COMMIX-1A Analysis of Fluid and Thermal Mixing in a Model Cold Leg and Downcomer of a PWR

Abstract

Fluid and thermal mixing in a model cold leg and downcomer of a PWR was analyzed using COMMIX-1A. The present analysis differs from previous analyses in three major aspects. First, extremely fine meshes were used to minimize numerical diffusion in the analysis. Second, one-equation (k) turbulence model was used to better model the turbulent flow. Third, curved surfaces were modeled by,several slanted planes to better represent the geometries. By using these improvements, CREARE 1/5-scale test No. 51 was reanalyzed. Significant improvements were achieved in the comparisons between the COMMIX calculations and the experimental data.