Passive residual heat removal system and lead-based fast neutron high-flux research reactor

Abstract

The invention relates to the technical field of nuclear reactors, in particular to a passive residual heat removal system and a lead-based fast neutron high-flux research reactor. The residual heat removal system comprises a reflecting layer structural part which is of a hollow structure with through holes formed in the two ends, the reflecting layer structural part is vertically arranged on the outer side of the fuel assembly in a surrounding mode in the working state, and an inner cavity and a cooling runner of the fuel assembly are arranged in parallel; the lower end of the closed air cooling container is provided with an air inlet channel, the upper end of the closed air cooling container is provided with an exhaust channel, and the air inlet channel can be opened and closed and is hermetically sleeved outside the reaction area of the reactor container in a working state; the discharge chimney is vertically arranged, and the lower end of the discharge chimney is connected with the exhaust channel, so that the residual fission heat and decay heat of the reactor core can be efficiently exported under the working condition of long-term normal shutdown or accident shutdown of the reactor, and the damage of in-reactor fuel elements and in-reactor components caused by overheating of the reactor core is avoided; and the inherent safety of the lead-based fast neutron high-flux research reactor is obviously improved. The research stack is loaded with the waste heat removal system.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor technology, specifically to a passive residual heat removal system and a lead-based fast neutron high-flux research reactor. Background Technology

[0002] Lead-based fast neutron high-flux research reactors are comprehensive experimental nuclear facilities that utilize high-temperature liquid lead-based alloys as coolants to provide high-quality, high-flux fast neutron irradiation resources. Within dedicated large-size irradiation test channels, they conduct accelerated irradiation tests of nuclear fuels and materials, tests of key technologies for advanced nuclear reactors, and the production of low-neutron absorption or long-burnup-chain isotope irradiation. They possess significant advantages such as high neutron flux levels, a hard neutron energy spectrum, good inherent safety, simple operation, large experimental space, and flexible operation, representing an important development direction for future metal-cooled fast neutron high-flux research reactors. "Fast neutron high-flux" refers to a special nuclear environment capable of generating an extremely dense high-energy neutron field (where the proportion of neutrons with energies higher than 0.1 MeV is greater than 70%).

[0003] To ensure the safety of the lead-based fast neutron high flux research reactor, the heat released by the fuel elements in the reactor core must be removed during normal or accidental shutdowns to prevent damage to the fuel elements or internal components due to core overheating. Therefore, a safe and reliable residual heat removal system is a core component and an important safety system of the lead-based fast neutron high flux research reactor.

[0004] Compared to other power reactors, lead-based fast neutron high-flux research reactors require a large number of experimental devices and ample operating space inside, outside, top and bottom. The internal structure is complex, and it is not possible to install residual heat removal heat exchangers similar to those in pressurized water reactors, sodium-cooled fast neutron reactors or lead-cooled fast neutron reactors inside the reactor vessel to remove residual heat from the reactor core.

[0005] Against this backdrop, it is essential to propose a safer and simpler long-term passive residual heat removal system based on the design characteristics of the lead-based fast neutron high flux research reactor, thereby improving inherent safety and providing strong support for the project construction. Summary of the Invention

[0006] This invention provides a passive residual heat removal system and a lead-based fast neutron high-flux research reactor, which can ensure that the reactor can efficiently remove the residual fission heat and decay heat from the reactor core under long-term normal shutdown or accident shutdown conditions, avoid damage to the fuel elements and internal components caused by core overheating, and significantly improve the inherent safety of the lead-based fast neutron high-flux research reactor.

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

[0008] In a first aspect, the present invention provides a passive waste heat removal system, comprising: a reflective layer structure, which is a through structure with through holes at both ends, vertically surrounding the outside of the fuel assembly in the working state, and the inner cavity being arranged in parallel with the cooling channel of the fuel assembly; a sealed air-cooled container, with an air inlet channel at the lower end and an exhaust channel at the upper end, the air inlet channel being openable and closable, and sealed outside the reaction zone of the reactor vessel in the working state; and an exhaust chimney, vertically arranged, with its lower end connected to the exhaust channel.

[0009] The passive waste heat removal system provided by this invention includes a reflector structure, a sealed air-cooled container, and an exhaust chimney. The reflector structure is a through-hole structure with through holes at both ends, and in the working state, it is vertically arranged around the outside of the fuel assembly, with its inner cavity connected in parallel with the cooling channel of the fuel assembly. Thus, under normal core operating conditions, the lead-based coolant entering the core simultaneously flows into the cavity of the reflector structure and the cooling channel of the fuel assembly to cool both the reflector structure and the fuel assembly at the same time, and the lead-based coolant in the cavity of the reflector structure and the cooling channel of the fuel assembly flows in the same direction.

[0010] Meanwhile, the sealed air-cooled container is equipped with an air intake channel at the lower end and an exhaust channel at the upper end. The air intake channel can be opened and closed, and the exhaust chimney is vertically arranged with its lower end connected to the exhaust channel. In the working state, it is sealed and fitted outside the reaction zone of the reactor vessel, so that the middle and lower part of the reactor vessel is completely surrounded by the sealed air cooler. Under the normal operating conditions of the reactor core, the air intake channel is closed, so that the sealed air-cooled container is in a relatively closed state to form a hollow gas insulation layer. The sealed air cooler also undertakes the insulation function to reduce the heat loss of the reactor vessel.

[0011] Based on the above structure, during reactor accident shutdown or normal shutdown, the main pump (lead-based coolant main circulation pump) stops operating, the lead-based coolant stops circulating, and lead-based coolant no longer flows in or out of the reactor vessel. At this time, a certain amount of lead-based coolant is stored in the cavity of the reflector structure, the cooling channels of the fuel assemblies, and the cavity of the reactor vessel. Due to the residual heat of the core and the fact that the reflector structure is located outside the fuel assemblies, the temperature of the lead-based coolant in the cooling channels of the fuel assemblies is high, while the temperature of the lead-based coolant in the cavity of the reflector structure is low. This causes the lead-based coolant in the fuel assembly coolant channels to flow out from the top and into the reflector structure through the upper through-hole, flowing downwards simultaneously with the lead-based coolant in the reflector structure. After entering the lower chamber of the reactor vessel, it mixes and then flows out from the lower end of the fuel assembly coolant channels. The heat enters and flows upward, carrying away the residual heat generated by the fuel assemblies, and finally flows out from the top of the fuel assemblies, forming a natural circulation flow phenomenon. Thus, through the natural circulation flow within the reactor, the residual heat of the core is carried from the fuel assembly area to the reflector structure area. Then, through the mixing of the lead-based coolant between the core basket and the reactor vessel, the residual heat of the core is gradually conducted to the reactor vessel. In turn, the reactor vessel heats the air in the sealed air-cooled container. Under the chimney effect, the cold air enters the sealed air-cooled container from the air intake channel, cools the reactor vessel, and after being heated in the sealed air-cooled container, it is discharged upward through the exhaust channel and the exhaust chimney, thus releasing the residual heat of the core into the atmosphere. This achieves passive emission of the residual heat of the core, avoids damage to the fuel elements and internal components caused by core overheating, and significantly improves the inherent safety of the lead-based fast neutron high-flux research reactor.

[0012] The passive residual heat removal system provided by this invention removes core residual heat. Compared to the shielding and reflector assemblies used in existing metal-cooled fast neutron reactors, this system, while serving as both a core reflector and a test vessel, allows for natural core circulation during shutdown. This cools the core fuel assemblies and carries the heat to the reflector structure, which is then conducted to the reactor vessel. The system is simple, stable, reliable, and lower in cost, achieving a fully integrated functional design. Furthermore, this invention utilizes the "chimney effect" principle, relying on natural forces to cool the reactor vessel with air, carrying away core residual heat and continuously releasing it into the atmosphere. It requires no active equipment, is simple, requires few components, is stable and reliable, and can operate long-term.

[0013] Therefore, the passive residual heat removal system provided by this invention can ensure that the reactor can efficiently remove the residual fission heat and decay heat from the reactor core under long-term normal shutdown or accident shutdown conditions, avoid damage to the fuel elements and internal components caused by core overheating, and significantly improve the inherent safety of the lead-based fast neutron high flux research reactor.

[0014] In an optional embodiment of this application, the reflective layer structure is a hollow shell structure to ensure that the inner cavity of the reflective layer structure has sufficient capacity to accommodate a sufficient amount of lead-based coolant, thereby ensuring that it has the function of a core reflective layer while providing sufficient low-temperature lead-based coolant under shutdown conditions.

[0015] In an optional embodiment of this application, the upper end of the reflective layer structure is an open structure, which facilitates the installation, debugging and testing of the irradiation target or irradiation test device, and serves as a container for the test device.

[0016] In an optional embodiment of this application, the outer side of the reflective layer structure is arc-shaped, and in the working state, the outer wall of the reflective layer structure is attached to the inner wall of the core basket to closely match the inner side of the core basket, which can prevent a large amount of lead-based coolant from flowing between the side wall of the reflective layer structure and the inner wall of the core basket.

[0017] In an optional embodiment of this application, in the operating state, the inner wall of the reflective layer structure can be attached to the outer wall of the fuel assembly to reduce the side flow of the core lead-based coolant.

[0018] In an optional embodiment of this application, multiple reflective layer structures are provided, and the multiple reflective layer structures can be arranged to form a hollow cylindrical structure, and the cavity formed by the multiple reflective layer structures is used to accommodate the fuel assembly.

[0019] In an optional embodiment of this application, the reflective layer structure is made of stainless steel to ensure that the reflective layer structure has sufficient resistance to high temperature and corrosion by lead-based alloy coolants.

[0020] In an optional embodiment of this application, a lower tube seat is provided at the lower end of the reflective layer structure. The lower tube seat is a through-hole structure. In the working state, the lower tube seat is inserted into the lower grid plate of the reactor to facilitate the installation and fixing of the reflective layer structure.

[0021] In an optional embodiment of this application, the air intake channel is adapted to be equipped with an air inlet component to ensure that cold air can smoothly enter the sealed air-cooled container.

[0022] In an optional embodiment of this application, the air intake passage is connected in series with a switching valve to facilitate control of the opening and closing of the air intake passage.

[0023] Secondly, the present invention also provides a lead-based fast neutron high-flux research reactor, including a reactor vessel, wherein the reactor vessel is adapted with the aforementioned passive residual heat removal system, which can ensure that the reactor can efficiently remove the residual fission heat and decay heat of the reactor core under long-term normal shutdown or accident shutdown conditions, avoid damage to the fuel elements and internal components in the reactor core due to overheating of the reactor core, and significantly improve the inherent safety of the lead-based fast neutron high-flux research reactor.

[0024] In an optional embodiment of this application, a core basket is adapted to be installed inside the reactor vessel, and the sidewall of the core basket is spaced apart from the sidewall of the reactor vessel; a fuel assembly is loaded in the middle of the core basket, and the reflector structure is arranged around the outside of the fuel assembly to facilitate the installation of the reflector structure, while ensuring that a certain amount of lead-based coolant is stored between the sidewall of the core basket and the sidewall of the reactor vessel, so that the residual heat of the core can be quickly transferred to the reactor vessel under shutdown conditions.

[0025] In an optional embodiment of this application, the reactor vessel is equipped with a coolant inlet and a coolant outlet, with the coolant outlet located above the coolant inlet; the coolant inlet is located above the sealed air-cooled container, and the coolant inlet communicates with the cavity between the sidewall of the core basket and the sidewall of the reactor vessel, to ensure that in the event of reactor shutdown, the lead-based coolant in the reactor vessel can submerge the fuel assemblies and reflector structures.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] 1. The passive waste heat removal system provided by this invention includes a reflector structure, a sealed air-cooled container, and an exhaust chimney. The reflector structure is a through-hole structure with through holes at both ends, and in the working state, it is vertically arranged around the outside of the fuel assembly, with its inner cavity connected in parallel with the cooling channels of the fuel assembly. Under normal core operating conditions, the lead-based coolant in the cavity of the reflector structure and the cooling channels of the fuel assembly flows in the same direction. Under shutdown conditions, the temperature of the lead-based coolant in the cooling channels of the fuel assembly is high, while the temperature of the lead-based coolant in the inner cavity of the reflector structure is low. A natural circulation flow phenomenon is formed, which carries the core residual heat from the fuel assembly area to the reflector structure area. Then, through the mixing of lead-based coolant between the core basket and the reactor vessel, the core residual heat is gradually conducted to the reactor vessel. Under the chimney effect, air enters the sealed air-cooled vessel and is discharged upward through the exhaust channel and exhaust chimney, thereby releasing the core residual heat into the atmosphere. This achieves passive emission of core residual heat, avoids damage to the fuel elements and internal components caused by core overheating, and significantly improves the inherent safety of the lead-based fast neutron high flux research reactor.

[0028] 2. The passive waste heat removal system provided by the present invention is sealed and installed outside the reaction zone of the reactor vessel in the working state, so as to completely surround the middle and lower part of the reactor vessel through the sealed air cooler. Under the normal operation of the reactor core, the air intake channel is closed, so that the sealed air cooler is in a relatively closed state to form a hollow gas insulation layer. The sealed air cooler also undertakes the insulation function, reducing the heat loss of the reactor vessel.

[0029] 3. The passive residual heat removal system provided by this invention, compared with the shielding components and reflector components used in existing metal-cooled fast neutron reactors, undertakes the functions of the core reflector layer and the test device container, while realizing the natural circulation of the core under shutdown conditions, cooling the core fuel assemblies, and carrying the heat to the reflector layer structural component area, and then conducting it to the reactor container. It has a simple structure, is stable and reliable, and has a lower cost, fully realizing the integrated design of function and structure.

[0030] 4. The passive waste heat removal system provided by this invention utilizes the "chimney effect" principle, relies on natural forces, uses air to cool the reactor vessel, removes the waste heat from the reactor core, and continuously discharges it into the atmosphere. It does not require active equipment, the system is simple, requires few devices, is stable and reliable, and can operate for a long time.

[0031] 5. The lead-based fast neutron high-flux research reactor also provided by the present invention includes a reactor vessel, wherein the reactor vessel is adapted to the above-mentioned passive residual heat removal system, which can ensure that the reactor can efficiently remove the residual fission heat and decay heat of the reactor core under long-term normal shutdown or accident shutdown conditions, avoid damage to the fuel elements and internal components in the reactor core due to overheating of the reactor core, and significantly improve the inherent safety of the lead-based fast neutron high-flux research reactor. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the 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 regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] In the attached diagram:

[0034] Figure 1 This is a schematic diagram of the radial arrangement of the core of a lead-based fast neutron high flux research reactor provided in an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of the radial (lateral) arrangement of the reflective layer structure provided in an embodiment of the present invention;

[0036] Figure 3A schematic diagram of the axial (vertical) arrangement of the reflective layer structure provided in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of coolant flow under normal operating conditions of a lead-based fast neutron high flux research reactor, provided in an embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of coolant flow during shutdown of a lead-based fast neutron high flux research reactor, provided as an embodiment of the present invention.

[0039] Figure 6 This is a schematic diagram of the external pipeline system of the passive waste heat removal system provided in an embodiment of the present invention.

[0040] The attached figures include reference numerals and their corresponding component names:

[0041] 1-Fuel assembly, 2-Reflector structure, 3-Core basket, 4-Reactor vessel, 5-Inner wall of structure, 6-Outer wall of structure, 7-End wall of structure, 8-Upper port of structure, 9-Lower pipe seat of structure, 10-Coolant channel of structure, 11-Coolant inlet, 12-Coolant outlet, 13-Coolant level, 14-Lower chamber of reactor vessel, 15-Sealed air-cooled vessel, 16-Air inlet component, 17-Switch valve, 18-Intake passage, 19-Exhaust passage, 20-Emission chimney. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0044] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0045] In the description of the embodiments of this application, the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of this application is usually placed in when in use, or the orientation or positional relationship that is commonly understood by those skilled in the art. It is only for the convenience of describing this application and simplifying the description, and is not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0046] In the description of this application, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" 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 direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0047] Example 1

[0048] Combination Figure 1 and Figure 6 This embodiment provides a passive waste heat removal system, including: a reflective layer structure 2, which is a through structure with through holes at both ends, vertically surrounding the outside of the fuel assembly 1 in the working state, and the inner cavity is arranged in parallel with the cooling channel of the fuel assembly 1; a sealed air-cooled container 15, with an air intake channel 18 at the lower end and an exhaust channel 19 at the upper end, the air intake channel 18 being openable and closable, and sealed outside the reaction zone of the reactor vessel 4 in the working state; and an exhaust chimney 20, vertically arranged, with its lower end connected to the exhaust channel 19.

[0049] Specifically, the reflective layer structure 2 is a hollow shell structure to ensure that the inner cavity of the reflective layer structure 2 has sufficient capacity to accommodate enough lead-based coolant, thereby ensuring that it has the function of a core reflective layer while providing sufficient low-temperature lead-based coolant under shutdown conditions.

[0050] Generally, the upper end of the reflective layer structure 2 is an open structure, which facilitates the installation, debugging and testing of the irradiation target or irradiation test device, and serves as a container for the test device.

[0051] Combination Figure 2 The outer side of the reflective layer structure 2 is arc-shaped, and in the working state, the outer wall of the reflective layer structure 2 is attached to the inner wall of the core basket 3 to closely match the inner side of the core basket 3, which can prevent a large amount of lead-based coolant from flowing between the side wall of the reflective layer structure 2 and the inner wall of the core basket 3.

[0052] In this embodiment, the inner wall of the reflective layer structure 2 can be attached to the outer wall of the fuel assembly 1 in the working state to reduce the side flow of the core lead-based coolant.

[0053] It is known that multiple reflective layer structural members 2 are provided, and the multiple reflective layer structural members 2 can be arranged to form a hollow cylindrical structure, and the cavity formed by the multiple reflective layer structural members 2 is used to accommodate the fuel assembly 1.

[0054] Optionally, the reflective layer structure 2 is made of stainless steel to ensure that the reflective layer structure has sufficient resistance to high temperature and corrosion by lead-based alloy coolants.

[0055] Combination Figure 3 The lower end of the reflective layer structure 2 is provided with a lower tube seat 9, which is a through structure. In the working state, the lower tube seat 9 is inserted into the lower grid plate of the reactor to facilitate the installation and fixation of the reflective layer structure 2.

[0056] In other words, this embodiment divides the area between the periphery of the active zone of the reactor core and the inner side of the basket into several regular areas. Each area is equipped with a structural component covering that area—a reflector structure 2. The reflector structure 2 is constructed with a closed box wall made of stainless steel material that is resistant to high temperature and corrosion by lead-based alloy coolant. The interior of the reflector structure 2 is a cavity to contain the liquid lead-based alloy coolant of the reactor core. The upper port is completely open, and the lower tube seat is provided with a coolant flow channel. The lead-based coolant fills the structure and performs the function of the reactor core reflector.

[0057] The inner surface of the reflector structure 2, which is adjacent to the fuel assembly 1 in the core active zone, has an irregular shape, allowing it to closely match the outer surface of the outermost assembly in the core active zone (fuel assembly 1 is hexagonal), reducing the bypass flow of core coolant. The outer surface of the reflector structure 2, which is adjacent to the inner surface of the core basket 3, has an arc shape, allowing it to closely match the inner surface of the core basket 3, reducing the bypass flow of core coolant. The upper port of the reflector structure 2 is completely open. The distance between the inner and outer surfaces of the reflector structure 2 is determined by the required core reflector thickness. The two end walls of the reflector structure 2 are flat, allowing them to fit tightly with adjacent reflector structures 2.

[0058] In addition, a lower tube seat is provided at the lower end of the reflector structure 2. The lower tube seat is fixed to the lower grid plate of the reactor. If no damage occurs, it does not need to be replaced during the entire life cycle of the reactor. The lower tube seat is provided with a coolant flow channel. The flow area of ​​the flow channel depends on the maximum allowable bypass flow rate of the reactor.

[0059] Combination Figure 6The air intake channel 18 is equipped with an air inlet component 16 to ensure that cold air can smoothly enter the sealed air-cooled container 15.

[0060] Correspondingly, the air intake passage 18 is connected in series with a switching valve 17 to control the opening and closing of the air intake passage 18.

[0061] That is, in order to cool the reactor vessel 4, this embodiment constructs a final heat sink system based on the chimney effect, which includes an air inlet component 16, an inlet pipe (air intake channel 18), an electric valve (on / off valve 17), a closed air cooler, an outlet pipe (exhaust channel 19), and an exhaust chimney 20; the closed air cooler completely surrounds the middle and lower part of the reactor vessel 4, the inlet pipe is connected to the lower part of the closed air cooler, the outlet pipe is connected to the upper part of the closed air cooler, and the electric valve is installed on the inlet pipe.

[0062] In summary, the passive residual heat removal system provided in this embodiment includes a reflector structure 2, a sealed air-cooled container 15, and an exhaust chimney 20. Under normal core operating conditions, the coolant temperature in the fuel assembly 1 area of ​​the core is high, while the coolant temperature in the reflector structure 2 area is low. The main pump provides power, and low-temperature lead-based coolant flows in from the inlet of the reactor vessel 4, while high-temperature lead-based coolant flows out from the outlet of the reactor vessel 4. The coolant flow rate and velocity in the core area are high, and the coolant level in the reactor vessel is high. The coolant flow direction of the fuel assembly 1 and the reflector structure 2 is consistent (upward or downward).

[0063] Combination Figure 4 In operation, the sealed air-cooled container 15 is sealed outside the reaction zone of the reactor vessel 4, so that the middle and lower part of the reactor vessel 4 is completely surrounded by the sealed air-cooler. Under normal operating conditions of the reactor core, the air intake passage 18 is closed, so that the sealed air-cooled container 15 is in a relatively closed state, forming a hollow gas insulation layer, so that the sealed air-cooler also undertakes the insulation function, reducing the heat loss of the reactor vessel 4.

[0064] Combination Figure 5During reactor accident shutdown or normal shutdown, the main pump (lead-based coolant circulation pump) stops operating, the lead-based coolant stops circulating, and the lead-based coolant no longer flows in or out of the reactor vessel 4. At this time, a certain amount of lead-based coolant is stored in the cavity of the reflector structure 2, the cooling channel of the fuel assembly 1, and the cavity of the reactor vessel 4. Due to the residual heat of the reactor core and the fact that the reflector structure 2 is located outside the fuel assembly 1, the temperature of the lead-based coolant in the cooling channel of the fuel assembly 1 is high, while the temperature of the lead-based coolant in the cavity of the reflector structure 2 is low. This causes the lead-based coolant in the coolant channel of the fuel assembly 1 to flow out from the top and flow in through the upper end of the reflector structure 2. It flows downward at the same time as the lead-based coolant in the reflector structure 2, enters the lower chamber 14 of the reactor vessel, mixes with it, and then enters from the lower end of the coolant channel of the fuel assembly 1, flows upward, carries away the residual heat generated by the fuel assembly 1, and finally flows out from the upper end of the fuel assembly 1, forming a natural circulation phenomenon. Thus, through natural circulation within the reactor, the residual heat of the reactor core is carried from the fuel assembly 1 area to the reflector structure 2 area. Then, through the mixing of the lead-based coolant between the core basket 3 and the reactor vessel 4 (and the lead-based coolant in the annular cavity between the core basket 3 and the reactor vessel 4 does not flow), the residual heat of the reactor core is gradually conducted to the reactor vessel 4, and then the air in the sealed air-cooled container 15 is heated by the reactor vessel 4.

[0065] At the same time, the switch valve 17 opens automatically. Under the chimney effect, cold air enters the sealed air-cooled container 15 from the air intake channel 18 to cool the reactor vessel 4. After entering the sealed air-cooled container 15 and being heated, the air is discharged upward through the exhaust channel 19 and the exhaust chimney 20, thereby releasing the core waste heat into the atmosphere. This achieves passive discharge of core waste heat, avoids damage to fuel elements and internal components caused by core overheating, and significantly improves the inherent safety of the lead-based fast neutron high flux research reactor.

[0066] Compared to existing metal-cooled fast neutron reactors that use shielding and reflector assemblies, which simultaneously function as a core reflector and test vessel, this embodiment achieves natural core circulation during shutdown conditions. This circulation cools the core fuel assembly 1 and carries the heat to the reflector structure 2, which in turn conducts it to the reactor vessel 4. The structure is simple, stable, reliable, and lower in cost, fully realizing an integrated functional and structural design. Furthermore, this invention utilizes the "chimney effect" principle, relying on natural forces to cool the reactor vessel 4 with air, removing residual core heat and continuously releasing it into the atmosphere. No active equipment is required; the system is simple, requires few components, is stable and reliable, and can operate long-term.

[0067] In summary, the passive residual heat removal system provided in this embodiment can ensure that the reactor can efficiently remove the residual fission heat and decay heat from the reactor core under long-term normal shutdown or accident shutdown conditions, avoid damage to the fuel elements and internal components caused by core overheating, and significantly improve the inherent safety of the lead-based fast neutron high flux research reactor.

[0068] Example 2

[0069] Combination Figure 1 and Figure 6 This embodiment provides a lead-based fast neutron high-flux research reactor, including a reactor vessel 4, which is equipped with the passive residual heat removal system described in Embodiment 1.

[0070] Specifically, the reactor vessel 4 is equipped with a core basket 3, and the sidewalls of the core basket 3 are spaced apart from the sidewalls of the reactor vessel 4. The core basket 3 is loaded with a fuel assembly 1 in the middle, and the reflector structure 2 is arranged around the outside of the fuel assembly 1 to facilitate the installation of the reflector structure 2. At the same time, it ensures that a certain amount of lead-based coolant is stored between the sidewalls of the core basket 3 and the reactor vessel 4, so that the residual heat of the core can be quickly transferred to the reactor vessel 4 under shutdown conditions.

[0071] It is understood that the reactor vessel 4 is equipped with a coolant inlet 11 and a coolant outlet 12, with the coolant outlet 12 located above the coolant inlet 11; the coolant inlet 11 is located above the sealed air-cooled container 15, and the coolant inlet 11 communicates with the cavity between the side wall of the core basket 3 and the side wall of the reactor vessel 4, to ensure that in the event of reactor shutdown, the lead-based coolant in the reactor vessel 4 can submerge the fuel assembly 1 and the reflector structure 2.

[0072] Combination Figure 1 In a specific engineering example, several hexagonal fuel assemblies 1 are arranged in the active zone of the reactor core. The area between the outermost fuel assembly 1 and the core basket 3 is divided into six regions with identical shapes and areas. Each region is equipped with a reflective layer structure 2 that can cover the region. The annular cavity between the core basket 3 and the reactor vessel 4 is the core coolant flow channel. At the same time, the radial direction of the reflective layer structure 2 is completely closed, the interior is a cavity filled with lead-based coolant.

[0073] Combination Figure 4Under normal core operation, the air intake passage 18 is closed, leaving the sealed air-cooled container 15 in a relatively closed state to form a hollow gas insulation layer. This layer, through the sealed air cooler, also serves as an insulation layer, reducing heat loss from the reactor vessel 4. In this state, the lead-based coolant level 13 in the reactor vessel 4 is higher than the coolant outlet 12. The low-temperature lead-based coolant enters from the reactor vessel inlet, flows downward through the annular cavity between the core basket 3 and the reactor vessel 4, and flows into the lower chamber 14 of the reactor vessel. After thorough mixing, it flows upward through the lower ends of the fuel assembly 1 and the reflector structure 2, entering the core active zone to cool the core fuel assembly 1 and the reflector structure 2. Finally, it flows upward through the reactor vessel outlet and out of the reactor vessel 4.

[0074] Combination Figure 5 In the event of a reactor accident shutdown or a normal shutdown, the main pump (lead-based coolant circulation pump) stops operating, the lead-based coolant stops circulating, and the lead-based coolant no longer flows into or out of the reactor vessel 4. The lead-based coolant level 13 in the reactor vessel 4 is lower than the reactor vessel coolant outlet 12. At this time, a certain amount of lead-based coolant is stored in the cavity of the reflector structure 2, the cooling channel of the fuel assembly 1, and the cavity of the reactor vessel 4. Due to the residual heat of the reactor core and the fact that the reflector structure 2 is located outside the fuel assembly 1, the temperature of the lead-based coolant in the cooling channel of the fuel assembly 1 is high, while the temperature of the lead-based coolant in the cavity of the reflector structure 2 is low. This causes the lead-based coolant in the coolant channel of the fuel assembly 1 to flow out from the top and into the through hole at the top of the reflector structure 2. It flows downward at the same time as the lead-based coolant in the reflector structure 2, enters the lower chamber 14 of the reactor vessel, mixes with it, and then enters from the bottom of the coolant channel of the fuel assembly 1, flows upward, carries away the residual heat generated by the fuel assembly 1, and finally flows out from the top of the fuel assembly 1, forming a natural circulation flow phenomenon.

[0075] Thus, through natural circulation within the reactor, the residual heat of the reactor core is carried from the fuel assembly 1 area to the reflector structure 2 area. Then, through the mixing of the lead-based coolant between the core basket 3 and the reactor vessel 4 (and the lead-based coolant in the annular cavity between the core basket 3 and the reactor vessel 4 does not flow), the residual heat of the reactor core is gradually conducted to the wall of the reactor vessel 4, and then the air in the sealed air-cooled container 15 is heated by the reactor vessel 4.

[0076] At the same time, the switch valve 17 opens automatically. Under the chimney effect, cold air enters the sealed air-cooled container 15 from the air intake channel 18 to cool the reactor vessel 4. After entering the sealed air-cooled container 15 and being heated, the air is discharged upward through the exhaust channel 19 and the exhaust chimney 20, thereby releasing the core waste heat into the atmosphere. This achieves passive discharge of core waste heat, avoids damage to fuel elements and internal components caused by core overheating, and significantly improves the inherent safety of the lead-based fast neutron high flux research reactor.

[0077] In summary, this embodiment can ensure that the reactor can efficiently remove the residual fission heat and decay heat from the core under long-term normal shutdown or accident shutdown conditions, avoid damage to the fuel elements and internal components caused by core overheating, and significantly improve the inherent safety of the lead-based fast neutron high flux research reactor.

[0078] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is 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.

Claims

1. A passive waste heat removal system, characterized in that, include: The reflective layer structure (2) is a through structure with through holes at both ends. In the working state, it is vertically arranged around the outside of the fuel assembly (1), and the inner cavity is arranged in parallel with the cooling channel of the fuel assembly (1). The sealed air-cooled container (15) has an air inlet channel (18) at the lower end and an exhaust channel (19) at the upper end. The air inlet channel (18) can be opened and closed and is sealed outside the reaction zone of the reactor container (4) in the working state. The exhaust chimney (20) is vertically arranged and its lower end is connected to the exhaust channel (19).

2. The passive waste heat removal system according to claim 1, characterized in that, The reflective layer structure (2) is a hollow shell structure.

3. The passive waste heat removal system according to claim 2, characterized in that, The upper end of the reflective layer structure (2) is an open structure.

4. The passive waste heat removal system according to claim 1, characterized in that, The outer side of the reflective layer structure (2) is arc-shaped, and in the working state, the outer wall of the reflective layer structure (2) is attached to the inner wall of the core basket (3).

5. The passive waste heat removal system according to claim 4, characterized in that, In operation, the inner wall of the reflective layer structure (2) can be attached to the outer wall of the fuel assembly (1).

6. The passive waste heat removal system according to claim 5, characterized in that, The reflective layer structure (2) is provided in multiple ways, and the multiple reflective layer structure (2) can be enclosed to form a hollow cylindrical structure, and the cavity enclosed by the multiple reflective layer structure (2) is used to accommodate the fuel assembly (1).

7. The passive waste heat removal system according to any one of claims 1 to 6, characterized in that, The reflective layer structure (2) is made of stainless steel.

8. The passive waste heat removal system according to claim 7, characterized in that, The lower end of the reflector structure (2) is provided with a lower tube seat (9), which is a through structure. In the working state, the lower tube seat (9) is inserted into the lower grid plate of the reactor.

9. The passive waste heat removal system according to claim 1, characterized in that, The air intake passage (18) is adapted to be equipped with an air inlet component (16).

10. The passive waste heat removal system according to claim 9, characterized in that, The intake passage (18) is connected in series with a switching valve (17).

11. A lead-based fast neutron high-flux research reactor, characterized in that, It includes a reactor vessel (4), which is adapted with a passive waste heat removal system according to any one of claims 1 to 10.

12. The lead-based fast neutron high-flux research reactor according to claim 11, characterized in that, The reactor vessel (4) is equipped with a core basket (3), and the side wall of the core basket (3) is spaced apart from the side wall of the reactor vessel (4). The fuel assembly (1) is loaded in the middle of the core basket (3), and the reflector structure (2) surrounds the outside of the fuel assembly (1).

13. The lead-based fast neutron high-flux research reactor according to claim 12, characterized in that, The reactor vessel (4) is adapted to have a coolant inlet (11) and a coolant outlet (12), the coolant outlet (12) being located above the coolant inlet (11); The coolant inlet (11) is located above the sealed air-cooled container (15), and the coolant inlet (11) is connected to the cavity between the side wall of the core basket (3) and the side wall of the reactor container (4).

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