increasing the cooling rate. This is called water ingression. The water ingression model presented here is partly based on experimental data obtained for rocks, and thus it is not clear if it can be used in the case of corium pools. If it is permissible to extrapolate this theory to relatively high-temperature corium, the water ingression is not possible with the corium pools. However, the theory is sensitive to errors with high temperatures. Experiments have shown that the cooling rate of the corium pools is higher than it should be with conduction only and careful analyses of experiments are required to verify the nature and scale of water ingression process.