Numerical simulation of the SURC-2 and SURC-4 MCCI experiments by MPS method

The molten corium-concrete interaction (MCCI) phenomenon was analyzed based on the Moving Particle Semi-implicit (MPS) method. The developed code was applied to one-dimensional SURC-2 and SURC-4 experiments, in which a mixture composed of UO₂-ZrO₂-Zr and Steel-Zr was used as the melt materials. The phase transition of the melt and the concrete was modeled based on a phase transition model for mixture. The effect of Zr oxidation on the concrete ablation was taken into consideration by introducing the reaction heat of Zr/SiO₂ obtained from the condensed phase chemical equations into the melt pool. The calculated concrete ablation rate was compared with the experimental measurements and the simulation results of the CORCON code. The simulation results by MPS agreed well with the experimental measurements. The experimental and MPS results both indicated that for both experiments Zr oxidation could significantly increase the ablation rate. On the other hand, crust formation and remelting was observed to occur on the interface between the melt and the concrete in the MPS simulation. During the period before crust remelted, the concrete ablation rate calculated by MPS decreased significantly. It was indicated by the MPS results that the crust formation could play an important part in MCCI since it could slow down the concrete ablation rate by preventing the melt from interacting with the concrete. Although the experiments did not clarify this observation, the proof for this phenomenon could be deduced from the decreased concrete ablation rate during the same period of interaction presented by the experimental results.