Spent fuel storage grillwork inner chamber assembling method

Abstract

The invention relates to a spent fuel storage grillwork inner chamber assembly method, and belongs to the technical field of frame mechanical process assembly. The method comprises the following steps: starting from the fixation of a peripheral plate and an erected bottom plate, assembling longitudinal partition plates one by one layer by layer, repeatedly entering and exiting between the longitudinal partition plates by using an auxiliary tool assembled by a supporting assembly and a positioning plate, sleeving inner chambers in gaps between the longitudinal partition plates one by one layer by layer, assembling transverse partition plates one by layer, and finally assembling the longitudinal partition plates. And finally, the rest three surfaces of the assembled inner chamber are surrounded and fixed by three peripheral plates, so that the assembly of the whole spent fuel storage grillwork inner chamber is completed. By means of the method, the inner chamber, formed by splicing boron steel, of the spent fuel storage grillwork does not fall apart and deform in the assembling process, accurate positioning is provided, and therefore the assembling efficiency and the assembling quality of the spent fuel storage grillwork are improved, and certain interchangeability is achieved.

Description

Technical Field

[0001] The present invention relates to an assembly method for the inner chamber of a spent fuel storage grid, which is used to achieve the precise positioning and auxiliary support of the boron steel inner chamber during the manufacturing process of the spent fuel storage grid, and belongs to the technical field of frame mechanical process assembly. Background Art

[0002] The spent fuel storage grid is an important device in the fuel operation and storage system of a nuclear power plant. It is installed in the fuel building and plays a crucial role in ensuring the normal operation of the nuclear power plant.

[0003] Currently, the commonly used boron steel spent fuel storage grids are all dense grids. To prevent the spent fuel from colliding and squeezing, the grid size accuracy requirements are high and the manufacturing difficulty is great. Usually, the tolerance of the grid pitch positioning dimension between each inner chamber is within ±1 mm, and the requirements for the perpendicularity and flatness of the inner chamber itself are also extremely high. Boron steel is often used as a neutron absorption material for the spent fuel storage grid. To prevent damage to the boron steel caused by welding and possible intergranular corrosion problems, the inner chambers of the spent fuel storage grid made of boron steel are usually not welded. Therefore, during the assembly process, the inner chambers are more likely to be misaligned and deformed, and corresponding manufacturing methods and auxiliary tooling are required to control the positioning and deformation during assembly. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: how to improve the assembly efficiency and assembly quality of the boron steel inner chamber of the spent fuel storage grid during installation.

[0005] The technical solution proposed by the present invention to solve the above technical problem is: an assembly method for the inner chamber of a spent fuel storage grid, including the following steps: Step 1: Lay a rectangular grid outer plate flat on the installation plane, stand the grid bottom plate perpendicular to the grid outer plate, so that the side surface of the grid bottom plate presses on one end of the grid outer plate. The end surface of the bottom plate is placed parallel to the short side of the outer plate. Weld and fix the joint where the bottom plate contacts the outer plate, and weld and fix the first triangular brace on the outer side surface of the bottom plate; there are rows of multiple first long slotted holes and columns of multiple first short slotted holes spaced perpendicular to the rows of first long slotted holes on the outer plate, and rows of multiple round holes are opened on the bottom plate; Step 2: Install multiple long strip-shaped first-layer longitudinal partitions on the outer plate. The two long sides of the longitudinal partition are respectively provided with tabs. Vertically insert the multiple first-layer longitudinal partitions into the outer plate. The tab on one long side of the first-layer longitudinal partition is tenoned with the first long slotted hole on the outer plate; Step 3: Assemble the support component and the positioning plate into an auxiliary tooling; The support assembly includes a long rectangular tube. Insertion holes are formed in the four side walls of the long rectangular tube and respectively insert one folded edge of an L-shaped plate. A telescopic cylinder inserted into the insertion hole is fixed to one folded edge of the L-shaped plate inserted into the insertion hole. The other folded edge of the L-shaped plate extending out of the insertion hole is fixedly attached to the outer side wall of the long rectangular tube. Support plates are distributed outside the four side walls of the long rectangular tube. The end of the extending rod of the telescopic cylinder extends out of the insertion hole and is fixed to the support plate. A square sleeve is sleeved on one end of the long rectangular tube, and a circular boss is fixedly provided on the other end face of the long rectangular tube. The positioning plate has the same size as the grid bottom plate. On one surface of the positioning plate, multiple rows of square bumps, with multiple bumps in each row, are welded at intervals. A second triangular brace is welded on the other surface of the positioning plate. After the square sleeves at one ends of the long rectangular tubes of multiple support assemblies in the first row are respectively sleeved and installed with the multiple square bumps in the first row on the positioning plate one by one, an auxiliary tooling is formed. Step 4: Push the installed auxiliary tooling as a whole into the gaps between multiple first-layer longitudinal partitions on the peripheral plate. The circular bosses at the other ends of the long rectangular tubes of the support assembly are inserted into the circular holes in the first row of the grid bottom plate. Open the telescopic cylinders on the two transverse sides inside the long rectangular tube so that the support plates on the two transverse sides support on the first-layer longitudinal partitions, and weld and fix the contact seams between the first-layer longitudinal partitions and the peripheral plate. After welding and cooling, close the telescopic cylinders, and the support plates retract away from the first-layer longitudinal partitions. Withdraw the auxiliary tooling as a whole from the first-layer longitudinal partitions. Step 5: Lift and place the inner chamber of the first layer into the gaps between the first-layer longitudinal partitions. The inner chamber is surrounded by four boron stainless steel plates on four sides. Grooves and protrusions are formed at the edges of each steel plate. The grooves and protrusions at the edges of adjacent two steel plates are correspondingly tenoned to form a rectangular cross-section inner chamber surrounded on four sides. An L-shaped clamp is provided on the outer side of the inner chamber, and a flange is formed on the side of the L-shaped clamp. Push the auxiliary tooling as a whole into the gaps between the first-layer longitudinal partitions again. The long rectangular tubes of the support assembly are inserted into the inner chamber along the axial direction of the inner chamber. Open the telescopic cylinders on the four sides inside the long rectangular tube again to drive the support plates on the four sides to support the four side walls of the first-layer longitudinal partitions. Then lay the first-layer transverse partition flat on the first-layer inner chamber. Second long slotted holes and second short slotted holes are formed in the transverse partition. Multiple spaced small convex edges are formed on the two long sides of the transverse partition. Tenon the convex piece on the other long side of the first-layer longitudinal partition with the second long slotted hole on the transverse partition. At the same time, tenon the flange on the bottom side of the clamp with the first short slotted hole on the peripheral plate, and tenon the flange on the top side of the clamp with the second short slotted hole on the transverse partition. Then weld and fix the tenoned parts. After welding and cooling, close the telescopic cylinders, and the support plates retract away from the four side walls of the first-layer longitudinal partitions. Withdraw the auxiliary tooling as a whole from the first-layer longitudinal partitions again. Step 6: Install multiple second-layer longitudinal partitions in the second row on the first-layer cross partition. The tabs on one long side of each second-layer longitudinal partition are tenoned with the second long slotted holes of the first-layer cross partition. Repeat Step 3, and respectively and successively fit and install the square sleeves at one end of the long square tubes of multiple support components in the second row with multiple square bumps in the second row on the positioning plates of the support components one by one. Repeat Steps 4 - 5 to complete the installation of the inner chamber of the second layer between the second-layer longitudinal partitions and the welding and fixation between the second-layer longitudinal partitions and the first-layer cross partition. Repeat Step 6 to complete the installation of the second-layer cross partition. Repeat Steps 3 - 6 in this way to continue to complete the installation and fixation of multiple layers of longitudinal partitions, multiple layers of inner chambers, and multiple layers of cross partitions. Step 7: Successively complete the supplementation of the peripheral plates on the remaining three sides of the spent fuel storage rack. Tenon the small tabs on the two long side edges of the multiple-layer cross partitions with the first long slotted holes on the peripheral plates on both sides. At the same time, tenon the flanges on both sides of the clamp of the multiple-layer inner chamber with the first short slotted holes on the peripheral plates on both sides. Then tenon the tabs of the topmost-layer longitudinal partition with the first long slotted holes on the peripheral plate of the top surface. At the same time, tenon the flanges on the top side of the clamp of the topmost-layer inner chamber with the first short slotted holes on the peripheral plate of the top surface. Finally, weld and fix the seams between the four peripheral plates and the seams between the peripheral plates of the remaining three sides and the bottom plate to complete the installation of the entire spent fuel storage rack.

[0006] Through the assembly method provided in the present invention, the inner chamber of the spent fuel storage rack made of boron steel can be prevented from falling apart and deforming during the assembly process, and precise positioning can be provided, thereby improving the assembly efficiency and assembly quality of the spent fuel storage rack and having a certain interchangeability. It provides a practical assembly method for batch installation of the inner chamber of the spent fuel storage rack.

[0007] Furthermore, in Steps 4 and 5, a laser scanner is used to align the auxiliary tooling with the first-layer longitudinal partition on the peripheral plate. Description of the Drawings

[0008] Figure 1 It is a schematic structural diagram of the assembly state of Step 1 of the inner chamber assembly method of the spent fuel storage rack in the embodiment.

[0009] Figure 2 It is a schematic structural diagram of the assembly state of Step 2 of the inner chamber assembly method of the spent fuel storage rack in the embodiment.

[0010] Figure 3 It is a schematic structural diagram of the assembly state of the auxiliary tooling in Step 3 of the inner chamber assembly method of the spent fuel storage rack in the embodiment.

[0011] Figure 4It is a schematic structural diagram of the support component.

[0012] Figure 5 It is Figure 4 a sectional view.

[0013] Figure 6 It is a schematic structural diagram of the assembly state of step 4 in the method for assembling the inner chamber of the spent fuel storage grid frame of the embodiment.

[0014] Figure 7 It is a schematic structural diagram of the first assembly state of step 5 in the method for assembling the inner chamber of the spent fuel storage grid frame of the embodiment.

[0015] Figure 8 It is a schematic structural diagram of the inner chamber of the spent fuel storage grid frame of the embodiment.

[0016] Figure 9 It is Figure 8 a sectional view.

[0017] Figure 10 It is a schematic structural diagram of the second assembly state of step 5 in the method for assembling the inner chamber of the spent fuel storage grid frame of the embodiment.

[0018] Figure 11 It is a schematic structural diagram of the third assembly state of step 5 in the method for assembling the inner chamber of the spent fuel storage grid frame of the embodiment.

[0019] Figure 12 It is Figure 11 a schematic structural diagram of the transverse partition in

[0020] Figure 13 It is a schematic structural diagram of the assembly state in step 6 of the method for assembling the inner chamber of the spent fuel storage grid frame of the embodiment.

[0021] Figure 14 It is a schematic structural diagram of the assembly state in step 7 of the method for assembling the inner chamber of the spent fuel storage grid frame of the embodiment. Detailed implementation mode Embodiment

[0022] For the method for assembling the inner chamber of the spent fuel storage grid frame of this embodiment, the inner chamber of the spent fuel storage grid frame has a size of 222×222 mm, the distance between longitudinal partitions is 280 mm, and the center distance between adjacent inner chambers is 280 mm. The installation method includes the following steps: Step 1: As Figure 1As shown in the figure, lay a rectangular grid frame outer plate 1 flat on the installation plane (such as the floor or the plane of other installation platforms). Use a crane to erect the grid frame bottom plate 2 perpendicular to the grid frame outer plate 1, so that the side of the grid frame bottom plate 2 presses on one end of the grid frame outer plate 1. The end face of the bottom plate 2 is placed parallel to the short side of the outer plate 1. Weld the joint where the bottom plate 2 contacts the outer plate 1 to fix the bottom plate 2 and the outer plate 1. Weld and fix the first triangular brace 3 on the outer side of the bottom plate 2 to assist in supporting the bottom plate 1. There are five rows of fifteen first long slotted holes 4 and eight columns of six first short slotted holes 24 spaced perpendicular to the rows of first long slotted holes 4 on the outer plate 1. Six rows of six circular holes 5 are opened on the bottom plate 2. Step 2: As Figure 2 shown in the figure, install five long strip-shaped first-layer longitudinal partition plates 7 on the outer plate 1. There are tabs 8 on the two long sides of the longitudinal partition plates 7. Vertically insert the six first-layer longitudinal partition plates 7 into the outer plate 1. The tab 8 on one long side (the bottom long side) of the first-layer longitudinal partition plate 7 is tenoned with the first slotted hole 4 on the outer plate 1.

[0023] Step 3: As Figure 3 shown in the figure, assemble the support component 9 and the positioning plate 10 into an auxiliary tooling 100. The auxiliary tooling 100 is assembled from the support component 9 and the positioning plate 10. First, introduce the support component 9 and the positioning plate 10 separately.

[0024] As Figure 4 and Figure 5 shown, the support component 9 includes a long strip square tube 11. Jacks are opened on the four side walls of the long strip square tube 11 and one fold of the L-shaped plate 12 is inserted into each jack respectively. A telescopic cylinder 13 inserted into the jack is fixed to one fold of the L-shaped plate 12 inserted into the jack. The other fold of the L-shaped plate 12 extending out of the jack is attached and fixed to the outer side wall of the long strip square tube. Support plates 14 are distributed outside the four side walls of the long strip square tube. The end of the extending rod of the telescopic cylinder 13 extends out of the jack and is fixed to the support plate 14.

[0025] As Figure 3 and Figure 4 shown, a square sleeve 15 is sleeved on one end of the long strip square tube 11. The square sleeve 15 and the long strip square tube 11 are fixed by bolts. A circular boss 16 is fixed on the other end face of the long strip square tube 11. The circular boss 16 cooperates with the circular hole 5 of the grid frame bottom plate 2 for positioning.

[0026] As Figure 3 shown, the positioning plate 10 has the same size as the grid frame bottom plate 2. Six rows of six square bumps 17 are welded on one side of the positioning plate 10 at an interval of 280 mm. The second triangular brace 18 is welded on the other side (the back) of the positioning plate 10.

[0027] The assembly process of the auxiliary tooling 100 is as follows: One by one, the square sleeves 15 at one end of the long square tubes 11 of the six support components 9 in the first row are respectively sleeved and installed with the six square bumps 17 on the first row (in this embodiment, it refers to the bottommost row) of the positioning plate 10 to form the auxiliary tooling 100.

[0028] Step 4: As Figure 6 shown, push the assembled positioning plate 10 and the auxiliary tooling of the support component 9 as a whole into the gaps between the six first-layer longitudinal partitions 7 on the peripheral plate 1 (i.e., the installation positions of the inner chambers in the first row). The circular bosses 16 at the other ends of the long square tubes 11 of the six support components 9 are inserted into the six round holes 5 in the first row (in this embodiment, it refers to the lowest row) of the grid floor 2. After aligning the auxiliary tooling with the six first-layer longitudinal partitions 7 on the peripheral plate 1 using a laser scanner, turn on the telescopic cylinders 13 on both transverse sides inside the long square tubes 11 so that the relative distance between the support plates 14 on both transverse sides reaches 280 mm and supports on the first-layer longitudinal partitions 7, and weld and fix the contact seams between the first-layer longitudinal partitions 7 and the peripheral plate 1. (At this time, the telescopic cylinders 13 and their support plates 14 can ensure that the longitudinal partitions 7 do not deform during welding.) After welding, wait for cooling and then turn off the telescopic cylinders 13, and the support plates 14 retract and leave the first-layer longitudinal partitions 7, and withdraw the auxiliary tooling as a whole from the first-layer longitudinal partitions 7.

[0029] Step 5: As Figure 7 shown, hoist and place the inner chamber 19 of the first layer into the gaps between the first-layer longitudinal partitions. As Figure 8 shown, the inner chamber 19 is surrounded by four boron stainless steel plates on four sides. Grooves and protrusions are made on the edges of each steel plate, and the grooves and protrusions on the edges of adjacent two steel plates correspond to each other and are tenoned to form a rectangular cross-section inner chamber on four sides. As Figure 9 shown, two butt-welded L-shaped clamps 22 are used to tighten the outside of the inner chamber 19, and flanges 23 are made on the sides of the L-shaped clamps 22.

[0030] As Figure 10 shown, push the auxiliary tooling as a whole into the gaps between the first-layer longitudinal partitions 7 again. Among them, the long square tubes 11 of the six support components 9 are inserted into the inner chamber along the axial direction of the inner chamber. After aligning the auxiliary tooling with the first-layer longitudinal partitions 7 again using a laser scanner, turn on the telescopic cylinders 13 on the four sides inside the long square tubes 11 again, drive the support plates 14 on the four sides to protrude and the distance between the opposite two-by-two support plates 14 reaches the required size of the inner chamber, 222 mm, and the support plates 14 on the four sides support the four side walls of the first-layer longitudinal partitions 7. As Figure 11 shown, then lay the first-layer transverse partition 20 flat on the first-layer inner chamber 19. As Figure 12As shown, the diaphragm 20 is provided with a second long slotted hole 25 and a second short slotted hole 26. Multiple spaced small convex edges 27 are formed on the two long sides of the diaphragm 20, and the small convex edges 27 correspond to the first long slotted holes 4 on the peripheral plate 1. The tab 8 on the other long side (top long side) of the first layer of longitudinal partition 7 is tenoned with the second long slotted hole 25 on the diaphragm 20, and then the flange 23 on the bottom side of the clamp 22 is tenoned with the first short slotted hole 24 on the peripheral plate 1. At the same time, the flange 23 on the top side of the clamp 22 is tenoned with the second short slotted hole 26 on the diaphragm 20. Then, the tenoned parts are welded and fixed. After the welding cools down, the telescopic cylinder 13 is closed, and the support plate 14 retracts away from the four side walls of the first layer of longitudinal partition 7, and the whole auxiliary tooling is withdrawn from the first layer of longitudinal partition 7 again; Step 6: As Figure 13 shown, install five longitudinal partitions 21 of the second layer in the second row on the diaphragm 20 of the first layer. The tab 8 on one long side (bottom long side) of the longitudinal partition 21 of the second layer is tenoned with the second long slotted hole 25 of the diaphragm 20 of the first layer; Repeat step 3, and respectively and successively fit and install the square sleeves 15 at one ends of the long square tubes 11 of the six support assemblies 9 in the second row with the six square convex blocks 17 in the second row on the positioning plates 10 of the support assemblies 9 one by one; Repeat steps 4 - 5 to complete the installation of the inner chamber 19 of the second layer between the longitudinal partitions 21 of the second layer and the welding and fixing between the longitudinal partitions 21 of the second layer and the diaphragm 20 of the first layer; Repeat step 6 to complete the installation of the diaphragm 20 of the second layer; Repeat this way to complete the installation and fixing of six longitudinal partitions, six inner chambers and five diaphragms in total six layers and six rows; Step 7: Complement the three peripheral plates 1 on the remaining three sides of the spent fuel storage grid. The small convex edges 27 on the two side long sides of the five - layer diaphragm are tenoned with the first long slotted holes 4 on the peripheral plates 1 on the two side surfaces. At the same time, the flanges 23 on both sides of the clamp 22 of the six - layer inner chamber 19 are tenoned with the first short slotted holes 24 on the peripheral plates 1 on the two side surfaces; then the tab 8 of the longitudinal partition of the fifth layer (the topmost layer) is tenoned with the first long slotted hole 4 on the top peripheral plate 1, and at the same time, the flange 23 on the top side of the clamp 22 of the six - layer (the last or topmost layer) inner chamber 19 is tenoned with the first short slotted hole 24 on the top peripheral plate 1; finally, weld and fix the seams between the four peripheral plates 1 and the seams between the peripheral plates 1 on the remaining three sides and the bottom plate 2 to complete the installation of all the spent fuel storage grids in this embodiment, as Figure 14 shown.

[0031] Through the assembly method and tooling provided in the present invention, the inner chamber of the spent fuel storage grid formed by splicing boron steel can be prevented from falling apart and deforming during the assembly process, and precise positioning can be provided, improving the assembly efficiency and quality of the spent fuel storage grid, and having a certain interchangeability. A practical method is provided for batch installation of the inner chamber of the spent fuel storage grid.

[0032] The above are only the preferred embodiments of the present invention, but the present invention is not limited thereto. For example, the installation process of the inner chamber, longitudinal partition plates with six layers and six channels, and transverse partition plates with five layers are given in the embodiments. Of course, it can also be extended to three layers and four channels, seven layers and seven channels, or other numbers of layers and channels; all equivalent replacements or equivalent changes made according to the concept and technical solution of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for assembling the inner chamber of a spent fuel storage grid, comprising the following steps: Step 1: Lay a rectangular grid peripheral plate flat on the installation plane, stand the grid bottom plate perpendicular to the grid peripheral plate so that the side surface of the grid bottom plate presses on one end of the grid peripheral plate, the end surface of the bottom plate is placed parallel to the short side of the peripheral plate, weld and fix the seam where the bottom plate contacts the peripheral plate, and weld and fix the first triangular brace on the outer side surface of the bottom plate; a row of multiple first long slotted holes and multiple first short slotted holes arranged in columns and perpendicular to the row of first long slotted holes are provided on the peripheral plate, and multiple circular holes arranged in rows are provided on the bottom plate; Step 2: Install multiple long strip-shaped first-layer longitudinal partitions on the peripheral plate. Flanges are provided on the two long sides of the longitudinal partition. Vertically insert the multiple first-layer longitudinal partitions into the peripheral plate, and the flange on one long side of the first-layer longitudinal partition is tenoned with the first long slotted hole on the peripheral plate; Step 3: Assemble the support component and the positioning plate into an auxiliary tooling; The support component includes a long strip square tube. Insertion holes are opened on the four side walls of the long strip square tube and respectively insert one folded edge of the L-shaped plate. A telescopic cylinder inserted into the insertion hole is fixed to one folded edge of the L-shaped plate inserted into the insertion hole. The other folded edge of the L-shaped plate extending out of the insertion hole is attached and fixed to the outer side wall of the long strip square tube. Support plates are distributed outside the four side walls of the long strip square tube. The end of the extending rod of the telescopic cylinder extends out of the insertion hole and is fixed to the support plate; a square sleeve is sleeved on one end of the long strip square tube, and a circular boss is fixed on the other end surface of the long strip square tube; The positioning plate has the same size as the grid bottom plate. Multiple rows of multiple square bumps are welded at intervals on one surface of the positioning plate, and a second triangular brace is welded on the other surface of the positioning plate; After respectively sleeving and installing the square sleeves at one ends of the long strip square tubes of the first row of multiple support components with the multiple square bumps in the first row on the positioning plate one by one, an auxiliary tooling is formed; Step 4: Push the assembled auxiliary tooling as a whole into the gap between the multiple first-layer longitudinal partitions on the peripheral plate. The circular boss at the other end of the long strip square tube of the support component is inserted into the first row of circular holes on the grid bottom plate; Open the telescopic cylinders on the transverse two sides inside the long strip square tube so that the support plates on the transverse two sides support on the first-layer longitudinal partitions, weld and fix the seam where the first-layer longitudinal partition contacts the peripheral plate. After welding and cooling, close the telescopic cylinders, and the support plates retract away from the first-layer longitudinal partitions. Withdraw the auxiliary tooling as a whole from the first-layer longitudinal partitions; Step 5: Lift and place the inner chamber of the first layer into the gap between the first-layer longitudinal partitions; The inner chamber is surrounded by four boron stainless steel plates on four sides. Grooves and protrusions are made on the edges of each steel plate. The grooves and protrusions on the edges of adjacent two steel plates are correspondingly tenoned to form a rectangular cross-section inner chamber surrounded on four sides; An L-shaped clamp is provided on the outer side of the inner chamber, and a flange is made on the side of the L-shaped clamp; Push the auxiliary tooling as a whole into the gap between the longitudinal partitions of the first layer again, insert the long square tube of the supporting assembly into the inner chamber along the axial direction of the inner chamber, open the telescopic cylinders on the four sides of the long square tube again, drive the support plates on the four sides to support the four side walls of the longitudinal partition of the first layer; then lay the transverse partition of the first layer flat on the inner chamber of the first layer, the transverse partition is provided with a second long slit hole and a second short slit hole, and the two long sides of the transverse partition are provided with a plurality of spaced small convex edges; mortise and tenon the convex piece on the other long side of the longitudinal partition of the first layer with the second long slit hole on the transverse partition, and then mortise and tenon the flange on the bottom side of the clamp with the first short slit hole on the outer plate, and at the same time mortise and tenon the flange on the top side of the clamp with the second short slit hole on the transverse partition, and then weld and fix the mortise and tenon joint, close the telescopic cylinder after the welding is cooled, and the support plate retracts to leave the four side walls of the longitudinal partition of the first layer, and the auxiliary tooling as a whole is withdrawn from the longitudinal partition of the first layer again; Step 6: Install the second row of multiple second-layer longitudinal partitions on the first-layer transverse partition, and mortise and tenon the protruding piece on one long side of the second-layer longitudinal partition with the second long slot hole of the first-layer transverse partition; Repeat step 3 to fit the square sleeves at one end of the second row of multiple square tubes of the supporting components to the second row of multiple square protrusions on the positioning plate of the supporting components one by one; Repeat steps 4-5 to complete the installation of the second-layer inner chamber between the second-layer longitudinal partitions, and the welding and fixing of the second-layer longitudinal partitions to the first-layer transverse partitions; Repeat step 6 to complete the installation of the second layer of diaphragms; Repeat steps 3-6 to complete the installation and fixing of multi-layer longitudinal partitions, multi-layer inner chambers and multi-layer transverse partitions; Step 7: fill in the outer plates of the remaining three sides of the spent fuel storage grid in sequence, mortise and tenon the small convex edges on the two long sides of the multi-layer transverse partition with the first long slit holes on the outer plates of the two sides, and mortise and tenon the flanges on both sides of the clamps of the multi-layer inner chamber with the first short slit holes on the outer plates of the two sides; then mortise and tenon the convex pieces of the longitudinal partition of the top layer with the first long slit holes on the outer plates of the top surface, and mortise and tenon the flange on the top side of the clamps of the inner chamber of the top layer with the first short slit holes on the outer plates of the top surface; finally, weld and fix the joints between the four outer plates and the joints between the outer plates of the remaining three sides and the bottom plate to complete the installation of the inner chamber of the spent fuel storage grid.

2. The method for assembling the inner chamber of the spent fuel storage grid according to claim 1, characterized in that: In step 4 and step 5, the auxiliary tooling is aligned with the first layer of longitudinal partitions on the peripheral plate using a laser scanner.

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