Determination of the Effect of Uranium Levels on Sludge Batch 2 Processing

Herman, D.T.

doi:10.2172/820575

Cited by 2 publications

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“…Rheological measurements were not made on, nor a sample pulled, at the minimum pH point of the SRAT cycle due to the smaller scale of these SRAT cycles than those in previous work 5 . Measurements were made with a viscosity standard to ensure that the rheometer was performing within expected limits.…”

Section: Rheologymentioning

confidence: 94%

“…The soluble uranium in the feeds was negligible, but due to refinement of the detection limits since the initial data given in Table 2-2, the level was measurable, on the order of 1-3 ppm. Previous work 5 had an actual U range from zero to 11.4 wt %, also below the target values, but soluble U levels in the starting feeds were not measured.…”

Section: Chemical Characterizationmentioning

confidence: 97%

“…The 15 wt % level represented a high concentration to determine if increasing the content of uranium impacts simulant properties during Chemical Processing Cell (CPC) processing. The initial work conducted in this area indicated the 0-15 wt % interval may have bracketed the range of uranium content that adversely impacts the physical properties of the slurry 5 . In light of this, two additional uranium levels were included in this study to better understand this phenomenon.…”

Section: Simulant Preparationmentioning

confidence: 99%

“…Samples used a series of uranium levels in a simulant of SB2. The samples with different uranium contents were compared with each other before and after undergoing a simulated SRAT cycle process.Documented in this report are:• Preparation and evaluation of SB2 simulants containing a series of depleted uranium concentrations.• Demonstration of the DWPF SRAT process using SB2 based simulants with varying levels of uranium.• Rheological properties of uranium containing SB2 simulants before and after SRAT processing.• Comparison of the rheology with other SB2 simulants.• Resolution of several issues raised in the previous work with uranium 5 .a Note: Batch 208 was actually the first batch of SB2. …”

mentioning

confidence: 99%

“…The titrations were performed with the SRNL Shielded Cells protocol using a 20 -30 g sample with 1 mL additions of acid, mixing for three minutes, followed by a pH reading. No attempt was made to address the rate of acid addition issues raised in the previous study 5 , since these are being addressed in other ongoing studies. Table 2-10 summarizes the pH measurements and the titration data measurements for the best two of three titrations.…”

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confidence: 99%

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Impact of Uranium Levels ON Sludge Batch 2 Simulant Processing

Bannochie¹

2004

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EXECUTIVE SUMMARYThis study was conducted to address in part whether uranium contributes significantly to processing issues in the Defense Waste Processing Facility. The processing observations for Sludge Batch 2 (SB2) included the ability to transfer process slurries and feed the melter, difficulty maintaining heat transfer in the Slurry Mix Evaporator, and degradation of the operation of the melter. The Savannah River National Laboratory (SRNL) conducted small-scale tests designed to determine the effect of different levels of uranium on sludge processing at the same redox and stoichiometric factor, 0.20 and 130% respectively. Samples used a series of uranium levels, co-precipitated during sludge makeup, in a simulant of SB2. The samples with the different uranium contents were characterized and compared with each other before and after a simulated SRAT cycle process.The following observations and conclusions were drawn from this study.• Co-precipitation of U during simulant sludge makeup results in the formation of Clarkeite, Na((UO 2 )O(OH)), a hydrated uranate containing U(VI), as the final uranium species. This same species has been identified in actual tank waste for SB2.• There is no increase in calculated acid demand at room temperature as a result of increasing levels of U in SRAT feed. Whether or not there is an impact on acid demand at elevated temperature or in the presence of mixed acids has not been addressed.• Essentially no soluble U was found in the SRAT products with pH values above pH 6. This is consistent with observations from SRNL Shielded Cells SRAT cycles with SB2/3 blended waste 17 and SB3 waste 18 which did see soluble U in the SRAT products but which had final pH's below 6. Since DWPF operated SB2 processing at approximately pH 5.5, they should have seen more soluble U and potentially thinner SRAT products.• Different U species can be produced in the SRAT product suggesting the potential for some U redox activity. The primary species, U 2 O 7 2-contained fully oxidized U(VI), while one product contained the mixed U oxidation state species U 3 O 9 2-. The impact of redox target on the SRAT product U species could not be addressed since only a single redox target was studied.• XRD data suggests there was some dissolution and re-precipitation of U as a result of SRAT processing since the SRAT product U-containing species were fine and not fully crystalline.• SRAT vessel contents entrain gas and the volume increases during processing when the temperature is raised from 93 to 100 °C, and the degree of expansion is greatest at the highest levels of U (Batches 11.25 and 15).• All six sludges and seven SRAT products were thixotropic slurries, i.e. the apparent viscosity decreased with time under shear on a time scale of ten minutes. This produced down ramp flow curves that were always below the up ramp flow curves.• The six sludges and seven SRAT products were generally pseudo-plastic slurries, i.e. the apparent viscosity decreased with increasing shear rate. There were some transient phenome...

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Section: Rheologymentioning

confidence: 94%

Section: Chemical Characterizationmentioning

confidence: 97%

Section: Simulant Preparationmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Impact of Uranium Levels ON Sludge Batch 2 Simulant Processing

Bannochie¹

2004

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A Comparison of Rheology Data for Radioactive and Stimulant Savannah River Site Waste

Koopman¹

2004

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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.

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Determination of the Effect of Uranium Levels on Sludge Batch 2 Processing

Cited by 2 publications

References 1 publication

Impact of Uranium Levels ON Sludge Batch 2 Simulant Processing

Impact of Uranium Levels ON Sludge Batch 2 Simulant Processing

A Comparison of Rheology Data for Radioactive and Stimulant Savannah River Site Waste

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