Radiation Effects and Radioactive Waste Management
Research Group

Colloids are particles with dimensions between a nanometer and a micrometer.  Colloids can be mineral fragments, hydrolyzed metal agglomerations, humic or fulvic acids, microbes, or clay or soil fragments: the definition is strictly related to size, not composition.  Because of their high surface area to volume ratios, colloids are extremely surface active and can adsorb contaminants from solution.  Not only can this increase the concentration of the contaminant in solution, but when adsorbed to the colloid the contaminant is present in a potentially highly mobile form.  Indeed, colloids have enhanced subsurface transport of radionuclides at numerous DOE facilities, as well as the Nevada Test Site (NTS), the location of over 800 nuclear explosions and located adjacent to the proposed radioactive waste repository at Yucca Mountain.

We have been using high angle annular dark field high resolution transmission electron microscopy (HAADF-HRTEM) to analyze colloids collected from the groundwater at NTS and have found fissiogenic elements associated with Fe and P phases.

In addition, we are creating colloid suspensions from various Mn and Fe oxide minerals and adsorbing various metals (i.e., Ce, Cs, Sr, Se, and U) onto the colloids.  Using HAADF-STEM we analyze the metal-bearing colloids and hope to discern fundamental knowledge about adsorption of radionuclides.  For instance, does adsorption preferentially occur at surface defect sites, such as kinks, dislocation, or vacancies?.

Publications

Traexler, K. A., and Ewing, R.C. (January 2002) Colloid Formation and the Potential Effects on Radionuclide Transport in a Geologic Repository for Spent Nuclear Fuel.  Department of Energy. (DOE/SNF/REP-070). PDF (9 Mb)