Analysis of Trace Thorium in Uranium Sample Using Isotope Dilution Mass Spectrometry

Separation and purification methods for trace thorium and other impurity elements in uranium are important. Accurate and precise measurements can be made using isotope dilution mass spectrometry. In this study, we spiked samples with Th-230 using alkaline anion exchange and tri-n-butyl phosphate (TBP) extraction chromatography stack columns for separating trace thorium and other impurity elements in uranium from an 8 mol.L-1 nitric acid medium. In this separation method, thorium was adsorbed on the alkaline anion exchange resin, uranium was adsorbed on the TBP chromatography powder, and other impurity elements were not adsorbed on the alkaline anion exchange resin or the TBP chromatography powder. The purified thorium samples were analyzed using thermal ionization mass spectrometry. The results showed that the thorium content in uranium was (59.3 +/- 0.1) mu g.g(-1), the expanded factor (k) was 2, and the confidence was 95%.