Abstract: A method of and apparatus for securing tubes within a steam generator against vibration with a metallic anti-vibration bar in a tube bundle. The tube bundle has a plurality of tubes, arranged in rows and columns, with lanes between the tube columns. The method comprises the steps of: inserting the anti-vibration bar in the tube bundle; plastically expanding the wall of the anti-vibration bar from an unexpanded position to an expanded position. In the unexpanded position there are a plurality of gaps between the anti-vibration bar and the tubes of the tube bundle. The gaps decrease in size as the wall of the anti-vibration bar moves from the unexpanded position to the expanded position.

Abstract: An array grid includes a plurality of interlocking elongate strips. The strips are structured and configured to provide sufficient lateral support for steam generator tubing while minimizing the risk of attack by stress corrosion cracking to the steam generator tubes.