Host: The Japan Radiation Research Society
Radiation doses for the atomic bomb survivors have been reevaluated repeatedly. The first systematic dosimetry was done in 1957 (T57D). In 1965, this dose was evaluated by the collaboration between US and Japan and obtained as Tentative 1965 Doses (T65D)). The T65D was named with Tentative. However this was obtained according to the actual experiments with nuclear explosions etc. for 10 years of study, of which doses were thought to be the final evaluation. From the T65D radiation risks was obtained using the epidemiology study in Radiation Effects Research Foundation (RERF). After the T65D, US scientists found some problems comparing with the obtained dose results by using a super computer in 1970s. In 1981 reevaluation of this T65D was begun. In 1987, the new Dosimetry Study 1986 (DS86)) was obtained. The major change of DS86 was the decrease of neutron dose in Hiroshima, of which change was from 1/5 to 1/9 of T65D. In T65D neutron doses in Hiroshima was large and Nagasaki's was negligible and successfully explained the difference of leukemia incidence by assuming a neutron RBE. However, by the DS86, neutron doses in Hiroshima and Nagasaki became negligible; therefore neutron RBE data could not be estimated after DS86. Again in this DS86 there found some discrepancy between calculation and measurements in the Hiroshima's neutron doses. US-Japan joint study was begun and new Dosimetry Study 2002 (DS02)) was established. The difference between DS02 and DS86 was the increase of gamma rays about 10% for both in Hiroshima and Nagasaki. US group calculated organ doses and they will calculate radiation risks. These risks will be discussed at the International Congress of Radiation Protection (ICRP) and will be introduced in each country's law of radiation protection, which limits radiation exposures for radiation workers and general people.
