JPH09225644A - Resistance welding equipment for fuel rod end plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate removal of a covered tube after resistance welding. SOLUTION: A tube electrode for feeding power to a covered tube 2 by abutting on the side of the covered tube is divided into an upper electrode 6a and a lower electrode 6b, which are each provided in the upper holder 7 and the lower holder 8 of the divided tube electrode holder 9. These upper and lower holders 7, 8 are provided, in the part in contact with the covered tube 2, with sealing packing 33, 34 that fits recessed grooves 37, 35. The recessed grooves 37, 35 are a cross-sectionally dovetail groove while the sealing packing 33, 34 is a trapezoidal shape in the cross section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel rod end plug resistance welding apparatus for resistance welding a fuel rod cladding tube and an end plug.

[0002]

2. Description of the Related Art A fuel rod used as a fuel for a nuclear reactor has a large number of fuel pellets inserted into a cylindrical cladding tube, and end plugs are welded to both ends of the cladding tube for sealing. Further, in the cladding tube, a plenum spring is interposed between the end plug on one end side and the fuel pellet to press and hold the fuel pellet on the other end side, and helium gas or the like is enclosed. The TIG welding method is adopted as an example of means for welding the end plug to the cladding tube. In manufacturing a fuel rod having such a structure, conventionally, after welding end plugs to both ends of a cladding tube, respectively, helium gas is filled in a preformed hole of the end plug on the side where the plenum spring is inserted. However, a complicated process of subsequently sealing the hole by welding or the like has been adopted.

For the purpose of simplifying the welding process of the cladding tube and the end plug, the filling of the helium gas into the cladding tube and the welding of the end plug to the cladding tube are performed as continuous steps. A resistance welding device that can be used has been proposed. In such a resistance welding device, the end portion of the cladding tube and the end plug are positioned with a slight gap in an airtight chamber, helium gas or the like is supplied into the chamber to fill the cladding tube, and then the end plug is covered. Resistance welding is performed by pressure contacting the ends. An airtight chamber in which the cladding tube side electrode and the end plug side electrode hold the side surfaces of the cladding tube and the end plug, respectively, and the ends of the cladding tube side and the end plug side are sealed by packing, respectively. Inside, place the end of the cladding tube and the end plug with a slight gap, supply helium gas, etc. into the chamber to fill the inside of the cladding tube, and then press the end plug into the end of the cladding tube for resistance welding. It has become.

[0004]

By the way, in resistance welding, since the cladding tube has a small thickness and a heat capacity smaller than that of the end plug, it is necessary to release heat from the cladding tube side electrode which is held in contact with the cladding tube. It is necessary to increase the circumferential contact area of the cladding tube side electrode with respect to the cladding tube.
Therefore, during resistance welding, it is preferable that the cladding tube-side electrode is in contact with the cladding tube over the entire circumference thereof. On the other hand, due to the resistance welding, the welded portion between the end plug and the cladding tube rises to the outside by the upset and becomes larger than the outer diameter of the cladding tube by about 2 mm at maximum. Therefore, when taking out the resistance welded cladding tube from the resistance welding device, it must be provided on the cladding tube side electrode for keeping the chamber airtight unless the raised portion of the welded portion is ground and removed beforehand. It has a drawback that it cannot be passed through a seal packing or the like. In particular, the cladding tube is long, and when the cladding tube side electrode is brought into contact with the entire circumference of the cladding tube, it becomes difficult to remove the cladding tube from the cladding tube side electrode side.

In view of the above problems, the present invention has a large contact area with the cladding tube during resistance welding, and enables the cladding tube after welding to be removed without removing the raised portion of the resistance welding portion. It is an object of the present invention to provide a fuel rod end plug resistance welding device as described above.

[0006]

A fuel rod end plug resistance welding apparatus according to the present invention is provided with a first electrode that abuts a side surface of a cladding tube to supply power to the cladding tube and a second electrode to supply power to the end plug. ,
In a resistance welding device for fuel rod end plugs, in which a resistance welding is performed by energizing between the first and second electrodes in a state where the end plug is pressed against the cladding tube end in an airtight chamber, a plurality of first electrodes are provided. It is characterized by being divided into. At the time of resistance welding, the divided first electrodes are combined and joined, and the resistance welding is performed by feeding power while abutting on the side surface of the cladding tube.When removing the cladding tube after welding, separate the first electrodes from each other. If so, even if there is a raised portion due to welding, it is easy to remove the cladding tube. In particular, it is preferable that the divided first electrodes contact the entire circumference of the cladding tube in a joined state.
The airtight chamber may be capable of airtightly holding the abutting region of the coating tube end and the end plug in a state where the coating tube end and the end plug are coaxial and face each other with a gap.

A seal packing is provided in a recessed groove at the abutting portion of the divided first electrode or the divided first electrode holder for holding each of the first electrodes with the covering tube. A protrusion may be formed in the concave groove of the bent portion of the packing which is in contact with the coating tube. Since the protrusion is provided on the bottom of the concave groove of the bent portion, the packing that fits into this will surely project to the outside of the concave groove without the curved portion curving and expanding into the concave groove. When the divided first electrodes or first electrode holders are joined together, they will surely come into pressure contact with the divided first electrodes or similar packings of the bent portion of the first electrode holder, and the joining by these packings The sealing property of the part becomes more reliable.

Further, a seal packing is fitted in the concave groove at the contact portion of the divided first electrodes or the divided first electrode holders respectively holding the first electrodes with the covering tube. The groove may have a cross section and may be formed in a groove shape. Due to the cross-sectional shape of this groove, when sealing with packing, the packing is pressed and spreads inside the groove and is compressed, and the amount protruding from the top opening of the groove is small, so the packing that adheres to the cladding tube during pressurization Area becomes smaller and the contact area between the first electrode and the cladding tube increases,
The power feeding area increases. The packing has a trapezoidal cross section, and if the width of the bottom surface is larger than the width of the opening of the concave groove, it helps prevent the packing from falling off.

[0009]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIGS. FIG. 1 is an exploded perspective view of a main part of a resistance welding apparatus according to an embodiment, FIG. 2 is a cross-sectional view of a main part showing a state in which an end portion of a coating pipe and an end plug are butted to form an airtight chamber, and FIG. The same view as in FIG. 2 when resistance welding is performed with the pipe and the end plug pressed together, FIG. 4 is an exploded perspective view showing the electrode and the packing in a partially broken state, and FIG. 5 is a portion of the lower holder along the longitudinal direction of the packing. 6 and 7 are sectional views showing the packing and the concave groove, and FIG. 6 is a separated state, FIG.
FIG. 4 is a diagram showing a pressed state. Resistance welding device 1 shown in FIG.
In the above, the cladding tube 2 of the fuel rod is sandwiched between a plurality of divided (in the figure, two divided) clamp members 3. The clamp members 3 are, for example, substantially half in cross section on the cladding tube sandwiching surface. The upper clamp portion 3a and the lower clamp portion 3b having the circular recesses 4a and 4b are formed so as to face each other. Further, with the extension line of the central axis of the cladding tube 2 as the axis O, for example, the upper clamp portion 3a can be moved by the actuator 5 in the direction orthogonal to the axis O (direction A) to open and close both clamp portions 3a, 3b. Thus, the cladding tube 2 is opened and pinched.

The tip 2 of the cladding tube 2 with respect to the clamp member 3
On the a side, a plurality of (two in the figure) tube electrodes 6 for the cladding tube are attached to the divided tube electrode holders 9 for abutting the entire side surface of the cladding tube 2 and supplying power. ing. That is, the divided upper holder 7 and lower holder 8 of the tube electrode holder 9 each have an upper electrode portion 6a in which a recess having a semicircular cross section is formed (in FIG. 1, the upper holder 7 and the upper electrode portion 6a are And a lower electrode portion 6b are formed so as to face each other. The upper and lower holders 7 and 8 can be relatively moved by an actuator 11 in a direction (direction A) orthogonal to the axis O of the cladding tube 2, whereby the upper electrode portion 6a and the lower electrode portion 6b are separated from each other. Contact is made so that power can be supplied over the entire circumference of the cladding tube 2 in a contact state. Electrode terminals 10a connected to a power source for resistance welding (not shown) are connected to the upper and lower electrode portions 6a and 6b, respectively.

In a region facing the tube electrode 6, a substantially cylindrical slide chamber 12 is provided coaxially with the axis O, and a pair of first cylinders are provided via a slide plate 13 attached to the rear end side. It is connected to 14. And
By operating the first cylinder 14, the slide chamber 12 can be moved back and forth in parallel with the axis O. Inside the slide chamber 12, the slide plate 1
The electrode shaft 15 penetrating 3 and protruding to the rear of the electrode 3 is slidably fitted into the slide chamber 12.
A second cylinder 16 for reciprocally sliding the electrode shaft 15 is attached to the rear end thereof.

A concentric, substantially cylindrical recess 17 is formed on the tip side of the electrode shaft 15, and a substantially cylindrical end plug electrode 18 is disposed in the recess 17. Between the outer peripheral surface of the end plug electrode 18 and the inner peripheral surface of the concave portion 17, a substantially cylindrical collet 19 formed by a plurality of dividing claws 19a extending in the direction of the axis O is disposed, and each dividing portion is formed. The claw 19a is formed in a tapered cross-section so that its thickness gradually decreases from the front end side of the slide chamber 12 toward the rear end side thereof. Collet 1
An insulating material 19b is attached to the inner peripheral surface of 9 (see FIGS. 2 and 3). Further, an electrode terminal 10b for power supply is connected to the end plug electrode 18. In addition, in FIG. 1, a part of the collet 19 and the like is shown by a fracture surface. Further, a tapered surface 17a is formed on the inner peripheral surface of the concave portion 17 with which the collet 19 abuts and slides so that the inner diameter of the concave portion 17 gradually decreases from the distal end side toward the rear side.
Are formed in a ring shape. Further, a rear portion of the tapered surface 17a on the inner peripheral surface of the recess 17 is cut out in a ring shape to form a groove 17b, and a ring-shaped collet piston for advancing and retracting the collet 19 in the direction of the axis O is formed in the groove 17b. Two
0 is connected to the rear end of the collet 19 and the end plug electrode 18
It is slidably fitted in.

Moreover, the collet piston 20 has a concave groove 17
The first space 22a and the second space 2 which are ring-shaped by partitioning the inside of b
A packing 20a which forms 2b and holds the first space 22a airtight is provided. And the second space 2
An elastic member, for example, a coil spring 23 is mounted in a compressed state in 2b, so that the collet piston 2
0 is urged toward the rear side, that is, in the direction of narrowing the first space 22a. A communication hole 24 that communicates the first space 22a of the groove 17b with the outside in the vicinity of the second cylinder 16 is provided in the electrode shaft 15. Therefore, the communication hole 24
By introducing compressed air into the first space 22a via the collet piston 20, the collet piston 20 can be pushed toward the tip side along the electrode shaft 15 against the biasing force of the coil spring 23, and the collet 19 is the same. It can be pushed in the direction. The collet 19 is expanded and contracted by advancing and retracting the collet 19 with respect to the tapered surface 17a.

On the tip side of the slide chamber 12, the collet 19 partially projects from the end plug electrode 18 toward the tip side (see FIG. 2), and the end plug 25 is fitted and held on the tip side of the collet 19. I'm supposed to get it. Therefore, the end plug electrode 18 abuts against the back surface of the end plug 25 and can be pushed. In addition, an air supply / exhaust hole 26 penetrating in the radial direction of the slide chamber 12 is formed on the tip side of the slide chamber 12, and the electrode shaft 15 on the inner peripheral surface of the slide chamber 12 is formed.
It communicates with the space on the tip side of the. A ring-shaped packing 27 is fitted over the entire circumference of the tip surface 12a of the slide chamber 12. And
As shown in FIG. 2, the front end surface 12 of the slide chamber 12
When a is pressed against the tip surfaces 7a and 8a of the tube electrode holder 9 and the packing 27 is pressed, an airtight chamber 28 is formed inside the slide chamber 12 on the tip side. The tip 2a of the coating tube 2 and the end plug 25 can be abutted in the chamber 28 with a gap (see FIG. 2). The chamber 28 is evacuated through the air supply / exhaust hole 26 and can be filled with gas such as helium gas.

In FIG. 1, between the tube electrode 6 and the slide chamber 12, a tube positioning means 30 for setting the tip 2a of the coating tube 2 supported by the clamp member 3 at the welding position is provided with an axis O. It is arranged so that it can move forward and backward. Further, an end plug supply means 31 is provided between the tube electrode 6 and the slide chamber 12 to move back and forth on the axis O to supply the end plug 25 to the tip of the collet 19 and hold it.

The upper and lower holders 7 and 8 are provided with packings 33 and 34 which can seal the periphery of the tip 2a of the coating tube in order to form an airtight chamber 28. That is, as shown in FIG. 4, the lower holder 8 has a tip surface 8 a and a contact surface 8 b with which the upper holder 7 abuts.
The lower electrode portion 6b is attached to the corner portion of
Around the lower electrode portion 6b, a single groove 35 into which the packing 34 fits is provided. The recessed groove 35 forms a pair of straight line portions 35a extending vertically on both sides of the covering tube 2 in the region of the tip surface 8a of the lower holder 8, and in the region of the contact surface 8b, in plan view following the straight line portion 35a. A convex portion 35b is formed so as to surround the lower electrode portion 6b.
Moreover, in the contact surface 8b, the seating portion 8c of the covering tube 2 has a semi-cylindrical concave shape, and the convex portion 35b of the concave groove 35 also has a semi-circular concave portion 35c in this region as shown in FIG. It is said that. Moreover, the projections 36 are formed on the bottom surfaces (or the side surfaces) at both ends of the concave portion 35c of the concave groove 35 (only one is shown in FIG. 5), and the bent portion 34a of the packing 34 fitted in this portion is formed. Due to the projection 36, the groove 36 is projected outward. In addition, the concave groove 35 is shown in FIG.
As shown in FIG. 7 and FIG. 7, it has a groove shape with a cross section orthogonal to its longitudinal direction. Moreover, the packing 34 that fits into the groove 35 also has a trapezoidal cross-sectional shape, and the trapezoidal cross-sectional shape of the packing 34 is in the non-pressed state shown in FIG.
The bottom surface 34b is narrower than the bottom surface 35d of the concave groove 35 and wider than the opening 35e, and the top surface 34c is formed to protrude outward from the opening 35e of the concave groove 35 and narrower than the opening 35e.

Also in the upper holder 7, the packing 3 is inserted into the groove 37 having the same shape as the groove 35 of the lower holder 8.
4, the packing 33 having the same shape as that of the packing 4 is fitted, and the recesses 37 and 35 in the upper and lower holders 7 and 8 and the packing 3
3, 34 are arranged substantially symmetrically (see FIG. 4). Therefore, at the time of pressurization shown in FIG. 7, the packings 33 and 34 are pressed against each other in a state where the upper and lower holders 7 and 8 are joined, and the packings 33 and 34 spread into the concave grooves 37 and 35 and are compressed. The upper and lower holders 7 and 8 are substantially flush with each other. Therefore, the contact area when each packing 33, 34 comes into close contact with the covering tube 2 at the time of pressurization is minimized. The packing 27 is also fitted in a dovetail groove similar to the packings 33 and 34.

The end plug resistance welding apparatus according to the present embodiment is constructed as described above, and its operation will be described below.
First, in order to hold the cladding tube 2, the upper and lower clamp portions 3a and 3b of the clamp member 3 and the upper and lower holders 7 and 8 of the tube electrode holder 9 are held by the respective actuators 5 and 11 in a separated state, and not shown. The coating pipe 2 delivered from the coating pipe supply means is placed on the lower clamp portion 3b and the lower holder 8. At that time, the tip 2a of the covering tube 2 is made to project from the welding position to the tip side in the direction of the axis O (on the side of the slide cylinder 12). Then, the pipe positioning means 30 is actuated on the axis O to push back the cladding pipe tip 2a by a minute amount so as to come to a predetermined welding position. In this state, the upper clamp part 3a
Then, the upper holder 7 is lowered to firmly clamp the covering pipe 2 between the upper clamp portion 3a and the lower clamp portion 3b, and the upper and lower electrode portions 6a and 6b are brought into contact with the entire circumference of the covering pipe 2 to enable power supply. . Then, the pipe positioning means 30 is retracted from the axis O and returned to the initial position.

In this state, the packings 33 and 34 of the upper and lower holders 7 and 8 of the tube electrode holder 9 are pressed against each other as shown in FIG. 7, and the circumference of the cladding tube 2 is sealed.
At this time, since the protrusions 36 are formed at both ends of the recesses 35c of the recessed grooves 37, 35 of the packings 33, 34, the bent portions 33a, 34a of the packings 33, 34 are recessed into the recessed groove 3c.
It is held in a state of protruding from 7, 35 (see FIG. 5), and when pressed against the covering tube 2, they come into close contact with each other around the covering tube 2 and a sufficient seal can be achieved with respect to the covering tube 2. On the other hand, in the conventional seal structure, as shown in FIG.
Since there is no such protrusion inside 7,35, packing 3
Since the bent portion 34a 'of No. 4 (33) was curved in an R shape and fell into the concave groove, the sealing in this region was insufficient.

Next, when the collet 19 does not hold the end plug 25, the second actuator 16 is driven to slide the electrode shaft 15, and the electrode shaft 15 and the collet 19 are moved relative to the slide chamber 12. Move to near the tip opening. In this state, the compressed air is supplied to the first space 22a in the concave groove 17b through the communication hole 24 to pressurize the inside, and the collet piston 20 moves to the coil spring 23.
It is pushed along the end plug electrode 18 against the urging force of. As a result, the collet 19 is pushed in the direction of the coating tube 2, so that the tightening of the collet 19 is loosened and the diameter of the collet 19 is expanded. Further, the end plug supply means 31 is positioned coaxially with the axis O while the end plug 25 is held, and the end plug 25 is supplied into the expanded collet 19 so that its end face is the electrode shaft. It is held in contact with the tip end surface of 15.

Then, by lowering the compressed air in the first space 22a, the collet piston 20 is returned toward the support plate 13 by the urging force of the coil spring 23, and the split claws of the collet 19 sliding integrally with the collet piston 20. The diameter of 19a is reduced while being guided by the tapered surface 17a of the concave portion 17, and the end plug 25 is clamped and held. Also, the end plug supply means 31
Is withdrawn from the axis O and returned to its initial position. Next, the second actuator 16 is driven in the opposite direction to move the electrode shaft 1
When 5 is slightly retracted in the slide chamber 12, the state shown in FIG. 1 is obtained.

From this state, by driving the first and second actuators 14 and 16, the slide chamber 12 and the electrode shaft 15 are moved along the axis O in the direction of the coating tube 2 and the tip surface of the slide chamber 12 is moved. The tip surfaces 7a and 8a of the tube electrode holder 9 are pressed into contact. As a result, the packing 27 on the front end surface of the slide chamber 12 and the packings 33, 34 on the front end surfaces 7a, 8a of the tube electrode holder 9 are pressed against each other so that an airtight chamber 28 is formed in the slide chamber 12. (See FIG. 2). In this state, the chamber 28 is evacuated through the air supply / exhaust holes 26 of the slide chamber 12, and then helium gas or the like is filled and pressurized to replace the chamber 28 and the coating tube 2 with helium gas or the like. After that, the second actuator 16 is driven to push the electrode shaft 15 toward the tip side, and the end plug 25 is pressed against the tip 2a of the covering tube 2 via the end plug electrode 18. In this state, the tube electrode 6 and the end plug electrode 1
Power is supplied to 8 and the end plug 25 and the cladding tube tip 2a are resistance-welded. At this time, power is supplied to the end plug 25 from the back surface of the end plug 25 through the end plug electrode 18 that abuts against the back surface of the end plug 25.

After the resistance welding is completed in this way,
By supplying compressed air into the first space 22a through the communication hole 24 of the electrode shaft 15 and pushing the collet piston 20 against the biasing force of the coil spring 23, the diameter of the collet 19 is expanded. As a result, the end plug 25 becomes the collet 19.
Be released from. Further, the inside of the chamber 28 is returned to normal pressure, and the slide chamber 12 and the electrode shaft 15 are returned to the initial position shown in FIG. Then, the upper holder 7 (upper electrode portion 6a) and the upper clamp portion 3a of the tube electrode holder 9 are separated from the lower holder 8 (lower electrode portion 6b) and the lower clamp portion 3b, respectively, and the covering tube 2 is removed, Replace with cladding tube 2.

As described above, according to the present embodiment, since the tube electrode 6 is divided into two parts together with the tube electrode holder 9, power can be supplied by contacting the entire circumference of the cladding tube 2 during welding. Together with the end plug 25 and the cladding tube 2 during resistance welding
Upper and lower holders (upper and lower electrode portions 6a, 6b) even if a raised portion due to upset is formed in the resistance welding portion with
By separating 7 and 8 in the radial direction of the covering tube 2, the covering tube 2 can be easily removed with the raised portion left. In addition, the concave groove 37 of the upper and lower holders 7, 8,
Since the projections 36 are formed inside the bottom surfaces or the side surfaces of the semicircular recess 35c that seals the covering tube 2 of 35, the packings 33 and 34 are located outside the recessed grooves 37 and 35 at the bent portions 33a and 34a. And the sealing performance around the cladding tube 2 is improved. Further, the packings 33 and 34 respectively provided on the upper and lower holders 7 and 8 to form the airtight chamber 28 and the packing 27 of the slide chamber 12 have a trapezoidal cross section, and the recessed grooves 37 and 35 to be fitted therein.
Since the groove shape is present, the area of close contact with the cladding tube during pressure contact is small, and the area of contact with the tube electrode 6 in the circumferential direction of the cladding tube 2 is relatively large. Moreover, there is little risk that the packing will fall out from the concave grooves 37, 35.

In the above-mentioned embodiment, the tube electrode 6 is divided into the upper and lower electrode portions 6a and 6b and fixed to the upper and lower holders 7 and 8, respectively. However, the present invention is not limited to this. The electrodes and holder may be divided into three or more parts. Alternatively, without providing the tube electrode holder 9, only the tube electrode 6 may be arranged, and the tube electrode holder 9 may be divided into a plurality of pieces so as to be joined and separated. In this case, as in the above embodiment,
You may make it form the recessed groove in the area | region which contact | abuts the coating | coated tube 2 of the divided | segmented tube electrode 6, and may make packing 33 and 34 fit, respectively.

Further, in the above embodiment, the concave grooves 37,
There is a groove 35 and the packing 33, 34 has a groove 3
Although the trapezoidal cross-sectional shape for fitting with 7, 35 is used, the cross-sectional shape of the packing is not limited to this, and the concave groove 3 can be used during press contact.
An appropriate cross-sectional shape such as an ellipse can be adopted as long as it is flush with the openings 7 and 35 or slightly protrudes. still,
The tube electrode 6 constitutes a first electrode, and the end plug electrode 18 constitutes a second electrode.

[0027]

As described above, in the nuclear fuel rod end plug resistance welding apparatus according to the present invention, the first electrode that abuts on the side surface of the cladding tube is divided into a plurality of pieces. It is possible to supply power in a state where it is joined to the side surface of the cladding tube widely, and when removing the cladding tube after welding, if the first electrodes are separated from each other, even if there is a bulge due to welding, The cladding tube can be easily removed.

A seal packing is fitted in the concave groove at the contact portion of the divided first electrodes or the divided first electrode holders respectively holding these first electrodes with the covering tube. Since the protrusions are formed in the concave groove of the bent portion that comes into contact with the coating tube of these packings, each packing is curved at the bent portion and inside the concave groove when the first electrode or the first electrode holder is joined. It does not spread to the outside and protrudes to the outside of the recessed groove, and it will surely come into contact with the other split first electrode or the packing of the similar bent portion of the first electrode holder and be pressed into contact therewith. At the time of joining the first electrodes or the first electrode holders, the sealing property of the joining portion by these packings becomes more reliable. In addition, a seal packing is provided in a groove to be fitted to a contact portion of each divided first electrode or each divided first electrode holder holding each of these first electrodes with the covering tube. Since this groove has a groove shape with a cross section, when sealing with packing, the packing is pressed and spreads inside the groove and is compressed, and the amount protruding from the top opening of the groove is small,
The area of the packing that comes into close contact with the covering tube during pressurization decreases, and the contact area between the first electrode and the covering tube increases.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a schematic configuration of a nuclear fuel rod end plug resistance welding device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of relevant parts showing a state in which the tip of the cladding tube and the end plug are butted against each other in the chamber with respect to the resistance welding apparatus shown in FIG.

FIG. 3 is a cross-sectional view of a main part of the resistance welding apparatus shown in FIG. 1, showing a resistance welding state in which a tip of a covering tube and an end plug are brought into pressure contact with each other in a chamber.

FIG. 4 is an exploded perspective view of a tube electrode holder.

FIG. 5 is a partial cross-sectional view of the packing of the lower holder of the tube electrode holder, taken along the longitudinal direction of the groove.

FIG. 6 is a cross-sectional view showing a structure of a packing and a concave groove on a joint surface of an upper holder and a lower holder in a separated state.

7 is a transverse cross-sectional view showing a pressed state of the packing shown in FIG.

FIG. 8 is a partial sectional view similar to FIG. 5, showing a conventional packing.

[Explanation of symbols]

 1 Resistance Welding Device 2 Covering Tube 6 Tube Electrode 6a Upper Electrode 6b Lower Electrode 7 Upper Holder 8 Lower Holder 9 Tube Electrode Holder 18 End Plug Electrode 25 End Plug 27, 33, 34 Packing 35, 37 Recessed Groove 36 Protrusion

Claims (3)

[Claims] 1. A first electrode for contacting a side surface of a cladding tube to feed power to the cladding tube and a second electrode for feeding power to an end plug are provided, and the end plug is pressed against the end of the cladding tube in an airtight chamber. In a fuel rod end plug resistance welding device configured to perform resistance welding by energizing between the first and second electrodes in a closed state, the first electrode is divided into a plurality of fuel rod ends. Plug resistance welding equipment. 2. A seal packing is fitted in a concave groove in a contact portion of the divided first electrode or each divided first electrode holder holding each of the first electrodes with the coating tube. 2. The fuel rod end plug resistance welding device according to claim 1, wherein protrusions are formed in the concave groove of a bent portion of the packing which is in contact with the cladding tube. 3. A seal packing is fitted in a concave groove in a contact portion of the divided first electrode or each divided first electrode holder holding each of the first electrodes with the coating tube. The fuel rod end plug resistance welding device according to claim 1 or 2, wherein the groove is provided in a combined shape and the groove has a cross-section.