Chromium phase behavior in a multi-component borosilicate glass melt

This paper reports the phase behavior of a multi-component borosilicate glass melt with 0–3 mass% Cr₂O₃ at 800–1500 °C in equilibrium with air. Both upper and lower liquidus temperatures were observed. When the temperature was between the upper and lower liquidus temperatures, eskolaite (Cr₂O₃) formed in melts with >2 mass% Cr₂O₃. Below the lower liquidus temperature, a dispersed chromate phase appeared in the melt that eventually became macroscopically segregated. The chemical durability of the glasses was virtually unaffected by chromium concentration. The particular glass studied was prototypic for vitrifying high-Cr high-level radioactive wastes stored in underground tanks at the Hanford site. The results suggest a significant potential cost benefit for Hanford tank waste cleanup through increased waste solubility in glass.