Novel model of concrete decomposition and melting in during MCCI in an LWR concrete pit during a severe accident

The paper considers refined approaches to solving two problems of modeling MCCI: $(1)$ a thermodynamical model of chemical reactions of the concrete components with the melt was constructed, as well as a model of concrete decomposition including universal procedures for calculating the heat capacity and density of concrete, independently on its type; $(2)$ a self-consistent, cost-effective model of concrete ablation progression was constructed, taking into account heating of the concrete; this model numerically solves the heat conduction equation on an adaptive grid. The models are described and verified.