Model for the conversion of nuclear waste melter feed to glass
The rate of batch-to-glass conversion is a primary concern for the vitrification of nuclear waste, as it directly influences the life cycle of the cleanup process. This study describes the development of an advanced model of the cold cap, which augments the previous model by further developments on the structure and the dynamics of the foam layer. The foam layer on the bottom of the cold cap consists of the primary foam, cavities, and the secondary foam, and forms an interface through which the heat is transferred to the cold cap. Other model enhancements include the behavior of intermediate crystalline phases and the dissolution of quartz particles. The model relates the melting rate to feed properties and melter conditions, such as the molten glass temperature, foaminess of the melt, or the heat fraction supplied to the cold cap from the plenum space. The model correctly predicts a 25% increase in melting rate when changing the alumina source in the melter feed from Al(OH)3 to AlO(OH). It is expected that this model will be incorporated in the full glass melter model as its integral component.
Effect of bubbles and silica dissolution on melter feed rheology during conversion to glass.
Nuclear-waste melter feeds are slurry mixtures of wastes with glass-forming and glass-modifying additives (unless prefabricated frits are used), which are converted to molten glass in a continuous electrical glass-melting furnace. The feeds gradually become continuous glass-forming melts. Initially, the melts contain dissolving refractory feed constituents that are suspended together with numerous gas bubbles. Eventually, the bubbles escape, and the melts homogenize and equilibrate. Knowledge of various physicochemical properties of the reacting melter feed is crucial for understanding the feed-to-glass conversion that occurs during melting. We studied the melter feed viscosity during heating and correlated it with the volume fractions of dissolving quartz (SiO2) particles and the gas phase. The measurements were performed with a rotating spindle rheometer on the melter feed heated at 5 K/min, starting at several different temperatures. The effects of undissolved quartz particles, gas bubbles, and compositional inhomogeneity on the melter feed viscosity were determined by fitting a linear relationship between the logarithm of viscosity and the volume fractions of suspended phases.
Viscosity of many-component glasses
Abstract The effect of composition on the viscosity ( η ) of multicomponent glasses is expressed as B = ∑ i = 1 N B i x i where B = T ln ( η / η ∞ ) is the activation energy (in K), B i is the i -th component coefficient, x i is the i -th component mass fraction, T is the absolute temperature, and η ∞  ≈ 10 −5  Pa ⋅ s. The B i coefficients for three composition regions (labeled as CVS-1&2, CVS-3, and CVS-4) containing various subsets of Al 2 O 3 , B 2 O 3 , Bi 2 O 3 , CaO, Cr 2 O 3 , F, Fe 2 O 3 , K 2 O, Li 2 O, MgO, MnO, Na 2 O, NiO, P 2 O 5 , SiO 2 , UO 2 , and ZrO 2 as major components are summarized and compared. This paper presents a detailed account of the recent experimental study that generated viscosity data for the CVS-4 region of glass composition. Whereas CVS-1&2 is a well publicized dataset, CVS-3 viscosity data, though produced in 1995, are published and evaluated here for the first time. Limits of applicability of the composition models are discussed.