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In early October 2006, the Liquid Waste Organization (LWO) began to consider decanting Tank 40 at the end of Sludge Batch 3 (SB3) processing and transferring the aqueous phase from the decant to Tank 51. This transfer would be done to decrease Tank 51 yield stress and facilitate the transfer of the contents of Tank 51 to Tank 40. The projected composition of Sludge Batch 4 (SB4) was adjusted by LWO to reflect the impact of the Tank 40 decant leading to new projected compositions for SB4, designated as the 10-04-06 and the 10-10-06 compositions. A comparison between these SB4 compositions and those provided in June 2006 indicates that the new compositions are slightly higher in Al2O3, Fe2O3, and U3O8 and slightly lower in SiO2. The most dramatic change, however, is the new projection's Na2O concentration, which is more than 4.5 wt% lower than the June 2006 projection. This is a significant change due to the frit development team's approach of aligning the Na2O concentration in a candidate frit to the Na2O content of the sludge. This approach enhances the projected operating window and the waste throughput potential for the resulting glass system while eliminating the potential for nepheline crystallization. Nepheline can have a detrimental impact on durability. Questions surfaced regarding the applicability of Frit 503 to these revised compositions since the Savannah River National Laboratory (SRNL) recommended Frit 503 for use with SB4 based on the June 2006 compositional projection without the Tank 40 decant. Based on the paper study assessments, the change in SB4's expected Na2O content had a significant, negative impact on the projected operating window for the Frit 503/SB4 glass system. While Frit 418 had slightly smaller waste loading (WL) intervals for the June 2006 SB4 projections as compared to Frit 503 and the Frit 418 glass systems were nepheline limited, Frit 418 had a slightly larger operating window for the 10-04-06 projection (as compared to Frit 503) and the Frit 418/10-04-06 glass system was no longer nepheline limited. Thus, strictly from the perspective of this paper study, Frit 418 was more attractive than Frit 503 for the new SB4 projected compositions. This comparison, however, does not reflect other aspects of interest for the glass systems such as their respective melt rates or the development of alternative frits to balance the projected operating windows, melt rate, waste throughput, and robustness to compositional variation. In discussions with Waste Solidification Engineering (WS-E) regarding the results being presented in this report, their decision was to utilize Frit 418 for initial processing of SB4. This decision was not only based on the paper study assessments presented in this report, but also on the fact that Frit 418 is currently being used to process SB3 and, perhaps more importantly, frit optimization efforts for SB4 may be premature given the uncertainties in tank transfer and heel volumes associated with the SB4 flowsheet. More specifically, WS-E indicated their plan to initiate processing with Frit 418 with subsequent authorization for the frit development team to optimize a frit based on the measured composition of SB4 after determination of the actual SB4 blend composition (i.e., both the SB3 and SB4 compositions and masses are known). Given this decision and recognizing that a SB4/Frit 503 variability study had been initiated as part of the qualification process, questions regarding the need for a supplemental variability study to demonstrate applicability of the process control models for a Frit 418 based system surfaced. This report addresses the need for a supplemental study and defines additional glasses to fill the compositional gaps. A total of 13 glasses (based on the 10-10-06 projection) were selected for the supplemental SB4/Frit 418 variability study. These glasses will be batched and melted following standard SRNL procedures, and a suite of characterization testing will be completed to measure the chemical durability of each glass composition

SLUDGE BATCH 4 (SB4) AFTER A TANK 40 DECANT: CANDIDATE FRITS, MAR ASSESSMENTS, AND GLASSES FOR A VARIABILITY STUDY