5 Matching Results

Search Results

Advanced search parameters have been applied.

SETTLING OF SPINEL IN A HIGH-LEVEL WASTE GLASS MELTER

Description: High-level nuclear waste is being vitrified, i.e., converted to a durable glass that can be stored in a safe repository for hundreds of thousands of years. Waste vitrification is accomplished in reactors called melters to which the waste is charged together with glass-forming additives. The mixture is electrically heated to a temperature as high as 1150 decrees C to create a melt that becomes glass on cooling.
Date: January 7, 2002
Creator: Hrma, Pavel; Schill, Pert & Nemec, Lubomir
Partner: UNT Libraries Government Documents Department

Settling of Spinel in A High-Level Waste Glass Melter

Description: High-level nuclear waste is being vitrified, i.e., converted to a durable glass that can be stored in a safe repository for hundreds of thousands of years. Waste vitrification is accomplished in reactors call melters to which the waste is charged together with glass-forming additives. The mixture is electrically heated to a temperature as high as 1150 degree C (or even higher in advanced melters) to create a melt that becomes glass on cooling. This process is slow and expensive. Moreover, the melters that are currently in use or are going to be used in the U.S. are sensitive to clogging and thus cannot process melt in which solid particles are suspended. These particles settle and gradually accumulate on the melter bottom. Such particles, most often small crystals of spinel ( a mineral containing iron, nickel, chromium, and other minor oxides), inevitably occurred in the melt when the content of the waste in the glass (called waste loading) increases above a certain limit. To avoid the presence of solid particles in the melter, the waste loading is kept rather low, in average 15% lower than in glass formulated for more robust melters.
Date: January 7, 2002
Creator: Hrma, Pavel; Schill, Pert & Nemec, Lubomir
Partner: UNT Libraries Government Documents Department

Settling of Spinel in a High-Level Waste Glass Melter

Description: High-level nuclear waste is being vitrified, i.e., converted to a durable glass that can be stored in a safe repository for hundreds of thousands of years. Waste vitrification is accomplished in reactors called melters to which the waste is charged together with glass-forming additives. The mixture is electrically heated to a temperature as high as 1150?C (or even higher in advanced melters) to create a melt that becomes glass on cooling. This process is slow and expensive. Moreover, the melters that are currently in use or are going to be used in the U.S. are sensitive to clogging and thus cannot process melt in which solid particles are suspended. These particles settle and gradually accumulate on the melter bottom. Such particles, most often small crystals of spinel (a mineral containing iron, nickel, chromium, and other minor oxides), inevitably occur in the melt when the content of the waste in the glass (called waste loading) increases above a certain limit. To avoid the presence of solid particles in the melter, the waste loading is kept rather low, in average 15% lower than in glass formulated for more robust melters.
Date: January 18, 2002
Creator: Hrma, Pavel R.; Schill, Pert & Nemec, Lubomir
Partner: UNT Libraries Government Documents Department

Modeling of Spinel Settling in Waste Glass Melter

Description: Each 1% increase of waste loading (W), defined as the high-level waste (HLW) mass fraction in glass, can save the U.S. Department of Energy (DOE) over a half billion U.S. dollars for vitrification and disposal. For a majority of Hanford and Savannah River waste streams, W is limited by spinel precipitation and settling in waste glass melters. Therefore, a fundamental understanding of spinel behavior is crucial for economy and the low-risk operation of HLW vitrification. The goal of this research is to develop a basic understanding of the dynamics of spinel formation and motion in velocity, temperature, and redox fields that are characteristic for the glass-melting process. This goal is being achieved by directly studying spinel formation and settling in molten glass and by developing a mathematical tool for predicting the spinel behavior and accumulation rate in the melter. The main potential benefit of this study is achieving a lower waste-glass volume, which translates into a shorter cleanup time, a smaller processing facility, a smaller repository space, and, hence, a reduced investment of time and money to reach acceptable technical risks. Additional benefits include (1) more accurately assessing sensible limits for problem constituents (such as chromium) in the melter feed, (2) reducing the blending requirements, and (3) comparing cost and risk with other options (pretreatment, blending or diluting the waste) to determine the best path forward. The results of this study will allow alternate melter designs and operating conditions to be evaluated. The study will also address the option of removing the settled sludge from the melter.
Date: June 1, 1999
Creator: Hrma, Pavel R.; Nemec, Lubomir & Schill, Petr
Partner: UNT Libraries Government Documents Department

Modeling of Spinel Settling in Waste Glass Melter

Description: Our objective is to determine the fraction and size of spinel crystals in molten HLW glass that are compatible with low-risk melter operation. To this end, we are investigating spinel behavior in HLW glass and obtaining data to be used in a mathematical model for spinel settling in a HLW glass melter. We will modify the current glass-furnace model to incorporate spinel concentration distribution and to predict the rate of spinel settling. Also, we will determine the nucleation agents that control the number density and size of spinel crystals in HLW glass.
Date: June 1, 2000
Creator: Hrma, Pavel; Schill, Petr; Nemec, Lubomir; Klouzek, Jaroslav, Mika, Martin & Brada, Jiri Glass Service, Ltd., Vsetin, Czech Republic
Partner: UNT Libraries Government Documents Department