DEPARTMENT OF GEOLOGICAL SCIENCES
CENTER FOR INTERNATIONAL SECURITY AND COOPERATION
Throughout the nuclear fuel cycle materials are subjected to extreme conditions. Nuclear fission and decay yield high temperatures in fuels and wastes, while mechanical stresses are encountered during fuel swelling and in the geological environments associated with actinide extraction and disposal. Irradiation with fission products and alpha particles causes the dense excitation of electrons, modifying chemical bonding. Under these conditions, which are often encountered simultaneously, many materials degrade. Thus, a central challenge in advanced fuel cycle concepts is the development of materials that maintain their atomic structures, and therefore their critocal properties, under extreme conditions.
This talk describes a number of experimental studies in which extreme fuel cycle conditions are simulated in the laboratory. By coupling laser and resistive heating, diamond anvil pressure cells, and heavy ion accelerators, the structural and chemical behavior of nuclear materials in fuel cycle environments can be observed and elucidated. Recent accomplishments include the demonstration of irradiation‐induced redox reactions in uranium oxides and the atomic‐scale nature of nuclear waste form disordering by temperature, pressure, and irradiation.
While this approach is useful for the design of materials that are resistant to modification by extreme environments, such conditions can also be harnessed to produce new materials not accessible through conventional processing techniques. For example, the irradiation of lanthanide sesquioxides with heavy ions yields previously unreported metastable phases, and exposure of multicomponent equiatomic alloys to extreme mechanical stresses yields new, high‐hardness phases.
Dr. Cameron L. Tracy is a postdoctoral fellow in the Department of Geological Sciences and the Center for International Security and Cooperation at Stanford University. He received his PhD in materials science and engineering from the University of Michigan, and his BS from the University of California, Davis. His PhD work was supported by a National Science Foundation Graduate Research Fellowship, and in 2015 he received a Young Scientist Award from the European Materials Research Society. Cameron’s research addresses the behavior of nuclear materials, including complex oxides and multicomponent alloys, in extreme temperature, pressure, and radiation environments. He previously worked as a research assistant at Los Alamos National Laboratory.