STP939

    Oxidation of Zircaloy-4 in Steam at 1300 to 2400°C

    Published: Jan 1987


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    Abstract

    The oxidation kinetics of Zircaloy-4 in steam have been extended to 2400°C. Growth of the ZrO2 and α-Zr(O) layers display parabolic behavior over the entire temperature range studied; however, a discontinuity in the oxidation kinetics above 1510°C causes rates to increase above those previously established by the Baker-Just relationship. This increase coincides with the tetragonal-to-cubic phase transformation in ZrO2−x. No additional discontinuity in the oxide-growth rate is observed upon melting of Zr(O). The effects of temperature gradients have also been taken into account, and corrected values representative of near-isothermal conditions have been computed.

    Experiments have been performed in steam-hydrogen mixtures at 1565 and 1815°C. Concentrations of hydrogen up to 90 mol% have no effect on the oxidation kinetics. The rate-controlling factor appears to be the available flux of oxygen atoms incident to the reaction surface and is not dependent upon hydrogen content.

    Keywords:

    zirconium, zirconium alloys, oxidation, steam reaction, hydrogen, reaction kinetics, microstructure, loss-of-coolant accident


    Author Information:

    Prater, JT
    Senior Research Scientist and Section Manager, Pacific Northwest Laboratory, Richland, WA

    Courtright, EL
    Senior Research Scientist and Section Manager, Pacific Northwest Laboratory, Richland, WA


    Paper ID: STP28139S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP28139S


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