Nuclear reactor control rod drive shaft radiation protection shielding device

Abstract

This disclosure pertains to the field of nuclear power technology, specifically relating to a radiation protection shielding device for the drive shaft of a nuclear reactor control rod. The device addresses the compatibility issues of lead plates of different specifications or with different opening positions by incorporating adjustable bolts and movable lead plates. The cooperation between the bottom guide mounting hole and the guide rod enables blind installation and rapid positioning in complex underwater environments, effectively reducing the time personnel spend in high-radiation areas. Furthermore, the modular, separable design reduces maintenance difficulty and space occupation during non-use periods.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power technology, specifically relating to a radiation protection shielding device for the drive shaft of a nuclear reactor control rod. Background Technology

[0002] After the reactor core of a pressurized water reactor nuclear power plant becomes critical, all equipment within the core becomes highly radioactive, especially the in-core components that carry the nuclear fuel assemblies. Core thermocouples, part of the core temperature measurement system, are installed on the in-core components to measure the reactor core outlet temperature. The replacement and maintenance of core thermocouples primarily involves the four thermocouple bundles on the in-core components. The radiation dose rate at the work site is high, the procedures are complex, and the work is time-consuming.

[0003] Following the ALARA principle, it is necessary to ensure that the radiation dose received by technicians performing thermocouple replacement work is within the limits permitted by regulations. Analysis revealed that the radiation dose from core thermocouple replacement and maintenance work primarily originates from the control rod drive shaft storage point. This storage point, used to centrally store dismantled control rod drive shafts, possesses very high levels of radioactivity. Therefore, it is urgently necessary to establish effective radiation shielding for the control rod drive shaft storage point to ensure the smooth conduct of maintenance work. Summary of the Invention

[0004] To overcome the problems existing in related technologies, a radiation protection shielding device for the control rod drive shaft of a nuclear reactor is provided. The device includes: a shielding frame and multiple movable lead plates. The shielding cover frame is a columnar frame structure with multiple vertically arranged columns. A horizontally arranged slide rail is provided between every two adjacent columns near the top of the column. The slide rail is equipped with multiple bolts that can move along the slide rail. Each movable lead plate has an opening at the top that matches the bolt, so that each movable lead plate is fixedly installed on the slide rail by the corresponding bolt and the anti-loosening nut that matches the bolt. The adjacent movable lead plates are arranged closely together to fully shield the sides of the shielding frame. Each column has a guide mounting hole at its bottom, which is used to cooperate with the guide rods corresponding to the upper part of the drive shaft storage rack to guide the shield frame to be hoisted into place as a whole.

[0005] In one possible implementation, the shielding frame and the movable lead plate are stored separately when not in use, and when in use, the movable lead plate is assembled to the side of the shielding frame by the bolts and lock nuts.

[0006] In one possible implementation, the device includes a variety of movable lead plates of different specifications, and the distance between every two adjacent bolts in the slide rail can be arbitrarily adjusted to accommodate movable lead plates of different specifications.

[0007] In one possible implementation, the multiple movable lead plates mounted on the side of the shielding frame are either identical in some aspects or different from each other.

[0008] In one possible implementation, the anti-loosening nut is a double-nut locking structure or a self-locking nut.

[0009] In one possible implementation, each guide mounting hole is a blind hole or a through hole structure, and the inner diameter of each guide mounting hole forms a clearance fit or a transition fit with the outer diameter of the corresponding guide rod.

[0010] In one possible implementation, the slide rail is a C-shaped steel slide rail or an I-beam steel slide rail, and the head of each bolt is slidably embedded in the internal cavity of the slide rail.

[0011] In one possible implementation, the top of the shielding frame is fixedly provided with lifting lugs for connection with hoisting equipment.

[0012] The beneficial effects of this disclosure are as follows: The radiation shielding device for nuclear reactor control rod drive shafts provided by this disclosure is used for radiation shielding protection when high-radioactivity control rod drive shafts removed from reactor internals are stored in a centralized manner. This aims to significantly reduce the environmental dose rate and radiation dose to technicians during thermocouple replacement work. As a specialized piece of equipment in the reactor core thermocouple replacement and maintenance process, the device provided by this disclosure breaks the foreign monopoly on reactor core thermocouple maintenance technology, enabling China to independently replace and maintain thermocouples for the first time. Attached Figure Description

[0013] Figure 1 This is a perspective view of a radiation protection shielding device for a nuclear reactor control rod drive shaft, as shown in an embodiment of this disclosure.

[0014] Figure 2 This is a perspective view of the shielding frame of a radiation protection shielding device for a nuclear reactor control rod drive shaft, as shown in an embodiment of this disclosure.

[0015] Figure 3 This is a bottom view of a radiation protection shielding device for a nuclear reactor control rod drive shaft, as shown in an embodiment of this disclosure.

[0016] In the picture: 1. Shielding frame; 2. Movable lead plate; 3. Bolts; 4. Locking nuts; 11. Column; 12. Slide rail; 13. Lifting lug; 111. Guide mounting hole. Detailed Implementation

[0017] The present disclosure will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0018] Unless otherwise defined, the technical and scientific terms used in this disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains; the terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure; the term "comprising" and any variations thereof in this disclosure are intended to cover non-exclusive inclusion. Clearly, the embodiments described in this disclosure are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0019] In this disclosure, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this disclosure. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0020] See Figure 1 and Figure 2 The shielding frame 1 serves as the main load-bearing skeleton, consisting of multiple vertically arranged columns 11 and multiple horizontal and vertical beams connecting adjacent columns 11, forming a columnar frame structure. For ease of hoisting, lifting lugs 13 are fixedly installed at the top corners or on the horizontal beams of the shielding frame 1. A guide mounting hole 111 is provided at the center of the bottom end face of each column 11. This guide mounting hole 111 is a blind hole structure with a preset depth; its inner diameter is slightly larger than the outer diameter of the corresponding guide rod installed on the upper part of the drive shaft storage rack, forming a clearance fit or transition fit to facilitate smooth guidance and precise positioning during hoisting and descent.

[0021] A horizontally arranged slide rail 12 is installed between each two adjacent columns 11 near the top of the column 11. The slide rail 12 can be, for example, a C-shaped steel slide rail or an I-beam slide rail, with the opening of the slide rail 12 facing outwards from the frame. Multiple bolts 3 are slidably embedded in the inner cavity of the slide rail 12. The heads of the bolts 3 are confined within the C-shaped cavity, with only the threaded portion extending outside the slide rail 12. Under the action of external force, the bolts 3 can slide freely along the length of the slide rail 12 to adjust their specific position on the slide rail 12.

[0022] The movable lead plate 2 can be a plate-like structure made of heavy metal materials such as lead or lead alloys, used to absorb and shield ionizing radiation. The dimensions of the movable lead plate 2 are adapted to the opening dimensions of the side and top surfaces of the shielding frame 1. Multiple openings are provided at the edges of the movable lead plate 2. The number, position, and spacing of the openings correspond to the configuration range of the bolts 3 preset on the slide rail 12.

[0023] In this disclosure, the shielding device is used in the replacement and maintenance of thermocouples in the reactor core of a nuclear power plant, and the drive shaft storage rack is located in the component pool. Before radiation protection work is required, the shielding frame 1 and the movable lead plate 2 are stored separately to reduce the occupation of the storage area during non-working periods and to facilitate transportation and storage.

[0024] When storing the control rod drive shaft, first, lay the shielding frame 1 flat or on its side on the workbench. Adjust the position of the bolts 3 inside the slide rail 12 according to the specific location of the opening 21 on the selected movable lead plate 2. The operator uses tools or manually to push the screws, causing the bolts 3 to slide along the slide rail 12 until they align with the openings on the movable lead plate 2. Then, place the movable lead plate 2 against the outside of the shielding frame 1, allowing the bolt 3's threaded end to pass through the corresponding opening 21. Finally, screw the lock nut 4 onto the threaded end and tighten it, securely locking the movable lead plate 2 to the shielding frame 1. The lock nut 4 can be, for example, a double-nut locking structure or a self-locking nut with a nylon insert, to prevent loosening due to water flow fluctuations or lifting vibrations in a pool environment.

[0025] Next, the assembled shielding device is connected to a circular crane or special lifting equipment inside the nuclear power plant building via lifting lug 13. The crane is used to lift the entire shielding device and slowly move it above the component pool, aligning it with the drive shaft storage rack. The guide mounting holes 111 at the bottom of the uprights 11 of the shielding frame 1 are aligned with the corresponding guide rods of the drive shaft storage rack. After confirming that the guide mounting holes 111 and guide rods are aligned, the crane is used to smoothly lower the shielding device. Under gravity, the guide rods gradually insert into the guide mounting holes 111, guiding the entire shielding frame 1 to sit precisely above the drive shaft storage rack. Because the cooperation between the guide rods and the guide mounting holes 111 ensures the horizontal position and alignment of the device, and the shielding device's own weight is sufficient to maintain stability, this device does not require additional fasteners for bolt connection to the storage rack after installation, making the installation process extremely convenient.

[0026] Once installed, workers can hoist and store the control rod drive shaft under the protection of the shielding device. The movable lead plate 2 significantly attenuates the radiation dose generated by the drive shaft, thereby significantly reducing the radiation level in the component's water tank working environment.

[0027] After maintenance is completed, the shielding cover can be lifted off the drive shaft storage rack by a crane to complete disassembly. For long-term storage or transportation, the anti-loosening nut 4 can be loosened, and the movable lead plate 2 can be removed from the frame to separate the frame from the lead plate for storage.

[0028] This disclosed device solves the compatibility problem of lead plates of different specifications or with different opening positions by setting adjustable bolts and movable lead plates; through the cooperation of the guide mounting hole at the bottom and the guide rod, it realizes blind installation and rapid placement in complex underwater environments, effectively shortening the time that operators spend in high-radiation areas; through modular and separable design, it reduces the difficulty of maintenance and space occupation when not in use. This device fills the gap in the domestic supply of shielding equipment for control rod drive shaft storage brackets, and has high practical value and promising prospects for promotion.

[0029] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A radiation protection shielding device for the control rod drive shaft of a nuclear reactor, characterized in that, The device includes: a shielding frame (1) and multiple movable lead plates (2). The shielding frame (1) is a columnar frame structure with multiple vertically arranged columns (11). A horizontally arranged slide rail (12) is provided between each two adjacent columns (11) near the top of the column (11). The slide rail (12) is provided with multiple bolts (3) that can move along the slide rail. Each movable lead plate (2) has an opening (21) on its upper part that matches the bolt (3), so that each movable lead plate (2) is fixedly installed on the slide rail (12) by the corresponding bolt (3) and the anti-loosening nut (4) that matches the bolt. The adjacent movable lead plates (2) are arranged closely together, which fully shields each side of the shielding frame (1). Each column (11) has a guide mounting hole (111) at its bottom, which is used to cooperate with the guide rods corresponding to the upper part of the drive shaft storage rack to guide the shield frame (1) to be hoisted into place as a whole.

2. The radiation protection shielding device for the nuclear reactor control rod drive shaft according to claim 1, characterized in that, The shielding frame (1) and the movable lead plate (2) are stored separately when not in use. When in use, the movable lead plate (2) is assembled to the side of the shielding frame (1) by the bolts (3) and the anti-loosening nuts (4).

3. The radiation protection shielding device for the nuclear reactor control rod drive shaft according to claim 1, characterized in that, The device includes movable lead plates (2) of various specifications. The distance between every two adjacent bolts (3) in the slide rail (12) can be adjusted arbitrarily to accommodate movable lead plates (2) of different specifications.

4. The radiation protection shielding device for the nuclear reactor control rod drive shaft according to claim 3, characterized in that, The multiple movable lead plates (2) installed on the side of the shielding frame (1) are all the same, partially the same, or different from each other.

5. The radiation protection shielding device for the nuclear reactor control rod drive shaft according to claim 1 or 3, characterized in that, The anti-loosening nut (4) is a double nut locking structure or a self-locking nut.

6. The radiation protection shielding device for the nuclear reactor control rod drive shaft according to claim 1, characterized in that, Each guide mounting hole (111) is a blind hole or through hole structure, and the inner diameter of each guide mounting hole (111) forms a clearance fit or transition fit with the outer diameter of the corresponding guide rod.

7. The radiation protection shielding device for the nuclear reactor control rod drive shaft according to claim 1, characterized in that, The slide rail (12) is a C-shaped steel slide rail or an I-beam steel slide rail, and the head of each bolt (3) is slidably embedded in the internal cavity of the slide rail (12).

8. The radiation protection shielding device for the nuclear reactor control rod drive shaft according to claim 1, characterized in that, The top of the shielding frame (1) is fixedly provided with a lifting lug (13) for connecting with the hoisting equipment.

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