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|Title:||ALS Seminar: Olga Batuk (2-400F)|
|When:||10/16/2012 2:00 PM - 3:00 PM|
“Colloid-mediated actinide transport: investigation of laboratory-made samples and contaminated soils from various locations by synchrotron-radiation techniques”
Presented by: Olga N. Batuk
Tuesday October 16, 2pm, 2-400F Conf Room
One of the key concerns for safe disposal of spent nuclear fuel (SNF) and radioactive waste is the possibility of leaching of radionuclides and their migration to the environment. Geochemical conditions (e.g. pH, Eh, dissolved oxygen concentration, carbonate and other anion concentrations) as well as high radiation and thermal fields would affect the leaching rates and radionuclide speciation. To clarify these issues, we performed UO2 sample leaching experiment at 70 C and 150 C in simulated ground water, also we investigated the interaction of uranium with silica and iron oxide colloids. As a model of true colloids for their structural investigation we synthesized ThO2 and CeO2. To support our laboratory experiment we also analyzed a number of soils from contaminated sites. X-ray fluorescence maps and X-ray Absorption Fine Structure spectra have been measured on U- and Pu-containing particles and bulk soil samples from Chernobyl, McGuire AFB, Mayak, Rocky Flats, Hanford, and Los Alamos, collected years to decades after their original deposition. In addition to the expected schoepite and PuO2+x speciation that are the most stable forms for U and Pu equilibrated with air and water in the laboratory, a number of other morphologies and compositions are found. These findings therefore point to novel chemical processes that may originate in transitory local conditions and the resulting mesoscale chemistry. They also demonstrate that, contradicting the current dogma, actinide contaminants in soil and water do not quickly react to form their thermodynamic minima nor is the experimentally determined bulk “average” speciation necessarily a useful parameter as input to or validation of models for environmental and forensic systems.