Measurements of thermal-neutron capture cross-section and resonance integral of neptunium-237

Abstract

ABSTRACT The thermal-neutron capture cross-section (σ 0) and resonance integral (I 0) were measured for the 237Np(n,γ) 238Np reaction by an activation method. A method with a Gadolinium filter, which is similar to the Cadmium difference method, was used to measure the σ 0 with paying attention to the first resonance at 0.489 eV of 237Np, and a value of 0.133 eV was taken as a cut-off energy. Neptunium-237 samples were irradiated at the pneumatic tube of the Kyoto University Research Reactor in Institute for Integral Radiation and Nuclear Science, Kyoto University. Wires of Co/Al and Au/Al alloys were used as monitors to determine thermal-neutron fluxes and epi-thermal Westcott’s indices at an irradiation position. A γ-ray spectroscopy was used to measure activities of 237Np, 238Np and neutron monitors. On the basis of Westcott’s convention, the σ 0 and I 0 values were derived as 186.9 ± 6.2 barn, and 1009 ± 90 barn, respectively.