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Formation de blisters d'hydrures et effet sur la rupture de gaines en Zircaloy-4 en conditions d'accident d'injection de réactivité

Abstract : Our aim is to study the cladding fracture with mechanical tests more representative of RIA conditions, taking into account the hydrides blisters, representative strain rates and stress states. To obtain hydride blisters, we developed a thermodiffusion setup that reproduces blister growth in reactor conditions. By metallography, nanohardness, XRD and ERDA, we showed that they are constituted by 80% to 100% of delta hydrides in a Zircaloy-4 matrix, and that the zirconium beneath has some radially oriented hydrides. We modeled the blister growth kinetic taking into account the hysteresis of the hydrogen solubility limit and defined the thermal gradient threshold for blister growth. The modeling of the dilatometric behavior of hydrided zirconium indicates the important role of the material crystallographic texture, which could explain differences in the blister shape. Mechanical tests monitored with an infrared camera showed that significant local heating occurred at strain rates higher than 0.1/s. In parallel, the Expansion Due to Compression test was optimized to increase the biaxiality level from uniaxial stress to plane strain (HB-EDC and VHB-EDC tests). This increase in loading biaxiality lowers greatly the fracture strain at 25°C and 350°C only in homogeneous material without blister. Eventually, a fracture criterion of unirradiated Zircaloy-4 cladding tube taking into account the blister depth is proposed.
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https://pastel.archives-ouvertes.fr/pastel-00818358
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2012ENMP0068.pdf
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  • HAL Id : pastel-00818358, version 1

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Arthur Hellouin de Menibus. Formation de blisters d'hydrures et effet sur la rupture de gaines en Zircaloy-4 en conditions d'accident d'injection de réactivité. Autre. Ecole Nationale Supérieure des Mines de Paris, 2012. Français. ⟨NNT : 2012ENMP0068⟩. ⟨pastel-00818358⟩

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