Iodine solubility in a low-activity waste borosilicate glass at 1000 °C

The purpose of this study was to determine the solubility of iodine in a low-activity waste borosilicate glass when heated inside an evacuated and sealed fused quartz ampoule. The iodine was added to glass frit as KI in quantities of 99.4-24,005 ppm iodine (by mass). Each mixture was added to an ampoule, heated at 1000 °C for 2 h, and then air quenched. In samples with ⩾11,999 ppm iodine, low viscosity salt phases were observed on the surface of the melts that solidified into a white coating upon cooling. These salts were identified by X-ray diffraction as mixtures of KI, NaI, and Na2SO4. Iodine concentrations in glass specimens were analyzed with inductively-coupled plasma mass spectrometry, and the overall iodine solubility was determined to be 10,000 ppm. Several crystalline inclusions of iodine sodalite, Na8(AlSiO4)6I2, were observed in the 24,005 ppm specimen.