Concentration, distribution and characteristics of depleted uranium ...

Journal of Radioanalytical and Nuclear Chemistry, Vol. 260, No. 3 (2004) 481–494

Concentration, distribution and characteristics of depleted uranium (DU) in the Kosovo ecosystem: A comparison with the uranium behavior in the environment uncontaminated by DU Guogang Jia, M. Belli, U. Sansone, S. Rosamilia, S. Gaudino Italian National Environmental Protection Agency, Via V. Brancati 48, 00144 Rome, Italy (Received June 2, 2003)

The smear samples of the penetrator were analyzed for the determination of the uranium composition. The obtained relative composition (m/m) of uranium isotopes in all the smear samples is in the range of 99.76–99.78% for 238U, 0.000659–0.000696% for 234U, 0.213–0.234% for 235U, and 0.00274–0.00328% for 236U, showing characteristics of depleted uranium (DU). The uranium concentrations in Kosovo soil and water samples as well as biological samples were investigated. It was found that the uranium concentrations in the Kosovo soil samples are in the range of 11.3–2.26.105 Bq.kg–1 for 238U, 10.3–3.01.104 Bq.kg–1 for 234U, 0.60–3251 Bq.kg–1 for 235U, and 0.019–1309 Bq.kg–1 for 236U. The obtained activity ratios are in the range of 0.112–1.086 for 234U/238U, 0.0123–0.1144 for 235U/238U, and 0–0.0078 for 236U/238U, indicating the presence of DU in about 77% of the surface soil samples. At a specific site, the DU inventory in the surface soil is about 140 mg.cm–2, which is 1.68.106 times higher as the estimated mean DU dispersion rate in the region. The uranium concentrations in Kosovo lichen, mushroom, bark, etc., are in the range of 1.97–4.06.104 Bq.kg–1 for 238U, 0.48–5158 Bq.kg–1 for 234U, 0.032–617 Bq.kg–1 for 235U, and 0.019–235 Bq.kg–1 for 236U with mean activity ratios of 0.325±0.0223 for 234U/238U, of 0.0238±0.0122 for 235U/238U, and 0.0034±0.0028 for 236U/238U, indicating the presence of DU in the entire sample. On the contrary, the uranium concentrations in Kosovo water samples are low, compared with the water samples collected in central Italy, indicating the presence of negligible amount of DU. The uranium isotopes in Kosovo waters do not constitute a risk of health at the present time.

Introduction The accumulation of hazardous radionuclides in the environment started after the first nuclear weapon testing and has continued ever since. A number of severe radioactivity release events are responsible for the worldwide radionuclide contamination, such as the fallout from atmospheric nuclear weapons testing in the 1950s and 1960s1 and later from Chernobyl nuclear reactor accident in 1986. The depleted uranium (DU) dispersion or contamination in the environment of the Persian Gulf (Kuwait and Iraq) and the Balkan regions as a result of the Gulf War in 1991 and the Balkans (Kosovo) War in 1999 can be considered as the most recent, severe and widespread radioactive contamination.2–4 DU is a radioactive heavy metal that emits ionizing radiation of three types: alpha, beta and gamma due to its own decay, its daughters and fission and/or activation products. It is a by-product in the process of enriching 235U for use as fuel in nuclear reactors and nuclear weapons. There are three types of DU: (1) Natural depleted uranium (NDU), 235U-depleted uranium which remains after extraction of the fissile nuclide 235U from natural uranium; (2) Reprocessed depleted uranium (RDU). After its use in a nuclear reactor the spent fuel is removed and then subjected to chemical processing in order to extract pure uranium free from other radionuclides; and (3) Unprocessed depleted uranium (UDU), commonly present in the vicinity of nuclear reprocessing plants, or after accidents involving irradiated fuel rods, e.g., Chernobyl accident. 0236–5731/2004/USD 20.00 © 2004 Akadémiai Kiadó, Budapest

Determining the depletion degree of 235U and the disequilibria between 234U and 238U, and the presence of ultra-trace amounts of 236U as a contaminant in spent uranium fuel, together with the characteristic of fission and activation radionuclides (Cs, Pu and Am), we can identify NDU, RDU and UDU. Because of DU’s high density (19.05 g.cm–3), availability and low relative cost, the DU metal has been incorporated into projectiles and armour by the United States and United Kingdom and was used in some war.5,6 During the Kosovo conflict, it is reported that over thirty thousand rounds, each containing a conical DU penetrator of about 300 g, have been fired with a DU deposition inventory of >10 t in the Kosovo environment in an area of less than 1.2.104 km2 (mean dispersion rate: 833 g.km–2) (UNEP 2001). As far as the Gulf conflict is concerned, the reported DU inventory is about 320 t.4,6–8 Due to the increased public attention to the environmental contamination of the military use of DU and to the potential public health effects, the United Nations Environment Programme (UNEP) has organized several missions participated by experts from intergovernmental agencies, well-known institutions and other interested parties to conduct the overall assessment of the consequences of the post-conflicts on the environment and human settlements. As a part of the assessment of the DU impact of the Kosovo conflict on the environment and population, during 5–19 November 2000 the Italian National Environmental Protection Agency (ANPA) participated the field mission to Kosovo. During the mission, water, Akadémiai Kiadó, Budapest Kluwer Academic Publishers, Dordrecht

GUOGANG JIA et al.: CONCENTRATION, DISTRIBUTION AND CHARACTERISTICS OF DEPLETED URANIUM

vegetation, soil and smear samples were collected. Uranium was separated from the samples and purified by a radioanalytical chemistry procedure and measured by alpha-spectrometry. The analytical technique can be used as a method for isotopic tracing of depleted (234U/238U 0.15), highly enriched (234U/238U 100) and natural (234U/238U 1) forms of uranium via their activity ratios and can also provide more accurate dose assessment information in human and environmental monitoring application.9 In this paper the uranium activity concentrations in the collected samples from Kosovo are presented in detail, and also are compared with the samples uncontaminated by DU and collected in Italy. These data can be served as basic information for the locations of the affected sites, the quantity and quality of DU used in the conflict, and the evaluation of the potential effects of DU on human health and/or the environment.

Sampling sites Figure 1 is a map of Kosovo region of the Federal Republic of Yugoslavia, which is divided into five sectors (American, British, French, Italian and German sectors) according to the activity areas of different peace keeping forces (KFOR) in Kosovo. The marks in the map indicate the sites identified as being targeted by ordnance containing DU. Sampling occurred in two KFOR sectors – Italian and German sectors, – which is approximately 12% of total number of DU-targeted sites provided by the North Atlantic Treaty Organization (NATO). The chosen sites were located at the most heavily targeted areas, as well as in/or closest to inhabited areas. In selecting the sites, variation was also sought in the surrounding natural environment, soil types and biodiversity. Sampling was limited by the fact that the sites had not been cleared of mines and unexploded ordnance.

Experimental Sampling and sample preparation Apparatus and reagents The uranium sources were counted by alphaspectrometry (Canberra, U.S.A.) with a counting efficiency of 31.2% and a background of 2.10–6 s–1 in the interested energy region. The electrodeposition apparatus (Model PL320QMD; Thurlby Thandar Instruments, Ltd., England) was used with Perspex cells of 25 mm internal diameter and stainless-steel disks of 20 mm diameter. Chromatographic columns were 150 mm long and with a 9 mm internal diameter. 232U and/or 236U standard solution, Microthene (microporous polyethylene, 60–140 mesh), tri-octylphosphine oxide (TOPO, 99%) were supplied by Amersham (G. B.), Ashland (Italy), and Fluka (Switzerland), respectively. FeCl3 was used to prepare the carrier solution for uranium separation in water sample and all other reagents were analytical grade (Merck, Germany).

Smear samples of penetrators were taken directly from the penetrators (PGU-14 Armour Piercing Incendiary) found on the surface soil. Water samples were collected from private potable wells, streams and

Column preparation A solution (50 ml) of 0.3M TOPO in cyclohexane was added to 50 g of Microthene; the mixture was stirred for several minutes until homogeneous and was than evaporated to eliminate cyclohexane at 50 °C. The porous powder thus obtained contained about 10.4% TOPO. A portion (1.6 g) of the Microthene-TOPO powder, mixed with 3 ml concentrated HCl and some water, was transferred to a chromatographic column; after conditioning with 30 ml of 2M HNO3, the column was ready for use.

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Fig. 1. Map of Kosovo region of the Federal Republic of Yugoslavia. : American Zone; : British Zone; : French Zone; : Italian Zone; : German Zone; : sites identified as being targeted by ordnance containing DU


reservoirs and preserved in polyethylene bottles by adjusting their pH to 2 mm and split into sub-samples of 20 g each, using a stainless steel sample splitter. Each sub-sample was separately ground and homogenized in a ceramic miller. Three sub-samples were analyzed for the uranium isotopes for each soil sample. Lichen and bark samples were collected from the mature tree trunks, which are as much as possible in vertical position. At each location at least three sites were selected with the same species and no visual differences in community structure. In order to minimize effects of the crosscontamination, the samples were cleaned to remove all the visible soil particles and foreign bodies, then dried at 105 °C, ground and homogenized. In order to evaluate the potential radiological impact of DU on the Kosovo environment, some environmental samples (water and lichen) unexposed by DU and collected from central Italy (Roma, Urbino) as control sites were also analyzed. Detailed information about the control sites can be found elsewhere.10 Method As shown in Fig. 2, the radioanalytical procedure for determination of uranium isotopes in water, lichen, smear and soil samples mainly includes steps of sample pretreatment, leaching, uranium separation by a Microthene-TOPO column, electrodeposition and measurement by alpha-spectrometry. For more detailed procedure, please refer to Reference 9. In order to evaluate the reliability of the method, five reference or certified materials (IAEA-135 Sediment, IAEA-315 Sediment, IAEA-326 Soil, IAEA-327 Soil and IAEA-368 Sediment) have been analyzed and the obtained results all are within the 95% confidence interval of the recommended or information values. The lower limits of detection of the method are 0.37 Bq.kg–1 (soil) and 0.22 mBq.l–1 (water) for 238U and 234U and 0.038 Bq.kg–1 (soil) and 0.022 mBq.l–1 (water) for 235U and 236U if 0.5 g of soil and 1 liter of water are analyzed. The average uranium yields for waters, lichens and soils are 74.5±9.0%, 77.8±4.9% and 89.4±9.7%, respectively.

Results and discussion The obtained uranium isotope concentrations given in Tables 1–6. The reported uncertainty individual analysis in the tables is 1 , which estimated from the uncertainties associated with tracer (232U) activity, the addition of the tracer to sample and the counting statistics of the sample and blank, etc.

are for are the the the

Uranium isotope composition in smear samples The type of DU round (PGU-14 Armour Piercing Incendiary) fired by NATO A-10 aircraft in Kosovo has a length of 173 mm and a diameter of 30 mm. Inside the round is a conical DU ‘penetrator’, 95 mm in length and with a diameter at the base of 16 mm. The DU weight of one penetrator is about 300 g. Table 1 shows the uranium isotope activities in smear samples of the penetrators collected in Kosovo, which are in the range of 12.3–42.4 Bq/sample for 238U, 1.51–5.37 Bq/sample for 234U, 0.175–0.635 Bq/sample for 235U and 0.008– 0.040 Bq/sample for 236U. Although these data are not expressed in the specific activities (Bq.kg–1), they can provide all the information about their isotopic compositions of the penetrators. The obtained activity ratios are 0.126±0.003 for 234U/238U, 0.0144±0.0006 for 235U/238U and 0.0057±0.0004 for 236U/238U. The natural composition is characterized by 234U/238U and 235U/238U activity ratios of about 1 and 0.046, respectively. Enriched uranium has higher 234U/238U and 235U/238U ratios, whereas depleted uranium has lower 234U/238U and 235U/238U ratios. From the obtained results it is confirmed that the material containing in the smear samples is DU due to their lower 234U/238U and 235U/238U ratios. The relative composition (m/m) of uranium isotopes calculated in all the smear samples is in the range of 99.76–99.78% for 238U, 0.000659–0.000696% for 234U, 0.213–0.234% for 235U, and 0.00274–0.00328% for 236U. It is indicated that (1) the same kind of DU material was used in PGU14 Armour Piercing Incendiary due to the fact that the ratios of 234U/238U or 235U/238U or 236U/238U in all the collected penetrators are nearly the same, (2) some of the DU material has been in nuclear reactor due to presence of 236U which is an activation product of 235U, and (3) on the outer surface of the penetrators exists easily removable uranium even if the penetrators have characteristics of hardness and high specific density. The risk assessment of DU to public is mainly associated with its radiological (external and internal exposures) and chemical effects (chemical toxicity), which depend on physical and chemical behavior of DU, concentration level in the environment media, contamination level in bodies and so on.

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The characteristics and behavior of DU anti-armour rounds fired by A-10 aircraft in the environment can principally be classified into two scenarios. First, when rounds hit either non-armoured targets or miss targets, they will generally remain intact, passing through the target and/or becoming buried in the ground. The depth depends on the angle of the round, the speed of the plane, the type of target and the nature of the

ground surface. In clay soils, the penetrators may reach more than two meters depth. In this scenario, there are risks of external exposure and underground water contamination due to the mobilization of DU in soil profile after corrosion and dissolution by of the acidity and reducing properties of the environment and the hydrological characteristics of the region.

Fig. 2. Recommended procedure for determination of uranium in environmental samples by -spectrometry

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Second, when rounds hit the armoured or hard targets, normally 10–35% (maximum of 70%) of the penetrators become an aerosol by impact with the armour and the DU dust catches fire.11 Most of the dust particles are