STP1023

    Accelerated Irradiation Growth of Zirconium Alloys

    Published: Jan 1989


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    Abstract

    Sponge zirconium and Zr-2.5 wt% Nb, Zircaloy, or Excel alloys all exhibit accelerated irradiation growth compared with high-purity crystal-bar zirconium for irradiation temperatures between 550 to 710 K and fluences between 0.1 to 10 × 1025 n ∙ m-2 (E > 1 MeV). There is generally an incubation period or fluence before the onset of accelerated or “breakaway” growth, which is dependent on the particular material being irradiated, its metallurgical condition before irradiation, and the irradiation temperature.

    Transmission electron microscopy has shown that there is a correlation between accelerated irradiation growth and the appearance of c-component vacancy loops on basal planes. Measurements in some specimens indicate that a significant fraction of the strain can be directly attributed to the loops themselves. There is considerable evidence to show that their formation is dependent both on the specimen purity and on the irradiation temperature. Materials that have a high interstitial-solute content contain c-component loops and exhibit high growth rates even at low fluences (<1 × 1025 n ∙ m-2, E > 1 MeV). For sponge zirconium and the Zircaloys, c-component loop formation and the associated acceleration of growth (breakaway) during irradiation occurs because the intrinsic interstitial solute (mainly, oxygen, carbon and nitrogen) in the zirconium matrix is supplemented by interstitial iron, chromium, and nickel from the radiation-induced dissolution of precipitates; iron is the most important element. Zr-2.5 wt% Nb and Excel alloys exhibit accelerated growth which has similar characteristics.

    Keywords:

    zirconium, zirconium alloys, neutron irradiation, irradiation growth, fluences, solutes, dislocations, stacking-faults, anisotropic diffusion


    Author Information:

    Griffiths, M
    Metallurgists, Chalk River Nuclear Laboratories, Chalk River, Ontario

    Gilbert, RW
    Metallurgist, Chalk River Nuclear Laboratories, Chalk River, Ontario

    Fidleris, V
    Metallurgists, Chalk River Nuclear Laboratories, Chalk River, Ontario


    Paper ID: STP18892S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP18892S


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