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Enhanced Radionuclide Immobilization and Flow Path Modifications by Dissolution and Secondary Precipitates

Pacific Northwest National Laboratory, P.O. Box 999, MS P7-22, Richland, WA 99354

View larger version (27K): [in a new window]   Fig. 1. Dissolved Si and Al concentrations with time. (a) Quartz samples with and without 0.01 M Al, and the mixed sample (qz and biotite); (b) Warden soil sample with 0.01 M Al.

View larger version (46K): [in a new window]   Fig. 2. (a) X-ray diffraction (XRD) patterns of quartz and the mixed sample after 14 d of reaction (Q, quartz; B, biotite; C, cancrinite; S, sodalite); (b) XRD patterns of reacted quartz as a function of time. Arrows indicate typical peaks of cancrinite. Single mineral nitrate cancrinite was separately synthesized according to Buhl et al. (2000).

View larger version (21K): [in a new window]   Fig. 3. Fourier transform infrared (FTIR) spectra of 30-d reacted quartz.

View larger version (165K): [in a new window]   Fig. 4. Field emission scanning electron microscopy (FESEM) images of secondary precipitates: (a) after 3 d of reaction on quartz surfaces; (b) after 14 d of reaction on quartz surfaces; (c) after 14 d of reaction on mixed sample; (d) cancrinites and analcimes on Warden soil after 22 d of reaction in the middle of the column.

View larger version (25K): [in a new window]   Fig. 5. Changes of (a) Si concentration and (b) Al concentration versus time in flow-through column experiments.

View larger version (191K): [in a new window]   Fig. 6. Computed tomography (CT) scans for quartz columns collected at the middle of the column (40 mm from the inlet). Digitized images (c and d) are shown with different colors (blue, red, and green for black, gray, and white spots, respectively) in a limited square field area (212.1 mm2). (a) Dry column; (b) initial water saturated column; (c) after 8 d of reaction; (d) after 22 d of reaction.

View larger version (201K): [in a new window]   Fig. 7. Computed tomography (CT) scans for quartz column collected from different locations (bottom and top) after 8 and 22 d of reaction. (a) Bottom (20 mm from the inlet) after 8 d of reaction; (b) top (60 mm from the inlet) after 8 d of reaction; (c) bottom (20 mm from the inlet) after 22 d of reaction; (d) top (60 mm from the inlet) after 22 d of reaction.

View larger version (153K): [in a new window]   Fig. 8. Computed tomography (CT) images for mixed (a and b) and Warden soil (c and d) columns collected at the middle of the column after 8 and 22 d of reaction, respectively.