STUDIES OF RADIOACTIVITY PRODUCED BY THE HIROSHIMA ATOMIC-BOMB .1. NEUTRON-INDUCED RADIOACTIVITY MEASUREMENTS FOR DOSE EVALUATION

This review summarizes measurements made of Eu-152 and Co-60 radioactivity induced by neutron radiation from the Hiroshima atomic bomb (A-bomb) with the goal of estimating the neutron dose released by the bomb. Prior to these measurements, A-bomb-irradiated specimens such as rocks and pieces of concrete, which had not been shielded were collected. The specific radioactivity obtained (in bequerels per gram of Eu or Co) were compared with those calculated from DS86 neutrons. Findings of usefulness of Eu-152 data within 700 m ground range are reported and systematic differences between measured activities and calculations are discussed. The Eu-152 data were also useful for the discussion of circular asymmetry, and there was no asymmetry within the experimental errors. This review also covers the similar difference found in P-32 data, which were measured immediately after the A-bomb, along with the other Eu-152 and Co-60 data. The need for more measurements of Eu-152 activity in samples farther away from the hypocenter in order to verify the DS86 calculations is also discussed.