Engineering and Development Laboratory (EDL)

Corium Coolability Experiments

The water ingression facility is used to determine the heat flux through the surface of corium (the molten constituents of a reactor core) when cooled by an overlying water pool. For the experiments, corium is simulated by a mixture of uranium dioxide and other materials that is heated with a chemical reaction to over 2000°C. Soon afterwards, water is injected into the reaction vessel to form a shallow pool over the melt. Heat transfer from the corium to the pool generates steam, which is condensed and collected to determine the heat transfer rate.

These tests are of interest because they provide information regarding the ability to cool a molten core and the likelihood of retaining it within the reactor pressure vessel. The experiments are also used to assess the coolability of corium if it escaped the pressure vessel and was deposited within the reactor containment building.

The cooling rate of corium is difficult to predict analytically because of large uncertainties in the morphology. The formation of cracks and porous structures as the corium solidifies can enhance cooling beyond what one would predict for an impermeable solid. The basic premise of the experiments is to measure the heat flux from the melt to the overlying water layer and then compare it with the analytical solution for conduction-limited heat transfer to determine the extent to which the porous structures enhance cooling.

The morphology of corium is highly dependent upon the constituents and so prototypical materials must be used to obtain meaningful results. Experiments with these materials require special precautions and so they are conducted within the sealed containment building that is a part of the Large-Scale Materials Test Facility.