PNNL

Abstract

Uranium analysis is consistently needed throughout the fuel cycle, from mining to fuel fabrication to environmental monitoring. Although most of the world’s uranium is immobilized as pitchblende or uraninite, there exists a plethora of secondary uranium minerals, nearly all of which contain the uranyl cation. Analysis of uranyl compounds can provide clues as to a sample’s facility of origin and chemical history. X-ray absorption spectroscopy is one technique that could enhance our ability to identify uranium minerals. Although there is limited chemical information to be gained from the uranium X-ray absorption edges, recent studies have successfully used ligand NEXAFS to study the physical chemistry of various uranium compounds. This study extends the use of ligand NEXAFS to analyze a suite of uranium minerals. We find that major classes of uranyl compounds (carbonate, oxyhydroxide, silicate, and phosphate) exhibit characteristic lineshapes in the oxygen K-edge absorption spectra. As a result, this work establishes a library of reference spectra that can be used to classify unknown uranyl minerals.