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Archaeological glasses with prolonged exposure to biogeochemical processes in the environment can be used to understand glass alteration, which is important for the safe disposal of vitrified nuclear waste. Samples of mafic and felsic glasses with different chemistries, formed from melting amphibolitic and granitoid rocks, were obtained from Broborg, a Swedish Iron Age hillfort. Glasses were excavated from the top of the hillfort wall and from the wall interior. A detailed microscopic, spectroscopic, and diffraction study of surficial textures and chemistries were conducted on these glasses. Felsic glass chemistry was uniform, with a smooth surface showing limited chemical alteration (

The complex distribution of particle charge states resulting from neutralization processes by radioactive or soft X-ray charge neutralizers is a well-documented problem in aerosol science. Here, we demonstrate that non-idealities in the collection efficiency of an impactor allows for the transmission of an unexpected population of multiply charged particles by a differential mobility analyzer that can bias optical measurements. The extinction cross sections (Cext) of ammonium sulfate particles were quantified using cavity ring-down spectroscopy and particle counting. Particles were selected by electrical mobility (i.e., a metric of particle size) using a differential mobility analyzer (DMA) or electrical mobility and mass selected by a tandem DMA and aerosol particle mass analyzer (APM), respectively, to elucidate multiple charging artifacts. Measured Cext exhibited statistically significant differences at particle sizes near the impactor cut point implying that these multiply charged particles should not be present and could not be confirmed by parallel size distribution measurements. Additionally, comparison of Cext with Mie theory demonstrates that misclassification of the multiply charged particles can give rise to numerically accurate results. To understand these observations, the collection efficiency (CE) of four impactors from similar electrostatic classifiers was investigated. From these measurements, it was determined that the nominal and actual diameters of the impactors differed by −0.5% (457 μm vs. (455 ± 1) μm, respectively (uncertainty is 1σ standard deviation)) but the average Stk50 (the Stokes number at the cut-point, D50) values differed by ≈ 23% (0.23 vs. 0.18 ± 0.01, respectively). The measured CE as a function of √Stk (a metric of particle aerodynamic size) exhibits a long tail toward higher √Stk values, allowing for transmission of the larger and multiply charged particles observed in the optical measurements. These measurements highlight the utility of using orthogonal, spectroscopic methods to quantify the presence of multiply charged particles. Copyright © 2023 American Association for Aerosol Research

Li distribution within the battery electrode material is quantified using neutron depth profiling (NDP) as a function of depth in real-time.

Because microbes cannot be eliminated from radioactive waste disposal facilities, the consequences of bio-colonization must be understood. At a pre-Viking era vitrified hillfort, Broborg, Sweden, a...

To realize high specific capacity Li-metal batteries, a protection layer for the Li-metal anode is needed. We are carrying out combinatorial screening of Li-alloy thin films as the protection layer...

The United States Centers for Disease Control and Prevention and World Health Organization recognize that wearing cloth face coverings can slow the transmission of respiratory diseases via source control. Adding a partial layer of material with a high filtration efficiency (FE,ie/i.ig/i., polypropylene sheets that meet the HEPA standard) as an insert can potentially provide additional personal protection; however, data on the necessary areal coverage are sparse. The relationship between insert area ratio (IAR) relative to fabric area, FE, differential pressure (ΔiP,/ia surrogate for breathability), and quality factor (QF, a ratio including FE and ΔiP/i) utilizing two fabrics (rayon and 100% cotton lightweight flannel) and three insert materials (HEPA vacuum bag, sterilization wrap and paper coffee filter) was investigated. The effect of inserts on particle flows mimicking human exhalation is semiquantitatively and qualitatively examined using flow visualization techniques. The following was found: (1) The relationship between FE, ΔiP/i, and QF is complex, and a trade-off exists between personal protection from filtration during inhalation and source control from leakage during exhalation; (2) FE and ΔiP/iof the composite covering increase with IAR, and the rate is dependent upon insert type; (3) improvements (decrements) in the QF of the composite assemblage require inserts with a higher (lower) QF than the fabric and larger differences yield greater gains (losses); (4) the increased ΔiP/ifrom an insert results in increased leakage during exhalation; (5) to minimize leaks, ΔiP/imust be as low as possible; and (6) small relative areas not covered by an insert (ii/i.ie/i., IAR slightly smaller than 1) strongly deteriorate the benefits of an insert similar to small leaks in a covering.

Dilute aqueous pertechnic acid has long been known as strong monoprotic acid that behaves as a simple pertechnetate ion in aqueous solution. As pertechnic acid concentrates by evaporation, it becomes yellow and then dark red, and dark-red crystalline material may ultimately be obtained. We show that as pertechnic acid concentrates, at least three compounds are formed: a yellow viscous liquid, a colorless (not red) crystalline solid, and a small amount of an intensely colored red-purple compound. The colorless crystalline compound melts at 118 °C and can be melted and recrystallized several times with little decomposition. The red-purple compound is apparently not stable at room temperature and quickly decomposes if it is isolated. UV-vis spectra show that Beer's law does not hold as pertechnic acid concentrates by evaporation. We report densities, 99Tc nuclear magnetic resonance spectra, and ultraviolet-visible absorption spectra for highly pure aqueous pertechnic acid (accompanied by the other technetium compounds that form) ranging from 1 to 14 M in technetium concentration.

Surface contamination and degradation are two main issues leading to performance decay of ceramic-based solid-state electrolytes (SSEs). The typical strategies used to clean surface contaminants and restore ceramic materials involve mechanical polishing or high temperature thermal treatment. However, mechanical polishing can cause other side reactions and cannot clean contaminants on the grain boundaries of SSEs, while conventional thermal treatment using a furnace is often energy- and time-intensive, as the heating and cooling processes are slow. In this work, we for the first time demonstrate a high temperature thermal pulse technique for rapid ceramic surface processing. As a demonstration, we cleaned a garnet-based Li conductive SSE featuring lithium carbonate surface contamination in less than 2 s. The thermal pulsed garnet SSE exhibits an improved ionic conductivity of 3.2 × 10−4 S/cm—a two-fold increase compared to the starting material. Symmetric cells featuring the thermal pulsed garnet SSE can cycle at current densities up to 500 µA/cm2, while control cells short-circuit at a current density of 100 µA/cm2.

Understanding the chemical durability of neutron shielding materials is necessary when assessing their long-term service potential. In this study, the chemical durability of a 6Li enriched neutron shielding glass that has been exposed to natural, near-operational conditions is assessed by Prompt Gamma Activation Analysis (PGAA) and Neutron Depth Profiling (NDP). These non-destructive, nuclear analysis techniques are sensitive to 6Li, and PGAA is uniquely able to detect H in low quantities in solids. It was determined that the enriched alumino-silicate glass can alter within 2 months of exposure to the natural environment. This exposure resulted in an average surface alteration layer thickness of ≈22 μm. The alteration layer contained ≈47% less 6Li than the bulk glass. Alternatively, a 3 years exposed sample of the glass had a surface alteration depth of ≈30 μm and 6Li depletion levels in the alteration layer were between 47% and 75% less 6Li than the bulk glass. When the alteration layer on the 3 years sample was removed, the H content of the glass's surface was nearly eliminated. This sample also showed variable Li concentrations throughout the alteration volume, which contrasts with near static Li concentration in the alteration volume of the 2 months sample. From these findings it was determined that the depletion in Li at the surface of the glass will not affect the glass's neutron shielding properties, but it may change the mechanical stability of the glass's surface and, due to increased H content in the alteration layer, make it an inappropriate material for the lining of certain neutron analysis instruments.

Glass alteration in the presence of microorganisms has been a topic of research for over 150 years. Researchers from a variety of disciplines, including material science, biology, chemistry, geology, physics, and cultural heritage materials preservation have conducted experiments in this area to try and understand when, how, and why microorganism may interact and subsequently influence the alteration of glass. The breadth and depth of these studies are the topic of this review. This review presents a detailed history and a comprehensive overview of this field of research, while maintaining focus on the terrestrial alteration of anthropogenic silicate glasses. Within this manuscript is a schema for bio-interaction with silicate glasses and an outline of an evidence-based hypothesis on how these interactions may influence glass alteration processes. Topics discussed include microbial colonization of glass, development, and interactions of biofilms with glass surface, abiotic vs. biotic alteration processes, and signatures of bio-alteration. Future research needs and a discussion of practical drivers for this research are summarized.

Electrode-electrolyte interfaces (EEIs) affect the rate capability, cycling stability, and thermal safety of lithium-ion batteries (LIBs). Designing stable EEIs with fast Li+ transport is crucial for developing advanced LIBs. Here, we study Li+ kinetics at EEIs tailored by three nanoscale polymer thin films via chemical vapor deposition (CVD) polymerization. Small binding energy with Li+ and the presence of sufficient binding sites for Li+ allow poly(3,4-ethylenedioxythiophene) (PEDOT) based artificial coatings to enable fast charging of LiCoO2. Operando synchrotron X-ray diffraction experiments suggest that the superior Li+ transport property in PEDOT further improves current homogeneity in the LiCoO2 electrode during cycling. PEDOT also forms chemical bonds with LiCoO2, which reduces Co dissolution and inhibits electrolyte decomposition. As a result, the LiCoO2 4.5 V cycle life tested at C/2 increases over 1700% after PEDOT coating. In comparison, the other two polymer coatings show undesirable effects on LiCoO2 performance. These insights provide us with rules for selecting/designing polymers to engineer EEIs in advanced LIBs.

Under high humidity conditions that mimic respiration, the filtration efficiency (FE) of hydrophilic fabrics increases when challenged with hygroscopic nanoparticles, for example, respiratory droplets containing SARS-CoV-2. The FE and differential pressure (ΔP) of natural, synthetic, and blended fabrics were measured as a function of relative humidity (RH) for particles with mobility diameters between 50 and 825 nm. Fabrics were equilibrated at 99% RH, mimicking conditions experienced when worn as a face mask. The FE increased after equilibration at 99% RH by a relative percentage of 33 ± 12% for fabrics composed of two layers of 100% cotton when challenged by 303 nm-mobility-diameter NaCl aerosol. The FE for samples of synthetics and polyester/cotton blends was unchanged upon equilibration at 99% RH. Increases in FE for 100% cotton fabrics were a function of particle size with a relative increase of 63% at the largest measured particle size (825 nm). The experimental results are consistent with increased particle capture due to H2O uptake and growth as the particles traverse the fabric.

Filtration efficiency (FE), differential pressure (ΔP), quality factor (QF), and construction parameters were measured for 32 cloth materials (14 cotton, 1 wool, 9 synthetic, 4 synthetic blends, and 4 synthetic/cotton blends) used in cloth masks intended for protection from the SARS-CoV-2 virus (diameter 100 ± 10 nm). Seven polypropylene-based fiber filter materials were also measured including surgical masks and N95 respirators. Additional measurements were performed on both multilayered and mixed-material samples of natural, synthetic, or natural-synthetic blends to mimic cloth mask construction methods. Materials were microimaged and tested against size selected NaCl aerosol with particle mobility diameters between 50 and 825 nm. Three of the top five best performing samples were woven 100% cotton with high to moderate yarn counts, and the other two were woven synthetics of moderate yarn counts. In contrast to recently published studies, samples utilizing mixed materials did not exhibit a significant difference in the measured FE when compared to the product of the individual FE for the components. The FE and ΔP increased monotonically with the number of cloth layers for a lightweight flannel, suggesting that multilayered cloth masks may offer increased protection from nanometer-sized aerosol with a maximum FE dictated by breathability (i.e., ΔP).

Models for long-term glass alteration are required to satisfy performance predictions of vitrified nuclear waste in various disposal scenarios. Durability parameters are usually extracted from short-term laboratory tests, and sometimes checked with long-term natural experiments on glasses, termed analogues. In this paper, a unique potential ancient glass analogue from Sweden is discussed. The hillfort glass found at Broborg represents a unique case study as a vitrified waste glass analogue to compare to Low Activity Waste glass to be emplaced in near surface conditions at Hanford (USA). Glasses at Broborg have similar and dissimilar compositions to LAW glasses, allowing the testing of long-term alteration of different glass chemistries. In addition, the environmental history of the site is reasonably well documented. Initial investigations on previously collected samples established methodologies for handling and characterizing these artifacts by laboratory methods while preserving their alteration layers and cultural context. Evidence of possible biologically influenced glass alteration, and differential alteration in the 2 types of glass found at the Broborg site is presented.

Though not often discussed explicitly in literature, sample handling and preparation for advanced characterization techniques is a significant challenge for radiological materials. In this contribution, a detailed description is given of method development associated with characterization of highly radioactive and, in some cases, hygroscopic oxides of technetium. Details are given on developed protocols, fixtures, and tooling designed for x-ray and neutron diffraction, x-ray absorption, Raman spectroscopy, magic angle spinning nuclear magnetic resonance, and electron paramagnetic resonance. In some cases, multiple iterations of improved sample holder design are described. Lessons learned in handling Tc compounds for these and similar characterization methods are discussed.

A challenge to the incorporation of 99Tc into a glass matrix is that 99Tc is volatile at vitrification temperatures. Understanding how this volatilization occurs requires knowledge of the multiple chemistries which Tc may take during vitrification. This paper presents an overview of how the localized chemistry of 99Tc has been determined in a series of 99Tc-bearing glasses by chemometric analyses of X-ray absorption near edge spectra (XANES). Linear combination fitting and principal component analysis of the glasses’ XANES spectra suggested that the glasses contained 3–4 chemically distinct Tc environments. The identity of the detected chemistries were pertechnetates, (Tc(VII) as isolated oxyanions, or locally coordinated by Na or K), or isolated Tc(IV) species. The linear combination fitting distribution of local Tc sites agrees with reanalyzed Raman spectra, suggesting that as targeted KTcO4 incorporation increases, a significant ion exchange takes place, and speciation in the glass changes to favor Tc(VII) formation, specifically NaTcO4. Based on the statistical suggestion that not all Tc environments are accounted by the available standards, a new mechanism for the behavior of Tc during vitrification is proposed.

The local chemistry of technetium-99 (99Tc) in oxide glasses is important for understanding the incorporation and long-term release of Tc from nuclear waste glasses, both those for legacy defense wastes and fuel reprocessing wastes. Tc preferably forms Tc(VII), Tc(IV), or Tc(0) in glass, depending on the level of reduction of the melt. Tc(VII) in oxide glasses is normally assumed to be isolated pertechnetate TcO4− anions surrounded by alkali, but can occasionally precipitate as alkali pertechnetate salts such as KTcO4 and NaTcO4 when Tc concentration is high. In these cases, Tc(VII) is 4-coordinated by oxygen. A reinvestigation of the chemistry of alkali-technetium-oxides formed under oxidizing conditions and at temperatures used to prepare nuclear waste glasses showed that higher coordinated alkali Tc(VII) oxide species had been reported, including those with the TcO5− and TcO6− anions. The chemistry of alkali Tc(VII) and other alkali-Tc-oxides is reviewed, along with relevant synthesis conditions. Additionally, we report attempts to make 5- and 6-coordinate pertechnetate compounds of K, Na, and Li, i.e. TcO5− and TcO6−. It was found that higher coordinated species are very sensitive to water, and easily decompose into their respective pertechnetates. It was difficult to obtain pure compounds, but mixtures of the pertechnetate and other phase(s) were frequently found, as evidenced by x-ray absorption spectroscopy (XAS), neutron diffraction (ND), and Raman spectroscopy. Low temperature electron paramagnetic resonance (EPR) measurements showed the possibility of Tc(IV) and Tc(VI) in Na3TcO5 and Na5TcO6 compounds. It was hypothesized that the smaller counter cation would result in more stable pertechnetates. To confirm the synthesis method, LiReO4 and Li5ReO6 were prepared, and their Raman spectra match those in the literature. Subsequently, the Tc versions LiTcO4 and Li5TcO6 were synthesized and characterized by ND, Raman spectroscopy, XANES, and EXAFS. The Li5TcO6 was a marginally stable compound that appears to have the same structure as that known for Li5ReO6. Implications of the experimental work on stability of alkali technetate compounds and possible role in the volatilization of Tc are discussed.

Understanding the chemical durability of neutron shielding materials is necessary when assessing their long-term service potential. In this study, the chemical durability of a

Apart from increasing the battery size of electric vehicles (EVs), another approach to reduce range anxiety and to achieve mass market penetration is to increase the charging power and thus significantly lower charging times. To date, commercial lithium-ion battery (LIB) cells are almost exclusively based on graphite as anode material.[1] Here, owing to the low potential of the graphite electrode during charge, the charging rate must be limited in order to avoid lithium plating, which can thermodynamically occur in regions of the electrode where the potential drops below 0 V vs. Li+/Li. Plated lithium is very reactive, leading to irreversible reactions with the electrolyte and therefore strongly reduces lifetime and safety of a battery.[2] Studying lithium plating in a battery cell is very challenging since post mortem diagnostics do not reflect the electrode state during operation, since plated lithium will reintercalate into the active graphite material on a timescale of minutes at room temperature.[3] , [4] Hence, non-destructive operando techniques[5] , [6] are necessary to elucidate and follow lithium plating mechanisms in an operating cell. In this study, we present data collected via Neutron Depth Profiling (NDP) during lithium plating induced by fast charging of a graphite electrode at a rate of 2 C. NDP is a lithium-sensitive, non-destructive technique utilizing the neutron capture reaction of 6Li atoms to quantitatively measure the lithium distribution over the thickness of an electrode by probing the energy loss of charged particles formed by the neutron capture reaction.[7] We employ a recently developed operando NDP cell that shows a cycling performance comparable to a commercial cell even at high charging rates, and at the same time allows charged particles to exit the cell through a thin Kapton® window.[8] We were able to resolve the lithium depth distribution changes during the open circuit voltage (OCV) phase after a constant current charge with a time resolution of 2 min. This exceptionally high time resolution was achieved by combining the high cold neutron flux of 2.7×109 ncm-2s-1 at the NIST Center for Neutron Research (Washington D.C., USA) with a 6Li enriched electrolyte and a 6LiFePO4 cathode, which enhances the signal by an additional factor of 12. In order to achieve lithium plating already at a rate of 2 C, the LiPF6 salt concentration in the EC/EMC = 3/7 (w/w) electrolyte was reduced to 0.3 M. Figure 1 shows the NDP signal intensity as a function of the energy of the detected tritium particles, which translates into a depth profile: signals at an energy of ca. 2400 keV represent lithium at the interface between the graphite electrode and the Cu current collector, and signals at decreasing energies represent lithium from increasing depth into the graphite electrode, with signals at an energy of ca. 800 keV deriving from the graphite anode / separator interface. It is clearly visible that lithium plating starts towards the separator facing side of the graphite anode, caused by the lithium-ion concentration gradient forming over the thickness of the electrode during fast charging (dark blue profile); during the subsequent OCV phase, lithium re-distributes over the anode thickness, whereby this equilibration process is observed to be completed within ca. 24 min. References [1] C. Pillot, “The Rechargeable Battery Market and Main Trends 2014-2025”, 32nd International Battery Seminar and Exhibit, 3/9/2015, Presentation. [2] J. C. Burns, D. A. Stevens, J. R. Dahn, J. Electrochem. Soc. 2015, 162, A959. [3] Z. Y. Tang, J. J. Xue, C. Y. Liu, X. G. Zhuang, Acta Phys. - Chim. Sin. 2001, 17, 388. [4] M. Park, X. Zhang, M. Chung, G. B. Less, A. M. Sastry, J. Power Sources 2010, 195, 7904. [5] J. Wandt, P. Jakes, J. Granwehr, R. A. Eichel, H. A. Gasteiger, Mater. Today 2018, 21, 231. [6] R. Bhattacharyya, B. Key, H. Chen, A. S. Best, A. F. Hollenkamp, C. P. Grey, Nat. Mater. 2010, 9, 504. [7] M. Trunk, M. Wetjen, L. Werner, R. Gernhäuser, B. Märkisch, Z. Révay, H. A. Gasteiger, R. Gilles, Mater. Charact. 2018, 146, 127. [8] F. Linsenmann et al., A Lithium-Ion Battery Cell Design for Operando Neutron Depth Profiling, to be submitted. Acknowledgements This work is financially supported by the BMBF within the Projects “ExZellTUM II” (grant no. 03X4633A) and “N4DP” (grant number 05K16WO1), respectively. Figure 1

Designing smaller, safer, cheaper, and more stable batteries necessitates thorough understanding of the electrochemical processes governing their operation at multiple length scales. In all-solid-state power sources the electrolyte is no-flammable and can be made ultimately thin, making them safer and more compact. Yet, experimental evidence suggests that the multiple internal interfaces in their layered structure give rise to high impedances, limiting their performance. Studying these nanoscopic interfaces requires microscopic tools. Here, we employ in operando Kelvin Probe Force Microscopy (KPFM) to quantitatively measure the potential distribution in a solid-state Li-ion battery as a function of its state of charge. The battery was fabricated by sequentially depositing thin layers of Pt (110-130 nm), LiCoO2 (280-420 nm), LIPON (1100-1200 nm), Si (50-240 nm) Cu or Pt (150-200 nm) onto a Si/SiO2 wafer (oxide thickness 100 nm). The fabricated battery was cleaved in an Ar atmosphere to expose the stacked layers, mounted on a holder, wired, and safely transferred without exposing to air into a dual-beam instrument that combines a scanning electron microscope (SEM), a Ga-ion focused ion beam (FIB) and an atomic force microscope (AFM) in one vacuum chamber (residual pressure of 10-4 Pa). The stacked battery was milled to expose a cross-section of the layers, and imaged using SEM and KPFM, while cycling the battery. The acquired potential maps reveal a highly non-uniform interelectrode potential distribution, with most of the potential drop occurring at the electrolyte-Si anode interface in the pristine battery. During the first charge, the potential distribution gradually changes, revealing complex polarization within the LIPON layer due to Li-ion redistribution. Cycling the battery at high rate significantly decreased its capacity, although the capacity loss can be recovered. KPFM imaging allowed the detection of the interface responsible for this capacity loss. Li distribution in the battery was also measured using Neutron Depth Profiling as a function of the state of charge. The acquired data was compared to first principles calculations shedding light onto the interfacial Li-ion transport in the battery and its reversibility. ES acknowledges support under the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Center for Nanoscale Science and Technology, Award 70NANB14H209, through the University of Maryland.

We report on the influence of Fe2O3 on the crystallization kinetics of nepheline (Na2O·Al2O3·2SiO2)-based sodium aluminosilicate glasses. A series of glasses with varying Al2O3/Fe2O3 content were synthesized in the system 25Na2O–(25–x) Al2O3–xFe2O3–50SiO2 (x varies between 0 and 5 mol%) through melt-quench technique. A systematic set of experiments were performed to elucidate the influence of iron speciation (Fe2+/Fe3+) on the crystallization kinetics of these glasses including: (1) obtaining the details of nonisothermal crystallization kinetics by differential scanning calorimetry, (2) determining the influence of heat treatment on the structure and iron coordination in glasses by X-ray photoelectron spectroscopy and wet chemistry, and (3) following the crystalline phase evolution in glasses in air and inert environments by X-ray diffraction and scanning electron microscopy. The crystallization of two polymorphs of NaAlSiO4—carnegieite (orthorhombic) and nepheline (hexagonal)—was observed in all the glasses, wherein the incorporation of iron promotes the formation of nepheline over carnegieite while shifting the crystallization mechanism from surface to volume. The influence of environment (air versus inert) and iron content on the crystallization kinetics of these glasses is contextualized from the perspective of the devitrification problem usually observed in sodium- and alumina-rich high level nuclear waste glasses.

A spectroscopic study was conducted on six simulant nuclear waste glasses using multi-nuclear NMR, Raman, and Mossbauer spectroscopies exploring the role of Si, Al, B, Na, and Fe in the glass network with the goal of understanding melt structure precursors to deleterious nepheline crystal formation. NMR showed two sites each for Al, Si, and Na in the samples which crystallized significant amounts of nepheline, and B speciation changed, typically resulting in more B(IV) after crystallization. Raman spectroscopy suggested that some of the glass structure is composed of metaborate chains or rings, thus significant numbers of non-bridging oxygen and a separation of the borate from the alumino-silicate network. Mossbauer, combined with Fe redox chemical measurements, showed Fe playing a minor role in these glasses, mostly as Fe3 +, but iron oxide spinel forms with nepheline in all cases. A model of the glass network and allocation of non-bridging oxygens (NBOs) was computed using experimental B(IV) fractions which predicted a large amount of NBO consistent with Raman spectra of metaborate features.

A complete understanding of radioactive waste glass interactions with near-field materials is essential for appropriate nuclear waste repository performance assessment. In many geologic repository designs, Fe is present both in the natural environment and in the containers that will hold the waste glasses. In this paper we discuss investigations of the alteration of International Simple Glass (ISG) in the presence of Fe0 foil and hematite (Fe2O3). Based on solid analysis, ISG alteration is more pronounced in the presence of Fe0 than with hematite. Additionally, typical glass corrosion is observed for distances of 5 mm between Fe materials and ISG, but incorporation of Fe in the alteration layer is only observed for systems exhibiting full contact between Fe0 material and ISG. Solution analysis results indicate that diatomaceous earth minimizes corrosion to a larger extent than fumed silica does when present with iron and ISG.

In this study wet chemical methods combined with UV-Vis spectroscopy were performed to quantify Fe(II)/Fe(III) ratios and total iron content of quenched alkali alumino-boro-silicate (simulated nuclear waste) glasses, applying a colorimetric method. We report lessons learned from experimental challenges encountered associated with the colorimetric method, where 1,10 phenanthroline method is complexed with dissolved glass powder and the resulting solution measured for absorbance at 520 nm to determine Fe(II). To obtain total iron, the solution was then equilibrated with a mild reducing agent to chance all Fe to Fe(II), and the absorbance measured again at 520 nm. These absorbance values allowed for calculation of the Fe(II)/Fe(III) ratio, and the total iron content in the glasses. Total Fe measured is somewhat higher than as-batched target values for waste glasses, but very accurate for reference BCR-2G glass. All quenched alumino-boro-silicate glasses analyzed showed a Fe(II)/Fe(III) ratio between 0.06 (± 0.01) and 0.04 (± 0.01). These values are consistent with those obtained for similar glass compositions melted under analogous conditions, indicating a composition of ca. 94-96% Fe(III).

The determination of the long-term stability and corrosion of vitrified nuclear waste is an important aspect of research for the U.S. Department of Energy (DOE). It is necessary to understand the rate and mechanisms of Nuclear Waste Glass (NWG) corrosion to determine whether or not the glassy matrix will be able to retain radionuclides for the required repository performance time period. Glass corrosion and the rate of glass corrosions is determined by both chemical and microscopy. Electron Microprobe Analysis (EPMA) is a common and powerful method utilized in the examination of the chemographic difference between corroded and uncorroded NGWs. In this work, two forms of quantitative and semi-quantitative EPMA methods are defined by optimizing the instruments counting statistics against a standard glass and NIST minerals that have compositions similar to the glasses under examination. Data collected on both the planar and cross-sectioned surfaces of an unaltered simulated NWG by Standard based Wavelength Dispersive Spectroscopy (WDS) was found to be comparable to the theoretical composition of the glass. Conventional standardless Energy Dispersive Spectroscopy (EDS) data collected on the same surfaces was not comparable. However, standard-based EDS analysis is shown to be able to discriminate between unaltered and corroded glass surfaces.

Insight into the solid-state chemistry of pure technetium-99 (99Tc) oxides is required in the development of a robust immobilization and disposal system for nuclear waste stemming from the radiopharmaceutical industry, from the production of nuclear weapons, and from spent nuclear fuel. However, because of its radiotoxicity and the subsequent requirement of special facilities and handling procedures for research, only a few studies have been completed, many of which are over 20 years old. In this study, we report the synthesis of pure alkali pertechnetates (sodium, potassium, rubidium, and cesium) and analysis of these compounds by Raman spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), solid-state nuclear magnetic resonance (static and magic angle spinning), and neutron diffraction. The structures and spectral signatures of these compounds will aid in refining the understanding of 99Tc incorporation into and release from nuclear waste glasses. NaTcO4 shows aspects of the relatively higher el...

Compositional Imaging and Analysis of Late Iron Age Glass from the Broborg Vitrified Hillfort, Sweden

Nuclear waste must be deposited in such a manner that it does not cause significant impact on theenvironment or human health. In some cases, the integrity of the repositories will need to sustain fortens to hundreds of thousands of years. In order to ensure such containment, nuclear waste is frequentlyconverted into a very durable glass. It is fundamentally difficult, however, to assure the validity ofsuch containment based on short-term tests alone. To date, some anthropogenic and natural volcanicglasses have been investigated for this purpose. However, glasses produced by ancient cultures for thepurpose of joining rocks in stonewalls have not yet been utilised in spite of the fact that they might offersignificant insight into the long-term durability of glasses in natural environments. Therefore, a projectis being initiated with the scope of obtaining samples and characterising their environment, as well asto investigate them using a suite of advanced materials characterisation techniques. It will be analysedhow the hillfort glasses may have been prepared, and to what extent they have altered under in-situconditions. The ultimate goals are to obtain a better understanding of the alteration behaviour of nuclearwaste glasses and its compositional dependence, and thus to improve and validate models for nuclearwaste glass corrosion. The paper deals with project planning and initiation, and also presents some earlyfindings on fusion of amphibolite and on the process for joining the granite stones in the hillfort walls.Keywords: ageing, amphibolite, analogue, anthropogenic, Broborg, glass, hillfort, hill-fort, leaching,long-lived, nuclear, rampart, waste. Konferensartikel i tidskrift