Patent Number: 046559930
Section: description

Referring now to the figures of the drawings in detail and first particularly to FIG. 1 thereof, there is seen a mooring 1 in solid lines shown during its deposition motion onto an upper surface 2 of fuel assembly storage racks 3 which are shown in broken lines and which are disposed in a non-illustrated water pit. Pins 4 jut out downward from a base plate 5 of the mooring 1 and serve for locking the mooring at reference points of the storage racks. As shown in FIG. 7, the pins are guided and fastened in T-slots 6 which are worked into the lower surface of the base plate in diagonally crossing directions. The bolts are constructed in the form of sliding blocks and allow easy adjustment of the bolts to different dimensions of the storage rack. A manipulator 7, a fuel assembly 9 to be tested and a hook 8 of a non-illustrated lifting device at the fuel assembly, are also shown in broken lines above the mooring. The fuel assembly 9 and the manipulator 7 are located in this case under a water layer several meters deep. As will be explained below, probes 10 move within the water. The manipulator 7 is supported on a carriage 13 through dowel pins 12 linked to a base plate 11 of the manipulator. The dowel pins 12 extend into corresponding fitting holes 14 of the carriage 13 and are secured by means of washers 15 and screws 16, as seen in FIG. 3. As can also be seen from FIG. 2, the carriage 13 is formed of a plate 18 which has a cutout 17 formed therein and which is provided with rolling bodies 19 on opposite sides thereof. The carriage 13 can be moved in the direction of the arrow 21 by means of the rolling bodies disposed in tracks 20 fastened to the base plate 5. A centering receptacle 22 is also disposed on the base plate 5. The receptacle 22 is formed of an abutment 23 which can be adjusted in the direction of the arrow 25 due to a fastening 24 thereof through an elongated hole, for the purpose of adapting it to different sizes of a fuel assembly base 26. Opposite the abutment 23, a holding device 27 for an eccentric shaft 28 is fastened on the base plate 5. A rocker 30 is disposed on a shoulder 29 of the eccentric shaft. The free ends of the rocker 30 are fastened to non-illustrated cables. The eccentric shaft 28 can be rotated by these cables. The shoulder 29 also has a stop 31 disposed thereon, which comes to rest on the base plate with an appropriate adjustment, in such a manner that the eccentric shaft 28 is applied to the base of the fuel assembly to be centered before it reaches its highest point. A lifting device engages the head 32 of the fuel assembly, so that the fuel assembly 9 is suspended freely and is centered by the fuel assembly base 26. In vicinity of the fuel assembly to be centered, the base plate has a cutout 36 formed therein, so that the fuel assembly cannot make contact at that location. As an alternative to the centering receptacle described, it may be formed of two jaws 34 which can move in opposite directions along a guide 35, as seen in FIG. 2a. The carriage 13, which is provided with the cutout 17 for the purpose of saving weight, can be moved into a test position close to the fuel assembly (as shown in FIG. 2) and into a position distant from the fuel assembly. The motion cycle takes place under remote control by bringing a non-illustrated rod-shaped rod tool into engagement, from a location outside the water pit, with a fulcrum 37 of a linkage 38 and rotating the tool about the fulcrum. Two straps 40 jut out from the base plate 5. The straps have a through-hole 39 formed therein and are fastened to the underside of the base plate. A threaded bolt 41 can be turned into these through-holes by means of the same rod-shaped tool, for the purpose of securing the carriage 13. The distance between the through-holes is therefore equal to the travel distance of the carriage. The threaded bolt is guided in a strap 42 which is fastened to the upper surface. Not far from this strap, a holding element 43 also juts out from the upper surface of the carriage 13. The holding element 43 is engaged by the linkage 38 and triggers the lengthwise motion of the carriage 13. The carriage can also be moved by hydraulic or pneumatic driving elements. The manually-controllable linkage control, however, is preserved so that in the event of disturbances in the manipulator control, the return of the probes 10 from the fuel assembly is always assured. If the carriage could not be returned, disassembly would be necessary and would lead to damage to the probes, the manipulator and the fuel assembly. FIGS. 3 to 6 show the manipulator and subassemblies thereof for moving the probes carrying ultrasonic testing heads 44. The base plate 11, from which the dowel pins 12 lead toward the carriage 13 of the mooring 1, and a cover hood 45, define a waterproof space 46 which encloses the driving elements. The cover hood 45 is fastened by means of screws 47 to the base plate 11 with the interposition of an O-ring 48. Electrical supply cables are led into the waterproof space 46 through a screw connection 49. Pressure is admitted to the waterproof space by a compressed-air source 50 at a pressure which is higher than the pressure prevailing in the surrounding water 51. Possible leaks in vicinity of the seals do not lead to damage to the driving elements, since monitoring devices 52 signal a pressure loss, so that countermeasures for sealing can be initiated in time. A part 53 of the apparatus required for the conversion of linear into rotary motion and from rotary motion back into similar linear motion, is shown in FIG. 3 in interaction with the driving elements, and is shown in FIG. 6 with its individual parts. The part 53 has a flange 54 which passes through the base plate 11 and is rigidly connected to the base plate by screws 55. In vicinity of the passage of the flange 54 through the base plate 11, O-rings 56 accomplish the required sealing. A solid shaft 57 and a hollow shaft 58 are disposed coaxially with respect to each other and with respect to the flange 54. The hollow shaft 58 is guided by ball bearings 59 in the flange 54 with the interposition of a spacer sleeve 60 and is supported in the axial direction. A flange 62 is provided for axially fixing the hollow shaft 58. The flange 62 is bolted to the shaft 58 through a claw coupling 61 and simultaneously contributes to the radial guidance of the solid shaft 57 with a ball bearing 63. The solid shaft receives its further radial support through a ball bearing 63' which is directly guided in the hollow shaft. The end of the solid shaft 57 extending into the waterproof space 46 of the manipulator 7, is provided with a square 64. The square 64 is plugged and centered into a carrier 65 and is secured by means of a clamping screw 66. With the interposition of a spacer sleeve 67, the carrier 65 serves for supporting the solid shaft in the axial direction relative to the hollow shaft and the flange 54. The ball bearings facing the water 51 are protected against the penetration of water by means of O-rings 68 and shaft sealing rings 69. The respective ends of the solid shaft disposed in the water have a carrier 70 rigidly connected thereto and the hollow shaft has a hub 71. Levers 72, 73 are bolted to the carriers 65, 70 of the solid shaft 57. The levers 72, 73 are constructed with mirror symmetry and are disposed relative to each other in mirror symmetry, so that the lever 73 disposed in the water of the pit executes the same motion as the lever 72 disposed in the waterproof space 46. The levers are accurately positioned by a slot-and-key connection 74. Levers 76, 77 which are similarly connected to the hub 71 and the flange 62 of the hollow shaft, are constructed with mirror symmetry and are disposed relative to each other with mirror symmetry. The manner of fastening the levers can be seen in FIG. 5a, which uses the connection to the carrier 65 as an example. As FIG. 3 shows, the free end of the lever 72 fastened to the carrier 65 of the solid shaft is articularingly connected in the waterproof space to a further lever 78 through a pin 75 supported by ball bearings. In the same manner, the lever 77 which is fastened to the flange 62 of the hollow shaft 58, is likewise connected to a further lever 80 through a pin 79 supported in ball bearings. The free ends of the further levers 78, 80 are brought together at a fulcrum 81, about which they can move via ball bearings 82. A threaded bolt 83, about which both levers 78, 80 can move, is screwed into a slider 84 and forms a funcrum 85 which can be moved in the X or Y-direction together with the slider 84. In FIG. 4, the levers 72, 76, 78, 80 are only indicated by broken lines, so that the slider 84 and its driving elements can be seen better. The slider 84 is supported by a nut 86 which is associated with a ball bushing spindle 87. A rod 88 extends parallel to the spindle 87 and contributes to the guidance of the spindle 87 during motion in the Y-direction through slide bearings 89 associated with the slider 84. If such a motion is to take place, the ball bushing spindle 87 is set in rotation by a stepping motor 90 through a serrated belt drive 91 and moves the nut 86 with the slider 84. An identical stepping motor 92 provides for the movement of the slider 84 in the X-direction, through a ball bushing spindle 93 which is likewise driven by a serrated belt, and through a rod 94 extended parallel thereto. To this end it is necessary for the ball bushing spindle 93 and the rod associated with it to be fastened directly to the base plate 11 through pillow blocks 95. The slider 84 and the associated driving elements, on the other hand, are supported by a frame 96 which is associated with a nut 97 of the ball bushing spindle 93 and a slide bearing 99 of the rod 94. Initiators or primers 98 ensure that the movements of the slider 84 cannot go beyond predeterminable end positions. According to FIGS. 3 and 6, the levers 76, 73 which are disposed with mirror symmetry relative to the levers 72, 77 on the hub 71 of the hollow shaft 58 and on the carrier 70 of the solid shaft 57 in the water of the pit, are each associated with further levers 100, 101 through a respective bearing-supported pin 102. The free ends of the levers 100, 101 form a common fulcrum 103 which has a fixed point 106 screwed in at that location to a slider 104 carrying the probes, by a threaded bolt 105. The fulcrum 85 of the slider 84 which is disposed in the waterproof space 46, and the fixed point 106 of the slider 104 carrying the probes 10, are therefore disposed vertically on top of each other. The part 53 which passes through the base plate 11 ensures the accurate movement of the two fixed points 85, 106. The slider 104 can be moved in the X-direction through a rod and slide bearing guide 108 which is located in a housing 107. Two rods 110 fastened to the underside of the base plat 11 by pillow blocks 109, take care of guiding the slider 104 in the Y-direction. One rod 110 is surrounded by a slide bearing 111, while only a roller 112 runs on the other rod 110. A supply line 114 which passes on the signals of the ultrasonic testing heads 44 to a non-illustrated evaluation unit, leads away from a probe mount 113. The probe mount 113 is furthermore associated with a force pickup 116 which is supplied through an electric lead 115, so that the running motion of the probes is stopped when they run up on an obstacle. The probe mount is furthermore provided with a guiding piece 117 matched to the cross section of the probes, so as to support the probes in their running motion. FIG. 8 shows another embodiment of a device for carrying out the method. Accordingly, the fuel assembly 9 is inserted into a fuel assembly container 118 of a fuel assembly repair station 119 and held in its vertical position. A guide rail 120 of the repair station 119 is held at the bottom 121 and at one side wall 122 of a fuel assembly storage pit 123. The interposition of a cable drive 124 for a vertical movement of the fuel assembly container 118 along the guide rail 120 and a driving unit 125 for a tilting motion of the fuel assembly container about the axis 126, permit the container to be supported by the guide rail. In the conventional repair station, the defective fuel rods (formed of cladding tubes which contain fuel pellets and are closed off by end plugs) which have been localized outside the repair station, are disassembled. The method according to the invention permits the localization of the defective fuel rods within the repair station. To this end, the fuel assembly is braced and locked at the upper end of the fuel assembly container through a fuel assembly head 32. The fuel assembly is freely suspended downward in the fuel assembly container and extends with its fuel assembly base 27 beyond the lower edge 128 of the container so far that the cladding tubes 128' protrude at least 10 mm out of the container. The container is formed of a steel skeleton. A bracket 129 fastened to the guide rail 120 has a bracket plate 130 which carries the manipulator 7, as is shown in detail in FIG. 3. The manipulator 7 is supported by three dowel holes 14a and dowel pins 12 supported at the plate 130. A lock engaging at the head 32 is matched to the dowel holes in the bracket in such a manner that the probes 10 of the manipulator 7 can run through the spaces between the cladding tubes 128. With this novel combination of a repair station and a manipulator, the localization and the replacement of defective fuel rods can be combined in a single device. The foregoing is a description corresponding in substance to German application No. P 33 37 084.2, filed Oct. 12, 1983, the International priority of which is being claimed for the instant application, and which is hereby made part of this application. Any material discrepancies between the foregoing specification and the aforementioned corresponding German application are to be resolved in favor of the latter.