New insight into crack formation during corrosion of zirconium-based metal-oxide systems |
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Authors: | Natasha Vermaak Guillaume Parry Rafael Estevez Yves Bréchet |
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Affiliation: | SIMaP-Université de Grenoble, UMR 5266 CNRS/INPG/UJF, 1130 rue de la Piscine, BP 75, F-38402 St. Martin d’Héres Cedex, France |
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Abstract: | Zirconium alloys are typically used in nuclear pressurized water reactors (PWR) as fuel cladding tubes due to their chemical stability and their mechanical strength at operating temperatures (≈300 °C). However, the corrosion of Zr-based cladding tubes is one of the factors limiting the burn-off rate in PWRs. It is commonly accepted that the corrosion kinetics involves a periodic succession of growth where the oxide thickness varies parabolically with time. As the oxide thickens, a cracking structure forms. The oxide appears striated with periodic layers of cracks running parallel to the metal/oxide interface. This cracking structure has been experimentally related to the periodicity of the oxide growth. In the present work, a finite-element study is used to investigate the development of stresses in the oxide under the combined influence of molar volume expansion during oxide formation, metal/oxide interface geometry and metallic substrate creep. The generation of tensile stresses capable of initiating the cracks that are observed experimentally is explored. |
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Keywords: | Oxide cracks Creep Metal/oxide interface undulations Failure Zircaloy-4 |
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