Patent Number: 051695944
Section: summary

BACKGROUND OF THE INVENTION The present invention relates to a method of remotely installing or removing a nozzle dam of a nuclear stem generator system of the type disclosed in U.S. Pat. No. 5,032,350, assigned to the assignee of the present application. The disclosure of that patent, as well as the disclosures of U.S. Pat. Nos. 4,482,076; 4,744,392; 4,770,235 and 4,483,457 mentioned therein are hereby incorporated by reference. In performing the sliding assembly or disassembly operation of U.S. Pat. No. 5,032,350 it has been found useful to torque the segments about the mating surfaces which slide relative to each other to reduce the sliding friction force required. This is done to limit the segment edge face to edge face sliding contact and provide a slight gap therebetween. Thus, in assembly and disassembling it would be convenient to have a method to accomplish the sliding and described torquing operations from outside the head away from major radiation exposure. Accordingly, it has been desirable to have a method of facilitating all of the assembly and disassembly operations necessary to remotely install or remove a nozzle dam from its useful position, other than those performed by a manipulator as in U.S. Pat. No. 5,032,350 or its parent application, U.S. Pat. No. 4,954,312. The ideal method would include a procedure to assemble and disassemble the dam subassembly with slidlingly assembled segments; to secure or release rib mounted spring loaded camlock components for securement or detachment of the segments; to install and tension a tabbed seal diaphragm on the dam subassemble or remove same; and, to connect and disconnect push-pull operating quick-connects to connect or disconnect the subassembly mounted remotely actuated radial dam locking pins, fluid lines; all without entry of the head of the steam generator with attendant radiation exposure. SUMMARY OF THE INVENTION The invention is a method of remotely installing or removing a nozzle dam in a nuclear steam generator. The steam generator has at its lower end, a head, a manway penetrating the head, a nozzle penetrating the head and a manipulator having a free end in the head. The manipulator includes a clamp mechanism for holding and orienting an inner or center nozzle dam segment while outer nozzle dam segments are secured thereto or detached, at least partially, therefrom by a sliding or a hinged action. The dam segments are sized to pass through the manway and each has means for engaging its adjacent segments thereon for assembly and secured by components into a dam subassembly which can also be disassembled by the method. A Titan 7F manipulator or the like is mounted and arranged for orienting and translating the dam subassembly within the head to move the dam subassembly to its seat within the nozzle where it is to be locked and radially secured therein by subassembly mounted remotely activated radial pins. The manipulator also is used to move the dam from the seat after it is unlocked for removal from the seat and disassembly. The novel method of the invention is for use in the just described broad method and is the specific procedure which involves providing and using a tool set having a plurality of elongated tools for engagement and disengagement with the dam segments and components for securement during assembly and for disassembly. This includes manually operating the tools in association with the manipulator from outside the head for operator protection and ease of use of the manipulator. The method includes the step of physical manipulation of the elongated tools of the set from outside the head to minimize exposure of the tool operator to radiation from within the head and to avoid the necessity of the operator to enter the head while: 1. aligning the segments relative to each other for movement into or out of assembled position during manipulation of the elongated tools; and, PA1 2. securing or detaching the segments in or from proper aligned position to form or disassemble a dam subassembly secured by components of the dam subassembly. The aligning of the segments is a method which includes using an elongated bifurcated tool of the set to engage a segment edge and torquing one segment relative to the other to relieve edgewise sliding frictional surface contact by a resulting alignment of the segments. The novel procedure for securing or detaching the segments is a method which includes using an elongated tool with a double offset T-shaped end to operate segment rib mounted spring loaded camlock components of the type disclosed in U.S. Pat. No. 4,744,392 "Nozzle Dam Segment Bolt and Keeper". The method includes use of yet another elongated tool which can be manipulated from outside the head over and between the ribs of the segments to operate quick-connects in fluid lines to subassembly mounted remotely actuated radial pins including fluid lines, for example, to disconnect the fluid lines during disassembly of the segments for removal from the head. This tool includes an offset and transverse body-straddling bifurcated end for engaging the end of a quick-connect sleeve. The offset provides a portion with an axis substantially parallel to the stem and body, such that by engagement and physical manipulation of the bifurcated end against the quick connect sleeve, from the handle end at the opposite end of a shaft portion, the offset bifurcation pulls back the body sleeve to accomplish disconnection. The typical quick-connect used is a SWAGELOK.RTM. "Keyed" quick-connect, Model QC6 (KS Blue), with the ball check removed for free flow. It is available from The Crawford Fitting co. of Solon, Oh. Another elongated tool used in the method of the invention facilitates tensioning of the diaphragm seal tabs to install or remove the diaphragm from the dam subassembly. The tabs extend from the diaphragm periphery and preferably have an opening for hooked engagement with projections, typically screws, spaced on the subassembly peripheral margin to face the inside of the head. The tabs are tensioned for hooking and unhooking operations by providing and using an elongated tool from the tool set. It is characterized by an elongated shaft portion with a transversely extending hook end and an opposite handle end for manipulation from outside the head. The tensioning includes the step of inserting the hook end in a tab opening to provide hooking or unhooking clearance within that tab opening or an adjacent tab opening for movement of the tab into or out of hooked engagement with one of the projections. Preferably there are multiple tab openings in the tab and the opening engaged by the hooked end of the tool to which the tension is applied, is closer to the tab end than the tab opening that creates the hooked tension connection of the diaphragm to the subassembly. The invention, then is the method of using the tools to remotely install and/or remove a nozzle dam without entering the head.