Determination of Specific Activity of Cobalt (⁶⁰Co/Co) in Steel Samples Exposed to the Atomic Bomb in Hiroshima

Abstract

Specific activity ⁶⁰Co/Co in two steel samples taken at 687m S and 1295m NNW from the hypocenter was measured by gamma-ray spectrometry and neutron activation analysis. The results were, respectively, (2.64 ± 0.38) × 10¹ and (3.09 ± 0.48) × 10^-1 dpm/mg Co at the time of bombing, which are consistent with previous data by Hashizume et al. for steel rings on the surface of roofs of buildings. The present data are expected to serve as verification of the bomb neutron transport calculations.
Content of nickel and copper in the samples, determined by colorimetric and neutron activation methods, respectively, was too small to account for any significant ⁶⁰Co production by the (n, p) and (n, α) reactions.