Mechanisms of oxidation of fuel cladding alloys revealed by high resolution APT, TEM and SIMS analysis

C R M Grovenor, N Ni, D Hudson, S S Yardley, K L Moore, G D W Smith, S Lozano-Perez, J M Sykes

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    Aqueous corrosion of zirconium alloys has become the major factor limiting prolonged fuel campaigns in nuclear plant. Studies using SEM, TEM and electrochemical impedance measurements have been interpreted as showing a dense inner-most oxide layer, and an increased thickness of the layer has been correlated to a better corrosion resistance. Many authors have reported that an 'intermediate layer' at the metal oxide interface has a complex structure or/and stochiometry different to that of both the bulk oxide and bulk metal, sometimes claimed to be a suboxide phase. Diffraction evidence has suggested the presence of both cubic ZrO and rhombohedral Zr 3O phases, and compositional analysis has revealed similar variations in local oxygen stoichiometry. We have carried out a systematic investigation of the structure and chemistry of the metal/oxide interface in samples of commercial ZIRLO corroded for times up to 180 days. We have developed new experimental techniques for the study of these interfaces both by Electron Energy Loss Spectroscopy (EELS) analysis in the Transmission Electron Microscope (TEM) and by Atom Probe Tomography (APT), and exactly the same samples have been investigated by both techniques. Our results show the development of a clearly defined suboxide layer of stoichiometry close to ZrO, and the subsequent disappearance of this layer at the first of the characteristic 'breakaway' transitions in the oxidation kinetics. We can correlate this behaviour with changes in the structure of the oxide layer, and particularly the development of interconnected porosity that links the corroding interface with the aqueous environment. Using high resolution SIMS analysis of isotopically spiked samples we demonstrate the penetration of the oxidising species through these porous outer oxide layers. © 2012 Materials Research Society.
    Original languageEnglish
    Title of host publicationhost publication
    Pages101-112
    Number of pages12
    Volume1383
    DOIs
    Publication statusPublished - 2012
    Event2011 MRS Fall Meeting - Boston, MA
    Duration: 1 Jan 1824 → …
    http://www.scopus.com/inward/record.url?eid=2-s2.0-84864885184&partnerID=40&md5=b4b4fca561581c35b8178849f9067285

    Conference

    Conference2011 MRS Fall Meeting
    CityBoston, MA
    Period1/01/24 → …
    Internet address

    Keywords

    • Aqueous corrosion
    • Aqueous environment
    • Atom-probe tomography
    • Bulk metals
    • Bulk oxides
    • Complex structure
    • Compositional analysis
    • Electrochemical impedance measurements
    • Experimental techniques
    • Fuel cladding
    • High resolution
    • Interconnected porosity
    • Intermediate layers
    • Major factors
    • Metal oxide interface
    • Nuclear plant
    • Oxidation kinetics
    • Oxide layer
    • Oxygen stoichiometry
    • Spiked samples
    • Stochiometry
    • Systematic investigations
    • Transmission electron microscope
    • Corrosion resistance
    • Metallic compounds
    • Stoichiometry
    • Transmission electron microscopy
    • Zirconium
    • Zirconium alloys
    • Electron energy loss spectroscopy

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