Micro-stack-based recompression Brayton-Rankine combined cycle power generation system

Abstract

The invention relates to a recompression Brayton-Rankine combined cycle power generation system based on a micro reactor, aims to solve the problems of insufficient heat energy recovery of a Brayton cycle cold end, mismatching of a dead steam temperature and an organic working medium evaporation interval and the like, and realizes efficient power generation of a micro nuclear reactor through combination of a compact integrated reactor core design and an efficient thermodynamic cycle. The reactor core adopts a fuel element to be matched with a control element, and is assisted by upper and lower reflecting layers, a radial reflecting layer and a shielding layer, so that the fuel utilization rate and the power density are improved on the premise of ensuring the safety and controllability of the reactor; the power conversion part utilizes heat energy in a gradient mode in a Brayton-Rankine combined cycle mode, the high-temperature section directly converts the heat energy into electric energy through a Brayton cycle turbine, and the low-temperature waste heat section further generates electricity through an organic Rankine cycle turbine. Through organic combination of the Brayton main loop for recompression heat regeneration and the organic Rankine waste heat recovery loop, the heat efficiency of the whole system is greatly improved, and waste heat emission is reduced. The invention relates to the technical field of miniature reactors.

Description

Technical Field

[0001] The present invention relates to the technical field of microreactors, and in particular to a recompression Brayton-Rankine combined cycle power generation system based on a microreactor. Background Art

[0002] The existing energy supply system generally relies on diesel generators, solar energy, and wind power, but these systems have significant limitations in practical application. Diesel generators are highly dependent on fuel reserves, resulting in high transportation costs and environmental pollution from combustion emissions. Solar and wind energy are highly intermittent and uncertain, limiting their ability to provide stable energy in areas with harsh climates or resource scarcity. This is particularly true in plateau regions, where winter temperatures are severe and heating loads are high. In remote areas such as isolated islands, freshwater resources are scarce, and desalination facilities are significantly dependent on electricity. Fluctuations in the energy system directly impact freshwater supply and basic livelihoods. Therefore, in scenarios such as post-disaster emergency response, remote deployments, and military support, there is an urgent need for a clean, high-density, stable, and reliable heat source system to provide continuous, efficient, and environmentally friendly energy support. Research indicates that nuclear energy systems are the only viable option currently capable of meeting these requirements.

[0003] According to mainstream international technical definitions, nuclear power plants with a thermal power output of 20MW are classified as microreactors or very small modular reactors (vSMRs). These reactors typically have an electrical power output of 1–10MW and are highly integrated and modular, exhibiting three core technical advantages: First, the system architecture adheres to modular design principles, enabling rapid "plug-and-play" deployment; second, the overall unit package size complies with standard transportation specifications for road, rail, and sea transportation, ensuring excellent engineering adaptability; and third, an intelligent operation control system and passive safety mechanisms support adaptive operating conditions, reducing reliance on highly skilled operators while enabling preventive response to core temperature runaway.

[0004] From the perspective of application scenarios, micro reactors have extensive energy supply potential. In remote off-grid areas, they can replace traditional diesel generators to build regional distributed energy networks. In industrial scenarios, they can meet the continuous power supply needs of low-load processes, while realizing multi-energy collaborative applications such as combined heating, seawater desalination, and green hydrogen production. In terms of emergency energy security, with its modular structure and rapid deployment capabilities, it can form a mobile emergency energy platform to provide highly reliable energy support for natural disasters, emergencies, and field operations. More strategically significant is that micro reactor systems can complement intermittent renewable energy sources such as wind power and photovoltaics to build a hybrid energy system that achieves continuous energy output and stable power regulation under the microgrid structure. These characteristics give micro reactors a key position in the national energy structure transformation and energy security strategy.

[0005] Compared with traditional pressurized water reactor systems, the liquid metal-cooled fast reactor on which the supercritical CO2 system relies has a lower operating pressure, which significantly reduces the pressure design requirements of the equipment; its critical temperature is close to room temperature, making system cooling less difficult, which is conducive to improving overall operational safety and environmental adaptability. In terms of chemical stability, CO2 is extremely inert and has long-term compatibility with commonly used materials in nuclear reactors (such as T91 stainless steel, lead-bismuth coolant, etc.), avoiding corrosion and deposition problems. The full life cycle economic assessment shows that the unit power generation cost of the sCO2 Brayton cycle is about 15% lower than that of the steam cycle, forming a good economic synergy with the miniaturized deployment strategy of the micro-reactor system.

[0006] Defects and shortcomings of existing technology:

[0007] 1. The current energy security system faces significant technical adaptability issues in extreme application scenarios. Traditional energy supply methods, such as diesel generators, photovoltaic systems, and wind turbines, struggle to operate stably in complex environments such as plateaus, isolated islands, extreme cold, and drought. Limited by fuel transportation, resource volatility, and system redundancy, they cannot achieve highly reliable and continuous energy output.

[0008] 2. In existing nuclear energy-Brayton cycle systems, the condenser inlet temperature is typically above 120°C, significantly higher than the ambient temperature range (25–40°C). This results in a large amount of low-temperature waste heat (80–150°C) released by the working fluid at the cold end not being effectively recovered, but instead being directly discharged to the environment through forced air cooling, resulting in energy waste. This phenomenon is mainly due to the traditional Brayton system's single-stage cooling structure and the lack of an adaptive control mechanism for changes in the working fluid's physical properties near the critical point.

[0009] 3. In the Brayton-Rankine combined cycle architecture, there's a significant mismatch between the exhaust steam temperature of the Brayton cycle and the evaporation temperature range of the organic working fluid in the Rankine cycle. This reduces the heat transfer driving capacity between the two cycles in the low-temperature range, impacting waste heat recovery efficiency. Furthermore, the coupling and coordinated control mechanisms for the thermal performance of the two working fluids (CO2 and organic working fluid) are still imperfect, resulting in a decline in the system's thermal economy and a higher-than-expected levelized cost of electricity (LCOE). Summary of the Invention

[0010] In order to solve the problems of insufficient heat recovery at the cold end of the existing Brayton cycle, mismatch between the exhaust steam temperature and the evaporation range of the organic working fluid, low combined cycle efficiency and high power generation cost, the present invention is based on the second law of thermodynamics and the principle of energy cascade utilization, and further proposes a recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor.

[0011] The technical solution adopted by the present invention to solve the above problems is:

[0012] The present invention provides a micro-reactor-based recompression Brayton-Rankine combined cycle power generation system comprising:

[0013] A lead-bismuth microreactor comprises a reactor vessel, a radial reflective layer, a shielding layer and a core module, wherein the core module is located in the reactor vessel, and a reflective layer and a shielding layer are sequentially arranged on the outside of the reactor vessel;

[0014] The main loop of the Brayton cycle includes a Brayton cycle turbine, a Brayton cycle generator, a high-temperature regenerator, a low-temperature regenerator, a working medium separation valve, a tube-fin heat exchanger, a cycle main compressor, a cycle recompressor and a mixing valve.

[0015] The inlet of the Brayton cycle turbine is connected to the high-temperature and high-pressure working fluid outlet of the lead-bismuth microreactor; the outlet of the Brayton cycle turbine is connected to the hot end inlet of the high-temperature regenerator; the hot end outlet of the high-temperature regenerator is connected to the hot end inlet of the low-temperature regenerator; the hot end outlet pipeline of the low-temperature regenerator is connected to the first branch and the second branch respectively through a working fluid separation valve; the first branch is connected to the tube-fin heat exchanger and the cycle main compressor in sequence, and returns to the cold end inlet of the low-temperature regenerator; the second branch is compressed by the circulation recompressor and directly output; the mixing valve mixes the working fluid at the cold end outlet of the low-temperature regenerator with the working fluid at the outlet of the circulation recompressor, and transports it to the cold end inlet of the high-temperature regenerator, and finally returns to the lead-bismuth microreactor, forming a closed cycle;

[0016] The Rankine cycle sub-loop includes an organic working fluid evaporator, a Rankine cycle turbine, a circulating working fluid pump and a dry cooling heat exchanger. The hot side inlet of the organic working fluid evaporator is connected to the outlet of the low-temperature regenerator through an electric valve to receive waste heat; the Rankine cycle turbine receives the high-pressure organic working fluid vapor generated by the organic working fluid evaporator and expands to do work to drive the generator to generate electricity; the outlet of the Rankine cycle turbine is connected to the dry cooling heat exchanger, and the outlet end of the dry cooling heat exchanger is connected to the organic working fluid evaporator through the circulating working fluid pump to form a closed loop.

[0017] Furthermore, the core module includes a plurality of fuel elements and a plurality of control elements, and the control assembly is located in the gaps between the fuel elements and is used to adjust the reactivity of the core.

[0018] Furthermore, the plurality of fuel elements adopt various enrichments and are compactly arranged at regular triangle intervals.

[0019] Furthermore, the enrichment of the fuel element is 20%, 30% and 40%.

[0020] Furthermore, each of the fuel elements includes a fuel element upper end plug, a fission gas cavity, an upper reflector, and a fuel pellet; a fuel element wall, a lower reflector, and a fuel element lower end plug; the fuel pellet is located within the fuel element wall, the upper end of the fuel element wall is provided with a fuel element upper end plug, and the lower end of the fuel element wall is provided with a fuel element lower end plug; between the fuel element upper end plug and the fuel element lower end plug, a fission gas cavity, an upper reflector, a fuel pellet, and a lower reflector are provided in sequence from top to bottom.

[0021] Furthermore, the reactor container is made of T91 stainless steel and is filled with liquid lead-bismuth alloy coolant.

[0022] Furthermore, the upper reflection layer and the lower reflection layer are both magnesium oxide reflection layers; the fuel pellets are uranium dioxide pellets; and the fuel element wall, the fuel element upper end plug and the fuel element lower end plug are all made of T91 stainless steel.

[0023] Furthermore, each of the control elements includes a control element upper end plug, a control element cavity, a neutron absorber, a control element wall and a control element lower end plug, and the neutron absorber is located inside the control element wall; the upper end and the lower end of the control element wall are respectively provided with a control element upper end plug and a control element lower end plug, and a control element cavity is provided between the neutron absorber and the control element upper end plug.

[0024] Furthermore, the neutron absorber is a boron carbide neutron absorber.

[0025] Furthermore, the shielding layer is made of boron carbide, and the radial reflection layer is made of magnesium oxide.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention achieves the cascade utilization of nuclear heat in the high-temperature and medium-low-temperature ranges by constructing a dual-working fluid combined power generation system of a micro-nuclear reactor recompressing supercritical CO2 Brayton cycle and an organic Rankine cycle. This is significantly superior to traditional Brayton or steam single cycles, reduces cold-end exhaust steam loss, and improves system energy utilization.

[0028] 2. The miniature lead-bismuth reactor of the present invention uses a compact arrangement of fuels with multiple enrichments, has a lifespan of more than 10 years, and has a good subcritical margin for accident conditions;

[0029] 3. The Brayton cycle of this invention utilizes supercritical CO2 as the working fluid, employing a recompression bypass path to optimize cold-end compression power consumption, and a two-stage regenerator arrangement to enhance the thermal efficiency of the main cycle. The exhaust steam is diverted via an electric valve into the evaporator on the Rankine cycle side, where it exchanges heat with the Rankine working fluid (such as R1233zd or low-pressure CO2), fully recovering previously unusable low-temperature thermal energy (approximately 80–120°C). By optimizing the matching temperature range of the Brayton cycle exhaust steam with the phase transition temperature of the Rankine cycle organic working fluid, the overall waste heat utilization rate of the system is significantly improved.

[0030] 4. By introducing a recompression path and optimized working fluid thermal matching, this invention improves the coupling efficiency between the Brayton and Rankine cycles, reduces low-temperature waste heat, and reduces system operating pressure and component design complexity. Furthermore, by employing environmentally friendly working fluids and a standard modular design, it offers a low levelized cost of electricity and excellent potential for industrial adoption.

[0031] 5. This invention not only solves the energy waste problem at the low-temperature end of the traditional Brayton cycle but also establishes a thermodynamic structure system with dual working fluids working in synergy, significantly reducing power generation costs and improving energy conversion efficiency. Ultimately, this system achieves a high-density clean energy system that is compact, easy to transport, flexible to deploy, and responsive, suitable for remote and extreme scenarios. It can meet the needs of diverse applications, including post-disaster emergency response, military field operations, island and reef garrisons, and border defense energy supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0033] Figure 2 This is a schematic diagram of the reactor structure;

[0034] Figure 3 for Figure 2 Top view of .

[0035] Figure: 1. Lead-bismuth microreactor; 2. Brayton cycle turbine; 3. Brayton cycle generator; 4. High-temperature regenerator; 5. Low-temperature regenerator; 6. Working fluid separation valve; 7. Mixing valve; 8. Dry-cooling heat exchanger fan; 9. Tube-fin heat exchanger; 10. Brayton cycle main compressor; 11. Recompression electric control valve; 12. Recycle recompressor; 13. Mixing valve; 14. Exhaust steam electric valve; 15. Organic working fluid evaporator; 16. Organic working fluid or subcritical carbon dioxide working fluid; 17. Rankine cycle turbine; 1 8. Circulating medium pump; 19. Dry-cooling heat exchanger fan; 20. Dry-cooling heat exchanger; 21. Fuel element; 22. Control element; 23. Shielding layer; 24. Radial reflector; 25. Reactor vessel; 26. Fuel element upper end plug; 27. Fission gas cavity; 28. Upper reflector; 29. ​​Fuel pellet; 30. Fuel element wall; 31. Lower reflector; 32. Fuel element lower end plug; 33. Control element upper end plug; 34. Control element cavity; 35. Neutron absorber; 36. Control element wall; 37. Control element lower end plug. DETAILED DESCRIPTION

[0036] Specific Embodiment 1: This embodiment utilizes a Brayton-Rankine combined cycle thermal energy conversion scheme, with the primary circuit being a Brayton cycle supplemented by an organic Rankine cycle for waste heat utilization. Specifically, heat from the reactor core is first used to heat the Brayton cycle working fluid, which can be high-pressure CO2. Heat released by the core coolant is absorbed by a heat exchanger within the reactor 1 or its primary circuit, significantly increasing the working fluid's temperature and pressure. The heated, high-temperature, high-pressure working fluid then flows from the reactor 1 and enters the Brayton cycle turbine 2, where it expands and produces work. This turbine rotates and drives a coaxially connected generator 3, generating electricity, converting the core thermal energy into mechanical and electrical energy. After adiabatically expanding through the turbine 2, the working fluid's pressure decreases. While its temperature decreases, it still remains at a high level, carrying a significant amount of waste heat. To improve thermal cycle efficiency, a regenerator element is incorporated into the primary circuit to recover waste heat from the working fluid for use in the preheating circuit. After exiting the turbine, the working fluid first enters the hot side of the high-temperature regenerator 4, where it transfers some of its waste heat to the high-pressure, cold working fluid from the compressor on the other side, achieving initial preheating. After passing through the high-temperature regenerator 4, the temperature of the working fluid is reduced, and then it enters the hot side of the low-temperature regenerator 5, further transferring the remaining heat to the colder working fluid flow in the loop. After the heat exchange in the two-stage regenerator, the temperature of the working fluid drops significantly, completing the internal heat energy recovery process. At this time, in order to prepare for the next cycle, the working fluid needs to be cooled and compressed back to the initial high-pressure state. In the cooling and compression stage, this embodiment adopts a recompression-Brayton cycle design, which further improves the cycle efficiency by diverting the working fluid for parallel compression. Specifically, after leaving the high-temperature regenerator 4, the working fluid enters the hot end of the low-temperature regenerator 5, releases the residual heat, and flows out of the low-temperature regenerator and enters the dry cooling heat exchanger 9 where the working fluid separation valve 6 divides the flow path into two, and the first branch is air-cooled. In the dry cooling heat exchanger 9, the working fluid is cooled by air convection with the help of the dry cooling heat exchanger fan 8, and the temperature is reduced to close to the ambient temperature, causing the working fluid to condense or cool to a state suitable for compression. The cooled working fluid then enters the main compressor 10, where it is compressed to a higher pressure and then preheated by utilizing the residual heat within the low-temperature regenerator. The second branch, controlled by the recompression electric control valve 11, bypasses the low-temperature regenerator and cooler, directly introducing the still-intermediate-temperature working fluid into the recompressor 12 for compression. Because the second branch has not been fully cooled, its temperature is higher than that of the working fluid entering the main compressor from the first branch. The recompressor 12 performs additional compression on this branch, raising both streams to the high pressure required at the reactor inlet. The two high-pressure working fluids then merge at the mixing valve 13 and combine into a single stream. The mixed high-pressure working fluid then passes through the cold end of the high-temperature regenerator 4, where it absorbs the residual heat released by the first branch and is preheated. The remaining heat is then recovered from the turbine exhaust, further raising its temperature. The working fluid, preheated by the regenerator, eventually returns to a temperature close to the core outlet and circulates back into the reactor 1, absorbing core heat again. This cycle repeats, achieving continuous operation of the Brayton cycle.With the help of the above-mentioned recompression diversion and heat recovery design, the entire Brayton main circuit significantly recovers the waste heat of the turbine exhaust, reduces cooling losses, and thus improves the thermal cycle efficiency and output power.

[0037] Specific Embodiment 2: To maximize waste heat utilization and improve overall power generation efficiency, this system incorporates a Rankine cycle (ORC) sub-circuit, in addition to the Brayton cycle main loop, using an organic working fluid as the working fluid, forming a combined cycle. This ORC side receives low-grade waste heat from the Brayton cycle that has not yet been utilized by the regenerator. The Brayton cycle cooling section is equipped with an evaporator 15, whose connection to the Brayton working fluid flow path is controlled by a motorized valve 14. When the working fluid discharged from the Brayton cycle turbine still contains usable waste heat after passing through the low-temperature regenerator 5, the motorized valve 14 opens, allowing some of the hot working fluid to flow through the heat exchange piping of the evaporator 15, transferring heat to the organic working fluid 16 of the ORC. After this process is completed, the working fluid passes through the working fluid mixing valve 7, fully mixed with the hot working fluid, and then enters the dry cooling heat exchanger. The organic working fluid 16 is heated and vaporized in the evaporator 15. The high-pressure organic working fluid vapor is then introduced into the Rankine turbine 17, where it expands and generates work, driving the generator on the Rankine side to generate electricity. After the work energy is extracted, the organic working fluid vapor pressure and temperature decrease, and it enters the Rankine cycle's condensing heat exchanger 20. In condenser 20, the organic working fluid is condensed into a liquid state by forced air cooling from the dry-cooling heat exchanger fan 19. This liquid is then returned to the evaporator 15 by the working fluid pump 18, completing the organic Rankine cycle. Adjusting the opening of the electric valve 14 controls the ratio of heat output from the Brayton main circuit to the Rankine sub-circuit. When sufficient waste heat is available, valve 14 is opened to allow the ORC sub-circuit to participate in heat recovery, increasing overall power output. When core power decreases or additional power output is not required, valve 14 can be appropriately closed to reduce or shut off the flow of the Brayton working fluid through the evaporator 15, ensuring that the main circuit working fluid is primarily cooled by the dry-cooling heat exchanger 9 and maintaining system stability.

[0038] The other components and connection relationships of this embodiment are the same as those of the first embodiment.

[0039] Specific embodiment three: The lead-bismuth microreactor 1 described in this embodiment includes a reactor vessel 25, a radial reflection layer 24, a shielding layer 23 and a core module. The core module is located in the reactor vessel 25, and the outer side of the reactor vessel 25 is provided with a radial reflection layer 24 and a shielding layer 23 in sequence; the radial reflection layer 24 and the shielding layer 23 use neutron reflection materials to bounce neutrons that are not absorbed by the fuel back to the core to improve fuel utilization, and reduce the outward radiation dose of the core through radiation shielding materials.

[0040] like Figure 2 and Figure 3As shown, the core module comprises multiple fuel elements 21 and multiple control elements 22, each of which is a sealed structure. These multiple fuel elements 21 and multiple control elements 22 are enclosed in a reactor vessel 25, forming a compact, integrated, and integrated core module. The reactor vessel 25 is filled with a liquid lead-bismuth alloy coolant. During operation, the coolant is driven to flow between the core fuel elements, removing the high-temperature heat energy generated by fission. The lead-bismuth alloy coolant has a high boiling point and excellent thermal conductivity, enabling stable operation at high temperatures and transferring heat to the power conversion system without boiling.

[0041] Fuel elements 21, with varying enrichments, are compactly arranged in a regular triangle pattern within the microreactor core. Based on the design principles of fast reactors and pressurized water reactors, three different fuel elements 21 with enrichments of 20%, 30%, and 40% are installed within the core to create a zoned, optimized fuel arrangement. Control elements 22 are also included to regulate core reactivity. These contain neutron absorbers 35, which can be inserted or removed from the core during normal operation to precisely control the power level of the fission chain reaction. In the event of an abnormal operating condition, scram elements can be rapidly deployed into the core to absorb excess neutrons, instantly terminating the nuclear reaction and ensuring system safety.

[0042] Each fuel element 21 includes an upper fuel element plug 26, a fission gas cavity 27, an upper reflector 28, and fuel pellets 29; a fuel element wall 30, a lower reflector 31, and a lower fuel element plug 32. The fuel pellets 29 are located within the fuel element wall 30. The upper and lower fuel element plugs 26 and 32 are located at the upper and lower ends of the fuel element wall 30, respectively, to secure the fuel element and seal the interior of the element. Between the upper fuel element plug 26 and the lower fuel element plug 27, the fission gas cavity 27, the upper reflector 28, the fuel pellets 29, and the lower reflector 31 are located in this order. The upper and lower reflectors 28 and 31 reduce neutron leakage from the top and bottom of the core. A fuel element cavity 34 is reserved within the fuel element 21. The fission gas cavity 27 is formed at the top of the fuel element 21 to collect fission product gases released during fuel combustion and prevent excessive internal pressure within the element. A fuel element wall 30 is provided around the fuel element 21 to support and position the fuel element bundle and guide the flow of coolant.

[0043] Preferably, the reactor vessel 25, the fuel element wall 30, the fuel element upper end plug 26 and the fuel element lower end plug 32 are all made of T91 stainless steel; the upper reflective layer 28 and the lower reflective layer 31 are both magnesium oxide reflective layers; and the fuel pellets 29 are uranium dioxide pellets.

[0044] Each of the control elements includes a control element upper end plug 33, a control element cavity 34, a neutron absorber 35, a control element wall 36 and a control element lower end plug 37, wherein the neutron absorber 35 is located within the control element wall 36; the upper end and the lower end of the control element wall 36 are respectively provided with a control element upper end plug 33 and a control element lower end plug 37, wherein the control element upper end plug 33 is used to connect with the driving mechanism; a control element cavity 34 is provided between the neutron absorber 35 and the control element upper end plug 33.

[0045] Preferably, the neutron absorber 35 is a boron carbide neutron absorber;

[0046] This embodiment adheres to reactor physics and thermal-hydraulic design principles, referencing fast reactor layout principles. The core structure is constructed using a compact equilateral triangle arrangement, with fuel elements of three different fuel enrichments and rod diameters installed to achieve radial power flattening. The core module integrates the fuel elements and control components, and is encased in upper and lower reflectors, radial reflectors, and shielding layers, effectively improving neutron utilization and structural safety redundancy. The coolant in the reactor vessel 25 is a lead-bismuth eutectic alloy (Pb–Bi eutectic), which boasts high thermal conductivity and stability. The reactor is rated at 8 MWe. The fuel pellets 29 are made of mature uranium dioxide, and the cladding material is T91 stainless steel, which offers excellent corrosion resistance and high-temperature mechanical properties, making it suitable for high-density, high-temperature heat exchange conditions. Regarding the system's thermal structure, this invention proposes a combined nuclear microreactor-recompressed supercritical CO2 Brayton-organic Rankine dual cycle system. The Brayton cycle, based on supercritical CO2 as the working fluid, employs a recompression bypass to optimize cold-end compression power consumption, and a two-stage regenerator layout improves the main cycle's thermal efficiency. Its exhaust steam is diverted via an electric valve into the Rankine cycle's evaporator, where it exchanges heat with the Rankine cycle working fluid (such as R1233zd or low-pressure CO2), fully recovering previously unusable low-temperature thermal energy (approximately 80–120°C). By optimizing the temperature range of the Brayton cycle exhaust steam and the phase transition temperature of the Rankine cycle's organic working fluid, the system's overall waste heat utilization rate is significantly improved.

[0047] The other components and connection relationships of this embodiment are the same as those of the first or second embodiment.

[0048] In summary, the present invention achieves efficient power generation in a micro-nuclear reactor by combining a compact, integrated core design with an efficient thermodynamic cycle. The core utilizes multi-enrichment fuel elements 21 with control elements 22, supplemented by upper and lower reflectors 28 and 31, radial reflectors 24, and shielding 23. This improves fuel utilization and power density while ensuring reactor safety and controllability. A high-boiling-point lead-bismuth alloy is used as the coolant, ensuring reliable heat transfer within the reactor vessel 25. The power conversion system utilizes a Brayton-Rankine combined cycle for cascaded thermal energy utilization. The high-temperature section directly converts thermal energy into electricity via the Brayton cycle turbine 2, while the low-temperature waste heat section generates further electricity via the organic Rankine cycle turbine 17. The integration of the recompression and heat recovery Brayton main circuit and the organic Rankine waste heat recovery circuit significantly improves overall system thermal efficiency and reduces waste heat emissions. This embodiment boasts a compact structure and a clear thermodynamic flow, enabling stable and efficient nuclear power generation and is suitable for practical application in miniaturized, modular nuclear power plants.

[0049] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement of the above embodiments made according to the technical essence of the present invention, within the spirit and principles of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor, characterized in that: include: A lead-bismuth microreactor (1) comprises a reactor vessel (25), a radial reflection layer (24), a shielding layer (23) and a core module, wherein the core module is located in the reactor vessel (25), and the radial reflection layer (24) and the shielding layer (23) are sequentially provided on the outside of the reactor vessel (25); A Brayton cycle main loop comprises a Brayton cycle turbine (2), a high-temperature regenerator (4), a low-temperature regenerator (5), a working medium separation valve (6), a tube-fin heat exchanger (9), a cycle main compressor (10), a cycle recompressor (12) and a mixing valve (13), wherein the inlet of the Brayton cycle turbine (2) is connected to the high-temperature and high-pressure working medium outlet of the lead-bismuth microreactor (1); the outlet of the Brayton cycle turbine (2) is connected to the hot end inlet of the high-temperature regenerator (4); the hot end outlet of the high-temperature regenerator (4) is connected to the hot end inlet of the low-temperature regenerator (5); the hot end outlet pipeline of the low-temperature regenerator (5) is respectively connected to a first branch and a second branch through a working medium separation valve (6); the first branch is sequentially connected to the tube-fin heat exchanger (9) and the cycle main compressor (10), and the outlet of the cycle main compressor (10) is connected to the cold end inlet of the low-temperature regenerator (5); The second branch is compressed by the recirculating recompressor (12) and then directly outputted; the mixing valve (13) mixes the working fluid at the cold end outlet of the low-temperature regenerator (5) with the working fluid at the outlet of the recirculating recompressor (12), and transports the mixed working fluid to the cold end inlet of the high-temperature regenerator (4), and finally returns to the lead-bismuth microreactor (1), forming a closed cycle; The Rankine cycle sub-loop comprises an organic working fluid evaporator (15), a Rankine cycle turbine (17), a circulating working fluid pump (18) and a dry cooling heat exchanger (20). The hot side inlet of the organic working fluid evaporator (15) is connected to the outlet of the low-temperature regenerator (5) through an electric valve (14) for receiving waste heat; the Rankine cycle turbine (17) receives the high-pressure organic working fluid vapor generated by the organic working fluid evaporator (15) and expands and performs work to drive a generator to generate electricity; the outlet of the Rankine cycle turbine (17) is connected to the dry cooling heat exchanger (20), and the outlet end of the dry cooling heat exchanger (20) is connected to the organic working fluid evaporator (15) through the circulating working fluid pump (18), forming a closed loop.

2. The recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor according to claim 1, characterized in that: The core module comprises a plurality of fuel elements (21) and a plurality of control elements (22), wherein the control assembly (22) is located in the gaps between the fuel elements (21).

3. The recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor according to claim 1, characterized in that: The plurality of fuel elements (21) are of various enrichments and are compactly arranged at regular triangle intervals.

4. The recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor according to claim 3, characterized in that: The enrichment of the fuel element (21) is 20%, 30% and 40%.

5. A micro-reactor-based recompression Brayton-Rankine combined cycle power generation system according to any one of claims 2 to 4, characterized in that: Each fuel element (21) comprises a fuel element upper end plug (26), a fission gas cavity (27), an upper reflector (28), and a fuel pellet (29); a fuel element wall (30), a lower reflector (31), and a fuel element lower end plug (32); the fuel pellet (29) is located in the fuel element wall (30); the upper end of the fuel element wall (30) is provided with a fuel element upper end plug (26), and the lower end of the fuel element wall (30) is provided with a fuel element lower end plug (32); between the fuel element upper end plug (26) and the fuel element lower end plug (27), the fission gas cavity (27), the upper reflector (28), the fuel pellet (29), and the lower reflector (31) are sequentially provided from top to bottom.

6. The recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor according to claim 5, characterized in that: The reactor container (25) is made of T91 stainless steel and is filled with liquid lead-bismuth alloy coolant.

7. The recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor according to claim 5, characterized in that: The upper reflection layer (28) and the lower reflection layer (31) are both magnesium oxide reflection layers; the fuel pellets (29) are uranium dioxide pellets; the fuel element wall (30), the fuel element upper end plug (26) and the fuel element lower end plug (32) are all made of T91 stainless steel.

8. The recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor according to claim 1, characterized in that: Each of the control elements comprises a control element upper end plug (33), a control element cavity (34), a neutron absorber (35), a control element wall (36) and a control element lower end plug (37); the neutron absorber (35) is located in the control element wall (36); the upper end and the lower end of the control element wall (36) are respectively provided with a control element upper end plug (33) and a control element lower end plug (37); a control element cavity (34) is provided between the neutron absorber (35) and the control element upper end plug (33).

9. The recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor according to claim 8, characterized in that: The neutron absorber (35) is a boron carbide neutron absorber.

10. The recompression Brayton-Rankine combined cycle power generation system based on a micro-reactor according to claim 1, characterized in that: The shielding layer (23) is boron carbide, and the radial reflection layer (24) is magnesium oxide.

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