A method for assembling and welding hexagonal nuclear fuel assemblies for pressurized water reactors

Abstract

This invention specifically relates to a method for assembling and welding a hexagonal nuclear fuel assembly for a pressurized water reactor (PWR), comprising the following steps: compressing and releasing a spring within the upper tube seat component of the nuclear fuel assembly using a spring compression device to achieve a snap-fit ​​connection between the upper tube seat component and the rod bundle component; pushing the lower tube seat component into the lower grid plate of the rod bundle component; fixing the welding area between the lower tube seat component and the lower grid plate of the rod bundle component using TIG symmetrical spot welding; and then performing symmetrical weld seams on the welding area to complete the welding of the rod bundle component and the lower tube seat component. This invention also relates to an assembly fixture for a hexagonal nuclear fuel assembly for a PWR. This invention enables the precise assembly and reliable manufacturing of hexagonal nuclear fuel assemblies for PWRs.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel assembly manufacturing technology for nuclear power plants, and in particular to a method for assembling and welding a hexagonal structure nuclear fuel assembly for a pressurized water reactor. Background Technology

[0002] Nuclear fuel assemblies are the core components of a nuclear power plant reactor core, consisting of rod bundle assemblies, upper tube assembly assemblies, and lower tube assembly assemblies. See also... Figure 1 The hexagonal structure of pressurized water reactor (PWR) fuel assemblies is characterized by high burnup and long lifespan. The assembly method for PWR hexagonal fuel assemblies differs from that used in existing commercial nuclear power plants. Current megawatt-class commercial nuclear power plants use expansion joints to connect the rod bundle components to the upper and lower tube assembly components; this assembly method is unsuitable for the assembly of PWR hexagonal fuel assemblies. For example... Figure 2-4 As shown, the rod bundle component of the hexagonal fuel assembly in a pressurized water reactor (PWR) is connected to the upper tube assembly using a snap-fit ​​method. The lower tube assembly is connected to the rod bundle component using a welding method. The welded joint is a non-closed hexagon with uneven clearance, resulting in incomplete penetration during welding. Increasing the welding current leads to burn-through in some welded areas. The welded areas are shown below. Figure 5 As shown, the different shapes and heat capacities of the various parts of the weld bead vary greatly, making it difficult to obtain a uniform weld.

[0003] Therefore, it is necessary to invent a method for assembling and welding hexagonal nuclear fuel assemblies for pressurized water reactors, so as to realize the reliable manufacturing of hexagonal nuclear fuel assemblies for pressurized water reactors. Summary of the Invention

[0004] One of the objectives of this invention is to provide a tooling for assembling hexagonal nuclear fuel assemblies for pressurized water reactors, thereby enabling the precise assembly of hexagonal nuclear fuel assemblies for pressurized water reactors.

[0005] The second objective of this invention is to provide a method for assembling and welding a hexagonal nuclear fuel assembly for a pressurized water reactor, thereby achieving a reliable snap-fit ​​connection between the rod bundle component and the upper tube seat component of the hexagonal nuclear fuel assembly, and a reliable welding between the rod bundle component and the lower tube seat component, thus enabling the reliable manufacturing of the hexagonal nuclear fuel assembly for a pressurized water reactor.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A hexagonal nuclear fuel assembly assembly fixture for a pressurized water reactor includes an assembly platform, a clamping frame, a lower tube seat assembly fixture, and an upper tube seat assembly fixture fixedly connected along the length of the assembly platform, as well as a spring compression device. The clamping frame is matched to the nuclear fuel assembly for laterally fixing the assembly. The lower tube seat assembly fixture is matched to the lower tube seat of the nuclear fuel assembly for positioning against its bottom. The upper tube seat assembly fixture is matched to the upper tube seat of the nuclear fuel assembly for positioning it. The spring compression device is connected to a spring within the upper tube seat of the nuclear fuel assembly for compressing and releasing the spring, thereby securing the step of the guide connecting tube of the upper tube seat within the groove of the guide positioning ring of the rod bundle component. The guide connecting tube of the upper tube seat is located within the spring of the upper tube seat.

[0008] The pressurized water reactor hexagonal nuclear fuel assembly assembly fixture of the present invention achieves precise assembly of the pressurized water reactor hexagonal nuclear fuel assembly. The nuclear fuel assembly is laterally fixed by a clamping frame, the lower tube seat assembly fixture positions the lower tube seat component of the nuclear fuel assembly, the upper tube seat assembly fixture positions the upper tube seat component of the nuclear fuel assembly, and the spring compression device compresses and releases the spring in the upper tube seat component of the nuclear fuel assembly to achieve a snap-fit ​​connection between the step of the guide connecting pipe of the upper tube seat component of the nuclear fuel assembly and the groove of the positioning ring of the guide pipe of the rod bundle component of the nuclear fuel assembly.

[0009] Furthermore, the spring compression device includes a tightening wrench, a support frame, and a compression platform; the compression platform is used to place the upper tube seat component of the nuclear fuel assembly thereon; the support frame has an opening at the bottom and is detachably fixedly connected to the top of the compression platform, for fitting the upper tube seat component of the nuclear fuel assembly placed on the compression platform inside it; the tightening wrench is used to pass through the top of the support frame and the top of the upper tube seat component of the nuclear fuel assembly and connect to the spring inside the upper tube seat component of the nuclear fuel assembly.

[0010] The present invention also provides a method for assembling and welding a hexagonal nuclear fuel assembly for a pressurized water reactor, comprising the following steps:

[0011] Step 1: Compress and release the spring in the upper tube seat component of the nuclear fuel assembly using a spring compression device to achieve a snap-fit ​​connection between the step of the guide connecting tube of the upper tube seat component of the nuclear fuel assembly and the groove of the positioning ring of the guide tube of the guide tube of the nuclear fuel assembly rod bundle component, thus completing the snap-fit ​​connection between the nuclear fuel assembly rod bundle component and the upper tube seat component of the nuclear fuel assembly.

[0012] Step 2: Push the lower tube seat component of the nuclear fuel assembly into the lower grid plate of the nuclear fuel assembly rod bundle component. Fix the welding area between the lower tube seat component of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component by TIG symmetrical spot welding. Then, perform symmetrical welds on the welding area to complete the welding of the nuclear fuel assembly rod bundle component and the lower tube seat component of the nuclear fuel assembly.

[0013] The assembly and welding method of the hexagonal structure nuclear fuel assembly for pressurized water reactors of the present invention achieves a snap-fit ​​connection between the nuclear fuel assembly rod bundle component and the nuclear fuel assembly upper tube seat component by compressing and releasing the spring in the upper tube seat component of the nuclear fuel assembly through a spring compression device; the welding area between the lower tube seat component of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component is fixed by TIG symmetrical spot welding, thereby controlling the consistency of the fitting clearance in the welding area; and welding deformation is effectively prevented by symmetrical weld seam welding in the welding area.

[0014] Furthermore, prior to step 1, the process includes: checking and confirming that the appearance of the nuclear fuel assembly rod bundle component, the nuclear fuel assembly lower tube seat component, and the nuclear fuel assembly upper tube seat component are free from mechanical damage exceeding the technical requirements; and checking and confirming the cleanliness of the pressurized water reactor hexagonal structure nuclear fuel assembly assembly tooling.

[0015] Furthermore, after step 2, the procedure also includes: conducting an external dimensional inspection of the nuclear fuel assembly to ensure that the external dimensions of the nuclear fuel assembly meet the technical requirements.

[0016] Further, step 1 includes the following steps:

[0017] Step 11: Horizontally fix the nuclear fuel assembly rod bundle component onto the corresponding clamping frame of the assembly platform;

[0018] Step 12: Install the spring compression device on the upper tube seat component of the nuclear fuel assembly. Compress the spring inside the upper tube seat component of the nuclear fuel assembly by the spring compression device, so that the step of the guide connecting pipe of the upper tube seat component of the nuclear fuel assembly extends out of the upper tube seat component of the nuclear fuel assembly.

[0019] Step 13: Horizontally fix the compressed nuclear fuel assembly upper tube seat component onto the corresponding clamping frame, and position it using the upper tube seat component assembly tooling.

[0020] Step 14: Push the upper tube seat of the nuclear fuel assembly toward the nuclear fuel assembly rod bundle component, and insert the guide connecting tube of the upper tube seat of the nuclear fuel assembly into the positioning ring of the guide tube of the nuclear fuel assembly rod bundle component;

[0021] Step 15: Release the compression of the spring inside the upper tube seat component of the nuclear fuel assembly. The spring inside the upper tube seat component of the nuclear fuel assembly rebounds, and the step of the guide connecting tube of the upper tube seat component of the nuclear fuel assembly is locked in the groove of the positioning ring of the guide tube of the nuclear fuel assembly rod bundle component, thus completing the snap-fit ​​connection between the nuclear fuel assembly rod bundle component and the upper tube seat component of the nuclear fuel assembly.

[0022] Furthermore, in step 11, the nuclear fuel assembly rod bundle component is laterally lifted by a crane to the corresponding clamping frame, and the nuclear fuel assembly rod bundle component is fixed on the corresponding clamping frame, thereby achieving lateral fixation of the nuclear fuel assembly rod bundle component on the corresponding clamping frame.

[0023] Furthermore, after step 11 and before step 12, the process also includes: wiping the guide tubes extending from the nuclear fuel assembly rod bundle with a dry cotton cloth.

[0024] Further, in step 12, the upper tube seat component of the nuclear fuel assembly is placed on the compression platform by a crane, the support frame is fitted onto the upper tube seat component of the nuclear fuel assembly, the bottom of the support frame is detachably and fixedly connected to the top of the compression platform, and the tightening wrench is passed through the top of the support frame and the top of the upper tube seat component of the nuclear fuel assembly and connected to the spring inside the upper tube seat component of the nuclear fuel assembly, thereby realizing the installation of the spring compression device on the upper tube seat component of the nuclear fuel assembly.

[0025] Furthermore, after step 12 and before step 13, the process also includes: disconnecting the support frame from the compression platform.

[0026] Furthermore, in step 13, the upper tube socket component of the nuclear fuel assembly with tightening wrench and support frame is laterally lifted by a crane to the corresponding clamping frame, and the upper tube socket component of the nuclear fuel assembly with tightening wrench and support frame is fixed on the corresponding clamping frame, thereby achieving lateral fixation of the upper tube socket component of the nuclear fuel assembly with tightening wrench and support frame on the corresponding clamping frame.

[0027] Furthermore, in step 15, the connection between the tightening wrench and the spring of the upper tube seat component of the nuclear fuel assembly, as well as the connection between the tightening wrench and the support frame, is released to relieve the compression of the spring of the upper tube seat component of the nuclear fuel assembly.

[0028] Further, step 2 includes the following steps:

[0029] Step 21: The nuclear fuel assembly lower tube seat component is horizontally fixed on the corresponding clamping frame, and positioning is achieved by the bottom of the nuclear fuel assembly lower tube seat component fitting with the lower tube seat component assembly fixture;

[0030] Step 22: Push the lower tube seat component of the nuclear fuel assembly into the lower grid plate of the nuclear fuel assembly rod bundle component and make it tightly adhere to the lower grid plate of the nuclear fuel assembly rod bundle component;

[0031] Step 23: Use a TIG welding machine to symmetrically spot weld and fix the welding area between the lower tube seat component of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component;

[0032] Step 24: Use a TIG welding machine to symmetrically weld the welding area on both sides each time to complete the welding of the six sides of the welding area.

[0033] Furthermore, in step 21, the lower tube seat component of the nuclear fuel assembly is laterally hoisted to the corresponding clamping frame by a crane, and the lower tube seat component of the nuclear fuel assembly is fixed on the corresponding clamping frame, thereby achieving lateral fixation of the lower tube seat component of the nuclear fuel assembly on the corresponding clamping frame.

[0034] Furthermore, after step 21 and before step 22, the process also includes: cleaning the welding area of ​​the lower tube seat component of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component with a silk cloth soaked in alcohol.

[0035] Furthermore, after step 22 and before step 23, the process also includes: inspecting the incoming electrodes, argon gas, and welding wire; turning on the TIG welding machine to put it into operation and setting the welding parameters.

[0036] Further, see Figure 6 In step 23, the welding area is hexagonal. The six sides of the welding area are symmetrically spot welded and fixed by a TIG welding machine at a welding current of 90A, with two spots welded on each side.

[0037] Furthermore, after step 23 and before step 24, the process also includes: polishing the solder joints until they are shiny and wiping them with a silk cloth soaked in alcohol.

[0038] Furthermore, in step 24, the welding area is welded with six welds on six sides by symmetrical welding on both sides at a welding current of 90-130A using a TIG welding machine. The start and end portions of adjacent welds are allowed to overlap.

[0039] Furthermore, after step 24, the steps also include: polishing the weld to a shine, wiping the weld with a silk cloth soaked in alcohol; and self-checking the appearance quality of the weld to ensure that there is no oxidation color on the outer surface of the weld.

[0040] Beneficial technical effects of the present invention:

[0041] The pressurized water reactor hexagonal nuclear fuel assembly assembly tooling of the present invention achieves precise assembly of the pressurized water reactor hexagonal nuclear fuel assembly. The nuclear fuel assembly is laterally fixed by a clamping frame, the lower tube seat assembly tooling positions the lower tube seat component of the nuclear fuel assembly, the upper tube seat assembly tooling positions the upper tube seat component of the nuclear fuel assembly, and the spring compression device compresses and releases the spring in the upper tube seat component of the nuclear fuel assembly, thereby achieving a snap-fit ​​connection between the step of the guide connecting pipe of the upper tube seat component of the nuclear fuel assembly and the positioning ring of the guide pipe of the rod bundle component of the nuclear fuel assembly.

[0042] The assembly and welding method of the pressurized water reactor hexagonal nuclear fuel assembly of the present invention uses a spring compression device to compress and release the spring in the upper tube seat component of the nuclear fuel assembly, thereby achieving a snap-fit ​​connection between the step of the guide connecting pipe of the upper tube seat component and the positioning ring of the guide pipe of the nuclear fuel assembly rod bundle component; the welding area of ​​the lower tube seat component of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component is fixed by TIG symmetrical spot welding, thereby controlling the consistency of the fitting clearance in the welding area; and the welding deformation is effectively prevented by symmetrical weld welding of the welding area, ultimately achieving reliable manufacturing of the pressurized water reactor hexagonal nuclear fuel assembly. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the external structure of a hexagonal nuclear fuel assembly in a pressurized water reactor.

[0044] Figure 2 A schematic diagram of the upper tube seat component of a hexagonal nuclear fuel assembly for a pressurized water reactor before assembly.

[0045] Figure 3 A schematic diagram of the rod bundle component of a hexagonal nuclear fuel assembly for a pressurized water reactor before assembly.

[0046] Figure 4 A front view of the upper tube assembly and rod bundle assembly of a hexagonal nuclear fuel assembly for a pressurized water reactor after assembly;

[0047] Figure 5 A rearward view of the assembly of the upper tube assembly and rod bundle assembly of the hexagonal nuclear fuel assembly of a pressurized water reactor;

[0048] Figure 6 A schematic diagram of the assembly of a hexagonal nuclear fuel assembly for a pressurized water reactor.

[0049] Figure 7 This is a schematic diagram of the use of a spring compression device;

[0050] Figure 8 This is a schematic diagram of the symmetrical weld seam of the welding area between the lower tube assembly and the rod bundle assembly of a hexagonal nuclear fuel assembly in a pressurized water reactor.

[0051] In the diagram, 1. Upper tube seat component of nuclear fuel assembly; 2. Rod bundle component of nuclear fuel assembly; 3. Lower tube seat component of nuclear fuel assembly; 4. Assembly fixture for upper tube seat component; 5. Assembly platform; 6. Clamping frame; 7. Assembly fixture for lower tube seat component; 8. Tightening wrench; 9. Support frame; 10. Compression platform; 11. Guide connecting pipe for upper tube seat component of nuclear fuel assembly; 21. Positioning ring for guide pipe of rod bundle component of nuclear fuel assembly. Detailed Implementation

[0052] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] In the description of this invention, it should be understood that the terms "top", "bottom", "above", "below", "external", "internal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0054] See Figure 6-7 This embodiment provides an assembly fixture for a hexagonal nuclear fuel assembly of a pressurized water reactor, including an assembly platform 5, a clamping frame 6, a lower tube seat assembly fixture 7, and an upper tube seat assembly fixture 4 fixedly connected along the length of the assembly platform 5, and a spring compression device. The clamping frame 6 matches the nuclear fuel assembly and is used to laterally fix the nuclear fuel assembly. The lower tube seat assembly fixture 7 matches the lower tube seat component 3 of the nuclear fuel assembly and is used to fit and position itself against the bottom of the lower tube seat component 3. The upper tube seat assembly fixture 4 matches the upper tube seat component 1 of the nuclear fuel assembly and is used to position the upper tube seat component 1. The spring compression device is connected to a spring inside the upper tube seat component 1 of the nuclear fuel assembly and is used to compress and release the spring inside the upper tube seat component 1 of the nuclear fuel assembly, so that the step of the guide connecting pipe 11 of the upper tube seat component of the nuclear fuel assembly is locked in the groove of the positioning ring 21 of the guide pipe of the rod bundle component of the nuclear fuel assembly. The guide connecting pipe 11 of the upper tube seat component of the nuclear fuel assembly is inside the spring of the upper tube seat component 1 of the nuclear fuel assembly.

[0055] In this embodiment, the spring compression device includes a tightening wrench 8, a support frame 9, and a compression platform 10; the compression platform 10 is used to place the upper tube seat component 1 of the nuclear fuel assembly on it; the support frame 9 has an opening at the bottom and is detachably and fixedly connected to the top of the compression platform 10, and is used to fit the upper tube seat component 1 of the nuclear fuel assembly placed on the compression platform 10 inside it; the tightening wrench 8 is used to pass through the top of the support frame 9 and the top of the upper tube seat component 1 of the nuclear fuel assembly and connect to the spring inside the upper tube seat component 1 of the nuclear fuel assembly.

[0056] The pressurized water reactor hexagonal nuclear fuel assembly assembly fixture of this embodiment achieves precise assembly of the pressurized water reactor hexagonal nuclear fuel assembly. The nuclear fuel assembly is laterally fixed by the clamping frame 6, the lower tube seat assembly fixture 7 positions the lower tube seat assembly 3 of the nuclear fuel assembly, the upper tube seat assembly fixture 4 positions the upper tube seat assembly 1 of the nuclear fuel assembly, and the spring in the upper tube seat assembly 1 of the nuclear fuel assembly is compressed and released by the spring compression device to achieve the snap-fit ​​connection between the step of the guide connecting pipe 11 of the upper tube seat assembly and the groove of the positioning ring 21 of the guide pipe of the nuclear fuel assembly rod bundle assembly.

[0057] This embodiment also provides a method for assembling and welding a hexagonal nuclear fuel assembly for a pressurized water reactor, using the aforementioned assembly fixture, including the following steps:

[0058] Step 1: Compress and release the spring in the upper tube seat component 1 of the nuclear fuel assembly by spring compression device, so as to realize the snap-fit ​​connection between the step of the guide connecting pipe 11 of the upper tube seat component of the nuclear fuel assembly and the groove of the positioning ring 21 of the guide pipe of the guide pipe of the nuclear fuel assembly rod bundle component, and complete the snap-fit ​​connection between the nuclear fuel assembly rod bundle component 2 and the upper tube seat component 1 of the nuclear fuel assembly.

[0059] Step 2: Push the lower tube seat component 3 of the nuclear fuel assembly into the lower grid plate of the nuclear fuel assembly rod bundle component 2. Fix the welding area between the lower tube seat component 3 of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component 2 by TIG symmetrical spot welding. Then, perform symmetrical welds on the welding area to complete the welding of the nuclear fuel assembly rod bundle component 2 and the lower tube seat component 3 of the nuclear fuel assembly.

[0060] In this embodiment, before step 1, the following steps are also included: checking and confirming that the appearance of the nuclear fuel assembly rod bundle component 2, the nuclear fuel assembly lower tube seat component 3, and the nuclear fuel assembly upper tube seat component 1 are free from mechanical damage exceeding the technical requirements; and checking and confirming the cleanliness of the pressurized water reactor hexagonal structure nuclear fuel assembly assembly tooling.

[0061] In this embodiment, after step 2, the method further includes: performing an external dimension inspection of the nuclear fuel assembly to ensure that the external dimension of the nuclear fuel assembly meets the technical requirements.

[0062] In this embodiment, step 1 includes the following steps:

[0063] Step 11: Horizontally fix the nuclear fuel assembly rod bundle component 2 onto the corresponding clamping frame 6 of the assembly platform;

[0064] Step 12: Install the spring compression device on the upper tube seat component 1 of the nuclear fuel assembly, and compress the spring in the upper tube seat component 1 of the nuclear fuel assembly by the spring compression device, so that the step of the guide connecting pipe 11 of the upper tube seat component of the nuclear fuel assembly extends out of the upper tube seat component 1 of the nuclear fuel assembly.

[0065] Step 13: The compressed nuclear fuel assembly upper tube seat component 1 is horizontally fixed on the corresponding clamping frame 6 and positioned by the upper tube seat component assembly tooling 4.

[0066] Step 14: Push the upper tube seat component 1 of the nuclear fuel assembly towards the direction of the nuclear fuel assembly rod bundle component 2, and insert the guide connecting tube 11 of the upper tube seat component of the nuclear fuel assembly into the positioning ring 21 of the guide tube of the nuclear fuel assembly rod bundle component;

[0067] Step 15: Release the compression of the spring inside the upper tube seat component 1 of the nuclear fuel assembly. The spring inside the upper tube seat component 1 of the nuclear fuel assembly rebounds, and the step of the guide connecting pipe 11 of the upper tube seat component of the nuclear fuel assembly is locked in the groove of the positioning ring 21 of the guide pipe of the nuclear fuel assembly rod bundle component, thus completing the snap-fit ​​connection between the nuclear fuel assembly rod bundle component 2 and the upper tube seat component 1 of the nuclear fuel assembly.

[0068] In this embodiment, in step 11, the nuclear fuel assembly rod bundle component 2 is laterally lifted by a crane to the corresponding clamping frame 6, and the nuclear fuel assembly rod bundle component 2 is fixed on the corresponding clamping frame 6, thereby achieving lateral fixation of the nuclear fuel assembly rod bundle component 2 on the corresponding clamping frame.

[0069] In this embodiment, after step 11 and before step 12, the method further includes wiping the guide tube extending from the nuclear fuel assembly rod bundle component 2 with a dry cotton cloth.

[0070] In this embodiment, in step 12, the upper tube seat component 1 of the nuclear fuel assembly is placed on the compression platform 10 by a crane, the support frame 9 is fitted onto the upper tube seat component 1 of the nuclear fuel assembly, the bottom of the support frame 9 is detachably and fixedly connected to the top of the compression platform 10, and the tightening wrench 8 is passed through the top of the support frame 9 and the top of the upper tube seat component 1 of the nuclear fuel assembly and connected to the spring inside the upper tube seat component 1 of the nuclear fuel assembly, so as to realize the installation of the spring compression device on the upper tube seat component 1 of the nuclear fuel assembly.

[0071] In this embodiment, after step 12 and before step 13, the method further includes: disconnecting the support frame 9 from the compression platform 10.

[0072] In this embodiment, in step 13, the upper tube seat component 1 of the nuclear fuel assembly with tightening wrench 8 and support frame 9 is laterally lifted by a crane to the corresponding clamping frame 6, and the upper tube seat component 1 of the nuclear fuel assembly with tightening wrench 8 and support frame 9 is fixed on the corresponding clamping frame 6, thereby achieving lateral fixation of the upper tube seat component 1 of the nuclear fuel assembly with tightening wrench 8 and support frame 9 on the corresponding clamping frame.

[0073] In this embodiment, in step 15, the connection between the tightening wrench 8 and the spring of the upper tube seat component 1 of the nuclear fuel assembly, as well as the connection between the tightening wrench 8 and the support frame 9, is released to relieve the compression of the spring of the upper tube seat component 1 of the nuclear fuel assembly.

[0074] In this embodiment, step 2 includes the following steps:

[0075] Step 21: The nuclear fuel assembly lower tube seat component 3 is horizontally fixed on the corresponding clamping frame 6, and the positioning is achieved by the bottom of the nuclear fuel assembly lower tube seat component 3 fitting with the lower tube seat component assembly fixture 7.

[0076] Step 22: Push the lower tube seat component 3 of the nuclear fuel assembly into the lower grid plate of the nuclear fuel assembly rod bundle component 2 and make it closely adhere to the lower grid plate of the nuclear fuel assembly rod bundle component 2;

[0077] Step 23: Use a TIG welding machine to symmetrically spot weld and fix the welding area between the lower tube seat component 3 of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component 2;

[0078] Step 24: Use a TIG welding machine to symmetrically weld the welding area on both sides each time to complete the welding of the six sides of the welding area.

[0079] In this embodiment, in step 21, the lower tube seat component 3 of the nuclear fuel assembly is laterally hoisted to the corresponding clamping frame 6 by a crane, and the lower tube seat component 3 of the nuclear fuel assembly is fixed on the corresponding clamping frame 6, thereby achieving lateral fixation of the lower tube seat component 3 of the nuclear fuel assembly on the corresponding clamping frame.

[0080] In this embodiment, after step 21 and before step 22, the method further includes: cleaning the welding area between the lower tube seat component 3 of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component 2 with a silk cloth soaked in alcohol.

[0081] In this embodiment, after step 22 and before step 23, the following steps are also included: inspecting the incoming electrodes, argon gas, and welding wire; turning on the TIG welding machine to put it into working condition and setting the welding parameters.

[0082] In this embodiment, see Figure 8 In step 23, the welding area is hexagonal. The six sides of the welding area are symmetrically spot-welded and fixed by a TIG welding machine at a welding current of 90A, with two spots welded on each side.

[0083] In this embodiment, after step 23 and before step 24, the method further includes: polishing the solder joints until they are shiny and wiping them with a silk cloth soaked in alcohol.

[0084] In this embodiment, in step 24, the welding area is welded with six welds on six sides by a TIG welding machine at a welding current of 90-130A each time, with each weld being symmetrically welded on both sides. The start and end parts of adjacent welds are allowed to overlap.

[0085] In this embodiment, after step 24, the method further includes: polishing the weld to a bright finish and wiping the weld with a silk cloth soaked in alcohol; and checking the appearance quality of the weld to ensure that there is no oxidation color on the outer surface of the weld.

[0086] The assembly and welding method of the hexagonal nuclear fuel assembly of the pressurized water reactor in this embodiment uses a spring compression device to compress and release the spring in the upper tube seat component 1 of the nuclear fuel assembly, thereby achieving a snap-fit ​​connection between the nuclear fuel assembly rod bundle component 2 and the upper tube seat component 1 of the nuclear fuel assembly; the welding area between the lower tube seat component 3 of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component 2 is fixed by TIG symmetrical spot welding, thereby controlling the consistency of the fitting clearance in the welding area; and welding deformation is effectively prevented by symmetrical weld seam welding in the welding area.

[0087] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for assembling and welding a hexagonal nuclear fuel assembly for a pressurized water reactor, using a pressurized water reactor hexagonal nuclear fuel assembly assembly fixture, the fixture comprising an assembly platform (5), a clamping frame (6) fixedly connected along the length of the assembly platform (5), a lower tube seat assembly fixture (7) and an upper tube seat assembly fixture (4), and a spring compression device; the clamping frame (6) is matched with the nuclear fuel assembly for laterally fixing the nuclear fuel assembly; the lower tube seat assembly fixture (7) is matched with the lower tube seat component (3) of the nuclear fuel assembly for fitting and positioning against the bottom of the lower tube seat component (3); the upper tube seat assembly fixture (4) is matched with the upper tube seat component (1) of the nuclear fuel assembly for positioning the upper tube seat component (1); the spring compression device is connected to the upper tube seat component (1) of the nuclear fuel assembly. The spring connection is used to compress and release the spring in the upper tube seat component (1) of the nuclear fuel assembly, so that the step of the guide connecting pipe (11) of the upper tube seat component of the nuclear fuel assembly is locked in the groove of the positioning ring (21) of the guide pipe of the guide pipe of the nuclear fuel assembly rod bundle component; the spring compression device includes a tightening wrench (8), a support frame (9) and a compression platform (10); the compression platform (10) is used to place the upper tube seat component (1) of the nuclear fuel assembly thereon; the support frame (9) has an open bottom and is detachably fixedly connected to the top of the compression platform (10) for fitting the upper tube seat component (1) of the nuclear fuel assembly placed on the compression platform (10) thereon; the tightening wrench (8) is used to pass through the top of the support frame (9) and the top of the upper tube seat component (1) of the nuclear fuel assembly and connect with the spring in the upper tube seat component (1) of the nuclear fuel assembly; characterized in that, Includes the following steps: Step 1: Compress and release the spring in the upper tube seat component (1) of the nuclear fuel assembly by spring compression device to achieve the snap-fit ​​connection between the step of the guide connecting pipe (11) of the upper tube seat component of the nuclear fuel assembly and the groove of the positioning ring (21) of the guide pipe of the guide tube of the nuclear fuel assembly rod bundle component, and complete the snap-fit ​​connection between the nuclear fuel assembly rod bundle component (2) and the upper tube seat component (1) of the nuclear fuel assembly. Step 2: Push the lower tube seat component (3) of the nuclear fuel assembly into the lower grid plate of the nuclear fuel assembly rod bundle component (2), fix the welding area of ​​the lower tube seat component (3) of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component (2) by TIG symmetrical spot welding, and then perform symmetrical weld welding on the welding area to complete the welding of the nuclear fuel assembly rod bundle component (2) and the lower tube seat component (3) of the nuclear fuel assembly. Step 1 includes the following steps: Step 11: Horizontally fix the nuclear fuel assembly rod bundle component (2) onto the corresponding clamping frame (6) of the assembly platform; Step 12: Install the spring compression device on the upper tube seat component (1) of the nuclear fuel assembly, and compress the spring in the upper tube seat component (1) of the nuclear fuel assembly by the spring compression device, so that the step of the guide connecting pipe (11) of the upper tube seat component of the nuclear fuel assembly extends out of the upper tube seat component (1). Step 13: The compressed nuclear fuel assembly upper tube seat component (1) is horizontally fixed on the corresponding clamping frame (6) and positioned by the upper tube seat component assembly fixture (4); Step 14: Push the upper tube seat component (1) of the nuclear fuel assembly towards the direction of the nuclear fuel assembly rod bundle component (2), and insert the guide connecting pipe (11) of the upper tube seat component of the nuclear fuel assembly into the positioning ring (21) of the guide pipe of the nuclear fuel assembly rod bundle component; Step 15: Release the compression of the spring inside the upper tube seat component (1) of the nuclear fuel assembly. The spring inside the upper tube seat component (1) of the nuclear fuel assembly rebounds. The step of the guide connecting pipe (11) of the upper tube seat component of the nuclear fuel assembly is locked in the groove of the positioning ring (21) of the guide pipe of the nuclear fuel assembly rod bundle component, thus completing the snap-fit ​​connection between the nuclear fuel assembly rod bundle component (2) and the upper tube seat component (1) of the nuclear fuel assembly. In step 12, the upper tube seat component (1) of the nuclear fuel assembly is placed on the compression platform (10) by a crane, the support frame (9) is fitted onto the upper tube seat component (1) of the nuclear fuel assembly, the bottom of the support frame (9) is detachably and fixedly connected to the top of the compression platform (10), and the tightening wrench (8) is passed through the top of the support frame (9) and the top of the upper tube seat component (1) of the nuclear fuel assembly and connected to the spring inside the upper tube seat component (1) of the nuclear fuel assembly, so as to realize the installation of the spring compression device on the upper tube seat component (1) of the nuclear fuel assembly.

2. The method for assembling and welding hexagonal nuclear fuel assemblies for pressurized water reactors according to claim 1, characterized in that, After step 12 and before step 13, the process also includes: disconnecting the support frame (9) from the compression platform (10).

3. The method for assembling and welding hexagonal nuclear fuel assemblies for pressurized water reactors according to claim 2, characterized in that, In step 15, the connection between the tightening wrench (8) and the spring of the upper tube seat component (1) of the nuclear fuel assembly is released, as well as the connection between the tightening wrench (8) and the support frame (9), thereby releasing the compression of the spring of the upper tube seat component (1) of the nuclear fuel assembly.

4. The method for assembling and welding hexagonal nuclear fuel assemblies for pressurized water reactors according to claim 1, step 2 includes the following steps: Step 21: The nuclear fuel assembly lower tube seat component (3) is horizontally fixed on the corresponding clamping frame (6), and the positioning is achieved by the bottom of the nuclear fuel assembly lower tube seat component (3) fitting with the lower tube seat component assembly fixture (7); Step 22: Push the lower tube seat component (3) of the nuclear fuel assembly into the lower grid plate of the nuclear fuel assembly rod bundle component (2) and make it close to the lower grid plate of the nuclear fuel assembly rod bundle component (2); Step 23: Use a TIG welding machine to symmetrically spot weld and fix the welding area of ​​the lower tube seat component (3) of the nuclear fuel assembly and the lower grid plate of the nuclear fuel assembly rod bundle component (2); Step 24: Use a TIG welding machine to symmetrically weld the welding area on both sides each time to complete the welding of the six sides of the welding area.

5. The method for assembling and welding hexagonal nuclear fuel assemblies for pressurized water reactors according to claim 3, characterized in that, In step 23, the welding area is hexagonal. The six sides of the welding area are symmetrically spot-welded and fixed using a TIG welding machine at a welding current of 90A, with two spots welded on each side.

6. The method for assembling and welding hexagonal nuclear fuel assemblies for pressurized water reactors according to claim 3, characterized in that, In step 24, the welding area is welded with six welds on six sides by symmetrical welding on both sides at a welding current of 90-130A using a TIG welding machine. The start and end parts of adjacent welds are allowed to overlap.

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