Nuclear fuel mechanism and assembly method therefor

Abstract

A nuclear fuel mechanism and an assembly method for the nuclear fuel mechanism. The nuclear fuel mechanism comprises a lower end plug (1) of a fuel rod, a lower nozzle assembly (2), and an adjustment assembly (3). An adjustment member (32) can drive a connecting member (31) to move, causing a debris prevention plate (21) to move horizontally relative to a nozzle body (22). In this case, the central axis of a constraint through hole (211) in the debris prevention plate (21) is misaligned with the central axis of a constraint counterbore (221) in the nozzle body (22), such that a limiting portion (12) of the lower end plug (1) of the fuel rod is restricted below the debris prevention plate (21). By means of restricting the limiting portion (12) of the lower end plug (1) of the fuel rod between the debris prevention plate (21) and the nozzle body (22), the axial movement of the fuel rod is limited. When the clamping force of a spacer grid is lost, it is ensured that the fuel rod does not move axially under a hydraulic lifting force or when a fuel assembly is subjected to an axial impact load, thereby avoiding exacerbating fretting wear between the grid and the fuel rod, and preventing failure of the fuel rod caused by the fuel rod falling and impacting the lower nozzle assembly (2).

Description

Nuclear fuel mechanism and its assembly method Technical Field

[0001] This invention relates to the field of nuclear reactor fuel, and more particularly to a nuclear fuel mechanism and its assembly method. Background Technology

[0002] A nuclear fuel assembly typically comprises several fuel rods, several guide tubes and positioning grids, as well as an upper and lower tube assembly. Within the fuel assembly, the fuel rod bundle is axially positioned between the upper and lower tube assemblies by multiple layers of positioning grids. Reactor coolant enters the fuel rod bundle from the lower tube assembly and flows out of the fuel assembly through the upper tube assembly, carrying away the heat generated by the nuclear reaction in the fuel rod bundle.

[0003] When the clamping force of the positioning grid is lost in the existing fuel rod bundle restraint scheme, the fuel rods may move axially under the action of hydraulic lifting force or when the fuel assembly is subjected to axial impact load. This will aggravate the fretting erosion between the fuel rods and the positioning grid. Furthermore, the fuel rods may fail if they fall and impact the lower tube seat after axial movement. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a nuclear fuel mechanism and its assembly method.

[0005] The technical solution adopted by the present invention to solve its technical problem is: to construct a nuclear fuel mechanism, which includes a fuel rod lower end plug, a lower tube seat assembly and an adjustment assembly;

[0006] The lower end plug of the fuel rod includes a positioning part and a limiting part fixedly connected to the positioning part;

[0007] The lower tube seat assembly includes a foreign object prevention plate and a seat body. The foreign object prevention plate is provided with a constraint through hole and a through hole. The constraint through hole is for the lower end plug of the fuel rod to pass through.

[0008] The upper surface of the base is provided with a constraint countersunk hole corresponding to the constraint through hole and an action groove corresponding to the through hole. The constraint countersunk hole is used to accommodate the limiting part.

[0009] The side wall of the seat is provided with a communicating hole that communicates with the function groove. The adjustment component includes a connector and an adjustment component. The connector is installed in the through hole and its end is located in the function groove. The adjustment component is installed in the communicating hole and the connector is connected to the adjustment component in a transmission manner.

[0010] The adjusting member can drive the connecting member to move, causing the anti-foreign object plate to move horizontally relative to the seat body, so that the limiting part restricts the anti-foreign object plate from below.

[0011] In some embodiments, the adjusting member has a first threaded portion, and the end of the connecting member has a second threaded portion that matches the first threaded portion.

[0012] In some embodiments, the adjusting member is further provided with a mating groove.

[0013] In some embodiments, the nuclear fuel mechanism further includes an anti-rotation component, which has a protrusion that matches the mating groove, and a receiving groove is formed on the side of the anti-rotation component facing away from the protrusion.

[0014] In some embodiments, the side wall of the base is further provided with a mounting groove for installing the anti-rotation component, and the mounting groove is correspondingly provided with the communicating hole.

[0015] In some embodiments, the nuclear fuel mechanism further includes a fuel assembly guide tube, the foreign object shield has a first mounting hole for the fuel assembly guide tube to pass through, and the base has a second mounting hole corresponding to the first mounting hole.

[0016] In some embodiments, the through hole is perpendicular to the connecting hole.

[0017] In some embodiments, the connector is welded to the foreign object protection plate.

[0018] In this embodiment, a method for assembling a nuclear fuel mechanism is also constructed, which is based on the aforementioned nuclear fuel mechanism and includes the following steps:

[0019] S1. Install the adjusting component in the connecting hole of the base body, and install the connecting component in the through hole of the anti-foreign object plate. After the first threaded part of the adjusting component and the second threaded part of the connecting component are matched and connected in the function groove of the base body, weld the connecting component to the anti-foreign object plate.

[0020] S2. Adjust the position of the anti-foreign object plate using the adjusting parts, and align the constraint through hole on the anti-foreign object plate with the constraint countersunk hole on the base.

[0021] S3. Pass the lower end plug of the fuel rod through the constraint through hole and place the limiting part of the lower end plug of the fuel rod in the constraint countersunk hole;

[0022] S4. Rotate the adjusting member to cause the foreign object prevention plate to move horizontally relative to the seat body, so that the limiting part of the lower end plug of the fuel rod is restricted below the foreign object prevention plate.

[0023] In some embodiments, the steps further include:

[0024] S5. Install the anti-rotation component into the mounting groove, so that the protrusion of the anti-rotation component is engaged with the mating groove of the adjusting component.

[0025] S6. Secure the fuel assembly guide tube and seat using fasteners.

[0026] The present invention has the following beneficial effects: the lower end plug of the fuel rod can pass through the constraint through hole of the anti-foreign object plate, and then the limiting part of the lower end plug of the fuel rod sits in the constraint countersunk hole of the seat body. The limiting part contacts the radial wall of the constraint countersunk hole, thereby providing radial constraint for the lower end plug of the fuel rod and reducing the flow-induced vibration of the lower end plug of the fuel rod in the horizontal direction. The connecting part can be moved by the adjusting member, so that the anti-foreign object plate moves horizontally relative to the seat body. At this time, the central axis of the constraint through hole of the anti-foreign object plate is misaligned with the central axis of the constraint countersunk hole of the seat body, so that the limiting part of the lower end plug of the fuel rod is restricted below the anti-foreign object plate. By restricting the limiting part of the lower end plug of the fuel rod between the anti-foreign object plate and the seat body, the axial movement of the fuel rod is restricted. When the clamping force of the positioning grid is lost, it is ensured that the fuel rod will not move axially under the action of hydraulic lifting force or when the fuel assembly is subjected to axial impact load, thus avoiding the aggravation of fretting erosion of the grid and fuel rod and avoiding the fuel rod falling and hitting the lower tube seat, which would cause fuel rod failure. Attached Figure Description

[0027] 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 should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort. In the drawings:

[0028] Figure 1 is a partial structural schematic diagram of the nuclear fuel mechanism in some embodiments of the present invention;

[0029] Figure 2 is a schematic diagram of the installation structure of the nuclear fuel mechanism in some embodiments of the present invention;

[0030] Figure 3 is a schematic diagram of the structure of the lower tube seat assembly in some embodiments of the present invention;

[0031] Figure 4 is a schematic diagram of the structure of the base in some embodiments of the present invention;

[0032] Figure 5 is an enlarged view of point A in Figure 4;

[0033] Figure 6 is a schematic diagram of the structure of the foreign object protection plate in some embodiments of the present invention;

[0034] Figure 7 is a schematic diagram of the structure of the adjusting member in some embodiments of the present invention;

[0035] Figure 8 is a schematic diagram of the structure of the connector in some embodiments of the present invention;

[0036] Figure 9 is a schematic diagram of the anti-rotation component in some embodiments of the present invention;

[0037] Figure 10 is a schematic diagram of the structure of the lower end plug of the fuel rod in some embodiments of the present invention. Detailed Implementation

[0038] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on this invention.

[0039] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0040] Referring to Figures 1 to 10, a nuclear fuel mechanism is shown in some embodiments of the present invention, which includes a fuel rod lower end plug 1, a lower tube seat assembly 2, and an adjustment assembly 3. As shown in Figure 10, the fuel rod lower end plug 1 includes a positioning part 11 and a limiting part 12 fixedly connected to the positioning part 11. The positioning part 11 is cylindrical, and the limiting part 12 is conical. The size of the upper end surface of the limiting part 12 is larger than the size of the positioning part 11. In some embodiments, the positioning part 11 is integrally formed with the limiting part 12, thereby increasing the stability between the positioning part 11 and the limiting part 12.

[0041] As shown in Figures 1 to 6, where Figure 1 is a partial structural schematic diagram of the nuclear fuel mechanism, the lower tube seat assembly 2 includes a foreign object shield 21 and a seat body 22. The foreign object shield 21 has a constraint through hole 211 and a through hole 212. The constraint through hole 211 allows the lower end plug 1 of the fuel rod to pass through. The upper surface of the seat body 22 has a constraint countersunk hole 221 corresponding to the constraint through hole 211 and an action groove 222 corresponding to the through hole 212. The constraint countersunk hole 221 is used to accommodate the limiting part 12. The side wall of the seat body 22 has a connecting hole 223 communicating with the action groove 222. The adjustment assembly 3 includes a connector 31 and an adjustment member 32. The connector 31 is installed in the through hole 212 and its end is located in the action groove 222. The adjustment member 32 is installed in the connecting hole 223 and the connector 31 and the adjustment member 32 are connected in a transmission manner. The adjusting member 32 can drive the connecting member 31 to move, causing the anti-foreign object plate 21 to move horizontally relative to the seat 22, so that the limiting part 12 is restricted below the anti-foreign object plate 21. When the limiting part 12 is located in the constraint countersunk hole 221, the positioning part 11 is located in the constraint through hole 211.

[0042] The countersunk hole 221 is shaped to match the limiting part 12. In this embodiment, the positioning part 11 is cylindrical, the limiting part 12 is conical, and the countersunk hole 221 is a conical hole that matches the shape of the limiting part 12. Furthermore, the through hole 212 and the connecting hole 223 are perpendicularly arranged, and the connector 31 is welded to the anti-foreign object plate 21. The base 22 also has multiple drainage holes 226.

[0043] Understandably, the lower end plug 1 of the fuel rod can pass through the constraint through hole 211 of the foreign object protection plate 21, and then the limiting part 12 of the lower end plug 1 of the fuel rod sits on the constraint countersunk hole 221 of the seat body 22. The limiting part 12 contacts the radial wall of the constraint countersunk hole 221, thereby providing radial constraint for the lower end plug 1 of the fuel rod and reducing the flow-induced vibration of the lower end plug 1 of the fuel rod in the horizontal direction. The adjusting member 32 can drive the connecting member 31 to move, causing the anti-foreign object plate 21 to move horizontally relative to the seat 22. At this time, the central axis of the constraint through hole 211 of the anti-foreign object plate 21 is misaligned with the central axis of the constraint countersunk hole 221 of the seat 22, so that the limiting part 12 of the lower end plug 1 of the fuel rod is restricted below the anti-foreign object plate 21. By restricting the limiting part 12 of the lower end plug 1 of the fuel rod between the anti-foreign object plate 21 and the seat 22, the axial movement of the fuel rod is restricted. When the clamping force of the positioning grid is lost, it is ensured that the fuel rod will not move axially under the action of hydraulic lifting force or when the fuel assembly is subjected to axial impact load, thus avoiding the aggravation of fretting erosion of the grid and fuel rod and avoiding the fuel rod falling and hitting the lower tube seat, which would cause the fuel rod to fail.

[0044] The adjusting component 32 can be an adjusting bolt, and the connecting component 31 can be a pin. The adjusting component 32 drives the connecting component 31 to move, thereby adjusting the horizontal position of the anti-foreign object plate 21 on the seat 22. This can achieve misalignment or alignment between the central axis of the constraint through hole 211 on the anti-foreign object plate 21 and the central axis of the constraint countersunk hole 221 on the seat 22.

[0045] As shown in Figures 7 and 8, the adjusting member 32 has a first threaded portion 321, and the end of the connecting member 31 has a second threaded portion 311 that matches the first threaded portion 321, so that the adjusting member 32 and the connecting member 31 form a threaded connection, allowing the adjusting member 32 to drive the connecting member 31 to move. The adjusting member 32 also has a mating groove 322, which is specifically a slotted groove, allowing external tools to be inserted to achieve rotation of the adjusting member 32 in the base 22.

[0046] As shown in Figures 1, 2, and 9, the nuclear fuel mechanism also includes an anti-rotation component 4. The anti-rotation component 4 has a protrusion 41 that matches the mating groove 322, and a receiving groove 42 is formed on the side of the anti-rotation component 4 facing away from the protrusion 41. Specifically, the protrusion 41 is in the shape of a straight line, matching the shape of the mating groove 322. The anti-rotation component 4 is used to prevent the adjustment component 32 from rotating and causing the foreign object protection plate 21 to shift position. The receiving groove 42 is specifically a straight groove, which can be used to allow external tools to be inserted to assemble the anti-rotation component 4. As shown in Figure 5, the side wall of the base 22 is also provided with an installation groove 224 for installing the anti-rotation component 4. The installation groove 224 is correspondingly provided with the connecting hole 223. The size of the installation groove 224 is larger than the size of the connecting hole 223. Specifically, the installation groove 224 is an arc-shaped groove opened in the circumferential direction of the connecting hole 223. When the anti-rotation component 4 is engaged with the adjusting component 32, the thin wall of the anti-rotation component 4 can be expanded into the installation groove 224, so that the anti-rotation component 4 is fixed in the installation groove 224 to achieve the anti-rotation function.

[0047] As shown in Figures 1, 4, and 6, the nuclear fuel mechanism also includes a fuel assembly guide tube 5. A first mounting hole 213 is provided on the foreign object shield 21 for the fuel assembly guide tube 5 to pass through, and a second mounting hole 225 corresponding to the first mounting hole 213 is provided on the base 22. The first mounting hole 213 longitudinally penetrates the foreign object shield 21, and the second mounting hole 225 longitudinally penetrates the base 22. Both the first mounting hole 213 and the second mounting hole 225 are used for assembling the fuel assembly guide tube 5.

[0048] In this embodiment, a method for assembling a nuclear fuel mechanism is also constructed, which includes the following steps:

[0049] S1. Install the adjusting member 32 in the connecting hole 223 of the base 22, and install the connecting member 31 in the through hole 212 of the anti-foreign object plate 21. After the first threaded part 321 of the adjusting member 32 and the second threaded part 311 of the connecting member 31 are matched and connected, weld the connecting member 31 to the anti-foreign object plate 21.

[0050] S2. Adjust the position of the anti-foreign object plate 21 using the adjusting member 32, and align the constraint through hole 211 on the anti-foreign object plate 21 with the constraint countersunk hole 221 on the base body 22.

[0051] S3. Pass the lower end plug 1 of the fuel rod through the constraint through hole 211, and place the limiting part 12 of the lower end plug 1 of the fuel rod in the constraint countersunk hole 221.

[0052] S4. Rotate the adjusting member 32 to cause the foreign object protection plate 21 to move horizontally relative to the seat body 22, so that the limiting part 12 of the fuel rod lower end plug 1 is restricted below the foreign object protection plate 21.

[0053] Specifically, in step S1, the anti-foreign object plate 21 is placed above the base 22, with the through hole 212 of the anti-foreign object plate 21 and the connecting hole 223 of the base 22 on the same side. The adjusting member 32 is inserted into the connecting hole 223 and rotated to an appropriate position. Then, the connecting member 31 is inserted into the working groove 222 through the through hole 212, and the first threaded portion 321 of the adjusting member 32 is matched and connected with the second threaded portion 311 of the connecting member 31. Then, the upper part of the connecting member 31 is welded and fixed to the anti-foreign object plate 21. The principles of steps S2 to S4 have been discussed in detail above and will not be repeated here.

[0054] The assembly method for this nuclear fuel mechanism also includes the following steps:

[0055] S5. Install the anti-rotation component 4 into the mounting groove 224, so that the protrusion 41 of the anti-rotation component 4 is engaged with the mating groove 322 of the adjusting component 32.

[0056] S6. The fuel assembly guide tube 5 and the seat 22 are fixedly connected by a fastener 6, which can be a bolt.

[0057] When removing the fuel rods, first remove the anti-rotation component 4, and then adjust the position of the anti-foreign object plate 21 by rotating the adjusting component 32 to complete the removal operation.

[0058] In summary, the beneficial effects of this nuclear fuel mechanism and its assembly method are as follows:

[0059] 1. Provide axial constraint for the lower end plug 1 of the fuel rod to maintain the axial position of the fuel rod bundle in the fuel assembly, prevent the fuel rod from axially moving under the action of hydraulic lifting force or when the fuel assembly is subjected to axial impact load when the clamping force of the positioning grid is lost, avoid aggravating the fretting erosion between the fuel rod and the positioning grid, and avoid the fuel rod from falling and impacting the lower tube seat after axial movement, causing fuel rod failure.

[0060] 2. This invention does not introduce new constraint structures outside the lower tube seat component, has no impact on the coolant flow channel of the fuel assembly, can maintain the pressure drop performance of the fuel assembly, and does not pose a risk of damage to the fuel assembly caused by the newly added constraint structure being damaged or loosened and forming foreign objects under the flushing of the coolant.

[0061] 3. Provide radial constraint for the lower end plug 1 of the fuel rod to reduce flow-induced vibration of the lower end plug 1 of the fuel rod;

[0062] 4. The axial constraint provided by the present invention for fuel rods is easy to adjust. Without disassembling the lower tube assembly 2, the axial constraint of the fuel rods can be adjusted by rotating the adjusting component 32, which facilitates the removal and replacement of fuel rods inside and outside the reactor.

[0063] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A nuclear fuel mechanism, characterized in that, It includes a fuel rod lower end plug (1), a lower pipe seat assembly (2), and an adjustment assembly (3); The lower end plug (1) of the fuel rod includes a positioning part (11) and a limiting part (12) fixedly connected to the positioning part (11). The lower tube seat assembly (2) includes a foreign object prevention plate (21) and a seat body (22). The foreign object prevention plate (21) is provided with a constraint through hole (211) and a through hole (212). The constraint through hole (211) is for the fuel rod lower end plug (1) to pass through. The upper surface of the seat (22) is provided with a constraint countersunk hole (221) corresponding to the constraint through hole (211) and an action groove (222) corresponding to the through hole (212). The constraint countersunk hole (221) is used to accommodate the limiting part (12). The side wall of the seat (22) is provided with a connecting hole (223) communicating with the function groove (222). The adjustment component (3) includes a connector (31) and an adjustment component (32). The connector (31) is installed in the through hole (212) and its end is located in the function groove (222). The adjustment component (32) is installed in the connecting hole (223) and the connector (31) and the adjustment component (32) are connected in a transmission manner. The adjusting member (32) can drive the connecting member (31) to move, so that the anti-foreign object plate (21) moves horizontally relative to the seat (22), so that the limiting part (12) is restricted below the anti-foreign object plate (21).

2. The nuclear fuel apparatus according to claim 1, characterized in that, The adjusting member (32) is provided with a first threaded portion (321), and the end of the connecting member (31) is provided with a second threaded portion (311) that matches the first threaded portion (321).

3. The nuclear fuel apparatus according to claim 1, characterized in that, The adjusting member (32) is also provided with a mating groove (322).

4. The nuclear fuel apparatus according to claim 3, characterized in that, The nuclear fuel mechanism also includes an anti-rotation component (4), on which a protrusion (41) matching the mating groove (322) is provided, and a receiving groove (42) is provided on the side of the anti-rotation component (4) facing away from the protrusion (41).

5. The nuclear fuel apparatus according to claim 4, characterized in that, The side wall of the seat (22) is also provided with an installation groove (224) for installing the anti-rotation component (4), and the installation groove (224) is correspondingly provided with the connecting hole (223).

6. The nuclear fuel apparatus according to claim 1, characterized in that, The nuclear fuel mechanism also includes a fuel assembly guide tube (5), and the foreign object protection plate (21) is provided with a first assembly hole (213) for the fuel assembly guide tube (5) to pass through, and the base (22) is provided with a second assembly hole (225) corresponding to the first assembly hole (213).

7. The nuclear fuel apparatus according to claim 1, characterized in that, The through hole (212) is perpendicular to the connecting hole (223).

8. The nuclear fuel apparatus according to claim 1, characterized in that, The connector (31) is welded to the anti-foreign object plate (21).

9. A method for assembling a nuclear fuel mechanism, based on the nuclear fuel mechanism according to any one of claims 1 to 8, characterized in that, Including the following steps: S1. Install the adjusting part (32) in the connecting hole (223) of the seat (22), and install the connecting part (31) in the through hole (212) of the anti-foreign object plate (21). After the first threaded part (321) of the adjusting part (32) and the second threaded part (311) of the connecting part (31) are matched and connected in the function groove (222) of the seat (22), weld the connecting part (31) to the anti-foreign object plate (21). S2. Adjust the position of the anti-foreign object plate (21) using the adjusting component (32) and align the constraint through hole (211) on the anti-foreign object plate (21) with the constraint countersunk hole (221) on the base (22); S3. Pass the lower end plug (1) of the fuel rod through the constraint through hole (211) and place the limiting part (12) of the lower end plug (1) of the fuel rod in the constraint countersunk hole (221); S4. Rotate the adjusting member (32) to cause the foreign object protection plate (21) to move horizontally relative to the seat (22) so that the limiting part (12) of the lower end plug (1) of the fuel rod is restricted below the foreign object protection plate (21).

10. The assembly method of the nuclear fuel mechanism according to claim 9, characterized in that, It also includes the following steps: S5. Install the anti-rotation component (4) into the mounting groove (224) so ​​that the protrusion (41) of the anti-rotation component (4) is engaged with the mating groove (322) of the adjusting component (32); S6. Secure the fuel assembly guide tube (5) and the seat (22) using fasteners (6).

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