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    STP1597

    Mechanical Behavior at High Temperatures of Highly Oxygen- or Hydrogen-Enriched α and Prior-β Phases of Zirconium Alloys

    Published: 2018


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    Abstract

    During a hypothetical loss-of-coolant accident, zirconium alloy fuel claddings can be loaded by internal pressure and exposed to steam at high temperatures (HTs) up to 1,200°C and then cooled and quenched in water. A significant fraction of the oxygen that reacts with the cladding during HT oxidation diffuses beneath the oxide through the metallic substrate. This induces a progressive transformation of the metallic βZr-phase layer into an intermediate layer of αZr(O) phase containing up to 7 weight % (wt.%) oxygen. Furthermore, in some specific conditions, the cladding may rapidly absorb a significant amount of hydrogen during steam exposition at HTs. As a βZr stabilizer, hydrogen would mainly diffuse and concentrate up to several thousands of parts per million by weight (wppm) into the inner βZr-phase layer. This study intends to provide new and more comprehensive data on the HT mechanical behavior of the αZr(O) and (prior-)βZr phases containing high contents of oxygen and hydrogen, respectively. Model samples produced from M5® and Zircaloy-4 cladding tubes homogeneously charged in oxygen (less than or equal to 6 wt.%) and hydrogen (less than or equal to 3,000 wppm), respectively, were prepared. Their mechanical behavior was determined under vacuum between 800 and 1,100°C for the oxygen-enriched αZr phase and in air between 700 and 20°C after cooling from the βZr temperature domain for the hydrogen-enriched (prior-)βZr phase. The αZr phase was substantially strengthened and embrittled by oxygen. The contribution of the αZr(O) layer to the HT creep behavior of an oxidized fuel cladding tube subjected to internal pressure is evaluated by finite element analysis. Mechanical strength and ductility of the model (prior-)βZr phase appear to be affected by hydrogen contents of 2000–3000 wppm in ways that depend on temperature.

    Keywords:

    Zircaloy-4, M5, oxygen, hydrogen, LOCA, mechanical behavior, high temperature


    Author Information:

    Turque, Isabelle
    DEN, Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, Gif-sur-Yvette,

    MINES ParisTech, PSL Research University, Evry Cedex,

    Chosson, Raphaël
    DEN, Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, Gif-sur-Yvette,

    MINES ParisTech, PSL Research University, Evry Cedex,

    Saux, Matthieu Le
    DEN, Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, Gif-sur-Yvette,

    Brachet, Jean-Christophe
    DEN, Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, Gif-sur-Yvette,

    Vandenberghe, Valérie
    DEN, Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, Gif-sur-Yvette,

    Crépin, Jerome
    MINES ParisTech, PSL Research University, Evry Cedex,

    Gourgues-Lorenzon, Anne-Francoise
    MINES ParisTech, PSL Research University, Evry Cedex,


    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP159720160063