Experimental and Modeling Approach of Irradiation Defects Recovery in Zirconium Alloys: Impact of an Applied Stress

    Volume 5, Issue 3 (March 2008)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 27 March 2008

    Page Count: 21


    Ribis, Joël
    CEA-DEN/DANS, DMN/SRMA, CEA/Saclay,

    Onimus, Fabien
    CEA-DEN/DANS, DMN/SRMA, CEA/Saclay,

    Béchade, Jean-Luc
    CEA-DEN/DANS, DMN/SRMA, CEA/Saclay,

    Doriot, Sylvie
    CEA-DEN/DANS, DMN/SRMA, CEA/Saclay,

    Cappelaere, Chantal
    CEA-DEN/DANS, DMN/SEMI, CEA/Saclay,

    Lemaignan, Clément
    CEA-DEC, Dir, CEA/Grenoble,

    Barbu, Alain
    CEA-DEN/DANS, DMN/SRMP CEA/Saclay,

    Rabouille, Olivier
    CEA-DEN/DANS, DMN/SEMI, CEA/Saclay,

    (Received 9 March 2007; accepted 6 February 2008)

    Abstract

    During neutron irradiation, both interstitial and vacancy loops are formed in high concentration in zirconium alloys. Due to this high density of loops, the material is considerably hardened, but the recovery of the radiation damage during a heat treatment leads to a progressive softening of the irradiated material. The recovery of the radiation induced hardening has been investigated using microhardness tests. Transmission electron microscopy (TEM) observations performed on irradiated foils have also shown that the loop density falls while the loop size increases during the thermal annealing. Furthermore, the TEM analysis has revealed that only vacancy loops are present in the material after long term annealing, the interstitial loops having entirely disappeared. A numerical cluster dynamic modeling has also been used in order to reproduce the material recovery for various annealing conditions. The microstructural evolution during mechanical testing with various loading conditions has also been studied. It has been shown that during a creep test with low applied stress (130 MPa) and high temperature (450°C), the microstructure evolution can essentially be explained by the thermal recovery of the loops leading to glide of dislocations as found for an non-irradiated material. At intermediate temperature (400°C), it is shown that for low stress level (130 MPa) the microstructure evolution can also be explained by the thermal recovery of loops, whereas for higher stress (250 MPa), sweeping of loops by gliding dislocations can also occur. In addition, for an applied stress of 130 MPa and a temperature of 400°C, dislocation density is higher in the irradiated material than in the non-irradiated material deformed in the same conditions. It is also shown that secondary slip systems are more activated in the irradiated material than in the non-irradiated material. From this detailed analysis, the mechanical behavior during creep is interpreted in terms of microscopic deformation mechanisms.


    Paper ID: JAI101118

    DOI: 10.1520/JAI101118

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    Author
    Title Experimental and Modeling Approach of Irradiation Defects Recovery in Zirconium Alloys: Impact of an Applied Stress
    Symposium 15th International Symposium on Zirconium in the Nuclear Industry, 2007-06-28
    Committee B10