Application of New Icrp Recommendations on Dose Calculation for Workers after Inhalation Intake of Uranium Radionuclides

Purpose: Harmonization and improvement of the system for regulating the internal radiation exposure of workers and the basic requirements for ensuring radiation safety, taking into account the application of new international requirements and recommendations. Material and methods: A brief description of the procedure for calculating absorbed and equivalent doses in organs and tissues after the intake of radionuclides into the human body is presented, using the biokinetic and dosimetric models adopted in the new ICRP recommendations, as well as a discussion of the impact of these changes on the results of calculating dose coefficients for the case of inhalation intake of uranium-235 radionuclide. Results: The effective dose values and equivalent doses to organs and tissues for workers were calculated depending on the time after a single inhalation intake of uranium-235 aerosol, according to new models [1–12] and according to previous ICRP models [15, 16]. The calculation of the effective dose according to the new models included calculations of equivalent doses for 14 main organs and tissues and 13 organs and tissues classified as “remainder tissues” as described in ICRP Publication 103 [3]. The committed effective dose was then calculated according to the new approach using the average of the equivalent doses for the reference adult male, HTM, and the reference adult female, HTF, as well as the tissue and organ weighting factors, WT, adopted in ICRP Publication 103. The values of the effective dose and equivalent doses on the red bone marrow, lungs and remainder tissues vs time in the range from several days to 18250 days (50 years) after a single inhalation intake of an aerosol of uranium-235 for standard value AMAD=5 µm and types of compounds F, M, S, F/M and M/S are presented according to new and previous ICRP models. It is shown that the value of the dose coefficient for type F, calculated by new models, is 2.6 times (2.3E-07÷6.0E-07) less than that calculated by previous ICRP models, and the value of the dose coefficient for type F/M calculated by new models is 1.6 times (3.8E-07÷6.0E-07) less than the value of the dose coefficient for type F calculated by previous ICRP models. For uranium trioxide UO3, taking into account its transition from compound type M to F/M, the value of the dose coefficient for committed effective dose according to the updated model of the respiratory tract is 4.7 times (3.8E-07÷1.8E-06) less than the corresponding value for the previous model of the type M respiratory tract. The committed effective dose value for compound type M, calculated using the new models, is 1.4 times (1.3E-06÷1.8E-06) less than the same value calculated using the previous ICRP models. The value of the committed effective dose for type M/S compounds (which, according to the new model of the respiratory tract, include uranium oxide U3O8 and dioxide UO2), calculated according to new models, is 1.2 times (5.1E-06÷6.1E-06) less than the value calculated from previous ICRP models for type S compounds (which included U3O8 and UO2 in the previous respiratory tract model). Conclusion: From the above data it follows that in case of the adoption of national radiation safety standards to new ICRP models, differences in the values of dose coefficients will result in a change of annual limits of intake (ALI) in the corresponding proportion for the types of uranium aerosol compounds noted above.