Three-dimensional numerical study on the effect of sidewall crust thermal resistance on transient MCCI by improved MPS method

•3-D simulation of a MCCI test was presented with improved MPS method.•Three crust heat transfer models or assumptions were applied to explore the effect of crust thermal resistance on MCCI.•Difference ablation patterns were obtained due to the lower melt pouring rate. Molten Corium and Concrete Interaction (MCCI) is the phenomenon that could occur in the severe accident of nuclear power plant (NPP) after the failure of reactor pressure vessel (RPV). There are considerable uncertainties regarding the MCCI initial conditions, including melt pouring, which is harder to be considered in many severe accident analysis codes. In this study, the improved MPS method with explicit pressure method was used to simulate the pouring stage of HECLA-3 transient MCCI experiment. The anisotropic ablation was obtained at a lower pouring rate, which was in good agreement with the experiment. It is found that the initial sidewall crust formation is the main reason for the ablation difference of MCCI caused by low melt pouring rate. And the mechanism of adiabatic effect of the crust layer on MCCI was revealed by the comparison of simulation results with three different crust heat transfer models or assumptions.