Cooling system and method for ocean floating nuclear energy platform reactor

Abstract

The invention relates to the technical field of reactor waste heat removal, in particular to a heat dissipation system and method for an ocean floating nuclear energy platform reactor, and the heat dissipation system comprises a loop subsystem, a natural circulation loop, a steam power generation subsystem and an ocean hot trap; the first loop subsystem comprises a reactor core, a pressure container and a coolant pipeline; the natural circulation loop comprises an intermediate heat exchanger, a seawater circulation pipeline and a waste heat discharge main pipeline, and the intermediate heat exchanger is connected with the loop subsystem through a coolant pipeline and used for discharging waste heat to the outside through natural circulation; the ocean heat trap takes external seawater as a final heat trap and is connected with a seawater circulating pipeline, a residual heat discharge main pipeline and a steam power generation subsystem; through the dual design of vapor-liquid separation and pressurization backflow prevention, the core condition for generating a condensation water hammer is avoided from the source, pipeline burst is effectively prevented, and the operation safety of the reactor heat dissipation system of the marine floating nuclear energy platform is remarkably improved.

Description

A heat dissipation system and method for a marine floating nuclear power platform reactor. Technical Field

[0001] This invention relates to the field of reactor waste heat removal technology, and specifically to a heat dissipation system and method for a marine floating nuclear power platform reactor. Background Technology

[0002] Against the backdrop of increasing demand for carbon emission reduction and marine resource development and utilization in the marine sector, nuclear energy, as a safe, economical, zero-carbon, and clean new energy source, has once again attracted global attention. Marine floating nuclear energy platforms are an organic combination of small modular reactors and marine floating structures, which can provide energy supply for near-shore and offshore islands and oil and gas extraction platforms. For such platforms, due to the space limitations of the floating structure's reactor compartment and the need to make full use of seawater for unlimited heat dissipation, their passive waste heat removal system usually adopts an equal-elevation design, that is, the heat exchanger is connected to the marine environment through two parallel horizontal pipes.

[0003] While such systems can fully utilize the abundant heat dissipation advantages of the marine environment and reduce the space requirements of the reactor compartment, they also bring serious challenges. The near-zero height difference between the heat source and the heat sink results in a relatively weak driving force for natural circulation. At the same time, during the open natural circulation process, the waste heat discharge pipe connected to the seawater side is prone to low-temperature seawater backflow. When the backflowing low-temperature seawater comes into direct contact with the high-temperature steam in the system, it will trigger a violent condensation water hammer phenomenon, generating transient pressure peaks of up to tens of megapascals. In severe cases, it can cause the steam pipe to burst, directly endangering the safe operation of the system.

[0004] Therefore, effectively suppressing condensate hammer is crucial for the engineering application of waste heat removal systems in marine nuclear power equipment. However, this work faces three major challenges: 1. The formation mechanism of condensate hammer is significantly affected by geometric structure and thermal parameters, making it difficult to apply suppression solutions universally across different application scenarios; 2. Condensate hammer often occurs during emergency shutdown accidents, and suppression methods must meet the passive property requirement, i.e., not relying on external power; 3. Systems designed for floating platforms have equal elevation differences and low-pressure operation characteristics, and the natural circulation driving force is already weak, so no suppression solution can increase additional flow resistance.

[0005] Given the aforementioned severe challenges and urgent needs, there is an urgent need in this field to develop an innovative method for suppressing condensate hammer. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a heat dissipation system and method for a marine floating nuclear energy platform reactor, which solves the problem that the driving force of natural circulation is relatively weak due to the near-zero height difference between the heat source and the heat sink in the prior art.

[0007] To solve the above problems, the technical solution of the present invention is as follows: A heat dissipation system for a marine floating nuclear power platform reactor includes a primary loop subsystem, a natural circulation loop, a steam power generation system, and a marine heat sink; the primary loop subsystem includes a reactor core 1, a pressure vessel 2, and coolant pipes 3, used to generate and transfer residual heat from the reactor core; the natural circulation loop includes an intermediate heat exchanger 5, a seawater circulation pipe 6, and a main residual heat discharge pipe 8, the intermediate heat exchanger 5 being connected to the primary loop subsystem via the coolant pipes 3, used to discharge residual heat to the outside through natural circulation; the marine heat sink 15 uses external seawater as the final heat sink and is connected to the seawater circulation pipe 6, the main residual heat discharge pipe 8, and the steam power generation system.

[0008] The steam generator system is connected to the waste heat discharge main pipeline 8.

[0009] Furthermore, the steam power generation system includes a gas duct 10, a centripetal turbine 11, a generator 12, a booster pump 13, and a steam flow pipe 14. The gas duct 10 is connected to the waste heat discharge main pipe 8, and the steam flow pipe 14 is connected to the marine heat trap 15.

[0010] Furthermore, the angle between the air guide pipe 10 and the waste heat discharge main pipe 8 in terms of heat flow advancement is 40-50 degrees.

[0011] Furthermore, a shut-off valve 7 is installed on the seawater circulation pipeline 6.

[0012] Furthermore, the intermediate heat exchanger 5 is provided with fins 4 to increase the contact area between the coolant and the seawater.

[0013] The heat dissipation method for a heat dissipation system of a marine floating nuclear power platform reactor includes the following steps: S1, primary loop subsystem operation: The residual heat generated by the reactor core 1 heats the coolant, making the coolant reach a vapor-liquid two-phase flow state. It flows into the intermediate heat exchanger 5 through the coolant pipe 3, and after exchanging heat with the low-temperature seawater inside, the coolant flows back to the reactor core 1. In this stage, the low-temperature seawater in the intermediate heat exchanger 5 absorbs heat and its temperature rises. The density difference caused by the temperature difference forms a buoyancy force, driving the seawater to flow along the coastal water circulation pipe 6 and the residual heat discharge main pipe 8 towards the marine heat sink 15, forming a natural circulation; S2, single-phase natural circulation stage: The residual heat discharge main pipe 8 contains single-phase high-temperature seawater. Because the seawater has a higher density, the pressure difference driving force in the area of ​​the gas guide pipe 10 is less than the gravity of the seawater. The high-temperature seawater flows directly into the marine heat sink along the residual heat discharge main pipe 8. 15. Steam power generation system does not intervene; S3. Vapor-liquid two-phase natural circulation stage: As heat exchange continues, the seawater in the intermediate heat exchanger 5 continues to absorb heat to boiling, forming a vapor-liquid two-phase flow and flowing into the waste heat discharge main pipe 8. When the vapor-liquid two-phase flow reaches the position of the gas guide pipe 10, under the action of the pressure difference inside and outside the system, the low-density high-temperature steam is separated and introduced into the gas guide pipe 10, while the high-density seawater continues to flow along the waste heat discharge main pipe 8 and is discharged to the ocean heat trap 15, thereby realizing vapor-liquid separation; S4. Steam power generation and pressurization to prevent backflow: The high-temperature steam flows through the centripetal turbine 11 to do work, driving the generator 12 to generate electricity. The generated electrical energy provides power for the booster pump 13. The booster pump 13 pressurizes the exhaust steam after it has done work, making the pressure inside the steam flow pipe 14 greater than the pressure outside the pipe. The exhaust steam is discharged to the ocean heat trap 15, while suppressing the backflow of low-temperature seawater.

[0014] Furthermore, in S3, vapor-liquid separation is driven by both the pressure difference between the inside and outside of the system and the density difference between the vapor and liquid phases, specifically satisfying the following conditions: ,in, , The pressure generated inside the intermediate heat exchanger 5 due to saturated boiling. The pressure at the outlet of the main waste heat discharge pipeline 8, connected to the marine heat trap 15, is close to standard atmospheric pressure. The density of high-temperature steam, The density of the circulating seawater, It is the acceleration due to gravity. The difference in inclination height of the air duct 10 is the vertical lifting height of the steam and seawater flowing inside the air duct 10.

[0015] Compared with existing technologies, this invention has the following advantages: Through the dual design of vapor-liquid separation and pressurization to prevent backflow, the core conditions for condensate hammer are avoided from the source. In the vapor-liquid two-phase stage, the pressure difference inside and outside the system and the density difference between vapor and liquid are used to achieve efficient separation of steam and seawater, avoiding direct contact between high-temperature steam and low-temperature seawater. At the same time, the pressurization pump makes the pressure inside the steam flow pipe greater than that outside the pipe, completely suppressing the backflow of low-temperature seawater, eliminating the transient high pressure caused by violent condensation, effectively preventing pipe rupture, and significantly improving the operational safety of the reactor heat dissipation system of the marine floating nuclear power platform.

[0016] The steam separation process relies on the system's own pressure difference and vapor-liquid density difference to trigger autonomously, without the need for human operation or external control. The booster pump is powered by high-temperature steam driving the centripetal turbine to generate electricity, without relying on an external power source. It fully meets the passive operation requirements under emergency shutdown, power outage and other accident conditions, and is suitable for the special operating conditions of marine floating nuclear power platforms.

[0017] The steam generator system is an independent branch, and the gas duct is connected to the main waste heat discharge pipeline at an inclined angle. It does not interfere with the main flow during the single-phase natural circulation stage, thus avoiding additional resistance to the natural circulation. After the steam-liquid separation, the seawater still flows smoothly along the main pipeline. Combined with the internal fins of the intermediate heat exchanger to expand the heat exchange area and enhance the heat transfer efficiency, it ensures that the driving force of the natural circulation is not affected, and achieves a balance between waste heat discharge efficiency and water hammer suppression effect.

[0018] Designed for the structural characteristics of high-altitude, low-pressure operation of marine floating nuclear power platforms, the system employs a separation mechanism driven by pressure and density differences. This mechanism can adapt to the condensate hammer suppression requirements under different geometric structures and thermal parameters, solving the problem of poor versatility of traditional solutions. The system has a simple structure and clear collaborative logic among its components, allowing it to be integrated into existing passive waste heat removal systems without complex modifications. This results in low engineering application costs and strong practicality. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the heat dissipation system structure of the present invention; Figure 2 is a schematic diagram of the condensation hammer suppression principle of the present invention; Figure 3 is a schematic diagram of the condensation hammer principle; Figure 4 is a schematic diagram of the operating principle of the present invention.

[0020] In the diagram: 1. Reactor core; 2. Pressure vessel; 3. Coolant piping; 4. Fins; 5. Intermediate heat exchanger; 6. Seawater circulation piping; 7. Shut-off valve; 8. Main exhaust pipe for residual heat; 9. Reactor compartment; 10. Gas duct; 11. Centripetal turbine; 12. Generator; 13. Booster pump; 14. Steam flow piping; 15. Marine heat sink. Detailed Implementation

[0021] This application provides a heat dissipation system and method for a marine floating nuclear power platform reactor. Through innovative vapor-liquid separation and passive steam power generation pressurization technology, it effectively suppresses condensate hammer and ensures system safety. The heat dissipation system is mainly composed of a primary loop subsystem, a natural circulation loop, a steam power generation system, and a marine heat sink 15, as shown in Figure 1. The specific structure is as follows: Primary loop subsystem: The reactor core 1 is encapsulated inside the pressure vessel 2. The two ends of the coolant pipe 3 are sealed and connected to the coolant outlet of the pressure vessel 2 and the coolant inlet of the intermediate heat exchanger 5, respectively, forming a closed loop circulation circuit.

[0022] Natural circulation loop: includes intermediate heat exchanger 5, seawater circulation pipe 6, and waste heat discharge main pipe 8. A shut-off valve 7 can be installed on the seawater circulation pipe 6 for maintenance or isolation. Fins 4 can be installed inside the intermediate heat exchanger 5 to increase the contact area between the coolant and the seawater and enhance heat transfer. The intermediate heat exchanger 5 is the heat exchange site between the primary loop subsystem and the natural circulation loop. The high-temperature coolant from the primary loop flows into the intermediate heat exchanger 5 through the coolant pipe 3, transferring its heat to the low-temperature seawater in the loop. The heated seawater, due to its reduced density, flows into the waste heat discharge main pipe 8 through the seawater circulation pipe 6 under the drive of buoyancy, and is finally discharged to the ocean heat trap 15, forming a natural circulation.

[0023] Steam power generation system: One end of the vent pipe 10 is welded to the side wall of the waste heat discharge main pipe 8. The angle between the vent pipe 10 and the waste heat discharge main pipe 8 in the direction of heat flow is set to 40°-50° to facilitate the separation and output of high-temperature steam. The other end of the vent pipe 10 is connected to the steam inlet of the centripetal turbine 11, the steam outlet of the centripetal turbine 11 and the power input end of the generator 12 through a coupling. The power output end of the generator 12 is electrically connected to the motor input end of the booster pump 13. The inlet of the booster pump 13 is connected to the exhaust steam outlet of the centripetal turbine 11. The outlet of the booster pump 13 is connected to the marine heat trap 15 through the steam flow pipe 14, forming a complete steam flow and energy conversion branch.

[0024] Ocean heat sink 15: It directly uses the external seawater in the sea area where the floating nuclear power platform is located as the final heat sink for the system's waste heat discharge. It is connected to the seawater circulation pipe 6, the main waste heat discharge pipe 8, and the steam flow pipe 14 to ensure efficient dissipation of waste heat.

[0025] The heat dissipation method of the present invention is based on the operating conditions of the system at different operating stages, and realizes the discharge of residual heat and suppression of condensate hammer in steps, as shown in Figure 4. The specific operation process is as follows: S1: Operation of the primary loop subsystem and establishment of natural circulation: The reactor is started, and the residual heat generated by the reactor core 1 heats the coolant inside it. The heated coolant flows into the intermediate heat exchanger 5 through the coolant pipe 3. In the intermediate heat exchanger 5, the high temperature coolant exchanges heat with the low temperature seawater on the shell side. After the coolant temperature decreases, it flows back to the reactor core 1 and is heated again, forming a primary loop. At the same time, the low temperature seawater in the intermediate heat exchanger 5 absorbs heat and its temperature rises. The density of the heated seawater decreases, and the density difference with the colder seawater in the loop forms a buoyancy force. This buoyancy force serves as the driving force for natural circulation, pushing the seawater along the coastal water circulation pipe 6 to the main residual heat discharge pipe 8 at a higher position.

[0026] Step S2: Single-phase natural circulation stage: In this stage, although the seawater in the intermediate heat exchanger 5 is heated, it does not reach a saturated boiling state. Therefore, the working fluid flowing into the waste heat discharge main pipe 8 is single-phase high-temperature seawater. Driven by natural circulation, the high-temperature seawater flows directly into the ocean heat trap 15 along the waste heat discharge main pipe 8. Since the working fluid is single-phase seawater with a relatively high density at this time, the pressure difference driving force acting on the air guide pipe 10 region is... The force required to overcome the gravity of seawater is less than the force needed to satisfy the inequality. Therefore, seawater will not enter the air duct 10, and the steam generator system is in standby mode, which does not add any resistance to the main natural circulation flow.

[0027] Step S3: Vapor-Liquid Two-Phase Natural Circulation Stage and Steam Separation: As heat exchange continues, the seawater in the intermediate heat exchanger 5 absorbs enough heat to reach saturation and begins to boil, forming a vapor-liquid two-phase flow. There is a risk of condensate hammer, the principle of which is shown in Figure 3. This two-phase flow enters the waste heat discharge main pipe 8. When it reaches the position of the gas guide pipe 10, vapor-liquid separation occurs, as shown in Figure 2. The separation process is driven by the pressure difference between the inside and outside of the system. With vapor-liquid phase density difference For a joint drive to occur, the following critical conditions must be met: ,in, , The pressure generated inside the intermediate heat exchanger 5 due to saturated boiling. The pressure at the outlet of the main waste heat discharge pipeline 8, connected to the marine heat trap 15, is close to standard atmospheric pressure. The density of high-temperature steam, The density of the circulating seawater, It is the acceleration due to gravity. The difference in inclination height of the air duct 10 is the vertical lifting height of the steam and seawater flowing inside the air duct 10.

[0028] Under these pressure and density differences, the net driving force on steam with extremely low density is... The value is positive, and it is drawn into the air duct 10, while the net driving force of the dense seawater is... Negative value The cross-sectional area of ​​the gas guide pipe 10 continues to flow along the main pipe, thereby achieving efficient and passive separation of steam and seawater. This avoids contact between the two in the main pipe from the source, suppresses the generation of condensate hammer, and the separated seawater single-phase flow continues to be discharged into the ocean heat trap 15.

[0029] Step S4: Steam Power Generation and Pressurization to Prevent Backflow: The high-temperature steam separated into the steam duct 10 first flows through the centripetal turbine 11. The steam expands within the turbine, converting its thermal energy into mechanical energy, driving the turbine to rotate. The centripetal turbine 11 directly drives the generator 12 to rotate and generate electricity. The electrical energy generated by the generator 12 is immediately supplied to the booster pump 13. The booster pump 13 pressurizes the low-pressure exhaust steam discharged from the centripetal turbine 11, and then discharges the pressurized exhaust steam to the marine heat trap 15 through the steam flow pipe 14. The core function of the booster pump 13 is to maintain the pressure within the steam flow pipe 14. The pressure is always higher than that of the seawater outside the pipe. The sum of the pressure head and the hydrostatic head of a section of seawater satisfies the pressure balance formula: ,in, The pressure condition, which is the height difference between the pipe outlet and the free liquid surface of the heat sink, ensures the smooth discharge of waste steam and fundamentally inhibits the possibility of low-temperature seawater flowing back through the steam flow pipe 14, thus forming a second line of defense against water hammer.

[0030] This application employs a dual design of vapor-liquid separation and pressurization to prevent backflow. On one hand, it utilizes the gas guide pipe 10 to achieve physical separation of steam and seawater, avoiding severe condensation. On the other hand, it maintains a positive pressure environment within the steam flow pipeline 14 through the booster pump 13, preventing low-temperature seawater backflow. This dual protection eliminates the damage to the pipeline caused by transient high pressure (tens of megapascals) generated by condensate hammer. The steam separation process is autonomously triggered by the system's own pressure difference and vapor-liquid density difference, requiring no manual operation. The booster pump 13 is powered by high-temperature steam driving the centripetal turbine 11 to generate electricity, completely independent of external power sources, and adaptable to emergency shutdown, power outage, and other accident conditions. The steam power generation system is an independent branch that does not intervene in the main flow during the single-phase natural circulation stage, thus not increasing the additional resistance of the natural circulation. The fins 4 within the intermediate heat exchanger 5 enhance heat exchange efficiency, ensuring that the natural circulation driving force is not affected, achieving a balance between waste heat removal efficiency and system safety.

[0031] The above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A heat dissipation system for a marine floating nuclear power platform reactor, characterized in that: It includes a primary loop subsystem, a natural circulation loop, a steam power generation system, and an ocean heat sink; the primary loop subsystem includes a reactor core (1), a pressure vessel (2), and coolant pipes (3) for generating and transferring residual heat from the reactor core; the natural circulation loop includes an intermediate heat exchanger (5), a seawater circulation pipe (6), and a main residual heat discharge pipe (8); the intermediate heat exchanger (5) is connected to the primary loop subsystem via the coolant pipes (3) for discharging residual heat to the outside through natural circulation; the ocean heat sink (15) uses external seawater as the final heat sink and is connected to the seawater circulation pipe (6), the main residual heat discharge pipe (8), and the steam power generation system; the steam power generation system is connected to the main residual heat discharge pipe (8).

2. The heat dissipation system according to claim 1, characterized in that: The steam generator system includes a gas duct (10), a centripetal turbine (11), a generator (12), a booster pump (13), and a steam flow pipe (14). The gas duct (10) is connected to the waste heat discharge main pipe (8), and the steam flow pipe (14) is connected to the marine heat trap (15).

3. The heat dissipation system according to claim 2, characterized in that: The angle between the air duct (10) and the waste heat discharge main pipe (8) in terms of heat flow is 40-50 degrees.

4. The heat dissipation system according to claim 1, characterized in that: A shut-off valve (7) is installed on the seawater circulation pipe (6).

5. The heat dissipation method according to claim 1, characterized in that: The intermediate heat exchanger (5) is equipped with fins (4) to increase the contact area between the coolant and the seawater.

6. A heat dissipation method for a heat dissipation system of a marine floating nuclear power platform reactor according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Operation of the primary loop subsystem: The residual heat generated by the reactor core (1) heats the coolant, making the coolant reach a vapor-liquid two-phase flow state. It flows into the intermediate heat exchanger (5) through the coolant pipe (3), and after exchanging heat with the low-temperature seawater inside, the coolant flows back to the reactor core (1). During this stage, the low-temperature seawater in the intermediate heat exchanger (5) absorbs heat and its temperature rises. The density difference caused by the temperature difference forms a buoyancy force, which drives the seawater to flow along the coastal water circulation pipe (6) and the residual heat discharge main pipe (8) to the ocean heat sink (15), forming a natural circulation. S2. Single-phase natural circulation stage: The residual heat discharge main pipe (8) contains single-phase high-temperature seawater. Because the seawater has a large density, the pressure difference driving force in the area of ​​the gas guide pipe (10) is less than the gravity of the seawater. The high-temperature seawater flows directly into the ocean heat sink (15) along the residual heat discharge main pipe (8), and the steam generator system does not intervene. S3. Steam- Liquid two-phase natural circulation stage: As heat exchange continues, the seawater in the intermediate heat exchanger (5) continues to absorb heat to boiling, forming a vapor-liquid two-phase flow and flowing into the waste heat discharge main pipe (8). When the vapor-liquid two-phase flow reaches the position of the gas guide pipe (10), under the action of the pressure difference inside and outside the system, the low-density high-temperature steam is separated and introduced into the gas guide pipe (10), while the high-density seawater continues to flow along the waste heat discharge main pipe (8) and is discharged to the ocean heat trap (15), thereby realizing vapor-liquid separation; S4, Steam power generation and pressurization to prevent backflow: The high-temperature steam flows through the centripetal turbine (11) to do work, driving the generator (12) to generate electricity. The generated electrical energy provides power for the booster pump (13). The booster pump (13) pressurizes the exhaust steam after it has done work, making the pressure inside the steam flow pipe (14) greater than the pressure outside the pipe. The exhaust steam is discharged to the ocean heat trap (15), while suppressing the backflow of low-temperature seawater.

7. The heat dissipation method according to claim 6, characterized in that: In S3, vapor-liquid separation is driven by both the pressure difference between the inside and outside of the system and the density difference between the vapor and liquid phases, specifically satisfying the following conditions: ,in, ， The pressure generated inside the intermediate heat exchanger (5) due to saturated boiling, The pressure at the outlet of the main heat exhaust pipe (8) connected to the marine heat trap (15) is close to standard atmospheric pressure. The density of high-temperature steam, The density of the circulating seawater, It is the acceleration due to gravity. The difference in inclination height of the air duct (10) is the vertical lifting height of the steam and seawater flowing in the air duct (10).

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