Hydride blisters formation, characterization and effect on the fracture of Zircaloy-4 cladding tubes under reactivity initiated accident conditions - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2012

Hydride blisters formation, characterization and effect on the fracture of Zircaloy-4 cladding tubes under reactivity initiated accident conditions

Résumé

This work is part of the global research effort carried out at the CEA to improve the understanding of cladding failure under reactivity initiated accident (RIA) conditions, based on analytical mechanical testing techniques. The detrimental effect of hydride blisters, localized high hydrogen concentration zones, on the cladding resistance was observed in integral tests in dedicated research reactors. In order to better quantify this effect, the present study is focused on mechanical tests representative of RIA loading conditions on samples containing such blisters. A cold spot technique was developed to generate hydride blisters on Zircaloy-4 cold work stress relieved (CWSR) unirradiated pre-hydrided claddings tubes. The hydrogen concentration field in and around the blister was measured by Micro Elastic Recoil Detection Analysis (µ-ERDA) and with micro- and nano-hardness techniques. Hydrogen concentration was found to decrease from the center of the blisters toward their borders. Finally, the nature of hydride phases characterized by X-Ray diffraction was found to be exclusively ? in the blister. Hydrides blisters detrimental effect on cladding mechanical resistance was assessed at 25°C, 350°C and 480°C with different mechanical tests performed on tubular samples. A newly developed test named Controlled Loading Path Expansion Due to Compression (CLP-EDC) was developed to reach biaxiality ratio of 0.5 while the standard EDC test biaxiality is limited to -0.5. The comparison between both tests show the clear effect of increasing the biaxiality on cladding failure without blister: Standard EDC tests biaxiality level is not sufficient to induce cladding fracture at 350°C. Similar tests were performed on samples with blisters of various depths. The results show the loading biaxiality effect seems to be much limited in presence of such defects. This work provides extensive experimental characterization of hydrides blisters, and analysis of the detrimental effect of blisters on the mechanical behavior of Zircaloy-4 cladding based on a new mechanical test that have all the characteristics needed for use on irradiated materials in shielded cells in the near future. The next step is to perform numerical computations to simulate the blister induced embrittlement.
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Dates et versions

hal-01057285 , version 1 (22-08-2014)

Identifiants

  • HAL Id : hal-01057285 , version 1

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Arthur Hellouin de Menibus, Quentin Auzoux, Ousmane Dieye, Vincent Macdonald, Jacques Besson, et al.. Hydride blisters formation, characterization and effect on the fracture of Zircaloy-4 cladding tubes under reactivity initiated accident conditions. 21st International conference Nuclear Energy for New Europe, Sep 2012, Ljubljana, Slovenia. ⟨hal-01057285⟩
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