Differential neutron spectrum measurements on U233/BeO and U235/BeO assemblies in the reactor MOATA.

Abstract

Differential spectrum measurements were made on a series of U233 and U235 fuelled, beryllia moderated assemblies with fuel to moderator atomic ratios ranging from 1/6500 to 1/700. A preliminary comparison has been made with calculations of the spectra and, in the thermal region, fair agreement was found for the U235 lattices, but for U233 the experimental thermal flux was significantly higher than that calculated. In the epithermal region above 50eV, the experimental flux was higher than that calculated for the U235 assemblies, but was in reasonable agreement with calculation for U233.