PULLMAN, Wash. — Markus Flury, Washington State University professor of soil physics, and Jim Harsh, WSU professor of soil chemistry, and colleagues from the Pacific Northwest National Laboratory in Richland, the Los Alamos National Laboratory in New Mexico, and the Idaho National Laboratory in Idaho Falls, have received a three-year $1 million grant from the U.S. Department of Energy to continue research on the fate of radioactive waste that has leaked from underground tanks into the soil.
WSU, the lead institution in the project, will receive $478,000 while the balance will be divided among the collaborating agencies.
The project will focus on development of a defensible conceptual model for long-term colloid mobilization and colloid-facilitated transport of radioactive waste in the semi-arid vadose zone at the Hanford site in Washington State.
The vadose zone is the zone between the soil surface and the water table that is unsaturated or partially saturated. Colloids are soil or sediment particles smaller than about 10 micrometers in diameters. They may speed the movement of Cesium-137 and other radionuclides.
“The importance of this work is to understand the basic mechanism of how contaminants move through the soil, so we can make predictions for the future and enable DOE to make long-term predictions for cleanup,” Flury said.
Many radioactive elements are known to attach very strongly to soil particles–but colloids in the soil can carry them farther than one would expect. Soil typically contains a lot of colloids to which radioactive particles can attach, but is not known how these colloids move through soil material, particularly in arid regions where water content is low. This study seeks to determine what happens if the soil particles themselves detach and move, becoming an important mechanism for movement of contaminants through the soil system.
“We use experiments and models to provide a basic understanding of how these contaminants can potentially move by way of colloids and predict its magnitude. For example, although Hanford is typically very dry, what happens with contaminants in situations of extraordinary rainfall or snow melt?“ Flury said.
The experiments proposed in this study will use conditions specific to the semi-arid Hanford site, yet the models will be extendable to other waste sites in arid regions such as the Yucca Mountain site near Las Vegas in Nevada.