Numerical modeling of sodium fire—Part I: Spray combustion

Abstract

A sodium cooled fast reactor is one of the fourth generation advanced reactor designs. Liquid sodium is used as a coolant in such a reactor as it has excellent thermophysical properties. However liquid sodium can react violently when exposed to air or water. A sodium-air reaction typically occurs in two dominant modes: spray and pool. Typically, the spray mode of burning is considered as more severe than the pool model of burning. The focus of this paper is on sodium spray combustion.For the safety of a sodium cooled fast reactor, sodium-air reactions should be avoided. To avoid and to mitigate the consequences if a sodium fire occurs, it is essential to understand various physical phenomena involved in a sodium-air reaction. Computational fluid dynamics based numerical methods can be used for this purpose as they are known to resolve all spatial and temporal scales and simulate various physical processes governing sodium-air reaction. The goal of the work presented within this paper is to propose a numerical method to simulate sodium spray combustion and validate this method against experiments.A single sodium droplet combustion experiments is used for the validation. The model predictions of falling velocity and burned mass are in good agreement with experimental data. Additionally, parametric studies were performed to investigate the effects of initial droplet diameter, temperature and oxygen concentration on burning rate and on ignition time delay. Once sufficiently validated, the present method can be used for safety evaluation of a sodium fast reactor.