FIDAP, one of Fluent's general purpose software codes, was used to assess the capabilities of SCDAP/RELAP5/MOD3.2 to compute the heat transfer in the lower head of a reactor vessel filled with molten material during the late-phase of a severe accident. FIDAP was used for validation of the RELAP5 predictions of the same accident scenario, since little experimental information is available for the late phase of this type of accident. These FIDAP results have provided helpful insight into the nature of natural convection currents in the molten metal, as well as the temperature distribution and solid crust formation as the system approaches steady state.

The fuel melt in the failed reactor vessel
Courtesy of Bechtel BWXT Idaho

The velocity field in the molten pool along with isotherms that mark the solid crust that has formed at the base of the container. Courtesy of Bechtel BWXT Idaho