JPH095483A - Drive shaft removing tool for reactor control rod - Google Patents

Abstract

PURPOSE: To smoothly remove a control rod drive shaft from a reactor control rod regardless of the biting of foreign matter or the fixing by seisure. CONSTITUTION: The removing tool 60 of a drive shaft is constituted of a skeleton structural body, a grip fixing mechanism 90, and a removing mechanism 100. The skeleton structural body is constituted of a hoisting handle 61, a support plate 65, a hollow support tube 71, a cylinder support plate 77, an upper support barrel 73, a lower support barrel 75, a support tube 81, and a housing. The grip fixing mechanism 90 is constituted of a grip finger, an action sleeve, a cylinder 45, and a piston rod 91. The removing mechanism 100 is constituted of a cylinder 101, a piston rod 103, an operation shaft 107, an action shaft 115, a shaft, an action button, and a gripper. A shock load adding mechanism constituted of a hammering plate 109 and a moving grip 123 is provided on the operation shaft 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool used for inspection and maintenance in a nuclear reactor, and more particularly to a drive shaft removing tool for separating a control rod and a control rod drive shaft of a pressurized water reactor.

[0002]

2. Description of the Related Art For example, in a pressurized water nuclear reactor, a control rod cluster or assembly (hereinafter simply referred to as a control rod), which is generally composed of a large number of thin control rods, is used.
This is inserted into and removed from the reactor fuel assembly in the core by the control rod drive mechanism provided on the upper lid of the reactor vessel to control the reaction in the reactor. At this time, the drive shaft is used by being connected to the upper end of the control rod. However, the fuel used for combustion in the core needs to be replaced if the content of fissile material decreases below a predetermined amount, and for this reason, or for regular inspections by laws and regulations aimed at ensuring safe operation, etc. Therefore, it is taken out of the reactor vessel. At the time of such fuel exchange or inspection, it is necessary to separate the control rod and its drive shaft left in the fuel assembly, that is, to remove the drive shaft, which is performed as described later.

In FIG. 9 showing a step such as refueling, a drive shaft 3 extending from a control rod (not shown) in a fuel assembly 2 in a reactor vessel 1 is a reactor upper structure. It extends from the cluster guide tube 4 into the shielding water above. The hoist 6, the spring scale 7, and the chain block 8 are attached to the manipulator crane 5 on the reactor cavity.
The drive shaft 3 is separated from the control rod by a removal tool 9 which is hung and supported via.

The separation of the drive shaft 3 and the control rod will be described in some detail. The drive shaft 3 standing in the cluster guide tube 4 in FIG. 10 is hollow and has a detachable shaft 11 inserted therein. . A removal button 13 is formed on the upper end of the removal shaft 11, and a lock button 15 and a positioning nut 17 are formed on the lower end thereof. The lock button 1
5 and the positioning nut 17 spread the elastic joint 19 formed at the lower end of the drive shaft 3 and engage with the uneven surface of the connecting hole of the spider body of the control rod 21 to connect the drive shaft 3 and the control rod. Has been done. Therefore, in order to separate the control rod 21 and the drive shaft 3, two operations, that is, an operation of first grasping and fixing the drive shaft 3 and an original separation operation, are required.

Removal tool 9 used for such operation
The skeleton is formed by the lifting handle 31, which is hung on the chain block 8, the long support tube 33, the support barrel 35, the housing 37, and the like, and supports the operation mechanism. To grip and fix the drive shaft 3, the upper end of the drive shaft 3 is guided and fitted using the flare-shaped adapter 39 at the lower end of the housing 37, and the gripping finger 41 is pivoted. The actuating sleeve 43 and the air cylinder 45 are used to pivotally open and close the gripping fingers 41. On the other hand, the drive shaft 3 and the control rod 2
Separation from 1, i.e., removal, is performed by displacing the positioning nut 17 of the removal shaft 11 and the lock button 15 in the upward direction by pivoting and relative raising of the gripper 47. An air cylinder 49 and an operating button 51 connected to its piston rod are used to pivot the gripper 47.

[0006]

In the conventional removal tool as described above, the elastic joint connecting the control rod drive shaft and the control rod is moved relative to the positioning nut or lock button at the lower end of the removal shaft. The drive shaft is removed by releasing the drive shaft. However, since these members are provided in a very narrow space, if foreign matter or the like is caught during use, the relative displacement described above may be hindered, and the members may not be removable. Also, if the lock button etc. is sticking to the elastic joint and seizure,
Since these relative displacements become difficult, it is also impossible to smoothly remove the drive shaft. Also, since the control rod and its drive shaft are in the radiation shielded water, most of the removal tool must be put in the shielded water to perform the above-mentioned removal work, and radioactive contaminated water enters the cylinder. May remain. These contaminated water may leak out when the removal tool is disassembled, which is not preferable for maintaining the health of the workers. The present invention has been made in view of the above-described problems, and it is possible to reliably remove the drive shaft from the control rod even if foreign matter is caught in the connecting portion of the control rod drive shaft or its periphery, and seizure is fixed. It is an object of the present invention to provide a tool for removing a drive shaft of a nuclear reactor control rod, which is capable of achieving the above and does not have residual radioactive contamination water.

[0007]

In order to achieve the above object, according to the present invention, a tool for removing a control rod drive shaft connected by fitting an elastic joint in a connecting hole of a control rod is provided.
A skeletal structure suspended by a crane or the like, and a gripping fixing mechanism including a gripping finger supported by the skeletal structure and engaging with an upper end portion of the drive shaft, and a first air cylinder that pivotally opens and closes the finger. A gripper that is supported by the skeletal structure and that engages and grips the upper end of the removal shaft of the drive shaft, and a removal mechanism that includes a second air cylinder that pivotally opens and closes the gripper and that lifts the removal shaft. The impact load applying mechanism is attached to the operation shaft extending upward from the piston shaft of the second air cylinder of the removal mechanism. In a preferred embodiment of the present invention, a hammering plate is fixed to an upper end portion of an operation shaft extending upward from a piston shaft of the second air cylinder of the above-mentioned removal mechanism, and a movable grip is loosely fitted to the operation shaft. Constitutes an impact load applying mechanism.

[0008]

In the present invention having the above construction, the skeletal structure is suspended by the crane to support the entire removal tool, and the upper end of the drive shaft is gripped and fixed by the grip fixing mechanism. After that, the upper end of the removal shaft of the drive shaft is gripped by the gripper of the removal mechanism and lifted to release the connection between the drive shaft and the control rod. When the elastic joint of the connecting portion is stuck and cannot be removed, the movable grip of the impact load applying mechanism is struck against the hammering plate to generate an impact load, and the above-mentioned attachment is peeled off for removal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. It should be noted that the same reference numerals are given to the same portions throughout the drawings, including the drawings for explaining the above-mentioned conventional apparatus, to facilitate understanding of the embodiments of the present invention. In FIG. 1 showing an overall elevational view of a removal tool according to an embodiment of the present invention and FIG.
The skeleton structure of No. 0 has an inverted U-shaped elongated lifting handle 61, a support plate 65 fastened to it with nuts 62 and 63, a boss 67 screwed to the upper end, and a nut 68 to sandwich the support plate 65. The hollow support pipe 71, the upper support cylinder 73, the lower support cylinder 75, and the cylinder support plate 77, the cylinder mounting flange 79, and the hollow support tube 8 which are fixed to the upper part of the hollow support pipe 71, the upper support cylinder 73, the lower support cylinder 75, and the hollow support pipe 8
1. Housing mounting flange 83 and housing 37
It is mainly formed from (FIG. 2). Housing 37
A flare-shaped adapter 39 having a guiding function for facilitating the alignment and joining of the removal tool 60 and the drive shaft 3 is formed at the lower end of the. This skeletal structure supports a mechanism as described below when the removal tool 60 is used.

Next, a grip fixing mechanism for gripping the drive shaft 3 and fixing it to the removal tool 60 will be described. With reference to FIG. 2 in particular, a grip finger 41 pivotally mounted in a cavity of the housing 37 and a cylindrical shape. A first air cylinder, that is, a gripping cylinder 45, which is erected side by side on an operating sleeve 43 axially movably fitted to the outer surface of the housing 37 and a cylinder mounting flange 79 (FIG. 1), is a gripping and fixing mechanism 90.
Forming a piston rod 9 extending from the cylinder 45
1 is pin-joined to move the operating sleeve 43 up and down. That is, when the cylinder 45 is actuated to move the actuating sleeve 43 to the upper position (the position shown in the drawing) via the piston rod 91, the claws at the lower end of the gripping fingers 41 spread radially outward, and the drive shaft 3 grips. It is not. When the piston rod 91 is pushed out from this position and the operating sleeve 43 is moved downward (in the figure), the lower end of the operating sleeve 43 grips the lower end of the finger 41 and its claw forms a circle on the upper end of the drive shaft 3. Grasp the circumferential groove 12. When the lower end portion of the gripping finger 41 is narrowed, the upper end portion thereof is exposed to the outside, but this does not interfere with each other because it is escaped by the notch provided in the operating sleeve 43. It should be noted that the cylinder mounting flange 79 is located at a relatively high position (further away from the gripping fingers 41, etc.) as compared with the conventional one, so that the piston rod 91 is long and the cylinder 45 is not operated during operation.
Does not enter shielded water.

Further, the structure of the removing mechanism 100 will be described. The removing shaft 11 is inserted in the drive shaft 3 as described above, and the removing button 13 is formed at the upper end portion thereof. First, referring to FIG. 1, a second air cylinder, that is, a cylinder 101, which is larger than the conventional one as much as space allows, is erected on a cylinder support plate 77, and an upper end of its piston rod 103 is The joint 105 is connected to the operation shaft 107. The operation axis 107 is
The hollow supporting tube 71 and the supporting plate 65 are penetrated to extend to the portion of the lifting handle 61, and the disc-shaped hammering plate 109 and the eyeball fitting 111 are fixed to the upper end portion.
On the other hand, the lower end of the piston rod 103 is connected to the actuating shaft 115 via the joint 113 and further connected to the shaft 117. The shaft 117 of the removal mechanism 100 and the structure below it are best shown in FIG.

In FIG. 2, an operating button 51 is formed at the tip of the shaft 117 to pivotally open and close the gripper 47 pivotally mounted in the housing 37. That is, the cylinder 101 is operated, the piston rod 103,
If the operating shaft 115 and the shaft 117 are pulled upward and the operating button 51 is lifted from the position shown in the drawing, the gripper 4
Open the upper end of 7 and narrow the lower end. In this way, the claw 47a at the lower end of the gripper 47 grips the upper end of the removal button 13. In this state, if the actuating button 51 is further pulled up against the spring 121, the detaching shaft 11 moves upward relative to the main body of the drive shaft 3, and the drive shaft 3 becomes a control rod as described later. It is separated from 21 and removed. Returning to FIG. 1 again, the operating shaft 107 of the removing mechanism 100 is loosely fitted with a movable grip 123 having a generally cylindrical shape and a lower end widening so as to wrap around the nut 68, and impact load together with the hammering plate 109. It forms an additional mechanism.

The control rod drive shaft 3 is connected to the control rod 21 by using the removal tool 60 having the above-mentioned structure and basic functions.
The process of removing from will be described with reference to FIGS. 3 and 4.
In FIG. 1, the supply and discharge pipes for the working fluid to and from the cylinders 45 and 101, control valves, etc. are not shown because they are ordinary ones, and therefore will not be described in detail in the following description of the operation. . Adapter 37 for housing 37
3 (a) shows a state in which the drive shaft 3 and the removal tool 60 are aligned and joined by using 9, and the operating sleeve 43 is displaced to the lower position by the cylinder 45. As described above, in this state, the gripping finger 41 is narrowed downward by the operating sleeve 43, and the lower end claw holds the circumferential groove 12 at the upper end of the drive shaft 3. Piston rod 91
A compression spring 93 is interposed in the mounting flange 83, and the piston rod 91 and thus the operating sleeve 43 are biased downward. Therefore, unless the cylinder 45 is actively moved, the actuating sleeve 43 is in the lower position, and the gripping finger 41 remains gripping the drive shaft 3 even if the supply of the working fluid is interrupted for some reason. The operation button 51 of the removal mechanism 100 is at the lower position, and the gripper 47 does not grasp the removal button 13 of the drive shaft 3.

Next, when the cylinder 101 is operated and the operation button 51 is pulled up, the gripper 47 grasps the removal button 13 of the removal shaft 11 as described above. In that state, when the operating shaft 115 and thus the operating button 51 are further pulled up by the cylinder 101, the gripper 47 causes the spring 1 to move.
It is displaced upwards against 21. That is, as shown in FIG. 3B, the removal shaft 11 and the lock button 15 are relatively displaced upward with respect to the main body of the drive shaft 3. However, the removal tool 60
Since the position itself has not changed, the elastic joint 19 at the lower end is
Is in the connecting hole of the spider body of the control rod 21.
Then, if the removal tool 60 is lifted upward by the crane as it is, as shown in FIG.
1 and the drive shaft 3 are separated, and the removal is completed. Although the drive shaft 3 is transferred in this state, the drive shaft 3 does not fall accidentally due to the action of the compression spring 93 as described above.

Although the above description has focused on the movement of each member of the removal tool 60, the removal situation will be described in more detail below centering on the movement of the connecting portion between the control rod 21 and the drive shaft 3. . FIG. 4A shows the drive shaft 3 and the control rod 21.
Shows the combined state of. At this point, the removal tool 60 is moved right above the drive shaft 3 and hung down until it is placed on the drive shaft 3. The gripping finger 41 and the gripper 47 are operated, and the removal tool 60 is slightly lifted by the chain block of the crane, and it is confirmed that a weight equal to the tool weight + driving shaft weight + control rod weight appears in the load cell.
In FIG. 4B, the removal tool 60 is hung by the chain block until the indicated value of the load cell becomes zero, and the dimension is confirmed at a predetermined dimension measurement point. Then, the operating shaft 107 is raised to the upper limit position by the operating valve.
Along with this operation, the lock button 15 and the positioning nut 17 at the lower end of the removal shaft 11 of the drive shaft 3 are raised to the upper limit position, and the pulling up of the removal shaft 11 is completed (FIG. 3).
(Corresponds to (b)). The lock spring 18 has a lock button 15
Is biased in the downward extension direction. At this time, the removal mechanism 1
Since the diameter of the cylinder 101 of 00 is larger than that of the conventional tool, the pulling force of the removal shaft 11 causes the adhesion of the clad due to the magnetization inside the drive shaft 3 and the inclusion of foreign matter from the elastic joint 19 portion. Foreign matter is caught due to various factors of
Alternatively, the removal shaft 11 due to seizure or sticking of the drive shaft 3
The increase in the drag force of the above is sufficiently overcome, and the work is not interrupted by the event. In FIG. 4 (c), the removal tool 60 is lifted while monitoring the indicated value of the load cell, etc., and since there is nothing forcing the elastic joint 19, the leaf spring action causes it to contract. In FIG. 4D, the drive shaft 3 and the control rod 21 are separated, and it is confirmed by the recorded value that the total weight of the weight of the removal tool 60 and the weight of the drive shaft 3 becomes equal to a predetermined value (FIG. 3). (Corresponding to (c)). In FIG. 4E, the operation shaft 107 is lowered by the operation valve, and the removal shaft 11 is lowered to the lower limit position. Therefore, the lock button 15
The positioning nut 17 is returned to the connecting position inside the elastic joint 19. Further, in FIG. 4 (f), the removal tool 60 is hung down on the chain block until the indicated value of the load cell or the like becomes zero, and it is temporarily placed on the upper end of the spider body of the control rod 21. Is confirmed to be equivalent to. This completes the removal of the drive shaft 3.

The above is a description of the normal removal condition.
If foreign matter or the like is caught or seized and adhered to the relevant portion of the removal shaft 11, the removal shaft 1 will not be operated even if the cylinder 101 is operated.
In some cases, the operating shaft 107 may not move upward relatively. This can be determined from the behavior of the eyepiece fitting 111 of the operation shaft 107. In this case, the movable grip 123 may be gripped as shown in FIG. 5 and moved as indicated by the chain line and the arrow to strike the hammering plate 109. The action of the impact load applying mechanism as described above is appropriately repeated to overcome the rising obstacle of the operation shaft 107 due to the foreign matter being caught and adhered.

When a large force is applied to the drive shaft 3 by the impact load applying mechanism, if the load is too large, the drive shaft itself may be damaged, and this must be avoided. For this reason, the relationship between the impact load and the generated force was tested with a test device as shown in FIG. In FIG. 6A, the speed sensor 131 attached to the lifting handle 61 is a movable grip 12.
The strain gauge 133 attached to the operation shaft 107 measures the input load F ₁ to the tool 60. 6 (b) and 6 (c) respectively simulate the fixed state of the removal shaft 11 and the foreign matter trapped state. That is, in FIG. 6B, the lower end of the removal shaft 11 of the simulated drive shaft 130 is completely fixed, and in FIG. 6C, the removal shaft 11 is laterally pressed by a jig. Here, the strain gauge 1 attached to the lower end of the removal shaft 11
Reference numeral 35 measures the force F ₂ acting on the removal shaft 11. FIG. 7 shows the relationship between the measured value of the final velocity v of the movable grip 123 and the measured values of the loads or the forces F ₁ and F ₂ .
FIG. 8 shows the relationship between the stroke x of the movable grip 123 and the final speed v. Since the actual weakest cross section of the control rod drive shaft 3 can be known in advance from design drawings and the like, the impact load applying mechanism may be used in a manner that does not cause a problem by appropriately considering the above test results and the like. For example, if the limit load near the weakest point is 373 Kg, the final speed v of the movable grip 123 is set to 1.5 m / s. To achieve this final velocity v, the stroke x may be set to about 55 mm.

[0018]

As described above, according to the first aspect of the invention, when the second cylinder is actuated and the control rod drive shaft is removed, when the operation resistance force becomes large due to foreign matter being caught or the like, Since the impact load applying mechanism generates a large impact load to eliminate the obstacle, the control rod drive shaft can be smoothly removed. Further, since the cylinder of the gripping fixing mechanism and the cylinder of the removing mechanism are both at a high position and above the shielding water during the removing work, it is possible to prevent radioactive contamination water from entering and coming out at a later date. According to the invention of claim 2, since the impact load adding mechanism is constituted by the movable grip loosely fitted on the operation shaft and the hammering plate, the impact load can be generated by a simple operation, and the control rod drive shaft It can be removed smoothly.

[Brief description of drawings]

FIG. 1 is a partially cutaway vertical sectional view showing the overall structure of an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a II part in FIG.

FIG. 3 is an explanatory view of the operation of the above embodiment.

FIG. 4 is an explanatory view of the operation of the above embodiment.

FIG. 5 is an explanatory view of the operation of the above embodiment.

FIG. 6 is an explanatory diagram showing a situation of a preliminary test performed when the embodiment is applied.

FIG. 7 is a graph showing the results of the test.

FIG. 8 is a graph showing the results of the test.

FIG. 9 is a work explanatory view showing a situation in which the removal tool of the present invention is used.

FIG. 10 is a partially cutaway vertical sectional view showing a usage state of a conventional tool.

[Explanation of symbols]

 3 Drive Shaft 21 Control Rod 37 Housing 41 Gripping Finger 43 Operating Sleeve 45 Cylinder 47 Gripper 51 Operating Button 60 Removal Tool 61 Lifting Handle 65 Support Plate 71 Hollow Support Tube 73 Upper Support Body 75 Lower Support Body 81 Support Tube 90 Grip Fixing Mechanism 91 Piston rod 100 Detachment mechanism 101 Cylinder 103 Piston rod 107 Operating shaft 109 Hammering plate 115 Operating shaft 117 Shaft

Front page continuation (72) Inventor Hiroshi Mochizuki 1-1-1, Wadasaki-cho, Hyogo-ku, Kobe-shi, Hyogo Prefecture Mitsubishi Heavy Industries Ltd. Kobe Shipyard

Claims (2)

[Claims] 1. A tool for removing a control rod drive shaft connected by fitting an elastic joint to a connecting hole of a control rod, the frame structure being hung by a crane or the like; A grip fixing mechanism including a grip finger that is supported and engages with an upper end portion of the drive shaft, and a first air cylinder that pivotally opens and closes the finger; and a grip shaft that is supported by the skeletal structure and that is a detach shaft of the drive shaft. A gripper that engages and grips an upper end portion and a removal mechanism including a second air cylinder that pivotally opens and closes the gripper and that lifts the removal shaft, the gripping mechanism being upward from a piston shaft of a second air cylinder of the removal mechanism. A tool for removing the drive shaft of a reactor control rod, characterized in that an impact load applying mechanism is attached to the operation shaft extending to the. 2. A shock load applying mechanism, wherein a hammer ring plate is fixed to an upper end portion of an operating shaft extending upward from a piston shaft of a second air cylinder of a detaching mechanism, and a movable grip is loosely fitted to the operating shaft. The drive shaft removing tool for a reactor control rod according to claim 1, which is configured.