Fuel rod upper end plug and fuel rod

Abstract

The utility model provides a fuel rod upper end plug and a fuel rod, the fuel rod upper end plug comprises an end plug main body, the end plug main body comprises an upper end boss, a clamping concave table, an end plug column and a lower end ring table which are sequentially arranged in the axial direction, and a clamping ring groove is formed at the butt joint position of the clamping concave table and the end plug column; an air inflation through hole is formed in the end plug body and penetrates through the lower end ring table in the axial direction, and an air inlet hole is formed in the side face of the end plug column and communicates with the air inflation through hole through an air flow channel. The fuel rod is reasonable in structure, the fuel rod is convenient to replace, side face inflation is achieved, and the problem that holes are blocked by the fuel rod is avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of fuel elements for nuclear reactors and relates to a fuel rod upper end plug and a fuel rod. Background Art

[0002] A pressurized water reactor fuel assembly typically consists of fuel rods and a fuel frame. The fuel rods include upper and lower end plugs, uranium dioxide pellets, support tubes, and support blocks. The fuel frame consists of upper and lower tube sockets, guide tubes, instrument tubes, and a grid.

[0003] When conventional fuel rods are installed into the fuel assembly, they can only be pulled in from the lower end due to the structural limitations of the fuel rod's upper end plug. If an individual fuel rod is damaged or abnormal, the upper and lower fuel rod sockets must be removed, the damaged or abnormal fuel rod pulled out from the bottom of the fuel assembly, and a new fuel rod pulled in from the bottom of the fuel assembly before the upper and lower sockets are installed. This entire operation requires not only the removal of the upper and lower sockets, but also the removal of the corresponding 24 locking tubes and 24 locking screws. This can easily introduce small screw debris or other foreign matter into the fuel assembly, ultimately abrading the fuel rods and damaging the assembly. Furthermore, the removal and installation of the upper and lower sockets and the corresponding screws takes a long time, increasing the radiation dose to personnel and posing a health risk.

[0004] Therefore, how to simplify the replacement operation of fuel rods is very important for the operation and production of fuel assemblies. Utility Model Content

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a fuel rod upper end plug and a fuel rod, which have inflation holes opened on the side to avoid the problem of fuel rod hole blockage and have a reasonable structure, making the operation of replacing fuel rods simpler.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the utility model provides an upper end plug of a fuel rod, which includes an end plug body, and the end plug body includes an upper end boss, a clamping recess, an end plug column and a lower end ring platform arranged in sequence along the axial direction, and a clamping ring groove is formed at the joint between the clamping recess and the end plug column; an inflation hole is provided inside the end plug body, and the inflation hole passes through the lower end ring platform along the axial direction, and an air inlet hole is opened on the side of the end plug column, and the air inlet hole is connected to the inflation hole through an air flow channel.

[0008] The utility model has a reasonable structure and can pull the fuel rod out of and push it into the fuel assembly from its upper end plug, making it more convenient to replace the fuel rod. In addition, the inflation hole is opened on the side to avoid the problem of hole blockage after inflation of the end plug top.

[0009] As a preferred technical solution of the present invention, the upper end boss is a conical boss, and the angle of the end face of the conical boss away from the clamping recess is 45° to 60°, for example, it can be 45°, 48°, 50°, 55° or 60°, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0010] As a preferred technical solution of the present invention, the engaging recess is provided with a limiting protrusion along the circumferential direction on the outer edge of the end surface on the side connected to the upper end protrusion.

[0011] The utility model forms a groove structure on the upper end surface of the clamping recess by arranging a limiting protrusion, so as to clamp the pushing assembly for pushing in the fuel rod, thereby pushing the fuel rod in through the upper end plug and simplifying the operation of replacing the fuel rod.

[0012] As a preferred technical solution of the present invention, both ends of the snap ring groove transition to the snap-fit ​​recess and the end plug in circular arcs, and the turning angles of the circular arc transitions are the same.

[0013] As a preferred technical solution of the present invention, the turning angle of the arc transition is 45° to 60°, for example, it can be 45°, 48°, 50°, 55° or 60°, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0014] As a preferred technical solution of the present invention, the end plug has a cylindrical structure, and the outer diameter of the end plug is greater than the outer diameter of the upper end boss.

[0015] The corner of the end surface of the end plug close to the clamping recess is a rounded transition.

[0016] As a preferred technical solution of the present invention, the lower end ring platform includes a cladding fixed section and a guide gradual change section arranged in sequence along the axial direction, the cladding fixed section is a cylindrical surface, and the guide gradual change section is an inclined surface.

[0017] The outer radial direction of the guide gradual change section decreases gradually in the direction away from the cladding fixed section.

[0018] One end of the end plug away from the clamping ring groove transitions to the cladding fixing section at a right angle.

[0019] The outer diameter of the cladding fixing section is smaller than the outer diameter of the end plug.

[0020] As a preferred technical solution of the present invention, the inclination angle of the guide gradient section is 45° to 60°, for example, it can be 45°, 48°, 50°, 55° or 60°, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0021] It should be noted that the inclination angle of the guide gradient section refers to the angle formed by the lower end surface of the cladding fixed section and the inclined surface of the guide gradient section.

[0022] The length of the guide gradient section is 0.5 to 0.8 mm, for example, it can be 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm or 0.8 mm, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, the inflation hole is arranged at the center of the lower end ring platform.

[0024] The air flow channel includes a transverse channel, a longitudinal channel and a gradual channel that are connected in sequence.

[0025] The transverse channel extends in an axial direction perpendicular to the end plug body, the transverse channel has the same aperture as the longitudinal channel, the aperture of the inflation hole is larger than the aperture of the longitudinal channel, and the end of the gradual channel away from the longitudinal channel is connected to the inflation hole.

[0026] The utility model can quickly dissipate heat through the side of the end plug column during welding, thereby preventing the end plug body from forming an oxidized color, and an air inlet hole is provided on the side, thereby avoiding the problem of leakage of the fuel rod plugging weld due to water flow impact corrosion after the end of the upper end plug is plugged and welded into the stack, thereby preventing the fuel rod from being damaged.

[0027] In a second aspect, the present invention provides a fuel rod, wherein the fuel rod comprises the fuel rod upper end plug described in the first aspect.

[0028] The fuel rod of the utility model can be pulled out and pushed in by the plug portion at the upper end thereof, which greatly simplifies the replacement operation and avoids damage to the fuel rod during the welding process.

[0029] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] The utility model provides a fuel rod upper end plug and fuel rod, which have a reasonable structure. Any fuel rod in the fuel assembly can be easily replaced without removing the lower tube seat and its corresponding screws, which simplifies the operation steps and reduces the risk of introducing foreign matter. In addition, the inflation hole is arranged on the side, which also avoids the problem that after the top of the upper end plug is welded into the stack, the plugging weld point is corroded due to the impact of water flow, causing leakage of the fuel rod plugging weld and even damage to the fuel rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic structural diagram of the fuel rod upper end plug provided in Example 1 of the present utility model;

[0033] Figure 2 This is a top view of the fuel rod upper end plug provided in Example 1 of the present utility model.

[0034] Among them, 100-end plug body; 1-upper end boss; 2-clamping recess; 21-limiting protrusion; 3-end plug column; 4-lower end ring platform; 41-cladding fixed section; 42-guide gradient section; 5-clamping ring groove; 6-inflating hole; 7-air inlet hole; 8-air flow channel; 81-transverse channel; 82-longitudinal channel; 83-gradual channel. DETAILED DESCRIPTION

[0035] It should be understood that in the description of the present invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0036] It should be noted that, in the description of this utility model, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0038] In one embodiment, the present invention provides a fuel rod upper end plug, comprising an end plug body having an axially tapered upper portion and thicker lower portion. The end plug body comprises an upper end boss, a clamping recess, an end plug column, and a lower end ring, which are sequentially arranged along the axial direction.

[0039] The uppermost end of the end plug body is an upper end boss, specifically a conical boss, and the angle of the end face away from the clamping recess is 45° to 60°, preferably 45°.

[0040] The clamping recess is used to push the fuel rod into the skeleton or fuel assembly. Its size is larger than the conical boss, and a limiting protrusion is provided along the circumferential direction on the outer edge of the end surface of the clamping recess on the side connected to the upper end boss. A groove structure is formed on the upper end surface of the clamping recess, which can clamp the push tube used to push the fuel rod into the fuel rod onto the upper end plug of the fuel rod, thereby realizing the fuel rod pushing operation by the upper end plug.

[0041] A snap ring groove is formed at the junction of the engaging recess and the end plug, providing a secure groove for pulling the fuel rod out of the skeletal frame or fuel assembly, enabling fuel rod extraction from the upper end plug. Specifically, the ends of the snap ring groove transition to the engaging recess and end plug in circular arcs, with the transition angles being the same. Furthermore, the transition angle is between 45° and 60°, preferably 45°.

[0042] According to the utility model, when replacing a fuel rod, the upper tube seat is removed and then pulled out, and the original abnormal fuel rod is grasped by the claw head to the clamping ring groove of the upper end plug to pull back the fuel rod to pull out, and then the front end of the rod tube is pushed to clamp the clamping concave platform of the upper end plug, and the new fuel rod is pushed into the set position of the skeleton or fuel assembly, thereby reducing the time of exposure to dose when removing the fuel rod and reducing the risk of foreign matter introduced when removing the lower tube seat.

[0043] The end plug has a cylindrical structure, with an outer diameter greater than that of the upper end boss, forming a thinner top and thicker bottom profile. The end surface of the end plug, near the engaging recess, has a rounded corner transition, preferably at 45°. The present invention does not impose specific restrictions on the outer diameters of the end plug and the upper end boss; those skilled in the art may adapt these to the actual fuel rod dimensions.

[0044] The end plug body is internally provided with an air filling hole, which axially extends through the lower end ring platform. The end plug column is provided with an air inlet hole on its side, which is connected to the air filling hole via an airflow channel. The air inlet hole is connected to the outside world and is used for operations such as filling the fuel rod with helium or argon. When the upper end plug is welded using this utility model, heat from the upper end plug is quickly dissipated through the side of the end plug column, preventing the upper end plug from forming an oxidized color and ensuring the appearance quality of the upper end plug.

[0045] Specifically, the inflation hole is provided at the center of the lower end ring platform. The airflow channel includes a transverse channel, a longitudinal channel, and a gradient channel that are sequentially connected. The transverse channel extends in an axial direction perpendicular to the end plug body. The transverse channel and the longitudinal channel have the same aperture. The aperture of the inflation hole is larger than the aperture of the longitudinal channel. The gradient channel is connected to the inflation hole at one end away from the longitudinal channel. The present invention does not impose specific restrictions on the outer diameters and apertures of the transverse channel, the longitudinal channel, and the inflation hole. Those skilled in the art can make adaptive adjustments based on the actual fuel rod size requirements, inflation needs, etc.

[0046] The lower end annular platform, designed to mate with the cladding tube, specifically comprises a cladding fixing section and a guide gradient section, arranged axially in sequence. The cladding fixing section is a cylindrical surface, while the guide gradient section is an inclined surface, with the outer diameter of the guide gradient section decreasing as it moves away from the cladding fixing section. The end of the end plug, away from the retaining ring groove, transitions at a right angle to the cladding fixing section. The outer diameter of the cladding fixing section is smaller than that of the end plug, and larger than that of the upper end boss.

[0047] Furthermore, the inclination angle of the guide gradient section is 45° to 60°, preferably 45°; and the length of the guide gradient section is 0.5 to 0.8 mm.

[0048] The present invention does not impose any specific limitation on the material of the end plug body, and stainless steel, zirconium alloy, etc. commonly used by those skilled in the art can be used.

[0049] The fuel rod upper end plug of the utility model has a wide range of applications, and is particularly suitable for AP1000 series and CAP1400 series fuel rods and fuel assemblies thereof.

[0050] In another specific embodiment, the present invention provides a fuel rod, which includes a fuel rod upper end plug according to a specific embodiment.

[0051] The fuel rod of the present invention also necessarily includes a cladding tube and a lower end plug, which are well known to those skilled in the art, and the upper end plug and the lower end plug are respectively arranged at the two ends of the cladding tube. The cladding tube has a slender tubular shape and can be made of ceramic or alloy materials. The upper end plug cooperates with the cladding tube to pull out and push in the fuel rod, and the lower end plug is used to fix the fuel rod to prevent it from moving under the impact of the core coolant. The fuel rod is fixed in the lower tube seat of the skeleton or fuel assembly through a screw connection, a snap connection, a C-ring connection, or a pin connection commonly used in the art.

[0052] Example 1

[0053] This embodiment provides a fuel rod upper end plug, which is suitable for AP1000 series fuel rods. The upper end plug includes an end plug body 100, such as Figure 1 and Figure 2 As shown, the end plug body 100 includes an upper boss 1, a snap-fit ​​recess 2, an end plug column 3, and a lower ring platform 4, which are arranged in sequence along the axial direction. A snap-fit ​​groove 5 is formed at the junction of the snap-fit ​​recess 2 and the end plug column 3. The upper boss 1 is a conical boss with an outer diameter of 6.6 mm. The angle of its end face away from the snap-fit ​​recess 2 is 45°. The outer diameter of the snap-fit ​​recess 2 is 8.2 mm. A limiting protrusion 21 is circumferentially provided on the outer edge of the end face connecting to the upper boss 1. The ends of the snap-fit ​​groove 5 transition to the snap-fit ​​recess 2 and the end plug column 3 in a circular arc, and the transition angles are the same, both 45°. The end plug column 3 has a cylindrical structure with an outer diameter of 9.6 mm. The corner of its end face near the snap-fit ​​recess 2 is a rounded transition with a 45° angle. The lower ring platform 4 includes a cladding fixed section 41 and a guide gradient section 42, which are arranged in sequence along the axial direction. The cladding fixing section 41 is cylindrical with an outer diameter of 8.4 mm. The end of the end plug 3 away from the retaining ring groove 5 transitions at a right angle to the cladding fixing section 41. The guide gradient section 42 is an inclined surface, with its outer diameter decreasing away from the cladding fixing section 41. The inclination angle is 45° and the length is 0.7 mm.

[0054] The end plug body 100 is internally provided with an air filling hole 6, which axially extends through the lower end ring platform 4 and is located at the center of the lower end ring platform 4. An air inlet hole 7 is provided on the side of the end plug column 3, which is connected to the air filling hole 6 via an air flow channel 8. The air flow channel 8 includes a transverse channel 81, a longitudinal channel 82, and a gradient channel 83, which are connected in sequence. The transverse channel 81 extends in a direction perpendicular to the axial direction of the end plug body 100. The apertures of the transverse channel 81 and the longitudinal channel 82 are both 1 mm. The aperture of the air filling hole 6 is 2 mm. The gradient channel 83 is connected to the air filling hole 6 at the end away from the longitudinal channel 82.

[0055] The upper end plug of this embodiment can facilitate pulling out or pushing in the fuel rod from the upper end of the fuel assembly. Compared with the traditional replacement operation when replacing a damaged single fuel rod, it is necessary to remove the upper and lower tube seats, pull the fuel rod in from the upper end of the assembly, and then pull out the lower end. In this embodiment, when replacing the fuel rod, it is only necessary to remove the upper tube seat and then pull it out. The original abnormal fuel rod is grasped by the claw head through the clamping ring groove 5 of the upper end plug to pull back the fuel rod to pull out. Then, the front end of the rod tube is pushed to clamp the clamping concave platform 2 of the upper end plug, and the new fuel rod is pushed into the set position of the skeleton or fuel assembly. This greatly simplifies the operation of replacing the fuel rod.

[0056] Example 2

[0057] This embodiment provides a fuel rod, comprising an upper end plug, a cladding tube, and a lower end plug that are detachably connected in sequence, wherein the upper end plug is the upper end plug provided in Example 1.

[0058] The applicant declares that the above is only a specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Technicians in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technicians in the relevant technical field within the technical scope disclosed in the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A fuel rod upper end plug, characterized in that: The fuel rod upper end plug includes an end plug body, which includes an upper end boss, a clamping recess, an end plug column, and a lower end ring column arranged in sequence along the axial direction. A clamping ring groove is formed at the junction of the clamping recess and the end plug column. An air filling hole is provided inside the end plug body, and the air filling hole axially passes through the lower end ring platform. An air inlet hole is provided on the side of the end plug column, and the air inlet hole is connected to the air filling hole through an air flow channel.

2. The fuel rod upper end plug according to claim 1, characterized in that: The upper end boss is a conical boss, and the angle of the end surface of the conical boss away from the clamping recess is 45° to 60°.

3. The fuel rod upper end plug according to claim 2, characterized in that: The clamping recess is provided with a limiting protrusion along the circumferential direction on the outer edge of the end surface on the side connected to the upper end protrusion.

4. The fuel rod upper end plug according to claim 1, characterized in that: The two ends of the clamping ring groove are respectively transitioned to the clamping recess and the end plug in circular arcs, and the turning angles of the circular arc transitions are the same.

5. The fuel rod upper end plug according to claim 4, characterized in that: The turning angle of the arc transition is 45° to 60°.

6. The fuel rod upper end plug according to claim 1, characterized in that: The end plug has a cylindrical structure, and the outer diameter of the end plug is larger than the outer diameter of the upper end boss; The corner of the end surface of the end plug close to the clamping recess is a rounded transition.

7. The fuel rod upper end plug according to claim 1, characterized in that: The lower end ring platform includes a cladding fixed section and a guide gradient section arranged in sequence along the axial direction, the cladding fixed section is a cylindrical surface, and the guide gradient section is an inclined surface; The outer radial direction of the guide gradient section decreases in the direction away from the cladding fixed section; One end of the end plug away from the snap ring groove transitions to the cladding fixing section at a right angle; The outer diameter of the cladding fixing section is smaller than the outer diameter of the end plug.

8. The fuel rod upper end plug according to claim 7, characterized in that: The inclination angle of the guide gradient section is 45° to 60°; The length of the guide gradient section is 0.5 to 0.8 mm.

9. The fuel rod upper end plug according to claim 1, characterized in that: The inflation hole is arranged at the center of the lower end ring platform; The air flow channel includes a transverse channel, a longitudinal channel and a gradual channel that are connected in sequence; The transverse channel extends in an axial direction perpendicular to the end plug body, the transverse channel has the same aperture as the longitudinal channel, the aperture of the inflation hole is larger than the aperture of the longitudinal channel, and the gradient channel is connected to the inflation hole at one end away from the longitudinal channel.

10. A fuel rod, characterized in that: The fuel rod comprises the fuel rod upper end plug according to any one of claims 1 to 9.

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