Numerical simulation of a self-leveling experiment using a hybrid method

Abstract

The postulated core disruptive accidents (CDAs) are regarded as particular difficulties in the safety analysis of liquid-metal fast reactors (LMFRs). In the CDAs, the self-leveling behavior of debris bed is a crucial issue, which greatly affects the relocation process and heat-removal capability of molten core. SIMMER-III is a fast reactor safety analysis code and successfully applied to a series of the CDA assessments. It is a 2D, multi-velocity-field, multiphase, multicomponent, Eulerian, fluid dynamics code coupled with a fuel-pin model and a space- and energy-dependent neutron kinetics model. However, strong interactions between solid particles, as well as particle characteristics, in multiphase flows with particles are not taken into consideration in SIMMER-III. In this article, a hybrid method is developed by coupling the discrete element method (DEM) with the multi-fluid model of SIMMER-III, and the numerical simulation of a simplified self-leveling experiment is presented. In the coupling algorithm, the governing equations of gas and liquid phases are solved by a time-factorization (time-splitting) method. Contact forces between particles and interactions between particles and fluid are considered in the DEM. Reasonable agreement between simulation results and corresponding experimental data can demonstrate the validity of the present method in simulating the self-leveling behavior of debris bed.

Keywords

• self-leveling
• hybrid method
• postulated core disruptive accident
• simmer-iii
• discrete element method