Calculating Capstone depleted uranium aerosol concentrations from beta activity measurements.
U.S. Army Center for Health Promotion and Preventive Medicine, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010-5403, USA.Health physics (Impact Factor: 1.27). 04/2009; 96(3):238-50. DOI: 10.1097/01.HP.0000290612.27848.cd
Beta activity measurements were used as surrogate measurements of uranium mass in aerosol samples collected during the field testing phase of the Capstone Depleted Uranium (DU) Aerosol Study. These aerosol samples generated by the perforation of armored combat vehicles were used to characterize the DU source term for the subsequent Human Health Risk Assessment (HHRA) of Capstone aerosols. Establishing a calibration curve between beta activity measurements and uranium mass measurements is straightforward if the uranium isotopes are in equilibrium with their immediate short-lived, beta-emitting progeny. For DU samples collected during the Capstone study, it was determined that the equilibrium between the uranium isotopes and their immediate short-lived, beta-emitting progeny had been disrupted when penetrators had perforated target vehicles. Adjustments were made to account for the disrupted equilibrium and for wall losses in the aerosol samplers. Values for the equilibrium fraction ranged from 0.16 to 1, and the wall loss correction factors ranged from 1 to 1.92. This paper describes the process used and adjustments necessary to calculate uranium mass from proportional counting measurements.
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ABSTRACT: During the Capstone Depleted Uranium (DU) Aerosol Study, aerosols containing DU were produced inside unventilated armored vehicles (i.e., Abrams tanks and Bradley Fighting Vehicles) by perforation with large-caliber DU penetrators. These aerosols were collected and characterized, and the data were subsequently used to assess human health risks to personnel exposed to DU aerosols. The DU content of each aerosol sample was first quantified by radioanalytical methods, and selected samples, primarily those from the cyclone separator grit chambers, were analyzed radiochemically. Deposition occurred inside the vehicles as particles settled on interior surfaces. Settling rates of uranium from the aerosols were evaluated using filter cassette samples that collected aerosol as total mass over eight sequential time intervals. A moving filter was used to collect aerosol samples over time, particularly within the first minute after a shot. The results demonstrate that the peak uranium concentration in the aerosol occurred in the first 10 s after perforation, and the concentration decreased in the Abrams tank shots to about 50% within 1 min and to less than 2% after 30 min. The initial and maximum uranium concentrations were lower in the Bradley vehicle than those observed in the Abrams tank, and the concentration levels decreased more slowly. Uranium mass concentrations in the aerosols as a function of particle size were evaluated using samples collected in a cyclone sampler, which collected aerosol continuously for 2 h after perforation. The percentages of uranium mass in the cyclone separator stages ranged from 38 to 72% for the Abrams tank with conventional armor. In most cases, it varied with particle size, typically with less uranium associated with the smaller particle sizes. Neither the Abrams tank with DU armor nor the Bradley vehicle results were specifically correlated with particle size and can best be represented by their average uranium mass concentrations of 65 and 24%, respectively.Health physics 04/2009; 96(3):251-65. DOI:10.1097/01.HP.0000311549.85594.a3 · 1.27 Impact Factor
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ABSTRACT: Depleted uranium (DU) intake rates and subsequent dose rates were estimated for personnel entering armored combat vehicles perforated with DU penetrators (level II and level III personnel) using data generated during the Capstone DU Aerosol Study. Inhalation intake rates and associated dose rates were estimated from cascade impactors worn by sample recovery personnel and from cascade impactors that served as area monitors. Ingestion intake rates and associated dose rates were estimated from cotton gloves worn by sample recovery personnel and from wipe-tests samples from the interior of vehicles perforated with large-caliber DU munitions. The mean DU inhalation intake rate for level II personnel ranged from 0.447 mg h(-1) based on breathing zone monitor data (in and around a perforated vehicle) to 14.5 mg h(-1) based on area monitor data (in a perforated vehicle). The mean DU ingestion intake rate for level II ranged from 4.8 mg h(-1) to 38.9 mg h(-1) based on the wipe-tests data including surface-to-glove transfer factors derived from the Capstone data. Based on glove contamination data, the mean DU ingestion intake rates for level II and level III personnel were 10.6 mg h(-1) and 1.78 mg h(-1), respectively. Effective dose rates and peak kidney uranium concentration rates were calculated based on the intake rates. The peak kidney uranium concentration rate cannot be multiplied by the total exposure duration when multiple intakes occur because uranium will clear from the kidney between the exposures.Health physics 04/2009; 96(3):363-79. DOI:10.1097/01.HP.0000334063.95622.f9 · 1.27 Impact Factor
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ABSTRACT: The rationale for the Capstone Depleted Uranium (DU) Aerosol Characterization and Risk Assessment Study and its results and applications have been examined in the previous 13 articles of this special issue. This paper summarizes the study's results and discusses its successes and lessons learned. The robust data from the Capstone DU Aerosol Study have provided a sound basis for assessing the inhalation exposure to DU aerosols and the dose and risk to personnel in combat vehicles at the time of perforation and to those entering immediately after perforation. The Human Health Risk Assessment provided a technically sound process for evaluating chemical and radiological doses and risks from DU aerosol exposure using well-accepted biokinetic and dosimetric models innovatively applied. An independent review of the study process and results is summarized, and recommendations for possible avenues of future study are provided by the authors and by other major reviews of DU health hazards.Health physics 04/2009; 96(3):393-409. DOI:10.1097/01.HP.0000339006.09037.56 · 1.27 Impact Factor
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