This study supports in-tank sludge washing and delivery of initial feed to the Hanford High-Level Waste vitrification facility by characterizing particle populations in 241-AN-106 wastes from the southeast quadrant of the Hanford Site. We developed computational tools to determine particle size distributions for specific mineralogical phases within these heterogeneous sludges. Automated Particle Analysis (APA), combining scanning electron microscopy (SEM) imaging with energy-dispersive X-ray spectroscopy (EDS), was used to quantify particle morphology and composition for tens of thousands of individual particles, providing phase-resolved particle size distributions that are more representative than manual measurements. Phase-specific size distributions were compared among positions within a series of 241-AN-106 core-samples, and the Kolmogorov–Smirnov statistic was applied to test for statistically significant differences. Results demonstrate measurable size separation of gibbsite particle populations with position within the sludge layers, where larger gibbsite particles partitioned to the lower segments. This study illustrates how high-throughput, phase-resolved particle sizing can improve understanding of waste heterogeneity relevant to washing and feed delivery.

Np(VII) compounds with [Co(NH3)6]3+ cations were synthesized and structurally examined using powder X-ray diffraction. Multiple phases were observed, consisting of octahedral [Co(NH3)6]3+ cations, discrete tetragonal bipyramidal [NpO4(OH)2]3-anions, and waters of hydration. Electric field gradient tensors at Co sites were measured by solid state 59Co nuclear magnetic resonance (NMR) spectroscopy and compared with theoretical calculations. The relative contributions of the chemical shift and electric field tensors to the NMR lineshape were determined by recording spectra at field strengths of 7.04 and 11.74 Tesla. Further, the evolution of structure and morphology as a function of sample age and the effects on NMR spectral parameters has also been investigated. These results demonstrate the use of NMR at multiple fields to expand understanding of the stability and electronic structure of high valent neptunium compounds.

On 2 May 2019, during the 137 Cs source recovery operation, a source capsule in a research irradiator containing approximately 77.1 TBq was breached. Based on a geometric reconstruction analysis of the damage to the capsule, approximately 46.3 GBq (0.04%) was impacted by the chop saw (grinder) inside a mobile hot cell on the loading dock at the University of Washington Harborview Research and Training (HRT) Building. A very small fraction of the material impacted, less than 1%, was released from the mobile hot cell and then to the rest of the HRT Building. The objectives of this project were to assess the accidental release of 137 CsCl and its implications related to emergency response methods and the ramifications of 137 CsCl transport. The phenomenology of this event was also compared with past alkali halide dispersal events. The vast number of measurements and samples collected by the remediation contractors, the Department of Energy’s Nuclear Emergency Support Team, and the small number of retrospective samples collected by the authors informed the analysis. The techniques included (1) autoradiography and electron microscopy of samples collected from the HRT Building and the irradiator, (2) 3D visualization of deposition on surfaces and within the ventilation system, and (3) a study of the damage to the source capsule to evaluate the Cs particle size and particle composition due to the grinding accident. Subsequently, the cesium contaminant transport through the numerous pathways in the building was reconstructed to assess the deposition on surfaces as a function of particle size. The implications for emergency response are relevant to data quality and management. A Data Quality Objective guides data collection methods so that they have appropriate accuracy and precision for the intended application. Recommendations were made with respect to the sample collection protocols and archiving of samples.

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 degradation of the internal structure of plutonium (IV) oxalate during calcination was investigated with Transmission Electron Microscopy (TEM), electron diffraction, Electron Energy-Loss Spectroscopy (EELS), and 4D Scanning TEM (STEM). TEM lift-outs were prepared from samples that had been calcined at 300°C, 450°C, 650°C and 950°C. The resulting phase at all calcination temperatures was identified as PuO2 with electron diffraction. The grain size range was obtained with high-resolution TEM. In addition, 4D STEM images were analyzed to provide grain size distributions. In the 300°C calcined sample, the grains were <10 nm in diameter, at 650°C, the grains ranged from 10 to 20 nm, and by 950°C, the grains were 95–175 nm across. Using the Kolmogorov-Smirnov (K-S) two sample test, it was shown that morphological measurements obtained from 4D-STEM provided statistically significant distributions to distinguish samples at the different calcination conditions. Using STEM-EELS, carbon was shown to be present in the low temperature calcined samples associated with oxalate but had formed carbon (possibly graphite) deposits in the 950°C calcined sample. This work highlights the new methods of STEM-EELS and 4D-STEM for studying the internal structure of special nuclear materials (SNM).

Multiple bench-scale filtration campaigns of Hanford tank waste supernatant on a backpulseable dead-end filtration skid have provided greater insight into the solids that cause fouling and reduce filter performance. The solids collected during each campaign were concentrated from the backpulse solutions and examined using automated particle analysis (APA) methods with scanning electron microscopy and X-ray energy dispersive spectroscopy to categorize particle types and their morphological characteristics. We show that with APA, thousands of particles can be analyzed to provide accurate insight into the phases that may be impacting filter performance.

The sluggish oxygen evolution reaction (OER) remains a major bottleneck in hydrogen generation through electrolysis, particularly at large current operations. Thus, there is a huge interest in the development of...

Accurate, high-throughput, and unbiased analysis of plutonium oxide particles is necessary for analysis of the underlying phenomena associated with the process parameters involved in its synthesis. Compared to qualitative and taxonomic descriptors, quantitative descriptors of particle morphology using scanning electron microscopy (SEM) have shown success in analyzing process parameters of uranium oxides. Among other candidates, a neural network called Vector Quantized Variational Autoencoder (VQ-VAE) has shown the ability to quantitatively describe particle morphology with >85% accuracy from uranium oxide processing routes. In this study, we utilized VQ-VAE to analyze synthesized plutonium dioxide (PuO2) particles to investigate the underlying phenomena and predict its process parameters. The surface morphology of PuO2 powders calcined from plutonium oxalates precipitated under varying synthesis conditions related to concentrations, temperature, addition and digestion times, precipitant feed, and strike order was performed using SEM. A pipeline was developed to extract and quantify useful images of individual particles with VQ-VAE which was followed by further reduction of the dimensionality of the feature space using a bottlenecking neural network fit to perform multiple classification tasks simultaneously. The reduced feature space could predict process parameters for a single particle with >80% accuracy for some parameters. It also demonstrated potential in successfully grouping particles with similar surface morphology. The clustering and classification results revealed valuable information regarding the chemical process parameters that predominantly influence the PuO2 particle morphology, which includes strike order and oxalic acid feed stock, respectively. Repeating the analysis with multiple particles improved the classification accuracy of each process parameter compared to results yielded using single particle, with statistically significant results being yielded with as few as four particles.

We report the structural, vibrational, and optical properties of americium formate (Am(CHO2 )3 ) crystals synthesized via the in situ hydrolysis of dimethylformamide (DMF). The coordination polymer features Am3+ ions linked by formate ligands into a three-dimensional network that is isomorphous to several lanthanide analogs, (e. g., Eu3+ , Nd3+ , Tb3+ ). Structure determination revealed a nine-coordinate Am3+ metal center that features a unique local C3v symmetry. The metal-ligand bonding interactions were investigated by vibrational spectroscopy, natural localized molecular orbital calculations, and the quantum theory of atoms in molecules. The results paint a predominantly ionic bond picture and suggest the metal-oxygen bonds increase in strength from Nd-O<Eu-O<Am-O. The optical properties were probed using diffuse reflectance and photoluminescence spectroscopies. Notably, the rarely reported 5 D1' →7 F0' emission band is observed and dominates the emission spectrum. This behavior is unusual and is attributed to the C3v coordination environment of the metal center.

Journal Article Irradiation Effect on Noble Metal Particles in Water Using in situ Liquid Cell STEM Observation Get access Jaeyoung Heo, Jaeyoung Heo Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Bruce K McNamara, Bruce K McNamara Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Dongsheng Li, Dongsheng Li Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, United States Corresponding author: Dongsheng.Li2@pnnl.gov, edgar.buck@pnnl.gov Search for other works by this author on: Oxford Academic Google Scholar Edgar C Buck Edgar C Buck Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, United States Corresponding author: Dongsheng.Li2@pnnl.gov, edgar.buck@pnnl.gov Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 1557–1558, https://doi.org/10.1093/micmic/ozad067.801 Published: 22 July 2023

An ab initio study on the plutonium oxalate hydrates: Pu2(C2O4)3⋅10H2O and Pu(C2O4)2⋅6H2O, using PBE exchange-correlation with D3 dispersion correction and Hubbard correction for the plutonium atoms was performed and compared to experimental vibrational spectral and thermodynamic property values. We demonstrated that this technique can accurately predict the experimental infrared spectra Pu(III) oxalate hydrate, as well as the Raman peak of PuO2 (used to calculate the thermodynamic properties of the oxalates). For Pu(IV) oxalate hydrate, we found that our predicted structure agreed qualitatively with PXRD measurements, the only available experimental determination of the structure. Using this method at standard temperature and pressure, we predicted standard enthalpies of formation of -6,755 kJ mol−1 and -3,923 kJ mol−1 and standard Gibbs free energy of formation of -5,899 kJ mol−1 and -3,386 kJ mol−1 for Pu2(C2O4)3⋅10H2O and Pu(C2O4)2⋅6H2O, respectively.

High-performance energy storage devices (HPEDs) play a critical role in the realization of clean energy and thus enable the overarching pursuit of nonpolluting, green technologies. Supercapacitors are one class of such lucrative HPEDs; however, a serious limiting factor of supercapacitor technology is its sub-par energy density. This report presents hitherto unchartered pathway of physical deformation, chemical dealloying, and microstructure engineering to produce ultrahigh-capacitance, energy-dense NiMn alloy electrodes. The activated electrode delivered an ultrahigh specific-capacitance of 2700 F/cm3 at 0.5 A/cm3. The symmetric device showcased an excellent energy density of 96.94 Wh/L and a remarkable cycle life of 95% retention after 10,000 cycles. Transmission electron microscopy and atom probe tomography studies revealed the evolution of a unique hierarchical microstructure comprising fine Ni/NiMnO3 nanoligaments within MnO2-rich nanoflakes. Theoretical analysis using density functional theory showed semimetallic nature of the nanoscaled oxygen-vacancy-rich NiMnO3 structure, highlighting enhanced carrier concentration and electronic conductivity of the active region. Furthermore, the geometrical model of NiMnO3 crystals revealed relatively large voids, likely providing channels for the ion intercalation/de-intercalation. The current processing approach is highly adaptable and can be applied to a wide range of material systems for designing highly efficient electrodes for energy-storage devices.

Approximately 9 liters of supernatant from Hanford waste tank 241-SY-101 was delivered by Washington River Protection Solutions to the Radiochemical Processing Laboratory (RPL) at Pacific Northwest National Laboratory. The thirty-six SY-101 sample bottles were comprised of six sets of six samples, with each set pulled from a unique tank sampling level. Prior to testing, samples from each level were composited to provide nominally level-independent feed for dead end filtration and ion exchange testing. The composited 241-SY-101 supernatant was chilled to 16 °C for 1 week prior to testing. Filtration testing was then conducted using a backpulse dead-end filter (BDEF) system equipped with a feed vessel and a Mott inline filter Model 6610 (Media Grade 5) in the hot cells of the RPL. This was done to provide waste processing benchmarks for 200 West Area wastes in the West Area Risk Management project. The feed was filtered through the BDEF system at a targeted flux of 0.065 gpm/ft2. During filtration of the differential pressure required to effect filtration at 0.065 gpm/ft2 increased little over the filtration campaign and never reached 2 psid (the Tank Side Cesium Removal system action limit). This indicates that the Media Grade 5 filter should perform well when processing SY-101 supernatant. After completing filtration of the SY-101 feed, the filter was cleaned. Solids concentrated from the backpulse solutions displayed calcium phosphate, aluminum oxides, aluminum-chromium nanoparticle agglomerates. Electron diffraction was used to determine the types of phases that were present in the solids. Most of the phases found were only weakly crystalline, possibly owing to their rapid precipitation during the process water treatment. The identifications of the phases therefore are tentative.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

To identify the role of waste composition and sediment interactions in controlling Pu and Am mobility in contaminated sediments at Hanford, a legacy nuclear site, Pu and Am concentrations in solutions equilibrated with contaminated sediments from beneath the 216-Z-9 (Z-9) Trench were compared to the solubilities of PuO2 materials, synthesized by methods representative of the disposed wastes, in the absence of sediments. This work shows that the solubilities of PuO2 materials synthesized by different methods, and with varying particle sizes, agree with PuO2(am,hyd), although dissolution kinetics differed between materials. According to saturation index (SI) calculations, PuO2(am,hyd) is likely also controlling Pu release from sediments under conditions where phosphate concentrations are low. However, both Pu-phosphate and Am-phosphate phases, identified in SI calculations and by high resolution transmission electron microscopy, play roles in controlling release in low pH, high phosphate, shallow sediments just below the Z-9 Trench. The elevated phosphate is likely due to decomposition of tributyl phosphate from waste solutions over time. Sediments from deeper in the subsurface beneath the Z-9 Trench are less acidic and contain less phosphate, with Pu solubility likely controlled by PuO2(am,hyd) that precipitated following neutralization of the acidic waste stream. Controls on Am concentrations in deeper sediments are more complex and potentially involve sediment adsorption and/or release from Pu(1-x)AmxO2 following Am in-growth. The concentrations of both Pu and Am were elevated in the colloidal fraction associated with shallow sediments, but not in PuO2 experiments, suggesting the presence of Pu/Am pseudocolloids (e.g., Pu/Am associated with mineral colloids). However, Pu and Am association with the colloidal size fraction was not observed in deeper sediments, suggesting transport of Pu and Am to these depths beneath the Z-9 Trench was not due to colloidal transport.

Reported is the synthesis, crystal structure, and solid-state characterization of a new americium containing metal-organic framework (MOF), [Am(C9H3O6)(H2O)], MOF-76(Am). This material is constructed from Am3+ metal centers and 1,3,5-tricarboxylic acid (BTC) ligands, forming a porous three-dimensional framework that is isostructural with several known trivalent lanthanide (Ln) analogs (e.g., Ce, Nd, and Sm-Lu). The Am3+ ions have seven coordinates and assume a distorted, capped trigonal prismatic geometry with C1 symmetry. The Am3+-O bonds were studied via infrared spectroscopy and compared to several MOF-76(Ln) analogs, where Ln = Nd3+, Eu3+, Tb3+, and Ho3+. The results show that the strength of the ligand carboxylate stretching and bending modes increase with Nd3+ < Eu3+ < Am3+ < Tb3+ < Ho3+, suggesting the metal-oxygen bonds are predominantly ionic. Optical absorbance spectroscopy measurements reveal strong f-f transitions; some exhibit pronounced crystal field splitting. The photoluminescence spectrum contains weak Am3+-based emission that is achieved through direct and indirect metal center excitation. The weak emissive behavior is somewhat surprising given that ligand-to-metal resonance energy transfer is efficient in the isoelectronic Eu3+ (4f6) and related Tb3+ (4f8) analogs. The optical properties were explored further within a series of heterometallic MOF-76(Tb1-xAmx) (x = 0.8, 0.2, and 0.1) samples, and the results reveal enhanced Am3+ photoluminescence.

Approximately 9 liters of supernatant from Hanford waste tank 241-AP-105 was delivered by Washington River Protection Solutions to the Radiochemical Processing Laboratory (RPL) at Pacific Northwest National Laboratory. The as-received AP-105 waste was diluted with process water (Columbia River water) from approximately 8.7 M sodium (nominal tank concentration) and partitioned into a batch of 7 M sodium and a batch of 5.5 M sodium. Dilution increased the combined volume of the two batches to approximately 7.8 liters of 7 M Na feed and 4.4 liters of 5.5 M Na feed. These two batches of 241-AP-105 supernatant were chilled to 16 °C for 1 week prior to testing. Filtration testing was then conducted using a backpulse dead-end filter (BDEF) system equipped with a feed vessel and a Mott inline filter Model 6610 (Media Grade 5) in the hot cells of the RPL. This was done to assess the performance of the anticipated third feed to the Tank Side Cesium Removal (TSCR) system. Similar to samples from tanks 241-AP-101 and 241-AP-107, no visible solids were observed in the as-received or diluted samples. The feed was filtered through the BDEF system at a targeted flux of 0.065 gpm/ft2 to match the prototypic operation of the TSCR system. During filtration of the 5.5 M sodium batch, the differential pressure required to effect filtration at 0.065 gpm/ft2 increased steadily over the filtration campaign. Once the bottoms of the bottles were added to the slurry, reservoir pressure rise increased and required two backpulses as the transmembrane pressure (TMP) reached 2 psid (the TSCR action limit). In contrast, the 7 M sodium batch did not require a backpulse for the feed volume tested. This indicates that the higher dilution of the feed resulted in more solids precipitating and these solids do settle over time. The prototypic filter cleaning process effectively restored filter performance. Solids concentrated from the backpulse solutions displayed sodium nitrate, sodium carbonate, calcium sulfate, iron oxide, steel particles, titanium oxide particles, and aluminum oxides. Electron diffraction was used to determine the types of phases that were present in the solids. The possible identifications of gibbsite, natrite, nitrite, gypsum, anatase, allophane, and cancrinite were made during this investigation. Most of the phases found were only weakly crystalline, possibly owing to their rapid precipitation during the process water treatment. The identifications of the phases therefore are tentative.

Introduction: This study aims to develop a microgram-scale microfluidic electrochemical cell (E-cell) for investigating the redox behavior of uranium oxide (UO 2 ). The traditional bulk electrochemical methods may require shielded facilities to investigate the hazardous materials, e.g., spent nuclear fuel, due to high radiation levels. Microfluidic E-cells offer advantages such as reduced radiation exposure, control over fluid flow rates, and high-throughput capabilities. Methods: The design of the E-cell considers electrode morphology, adhesion to a thin membrane, electrode configuration, and vacuum compatibility. Three techniques, including FIB-SEM lift-out, Au coating, and polyvinylidene fluoride (PVDF) binder, are explored for fabricating and attaching microgram quantities of UO 2 as working electrodes. The PVDF binder method proves to be the most effective, enabling the creation of a vacuum-compatible microfluidic E-cell. Results and discussion: The PVDF binder method demonstrates successful electrochemical responses and allows for real-time monitoring of UO 2 electrode behavior at the microscale. It offers chemical imaging capabilities using in situ SEM/EDS analysis. The technique provides consistent redox outcomes similar to bulk electrochemical analysis. Conclusion: The development of a microgram-scale microfluidic electrochemical cell using the PVDF binder technique enables the investigation of UO 2 redox behavior. It offers a low-risk approach with reduced radiation exposure and high-throughput capabilities. The technique provides real-time monitoring and chemical imaging capabilities, making it valuable for studying spent nuclear fuel systems and material characterization.

SPECIALTY GRAND CHALLENGE article Front. Nucl. Eng., 04 August 2022Sec. Nuclear Materials https://doi.org/10.3389/fnuen.2022.975132