Analysing the Ablation of Concrete, Heat and Mass Transfer during Molten Corium-Concrete Interaction Phenomena

Abstract

Molten corium, a mixture of nuclear fuel, cladding, and structural elements, forms after the meltdown of a reactor core in the event of a severe accident at a nuclear power plant. This paper presents the development and implementation of a new numerical mixing model in OpenFOAM for a comprehensive analysis of concrete ablation during the Molten Corium-Concrete Interaction (MCCI) process. The well-researched CCI-2 experiment served as the benchmark for model validation. The model can forecast heat transfer, concrete ablation, phase change, mass transfer, and the mixing of concrete and corium. Additionally, the effect of concrete melting temperature on concrete ablation was investigated. We observed that concrete with a low melting temperature exhibited significantly reduced ablation, as well as controlled temperature, velocity, and density fields. Specifically, at a low concrete melting temperature of 1380 K, 90 percent of the concrete was ablated. However, when the melting temperature of the concrete was increased to 1480 K and 1580 K, the ablation decreased to 80 percent and 60 percent, respectively. Our results also revealed that melted concrete and corium, despite having different densities, form a single phase/mixer that enhances concrete ablation.