Heterogeneous critical assemblies of enriched uranium metal plates and polyethylene

A series of measurements was performed in 1969 with polyethylene-moderated enriched uranium metal plates at the Oak Ridge Critical Experiments Facility (ORCEF) of Oak Ridge National Laboratory. The purpose of these experiments was to provide subcritical configurations for prompt neutron decay constant measurements; they were not significantly reported as critical experiments. These assemblies at delayed criticality provide systems with varying amounts of fissions induced by intermediate-energy neutrons and can be used to validate calculational methods for nuclear criticality safety. Most of the experiments described in this paper are restricted mainly to delayed critical configurations with cylindrical symmetry to also permit validation of Sn transport theory methods. The purpose of the paper is to make the criticality safety specialists aware of these measurements and to incorporate as much detail in this summary as practical. Further experimental details can be obtained from the author who has the logbook for the experiment