Development of a function calculating deposition probabilities of inhaled aerosols compatible with the revised Human Respiratory Tract Model

Manabe, Kentaro   ; Takahashi, Fumiaki  

A dose estimation system which integrates external and internal exposure is being developed to contribute to radiation protection for members of the public from radionuclides released into the environment. For internal exposure, inhalation of radioactive aerosols should be considered, and internal doses by inhalation depend on their diameters, densities, shape. However, dose coefficients published by the International Commission on Radiological Protection (ICRP) are developed with the assumption that distribution of particle diameters has a specific log-normal distribution. In addition, the existing codes can consider only a single value or a log-normal distribution for diameters of particles and do not fit the divisions of particle deposition determined by the revised Human Respiratory Tract Model (revised HRTM). Therefore, we developed a function of the dose estimation system which can calculate deposition fractions of inhaled particles having a given diameter distribution, density, and shape factor using the deposition model of ICRP. This function reproduced the deposition fractions for adult males in a light exertion level. In future, this function will be put in the dose estimation system to calculate internal dose coefficients under various conditions.