KR820000309B1 - Apparatus for welding an end plug in a unclear fuel tuhe - Google Patents

Abstract

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Description

Devices for welding end plugs in nuclear fuel pipes

1 is a front view showing an arrangement used to accurately circumferentially form a cylindrical joint formed by a fuel pipe and a plug end in a welding chamber.

2 is an enlarged front view showing the position of the electrode tip for the fuel rod to be welded.

3 is a modified view of the invention in FIG.

The present invention relates to an apparatus for welding a plug at the end of a reactor fuel rod.

In the prior art, after the fuel pellets have accumulated in the fuel pipe, the end plugs located at the end of the tube adequately weld the pipe at the seam formed by contact at the plug fuel pipe boundary to form a fuel rod. One of the plugs is opened to introduce a gas fuel rod before starting and during welding. As circumferential welding at the seam, the side openings of the plug are welded in the pressure chamber to adhere to the inner region of the fuel rod under high pressure.

According to the reality, the end plug is welded onto the fuel pipe by inserting the plug pipe into the welding chamber, and the rotation stop therein is arranged so that the welding electrode ends are positioned at a fixed point with respect to the pipe plug seam. .

These points are now located on the plug, about 0.75 mm from the pipe plug seam for good weld parameters.

In the case of fuel rods, stops are not accurately located in the weld chamber, and small displacements away from the seam invert the volume permeation from the seam to the metal. Analysis of the welding action is carried out on a case-by-case basis and the welder does not push the end plug firmly against the stop in the welding room. Eventually, welding to the perimeter is done outside the area where effective welding can be obtained, and sometimes welding is not good because the transmission is not sufficient for sealing at the end plug seam.

There is a tendency to use a chuck to pull the fuel rods away from the stopper on which the fuel rod end plugs are located after the fuel rods are gripped. This is due to a displacement of about 0.15 millimeters in the seam and results in bad welding.

It is an object of the present invention to provide an apparatus for automatic welding of a plug at the end of a fuel rod during welding, which occurs only when the rod and plug are properly positioned relative to the welding electrode.

Characterized by a device with stopper 26 to prevent excitation of the welding electrode 28 when the fuel rod 22 is not properly positioned within the stopper 26, and is inert through the welding chamber during the welding period. A device for sealing the fuel rod in the stopper welding chamber located in the welding chamber so that the end plug is held in place in the proper position with respect to the device for circulating gas and the fixed welding electrode; Apparatus for welding end plugs into a nuclear fuel rod comprising a device for holding and rotating a fuel rod and a housing having a welding chamber, such as a fixed welding electrode therein, the housing having an opening for receiving the fuel rod. It is an intention of the invention.

In FIG. 1, the fuel rod end plug is snugly secured to the opening of the fuel rod stopper to accurately position the tube end plug seam with respect to the electrode end. The device consists of a base 10 supporting a spherical or cylindrical housing 12 having a bore 14 immersed into a diameter of 16 which again enters the distribution 18. The wall of bore 16 forms gas chamber 20 into which the end of rod 22 is inserted.

The rod 22 is closed by a plug 24 which is distributed and fixed to the end of the opening and the end of the plug 24 is in a supplementary opening formed in the end face of the stop 26.

As a general practice, the electrode 28 welds the end plug to the fuel pipe 22 circumferentially at the joint formed by the contact surface between the plug and the pipe. The components of bore 14 simultaneously seal the gas chamber 20 while holding the fuel rods 22 during the circumferential weld.

Although these components are well known by design, one can see the rotating bushing 36 and the pair of bearings 38 in the bore 14 rotating.

The pod 40 on the rotary bushing 36 enlarges the ends of faces 42 and 44, while the face 44 is arranged to select and slave the ram 46 at the end of the bushing 36. The collet halter 48 has a bore 50 that enters into the cone-shaped opening defined by the branch wall 52. The collect 54 is mounted as an axial opening 56 in the cone wall 52, the diameter of which allows the fuel rod 22 to be inserted through the central opening in the collect halter and the collet and ram 46 are shown in FIG. Rotary bushing 36 is primarily an entity, with rods 40 and ram 46 allowing the rotation of these components.

On the left side of FIG. 1, colletholter 48 is supplied with a radially extending flange 58 which bears against bearing 60 located on support plate 62. The mechanical and hydraulic cylinders 64 each have a reverse piston connected to the support plate 62 via connecting rods 66 and the arrangement is adapted to move to the right like the piston in the mechanical or hydraulic cylinders as in FIG. The support plate 62 has a flange face that encloses the fuel rod 22 and forces the collet holder to move the collet 54 to the right, thereby bringing it into an unmovable position. This action also actuates the fuel rod end plug in instant contact with the replenishment surface on the stop which helps to place the fuel rod joint in the correct position with respect to the electrode end 28. This left shift also causes the ram 46 to tighten the urethane enclosure 74 densely around the rod surface and prevents gas leakage from the gas chamber 20 during the welding period.

While the specific design of the welding chamber has been found, it is evident that in order to simplify the use of the welding chamber, including the seal, the end of the fuel rod is extended so that the fuel rod is rotated by the motor during welding.

As mentioned above, the electrode end is located within 0.75 mm of the tube end plug seam and high quality welding parameters are set for high purity and reliable welding. If the electrode ends are separated by small claws at the desired point, the weld penetration at the joint is inadequate. Since the fuel rods are manually positioned in the fuel chamber, they are assisted by the collet halter and the discrepancy in the welding position where the fuel rod plugs make instantaneous contact with the replenishment surface on the stopper may occur if the rods are correctly positioned in the stopper or off the bottom. Occurs. There is also the possibility that the plug end of the rod will always come out of its position immediately under the welding electrode, even if it pushes the rod with the welder attached and pushes the end plug against the stopper each time. Since most fuel rods are rotated by a rotary chuck, the chuck tends to pull the rod from the stopper that initiates the fuel rod rotation. In some cases a displacement of 0.015 cm is measured and this amount is derived from a defective electrode. It should also be noted that welding is not performed in the proper position every time since it is not easily detected in the poor weld radiograph due to low penetration of the welding material. In other words, low permeable welding rods may be inadvertently mounted in a reactor with the substantial potential for welding failures that occur during reactor operation.

The invention disclosed here overcomes the disadvantages listed above by using a vacuum switch mounted in a vacuum line leading to a stopper attached to the fuel rod end plug. As the vacuum rises to a predetermined level, during the introduction of the fuel rod, the fuel rod end plug is outside the bottom in the stop, in the correct position relative to the welding electrode in the gas chamber, and the vacuum switch initiates the welding process, thus closing the electrical circuit for the electrode. Structures employed to perform these functions include passages 76 in the end plugs that provide flow between the atmosphere and the interior of fuel rod 22. A similar passage 78 is formed centrally at stop 26, which leads to junction 84 via junction box 80 and pipe 82. The flowmeter 86 and the vacuum gauge 88 are connected to the connector 84 together with the vacuum switch.

Vacuum switches are well known in the art and are arranged to react to vacuum in the welding chamber when they reach a predetermined low value, which switches off the circuit from the power supply and powers unit 92 supplying electrode 28.

When attempting to weld the end plug 24 to the end of the fuel pipe 22, the pipe is manually pushed through the colletholder 48 so that the end plug advances out of the bottom in the stop. Since the end plug face depends on the replenishment opening formed in the stop 26, the actuator ensures that the fuel pipe end plug is positioned to purge the welding electrode. Plate 62 moves to the right, as shown in Figure 1, for the colletholder to grab the fuel rod 22, and in progress, the ram 46 moves to the right to tighten the urethane seal 75 tightly around the fuel pipe. The drive then rotates the fuel rod past the pulley 68. At about the same time, introducer or vacuum pump 86 creates a vacuum in lines 82 and passages 78 and 76, reducing the pressure in the fuel rod 22. Helium gas under micropressure is also allowed to flow from the inlet 94 through the weld chamber to ensure the continuation of the inert atmosphere to provide an inert atmosphere for welding.

The vacuum switch closes the circuit welding the unit 92 and the electrode 28 for the start of the welding operation when the vacuum pump reaches its intended low vacuum by continuing the operation to lower the fuel rod.

If the fuel rod end plug is not bottomed in the stopper, helium flows from the gas chamber through the outer surface or the space between the end plug and the replenishment opening in the stopper 26. Helium leakage enters passage 78 and line 82, which excludes the necessary vacuum setting, so the vacuum switch does not close the circuit for the electrode and no welding occurs. Therefore, if any end plug is not properly in the stop 26, no welding is made into the fuel pipe and the position indicating whether the electrode 28 is in the correct position relative to the fuel pipe end plug seam.

In a modification, the stopper 26 comprises a central cavity surrounding the continuous switch 95 which is contacted by the end of the fuel pipe end plug 24 when the fuel rod is manually positioned in the welding chamber. The switch is connected to relay 96 via conductor 97 and lubrication ring 98. The lubrication ring is necessary because it rotates the switch during welding, the housing of the stopper 26. When the end plug 24 contacts and closes the continuous switch, the circuit is closed and completely made to the relay 96 to power the welding device 92 and the electrode 28. Again, the distance is arranged to be the exact dependence of the end plug with the continuous switch and the fuel pipe end plug seam is located within 0.030 of the fixed electrode in the welding chamber.

It is desirable to position the electrode past the end plug side of the seam to ensure proper weld penetration.

The stopper 26 can be moved axially by the end of the fuel rods when subordinated by the fuel rod plugs to close the continuous switch located in the relay 96.

Claims (1)

It is characterized by a device with the stopper 26 to prevent the welding electrode 28 from being excited when the fuel rod 22 is not properly positioned in the stopper 26, and inert gas through the welding chamber during the welding period. When the end plug is in place in the proper position with respect to the device for circulating the fixed welding electrode and the stopper located in the welding chamber to be fixed by the fuel rod end plug, the device for sealing the fuel rod in the welding chamber and the fuel rod An apparatus for welding an end plug into a nuclear fuel rod, comprising a device for holding and rotating, the housing having an opening for receiving a fuel rod, the housing having a welding chamber with a fixed welding electrode therein.

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