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Geochemical Processes Controlling Migration of Tank Wastes in Hanford's Vadose Zone

^a Pacific Northwest National Lab., P.O. Box 999, MS K8-96, Richland, WA 99354
^b CH2M-HILL Hanford Group, Inc., Richland, WA
^c Fluor Hanford, Richland, WA

View larger version (152K): [in this window] [in a new window]   FIG. 1. The S-SX single-shell tank farm under construction in 1941. Note cranes for scales. The tank bottoms were 16.8 m below ground surface. (From Knepp, 2002a.)

View larger version (53K): [in this window] [in a new window]   FIG. 2. Distribution of sorbed 137Cs+ beneath leaked tanks SX-108, SX-109, and others in S-SX tank farm. Data collected by downhole spectral gamma monitoring through an extensive dry borehole array. Three-dimensional data obtained by kriging. (From Knepp, 2002a.)

View larger version (36K): [in this window] [in a new window]   FIG. 3. North–south geological transect through Hanford's 200A plateau where waste processing facilities and tank farms exist. (From Serne et al., 2004a.)

View larger version (21K): [in this window] [in a new window]   FIG. 4. X-ray diffractograms of the clay-sized fraction (<2.0 µm) isolated from deep vadose zone sediments collected beneath the TX tank farm (borehole C3832). Samples 69 and 104 are from the Hanford formation; sample 110 is from the Cold Creek formation.

View larger version (48K): [in this window] [in a new window]   FIG. 5. Depth distribution of water-extractable ions in sediments beneath leaked single-shell tank SX-115. Note the tank waste front at 45.8 m (150 ft) below ground surface. SX-115 released tank waste of intermediate composition. (From Serne et al., 2002e.)

View larger version (40K): [in this window] [in a new window]   FIG. 6. Digital autoradiography of 90Sr contaminated sediments from borehole 299-E33-46 (Serne et al., 2002a) near tank B-110; 90Sr-containing lithic fragments are white (inverted) or black (not inverted). The backscattered electron (BSE) image shows millimeter-sized lithic fragments (from McKinley et al., 2007).

View larger version (98K): [in this window] [in a new window]   FIG. 7. Chemical composition of 90Sr-containing domains from Fig. 6. All are secondary phyllosilicate domains (saponites-C) with characteristic Mg-zonation. (From McKinley et al., 2007.) P, plagioclase; A, augite, G, glass, C, cmectite; T, titanomagnetite.

View larger version (73K): [in this window] [in a new window]   FIG. 8. Distribution of Cs+ within muscovite collected from Hanford's S-SX tank farm as measured by synchrotron X-ray fluorescence. Cesium is strongly localized at selected regions on the crystallite edge. (From Liu et al., 2003.)

View larger version (153K): [in this window] [in a new window]   FIG. 9. Secondary feldspathic precipitates resulting from the reaction of Na+/NO3–/OH– tank waste simulant with Hanford sediment. The dissolution of primary aluminosilicates and reprecipitation of various secondary phases neutralizes the high pH of tank waste. (From Qafoku et al., 2003.) Reproduced with permission from Environ. Sci. Technol. 2003. 37:3640–3646. Copyright 2003 American Chemical Society.

View larger version (64K): [in this window] [in a new window]   FIG. 10. (a) X-ray absorption near edge structure (XANES) spectra of Cr-contaminated sediment from SX-108 borehole C3082 where the height of the pre-edge feature is proportional to the Cr(VI) content. (From Zachara et al., 2004.) (b) Synchrotron X-ray fluorescence map of SX-108 sediment 7A, overlain on a backscattered electron micrograph. Cr concentration increases from green to red.

View larger version (10K): [in this window] [in a new window]   FIG. 11. Adsorption measured by distribution coefficient (Kd) of 1 µmol L–1 U(VI) on 1 mmol L–1 of ferrihydrite, one of the most important subsurface sorbents of uranium. (From Davis et al., 2004.)

View larger version (22K): [in this window] [in a new window]   FIG. 12. (a) Adsorption of µmol L–1 U(VI) on a calcite-containing, deep vadose zone sediment (100 g L–1) from Hanford's 200A plateau (S-SX tank farm) = untreated sediment; = sediment with calcite removed. (b) Computed aqueous speciation of U(VI) in calcite-saturated 0.05 mol L–1 NaNO3. (From Dong et al., 2005.) Reproduced with permission from Environ. Sci. Technol. 2005. 39:7949–7955. Copyright 2005 American Chemical Society.

View larger version (38K): [in this window] [in a new window]   FIG. 13. Derived (Dil. Cor.) and actual (UFA) pore water composition of mobile metals in borehole C4104 collected near T-106. The leading edge of the tank waste plume is defined by 99Tc. (From Serne et al., 2004b.)

View larger version (132K): [in this window] [in a new window]   FIG. 14. Scanning electron micrograph of radiation-resistant bacteria Deinoccus radiodurans isolated from sediments collected from beneath leaked single-shell tank SX-108.