LAUSR

Abstract The path for immobilizing low-activity waste (LAW), a mixture of salts, for long-term storage is adding glass-forming and modifying additives and minerals to the solution and vitrifying the resulting slurry in an electric melter. Technetium-99 (99Tc), a long-lived radionuclide present in LAW, is highly volatile at the elevated temperatures in a glass melt. An off-gas system was designed for capturing volatile 99Tc or Re, its nonradioactive surrogate, during continuous charging of a LAW melter feed in a laboratory-scale melter (LSM). The Re retention in the glass was determined via the measured amount of volatilized Re in the off-gas during a time period when the reacting melter feed was at a quasi-steady-state. This study was performed in preparation for the LSM system to be applied for melter feeds containing either a LAW simulant spiked with 99Tc or an actual tank waste.