Sludge Batch 3 Qualification in the SRTC Shielded Cells

Pareizs, J.M.

doi:10.2172/827479

Cited by 12 publications

(19 citation statements)

References 6 publications

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“…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.…”

supporting

confidence: 90%

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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supporting

confidence: 90%

Impact of Uranium Levels ON Sludge Batch 2 Simulant Processing

Bannochie¹

2004

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“…As with the SB3 Qualification sample, appreciable soluble uranium was found in the SRAT product 1 . Initially this level of soluble uranium was believed to not have been previously observed, but we now believe it may be that it was not commonly measured or when it was measured, the final SRAT product pH was above 6 and appreciable soluble U was not produced.…”

Section: Recommendations/path Forwardmentioning

confidence: 71%

“…High levels of soluble uranium were also found in the SB3 Qualification SRAT product 1 and initially attributed to the plutonium and neptunium streams added to the waste. It turns out that the vast majority of this freshly precipitated uranium comes from the Am/Cm stream added to Tank 51 prior to sampling for qualification 21 ; roughly 9% of the total uranium in SB3.…”

Section: Srat Cycle Product Characterizationmentioning

confidence: 95%

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Sludge Batch 2/3 Blend SRAT Cycle in the SRNL Shielded Cells

Bannochie¹

2004

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“…Recently a campaign in the Shielded Cells of SRNL has shown that this is the case in the SRAT and SME for Sludge Batch 3 (SB3). [2] Studies with nonradioactive sludges prepared to simulate the final composition of SB3 were also used to support processing SB3. [3] Approximately two years are usually required for the SRS Closure Business Unit (CBU) to prepare a sludge batch by blending and washing sludges from selected tanks to form a final sludge batch.…”

Section: Introductionmentioning

confidence: 99%

Measuring and Predicting Fission Product Noble Metals in SRS HLW Sludges

Bibler¹

2005

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EXECUTIVE SUMMARYThe noble metals Ru, Rh, Pd, and Ag were produced in the Savannah River Site (SRS) reactors as products of the fission of U-235. Consequently they are in the High Level Waste (HLW) sludges that are currently being immobilized into a borosilicate glass in the Defense Waste Processing Facility (DWPF). The noble metals are a concern in the DWPF because they catalyze the decomposition of formic acid used in the process to produce the flammable gas hydrogen. As the concentration of these noble metals in the sludge increases, more hydrogen will be produced when this sludge is processed.a In the SRS Tank Farm it takes approximately two years to prepare a sludge batch for processing in the DWPF. This length of time is necessary to mix the appropriate sludges, blend them to form a sludge batch and then wash it to enable processing in the DWPF. This means that the exact composition of a sludge batch is not known for ~two years. During this time, studies with simulated nonradioactive sludges must be performed to determine the desired DWPF processing parameters for the new sludge batch. Consequently, prediction of the noble metal concentrations is desirable to prepare appropriate simulated sludges for studies of the DWPF process for that sludge batch. These studies give a measure of the amount of hydrogen that will be produced when that sludge batch is processed. This report describes in detail the measurement of these noble metal concentrations in sludges and a way to predict their concentrations from an estimate of the lanthanum concentration in the sludge. Results for two sludges are presented in this report. These are Sludge Batch 3 (SB3) currently being processed by the DWPF and a sample of unwashed sludge from Tank 11 that will be

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Sludge Batch 3 Qualification in the SRTC Shielded Cells

Cited by 12 publications

References 6 publications

Impact of Uranium Levels ON Sludge Batch 2 Simulant Processing

Impact of Uranium Levels ON Sludge Batch 2 Simulant Processing

Sludge Batch 2/3 Blend SRAT Cycle in the SRNL Shielded Cells

Measuring and Predicting Fission Product Noble Metals in SRS HLW Sludges

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