Measurements of 60Co in massive steel samples exposed to the Hiroshima atomic bomb explosion

Abstract

To study discrepancies in retrospective Hiroshima dosimetry, the specific activity of 60Co in 16 steel samples from Hiroshima was measured using gamma-ray spectrometry in underground laboratories. There is general agreement between these new activity measurements and the specific activities derived from previously calculated dose values on the one hand and former measurements of samples gathered at distances less than 1,000 m from the center of the explosion (less tahn 1,000 m slant range) on the other. It was found that activities at long range (more than 1,300 m slant range) were mainly cosmogenically induced. Furthermore, at long range, these results are in disagreement with older measurements whose specific activity values were 10 to 100 times higher than predicted by computer model calculations in DS86 and DS02. As a consequence, the previously reported discrepancy is not confirmed.