Determination of 236U and transuranium elements in depleted uranium ammunition by α-spectrometry and ICP-MS

It is well known that ammunition containing depleted uranium (DU) was used by NATO during the Balkan conflict. To evaluate the origin of DU (the enrichment of natural uranium or the reprocessing of spent nuclear fuel) it is necessary to directly detect the presence of activation products (U-236, Pu-239 Pu-240 Am-241, and Np-237) in the ammunition. In this work the analysis of actinides by alpha-spectrometry was compared with that by inductively coupled plasma mass spectrometry (ICP-MS) after selective separation of ultratraces of transuranium elements from the uranium matrix. Pu-242 and Am-243 were added to calculate the chemical yield. Plutonium was separated from uranium by extraction chromatography, using tri-n-octylamine (TNOA), with a decontamination factor higher than 106; after elution plutonium was determined by ICP-MS (Pu-239 and Pu-240) and alpha-spectrometry (Pu239+240) after electroplating. The concentration of Pu in two DU penetrator samples was 7x10(-12) g g(-1) and 2x10(-11) g g(-1). The Pu-240/Pu-239 isotope ratio in one penetrator sample (0.12+/- 0.04) was significantly lower than the Pu-240/Pu-239 ratios found in two soil samples from Kosovo (0.35 +/- 0.10 and 0.27 +/- 0.07). Am-241 was separated by extraction chromatography, using di(2-ethylhexyl)phosphoric acid (HDEHP), with a decontamination factor as high as 10(7). The concentration of Am-241 in the penetrator samples was 2.7x10(-14) g g(-1) and <9.4x10(-15) g g(-1). In addition Np-237 was detected at ultratrace levels. In general, ICP-MS and α-spectrometry results were in good agreement. The presence of anthropogenic radionuclides (U-236, Pu-239, Pu-240, Am-241, and Np-237) in the penetrators; indicates that at least part of the uranium originated from the reprocessing of nuclear fuel. Because the concentrations of radionuclides are very low, their radiotoxicological effect is negligible.