Construction of the new dosimetry system instead of DS86 according to the joint study with US and analysis of radiation effects

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Reevaluation of atomic bomb doses for the survivors in Hiroshima and Nagasaki which was named as "Dosimetry system 1986 (DS86)" have been performed by the effort of US-Japan joint study. Last year in Mach 2003, the senior committee was held in Tokyo and new dosimetry system 2002 (DS02) was approved. There were two major points in this reevaluation study. One was the difference between DS86 and Eu-152 data at long distances (more than 1km). Sometimes the data were 5-10 times larger than DS86 estimation. The other was the difference between the same Eu data and DS86 at the short distance. To the contrary, the Eu-152 data are smaller than the DS86. The long distance problem was solved according to the intercomparison study of Eu-152 and C1-36 using 18 samples, which were stored at Research Institute for Radiation Biology and Medicine, Hiroshima University. The plan was proposed by this head investigator. Conclusion was simple, because the data were reduced and agreed with DS86. The samples used were about 1kg, which were about 10 times heavier than before and ultra low background gamma-ray measurement system in Ogoya of Kanazawa University was used by Dr. Komura. These were much better improvements of the measurements than before. Maybe due to background gamma-ray's contamination in Eu-152 gamma-rays used for measurements, the data reduced. The short distance problem was solved to elevate the explosion height 20m.However, a Nature paper indicating Ni-63 data was published on 31 July 2003 without any permission to US and Japanese working groups. It said that the problem of neutron discrepancy was solved by the Ni-63 measurements, however, it is solved by the intercomparison study and the other information. Both sides sent Nature their addendum in December 2003 and Nature responded in March 2004. We are now waiting results.