A compact control rod drive mechanism for a liquid heavy metal cooled reactor

Abstract

This invention discloses a compact control rod drive mechanism for a liquid heavy metal cooled reactor, comprising a motor-driven transmission mechanism, an outer cylinder, a rack, a connecting rod, a rod position measuring device, an auxiliary spring, a guide tube, and a gas protection system. In the motor-driven transmission mechanism, a gearbox is fixedly installed in the middle of the outer cylinder, and internally, a first bevel gear, a second bevel gear, a bearing, a drive shaft, an electromagnetic clutch, and a gear are sequentially installed. A reducer and a drive motor are sequentially installed at the top. A rack is fixedly installed at the upper part of the connecting rod, and its lower end is fixedly connected to the control rod, coaxially movably disposed within the outer cylinder and guide tube, with the rack meshing with the gear. The rod position measuring device is mounted on the outer wall of the outer cylinder. This invention employs a single-motor driven rack and pinion system, utilizing the buoyancy of liquid heavy metal, the auxiliary spring, and the electromagnetic clutch to achieve control rod adjustment and rapid rod lowering functions. The structure is compact, safe, and reliable, effectively reducing the axial dimension and weight of the control rod drive mechanism.

Description

Technical Field

[0001] This invention relates to the field of reactor engineering technology, and more specifically to a compact control rod drive mechanism for a liquid heavy metal cooled reactor. Background Technology

[0002] Liquid heavy metals (such as lead / lead-bismuth eutectic alloys) possess significant advantages, including low melting point, high boiling point, high heat transfer efficiency, and weak neutron moderation, making them the primary coolant for fast neutron reactors. Lead-based reactors, using lead or lead alloys as coolants, offer marked advantages in physical and thermal performance as well as safe operation. Lead-cooled fast reactors are widely recognized as the fourth-generation industrial demonstration reactor type capable of achieving industrialization most rapidly. Since the beginning of the 21st century, numerous countries worldwide have actively promoted and conducted research on lead-based reactor technologies. Major nuclear power developing countries such as Russia, the United States, and the European Union have actively promoted the commercial application of lead-based reactors, and small lead-based reactors have become a major development direction.

[0003] The control rod drive mechanism is the actuator of the reactor control system and safety protection system. It is a crucial mechanical device in the nuclear reactor system and an integral part of the reactor control and protection system. It drives the control rod assembly from the reactor core, holds it in a specific position, inserts it from any operating position, or rapidly inserts it into the core according to the instructions of the reactor control system and safety protection system. This enables functions such as reactor startup, power regulation, power maintenance, reactivity compensation, normal shutdown, and rapid shutdown in emergency situations. Currently, various types of control rod drive mechanisms are used in different reactors. The main drive methods are magnetic lifting, ball nut, and rack and pinion. They generally employ a dual-motor drive system, with one motor driving the up-and-down movement and the other driving the opening and closing of the gripper. Overall, their size and weight are relatively large. Liquid heavy metal reactors, due to the high temperature and buoyancy, often employ counterweights in current designs, further increasing the axial dimension and overall weight of the control rod drive mechanism, limiting its application in small modular reactors (SMRs). Micro-small lead-based reactors, due to space and weight limitations and high-temperature requirements, present new challenges to the control rod drive mechanism. To address this issue, Chinese patent application CN117174344A (A Control Rod Drive Mechanism for a Liquid Heavy Metal-Cooled Miniature Reactor) proposes a mechanism using a single inverted motor-driven ball screw nut, combined with the buoyancy of the liquid heavy metal, to achieve the up-and-down movement and dropping of the control rod, thus miniaturizing the mechanism. However, because the motor at the top of this mechanism occupies a relatively large volume, using this control rod drive mechanism across the board is not conducive to a compact core design. Furthermore, according to nuclear reactor operation regulations, to ensure the safe operation of the reactor, independent reactivity control systems based on different principles are required. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a compact control rod drive mechanism for liquid heavy metal cooled reactors. It features a compact structure, high safety and reliability, and can adapt to the high-temperature environment of liquid heavy metal coolants, while effectively reducing the axial height and overall weight of the control rod drive mechanism. This invention proposes a control rod drive mechanism with a single motor-driven rack and pinion gear arrangement in the middle position, which effectively solves the problems of reactor miniaturization and safe operation.

[0005] To achieve the above objectives, the present invention proposes the following technical solution:

[0006] A compact control rod drive mechanism for a liquid heavy metal cooled reactor includes a motor drive transmission mechanism, an outer cylinder, a rack, a connecting rod, a rod position measuring device, an auxiliary spring, a guide tube, and a gas protection system.

[0007] The motor drive transmission mechanism includes a drive motor, a reducer, and a gear transmission box; the gear transmission box is fixedly installed in the middle of the outer cylinder, and a first bevel gear, a second bevel gear, a bearing, a drive shaft, an electromagnetic clutch, and a gear are installed inside in sequence; the drive motor and the reducer are installed in sequence on the upper part of the gear transmission box to drive the first bevel gear to rotate, thereby driving the gear to rotate;

[0008] A rack is fixedly mounted on the upper part of the connecting rod, a slider is fixedly mounted on the reverse side, and the lower end is fixedly connected to the control rod. It is coaxially and movably disposed inside the outer cylinder and the guide tube. The rack meshes with the gear. A guide rail is installed in the middle of the inner wall of the outer cylinder, which slides with the slider.

[0009] The rod position measuring device includes a transmitter, a magnetic block, and a measuring rod; the transmitter and measuring rod are fixedly installed on the outer wall of the outer cylinder; the magnetic block is fixedly installed on the upper end of the connecting rod and moves up and down with the connecting rod;

[0010] The gas protection system includes an exhaust port, an inflation port, and a sealing and heat insulation layer; the exhaust port and the inflation port are respectively located on the upper and lower ends of the outer cylinder; the sealing and heat insulation layer is installed on the lower inner end of the outer cylinder, forming a sealed chamber inside the outer cylinder.

[0011] Furthermore, the second bevel gear, bearing, electromagnetic clutch, and gear are sequentially and coaxially mounted on the transmission shaft.

[0012] Furthermore, the first bevel gear is meshed with the second bevel gear, and the first bevel gear is coaxially mounted below the reducer.

[0013] Furthermore, one end of an auxiliary spring is fixedly installed on the upper surface of the sealing and heat insulation layer, and the auxiliary spring is sleeved on the connecting rod.

[0014] Furthermore, the upper end of the auxiliary spring is a movable end; when the gear drives the rack and connecting rod downward, the lower end of the rack contacts and compresses the auxiliary spring, and the auxiliary spring stores energy.

[0015] Furthermore, a limiter is provided at the top of the outer cylinder. When the magnetic block contacts the limiter, the connecting rod reaches the highest position and stops moving upward.

[0016] Furthermore, the outer cylinder is connected to the stack top cover plate via a flange at its lower part, and a guide tube is coaxially arranged at its lower end.

[0017] Furthermore, a ring of drain holes is provided at the upper end of the guide tube. When the connecting rod drives the control rod to move upward, the liquid metal in the guide tube is discharged outward through the drain holes.

[0018] Furthermore, a coupling is provided at the lower part of the connecting rod to disengage the control rod from the upper drive mechanism during material loading and unloading.

[0019] Furthermore, the protective gas introduced into the gas protection system is an inert gas, and the pressure of the inert gas is higher than the metal vapor pressure inside the reactor.

[0020] The advantages of this invention compared to the prior art are as follows:

[0021] 1) This invention uses a single motor to drive a gear rack and pinion and an electromagnetic clutch to connect and disconnect the transmission. It utilizes the buoyancy of liquid heavy metal and the energy storage and release of an auxiliary spring to realize the up-and-down adjustment of the control rod and the function of rapid rod dropping. The structure is compact, safe and reliable, and effectively reduces the axial height and weight of the control rod drive mechanism, which is conducive to the miniaturization of the reactor.

[0022] 2) This invention adopts a split-type magnetostrictive rod position measurement scheme, which overcomes the influence of high temperature. Combined with motor stroke detection, it can accurately detect the real-time position of the drive shaft, thus improving the accuracy of the operation of this invention.

[0023] 3) The present invention is equipped with an inert gas protection system to prevent metal vapor from escaping into the cavity of the control rod drive mechanism, thereby improving the safety of the device. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1This is a schematic diagram of the control rods of a compact liquid heavy metal cooled reactor control rod drive mechanism according to the present invention, showing the control rods located in the reactor core structure.

[0026] Figure 2 This is a schematic diagram of the initial state of the control rods in a compact liquid heavy metal cooled reactor control rod drive mechanism according to the present invention.

[0027] Figure 3 This is a top view of a compact control rod drive mechanism for a liquid heavy metal cooled reactor according to the present invention.

[0028] The meanings of the reference numerals in the figure are as follows: 1. Drive motor; 2. Reducer; 3. Gearbox; 4. Outer cylinder; 5. Rack; 6. Connecting rod; 7. Rod position measuring device; 8. Limiter; 9. Exhaust port; 10. Auxiliary spring; 11. Inflation port; 12. Sealing and heat insulation layer; 13. Stack top cover plate; 14. Coupling; 15. Guide tube; 16. Control rod; 17. Guide rail; 18. Slider; 301. First bevel gear; 302. Second bevel gear; 303. Bearing; 304. Drive shaft; 305. Electromagnetic clutch; 306. Gear; 701. Transmitter; 702. Magnetic block; 703. Measuring rod; 151. Drain hole. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are within the scope of protection of the present invention.

[0030] Example:

[0031] like Figures 1-3 As shown, a compact control rod drive mechanism for a liquid heavy metal cooled reactor according to the present invention consists of a motor drive transmission mechanism, an outer cylinder 4, a rack 5, a connecting rod 6, a rod position measuring device 7, an auxiliary spring 10, a guide tube 15, and a gas protection system.

[0032] The motor drive transmission mechanism includes a drive motor 1, a reducer 2, and a gear transmission box 3. The gear transmission box 3 is fixedly installed in the middle of the outer cylinder 4, and a first bevel gear 301, a second bevel gear 302, a bearing 303, a transmission shaft 304, an electromagnetic clutch 305, and a gear 306 are installed inside in sequence. The drive motor 1 and the reducer 2 are installed on the upper part of the gear transmission box 3 to drive the first bevel gear 301 to rotate, thereby driving the gear 306 to rotate.

[0033] The upper part of the connecting rod 6 is fixedly equipped with a rack 5, the reverse side is fixedly equipped with a slider 18, and the lower end is fixedly connected to the control rod 16. It is coaxially and movably arranged in the outer cylinder 4 and the guide tube 15. The rack 5 is meshed with the gear 306. The guide rail 17 is installed in the middle of the inner wall of the outer cylinder 4 and slides with the slider 18 to ensure that the connecting rod 6 drives the control rod 16 to move stably up and down in the guide tube 15.

[0034] The second bevel gear 302, bearing 303, electromagnetic clutch 305, and gear 306 are sequentially and coaxially mounted on the transmission shaft 304.

[0035] The first bevel gear 301 is meshed with the second bevel gear 302, and the first bevel gear 301 is coaxially mounted below the reducer 2.

[0036] One end of the auxiliary spring 10 is fixedly installed on the upper surface of the sealing and heat insulation layer 12, and the auxiliary spring 10 is sleeved on the connecting rod 6.

[0037] The upper end of the auxiliary spring 10 is the movable end; when the gear 306 drives the rack 5 and the connecting rod 6 downward, the lower end of the rack 5 contacts and compresses the auxiliary spring 10, and the auxiliary spring stores energy.

[0038] A limiter 8 is provided at the top of the outer cylinder 4.

[0039] The outer cylinder 4 is connected to the stack top cover plate 13 via a flange at its lower part, and a guide pipe 15 is coaxially arranged at its lower end.

[0040] A limiter 8 is provided at the top of the outer cylinder 4. When the magnetic block 702 contacts the limiter 8, the connecting rod 6 reaches the highest position and stops moving upward.

[0041] Preferably, the upper end of the guide tube 15 is provided with a ring of drain holes 151. When the connecting rod 6 drives the control rod 16 to move upward, the liquid metal in the guide tube 15 is discharged outward through the drain holes 151.

[0042] A coupling 14 is provided at the lower part of the connecting rod 6, which is used to disengage the control rod 16 from the upper drive mechanism when loading and changing materials.

[0043] The working process of this embodiment includes the following steps:

[0044] Up and down movement steps: When the electromagnetic clutch 305 is in the energized connection state, the drive motor 1 drives the gear 306 to rotate through the action of various components in the gear transmission box 3, drives the rack 5 to move up and down, and drives the connecting rod 6 to move up and down. With the support and sliding cooperation of the guide rail 17 and the slider 18, the control rod 16 is stably stopped at the predetermined position.

[0045] Control rod descent steps: After the core is loaded, the electromagnetic clutch 305 is energized and connected. The drive motor 1 drives the gear 306 to rotate clockwise, driving the rack 5 to move downward. The lower end of the rack 5 compresses the auxiliary spring 10 to the maximum preload, and the control rod 16 stops directly below the core.

[0046] Rapid rod dropping procedure: The electromagnetic clutch 305 is de-energized and disconnected, the gear 306 is in a free-spinning state, the auxiliary spring 10 returns to its original state and releases the preload. Under the combined action of buoyancy and elasticity, the connecting rod 6 drives the control rod 16 to move rapidly upward to the position of the top limiter 8, and the control rod 16 is quickly inserted into the core.

[0047] Initial charging and refueling procedures: During initial charging, no liquid heavy metal coolant is added. Coupling 14 is disassembled, the upper drive mechanism is separated from the control rod, and the control rod 16 is stopped in the core position by external auxiliary components. During refueling, the motor-driven transmission mechanism drives the connecting rod 6 to move upward to the uppermost position, and the control rod 16 is inserted into the core.

[0048] Preferred, such as Figures 1-3 As shown, the rod position measuring device 7 includes a transmitter 701, a magnetic block 702, and a measuring rod 703; the transmitter 701 and the measuring rod 703 are fixedly installed on the outer wall of the outer cylinder 4; the magnetic block 702 is fixedly installed on the upper end of the connecting rod 6 and moves up and down with the connecting rod 6. The measuring rod 703 transmits the position information of the magnetic block 702 to the transmitter 701 for conversion and then to the control system.

[0049] Preferred, such as Figures 1-3 As shown, the gas protection system includes an exhaust port 9, an inflation port 11, and a sealing and heat insulation layer 12. The exhaust port 9 and the inflation port 11 are respectively located on the upper and lower ends of the outer cylinder 4. The sealing and heat insulation layer 12 is installed at the lower end of the outer cylinder 4. Each installation port is equipped with a high-temperature sealing ring. A sealed cavity is formed inside the main body of the control rod drive mechanism. The protective gas filled in the cavity is an inert gas, such as argon. The gas pressure is higher than the metal vapor pressure inside the reactor, preventing metal vapor from escaping into the upper cavity and protecting the components inside the cavity.

[0050] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes will be obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A compact control rod drive mechanism for a liquid heavy metal cooled reactor, characterized in that: The system includes a motor-driven transmission mechanism, an outer cylinder (4), a rack (5), a connecting rod (6), a rod position measuring device (7), an auxiliary spring (10), a guide tube (15), and a gas protection system. The motor-driven transmission mechanism includes a drive motor (1), a reducer (2), and a gear transmission box (3). The gear transmission box (3) is fixedly installed in the middle of the outer cylinder (4), and a first bevel gear (301), a second bevel gear (302), a bearing (303), a transmission shaft (304), an electromagnetic clutch (305), and a gear (306) are installed inside in sequence. The drive motor (1) and the reducer (2) are installed on the upper part of the gear transmission box (3) in sequence to drive the first bevel gear (301) to rotate, thereby driving the gear (306) to rotate. The upper part of the connecting rod (6) is fixedly equipped with a rack (5), the reverse side is fixedly equipped with a slider (18), and the lower end is fixedly connected to the control rod (16). It is coaxially and movably arranged in the outer cylinder (4) and the guide tube (15). The rack (5) is meshed with the gear (306). The guide rail (17) is installed in the middle position of the inner wall of the outer cylinder (4) and slides with the slider (18). The rod position measuring device (7) includes a transmitter (701), a magnetic block (702), and a measuring rod (703); the transmitter (701) and the measuring rod (703) are fixedly installed on the outer wall of the outer cylinder (4); the magnetic block (702) is fixedly installed on the upper end of the connecting rod (6) and moves up and down with the connecting rod (6); The gas protection system includes an exhaust port (9), an inflation port (11), and a sealing and heat insulation layer (12); the exhaust port (9) and the inflation port (11) are respectively located on the upper and lower ends of the outer cylinder (4); the sealing and heat insulation layer (12) is installed at the lower end of the outer cylinder (4), and a sealed chamber is formed inside the outer cylinder (4); The second bevel gear (302), bearing (303), electromagnetic clutch (305), and gear (306) are sequentially and coaxially mounted on the transmission shaft (304); The first bevel gear (301) is meshed with the second bevel gear (302); the first bevel gear (301) is coaxially mounted below the reducer (2).

2. The compact control rod drive mechanism for a liquid heavy metal cooled reactor according to claim 1, characterized in that: One end of an auxiliary spring (10) is fixedly installed on the upper surface of the sealing and heat insulation layer (12), and the auxiliary spring (10) is sleeved on the connecting rod (6).

3. The compact control rod drive mechanism for a liquid heavy metal cooled reactor according to claim 2, characterized in that: The upper end of the auxiliary spring (10) is the movable end; when the gear (306) drives the rack (5) and connecting rod (6) to move downward, the lower end of the rack (5) contacts and compresses the auxiliary spring (10).

4. The compact control rod drive mechanism for a liquid heavy metal cooled reactor according to claim 1, characterized in that: A limiter (8) is provided at the top of the outer cylinder (4). When the magnetic block (702) contacts the limiter (8), the connecting rod (6) reaches the highest position and stops moving upward.

5. The compact control rod drive mechanism for a liquid heavy metal cooled reactor according to claim 1, characterized in that: The outer cylinder (4) is connected to the stack top cover plate (13) via a flange provided at its lower part, and a guide pipe (15) is coaxially provided at the lower end of the outer cylinder (4).

6. A compact control rod drive mechanism for a liquid heavy metal cooled reactor according to claim 1 or 5, characterized in that: The upper end of the guide tube (15) is provided with a drain hole (151). When the connecting rod (6) drives the control rod (16) to move upward, the liquid metal in the guide tube (15) is discharged outward through the drain hole (151).

7. The compact control rod drive mechanism for a liquid heavy metal cooled reactor according to claim 1, characterized in that: A coupling (14) is provided at the lower part of the connecting rod (6) for disengaging the control rod (16) from the upper drive mechanism when loading and changing materials.

8. The compact control rod drive mechanism for a liquid heavy metal cooled reactor according to claim 1, characterized in that: The protective gas supplied to the gas protection system is an inert gas, and the pressure of the inert gas is higher than the pressure of the metal vapor inside the reactor.

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