WO2018232498A1

WO2018232498A1 - Apparatus and method for locating a calandria tube

Info

Publication number: WO2018232498A1
Application number: PCT/CA2018/050673
Authority: WO
Inventors: Andrzej SZCZEPAN; Robert Jamieson
Original assignee: Candu Energy Inc.
Priority date: 2017-06-23
Filing date: 2018-06-05
Publication date: 2018-12-27

Abstract

A method of inserting a calandria tube in a reactor includes engaging an insertion tool with an inner surface of the calandria tube, inserting a portion of the calandria tube through a first calandria tube sheet bore via the insertion tool, inserting a guide tool into the inner surface of the calandria tube and guiding a portion of the calandria tube through a second calandria tube sheet bore via the insertion tool and the guide tool.

Description

APPARATUS AND METHOD FOR LOCATING A CALANDRIA TUBE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims all benefit including priority to United States Provisional Patent Application 62/524,330, entitled "APPARATUS AND METHOD FOR LOCATING A CALANDRIA TUBE", and filed June 23, 2017; and Romanian Patent Application

a 2018 00139, filed February 28, 2018.

[0002] These applications are hereby incorporated by reference in their entireties. FIELD

[0003] The following application relates to inserting a calandria tube in a reactor, and in particular to an apparatus and method for inserting the calandria tube in the reactor using an insertion tool and a guide tool.

BACKGROUND

[0004] A nuclear reactor has a limited life of operation. 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 "re-tubing" process can extend the life of a reactor significantly, as an alternative to decommissioning the reactor. Nuclear reactor re-tubing 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, and severing and removing pressure tubes and calandria tubes.

[0005] 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 may 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 tube sheet bore is to specification and that the tube sheet bore is ready for insertion of a new fuel channel assembly.

[0006] 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.

SUMMARY

[0007] In some embodiments, the invention provides a method of inserting a calandria tube in a reactor. The method includes engaging an insertion tool with an inner diameter of the calandria tube, inserting a portion of the calandria tube through a first calandria tube sheet bore via the insertion tool, inserting a guide tool into the inner diameter of the calandria tube and guiding a portion of the calandria tube through a second calandria tube sheet bore via the insertion tool and the guide tool.

[0008] The invention also provides an apparatus for locating a calandria tube relative to a first calandria tube sheet bore and a second calandria tube sheet bore of a reactor. The apparatus includes a worktable mounted on a re-tubing platform located adjacent to the reactor, an insertion tool mounted to the worktable and engageable with an inner diameter of the calandria tube through the first calandria tube sheet bore, and a guide tool engageable with an inner diameter of the calandria tube through the second calandria tube sheet bore.

[0009] The invention provides a method including removing a first calandria tube from a calandria tube bore via an insertion/removal tool and inserting a second calandria tube into the calandria tube bore via the insertion/removal tool.

[0010] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Various aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

[0012] Figure 1 is a perspective view of a reactor core of a nuclear reactor. [0013] Figure 2 is a cut-away view of the fuel channel assembly.

[0014] Figure 3 is a schematic view of an insertion tool and a plurality of support members for a calandria tube.

[0015] Figure 4 is a schematic view of the insertion tool of Fig. 3 with a calandria tube.

[0016] Figure 5 is a schematic view of the insertion tool and calandria tube of Fig. 4 with a guide tool.

[0017] Figure 6 is a schematic view of the insertion tool and the calandria tube with an alternative guide tool.

[0018] Figure 7 is a schematic view of the insertion tool and the calandria tube with another alternative guide tool.

[0019] Figure 8A is a schematic view of the insertion tool and the calandria tube with yet another alternative guide tool.

[0020] Figure 8B is a front view of the guide tool shown in Fig. 8A. DETAILED DESCRIPTION

[0021] 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

accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. [0022] Fig. 1 is a perspective of a reactor core of a CA DU -type reactor 6, for example a 900MW CANDU™ reactor. Alternatively, the reactor 6 may be a 100-300MW CANDU™ reactor, a 600MW CANDU™ reactor, a 1000MW CANDU™ reactor, or another pressurized heavy water reactor (PHWR). The reactor core is typically contained within a vault that is sealed with an air lock for radiation control and shielding. Although aspects of the invention are described with particular reference to the CANDU™-type reactor 6 for convenience, the invention is not limited to CANDU™-type reactors, and may be useful outside this particular field as well. Returning to Fig. 1, a generally cylindrical vessel, known as the calandria 10 of the CANDU™-type reactor 6, 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 apertures (referred to herein as "bores") 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 10 from the first end 22 to the second end 24.

[0023] As in the illustrated embodiment, 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 (i.e., in the tube sheet 18 and the end shield 64, respectively).

[0024] 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 in the tube sheets 18. In some embodiments, a CT rolled joint insert 34 is used to secure the CT 32 to the tube sheet 18 within the bores. 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.

[0025] 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 59. 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.

[0026] Returning to Fig. 2, 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. [0027] Fig. 3 illustrates an insertion tool 110 for inserting the calandria tube 32 into a calandria tube bore in the tube sheets 18 (Figs. 1, 4). Specifically, the insertion tool 110 inserts the calandria tube 32 through a bore in a first tube sheet 18 (on a first side of the reactor 6) and through a bore in a second tube sheet 18 (on a second side of the reactor 6, opposite the first side). As shown, the insertion tool 110 is a telescoping ram including a first support 112, a second support 114, a telescoping arm 116, and a mounting portion 118, for mounting the insertion tool 110 to a worktable 100 on a re-tubing platform, located adjacent to the reactor 6.

[0028] The first and second supports 112, 114 are spaced apart from each other. The first and second supports 112, 114 are mounted to the telescoping arm 116 at a distance apart from one another and are configured to simultaneously engage with an inner surface of the calandria tube 32, as shown in Fig. 4. Though schematically shown as being cylindrical, the supports 112, 114, may be spoked or otherwise designed to engage with and support the calandria tube 32. Utilizing two distinct supports 112, 114 provides a cantilevered support system, thereby decreasing the rotational moment of the calandria tube 32 when one end 22 of the calandria tube 32 is mounted on the tool 110.

[0029] The telescoping arm 116 is configured to extend and retract along a longitudinal axis 120. The longitudinal axis 120 is aligned with or is parallel to a longitudinal axis of the calandria tube 32 so that extension of the telescoping arm 116 extends the calandria tube 32 along its axis and retraction of the telescoping arm 116 retracts the calandria tube 32 along its axis. The telescoping arm 116 is fixed to the mounting portion 118. The mounting portion 118 is movable along the worktable 100 so that the insertion tool 110 can be aligned with various points along the reactor face. Specifically, the insertion tool 110 is movable to align the telescoping arm with the bore in the first tube sheet 18.

[0030] As shown in Figs. 3-4, the worktable 100 further supports a plurality of support members 124. As shown, the support members 124 are spaced apart in the longitudinal direction of the calandria tube 32. Four support members 124 are shown, though more or less may be used (e.g., 1-3 support members, 5+ support members) to support the calandria tube 32 radially (i.e., providing a force in the radial direction of the calandria tube 32) and further reduce the moment of the cantilevered tube 32 and the resulting sagging of the distal end 24 of the tube 32. The support members 124 may apply a force on an outer surface of the calandria tube 32. As depicted in Fig. 4, the support members 124 may apply forces that are spaced apart in the longitudinal direction of the calandria tube 32. The support members 124 may be, for example, hydraulically-controlled plungers, pneumatically-controlled plungers, or electrically-controlled solenoids.

[0031] As shown in Figs. 5-8B, a guide tool 130A-D is further provided to control the movement of the calandria tube 32. The guide tool 130A, as shown in Fig. 5, extends into an end of the calandria tube 32. Specifically, the guide tool 130 extends into the second end 24 of the calandria tube 32 opposite to the first end 22 through which the insertion tool 110 extends. The guide tool 130A shown in Fig. 5 is a cylindrical rod 132 that contacts an inner surface of the calandria tube 32 and includes a tapered end to improve the accuracy of insertion.

[0032] At least the second end 24 of the calandria tube 32 is a belled end, with a larger diameter than that of the rest of the tube 32. The guide tool 130B shown in Fig. 6 is a cylindrical rod, but unlike the guide tool 130A, the guide tool 130B terminates with a larger end for engaging the belled end 24 of the calandria tube 32. The larger end of the guide tool 130B may be tapered (as shown) to improve the accuracy of insertion. When engaged with the belled end 24, the guide tool 130B is axially aligned with the second end 24 of the calandria tube 32.

[0033] As shown in Fig. 7, the guide tool 130C is provided with fingers 134 that extend radially from the cylindrical body 132 to engage the inner surface of the calandria tube 32. As shown, the fingers 134 are offset from one another by ninety degrees, though this may be increased or decreased based on the density of the fingers 134. The fingers may be made of a resilient material to support off-center insertion of the guide tool 130C into the calandria tube 32 yet still provide structural support to hold the calandria tube 32 relative to the cylindrical body 132.

[0034] As shown in Figs. 8A-8B, the guide tool 130D is provided with a cam 136 fixed to the distal end of the cylindrical body 132. The cam 136 is provided with an egg-shaped profile 138 (Fig. 8B) and is mounted off-center to the cylindrical body 132. Therefore, when the cam 136 is inserted into the end 24 of the calandria tube 32, rotation of the cylindrical body 132 varies the position of the end 24 of the calandria tube 32. [0035] To replace a calandria tube 32, the old calandria tube 32 is removed and the bores in the first and second tube sheets 18 are prepared for a new calandria tube 32. The insertion tool 110 is moved along the support platform to align the telescoping arm 116 with a prepared bore in the first tube sheet 18. Once aligned, the insertion tool 110 is provided with the new calandria tube 32. The supports 112, 114 of the insertion tool 110 are inserted into the first end 22 of the calandria tube 32, engaging the inner surface of the tube 32, thereby supporting it in a cantilevered fashion. The telescoping arm 116 extends, inserting the second end 24 of the calandria tube 32 towards the bore of the first tube sheet 18. To support the tube 32 further, the support members 124 are extended to radially support the tube 32 from below. The support members may use distance sensors (not shown) to determine the correct actuation distance to support (e.g., to support the belled end 24 at one actuated displacement and the center of the tube 32 at a second actuated displacement). With the aforementioned alignment and support, the second end 24 of the calandria tube 32 is inserted through the bore of the first tube sheet 18.

[0036] As the calandria tube 32 is moved through the bore in the first tube sheet 18, the second end 24 begins to sag, moving out of alignment with the bore in the second tube sheet 18. When the second end 24 of the calandria tube 32 is a predetermined distance away from the second tube sheet 18, the guide tool 130A-D is inserted through the bore of the second tube sheet 18 to engage the second end 24 of the calandria tube 32. More specifically, the guide tool 130 extends into the second end 24 of the calandria tube 32 to engage the inner surface of the calandria tube 32. The guide tool 130A-D prevents further sagging of the calandria tube 32 between the two tube sheets 18 and aligns the tube 32 with the destination bore in the second tube sheet 18. The guide tool 130A-D also serves to align the calandria tube 32 with the bore of the second tube sheet 18 in situations in which the bore in the first tube sheet 18 is not in perfect alignment with the bore in the second tube sheet 18.

[0037] With the guide tool 130A-D engaged with the inner surface of the tube 132, the insertion tool 110 continues to push the second end 24 toward the bore in the second tube sheet 18. Certain guide tools (e.g., guide tool 130C) may additionally provide a pulling force to aid the pushing force of the insertion tool 110. Adjustments to the position of the second end 24 of the tube 32 may be effected by the guide tool 130A-D in response to sensor outputs (e.g., position sensors, etc.) as the second end 24 approaches the bore of the second tube sheet 18. For example, the guide tool 130D may be rotated to rotate the cam 136 relative to the tube 32, thereby modifying the position of the calandria tube 32 relative to the bore of the tube sheet 18.

[0038] Once the second end 24 is safely through the second bore, additional sensors (not shown) verify that the tube 32 is fully inserted and properly seated. If the calandria tube 32 is properly located, the guide tool 130 and insertion tool 110 are disengaged from the inner surface of the tube 32 and are removed. The insertion tool 110 is moved to a new location along the worktable 100 to insert a calandria tube 32 into a different bore.

[0039] The system above is provided with a control system and a plurality of sensors that provide feedback regarding the position of the calandria tubes 32. Therefore, the process can be automated to install the tubes 32 without direct user contact, thereby limiting human exposure around the reactor. Further, as the process is repeated for every calandria tube 32 (dozens to hundreds of tubes 32 per reactor 6), the control system can use information gathered from previous tube installations to anticipate necessary corrections to, for example, the insertion angle of the tube 32, thereby improving in efficiency after each completed insertion. Alternatively, the process described above may be completed via human interaction to actuate the insertion tool 110 and the guide tool 130A-D.

[0040] It should also be noted that the embodiments described above and illustrated in the accompanying figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims.

Claims

CLAIMS What is claimed is:

1. A method of inserting a calandria tube in a reactor, the method comprising:

engaging an inner surface of the calandria tube with an insertion tool;

inserting a portion of the calandria tube through a first calandria tube sheet bore using the insertion tool;

inserting a guide tool into the calandria tube to engage the inner surface of the calandria tube with the guide tool; and

guiding the portion of the calandria tube through a second calandria tube sheet bore using the insertion tool and the guide tool.

2. The method of claim 1, further comprising inserting the guide tool through the second calandria tube sheet bore prior to engaging the inner surface of the calandria tube with the guide tool.

3. The method of claim 1, wherein engaging the inner surface of the calandria tube with the insertion tool further comprises engaging the inner surface of the calandria tube at a plurality of points spaced apart along a length of the calandria tube.

4. The method of claim 1, wherein the calandria tube is inserted through the first and second calandria sheet bores in a longitudinal direction, the method further comprising supporting an outer surface of the calandria tube in a radial direction perpendicular to the longitudinal direction.

5. The method of claim 1, wherein guiding the portion of the calandria tube through the second calandria tube sheet bore comprises:

axially displacing the calandria tube using the insertion tool; and

aligning a leading end of the calandria tube with the second calandria tube sheet bore using the guide tool.

6. The method of claim 5, wherein aligning the leading end of the calandria tube with the second calandria tube sheet bore further comprises displacing the guide tool.

7. The method of claim 5, wherein aligning the leading end of the calandria tube with the second calandria tube sheet bore further comprises rotating the guide tool relative to an insertion direction.

8. The method of claim 1, wherein guiding the portion of the calandria tube through the second calandria tube sheet bore comprises:

pushing the calandria tube using the insertion tool; and

pulling the calandria tube using the guide tool.

9. The method of claim 1, further comprising mounting the insertion tool to a platform adjacent the reactor.

10. The method of claim 1, wherein the guide tool is engaged with the inner surface of the calandria tube after the portion of the calandria tube is inserted through the first calandria tube sheet bore.

11. An apparatus for locating a calandria tube relative to a first calandria tube sheet bore and a second calandria tube sheet bore of a reactor, the apparatus comprising:

a worktable located on a re-tubing platform located adjacent to the reactor;

an insertion tool mounted to the worktable and engageable with an inner surface of the calandria tube through the first calandria tube sheet bore; and

a guide tool engageable with the inner surface of the calandria tube through the second calandria tube sheet bore.

12. The apparatus of claim 11, wherein the insertion tool is a telescoping ram.

13. The apparatus of claim 11, wherein the insertion tool includes a first support and a second support axially spaced apart from the first support, wherein the first support and the second support are engageable with the inner surface of the calandria tube.

14. The apparatus of claim 11, further comprising a plurality of support members engageable with an outer surface of the calandria tube.

15. The apparatus of claim 14, wherein the plurality of support members are hydraulically- controlled plungers, pneumatically-controlled plungers, or electrically-controlled solenoids.

16. The apparatus of claim 11, wherein the insertion tool is engageable with a first end of the calandria tube and the guide tool is engageable with a second end of the calandria tube, the second end opposite the first end.