JPH0615000U - Seam welding equipment for end plugs - Google Patents

Abstract

(57) [Abstract] [Purpose] A seam welding device for end plugs that welds a perforated end plug to the opening of a cladding tube by a nuclear fuel rod used in a nuclear reactor, prevents welding defects due to air bubbles, It aims to improve the soundness, quality and reliability of welding. In a seam welding apparatus for welding a perforated end plug to an open end of a nuclear fuel rod, a welding chamber 1 and an airtight chamber 2 are provided.
And a gas supply pipe 21 for supplying an inert gas to the airtight chamber 2, a first control valve 20 for controlling the pressure in the airtight chamber 2 is provided on the gas supply pipe 21, and the outer periphery of the end plug 10 A seal member 24 is disposed between the end portion and the inner peripheral surface of the end plug holder 22 that holds the end plug, and the communication hole 1 of the end plug 10 is provided during welding.
The space inside the end plug holder 22 communicating with the inside of the cladding tube 6 via 0a is cut off from the airtight chamber 2, and the pressure in the space inside the end plug holder 22 that is cut off from the airtight chamber 2 is controlled. The second control valve 25 is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an end plug seam welding apparatus for welding a perforated end plug to an opening of a cladding tube of a nuclear fuel rod used in a nuclear reactor, for example.

[0002]

[Prior art]

 Conventionally, this type of seam welding device for end plugs is configured as shown in FIGS. 6 and 7.

That is, in FIGS. 6 and 7, an airtight chamber 2 is formed in the center of a welding chamber 1 having a substantially rectangular shape in a seam welding apparatus, and a control valve 3 is formed in the airtight chamber 2. The gas supply pipe 4 it has is connected. Further, in the welding chamber 1, a nuclear fuel rod 5 in which a large number of oxide ceramic sintered bodies 7 made of uranium or plutonium are loaded in a cladding tube 6 is rotatably fitted. It is horizontally inserted into the central portion, and the open end portion 6a of the covering tube 6 extends substantially in the central portion of the airtight chamber 2.

On the other hand, an end plug holder 8 is horizontally provided in the welding chamber 1 so as to face the open end 6 a of the coating tube 6, and the end plug holder 8 is attached by an end plug press-fitting mechanism 9. Therefore, the welding chamber 1 is provided so as to be able to advance and retreat toward the center. Further, the end plug holder 8 is provided with a perforated end plug 10 so as to be inserted into the open end portion 6a of the covering pipe 6, and the perforated end plug 10 has a communication hole 10a. One end opening is bored in the axial direction, and the other end opening is bored so as to communicate with the outer peripheral portion of the perforated end plug 10, and this communication hole 10a is provided with the perforated end plug 10 and the opening 6a. When the anastomosis is made, the inside of the covering tube 6 and the airtight chamber 2 are communicated with each other through the communication hole 10a. Further, a seam welding device 11 is installed vertically in the welding chamber 1 located right above the opening 6a, and a seam torch 11a of the seam welding device 11 is arranged in the axial direction of the cladding tube 6. Are provided orthogonally. An exhaust pipe 12 equipped with an on-off valve (not shown) is provided in the lower part of the welding chamber 1 so as to communicate with the airtight chamber 2. The other end of the exhaust pipe 12 has a vacuum. A pump (not shown) is connected.

Therefore, in the seam welding apparatus for end plugs described above, the cladding tube 6 of the nuclear fuel rod 5 is fitted into the welding chamber 1 in advance and inserted into the airtight chamber 2 at a substantially central portion, and the end plug ho The perforated end plug 10 is inserted into the rudder 8 so as to face the opening 6a of the covering tube 6.

Next, the airtight chamber 2 is evacuated to a vacuum by a vacuum pump, and then the control valve 3 is opened to supply an inert gas through the gas supply pipe 4 to the airtight chamber 2 and the coating pipe 6. To fill. As a result, the pressure in the airtight chamber 2 and the internal pressure of the nuclear fuel rod 5 become equal.

Next, the end plug holder 8 anastomoses the perforated end plug 10 into the opening 6 a of the covering tube 6. Then, the airtight chamber 2 and the inside of the coating tube 6 are communicated with each other through the communication hole 10a. After that, the seam torch 11a of the seam welding device 11 seam-welds the end of the opening 6a and the joint surface of the perforated end plug 10 while rotating the covering pipe 6 and the end cap holder 8 together. .

[0008]

[Problems to be solved by the device]

 However, in the above-described seam welding device for end plugs, the pressure in the hermetic chamber 2 and the internal pressure in the nuclear fuel rods 5 are equal, so that the metal a melted by seam welding is enlarged as shown in FIG. The weight becomes larger than the surface tension, the molten metal a melts down into the cladding tube 6 of the nuclear fuel rod 5, the molten metal a catches the void b, and as a result, bubbles c are generated. However, this causes welding defects, which impairs the integrity of the welding and causes problems in quality and reliability.

In order to solve the above problems, the present invention provides a seam welding device for end plugs, which prevents the occurrence of welding defects due to air bubbles and improves the soundness, quality and reliability of welding. The purpose is to do.

[0010]

[Means for Solving the Problems]

 The present invention is a seam welding device for welding a perforated end plug to an open end of a nuclear fuel rod, in which a hermetic chamber is formed in the welding chamber, and a gas supply pipe is provided to supply the inert gas to the hermetic chamber. A seal provided between the outer peripheral portion of the end plug and the inner peripheral portion of the end plug holder holding the end plug, the first control valve being provided in the gas supply pipe so as to control the pressure into the airtight chamber. A member is provided so as to block a space in the end plug holder from the airtight chamber, and the above end plug holder is provided with a second control valve for controlling the pressure in the space in the end plug holder which is blocked from the airtight chamber. It is a thing.

[0011]

[Action]

 In advance, a cladding tube of a nuclear fuel rod was fitted into the welding chamber and inserted into the airtight chamber at a substantially central portion, and a part of the end stopper holder was provided with a perforated end plug facing the opening of the cladding tube. The seal member is placed between the outer peripheral portion of the end plug and the inner peripheral portion of the end plug holder that holds the end plug to shut off the space inside the end plug holder from the airtight chamber. Then, the airtight chamber is evacuated to a vacuum, and then the first control valve is opened to supply an inert gas to the airtight chamber through a gas supply pipe to control the airtight chamber to a predetermined pressure. After that, the perforated end plug is anastomosed with the opening of the covering pipe, and the seam torch of the seam welding device is used to rotate the covering pipe and the holding body at the joint surface between the end of the opening and the perforated end plug. Seam weld. Then, as the temperature rises due to welding, the second control valve is opened to discharge the inert gas in the cladding tube through the communication hole of the perforated end plug and the gas tube, and seam welding is performed while controlling the cladding tube to a predetermined pressure. .

[0012]

【Example】

 Hereinafter, the present invention will be described with reference to an illustrated embodiment in which a perforated end plug is welded to an opening of a cladding tube by a nuclear fuel rod.

The present invention will be described by giving the same reference numerals to the same components as those of the above-described specific example.

In FIG. 1, reference numeral 1 denotes a substantially quadrangular welding chamber in a seam welding machine. An airtight chamber 2 is formed in the center of the welding chamber 1, and the airtight chamber 2 is formed in the airtight chamber 2. Is connected to and connected to a gas supply pipe 21 having a first control valve 20. Further, the welding chamber 1 is rotatably fitted with a cladding tube 6 of a nuclear fuel rod 5 in which a large number of oxide ceramic sintered bodies 7 made of uranium or plutonium are loaded in the cladding tube 6. The open end portion 6a of the covering pipe 6 extends to a substantially central portion of the airtight chamber 2.

On the other hand, in the welding chamber 1, an end plug holder 22 is horizontally provided so as to face the open end portion 6 a of the coating pipe 6, and the end plug holder 22 is operated by the end plug press-fitting mechanism 9. The welding chamber 1 is provided so as to be able to advance and retreat toward the center side. The end plug holder 22 is formed with a space for holding the perforated end plug 10 to be inserted into the opening 6a of the covering pipe 6 and mounted, and the perforated end plug 10 has one end thereof. A communication hole 10a is formed in the tip surface of the stopper 10 and has the other end communicating with the outer peripheral portion of the end stopper 10. Further, in the end plug holder 22, for example, a sealing member 24 such as an O-ring is provided on the outer peripheral part of the perforated end plug 10 and the inner peripheral part of the end plug holder 22 which holds the perforated end plug 10. It is provided so as to block the space between them, that is, the inside of the coating tube 6 from the airtight chamber 2. The end plug holder 22 communicates with the space inside the end plug holder 22, and A gas pipe 26 having a control valve 25 is provided.

On the other hand, a seam welding device 11 is vertically installed in the welding chamber 1 located right above the opening 6 a. It is provided orthogonal to the direction of the heart. An exhaust pipe 12 equipped with an on-off valve (not shown) is provided in the lower portion of the welding chamber 1 so as to communicate with the airtight chamber 2. The other end of the exhaust pipe 12 is provided with a vacuum. Pump (not shown) is connected.

The operation of the present invention will be described below.

Therefore, the cladding tube 6 of the nuclear fuel rod 5 is fitted in the welding chamber 1 in advance and inserted into the substantially central portion of the airtight chamber 2, and the perforated end plug 10 is inserted into the end plug holder 22. Then, the ruler member 24 is pulled through to face the opening 6a of the covering tube 6 and be inserted and inserted.

Thereafter, the airtight chamber 2 is evacuated by a vacuum pump to make it vacuum, and then the first control valve 20 is opened to supply an inert gas to the airtight chamber 2 through the gas supply pipe 21. The airtight chamber 2 and the coating tube 6 are controlled to have a predetermined pressure. Further, the perforated end plug 10 is pushed out through the end plug holder 22 into the opening 6a of the covering tube 6 and anastomosed.

Then, the seam torch 11 a of the seam welding device 11 seam-welds the end of the opening 6 a and the joint surface of the perforated end plug 10 while rotating the covering pipe 6 and the holding body 9.

However, since the inside of the airtight chamber 2 and the inside of the covering pipe 6 are blocked by the seal member 24 as described above, the pressure P inside the covering pipe 6 is as shown by the solid line in FIG. As the temperature rises due to welding, the internal pressure of the cladding tube 6 may rise and exceed the welding limit ΔP, and gas may be ejected from the weld metal portion into the hermetic chamber 2 to make welding impossible.

Therefore, in the present invention, an increase in the internal pressure of the coating pipe 6 is measured, the opening degree of the second control valve 25 is controlled according to the progress of welding, and the communication hole 10a and the gas pipe 26 are passed through. Then, the pressure of the covering pipe 6 is controlled to the pressure Pr as shown by the dotted line in FIG.

Therefore, according to the present invention, during seam welding, the internal pressure of the cladding tube 6 is controlled by the opening operation of the second control valve 25, and the internal pressure of the cladding tube 6 is set to a pressure at which molten metal does not melt down. Since the seam-welding is performed between the perforated end plug 10 and the opening 6a of the covering tube 6 while holding the welding, it is possible to prevent the occurrence of welding defects due to bubbles.

Next, FIG. 2 is a view showing another embodiment of the present invention. Instead of the gas pipe 26 having the second control valve 25 in the above-mentioned embodiment, the inside of the end plug holder 22 is replaced. Is formed with a buffer tank 27 communicating with the inside of the coating pipe 6 through the communication hole 10a.

Therefore, when the pressure inside the cladding tube 6 increases during the welding process, the inside pressure of the cladding tube 6 is controlled because the inside of the cladding tube 6 communicates with the buffer tank 27, and the welding limit ΔP or less is reached. can do.

In the above embodiment, the internal pressure of the cladding tube 6 is controlled, but the control of the first control valve 20 can prevent the occurrence of welding defects.

That is, as shown in FIG. 4, the opening degree of the first control valve 20 is controlled according to the increase of the internal pressure Pr of the cladding tube 6 to control the pressure Pc of the airtight chamber 2, and the airtight chamber 2 is always maintained. Is controlled so that the internal pressure P c thereof is larger than the internal pressure Pr of the cladding tube 6 of the nuclear fuel rod 5 and the difference is below the welding limit ΔP. Thus, it is possible to prevent the molten metal from melting down into the coating tube 6 due to the pressure difference between the coating tube 6 and the airtight chamber 2. Further, by controlling both the first control valve 20 and the second control valve 25, the pressure inside the airtight chamber 2 and the cladding tube 6 can be controlled as shown in FIG.

[0028]

[Effect of device]

 As described above, according to the present invention, the sealing member disposed between the outer peripheral portion of the end plug and the inner peripheral surface of the end plug holder that holds the end plug allows the end plug to be connected through the communication hole during welding. A second control valve for controlling a pressure in a space in the end plug holder, which is cut off from the airtight chamber, is provided in the end plug holder so that a space in the end plug holder communicating with the cladding tube is shut off from the airtight chamber. Therefore, the relative pressure between the cladding tube and the airtight chamber can be controlled during seam welding, seam welding can be performed to prevent molten metal from spilling into the cladding tube, and welding defects due to air bubbles can be prevented, and at the same time, welding can be performed. It has excellent effects such as improvement of soundness, quality and reliability.

[Brief description of drawings]

FIG. 1 is a front view showing a broken part of a seam welding device for an end plug according to the present invention.

FIG. 2 is a front view showing another embodiment of the present invention.

FIG. 3 is a graph showing an internal pressure rise curve of a cladding tube of a nuclear fuel rod of the present invention.

FIG. 4 is a graph showing the relationship between the pressure resistant chamber pressure of the present invention and the internal pressure of a nuclear fuel rod.

FIG. 5 is a graph showing the relationship between the pressure resistant chamber pressure of the present invention and the internal pressure of a nuclear fuel rod.

FIG. 6 is a front view in which a part of a conventional seam welding device for end plugs is broken and shown.

FIG. 7 is an enlarged view for explaining the operation of the conventional seam welding device for end plugs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding chamber 2 Airtight chamber 6 Cover pipe 10 Hole end plug 20 First control valve 21 Gas supply pipe 22 End plug holder 23 Holding body 24 Seal member 25 Second control valve 26 Gas pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Kurosawa 2-3-3 Kawa, Yokosuka City, Kanagawa Nihon Niclear Clear Fuel Co., Ltd.

Claims (2)

[Scope of utility model registration request] 1. In a seam welding apparatus for welding a perforated end plug to an open end of a nuclear fuel rod, an airtight chamber formed in a welding chamber, a gas supply pipe for supplying an inert gas to the airtight chamber, and A first control valve that is provided in the first gas supply pipe and controls the pressure into the airtight chamber, and is disposed between the outer peripheral portion of the end plug and the inner peripheral surface of the end cap holder that holds the end plug. ,
A sealing member that communicates with the inside of the cladding tube through the communication hole of the end plug during welding to isolate the space in the end plug holder from the airtight chamber, and the pressure in the space in the end plug holder that is shielded from the airtight chamber And a second control valve for controlling the end plug seam welding device. 2. A seam welding device for welding a perforated end plug to an open end of a nuclear fuel rod, wherein a hermetic chamber formed in the welding chamber, a gas supply pipe for supplying an inert gas to the hermetic chamber, and A first control valve that is provided in the first gas supply pipe and controls the pressure into the airtight chamber, and is disposed between the outer peripheral portion of the end plug and the inner peripheral surface of the end cap holder that holds the end plug. ,
It has a seal member for blocking a space in the end plug holder, which communicates with the inside of the cladding tube through the communication hole of the end plug during welding, from the airtight chamber, and a buffer tank which communicates with the space in the end plug holder. A seam welding device for end plugs.