Measurement of thermal neutron cross section and resonance integral for the 158Gd(n, γ)159Gd reaction by using a 55Mn monitor

Abstract

The thermal neutron cross section and the resonance integral for the 158Gd(n, γ)159Gd reaction were measured by the activation method with using the 55Mn(n, γ)56Mn monitor reaction. The analytical grade MnO2 and Gd2O3 were mixed separately with Al2O3 powder to reduce both thermal and epithermal neutron self-shielding effects. Then, they were irradiated with and without a cadmium shield box in an isotropic neutron field provided by three 241Am–Be neutron sources. The induced activities in the samples were measured by a p-type HPGe detector. For the irradiated samples, epithermal neutron spectrum-shape factor (α), correction factors required for thermal and epithermal neutron self-shielding and for the measured γ-rays, self-absorption and true coincidence summing effects were taken into account. The thermal neutron cross section was measured to be 2.15±0.14b for the 158Gd(n, γ)159Gd reaction. The previously reported experimental data for the thermal neutron cross section are distributed from 0.9 to 3.89b. According to the definition of Cd cut-off energy at 0.55eV, the resonance integral cross section was measured as 75.3±7.0b. The present resonance integral value agrees with some previously reported experimental and evaluated values for the 158Gd(n, γ)159Gd reaction, e.g. 80b measured by Van DerLinden et al. (1974), 72.06 b evaluated by JENDL-4.0 (Shibata et al., 2011), 73b reported by Mughabghab (2006) and Holden (1999).