JPS6123593A - Vaporized elements removing device for zircalloy tubes - Google Patents

Abstract

PURPOSE:To exhaust easily vaporized components in a tube by providing a ventilating passage for discharging vaporized components to a heating chamber from the tip of a tube end receiver butt-welded on the end of the zircalloy tube, and projecting the tip in the heating chamber. CONSTITUTION:A zircally tube 21 is rotated by a rotary gear 22, while the end of the zircally tube 21 is heated up by a laser heater 25. Natorium component is then vaporized and removed from the beads remaining in the inner end of the tube 21. The vaporized natorium component is guided to a heating chamber 20 through a ventilating passage 24d provided in the tube end receiver 24 and then discharged out of the heating chamber 20 together with inactive gasse generated in the chamber 20.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to the use of vaporized components generated from beads, etc. inside the pipe when welding the inner peripheral surface of a Zircaloy pipe after bead blasting. This invention relates to a removal device for removing.

[Prior art]

First, the Zircaloy pipe and the Zircaloy parts welded thereto will be described. As shown in FIG. 2, for example, there are a Zircaloy cladding tube 2 and a Zircaloy end plug 3 that constitute a fuel rod 1 used in a light water nuclear reactor. The cladding tube 2 houses the pellets 4 and the spring 5 therein, and the end plugs 3 seal the openings at both ends of the cladding tube 2. Then, these cladding tube 2 and end plug 3 are welded, for example, as shown in FIG. 3. That is, the end plug 3 is supported by the end plug receiver 7 rotatably provided in the frame 6 defining the welding chamber S, the cladding tube 2 is supported by the rotation ta8, and the fitting part 9 is connected to the welding electrode 1.
Welding is carried out by 0. Note that for welding the cladding tube 2 and the end plug 3, the welding chamber S is usually set in an inert gas atmosphere such as helium or argon, and the tungsten welding electrode 10 and the fitting part 9 are welded together with the air shut off. T that generates an arc between the two and welds with the heat of this arc.
IG welding is used.

Incidentally, the cladding tube 2 used in the above-mentioned fuel rod 1 is subjected to an acid cleaning treatment in order to remove foreign matter adhering to the inner and outer surfaces of the tube in the final step of the manufacturing process. In order to prevent adverse effects on the tube, the acid remaining on the inner and outer surfaces of the tube is removed. In this case, regarding the acid remaining on the outer surface of the cladding tube 2,
Although it can be removed by mechanical methods such as grinding, such methods cannot be used for the inner surface, and a bead blasting process is adopted in which glass beads are sprayed onto the inner surface of the cladding tube 2, thereby removing the inner surface. This will remove any remaining acid.

Bead materials used in such bead blasting include soda lime glass [main components: 5 tOz (72%), NazO
(13%), Ca0 (9%), Feo (3%)] are used.

[Problem that the invention seeks to solve]

However, when the end plug 3 is welded to the cladding tube 2 which has been subjected to such bead blasting, porosity (micro bubble-like pores that make the weld M brittle) were discovered during an X-ray inspection of the weld. Furthermore, the porosity incidence rate was as high as 3% on average based on the number of pipes. Therefore, the inventor investigated the cause of the porosity and found that the cause was sodium contained in the beads. That is, the sodium component contained in the beads vaporizes when the temperature reaches 1500°C to 1600°C. However, the welding temperature of the welding part 13 is 2000°C because the cladding tube 2 and the end plug 3 are made of Zircaloy.
reach more than that.

For this reason, sodium is removed from the beads during the welding process.
(The aluminum component vaporized and entered the molten metal of the welded part M, forming porosity.

This invention was made based on the above knowledge, and when welding a bead blasted Zircaloy tube and other Zircaloy parts, sodium and other substances generated inside the Zircaloy tube. The problem is the vaporized components.

[Means for solving problems]

The vaporized component removal device of the present invention is comprised of a heating chamber, a Zircaloy tube, a tube end receiver of the Zircaloy tube, and a heating machine that heats at least until sodium is vaporized. A communication path for discharging vaporized components inside the Zircaloy tube generated by heating into the heating chamber is provided so as to face the inner side of the heating chamber from the tip of the tube end holder that is abutted against one end of the Zircaloy tube. .

[For production]

One end of the Zircaloy tube is supported by a tube end holder, and while these are rotated in one direction, one end of the Zircaloy tube (around the part to be welded) is heated by a heating machine. Vaporized components such as sodium generated inside the Zircaloy tube are
It is discharged into the heating chamber via the communication path.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Reference numeral 20 in the figure is a heating chamber that can withstand sodium vaporization temperature. In the heating chamber 20, a Zircaloy tube 21 is placed.
It is rotatably provided with one end facing the inside of the heating chamber 20. On the other end side of the Zircaloy tube 21 and on the outside of the heating chamber 20, a rotation ta22 for rotating the Zircaloy tube 21 is connected.

The opening 21a on the one end side of the Zircaloy tube 21 connects the tip 24a of the tube end holder 24, which is formed in the shape of a truncated cone.
They are supported in a removably abutted state. This tube end support 24 includes the above-mentioned tip portion 24a and this tip portion 24a.
It consists of a flat disk-shaped support part 24b that supports the , and a shaft part 24c that is provided integrally with the support part 24b. The shaft portion 24c of the tube end bearing 24 is rotatably supported by the heating chamber 20 via a thrust bearing 25 between the support portion 24b and the inner wall of the heating chamber 20. The Zircaloy tube 21 and the tube end support 24 are configured to rotate together in one direction. A communication path 24d is formed from the tip 24a of the tube end receiver 24 to the support portion 24b, through which vaporized components such as sodium vaporized in the Zircaloy tube 21 due to heating are discharged into the heating chamber 20. When the tip 24a of the tube end support 24 is brought into contact with one end of the Zircaloy tube 21, the inlet of the communication passage 24d is located inside the Zircaloy tube 21, and the outlet thereof is located inside the Zircaloy tube 21. 21 and facing the inside of the heating chamber.

Inside the heating chamber 20 and above the part to be welded at one end of the Zircaloy tube 21, a laser heating machine 25 is installed which heats at least the sodium until it is vaporized (1500 DEG C. to 1600 DEG C.).

This laser heating device 25 has a well-known configuration, for example, uses a mixed gas of CO2-N2-1-1e as a laser material, has a laser beam focusing width of 3 mm, and has a portion heated by irradiating the laser beam ( The temperature of the part to be welded is set to 1500
It is necessary to have the ability to maintain temperatures between 1600 and 1600 degrees Celsius for about 3 seconds.

Note that the heating chamber 20 is preferably provided with a suction means for removing vaporized components such as vaporized sodium. As the suction means, any means such as the pump 26 may be used as long as it is a means that makes the inside of the heating chamber 20 have a more negative pressure than the inside of the Zircaloy tube 21. In addition, in the illustrated example, the Zircaloy tube 21 and the shaft portion 24c of the tube end receiver 24, and the heating chamber 2 through which these are inserted.
Although there is a gap between the hole and hole 0, it is actually sealed airtight. The inside of the Zircaloy tube 21 and the inside of the heating chamber 20 are filled with an inert gas.

When the sodium component is removed from the beads remaining at the end of the Zircaloy tube 21 with the removal device having the above configuration, the Zircaloy tube 21 is rotated at a speed of about one revolution every 3 seconds by the rotation lI22. At the same time as this rotation, the end of the Zircaloy tube 21 is heated by laser Ia25.
Heating is performed at a temperature of 1,500°C to 1,600°C for 3 to 5 seconds. Then, the sodium component is vaporized and removed from the beads remaining at the inner end of the Zircaloy tube 21. The vaporized sodium component is guided into the heating chamber 20 through a communication path 24d formed in the tube end support 24, and is discharged to the outside of the heating chamber 20 together with the inert gas inside the heating chamber 20.

After removing the sodium component in this way,
Although 200 Zircaloy pipes 21 were actually TIG welded, no porosity occurred in the welded parts.

[Effects of the Invention] The device for removing vaporized components of the present invention uses a heater to heat the welded portion of a Zircaloy pipe to vaporize the sodium components inside and discharge them from the inside of the pipe. be. Therefore, even if other members are welded to the welded part of the Zircaloy pipe, porosity will not occur in the welded part. In addition, it not only eliminates defective products and improves quality, but also has excellent advantages such as improving product yield and reducing costs.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and is a schematic diagram showing a device for removing vaporized components in a Zircaloy tube. FIGS. 2 to 4 show conventional welding methods, etc. for this invention.1. FIG. 2 is a sectional view showing a fuel rod equipped with a Zircaloy cladding tube and a Zircaloy end plug, which is an example of the object of the present invention, and FIG. 3 is an example of a welding device for welding these cladding tubes and end plugs. FIG. 4 is an enlarged sectional view showing the end of the fuel rod shown in FIG. 2. 20... Heating chamber, 21... Zircaloy pipe, 24... Tube end holder, 24a... Tip, 24d... Connection Aisle, 25...Heating machine. Applicant: Mitsubishi Nuclear Fuel Co., Ltd. Figure 1-9 Figure 2 Figure 3 Figure 4 5

Claims (1)

[Claims] A heating chamber, a Zircaloy tube whose open end is rotatably disposed within the heating chamber, and a distal end supported at one end of the Zircaloy tube, and integrated with the Zircaloy tube with the distal end supported. It consists of a rotating tube end holder for the Zircaloy tube and a heating machine that heats the welded part of the Zircaloy tube until at least the sodium component is vaporized inside the heating chamber. A device for removing vaporized components in a Zircaloy tube, characterized in that a communication path for discharging into the heating chamber is provided so as to face the inside of the heating chamber from the tip of a tube end holder fitted into one end of the Zircaloy tube. .