Direct tube repair by laser welding

A method for repairing a wall of a heat exchanger tube of a nuclear steam generator, the wall having a degraded area, comprising the steps of:

• placing a welding head into the tube at the degraded area;
• activating and moving the welding head relative to the tube, said activating being at a sufficient power level and said moving being at a sufficiently low speed so as to melt a localized area that is advanced along a line of welding on a surface of the wall, the degraded area being thereby melted over a first welding width along the line of welding, at least to a depth of 80% of the thickness of the wall, and solidified with cooling following passage of said welding head;
• and,
• laterally advancing the line of welding and continuing said welding to melt the degraded area over a further width adjacent the first welding width, thereby successively melting and fusing the wall along linear sections.

A method for restoring a heat exchanger tube with a wall having a thickness, the wall being characterized by a degraded area extending into the thickness, the method comprising the steps of:

• melting a localized area of the wall to a depth of at least 80% of said thickness in the degraded area;
• allowing the localized area to cool and solidify, thereby reforming the localized area to said depth;
• and,
• proceeding to melt a further localized area of the wall in the degraded area and allowing the further localized area to cool, continuing to melt and cool successive localized areas to substantially encompass the degraded area of the wall.