Control rod, lead-based fast neutron high-flux research reactor and experimental method thereof

Abstract

The invention relates to the technical field of nuclear reactors, in particular to a control rod, a lead-based fast neutron high-flux research reactor and an experimental method thereof. Wherein the research reactor comprises a reactor container, a supporting platform, a shielding layer, a reactor lower chamber, a guide pipe and a control rod; a fuel assembly is arranged in the reactor container; one end of the guide pipe is located in the reactor container and is of a sealed structure, the length direction of the guide pipe is parallel to the length direction of the fuel assembly, the other end of the guide pipe sequentially penetrates through the reactor container, the supporting platform, the shielding layer and the under-reactor chamber and is located in the under-reactor chamber, and a driving mechanism matched with the guide pipe is arranged in the under-reactor chamber; the control rod is located in the guide pipe and can be driven by the driving mechanism to move in the length direction of the guide pipe. In a working state, the height of one end of the sealing structure of the guide pipe is not lower than that of the fuel assembly. According to the invention, the control rod can be installed, enough top space is reserved for the reactor vessel, and the reactor vessel has inherent safety characteristics.

Description

Technical Field

[0001] This application relates to the field of nuclear reactor technology, specifically to a control rod, a lead-based fast neutron high-flux research reactor, and its experimental methods. Background Technology

[0002] High-flux research reactors (HFRs) are large-scale nuclear facilities that provide high-quality neutron sources and realistic service environments to meet critical needs such as long-term irradiation testing and performance evaluation of advanced nuclear fuels and materials, testing and verification of key technologies for advanced nuclear reactors, and isotope irradiation production. They also support cutting-edge research in fields such as neutron science, materials science, energy science, and bioscience. Currently, global fast neutron irradiation resources are extremely scarce, severely restricting the innovative development of advanced nuclear energy technologies based on fast neutron spectra and innovative nuclear reactor technologies. Compared to sodium-cooled fast neutron HFRs, lead-based HFRs offer more significant inherent safety advantages, simpler coolant system configuration, and more flexible operation, making them an important development direction in the field of metal-cooled fast neutron HFRs.

[0003] To meet the specific requirements of installation, commissioning, operation, and testing of various irradiation test facilities, lead-based fast neutron high-flux research reactors require ample experimental operating space at the top. Currently, operating and under-construction metal-cooled fast neutron reactors, as well as metal-cooled fast neutron high-flux research reactors, such as Russia's BOR-60 and MBIR, the United States' VTR, and Belgium's MYRRHA, all adopt a technical approach similar to traditional pressurized water reactors, with the control rod drive mechanism located at the top of the reactor. This occupies a significant amount of space above the reactor, severely impacting the installation, commissioning, operation, and testing of the irradiation test facility. Summary of the Invention

[0004] This application aims to solve at least one of the technical problems in the background art by providing a control rod, a lead-based fast neutron high-flux research reactor, and its experimental method.

[0005] This application is achieved through the following technical solution:

[0006] In a first aspect, this application provides a control rod comprising a casing and a strong neutron absorber segment, a gas cavity segment, and a fast neutron irradiation shielding segment arranged sequentially within the casing along the axial direction of the control rod, wherein the axial lengths of the strong neutron absorber segment and the gas cavity segment are equal.

[0007] In some alternative embodiments, the absorber within the strong neutron absorber segment is a highly enriched boron carbide core.

[0008] In some alternative embodiments, the absorber within the fast neutron irradiation shielding section is formed from a mixture of lead-boron polyethylene, pure lead, depleted uranium, or highly enriched boron carbide cores.

[0009] In a second aspect, this application provides a lead-based fast neutron high-flux research reactor, which includes a reactor vessel, a support platform, a shielding layer, a subreactor chamber, a guide tube, and any of the control rods described in the first aspect;

[0010] The reactor vessel is equipped with fuel assemblies;

[0011] One end of the guide tube is located inside the reactor vessel and is sealed. The length direction of the guide tube is parallel to the length direction of the fuel assembly. The other end of the guide tube passes through the reactor vessel, the support platform, the shielding layer and the under-reactor chamber in sequence and is located inside the under-reactor chamber. A drive mechanism that cooperates with the guide tube is arranged inside the under-reactor chamber.

[0012] The control rod is located in the guide tube, and the control rod can move along the length direction of the guide tube under the drive of the drive mechanism;

[0013] In operation, the reactor vessel, support platform, shielding layer, and under-reactor chamber are arranged from top to bottom, and the height of one end of the sealing structure of the guide tube is not lower than the height of the fuel assembly.

[0014] In some alternative embodiments, the reactor vessel is equipped with a basket, the bottom of which is provided with a support box, and multiple fuel assemblies are arranged in parallel at intervals and fixedly connected to the support box respectively.

[0015] In some alternative embodiments, the fuel assembly includes a first gas chamber section, an active section, and a second gas chamber section arranged sequentially along the axial direction.

[0016] In some alternative embodiments, the axial length of the strong neutron absorbing section of the control rod is equal to the axial length of the active section.

[0017] In some alternative embodiments, there is a gap between the support housing and the bottom wall of the reactor vessel to form a lower chamber.

[0018] In some alternative implementations, when the control rod is in the initial position of its stroke, the height of the strong neutron absorber segment of the control rod is flush with the height of the active segment.

[0019] In some alternative implementations, when the control rod is at the initial position of the stroke, the control rod is in a fully inserted state in the guide tube; when the control rod is at the end position of the stroke, the control rod is in a fully lifted state in the guide tube.

[0020] Thirdly, this application provides an experimental method for a lead-based fast neutron high-flux research reactor, which is implemented based on any of the lead-based fast neutron high-flux research reactors described in the second aspect. When starting up or operating the lead-based fast neutron high-flux research reactor for a long period of time, the control rods are gradually moved upward under the drive of the drive mechanism so that the strong neutron absorber segment is gradually offset from the active segment of the fuel assembly in the radial direction.

[0021] In some alternative implementations, as the lead-based fast neutron high flux research reactor reaches the end of its service life, the gas cavity section is radially aligned with the active section of the fuel assembly.

[0022] Compared with the prior art, this application has the following advantages and beneficial effects:

[0023] 1. This application provides a control rod, a lead-based fast neutron high-flux research reactor, and its experimental method. The reactor control rod is inserted into the reactor core from the bottom upwards, and no control rod drive mechanism is set at the top of the reactor. This provides ample top space and a good operating environment for the installation, commissioning, operation, and testing of irradiation test devices of different types and sizes. It can maximize the utilization of the irradiation resources of the lead-based fast neutron high-flux research reactor, thereby significantly improving the design performance of the lead-based fast neutron high-flux research reactor.

[0024] 2. This application provides a control rod, a lead-based fast neutron high-flux research reactor, and its experimental method. The control rod guide tube adopts a sealed blind tube at the top, completely isolating the control rod inside the tube from the reactor coolant outside the tube. Furthermore, the control rod guide tube passes downwards through the reactor vessel support platform and the bottom shield, connecting to the control rod drive mechanism located in the bottom chamber, achieving complete sealing at both ends of the control rod guide tube. A fast neutron irradiation shielding section is provided at the lower end of the control rod, extending to the control rod drive mechanism. These measures not only avoid the risk of core coolant leakage through the control rod channel but also ensure that the irradiation dose to the control rod drive mechanism remains within the design limits.

[0025] 3. This application provides a control rod, a lead-based fast neutron high flux research reactor and its experimental method. During reactor operation, when the control rod in the guide tube is at its highest position, it is in a fully lifted state, and when it is at its lowest position, it is in a fully inserted state. If a plant power outage or other accident occurs requiring emergency shutdown, the control rod can fall rapidly under gravity, introducing negative reactivity into the reactor core to achieve emergency shutdown, fully considering the inherent safety characteristics of the reactivity control system. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the exemplary embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0027] Figure 1 This is a schematic diagram of the control rod structure provided in an embodiment of this application;

[0028] Figure 2 This is a schematic diagram of the radial cross-sectional structure of a strong neutron absorber segment provided in an embodiment of this application;

[0029] Figure 3 A schematic diagram of the lead-based fast neutron high flux research reactor structure when the control rods are in the initial position of the stroke, as provided in an embodiment of this application.

[0030] Figure 4 A schematic diagram of the operational structure of the lead-based fast neutron high flux research reactor provided in this application embodiment;

[0031] Figure 5 A schematic diagram of the lead-based fast neutron high flux research reactor structure when the control rod is at the end of its stroke, as provided in an embodiment of this application.

[0032] The attached diagram shows the markings and corresponding component names:

[0033] 1-Strong neutron absorber section, 2-Gas cavity section, 3-Fast neutron irradiation shielding section, 4-Strong neutron absorber, 5-Cloaking, 6-Reactor container, 7-Underfill chamber, 8-Basket, 9-Support platform, 10-Shielding layer, 11-Fuel assembly, 12-First gas cavity section, 13-Active section, 14-Second gas cavity section, 15-Support box, 16-Guide tube, 17-Control rod, 18-Drive mechanism, 19-Underfill chamber. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.

[0035] To provide sufficient overhead space at the top of the reactor for the installation, commissioning, operation, and testing of the irradiation experimental device, the inventors proposed that the control rods enter and exit the core from the bottom upwards, with the control rod drive mechanism located at the bottom, providing ample space at the top. However, this presents the following problems: 1) There is a risk of leakage of lead-based coolant from the core along the control rod channels; 2) There are radiation protection issues for the control rod drive mechanism, as the active region of the core is very close to the bottom, and the neutron flux is relatively high, which is detrimental to the long-term operation of the control rod drive mechanism. Based on this, the following provides a detailed description of the control rods, lead-based fast neutron high-flux research reactor, and its experimental methods provided in this application.

[0036] Firstly, such as Figures 1-2 As shown in the figure, this application provides a control rod, which includes a shell 5 and a strong neutron absorber segment 1, a gas cavity segment 2 and a fast neutron irradiation shielding segment 3 arranged sequentially within the shell 5 and along the axial direction of the control rod. The axial lengths of the strong neutron absorber segment 1 and the gas cavity segment 2 are equal.

[0037] The control rod provided in this application embodiment is designed with equal axial lengths for the strong neutron absorber segment 1 and the gas cavity segment 2. For example, if the height of the core active segment 13 is 80 cm, the heights of both the strong neutron absorber segment 1 and the gas cavity segment 2 can be set to 80 cm. The height of the fast neutron irradiation shielding segment 3 can be adaptively designed based on constraints such as the core neutron flux rate and the radiation protection limit of the control rod drive mechanism. During the experimental stage, by driving the axial displacement of the control rod, the strong neutron absorber segment 1 and the gas cavity segment 2 can alternately be in a predetermined position. For example, by driving the axial displacement of the control rod, the strong neutron absorber segment 1 can be aligned with the active region of the fuel assembly 11, or the gas cavity segment 2 can be aligned with the active region of the fuel assembly 11.

[0038] In some alternative embodiments, the absorber within the strong neutron absorber segment 1 is a highly enriched boron carbide core.

[0039] In this embodiment, the boron-10 isotope in the high-enrichment boron carbide pellet has an extremely high absorption cross-section for fast neutrons, which can effectively control the neutron flux in the nuclear reactor, thereby achieving precise adjustment of the reactor power. In addition, boron carbide does not produce long-lived radioactive products after absorbing neutrons, simplifying the nuclear waste disposal process and reducing environmental and safety risks. Boron carbide also has good radiation stability and self-healing ability, enabling it to work stably for a long time in high-irradiation environments, reducing the replacement frequency of control rod 17 and improving the operational reliability of the reactor. At the same time, the high-enrichment boron carbide pellet has a relatively low cost and a wide range of raw material sources, which helps to reduce the construction and operation costs of the nuclear reactor.

[0040] In some alternative embodiments, the absorber within the fast neutron irradiation shielding section 3 is formed from a mixture of lead-boron polyethylene, pure lead, depleted uranium, or highly enriched boron carbide cores.

[0041] In this embodiment, lead-boron polyethylene has good neutron absorption capacity and low secondary radiation; pure lead has high density and good plasticity, which helps to improve the mechanical strength and stability of the shielding section; depleted uranium can effectively absorb neutrons, and its high density helps to increase the weight of the shielding section, thereby improving the insertion efficiency of the control rods; while the high absorption cross section and low secondary radiation characteristics of high-enriched boron carbide cores for fast neutrons can significantly improve the shielding effect; by using a mixture of multiple materials, not only can the shielding capability of the control rods against fast neutrons be enhanced, neutron leakage reduced, and the environment and equipment around the reactor protected, but the physical and mechanical properties of the control rods can also be optimized through the combination of different materials, improving their adaptability and reliability in nuclear reactors.

[0042] Secondly, such as Figures 3-5As shown in the figure, this application provides a lead-based fast neutron high-flux research reactor, which includes a reactor vessel 6, a support platform 9, a shielding layer 10, a subreactor chamber 7, a guide tube 16, and any of the control rods 17 described in the first aspect; the reactor vessel 6 is equipped with fuel assemblies 11. The reactor vessel 6 is usually cylindrical, but it is not excluded that it can be designed as a quadrilateral, hexagon, or other irregular shape in other application environments. It can be adapted to specific design requirements and spatial layout. The reactor vessel 6 needs to ensure sufficient strength and stability to withstand the internal high pressure and high temperature environment, while also ensuring good coolant flow characteristics. The reactor vessel 6 has Multiple fuel assemblies 11 are provided, with their length parallel to the axial direction of the reactor vessel 6 to ensure uniform distribution within the reactor core. A clearance perforation is located at the center of the bottom of the reactor vessel 6. One end of a guide tube 16 is located inside the reactor vessel 6 and is sealed. The length of the guide tube 16 is parallel to the length of the fuel assemblies 11. The other end of the guide tube 16 passes sequentially through the clearance perforation, support platform 9, shielding layer 10, and subreactor chamber 7 on the reactor vessel 6 and is located within the subreactor chamber 7, indicating that the guide tube 16 is positioned at the center of the multiple fuel assemblies 11. A seal is applied between the guide tube 16 and the clearance perforation to prevent coolant leakage; this seal can be made of rubber, polytetrafluoroethylene, or other suitable materials. Other high-performance sealing materials can be used for sealing. Depending on different pressure and temperature conditions, O-rings or gaskets can be selected to seal the guide tube 16 and the reactor vessel 6. The underreaming chamber 7 is equipped with a drive mechanism 18 that cooperates with the guide tube 16. The drive mechanism 18 includes, but is not limited to, electric drives that use an electric motor to provide power and move the control rod 17 via gear or belt transmission; hydraulic drives that use a hydraulic system to generate thrust and push the control rod 17 to move within the guide tube 16; pneumatic drives that use compressed air or other gases as a power source and drive the control rod 17 via a cylinder; or magnetic drives that use magnetic force to attract or repel the control rod 17 to achieve its movement within the guide tube 16. The drive mechanism 18 can be configured with a position sensor. The sensor enables precise position control of the control rod 17. The control rod 17 is located in the guide tube 16 and can move along the length of the guide tube 16 under the drive of the drive mechanism 18, ensuring the operational flexibility of the control rod 17 and ensuring precise alignment between the control rod 17 and the fuel assembly 11. The strong neutron absorber segment 1 on the control rod 17 is equal in length to the active segment 13 of the fuel rod in the fuel assembly 11. This means that in the radial direction of the control rod 17, the strong neutron absorber segment 1 can be completely aligned with the active segment 13 of the fuel rod. Under the drive of the drive mechanism 18, the control rod 17 can move upward, thereby making the gas chamber segment 2 of the control rod 17 completely aligned with the active segment 13 of the fuel rod, achieving precise neutron absorption control.In operation, the reactor vessel 6, support platform 9, shielding layer 10, and underreaming chamber 7 are arranged from top to bottom, and the height of one end of the sealing structure of the guide pipe 16 is not lower than the height of the fuel assembly 11.

[0043] In this embodiment, by arranging the reactor vessel 6, support platform 9, shielding layer 10, and under-reactor chamber 7 from top to bottom, and by setting a guide tube 16 on the reactor vessel 6, the control rod 17 can be installed from the bottom of the reactor vessel 6. This ensures that the top of the reactor vessel 6 has sufficient space for the installation, commissioning, operation, and testing of the irradiation test apparatus. When installing the control rod 17, a robotic arm can be used to grasp the control rod 17, making it cooperate with the drive mechanism 18, and inserting the control rod 17 into the guide tube 16. Then, the drive mechanism 18 drives the control rod 17 to move along the length of the guide tube 16. The strong neutron absorber segment 1 on the control rod 17 is equal in length to the active segment 13 of the fuel rod in the fuel assembly 11, meaning that the strong neutron absorber segment 1 on the control rod 17 can be completely aligned with the active segment 13 of the fuel rod in the radial direction. Driven by the drive mechanism 18, the control rod 17 can move upward, thereby making the gas chamber segment 2 of the control rod 17 completely aligned with the active segment 13 of the fuel rod.

[0044] In some optional embodiments, a basket 8 is provided inside the reactor vessel 6 to serve as a support and fixing foundation for the fuel assemblies 11, ensuring the stable operation of the fuel assemblies 11 within the reactor vessel 6. A support box 15 is provided at the bottom of the basket 8, and multiple fuel assemblies 11 are arranged in parallel at intervals and fixedly connected to the support box 15 respectively. The parallel and spaced arrangement of multiple fuel assemblies 11 helps to improve the thermal efficiency and fuel utilization of the reactor, ensuring sufficient space between the fuel assemblies 11 to facilitate the flow of coolant, thereby improving heat transfer efficiency. At the same time, this arrangement also helps to reduce the mutual influence between the fuel assemblies 11, improving the operational safety of the reactor.

[0045] In some alternative embodiments, the fuel assembly 11 includes a first gas chamber section 12, an active section 13, and a second gas chamber section 14 arranged sequentially along the axial direction.

[0046] In this embodiment, the first gas chamber section 12 is typically located at the top of the fuel assembly 11, meaning it is usually positioned upwards. This provides necessary support and positioning for the fuel assembly 11, ensuring its vertical stability within the reactor. It also provides compensation space for potential thermal expansion of the fuel assembly 11 during reactor operation, reducing thermal stress, extending service life, and promoting uniform coolant flow, thus improving heat transfer efficiency. The second gas chamber section 14 is located at the bottom of the fuel assembly 11, serving a similar function to the first gas chamber section 12, but focusing more on bottom support and positioning. It also provides thermal expansion compensation space for the fuel assembly 11 and influences coolant flow, improving heat transfer efficiency. Overall, this design of the fuel assembly 11 enhances the reactor's operational flexibility and adaptability to a certain extent, improving the overall performance and efficiency of the lead-based fast neutron high-flux research reactor, and contributing to improved reactor performance, safety, and economy.

[0047] In some alternative embodiments, there is a gap between the support housing 15 and the bottom wall of the reactor vessel 6 to form a lower chamber 19.

[0048] In this embodiment, the lower chamber 19 can collect a certain amount of coolant, while spatially isolating the fuel assembly 11 from the bottom of the reactor vessel 6, thus preventing the bottom of the reactor vessel 6 from overheating and preventing the support platform 9 from overheating.

[0049] In some optional embodiments, when the control rod 17 is in the initial position of its stroke, the height of the strong neutron absorber segment 1 of the control rod 17 is flush with the height of the active segment 13, and the control rod 17 is fully inserted in the guide tube 16 when it is in the initial position of its stroke; when the control rod 17 is in the final position of its stroke, the control rod 17 is fully lifted in the guide tube 16. This means that when the control rod 17 is not driven by the drive mechanism 18, the strong neutron absorber segment 1 in the control rod 17 is radially aligned with the active segment 13 of the fuel assembly 11. If the system experiences an unexpected power failure or emergency shutdown, the control rod 17, in its fully lifted state, will fall freely under its own weight, and the strong neutron absorber segment 1 in the control rod 17 will be radially aligned with the active segment 13 of the fuel assembly 11, thereby maximally suppressing the reactive release of the active segment 13 and ensuring reactor safety.

[0050] Thirdly, embodiments of this application provide an experimental method for a lead-based fast neutron high-flux research reactor, implemented based on any of the lead-based fast neutron high-flux research reactors described in the second aspect, such as... Figure 4 As shown, when starting up or operating the lead-based fast neutron high flux research reactor for a long period of time, the control rod 17 is moved upward gradually under the drive mechanism 18 so that the strong neutron absorber segment 1 is gradually offset from the active segment 13 of the fuel assembly 11 in the radial direction.

[0051] In this embodiment, as the control rod 17 gradually moves upward, the radial length of the strong neutron absorber segment 1 in the control rod 17 corresponding to the active segment 13 of the fuel assembly 11 gradually decreases, and the reactivity of the active segment 13 in the fuel assembly 11 is gradually released. When the control rod 17 is at the end of its stroke, the gas chamber segment 2 in the control rod 17 will be completely aligned radially with the active segment 13 of the fuel assembly 11. At this time, the suppression of the reactivity of the active segment 13 of the fuel assembly 11 by the control rod 17 reaches its minimum, and the fuel assembly 11 will release all remaining reactivity. When the system experiences an unexpected power failure or emergency, the drive mechanism 18 no longer limits the control rod 17, and the control rod 17 will rapidly move under its own gravity. The rapid drop of the control rod 17 ensures that the strong neutron absorber segment 1 in the control rod 17 is fully aligned radially with the active segment 13 of the fuel assembly 11. At this point, the suppression of the active segment 13 of the fuel assembly 11 by the control rod 17 reaches its maximum, i.e., the maximum negative reactivity is introduced into the reactor, achieving the purpose of emergency shutdown. Thus, the lead-based fast neutron high-flux research reactor provided in this application, with the concept of bottom-mounted control rod 17, can automatically introduce the maximum negative reactivity into the reactor to achieve emergency shutdown in the event of unexpected power failure or emergency. No backup drive or manual operation is required, and the system is safe, stable, and reliable. Furthermore, after the control rod 17 drops, it can quickly re-engage with the drive mechanism 18, which can improve the efficiency during restart.

[0052] In some alternative implementations, such as Figure 5 As shown, when the lead-based fast neutron high flux research reactor reaches the end of its service life, the gas cavity section 2 is aligned radially with the active section 13 of the fuel assembly 11.

[0053] In summary, the embodiments of this application provide a control rod, a lead-based fast neutron high-flux research reactor, and an experimental method thereof, wherein:

[0054] The control rod includes a casing 5 and a strong neutron absorber segment 1, a gas cavity segment 2, and a fast neutron irradiation shielding segment 3 arranged sequentially within the casing 5 along the axial direction of the control rod. The strong neutron absorber segment 1 and the gas cavity segment 2 have equal axial lengths.

[0055] The lead-based fast neutron high-flux research reactor includes a reactor vessel 6, a support platform 9, a shielding layer 10, a subreactor chamber 7, a guide tube 16, and any of the control rods 17 described in the first aspect; fuel assemblies 11 are disposed within the reactor vessel 6; one end of the guide tube 16 is located within the reactor vessel 6 and is sealed, the length direction of the guide tube 16 is parallel to the length direction of the fuel assembly 11, and the other end of the guide tube 16 passes sequentially through the reactor vessel 6, the support platform 9, the shielding layer 10, and the subreactor chamber. The reactor vessel 6, support platform 9, shielding layer 10, and under-reactor chamber 7 are arranged from top to bottom, and the height of one end of the sealing structure of the guide tube 16 is not lower than the height of the fuel assembly 11.

[0056] The experimental method for the lead-based fast neutron high flux research reactor includes, during startup or long-term operation of the lead-based fast neutron high flux research reactor, gradually moving the control rod 17 upward under the drive mechanism 18 so that the strong neutron absorber segment 1 is gradually offset from the fuel assembly 11 in the radial direction.

[0057] It has the following technical effects:

[0058] 1. The embodiments of this application provide a control rod, a lead-based fast neutron high-flux research reactor and its experimental method. The reactor control rod 17 is inserted into the reactor core from the bottom upwards. The control rod 17 drive mechanism 18 is not set at the top of the reactor. It provides ample top space and a good operating environment for the installation, commissioning, operation and testing of irradiation test devices of different types and sizes. It can maximize the utilization of the irradiation resources of the lead-based fast neutron high-flux research reactor, thereby significantly improving the design performance of the lead-based fast neutron high-flux research reactor.

[0059] 2. This application provides a control rod, a lead-based fast neutron high-flux research reactor, and its experimental method. The control rod 17 guide tube 16 adopts an upper-end sealed blind tube to completely isolate the control rod 17 inside the tube from the reactor coolant outside the tube. In addition, the control rod 17 guide tube 16 passes downward through the reactor vessel 6 support platform 9 and the bottom shield, and connects to the control rod 17 drive mechanism 18 located in the bottom chamber, achieving complete sealing at both ends of the control rod 17 guide tube 16. Furthermore, a fast neutron irradiation shielding section 3 is provided at the lower end of the control rod 17, extending to the control rod 17 drive mechanism 18. Through the above measures, not only is the risk of core coolant leakage through the control rod 17 channel avoided, but the irradiation dose received by the control rod 17 drive mechanism 18 is also ensured to be within the design limit range.

[0060] 3. The embodiments of this application provide a control rod, a lead-based fast neutron high flux research reactor and its experimental method. During reactor operation, when the control rod 17 in the guide tube 16 is at its highest position, it is in a fully lifted state, and when it is at its lowest position, it is in a fully inserted state. If a plant power outage or other accident occurs and an emergency shutdown is required, the control rod 17 can fall rapidly by gravity, introducing negative reactivity into the reactor core to achieve an emergency shutdown, which fully considers the inherent safety characteristics of the reactivity control system.

[0061] The specific embodiments described above illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application is presented in conjunction with some embodiments, this does not mean that the features of this application are limited to this embodiment. On the contrary, the purpose of describing the application in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many specific details are included in the above description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0062] It should be noted that in this specification, similar reference numerals and letters in the above figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, and are only for the convenience of describing this application 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 on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this application, it should be noted that unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" 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 an electrical 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 elements. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0063] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A control rod, characterized in that, It includes a shell (5) and a strong neutron absorber segment (1), a gas cavity segment (2) and a fast neutron irradiation shielding segment (3) arranged sequentially within the shell (5) along the axial direction of the control rod. The strong neutron absorber segment (1) and the gas cavity segment (2) have the same axial length.

2. The control rod according to claim 1, characterized in that, The absorber in the strong neutron absorber segment (1) is a high-enriched boron carbide core.

3. The control rod according to claim 1, characterized in that, The absorber in the fast neutron irradiation shielding section (3) is formed by mixing lead-boron polyethylene, pure lead, depleted uranium or high-enriched boron carbide core blocks.

4. A lead-based fast neutron high-flux research reactor, characterized in that, It includes a reactor vessel (6), a support platform (9), a shielding layer (10), a subreactor chamber (7), a guide tube (16), and a control rod (17) as described in any one of claims 1 to 3. The reactor vessel (6) is equipped with fuel assemblies (11). One end of the guide tube (16) is located inside the reactor vessel (6) and is a sealed structure. The length direction of the guide tube (16) is parallel to the length direction of the fuel assembly (11). The other end of the guide tube (16) passes through the reactor vessel (6), the support platform (9), the shielding layer (10) and the under-reactor chamber (7) in sequence and is located inside the under-reactor chamber (7). The under-reactor chamber (7) is equipped with a drive mechanism (18) that cooperates with the guide tube (16). The control rod (17) is located in the guide tube (16), and the control rod (17) can move along the length direction of the guide tube (16) under the drive of the drive mechanism (18); In the working state, the reactor vessel (6), support platform (9), shielding layer (10) and under-reactor chamber (7) are arranged from top to bottom, and the height of one end of the sealing structure of the guide tube (16) is not lower than the height of the fuel assembly (11).

5. The lead-based fast neutron high-flux research reactor according to claim 4, characterized in that, The reactor vessel (6) is equipped with a basket (8), and a support box (15) is provided at the bottom of the basket (8). Multiple fuel assemblies (11) are arranged in parallel at intervals and are fixedly connected to the support box (15).

6. The lead-based fast neutron high-flux research reactor according to claim 4, characterized in that, The fuel assembly (11) includes a first gas chamber section (12), an active section (13), and a second gas chamber section (14) arranged sequentially along the axial direction.

7. The lead-based fast neutron high-flux research reactor according to claim 6, characterized in that, The axial length of the strong neutron absorption section of the control rod (17) is equal to the axial length of the active section (13).

8. The lead-based fast neutron high-flux research reactor according to claim 5, characterized in that, There is a gap between the support box (15) and the bottom wall of the reactor vessel (6) to form a lower chamber (19).

9. The lead-based fast neutron high-flux research reactor according to claim 4, characterized in that, When the control rod (17) is in the initial position of the stroke, the height of the strong neutron absorber segment (1) of the control rod (17) is flush with the height of the active segment (13).

10. The lead-based fast neutron high-flux research reactor according to claim 4, characterized in that, When the control rod (17) is at the initial position of the stroke, the control rod (17) is in a fully inserted state in the guide tube (16); when the control rod (17) is at the end position of the stroke, the control rod (17) is in a fully lifted state in the guide tube (16).

11. An experimental method for a lead-based fast neutron high-flux research reactor, implemented based on the lead-based fast neutron high-flux research reactor as described in any one of claims 4 to 10, characterized in that, When starting up or operating the lead-based fast neutron high flux research reactor for a long period of time, the control rod (17) is moved upward gradually under the drive mechanism (18) so that the strong neutron absorber section (1) is gradually offset from the active section (13) of the fuel assembly (11) in the radial direction.

12. The experimental method for a lead-based fast neutron high-flux research reactor according to claim 11, characterized in that, When the lead-based fast neutron high flux research reactor reaches the end of its service life, the gas cavity section (2) is aligned radially with the active section (13) of the fuel assembly (11).

Images