CA2766472C - Calandria tube insert removal for reactor retubing - Google Patents

Abstract

Methods, apparatuses, and systems for removing an insert attaching a calandria tube to a tube sheet in a nuclear reactor during retubing of the reactor. One method includes (a) advancing a removal tool into a lattice site including a calandria tube and an insert until a head of the removal tool is positioned within a diameter of the calandria tube, (b) expanding at least one retractor of the removal tool radially to align the at least one retractor inboard of the insert, (c) retracting the at least one retractor axially to remove the insert from the calandria tube and the tube sheet and collect the insert on the removal tool, and (d) retracting the removal tool, with the collected insert, from the lattice site.

Description

Attorney Docket No . 027813-9037-CA00 CALANDRIA TUBE INSERT REMOVAL FOR REACTOR RETUBING
RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional Application No.
61/433,471 of the same title filed January 17, 2011.
FIELD OF THE INVENTION

[0002] The present invention relates to methods and systems for retubing nuclear reactors.
SUMMARY

[0003] A nuclear reactor has a limited life of operation. For example, second generation CANDUTm-type reactors ("CANada Deuterium Uranium") are designed to operate for approximately 25 to 30 years. After this time, the existing fuel channels can be removed and new fuel channels can be installed. Performing this "retubing" process can extend the life of a reactor. For example, retubing a CANDUTm-type reactor can extend the reactor's life by an additional 25 to 40 years. Without performing the retubing a reactor that reaches the end of its useful life is typically decommissioned and replaced with a new reactor, which poses significant costs and time. Alternatively, replacement energy sources may be used to extend the life of a reactor. However, replacement energy sources are often more expensive than installing a new reactor, and can be difficult to acquire.

[0004] In some nuclear reactors, an insert is provided between each calandria tube (which is a conduit for a pressure tube and the fuel and fluid it contains during operation of the reactor) and a wall or "tube sheet" through which the calandria tube extends. The insert can take various forms, and in some cases is in the form of a sleeve or short tube. The insert is typically employed to secure and seal the calandria tube to the tube sheet to prevent fluid from escaping the interior of the calandria, especially in cases where the calandria tube and the tube sheet are constructed of different materials making welding and other attaching and sealing manners impractical or impossible. The calandria tube insert is often rolled (via a roller extrusion Attorney Docket No. 027813-9037-CA00 process) into shape within its respective tube sheet bore, and must typically be removed for replacement during reactor re-tubing operations.

[0005] Embodiments of the present invention provide methods and systems for removing a calandria tube insert for reactor retubing. The method can include removing a shield plug from a lattice site, installing a hardstop sleeve in the lattice site to an outer surface of a tube sheet, advancing a removal tool into a calandria tube, gripping the calandria tube with the removal tool, and extracting the calandria tube insert. The method can also include retracting the removed calandria tube insert contained on the removal tool into a shielding flask, and stripping the removed calandria tube insert from the removal tool to place the calandria tube insert into the flask for transportation and disposal.

[0006] In particular, one embodiment of the invention provides a method for removing an insert attaching a calandria tube to a tube sheet in a nuclear reactor during retubing of the reactor.
The method includes (a) advancing a removal tool into a lattice site including a calandria tube and an insert until a head of the removal tool is positioned within a diameter of the calandria tube, (b) expanding at least one retractor of the removal tool radially to align the at least one retractor inboard of the insert, (c) retracting the at least one refractor axially to remove the insert from the calandria tube and collect the insert on the removal tool, and (d) retracting the removal tool, with the collected insert, from the lattice site.

[0007] Another embodiment of the invention provides a tool for removing an insert attaching a calandria tube to a tube sheet in a nuclear reactor during retubing of the reactor. The tool includes a ram body and at least one retractor positioned on the ram body. The ram body is configured to be advanced into a lattice site containing a calandria tube and an insert until a head of the ram body is positioned within a diameter of the calandria tube. The at least one retractor is configured to expand radially to be aligned inboard of the insert and to retract axially to remove the insert from the calandria tube. The ram body is also configured to collect the removed insert and be retracted from the lattice site with the collected insert.

[0008] Yet another embodiment of the invention provides a system for removing an insert attaching a calandria tube to a tube sheet in a nuclear reactor during retubing of the reactor. The system includes a removal tool, a removal pallet system, and a flask. The removal tool is Attorney Docket No. 027813-9037-CA00 =
mounted on the removal pallet system and is configured to be advanced into a lattice site including a calandria tube and an insert until a head of the removal tool is positioned within a minor diameter of the calandria tube, to grip at least a portion of the minor diameter of the calandria tube, to expand at least one retractor radially to align the at least one retractor inboard of the insert, to retract the at least one retractor axially to remove the insert from the calandria tube and collect the insert on the removal tool, to release the head of the removal tool from the minor diameter of the calandria tube, and to be retracted, with the collected insert, from the lattice site. The removal pallet system is configured to advance the removal tool into the lattice site and retract the removal tool from the lattice site. The flask is mounted on the removal pallet system and is configured to receive the removal tool, with the collected insert, after the removal tool is retracted from the lattice site and strip the collected insert from the removal tool as the removal tool is retracted from the flask.

[0009] Other aspects of the present invention will become apparent by consideration of the detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a perspective view of a reactor core of a CANDUTm-type nuclear reactor.

[0011] FIG. 2 is a cut-away view of a CANDUTm-type nuclear reactor fuel channel assembly.

[0012] FIG. 3 is a perspective view of a calandria tube insert removal tool according to an embodiment of the invention.

[0013] FIG. 4 is a perspective view of a calandria tube insert hardstop sleeve according to an embodiment of the invention.

[0014] FIG. 5 is a perspective view of a sleeve carriage according to an embodiment of the invention.

[0015] FIG. 6 is a perspective view of a calandria tube insert removal system.

[0016] FIG. 7 is a flowchart illustrating a calandria tube insert removal process according to an embodiment of the invention.

Attorney Docket No. 027813-9037-CA00

[0017] FIG. 8 is a side cut-away view of the calandria tube insert removal system of FIG. 6, shown in a retracted configuration.

[0018] FIG. 9 is a side cut-away view of the calandria tube insert removal system of FIG. 6, shown installing the hardstop sleeve of FIG. 4 into a lattice site.

[0019] FIG. 10 is a side cut-away view of the calandria tube insert removal system of FIG. 6, with the ram of the removal tool of FIG. 3 advanced to position the head of the removal tool at the minor diameter of a calandria tube inside the lattice site.

[0020] FIG. 11 is a cut-away view of the head of the removal tool of FIG.
3, shown positioned at the minor diameter of the calandria tube inside the lattice site as illustrated in FIG.
10.

[0021] FIG. 12 is a cut-away view of the head of the removal tool of FIG.
3, shown with retractors of the removal tool expanded.

[0022] FIG. 13 is a cut-away view of the head of the removal tool of FIG.
3, shown with the retractors retracted to remove the calandria tube insert.

[0023] FIG. 14 is a cut-away view of the head of the removal tool of FIG. 3 illustrating a reaction force load path when the removal tool removes the calandria tube insert.

[0024] FIG. 15 is a cut-away view of the head of the removal tool of FIG.
3, shown released from the minor diameter of the calandria tube.

[0025] FIG. 16 is a side cut-away view of the calandria tube insert removal system of FIG. 6, with ram of the removal tool of FIG. 3 and the removed calandria tube insert retracted into a flask.

[0026] FIG. 17 is a side cut-away view of the calandria tube insert removal system of FIG. 6, shown retracted from the lattice site.

[0027] FIG. 18 is a side view of a profile of a cam tube included in the removal tool of FIG.
3.

Attorney Docket No. 027813-9037-CA00

[0028] FIG. 19 is a cut-away view of the removal tool of FIG. 3, shown with multiple calandria tube inserts contained on the ram.

[0029] FIG. 20 is a top cut-away view of the removal tool of FIG. 3, shown with posts included in the flask that strip calandria tube inserts off the ram of the removal tool.

[0030] FIG. 21 is a side cut-away view of the calandria tube insert removal system of FIG. 6, shown with the removal tool of FIG. 3 retracted through the flask and the removed calandria tube inserts contained within the flask.
DETAILED DESCRIPTION

[0031] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

[0032] FIG. 1 is a perspective of a reactor core of a CANDUTm-type reactor 6. The reactor core is typically contained within a vault that is sealed with an air lock for radiation control and shielding. A generally cylindrical vessel, known as a calandria 10, contains a heavy-water moderator. The calandria 10 has an annular shell 14 and a tube sheet 18 at a first end 22 and a second end 24. The tube sheets 18 include a plurality of bores that accept a fuel channel assembly 28. As shown in FIG. 1, a number of fuel channel assemblies 28 pass through the tube sheets 18 of calandria 10 from the first end 22 to the second end 24.

[0033] FIG. 2 is a cut-away view of the fuel channel assembly 28. As illustrated in FIG. 2, each fuel channel assembly 28 is surrounded by a calandria tube ("CT") 32. The CT 32 forms a first boundary between the heavy water moderator of the calandria 10 and the fuel bundles or assemblies 40. The CTs 32 are positioned in the bores on the tube sheet 18. A
CT rolled joint insert 34 within each bore is used to secure the CT 32 to the tube sheet 18.

[0034] A pressure tube ("PT") 36 forms an inner wall of the fuel channel assembly 28. The PT 36 provides a conduit for reactor coolant and the fuel bundles or assemblies 40. The PT 36, Attorney Docket No. 027813-9037-CA00 for example, generally holds two or more fuel assemblies 40 and acts as a conduit for reactor coolant that passes through each fuel assembly 40. An annulus space 44 is defined by a gap between the PT 36 and the CT 32. The annulus space 44 is normally filled with a circulating gas, such as dry carbon dioxide, helium, nitrogen, air, or mixtures thereof.
The annulus space 44 and gas are part of an annulus gas system. The annulus gas system has two primary functions.
First, a gas boundary between the CT 32 and PT 36 provides thermal insulation between hot reactor coolant and fuel within the PTs 36 and the relatively cool CTs 32.
Second, the annulus gas system provides an indication of a leaking CT 32 or PT 36 via the presence of moisture, deuterium, or both in the annulus gas.

[0035] An annulus spacer or garter spring 48 is disposed between the CT 32 and PT 36. The annulus spacer 48 maintains the gap between the PT 36 and the corresponding CT
32, while allowing the passage of the annulus gas through and around the annulus spacer 48. Maintaining the gap helps ensure safe and efficient long-term operation of the reactor 6.

[0036] As also shown in FIG. 2, an end fitting 50 is attached at the fuel channel assembly 28 outside of the tube sheet 18 at each end 22, 24. At the front of each end fitting 50 is a closure plug 52. Each end fitting 50 also includes a feeder assembly 54. The feeder assemblies 54 feed reactor coolant into or remove reactor coolant from the PTs 36. In particular, for a single fuel channel assembly 28, the feeder assembly 54 on one end of the fuel channel assembly 28 acts as an inlet feeder, and the feeder assembly 54 on the opposite end of the fuel channel assembly 28 acts as an outlet feeder. As shown in FIG. 2, the feeder assemblies 54 can be attached to the end fitting 50 using a coupling assembly 56 including a number of screws, washers, seals, and/or other types of connectors.

[0037] Coolant from the inlet feeder assembly flows along an annular perimeter channel of the end fitting 50 until it reaches a shield plug 58. The shield plug 58 is contained inside the end fitting 50 and provides radiation shielding. The shield plug 58 also includes a number of openings that allow the coolant provided by the inlet feeder assembly to enter an end of a PT 36.
A shield plug 58 located within the end fitting 50 at the other end of the fuel channel assembly 28 includes similar openings that allow coolant passing through the PT 36 to exit the PT 36 and flow to the outlet feeder assembly 54 through a perimeter channel of another end fitting 50 at the Attorney Docket No. 027813-9037-CA00 opposite face of the reactor 6. As shown in FIG. 1, feeder tubes 59 are connected to the feeder assemblies 54 that carry coolant to or away from the reactor 6.

[0038] Returning to FIG. 2, a positioning hardware assembly 60 and bellows 62 are also coupled to each end fitting 50. The bellows 62 allows the fuel channel assemblies 28 to move axially. The positioning hardware assemblies 60 are used to set an end of a fuel channel assembly 28 in either a locked or unlocked position. In a locked position, the end of the fuel channel assembly 28 is held stationary. In an unlocked position, the end of the fuel channel assembly 28 is allowed to move. A tool can be used with the positioning hardware assemblies 60 to switch the position of a particular fuel channel assembly 28.

[0039] The positioning hardware assemblies 60 are also coupled to an end shield 64. The end shields 64 provide additional radiation shielding. Positioned between the tube sheet 18 and the end shield 64 is a lattice sleeve or tube 65. The lattice tube 65 encases the connection between the end fitting 50 and the PT 36 containing the fuel assemblies 40.
Shielding ball bearings 66 and cooling water surround the exterior the lattice tubes 65, which provides additional radiation shielding.

[0040] It should be understood that although a CANDUTm-type reactor is illustrated in FIGS.
1 and 2, the methods and systems described below for retubing a reactor also apply to other types of reactors containing similar components as illustrated in FIGS. 1 and 2.

[0041] As described above, the reactor 6 can be retubed to extend its useful life. The retube process can include various steps and series of steps. For example, to prepare for retubing, the reactor 6 can be shut down and the reactor vault can be prepared for retubing.
A variety of material-handling equipment, tools, supports, and systems can also be installed and implemented to aid the retubing process. In some embodiments, a retube tool platform ("RTP") is installed.
The RTP is an adjustable platform upon which much of the fuel channel removal operations are performed. One or more heavy work tables ("HWTs") can be installed and mounted on the RTP, which can serve as the basis for tool delivery during the removal process. The HWTs provide a platform that supports retubing equipment. Various control and observation systems can also be installed and commissioned at this point in the process, such as a retube control center ("RCC"), a vault observation system ("VOS"), and a vault communication system ("VCS").

Attorney Docket No. 027813-9037-CA00

[0042] Once the reactor 6 is prepared for retubing, various initial components can be removed from the reactor 6, such as the closure plugs 52 and the positioning hardware assemblies 60. The feeder assemblies 54 can also be disconnected from the end fittings 50.
Also, in preparation for removing the fuel channel assemblies 28, the bellows 62 and the PTs 36 can be severed.

[0043] A removal pallet system (also referred to as a "pallet") can be installed and implemented at an end of the reactor 6 on a RTP after severing the PTs 36 from the bellows 62 to remove additional components from the reactor 6. The pallet is designed to serve as a modular base for mounting and supporting various tooling systems. The pallet can be mounted on a HWT and can be controlled by one or more workstations. In some embodiment, a first workstation is used to manipulate shielding, and the another workstation is used to control a rigid chain to drive and deliver end effectors. Once installed, the pallet can remain on the HWT for the majority of the removal series.

[0044] After the pallet is installed, the end fittings 50 can be removed.
With the end fittings 50 removed, the PTS 36 and CTs 32 can be removed. However, as described above, the CT
inserts 34 (also referred to as "CTIs") attach the CTs 32 to the tube sheets 18 and hold the CTs 32 in place with a rolled joint. Therefore, before the CTs 32 can be removed, the CTIs 34 are removed. Also in some embodiments, the CTIs 34 are released before they are removed (e.g., through induction heating, milling, or other means). The processes of releasing and removing the CTIs 34 can be coordinated such that they are performed in parallel at different lattice sites.
In other embodiments, the release and removal processes can be performed sequentially, which can require less coordination. The CTIs 34 can be released or prepared for removal using various methods and systems, including using heat induction. Once so prepared, the CTIs 34 can be removed from the reactor 6.

[0045] As described in more detail below, during a CTI removal series, removal tooling (also described in more detail below) removes one CTIs 34 at a time, until a predetermined quantity of CTIs 34 (e.g., approximately ten CTIs 34) have been accumulated. The accumulated CTIs 34 are then placed into a shielded flask. The flask provides shielding from the removed CTIs 34 and minimizes radioactive exposure to personnel while performing their duties (e.g., removing a Attorney Docket No. 027813-9037-CA00 full flask or troubleshooting the removal tooling). When a flask is full, the RTP can be lowered to the vault floor for hoisting the full flask to a vault trolley system. The vault trolley system transports the full flask out of the vault for loading onto a truck. An empty flask 178 is then transported into the vault by the trolley system, and can be hoisted onto the RTP. The RTP can then be elevated to the designated row where the tooling continues removing CTIs 34.

[0046]
In some embodiments, the CTI removal series can be divided into automated and manual operations. The automated operations may be controlled via a local tethered pendant, or may be controlled remotely from the RCC, and can include those operations associated with reactor face operations where tooling is mounted on the HWTs. These remote operations can be performed for "as low as reasonably achievable' ("ALARA") purposes, so that although the radioactive components are behind shielding, people may be positioned away from highly radioactive operations as much as possible. On the other hand, the manual operations can be those operations associated with the hoisting and transportation of the flasks 178.

[0047]
The CTI removal process can be performed using one or two HWTs 174 on each face of the reactor 6, and HWTs 174 on the same and opposite faces can be operated independently from the other HWTs 174. Tooling used on the HWTs 174 at each face can be identical, and CTIs 34 can be removed simultaneously in a staggered fashion (e.g., from the opposite reactor faces) to accommodate flask trolley vault traffic.

[0048]
Removal tooling used in the CTI removal process can include a CTI removal tool.
FIG. 3 is a perspective view of a CTI removal tool 100 according to an embodiment of the invention. In some embodiments, the CTI removal tool 100 is mounted to the pallet. In some embodiments, by way of example only, the CTI removal tool 100 can be approximately 12 feet long, 20 inches wide, and 1 foot tall, and can weigh approximately 500 pounds.

[0049]
As shown in FIG. 3, the illustrated CTI removal tool 100 includes a backstop 101, a ram body 104, retractors 105, and optional grippers 106. The removal tool 100 can use the pallet's rigid "push pull" chain (e.g., a rigid push pull chain manufactured by Serapid, Inc.) to advance and retract the ram 104. As will be discussed in greater detail below, the ram 104 reaches through a flask to obtain a CTI 34 and extract it into the flask. The grippers 106 can be configured to grip a diameter of a CT 32 (e.g., a minor diameter or a bell section of the CT 32) to Attorney Docket No. 027813-9037-CA00 prevent the CT 32 from moving while the CTI 34 is removed. The grippers 106 can include shoes, expanding split rings, bungs, wedges, cams, rotating pie-shaped grippers or circular grippers, or other mechanisms for gripping a portion of the CT 32 while the CTI 34 is removed.
The removal tool 100 directs the reaction load from removing the CTI 34 against the flask. The removal tool 100 can remove CTIs 34 one at a time, and can accumulate any desired number (e.g., ten CTIs 34) on the ram 104. After a CTI 34 is removed, if the optional grippers 106 where used, the removal tool 100 un-grips or releases the minor diameter of the CT 32 to prevent the CT 32 from moving while the ram 104 is retracted. The removal tool 100 uses the flask where removed CTIs 34 are deposited for shielding, and can operate with automated systems. In some embodiments, the removal tool 100 also operates manually for contingency purposes.
100501 The retractors 105 retract the CTIs 34 from the lattice site. In particular, the retractors 105 can be radially expandable to be engaged with or aligned inboard of (i.e., behind) a released CTI 34, such that when the retractors 105 are retracted axially, the CTI is also retracted. The retractors 105 illustrated and described in the present application include shoes that are radially expandable and axially retractable. However, similar to the grippers 106, it should be understood that the retractors 105 can include expanding split rings, bungs, wedges, cams, rotating pie-shaped or circular grippers, or other mechanisms for engaging and retracting a released CTI 34 from a lattice site.
100511 The CTI removal tool 100 can be transported in the vault on floor dollies, and can be installed or removed from the pallet by hoisting. In some embodiments, the CTI
removal tool 100 uses off-the-shelf, commercially available servo drives, linear drives, and a gear box. A
frame 107 of the CTI removal tool 100 can be mounted to the top surface of the pallet by brackets 108, which bring the working axis of the pallet and the CTI removal tool 100 into alignment. The pallet's rigid push pull chain attaches to the back of a carriage 110 of the tool 100 at a flange 112. As shown in FIG. 3, the removal tool 100 also includes linear bearings 114 and rails 116. The frame 107, rails 116, linear bearings 114, carriage 110, and the cantilevered ram body 104 form a ram axis that is advanced or retracted by the rigid push pull chain. In the illustrated embodiment, the grippers 106 and the retractors 105 are actuated by a pull rod and linear drive assembly 118 also included in the CTI removal tool 100. The drive 118 can derive its power through a cable track 120, which accommodates the z-motion of the carriage 110. The Attorney Docket No. 027813-9037-CA00 illustrated ram body 104 is designed to hold approximately ten removed CTIs 34, and the backstop 101 prevents the removed CTIs 34 from traveling lengthwise along the ram body 104 toward the carriage 110 as the ram body 104 is retracted from the lattice site.
[0052] In some embodiments, the CTI removal tool 100 is designed to be maintenance free during a retube outage. However, the CTI removal tool 100 may require maintenance between retube outages. It should be understood that multiple removal tools 100 can be used during a retube process for production or training or for the purpose of keeping a spare on hand.
[0053] In some embodiments, a CTI hardstop sleeve can be used to remove the CTIs 34.
The hardstop sleeve provides a path for the reaction load between the flask where removed CTIs 34 are deposited and the outboard face of the tube sheet 18 surrounding the lattice site where the CTI 34 is removed from. The hardstop sleeve can be used if high loads are required to remove the CTIs 34 (i.e., to provide additional support to the removal tooling). In particular, one purpose of the hardstop sleeve is to provide additional rigidity to the removal tooling in cases where the removal forces are very high. This situation can occur if the release tooling did not do a nominal job of releasing a CTI 34 and several thousands pounds of force is needed to extract the CTI 34 from the tube sheet 18 and the CT 32. Without the hardstop sleeve, the reaction load is taken by the flask receiving removed CTIs 34 butting up against the lattice sleeve assemblies (i.e., thumbtacks) or by the RTP.
[0054] FIG. 4 is a perspective view of an example of a CTI hardstop sleeve 130 according to an embodiment of the invention. The sleeve 130 is designed to accommodate removed CTIs 34 through its opening. For example, the sleeve 130 can be approximately 4 feet long and 6 inches in diameter, and can weigh approximately 50 pounds. In some embodiments, the sleeve 130 is mounted to a sleeve carriage 140, as described below.
[0055] For ALARA purposes, installation and removal of the CTI hardstop sleeve 130 from a lattice site can be fully automated through advance and retract operations of the pallet and the sleeve carriage 140, which keeps people away from potential open radiation beams. The CTI
hardstop sleeve 130 can be designed to be maintenance free during a retube outage, but may require maintenance between retube outages. In some embodiments, the CTI
hardstop sleeve 130 can be removed from the sleeve carriage 140 with relative ease for maintenance as needed.

Attorney Docket No. 027813-9037-CA00 It should be understood that multiple sleeves 130 can be used during a retube process for production or training or for the purpose of keeping spares on hand. Also, in some embodiments, the hardstop sleeve 130 may not be used, and the existing lattice tube sleeve 65 can be used to perform the same functionality provided by the sleeve 130.
Using the lattice tube 65 in place of the hardstop sleeve 130 can shorten the length of the CTI
removal tooling and, in some embodiments, allows the flasks containing removed CTIs 34 to be lowered through a back hatch of the RTP.
[0056] As previously mentioned, the CTI hardstop sleeve 130 can be mounted on a sleeve carriage 140. FIG. 5 is a perspective view of a sleeve carriage 140 according to an embodiment of the invention. The sleeve carriage 140 can be used in the CTI removal process to mount the CTI hardstop sleeve 130.
[0057] The sleeve carriage 140 mounts and aligns the sleeves 130 with the working axis of the pallet. The sleeve carriage 140 can allow for easier insertion and removal of the sleeves 130 from a lattice site by providing some compliance to the sleeve alignment. In addition, clearance to the inboard end of the flask is provided when pallet tooling is in a retracted position. This clearance facilitates easier change-out of the flasks. In addition, the sleeve carriage 140 provides clearance at the front of the flask collecting the removed CTIs 34 such that the flask can be closed for ALARA purposes when the pallet is moved to an advanced position.
[0058] In some embodiments by way of example only, the sleeve carriage 140 is approximately 3 feet long, 3 feet high, and 18 inches wide, and can weigh approximately 400 pounds. As shown in FIG. 5, the sleeve carriage 140 consists of shielding 142, a compliant mount 144, a bracket 146, linear bearings 148, and a hitch 150. The hardstop sleeve 130 can be attached to the shielding 142 by the compliant mount 144 so that the sleeve deflects slightly in the x and y directions when advanced or retracted from the lattice site. This deflection ability accommodates some misalignment of tooling to the lattice site, so that less critical path time is spent troubleshooting tool alignment.
[0059] The shielding 142 is provided between the front of the flask collecting removed CTIs 34 and the lattice sleeve assembly ("LSA") for ALARA purposes so that when the CTI 34 is being removed there is minimal radiation originating from that area. The shielding 142 is k.

Attorney Docket No. 027813-9037-CA00 supported by the bracket 146 mounted to the linear bearings 148. The linear bearings 148 can engage HWT rails for motion in the z-direction, which can also be the same rails that the pallet uses for its z-axis motion. The sleeve carriage 140 aligns the sleeves 130 with the working axis of tooling mounted on the pallet while allowing movement in the z-direction.
In some embodiments, the flask collecting the removed CTIs 34 abuts the shielding 142 to conduct the reaction force generated with CTI removal.
100601 The hitch 150 of the illustrated sleeve carriage 140 connects the sleeve carriage 140 to the pallet. When the pallet is in a retracted position, the hitch 150 functions to push the shielding 142 a few inches away from the flask collecting the removed CTIs 34 along the HWT
rails. This provides clearance to allow easier and safer hoisting of the flask. When the pallet is advanced to engage a lattice site, a sensor in the hitch 50 can detect if the front end of the sleeve 130 is not being inserted freely and, if so, can signal the automated system to stop, which allows operators to troubleshoot. The sleeve carriage 140 can be designed to be maintenance free during a retube outage, but may require maintenance between retube outages.
The compliant mount 144 can be designed so that the sleeves 130 can be removed easily for maintenance as needed. It should be understood that multiple sleeve carriages 140 can be used during a retube process for production, training, or for to be kept as a spare.
100611 Additional tooling can also be used to remove the CTIs 34. For example, a lattice sleeve/shield plug insertion and removal tool ("LS-SPIRT") 160 (see FIG. 6) can be used to remove the shield plug 58 of the LSA to gain access to the CTI 34 for removal thereof, and to re-insert the shield plug 58 after the CTI 34 has been removed. A vision tool can also be used to ensure proper alignment and operation of the tooling used during the removal process.
100621 Other contingency tools can be used during the process of removing the CTIs 34. For example, flask shielding allows (e.g., manual) troubleshooting be performed directly on the removal tool 100 if necessary. Also, the z-drive of the pallet, which advances and retracts the CTI removal tool 100, and the rigid push pull chain can switch to alternate servo drives if they should become inoperable. These drives can also be driven manually, if necessary, to further support recovery. In some embodiments, if the CTI removal tool 100 drags or drops a CTI 34 into the lattice sleeve 65, a camera on a boom or a CTI reinstallation tool can be used to insert Attorney Docket No. 027813-9037-CA00 the CTI 34 back into the bore of the tube sheet 18 where it can be removed again using the CTI
release tool 100.
[0063] FIG. 6 is a perspective view of a CTI removal system 170 according to an embodiment of the present invention. The system 170 includes the CTI removal tool 100, the hardstop sleeve 130, the sleeve carriage 140, and the LS-SPIRT 160. As shown in FIG. 6, the CTI removal tool 100 is mounted on a pallet 172, which is supported by a HWT
174 including a front extension 176. The LS-SPIRT 160 is also supported by the HWT 174 in this embodiment, and a CTI flask 178 is mounted in front of the removal tool 100 on the pallet 172. At the front of the HWT 174, the CTI hardstop sleeve 130 is mounted on the sleeve carriage 140. If a vision tool 180 is used during the CTI removal process, it can also be mounted toward the front of the HWT 174. It should be understood that in some embodiments, a CTI removal system 170 as illustrated in FIG. 6 is set up on each end of the reactor 6. Therefore, a CTI
34 can be removed from a lattice site on each end of the reactor 6.
[0064] In some embodiments, most of the tooling used from the previous series of steps (e.g., the steps performed for releasing CTI 34) in the retubing process can be re-used during the CTI
removal series. For example, the front extensions 176 of the HWT 174 can remain installed on the front of the HWT 174 and the pallet 172, LS-SPIRT 160, and vision system 180 can be re-used. These common features benefit ALARA and critical path time by eliminating the need to remove, install, and commission new tools between each series of steps in the retubing operation.
Additional tooling needed for the CTI removal process, such as the CTI removal tool 100, the hardstop sleeve 130, the sleeve carriage 140, and the flask 178, can be moved on to the RTP
using a floor trolley and hoisted by a vault crane to the RTP.
[0065] FIG. 7 is a flow chart illustrating a CTI removal process in more detail. As illustrated in FIG. 7, the exemplary process initially starts by mounting the flask 178 to the pallet 172 (at 200). Once the flask is mounted, the RTP can be positioned at the designated row (at 202), and the HWT 174 can be moved to the designated column (at 204), such that the CTI
removal tooling is positioned in front of a designated lattice site where a CTI 34 is to be removed. Once the tooling is in place, the LS-SPIRT 160 removes the shield plug 58 (at 206). If the LS-SPIRT 160 Attorney Docket No. 027813-9037-CA00 has difficulty aligning to the site, the vision system 180 can be used to perform alignment for troubleshooting purposes.
[0066] Next, the HWT 174 moves sideways a predetermined amount to align the working axis of the CTI removal tool 100 to the lattice site (at 208). If the CTI
removal tool 100 has difficulty aligning to the lattice site, the vision system 180 can be used to perform alignment for troubleshooting purposes. At this point, the CTI removal tooling is in its initial retracted configuration in front of a designated lattice site 209, as shown in FIG. 8.
100671 Next, the CTI hardstop sleeve 130 is optionally installed into the lattice site 209 (at 210), as shown in FIG. 9. The ram 104 of the CTI removal tool 100 is then advanced through the flask 178, the CTI hardstop sleeve 130, and a released CTI 34 to a diameter of the CT 32 (at 212), as shown in FIGS. 10-11. The CTI removal tool 100 then expands the retractors 105 radially to align the retractors 105 inboard of (i.e., behind) the CTI 34 (at 214), as shown in FIG.
12. Optionally, grippers 106 can be simultaneously expanded with the retractors 105 to grip at least a portion of the diameter of the CT 32 (at 216), as also shown in FIG.
12. In some embodiments, the grippers 106 grip a CT bell 213 or a minor diameter of the CT
32. Gripping the CT 32 with the grippers 106 prevents or limits the CT 32 from moving when the CTI 34 is removed in a later step. It should be understood, however, that gripping the CT 32 is optional and may not be needed in some situations depending on how the CTI 34 are released and, consequently, how much force is needed to remove the CTIs 34.
[0068] After the retractors 105 are radially extended, the retractors 105 are retracted axially to remove the CTI 34 (at 218), as shown in FIG. 13. It should be understood that in some embodiments, the retractors 105 do not engage an inner surface of the CTI 34 when they are initially expanded. For example, once the retractors 105 have been expanded radially, there can be approximately 'A of an inch axial clearance between the back edge of the retractors 105 and the inner edge of the CTI 34. In this situation, the expanded retractors 105 engage the CTI 34 as the retractors 105 are retracted. In other embodiments, however, the retractors 105 can be radially expanded to engage an inner surface of the CTI 34 even before the retractors 105 are retracted from the lattice site.

Attorney Docket No. 027813-9037-CA00 [0069] The reaction force generated by the ram 104 as the CTI 34 is removed is taken by the ram tube and is directed through the flask 178, the CTI hardstop sleeve 130, and onto an outboard face 221 of the calandria tube sheet 18, as shown in FIG. 14. With the CTI 34 removed, if the optional grippers 106 were used, the grippers 106 un-grip or release the CT 32 (at 220) as shown in FIG. 15. Next, the ram 104 and the removed CTI 34 are retracted back into the CTI flask 178 (at 222) as shown in FIG. 16, and the CTI removal tooling is retracted from the LSA (at 224) as shown in FIG. 17. The CTI hard stop sleeve 130 can then be removed (at 226), and the LS-SPIRT 160 can reinstall the shield plug 58 (at 228).
100701 In some embodiments, the grippers 106 and the retractors 105 are actuated by a central rod 300 (see FIGS. 11-13 and 15). For example, linear bearings 302 are incorporated into the grippers 106 and in a housing 304 of the CTI removal head to guide the grippers 106 radially.
Rollers 306 are also incorporated into the grippers 106 that ride on a profile of a cam tube 308.
Mechanical springs (not shown) apply loads to the grippers 106 to contract the grippers 106 in a compliant manner onto the profile of the cam tube 308. As shown in FIG. 18, the profile of the cam tube 308 includes a first low surface 310, a raised surface 312, and a second low surface 314 with sloped transitions 316 between each surface. The cam tube 308 is moved axially by the central rod 300 that extends back along the ram body 104 to a servo drive unit. When the rollers 306 are on the first and second low surfaces 310 and 314, the grippers 106 are retracted (i.e., not gripping the CT 32) (see FIGS. 11 and 15), and when the rollers 306 are on the raised surface 312, the grippers 106 are extended (i.e., gripping the CT 32) (see FIG. 12).
[0071] Similarly, the retractors 105 (illustrated as shoes 105 in FIGS. 11-13 and 15) are configured to move radially and axially with respect to the housing 304, and a mechanical wedge 320 is used to actuate the shoes 105 radially when the central rod 300 is actuated axially. A
compliant sleeve 322 is configured with a compression spring 324 so that it can be moved axially by the shoes 105 when sufficient force is applied. When the central rod 300 is in its extended position (see FIG. 11), the wedge 320 is disengaged. From its forward position, when the central rod 300 is first retracted, light force engages the wedge 320 until the shoes 105 are fully expanded (see FIG. 12). Once fully expanded, the shoes 105 hard-stop and additional force moves the compliant sleeve 322, which allows the shoes 105 to move axially (see FIGS. 13 and 15).

Attorney Docket No. 027813-9037-CA00 [0072] Therefore, in operation the central rod 300 operates both the grippers 106 and the retractors 105 simultaneously. For example, the central rod 300 starts in the fully extended position, in which the grippers 106 are retracted (i.e., the rollers 306 are on the first low surface 310 of the cam tube 308) and the shoes 105 are retracted (i.e., the wedge 320 is disengaged) (see FIG. 11.). As shown in FIG. 11, in this position, the CTI removal tool 100 is deployed to the lattice site to a depth such that the grippers 106 are aligned axially with the minor diameter of the CT 32 next to the bell 213 and the lip of the shoes 105 are aligned to clear the inboard edge of the CTI 34 by approximately 'A of an inch. Once the CTI removal tool 100 is positioned, the central rod 300 is pulled a short distance, such that the grippers 106 become fully expanded to grip the CT 32 (i.e., the rollers 306 are on the raised cam surface 312), and the shoes 105 become fully expanded (i.e., the wedge 320 is engaged) (see FIG. 12).
[0073] To retract the shoes 105 axially, the central rod 300 is pulled a further distance, which causes the compliant sleeve 322 and the shoes 105 to move axially (see FIG.
13) and remove the CTI 34 while the grippers 106 remain engaged with the CT 32 (i.e., to ensure the CT 32 is not pulled out with the CTI 34). The central rod 300 is then pulled to its maximum position, which moves the shoes 105 and the removed CTI 34 further along the ram body 104 and retracts the grippers 106 (i.e., the rollers 306 are on the second low surface 314 of the cam tube 308) (see FIG. 15). The CTI removal tool 100 is then retracted from the lattice site.
[0074] As shown in FIG. 7, after removing a CTI 34, the removal tooling can be moved to the next lattice site. For example, if the next lattice site is in the same row, the HWT 174 can be moved sideways to align the tooling with the next lattice site (at 204). If the next lattice site is in the next row, the RTP can be vertically repositioned to the new row (at 202).
Once re-aligned, the tooling can repeat steps 206 through 228 until multiple CTIs 34 (e.g., ten) have been removed and collected on the ram 104. It should be understood that number of CTIs 34 that can be removed and collected on the ram 104 may vary based on the size of the CTI
34, the size of the removal tooling, and the size of the flask 178. For example, as shown in FIG. 19, when ten CTIs 34 are removed in the illustrated embodiment, the ram 104 is filled with CTIs 34 that must be removed to make room for additional CTIs 34.

Attorney Docket No. 027813-9037-CA00 [0075] To remove the CTIs 34 from the ram 104, the flask 178 can include fixed posts 430 on a side of the flask 178 behind the outboard CTI on the ram 104 when the ram 104 is positioned in the flask 178, as shown in FIG. 20. The posts 430 can be used to strip the CTIs 34 off the ram 104 as the ram 104 is retracted out of the flask 178, as shown in FIG. 21. Therefore, although the ram 104 is retracted from the flask 178, the posts 430 block the CT! 34 from also being retracted, and the CTI 34 remain in the flask 178. If the flask 178 is full, it can be removed from the pallet 172, and an empty flask 178 can be mounted on the pallet 172 if additional CTIs 34 still need to be removed from the reactor 6 (at 200). Thereafter, the process can be repeated again (steps 202 through 228) as additional empty flasks 178 are needed, and until all CTIs 34 have been removed from the reactor 6. In some embodiments, the reactor 6 includes approximately 760 to 960 CTIs 34 that are removed and disposed of as radioactive waste. Using the methods and systems described above, in some embodiments, CTIs 34 can be removed at a rate of approximately 90 per day.
[0076] Thus, embodiments of the invention provide, among other things, methods and systems for removing CTIs for retubing a nuclear reactor. It should be understood, however, that the methods and systems described above can be performed in various orders and configurations, and some steps can be performed in parallel to other steps. Some steps can also be combined or distributed among more steps. Also, the details of the methods and systems can be modified according to the specific configuration of the CT, the CTI, and/or the reactor being retubed.
[0077] Various features and advantages of the invention are set forth in the following claims.

Claims (21)

Claims What is claimed is:

1. A method of removing an insert attaching a calandria tube to a tube sheet in a nuclear reactor during retubing of the reactor, the method comprising:
(a) advancing a removal tool into a lattice site including a calandria tube and an insert until a head of the removal tool is positioned within a diameter of the calandria tube;
(b) expanding at least one retractor of the removal tool radially to align the at least one retractor inboard of the insert;
(c) retracting the at least one retractor axially to remove the insert from the calandria tube and the tube sheet and collect the insert on the removal tool; and (d) retracting the removal tool, with the collected insert, from the lattice site.

2. The method of Claim 1, further comprising gripping, with the head of the removal tool, at least a portion of the diameter of the calandria tube and releasing the head of the removal tool from the diameter of the calandria tube after the insert is removed from the calandria tube.

3. The method of Claim 2, wherein gripping at least a portion of the diameter of the calandria tube includes gripping at least a portion of a minor diameter of the calandria tube.

4. The method of Claim 2, wherein gripping at least a portion of the diameter of the calandria tube includes gripping at least a portion of a bell section of the calandria tube.

5. The method of Claim 1, further comprising mounting the removal tool on a removal pallet system configured to advance and retract the removal tool into and out of the lattice site.

6. The method of Claim 5, further comprising mounting a flask on the removal pallet system in front of the lattice site.

7. The method of Claim 6, wherein advancing the removal tool into the lattice site includes advancing, with the removal pallet system, the removal tool through the flask and into the lattice site.

8. The method of Claim 1, further comprising installing a hardstop sleeve into the lattice site before advancing the removal tool into the lattice site.

9. The method of Claim 8, further comprising removing the hardstop sleeve from the lattice site after retracting the removal tool from the lattice site.

10. The method of Claim 1, further comprising repeating steps (a) through (d) for a predetermined number of lattice sites to collect the predetermined number of inserts on the removal tool.

11. The method of Claim 10, further comprising retracting the removal tool with the predetermined number of inserts from a flask and stripping the predetermined number of inserts from the removal tool using at least one post mounted inside the flask.

12. A tool for removing an insert attaching a calandria tube to a tube sheet in a nuclear reactor during retubing of the reactor, the tool comprising:
a ram body configured to be advanced into a lattice site containing a calandria tube and an insert until a head of the ram body is positioned within a diameter of the calandria tube; and at least one retractor positioned on the ram body, the at least one retractor configured to expand radially to be aligned inboard of the insert and to retract axially to remove the insert from the calandria tube and the tube sheet, the ram body configured to collect the removed insert and be retracted from the lattice site with the collected insert.

13. The tool of Claim 12, further comprising at least one gripper positioned on the head of the ram body, the at least one gripper configured to grip at least a portion of the diameter of the calandria tube and to release the diameter of the calandria tube after the insert is removed from the calandria tube.

14. The tool of Claim 13, wherein the diameter of the calandria tube includes a minor diameter of the calandria tube.

15. The tool of Claim 13, wherein the diameter of the calandria tube includes a bell section of the calandria tube.

16. The tool of Claim 12, further comprising a frame for mounting the tool on a removal pallet system configured to advance and retract the ram body.

17. The tool of Claim 16, further comprising a carriage coupled to the ram body, the carriage advanced and retracted by the removal pallet system.

18. The tool of Claim 12, further comprising a pull rod and linear drive assembly configured to actuate the at least one retractor.

19. The tool of Claim 12, further comprising a backstop positioned on the ram body and configured to prevent the collected removed insert from traveling lengthwise along the ram body in at least one direction as the ram body is retracted from the lattice site.

20. The tool of Claim 12, wherein the at least one retractor is further configured to be expanded radially to engage in inner surface of the insert.

21. A system for removing an insert attaching a calandria tube to a tube sheet in a nuclear reactor during retubing of the reactor, the system comprising:
a removal tool configured to be advanced into a lattice site including the calandria tube and the insert until a head of the removal tool is positioned within a minor diameter of the calandria tube, to grip at least a portion of the minor diameter of the calandria tube, to expand at least one retractor radially to align the at least one retractor inboard of the insert, to retract the at least one retractor axially to remove the insert from the calandria tube and the tube sheet and collect the insert on the removal tool, to release the head of the removal tool from the minor diameter of the calandria tube, and to be retracted, with the collected insert, from the lattice site;
a removal pallet system configured to advance the removal tool into the lattice site and retract the removal tool from the lattice site, wherein the removal tool is mounted on the removal pallet system; and a flask mounted on the removal pallet system and configured to receive the removal tool, with the collected insert, after the removal tool is retracted from the lattice site and strip the collected insert from the removal tool as the removal tool is retracted from the flask.