STP1023: The Effect of Temperature on the Irradiation Growth of Cold-Worked Zr-2.5 Nb

    Holt, RA
    Unit head of Deformation Mechanisms and supervising engineer, Materials Integrity Section, Toronto, Ontario

    Fleck, RG
    Unit head of Deformation Mechanisms and supervising engineer, Materials Integrity Section, Toronto, Ontario

    Pages: 16    Published: Jan 1989


    Abstract

    Specimens of cold-worked Zr-2.5% Nb pressure tube material fabricated by several different routes have been irradiated unstressed in the Dido reactor at Atomic Energy Research Establishment (AERE) Harwell to fluences up to 7.5 × 1025 n/m2, E & 1 MeV (about 18 dpa). Their irradiation growth behavior has been investigated as a function of temperature in the range 553 to 623 K.

    The growth strains and strain rates in the axial direction are found to decrease with increased irradiation temperature even though the long-term growth rate in the axial direction may be either negative or positive. The effect of temperature on the transverse growth is the reverse of the effect on axial growth. Increasing the irradiation temperature incrementally from 553 K by 30 or 70 K produces a transient negative growth strain in the axial direction which increases in magnitude with the magnitude of the temperature increment. Decreasing the temperature from 623 or 583 K produces a transient which is approximately the reverse of that observed with a temperature increment.

    These results are discussed in terms of a model in which growth is driven by the size interaction (SI) between point defects and dislocations and by the difference in diffusional anisotropy (DAD) between vacancies and self interstitial atoms (SIAs). Several microstructural features compete as sinks for the vacancies and SIAs produced by the fast neutron flux. It appears that changing the temperature in this range may change the balance in the net point defect fluxes to the sinks because of different temperature dependencies of the SI and the DAD.

    Keywords:

    Zr-2.5 Nb, irradiation growth, microstructure, dislocation density, grain size, pressure tubes


    Paper ID: STP18895S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP18895S


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