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Degradation of nuclear steam generator tubing via outside surface initiated - corrosion, -stress corrosion cracking, and -fatigue, often leads to costly forced outages and system de-rating (i.e. tube plugging). A commonly applied approach to system rehabilitation has been to repair the damaged areas of tubes by the application of tubular ‘sleeves’ which are either welded or mechanically bonded at their extremities to the host tubing; the applied sleeve restoring the mechanical integrity of the damaged region to its original state (i.e., pressure boundary). An alternative in-situ repair technology involving the electrodeposition of a continuously bonded, fully dense, integral sleeve of nanocrystalline nickel to the host tubing has recently been developed and successfully field-demonstrated in both CANDU and PWR systems. In this paper, the Electrosleeve™ process, which represents one of the first large scale industrial applications for nanostructured materials, is described. Emphasis is placed on the unique properties of the nanostructured sleeve material - i.e., microstructure, mechanical strength, corrosion resistance, thermal stability, etc. |
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