Measurements of the Protactinium-233 Resonance Integral

The neutron-capture resonance integral of ²³³Pa has been measured by irradiating cadmium-covered thorium wires, and, after suitable chemical separations, determining the quantity of ²³⁴U produced. Results are reported for two methods of measuring the irradiating flux. Monitor wires of cobalt in aluminum alloy give integrated fluxes based upon a value of 72.0 b for the resonance integral of ⁵⁹Co. Alternatively, measurements of the ²³³U produced by the irradiations give integrated fluxes based upon an effective resonance integral of 36.5 b measured for the ²³²Th wires. The experiments provide ²³³Pa resonance integral results of 846 ± 43 b employing cobalt-monitored fluxes, and 837 ± 43 b employing thorium-monitored fluxes. These results, which have an average value of 842 ± 35 b, include the l/ν component of the cross section, and are appropriate for a 1/E spectrum and a perfect filter with a low energy cutoff of 0.50 eV.