Data on neutrons in Hiroshima

Study of A-bomb radiation dosimetry began with collection of exposed samples for studying neutrons and gamma rays in Hiroshima. For neutrons, dosimetric information is found in the radioactivities of 60Co and 152Eu. These radioactivities, among those produced by neutrons from the A-bomb, have remained to date and can be relatively easily measured. They are found in iron and granite materials and are produced almost entirely by thermal neutrons (0.025 eV) and by slow neutrons (0 to 1 keV) containing thermal neutrons. Types, characteristics, and problems of the data on neutrons are described, and these are all related to specific activities as the basic quantity. It is necessary to study further the significance of the data for evaluation of neutron spectrum and dose, and to review to what extent these can be analyzed during the evaluation process