JP3113174B2 - Nuclear fuel cladding welding method and welding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for welding end plugs of a nuclear fuel cladding tube.

[0002]

2. Description of the Related Art Generally, when an end plug is inserted and welded at the open end of a nuclear fuel cladding tube, the welding is performed in a welding chamber in an inert gas atmosphere.

FIG. 4 is a view showing a conventional welding apparatus for a nuclear fuel cladding tube. An opening through which one opening end side of the nuclear fuel cladding tube 2 can be hermetically inserted is provided on one side wall of the welding chamber 1. It is provided, and in the part facing this opening,
An end plug holder 4 for holding the end plug 3 is provided facing the open end of the cladding tube inserted into the welding chamber, and an end plug held by the end plug holder 4 is provided outside the end plug holder. An end plug press-fitting mechanism 5 for pressing the end 3 into contact with the cladding tube end is provided, and a welding torch 6 is vertically provided on the top wall.

In order to mount and weld an end plug on the nuclear fuel cladding tube 2, one end of the nuclear fuel cladding tube 2 on which the end plug is to be mounted is inserted into the welding chamber 1 and the other opening is provided. After holding the end side with the airtight holding tool 7,
The inside of the welding chamber 1 and the inside of the nuclear fuel cladding tube 2 are evacuated to a predetermined degree of vacuum. Thereafter, an inert gas is introduced into the welding chamber 1 to bring the interior of the welding chamber into a substantially atmospheric pressure state.

From this state, the end plug press-fitting mechanism 5
The end plug holder 4 holding the end plug 3 at the tip is advanced, and the end plug 3 is pressed into the open end of the nuclear fuel cladding tube 2.

Next, the nuclear fuel cladding tube 2 is rotated by the rotating mechanism 8.
Is rotated around the axis while the nuclear fuel cladding tube 2 and the end plug 3 are rotated.
Girth weld the butted surface of.

[0007]

However, in welding by the above-described apparatus, the gas in the cladding tube 2 expands due to the heat effect at the time of welding, causing a slight increase in the internal pressure. In other words, as shown in FIG. 5, the cladding internal pressure exceeds the limit pressure indicated by the dotted line according to the welding time, and as shown in FIG. D becomes large, or
As shown in (b), a swelling portion 11 is formed in a part of the molten metal 10, and the allowable thickness t of the nuclear fuel cladding tube 2 may be reduced, and the welding quality is not stable and the yield is reduced. There is.

Therefore, it has been proposed to solve the above problem by increasing the pressure in the welding chamber 1 during welding. However, in this pressurized state, as shown in FIG. The molten metal melts down into the inside of the cladding tube 2 to take in air bubbles between the end plug 3 and generate pores 13, and a concave portion 14 is generated in the molten metal to impair the appearance of the welded portion. There is a problem.

In view of the foregoing, the present invention provides a nuclear fuel cladding welding method and apparatus capable of controlling the internal pressure rise of the cladding due to the heat effect during welding of the nuclear fuel cladding within the limit pressure at which welding defects occur. The purpose is to gain.

[0010]

According to a first aspect of the present invention, an end plug welding side end of a nuclear fuel cladding tube is inserted into a welding chamber, and the other end side is held by a holder. A nuclear fuel cladding welding method for welding an end plug to one opening end of a cladding tube, the pressure reducing device having a cylinder chamber communicating with the inside of the nuclear fuel cladding tube at an opening end of the nuclear fuel cladding tube protruding outside from the welding chamber. Is mounted in an airtight manner, and a piston slidably disposed in the cylinder chamber is moved in a direction opposite to the cladding tube, whereby a pressure rise in the cladding tube during welding is reduced.

According to a second aspect of the present invention, a pressure reducing device having a cylinder chamber communicating only inside the nuclear fuel cladding tube is hermetically attached to an open end of the nuclear fuel cladding tube projecting outside from the welding chamber. The capacity in the cylinder chamber is changed at the time of welding by moving a piston disposed in the cylinder chamber in a direction opposite to the cladding tube.

[0012]

By pressure-tightly mounting a pressure reducing device having a vacant chamber of a predetermined volume communicating with the inside of the cladding tube at the open end of the nuclear fuel cladding tube, the internal pressure in the cladding tube at the time of welding of the plug is increased by the pressure. It is reduced according to the volume of the reduction device, and the internal pressure rise of the cladding tube can be controlled within the limit pressure at which welding defects occur.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a welding chamber. On one side of the welding chamber 1, a rotation for rotating a nuclear fuel cladding tube 2 having a welding end inserted into the welding chamber 1 around its axis. A mechanism portion 8 is provided, and an end plug holder 4 is provided on the other side wall portion of the welding chamber 1 on the same axis as the cladding tube inserted into the welding chamber. 4 can be moved back and forth by an end plug press-fitting mechanism 5.

On the other hand, a cladding holder 7 for holding the outer end of the nuclear fuel cladding 2 in an airtight manner is provided on one side of the welding chamber 1, and the cladding holder 7 has a pressure reducing device. 20 are connected.

The pressure reducing device 20 has a cylinder chamber 21 communicating with the inside of the cladding tube 2, and a piston 22 is slidably disposed in the cylinder chamber 21.
A female screw member 24 is provided via a connecting member at an end of a piston rod 23 projecting in a direction opposite to the cladding tube 2, and the female screw member 24 is screwed to a screw shaft 26 rotationally driven by a motor 25. Have been.

The end plug 3 is attached to the end of the nuclear fuel cladding tube 2.
Is welded, one open end of the nuclear fuel cladding tube 2 is inserted into the welding chamber 1, and the other open end is held by the cladding tube holder 7. And the welding chamber 1
After the inside of the cladding tube 2 is evacuated to a predetermined degree of vacuum, the welding chamber 1 is filled with an inert gas to make it substantially at atmospheric pressure.

Thereafter, the end plug 3 is pressed into the nuclear fuel cladding tube 2 in the above-mentioned state, and the butt surface of the end plug 3 and the nuclear fuel cladding tube 2 is circumferentially welded while rotating the nuclear fuel cladding tube 2.

In this case, the internal pressure of the nuclear fuel cladding tube 2 rises due to the heat effect of the welding. The motor 25 is driven in response to the rise in the internal pressure, and the piston 22 is driven through the screw shaft 26, the female screw 24 and the piston rod 23. Is moved outward (to the left in the figure).

Therefore, the volume of the cavity communicating with the nuclear fuel cladding tube 2 is controlled to increase, and the nuclear fuel cladding tube 2 is controlled.
The internal pressure is kept within the limit pressure at which a welding defect occurs, thereby preventing an increase in the finished diameter of the weld, a lack of wall thickness or the generation of pores.

FIG. 2 is a view showing a situation where the internal pressure rises during welding of the nuclear fuel cladding tube 2 when the above-mentioned pressure reducing device is used. As shown by a solid line, the internal pressure at the time of welding corresponds to the welding time. A critical pressure at which welding defects such as an increase in the weld finish diameter and a lack of wall thickness as indicated by a dashed line A occur,
It is between the welding appearance shown by the dashed line B and the critical pressure that occurs when welding defects such as pores occur.

In actual welding, since the heat input condition is constant and the internal pressure of the nuclear fuel cladding rises repetitively, as shown in FIG.
2 may be manually moved by the screw shaft 27 to make the capacity variable.

[0023]

As described above, according to the present invention, a pressure reducing device having a cylinder chamber communicating with the inside of a nuclear fuel cladding tube is hermetically mounted at the open end of the nuclear fuel cladding tube projecting outside from the welding chamber. By moving the piston slidably disposed in the cylinder chamber in the opposite direction to the cladding tube, the pressure rise in the cladding tube during welding is reduced. It is possible to reduce the rise in internal pressure of the pipe, prevent the molten metal from being pushed up from the inside by the influence of the internal pressure, and prevent the weld finish outer diameter from becoming large, or prevent the occurrence of bulging parts, and the occurrence of welding defects Can be prevented and welding quality can be stabilized.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic configuration of a welding apparatus for a nuclear fuel cladding tube of the present invention.

FIG. 2 is a view showing the relationship between the cladding internal pressure during welding and the critical pressure at which welding defects occur.

FIG. 3 is a diagram showing another embodiment of the pressure reducing device of the present invention.

FIG. 4 is a schematic explanatory view of a conventional welding device.

FIG. 5 is a diagram showing the relationship between the cladding internal pressure during welding and the critical pressure at which welding defects occur in a conventional apparatus.

FIG. 6 is a diagram showing a specific example of a welding defect in a conventional method.

FIG. 7 is a diagram showing a specific example of another welding defect in the conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding chamber 2 Nuclear fuel cladding tube 3 End plug 7 Cladding tube holder 20 Pressure reducing device 21 Cylinder chamber 22 Piston 25 Motor 26 Screw shaft

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Kurosawa 2-3-1, Kawakawa, Yokosuka City, Kanagawa Prefecture Inside Nihonkuri Fuyuer Co., Ltd. (72) Ryosuke Nishikawa 2-3-3 Kawa, Yokosuka City, Kanagawa Prefecture No. 1 Inside Nihonkuri Fuyuer Co., Ltd. (56) References JP-A-62-227580 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21C 3/16 G21C 21/02

Claims (2)

(57) [Claims] 1. An end plug welding end of a nuclear fuel cladding tube is inserted into a welding chamber, and the other end is held by a holder.
In the nuclear fuel cladding welding method for welding an end plug to one opening end of the nuclear fuel cladding in the welding chamber, the nuclear fuel cladding communicates with the opening end of the nuclear fuel cladding projecting outside from the welding chamber into the nuclear fuel cladding. A pressure reduction device having a cylinder chamber is hermetically mounted, and a piston slidably disposed in the cylinder chamber is moved in a direction opposite to the cladding tube, thereby reducing a pressure rise in the cladding tube during welding. A method for welding a nuclear fuel cladding tube, the method comprising: 2. An end plug welding side end of a nuclear fuel cladding tube is inserted into a welding chamber, and the other end side is held by a holder.
In a nuclear fuel cladding welding apparatus for welding an end plug to one opening end of the nuclear fuel cladding tube in the welding chamber, an opening end of the nuclear fuel cladding tube protruding outside from the welding chamber communicates only with the nuclear fuel cladding tube. A pressure reducing device having a cylinder chamber to be airtightly mounted, and by moving a piston disposed in the cylinder chamber in a direction opposite to the cladding tube, the capacity of the cylinder chamber is changed at the time of welding. A nuclear fuel cladding tube welding device.