Thermal neutron cross-section and resonance integral of the 186W(n, γ)187W reaction

We measured the thermal neutron cross-section and the resonance integral of the reaction 186W(n, γ)187W by the activation method using a 197Au(n, γ)198Au monitor reaction as single comparator. The high-purity natural W and Au metallic foils with and without a cadmium shield case of 0.5 mm thickness were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the samples were measured by high-resolution γ-ray spectrometry with a calibrated p-type high-purity Ge detector. The necessary correction factors for γ-ray attenuation (Fg), thermal neutron self-shielding (Gth), and resonance neutron self-shielding (Gepi) effects, and the epithermal neutron spectrum shape factor (α) were taken into account. The thermal neutron cross-section for the 186W(n, γ)187W reaction has been determined to be 37.2 ± 2.1 barn, relative to the reference value of 98.65 ± 0.09 barn for the 197Au(n, γ)198Au reaction. The present result is, in general, in good agreement with most of the experimental data and the recently evaluated value of ENDF/B-VII.0 by 5.7%. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral obtained is 461 ± 39 barn, which is determined relative to the reference values of 1550 ± 28 barn for the 197Au(n, γ)198Au reaction. The present resonance integral value is in general good agreement with the recently measured values by 9%. The present result is lower than the evaluated ones by 10–13%.