JP2000039495A - Nuclear fuel rod end plug welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a welding fault of an end plug to a cladding tube by reducing influences of thermal expansion or solidification contraction of a welded part and a spring load of a coiled spring. SOLUTION: The nuclear fuel rod end plug welding machine press injects an end plug 3 held at an end plug holder to an open end of a cladding tube 1, and welds the plug to the tube 1. The machine has a sequence controller 22 for operating a presser for giving a large pressing force to a movable shaft 11 at the time of pressing the plug 3, weakening the force of the shaft 11 by the presser before starting welding, and braking a brake unit 23 to fixedly hold the shaft 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nuclear fuel rod end plug welding apparatus for sealingly welding an end plug to a cladding tube loaded with a nuclear fuel material under a pressurized atmosphere.

[0002]

2. Description of the Related Art FIG. 3 is a cross-sectional view showing the structure of a general nuclear fuel rod. End plugs 2 and 3 are welded to both ends of a cladding tube 1, respectively. A number of pellets 4 are loaded, a coil spring 5 is interposed between the pellets 4 and one end plug 3, and the cladding tube 1 is filled with an inert gas.

[0003] That is, in the above-mentioned nuclear fuel rod, after a plug 2 is attached to one end of the cladding tube 1 by welding, a predetermined number of pellets 4 are loaded into the cladding tube 1 from the opening end side, and the pellet 4 and the cladding tube 1 are loaded. A coil spring 5 is inserted into a space 6 formed between the end plug 3 and the end plug 3 while the inside of the cladding tube is kept under an inert gas atmosphere. Are hermetically welded under a pressure condition against the force of the coil spring 5.

FIG. 4 is a view showing a schematic structure of the end plug welding apparatus for a nuclear fuel rod. A nuclear fuel rod holding apparatus 8 is provided on the minus side of the welding chamber 7, and an end plug pressing apparatus is provided on the other side. 9 are provided. The nuclear fuel rod holding device 8 holds the cladding tube 1 in a horizontal state and rotates the cladding tube 1 around its axis by a rotating device 10. One open end is adapted to be inserted into the welding chamber 7.

On the other hand, in the welding chamber 7, on the side wall opposite to the side wall in which the cladding tube 1 held by the nuclear fuel rod holding device 8 is inserted, the cladding tube 1 is disposed on the same axis as the cladding tube 1. A movable shaft 11 movable in the axial direction is provided. The tip of the movable shaft 11 is the welding chamber 7
An end plug holder 12 is attached to the tip of the end facing the open end of the cladding tube 1, and the rear end of the movable shaft 11 is connected to a pressing air cylinder device 13. I have.

A welding torch 14 is provided in the welding chamber 7 at a position corresponding to the welded portion of the end plug 3 pressed into the open end of the cladding tube 1, and an exhaust port 15 is provided on the top wall.
Is provided.

When the end plug 3 is fixed to the cladding tube 1 of the nuclear fuel rod by welding, the open end of the cladding tube 1 whose intermediate portion is held by the nuclear fuel rod holding device 8 is inserted into the welding chamber 7. At the same time, the end plug 3 mounted on the end plug holder 12 is positioned so as to be close to and opposed to the open end of the cladding tube 1 via the movable shaft 11. Next, the air in the welding chamber 7 is exhausted, and the welding torch 14
The welding chamber 7 is filled with inert gas. Thereafter, the press air cylinder device 13 is operated, the end plug holder 12 is moved leftward in FIG. 4, and the end plug 3 is pressed into the open end of the cladding tube 1. And
When press fitting of the end plug 3 into the cladding tube 1 is completed, the cladding tube 1 is rotated around the axis by the rotating device 10 and the end plug 3 and the cladding tube 1 are welded by the welding torch 14.

[0008]

However, in such an end plug welding apparatus, since welding is performed under the condition that the force of the coil spring is applied to the end plug, the pressurized air cylinder device 13 is not press-fitted. Therefore, if the end plug is left in a press-fit state after the start of welding, an external force is applied to the welded portion, and this external force may cause the welded portion to be crushed.

Therefore, the welding is started, a part of the entire circumference of the cladding tube is melted and solidified, and at the same time, the pressing air cylinder device 1 is formed.
The air of No. 3 is evacuated, the movable shaft 11 is set in a free state, and welding is performed under these conditions. On the other hand, in a welding apparatus of the above type, there is a case in which a fuel rod is filled and sealed with helium gas at a pressure higher than the atmospheric pressure. In this case, the inert gas charged into the welding chamber is raised above the atmospheric pressure, and under this pressurized condition, If the movable shaft is set to the free state during welding when performing sealing welding of the end plug, the movable shaft retreats in the direction of the cylinder device due to the pressure of the inert gas in the welding chamber, and the end plug cannot be held. There is a problem that a welding failure may be caused, for example, the portion may be stretched by an internal coil spring, or the end plug may be welded to the cladding tube in a bent state.

Therefore, as shown in FIG. 5, a holding device 16 for holding or releasing the movable shaft 11 and an operating device 17 thereof are provided in the pressing air cylinder device 13 so that the pressing air cylinder device 13 is in an inoperative state, ie, the cylinder is not operated. When air is removed from the device and the movable shaft is in a free state, the operating device 17 is operated in conjunction with the movable shaft 1 by the holding device 16.
There has also been proposed one in which 1 is fixedly held.

That is, simultaneously with the start of welding, the operating device 17
, And at the same time, the air of the pressing air cylinder device 13 is evacuated, so that the movable shaft 11 is fixedly held at the position by the holding device 16, whereby the return of the movable shaft 11 is eliminated, and the end plug holder 12 is used. Welding is performed with the end plug 3 held.

However, such a device can suppress the crushing action of the welded portion and the effect of stretching the welded portion due to the internal spring, which have conventionally occurred, and prevent the disadvantage that the welded portion is significantly deformed. In some cases, slippage occurs when the movable shaft is tightened by the clamping member and fixedly held at that position, and the movable shaft is held with preload applied to the welded part and the When crushing occurs, or when sliding toward the cylinder device in the opposite direction, there is a problem that a gap may be formed between the end plug holder and the end plug. Furthermore, since the welded portion thermally expands in the axial direction during melting and condenses and contracts during cooling, even when the movable shaft is fixed and held as described above, the thermal expansion during melting is prevented, and compressive stress is reduced during welding. There is a problem that the receiving welded portion is slightly crushed, and a gap is formed between the end plug holder and the end plug at the time of solidification and contraction, so that the end plug cannot be held.

In view of the foregoing, the present invention has been made to reduce the effects of thermal expansion, solidification and shrinkage of a welded portion and the spring load of a coil spring, thereby eliminating poor welding of an end plug to a cladding tube. It is intended to obtain a rod end plug welding device.

[0014]

A first invention is provided on a minus side of a welding chamber having a welding torch and holds a nuclear fuel rod holding device for holding a cladding tube of a nuclear fuel rod, and is held by the nuclear fuel rod holding device. The movable shaft, which is disposed on the same line as the cladding tube and has an end plug holder attached to the distal end inserted into the welding chamber, and the movable shaft, which is disposed on the other side of the welding chamber, And a pressing device for axially moving back and forth, wherein the end plug held by the end plug holder is press-fitted into the open end of the cladding tube, and the welding is performed on the nuclear fuel rod end plug welding device. At the time of pressing, the pressing device is operated so that a large pressing force is applied to the movable shaft, and the pressing force of the movable shaft by the pressing device is reduced before the start of welding, and a brake is applied to the brake device that fixedly holds the movable shaft. Characterized in that a sequence control device causes I.

[0015] In a second aspect of the present invention, the end plug holder includes:
It is characterized in that an elastic stopper for contacting the end of the end plug is provided.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In addition, FIG.
The same reference numerals are given to the same portions as FIG. 5 and the detailed description thereof will be omitted.

In FIG. 1, reference numeral 20 denotes an electric motor, and the electric motor 20 controls the movement of the movable shaft 11 in the axial direction. The rotation torque of the electric motor 20 is controlled by a control signal from a sequence control unit 22 via a motor driver 21, and a force for pressing the end plug 12 via the end plug holder 12 is arbitrarily controlled. . That is, the rotational torque and the command voltage are in a proportional relationship, and the thrust of the movable shaft 11 can be arbitrarily controlled by instructing the voltage value from the sequence control unit 22. The sequence control unit 22 is a control method using a computer. The sequence control unit 22 manages and controls each process of the welding operation, and controls the propulsive force of the movable shaft 11 to an appropriate value according to the process flow.

In the vicinity of the electric motor 20,
An electromagnetic brake 23 is provided to lock the movable shaft 11 at an arbitrary position. This electromagnetic brake 23
Is also controlled by the sequence control unit 22, and the movable shaft 11 can be locked by operating the electromagnetic brake 23 during welding.

On the other hand, the end plug holder 12 is mounted on the movable shaft 11 via a bearing 24 as shown in FIG. This bearing 24 is adapted to rotate the cladding tube 1 of the nuclear fuel rod and the end plug 3 so that the end plug holder 12 can rotate smoothly even when the pressing force of the movable shaft 11 is applied. Bearings are used.

Further, the end plug holding hole 12 of the end plug holder 12 is provided.
An elastic stopper 25 such as a resin is provided at the inner end of "a", and has a structure capable of being elastically deformed by an axial pressing force. As the structure of the nuclear fuel rod, the coil spring 5 is built in the cladding tube 1 as described above.
The pellet is pressed in the axial direction by a force equivalent to about 10 kg · f. The fitting portion between the end plug 3 and the cladding tube 1 is tightly fitted to each other to have a tolerance, and the end plug is press-fitted by the pressing force of the movable shaft 11. When the end plug 3 is press-fitted into the cladding tube 1, the pressing force from the movable shaft 11 is set to 50 kg · f or more to cover the end plug 3 in order to make the fitting state before welding appropriate. It is desirable that a gap is not formed in the butt surface with the tube 1.

Therefore, if proper press-fitting is performed, the fitted state is maintained even when the tension of the internal coil spring 5 is applied, so that even if the pressing force from the movable shaft 11 is canceled, The end plug does not come off due to the internal coil spring force. However, when the fitting portion between the end plug and the cladding tube is melted at the time of welding, a force for extending the fusion portion is applied to the fusion portion by the extension tension of the internal coil spring.

Therefore, it is necessary to hold down this force, and the end plug holder 12 normally supports the force. Therefore, in the present invention, the stopper 25 made of non-metal is mounted in the end plug holder 12 as described above.
It is desirable to select a material that is elastically deformed by about 0.2 mm to 0.3 mm with respect to an external force of 0 kg · f.

When welding the end plug to the cladding tube of the nuclear fuel rod, the open end side of the cladding tube 1 is inserted into the welding chamber 7 and fixed in the axial direction by the nuclear fuel rod holding device 8.
On the other hand, the end plug 3 is set in the end plug holder 12,
An appropriate distance is maintained between the end plug 3 and the cladding tube 1. Therefore, the inside of the cladding tube 1 is evacuated by evacuating the inside of the welding chamber 7 by a vacuum exhaust device installed outside the exhaust hole 15. Thereafter, an inert gas is introduced from the welding torch 14 to replace the inside of the welding chamber 7 with a gas pressure higher than the atmospheric pressure. Then, when it is confirmed that the inside of the welding chamber 7 is maintained at a predetermined inert gas pressure, the end plug 3 is pressed into the end of the cladding tube 1.

More specifically, an electric command is given to the motor driver 21 from the sequence control unit 22, and a rotational torque of the propulsion force commanded to the electric motor 20 is generated.
The movable shaft 11 is propelled to the welding chamber 7 side, and the end plug 3 is press-fitted. The propulsion force applied to the movable shaft 11 is higher than the force (PO) for pushing back by the chamber internal pressure, and is set to a total propulsion force of 50 kg · f or more. Here, since the force of the PO can be uniquely determined by the pressure of the welding chamber and the diameter of the movable shaft, the force suitable for press-fitting the end plug can be input to the sequence control unit 22 in advance by a program.

Then, when the end plug 3 is fitted to the cladding tube 1 and it is confirmed that the press-fitting is sufficient, the pressing force command from the sequence control unit is changed, and the propulsive force is reduced. Suitable conditions for the propulsion force of the movable shaft 11 are desirably in the range of PO + 1 kg · f to PO + 10 kg · f. Therefore, an electric command corresponding to this proper propulsion force is pre-programmed into the sequence control unit, executed after press-fitting the end plug, controlling the movable shaft 11 via the motor drive, and pressing and supporting the end plug 3 with a weak force. I do. Thereafter, an electric command is sent from the sequence control unit to the electromagnetic brake 23 while maintaining the pressed state, and the movable shaft 11 is locked.

By the above operation, the welding can be started with the compressive force in the axial direction of the material to be welded set to a small force.

The welding is performed by rotating the cladding tube 1 by the rotating device 10, but a load and an elongation are generated in the axial direction due to the elongation of the coil spring and the thermal expansion of the material to be welded. However, at this time, since the stopper 25 provided on the end plug holder 12 is elastically deformed and absorbs the load and elongation, the welded portion is not crushed or stretched. During coagulation and contraction, the stopper 25 acts as a spring, and can play the role of a stopper following the axial movement of the end plug 3.

[0028]

As described above, according to the present invention, when the end plug is pressed, the pressing device is operated so that a large pressing force is applied to the movable shaft. And a brake operation for holding and holding the movable shaft is performed, so that the welded portion is abnormally stretched by the extension of the coil spring and fixed by welding, or the pressing force of the movable shaft causes the welded portion to be fixed. Welding can be performed without causing any crushing action and generating unnecessary stress on the end plug welded portion.
Further, when an elastic stopper that contacts the end of the end plug is provided in the end plug holder, thermal expansion in the axial direction at the time of melting generated at the welded portion or solidification and contraction at the time of cooling is performed by the elastic stopper. It is appropriately absorbed, and it is possible to reliably prevent the welded portion from being crushed or the end plug from being difficult to hold, and to provide effects such as being able to perform welding without generating unnecessary compression or tensile stress.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an end plug welding device of the present invention.

FIG. 2 is a partial sectional view showing a configuration of an end plug holder according to the present invention.

FIG. 3 is a cross-sectional side view of a general nuclear fuel rod.

FIG. 4 is a diagram showing a schematic configuration of a conventional end plug welding device.

FIG. 5 is a diagram showing another example of a conventional end plug welding device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Clad tube 2, 3 End plug 4 Pellet 5 Coil spring 7 Welding chamber 8 Nuclear fuel rod holding device 9 End plug pressing device 11 Movable shaft 14 Welding torch 20 Electric motor 21 Motor driver 22 Sequence control unit 23 Electromagnetic brake 24 Bearing 25 Elastic stopper

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[Procedure amendment]

[Submission date] August 4, 1999 (1999.8.4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[0014]

A first invention is provided on a minus side of a welding chamber having a welding torch and holds a nuclear fuel rod holding device for holding a cladding tube of a nuclear fuel rod, and is held by the nuclear fuel rod holding device. The movable shaft, which is disposed on the same line as the cladding tube and has an end plug holder attached to the distal end inserted into the welding chamber, and the movable shaft, which is disposed on the other side of the welding chamber, And a pressing device for axially moving back and forth, wherein the end plug held by the end plug holder is press-fitted into the open end of the cladding tube, and the welding is performed on the nuclear fuel rod end plug welding device. An electric motor-driven pressing device that acts to apply a large pressing force to the movable shaft at the time of pressing and weakens the pressing force of the movable shaft to a value that the end plug can hold before starting welding, and during welding of the end plug. Fixedly holds the movable shaft And having a magnetic brake apparatus, and a sequence controller for sequence controlling the sequence of operation of the electric motor-driven pressing device and the electromagnetic brake device.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryosuke Nishikawa 2-3-1 Kawakawa, Yokosuka City, Kanagawa Prefecture F-term in Niuclear / Fuyell Co., Ltd. (reference) 4E081 AA02 EA11 EA43 EA47 EA56 FA17 YS02 YY01

Claims (3)

[Claims] 1. A nuclear fuel rod holding device provided on a negative side of a welding chamber having a welding torch and holding a cladding tube of a nuclear fuel rod, and disposed on the same line as the cladding tube held by the nuclear fuel rod holding device. A movable shaft having an end plug holder attached to a tip portion inserted into the welding chamber,
A pressing device that is disposed on the other side of the welding chamber and moves the movable shaft forward and backward in the axial direction, and press-fits the end plug held by the end plug holder into the open end of the cladding tube to perform welding. In the nuclear fuel rod end plug welding device that is performed, when the end plug is pressed, the pressing device is operated so that a large pressing force is applied to the movable shaft, and before the welding starts, the pressing force of the movable shaft by the pressing device is reduced. A nuclear fuel rod end plug welding device, further comprising a sequence control device for causing a brake device for fixedly holding the movable shaft to perform a brake operation. 2. The nuclear fuel rod end plug welding device according to claim 1, wherein the pressing device is an electric motor driven pressing device, and the brake device is an electromagnetic brake. 3. An end stopper holder is provided with an elastic stopper in contact with an end of the end plug.
3. The welding device for end plugs of a nuclear fuel rod according to claim 1.