ABSTRACT
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.
Subject(s)
Radiation Exposure , Radioisotopes/administration & dosage , Radioisotopes/pharmacokinetics , Algorithms , Americium/administration & dosage , Americium/pharmacokinetics , Eating , Humans , Inhalation Exposure , Lung/metabolism , Lung/radiation effects , Models, Biological , Occupational Exposure , Plutonium/administration & dosage , Plutonium/pharmacokinetics , Prospective Studies , Radiation Dosage , Radiation Protection , Retrospective Studies , Risk Assessment , SoftwareABSTRACT
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.
Subject(s)
Radiation Dosage , Radiation Monitoring/standards , Uranium/metabolism , Adult , Biological Transport , Female , Humans , Male , Occupational Exposure , Recommended Dietary AllowancesABSTRACT
Radioactive noble-gas monitoring is necessary in nuclear facilities. A NaI(Tl)-based radioactive noble-gas monitoring system was developed. In order to increase the amount of air to be measured, the sample vessel of this system was larger than that of other systems, and was pressurized to about 5 × 105 Pa. In a laboratory experiment, technical ways to reduce the memory effect were investigated. In field tests, a method of spectra analysis was established and calibration coefficients and minimum detectable concentrations of 133Xe, 135Xe and 41Ar were calculated. Finally, detection ability was compared with other online monitoring systems.
ABSTRACT
The G(E) function method is a spectrometric method for the exposure dose estimation; this paper describes a method based on Monte Carlo method to determine the G(E) function of a 4â³ × 4â³ × 16â³ NaI(Tl) detector. Simulated spectrums of various monoenergetic gamma rays in the region of 40 -3200 keV and the corresponding deposited energy in an air ball in the energy region of full-energy peak were obtained using Monte Carlo N-particle Transport Code. Absorbed dose rate in air was obtained according to the deposited energy and divided by counts of corresponding full-energy peak to get the G(E) function value at energy E in spectra. Curve-fitting software 1st0pt was used to determine coefficients of the G(E) function. Experimental results show that the calculated dose rates using the G(E) function determined by the authors' method are accordant well with those values obtained by ionisation chamber, with a maximum deviation of 6.31 %.
