A Crack Model of the Hiroshima Atomic Bomb: Explanation of the Contradiction of "Dosimetry System 1986"

概要

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There has been a large discrepancy between the Dosimetry system 1986 (DS86) 'and measured data,　some of which data in Hiroshima at about 1.5 km ground distance from the hypocenter are about 10 times　larger than the calculation. Therefore its causes have long been discussed　, since it will change the　estimated radiation risks obtained based on the Hiroshima and Nagasaki data. In this study the contradiction　was explained by a bare-fission-neutron leakage model through a crack formed at the time of neutron　emission. According to the present calculation, the crack has a 3 cm parallel spacing, which is symmetric with respect to the polar axis from the hypocenter to the epicenter of the atomic bomb. We made also an　asymmetric opening closing 3/4 0f this symmetric geometry, because there are some data which shows　asymmetry '' . In addition, the height of the neutron emission point was elevated 90 m. By using the　asymmetric calculation, especially for long distant data located more than 1 km, it was verified that all of the　activity data induced by thermal and fast neutrons, were simultaneously explained within the data　scattering. The neutron kerma at a typical 1.5 km ground distance increases 3 and 8 times more than DS86　based on the symmetric and asymmetric model, respectively.
日本放射線影響学会の論文