Download or read book Optimization of High level Waste Loading in a Borosilicate Glass Matrix by Using Chemical Durability Modeling Approach written by Javeed Mohammad and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A laboratory scale study was carried out on a set of 6 borosilicate waste glasses made from simulated high-level nuclear waste. The test matrix was designed to explore the composition region suitable for the long-term geologic disposal of high-temperature-and high-waste-containing glasses. The glass compositions were selected to achieve maximum waste loading without a sacrifice in glass durability. The relationship between glass composition and chemical durability was examined. The qualitative effect of increasing B2O3 content on the overall waste glass leaching behavior has also been addressed. The glass composition matrix was designed by systematically varying the factors: %waste loading and (SiO2+Frit):B2O3 ratio, with (SiO2:Frit) ratio being held constant. In order to assess the chemical durability, the Product Consistency Test (ASTM C-1285) was performed. Under PCT protocol, crushed glass was allowed to react with ASTM type I water under static conditions. All leachate solutions were analyzed by the technique; Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). A statistical regression technique was utilized to model the normalized release of the major soluble elements, Na, Si, and B, as a function of the individual as well as interactive chemical effects (B2O3, Al2O3, Fe2O3, MnO, SiO2, SrO, Na2O, B2O3*SiO2, B2O3*Al2O3, Fe2O3*Na2O, Al2O3*Na2O, and MnO*SiO2). Geochemical modeling was performed using the computer code EQ3/6 to: (1) determine the saturation states of the possible silicate minerals, a-cristobalite and chalcedony; and (2) predict the most stable mineral phase based on the mineral thermodynamic data. Mineral/water interactions were analyzed by representing the resultant glass data on a Na-Al-Si-O-H stability diagram.

Download or read book OPTIMIZATION OF HIGH LEVEL WASTE LOADING IN A BOROSILICATE GLASS MATRIX BY USING CHEMICAL DURABILITY MODELING APPROACH written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A laboratory scale study was carried out on a set of 6 borosilicate waste glasses made from simulated high-level nuclear waste. The test matrix was designed to explore the composition region suitable for the long-term geologic disposal of high-temperature-and high-waste-containing glasses. The glass compositions were selected to achieve maximum waste loading without a sacrifice in glass durability. The relationship between glass composition and chemical durability was examined. The qualitative effect of increasing B2O3 content on the overall waste glass leaching behavior has also been addressed. The glass composition matrix was designed by systematically varying the factors: %waste loading and (SiO2+Frit):B2O3 ratio, with (SiO2:Frit) ratio being held constant. In order to assess the chemical durability, the Product Consistency Test (ASTM C-1285) was performed. Under PCT protocol, crushed glass was allowed to react with ASTM type I water under static conditions. All leachate solutions were analyzed by the technique; Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). A statistical regression technique was utilized to model the normalized release of the major soluble elements, Na, Si, and B, as a function of the individual as well as interactive chemical effects (B2O3, Al2O3, Fe2O3, MnO, SiO2, SrO, Na2O, B2O3*SiO2, B2O3*Al2O3, Fe2O3*Na2O, Al2O3*Na2O, and MnO*SiO2). Geochemical modeling was performed using the computer code EQ3/6 to: (1) determine the saturation states of the possible silicate minerals, a-cristobalite and chalcedony; and (2) predict the most stable mineral phase based on the mineral thermodynamic data. Mineral/water interactions were analyzed by representing the resultant glass data on a Na-Al-Si-O-H stability diagram.

Download or read book Optimization of Waste Loading in High level Glass in the Presence of Uncertainty written by and published by . This book was released on 1995 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hanford high-level liquid waste will be converted into a glass form for long-term storage. The glass must meet certain constraints on its composition and properties in order to have desired properties for processing (e.g., electrical conductivity, viscosity, and liquidus temperature) and acceptable durability for long-term storage. The Optimal Waste Loading (OWL) models, based on rigorous mathematical optimization techniques, have been developed to minimize the number of glass logs required and determine glass-former compositions that will produce a glass meeting all relevant constraints. There is considerable uncertainty in many of the models and data relevant to the formulation of high-level glass. In this paper, we discuss how we handle uncertainty in the glass property models and in the high-level waste composition to the vitrification process. Glass property constraints used in optimization are inequalities that relate glass property models obtained by regression analysis of experimental data to numerical limits on property values. Therefore, these constraints are subject to uncertainty. The sampling distributions of the regression models are used to describe the uncertainties associated with the constraints. The optimization then accounts for these uncertainties by requiring the constraints to be satisfied within specified confidence limits. The uncertainty in waste composition is handled using stochastic optimization. Given means and standard deviations of component masses in the high-level waste stream, distributions of possible values for each component are generated. A series of optimization runs is performed; the distribution of each waste component is sampled for each run. The resultant distribution of solutions is then statistically summarized. The ability of OWL models to handle these forms of uncertainty make them very useful tools in designing and evaluating high-level waste glasses formulations.

Download or read book Glass as a Waste Form and Vitrification Technology written by National Research Council and published by National Academies. This book was released on 1997-03-02 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nuclear Waste Research written by Arnold P. Lattefer and published by Nova Publishers. This book was released on 2008 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radioactive wastes are waste types containing radioactive chemical elements that do not have a practical purpose. They are sometimes the products of a nuclear processes, such as nuclear fission. However, other industries not directly connected to the nuclear industry can produce large quantities of radioactive waste. For instance, over the past 20 years it is estimated that just the oil-producing endeavours of the US have accumulated 8 million tons of radioactive wastes. The majority of radioactive waste is "low-level waste", meaning it has low levels of radioactivity per mass or volume. This type of waste often consists of used protective clothing, which is only slightly contaminated but still dangerous in case of radioactive contamination of a human body through ingestion, inhalation, absorption, or injection. The issue of disposal methods for nuclear waste was one of the most pressing current problems the international nuclear industry faced when trying to establish a long term energy production plan, yet there was hope it could be safely solved. In the U.S., the DOE acknowledged much progress in addressing the waste problems of the industry, and successful remediation of some contaminated sites, yet also major uncertainties and sometimes complications and setbacks in handling the issue properly, cost effectively, and in the projected time frame. In other countries with lower ability or will to maintain environmental integrity the issue would be more problematic. This new book presents the latest research in the field.

Download or read book Immobilization of Simulated High level Radioactive Waste in Borosilicate Glass written by and published by . This book was released on 1991 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Integrated DWPF Melter System (IDMS), operated by the Savannah River Laboratory, is a pilot scale facility used in support of the start-up and operation of the Department of Energy's Defense Waste Processing Facility. The IDMS has successfully demonstrated, on an engineering scale (one-fifth), that simulated high level radioactive waste (HLW) sludge can be chemically treated with formic acid to adjust both its chemical and physical properties, and then blended with simulated precipitate hydrolysis aqueous (PHA) product and borosilicate glass frit to produce a melter feed which can be processed into a durable glass product. The simulated sludge, PHA and frit were blended, based on a product composition program, to optimize the loading of the waste glass as well as to minimize those components which can cause melter processing and/or glass durability problems. During all the IDMS demonstrations completed thus far, the melter feed and the resulting glass that has been produced met all the required specifications, which is very encouraging to future DWPF operations. The IDMS operations also demonstrated that the volatile components of the melter feed (e.g., mercury, nitrogen and carbon, and, to a lesser extent, chlorine, fluorine and sulfur) did not adversely affect the melter performance or the glass product.

Download or read book Chemical Analysis of Simulated High Level Waste Glasses to Support Sulfate Solubility Modeling written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The U.S. Department of Energy (DOE), Office of Environmental Management (EM) is sponsoring an international, collaborative project to develop a fundamental model for sulfate solubility in nuclear waste glass. The solubility of sulfate has a significant impact on the achievable waste loading for nuclear waste forms both within the DOE complex and to some extent at U.K. sites. The development of enhanced borosilicate glass compositions with improved sulfate solubility will allow for higher waste loadings and accelerated cleanup missions. Much of the previous work on improving sulfate retention in waste glasses has been done on an empirical basis, making it difficult to apply the findings to future waste compositions despite the large number of glass systems studied. A more fundamental, rather than empirical, model of sulfate solubility in glass, under development at Sheffield Hallam University (SHU), could provide a solution to the issues of sulfate solubility. The model uses the normalized cation field strength index as a function of glass composition to predict sulfate capacity, and has shown early success for some glass systems. The objective of the current scope is to mature the sulfate solubility model to the point where it can be used to guide glass composition development for DOE waste vitrification efforts, allowing for enhanced waste loadings and waste throughput. A series of targeted glass compositions was selected to resolve data gaps in the current model. SHU fabricated these glasses and sent samples to the Savannah River National Laboratory (SRNL) for chemical composition analysis. SHU will use the resulting data to enhance the sulfate solubility model and resolve any deficiencies. In this report, SRNL provides chemical analyses for simulated waste glasses fabricated SHU in support of sulfate solubility model development. A review of the measured compositions revealed that there are issues with the B2O3 and Fe2O3 concentrations missing their targeted values by a significant amount for several of the study glasses. SHU is reviewing the fabrication of these glasses and the chemicals used in batching them to identify the source of these issues. The measured sulfate concentrations were all below their targeted values. This is expected, as the targeted concentrations likely exceeded the solubility limit for sulfate in these glass compositions. Some volatilization of sulfate may also have occurred during fabrication of the glasses. Measurements of the other oxides in the study glasses were reasonably close to their targeted values.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1989 with total page 1364 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Festschrift zum 115 j hrigen Bestehen mit Fahnweihe des MGV 1847 Asselheim an der Weinstra e written by and published by . This book was released on 1962 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Critical Review of Glass Performance Modeling written by and published by . This book was released on 1994 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Borosilicate glass is to be used for permanent disposal of high-level nuclear waste in a geologic repository. Mechanistic chemical models are used to predict the rate at which radionuclides will be released from the glass under repository conditions. The most successful and useful of these models link reaction path geochemical modeling programs with a glass dissolution rate law that is consistent with transition state theory. These models have been used to simulate several types of short-term laboratory tests of glass dissolution and to predict the long-term performance of the glass in a repository. Although mechanistically based, the current models are limited by a lack of unambiguous experimental support for some of their assumptions. The most severe problem of this type is the lack of an existing validated mechanism that controls long-term glass dissolution rates. Current models can be improved by performing carefully designed experiments and using the experimental results to validate the rate-controlling mechanisms implicit in the models. These models should be supported with long-term experiments to be used for model validation. The mechanistic basis of the models should be explored by using modern molecular simulations such as molecular orbital and molecular dynamics to investigate both the glass structure and its dissolution process.

Download or read book INTERNATIONAL STUDY OF ALUMINUM IMPACTS ON CRYSTALLIZATION IN U S HIGH LEVEL WASTE GLASS written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this task was to develop glass formulations for (Department of Energy) DOE waste streams with high aluminum concentrations to avoid nepheline formation while maintaining or meeting waste loading and/or waste throughput expectations as well as satisfying critical process and product performance related constraints. Liquidus temperatures and crystallization behavior were carefully characterized to support model development for higher waste loading glasses. The experimental work, characterization, and data interpretation necessary to meet these objectives were performed among three partnering laboratories: the V.G. Khlopin Radium Institute (KRI), Pacific Northwest National Laboratory (PNNL) and Savannah River National Laboratory (SRNL). Projected glass compositional regions that bound anticipated Defense Waste Processing Facility (DWPF) and Hanford high level waste (HLW) glass regions of interest were developed and used to generate glass compositions of interest for meeting the objectives of this study. A thorough statistical analysis was employed to allow for a wide range of waste glass compositions to be examined while minimizing the number of glasses that had to be fabricated and characterized in the laboratory. The glass compositions were divided into two sets, with 45 in the test matrix investigated by the U.S. laboratories and 30 in the test matrix investigated by KRI. Fabrication and characterization of the US and KRI-series glasses were generally handled separately. This report focuses mainly on the US-series glasses. Glasses were fabricated and characterized by SRNL and PNNL. Crystalline phases were identified by X-ray diffraction (XRD) in the quenched and canister centerline cooled (CCC) glasses and were generally iron oxides and spinels, which are not expected to impact durability of the glass. Nepheline was detected in five of the glasses after the CCC heat treatment. Chemical composition measurements for each of the glasses were conducted following an analytical plan. A review of the individual oxides for each glass revealed that there were no errors in batching significant enough to impact the outcome of the study. A comparison of the measured compositions of the replicates indicated an acceptable degree of repeatability as the percent differences for most of the oxides were less than 5% and percent differences for all of the oxides were less than 10 wt%. Chemical durability was measured using the Product Consistency Test (PCT). All but two of the study glasses had normalized leachate for boron (NL [B]) values that were well below that of the Environmental Assessment (EA) reference glass. The two highest NL [B] values were for the CCC versions of glasses US-18 and US-27 (10.498 g/L and 15.962 g/L, respectively). Nepheline crystallization was identified by qualitative XRD in five of the US-series glasses. Each of these five glasses (US-18, US-26, US-27, US-37 and US-43) showed a significant increase in NL [B] values after the CCC heat treatment. This reduction in durability can be attributed to the formation of nepheline during the slow cooling cycle and the removal of glass formers from the residual glass network. The liquidus temperature (T{sub L}) of each glass in the study was determined by both optical microscopy and XRD methods. The correlation coefficient of the measured XRD TL data versus the measured optical TL data was very good (R2 = 0.9469). Aside from a few outliers, the two datasets aligned very well across the entire temperature range (829 C to 1312 C for optical data and 813 C to 1310 C for XRD crystal fraction data). The data also correlated well with the predictions of a PNNL T{sub L} model. The correlation between the measured and calculated data had a higher degree of merit for the XRD crystal fraction data than for the optical data (higher R2 value of 0.9089 versus 0.8970 for the optical data). The SEM-EDS analysis of select samples revealed the presence of undissolved RuO2 in all glasses due to the low solubility of RuO2 in borosilicate glass. These particles tended to form agglomerates with varying sizes and shapes that were located close to the bottom of crucibles. The results of this study provide further insight into the ability of borosilicate waste glass to incorporate increased (>16 wt %) concentrations of aluminum. The glass composition and properties data will be incorporated into a database of glass composition-property relationships (ComPro) to support further optimization of waste glass compositions at DOE sites.

Download or read book Chemical Analysis of Simulated High Level Waste Glasses to Support Stage III Sulfate Solubility Modeling written by and published by . This book was released on 2016 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: The U.S. Department of Energy (DOE), Office of Environmental Management (EM) is sponsoring an international, collaborative project to develop a fundamental model for sulfate solubility in nuclear waste glass. The solubility of sulfate has a significant impact on the achievable waste loading for nuclear waste forms within the DOE complex. These wastes can contain relatively high concentrations of sulfate, which has low solubility in borosilicate glass. 1 This is a significant issue for low activity waste (LAW) glass and is projected to have a major impact on the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Sulfate solubility has also been a limiting factor for recent high level waste (HLW) sludge processed at the Savannah River Site (SRS) Defense Waste Processing Facility (DWPF).2-5 The low solubility of sulfate in glass, along with melter and off-gas corrosion constraints, dictate that the waste be blended with lower sulfate concentration waste sources or washed to remove sulfate prior to vitrification. The development of enhanced borosilicate glass compositions with improved sulfate solubility will allow for higher waste loadings and accelerate mission completion. The objective of the current scope being pursued by SHU is to mature the sulfate solubility model to the point where it can be used to guide glass composition development for DWPF and WTP, allowing for enhanced waste loadings and waste throughput at these facilities. A series of targeted glass compositions was selected to resolve data gaps in the model and is identified as Stage III. 10 SHU fabricated these glasses and sent samples to SRNL for chemical composition analysis. SHU will use the resulting data to enhance the sulfate solubility model and resolve any deficiencies. In this report, SRNL provides chemical analyses for the Stage III, simulated HLW glasses fabricated by SHU in support of the sulfate solubility model development.

Download or read book Systems Approach to Nuclear Waste Glass Development written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of a host solid for the immobilization of nuclear waste has focused on various vitreous wasteforms. The systems approach requires that parameters affecting product performance and processing be considered simultaneously. Application of the systems approach indicates that borosilicate glasses are, overall, the most suitable glasses for the immobilization of nuclear waste. Phosphate glasses are highly durable; but the glass melts are highly corrosive and the glasses have poor thermal stability and low solubility for many waste components. High-silica glasses have good chemical durability, thermal stability, and mechanical stability, but the associated high melting temperatures increase volatilization of hazardous species in the waste. Borosilicate glasses are chemically durable and are stable both thermally and mechanically. The borosilicate melts are generally less corrosive than commercial glasses, and the melt temperature miimizes excessive volatility of hazardous species. Optimization of borosilicate waste glass formulations has led to their acceptance as the reference nuclear wasteform in the United States, United Kingdom, Belgium, Germany, France, Sweden, Switzerland, and Japan.

Download or read book High level Nuclear Waste Borosilicate Glass written by and published by . This book was released on 1992 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the imminent startup, in the United States, of facilities for vitrification of high-level nuclear waste, a document has been prepared that compiles the scientific basis for understanding the alteration of the waste glass products under the range of service conditions to which they may be exposed during storage, transportation, and eventual geologic disposal. A summary of selected parts of the content of this document is provided. Waste glass alterations in a geologic repository may include corrosion of the glass network due to groundwater and/or water vapor contact. Experimental testing results are described and interpreted in terms of the underlying chemical reactions and physical processes involved. The status of mechanistic modeling, which can be used for long-term predictions, is described and the remaining uncertainties associated with long-term simulations are summarized.

Download or read book Chemical Durability of Lead Borosilicate Glass Matrix Under Simulated Geological Conditions written by Vrunda S. Yalmali and published by . This book was released on 2002 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High level Waste Glass Compendium what it Tells Us Concerning the Durability of Borosilicate Waste Glass written by and published by . This book was released on 1993 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Facilities for vitrification of high-level nuclear waste in the United States are scheduled for startup in the next few years. It is, therefore, appropriate to examine the current scientific basis for understanding the corrosion of high-level waste borosilicate glass for the range of service conditions to which the glass products from these facilities may be exposed. To this end, a document has been prepared which compiles worldwide information on borosilicate waste glass corrosion. Based on the content of this document, the acceptability of canistered waste glass for geological disposal is addressed. Waste glass corrosion in a geologic repository may be due to groundwater and/or water vapor contact. The important processes that determine the glass corrosion kinetics under these conditions are discussed based on experimental evidence from laboratory testing. Testing data together with understanding of the long-term corrosion kinetics are used to estimate radionuclide release rates. These rates are discussed in terms of regulatory performance standards.

Download or read book Waste Glass Corrosion Modeling written by and published by . This book was released on 1993 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: A chemical model of glass corrosion will be used to predict the rates of release of radionuclides from borosilicate glass waste forms in high-level waste repositories. The model will be used both to calculate the rate of degradation of the glass, and also to predict the effects of chemical interactions between the glass and repository materials such as spent fuel, canister and container materials, backfill, cements, grouts, and others. Coupling between the degradation processes affecting all these materials is expected. Models for borosilicate glass dissolution must account for the processes of (1) kinetically-controlled network dissolution, (2) precipitation of secondary phases, (3) ion exchange, (4) rate-limiting diffusive transport of silica through a hydrous surface reaction layer, and (5) specific glass surface interactions with dissolved cations and anions. Current long-term corrosion models for borosilicate glass employ a rate equation consistent with transition state theory embodied in a geochemical reaction-path modeling program that calculates aqueous phase speciation and mineral precipitation/dissolution. These models are currently under development. Future experimental and modeling work to better quantify the rate-controlling processes and validate these models are necessary before the models can be used in repository performance assessment calculations.