Neutron Spectra and Kinetic Properties in Fast Subcritical Assemblies Containing Uranium-235, Uranium-238, and Carbon

A subcritical time-of-flight spectrum facility (STSF) has been used to study the neutron spectra and kinetics of two fast assemblies designated STSF-2 and STSF-2A. Neutron spectra have been measured by the time-of-flight method between 5 MeV and 500 eV in the core and the reflector of the STSF-2 which is essentially the same as the ZPR-3 Assembly 17. The STSF-2 core was loaded with plate type elements and the neutron spectrum was determined at the surface of a graphite plate, an enriched uranium plate, and a depleted uranium plate. Detailed transport calculations have been performed with ENDF/B version 1 cross sections and compared to the experimental data which had been reduced by an original method. Finally, kinetic measurements have been performed on assembly STSF-2A which confirm the validity of the time-dependent calculations involved in the time-of-flight data analysis.