RÉSUMÉ
Objective To provide a reference for avoiding the harm to critical target organs following considerable inhalation exposure to the transuranium element americium (Am) as well as post-accident decorporation or other radiation protection measures. Methods We established calculation programs based on the generic criteria for internal radiation emergency preparedness and response in the IAEA Safety Guide No.GSG-2 and current new ICRP biokinetic models and parameters, taking an inhalation of 241Am (activity mean aerodynamic diameter of 5 μm, σ = 2.5) by an adult worker as an example; and determined that the critical target organs were the lung AI region, red bone marrow, and the main source organs leading to acute doses to the critical target organs were the lung AI region, blood, and trabecular bone surface. Results The retention fractions in the main source organs over time after 241Am inhalation were calculated. Conclusion After being absorbed into blood, Am moves quickly to other parts, and Am of different absorption types shows similar early changes in retention fractions in blood: the retention fractions of Am of S, M, and F types in blood peak around 0.03 d, and then halve around 1.7 d. Inhaled Am shows different changes over time in retention fractions in the lung AI region and trabecular bone surface in the early stage: the retention fractions of S- and M-type Am in the lung AI region change little with time, while F-type Am transfers quickly from the lung to blood; In trabecular bone surface, S-type Am increases quickly in the first 7 d, M-type Am gradually increases mainly in the first 2 weeks, and F-type Am increases quickly in the first 2 d.