Thermoluminescence Dosimetry of Gamma Rays from Atomic Bombs in Hiroshima and Nagasaki

Abstract

Thermoluminescence dosimetry techniques and typical roof tiles were used to obtain the distribution of the gamma ray dose from the atomic bombs dropped on Hiroshima and Nagasaki. Samples of roof tiles were chosen whose exact locations at the time of the bombings were known; none had been exposed to the fire which occurred in both cities shortly after the explosions. After being ground, washed and separated by a magnetic method, 300 mg of each sample powder was used to observe the thermoluminescence glow curve contributed from the bomb radiation. The same sample was exposed to 60Co gamma rays and after it had absorbed a known amount of gamma dose, the new glow curve was recorded for calibrating the thermoluminescence sensitivity. The equivalent gamma dose of the bomb radiation was obtained by comparing the bomb glow with the 60Co glow curve. The possible sources of error involved in this dosimetry are discussed in detail and the corrected gamma doses are compared with York's theoretical results. In the case of Nagasaki, our experimental values show excellent agreement with YORK'S values but in the case of Hiroshima, our values were about 30 per cent lower than York's.