A double containment wing nuclear fuel assembly positioning grid based on additive manufacturing

Abstract

A double-layer stirred wing nuclear fuel assembly positioning grid based on additive manufacturing includes internal grid units, edge grid units and corner grid units; wherein the internal grid units are connected to each other to form a square matrix; the edge grid units are arranged along the four edges of the square matrix to surround the edges of the square matrix except the four corners; the edge grid units at the ends of each edge are respectively connected to the corner grid units to realize the transition of the edges and corners; the grid units are connected through partially overlapped boundaries; the internal unit grid, the edge grid unit and the corner grid unit respectively have eight, four and three stirred wings in two layers; the positioning grid is integrally formed from bottom to top by metal 3D printing, and the material is selected from zirconium alloy or high-temperature alloy; the invention realizes the effect of longer stirred wings and larger stirring range, facilitates the assembly of fuel rods and the positioning grid, reduces the manufacturing difficulty and cost, and shortens the design and manufacturing cycle.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel assembly technology, and more specifically to a positioning grid for a double-layer turbulence wing nuclear fuel assembly based on additive manufacturing. Technical Background

[0002] Nuclear fuel assemblies, as the core components of a nuclear reactor, are composed of multiple fuel elements, control rod guide tubes, upper and lower tube seats, and positioning grids. Their core function is to maintain the regular spatial arrangement of the nuclear fuel rod bundles. During a nuclear reaction, coolant flows at high speed through the gaps between the fuel rods, continuously removing fission heat and creating high-temperature and high-pressure conditions. This characteristic makes reactor operation safety closely related to the materials and structural properties of the components.

[0003] As the core device for constraining the spatial positioning of fuel rods, the positioning grid's primary design objective is to ensure precise control of the rod bundle spacing. The installation process requires pre-fixing the grid's position before inserting the fuel rod array, necessitating excellent assembly adaptability of the grid structure. Reactor heat transfer efficiency is significantly affected by the coolant flow direction and velocity; therefore, the grid must possess fluid guiding capabilities. The temperature changes, turbulence, and vibrations generated as the cooling medium flows through the grid impose specific requirements on its mechanical strength.

[0004] Existing positioning grids, such as the patent application titled "A Strip, Nuclear Fuel Positioning Grid and Nuclear Fuel Assembly" (publication number CN204884577U) and the patent application titled "Positioning Grid and Fuel Assembly with Streamlined Low-Pressure Drop Flow Channel" (publication number CN104318962A), generally adopt an inner and outer composite strip structure. The outer strip is equipped with positioning bosses and elastic elements on both sides to achieve precise clamping and positioning of the fuel rod bundle. In addition to a similar structure, the inner strip usually adds turbulence blades at the edge. The turbulence blade structure distributed in multiple regions induces the coolant to generate lateral flow to optimize the flow field distribution. This type of design has the problem of structural complexity, which leads to challenges in processing and manufacturing. At the same time, due to the miniaturization characteristics, the precision control during the assembly process is more difficult, which can easily lead to the degradation of structural strength and performance indicators. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a positioning grid for a double-layer turbulence wing nuclear fuel assembly based on additive manufacturing, which can achieve a larger hollow area and a longer turbulence wing. It also utilizes the characteristics of additive manufacturing technology to design an integrated positioning and clamping structure, which facilitates the assembly of fuel rods and positioning grid, reduces manufacturing difficulty and cost, and shortens the design and manufacturing cycle.

[0006] To achieve the above objectives, the design scheme adopted by the present invention is as follows:

[0007] A positioning grid for a double-layer turbulence wing nuclear fuel assembly based on additive manufacturing includes an inner grid unit 1, an edge grid unit 2, and a corner grid unit 3; wherein the inner grid units 1 are interconnected to form a square array; the edge grid units 2 extend along the four sides of the square array and surround the edges of the square array excluding the four corners; the edge grid units 2 located at the end of each edge are respectively connected to the corner grid units 3 to achieve edge-corner transition; the grid units are connected to each other through partially overlapping boundaries;

[0008] The internal cell frame 1, edge frame unit 2, and corner frame unit 3 each have two layers with a total of eight, four, and three swirling wings, respectively.

[0009] The positioning grid is integrally formed from bottom to top by metal 3D printing, and the material is selected as zirconium alloy or high-temperature alloy.

[0010] The internal grid unit 1 includes a first hollow guide ring 1-4 in the middle layer, from which four first upper torsion turbulence wings 1-3 grow upward. The width of the first upper torsion turbulence wings 1-3 gradually decreases upward and twists outward, eventually connecting with the uppermost first upper hollow frame ring 1-2. Four first upper claw-type elastic clamping components 1-1 are evenly distributed inside the first upper hollow frame ring 1-2. Four first lower torsion turbulence wings 1-5 grow downward from the lower edge of the first hollow guide ring 1-4. The width of the first lower torsion turbulence wings 1-5 gradually decreases downward and twists outward, eventually connecting with the lowermost first lower hollow frame ring 1-7. The arrangement positions of the first lower torsion turbulence wings 1-5 and the first upper torsion turbulence wings 1-3 have an angular difference of 15°. Four first lower claw-type elastic clamping components 1-6 are evenly distributed inside the first lower hollow frame ring 1-7. The configuration of the first lower claw-type elastic clamping components 1-6 is the same as that of the first upper claw-type elastic clamping components 1-1.

[0011] When the nuclear fuel rod 4 is not clamped, the central axis of the clamping surface of the first upper claw type elastic clamping component 1-1 and the first lower claw type elastic clamping component 1-6 forms a small angle of less than 12° with the central axis of the first upper hollow frame ring 1-2 and the first lower hollow frame ring 1-7. Assuming that the diameter of the nuclear fuel rod 4 to be installed is D, the diameter enclosed by the uppermost clamping point of the first upper claw type elastic clamping component 1-1 and the first lower claw type elastic clamping component 1-6 is D-0.5mm, and the diameter enclosed by the lowermost clamping point is D+0.18mm.

[0012] The inner diameters of the first upper hollow frame ring 1-2 and the first lower hollow frame ring 1-7 are the same, D+2.6mm, and the inner diameter of the first hollow guide ring 1-4 is D+1.1mm.

[0013] The first lower torsional turbulence wing 1-5, after being impacted by coolant from below, guides part of the water flow into the interior of the first hollow guide ring 1-4, and forms a transverse secondary flow at a certain speed under the action of the torsional structure; the first upper torsional turbulence wing 1-3, due to the 15° deflection angle with the first lower torsional turbulence wing 1-5, receives the remaining coolant impact and guides the water flow to the outside, participating in the turbulence between other grid units, and forms a transverse secondary flow at a certain speed under the action of the torsional structure.

[0014] The edge grid unit 2 includes a second hollow guide ring 2-4 in the middle layer, from which two second upper torsion turbulence wings 2-3 grow upward. The width of the second upper torsion turbulence wings 2-3 gradually decreases upward and twists outward, eventually connecting with the uppermost second upper hollow frame ring 2-2. Simultaneously, near the outer periphery, a first upper irregular connecting component 2-8 assists in connecting the second hollow guide ring 2-4 and the second upper hollow frame ring 2-2. Four second upper claw-shaped elastic clamping components 2-1 are evenly distributed inside the second upper hollow frame ring 2-2. Two second lower torsion turbulence wings 2-3 grow downward from the lower edge of the second hollow guide ring 2-4. The second lower twisting turbulence wing 2-5 gradually decreases in width downwards and twists outwards, eventually connecting with the lowest second lower hollow frame ring 2-7. At the same time, the second hollow guide ring 2-4 and the second lower hollow frame ring 2-7 are connected by the first lower irregular connecting component 2-9 in the direction close to the periphery. The second lower twisting turbulence wing 2-5 and the second upper twisting turbulence wing 2-3 have a 40° angle difference in their arrangement positions. Four second lower claw-type elastic clamping components 2-6 are evenly distributed inside the second lower hollow frame ring 2-7. The configuration of the second lower claw-type elastic clamping components 2-6 is the same as that of the second upper claw-type elastic clamping components 2-1.

[0015] The corner frame unit 3 includes a third hollow guide ring 3-4 in the middle layer, from which two third upper torsion turbulence wings 3-3 grow upward. The width of the third upper torsion turbulence wings 3-3 gradually decreases upward and twists outward, eventually connecting with the uppermost third upper hollow frame ring 3-2. At the same time, the third hollow guide ring 3-4 and the third upper hollow frame ring 3-2 are connected by a second upper irregular connecting component 3-8 near the outer periphery. Four third upper claw-shaped elastic clamping components 3-1 are evenly distributed inside the third upper hollow frame ring 3-2. Growing downward from the lower edge of the third hollow guide ring 3-4... A third lower twisting and stirring wing 3-5 is produced. The width of the third lower twisting and stirring wing 3-5 gradually decreases downward and twists outward, eventually connecting with the lowest third lower hollow frame ring 3-7. At the same time, the third hollow guide ring 3-4 and the third upper hollow frame ring 3-7 are connected by the second lower irregular connecting component 3-9 in the direction close to the outer perimeter. The third lower twisting and stirring wing 3-5 and the third upper twisting and stirring wing 3-3 are arranged at an angle difference of 40°. Four third lower claw-type elastic clamping components 3-6 are evenly distributed inside the third lower hollow frame ring 3-7, with the same configuration as the third upper claw-type elastic clamping component 3-1.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention utilizes 3D printing technology in additive manufacturing to create a one-piece, complex nuclear fuel assembly positioning grid structure. Compared to the multi-process, multi-mold characteristics required by traditional positioning grid manufacturing processes, this invention reduces manufacturing difficulty and time. The open grid units form directional flow channels, enhancing the circulation capacity of the cooling medium around the nuclear fuel rods. The streamlined torsional turbulence blades expand the fluid disturbance range while separately turbulenting different flow domains on the surface of the nuclear fuel rods and between the grid units, thereby improving coolant mixing performance. Simultaneously, the claw-type elastic clamping structure can not only achieve positioning and clamping simultaneously but also provide auxiliary guidance during the installation of nuclear fuel rods. Furthermore, the clamping force can be directly modified by adjusting the tilt angle of the clamping structure to adapt to the actual working environment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention.

[0019] Figure 2 This is a top view of an embodiment of the present invention.

[0020] Figure 3 This is an isometric view of the internal lattice unit in an embodiment of the present invention.

[0021] Figure 4 This is a top view of the internal grid unit in an embodiment of the present invention.

[0022] Figure 5 This is an isometric view of the edge grid unit according to an embodiment of the present invention.

[0023] Figure 6 This is a top view of the edge grid unit according to an embodiment of the present invention.

[0024] Figure 7 This is an isometric view of the corner lattice unit according to an embodiment of the present invention.

[0025] Figure 8 This is a top view of the corner lattice unit according to an embodiment of the present invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer definition of the scope of protection of the present invention.

[0027] Reference Figure 1 and Figure 2 A positioning grid for a double-layer turbulence wing nuclear fuel assembly based on additive manufacturing includes an inner grid unit 1, an edge grid unit 2, and a corner grid unit 3. Taking a 5×5 grid as an example, nine inner grid units 1 are interconnected to form a 3×3 square array, and twelve edge grid units 2 extend along the four sides of the square array, surrounding the edges of the square array except for the four corners. The edge grid units 2 located at the end of each edge are connected to the corner grid units 3 to achieve edge-corner transition, for a total of four. The grid units are connected by partially overlapping boundaries to form an integrated positioning grid.

[0028] The internal cell frame 1, edge frame unit 2, and corner frame unit 3 each have two layers with a total of eight, four, and three swirling wings, respectively.

[0029] The positioning grid is made of high-temperature alloy or zirconium alloy and is integrally formed from bottom to top using 3D printing technology. During assembly, 25 nuclear fuel rods 4 with a ball end and a diameter of 9.5mm are inserted into the positioning grid from bottom to top. The clamping structure automatically positions and clamps them. Water flows from bottom to top through two layers of twisting and turbulence blades to improve heat exchange efficiency.

[0030] Reference Figure 3 and Figure 4The internal grid unit 1 includes a first hollow guide ring 1-4 in the middle layer, from which four first upper torsion turbulence wings 1-3 grow upward. The width of the first upper torsion turbulence wings 1-3 gradually decreases upward and twists outward, eventually connecting with the uppermost first upper hollow frame ring 1-2. Four first upper claw-type elastic clamping components 1-1 are evenly distributed inside the first upper hollow frame ring 1-2. Four first lower torsion turbulence wings 1-5 grow downward from the lower edge of the first hollow guide ring 1-4. The width of the first lower torsion turbulence wings 1-5 gradually decreases downward and twists outward, eventually connecting with the lowermost first lower hollow frame ring 1-7. The arrangement of the first lower torsion turbulence wings 1-5 and the first upper torsion turbulence wings 1-3 has an angular difference of 15°. Four first lower claw-type elastic clamping components 1-6 are evenly distributed inside the first lower hollow frame ring 1-7, with the same configuration as the first upper claw-type elastic clamping components 1-1.

[0031] In this embodiment, the central axis of the clamping curved surface of the first upper claw type elastic clamping component 1-1 and the first lower claw type elastic clamping component 1-6 forms a small angle of 8° with the central axis of the first upper hollow frame ring 1-2 and the first lower hollow frame ring 1-7 when the nuclear fuel rod 4 is not clamped. In this embodiment, the diameter of the nuclear fuel rod 4 to be installed is 9.5mm. The diameter enclosed by the uppermost clamping point of the first upper claw type elastic clamping component 1-1 and the first lower claw type elastic clamping component 1-6 is 9mm, and the diameter enclosed by the lowermost clamping point is 9.68mm. The larger lower diameter facilitates the entry of the nuclear fuel rod 4 into the first upper claw type elastic clamping component 1-1 and the first lower claw type elastic clamping component 1-6, providing an auxiliary guiding function for the installation of the nuclear fuel rod 4. The cylindrical clamping surface provides a positioning function, and after positioning, the elastic force generated by the structural deformation provides a clamping force to clamp.

[0032] The first upper hollow frame ring 1-2 and the first lower hollow frame ring 1-7 have the same thickness, height, and inner diameter, which are 0.5mm, 5mm, and 12.1mm respectively, and the total height of the grid is 35mm; the inner diameter of the first hollow guide ring 1-4 is 10.6mm, and the distance between the first upper hollow frame ring 1-2 and the first hollow guide ring 1-4 is 10mm, which is the same as the distance between the first lower hollow frame ring 1-7 and the first hollow guide ring 1-4.

[0033] The first lower torsional turbulence blade 1-5, after being impacted by coolant from below, guides part of the water flow into the interior of the first hollow guide ring 1-4, forming a transverse secondary flow at a certain speed under the action of the torsional structure. The first upper torsional turbulence blade 1-3, due to its 15° deflection angle with the first lower torsional turbulence blade 1-5, can receive the remaining coolant impact and guide the water flow outwards to participate in the turbulence between other grid units, forming a transverse secondary flow at a certain speed under the action of the torsional structure. In this embodiment, the thickness of both the first upper torsional turbulence blade 1-3 and the first lower torsional turbulence blade 1-5 is 0.5 mm, and the torsional angle is 65°.

[0034] Reference Figure 5 and Figure 6 The edge grid unit 2 includes a second hollow guide ring 2-4 in the middle layer, from which two second upper twisting and stirring wings 2-3 grow upward. The width of the second upper twisting and stirring wings 2-3 gradually decreases upward and twists outward, eventually connecting with the uppermost second upper hollow frame ring 2-2. Simultaneously, near the outer periphery, a first upper irregular connecting component 2-8 assists in connecting the second hollow guide ring 2-4 and the second upper hollow frame ring 2-2. Four second upper claw-shaped elastic clamping components 2-1 are evenly distributed inside the second upper hollow frame ring 2-2. From the lower edge of the second hollow guide ring 2-4 downward… Two second lower twisting and stirring wings 2-5 extend outwards. The width of the second lower twisting and stirring wings 2-5 gradually decreases downwards and twists outwards, eventually connecting with the lowest second lower hollow frame ring 2-7. At the same time, the second hollow guide ring 2-4 and the second upper hollow frame ring 2-7 are connected by the first lower irregular connecting component 2-9 near the outer perimeter. The second lower twisting and stirring wings 2-5 and the second upper twisting and stirring wings 2-3 are arranged at an angle difference of 40°. Four second lower claw-type elastic clamping components 2-6 are evenly distributed inside the second lower hollow frame ring 2-7, with the same configuration as the second upper claw-type elastic clamping component 2-1.

[0035] Reference Figure 7 and Figure 8The corner frame unit 3 includes a third hollow guide ring 3-4 in the middle layer, from which two third upper torsion turbulence wings 3-3 grow upward. The width of the third upper torsion turbulence wings 3-3 gradually decreases upward and twists outward, eventually connecting with the uppermost third upper hollow frame ring 3-2. At the same time, the third hollow guide ring 3-4 and the third upper hollow frame ring 3-2 are connected by a second upper irregular connecting component 3-8 near the outer periphery. Four third upper claw-shaped elastic clamping components 3-1 are evenly distributed inside the third upper hollow frame ring 3-2. Growing downward from the lower edge of the third hollow guide ring 3-4... A third lower twisting and stirring wing 3-5 is produced. The width of the third lower twisting and stirring wing 3-5 gradually decreases downward and twists outward, eventually connecting with the lowest third lower hollow frame ring 3-7. At the same time, the third hollow guide ring 3-4 and the third upper hollow frame ring 3-7 are connected by the second lower irregular connecting component 3-9 in the direction close to the outer perimeter. The third lower twisting and stirring wing 3-5 and the third upper twisting and stirring wing 3-3 are arranged with an angle difference of 40°. Four third lower claw-type elastic clamping components 3-6 are evenly distributed inside the third lower hollow frame ring 3-7, with the same configuration as the third upper claw-type elastic clamping component 3-1.

[0036] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A positioning grid for a double-layer turbulence-wing nuclear fuel assembly based on additive manufacturing, characterized in that: It includes internal grid units (1), edge grid units (2) and corner grid units (3); wherein the internal grid units (1) are interconnected to form a square array; the edge grid units (2) extend along the four sides of the square array and surround the edges of the square array excluding the four corners; the edge grid units (2) located at the end of each edge are connected to the corner grid units (3) to achieve edge-corner transition; the grid units are connected to each other through partially overlapping boundaries; The internal grid unit (1), edge grid unit (2), and corner grid unit (3) have two layers with a total of eight, four, and three turbulence wings, respectively; The positioning grid is integrally formed from bottom to top by metal 3D printing, and the material is selected as zirconium alloy or high temperature alloy; The internal grid unit (1) includes a first hollow guide ring (1-4) in the middle layer, and four first upper twisting turbulence wings (1-3) grow upward from its upper edge. The width of the first upper twisting turbulence wings (1-3) gradually decreases upward and twists outward, eventually connecting with the uppermost first upper hollow frame ring (1-2). Four first upper claw-shaped elastic clamping components (1-1) are evenly distributed inside the first upper hollow frame ring (1-2). Four first lower twisting turbulence wings (1-1) grow downward from the lower edge of the first hollow guide ring (1-4). The stirring wings (1-5) have a gradually decreasing width and outward twisting of the first lower twisting stirring wings (1-5), and finally connect with the bottom first lower hollow frame ring (1-7). The arrangement positions of the first lower twisting stirring wings (1-5) and the first upper twisting stirring wings (1-3) have an angle difference of 15°. Four first lower claw-type elastic clamping components (1-6) are evenly distributed inside the first lower hollow frame ring (1-7). The configuration of the first lower claw-type elastic clamping components (1-6) is the same as that of the first upper claw-type elastic clamping components (1-1). The edge grid unit (2) includes a second hollow guide ring (2-4) in the middle layer, and two second upper twisting turbulence wings (2-3) grow upward from its upper edge. The width of the second upper twisting turbulence wings (2-3) gradually decreases upward and twists outward, eventually connecting with the uppermost second upper hollow frame ring (2-2). At the same time, the second hollow guide ring (2-4) and the second upper hollow frame ring (2-2) are connected by a first upper irregular connecting component (2-8) in the direction close to the periphery. Four second upper claw-shaped elastic clamping components (2-1) are evenly distributed inside the second upper hollow frame ring (2-2). Two second lower twisting wings grow downward from the lower edge of the second hollow guide ring (2-4). The stirring wing (2-5) and the second lower twisting stirring wing (2-5) gradually decrease in width downwards and twist outwards, eventually connecting with the lowest second lower hollow frame ring (2-7). At the same time, the second hollow guide ring (2-4) and the second lower hollow frame ring (2-7) are connected by the first lower irregular connecting component (2-9) in the direction close to the periphery. The second lower twisting stirring wing (2-5) and the second upper twisting stirring wing (2-3) have a 40° angle difference in their arrangement positions. Four second lower claw-type elastic clamping components (2-6) are evenly distributed inside the second lower hollow frame ring (2-7). The configuration of the second lower claw-type elastic clamping components (2-6) is the same as that of the second upper claw-type elastic clamping component (2-1). The corner frame unit (3) includes a third hollow guide ring (3-4) in the middle layer, and two third upper twisting and stirring wings (3-3) grow upward from its upper edge. The width of the third upper twisting and stirring wings (3-3) gradually decreases upward and twists outward, eventually connecting with the uppermost third upper hollow frame ring (3-2). At the same time, the third hollow guide ring (3-4) and the third upper hollow frame ring (3-2) are connected by a second upper irregular connecting component (3-8) in the direction close to the periphery. Four third upper claw-shaped elastic clamping components (3-1) are evenly distributed inside the third upper hollow frame ring (3-2). It grows downward from the lower edge of the third hollow guide ring (3-4). A third lower twisting and stirring wing (3-5) is produced. The width of the third lower twisting and stirring wing (3-5) gradually decreases downward and twists outward, eventually connecting with the lowest third lower hollow frame ring (3-7). At the same time, the third hollow guide ring (3-4) and the third lower hollow frame ring (3-7) are connected by the second lower irregular connecting component (3-9) in the direction close to the periphery. The third lower twisting and stirring wing (3-5) and the third upper twisting and stirring wing (3-3) are arranged at an angle difference of 40°. Four third lower claw-type elastic clamping components (3-6) are evenly distributed inside the third lower hollow frame ring (3-7), with the same configuration as the third upper claw-type elastic clamping component (3-1).

2. The double-layer turbulence wing nuclear fuel assembly positioning grid according to claim 1, characterized in that: When the nuclear fuel rod (4) is not clamped, the central axis of the clamping surface of the first upper claw type elastic clamping component (1-1) and the first lower claw type elastic clamping component (1-6) forms a small angle of less than 12° with the central axis of the first upper hollow frame ring (1-2) and the first lower hollow frame ring (1-7). Assuming that the diameter of the nuclear fuel rod (4) to be installed is D, the diameter enclosed by the uppermost clamping point of the first upper claw type elastic clamping component (1-1) and the first lower claw type elastic clamping component (1-6) is D-0.5mm, and the diameter enclosed by the lowermost clamping point is D+0.18mm.

3. The double-layer turbulence wing nuclear fuel assembly positioning grid according to claim 1, characterized in that: The inner diameters of the first upper hollow frame ring (1-2) and the first lower hollow frame ring (1-7) are the same, D+2.6mm, and the inner diameter of the first hollow guide ring (1-4) is D+1.1mm.

4. The double-layer turbulence wing nuclear fuel assembly positioning grid according to claim 1, characterized in that: The first lower torsional turbulence blade (1-5) guides part of the water flow into the first hollow guide ring (1-4) after being impacted by the coolant from below, and forms a transverse secondary flow at a certain speed under the action of the torsional structure; the first upper torsional turbulence blade (1-3) receives the remaining coolant impact due to the 15° deflection angle with the first lower torsional turbulence blade (1-5), and guides the water flow to the outside to participate in the turbulence between other grid units, and forms a transverse secondary flow at a certain speed under the action of the torsional structure.

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