Integral Measurements of the Epithermal Neutron Capture-to-Fission Cross-Section Ratios of ²³³U and ²³⁵U

Samples of uranium enriched in ²³³U and in ²³⁵U have been irradiated with cobalt monitors in high-flux facilities in both cadmium-covered and bare assemblies. Radiometric analyses of irradiation samples provide data concerning thermal and epithermal capture and fission reactions from which experimental results are obtained. The epithermal capture-to-fission cross-section ratios of ²³³U and ²³⁵U at infinite dilution are 0.175 ± 0.006 and 0.499 ± 0.016, respectively, for a l/E spectrum with a low-energy cutoff of 0.50 eV. Resonance integrals for capture and fission are evaluated in terms of cobalt cross sections.