Immobilization of Hanford LAW in iron phosphate glasses

Iron phosphate glasses containing 30 w% of a high sodium and sulfur Hanford low-activity waste (LAW) simulant was successfully melted in electric furnaces at 1000–1050 °C for 2–3 h. No sulfate salt segregation or crystalline phases were detectable in the glassy wasteform when examined by scanning electron microscope and X-ray diffractometer. This suggests that the waste loading in the iron phosphate glasses will not be limited by the SO3 content of the LAW as is currently the case in borosilicate glasses. At 30 wt% LAW, the iron phosphate glass wasteform satisfies DOE’s product consistency test and vapor hydration test requirements for aqueous chemical durability, but the chemical durability depends upon the overall composition. The high fluidity and electrical conductivity of the iron phosphate melts suggest that iron phosphate wasteforms can be melted in a hot or cold crucible induction melter as an alternative to melting in a joule-heated melter. These properties combined with a significantly higher waste loading offer a considerable savings in time, energy and cost for vitrifying the Hanford LAW in iron phosphate glasses.