Flow characteristic inside a single basket includes a fuel assembly

Flow characteristics inside a fuel basket containing a spent nuclear fuel assembly were analyzed. Since the geometry of a nuclear fuel assembly is very complicated, a porous media model and effective thermal conductivity were used to simplify the fuel assembly geometry. The permeability was calculated in three different ways. These included a theoretical approach using the friction force assuming laminar flow; a computational fluid dynamics (CFD) calculation using shear stress; and a CFD calculation using pressure drop. The results of the CFD calculations by shear stress and pressure drop showed good agreement. The result of the theoretical approach was 50% less than the CFD results. This was because the theoretical approach did not fully consider the flow resistance resulting from the complex geometry of the spacer grid and fuel rods