Nuclear fuel assembly lower pipe seat

Abstract

The utility model discloses a lower tube seat of a nuclear fuel assembly, which is used for being connected with a fuel rod of the nuclear fuel assembly and comprises a seat body, a foreign matter prevention plate arranged on the seat body and a positioning pin used for connecting the seat body and a lower end plug of the fuel rod. According to the nuclear fuel assembly lower tube seat, the multiple constraint through holes are formed in the foreign matter preventing plate, the multiple constraint counter bores and the positioning pin grooves corresponding to the constraint counter bores are formed in the seat body, and positioning pins are used for positioning and supporting the lower end plug of a fuel rod together. Axial constraint is provided for the fuel rods, the axial position of the fuel rod bundle in the fuel assembly is maintained, and the fuel rods are prevented from axially moving under the action of hydraulic lifting force or when the fuel assembly bears axial impact loads. Meanwhile, radial constraint is provided for the lower end of the fuel rod, the transverse layout of the lower end of the fuel rod is maintained, flow-induced vibration of the lower end of the fuel rod is reduced, anti-rotation constraint is provided for the lower end of the fuel rod, and the fuel rod is prevented from rotating around the axis of the fuel rod.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of reactor nuclear fuel, especially, a nuclear fuel assembly lower tube seat. BACKGROUND

[0002] The nuclear fuel assembly usually includes a plurality of fuel rods, a plurality of guide tubes, a positioning grid, an upper tube seat assembly and a lower tube seat assembly. The fuel assembly is clamped by the multi-layer positioning grid to axially position the fuel rod bundle between the upper tube seat assembly and the lower tube seat assembly. The nuclear fuel assembly is located between the upper and lower plates of the reactor core, and the coolant enters the fuel rod bundle inside the fuel assembly from the plate hole reserved by the core plate, flows out of the fuel assembly through the upper tube seat assembly, and carries away the heat generated by the nuclear reaction of the fuel rod bundle.

[0003] The existing lower tube seat design cannot provide axial constraint for the fuel rod bundle. For the fuel assembly design without the positioning grid, such as the wire-wound fuel rod bundle fuel assembly, an additional positioning structure is needed for the axial positioning of the fuel rod bundle. The introduction of the new positioning structure may increase the pressure drop of the fuel assembly and reduce the pressure drop performance of the fuel assembly. SUMMARY

[0004] The technical problem to be solved by the utility model is to provide a nuclear fuel assembly lower tube seat.

[0005] The utility model adopts the technical scheme in the technical solution: a nuclear fuel assembly lower tube seat is constructed for connection with the fuel rods of the nuclear fuel assembly, which includes a seat body, a foreign matter prevention plate arranged on the seat body, and a positioning pin for connecting the seat body and the lower end plug of the fuel rod;

[0006] A plurality of constraint through holes corresponding to the lower end plug of the fuel rod are arranged on the foreign matter prevention plate, and the constraint through holes longitudinally penetrate the foreign matter prevention plate;

[0007] A plurality of constraint counterbores and a plurality of positioning pin grooves are arranged on the seat body, the constraint counterbores are arranged correspondingly to the constraint through holes, the positioning pin is connected to the lower end plug of the fuel rod and accommodated in the positioning pin groove, and the positioning pin groove is arranged correspondingly to the constraint counterbores.

[0008] In some embodiments, a plurality of first assembly holes corresponding to the guide tubes of the nuclear fuel assembly are arranged on the foreign matter prevention plate, the first assembly holes are arranged staggeredly to the constraint through holes, and the first assembly holes longitudinally penetrate the foreign matter prevention plate;

[0009] A plurality of second assembly holes corresponding to the first assembly holes are arranged on the seat body, and the second assembly holes longitudinally penetrate the seat body.

[0010] In some embodiments, a plurality of first water flow holes for providing coolant flow passage inlets for the nuclear fuel assembly are arranged on the anti-foreign matter plate, and a plurality of second water flow holes corresponding to the first water flow holes are arranged on the seat body.

[0011] In some embodiments, the first assembly holes are arranged staggered with the first water flow holes.

[0012] The second assembly holes are arranged staggered with the second water flow holes.

[0013] In some embodiments, the first water flow holes longitudinally penetrate the anti-foreign matter plate, and the second water flow holes longitudinally penetrate the seat body.

[0014] In some embodiments, a plurality of coolant filter holes are arranged in each of the first water flow holes.

[0015] In some embodiments, the first assembly holes and the first water flow holes are uniformly distributed on the anti-foreign matter plate.

[0016] In some embodiments, the second assembly holes, the second water flow holes and the constraint counterbores are uniformly distributed on the seat body.

[0017] In some embodiments, the positioning pin slots are rectangular structures, and each of the positioning pin slots penetrates the center of the constraint counterbores.

[0018] In some embodiments, one end of the positioning pin is accommodated in the connecting slot of the lower end plug of the fuel rod.

[0019] The utility model discloses the following beneficial effects: the nuclear fuel assembly lower tube seat passes through the anti-foreign matter plate and sets up a plurality of constraint through -holes, and passes through the seat body and sets up a plurality of constraint counterbores and the positioning pin slot corresponding with constraint counterbores, also utilizes the positioning pin, and is positioned together for the lower end plug of fuel rod and supports, provides axial constraint for fuel rod, maintains the axial position of fuel rod bundle in fuel assembly, avoids the axial displacement of fuel rod under the action of hydraulic lifting force or when fuel assembly bears axial impact load. At the same time, the radial constraint is provided for the lower end part of fuel rod, maintains the transverse layout of the lower end part of fuel rod, and reduces the flow-induced vibration of the lower end part of fuel rod, also provides the anti-rotation constraint for the lower end part of fuel rod, prevents the rotation of fuel rod around its own axis, avoids the aggravation of the fretting wear between fuel rod and adjacent structure caused by the rotation of fuel rod. At the same time, the positioning structure is also avoided in fuel assembly, and the pressure drop of fuel assembly is reduced, and the pressure drop performance of fuel assembly is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical scheme of the utility model, the utility model will be further described below in conjunction with the drawings and embodiments, it should be understood that the following drawings only show some embodiments of the utility model, therefore should not be regarded as the limitation to the scope, for the ordinary skilled person in the art, under the premise of not paying the creative labor, still can obtain other related drawings according to these drawings. In the drawings,

[0021] Figure 1 It is the structural schematic diagram of the lower tube base of nuclear fuel assembly in some embodiments of the utility model;

[0022] Figure 2 It is the structural schematic diagram of the seat body in some embodiments of the utility model;

[0023] Figure 3 It is the structural schematic diagram of the anti-foreign body plate in some embodiments of the utility model;

[0024] Figure 4 It is the cooperation structural schematic diagram of the lower tube base of nuclear fuel assembly and fuel rod in some embodiments of the utility model;

[0025] Figure 5 It is the structural schematic diagram of the lower end plug of the utility model. DETAILED DESCRIPTION

[0026] In order to have more clear understanding of the technical features, object and effect of the utility model, now the specific implementation mode of the utility model will be described in detail with reference to the drawings. In the following description, it should be understood that "front", "rear", "upper", "lower", "left", "right", "vertical", "horizontal", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", "tail" and other indicated orientation or position relationship are based on the orientation or position relationship shown in the drawings, with the particular orientation structure and operation, only for the convenience of describing the technical scheme, and not indicate that the indicated device or element must have the particular orientation, therefore can not be understood as the limitation to the utility model.

[0027] It should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing", "setting" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements. When an element is referred to as "on" or "below" another element, the element can be "directly" or "indirectly" above the other element, or one or more intervening elements can be present. The terms "first", "second", "third" and the like are only for the convenience of describing the technical solutions, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features with "first", "second", "third" and the like can be explicitly or implicitly included one or more of the features. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0028] Referring to Figures 1 to 4 , the lower tube seat of the nuclear fuel assembly in some embodiments of the present application is used to connect with the fuel rod of the nuclear fuel assembly, which comprises a seat body 1, a foreign matter prevention plate 2 arranged on the seat body 1, and a positioning pin 4 for connecting the seat body 1 and the lower end plug 31 of the fuel rod. The foreign matter prevention plate 2 is provided with a plurality of constraint through holes 22 corresponding to the lower end plug 31 of the fuel rod, the constraint through holes 22 longitudinally penetrate the foreign matter prevention plate 2, the seat body 1 is provided with a plurality of constraint counterbores 12 and a plurality of positioning pin grooves 13, the constraint counterbores 12 are arranged correspondingly with the constraint through holes 22, the positioning pin 4 is connected to the lower end plug 31 of the fuel rod and is accommodated in the positioning pin groove 13, and the positioning pin groove 13 is arranged correspondingly with the constraint counterbores 12.

[0029] Specifically, the positioning pin groove 13 is a rectangular structure, the positioning pin 4 can be fixedly connected to the lower end plug 31 of the fuel rod, and the positioning pin groove 13 is matched with the shape of the positioning pin 4. Each positioning pin groove 13 penetrates the center of the constraint counterbores 12, and the directions of all the positioning pin grooves 13 are consistent. The foreign matter prevention plate 2 is a square plate structure. The constraint counterbores 12 play a role in restraining the vibration of the fuel rod, reducing the vibration of the fuel rod caused by external force, and at the same time realizing the protection of the end of the fuel rod by the nuclear fuel assembly lower tube seat, avoiding the abrasion between the end of the fuel rod and the tube seat caused by vibration. As shown in Figure 5 , the lower end plug 31 of the fuel rod has a connecting groove 311, one end of the positioning pin 4 is accommodated in the connecting groove 311 of the lower end plug 31 of the fuel rod, and the other end of the positioning pin 4 is accommodated in the positioning pin groove 13.

[0030] It can be understood that the lower nozzle of the nuclear fuel assembly is positioned and supported by the plurality of constraint through holes 22 provided on the anti-foreign matter plate 2, the plurality of constraint counterbores 12 and the positioning pin grooves 13 corresponding to the constraint counterbores 12 provided on the seat body 1, and the positioning pin 4, which are collectively used for the lower end plug of the fuel rod. The axial constraint is provided for the fuel rod, the axial position of the fuel rod bundle in the fuel assembly is maintained, and the axial movement of the fuel rod under the action of the hydraulic lifting force or when the fuel assembly bears the axial impact load is avoided. At the same time, the radial constraint is provided for the lower end of the fuel rod, the transverse layout of the lower end of the fuel rod is maintained, and the flow-induced vibration of the lower end of the fuel rod is reduced. The anti-rotation constraint is also provided for the lower end of the fuel rod, the rotation of the fuel rod around its own axis is prevented, and the micro-motion abrasion between the fuel rod and the adjacent structure caused by the rotation of the fuel rod is avoided. At the same time, the positioning structure is also avoided to be additionally added in the fuel assembly to increase the pressure drop of the fuel assembly and reduce the pressure drop performance of the fuel assembly.

[0031] Further, the anti-foreign matter plate 2 is provided with a plurality of first assembly holes 21 corresponding to the guide tubes of the nuclear fuel assembly, the first assembly holes 21 are arranged staggered with the constraint through holes 22, the first assembly holes 21 longitudinally penetrate the anti-foreign matter plate 2, and the seat body 1 is provided with a plurality of second assembly holes 11 corresponding to the first assembly holes 21, the second assembly holes 11 longitudinally penetrate the seat body 1. The first assembly holes 21 and the second assembly holes 11 are collectively used for the assembly of the guide tubes of the nuclear fuel assembly.

[0032] Among them, the anti-foreign matter plate 2 is also provided with a plurality of first water flow holes 24 for providing the nuclear fuel assembly with coolant flow entrances, and the seat body 1 is provided with a plurality of second water flow holes 14 corresponding to the first water flow holes 24. The first water flow holes 24 and the second water flow holes 14 can all provide the fuel assembly with coolant flow entrances, the first water flow holes 24 are matched with the second water flow holes 14 in shape, and the first water flow holes 24 longitudinally penetrate the anti-foreign matter plate 2, and the second water flow holes 14 longitudinally penetrate the seat body 1.

[0033] The first assembly holes 21 and the first water flow holes 24 are arranged staggered, and the second assembly holes 11 and the second water flow holes 14 are arranged staggered. Since the positioning pin 4 of the fuel assembly is staggered with the water flow hole position of the lower nozzle, no additional pressure drop is introduced for the fuel assembly, and the pressure drop performance of the fuel assembly is not reduced. In the embodiment, the first assembly holes 21 and the first water flow holes 24 are uniformly distributed on the anti-foreign matter plate 2, and the second assembly holes 11, the second water flow holes 14 and the constraint counterbores 12 are uniformly distributed on the seat body 1.

[0034] In addition, a plurality of coolant filter holes are arranged in each first water flow hole 24. The coolant filter hole is a through hole defined by the intersection of a plurality of partitions in the water flow hole, which is used for the coolant to flow into the fuel assembly rod bundle area, and also plays a role of filtering and blocking foreign matters in the coolant flow.

[0035] It can be understood that the above embodiments only express the preferred embodiments of the utility model, the description is more specific and detailed, but it can not be understood as the limitation of the utility model patent scope; it should be pointed out that for ordinary skilled person in the art, the above technical features can be freely combined without departing from the concept of the utility model, and a number of modifications and improvements can be made, which belong to the protection scope of the utility model; therefore, any equivalent transformation and modification within the scope of the utility model patent claim should belong to the scope of the utility model patent claim.

Claims

1. A lower connector for a nuclear fuel assembly, used for connecting to the fuel rods of the nuclear fuel assembly, characterized in that, Includes a base (1), a foreign object protection plate (2) provided on the base (1), and a positioning pin (4) for connecting the base (1) and the lower end plug (31) of the fuel rod; The foreign object protection plate (2) is provided with a plurality of constraint through holes (22) corresponding to the lower end plug (31) of the fuel rod, and the constraint through holes (22) penetrate the foreign object protection plate (2) longitudinally; The base (1) is provided with a plurality of constraint countersunk holes (12) and a plurality of positioning pin grooves (13). The constraint countersunk holes (12) are provided corresponding to the constraint through holes (22). The positioning pins (4) are connected to the lower end plugs (31) of the fuel rod and are accommodated in the positioning pin grooves (13). The positioning pin grooves (13) are provided corresponding to the constraint countersunk holes (12).

2. The nuclear fuel assembly lower tube socket according to claim 1, characterized in that, The foreign object shield (2) is provided with a plurality of first assembly holes (21) corresponding to the guide tubes of the nuclear fuel assembly. The first assembly holes (21) are offset from the constraint through holes (22). The first assembly holes (21) penetrate the foreign object shield (2) longitudinally. The base (1) is provided with a plurality of second mounting holes (11) corresponding to the first mounting hole (21), and the second mounting holes (11) extend longitudinally through the base (1).

3. The nuclear fuel assembly lower tube socket according to claim 2, characterized in that, The foreign object protection plate (2) is also provided with a plurality of first water flow holes (24) that provide coolant flow inlets for nuclear fuel assemblies, and the base (1) is provided with a plurality of second water flow holes (14) corresponding to the first water flow holes (24).

4. The nuclear fuel assembly lower tube socket according to claim 3, characterized in that, The first assembly hole (21) is offset from the first drainage hole (24); The second assembly hole (11) is offset from the second drainage hole (14).

5. The nuclear fuel assembly lower tube socket according to claim 3, characterized in that, The first water flow hole (24) penetrates the anti-foreign object plate (2) longitudinally, and the second water flow hole (14) penetrates the base (1) longitudinally.

6. The nuclear fuel assembly lower tube socket according to claim 3, characterized in that, Each of the first water outlets (24) is provided with multiple coolant filter holes.

7. The nuclear fuel assembly lower tube socket according to claim 3, characterized in that, The first assembly hole (21) and the first drainage hole (24) are evenly distributed on the foreign object protection plate (2).

8. The nuclear fuel assembly lower tube socket according to claim 3, characterized in that, The second assembly hole (11), the second drainage hole (14), and the constraint countersunk hole (12) are evenly distributed on the base (1).

9. The nuclear fuel assembly lower tube socket according to claim 1, characterized in that, The positioning pin groove (13) has a rectangular structure, and each positioning pin groove (13) passes through the center of the constraint countersunk hole (12).

10. The nuclear fuel assembly lower tube socket according to claim 1, characterized in that, One end of the positioning pin (4) is accommodated in the connecting groove (311) of the lower end plug (31) of the fuel rod.

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