STP1354

    Contribution to the Understanding of the Effect of the Water Chemistry on the Oxidation Kinetics of Zircaloy-4 Cladding

    Published: Jan 2000


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    Abstract

    Zircaloy-4 cladding has been oxidized in autoclave at 633 K with various chemistry conditions ([Li+] = 0, 10, 70, 700 ppm and [B] = 0, 650 ppm as boric acid) to quantify the effect of lithium hydroxide and boric acid on the oxidation kinetics and to provide oxide films that have been analyzed by SIMS, SEM, and RAMAN spectroscopy to improve our knowledge of the oxidation process in a lithiated environment. Additional specific tests consisting of isotopic exchanges (6Li+/7Li+) have also been conducted to study the incorporation of lithium in the oxide films.

    The main results are that: • Depending on the water chemistry, the lithium hydroxide has two effects on the oxidation kinetics: a decrease of the time to transition and a strong enhancement of the post-transition oxidation rate. • The boric acid strongly reduces these two effects of lithium hydroxide. • In the oxide film, the lithium is located mainly in the pores (or adsorbed on their walls). • The lithium has a quick access to the bulk of the oxide film, even in the inner barrier layer (considered as not completely impervious). • The enhancement of the oxidation rate due to lithium hydroxide is linked to the degradual alteration of the inner barrier layer, up to its quasi-disappearance.

    These experimental results are described extensively, and several factors involved in the alteration of the inner barrier layer, such as lithium pickup in the ZrO2 film, evolution of the morphology of the oxide grains, tetragonal zirconia phase transformation, and hydriding, are then discussed.

    Keywords:

    Zircaloy, lithium hydroxide, boric acid, oxidation, zirconia, oxide film, barrier layer


    Author Information:

    Pêcheur, D
    Research engineer, CEA-Cadarache, DRN/DEC/SH2C,

    Godlewski, J
    Research engineer, CEA-Cadarache, DRN/DEC/SH2C,

    Peybernès, J
    Research engineer, CEA-Cadarache, DRN/DEC/SH2C,

    Fayette, L
    Research engineer, CEA-Cadarache, DRN/DEC/SH2C,

    Noé, M
    Research engineer, CEA-Cadarache, DRN/PAZ,

    Frichet, A
    Research engineer, FRAMATOME, Lyon,

    Kerrec, O
    Research engineer, EDF, R & D Division, DEM, Moret sur Loing,


    Paper ID: STP14328S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP14328S


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