Cation exchange reactions controlling desorption of 90Sr2+ from coarse-grained contaminated sediments at the Hanford site, Washington

McKinley, James P.; Zachara, John M.; Smith, Steven C.; Liu, Chongxuan

doi:10.1016/j.gca.2006.09.027

Cited by 47 publications

(56 citation statements)

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“…The behaviour of Sr is characterised by reversible ion exchange which is similar to the behaviour of Sr-90 in radioactively contaminated sediments elsewhere [2]. The exchanger phase in the Dounreay Shore Formation is most probably corrensite (mixed-layer smectite-chlorite) present in the bulk rock matrix.…”

Section: Model Inputsupporting

confidence: 54%

Understanding Radionuclide Migration From the D1225 Shaft, Dounreay, Caithness, UK

et al. 2009

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A 65 m vertical shaft was sunk at Dounreay in the 1950s to build a tunnel for the offshore discharge of radioactive effluent from the various nuclear facilities then under construction. In 1959, the Shaft was licensed as a disposal facility for radioactive wastes and was routinely used for the disposal of ILW until 1970. Despite the operation of a hydraulic containment scheme, some radioactivity is known to have leaked into the surrounding rocks. Detailed logging, together with mineralogical and radiochemical analysis of drillcore has revealed four distinct bedding-parallel zones of contamination. The data show that Sr-90 dominates the bulk beta/gamma contamination signal, whereas Cs-137 and Pu-248/249 are found only to be weakly mobile, leading to very low activities and distinct clustering around the Shaft. The data also suggest that all uranium seen in the geosphere is natural in origin. At the smaller scale, contamination adjacent to fracture surfaces is present within a zone of enhanced porosity created by the dissolution of carbonate cements from the Caithness flagstones during long-term rockwater interactions. Quantitative modelling of radionuclide migration, using the multiphysics computer code QPAC shows the importance of different sorption mechanisms and different mineralogical substrates in the Caithnesss flagstones in controlling radionuclide migration.

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Section: Model Inputsupporting

confidence: 54%

Understanding Radionuclide Migration From the D1225 Shaft, Dounreay, Caithness, UK

et al. 2009

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“…In fact, acid extraction has been used to remove 90 Sr for measurement (McKinley et al 2007). Sorption coefficients have not been found in the literature for pH values as low as what was calculated for the assumed FRG canister waste chemistry, although experimental data do show a marked decrease in cesium and strontium sorption on clays at pH values between 2 and 3 (Papelis and Um 2003).…”

Section: Ion-exchange Reactionsmentioning

confidence: 99%

“…Selectivity coefficients were not directly measured for this study, but a number of other studies have been performed with Hanford sediments to determine selectivity coefficients for exchange reactions involving Sr 2+ and Cs + . For example, McKinley et al (2007) reported selectivity coefficients for exchange reactions involving Sr 2+ that were estimated by fitting experimental data (Lichtner and Zachara 2005). Zachara et al (2002) and Liu et al (2004) developed different models and associated parameters describing Cs + sorption in Hanford sediments.…”

Section: Ion-exchange Reactionsmentioning

confidence: 99%

“…Based on these considerations, an intermediate value between the strong (K v I ) and weak (K v II ) sorption site selectivity coefficients reported by Liu et al (2004) was used to represent Cs-Na exchange. The selectivity coefficients reported by McKinley et al (2007) were used to represent Sr 2+ and exchange reactions for other major cations. These parameters are summarized in Section 3.2.3 of this report.…”

Section: Ion-exchange Reactionsmentioning

confidence: 99%

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Numerical Modeling of 90Sr and 137Cs Transport from a Spill in the B-Cell of the 324 Building, Hanford Site 300 Area

Rockhold¹,

Bacon²,

Freedman³

et al. 2012

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SummaryIn October 1986, a spill of a highly radioactive waste stream containing cesium ( 137 Cs) and strontium ( 90 Sr) occurred in the B-Cell of the 324 Building in the 300 Area of the Hanford Site. The spill is estimated to have contained approximately 1.3 million curies of radioactivity. An unknown fraction of this spill was lost to the subsurface through a leak in the sump in the floor of B-Cell.To characterize the extent of contamination under the 324 Building, a pit was excavated on the north side of the building in 2010 by Washington Closure Hanford LLC (WCH). Horizontal closed-end steel access pipes were installed under the foundation of the building from this pit and were used for measuring temperatures and exposure rates under the B-Cell. The deployed sensors measured elevated temperatures of up to 61 °C (142 °F) and exposure rates of up to 8,900 R/hr. WCH suspended deactivation of the facility because it recognized that building safety systems and additional characterization data might be needed for remediation of the contaminated material. The characterization work included additional field sampling, laboratory measurements, and numerical flow and transport modeling.Laboratory measurements of sediment physical, hydraulic, and geochemical properties were performed by Pacific Northwest National Laboratory (PNNL) and others. Geochemical modeling and subsurface flow and transport modeling also were performed by PNNL to evaluate the possible extent of contamination in the unsaturated sand and gravel sediments underlying the building. Historical records suggest that the concentrated 137 Cs-and 90 Sr-bearing liquid wastes that were spilled in B-Cell were likely from a glass-waste repository testing program associated with the Federal Republic of Germany (FRG). Incomplete estimates of the aqueous chemical composition (no anion data provided) of the FRG waste solutions were entered into a geochemical speciation model and were charge balanced with nitrate to estimate waste composition. Additional geochemical modeling was performed to evaluate reactions of the waste stream with the concrete foundation of the building prior to the stream entering the subsurface.One-dimensional (1-D) and three-dimensional (3-D) flow and transport simulations were performed using the STOMP simulator. Vertically oriented 1-D reactive transport simulations were conducted for three different water release scenarios using a reaction network that considered aqueous speciation, ion exchange, and mineral precipitation and dissolution reactions. The 1-D simulations were performed to evaluate the potential influence of waste chemistry and ion-exchange processes on vertical radionuclide transport for a range of possible water release rates. Three-dimensional simulations were also performed using a linear adsorption isotherm (K d ) model to provide estimates of the possible extent of contamination in both the vertical and lateral directions underlying the B-Cell. K d values in the 3-D model were adjusted, although not optimized, to obtain im...

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“…Natural minerals that contain uranium include betafite C [Ca 0.92 U 1.08 (Ti 2 O 7 )], most likely from granitic clasts commonly found in Hanford Site sediments (15% to 35% [Zachara et al 2007] (Finch and Murakami 1999;Liu et al 2004). Uranium and plutonium enrichment processes at the Hanford Site have resulted in the release of 202,703 kg of uranium to the ground surface (Simpson et al 2006) in a variety of aqueous solutions (acidic, basic, with organic complexants [citrate, ethylenediaminetetraacetic acid]) and inorganic ligands (CO 3 , PO 4 ), which would influence the uranium migration behavior.…”

Section: Uranium Mobility In the Hanford Site Vadose Zonementioning

confidence: 99%

Remediation of Uranium in the Hanford Vadose Zone Using Gas-Transported Reactants: Laboratory Scale Experiments in Support of the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau

Szecsody¹,

Truex²,

Zhong³

et al. 2010

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This laboratory-scale investigation focused on decreasing uranium mobility in subsurface contaminated sediments in the vadose zone by in situ geochemical manipulation at low water content. This geochemical manipulation of the sediment surface phases included reduction, pH change (acidic and alkaline), and additions of chemicals (phosphate and ferric iron) to form specific precipitates. Reactants were advected into one-dimensional columns packed with uranium-contaminated sediment from the 200 Area of the Hanford Site as a reactive gas (for CO 2 , NH 3 , H 2 S, SO 2 ), with a 0.1% water content mist [for NaOH, Fe(III), HCl, PO 4 ] and with a 1% water content foam (for PO 4 ).Uranium is present in the sediment in multiple phases that include (in decreasing mobility) the following: aqueous U(VI) complexes, adsorbed uranium, reduced U(IV) precipitates, rind-carbonates, total carbonates, oxides, silicates, and phosphates. Geochemical changes were evaluated in the ability to change the mixture of surface uranium phases to less mobile forms, as defined by a series of liquid extractions that dissolve progressively less soluble phases. Although liquid extractions provide some useful information as to the generalized uranium surface phases (and are considered operational definitions of extracted phases), positive identification of surface phase changes by electron microprobe analysis is in progress. Some of the changes in uranium mobility directly involve uranium phases, whereas other changes result in precipitate coatings on uranium surface phases. The long-term implication of the uranium surface phase changes to alter uranium mass mobility in the vadose zone was then investigated using simulations of one-dimensional infiltration and downward migration of six uranium phases to the water table.In terms of the short-term decrease in uranium mobility (in decreasing order), NH 3 , NaOH mist, CO 2 , HCl mist, and Fe(III) mist showed 20% to 35% change in uranium surface phases. Difference in treatment effectiveness between sediments likely reflects mineralogy. Phosphate addition (mist or foam advected) showed inconsistent change in aqueous and adsorbed uranium, but significant coating (likely phosphates) on uranium carbonates. The two reductive gas treatments (H 2 S and SO 2 ) showed little change. For long-term decrease in uranium reduction, mineral phases created that had low solubility (phosphates and silicates) were desired, so NH 3 , phosphates (mist and foam delivered), and NaOH mist showed the greatest formation of these minerals. In addition, simulations of uranium movement in the vadose zone showed that these treatments greatly decreased uranium transport to groundwater. Advection of reactive gasses was the easiest to implement into low water content sediments at the laboratory-scale (and presumably field-scale) experiments. Both mist and foam advection show potential and need further development, but current implementation techniques move reactants shorter distances relative to reactive gasses. Overall, the am...

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Cation exchange reactions controlling desorption of 90Sr2+ from coarse-grained contaminated sediments at the Hanford site, Washington

Cited by 47 publications

References 45 publications

Understanding Radionuclide Migration From the D1225 Shaft, Dounreay, Caithness, UK

Understanding Radionuclide Migration From the D1225 Shaft, Dounreay, Caithness, UK

Numerical Modeling of 90Sr and 137Cs Transport from a Spill in the B-Cell of the 324 Building, Hanford Site 300 Area

Remediation of Uranium in the Hanford Vadose Zone Using Gas-Transported Reactants: Laboratory Scale Experiments in Support of the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau

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