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

Abstract.

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 (²³⁶U, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Am, and ²³⁷Np) in the ammunition. In this work the analysis of actinides by α-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. ²⁴²Pu and ²⁴³Am 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 (²³⁹Pu and ²⁴⁰Pu) and α-spectrometry (^239+240Pu) after electroplating. The concentration of Pu in two DU penetrator samples was 7×10^–12 g g^–1 and 2×10^–11 g g^–1. The ²⁴⁰Pu/²³⁹Pu isotope ratio in one penetrator sample (0.12±0.04) was significantly lower than the ²⁴⁰Pu/²³⁹Pu ratios found in two soil samples from Kosovo (0.35±0.10 and 0.27±0.07). ²⁴¹Am was separated by extraction chromatography, using di(2-ethylhexyl)phosphoric acid (HDEHP), with a decontamination factor as high as 10⁷. The concentration of ²⁴¹Am in the penetrator samples was 2.7×10^–14 g g^–1 and <9.4×10^–15 g g^–1. In addition ²³⁷Np was detected at ultratrace levels. In general, ICP–MS and α-spectrometry results were in good agreement.

The presence of anthropogenic radionuclides (²³⁶U, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Am, and ²³⁷Np) 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.