SUMMARY

This dissertation describes computational studies that explore the atomistic mechanisms and characteristics of radiation damage formation, and how these properties and behaviors contribute to the radiation tolerance of nanostructured materials. The need for materials that can withstand radiation environments for extended periods of time has increased as we have developed more advanced nuclear technologies. Both experiments and computational simulations have shown that nanostructured materials with high densities of defect sinks such as grain boundaries or free surfaces have enhanced radiation tolerance, being able to withstand high radiation doses without accumulating radiation damage in the same ways as conventionally structured materials. What remains to be determined are the atomistic mechanisms that allow for these microstructures to inhibit the formation and accumulation of radiation damage, as well as a determination of how these microstructures will evolve under continued exposure to radiation environments. To that end, we have used computational techniques to study radiation damage across the range of length- and time-scales within which it develops, with an emphasis on considering the impact that microstructure and defect configuration have on the formation and evolution of radiation damage. Atomistic simulations were used to compute point defect energetics in single crystal niobium and uranium-zirconium alloys as well as to probe radiation damage mechanisms in niobium and gold nanostructures. Additionally, a phase field model was developed to simulate atomic segregation in binary alloys due to radiation-induced defect formation.