A multi-stage dynamic oxygen control system and method for a nuclear power plant feedwater system

Abstract

The application discloses a kind of multi-stage dynamic oxygenation control system and method of nuclear power unit feedwater system, the outlet of low-pressure cylinder is sequentially communicated with the inlet of high-pressure cylinder through condensate oxygenation point, condensate flowmeter, deaerator inlet dissolved oxygen meter, deaerator, main feedwater oxygenation point, feedwater flowmeter, steam generator inlet dissolved oxygen meter, steam generator outlet dissolved oxygen meter, the outlet of high-pressure cylinder is sequentially communicated with the inlet of low-pressure cylinder through steam-water separator, the shell side of first reheater and second reheater, the steam extraction pipeline of reheater is sequentially communicated with the shell side of No.4 low-adding drain pump through first reheater oxygenation point, the tube side of first reheater, the tube side of No.3 low-adding and low-adding drain pump, the steam extraction pipeline of No.5 low-adding is sequentially communicated with the tube side of No.3 low-adding through low-adding steam extraction oxygenation point, the tube side of No.5 low-adding and the tube side of No.4 low-adding, which can avoid the problem that local oxygen concentration is too high to cause the destruction of oxidation film structure, or too low to cause the problem of intensified corrosion.

Description

Technical Field

[0001] This invention belongs to the field of water chemistry control technology for nuclear power units, and relates to a multi-stage dynamic oxygenation control system and method for nuclear power unit feedwater systems. Background Technology

[0002] Traditional pressurized water reactor (PWR) nuclear power units employ AVT(R) water chemistry with hydrazine deoxygenation to reduce oxidation and corrosion of the unit's metallic materials. However, for high-parameter fourth-generation nuclear reactors such as high-temperature gas-cooled reactors and sodium-cooled fast reactors, flow-accelerated corrosion (FAC) of the feedwater can easily lead to blockage of the steam generator throttling components and deposition on heat transfer tubes. Oxygenation of the feedwater not only forms a dense oxide film on the feedwater pipes and evaporator inner walls, slowing down the rate of FAC in the feedwater and condensate systems and effectively reducing the rate of evaporator corrosion and scaling, but also eliminates Fe3O4 deposition at the throttling valves of the evaporator heat transfer tubes, reduces the rate of pressure differential rise on the DC side of the nuclear power unit's evaporator, and eliminates inter-tube temperature deviations caused by scaling at the throttling valves. Furthermore, oxygenation of the feedwater can extend the fine treatment cycle, offering significant economic advantages.

[0003] The most common methods for oxygenating feedwater are pure oxygen, compressed air, and oxygen-enriched water. Oxygenation points are typically set up using a single point of condensate oxygenation, a two-point oxygenation system with the main feedwater added, or a three-point oxygenation system with the high-pressure heater's condensate added. However, these methods suffer from problems such as insufficient protection for the steam-water separator, inadequate protection for the low-pressure heater, and poor oxygenation uniformity. Flow-accelerated corrosion (FAC) is more likely to occur in the temperature range of 120–180°C. Nuclear power units typically have about five low-pressure heaters, with water temperature variations ranging from 20–150°C. This is especially true in the last two low-pressure heaters, where the condensate temperature inside the heater core is 100–150°C, and the shell-side cycle temperature is 120–180°C, highly overlapping with the temperature range where FAC is most likely to occur. Two- or three-point oxygenation can only protect the inner wall of the low-pressure heat exchange tube, but it does not protect the outer wall of the low-pressure heat exchange tube. However, the low-pressure heater has a huge heat exchange area, which undoubtedly further exacerbates the flow-accelerated corrosion (FAC) effect.

[0004] The current oxygenation method has too long a pipeline distance between the dissolved oxygen measurement point and the oxygen addition point, which may lead to excessively high local oxygen concentration, causing damage to the oxide film structure, or too low oxygen concentration, causing accelerated corrosion. In terms of control, it relies on manual adjustment or simply feedforward and feedback price adjustment, which cannot adapt to unit load fluctuations and changes in water quality parameters, and has insufficient dynamic response capability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-stage dynamic oxygenation control system and method for nuclear power unit feedwater systems. This system and method can avoid the problems of excessively high local oxygen concentration leading to damage to the oxide film structure or excessively low local oxygen concentration leading to accelerated corrosion.

[0006] To achieve the above objectives, this invention discloses a multi-stage dynamic oxygenation control system for a nuclear power unit feedwater system, including a low-pressure cylinder, a high-pressure cylinder, a reheater extraction steam pipeline, and a No. 5 low-pressure heater extraction steam pipeline.

[0007] The outlet of the low-pressure cylinder is connected to the inlet of the high-pressure cylinder via the condenser, condensate oxygenation point, condensate flow meter, shell side of No. 3 low-pressure heater, shell side of No. 4 low-pressure heater, shell side of No. 5 low-pressure heater, dissolved oxygen meter at the deaerator inlet, deaerator, main feedwater oxygenation point, main feedwater pump, feedwater flow meter, high-pressure heater, dissolved oxygen meter at the steam generator inlet, steam generator, dissolved oxygen meter at the steam generator outlet, and the inlet of the high-pressure cylinder. The outlet of the high-pressure cylinder is connected to the inlet of the low-pressure cylinder via the steam-water separator, shell side of the first-stage reheater, and second-stage reheater. The reheater extraction steam pipeline is connected to the shell side of No. 4 low-pressure heater via the oxygenation point of the first-stage reheater, tube side of the first-stage reheater, tube side of No. 3 low-pressure heater, and low-pressure heater drain pump. The extraction steam pipeline of No. 5 low-pressure heater is connected to the tube side of No. 3 low-pressure heater via the extraction steam oxygenation point of low-pressure heater, tube side of No. 5 low-pressure heater, and tube side of No. 4 low-pressure heater.

[0008] Furthermore, the outlet of the low-pressure cylinder is connected in sequence to the condenser, condensate oxygenation point, condensate pump, fine treatment device, condensate flow meter, No. 1 and No. 2 combined low-pressure heaters, the shell side of No. 3 low-pressure heaters, the shell side of No. 4 low-pressure heaters, the shell side of No. 5 low-pressure heaters, the dissolved oxygen meter at the deaerator inlet, the deaerator, the main feedwater oxygenation point, the main feedwater pump, the feedwater flow meter, the high-pressure heater, the dissolved oxygen meter at the steam generator inlet, the steam generator, and the dissolved oxygen meter at the steam generator outlet, and is connected to the inlet of the high-pressure cylinder.

[0009] Furthermore, it also includes a control module, which is connected to the condensate pump, condensate flow meter, low-pressure heater drain pump, main feedwater pump, feedwater flow meter, condensate oxygenation point, low-pressure heater extraction steam oxygenation point, first-stage reheater oxygenation point, main feedwater oxygenation point, deaerator inlet dissolved oxygen meter, steam generator inlet dissolved oxygen meter, and steam generator outlet dissolved oxygen meter.

[0010] Furthermore, the number of dissolved oxygen meters at the steam generator outlet is two, and the two steam generator outlet dissolved oxygen meters are operated in a one-for-one standby mode.

[0011] Furthermore, the oxygenation medium at the condensate oxygenation point, the low-pressure steam extraction oxygenation point, the first-stage reheater oxygenation point, and the main feedwater oxygenation point is power plant demineralized water, compressed air, oxygen cylinders, or oxygen-enriched water.

[0012] This invention discloses a multi-stage dynamic oxygenation control method for a nuclear power unit feedwater system, comprising:

[0013] The oxygenation rate at the condensate oxygenation point is 40% of the oxygen required for the system's over-the-air (OT) operation.

[0014] The oxygen supply at the low-pressure steam extraction oxygen supply point is less than or equal to 20% of the oxygen required for the system's over-the-air (OT) operation.

[0015] The amount of oxygen added at the oxygenation point of the first-stage reheater is less than or equal to 20% of the oxygen required for the system's OT operation;

[0016] The oxygenation rate at the main feedwater oxygenation point is less than or equal to 20% of the oxygen required for the system's over-the-air (OT) operation.

[0017] Furthermore, the amount of oxygen added at the condensate oxygenation point is controlled based on the condensate flow rate information measured by the condensate flow meter.

[0018] Furthermore, the extraction steam flow rate of No. 4 and No. 5 low-pressure heaters controls the oxygen addition at the extraction steam oxygenation point of the low-pressure heaters.

[0019] Furthermore, the amount of oxygen added at the oxygenation point of the first-stage reheater is controlled based on the reheater extraction steam flow rate of the first-stage reheater.

[0020] Furthermore, when the dissolved oxygen level measured by the dissolved oxygen meter at the steam generator inlet or outlet reaches the preset protection value, the control module issues a command to stop oxygen supply and triggers an alarm.

[0021] Furthermore, the control module employs a PID control method.

[0022] The present invention has the following beneficial effects:

[0023] The multi-stage dynamic oxygenation control system and method for nuclear power unit feedwater systems described in this invention, in specific operation, sets up four oxygenation points: the inlet of the condensate pump, the extraction steam inlet of the No. 5 low-pressure heater, the extraction steam inlet of the first-stage reheater, and the outlet of the deaerator. The condensate pump inlet oxygenation point serves as the system's basic oxygenation point, providing 40% of the oxygen required for system OT operation. The other three oxygenation points serve as subsequent stages of oxygenation points, each responsible for 20% of the oxygen supply. This protects the tube and shell sides of the low-pressure heaters, which are prone to flow-accelerated corrosion, as well as the steam-water separation reheater. In terms of control, a comprehensive control logic combining multi-signal collaborative feedback, feedforward compensation, and adaptive algorithms is employed, enabling precise and balanced control of the system's oxygenation supply and improving the response speed and stability of the oxygenation system during system operating condition fluctuations. Attached Figure Description

[0024] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 This is a structural diagram of the present invention.

[0026] Among them, 1 is the low-pressure cylinder, 2 is the condenser, 3 is the condensate pump, 4 is the fine treatment device, 5 is the condensate flow meter, 6 is the No. 1 and No. 2 combined low-pressure heater, 7 is the No. 3 low-pressure heater, 8 is the low-pressure heater drain pump, 9 is the No. 4 low-pressure heater, 10 is the No. 5 low-pressure heater, 11 is the deaerator, 12 is the main feedwater pump, 13 is the feedwater flow meter, 14 is the high-pressure heater, 15 is the steam generator, 16 is the high-pressure cylinder, 17 is the steam-water separator, 18 is the first stage reheater, 19 is the second stage reheater, 20 is the reheater extraction steam pipeline, 21 is the No. 5 low-pressure heater extraction steam pipeline, 31 is the condensate oxygenation point, 32 is the low-pressure heater extraction steam oxygenation point, 33 is the first stage reheater oxygenation point, 34 is the main feedwater oxygenation point, 41 is the deaerator inlet dissolved oxygen meter, 42 is the steam generator inlet dissolved oxygen meter, 43 is the steam generator outlet dissolved oxygen meter, and 50 is the control module. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0029] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0030] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0031] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0032] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0035] Example 1

[0036] refer to Figure 1The multi-stage dynamic oxygenation control system of the nuclear power unit feedwater system of the present invention includes a low-pressure cylinder 1, a condenser 2, a condensate pump 3, a fine treatment device 4, a condensate flow meter 5, a combined low-pressure heater (No. 1 and No. 2) 6, a low-pressure heater (No. 3) 7, a low-pressure heater drain pump 8, a low-pressure heater (No. 4) 9, a low-pressure heater (No. 5) 10, a deaerator 11, a main feedwater pump 12, a feedwater flow meter 13, a high-pressure heater 14, a steam generator 15, a high-pressure cylinder 16, a steam-water separator 17, a first-stage reheater 18, a second-stage reheater 19, a reheater extraction steam pipe 20, a No. 5 low-pressure heater extraction steam pipe 21, a condensate oxygenation point 31, a low-pressure heater extraction steam oxygenation point 32, a first-stage reheater oxygenation point 33, a main feedwater oxygenation point 34, a deaerator inlet dissolved oxygen meter 41, a steam generator inlet dissolved oxygen meter 42, a steam generator outlet dissolved oxygen meter 43, and a control module 50.

[0037] The outlet of low-pressure cylinder 1 passes sequentially through condenser 2, condensate oxygenation point 31, condensate pump 3, fine treatment device 4, condensate flow meter 5, combined low-pressure heaters 6 (number 1 & 2), shell side of low-pressure heater 7 (number 3), shell side of low-pressure heater 9 (number 4), shell side of low-pressure heater 10 (number 5), dissolved oxygen meter 41 at the deaerator inlet, deaerator 11, main feedwater oxygenation point 34, main feedwater pump 12, feedwater flow meter 13, high-pressure heater 14, dissolved oxygen meter 42 at the steam generator inlet, steam generator 15, dissolved oxygen meter 43 at the steam generator outlet, and high-pressure cylinder 1. The inlet of cylinder 6 is connected, and the outlet of high-pressure cylinder 16 is connected to the inlet of low-pressure cylinder 1 via steam-water separator 17, shell side of first-stage reheater 18 and second-stage reheater 19. Reheater extraction steam pipe 20 is connected to the shell side of No. 4 low-pressure heater 9 via oxygenation point 33 of first-stage reheater, tube side of first-stage reheater 18, tube side of No. 3 low-pressure heater 7 and low-pressure heater drain pump 8. No. 5 low-pressure heater extraction steam pipe 21 is connected to the tube side of No. 3 low-pressure heater 7 via low-pressure heater extraction steam and oxygenation point 32, tube side of No. 5 low-pressure heater 10 and tube side of No. 4 low-pressure heater 9.

[0038] The preferred oxygenation medium for the four oxygenation points is demineralized water from a power plant, followed by compressed air, oxygen cylinders, or oxygen-enriched water.

[0039] There are two dissolved oxygen meters 43 at the steam generator outlet. The dissolved oxygen signal is sent to the control module 50 through two channels. When the logic is normal, the higher value between the two is taken. When a dissolved oxygen meter 43 or channel signal at the steam generator outlet fails, the signal is automatically switched to the other channel signal.

[0040] Example 2

[0041] The specific working process of this invention is as follows:

[0042] 1) Main control signal selection (feedback quantity)

[0043] Signal 1: Real-time dissolved oxygen concentration, using a high-precision oxygen sensor with an accuracy of ±0.1ppb, located at least 5 meters downstream of the oxygenation point.

[0044] Signal 2: Target oxygen concentration setpoint. Dynamically adjusted according to unit load (10%-100%) and water flow. When unit power is below 10%, control module 50 automatically stops oxygenation.

[0045] 2) Selection of auxiliary control signals (feedforward quantity)

[0046] Signal 1: Feedwater flow rate. The oxygenation amount at condensate oxygenation point 31 is 40% of the oxygen required for the system's OT operation. The oxygenation amount is provided by the flow input signal from condensate flow meter 5.

[0047] Signal 2: Extraction steam flow rate. The oxygen supply at point 32 of the low-pressure heater extraction steam oxygenation station shall not exceed 20% of the oxygen required for the system's OT operation. The oxygen supply is provided by the extraction steam flow rate of low-pressure heater No. 4 (9) and low-pressure heater No. 5 (10).

[0048] Signal 3: The oxygen supply at oxygen supply point 33 of the first-stage reheater shall not exceed 20% of the oxygen required for system OT operation. The oxygen supply is provided by the flow input signal from the reheater extraction steam flow of the first-stage reheater 18.

[0049] Signal 4: Unit load signal. Changes in unit load (0%-100%) affect the dissolved oxygen in the feedwater and serve as an auxiliary control signal.

[0050] Signal 5: Oxygenation unit valve opening signal. The opening degree (0%-100%) of the oxygenation unit valve, its linearity, valve speed, and other inherent lag characteristics serve as auxiliary control signals to correct the control logic.

[0051] 3) Control Logic

[0052] PID controller optimization: Split-range PID control is adopted, dividing the dissolved oxygen concentration deviation in the water into three ranges: when the deviation between the actual value and the set value of dissolved oxygen concentration is >5ppb, the fast response mode is activated (proportional gain is increased by 50%); when the deviation is 2-5ppb, conventional PID adjustment is used; when the deviation is <2ppb, the integral action of the control system is dominant to prevent overshoot.

[0053] Fuzzy adaptive logic: Dynamically adjusts PID parameters based on unit flow rate and load change rate. When load or flow rate suddenly increases, the integral time constant is increased in advance; when load or flow rate suddenly decreases, the integral time constant is decreased in advance.

[0054] 4) Hierarchical system control

[0055] Dynamic allocation of three-level oxygenation points:

[0056] Condensate oxygenation point 31: Provides basic oxygen (40% of total demand) and is used for coarse adjustment of system oxygen levels;

[0057] Low-pressure steam extraction oxygenation point 32: Used for dissolved oxygen consumption for protection on the low-pressure steam side, and at the same time to compensate for dissolved oxygen consumption loss in condensate from the upstream primary oxygenation point (not exceeding 20% ​​of the total demand);

[0058] First-stage reheater oxygenation point 33: Used for dissolved oxygen consumption for protection of the extraction steam side of the first-stage reheater 18, and at the same time to compensate for the dissolved oxygen consumption loss of condensate at the upstream first-stage oxygenation point (not exceeding 20% ​​of the total demand).

[0059] Main water supply oxygenation point 34: Precise fine-tuning (not exceeding 20% ​​of total demand) provides oxygen consumption for high-pressure heater 14 and upstream and downstream pipelines, while suppressing fluctuations in dissolved oxygen at the end.

[0060] Priority logic: When an oxygenation point reaches its valve limit, the redundant amount is automatically allocated to the next higher oxygenation point.

[0061] Protection logic: When the dissolved oxygen level measured by the dissolved oxygen meter 42 at the inlet of the steam generator or the dissolved oxygen meter 43 at the outlet of the steam generator reaches the preset protection value, the control module 50 issues a command to stop oxygen supply and triggers an alarm.

[0062] Example 3

[0063] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of a multi-level dynamic oxygenation control method for a nuclear power unit feedwater system. The memory may include main memory, such as high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device. The processor, network interface, and memory are interconnected via an internal bus, which may be an industry-standard architecture bus, a peripheral component interconnection standard bus, or an extended industry-standard architecture bus. The bus can be categorized as an address bus, data bus, and control bus. The memory stores the program; specifically, the program may include program code, which includes computer operation instructions. The memory may include main memory and non-volatile memory, and provides instructions and data to the processor.

[0064] Example 4

[0065] A computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of a multi-stage dynamic oxygenation control method for a nuclear power unit feedwater system. Specifically, the computer-readable storage medium includes, but is not limited to, volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache memory, etc. The non-volatile memory may include read-only memory (ROM), hard disk, flash memory, optical disk, magnetic disk, etc.

[0066] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0067] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0068] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0069] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0070] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0071] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0072] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A multi-stage dynamic oxygenation control system for a nuclear power unit feedwater system, characterized in that, It includes a low-pressure cylinder (1), a high-pressure cylinder (16), a reheater extraction steam pipe (20), and a No. 5 low-pressure heater extraction steam pipe (21); The outlet of the low-pressure cylinder (1) is connected to the inlet of the high-pressure cylinder (16) via the condenser (2), condensate oxygenation point (31), condensate flow meter (5), shell side of the No. 3 low-pressure heater (7), shell side of the No. 4 low-pressure heater (9), shell side of the No. 5 low-pressure heater (10), dissolved oxygen meter at the deaerator inlet (41), deaerator (11), main feedwater oxygenation point (34), main feedwater pump (12), feedwater flow meter (13), high-pressure heater (14), dissolved oxygen meter at the steam generator inlet (42), steam generator (15), and dissolved oxygen meter at the steam generator outlet (43). The outlet of the gas heater is connected to the inlet of the low-pressure cylinder (1) via the steam-water separator (17), the shell side of the first reheater (18) and the second reheater (19). The reheater extraction steam pipe (20) is connected to the shell side of the fourth low-pressure heater (9) via the oxygenation point (33) of the first reheater, the pipe side of the first reheater (18), the pipe side of the third low-pressure heater (7) and the low-pressure heater drain pump (8). The fifth low-pressure heater extraction steam pipe (21) is connected to the pipe side of the third low-pressure heater (7) via the oxygenation point (32) of the low-pressure heater extraction steam pipe (32), the pipe side of the fifth low-pressure heater (10) and the pipe side of the fourth low-pressure heater (9).

2. The multi-stage dynamic oxygenation control system for the feedwater system of a nuclear power unit according to claim 1, characterized in that, The outlet of the low-pressure cylinder (1) is connected to the inlet of the high-pressure cylinder (16) in sequence via the condenser (2), condensate oxygenation point (31), condensate pump (3), fine treatment device (4), condensate flow meter (5), No. 1 and No. 2 combined low-pressure heater (6), No. 3 low-pressure heater (7) shell side, No. 4 low-pressure heater (9) shell side, No. 5 low-pressure heater (10) shell side, deaerator inlet dissolved oxygen meter (41), deaerator (11), main feedwater oxygenation point (34), main feedwater pump (12), feedwater flow meter (13), high-pressure heater (14), steam generator inlet dissolved oxygen meter (42), steam generator (15), steam generator outlet dissolved oxygen meter (43); It also includes a control module (50), which is connected to the condensate pump (3), condensate flow meter (5), low-pressure heater drain pump (8), main feed water pump (12), feed water flow meter (13), condensate oxygenation point (31), low-pressure heater extraction steam oxygenation point (32), first stage reheater oxygenation point (33), main feed water oxygenation point (34), deaerator inlet dissolved oxygen meter (41), steam generator inlet dissolved oxygen meter (42) and steam generator outlet dissolved oxygen meter (43).

3. The multi-stage dynamic oxygenation control system for the feedwater system of a nuclear power unit according to claim 1, characterized in that, The number of dissolved oxygen meters (43) at the outlet of the steam generator is two, and the two dissolved oxygen meters (43) at the outlet of the steam generator are operated in a standby mode.

4. The multi-stage dynamic oxygenation control system for the feedwater system of a nuclear power unit according to claim 1, characterized in that, The oxygenation media for the condensate oxygenation point (31), the low-pressure steam extraction oxygenation point (32), the first-stage reheater oxygenation point (33), and the main feedwater oxygenation point (34) are power plant demineralized water, compressed air, oxygen cylinders, or oxygen-enriched water.

5. A multi-stage dynamic oxygenation control method for a nuclear power unit feedwater system, characterized in that, The multi-level dynamic oxygenation control system for the nuclear power unit feedwater system according to claim 2 includes: The oxygenation amount at the condensate oxygenation point (31) is 40% of the oxygen required for the system's OT operation; The amount of oxygen added at the low-pressure steam extraction oxygenation point (32) is less than or equal to 20% of the oxygen required for the system's OT operation; The amount of oxygen added at the oxygenation point (33) of the first-stage reheater is less than or equal to 20% of the oxygen required for the system's OT operation; The oxygenation amount at the main feedwater oxygenation point (34) is less than or equal to 20% of the oxygen required for the system's OT operation.

6. The multi-stage dynamic oxygenation control method for a nuclear power unit feedwater system according to claim 4, characterized in that, The amount of oxygen added at the condensate oxygenation point (31) is controlled based on the condensate flow rate information measured by the condensate flow meter (5).

7. The multi-stage dynamic oxygenation control method for a nuclear power unit feedwater system according to claim 4, characterized in that, The extraction steam flow rate of the No. 4 low-pressure heater (9) and the No. 5 low-pressure heater (10) controls the amount of oxygen added at the low-pressure heater extraction oxygenation point (32).

8. The multi-stage dynamic oxygenation control method for a nuclear power unit feedwater system according to claim 4, characterized in that, The amount of oxygen added at the oxygenation point (33) of the first-stage reheater is controlled according to the reheater extraction steam flow rate of the first-stage reheater (18).

9. The multi-stage dynamic oxygenation control method for a nuclear power unit feedwater system according to claim 4, characterized in that, When the dissolved oxygen level measured by the dissolved oxygen meter (42) at the inlet of the steam generator or the dissolved oxygen meter (43) at the outlet of the steam generator reaches the preset protection value, the control module (50) issues a command to stop oxygen supply and triggers an alarm.

10. The multi-stage dynamic oxygenation control method for a nuclear power unit feedwater system according to claim 4, characterized in that, The control module (50) uses PID control.

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