Most nuclear waste repository options include an engineered barrier system surrounding waste containers in order to minimize the release of radioactive contaminants into the environment after waste package failure and waste form degradation. The proposed buffer material in these barrier systems is compacted bentonite, a natural, geologic material largely consisting of montmorillonite clay. Uranium (U) is the primary element in spent nuclear fuel, and a relevant, environmental contaminant of water resources. Uranium sorption onto clay and its slow diffusive transport away from waste canisters are expected to limit U(VI) mobility in future engineered barrier systems. However, a prediction of these processes is complicated by the complex mineralogical structure of montmorillonite clay, and the effects of evolving chemical and thermal conditions on U(VI) solution speciation, sorption and transport behavior. In this talk, we will provide an overview of the relevant parameters and processes that are expected to govern uranium mobility in future engineered barrier systems, and characterize the effects of chemical solution conditions and temperature on U(VI) sorption and diffusion behavior based on results from our ongoing experimental and modeling studies.
This research is being performed using funding received from the DOE Office of Nuclear Energy's Nuclear Energy University Program (Federal Grant Number: DE-NE0008683).
Ruth M. Tinnacher has been an Assistant Professor in the Department of Chemistry & Biochemistry at California State University East Bay since Fall 2016. She completed M.S. and Ph.D. degrees in ‘Environmental Science and Engineering’ at the Colorado School of Mines in May 2001 and December 2008, as well as a Dipl. Ing. (Equiv. M.Eng.) in ‘Chemical Process Engineering in Industrial Environmental Protection’ at the University of Leoben, Austria in 2000. After working as a Postdoctoral Fellow at Lawrence Livermore National Laboratory for three years, she joined Lawrence Berkeley National Laboratory as a Project Scientist in July 2011. In her research, Dr. Tinnacher investigates environmental geochemistry problems that are driven by energy- and climate-related questions. Her primary research focus has been on the environmental impacts of nuclear energy and waste, with a particular interest in the mobility of radioactive contaminants in subsurface environments. In addition, she is also interested in the impacts of geologic CO2 sequestration and hydraulic fracturing on groundwater quality, and the link between environmental geochemistry and carbon cycling.