Determination of Specific Activity of 60Co in Steel Samples Exposed to the Atomic Bomb in Hiroshima.

Specific activities 60Co/Co in a steel sample from Yokogawa Bridge, 1295 m NNW, and three steel samples from the Atomic-Bomb Dome, 161 m NW from the hypocenter were measured by gamma-ray spectrometry and neutron activation analysis. The results expressed in a unit of dpm/mgCo were, 0.212±0.06 for Yokogawa Bridge, and 529±40, 561 ±38, and 524±74 for the Atomic Bomb Dome, 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 data are expected to serve for verification of the bomb neutron transport calculation.