Chemical Interactions of Molten Steel with (U-Zr-O) Corium: Main Outcomes of the CORDEB Program

•Chemical interactions between (U-Zr-O) molten corium and molten steel are performed to study the impact of temperature difference and presence of crust between stratified phases.•The existence of a crust between stratified oxide and metal phases does not prevent mass transfers and a possible inversion of stratification due to changes in metal composition.•Under oxidizing atmosphere, two main processes may limit the rate of oxidation: the presence of a top crust or the oxidant starvation.•Chemical interactions between (U-Zr-O) porous debris bed and molten steel are performed to study the impact of temperature and oxidizing atmosphere on the progression of molten metal.•Under non-oxidizing atmosphere, an eutectic metallic mixture is formed around 900 °C and progresses easily through the oxide particle bed. Under oxidizing atmosphere, metal wettability is reduced and progression is stopped.