Depleted Uranium and Its Characterization

DU is formed in the tails stream of the enrichment process and contains 0.72% of U (the natural content), usnally 0.2%-0.4%. The chemical, physical, and mechanical properties of DU are identical to those of natural uranium (NU) and the radioactivity is slightly lower dne mainly to the reduction in the U content (usually about half to two-thirds of NU). The world inventory of DU is estimated at abont 

Unfortunately, we conld not find detailed specifications for DU that are similar to those publicly available from the ASTM, for example, for nuclear grade UFg, UO2, 

A certified reference material (CRM-115) for characterization of the isotopic composition of DU metal was prepared and can be used for precise determination of the minor isotopes (Mathew et al. 2013). Modified total evaporation (MTE) with a TRITON TIMS device was used for highly accurate determination of the UP U, U/ U, and 236U/238U ratios, and establishing that the U/ U ratio was below 5 10 . 

As mentioned earlier, specifications for DU whether it is intended for use in munitions, radiation shielding, or aircraft ballast are difficult to find. In any case, the analytical procedures for its characterization, described earlier for other uranium compounds, are valid also for DU. Dissolution of the metal samples in concentrated nitric acid (HF may be added if residues remain) is required for meticulous analysis of impurities by ICP-OES, ICP-MS, or/and other suitable analytical method. Conversion to UjO in a muffle furnace with steam for impurity determination by DC-arc is also an option. Determination of the H, C, N, O, and S content with dedicated instrumentation may also be carried out. On the other hand, the impurity requirements for DU are not as strictly controlled as they are for other nuclear materials. If the depleted uranium is alloyed, as mentioned earlier to improve the mechanical properties, the concentration of the alloying element must be determined according to specifications. 

Probably the most comprehensive published assay of DU used in armor pen-etrators was reported on the basis of analysis of an unfired CHARM-3 penetrator (Trueman et al. 2004). A sample from the penetrator was dissolved in 9 M HCl, spiked with U as a yield monitor, and the uranium was separated from impurities on an ion-exchange resin. The isotopic composition of uranium was determined by mass spectrometric techniques. Actinides ( - Am and Np) were determined in the uranium-free solution by gamma spectrometry and 239+24opy and Pu were measured by alpha spectrometry and their presence was confirmed by ICPMS. Technetium-99 was determined by ICPMS when rhenium was used as a carrier and interferences from iron were eliminated by precipitating with ammonia while ruthenium and molybdenum were removed by separation on a chromatographic resin. The content of these radioactive nuclides is summarized in Table 2.7. 

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