JPH116890A - Laser marking method for cladding tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs and prevent a cladding tube from igniting due to heat generation by marking the surface of the cladding tube with laser light while cooling it in an atmosphere of an oxygen gas. SOLUTION: A cladding tube 1 is held in a marking chamber in a sealed condition, and the inside of the chamber is wholly filled with an oxygen gas. Then, cooling air is blown into the cladding tube 1 from a nozzle part 15a of an air nozzle 15 to cool the tube 1 from inside. Under this condition, laser light L is oscillated from a laser oscillator 12 and is scanned by driving a galvano mirror 13 in the X and Y axes directions to the surface of the cladding tube 1 if necessary in order to imprint and indicate bar codes, characters and symbols on the surface of the cladding tube 1. On this occasion, the cooling of the cladding tube 1 from inside makes it possible to restrain the heat generation caused by the laser beam irradiation and to prevent zircalloy, a material for the cladding tube 1, from igniting. Moreover, the use of an oxygen gas can reduce costs and can retard imprinted parts from corroding because an oxide layer is formed on the surface of the cladding tube 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser marking method for marking bar codes, characters, symbols, and the like on the surface of a cladding tube of a nuclear fuel rod using a laser beam.

[0002]

2. Description of the Related Art In fuel rods of a fuel assembly used in nuclear power generation, cladding tubes of the fuel rods are identified and managed so that individual fuel rods can be tracked in each process of manufacturing, transporting, storing, and using the fuel rods. It is required to be able to do it. As a means for identifying a fuel rod, a bar code, a character, a symbol, or the like is marked on a surface of a cladding tube using a laser beam. As an example of such a conventional technique, there is one disclosed in Japanese Patent No. 2585781. In this laser marking method, as shown in FIG. 2, a cladding tube 1 of a fuel rod before inserting a fuel pellet is inserted and held in a marking chamber 2, and a mixed gas of argon gas and oxygen gas is used as an atmosphere gas. The inside of the chamber 2 is filled. Then, a laser beam is irradiated from outside the chamber 2,
A bar code or the like was marked on the surface of the cladding tube 1 by engraving via the rollable reflection mirrors 3 and 4 in the chamber 2. For example, FIG.
The bar code 5 is displayed as shown in FIG. 1, and is read and identified by a laser beam in each step.

[0003]

However, in such a laser marking method, the mixed gas of the argon gas and the oxygen gas used as the atmosphere gas is a special gas, which is not easy to obtain and is expensive. is there. In view of such problems, an object of the present invention is to provide a laser marking method of a cladding tube which is inexpensive and does not cause ignition.

[0004]

A laser marking method for a cladding tube according to the present invention is characterized in that the cladding tube is cooled in an oxygen gas atmosphere and the cladding tube is marked by a laser beam. is there. The cooling of the cladding tube may be performed by blowing a cooling medium (gas such as air) into the cladding tube.

[0005] By using oxygen gas as an atmospheric gas, marking can be performed at a lower cost than before, and by cooling the cladding at the time of marking with a laser beam, the heat input by the laser beam at the time of marking is reduced. The danger of ignition of the vehicle can be eliminated. By marking in an oxygen gas atmosphere, cooling can be performed in a shielded state without bringing atmospheric nitrogen into contact with the cladding tube surface, and further, marking can be performed on the cladding tube surface while cooling from inside the cladding tube.

[0006]

FIG. 1 is a block diagram showing an embodiment of the present invention.
However, the same members as those described above are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 is a schematic configuration diagram of a marking method according to an embodiment. In the laser marking device 10 shown in FIG. 1, the cladding tube 1 is inserted and held in a marking chamber 11 (hereinafter, sometimes referred to as a chamber). A laser oscillator 12 is provided outside the chamber 11, and the laser oscillator 1
On the optical path of the laser beam L oscillated from the laser beam L, the laser beam L
As a reflection mirror for directing the light into the chamber 11 through the transmission window 11a of the chamber 11,
The galvanomirror 13 can scan the laser beam L in the X-Y direction by a driving unit (not shown) for engraving. A condenser lens 14 is provided between the galvanometer mirror 13 and the transmission window 11a.

In addition, the cladding tube 1 is in a state before the fuel pellets are inserted and both ends are open, and a cooling air nozzle 15 is provided at an end opening 1 a of the cladding tube 1 located outside the chamber 11. Is inserted, and air can be blown into the inside of the cladding tube 1 as a cooling medium. An atmosphere gas introduction path 16 is formed in the marking chamber 11, and a 100% oxygen gas is introduced into the chamber 11 as an atmosphere gas. The reason why the oxygen gas is used as the atmosphere gas is that it is relatively inexpensive and that it is effective in forming an oxide film on the surface of the cladding tube marked by laser. If oxygen gas is used as the atmosphere gas, since the oxygen gas is an active gas, there is a danger that the base material of the zircaloy alloy, which is the material of the cladding tube 1, will ignite during the marking by the laser beam. However, by simultaneously cooling the inside of the cladding tube 1 with a cooling medium such as air, the cladding tube 1 at the time of laser beam irradiation is cooled.
It is possible to reduce the heat input temperature and eliminate the risk of ignition.

[0008] The laser marking apparatus 10 according to the present embodiment is configured as described above. Next, a laser marking method will be described. First, the cladding tube 1 is inserted into the marking chamber 11, held in a sealed state, and the inside of the chamber is filled with 100% oxygen gas. And
Cooling air is blown into the cladding tube 1 from the nozzle portion 15a of the air nozzle 15 to cool the cladding tube 1 from the inside. In this state, laser light is oscillated from the laser oscillator 12,
The laser beam is irradiated onto the surface of the cladding tube 1 in the marking chamber 11 by condensing the light with a condenser lens 14 via a galvanometer mirror 13. By appropriately shaking the galvanomirror 13 with respect to the cladding tube 1 in the X-axis and Y-axis directions, the bar code 5, characters, symbols, and the like can be engraved and displayed on the cladding tube surface by scanning the laser beam. At this time, since the cladding tube 1 is air-cooled from the inside, heat generation during marking can be reduced and cooling can be performed. Therefore, there is no risk of ignition during marking.

As described above, according to the present embodiment, since the oxygen gas is used as the atmosphere gas, the cost is reduced, and the corrosion of the engraved portion can be suppressed by forming an oxide film on the surface of the engraved cladding tube. . Moreover, by cooling the inside of the cladding tube 1 at the time of marking, heat generation due to laser beam irradiation can be suppressed, and ignition of the zircaloy alloy as a material of the cladding tube 1 can be prevented. Further, the corrosion resistance and the strength of the engraved portion of the cladding tube 1 are good, and the soundness of the marking can be secured.

In the above-described embodiment, the reason why air is used as the cooling medium is that it is necessary to clean the cladding tube 1 and dry the inside when fuel pellets are inserted. A liquid such as water or a refrigerant gas other than air may be used.

[0011]

As described above, in the method for laser cladding of a cladding tube according to the present invention, the cladding tube is cooled in an oxygen gas atmosphere and the cladding tube is marked by a laser beam. The use of oxygen gas reduces the cost, and the formation of an oxide film on the surface of the cladding tube can suppress the corrosion of the engraved portion. In addition, by cooling the cladding at the time of marking, heat generation due to laser beam irradiation can be suppressed, and ignition of the zircaloy alloy, which is a material of the cladding, can be prevented. In addition, the corrosion resistance and strength of the engraved portion of the cladding tube are good, and the soundness of the marking can be secured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser marking device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a conventional laser marking device.

FIG. 3 is a partial side view showing a cladding tube on which a bar code is imprinted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Clad tube 12 Laser oscillator 13 Galvano mirror 15 Air nozzle

Claims (1)

[Claims] 1. A laser marking method for a cladding tube, wherein the cladding tube is cooled in an oxygen gas atmosphere to mark the cladding tube with a laser beam.