Foreign matter prevention lower tube seat and nuclear fuel assembly

Abstract

The invention discloses an anti-foreign-matter lower pipe seat and a nuclear fuel assembly, belongs to the technical field of nuclear fuel assemblies, and mainly aims to give consideration to low flow resistance, uniform flow distribution and reliable foreign matter filtration at the same time and guarantee safe and stable operation of fuel rods in equipment such as a nuclear reactor. According to the main technical scheme, the foreign matter prevention lower pipe seat comprises a foreign matter prevention plate; the foreign matter preventing plate is composed of a plurality of filtering units arranged in an array mode, and each filtering unit is provided with a filtering hole in a penetrating mode, wherein the filtering hole is used for allowing a cooling medium to flow and filtering foreign matter. Each filtering unit comprises a basic repeating unit and three derivative repeating units; the three derivative repeating units are respectively formed by symmetrically expanding the basic repeating unit by using a first mirror image surface, a second mirror image surface and a third mirror image surface; wherein the basic repeating unit is a special-shaped body, and the surface wall of the special-shaped body is an extremely small curved surface.

Description

Technical Field

[0001] This application belongs to the field of nuclear fuel assembly technology, specifically relating to a foreign object-proof lower tube seat and a nuclear fuel assembly. Background Technology

[0002] In nuclear reactors and other equipment that rely on fuel rods for energy conversion, efficient and stable delivery of the cooling medium is a core prerequisite for ensuring the safe operation of the fuel rods. To avoid performance degradation or safety risks caused by excessively high local temperatures in the fuel rods, it is necessary to ensure that the cooling medium can quickly reach the surface of the fuel rods and form a uniform flow distribution among them. This places clear functional requirements on the lower pipe seat, a key component of the cooling system: it must have low flow resistance to accelerate medium delivery, and at the same time, it must have the ability to distribute the flow evenly to ensure consistent heat dissipation.

[0003] Meanwhile, during long-term operation or maintenance, various foreign objects can easily mix into the cooling medium, such as metal shavings left over from equipment installation or maintenance, fragments of gaskets used for pipe sealing, and solid impurities generated during medium circulation. If these foreign objects enter the cooling channels of the fuel rods with the cooling medium, they can cause localized blockages, further disrupting flow uniformity, or even directly wear down the fuel rod structure, leading to serious equipment safety hazards. Therefore, in addition to meeting the core requirements of low flow resistance and uniform flow, the lower pipe seat must also have a reliable foreign object filtration function to intercept impurities in the cooling medium.

[0004] However, existing lower pipe socket designs struggle to balance these multiple functional requirements simultaneously. Some designs, in pursuit of low resistance and flow uniformity, simplify the filter structure, resulting in insufficient foreign object interception. Other designs, while enhancing filtration capabilities, often employ filter screens or grid structures that increase media flow resistance. Furthermore, improper arrangement of filter units can disrupt the originally uniform flow distribution, ultimately failing to balance the equipment's heat dissipation efficiency and operational safety. Summary of the Invention

[0005] In view of this, this application provides a foreign object-proof lower tube seat and nuclear fuel assembly, the main purpose of which is to simultaneously take into account low flow resistance, uniform flow distribution and reliable foreign object filtration, so as to solve the problem that existing lower tube seats are difficult to balance multiple functions and ensure the safe and stable operation of fuel rods in nuclear reactors and other equipment.

[0006] To achieve the above objectives, this application mainly provides the following technical solutions: One aspect of this application provides a foreign object prevention lower pipe seat, including a foreign object prevention plate; the foreign object prevention plate is composed of multiple filter units arranged in an array, each filter unit having a filter hole through which a cooling medium flows and filters foreign objects; each filter unit includes a basic repeating unit and three derivative repeating units; the three derivative repeating units are symmetrically extended from the basic repeating unit with a first mirror surface, a second mirror surface, and a third mirror surface, respectively; wherein, the basic repeating unit is an irregular shape, and the surface wall of the irregular shape is a minimal curved surface.

[0007] Optionally, the first mirror plane and the second mirror plane are two mutually perpendicular vertical planes of the filtering unit, and the third mirror plane is the vertical plane containing the first spatial diagonal of the filtering unit.

[0008] Optionally, the cross-section of the filter unit along the thickness direction is square, the first spatial diagonal is the spatial diagonal connecting two opposite vertices of the filter unit, and the third mirror plane is only the symmetry plane of the filter unit as a whole, not the symmetry plane of the basic repeating unit itself.

[0009] Optionally, the minimum surface is a three-period minimum surface.

[0010] Optionally, the three-period minimum surface conforms to the formula: .

[0011] Optionally, the irregular body has an outwardly extending protrusion, the end face of the protrusion away from the body of the irregular body is flat, and the end faces of all the protrusions located on the same side of the filter unit are kept flush.

[0012] Optionally, the filter holes include vertically arranged filter holes and horizontally arranged filter holes; the vertically arranged filter holes penetrate the filter unit along the thickness direction of the filter unit, and the horizontally arranged filter holes penetrate the filter unit along the length direction and width direction of the filter unit respectively, and in the same filter unit, the vertically arranged filter holes and the horizontally arranged filter holes are interconnected to form a passage for the flow of cooling medium.

[0013] Optionally, in two adjacent filter units, the horizontal filter holes of one unit are connected to the horizontal filter holes of the other unit.

[0014] Optionally, the anti-foreign object lower tube seat further includes a square frame and support legs; the square frame is fixed around the outer periphery of the anti-foreign object plate; four support legs are provided, respectively located at the four corners of the bottom of the square frame, wherein at least two of the support legs arranged opposite each other are provided with pin holes for installation and fixing.

[0015] Another aspect of this application provides a nuclear fuel assembly including the foreign object protection lower tube as described in any of the above claims.

[0016] By employing the above technical solution, this application has at least the following beneficial effects: The foreign object shielding lower tube and nuclear fuel assembly provided in this application utilize a foreign object shielding plate composed of multiple filter units arranged in an array. Each filter unit is formed by multi-directional mirror-symmetric expansion of a basic repeating unit, and the basic repeating unit is an irregular shape with a surface of minimal curvature. Because minimal curvature has the characteristic of zero average curvature everywhere, this curved surface structure allows the cooling medium to pass smoothly through the foreign object shielding plate, significantly reducing the resistance generated during the flow of the cooling medium. Simultaneously, the arrayed layout of the filter units guides the cooling medium to distribute evenly during flow, thereby ensuring consistent heat dissipation of each fuel rod within the nuclear reactor and preventing performance degradation or safety risks caused by excessively high local temperatures. Furthermore, the filter unit, formed by the expansion of the basic repeating unit into an irregularly shaped structure, combined with the through-hole filter holes, enhances the interception of foreign objects such as metal shavings and gasket fragments in the cooling medium through its special irregular shape, effectively preventing foreign objects from entering the fuel rod cooling channel and causing blockage or wear. On the other hand, compared with traditional filter screens or grid structures, this design does not significantly increase the flow resistance of the cooling medium and avoids disrupting the flow uniformity due to unreasonable arrangement of filter units. Ultimately, it solves the pain point of the existing lower tube seat design where it is difficult to balance filtration effect and delivery efficiency, and improves the operating efficiency and safety of the nuclear reactor cooling system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the anti-foreign object lower tube seat from one viewpoint of an optional embodiment of this application; Figure 2 This is a schematic diagram of the structure of the anti-foreign object lower tube seat of an optional embodiment of this application from another perspective. Figure 3 This is a schematic diagram of the structure of a filtering unit in one optional embodiment of this application; Figure 4 This is a top view of the filtering unit in one optional embodiment of this application; Figure 5 This is a side view of the filtering unit of an optional embodiment of this application; Figure 6 This is a schematic diagram of the structure of a basic repeating unit in an optional embodiment of this application.

[0018] The reference numerals in the attached figures are as follows: 1. Foreign object protection plate; 11. Filter unit; 111. Irregular body; 112. Protrusion; 113. Filter hole; 1131. Vertical filter hole; 1132. Horizontal filter hole; 2. Square frame; 3. Support leg; 31. Pin hole. Detailed Implementation

[0019] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0021] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0022] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0023] See also Figures 1 to 6 As shown, according to an embodiment of this application, a foreign object prevention lower pipe seat is provided, including a foreign object prevention plate 1; the foreign object prevention plate 1 is composed of a plurality of filter units 11 arranged in an array, each filter unit 11 having a filter hole 113 through which a cooling medium flows and filters foreign objects; each filter unit 11 includes a basic repeating unit and three derivative repeating units; the three derivative repeating units are formed by symmetrically extending the basic repeating unit with a first mirror surface, a second mirror surface, and a third mirror surface; wherein, the basic repeating unit is an irregular shape, and the surface wall of the irregular shape is a minimal curved surface.

[0024] The foreign object shielding lower tube seat provided in the embodiments of this application is configured with a foreign object shielding plate 1, which is composed of multiple filter units 11 arranged in an array. Each filter unit 11 is formed by multi-directional mirror symmetry expansion of a basic repeating unit, and the basic repeating unit is an irregular shape with a surface of minimal curvature. Since the minimal curvature has the characteristic that the average curvature is zero everywhere, this curved surface structure allows the cooling medium to pass smoothly through the foreign object shielding plate 1, greatly reducing the resistance generated during the flow of the cooling medium. At the same time, the arrayed layout of the filter units 11 can guide the cooling medium to be evenly distributed during the flow process, thereby ensuring the consistency of heat dissipation of each fuel rod in the nuclear reactor and avoiding performance degradation or safety risks caused by excessively high local temperatures. Furthermore, the filter unit 11, formed by expanding the basic repeating unit into an irregular shape, is combined with the through-hole filter 113. On the one hand, the special irregular shape enhances the interception capability of foreign objects such as metal shavings and gasket fragments in the cooling medium, effectively preventing foreign objects from entering the fuel rod cooling channel and causing blockage or wear. On the other hand, compared with traditional filter screens or grid structures, this design does not significantly increase the flow resistance of the cooling medium and can also avoid disrupting the flow uniformity due to unreasonable arrangement of the filter unit 11. Ultimately, it solves the pain point of the existing lower tube seat design where it is difficult to balance filtration effect and delivery efficiency, and improves the operating efficiency and safety of the nuclear reactor cooling system.

[0025] The basic repeating unit is the design prototype of the entire filter unit 11, and its shape determines the characteristics of the filter unit 11.

[0026] Specifically, the filter unit 11 is an extended combination of the basic repeating unit. Its overall structure consists of one basic repeating unit and three derived repeating units. The three derived repeating units are all based on the basic repeating unit, formed through symmetrical expansion of the first, second, and third mirror surfaces, respectively. That is, the basic repeating unit is the core of the filter unit 11, and the overall framework of the filter unit 11 is entirely built upon the form of the basic repeating unit through symmetrical replication and directional expansion; the two are in a prototype-derived combination relationship. Here, since the derived repeating units are mirror-symmetric structures of the basic repeating unit, the overall morphological characteristics of the filter unit 11, such as surface curvature, contour orientation, and spatial form, are entirely inherited from the irregular body properties of the basic repeating unit. Based on this, the core feature of the basic repeating unit's surface being a minimal surface can be directly transferred to the entire filter unit 11 through symmetrical expansion, so that the surface of the filter unit 11 also possesses a morphological basis composed of minimal surfaces.

[0027] In mathematics, a minimum surface is defined as the surface with the smallest area among surfaces whose boundaries have a given closed curve. Based on this, the minimum surface directly produces the following two core functions: First, its special surface shape can guide and intercept foreign objects entrained in the cooling medium. When foreign objects flow through the surface, due to the curvature change and area minimization characteristics, they will gradually leave the flow path and remain, preventing foreign objects from accumulating at the opening of the filter hole 113, thereby reducing obstruction to the cooling medium. Second, the smooth transition characteristics of the minimum surface result in only weak flow resistance when the cooling medium comes into contact with it. This ensures flow uniformity through the arrangement of the filter holes 113 while avoiding excessive pressure loss of the cooling medium, thus balancing the contradiction between filtration interception and flow efficiency.

[0028] Furthermore, to enhance the above effects, multiple filter units 11 can adopt a multi-layer, multi-row, multi-column array structure, making the volume of a single filter unit 11 sufficiently small. The multi-directional curvature characteristics of the minimal surface are perfectly combined with the small volume unit, allowing the cooling medium to be diverted in multiple directions when it comes into contact with the curved surface, further promoting the uniform distribution of the cooling medium throughout the entire range. At the same time, the combination of the small volume filter unit 11 and the minimal surface continues the low resistance advantage. The resistance of the cooling medium in contact with the foreign object protection plate 1 is dispersed to multiple filter units 11, further reducing the overall flow loss and pressure loss. Ultimately, this ensures that when the cooling medium flows through the foreign object protection plate 1, it can efficiently filter foreign objects while maintaining a stable flow effect.

[0029] Specifically, the length of a single filter unit 11 is 16mm to 20mm, the width is 16mm to 20mm, and the thickness is 25mm to 55mm. It is understood that multiple filter units 11 can be an integrated structure, processed by additive manufacturing; or they can be non-integrated structures, connected by welding.

[0030] The filter holes 113 facilitate the flow of the cooling medium, and the aperture size of the filter holes 113 can filter foreign objects such as chips or gaskets entrained in the cooling medium, preventing foreign objects from passing through and scratching the fuel rods.

[0031] Specifically, the filter orifice 113 is not a straight orifice, but rather a curved orifice structure adapted to the extremely small curved surface shape. The orifice wall of this curved orifice structure continues the curved surface characteristics of the basic repeating unit surface, allowing the cooling medium to flow along a smooth curved surface when passing through the filter orifice 113, further reducing local resistance; at the same time, the non-linear channel design of the filter orifice 113 extends the passage path of foreign objects, and combined with the limitation of the orifice size, it can more efficiently intercept foreign objects of different shapes, preventing them from directly passing through the orifice and contacting the fuel rod, thus enhancing the protective effect while ensuring the flow of cooling medium.

[0032] It should be noted that the filter holes 113 with curved holes are not independent holes created after the filter unit 11 is formed. Rather, they are channel spaces formed by the mutual enclosure and natural definition of the extremely small curved surface walls of each repeating unit when the basic repeating unit and three derived repeating units are expanded through mirror symmetry to form an overall irregular shape structure. In other words, after the irregular shape of the basic repeating unit is transformed into derived repeating units through mirror symmetry in three directions, the curved surface walls of the four repeating units will connect and enclose each other in space, and the naturally formed through gaps between their curved surfaces constitute the curved hole structure of the filter holes 113. The shape and orientation of these curved holes are entirely determined by the extremely small curved surface contours of each repeating unit, and are formed synchronously with the overall structure of the filter unit 11, rather than being additionally processed later through drilling or other methods. Therefore, they can be highly adapted to the curved surface shape of the filter unit 11 while maintaining the integrity and stability of the structure.

[0033] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 3 As shown, the first and second mirror surfaces are two mutually perpendicular vertical surfaces of the filter unit 11, and the third mirror surface is the vertical surface where the first spatial diagonal of the filter unit 11 is located.

[0034] In this embodiment, by defining the specific positional relationships of the first, second, and third mirror surfaces, precise mirror expansion of the basic repeating unit in three directions is achieved, forming the overall irregular shape structure of the filter unit 11. This not only ensures the complete transmission of the minimal curvature characteristics of the filter unit 11's surface, but also ensures that the filter holes 113 formed by these curved surfaces have a matching curved hole structure. This efficiently guides the cooling medium to flow smoothly and distribute evenly, while effectively intercepting foreign objects in the cooling medium, preventing them from entering the fuel rod cooling channels and causing blockages or wear. This improves the operating efficiency and safety of the nuclear reactor cooling system, achieving the dual goals of minimizing cooling medium flow resistance and maximizing foreign object interception.

[0035] The first mirror surface extends along the length of the filter unit 11 and passes through the geometric center of the filter unit 11, symmetrically dividing the filter unit 11 into two parts with identical shape and size along the length.

[0036] The second mirror surface extends along the width direction of the filter unit 11 and passes through the geometric center of the filter unit 11, symmetrically dividing the filter unit 11 into two parts with identical shape and size along the width direction. The first mirror surface and the second mirror surface are perpendicular to each other at the geometric center, together forming an orthogonal symmetric reference for the filter unit 11 in a two-dimensional plane.

[0037] The third mirror surface extends along the diagonal direction of the filter unit 11 and also passes through the geometric center of the filter unit 11, symmetrically dividing the filter unit 11 into two parts with completely identical shape and size along the diagonal direction.

[0038] It should be noted that the combination of the first, second, and third mirror surfaces constructs a multi-directional, cross-dimensional symmetric reference, enabling the basic repeating unit to complete mirror expansion along the horizontal orthogonal direction and the spatial diagonal direction. The resulting filter unit 11 has more comprehensive symmetry in three-dimensional space, which not only ensures the balance of the structural form, but also allows the characteristics of the minimal surface to be uniformly transmitted in multiple spatial directions, thereby optimizing the three-dimensional flow field distribution of the cooling medium and the foreign object interception effect.

[0039] In the above embodiments, see Figure 3 and Figure 4 As shown, the cross-section of the filter unit 11 along the thickness direction is square, the first spatial diagonal is the spatial diagonal connecting the two opposite vertices of the filter unit 11, and the third mirror plane is only the symmetry plane of the filter unit 11 as a whole, not the symmetry plane of the basic repeating unit itself.

[0040] When the cross-section of the filter unit 11 along the thickness direction is square, the three-dimensional structure of the filter unit 11 can be understood as a square cylinder, and the first spatial diagonal is the longest line segment that runs through the square cylinder and connects the opposite vertices.

[0041] Specifically, the third mirror plane is the plane of symmetry of the entire filter unit 11. The complete filter unit 11, consisting of one basic repeating unit and three derived repeating units, is divided along this plane, with both sides having the same shape and size. However, the third mirror plane is not the plane of symmetry of the basic repeating unit itself. When the basic repeating unit is taken out alone, it cannot be divided into two symmetrical parts through this plane. Thus, it is clear that the basic repeating unit is the design prototype of the filter unit 11, and the filter unit 11 is a combination of the basic repeating unit after symmetrical expansion.

[0042] In some possible implementations disclosed in this application, the minimum surface is a three-period minimum surface.

[0043] Minimal surfaces can be classified into single-periodic, double-periodic, and triple-periodic surfaces based on the dimension of their periodic extension into the surrounding space.

[0044] It should be noted that the three-period minimal surface has advantages such as full connectivity, high smoothness, spatial porous channels, and full mathematical expression. Specifically, these advantages are reflected in three aspects: full connectivity ensures that even if individual through-hole channels are blocked by foreign objects, subsequent through-hole channels can still allow the cooling medium to flow through, thereby reducing the frequency of cleaning and maintenance and extending the service life of the foreign object protection plate 1; high smoothness helps to reduce the resistance encountered by the cooling medium when it flows through the structure; and spatial porous channels are conducive to achieving uniform distribution of the cooling medium.

[0045] In the above embodiment, the three-period minimum surface conforms to the formula: .

[0046] Here, x, y, and z represent three mutually perpendicular directions in three-dimensional space, corresponding to the length, width, and thickness directions of the basic repeating unit.

[0047] Specifically, firstly, the mathematical values ​​of x, y, and z are linked to the actual dimensions of the basic repeating unit. For example, x is set to correspond to the length direction, y to the width direction, and z to the thickness direction, establishing a direct relationship between mathematical coordinates and physical space. Then, the formula is solved through mathematical calculations. The process involves obtaining all the discrete points in space that constitute the minimal surface; finally, the set of discrete points is fitted into a continuous surface, and the shape is observed through visualization tools to verify whether it meets the functional requirements of low resistance and high filtering.

[0048] It should be noted that when the length of a single filter unit 11 is 16mm to 20mm, the width is 16mm to 20mm, and the thickness is 25mm to 55mm, the length of the basic repeating unit is 4mm to 5mm, the width is 4mm to 5mm, and the thickness is 25mm to 55mm.

[0049] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 3 and Figure 6 As shown, the irregular body has an outwardly extending protrusion 112. The end face of the protrusion 112 away from the body 111 of the irregular body is flat, and the end faces of all protrusions 112 located on the same side of the filter unit 11 are flush.

[0050] In this embodiment, by setting the end face of the protrusion 112 away from the irregular body 111 to be flat, and keeping the end faces of all protrusions 112 on the same side of the filter unit 11 flush, the edge shape of the filter unit 11 can be relatively regular. When adjacent filter units 11 come into contact, the flat end faces of the protrusions 112 can form a stable and sufficient contact area, avoiding localized force concentration or excessive gaps caused by irregular contact surfaces. Based on this, not only can the overall structural stability of multiple filter units 11 arrayed together be improved, preventing misalignment or loosening due to long-term impact or vibration of the cooling medium, but also the localized eddies caused by uneven gaps between adjacent units can be reduced, avoiding additional resistance or foreign matter accumulation caused by eddies. At the same time, it provides a clear benchmark for the assembly and positioning of the filter unit 11, reducing installation difficulty, further ensuring the reliability of the overall structure of the anti-foreign matter plate 1 and the stability of the cooling medium flow, indirectly enhancing the operational safety and service life of the anti-foreign matter lower tube seat.

[0051] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the filter hole 113 includes a vertically arranged filter hole 1131 and a horizontally arranged filter hole 1132. The vertically arranged filter hole 1131 penetrates the filter unit 11 along the thickness direction of the filter unit 11, and the horizontally arranged filter hole 1132 penetrates the filter unit 11 along the length direction and the width direction of the filter unit 11, respectively. In the same filter unit 11, the vertically arranged filter hole 1131 and the horizontally arranged filter hole 1132 are interconnected and together form a passage for the flow of cooling medium.

[0052] In this embodiment, by dividing the filter holes 113 into vertically arranged filter holes 1131 and horizontally arranged filter holes 1132, and making the two interconnected, the cooling medium can first flow in the filter unit 11 in three directions: thickness, length, and width. This breaks the limitation of a single-direction flow channel and avoids local congestion caused by a single flow direction, thus significantly improving the overall flow efficiency. Secondly, the interconnected flow channel structure extends the flow path of the cooling medium in the filter unit 11, and the filter hole walls in different directions can intercept foreign objects from multiple angles. Even if some small foreign objects pass through a filter hole in one direction, they may be intercepted when they turn to flow in another direction. At the same time, the interconnected structure can also reduce the accumulation and blockage of foreign objects in a single filter hole. This ensures the smooth flow of the cooling medium and comprehensively improves the filtration effect of foreign objects from both the perspectives of path extension and multi-directional interception, ultimately achieving a dual optimization of flow efficiency and filtration performance.

[0053] In the above embodiments, see Figure 3 and Figure 5 As shown, in two adjacent filter units 11, the horizontal filter hole 1132 of one unit is connected to the horizontal filter hole 1132 of the other unit.

[0054] Here, by connecting the transverse filter holes 1132 of adjacent filter units 11, the flow channel boundary of a single filter unit 11 is first broken, allowing the cooling medium to flow laterally along the length and width directions between multiple filter units 11, forming a three-dimensional flow network across units. This avoids local flow interruptions caused by flow channel blockage within a single unit, significantly improving the stability and redundancy of the overall cooling medium flow. Secondly, the connected transverse filter holes 1132 can further optimize the uniformity of cooling medium distribution, allowing cooling medium originally concentrated in some units to be diverted to surrounding units through transverse channels, ensuring the core... Consistent heat dissipation of fuel rods in different areas of the reactor prevents localized overheating. At the same time, the cross-unit interconnected flow channels can extend the flow path of foreign objects in the filtration system. During the lateral flow, foreign objects will be intercepted by the filter pore walls of more filter units 11, further reducing the probability of foreign objects entering the fuel rod cooling channels. Even if the horizontal filter pores 1132 of individual filter units 11 are blocked, the cooling medium can still bypass through the connecting channels of adjacent units, ensuring the continuous stability of the overall filtration and cooling functions. Ultimately, this enhances the operational reliability of the foreign object protection lower tube seat and the safety of the nuclear reactor cooling system.

[0055] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 1 and Figure 2 As shown, the anti-foreign object lower tube seat also includes a square frame 2 and support legs 3; the square frame 2 is fixed around the outer periphery of the anti-foreign object plate 1; there are four support legs 3, which are respectively set at the four corners of the bottom of the square frame 2, and at least two opposite support legs 3 are provided with pin holes 31 for installation and fixing.

[0056] In this embodiment, by setting up a square frame 2 and support legs 3 with pin holes 31, firstly, the square frame 2 is fixed around the outer periphery of the foreign object shield 1, which can form a stable boundary support for the foreign object shield 1, preventing the edge deformation and cracking of the foreign object shield 1 due to long-term impact or vibration of the cooling medium, and at the same time, it regulates the shape of the foreign object shield 1, which facilitates its assembly and docking with other components of the nuclear reactor; secondly, the four support legs 3 are respectively set at the four corners of the bottom of the square frame 2, which can stably support the lower pipe seat of the foreign object shield on the mounting plane, ensuring that the foreign object shield 1 maintains a reasonable distance from the structure below. The spacing provides ample space for the inflow and outflow of cooling medium, preventing flow channel blockage caused by close contact. Furthermore, the pin holes 31 on at least two opposing legs 3 can achieve precise positioning and fixation of the anti-foreign object lower tube seat through connectors such as pins, preventing displacement or deviation during operation, ensuring the alignment accuracy of the filter unit 11 and the fuel rod cooling channel, and avoiding uneven distribution of cooling medium or leakage of foreign objects due to misalignment. Ultimately, the overall reliability of the anti-foreign object lower tube seat is enhanced from three aspects: structural support, installation positioning, and flow channel protection, adapting to the harsh operating environment requirements of nuclear reactors.

[0057] Among them, the square box body 2 is in a mouth shape and has a certain thickness. Its two ends are open to facilitate the flow of the cooling medium.

[0058] Specifically, the square box body 2 is used to wrap the outermost side of the filter unit 11 at the edge of the foreign object prevention plate 1, which can fix all the filter units 11, ensure the structural stability of the foreign object prevention plate 1, and prevent the separation of multiple filter units 11 when impacted by the cooling medium.

[0059] It should be noted that the foreign object prevention plate 1 and the square box body 2 can be an integrated structure and processed by additive manufacturing; or they can not be an integrated structure, and the two are connected by welding.

[0060] Furthermore, an embodiment of the present application also provides a nuclear fuel assembly, including the foreign object prevention lower nozzle of any one of the above.

[0061] Among them, the nuclear fuel assembly includes a bottom device, an upper device, a plurality of guide tubes, a plurality of grids and a plurality of fuel rods. The guide tubes are arranged longitudinally, and both ends are respectively fixed in the bottom device and the upper device. The bottom device allows the cooling medium to enter the nuclear fuel assembly, and the upper device allows the cooling medium to come out of the nuclear fuel assembly. The grids are arranged horizontally and are fixedly arranged at intervals in the length direction of the guide tubes. The grids have a plurality of grilles, and the fuel rods are respectively inserted through the corresponding grilles. The nuclear fuel assembly is vertically placed during use, and its bottom device is located on the upper surface of the lower core plate of the nuclear reactor by relying on the support legs 3. A water flow channel is formed in the bottom device. Correspondingly, a water flow channel is also formed on the lower core plate. The water flow channel of the lower core plate is opposite to the bottom device, so that the reactor cooling medium sequentially passes through the lower core plate and the bottom device, contacts the fuel rods and cools the fuel rods. In this way, heat exchange between the cooling medium and the fuel rods is formed. In this embodiment, the foreign object prevention lower nozzle can be understood as the bottom device of the nuclear fuel assembly.

[0062] Specifically, in order to adapt to the nuclear fuel assembly, guide tube holes and instrument tube holes are opened on the foreign object prevention plate 1 of the foreign object prevention lower nozzle. The guide tube holes are used to accommodate the guide tubes, and the instrument tube holes are used to accommodate the instrument tubes, so as to respectively fix and limit the guide tubes and the instrument tubes, and prevent their positions from easily changing when impacted by the flow of the cooling medium.

[0063] The guide tubes on the inner side are eight in a square arrangement, with three guide tubes on each side of the square. These eight guide tubes are located near the center of the foreign object shield 1. The guide tubes on the outer side are sixteen in a ring arrangement, located near the square frame 2 of the foreign object shield 1. Additionally, there is one instrument tube located at the center of the foreign object shield 1. It is understood that the specific number of guide tubes and their arrangement can be different. Here, the foreign object shield 1 formed by the guide tubes, instrument tubes, and multiple filter units 11 can be an integrated structure, manufactured using additive manufacturing.

[0064] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.

[0065] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A foreign object prevention lower tube seat, characterized in that, The system includes a foreign object blocking plate; the foreign object blocking plate is composed of multiple filter units arranged in an array, each filter unit having a filter hole through which the cooling medium flows and filters foreign objects; each filter unit includes a basic repeating unit and three derivative repeating units; the three derivative repeating units are formed by symmetrically extending the basic repeating unit with a first mirror surface, a second mirror surface, and a third mirror surface, respectively; wherein, the basic repeating unit is an irregular shape, and the surface wall of the irregular shape is a minimal curved surface.

2. The anti-foreign-object lower pipe seat according to claim 1, characterized in that, The first mirror plane and the second mirror plane are two mutually perpendicular vertical planes of the filter unit, and the third mirror plane is the vertical plane containing the first spatial diagonal of the filter unit.

3. The anti-foreign-object lower tube seat according to claim 2, characterized in that, The cross-section of the filter unit along the thickness direction is square, the first spatial diagonal is the spatial diagonal connecting the two opposite vertices of the filter unit, and the third mirror plane is only the symmetry plane of the filter unit as a whole, not the symmetry plane of the basic repeating unit itself.

4. The anti-foreign-object lower pipe seat according to claim 1, characterized in that, The minimum surface is a three-period minimum surface.

5. The anti-foreign-object lower pipe seat according to claim 4, characterized in that, The three-period minimum surface conforms to the formula: 。 6. The anti-foreign-object lower pipe seat according to claim 1, characterized in that, The irregular body has outwardly extending protrusions, the end face of the protrusions away from the body of the irregular body is flat, and the end faces of all the protrusions located on the same side of the filter unit are flush.

7. The anti-foreign-object lower pipe seat according to claim 1, characterized in that, The filter holes include vertically placed filter holes and horizontally placed filter holes; the vertically placed filter holes penetrate the filter unit along the thickness direction of the filter unit, and the horizontally placed filter holes penetrate the filter unit along the length direction and width direction of the filter unit respectively. In the same filter unit, the vertically placed filter holes and the horizontally placed filter holes are interconnected to form a passage for the flow of cooling medium.

8. The anti-foreign-object lower pipe seat according to claim 7, characterized in that, In two adjacent filter units, the horizontal filter holes of one unit are connected to the horizontal filter holes of the other unit.

9. The anti-foreign-object lower pipe seat according to claim 1, characterized in that, It also includes a square frame and legs; the square frame is fixed around the outer periphery of the foreign object protection plate; there are four legs, which are respectively set at the four corners of the bottom of the square frame, and at least two of the opposite legs have pin holes for installation and fixing.

10. A nuclear fuel assembly, characterized in that, Includes the foreign object prevention lower tube seat as described in any one of claims 1-9.

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