Nickel-63 production in copper samples exposed to the Hiroshima atomic bomb: estimation based on an excitation function obtained by neutron irradiation experiments

The upper and lower limits of the excitation function of the 63 Cu(n,p) 63 Ni reaction were experimentally determined, and the number of 63 Ni nuclei produced in copper samples exposed to atomic bomb neutrons in Hiroshima was estimated by using the experimental excitation functions and the neutron fluences given in the DS02 dosimetry system. The estimated number of 63 Ni nuclei was compared with that measured and with that calculated using the DS02 dosimetry system and the corresponding ENDF/B-VI cross section. In comparison with DS02, there is about a 60% maximum difference in 63 Ni production at the hypocenter when the experimental upper cross section values are used. The difference becomes smaller at greater distances from the hypocenter and decreases, for example, to less than 30 and 5% when using the upper and lower experimental cross sections at 1,000 m, respectively.