Method of repairing partly burnt-off fuel elements in the fuel-element pit pressurized water reactors and device therefor

Device for exchanging fuel rods of partly burnt-off fuel element assembly in a water filled fuel-element pit of a pressurized-water reactor by removing the fuel element assembly head or foot, removing defective fuel rods and replacing them with new intact fuel rods, comprising a tubular apparatus being operable from a service side of the pit including an outer support tube having a lower end, a guide tube being concentrically disposed within said outer support tube and being spaced from said outer support tube defining a first space therebetween and a second space within said guide tube being in communication with said first space, a pulling tube being disposed in and sealed to said guide tube and having an inner diameter substantially corresponding to the diameter of the fuel rods, a lockable gripper connected to said pulling tube, a water discharge pipe being in communication with said first and second spaces, an eddy current measuring probe being disposed at said lower end of said outer support tube, a centering plate being attachable to a fuel element after removal of the head or foot thereof, said centering plate having centering bores formed therein through which said gripper is passable for reaching the fuel rods, a suction pump connected to said water discharge pipe, a gas separator connected to said suction pump, and a purification and waste gas collecting system connected to said gas separator.