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A program has been established for DOE Environmental Restoration and Waste Management (EM) to evaluate factors that are likely to affect waste glass reaction ,during repository disposal, with emphasis on an unsaturated environment typical of what may be expected for the proposed Yucca Mountain repository site. This report covers progress in FY 1991 on the following tasks: 11 A critic_ review of those parameters that affect the reactivity of glass in an unsaturated environment is in progress. This effort involves a search of the literature to identify the important parameters. Temperature and glass compositions are the first parameters examined in detail. 2, An interface between waste producers and the repository program is being implemented. 3. A series of tests has been started to evaluate the reactivity of fully radioactive glasses in a high-level waste repository environment mad compare it to the reactivity of synthetic glasses of similar composition. 4. The effect of radiation upon the durability of waste glasses at a high glass surface. _ea-tc)-liquid volume fSA/V) _ttio m3d higl_ gas-to-liquid volume ratio will be assessed. These tesLsaddress both vapor m_d high SA/V liquid conditions. 5. A series of test:_ is being performed to compare the extent of reaction (_t" nuclear waste glasses at various SA/V ratios, Such differences in the SA/V ratio may significantly affect glass durability. 6. An_ytical electron microscopy (AEM), infrared spectroscopy, and nuclear : resonant profiling are being used to assess the glass/water reaction pathway by identil'ying intermediate phases that appear on the reacting glass. Additionally, colloids trom the leach solutions are being studied using AEM.

Novel chemically bonded phosphate ceramics (CBPCs) are being developed and fabricated for low-temperature stabilization and solidification of mixed waste streams which are not amenable to conventional high-temperature stabilization processes due to presence of volatiles such as heavy metal chloride and fluorides and/or pyrophorics in the wastes. Phosphates of Mg, Mg-Na and Z r are being developed as candidate matrix materials. In this paper, we present the fabrication procedures of phosphate waste forms using surrogates compositions of three typical mixed wastes streamsash, cement sludges, and salts. The performance of the final waste forms such as compression strength, leachability of the contaminants, durability in aqueous environment were conducted. In addition, parameteric studies have been conducted to establish the optimal waste loading in a particular binder system. Based on the results, we present potential applications in the treatment of various mixed waste streams.-* Work supported by US. Department of Energy, Office of Technology Development, as part of the Mixed Waste Integrated Program, under Contract W-3 1-109-Eng-38.

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