Lower lock for a nuclear reactor fuel assembly

Abstract

The application discloses a lower locking device of a reactor fuel assembly, which comprises a lower core plate provided with a mounting hole and a locking groove; a lower pipe leg connected with the fuel assembly is inserted into the mounting hole and is provided with a through hole; a locking cam is rotationally arranged in the lower pipe leg and is provided with locking positions and unlocking positions at intervals in the circumferential direction; a limiting structure is arranged at a preset position in the lower pipe leg to axially limit the locking cam; each locking assembly can radially slide out of or into the through hole; a guide rod is connected with the locking cam and extends upward along the axial direction of the fuel assembly; the guide rod drives the locking cam to rotate to the locking position and abut against the locking assembly, the locking assembly partially extends out of the through hole and is inserted into the locking groove, and the device is in a locked state; the guide rod drives the locking cam to rotate to the unlocking position and abut against the locking assembly, the extending part of the locking assembly is retracted into the through hole and is separated from the locking groove, and the device is in an unlocked state. The device adopts artificial external force applied to the guide rod to realize locking and unlocking, and has a simple and reliable structure.

Description

Technical Field

[0001] This invention relates to the field of reactor fuel assembly technology, and more particularly to a lower locking device for a reactor fuel assembly. Background Technology

[0002] The fuel assembly is located between the upper and lower core plates in the reactor core. During service, the fuel assembly is fixed by the upper and lower core plates. When the fuel assembly is unloaded and refueled, the fuel assembly is unlocked from the core plate. Therefore, the fuel assembly must have locking and unlocking functions with the lower core plate.

[0003] Existing lead-based reactor fuel assembly buoyancy locking mechanisms, such as Figure 1 As shown, the buoyancy of a floating tube is used to push the ball anchor outward into the pre-drilled holes in the core grid plate, and the fuel assembly is locked in place by the cooperation between the ball anchor and the holes. This locking method relies on the buoyancy of the floating tube to move the ball anchor outward. However, the designed floating tube is a circular tube with a limited volume, and the density difference between stainless steel and lead-bismuth is small. Therefore, the buoyancy provided by the floating tube is limited, and the radial component of the force on the ball anchor is even more limited. Consequently, this locking method is unreliable.

[0004] The unlocking of this locking method relies on external force pushing down the floating slide, which provides space for the ball anchor to retract. However, the power for the ball anchor to retract comes from the relative movement of the fuel assembly and the core grid plate. When the depth of the ball hole in the core grid plate is close to the radius of the ball anchor, there may be a jamming phenomenon between the ball anchor and the ball hole, making it impossible to pull out the fuel assembly.

[0005] In addition, lead-based coolants are highly corrosive. At high temperatures, the structural materials of the fuel assembly are subjected to strong scouring and corrosion by the lead-based coolant, resulting in a decrease in the surface quality of the fuel assembly structural materials and an increase in mutual friction. Under these circumstances, the friction between the ball anchor, the ball hole, and the floating slide increases, making it more likely for the ball anchor to jam. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a lower locking device for reactor fuel assemblies.

[0007] The technical solution adopted by this invention to solve its technical problem is: a lower locking device for reactor fuel assemblies, comprising:

[0008] The lower core plate is provided with longitudinal mounting holes and several transverse locking grooves, wherein the locking grooves are connected to the mounting holes;

[0009] The lower tube leg, which is connected to the fuel assembly, is inserted into the mounting hole and has several through holes that connect with the locking groove;

[0010] A locking cam is rotatably mounted inside the lower tube leg and has locking and unlocking positions spaced apart circumferentially;

[0011] A limiting structure is provided at a preset position inside the lower tube leg to axially limit the locking cam;

[0012] A plurality of locking components, each of which can be radially slidably protruding or retracted into the through hole;

[0013] A guide rod, connected to the locking cam, extends upward along the axial direction of the fuel assembly;

[0014] The lower locking device of the reactor fuel assembly includes a locked state and an unlocked state; the guide rod drives the locking cam to rotate to the locked position and abut against the locking assembly, the locking assembly part extends out of the through hole and is inserted into the locking groove, which is the locked state; the guide rod drives the locking cam to rotate to the unlocked position and abut against the locking assembly, the extended part of the locking assembly retracts into the through hole and disengages from the locking groove, which is the unlocked state.

[0015] In some embodiments, the locking cam has a variable diameter structure, the diameter of the locking position is larger than the diameter of the unlocking position, and the diameter gradually decreases from the locking position to the unlocking position.

[0016] In some embodiments, the locking assembly includes an elastic element and a locking element. The elastic element is sleeved around the locking element, and its two ends abut against the end of the locking element and the inner wall of the lower tube leg, respectively, to push the locking element into the through hole.

[0017] In some embodiments, the locking member includes a locking section and an abutment section connected together, the diameter of the locking section being smaller than the diameter of the abutment section, the locking section being slidably inserted into the through hole, and the elastic member being sleeved on the locking section and abutting against the abutment section and the inner wall of the lower tube leg respectively.

[0018] In some embodiments, the outer surface of the abutment section facing the locking cam is an arc surface.

[0019] In some embodiments, the limiting structure includes an upper limit structure and a lower limit structure. The upper limit structure is disposed on the upper part of the locking cam and is connected and fixed to the lower tube leg. The lower limit structure is disposed on the lower part of the locking cam and is detachably connected to the lower tube leg.

[0020] In some embodiments, the upper limit structure is a plurality of protruding ribs disposed inside the lower leg, wherein the protruding ribs are dot-shaped, block-shaped, or ring-shaped.

[0021] In some embodiments, the lower limit structure is a strip that is radially inserted into the lower tube leg and carries the locking cam.

[0022] In some embodiments, in the locked state, the locking cam is locked to the guide rod by an external component to prevent rotation.

[0023] In some embodiments, the lower locking device further includes a plurality of external limiting ribs, which are fixed to the external connection of the lower tube leg and abut against the upper part of the lower core plate.

[0024] The external limiting ribs are dot-shaped, block-shaped, or ring-shaped.

[0025] By implementing this invention, the following beneficial effects are achieved:

[0026] The lower locking device for reactor fuel assemblies of this invention uses a guide rod to rotate a locking cam to the locking position, where it abuts against a locking component. A portion of the locking component extends out of the through-hole and inserts into the locking groove, thus locking the fuel assembly. The guide rod then rotates the locking cam to the unlocking position, where it abuts against the locking component. The extended portion of the locking component retracts into the through-hole and disengages from the locking groove, thus unlocking the fuel assembly. This lower locking device has a simple structure and uses manual external force to adjust the abutment position between the locking cam and the locking component, thereby locking the fuel assembly. Unlocking is achieved by applying a torque opposite to the locking force. Both locking and unlocking of the fuel assembly are done manually, offering high controllability. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0028] Figure 1 This is a schematic diagram of the existing buoyancy locking mechanism for lead-based reactor fuel assemblies;

[0029] Figure 2 This is a schematic diagram of the structure of the lower locking device of a reactor fuel assembly according to an embodiment of the present invention;

[0030] Figure 3 yes Figure 2 A cross-sectional view of the lower locking device in the locked state;

[0031] Figure 4 yes Figure 3 A schematic diagram showing the relative positions of the lower tube leg, locking cam, and locking assembly in the locked state;

[0032] Figure 5 yes Figure 2 A cross-sectional view of the lower locking device in the unlocked state;

[0033] Figure 6 yes Figure 5 A schematic diagram showing the relative positions of the lower tube leg, locking cam, and locking assembly in the unlocked state;

[0034] Figure 7 yes Figure 2 A schematic diagram of the locking cam and guide rod in the middle;

[0035] Figure 8 yes Figure 7 A top view of the locking cam in the middle;

[0036] Figure 9 yes Figure 2 A schematic diagram of the locking assembly in the middle;

[0037] Figure 10 yes Figure 2 A schematic diagram of the lower leg in the middle;

[0038] Figure 11 yes Figure 2 A schematic diagram of the lower core plate in the diagram. Detailed Implementation

[0039] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0040] In the description of the invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of the invention, unless otherwise stated, "a plurality of" means two or more.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 a chemical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] See Figures 2 to 11 One embodiment of the present invention discloses a lower locking device for reactor fuel assemblies, particularly suitable for locking and unlocking the lower part of fuel assemblies in lead-based reactors, unaffected by the corrosiveness of lead-based coolants. Furthermore, it is also applicable to water reactors, sodium metal reactors, and molten salt reactors.

[0043] like Figure 2 As shown, the lower locking device includes a lower core plate 1, a lower tube leg 2 connected to the fuel assembly, a locking cam 3, a limiting structure 4, several locking components 5, and a guide rod 6. Figure 11 As shown, the lower core plate 1 has a longitudinal mounting hole 11 and several transverse locking grooves 12, which are connected to the mounting hole 11. The lower tube leg 2 is inserted into the mounting hole 11 and has several through holes 21 that are connected to the locking grooves 12. Each locking component 5 can slide radially out or retract into the through hole 21. The locking cam 3 is rotatably disposed inside the lower tube leg 2 and has locking positions 31 and unlocking positions 32 spaced circumferentially. The limiting structure 4 is disposed at a preset position inside the lower tube leg 2 to axially limit the locking cam 3. The guide rod 6 is connected to the locking cam 3 and extends upward along the axial direction of the fuel assembly. The number of locking components 5 can be one, two, or more. In this embodiment, two locking components 5 are used as an example for explanation, and multiple locking components 5 are implemented in the same way. Similarly, the locking positions 31 and unlocking positions 32 are set one-to-one with the locking components 5.

[0044] The lower locking device of the reactor fuel assembly includes a locked state and an unlocked state. For example... Figure 3 and Figure 4 As shown, the guide rod 6 drives the locking cam 3 to rotate to the locking position 31, where it abuts against the locking assembly 5. Part of the locking assembly 5 extends out of the through hole 21 and inserts into the locking groove 12, thus achieving the locked state. Figure 5 and Figure 6 As shown, the guide rod 6 drives the locking cam 3 to rotate to the unlock position 32 and abut against the locking component 5. The protruding part of the locking component 5 retracts into the through hole 21 and disengages from the locking groove 12, which is the unlocked state.

[0045] By manually applying external force to the guide rod 6, its movement is controlled, causing the locking cam 3 to rotate. In the locked state, the external component can be locked to the guide rod 6 to prevent the locking cam 3 from rotating. To unlock, the external component is first unlocked from the guide rod 6, and then the guide rod 6 is operated to unlock the fuel assembly. The guide rod 6 can be directly and rigidly connected to the locking cam 3, and its rotation synchronously drives the locking cam 3 to rotate. Alternatively, an adapter can be used to convert the axial movement of the guide rod 6 into the rotational movement of the locking cam 3. This solution is more complex and not the focus of this invention, so it will not be elaborated upon here.

[0046] The lower locking device of the present invention has a simple structure and does not rely on the buoyancy of the fuel assembly components. It uses manual external force to lock the fuel assembly, and applies a torque opposite to the locking force to unlock it.

[0047] In some embodiments, such as Figure 7 and Figure 8 As shown, the locking cam 3 has a variable diameter structure, with the diameter of the locking position 31 being larger than the diameter of the unlocking position 32, and the diameter gradually decreasing from the locking position 31 to the unlocking position 32. The variable diameter structure of the locking cam 3, along with the outer peripheral wall surface being an arc surface of varying diameters, reduces friction between the locking cam 3 and the locking assembly 5, facilitating the operation of the guide rod 6, reducing wear on both the locking cam 3 and the locking assembly 5, protecting the integrity of the parts, and lowering the risk of failure. Figure 8 The specific outline of the locking cam 3 is shown. The diameter of the locking position 31 refers to the outer diameter of the locking cam 3 on the locking position 31, and the diameter of the unlocking position 32 refers to the outer diameter of the locking cam 3 on the unlocking position 32. The maximum outer diameter of the locking cam 3 is the same as the inner diameter of the lower tube leg 2 to achieve radial limiting and prevent the locking cam 3 from moving radially.

[0048] Specifically, the outer wall surface of the locking cam 3 on the locking position 31 is closer to the inner wall of the lower tube leg 2 than the outer wall surface of the locking cam 3 on the unlocking position 32. Generally, the distance between the locking position 31 and the inner wall of the locking groove 12 of the lower core plate 1 is greater than or equal to the length of the locking assembly 5, to ensure that when the locking position 31 abuts against the locking assembly 5, the protruding part of the locking assembly 5 can be inserted into the locking groove 12, thereby achieving lower locking of the fuel assembly. The distance between the unlocking position 32 and the outer wall of the lower tube leg 2 is the same as or similar to the length of the locking assembly 5, to ensure that when the unlocking position 32 abuts against the locking assembly 5, the locking assembly 5 can just retract the protruding part into the through hole 21 and disengage from the locking groove 12, thereby achieving lower unlocking of the fuel assembly.

[0049] In some embodiments, such as Figure 9 As shown, the locking assembly 5 includes an elastic element 51 and a locking element 52. The elastic element 51 is sleeved around the locking element 52, and its two ends abut against the end of the locking element 52 and the inner wall of the lower tube leg 2, respectively, to push the locking element 52 into the through hole 21. The locking element 52 is used to insert into the locking groove 12 to achieve the locking function and to retract into the through hole 21 to achieve the unlocking function. The elastic element 51 provides elastic force in the locked state, the unlocked state, and during the transition between the two states. The elastic element 51 can be a spring. The locking element 52 can be a pin.

[0050] Specifically, when the locking member 52 abuts against the locking cam 3 at the locking position 31, the elastic member 51 remains in a compressed state. As the locking cam 3 rotates, from the moment the locking member 52 abuts against the locking position 31 to the moment it abuts against the unlocking position 32, the elastic force keeps the locking member 52 and the locking cam 3 in contact, gradually retracting the protruding part of the locking member 52 into the through hole 21, until the locking member 52 and the locking cam 3 abut against each other at the unlocking position 32, at which point the elastic member 51 can remain in a normal or compressed state.

[0051] In some embodiments, the locking member 52 includes a locking section 521 and an abutment section 522 that are connected to each other. The diameter of the locking section 521 is smaller than the diameter of the abutment section 522. The locking section 521 is slidably inserted into the through hole 21. The elastic member 51 is sleeved on the locking section 521 and abuts against the abutment section 522 and the inner wall of the lower tube leg 2, respectively. The locking section 521 is used to insert into the locking groove 12 to achieve a locking function and to retract into the through hole 21 to achieve an unlocking function. The abutment section 522 is used to receive the elastic force from the elastic member 51 and the thrust from the locking cam 3, and transmits it to the locking section 521 to achieve corresponding movements. Preferably, the outer surface of the abutment section 522 facing the locking cam 3 is an arc surface. Similar to the fact that the outer peripheral wall of the locking cam 3 is curved, the friction between the abutment section 522 and the locking cam 3 can be reduced, making it easier to operate the guide rod 6, reducing wear between the abutment section 522 and the locking cam 3, protecting the integrity of the parts, and reducing the risk of failure.

[0052] In some embodiments, such as Figure 10 As shown, the limiting structure 4 includes an upper limit structure 41 and a lower limit structure 42. The upper limit structure 41 is located on the upper part of the locking cam 3 and is fixedly connected to the lower tube leg 2. The lower limit structure 42 is located on the lower part of the locking cam 3 and is detachably connected to the lower tube leg 2. The distance between the upper limit structure 41 and the lower limit structure 42 is slightly greater than or equal to the thickness of the locking cam 3. The upper limit structure 41, used to limit the axial upward movement of the locking cam 3, consists of several protruding ribs located inside the lower tube leg 2. These ribs can be dot-shaped, block-shaped, or ring-shaped. The lower limit structure 42, used to limit the axial downward movement of the locking cam 3, is a strip that is radially inserted into the lower tube leg 2 and supports the locking cam 3. Preferably, the lower tube leg 2 has at least two insertion holes 22 for detachable connection of the lower limit structure 42.

[0053] In some embodiments, the lower locking device further includes a plurality of external limiting ribs 43, which are fixedly connected to the external portion of the lower tube leg 2 and abut against the upper portion of the lower core plate 1. The external limiting ribs 43 are dot-shaped, block-shaped, or ring-shaped. The external limiting ribs 43 are used to restrict the downward movement of the lower tube leg 2 and ensure accurate installation and positioning.

[0054] During the initial assembly of the lower locking device, after the locking cam 3 is assembled with the lower tube leg 2, the lower limit structure 42 is assembled to position the locking cam 3. After the locking member 52 and the elastic member 51 are assembled, they are assembled inside the lower tube leg 2 along with the locking cam 3. The locking member 52 is retracted by the elastic force of the elastic member 51, and the lower locking device is in the unlocked state, that is, the fuel assembly is in the unlocked state.

[0055] The lower locking device of the present invention is used as follows:

[0056] Locking method: After the fuel assembly is assembled onto the lower core plate 1, i.e., the lower tube leg 2 is inserted into the mounting hole 11 of the lower core plate 1, the external limiting rib 43 abuts against the upper part of the lower core plate 1 to achieve installation positioning. An external force is applied to the guide rod 6 to rotate the locking cam 3 counterclockwise. The locking member 52 is pushed outward by the outward force to overcome the elastic force of the elastic member 51 and moves outward. The locking member 52 cooperates with the lower core plate 1 and is inserted into the locking groove 12 to complete the locking of the fuel assembly.

[0057] Unlocking method: When the fuel assembly needs to be unlocked from the lower core plate, an external force is applied to the guide rod 6 to rotate the locking cam 3 clockwise. The locking member 52 returns under the elastic force of the elastic member 51, and the protruding part of the locking member 52 is finally completely retracted into the through hole 21, that is, retracted into the lower tube leg 2, thus completing the unlocking of the fuel assembly. The fuel assembly can then be pulled out from the lower core plate 1.

[0058] By implementing this invention, the following beneficial effects are achieved:

[0059] The lower locking device for reactor fuel assemblies of the present invention uses a guide rod 6 to rotate a locking cam 3 to the locking position 31, where it abuts against a locking component 5. A portion of the locking component 5 extends out of the through hole 21 and inserts into the locking groove 12, thus locking the fuel assembly. The guide rod 6 then rotates the locking cam 3 to the unlocking position 32, where it abuts against the locking component 5. The extended portion of the locking component 5 retracts into the through hole 21 and disengages from the locking groove 12, thus unlocking the fuel assembly. The lower locking device of the present invention has a simple structure and uses manual external force to adjust the abutment position of the locking cam 3 and the locking component 5, thereby locking the fuel assembly. Unlocking is achieved by applying a torque opposite to the locking torque. Both locking and unlocking of the fuel assembly are done manually, providing high controllability.

[0060] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that for those skilled in the art, the above embodiments or technical features can be freely combined, and several modifications and improvements can be made without departing from the concept of the present invention. These all fall within the protection scope of the present invention. That is, the embodiments described "in some embodiments" can be freely combined with any of the embodiments above and below. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A lower locking device for a reactor fuel assembly, characterized in that, include: The lower core plate (1) is provided with a longitudinal mounting hole (11) and a number of transverse locking grooves (12), wherein the locking grooves (12) are connected to the mounting hole (11); The lower pipe leg (2) connected to the fuel assembly is inserted into the mounting hole (11) and has several through holes (21) that are connected to the locking groove (12). A locking cam (3) is rotatably disposed inside the lower tube leg (2) and is provided with a locking position (31) and an unlocking position (32) at circumferential intervals. The locking cam (3) is a variable diameter structure, the diameter of the locking position (31) is larger than the diameter of the unlocking position (32), and the diameter of the locking position (31) to the unlocking position (32) gradually decreases. The limiting structure (4) is located at a preset position inside the lower tube leg (2) to axially limit the locking cam (3). A plurality of locking components (5), each of the locking components (5) being radially slidable protruding or retracting into the through hole (21); the locking component (5) includes an elastic element (51) and a locking element (52), the elastic element (51) being sleeved around the locking element (52), and both ends abutting between the end of the locking element (52) and the inner wall of the lower tube leg (2) respectively, so as to push the locking element (52) into the through hole (21); The guide rod (6) is connected to the locking cam (3) and extends upward along the axial direction of the fuel assembly; The lower locking device of the reactor fuel assembly includes a locked state and an unlocked state; the guide rod (6) drives the locking cam (3) to rotate to the locked position (31) and abut against the locking member (52) of the locking assembly (5), and the locking member (52) of the locking assembly (5) extends out of the through hole (21) and is inserted into the locking groove (12), which is the locked state; the guide rod (6) drives the locking cam (3) to rotate to the unlocked position (32) and abut against the locking member (52) of the locking assembly (5), and the extended part of the locking member (52) of the locking assembly (5) retracts into the through hole (21) and disengages from the locking groove (12), which is the unlocked state; In the unlocked state, the elastic element (51) assists in pushing the locking element (52) into the through hole (21); in the locked state, the locking element (52) overcomes the elastic force of the elastic element (51) and extends out of the through hole (21).

2. The lower locking device for reactor fuel assemblies according to claim 1, characterized in that, The locking member (52) includes a locking section (521) and an abutment section (522) connected to each other. The diameter of the locking section (521) is smaller than the diameter of the abutment section (522). The locking section (521) is slidably inserted into the through hole (21). The elastic member (51) is sleeved on the locking section (521) and abuts against the abutment section (522) and the inner wall of the lower tube leg (2).

3. The lower locking device for reactor fuel assemblies according to claim 2, characterized in that, The outer surface of the abutting section (522) facing the locking cam (3) is an arc surface.

4. The lower locking device for reactor fuel assemblies according to claim 1, characterized in that, The limiting structure (4) includes an upper limit structure (41) and a lower limit structure (42). The upper limit structure (41) is located on the upper part of the locking cam (3) and is connected and fixed to the lower tube leg (2). The lower limit structure (42) is located on the lower part of the locking cam (3) and is detachably connected to the lower tube leg (2).

5. The lower locking device for reactor fuel assemblies according to claim 4, characterized in that, The upper limit structure (41) consists of several protruding ribs located inside the lower tube leg (2), and the protruding ribs are dot-shaped, block-shaped, or ring-shaped.

6. The lower locking device for reactor fuel assemblies according to claim 4, characterized in that, The lower limit structure (42) is a strip that is radially inserted into the lower tube leg (2) and carries the locking cam (3).

7. The lower locking device for reactor fuel assemblies according to any one of claims 1 to 6, characterized in that, In the locked state, the locking cam (3) is locked to the guide rod (6) by the external component to prevent the locking cam (3) from rotating.

8. The lower locking device for reactor fuel assemblies according to any one of claims 1 to 6, characterized in that, The lower locking device also includes several external limiting ribs (43), which are fixed to the external connection of the lower tube leg (2) and abut against the upper part of the lower core plate (1). The external limiting rib (43) is dot-shaped, block-shaped, or ring-shaped.

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