Determination of uranium and thorium in geological materials using extraction chromatography

Abstract

A procedure has been developed for the determination of uranium and thorium in geological samples using extraction chromatography. Following sample preparation, uranium and thorium are pre-concentrated by precipitation with iron(III) hydroxide and then separated using UTEVA resin. The separated uranium and thorium are electrodeposited onto stainless-steel discs and then measured by alpha spectrometry. The procedure was evaluated using uraninite ore, coral and granite reference materials. The uranium and thorium concentrations and the ²³⁴U/²³⁸U and ²³⁰Th/²³⁴U activity ratio values determined for the reference materials were in good agreement with the certified values. The presence of plutonium was found to interfere with the separation, but the inclusion of a reduction step using iron(II) sulfamate eliminated the problem. Chemical recoveries for the procedure are similar to those for an anion-exchange procedure, but the extraction-chromatography procedure provides a more rapid separation using less reagents.