Patent Number: 051695944
Section: description

DETAILED DESCRIPTION OF THE INVENTION The numeral 10 generally designates the nozzle dam or subassembly thereof, for which the method of assembly and tool set used therein comprise the invention. As seen in FIG. 1, a portion of the lower head 12 of a nuclear steam generator has a substantially circular manway 14 penetration having a first diameter and a circular or tapered nozzle 16 penetration having a second, larger diameter. The nozzle is connected to a hot or cold leg pipe 18, which contains, during normal operation, a flow of primary coolant from the nuclear reactor vessel into the steam generator. The upper portion of the lower head is defined by a tube sheet 20 which in FIG. 1 is schematically shown, and which is further shown supporting a manipulator 22 for maintenance purposes. The manipulator, typically, may be a Titan 7F available from Schilling Development Inc. of Davis, Cal. and is typically used as fully disclosed and described in U.S. Pat. No. 5,032,350 to install and remove a nozzle dam 10 in nozzle 16. It is immaterial to the instant novel method whether the manipulator 22 is mounted within head 12, for example on tube sheet 20, or outside of head 12. The important requirement is that the manipulator 22 have, for use in head 12, a free end which includes a clamp mechanism 24 for holding an inner nozzle dam segment 30, by means of handle 31 with transverse projection 31a, while outer dam segments 32 are secured thereto or detached therefrom. The dam segments 30 and 32 are sized to pass through the manway 14 and each has means on its edge surface or surfaces facing adjacent segments for engaging its adjacent segments 30 or 32 for assembly and securement by means of the spring loaded camlock component generally designated 36 in FIG. 13. The manipulator 22 is mounted and arranged such that its free end with clamp mechanism 24 can translate the dam subassembly or assembly 10 within the head until the dam subassembly seats within the nozzle 14 to be locked and radially secured therein or released therefrom, by remotely pneumatically actuated radial pins 38 mounted on the dam subassembly or assembly as shown in FIGS. 2 and 14. The means on the edge surface or surfaces of the segments 30 and 32 facing adjacent segments for engaging them for assembly and securement or detachment and disassembly are called sliding brackets and cooperating support bars. In the embodiment illustrated in FIGS. 2 to 5, a sliding bracket 40 is attached by screws 42 to the outer nozzle dam segments 32 and a support bar 44 is attached by screws 42 to either side of center nozzle dam segment 30 for sliding cooperation with the sliding brackets 40. A stop block 46 is fixedly mounted on the end of the support bars 44 to engage stop surfaces 48 on sliding brackets 40 with the completion of the proper amount of sliding action to create the dam subassembly of center segment 30 and adjacent outer segments 32 is accomplished. FIGS. 6 to 8B illustrate alternative sliding bracket, support bar and stop block combinations to those shown in FIGS. 2 to 5. The primed and double primed numbers used in FIGS. 6 to 8B, respectively, correspond to numbers and parts in FIGS. 2 to 5. The major differences between the embodiment of FIGS. 2 to 5 and the alterantives of FIGS. 6, 6A; 7, 7A; and, 8, 8A, 8B are in the shapes and in the amount of "capture" of the support bars 44, 44' and 44'' by the corresponding sliding brackets 40, 40' and 40''. Also, the holes for screws 42 are oriented at 90.degree. in the alternative embodiment of FIGS. 8 to 8B, relative to the embodiments of FIGS. 2 to 7A. Notice that there can be no edgewise assembly or disassembly in FIGS. 6 to 8B, as opposed to FIGS. 2 to 5. The sliding action between segments 30 and 32 is facilitated by orienting the center segment 30 with support bars 40 attached thereto in a generally horizontal position adjacent manway 14 by means of clamp mechanism 24, as opposed to the position of orientation schematically shown in FIG. 1. Then as a sliding bracket 40 on segment 32 moves forward toward stop block 46 for assembly, and away from block 46 for disassembly, the segments 30 and 32 are aligned relative to each other (See FIG. 5) by the application of torque, for example, in the direction of arrow "T" to move segment 32 relative to the manipulator held segment 30. The torquing in the direction of arrow "T", will align the segments 30 and 32 such that their faces 30a and 32a in FIG. 5 are substantially slightly out of contact. This will minimize sliding physical contact between surface 30a and 32a and facilitate relative sliding between the sliding bracket 40 and the support bar 44. In order to facilitate torquing in the direction of arrow "T", for example, and for other assembly and disassembly operations to be described, a tool set is provided and used having a plurality of elongated tools as shown in FIGS. 15-21 for engagement and disengagement with said dam segments 30 and 32; spring loaded camlock components 36; and pneumatically remotely actuated radial pins 38 and fluid lines 50 with quick-connects 52 therefor. The method includes the step of providing and using the tool set of elongated tools of FIGS. 15-21, and within this step are component or subsidiary procedural steps of physical manipulation of the elongated tools of the set from outside the head 12 through the manway 14 to minimize exposure of the tool operator to radiation from within the head 12 and to avoid the necessity of the operator to enter the head. In the case of the torquing operation functionally described above, the tool 60 of FIGS. 15 and 16 is used. Tool 60 is an elongated nozzle dam segment torquing or lifting tool. It is bifurcated and has spaced opposing members 62 and 64 which can engage the peripheral margin or rim 32c of segments 32 from outside the head 12. Torque in the direction of arrow "T" in FIG. 5 is created on segment 32 as the torquing handle 66 on the opposite end from the bifurcation formed by members 62 and 64 to separate surfaces 32a and 30a to reduce sliding friction contact therebetween. At the same time as torquing, or "lifting" as it can be termed when segments 30 and 32 are oriented generally horizontally by the manipulator 22, a pushing action for assembly toward stop block 46 can be accomplished by the tool material joining members 62 and 64. Because this portion of tool 60 is transversely extending it could also engage transverse stiffening ribs 70 of the dam subassembly 10 or the peripheral rim 32c of segments 32 for pulling to slidingly disassembly the segments 30 and 32. The method of the invention includes providing and using an elongated nozzle dam camlock operating tool 80, as shown in FIGS. 17 and 18, as part of the tool set for operation of the components 36 used in the dam subassembly for securing or detaching the aligned dam segments 30, 32 in assembled relation. The camlock operating tool 80 is used on the initially provided camlocks 36 which are mounted in openings 72 through ribs formed by the sliding face to face surfaces 30a and 32a. The tool 80 operates camlocks 36 by means of the levers 36a thereon which are oriented generally parallel to and spaced from the ribbed concave segment surface to face the inside of the head. Some of the ribs create the segment interface surfaces 32a and 32b and some of the ribs 70 are transverse thereto for stiffening the subassembly 10. The elongated tool 80 for operation of the components 36 is manipulated during use over and between the ribs to engage the levers 36a to operate the rib mounted spring loaded camlock components 36 for use in securement or detachment of the segments 30 and 32 into or from a dam subassembly 10. Tool 80 as provided and used has an elongated shaft portion 82 with a handle end 82a and an opposite lever 36a engaging generally T-shaped end with the stem 84 and cross-member 86 of the T-shaped end offset by arm 88 from the axis of shaft 82 to permit operation of the rib mounted spring loaded camlock components 36 of the T-shaped end for securement of the segments 30 and 32 into, or detachment from, a dam subassembly 10 by engagement and manipulation of the T-shaped end 84, 86 against the lever 36a despite the lever 36a being somewhat behind the ribs 70 and 30a, 32a from the manway 14. The method of the invention also includes the providing and using of an elongated nozzle dam quick-connect operating tool or wrench 90 for disconnection of subassembly 10 mounted remotely actuated radial pins 38 including fluid lines 50 which include quick-connects having push-pull operation for stem 50a and body portion 50b connection and disconnection by means of a spring biased body sleeve 50c, in known manner as mentioned above as a "QC" Model. The tool 90 of FIGS. 19 and 20 includes at one end of a shaft portion 92 an offset 94 and a transverse quick-connect body-straddling bifurcated end 96 for engaging the end of spring biased sleeve 50c. A handle end 98 for manipulation outside of head 12 is provided at the opposite end of the shaft portion 92. The offset 94 provides a portion with an axis substantially parallel to the stem 50a and body 50b such that by engagement and physical manipulation of the bifurcated end 96 against the end of the sleeve 50c, from the handle end, the quick-connect "pull" operation to disconnect stem 50a and body 50b can be accomplished to disconnect the subassembly 10 mounted remotely actuated radial pins 38 fluid lines 50. The method of the invention also includes the providing and using an elongated nozzle dam subassembly sealing diaphragm 100 removing and installing tool 102 as shown in FIG. 21. The sealing diaphragm, as seen in FIGS. 2, and 12 have peripheral tabs 104 tensionable, by means of openings 106 in the tabs, into hooked engagement with other tab openings 108 with projections 110 spaced on the subassembly 10 peripheral margin to face the inside of the head 12. The tabs 104 are tensioned for hooking and unhooking operations by providing and using the elongated nozzle dam seal tab tensioning or locking tool 102, for removing and installing the diaphragm 100 on subassembly 10. The elongated tool 102 of the tool set of the method of the invention has an elongated shaft portion 110 with a transversely extending hook end 112 and an opposite handle end 114 for manipulation from outside the head 12. The tensioning of the tab includes the step of inserting the hook end 112 in a tab 104 opening 106 to provide hooking or unhooking clearance within a tab opening 108 for movement of tab 104 into or out of hooked engagement with the projection 110. A tapped hole 109 is used with a screw to provide the projection 110. The tab opening 106 is closer to the tab end than the opening 108 to facilitate use of the tool 102 in the operation. It should be clear that a single larger hole 108 could be used, however, if there were enough clearance provided for both the tool end 112 and the projection or screw 110. Thus, it will be seen that an improved method of remotely installing or removing a nozzle dam in a nuclear steam generator without entering the generator head and by use of a set of elongated tools is provided.