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A predictive model of melt rate in waste glass vitrification operations is needed to inform melter operations during normal and off‐normal operations. This paper describes the development of a model of the cold cap (the reacting melter feed floating on molten glass in a glass melter) that couples heat transfer with the feed‐to‐glass conversion kinetics. The model was applied to four melter feeds designed for high‐level and low‐activity nuclear waste feeds using the material properties, either measured or estimated, to obtain temperature and conversion distribution within the cold cap. The cold cap model, when coupled with a computational fluid dynamics model of a Joule‐heated glass melter, allows the prediction of the glass production rate and power consumption. The results show reasonable agreement with the melting rates measured during pilot‐scale melter tests.

Mathematical models of glass melting furnaces are incomplete in the sense that they do not estimate the rate of glass production (the rate of melting). Instead, they attempt to optimize melter efficiency and product quality for a specified production rate with other experimentally measured data. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The melting rate correlation (MRC) attempts to bypass this

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Low-activity waste (LAW) stored in underground tanks on the Hanford Site in Washington State is planned to be filtered for solids removal and processed through ion exchange columns for cesium removal. These pretreatment steps will allow the waste to be transferred to the Hanford Tank Waste Treatment and Immobilization Plant's LAW Facility for immobilization into glass. The liquid waste will be combined with glass-forming chemicals (GFCs) to form a waste feed slurry that can be fed to electric melters for vitrification. The process of continuously converting the aqueous feed slurry into a melt is dynamic and includes multiple reactions, degassing, and dissolution processes that depend on heat from the melt below. In this conversion process, waste components are partitioned into one of two streams: glass and off-gas. Washington River Protection Solutions has requested processing information and chemical information associated with these waste products for actual waste from Hanford tank 241-AP-107 (referred to herein as AP-107). To acquire this type of information, a small-scale melter system was designed that would not require high volumes of input waste or the large resource commitment of a full-scale melter system, while also providing dynamic information that would be difficult to determine from batch reactions in a crucible system. A continuous laboratory-scale melter (CLSM) has been designed to operate with a continuous feeding process while periodically pouring glass product and collecting off-gas. The CLSM vessel has been sized to collect the relevant process and chemical information from obtainable volumes of AP-107 waste samples. A total 8.6 L of actual AP-107 tank waste were received after filtering for solids removal and ion exchange for cesium removal. This volume of AP-107 waste was mixed with GFCs to form an estimated 11.8 L of melter feed slurry. A mass of 7.01 kg of glass product were poured from the CLSM vessel during 10.07 hours of charging the AP-107 melter feed, indicating that about 15.0 kg of melter feed was vitrified into glass. These production values and other processing results from the AP-107 waste vitrification in the CLSM system are shown in Table ES.1. The CLSM system was also designed with the capability to fully divert the flow of off-gas produced in the CLSM vessel to a sampling line that could capture the volatile species of interest, such as technetium-99 (99 Tc). This novel sampling system avoided the difficulties of slipstream sampling and could be activated once the feeding reached a steady state within the CLSM vessel. Off-gas product samples captured via high-efficiency particulate air (HEPA) filters using this method, as well as selected glass product samples were sent to an analytical lab for chemical analysis. The calculated average retention of 99 Tc (mass of 99 Tc output in the glass per mass of 99 Tc input in the melter feed) during the off-gas sampling is shown in Table ES.1. The measured composition of the AP-107 glass product, compared to the target composition, is s...