Electrodeposited nanostructured nickel for in-situ nuclear steam generator repair

Degradation of nuclear steam generator tubing via outside surface initiated - corrosion, -stress corrosion cracking, and -fatigue, often leads to costly forced outages and system derating (i.e. tube plugging). A commonly applied approach to system rehabilitation has been to repair the damaged areas of tubes via the insertion 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). Ontario Hydro Technologies has recently developed and successfully field implemented an alternative in-situ repair technology, termed the 'Electrosleeve(TM)' process, which involves the electroforming of a continuously bonded integral sleeve of nanocrystalline nickel to the host tubing. In this paper, the microalloyed Electrosleeve(TM) 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 - ie. microstructure, mechanical strength, corrosion resistance, and thermal stability among other properties.