Patent Number: 056028873
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS During the installation procedure, the tie rod/lower spring assembly (items 54 and 56 in FIG. 2) is lowered into the downcomer annulus 8. This is accomplished using a crane (not shown) on the refueling floor of the reactor. First, the tie rod/lower spring assembly must be raised from horizontal position on the refueling floor to a vertical position suspended from the end of the crane cable. This is accomplished by means of a tie rod adaptor which couples the upper end of the tie rod to the end of the cable. When the cable is wound, the upper end of the tie rod is lifted off the refueling floor into an upright position with all of the weight of the tie rod being supported by the cable. The tie rod/lower spring assembly can then be lowered into the annulus by unwinding the cable. Referring to FIG. 2, when vertical access to the downcomer annulus 8 is limited by internal reactor structures such as the feedwater sparger 26 and core spray header 28, a rigid frame or strongback 90 can be used to bypass the obstruction. The strongback is designed to circumvent the piping obstructions so that the tie rod/lower spring assembly is freely suspended from the end of the cable and the cable remains plumb. The tie rod strongback 90 is suspended from cable 84 via a cable adaptor 86 at its upper end. The lower end of the strongback 90 is coupled to the tie rod adaptor 88, which in turn couples to the top of the tie rod 54. As the cable is lowered, the tie rod/lower spring assembly 54/56 must be guided into the narrow space between adjacent jet pump assemblies 44a and 44b (see FIG. 2). Maneuvering of the tie rod/lower spring assembly must be done with extreme care to avoid damaging reactor hardware such as the jet pump restrainer brackets 48a, 48b and the jet pump sensing lines (not shown). In a specific application, the bottom end of the assembly is displaced radially inward until the clevis hook clears the clevis pin installed on the gusset plate. Then the tie rod assembly is lowered a few inches until the tip of the clevis hook clears the bottom of the clevis pin. During this brief descent of the tie rod assembly, it slides against the saddle of the pusher tool. The saddle is made of ultra-high-molecular weight (UHMW) polyethylene or other suitable material to prevent scratching of the tie rod assembly. Alternatively, only the surface layer of the saddle is made of UHMW polyethylene. When the pressurized fluid to the spreader is cut off, the suspended tie rod assembly drifts radially outward, causing the clevis pin to enter the clevis hook. Then the tie rod assembly is lifted to fully engage the clevis pin in the clevis hook prior to installing a vertical support tool which braces the clevis hook against the clevis pin from below. Ultimately, the assembly is positioned so that it hangs plumb over the gusset plate 18. At this juncture, the tie rod/lower spring assembly must be maneuvered so that the clevis hook 56c is hooked underneath the clevis pin 20 on the gusset plate 18, as seen in FIG. 3. To accomplish this, the clevis hook at the bottom of the suspended assembly must be displaced radially inward in the downcomer annulus until there is radial clearance vis-a-vis the clevis pin. With the clevis hook in this radially inwardly displaced position, the tie rod assembly is lowered a few inches until the tip T of the clevis hook 56c clears the bottom of the clevis pin 20. Then the force displacing the bottom end of the suspended tie rod assembly radially inward is removed, allowing the lower spring clevis 56c to "drift" under the clevis pin 20 until the latter contacts the inclined surface S of the clevis hook slot. The tie rod assembly is now properly positioned and simply lifted up to fully engage the clevis pin 20 in the clevis hook. Referring to FIGS. 4A and 4B, the pusher tool 100 in accordance with one preferred embodiment of the invention comprises a pole adaptor 102 for coupling to the end of a service pole (not shown). In particular, the pole adaptor 102 has a pair of J-shaped slots 102a (only one of which is visible in FIG. 4A) for receiving respective pins on the end of the service pole (not shown). Pusher tool 100 further comprises a pole adaptor extension 104, the upper end of which is attached to the pole adaptor 102. Preferably, extension 104 is a rod made of aluminum alloy. The lower end of extension 104 has a clevis which is coupled to a support post 108 by a clevis pin 106, as best seen in FIG. 4B. The clevis arrangement allows the extension 104 and support post 108 to articulate, which facilitates passage of the tool through tight spots in the annulus during insertion and removal. The support post 108 is securely mounted on a mounting channel 110. In particular, the support post can be inserted in a pair of coaxial holes (not shown) formed in the arms of the channel 110. The support post and channel are also preferably made of aluminum alloy. The arms of channel 110 may optionally have contoured reaction surfaces which conform to the contour of the cladded surface 11 of the RPV wall 10, which the channel is placed in contact with, as seen in FIG. 5. The face of the channel 110 is preferably planar and supports a hydraulic spreader or pry bar. The hydraulic spreader, which resembles a duckbill, has a fixed member or jaw 112 attached to the mounting channel 110 by screws 134 and a pivoting member or jaw 114 which is pivotably coupled to the fixed member 112 by means of a pivot pin 116. The pivoting member 114 pivots relative to the fixed member 112 about an axis which lies generally parallel to the flat face of mounting channel 110 in response to the supply of pressurized fluid, e.g., water, to a hydraulic cylinder 118 situated between the fixed and pivoting members. Hydraulic cylinder 118 is arranged such that the pivoting member 114 is pushed open when the piston of the hydraulic cylinder is extended. The hydraulic cylinder 118 is connected to a source (not shown) of pressurized fluid via a hydraulic line 122 and a quick disconnect coupling 124. The piston of hydraulic cylinder is extended when pressurized fluid, e.g., water, is supplied to the cylinder and retracted when the supply of pressurized fluid is cut off. The end of the piston contacts the pivoting member 114 of the hydraulic spreader at a point which is offset from the axis of pivot pin 116. Thus, extension of the piston in response to actuation of the hydraulic cylinder produces a torque on the pivoting member 114 which causes it to rotate away from the fixed member 112. Preferably, a spring return is provided so that the pivoting member 114 retracts automatically when the hydraulic pressure is released. The pusher tool 100 further comprises an adaptor bracket 120 having a proximal end connected to the pivoting member 114 of the hydraulic spreader via a set of four screws 132. The adaptor bracket 120 is a weldment of a plate 120a and a channel 120b, as best seen in FIG. 5. Plate 120a has four holes for passage of screws 132. At a distal end of the channel 120b, the channel arms have a pair of coaxial holes (not shown) for receiving a socket head shoulder screw 138. Screw 138, which is coupled to channel 120b by a nut 140, serves as a pivot pin for a rocker plate 126. The axis of pivot pin 138 is parallel to the axis of pivot pin 116 of the hydraulic spreader. The plate 120a, channel 120b and rocker plate 126 are all preferably made of aluminum alloy. A saddle 130 is securely mounted on the rocker plate 126 by means of a pair of screws 136. (Preferably, screws 132, 134 and 136 are socket head cap screws.) Saddle 130 has a shallow depression 130a for receiving member 56d of the lower spring 56, as shown in FIG. 5. Depression 130a extends for the full height of the saddle and defines a contact surface which is a cylindrical section having a curved concave profile. The depression resists any tendency for the pushed member 56d to slide off of the saddle. Saddle is made of UHMW polyethylene or other suitable material to prevent scratching of member 56d as the latter descends relative to saddle 130 while in contact therewith. The rocker plate 126 is pivotable about pivot pin 138 to allow the saddle 130 to adjust its orientation Vis-a-vis the pushed member. As seen in FIG. 5, counterclockwise rotation of the rocker plate 126 relative to the adaptor bracket 120 will be blocked when the rocker plate contacts the base of the channel 120b. Conversely, clockwise rotation of the rocker plate 126 relative to the adaptor bracket 120 will be blocked when the rocker plate contacts a restrictor plate 128 which is affixed to the endface of channel 120b. Rocker plate 126 comprises a base 126a pivotably mounted on pivot pin 138 and an extension 126b on one side which extends generally perpendicular to said base 126a and beyond the portion of saddle 130 furthermost from base 126a. The projecting end of extension 126b of rocker plate 126 prevents side slippage of member 56d off of the saddle. Referring to FIG, 5, the open state of the pusher tool is shown in solid lines and the closed state of the pusher tool is shown in dashed lines. In response to actuation of the hydraulic spreader, the pivot pin 138 travels along an arc. When the saddle contacts the member 54d, the rocker plate 126 adjusts so that the saddle will push member 54d radially inward. The amount of this radially inward displacement is a function of the length of the adaptor bracket 120 and the angle of rotation of pivoting member 114 of the hydraulic spreader. For different applications using the same hydraulic spreader, the radially inward displacement can be controlled by proper selection of the length of the adaptor bracket, or more specifically, the distance between the axis of pivot pin 116 and the axis of pivot pin 138. Interchangeable adaptor brackets can be attached to the hydraulic spreader using screws 132. Similarly, interchangeable rocker plates can be attached to the end of the adaptor bracket. For example, as shown in FIG. 6, a rocker plate 126' carrying a roller 146 can be substituted for the rocker plate 126 and saddle 130 of the first preferred embodiment. The rocker plate 126' is in the form of a channel having apertured arms which support a pivot pin 142 coupled thereto by a nut 144. The roller is rotatably mounted on the pivot pin 142. A pusher tool having a roller is preferred when the member being pushed by the tool undergoes a lengthy descent while in contact with the pusher tool. For example, the roller can be configured to roll against the tie rod of the tie rod/lower assembly while the assembly is being lowered into the downcomer annulus. Roller 146 has a shallow depression 146a for receiving the tie rod 54. This depression extends around the circumference of the roller and defines a contact surface having a curved concave profile. The depression 146a resists any tendency for the tie rod 54 to slide off of the roller. Roller 146 is made of UHMW polyethylene or other suitable material to prevent scratching of the tie rod 54 as the assembly descends relative to roller 146 while in contact therewith. The cost of fabricating shroud repair installation tools for specific applications can be further reduced in accordance with the present invention by providing a support structure wherein support post 108 is connected to extension 104 by a clevis pin 106. By adopting this as a standard connection, the same adaptor/extension assembly (102/104) can be used interchangeably in conjunction with multiple alternative tools. The preferred embodiments of the hydraulic pusher tool in accordance with the present invention have been disclosed for the purpose of illustration. Variations and modifications of the disclosed structure which fall within the concept of this invention will be readily apparent to persons skilled in the art of tooling design. All such variations and modifications are intended to be encompassed by the claims set forth hereinafter.