｀２３９´Ｐｕの吸入被ばくにおける線量の人体特性パラメータによる変動の試算

Abstract

The International Commission on Radiological Protection has recently recommended a new dosimetric model of the human respiratory tract, which was issued as ICRP Publication 66. This model permits us to calculate the deposition of inhaled particles for the subjects with different values of anatomical and physiological parameters in the respiratory tract. Using this model, we studied the variation of doses of 239Pu observed for varying body sizes, levels of physical exertion and breathing habits. The results are as follows. 1) The ratio of doses between the subjects with different body sizes does not exceed the reciprocal of the ratio of their body weights, because the deposition in the thoracic region decreases with decreasing body size, which partly compensates for the increase in the SAF (specific absorbed fraction) of α-particle energy in the smaller body size. 2) The effective dose per unit intake of 239Pu via nose breathing decreases with increasing level of physical exertion. 3) It is notable that breathing through the mouth enhances markedly the effective dose.