First Principles Calculations on Grain Boundary and Corrosion Effects in Nuclear Materials*

We studied defects in amorphous UO2 and corrosion at UN and Zr surfaces. Amorphous UO2 was investigated to simulate grain boundary behavior. Effects of irradiation damage were calculated via formation enthalpies of O adatom and vacancy defects in the most stable amorphous structure, and the vacancy was found to be favorable. Fission products I, Te, and Xe were also considered. The stable defects occurred for fission products at O vacancies. Unlike UO2, UN is susceptible to corrosion when exposed to air. We studied the energetics of UN (100) and (110) surfaces and their stability in the presence of dissociated water with and without added oxygen content. Similar studies were applied to cladding component Zr. This presentation will discuss the effects of defects at the grain boundary in UO2 and the interactions of UN and Zr surfaces with dissociated water on the atomic scale.