STP1354

    Correlation Between Characteristics of Oxide Films Formed on Zr Alloys in BWRs and Corrosion Performance

    Published: Jan 2000


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    Abstract

    The electric resistance of oxide films formed on various Zr alloys in steam at 673 K and in BWRs were measured by an a-c impedance method to investigate the mobilities of the electric charges. The effects of oxide microstructure on transport of electric charges were investigated by TEM.

    Impedance responses differed significantly between unirradiated pre- and post-transition films, although TEM observations gave no clear difference in crystal shapes and sizes of the oxide films. The results of a-c impedance measurements showed that the pre-transition oxide films had a fairly low electronic conductivity. This high resistance corresponded to the presence of a space charge layer near the outer surface of the oxide films which was in contact with the electrolyte. On the other hand, electronic conductivity of post-transition oxide films was about a thousand times higher than that of the pre-transition films.

    The a-c impedance method was applied to ten kinds of Zr alloys irradiated in a BWR for four cycles. Only high Fe,Ni/Zry-2 and high Fe/Zry-2 alloys indicated responses similar to those of unirradiated pre-transition oxide films. This implied good corrosion performance for up to four irradiation cycles without oxidation rate transition. Furthermore, the alloys whose oxide had a lower electronic conductivity showed a smaller weight gain.

    Keywords:

    Zircaloy-2, corrosion, impedance, transition, oxide, BWR, electric resistance, electric conductivity, electronic conductivity


    Author Information:

    Nanikawa, S
    Researcher, senior researcher, and chief researcher, Nippon Nuclear Fuel Development Co., Ltd., Ibaraki-ken,

    Etoh, Y
    Researcher, senior researcher, and chief researcher, Nippon Nuclear Fuel Development Co., Ltd., Ibaraki-ken,

    Shimada, S
    Researcher, senior researcher, and chief researcher, Nippon Nuclear Fuel Development Co., Ltd., Ibaraki-ken,

    Kubo, T
    Senior engineer, Hitachi Ltd., Ibaraki-ken,

    Ito, K
    Deputy manager, Toshiba Corp., Kanagawa-ken,

    Harada, H
    Researcher, Tokyo Electric Power Co., Kasagawa-ken,


    Paper ID: STP14329S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP14329S


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