A molten salt reactor cooling system with check valves

Abstract

The application discloses a molten salt reactor cooling system with a check valve, which comprises a reactor core, a primary loop pipeline, a primary loop heat exchanger, a secondary loop pipeline, a secondary loop heat exchanger, a check valve, air cooling equipment and an air cooling tower. The reactor core is connected with the primary loop heat exchanger through the primary loop pipeline, the secondary side of the primary loop heat exchanger is connected with the secondary loop pipeline which is divided into a heat exchange branch and a waste heat discharge branch, and the waste heat discharge branch is connected with the check valve in series. The primary loop pipeline and the secondary loop pipeline form independent passive circulation loops by means of the vertical center elevation difference of the equipment during shutdown. The application can lead out the decay heat without discharging the fuel salt of the reactor core, and can eliminate the risk of radioactive medium transfer leakage. A single set of secondary loop pipelines is shared, so that the matching equipment is simplified. The pipeline self-heat preservation is realized by means of the pressure difference of the pipelines in normal conditions and the check valve, and the whole line electric heat tracing device is saved. During shutdown, the secondary loop heat exchanger can be physically isolated and degraded to a non-safety class equipment, so that the high inherent operation safety and the project construction and operation economy are simultaneously considered.

Description

Technical Field

[0001] This invention belongs to the field of molten salt reactor thermal management technology, specifically relating to a molten salt reactor cooling system with a one-way valve. Background Technology

[0002] Liquid fuel molten salt reactors are fourth-generation nuclear reactors. Compared with other types of nuclear reactors, they have a variety of fuel options, high utilization rate, operate at atmospheric pressure, have good inherent safety and economy, and are waterless and flexible in site selection.

[0003] Even after a planned shutdown or emergency shutdown following an accident, decay heat continues to be generated. This residual heat remains substantial for a considerable period and must be removed to the final heat sink via a specially designed residual heat removal system. Otherwise, the accumulated heat within the reactor will cause a temperature rise, potentially leading to the failure of the reactor safety barrier, resulting in the release of radioactivity and a serious nuclear safety accident.

[0004] The earliest passive heat transfer concept for molten salt reactors was disclosed in the Oak Ridge National Laboratory's MSRE project in the 1960s. Subsequent patents (CN201310286718.7, CN201610899803.4, CN201710566887.4, and CN202011538069.1) all followed this basic principle, relying entirely on water as the heat transfer medium. This technology is only suitable for extreme accident scenarios where the core circuit is damaged and all fuel salt must be transferred to a brine tank. Clearly, this approach relies on water resources, making it unsuitable for arid regions. Furthermore, it only addresses extreme accidents requiring fuel salt removal and is completely unsuitable for planned shutdowns where equipment is intact and salt removal is not necessary, or for most conventional accident scenarios. Moreover, the transfer of fuel salt from the core to the brine tank involves delays, and the pipelines and tanks pose a risk of radioactive leakage during the transfer process, resulting in insufficient safety redundancy.

[0005] In response to water shortage scenarios, CN202411593809.X disclosed a solution for removing residual heat from a waterless cooling salt tank, but it still has not escaped the core limitation of "requiring the core fuel salt to be discharged to the storage tank for heat dissipation", and still cannot solve the problem of residual heat removal under the condition that the core loop is intact.

[0006] CN202511005019.X discloses a three-flow structure heat exchanger supporting molten salt reactor cooling system, the core improvement idea of which is to divide the independent heat exchange flow channel in the primary loop heat exchanger, respectively pass in the waste heat discharge medium and the conventional secondary loop heat transfer medium, and complete the heat exchange with the reactor core fuel salt at the same time. However, in order to accommodate two heat exchange fluids, the overall volume of the primary loop heat exchanger is greatly increased, the manufacturing and processing difficulty of the equipment is significantly improved, and the cost is also significantly improved; at the same time, after the expansion of the heat exchanger, more expensive radioactive fuel salt needs to be filled, which greatly increases the overall construction cost of the reactor and seriously reduces the economic competitiveness of the molten salt reactor project. SUMMARY

[0007] In order to solve the problem that the existing waste heat discharge system of the molten salt reactor must discharge the reactor core fuel salt, which has the risk of leakage of radioactive medium transfer, or the volume of the heat exchanger is expanded and the filling cost of the fuel salt is high, the present application aims to provide a molten salt reactor cooling system with a one-way valve.

[0008] The molten salt reactor cooling system with a one-way valve according to the present application comprises a reactor core, a primary loop pipeline, a primary loop heat exchanger, a secondary loop pipeline, a secondary loop heat exchanger, a one-way valve, an air cooling device and an air cooling tower; the reactor core is connected to the primary loop heat exchanger through the primary loop pipeline; the secondary side of the primary loop heat exchanger is connected to the secondary loop pipeline, which is divided into a heat exchange branch and a waste heat discharge branch in parallel, the heat exchange branch is connected to the secondary loop heat exchanger, and the waste heat discharge branch is connected in series with the one-way valve and the air cooling device; the primary loop pipeline flows with the primary loop medium, and under the shutdown condition, the first passive circulation loop is formed by the first equipment center vertical height difference between the reactor core and the primary loop heat exchanger to guide the decay heat out of the reactor core; the secondary loop pipeline flows with the secondary loop medium, and under the shutdown condition, the second passive circulation loop is formed by the second equipment center vertical height difference between the primary loop heat exchanger and the air cooling device only in the waste heat discharge branch. The present application can continuously guide the decay heat without transferring the fuel salt in the reactor core by setting two levels of passive circulation loops driven by the equipment center vertical height difference, and setting parallel double-function branches with a single secondary loop pipeline, which can eliminate the leakage risk of radioactive medium caused by the transfer of fuel salt, simplify the system pipeline supporting equipment, and also does not need to expand the primary loop heat exchanger, thereby reducing the filling amount of expensive radioactive heat transfer medium and the overall cost of the equipment.

[0009] In a preferred embodiment, the heat exchange branch is provided with an isolation valve; the isolation valve is opened during normal reactor operation and closed during reactor shutdown; after the isolation valve cuts off the outflow and return passages of the heat exchange branch, the secondary loop heat exchanger is separated from the safety boundary of the residual heat removal system and complies with non-safety-class equipment manufacturing standards. According to the present invention, by synchronously providing switchable isolation valves at both the outflow and return ends of the heat exchange branch to achieve complete physical isolation during reactor shutdown, the secondary loop heat exchanger can be excluded from the safety management and control system of the residual heat removal system, the manufacturing and inspection safety standards for this equipment can be lowered, and the equipment construction and long-term operation and maintenance costs can be significantly reduced.

[0010] In a preferred embodiment, the check valve is a fluid diode; during normal reactor operation, the secondary circulating pump matched with the secondary loop heat exchanger generates a pipeline pressure difference, which drives a trace amount of secondary loop medium to continuously flow backward through the check valve and the residual heat removal branch, and the nuclear heat of the reactor core itself is relied on to maintain the pipeline temperature of the residual heat removal branch. According to the present invention, the high reverse resistance characteristic of the fluid diode ensures that only a trace amount of the secondary loop medium is diverted to the residual heat removal branch for circulation during normal reactor operation, the nuclear heat of the reactor itself can be used to continuously keep all pipelines of the residual heat removal system warm, the full-line electric heat tracing supporting equipment is omitted, the number of system supporting equipment is reduced, the long-term operation energy consumption is lowered, and the problem that the heat transfer medium solidifies at normal temperature and blocks the pipeline is fundamentally avoided at the same time.

[0011] In a preferred embodiment, the residual heat removal branch is connected in series with an auxiliary circulating pump; when the vertical elevation difference of the second equipment center is insufficient to drive the second passive circulation loop, the auxiliary circulating pump supplements the driving force for fluid circulation. According to the present invention, by adding the auxiliary circulating pump on the residual heat removal branch as a backup power source, the stable operation of the second passive circulation loop can be guaranteed when the driving force of gravity natural circulation is insufficient, and the operation redundancy of the residual heat removal system and the adaptability to extreme accident conditions are improved.

[0012] In a preferred embodiment, the primary loop pipeline includes a reactor core outflow pipeline, a reactor core return pipeline, and a primary circulating pump; the reactor core outflow pipeline connects the reactor core outlet with the primary side inlet of the primary loop heat exchanger, and the reactor core return pipeline connects the reactor core inlet with the primary side outlet of the primary loop heat exchanger. According to the present invention, an independent gravity passive circulation flow channel is constructed on the primary loop pipeline, which can continuously derive the decay heat of the reactor core after the primary circulating pump unit fails and the reactor is shut down, without discharging the reactor core fuel salt to an external storage tank for heat dissipation, thus avoiding the dual risks of fuel salt transfer delay and radioactive medium leakage.

[0013] In a preferred embodiment, the secondary loop pipeline includes a main outflow pipeline and a main return pipeline. One end of the main outflow pipeline connects to the secondary side outlet of the primary loop heat exchanger, and the other end branches to connect to a heat exchange branch and a waste heat discharge branch. One end of the main return pipeline connects to the secondary side inlet of the primary loop heat exchanger, and the other end branches to connect to a heat exchange branch and a waste heat discharge branch. This invention, through an integrated structure where a single set of secondary loop pipelines branches to form two parallel functional branches, abandons the conventional design approach of two completely independent loops, reduces the number of supporting equipment, simplifies plant pipeline layout, and lowers civil construction and equipment procurement costs.

[0014] In a preferred embodiment, the air-cooling device is arranged inside an air-cooling tower, and the outside of the air-cooling device directly exchanges heat with the air inside the air-cooling tower through convection, with the heat being directly discharged into the atmospheric environment. This invention, by embedding the air-cooling device within an air-cooling tower and directly using atmospheric air as the final heat sink, enables waste heat discharge without relying on water resources throughout the entire process. This breaks the rigid limitations of traditional water-cooled waste heat systems on the site's water source and broadens the range of molten salt reactor site selection.

[0015] In a preferred embodiment, a third vertical elevation difference between the center of the air-cooled equipment and the top of the air-cooled tower creates natural air convection within the tower. This invention utilizes the elevation difference between the air-cooled equipment and the top of the tower to create a chimney-like natural draft, achieving air convection cooling even without a fan, thus improving the ability to remove waste heat during a plant-wide power outage.

[0016] In a preferred embodiment, the air-cooled tower is equipped with an airflow control valve; the airflow control valve is closed during normal reactor operation; and the airflow control valve is opened passively during reactor shutdown. This invention, through an airflow control valve linked to reactor operating conditions, can reduce heat loss and ensure reactor thermal efficiency during normal operation, while automatically enhancing ventilation and heat dissipation capacity during shutdown accidents, thus balancing system operating economy and the safety of residual heat removal during shutdown.

[0017] In a preferred embodiment, the secondary side of the secondary loop heat exchanger is connected to a tertiary loop pipeline, which is a power generation loop pipeline, an energy storage loop pipeline, or a heating loop pipeline. This invention broadens the universal compatibility of the entire device by allowing the same molten salt reactor cooling system to adapt to different thermal application scenarios such as power generation, energy storage, and heating, thereby improving equipment reusability and reducing the research and development and construction costs of designing separate cooling systems for different scenarios.

[0018] The molten salt reactor cooling system with a one-way valve according to the present invention adopts a passive circulation loop driven by a two-stage vertical center elevation difference, combined with a shared secondary loop pipeline dual-branch overall architecture. On the one hand, it can remove decay heat without discharging the reactor core fuel salt, eliminating the risk of radioactive transfer and leakage; on the other hand, it does not require expansion of the primary loop heat exchanger, reducing the amount of expensive radioactive media filling; during normal operation, it relies on reverse micro-circulation of fluid diodes to achieve pipeline self-insulation, eliminating the need for full-line electric heat tracing; during reactor shutdown, the isolation valve can isolate the secondary loop heat exchanger, allowing it to adopt non-safety-grade manufacturing standards; the system has fewer supporting equipment, lower construction costs and operating energy consumption, and can still stably discharge residual heat by gravity when the entire plant is powered off and there is no external power. It simultaneously solves the multiple defects of existing solutions, such as high leakage risk, high cost, complex equipment, and pipeline freezing, and has both high inherent safety and project economic advantages. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of a molten salt reactor cooling system with a one-way valve according to a preferred embodiment of the present invention, showing the direction of fluid flow under shutdown conditions.

[0020] Figure 2 yes Figure 1 A schematic diagram of the principle of a one-way valve.

[0021] Figure 3 yes Figure 1 A schematic diagram of the fluid flow direction of a molten salt reactor cooling system under normal operating conditions. Detailed Implementation

[0022] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0023] like Figure 1 As shown, the molten salt reactor cooling system with a one-way valve according to the present invention includes a reactor core 1, a primary loop pipe 2, a primary loop heat exchanger 3, a secondary loop pipe 4, a secondary loop heat exchanger 5, a one-way valve 6, an air-cooled device 7, an air-cooled tower 8, a primary circulation pump 10, a secondary circulation pump 11, an auxiliary circulation pump 12, isolation valves 13-1 and 13-2, and an airflow control valve 15.

[0024] In this article, the vertical elevation difference of the equipment center refers to the vertical elevation difference of the geometric center of the corresponding equipment. When the system is arranged, the installation elevation of the core 1 is lower than that of the primary loop heat exchanger 3, and the installation elevation of the primary loop heat exchanger 3 is lower than that of the air-cooled equipment 7. The gravity circulation driving force is provided by the installation elevation difference.

[0025] In this paper, the primary side of the primary loop heat exchanger 3, the secondary loop heat exchanger 5, and the air-cooled equipment 7 refers to the heat source side, and the secondary side refers to the heat load side (i.e., the cold side). The fluid on the primary side transfers heat to the fluid on the secondary side through heat exchange via the indirect heat exchanger. For example, in a shell-and-tube heat exchanger, if the heat source fluid flows inside the tubes, the inside of the tubes is the primary side, and the outside of the tubes is the secondary side. Alternatively, the heat source fluid can flow outside the tubes, in which case the outside of the tubes is the primary side, and the inside of the tubes is the secondary side, depending on which side the heat source is on. Specifically, the primary loop medium in the primary loop pipe 2 and the secondary loop medium in the secondary loop pipe 4 exchange heat in the primary loop heat exchanger 3, and the secondary loop medium in the secondary loop pipe 4 and the medium in the tertiary loop pipe (not shown) exchange heat in the secondary loop heat exchanger 5. The primary loop medium and the secondary loop medium are solid at room temperature but become liquid after heating; they can be molten salts or liquid metals. It should be understood that the structural forms of the primary heat exchanger 3, the secondary heat exchanger 5, and the air-cooled equipment 7 can be varied, such as U-tube type, spiral tube type, plate type, etc.

[0026] 1) First loop

[0027] The reactor core 1 is connected to the primary side of the primary heat exchanger 3 via the primary loop pipe 2 and the primary circulation pump 10. There is a vertical elevation difference between the equipment center of the reactor core 1 and the primary loop heat exchanger 3. The primary loop pipe 2, the primary circulation pump 10, and the primary side of the primary loop heat exchanger 3 together constitute the primary heat exchange loop.

[0028] Core 1 includes core inlet 1-1 and core outlet 1-2. The molten fuel salt flowing inside core 1 is the primary circuit medium. Core outlet 1-2 is the outlet end of the high-temperature primary circuit medium, and core inlet 1-1 is the return end of the cooled primary circuit medium.

[0029] The primary side of the primary circuit heat exchanger 3 is equipped with a primary side inlet 3-1 and a primary side outlet 3-2.

[0030] The primary loop piping 2 is divided into core outflow piping 2-1 and core return piping 2-2. Core outflow piping 2-1 is connected to the core outlet 1-2 and the primary side inlet 3-1 of the primary loop heat exchanger 3, respectively. Core return piping 2-2 is connected to the core inlet 1-1 and the primary side outlet 3-2 of the primary loop heat exchanger 3, respectively. Core 1, core outflow piping 2-1, the primary side of the primary loop heat exchanger 3, and core return piping 2-2 form a closed-loop primary heat exchange loop.

[0031] The primary circulation pump 10 is connected in series in the primary side flow channel of the primary loop heat exchanger 3. The primary circulation pump 10 can be integrated with the primary loop heat exchanger 3 into a common tank structure, or it can be arranged separately.

[0032] Under normal operating conditions, the primary loop medium flow is powered by the primary circulation pump 10, which forces circulation to remove core heat and transfer it to the secondary side of the primary loop heat exchanger 3.

[0033] When a reactor shutdown or primary circulation pump 10 fails and stops, a first passive circulation loop is formed based on the vertical elevation difference H1 between the equipment centers of reactor core 1 and primary loop heat exchanger 3: the high-temperature medium in the reactor core has a low density and flows upward. After being cooled by heat exchange in primary loop heat exchanger 3, the medium density increases and flows downward back, without the need for external power to continuously remove residual heat from the reactor core.

[0034] This invention allows for the direct extraction of residual core heat when the core circuit is intact through the first passive circulation loop. The entire process does not require the transfer of fuel salt, nor does it require increasing the volume of the primary loop heat exchanger or filling a large amount of expensive radioactive heat transfer medium, thus significantly reducing equipment manufacturing and fuel procurement costs.

[0035] 2) Second circuit

[0036] The secondary side of the primary loop heat exchanger 3 is connected to the secondary loop pipe 4. The secondary loop pipe 4 is divided into two parallel branches, which are respectively connected to the secondary loop heat exchanger 5 and the air-cooled equipment 7. The secondary loop heat exchanger 5 is equipped with a secondary circulation pump 11 to form the normal heat exchange branch, and the air-cooled equipment 7 is equipped with a one-way valve 6 and an auxiliary circulation pump 12 to form the waste heat discharge branch. The secondary loop pipe 4, the secondary loop heat exchanger 5, the air-cooled equipment 7, and the one-way valve 6 together form the secondary diversion loop.

[0037] The secondary loop heat exchanger 5 is equipped with a primary side inlet 5-1 and a primary side outlet 5-2.

[0038] The air-cooled equipment 7 is equipped with a primary side inlet 7-1 and a primary side outlet 7-2.

[0039] The primary loop heat exchanger 3 has a secondary side inlet 3-3 and a secondary side outlet 3-4, which correspond to the low-temperature reflux and high-temperature outflow of the secondary loop, respectively.

[0040] The secondary loop pipeline 4 is divided into a main outflow pipeline 4-1 and a main return pipeline 4-2. The two pipelines branch off at the end to form two parallel branches.

[0041] One end of the main outflow pipe 4-1 connects to the secondary side outlet 3-4 of the primary loop heat exchanger 3, and the other end branches into heat exchange branch 4-1-1 and waste heat discharge branch 4-1-2. Heat exchange branch 4-1-1 connects to the primary side inlet 5-1 of the secondary loop heat exchanger 5, and an isolation valve 13-1 is connected in series on the branch. Waste heat discharge branch 4-1-2 connects to the primary side inlet 7-1 of the air-cooled equipment 7, and an auxiliary circulating pump 12 is connected in series on the branch.

[0042] One end of the main return pipe 4-2 connects to the secondary inlet 3-3 of the primary loop heat exchanger 3, and the other end branches into heat exchange branch 4-2-1 and waste heat discharge branch 4-2-2. Heat exchange branch 4-2-1 connects to the primary outlet 5-2 of the secondary loop heat exchanger 5, with a disconnect valve 13-2 connected in series on the branch. Waste heat discharge branch 4-2-2 connects to the primary outlet 7-2 of the air-cooled equipment 7, with a check valve 6 connected in series in the middle of the branch. It should be understood that there may be more than one check valve 6.

[0043] The secondary circulation pump 11 is connected in series in the primary side flow channel of the secondary loop heat exchanger 5. The secondary circulation pump 11 can be integrated with the secondary loop heat exchanger 5 into a common tank structure, or it can be arranged separately.

[0044] Under normal operating conditions, the flow power of the secondary loop medium is provided by the secondary circulation pump 11, which transfers heat to the secondary side of the secondary loop heat exchanger 5 through forced circulation.

[0045] When a reactor shutdown or secondary circulation pump 11 fails and stops, a second passive circulation loop is formed based on the vertical elevation difference H2 between the equipment centers of the primary loop heat exchanger 3 and the air-cooled equipment 7.

[0046] The auxiliary circulation pump 12 is connected in series in the waste heat discharge branch 4-1-2. When the vertical elevation difference H2 between the equipment centers of the primary heat exchanger 3 and the air-cooled equipment 7 is insufficient, and the natural circulation driving force is insufficient, the auxiliary circulation pump 12 can serve as a backup power source to ensure the stable operation of the second passive circulation loop and improve the system's operational redundancy under emergency conditions. It should be understood that the positions of the auxiliary circulation pump 12 and the one-way valve 6 can be interchanged, or both can be connected in series in the waste heat discharge branch 4-1-2 or 4-2-2; omitting the auxiliary circulation pump 12 and relying solely on the vertical elevation difference H2 between the equipment centers to drive the second passive circulation loop is entirely feasible.

[0047] The air-cooled unit 7 is entirely housed inside the air-cooled tower 8. The outer side of the air-cooled unit 7 (i.e., the secondary side) directly exchanges heat with the air inside the air-cooled tower 8 via convection. Natural air convection is formed by the vertical elevation difference H3 between the center of the air-cooled unit 7 and the top of the air-cooled tower 8, and the heat generated is directly discharged into the atmosphere. It should be understood that the air-cooled tower 8 can also be equipped with a fan 14, which serves as a backup power source for airflow when the vertical elevation difference H3 is insufficient.

[0048] Air-cooled tower 8 is equipped with an airflow control valve 15, which is used to regulate the airflow within the tower. During normal reactor operation, the airflow control valve 15 is closed, with only a small airflow undergoing natural convection heat exchange on the secondary side of the air cooler 7. This maintains natural circulation by creating a small temperature difference in the exhaust loop fluid while ensuring minimal heat loss during normal reactor operation. In the event of a planned reactor shutdown or a partial accident shutdown, the airflow control valve 15 opens immediately via a passive mechanism, increasing the ventilation and heat exchange flow of the air-cooled equipment 7, allowing sufficient air to flow through the equipment for full-load heat dissipation. The passive opening mechanism can be achieved through electromagnetism, gravity, pneumatics, etc.

[0049] Isolation valves 13-1 and 13-2 are connected in series on the primary side inlet and outlet pipes of the secondary loop heat exchanger 5, respectively. They can be electric valves, pneumatic valves, or other actuation methods. Under normal reactor operation, the valves remain open to ensure the flow of heat exchange branches; under planned shutdown or accident shutdown, the valves close synchronously to physically isolate the secondary loop heat exchanger 5 from the residual heat discharge branch.

[0050] 3) Three-circuit

[0051] The secondary loop heat exchanger 5 is equipped with a secondary side inlet 5-3 and a secondary side outlet 5-4, which are respectively connected to a tertiary loop pipeline (not shown in the figure). The tertiary loop pipeline can be a power generation loop pipeline, an energy storage loop pipeline, or a heating loop pipeline. The medium in the power generation loop pipeline may be a thermodynamic circulation medium such as water vapor or supercritical carbon dioxide. The medium in the energy storage loop pipeline may be tertiary loop molten salt or other fluids. The medium in the heating loop pipeline may be tertiary loop molten salt or steam.

[0052] like Figure 2 As shown, the one-way valve 6 adopts a fluid diode structure, featuring low resistance in the forward direction and high resistance in the reverse direction: the flow resistance coefficient is extremely small when the fluid flows in the forward direction as shown in the figure, and extremely large when flowing in the reverse direction, allowing only a small amount of fluid to pass through in the reverse direction. The one-way valve 6 is made of high-temperature and corrosion-resistant alloy material, suitable for high-temperature molten salt flow conditions, and has no easily clogged sealing structure, ensuring long-term stable flow of molten salt media.

[0053] One-way valve 6 is arranged in series on waste heat discharge branches 4-1-2 and 4-2-2, working in conjunction with the dual-branch diversion structure of the secondary circuit pipeline to produce a dual technical effect:

[0054] Normal operating conditions: The operation of the secondary circulation pump 11 creates a negative pressure at the inlet and a positive pressure at the outlet of the primary side of the secondary loop heat exchanger. The pressure difference in the pipeline drives the secondary loop medium to continuously flow through the waste heat discharge branches 4-2-2 and 4-1-2. Due to the extremely high reverse resistance coefficient of the one-way valve 6, only a small amount of the fluid is allowed to flow in reverse. The heat loss of the waste heat discharge branches 4-2-2 and 4-1-2 is continuously replenished by the nuclear heat of the reactor itself. There is no need to add an additional electric heat tracing and insulation device for the entire line, which avoids the medium solidifying and blocking the pipes at room temperature. Compared with the traditional solution of adding a complete set of heat tracing equipment for the independent waste heat discharge branch, the number of equipment is reduced and the long-term operating energy consumption is reduced.

[0055] Reactor shutdown condition: Secondary circulation pump 11 is shut down, and the secondary loop medium circulates in one direction along the path of "secondary side outlet of primary loop heat exchanger 3 → air-cooled equipment 7 → check valve 6 → secondary side inlet of primary loop heat exchanger 3". Since the positive resistance coefficient of check valve 6 is extremely small, it allows a large flow rate of the fluid to flow in the positive direction, ensuring the stable and continuous discharge of decay heat.

[0056] All pipes and heat exchanger equipment in the system can be covered with heat tracing and insulation devices. The insulation and covering function to reduce heat loss under normal operating conditions and assist in preventing freezing and blockage in micro-circulation. The primary and secondary loop media can be selected from fluoride salts, chloride salts, or lead-bismuth alloy liquid metals. They are solid at room temperature and pressure and completely liquefy within the operating temperature range. The two loops can use the same or different heat transfer media.

[0057] The following briefly describes two operating conditions of the molten salt reactor cooling system with a one-way valve of the present invention.

[0058] 1) such as Figure 3 As shown, the reactor is operating normally.

[0059] The primary loop medium flow includes: the primary loop medium absorbs nuclear heat and heats up inside the reactor core 1, and then flows along the core outlet 1-2 → core outflow pipeline 2-1 → primary side inlet 3-1 of the primary loop heat exchanger 3 to enter the primary side of the primary loop heat exchanger 3 to complete heat exchange and cooling; after cooling, it flows back to the reactor core 1 through the primary side outlet 3-2 of the primary loop heat exchanger 3 → core return pipeline 2-2 → core inlet 1-1, and the circulation power is continuously provided by the primary circulation pump 10.

[0060] The flow direction of the secondary medium in the heat exchange branch includes: the secondary medium absorbs heat and rises in temperature on the secondary side of the primary heat exchanger 3, flows out from the secondary side outlet 3-4 of the primary heat exchanger 3 into the main outflow pipe 4-1, flows into the heat exchange branch 4-1-1 through the normally open isolation valve 13-1 → the primary side inlet 5-1 of the secondary heat exchanger 5; inside the secondary heat exchanger 5, it transfers heat to the tertiary medium, and after cooling, it flows through the primary side outlet 5-2 of the secondary heat exchanger 5, the normally open isolation valve 13-2, and the heat exchange branch 4-2-1. Most of the medium enters the main return pipe 4-2, and finally flows back to the secondary side of the primary heat exchanger 3 through the secondary side inlet 3-3. The circulation power is provided by the secondary circulation pump 11.

[0061] The secondary loop medium flow direction in the waste heat discharge branch includes: the secondary circulation pump 11 generates pipeline pressure difference during operation, the secondary loop medium is slightly diverted to the waste heat discharge branch 4-2-2 after passing through the heat exchange branch 4-2-1, flows in reverse through the one-way valve 6, enters the primary side outlet 7-2 of the air-cooled equipment 7, after slight heat dissipation by the air-cooled equipment 7, flows out from the primary side inlet 7-1 of the air-cooled equipment 7, and merges into the heat exchange branch 4-1-1 along the waste heat discharge branch 4-1-2; the continuous forced flow of the small amount of secondary loop medium keeps the waste heat discharge branches 4-2-2 and 4-1-2 at a high temperature throughout, automatically preventing the medium from solidifying, and eliminating the need for an external electric heat tracing device for the entire line.

[0062] The air volume control valve 15 of the air-cooled tower 8 remains closed, allowing only a small amount of air to circulate naturally, reducing heat loss during normal operation of the nuclear reactor.

[0063] 2) such as Figure 1 As shown, planned shutdown / emergency shutdown due to accident

[0064] The primary circulation pump 10 and the secondary circulation pump 11 stop operating; the isolation valves 13-1 and 13-2 close synchronously, completely isolating the heat exchange branches 4-1-1 and 4-2-1; the air volume control valve 15 of the air-cooled tower is passively and automatically opened by gravity / electromagnet / pneumatic force.

[0065] The first passive circulation loop (primary heat exchange loop, relying on the vertical elevation difference H1 between the equipment centers) includes: the core decay heat continuously heats the primary loop medium, the high-temperature medium density decreases and flows upward, entering the primary side of the primary loop heat exchanger 3 along the core outlet 1-2 and the core outflow pipe 2-1 to release heat; the medium with increased density after cooling flows back to the core inlet 1-1 along the core return pipe 2-2 by gravity, continuously and stably removing the core residual heat, without the need to discharge the radioactive fuel salt inside the core throughout the process.

[0066] The second passive circulation loop (only the waste heat discharge branch, with the vertical elevation difference H2 at the center of the equipment cooperating with the one-way valve 6) includes: the secondary medium, after absorbing heat on the secondary side of the primary heat exchanger 3, becomes less dense and flows upward, flowing into the primary side inlet 7-1 of the air-cooled equipment 7 along the secondary side outlet 3-4 of the primary heat exchanger 3 → the main outflow pipe 4-1 → the waste heat discharge branch 4-1-2; the medium transfers heat to the atmospheric air in the air-cooled equipment 7, and after cooling, becomes more dense and flows downward, passing through the one-way valve 6 in the positive direction through the primary side outlet 7-2 of the air-cooled equipment 7, and entering the main return pipe 4-2 along the waste heat discharge branch 4-2-2, returning to the secondary side inlet 3-3 of the primary heat exchanger 3, forming a complete closed natural circulation; if the driving force of the vertical elevation difference H2 at the center of the equipment is insufficient, the auxiliary circulation pump 12 can be started to supplement the circulation power.

[0067] Since there is no cold source for heat exchange in the secondary loop heat exchanger 5 after the reactor is shut down, there is no difference in the cold and hot density of the secondary loop medium in the heat exchange branches 4-1-1 and 4-2-1, so natural circulation cannot be established. Only the residual heat is discharged through the branch 4-1-2, and 4-2-2 forms a stable second passive circulation loop.

[0068] After the isolation valves 13-1 and 13-2 are closed, the heat exchange branches 4-1-1 and 4-2-1 are completely cut off, and there is no fluid flow in the branches. The secondary loop heat exchanger 5 is completely removed from the residual heat discharge safety system, and there is no need to meet the nuclear safety grade equipment standards, which significantly reduces the equipment cost and inspection standards.

[0069] With the air volume control valve 15 of the air-cooled tower 8 fully open, a large amount of air flows through the air-cooled equipment 7, carrying away heat, relying on the vertical elevation difference H3 at the center of the equipment. The decay heat is eventually discharged into the atmospheric environment. The entire system is a waterless heat exchange system, suitable for water-scarce plant sites.

[0070] Compared to traditional salt tank solutions, this invention eliminates the need to transfer core fuel salts, thus eliminating the risk of radioactive media leakage. It covers planned shutdowns and most accident scenarios, and its waterless cooling method is suitable for arid regions. Compared to integrated three-flow heat exchanger solutions, this invention does not require expansion of the primary loop heat exchanger or additional consumption of expensive radioactive heat transfer media, significantly reducing project construction costs. The secondary loop of this invention shares a single secondary pipeline, relying on one-way valves for reverse micro-circulation to achieve self-insulation. This eliminates the need for all electric heat tracing equipment and allows the secondary loop heat exchanger to be downgraded to a non-safety-grade device, simultaneously reducing the number of equipment required and long-term maintenance costs. Furthermore, the entire system employs a two-stage passive gravity natural circulation system, enabling continuous discharge of core decay heat even during a plant power outage, significantly improving the reactor's inherent safety performance.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A molten salt reactor cooling system with a one-way valve, characterized in that, Includes reactor core (1), primary loop piping (2), primary loop heat exchanger (3), secondary loop piping (4), secondary loop heat exchanger (5), check valve (6), air-cooled equipment (7), and air-cooled tower (8). The core (1) is connected to the primary side of the primary heat exchanger (3) via a primary loop pipe (2); The secondary side of the primary loop heat exchanger (3) is connected to the secondary loop pipeline (4). The secondary loop pipeline (4) is provided with parallel heat exchange branches (4-1-1, 4-2-1) and waste heat discharge branches (4-1-2, 4-2-2). The heat exchange branches (4-1-1, 4-2-1) are connected to the secondary loop heat exchanger (5). The waste heat discharge branches (4-1-2, 4-2-2) are connected in series with a one-way valve (6) and an air-cooled device (7). The primary loop pipe (2) flows with the primary loop medium. Under shutdown conditions, the primary loop pipe (2) relies on the vertical elevation difference (H1) between the first equipment center between the reactor core (1) and the primary loop heat exchanger (3) to form the first passive circulation loop to exhaust the reactor core decay heat. The secondary loop medium flows through the secondary loop pipeline (4). Under the shutdown condition, only the residual heat discharge branch (4-1-2, 4-2-2) forms a second passive circulation loop by relying on the vertical elevation difference (H2) between the second equipment center between the primary loop heat exchanger (3) and the air-cooled equipment (7).

2. The molten salt reactor cooling system with a one-way valve according to claim 1, characterized in that, Isolation valves (13-1, 13-2) are provided on the heat exchange branches (4-1-1, 4-2-1). Isolation valves (13-1, 13-2) are opened when the reactor is running normally and closed when the reactor is shut down. After the isolation valves (13-1, 13-2) cut off the outflow and return channels of the heat exchange branches (4-1-1, 4-2-1), the secondary loop heat exchanger (5) is removed from the safety boundary of the waste heat discharge system and is adapted to the non-safety level equipment manufacturing standards.

3. The molten salt reactor cooling system with a one-way valve according to claim 2, characterized in that, The one-way valve (6) is a fluid diode. When the reactor is running normally, the secondary circulation pump (11) of the secondary loop heat exchanger (5) generates a pipeline pressure difference, which drives a small amount of secondary loop medium to flow continuously in the reverse direction through the one-way valve (6) and the residual heat discharge branch (4-2-2, 4-1-2). The temperature of the residual heat discharge branch (4-2-2, 4-1-2) is maintained by the nuclear heat of the reactor core (1).

4. The molten salt reactor cooling system with a one-way valve according to claim 1, characterized in that, The waste heat discharge branch (4-1-2, 4-2-2) is connected in series with an auxiliary circulation pump (12); when the vertical elevation difference (H2) of the center of the second equipment is insufficient to drive the second passive circulation loop, the auxiliary circulation pump (12) supplements the fluid circulation driving force.

5. The molten salt reactor cooling system with a one-way valve according to claim 1, characterized in that, The primary loop pipeline (2) includes a core outflow pipeline (2-1), a core return pipeline (2-2), and a primary circulation pump (10). The core outflow pipeline (2-1) connects the core (1) outlet (1-2) to the primary side inlet (3-1) of the primary loop heat exchanger (3), and the core return pipeline (2-2) connects the core (1) inlet (1-1) to the primary side outlet (3-2) of the primary loop heat exchanger (3).

6. The molten salt reactor cooling system with a one-way valve according to claim 1, characterized in that, The secondary loop pipeline (4) includes a main outflow pipeline (4-1) and a main return pipeline (4-2). One end of the main outflow pipeline (4-1) is connected to the secondary side outlet (3-4) of the primary loop heat exchanger (3), and the other end is branched to connect to the heat exchange branch and the waste heat discharge branch. One end of the main return pipeline (4-2) is connected to the secondary side inlet (3-3) of the primary loop heat exchanger (3), and the other end is branched to connect to the heat exchange branch and the waste heat discharge branch.

7. The molten salt reactor cooling system with a one-way valve according to claim 1, characterized in that, The air-cooled device (7) is arranged inside the air-cooled tower (8). The outside of the air-cooled device (7) directly exchanges heat with the air inside the air-cooled tower (8) through convection, and the heat is directly discharged into the atmospheric environment.

8. The molten salt reactor cooling system with a one-way valve according to claim 7, characterized in that, The third vertical elevation difference (H3) between the center of the air-cooled equipment (7) and the top of the air-cooled tower (8) forms natural air convection inside the tower.

9. The molten salt reactor cooling system with a one-way valve according to claim 7, characterized in that, The air-cooled tower (8) is equipped with an air volume control valve (15); the air volume control valve (15) is closed when the reactor is running normally; the air volume control valve (15) is opened in a passive manner when the reactor is shut down.

10. The molten salt reactor cooling system with a one-way valve according to claim 1, characterized in that, The secondary side of the dual-loop heat exchanger (5) is connected to an external energy conversion circuit, which is a power generation circuit, an energy storage circuit, or a heating circuit.

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