Vitrification of low-level radioactive mixed waste at Argonne National Laboratory

Argonne National Laboratory-East (ANL-E) is proceeding with plans to use vitrification to treat low-level radioactive mixed wastes (LLMW) generated on-site. The objective is to install a full-scale vitrification system at ANL-E capable of processing the entire annual generation of selected LLMW streams. Crucible glass studies with actual mixed waste streams have produced sodium borosilicate glasses under conditions achievable in commercially available melters. These same glass compositions, spiked with toxic metals above the expected levels in actual wastes, pass the Toxicity Characteristic Leaching Procedure (TCLP) test. Earlier evaluations of the likely off-gases that will result from vitrification indicated that the primary off-gases will include compounds of SOx, NOx, and CO2. These evaluations are being experimentally confirmed with a mass spectrometer analysis of the gases evolved from samples of the ANL-E wastes. The composition of the melter feed can be adjusted to minimize volatilization of some components, if necessary. The full-scale melter will be designed to handle the annual generation of at least three LLMW waste streams: evaporator concentrator bottoms sludge (ECB), storage tank sludge (STS), and HEPA filter media. Each waste stream is mixed waste by virtue of its failure to pass the TCLP test with respect to toxic metal leaching. Additional LLMW streams under consideration for vitrification include historical mixed waste glass from past operations and spent abrasive from a planned decontamination facility