About the event
Date: Friday, April 9th, at 4:10 p.m., Zoom Only
Presenter: Holly McEnaney and Ashley Knapp
Group: Clark (McEnaney) and Moreau (Knapp)
Title: The Study of Complex Chemical Phenomena for Practical Application at the Hanford Site
Abstract: The complexity of the chemistry found in the Hanford Site’s 177 radioactive waste storage tanks has been subject of research for many years. Originally constructed to produce plutonium in 1943 for United States use in World War II, the cores at Hanford manufactured approximately 65% of the nation’s entire stockpile. In 1989, the site was turned into a waste management facility that still poses many unique challenges to the scientific community. There are myriad societal controversies surrounding waste management, nuclear weapons, and the military in general, all contributing to the problems facing the Hanford Site and the surrounding area. Not only do the tanks contain many different complex systems impossible to physically replicate outside of the Hanford Site, but early processing and general information had to be kept secret. The heavy population of Al species in various coordination environments allows formation of solids boehmite and gibbsite, making Al particularly abundant in the tank waste still, after many years of processing and generations of chemists working on the issue. In all systems including the tank waste, that are far from equilibrium, chemical phenomenon will occur if certain conditions are met. In previous work, aluminate systems in the environment of the Hanford tank wastes were studied and an interesting ion pairing behavior was observed. The ion interactions found may have implications for Al-containing system equilibria. Current and future work will focus on attempting to observe and understand the mechanism of this phenomenon. Then, interactions with species relevant to the Hanford tank environments will be introduced to observe how the phenomenon might affect equilibria of the various aluminate reactions present in the tanks.
Title: Exploring the atomic structure of uranium oxide surfaces
Abstract: Uranium plays a significant role in nuclear energy as the primary substituent of nuclear fuel. Due to this, extensive studies have been done to understand its temperature and pressure dependent phase changes. I will go over studies that have explored structure and surface dependent properties of uranium oxide systems, including UO2 as well as other stable oxide phases such as U4O9, U308, and UO3 (often referred to as UO2(+x)). Symmetry inherent in the well-defined UO2 fluorite crystal greatly decreases as additional oxygen atoms are incorporated in the crystal lattice and new physical properties emerge. It is well established that substoichiometric surface atoms will minimize surface energy in the presence of excess oxygen by either 1) lattice relaxation, or 2) the formation of defects. Therefore, studies on how excess oxygen may affect uranium oxide surface speciation will be discussed – namely single crystal studies on facet energies. The rich surface chemistry of uranium oxides can be attributed to the various coordination and oxidation environments accessible to uranium and resultantly, many reactions including oxidation/reduction, bond activation, and catalytic cycles can take place. A few of these chemical reactions include the reaction of CO and catalytic oxidation utilizing U308 will be mentioned.
Meeting ID: 938 0915 3065