JPH0972992A - End plug holding device for fuel rod welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent adverse effect of compression and stretch in the axial direction and torsion in the rotational direction, etc., to a welding part at welding. SOLUTION: On the same axial line as that of coated tube of the fuel rod insertedly mounted to a welding chamber 1, a spindle 14 rotating synchronized with a coated tube 7 is arranged, and in the spindle 14, an end plug holding core 5 is concentrically attached movably in the axial direction and rotationally. On the same axial line as the core 5, a core drive mechanism 20 which supports the back end face of end plug holding core 5 and can be movably adjusted in the axial direction is provided.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Fuel rod welding is generally carried out by attaching an end plug to the end of a cladding tube and rotating the fuel rod by a heat source such as tungsten arc welding to weld the end plug and the cladding tube. It is carried out by welding the joint portion with and in the circumferential direction.

FIG. 5 is a diagram showing a schematic structure of the welding device for the end plugs. In the figure, reference numeral 1 is an airtight welding chamber, and one side wall of the welding chamber 1 has one end of the fuel rod 2. Is inserted and mounted so as to be rotatable about its axis.
On the other hand, an end plug holding shaft 3 is mounted on the opposite wall portion of the welding chamber 1 on the same axis as the fuel rod 2, and an end portion of the end plug holding shaft 3 is attached via a ball bearing 4 to the end portion. A stopper holding core 5 is mounted concentrically with the end stopper holding shaft 3 and rotatable about its axis. A cavity 5a for supporting the rear end of the end plug 6 is formed at the tip of the end plug holding core 5, and the end of the fuel rod 2 attached to the end of the cladding tube 7 is attached. The rear end of the stopper 6 is inserted and supported in the space 5a.

Therefore, the welding electrode 8 is set at a predetermined position, the coating pipe 7 is rotated, and the end plug 6 is rotated while following the rotation, while the welding arc is generated from the electrode 8 to perform welding. . By welding while holding the end plug 6 in this manner, it is possible to prevent the end plug 6 from being attached in a bent state with respect to the axis of the covering tube 7.

By the way, in the device shown in FIG. 5, the end plug 6 rotates following the cladding tube 7 as described above, but the end plug holding shaft 3 is positively connected to the fuel rod 2. It is also proposed to rotate synchronously so that relative rotation does not occur between the cladding tube 7 and the end plug 6.

FIG. 6 shows a structure in which the end plug holding shaft 3 is positively rotated. An end plug holding core 5 is fixed to the end plug holding shaft 3 by a screw portion 9, and Pulleys 12a and 12b are provided on a shaft 11 that is driven to rotate by a motor 10, respectively.
drive transmission belts 13a and 13b wound around a and 12b
The fuel rod 2 and the end plug holding shaft 3 are rotated in synchronization with each other.

However, when the end plug 6 is welded, the fuel rod 2 and the end plug 6 are synchronously rotated via the shaft 11 and the drive transmission belts 13a and 13b, and a twist in the rotational direction occurs between them. Is prevented.

However, when welding end plugs of fuel rods,
The welding heat input at that time may cause the end plug to expand / contract in the axial direction of the fuel rod and also to be twisted in the rotational direction.

That is, in the above-mentioned conventional apparatus, since the end plug holding shaft holding the end plug is fixed or left in the axial direction, the heat input during welding causes free expansion during, for example, axial thermal expansion. It is conceivable that compressive stress is generated in the welded part due to the inhibition of heat treatment, or tensile stress acts on the welded part when heat shrinks due to solidification. Further, the end plug tends to bend with respect to the axis of the cladding tube even when the end plug holding core and the end plug are slightly separated due to the thermal contraction of the fuel rod in the axial direction. Further, when twisting in the rotational direction occurs due to welding heat, it is not always possible to deal with the above twisting simply by rotating the fuel rod and the end plug holding shaft in synchronization as in the device shown in FIG.

Axial compression that occurs during these weldings,
Tension and twist in the direction of rotation do not immediately lead to defects, but if left unchecked, it may cause defects such as cracks in welds depending on the relationship with other stresses. .

In view of the above points, the present invention has an object to provide an end plug holding device for fuel rod welding, which is capable of preventing the occurrence of defects due to stress during welding.

[0012]

According to the present invention, a spindle that rotates in synchronization with the cladding tube is provided on the same axis as the axis of the cladding tube of a fuel rod inserted and mounted in an airtight welding chamber. , The end plug holding core is concentrically mounted in the spindle so as to be axially movable and rotatable, and the end plug holding core rear end face is on the same axis as the end plug holding core. A core drive mechanism that supports the core and is adjustable in the axial direction is provided, and the core for holding the end plug is made flexible according to the axial movement of the end plug due to thermal expansion or contraction of the fuel rod during welding. In addition to being movable, it can flexibly handle twists in the rotational direction.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. In addition, in FIG.
The same parts as those in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, in the welding chamber 1, a cylindrical spindle 14 is provided on the side wall surface portion facing the wall surface on which the fuel rod 2 is mounted, on the same axis as the fuel rod 2 mounted on the welding chamber 1. It is mounted so that it can rotate around. The spindle 14 is rotatably supported by a bearing 16 on a fixing member 15.
A driven pulley 17 is integrally provided at the outer end of the drive pulley 13, and a drive transmission belt 13b is wound between the driven pulley 17 and a pulley 12b provided on a shaft that is driven to rotate by the motor 10.

On the other hand, the base end portion of the end plug holding core 5 is concentrically inserted in the central space of the spindle 14 and is rotatably supported by the stroke ball bearing 18 relative to the spindle 14. It is supported.

A core drive mechanism 20 is arranged on the outer end side of the spindle 14. That is, the base 21
An air cylinder 22 is provided on the same axis as the core 5 for holding the end plug, and a piston rod 23 of the air cylinder 22 has a load cell 24 for compression and tension load measurement and a relay metal fitting 25. A supporting rod 26 is provided in a projecting manner, and a rotary bearing 27 is attached to the tip of the supporting rod 26.
The ends of the end plug holding core 5 are connected to each other via. Further, a large diameter portion 26a is formed at the tip portion of the support rod 26, and the outer circumference of the large diameter portion 26a is slidably contacted with the inner surface of the spindle 14 to keep the welding chamber 1 airtight. A ring 28 is provided.

Further, an L metal fitting 29, which moves integrally with the relay metal fitting 25 in the axial direction, is connected to the relay metal fitting 25. The tip of the displacement gauge 30 is brought into contact with the L metal fitting 29, and the displacement gauge 30 is displaced.
By this, the axial movement of the end plug holding core 5 can be detected.

Therefore, the end plug portion can be pressed through the end plug holding core 5 or the like by the forward and backward stroke of the piston rod 23 of the air cylinder 22 or can be operated in the direction of separating from the covering pipe.

Next, the operation will be described.

As a pre-welding operation, it is necessary to attach the end plug 6 to the covering pipe 7 by press-fitting or the like. At that time, the propulsion pressing force of the air cylinder 22 is increased to bring it into a proper press-fitting state. After the press-fitting, the propulsive force of the air cylinder 22 is weakened to change to the normal pressing force required for holding the end plug. Specifically, the pressing force is preferably about 0.5 to 5 kgf.

After the end plug 6 is press-fitted in this way, the motor 10 drives the drive transmission belts 13a and 13b.
The joint portion is welded in the circumferential direction by tungsten, arc welding or the like while synchronously rotating the coating tube 7 and the spindle 14 via the above.

By the way, since the end plug holding core 5 is rotatably supported by the stroke ball bearing 18, it is possible to omit the rotation of the spindle 14, but when the rotation of the spindle 14 is omitted. , Core 5 for holding end plugs constantly and stroke ball bearing 18
Since it constantly rotates, it is difficult to maintain the rotation accuracy from the viewpoint of wear resistance, and the rotating inertia of the end plug holding core 5 is taken over by the rotating force of the cladding tube 7, so that welding is performed. There is a possibility that torsional stress will occur on the part. In addition, there is a possibility that abrasion may occur due to the rotary contact between the end plug 6 and the end plug holding core 5.

On the other hand, in the present invention, as described above, the spindle 14 itself rotates in synchronization with the coating tube 7 to solve the above-mentioned problems.

On the other hand, at the time of welding, the welded portion thermally expands due to welding heat input and extends axially toward the air cylinder 22 side. In this case, the air cylinder 22 is monitored while the pressing force of the end plug holding core 5 is monitored by the load cell 24. The core 5 for holding the end plug can be flexibly moved by following the extension of the welded portion of the cladding tube through the support rod 26.

After the welding, the welded part shrinks toward the cladding tube due to the solidification shrinkage of the welded part, but the core for holding the end plug is also moved by the air cylinder 22. In addition, during welding, due to the thermal stress balance of the welded part, a twisting action occurs in the rotational direction different from the rotational angular velocity of the machine.
The stroke ball bearing 18 allows the end-plug holding core 5 to freely rotate, thereby alleviating the generation of torsional stress in the welded portion.

Although the air cylinder is used in the above-mentioned embodiment, the same operation can be performed by using a drive source such as an actuator other than the air cylinder.

FIG. 2 shows the air cylinder 2 in the above device.
2 is a diagram showing a pressing force control method of No. 2, in which the measured values of the compression / tensile load measuring load cell 24 and the displacement meter 30 are input to the computer unit 31, and an appropriate pressing force is applied to the electropneumatic converter 32.
Is converted into air pressure by the air cylinder 22 and input to the air cylinder 22, and the air cylinder 22 is operated so as to have an appropriate pressing force.

Therefore, it is possible to set the load pattern in advance and operate the air cylinder 22 to hold the end plug so that the set load is applied to the end plug during welding. The pressing force of the air cylinder 22 can be feedback-controlled so as to be within the specified value range.

In the above embodiment, the O-ring 28 is provided on the outer circumference of the large diameter portion of the support rod 26 in order to maintain the airtightness of the spindle 14, but the sliding resistance of the O-ring 28 is The static or dynamic frictional force fluctuates at less than the usual 3 kgf. Therefore, as shown in FIG. 3, the spindle 14 and the large-diameter portion 26a of the support rod 26 are slid by using a metal bellows 33, or by using a rubber bellows drum 34 as shown in FIG. It is possible to reduce the dynamic resistance and improve the controllability of the appropriate pressing or pulling back force of the core for holding the end plug.

[0030]

As described above, according to the present invention, the end plug holding core is axially movable and rotatably mounted in the spindle which rotates in synchronization with the cladding tube. Since the core drive mechanism allows axial movement adjustment, the end plug can be held with a constant pressing force in the axial direction during welding, and welding can be performed without applying excessive force to the welded portion, further improving quality. Can be improved. If a sensor that measures the load applied by the end plug holding core is provided, the axial load that acts on the weld during welding and the amount of axial expansion and contraction due to welding heat can also be measured. It is also possible to improve work management.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view showing an end plug holding device for fuel rod welding according to the present invention.

FIG. 2 is a diagram showing a pressing force control method of the apparatus of FIG.

FIG. 3 is a diagram showing an example of a seal portion of a welding chamber.

FIG. 4 is a view showing another example of the sealing portion of the welding chamber.

FIG. 5 is a partial cross-sectional view showing a conventional end plug support device.

FIG. 6 is a partial cross-sectional view showing another example of the conventional end plug support device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding chamber 2 Fuel rod 5 End plug holding core 6 End plug 7 Cladding pipe 13a, 13b Drive transmission belt 14 Spindle 18 Stroke ball bearing 20 Core drive mechanism 22 Air cylinder 24 Load cell 25 for compression / tensile load measurement 25 Relay fitting 26 Support Rod 27 Rotation Bearing 28 0 Ring 30 Displacement Meter

Claims (4)

[Claims] 1. When welding end plugs to the ends of fuel rod cladding tubes,
In the fuel rod welding end plug holding device for holding the end plug to be welded, a spindle rotating in synchronization with the cladding tube is provided on the same axis as the axis of the cladding tube inserted and mounted in the airtight welding chamber. The end plug holding core is coaxially mounted in the spindle so as to be movable and rotatable in the axial direction, and the end plug holding core is held on the same axis as the end plug holding core. A core drive mechanism that supports the rear end surface of the core and is adjustable in movement in the axial direction is provided.
End plug holding device for fuel rod welding. 2. The core drive mechanism is provided with a sensor for measuring a load value applied by the core and a device for measuring an axial movement amount of the core. End plug holding device for fuel rod welding. 3. The fuel rod welding end according to claim 2, wherein the core driving mechanism is adjusted so that the load by the end plug holding core becomes a set value when welding the end plug. Plug holding device. 4. A sealing device is provided on an outer peripheral surface of a supporting member of a core for holding an end plug provided at a tip end portion of a core driving mechanism so as to maintain airtightness with an inner surface of a spindle. The end plug holding device for welding a fuel rod according to claim 1, which is characterized in that.