Tetsuji Imanaka
Research Reactor Institute, Kyoto University

Abstract

In order to provide basic information for the HiSoF project, current knowledge is reviewed about the process of atomic bomb cloud formation and radioactivity distribution. Based on the results of hydrodynamic simulation as well as observations at Nevada test site in US, the time course of the atomic bomb cloud formation was discussed. The amount of radioactivity that could be the origin of local fallout was calculated both for fission products and neutron-induced radioactivity.
From the preliminary analysis using simple assumptions, 0.1 % deposition of fission product radionuclides in the atomic bomb cloud could cause radiation exposure more than 10 mGy, while radiation exposure was at most 1 mGy from the deposition of neutron-induced radionuclides in dust or fire ash after the bombing. More detailed and reliable evaluation is expected through the efforts of HiSoF.