Flow-Through Dissolution of Uranium-Thorium Ore Dust, Uranium Concentrate, Uranium Dioxide, and Thorium Alloy in Simulated Lung Fluid

Duport, P.; Robertson, R.F.S.; Ho, Kim Eung; Horvath, F.J.

doi:10.1093/rpd/38.1-3.121

Cited by 3 publications

(2 citation statements)

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“…4). Previous work demonstrated that a pH shift from 7 to 8 reduced the dissolved fraction by a factor ≈0.8 for UO 2 material (Duport et al 1991). Sutton and Burastero (2004) used a chemical thermodynamic speciation code to model dissolution characteristics of uranium in simulated lung fluid.…”

Section: Uncertaintiesmentioning

confidence: 98%

Particle Size-dependent Dissolution of Uranium Aerosols in Simulated Lung Fluid: A Case Study in a Nuclear Fuel Fabrication Plant

et al. 2022

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Inhalation exposure to uranium aerosols can be a concern in nuclear fuel fabrication. The ICRP provides default absorption parameters for various uranium compounds but also recommends determination of material-specific absorption parameters to improve dose calculations for individuals exposed to airborne radioactivity. Aerosol particle size influences internal dosimetry calculations in two potentially significant ways: the efficiency of particle deposition in the various regions of the respiratory tract is dependent on aerodynamic particle size, and the dissolution rate of deposited materials can vary according to particle size, shape, and porosity because smaller particles tend to have higher surfaceto-volume ratios than larger particles. However, the ICRP model assumes that deposited particles of a given material dissolve at the same rate regardless of size and that uptake to blood of dissolved material normally occurs instantaneously in all parts of the lung (except the anterior portion of the nasal region, where zero absorption is assumed). In the present work, the effect of particle size on dissolution in simulated lung fluid was studied for uranium aerosols collected at the plant, and its influence on internal dosimetry calculations was evaluated. Size fractionated uranium aerosols were sampled at a nuclear fuel fabrication plant using portable cascade impactors. Absorption parameters, describing dissolution of material according to the ICRP Human Respiratory Tract Model, were determined in vitro for different size fractions using simulated lung fluid. Samples were collected at 16 time-points over a 100-d period. Uranium content of samples was determined using inductively coupled plasma mass spectrometry and alpha spectrometry. In addition, supplementary experiments to study the effect of pH drift and uranium adsorption on filter holders were conducted as they could potentially influence the derived absorption parameters. The undissolved fraction over time was observed to vary with impaction stage cut-point at the four main workshops at the plant. A larger fraction of the particle activity tended to dissolve for small cut-points, but exceptions were noted. Absorption parameters (rapid fraction, rapid rate, and slow rate), derived from the undissolved fraction over time, were generally in fair agreement with the ICRP default recommendations for uranium compounds. Differences in absorption parameters were noted across the four main workshops at the plant (i. e., where the aerosol characteristics are expected to vary). The pelletizing workshop was associated with the most insoluble material and the conversion workshop with the most soluble material. The correlation between derived lung absorption parameters and aerodynamic particle size (impactor stage cut-point) was weak. For example, the mean absorption parameters derived from impaction stages with low (taken to be <5 mm) and large (≥5 mm) cut-points did not differ significantly. Drift of pH and adsorption on filter holders appeared to be of secondary import...

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Section: Uncertaintiesmentioning

confidence: 98%

Particle Size-dependent Dissolution of Uranium Aerosols in Simulated Lung Fluid: A Case Study in a Nuclear Fuel Fabrication Plant

et al. 2022

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“…For example, attention has been focused on the properties of the alveolar lining layer, airway mucus, or interstitial fluid. This has led to experimental models estimating dissolution rates of particles in serum or simulated lung fluids (32). There is growing evidence that such models are inappropriate.…”

Section: Intracellular Particle Dissolutionmentioning

confidence: 99%

In vivo evaluation of chemical biopersistence of nonfibrous inorganic particles.

Brain¹,

Godleski²,

Kreyling³

1994

Environ Health Perspect

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The lung's response to deposited particles may depend upon the physical-chemical properties of the particles, the amount initially deposited, and the persistence of the particles. Clearance involves mucociliary transport as well as the action of phagocytic cells in nonciliated regions of the lung. Depending on the animal species studied, particle type, and particle load, inorganic materials are ingested by macrophages on alveolar surfaces with half-times of 0.6 to 7 hr. Particle-laden macrophages may migrate to airways, but we believe that an important mechanism of clearance is the dissolution of particles within alveolar macrophages and the subsequent translocation of dissolved materials to the blood. Particle dissolution in situ has long been recognized but was often thought to be carried out extracellularly in the alveolar lining layer, airway mucus, or interstitial fluid. However, many particles such as cobalt oxide or iron oxide which dissolve very little in simulated lung fluid, are solubilized more rapidly within alveolar macrophages. Clearance of particles from the lungs can be followed by a number of techniques, both invasive and noninvasive. The approaches vary in expense and resolution, and can be directed toward quantifying mechanical removal of particles versus their intracellular dissolution. Noninvasive methods permit repeated measurements of particle retention in the lungs of the same animal or human and thus allow replications and serial measurements. Greater precision with respect to the sites of retention and redistribution is achieved with quantitative morphometric methods that utilize fixation followed by physically dividing the respiratory tract into individual pieces. Microwave drying or slam-freezing can eliminate the possibility of significant particle redistribution or loss of particles and dissolved elements during tissue processing. Detection of particles and therefore evidence of clearance can rely upon any distinctive property of the aerosol. Particles may be radioactive, fluorescent, or magnetic, or may have a characteristic visual appearance. Detection techniques include radiography, analyses of radioactivity, magnetometry, and microscopic approaches such as fluorescence and confocal microscopy, X-ray emission analysis, and electron energy loss spectrometry (EELS). Using these approaches, considerable evidence has been accumulated to conclude that particle dissolution in situ within alveolar macrophages and subsequent absorption by the circulation, rather than bulk transport, is the dominant mechanism for the long-term clearance of many insoluble minerals from the lungs. -Environ Health Perspect 102(Suppl 5): 119-125 (1994)

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Controlling intake of uranium in the workplace: Applications of biokinetic modeling and occupational monitoring data

Leggett¹,

Eckerman²,

McGinn³

et al. 2012

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This report provides methods to interpret and apply occupational uranium monitoring data. The methods are based on current international radiation protection guidance, current information on the chemical toxicity of uranium, and best available biokinetic models for uranium. Emphasis is on air monitoring data and three types of bioassay data: the concentration of uranium in urine; the concentration of uranium in feces; and the externally measured content of uranium in the chest. Primary Reference guidance levels for prevention of chemical effects and limitation of radiation effects are selected based on a review of current scientific data and regulatory principles for setting standards. Generic investigation levels and immediate action levels are then defined in terms of these primary guidance levels. The generic investigation and immediate actions levels are stated in terms of radiation dose and concentration of uranium in the kidneys. These are not directly measurable quantities, but models can be used to relate the generic levels to the concentration of uranium in air, urine, or feces, or the total uranium activity in the chest. Default investigation and immediate action levels for uranium in air, urine, feces, and chest are recommended for situations in which there is little information on the form of uranium taken into the body. Methods are prescribed also for deriving case-specific investigation and immediate action levels for uranium in air, urine, feces, and chest when there is sufficient information on the form of uranium to narrow the range of predictions of accumulation of uranium in the main target organs for uranium: kidneys for chemical effects and lungs for radiological effects. In addition, methods for using the information herein for alternative guidance levels, different from the ones selected for this report, are described. v FOREWORDThis report provides a detailed description of uranium biokinetics and bioassays applicable to evaluation of health risks from potential intakes in an occupational setting. The report addresses both the radiotoxicity and chemical (renal) toxicity of uranium. For reference occupational exposure scenarios, predictions of the time-dependent concentration of uranium in tissues and bioassay are based on biokinetic models currently recommended by the International Commission on Radiological Protection (ICRP). The ICRP's models and default assumptions for uranium were based primarily on data for human subjects exposed to uranium in controlled studies or in occupational or environmental settings. In addition, the ICRP considered an extensive database for uranium in laboratory animals. Sensitivity studies examine the robustness of these models and assumptions to ensure that radiation doses and accumulation of uranium in the kidneys are not underestimated. For example, analyses indicate that a default 5 µm activity median aerodynamic diameter particle size can lead to an underestimation of radiation dose as well as the concentration of uranium in the kidneys if inhal...

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Flow-Through Dissolution of Uranium-Thorium Ore Dust, Uranium Concentrate, Uranium Dioxide, and Thorium Alloy in Simulated Lung Fluid

Cited by 3 publications

References 0 publications

Particle Size-dependent Dissolution of Uranium Aerosols in Simulated Lung Fluid: A Case Study in a Nuclear Fuel Fabrication Plant

Particle Size-dependent Dissolution of Uranium Aerosols in Simulated Lung Fluid: A Case Study in a Nuclear Fuel Fabrication Plant

In vivo evaluation of chemical biopersistence of nonfibrous inorganic particles.

Controlling intake of uranium in the workplace: Applications of biokinetic modeling and occupational monitoring data

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