Environmental scientists at Clemson University have received a three-year, $1.2 million grant from the U.S. Department of Energy to study how plutonium, a byproduct of used nuclear fuel, interacts with soil.
The research has implications for nuclear cleanup efforts and could help the Department of Energy more accurately estimate the risk posed by long-term nuclear waste disposal.
"Plutonium contamination in soils can be transported in groundwater away from the site and possibly contaminate drinking water supplies for populated areas," said Brian Powell, an assistant professor of environmental engineering and Earth science and principal investigator on the project.
"The way to predict how much and how fast plutonium moves through the groundwater is to look at the dominant geochemical processes that control plutonium's behavior in the subsurface.
"In this project, we're trying to gain a better understanding of what is happening between plutonium and the soil underground," Powell said. "Rainwater may carry plutonium through the ground; as it moves, it sticks to the soil and is removed from the water. How much sticks is what we're trying to find out."
Powell will examine how plutonium interacts with the soil by calculating the amount of energy used in that process. He'll use this information to develop mathematical models that will allow scientists to better predict how fast plutonium will move underground and be transported away from a waste disposal site.
"Sorption of plutonium to soil particles is the primary means of minimizing transport of plutonium into the environment," Powell said. "Accurate prediction is extremely important for containment and remediation, but our inability to understand the fundamental controls of plutonium mobility limits the effectiveness of current models to predict where it will go and how fast it will go underground."
Powell will use both experimental and computational studies to gain a better picture of how plutonium moves through soil. He will study plutonium interaction with soils from the energy department's Savannah River Site in South Carolina and its Hanford Site on the Columbia River in the state of Washington. He'll then combine that research with quantum-mechanical calculations and X-ray absorption spectroscopy to determine exactly how plutonium interacts with minerals and soils.
Co-principal investigator Yuji Arai, an assistant professor in Clemson's entomology, soil and plant science department, will oversee the spectroscopy experiments. Co-principal investigators Udo Becker and Rodney Ewing at the University of Michigan will oversee quantum mechanical calculations and high-resolution electron microscopy experiments.
"The central part of this work is quantifying the energetics of chemical reactions occurring between plutonium and the soil particles," Powell said. "When plutonium sticks to a soil particle, we don't know how much energy is involved and what the driving forces for the reactions are. If we can determine how much energy is transferred, it will be easier to predict how fast it can move through the subsurface."
This material is based upon work supported by the U.S. Department of Energy under grant number DE-SC0004883. Opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the U.S. Department of Energy.
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