Method and means for in situ repair of heat exchanger tubes in nuclear installations or the like

A method of sealing leaky heat exchanger tubes in situ in nuclear installations is described which consists of the steps of: providing a sleeve having an outer diameter slightly larger than the inner diameter of the tube whose leak is to be sealed and having a length shorter than the length of the tube yet sufficient to overlap the leak and having a flange at one end thereof, the flange being dimensioned larger than the inner diameter of the tube for limiting insertion of the sleeve into the tube; cooling the sleeve to a temperature at which its outer diameter is sufficiently reduced to allow insertion of the sleeve into the tube; inserting the cooled sleeve into the tube to be sealed through one end of the tube to overlap the leaky portion while the sleeve is so cooled until the insertion is limited by the flange; allowing the sleeve to warm up to the temperature of the tube; the sleeve being open at both ends such that fluids flowing through the heat exchanger tube flow through the sleeve also; and guiding the sleeve into position for insertion by means of a guide fabricated of material which is solid at insertion temperatures but becomes fluid at room temperature, and allowing the guide to become fluid when the insertion of the sleeve is complete, whereby the sleeve forms with the inside of the tube in the region of the leak a leak-proof sealing bond with a generally uniform hoop stress thereby repairing the leak