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Fox, K

Publications and source records attributed to Fox, K.

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DOE OSTI2010

MELT RATE TESTING FOR SLUDGE BATCH 6

The Savannah River National Laboratory (SRNL) was requested to provide Savannah River Remediation (SRR) with a recommended frit composition for Sludge Batch 6 (SB6) to optimize processing at the Defense Waste Processing Facility (DWPF). This report discusses the results of a series of melt rate experiments that were completed in support of the frit recommendation and the preparation of the feed used in the testing. The objective of the work was to identify the impact of individual frit component concentrations on melt rate for both SB6 and for DWPF sludge batches in general. The dry fed, Melt Rate Furnace (MRF) was used to compare the relative melt rate performance of several candidate frit compositions. Sludge composition projection changes and variation led to the fabrication and testing of several new frits along with Frit 418, which is currently utilized at the DWPF for Sludge Batch 5 (SB5) processing. The melt rate testing results show that changes in the frit composition, such as increases in B{sub 2}O{sub 3} or Li{sub 2}O concentrations, can provide a faster melt rate for SB6 relative to Frit 418. However, the composition of SB6 as currently projected (February 2010 blended with a 40 inch heel of SB5) does not allow for significant changes in frit composition relative to Frit 418 without compromising the projected operating windows. Only one of the new frits tested, Frit IS7, remains viable for SB6 processing based on the current composition projections. The melt rate results also demonstrated that a low Na{sub 2}O concentration frit (particularly Frit IS7) can provide reasonable melt rates if the concentrations of Li{sub 2}O or B{sub 2}O{sub 3} in the frit are increased. The measured melt rate for Frit IS7 with the simulated SB6 feed was about 15% faster than that for Frit 418. The projected operating windows for Frits 418 and IS7 are very similar with the current SB6 projections. However, waste loadings with Frit IS7 are limited by low viscosity predictions, while waste loadings with Frit 418 are limited by predictions of nepheline crystallization. It is recommended that SRNL reevaluate the final SB6 composition once washing and blending are complete to determine whether a change in frit composition could provide improved operating windows, improved sulfate solubility, and/or increased waste throughput.

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DOE OSTI2010

FRIT DEVELOPMENT FOR SLUDGE BATCH 6

The Savannah River National Laboratory (SRNL) evaluated a large number of Sludge Batch 6 (SB6) composition projections to support frit optimization for SB6 vitrification at the Defense Waste Processing Facility (DWPF). The evaluations discussed in this report occurred over a period of about 4 months, and included about 40 composition projections, developed by both Savannah River Remediation (SRR) and SRNL. Paper study assessments were used to evaluate the sludge composition projections with arrays of potential frit compositions using the predictive models in the DWPF Product Composition Control System (PCCS). Both nominal sludge compositions and sludge compositions with anticipated compositional variation were considered. The model predictions were used to identify candidate frit compositions for each SB6 projection and to provide some guidance to SRR on washing and blending strategies for SB6 preparation. This report presents a chronological review of this process and summarizes the findings at each stage. Following initial feedback from this work, the number of washes in Tank 51 was reduced to increase the projected sodium concentration in SB6. Analyses of predicted frit performance before and after a potential decant of Tank 40 showed that the post-decant SB6 composition would be difficult to process with any frit composition and that this scenario should be avoided. Based on the most recent SB6 projections (February 2010 SB6 composition projections developed at SRNL using the measured SB6 qualification sample composition and the revised Tank Farm washing plan), Frit 418 appears to be viable for SB6 processing at a target waste loading of 36%. A Nominal Stage PCCS Measurement Acceptability Region (MAR) assessment gave projected operating windows of 25-41% waste loading, limited by predictions of nepheline crystallization. The projected operating window is reduced to 25-38% waste loading when anticipated compositional variation is considered, again limited by predictions of nepheline crystallization. Blend points between 62 and 40 inches of Sludge Batch 5 (SB5) heel in Tank 40 had no practical impact on the projected performance of Frit 418. This assessment is made from a paper study approach only and assumes that no decant of Tank 40 will occur during SB6 processing. A decant of Tank 40 would reduce the Na2O concentration in Tank 40 to a point where it would be very difficult to target a waste loading of 36% for SB6 with Frit 418. The performance of Frit 418 with SB6 is limited by predictions of nepheline crystallization, which is a durability limiting constraint. Alternatives to Frit 418 are available that can provide equivalent projected operating windows and are limited by process related constraints (i.e., liquidus temperature predictions) rather than durability limiting constraints. A separate memorandum has recently been issued that discusses the use of Frit 418 for SB6 vitrification.1 potential differences in melt rate among these alternative frits will be discussed in a forthcoming technical report.

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