JP3976456B2 - Fuel rod welding equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a welding apparatus used for sealing both ends of a cladding tube containing fuel pellets when, for example, a fuel rod constituting a fuel assembly of a boiling water reactor is manufactured.
[0002]
[Prior art]
The fuel assembly of the boiling water reactor is constructed by inserting fuel pellets 21 into a cladding tube 20 as shown in, for example, the schematic longitudinal sectional view of FIG. A rectangular tubular channel box in which rod-shaped fuel elements sealed by end plugs 22 and lower end plugs 23 are supported by an upper tie plate and a lower tie plate as upper and lower ends as a bundle of square lattices. It is housed and configured.
[0003]
As a suitable sealing method of the upper and lower end plugs for the cladding tube in each fuel element, there is an inert gas arc welding called a TIG (tungsten inert gas) method using a tungsten electrode. The arc column generated at the time of welding is very high in temperature, and the arc startability and arc stability are lost due to deformation of the electrode tip shape due to heat, vapor deposition of the workpiece to the electrode, and the like. Thus, when the arc is unstable, the problem of soundness of the welded portion occurs, and therefore the tungsten electrode needs to be replaced periodically.
[0004]
In addition, when welding the upper end plug after the fuel pellet is sealed in the cladding tube, the inside of the fuel element is filled with an inert gas such as He gas as the sealing gas in order to improve the heat transfer coefficient between the fuel pellet and the cladding tube. is doing. On the other hand, when end plugs are joined by circumferential welding, the welding atmosphere is set to a pressure equivalent to that of the fuel element.
[0005]
Therefore, the gas pressure in the atmosphere to be welded increases as the gas pressure sealed inside the fuel element increases. However, as the gas pressure in the welding atmosphere increases, the deterioration and loss of the electrode become more severe due to the thermal pinch effect. However, in recent years, the pressure enclosed in the fuel element has increased, and the deterioration / depletion of the electrodes has become more significant, and the frequency of electrode replacement has increased accordingly. In order to maintain work efficiency, it is desirable that the electrode replacement work be performed in a short time.
[0006]
On the other hand, if the electrode position is not stable at the time of welding, disturbance of the welding beat occurs, which causes a problem in the sealing performance of the fuel element. For this reason, a welding apparatus needs to have a mechanism which can fix an electrode reliably and can adjust the space | interval of an electrode and a to-be-welded object.
[0007]
In the conventional welding apparatus, for example, the fixing of the electrode and the height position adjustment are generally performed by a screwing method as shown in FIG. This is above the welding chamber 30 provided with a cladding tube rotating holder 31 and an end plug holder 32 that rotatably support the tip end portion of the cladding tube 20 to be joined and the upper end plug 22 inside. A male screw portion 33 having a through hole that can be introduced into the chamber from a direction intersecting the axial direction of the cladding tube and the end plug is formed in the chamber together with the electrode holder 36 that holds the welding electrode 39, and the electrode holder 36 is attached. The electrode holding portion 34 includes a female screw portion 35 that is screwed into the male screw portion 33.
[0008]
That is, when the electrode holder 36 is introduced into the through hole and the electrode holding portion 34 is rotated with respect to the male screw portion 33 to advance the screwing of the female screw portion 35, the electrode holder 36 gradually enters the chamber 30. Then, the welding electrode 39 held at the tip of the electrode holder 36 approaches the part to be joined between the cladding tube 8 and the end plug 7, and the position of the welding electrode 39 is adjusted by adjusting the screwing of the screw mechanism. .
[0009]
[Problems to be solved by the invention]
However, in the screwing method in the conventional welding apparatus as described above, the screw mechanism serves as both a fixing mechanism for the electrode to the welding chamber and a welding position adjusting mechanism, and the electrode holder is rotated when the electrode is replaced. Thus, the screw mechanism must be unscrewed, and the electrode holder must be removed from the apparatus, and the electrode holder must be removed from the electrode holder.
[0010]
In such a screw type, since it is handled manually, the electrode replacement operation is complicated and troublesome. In particular, it is difficult to finely adjust the positioning of the electrode, and it takes time for each electrode replacement. This hinders improvement in the working efficiency of the fuel rod manufacturing process, and makes it difficult to reduce the working time to cope with the recent increase in electrode replacement frequency.
[0011]
In view of the above-described problems, an object of the present invention is to provide a fuel rod welding apparatus capable of easily positioning a welding electrode with higher accuracy than in the prior art and efficiently exchanging electrodes in a short time.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a fuel rod welding apparatus according to the first aspect of the present invention provides a fuel rod welding apparatus according to the first aspect of the present invention, in order to seal a joint portion between a cladding tube and an end plug of a nuclear fuel rod by TIG welding. And an electrode holding and moving mechanism for holding the welding electrode so as to be able to approach and move away from the joint from a direction intersecting the axis with respect to a cladding tube and an end plug that are rotatably supported around the axis. In the fuel rod welding apparatus, the electrode holding and moving mechanism includes an electrode holder for holding a welding electrode, a first moving mechanism for positioning and moving the electrode holder along the approaching / separating direction, and the first moving mechanism. And a second moving mechanism that moves the electrode holder at a high speed in the approaching / separating direction, and the electrode holder is provided with a displacement of the external fixing member or a restraint by the fixing member. At least one In which is provided with a gripping mechanism to release the holding of the welding electrode in displacement.
[0013]
A fuel rod welding apparatus according to a second aspect of the present invention is the fuel rod welding apparatus according to the first aspect, wherein the fixing member includes a push-up fitting that performs a displacement for opening the gripping mechanism. And a sandwiching portion for gripping the welding electrode.
[0014]
In the present invention, a first moving mechanism for positioning and moving an electrode holder for holding a welding electrode in a direction in which the electrode holder is moved toward and away from the bonded portion of the cladding tube and the end plug, and the first moving mechanism is moved in the approaching and separating direction. Since the welding electrode is roughly positioned by movement by the second moving mechanism, fine adjustment of the positioning of the electrode is performed by the first moving mechanism. It can be carried out.
[0015]
Since these two-stage position adjustments are all performed only by linear movement, it is possible to move quickly for positioning as compared to the conventional approach of moving away from the screw by manual screw rotation. At the same time, since mechanical control is easy, it is possible to automate the process of moving the electrode holder and positioning the electrode in the electrode replacement work, and the work efficiency is expected to be greatly improved. Furthermore, fine adjustment by the first moving mechanism is also simplified, and positioning of the welding electrode can be performed in a short time while being highly accurate.
[0016]
In addition, since the second moving mechanism can be moved linearly over a relatively large range for each first moving mechanism, the electrode holder is attached to the electrode by the second moving mechanism when replacing the electrodes. The electrode can be pulled up to the exchange position at a high speed, and the electrode can be moved quickly for electrode exchange, thereby shortening the electrode exchange work time. As such first and second moving mechanisms, a fluid cylinder such as air or hydraulic pressure or an electric servo motor may be used for the driving mechanism. In particular, the second moving mechanism preferably has, for example, a structure in which a ball screw is combined with a servo motor so that accurate position adjustment can be performed.
[0017]
Further, in the welding apparatus of the present invention, the mechanism for gripping the welding electrode by the electrode holder uses the displacement of the external fixing member or the displacement of the electrode holder by the first or second moving mechanism in the restrained state by the fixing member. The electrode can be easily detached between the holding state and the open state, so that the electrode can be quickly attached and detached, and the electrode holder need not be removed from the device, so the welding electrode can be replaced in a very short time. .
[0018]
As such a gripping mechanism, a collet chuck that can be opened and closed for holding the tail end portion of the electrode is provided inside the electrode holder, and the collet chuck is shifted between an open state and a closed state according to the displacement of the collet chuck. It is convenient to provide a so-called torch part at the tip of the electrode holder.
[0019]
Specifically, in a natural state, a cap-shaped member (hereinafter referred to as a torch cap) is positioned below the electrode holder by urging by a spring mechanism or the like so that the collet chuck is closed and the electrode tail end can be clamped. The collet chuck is released by lifting the torch cap upward against the electrode holder against the bias of the spring, and the clamping state of the electrode is released, or conversely the electrode tail end is opened in the center of the chuck when the collet chuck is released. The electrode is clamped by being inserted into the part and then returned to the closed state.
[0020]
In this case, it is necessary to relatively displace the torch cap in the vertical direction with respect to the electrode holder, but it is possible to obtain an open state of the collet chuck by pushing up the torch cap with the fixing member in a state where the position of the electrode holder is fixed. The torch cap position can be fixed by restraining with an external fixing member, and the collet chuck is opened by relatively displacing the torch cap by moving the electrode holder downward by the first or second moving mechanism. Can be obtained.
[0021]
In the open state of the collet chuck obtained by the above operations, the electrode can be pulled out or inserted from the center of the collet chuck clamping part, but the collet chuck opening / closing operation is performed by mounting and moving the electrode holder to the apparatus. Therefore, the replacement work itself can be performed very efficiently and easily.
[0022]
In addition, since the opening and closing of the collet chuck as described above can be controlled mechanically, if the electrode insertion / removal operation in the chuck open state is also mechanically controlled, the electrode replacement operation itself can be automated, and further steps Can be shortened. For example, the external fixing member may be provided with a drive system that holds the electrode partially independently of the restraining portion for fixing or pushing up the torch cap and moves it toward and away from the collet chuck.
[0023]
As an example of a simple configuration, the fixing member is provided with a clamping part and a push-up metal that can be driven separately from each other, and while holding the welding electrode with the clamping part, the push-up metal is driven separately to displace the torch cap. There is a configuration in which the gripping mechanism can be in an open state, and the holding portion that grips the welding electrode is driven separately from the push-up fitting in a predetermined positioning state of the torch cap by the push-up fitting.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
As one embodiment of the present invention, a fuel rod welding apparatus for TIG welding is shown in FIGS. FIG. 1 shows a schematic configuration of the entire welding apparatus, which is a front view including a longitudinal sectional view of a welding chamber portion, where (a) shows a state where an electrode is in a welding position, and (b) shows that an electrode is exchanged. Each of the states in the position for is shown. FIG. 2 is a schematic view when the electrode holding and moving mechanism is viewed from the bottom surface (welding chamber) side of the welding apparatus of FIG.
[0025]
FIG. 3 is a partial configuration diagram illustrating a holding mechanism for attaching / detaching the welding electrode of the electrode holder, and FIG. 4 is a schematic diagram illustrating a process of exchanging the welding electrode using an external fixing member. Yes, (a) shows the process of removing used electrodes, and (b) shows the process of attaching new electrodes.
[0026]
This welding apparatus mainly includes a welding chamber 10 that is a welding chamber for performing TIG welding inside, and an electrode holder 6 that holds a welding electrode 9 made of tag stainless that is installed in the upper portion of the welding chamber 10. The electrode holding and moving mechanism is composed of a first moving mechanism for positioning and moving along the vertical direction and a second moving mechanism for moving the first moving mechanism at high speed in the vertical direction.
[0027]
The welding chamber 10 includes a cladding tube rotating holder 11 and an end plug holder 12 that support the distal end portion of the cladding tube 20 to be joined and the upper end plug 22 or the lower end plug 23 so as to be axially rotatable. On the upper side, there is provided an insulator 13 that forms an insertion path for introducing the electrode holder 6 holding the welding electrode 9 into the chamber. Further, the welding chamber in the chamber 10 is sealed by the sealing member S on the outer periphery of the electrode holder 6.
[0028]
Among the electrode holding and moving mechanisms, the first moving mechanism is such that the electrode holder 6 is attached, and the slide member 1 on which the driving unit M made of an electric motor is mounted is vertically moved on the surface of the flat plate-like first stage 3, that is, It is moved by the control of the drive unit M along the first guide rail 2 formed in the proximity and separation direction with respect to the welding position in the chamber 10.
[0029]
Further, in the second moving mechanism, the first stage 3 is formed on the surface of the second stage 5 in the vertical direction, that is, in the direction of approaching and separating from the welding position in the chamber 10 by a driving mechanism (not shown). It is moved along the second guide rail 4 at high speed.
[0030]
Therefore, when performing the welding operation, first, the first stage 3 is moved along the second guide rail 4 on the second stage 5 in order to roughly adjust the positions of the electrode holder 6 and the welding electrode 9 in the second moving mechanism. Then, the welding electrode 9 is introduced into the welding chamber from the insertion port formed by the insulating portion 13 of the welding chamber 10 with the slide member 1 on the first stage 3 by moving the welding electrode 10 at a high speed.
[0031]
Next, in order to finely adjust the position of the welding electrode 9 in the first moving mechanism, the slide member 1 is positioned on the second stage 5 by the driving unit M and the first guide is already positioned on the second stage 5. By moving close to or away from the welding chamber 10 along the rail 2, the position of the welding electrode 9 at the lower end of the slide member 1 is finely adjusted to come to a predetermined welding position.
[0032]
After the positioning is completed, the end plugs (22, 23) are held by the end plug holder 12 in the welding chamber, the cladding tube 20 is inserted into the cladding tube rotating holder 11, and the tip is projected into the welding chamber. The TIG welding may be performed over the outer periphery of the joint while holding both the members in a state of being fitted and rotating both members in the same direction and at the same speed.
[0033]
As described above, the positioning of the welding electrode 9 is performed in two stages, but the first stage is performed within a relatively wide range at high speed, and the second stage is a fine adjustment movement within a small range. In addition, the movement / positioning of the welding electrode 9 is performed efficiently and with high accuracy.
[0034]
Further, when the welding electrode 9 is replaced, the first stage 3 is moved away from the welding chamber 10 along the second guide rail 4 on the second stage 5 with the slide member 1, in this embodiment. Then, by moving at a high speed in the upward direction, the welding electrode 9 and the electrode holder 6 can be immediately separated from the welding chamber 10, and the operation can be quickly shifted to the electrode replacement operation.
[0035]
Next, the electrode holding mechanism of the electrolytic holder 6 uses a so-called collet chuck mechanism. That is, a collet chuck 7 formed of a cylindrical shaft core provided in a hollow portion of the electrode holder 6 and having a tapered outer periphery formed by a plurality of cuts along the axial direction, and an electrode The torch cap 8 is provided at the tip of the holder 6 and is urged downward in a natural state by a spring member or the like.
[0036]
A tapered hole is formed in the torch cap 8 so as to be fitted to the outer periphery of the tip portion (claw portion) of the shaft core 7, and the tip portion of the shaft core 7 moves relative to the taper hole in the axial direction. As a result, the claw portion is closed as shown in FIG. 3 (a), or the claw portion is opened as shown in FIG. 3 (b).
[0037]
In the present embodiment, the torch cap 8 is gripped by the tail end portion of the electrode 9 that is sandwiched between the claws of the collet chuck 7 in a natural state where the torch cap 8 is positioned below the electrode holder 6 and the collet chuck 7. When the torch cap 8 moves upward relative to the electrode holder 6 and the shaft core 7, the claw portion of the collet chuck 7 is opened, and the tail end portion of the electrode 9 sandwiched therein is released from the sandwiched state. The configuration.
[0038]
The relative movement of the torch cap 8 with respect to the electrode holder 6 as described above is performed using an external fixing member 15. In addition, the fixing member 15 of this apparatus not only works for the relative movement of the torch cap 8 but also has a mechanism for attaching and detaching the electrode 9.
[0039]
As shown in FIG. 4, the fixing member 15 includes a push-up jig 16 for pushing up the torch cap 8 upward and a clamping part 17 for gripping the electrode 9. The fixing member 15 drives the push-up jig 16 and the clamping part 17 from a state where it is installed at a predetermined position below the electrode holder 6 by a dedicated drive mechanism (not shown). The driving of the unit 17 is partially independent and interlocked. The push-up jig 16 is made of a ring-shaped member, and both of the holding portions 17 are located on the same axis as the central axis of the electrode holder 6, and both members are controlled to move along this axial direction.
[0040]
For example, the operation when removing the used electrode 9a from the electrode holder 6 is as follows. First, as described above, the welding electrode 9 and the electrode holder 6 are immediately moved to the welding chamber by moving the first stage 3 along the second guide rail 4 on the second stage 5 with the slide member 1 at a high speed. The electrode holder 6 is moved to the upper electrode replacement work position 10 to fix the position of the electrode holder 6.
[0041]
Next, as shown in FIG. 4A, the external fixing member 15 is set at a position coaxial with the welding electrode 9 below the electrode holder 6. The push-up jig 16 and the clamping part 17 of the fixing member 15 are both moved upward until the push-up jig 16 contacts the lower end surface of the surrounding torch cap 8 from which the electrode 9a protrudes. In this state, the clamping unit 17 is driven to grip the tip of the electrode 9a.
[0042]
Further, while the electrode 9 a is held by the clamping part 17, only the push-up jig 16 is moved upward, and the torch cap 8 is pushed up with respect to the electrode holder 6. At this time, the collet chuck 7 is relatively moved to the opening side of the tapered hole in the torch cap 8, the tip claw portion of the collet chuck 7 is opened, and the clamping state of the tail end portion of the electrode 9a is released.
[0043]
The electrode 9a is moved from the collet chuck 7 by moving only the clamping part 17 holding the tip part of the electrode 9a downward in the axial direction while maintaining the open state of the tip claw part of the collet chuck 7 by the push-up metal 16 being pushed up. Extract. The push-up bracket 16 is lowered and the fixing member 15 is removed from the lower position of the electrode holder 6 together with the used electrode 9a.
[0044]
Subsequently, a new electrode 9b is mounted on the electrode holder 6 by the operation opposite to the operation for removing the used electrode 9a. That is, as shown in FIG. 4B, first, the fixing member 15 in a state where the tip of the new electrode 9b is gripped by the sandwiching portion 17 is coaxial with the electrode holder 6 after the used electrode 9a is removed. Set to position.
[0045]
Next, only the push-up bracket 16 is moved upward in the axial direction, the torch cap 8 is pushed up with respect to the electrode holder 6, and the collet chuck 7 is relatively moved axially toward the opening side of the tapered hole in the torch cap 8 to collet. The claw portion at the tip of the chuck 7 is set in a flattened state.
[0046]
While maintaining the open state of the tip claw portion of the collet chuck 7 by pushing up the push-up fitting 16, the holding portion 17 holding the tip portion of the electrode 9b is moved upward in the axial direction so that the tail end portion of the electrode 9b is moved to the collet chuck. 7 is inserted in the center between the open claws.
[0047]
By moving the push-up fitting 16 downward in the axial direction and releasing the push-up state of the torch cap 8 while fixing the position of the insertion state of the tail end portion of the electrode 9b by the sandwiching portion 17 to the central portion between the claws, The torch cap 8 is moved downward relative to the electrode holder 6. As a result, the collet chuck 7 relatively moves axially toward the reduced diameter side of the tapered hole of the torch cap 8, and the claw portion at the tip is closed to sandwich the tail end portion of the electrode 9 b.
[0048]
Then, the clamping part 17 is driven, the tip part of the electrode 9b is opened, it moves to the lower part of the electrode 9b together with the push-up fitting 16, and the fixing member 15 is removed from the lower part of the electrode holder 6. The mounting of the new electrode 9b to the electrode holder 6 is completed through the above steps.
[0049]
The fixing member used when removing the used electrode 9a from the electrode holder 6 and the fixing member used when attaching the new electrode 9b to the electrode holder 6 may be the same member or different members. Either way is fine. However, with the same fixing member, the apparatus configuration may be small, but it is necessary to remove the used electrode 9a from the clamping part 17 and grasp a new electrode 9b. If it is set as the structure using a fixing member, after removing the used electrode 9a, the mounting | wearing operation | work of the new electrode 9b can be started immediately.
[0050]
Further, even when the electrodes are exchanged with the same fixing member, as shown in FIG. 5, a second clamping portion 18 is further provided on the push-up bracket 16 and the clamping portion 17, and one of them holds the used electrode 9a. If the other electrode 9b is to be clamped and both the clamping portions (17, 18) can be driven to move horizontally, the used electrode 9 can be removed while using one fixing member. Since the operation and the mounting operation of the new electrode 9b can be performed continuously, the apparatus can be prevented from being enlarged and the electrode replacement operation can be performed efficiently.
[0051]
In the above embodiment, the relative movement of the torch cap for opening and closing the claw portion of the collet chuck is performed by raising and lowering the push-up bracket of the fixing member, but may be performed by movement on the electrode holder side. That is, if the electrode holder is lowered by the first or second moving mechanism while the push-up fitting is brought into contact with the lower end surface of the torch cap and the position of the torch cap is fixed, the torch cap is moved relative to the electrode holder. be able to.
[0052]
【The invention's effect】
As described above, according to the fuel rod welding apparatus of the present invention, since positioning of the welding electrode can be performed easily and accurately and the electrode can be replaced efficiently in a short time, the entire process time of the fuel rod welding operation can be reduced. There is an effect that shortening can be realized.
[Brief description of the drawings]
FIG. 1 shows a schematic configuration of a fuel welding apparatus according to an embodiment of the present invention, and is a front view including a longitudinal sectional view of a welding chamber portion, where (a) shows a state in which an electrode is in a welding position. , (B) shows the state in which the electrode is in a position for replacement.
2 is a schematic view when an electrode holding and moving mechanism is viewed from the bottom surface (welding chamber) side of the welding apparatus of FIG. 1; FIG.
3 is a partial configuration diagram illustrating a holding mechanism by a collet chuck for attaching and detaching a welding electrode in the electrode holder of FIG. 1, wherein (a) shows a closed state of the collet chuck, and (b) shows an opened state of the collet chuck. It is a schematic diagram shown.
4A and 4B are schematic diagrams for explaining a process of exchanging a welding electrode using an external fixing member for the welding apparatus of FIG. 1, wherein FIG. 4A is a process of removing a used electrode, and FIG. Each of the attachment processes is shown.
FIG. 5 is a schematic diagram for explaining a process of exchanging welding electrodes when a fixing member having a configuration different from that of the fixing member shown in FIG. 4 is used.
FIG. 6 is a longitudinal sectional view showing a schematic configuration of a boiling water nuclear reactor fuel rod.
FIG. 7 is a schematic configuration diagram showing an example of a conventional fuel rod welding apparatus, (a) is a side sectional view showing a state in which an electrode is in a position for replacement, and (b) shows a welding state. It is a sectional side view.
[Explanation of symbols]
1: Slide member 2: First guide rail M: Drive unit 3: First stage 4: Second guide rail 5: Second stage 6, 36: Electrode holder S, 37: Seal member 7: Collet chuck 8: Torch cap 9, 39: welding electrode 9a: used welding electrode 9b: new welding electrode 10, 30: welding chamber 11, 31: cladding tube rotating holder 12, 32: end plug holder 13: insulator 15: fixing member 16: Push-up bracket 17: clamping part 18: second clamping part 20: cladding tube 21: fuel pellet 22: upper end plug 23: lower end plug 24: plenum spring 33: male thread part 34: electrode holding part 35: female thread part

Claims (2)

In order to seal the joint between the cladding tube and the end plug of the nuclear fuel rod by TIG welding, the cladding is formed with respect to the cladding tube and the end plug that are supported rotatably around the axis. In a fuel rod welding apparatus provided with an electrode holding and moving mechanism for holding a welding electrode so as to be able to approach and separate from the joint from a direction intersecting the axis.
The electrode holding and moving mechanism includes an electrode holder for holding a welding electrode, a first moving mechanism for positioning and moving the electrode holder along the approaching / separating direction, and the first moving mechanism in the approaching / separating direction. And a second moving mechanism for moving at a high speed,
The electrode holder has a gripping mechanism that releases the holding of the welding electrode by displacement of an external fixing member or displacement by at least one of the first or second moving mechanism under the restraint by the fixing member. A fuel rod welding device characterized by the above. 2. The fuel rod welding apparatus according to claim 1, wherein the fixing member includes a push-up fitting that performs displacement for opening the gripping mechanism, and a clamping portion that grips the welding electrode. 3.

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