Patent Number: 046735453
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, a typical fuel rod assembly 30 includes fuel rods 22, a plurality of fuel rod spacers 46, and a top cap 47. A number of anti-baffle jetting or anti-fretting clips 31 are shown installed at various positions on the rods 22 of the fuel assembly 30 for substantially preventing fretting or vibrational damage to the rods 22. FIG. 2 is a cross-sectioanl view along lines 2--2 of fuel assembly 30, showing a top view of a clip 31 securing together a number of fuel rods 22, and an inert rod 40. The inert rod 40 is shown with a tab 41 welded along its length, which tab 41 abutts the fuel assembly or fuel rod spacers 42 and 43. FIG. 3 is a close-up pictorial view of an enlarged portion of a clip 31 as installed to secure a number of fuel rods 22 and inert rod 40 together. For greater detail of the use and design of the clips 31, reference is made to previously mentioned co-pending U.S. Ser. No. 487,907, filed Apr. 25, 1983, and assigned to the same assignee as the present invention. In the typical nuclear electrical generating power station a large tank of water is utilized to enclose spent or irradiated nuclear fuel rod assemblies. Such an installation is shown in FIG. 4, and includes a pictorial of the apparatus of the subject invention. As shown, a deep tank 50 is substantially filled with water 52, for safely storing a number of irradiated fuel assemblies 30 in a spent or irradiated fuel assembly rack 54 located in the bottom of tank 50. A long grapple 56 extending from an overhead crane (not shown), is shown connected via a grapple rod 58 and grapple stop plate assembly 60 to one of the fuel rod assemblies 30 partially inserted in a cell 138 of the fuel rack 54. The combination of the overhead crane and long grapple 56 is operable for moving fuel assemblies 30 about the tank 50, and either into or out of the spent fuel rack 54. A working platform 62 is mounted above the tank 50 and protrudes partly over the water 52. A safety railing 64 surrounds the perimeter of the working platform 62 to help prevent an operator 66 from falling off the platform 62. An operator and tool support bracket is formed by a beam 68 secured to the working platform 62. The beam 68 has a cantilever portion projecting from the working platform 62 over the water 52 of the tank 50 as shown. A "fresh fuel elevator assembly" 70 is mounted in the tank as shown, and includes a motor 72 rigidly held above the surface of the water 52, as shown. As shown by the arrow path 74, the long grapple 56 is used for moving fuel assemblies 30 between the fuel rack 54 and the fresh fuel elevator 70. An irradiated fuel assembly 30, as depicted by the arrow 76 is shown just after being moved from the fuel rack 54 to mounting upon the fresh fuel elevator assembly 70. Clips 31 must be removed from this fuel assembly 30. PG,9 The present apparatus for permitting the removal of clips 31 from a fuel assembly 30 includes the operator support bracket 68, a disposal basket 78 suspended by a cable 80 having a hook 82 at one end for coupling to an eyelet 84 rigidly connected to the end of the cantilever beam comprising the operator support bracket 68. The other end of the cable 80 is secured to another hook 86 for coupling to a suspension ring 88 secured to the clip disposal basket 78. The disposal basket 78 also includes an access window 90 for receiving clips 31 removed from fuel assembly 30. A television monitor 92 is secured to the top of the railing 62 in an appropriate position for viewing by an operator 66 positioned as shown. The operator 66 is shown in the act of positioning a clip removal tool assembly 94. The clip removal tool assembly 94 includes a tool support pole or tubing 96 secured at an upper portion thereof to a carriage assembly 98, thereby establishing the height of the tubing 96 protruding above the operator support bracket 68, and corresponding the length of the tubing 96 protruding below the operator support bracket 68 to a predetermined depth (about 40 feet, for example) within the water 52 of tank 50. A spoked wheel 100 is rigidly connected to an uppermost portion of the tubing 96. The lowermost end of the support tubing 96 is rigidly connected to the top of a frame 102 of a clip removal tool 104, thereby establishing the location of the clip removal tool 104 at a predetermined depth and area within tank 50. As shown, the frame 102 includes upright brackets 106 for rigidly mounting a television camera 108 at a predetermined angle in the tool 104 for viewing the operating area of a jaw assembly 110. The jaw assembly 110 is rigidly mounted to the bottom of a generally U-shaped frame 112. The frame 112 is rigidly attached to the upper frame 102 via rigid mounting straps 114, as shown. A portion of a hydraulic cylinder 116 is shown mounted between the rear of the jaw assembly 110 and a cross bracket 118 rigidly mounted between the inside faces of the mounting straps 114. Also shown is a right-hand portion of a mirror system 120, which includes an air or hydraulic cylinder 122 mounted to a bottom surface of a jaw assembly 110 for providing selective positioning of the right-hand mirror 124. An identical mirror system is included on the left-hand side of the jaw assembly 110, but is not shown in the view given in FIG. 4. Note that the fresh fuel elevator 70, although not part of the present apparatus, is used in conjunction with the operation of the present apparatus in order to accomplish the removal of the clips. The fresh fuel elevator 70 includes a carrier 126 which is moved up and down along a central post 128, and two guide posts 130 and 132, as shown. The motor 72 is used to rotate a pulley 134 for winding and unwinding a cable 136 attached to the carrier 126 for positioning the carrier 126 at a desired vertical location in the tank. As previously mentioned, the fresh fuel elevator 70 is typically for use in facilitating handling of fuel assemblies 30 within the water tank 50. With reference to FIGS. 4 and 5, a general description of the operation of the present apparatus will now be given. Typically, an irradiated fuel assembly 30 is stored in the spent fuel rack 54 until such time it si to be either disposed of or installed in a reactor core. An irradiated fuel assembly 30 removed from a peripheral location in a reactor core (not shown), may be temporarily stored in the spent fuel rack 54 until such time that the clips 31 are to be removed therefrom, for permitting the irradiated fuel bundle 30 to be restrained in an interior location of the reactor core. Assume that as shown in FIG. 4, the grapple 56, shown attached at an upper end to the hook and cable assembly 140 of an overhead crane (not shown), and connected at its other end to an irradiated fuel assembly 30 previously stored in a cell 138 of fuel rack 54, was operated to lift the fuel assembly from the fuel rack 54 to a position in the fresh fuel elevator carrier 126 (see arrow 76) as shown. The grapple stop plate 60 serves to hold the fuel assembly 30 in place in carrier 126 via the coupling rod 142. The fuel assembly 30 was previously dropped through a hole in the carrier now covered by the grapple stop plate 60 until the stop plate 60 seats on the carrier plate 126 with the fuel assembly 30 appropriately oriented to the clip removal tool assembly 104, for removal of certain ones of the clips 31 from the assembly 30. By observing the positioning of the jaw assembly 110 to the fuel assembly 30, the operator 66 first operates the fresh fuel elevator 70 controls (not shown) to position a clip 31 to be removed in the same horizontal plane as the jaw assembly 110. The operator 66 next proceeds to grasp the spoked wheel 100 to both turn the spoked wheel 100 and push the carriage assembly 98 forward and backwards as required along a slot 99 in the operator support bracket 68, for positioning the jaws 110 immediately opposite and typically within an inch of the clip 31 to be removed. This is accomplished by observing the view of the area about the jaw assembly 110 on the television monitor 92, and also by operating the appropriate controls (not shown) for operating the mirror system 120 (and the mirro system on the opposite side of the jaw assembly 110) to obtainthe best view of the area about the jaw assembly 110. The operator 66 next pushes the spoked wheel 100 in a direction away from the fuel assembly 30, thereby causing the carriage assembly 98 and tubing 96 to "tilt" in a direction forcing the jaw assembly 110 into contact with portions of fuel rods 22. When properly positioned, the upper and lower jaws 144, 146, respectively, are in the open position about a clip 31 as shown in FIG. 5A. As will be described in greater detail later, as also shown in the view, an upper support plate 148, and a lower support plate 150, are abutted against portions of the fuel rods 22 (shown in phantom in view A of FIG. 5) above and below the clip 31 to be removed. The hydraulic actuator 116 is then operated for causing the jaws 144 and 146 to close on the top and bottom edges of the clip 31, as shown in FIG. 5B. Continued operation of the hydraulic actuator 116 causes the jaws 144 and 146 to move away from the fuel rods 22, thereby pulling the clip 31 away from engagement with the fuel rods 22, as shown in FIG. 5C. The operator 66 next proceeds to pull the spoked wheel 100 toward the fuel assembly to "tilt" the jaw assembly 110 away from the fuel assembly 30. The spoked wheel 100 is then turned in a clockwise direction, in this example, to position the front of the jaw assembly 110 within the window 90 of the disposal basket 78. The last step in the quick removal operation, is for the operator 66 to reverse the previous operation of the hydraulic actuator 116 for moving the jaws 144 and 146 forward towards the front of the jaw assembly 110 to their open position, as shown in FIG. 5D. The operator 66 next operates a pair of ejector cylinders (to be described later) for causing a pair of ejector plungers 148 (shown in phanthom in FIG. 5D) to move forward for pushing the clip 31 out of the jaw assembly 110 and into the basket 78. the next clip 31 to be removed from the fuel assembly 30 is so removed by repeating the previously described sequence of operation, including operation of the fresh fuel elevator 70, if necessary. Note that as the jaws 144, 146 are moved back and forth between the upper and lower support plates 148,150, cam-like surfaces 145 and 147 of jaws 144,146, respectively, interact with cam surfaces 149 and 150 on the inside faces of the upper and lower support plates 148,150, respectively, for opening and closing the jaws 144,146, as shown. Details of the carriage assembly 98 will now be described with reference to FIGS. 6 through 10. The carriage assembly 98 includes a base plate 154, an upper plate 156, cap screws 158, tube clamp 160, carriage travel control bar 162, pivot bar spacers 164, clamping plates 166, a tube protection cap 168, machine screws 170, auto track ball transfers 172 tack welded in place, bearings 174, and jam nuts 176. These components are assembled as shown in FIGS. 6 through 10. Note that two carriage control bars 162 may be secured on either side of the base plate 154 across the slotway 99 in order to limit the movement of the carriage assembly 98 in the forward and backward positional extremes. The support tubing 96 is rigidly secured at an appropriate portion thereof, via the tubing clamp 160. As shown, the tubing clamp 160 includes two halves 178 and 180. The half tubing clamp portion 178 includes a pair of threaded holes for receiving cap screws 158 inserted in holes in the other half portion 180, for securing the tubing clamp 160 to the tubing 96, as shown. As shown in FIG. 4, a hole 182 is provided in the upper portion of the tubing 96 near the working platform 62 for receiving control cables 184 (note that the cables include electrical wires and hydraulic or pressurized air lines) for connection to the TV camera 108, the hydraulic actuator 116, and the mirror systems including system 120. A pictorial view of the carriage mechanism 98 is shown in FIG. 11, and also includes a pictorial view of a typical spoked wheel 100 connected to tubing 96 shown in ghost or phantom view. In this example, the spoked wheel 100 is shown to include two sections which are clamped about tubing 96, and also shown protruding from each half section of the spoked wheel 100 are spokes or handles 190. By turning the spoked wheel 100 clockwise or counterclockwise the tubing 96 is easily rotated via the corresponding rotation of the upper carriage plate 156 upon the ball-like bearings 172 mounted on the top of the carriage base plate 154. Also, by either pushing or pulling on the handles 190, the tubing 96 is easily moved forward or backwards within a range along the slotway 99 in the operator support bracket 68, via the interaction between the ball-like bearings 172 on the bottom of the carriage base plate 154 rolling along the top surface of the operator support bracket 68, and the interaction between the roller-like bearings 174 rolling along the inside faces of the operator support bracket 68. Design details of the jaw assembly 110 follow with reference to FIGS. 12 through 15. As shown, the jaw assembly 110 includes an upper support plate 148 having finger-like projections 182 along the width of its front or leading edge for engaging juxtaposed fuel rods 22 (five in this example) about portions of the fuel rods 22 above a clip 31 to be removed (see FIG. 12), thereby supporting the fuel rods 22 above a clip 31 to be removed. Further included are a pivot bracket 184 for connecting hydraulic or air cylinder 116 to the cross bracket 118, cap screw 186, machine screws 188, a right-hand side plate 190, a left-hand side plate 192, a set collar 194, an upper support plate 148, a jaw actuator cam 149, a lower support plate 150, a jaw actuator cam 151, an upper clip removal jaw 144, a lower clip removal jaw 146, jaw support pins 196, a ball bushing 198, a jaw support block 200, a linear bearing support block 202, a retaining ring 204, an actuator shaft 206, a hex nut 208, an actuator handle 210, a straight linkage 212, a bent linkage 214, a plunger 216 of cylinder 116 and secondary actuator shaft 218, all assembled as shown. As shown in FIGS. 14 and 15, the clip removal jaws 144 and 146 are identical. The jaws 144 and 146 include finger-like projections 220 (four such fingers 220 are shown in this example), with semi-circular cutouts 222 provided between the fingers 220 for permitting the fingers 220 to slip between three juxtaposed fuel rods 222 to a depth where the notches 224 of each finger 220 can be placed over an edge of a clip 31 to be removed from a fuel assembly 30. As previously described, the jaws 144, 146 include identical cam surfaces 145 and 147, contoured in this example to have angles alpha (.alpha.) of 30.degree., beta (.beta.) of 45.degree., gamma (.gamma.) of 7.degree., and rho (.rho.) of 10.degree. (the latter angle being associated with the notch 224). A hole 226 is provided for receiving pins 196 for pinning the jaws 144, 146 to the jaw support block 200 (see FIG. 20). In FIG. 16, a pictorial view is shown of the jaw support block 200. Mounted on the back or rear face of the jaw support block 200 are two relatively small air cylinders 228, in this example, screwed into threaded holes of the former. As will be later described in more detail, actuation of the cylinders 228 causes respective plungers to rapidy move outward from the front face of the jaw block 200 for pushing a clip 31 out of the jaw assembly 110 (see FIG. 21). The jaw block 200 also includes a threaded hole 232 for receiving the threaded end of the actuator shaft 206 (see FIG. 13). Details of the right and left-hand mirror assemblies 120, 232, respectively, are shown in FIGS. 17 and 18. As shown, the mirror assemblies 120 and 232 are identical, and each include in this example a circular mirror 234, a mirror extension bolt 236, a hex lock nut 238, a support arm end fitting 240, a mirror support arm extension 242, Allan Head set screws 244, cap screws 246, hydraulic or pneumatic activator cylinders 248, connecting bolts 250, flat washers 252, swivel busings 254, pivot bolts 256, and lock nuts 258, assembled as showm. Individual actuation of either one of the actuator cylinders 248 permit an operator 66 to change the angular orientation of either of the mirrors 234 relative to the front of the jaw assembly 110, for changing the field of view reflected from the mirrors 234 to the television camera 108. FIG. 19 shows a typical field of view as viewed from the television monitor 92 (the field of view shown is that actually viewed from the camera 108). A more detailed description of the operation of the present invention, particularly the jaw assembly 110, will now be given with reference to FIGS. 4, 13, and 20, for removing a clip 31 from a fuel assembly 30. The operator 66, as previously described, operates the fuel elevator 70, in conjunction with turning, pushing and pulling the spoked wheel 100 and moving the carriage assembly 98 forward or backward, as required, to position the tool 104 with its jaw assembly 110 positioned about a clip 31 as shown in FIG. 20. As shown in FIG. 20, the jaws 144 and 146 are open with their notches 224 immediately over the top and bottom edges of the clip 31. The fingers 182 of the upper support plate 148 support the fuel rods 2 at portions above the clip 31, whereas the leading edge of the lower support plate 150 supports the fuel rods 22 below the clip 31 to be removed. The operator 66 may periodically activate either or both of the cylinders 248 for repositioning the mirrors 234 for improving his view of the area about the clip 31 to be removed. With the jaws 144 and 146 in the open position, the actuator cylinder 116 has its plunger 216 positioned as shown in FIG. 13, whereby the actuator shaft is positioning the jaw support block 20 in its forwardmost position, where the interaction between the jaws 144 and 146, with the cams 149 and 151, respectively, holding the jaws 144, 146 in their open position. The operator 66 next activates the cylinder 116 for causing the plunger 216 thereof to move towards the positions shown in phantom in FIG. 13, causing the jaw block 200 to move rearward, whereby the interaction between the jaws 144 and 146, and cams 149 and 151, respectively, causes the jaws 144, 146 to very rapidly close for tightly grasping the top and bottome dges of the clip 31 in the jaw notches 224 (occurs upon only slight rearward movement of the jaw block 200). As the plunger 216 continues to move toward the phantom position shown in FIG. 13, the jaw block 200 continues to move rearward pulling the clip 31 away from the fuel assembly 30, whereby when the plunger 216 reaches the phantom position of FIG. 13, the clip 31 will be completely removed from the fuel assembly 30. Once a clip has been removed from a fuel assembly 30, the operator 66 must next proceed to deposit the removed clip 31 into the disposal basket 78 (see FIG. 4). To accomplish this, the operator 66 observes the TV monitor 92 and manipulates the spoked wheel 100 for positioning the front of the jaw assembly 110 into the window 90 of disposal basket 78. The operator 66 then activates the activator cylinder 116 for moving the jaw support block 200 forward to cause the jaws 144 and 146 to open. Next, the ejector cylinders 228 are activated for causing their respective plungers 230 to move rapidly outward from holes 242 and 244 within a recess 240 of the jaw block 200 (see FIG. 21), causing the removed clip 31 to be ejected into the disposal basket 78. In this manner, the apparatus of the present invention permits irradiated clips 31 to be safely removed from an irradiated fuel assembly 30. While the present invention has been described in connection with the preferred embodiments thereof, it should be understood that there may be other obvious modifications or embodiments of the present invention which fall within the spirit and scope of the invention as defined by the appended claims.