Dosimetric analysis of initial radiation at 1.2 km from ground zero: Neutron and gamma flash determination for the little boy air burst

This work is devoted to a precision dosimetric reconfiguration of the ionizing radiation field formed as a result of the air nuclear explosion of the uranium-type device Little Boy over Hiroshima on 6 August 1945. The focus is on computational-analytical modeling of the propagation of the combined flux of fast neutrons and secondary gamma quanta at a slant distance S=1341.6 mS=1341.6m (corresponding to a ground range Rg=1200 mRg=1200m at a burst height h=600 mh=600m). Using the standardized revisions of the DS86 and DS02 dosimetry systems, the absorbed dose and dose equivalent reaching a total value on the order of 5 Sv were calculated. The processes of inelastic neutron scattering on atmospheric nitrogen and oxygen nuclei, the generation of radiative capture, and the radiobiological consequences of mixed radiation exposure on critical human organs within the framework of the development of severe acute radiation syndrome (ARS) are considered.