System and method for vacuuming containment of nuclear power plant

Abstract

The present invention relates to a system and method for vacuuming a containment of a nuclear power plant. The system comprises a pressure vessel, wherein a containment is sleeved outside of the pressure vessel, a cavity is formed between the containment and the pressure vessel, the top of the containment is connected to each of a vacuum ejector and a vacuum pump by means of pipelines, the containment is vacuumized by means of the vacuum ejector and the vacuum pump, and a vacuum environment in the containment is established. The present invention can not only reduce the layout space of an apparatus and the pipelines, but can also reduce the heat loss of the apparatus and the pipelines, has the functions of monitoring reactor coolant pressure boundary leakage and draining water inside the containment before reactor startup, and meets the requirements of small modular reactors.

Description

A nuclear power plant containment vacuum pumping system and method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202310921890.9, filed on July 25, 2023, entitled “A Nuclear Power Plant Containment Vacuum Evacuation System and Method,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of nuclear reactors, and in particular to a vacuum pumping system and method for a containment vessel of a nuclear power plant. Background Art

[0004] Nowadays, pressurized water reactors are developing towards small integrated modularization and tend to adopt an integrated structure. The integrated reactor includes a pressure vessel and core components such as a pressurizer located in the upper head of the pressure vessel, a built-in steam generator module, nuclear fuel assemblies and control rods. The integrated reactor is located in a closed containment vessel to prevent the escape of radioactive materials. It is a compact and more economical design.

[0005] However, in traditional designs, pressure vessels and process pipelines need to be insulated with thermal insulation materials. In this case, the equipment and pipelines need to occupy a large layout space, which makes it difficult to adapt to the needs of small integrated modular reactors.

[0006] During the reactor shutdown, cooling, and refueling phases, an appropriate amount of cooling water must be injected into the containment vessel. Heat is exchanged between the containment vessel walls and the cooling water in the pool. Before restarting the reactor, the cooling water must be drained to establish a vacuum environment. Because the containment vessel is typically more than 10 meters tall, conventional pumps are unable to pump out the cooling water at ambient pressure. Consequently, the containment vessel drains slowly, hindering normal reactor startup.

[0007] Summary of the Invention

[0008] In response to the shortcomings of the existing technology, the present invention provides a nuclear power plant containment vacuum pumping system and method, which can not only reduce the layout space of equipment and pipelines, but also reduce the heat loss of equipment and pipelines. At the same time, it also has the functions of reactor coolant pressure boundary leakage monitoring and shell drainage before reactor startup, meeting the requirements of small modular reactors.

[0009] The first aspect of the present invention provides a nuclear power plant containment vacuum pumping system, comprising: a pressure vessel; a containment shell, which is arranged on the outside of the pressure vessel, forming a cavity between the containment shell and the pressure vessel; a vacuum ejector, which is connected to the top of the containment shell through a pipeline, and the vacuum ejector establishes a vacuum environment for the containment shell through compressed air; and a vacuum pump, which is connected to the top of the containment shell through a pipeline to vacuum the containment shell.

[0010] Preferably, the containment vessel is placed in a water pool, and a heater is provided in the water pool.

[0011] Preferably, the containment vessel is provided with a radiation monitoring instrument, a pressure monitoring instrument and a pressure vessel liquid level gauge.

[0012] Preferably, a containment isolation valve is also provided on the pipeline to control the communication between the containment and the pipeline.

[0013] Preferably, an ejector control valve and a check valve are provided between the vacuum ejector and the safety isolation valve to ensure the flow direction of the gas in the pipeline.

[0014] Preferably, the air outlet of the vacuum pump is connected to the air inlet of the condenser, and the liquid outlet of the condenser is connected to the condensate collecting tank. The condensate collecting tank is provided with a condensate collecting tank level gauge for detecting the liquid level in the condensate collecting tank.

[0015] Preferably, the bottom of the condensed water collection tank is connected to a radioactive waste liquid treatment system via a pipeline.

[0016] Preferably, the air outlet of the condenser is connected to the ventilation system through a pipe, and a filter is also provided on the pipe between the ventilation system and the condenser.

[0017] A second aspect of the present invention provides a method for evacuating a containment vessel of a nuclear power plant, utilizing the nuclear power plant containment vessel evacuation system provided by the first aspect of the present invention. The method comprises the following steps:

[0018] During the reactor startup phase, keep the vacuum pump closed, open the containment isolation valve, and start the vacuum ejector to evacuate the space between the pressure vessel and the containment to establish the initial vacuum degree of the containment;

[0019] monitoring the vacuum degree in the containment vessel using a pressure monitoring instrument, and closing the vacuum ejector and the ejector control valve when the vacuum degree reaches a first set value;

[0020] The vacuum pump is started to continue to increase the vacuum degree to a second set value, and when the start-up requirements are met, the vacuum pump is stopped.

[0021] Preferably, the containment vessel is placed in a water pool, and a heater is provided in the water pool. The method for evacuating the containment vessel of a nuclear power plant further comprises the following steps:

[0022] During the reactor refueling and restart phase, the vacuum ejector is activated to continuously reduce the pressure in the containment vessel, and the water in the water pool is heated by the heater to ensure that the temperature of the cooling water in the containment vessel is above the set temperature;

[0023] The vacuum ejector is used to pump air to accelerate the boiling of cooling water in the containment, thereby accelerating the pumping rate until a vacuum environment is established in the containment.

[0024] Preferably, after the vacuum degree in the containment is established, the containment pressure is monitored in real time by a pressure monitoring instrument to ensure the vacuum degree in the containment. When the vacuum degree drops below the set value, the vacuum pump is started to extract the gas in the containment and re-establish the vacuum degree.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention establishes a vacuum environment inside the containment vessel by arranging a vacuum ejector and a vacuum pump, and uses vacuum insulation technology to reduce heat loss of the integrated reactor. This can eliminate the insulation design of reactor-related equipment, reduce layout space, and meet the needs of small integrated modular reactors. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application.

[0028] FIG1 is a schematic diagram of a nuclear power plant containment vacuum pumping system according to a specific embodiment of the present invention.

[0029] Figure numerals: 100-nuclear power plant containment vacuum system; 1-pressure vessel; 2-containment; 3-water pool; 4-heater; 5-vacuum pump; 6-condenser; 7-vacuum ejector; 8-condensate collection tank; 9-filter; 10-safety isolation valve; 11-ejector control valve; 12-check valve; 13-condensate collection tank level gauge; 14-radiation monitoring instrument; 15-pressure monitoring instrument; 16-pressure vessel level agent; 17-collection tank control valve; 18-cavity. DETAILED DESCRIPTION

[0030] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0031] The present invention combines the characteristics of a small integrated modular reactor and utilizes vacuum insulation technology to design a nuclear power plant containment vacuum pumping system and method. This system can not only reduce the layout space of equipment and pipelines, but also reduce heat loss of equipment and pipelines. At the same time, it also has the functions of reactor coolant pressure boundary leakage monitoring and shell drainage before reactor startup, making the system configuration of the small modular reactor more simplified and economical.

[0032] FIG1 is a schematic diagram of a nuclear power plant containment vacuum pumping system according to a specific embodiment of the present invention.

[0033] As shown in FIG1 , the nuclear power plant containment vacuum pumping system 100 of this embodiment includes a pressure vessel 1 , a containment 2 , a vacuum ejector 7 and a vacuum pump 5 .

[0034] The containment shell 2 is mounted on the outside of the pressure vessel 1, and a cavity 18 is formed between the containment shell 2 and the pressure vessel 1; the vacuum ejector 7 is connected to the top of the containment shell 2 through a pipeline, and the vacuum ejector 7 establishes a vacuum environment for the containment shell through compressed air; the vacuum pump 5 is connected to the top of the containment shell 2 through a pipeline to evacuate the containment shell 2.

[0035] The vacuum ejector 7 offers greater efficiency in evacuating large spaces. Within the vacuum ejector 7, two fluids of different pressures mix, exchanging energy and ultimately forming a mixed fluid at an intermediate pressure. The higher-pressure fluid is called the working fluid, while the lower-pressure fluid removed is called the ejector fluid. In this embodiment, the working fluid is compressed air, and the ejector fluid is the gas extracted from the containment vessel 2, thereby establishing a vacuum.

[0036] During the reactor startup phase, vacuum pump 5 remains off and vacuum ejector 7 is activated to evacuate cavity 18 between pressure vessel 1 and containment vessel 2, establishing an initial vacuum level in containment vessel 2. When the vacuum level reaches a first set value, vacuum ejector 7 is closed and vacuum pump 5 is activated to continue raising the vacuum level to a second set value. When the startup requirements are met, vacuum pump 5 is deactivated.

[0037] In one embodiment, a nuclear power plant containment vacuum system 100 is equipped with two vacuum ejectors 7 and a vacuum pump 5. The two vacuum ejectors 7 are connected in series, providing enhanced vacuum performance and achieving a higher vacuum level. The two vacuum pumps 5 are connected in parallel to the circuit, providing design redundancy. During normal operation, if one pump fails, the backup pump is activated to support normal system operation.

[0038] The nuclear power plant containment evacuation system 100 of this embodiment utilizes a vacuum ejector 7 and a vacuum pump 5 to establish a vacuum environment within the containment vessel 2. This system primarily reduces heat loss from the integrated reactor through vacuum insulation technology, ensuring safe operation. Furthermore, under vacuum conditions, the insulation design of reactor-related equipment can be eliminated, reducing layout space.

[0039] The containment vessel 2 is provided with a radiation monitoring instrument 14 , a pressure monitoring instrument 15 and a pressure vessel liquid level gauge 16 .

[0040] After the vacuum degree in the containment shell 2 is established, the pressure of the containment shell 2 is monitored in real time to ensure the vacuum degree in the containment shell 2. When the vacuum degree drops below the set value, the vacuum pump 5 is started to extract the gas in the shell and re-establish the vacuum degree.

[0041] The radiation monitoring instrument 14 is used to monitor the radioactivity of gaseous particles in the containment vessel 2 in real time, thereby performing leakage monitoring inside the containment vessel 2 .

[0042] The pressure monitoring instrument 15 is used to monitor the pressure of the containment shell 2 to ensure the vacuum degree inside the containment shell 2. At the same time, when the medium inside the containment shell 2 leaks, it will be gasified immediately. By monitoring the pressure of the containment shell 2 through the pressure monitoring instrument 15, the leakage rate can be calculated using the ideal gas state equation.

[0043] The pressure vessel level gauge 16 is used to detect the water level in the containment vessel 2. During the loading and refueling and restart phases of the reactor, the water level in the containment vessel 2 is monitored to ensure that the cooling water in the containment vessel 2 is discharged.

[0044] The radiation monitoring instrument 14 , the pressure monitoring instrument 15 and the pressure vessel level gauge 16 are all common products on the market, as long as they can achieve the above functions.

[0045] The top of the containment shell 2 is connected to the vacuum ejector 7 and the vacuum pump 5 through pipelines. A containment shell isolation valve 10 is also provided on the pipeline to control the communication between the containment shell 2 and the pipeline.

[0046] The vacuum ejector 7 is connected to the compressed air pipeline and provides a vacuum environment through compressed air. An ejector control valve 11 and a check valve 12 are provided between the vacuum ejector 7 and the safety isolation valve 10 to ensure the flow direction of the gas in the pipeline.

[0047] During the reactor startup phase, to establish a vacuum between reactor 1 and containment vessel 2, containment vessel isolation valve 10 is opened, and the highly efficient vacuum ejector 7 is activated to establish an initial vacuum in containment vessel 2. Vacuum pump 5 remains off. When the vacuum reaches 90%, vacuum ejector 7 and ejector control valve 11 are closed, and vacuum pump 5 is activated to continue raising the vacuum to 95%, meeting startup requirements. Vacuum pump 5 is then shut down.

[0048] During the shutdown, cooling and refueling phases of the reactor, an appropriate amount of cooling water needs to be injected into the containment vessel 2 to continuously remove the decay heat of the core. Before restarting the reactor, the cooling water in the containment vessel 2 needs to be drained to establish a vacuum environment. Since the height of the containment vessel 2 is generally much higher than 10m, the cooling water in the containment vessel cannot be pumped out by conventional pumps under ambient pressure. At this stage, the pressure in the containment vessel 2 can be continuously reduced by operating the nuclear power plant containment vacuum system 100. When the liquid phase and saturated vapor phase of the cooling water coexist in equilibrium, the evaporated water is immediately pumped away without condensing. The cooling water level will continue to drop until a vacuum environment is established in the containment vessel.

[0049] In order to achieve the equilibrium coexistence of the liquid phase and saturated vapor phase of the cooling water, the containment vessel 2 is placed in a water pool 3, in which a heater 4 is provided. A certain amount of water is placed in the water pool 3, and the containment vessel 2 is placed in the water. During the loading and refueling and restarting stages of the reactor, the heater 4 is used to heat the water in the water pool 3 to keep the cooling water in the containment vessel 2 above the set temperature. The vacuum ejector 7 is used to draw a vacuum to accelerate the discharge of the cooling water in the containment vessel 2.

[0050] By placing the containment shell 2 in the water pool 3 and arranging a heater 4 in the water pool 3, the pool water is heated by the external heater 4 of the water pool 3 to ensure that the cooling water temperature in the shell is above the set value, and the vacuum ejector 7 is used to pump air to accelerate the boiling of the cooling water in the shell, thereby accelerating the pumping rate and accelerating the discharge of the cooling water in the containment shell 2.

[0051] The vacuum ejector 7 is connected to the ventilation system through a pipeline, and the gas in the containment vessel 2 is extracted through the vacuum ejector 7. Although the radioactivity level of the gas in the containment vessel 2 is low, it still needs to be purified through the connected ventilation system before it is allowed to be discharged into the atmosphere to avoid the discharge of radioactive gas into the atmospheric environment.

[0052] The nuclear power plant containment vacuum system 100 also includes a condenser 6 and a condensate collection tank 8. The air outlet of the vacuum pump 5 is connected to the air inlet of the condenser 6, and the liquid outlet of the condenser 6 is connected to the condensate collection tank 8. The condensate collection tank 8 is provided with a condensate collection tank level gauge 13 for detecting the liquid level in the condensate collection tank 8.

[0053] The bottom of the condensate collection tank 8 is connected to the radioactive waste liquid treatment system through a pipeline. A collection tank control valve 17 is provided between the condensate collection tank 8 and the radioactive waste liquid treatment system. According to the reactor operation requirements, the collection tank control valve 17 regularly discharges the radioactive medium in the condensate collection tank 8 into the radioactive waste liquid treatment system.

[0054] In one embodiment, liquid sampling of the radioactive medium discharged from the condensate collection tank 8 can also be performed, and chemical and radiochemical analysis can be performed in a chemical laboratory through regular condensate sampling to monitor and understand the operation status of the reactor.

[0055] The condenser 6 can remove the liquid medium containing radioactive substances in the extracted gas, and monitor the leakage of the process system in the containment during operation through the condensate collection tank level gauge 13 on the condensate collection tank 8, so as to grasp the operation status of the reactor.

[0056] The air outlet of the condenser 6 is connected to the ventilation system through a pipe. A filter 9 is also provided on the pipe between the ventilation system and the condenser 3. The gas separated by the condenser 6 is processed by the filter 9 and then discharged to the ventilation system.

[0057] In one embodiment, gas sampling can also be performed on the gas discharged from the gas outlet of the condenser 6 and the gas outlet of the vacuum ejector 7. Chemical and radiochemical analysis can be performed in a chemical laboratory through regular gas sampling to monitor the level of gas emissions into the atmosphere and understand the operation status of the reactor.

[0058] FIG2 is a flow chart of a method for evacuating a containment vessel of a nuclear power plant according to a specific embodiment of the present invention.

[0059] As shown in FIG2 , the nuclear power plant containment vacuum pumping method of this embodiment utilizes the nuclear power plant containment vacuum pumping system 100 to vacuum the containment. The method includes the following steps:

[0060] Step S1, during the reactor startup phase, keep the vacuum pump 5 closed, open the containment isolation valve 10, and start the vacuum ejector 7 to evacuate the cavity 18 between the pressure vessel 1 and the containment 2 to establish an initial vacuum degree of the containment 2.

[0061] In step S2, the vacuum level in the containment vessel 2 is monitored using the pressure monitoring instrument 14. When the vacuum level reaches a first set value, the vacuum ejector 7 and the ejector control valve 11 are closed. In one embodiment, the first set value is 90%. When the vacuum level in the containment vessel 2 reaches 90% as monitored by the pressure monitoring instrument 14, the vacuum ejector 7 and the ejector control valve 11 are closed.

[0062] Step S3: Start vacuum pump 5 and continue to increase the vacuum level to a second set value. When the startup requirements are met, vacuum pump 5 is shut down. In one embodiment, the second set value is 95%. When the vacuum level in containment vessel 2 reaches 95% as measured by pressure monitoring instrument 14, which satisfies the startup requirements, vacuum pump 5 is shut down.

[0063] As an embodiment, the containment vessel 2 is placed in a water pool 3, a heater 4 is provided in the water pool 3, and the method for evacuating the containment vessel of a nuclear power plant further includes the following steps:

[0064] Step S4, during the reactor refueling and restart phase, the vacuum ejector 7 is started to continuously reduce the pressure in the containment vessel 2, and the water in the water pool 3 is heated by the heater 4 to ensure that the cooling water temperature in the containment vessel 2 is above the set temperature.

[0065] In step S5, vacuum ejector 7 is used to pump air to accelerate the boiling of cooling water in containment vessel 2, thereby accelerating the pumping rate until a vacuum environment is established in containment vessel 2.

[0066] During the shutdown, cooling and refueling phase of the reactor, an appropriate amount of cooling water needs to be injected into the containment vessel 2, and heat is exchanged between the wall of the containment vessel 2 and the cooling water in the water pool 3 to continuously remove the decay heat of the core. Before restarting the reactor, the cooling water in the containment vessel 2 needs to be drained to establish a vacuum environment. Since the height of the general containment vessel 2 is much higher than 10m, the cooling water in the containment vessel 2 cannot be pumped out by a conventional pump under ambient pressure. At this stage, the pressure in the containment vessel 2 can be continuously reduced by the operation of the nuclear power plant containment vacuum system 100. When the liquid phase and saturated vapor phase of the cooling water coexist in equilibrium, the evaporated water is immediately pumped away without condensing. The cooling water level will continue to drop until a vacuum environment is established in the containment vessel 2.

[0067] Therefore, when the reactor is in the stage of loading and refueling and restarting, there is a small amount of cooling water in the containment 2 that needs to be discharged to establish a vacuum environment inside the shell. At this time, the vacuum ejector 7 is started to continuously reduce the pressure inside the containment 2, and the pool water in the water pool 3 is heated by the heater 4 to ensure that the cooling water temperature in the containment 2 is above 42°C. The boiling of the cooling water in the containment 2 is accelerated by pumping, thereby accelerating the pumping rate until the vacuum environment in the containment 2 is established.

[0068] In one embodiment, the method for evacuating the containment of a nuclear power plant further includes step S6. During the power operation phase, after the vacuum degree in the containment vessel 2 is established, the pressure of the containment vessel 2 is monitored in real time by a pressure monitoring instrument 15 to ensure the vacuum degree in the containment vessel 2. When the vacuum degree drops below a set value, the vacuum pump 5 is started to extract the gas in the containment vessel and re-establish the vacuum degree.

[0069] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A nuclear power plant containment vacuum system, characterized in that: include: Pressure vessels; A containment shell is sleeved on the outside of the pressure vessel, and a cavity is formed between the containment shell and the pressure vessel; A vacuum ejector connected to the top of the containment vessel through a pipeline, and the vacuum ejector establishes a vacuum environment of the containment vessel through compressed air; A vacuum pump is connected to the top of the containment vessel through a pipeline to evacuate the containment vessel.

2. The nuclear power plant containment vacuum system according to claim 1, characterized in that: The containment vessel is placed in a water pool, and a heater is arranged in the water pool.

3. The nuclear power plant containment vacuum system according to claim 1, characterized in that: The containment vessel is provided with a radiation monitoring instrument, a pressure monitoring instrument and a pressure vessel liquid level gauge.

4. The nuclear power plant containment vacuum system according to claim 1, characterized in that: A containment isolation valve is also provided on the pipeline connecting the top of the containment to the vacuum ejector and the vacuum pump, for controlling the communication between the containment and the vacuum ejector and the vacuum pump.

5. The nuclear power plant containment vacuum system according to claim 4, characterized in that: An ejector control valve and a check valve are provided between the vacuum ejector and the safety isolation valve to ensure the flow direction of the gas in the pipeline.

6. The nuclear power plant containment vacuum system according to claim 1, characterized in that: It also includes a condenser and a condensed water collecting tank. The air outlet of the vacuum pump is connected to the air inlet of the condenser, and the liquid outlet of the condenser is connected to the condensed water collecting tank. The condensed water collecting tank is provided with a condensed water collecting tank level gauge for detecting the liquid level of the liquid in the condensed water collecting tank.

7. The nuclear power plant containment vacuum system according to claim 6, characterized in that: The bottom of the condensed water collection tank is connected to a radioactive waste liquid treatment system through a pipeline.

8. The nuclear power plant containment vacuum system according to claim 6, characterized in that: The air outlet of the condenser is connected to the ventilation system through a pipeline, and a filter is also arranged on the pipeline between the ventilation system and the condenser.

9. A method for evacuating a containment vessel of a nuclear power plant, using the evacuation system for the containment vessel of a nuclear power plant as claimed in claim 1, characterized in that: The following steps are involved: During the reactor startup phase, the vacuum pump is kept closed and the vacuum ejector is started to evacuate the cavity between the pressure vessel and the containment to establish the initial vacuum degree of the containment; monitoring the vacuum degree in the containment vessel, and closing the vacuum ejector when the vacuum degree reaches a first set value; The vacuum pump is started to continue to increase the vacuum degree to a second set value, and when the start-up requirements are met, the vacuum pump is stopped.

10. The method for evacuating a containment vessel of a nuclear power plant according to claim 9, characterized in that: The containment vessel is placed in a water pool, a heater is provided in the water pool, and the method further comprises the following steps: During the reactor refueling and restart phase, the vacuum ejector is started to continuously reduce the safety The full shell pressure, and the pool water in the pool is heated by the heater to ensure that the cooling water temperature in the containment is above the set temperature; The vacuum ejector is used to pump air to accelerate the boiling of cooling water in the containment, thereby accelerating the pumping rate until a vacuum environment is established in the containment.

11. The method for evacuating a containment vessel of a nuclear power plant according to claim 10, characterized in that: After the vacuum environment in the containment is established, the pressure in the containment is monitored in real time by a pressure monitoring instrument to ensure the vacuum degree in the containment. When the vacuum degree drops below a set value, the vacuum pump is started to extract the gas in the containment and re-establish the vacuum environment in the containment.

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