Application of Visible/Near-Infrared Reflectance Spectroscopy to Uranium Ore Concentrates for Nuclear Forensic Analysis and Attribution

Abstract

Uranium ore concentrates (UOCs) are produced at mining facilities from the various types of uranium-bearing ores using several processes that can include different reagents, separation procedures, and drying conditions. The final UOC products can consist of different uranium species, which are important to identify to trace interdicted samples back to their origins. Color has been used as a simple indicator; however, visual determination is subjective and no chemical information is provided. In this work, we report the application of near-infrared (NIR) spectroscopy as a non-contact, non-destructive method to rapidly analyze UOC materials for species and/or process information. Diffuse reflectance spectra from 350 to 2500 nm were measured from a number UOC samples that were also characterized by X-ray diffraction. Combination and overtone bands were used to identify the amine and hydroxyl-containing <bold/> species, such as ammonium uranates or ammonium uranyl carbonate, while other uranium oxide species (e.g., uranium trioxide [UO3] and triuranium octoxide [U3O8]) exhibit absorption bands arising from crystal field effects and electronic transitions. Principal component analysis was used to classify the different UOC materials.

Identification of Uranium Minerals in Natural U-Bearing Rocks Using Infrared Reflectance Spectroscopy

“…7 Moreover, chemical characterization utilizing this technique has the potential to provide further insight into the manufacturing process and possibly even the origin of the sample. 3,8–11…”

“…7 Moreover, chemical characterization utilizing this technique has the potential to provide further insight into the manufacturing process and possibly even the origin of the sample. 3,[8][9][10][11] There have been some prior studies that characterize uranium minerals and chemicals using spectroscopic methods. For example, Varga et al were able to distinguish between various uranium ore concentrates (UOCs) using traditional IR transmission spectroscopy with small amounts of the uranium compounds in KBr pellets.…”

“…For example, Varga et al were able to distinguish between various uranium ore concentrates (UOCs) using traditional IR transmission spectroscopy with small amounts of the uranium compounds in KBr pellets. 12 Plaue et al 7,8 have used reflectance spectroscopy in the visible-near-infrared (VNIR) spectral region (350-2500 nm) to reveal process signatures in uranium oxides. These methods were applied to examine and distinguish various precipitates and oxides by identifying spectral features consistent with conversions in chemical species due to various process parameters.…”

“…These methods were applied to examine and distinguish various precipitates and oxides by identifying spectral features consistent with conversions in chemical species due to various process parameters. It was found 7,8 that the spectroscopic signatures can be indicative of the chemical processes such as separation procedures, reagents, and the drying conditions for the concentrates. 7 Ho et al 4 applied a different approach by analyzing uranium compounds using Raman spectroscopy combined with multivariate analysis for classification.…”

Expanding the nuclear forensic toolkit: chemical profiling of uranium ore concentrate particles by synchrotron X-ray microanalysis

“…[2][3][4] One particular area of interest is characteristics related to the chemical processing history of nuclear materials, which can link specic samples to particular operations or events. 1,5,6 The focus for much of the development of nuclear forensic science has been providing a rapid capability for the characterisation of materials in scenarios where a bulk quantity has been discovered or seized. 1 However, in some scenarios it will be necessary to investigate trace evidence, such as environmental residues or contaminated items, for links with specic processes or materials.…”