A crucible salt saturation method for determining sulfur solubility in glass melt

Abstract Experiments were conducted to determine sulfur solubility in Hanford low‐activity waste ( LAW ) glass melts by a sulfur saturation method. Sulfur‐incorporated glass melts were prepared by salt saturation and bubbling methods. The salt saturation method was performed by mixing crushed premelted baseline glasses with an excess amount of Na ₂ SO ₄ prior to melting the mixture at 1150°C for 1 hour. The bubbling method involved bubbling the glass melt at 1150°C in a Pt crucible with an SO ₂ /O ₂ /N ₂ gas mix to equilibrate the melt at a known pressure of SO ₃ . Preliminary results suggested that performing 1 cycle of mixing and melting was not sufficient to saturate the glass. The bubbling method successfully incorporated sulfur into the glass but caused significant losses of sodium from the melt. In order to saturate the glass melt with sulfate without causing noticeable sodium loss, a modified crucible salt saturation method was developed by repeating the mixing and melting of the glass and salt mixture. For all 3 representative LAW glasses tested in this study, it was found that after 3 mixing and melting cycles, the sulfur concentration reaches a plateau, indicating reasonable sulfur saturation.