A plug welding torch for the upper end plug of a nuclear fuel rod

Abstract

The present invention belongs to the technology of nuclear fuel manufacturing, and particularly relates to a plug hole welding torch for the upper end plug of a nuclear fuel rod, which comprises an insulating bakelite sleeve, a tungsten electrode positioning seat coaxially arranged in the insulating bakelite sleeve, and a tungsten electrode rod coaxially arranged in the tungsten electrode positioning seat. An adjusting screw is arranged at the end of the tungsten electrode rod. A compression screw, a flange cover and a gun body positioning block are coaxially arranged outside the insulating bakelite sleeve. The gun body positioning block is hermetically connected with the insulating bakelite sleeve. The gun body positioning block is located inside the flange cover. The compression screw outside the insulating bakelite sleeve passes through the bottom of the flange cover, and the end of the compression screw contacts the bottom of the gun body positioning block. This device can be freely adjusted up, down, left and right, so as to quickly align with the end plug hole of the fuel rod, and the tungsten electrode can be replaced and adjusted at will, without affecting the helium pressure and vacuum degree in the welding container during production.

Description

Technical Field

[0001] The present invention belongs to the technology of nuclear fuel manufacturing, and particularly relates to a welding torch. Background Art

[0002] In a pressurized water reactor fuel assembly, the fuel rod is the core component of the entire fuel assembly. The plug hole welding station is a key process in the welding manufacturing of the entire fuel rod, and has important practical significance for the manufacturing precision of the entire fuel assembly.

[0003] In order to solve the problem of the plug hole welding torch for the upper end plug of the fuel rod in the pressurized water reactor fuel assembly. The structure of the existing gun body is as follows: An electrode rod is rotated inside a sintered ceramic, and there is one or two sealing rubber rings on both the sintered ceramic and the electrode rod. The sintered ceramic is fixed on the welding chamber, and then the electrode rod is screwed into the inner hole of the ceramic.

[0004] Since the inner hole and outer circle of the sintered ceramic component are formed by sintering, the geometric tolerance dimensions of each part cannot meet the technical requirements. The production of plug hole welding of the fuel rod is too large, the tungsten electrode is burned out quickly, and the tungsten electrode needs to be adjusted or replaced frequently. And when plugging the hole of the fuel rod, helium gas above 2 MPa needs to be flushed into the cladding tube, and the welding vacuum needs to reach below 5 Pa. Therefore, in the past, the vacuum of the welding chamber often could not reach the specified value for a long time, and the helium pressure decreased extremely rapidly after flushing helium. And the original gun body is fixed on the wall of the welding chamber by itself, and the tungsten electrode cannot be effectively adjusted to be centered with the central hole of the upper end plug of the fuel rod. Thus, the quality stability of the product cannot be effectively guaranteed, and it is not suitable for large-scale automatic production. Therefore, it is very important to redesign the structure of the gun body for plugging the hole of the fuel rod end plug.

[0005] Since during each shift of work, with the burning of the tungsten electrode, the tungsten electrode and the tungsten electrode rod of the gun body need to be adjusted and locked dozens of times. Therefore, a certain shearing force will inevitably be generated on each connection part of the gun body. Therefore, when designing, it is necessary to consider (1) the fastening of each connection part after long-term work. If it becomes loose, it will affect the decrease of the vacuum and helium pressure in the welding container. Consequences: Directly affect the product quality, continuous maintenance of the equipment, and the end of production. (2) Also, it is necessary to consider the convenience for the operator to quickly operate and the durability of each component of the gun body. Summary of the Invention

[0006] The purpose of the present invention is to provide a welding torch for plugging the hole of the upper end plug of a nuclear fuel rod, which can ensure the technical conditions required for plug hole welding of the fuel rod.

[0007] The technical solution of the present invention is as follows:

[0008] A plug hole welding torch for the upper end of a nuclear fuel rod, comprising an insulating bakelite sleeve, a tungsten electrode positioning seat coaxially arranged inside the insulating bakelite sleeve, and a tungsten electrode rod coaxially arranged inside the tungsten electrode positioning seat. An adjusting screw is provided at the end of the tungsten electrode rod. A compression screw, a flange cover, and a gun body positioning block are coaxially arranged outside the insulating bakelite sleeve. The gun body positioning block is hermetically connected to the insulating bakelite sleeve. The gun body positioning block is located inside the flange cover. The compression screw outside the insulating bakelite sleeve passes through the bottom of the flange cover, and the end of the compression screw contacts the bottom of the gun body positioning block.

[0009] One end of the tungsten electrode positioning seat extends out of the insulating bakelite sleeve, and a nut is installed outside the extended part through a thread.

[0010] The nut is connected to the welding power supply.

[0011] A sealing nut and a locking nut are installed at the left end of the tungsten electrode positioning seat, and the left end of the adjusting screw passes through the sealing nut and the locking nut.

[0012] A sealing gasket II is installed between the installation surface inside the sealing nut and the end face of the tungsten electrode positioning seat, and a sealing gasket I is provided between the installation surface inside the sealing nut and the installation surface of the adjusting screw.

[0013] The outer wall of the insulating bakelite sleeve has a boss, and the gun body positioning block is installed outside the boss.

[0014] The gun body positioning block is hermetically connected to the boss part.

[0015] The gun body positioning block is disc-shaped, and a stepped installation hole is machined in the center. The insulating bakelite sleeve is coaxially installed in the installation hole of the gun body positioning block.

[0016] A number of adjusting screws are installed on the side of the flange cover, and the direction of the adjusting screws is along the radial direction of the flange cover. The number of adjusting screws is evenly distributed in the circumferential direction of the cross-section of the flange cover.

[0017] The remarkable effects of the present invention are as follows:

[0018] The gun body can be freely adjusted up, down, left, and right, so as to quickly align with the end plug hole of the fuel rod, and the tungsten electrode can be replaced and adjusted at will, without affecting the helium pressure and vacuum degree inside the welding container during production.

[0019] The gun body is made of 2Cr13 stainless steel. During the plug hole welding process of the fuel rod, it is necessary to ensure the cleanliness inside the welding container. If other materials are used, it is inevitable that an oxide layer will be brought into the container. The tungsten electrode rod, the tungsten electrode positioning structure, and the tungsten electrode rod locking structure are made of beryllium cobalt copper because this copper is stronger than other copper materials in terms of comprehensive performance such as conductivity, hardness, and wear resistance (in a high-temperature and high-pressure environment state).

[0020] The insulator is made of insulating bakelite because the cylindricity accuracy of the holes is good after processing and the hardness is better than that of other materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of a welding torch for plugging holes at the upper end of a nuclear fuel rod;

[0022] In the figure: 1. Adjusting screw; 2. Locking nut; 3. Sealing gasket I; 4. Sealing nut; 5. Sealing gasket II; 6. Nut; 7. Tungsten electrode rod; 8. Insulating bakelite sleeve; 9. Compression screw; 10. Flange cover; 11. Adjusting screw; 12. Gun body positioning block; 13. Tungsten electrode positioning seat. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be further described below with reference to the drawings and specific embodiments.

[0024] The insulating bakelite sleeve 8 has a cylindrical structure, and the tungsten electrode positioning seat 13 is tightly installed inside it by screwing. The left end of the tungsten electrode positioning seat 13 (as Figure 1 shown) extends out of the insulating bakelite sleeve 8, and the outer wall of the extended part is processed with threads. The right end of the tungsten electrode positioning seat 13 is located inside the insulating bakelite sleeve 8, and a boss structure is processed at a section of the right end of the tungsten electrode positioning seat 13, and the boss is in sealed contact with the insulating bakelite sleeve 8.

[0025] The tungsten electrode rod 7 is installed inside the tungsten electrode positioning seat 13 by threads, and the left end of the tungsten electrode rod 7 is installed with the adjusting screw 1, and the right end extends out of the tungsten electrode positioning seat 13.

[0026] A nut 6 is installed on the outside of the part of the tungsten electrode positioning seat 13 that extends out of the insulating bakelite sleeve 8 by threads, and the nut 6 is connected to the welding power supply.

[0027] The sealing nut 4 and the locking nut 2 are installed at the left end of the tungsten electrode positioning seat 13. The left end of the above-mentioned adjusting screw 1 passes through the sealing nut 4 and the locking nut 2. A sealing gasket II 5 is installed between the installation surface in the sealing nut 4 and the end surface of the tungsten electrode positioning seat 13, and a sealing gasket I 3 is provided between the installation surface in the sealing nut 4 and the installation surface of the adjusting screw 1.

[0028] As Figure 1 shown, a compression screw 9, a flange cover 10 and a gun body positioning block 12 are installed on the outside of the insulating bakelite sleeve 8 from left to right. Among them, the gun body positioning block 12 is installed outside the part of the outer wall of the insulating bakelite sleeve 8 with a boss, and the gun body positioning block 12 is in sealed connection with the boss part. The gun body positioning block 12 is disc-shaped, and a stepped installation hole is processed in the center. The insulating bakelite sleeve 8 is coaxially installed in the installation hole of the gun body positioning block 12.

[0029] An installation hole is processed at the center of the bottom of the flange cover 10, and the insulating bakelite sleeve 8 is coaxially installed with the flange cover 10 through the installation hole.

[0030] Meanwhile, the above-mentioned gun body positioning block 12 is located inside the flange cover 10.

[0031] The pressing screw 9 outside the insulating bakelite sleeve 8 passes through the bottom of the flange cover 10, and the end of the pressing screw 9 contacts the bottom of the above-mentioned gun body positioning block 12.

[0032] A number of adjusting screws 11 are installed on the side of the flange cover 10, and the direction of the adjusting screws 11 is along the radial direction of the flange cover 10. The number of adjusting screws 11 is evenly distributed in the circumferential direction of the cross-section of the flange cover 10.

[0033] The adjusting screws 11 designed on the flange cover 10 can position the gun body positioning block 12 radially.

[0034] The function of the pressing screw 9 is to tightly install the flange cover 10 and the gun body positioning block 12 on the end face.

[0035] Both the insulating bakelite sleeve 8 and the gun body positioning block 12, and the insulating bakelite sleeve 8 and the tungsten electrode positioning seat 13 are connected and matched by left-handed fine-threaded threads, and O-ring seals are placed at the root of the end of each left-handed fine-threaded thread mating part for sealed installation.

[0036] The tungsten electrode positioning seat 13 is screwed into the insulating bakelite sleeve 8 (left-handed), and the insulating bakelite sleeve 8 is screwed into the adjusting positioning block 12 (left-handed). Both end faces of the gun body positioning block 13 have a certain roughness.

[0037] The tungsten electrode rod 7 is screwed into the tungsten electrode positioning seat 13 in a right-handed thread manner, and the tail of the tungsten electrode rod 7 is screwed into the tungsten electrode positioning seat 13 in a right-handed manner, and the locking nut 2 is used to lock the sealing nut 4.

[0038] The assembled gun body is placed into the gun body positioning block 12, and the gun body positioning block 12 is installed inside the flange plate 10.

[0039] After such a mating connection, when the operator tightens (right-handed) the rear end of the tungsten electrode rod 7, since all the connection parts adopt left-handed fine-threaded connections, it will inevitably make each connection part tighter and tighter when rotated, and it will not cause the gun body to affect the fit of each part due to the temperature inside the container and other reasons. Therefore, it will not affect the fluctuations of the vacuum and helium pressure inside the container due to the gun body.

[0040] Adjust the tungsten electrode

[0041] When the tungsten electrode rod 7 exceeds the specified dimension from the welding end face of the fuel rod end plug, loosen the locking nut 2, and rotate the adjusting screw rod 1 forward or backward, so that the tungsten electrode rod 7 with the tungsten electrode moves forward and backward, so that the tungsten electrode rod 7 reaches the specified distance from the welding end face of the fuel rod end plug, and then lock the locking nut 2.

[0042] Replace the tungsten electrode

[0043] When the tungsten electrode is damaged and needs to be replaced, loosen and remove the tungsten electrode rod 7 and the locking nut 2, screw out the tungsten electrode rod 7 to remove the tungsten electrode and replace it.

[0044] Alignment of the tungsten electrode with the end plug

[0045] When the tungsten electrode is reinstalled or the length of the tungsten electrode is adjusted, the tungsten electrode may be misaligned with the center of the end plug. First, loosen the four compression screws 9 on the end face of the flange 10, then adjust the four adjusting screws 11 on the side of the flange 10 to align the tungsten electrode with the center of the end plug, and then tighten the four compression screws 9 on the end face of the flange 10.

[0046] The compression screw 9, the flange cover 10, the adjusting screw 11 and the gun body positioning block 12 are made of 2Cr13 stainless steel after heat treatment. The insulating bakelite sleeve 8 is made of insulating bakelite. The tungsten electrode rod 7, the adjusting screw rod 1, the locking nut 2, the sealing nut 4, the sealing gasket and the tungsten electrode positioning seat 13 are made of beryllium cobalt copper material.

[0047] The 2Cr13 stainless steel is selected because it is necessary to ensure the cleanliness inside the welding container during the welding process of plugging the fuel rod holes. If other materials are used, it is inevitable that an oxide layer will be brought into the container. The beryllium cobalt copper material is used because this copper has stronger comprehensive properties (in a high-temperature and high-pressure environment state) in terms of conductivity, hardness and wear resistance compared with other copper materials.

[0048] The insulating bakelite is selected as the insulator because the cylindricity accuracy of the hole is better after processing and the hardness is better than that of other materials.

[0049] This device is applied in the fuel rod end plug hole plugging machine. The end plug holes of the fuel rods to be plugged and welded meet the welding technical requirements in terms of physical and chemical inspections such as metallography and corrosion; the entire gun body runs stably, meeting the technical conditions and usage requirements. This gun body has been put into production operation. So far, hundreds of thousands of various types of cladding tube end plugs have been welded, and the finished product rate has reached 100%.

Claims

1. A plug-hole welding torch for the upper end plug of a nuclear fuel rod, comprising an insulating bakelite sleeve (8), a tungsten electrode positioning seat (13) coaxially arranged inside the insulating bakelite sleeve (8), and a tungsten electrode rod (7) coaxially arranged inside the tungsten electrode positioning seat (13). Characterized in that: An adjusting screw rod (1) is arranged at the end of the tungsten electrode rod (7), and a compression screw (9), a flange cover (10) and a gun body positioning block (12) are coaxially arranged outside the insulating bakelite sleeve (8). The gun body positioning block (12) is hermetically connected to the insulating bakelite sleeve (8). The gun body positioning block (12) is located inside the flange cover (10). The compression screw (9) outside the insulating bakelite sleeve (8) passes through the bottom of the flange cover (10), and the end of the compression screw (9) contacts the top of the gun body positioning block (12). One end of the tungsten electrode positioning seat (13) extends out of the insulating bakelite sleeve (8), and a nut (6) is installed on the outside of the extended part through a thread. The outer wall of the insulating bakelite sleeve (8) has a boss, and the gun body positioning block (12) is installed outside the boss. The gun body positioning block (12) is hermetically connected to a part of the boss. The gun body positioning block (12) is disc-shaped, and a stepped mounting hole is machined in the center. The insulating bakelite sleeve (8) is coaxially installed in the mounting hole of the gun body positioning block (12). A number of adjusting screws (11) are installed on the side surface of the flange cover (10), and the direction of the adjusting screws (11) is along the radial direction of the flange cover (10). The number of adjusting screws (11) is evenly distributed in the circumferential direction of the cross-section of the flange cover (10).

2. A plug-hole welding torch for the upper end plug of a nuclear fuel rod according to claim 1, Characterized in that: The nut (6) is connected to a welding power source.

3. A plug-hole welding torch for the upper end plug of a nuclear fuel rod according to claim 2, Characterized in that: A sealing nut (4) and a locking nut (2) are installed at the left end of the tungsten electrode positioning seat (13), and the left end of the adjusting screw rod (1) passes through the sealing nut (4) and the locking nut (2).

4. A plug-hole welding torch for the upper end plug of a nuclear fuel rod according to claim 3, Characterized in that: A sealing gasket II (5) is installed between the inner mounting surface of the sealing nut (4) and the end face of the tungsten electrode positioning seat (13). A sealing gasket I (3) is arranged between the inner mounting surface of the sealing nut (4) and the mounting surface of the adjusting screw rod (1).

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