A pressurized-water steam generator of the U-shaped tube bundle type, has its primary header provided with a horizontal pipe which extends through the header's wall and curves upwardly, rotation of the pipe permitting the upwardly curved inner end to register with any of the inlet ends of a distributor having outer or upper ends which register with the tubes of the tube bundle. The horizontal pipe can be moved longitudinally to move the distributor from one row of tubes to another, rotation of the pipe permitting registration with any of the tubes via the distributor. With this system a flexible tube inspection or repair tool carrier may be pushed through the horizontal pipe from the outside of the header and guided to any of the heat-exchanger tubes via the distributor, avoiding the need for a workman to enter the header to register the flexible carrier with the end of the tube to be inspected or repaired. The usual flexible carrier comprises a rubber rod or hose having an end for carrying an inspection or repair device, the carrier being capable of being pushed and pulled through the heat-exchanger tube and having adequate flexibility for its purpose.