First-principles study of the stability and migration of Xe and Cs in U 3 Si.

In the past several years, the U 3 Si has been suggested as an alternative nuclear fuel for light water reactors due to its high uranium density and outstanding thermal conductivity. In order to gain fundamental insights into the behavior of fission products in U 3 Si, the trapping and migration behaviors of the fission products Xe and Cs in U 3 Si are investigated using density functional theory calculations in this work. Under U -rich and Si-rich conditions, both the Xe and Cs atoms prefer to substitute for Si and U atoms, respectively. Besides, both Xe and Cs tend to migrate through the vacancy-mechanism. It is noticeable that Xe diffuses faster and forms Xe bubbles more easily than Cs, which is mainly caused by the weaker interaction between Xe and its surrounding atoms.