A Simple Model for the Calculation of the Sodium-Voiding Effect on Neutron Leakages in a Fast Reactor Lattice II. Numerical Results for Hexagonal Lattices

On the basis of the simple formalism, numerical results for a set of hexagonal fast reactor lattices are presented. This allows the influence of lattice parameters on the diffusion coefficients and the sodium-voiding effect to be pointed out. Comparisons with calculations based on a cylindrical cell model are also given. They lead to the conclusion that the Wigner-Seitz approximation can underestimate the diffusion coefficients in fast lattices with larger gap widths.