JPH0814638B2 - End plug welding device for nuclear fuel rods - Google Patents

Description

TECHNICAL FIELD The present invention relates to an end plug welding apparatus for nuclear fuel rods.

[Conventional technology]

Conventionally, a nuclear fuel rod used in a nuclear reactor has a required number of pellets 2 in a cladding tube 1 made of a zirconium alloy or stainless steel having one end plugged with an end plug 4, as shown in FIG. It is filled with a spring 3 for pressing the pellet 2 against one side. The cladding tube 1 is filled with an inert gas 6. Generally, when manufacturing the above nuclear fuel rod, a method of filling the pellet 2 and the spring 3 and then replacing the inside of the cladding tube 1 with an inert gas 6 and then attaching an end plug 5 to the other end and hermetically welding is adopted. Has been. Sealing welding methods include laser welding and TIG (tungsten inert gas welding) welding methods.

The conventional laser welding method is, as described in JP-A-60-113198, that one end of the cladding tube is inserted into the welding chamber through an opening in which the cladding tube provided on the side wall of the welding chamber can be inserted. , Focusing the laser light from a laser light introduction window provided in a part of the welding chamber side wall orthogonal to the opening, while rotating the cladding tube in the welding chamber replaced by an inert gas and end cap Weld the cladding. One of the important functions here is the sealing property of the opening for inserting the cladding tube. This seal replaces the inside of the welding chamber with inert gas to prevent leakage during vacuum evacuation, withstand pressure to withstand the pressure after the introduction of inert gas, and wear and wear due to rotary sliding when rotating the cladding during welding. It is required to have functions such as the absence and presence, and the ability to open and close when inserting and removing the cladding tube. In the above conventional method, when the pressure of the inert gas is atmospheric pressure or a low pressure close to atmospheric pressure, the conventional general seal is satisfied, but the inside of the nuclear fuel rod is pressurized to a high pressure (generally 5 to 30 atmospheric pressure). When welding by welding, it is impossible to satisfy all the functions of the above-mentioned seal.

On the other hand, the TIG welding method in which a conventional nuclear fuel rod is filled with a high-pressure inert gas and the end plugs are hermetically welded is disclosed in Japanese Patent Publication No. 53-38396. One end is inserted, and then the joint portion of the end plug having a small hole-shaped orifice communicating with the inside of the fuel rod is welded with a TIG electrode. That is, in order to protect the seal of the cladding tube insertion opening, at the atmospheric pressure (low pressure), the welding of the cladding tube and the end plug is performed in the welding chamber in the circumferential direction while rotating the cladding tube, and then afterwards. The rotation of the cladding tube is stopped, and the inert gas is pressurized to a high pressure by the same chamber or another chamber, and the orifice of the end plug attached to the cladding tube is sealed by TIG welding or laser welding. There is also a method in which the cladding pipe and the end plug are circumferentially welded, and at the same time, the seal welding of the orifice is sealed by TIG welding.

[Problems to be solved by the invention]

In the above-mentioned prior art, in order to fill the nuclear fuel rod with a high-pressure inert gas through the welding chamber and seal-weld the end plug to the cladding tube, the pressure resistance, the vacuum leakage prevention property, and the elasticity for opening and closing, Severe conditions such as wear resistance of the seal when the cladding tube rotates are required to seal the cladding tube opening of the welding chamber. However, a seal satisfying all the above conditions has not yet been developed. Therefore, it is necessary to perform two combinations of welding chambers that perform circumferential welding of cladding and end plugs under atmospheric pressure (low pressure), and welding chambers that perform orifice sealing welding of end plugs at high pressure. The fuel rod manufacturing device is a mechanically complicated device. Further, in TIG welding at high pressure, the degree of wear of the electrode is great and the arc gap during welding changes, making reliable welding difficult, and the electrode must be frequently replaced. When laser welding is used, since there is no electrode, such frequent electrode replacement is unnecessary and highly reliable welding can be performed. However, even in laser welding, it is necessary to rotate the cladding tube, and the above-mentioned problem of sealing property remains. In addition, the method of sealing and welding the orifice after pressurizing it to a high pressure through the orifice of the end plug naturally has a space in the orifice so that the weld penetration is shallow and the weld has sufficient reliability against pressure resistance. I can't.

An object of the present invention is to provide an end plug welding device for a nuclear fuel rod, which can improve the sealing performance between the cladding tube and the welding chamber.

[Means for solving problems]

The above-mentioned object is a welding chamber that surrounds one end of the cladding tube of the nuclear fuel inserted therein, and the welding chamber is constituted by a member through which the laser passes, and the end that closes the cladding tube and the end portion of this cladding tube. A welding chamber having a laser entrance that continuously surrounds the periphery of the weld with the stopper, a means for replacing the gas in the welding chamber with an inert gas, and at least a first line on the extension of the axis of the cladding tube. The laser guide means in which the first laser emission port is located, and the laser introduction port arranged opposite to the first laser emission port, to the second laser emission port provided opposite to the laser incident port. Tell
Further, it can be achieved by including a laser irradiation means having a laser transmission means rotatably provided around the axis of the cladding tube and a means for rotating the laser transmission means.

[Action]

Since the laser can be welded while rotating the laser along the welded portion between the cladding and the end plug by the rotation of the laser processing means, it is not necessary to rotate the cladding. Therefore, the seal between the welded chamber and the cladding tube only needs to maintain the airtightness between the sheathed tube that does not rotate and the welded chamber, and the sealing function is significantly improved.

〔Example〕

An end plug welding apparatus for a nuclear fuel rod, which is an embodiment of the present invention, will be described below with reference to FIGS. 1 and 2. Welding chamber 7
Is the first container portion 7a, the second container portion 7b, and the laser light introduction window 7c.
The laser light introducing window 7c is arranged in the middle between the first container portion 7a and the second container portion 7b, and the annular laser light introducing window is formed.
7c is firmly fixed to the first container part 7a and the second container part 7b. The laser light introduction window 7c is continuous in the circumferential direction of the welding chamber 7. The laser light introducing window 7c is made of a material which is equivalent to the material of the lens generally used for laser projection and which is heat resistant and transparent (for example, glass). The first container portion 7a is provided with an opening for inserting the cladding tube 1 into the welding chamber 7, and this opening is provided with a seal 8 made of an elastic body. The seal 8 is pressed against the outer surface of the coating tube 1 and the first container portion 7 by the operation of the cylinder 9 and the ram 10, and is brought into close contact with the outer surface of the coating tube 1. In this state, the airtightness inside and outside the welding chamber 7 is maintained. When the cladding tube is removed from the welding chamber 7, a gap is created between the inner surface of the seal 8 and the outer surface of the cladding tube 1 by moving the cylinder 9 in the direction of separating the ram 10 from the seal 8. Therefore, the cladding tube 1 can be pulled out from the welding chamber 7. Reference numeral 26 is a chuck for gripping the cladding tube 1.
The roller 11 horizontally supports the cladding tube 1 and
Has a role of a guide when inserting into the welding chamber 7. The end plug holder 12 provided in the second container portion 7b is provided with the end plug 5
To support the end plug 5 during welding.
The end plug holder 12 is movable by a cylinder 25 in the axial direction. A vacuum exhaust pipe 13 which is a gas replacement device and an inert gas supply pipe 14 are connected to the welding chamber 7. Valves are provided in the vacuum exhaust pipe 12 and the inert gas supply pipe 14, respectively, as shown in FIG.

The laser irradiation device 15 has a laser processing head 15A and a laser guide tube 16. The laser processing head 15A is provided at the tip of the laser guide tube 16. A lens 24 is provided at the laser emission port 31 of the laser processing head 15A. The laser guide tube 16 has a crankshaft shape. A part of the laser guide tube 16 is located on the extension line of the axis of the cladding tube 1,
Supported by 17. A laser reflector 32, which is a laser transmission cutoff, is provided in the laser guide tube 16 and the laser processing head 15A. The laser guide tube 16 is rotated by a driving unit that is provided on the laser guide tube 16 and includes a pulley 18, a belt 19, a pulley 20 and a motor 21. The laser guide tube 22 guides the laser light 23 to the laser guide tube 16 from a laser oscillator (not shown), and is fixedly installed. Laser guide port 16 of laser guide tube 16 and laser guide tube
The axis of the laser emission port 33 of 22 is on an extension of the axis of the cladding tube 1.

In the above-described embodiment, when welding the end plug 5 to one end of the cladding tube 1, the cladding tube 1 is inserted into the welding chamber 7 by the roller 11 and the tube end of the cladding tube is inserted below the lens 24. Then, the jacket 26 is gripped and fixed by the chuck 26. At this time, the end plug 4 is already welded to one end of the cladding tube 1 outside the welding chamber 7, the fuel pellet 2 is filled in the cladding tube 1, and the spring 3 is inserted. The spring 3 is on the side of the welding chamber 7. Next, the seal 8 is brought into close contact with the coating pipe 1 by the cylinder 9 to seal the welding chamber 7 and the air inside the welding chamber 7 and the coating pipe 1 is removed by a vacuum exhaust device (not shown) connected to the vacuum exhaust pipe 13. Exclude. Then, the valve of the vacuum exhaust pipe 13 is closed and the valve of the inert gas supply pipe 14 is opened to supply the high pressure inert gas (He) inert gas supply pipe 14 into the welding chamber 7. The inert gas is also filled in the cladding tube 1.
The piston 25 is moved to the left in FIG. 1 to press the end plug 5 held by the end plug holder 12 against the open end of the cladding tube 1 (existing in the welding chamber 7). In the above state, the laser light 23 is guided to the laser processing head 15A through the laser guide cylinder 22 and the laser guide cylinder 16, and the laser light 23 is reflected by the lens 24.
Is projected onto the joint between the cladding tube 1 and the end plug 5 through the laser beam introduction window 7c. The laser irradiation device 15 is rotated by the motor 21. Therefore, a part of the laser guide tube 16 and the laser processing head 15A swirl outside the welding chamber 7, so that the laser light 23 focused by the lens 24 is welded to the cladding tube 1 and the end plug 5. It moves the entire circumference of the weld while being irradiated. In this way, the cladding tube 1 and the end plug 5 are welded.
According to the present embodiment, it is possible to maintain sufficient airtightness between the welding chamber 7 and the cladding tube 1 at the time of welding without deteriorating the features of laser welding in which the electrodes need not be replaced and the reliability of the welded portion is high. To be done. Therefore, there is an effect that the nuclear fuel rod can be easily manufactured under a stable pressure without the leakage of the inert gas. Moreover, since the rotating operation of the cladding tube 1 is eliminated, the wear of the seal 8 is reduced and the damage is also eliminated, and the life of the seal 8 becomes longer than in the conventional case. Further, since it is not necessary to provide the end plug 5 with the orifice for gas replacement, welding for sealing the orifice provided on the end plug is eliminated. Therefore, the time required for end plug welding is significantly shortened and the reliability of the fuel rod is improved. Furthermore, the equipment required for end plug welding can be significantly reduced. Further, by laser welding, welding with a narrow bead width and a good bead shape can be performed with high reliability.

Another embodiment of the present invention will be described with reference to FIGS. 3 and 4. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and the description thereof will be omitted. This embodiment is a laser irradiation device.
A laser processing head 15A for projecting a laser beam 23 of 15C is provided in parallel with the axial center of the cladding tube 1 so as to face the side end of the welding chamber 7D. The annular laser beam introduction window 7C is provided at the side end of the welding chamber 7D. An annular laser beam redirecting mirror 27 is provided in the welding chamber 7D so as to be fixed concentrically with the axis of the cladding tube 1. Laser processing head 15A lens 2
4 is opposed to the laser light introduction window 7C. Welding in the present embodiment is similar to the above-described embodiment, the laser irradiation device 17
C is rotated by a motor 20 concentrically with the axis of the cladding tube 1. The laser light 23 focused and projected from the lens 24 of the laser processing head 15A enters the welding chamber 7D from the laser light introduction window 7C and the cladding tube 1 and the end plug 5 via the laser light redirecting mirror 27.
According to the present embodiment in which the joint portion is irradiated and the joint portion is welded over the entire circumference, the present embodiment has the same effect as that of the above-mentioned embodiment, and the spatial coupling of the peripheral equipment makes it possible to obtain the same effect as the above-mentioned embodiment. When the outer circumference of the welding chamber can be used, laser light can be emitted from the side edge of the welding chamber, which is effective in reducing the space used.

〔The invention's effect〕

According to the present invention, the seal of the welding chamber that is closely attached to the outer surface of the cladding tube does not require the rotating operation of the cladding tube, so that the inside and outside of the welding chamber can be easily and firmly sealed without wear or scratches, so that it can be evacuated. The inert gas can be filled into the nuclear fuel rods at a stable pressure without air mixing into the welding chamber from the outside and no gas leakage when the high-pressure inert gas is supplied.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of an end plug welding apparatus for nuclear fuel rods, which is an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II of FIG. 1, and FIG. FIG. 4 is a vertical sectional view of another embodiment of the invention, and FIG.
-II sectional view and FIG. 5 are longitudinal sectional views of nuclear fuel rods. 1 ... Cladding tube, 2 ... Fuel pellet, 4,5 ... End plug, 6
…… Inert gas, 7C …… Laser light introduction window, 7D …… Welding chamber, 8 …… Seal, 12 …… End plug holder, 13 …… Vacuum exhaust pipe, 14 …… Inert gas supply pipe, 15, 15C: Laser irradiation device, 15A: Laser processing head, 16,22 ... Laser guide tube, 21 ... Motor, 23 ... Laser light, 24 ... Lens,
27 …… Laser light redirecting mirror.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyasu Ito 3-1, 1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi Factory (72) Inventor Hidenori Hanami Saiin Oiwake, Kyoto, Kyoto Prefecture Town 25, Shimadzu Corporation Gojo Factory (72) Inventor Shigeo Kunishima 25, Saiin Oiwakecho, Ukyo-ku, Kyoto City Kyoto Prefecture Shimazu Factory Gojo Factory (56) Reference JP-A-63-302399 ( JP, A) JP 63-79098 (JP, A) JP 54-99750 (JP, A) JP 54-133443 (JP, A) JP 60-115391 (JP, A) JP 47-14600 (JP, A)

Claims (1)

[Claims] 1. A welding chamber that surrounds one end of a cladding tube for nuclear fuel inserted therein, the welding chamber being constituted by a member through which a laser passes, and the end for sealing the cladding tube and the end portion of the cladding tube. A welding chamber having a laser entrance that continuously surrounds the periphery of the weld with the stopper, a means for replacing the gas in the welding chamber with an inert gas, and at least a first line on the extension of the axis of the cladding tube. The laser guide means in which the first laser emission port is located, and the laser introduction port arranged opposite to the first laser emission port, to the second laser emission port provided opposite to the laser incident port. An end plug of a nuclear fuel rod, comprising: a laser irradiating means having a laser transmitting means that transmits and is rotatable about an axis of the cladding tube; and a means for rotating the laser transmitting means. Welding equipment Place.