ULTRA-SEPARATION OF NICKEL FROM COPPER METAL FOR THE MEASUREMENT OF NI-63 BY AMS

Measurements of Ni-63 (t(1/2) = 100 yr) produced by the reaction Cu-63 (n,p)Ni-63 could be used in the assessment of fast-neutron fluence fro m the Hiroshima atomic bomb, Such measurements would add new informati on to help resolve the current discrepancy between measured thermal ne utron activation values and those calculated with the DS86 dosimetry s ystem, It has been estimated that the Ni-63 production at 5 m from the hypocenter was (1.4 +/- 0.1) x 10(7) atoms/g Cu. Because of its sensi tivity, accelerator mass spectrometry (AMS) is ideal for measurements at this low level, However, Ni-63 has to be separated from large amoun ts of stable atomic isobar Cu-63 (69% of pure Cu), In this study, a pr ocedure is presented for the electrochemical separation of ultra-low a mounts of Ni from Cu. The method was developed using samples of electr ical Cu wire that were irradiated with fission neutrons from a Cf-252 source, The wire samples were electrochemically dissolved in a solutio n containing 1 mg of Ni carrier, The Cu was selectively deposited on a cathode at controlled potential. Measurements of total Ni after elect roseparation indicate similar to 100% carrier recovery, To prevent Cu contamination, AMS targets were prepared by nickel carbonyl generation , The AMS results show a successful quantitative separation of similar to 10(7) atoms of Ni-63 from 2-20 g samples of Cu.