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The understanding of the mechanisms of high temperature growth of zirconium oxide on zircaloy alloys is of considerable importance owing to the world-wide use of zirconium in nuclear plants. Spallations and growth recovery are known to originate in structural changes of the oxide, but the induced modifications in the oxygen transport have still to be investigated. The zirconia is known to grow mainly by anionic transport, but, due to the very high solubility of oxygen in zirconium, the oxygen penetration profile may be rather complex and extend beyond the oxide/metal interface. The nuclear microprobe offers an attractive way to investigate the oxygen penetration, both from RBS and NRA. In the case of parallel mechanical loading and high temperature oxidation, the oxygen diffusivity is very sensitive to the generated defects in the oxide scales. The use of alternate 16O/18O atmosphere and subsequent local microanalysis by means of 18O(p,α)15N nuclear reaction allows to investigate the effect of the mechanical loading on the oxygen penetration. |
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