JP3162207B2 - Welding apparatus and welding method for end plug in fuel rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for welding an end plug to a fuel rod in which nuclear fuel pellets are inserted.

[0002]

2. Description of the Related Art Generally, a large number of fuel pellets are inserted into a plurality of fuel rods constituting a fuel assembly used in a nuclear reactor.

Conventionally, to manufacture this fuel rod, a predetermined amount of fuel pellets is inserted into a fuel rod having one end sealed, and a spring is inserted to fix the fuel pellets in a pipe. The other end is sealed with an end plug. In this case, the fuel pellet and the spring are inserted into the pipe and the end plug is welded. In order to make the end of the fuel rod and the end plug abut against the inserted spring, the end plug is connected to the fuel rod. And press-fitted them once to bring them into contact with each other, and then welded end plugs to the fuel rods.

[0004]

By the way, the configuration of the fuel rod prevents the end plug from loosening due to thermal expansion during welding.
In addition, when welding is performed with the positional relationship between the fuel rod and the end plug fixed in order to obtain a constant welding state, thermal deformation of the fuel rod during welding, that is, stress due to axial expansion and contraction of the fuel rod occurs. Therefore, there is a problem that the welding state is not uniform because the contact state between the fuel rod and the end plug changes, and considerable skill is required to perform high-precision welding.

The present invention has been made in view of the above circumstances, and has as its object to weld an end plug to a fuel rod without being affected by thermal deformation during welding. Welding apparatus and welding of end plugs in fuel rods that can maintain the contact pressure between the plugs in a desired state and obtain a uniform and good quality weld.
It is to provide a method .

[0006]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a fuel rod in which a fuel pellet is contained and an end plug is attached to an end thereof. A welding apparatus for welding, wherein the fuel rod is inserted thereinto, and a gripping mechanism for gripping an outer periphery of the fuel rod, and provided opposite to the gripping mechanism, and wherein the fuel rod is inserted into the gripping mechanism. And a torch provided between the gripping mechanism and the abutting member, and facing the outer periphery of the tip end of the fuel rod from the diametric direction of the fuel rod when the end plug comes into contact. Is provided on one of the gripping mechanism and the contact member provided so as to be able to approach and separate from each other.
A pressing mechanism that presses the gripping mechanism and the abutting member in a direction approaching each other ;
Control means for adjusting the pressure is provided.
The pressure between the fuel rod and the end plug gradually increases from the second half of welding
The power is reduced.

According to a second aspect of the present invention, one of the gripping mechanism and the contact member is fixed to a predetermined position prior to welding of the end plug, and the fixing is released when the end plug is welded. A positioning mechanism is provided.

[0008] Further, a third aspect of the present invention is provided with a measuring means for measuring a pressure between the end plug contacting the contact member and the fuel rod gripped by the gripping mechanism. hand
The control means controls the pressurizing mechanism based on the measured value of the step.
That's what I did .

Further, claim 4 of the present invention has an internal
Fuel pellets are stored and end plugs are attached at the ends.
A welding method for welding the end plugs of the fuel rods.
A fuel rod with an end plug attached to its end
Insert the end plug into the inside of
After the fuel rod is gripped by the gripping mechanism,
Press the mechanisms or contact members in the direction to approach each other
While the fuel rod and end plug are pressed against each other at the desired pressure,
Weld the end plug of the fuel rod, and gradually from the latter half of the welding, the fuel rod and end plug
Characterized by reducing the pressure between
Things.

[0010]

In the first aspect of the present invention, the fuel rod is gripped by the gripping mechanism, and the fuel rod is pressed by the torch with the pressing mechanism pressing the gripping mechanism or the abutting member in a direction approaching each other. Weld end plugs.

According to a second aspect of the present invention, prior to welding of the end plug, a positioning mechanism is used in advance by a positioning mechanism.
With the gripping mechanism or contact member fixed at a predetermined position, a fuel rod with an end plug attached to the tip is inserted through the tip of the fuel rod into the inside of the gripping mechanism, and the end plug attached to the fuel rod is contacted. After contacting the contact member, and then grasping a predetermined position of the fuel rod by the grasping mechanism, the fixed state by the positioning mechanism is released to make the grasping mechanism or the contact member movable.

Further, according to a third aspect of the present invention, the control means controls the pressurizing mechanism based on the pressure value between the end plug and the fuel rod measured by the measuring means, thereby controlling the welding mechanism during welding. Adjust the pressure between the end plug and the fuel rod.

Still further, according to a fourth aspect of the present invention, the fuel rod and the end plug are maintained at a constant pressure until welding is performed, and
Fine-grained control such as gradually reducing the pressure in the latter half of welding
Control becomes possible. This leaves residual stress in the weld
No inner undercut, welded outer diameter
The occurrence of weld defects such as bar size is also prevented,
High quality welds can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a first embodiment of a welding apparatus for an end plug in a fuel rod according to the present invention (hereinafter referred to as the present apparatus). Outline,
A main shaft 1 through which the fuel rod P is inserted, a gripping mechanism F3 attached to one end of the main shaft 1 and gripping the fuel rod P into which the end plug C is press-fitted, and a fuel rod P inserted through the main shaft 1
And a torch 16 (see FIG. 6) for welding the fuel rod P and the end plug C to each other.
Further, when the fuel rod P is gripped by the gripping mechanism F3, the gripping mechanism F3 is fixed, and the main shaft 1 is brought into contact with the positioning mechanism F2 for releasing the fixing when the end plug C is welded. A pressure mechanism F1 for pressing the member 19 at a predetermined pressure is provided.

Hereinafter, the present apparatus will be described in detail.
Is formed hollow so that the fuel rod P can be inserted, and a gripping mechanism F3 is provided at the tip thereof. The gripping mechanism F3 includes a collet 2 screwed to the tip of the spindle 1, and a collet closure 4 mounted around the outer periphery of the collet 2.
And a nose ring 3, a chuck cylinder 6 and a piston 8 for pressing the collet closure 4 toward the distal end of the main shaft 1.

The collet 2 of the gripping mechanism F3 includes a spindle 1
The tip end of the fuel rod P inserted through is formed to be protrudable,
Further, the fuel rod P is divided into a plurality in the radial direction so as to hold the outer periphery of the fuel rod P. As shown in FIG. 3, the collet 2 is formed such that the vicinity of the tip of the protruding side of the fuel rod P is tapered to increase in diameter in the direction in which the fuel rod P protrudes. The outer periphery of the tip side of the portion is stepped.

For convenience of explanation, the axial direction of the main shaft 1, that is, the insertion direction of the fuel rod P is referred to as the axial direction, and the end portion of the fuel rod P to which the end plug C is welded is projected from the collet 2. Is called one end, and the opposite end is called the other end.

At one end of the main shaft 1 to which such a collet 2 is attached, a cylindrical donut-shaped flange is attached at the other end, and the collet 2 is attached to the inner peripheral surface of the tip at one end. A collet closure 4 having a tapered portion that engages with the tapered portion is annularly mounted, and slides in the axial direction on the peripheral surface of the main shaft 1 to reduce or open the collet 2. .

A cylindrical nose ring 3 having an open bottom at one end is provided on the outer periphery of the collet closure 4.
The collet 2 is locked at the bottom of the opening so that only the tip of the collet 2 projects in the axial direction of the fuel rod P. Further, a flange is provided on the other end side of the nose ring 3, and an elastic member 9 is interposed between the flange of the nose ring 3 and the flange of the collet closure 4 so as to be separated from each other in the axial direction. Biased in the direction.

The collet closure 4 and the nose ring 3 are formed so as to be rotatable together with the rotation of the main shaft 1 and the collet 2. The rotating portions of the main shaft 1, the collet 2, the collet closure 4 and the nose ring 3 A bearing 6 is attached to a chuck cylinder 6 which is also a housing and a collet adjusting ring 5 screwed to the chuck cylinder 6.
It is rotatably supported via b, 8b, 5b.

The chuck cylinder 6 is a cylinder formed in the shape of a double cylinder with a bottom. The outer cylinder 6j and the inner cylinder 6
and k, an annular cylinder chamber 6v is formed. The main shaft 1 is supported by the bearing 6b attached to the inner cylinder 6k. And
A donut-shaped piston 8 is inserted into the cylinder chamber 6v, and the piston 8 is advanced and retracted in the axial direction by a separately provided pressurizing means such as a hydraulic pressure or a pneumatic pressure.

Reference numeral 7 denotes a conduit block in which an inlet conduit for introducing a pressurized medium such as oil or air into the cylinder chamber 6v is formed. Reference numerals 8c and 8c denote seal members such as O-rings. is there.

In order to transmit the axial movement of the piston 8 to the collet closure 4 which rotates together with the main shaft 1, the end face of one end of the piston 8 is provided on the board surface at the other end of the flange of the collet closure 4. And the bearing 8b is attached.

On the other hand, the collet adjusting ring 5 screwed to one end of the chuck cylinder 6 is mounted around the main shaft 1 and the collet closure 4 and rotates the nose ring 3 which rotates together with the main shaft 1 and the collar. And finely adjusts the relative position in the axial direction of the main shaft 1 and the collet 2 attached to one end thereof with respect to the chuck cylinder 6 through a bearing 5b interposed therebetween. In the drawing, reference numeral 5e denotes a lock nut of the collet adjusting ring 5.

The main shaft 1 is, as shown in FIG.
The other end is rotatably supported by a slide bearing 31 and movably in the axial direction.

As shown in FIG. 1 and FIG. 6 which is a plan cross section, the abutting member 19 has an end on one end side facing the one end side of the main shaft 1 supported movably in the axial direction. Stopper C
When the fuel rod P press-fitted is inserted through the main shaft 1, the contact portion between the fuel rod P and the end plug C passes through the collet 2 of the gripping mechanism F <b> 3 and projects from the collet 2. At this position, one end surface of the end plug C abuts, and the fuel rod P stops. Then, with the end plug C abutting,
It is formed coaxially with the main shaft 1 and rotatably so as to rotate with the rotation of the fuel rod P.

The end plug C, which is welded to one end of the fuel rod P, is of a fixed shape formed in a roughly two-stage cylindrical body, and its small diameter portion is press-fitted into one end of the fuel rod P in advance. The step with the large diameter portion substantially equal to the outer diameter of the fuel rod P is brought into contact with the end of the fuel rod P, and the contact part is welded. Therefore, the contact member 19 is disposed at a fixed position so that the end plug C is always located at a predetermined position in the axial direction.
This defines the welding position in this device.

The end plug C of the fuel rod P protruding from the collet 2 is brought into contact with the outer periphery of the contact member 19 in order to maintain a good gas shield state during welding. Occasionally, a chamber 18 surrounding the welded portion between the fuel rod P and the end plug C is provided.

As shown in FIG. 6 showing the plane of the collet 2 holding the contact member 19 and the fuel rod P, a welding torch 16 is provided adjacent to the collet 2 from the outer peripheral side of the chamber 18. Has been inserted. That is, the torch 16 faces the outer peripheral edge of one end of the fuel rod P, which is brought into contact with the end plug C held by the contact member 19, from the diameter direction of the fuel rod P.

As described above, in the present apparatus, the fuel rod P is gripped at a predetermined position by pressurizing means such as hydraulic pressure and pneumatic pressure of the gripping mechanism F3, and the fuel rod P and the end plug C pressed into one end thereof are pressed. And a positioning mechanism F2 shown in FIGS. 1 and 4 is provided.

When the gripping mechanism F3 grips the fuel rod P, which is inserted into the main shaft 1 and reaches a predetermined position where it abuts against the abutting member 19, the positioning mechanism F2 has a predetermined axial position of the fuel rod P. The gripping mechanism F3 is fixed at the position, and the fixing is released when the end plug C is welded.

FIG. 2 shows a side view of the apparatus. The chuck cylinder 6 rotatably supporting one end of the main shaft 1 is mounted on a base B of the apparatus by a guide 21. It is formed so as to move in the axial direction together with the main shaft 1. On the other hand, the slide bearing 31 that supports the other end side of the main shaft 1 and the contact member 19 with which the end plug C is in contact,
It is fixed on a base B.

The positioning mechanism F2 includes a cylinder device 23 disposed on the base B, a rack 24 extending parallel to the main shaft 1 on a rod of the cylinder device 23, and extending and retracting in the axial direction. A pair of cams 26, 26 which rotate in the same direction by reciprocating movement of the cam 24;
And a lever 15 sandwiched between them.

As shown in FIG. 1 and FIG. 4 which is a front sectional view of the positioning mechanism F2, the rack 24 which advances and retreats in the axial direction is provided with a pair of rotatable shafts 29 provided orthogonally to the axial direction. , 29, respectively, and engages with the concave portions of a pair of guide rollers 25, 25 having concave portions formed on the peripheral surfaces thereof, and is always kept parallel to the main shaft 1.
Further, pinion gears 27, 27 respectively attached to a pair of rotatable shafts 28, 28 provided orthogonally to the axial direction are screwed to the tooth surfaces of the rack 24. Then, the shaft 2 to which each pinion gear 27 is attached
8, the cam 26 is attached.

The racks 24 are provided on the shafts 28, 28.
The pair of cams 26, 26 that rotate in the same direction by
As shown in FIG. 1, the pinion gears 27 are screwed into the rack 24 so that the levers 15 inserted between the cams 26 and 26 are arranged symmetrically with each other in a side view. ing.

Further, the pressurizing mechanism F1 in the present apparatus is
It is provided on the outer periphery of the main shaft 1 irrespective of the rotation of the main shaft 1, and as shown in FIGS. 1 and 5, a double cylindrical pressurizing cylinder 11, a piston 13, a connecting ring 1
And 4. The pressurizing cylinder 11 includes an outer cylinder 11j and an inner cylinder 11k having a shorter axis than the outer cylinder 11j and seals the other end of the outer cylinder 11j. Cylinder chamber 11v between
Are formed.

One end of the substantially cylindrical piston 13 inserted into the piston 13 is formed into a thick large-diameter portion, and the large-diameter portion is fitted into the inner peripheral surface of the outer cylinder 11j to constitute a piston. The cylindrical portion is fitted on the inner peripheral surface of the inner cylinder 11k to form a piston shaft. Further, the inner diameter of the cylindrical piston 13 in the pressurizing mechanism F1 is formed to be slightly larger than the main shaft 1 so as to function independently of the movement of the main shaft 1.

Although not shown, the cylinder chamber 11v is pressurized by pressurizing means such as hydraulic pressure or pneumatic pressure, so that the piston 13 moves forward and backward in the axial direction. Further, when the cylinder chamber 11v is pressurized,
A pressure control function is provided to maintain the cylinder chamber 11v at a predetermined pressure.

The connecting ring 14 transmits the movement of the piston 13 which advances and retreats in the axial direction to the chuck cylinder 6 which supports the main shaft 1, and has a flange provided on one end side. The flange is attached to the other end surface of the chuck cylinder 6, and the other end of the cylinder is attached to one end surface of the piston 13. Reference numeral 12 is a conduit block in which an inlet conduit for introducing a pressurized medium into the cylinder chamber 11v is formed, and reference numerals 11c and 13c are seal members such as O-rings.

Next, a plurality of fuel pellets and an elastic member for urging the fuel pellets are inserted, and the end plug C is welded to the fuel rod P in which the end plug C is press-fitted in one end in advance. The operation of the present device when P is sealed will be described.

The fuel rod P is provided with a main shaft 1 formed hollow in the apparatus, and a collet 2 screwed to one end of the main shaft 1.
When the end plug C is inserted from one end into which it is press-fitted, a contact member 19 formed coaxially with the main shaft 1 is provided in front of the main shaft 1 so as to face the collet 2. End plug C
End of the collet 2 abuts against the contact member 19 so that the contact portion between the fuel rod P to be welded and the end plug C is always at a fixed position from the other end of the contact member 19. Can be done.

On the other hand, the chuck cylinder 6 which rotatably supports the main shaft 1 and the collet closure 4 and the nose ring 3 mounted on the main shaft 1 is mounted on the guide B on the base B of the apparatus.
1 so as to be movable in the axial direction.
Includes a cylinder device 23, a rack 24 provided in the cylinder device 23, which advances and retreats in parallel with the main shaft 1, a pair of cams 26, 26 which rotate in the same direction by reciprocation of the rack 24, A positioning mechanism F2, which is provided on the outer periphery of the motor 6 and is constituted by the lever 15 sandwiched between the pair of cams 26, 26, is provided.

Therefore, when the rack 24 is moved forward and backward by the driving of the cylinder device 23, the pair of cams 26, 26 rotate and the levers are moved to the pair of cams 26, 26 as shown in FIG. 15 is pinched in place,
Thus, the chuck cylinder 6 can always be located at a predetermined position in the axial direction of the fuel rod P, and the fuel rod P can be projected from the collet 2 by a predetermined length.

Therefore, the main shaft 1 has a collet 2 screwed to the tip of the main shaft 1, a collet closure 4 and a nose ring 3 mounted around the outer periphery of the collet 2.
And a gripping mechanism F3 composed of a chuck cylinder 6 and a piston 8 for pressing the collet closure 4 toward the distal end of the main shaft 1, so that the fuel rod P is gripped by the gripping mechanism F3.

That is, since the cylinder chamber 6v is formed in the chuck cylinder 6, the cylinder chamber 6v
Is pressurized at a predetermined pressure by pressurizing means (not shown), the donut-shaped piston 8 inserted into the chuck cylinder 6 moves toward one end in the axial direction.

Then, the piston 8 presses the flange provided on the other end of the collet closure 4 mounted on the collet 2 via the bearing 8b, and moves the collet closure 4 to one end in the axial direction. . In addition, the nose ring 3 is mounted around the collet closure 4, and the collet closure 4 and the nose ring 3 are always urged by the elastic member 9 in the direction away from each other,
Further, at one end of the nose ring 3 mounted on the collet closure 4, the collet 2 extends in the direction in which the fuel rod P projects.
, The collet closure 4 approaches one end of the collet 2 against the elastic member 9.

The collet 2 is divided into a plurality of pieces in the radial direction, and the outer periphery is formed in a taper whose diameter increases as the fuel rod P protrudes. Is formed with a tapered portion that engages with the tapered portion of the collet 2, so that the tapered portion of the collet closure 4 is
And presses the fuel rod P inserted therein.

As described above, when the fuel rod P is gripped by the collet 2, the cylinder device 23 of the positioning mechanism F2 is driven to move the rack 24 forward and backward again to rotate the pair of cams 26. These pair of cams 26,
The lever 15 sandwiched by 26 is released, the fixing of the main shaft 1 by the positioning mechanism F2 is released, and therefore, the restriction of the gripping mechanism F3 that grips the fuel rod P in the axial direction is also released.

Next, the main shaft 1 is formed so as to be movable in the axial direction as described above, and further comprises a pressurizing cylinder 11, a piston 13 and a connecting ring 14. Since the pressing mechanism F1 for pressing is provided, the main shaft 1 is pressed by the pressing mechanism F1.

That is, the pressurizing cylinder 11 is formed by an outer cylinder 11j and an inner cylinder 11k.
Cylinder chamber 11v formed between 1j and inner cylinder 11k
Is pressurized by pressurizing means (not shown) such as hydraulic pressure, pneumatic pressure, etc., is inserted therein, and the large-diameter portion at one end is fitted into the inner peripheral surface of the outer cylinder 11j to form a piston. The piston 13 that has the cylindrical portion fitted into the inner peripheral surface of the inner cylinder 11k and constitutes the piston shaft is pressed to one end side along the axial direction of the main shaft 1.

At this time, since the pressurizing means for pressurizing the cylinder chamber 11v has a pressure control function, the pressurizing means has a level which is substantially equilibrium with the urging force of the elastic member inserted into the fuel rod P at first. The cylinder chamber 11v is pressurized to a predetermined pressure.

A connecting ring 14 is attached to one end of the piston 13 pressed as described above, and a flange attached to one end of the connecting ring 14 is attached to the other end of the chuck cylinder 6. Since it is attached, the movement of the piston 13 that is going to move forward to one end side in the axial direction can be transmitted to the chuck cylinder 6 that supports the main shaft 1.

As described above, the fuel rod P gripped by the gripping mechanism F3 provided on the main shaft 1 by the pressing by the pressure mechanism F1 causes the end plug C press-fitted at one end thereof to abut against the contact member 19. The fuel rod P and the end plug C
Are pressed against each other with a constant pressure.

That is, the fuel rod P previously inserted into the main shaft 1 is inserted into a predetermined position in the present apparatus, and
Since the gripping mechanism F3 provided on the spindle 1 together with the spindle 1 is fixed at a predetermined position on the fuel rod P by the positioning mechanism F2, the fuel rod P is gripped, and then the fuel rod P is pressed with a constant pressure. The fuel rods P supplied to the apparatus can always maintain a contact state with the end plug C with a constant pressing force.

Next, the rotating part of the gripping mechanism F3 of the main shaft 1, the collet 2, the collet closure 4, and the nose ring 3 is attached to the chuck cylinder 6 and the collet adjusting ring 5 screwed to the bearings 6b, 8b, Since they are rotatably supported via the base 5b, they are rotated at a predetermined speed by a separately provided driving device (not shown).

A torch 16 is inserted into the outer peripheral edge of one end of the fuel rod P adjacent to the rotating collet 2 and facing the fuel rod P in the diametrical direction. And the end plug C is welded. Then, as described above, the contact portions between the fuel rods P and the end plugs C are pressed and held at a predetermined pressure by the pressurizing mechanism F1, and the pressurizing mechanism F1 is controlled by the pressure control means. (Not shown), the pressure is always maintained at a constant level, and the cylinder chamber 11v is constantly maintained at a constant pressure in response to a change in the pressing force due to thermal deformation of the fuel rod P during welding. The welded portion between the fuel rod P and the end plug C is always kept at a constant contact pressure, and a uniform welding state can be obtained over the entire welded portion without any change in stress.

Further, since the chamber 18 is provided on the outer periphery of the contact member 19 and covers the welding portion of the fuel rod P projecting from the collet 2 with the end plug C, so that the gas shield state at the time of welding is good. Can be kept.

As described above, in the present device, the fuel rods P inserted in advance into the main shaft 1 are inserted to a predetermined position in the present device, and the gripping mechanism F provided on the main shaft 1 is provided.
3 is positioned at a predetermined position of the fuel rod P by the positioning mechanism F2, the predetermined position of the fuel rod P is gripped, and then the fuel rod P is pressed with a constant pressure. In each case, the contact state with the end plug C can be ensured by the pressing force without constant variation. Then, in a state where the pressing force is held at a predetermined pressure, and at the time of welding, the pressing mechanism F1 always holds the pressure at a constant pressure in response to a change in the pressing force due to thermal deformation of the fuel rod P during welding. Therefore, the welded portion between the fuel rod P and the end plug C is always kept at a constant contact pressure, and the stress does not change.
Therefore, a uniform welding state can be obtained over the entire circumference of the welded portion.

FIG. 7 is a view showing a schematic structure of the first embodiment.
When the gripping mechanism F3 is pressed toward the chamber 18 (contact member 19) by the pressing mechanism F1 consisting of, the pressing force is changed from before welding to during welding and after welding as shown in FIG. It is kept almost constant. On the other hand, when welding is performed with the positional relationship between the fuel rods and the end plugs fixed using the conventional fixed holding mechanism and chamber (contact member), as shown in FIG. During the process, the pressing force increases due to the thermal deformation of the fuel rod, and the contact state between the fuel rod and the end plug changes, so that the welding state cannot be maintained uniformly.

In the first embodiment, a fluid pressure cylinder is used as the pressurizing mechanism F1, and there is a limit in performing fine control of the pressing force due to its structural friction. For this reason, when it is desired to control the pressing force more finely, as shown in FIG. 10, the gripping mechanism F4 is in a fixed state as in the prior art, that is, in the first embodiment shown in FIGS. Uses the one in which the guide 21 is removed and the chuck cylinder 6 is directly fixed to the base B, and the fuel rod P is gripped without mounting the pressing mechanism F1 and the positioning mechanism F2 on the gripping mechanism F4 side. While having only the function, the contact member 1
9 is mounted through a guide 41,
A positioning mechanism (not shown) having the same configuration as the positioning mechanism F2 is disposed on the base B so as to be movable in the horizontal direction, and a pressing mechanism for pressing the chamber 40 toward the gripping mechanism F4 is provided on the chamber 40. The pressure mechanism F5, measuring means (load converter, load cell) 42 for measuring the pressure between the end plug C and the fuel rod P, and the pressurizing mechanism F5 is controlled based on the measured value of the measuring means 42. The control means 43 is additionally provided.

The pressurizing mechanism F5 is connected to the chamber 40
(Spring member) 4 that presses the gripper toward the gripping mechanism F4
4 and the spring 44
It comprises a nut body 45 for horizontally moving the nut 4, a ball screw shaft 46 screwed into the nut body 45, and a pulse motor 47 connected to the ball screw shaft 46 and rotating the ball screw shaft 46. The nut body 45 and the ball screw shaft 46 constitute a transmission mechanism for converting the rotation of the pulse motor 47 into a linear motion.

The measuring means 42 measures the pressure applied to the contact member 19. The measured value measured by the measuring means 42 is input to the controller 48 of the control means 43. In the controller 48, the measured value is added to the pressing force setting data which has been input and stored in advance. Are configured to perform feedback control of the pulse motor 47 via a driver 49 so that the values of.

In the second embodiment of the present invention constructed as described above, first, with the chamber 40 (contact member 19) fixed at a predetermined position by a positioning mechanism (not shown), Through the fuel rod P,
After the end plug C attached to the tip of the fuel rod P is brought into contact with the contact member 19, the fuel rod P is gripped by the gripping mechanism F4. Next, the chamber 40 by the positioning mechanism is used.
When the fixed state of the (contact member 19) is released and the movable member becomes movable, the chamber 40 (contact member 19) is pressed against the gripping mechanism F4 by the pressing force of the spring 44. In this state, welding of the end plug C of the fuel rod P is performed.

In this case, the pulse motor 47 is driven by the driver 49 via the driver 49 by the controller 48 so that the measured value of the pressing force measured by the measuring means 42 matches the previously input set value. By controlling, the pressing force is adjusted according to the set value input in advance. For example, the pressing force as shown in FIG. 11, that is, a constant pressure until the middle of welding, and the cooling process from the latter half of welding. Fine control, such as gradually reducing the pressure, becomes possible. As a result, no residual stress remains in the welded portion, and the occurrence of defects in the welded portion, such as an undercut of the inner surface and an oversize of the outer diameter of the welded portion, is prevented.

In the second embodiment, the pulse motor 47 of the pressurizing mechanism F5 is controlled by the control means 43 to adjust the movement of the chamber 40 (contact member 19). Although the pressure between the fuel rod P and the fuel rod P has been described as being operated, the present invention is not limited to this. In the first embodiment shown in FIGS. Arrange the mechanism F5,
The movement of the gripping mechanism F3 may be adjusted.

[0067]

As described above, according to the first aspect of the present invention,
Is a welding device for welding the end plug of a fuel rod having a fuel pellet accommodated therein and having an end plug attached to an end thereof, wherein the fuel rod is inserted thereinto, and an outer periphery of the fuel rod is provided. A gripping mechanism for gripping the gripping mechanism, a contact member provided opposite to the gripping mechanism, and the end plug abutting when the fuel rod is inserted into the gripping mechanism; and the gripping mechanism and the abutting member. A torch provided between the fuel rods and facing the outer periphery of the tip of the fuel rod from the diameter direction of the fuel rod ;
A pressing mechanism that is provided on one of the gripping mechanism and the abutting member that is provided so as to be able to approach and separate from each other, and that presses the gripping mechanism and the abutting member in a direction approaching each other ; Pressure mechanism
Control means to control the pressure between the fuel rod and the end plug
A step is provided, and the control means determines whether the welding is in the latter half of the welding.
Gradually reduce the pressure between the fuel rod and the end plug.
Since the fuel rod is gripped by the gripping mechanism and the pressing mechanism presses the gripping mechanism or the contact member in a direction approaching each other, by welding the end plug of the fuel rod with a torch, In welding the end plug to the fuel rod, the contact pressure between the fuel rod and the end plug can be maintained in a desired state without being affected by thermal deformation during welding, and is uniform and good. Quality welds can be obtained. As a result, residual stress
Is not left, and the inner undercut, weld
The occurrence of weld defects such as oversize of the outer diameter is also prevented.
As a result, a weld having better quality can be obtained.

According to a second aspect of the present invention, one of the gripping mechanism and the contact member is fixed to a predetermined position prior to welding of the end plug, and the fixing is released when the end plug is welded. Since the positioning mechanism is provided, prior to welding the end plug, the fuel rod having the end plug attached to the tip is fixed by the positioning mechanism in advance with the gripping mechanism or the contact member fixed at a predetermined position. Then, the end plug is inserted into the inside of the gripping mechanism, the end plug attached to the fuel rod is brought into contact with the contact member, and then the fuel rod is gripped at a predetermined position by the gripping mechanism, and then fixed by the positioning mechanism. By releasing the state and making the gripping mechanism or the abutting member movable, the movable gripping mechanism or the abutting member can be returned to the initial position prior to welding, and the gripping mechanism can be returned. Fee predetermined position of the bar can be gripped, and be welded to repeat many end plug can always keep the welding conditions constant.

Further, a third aspect of the present invention is provided with a measuring means for measuring a pressure between the end plug in contact with the contact member and the fuel rod gripped by the gripping mechanism. hand
The control means controls the pressurizing mechanism based on the measured value of the step.
Since it is obtained by the so that, on the basis of the pressure value between the measured end plug and the fuel rods by the measuring means, the end plug and the fuel rods during welding by controlling the pressure mechanism by the control means By adjusting the pressure between them, it is possible to finely control the pressing force, prevent the residual stress from remaining in the welded portion, and also prevent defects in the welded portion such as inner undercut, oversized outer diameter of the welded portion, etc. Can be prevented, and a welded part having better quality can be obtained.

[0070] Further, Claim 4 of the present invention, the tip
From the tip of the fuel rod with the end plug attached,
Insert the end plug into the inside to abut the contact member, and then
After gripping the fuel rod by the gripping mechanism,
Press the structures or abutment members in the
The fuel rod and the end plug are pressed against each other at the desired pressure.
Weld the end plugs of the rod, and gradually add fuel rods and end plugs from the second half of welding.
Between the fuel rod and end plug
At a constant pressure until the middle of welding, and gradually from the second half of welding.
Fine control, such as decreasing the pressure, is possible.
This ensures that no residual stress remains in the weld,
Also, inner undercut, oversized outer diameter of welded part, etc.
The occurrence of defects in the welds is also prevented, resulting in better quality
A weld is obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a first embodiment of the present invention.

FIG. 2 is a side view showing the appearance of the first embodiment of the present invention.

FIG. 3 is a side sectional view showing a gripping mechanism.

FIG. 4 is a front sectional view of a positioning mechanism.

FIG. 5 is a side sectional view showing a pressing mechanism.

FIG. 6 is a cross-sectional plan view showing a spindle tip, a contact member, and a torch for welding.

FIG. 7 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a change in pressing force when the first embodiment of the present invention is used.

FIG. 9 is a characteristic diagram showing a change in pressing force when a conventional end plug welding device is used.

FIG. 10 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 11 is a characteristic diagram showing a change in pressing force when the second embodiment of the present invention is used.

[Explanation of symbols]

 16 Torch 19 Contact member 42 Measurement means (load converter, load cell) 43 Control means 44 Spring (elastic member) 45 Nut body 46 Ball screw shaft 47 Pulse motor F1 Pressurizing mechanism F2 Positioning mechanism F3 / F4 Gripping mechanism F5 Pressurizing Mechanism P Fuel rod C End plug

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Minoru Murata 622 Funaishikawa, Tokai-mura, Naka-gun, Ibaraki Pref. 1 Inside the Tokai Works of Mitsubishi Nuclear Fuel Co., Ltd. (56) References JP-A-47-34135 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G21C 21/02 G21C 3/10

Claims (4)

(57) [Claims] 1. A welding device for welding an end plug of a fuel rod having a fuel pellet accommodated therein and having an end plug attached to an end, wherein the fuel rod is inserted through the fuel rod, A gripping mechanism that grips the outer periphery of the rod, a contact member that is provided to face the gripping mechanism, and that contacts the end plug when the fuel rod is inserted into the gripping mechanism; It is provided between the contact member and the torch which faces the diametrical direction of the fuel rods in the outer periphery of the distal end portion of the fuel rod, against each other
A pressing mechanism that is provided on one of the gripping mechanism and the abutting member that is provided so as to be able to approach and separate, and that presses the gripping mechanism and the abutting member in a direction approaching each other; and controls the pressing mechanism.
Control means for adjusting the pressure between the fuel rod and the end plug
The fuel rod and the end plug are gradually provided from the latter half of welding by the control means.
Characterized by reducing the pressure during
Welding device for end plugs on a rod. 2. A positioning mechanism for fixing one of a gripping mechanism and a contact member to a predetermined position prior to welding of an end plug and releasing the fixing when welding the end plug. The welding device for an end plug in a fuel rod according to claim 1, wherein: 3. A measuring means for measuring a pressure between the end plug in contact with the contact member and the fuel rod gripped by the gripping mechanism.
Control means based on the measured value of the measuring means.
3. The welding device for an end plug in a fuel rod according to claim 1 , wherein the pressurizing mechanism is controlled in stages . 4. A fuel pellet is housed inside the fuel pellet,
Weld the above end plug of fuel rod with end plug attached to the part
A welding method, in which a fuel rod having an end plug attached to the tip is gripped from the tip.
The end plug is brought into contact with the contact member by passing through the inside of the mechanism,
Next, after the fuel rod is gripped by the gripping mechanism, the fuel rod is gripped.
Press the holding mechanism or contact members in the direction
With the fuel rod and end plug pressed together at the desired pressure.
Weld the end plug of the fuel rod,
The pressure between the stopper and the plug is reduced.
Method of welding end plugs on fuel rods.