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

Abstract

We measured the thermal neutron cross-section and the resonance integral of the reaction W-186(n, gamma)W-187 by the activation method using a Au-197(n, gamma)Au-198 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 gamma-ray spectrometry with a calibrated p-type high-purity Ge detector. The necessary correction factors for gamma-ray attenuation (F-g), thermal neutron self-shielding (G(th)), and resonance neutron self-shielding (G(epi)) effects, and the epithermal neutron spectrum shape factor (alpha) were taken into account. The thermal neutron cross-section for the W-186(n, gamma)W-187 reaction has been determined to be 37.2 +/- 2.1 barn, relative to the reference value of 98.65 +/- 0.09 barn for the Au-197(n, gamma)Au-198 reaction. The present result is, in general, in good agreement with most of the experimental data and the recently evaluated value of ENDF/BVII.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 Au-197(n, gamma)Au-198 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%. (C) 2008 Elsevier B.V. All rights reserved.