A lower end plug for a nuclear fuel rod and a fuel rod

Abstract

The present application relates to the technical fields of nuclear reactor fuel element, in particular to a kind of nuclear fuel rod lower end plug and fuel rod, end plug body is sequentially provided with insertion end along its axial direction in sequence: it can be inserted into cladding tube, including necking platform and necking section connected along the axial direction of the end plug body in sequence, the necking platform is used to support the element in cladding tube;Welding platform is used for welding with cladding tube, including welding section and bearing section connected along the axial direction of the end plug body in sequence, the welding section is connected with the necking section;Restraining section is connected with the bearing section, for connecting lower tube base, and the outer diameter of the restraining section gradually reduces from one end connected with the bearing section to the other end, the self-locking and bottoming of fuel rod are realized by restraining section cooperation tube base, the safety of fuel rod and its in-pile operating performance can be ensured.Fuel rod is adapted with the above-mentioned nuclear fuel rod lower end plug in the lower end of cladding tube.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor fuel element technology, specifically to a lower end plug for a nuclear fuel rod and the fuel rod itself. Background Technology

[0002] Nuclear reactor fuel rods are generally formed by encapsulating fuel pellets with cladding tubes and upper and lower end plugs. The resulting individual fuel rods are then installed in a frame with clamping and supporting structures to form fuel assemblies. During reactor operation, fuel rods are exposed to harsh in-reactor environments characterized by neutron irradiation, high temperature and pressure, and complex thermal-hydraulic conditions. Crossflow at the core inlet and insufficient grid clamping force can cause fuel rod vibration, leading to the risk of erosion and breakage between the fuel rods and the grid. Furthermore, existing all-zirconia positioning grids exhibit rapid relaxation of clamping force with irradiation, which, under the traditional axial positioning design concept of 12-foot fuel assemblies, cannot meet the problem of effective axial positioning of fuel elements throughout their entire lifespan. In addition, with the trend towards high burnup, irradiated growth of fuel rods is a key factor affecting increased burnup. Therefore, while meeting the basic function of the fuel rod end plugs (sealing the fuel rods), it is necessary to conduct functional extension designs for the end plug structure. Summary of the Invention

[0003] This invention provides a lower end plug for nuclear fuel rods and the fuel rods themselves. The funnel-shaped cone in the middle of the end plug body, in conjunction with the tube seat, enables the fuel rods to self-lock and settle, forming a lateral constraint on the end plug body and the fuel rods it constitutes. This alleviates vibrations caused by lateral flow at the core inlet and relaxation of the clamping force of the positioning grid, reduces the possibility of abrasion damage to the fuel rods and grid, provides more upper space for fuel rod growth, and solves the problem of effective axial positioning of fuel elements throughout their entire lifespan, ensuring the safety of the fuel rods and their in-reactor operating performance.

[0004] This invention is achieved through the following technical solution:

[0005] In a first aspect, the present invention provides a lower end plug for a nuclear fuel rod, comprising an end plug body, wherein the end plug body is provided with the following components arranged sequentially along its axial direction: an insertion end capable of being inserted into a cladding tube, comprising a reduced-diameter platform and a reduced-diameter section connected sequentially along the axial direction of the end plug body, the reduced-diameter platform being used to support components inside the cladding tube; a welding station for welding to the cladding tube, comprising a welding section and a support section connected sequentially along the axial direction of the end plug body, the welding section being connected to the reduced-diameter section; and a constraint section connected to the support section for connecting to a lower tube seat, wherein the outer diameter of the constraint section gradually decreases from one end connected to the support section to the other end.

[0006] In other words, the nuclear fuel rod lower end plug provided by this invention has an insertion end, a welding station, and a constraint section arranged sequentially along its axial direction. The insertion end includes a reduced-diameter flat section and a reduced-diameter section connected in sequence. The welding section includes a welding section and a bearing section connected in sequence, with the welding section connected to the reduced-diameter section and the diameter of the welding section being larger than the maximum diameter of the reduced-diameter section. The constraint section is connected to the bearing section, and the outer diameter of the constraint section gradually decreases from the end connected to the bearing section to the other end. In use, the insertion end is inserted into the lower end of the cladding tube and welded to the cladding tube using the welding station. The constraint section is then inserted into the mounting hole of the lower tube seat.

[0007] The insertion end features a reduced-diameter platform that provides support for the fuel core or components inside the cladding. This reduced-diameter section also provides space for the internal weld beads formed by pressure resistance welding, preventing contact or even compression between the weld beads and the fuel core or components. Simultaneously, the welding table, facing the constraint section, serves as a bearing surface for the push-type fuel rod installation method, enabling the push-mounting of fuel rods formed by the end plugs.

[0008] Furthermore, the outer diameter of the restraint section gradually decreases from the end connected to the bearing section to the other end, enabling the end plug body to be seated in the mounting hole of the lower tube seat through surface contact. This provides lateral restraint to the end plug body, mitigating fuel rod vibration caused by lateral flow at the core inlet and relaxation of the clamping force of the positioning grid. The height of the restraint section can also be adjusted by controlling its generatrix inclination angle, thereby regulating the height and overall length of the end plug body and the fuel rods it constitutes. As the fuel rods grow under irradiation, the end plug body and the lower tube seat gradually achieve self-locking and settling. Moreover, when the upper part of the fuel rods formed by the end plug body loses its axial clamping and positioning, the cooperation between the restraint section and the lower tube seat ensures that the fuel rods will not fall downwards.

[0009] In summary, the nuclear fuel rod end plug provided by this invention, through the funnel-shaped cone in the middle of the end plug body, in conjunction with the tube seat, achieves self-locking and bottoming of the fuel rod, forming a lateral constraint on the end plug body and the fuel rod it constitutes, alleviating vibrations caused by lateral flow at the core inlet and loosening of the clamping force of the positioning grid, reducing the possibility of abrasion damage between the fuel rod and the grid, providing more upper space for fuel rod growth, and solving the problem of effective axial positioning of fuel elements throughout the entire lifespan, ensuring the safety of the fuel rod and its in-reactor operating performance.

[0010] In an alternative embodiment, the diameter of the bearing section is larger than the diameter of the welding section.

[0011] In an alternative implementation, the diameter of the bearing segment is greater than the maximum diameter of the constraint segment.

[0012] In an alternative embodiment, the load-bearing segment is connected to the constraint segment via a tapered connecting segment.

[0013] In an optional embodiment, the end plug body is further provided with a guide head connected to the end of the constraint section away from the welding section.

[0014] In an optional implementation, the guide head has a spherical structure.

[0015] In an optional embodiment, a gripping groove is provided between the guide head and the constraint segment.

[0016] In an optional embodiment, a gripping ramp is provided between the gripping groove and the guide head.

[0017] In an optional embodiment, the angle between the outer surface generatrix of the constraint segment and the axis of the constraint segment is 5 to 20°.

[0018] Secondly, the present invention provides a nuclear fuel rod, including a cladding tube, wherein the lower end of the cladding tube is adapted to the aforementioned nuclear fuel rod lower end plug.

[0019] The nuclear fuel rod provided by this invention has a lower end plug adapted to the lower end of the cladding tube. The end plug body can achieve self-locking and bottoming of the fuel rod through the funnel-shaped cone in the middle of the end plug body, in conjunction with the tube seat. This forms a lateral constraint on the end plug body and the fuel rod it constitutes, which alleviates the vibration caused by the lateral flow at the core inlet and the loosening of the clamping force of the positioning grid, reduces the possibility of abrasion and damage between the fuel rod and the grid, provides more upper space for fuel rod growth, and solves the problem of effective axial positioning of fuel elements throughout the entire service life, ensuring the safety of the fuel rod and its in-reactor operation performance.

[0020] The present invention has the following advantages and beneficial effects:

[0021] 1. The nuclear fuel rod lower end plug provided by the present invention has an insertion end, a welding platform, and a constraint section arranged sequentially along its own axial direction. The insertion end includes a diameter reduction platform and a diameter reduction section connected in sequence. The welding section includes a welding section and a bearing section connected in sequence. The welding section is connected to the diameter reduction section, and the constraint section is connected to the bearing section. The outer diameter of the constraint section gradually decreases from the end connected to the bearing section to the other end. This allows the fuel rod to self-lock and sit on the bottom through the funnel-shaped cone in the middle of the end plug body, in conjunction with the tube seat. This forms a lateral constraint on the end plug body and the fuel rod it constitutes, alleviating the vibration caused by the lateral flow at the core inlet and the loosening of the clamping force of the positioning grid. This ensures the safety of the fuel rod and its in-reactor operating performance.

[0022] 2. The nuclear fuel rod lower end plug provided by the present invention has a reduced diameter platform at the insertion end, which can provide support for the fuel core or components inside the cladding, while the reduced diameter section can provide space for the internal weld bead formed by pressure resistance welding, avoiding contact or even compression between the weld bead and the fuel core or components.

[0023] 3. The nuclear fuel rod lower end plug provided by the present invention has a welding station facing one end of the constraint section, which can serve as a bearing surface for the push-type rod installation method, and can push the fuel rod formed by the end plug to install.

[0024] 4. The nuclear fuel rod lower end plug provided by the present invention can adjust the height of the constraint section by controlling the inclination angle of the constraint section generatrix, thereby adjusting the height and total length of the end plug body and the fuel rods it constitutes.

[0025] 5. The lower end plug of the nuclear fuel rod provided by the present invention has an outer diameter of the constraint section that gradually decreases from one end connected to the bearing section to the other end. As the fuel rod grows under irradiation, the end plug body and the lower tube seat gradually achieve self-locking and bottoming.

[0026] 6. The lower end plug of the nuclear fuel rod provided by the present invention has an outer diameter of the constraint section that gradually decreases from one end connected to the bearing section to the other end. When the upper part of the fuel rod, which is composed of the end plug body, loses its axial clamping and positioning, the cooperation between the constraint section and the lower tube seat can ensure that the fuel rod will not fall downward.

[0027] 7. The nuclear fuel rod provided by the present invention has a lower end plug adapted to the lower end of the cladding tube. The end plug body can achieve self-locking and bottoming of the fuel rod through the funnel-shaped cone in the middle of the end plug body, in conjunction with the tube seat. This forms a lateral constraint on the end plug body and the fuel rod it constitutes, which alleviates the vibration caused by the lateral flow at the core inlet and the loosening of the clamping force of the positioning grid, reduces the possibility of abrasion and damage between the fuel rod and the grid, provides more upper space for fuel rod growth, and solves the problem of effective axial positioning of fuel elements throughout the entire service life, ensuring the safety of the fuel rod and its in-reactor operation performance. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] In the attached diagram:

[0030] Figure 1 This is a schematic diagram of the structure of the lower end plug of the nuclear fuel rod according to the first embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the structure of the lower end plug of the nuclear fuel rod according to the second embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the structure of the lower end plug of the nuclear fuel rod according to the third embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of the structure of the lower end plug of the nuclear fuel rod according to the fourth embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram of the structure of the lower end plug of the nuclear fuel rod according to the fifth embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the structure of the lower end plug of the nuclear fuel rod according to the sixth embodiment of the present invention;

[0036] Figure 7 This is a schematic diagram of the structure of the lower end plug of the nuclear fuel rod according to the seventh embodiment of the present invention.

[0037] In the attached diagram:

[0038] 10-Insertion end, 11-Reduced diameter platform, 12-Reduced diameter section, 13-Support platform, 20-Welding platform, 21-Welding section, 22-Bearing section, 23-Conical connection section, 30-Constraint section, 31-Frustum section, 32-Transition step, 40-Guide head, 50-Grabbing groove, 51-Grabbing inclined surface. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0040] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Unless otherwise specified, embodiments and features in the embodiments of this invention can be combined with each other.

[0041] In the description of the embodiments of the present invention, the terms "center", "upper", "lower", "left", "right", "vertical", "longitudinal", "lateral", "horizontal", "inner", "outer", "front", "rear", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of the present invention and to simplify the description, and are not intended to 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 the present invention.

[0042] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set up," "have," "install," "connect," and "link" 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 of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] Example 1

[0044] Combination Figure 1 This embodiment provides a lower end plug for nuclear fuel rods, including an end plug body. The end plug body has the following components arranged sequentially along its axial direction: an insertion end 10, which can be inserted into the cladding tube, including a reduced-diameter platform 11 and a reduced-diameter section 12 connected sequentially along the axial direction of the end plug body, the reduced-diameter platform 11 being used to support components inside the cladding tube; a welding station 20, used for welding with the cladding tube, including a welding section 21 and a support section 22 connected sequentially along the axial direction of the end plug body, the welding section 21 being connected to the reduced-diameter section 12; and a constraint section 30, connected to the support section 22, used for connecting to the lower tube seat, and the outer diameter of the constraint section 30 gradually decreases from the end connected to the support section 22 to the other end.

[0045] In other words, the nuclear fuel rod lower end plug provided by the present invention has an insertion end 10, a welding station 20 and a constraint section 30 arranged sequentially along its own axial direction. The insertion end 10 includes a diameter reduction plate and a diameter reduction section 12 connected in sequence. The welding section 21 includes a welding section 21 and a bearing section 22 connected in sequence. The welding section 21 is connected to the diameter reduction section 12 and the diameter of the welding section 21 is greater than the maximum diameter of the diameter reduction section 12. The constraint section 30 is connected to the bearing section 22 and the outer diameter of the constraint section 30 gradually decreases from the end connected to the bearing section 22 to the other end.

[0046] Specifically, the end plug can be made of the same or a different type of zirconium alloy material as the cladding.

[0047] For the insertion end 10, in this embodiment, the end (upper / right end) of the end plug body adopts a chamfer at an angle of 10 to 60° with the horizontal plane to form an upper end diameter reduction platform 11. The diameter reduction platform 11 can provide support for the fuel core or components inside the casing, and the diameter reduction section 12 can provide space for the internal weld bead formed by pressure resistance welding, avoiding contact between the weld bead and the fuel core or components.

[0048] For the welding table 20, a stepped frustum structure is adopted. It can be understood that the outer diameter of the bearing section 22 in the welding table 20 is larger than the outer diameter of the welding section 21, that is, the diameter of the bearing section 22 is larger than the diameter of the welding section 21. The outer diameter of the bearing section 22 is consistent with the outer diameter of the shell tube, and the outer diameter of the welding section 21 is larger than the inner diameter of the shell. It serves as the welding implementation part so as to realize the pressure resistance welding of the end plug and the shell, and can be upsetting.

[0049] Typically, the diameter of the supporting section 22 is larger than the maximum diameter of the restraining section 30. The additional stepped surface can serve as a supporting surface for the push-type fuel rod installation method, enabling the push-mounting of the fuel rods formed by the end plug body. In this embodiment, the supporting section 22 is connected to the restraining section 30 via a tapered connecting section 23, so that the tapered surface supports the end plug body, enabling the pulling and pushing of the end plug, facilitating the installation of the fuel rods.

[0050] The constraint section 30 is usually composed of a truncated cone (funnel-shaped). The outer diameter of the truncated cone gradually increases from the end closer to the top of the end plug to the end of the end plug. The outer diameter at the maximum cross-section is not less than the diameter of the mating hole on the upper surface of the lower tube seat. After the end plug body is seated on the lower tube seat, the constraint section 30 (cone) makes conical contact with the tube seat, and at the same time forms a lateral constraint on the end plug.

[0051] In this embodiment, the angle between the generatrix of the outer surface of the constraint section 30 and the axis of the constraint section 30 is 5-20°. This angle ensures that after the end plug body sits in the mounting hole of the lower tube seat, the end plug body can obtain effective lateral and axial downward constraint. Simultaneously, the outer surface area of ​​the constraint section 30 can be adjusted to ensure that the contact area between the end plug body and the lower tube seat is sufficiently large. Through the cooperation of the constraint section 30 and the lower tube seat, the fuel rod composed of the end plug body can be moved downwards axially as a whole. After improving fuel consumption operation, this provides more upper space for the growth of the fuel rod, meeting the characteristics of high fuel consumption. At the same time, it avoids excessive bending moment at the lower end of the fuel rod due to lateral loads caused by water flow scouring.

[0052] Based on this, the end plug body is also provided with a guide head 40, which is connected to the end of the constraint section 30 away from the welding section 21. Generally, the guide head 40 has a spherical structure.

[0053] Furthermore, a gripping groove 50 is provided between the guide head 40 and the constraint section 30, and a gripping and pulling inclined surface 51 is provided between the gripping groove 50 and the guide head 40, which helps the gripper head to retract and expand during the gripping process and plays a guiding role.

[0054] Understandably, after the end plug body is used in conjunction with the corresponding gripper, it can grasp and pull the fuel rod for installation; while the guide head 40 mainly plays the role of guiding and mitigating collision impact during the fuel rod installation process. Thus, it is easy to realize the bottom installation of the fuel rod composed of the end plug, avoiding damage to the mating surface of the lower tube seat from bumps.

[0055] It should be noted that, when using the nuclear fuel rod lower end plug provided in this embodiment, the insertion end 10 is inserted into the lower end of the cladding tube and fixed to the cladding tube by welding table 20, and the restraint section 30 is inserted into the mounting hole of the lower tube seat.

[0056] The insertion end 10 has a reduced-diameter platform 11, which provides support for the fuel core or components inside the casing. The reduced-diameter section 12 provides space for the internal weld beads formed by pressure resistance welding, preventing the weld beads from contacting or even squeezing the fuel core or components. Meanwhile, the welding table 20, facing the constraint section 30, can serve as a bearing surface for the push-type rod installation method, enabling the installation of fuel rods composed of end plugs.

[0057] Furthermore, the outer diameter of the restraint section 30 gradually decreases from one end connected to the bearing section 22 to the other, enabling the end plug body to be seated in the mounting hole of the lower tube seat in a surface contact manner. This provides lateral restraint to the end plug body, mitigating fuel rod vibration caused by lateral flow at the core inlet and relaxation of the clamping force of the positioning grid. The height of the restraint section 30 can also be adjusted by controlling the inclination angle of its generatrix, thereby regulating the height and overall length of the end plug body and the fuel rods it constitutes. As the fuel rods grow under irradiation, the end plug body and the lower tube seat gradually achieve self-locking and settling. Moreover, when the upper part of the fuel rods formed by the end plug body loses its axial clamping and positioning, the engagement between the restraint section 30 and the lower tube seat ensures that the fuel rods will not fall downwards.

[0058] In summary, the nuclear fuel rod lower end plug provided in this embodiment, through the funnel-shaped cone in the middle of the end plug body, in conjunction with the tube seat, achieves self-locking and bottoming of the fuel rod, forming a lateral constraint on the end plug body and the fuel rod it constitutes, alleviating vibrations caused by lateral flow at the core inlet and loosening of the clamping force of the positioning grid, reducing the possibility of abrasion damage to the fuel rod and the grid, providing more upper space for fuel rod growth, and solving the problem of effective axial positioning of fuel elements throughout the entire lifespan, ensuring the safety of the fuel rod and its in-reactor operating performance.

[0059] Example 2

[0060] Combination Figure 2 This embodiment provides a lower end plug for nuclear fuel rods. Based on embodiment 1, the difference is that the length of the constraint section 30 is less than the length of the constraint section 30 described in embodiment 1, which reduces the axial height of the end plug body and provides more space for the growth of the upper fuel rod.

[0061] Meanwhile, the inclination angle of the busbar of the constraint section 30 is greater than the inclination angle of the busbar of the constraint section 30 described in Example 1, which compensates for the reduced contact area between the constraint section 30 and the lower pipe seat mounting hole due to the reduction in height.

[0062] In addition, this embodiment adds a transition step surface between the constraint section 30 and the gripping groove 50 to serve as a gripping guide surface for the gripper head.

[0063] Furthermore, in this embodiment, the tapered connecting section 23 is omitted, so that the bearing section 22 and the constraint section 30 can directly achieve surface contact with the lower tube seat to sit on the bottom.

[0064] Example 3

[0065] Combination Figure 3 This embodiment provides a lower end plug for a nuclear fuel rod. Based on embodiment 1, the difference is that an annular cylindrical structure is used instead of the guide head 40 to match the inner gripping head and achieve the pulling of the end plug body to form the fuel rod.

[0066] Example 4

[0067] Combination Figure 4 This embodiment provides a lower end plug for nuclear fuel rods. Based on embodiment 1, the difference is that the guide head 40 is a top spherical cap structure, that is, it is formed by a top truncated cone and a transition truncated cone between the two, thereby playing a guiding function and facilitating plugging.

[0068] Example 5

[0069] Combination Figure 5 This embodiment provides a lower end plug for nuclear fuel rods, based on Embodiment 1, except that the insertion end 10 is a chamfered frustum structure. This embodiment is suitable for TIG welding to increase the welding applicability of the bottom-mounted lower end plug.

[0070] Example 6

[0071] Combination Figure 6 This embodiment provides a lower end plug for nuclear fuel rods. Based on embodiments 4 and 5, the constraint section 30 and the gripping groove 50 are directly provided with a frustum section 31, so that the frustum section 31 is used as the clamping area of ​​the electrode chuck for resistance welding.

[0072] Meanwhile, the transition step surface between the constraint section 30 and the gripping groove 50 serves as a guide surface for the gripper head.

[0073] Furthermore, a support platform 13 is provided at the end of the reduced diameter platform 11. The support platform 13 is larger than the reduced diameter platform 11 but smaller than the maximum diameter of the reduced diameter section 12, so as to increase the welding applicability of the bottom-mounted lower end plug.

[0074] Example 7

[0075] Combination Figure 7 This embodiment provides a lower end plug for nuclear fuel rods. Based on embodiment 4, a transition step is provided on the side of the constraint section 30 facing the gripping groove 50 to serve as a gripping guide surface for the gripper head.

[0076] Example 8

[0077] This embodiment provides a nuclear fuel rod, including a cladding tube, the lower end of which is fitted with a nuclear fuel rod lower end plug as described in any one of embodiments 1 to 7.

[0078] The nuclear fuel rods provided in this embodiment are fitted with a lower end plug of any one of the nuclear fuel rods described in Embodiments 1 to 7 at the lower end of the cladding tube. The end plug body can achieve self-locking and bottoming of the fuel rods through the funnel-shaped cone in the middle of the end plug body, in conjunction with the tube seat. This forms a lateral constraint on the end plug body and the fuel rods it constitutes, alleviating vibrations caused by lateral flow at the core inlet and loosening of the clamping force of the positioning grid, reducing the possibility of abrasion and damage between the fuel rods and the grid, providing more upper space for fuel rod growth, and solving the problem of effective axial positioning of fuel elements throughout the entire lifespan, ensuring the safety of the fuel rods and their in-reactor operating performance.

[0079] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0080] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lower end plug for a nuclear fuel rod, comprising an end plug body, characterized in that, The end plug body is provided with the following sequentially along its own axial direction: The insertion end (10) can be inserted into the casing tube and includes a reduced diameter platform (11) and a reduced diameter section (12) connected sequentially along the axial direction of the end plug body. The reduced diameter platform (11) is used to support the components inside the casing tube. A welding station (20) is used for welding with a casing tube, including a welding section (21) and a bearing section (22) connected sequentially along the axial direction of the end plug body. The welding section (21) is connected to the reduced diameter section (12), and the diameter of the bearing section (22) is larger than the diameter of the welding section (21). The constraint section (30) is connected to the bearing section (22) and is used to connect the lower pipe seat. The outer diameter of the constraint section (30) gradually decreases from the end connected to the bearing section (22) to the other end. The bearing section (22) is connected to the constraint section (30) through a tapered connecting section, and the angle between the outer surface generatrix of the constraint section (30) and the axis of the constraint section (30) is 5 to 20°.

2. The lower end plug of the nuclear fuel rod according to claim 1, characterized in that, The diameter of the bearing section (22) is greater than the maximum diameter of the constraint section (30).

3. The lower end plug of the nuclear fuel rod according to claim 1, characterized in that, The end plug body is also provided with a guide head (40), which is connected to the end of the constraint section (30) away from the welding section (21).

4. The lower end plug of the nuclear fuel rod according to claim 3, characterized in that, The guide head (40) has a spherical structure.

5. The lower end plug of the nuclear fuel rod according to claim 3, characterized in that, A gripping groove (50) is provided between the guide head (40) and the constraint section (30).

6. The lower end plug of the nuclear fuel rod according to claim 5, characterized in that, A gripping ramp (51) is provided between the gripping groove (50) and the guide head (40).

7. A nuclear fuel rod, comprising a cladding tube, characterized in that, The lower end of the cladding tube is adapted to be fitted with a nuclear fuel rod lower end plug as described in any one of claims 1 to 6.

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