IN-SITU NUCLEAR STEAM-GENERATOR REPAIR USING ELECTRODEPOSITED NANOCRYSTALLINE NICKEL

Degradation of nuclear steam generator tubing via outside surface init iated -corrosion, -stress corrosion cracking, and -fatigue, often lead s to costly forced outages and system de-rating (i.e. tube plugging). A commonly applied approach to system rehabilitation has been to repai r the damaged areas of tubes by the applicant of tubular 'sleeves' whi ch are either welded or mechanically bonded at their extremities to th e host tubing; the applied sleeve restoring the mechanical integrity o f the damaged region to its original state (i.e., pressure boundary). An alternative in-situ repair technology involving the electrodepositi on of a continuously bonded, fully dense, integral sleeve of nanocryst alline nickel to the host tubing has recently been developed and succe ssfully field-demonstrated in both CANDU and PWR systems. In this pape r, the Electrosleeve(TM) process, which represents one of the first la rge scale industrial applications for nanostructured materials, is des cribed. Emphasis is placed on the unique properties of the nanostructu red sleeve material - i.e., microstructure, mechanical strength, corro sion resistance, thermal stability, etc. (C) 1997 Acta Metallurgica In c.