Interference Effect of Neutron Streaming Between Different Fast Critical Assembly Cells

An approximate method for calculating the interference of neutron streaming between different regions (drawers) in fast critical assemblies is described by applying the well-known Benoist formula to super cell problems. The interference effect on the diffusion coefficient was numerically evaluated and the results are compared with those obtained by Yoshida’s method. Sodium void worths in control rod positions (control rod follower channel) relative to the sodium-filled channel are calculated on the basis of diffusion theory with the interference effect and compared with the results obtained from transport calculations. The comparison reveals that the inclusion of the interference effect improves the calculational accuracy remarkably.