Numerical Methodology of Sodium-Water Reaction with Multiphase Flow Analysis

A numerical methodology of sodium-water reaction (SWR) and a coupling method of SWR and multiphase flow analysis are proposed. Two SWR models are considered. One is a surface reaction model, which assumes that water vapor reacts with liquid sodium at the gas-liquid interface. The surface reaction is likely to be dominant in the initial phase of SWR. The analogy between mass and heat transfers is assumed to evaluate the diffusion-controlled reaction rate. The other is a gas-phase reaction model. If chemical reaction heating due to the surface reaction is large enough to vaporize the liquid sodium, it turns over in the gas-phase reaction. In the gas-phase reaction, water vapor reacts with sodium gas. The reaction mechanisms in the gas-phase reaction are investigated using an ab initio molecular orbital method. The reaction rate of the gas-phase reaction described by the Arrhenius law is obtained from the transition-state theory or the capture theory. The reaction models are employed in a compressible multifluid and one-pressure model using the Highly Simplified Marker and Cell method for multiphase flow analysis. As numerical examples, surface reaction with multiphase flow analysis and simplified gas-phase reaction analyses are carried out. It is confirmed that the present method is practically applicable to the coupling phenomena of SWR and multiphase flow.