JPH01306094A - Laser beam welding equipment - Google Patents

Abstract

PURPOSE:To prevent soot of metallic vapor from moving to the side of a window and the window from being eroded or broken by providing a partition having through holes passed by laser beams at both ends and in the intermediate part of a pressurized room. CONSTITUTION:A fuel rod A is inserted into a screw member 34 and the left end part is brought into contact with the edge part of a hole of a cylindrical body 25. Then, the end face of a wind mount 8 is pressed to the end face of a chamber 20, the air in the pressurized room 26 is evacuated. Then, helium gas is supplied from an inlet into the pressurized room 26 to substitute the inner part of the fuel rod A for helium gas. The laser beams are focused by a lens 40, transmits the window 10, irradiates the end part of the fuel rod A, welds and blocks the hole formed at a terminal plug of the fuel rod A. At this time, metallic vapor makes soot but it is hard for the soot to move to the window side by the partition of the cylindrical body 24. Then, if helium gas is discharged from the outlet, it flows from a room 26a to a room 26b, the soot, too, moves to the room 26b side but since the inside of the partition is tapered, the soot moves smoothly, hardly adheres to the window 10 and the window 10 is prevented from being eroded or broken.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser welding device suitable for use in welding the ends of fuel rods used in nuclear reactors.

[Prior Art] For example, a fuel rod used in a nuclear reactor such as a pressurized water reactor has a large number of fuel pellets housed inside a cladding tube, and both ends of the fuel pellets are closed with end plugs. Inside,
High-pressure helium gas is sealed in the cladding tube to prevent pressure loss inside the reactor.

When filling helium gas into the cladding tube, a hole is formed in one end plug that communicates with the inside and outside of the cladding tube, and the hole in the end plug is laser welded in a high-pressure helium gas atmosphere. I'm trying to block it. Laser welding equipment that performs such welding conventionally has a pressurized chamber inside with a glass window, and a fuel rod is inserted into the chamber and the end plug is exposed inside the pressurized chamber. The hole in the end plug is welded by laser light transmitted through the glass window.

[Problems to be Solved by the Invention] By the way, when the above laser welding device is used, metal vapor generated by welding becomes soot and gradually adheres to the glass window. Therefore, such soot is melted by the laser beam, and the heat causes the glass window to melt or break.

[Purpose of the Invention] This invention has been made to solve the above problems, and can prevent soot from metal vapor from adhering to glass windows, thereby preventing melting and breakage of glass windows. It is an object of the present invention to provide a laser welding device that can prevent such occurrence.

[Means for Solving the Problems] The laser welding apparatus of the present invention is constructed by providing a partition between both ends of a pressurizing chamber, which defines a through hole through which a laser beam passes.

[Function] The presence of the partition makes it difficult for soot from metal vapor generated by welding to move toward the window. Furthermore, when soot enters the beam of laser light, it is heated by the laser beam, becomes ionized, and moves actively, scattering out of the beam. Therefore, soot is also prevented from moving toward the window through the through-hole of the partition.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a plan cross-sectional view showing a laser welding apparatus according to an embodiment, and FIG. 2 is a view taken in the direction of arrow (■) in FIG.

In these figures, reference numeral 1 indicates a base. A hydraulic cylinder 2 is attached to the center of the base 1, with a piston rod 2a directed leftward in the figure.

An index case 3 is fitted into the piston rod 2a of the hydraulic cylinder 2. As shown in FIG. 4, the index case 3 is formed with a flange 3a having a larger diameter than the other end 3b at one end, and an N-shape in the circumferential direction on the outer periphery of the other end 3b. Continuous grooves 4 are formed at a pitch of 60°. This index case 3 is fitted into a cylinder 5 attached to the hydraulic cylinder 2 so as to be relatively rotatable. In the cylinder 5, a plurality of bottles 6 whose axes are oriented in the radial direction are arranged at equal intervals in the circumferential direction. The bin 6 is urged toward the center by a coil spring 7, and its tip is engaged with the groove 4 of the index case 3. As a result, the index case 3 is rotated 60' clockwise along the groove 4 by extending the piston rod 2a.

Further, a wind mount 8 whose center portion is penetrated by the piston rod 2a is attached to the flange 3a of the index case 3, and a wind mount 8 is attached to the flange 3a of the index case 3.
It is tightened to the index case 3 side by a NAND 9 attached to the tip of the piston rod 2a.
It is designed to prevent relative rotation. Therefore, the wind mount 8 rotates together with the index case 3 and the piston mouth 2a by extending the piston rod 2a.

The window mount 8 is disk-shaped, and six glass windows io are fitted at the ends thereof at equal intervals in the circumferential direction. FIG. 3 is a plan view showing the runt 8 in the window. Reference numeral 11 in the figure is a fixture for attaching the window 10 to the window mount 8, and a hole 1], a through which a laser beam passes is formed in the center of the fixture.

On the other hand, a chamber 20 is attached to the base 1. Cylindrical holes 21.22 are formed at both ends of the chamber 20, and these cylindrical holes 21.22 are communicated with each other through a communication hole 23.

Two cylindrical bodies 24, 25 are fitted into the left cylindrical hole 21. The cylindrical bodies 24 and 25 have a cylindrical shape with a bottom, and through holes 24a and 25a are formed in the bottoms of the bodies, respectively (see FIG. 5).

Further, the inner surface of the bottom (partition) 24b of the left cylindrical body 24 is formed in a tapered shape whose diameter gradually decreases toward the right side. The internal space of these cylindrical bodies 24 and 25 is a pressurizing chamber 26, and this pressurizing chamber 26 is connected to the left cylindrical body 24.
It is divided into eleventh and second chambers 26a and 26b by the bottom 24b of the fourth chamber.

Note that the reference numeral 27 is a screw for fixing the cylindrical body 24, 25.

Further, a plurality of holes 28 are formed in the outer peripheral wall of each cylindrical body 24,25. On the other hand, a recess 21 a is formed on the inner periphery of the cylindrical hole 21 so as to surround the hole 28 . and,
An intake port 29 and an exhaust port 30 that communicate with each recess 21a are formed in the chamber/(-20).

Next, spacers 31, 31, a packing 32 disposed between the spacers 31, 31, and a thrust bearing 33 are fitted into the right cylindrical hole 22. A screw member 34 is screwed onto the right side of the thrust bearing 33, and a nut 35 is screwed onto the outer periphery of the screw member 34. and,
Spacer 31, packing 32, thrust bearing 3
The fuel rod A is inserted through the central portion of the screw member 3 and the screw member 34.

At the left end of the chamber 20 configured in this way, m
The right end surface of the window mount 8 described in J is pressed down, and in this state, the axis of the window 10 and the axis of the fuel rod A are aligned. Note that the reference numeral 38 is an O-ring for airtightly closing the gap between the window mount 8 and the chamber 20.

The base 1 also has a mount receiver 39 for the hydraulic cylinder 2.
It is attached to the opposite side of the chamber 20 with the two sides in between. The mount receiver 39 supports the wind mount 8 so that no bending moment is applied to the piston rod 2a of the hydraulic cylinder 2 due to the pressure in the pressurizing chamber 26, and also cleans the end surface of the window 10. For example, a rotating brush is arranged inside.

Next, the operation when welding the end portion of the fuel rod A using the laser welding device will be described.

First, the fuel rod A is inserted into the screw member 34, and its left end is brought into contact with the edge of the hole 25a of the cylindrical body 25. Next, with the end surface of the wind mount 8 pressed against the end surface of the chamber 20, the air in the pressurizing chamber 26 is exhausted from the exhaust port 30, and the inside of the pressurizing chamber 26 and the fuel rod A are made almost vacuum. Next, helium gas is fed into the pressurizing chamber 26 from the intake port 29, whereby the inside of the fuel rod A is replaced with helium gas, and the pressure inside the pressurizing chamber 26 is set to, for example, about 35 atmospheres.

Next, a laser beam (indicated by a two-dot chain line in FIG. 1) is irradiated by a laser beam generation mechanism (not shown).

The laser light is focused by the lens 40, passes through the window 10, and is irradiated onto the end of the fuel rod A. This laser beam welds and closes the hole formed in the end plug of the fuel rod A. At this time, metal vapor is generated and becomes soot,
The presence of the bottom 24b of the cylindrical body 24 makes it difficult to move toward the window 10 side. Furthermore, when soot enters the beam of laser light, it is heated by the laser beam, becomes ionized, and moves actively, scattering out of the beam. Therefore, soot is also prevented from moving toward the window 10 through the hole 24a of the cylindrical body 24.

Next, the exhaust port 30 also exhausts the helium gas in the pressurized chamber 26 to the outside. At this time, the helium gas
Since the soot flows to the second chamber 26b side, the soot that has moved to the first chamber 26a side moves to the second chamber 26b side. In addition, the first chamber 26
Since the inner surface of the bottom 24b of the cylindrical body 24 is tapered, soot can move smoothly.

Next, when the pressure inside the pressurizing chamber 26 reaches atmospheric pressure, the piston rod 2a of the hydraulic cylinder 2 is brought into an extended state. Then, the index case 3 rotates 60 degrees along the groove 4, and the wind mount 8 and the piston rod 2a also rotate.S0 Next, the piston rod 2a is reduced and the wind mount 8 is moved into the chamber 20. Press it against the end face and perform the same process as above. Further, while the end portions of the fuel rods A are being welded in this manner, the windows 10 in the mount receivers 39 are cleaned.

In the above laser welding device, the bottom 24 of the cylindrical body 24
b makes it difficult for soot to move toward window 10, so window 1
It is possible to reduce the adhesion of soot to the window 10, and prevent the occurrence of melting and damage to the window 10. In addition, the intake port 29 is placed on the first chamber 26a side, and the exhaust port 30 is placed on the second chamber side. Since the soot in the first chamber 26a is returned to the second chamber 26b every time the end welding of the fuel rod A is completed, the adhesion of soot to the window 10 can be further reduced. can. Moreover, since multiple windows 10 are sequentially used while rotating the window mount 8, and each window 10 is cleaned using the mount receiver 39, even if a small amount of soot gets on the window 10, it can be cleaned immediately. It can be brushed off. Therefore, it can be used continuously for a long period of time without maintenance and inspection.

In the above embodiment, the pressurized chamber 26 is divided into the first chamber 26a and the second chamber 26b, but if it is divided into a large number of chambers, the movement of soot toward the window 10 can be further reduced. be able to. Further, the inner walls of the cylindrical bodies 24 and 25 may be formed into a wave shape or a labyrinth shape.

[Effects of the Invention] As explained above, the laser welding device of the present invention has the following effects:
The pressurized chamber is constructed with a partition between both ends that has a through hole for the laser beam to pass through, which reduces the movement of metal vapor soot generated by welding toward the window. .

Therefore, it is possible to prevent the occurrence of melting and damage to the window due to the adhesion of soot.

[Brief explanation of the drawing]

1 to 5 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a plan sectional view showing a laser welding device, FIG. FIG. 4 is a plan view showing the window mount, FIG. 4 is a side view showing the index case, and FIG. 5 is a plan cross-sectional view showing details of the chamber. 10...Window, 20...Chamber, 2
6... Pressure chamber, 24a... Through hole, 2
4b...Bottom (partition). Applicant: Mitsubishi Nuclear Fuel Co., Ltd. Figure 2 Figure 4 /3 No.

Claims (1)

[Claims] An opening communicating with one end of the pressurizing chamber is provided at one end of a chamber having a pressurizing chamber inside, and the opening is airtightly closed and the other end of the pressurizing chamber is accessed from the outside of the chamber. A window is provided that transmits the laser beam irradiated to the side, and the object to be welded is hermetically inserted through the other end of the chamber so that the welding end of the object to be welded faces the other end of the pressurizing chamber. A laser welding device provided with a hole, characterized in that a partition having a through hole through which a laser beam passes is provided at an intermediate portion between both ends of the pressurizing chamber.