Effective Dose Coefficients for Intakes of Uranium Via Contaminated Wounds for Reference Adults.

ABSTRACT: Effective dose coefficients for intakes of uranium radionuclides via contaminated wounds have been calculated for reference adults following the procedures in the ICRP 103 series. The number of transformations in each source region for all members of the radioactive series from time of intake to 50 y post intake are calculated by coupling the NCRP 156 wound model to the ICRP 137 systemic models and ICRP 100 human alimentary tract model. Together with the ICRP 107 nuclear decay data for dosimetric calculations, the ICRP 133 specific absorbed fractions are implemented to calculate the radiation-weighted S coefficient deposited in each target organ or tissue from each transformation in each source region. Effective dose coefficients for different categories of intake materials via contaminated wounds are calculated for the three major uranium isotopes-238U, 235U, and 234U. Originating from the combined effects of the new absorbed fractions, biokinetic and dosimetric models, the new coefficients are generally reduced by a percentage of 23-28% as compared to the old ones. The new dose coefficients benefit the assessment of internal exposures for intakes of uranium via contaminated wounds in actual applications.

Biokinetic Method on Simultaneous Intake of Radionuclides from Multiple Intake Scenarios for Application in Internal Exposures.

Biokinetics underlies the basis for assessment of internal exposures. This paper develops a biokinetic method on simultaneous intake of radionuclides from multiple intake scenarios in internal exposures. With numerical techniques that transform the whole biokinetics between the coupled and decoupled representations of the same problem, this method applies to coupled biokinetics with complex structures and has no restrictions of practical importance on the number of intake scenarios, the number of intake parent radionuclides and decay products, and the complexity of decay relationships between parent and progeny nuclides. For illustration, this method is applied to an assumed case of mixed inhalation and ingestion of weapon-grade plutonium material for reference workers that is focused on Pu and Am. Due to coupled biokinetics between the direct intake and ingrowth parts in different intake pathways, the multiple intake results (the contents of lungs, daily excretions, and cumulative contents) display richer behaviors as compared to single intake cases. This method benefits both the prospective and retrospective assessment of internal exposures for complex intake cases in actual applications.

The Influence of Aerosol Density and Shape Factor on the Assessment of Internal Exposure to 239Pu.

Internal exposure due to inhalation of aerosols depends on the ratio of aerodynamic shape factor (χ) to aerosol mass density (ρ). Inhaled aerosol parameters may differ from the default ρ and χ values provided by the International Commission on Radiological Protection, which are adopted for the assessment of internal exposures. This paper focuses on the influences of χ/ρ on the assessment of internal exposure to Pu for reference workers. Regional deposition fractions are found to decrease with increasing χ/ρ, and larger decreases are observed with smaller activity median aerodynamic diameter aerosols, while the slow clearance fractions (fs) in the tracheobronchial region are more sensitive for larger activity median aerodynamic diameter aerosols. Results from biokinetics calculations reveal that both the time-dependent content (excretion) and cumulative activities are determined mainly for particles initially deposited in the alveolar-interstitial region, while fs affects the local cumulative activities in the tracheobronchial region. χ/ρ is proven to have different influences for aerosols with different activity median aerodynamic diameters. The default χ/ρ values can be used when activity median aerodynamic diameters are greater than 1 µm, while one should pay attention to the value of χ/ρ when activity median aerodynamic diameters are less than 1 µm, where significant influence may be anticipated.