Investigation of high-level waste glass melting using X-ray computed tomography

A method has been developed to quantitatively assess the melting behavior of simulated nuclear waste glasses in a 5-cm-diameter stainless steel beaker heated from the bottom. The method applies X-ray scanning and computed tomography to build three-dimensional volumetric data of a heat-treated sample and performs an adaptive segmentation analysis of the volumetric data to identify morphologically distinct regions in the sample matrix and quantify the amount of material in each region based on computed tomography density. The method was applied to two different series of simulated high-level waste glass melter feeds, and the results showed that it provides detailed images of samples at various stages of melting, including distribution of gas bubbles of varying sizes within the sample matrix, as well as a quantitative measure of how fast various waste/frit feeds melted relative to each other. The results show that the melting rate is influenced by the rate of calcine gas evolution, melt viscosity, and the presence of modifier ions in the feed.