Reactor pit natural circulation heat extraction system, nuclear power plant reactor and heat extraction method thereof

Abstract

The invention belongs to the technical field of nuclear power, and particularly relates to a reactor pit natural circulation heat extraction system, a nuclear power plant reactor and a heat extraction method thereof. The reactor pit natural circulation heat extraction system comprises a reactor pit exhaust system and an air draft chimney. The pile pit exhaust system comprises an air inlet pipeline, an air outlet pipeline, an air inlet fan, a first valve, a second valve, a third valve and an exhaust fan. The air inlet fan and the first valve are sequentially arranged on the air inlet pipeline in series in the air inlet direction of the air inlet pipeline. And the second valve is arranged on a branch pipeline communicated with the air inlet pipeline. The third valve and the exhaust fan are sequentially arranged on the air outlet pipeline in series in the air outlet direction of the air outlet pipeline. The air inlet pipeline penetrates through the side face of the reactor hall and the containment and then is connected with the reactor pit. According to the invention, the heat of the reactor pit is taken away in a passive natural circulation mode, so that the technical problems that the natural circulation heat extraction design and application of the reactor pit are not considered in the existing fast reactor and the design of a reactor pit ventilation system is relatively complicated are solved.

Description

Technical Field

[0001] The present application belongs to the field of nuclear power technology, and specifically relates to a natural circulation heat removal system for a reactor pit, a nuclear power plant reactor and a heat removal method thereof. Background Art

[0002] Fast reactors that use liquid metal as coolant are typical high-temperature systems. The reactor pit is subject to high temperatures both in normal and accident situations. The original design was to set up a complex ventilation system to ensure that the pit temperature was below the temperature at which the concrete loses its crystallization water under normal conditions. In accident conditions, it was also necessary to consider whether the auxiliary facilities would fail, leading to further expansion of the accident consequences.

[0003] When a fast reactor nuclear power plant is operating normally, the fans of the reactor ventilation system operate normally, continuously displacing the air in the reactor pit, discharging it into the atmosphere through ventilation ducts and chimneys, and maintaining the reactor pit in a negative pressure state. The negative pressure design ensures that the gas flows from the reactor building to the reactor pit during normal operation, preventing the extremely small amount of radioactive materials released by the reactor from entering the reactor hall and threatening the safety of operating personnel. Radiation monitoring monitors the radioactivity level in the reactor building and the reactor top protective cover in real time.

[0004] When a sodium-cooled fast reactor nuclear power plant has a design basis accident, the primary loop boundary can remain intact and the radioactive materials in the reactor are contained within the primary loop boundary. Therefore, the reactor pit does not need to bear the function of radioactive containment in most cases; however, there is a certain amount of heat dissipation on the surface of the reactor container, which needs to be discharged in order to maintain the temperature of the reactor body and the equipment in the reactor pit within a certain range. At present, the equipment inside the reactor pit is cooled by setting up a reactor pit exhaust system and driving the gas inside the reactor pit to be discharged through a fan.

[0005] In the event of a serious accident, the radioactive material in the reactor main container leaks into the containment through the equipment on the top of the main container. When the containment radiation monitoring system detects radioactive anomalies, the containment isolation system is triggered to operate, and the isolation valves on the coolant pipes and ventilation pipes that run through the containment device are automatically isolated. At this time, the inner containment is in a sealed state, which can effectively prevent radioactive materials from leaking into the environment in the event of a serious accident and causing environmental impact. After the containment device has been sealed for a period of time, the short-lived radioactive materials that account for a large proportion of the radioactive materials decay, leaving only a small amount of long-lived radioactive materials. At this time, the containment isolation state is released, the reactor ventilation system is started, and the radioactive materials are filtered and discharged in a controlled elevated manner.

[0006] However, current fast reactors have not considered the design and application of natural circulation heat removal in the reactor pit, and the design of the reactor pit ventilation system is relatively complex. Summary of the invention

[0007] In view of this, the present application is committed to providing a natural circulation heat removal system for a reactor pit, a nuclear power plant reactor and a heat removal method thereof, which removes the heat from the reactor pit by means of passive natural circulation, in order to solve the technical problem that the current fast reactors do not consider the design and application of natural circulation heat removal for the reactor pit, and the design of the reactor pit ventilation system is relatively complex.

[0008] The first aspect of the present application provides a natural circulation heat removal system for a reactor pit, which is applied to the nuclear island part of a nuclear power plant. The nuclear island part of a nuclear power plant includes a reactor body, a reactor pit, a containment shell and a reactor hall. The reactor body is located in the reactor pit, and the upper part of the reactor body and the reactor pit is the containment shell. The reactor hall is surrounded by the outer side of the containment shell. The natural circulation heat removal system for the reactor pit includes a reactor pit exhaust system and an air extraction chimney. The reactor pit exhaust system includes an air inlet duct, an air outlet duct, an air inlet fan, a first valve, a second valve, a third valve and an exhaust fan. The air inlet fan and the first valve are sequentially arranged on the air inlet duct along the air inlet direction of the air inlet duct and are located in the area between the containment shell and the reactor hall. The second valve is arranged on a branch duct connected to the air inlet duct and is located on the side of the first valve close to the containment shell. The second valve and the branch duct are both located in the area between the containment shell and the reactor hall. The third valve and the exhaust fan are sequentially arranged on the air outlet duct along the air outlet direction of the air outlet duct and are located in the area between the containment shell and the reactor hall. The air outlet duct passes through the containment and is connected to the reactor pit. The air extraction chimney is connected to the air outlet of the air outlet duct and is located outside the reactor hall. The air inlet duct passes through the side of the reactor hall and the containment and is connected to the reactor pit.

[0009] In a specific embodiment of the present application, the air inlet duct extends to a first linear distance from the bottom surface of the pile pit, and the air outlet duct extends to a second linear distance from the bottom surface of the pile pit, and the second linear distance is greater than the first linear distance.

[0010] In a specific embodiment of the present application, the stack body is a liquid metal reactor stack body.

[0011] In a specific embodiment of the present application, the core outlet temperature of the liquid metal reactor body is greater than 500°C.

[0012] In a specific embodiment of the present application, the liquid metal reactor body is a sodium-cooled fast reactor body.

[0013] In a specific embodiment of the present application, the height and arrangement position of the wind extraction chimney are obtained by coupling calculation of the natural circulation driving force and the flow resistance.

[0014] A second aspect of the present application provides a nuclear power plant reactor, which includes a nuclear island portion of the nuclear power plant and a natural circulation heat removal system for a reactor pit according to the first aspect of the present application.

[0015] The third aspect of the present application provides a heat removal method for a nuclear power plant reactor, which comprises: when the reactor is in a normal power operation condition, opening the first valve and the third valve of the natural circulation heat removal system of the reactor pit in the embodiment of the present application, closing the second valve, and the exhaust fan and the air extraction chimney discharge the air in the reactor pit into the environment after filtering; when the reactor is in a shutdown and refueling condition, closing the air inlet fan and the exhaust fan, adopting the natural circulation mode, maintaining the temperature and negative pressure of the reactor pit; when the reactor is in an accident condition, the containment is automatically isolated, and then, the third valve is opened, and the second valve is set to a valve opening of 5%.

[0016] The beneficial effects of the technical solution of the present application are: by arranging an extraction chimney outside the reactor hall, and connecting the extraction chimney to the reactor pit through an air outlet duct, by setting a first valve, a second valve and a third valve, and utilizing the opening and closing of the first valve, the second valve and the third valve to remove the heat from the reactor pit in a passive natural circulation manner, it is beneficial to maintain the structural integrity of the reactor body and the reactor pit, and to assist in enhancing the natural circulation capacity in the reactor, improve the safety and economy of the reactor, and simplify the operation. In addition, the natural circulation heat removal system of the reactor pit can maintain the natural circulation heat discharge of the reactor pit when there is no damage to the primary pressure boundary or the impact of the leakage of radioactive nuclides is not higher than the minor damage required by the national standard for annual emissions. Under accident conditions, the heat can be reliably discharged through the natural circulation method through the natural circulation heat removal system of the reactor pit, while realizing the filtered and organized discharge of the gas in the containment, and can play an auxiliary role in the discharge of residual heat from reactor accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a schematic diagram of a nuclear power plant reactor provided in one embodiment of the present application. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] At least one embodiment of the present application provides a natural circulation heat removal system for a reactor pit, which is applied to the nuclear island part of a nuclear power plant. The nuclear island part of a nuclear power plant includes a reactor body 1, a reactor pit 2, a containment shell 3 and a reactor hall 10. The reactor body 1 is located in the reactor pit 2, and the upper part of the reactor body 1 and the reactor pit 2 is the containment shell 3. The reactor hall 10 is surrounded by the outer side of the containment shell 3. The natural circulation heat removal system for the reactor pit includes a reactor pit exhaust system and an air extraction chimney 9. The reactor pit exhaust system includes an air inlet duct, an air outlet duct, an air inlet fan 4, a first valve 5, a second valve 6, a third valve 7 and an exhaust fan 8. The air inlet fan 4 and the first valve 5 are sequentially arranged on the air inlet duct along the air inlet direction of the air inlet duct and are located in the area between the containment shell 3 and the reactor hall 10. The second valve 6 is arranged on a branch pipe connected to the air inlet duct and is located on the side of the first valve 5 close to the containment shell 3. The second valve 6 and the branch pipe are both located in the area between the containment shell 3 and the reactor hall 10. The third valve 7 and the exhaust fan 8 are sequentially arranged on the air outlet duct along the air outlet direction of the air outlet duct and are located in the area between the containment shell 3 and the reactor hall 10. The air outlet duct passes through the containment shell 3 and is connected to the reactor pit 2. The air extraction chimney 9 is connected to the air outlet of the air outlet duct. The air inlet duct passes through the side of the reactor hall 10 and the containment shell 3 and is connected to the reactor pit 2.

[0020] It should be noted that the reactor body 1 refers to all components in the entire reactor vessel, including the core and the primary circuit system, etc. The wind chimney 9 can be located outside the reactor hall 10, or part of it can be outside the reactor hall 10 and the other part can be inside the reactor hall 10. The air outlet duct can also pass through the top of the reactor hall and the containment 3 and then be connected to the reactor pit 2.

[0021] Next, combine Figure 1 , the working principle of the natural circulation heat removal system of the pile pit is explained in detail.

[0022] When the reactor is in normal power operation, the reactor body 1 is in a high temperature state. When the natural circulation heat removal system of the reactor pit is started, the first valve 5 and the third valve 7 are opened, the second valve 6 is closed, and the exhaust fan 8 and the air extraction chimney 9 filter the air in the reactor pit 2 and discharge it into the environment.

[0023] When the reactor is in the shutdown and refueling condition, the first valve 5 and the third valve 7 are in the open state, the second valve 6 is in the closed state, the temperature of the reactor body 1 is low, and the heat load of the reactor pit is small, then the air inlet fan 4 and the exhaust fan 8 can be closed, and the natural circulation mode is adopted to maintain the temperature and negative pressure of the reactor pit 2.

[0024] When the reactor is in an accident condition, the first valve 5 is closed, the containment 3 is automatically isolated, and the short half-life nuclides decay first. At this time, the temperature in the reactor pit 2 will rise and the radioactivity level will accumulate. After that, the third valve 7 is opened, and the second valve 6 is set to a small opening (e.g., 5% valve opening) to maintain the natural circulation cooling of the reactor pit 2 and achieve the filtered and organized discharge of residual radioactivity.

[0025] The natural circulation heat removal system for the reactor pit provided in the embodiment of the present application is provided by arranging an extraction chimney 9 outside the reactor hall 10, and connecting the extraction chimney 9 to the reactor pit 2 through an air outlet duct, and by setting a first valve 5, a second valve 6 and a third valve 7, the heat of the reactor pit is taken away in a passive natural circulation manner by opening and closing the first valve 5, the second valve 6 and the third valve 7, which is beneficial to maintaining the structural integrity of the reactor body 1 and the reactor pit 2, and assisting in enhancing the natural circulation capacity in the reactor, improving the safety and economy of the reactor, and simplifying the operation. In addition, the natural circulation heat removal system for the reactor pit can maintain the natural circulation heat removal of the reactor pit 2 when there is no damage to the primary pressure boundary or the impact of the leakage of radioactive nuclides is not higher than the minor damage required by the national standard for annual emission. Under accident conditions, the heat can be reliably discharged through the natural circulation method through the natural circulation heat removal system for the reactor pit, and the filtered and organized emission of the gas in the containment 3 is realized at the same time, and it can play an auxiliary role in the discharge of residual heat from the reactor accident.

[0026] In at least one embodiment of the present application, the air inlet duct extends to a distance S from the bottom surface of the pit 2. 底 The first straight line distance D1. The air outlet duct extends to the bottom surface S of the pile pit 2. 底 The second straight line distance D2 is greater than the first straight line distance D1. In this way, by reasonably designing the air inlet duct and the air outlet duct to extend to the position in the pile pit 2, the efficiency of natural circulation heat removal is higher.

[0027] It should be noted that the air inlet fan 4 can be installed on the horizontal ground S of the reactor hall 10. 1 superior.

[0028] In at least one embodiment of the present application, the stack body 1 is a liquid metal reactor stack body. Further, in some embodiments, the core outlet temperature of the liquid metal reactor stack body is greater than 500°C.

[0029] It should be noted that the liquid metal reactor body includes but is not limited to a sodium-cooled fast reactor body or a lead-cooled fast reactor body, and the present application embodiment does not specifically limit this. For example, the core outlet temperature of the sodium-cooled fast reactor body can be 565°C. The core outlet temperature of the lead-cooled fast reactor body can be 540°C.

[0030] In at least one embodiment of the present application, the height and arrangement position of the air extraction chimney 9 are obtained by coupling calculation of the natural circulation driving force and the flow resistance. In this way, the height and arrangement position of the air extraction chimney 9 can meet the requirements of natural circulation ventilation under normal power operation conditions and accident conditions.

[0031] It should be noted that the resistance can be determined by geometric parameters such as pipeline length, inner diameter of the pipe, and inner elbows of the pipe, and the driving force of natural circulation can be determined by reasonably setting the height of the extraction chimney.

[0032] At least one embodiment of the present application also provides a nuclear power plant reactor, which includes a nuclear island portion of the nuclear power plant and a natural circulation heat removal system for a reactor pit in any of the above embodiments of the present application. The nuclear island portion of the nuclear power plant includes a reactor body 1, a reactor pit 2, a containment vessel 3 and a reactor hall 10. The containment vessel 3 is placed in the reactor pit 2, and the reactor body 1 is located inside the reactor pit 2 and the containment vessel 3. The reactor hall 10 is surrounded on the outside of the containment vessel 3. The natural circulation heat removal system for the reactor pit includes a reactor pit exhaust system and an air extraction chimney 9. The reactor pit exhaust system includes an air inlet duct, an air outlet duct, an air inlet fan 4, a first valve 5, a second valve 6, a third valve 7 and an exhaust fan 8. The air inlet fan 4 and the first valve 5 are sequentially arranged in series on the air inlet duct along the air inlet direction of the air inlet duct and are located in the area between the containment vessel 3 and the reactor hall 10. The second valve 6 is arranged on a branch pipe connected to the air inlet pipe and is located on the side of the first valve 5 close to the containment shell. The second valve 6 and the branch pipe are both located in the area between the containment shell 3 and the reactor hall 10. The third valve 7 and the exhaust fan 8 are sequentially arranged on the air outlet pipe along the air outlet direction of the air outlet pipe and are located in the area between the containment shell 3 and the reactor hall 10. The air outlet pipe is connected to the reactor pit 2 after passing through the containment shell 3. The air extraction chimney 9 is connected to the air outlet of the air outlet pipe and is located outside the reactor hall 10. The air inlet pipe is connected to the reactor pit 2 after passing through the side of the reactor hall 10 and the containment shell 3.

[0033] It should be noted that the nuclear power plant reactor includes a natural circulation heat removal system for the reactor pit in any of the above embodiments of the present application, has corresponding technical features, and can achieve corresponding technical effects, which will not be repeated here.

[0034] The nuclear power plant reactor provided in the embodiment of the present application simplifies the traditional pit ventilation system and containment design, and at the same time enables the pit natural circulation heat removal system in the nuclear power plant reactor to have a partial auxiliary heat removal function. By designing the air extraction chimney 9 connected to the pit 2, the demand for the ventilation system under normal power operation conditions and accident conditions is reduced, and the passive safety of the reactor is improved.

[0035] At least one embodiment of the present application further provides a method for removing heat from a nuclear power plant reactor. The method for removing heat from a nuclear power plant reactor includes the following steps.

[0036] S100: When the reactor is in normal power operation, the first valve 5 and the third valve 7 of the natural circulation heat removal system of the reactor pit in the embodiment of the present application are opened, the second valve 6 is closed, and the exhaust fan 8 and the air extraction chimney 9 filter the air in the reactor pit 2 and discharge it into the environment.

[0037] S200: When the reactor is in a shutdown and refueling condition, the air inlet fan 4 and the exhaust fan 8 are turned off, and the natural circulation mode is adopted to maintain the temperature and negative pressure of the reactor pit 2.

[0038] S300: When the reactor is in an accident condition, the containment vessel 3 is automatically isolated, after which the third valve 7 is opened and the second valve 6 is set to a valve opening of 5%.

[0039] The heat removal method of the nuclear power plant reactor can refer to the above-mentioned specific description of the working principle of the natural circulation heat removal system of the pile pit, which will not be repeated here. The heat removal method of the nuclear power plant reactor uses the natural circulation heat removal system of the pile pit in the above-mentioned embodiment of the present application, includes corresponding technical features, and can achieve corresponding technical effects, which will not be repeated here.

[0040] It should be noted that the combination of the various technical features in the embodiments of the present application is not limited to the combination described in the embodiments of the present application or the combination described in the specific embodiments, and all technical features described in the present application can be freely combined or combined in any way unless there is a contradiction between them.

[0041] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the term "comprising" only indicates that the steps and elements that have been clearly identified are included, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0042] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A natural circulation heat removal system for a pile pit, characterized in that: Applied to the nuclear island part of a nuclear power plant, wherein the nuclear island part of a nuclear power plant includes a reactor body, a reactor pit, a containment shell and a reactor hall. The reactor body is located in the reactor pit, the upper part of the reactor body and the reactor pit is the containment shell, and the reactor hall is surrounded by the outer side of the containment shell. The natural circulation heat removal system of the reactor pit includes a reactor pit exhaust system and an air extraction chimney. The reactor pit exhaust system includes an air inlet duct, an air outlet duct, an air inlet fan, a first valve, a second valve, a third valve and an exhaust fan. The air inlet fan and the first valve are sequentially arranged in series on the air inlet duct along the air inlet direction of the air inlet duct and are located in the area between the containment shell and the reactor hall; the second valve is arranged on a branch duct connected to the air inlet duct and is located on the side of the first valve close to the containment shell; the second valve and the branch duct are both located in the area between the containment shell and the reactor hall; the third valve and the exhaust fan are sequentially arranged in series on the air outlet duct along the air outlet direction of the air outlet duct and are located in the area between the containment shell and the reactor hall; the air outlet duct is connected to the reactor pit after passing through the containment shell, the air extraction chimney is connected to the air outlet of the air outlet duct and is located outside the reactor hall, and the air inlet duct is connected to the reactor pit after passing through the side of the reactor hall and the containment shell.

2. A natural circulation heat removal system for a pile pit according to claim 1, characterized in that: The air inlet duct extends to a first linear distance from the bottom surface of the stacking pit, and the air outlet duct extends to a second linear distance from the bottom surface of the stacking pit, and the second linear distance is greater than the first linear distance.

3. The natural circulation heat removal system for a pile pit according to claim 1, characterized in that: The stack body is a liquid metal reactor stack body.

4. The natural circulation heat removal system for a pile pit according to claim 3 is characterized in that: The core outlet temperature of the liquid metal reactor body is greater than 500°C.

5. The natural circulation heat removal system for a pile pit according to claim 3 is characterized in that: The main body of the liquid metal reactor is a sodium-cooled fast reactor.

6. A natural circulation heat removal system for a pile pit according to any one of claims 1 to 5, characterized in that: The height and layout of the wind chimney are obtained through the coupling calculation of the natural circulation driving force and flow resistance.

7. A nuclear power plant reactor, characterized in that: include: The nuclear island portion of a nuclear power plant; as well as, A natural circulation heat removal system for a pile pit as claimed in any one of claims 1 to 6.

8. A method for removing heat from a nuclear power plant reactor, characterized in that: When the reactor is in normal power operation, the first valve and the third valve of the natural circulation heat removal system of the reactor pit according to claim 1 are opened, the second valve is closed, and the exhaust fan and the air extraction chimney filter the air in the reactor pit and discharge it into the environment; When the reactor is shut down for refueling, the air inlet and exhaust fans are turned off and the natural circulation mode is adopted to maintain the temperature and negative pressure of the reactor pit. When the reactor is in an accident condition, the containment is automatically isolated, after which the third valve is opened and the second valve is set to a 5% valve opening.

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