Fuel assembly grillwork

Abstract

The invention discloses a fuel assembly grillwork which comprises a plurality of strips and a plurality of supporting insertion pieces, and the strips intersect with one another to form a plurality of grid units for fuel rods and control rods to be inserted; the supporting insertion piece is arranged at the crossed position of the strips and comprises a connecting part and a plurality of supporting parts which are arranged at intervals; each supporting part extends in the direction parallel to the axial direction of the fuel rod, and one end of each supporting part is connected with the connecting part; a first slot is formed between every two adjacent supporting parts, and the size of each first slot is equal to the thickness size of the strip. Notches do not need to be formed in the strips, the connecting strength of the whole grillwork is improved, then the buckling strength and safety are improved, the structure is relatively simple, manufacturing and mounting are convenient, and the manufacturing cost is reduced. And the fuel rods can be further stably clamped in the grid units through the extrusion parts which are in linear contact with the fuel rods, so that the stability and the safety are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power reactor fuel assemblies, and particularly to a fuel assembly grid. Background Art

[0002] The structure grid is one of the key components of the fuel assembly in the reactor. Its function is to laterally support the fuel rods and at the same time ensure the lateral spacing between the fuel rods during the service life of the fuel assembly. The structure grid is generally formed by inserting the inner strips and the outer strips. On two orthogonally perpendicular planes, each fuel rod is clamped by the rigid protrusions and the opposite spring pieces on the strips.

[0003] Usually, the rigid protrusions and the springs are formed by punching on the grid strips or the springs are hung on the strips after slotted on the grid. No matter which form, slotting is required on the strips. This will reduce the buckling strength of the grid, and further reduce the safety margin for the smooth falling of the control rod under seismic conditions.

[0004] In addition, the commonly used structure grids currently are usually in contact with the fuel rods through the clamping points. The fuel rods will undergo fretting wear with the structure grid due to flow-induced vibration in the nuclear reactor, which easily leads to the breakage of the fuel rods, shortens the service life, increases the maintenance cost, and has a more complex design, a large manufacturing difficulty and a high manufacturing cost. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a fuel assembly grid.

[0006] The technical solution adopted by the present invention to solve its technical problems is: constructing a fuel assembly grid, including: a plurality of strips and a plurality of support inserts, the strips intersect with each other to form a plurality of grid units for inserting fuel rods and control rods; the support inserts are arranged at the intersection positions of the strips, and include: a connecting part and a plurality of spaced support parts; each support part extends along a direction parallel to the axial direction of the fuel rod, and one end is connected to the connecting part; a first slot is arranged between adjacent support parts, and the size of the first slot is equivalent to the thickness size of the strip; the support part is arranged in the grid unit and includes at least one section of extrusion part protruding towards the center of the grid unit and in line contact with the fuel rod.

[0007] Further, the support part further includes an elastic part, the elastic part is connected to the connecting part, the extrusion part and the elastic part of the same support part are both arranged in the same grid unit, and the extrusion part is closer to the fuel rod than the elastic part; the elastic part provides a movement tendency for the extrusion part to approach the fuel rod.

[0008] Further, the extrusion part is arranged along a direction parallel to the axis of the fuel rod.

[0009] Furthermore, the cross-section of the connecting part is arc-shaped, circular ring-shaped, partially arc-shaped or polygonal; the supporting parts are arranged at intervals on the circumference of the connecting part to form a hollow tubular structure.

[0010] Furthermore, the cross-section of the supporting part is arc-shaped or polygonal.

[0011] Furthermore, there are three supporting parts, which are connected to the connecting part in a C-shaped distribution, and the three supporting parts are correspondingly arranged in three adjacent grid units; a notch for avoiding the control rod is arranged on the connecting part.

[0012] Furthermore, there are four supporting parts, which are evenly distributed and connected to the connecting part, and the four supporting parts are correspondingly arranged in four adjacent grid units to surround the crossing position of the strip.

[0013] Furthermore, the strip includes an outer strip and an inner strip. Multiple grid units for inserting fuel rods and control rods are formed by the intersection of the inner strips. The outer strip surrounds the periphery of the multiple grid units and is fixedly connected to the inner strip. The grid also includes the above-mentioned support insert, and the support insert is arranged at the intersection position of the inner strip or / and the outer strip and the inner strip.

[0014] Furthermore, the inner strip includes a plurality of longitudinal strips and a plurality of transverse strips. A plurality of first slots are formed on the longitudinal strips, and a plurality of second slots corresponding to the plurality of first slots are formed on the transverse strips. The transverse strips are installed on the longitudinal strips through the cooperation of the first slots and the second slots.

[0015] Furthermore, the grid of the fuel assembly further includes a plurality of flow guiding fins. Each flow guiding fin is inclined on one side of the inner strip close to the supporting part, and the flow guiding fin is inclined towards the fuel rod.

[0016] Implementing the present invention has the following beneficial effects:

[0017] The support insert is conveniently installed on the strip by using the first slot, which is convenient for operation. There is no need to open a notch on the strip, which improves the connection strength of the entire grid, thereby improving the buckling strength and safety. Moreover, the structure is relatively simple, which is convenient for manufacturing and installation, and reduces the manufacturing cost. The elastic force is generated by the deformation characteristics of the material of the extrusion part to clamp the fuel rod in the grid unit, thereby prolonging the service life of the fuel rod and reducing the maintenance cost. Moreover, the extrusion part in line contact with the fuel rod can further stably clamp the fuel rod in the grid unit, improving the stability and safety. Description of the Drawings

[0018] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative work, other related drawings can also be obtained based on these drawings.

[0019] In the accompanying drawings:

[0020] Figure 1 is a schematic structural diagram of a fuel assembly grid provided by an embodiment of the present invention;

[0021] Figure 2 is a front view of a fuel assembly grid provided by an embodiment of the present invention;

[0022] Figure 3 is a front view of a strip and a support insert provided by an embodiment of the present invention;

[0023] Figure 4 is a schematic structural diagram of a support insert provided by an embodiment of the present invention;

[0024] Figure 5 is a schematic structural diagram of a support insert in some embodiments of the present invention;

[0025] Figure 6 is a schematic structural diagram of a support insert in some embodiments of the present invention;

[0026] Figure 7 is a partial schematic structural diagram of a longitudinal strip and a transverse strip provided by an embodiment of the present invention;

[0027] Figure 8 is a schematic diagram of the installation position of a support insert provided in some embodiments of the present invention.

[0028] Description of Marks in the Figures

[0029] Support insert 1, connecting portion 11, notch 111, supporting portion 12, pressing portion 121, elastic portion 122, first slot 13, outer strip 2, inner strip 3, longitudinal strip 31, first card slot 311, transverse strip 32, second card slot 321, grid unit 4, flow guide vane 5. Detailed implementation manners

[0030] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientation or positional relationships indicated by terms such as "front", "rear", "upper", "lower", "left", "right", "longitudinal", "transverse", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", "tail", etc. are based on the orientation or positional relationships shown in the drawings and are specific orientations for construction and operation, solely for the convenience of describing the present technical solution, rather than indicating that the indicated devices or elements must have a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0031] It should also be noted that, unless otherwise clearly defined and limited, terms such as "install", "connect", "link", "fix", "set", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located above the other element, or there may also be one or more intermediate elements. Terms such as "first", "second", "third", etc. are only for the convenience of describing the present technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, in order to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0033] Please refer to Figures 1-4, in the fuel assembly grid of the first embodiment of the present invention, it includes: a plurality of strips and a plurality of support inserts 1, the strips cross each other to form a plurality of grid units 4 for inserting fuel rods and control rods. The support inserts 1 are arranged at the crossing positions of the strips and include: a connecting portion 11 and a plurality of spaced-apart support portions 12. Each support portion 12 extends in a direction parallel to the axial direction of the fuel rod, and one end is connected to the connecting portion 11. A first slot 13 is provided between adjacent support portions 12, and the size of the first slot 13 is equivalent to the thickness size of the strip. The support portion 12 is arranged in the grid unit 4 and includes at least one section of an extrusion portion 121 that protrudes towards the center of the grid unit 4 and is in line contact with the fuel rod.

[0034] In this application, through the connecting portion 11 and a plurality of spaced-apart support portions 12, each support portion 12 extends in a direction parallel to the axial direction of the fuel rod, and one end is connected to the connecting portion 11. A first slot 13 is provided between adjacent support portions 12, and the size of the first slot 13 is equivalent to the thickness size of the strip. Among them, one end of the first slot 12 away from the connecting portion 11 is open, and the operator can insert the strip into the first slot 13 through the opening, so that the strip separates each support portion 12 individually in the grid unit 4. The support insert 1 is conveniently installed on the strip by using the first slot 13. Then, through the welding technology, the support insert 1 and the strip are kept relatively stationary, which is convenient for operation. There is no need to open slots on the strip, improving the connection strength of the entire grid, thereby improving the buckling strength and safety. Moreover, the structure is relatively simple, facilitating production and installation, and reducing the production cost.

[0035] The support portion 12 of this application is arranged in the grid unit 4. Each support portion 12 includes at least one section of an extrusion portion 121 that protrudes towards the center of the grid unit 4 and is in line contact with the fuel rod. The elastic force is generated by the deformation characteristics of the material of the extrusion portion 121 itself to clamp the fuel rod in the grid unit 4. The installation is more convenient, saving the production cost. And by installing the extrusion portion 121 in the grid unit 4, the contact area between the support insert 1 and the strip can be increased, thereby improving the connection strength after welding and extending the service life. Using a section of the extrusion portion 121 of a plurality of different support inserts 1 to clamp the fuel rod in the grid unit 4 can realize the line contact extrusion between the extrusion portion 121 and the fuel rod, thereby reducing the wear between the fuel rod and the support insert 1 to a certain extent. Furthermore, the service life of the fuel rod is extended, the maintenance cost is reduced, and the fuel rod can be further stably clamped in the grid unit 4 through the extrusion portion 121 in line contact with the fuel rod, improving the stability and safety.

[0036] Please refer to Figures 1-4, in some embodiments of the present invention, the support portion 12 further includes an elastic portion 122. The elastic portion 122 is connected to the connecting portion 11. The pressing portion 121 and the elastic portion 122 of the same support portion 12 are both disposed within the same grid cell 4. The pressing portion 121 is closer to the fuel rod than the elastic portion 122. The elastic portion 122 provides a movement tendency for the pressing portion 121 to approach the fuel rod.

[0037] In the present invention, the support portion 12 includes: a pressing portion 121 and an elastic portion 122. The elastic portion 122 is connected to the connecting portion 11. The pressing portion 121 is connected to the elastic portion 122. The pressing portion 121 and the elastic portion 122 of the same support portion 12 are both disposed within the same grid cell 4. The pressing portion 121 is closer to the fuel rod than the elastic portion 122. The elastic portion 122 is connected to the strip on both sides of the pressing portion 121. For the support portion 12 located in the same grid cell 4, the elastic portions 122 on both sides squeeze the pressing portion 121 towards the center of the grid cell 4, so that the elastic portion 122 provides a movement tendency for the pressing portion 121 to approach the fuel rod, and the elastic portion 122 squeezes the pressing portion 121 against the fuel rod by using the elasticity generated by itself. The fuel rod located in this grid cell 4 is clamped by a plurality of pressing portions 121 in the same grid cell 4. Thus, the production is simple, the production cost is reduced, and the installation is facilitated. Moreover, the overall structure of the strip is not damaged, the connection strength of the strip is stronger, the safety is improved, and the later maintenance cost is reduced.

[0038] Please refer to Figures 1-4 , in some embodiments of the present invention, the pressing portion 121 is disposed along a direction parallel to the axis of the fuel rod.

[0039] In this application, since the pressing portion 121 is disposed along a direction parallel to the axis of the fuel rod, the contact segments of the plurality of pressing portions 121 located in the same grid cell 4 with the fuel rod are all parallel to the axis of the fuel rod. Furthermore, the clamping forces of the plurality of pressing portions 121 located in the same grid cell 4 on the fuel rod are more uniform, which can improve the stability of clamping the fuel rod, and it is convenient for the staff to clamp the fuel rod in the grid cell 4, and the operation is more labor-saving and convenient, thus improving the installation efficiency. The wear between the fuel rod and the plurality of pressing portions 121 due to flow-induced vibration in the nuclear reactor is reduced, further prolonging the service life of the fuel rod, and thus reducing the maintenance cost.

[0040] Please refer to Figures 1-4 , in some embodiments of the present invention, the cross-section of the connecting portion 11 is circular arc, circular ring, partial circular arc or polygon; the support portions 12 are spaced apart on the circumference of the connecting portion 11 to form a hollow tubular structure.

[0041] In this application, the cross-section of the connecting portion 11 is circular arc-shaped or circular ring-shaped. The connecting portion 11 in the shape of a circular arc or circular ring can drive the elastic portion 122 above to generate more elastic force tending to the extrusion portion 121, so that multiple extrusion portions 121 in the same grid unit 4 can clamp the fuel rod more stably. Among them, the connecting portion 11 in the shape of a circular arc or circular ring can bear a greater load, is not easy to deform, and is easy to manufacture.

[0042] In this application, the cross-section of the connecting portion 11 is partially circular arc-shaped or polygonal. The connecting portion 11 with a partially circular arc-shaped cross-section can be adjusted according to the actual use situation on site, saving the occupied space of the entire support insert 1, reducing the interference of the coolant during the process of flushing the fuel rod, thereby expanding the applicable range, fitting better with the strips in the grid unit 4, and appropriately increasing the connection strength. The connecting portion 11 with a polygonal cross-section can be set to match the shape of the strips in the grid unit 4, which can be a regular polygon or an irregular polygon. Among them, the connecting portion 11 can also be formed by a partial arc method combining an arc and a polygon. Thus, when the connecting portion 11 can perfectly fit with the strips in the grid unit 4, it can also generate more elastic force tending to the extrusion portion 121 for the elastic portion 122 above, not only increasing the connection strength but also enhancing the clamping ability.

[0043] In this application, the support portions 12 are arranged at intervals on the circumference of the connecting portion 11 to form a hollow tubular structure. The support portions 12 arranged at intervals can avoid both sides of the strip, enabling the support portions 12 to be inserted into the grid unit 4, increasing the contact area between the support portions 12 and the strips in the grid unit 4. Then, through welding technology, the connection strength between the support portions 12 and the strips can be increased, thereby extending the service life, making the clamped fuel rod more stable and facilitating installation. By arranging the support portions 12 on the circumference of the connecting portion 11 to form a hollow tubular structure, the elastic force generated by the elastic portion 122 can be further improved through the hollow tubular structure, enhancing the clamping strength of the fuel rod, reducing the impact of the coolant in the reactor, thereby reducing the flow-induced vibration, playing a certain protective role for the entire grid, extending the service life of the entire grid, and making it safer and more stable during operation.

[0044] Please refer to Figures 1-4 、 Figure 8 , in some embodiments of the present invention, the cross-section of the support portion 12 is circular arc-shaped or polygonal.

[0045] In the present application, the cross-section of the supporting part 12 is arc-shaped. The arc-shaped supporting part 12 can generate a large elasticity for the fuel rod, and the elastic range is larger, which can be applicable to more usage environments, facilitating the staff to clamp the fuel rod in the grid unit 4. In the present application, the cross-section of the supporting part 12 is polygonal. Among them, the extrusion part 121 of the polygonal supporting part 12 is located on the edge or side surface of the polygon. The extrusion force for extruding the fuel rod is generated on the fuel rod by using the two side lengths on both sides of the edge or side surface, and the fuel rod is stably extruded inside the grid unit 4. The polygonal supporting part 12 can change the number of sides and side lengths according to the on-site usage environment, and is applicable to grid units 4 of different specifications, further expanding the applicable range. Moreover, the polygonal supporting part 12 is convenient for manufacturing, further saving the manufacturing cost. Among them, the polygonal supporting part 12 can form a stable triangle with the strip, further improving the rigidity and stability of the supporting part 12 itself, and then improving the stability of clamping the fuel rod, and it is not easy to deform, extending the service life.

[0046] Please refer to Figures 1-5 , in some embodiments of the present invention, there are three supporting parts 12, which are connected to the connecting part 11 in a C-shaped distribution. The three supporting parts 12 are correspondingly arranged in three adjacent grid units 4. A notch 111 for avoiding the control rod is arranged on the connecting part 11.

[0047] In the present application, there are three supporting parts 12 which are connected to the connecting part 11 in a C-shaped distribution. The three supporting parts 12 are correspondingly arranged in three adjacent grid units 4. There is a grid unit 4 for connecting with the control rod arranged on the strip. This grid unit 4 occupies the surrounding space, and the remaining grid units 4 around this grid unit 4 form a situation where three grid units 4 are adjacent in a C shape. By connecting the three supporting parts 12 in a C-shaped distribution to the connecting part 11 and correspondingly arranging them in the three grid units 4, it will not affect the control rod, improving the applicable ability, and enabling the remaining grid units 4 to also maintain a good clamping ability for the fuel rod therein. Among them, a notch 111 for avoiding the control rod is arranged on the connecting part 11, which can further reduce the interference with the control rod, make the connection between the control rod and the strip closer, and further improve the stability of the grid.

[0048] Please refer to Figures 1-6 , in some embodiments of the present invention, there are four supporting parts 12, which are evenly distributed and connected to the connecting part 11. The four supporting parts 12 are correspondingly arranged in four adjacent grid units 4, surrounding the cross position of the strip.

[0049] In this application, there are four supporting parts 12, which are evenly distributed and connected to the connecting part 11. The four supporting parts 12 are correspondingly arranged in four adjacent grid cells 4, surrounding the crossing position of the strip. By surrounding the crossing position of the strip with the four supporting parts 12, and each supporting part 12 is arranged in a corresponding grid cell 4, it can save the occupied space of the supporting insert 1, make the connection between the supporting insert 1 and the strip tighter. Among them, due to the restriction of the strip around the grid cell 4, the elastic part 122 will not easily undergo irreversible deformation, thereby extending the service life and enabling the pressing part 121 to firmly clamp the fuel rod inside the grid cell 4 for a long time.

[0050] Please refer to Figures 1-6 , in some embodiments of the present invention, the strip includes an outer strip 2 and an inner strip 3. Inside the inner strip 3, there are multiple grid cells 4 formed by intersecting each other for inserting fuel rods and control rods. The outer strip 2 surrounds the outside of the multiple grid cells 4 and is fixedly connected to the inner strip 3. The grid frame further includes the supporting insert 1 in the above embodiments, and the supporting insert 1 is arranged at the crossing position of the inner strip 3 or / and the outer strip 2 and the inner strip 3.

[0051] In this application, the supporting insert 1 does not require notches for installing rigid protrusions and springs on the outer strip 2 and / or the inner strip 3, thereby improving the connection strength of the entire strip, enhancing the buckling strength and safety. Moreover, the structure is relatively simple, facilitating manufacturing and installation, and reducing the manufacturing cost. The supporting insert 1 facilitates the installer to clamp the fuel rod in the grid cell 4, further improving the installation efficiency. The supporting insert 1 arranged at the crossing position of the inner strip 3 or / and the outer strip 2 and the inner strip 3 can save the occupied space after installation, thereby reducing fluid-induced vibration, extending the service life of the entire grid frame, improving safety, and also reducing the weight of the entire grid frame, further facilitating installation.

[0052] Please refer to Figures 1-7 , in some embodiments of the present invention, the inner strip 3 includes: a plurality of longitudinal strips 31 and a plurality of transverse strips 32. A plurality of first card slots 311 are formed on the longitudinal strips 31, and a plurality of second card slots 321 corresponding to the plurality of first card slots 311 are formed on the transverse strips 32. The transverse strips 32 are installed on the longitudinal strips 31 through the cooperation of the first card slots 311 and the second card slots 321.

[0053] In this application, a plurality of first card slots 311 are provided on the longitudinal strip 31, and a plurality of second card slots 321 corresponding to the plurality of first card slots 311 are provided on the transverse strip 32. The transverse strip 32 is installed on the longitudinal strip 31 through the cooperation of the first card slot 311 and the second card slot 321. By utilizing the mutual cooperation of the second card slot 321 and the first card slot 311, a plurality of longitudinal strips 31 and transverse strips 32 can be located in the same plane, looking neater on the outside, facilitating installation and fixation, making the entire grid more stable during operation, further reducing flow-induced vibration, and extending the service life of the entire grid.

[0054] Please refer to Figures 1-7 , in some embodiments of the present invention, the fuel assembly grid further includes a plurality of flow guiding vanes 5. Each flow guiding vane 5 is inclined and arranged on one side of the inner strip 3 close to the supporting part 12, and the flow guiding vane 5 is inclined towards the fuel rod.

[0055] In this application, the grid of the fuel assembly further includes a plurality of flow guiding vanes 5. Each flow guiding vane 5 is inclined and arranged on one side of the inner strip 3 close to the supporting part 12, and the flow guiding vane 5 is located above the space surrounded by the supporting part 12 and the inner strip 3. Each flow guiding vane 5 is inclined towards the fuel rod. When the coolant passes through the surrounded space and reaches the flow guiding vane 5, the flow guiding vane 5 will push the coolant towards the fuel rod direction, causing the coolant to wash the fuel rod, avoiding the occurrence of turbulent flow, and maximizing the mixing length. It can effectively reduce the leakage of the coolant from the gap between the flow guiding vane 5 and the fuel rod, so that more coolant flows downstream along the inclined bending direction of the flow guiding vane 5, thereby greatly improving the thermal performance of the flow guiding vane 5.

[0056] It can be understood that the above embodiments only represent the preferred embodiments of the present invention, and the description is relatively specific and detailed, but it cannot be construed as a limitation on the scope of the invention patent; it should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can also be made, which all belong to the protection scope of the present invention; therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. A fuel assembly grid, characterized in that, Comprising: A plurality of strips and a plurality of support inserts (1), the strips intersecting each other to form a plurality of grid units (4) for inserting fuel rods and control rods; The support insert (1) is arranged at the intersection position of the strips and includes: a connecting portion (11) and a plurality of spaced-apart support portions (12); each support portion (12) extends in a direction parallel to the axial direction of the fuel rod, and one end thereof is connected to the connecting portion (11); A first slot (13) is provided between adjacent support portions (12), and the size of the first slot (13) is equivalent to the thickness size of the strip; The support portion (12) is arranged within the grid unit (4) and includes at least one pressing portion (121) that protrudes towards the center of the grid unit (4) and is in line contact with the fuel rod; 2. The fuel assembly grid according to claim 1, wherein, The support portion (12) further includes an elastic portion (122), the elastic portion (122) is connected to the connecting portion (11), the pressing portion (121) and the elastic portion (122) of the same support portion (12) are both arranged within the same grid unit (4), and the pressing portion (121) is closer to the fuel rod than the elastic portion (122); the elastic portion (122) provides a movement tendency for the pressing portion (121) to approach the fuel rod; 3. The fuel assembly grid according to claim 1, wherein The pressing portion (121) is arranged in a direction parallel to the axis of the fuel rod; 4. The fuel assembly grid according to claim 1, characterized in that, The cross-section of the connecting portion (11) is arc-shaped, circular ring-shaped, partially arc-shaped or polygonal; the support portions (12) are spaced apart on the circumference of the connecting portion (11) to form a hollow tubular structure; 5. The fuel assembly grid according to claim 1, characterized in that, The cross-section of the support portion (12) is arc-shaped or polygonal; 6. The fuel assembly grid according to claim 1, wherein There are three support portions (12), which are connected to the connecting portion (11) in a C-shaped distribution, and the three support portions (12) are correspondingly arranged in three adjacent grid units (4); a notch (111) for avoiding the control rod is provided on the connecting portion (11); 7. The fuel assembly grid according to claim 1, characterized in that, There are four support portions (12), which are evenly distributed and connected to the connecting portion (11), and the four support portions (12) are correspondingly arranged in four adjacent grid units (4) to enclose the intersection position of the strips; 8. The fuel assembly grid according to claim 7, wherein, The strip includes an outer strip (2) and an inner strip (3), a plurality of grid units (4) for inserting fuel rods and control rods are formed by the intersection within the inner strip (3), the outer strip (2) surrounds the periphery of the plurality of grid units (4) and is fixedly connected to the inner strip (3), and the support insert (1) is arranged at the intersection position of the inner strip (3) or / and the outer strip (2) and the inner strip (3); 9. The fuel assembly grid according to claim 8, characterized in that, The inner strip (3) includes: a plurality of longitudinal strips (31) and a plurality of transverse strips (32). A plurality of first card slots (311) are formed on the longitudinal strips (31), and a plurality of second card slots (321) corresponding to the plurality of first card slots (311) are formed on the transverse strips (32). The transverse strips (32) are installed on the longitudinal strips (31) through the cooperation of the first card slots (311) and the second card slots (321).

10. The fuel assembly grid according to claim 8, wherein, The fuel assembly grid further includes a plurality of flow guiding fins (5). Each flow guiding fin (5) is inclined on one side of the inner strip (3) close to the supporting portion (12), and the flow guiding fin (5) is inclined towards the fuel rod direction.

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