Advances in Geochemical Testing of Key Contaminants in Residual Hanford Tank Waste

Deutsch, William J.; Krupka, Kenneth M.; Cantrell, Kirk J.; Brown, Christopher F.; Lindberg, Michael J.; Schaef, Herbert T.; Heald, Steve M.; Arey, Bruce W.; Kukkadapu, Ravi

doi:10.2172/878278

Cited by 8 publications

(14 citation statements)

References 48 publications

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“…However, the hexagonal, rod-like dissolution pits observed in some of the U-Na-C-O-P±H residual (post-retrieval) particles (see Figure 3.11) are consistent with the possible prior existence of hexagonal, acicular crystals of čejkaite in this post-retrieval residual sludge. The identification of the possible presence of goethite [α-FeO(OH)], maghemite (γ-Fe 2 O 3 ), and the Na uranates clarkeite Na[(UO 2 )O(OH)](H 2 O) 0-1 ] and/or Na 2 U 2 O 7 in the water-leached pre-retrieval waste from tank C-203 (Deutsch et al , 2005) is generally consistent with the Fe oxide and U-Na phases identified by SEM/EDS in the unleached and leached C-202 and C-203 (post retrieval) residual sludges. The pre-retrieval wastes from tanks C-203 and C-204 also contained a significant fraction of amorphous solids as do the residual waste samples characterized in this study.…”

Section: Comparison Of Sem/eds Results For Residual (Post Retrieval) mentioning

confidence: 99%

“…This creates a significant reduction in the background signal over the key actinide atomic mass range (237-239), resulting in instrument limits of quantification in the range of 7.1 pCi/L for 237 Np and 310 pCi/L for 239 Pu. Successful analysis of fusions from tank C-106 residual sludge material using conventional ICP-MS analysis has been documented by Deutsch et al (2005). However, tank C-106 sludge samples contained nearly three orders of magnitude less uranium than sludge samples from tanks C-202 and C-203.…”

Section: Single Contact Sludge Extraction Testsmentioning

confidence: 99%

“…3.71 Analyses by synchrotron-based µXRD indicated the possible presence of goethite [α-FeO(OH)], maghemite (γ-Fe 2 O 3 ), and the Na uranates clarkeite and/or Na 2 U2O 7 in DDI water-leached pre-retrieval waste from tank C-203 (Deutsch et al 2005). A synchrotron focused x-ray beam was used to collect transmission µXRD patterns on several ~5-µm diameter areas of relatively large (approximately 20 to 100 μm) U-and Fe-rich particles identified by microscanning x-ray fluorescence (µSXRF) in the sample of C-203 pre-retrieval waste.…”

Section: C-203 Post-retrieval Residual Sludgementioning

confidence: 99%

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Hanford Tanks 241-C-202 and 241-C-203 Residual Waste Contaminant Release Models and Supporting Data

Deutsch¹,

Krupka²,

Lindberg³

et al. 2007

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SummaryAs directed by Congress, the U.S. Department of Energy (DOE) established the Office of River Protection in 1998 to manage DOE's largest, most complex environmental cleanup project -retrieval of radioactive waste from Hanford tanks for treatment and eventual disposal. Sixty percent by volume of the nation's high-level radioactive waste is stored at Hanford in aging deteriorating tanks. If not cleaned up, this waste is a threat to the Columbia River and the Pacific Northwest.CH2M HILL Hanford Group, Inc. is the Office of River Protection's prime contractor responsible for the storage, retrieval, and disposal of Hanford's tank waste. As part of this effort, CH2M HILL Hanford Group, Inc. contracted with Pacific Northwest National Laboratory (PNNL) to develop release models for key contaminants that are present in residual sludge remaining in Hanford Tanks 241-C-202 (C-202) and 241-C-203 (C-203). The release models were developed from data generated by laboratory characterization and testing of samples from these two tanks. These release models are being developed to support the tank risk assessments performed by CH2M HILL Hanford Group, Inc. for DOE.The contaminant release models developed for these tanks are based on empirical solubility release models. Sludge testing was not successful in identifying minerals in the solids that may be limiting contaminant release; thus, it was not possible to develop mechanistic release models for the residual sludge in these tanks. The empirical release models apply to two different tank scenarios. In the first scenario the tank is filled with a relatively inert material, such as sand, and the leaching solution that contacts sludge in the future is in equilibrium with calcite (CaCO 3 ). Equilibrium with calcite is the typical condition for Hanford vadose zone porewater and groundwater, and Ca 2+ and CO 3 2-/HCO 3 -are the common major cation and anions in solution. Alternatively, the tanks might be filled with a cementitious material, which would produce a Ca(OH) 2 dominated leaching solution while the cement is fresh. As the cement reacts with infiltrating water and ages, it would evolve to resemble the CaCO 3 solution of the first scenario. Empirical solubility release models for the primary contaminants of interest (U, Cr, and 99 Tc) have been developed from laboratory leaching tests of sludge samples using the Ca(OH) 2 and CaCO 3 leaching solutions. Results for 129 I results were below the detection limit.Key results from this work are that future release concentrations from these tanks of the primary contaminants of concern in most cases represent less than 10% of the total contaminant concentration in the sludge. That is, the contaminants are not appreciably soluble in the Ca(OH) 2 and CaCO 3 leaching solutions. For example, the cumulative amount of U leached by the Ca(OH) 2 leaching solution during six sequential stages of leaching represented only 0.13% and 0.11% of the total uranium in tanks C-202 and C-203, respectively. The corresponding percentages of U leached...

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Section: Comparison Of Sem/eds Results For Residual (Post Retrieval) mentioning

confidence: 99%

Section: Single Contact Sludge Extraction Testsmentioning

confidence: 99%

Section: C-203 Post-retrieval Residual Sludgementioning

confidence: 99%

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Hanford Tanks 241-C-202 and 241-C-203 Residual Waste Contaminant Release Models and Supporting Data

Deutsch¹,

Krupka²,

Lindberg³

et al. 2007

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“…Figure 4.3 shows a comparison of the XRD patterns for the 1-month Ca(OH) 2 -and 1-month CaCO 3 -leached samples of C-106 residual waste. Table 4.15 gives a comparison of the XRD and SEM/EDS results for the Ca(OH) 2 -and CaCO 3 -leached samples relative to those from Deutsch et al (2005b) for the C-106 residual waste used as starting material for these leaching tests. Except for the presence of calcite (CaCO 3 ), the phases identified from the XRD patterns for the Ca(OH) 2 -and CaCO 3 -leached samples were also present in the XRD patterns for the C-106 starting material.…”

Section: Xrd Resultsmentioning

confidence: 99%

“…The SEM system is equipped with an Oxford (a) INCA EDS software system that was used for semi-qualitative element analysis. As noted in Deutsch et al (2005b), the JEOL JSM-840 SEM was upgraded in late calendar year 2005 to the Oxford INCA software to automate the collection of EDS spectra over multi-micrometer-size areas of an SEM-imaged sample. This upgrade permits the mapping of the spatial distributions over user-selected areas and/or lines of the relative concentrations of any user-specified element detectable by EDS.…”

Section: Sem/eds Analysismentioning

confidence: 99%

Hanford Tank 241-C-106: Impact of Cement Reactions on Release of Contaminants from Residual Waste

Deutsch¹,

Krupka²,

Lindberg³

et al. 2006

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This document was printed on recycled paper.The cover image shows an SEM micrograph of particles present in tank C-106 residual waste after leaching of the material with a Ca(OH) 2 solution. EDS analysis indicates that the major elements in most of these phases are Ca, Al, Mn, O, and C. Cover design is by S.B. Neely, Pacific Northwest National Laboratory, Richland, Washington. PNNL-15544Hanford Tank SummaryThe CH2M HILL Hanford Group, Inc. (CH2M HILL) is producing risk/performance assessments to support the closure of single-shell tanks at the U.S. Department of Energy's Hanford Site. As part of this effort, staff at Pacific Northwest National Laboratory were asked to develop release models for contaminants of concern that are present in residual sludge remaining in tank 241-C-106 (C-106) after final retrieval of waste from the tank. Initial work to produce release models was conducted on residual tank sludge using pure water as the leaching agent. The results were reported in Deutsch et al. (2005a). One of the options under consideration for closure after waste retrieval is to fill the tanks with a cementitious grout to minimize infiltration and maintain the physical integrity of the tanks. The presence of a cementitious grout above the residual waste may impact contaminant leaching. This report describes testing of the residual waste with a leaching solution that simulates the composition of water passing through a grout and contacting the residual waste at the bottom of the tank.The primary contaminants of concern in the sludge are 99 Tc, 238 U, 129 I, and Cr because of their potential mobility in the environment and the long half-lives of the radionuclides. A key result from this work is that high percentages (≥90%) of these primary contaminants are not readily leachable from the residual waste in contact with pure water or with the cementitious grout simulants. This minimizes their future release to the environment, and is similar to results found in related studies of sludges from tanks AY-102, C-203, and C-204.The simulants selected to represent the solutions that will contact the residual sludge consisted of a 0.01 M Ca(OH) 2 solution and a solution in equilibrium with calcite (CaCO 3 ). The Ca(OH) 2 solution represented fresh grout and the CaCO 3 solution represented aged grout in which calcite had precipitated on the surfaces of the grout and this mineral controlled the major ion composition of the solution in contract with the grout. Laboratory tests were conducted to evaluate the leachability of sludge constituents and to characterize the sludge solid phases before and after leaching. The leaching tests consisted of single-contact batch tests and six stages of sequential batch leaching tests. Solid phase analyses consisted of x-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) analyses to identify reactive phases and estimate their composition.The results of the leaching tests with the grout simulants were compared to the results for the pure water test...

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Hanford tank residual waste – Contaminant source terms and release models

Deutsch

Cantrell

Krupka

et al. 2011

Applied Geochemistry

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Advances in Geochemical Testing of Key Contaminants in Residual Hanford Tank Waste

Cited by 8 publications

References 48 publications

Hanford Tanks 241-C-202 and 241-C-203 Residual Waste Contaminant Release Models and Supporting Data

Hanford Tanks 241-C-202 and 241-C-203 Residual Waste Contaminant Release Models and Supporting Data

Hanford Tank 241-C-106: Impact of Cement Reactions on Release of Contaminants from Residual Waste

Hanford tank residual waste – Contaminant source terms and release models

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