Unsteady RANS analysis of CNL corium convection experiment

Abstract

In the event of a severe accident, it is essential to maintain radiological material within the calandria vessel. Thermal stresses at the vessel wall have been identified as a dominant failure mechanism. There is therefore a need to analyze the heat transfer processes in the molten corium to determine if the heat removal at the exterior of the vessel wall is sufficient to maintain vessel integrity. The current research uses computational fluid dynamics (CFD) to simulate the natural convection flows and crust formation within the molten corium, including the conjugate heat transfer at the vessel wall. Unsteady Reynolds-Averaged Navier-Stokes (RANS) is used to model the effects of turbulence in the fluid. This paper presents the results of a validation study on a 1/5 scale CANDU calandria vessel using molten salts as the corium simulant. Numerical predictions are compared to the experimental results provided by Canadian Nuclear Laboratories (CNL).