Lead-based fast neutron high-flux research reactor and reflecting layer structure thereof

Abstract

The invention relates to the technical field of nuclear reactors, and particularly discloses a lead-based fast neutron high-flux research reactor and a reflecting layer structure thereof. The plurality of reflecting layer structures are arranged around a fuel assembly of the reactor core active assembly; the box walls of the reflecting layer structures are made of high-temperature-resistant and lead-based alloy corrosion-resistant materials, and each reflecting layer structure is provided with a cavity to form a neutron reflecting layer; the upper end of the reflecting layer structure forms a completely open structure, the lower end of the reflecting layer structure is fixed on a lower grid plate of the reactor core, and at least one coolant runner is arranged at the lower end of the reflecting layer structure, so that a coolant can only flow up and down in the cavity; the shape of the inner surface of the reflecting layer structure is matched with that of the outer surface of the outermost fuel assembly of the reactor core active assembly, and the shape of the outer surface is matched with that of the inner side surface of the reactor core hanging basket. The lead-based fast neutron high-flux research reactor has a reflecting layer structure. Therefore, the reactor core coolant bypass flow is effectively reduced, the material changing operation is simplified, and the flexible arrangement requirements of positioning cylinders and irradiation devices with different sizes are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear reactors, in particular to a lead-based fast neutron high-flux research reactor and a reflector structure thereof. BACKGROUND

[0002] At present, fast neutron irradiation resources are very scarce worldwide, which seriously restricts the research and development of advanced nuclear energy systems and new nuclear reactor technologies mainly based on fast neutron energy spectrum, and it is urgent to build a metal-cooled fast neutron high-flux research reactor. The lead-based fast neutron high-flux research reactor has become an important development direction of metal-cooled high-flux research reactors due to its outstanding inherent safety, simplified coolant system configuration, and flexible operation characteristics.

[0003] In order to fully utilize the neutrons generated in the core, reduce neutron leakage, and improve neutron utilization efficiency, a large number of reflector assemblies are usually arranged outside the active region of the existing high-flux research reactor. These assemblies are mostly made of structural materials and have a geometric size comparable to that of the fuel assemblies. According to the needs of different irradiation tasks, the reflector region can be installed with various in-pile irradiation devices or irradiation positioning cylinders with variable operating test devices, while the reflector assemblies at the corresponding positions need to be removed from the reactor.

[0004] However, the lead-based coolant has the characteristics of high density, strong corrosion, and opacity, etc. When using the above reflector structure, the following problems are exposed: the large number of reflector assemblies results in high overall manufacturing cost; the large flow of invalid coolant through the reflector assembly area causes prominent core coolant bypass phenomenon, which not only increases the design difficulty of the main pump in terms of head and flow, but also increases the technical threshold of system operation; the large number of reflector assemblies increases the complexity of the refueling operation of the lead-based fast neutron high-flux research reactor which generally uses a non-opening type refueling device; due to the diversity and different sizes of irradiation samples and targets, when installing in-pile irradiation devices or variable operating irradiation test positioning cylinders, multiple reflector assemblies often need to be removed, and irregular structural components need to be additionally installed to block the peripheral area of the positioning cylinder and reduce coolant bypass, resulting in more complex core structure and further increasing the design and operation difficulty.

[0005] Therefore, in order to effectively reduce the core coolant bypass flow, reduce or even eliminate the reflector assemblies, control the cost of the reactor, simplify the refueling operation, and adapt to the flexible arrangement requirements of different size positioning cylinders and irradiation devices, it is urgent to optimize and improve the lead-based fast neutron high-flux research reactor to solve the many problems existing in the prior art. SUMMARY

[0006] The purpose of this invention is to provide a lead-based fast neutron high-flux research reactor and its reflector structure, which can effectively reduce the flow rate of the core coolant, control the reactor cost, simplify the refueling operation, and adapt to the flexible arrangement requirements of positioning cylinders and irradiation devices of different sizes.

[0007] This invention is achieved through the following technical solution:

[0008] A reflector structure for a lead-based fast neutron high flux research reactor, comprising multiple reflector structures arranged around the fuel assemblies of the reactor core active components; wherein the box walls of the reflector structure are made of a material resistant to high temperature and lead-based alloy corrosion, and each reflector structure has a cavity for filling with liquid lead-based alloy coolant to form a neutron reflector layer.

[0009] The upper end of the reflective layer structure is formed as a fully open structure, and its lower end is fixed to the lower grid plate of the core. The lower end of the reflective layer structure is provided with at least one coolant flow channel, so that the coolant can only flow up and down in the cavity.

[0010] The inner surface shape of the reflective layer structure matches the outer surface of the outermost fuel assembly of the core active component, and the outer surface shape matches the inner side of the core basket.

[0011] In one possible design, the cross-sectional area of ​​the coolant flow channel is configured such that the coolant velocity flowing through the cavity is less than 0.1 m / s and the flow rate is less than 5% of the total core flow rate.

[0012] In one possible design, the wall thickness of the reflective layer structure is 1-10 mm.

[0013] In one possible design, the number of reflective layer structures is 4-8.

[0014] In one possible design, the coolant is a lead-bismuth alloy, a lead-lithium alloy, or pure lead.

[0015] A lead-based fast neutron high-flux research reactor includes a reactor pressure vessel, a core basket, a reflector structure, and a core active component. The core basket is disposed in the reactor pressure vessel, the core active component is disposed in the core basket, and the reflector structure is located in the region between the core active component and the core basket.

[0016] The reactor core active assembly includes multiple fuel assemblies, each fuel assembly having an N-sided cross-sectional shape, and the multiple fuel assemblies are arranged closely and regularly, where N is a natural number greater than or equal to 3;

[0017] One side of the reflector structure is formed into a zigzag shape that matches the edge of the core active assembly; the other side is arc-shaped to fit tightly against the inner wall of the core basket. The flow path of the coolant is as follows: after entering the reactor pressure vessel, it flows downward along the annular cavity between the core basket and the reactor pressure vessel into the lower chamber of the reactor pressure vessel, then upward into the fuel assembly and reflector structure, and finally out of the reactor pressure vessel.

[0018] In one possible design, the fuel assembly is a regular hexagon; six reflector structures are configured based on the outline of the core active assembly, and each reflector structure has the same geometry and size;

[0019] The inner wall of the reflector structure is a polygonal surface that matches the outer surface of the regular hexagonal fuel assembly, and the outer wall is an arc surface that matches the inner sidewall of the core basket.

[0020] In one possible design, the fuel assembly is square, and the reflective layer structure formed based on the outline of the core active assembly includes a first reflective layer structure and a second reflective layer structure; the first reflective layer structure and the second reflective layer structure are arranged adjacent to each other.

[0021] The inner wall of the first reflective layer structure is a plane, and the outer wall is an arc surface that matches the inner side wall of the core basket; the inner wall of the second reflective layer structure is a polygonal surface that matches the outer surface of the square fuel assembly, and the outer wall is an arc surface that matches the inner side wall of the core basket.

[0022] In one possible design, there are four of each of the first and second reflective layer structures, and they have the same geometry and size as the reflective layer structures.

[0023] In one possible design, the lead-based fast neutron high-flux research reactor further includes a positioning cylinder detachably connected to a positioning structure at the bottom of the reflector structure; the positioning cylinder contains a variable-condition irradiation test device, and the upper part of the variable-condition irradiation test device passes through the top cover of the reactor vessel and extends to the outside.

[0024] In one possible design, the lead-based fast neutron high-flux research reactor also includes an irradiation target and an irradiation test apparatus, both of which are detachably connected to a positioning structure on the reflector structure, and none of them contact the lower grid plate.

[0025] In one possible design, a positioning structure is provided within the cavity of the reflective layer structure; the positioning structure includes at least one of a positioning groove, a positioning platform, a positioning buckle, and a positioning slot.

[0026] The advantages of this invention over the prior art are as follows:

[0027] (1) The reflective layer structure is simple, low in cost, and small in quantity, making it economical;

[0028] (2) The reflector structure can be directly fixed to the lower grid plate of the reactor. It does not need to be replaced during the entire life cycle of the reactor. It is easy to install, simple to operate, and has low technical difficulty.

[0029] (3) The amount of structural material loaded in the core reflector region is reduced. Liquid lead-based coolant with a smaller neutron absorption cross section and a larger scattering cross section is used as the reflector material, resulting in higher neutron utilization and better neutron economy in the core.

[0030] (4) The reflector structure can be loaded with a large amount of high-temperature liquid lead-based alloy coolant, which increases the amount of lead-based coolant loaded in the core. Under accident conditions, it can effectively slow down the rate of temperature rise in the core and ensure the safety of the core.

[0031] (5) The number of reflector structures is small and the flow area of ​​the core coolant is controllable, which can reduce the side flow of the core lead-based coolant in the reflector area, thereby reducing the total flow of the reactor and its performance requirements for the head and flow of the main pump.

[0032] (6) The irradiation target, the reactor irradiation device and the variable operating condition irradiation test device fixed in the positioning cylinder do not contact the lower grid plate of the reactor. The installation, commissioning and operation of the irradiation target and the irradiation test device are simpler and more flexible, have less impact on the reactor structure and are more reliable.

[0033] (7) The interior of the reflector structure is filled with liquid lead-based coolant, which allows for the installation of more and larger irradiation positioning cylinders, more irradiation targets and irradiation test devices, providing more ample irradiation space and making more efficient use of fast neutrons generated by the reactor core;

[0034] (8) Completely eliminating reflector components with structural materials as the main component can reduce the load-bearing weight of the core basket and reactor vessel, and improve the safety of the core basket and reactor vessel.

[0035] This invention can effectively improve the economy and safety of lead-based fast neutron high-flux research reactors, as well as the flexibility of irradiation positioning tube arrangement, and the convenience of installation, commissioning and operation of reactor irradiation devices and variable-condition irradiation test devices, thereby improving the design performance and engineering feasibility of lead-based fast neutron high-flux research reactors. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, 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 the present invention 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:

[0037] Figure 1 This is a schematic diagram of the lead-based fast neutron high-flux research reactor provided by the present invention in one embodiment, and it shows the fluid flow direction;

[0038] Figure 2 This is a cross-sectional schematic diagram of the reflector structure for a lead-based fast neutron high-flux research reactor provided by the present invention in one embodiment, and shows the fluid flow direction;

[0039] Figure 3 This is a top view schematic diagram of the reflector structure for a lead-based fast neutron high-flux research reactor provided by the present invention, wherein the fuel assembly is formed as a regular hexagonal fuel assembly.

[0040] Figure 4 This is a top view schematic diagram of the reflector structure for a lead-based fast neutron high flux research reactor provided by the present invention, wherein the fuel assembly is formed as a regular hexagonal fuel assembly;

[0041] Figure 5 This is a top view schematic diagram of the reflector structure for a lead-based fast neutron high-flux research reactor provided by the present invention, wherein the fuel assembly is formed as a square fuel assembly.

[0042] Figure 6 This is a top view of the first reflector structure in the reflector structure of the lead-based fast neutron high flux research reactor provided by the present invention, wherein the fuel assembly is formed as a square fuel assembly.

[0043] Figure 7 This is a top view schematic diagram of the second reflector structure in the reflector structure of the lead-based fast neutron high flux research reactor provided by the present invention, wherein the fuel assembly is formed as a square fuel assembly.

[0044] The attached diagram shows the following components and their corresponding names: 1-Reactor pressure vessel, 2-Core basket, 3-Fuel assembly, 301-Regular hexagonal fuel assembly, 302-Square fuel assembly, 4-Reflector structure, 41-Box wall, 42-Fully open structure, 43-Coolant channel, 401-First reflector structure, 402-Second reflector structure, 5-Positioning cylinder, 61-Variable operating condition irradiation test device, 62-In-reactor irradiation device, 7-Lower grid plate, 8-Top cover. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that while the description of these embodiments is intended to aid in understanding the invention, it does not constitute a limitation thereof. The specific structural and functional details disclosed herein are only for describing exemplary embodiments of the invention. However, the invention can be embodied in many alternative forms and should not be construed as being limited to the embodiments described herein.

[0046] According to a first aspect of this disclosure, a reflector structure for a lead-based fast neutron high-flux research reactor is provided. Wherein, Figures 1 to 7 Specific embodiments thereof are shown.

[0047] See Figures 1 to 7 As shown, multiple reflector structures 4 are configured and arranged around the fuel assembly 3 in the reactor core. The box wall 41 of the reflector structure 4 is made of a material that is resistant to high temperature and lead-based alloy corrosion. Each reflector structure 4 has a cavity for filling with liquid lead-based alloy coolant to form a neutron reflector layer. The upper end of the reflector structure 4 is formed as a fully open structure 42, and its lower end is fixed to the lower grid plate 7 of the reactor core. The lower end of the reflector structure 4 is provided with at least one coolant flow channel 43, so that the coolant can only flow up and down in the cavity. The inner surface shape of the reflector structure 4 matches the outer surface of the outermost fuel assembly 3 of the reactor core active assembly, and the outer surface shape matches the inner side of the reactor core basket 2.

[0048] The reflector structure 4 utilizes a fixed liquid lead-based alloy to replace traditional detachable solid reflector components, achieving a triple function of core neutron reflection, irradiation space provision, and coolant bypass flow control. The specific working process of the reflector structure 4 is as follows:

[0049] 1. Neutron Reflection: During reactor operation, the fuel assemblies in the active zone of the reactor core generate a large number of fast neutrons. When neutrons leak into the outer reflector structure 4, the liquid lead-based alloy coolant filling its internal cavity, due to its large atomic nuclei and large neutron scattering cross-section, can effectively scatter and "reflect" these leaked fast neutrons back into the active assemblies of the core. This not only reduces neutron leakage losses and improves neutron utilization, but also makes the neutron flux distribution in the core flatter, which is beneficial for maintaining the efficiency and stability of the chain reaction.

[0050] 2. Coolant Flow and Heat Management: The lead-based coolant driven by the main system enters from the inlet of the reactor pressure vessel 1, flows through the annular cavity between the core basket 2 and the vessel, and then enters the lower chamber. A portion of the coolant flows slowly upward into the cavity of the reflector structure 4 through the coolant flow channel 43 located at the lower end of the reflector structure 4. By restricting the flow direction, it is beneficial to ensure the controllability of the flow path, allowing the coolant to carry away the heat generated by the various irradiation devices installed inside the reflector in a slow and small flow state.

[0051] 3. Provision and Utilization of Irradiation Space: The upper end of the reflector structure 4 is completely open, which greatly facilitates the installation and operation of irradiation devices. Various irradiation devices (such as the reactor-on-reactor irradiation device 62 and the positioning cylinder 5 containing the test device) can be directly inserted into or fixed in the cavity of the reflector structure 4 from above the reactor core. The liquid lead-based alloy serves not only as the reflector medium but also as the cooling and irradiation environment for these irradiation devices.

[0052] The above technical solutions simplify the core structure, reduce the manufacturing cost of the reflector region, and eliminate the need for frequent loading and unloading of reflector components during reactor refueling operations, thus reducing the technical difficulty and complexity of the operation. The inner and outer surfaces of the reflector structure 4 are tightly fitted to the core fuel assembly 3 and the core basket 2. Simultaneously, the internal cavity restricts the lateral flow of coolant, reducing the coolant bypass flow through the ineffective areas surrounding the core, thereby lowering the total circulating flow of the reactor. This indirectly reduces the head and flow requirements of the main pump, improving the economy and engineering feasibility of the entire reactor system.

[0053] Liquid lead-based alloys, used as reflector materials, have a smaller neutron absorption cross-section and stronger scattering ability, allowing more neutrons to be effectively reflected back to the reactor core, resulting in higher neutron utilization and improved neutron economy of the reactor. The cavity design, open at the top and filled with liquid metal, provides a highly flexible and uniform installation space for irradiation devices of different geometries and experimental requirements. It eliminates the need to disassemble multiple reflector components and install complex blocking blocks to accommodate devices of different sizes, greatly improving the utilization efficiency and layout flexibility of the irradiation space in the reflector area, and facilitating the efficient use of high-flux fast neutrons generated by the reactor core.

[0054] The large amount of liquid lead-based alloy coolant filled inside reflector structure 4 increases the total heat capacity of the core region. Under accident conditions, this huge heat capacity can effectively slow down the rate of core temperature rise, buying more valuable time for accident handling and safety response, and improving the inherent safety of the reactor.

[0055] It should be noted that directional terms such as "inner" and "outer" refer to "inner" and "outer" relative to the outline of the component. "Inner" refers to the direction towards the inside of the component, and "outer" refers to the direction away from it. Furthermore, terms such as "first" and "second" are used to distinguish one element from another and do not indicate sequence or importance. Moreover, in the following descriptions with accompanying drawings, the same reference numerals in different drawings represent the same element. The phrase "and / or" in the text refers to A and / or B, indicating that there are three possible scenarios: only A, only B, and both A and B. The phrase " / and" in the text refers to A and B, indicating that there are two possible scenarios: only A and both A and B.

[0056] In one embodiment provided in this disclosure, the coolant channel 43 is configured such that the coolant flow velocity through the cavity is less than 0.1 m / s and the flow rate is less than 5% of the total coolant flow rate of the reactor core.

[0057] This low-velocity, low-flow-rate design reduces coolant bypass flow through the reflector region, effectively decreasing the total circulating flow of the reactor main system and lowering the head and flow performance requirements of the main pumps. The continuously flowing coolant is sufficient to remove residual heat generated by the irradiation test equipment or targets installed inside the reflector, and maintains the temperature of the reflector structure 4 components within a safe range, ensuring their structural integrity and long-term service reliability. Simultaneously, the lower flow rate minimizes the erosion and corrosion of the reflector structure 4's box wall 41 and its internal components by the high-density lead-based coolant, extending the service life of critical components. Based on the limitations of coolant flow rate and velocity, the large amount of liquid lead-based alloy within the reflector remains relatively stationary, forming a stable and uniform neutron reflection environment, which is beneficial for maintaining the stability of the reactor core's physical properties.

[0058] In one embodiment provided in this disclosure, the wall 41 of the reflector structure 4 has a thickness of 1-10 mm. This allows it to withstand the static pressure and potential flow impact of the liquid lead-based alloy coolant during core operation, while also possessing sufficient mechanical strength to support the irradiation device installed inside. Simultaneously, it reduces the amount of structural material used in the reflector region, effectively lowering its parasitic absorption of neutrons, allowing more neutrons to be effectively scattered back into the core region by the liquid metal reflector, thereby improving neutron utilization efficiency.

[0059] The relatively thin box wall 41, ranging from 1 to 10 mm in thickness, facilitates faster heat transfer from the interior of the reflector layer to the flowing coolant, improving the component's heat dissipation performance. Simultaneously, it reduces the overall weight of the reflector layer structure 4, correspondingly lowering the load on the core basket 2 and reactor pressure vessel 1, thus contributing to increased safety margins for the overall reactor structure.

[0060] In one embodiment provided in this disclosure, the number of reflective layer structures 4 is 4-8. This range ensures that the reflective layers can completely surround the active components of the reactor core to form an effective neutron reflective layer, while also simplifying the reactor core structure through modular design. Each reflective layer structure 4 has sufficient size to accommodate liquid lead-based alloy to form a reflective layer of sufficient thickness, providing ample space for irradiation experiments, ensuring the uniformity of the coolant flow field around the reactor core, and avoiding flow field turbulence caused by too many components. In addition, this range of numbers allows for flexible arrangement of irradiation devices of different sizes, meeting the installation requirements of large-size experimental positioning cylinders 5 while maintaining the integrity and symmetry of the reactor core structure.

[0061] In one embodiment provided in this disclosure, the coolant is a lead-bismuth alloy, a lead-lithium alloy, or pure lead. Lead-based coolants possess excellent thermophysical properties, effectively utilizing their neutron reflection function. Simultaneously, they exhibit minimal neutron moderation, maintaining the fast neutron energy spectrum of the reactor core and ensuring the accuracy of irradiation experiments.

[0062] Lead-based coolants exhibit good chemical compatibility with stainless steel structural materials, effectively reducing the risk of corrosion to the reflector box wall 41. Furthermore, the high boiling point of lead-based coolants allows the reactor to operate at or near atmospheric pressure, simplifying system design and enhancing inherent safety. The high heat capacity of liquid heavy metal coolants also enhances the reactor's thermal inertia, providing a more ample time window for temperature control and safety response under accident conditions.

[0063] According to a second aspect of this disclosure, a lead-based fast neutron high-flux research reactor is provided.

[0064] This lead-based fast neutron high-flux research reactor comprises a reactor pressure vessel 1, a core basket 2, a reflector structure 4, and core active assemblies. The core basket 2 is housed within the reactor pressure vessel 1, and the core active assemblies are housed within the core basket 2. The reflector structure 4 is located in the region between the core active assemblies and the core basket 2. The core active assemblies include multiple fuel assemblies 3, each with an N-sided cross-section, arranged closely and regularly, where N is a natural number greater than or equal to 3. One side of the reflector structure 4 is formed into a zigzag shape to fit the edge of the core active assemblies; the other side is arc-shaped to fit tightly against the inner wall of the core basket 2. The coolant flows as follows: after entering the reactor pressure vessel 1, it flows downwards along the annular cavity between the core basket 2 and the reactor pressure vessel 1 into the lower chamber of the reactor pressure vessel 1, then upwards into the fuel assemblies 3 and the reflector structure 4, and finally out of the reactor pressure vessel 1.

[0065] The specific working process of this lead-based fast neutron high-flux research reactor is as follows:

[0066] 1. Chain Reaction and Power Generation. Within the active components of the reactor core, the fission reaction zone is formed by closely arranged N-sided fuel assemblies 3. A controlled nuclear fission chain reaction occurs in this region, releasing a large amount of energy and high-flux fast neutrons. These fast neutrons constitute the main neutron source required for irradiation experiments.

[0067] 2. Neutron Reflection and Utilization. Fast neutrons leaking from the active components of the reactor core enter the outer reflector structure 4. This structure is filled with liquid lead-based alloy. Due to the heavy mass of the lead-based alloy nuclei, it has a strong scattering ability for fast neutrons, effectively reflecting most of the leaked neutrons back to the active components of the reactor core. This reduces neutron leakage losses, improves neutron economy, and allows the chain reaction to be maintained more economically. It also maintains the neutron flux at the core edge, providing a powerful neutron source for the irradiation space arranged in the reflector region.

[0068] 3. Heat Removal and Cooling. The flow path of the lead-based alloy coolant is as follows: After entering the reactor pressure vessel 1, it first flows downward along the annular cavity between the core basket 2 and the pressure vessel, entering the lower chamber; subsequently, the coolant turns upward, with a portion flowing through the fuel assemblies 3 of the core active components, directly carrying away the enormous heat generated by nuclear fission; the other portion flows into the cavity of the reflector structure 4, carrying away the heat generated by the reflector itself and any irradiation test equipment that may be installed inside. Finally, all the heated coolant converges and flows out of the reactor pressure vessel 1, entering the subsequent heat exchange system.

[0069] 4. Provision of Irradiation Space. One side of the reflector structure 4 is designed as a polygonal shape that matches the edge of the active components in the reactor core, allowing the reflector to tightly surround the core. The cavity formed inside constitutes a ring-shaped irradiation space surrounding the core. This space can be used to accommodate various irradiation test devices, making full use of the fast neutrons captured by the reflector for scientific research activities such as materials testing and isotope production.

[0070] Through the above technical solutions, the fuel assemblies in the active zone of the reactor core and their combination with liquid lead-based coolant can maintain a strong fast neutron energy spectrum. The unique reflector structure 4 uses liquid lead-based alloy as the reflector material, which has a large neutron scattering cross section and a small absorption cross section, and can efficiently reflect leaked neutrons back to the reactor core, greatly improving the neutron utilization rate and reducing the amount of fuel loading or enrichment required to compensate for neutron loss.

[0071] The outer side of the reflector structure 4 is arc-shaped to the inner wall of the core basket 2, and the inner side is zigzag-shaped to the core. This close-fitting structure minimizes unnecessary flow gaps. Combined with a top-down forced flow path, it effectively guides the coolant to the active zone of the core, reducing the side flow that does not participate in effective cooling. This lowers the overall flow rate and head requirements of the main pump, improving operating efficiency and economy.

[0072] Lead-based coolants have a high boiling point, allowing the system to operate at or near atmospheric pressure, thus avoiding the risk of loss-of-coolant accidents caused by high pressure. The large coolant load (including the portion within the reflector cavity) provides the reactor with strong thermal inertia, effectively slowing the temperature rise under accident conditions and buying valuable time for safety measures.

[0073] In one possible design, the fuel assembly 3 is a regular hexagon; six reflective layer structures 4 are formed based on the outline of the core active assembly, and each reflective layer structure 4 has the same geometry and size; the inner wall of the reflective layer structure 4 is a polygonal surface that matches the outer surface of the regular hexagonal fuel assembly 301, and the outer wall is an arc surface that matches the inner sidewall of the core basket 2.

[0074] The close arrangement of the hexagonal fuel assemblies 301, combined with the six identical reflector structures 4, forms a highly symmetrical core geometry. This symmetry ensures the uniformity of neutron flux distribution around the core, which is beneficial for maintaining a stable core power distribution. The standardized design of the six identical reflector structures 4 simplifies the manufacturing process, reduces production costs, and improves the interchangeability between components, greatly facilitating installation and maintenance. The inner wall of the reflector structure 4 adopts a polygonal surface design that matches the outer surface of the hexagonal fuel assembly 301, achieving a close fit with the outermost components of the fuel assembly in the active region of the core. This close fit effectively reduces coolant leakage channels between the core and the reflector, reducing ineffective coolant bypass flow. Simultaneously, the outer wall of the reflector structure 4 is designed as an arc surface that matches the inner wall of the core basket 2, fully utilizing the annular space within the core basket 2 while ensuring a smooth transition of the coolant flow channels 43, avoiding the formation of flow dead zones. The six reflector structures 4 are interconnected through their planar sidewalls, forming a complete and continuous annular reflector layer inside the core basket 2. This ensures the integrity of the neutron reflection effect and provides a continuous irradiation experimental space.

[0075] In another possible design, the fuel assembly 3 is square, and the reflective layer structure 4 formed based on the contour of the core active assembly includes a first reflective layer structure 401 and a second reflective layer structure 402; the first reflective layer structure 401 and the second reflective layer structure 402 are arranged adjacent to each other. The inner wall surface of the first reflective layer structure 401 is a plane, and the outer wall surface is an arc surface that matches the inner sidewall of the core basket 2; the inner wall surface of the second reflective layer structure 402 is a polygonal surface that matches the outer surface of the square fuel assembly 302, and the outer wall surface is an arc surface that matches the inner sidewall of the core basket 2.

[0076] The design employing a square fuel assembly 302 with adjacent first and second reflective layer structures 401 and 402 exhibits several technical advantages. This design achieves optimal matching with the square reactor core profile by differentiating the reflective layer structures 402 into two types. The inner wall of the second reflective layer structure 402 uses a polygonal surface that precisely matches the outer surface of the square fuel assembly 302, ensuring a tight fit with the core edge and effectively reducing coolant leakage channels. Meanwhile, the inner wall of the first reflective layer structure 401 adopts a planar design, maintaining structural simplicity while working in conjunction with the second reflective layer structure 402 to form a complete reflective layer ring.

[0077] Both types of reflector structures 4 have outer walls designed as arc surfaces that match the inner wall of the core basket 2. This design fully utilizes the annular space within the core basket 2, ensuring a smooth transition of the coolant flow channels 43. Furthermore, the uniform outer wall curvature simplifies the fit with the core basket 2, reducing manufacturing and assembly difficulties. In addition, the regular flow channels formed between adjacent reflector structures 4 help maintain the stability of coolant flow and avoid the generation of flow dead zones.

[0078] In one embodiment, there are four of each of the first reflective layer structure 401 and the second reflective layer structure 402, and they are identical in geometry and size to the reflective layer structure 4. This allows for component serialization and standardization while meeting the requirements for matching the square reactor core, reducing mold manufacturing costs and machining difficulties. Furthermore, the eight reflective layer structures 4 are symmetrically distributed around the reactor core, ensuring uniformity of neutron reflection and promoting a circumferentially uniform distribution of the coolant flow field.

[0079] Furthermore, this symmetrical four-plus-four combination is highly compatible with the geometric characteristics of the square core. It achieves a close fit with the core edge through the folded inner surface of the second reflective layer structure 402, while maintaining the simplicity of the structure through the planar inner surface of the first reflective layer structure 401, thus achieving a good balance between functional completeness and manufacturing economy.

[0080] In this disclosure, the lead-based fast neutron high-flux research reactor also includes a positioning cylinder 5, which is detachably connected to a positioning structure at the bottom of the reflector structure 4. The positioning cylinder 5 houses a variable-condition irradiation test device 61, the upper part of which extends through the top cover 8 of the reactor vessel and outwards. This greatly enhances the flexibility and operability of irradiation experiments, allowing researchers to adjust irradiation experimental parameters in real time by operating the extended test device without extensive dismantling of the reactor internal structure, thus enabling precise studies of material behavior or fuel performance under different operating conditions. The detachable connection between the positioning cylinder 5 and the positioning structure at the bottom of the reflector structure 4 provides a standardized interface for test devices of different sizes and functions, simplifying the device replacement process and improving experimental efficiency.

[0081] Meanwhile, this modular installation structure ensures the experimental device remains precisely positioned during irradiation, preventing displacement caused by coolant flow impact and guaranteeing the reliability of experimental data. The design extending to the outside of the reactor also facilitates online monitoring and data transmission, enabling researchers to obtain experimental parameters in real time. Furthermore, the structure maintains the integrity of the coolant flow channels 43 within the reflector layer and ensures the cooling effect of the liquid lead-based alloy on the experimental device, guaranteeing the safe conduct of the experiment.

[0082] Specifically, the lead-based fast neutron high-flux research reactor also includes an irradiation target and an irradiation test device. Both the irradiation target and the irradiation test device are detachably connected to the positioning structure on the reflector structure 4, and none of them contact the lower grid plate 7.

[0083] Specifically, the irradiation test apparatus includes a reactor-on-deployment irradiation apparatus 62 and a variable-condition irradiation test apparatus 61.

[0084] In this embodiment of the invention, the irradiation target, the in-reactor irradiation device 62, and the variable-condition irradiation test device 61 are all configured as positioning structures that are detachably connected to the reflector structure 4, and none of them contact the lower grid plate 7. This unified positioning structure enables the detachable installation of all types of irradiation devices, improving the flexibility and modularity of irradiation experiments. Different types of devices can be quickly replaced according to experimental needs without requiring complex modifications to the in-reactor structure.

[0085] All devices remain in a non-contact state with the lower grid plate 7, which effectively isolates the mechanical coupling between the irradiation device and the core support structure of the reactor core. This avoids potential impacts on the structure of the lower grid plate 7 and prevents interference from factors such as core vibration on the irradiation experiment, ensuring the accuracy of experimental data and the safety of the device.

[0086] Meanwhile, this suspended installation method greatly facilitates centralized operations from above the reactor core. During refueling or equipment replacement, all equipment can be retrieved or placed in a single operation, improving maintenance efficiency. Furthermore, the modular design allows different irradiation tasks to be carried out in parallel, enhancing the utilization efficiency of the reflector irradiation space.

[0087] In this disclosure, a positioning structure is provided within the cavity of the reflective layer structure 4; the positioning structure includes at least one of a positioning groove, a positioning platform, a positioning buckle, and a positioning slot. This diverse positioning method can adapt to the installation requirements of irradiation targets, irradiation test devices, in-feed irradiation devices 62, and variable-condition irradiation test devices 61 of different shapes and sizes, providing a high degree of layout flexibility. The establishment of the positioning structure ensures that various devices maintain a stable spatial position in the liquid lead-based alloy coolant flow environment, effectively preventing displacement or vibration caused by coolant scouring, thereby ensuring the accuracy and repeatability of irradiation experiments. At the same time, the standardized positioning interface design simplifies the installation and replacement process of the device, and operators can complete the accurate positioning of the device through simple alignment operations, improving the efficiency of material change and experimental preparation. This modular positioning scheme also facilitates the rapid conversion of devices, allowing the same reflective layer cavity to be flexibly configured with different types of irradiation devices according to experimental needs, improving the utilization efficiency of the reflective layer irradiation space.

[0088] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0089] Finally, it should be noted that this invention is not limited to the optional embodiments described above, and anyone can derive other various forms of products under the guidance of this invention. The specific embodiments described above should not be construed as limiting the scope of protection of this invention, which should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A reflector structure for a lead-based fast neutron high flux research reactor, characterized in that, The reflection layer structure is arranged in multiple and surrounds the fuel assemblies of the core active assembly; wherein the box wall of the reflection layer structure is made of a material resistant to high temperature and corrosion of lead-based alloy, each reflection layer structure has a cavity for filling liquid lead-based alloy coolant to form a neutron reflector; The upper end of the reflection layer structure is formed as a fully open structure, the lower end is fixed on the lower grid plate of the core, and the lower end of the reflection layer structure is provided with at least one coolant flow channel, so that the coolant can only flow up and down in the cavity; The inner surface of the reflection layer structure is matched with the outer surface of the outermost fuel assembly of the core active assembly, and the outer surface is matched with the inner side of the core basket.

2. The reflector structure for a lead-based fast spectrum high flux research reactor according to claim 1, characterized in that, The cross-sectional area of the coolant flow channel is configured to make the flow rate of the coolant flowing through the cavity less than 0.1 m / s, and the flow rate is less than 5% of the total flow rate of the core.

3. The reflector structure for a lead-based fast spectrum high flux research reactor according to claim 1, characterized in that, The thickness of the box wall of the reflection layer structure is 1-10 mm.

4. The reflector structure for a lead-based fast spectrum high flux research reactor according to claim 1, characterized in that, The number of the reflection layer structures is 4-8.

5. The reflector structure for a lead-based fast spectrum high flux research reactor according to claim 1, wherein The coolant is lead-bismuth alloy, lead-lithium alloy or pure lead.

6. A lead-based fast neutron high flux research reactor comprising a reactor pressure vessel, a core basket disposed in the reactor pressure vessel, a reflector structure, and a core active assembly disposed in the core basket, the reflector structure being located in a region between the core active assembly and the core basket, characterized in that, The reflection layer structure is the reflection layer structure of any one of claims 1-5; The core active assembly comprises a plurality of fuel assemblies, the cross-sectional shape of the fuel assembly is N-sided polygon, and the plurality of fuel assemblies are arranged closely and regularly, wherein N is a natural number greater than or equal to 3; One side of the reflection layer structure is formed as a fold line shape matched with the edge of the core active assembly, and the other side is arc-shaped to closely fit the inner side wall of the core basket; The flow path of the coolant is: after entering the reactor pressure vessel, flowing into the lower chamber of the reactor pressure vessel along the annular cavity between the core basket and the reactor pressure vessel, flowing into the fuel assembly and the reflection layer structure upwards, and then flowing out of the reactor pressure vessel.

7. The lead-based fast neutron high-flux research reactor of claim 6, wherein, The fuel assembly is a regular hexagon; the reflection layer structure formed based on the contour of the core active assembly is arranged in six, and the geometric shape and size of each reflection layer structure are the same; The inner wall surface of the reflection layer structure is a fold line surface matched with the outer surface of the regular hexagonal fuel assembly, and the outer wall surface is a circular arc surface matched with the inner side wall of the core basket.

8. The lead-based fast neutron high-flux research reactor of claim 6, wherein, The fuel assembly is a square, and the reflection layer structure formed based on the contour of the core active assembly comprises a first reflection layer structure and a second reflection layer structure; the first reflection layer structure and the second reflection layer structure are arranged adjacently; The inner wall surface of the first reflection layer structure is a plane, and the outer wall surface is a circular arc surface matched with the inner side wall of the core basket; the inner wall surface of the second reflection layer structure is a fold line surface matched with the outer surface of the square fuel assembly, and the outer wall surface is a circular arc surface matched with the inner side wall of the core basket.

9. The lead-based fast neutron high-flux research reactor of claim 8, wherein, The number of the first reflection layer structure and the second reflection layer structure is four, and the geometric shape and size of the same reflection layer structure are completely the same.

10. The lead-based fast neutron high-flux research reactor of any of claims 6-9, wherein, The lead-based fast neutron high-flux research reactor further comprises a positioning cylinder which is detachably connected to the positioning structure at the bottom of the reflection layer structure; the positioning cylinder is provided with a variable working condition irradiation test device, and the upper part of the variable working condition irradiation test device penetrates through the top cover of the reactor vessel and extends to the outside.

11. The lead-based fast neutron high-flux research reactor of any of claims 6-9, wherein, The lead-based fast neutron high-flux research reactor further comprises an irradiation target and an irradiation test device, which are detachably connected to a positioning structure on the reflector structure and do not contact the lower grid plate.

12. The lead-based fast neutron high-flux research reactor of any of claims 6-9, wherein, The positioning structure is arranged in the cavity of the reflector structure; and the positioning structure comprises at least one of a positioning groove, a positioning table, a positioning buckle and a positioning clamping groove.

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