title: Neutron spectrum and yield of the Hiroshima A-bomb deduced from radionuclide measurements at one location.
abstract: In this paper measurements of the radionuclides of 36Cl, 41Ca, 60Co, 152Eu and 154Eu in samples from Hiroshima, which were exposed to neutrons of the A-bomb explosion, are interpreted. In order to calculate the neutron spectrum at the sample site, neutron transport calculations using Monte Carlo techniques were carried out. Activation profiles in a granite mock-up irradiated with reactor neutrons could be reproduced by this method using DS86 input parameters. The calculated neutron spectrum at the sample site for non-thermal neutrons is identical to that obtained in DS86, but contains some 50% more thermal neutrons. The influence of parameters like soil composition, source terms and air humidity on the activation of these radioisotopes is discussed. The granite-covered earth at the sample site, for example, hardens the spectrum in comparison with DS86 values. Even when using a fission spectrum pointing downward and neglecting air humidity one cannot explain our 36Cl measurements. If the effective thermal neutron fluences, that have a similar ratio of resonance integral to thermal neutron capture cross sections obtained from 36Cl, 41Ca and 152Eu, are averaged, a bomb yield of about 16 kt is deduced in agreement with a bomb yield of (15 +/- 3) kt estimated in DS86.
authors.affiliation: Suzugamine Women's College, Hirosima, Japan.
authors.forename: W
authors.initials: W
authors.lastname: Rühm
authors.forename: K
authors.initials: K
authors.lastname: Kato
authors.forename: G
authors.initials: G
authors.lastname: Korschinek
authors.forename: H
authors.initials: H
authors.lastname: Morinaga
authors.forename: E
authors.initials: E
authors.lastname: Nolte
mesh_terms: D002132:Calcium Radioisotopes / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D003037:Cobalt Radioisotopes / Q000032:analysis; D005063:Europium / Q000032:analysis; D007564:Japan; D009502:Neutrons; D009689:Nuclear Warfare; D011868:Radioisotopes / Q000032:analysis*
chemical_list: D002132:Calcium Radioisotopes; D003037:Cobalt Radioisotopes; D011868:Radioisotopes; D005063:Europium; D002713:Chlorine