Criticality Measurements on Nearly Homogeneous Enriched Uranium-Graphite Systems

Accurate critical parameters have been obtained for bare, nearly homogeneous assemblies of enriched uranium and graphite having C/U atom ratios in the range 960 to 23 000. Among the quantities measured were k_eff, critical bucklings, extrapolation distances, spectral indices, and neutron lifetimes. Particular attention was paid to the problem of neutrons returning from the surroundings.