Scanning electron microscopy of uranium particulate in two soil samples at a depleted uranium munitions strike site from the Kosovo Conflict

Milodowski, A.E.. 2001 Scanning electron microscopy of uranium particulate in two soil samples at a depleted uranium munitions strike site from the Kosovo Conflict. Nottingham, UK, British Geological Survey, 18pp. (CR/01/261N) (Unpublished)

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Abstract/Summary

Recent public debate has highlighted the concern over the potential long-term environmental and health effects arising from the use of depleted uranium (DU) munitions in recent military conflicts (Royal Society, 2001). DU munitions were used by NATO anti-tank (A-10) aircraft against Serbian targets during the recent conflict in Kosovo. In the United Kingdom, the Defence Science and Technology Laboratories (DSTL) are investigating the radiological and toxicological risk from DU munitions used in Kosovo. On behalf of the DSTL the British Geological Survey (BGS) undertook the analysis of two soil samples collected from a DU munitions strike site (the old VJ Barracks, near Podujevo) to characterise the nature of uranium-rich particulate material in DU-contaminated material. The samples were analysed by scanning electron microscopy techniques, using backscattered scanning electron microscopy (BSEM) to locate the uraniferous particles, and secondary electron imaging (SEM) to observe the morphology of the particles. Phase identification was supported by semi-quantitative microchemical information obtained from the phases by simultaneous energy-dispersive X-ray microanalysis (EDXA) during BSEM and SEM observation. This report details the analytical methods used and presents the observations and conclusions from this study. BSEM proved very successful in locating dense uranium particulate on the surfaces of soil fragments because the very high atomic number of uranium produces high electron backscattering effects. Uraniferous particles were found covering the surfaces of soil fragments in both samples examined in this study. It is concluded that these particulate represents DU dust since no similar uraniferous material was found within the interior of the soil fragments. Uranium isotope analyses determined by inductively-coupled plasma – mass spectrometry (reported separately to DSTL by Gowing & Chenery, 2001) confirm that the soils contain uranium with an isotopic composition consistent with the presence of DU contamination. Much of the uraniferous particulate material falls into two main size classes: (i) very fine material with a particle size less than 1 μm and generally less than 0.2 μm; and (ii) coarser particles, typically 5-25 μm in size. As found in the earlier report (Milodowski, 2001) describing DU particulate in building debris, none of the uraniferous particles observed illustrated the typical spherical morphology of DU particulate reported previously from test firing of DU munitions against hard targets (cf. Patrick & Cornette, 1978). Instead, the observed DU particles from the soil samples are mainly flaky or irregular in morphology (single particles), or consist of colloform coatings and fine granular aggregates of secondary phases formed as secondary alteration products on the surfaces of primary uraniferous particles. The coarser DU particulate material is mainly composed of uranium oxide, although some particles appear to relicts of uranium metal shards, which have been only partially oxidised. The fine-grained particles are composed mainly of uranium, calcium and oxygen, often with minor amounts of phosphorus and sulphur. They are interpreted as primarily a calcium-uranium carbonate or oxide/oxyhydroxide-like phase. The presence of sulphur and phosphorus suggest that the assemblage of phases may be more complex and may also include sulphate and phosphate phases. Material of a similar composition was also found as micro-granular and colloform coatings forming as alteration products on the surfaces of coarser uraniferous particles. The petrographical relationships observed by SEM indicate that the calcium-uranium-phosphorus-sulphur-bearing phases are formed by alteration of primary uranium oxide or uranium metal particulate within the soil environment. Uranium silicate has also been identified as an alteration product or the metallic uranium particles. A small amount of titanium (estimated to be of the order of 1-3 % by weight) was observed in most of the particles and is most probably derived from titanium alloyed with uranium in the DU alloy. Silicon, aluminium, potassium and iron are commonly observed in the EDXA spectra recorded from the uraniferous particles, particularly from the finer grained material. However, it is likely that these elements in the EDXA analyses are influenced by background X-ray emission from the soil matrix, which contains fine-grained quartz, illite and iron oxides. Rarer, but much coarser, irregular fragments of uranium-rich material, up to 100 μm were also observed. They are usually fractured and often appear to be breaking down into smaller particles within the soil. EDXA indicates that these particles are partially oxidised metallic fragments of uranium that are altering to the same calcium-uranium-phosphorus-sulphur-rich phase observed in the finer grained uraniferous particles. In addition to uraniferous particles, some fine-grained lead oxide rich particles and chromium-iron oxide particles were also observed. The origin of these particles is not clear, although it is conceivable that the lead is also munitions-derived.

Item Type:	Publication - Report
Programmes:	BGS Programmes > Other
Funders/Sponsors:	British Geological Survey, Defence Science and Technology Laboratories
Additional Information. Not used in RCUK Gateway to Research.:	This item has been internally reviewed, but not externally peer-reviewed. Report made open in 2006.
Date made live:	25 Sep 2024 15:12 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538079

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