Device for fixing a fuel assembly to the lower core plate of a nuclear reactor, comprising a fastening element (23) fixed to the lower core plate (18), in the central part of the opening (19) in this plate (18) corresponding to the assembly, an expandable sleeve fixed to the lower end (3) of the assembly in its central part, a guide tube (10) passing through the assembly in its central part in the axial direction, a rod (25) mounted for sliding movement in the tube (10) and fixed to an oval locking knob (38), and a socket (26) fixed to the upper end of the bar (25) and having a gripping surface for a lifting tool. The fastening element has an axial opening (31) for engagement of the expandable sleeve. The bar (25) and the socket (26) allow displacement of the oval knob (38) between service and out-of-service positions in which the latter spreads the expandable sleeve inside the opening (31) in order to fix the assembly.
An apparatus and method are provided for remotely inserting and feeding a sleeve within a selected tube to be serviced mounted in a tubesheet of a nuclear steam generator, so as to relieve reverse forces generated during the insertion and feeding of the sleeve and to reduce operator interaction. The device includes a tool having a frame, at least one gripper unit having gripping fingers which extend from a top plate of the tool for detachably suspending the frame from a tube in close proximity to the selected tube. The gripper unit also includes a hydraulically actuated cylinder for retracting the gripping fingers toward the top plate of the tool to forcibly position the tool against the underside of the tubesheet. An advancing assembly supported by the frame is also provided for remotely inserting and feeding the sleeve into the selected tube. This advancing assembly is vibrated by way of a vibrator mounted thereon. Therefore, by forcibly positioning the tool against the underside of the tubesheet and vibrating the advancing assembly during the feeding of the sleeve, reverse forces exerted on the tool and the tubesheet are relieved to allow the sleeve to be smoothly fed into the selected tube, which accelerates the sleeving operation and minimizes the exposure of the equipment operator to potentially harmful radiation.
