SummaryThe loading of Idaho National Engineering and Environmental Laboratory sodium bearing waste (SBW) in glass will be limited by the allowable concentration of sulfate in the feed which is defined by the highest concentration that can be vitrified into glass at an acceptable rate without the accumulation of molten salt on the melt surface. This allowable concentration of sulfate in the feed is determined by many chemical (e.g., waste composition, chemistry of glass forming additives, waste loading, acid or reductant addition) and physical (e.g., melter-feed rate, plenum temperature, heat-transfer rate to the cold cap) parameters. This report documents the status of an ongoing study to determine the impacts of key processing parameters on the partitioning of sulfur species between the glass, a molten salt phase, and the off gas. As this study is continuing, the nature of these results is preliminary and incomplete. However, this report does give an indication of the relative importance of many parameters and the range of expected sulfur-partition coefficients during SBW vitrification.A series of tests was conducted to measure the partitioning of sulfur species between glass, the off gas, and a molten salt. In crucible tests, between 79 and 100% of the total sulfur was found to remain in the glass, and molten salts were not formed until the target concentration of sulfur in the glass exceeded roughly 1 mass% on an SO 3 basis. The use of high gas purge rates (e.g., 2300 ccm) in crucible tests decreased the fraction of sulfur in the glass to roughly 23% of that targeted. The influence of sugar concentration, heating rate, and starting feed pH were found to be minimal on the partitioning of sulfur species in these tests. Glass-forming additive composition was found to influence the formation of a salt layer. Details of the crucible tests are reported by Peeler et al. (2001).Three melter tests were performed with simulated SBW feed. The first test (EV-16-1999-1) was performed using the pilot-scale Envitco EV-16 melter at Clemson University in April 1999. The asbatched glass composition for this test contained 1.07 mass% of SO 3 . The measured concentration of sulfur in the glass produced was roughly 0.58 mass% based on SO 3 . No salt layer was observed during or after the test, suggesting that the remaining sulfur was driven to the off gas. However, power excursions occurred during the test, which occasionally brought the melt temperature to 1350°C. These excursions may have had a strong influence on the partitioning of sulfur during the test. Results of this test have yet to be published; highlights are described in Section 3.1.The second melter test (RSM-01-1) with simulated SBW feed was performed using the ResearchScale Melter (RSM) at Pacific Northwest National Laboratory in January 2001. This test was conducted in eight segments. The waste loading (30 to 35 mass% on a dry, non-volatile oxide basis), sulfur concentration (1.07 to 1.75 mass% based on SO 3 ), and sugar concentration (135 to 197 g/L of waste simu...