Thermal-Neutron Capture Cross Sections and Resonance Integrals of the ^<80>Se(n,γ)^<81m,81g>Se Reactions

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The thermal-neutron capture cross sections (σ0,m and σ0,g) and resonance integrals (I0,m and I0,g) leading to the isomeric and ground states of 81Se were measured by the activation method. Samples of high-purity (99.99%) selenium oxide were irradiated in a rotary specimen rack of the research reactor of Rikkyo University. Wires of Co/Al and Au/Al alloys, which have different sensitivities to neutrons in the thermal and epithermal energy regions, were irradiated to monitor the thermal neutron fluxes and the epithermal components at the same position of the rotary specimen rack. The cadmium-shielded samples were also irradiated to obtain the cadmium ratio and the resonance integrals (I0,m and I0,g). A high-purity Ge detector was used to measure the γ-rays emitted from the irradiated samples and wires, and reaction rates were calculated from γ-ray yields. On the basis of Westcott’s convention, the cross sections were obtained as follows: σ0,m=0.057±0.003 b and I0,m=0.186±0.014 b leading to 81mSe, and σ0,g=0.536±0.046 b and I0,g=0.867±0.102 b leading to 81gSe.
社団法人日本原子力学会の論文
2008-02-25