A numerical analysis on molten droplet hydrodynamics in sodium pool

Abstract

The risk and consequences of vapor explosion during severe accidents are among the most critical safety problems to be considered in next-generation sodium-cooled fast reactors. The melt of the core material (corium) may be produced in the event of inadequate core cooling and/or during Loss of Coolant Accident (LOCA) leading to Core Disruptive Accident (CDA). Corium displacement can then lead to powerful fuel-coolant interactions (FCIs). One of the consequences of this molten corium-coolant interaction is that vapor formation and hence explosion may occur. Due to the problem complexity, only hydrodynamic effects of the multiphase system of a single-droplet vapor explosion phenomenon, without heat transfer, is considered. The present study focuses on simulating a molten droplet pre-conditioning (deformation before breakup) through the early stages of the molten fuel coolant interaction. In order to efficiently capture the melt-sodium interfaces and predict droplet behavior with appropriate mass conservation, calculations were conducted using the CFD code of STAR CCM+ for several melt coolant two-phase system configurations. The results demonstrate that the melt properties and velocity are the dominant factors on the melt droplet pre-conditioning behavior.