Patent Number: 059189118
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the preferred embodiments illustrated in the drawings are described below in connection with replacement of a welded nozzle in the pressurizer vessel and reactor coolant piping of a nuclear power facility, the invention is not limited to that and encompasses installation of nozzles in other vessels and piping and the repair of existing nozzles. The invention further encompasses the initial installation of nozzles in new as well as in existing vessels and piping. Further, the invention inherently encompasses replacement and repair of nozzles that were previously replaced or repaired. As specifically indicated or suggested herein, or as will be apparent to those of skill in the art, an attachment or sealing system of an embodiment or embodiments described herein, or a feature or features of an embodiment or embodiments described herein may be applicable to, or incorporatable in, other embodiments. The embodiments of full replacement nozzles and assemblies depicted in FIGS. 3-7 are identical to those in FIGS. 6, 7, 9, 10 and 12, respectively, of the prior application. In those embodiments, the original welded nozzle 26 (FIG. 2) has been completely removed, leaving the J-groove weld. 34 and the cladding 29 surrounding the bore 30 for the nozzle substantially in tact. The old nozzle may be machined or drilled out; therefore destroying the nozzle. In the embodiments depicted in FIGS. 3-7 herein, and in the prior application, the replacement nozzle may be clamped, bolted, flanged, or interference fitted in the bore or hole of the vessel. Full nozzle replacement assembly 61 depicted in FIG. 3 (FIG. 6 in the prior application), employs a compressive loading system for mechanically attaching a nozzle body 62 to vessel 20. The compressive loading of the nozzle body 62 is accomplished by bolting a cylindrical sleeve 68 to the bore against the nozzle body 62, which loads the nozzle body in compression within the bore. Here, the nozzle assembly 61 includes the nozzle body 62 and the cylindrical sleeve 68. Loading the nozzle body in compression makes it less susceptible to PWSCC. If a crack developed in the nozzle body due to PWSCC (or any other mechanism), since the nozzle body is loaded in compression, the crack will not propagate, or at least is less likely to propagate. This principle is applied in other mechanical nozzle replacements discussed below. The nozzle body 62 has a tapered portion 63 which may be a full or partial length taper ending in a smaller diameter end 64 projecting from the interior entrance of the bore 60 in the vessel 20 and a larger diameter end 65 within bore 60. The nozzle body 62 also includes a tubular portion 66 projecting from the exterior of the vessel 20. The diameter of the tubular portion 66 is smaller than the larger diameter end 65 of the tapered portion 63, and a flange 67 is formed where the diameter of the bore changes from the smaller to the larger diameter. The nozzle assembly 61 also includes an externally threaded cylindrical sleeve 68, and the bore 60 includes a threaded cylindrical portion 69 and a tapered portion 70. The sleeve 68 has wrenching flats 59 on the exterior circumference thereof for tightening the sleeve in the bore. Tightening the sleeve 68 in the threaded bore portion 69 against the flange 65 of the nozzle body forces the tapered portion 63 of the nozzle body into a compressive mechanical engagement with the tapered portion 70 of the bore 60 to mechanically attach the nozzle body 62 to the vessel 20. A mechanical seal is obtained between the contacting surfaces of the tapered nozzle portion 63 and the tapered bore portion 70 by engagement of the two surfaces, which are polished as described above and in the prior application. Sleeve 68 is tightened sufficiently to ensure that the seal is obtained. Instead of polished surfaces, sealing material as described in the prior application and herein may be positioned within bore portion 70 between the bore wall and the exterior of the nozzle body 63 to create the seal. If necessary, a spring washer as described in the prior application or a Belville washer may be employed between nozzle sleeve 68 and the flange 65 of the nozzle body 62 to live load the seal, i.e., maintain a resilient compressive loading on the seal which self compensates over time due to seal shrinkage or other factors. The seals in most of the embodiments described herein may similarly be live-loaded by a spring or washer, and specific reference thereto is not made in every such embodiment The sealing material may comprise gasket material or packing material, for example, Grafoil seal material, Grafoil seal rings, packing glands etc., as is known in the art. Typically, rings and packing materials may be employed where the seal is radially restrained, e.g., the sealing material 56 in FIG. 8 between the bore shoulder 156 and the nozzle flange 159; and gasket material may be employed elsewhere, e.g., the sealing material 56 in FIG. 8 between the end 162 of the nozzle stub 152 and the end 73e of the nozzle 71e. The packing material and packing gland may be of Grafoil, e.g., a Grafoil seal ring as disclosed, for example, in U.S. Pat. No. 4,826,217 (cited above). FIG. 4 (FIG. 7 in the prior application) illustrates a replacement nozzle 71 bolted to the vessel. Full nozzle 71 is similar to fill nozzle replacement assembly 61, but is one-piece, and includes a tapered nozzle body 72 having a smaller diameter end 73 at the interior entrance of the tapered bore 60 in the vessel 20, a tubular end 75 projecting from the exterior of the vessel 20 and a larger diameter, tubular threaded portion 76. The diameter of the nozzle body 72 increases from the interior end 73 to the threaded portion 76. (Reference numeral 60 indicates a bore with a full or partial taper in it and numeral 30 indicates a cylindrical bore of a single diameter or a plurality of diameters.) The diameter of bore 60 similarly increases from the interior end of the bore to a cylindrical threaded portion 77 at the exterior end of the bore. Wrenching flats 59 are provided on nozzle body 72 adjacent the threaded portion 76 for tightening the nozzle into the threaded portion 77 of the bore 60. The nozzle 71 is structurally attached to the vessel 20 by tightening the nozzle into the bore, which forces the tapered portion of the nozzle body 72 into compressive mechanical engagement with the tapered bore 60 to mechanically bolt the nozzle body 72 to the vessel 20. A mechanical seal is obtained between the contacting surfaces of the tapered nozzle portion 72 and the tapered bore 60 by engagement of the two surfaces, as described above in connection with FIG. 3 and in the prior application. Referring to FIG. 5 (FIG. 10 in the prior application), full nozzle replacement assembly 71c is bolted to vessel 20 by an exterior flange 86c and bolts 88c. Both the nozzle body 72c and the bore 30 are cylindrical, and the mechanical attachment of the nozzle assembly 71c to the vessel is achieved by bolting the flange 86c directly against the exterior wall of the vessel. The flange 86c is a separate piece from the nozzle body 72c and may be attached to the nozzle body in any suitable manner, e.g., by a weld 87 (which should be stressed relieved prior to installation). However, the flange 86c and nozzle body 72c may be formed as one piece, as shown in FIG. 11 of the prior application. The flange 86c is contoured to follow the contour of the exterior wall of the vessel 20 against which it bears. Spacers 91 are provided between the heads of bolts 88c and the flange 86c. A thin corrosion resistant sleeve 89, e.g., made of Alloy 690, is shrink fitted or rolled into bore 30 so as to mechanically seal the sleeve 89 to the bore 30. Sealing material 56 between flange 86c and the exterior vessel wall provides the pressure retaining mechanical seal. Full nozzle replacement assembly 71b depicted in FIG. 6 (FIG. 9 in the prior application) is compressively mechanically attached to vessel 20 by an exterior flange 86 bolted to the vessel 20 by a plurality of bolts 88 and threaded holes 90 in the exterior wall of the vessel Exterior flange 86 is a separate piece from nozzle 71b (or in an alternate embodiment may be one-piece with or without welding to the nozzle), and is engaged with nozzle assembly 71b as follows. Nozzle assembly 71b includes a tubular end 75b of reduced diameter projecting from the vessel 20 which forms a circular shoulder or flange 92. Flange 86 includes a circular recess 94 with a central hole 96 therein. The shoulder 92 on the nozzle assembly 71b is received in the recess 94 in the flange 86 with the tubular portion 75b of the nozzle body 72b passing through the central hole 96 in the flange's recess 94. Bore 60 and nozzle body 72b are tapered generally as described for nozzle 71 in FIG. 4, and tightening bolts 88 causes the flange 86 to draw the nozzle body 72b into bore 60 into compressive frictional engagement therewith. If necessary, spring washers (not shown) may be provided between the heads of bolts 88 and flange 86. A mechanical seal is obtained between the exterior of the nozzle body 72b and the walls of bore 60, as described above in connection with FIGS. 3 and 4. Full nozzle replacement 110 shown in FIG. 7 (FIG. 12 in the prior application) is frictionally attached to the vessel 20 and mechanically sealed by an interference fit of the nozzle 110 in the bore 30. Nozzle 110 is tubular and bore 30 is cylindrical. At equal temperatures of the nozzle 110 and the vessel portion 20 surrounding the bore 30, the diameter of the nozzle is slightly larger than the diameter of the vessel bore. The nozzle 110 is inserted into the bore by creating a substantial temperature gradient between the two so that the diameter of the nozzle is reduced or the diameter of the bore is increased, or both. The temperature of the vessel 20 surrounding the bore 30 is increased to expand the diameter of the bore, or the nozzle 110 is cooled to reduce its diameter, or both. After the nozzle 110 has been inserted into the bore 30, the temperature gradient is reduced so that the nozzle 110 frictionally engages the wall of the bore 30 in an interference fit to both mechanically attach the nozzle and mechanically seal its exterior with the wall of the bore at the operating temperatures of interest. The exterior of the nozzle and the bore are polished to assist in creating a seal therebetween. If desired, a mechanical seal or seals, in addition to the mechanical seal obtained from the interference fit and polished surfaces, may be provided as discussed herein and in the prior application. FIGS. 8-20 illustrate embodiments of full and partial nozzle replacement assemblies which are improvements over the embodiments illustrated in the prior application (including FIGS. 3-7 of this application which are identical to FIGS. 6, 7, 9, 10 and 12, respectively, of the prior application), and which introduce features not disclosed in the prior application as well as applying features disclosed in the prior application for improved full nozzle replacement and partial nozzle replacement, which may also be applied to nozzle repair. As indicated above, individual features, or combinations of features, from the embodiments of FIGS. 8-20 may be applied to other embodiments, or combined in various combinations. FIGS. 8, 9, 10, 11 and 12 show variations of the full nozzle replacement 71 of FIG. 4 for partial nozzle replacement assemblies 150, 170, 180, 190 and 190a that include the part (or stub) 152 of an existing nozzle adjacent the interior of the vessel 20 and a partial replacement nozzle 71e, 71f, 71g, 71h and 71i, respectively. For FIG. 10A, the partial nozzle replacement assembly 185 is a variation of the full nozzle replacement of FIG. 7, which includes an existing nozzle stub 152 and a partial replacement nozzle 110a. In the embodiments of FIGS. 8, 9, 10, 10A, 11 and 12, a portion of the existing nozzle is removed leaving the nozzle stub 152 extending into or flush to the bore from the interior of the vessel. Both the nozzle stub 152 and its J-groove weld 34 are left in tact and substantially undisturbed. Removal may be accomplished as described above for removal of the entire nozzle, and in other ways which are known to those of skill in this art. The vessel bore may be altered only to the extent of threading it adjacent the exterior of the vessel, and/or it may be enlarged or tapered as described below. Referring to FIG. 8, a portion 77e of the bore 30 adjacent the exterior of the vessel is enlarged in diameter and threaded. A shoulder 156 is formed in the bore 30 at the interface of the larger diameter portion 77e and a smaller diameter portion 30e. The replacement nozzle 71e likewise includes a smaller diameter portion 158 sized to be received in the smaller diameter bore portion 30e and a threaded larger diameter portion 76e to be threadedly received in the larger diameter bore portion 77e, and a flange 159 at the interface of the smaller and larger diameter portions. Sealing material 56 (e.g., packing material) is positioned in the bore between the bore shoulder 156 and the nozzle flange 159. The replacement nozzle 71e is tightened to the bore (using the wrenching flats 59) to compressively mechanically and structurally attach the replacement nozzle 71e to the vessel 20. Also, tightening the replacement nozzle 71e in the bore compresses the sealing material 56 between the bore shoulder 159 and the nozzle flange 157 to mechanically seal the replacement nozzle 71e to the vessel. Another mechanical seal may be provided in the bore between the interior end 73e of the replacement nozzle 71e and the end 162 of the nozzle stub 152 by sealing material 56 (e.g., gasket or packing material) which also is compressed by tightening the nozzle to the bore. Where a mechanical seal is provided between the annular edges of adjacent nozzle sections, such as the end 162 of nozzle stub 152 and the interior end 73e of replacement nozzle 71e, the edge is chambered at 163 for the new and existing nozzle (not shown) to cause the seal to compress radially into the nozzle and prevent the packing material from extruding through the gapped region between the two nozzles. Achieving the seal between nozzle stub 152 and replacement nozzle 71e requires some axial loading on the existing nozzle stub 152. Alternatively, a gap may be left between the replacement nozzle 71 and the existing nozzle stub 152 so that the existing nozzle stub 152 is not subjected to any axial or radial loading which might otherwise stress the J-groove weld 34. The length of tubular section 158 is selected so that some thread is available in the vessel bore after initial installation to further tighten the nozzle into the bore during service to compensate for shrinkage of the sealing material 56. The bore and nozzle or external compression sleeve are similarly threaded in FIGS. 3, 9, 10, 11, 12-24. The mechanical seals formed at bore shoulder 156 and the nozzle flange 159, and at the end 162 of nozzle stub 152 and the interior end 73e of replacement nozzle 71e are adjustably-loaded, i.e., the degree of compression of the respective sealing material 56 may be adjusted during service, for example, to compensate for seal shrinkage. In most the embodiments disclosed herein, the mechanical seals are similarly adjustably-loaded, and specific reference thereto will not be made in each embodiment. The partial nozzle replacement assembly 170 depicted in FIG. 9 differs from the partial nozzle replacement assembly 150 in FIG. 8 in that the replacement nozzle 7 If of FIG. 9 seals with the existing nozzle stub 152 around the circumference thereof without axially loading the nozzle stub 152. In this embodiment, the bore 30 from a point overlapping the end 162 of the nozzle stub 152 to the exterior of the vessel is enlarged in diameter to define the enlarged diameter portion 77f and a shoulder 156 in the portion of the enlarged bore overlapping the end 162 of the nozzle stud 152. The enlarged diameter bore portion 77f is threaded adjacent the exterior of the vessel. The replacement nozzle 71f is sized to be received in the larger diameter bore portion 77f and includes a threaded portion 76f threadedly received in the threaded portion of larger diameter bore portion 77f The ID of the replacement nozzle 71f at the interior end 174 thereof is enlarged to receive therein the end 162 of the nozzle stub 152. Sealing material 56 (e.g., packing or gland material) is positioned between the bore shoulder 156 and the end 174 of the replacement nozzle 71f surrounding the end of the nozzle stub 152. The replacement nozzle 71f is tightened to the bore to compressively, mechanically and structurally attach the replacement nozzle 71f to the vessel 20. Also, tightening the replacement nozzle 71f in the bore compresses the sealing material 56 against the shoulder 156 and against the outer circumference of the end 162 of the nozzle stub 152 to mechanically seal the replacement nozzle 71f to the vessel. Sealing material 56 (e.g. gasket material) may also be compressed between the end 162 of the existing nozzle stub 152 and shoulder 175 where the nozzle ID changes diameter however, this would axially load the nozzle stub. The partial nozzle replacement assembly 180 depicted in FIG. 10 differs from the partial nozzle replacement assembly 150 in FIG. 8 in that the replacement nozzle 71g seals axially only with the end 162 of existing nozzle stub 152. The bore 30 is threaded adjacent the exterior of the vessel, but unlike the nozzle replacement assembly 150, the bore 30 extending from the end of the nozzle stub 152 to the exterior of the vessel is not enlarged in diameter, and no shoulder is formed in the bore sufficient to insert a seal. The replacement nozzle 71g is sized to be received in the bore 30 and includes a threaded portion 76g threadedly received in the threaded portion of the bore. Tightening the replacement nozzle 71g to the bore mechanically bolts and structurally attaches the replacement nozzle 71g to the vessel 20. A mechanical seal is provided in the bore between the interior end of the replacement nozzle 71f and the end 162 of the nozzle stub 152 by sealing material 56 (e.g. gasket material) which is compressed therebetween when the nozzle is tightened to the bore. The nozzle replacement 170 (FIG. 9) without the sealing material 56 between the end 162 of nozzle stub 152 and the shoulder 175 of the nozzle 71f is presently preferred over this embodiment and the embodiment of FIG. 8 because those embodiments axially load the existing nozzle stub 152. The partial nozzle replacement assembly 185 depicted in FIG. 10A applies a sleeve 110a in the bore 30, as described for sleeve 110 of FIG. 7 to mechanically attach and seal the sleeve 110a in the bore 30. Additionally, sealing material 56 is compressed between the interior end of the sleeve 100a and the end of 162 of the nozzle stub 152 when the sleeve 110a is attached by hydraulically or other means forcing the nozzle into the vessel. FIG. 11 shows another variation of the full replacement nozzle 71 of FIG. 4 for a partial nozzle replacement assembly 190 that includes an existing nozzle stub 152 adjacent the interior of the vessel 20 and a replacement nozzle 71h. In this embodiment, the bore 60 from which the existing nozzle has been removed is enlarged in three sections. The bore is tapered in a first section 74h immediately adjacent the nozzle stub 152, increasing in diameter as the bore progresses towards the exterior of the vessel. In a second section 182 adjacent the tapered first section 74h, the bore is cylindrical having the largest diameter of the tapered section 74h. In a third section 77h, the bore has a diameter further enlarged from that of bore section 182 and is threaded. A shoulder 156 is formed in the bore 60 at the interface of the two larger diameter sections 182, 77h. The replacement nozzle 71h likewise includes a tapered portion 72h sized to be received in the tapered section 74h of the bore, a smaller cylindrical portion 184 sized to be received in the cylindrical section 182 of the bore, and a threaded larger diameter portion 76h sized to be threadedly received in the threaded larger diameter section 77h. The replacement nozzle 71h is structurally attached to the vessel 20 by tightening the nozzle into the bore, which forces the tapered portion 72h of the nozzle into mechanical engagement with the tapered section 74h of the bore to mechanically bolt the replacement nozzle 71h to the vessel 20. A mechanical seal is obtained between the contacting surfaces of the tapered nozzle portion 72h and the tapered bore section 74h by engagement of the two surfaces, as described above and in the prior application. A gap 186 is left between the end 162 of the nozzle stub 152 and the interior end of the replacement nozzle 71h. However, another mechanical seal may be provided in gap 186 as shown in FIG. 12 (described below). The partial nozzle replacement assembly 190a shown in FIG. 12 is identical to partial nozzle replacement assembly 190 except that no gap is left between the tapered nozzle portion 72h and the end 162 of the nozzle stub 152, and sealing material 56 (e.g., gasket or packing material) is positioned thereat and compressed when the replacement nozzle 71i is tightened to the bore to form another mechanical seal within the bore. In the embodiments of FIGS. 10, 11, and 12, a shoulder similar to shoulder 156 in FIG. 8 may be provided in the gap region 188 in the bore, and a flange may be provided on the nozzle similar to flange 159 in FIG. 8, and another mechanical seal may be provided in this gap, as shown in FIG. 8. (This additional mechanical seal may also be provided in the embodiments of FIGS. 13, 14, 15 and 16.) FIGS. 13-16 respectively illustrate full nozzle replacement assemblies 61a, 61b, 232 and 242 in which the existing nozzle has been completely removed. The nozzle replacement assemblies 61a, 61b and 232 in the embodiments of FIGS. 1315, respectively, employ full nozzles which extend to the interior of the vessel while the replacement nozzle assembly 242 in the embodiment of FIG. 16 employs a partial nozzle that terminates within the bore of the vessel sealed with respect to a shrink fit sleeve 244 that extends to the interior of the vessel and packing material 56. The full nozzle replacement assemblies 61a, 61b, 232 and 242 all utilize a nozzle assembly of at least two parts excluding the seals themselves which includes a drive or compression sleeve threaded to the bore of the vessel like the nozzle assembly 61 shown in FIG. 3. Referring to FIGS. 13-16, the procedure for the installing full nozzle replacement assemblies 61a, 61b, 232 and 242 removes the existing nozzle entirely, and the vessel bore is altered to provide tapered and/or larger diameter sections, and/or threads in the bore adjacent the exterior of the vessel. Full nozzle replacement assembly 61a depicted in FIG. 13, like the nozzle assembly 61 of FIG. 3, employs a compressive loading system for mechanically attaching the nozzle to vessel 20, and includes a nozzle body 62a having a tapered portion 63a having a smaller diameter end 64a projecting from the interior entrance of the bore 60 in the vessel 20 and a larger diameter end 65a within bore 60. The nozzle body 62a also includes a tubular portion 66a projecting from the exterior of the vessel 20. The diameter of the tubular portion 66a is smaller than the larger diameter end 65a of the tapered portion 63a, and a flange 67a is formed where the diameter of the nozzle changes from the smaller to larger diameter. The nozzle replacement assembly 61a also includes an externally threaded cylindrical drive sleeve 68a, and the bore 60, includes a threaded cylindrical portion 69a and a tapered portion 70a. Tightening the sleeve 68a (using wrenching flats thereof, not shown) into the threaded bore portion 69a against the flange 67a of the nozzle body forces the tapered portion 63a of the nozzle body into compressive mechanical engagement with the tapered portion 70a of the bore 60 to mechanically attach the nozzle body 62a to the vessel 20. A mechanical seal is obtained between the contacting surfaces of the tapered nozzle portion 63a and the tapered bore portion 70a by engagement of the two surfaces, as described above. Sleeve 68a is tightened sufficiently to ensure that the seal is obtained. The full nozzle replacement assembly 61a described so far with respect to FIG. 13 is basically the same as for the full nozzle assembly 61 of FIG. 3, except for the lengths of the tapers in the nozzle body 62a and the bore 60a the length of the taper in the bore and nozzle may vary from embodiment to embodiment. For example, the taper may be less than 1/2" in length. In addition, nozzle replacement assembly 61a provides packing material for a secondary seal at the interface of the tapered and cylindrical sections of the bore (i.e., at the flange 67a of the nozzle), and includes an anti-rotation device 206 described in detail below. Still referring to FIG. 13, a thrust bearing 202 is positioned between the flange 67a of the nozzle body 62a and the interior end of the nozzle drive sleeve 68a, which facilitates tightening the sleeve 68a in the bore 60a. Sealing material 56 (e.g., packing or gland material) is also positioned between the thrust bearing 202 and the interior end of the drive sleeve 68a. The anti-rotation device 206 is implemented in the full nozzle replacement assembly 61a of FIG. 13 as an optional feature by an axial slot defined by adjacent slot portions 207a, 207b in the bore 60 and in the tapered portion 63a of the nozzle body 62a, respectively, and key stock 208 projecting into engagement with both the axial slot portions 207a, and 207b in the bore and the nozzle. The full nozzle replacement assembly 61b shown in FIG. 14, like the full nozzle replacement assembly 61a of FIG. 13, is compressively mechanically attached to the vessel and utilizes a tapered bore/tapered nozzle, but does so without actually tapering the vessel bore. Full nozzle replacement assembly 61b similar to nozzle assembly 61a of FIG. 13, includes a nozzle body 62b and a threaded drive sleeve 68b. The nozzle body 62b includes a tapered portion 63b, a cylindrical portion 222 and a flange 224 at the interface of the cylindrical and tapered portions of the nozzle body. The bore 30 for full nozzle replacement assembly 220 does not include a tapered portion, and instead includes a smaller diameter cylindrical portion 226 and a larger diameter cylindrical portion 69b, which form a shoulder 67b at the interface thereof. Instead of a tapered bore section, a sleeve 204 having a cylindrical OD and a tapered ID is positioned in the smaller diameter bore section 226 sized to engage the tapered nozzle portion 63b when the drive sleeve 68b is tightened to the bore. The sleeve 204 has a flanged interior end 223 which engages the flange 67b in the bore to initially hold and position the sleeve 204 in the bore. Sealing material 56 (e.g., packing or gland material) is positioned between the nozzle flange 224 and the interior end of the drive sleeve 68b which is compressed when the drive sleeve is tightened to the bore. Tightening the drive sleeve 68b to the bore compressively loads the nozzle body 62b to the vessel. Full nozzle replacement assembly 61b provides a seal at the interface of the different diameter sections of the bore 226, in addition to the mechanical seal between the tapered surfaces of the nozzle and the sleeve 204. Alternatively, as shown in FIG. 16, the flange 224 on the nozzle body 62b may be omitted, the tubular section 222 of the nozzle body adjacent the exterior end of the drive sleeve 68b may be threaded along with drive sleeve 68b, to mechanically attach the nozzle body to the vessel and compress the sealing material 56 between the end of the drive sleeve and the flanged portion 223 of the sleeve 204, and lock nuts may be tightened against the drive sleeve to prevent the drive sleeve from loosening in the event the vessel or nozzle experiences vibration due to fluid-induced vibration or some other mechanism. As discussed above full nozzle replacement assembly 61b provides a seal at the interface of the different diameter sections of the bore, in addition to the mechanical seal between the tapered surfaces of the nozzle and the sleeve 204. This arrangement allows separate loadings for the two sealing surfaces, and can be applied to other embodiments as well. Referring to FIG. 15, full nozzle replacement assembly 232 employs a cylindrical bore 30 threaded adjacent the exterior of the vessel 20 and a full replacement nozzle that is mechanically attached to the vessel 20 by a drive or attaching sleeve 68b threaded to the vessel. Full nozzle replacement assembly 232 includes a nozzle body 233, and the drive sleeve 68b and a seal alignment spacer sleeve 235. The nozzle body 233 has tubular section 234 ending in a flanged end 236 projecting into the interior of the vessel 20. Spacer sleeve 235 and the end 236 of the nozzle body in the interior of the vessel are flanged at the angle of the ID of the vessel. Drive sleeve 68b, is threaded adjacent its exterior end and is sized to be threadedly received in the threaded portion of the bore 30 structurally attaching the sleeve and nozzle assemble to the vessel. The spacer sleeve 235 is positioned in the bore between the drive sleeve 68b and the flanged end 236 of the nozzle body 233. Sealing 56a (e.g., a first packing seal ring or gland is positioned between sleeves 68b and 235 and sealing material 56b (e.g., a second packing seal ring or gland) is positioned between sleeve 235 and the flanged end 236 of the nozzle body 233. The nozzle body 233 is positioned in the bore 60a, followed by sealing material 56b, the inner sleeve 235 and sealing material 56a. The drive sleeve 68b is threaded to the bore 30, and a nut 238 is tightened to a threaded section 229 of the tubular section 234 of the nozzle body 233 to mechanically compress sealing materials 56a and 56. Referring to FIG. 16, full nozzle replacement assembly 242 (referred to as a full nozzle since all of the existing nozzle is removed) employs a bore 30 similar to the one shown in FIG. 14, which includes a cylindrical section 226 of smaller diameter opening to the vessel interior and a cylindrical section 60b of larger diameter opening to the exterior of the vessel which is threaded adjacent the opening to the exterior of the vessel. The cylindrical bore sections 222 and 60b of different diameter form a shoulder 67b within the bore at the interface of the two sections. The full nozzle replacement assembly 242 includes a nozzle body 243 having a tubular section 222 and a drive sleeve 68b. The tubular section 222 terminates within the smaller diameter section 226 of the bore and projections therefrom in an exteriorly threaded section 229. The drive sleeve 68b is exteriorly threaded adjacent the interior end of the sleeve and sized to be threadedly received in bore section 60b. The drive sleeve 68b is interiorly threaded adjacent the end projecting from the vessel. The full nozzle replacement assembly 242 also includes a sleeve 244 shrink fitted to the cylindrical nozzle section 222 and extending to the shoulder 67b in the bore as described above in connection with nozzle 110 in FIG. 7, with the end 246 of the nozzle body 243 received in the end of the sleeve 244. Sealing material 56 (e.g., a packing seal ring or gland) is positioned in the bore between the shoulder 67b and the flange 204 of the nozzle body. After the sleeve 244 has been shrink fitted to the bore 30, the sealing material 56 is positioned at flange surface 67b and the drive sleeve 68b is tightened to the bore to compress the sealing material 56. The threaded section 229 of the nozzle body 243 is threaded to the drive sleeve 68b to structurally attach the nozzle body 243 to drive sleeve 68b which is structurally attached to the vessel with threads 69b. The locking nuts 228 prevent the nozzle from loosening. In the embodiments depicted in FIGS. 3-4, 6-16 and 21, mechanical seals are provided solely within the bore. In FIGS. 5, 17-20, and 22-25, mechanical seals are or may be provided also at the vessel OD. FIG. 17 shows a full nozzle replacement assembly 250 which is a variation of the full nozzle replacement assembly 61b shown in FIG. 14 and incorporates an anti-rotation device and two leak paths features. The function of the leak paths is to channel any reactor coolant leakage which may occur through a corrosion resistant leak path out past the exterior surface of the vessel in a visible manner, e.g., to the oxygenated environment where the coolant can flash steam without eroding the vessel. Like full nozzle replacement assembly 220 of FIG. 14, the bore 30 of full nozzle replacement assembly 250 includes a smaller diameter cylindrical portion 226 and a larger diameter cylindrical portion 69b, which form a shoulder 65b at the interface thereof. The full nozzle replacement assembly 250 is similar to that of nozzle assembly 61b of FIG. 14 in that nozzle assembly 250 includes a nozzle body 62b and a threaded drive sleeve 68b, with the nozzle body 62b including a tapered portion 63b, a cylindrical portion 222 and a flange 224 at the interface of the cylindrical and tapered portions of the nozzle body. As in the full nozzle replacement assembly 61b of FIG. 14, instead of a tapered bore section, the full nozzle replacement assembly 250 includes a sleeve 204 having a cylindrical OD and a tapered ID positioned in the smaller diameter bore section 226 sized to engage the tapered nozzle portion 63b when the drive sleeve 68b is tightened to the bore. Full nozzle replacement assembly 250 (FIG. 17) includes the following additional elements: a first anti-rotation device 255 for preventing rotation of the sleeve 204 in the bore; a second anti-rotation device 258 for preventing rotation of the nozzle body 62b in the bore, circumferential vapor collection groove 282, first packing seal ring or gland 56a, flat washer 260, Belville washer 262; lantern ring 264; two concentric packing seal rings or glands 56b, c; axial vapor channel slot 280, gasket 56; channeling sleeve 268; channeling passages 270, and jam nut 271. Full nozzle replacement assembly 250 provides a primary seal at the tapered sections 226, 63b of the sleeve 204 and the nozzle body 62b, a secondary seal at the packing seal ring 56a, and a tertiary seal at the packing seal rings 56b, c. The anti-rotation device 255 (FIG. 17) comprises registered slot portions 271a, b, in the vessel and the flange 223 of the sleeve 204 and a key stock 208 in the registered slot portions. The anti-rotation device 255 prevents the sleeve 226 from rotating relative to the bore. The anti-rotation device 258 comprises registered slot portions 271a, b in the sleeve flange 223 and on the nozzle body flange 224, and a cylindrical key stock 208 in the registered slot portions 271a, b. The anti-rotation device 258 prevents the nozzle body 62b from rotating relative to the sleeve 204, and thereby from rotating relative to the vessel 20. The slots 271a, b and the key stock 208 for anti-rotation devices 255 and 258 may be of circular or rectangular cross-section. The flat washer 260 and the Belville washer 262 assist in securely compressively loading the nozzle body 62b in the bore, and line-load the seals. As mentioned, the packing seal ring 56a provides a secondary seal to prevent leakage. The packing seal rings 56b, c. provide a tertiary seal forming a primary leak path with the inclusion of lantern ring 264 that axially projects between the concentric packing seal rings 56b, c and includes a series of passages 265 spaced circumferentially about the lantern ring extending axially therethrough from one end to the other. The passages 265 are positioned to extend between the spaced concentric packing seal rings 56b, c into circumferential groove 276 where the coolant collects and passes through a series of passages 270 spaced circumferentially (i.e., each having a circumferential width of substantially less than 360 degrees) extending axially from one end to the other of drive sleeve 68b and allows the coolant to escape to the atmosphere. The finction of the slot 268 in the lantern ring 264 is to collect any fluid which may leak past an assumed failed seal at the tapered nozzle body 63b and the tapered sleeve 226 interface or the bore to tapered sleeve 226 interface and the secondary packing seal ring 56a, and to channel the leaked fluid to the axial passages 265 in the lantern ring 264. Grooves 269 perpendicularly intersecting circumferential grooves 268 channel the leaked fluid to the circumferential grooves 268. The function of the slot 276 in the sleeve end 272 is to collect any fluid which passes through the passages 265 in the lantern ring 264 and to channel that fluid to the axial passages 270 in the sleeve 68b. Thus, the primary leak path directs any fluid passing between the tapered nozzle body portion 63b and the sleeve 204, and/or between the sleeve 204 and the bore, which also leaks past a failed secondary packing seal ring 56a, to the passages 265 in the lantern ring 264 and the passages 270 in the sleeve 68b, from which the leaking fluid is discharged at the end 274 of the drive sleeve 68b outside of the vessel. Although not shown, the lantern ring 264, packing seal ring 56c, and sleeve 274 could easily be modified to channel the primary leak path between sleeve 274 and nozzle body 62b. The groove 276 is of sufficient depth to allow additional compression by tightening sleeve 68b should the seal shrink with time. Elements defining the secondary leak path include: an axial slot 280 in drive sleeve 68b which the channeling sleeve 268 overlays; and a radial groove 282 extending 360.degree. in the circumference of the drive sleeve 68b closed by the channeling sleeve 268. The radial groove 282 starts in the axial channel 280 and extends in the drive sleeve 68b past the channeling sleeve 268 where it opens to the outside of the vessel. Gasket 56 prevents in leakage on to the vessel. Thus, the secondary leak path directs any fluid passing between the tapered nozzle body portion 63b and the sleeve 204, and/or between the sleeve 204 and the bore, which also leaks past a failed first packing seal ring 56a and a failed second packing seal ring 56b and/or c to the radial channel 282, which then directs the fluid to axial groove 280 from which the leaking fluid is discharged outside of the vessel in a corrosion resistant means such that leakage will not erode the vessel. FIG. 18 shows a partial nozzle replacement assembly 300 which is a variation of the full nozzle replacement assembly 250 of FIG. 17, and which incorporates a feature or features from the partial nozzle replacement assembly 170 of FIG. 9, to provide a partial nozzle replacement assembly that includes an existing nozzle stub 152 adjacent the interior of the vessel 20. In this embodiment, like nozzle replacement assembly 170 (FIG. 9), a portion of the existing nozzle is removed leaving the nozzle stub 152 extending into the bore from the interior of the vessel. Both the nozzle stub 152 and its J-groove weld 34 are left in tact and substantially undisturbed. The entire portion 77f of the bore 30 extending from the end of the nozzle stub 152 to the exterior of the vessel is enlarged in diameter, including a portion 174 overlapping the end 162 of the nozzle stub 152. A shoulder 65b is formed in the interface of the smaller and larger diameter portions. The enlarged diameter bore portion 77f is threaded adjacent the exterior of the vessel. The replacement nozzle assembly 300 includes a nozzle body 62c and a drive sleeve 68c, similar to nozzle replacement assembly 250 of FIG. 17. However, the nozzle body 62c is configured like the one piece nozzle 71f of FIG. 9 in that it overlaps the existing nozzle stub 152. The ID of the replacement nozzle body 62c at the interior end 174 thereof is enlarged to receive therein the end 162 of the nozzle stub 152, as in replacement nozzle 170 of FIG. 9. A packing seal ring 56a is positioned between the bore shoulder 67b and the end 174 of the nozzle body 62c, surrounding the end 162 of the nozzle stub 152, and another packing seal ring 56d is applied at the flanged end 174 of the nozzle body 62c. The anti-rotation device 310 of the partial nozzle replacement assembly 300, which differs from the anti-rotation devices of full nozzle replacement assembly 250, includes an axial slot 171a in the existing nozzle stub 152 and a tab 208a machined into the nozzle body 62c and radially projecting therefrom into the slot 171a. If tortional loads are high a plurality of axial slots and tabs can be used. Alternatively, the anti-rotation device 310 may be formed by axial groove portion, circular or tapered in nature, in the existing nozzle stub 152 and a similar groove in nozzle body 62c into which the key stock is inserted and held (several grooves and key stocks could be used if tortional loads demanded such). The nozzle groove is of sufficient length to allow further compression loading from time to time The nozzle replacement assembly 300 is otherwise as described for nozzle replacement assembly 250 depicted in FIG. 17, and includes the primary and secondary leak paths as described for nozzle replacement assembly 250. FIG. 19 depicts a partial nozzle replacement assembly 320 similar to the partial nozzle replacement assembly 300 shown in FIG. 18, but which bolts the nozzle sleeve 68d to the vessel exterior with a flange 87a similar to the one used to bolt nozzle assembly 71c to the vessel as shown in FIG. 5. The nozzle body 62d is inserted into the bore, and the flange 87a along with channeling sleeve 268 (fabricated and fillet welded 324 to flange) is sealed against an annular taper guide 322 and the vessel OD by sealing (e.g., gasket) material 56, and bolted to the vessel exterior with threaded bolts 88c in threaded holes 90c in the vessel. Taper guide 322 provides alignment of the nozzle to the vessel such that the nozzle may be compressed into the vessel to form a tight interference fit to resist external bending loads that may be applied to the nozzle. (Though not shown for the other embodiments this may be applied to all of the embodiments in this application.) The drive sleeve 68d is then tightened to channeling sleeve 268 to compressively load the nozzle body 62d to the vessel. The jam nut 271 is then tightened to prevent the drive sleeve 68d from loosening. This embodiment also provides the same primary and secondary leak paths and anti-rotation device as in the partial nozzle replacement assembly 300, and is otherwise the same as the partial nozzle replacement assembly 300. FIG. 20 depicts a partial nozzle replacement assembly 330 also similar to the partial nozzle replacement assembly 300 shown in FIG. 18, but which bolts the drive sleeve 68e to the vessel exterior with an external flange 86a similar to the one used to bolt nozzle assembly 71b to the vessel as shown in FIG. 6. Exterior flange 86a is a separate piece from drive sleeve 68e (or in an alternate embodiment may be one-piece with the drive sleeve), and is threaded to the drive sleeve 68e. The external flange 86a is bolted to the vessel exterior by threaded bolts 88 in threaded holes 90 with the sealing (e.g., gasket) material 56 surrounding the taper guide 332 compressed between the end of a sleeve portion 334 of the flange 86a and the exterior of the vessel. Flange 86a is bolted on in this manner such that it does not have to conform to the curvature of the vessel as does flange 87a of FIG. 19 which can be difficult for heater nozzles inserted on the hillside of the spherical shaped head at the bottom of the pressurizer vessel The drive sleeve 68e is threaded to the flange 86a to compress the packing seal rings 56a-d. This embodiment is otherwise like the partial nozzle replacement assembly 300 (FIG. 18) and provides the same primary and secondary leak paths and anti-rotation device. Although only a single key stock is shown for each anti-rotation device, depending on the tortional loads experienced by the nozzle, multiple key stocks could be used in combination. In the embodiments described above, a structurally welded and seal welded nozzle may be full or partially removed by cutting or machining operations. As mentioned, the invention is also applicable to replacement of nozzles attached and sealed in other ways, (e.g., as described in the prior art discussed above and by mechanical attachment and sealing as described herein). A full or partial nozzle replacement, similar to a nozzle repair described below, may be of the precautionary type in which the existing nozzle has not failed in any way and the full or partial nozzle replacement by mechanical means is made for precautionary purposes. Typically, a precautionary replacement will also be made when the system is shut down for other reasons, such as scheduled refueling in a nuclear facility. Further, the invention is applicable to the repair of existing nozzles which do not require removal of the existing nozzle. FIGS. 21-25 disclose repair embodiments which leave the existing nozzle within the bore in tact, and further attach the existing nozzle to the vessel and mechanically seal the existing nozzle to the vessel. A nozzle repair may be used in the event that the existing nozzle leaks or as a precaution in which the existing nozzle has not failed in any way and the mechanical sealing and further attachment of the nozzle to the vessel are made for precautionary purposes. In the embodiments of FIG. 21-25, the existing nozzle is mechanically sealed to the vessel, and may be further attached to the vessel by a fillet weld between the existing nozzle and a sleeve which is mechanically attached to the vessel. FIG. 26 provides a system applicable to the embodiments of FIGS. 21-25 which enables the drive sleeve to be torqued even after the fillet weld is applied to the existing nozzle. In the embodiments of FIGS. 21-24, the existing nozzle is cut off outside of the vessel to enable mechanical sealing to proceed, and in the embodiment of FIG. 25, the existing nozzle is left entirely in tact by use of a split seal and flange. FIGS. 21-25 apply to nozzle repair, features and techniques disclosed herein and in the prior application for full and/or partial nozzle replacement. Typically, a precautionary repair will be made when the system is shut down for other reasons, such as scheduled refueling in a nuclear facility. FIGS. 21-24 depict a nozzle repair assembly 350, 360, 370, and 380 in which an existing nozzle 352 is left entirely in tact within the bore 30 but is cut off at some point 354 outside of the vessel 20. nozzle repair assembly 350 of FIG. 21 applies a technique similar to the partial nozzle replacement assembly of FIG. 9 to nozzle repair. Referring to FIG. 21, the diameter of the bore 30 is enlarged starting at a point spaced in the bore from the J-groove weld 34 to provide an enlarged diameter bore section 77f as in FIG. 9. The bore section 77f is threaded adjacent the exterior of the vessel 20 and a sleeve 71f is threaded to the bore, as in FIG. 9. Sealing (e.g., packing) material 56 positioned between the interior end 174 of the sleeve 71f and the shoulder 156 formed where the larger diameter bore section 77f meets the smaller diameter bore 30, and is compressed when the sleeve is threaded to the bore to provide the mechanical attachment and the mechanical seal. The nozzle repair assembly 350 is the same as the partial nozzle replacement assembly of FIG. 9, except that the entire existing nozzle 352 is left within the bore and no changes are made to the existing nozzle (and bore). The existing nozzle 352 may be welded to the sleeve 71f with a fillet weld 356 to provide for further attachment of the nozzle 352 to the vessel 20, functioning as an anti-ejection device or the sleeve 71f may be modified and a clamping device 406 used as shown in FIGS. 26 and 27 (described below) to allow the sleeve to be torqued from time to time to compress the mechanical seal and prevent leakage. In the nozzle repair assemblies 360, 370 and 380 depicted in FIGS. 22-24, respectively, the techniques of the partial nozzle replacement assemblies 300, 320 and 330 of FIGS. 18-20, respectively, are applied to repairing a nozzle. The nozzle repair assemblies 360, 370 and 380 are the same as the partial nozzle replacement assemblies 300, 320 and 330 of FIGS. 18-20, except that the entire existing nozzle 352 is left within the bore. Also, the existing nozzle 352 in nozzle repair assemblies 360, 370 and 380 may be welded to the respective sleeve with a fillet weld 356 to provide for further attachment of the nozzle 352 to the vessel 20, functioning as an anti-ejection device, or the respective sleeves may be modified as shown in FIG. 26 for the reason stated above in connection with FIG. 21. The nozzle repair assemblies 360, 370 and 380 of FIGS. 22-24 utilize the leak paths of FIGS. 18-20 and other elements shown in FIGS. 18-20, respectively. Another difference between the embodiments of FIGS. 22 and 24 and those of FIGS. 18 and 20 and is that in FIGS. 22 and 24 the exterior mechanical seal between the respective sleeve or flange is made with packing material in a short enlarged bore diameter section 358 defining an annular groove between the bore and the sleeve at the OD of the vessel, while in FIGS. 18 and 20 the seal is made on the exterior surface of the vessel OD with gasket material. The nozzle repair assembly 390 depicted in FIG. 25 is a combination of the nozzle repair assembly 360 and 380 in FIGS. 22 and 24. Nozzle repair assembly 390 utilizes a flange 86c similar to the clamp device 86b of FIG. 24 and a portion 392 of a drive sleeve similar to the drive sleeve 68c of FIG. 22. In addition, the flange 86c is split and is clamped to the existing nozzle 352 by bolts 394. The split flange 86c frictionally engages the existing nozzle to mechanically attach the nozzle to the vessel. This enables the sleeve portion 392 and the clamp device 86c to be attached to the existing nozzle 352 and the vessel 20 without cutting the existing nozzle and without the need for a weld to provide additional structural support. The sleeve portion 392 mechanically seals the existing nozzle 352 in the same manner as the partial nozzle replacement assembly of FIG. 18 and the nozzle repair assembly of FIG. 22 are sealed, except that the clamp device 86c may be tightened to the vessel after initial assembly and tightening of the clamp device 86c, without breaking any weld, by tightening bolts 88 to compress the mechanical seals therein after initial installation. However, if desired, the nozzle 352 may also be fillet welded to the clamp device 86c to provide additional support. FIG. 26 depicts a technique for attaching the sleeve of FIGS. 21-24 to an existing nozzle 352 so that the sleeve may be tightened to the bore while attached to the existing nozzle. In the nozzle -to- sleeve attachment 400, the nozzle 352 is welded to a compression ring 402, and the sleeve 61 is rotatably coupled to the compression ring 402 rather than being welded to the existing nozzle 352. The compression ring 402 is internally threaded, and an externally threaded tubular sleeve 404 through which the existing nozzle 352 passes is threaded to the compression ring 402. The tubular sleeve section 404 has wrenching flats 59 is rotatably coupled to the drive sleeve 61 by a mechanical clamp arrangement 406 comprising circumferential grooves 408, 409 in adjacent ends of the drive sleeve 61 and the tubular sleeve section 404, and a split clamp 412 having annular projections 414, 415. The annular projections 414, 415 of the split clamp 412 are rotatably received and engaged in grooves 408, 409, respectively. A jam nut 418 is threaded on the tubular sleeve section 404 against the compression ring 402. After the drive sleeve 61 has initially been installed and tightened, the tubular sleeve section 404, compression ring 402 and jam nut 418 (loosened) are installed and clamped to the drive sleeve 61 with the clamp arrangement 406, as follows. The compression ring 402 is welded to the existing nozzle with the fillet weld 356. The tubular sleeve section 404 is turned in a counter clockwise direction such that tubular sleeve section 404 rotates out of compression ring 402 and compresses the nozzle, with minimal loading, into the compression ring 402 to load the drive sleeve 61. The jam nut 418 is then tightened. During service, the loading on the drive sleeve 61 may be adjusted without breaking the fillet weld 356 by backing off the jam nut 418 and rotating the tubular sleeve section 404 using the wrenching flats 59. The jam nut 418 is then re-tightened against the compression ring 402. Also, depending upon the torqued relationship of the compression ring 402, drive sleeve 404 and jam nut 418, the nozzle-to-sleeve attachment 400 may provide either tension or no load to the existing nozzle 352, or compression as described above. Where the existing nozzle 352 is either tensioned or not loaded, ring 402 would not be referenced to as a "compression" ring. FIG. 27 depicts a technique for attaching the sleeve of FIGS. 21-24 to an existing nozzle 352 so that the sleeve may be tightened to the bore while attached to the existing nozzle. In the nozzle -to- sleeve attachment 400 (FIG. 26), the nozzle 352 is welded to a compression ring 402, and the sleeve 61 is rotatably coupled to the compression ring 402 which is welded to the existing nozzle 352. In the embodiment of FIG. 27 no weld to the nozzle is employed, and instead the nozzle is frictionally clamped to the sleeve 61 by a split clamp 420. The split clamp 420 includes the annular projection 414 of clamp 412 which is rotatably received and engaged in the groove 408 of the sleeve 61. The other end of the split clamp 420 includes a split ring 424 extending into frictional engagement with the nozzle 352. Tightening the bolt 394 compresses the split ring 424 around the nozzle 352 to frictionally clamp the nozzle. The sleeve 61 may be tightened simply by loosening bolts 394 on the split clamp 420. Once sleeve 61 is tightened, bolts 394 are retorqued. As mentioned above, after implementing a repair according to the embodiments of FIGS. 21-25, a full or partial nozzle replacement may be made later as described herein for the applicable replacement, e.g., FIGS. 17-20. For example, after a repair according to FIGS. 22, 23 or 24 was made, a partial nozzle replacement according to FIGS. 18, 19 or 20, respectively, may be made, and after the repair shown in FIG. 22 was made, the full nozzle replacement shown in FIG. 17 may be made. Other variations will be apparent to those of skill in the art from the disclosure herein. As also mentioned above, the implementations described herein of the nozzle replacements and repairs avoid all or some of the problems discussed above, and the embodiment of FIG. 17 avoids all of the problems discussed above. The partial nozzle replacements, such as the embodiment of FIG. 18, avoid all the concerns except that of continued cracking. Partial nozzle replacements that do not have sealing between the new and existing nozzles, such as the embodiment of FIG. 11, may not over come all the corrosion concerns if they are placed in an environment that is not stagnant. While further analysis, evaluation and information is necessary to determine whether all of the embodiments disclosed herein are acceptable for the life of the facility, they are all believed to be acceptable for at least short term, most likely long term, and in most cases the life of plant given that they are installed in the locations for which they were designed, e.g., those embodiments with a gap between the existing and new partial nozzle are in stagnant environments, and repaired nozzles include fracture mechanic evaluations justifying that the nozzle will not continue to crack beyond the seal. However, the repair embodiments and the partial nozzle replacement embodiments not employing seals between the existing and new partial nozzle (in environments which may not be suitable for long term corrosion concerns) could at least be used for an interim period until such time it was determined necessary or prudent to replace the repaired nozzle or partial nozzle with one of the other full or partial nozzle replacement embodiments described herein. In certain circumstances, such as particular plant modes of operation, one repair or replacement embodiment or technique may be more suitable than another given these conditions. Those experienced in the art are capable of making the determination as to whether or not a particular embodiment or technique used for a particular application can be considered short term, long term, or a life of plant repair or replacement. In the event the repair or replacement is considered as interim and it becomes necessary, those experienced in the art can select the appropriate full or partial nozzle replacement that corresponds to the repair or partial nozzle previously used. As indicated above, rather than replace all or part of an existing nozzle or repair an existing nozzle, the invention can be applied to provide a plug, particularly for a heater sleeve. For example, in the case of a failed heater and heater sleeve, the heater sleeve may be fully or partially removed and replaced as described above but with a plug or capped nozzle rather than a nozzle due to the fact that a new heater may not be available. All of the embodiments depicted in FIGS. 3-26 may be used in large bore piping, as well as pressure vessels in general, and do not require entry into the vessel or pipe or a remote system to install them. In the claims, the term vessel is used in a broad sense and, unless otherwise indicated, is meant to include, but not to be limited to, vessels, piping, etc., of different types which may operate under pressure and which may be used in different nuclear and non-nuclear ASME pressure vessel applications, and the term nozzle is used in a broad sense and is meant to include, but not be limited to, nozzles, sleeves, large bore pipes, pipe portions, etc. Also, where applicable in the claims, "nozzle" encompasses a nozzle assembly, which may include a nozzle having one or more parts, seals, one or more anti-rotation devices, and one or more leak paths. While the invention has been described and illustrated in connection with preferred embodiments, many variations and modifications, as will be evident to those skilled in this art, may be made without departing from the spirit and scope of the invention. For example, it will be apparent that one or more features in one embodiment may be applicable to other embodiments, or applied to a full or partial nozzle replacement, or to a repair. Although many examples are described above, specific reference of the applicability of a feature described in connection with one embodiment is not made in every other applicable embodiment One such example is that the thrust bearing 202 in FIG. 13 may be used in the embodiments depicted in many of the other figures. Other examples will be apparent to those of skill in this art. Therefore, the invention, as set forth in the appended claims, is not to be limited to the precise details of construction set forth above, as such variations and modifications are intended to be included within the spirit and scope of the invention as defined in the appended claims.