Thermal neutron cross section and resonance integral measurements for the 133Cs(n,γ)134mCs reaction

Abstract

The thermal neutron cross section (σ0) and the resonance integral cross section (I0) for the formation of the isomeric state 134mCs by the 133Cs(n,γ)134mCs reaction were experimentally determined by using an activation method with a single monitor 55Mn. In this study, each of analytical grade MnO2 and Cs2CO3 powders was diluted separately with Al2O3 powder to reduce neutron self-shielding effects, and then they were irradiated with and without a cadmium shield case in an isotropic neutron field of the 241Am–Be neutron source. The activities produced in the samples were measured by a high resolution γ-ray spectrometry with a calibrated HPGe detector. The necessary correction factors for γ-ray self-attenuation, true coincidence summing effects, thermal and resonance neutron self-shielding effects, and epithermal spectrum-shape factor were taken into account. The σ0 and I0 values were determined to be σ0=2.77±0.14b and I0=22.8±1.7b for the 133Cs(n,γ)134mCs reaction. These results are discussed and compared to the previous measurements and the evaluated data. The present σ0 value is close to some of the previously reported experimental and evaluated data within the uncertainty limits. However, the present I0 value was found to be about 28–51% smaller than other experimentally reported ones appeared in the literature. The measured resonance integral cross section value agrees well only with the newest experimental data obtained by Nakamura et al. (1999) for the 133Cs(n,γ)134mCs reaction.