Multi-natural-circulation coupling heat extraction device for ocean nuclear power source

Abstract

The invention discloses a multi-natural circulation coupling heat extraction device for an ocean nuclear power source, which relates to the technical field of nuclear reactor safety, and is characterized by comprising an integrated pressure vessel structure, an energy conversion and residual heat removal integrated design loop structure and a condenser cooling water loop structure, the energy conversion and waste heat removal integrated design loop structure is connected with the integrated pressure container structure and the condenser cooling water loop structure. Research is carried out on an integrated pressure container designed in a marine nuclear power source and an energy conversion and waste heat removal integrated system, and three natural circulations are formed in a secondary loop and a condenser seawater section in the integrated pressure container respectively; all natural circulations are coupled into a whole through a steam generator heat transfer pipe and a condenser heat transfer pipe, and waste heat of a reactor core is discharged through coupling of multiple natural circulations, so that shutdown safety of a nuclear reactor is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear reactor safety, and more specifically to a multi-natural circulation coupled heat removal device for marine nuclear power sources. Background Art

[0002] Nuclear power is a way to generate electricity through a self-sustaining chain fission reaction using fissile nuclides. At present, nuclear power is widely used in land-based nuclear reactors to provide power for land-based power grids. my country has rich marine resources, including undeveloped islands in vast sea areas, offshore drilling platforms, seabed exploration and deep-sea detection workstations, etc., which require a stable and reliable power supply. Due to the complex deep-sea environment and extremely high requirements for equipment, traditional power supply methods are often difficult to meet the needs. Small nuclear power sources in marine environments have become an important energy choice in the process of marine resource development due to their high energy density, long life, and stable and reliable characteristics. They have broad application prospects in the field of marine resource development.

[0003] The existing designs of marine nuclear power systems mostly follow or draw on the original marine nuclear power technology. The system composition is relatively complex, construction and maintenance are difficult, and there is a great deal of uncertainty in both cost and cycle. Most small nuclear power designs adopt active and passive safety system design. The system is complex, which makes it difficult to arrange equipment and structures in offshore nuclear power systems. Among them, due to the different temperatures of different parts of the fluid and even phase changes, there is a density difference between different parts of the fluid. When the colder fluid is at a higher altitude than the hotter fluid, natural convection will occur under the influence of buoyancy. Its flow in the pipeline is also called natural circulation. The establishment and flow of natural circulation are affected by the floating driving force brought by the elevation difference between the cold and hot fluids, the resistance along the various parts of the flow channel, the local resistance brought by various equipment on the flow channel, such as valves, elbows, flow distribution plates, heat exchangers, etc., and the heat exchange between the fluid or working medium and the cold and heat sources in the circulation pipeline. The key parameter natural circulation flow rate fluctuates. The size of the driving force also determines whether the natural circulation flow can be fully established and run smoothly. There is also a great deal of uncertainty in the thermal conductivity of the entire loop.

[0004] Therefore, the present invention aims to provide a multi-natural circulation coupled heat removal device for marine nuclear power sources to solve the above-mentioned problems. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-natural cycle coupled heat removal device for marine nuclear power sources. The present invention conducts research on the integrated pressure vessel and the integrated system of energy conversion and waste heat removal designed in the marine nuclear power source, and can form three natural cycles in the integrated pressure vessel, the secondary circuit and the condenser seawater section respectively. Each natural cycle is coupled into one through the steam generator heat transfer tube and the condenser heat transfer tube. The core waste heat is discharged by relying on the multi-natural cycle coupling, which can be used to ensure the safety of nuclear reactor shutdown.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: a multi-natural circulation coupled heat removal device for marine nuclear power sources, comprising an integrated pressure vessel structure, an energy conversion and waste heat removal integrated design circuit structure, and a condenser cooling water circuit structure, wherein the energy conversion and waste heat removal integrated design circuit structure is respectively connected to the integrated pressure vessel structure and the condenser cooling water circuit structure;

[0007] The integrated pressure vessel includes a heat exchanger, a pressure stabilizer system and a temperature control and heating system; the heat exchanger is a plate heat exchanger, the pressure stabilizer system is arranged on a supporting platform above the side of the pressure vessel, and the temperature control and heating system is used to automatically cut off the power according to the highest temperature in the stack;

[0008] The energy conversion and waste heat discharge integrated design loop includes a steam turbine simulation body, a condenser, a deaerator simulation body, a feed water pump simulation body pipeline, a No. 1 water tank and a valve; the steam turbine simulation body is treated as a resistance component, the condenser adopts a shell and tube heat exchanger, the steam flows on the shell side, and the cooling water flows on the tube side. The condenser itself has a certain elevation difference to improve the natural circulation capacity of the cooling water on the tube side. The deaerator is simulated by a valve, the feed water pump simulation body pipeline is simulated by a valve, and the No. 1 water tank is used for loop filling and drainage;

[0009] The condenser cooling water circuit includes a condenser tube side and a No. 2 water tank; the condenser tube side adopts a U-tube layout, and multiple independent groups of pipelines are arranged in the condenser, which are synchronously connected to the cooling water tank No. 2 to ensure natural circulation capacity, as well as flow distribution and heat discharge balance of each loop; the No. 2 water tank is used to simulate the low temperature environment of ocean flow by slowly injecting and discharging equal flow rates of cold water.

[0010] The present invention is further configured as follows: a heat-insulating material is provided on the heat-exhaust device, and the heat-insulating material is coated on the heat-exhaust device to reduce energy leakage.

[0011] The present invention is further configured as follows: the heat removal device also includes a measuring instrument, and the measuring instrument is arranged on the heat removal device for measuring and monitoring the flow rate, temperature, pressure and liquid level.

[0012] The present invention is further configured as follows: the measuring instruments are specifically flow meters, thermocouples, pressure gauges and liquid level gauges, which are used to measure and monitor the flow, temperature, pressure and liquid level of the heat removal device.

[0013] The present invention is further configured as follows: the pressurizer system includes a pressurizer tank, a pressure-stabilizing gas cylinder and a safety valve, which are arranged on a support platform above the side of the pressure vessel.

[0014] The present invention is further configured as follows: the integrated pressure vessel structure in the test heating section is specifically designed to have an operating pressure of 1 MPa, a fluid temperature range of 135-180°C, and a single phase. The pressure vessel is made of 304 stainless steel, and a heating element through hole and a core simulation body are provided at the bottom to simulate the heat release of the core by electric heating.

[0015] The present invention is further configured as follows: the operating environment of the integrated energy conversion and waste heat discharge design loop structure is specifically designed to have a design operating pressure of 0.2 MPa, a temperature range of 30-120°C, the fluid working medium is in a single-phase-two-phase fluctuation change state, and a phase change occurs between the steam generator and the condenser to avoid flow instability.

[0016] The present invention is further configured as follows: the operating environment of the condenser cooling water loop structure is specifically designed to be under normal pressure conditions, with a temperature range of 20-80°C, the fluid working medium is in a single-phase state, boiling occurs, and natural circulation occurs on the condenser tube side. The heat source comes from the heat release of the condenser steam, and the cold source comes from the cold water in the water tank.

[0017] In summary, the present invention has the following beneficial effects:

[0018] 1. The present invention conducts research on the integrated pressure vessel and the integrated system of energy conversion and waste heat removal designed for marine nuclear power sources, and can form three natural cycles in the integrated pressure vessel, the secondary circuit and the condenser seawater section respectively. Each natural cycle is coupled into one through the steam generator heat transfer tube and the condenser heat transfer tube. The core waste heat is discharged by coupling multiple natural cycles, which can be used to ensure the safety of nuclear reactor shutdown;

[0019] 2. The present invention conducts system simulation, local area refined numerical simulation and multi-loop natural circulation coupled heat removal system experimental research, conducts research on the flow and heat transfer characteristics of low-level difference and high-flow resistance single-phase-two-phase coupled natural circulation system, verifies the feasibility and robustness of system operation, obtains the system transient response characteristics and stable operation boundary range, which are used to support the design of integrated marine nuclear power system and equipment structure optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a schematic structural diagram of a multi-natural circulation coupled heat removal device for a marine nuclear power source according to an embodiment of the present invention;

[0021] Figure 2 It is a simulation schematic diagram of the device prototype in the simulation experiment in the embodiment of the present invention.

[0022] In the figure: 1. Heat exchanger; 2. Electric heater; 3. Stabilizer tank; 4. Safety valve; 5. Pressure gauge; 6. Stabilizer gas cylinder; 7. Feedwater pump 1; 8. Water tank No. 1; 9. Feedwater pump 2; 10. Flow meter; 11. Thermocouple; 12. Condenser; 13. Turbine simulation body; 14. Deaerator simulation body; 15. Feedwater pump 3; 16. Water tank No. 2. DETAILED DESCRIPTION

[0023] The following is combined with Figure 1-2 The present invention is described in further detail.

[0024] Embodiment: A multi-natural circulation coupled heat removal device for a marine nuclear power source includes an integrated pressure vessel structure (primary circuit), an energy conversion and waste heat removal integrated design circuit structure (secondary circuit), and a condenser 12 cooling water circuit structure (third circuit). The energy conversion and waste heat removal integrated design circuit structure is respectively connected to the integrated pressure vessel structure and the condenser 12 cooling water circuit structure. Insulation material is coated on the heat removal device to reduce energy leakage. Measuring instruments are fixedly arranged on the heat removal device to measure and monitor flow, temperature, pressure and liquid level.

[0025] The design of thermal hydraulic operation parameters in this embodiment is shown in Table 1:

[0026] Table 1 Thermal hydraulic operation parameter design table

[0027] parameter One circuit Secondary circuit Three circuits Design under pressure ~1.5MPa ~0.5MPa ~0.1MPa Operating pressure ~1.0MPa ~0.1MPa(normal pressure) ~0.1MPa Circuit temperature range 135℃～170℃ 135℃～170℃ 135℃～170℃ Heating power 1KWe~100KWe \ \ Water tank temperature \ 80℃ 23℃ Water tank volume \ <![CDATA[1m 3 ]]> <![CDATA[2m 3 ]]> Design Integrated pressure vessel Dual loop, equipment sharing Multiple independent pipelines

[0028] The integrated pressure vessel in the test heating section is specifically designed to have an operating pressure of 1 MPa, a fluid temperature range of 135-180°C, and is single-phase. The pressure vessel is made of 304 stainless steel, and has a heating element through hole and a core simulation body at the bottom, which are used to simulate the heat release of the core by electric heating. The integrated pressure vessel is set on a supporting platform, and a distance of at least 0.2m is set between the integrated pressure vessel and the supporting platform to facilitate drainage and arrangement of heating element wires. At the same time, a discharge channel is set under the integrated pressure vessel for container drainage.

[0029] In this embodiment, the integrated pressure vessel (primary circuit) specifically includes a heat exchanger 1, a pressurizer system and a temperature control and heating system; wherein the heat exchanger 1 is a plate heat exchanger 1, the pressurizer system has a pressurizer tank 3, a matching pressure-stabilizing gas cylinder 6, a safety valve 4 and a water injection pipeline, and is arranged on a supporting platform above the side of the pressure vessel, and the temperature control and heating system can automatically cut off the power according to the maximum temperature in the reactor; constant power heating, or gradually reduce the power according to the actual reactor core decay heat curve.

[0030] The outer surface of the integrated pressure vessel is covered with insulation material. At the same time, the measuring instruments in the first circuit are specifically a flow meter 10 (set in the descending section of the two loops, used to measure the natural circulation flow of the first circuit), a thermocouple 11 (set at the end of the ascending section, used to monitor the fluid temperature and cut off the power in time; at the end of the descending section), a pressure gauge 5 (set at the stabilizer tank 3, used to maintain the system pressure stability), and a liquid level meter (set in the stabilizer tank 3 for liquid level monitoring, so as to facilitate timely water replenishment).

[0031] The operating environment of the integrated design loop for energy conversion and waste heat removal (secondary loop) is specifically designed to have a design operating pressure of 0.2 MPa, a temperature range of 30-120°C, and a fluid medium in a single-phase to two-phase fluctuation state, with a phase change occurring between the steam generator and the condenser 12, to avoid relying on natural circulation drive, which is prone to flow instability.

[0032] In this embodiment, the integrated design loop for energy conversion and waste heat discharge (secondary loop) specifically includes a steam turbine simulation body 13, a condenser 12, a deaerator simulation body 14, a feed pump simulation body pipeline, a No. 1 water tank 8 and a valve; wherein the steam turbine simulation body 13 is a steam turbine in the natural circulation process, which does not output shaft work to the outside and does not generate electrical energy, and the blades and the like are considered to be stationary, and there is no heat exchange with the surrounding environment, and therefore, it is used as a resistance component; in this embodiment, a resistance valve is used for simulation, and attention is paid to the inlet and outlet pressure difference, the flow rate determined by the size and other parameters, and bypass pipelines are respectively set on the two loops.

[0033] The condenser 12 is similar to a real condenser 12 device. Since the establishment of natural circulation has high requirements on heat exchange capacity, the experimental modeling should be as accurate as possible. Therefore, in this embodiment, a condenser 12 device close to the design of an ocean nuclear power source is used. The overall design of the ocean nuclear power source uses an annular condenser 12, and the upper part is directly connected to the end of the turbine volute, without a thin pipe in the middle. In this embodiment, a shell and tube heat exchanger 1 is adopted, and the steam goes to the shell side and the cooling water goes to the tube side. The condenser 12 itself has a certain elevation difference, which improves the natural circulation capacity of the cooling water on the tube side. The overall shape of the condenser 12 is a high, thin, long flat plate, and a structural design with low flow resistance is selected.

[0034] In the deaerator simulation body 14, the deaerator does not have a heat exchange function. In the waste heat discharge stage, it can only bring a certain flow resistance. In general, the deaerator adopts a spray valve design, and the flow resistance will be greatly increased. Therefore, in the natural circulation heat discharge stage, it is necessary to bypass and isolate the deaerator to improve the natural circulation capacity of the entire system. In the simulation of this embodiment, a valve is also used to simulate the deaerator, and bypass pipes are respectively set on the two loops.

[0035] When there is no shaft power input and output, the thermal hydraulic characteristics of rotating machinery such as pump equipment in the feed pump simulation body pipeline are similar to those of a steam turbine, and there is no heat exchange. In the simulation of this embodiment, valves are also used for simulation. Since the experimental research also includes the study of natural circulation heat dissipation startup, transition, steady state, transient and other characteristics, it is necessary to set a feed pump loop, an orifice resistance simulation body loop, and a bypass loop in the loop.

[0036] In this embodiment, water tank No. 1 8 is used for filling and draining the circuit. The specific design volume of water tank No. 1 8 is about 1, and it is at the same height as the water supply pump 7. Water tank No. 1 8 is connected to the natural circulation loop through a pipeline. Water is filled before operation and stored after operation. However, the natural circulation is isolated from the circuit during actual operation.

[0037] All equipment in the secondary circuit is wrapped with insulation material, and the heat leakage rate is <1%. Water filling and drainage ports are set at the lowest end of the water tank and the circuit for cleaning the equipment and draining the fluid. Support structures are set for each key equipment, especially the condenser 12, flow meter 10 (set at the inlet and outlet sections of the steam generator), thermocouple 11 (set at the inlet and outlet sections of the steam generator, the inlet and outlet of the condenser 12, and the No. 1 water tank 8 for real-time monitoring), pressure gauge 5 (set at the uppermost end of the secondary circuit and the lowest end of the secondary circuit), and liquid level meter (set for water level monitoring in the No. 1 water tank 8; bypass water level monitoring on the outside of the steam generator to monitor the height of phase change in the steam generator in real time).

[0038] The operating environment of the cooling water circuit (three circuits) of the condenser 12 is specifically designed to be under normal pressure conditions with a temperature range of 20-80°C. The fluid working medium is in a single-phase state and boiling occurs. Natural circulation occurs on the tube side of the condenser 12. The heat source comes from the heat release of the steam in the condenser 12, and the cold source comes from the cold water in the water tank. In the design of marine nuclear power sources, it comes from seawater. In the simulation of this embodiment, the low-temperature environment of marine flow is simulated by slowly injecting and discharging equal flow rates of cold water in the No. 2 water tank 16.

[0039] In this embodiment, the cooling water circuit (three circuits) of the condenser 12 specifically includes the tube side of the condenser 12 and the No. 2 water tank 16; wherein the tube side of the condenser 12 adopts a U-tube layout, and multiple independent groups of pipelines are arranged in the condenser 12, which are synchronously connected to the cooling water tank No. 2 16 to ensure the natural circulation capacity, as well as the flow distribution and heat discharge balance of each loop.

[0040] The water tank volume of water tank No. 2 16 is 2, open design, and cold water of equal flow rate is slowly injected and discharged from the top side and the bottom side, the water injection temperature is 23°C, the pipe on the tube side of condenser 12 is connected to the area below the water tank side (not on the same side as the cold water injection and discharge port), the water inlet and the water outlet have a certain height difference, and a water pump is arranged between the water tank and the cooling water inlet pipe of condenser 12; the measuring instruments specifically include flow meter 10 (arranged at the inlet section of the tube side of condenser 12), thermocouple 11 (arranged at the inlet section, outlet section, and cold water pipe inlet section of the tube side of condenser 12), and liquid level meter (arranged in water tank No. 2 16).

[0041] Working principle:

[0042] In order to form natural circulation in the multi-loop coupling system and couple the core simulated body heat, the system operation characteristics under several working conditions are verified, including system startup, transition from forced circulation to natural circulation, stable operation of natural circulation, and natural circulation system response under power transient conditions. The specific steps are: system equipment and debugging, primary loop sealing inspection, water filling in No. 1 and No. 2 water tanks 16, and detection of whether the temperature meets the requirements; water is injected into the primary loop from the top water injection pipeline to fill the pressure vessel with water, and exhaust operation is performed; open the pressure regulating gas cylinder 6, adjust the ventilation volume, maintain the pressure in the pressurizer tank 3 at 1.0MPa, and ensure that the water level in the pressurizer tank 3 is above the warning line; open the isolation valve of No. 1 water tank 8, start the secondary loop water supply pump 2 9, and start the electric heater 2 at the same time to make the secondary loop circulating water temperature reach 36℃; after the temperature meets the requirements, turn off the electric heater 2; turn on the electric heater 2, adjust the power to above the set value, continue heating until the primary loop water temperature reaches 165℃, and close the isolation valve of No. 1 water tank 8 The valve is turned off, and the valve of the energy-converting loop is opened to continuously remove the heat of the first loop in a forced circulation manner, and to assist the first loop in establishing a natural circulation, and the flow rate of the first loop and the temperature values ​​of each temperature measuring point are recorded at this time; the power of the electric heater 2 is reduced to the level of the residual heat of the core, and the second loop feed water pump 9 and the third loop feed water pump 15 are turned off, so that the second and third loops establish a multi-loop coupled natural circulation based on their own density difference, and the flow rate of each loop and the temperature value of each temperature measuring point are recorded in real time (the startup, transition and stable operation characteristics of the multi-loop natural circulation); the power of the electric heater 2 is increased to the set value, and the transient changes of the parameters such as the flow rate of each loop and the temperature value of each temperature measuring point in the multi-natural circulation loop are recorded; the power of the electric heater 2 is reduced to the set value, and the transient changes of the parameters such as the flow rate of each loop and the temperature value of each temperature measuring point in the multi-natural circulation loop are recorded; the power of the electric heater 2 is cut off, and the second loop feed water pump 9 and the third loop feed water pump 15 are turned on, and the temperature in the two loops is continuously reduced to room temperature, and the feed water pump is turned off, and the pressure-stabilizing gas cylinder 6 is turned off to drain the loop, tidy up the equipment, and complete the experiment.

[0043] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A multi-natural circulation coupled heat removal device for marine nuclear power source, characterized by: It comprises an integrated pressure vessel structure, an energy conversion and waste heat discharge integrated design loop structure, and a condenser (12) cooling water loop structure, wherein the energy conversion and waste heat discharge integrated design loop structure is connected to the integrated pressure vessel structure and the condenser (12) cooling water loop structure respectively; The integrated pressure vessel comprises a heat exchanger (1), a pressure stabilizer system and a temperature control and heating system; the heat exchanger (1) is a plate heat exchanger (1), the pressure stabilizer system is arranged on a supporting platform above the side of the pressure vessel, and the temperature control and heating system is used to automatically cut off power according to the highest temperature in the stack; The energy conversion and waste heat discharge integrated design loop comprises a steam turbine simulation body (13), a condenser (12), a deaerator simulation body (14), a feed water pump simulation body pipeline, a No. 1 water tank (8) and a valve; the steam turbine simulation body (13) is treated as a resistance component, the condenser (12) adopts a shell and tube heat exchanger (1), the steam flows on the shell side, and the cooling water flows on the tube side, the condenser (12) itself has a certain elevation difference, and the natural circulation capacity of the cooling water on the tube side is improved, the deaerator is simulated by a valve, the feed water pump simulation body pipeline is simulated by a valve, and the No. 1 water tank (8) is used for loop filling and drainage; The cooling water circuit of the condenser (12) comprises a condenser (12) tube side and a No. 2 water tank (16); the tube side of the condenser (12) adopts a U-shaped tube arrangement, and multiple sets of independent pipelines are arranged in the condenser (12), which are synchronously connected to the cooling No. 2 water tank (16) to ensure the natural circulation capacity and the balance of flow distribution and heat discharge of each loop; the No. 2 water tank (16) is used to simulate the low temperature environment of ocean flow by slowly injecting and discharging equal flow of cold water.

2. The multi-natural circulation coupled heat removal device for marine nuclear power source according to claim 1 is characterized by: The heat dissipation device is provided with a heat-insulating material, and the heat-insulating material is coated on the heat dissipation device to reduce energy leakage.

3. The multi-natural circulation coupled heat removal device for marine nuclear power source according to claim 1 is characterized in that: The heat removal device further comprises a measuring instrument, which is arranged on the heat removal device and is used to measure and monitor flow, temperature, pressure and liquid level.

4. The multi-natural circulation coupled heat removal device for marine nuclear power source according to claim 3 is characterized by: The measuring instruments are specifically a flow meter (10), a thermocouple (11), a pressure gauge (5) and a liquid level gauge, which are used to measure and monitor the flow, temperature, pressure and liquid level of the heat removal device.

5. The multi-natural circulation coupled heat removal device for marine nuclear power source according to claim 1 is characterized by: The pressure stabilizer system comprises a pressure stabilizer tank (3), a pressure-stabilizing gas cylinder (6) and a safety valve (4), which are arranged on a support platform above the side of the pressure vessel.

6. The multi-natural circulation coupled heat removal device for marine nuclear power source according to claim 1 is characterized by: The integrated pressure vessel structure in the test heating section is specifically designed to have an operating pressure of 1 MPa, a fluid temperature range of 135-180°C, and is single-phase. The pressure vessel is made of 304 stainless steel, and has a heating element through hole and a core simulation body at the bottom, which are used to simulate core heat release by electric heating.

7. The multi-natural circulation coupled heat removal device for marine nuclear power source according to claim 1 is characterized by: The operating environment of the integrated energy conversion and waste heat removal loop structure is specifically designed to have an operating pressure of 0.2 MPa, a temperature range of 30-120° C., a fluid medium in a single-phase to two-phase fluctuation state, and a phase change between the steam generator and the condenser (12) to avoid flow instability.

8. The multi-natural circulation coupled heat removal device for marine nuclear power source according to claim 1 is characterized by: The operating environment of the cooling water loop structure of the condenser (12) is specifically designed to be under normal pressure conditions, with a temperature range of 20-80°C. The fluid working medium is in a single-phase state and boils, and natural circulation occurs on the tube side of the condenser (12). The heat source comes from the heat released by the steam of the condenser (12), and the cold source comes from the cold water in the water tank.

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