Uranium separations using extraction chromatography

In the analysis of environmental samples for uranium and thorium pollutants and at natural levels for the dating of geological samples there was felt a need to develop better uranium and thorium separation procedures to replace the established anion exchange method used at AEA Technology plc. This was the first aim of the PhD research. Separation of uranium from thorium prior to measurement of the isotopes by alpha spectrometry was necessary due to the similar alpha energies of234U and 230Th. TRU and UTEVA extraction chromatography resins (EIChroM Industries) were investigated as potential replacements to the anion exchange separation method. The resins are claimed by EIChroM to offer the advantage of providing an actinide specific separation while reducing the separation time from 2 to 0.5 days; the volume of acidic waste produced by a factor of 3, therefore, the cost of analysis was reduced. A uranium and thorium separation procedure using the UTEVA extraction chromatography resin was developed. The uranium and thorium were sorbed by the UTEVA resin from 2M nitric acid. The thorium was then eluted from the resin with 5M hydrochloric acid and the uranium with 0.02M hydrochloric acid. The separation procedure was then evaluated using uraninite ore, coral, granite and lake sediment reference materials. The uranium and thorium concentrations and the 234U/238U and 23oTh/234U activity ratio values determined for the reference material were in good agreement with certified values. The presence of plutonium was found to interfere with the measurement of uranium and thorium by alpha spectrometry. This was due to the similar alpha energies of uranium, thorium and plutonium. The co-elution of plutonium with uranium and thorium from the UTEVA resin was prevented by the inclusion of a reduction step using iron (Il) sulphamate. The resulting plutonium (Ill) was not retained by the UTEVA column. The chemical recoveries for the procedure were similar to those for anion-exchange, but the extraction chromatography procedure provided a more rapid separation using less reagents…