Measurement of Thermal Neutron Capture Cross Section and Resonance Integral of the ^<129>I(n, γ)^<130>I Reaction
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To obtain fundamental data for research on the transmutation of nuclear wastes, the thermal neutron cross section and the resonance integral of the <SUP>129</SUP>I(n, γ)<SUP>130</SUP>I reaction have been measured using an activation method. The neutron cross sections for the formation of the ground (5<SUP>+</SUP>) state and the isomeric (2<SUP>+</SUP>) state of 130I were measured separately.<BR>Six <SUP>129</SUP>I targets were irradiated for 10min with thermal reactor neutrons; three of them containing 2.55-2.61 kBq of <SUP>129</SUP>I were irradiated within a Cd capsule, and the other three targets containing 259-261Bq of <SUP>129</SUP>I were irradiated without it. The Co/Al and Au/Al alloy wires were used to monitor the neutron flux and the fraction of the epithermal part (Westcott's epithermal index). The gamma-ray spectra from the irradiated samples were measured with a Ge detector.<BR>The thermal neutron capture cross section (the 2, 200m/s neutron cross section) and the resonance integral of the <SUP>129</SUP>I(n, γ)<SUP>130</SUP>I reaction were determined to be 12.5±0.5b and 15.6±0.7b for the formation of the groundstate <SUP>130g</SUP>I(5+), 17.8±0.7b and 18.2±0.8b for the formation of the isomeric state <SUP>130m</SUP>I(2+), and 30.3±1.2b and 33.8±1.4b for the formation of <SUP>130</SUP>I (the sum of the 2<SUP>+</SUP> and the 5<SUP>+</SUP> states), respectively. The sum of the thermal neutron capture cross sections forming the 2<SUP>+</SUP> and the 5<SUP>+</SUP> states was 12% larger than the evaluated values of JENDL-3.2 and ENDF/B-VI and that reported by Roy et al. This discrepancy is explained by the population of the isomeric level.
- Journal of Nuclear Science and Technology
Journal of Nuclear Science and Technology 33(4), p.283-289, 1996-04-25
Atomic Energy Society of Japan