A crack model of the Hiroshima atomic bomb: Explanation of the contradiction of "Dosimetry system 1986"

There has been a large discrepancy between the Dosimetry system 1986 (DS86) (1)) and measured data, some of which data in Hiroshima at about 1.5 km gro und distance from the hypocenter are about 10 times larger than the calcula tion. Therefore its causes have long been discussed(2-10)), since it will c hange the estimated radiation risks obtained based on the Hiroshima and Nag asaki data. In this study the contradiction was explained by a bare-fission -neutron leakage model through a crack formed at the time of neutron emissi on. According to the present calculation, the crack has a 3 cm parallel spa cing, 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 cl osing 3/4 of this symmetric geometry, because there are some data which sho ws asymmetry(5,12,13)). In addition, the height of the neutron emission poi nt was elevated 90 m. By using the asymmetric calculation, especially for l ong distant data located more than 1 km, it was verified that all of the ac tivity data induced by thermal and fast neutrons, were simultaneously expla ined within the data scattering. The neutron kerma at a typical 1.5 km grou nd distance increases 3 and 8 times more than DS86 based on the symmetric a nd asymmetric model, respectively.