Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (Suppl): 81-89.doi: 10.3866/PKU.WHXB2014Ac16

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Microdynamics Simulations of the Hydrogen-Corrosion Resistance of Passivation Layers on Pu Surface

SUN Bo, LIU Hai-Feng, SONG Hai-Feng, ZHENG Hui   

  1. Institute of Applied Physics and Computational Mathematics, Beijing 100094, P. R. China
  • Published:2015-05-20
  • Contact: SUN Bo E-mail:sun_bo@iapcm.ac.cn
  • Supported by:

    The project was supported by the Foundations for Development of Science and Technology of China Academy of Engineering Physics (9090707).

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Abstract:

Based on the non-local van der Waals density functional (vdW-DF)+U scheme, we have performed a first-principles molecular dynamics (FPMD) study of the interaction dynamics for H2 impingement against the Pu oxide (PuO2) and Pu nitride (PuN) passivation layers on Pu metal surface. Results show that, except for weak physisorption, both the PuO2 and PuN surfaces are so difficult to access that almost all of the H2 molecules will bounce back to the vacuum when their initial kinetic energies are not sufficient. Although dissociative adsorption of H2 on PuO2 surfaces is found to be very exothermic, the collision-induced dissociation barriers of H2 are calculated to be very high. Unfortunately, PuO2 can be reduced to α-Pu2O3 under oxygen-lean conditions. Molecular H2 can easily penetrate and diffuse in α-Pu2O3, and, as a result, α-Pu2O3 can promote the hydrogenation of Pu metal. Unlike PuO2, PuN is found to be a stable and uniform passivation layer against hydrogen-corrosion of Pu, and the interacting system of PuN and H is shown to be thermodynamically unstable. Overall, the current study reveals the different hydrogen-corrosion resistances of PuO2 and PuN passivation layers, which have implications for the interpretation of experimental observations and will be helpful to understand the surface corrosion and passivation of Pu metal.

Key words: Surface passivation, Plutonium oxide, Plutonium nitride, Surface hydrogen-corrosion, First-principles molecular dynamics