부산대학교 도서관

Radiation doses of gamma rays and neutrons initially released from the bombs at detonation have been well documented and a consensus of opinions was obtained among physicists as the Dosimetry system 2002 (DS02). However, as to the exposure from the presence of neutron activation products in the soil, or from fission products in the fallout, the discussion has still been continuing because of the lack of measurement data. We estimate radiation dose using enamel of molars donated by atomic bomb survivors using electron spin resonance (ESR) technique. In the present study, we measured individual doses of molars from atomic bomb survivors in Hiroshima who were present at distances of about 3 km or further from the hypocenter of the bomb, and have DS02 estimated doses of less than 5 mGy. A total of 56 molars that were donated from 49 atomic bomb survivors who were 10 years old or over at the time of the bombing. We cut each tooth into two parts (the buccal and lingual parts) and isolated enamel separately to find the effects of dental X rays. ESR signal intensity was used to calculate 60Co gamma-ray equivalent dose. The results from 56 molars provided estimated doses which vary from −200 mGy to 500 mGy, and the mean ±SD dose was 70±157 mGy for the buccal parts and 34±127 mGy for the lingual parts of the molars. Four survivors were within the estimated area of black rain, which their individual estimated doses were not outstandingly high. Three molars indicated estimated doses of 300 to 400 mGy for both buccal and lingual portions, which indicates their possible exposures to excess doses of penetrating radiation while their origins remain to be determined. The estimated doses from 49 distally exposed survivors provided no evidence to support claims that they received large doses (e.g., 1 Gy) of external penetrating radiation resulting from residual radiation exposures.