SUMMARYGlass-ceramic waste form development began in fiscal year (FY) 2010 by examining two combined waste stream options: Option 1) alkali/alkaline earth (CS) + lanthanide (Ln); and Option 2) + transition metal (TM) fission-product waste streams generated by the uranium extraction separations process. Glass ceramics were successfully developed for both options; however, Option 2 was selected over Option 1 at the conclusion of 2010, because Option 2 immobilized all three waste streams with only a minimal decrease in waste loading.During the first year, a series of three glass ceramics (Option 2) were fabricated that varied waste loading ([WL] 42, 45, and 50 mass%) at fixed molar ratios of CaO/MoO 3 and B 2 O 3 /alkali both at 1.75. These glass ceramics were slow-cooled and characterized in terms of phase assemblage and preliminary irradiation stability.This FY, further characterization was performed on the FY 2010 Option 2 glass ceramics in terms of static leach testing, phase analysis by transmission electron microscopy, and irradiation stability (electron and ion). In addition, a new series of glass ceramics were developed for Option 2 that varied the additives: Al 2 O 3 (0-6 mass%), molar ratio of CaO/MoO 3 and B 2 O 3 /alkali (1.75-2.25), and waste loading (50, 55, and 60 mass%). Phase-pure powellite and oxyapatite were then synthesized for irradiation studies.Results from this FY study showed compositional flexibility, chemical stability, and radiation stability in the current glass-ceramic system. First, the phase assemblages and microstructure of all of the FY 2010 and FY 2011 glass ceramics are very similar when subjected to the slow-cool heat treatment. The phases identified in these glass ceramics were oxyapatite, powellite, cerianite, and Ln-borosilicate. This shows that variations in waste loading or additives can be accommodated without drastically changing the phase assemblage of the waste form, thus making the processing and performance characteristics of the waste form more predictable/flexible. However, in the future, the glass phase still needs to be accurately characterized to determine the effects of waste loading and additives on the glass structure. Initial investigations show a borosilicate glass phase rich in silica.Second, the normalized concentrations of elements leached from the waste form during static leach testing were all below 0.6 g/L after 28 days at 90°C, by the product consistency test method B. These normalized concentrations are comparable to chemically durable waste glasses such as the low-activity reference material glass (Ebert and Zyryanov 2000). The release rates for the crystalline phases (oxyapatite and powellite) appear to be lower (more durable) than the glass phase based on the relatively low release rates of Mo, Ca, and Ln found in the crystalline phases compared to Na and B that are mainly observed in the glass phase. However, further static leach testing on individual crystalline phases is needed to confirm this statement.Third, ion irradiation and in situ trans...