Abstract Predictions of corium behavior are inconsistent and often conservative because severe accident tools frequently use simplified corium thermophysical properties and high-temperature data remains scarce. We present high-temperature density measurements for prototypical oxidic corium produced by cold crucible induction melting, combining in-situ melt height determination with ex-situ skull and ingot measurements. Independently, SEM/EDS was used to verify composition and microstructure. Our measurements extend the sparse dataset for multi-component corium density and reveal systematic differences in the modelling of density and its temperature dependence. At the same time, code comparisons show that updating models is essential for credible predictions of both in-vessel and ex-vessel behavior.
Sears et al. (2026) studied this question.