A core of a liquid heavy metal lead alloy coolant micro-reactor

Abstract

The present invention relates to a core of a liquid heavy metal lead alloy coolant micro-reactor, and the reactor core includes: a core active region composed of multiple fuel assemblies; a safety rod shutdown system is provided at the central position of the core active region; an active region barrel sleeved outside the core active region; a reflector sleeved outside the active region barrel; multiple uniformly distributed drum shutdown systems are provided in the reflector; a core barrel sleeved outside the reflector. Through the special structural design of the fuel assembly and the shutdown system, the present invention reduces the use of structural materials and the number of reactivity control rods in the core active region, makes the core design of the lead-based reactor further compact, realizes the miniaturization of the core size and the light weight of the fuel device, and still has good safety at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear engineering, and particularly relates to a core of a liquid heavy metal lead alloy coolant micro-reactor. Background Art

[0002] A liquid heavy metal lead alloy coolant reactor is a reactor cooled by a liquid lead-based material (lead, lead alloy), and is recommended as one of the six main advanced fourth-generation nuclear energy system solutions by the Generation IV International Forum (GIF).

[0003] The liquid heavy metal lead alloy coolant reactor has the following advantages: (1) Good safety. The reactor can operate under normal pressure, avoiding the high pressure-bearing requirements for the pressure vessel; the liquid lead-based material has good chemical stability, avoiding the explosion risk caused by the violent reaction of sodium with water and air when liquid sodium is used as the coolant. (2) Easy to miniaturize. The lead-based material has excellent heat-carrying performance, enabling a relatively high power density and a compact core design; the lead-based material has excellent γ shielding performance, which can reduce the volume of the γ radiation shielding system outside the reactor core. (3) Good economy. The neutron energy spectrum of the reactor is hard, and the fuel breeding and transmutation capabilities are relatively strong; the coolant outlet temperature is relatively high, enabling a high thermoelectric conversion efficiency.

[0004] Therefore, when designing a micro-reactor, liquid heavy metal lead alloy is often selected as the reactor coolant. However, when further reducing the core size of this lead-based reactor and reducing the core fuel loading to improve economy, factors such as the high proportion of structural materials in the core active zone and the need to arrange multiple reactivity control rods inside the active zone become design constraints. Summary of the Invention

[0005] The purpose of the present invention is to provide a core of a liquid heavy metal lead alloy coolant micro-reactor, which can solve the deficiencies in the prior art. Through the special design of the fuel assembly and the shutdown system structure, the use of structural materials in the core active zone and the number of reactivity control rods are reduced, making the core design of the lead-based reactor further compact, realizing the miniaturization of the core size and the lightening of the fuel device, while still having good safety.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A core of a liquid heavy metal lead alloy coolant micro-reactor, the reactor core comprising:

[0008] A core active zone, which is composed of multiple fuel assemblies; a safety rod shutdown system is arranged at the central position of the core active zone;

[0009] An active zone barrel, which is sleeved outside the core active zone;

[0010] A reflector, which is sleeved outside the active zone barrel; a plurality of uniformly distributed drum shutdown systems are arranged in the reflector;

[0011] A core barrel, which is sleeved outside the reflector.

[0012] Furthermore, the fuel assembly includes a plurality of fuel elements, an upper operation head arranged at the upper ends of the plurality of fuel elements, and a lower positioning plate arranged at the lower ends of the plurality of fuel elements;

[0013] Wrapping wires are wound around the fuel elements.

[0014] Furthermore, the safety rod shutdown system includes a guide tube, a buoyancy lifting component and a gravity falling component arranged in the guide tube, and a safety rod drive mechanism;

[0015] The safety rod drive mechanism includes a first drive motor, a second drive motor, a first fixing mechanism connected to the first drive motor, a second fixing mechanism connected to the second drive motor, a first transmission shaft connected to the buoyancy lifting component, and a second transmission shaft connected to the gravity falling component; the first fixing mechanism is respectively connected to the first transmission shaft and the second transmission shaft; the second fixing mechanism is respectively connected to the first transmission shaft and the second transmission shaft.

[0016] Furthermore, the drum shutdown system includes a plurality of drum bodies uniformly distributed in the reflector and a drum body drive mechanism for driving the movement of the drum bodies;

[0017] The drum body includes a drum shell, a rotating shaft penetrating and installed in the drum shell and connected to the drum body drive mechanism, and a neutron moderation material part, a neutron absorption material part and a beryllium oxide material part arranged inside the drum shell;

[0018] The neutron moderation material part and the neutron absorption material part adopt a laminated structure, the neutron moderation material part is close to the drum shell, and the neutron absorption material part is close to the rotating shaft;

[0019] Driven by the drum body drive mechanism, the rotating shaft drives the drum shell, the neutron moderation material part, the neutron absorption material part and the beryllium oxide material part to rotate together.

[0020] Furthermore, when the safety rod shutdown system works, driven by the first drive motor and the second drive motor, the buoyancy lifting component moves upward under the buoyancy of the liquid heavy metal lead alloy coolant, and the gravity falling component moves downward under the action of gravity. When the buoyancy lifting component or the gravity falling component moves to the set area, the reactor is safely shut down.

[0021] Furthermore, a limit baffle is provided on both the first fixing mechanism and the second fixing mechanism;

[0022] The limiting baffle is used to control the upward displacement of the buoyancy lifting component or the downward displacement of the gravity falling component.

[0023] Furthermore, an opening is provided at the lower part of the guide cylinder, and the liquid heavy metal lead alloy coolant in the reactor enters the inside of the guide cylinder through the opening.

[0024] Furthermore, the inside of the buoyancy lifting component is filled with boron carbide material whose density is lower than that of the liquid heavy metal lead alloy coolant;

[0025] The inside of the gravity falling component is filled with tungsten metal or hafnium metal material whose density is higher than that of the liquid metal lead alloy coolant.

[0026] Furthermore, the neutron absorption material part uses gadolinium metal or boron carbide;

[0027] The neutron moderation material part uses zirconium hydride or 6 lithium hydride enriched with Li isotope;

[0028] Both the neutron absorption material part and the neutron moderation material part are arc-shaped with the center of the drum body as the center of the circle, and the sector central angle range of the two is 120° to 150°.

[0029] Furthermore, the lower positioning plate is made of solid lead alloy with the same composition as the liquid heavy metal lead alloy coolant, and after the reactor core loading is completed, the lower positioning plate is removed by heating and melting with the liquid heavy metal lead alloy coolant.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] (1) In the reactor core of the present invention, the neutron absorption material part and the neutron moderation material part of the drum body adopt a laminated structure design. The fast neutrons in the core active area are moderated by the neutron moderation material and then absorbed by the neutron absorption material. Since the thermal neutron absorption cross section of the neutron absorption material is much larger than the fast neutron absorption cross section, the laminated structure design can improve the reactivity control value of the drum, thereby reducing the size requirement of the drum body in the diameter direction. Using zirconium hydride or lithium hydride as the neutron moderation material has good neutron moderation performance and can meet the high-temperature stability requirements of the material in the service environment of the reactor core.

[0032] (2) In the reactor core of the present invention, the fuel assemblies in the core active zone are arranged in an equilateral triangle pattern. The fuel assemblies have no outer casing, reducing the structural materials in the core active zone. There is no lower nozzle at the lower part of the fuel assembly, which is used to fix the fuel element rod bundle in the traditional nuclear reactor fuel assembly design, reducing the size of the fuel assembly in the height direction. To facilitate the installation of the fuel assembly in the reactor, a lower positioning plate is designed at the lower part of the fuel assembly, which can fix the lower end position of the fuel element rod bundle. Usually, the lower end of the fuel element is designed with a chamfer, which is beneficial to the in-core installation of the fuel assembly. The material composition of the lower positioning plate is the same as that of the liquid heavy metal lead alloy coolant, which is solid lead or lead alloy material. After the reactor core loading is completed, the lower positioning plate can be removed by heating and melting with the liquid heavy metal lead alloy coolant. Since the material composition of the lower positioning plate is the same as that of the liquid heavy metal lead alloy coolant, no impurity elements will be introduced into the reactor core after the lower positioning plate melts.

[0033] (3) In the reactor core of the present invention, the safety rod shutdown system only occupies one position at the center of the core active zone, making the core structure more compact and the fuel loading lower. At the same time, by designing two sets of drive motors, two sets of fixing mechanisms, two sets of transmission shafts and two shutdown rods (the two shutdown rods are the buoyancy lifting component and the gravity falling component), it is ensured that the safety rod shutdown system can still perform its shutdown function when a single failure is assumed to occur, ensuring the safety of the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural diagram of the liquid heavy metal lead alloy coolant micro-reactor core in the present invention;

[0035] Figure 2 It is a schematic structural diagram of the drum body of the present invention;

[0036] Figure 3 It is a schematic structural diagram of the fuel assembly in the present invention;

[0037] Figure 4 It is a schematic structural diagram of the safety rod shutdown system in the present invention.

[0038] Wherein:

[0039] 1. Fuel assembly, 1-1. Upper operation head, 1-2. Fuel element, 1-3. Lower positioning plate, 1-4. Wrapping wire, 2. Active zone barrel, 3. Reflector, 4. Core barrel, 5. Shutdown system, 5-1. Rotating shaft, 5-2. Beryllium oxide material part, 5-3. Neutron absorption material part, 5-4. Neutron moderation material part, 5-5. Drum shell, 5-6. Guide tube, 5-7. Buoyancy lifting component, 5-8. Transmission shaft 1, 5-9. Gravity dropping component, 5-10. Transmission shaft 2, 5-11. Fixing mechanism 2, 5-12. Fixing mechanism 1, 5-13. Driving motor 1, 5-14. Driving motor 2, 5-15. Shutdown command switch. Detailed implementation mode

[0040] The present invention will be further described below with reference to the accompanying drawings:

[0041] As Figure 1 shown, a core of a liquid heavy metal lead alloy coolant micro-reactor, which is applicable to a reactor using liquid heavy metals such as lead and lead-bismuth alloy as coolant working medium.

[0042] In this embodiment, the core of the liquid heavy metal lead alloy coolant micro-reactor includes a core active zone, an active zone barrel, a reflector, a core barrel and a shutdown system. The shutdown system includes 1 set of drum shutdown system and 1 set of safety rod shutdown system. By adopting this solution, while ensuring the safety of the reactor core, the requirement for the core size of the reactor can be reduced and the core nuclear fuel loading can be decreased.

[0043] As Figure 1 shown, the core active zone is composed of a total of 36 fuel assemblies 1 distributed in an equilateral triangle structure. Each fuel assembly 1 includes 19 fuel elements. The core active zone from the inside to the outside along its diameter is successively an active zone barrel 2 made of ferritic martensitic steel, a beryllium oxide reflector 3 and a core barrel 4 made of 316 stainless steel. The shutdown system 5 of the reactor includes 1 set of drum shutdown system and 1 set of safety rod shutdown system. The drum shutdown system includes 6 drum bodies with uniform sizes and a drum body driving mechanism for driving the rotation of the drum bodies. The 6 drum bodies are evenly distributed in a circular pattern in the reflector between the active zone barrel and the core barrel with the center of the core active zone as the center, and the drum bodies are installed in the middle area of the reflector 3. The safety rod shutdown system is located at the center of the core active zone, occupying the position space of 1 fuel assembly, and is composed of 1 guide tube component, a buoyancy lifting component, a gravity dropping component and a driving mechanism.

[0044] As Figure 2As shown in the figure, the drum body of the drum shutdown system is a cylinder, which consists of a rotating shaft 5-1 made of stainless steel, a beryllium oxide material part 5-2, a neutron absorption material part 5-3, a neutron moderation material part 5-4, and a drum shell 5-5. The neutron absorption material part 5-3 and the neutron moderation material part 5-4 are in a fan-shaped laminated structure, and the central angle of the sector is 120°. The rotating shaft 5-1 is made of 316 stainless steel. The neutron absorption material part 5-3 uses boron carbide ceramics, and the neutron moderation material part 5-4 uses 6 lithium hydride with a lithium isotope abundance of 90%. The drum shell 5-5 is made of 316 stainless steel.

[0045] As Figure 3 shown in the figure, the fuel assembly has no outer casing and consists of an upper operating head 1-1, a plurality of fuel elements 1-2 arranged in an equilateral triangle, and a lower positioning plate 1-3. The fuel element 1-2 consists of a seamless stainless steel cladding tube and a column of UO 2 ceramic pellets, an axial reflector material, a gas chamber, a spring, and upper and lower end plugs. All the fuel elements 1-2 are fixedly connected to the upper operating head 1-1, and the fuel elements 1-2 are in close fit with the lower positioning plate 1-3. The upper operating head 1-1 is made of 316 stainless steel. The lower positioning plate 1-3 uses a solid lead-bismuth alloy material with a bismuth metal content of 55% and the rest being lead, and this material is also the coolant material of the reactor. It melts and turns into a liquid when heated to above 130°C. A wire winding 1-4 with a diameter of 2 mm is welded to the outer wall surface of the fuel element 1-2 for radial restraint. The adjacent fuel elements 1-2 are separated from each other by the wire winding 1-4.

[0046] As Figure 4As shown in the figure, the drive mechanism of the safety rod shutdown system consists of a shutdown instruction switch 5-15, a first drive motor 5-13, a second drive motor 5-14, a first fixing mechanism 5-12, a second fixing mechanism 5-11, a first transmission shaft 5-8, and a second transmission shaft 5-10. The first drive motor 5-13 is connected to the first fixing mechanism 5-12, and the first fixing mechanism 5-12 is connected to the first transmission shaft 5-8 and the second transmission shaft 5-10. The second drive motor 5-14 is connected to the second fixing mechanism 5-11, and the second fixing mechanism 5-11 is connected to the first transmission shaft 5-8 and the second transmission shaft 5-10. The first transmission shaft 5-8 is connected to the buoyancy lifting component 5-7. The second transmission shaft 5-10 is connected to the gravity dropping component 5-9. The first transmission shaft 5-8, the second transmission shaft 5-10, the buoyancy lifting component 5-7, and the gravity dropping component 5-9 are all installed inside the guide cylinder 5-6. There are openings at the lower part of the guide cylinder 5-6, and the liquid heavy metal lead alloy coolant in the reactor enters the inside of the guide cylinder 5-6 through the openings at the lower part. The buoyancy lifting component 5-7 is filled with a boron carbide neutron absorption material with a density lower than that of the liquid heavy metal coolant, and the gravity dropping component 5-9 is filled with a tungsten metal neutron absorption material with a density higher than that of the liquid heavy metal coolant. A limit baffle is provided between the first fixing mechanism 5-12 and the first transmission shaft 5-8 and the second transmission shaft 5-10, and between the second fixing mechanism 5-11 and the first transmission shaft 5-8 and the second transmission shaft 5-10. The limit baffle is used to control the upward displacement of the buoyancy lifting component 5-7 and the downward displacement of the gravity dropping component 5-9.

[0047] The working principle of the present invention is as follows:

[0048] When the reactor is operating, the liquid heavy metal lead alloy coolant flows between the gaps of each fuel element and passes through the reactor core. The UO inside the fuel element 2The ceramic pellets column undergoes a fission reaction, releasing nuclear fission energy. This nuclear fission energy is transferred through the cladding tube of the fuel element to the liquid heavy metal lead alloy coolant flowing through the reactor core, and the heat is removed from the reactor core by the liquid heavy metal lead alloy coolant. At this time, the liquid heavy metal lead alloy coolant also enters the inside of the guide tube through the opening at the lower part of the guide tube. When the safety rod shutdown system operates, the shutdown command switch issues a shutdown command, and drive motor 1 and drive motor 2 act simultaneously and separately. Drive motor 1 drives the fixing mechanism 1 to act, and drive motor 2 drives the fixing mechanism 2 to act. The transmission shaft 1 is clamped by the fixing mechanism 1 and the fixing mechanism 2, and the transmission shaft 2 is clamped by the fixing mechanism 1 and the fixing mechanism 2. When drive motor 1 drives the fixing mechanism 1 to act, the fixing mechanism 1 no longer clamps the transmission shaft 1 and the transmission shaft 2. When drive motor 2 drives the fixing mechanism 2 to act, the fixing mechanism 2 no longer clamps the transmission shaft 1 and the transmission shaft 2. Therefore, when drive motor 1 drives the fixing mechanism 1 to act, or drive motor 2 drives the fixing mechanism 2 to act, or both drive simultaneously, the transmission shaft 1 and the transmission shaft 2 are no longer clamped, enabling the buoyancy lifting component to move upward under the buoyancy of the liquid heavy metal lead alloy coolant, and enabling the gravity dropping component to move downward under the action of gravity. After the buoyancy lifting component moves upward to a certain area, the reactor is achieved; the gravity dropping component moves downward to Figure 4 the middle area between the two dashed lines in

[0049] In summary, through the special structural design of the fuel assembly and the shutdown system, the present invention reduces the use of structural materials and the number of reactivity control rods in the active zone of the reactor core, making the reactor core design of the lead-based reactor more compact, achieving the miniaturization of the reactor core size and the light weight of the fuel device, while still having good safety.

[0050] The above-described embodiments are only used to describe the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A core of a liquid heavy metal lead alloy coolant micro-reactor, characterized in that, the reactor core includes: A core active zone, which is composed of multiple fuel assemblies (1); a safety rod shutdown system is arranged at the central position of the core active zone; An active zone shroud (2), which is sleeved outside the core active zone; A reflector (3), which is sleeved outside the active zone shroud (2); multiple uniformly distributed drum shutdown systems are arranged in the reflector (3); A core barrel (4), which is sleeved outside the reflector (3); The safety rod shutdown system includes a guide tube (5-6), a buoyancy lifting component (5-7) and a gravity dropping component (5-9) arranged in the guide tube (5-6), and a safety rod drive mechanism; The safety rod drive mechanism includes a drive motor one (5-13), a drive motor two (5-14), a fixing mechanism one (5-12) connected to the drive motor one (5-13), a fixing mechanism two (5-11) connected to the drive motor two (5-14), a transmission shaft one (5-8) connected to the buoyancy lifting component (5-7), and a transmission shaft two (5-10) connected to the gravity dropping component (5-9); the fixing mechanism one (5-12) is respectively connected to the transmission shaft one (5-8) and the transmission shaft two (5-10); the fixing mechanism two (5-11) is respectively connected to the transmission shaft one (5-8) and the transmission shaft two (5-10); The drum shutdown system includes multiple drum bodies uniformly distributed in the reflector and a drum body drive mechanism for driving the drum bodies to move; The drum body includes a drum shell (5-5), a rotating shaft (5-1) installed through the drum shell (5-5) and connected to the drum body drive mechanism, and a neutron moderation material part (5-4), a neutron absorption material part (5-3) and a beryllium oxide material part (5-2) arranged inside the drum shell (5-5); The neutron moderation material part (5-4) and the neutron absorption material part (5-3) adopt a laminated structure, the neutron moderation material part (5-4) is close to the drum shell (5-5), and the neutron absorption material part (5-3) is close to the rotating shaft (5-1); Driven by the drum body drive mechanism, the rotating shaft (5-1) drives the drum shell (5-5) and the neutron moderation material part (5-4), the neutron absorption material part (5-3) and the beryllium oxide material part (5-2) to rotate together.

2. The reactor core according to claim 1, characterized in that, the fuel assembly (1) includes multiple fuel elements (1-2), an upper operation head (1-1) arranged at the upper ends of the multiple fuel elements (1-2), and a lower positioning plate (1-3) arranged at the lower ends of the multiple fuel elements (1-2); Wrapping wires (1-4) are wound around the fuel elements (1-2).

3. The reactor core according to claim 1, characterized in that, When the safety rod shutdown system operates, driven by the first drive motor (5-13) and the second drive motor (5-14), the buoyancy lifting component (5-7) moves upward under the buoyancy of the liquid heavy metal lead alloy coolant, and the gravity falling component (5-9) moves downward under gravity. When the buoyancy lifting component (5-7) or the gravity falling component (5-9) moves to the set area, reactor safe shutdown is achieved.

4. The reactor core according to claim 1, characterized in that, both the first fixing mechanism and the second fixing mechanism are provided with a limit baffle; the limit baffle is used to control the upward displacement of the buoyancy lifting component (5-7) or the downward displacement of the gravity falling component (5-9).

5. The reactor core according to claim 1, characterized in that, the lower part of the guide cylinder (5-6) is provided with an opening, and the liquid heavy metal lead alloy coolant in the reactor enters the inside of the guide cylinder (5-6) through the opening.

6. The reactor core according to claim 1, characterized in that, the buoyancy lifting component (5-7) is filled with boron carbide material with a density lower than that of the liquid heavy metal lead alloy coolant; the gravity falling component (5-9) is filled with tungsten metal or hafnium metal material with a density higher than that of the liquid metal lead alloy coolant.

7. The reactor core according to claim 1, characterized in that, the neutron absorption material part (5-3) uses gadolinium metal or boron carbide; The neutron moderation material part (5-4) uses zirconium hydride or 6 lithium hydride enriched in Li isotopes; both the neutron absorption material part (5-3) and the neutron moderation material part (5-4) are arc-shaped with the center of the drum body as the center of the circle, and the sector central angle range of the two is 120° to 150°.

8. The reactor core according to claim 2, characterized in that, the lower positioning plate (1-3) is made of solid lead alloy with the same composition as the liquid heavy metal lead alloy coolant, and after the reactor core loading is completed, the lower positioning plate (1-3) is removed by heating and melting with the liquid heavy metal lead alloy coolant.

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