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    Failure Mechanisms of Irradiated Zr Alloys Related to PCI: Activated Slip Systems, Localized Strains, and Iodine-Induced Stress Corrosion Cracking

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    The impact of irradiation damage accumulated in fuel claddings on their mechanical behavior and their susceptibility to iodine-induced stress corrosion cracking (I-SCC) was studied in irradiated zirconium and standard Zircaloy-4 sheets subjected to interrupted tension tests in methanol/iodine solutions and in an inert environment. The study of the I-SCC cracks has been carried out by SEM, while the characterization of the irradiation defects and the activated slip systems used TEM.

    In irradiated material, the deformation appears to be entirely localized early in shear bands, which form much later in non-irradiated specimens. The analysis of the activated slip systems reveals in irradiated materials a large majority of basal slip with an ⟨a⟨ Burgers vector, while in non-irradiated material prismatic slip is widely predominant. These observations are analyzed as the result of the interaction between irradiation defects and slip systems.

    In the iodine environment, intergranular cracks are observed to be preferentially localized in these highly deformed regions where slip bands are emerging. Thus, the localization of the deformation in irradiated material is shown to make the SCC initiation step easier. When the test is not interrupted, in irradiated specimens the rupture occurs at about 3% total plastic strain, with a large amount of transgranular pseudo-cleavage and fluting, unlike the non-irradiated specimens tested in similar conditions.

    These observations are discussed in terms of an adsorption mechanism, irradiation-induced hardening, and strain softening.


    zirconium alloys, irradiation, deformation, stress corrosion cracking, strain softening

    Author Information:

    Fregonese, M
    CEA/Grenoble, DRN/DTP/SECC, Grenoble,

    Régnard, C
    CEA/Grenoble, DRN/DTP/SECC, Grenoble,

    Rouillon, L
    CEA/Grenoble, DRN/DTP/SECC, Grenoble,

    Magnin, T
    Ecole des Mines de Saint-Etienne, Centre des Matériaux, Saint-Etienne,

    Lefebvre, F
    CEA/Grenoble, DRN/DTP/SECC, Grenoble,

    Lemaignan, C
    CEA/Grenoble, DRN/DTP/SECC, Grenoble,

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP14309S