Method and system for reducing measurement uncertainty of main feed water flow of nuclear power plant

Abstract

The invention relates to a method and system for reducing uncertainty of measurement of main feed water flow of a nuclear power plant, and the method comprises the steps: collecting data of a plurality of measurement points in a main feed water pipeline according to a preset collection method, and obtaining the collection data of each measurement point; preprocessing the data to obtain preprocessed data of each measurement point; carrying out mean value processing on the preprocessed data to obtain a flow velocity representative value of each measurement point; performing calculation based on the flow velocity representative value of each measurement point to obtain a plurality of reference data; determining a flow calculation mode of the main water supply pipeline of the nuclear power plant according to the reference data; and calculating the flow in the main water supply pipeline of the nuclear power plant according to the flow calculation mode. The flow of the main water supply pipeline is calculated in different modes according to the change condition of the flow velocity, the uncertainty of the ultrasonic flowmeter is effectively reduced, the reactor power of a nuclear power plant is improved, and the economical efficiency is improved. Meanwhile, transient disturbance caused by power increasing and decreasing can be avoided, and safe and stable operation of the nuclear power plant is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plants, and more particularly to a method and system for reducing uncertainty in measuring main feed water flow in a nuclear power plant. Background Art

[0002] With the development of ultrasonic measurement technology, some nuclear power plants have adopted ultrasonic flowmeters for main feedwater flow measurement. Ultrasonic flowmeters for main feedwater flow measurement in nuclear power plants can achieve an accuracy of 0.3% and require high reliability, often using embedded installation. However, because feedwater temperatures can reach 220°C during nuclear power plant operation, current laboratory metrology verification and calibration procedures cannot meet these conditions, making it impossible to guarantee the accuracy of main feedwater flow measurement and, consequently, the safe operation of the nuclear units. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and system for reducing the uncertainty of the measurement of the main feed water flow of a nuclear power plant in response to the problems existing in the prior art.

[0004] The technical solution adopted by the present invention to solve the technical problem is to construct a method for reducing the uncertainty of the main feed water flow measurement of a nuclear power plant, comprising the following steps:

[0005] Collecting data from multiple measuring points in the main water supply pipe of the nuclear power plant according to a preset collection method to obtain collected data from each measuring point; the measuring points are installation locations of ultrasonic flow meters installed in the main water supply pipe of the nuclear power plant;

[0006] Preprocessing the collected data at each measuring point to obtain preprocessed data at each measuring point;

[0007] Performing mean processing on the pre-processed data of each measuring point to obtain a representative value of the flow velocity at each measuring point;

[0008] Calculating based on the representative flow velocity values of each measuring point to obtain a plurality of reference data;

[0009] determining a flow calculation method for the main feed water pipeline of the nuclear power plant according to the plurality of reference data;

[0010] Calculation is performed according to the flow calculation method to obtain the flow in the main water supply pipe of the nuclear power plant.

[0011] In the method for reducing the uncertainty of measurement of the main feed water flow of a nuclear power plant according to the present invention, collecting data from multiple measurement points in the main feed water pipeline of the nuclear power plant according to a preset collection method to obtain the collected data at each measurement point includes:

[0012] Determine the collection duration;

[0013] Determine the sampling frequency;

[0014] Data is collected at each measurement point according to the collection duration and the sampling frequency to obtain collected data at each measurement point.

[0015] In the method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to the present invention, preprocessing the collected data of each measuring point to obtain the preprocessed data of each measuring point includes:

[0016] The collected data at each measurement point are processed using an error discrimination criterion of 3 times the standard deviation;

[0017] The gross error data are eliminated according to the processing result of the error discrimination criterion to obtain the pre-processed data of each measuring point.

[0018] In the method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to the present invention, the flow velocity representative values of the respective measuring points include: a flow velocity representative value of a first measuring point, a flow velocity representative value of a second measuring point, a flow velocity representative value of a third measuring point, a flow velocity representative value of a fourth measuring point, a flow velocity representative value of a fifth measuring point, a flow velocity representative value of a sixth measuring point, a flow velocity representative value of a seventh measuring point, and a flow velocity representative value of an eighth measuring point; the plurality of reference data include: first reference data, second reference data, third reference data, and fourth reference data;

[0019] The calculating based on the representative flow velocity values of the respective measurement points to obtain a plurality of reference data comprises:

[0020] Calculate and take absolute values of the flow velocity representative value at the first measurement point and the flow velocity representative value at the second measurement point to obtain first reference data;

[0021] Calculating and taking absolute values based on the flow velocity representative value at the third measuring point and the flow velocity representative value at the fourth measuring point to obtain second reference data;

[0022] Calculating and taking absolute values based on the flow velocity representative value at the fifth measuring point and the flow velocity representative value at the sixth measuring point to obtain third reference data;

[0023] Calculation is performed based on the flow velocity representative value at the seventh measuring point and the flow velocity representative value at the eighth measuring point, and the absolute values are taken to obtain fourth reference data.

[0024] In the method for reducing the uncertainty of measurement of the main feed water flow rate of a nuclear power plant according to the present invention, the flow calculation method for determining the main feed water pipe of the nuclear power plant according to the multiple reference data includes:

[0025] comparing the first reference data, the second reference data, the third reference data, and the fourth reference data with a determination threshold value respectively;

[0026] If the first reference data, the second reference data, the third reference data and the fourth reference data are all less than or equal to the determination threshold, the flow calculation method is the first calculation method;

[0027] If any one or more of the first reference data, the second reference data, the third reference data, and the fourth reference data is greater than the determination threshold, the flow calculation method is the second calculation method.

[0028] In the method for reducing the uncertainty in measurement of the main feed water flow rate of a nuclear power plant according to the present invention, the first calculation method is:

[0029]

[0030] Among them, Q i The flow rate in the main water supply pipe, D is the inner diameter of the main water supply pipe, is the representative value of the flow velocity at each measuring point, L i is the length of the vocal tract at each measurement point, ω i is the Gaussian integration point weight factor.

[0031] In the method for reducing the uncertainty in measurement of the main feed water flow rate of a nuclear power plant according to the present invention, the second calculation method is:

[0032]

[0033] Among them, Q j is the flow rate in the main water supply pipe, V (r) is the average flow velocity of the sound channel at a distance r from the axis of the main water supply pipe, and R is the radius of the main water supply pipe.

[0034] In the method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant described in the present invention, each measurement point includes two ultrasonic flow meter probes, and the two ultrasonic flow meter probes are arranged orthogonally.

[0035] In the method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to the present invention, the method further comprises:

[0036] Obtaining the inner diameter of the main water feed pipe of the nuclear power plant;

[0037] Four Gaussian integration points are calculated along the diameter direction of the main water supply pipe according to the inner diameter of the main water supply pipe.

[0038] The present invention also provides a system for reducing the uncertainty of measurement of main feed water flow in a nuclear power plant, comprising:

[0039] A data acquisition unit, configured to acquire data from a plurality of measurement points in the main water supply pipe of the nuclear power plant according to a preset acquisition method, and obtain the collected data from each measurement point; the measurement points are installation locations of ultrasonic flow meters installed in the main water supply pipe of the nuclear power plant;

[0040] A data preprocessing unit, configured to preprocess the collected data of each measuring point to obtain preprocessed data of each measuring point;

[0041] a mean processing unit, configured to perform mean processing on the pre-processed data of each measuring point to obtain a representative value of the flow velocity at each measuring point;

[0042] a flow rate processing unit, configured to perform calculations based on the flow rate representative values of the respective measurement points to obtain a plurality of reference data;

[0043] a calculation method determining unit, configured to determine a flow calculation method for the main feed water pipeline of the nuclear power plant according to the plurality of reference data;

[0044] A flow calculation unit is used to calculate according to the flow calculation method to obtain the flow in the main water supply pipeline of the nuclear power plant.

[0045] The method and system for reducing the measurement uncertainty of the main feedwater flow rate of a nuclear power plant according to the present invention have the following beneficial effects: including: collecting data from multiple measurement points in the main feedwater pipeline according to a preset collection method to obtain collected data at each measurement point; preprocessing the data to obtain preprocessed data for each measurement point; averaging the preprocessed data to obtain a representative flow velocity value for each measurement point; calculating multiple reference data based on the representative flow velocity values of each measurement point; determining a flow calculation method for the main feedwater pipeline of the nuclear power plant according to the multiple reference data; and calculating the flow rate in the main feedwater pipeline of the nuclear power plant according to the flow calculation method. The present invention calculates the flow rate of the main feedwater pipeline using different methods based on the changes in flow velocity, effectively reducing the uncertainty of the ultrasonic flowmeter, increasing the reactor power of the nuclear power plant, and improving economic efficiency. At the same time, it can also avoid transient disturbances caused by power increases and decreases, ensuring the safe and stable operation of the nuclear power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0047] Figure 1 This is a flow chart of an embodiment of a method for reducing uncertainty in measurement of main feed water flow in a nuclear power plant provided by the present invention;

[0048] Figure 2 Schematic diagram of the installation position of the ultrasonic flowmeter provided by the present invention in a pipeline;

[0049] Figure 3 This is a schematic diagram of the orthogonal arrangement of ultrasonic probes provided by the present invention;

[0050] Figure 4 This is a schematic diagram of flow calculation integration provided by the present invention;

[0051] Figure 5 This is a flow chart of another embodiment of the method for reducing uncertainty in measurement of main feed water flow in a nuclear power plant provided by the present invention;

[0052] Figure 6 The present invention provides a logic block diagram of a system for reducing uncertainty in measurement of main feed water flow in a nuclear power plant. DETAILED DESCRIPTION

[0053] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0054] The present invention designs the installation position of the acoustic channel probe of the ultrasonic flowmeter and adopts a corresponding data processing method to calculate the flow in the main feed water pipeline of a nuclear power plant. This can effectively reduce the uncertainty of water flow measurement in the main feed water pipeline of a nuclear power plant, ensure that the flow measurement accuracy in the main feed water pipeline is higher than 0.3%, and further improve the accuracy of the core thermal power calculation, providing protection for the nuclear safety operation of the unit.

[0055] refer to Figure 1 , Figure 1 The present invention provides a flow chart of an embodiment of a method for reducing the uncertainty in measurement of the main feed water flow rate of a nuclear power plant.

[0056] Specifically, such as Figure 1 As shown, the method for reducing the measurement uncertainty of the main feed water flow of a nuclear power plant includes the following steps:

[0057] Step S100: collecting data from multiple measuring points in the main water supply pipeline of the nuclear power plant according to a preset collection method to obtain collected data from each measuring point.

[0058] The measurement points are where ultrasonic flowmeters are installed in the main feedwater pipes of nuclear power plants. Each measurement point includes two ultrasonic flowmeter probes, which are arranged orthogonally.

[0059] Specifically, in order to realize the method of reducing uncertainty in measurement of main feed water flow in a nuclear power plant, the present invention first specially designs the installation position of the ultrasonic flow meter sound channel probe. In the main feed water pipeline, 8 pairs of ultrasonic flow meter sound channel probes can be installed, specifically as follows: Figure 2 As shown, 8 pairs of channel probes are installed at Y1, Y2, Y3, Y4 and W1, W2, W3, W4 Gaussian integration points, in an orthogonal arrangement (as shown in Figure 3 As shown in the figure, the velocity values measured by the ultrasonic sound channel at the 8 measurement points are V1, V2, V3, V4, V5, V6, V7, and V8 respectively.

[0060] Before executing step S100, the inner diameter of the main water supply pipe of the nuclear power plant is first obtained; and four Gaussian integral points are calculated along the diameter direction of the main water supply pipe according to the inner diameter of the main water supply pipe. The calculation of the four Gaussian integral points is shown in Table 1 below.

[0061] Table 1. Gaussian integration points and weighting factors

[0062]

[0063] Optionally, in some embodiments, data from multiple measurement points within a nuclear power plant's main feedwater pipeline is collected according to a preset collection method. Obtaining the collected data from each measurement point includes: determining a collection duration; determining a sampling frequency; and collecting data from each measurement point based on the collection duration and sampling frequency to obtain the collected data from each measurement point. The collection duration can be set to 5 seconds, and the sampling frequency to 25 milliseconds. Specifically, in this embodiment of the present invention, the sound channels utilize a high-precision time-to-digital converter chip, achieving a time measurement accuracy of 22 ps. The sampling frequency for each pair of sound channels is set to 25 milliseconds, generating 200 data points in 5 seconds.

[0064] Step S200: pre-processing the collected data of each measuring point to obtain pre-processed data of each measuring point.

[0065] Optionally, in some embodiments, preprocessing the collected data at each measurement point to obtain the preprocessed data for each measurement point includes: processing the collected data at each measurement point using an error discrimination criterion of 3 times the standard deviation; and eliminating gross error data based on the processing results of the error discrimination criterion to obtain the preprocessed data for each measurement point. Specifically, the collected data at each measurement point is discriminated using an error difference criterion of 3 times the standard deviation. If the error difference is greater than or equal to 3 times the standard deviation (hereinafter referred to as 3δ), it is determined to be gross error data, and the gross error data is eliminated to obtain usable data, which is the preprocessed data.

[0066] Step S300: performing mean processing on the pre-processed data of each measuring point to obtain a representative value of the flow velocity of each measuring point.

[0067] Optionally, in some embodiments, the flow velocity representative value of each measuring point includes: the flow velocity representative value of the first measuring point, the flow velocity representative value of the second measuring point, the flow velocity representative value of the third measuring point, the flow velocity representative value of the fourth measuring point, the flow velocity representative value of the fifth measuring point, the flow velocity representative value of the sixth measuring point, the flow velocity representative value of the seventh measuring point, and the flow velocity representative value of the eighth measuring point. Specifically, after preprocessing the data of each measuring point to obtain available data, the available data are averaged as the flow velocity representative value within a 5-second period. Among them, the flow velocity representative values of the eight measuring points are:

[0068] Step S400: Calculate based on the representative value of the flow velocity at each measuring point to obtain a plurality of reference data.

[0069] In some embodiments, the plurality of reference data includes: first reference data, second reference data, third reference data, and fourth reference data. Calculating based on the flow velocity representative values at each measurement point to obtain the plurality of reference data includes: calculating based on the flow velocity representative value at the first measurement point and the flow velocity representative value at the second measurement point and taking their absolute values to obtain the first reference data; calculating based on the flow velocity representative value at the third measurement point and the flow velocity representative value at the fourth measurement point and taking their absolute values to obtain the second reference data; calculating based on the flow velocity representative value at the fifth measurement point and the flow velocity representative value at the sixth measurement point and taking their absolute values to obtain the third reference data; and calculating based on the flow velocity representative value at the seventh measurement point and the flow velocity representative value at the eighth measurement point and taking their absolute values to obtain the fourth reference data.

[0070] The first reference data may be expressed as Δ1, the second reference data may be expressed as Δ2, the third reference data may be expressed as Δ3, and the fourth reference data may be expressed as Δ4.

[0071] The first reference data can be expressed as Δ1 which can be calculated by the following formula:

[0072]

[0073] The second reference data can be expressed as Δ2 which can be calculated by the following formula:

[0074]

[0075] The third reference data can be expressed as Δ3 which can be calculated by the following formula:

[0076]

[0077] The fourth reference data can be expressed as Δ4 which can be calculated by the following formula:

[0078]

[0079] Step S500: determining a flow calculation method for a main feed water pipeline of a nuclear power plant according to a plurality of reference data.

[0080] In some embodiments, determining a flow calculation method for a main feedwater pipe of a nuclear power plant based on multiple reference data includes: comparing first, second, third, and fourth reference data with a determination threshold; if the first, second, third, and fourth reference data are all less than or equal to the determination threshold, the flow calculation method is the first calculation method; if any one or more of the first, second, third, and fourth reference data is greater than the determination threshold, the flow calculation method is the second calculation method. Optionally, the determination threshold may be 0.3%.

[0081] Step S600: Calculate according to the flow calculation method to obtain the flow in the main water supply pipeline of the nuclear power plant.

[0082] Specifically, when Δ1, Δ2, Δ3, and Δ4 are all ≤ 0.3%, the flow rate Q in the main water supply pipe is i Calculate using the first calculation method. The first calculation method is:

[0083]

[0084] Among them, Q i The flow rate in the main water supply pipe, D is the inner diameter of the main water supply pipe, is the representative value of the flow velocity at each measuring point, L i is the length of the vocal tract at each measurement point, ω i is the Gaussian integration point weight factor (see Table 1).

[0085] When any one or more of Δ1, Δ2, Δ3, and Δ4 are greater than 0.3%, the flow rate Q in the main water supply pipe j Calculate using the second calculation method. The second calculation method is:

[0086]

[0087] Among them, Q j is the flow rate in the main water supply pipe, V (r) is the average flow velocity of the sound channel at a distance r from the axis of the main water supply pipe, and R is the radius of the main water supply pipe.

[0088] Among them, the average flow velocity V of the sound channel at a distance r from the axis of the main water supply pipe is (r) (See Figure 4 ). V (r) According to Gauss's integral law, Numerical fitting of V (r) The relationship is formula (3).

[0089] V (r) =ar 3 +br 2 +cr+d(3).

[0090] (3) In the formula, a, b, c, and d are the coefficients of the polynomial, and their specific values can be obtained by polynomial fitting calculation based on 20 minutes of collected data.

[0091] like Figure 5 As shown, in another embodiment, a high-precision time-to-digital converter chip is first used to collect data within 5 seconds at a sampling frequency of 25ms. Data are collected from 8 measurement points (each measurement point has 200 data points). The error judgment criterion of 3 times the standard deviation (hereinafter referred to as 3δ) is applied to the 200 data points of each measurement point to eliminate gross errors. The remaining data is then averaged as the representative flow value within 5 seconds. and Apply the same rules to other channels and get make When Δ1, Δ2, Δ3, and Δ4 are all ≤0.3%, the flow rate Q in the main water supply pipe i Calculate according to formula (1). When one or more of Δ1, Δ2, Δ3, and Δ4 are greater than 0.3%, the flow rate Q in the main water supply pipe is j Calculate according to formula (2).

[0092] The present invention analyzes the measurement data of different sound channels and formulates corresponding judgment rules to determine the stability of the flow field, and calculates the flow of the main water supply pipeline in different ways based on different situations, thereby effectively reducing the uncertainty of flow measurement in the main water supply pipeline, which can generally be reduced to 0.3% or below.

[0093] The present invention can increase reactor power and improve economic efficiency in nuclear power plants. For example, a 1.7% increase for a 1 million-kilowatt unit can increase annual power generation by up to 50 million kilowatt-hours. Furthermore, the present invention maximizes unit availability while avoiding transient disturbances caused by power increases and decreases. It also addresses the issue of abnormal flow measurement by orifice plates during unit operation, requiring shutdowns. This ensures safe and stable operation of nuclear power plants and improves economic efficiency.

[0094] refer to Figure 6 The present invention provides a system for reducing the uncertainty of main feed water flow measurement in a nuclear power plant.

[0095] Specifically, such as Figure 6 As shown in FIG, the system for reducing the uncertainty of measurement of the main feed water flow rate of a nuclear power plant includes:

[0096] The data acquisition unit 601 is used to acquire data from multiple measurement points in the main water supply pipe of the nuclear power plant according to a preset acquisition method to obtain the collected data of each measurement point. The measurement points are the installation locations of ultrasonic flow meters installed in the main water supply pipe of the nuclear power plant.

[0097] The data preprocessing unit 602 is used to preprocess the collected data of each measuring point to obtain preprocessed data of each measuring point.

[0098] The mean processing unit 603 is used to perform mean processing on the pre-processed data of each measuring point to obtain a representative value of the flow velocity of each measuring point.

[0099] The flow rate processing unit 604 is configured to perform calculations based on the flow rate representative values of the respective measurement points to obtain a plurality of reference data.

[0100] The calculation method determination unit 605 is used to determine the flow calculation method of the main feed water pipeline of the nuclear power plant according to multiple reference data.

[0101] The flow calculation unit 606 is used to calculate according to the flow calculation method to obtain the flow in the main water supply pipeline of the nuclear power plant.

[0102] Specifically, the specific coordination operation process between the various units in the system for reducing the uncertainty of measurement of the main feed water flow of a nuclear power plant can refer to the above-mentioned method for reducing the uncertainty of measurement of the main feed water flow of a nuclear power plant, and will not be repeated here.

[0103] The present invention can effectively reduce the uncertainty of the ultrasonic flowmeter, increase the reactor power of the nuclear power plant, and improve the economy by specially designing the installation position of the ultrasonic flowmeter in the main water supply pipeline, performing data monitoring based on the special design, and selecting different flow calculation methods according to different situations.

[0104] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0105] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0106] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0107] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the present invention and implement it accordingly. They are not intended to limit the scope of protection of the present invention. All equivalent variations and modifications within the scope of the claims of the present invention are intended to be covered by the claims of the present invention.

Claims

1. A method for reducing the uncertainty of measurement of main feed water flow in a nuclear power plant, characterized in that: The following steps are involved: Collecting data from multiple measuring points in the main water supply pipe of the nuclear power plant according to a preset collection method to obtain collected data from each measuring point; the measuring points are installation locations of ultrasonic flow meters installed in the main water supply pipe of the nuclear power plant; Preprocessing the collected data at each measuring point to obtain preprocessed data at each measuring point; Performing mean processing on the pre-processed data of each measuring point to obtain a representative value of the flow velocity at each measuring point; Calculating based on the representative flow velocity values of each measuring point to obtain a plurality of reference data; determining a flow calculation method for the main feed water pipeline of the nuclear power plant according to the plurality of reference data; Calculation is performed according to the flow calculation method to obtain the flow in the main water supply pipe of the nuclear power plant.

2. The method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to claim 1, characterized in that: The data of multiple measurement points in the main water supply pipeline of the nuclear power plant are collected according to the preset collection method to obtain the collected data of each measurement point, which includes: Determine the collection duration; Determine the sampling frequency; Data is collected at each measurement point according to the collection duration and the sampling frequency to obtain collected data at each measurement point.

3. The method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to claim 1, characterized in that: Preprocessing the collected data at each measuring point to obtain the preprocessed data at each measuring point includes: The collected data at each measurement point are processed using an error discrimination criterion of 3 times the standard deviation; The gross error data are eliminated according to the processing result of the error discrimination criterion to obtain the pre-processed data of each measuring point.

4. The method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to claim 1, characterized in that: The flow velocity representative values of the respective measuring points include: a flow velocity representative value of a first measuring point, a flow velocity representative value of a second measuring point, a flow velocity representative value of a third measuring point, a flow velocity representative value of a fourth measuring point, a flow velocity representative value of a fifth measuring point, a flow velocity representative value of a sixth measuring point, a flow velocity representative value of a seventh measuring point, and a flow velocity representative value of an eighth measuring point; the plurality of reference data include: first reference data, second reference data, third reference data, and fourth reference data; The calculating based on the representative flow velocity values of the respective measurement points to obtain a plurality of reference data comprises: Calculate and take absolute values of the flow velocity representative value at the first measurement point and the flow velocity representative value at the second measurement point to obtain first reference data; Calculating and taking absolute values based on the flow velocity representative value at the third measuring point and the flow velocity representative value at the fourth measuring point to obtain second reference data; Calculating and taking absolute values based on the flow velocity representative value at the fifth measuring point and the flow velocity representative value at the sixth measuring point to obtain third reference data; Calculation is performed based on the flow velocity representative value at the seventh measuring point and the flow velocity representative value at the eighth measuring point, and the absolute values are taken to obtain fourth reference data.

5. The method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to claim 4, characterized in that: The method for calculating the flow rate of the main feed water pipeline of the nuclear power plant according to the plurality of reference data includes: comparing the first reference data, the second reference data, the third reference data, and the fourth reference data with a determination threshold value respectively; If the first reference data, the second reference data, the third reference data and the fourth reference data are all less than or equal to the determination threshold, the flow calculation method is the first calculation method; If any one or more of the first reference data, the second reference data, the third reference data, and the fourth reference data is greater than the determination threshold, the flow calculation method is the second calculation method.

6. The method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to claim 5, characterized in that: The first calculation method is: Among them, Q i The flow rate in the main water supply pipe, D is the inner diameter of the main water supply pipe, is the representative value of the flow velocity at each measuring point, L i is the length of the vocal tract at each measurement point, ω i is the Gaussian integration point weight factor.

7. The method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to claim 5, characterized in that: The second calculation method is: Among them, Q j is the flow rate in the main water supply pipe, V (r) is the average flow velocity of the sound channel at a distance r from the axis of the main water supply pipe, and R is the radius of the main water supply pipe.

8. The method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to any one of claims 1 to 7, characterized in that: Each measuring point includes two ultrasonic flow meter probes, and the two ultrasonic flow meter probes are arranged orthogonally.

9. The method for reducing the measurement uncertainty of the main feed water flow rate of a nuclear power plant according to claim 8, characterized in that: The method further comprises: Obtaining the inner diameter of the main water feed pipe of the nuclear power plant; Four Gaussian integration points are calculated along the diameter direction of the main water supply pipe according to the inner diameter of the main water supply pipe.

10. A system for reducing the uncertainty of main feed water flow measurement in a nuclear power plant, characterized in that: include: A data acquisition unit is used to collect data from multiple measurement points in the main water supply pipeline of the nuclear power plant according to a preset acquisition method to obtain the collected data of each measurement point; The measuring point is the installation position of the ultrasonic flowmeter installed in the main water feed pipe of the nuclear power plant; A data preprocessing unit, configured to preprocess the collected data of each measuring point to obtain preprocessed data of each measuring point; a mean processing unit, configured to perform mean processing on the pre-processed data of each measuring point to obtain a representative value of the flow velocity at each measuring point; a flow rate processing unit, configured to perform calculations based on the flow rate representative values of the respective measurement points to obtain a plurality of reference data; a calculation method determining unit, configured to determine a flow calculation method for the main feed water pipeline of the nuclear power plant according to the plurality of reference data; A flow calculation unit is used to calculate according to the flow calculation method to obtain the flow in the main water supply pipeline of the nuclear power plant.

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