A comparison of the behaviour of fission gases in UO2±x and α-U3O8-z

Atomistic simulation techniques have been used to study the behaviour of fission gas atoms in UO2± x and α-U3O8-2. In this paper, we show how the solution energies and migration mechanisms change as a function of the oxygen content of the fuel. In particular, it is shown that the calculated solution energies decrease from UO2-x to UO2+x but increase again on further oxidation to U3O8. Migration of Xe and Kr in UO2± x proceeds via a tetravacancy trap cluster. In U3O8-z, Xe and Kr movement is assisted by oxygen vacanciesk F120501805larly low activation energies for migration are predicted in the case of radiation-assisted vacancy formation. (orig.)