Radiative Heat Exchange in a Gas Cavity Above Reactor Core Melt During a Serious Accident

Abstract

A model of radiative heat-exchange, based on the Rosseland approximation, in a gas cavity was introduced into the HEFEST computational code designed for modeling the interaction of the core melt with NPP structures during a serious accident in VVER. This approach is admissible for optically dense gas and supplements the zonal heat exchange model, already existing in the code, for a cavity with a transparent gas. The conditions for using these two approaches in modeling radiative heat transfer at different stages of an accident are discussed. The numerical implementation of the diffusion model and its verification are described. The model was tested on the problem of radiative heat exchange during melt retention at the bottom of the vessel of a VVER-1000 reactor and the results are reported.