CROSS REFERENCE TO RELATED APPLICATIONS

[0001 ] This application claims priority from U.S. Provisional Patent Application No. 63/400,580, filed on August 24, 2022. The entire contents of U.S. Provisional Patent Application No. 63/400,580 is herein incorporated by reference for all purposes.

FIELD

[0002] The specification relates generally to nuclear reactors, and, more specifically, to an apparatus and method for removing an end fitting of a nuclear reactor.

BACKGROUND

[0003] A CANDU (Canada Deuterium Uranium) reactor assembly includes a horizontal cylindrical tank known as a calandria. The calandria typically has about 380 to 480 horizontal fuel channels aligned with an axis of the calandria. The calandria typically also has both vertical and horizontal reactivity control mechanisms oriented perpendicular to the axes of the calandria and fuel channels.

[0004] Decommissioning CANDU reactors necessitates disassembling and/or segmenting the existing calandria and fuel channels. Given the radiation hazard posed by the calandria and associated components, careful consideration needs to be given when designing systems and methods for disassembling and segmenting a calandria and fuel channel components.

[0005] There is a need for new systems and methods for disassembling and segmenting a calandria and fuel channels.

SUMMARY

[0006] The following summary is intended to introduce the reader to various aspects of the applicant’s teaching, but not to define any invention. [0007] According to some aspects, there is provided a method of removing an end fitting from a fuel channel of a nuclear reactor, comprising positioning an end fitting gripper at a position next to the end fitting; forcing, while the end fitting gripper is next to the end fitting, a first jaw of the end fitting gripper closed around the end fitting; forcing, while the end fitting gripper is next to the end fitting, a second jaw of the end fitting gripper closed around the end fitting at a location spaced apart from the first jaw; and pulling, while the first and second jaws are closed, the end fitting away from an end shield of the calandria.

[0008] In some examples, the end fitting gripper is mounted to a remotely operable robot.

[0009] In some examples, positioning the end fitting gripper at the position next to the end fitting includes operating the robot from a remote location to move the end fitting gripper.

[0010] In some examples, the remotely operable robot includes an arm, and the end fitting gripper is mounted to a free end of the arm.

[0011 ] In some examples, pulling the end fitting away from the end shield of the calandria includes operating the robot from a remote location to pull the end fitting gripper.

[0012] In some examples, pulling the end fitting away from the end shield of the calandria includes moving the end fitting linearly along a path that is perpendicular to an outer face of the end shield.

[0013] In some examples, the method further comprises cutting a tube assembly free from the end fitting prior to pulling the end fitting away from the end shield.

[0014] In some examples, cutting the pressure tube free includes making a cut inside the calandria at a location separated by the end shield of the calandria from the position next to the end fitting.

[0015] According to some aspects, there is provided a reactor end fitting gripper, comprising a frame having a first end and a second end spaced from the first end along a longitudinal axis of the frame; a robot coupling at the first end; a first gripping jaw mounted to the frame spaced from the robot coupling towards the second end, the first gripping jaw moveable between open and closed positions; a second gripping jaw mounted to the frame between the robot coupling and the first gripping jaw, the second gripping jaw moveable between open and closed positions; a first hydraulic assembly mounted to the frame and coupled to the first gripping jaw to force the first gripping jaw to the closed position; and a second hydraulic assembly mounted to the frame and coupled to the second gripping jaw to force the second gripping jaw to the closed position.

[0016] In some examples, the first hydraulic assembly is operable to drive a first linear motion and the second hydraulic assembly is operable to drive a second linear motion parallel to the first linear motion, and the first and second linear motions are each perpendicular to the longitudinal axis.

[0017] In some examples, only a single hydraulic cylinder is drivingly coupled to the first gripping jaw, the single hydraulic cylinder drivingly coupled to the first gripping jaw being part of the first hydraulic assembly, and wherein only a single hydraulic cylinder is drivingly coupled to the second gripping jaw, the single hydraulic cylinder drivingly coupled to the second gripping jaw being part of the second hydraulic assembly.

[0018] In some examples, a jaw spacing between the first gripping jaw and the second gripping jaw is at least three times as large as an offset between the robot coupling and the second gripping jaw.

[0019] In some examples, each the first and second jaws has an encompassing grip in the closed position.

[0020] In some examples, the first and second gripping jaws are arranged to hold the end fitting with a longitudinal axis of the end fitting extending generally parallel to the longitudinal axis of the frame.

[0021 ] In some examples, the frame includes a coupling body at the first end and a boom extending from the coupling body, the first and second gripping jaws mounted to the boom. [0022] In some examples, the first and second gripping jaws are mounted to the boom and depend down from an underside of the boom, and the first and second gripping jaws each include a mouth directed downward.

[0023] In some examples, the frame further includes a support extending between the boom and a portion of the coupling body that projects downwardly generally parallel to the gripping jaws.

[0024] In some examples, the frame includes a pair of supports each extending between the boom and the portion of the coupling body, and the second jaw is received between the pair of supports.

[0025] In some examples, the second gripping jaw includes fingers that move in a plane between the open and closed positions, and the supports extend at least as far downward in the plane as the fingers in each of the open and closed positions.

[0026] In some examples, the boom is a latticed boom and each support is a strut.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification and are not intended to limit the scope of what is taught in any way. In the drawings:

[0028] Figure 1 is a perspective view of a reactor end fitting removal system;

[0029] Figure 2 is a top perspective view of a reactor end fitting gripper;

[0030] Figure 3 is a side perspective view of the end fitting gripper of Figure 2;

[0031 ] Figure 4 is an end view of the end fitting gripper of Figure 2;

[0032] Figure 5 is a first side view of the end fitting gripper of Figure 2;

[0033] Figure 6 is a second side view of the end fitting gripper of Figure 2;

[0034] Figure 7 is a top view of the end fitting gripper of Figure 2;

[0035] Figure 8 is a bottom view of the end fitting gripper of Figure 2; [0036] Figure 9 is a perspective view of the end fitting gripper of Figure 2 with the jaws in the open position;

[0037] Figure 10 is a perspective view of the end fitting gripper of Figure 2 with the jaws closed around an end fitting; and,

[0038] Figure 11 is a flow diagram of a method of removing an end fitting from a fuel channel of a nuclear reactor.

DETAILED DESCRIPTION

[0039] Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or process described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or process described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim, or dedicate to the public any such invention by its disclosure in this document.

[0040] Referring to Figure 1 , illustrated is a calandria 100. Calandria 100 includes an interior 102. An end shield 104 closes one end of the interior 102. Inside the interior 102 are fuel channel assemblies 106. The fuel channel assemblies 106 may include an outer calandria tube with a pressure tube received inside the calandria tube. Each fuel channel assembly 106 extends to the end shield 104 and is joined to an end fitting 110 on the opposite end shield 104.

[0041 ] End fittings 110 project from the end shield. As exemplified in Figure 1 , end fittings 110 may extend generally perpendicular to a plane 112 and/or face 113 of the end shield 104. The end fittings 110 may be engaged by a robot 120 that is adjacent the end shield 104. The robot 120 is arranged outside the interior 102 on a floor 114 of a nuclear facility 116. The nuclear facility 116 includes a nuclear reactor 108 which includes the calandria 100, the fuel channel assemblies 106, and the end fittings 110. The robot 120 is moveable relative to the end fittings 110. The robot 120 is operable to engage the end fittings 110.

[0042] In some embodiments, a reactor end fitting removal system 128 includes the robot 120 and a reactor end fitting gripper 130. The robot 120 may be operable to engage the end fittings 110 using the reactor end fitting gripper 130, as described further below.

[0043] The robot 120 may be a rugged demolition robot. For example, the robot 120 may be a Brokk 900 Rotoboom™ demolition robot. The robot 120 includes an arm 122, which may be an articulating arm. The arm 122 allows the robot 120 to reach end fittings 110 across the end shield 104.

[0044] In some embodiments, the robot 120 is a remote controlled robot. A human operator at a remote location (e.g., a control room of the nuclear facility) may operate the robot 120. In some examples, the robot 120 is tethered and operated from a distance by pendent. The operator may use one or more camera of system 128, the camera(s) arranged with a view of the robot 120 and/or reactor end fitting gripper 130 to operate system 128. A remote controlled robot may allow an operator to be remote from radioactive or potentially-radioactive areas. However, it will be appreciated that in some embodiments the operator could also operate the robot 120 while in the same room and observing the system 128 directly, and system 128 may not include cameras.

[0045] A remote controlled robot may be cheaper or easier to use than an autonomous robot. A remote controlled robot may be precise enough for demolition work. However, it will be appreciated that the robot 120 may be autonomous or semi-autonomous in some embodiments. It will also be appreciated that the reactor end fitting gripper 130 may be used with various types or robots, or may be provided and/or used without a robot. [0046] Referring now to Figures 2 to 8, the reactor end fitting gripper 130 is illustrated. The end fitting gripper 130 includes a longitudinal axis 132 extending between a first end 134 and a second end 136 opposite the first end 134. The gripper 130 also includes a vertical axis 138 extending between an upper end 140 and a lower end 142 opposite the upper end 140. The vertical axis 138 is perpendicular to the longitudinal axis 132. The gripper 130 also includes a transverse axis 144 extending between a first lateral side 146 and a second lateral side 148. The transverse axis 144 is perpendicular to the longitudinal axis 132 and the vertical axis 138.

[0047] The gripper 130 includes a frame 150 supporting a fastening assembly 152. The fastening assembly 152 is configured to be releasably secured to an end fitting 110. The fastening assembly 152 may be operable to be releasably secured to the end fitting, e.g., magnetically and/or mechanically. A mechanical fastening assembly 152 may include, e.g., a jaw to close around the end fitting and/or a fastener operable to pierce the end fitting 110 (e.g., a screw or spike).

[0048] As exemplified, in some embodiments the fastening assembly 152 includes a jaw to close around the end fitting. A fastening assembly 152 using a jaw to grasp the end fitting 110 may hold the end fitting more securely, may be more easily operated, and/or may be less likely to cause a release of radioactive contamination than other ways of securing the gripper to the end fitting.

[0049] As exemplified, the gripper 130 includes two spaced-apart fastening assemblies 152 supported by the frame 150. A pair of assemblies 152 allows the end fitting 110 to be held at two spaced-apart locations for a more stable grip. It will be appreciated that more than two spaced-apart assemblies 152 may be used, although more than two may result in increased costs without comparable increased performance.

[0050] As exemplified, in some embodiments the frame 130 supports a first jaw 160 and a second jaw 162 spaced from the first jaw 160. The gripper 130 also includes a robot coupling 170. In some embodiments, as exemplified, the robot coupling 170 is formed in the frame 150. The exemplary robot coupling 170 includes a first coupling member 172 and a second coupling member 174 spaced from the first coupling member 172. The first and second coupling members 172, 174 allow the robot 120 to hold the gripper 130 via separate members of the robot 130 (i.e., separate arms or separate branches of the arm). Although it will be appreciated that one or more than two coupling members and/or locations may be used in some embodiments. The exemplary coupling members 174 each include a bore to receive a body of the robot 120, although it will be appreciated that any coupling member may be used.

[0051 ] In some embodiments, the gripper 130 is electrically and/or hydraulically coupled to the robot 120 in addition to being mechanically coupled to the robot 120 (e.g., to allow for electrically and/or fluid from the robot to power actuators of the gripper 130). In some embodiments, there is a quick-release coupling at the joint between the end fitting gripper 130 and the robot 120 to pass hydraulic and/or electrical power from a control panel up the robot arm to the end fitting gripper. It will be appreciated that movement of the jaws of the gripper 130 may be controlled via the robot control system, or via a separate control system.

[0052] As exemplified, the robot coupling 170 is at the first end 134. The first jaw 160 is mounted to the frame 150 spaced from the robot coupling 170 towards the second end 136. The second jaw 162 is mounted to the frame 150 between the robot coupling 170 and the first jaw 160. The robot coupling 170 is spaced from the second gripping jaw 162 by an offset distance 176. The first and second gripping jaws 160, 162 are spaced from each other by a jaw spacing distance 178. In some embodiments, the gripping jaw locations are selected as far apart as possible to improve stability (e.g., to have the jaws as far as possible from the end fitting center of gravity as possible). In some embodiments the jaw spacing distance 178 is at least three, four, or five times the size of the offset distance 176. The offset distance 176 may be relatively small to prevent a large moment arm. In some embodiments, the first and second gripping jaws 160, 162 are arranged to hold the end fitting 110 with a longitudinal axis 118 (Figure 1 ) of the end fitting 110 extending generally parallel to the longitudinal axis 132. [0053] As exemplified in Figures 2 to 8, in some embodiments the frame 150 includes a coupling body 180 at the first end 134 and a boom 182 extending from the coupling body 180. The robot coupling 170 is part of the coupling body 180. The boom 182 extends along the longitudinal axis 132. As exemplified, the coupling body 180 and/or the boom 182 may be a latticed structure. The exemplary coupling body 180 is a structure made of bars crossed and fastened together and to the first and second coupling members 172, 174. The exemplary boom 182 is a structure made of bars crossed and fastened together. A latticed structure makes for a lighter frame 150.

[0054] As exemplified, in some embodiments the jaws 160, 162 are mounted to the boom 182. In some embodiments, as exemplified, the frame 150 includes a support 184 extending between the boom 182 and a portion 186 of the coupling body 180 that projects downwardly generally parallel to the gripping jaws 160, 162.

[0055] In some embodiments, as exemplified, the gripper 130 includes a pair of supports 184, each extending between the boom and the portion of the coupling body. The second jaw 162 may be received between the pair of supports 184.

[0056] In some embodiments, the second gripping jaw 162 includes fingers 190 that move in a plane 188 between the open and closed positions, and the supports 184 extend at least as far downward in the plane 188 as the fingers 190 when the figures are in the open position, when the figures are in the closed position, or both. Each support 184 may be a strut, as illustrated. The exemplary supports 184 are each a linear beam extending at an angle between the boom 182 and the portion 186.

[0057] The jaws 160, 162 depend downward from an underside 192 of the boom 182. Each of the first and second jaws 160, 162 is moveable between an open position and a closed position. As exemplified, in some embodiments each of the jaws 160, 162 has a mouth 160a, 162a directed downwardly (i.e. , along the vertical axis). In use, the gripper 130 may be moved towards the end fitting 110 downwardly, although it will be appreciated that alternatively the gripper 130 may be moved axially along the longitudinal axis 132 around the end fitting 110. [0058] In some embodiments, the jaws 160, 162 are concurrently moved to a position around the end fitting 110. For example, the end fitting 110 may enter the mouths 160a, 162a concurrently. Alternatively, the end fitting 110 enters a first of the mouths 160a, 162a, and moves through that first mouth, and enters the other of the mouths 160a, 162a before it has been fully moved through the first mouth (i.e. , entering the second before it has fully cleared the first).

[0059] The gripper 130 includes an actuator 200. The actuator 200 is coupled to at least one of the fastening assemblies 152 to operate the fastening assembly or assemblies 152 to secure the gripper 130 to the end fitting 110. As exemplified, the gripper 130 includes an actuator 200 for each fastening assembly 152.

[0060] In some embodiments, as exemplified, the gripper 130 includes a first hydraulic assembly 202 mounted to the frame 150 and coupled to the first gripping jaw 160 operable to force the first gripping jaw 160 to the closed position. The gripper 130 also includes a second hydraulic assembly 204 mounted to the frame 150 and coupled to the second gripping jaw 162 operable to force the second gripping jaw 162 to the closed position.

[0061 ] Referring now to Figures 9 and 10, the jaws 160, 162 may be moved between an open position (Figure 9) and a closed position (Figure 10). The first hydraulic assembly 202 is operable to move the first jaw 160 between the open and closed positions. Hydraulic actuators provide strength to firmly hold the fitting 110 such that the fitting 110 can be pulled away from the end shield, though it will be appreciated that other types of actuators could alternatively or additionally be used.

[0062] As exemplified, the first hydraulic assembly 202 is operable to drive a first linear motion 208. As exemplified, the first hydraulic assembly 202 is operable to force fingers 206 of the first jaw 160 together to close around the end fitting 110. In some embodiments, the fingers 206 of the first jaw 160 also move within a plane 220 between open and closed positions. The plane 220 may be parallel to the plane 188. In some embodiments, each of the first and second jaws 160, 162 has an encompassing grip, as illustrated. [0063] The second hydraulic assembly 204 is operable to move the second jaw 162 between the open and closed positions. As exemplified, the second hydraulic assembly 204 is operable to drive a second linear motion 210. The second linear motion 210 may be parallel to the first linear motion 208. The first and/or second linear motion 208, 210 may be perpendicular to the longitudinal axis 132 and/or parallel to the plane 188 in which the fingers 190 of the second jaw 162 move. As exemplified, the second hydraulic assembly 204 is operable to force fingers 190 of the second jaw 162 together to close around the end fitting 110. In some embodiments, the first and second jaws 160, 162 are operable to close concurrently.

[0064] In some embodiments, as illustrated, only a single hydraulic cylinder 212 is drivingly coupled to the first gripping jaw 160, the single hydraulic cylinder 212 that is drivingly coupled to the first gripping jaw 160 being part of the first hydraulic assembly 202. Also, only a single hydraulic cylinder 214 is drivingly coupled to the second gripping jaw 162, the single hydraulic cylinder 214 that is drivingly coupled to the second gripping jaw 162 being part of the second hydraulic assembly 204.

[0065] In some embodiments, a jaw includes a fixed finger 190a, 206a and a pivoting finger 190b, 206b that is pivotally secured at a point 230, 232 such that a free end 234, 236 of the finger 190b, 206b spaced from the point 230, 232 moves between a position close to and a position removed from a free end 238, 240 of the fixed finger 190a, 206a.

[0066] In some examples, the hydraulic assemblies are operable to both open and close the jaws. The hydraulic cylinders may be bi-directional hydraulic cylinders to open and close the pivoting jaws.

[0067] Referring now to Figure 11 , illustrated is a method 300 of removing an end fitting from a fuel channel of a nuclear reactor.

[0068] In some embodiments, method 300 includes, at step 302, cutting a end fitting free from the pressure tube and bellows prior to pulling the end fitting away from the end shield. In some embodiments, step 302 includes making a cut inside the calandria at a location separated by the end shield of the calandria from the position next to the end fitting. In other words, the fuel channel assemblies may be cut apart inside the calandria before the end fitting is pulled free.

[0069] The method 300 includes, at step 304, positioning an end fitting gripper (e.g., gripper 130) at a position next to the end fitting (e.g., fitting 110). Step 304 may include positioning the gripper in position such that hydraulic actuation of jaws of the gripper will close the jaws against the fitting.

[0070] Step 304 may include securing the gripper to a robot (e.g., robot 120). The robot may be a remotely operable robot. The gripper may be secured to a free end of an arm of the robot. Step 304 may include operating the robot from a remote location to move the end fitting gripper.

[0071 ] The method 300 includes, at step 306, forcing, while the end fitting gripper is next to the end fitting, a first jaw (e.g., jaw 160) of the end fitting gripper closed around the end fitting.

[0072] The method 300 includes, at step 308, forcing, while the end fitting gripper is next to the end fitting, a second jaw (e.g., jaw 162) of the end fitting gripper closed around the end fitting at a location spaced apart from the first jaw. It will be appreciated that steps 304 and 306 may be performed in any order, and may be performed concurrently.

[0073] The method 300 includes, at step 310, pulling, while the first and second jaws are closed, the end fitting away from an end shield of the calandria. Step 308 may include operating the robot from a remote location to pull the end fitting gripper. In some embodiments, step 308 includes moving the end fitting linearly along a path that is perpendicular to an outer face of the end shield.

[0074] While the above description provides examples of one or more apparatus, methods, or systems, it will be appreciated that other apparatus, methods, or systems may be within the scope of the claims as interpreted by one of skill in the art.