Thermal neutron cross-section and resonance integral of the 98Mo(n,γ)99Mo reaction

Abstract

We measured the thermal neutron cross-section and the resonance integral of the 98Mo(n,γ)99 Mo reaction by the activation method using a 197Au(n,γ)198 Au monitor reaction as a single comparator. The high-purity natural Mo 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 activated foils were measured with a calibrated p-type high-purity Ge detector. The necessary correction factors for the γ-ray attenuation (Fg), the thermal neutron self-shielding (Gth) and the resonance neutron self-shielding (Gepi) effects, and the epithermal neutron spectrum shape factor (α) were taken into account. In addition, for the 99Mo activity measurements, the correction for true coincidence summing effects was also taken into account. The thermal neutron cross-section for the 98Mo(n,γ)99Mo reaction has been determined to be 0.136 ± 0.007 barn, relative to the reference value of 98.65 ± 0.09 barn for the 197Au(n,γ)198 Au reaction. The present result is, in general, in good agreement with most of the experimental data and the recently evaluated values of ENDF/B-VII.0, JENDL-3.3, and JEF-2.2 by 5.1% (1σ). By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral for the 98Mo(n,γ)99Mo reaction is 7.02 ± 0.62 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 previously reported data by 8.8% (1σ). © 2008 Elsevier B.V. All rights reserved.