Calculation of retention fractions in main source organs following acute americium inhalation based on ICRP biokinetic models
Objective To provide a reference for avoiding the harm to critical target organs following considerable inhala-tion exposure to the transuranium element americium(Am)as well as post-accident decorporation or other radiation protec-tion measures.Methods We established calculation programs based on the generic criteria for internal radiation emer-gency preparedness and response in the IAEA Safety Guide No.GSG-2 and current new ICRP biokinetic models and para-meters,taking an inhalation of241 Am(activity mean aerodynamic diameter of 5 μm,σ=2.5)by an adult worker as an ex-ample;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 after241 Am inhalation were calculated.Conclusion After being ab-sorbed into blood,Am moves quickly to other parts,and Am of different absorption types shows similar early changes in re-tention 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.
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