Reevaluation of atomic bomb dose 1986 (DS86) -Radiation effect for atomic bomb survivors according to new dosimetry system-

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There are residual problems concerning DS86, therefore we proceed the study of the reevaluation of atomic bomb dose in Hiroshima and Nagasaki. We have been performed collaboration with some of the US groups. In 1996 we had workshop between US group and decided to begin a formal joint study. In 1997 we had workshop at RERF and discussed further studies.Problems are as follows : 1. We aagreed that there exists the systematic discrepancy between neutron induced data and calculation according to the former studies. We should note especially that the discrepancy over the distance of 1km is very large. 2. Therefore we should make intercomparison measurement among different groups. 3. To measure directly fast neutrons, we collect copper samples and measure neutron-induced nickel 63 as a result of copper n, p reaction. 4. In the case of Nagasaki data there are two contradicting data groups.One has the same systematic discrepancy as Hiroshima and the other has a good agreement with DS86. We mus … More t collect samples and make intercomparison between the two groups. 5. I proposed an assumption of leakage of bare fission neutrons from a crack which was produced when the botoom of the atomic bomb was came off. I had an answer from US group that it is not plausible, however they promised me to bring back and consider among the specialists, because there are not good possible process to solve neutron discrepancy in Hiroshima except this way. I also proposed the assumption to solve everything in Hiroshima.They are (1) there was 5% leakage of bare fission neutrons from the crack, (2) elevate 90m of the height of explosion and (3) increase 20% of the yield. The US group agreed the (3) from the different evidence. The neutron data more than 1km in Hiroshima is too large to explain from the transport calculation, therefore, we need to consider background problem of the measured data. We proceed the research study according to these discussions to have accurate dose evaluating system for atomic bomb survivors in Hiroshima and Nagasaki. Less