MAGNOX:BUTEX URANIUM BEARING GLASSES PHYSICAL AND CHEMICAL ANALYSIS DATA PACKAGE (2011)

Sellafield Ltd (United Kingdom) has requested technical support from the Savannah River National Laboratory (SRNL) to characterize a series of uranium-bearing, mixed alkali borosilicate glasses [WFO (2010)]. The specific glasses to be characterized are based on different blends of Magnox (WRW17 simulant) and Butex (or HASTs 1 and 2) waste types as well as different incorporation rates (or waste loadings) of each blend. Specific Magnox:Butex blend ratios of interest include: 75:25, 60:40, and 50:50. Each of these waste blend ratios will be mixed with a base glass additive composition targeting waste loadings (WLs) of 25, 28, and 32% which will result in nine different glasses. The nine glasses are to be fabricated and physically characterized to provide Sellafield Ltd with the technical data to evaluate the impacts of various Magnox:Butex blend ratios and WLs on key glass properties of interest. It should be noted that the use of 'acceptable' in the Work for Other (WFO) was linked to the results of a durability test (more specifically the Soxhlet leach test). Other processing (e.g., viscosity ({eta}), liquidus temperature (T{sub L})) or product performance (e.g., Product Consistency Test (PCT) results - in addition to the Soxhlet leach test) property constraints were not identified. For example, a critical hold point in the classification of an 'acceptable glass' prior to processing high-level waste (HLW) through the Defense Waste Processing Facility (DWPF) is an evaluation of specific processing and product performance properties against pre-defined constraints. This process is referred to as Slurry Mix Evaporator (SME) acceptability in which predicted glass properties (based on compositional measurements) are compared to predefined constraints to determine whether the glass is acceptable [Brown and Postles (1995)]. As an example, although the nominal melter temperature at DWPF is 1150 C, there is a T{sub L} constraint (without uncertainties applied) of 1050 C. Any glass which has a T{sub L} predicted value > 1050 C would be classified as unacceptable and the SME product would not be transferred to the melter. As another example, consider durability (as defined by the PCT test) and its related constraints to determine acceptability. If the glass composition yields predicted normalized release values that exceed those associated with the Environmental Assessment (EA) glass (with uncertainties applied) then the glass is deemed unacceptable. The issue of acceptability plays a critical role in high level waste processing but without knowing the pre-defined constraints for the UK HLW system, assessments of acceptability of the glasses to be characterized in this study can not be made. The results of this study will be compared to DWPF constraints to provide a benchmark for determining acceptability. The objective of this task is to provide Sellafield Ltd. with the technical data to evaluate the impacts of various Magnox:Butex blend ratios and WLs on key glass properties of interest. The uranium bearing glasses span a compositional region of interest to Sellafield Ltd. and were physically characterized for key processing and product performance properties as defined in the WFO [WFO (2010)]. One of the specific technical issues (as defined in the WFO) is the potential impact of increasing aluminum concentrations on key properties (in particular viscosity).