Method for elimination of thermal sleeve

Abstract

Disclosed is an arrangement and apparatus for reducing and / or preventing wear on a thermal sleeve in a nuclear reactor. The arrangement includes a first structure provided on or one of the thermal sleeve and a second structure provided on or within the head-penetrating adapter. At least a portion of the first structure and at least another portion of the second structure interact to prevent resistance, reduction, and / or rotation of the thermal sleeve about its central axis relative to the head-penetrating adapter. The apparatus includes a base for coupling to a reactor guide tube and a plurality of protruding members extending upward from the base. Each member has a portion for engaging a corresponding portion of a guide funnel of the thermal sleeve.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Non - Provisional Application No. 16 / 883,339, filed on May 26, 2020, entitled "METHOD FOR THERMAL SLEEVE ELIMINATION", the content of which is hereby incorporated by reference in its entirety.

Background Art

[0002] In a nuclear reactor, a thermal sleeve serves four purposes. The thermal sleeve protects the rod cluster control assembly (RCCA) drive rod from fluid effects present in the reactor vessel head plenum (e.g., cross - flow). The thermal sleeve facilitates hydraulic communication (flow to the CRDM) during RCCA insertion (control rod drop). The thermal sleeve provides alignment to the control drive rod for installation of the vessel head. The thermal sleeve also protects the head penetration and the CRDM housing from thermal transients of the reactor coolant.

[0003] The thermal sleeve includes an outer diameter (OD) and an inner diameter (ID) and includes a flange. The thermal sleeve wears at the flange and at the OD / ID. Wear of the thermal sleeve has been observed between the upper head of the nuclear reactor and the CRDM penetration housing. This wear has been measured using laser gauging to determine the amount by which a particular thermal sleeve has "dropped".

Summary of the Invention

Problems to be Solved by the Invention

[0004] Thermal sleeve flanges and OD / ID wear result in periodic maintenance costs. Failure of the thermal sleeve due to OD / ID wear requires costly repairs before power can be restored. Wear prediction through the Pressurized Water Reactor Owners Group (PWROG) program can be used to identify sleeves that will ultimately need intervention. Aggressive removal of thermal sleeves can eliminate or significantly delay future thermal sleeve inspections for any type of wear.

[0005] A method has been developed for removing a worn thermal sleeve and replacing it with a temporary “compressible thermal sleeve”. The method does not require removal of the CRDM motor assembly from the upper side of the reactor head. However, the method does not address failure mechanisms due to thermal sleeve wear and CRDM penetration housing. Therefore, even the compressible thermal sleeve is most likely to continue to wear with the CRDM penetration housing.

[0006] Based on operating experience with thermal sleeve wear at several nuclear power plants, there is a clear need to eliminate thermal sleeves used in nuclear reactors. Thermal sleeve flanges and / or ID / OD wear have been identified during inspections of nuclear reactors. Further, there is a need to replace the thermal sleeve with an extension tube mounted directly to the CRDM penetration housing of the nuclear reactor. Therefore, there is a strong and recurring need for permanent thermal sleeve replacement to eliminate the need for multiple variable thermal sleeve inspections over time.

[0007] In one aspect, the present disclosure provides a method for installing an extension tube within a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a threaded head penetration nozzle and a thermal sleeve disposed therein. The method includes removing the thermal sleeve from the threaded head penetration nozzle and aligning the extension tube with the threaded end of the head penetration nozzle. The extension tube comprises a threaded end and a non-threaded end, the threaded end being sized and configured to threadably couple to the threaded head penetration nozzle. The method further includes threading the threaded end of the extension tube onto the threaded end of the threaded head penetration nozzle, applying torque to the extension tube relative to the threaded end of the threaded head penetration nozzle, measuring the alignment of the extension tube relative to the threaded head penetration nozzle, installing a retaining fillet weld between the extension tube and the threaded end of the threaded head penetration nozzle, and installing a guide funnel at the non-threaded end of the extension tube.

[0008] In one aspect, the present disclosure provides a method for installing an extension tube within a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a non-threaded head penetration nozzle and a thermal sleeve disposed therein. The method includes machining the non-threaded CRDM housing, installing and aligning a threaded adapter at the machined end of the non-threaded CRDM housing, joining the threaded adapter to the machined end of the non-threaded CRDM housing, machining the bore defined by the non-threaded CRDM housing, machining the bore defined by the threaded adapter, machining the outer diameter of the joint between the machined end of the non-threaded CRDM housing and the threaded adapter, installing the extension tube in the threaded adapter, and installing a retaining fillet weld between the extension tube and the threaded adapter.

[0009] In addition to the foregoing, various other method and / or system and / or program product aspects are described and explained in the teachings of the text of the present disclosure (e.g., the claims and / or the detailed description of the invention) and / or the drawings.

[0010] The foregoing is a summary and, accordingly, may include simplification, generalization, inclusion, and / or omission of details. Thus, those skilled in the art will understand that the summary is merely illustrative and not intended to limit in any way. Other aspects, features, and advantages of the apparatus and / or process and / or other subject matter described herein will become apparent in the teachings set forth herein.

[0011] In one or more various aspects, the related system includes, but is not limited to, circuitry and / or programming for achieving aspects of the methods referenced herein, and the circuitry and / or programming can be substantially any combination of hardware, software, and / or firmware configured to affect aspects of the methods referenced herein depending on the design choices of the system designer. In addition to the foregoing, various other method and / or system aspects are described and explained in the teachings of the text of the present disclosure (e.g., the claims and / or the detailed description of the invention) and / or the drawings.

[0012] Furthermore, it is understood that any one or more of the embodiments, forms of the embodiments, and examples described below can be combined with any one or more of the other embodiments, forms of the embodiments, and examples described below.

[0013] The foregoing summary is merely illustrative and not intended to limit in any way. In addition to the exemplary aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the detailed description of the invention below.

[0014] The novel features of the described embodiments are set forth in detail in the appended claims. However, the described embodiments may be best understood both as to organization and method of operation, by reference to the following description, which is to be read in conjunction with the accompanying drawings.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0016] This application relates to PCT / US2020 / 019116, Attorney Docket No. 200457PCT, filed on February 20, 2020, entitled "ANTI-ROTATION ARRANGEMENTS FOR THERMAL SLEEVES", which is hereby incorporated by reference in its entirety.

[0017] Before describing various aspects of a method for eliminating a thermal sleeve within a nuclear reactor, or more specifically, replacing the thermal sleeve with an extension tube that is directly attached to the control rod drive mechanism (CRDM) penetration housing of the nuclear reactor in detail, it should be noted that the exemplary aspects are not limited to the application or use in the configuration and arrangement details of the components illustrated in the accompanying drawings and description. The exemplary aspects can be implemented or incorporated in other aspects, variations, and modifications, and can be practiced or carried out in various ways. Further, unless otherwise indicated, the terms and expressions used herein are selected for the purpose of describing the exemplary aspects for the convenience of the reader and are not intended to be limiting.

[0018] Furthermore, it is understood that any one or more of the forms, expressions of forms, and examples described below can be combined with any one or more of the other forms, expressions of forms, and examples described below.

[0019] In one aspect, the present disclosure is directed to a method for eliminating a thermal sleeve within a nuclear reactor as described above. In another aspect, the present disclosure is directed to a method for replacing the thermal sleeve with an extension tube that is directly attached to the CRDM penetration housing of the nuclear reactor. In one aspect, the thermal sleeve can be removed from below the reactor vessel closure head (RVCH) using existing equipment and processes for thermal sleeve removal. An extension tube that is directly attached to the CRDM penetration housing is installed. According to one aspect, there are two main components required to eliminate the thermal sleeve. The first is a tube, and the second is an upper guide sleeve. The purpose of the upper guide sleeve is to provide final guidance of the drive rod to the CRDM through the latch stop plate.

[0020] Generally, there are two styles of CRDM penetration housings: threaded and non-threaded. The threaded penetration has 3 3 / 4”-8 UN-2A threads. The non-threaded penetration has a bare tube end with a radius on both the OD and ID for face-to-face transition.

[0021] In the case of threaded penetration, the extension tube can be manufactured to a specific length such that the funnel height will be set to the same height as the existing thermal sleeve when threaded and tightened. For non-threaded penetrations, a penetration nozzle can be welded to the penetration section to provide an appropriate male thread for attaching the extension tube.

[0022] A special compressible guide sleeve (CGS) is designed to provide the same function as the guide sleeve performs in, for example, the replacement of RVCH and AP1000 pressurized water reactors. The CGS can be installed from below the RVCH together with the extension tube. The present disclosure provides a new and innovative process for improving the extension tube to the in-service RVCH.

[0023] Thermal sleeves indicating flange and / or ID / OD wear are good candidates for the removal and replacement of the extension tube to eliminate the periodic maintenance costs and failures that require costly repairs before power restoration is possible. Wear prediction through the PWROG program can be used to identify the thermal sleeves that will ultimately require intervention. By combining proactive removal with engineering justification, future thermal sleeve inspections for various types of wear can be eliminated or significantly delayed.

[0024] FIG. 1 is a schematic cross-sectional view of an upper portion of a conventional nuclear reactor 2 showing a portion of a reactor vessel 4 penetrated by a plurality of head penetration nozzles 6 extending downwardly from a CRDM housing 8. FIG. 2 is a schematic cross-sectional view of a conventional reactor vessel head penetration showing the CRDM housing 8, the head penetration nozzles 6, and the thermal sleeves 10. Continuing to refer to the cross-sectional views of FIGS. 1 and 2, the thermal sleeves 10 including the guide funnels 12 are positioned within each head penetration nozzle 6 below each CRDM housing 8 such that each guide funnel 12 is located directly above and spaced from a corresponding guide tube 14 extending from an upper support plate 16 within the reactor vessel 4. The thermal sleeves 10 are housed within the head penetration nozzles 6 within the reactor vessel 4 except within the region 15 (FIG. 2) where the thermal sleeves 10 are exposed to the reactor coolant.

[0025] What is presently contemplated is that wear of the thermal sleeves 10 and the head penetration nozzles 6 in the region 13 shown in FIGS. 1 and 2 results from rotation of the thermal sleeves 10 within the head penetration nozzles 6 about the central axis 18 of the thermal sleeves 10. Vortices within the reactor coolant flowing within the reactor vessel 4 contact the thermal sleeves 10 (i.e., in the region 15), and it is thought that the thermal sleeves 10 rotate about their central axis 18 relative to the head penetration nozzles 6.

[0026] The present disclosure provides a method for eliminating the thermal sleeves 10 of a nuclear reactor 2, and more particularly, a method for replacing the thermal sleeves 10 of a nuclear reactor 2 with extension tubes directly attached to the CRDM penetration housings 6 of the nuclear reactor 2. These methods achieve a robust and recurring need for replacement of the permanent thermal sleeves 10 in order to eliminate the need for inspection of the plurality of varying thermal sleeves 10 over a long period of time.

[0027] Figure 3 is a cross-sectional view 100 of the thermal sleeve 110 and the CDRM housing 108 in a non-worn state. The thermal sleeve 110 includes a flange 112 that defines an outer diameter 114 (OD) and an inner diameter 116 (ID) that are subject to wear. The thermal sleeve 110 has been observed to wear between the upper head of the nuclear reactor and the CRDM penetration housing 108.

[0028] Figure 4 is a cross-sectional view 120 of the thermal sleeve 110 and the CDRM housing 108 in a substantially worn state. As described above, the thermal sleeve 110 shows substantial wear at the flange 112, as well as at the OD 114 and ID 116. This wear may be revealed by the dropping of the thermal sleeve 110.

[0029] Figure 5 is a cross-sectional view 140 of the thermal sleeve 110 and the CDRM housing in a worn state up to the separation point of the thermal sleeve 110. As shown, the thermal sleeve 110 has developed a crack 118 that results in the separation of the thermal sleeve 110. Cross-sectional view 140 also shows further wear of the flange 112, OD 114, and ID 116 relative to cross-sectional view 120 shown in Figure 4.

[0030] Referring to FIGS. 1-5, the extension tube can now be improved to the heads of various reactor vessels 4 (FIG. 1) where thermal sleeves 10 (FIGS. 1 and 2), 110 (FIGS. 3-5) are currently installed. A typical CRDM penetration design has either a "screw-in" or "non-screw-in" end that protrudes through the head of the reactor vessel 4. Referring also to FIG. 6, an extension tube 200 is shown that can be installed in the nuclear reactor 4 in place of the thermal sleeves 10, 110. The extension tube 200 includes a substantially cylindrical body 202 and a screw-in end 204 that will protrude through the head of the reactor vessel 4 once installed and is threadably coupled to a threaded penetration nozzle. FIG. 7 shows an extension tube 240 that can be installed in the nuclear reactor 4 in place of the thermal sleeves 10, 110. The extension tube 240 includes a substantially cylindrical body 242 and a non-screw-in end 244 that, for example, will protrude through the head of the reactor vessel 4 once installed and is coupled to a non-threaded penetration nozzle by suitable welding.

[0031] FIG. 8 is a schematic cross-sectional view of the upper portion of a conventional nuclear reactor 302 showing a portion of a reactor vessel head 304 penetrated by a plurality of head penetration nozzles 306 extending downward from a CRDM housing 308. An extension tube 310 is coupled to the distal end 314 of the head penetration nozzle 306. The distal end 316 of the extension tube includes a guide funnel 312. The head penetration nozzle 306 includes a compressible guide sleeve 318. A threaded penetration adapter 320 is coupled between the extension tube 310 and the head penetration nozzle 306. In one aspect, the threaded penetration adapter 320 is employed on the non-threaded head penetration nozzle 306 to facilitate installation of the extension tube 310 to the non-threaded head penetration nozzle 306. The threaded penetration adapter 320 is welded to the end of the non-threaded head penetration nozzle 306. The compressible guide sleeve 318 is further described in co-pending Patent Application No. PCT / US2019 / 015797, filed Jan. 30, 2019, entitled "THERMAL SLEEVE", the entire disclosure of which is hereby incorporated by reference.

[0032] FIG. 9 is a cross-sectional view of a threaded through adapter 320 coupled between an extension tube 310 and a head through nozzle 306. The threaded through adapter 320 includes a body 322 having an upper end portion adapted and configured to couple to a non-threaded end portion of the head through nozzle 306 and a lower end portion adapted and configured to couple to the extension tube 310. In one aspect, the upper end portion of the body 322 of the threaded through adapter 320 may be welded to the non-threaded head through nozzle 306 at a connection portion 324, and the lower end portion of the threaded adapter body 322 may be welded to the extension tube 310 at a connection portion 326. In one aspect, the connection portion 326 transitions to steel by a two-metal weld of the extension tube 310. In various aspects, the threaded through adapter 320 may include threads for threadably coupling to, for example, the non-threaded head through nozzle 306 and / or the extension tube 310.

[0033] FIG. 10 is a cross-sectional view of a head through nozzle 306 having an extension tube 310. The head through nozzle 306 extends downwardly from a latch housing 336 and penetrates a reactor vessel head 304. The latch housing 336 includes a CRDM motor 330 and a compressible guide sleeve 332. The latch housing 336 is coupled to the head through nozzle 306 via a two-metal weld 334. The head through nozzle 306 is coupled to the extension tube 310 within the reactor vessel head 304 through a threaded through adapter 320. The extension tube 310 is coupled to a guide funnel 312. As shown in FIG. 10, the thermal sleeve of the head through nozzle 306 is replaced by the extension tube 310.

[0034] FIG. 11 is a cross-sectional view of a head through nozzle 306 positioned through a reactor vessel head 304. The end portion of the head through nozzle outside the reactor vessel head 304 includes a CRDM head adapter 337. The head through nozzle 306 defines a space 338 that typically includes a significantly missing thermal sleeve.

[0035] FIG. 12 is a cross-sectional view of a head penetration nozzle 306 having an extension tube 310. The head penetration nozzle 306 is coupled to the extension tube 310 via an optional threaded penetration adapter 320. A compressible guide sleeve 332, shown in detail in FIG. 14, is normally contained within a space 340 defined by the head penetration nozzle 306.

[0036] FIG. 13 is a perspective view of a compressible guide sleeve 332 received within a space 340 defined by a head penetration nozzle 306 as shown in FIG. 12. The compressible guide sleeve 332 includes a three-leaf compressible flex section 342 for compressibility and rigidity. In various embodiments, the compressible guide sleeve may comprise at least two and three or more compressible sleeves. Each of the leaf compressible flex sections 342 includes a flange 344 positioned within the CRDM housing 308. The compressible guide sleeve 332 is installed within the CRDM penetration to facilitate guiding of the drive rod into the latch housing 336 (FIG. 10). The bottom end of the compressible guide sleeve 332 includes an alignment feature 346. The existing thermal sleeve exclusion modification in the new RVCH employs a smaller guide sleeve similar to the cut thermal sleeve. The purpose of the guide sleeve is to provide guidance of the drive rod to the CRDM latch assembly. The compressible guide sleeve 332 performs the same function as the guide sleeve and is installed from below the reactor vessel head 304 (FIGS. 8 - 12) after the extension tube 310 is installed on the head penetration nozzle 306. The design of the compressible guide sleeve 332 allows it to have sufficient flexibility to be installed through the CRDM penetration, yet is rigid / inflexible enough to require a dedicated fixture to compress the compressible guide sleeve 332 prior to installation. This rigidity is sufficient to maintain this rigidity in place under all of the design basis conditions of the nuclear power plant.

[0037] The entire installation process of the extension tube 310 occurs under the RVCH, requires no modification or removal of the CRDM, and requires no modification of the upper internal components. The Under-the-head installation process is known and has been developed by the owner of this application. By replacing the entire thermal sleeve with the extension tube 310, all future wear of the thermal sleeve at the installation location is eliminated. The extension tube 310 does not require wear inspection throughout its lifespan.

[0038] Figure 14 shows the extension tube 310 having a guide funnel 312 and a threaded through adapter 320. In one aspect, the guide funnel 312 is foldable and configured to fail before a CRDM or fuel damage occurs if it shifts during head installation. In one aspect, the threaded through adapter 320 includes a threaded end having an internal thread 348 that is threadably coupled to the external thread 349 of the head penetration nozzle 306 (Figs. 8 - 13). During the thermal sleeve replacement process, a retaining fillet weld 352 is provided between the threaded through adapter 320 and the head penetration nozzle 306 to stabilize the connection. The threaded through adapter 320 is coupled to the extension tube 310 by a weld 354. The extension tube 310 is coupled to the guide funnel 312 by a retaining fillet weld 356.

[0039] Figure 15 is a process 400 for removing the thermal sleeve that requires removal. Here, process 400 will be described with reference to Figs. 1 - 5 and Fig. 15. The thermal sleeves 10 (Figs. 1 and 2), 110 (Figs. 3 - 5) that require removal are identified at 402. The IDs of the thermal sleeves 10, 110 are flap-type and are cleaned at 404. An electrical discharge machining (EDM) head is installed on one section of the thermal sleeves 10, 110 at 406 and a series of cuts are made. When the series of cuts is completed, the thermal sleeves 10, 110 are removed at 408 and the head penetration nozzle 306 is cleaned and inspected at 410. The removal of the thermal sleeves 10, 110 is now complete at 412.

[0040] Figure 16 shows a process 440 for installing a threaded extension tube. Here, process 400 will be described with reference to FIGS. 1-5, 8-14, and 16. Thermal sleeves 10, 110 are removed at 442, and a threaded extension tube 310 is installed at 444. The extension tube 310 is torqued to the head penetration nozzle 306 using a torque tool at 446. The alignment of the extension tube 310 is measured at 448. A retaining fillet weld 352 is installed at 450. A compressible guide sleeve 332 is installed at 452, and the alignment of the extension tube 310 is finally measured at 454. The installation is now complete, and the extension tube 310 is in its final installed configuration at 456. Here, the details of the extension tube installation process 440 will be described in more detail.

[0041] Referring further to FIGS. 16, 17, and 18, process step 444 of installing the threaded extension tube 310 is shown. As shown in FIG. 17, the extension tube 310 with a threaded penetration adapter 320 aligns with a threaded head penetration nozzle 306 extending through the reactor vessel head 304. The threaded head penetration nozzle 306 includes a threaded end 307 having a male thread 349 configured to threadably engage a female thread 348 of the threaded end of the threaded penetration adapter 320. As previously discussed, the threaded penetration adapter 320 is coupled to the extension tube 310 by a weld 354. As shown in FIG. 18, the female thread 348 of the threaded end of the threaded penetration adapter 320 is threadably engaged with the male thread 349 of the threaded end 307 of the threaded penetration adapter 320.

[0042] Referring further to FIGS. 16-18, FIGS. 19 and 20 show applying torque to the extension tube 310 with respect to the head penetration nozzle 306 at 446 using a torque tool 500.

[0043] Referring further to FIGS. 16 - 20, FIGS. 21 - 23 show process 448 for measuring the alignment of extension tube 310 after appropriate torque has been applied to head penetration nozzle 306, where FIG. 21 is a cross - sectional view 520 of the alignment measurement test of extension tube 310, FIG. 22 is a perspective view of gauge 522 used in the measurement 448 process, and FIG. 23 is a cross - sectional view of the alignment of drive rod 530 with respect to extension tube 310. Gauge 522 is inserted into guide funnel 312 through extension tube 310 and head penetration nozzle 306 and into CRDM housing 308. Gauge 522 rotates and fits into guide funnel 312. The alignment of extension tube 310 is measured with respect to a nominal centerline having a maximum allowable offset from the nominal centerline. Data A is measured at points along extension tube 310, a first radial offset 524 extending radially from gauge 522 located at the end of extension tube 310 near guide tube 312, a second radial offset 526 located within head penetration nozzle 306 just outside reactor vessel head 304, and a third radial offset 528 located within CRDM housing 308. The amount of shift for data A is determined at each radial offset 524, 256, 528 location. In FIG. 23, the alignment of drive rod 532 is shown with respect to the entrance of guide funnel 312.

[0044] When the measurement 448 of the alignment of extension tube 310 is complete, a hold - fillet weld 352 is installed 450. Referring further to FIGS. 16 - 23, FIG. 24 shows hold - fillet weld 352 installed 450 between threaded end 307 of head penetration nozzle 306 and threaded penetration adapter 320 coupled to extension tube 310 by weld 354.

[0045] Following the installation 450 of the maintain fillet weld 352, a compressible guide sleeve 332 is installed 452. Further referring to FIGS. 16-24, FIGS. 25-29 show the process 452 of installing the compressible guide sleeve 332. As shown in FIG. 25, the three-leaf compressible flex section 342 of the compressible guide sleeve 332 is compressed to shrink the flange 344 of the compressible flex section 342 to a size suitable for introduction into the guide funnel 312. FIG. 26 shows a compression tool 536 that can be employed to compress the compressible guide sleeve 332 before inserting the compressible guide sleeve 332 into the guide nozzle 312. FIG. 27 shows the compressible guide sleeve 332 in its compressed configuration inserted through the head penetration nozzle 306 and the CRDM head adapter 337 such that the flange 344 of the compressible flex section 342 is positioned just above a counterbore ledge 536 defined within the CRDM head adapter 337 section of the head penetration nozzle 306. In FIG. 28, the compressible flex section 342 of the compressible guide sleeve 332 is released such that the flange 344 of the compressible flex section 342 engages a counterbore ledge 536 defined within the CRDM head adapter 337 section of the head penetration nozzle 306. The counterbore ledge 534 holds the compressible guide sleeve 332 within the CRDM head adapter 337 section of the head penetration nozzle 306. FIG. 29 shows the compressible guide sleeve 332 in its final installed state. Here, the final measurement 454 of the extension tube 310 can be performed.

[0046] Referring further to FIGS. 16 - 29, FIGS. 30 - 33 show the final installation arrangement 456 of the extension tube 310. FIG. 30 is a cross - sectional view of the reactor vessel head 304 showing the extension tube 310 coupled to the head penetration nozzle 306 installed inside the reactor vessel head 304. FIG. 31 is a detailed view of the installed extension tube 310 coupled to the head penetration nozzle 306 showing the extension tube retaining weld 352. FIG. 32 is a cross - sectional view of the extension tube 310 coupled to the head penetration nozzle 306 installed inside the reactor vessel head 304. FIG. 33 is an elevation view of the extension tube 310 coupled to the head penetration nozzle 306 installed inside the reactor vessel head 304.

[0047] FIG. 34 shows the head penetration nozzle 306 having a screw 552 that cannot be used due to wear, damage, or size mismatch. FIG. 35 is a cross - sectional view of the head penetration 306 nozzle shown in FIG. 34. Referring now to FIGS. 17, 34, and 35, in one aspect, a screw - in adapter 550 may be employed incidentally when the male screw 349 on the screwing end 307 of the CRDM head penetration nozzle 306 cannot be used due to wear, damage, or size mismatch. The screw - in adapter 550 is welded 554 under the male screw 349 of the head penetration nozzle 310. The screw - in adapter 550 includes a male screw 552 suitable for threadedly coupling a female screw 348 onto the screw - in adapter 320 of the extension tube 310.

[0048] The on - site installation of the extension tube 310 becomes more complex in nuclear power plants without a CRDM housing with a screwing head penetration nozzle 306. Additional field machining is required to prepare a non - screwing CRDM housing for welding and to perform post - welding cleaning. The design of the extension tube 310 remains common between the screwing CRDM housing and the non - screwing CRDM housing. The process for installing the extension tube 310 on the non - screwing CRDM housing is described below.

[0049] FIG. 36 is a process 600 for installing an extension tube on a non-screw-in CRDM housing. Referring also to FIGS. 37-39, process 600 begins with machining 602 of non-screw-in CRDM housing 650. In other words, CRDM housing 650 does not include a screw-in head penetration nozzle having a screw-in end 307 with male threads 349 as described with reference to FIGS. 3-35. FIG. 37 is a cross-sectional view of non-screw-in CRDM housing 650 before machining. Machining step 602 includes preparing surface 652 (FIG. 37, pre-machining) of the geometry of non-screw-in CRDM housing 650 for mechanical welding and restoring ID bore 654 of non-screw-in CRDM housing 650. FIG. 38 is a cross-sectional view of non-screw-in CRDM housing 650 after machining 602. FIG. 39 is a detailed view of the cross-sectional view of the non-screw-in CRDM housing shown in FIG. 38. As shown in FIGS. 38 and 39, surface 656 (after machining) of non-screw-in CRDM housing 650 has its radius removed and is machined to provide a preparation for welding. FIG. 39 shows a detailed view of machined surface 656 of non-screw-in CRDM housing 650.

[0050] FIG. 41 shows a gap 668 defined between machined end surface 656 of non-screw-in CRDM housing 650 and non-screw-in end 654 of screw-in adapter 660. Continuing to refer to FIGS. 36-39 and also referring to FIGS. 14, 40, and 41, the next step in process 600 is to install and align screw-in adapter 660 on machined non-screw CRDM housing 650. As shown in FIG. 40, screw-in adapter 660 includes male threads 662 sized and configured to receive female threads 348 of extension tube 310 (see, e.g., FIG. 14) and a non-screw end 664 configured to abut machined end surface 656 of non-screw CRDM housing 650. Screw-in adapter 660 also defines a bore 670. As shown in FIG. 41, gap 668 is defined between machined end surface 656 of non-screw-in CRDM housing 650 and the non-screw-in end of screw-in adapter 650.

[0051] Figure 42 shows a threaded adapter 660 joined to the non-threaded CRDM housing 650. Continuing to refer to FIGS. 36-41 and also referring to FIG. 42, the next step in process 600 is to join the threaded adapter 660 to the non-threaded CRDM housing 650 at 606. In one aspect, the threaded adapter 660 is joined to the CRDM housing by a penetration welding technique at 606 to form a joint 672. In one aspect, the threaded adapter 660 can be joined to the non-threaded CRDM housing 650 by a full penetration weld at 606 that has no gap between the filler material and the root of the joint 672. In one aspect, the threaded adapter 660 can be welded to the non-threaded CRDM housing 650, which can be performed, for example, using a special semi-automatic gas tungsten arc welding (GTAW) welding head.

[0052] Figure 43 shows the machined bores 654, 670 defined by the non-threaded CRDM housing and the threaded adapter. Continuing to refer to FIGS. 36-42 and also referring to FIG. 43, the next step in process 600 is to machine 608 the bore 670 defined by the threaded adapter 660 and / or the bore 654 defined by the non-threaded CRDM housing 650. In this step, the integral backing ring / alignment ring is removed.

[0053] Figure 44 shows the machined / ground OD 674 of the joint 672. Continuing to refer to FIGS. 36-43 and also referring to FIG. 44, the next step in process 600 is to machine / grind 610 the OD 674 of the joint 672, such as a penetration weld cap, for inspection. FIGS. 45 and 46 show the threaded adapter 660 installed in the non-threaded CRDM housing 650, which is installed under the reactor vessel head 304 and is ready to receive the extension tube 310.

[0054] Figure 47 shows the threaded adapter 320 of the extension tube 310 installed on a threaded adapter attached to the unthreaded CRDM housing from below the reactor vessel head 304. Continuing to refer to FIGS. 36-46 and also referring to FIGS. 14 and 47, the next step of process 600 is to install the threaded adapter 320 of the extension tube 310 on a threaded adapter 660 attached to the unthreaded CRDM housing from below the reactor vessel head 304. This step includes threading the extension tube 310 and applying torque on the threaded adapter 660 in a manner similar to the manner described above with reference to 17-20.

[0055] Figure 48 shows the fillet weld 674 for retention between the threaded adapter 320 of the extension tube 310 and the threaded adapter 660 of the unthreaded CRDM housing 650. Continuing to refer to FIGS. 36-47 and also referring to FIGS. 14 and 48, the next step of process 600 is to install the fillet weld 674 for retention 614. Process 600 may include, for example, installing the guide funnel 312 as described above with reference to FIGS. 8-14. Process 600 may further include measuring the alignment of the extension tube using the same process as described above with reference to FIGS. 21-23, for example. Process 600 may further include installing the compressible guide sleeve 332 using the same process as described above with reference to FIGS. 25-29, for example.

[0056] For purposes of illustration, specific embodiments have been shown and described herein, but a wide variety of alternative and / or equivalent embodiments or implementations calculated to achieve the same purpose may be substituted for the embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptation or variation of the embodiments discussed herein.

[0057] Examples of methods and / or systems of various aspects of the present disclosure are provided below. Aspects of the methods and / or systems may include any one or two or more of the examples described below, and any combination.

[0058] Method for installing an extension tube in a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a threaded head penetration nozzle and a thermal sleeve disposed therein. The method includes removing the thermal sleeve from the threaded head penetration nozzle and aligning the extension tube with the threaded end of the head penetration nozzle. The extension tube comprises a threaded end and a non-threaded end, and the threaded end is sized and configured to be threadably coupled to the threaded head penetration nozzle. The method further includes threading the threaded end of the extension tube onto the threaded end of the threaded head penetration nozzle, applying torque to the extension tube relative to the threaded end of the threaded head penetration nozzle, measuring the alignment of the extension tube relative to the threaded head penetration nozzle, installing a retaining fillet weld between the extension tube and the threaded end of the threaded head penetration nozzle, and installing a guide funnel at the non-threaded end of the extension tube.

[0059] Example 2 - The method according to Example 1, including installing a compressible guide sleeve in the CRDM housing.

[0060] Example 3 - The method according to Example 2, wherein installing the compressible guide sleeve in the CRDM housing includes compressing the compressible guide sleeve and inserting the compressed guide sleeve into the guide funnel through the extension tube, the head penetration nozzle, and the CRDM housing. Installing the compressible guide sleeve in the CRDM housing further includes releasing the compression of the compressible guide sleeve for retainable coupling to the CRDM housing.

[0061] Example 4 - The method according to Example 2 or 3, wherein the compressible guide sleeve comprises a plurality of leaf compressible flexure sections, and each of the plurality of leaf compressible flexure sections comprises a flange. The method includes compressing the plurality of leaf compressible flexure sections to contract the flange before inserting the compressed guide sleeve into the guide funnel, and releasing the compression of the compressible guide sleeve to engage the flange with a counterbore ledge defined by the CRDM housing after insertion into the CRDM housing.

[0062] Example 5 - The method according to any one of Examples 1 to 4, including performing a final measurement of the alignment of the extension tube.

[0063] Example 6 - The method according to any one of Examples 2 to 5, wherein the compressible guide sleeve is inserted into the guide funnel from a position below the reactor vessel head.

[0064] Example 7 - The method according to any one of Examples 1 to 6, wherein the extension tube is installed from a position below the reactor vessel head.

[0065] Example 8 - The method according to any one of Examples 1 to 7, including aligning the extension tube with the threaded end of the head penetration nozzle and joining a threading adapter to the threaded end of the threading head penetration nozzle before threading the threaded end of the extension tube into the threaded end of the threading head penetration nozzle, the threading adapter being sized and configured to threadably couple to the threaded end of the extension tube and comprising a male thread.

[0066] Method for installing an extension tube in a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a non-threaded head-through nozzle and a thermal sleeve disposed therein. The method includes machining the non-threaded CRDM housing, installing and aligning a threaded adapter at the machined end of the non-threaded CRDM housing, joining the threaded adapter to the machined end of the non-threaded CRDM housing, machining the bore defined by the non-threaded CRDM housing, machining the bore defined by the threaded adapter, machining the outer diameter of the joint between the machined end of the non-threaded CRDM housing and the threaded adapter, installing the extension tube in the threaded adapter, and installing a retaining fillet weld between the extension tube and the threaded adapter.

[0067] Example 10 - The method according to Example 9, wherein machining the non-threaded CRDM housing includes preparing the surface of the non-threaded CRDM housing and restoring the inner diameter of the bore defined by the non-threaded CRDM housing.

[0068] Example 11 - The method according to Example 9 or 10, wherein joining the threaded adapter to the machined end of the non-threaded CRDM housing includes performing a penetration welding technique to form the joint.

[0069] Example 12 - The method according to any one of Examples 9 to 11, wherein joining the threaded adapter to the machined end of the non-threaded CRDM housing includes performing a full penetration welding technique to form the joint.

[0070] Example 13 - The method according to any one of Examples 9 to 12, wherein installing the extension tube in the threaded adapter includes threading the extension tube onto the threaded adapter and applying torque to the extension tube with respect to the threaded adapter.

[0071] The method according to any one of Examples 9 to 13, including measuring the alignment of the threaded head penetration nozzle of the extension tube.

[0072] The method according to any one of Examples 9 to 14, including installing a guide funnel at the non-threaded end of the extension tube.

[0073] Example 16. The method according to any one of Examples 9 to 15, including installing a compressible guide sleeve in the non-threaded CRDM housing.

[0074] Example 17 - Installing a compressible guide sleeve in the non-threaded CRDM housing includes compressing the compressible guide sleeve and inserting the compressed guide sleeve through the extension tube, the head penetration nozzle, and the non-threaded CRDM housing. Installing the compressible guide sleeve in the non-threaded CRDM housing further includes releasing the compression of the compressible guide sleeve to removably couple it to the non-threaded CRDM housing.

[0075] Example 18 - The method according to Example 16 or 17, where the compressible guide sleeve comprises a compressible flex section of a plurality of leaves, and each of the compressible flex sections of the plurality of leaves comprises a flange. The method includes compressing the compressible flex section of the plurality of leaves to contract the flange before inserting the compressed guide sleeve into the extension tube, and releasing the compression of the compressible guide sleeve to engage the flange with a counterbore ledge defined by the non-threaded CRDM housing after insertion into the non-threaded CRDM housing.

[0076] The method according to any one of Examples 9 to 18, including performing a final measurement of the alignment of the extension tube.

[0077] Example 20 - The method according to any one of Examples 16 to 19, wherein the compressible guide sleeve is inserted into the guide funnel from a position below the reactor vessel head.

[0078] Example 21 - The method according to any one of Examples 9 to 20, wherein the extension pipe is installed from a position below the reactor vessel head.

Claims

1. A method for installing an extension tube in a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a threaded head through nozzle and a thermal sleeve disposed therein, comprising: removing the thermal sleeve from the threaded head through nozzle; installing the extension tube in place of the replacement thermal sleeve; installing a guide funnel at the non-threaded end of the extension tube; installing the extension tube in place of the replacement thermal sleeve comprises: aligning the extension tube with the threaded end of the threaded head through nozzle; wherein the extension tube comprises a threaded end and the non-threaded end, and the threaded end of the extension tube is sized and configured to be threadably coupled to the threaded end of the threaded head through nozzle; threading the threaded end of the extension tube onto the threaded end of the threaded head through nozzle; applying torque to the extension tube relative to the threaded end of the threaded head through nozzle; measuring the alignment of the extension tube relative to the threaded head through nozzle; installing a retaining fillet weld between the extension tube and the threaded end of the threaded head through nozzle; A method comprising the above steps.

2. The method according to claim 1, further comprising installing a compressible guide sleeve in the CRDM housing.

3. Installing the compressible guide sleeve in the CRDM housing comprises: compressing the compressible guide sleeve; inserting the compressed guide sleeve through the extension tube and the threaded head through nozzle into the guide funnel and into the CRDM housing; releasing the compression of the compressible guide sleeve to couple the compressible guide sleeve to the CRDM housing in a retainable manner; The method according to claim 2, comprising the above steps.

4. The compressible guide sleeve comprises a compressible flex section of a plurality of leaves; each of the compressible flex sections of the plurality of leaves comprises a flange; The method further comprises: compressing the compressible flex sections of the plurality of leaves to shrink the flange before inserting the compressed guide sleeve into the guide funnel; After insertion into the CRDM housing, releasing the flange and releasing the compression of the compressible guide sleeve to engage with a counterbore ledge defined by the CRDM housing; The method according to claim 2 or 3, comprising.

5. The method according to any one of claims 1 to 4, comprising performing measurement of the alignment of the extension tube.

6. The method according to any one of claims 2 to 4, wherein the compressible guide sleeve is inserted into the guide funnel from a position below the reactor vessel head of the nuclear reactor.

7. The method according to any one of claims 1 to 6, wherein the extension tube is installed from a position below the reactor vessel head of the nuclear reactor.

8. The method according to any one of claims 1 to 7, wherein the extension tube comprises a threaded adapter including the threaded end of the extension tube.

9. A method for installing an extension tube in a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a non-threaded head penetration nozzle and a thermal sleeve disposed therein, Removing the thermal sleeve from the CRDM housing; Machining an end of the non-threaded head penetration nozzle; Installing and aligning a threaded adapter on the machined end of the non-threaded head penetration nozzle; Joining the threaded adapter to the machined end of the non-threaded head penetration nozzle; Machining a bore defined by the non-threaded head penetration nozzle; Machining a bore defined by the threaded adapter; Machining an outer diameter of a joint between the machined end of the non-threaded head penetration nozzle and the threaded adapter; Installing the extension tube on the threaded adapter, wherein the threaded adapter and the extension tube are replaced with the thermal sleeve removed from the CRDM housing, installing the extension tube on the threaded adapter; Installing a retaining fillet weld between the extension tube and the threaded adapter; A method, comprising.

10. Machining the end of the non-threaded head penetration nozzle is, The method according to claim 9, comprising machining the surface of the non-threaded head through nozzle so as to shorten the length of a part of the peripheral portion of the non-threaded head through nozzle.

11. The method according to claim 9 or 10, wherein joining the threaded adapter to the machined end of the non-threaded head through nozzle includes performing a penetration welding technique to form the joint.

12. The method according to any one of claims 9 to 11, wherein joining the threaded adapter to the machined end of the non-threaded head through nozzle includes performing a full penetration welding technique to form the joint.

13. Installing the extension tube on the threaded adapter comprises threading the extension tube onto the threaded adapter, and applying torque to the extension tube with respect to the threaded adapter, and the method according to any one of claims 9 to 12.

14. The method according to any one of claims 9 to 13, comprising measuring the alignment of the extension tube with respect to the non-threaded head through nozzle.

15. The method according to any one of claims 9 to 14, comprising installing a guide funnel at the non-threaded end of the extension tube.

16. The method according to any one of claims 9 to 15, comprising installing a compressible guide sleeve on the non-threaded head through nozzle.

17. Installing the compressible guide sleeve on the non-threaded head through nozzle includes compressing the compressible guide sleeve, inserting the compressed guide sleeve through the extension tube and the non-threaded head through nozzle, and releasing the compression of the compressible guide sleeve to releasably couple the compressible guide sleeve to the non-threaded head through nozzle, and the method according to claim 16.

18. The compressible guide sleeve comprises a compressible flex section of a plurality of leaves, each of the compressible flex sections of the plurality of leaves comprises a flange, and the method includes compressing the compressible flex sections of the plurality of leaves to contract the flange before inserting the compressed guide sleeve into the extension tube. After insertion into the non-threaded head through nozzle, releasing the flange and releasing the compression of the compressible guide sleeve to engage with a counterbore ledge defined by the non-threaded head through nozzle, The method according to claim 16 or 17, comprising.

19. The method according to any one of claims 9 to 18, comprising performing measurement of the alignment of the extension tube.

20. Comprising installing a guide funnel at the non-threaded end of the extension tube, The method according to any one of claims 16 to 18, wherein the compressible guide sleeve is inserted into the guide funnel from a position below the reactor vessel head of the nuclear reactor.

21. The method according to any one of claims 9 to 20, wherein the extension tube is installed from a position below the reactor vessel head of the nuclear reactor.

22. A method for installing an extension tube in a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a non-threaded head through nozzle and a thermal sleeve disposed therein, Removing the thermal sleeve from the CRDM housing, Coupling a threaded adapter to an end of the non-threaded head through nozzle, Coupling the extension tube to the threaded adapter, wherein the threaded adapter and the extension tube are replaced with the thermal sleeve removed from the CRDM housing, coupling the extension tube to the threaded adapter, Comprising, a method.

23. Further comprising machining the end of the non-threaded head through nozzle, The method according to claim 22, wherein coupling the threaded adapter to the end of the non-threaded head through nozzle comprises coupling the threaded adapter to the machined end of the non-threaded head through nozzle.

24. Machining the end of the non-threaded head through nozzle is, The method according to claim 23, comprising machining the surface of the non-threaded head through nozzle so as to shorten the length of a part of the peripheral portion of the non-threaded head through nozzle.

25. The method according to claim 23, wherein coupling the threaded adapter to the machined end of the non-threaded head through nozzle comprises performing a welding technique to form a joint.

26. The method according to claim 25, further comprising machining an outer diameter of the joint defined between the machined end of the non-threaded head through nozzle and the threaded adapter.

27. Machining a bore defined by the non-threaded head through nozzle, and machining a bore defined by the threaded adapter, The method according to claim 22, further comprising.

28. The method according to claim 22, further comprising installing a retaining fillet weld between the extension tube and the threaded adapter.

29. A method for installing an extension tube in a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a threaded head through nozzle and a thermal sleeve disposed therein, removing the thermal sleeve from the threaded head through nozzle, and replacing the removed thermal sleeve with the extension tube, including coupling the extension tube to the threaded head through nozzle. A method including.

30. Coupling the extension tube to the threaded head through nozzle includes aligning a threaded end of the extension tube with a threaded end of the threaded head through nozzle, and applying torque to the extension tube relative to the threaded end of the threaded head through nozzle. The method according to claim 29, including.

31. The method according to claim 30, further comprising coupling a guide funnel to the extension tube.

32. Coupling the guide funnel to the extension tube includes coupling the guide funnel to a non-threaded end of the extension tube.

33. The method according to claim 31, further comprising installing a compressible guide sleeve in the CRDM housing.

34. Installing the compressible guide sleeve in the CRDM housing includes compressing the compressible guide sleeve, and inserting the compressed guide sleeve through the extension tube and the threaded head through nozzle into the guide funnel and into the CRDM housing. To removably couple the compressible guide sleeve to the CRDM housing, releasing the compression of the compressible guide sleeve, and The method according to claim 33, comprising.

35. The compressible guide sleeve comprises a compressible flex section of a plurality of leaves, Each of the compressible flex sections of the plurality of leaves comprises a flange, The method is, Compressing the compressible flex sections of the plurality of leaves to contract the flange before inserting the compressed guide sleeve into the guide funnel, After insertion into the CRDM housing, releasing the compression of the compressible guide sleeve to release the flange and engage a counterbore ledge defined by the CRDM housing, The method according to claim 34, further comprising.

36. The method according to claim 29, further comprising installing a retaining fillet weld between the extension tube and the threaded end of the threaded head through nozzle.

37. The method according to claim 29, wherein the extension tube is installed from a position below the reactor vessel head of the nuclear reactor.

38. The extension tube comprises a threaded adapter, The method according to claim 29, wherein coupling the extension tube to the threaded head through nozzle comprises coupling the threaded adapter to the threaded head through nozzle.

39. A method for installing an extension tube in a nuclear reactor comprising a control rod drive mechanism (CRDM) housing having a threaded head through nozzle and a thermal sleeve disposed therein, Removing the thermal sleeve from the threaded head through nozzle, Replacing the removed thermal sleeve with the extension tube and a threaded adapter, Coupling a first threaded end of the threaded adapter to the extension tube, Coupling a second threaded end of the threaded adapter to the threaded head through nozzle, Replacing the removed thermal sleeve with the extension tube and the threaded adapter, including, A method, including.

40. The method according to claim 39, further comprising coupling a guide funnel to the extension tube.

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