Jarrod V. Crum

LIQUIDUS TEMPERATURE-COMPOSITION MODEL FOR MULTI-COMPONENT GLASSES IN THE Fe, Cr, Ni, AND Mn SPINEL PRIMARY PHASE FIELD

Abstract We developed an extensive T L database of simulated high-level waste (HLW) glasses within the spinel primary phase field. Partial-molar T L s, T i , were determined for all components that were systematically varied in database glasses ( i =Al, B, Ca, Cr, Fe, K, Li, Mg, Mn, Na, Ni, Si, Ti, U, and Zr). A clear relationship was found between the T i values and ion potential. This led to a new model that can accurately predict the T L of glasses within component concentration ranges of the database. The model gives slightly better predictability than a first-order expansion of T L in composition while using only half of the fitted parameters and offers an improvement in predictability over previously published models. The success of this model gives insight to the nature of component effects on T L , which warrants further investigation. Specifically, the concentrations of glass components appear to be influential on T L in proportion to the character of their bonds or their ionic potential.

Mössbauer and optical spectroscopic study of temperature and redox effects on iron local environments in a Fe-doped (0.5 mol% Fe2O3) 18Na2O–72SiO2 glass

Local environments of ferric and ferrous irons were systematically studied with Mossbauer (at liquid helium temperature) and ultraviolet–visible–near infrared spectroscopic methods for various 18Na2O–72SiO2 glasses doped with 0.5 mol% Fe2O3. These were prepared at temperatures of 1300–1600 °C in ambient air or at 1500 °C under reducing conditions with oxygen partial pressures from 12.3 to 0.27×10−7 atmospheres. The Mossbauer spectroscopic method identified three types of local environments, which were represented by the Fe3+ sextet, the Fe3+ doublet, and the Fe2+ doublet. The Fe3+ sextet ions were assigned to ‘isolated’ octahedral ions. Under reducing conditions, the octahedral Fe3+ ions were readily converted into octahedral ferrous ions. The Fe3+ doublet exists both in octahedral and tetrahedral environment, mainly as tetrahedral sites in the reduced samples. The tetrahedral ions were found stable against reduction to ferrous ions. The Fe2+ doublet sites existed in octahedral coordination. Combining results from both spectroscopic studies, the 1120- and 2020-nm optical bands were assigned to octahedral ferrous ions with a different degree of distortion rather than different coordinations. Further, we assigned the 375-nm band to the transition of octahedral ferric ions that are sensitive to the change of oxygen partial pressure in glass melting and 415-, 435-, and 485-nm bands to the transitions of the tetrahedral ferric ions that are insensitive to oxidation states of the melt. The effect of ferric and ferrous ions with different coordination environments on the glass immiscibility was elucidated.

Liquidus temperatures of HLW glasses with zirconium-containing primary crystalline phases

Abstract Three empirical models are investigated for predicting liquidus temperatures ( T L ) as a function of glass composition for high-level waste (HLW) glasses with zirconium-containing primary crystalline phases. The three models are: (1) first-order multiple regression, (2) first-order single regression, and (3) second-order multiple regression. For each of two HLW data sets and their union, the models were developed using least squares regression on data from glasses with any zirconium-containing primary phase, and for the subset of glasses with zircon (ZrSiO 4 ) as the primary phase. The fitted models, evaluations of their performances, and interpretations of results are presented. The first- and second-order models fit very well for four of the six combinations of data set (A, B, A + B) and primary phase (zircon, zirconium-containing), and reasonably well for the other two combinations. For the composition regions and primary phases studied, T L is: (i) increased by ZrO 2 , Al 2 O 3 , and MgO, (ii) decreased by Na 2 O and Li 2 O, and (iii) moderately to negligibly affected by SiO 2 , B 2 O 3 , and CaO.

Tc Reductant Chemistry and Crucible Melting Studies with Simulated Hanford Low-Activity Waste

The FY 2003 risk assessment (RA) 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 main objective of this study was to reduce the mobile Tc species available within a BV disposal package by reducing the oxidation state of the Tc in the waste feed and/or during melting because Tc in its reduced form of Tc(IV) has a much lower volatility than Tc(VII). Reduced Tc volatility has a secondary benefit of increasing the Tc retention in glass.

Liquidus Temperature of High-Level Waste Borosilicate Glasses With Spinel Primary Phase

Liquidus temperatures (TL) were measured for high-level waste (HLW) borosilicate glasses covering a Savannah River composition region. The primary crystallization phase for most glasses was spinel, a solid solution of trevorite (NiFe2O4) with other oxides (FeO, MnO, and Cr2O3). The TL values ranged from 859 to 1310?C. Component additions increased the TL (per mass%) as Cr2O3 261?C, NiO 85?C, TiO2 42?C, MgO 33?C, Al2O3 18?C, and Fe2O3 18?C and decreased the TL (per mass%) as Na2O -29?C, Li2O -28?C, K2O -20?C, and B2O3 -8?C. Other oxides (CaO, MnO, SiO2, and U3O8) had little effect. The effect of RuO2 is not clear.

Formulation and Characterization of Waste Glasses with Varying Processing Temperature

This report documents the preliminary results of glass formulation and characterization accomplished within the finished scope of the EM-31 technology development tasks for WP-4 and WP-5, including WP-4.1.2: Glass Formulation for Next Generation Melter, WP-5.1.2.3: Systematic Glass Studies, and WP-5.1.2.4: Glass Formulation for Specific Wastes. This report also presents the suggested studies for eventual restart of these tasks. The initial glass formulation efforts for the cold crucible induction melter (CCIM), operating at {approx}1200 C, with selected HLW (AZ-101) and LAW (AN-105) successfully developed glasses with significant increase of waste loading compared to that is likely to be achieved based on expected reference WTP formulations. Three glasses formulated for AZ-101HLW and one glass for AN-105 LAW were selected for the initial CCIM demonstration melter tests. Melter tests were not performed within the finished scope of the WP-4.1.2 task. Glass formulations for CCIM were expanded to cover additional HLWs that have high potential to successfully demonstrate the unique advantages of the CCIM technologies based on projected composition of Hanford wastes. However, only the preliminary scoping tests were completed with selected wastes within the finished scope. Advanced glass formulations for the reference WTP melter, operating at {approx}1200 C, were initiated with selected specific wastes to determine the estimated maximum waste loading. The incomplete results from these initial formulation efforts are summarized. For systematic glass studies, a test matrix of 32 high-aluminum glasses was completed based on a new method developed in this study.

Development and Testing of ICV Glasses for Hanford LAW

Preliminary glass compositions for immobilizing Hanford low-activity waste (LAW) by the in-container vitrification (ICV) process were fabricated at crucible- and engineering-scale and tested at Pacific Northwest National Laboratory. This testing showed that glasses with LAW loading of 20 mass% can readily be made and meet all product constraints by a far margin. It was found that the response constraint of the vapor hydration test (VHT) of less than 50 g/(m2•d) alteration rate was the most restrictive constraint placed on LAW glasses. Glasses with over 22 mass% Na2O can be made to meet this constraint along with all other product quality and processability constraints imposed by this process. The results of crucible melts with simulants were scaled-up to engineering scale and also tested with actual (radioactive) LAW. All the results suggest that the baseline glass can be successfully processed by the ICV technology and can meet all the constraints related to product quality.

Redox-Active Metal–Organic Composites for Highly Selective Oxygen Separation Applications

A redox-active metal-organic composite material shows improved and selective O2 adsorption over N2 with respect to individual components (MIL-101 and ferrocene). The O2 sensitivity of the composite material arises due to the formation of maghemite nanoparticles with the pore of the metal-organic framework material.

Optical Basicity and Nepheline Crystallization in High Alumina Glasses

The 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 (NaAlSiO4) 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.

Laboratory Testing of Bulk Vitrified Low-Activity Waste Forms to Support the 2005 Integrated Disposal Facility Performance Assessment

The purpose of this report is to document the results from laboratory testing of the bulk vitri-fied (BV) waste form that was conducted in support of the 2005 integrated disposal facility (IDF) performance assessment (PA). Laboratory testing provides a majority of the key input data re-quired to assess the long-term performance of the BV waste package with the STORM code. Test data from three principal methods, as described by McGrail et al. (2000a; 2003a), are dis-cussed in this testing report including the single-pass flow-through test (SPFT) and product con-sistency test (PCT). Each of these test methods focuses on different aspects of the glass corrosion process. See McGrail et al. (2000a; 2003a) for additional details regarding these test methods and their use in evaluating long-term glass performance. In addition to evaluating the long-term glass performance, this report discusses the results and methods used to provided a recommended best estimate of the soluble fraction of 99Tc that can be leached from the engineer-ing-scale BV waste package. These laboratory tests are part of a continuum of testing that is aimed at improving the performance of the BV waste package.