A residual heat removal system for a nuclear reactor

Abstract

The utility model provides a kind of residual heat of reactor core lead-out system, comprising: containment;Pressure vessel located in containment;Main heat exchanger located in pressure vessel;Condensing heat exchanger and cooling water tank and steam generator located outside containment, and condensing heat exchanger is immersed in the cooling water of cooling water tank;First circulating pipeline, reactor core and main heat exchanger primary side are connected in series on first circulating pipeline;Second circulating pipeline, main heat exchanger secondary side and condensing heat exchanger are connected in series on second circulating pipeline, and first isolation valve is arranged on second circulating pipeline;Third circulating pipeline, main heat exchanger secondary side and steam generator primary side are connected in series on third circulating pipeline, and second isolation valve is arranged on third circulating pipeline;Make-up line, make-up line is connected on cooling water tank and steam generator secondary side, and third isolation valve is arranged on make-up line, and the above heat conduction system can reliably lead out residual heat of reactor core and containment by redundancy design, and safety and economy are considered.

Description

Technical Field

[0001] This utility model relates to the field of nuclear power technology, and in particular to a reactor core waste heat removal system. Background Technology

[0002] In the design of nuclear power plants, residual heat removal systems are required to cope with accidents such as power outages, in order to prevent the reactor core from overheating and melting down, as well as the leakage of radioactive materials into the environment due to the breach of the containment.

[0003] In existing technology, a third-generation reactor design incorporates a residual heat removal system comprising a passive core residual heat removal subsystem and a passive containment heat removal subsystem. The passive core residual heat removal subsystem includes pipelines connecting the main feedwater pipe to the steam generator and the main steam pipe, as well as residual heat removal heat exchangers connected in series on these pipelines. These heat exchangers are submerged in an emergency cooling water tank and are positioned higher than the steam generator. This allows condensate formed after the steam in the main steam pipe is cooled by the heat exchangers to flow back into the main feedwater pipe under gravity, creating a natural circulation to address the possibility of feedwater failure in the main feedwater pipe. The passive containment heat removal subsystem includes several sets of heat exchangers located inside the containment and a hot water tank located outside the containment. The heat exchangers and the hot water tank are connected in series via pipelines penetrating the containment, creating a natural circulation between steam and liquid water to remove heat from the containment. This type of residual heat removal system has the following problems:

[0004] 1) Both the passive core residual heat removal subsystem and the passive containment heat removal subsystem need to be equipped with large-capacity water tanks to ensure that natural circulation can proceed normally;

[0005] 2) The passive core residual heat removal subsystem and the passive containment heat removal subsystem do not overlap in function. If a single subsystem fails, they cannot form an effective complement.

[0006] In another type of third-generation reactor, the passive core residual heat removal subsystem comprises pipelines between the reactor coolant hot section and the steam generator cold section chamber connected to the reactor coolant pump inlet, and heat exchangers connected to these pipelines. The heat exchangers are submerged in a refueling tank located within the containment vessel, and are positioned above the reactor coolant system loop. When the reactor coolant pumps are unavailable, the heat exchangers allow the coolant to circulate naturally through the core, carrying away residual heat. The cooling water in the refueling tank absorbs heat and vaporizes into steam. This steam rises and condenses on the inner wall of the containment vessel, returning to the refueling tank via a condensate return tank. The passive containment heat removal subsystem mainly includes a cooling water tank located at the top of the containment vessel. In the event of an accident, water in the cooling water tank flows towards the containment vessel under gravity, forming a water film on the outer surface of the containment dome and sidewalls to remove heat from the containment vessel. This type of residual heat removal system has the following problems:

[0007] 1) Since the refueling water tank is located inside the containment, the core heat is not removed from the containment, so a passive containment heat removal subsystem needs to be installed;

[0008] 2) Given the need to maintain the water level in the refueling tank, a condensate return tank needs to be installed at a high position on the containment vessel, which places high demands on the layout.

[0009] 3) The passive core residual heat removal subsystem and the passive containment heat removal subsystem do not overlap in function. If a single subsystem fails, they cannot form an effective complement. Utility Model Content

[0010] The purpose of this invention is to provide a core waste heat removal system with a redundant backup design, which can remove core waste heat from the core and containment through multiple pipelines, while also taking into account safety and economy.

[0011] This utility model provides a reactor core residual heat removal system for use in nuclear power plants. The system includes: a containment vessel; a pressure vessel located within the containment vessel and used to house the reactor core; a main heat exchanger located within the pressure vessel; a condensing heat exchanger located outside the containment vessel; a cooling water tank located outside the containment vessel, with the condensing heat exchanger submerged in the cooling water within the tank; a steam generator located outside the containment vessel; and a first circulation pipe. The reactor core and the primary side of the main heat exchanger are connected in series on the first circulation pipeline; the secondary side of the main heat exchanger and the condenser heat exchanger are connected in series on the second circulation pipeline, and a first isolation valve is installed on the second circulation pipeline; the secondary side of the main heat exchanger and the primary side of the steam generator are connected in series on the third circulation pipeline, and a second isolation valve is installed on the third circulation pipeline; a makeup water pipeline is connected to the cooling water tank and the secondary side of the steam generator, and a third isolation valve is installed on the makeup water pipeline.

[0012] In one embodiment of the present invention, the second circulation pipeline is configured to allow condensate in the condenser heat exchanger to flow by gravity to the secondary side of the main heat exchanger.

[0013] In one embodiment of the present invention, the water supply pipeline is configured to allow the condensate in the cooling water tank to flow by gravity to the secondary side of the steam generator.

[0014] In one embodiment of the present invention, the third circulation pipeline is configured to allow condensate in the primary side of the steam generator to flow by gravity to the secondary side of the main heat exchanger.

[0015] In one embodiment of the present invention, the first isolation valve is disposed on the second circulation pipeline connecting the condensate outlet in the condenser heat exchanger and the cooling water inlet on the secondary side of the main heat exchanger.

[0016] In one embodiment of the present invention, the first isolation valve is an electric valve equipped with a storage battery.

[0017] In one embodiment of the present invention, an exhaust pipe connected to the atmosphere is connected to the steam outlet on the secondary side of the steam generator, and an atmosphere release valve is installed on the exhaust pipe.

[0018] In one embodiment of this utility model, the opening degree of the atmospheric release valve is adjustable.

[0019] In one embodiment of the present invention, a volume compensation box for adjusting the pressure inside the second circulation pipeline is provided.

[0020] In one embodiment of the present invention, a volume compensation box is provided on the third circulation pipeline for adjusting the pressure inside the pipeline.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] By using the main heat exchanger in the pressure vessel as the hub between the reactor core and the condensing heat exchanger or steam generator, the functions of reactor core residual heat removal and containment heat removal are coupled and overlapped. The system provides two independent heat removal paths, a second circulation pipeline and a third circulation pipeline, which are isolated and controlled by a first isolation valve and a second isolation valve. This allows the two overlapping pipelines to form effective backup and complement each other, greatly enhancing the reliability, safety and accident response capability of the overall system.

[0023] This invention requires only one cooling water tank outside the containment vessel, which serves as both a heat sink and a cooling water source. This reduces the construction cost, space requirements, and maintenance complexity of the facility. It eliminates the need for a large-capacity refueling water tank inside the containment vessel as an intermediate heat sink, as well as the need for complex condensate return devices such as condensate return tanks at high positions within the containment vessel. This simplifies the layout within the containment vessel, reduces the requirements for the internal structure and arrangement of the containment vessel, and improves the economic efficiency of the nuclear power plant. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0025] In the attached diagram:

[0026] Figure 1 A schematic diagram of a reactor core waste heat extraction system provided in an embodiment of the present invention;

[0027] The attached figures are labeled as follows:

[0028] 100. Containment vessel; 200. Pressure vessel; 310. Reactor core; 320. Main heat exchanger; 330. First circulation line; 410. Condensing heat exchanger; 420. Cooling water tank; 430. Second circulation line; 440. First isolation valve; 510. Steam generator; 511. Exhaust line; 512. Atmospheric relief valve; 520. Third circulation line; 530. Second isolation valve; 610. Makeup water line; 620. Third isolation valve; 700. Volumetric compensation tank; 800. Circulation pump; 900. Feedwater pump. Detailed Implementation

[0029] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0030] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0031] Please see Figure 1 The reactor core 310 residual heat removal system provided by this utility model is applied in a nuclear power plant. The reactor core 310 residual heat removal system includes: a containment 100; a pressure vessel 200 located inside the containment 100 and used to house the reactor core 310; a main heat exchanger 320 located inside the pressure vessel 200; a condensing heat exchanger 410 located outside the containment 100; a cooling water tank 420 located outside the containment 100, with the condensing heat exchanger 410 immersed in the cooling water within the cooling water tank 420; a steam generator 510 located outside the containment 100; and a first circulation pipeline 330 for the reactor core. The primary side of the main heat exchanger 310 and the main heat exchanger 320 are connected in series on the first circulation pipeline 330. In a specific embodiment, the main heat exchanger 320; the second circulation pipeline 430, the secondary side of the main heat exchanger 320 and the condensing heat exchanger 410 are connected in series on the second circulation pipeline 430, and a first isolation valve 440 is provided on the second circulation pipeline 430; the third circulation pipeline 520, the secondary side of the main heat exchanger 320 and the primary side of the steam generator 510 are connected in series on the third circulation pipeline 520, and a second isolation valve 530 is provided on the third circulation pipeline 520; and the water supply pipeline 610, the water supply pipeline 610 is connected to the cooling water tank 420 and the secondary side of the steam generator 510, and a third isolation valve 620 is provided on the water supply pipeline 610.

[0032] Please see Figure 1When no accident occurs at the nuclear power plant, the reactor core 310 undergoes fission, releasing a large amount of heat. The cooling water heated by the reactor core 310 in the pressure vessel 200 enters the primary side of the main heat exchanger 320 through the first circulation pipeline 330. After the cooling water in the secondary side of the main heat exchanger 320 exchanges heat with the primary side of the main heat exchanger 320, it vaporizes into water vapor and enters the primary side of the steam generator 510. The cooling water in the secondary side of the steam generator 510 is driven by the feedwater pump 900 on the feedwater pipeline and pressed into the cooling water inlet of the secondary side of the steam generator 510. After the cooling water in the secondary side of the steam generator 510 exchanges heat with the primary side of the steam generator 510, it vaporizes into water vapor that drives the steam turbine. The steam turbine then drives the generator to work. The water vapor in the primary side of the steam generator 510 is cooled into condensate and driven by the circulation pump 800 on the second circulation pipeline 430 and pressed into the cooling water inlet of the secondary side of the main heat exchanger 320, continuing the above cycle.

[0033] In the event of a power outage or other accident, the circulation pump 800 and feedwater pump 900 will cease normal operation, preventing the aforementioned circulation from continuing. This triggers the operation signal for the core 310 residual heat removal system, closing the second isolation valve 530 on the third circulation pipeline 520 and opening the first isolation valve 440 on the second circulation pipeline 430. At this time, water vapor in the secondary side of the main heat exchanger 320 enters the condensing heat exchanger 410 submerged in the cooling water tank 420. The water vapor is cooled by the cooling water in the cooling water tank 420 and converted into condensate. The condensate continues to flow through the second circulation pipeline 430 into the cooling water inlet on the secondary side of the main heat exchanger 320. This circulation continues, effectively removing residual heat from the core 310 to the cooling water tank 420 outside the containment 100. If the first isolation valve 440 or the second circulation pipeline 430 malfunctions, the second isolation valve 440 will be opened. Isolation valve 530 and third isolation valve 620 allow steam from the secondary side of the main heat exchanger 320 to enter the primary side of the steam generator 510. Cooling water from the cooling water tank 420 enters the secondary side of the steam generator 510 through the makeup water line 610. After heat exchange with the steam from the primary side of the steam generator 510, the water vaporizes into steam. The condensate formed by the steam from the primary side of the steam generator 510 is then condensed and flows into the cooling water inlet of the secondary side of the main heat exchanger 320 through the third circulation line 520. This cycle continues, allowing residual heat from the reactor core 310 to be transferred to the steam generator 510 located outside the containment 100. In other words, the cycle occurring between the secondary side of the main heat exchanger 320 and the steam generator 510 is the same as during normal operation of a nuclear power plant, except that the water supply method has changed. In this case, the cooling water tank 420 supplies water to the secondary side of the steam generator 510 through the makeup water line 610.

[0034] The above design makes the main heat exchanger 320 located in the pressure vessel 200 serve as the hub between the core 310 and the condensing heat exchanger 410 or steam generator 510, coupling and overlapping the residual heat removal function of the core 310 and the heat removal function of the containment 100. The system provides two independent heat removal paths, the second circulation pipeline 430 and the third circulation pipeline 520, which are isolated and controlled by the first isolation valve 440 and the second isolation valve 530. This makes the two overlapping pipelines form an effective backup and complement to each other, greatly enhancing the reliability, safety and accident response capability of the overall system.

[0035] This design only requires a cooling water tank 420 outside the containment 100, which serves as both a heat sink and a cooling water source. This reduces the construction cost, space requirements, and maintenance complexity of the facility. It eliminates the need for a large-capacity refueling water tank inside the containment 100 as an intermediate heat sink, and also eliminates the need for complex condensate return devices, such as condensate return tanks, at the high level of the containment 100. This simplifies the layout within the containment 100, reduces the requirements for the internal structure and arrangement of the containment 100, and improves the economics of the nuclear power plant.

[0036] Please see Figure 1 In one embodiment of this utility model, the second circulation pipeline 430 is configured to allow the condensate in the condenser heat exchanger 410 to flow by gravity to the secondary side of the main heat exchanger 320. This makes the circulation between the secondary side of the main heat exchanger 320 and the condenser heat exchanger 410 a passive operation mode that only relies on fluid density difference and gravity, without relying on any active components that require electricity, such as power pumps. The above-mentioned reliable return flow mode ensures that the circulation can continue, thereby improving the stability and reliability of the core 310 waste heat removal system. In a specific embodiment, the condenser heat exchanger 410 and the cooling water tank 420 can be set higher than the main heat exchanger 320.

[0037] Please see Figure 1 In one embodiment of the present invention, the water supply pipeline 610 is configured to allow the condensate in the cooling water tank 420 to flow by gravity to the secondary side of the steam generator 510, so that the cooling water tank 420 can supply water to the secondary side of the steam generator 510 in a passive manner driven only by gravity, thereby enabling this backup waste heat extraction circulation loop to operate continuously and stably. In a specific embodiment, the cooling water tank 420 can be set higher than the steam generator 510.

[0038] Please see Figure 1In one embodiment of the present invention, the third circulation pipeline 520 is configured to allow the condensate in the primary side of the steam generator 510 to flow by gravity to the secondary side of the main heat exchanger 320, so that the third circulation pipeline 520 is also a passive circulation relying solely on natural forces. In a specific embodiment, the steam generator 510 can be set higher than the main heat exchanger 320.

[0039] The two physically isolated, functionally overlapping, and completely passive second circulation line 430 and third circulation line 520 form a redundant and complementary relationship, greatly enhancing the reliability and resilience of the nuclear power plant in the face of severe accidents.

[0040] Please see Figure 1 In one embodiment of the present invention, the first isolation valve 440 is disposed on the second circulation pipeline 430 connecting the condensate outlet in the condenser heat exchanger 410 and the cooling water inlet on the secondary side of the main heat exchanger 320. The above arrangement allows the condenser heat exchanger 410 to be filled with condensate and to maintain a pressure in the condenser heat exchanger 410 that is almost the same as that on the secondary side of the main heat exchanger 320. This allows for rapid establishment of circulation after an accident to remove residual heat from the reactor core 310, thereby improving the response speed of the residual heat removal system of the reactor core 310.

[0041] Please see Figure 1 In one embodiment of this utility model, the first isolation valve 440 is an electric valve equipped with a storage battery. Compared with a manual valve, in case of an accident, especially when the main control room may be inaccessible, the operator can quickly open the valve by sending a signal from a remote station or directly by the protection system. Compared with a pneumatic valve, it does not have the problem of limited opening force caused by the pressure imbalance between the second circulation pipeline 430 and the secondary side of the main heat exchanger 320. In addition, more importantly, the storage battery provides the electric valve with a dedicated backup power supply independent of the nuclear power plant power supply. After the entire station loses power, the storage battery can ensure that the valve can still receive signals and perform multiple opening and closing operations.

[0042] Please see Figure 1In one embodiment of this utility model, an exhaust pipe 511 connected to the atmosphere is provided on the steam outlet of the secondary side of the steam generator 510, so that the water vapor in the secondary side of the steam generator 510 can be smoothly discharged into the atmosphere. This allows the atmosphere to serve as the final heat sink for the waste heat removal system of the reactor core 310, ensuring that the waste heat of the reactor core 310 can be smoothly removed from the reactor core 310 and the containment 100. In addition, since the steam generator 510 is located outside the containment 100 and the media in the primary and secondary sides of the steam generator 510 are not mixed, the steam discharged into the atmosphere is non-radioactive, which has higher environmental safety. An atmospheric release valve 512 is installed on the exhaust pipe 511. The atmospheric release valve 512 can be opened when the pressure in the exhaust pipe 511 reaches a certain value, thereby ensuring that there is sufficient pressure and temperature difference between the secondary side of the main heat exchanger 320 and the primary side of the steam generator 510 to drive natural circulation and prevent the steam generator 510 from overpressure, thus protecting the safety of the equipment itself.

[0043] In one embodiment of the present invention, the opening degree of the atmospheric release valve 512 is adjustable, thereby allowing the operator or automatic control system to precisely control the steam discharge rate so as to accurately stabilize the pressure on the secondary side of the steam generator 510 near the optimal set value. In a specific embodiment, in order to increase the temperature difference between the primary and secondary sides of the steam generator 510, the opening degree of the atmospheric release valve 512 can be opened according to a certain pressure reduction rate.

[0044] Please see Figure 1 In one embodiment of this utility model, a volume compensation tank 700 is provided on the second circulation pipeline 430 to regulate the pressure inside the pipeline. Since the second circulation pipeline 430 is a closed pipeline filled with liquid, the fluid will expand and contract due to temperature changes during startup and operation, which will cause the pressure inside the pipeline to rise or fall sharply. The volume compensation tank 700 provides additional buffer space to absorb the volume of fluid expansion and replenish the volume of fluid contraction, thereby maintaining the pressure of the entire second circulation pipeline 430 within a relatively stable range. This creates a crucial prerequisite for the establishment of natural circulation and long-term stable operation. In addition, the volume compensation tank 700 can also absorb the impact force on the pipeline caused by pressure fluctuations and water hammer when the system starts and stops. Furthermore, in a specific embodiment, the volume compensation tank 700 can be set at the high point of the second circulation pipeline 430, through which water can be added to the second circulation pipeline 430. After the system is initially filled with water or after maintenance, it can also be used to discharge non-condensable gases such as air from the pipeline.

[0045] Please see Figure 1In one embodiment of the present invention, a volume compensation box 700 for adjusting the pressure inside the third circulation pipeline 520 is provided. The technical effect produced by this volume compensation box 700 is similar to that of the volume compensation box 700 provided on the second circulation pipeline 430, and will not be described again.

[0046] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A reactor core waste heat removal system, applied in a nuclear power plant, characterized in that, include: Containment vessel; A pressure vessel located within the containment vessel, the pressure vessel being used to house the reactor core; The main heat exchanger is located inside the pressure vessel; A condensing heat exchanger, wherein the condensing heat exchanger is located outside the containment; A cooling water tank is located outside the containment structure, and the condensing heat exchanger is immersed in the cooling water in the cooling water tank. A steam generator, located outside the containment; The first circulation pipeline is connected in series with the reactor core and the primary side of the main heat exchanger. The second circulation pipeline is connected in series with the secondary side of the main heat exchanger and the condensing heat exchanger, and a first isolation valve is installed on the second circulation pipeline. The third circulation pipeline is connected in series between the secondary side of the main heat exchanger and the primary side of the steam generator, and a second isolation valve is installed on the third circulation pipeline. A water supply pipeline is provided, which is connected to the cooling water tank and the secondary side of the steam generator. A third isolation valve is installed on the water supply pipeline.

2. The reactor core waste heat removal system according to claim 1, characterized in that, The second circulation line is configured to allow condensate in the condenser heat exchanger to flow by gravity to the secondary side of the main heat exchanger.

3. The reactor core waste heat removal system according to claim 1, characterized in that, The water supply pipeline is configured to allow condensate in the cooling water tank to flow by gravity to the secondary side of the steam generator.

4. The reactor core waste heat removal system according to claim 1, characterized in that, The third circulation pipeline is configured to allow condensate from the primary side of the steam generator to flow by gravity to the secondary side of the main heat exchanger.

5. The reactor core waste heat removal system according to claim 1, characterized in that, The first isolation valve is installed on the second circulation pipeline between the condensate outlet in the condenser heat exchanger and the cooling water inlet on the secondary side of the main heat exchanger.

6. The reactor core waste heat removal system according to claim 1, characterized in that, The first isolation valve is an electric valve equipped with a storage battery.

7. The reactor core waste heat removal system according to claim 1, characterized in that, An exhaust pipe connected to the atmosphere is connected to the steam outlet on the secondary side of the steam generator, and an atmosphere release valve is installed on the exhaust pipe.

8. The reactor core waste heat removal system according to claim 7, characterized in that, The opening degree of the atmospheric release valve is adjustable.

9. The reactor core waste heat removal system according to claim 1, characterized in that, A volume compensation box is installed on the second circulation pipeline to regulate the pressure inside the pipeline.

10. The reactor core waste heat removal system according to claim 1, characterized in that, A volume compensation box is installed on the third circulation pipeline to regulate the pressure inside the pipeline.

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