Cold Cap Bubble Topology

Abstract

The feed composition of a high level nuclear waste (HLW) glass melter establishes the overall melting rate by influencing the thermo-physical and morphological properties of a relatively insulating cold cap layer over the molten phase. Data from X ray tomography of laboratory scale quenched cold caps provide insight into the distribution and morphology of bubbles, collectively known as primary foam, within this layer for various feed compositions at temperatures between 600°C and 1040°C. The images were digitally segmented to capture features of interest, then processed to obtain statistics that characterize the cold cap structure, including total pellet volume, void fraction, bubble radius distribution and morphology as a function of temperature. These statistics will be used to analyze the melting behavior of the waste glass as a function of silicate content. This temperature-dependent morphological data can be used in future investigations to synthetically generate cold cap structures for use in models of heat transfer through the upper layer of a HLW glass melter, with emphasis on nuclear waste remediation application at the Hanford Site in Washington, USA.