Radiochemical determination of neutron capture cross sections of 241Am

The thermal neutron capture cross sections and the neutron capture resonance integrals of 241Am leading to the production of the isomer 242mAm and the ground-state 242gAm were measured radiochemically by the Cd-ratio technique with neutron flux monitors of Co/Al and Au/Al alloy. Highly-purified 241Am targets were irradiated in an aluminum capsule by using JMTR. The neutron fluxes and their epithermal neutron fractions were determined by measuring γ-rays of 60Co and 198Au. The yields of 242mAm and 242gAm were decided by analyzing growth and decay curves of the α-ray activity ratios 242Cm/241Am. The resultant thermal neutron capture cross sections are 85.7 ± 6.3 b and 768 ± 58 b for 242mAm and 242gAm, and the resonance integrals 114 ± 7 b and 1,694 ± 146 b, respectively. The differences between the present results and the evaluated values by Mughabghab are 38-59%. The isomeric ratios, g/(m+g), of 0.90 ± 0.09 for thermal neutrons and 0.94 ± 0.11 for epithermal neutrons are, however, almost consistent with evaluated values. (author)