Specific Activities of ^<60>Co and ^<152>Eu in Samples Collected from the Atomic-Bomb Dome in Hiroshima

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Neutron induced activity/60Co/ 152Eu /Atomic Bomb/Gamma-ray spectroscopy Neutron-induced activities ^Co and 152Eu have been measured for samples collected from the Atomic-Bomb Dome locating at 161 m from the hypocenter of the Hiroshima Bomb. Specific activities ^Co/ Co and 152Eu/Eu at the time of the detonation have been determined as 10.0+1.0 Bq mg"1 (steel sample S4) and 80+9Bqmg"1 (granite sample Gl), respectively. Detailed measurements of 60Co and 152Eu activities for samples collected from various locations of the Dome show almost no directional dependence whether the sample faced to the epicenter,or not, nor vertical height dependence between 17 m height and the ground level. In addition, 152Eu was not detected in the sample collected from the basement. It has been shown that the present ^Co activity value, the nearest steel one to the hypocenter, as well as other short distance data are systematically lower than the calculated values based on the neutron fluence of the DS86.
日本放射線影響学会の論文