The impact of depleted uranium (DU) penetrators against an armored target causes erosion and fragmentation of the penetrators, the extent of which is dependent on the thickness and material composition of the target. Vigorous oxidation of the DU particles and fragments creates an aerosol of DU oxide particles and DU particle agglomerations combined with target materials. Aerosols from the Capstone DU aerosol study, in which vehicles were perforated by DU penetrators, were evaluated for their oxidation states using x-ray diffraction (XRD), and particle morphologies were examined using scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The oxidation state of a DU aerosol is important as it offers a clue to its solubility in lung fluids. The XRD analysis showed that the aerosols evaluated were a combination primarily of U3O8 (insoluble) and UO3 (relatively more soluble) phases, though intermediate phases resembling U4O9 and other oxides were prominent in some samples. Analysis of particle residues in the micrometer-size range by SEM/EDS provided microstructural information such as phase composition and distribution, fracture morphology, size distribution, and material homogeneity. Observations from SEM analysis show a wide variability in the shapes of the DU particles. Some of the larger particles were spherical, occasionally with dendritic or lobed surface structures. Others appear to have fractures that perhaps resulted from abrasion and comminution, or shear bands that developed from plastic deformation of the DU material. Amorphous conglomerates containing metals other than uranium were also common, especially with the smallest particle sizes. A few samples seemed to contain small bits of nearly pure uranium metal, which were verified by EDS to have a higher uranium content exceeding that expected for uranium oxides. Results of the XRD and SEM/EDS analyses were used in other studies described in this issue of Health Physics to interpret the results of lung solubility studies and in selecting input parameters for dose assessments.
These tests were conducted to develop a database that could be used to assess risks to soldiers from exposure to aerosolized metallic particulates when the crew compartment of an Abrams tank is perforated by a kinetic energy penetrator. Quantitative data are reported for aerosols produced by kinetic energy penetrators containing tungsten, nickel, and cobalt. The following are addressed: (1) concentrations and rates of particle settling inside the vehicle, (2) particle size distribution, (3) inhalable and respirable particulates, (4) distribution of aerosol particles by mass, and (5) particle shapes. The scenario described in this report simulates a rare occurrence. The lessons learned, however, highlight a requirement for developing protocols for analyses of metals in body fluids and urine as soon as practical, and also for implementing targeted postdeployment medical surveillance programs that monitor both body burden for respired metals and pulmonary function.
SummaryArmor-piercing, depleted-uranium (DU) munitions were used by the U.S. Armed Forces on the battlefield for the first time during the 1991 Gulf War Operation Desert Storm (ODS).( ) a Although the U.S. Army has conducted periodic impact tests on armored targets, the tests involved only limited sampling to characterize the aerosols that form when DU penetrators impact and perforate targets. As a consequence, the available data were insufficient for performing human health risk assessments. To remedy this, the U.S. Department of Defense (DoD) committed to obtaining more complete data about aerosols generated by the impact and perforation of armored vehicles by DU munitions to support a revised and updated personnel exposure assessment and human health risk characterization. The program arising from this commitment is the Capstone DU Aerosol Characterization and Risk Assessment Program consisting of two separate components. The first is the Capstone DU Aerosol Study, in which DU aerosols were generated through perforation of armored target vehicles, and the chemical and physical properties of aerosols generated were characterized. The study methods and results are presented in this report. The second component of the program is the Human Health Risk Assessment, documented in the Human Health Risk Assessment of Capstone Depleted Uranium Aerosols (Guilmette et al. 2004). S.1 PurposeUnder a program jointly sponsored by the Office of the Special Assistant for Gulf War Illnesses, Medical Readiness and Military Deployment (OSAGWI) ( ) b and the U.S. Army, the Army Heavy Metals Office provided oversight to the Capstone DU Aerosol Study, which was designed to quantify and characterize DU aerosols inside, on, and near Abrams tanks and Bradley Fighting Vehicles (also referred to as Bradley vehicles) struck by large-caliber DU (LC-DU) penetrators. This report, which documents the Capstone study, is the sourcebook of data from which reasonable and appropriate data could be selected for assessing exposure and characterizing human health risks to personnel who were exposed to aerosols during the Gulf War/ODS or potentially could be exposed to aerosols in future military activities. These data are expected to fill many gaps in available aerosol knowledge, thereby helping risk assessors to better estimate the health risks from DU aerosols to affected personnel.The aerosol data derived from this study provides the basis for modeling input parameters by summarizing the bounds and characteristics of typical aerosols generated by perforating armored vehicles with LC-DU penetrators. The test results will be used to update the human health risk characterizations for OSAGWI Gulf War/ODS exposure scenarios, and to determine if changes in personnel protective measures are warranted to reduce risks to DoD personnel in the future. S.2 Investigation TeamAn independent subject matter expert from Pacific Northwest National Laboratory (PNNL) directed the Capstone DU Aerosol Study. S.3 Study OverviewThe Capstone DU Aerosol Study involved ...
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