KR100390013B1 - Apparatus of laser welding for attachment of bearing pads of nuclear fuel elements - Google Patents

Abstract

The present invention relates to a laser welding device for attaching a support in the manufacture of nuclear fuel rods in the field of nuclear power, the support of the nuclear fuel rod is maintained at a constant interval with the adjacent fuel rods in the furnace during combustion, and is also attached to the fuel rod in the direction of the coolant flow fuel rod This prevents sheath wear, which can be caused by friction between the and pressure tubes. In particular, the coated tube and precision parts having a high melting point and good oxidation of zirconium alloy can be effectively applied in all economic aspects such as the improvement of welding performance using laser, mass production in production, and reduction of production cost. The present invention also relates to a laser welding device for attaching a nuclear fuel rod support such that a laser beam can be transmitted to an optical fiber and subjected to precision welding regardless of a welder's functional level.

Laser welding process apparatus using the optical fiber used in the present invention is a yag laser oscillator 1, optical fiber 2, protective gas box (3), simultaneous bundle branch (4), welding monitoring unit (5), support fixture ( 6), the welding object movement table (7) and the cylinder (8), the laser welding method for attaching the nuclear fuel rod support is the laser gas transmitted from the yag laser oscillator (1) to the optical fiber (2) the protective gas box (3) The simultaneous bundle diverging portion 4 composed of an optical coupler is connected to accurately focus on the support, which is the object to be welded, and is used by the welding fixture 6 for attaching the support. At this time, the position of the support was accurately focused using a diode laser and then determined by the CCD camera of the welding monitoring unit 5.

Description

Apparatus of laser welding for attachment of bearing pads of nuclear fuel elements

The present invention relates to a laser welding device for attaching a nuclear fuel rod support using an optical fiber, in particular, laser welding is very high precision, easy to automate and high-speed welding can increase the productivity, to date, the support or spacer of the nuclear fuel rod Has been known to be impossible with conventional resistance welding or electric arc welding. Therefore, as the high precision welding technology is required to improve the productivity in the manufacture of nuclear fuel rods, the laser processing, which is increasing in utilization, is a high technology, and the quality of the laser welding is made of high melting point material, zirconium alloy and thin coated tube. It can be effectively applied in all economic aspects such as improvement of mass production during production, reduction of production cost, and at the same time, the laser is transmitted to optical fiber by precisely welding power regardless of the welder's functional level. It's about technology.

In general, brazing and soldering methods have been used as a bonding method for attaching a nuclear fuel rod support.

Bonding of a support attached to a conventional nuclear fuel rod is mostly made by hand and does not have an automated facility for manufacturing equipment. In addition, the joining method of the support is generally brazing and soldering. In this case, when joining a delicate part, the heat distribution of the joint is not uniform or the bonding strength is weak due to poor absorption of the filler material. In addition, there was a problem that there is no monitoring function for the junction when the fuel rod support is attached.

The present invention has been made to solve the above problems, the laser welding focuses the high-density heat source to the micro-site, the metal thermal effect is smaller than the brazing method used for conventional nuclear fuel rod support bonding, and the thermal deformation is minimal In addition, since it can be reduced, and also non-contact process with the welded material, it is possible to fundamentally remove the contamination and surface scratches caused by brazing, and to achieve high speed welding, welding automation, and productivity improvement. That is, laser welding of the optical fiber transmission used in the present invention focuses thermal energy of photons with a high focusing speed of a single wavelength on a target material as an optical fiber. The transmitted laser is converted into thermal energy by absorption and the ultra-precision welding is possible because the size of the laser beam can be adjusted small. In particular, it is very suitable for the support having a small junction structure with a nuclear fuel rod made of a material of zirconium alloy having a high melting point. In this case, the purpose of the present invention is to provide a laser welding apparatus using an optical fiber because seam welding using a laser beam size of about 0.3 to 0.4 mm is required for supporting the support of the nuclear fuel rod.

1 is a schematic view of the whole laser welding apparatus of the present invention;

2A is a schematic perspective view of a support fixture required for a laser welding device according to the present invention;

Figure 2b is a front view showing the structure of the welding fixture for attaching the fuel rod support

Figure 2c is a detailed example of a spring fixing plate structure for fixing the support when using the fuel rod and the welding fixture

3 is a cross-sectional view of the nuclear fuel cladding tube and the support;

(a) is a conventional brazing bonding method

(b) is overlapped by laser welding according to the present invention.

<Description of the symbols for the main parts of the drawings>

(1): Yagra laser oscillator (2): Optical fiber

(3): Protective gas box (4): Simultaneous bundle branch

(5): welding monitoring part (6): support fixture

(7): welded object moving table (8): Bomb

(9): support 10: sheath

(11): spring fixing plate

Hereinafter, the configuration and operation of the present invention with reference to the accompanying drawings.

The constituent aspect of the present invention is that in performing laser welding of a support to be attached to a nuclear fuel rod coating tube, a simultaneous bundle diverging portion 4 connected to an optical fiber by a yag laser oscillation portion, and the simultaneous bundle diverging portion 4 are located at a middle point and The support fixture 6 placed on the target plate to be welded is located at the bottom, and the welding monitoring part 5 is composed of a protective gas box 3 located at the top to perform ultra-precision laser welding of the support to the nuclear fuel rod. Simultaneous bundle diverging part 4 is designed as an optical coupler, and the core welding with the laser beam size of 0.3 ~ 0.4m / m enables the remote welding of the welding structure of each support and the nuclear fuel automatically. The rod cladding tube 10 is embedded in the support fixture 6, and the support fixture 6 is placed in the welding target 7 and the spring fixing plate 11 is installed at one side of the upper cutout of the support fixture 6, Nuclear fuel 9 It is possible to clamp on the surface of the encapsulated tube (10), and as a methodology, the yaw laser oscillator (1), the optical fiber (2), the protective gas box (3), the simultaneous bundle branch (4), and the welding monitoring unit (5). The laser transmitted from the Yagra laser oscillator to the optical fiber by a simultaneous bundle branch configured as an optical coupler using an ultra-precision laser welding device composed of a support fixture (6), a weldable movable table (7) and a cylinder (8). After focusing accurately on the support supported by the support fixture in the box, and automatically performing remote welding on the support provided with each laser beam core welding having a size of 0.3 ~ 0.4mm determined by the CCD camera of the welding monitoring unit. Laser average output 50-60W, repetition rate 6-8PPS, energy 7-9J per pulse, welding speed is 20-30cm per minute, and 4 fiber core diameter 400um connected at the same time at optical fiber transmission, optical couple The focal length 95mm of the condenser lens and the optical lens ratio of the coupler are set to 0.7, and the laser welding device for attaching the support of the nuclear fuel rod is completed.

As shown in FIG. 1, a laser welding process apparatus for attaching a nuclear fuel rod support includes a yaw laser oscillator 1, an optical fiber 2, a protective gas box 3, a simultaneous bundle branch 4, and a welding monitoring unit ( 5), the support fixture (6), the object to be moved (7) and the cylinder (8), the laser welding process for attaching the nuclear fuel rod support is the laser transmitted to the optical fiber (2) from the laser oscillator (1) Was aligned using a simultaneous bundle diverging portion 4 composed of an optical coupler so that the focus is precisely on the support being the weldment within the protective gas box 3. At this time, the position of the welded object was focused on the material of the welded object by using a diode laser, and then determined by the CCD camera of the weld monitor 5. The four optical fibers 2 connected from the simultaneous bundle diverging part 4 of FIG. 1 are GI (Grade Index) multi-mode type with a core diameter of 600 um used for precision welding and the numerical aperture of the optical fiber 2 (Numerical Aperture). ) Was 0.2. The laser transmitted to the optical fiber 2 is focused at the simultaneous bundle branch 4 composed of an optical coupler to perform precision welding. At this time, since the material of the nuclear fuel rod zirconium alloy has a strong oxidation property, it is protected to prevent contamination or discoloration. A gas box (3) was used, wherein the protective gas was argon (UPC grade) of inert gas supplied from the bomb 8, and the flow rate of argon was 20 to 30 liters per minute. In addition, an X-Y-Z axis to-be-welded table 7 and a support fixture 6 for welding the fuel rod support 9 were manufactured and used.

The laser welding method for attaching the nuclear fuel rod support according to the present invention configured as described above is as follows.

Welding using laser has the characteristics that small bead width and deep penetration can be obtained and the welding state can be observed in real time. As described above, brazing, which is a conventional bonding method, has been performed in a state in which a filler material is inserted into and bonded to the nuclear fuel rod cladding tube 10 and the support 9, as shown in FIG. As to improve the problem according to the bonding method of, as shown in (b) of Figure 3 it can provide a simple overlapping structure that can be connected only to the nuclear fuel rod cladding tube 10 and the support (9), the laser Delicate welding was performed. In addition, the welding using the laser can be automatically performed in two places using the simultaneous bundle diverging portion 4 composed of the optical coupler of FIG. 1 in the horizontal direction. As described above, the apparatus according to the present invention can obtain a deep penetration while the beam size and the bead width without thermal deformation and discoloration of the welded part can be obtained, thereby improving welding quality, productivity and cost reduction, and furthermore, automating the welding process. Can be.

As described above, the manufacture of laser welding is a simple welding method that can be performed very simply, quickly and easily, and requires no welding function. In addition, it is possible not only to join welding of overlapping joint structure but also to fillet joint, butt joint and overlap joint which are widely used in welding structures of difficult materials such as titanium and nickel. Unlike brazing, the process time can be shortened. The laser welding process can automatically control the welding length, and has the effect of obtaining a healthy weld without thermal deformation, high welding strength, and no defects, thereby improving welding efficiency and productivity.

Hereinafter, the present invention will be described in detail through examples.

Example

Laser average power 50-60W, repetition rate 6-8PPS, energy 7-9J per pulse, welding speed is 20-30cm per minute, and 4 fiber core diameter 600um connected at the same time at optical fiber transmission, optical coupler The focal length 95mm of the condenser lens and the optical lens ratio of the coupler were prepared as 0.7, and the welding of the Zircaloy nuclear fuel rod support using the laser according to the present invention was carried out. However, the above laser condition is that four optical fibers 2 are transmitted from the simultaneous multiple branching unit 4.

Figure 3 shows a bonded cross section according to the present invention and the conventional method, which shows a large difference between the laser welded perspective view and the perspective view of the conventional method of the present invention. In the case of the present invention, on the enlarged longitudinal cross-sectional view, a healthy welded part in which no defects such as pores and undercuts are obtained is obtained, whereas in the related art, it is understood that the separation of interfaces occurs in the brazing method. Figure 3 is slightly different from the laser welding method according to the present invention and the conventional bonding method, but the common problem is that the bonding region by heat in all materials black color by oxidation and the strength is significantly weak will be. In addition, as shown in (a) of FIG. 3, the zirconium alloy material is bonded with a thick beryllium filler metal in order to join by conventional brazing, and unnecessary expenses generated in the manufacturing process by inserting the filler metal and strict quality inspection for the product. Is required. On the contrary, in the case of the present invention, the bead width and the depth of penetration can be adjusted by using only the welding conditions of the laser welding apparatus as shown in FIG. 1 using the optical fiber. As described above, a welded material having excellent strength is obtained.

(Variants, applications and legal interpretations)

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes are intended to fall within the scope of the claims.

In this way, by providing a connection having a welding structure of the support to be attached to the nuclear fuel rod cladding by transmitting the optical fiber according to the present invention, it is installed in a special fastener easily aligned in a line and not only a zirconium alloy but also a welding structure of nickel and titanium materials When the overlap joint and butt joint method is applied, it can be applied effectively in all economic aspects, such as production cost reduction and export effect, when manufacturing small quantities of various types of precision parts, and at the same time, welding function is completely irrespective of the welder's functional level. Even if not possessed, it is a beneficial and beneficial invention that can automatically perform remote welding by simply connecting the power to the laser device.

Claims (5)

Yagra laser oscillation unit for generating a laser beam, a closed protective gas box into which the inert gas is introduced, a bomb connected to the protective gas box to supply an inert gas, and a plurality of installed at the upper end of the protective gas box. Claims [1] A support welding device for a nuclear fuel rod for a heavy water reactor comprising a CCD camera and a welding target moving table installed at an inner lower end of the protective gas box; The support welding device of the nuclear fuel rod cladding tube, The support is placed in the upper part of the welded object moving table and the nuclear fuel rod cladding tube is inserted / secured therein, and the support is provided in contact with the upper surface of the exposed cladding tube while having a cutout at the top thereof to expose a portion of the cladding tube placed therein. A support fixture provided with a spring fixing plate for clamping, It is configured to include a simultaneous bundle branch consisting of the optical coupler having an optical lens ratio of 0.7, each connected by the four optical fibers having a yaw laser oscillator and a core diameter of 600um, Support for nuclear fuel rods characterized by ultra-precision laser welding of nuclear fuel rod cladding and support for heavy water reactors at a laser speed of 50-60 W, repetition rate of 6-8 PPS, energy per pulse of 7-9 J, and 20-30 cm per minute. Laser welding device for machine. delete delete delete delete