Ab <i>initio</i> molecular dynamics investigation on Zr corrosion in aqueous environments: The effects of temperature, boric acid, and alloying element Nb

A comprehensive investigation on Zr corrosion behavior in aqueous environments was implemented by using the ab initio molecular dynamics (AIMD) method, with a focus on the effects of temperature, boric acid, and alloying element Nb. The three primary stages, including adsorption, dissociation, and diffusion of water molecules, were identified in the initial Zr corrosion process. In addition, the specific structural characteristics of water and boric acid dissociation products were determined on Zr or Zr-Nb substrate. The hydrogen embrittlement at severe accident temperature was elucidated by the intense corrosion reactions and a large number of H radicals penetrating into the Zr substrate. Due to the further dissociation of boric acid complexes and release of more corrosive radicals, Zr corrosion was exacerbated at extremely high temperature, which was quite different from the Zr corrosion suppression of boric acid at low operating temperature. In addition, the introduction of Nb elements effectively inhibited Zr corrosion by altering the metallic bond strength while exhibiting a certain chemical inertness toward oxygen-containing radicals.