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NUCLEAR WASTE GLASSES CONTINUOUS MELTING AND BULK VITRIFICAITON
This contribution addresses various aspects of nuclear waste vitrification. Nuclear wastes have a variety of components and composition ranges. For each waste composition, the glass must be formulated to possess acceptable processing and product behavior defined in terms of physical and chemical properties that guarantee the glass can be easily made and resist environmental degradation. Glass formulation is facilitated by developing property-composition models, and the strategy of model development and application is reviewed. However, the large variability of waste compositions presents numerous additional challenges: insoluble solids and molten salts may segregate; foam may hinder heat transfer and slow down the process; molten salts may accumulate in container refractory walls; the glass on cooling may precipitate crystalline phases. These problems need targeted exploratory research. Examples of specific problems and their possible solutions are discussed
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CRYSTALLIZATION IN MULTICOMPONENT GLASSES
In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed
GLASS FORMULATION TESTING TO INCREASE SULFATE INCORPORATION - Final Report VSL-04R4960-1, Rev 0, 2/28/05, Vitreous State Laboratory, The Catholic University of American, Washington, D.C.
About 50 million gallons of high-level mixed waste is currently in storage in underground tanks at The United States Department of Energy's (DOE's) Hanford site in the State of Washington. The Hanford Tank Waste Treatment and Immobilization Plant (WTP) will provide DOE's Office of River Protection (ORP) with a means of treating this waste by vitrification for subsequent disposal. The tank waste will be separated into low- and high-activity fractions, which will then be vitrified respectively into Immobilized Low Activity Waste (ILAW) and Immobilized High Level Waste (IHLW) products. The ILAW product will be disposed of in an engineered facility on the Hanford site while the IHLW product will be directed to the national deep geological disposal facility for high-level nuclear waste. The ILAW and IHLW products must meet a variety of requirements with respect to protection of the environment before they can be accepted for disposal. The Office of River Protection is currently examining options to optimize the Low Activity Waste (LAW) facility and the LAW glass waste form. One option under evaluation is to enhance the waste processing rate of the vitrification plant currently under construction. It is likely that the capacity of the LAW vitrification plant can be increased incrementally by implementation of a variety of low-risk, high-probability changes, either separately or in combination. These changes include: (1) Operating at the higher processing rates demonstrated at the LAW Pilot Melter; (2) Increasing the glass pool surface area within the existing external melter envelope; (3) Increasing plant availability; (4) Increasing the glass waste loading; (5) Removing sulfate from the LAW stream; (6) Operating the melter at slightly higher temperature; (7) Installing the third LAW melter into the WTP plant; and (8) Other smaller impact changes. The melter tests described in this report utilized blended feed (glass formers plus waste simulant) prepared by Optima Chemicals according to VSL specifications. Sufficient feed was prepared to produce over nineteen hundred kilograms of glass during melter tests. The nominal reductant concentration (stoichiometric ratio of 0.5 {approx} 1 mole sucrose per 16 mole NOx or 3 mole carbon per 4 mole NOx) was maintained in all the tests by the addition of sugar at VSL. The DM 10 was used to screen the optimized glass formulation with two alternative aluminum sources (kyanite and zeolite) over a wide range of target sulfur concentrations. Subsequently, based on the DM10 results, nine 12- to 34-hour DM100 tests were conducted; six with kyanite as the aluminum additive at glass sulfur concentrations ranging from 0.75 to 1.5 wt.% SO{sub 3}, and the other three with zeolite as the aluminum additive at glass sulfur concentrations ranging from 0.75 to 1.5 wt. % SO{sub 3}. The DM 100-WV melter was used in order to provide a direct comparison with the LAW tests previously conducted on the same melter. Key operating parameters such as glass temperature and production rate were held constant to investigate the sulfur incorporation into the glass and the effects of varying the aluminum additive source. The bubbling rate was adjusted to achieve a production rate of 2000 kg/m{sup 2}/day with a near-complete cold cap (90-100% of melt surface covered with feed). Quantitative measurements of glass production rates, melter operating conditions (temperatures, pressures, power, flows, etc.), and off-gas characteristics (NOx, SO{sub 2}, CO, particulate load and composition, and acid gases) were made for each test. Glass samples taken from the glass pool and the discharge chamber were inspected throughout testing to determine the limit of salt-free operation in the melter
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CRYSTALLIZATION IN HIGH-LEVEL WASTE GLASSES U.S. DEPARTMENT OF ENERGY OFFICE OF RIVER PROTECTION WTP ENGINEERING DIVISION
Various circumstances influence crystallization in glassmaking, for example: (1) crystals nucleate and grow before the glass-forming melt occurs; (2) crystals grow or dissolve in flowing melt and during changing temperature; (3) crystals move under the influence of gravity; (4) crystals agglomerate and interact with gas bubbles; (5) high-level wastes (HLW) are mixtures of a large number of components in unusual proportions; (6) melter processing of HLW and the slow cooling of HLW glass in canisters provides an opportunity for a variety of crystalline forms to precipitate; (7) settling of crystals in a HLW glass melter may produce undesirable sludge at the melter bottom; and (8) crystallization of the glass product may increase, but also ruin chemical durability. The conclusions are: (1) crystal growth and dissolution typically proceed in a convective medium at changing temperature; (2) to represent crystallization or dissolution the kinetics must be expressed in the form of rate equations, such as dC/dt = f(C,T) and the temperature dependence of kinetic coefficients and equilibrium concentrations must be accounted for; and (3) non-equilibrium phenomena commonly occur - metastable crystallization, periodic distribution of crystals; and dendritic crystal growth
FINAL REPORT TESTING OF IRON PHOSPHATE LAW GLASS (VSL-11R2340-1) 04/25/2011 REV 0 06/10/2011
About 50 million gallons of high-level mixed waste is currently stored in underground tanks at The United States Department of Energy's (DOE's) Hanford site in the State of Washington. The Hanford Tank Waste Treatment and Immobilization Plant (WTP) will provide DOE's Office of River Protection (ORP) with a means of treating this waste by vitrification for subsequent disposal. The tank waste will be separated into low- and high-activity waste fractions, which will then be vitrified respectively into Immobilized Low Activity Waste (ILAW) and Immobilized High Level Waste (IHLW) products. The ILAW product will be disposed in an engineered facility on the Hanford site while the IHLW product will likely be directed to a national deep geological disposal facility for high-level nuclear waste. The ILA W and IHLW products must meet a variety of requirements with respect to protection of the environment before they can be accepted for disposal. The objectives of the work reported herein were to assess the corrosion of Inconel 690 and 693 in the FeP glass developed by MS&T and to measure key high temperature properties of the LAW iron phosphate glass. Specific objectives of these tests were the following: (1) Determination of the extent of corrosion of Inconel 690 and 693 in LAW FeP glass at 1050, 1l00, and 1150 C; (2) Determination of the extent of corrosion of Inconel 690 and 693 in LAW FeP glass in the presence of an electric field; (3) Measurement of the high temperature specific heat of the LAW FeP glass; (4) Measurement of the high temperature density of the LAW FeP glass; (5) Measurement of the high temperature thermal diffusivity of the LAW FeP glass; and (6) Calculation of the high temperature thermal conductivity of the LAW FeP glass from the above three measured properties
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Enhanced 99Tc retention in glass waste form using Tc(IV)-incorporated Fe minerals
Technetium (99Tc) immobilization by doping into iron oxide mineral phases may alleviate the problems with Tc volatility during vitrification of nuclear waste. Because reduced Tc, Tc(IV), substitutes for Fe(III) in the crystal structure by a process of Tc reduction from Tc(VII) to Tc(IV) followed by co-precipitation of Fe oxide minerals, two Tc-incorporated Fe minerals (Tc-goethite and Tc-magnetite/maghemite) were prepared and tested for Tc retention in glass melt samples at temperatures between 600 and 1000 °C. After being cooled, the solid glass specimens prepared at different temperatures at 600, 800, and 1000 °C were analyzed for Tc oxidation state using Tc K-edge XANES. In most samples, Tc was partially (<60%) oxidized from Tc(IV) to Tc(VII) as the melt temperature increased up to 600 °C. However, most of Tc(IV) was completely (>95%) oxidized to Tc(VII) at temperature above 800 °C. Tc retention in glass melt samples prepared using Tc-incorporated Fe minerals were slightly higher (∼10%) than in glass prepared using KTcO4 because of limited and delayed Tc volatilization
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DM100 AND DM1200 MELTER TESTING WITH HIGH WASTE LOADING GLASS FORMULATIONS FOR HANFORD HIGH-ALUMINUM HLW STREAMS
This Test Plan describes work to support the development and testing of high waste loading glass formulations that achieve high glass melting rates for Hanford high aluminum high level waste (HLW). In particular, the present testing is designed to evaluate the effect of using low activity waste (LAW) waste streams as a source of sodium in place ofchemical additives, sugar or cellulose as a reductant, boehmite as an aluminum source, and further enhancements to waste processing rate while meeting all processing and product quality requirements. The work will include preparation and characterization of crucible melts in support of subsequent DuraMelter 100 (DM 100) tests designed to examine the effects of enhanced glass formulations, glass processing temperature, incorporation of the LAW waste stream as a sodium source, type of organic reductant, and feed solids content on waste processing rate and product quality. Also included is a confirmatory test on the HLW Pilot Melter (DM1200) with a composition selected from those tested on the DM100. This work builds on previous work performed at the Vitreous State Laboratory (VSL) for Department of Energy's (DOE's) Office of River Protection (ORP) to increase waste loading and processing rates for high-iron HLW waste streams as well as previous tests conducted for ORP on the same waste composition. This Test Plan is prepared in response to an ORP-supplied statement of work. It is currently estimated that the number of HLW canisters to be produced in the Hanford Tank Waste Treatment and Immobilization Plant (WTP) is about 12,500. This estimate is based upon the inventory ofthe tank wastes, the anticipated performance of the sludge treatment processes, and current understanding of the capability of the borosilicate glass waste form. The WTP HLW melter design, unlike earlier DOE melter designs, incorporates an active glass bubbler system. The bubblers create active glass pool convection and thereby improve heat transfer and glass melting rate. The WTP HLW melter has a glass surface area of 3.75 m{sup 2} and depth of {approx}1.1 m. The two melters in the HLW facility together are designed to produce up to 7.5 MT of glass per day at 100% availability. Further increases in HLW waste processing rates can potentially be achieved by increasing the melter operating temperature above 1150 C and by increasing the waste loading in the glass product Increasing the waste loading also has the added benefit of decreasing the number of canisters for storage. The current estimates and glass formulation efforts have been conservative in terms of achievable waste loadings. These formulations have been specified to ensure that the glasses are homogenous, contain essentially no crystalline phases, are processable in joule-heated, ceramic-lined melters and meet WTP contract requirements. The WTP's overall mission will require the immobilization oftank waste compositions that are dominated by mixtures of aluminum (Al), chromium (Cr), bismuth (Bi), iron (Fe), phosphorous (P), zirconium (Zr), and sulfur (S) compounds as waste-limiting components. Glass compositions for these waste mixtures have been developed based upon previous experience and current glass property models. Recently, DOE has initiated a testing program to develop and characterize HLW glasses with higher waste loadings. Results of this work have demonstrated the feasibility of increases in waste-loading from about 25 wt% to 33-50 wt% (based on oxide loading) in the glass depending on the waste stream. It is expected that these higher waste loading glasses will reduce the HLW canister production requirement by about 25% or more
FINAL REPORT SUMMARY OF DM 1200 OPERATION AT VSL VSL-06R6710-2 REV 0 9/7/06
The principal objective of this report was to summarize the testing experience on the DuraMelter 1200 (DMI200), which is the High Level Waste (HLW) Pilot Melter located at the Vitreous State Laboratory (VSL). Further objectives were to provide descriptions of the history of all modifications and maintenance, methods of operation, problems and unit failures, and melter emissions and performance while processing a variety of simulated HL W and low activity waste (LAW) feeds for the Hanford Waste Treatment and Immobilization Plant (WTP) and employing a variety of operating methods. All of these objectives were met. The River Protection Project - Hanford Waste Treatment and Immobilization Plant (RPP-WTP) Project has undertaken a 'tiered' approach to vitrification development testing involving computer-based glass formulation, glass property-composition models, crucible melts, and continuous melter tests of increasing, more realistic scales. Melter systems ranging from 0.02 to 1.2 m{sup 2} installed at the Vitreous State Laboratory (VSL) have been used for this purpose, which, in combination with the 3.3 m{sup 2} low activity waste (LAW) Pilot Melter at Duratek, Inc., span more than two orders of magnitude in melt surface area. In this way, less-costly small-scale tests can be used to define the most appropriate tests to be conducted at the larger scales in order to extract maximum benefit from the large-scale tests. For high level waste (HLW) vitrification development, a key component in this approach is the one-third scale DuraMelter 1200 (DM 1200), which is the HLW Pilot Melter that has been installed at VSL with an integrated prototypical off-gas treatment system. That system replaced the DM1000 system that was used for HLW throughput testing during Part B1. Both melters have similar melt surface areas (1.2 m{sup 2}) but the DM1200 is prototypical of the present RPP-WTP HLW melter design whereas the DM1000 was not. In particular, the DM1200 provides for testing on a vitrification system with the specific train of unit operations that has been selected for both HLW and LAW RPP-WTP off-gas treatment
FINAL REPORT DETERMINATION OF THE PROCESSING RATE OF RPP WTP HLW SIMULANTS USING A DURAMELTER J 1000 VITRIFICATION SYSTEM VSL-00R2590-2 REV 0 8/21/00
This report provides data, analysis, and conclusions from a series of tests that were conducted at the Vitreous State Laboratory of The Catholic University of America (VSL) to determine the melter processing rates that are achievable with RPP-WTP HLW simulants. The principal findings were presented earlier in a summary report (VSL-00R2S90-l) but the present report provides additional details. One of the most critical pieces of information in determining the required size of the RPP-WTP HLW melter is the specific glass production rate in terms of the mass of glass that can be produced per unit area of melt surface per unit time. The specific glass production rate together with the waste loading (essentially, the ratio of waste-in to glass-out, which is determined from glass formulation activities) determines the melt area that is needed to achieve a given waste processing rate with due allowance for system availability. As a consequence of the limited amount of relevant information, there exists, for good reasons, a significant disparity between design-base specific glass production rates for the RPP-WTP LAW and HLW conceptual designs (1.0 MT/m{sup 2}/d and 0.4 MT/m{sup 2}/d, respectively); furthermore, small-scale melter tests with HLW simulants that were conducted during Part A indicated typical processing rates with bubbling of around 2.0 MT/m{sup 2}/d. This range translates into more than a factor of five variation in the resultant surface area of the HLW melter, which is clearly not without significant consequence. It is clear that an undersized melter is undesirable in that it will not be able to support the required waste processing rates. It is less obvious that there are potential disadvantages associated with an oversized melter, over and above the increased capital costs. A melt surface that is consistently underutilized will have poor cold cap coverage, which will result in increased volatilization from the melt (which is generally undesirable) and increased plenum temperatures due to increased thermal radiation from the melt surface (which mayor may not be desirable but the flexibility to choose may be lost). Increased volatilization is an issue both in terms of the increased challenge to the off-gas system as well as for the ability to effectively close the recycle loops for volatile species that must be immobilized in the glass product, most notably technetium and cesium. For these reasons, improved information is needed on the specific glass production rates of RPP-WTP HLW streams in DuraMelterJ systems over a range of operating conditions. Unlike the RPP-WTP LAW program, for which a pilot melter system to provide large-scale throughout information is already in operation, there is no comparable HLW activity; the results of the present study are therefore especially important. This information will reduce project risk by reducing the uncertainty associated with the amount of conservatism that mayor may not be associated with the baseline RPP-WTP HLW melter sizing decision. After the submission of the first Test Plan for this work, the RPP-WTP requested revisions to include tests to determine the processing rates that are achievable without bubbling, which was driven by the potential advantages of omitting bubblers from the HLW melter design in terms of reduced maintenance. A further objective of this effort became the determination of whether the basis of design processing rate could be achieved without bubbling. Ideally, processing rate tests would be conducted on a full-scale RPP-WTP melter system with actual HLW materials, but that is clearly unrealistic during Part B1. As a practical compromise the processing rate determinations were made with HL W simulants on a DuraMelter J system at as close to full scale as possible and the DM 1000 system at VSL was selected for that purpose. That system has a melt surface area of 1.2 m{sup 2}, which corresponds to about one-third scale based on the specific glass processing rate of 0.4 MT/m{sup 2}/d assumed in the RPP-WTP HLW conceptual design, but would correspond to larger than full scale if the typical Part A test results of about 2.0 MT/m{sup 2}/d were realized. The DM 1000 system was used with the existing off-gas treatment system in order to expedite the collection of this information; while that system is somewhat different from the RPP-WTP conceptual design, that should have no effect on the processing rate measurements. Subsequent tasks supported the later modification of that off-gas system to obtain large-scale system performance information on the baseline off-gas design and those modifications are now complete. Work planned for Part B2 includes similar pilot-scale testing with the prototypical off-gas system. Three HLW simulant compositions were used in the present tests: the tank AZ-101 waste (the first B2 HLW feed to the RPP-WTP), the 106-C/AY-102 blend (the largest B2 HLW tank), and the HLW composition processed at West Valley
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