CN113192656A

CN113192656A - Spring buckle type end plug, fuel rod and axial positioning structure of end plug

Info

Publication number: CN113192656A
Application number: CN202110328272.4A
Authority: CN
Inventors: 汤阳阳; 薛喆; 庞铮铮; 古成龙; 李伟才; 苏文
Original assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd; CGN Power Co Ltd; Lingao Nuclear Power Co Ltd
Current assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd; CGN Power Co Ltd; Lingao Nuclear Power Co Ltd; China Nuclear Power Institute Co Ltd
Priority date: 2021-03-26
Filing date: 2021-03-26
Publication date: 2021-07-30

Abstract

The invention discloses a snap-on end plug, a fuel rod and an axial positioning structure of the end plug, wherein the snap-on end plug comprises a connecting section matched with a cladding tube and an inserting section matched with an end plate and axially connected with the connecting end; the end part of the insertion section is provided with a tip with the diameter larger than that of the insertion section; the end head is provided with at least one through groove extending along the axial direction of the insertion section, and the through groove divides the end head into at least two elastic buckles which can approach each other oppositely; when the end head penetrates into the pore channel of the end plate from one surface of the end plate, the elastic buckle is close to the opposite surface penetrating through the pore channel to the end plate in opposite directions, and the elastic buckle is reset and buckled on the other surface to form a shaft shoulder limiting structure. The snap-on end plug disclosed by the invention is matched with the end plate in a snap-on mode to realize axial positioning, welding operation is not required, the problem of welding thermal deformation is avoided, and the verticality of a fuel rod is ensured; the fuel rod can be prevented from sliding without the support of a specific external structure, the limitation that the embedded fixation needs a hexagonal outer sleeve or a similar structure is overcome, and the application range is wide.

Description

Spring buckle type end plug, fuel rod and axial positioning structure of end plug

Technical Field

The invention relates to the technical field of nuclear fuel, in particular to a snap-on end plug, a fuel rod and an axial positioning structure of the end plug.

Background

The fuel rod mainly comprises a cladding tube, an upper end plug, a lower end plug and pellets, wherein the pellets are arranged in the cladding tube, and the upper end plug and the lower end plug are arranged at two ends of the cladding tube. The upper end plug and the lower end plug have two main functions: firstly, plugging two ends of a cladding tube so as to seal a core block; and secondly, a structural foundation is provided for fixing the fuel rods and assembling the fuel assembly rod bundle.

The fuel rods are clamped by the positioning grids in the pressurized water reactor and provide axial and transverse support, and the fuel rods are kept at the center of the grid cells and at the normal interval between the fuel rods. In fast reactors, the fuel rods are axially positioned by being fixed to the bundle end plate, since the spacing between fuel rods is usually small and the spacer grids are often difficult to place. The fuel rods are fixed on the rod bundle end plate in the following three ways: thread fixing, welding fixing and embedded fixing.

The screw thread is fixed to insert the fuel rod end plug into the rod bundle end plate, and the fuel rod is fixed on the rod bundle grid plate through the screw thread and the screw cap on the fuel rod end plug. However, this arrangement results in a much reduced flow path for coolant through the end plates of the bundle and a much higher resistance, so that fast reactors rarely use this positioning arrangement. In the existing fast reactor, more than all the fast reactors are fixed by welding and embedded to provide axial limit for the fuel rods.

The welded end plugs are constructed as shown in fig. 1, and have notches at the lower ends thereof, into which the bundle grids are inserted, and are then welded to be fixedly connected thereto. However, welding easily causes deformation of the bundle grid, and it is difficult to secure the fuel rods perpendicular to the grid in the above-described structure.

The structure of the embedded end plug is shown in figure 2, the lower end part of the end plug is provided with a notch with a special shape, the notch is embedded into a guide rail type grid plate with a corresponding section, and a fuel rod is pushed in along the guide rail type grid plate. The positioning structure has larger coolant flow channels, but the positioning structure is realized on the premise that a hexagonal outer sleeve or a similar structure exists outside the fuel rod, otherwise, the fuel rod can slide out along the guide rail type grid plate, and the application range of the positioning structure is narrow.

Disclosure of Invention

The invention aims to solve the technical problem of providing a snap-on end plug which is axially positioned with an end plate without welding, a fuel rod with the snap-on end plug and an end plug axial positioning structure.

The technical scheme adopted by the invention for solving the technical problems is as follows: providing a snap-on end plug for a fuel rod, the snap-on end plug comprising a connecting section for mating with a cladding tube, an insertion section for mating with an end plate and axially connecting with the connecting end;

the end part of the insertion section far away from the connecting section is provided with a tip with the diameter larger than that of the insertion section; the end head is provided with at least one through groove extending along the axial direction of the insertion section, and the through groove divides the end head into at least two elastic buckles which can approach each other oppositely;

when the end penetrates into the pore channel of the end plate from one surface of the end plate, the elastic buckle is close to the opposite surface penetrating through the pore channel to the end plate, and the elastic buckle is reset and buckled on the other surface to form a shaft shoulder limiting structure.

Preferably, the head is provided with a chamfer.

Preferably, the periphery of the insertion section is provided with an annular groove adjacent to the tip.

Preferably, the end head is provided with a central through hole which extends along the axial direction of the insertion section and is communicated with the through groove.

Preferably, the central through bore extends axially into the insert section.

Preferably, the axial length of the central through hole corresponds to the axial length of the through groove.

Preferably, the diameter of the insertion section is smaller than the diameter of the connection section.

Preferably, the snap-on end plug further comprises a ramp section axially connected between the connecting section and the insertion section.

The invention also provides a fuel rod, which comprises a cladding tube, an upper end plug, a lower end plug and fuel pellets; the fuel pellets are disposed within the cladding tube with the upper and lower end plugs fitted at opposite ends of the cladding tube, respectively; the upper end plug and/or the lower end plug are/is the snap-on end plug.

The invention also provides an axial positioning structure of the end plug, which comprises an end plate and the snap-type end plug;

the end plate is provided with a pore passage penetrating through two opposite surfaces of the end plate; the insertion section of the elastic buckle type end plug is arranged in the hole in a penetrating mode, the connecting section of the elastic buckle type end plug is located on one side of the end plate, the end socket of the elastic buckle type end plug is buckled on the opposite other side of the end plate, and axial movement of the elastic buckle type end plug is limited.

Preferably, the other surface of the end plate is provided with a positioning sheet;

the positioning piece is inserted into the through groove on the end head to limit the circumferential movement of the snap-on end plug.

Preferably, a plurality of rows of hole sets and a plurality of positioning pieces are arranged on the end plate, each row of hole sets comprises a plurality of holes which are arranged at intervals, and the plurality of positioning pieces are arranged at intervals corresponding to the plurality of rows of hole sets;

each positioning piece crosses a plurality of pore channels in the same row and is inserted into the through grooves of the end heads on the pore channels.

The snap-on end plug disclosed by the invention is matched with the end plate in a snap-on mode to realize axial positioning, welding operation is not required, the problem of welding thermal deformation is avoided, and the verticality of a fuel rod is ensured; the fuel rod can be prevented from sliding without the support of a specific external structure, the limitation that the embedded fixation needs a hexagonal outer sleeve or a similar structure is overcome, and the application range is wide.

The fuel rods are prevented from rotating and rotating by the aid of the positioning pieces additionally arranged on the end plates, and directionality of the rod bundles is guaranteed.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic view of a prior art welded end plug;

fig. 2 is a schematic structural view of a prior art mosaic end plug;

fig. 3 is a schematic perspective view of a snap-on end plug according to an embodiment of the present invention;

fig. 4 is a side view of a snap-on end plug of an embodiment of the present invention;

fig. 5 is a schematic view of a snap-on end plug and end plate according to an embodiment of the present invention;

fig. 6 is a schematic view of the mating of a single end plug to an end plate in the configuration of fig. 5.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in fig. 3-5, the snap-on end plug of one embodiment of the present invention comprises an axially connected connecting section 10, a ramp section 20 and an insertion section 30. The connecting piece 10 is intended to cooperate with the cladding tube in such a way that the end plug is fixed to the end opening of the cladding tube and seals it. The insert segment 30 is adapted to cooperate with the end plate 50 to axially secure the end plug to the end plate 50; the slope section 20 is a transition section with a slope on the outer peripheral surface, the diameter of the transition section is gradually smaller from one end to the other end, and the end with the smaller diameter is connected with the insertion section 30.

The connecting section 10 is a cylindrical structure, which may be an equal-diameter cylinder or a cylinder with multiple sections of different diameters, and may be specifically configured to cooperate with the cladding tube. The insertion section 30 is a cylindrical structure having a diameter smaller than the diameter of the connecting section 10 and is inserted into the hole 51 of the end plate 50 when engaged therewith. The diameters of the connecting section 10 and the inclined section 20 are larger than the aperture of the pore channel 51 on the end plate 50, and the connecting section and the inclined section do not enter the pore channel 51 along with the insertion section 30, so that the axial positioning effect on the end plug is achieved. The end of the beveled section 20 adjacent the insertion section 30 may mate with the entrance chamfer of the bore 51 to form a sealing engagement.

The end of the insertion section 30 far away from the connection section 10 is provided with a tip 40, and the diameter of the tip 40 is slightly larger than that of the insertion section 30 and the hole diameter of the pore channel 51 on the end plate 50; the axial direction of the tip 40 coincides with the axial direction of the insertion section 30. In particular, the end 40 is provided with at least one through slot 41 extending along the axial direction of the insertion section 30, the through slot 41 divides the end 40 into at least two snap fasteners 42, and the opening of the through slot 41 provides a movable space between the snap fasteners 42, so that the snap fasteners 42 can be moved toward or away from each other to be reset (rebounded).

When the insertion section 30 penetrates into the hole 51 of the end plate 50 from one side of the end plate 50, the end 40 is driven to penetrate into the hole, the snap fasteners 42 are pressed by the inner wall of the hole 51 to approach each other, and the diameter of the end 40 is reduced, so that the end 40 can penetrate through the hole 51 of the end plate 50; after the end plug 40 passes through the hole 51 to the opposite side of the end plate 50, the elastic buckle 42 is restored (naturally rebounded), and the end plug 40 recovers the original diameter, so that the elastic buckle 42 can be buckled on the other side of the end plate 50 to form a shaft shoulder limiting structure, play a role in axially positioning the end plug, and form a clamping form with the connecting section 10 or the inclined plane section 20 on the two sides of the end plate to the end plate 50, and limit the end plug to move in two axial directions relative to the end plate 50, as shown in fig. 6.

The head 40 is provided with a chamfered portion 43 to guide the head 40 into the tunnel 51.

The through groove 41 extends through the entire tip 40 in the axial direction. If desired, the through slot 41 may also extend onto the insertion section 30, extending through an end of the insertion section 30 away from the bevel section 20 in the axial direction of the insertion section 30.

In this embodiment, as shown in fig. 3, one through slot 41 is provided on the end 40 and extends transversely across two opposite sides of the end 40 in a straight line shape, so as to divide the end 40 into two snap fasteners 42. The through slots 41 extend in depth along the axial direction of the insertion section 30 to the insertion section 40.

Further, in the present embodiment, the outer periphery of the insertion section 30 is provided with an annular groove 31 adjoining the tip 40. The annular groove 31 serves to reduce the thickness of the portion of the insert section 30 where the annular groove is located, and also increases the fastening area of the elastic fastener 42, thereby improving the stability of the elastic fastener 40 fastened on the surface of the end plate 50.

In addition, in the present embodiment, the head 40 is provided with a central through hole 44 extending along the axial direction of the insertion section 30, so that the head 40 of the column structure forms a cylindrical structure. Also, the central through hole 44 communicates with the through groove 41, so that the snap 42 is formed by the end wall of the tip 40.

The axial length (depth) of the central through hole 44 is set to correspond to the axial length (depth) of the through groove 42. For example, for the through slots 42 extending into the insert section 30, the central through hole 44 also extends into the insert section 30, also resulting in a cylindrical structure at one end of the insert section 30. The bottom surface of the central through hole 44 and the bottom surface of the through groove 42 are positioned on the same plane; alternatively, the bottom surface of the central through hole 44 is slightly lower than the bottom surface of the through groove 42.

The snap-on end plug of the invention is used for fuel rods. For a fuel rod, it includes a cladding tube, an upper end plug, a lower end plug, and fuel pellets; the fuel pellets are disposed within the cladding tube with upper and lower end plugs respectively fitted at opposite ends of the cladding tube. Wherein, the upper end plug and/or the lower end plug of the fuel rod are/is a snap type end plug.

Optionally, one end plug of the fuel rod is a snap-on end plug, and the other end plug is a conventional end plug; the conventional end plugs and the corresponding end plates are not limited in the axial direction, and an irradiation growth space is provided for irradiation growth of the fuel rods.

The snap-on end plug of the invention is matched with the end plate 50, or the fuel rod with the snap-on end plug is matched with the end plate 50 to form an end plug axial positioning structure, so that the fuel rod is axially positioned in the fast reactor.

As shown in fig. 5 and 6, the axial end plug positioning structure includes the end plate 50 and the snap-type end plug.

The end plate 50 is provided with a passage 51 through opposite faces thereof for a snap-on end plug to fit therein. Generally, a plurality of fuel rods may be fixed to one end plate 50, so that the cells 51 are provided in plurality and the plurality of cells 51 are arranged in a plurality of rows in sequence; each row also has a plurality of spaced apart openings 51 forming a row of openings.

The hole diameter of the hole 51 is set corresponding to the diameter of the insertion section 30 of the snap-type end plug, so that the insertion section 30 can penetrate into the hole 51 to limit the penetration of the slope section 20.

In the axial positioning structure of the end plug, the insertion section 30 of the snap-on end plug is inserted into the hole 51, the connection section 10 and the inclined plane section 20 are located on one side of the end plate 50, the end 40 is fastened on the opposite side of the end plate 50, and a clamping form is formed on the end plate 50 to limit the axial movement of the snap-on end plug relative to the end plate 50, so that the axial positioning of the fuel rod on the end plate 50 is realized.

The entrance of the duct 51 at one side of the end plate 50 is chamfered to facilitate the insertion of the insertion section 30 of the snap-on end plug. Moreover, the inclination of the inclined plane section 20 of the snap-on end plug is arranged corresponding to the chamfer of the inlet of the pore channel, so that the end part of the inclined plane section 20 close to the insertion section 30 can be matched with the chamfer of the inlet to form a sealing matching structure.

In order to further position the fuel rods in the radial direction and limit the circumferential rotation of the fuel rods on the end plate 50, the other side of the end plate 50 corresponding to the tip 40 is provided with a positioning sheet 52, and the positioning sheet 52 is vertically arranged on the surface. The positioning piece 52 is inserted into the through groove 41 on the end head 40, so as to achieve the effect of limiting the circumferential movement of the snap-type end plug. In addition, the engagement of the locating tab 52 in the channel 41 also effectively limits the snap fasteners 42 from moving toward each other and out of the surface of the end plate 50.

The locating tab 52 may be integrally formed on the end plate 50, or may be fixed to the end plate 50 by spot welding, or may be removably inserted into the end plate 50.

A plurality of positioning sheets 52 are arranged on the end plate 50 corresponding to the plurality of rows of pore channel groups; a plurality of spacers 52 are spaced apart corresponding to the plurality of rows of porthole groups. Each spacer 52 spans a plurality of channels 51 in the same row and is inserted into the through slot 41 of the tip 40 of the plurality of channels 51, thereby ensuring the uniformity of the orientation of the fuel rods and preventing the fuel rods from rotating within the stack.

In addition, by arranging the insertion section 30 and the hole 51 in a non-circular shape (such as a polygon or an ellipse, etc.), the insertion section 30 can be restricted from moving circumferentially relative to the hole 51, and further the snap-on end plug is restricted from moving circumferentially relative to the hole 51, so as to position the fuel rod in the radial direction.

If desired, and with reference to fig. 6, a locating tab 52 may also be included in the snap-on end plug as a locating feature for mating with the through slot 41. The positioning plate 52 is inserted into the through groove 41 of the end 40, and both ends of the positioning plate respectively extend out of the through groove 41 to limit the insertion section 30 to move circumferentially relative to the positioning plate 52.

In conclusion, when the end plug is matched with the end plate, a welding process is not needed, so that the problems of welding thermal deformation of the rod bundle end plate and difficulty in ensuring the verticality of the fuel rods are solved, and the precision of the rod bundle is high after the rod bundle is installed; the fuel rod can be prevented from sliding without the support of a specific external structure, and the application range is wide. The positioning pieces are additionally arranged, so that the fuel rods are prevented from rotating and rotating, and the directionality of the rod bundles is ensured.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. A snap-on end plug for a fuel rod, comprising a connecting section for mating with a cladding tube, an insertion section for mating with an end plate and axially connecting with the connecting end;

2. The snap-on end plug of claim 1, wherein said tip is provided with a chamfer.

3. The snap-on end plug according to claim 1, wherein the outer circumference of the insertion section is provided with an annular groove adjoining the tip.

4. The snap-on end plug according to claim 1, wherein said tip is provided with a central through hole extending in the axial direction of said insertion section and communicating with said through groove.

5. The snap-on end plug according to claim 4, wherein said central through bore extends axially into said insertion section.

6. The snap-on end plug according to claim 5, wherein the axial length of the central through hole corresponds to the axial length of the through slot.

7. A snap-on end plug according to any one of claims 1-6, wherein the diameter of the insertion section is smaller than the diameter of the connection section.

8. The snap-on end plug of claim 7, further comprising a ramp segment axially connected between the connecting segment and the insertion segment.

9. A fuel rod comprising a cladding tube, an upper end plug, a lower end plug and fuel pellets; the fuel pellets are disposed within the cladding tube with the upper and lower end plugs fitted at opposite ends of the cladding tube, respectively; characterized in that the upper end plug and/or the lower end plug is a snap-on end plug according to any one of claims 1 to 8.

10. An axial end plug positioning structure, characterized by comprising an end plate and the snap-type end plug of any one of claims 1 to 8;

11. An axial positioning structure for an end plug according to claim 10, wherein the other face of the end plate is provided with a positioning piece;

12. An axial positioning structure for an end plug according to claim 11, wherein a plurality of rows of hole sets are provided on the end plate, each row of hole sets including a plurality of the holes arranged at intervals, and a plurality of positioning pieces are arranged at intervals corresponding to the plurality of rows of hole sets;