Atomistic Simulations of Zr-O-H Systems

Abstract

The ability of oxygen and hydrogen gas to diffuse through the oxidized Zircaloy sheath on CANDU fuel elements under accident conditions is investigated with a molecular-dynamics approach, employing the Modified Embedded Atom Method (MEAM). Experimental values of the binding energies and the lattice constants, along with the elastic constants of zirconia and zirconium hydride obtained by applying the deformation method based on ab initio data (calculated using the Density Functional Theory (DFT)), are used in the parameters of the model development. The calculated energies of vacancies were compared against the predictions by the CASTEP ab initio quantum mechanical program, employing density functional theory with Generalized Gradient Approximation. These simulations support previous work which highlights the importance of the effect of cracks and other defects enhanced diffusion) in modeling oxygen diffusion through fully oxidized Zircaloy sheathing.