Abstract: New types of fuel materials and ceramics are needed to be studied for the emerging and next generation nuclear reactor technology development. Their development requires our fundamental understanding and accurate description of structures, thermochemical stability, mechanical performance, and phase equilibria. In our group, we use a suite of structural-thermodynamic techniques to achieve this understanding. Specifically, high-temperature calorimetry is employed to directly determine the enthalpy quantities, such as heat capacity, heats of phase transition, heats of reaction, mixing and formation of fuel and waste systems to evaluate their stabilities under various conditions. To correlate the thermodynamic and thermal stability insights, we combine synchrotron X-ray techniques and ab initio modeling to determine the chemical states and structural/electronic origins of observed behaviors. In this talk, I will present our recent results of (1) fuel materials such as UO2, UN and UC ceramic fuels, and (2) nuclear waste form materials, including zircon- and brannerite-type ceramics.

Bio: Xiaofeng Guo is an associate professor of the Department of Chemistry and the Alexandra Navrotsky Institute for Experimental Thermodynamics at Washington State University. His current research interests are thermodynamics of f-block condensed matter systems. His radiological laboratories are equipped with various advanced high temperature calorimetric instruments capable of handling radionuclides in a large quantity. He also has expertise in synchrotron X-ray based scattering and absorption spectroscopies, and their applications in in situ high-pressure and high-temperature studies. Guo received his Ph.D. in Chemistry from the University of California, Davis in 2014. He was a G. T. Seaborg postdoctoral fellow at Los Alamos National Laboratory from 2015 to 2017. He is a recipient of the NSF CAREER Award in 2022, Early-Career and Emerging Researchers in Physical Chemistry in 2023, and Humboldt Fellow in 2025.