Thermoluminescence dosimetry of the Hiroshima atomic-bomb gamma rays between 1.59 km and 1.63 km from the hypocenter.

Gamma-ray kermas from the Hiroshima atomic bomb were measured by a thermoluminescence (TL) method using tile specimens collected from five locations on the rooftop of a building (Postal Saving Bureau), 1,591-1,635 m from the hypocenter. Four tile specimens each from five locations were sampled and quartz grains were extracted from them. TL of these grains were analyzed by the high temperature TL method and gamma-ray kermas were obtained. The results in tissue kerma, on average, are 21% higher (standard errors are 4.3-7.3%) than the DS86 estimation. The present data and the reported TL results indicate that the measured gamma-ray kermas begin to exceed the DS86 values at about 1.3 km and the discrepancy between them increases with ground distance. This discrepancy is attributed to errors in the DS86 neutron source spectrum and is supported by previous neutron activation measurements.