WO2018232526A1

WO2018232526A1 - Calandria tube insert release and removal tool and method

Info

Publication number: WO2018232526A1
Application number: PCT/CA2018/050770
Authority: WO
Inventors: Craig Richard; Andrzej Piotr SZCZEPAN; Robert William JAMIESON; Chuck Patterson; Jason DEADMAN; George Solti; Chris JACOBS
Original assignee: Candu Energy Inc.
Priority date: 2017-06-23
Filing date: 2018-06-22
Publication date: 2018-12-27
Also published as: RO134273A2; CA3066098A1; CN111418025B; KR20200019885A; CN111418025A; KR102607798B1

Abstract

A device for removing a rolled joint insert from between a calandria tube of a fuel channel assembly of a nuclear reactor and a tube sheet of the nuclear reactor, the rolled joint insert radially securing the calandria tube to the tube sheet. The device includes a body extending axially from a first end to a second end, opposite the first end; a heater for heating a rolled joint insert to a first temperature; a cooler for cooling the rolled joint insert to a second temperature; a ledge for axially engaging the rolled joint insert; and a gripper for gripping the calandria tube. The heater, the cooler, the ledge and the gripper are in axial alignment along the body of the device.

Description

CALANDRIA TUBE INSERT RELEASE AND REMOVAL TOOL AND METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from US Provisional Patent Application No. 62/524,085 filed on June 23, 2017, the contents of which are hereby incorporated by reference.

FIELD

[0002] This relates to the field of nuclear reactor fuel channel assemblies, and more particularly, removing nuclear reactor fuel channel assemblies at end of life.

BACKGROUND

[0003] A nuclear reactor has a limited operational life. For example, second generation CANDU™-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 significantly, as an alternative to decommissioning the reactor. Nuclear reactor retubing processes include removal of a large number of reactor components and include various other activities, such as shutting down the reactor, preparing the vault, and installing material handling equipment and various platforms and equipment supports. The removal process can also include removing closure plugs and positioning hardware assemblies, disconnecting feeder assemblies, severing bellows, removing end fittings, releasing and removing calandria tube inserts, severing and removing pressure tubes, and removing calandria tubes.

[0004] After the removal process is complete, an inspection and installation process is typically performed. For example, tube sheets positioned at each end of the reactor include a plurality of bores. Each of the plurality of bores supports a fuel channel assembly that spans between the tube sheets. When a fuel channel assembly is removed, each tube sheet bore is inspected to ensure that the removal of the fuel channel assembly has not damaged the tube sheet bore and that the tube sheet bore is ready for insertion of a new fuel channel assembly.

[0005] After the tube sheets are confirmed to be in suitable condition, the calandria tubes, pressure tubes, end fittings, and other components can be re-installed into the bores. For each fuel channel assembly, part of this process involves rolling the end of the calandria tube to the tube sheet of the calandria (e.g., using a deformable calandria insert), inserting an end fitting body into the bore, rolling the end of the pressure tube into the end fitting body, and inserting an end fitting liner into the end fitting.

[0006] The refurbishment of a nuclear reactor and retubing nprocess may take up to two years to complete. A substantial portion of that time may be spent on the removal process, described above. Accordingly, there is a need for improved and faster removal of components of a fuel channel assembly, to reduce time for refurbishment of a nuclear reactor.

SUMMARY

[0007] According to an aspect, there is provided a device for removing a rolled joint insert from between a calandria tube of a fuel channel assembly of a nuclear reactor and a tube sheet of the nuclear reactor, the rolled joint insert radially securing the calandria tube to the tube sheet, the device comprising: a body extending axially from a first end to a second end, opposite the first end; a heater for heating a rolled joint insert to a first temperature; a cooler for cooling the rolled joint insert to a second temperature; a ledge for axially engaging the rolled joint insert; and a gripper for gripping the calandria tube, wherein the heater, the cooler, the ledge and the gripper are in axial alignment along the body.

[0008] According to another aspect, there is provided a method for removing a rolled joint insert from between a calandria tube of a fuel channel assembly of a nuclear reactor and a tube sheet of the nuclear reactor, the rolled joint insert radially securing the calandria tube to the tube sheet, the method comprising: heating the rolled joint insert to a first temperature; following the heating, cooling the rolled joint insert to a second temperature, the second temperature less than the first temperature; gripping the calandria tube; and axially engaging the rolled joint insert while gripping the calandria tube, wherein the heating, the cooling, the gripping and the axially engaging are performed by a single tool head in axial movement along a defined axis.

[0009] In some embodiments, there is provided a tool for removing a calandria tube insert from a calandria tube sheet, the tool including a tool head sized to be received in an aperture of the calandria tube sheet. The tool head including a cooling portion and a gripping portion. In some embodiments, the tool head further includes a heating portion, whereas in other embodiments, the heating portion is positioned on a separate tool. The heating portion is configured to engage the calandria tube insert and rapidly heat (or shock heat) the calandria tube insert which causes the calandria tube insert to soften and deform because the calandria tube insert cannot expand due to the presence of the calandria tube sheet. Then, the cooling portion is positioned adjacent to or in abutment with the calandria tube insert to cool the insert such that the calandria tube insert contracts and separates from the calandria tube sheet. After cooling, the gripping portion of the tool head engages the calandria tube insert and then the tool head and insert are withdrawn from the aperture of the calandria tube sheet.

[0010] In some embodiments, there is provided a method of removing a calandria tube insert from a calandria tube sheet. The method includes heating the calandria tube insert without substantially heating the calandria tube sheet. The method further includes cooling the calandria tube insert by at least one of conduction and convection. The method further includes gripping the calandria tube insert and withdrawing the calandria tube insert from the calandria tube sheet. The method further includes removing a shield plug from the end shield and lattice tube prior to heating the calandria tube insert and inserting the shield plug into the end shield and lattice tube after withdrawing the calandria tube insert from the calandria tube sheet. In some

embodiments, the steps of heating and cooling are accomplished by a single tool head. In some embodiments, the steps of cooling and gripping are accomplished by a single tool head and the single tool head is not removed from the calandria tube sheet until the steps of heating, cooling and gripping are completed. In some embodiments, the steps of heating, cooling and gripping are accomplished by a single tool head. In some embodiments, the steps of heating, cooling and gripping are accomplished by three separate tools positioned on a common work table.

[0011] Other features will become apparent from the drawings in conjunction with the following description.

BRIEF DESCRIPTION OF DRAWINGS

[0012] In the figures which illustrate example embodiments:

[0013] FIG. 1 is a perspective view of a CANDU™-type reactor.

[0014] FIG. 2 is a cutaway view of a CANDU™-type nuclear reactor fuel channel assembly.

[0015] FIG. 3 illustrates a flow chart of a removal process for retubing a nuclear reactor according to some embodiments.

[0016] FIG. 4 is a perspective view of a work table and a calandria tube insert removal tool adjacent a face of the CANDU™-type reactor, according to an

embodiment.

[0017] FIG. 5A is a left perspective view of the work table, tool and reactor face of FIG. 4.

[0018] FIG. 5B is a right perspective view of the work table, tool and reactor face of FIG. 4.

[0019] FIG. 6 is a side view of a tool for removing a calandria tube insert from the CANDU™-type nuclear reactor, according to an embodiment.

[0020] FIG. 7 is a close up of a tool head of the tool of FIG. 6. [0021] FIG. 8A is a side view of a calandria insert removal tool, according to an embodiment.

[0022] FIG. 8B is the side view of the calandria insert removal tool of FIG. 8A, with a containment flask omitted.

[0023] FIG. 9 is a side view of a tool for removing a calandria tube insert from the CANDU™-type nuclear reactor, according to an embodiment.

[0024] FIG. 10 a close up of a tool head of the tool of FIG. 9.

[0025] FIG. 1 1 a further close up of the tool head of the tool of FIG. 9.

DETAILED DESCRIPTION

[0026] Before any embodiments are explained in detail, it is to be understood that the disclosure 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 accompanying drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0027] FIG. 1 is a perspective of a reactor core of a CANDU™-type reactor 6. The reactor core is typically contained within a vault that is sealed with an air lock for radiation control and shielding. Although aspects are described with particular reference to the CANDU™-type reactor 6 for convenience, the disclosure is not limited to CANDU™-type reactors, and may be useful outside this particular field as well. A generally cylindrical vessel, known as the calandria vessel 10 of the CANDU™-type reactor 6, contains a heavy-water moderator. The calandria vessel 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 apertures (referred to herein as bores 19) that each 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 vessel 10 from the first end 22 to the second end 24. [0028] As in the illustrated embodiment of Figs. 1 and 2, in some embodiments the reactor core is provided with two walls at each end 22, 24 of the reactor core: an inner wall defined by the tube sheet 18 at each end 22, 24 of the reactor core, and an outer wall 64 (often referred to as a "end shield") located a distance outboard from the tube sheet 18 at each end 22, 24 of the reactor core. A lattice tube 65 spans the distance between the tube sheet 18 and the end shield 64 at each pair of bores 19 (i.e., in the tube sheet 18 and the end shield 64, respectively).

[0029] FIG. 2 is a cutaway view of one fuel channel assembly 28 of the reactor core illustrated in FIG. 1 . As illustrated in FIG. 2, each fuel channel assembly 28 includes a calandria tube ("CT") 32 surrounding other components of the fuel channel assembly 28. The CTs 32 each span the distance between the tube sheets 18. Also, the opposite ends of each CT 32 are received within and sealed to respective bores 19 in the tube sheets 18. In some embodiments, a rolled joint insert, for example calandria tube insert 34, is used to secure the CT 32 to the tube sheet 18 within the bores 19. 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 fuel bundles or assemblies 40. The PT 36, 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 each PT 36 and its corresponding CT 32. The annulus space 44 is normally filled with a circulating gas, such as dry carbon dioxide, helium, nitrogen, air, or mixtures thereof. One or more annulus spacers or garter springs 48 are disposed between the CT 32 and PT 36. The annulus spacers 48 maintain the gap between the PT 36 and the corresponding CT 32, while allowing passage of annulus gas through and around the annulus spacers 48.

[0030] As also shown in FIG. 2, each end of each fuel channel assembly 28 is provided with an end fitting assembly 50 located outside of the corresponding tube sheet 18. Each end fitting assembly 50 includes an end fitting body 57 and an end fitting liner 58. At the terminal end of each end fitting assembly 50 is a closure plug 52. Each end fitting assembly 50 also includes a feeder assembly 54. The feeder assemblies 54 feed reactor coolant into or remove reactor coolant from the PTs 36 via feeder tubes 59 (FIG. 1 ). 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 assemblies 50 using a coupling assembly 56 including a number of screws, washers, seals, and/or other types of connectors. The lattice tube 65 (described above) encases the connection between the end fitting assembly 50 and the PT 36 containing the fuel assemblies 40. Shielding ball bearings 66 and cooling water surround the exterior of the lattice tubes 65, which provides additional radiation shielding.

[0031] A positioning hardware assembly 60 and bellows 62 are also coupled to each end fitting assembly 50. The bellows 62 allows the fuel channel assemblies 28 to move axially - a capability that can be important where fuel channel assemblies 28 experience changes in length over time, which is common in many reactors. The positioning hardware assemblies 60 can be used to set an end of a fuel channel assembly 28 in either a locked configuration that fixes the axial position, or an unlocked configuration. The positioning hardware assemblies 60 are also coupled to the end shield 64. The illustrated positioning hardware assemblies 60 each include a rod having an end that is received in a bore of the respective end shield 64. In some

embodiments, the rod end and the bore in the end shield 64 are threaded. Again, it should be understood that although a CANDU™-type reactor is illustrated in FIGS. 1 -2, the invention may also apply to other types of reactors, including reactors having components that are similar to those illustrated in FIGS. 1 -2.

[0032] FIG. 3 illustrates a flow chart of a removal process for retubing a nuclear reactor according to some embodiments. As shown in FIG. 3, the removal process starts with shutting down the reactor 6 (at step S70) and preparing the vault for retubing (at step S72). These steps can include various activities, such as defueling the reactor 6, draining the reactor's primary heat transport system, installing an isolation bulkhead, installing and removing a temporary platform on a reactor area bridge to drain the fuel channel assemblies 28, removing the reactor area bridge, upgrading one or more vault cranes, vacuum drying one or more of the reactor's heat transport systems, and other draining, drying, and ventilation activities. It should be understood that the steps needed to shut down the reactor 6 and prepare the vault can vary based on the specific configuration of the reactor.

[0033] At step S76, material handling equipment, a retube tooling platform

("RTP"), and other tool and equipment supports are installed. The RTP is an adjustable platform upon which much of the fuel channel component removal operations are performed. In some embodiments, the RTP is a stand-alone machine that does not rely on existing plant structures for positioning or movement. Therefore, minimal structural bracing to existing plant structures may be needed to install the RTP, and any bracing used is only temporarily installed. In some embodiments, reactor area bridge columns are used to install the RTP. In other embodiments, four new columns are used. The four new columns can be precision-located within the vault, relative to the center point of the calandria vessel 10, using laser tracker technology. By positioning the columns in this way, the RTP is positioned to the as-built location of the calandria vessel 10

(including pitch and yaw), which may reduce the time spent during each transition to a new removal step or series to align tooling, and provides a precision tooling base that may permit the use of high accuracy indexing to each lattice site.

[0034] Installed and mounted on the RTP, and serving as the basis for tool delivery during the removal phase, are one or more heavy work tables ("HWTs"). The HWTs provide a platform that supports retubing equipment. At the completion of a removal process, the HWTs can be replaced with installation work tables ("IWTs").

[0035] In preparation for removing the fuel channel assemblies 28, closure plugs 52 and positioning hardware assemblies 60 are removed from the fuel channel assemblies 28 (at steps S78, S80). Also, at step S82, feeder assemblies 54 are disconnected from the end fittings 50. These removals can be performed using manually installed and operated tooling. In some embodiments, two or more crews per reactor face can be used to perform these removals and disconnects. These series can be full face series; however, the manual nature and size of the tooling needed for these series permits overlap between these series. [0036] As shown in FIG. 3, to remove the fuel channel assemblies 28, the bellows 62 are also severed (at step S84). To sever the bellows 62, a fuel channel annulus bellows cutting tool can be installed on the HWT (e.g., supported by the RTP). The bellows 62 are typically cut from an end fitting attachment at the bellows flange. The PTs 36 are also severed (at step S86) using a PT severing tool. The PTs 36 are typically severed within the boundary of the end fitting 50 enveloping the PT 36.

However, the PTs 36 can be severed at different positions, including the center of the PT 36. The reach of the PT severing tool can be modified as needed to cut the PTs 36 at the desired location(s).

[0037] As mentioned above, the removal pallet system is used to remove the end fittings 50 (at step S88). To perform this removal process in some embodiments, the pallet starts with an end fitting gripper mounted on the end of a chain drive. A receiving flask is loaded onto the pallet from above using an overhead vault crane. The rigid chain system advances through the center of the receiving flask to grip the end fitting 50, and then draws the end fitting 50 into the receiving flask. In some embodiments, no operators are required on the RTP during end fitting removal. However, the equipment can be shielded and local control can be supported so that direct eyeball contact with the equipment may be accommodated. Removal of full flasks and the installation of empty flasks can occur while the RTP is at the "home" position, which is level with the vault floor. Once the removal system is prepared, the RTP can be elevated to the required row, and tooling can be operated to remove the end fittings.

[0038] Once the end fittings 50 are removed and placed into a receiving flask, they can be transported for disposal. For example, as described above, a trolley system or automated guided vehicle can be installed in the reactor vault that extends through the airlock, and is used to transfer removed components out of the vault. The systems may eliminate or reduce many hazardous involved in manually-operated transfers.

[0039] As illustrated in FIG. 3, after end fitting removal, the PTs 36 are removed (at step S90) by pushing on the PT 36 from one end of the reactor with a push tool mounted on the removal pallet on the opposite side of the reactor. A containment flask is mounted on the same pallet as used with the end fittings 50. The containment can be used to minimize the spread of contamination from the PT 36, and to capture any fragments of the annulus spacers 48. The containment can is pushed into the lattice tube 65 up to the CT 32. The pushing of the PT 36 can be performed from the opposite side of the reactor with a trailing bung that sweeps the annulus spacer 48 fragments into the containment. Cleaning of the annulus spacer 48 fragments from the flared area of the CT 32 can also be performed by this sweep.

[0040] Either before or after PT removal, calandria tube inserts 34 can be released and removed (at step S92). CT insert release and removal is described in greater detail below. After the calandria tube inserts 34 and PTs 36 are removed, the CTs 32 are removed (at step S94) and the removal process is complete.

[0041] FIG. 4 illustrates one embodiment of a heavy work table ("HWT") 96 installed on a retube tooling platform ("RTP") 95 adjacent the end 24 of the nuclear reactor. A similar HWT can be installed adjacent the end 22 of the nuclear reactor. The HWT 96 and any tools mounted on the HWT are controlled by a control station (not shown).

[0042] A calandria tube insert removal tool, CTI removal tool 100, is mounted on the HWT 96 and is positioned to remove calandria tube inserts 34 from tube sheet 18 at the end 24. The control of a position of the CTI removal tool 100 with respect to the end shield 64 and operation of the tool 100 may occur from the control station. Specifically, the operator can control the height of the RTP 95 along axis Y, the location of the CTI removal tool 100 on the HWT 96 along axis X and the pitch with respect to the end shield 64 to orient axis Z to be perpendicular to the end shield 64. In some

embodiments, the height of RTP 95 may be adjusted by ball screws, for example, by way of one ball screw at each corner of RTP 95.

[0043] When the CTI removal tool 100 is aligned with the selected opening in the end shield 64, the operator can insert the CTI removal tool 100 into the appropriate fuel channel along axis Z. The CTI removal tool 100 can include any number of suitable sensors and/or cameras to verify that the CTI removal tool 100 is properly aligned with the respective opening in the end shield 64.

[0044] An induction heating power supply and control system 98 shown in FIG. 4 may be used to control heating section 108, and more specifically, heating element 1 18 of CTI removal tool 100, described in more detail below.

[0045] FIG. 5A is a left perspective view of the HWT 96 and CTI removal tool 100. FIG. 5B is a right perspective view of the HWT 96, CTI removal tool 100, and the end shield 64 at the end 24 of the nuclear reactor 6. As will be understood, CTI removal tool 100 may operate on a HWT at opposite end 22 of the nuclear reactor 6. After the closure plugs 52, positioning hardware assemblies 60, feeder assemblies 54, and the end fittings have been removed, a temporary shield plug (not shown) is inserted through end shield 64 into lattice tube 65. In some embodiments, temporary shield plug may be contained with a lattice sleeve assembly ("LSA") also referred to as a "thumbtack" 68. In some embodiments, thumbtack 68 may include a sleeve, a temporary shield plug within the sleeve, and a flange. In some embodiments, bellows 62 may also be removed either before or after the temporary shield plug is inserted through end shield 64 into lattice tube 65.

[0046] In some embodiments, the CTI removal tool 100 is aligned with the end shield 64 via the thumbtack 68. The temporary shield plug of thumbtack 68 may be removed prior to the insertion of CTI removal tool 100. Thumbtack 68 may remain, and act as a sleeve that may protect bellows 62.

[0047] The CTI removal tool 100 may then be moved along the direction of arrow 102 to be inserted into the end shield 64. Any suitable means can be utilized to move the CTI removal tool 100 into and out of the tube sheet 18, such as a rigid push-pull chain or a servo rack drive. The position of the CTI removal tool 100 on the HWT 96 may be controlled by an operator via the control station. The CTI removal tool 100 may be precisely inserted to a desired depth as discussed in detail below. [0048] FIG. 6 illustrates the CTI removal tool 100, in an embodiment, in greater detail. FIG. 7 is a close up of a tool head of the CTI removal tool 100 of FIG. 6. CTI removal tool 100 includes a tool head 104 and a tool body 106 coupled to the tool head 104. The illustrated CTI removal tool 100 is inserted into the lattice tube 65. The CT 32 can be removed before or after the CTI removal tool 100 releases and removes the calandria tube insert 34 from the tube sheet 18. The CTI removal tool 100 is inserted in the insertion direction (arrow 102) until substantially the entire tool head 104 passes through the tube sheet 18.

[0049] As shown in FIGS. 6 and 7, the illustrated CTI removal tool head 104 includes three distinct sections: a heating section 108, a CTI removal section 1 10, cooling section (not shown) and a CT gripping section 1 12. In other embodiments, the heating section 108 may be positioned on a separate tool. In some embodiments, the CT gripping section 1 12 may be omitted from CTI removal tool 100. In some

embodiments, a cooling section may be omitted from CTI removal tool 100.

[0050] In some embodiments, heating section 108 includes a heater such as a heating element 1 18 that can abut the calandria tube insert 34 to heat the calandria tube insert 34 without substantially heating the calandria tube sheet. In some

embodiments, an induction heater is positioned in the heating section 108. In some embodiments, heating element 1 18 may include coils, as shown in FIGS. 6 and 7 perform heating by at least one of electromagnetic induction (creating eddy currents, and thus heat inside calandria tube insert 34), conduction or convention.

[0051] In some embodiments, CTI removal section 1 10 includes clamshells 120 that can be utilized to remove the calandria tube insert 34. In some embodiments, the clamshells 120 may include be three sets of clamshells positioned 120 degrees apart, four sets of clamshells positioned 90 degrees apart or two sets of clamshells positioned 180 degrees apart. In some embodiments, the gripping section 1 10 includes a shoulder feature with a roller that allows for movement along the CT 32 when the calandria tube insert 34 is pulled. The shoulder feature may include a ledge or a rim that may allow clamshells 120 to engage with calandria tube insert 34, and allow for axial movement of CTI removal tool 100, and hence clamshell 120, to remove calandria tube insert 34 from the fuel channel assembly 28. The clamshell 120 may be actuated by a pull rod or by rotation and then pull. In some embodiments, clamshells 120 may actuate radially or axially, independently of CTI removal tool 100. In some embodiments, clamshells 120 may be replaced by a ledge that may move axially and radially relative to CTI removal tool 100, and shaped to engage with the calandria tube insert 34 after cooling.

[0052] In some embodiments, the cooling section of CTI removal tool 100 includes at least one cooling element that cools the calandria tube insert 34 by at least one of conduction and convection. In some embodiments, the cooling element can include a cooling medium, such as liquid nitrogen, a cool air jet, cooling coils, an alcohol bath, liquid lead, helium or dry ice, etc., that contacts the calandria tube insert 34 either directly, for example, directed by nozzles on CTI removal tool 100, or through a barrier. In some embodiments, the cooling element can include a heat pipe. For example, the cooling medium can circulate within heat pipe of the cooling element and be surrounded by a thermally conductive material, such as metal, and the thermally conductive material of the heat pipe can contact the calandria tube insert 34 to actively cool the calandria tube insert 34. In some embodiments, the cooling section may include a radiator to absorb heat energy from calandria tube insert 34, for example, as a black body heat sink.

[0053] In some embodiments, the clamshells 120 includes a clam shell that can expand to abut the calandria tube insert 34 to perform cooling. In some embodiments, the clam shells contact the calandria tube insert 34 around at least a portion of the inner diameter of the calandria tube insert 34. In some embodiments, the clam shells contact a majority of the inner diameter of the calandria tube insert 34.

[0054] In some embodiments, CT gripping section 1 12 includes grippers 122 that can include double acting grippers or two separate sets of grippers that can be utilized to hold the CT 32 stationary while the calandria tube insert 34 is being removed. In some embodiments, grippers 122 can separately grip the CT 32 and grip the calandria tube insert 34, for example, to reset calandria tube 34 if it is misaligned. In some embodiments, grippers 122 may include be three sets of grippers positioned, for example, 160 degrees apart, 120 degrees apart, four sets of grippers at 90 degrees apart, or two sets of grippers at 180 degrees apart. The grippers 122 may use friction to grip the CT 32 or calandria tube insert 34 and may be actuated by a pull rod or rotation.

[0055] FIG. 9 illustrates the CTI removal tool 100, in another embodiment, including a cooling section, as described above, illustrated as cooling section 1 1 1 with a cooler, namely cooling elements 121 . FIG. 10 is a close up of the tool head of the CTI removal tool 100 of FIG. 9, and FIG. 1 1 a further close up of the tool head.

[0056] In other embodiments, the heating element 1 18, the clamshells 120 and the gripping element 122 can be positioned at different locations on the CTI removal tool head 104.

[0057] In use, the CTI removal tool 100 and its components may be used to performing heating of calandria tube insert 34, cooling of calandria tube insert 34, gripping of CT 32, and gripping of calandria tube insert 34 before axially removing calandria tube insert 34 from the fuel channel assembly 28. The CTI removal tool 100 may move axially within the fuel channel assembly 28 to allow access to the

components of CTI removal tool 100 that are used to perform these operations. These operations are discussed in further detail, below.

[0058] The illustrated CTI removal tool head 104 of FIGS. 6 and 7 is fully inserted into the calandria tube sheet 18 (along the direction of arrow 102) such that the heating section 108 is substantially aligned with the calandria tube insert 34. In some

embodiments, the heating element 1 18 is positioned in abutment with or adjacent to the calandria tube insert 34. In some embodiments, the heating element 1 18 is positioned within the inside diameter of the calandria tube insert 34.

[0059] In some embodiments, the calandria tube inserts 34 are separated from the calandria tube sheet 18 by induction heating. In some embodiments, the calandria tube insert 34 is heated by at least one of conduction or convection. [0060] In some embodiments, the calandria tube insert 34 is heated for a set time and/or to a set temperature. In some embodiments, heating may occur for a duration of between 1 and 10 seconds, in an example, 1 and 4 seconds, and in other embodiments more than 10 seconds. In some embodiments, heating may occur to reach a target temperature of between 800 and 1500 degrees Celsius of the calandria tube insert 34. In an example, the calandria tube insert 34 is heated to 1300 degrees Celsius in 1 .8 to 2.2 seconds. One or more sensors, such as an optical sensor, a thermocouple or other suitable sensor, can be utilized to measure various features of the calandria tube insert 34.

[0061] In some embodiments, electromagnetic parameters of the heating element 1 18 may be monitored, in an electromagnetic induction embodiment of the heating element 1 18. In some embodiments, a set time and temperature may be controlled by a control system, such as control system 98. Control system 98 may be calibrated to detect how much energy is being imparted to the calandria tube insert 34. This may provide feedback during a heating process to know how the calandria tube insert 34 is being heated, for example, by determining how much current or voltage is being applied to the induction system to perform the heating. The electromagnetic parameters of the heating element 1 18 may be monitored so as to deem a "pass" or "fail" of a heat cycle. For example, a "pass" or "fail" heat cycle may be flagged if a certain amount of energy was transmitted to the heating element.

[0062] In some embodiments, the inner diameter of the calandria tube insert 34 may be measured, for example, with a bore gauge, after heating and/or cooling, to confirm that a desired inner diameter is met. This may be done in testing or on initial sites. In some embodiments, this may allow a second heating to be performed, which may be performed by a heating element on the same tool that is used for inner diameter measurement. In some embodiments, the clamshells 120 or the grippers 122 may provide feedback on their positioning, and may provide sensing of positions of components within the fuel assembly 28. [0063] In some embodiments, the calandria tube insert 34 is "shock heated", for example, using induction heating, for a specific time and energy profile. The operator can use a timer or computer control to operate the heating element 1 18 for a set time. In some embodiments, control logic can be utilized to automatically actuate the heating element 1 18 until a specific time period has elapsed and/or until the calandria tube insert 34 reaches a set temperature or a desired level of energy has been transmitted.

[0064] After the calandria tube insert 34 has been heated by the heating element 1 18, the CTI removal tool head 104 is partially withdrawn from the calandria tube sheet 18, in an example, along the direction of arrow 1 14, to align the cooling section with the calandria tube insert 34.

[0065] At least one cooling element of the cooling section cools the calandria tube insert 34 by at least one of conduction and convection. Cooling may be performed as soon as the cooling section is positioned to perform the cooling.

[0066] In some embodiments, the cooling element cools the calandria tube insert 34 for a set time period and/or until the calandria tube insert 34 reaches a set temperature, for example, between room temperature (of approximately 20 degrees Celsius) and 500 degrees Celsius, in examples, 200 degrees Celsius, 180 degrees Celsius or 100 degrees Celsius. In some embodiments, the cooling duration may be between a few seconds (for example, between 3 and 5 seconds) and a few minutes (for example, between 3 and 5 minutes), or more.

[0067] One or more sensors, such as an optical sensor, a thermocouple or other suitable sensor, can be utilized to measure a temperature of the calandria tube insert 34. The operator can use a timer to operate the cooling element for a set time. In some embodiments, control logic can be utilized to automatically actuate the cooling element until a specific time period has elapsed and/or until the calandria tube insert 34 reaches a set temperature. This active cooling is performed in addition to any cooling occurring by radiation, conduction, or natural convection as the heat dissipates after the heating section 108 is removed from the calandria tube insert 34. [0068] The calandria tube insert 34 is deformed during heating which may cause the calandria tube insert 34 to reduce in diameter upon cooling. Heating the calandria tube insert 34 may cause plastic deformation, and adequate cooling may ensure that the calandria tube insert 34 is small enough to be removed.

[0069] During heating, the calandria tube insert 34 tries to thermally expand, however, it may be limited by the inner diameter of the bores 19 of tube sheet 18, so the heated material of calandria tube insert 34 is pushed out the front and back of bore 19. When the calandria tube insert 34 is then cooled, it cools to a different shape and smaller outside diameter, due to plastic deformation of the calandria tube insert 34 in the heating stage, and the cooling may prevent the excess material of the plastically deformed calandria tube insert 34 from re-entering bore 19.

[0070] In some embodiments, it may be advantageous to remove calandria tube insert 34 more quickly, for example, when calandria tube insert 34 is hotter and without cooling, which may have side effects such as heating up the CTI removal tool 100.

[0071] In some embodiments, it may be desirable to cool calandria tube insert 34 more quickly, to get better plastic deformation which may result in a reduction in the inner diameter of the calandria tube insert 34. If calandria tube insert 34 is cooled slowly with ambient cooling, the calandria tube insert 34 may plastically relax to closer to its original shape (pre-heating). In some embodiments, that may be avoidable by deforming the calandria tube insert 34 to a high temperature and cooling it quickly.

[0072] In some embodiments, following cooling, clamshells 120 of CTI removal section 1 10 axially engage the calandria tube insert 34 for removal, for example, by a ledge or rim of the shoulder feature of clamshells 120 engaging with the calandria tube insert 34. The grippers 122 of CT gripping section 1 12 may separately grip the CT 32. Then, the portions of the clamshells 120 move axially with respect to tool head 104 to separate the calandria tube insert 34 from the tube sheet 18. Embodiments having three sets of clamshells 120 positioned 120 degrees apart may ensure that the calandria tube insert 34 is removed squarely. [0073] In some embodiments, the clamshells 120 may also cool the calandria tube insert 34.

[0074] The clamshells 120 are used to pull the calandria tube insert 34 out of the tube sheet 18 while grippers 122 hold the CT 32 stationary in place. In some embodiments, the shoulder with a roller feature may ride along the CT 32 when the calandria tube insert 34 is pulled. Then, the clamshells 120 and/or a shoulder feature on the CTI removal tool 100 stay engaged to a rear face of the calandria tube insert 34 to pull the calandria tube insert 34 out axially as the CTI removal tool 100 is withdrawn. The CTI removal tool head 104 and calandria tube insert 34 may be withdrawn fully from the tube sheet 18 along the direction of arrow 1 14.

[0075] Following removal of the calandria tube insert 34, a shield plug may be inserted into the aperture in the lattice tube 65 to provide radiation shielding, for example, by thumbtack 68.

[0076] A similar process can be performed on each end 22, 24 of the calandria 6 to remove the calandria tube insert 34 from the other tube sheet 18. In some

embodiments, the processes are coordinated such that both calandria tube inserts 34 are removed from the same fuel channel at the same time. However, such coordination is not necessary.

[0077] The illustrated CTI removal tool 100 can perform three distinct functions: heating, cooling and removal. In some embodiments, a temporary shield plug may be removed from the lattice sleeve 65 before the CTI removal tool 100 is inserted into the lattice sleeve 65 and not replaced until after the calandria tube insert 34 is removed from the tube sheet 18.

[0078] In other embodiments, two or more tools can be utilized to perform these three distinct functions. The tools can be positioned on the same HWT 96 and can be inserted and removed in relatively quick succession, such that the shield plug does not need to be inserted between the tools. Therefore, after the shield plug is removed, the calandria tube insert 34 insert can be heated, cooled and removed prior to reinstalling the shield plug. If desired, a shielding can be utilized to provide partial shielding between the operations of the various tools and then can be replaced by a shield plug after the calandria tube insert 34 has been removed.

[0079] With reference to FIGS. 8A and 8B, the CTI removal tool 100 is shown on the HWT 96. FIG. 8A is a side view of a calandria insert removal tool according to some embodiments including a containment flask, flask 124. FIG. 8B is the side view of the CTI removal tool 100 of FIG. 8A, with flask 124 omitted.

[0080] As shown in FIG. 8A, flask 124 is positioned on the HWT 96 and the CTI removal tool 100 extends through the flask 124 and into the lattice tube 65 of the nuclear reactor. Flask 124 may be formed of lead encased in steel, or an appropriately dense material such as concrete, steel or tungsten. The removed calandria tube inserts 34 are retained in the flask 124 to minimize radiation exposure.

[0081] Calandria tube inserts 34 may be collected axially along the length of CTI removal tool 100 (for example, as shown in FIGS. 9 and 1 1 ) as CTI removal tool 100 removes calandria tube inserts from subsequent bore 19 locations of tube sheet 18. At each location, the calandria tube insert 34 is pushed axially back onto the CTI removal tool 100. In an example, up to ten calandria tube inserts 34 may be collected on CTI removal tool 100, prior to the calandria tube inserts 34 being deposited into flask 124.

[0082] In some embodiments, multiple (e.g., ten) calandria tube inserts 34 are removed by the CTI removal tool head 104 and then drawn into the flask 124 before the flask 124 is removed from the RTP 95 and replaced with an unloaded flask 124.

[0083] In some embodiments, flask 124 may be omitted, and calandria tube inserts 34 may be retained by a set of grippers or a transfer can, for example, on an overhead crane.

[0084] In some embodiments, an x-y gantry, having a gripper of two half-cylinder tubes, similar to a clamshell, to wrap around CTI removal tool 100. The gantry can lower and pick things up. CTI removal tool 100 may move to deposit the calandria tube inserts 34 at the gantry gripper, and a crane may transport the removed calandria tube inserts 34 to a waste area.

[0085] An induction heater transformer 126 is also illustrated in FIGS. 8A and 8B, and can be utilized to provide power to the CTI removal tool 100 to transform the current and voltage to the parameters needed to support the heating coil.

[0086] In a conventional retubing process, removing a calandria tube insert from a calandria tube sheet includes, at each fuel channel, calandria tube release followed by calandria tube insert removal. Calandria tube insert release includes: removing a shield plug from the end shield and lattice tube, inserting a heating tool in the end shield and lattice tube to reach the tube sheet, releasing the calandria tube inserts (for example by heating), removing the heating tool, and replacing the shield plug. The calandria tube removal process then includes: removing the shield plug, inserting a removal tool in the end shield and lattice tube to reach the tube sheet, acquiring the released calandria tube insert with the removal tool, removing the removal tool and the calandria tube insert, and replacing the shield plug.

[0087] As will be appreciated, the above calandria tube insert release and removal operations, performed at every insert location (i.e., every bore in the tube sheet), can be a time-intensive process.

[0088] As detailed above, in some embodiments, the two operations (calandria tube insert release and removal) may be combined in one visit and one tool insertion, for example, using CTI removal tool 100: removing a shield plug, inserting CTI removal tool 100, performing calandria tube insert release (for e.g., induction heating) and calandria tube insert removal (for e.g., calandria tube insert engaging and calandria tube gripping), and removing CTI removal tool 100 and the calandria tube insert before replacing the shield plug in the end shield and lattice tube. Thus, there may be savings in tooling transition time, and over all may save some time during the retubing process.

[0089] Furthermore, in a conventional retubing process, all calandria tube inserts on a single side of the reactor would first be released, for example, using a calandria tube insert release system using a conventional induction heating system. The tooling would then be switched out for a conventional calandria tube insert removal tool, used for calandria tube insert removal to pull out all of calandria tube inserts. In some instances, encountering a non-released or insufficiently released calandria tube insert would disrupt the entire workflow. If an insufficiently released calandria tube insert is encountered during removal, the calandria tube insert release system would need to be re-installed, and the calandria tube insert would need to be released using the induction heating system. This would likely consume significant amount of time (in an example, a few days).

[0090] By releasing and removing calandria tube insert 34 with CTI removal tool 100, as a single tool, the risk of encountering a non-released or insufficiently released calandria tube insert 34 when attempting to remove calandria tube insert 34 may be reduced. Having functions for both calandria tube insert release and calandria tube insert removal in one tool allows for an additional release to be performed quickly, for example, if an insufficiently released calandria tube insert is encountered, without exiting the channel or installing any additional tooling. Thus, time may be saved during retubing and the nuclear reactor refurbishment.

[0091] Of course, the above described embodiments are intended to be illustrative only and in no way limiting. The described embodiments are susceptible to many modifications of form, arrangement of parts, details and order of operation. The disclosure is intended to encompass all such modification within its scope, as defined by the claims.

Claims

WHAT IS CLAIMED IS:

1 . A device for removing a rolled joint insert from between a calandria tube of a fuel channel assembly of a nuclear reactor and a tube sheet of the nuclear reactor, the rolled joint insert radially securing the calandria tube to the tube sheet, the device comprising: a body extending axially from a first end to a second end, opposite the first end; a heater for heating a rolled joint insert to a first temperature; a cooler for cooling the rolled joint insert to a second temperature; a ledge for axially engaging the rolled joint insert; and a gripper for gripping the calandria tube, wherein the heater, the cooler, the ledge and the gripper are in axial alignment along the body.

2. The device of claim 1 , wherein the ledge is radially extendable and retractable.

3. The device of claim 1 , wherein the heater is positioned to define a no-heating region in which the tube sheet is not heated as the rolled joint insert is heated.

4. The device of claim 1 , wherein the first temperature is between 800°C and 1500°C.

5. The device of claim 1 , wherein the heater heats the rolled joint insert to the first temperature in 1 .8 to 2.2 seconds.

6. The device of claim 1 , wherein the second temperature is between 20°C and 180°C.

7. The device of claim 1 , wherein the gripper is for gripping the calandria tube in a stationary position.

8. A method for removing a rolled joint insert from between a calandria tube of a fuel channel assembly of a nuclear reactor and a tube sheet of the nuclear reactor, the rolled joint insert radially securing the calandria tube to the tube sheet, the method comprising: heating the rolled joint insert to a first temperature; following the heating, cooling the rolled joint insert to a second temperature, the second temperature less than the first temperature; gripping the calandria tube; and axially engaging the rolled joint insert while gripping the calandria tube, wherein the heating, the cooling, the gripping and the axially engaging are performed by a single tool head in axial movement along a defined axis.

9. The method of claim 8, further comprising axially withdrawing the rolled joint insert from the tube sheet.

10. The method of claim 8, wherein axially engaging the rolled joint insert comprises radially expanding a ledge to engage with the rolled joint insert.

1 1 . The method of claim 8, wherein the first temperature is between 800°C and 1500°C.

12. The method of claim 8, wherein the rolled joint insert reaches the first

temperature in 1 .8 to 2.2 seconds

13. The method of claim 8, wherein the second temperature is between 20°C and 180°C.

14. The method of claim 8, wherein the heating defines a heating region in which the tube sheet is not heated as the rolled joint insert is heated.

15. The method of claim 8, wherein the heating is by at least one of induction, conduction and convection.

16. The method of claim 8, wherein the cooling is by at least one of conduction and convection.

17. The method of claim 9, further comprising depositing the withdrawn rolled joint insert into a containment flask.