Pt3Zr alloy as a protective coating against oxidation and hydrogen attack on Zr-based components in nuclear reactors

Abstract

The adsorption of intact and dissociated water molecules on the surfaces of the Pt3Zr alloy and pure Zr have been investigated by means of density functional theory simulations. In each case, a varying amount of water molecules was placed on the surface until saturation coverage was reached. For both surfaces, all the energy barriers for the partial and complete decomposition of water were calculated. The partial dissociation of H2O into OH and H, and the complete dissociation into O and two H atoms are significantly more difficult on Pt3Zr surfaces, as compared to pure Zr surfaces: the dissociative adsorption energies are smaller and the activation barriers for dissociation are larger in Pt3Zr. In addition, the recombination of H atoms into H2 molecules and desorption of those molecules is easier on the Pt3Zr surfaces. The results suggest that the use of the Pt3Zr alloy as a protective coating in Zr-based metallic components used in nuclear reactors can indeed improve their performance, since the alloyed Pt3Zr layers are much more resistant towards oxidation and H attack than pure Zr in the presence of hot water vapor.