Numerical simulation for the thermal behavior of three-layer molten pool based on TROSE experiment

Abstract

In advancing the study of the In-Vessel Retention (IVR) strategy, a three-layer corium pool configuration has been proposed. Owing to density inversion and the thinning of the top metallic layer, the thermal focusing effect on the vessel sidewall becomes more pronounced, posing a higher risk to Reactor Pressure Vessel (RPV) integrity. To investigate the thermal behavior of this configuration, Computational Fluid Dynamics (CFD) simulations were conducted based on the TROSE experiment, which features a three-dimensional hemispherical vessel (diameter = 2.4 m) and employs mineral oil, water, and Cerrobend alloy as simulants. The results demonstrate that the Wall-Modeled Large Eddy Simulation (WMLES) turbulence model effectively captures the corium pool behavior under a Rayleigh number of 10¹⁵. Additionally, assuming only energy exchange (without mass transfer) across the interfacial boundaries is shown to be a reasonable simplification that improves computational efficiency. In Test-T3 of the TROSE experiment, strong natural convection in the light metallic layer produces a nearly uniform temperature field, whereas limited convection in the oxidic layer leads to significant thermal stratification. In the heavy metallic layer, heat transfer is dominated by conduction, accompanied by crust formation at the boundaries. These findings confirm the applicability of the CFD method for simulating three-layer molten pools and highlight its potential for future safety analyses in large-scale passive nuclear power plants.