Computational Modeling Towards Accelerating Accident Tolerant Fuel Concepts and Determining In-Pile Fuel Behavior

To mitigate global warming, we need to develop carbon-free ways to generate power. Nuclear energy currently generates more carbon-free power in the United States than all other sources combined at 55%. To make nuclear as viable a power source as possible, we need to maximize power density and safety. Both of these can be improved with Accident Tolerant Fuel (ATF) materials. Uranium nitride (UN), a candidate ATF material, offers high fuel economy due to its uranium density and improved safety margins from thermal properties. However, its instability in the presence of water, a reactor coolant, must be addressed. This dissertation employs Density Functional Theory-based methods to investigate the atomistic and electronic mechanisms in UN corrosion initiation. To ensure accuracy in future UN models, the effects of magnetic treatments on UN surface stability and corrosion properties are also determined. The performance of advanced nuclear materials must be tested in research reactors before they can be implemented in power reactors. To get real-time temperature data from these tests, sensors are required that can survive the high temperatures and irradiation. To meet these needs, Idaho National Laboratory has been developing High Temperature Irradiation Resistant Thermocouples (HTIR-TCs). Towards increasing temperature resolution and in-pile lifetime, an ab initio method has been developed to predict HTIR-TC performance. The method considers the effects of composition and temperature on performance and has been validated against experiment. To predict the interaction of HTIR-TCs with research reactor coolant, corrosion and oxidation mechanisms have been investigated. By examining the diffusion behaviors of water and oxygen, recommendations are made for which thermoelement materials may be the most resistant to corrosion and/or oxidation