Modeling of heat transfer and solidification in LIVE L3A experiment

In the field of research for Severe Accidents in Nuclear Reactors, and more specifically In-Vessel Corium Retention, prediction of transient heat loads on the vessel wall is necessary, which involves a number of complex physical and chemical phenomena. In this framework, understanding of the interfacial conditions between the melt and the solid are relevant issues, which govern the heat flux distribution on the vessel wall. The LIVE experiment was launched at KIT to investigate the thermalhydraulics of a non-eutectic melt in a hemispherical shaped pool that is volumetrically heated and cooled on its lateral boundaries. The present work proposes an analysis of the experimental data obtained in LIVE L3A in order to describe the phenomenology at the interface for both hydraulic and chemical aspects, during transient as well as in steady state. In particular, a model is developed to describe analytically the melt temperature evolution and the crust thickness variation. Notably it is shown that the temperature at the pool-crust interface is close to the liquidus temperature corresponding to the initial concentration in the liquid pool. The characteristic parameters relative to the solidification rate and the thermal conditions determined in this work constitute the input needed to study more deeply the crust formation and notably to determine if a planar front is stable.