The purpose of this study was to review historical rheology data for radioactive Savannah River Site (SRS) wastes from storage tanks through to the melter feeds in the Defense Waste Processing (DWPF) facility. SRS wastes were generated from either the Purex (high iron) or HM (high aluminum) processes. The available rheological data for SRS wastes were then compared to any historical simulant data for equivalent SRS wastes. The comparisons were accomplished by initially obtaining all available radioactive rheology data for sludge, Sludge Receipt and Adjustment Tank (SRAT) product, and Slurry Mix Evaporator (SME) tank product (equivalent to DWPF melter feed). These data were grouped as sludges, SRAT products, or SME products. The data within each group were then subdivided to reflect individual waste tanks or DWPF sludge batches, e.g. Tank 8 sludge or Sludge Batch 1B SRAT product. The comparability of a simulant and a radioactive waste was assessed primarily by the value of the Bingham Plastic model yield stress at equivalent weight % insoluble solids content. Values within 20-30% were considered to be giving "good agreement". Values different by a factor of two or more were considered to be giving "poor agreement". Intermediate cases were rated as "fair agreement". Rheological data for Purex sludges indicated good to fair agreement between real and simulant waste. The presence of HM sludge mixed with Purex sludge gave fair to poor agreement. Similar results were seen for SME products. There is insufficient SRAT product data to make a comparable conclusion. The differences between Tank 8 and Tank 40 sludges used to prepare Sludge Batch 2 also manifested as rheological differences. Similarly, Tank 40 simulant had an order-of-magnitude higher yield stress than Tank 8 simulant. Tank 8 simulant had good agreement with Tank 8 waste rheology. The Tank 8/40 blend that became sludge batch 2 (SB2), however, did not have good agreement in rheology. The implication is that real Tank 40 waste was more viscous than simulant Tank 40 waste, even though simulant Tank 40 waste had ten times the yield stress of both real and simulated Tank 8 waste. Large differences in yield stress in real waste tanks were seen in the work of B.A. Hamm. The main difference there was driven by waste type, Purex vs. HM. HM gave the higher yield stresses. Tank 8 was Purex, while Tank 40 contained a blend.

A study was undertaken to identify and clarify examples of unusual rheological behavior in Defense Waste Processing Facility (DWPF) simulant slurry samples. Identification was accomplished by reviewing sludge, Sludge Receipt and Adjustment Tank (SRAT) product, and Slurry Mix Evaporator (SME) product simulant rheological results from the prior year. Clarification of unusual rheological behavior was achieved by developing and implementing new measurement techniques. Development of these new methods is covered in a separate report, WSRC-TR-2004-00334. This report includes a review of recent literature on unusual rheological behavior, followed by a summary of the rheological measurement results obtained on a set of unusual simulant samples. Shifts in rheological behavior of slurries as the wt. % total solids changed have been observed in numerous systems. The main finding of the experimental work was that the various unusual DWPF simulant slurry samples exhibit some degree of time dependent behavior. When a given shear rate is applied to a sample, the apparent viscosity of the slurry changes with time rather than remaining constant. These unusual simulant samples are more rheologically complex than Newtonian liquids or more simple slurries, neither of which shows significant time dependence.

No abstract

No abstract

No abstract