Buckling and integral spectrum measurements in U235 fuelled sub-critical assemblies moderated by BeO/fertile material mixtures

Abstract

Exponential experiments have been carried out to give the materials buckling of a number of near—homogeneous U235/aluminium alloy fuelled systems having fertile oxides intimately mixed with the BeO moderator. Relative fission rates of U235, U233, and Pu239 were also measured in the equilibrium spectrum region of each assembly. Five assemblies having 5 w/o natural uranium oxide in BeO were investigated for a range of BeO/U235 atomic ratios from 1500: 1 to 5700: 1. A similar range covering four assemblies was examined for 5 w/o thorium oxide in BeO. A comparison of the experimental results with diffusion theory calculations is included.