The application of lithium (Li) metal anodes in rechargeable batteries is hindered by Li dendrite growth during Li deposition and low Li Coulombic efficiency (CE), where the nonaqueous electrolyte plays a critical role. In this work, the effects of different carbonate solvents and Li salts on Li deposition morphology and CE were systematically investigated. Typically, cyclic carbonates favor the formation of uniform Li films and improve Li CE more than linear carbonates do. Several specific cyclic carbonates that are conventionally used as solid electrolyte interphase (SEI) formation additives in Li-ion batteries can also improve the CE of Li anodes. Furthermore, among the nine electrolyte salts studied, LiAsF6 and lithium bis(oxalato)borate (LiBOB) lead to the highest CE. LiBOB also leads to better uniformity of deposited Li than other salts do. Considering the better safety of LiBOB as compared to LiAsF6, LiBOB is a promising salt for rechargeable Li metal batteries with high CE. By combining the best electrolyte solvent/salt that can lead to high CE with novel electrolyte additives that can prevent dendrite formation, it is possible to find an electrolyte that not only prevents Li dendrite formation but also leads to high CE during Li deposition/stripping processes.

SummaryThe purpose of this study was to find compositions that increase waste loading of high-alumina wastes beyond what is currently acceptable while avoiding crystallization of nepheline (NaAlSiO 4 ) on slow cooling. Nepheline crystallization has been shown to have a large impact on the chemical durability of high-level waste glasses. It was hypothesized that there would be some composition regions where high-alumina would not result in nepheline crystal production, compositions not currently allowed by the nepheline discriminator.Optical basicity (OB) and the nepheline discriminator (ND) are two ways of describing a given complex glass composition. This report presents the theoretical and experimental basis for these models. They are being studied together in a quadrant system as metrics to explore nepheline crystallization and chemical durability as a function of waste glass composition. These metrics were calculated for glasses with existing data and also for theoretical glasses to explore nepheline formation in Quadrant IV (passes OB metric but fails ND metric), where glasses are presumed to have good chemical durability. Several of these compositions were chosen, and glasses were made to fill poorly represented regions in Quadrant IV.To evaluate nepheline formation and chemical durability of these glasses, quantitative X-ray diffraction (XRD) analysis and the Product Consistency Test were conducted. A large amount of quantitative XRD data is collected here, both from new glasses and from glasses of previous studies that had not previously performed quantitative XRD on the phase assemblage.Appendix A critically discusses a large dataset to be considered for future quantitative studies on nepheline formation in glass. Appendix B provides a theoretical justification for choice of the oxide coefficients used to compute the OB criterion for nepheline formation.v

SUMMARYIn FY2009, the Pacific Northwest National Laboratory (PNNL) performed scoping studies to down-select two candidate waste forms for spent electrochemical salt, tellurite (TeO 2 -based) glasses and high-halide minerals. Both candidates showed promise with acceptable Product Consistency Test (PCT) responses (i.e., an assessment of chemical durability) and immobilization of at least 10 mass% fission product waste stream. These candidates were investigated in FY2010.Sodalite was successfully synthesized by the sol-gel method. The vast majority of the dried sol-gel consisted of sodalite with small amounts of alumino-silicates and unreacted salt. Upon firing the powders made by sol-gel, the primary phase observed was sodalite with the addition of various amounts of nepheline, carnegieite, lithium silicate, and lanthanide oxides. The amounts of sodalite, nepheline, and carnegieite varied with firing temperature, as did the bulk density of the fired pellets, sol-gel process chemistry, and the amount of glass sintering aid added to the batch. As the firing temperature was increased from 850°C to 950°C, chloride volatility increased, the fraction of sodalite decreased, and the fractions of nepheline and carnegieite increased. This indicates that the sodalite structure is not stable and begins to convert to nepheline and carnegieite under these conditions at 950°C. Density has an inverse relationship with firing temperature. The addition of NBS-1, a borosilicate glass sintering aid, had a positive effect on bulk density and increased the stability of the sodalite structure. A summary data table for FY2010 halide mineral investigations is presented in Table S1.1. Table S1.1. Summary data for FY2010 halide mineral investigations. "WL" denotes the waste loading (in mass%); "Firing T" denotes the firing temperature (in °C); For the Phase Assemblage, "S" denotes sodalite, "N" denotes nepheline + carnegieite, and "L" denotes lithium silicate phases determined by Xray diffraction. NL Na and NL Cl denote the sodium and chlorine normalized release, respectively, from the PCT. At the beginning of FY2010, an in-depth literature review kicked off the tellurite glasses study. The review was aimed at compiling data for chemical durability and mixed chloride incorporation for tellurite glasses. The literature review led the authors to four binary and one ternary systems for further investigation, which include TeO 2 plus the following: PbO, Al 2 O 3 -B 2 O 3 , WO 3 , P 2 O 5 , or ZnO. Each system was studied with and without a mixed-chloride simulated electrochemical salt waste stream, and the literature review provided the starting points for the baseline compositions as well as starting points for melting temperature, compatible crucible types, etc. The most promising glasses in each system were scaled up from 5 g scoping study batches to 20 g batches which were analyzed using the PCT. Both asfabricated samples and samples exposed to PCT were analyzed for phase separation or undissolved materials. Table S1.2 summarizes the result...

The FY 2003 risk assessment (RA) (Mann et al. 2003) of bulk vitrification (BV) waste packages used 0.3 wt% of the technetium (Tc) inventory as a leachable salt and found it sufficient to create a significant peak in the groundwater concentration in a 100-meter down-gradient well. Although this peak met regulatory limits, considering uncertainty in the actual Tc salt fraction, peak concentrations could exceed the maximum concentration limit (MCL) under some scenarios so reducing the leachable salt inventory is desirable.

The purpose of this study was to determine the solubility of iodine in a low-activity waste borosilicate glass when heated inside an evacuated and sealed fused quartz ampoule. The iodine was added to glass frit as KI in quantities of 100-24000 ppm iodine (by mass), each mixture was added to an ampoule, the ampoules were heated at 1000 °C for 2h, and then air quenched. In samples with ≥12000 ppm iodine, low viscosity salt phases were observed on the surface of the melts during cooling that solidified into a white coating upon cooling. These salts were identified as mixtures of KI, NaI, and Na 2 SO 4 with X-ray diffraction (XRD). The iodine concentrations in glass specimens were analyzed with inductively-coupled plasma mass spectrometry and the overall iodine solubility was determined to be 10000 ppm by mass. Several crystalline inclusions

In this study, multi-phase borosilicate-based glass-ceramics were investigated as an alternative waste form for immobilizing non-fissionable products from used nuclear fuel. Currently, borosilicate glass is the waste form selected for immobilization of this waste stream, however, the low thermal stability and solubility of MoO 3 in borosilicate glass translates into a maximum waste loading in the range 15-20 mass%. Glass-ceramics provide the opportunity to target chemically durable crystalline phases, e.g., powellite, oxyapatite, celsian, and pollucite that will incorporate MoO 3 as well as other waste components such as lanthanides, alkalis, and alkaline earths at levels twice the solubility limits of a single-phase glass. In addition a glassceramic could provide higher thermal stability, depending upon the properties of the crystalline and amorphous phases. Here, glass-ceramics were synthesized at waste loadings of 42, 45, and 50 mass% with the following glass additives: B 2 O 3 , Al 2 O 3 , CaO, and SiO 2 by slow-cooling from a glass melt. Glass-ceramics were characterized in terms of phase assemblage, morphology, and thermal stability. Only two of the targeted phases, powellite and oxyapatite, were observed, along with lanthanide-borosilicate and cerianite. Results of this initial investigation show promise of glass-ceramics as a potential waste form to replace single-phase borosilicate glass.

No abstract

99354High-alumina high-level waste (HLW) glasses are prone to nepheline precipitation during canister centerline cooling (CCC). If sufficient nepheline forms, the chemical durability of the glass will be significantly impacted. Overly conservative constraints have been developed and used to avoid the deleterious effects of nepheline formation in U.S. HLW glasses. The constraints used have been shown to significantly limit the loading of waste in glass at Hanford and therefore the cost and schedule of cleanup. A 90-glass study was performed to develop an improved understanding of the impacts of glass composition on the formation of nepheline during CCC. The CCC crystallinity data from these glasses were combined with 657 glasses found in the literature. The trends showed significant effects of Na on the propensity for nepheline formation. A pseudoternary submixture model was proposed to identify the glass composition region prone to nepheline precipitation. This pseudoternary with axes of SiO 2 + 1.98B 2 O 3 , Na 2 O + 0.653Li 2 O + 0.158CaO, and Al 2 O 3 was found to divide glasses that precipitate nepheline during CCC from those that do not. Application of this constraint is anticipated to increase the loading of Hanford high-alumina HLWs in glass by roughly one-third.