Main results of an in-vessel corium thermochemistry benchmark based on MASCA and CORDEB2 experimental data

Abstract

This paper is dedicated to an international benchmark on in-vessel corium thermochemistry. Composed of three different steps, it was constructed in the frame of the IAEA Coordinated Research Project on In-Vessel Melt Retention and focuses on the stratification of corium in the lower plenum of a reactor vessel during a severe accident. The experimental data obtained from the MASCA and CORDEB2 programs is utilized to validate and calibrate the models of the various codes employed by the participants. The paper gives an overview of the different models, including their underlying assumptions. The results show that the models are generally in good agreement with the experimental data, but further experimental data is needed for model validation. Besides the need for further work, this paper highlights the fact that integral models (published in the open literature for most of them) are available to account for the first-order phenomena associated with in-vessel corium. Accordingly, this paper may be useful for code developers that would like to upgrade their models in order to take into account transient stratification kinetics, a prerequisite for a state-of-the-art analysis of in-vessel melt retention.