This manuscript describes the chemical transformations that occur during hydrolysis of uranium tetrafluoride (UF4) due to its storage in humid air (85% and 50% relative humidity) at ambient temperatures. This hydrolysis was previously reported to proceed slowly or not at all (depending on the percent relative humidity); however, previous reports relied primarily on X-ray diffraction methods to probe uranium speciation. In our report, we employ a battery of physiochemical probing techniques to explore potential hydrolysis, including Raman spectroscopy, powder X-ray diffraction, 19F nuclear magnetic resonance spectroscopy, scanning electron microscopy, and focused ion beam microscopy with energy-dispersive X-ray spectroscopy. Of these, only Raman spectroscopy proved to be particularly useful at observing chemical changes to UF4. It was found that anhydrous UF4 slightly oxidizes over the course of thirteen days to Schoepite-like uranium complexes and possibly UO3. In contrast, UF4 exposed to 50% relative humidity slightly decomposes into UO2F2, Schoepite-like uranium complexes, and possibly a high order uranium oxide that eluded chemical assignment (UxOy). Despite the rich chemical speciation observed in our Raman spectroscopy measurements, X-ray diffraction and 19F NMR measurements on the same material showed no changes. Microscopy measurements suggest that the observed reactions between UF4 and water occur primarily on the surface of UF4 particulates via a method that is visually similar to surface corrosion of metals. Therefore, we postulate that NMR spectroscopy and X-ray diffraction, which are well-suited for bulk analysis, are less suited than Raman spectroscopy to observe the surface-based reactions that occur to UF4 when exposed to humid air. Considering the importance of UF4 in the production of nuclear fuel and weapons, the results presented herein are widely applicable to numerous nuclear science fields where uranium detection and speciation in humid environments is of value, including nuclear nonproliferation and nuclear forensics.

Vibrational and luminescence spectroscopy were used in the investigation of U and Pu-bearing compounds and soot from high explosives testing. Key spectroscopic signatures of UF4 and its hydrates, PuO 2 , and soot from different explosives will be presented. The United States Government retains and the publisher, by accepting this article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States Government purposes.

Uranium tetrafluoride (UF4) is an important intermediate in the production of UF6 and nuclear fuel. Historical characterization of UF4 with Raman spectroscopy was plagued with ambiguity until the first accurate Raman spectrum was published by our group in 2016. Although generally considered to be relatively stable, UF4 can hydrolyze to form numerous UF4 hydrates that may play a role in future uranium waste forms. In contrast to anhydrous UF4, the hydrates, with their OH stretch and HOH bending modes, can be spectroscopically characterized by the type and degree of water bonding in the crystal lattice, which can yield additional information about their crystal structure. Herein, vibrational spectroscopy (Raman and infrared) was used to characterize three different UF4 hydrates: UF4(H2O)0.33, U3F12(H2O), and UF4(H2O)2.5. Spectra show the different hydrates vary in the number of observed bands, full-width half-maximum of the bands, and band intensity. These differences are due to varying interactions between the OH stretch and HOH bending modes with UF4 and the polymeric UF4 structure in the crystal lattice. These vibrational data, in combination with spectral fitting and crystallographic structures measured with powder X-ray diffraction and single crystal X-ray diffraction, provide unique details on the location of water molecules in the crystal lattice of hydrated UF4, and provide an interesting contrast to the vibrational spectra of anhydrous UF4.

Uranium tetrafluoride (UF4) is an important intermediate in the production of UF6 and uranium metal. Room temperature hydrolysis of UF4 was investigated using a combination of Fluorine-19 nuclear magnetic resonance spectroscopy (19F NMR), Raman and infrared spectroscopy, powder X-ray diffraction, and microscopy measurements. UF4(H2O)2.5 was identified as the primary solid hydrolysis product when anhydrous UF4 was stirred in deionized water. Static NMR and 19F magic angle spinning NMR measurements revealed that a small amount of uranyl fluoride can also form when anhydrous UF4 is left in water, although this species comprises less than 5% of the total sample with the remaining parts being UF4(H2O)2.5. Since UF4 is generally considered to be stable under ambient conditions, these findings mark the first time that a room temperature reaction between UF4 and water has been detected and analyzed without interference from additional chemical reagents. The Raman characterization of UF4(H2O)2.5 presented herein is the first on record. Since UF4 is one of the most used intermediates during chemical conversion of uranium ore to uranium metal for nuclear fuel and weapons, the results presented herein are applicable to numerous nuclear science fields where solid state detection of uranium is of value, including nuclear nonproliferation, nuclear forensics, and environmental remediation.

Journal Article Micromanipulation, FIB, STEM, EDS and EELS of UF4 Particles Get access Lucille A Giannuzzi, Lucille A Giannuzzi L.A. Giannuzzi & Associates LLC, Fort Myers, FL USAEXpressLO LLC, Lehigh Acres, FL USA Corresponding author: Lucille.Giannuzzi@EXpressLO.com Search for other works by this author on: Oxford Academic Google Scholar Michael DeVore, II, Michael DeVore, II Savanah River National Laboratory, Aiken, SC USA Search for other works by this author on: Oxford Academic Google Scholar Michael Summer, Michael Summer Savanah River National Laboratory, Aiken, SC USA Search for other works by this author on: Oxford Academic Google Scholar Matthew Wellons Matthew Wellons Savanah River National Laboratory, Aiken, SC USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 25, Issue S2, 1 August 2019, Pages 1584–1585, https://doi.org/10.1017/S1431927619008651 Published: 01 August 2019

Aqueous disposition of non-Al clad fuels was studied in order to determine if H-Canyon would be a viable disposition option for this type of L-Basin fuel. A review of the L-Basin fuel types and its condition was done suggesting two major cladding types, Zircaloy and 304L stainless steel needed to be studied. Dissolution flowsheets options were reviewed. Sulfex and Zirflex processes were chosen as best for H-Canyon integration. Both process flowsheets were demonstrated on a lab scale to determine decladding rate, and off-gas and waste production. The resulting data suggested decladding in H-Canyon was an option but dissolver corrosion as well as off-gas and waste generation needed to be addressed. Small scale dissolution in a hot cell of smaller damaged fuel is a viable option with the flowsheets tested.

High-resolution 19F magic-angle spinning (MAS) NMR spectra were obtained for the uranium-bearing solid uranyl fluoride sesquihydrate (UO2F2·1.57H2O). While there are seven distinct crystallographic fluorine sites, the 19F NMR spectrum reveals six peaks at -33.3, 9.1, 25.7, 33.0, 39.0, and 48.2 ppm, with the peak at 33.0 ppm twice the intensity of all the others and therefore corresponding to two sites. To assign the peaks in the experimental spectra to crystallographic sites, 19F chemical shifts were calculated using the gauge including projector augmented waves (GIPAW) plane-wave pseudopotential approach for a DFT-optimized crystal structure. The peak assignments from DFT are consistent with two-dimensional double-quantum 19F MAS NMR experiments.

Journal Article Practical Utilization of Uranium-Containing Particulate Test Samples for SEM/EDS and SIMS Automated Particle Analysis Method Validation Get access Matthew S Wellons, Matthew S Wellons National Security Directorate, Savannah River National Laboratory, Aiken SC, USA Search for other works by this author on: Oxford Academic Google Scholar Michael A DeVore, II, Michael A DeVore, II National Security Directorate, Savannah River National Laboratory, Aiken SC, USA Search for other works by this author on: Oxford Academic Google Scholar Robert M Rogers, Robert M Rogers National Security Directorate, Savannah River National Laboratory, Aiken SC, USA Search for other works by this author on: Oxford Academic Google Scholar Joshua T Hewitt, Joshua T Hewitt National Security Directorate, Savannah River National Laboratory, Aiken SC, USA Search for other works by this author on: Oxford Academic Google Scholar Todd L Williamson, Todd L Williamson Chemistry Division, Los Alamos National Laboratory, Los Alamos NM, USA Search for other works by this author on: Oxford Academic Google Scholar Travis J Tenner, Travis J Tenner Chemistry Division, Los Alamos National Laboratory, Los Alamos NM, USA Search for other works by this author on: Oxford Academic Google Scholar Taghi Darroudi Taghi Darroudi Clemson Microscopy Center, Clemson University, Anderson SC, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 23, Issue S1, 1 July 2017, Pages 514–515, https://doi.org/10.1017/S1431927617003257 Published: 04 August 2017

Quinoxalinol salen ligands have been characterized as selective ligands for the rapid identification of uranyl. The absorption maximum of ligand 1 presented a hypsochromic (blue) shift with the addition of UO22+ (as the acetate salt), and a bathochromic (red) shift in the presence of Cu2+ or Co2+ acetate salts, resulting in distinct, visible color changes for all three metal ions. The absorption maximum of ligand 2 was not observed to change with the addition of UO22+; however, it does present a bathochromic shift with the addition of Cu2+, and a hypsochromic shift with Co2+ added. Using TDDFT calculations, it was demonstrated that the hypsochromic shift for UO22+ ion complexation with ligand 1 is caused by a ligand-to-metal charge transfer, while the bathochromic shift observed with Cu2+ ion addition was caused by a metal-to-ligand charge transfer. Finally, it was found that the addition of Cu2+ (as metal salts) to either ligand resulted in rapid, complete quenching of the ligand fluorescence.

Dithiophosphinate ligands with groups linked together by a bridging spacer to take advantage of a chelate effect for improved selectivity have been characterized. Extractions with each ligand were performed with the ligands dissolved in methylene chloride and the metal salts dissolved in aqueous phase at pH 4. H2L1 was found to have good differentiation between UO22+ and Gd3+, but only resulted in 50% extraction. H2L2 had lower selectivity; however, copper extractions approached 95% after 24h.

Here, we highlight some recent accomplishments in f-element coordination chemistry aimed at probing the fundamental chemical differences between the 4f elements, lanthanides, and the 5f elements, actinides. The studies of particular interest are those that target improving our knowledge of fundamental chemistry to aid in increased selectivity for extractions of actinides. Two components key to understanding the challenges of actinide separations are detailed here, namely, previously described separation methods and recent investigations into the fundamental coordination chemistry of actinides. Both are aimed at probing the critical features necessary for improved selectivity of separations. This is considered a critical goal in the safe remediation of contaminated sites and reprocessing of nuclear fuel sources used in either civilian and noncivilian energy production.