In this study, we demonstrate a new dual-field multicollector protocol for magnetic sector large-geometry secondary ion mass spectrometry (LG-SIMS) that enables concurrent analysis of U and Pu isotopes. We apply this analysis protocol to recently produced mixed U-Pu microparticle reference materials, called UPu-100A. These particles, loaded on a Si substrate, show highly reproducible U and Pu isotopic and U/Pu assay results, with particle-to-particle molar variability typically less than 1% relative, and down to 0.1% for 235U/238U and less than 0.3% for 240Pu/239Pu. We demonstrate the impact of surface and primary beam sputter chemistry on the acquisition and interpretation of mixed-actinide particle analyses. We show that, in general, consuming most of each particle within a single analysis yields the most reproducible results. Using O3- primary ions reduces sputter chemistry artifacts during particle depth profiling on Si relative to O- primary ions, which further enhances reproducibility. The Pu/U relative sensitivity factors for O3- and O- primary ions on Si were 2.036 +/- 0.016 (1 standard deviation, SD) and 2.142 +/- 0.034 (1 SD), respectively. This work highlights how integration of novel analytical protocols and fit-for-purpose reference materials can push the boundaries of particle-scale material characterization.

ABSTRACTRaman spectroscopy is an ideal tool in the characterization of materials including PuO2. The wavelength‐dependent absorptivity of the material defines the light penetration depth and the relative Raman scattering contribution from the bulk and the surface. The surface contribution to the total Raman scattering was investigated for PuO2 calcined at various temperatures and recorded with laser wavelengths of 355, 325, and 244 nm. These experiments provided the first glimpse of the wavelength‐dependent disappearance and emergence of new phonons and electronic bands from the PuO2 surface layers. The first indication of the wavelength transition in the Raman spectra was the loss of the 2LO2 (overtone, ~1155 cm−1) band and the weakening intensity of the Г1 → Γ5 electronic band (~2135 cm−1) with the 355‐nm excitation laser. The Γ5 electronic band was barely visible with the 244‐nm excitation. The electronic band located at ~1050 cm−1, corresponding to the Г1 → Γ4 electronic transition was observed to dramatically increase in intensity while the Г1 → Γ3 electronic band (2640 cm−1) sharpened as the UV wavelength was increased in energy from the near‐ to deep‐UV (355–325–244 nm). The FWHM of the T2g band was found to vary with calcination temperature (450°C and 900°C) with the 325‐nm laser and the 244‐nm laser. The T2g band attributes, the strong emergence of the Г1 → Γ4 electronic band, and the disappearance of the 2LO2 overtone acquired with the 244‐nm excitation for the different calcination temperatures suggest a shallow penetration depth.

A new monodisperse micrometre size U/Pu particle reference material has been synthesized and characterized. It is isotopically and elementally homogeneous and therefore ideal for calibration, quality control, and particle analysis method development.

The pivotal role of uranium and plutonium fluorides in the nuclear fuel cycle, particularly in the pyrochemical reduction process, is well recognized. Traditionally, the fluorination of uranium and plutonium materials relies on the use of highly toxic and corrosive gases (e.g., HF(g), F2(g)). Herein, we present an alternative approach using the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6](l)) and/or hexafluorophosphoric acid (HPF6(aq)) as fluorinating agents for the f-element oxalates MIII 2 (C2O4)3 & sdot; 9H2O(s)MIII 2 (C2O4)3 & sdot;9H2O(s) (MIII = Ce, Pu) and MIV(C2O4)2 & sdot;6H2O(s) (MIV = Th, U). Our findings demonstrate that [Bmim][PF6](l) and HPF6(aq) enable the ionothermal fluorination of f-element oxalates, resulting in the formation of anhydrous CeF3(s), ThF4(s), and UF4(s) within 2 hours at 200 degrees C. This method also facilitates the partial fluorination of plutonium(III) oxalate, yielding a mixture of anhydrous PuF3(s) and an unidentified phase. Overall, the ionothermal treatment approach offers a safer and more efficient means of producing anhydrous felement fluorides than conventional methods involving hazardous gases. In addition, we describe the morphology of UF4(s) materials as a function of production route and demonstrate the presence of morphological signatures that could be used during a nuclear forensic investigation.

Raman, FTIR, and diffuse reflectance spectroscopy were used to study the auto-radiolytic degradation of 240Pu and 242Pu oxalates. The significant differences in the lifetimes of 240Pu and 242Pu enabled the differentiation between environmental and radiolytic mechanisms. 240Pu oxalates were observed to decompose to PuOCO3 at intermediate times ( 20 weeks) followed by partial conversion to PuO2 at times greater than one year. Atmospheric oxidation was shown to be the primary decomposition mechanism for 242Pu(IV) oxalate, and the alpha radiolysis of aquo and oxalate ligands serves as a secondary decomposition mechanism. This study offers a fresh perspective on radiolytic aging, which is crucial for long-term storage applications.

Anhydrous plutonium tetrafluoride is an important intermediate in the production of metallic Pu. This historically important compound is also known to exist in at least two distinct, yet understudied hydrate forms, PuF4xH2O(s) (0.5 <= x <= 2) and PuF42.5H2O(s). X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) are the most common tools used to characterize these materials, often in a context for studying structural and morphological changes that arise from aging or calcination. However, fundamental electronic and vibrational spectroscopic information is rather scarce. Here, we measured the visible and shortwave infrared (SWIR) diffuse reflectance, Fourier transform infrared (FTIR), fluorescence and Raman spectra of PuF4(s) and PuF4xH2O(s) to obtain a better electronic and vibrational fingerprint. Our work provides clear indication of the polymeric structure of anhydrous PuF4, consistent with the Raman spectrum of UF4(s) and its hydrates. This is supplemented with XRD, TGA and SEM analysis. Findings in this study indicate that the spectra are modified by particle size, which in turn is influenced by synthetic technique.

The Savannah River National Laboratory (SRNL) has been developing advanced spectroscopic tools for the characterization of plutonium-bearing compounds with the intent to develop material and process signatures for nuclear forensics. Plutonium in a production, refining, or finishing facility will exist in many forms including oxide precursors (PuF4, PuF3, Pu oxalate, etc.), oxide, and metal. The ability to identify plutonium in each of these chemical forms and determine their processing history is crucial for the development of spectroscopic signatures. This presentation will focus on our work to develop and apply spectroscopic tools at SRNL using doubled-walled cells (DWC) to characterize the thermal decomposition of oxalates, calcination chemistry, alpha-decay-induced chemistry, age dating since last calcination, and other signatures related to plutonium processing.

Spectroscopic analysis of radiological materials has been historically limited to radiological labs with older or less advanced scientific instrumentation. The development of double-walled cells (DWCs) at the Savannah River National Laboratory (SRNL) has enabled Pu-bearing compounds to be removed from radiological laboratories and studied in our radiologically clean spectroscopy laboratory with state-of-the-art instrumentation. In this manuscript, we discuss the contributions of DWCs that have allowed the application of Raman spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), diffuse reflectance spectroscopy (DRS) in the shortwave infrared, and gamma spectroscopy at SRNL. Significant advances have been made in the understanding of the thermal decomposition of Pu(III) and Pu(IV) oxalates, alpha-induced damage to the PuO2 crystal lattice, and the effect of calcination temperatures on the quality of PuO2. These techniques have enabled methods to conduct PuO2 age dating since last calcination and estimate the calcination temperature with Raman spectroscopy and DRS. Additional spectroscopic information measured with DRIFTS has enabled the observation of the evolution of carbon species with calcination temperature, while gamma spectroscopy provides information on age dating since last purification.

Plutonium research has been stifled by the significant number of administrative controls and safety procedures, space and instrumentation limitations in radiological gloveboxes, and the potential for personnel and equipment contamination. To address the limited number of spectroscopic studies in Pu-bearing compounds in the current scientific literature, this work presents the use of double-walled cells (DWCs) in "clean" buildings/laboratories as an alternative to research in radiological gloveboxes. This study reports the first laser-induced breakdown spectroscopy (LIBS) experiments of a PuO2 pellet contained within a DWC, where the formation of elemental (atomic and ionic) species as well as the evolution from elemental to molecular products (PuxOy) was measured. Raman spectroscopy was also used to characterize the surface of the ablated pellet and the particulates deposited on the window of the inner cell. The full width half-maximum of the T2g band enabled us to obtain an estimate of the temperature at the pellet surface after the ablation pulse and the particulates based on the crystal lattice disorder. Particulates deposited on the window of the DWC during laser ablation were characterized using scanning electron microscopy, where molten irregular particulates and spheroids were observed. This exciting research conducted in a DWC describes our initial attempts to incorporate LIBS in the arsenal of spectroscopic tools for nuclear forensics applications.

This manuscript describes the synthesis of Os complexes supported by the diarylamido/bis(phosphine) PNP pincer ligand. Compound (PNP)OsH(CO) (3-Os) was prepared by analogy with the previously reported 3-Ru. However, attempts to make (PNP)OsH3 (4-Os) analogously to 4-Ru resulted in the formation of an unexpected compound (5-Os) that is a product of addition of a BH3 unit across the Os-N bond in 4-Os. Nonetheless, 4-Os was prepared via an alternative route. Unlike 4-Ru, 4-Os appears to be a classical trihydride. Compounds 3-Ru, 3-Os, 4-Os, 4-Ru, and 5-Os were tested as potential catalysts for (a) dehydrogenative borylation of terminal alkynes (DHBTA) and (b) dehydrogenative borylation of benzene. No catalytic C-H borylation was observed for any of them, but all of them catalyzed unselective hydroboration of 4-MeC6H4CCH.

Diversion of nuclear materialsfrom legitimate commercial processes for use by nefarious actors is a frightening and surreptitious problem. Smuggled nuclear material can be used to manufacture a simple radiological dispersion device (RDD) and potentially incorporated into the development of a nuclear weapon. With some frequency, smuggled nuclear material is interdicted in foreign countries as actors cross border checkpoints. Nuclear material interdicted in this way can be analyzed using a variety of tools. Plutonium-239 is commonly used as the fissile material in nuclear weapon production as an alternative to uranium-235. Plutonium in a production, refining, or finishing facility will exist in many forms including oxide precursors (PuF4, PuF3, Pu oxalate, etc.), oxide, and metal. The ability to identify plutonium in each of these forms and determine properties, characteristics, or history of these materials is crucial for determining if the processes occurring in a nuclear facility are legitimate or not. This presentation will focus on the development and application ofspectroscopic tools developed at SRNL using doubled-walled cells (DWC) to characterize Pu-bearing compounds. Advances in the use of vibrational spectroscopy techniques (Raman and IR), UV-VIS-SWIR diffuse reflectance spectroscopy, gamma emission spectroscopy, luminescence spectroscopy, laser-induced breakdown spectroscopy in conjunction with XRD and SEM in the characterization of Pu-bearing compounds will be presented with emphasis in material processing history.

The Raman spectrum of PuO2 was measured up to 13,000 cm(-1) with three different laser excitation wavelengths spanning the resonance (405 nm), near-resonance (457 nm), and preresonance (514 nm) energy range. Approximately 26 never-before-seen bands were observed between 3500 and 13,000 cm(-1). Given the very high energy of the Raman shifts of these bands and the relative insensitivity of their spectral position to the interrogating laser wavelength, they are believed to arise from an electronic origin. These bands are present in both freshly calcined and radiolytically aged PuO2, although a broad luminescence is observed in the aged material, which obscures many of the high frequency features. In situ laser annealing of the material attenuated this luminescence and allowed for clear observation of these never-before-seen spectral features. Discovery of these high-energy bands presents a new way of identifying PuO2 for nuclear nonproliferation and forensics purposes.

Diffuse reflectance spectroscopy measurements in the shortwave infrared (930-1600 nm) spectral region were acquired for Pu-2(C2O4)(3)center dot 9H(2)O and its thermal decomposition product, PuO2. We analyzed a total of eight PuO2 samples that were produced at different calcination temperatures (300, 350, 450, 525, 600, 675, 750, and 900 degrees C). Our goal was to identify spectroscopic fingerprints that could be used to gain retrospective information regarding the production parameters of these important nuclear compounds. The diffuse reflectance spectrum of Pu-2(C2O4)(3)center dot 9H(2)O features several broad bands that currently preclude detailed analysis. However, all PuO2 samples produced relatively sharp spectral features that got sharper and more intense for samples that were produced at higher calcination temperatures. The electronic band observed at 1433 nm in the diffuse reflectance spectra of PuO2 was found to be a sensitive indicator of crystallinity; a result that is corroborated by ancillary Raman spectroscopy measurements. Principal component analysis of diffuse reflectance spectra was able to clearly rank and categorize PuO2 samples based on the calcination temperature that was employed during their production. Thus, we show herein that important retrospective information pertaining to the process history of PuO2 can be gained through the relatively simplistic combination of diffuse reflectance spectroscopy and principal component analysis. This discovery presents a new method for determining the provenance and process history of PuO2 and should have an impact in the fields of nuclear forensics and nuclear nonproliferation.

The thermal decomposition of Pu(III) oxalate was analyzed by Raman microspectroscopy, infrared spectroscopy, scanning electron microscopy, and powder X-ray diffraction. These data show that crystalline Pu2(C2O4)3•9H2O progressively loses water and oxalate ligands as it is heated, which leads to a decrease in long-range lattice ordering, though minimal changes are observed in gross crystalline morphology. The onset of PuO2 formation was observed between 200 - 250 ℃. Thermal decomposition of oxalate ligands leads to the formation of CO2 and plutonium oxalate-carbonate moieties, which had not been observed in previously published thermogravimetric measurements of Pu(III) oxalate. Formation of plutonium oxalate-carbonate moieties is believed to be associated with a change in the plutonium oxidation state from 3+ to 4+, which occurs prior to PuO2 formation. The data provided herein demonstrate the rich spectroscopic nature of a rather underexplored, and technologically relevant, plutonium system. Ideally these results will further future investigations into the Pu(III) oxalate system both experimentally and computationally.

The effect of & gamma;-irradiation on physico-chemical properties of International Simple Glass (ISG) nuclear waste glass simulants with low iron impurities was investigated. The study was performed on glasses produced by Corning Inc. (named ISG-1, ISG-2) following a 0.95 MGy dose. Fourier-transform infrared and Raman spectroscopy, chemical durability tests, dilatometry, differential scanning calorimetry, electron paramagnetic resonance (EPR), optical absorption, and photoluminescence (PL) spectroscopy appraisals were done in comparison with pristine glasses. The data indicated that structural, chemical, and thermal properties were not significantly altered following & gamma;-ray exposure. EPR spectroscopy showed radiogenic signatures from spin defects for the & gamma;-irradiated glasses which were absent in the pristine. Optical absorption also changed significantly for the & gamma;-irradiated glasses which exhibited defects-related features around 3.45 and 2.25 eV. The optical band gap and Urbach energies were then determined and compared with those obtained for the & gamma;-irradiated original ISG produced by Mo-SCI Corporation. PL spectroscopy revealed distinct changes after irradiation showing enhanced high-energy emission, contrasting with the & gamma;-irradiated original ISG. The effects of thermal treatment on optical properties of & gamma;-irradiated glasses were finally evaluated. Potential causes at the origin of the contrasting results are discussed based on the effects of different impurities.

Despite its use in PuO2 production, the structure of anhydrous Pu(C2O4)2 is still not completely understood. Recently, two candidate structures for Pu(C2O4)2 were proposed via density functional theory (DFT), after which the first experimental optical vibrational spectra were reported. Here, we calculated the lattice dynamics of the candidate structures using DFT and found that the primary difference between them is the presence of a vibrational mode near 1380 cm−1 in one structure. The frequency and optical activity of this mode agree well with the published experimental results, providing strong support for this calculated structure as that of anhydrous Pu(C2O4)2.

For over 80 years, plutonium dioxide has been routinely produced via thermal decomposition of hydrated plutonium(IV) oxalate. Despite the longstanding utility of this process, the chemical structures of starting materials and intermediates produced during this thermal conversion remain ill-defined. To help resolve this uncertainty, we measured high-resolution Raman and infrared spectra of Pu(C2O4)(2)center dot 6H(2)O that was heated to 25, 100, 220, 250, 350, and 450 degrees C in air. Our measurements show that Pu(C2O4)(2)center dot 6H(2)O has a rich vibrational spectrum with at least 15 Raman bands between 180 cm(-1) and 1900 cm(-1) and 9 infrared bands between 800 cm(-1) and 4000 cm(-1). As Pu(C2O4)(2)center dot 6H(2)O is heated, water is liberated, and the oxalate ligand decomposes to produce plutonium oxycarbide species. When heated to 350 degrees C or higher, vibrational spectra are consistent with PuO2 with some residual carbon-containing species. Full vibrational spectra, powder X-ray diffraction, and scanning electron microscopy measurements of Pu(C2O4)(2)center dot 6H(2)O and its thermal degradation products are presented herein along with approximate assignments for observed spectral bands. These data can be used to validate and potentially improve existing computational models that describe the chemical structure of compounds produced during thermal degradation of plutonium (IV) oxalate. Given the utility of plutonium (IV) oxalate in synthesizing plutonium dioxide, these results are expected to provide value in the fields of nuclear fuel processing, nuclear nonproliferation, and nuclear forensics. (C) 2022 Elsevier B.V. All rights reserved.

the American Medical Isotope ACT which aimed to cease all Mo-99 production that requires HEU and support American based companies who have found safer production methods. Through this effort, a system was designed and developed to access irradiated material in processing hot cells for ease of material introduction and removal in the confined area. The proposed solution uses a double-door design that allows for easy access to material while also providing shielding through a mechanically manipulated carousel. A system was also designed to transport irradiated materials from target reactors to a target receipt box using a rail guide system, pneumatic motor, and lead screw drive.

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.