Monitoring Method and Device for Main Steam Pipe Leakage Rate at Low Reactor Power

Abstract

The present invention provides a method and device for monitoring the leakage rate of a main steam pipeline at low reactor power. The method includes: a detector detecting γ rays generated by the decay of N-16 at the leakage point of the heat transfer tubes of a primary loop steam generator and converting them into electrical signals for output. The detector is installed at a monitoring point of the secondary loop main steam pipeline. A signal acquisition and processing unit receives the electrical signals and processes them to obtain the pulse count value corresponding to γ rays with an energy of 511 keV, and calculates the leakage rate of the main steam pipeline corresponding to the pulse count value. The present invention can accurately obtain the leakage rate of the main steam pipeline at low reactor power and avoid the occurrence of abnormal high count alarms.

Description

Technical Field

[0001] The present invention specifically relates to a method and device for monitoring the leakage rate of a main steam pipeline under low reactor power. Background Art

[0002] The N-16 monitor is used to continuously monitor the leakage rate of the primary loop water to the secondary loop side caused by the breakage of the U-shaped tubes of the steam generator in a pressurized water reactor nuclear power plant under normal operation and accident conditions. Currently, the N-16 monitors used at home and abroad directly measure the full-energy peak of the 6.128 MeV γ-ray generated by the decay of N-16 when the reactor power is higher than 20%, and calculate the leakage rate of the main steam pipeline through the full-energy peak count. When the power is lower than 20%, only the total γ count of 0.2 - 2.2 MeV can be measured, and an accurate value for the leakage rate of the main steam pipeline cannot be obtained. False alarms often occur under low power conditions, which seriously affects the normal operation of the nuclear power plant. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and device for monitoring the leakage rate of a main steam pipeline under low reactor power, which can accurately obtain the leakage rate of the main steam pipeline under low reactor power and avoid the occurrence of abnormal high count alarms, aiming at the above deficiencies existing in the prior art.

[0004] The technical solution adopted to solve the technical problem of the present invention is as follows:

[0005] The present invention provides a method for monitoring the leakage rate of a main steam pipeline under low reactor power, including:

[0006] A detector detects the γ-rays generated by the decay of N-16 at the leakage point of the heat transfer tubes of the primary loop steam generator and converts them into electrical signals for output. The detector is installed at the monitoring point of the secondary loop main steam pipeline.

[0007] A signal acquisition and processing unit receives the electrical signals and processes them to obtain the pulse count value corresponding to the γ-rays with an energy of 511 keV, and calculates the leakage rate of the main steam pipeline corresponding to the pulse count value.

[0008] Low reactor power refers to the condition where the reactor power is lower than 20%.

[0009] Optionally, the leakage rate of the main steam pipeline corresponding to the pulse count value is calculated using Equation (1):

[0010] q = n / c (1)

[0011] Where:

[0012] q is the leakage rate of the main steam pipeline, with the unit of L / h;

[0013] n is the pulse count value corresponding to the 511 keV γ-ray entering the detector, with the unit of cps;

[0014] c is the leakage transmission coefficient of the heat transfer tube, with the unit of h / (L×s).

[0015] Optionally, the leakage transmission coefficient c of the heat transfer tube is calculated by Equation (2):

[0016] c = K×Av (2)

[0017] In the formula:

[0018] K is the N16 detection efficiency obtained by the MCNP program, with the unit of c×s -1 / (Bq×m -3 );

[0019] Av is the N16 radioactivity at the monitoring point of the main steam pipeline when the heat transfer tube leaks, with the unit of Bq×m -3 / (l×h -1 ).

[0020] Optionally, the N16 radioactivity Av at the monitoring point of the main steam pipeline when the heat transfer tube leaks is calculated by Equation (3):

[0021] Av = Ap×(ρP / 1000)×ρv×e -λt / (Q×3600) (3)

[0022] In the formula:

[0023] Ap: The specific activity of N-16 in the primary loop, Bq·kg -1 ;

[0024] ρP: The density of the coolant in the primary loop, kg·m -3 ;

[0025] ρv: The density of the steam at the outlet of the steam generator, kg·m -3 ;

[0026] Q: The steam flow rate in the main steam pipeline, kg·s -1 ;

[0027] λ: The γ decay constant of N-16, 0.0972 s -1 ;

[0028] t: The transfer time between the leakage point of the heat transfer tube and the monitoring point of the main steam pipeline for N-16, s.

[0029] Optionally, the signal acquisition and processing unit includes a signal conversion module and a data processing module,

[0030] The signal conversion module is electrically connected to the detector, and is configured to receive the electrical signal and process it to obtain a pulse count value corresponding to γ rays with an energy of 511 keV.

[0031] The data processing module is electrically connected to the signal conversion module, and is configured to calculate the main steam pipeline leakage rate corresponding to the pulse count value.

[0032] The present invention further provides a monitoring device for the main steam pipeline leakage rate under low reactor power, including: a detector and a signal acquisition and processing unit. The detector is installed at the monitoring point of the secondary circuit main steam pipeline.

[0033] The detector is configured to detect γ rays generated by the decay of N-16 at the leakage point of the heat transfer tube of the primary circuit steam generator, and convert them into electrical signals for output.

[0034] The signal acquisition and processing unit is electrically connected to the detector, and is configured to receive the electrical signal, process it to obtain a pulse count value corresponding to γ rays with an energy of 511 keV, and calculate the main steam pipeline leakage rate corresponding to the pulse count value.

[0035] Optionally, the signal acquisition and processing unit includes a signal conversion module and a data processing module.

[0036] The signal conversion module is electrically connected to the detector, and is configured to receive the electrical signal and process it to obtain a pulse count value corresponding to γ rays with an energy of 511 keV.

[0037] The data processing module is electrically connected to the signal conversion module, and is configured to calculate the main steam pipeline leakage rate corresponding to the pulse count value.

[0038] Optionally, the data processing module calculates the main steam pipeline leakage rate corresponding to the pulse count value according to Equation (1) stored therein:

[0039] q = n / c (1)

[0040] Where:

[0041] q is the main steam pipeline leakage rate, with the unit of L / h;

[0042] n is the pulse count value corresponding to γ rays with an energy of 511 keV entering the detector, with the unit of cps;

[0043] c is the leakage transmission coefficient of the heat transfer tube, with the unit of h / (L×s).

[0044] Optionally, the data processing module further calculates the leakage transmission coefficient c of the heat transfer tube according to Equation (2) stored therein:

[0045] c = K × Av (2)

[0046] Wherein:

[0047] K is the N16 detection efficiency calculated by the MCNP program, with the unit of c×s -1 / (Bq×m -3 );

[0048] Av is the N16 radioactivity at the monitoring point of the main steam pipeline during the heat transfer tube leakage, with the unit of Bq×m -3 / (l×h -1 ).

[0049] Optionally, the data processing module also calculates the N16 radioactivity Av at the monitoring point of the main steam pipeline during the heat transfer tube leakage according to Equation (3) stored during the period:

[0050] Av = Ap × (ρP / 1000) × ρv × e -λt / (Q×3600) (3)

[0051] Wherein:

[0052] Ap: Specific activity of N-16 in the primary loop, Bq·kg -1 ;

[0053] ρP: Density of the coolant in the primary loop, kg·m -3 ;

[0054] ρv: Steam density at the outlet of the steam generator, kg·m -3 ;

[0055] Q: Steam flow rate in the main steam pipeline, kg·s -1 ;

[0056] λ: γ decay constant of N-16, 0.0972s -1 ;

[0057] t: Transfer time between the heat transfer tube leakage point and the main steam pipeline monitoring point for N-16, s.

[0058] The applicant's research shows that according to on-site data and source term calculations, the escape peak of N-16 accounts for a relatively high proportion at low reactor power. At the same time, a more accurate leakage rate can be obtained by calculation and deduction of corresponding nuclides. Therefore, the present invention calculates the activity of N-16 by measuring the escape peak generated by the electron pair effect of high-energy γ rays at low reactor power, that is, the γ ray count with an energy of 511 keV, and calculates a more accurate leakage rate of the main steam pipeline at low reactor power, avoiding the occurrence of abnormal high count alarms. Description of the Drawings

[0059] Figure 1 Schematic diagram of the structure of the detector provided in Embodiment 2 of the present invention;

[0060] Figure 2 Monte Carlo simulation schematic diagram of the leak rate detector;

[0061] Figure 3 Energy spectrum diagram of the leak rate detector under low power operating conditions;

[0062] Figure 4 Frame diagram of the signal acquisition and processing unit. Specific embodiments

[0063] The following will clearly and completely describe the technical solutions in the present invention with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts belong to the scope of the present invention.

[0064] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper" is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of description and simplification, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0065] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0066] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, terms such as "connected", "set", "installed", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

[0067] The present invention provides a method for monitoring the leak rate of the main steam pipeline under low power of a reactor, including:

[0068] The detector detects the γ rays generated by the decay of N-16 at the leakage point of the heat transfer tube of the primary loop steam generator and converts them into electrical signals for output. The detector is installed at the monitoring point of the secondary loop main steam pipeline.

[0069] The signal acquisition and processing unit receives the electrical signal and processes it to obtain the pulse count value corresponding to the γ-ray with an energy of 511 keV, and calculates the main steam pipeline leakage rate corresponding to the pulse count value.

[0070] The present invention also provides a monitoring device for the main steam pipeline leakage rate under low reactor power, including: a detector and a signal acquisition and processing unit, where the detector is installed at the monitoring point of the secondary circuit main steam pipeline.

[0071] The detector is used to detect the γ-rays generated by the decay of N-16 at the leakage point of the heat transfer tube of the primary circuit steam generator and convert them into electrical signals for output.

[0072] The signal acquisition and processing unit is electrically connected to the detector, and is used to receive the electrical signal and process it to obtain the pulse count value corresponding to the γ-ray with an energy of 511 keV, and calculate the main steam pipeline leakage rate corresponding to the pulse count value.

[0073] Embodiment 1:

[0074] This embodiment provides a monitoring method for the main steam pipeline leakage rate under low reactor power, including:

[0075] The detector detects the γ-rays generated by the decay of N-16 at the leakage point of the heat transfer tube of the primary circuit steam generator and converts them into electrical signals for output. The detector is installed at the monitoring point of the secondary circuit main steam pipeline.

[0076] The signal acquisition and processing unit receives the electrical signal and processes it to obtain the pulse count value corresponding to the γ-ray with an energy of 511 keV, and calculates the main steam pipeline leakage rate corresponding to the pulse count value.

[0077] Based on the abnormal high count alarm phenomenon existing in the measurement of the main steam pipeline leakage rate of currently operating nuclear power plants, considering that under low power conditions, the full energy peak count of N-16 γ-rays will decrease, and at the same time, the detection efficiency of NaI for high-energy particles becomes poor. According to on-site data and source term calculations, the escape peak proportion of N-16 under low reactor power is relatively high, and at the same time, a more accurate leakage rate can be obtained by calculating and deducting the corresponding nuclides. Therefore, the present invention calculates the activity of N-16 by measuring the escape peak generated by the electron pair effect of high-energy γ-rays, that is, the γ-ray count with an energy of 511 keV, under low reactor power, and calculates a more accurate main steam pipeline leakage rate under low reactor power in this way, avoiding the occurrence of abnormal high count alarm phenomena.

[0078] In this embodiment,

[0079] The main steam pipeline leakage rate corresponding to the pulse count value is calculated using Equation (1):

[0080] q = n / c (1)

[0081] In the formula:

[0082] q is the leakage rate of the main steam pipeline, with the unit of L / h;

[0083] n is the pulse count value corresponding to the γ-ray with an energy of 511 KeV entering the detector, with the unit of cps;

[0084] c is the leakage transmission coefficient of the heat transfer tube, with the unit of h / (L×s).

[0085] In this embodiment, the leakage transmission coefficient c of the heat transfer tube is related to the detector geometric factor k1, the detector efficiency factor k2, and the transfer time between the leakage point of the heat transfer tube and the main steam pipeline monitoring point.

[0086] Specifically, the leakage transmission coefficient c of the heat transfer tube is calculated using Equation (2):

[0087] c = K×Av (2)

[0088] In the formula:

[0089] K(k1×k2) is the N16 detection efficiency calculated by the MCNP program, with the unit of c×s -1 / (Bq×m -3 );

[0090] Av is the N16 radioactivity at the main steam pipeline monitoring point during heat transfer tube leakage, with the unit of Bq×m -3 / (l×h -1 ).

[0091] Among them, k1 is an inherent property of the detector device, k2 is obtained through Monte Carlo simulation calculation, and Av can be calculated from the nuclear power plant design data.

[0092] Specifically, the N16 radioactivity Av at the main steam pipeline monitoring point during heat transfer tube leakage is calculated using Equation (3):

[0093] Av = Ap×(ρP / 1000)×ρv×e -λt / (Q×3600) (3)

[0094] In the formula:

[0095] Ap: Specific activity of N-16 in the primary loop, Bq·kg -1 ;

[0096] ρP: Density of the coolant in the primary loop, kg·m -3 ;

[0097] ρv: Steam density at the outlet of the steam generator, kg·m -3 ;

[0098] Q: Steam flow rate in the main steam pipeline, kg·s -1 ;

[0099] λ: γ decay constant of N-16, 0.0972 s -1 ;

[0100] t: Transfer time between the leakage point of the heat transfer tube in the primary loop and the monitoring point of the main steam pipeline, s.

[0101] Example 2:

[0102] This example provides a monitoring device for the leakage rate of the main steam pipeline under low reactor power, including: detector 1 and a signal acquisition and processing unit. Among them, detector 1 is installed at the monitoring point of the secondary loop main steam pipeline;

[0103] Detector 1 is used to detect the γ rays generated by the decay of N-16 at the leakage point of the heat transfer tube of the primary loop steam generator and convert them into electrical signals for output.

[0104] The signal acquisition and processing unit is electrically connected to the detector and is used to receive the electrical signal and process it to obtain the pulse count value corresponding to the γ ray with an energy of 511 keV, and calculate the leakage rate of the main steam pipeline corresponding to the pulse count value.

[0105] In this example, the signal acquisition and processing unit includes a signal conversion module 2 and a data processing module 3.

[0106] The signal conversion module 2 is electrically connected to the detector 1 and is used to receive the electrical signal and process it to obtain the pulse count value corresponding to the γ ray with an energy of 511 keV.

[0107] The data processing module 3 is electrically connected to the signal conversion module 2 and is used to calculate the leakage rate of the main steam pipeline corresponding to the pulse count value.

[0108] The structure of detector 1 under low power is shown in the appendix Figure 1 , and the detector model under low power is obtained through MCNP modeling, as shown in the appendix Figure 2 .

[0109] Geometric dimensions of the typical main steam pipeline of a million-kilowatt nuclear power plant reactor:

[0110] Outer diameter of the main steam pipeline at the detector position (m): 0.813

[0111] Thickness of the main steam pipeline (m): 0.037

[0112] Steam density (kg / m 3): 35.750

[0113] Main steam pipe material: P280GH

[0114] Thickness of the thermal insulation layer of the main steam pipe (m): 0.12

[0115] Density of the thermal insulation layer (kg / m 3 ): 80

[0116] Thermal insulation layer material: Fiberglass

[0117] Probe technical parameters:

[0118] The material densities commonly used by detectors at low power are shown in the following table:

[0119]

[0120]

[0121] Using the Monte Carlo program to calculate the energy spectrum under low power conditions, the calculation results are as Figure 3 shown. It can be seen that the detection efficiency and resolution at 511 KeV both meet the requirements.

[0122] See Figure 1 , the detector 1 of this embodiment includes a cladding, and a NaI crystal 11 and a photomultiplier tube 12 wrapped in the cladding. The NaI crystal 11 is used to detect the γ rays emitted by the leaked N-16, and the photomultiplier tube 12 is used to convert the γ ray signal into an electrical signal for output. The cladding includes an inner cylinder 13 and an outer cylinder 14, and a heat insulation layer 15 located between the inner cylinder 13 and the outer cylinder 14. In addition, a lead shielding layer 16 is provided outside the cladding.

[0123] See Figure 2 , the signal conversion module 2 is used to process the photoelectric conversion signal transmitted from the detector 1, including acquisition, shaping, amplitude discrimination, useful signal selection, digital signal conversion, and pulse counting, and finally send the pulse count value to the data processing module 3.

[0124] The data processing module 3 calculates the leakage rate of the main steam pipe under low power of the reactor by using the transmission coefficient calculation formula for the 511 KeV γ radiation counting rate of N-16: q = n / c.

[0125] In this embodiment,

[0126] The data processing module 3 calculates the leakage rate of the main steam pipe corresponding to the pulse count value according to Equation (1) stored during the period:

[0127] q = n / c (1)

[0128] Where:

[0129] q is the leakage rate of the main steam pipeline, with the unit of L / h;

[0130] n is the pulse count value corresponding to the γ-ray with an energy of 511 KeV entering the detector, with the unit of cps;

[0131] c is the leakage transmission coefficient of the heat transfer tube, with the unit of h / (L×s).

[0132] In this embodiment, the leakage transmission coefficient c of the heat transfer tube is related to the detector geometric factor k1, the detector efficiency factor k2, and the transfer time from the leakage point of the heat transfer tube to the monitoring point of the main steam pipeline.

[0133] Specifically, the data processing module also calculates the leakage transmission coefficient c of the heat transfer tube according to Equation (2) stored during the period:

[0134] c = K×Av (2)

[0135] In the formula:

[0136] K(k1×k2) is the N16 detection efficiency calculated by the MCNP program, with the unit of c×s -1 / (Bq×m -3 );

[0137] Av is the N16 radioactivity at the monitoring point of the main steam pipeline during the leakage of the heat transfer tube, with the unit of Bq×m -3 / (l×h -1 ).

[0138] In this embodiment, the data processing module also calculates the N16 radioactivity Av at the monitoring point of the main steam pipeline during the leakage of the heat transfer tube according to Equation (3) stored during the period:

[0139] Av = Ap×(ρP / 1000)×ρv×e -λt / (Q×3600) (3)

[0140] In the formula:

[0141] Ap: The specific activity of N-16 in the primary loop, Bq·kg -1 ;

[0142] ρP: The density of the coolant in the primary loop, kg·m -3 ;

[0143] ρv: The density of the steam at the outlet of the steam generator, kg·m -3 ;

[0144] Q: The steam flow rate in the main steam pipeline, kg·s -1 ;

[0145] λ: The γ decay constant of N-16, 0.0972 s -1 ;

[0146] t: The transfer time between the leakage point of N-16 in the heat transfer pipe and the monitoring point of the main steam pipeline, s.

[0147] The signal conversion module 2 and the data processing module 3 can be obtained by using conventional design methods and will not be elaborated here.

[0148] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present invention. However, the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims

1. A monitoring method for the leakage rate of the main steam pipeline under low reactor power, characterized in that Including: A detector detects γ rays generated by the decay of N-16 at the leakage point of the heat transfer tubes of the primary loop steam generator and converts them into electrical signals for output. The detector is installed at the monitoring point of the secondary loop main steam pipeline. When the power of the reactor is lower than 20%, the signal acquisition and processing unit receives the electrical signal and processes it to obtain the pulse count value corresponding to the γ rays with an energy of 511 keV, and calculates the leakage rate of the main steam pipeline corresponding to the pulse count value.

2. The method for monitoring the leakage rate of the main steam pipeline at low power of the reactor according to claim 1, wherein: The leakage rate of the main steam pipeline corresponding to the pulse count value is calculated using formula (1): q = n / c (1) Where: q is the leakage rate of the main steam pipeline, with the unit of L / h; n is the pulse count value corresponding to the γ rays with an energy of 511 keV entering the detector, with the unit of cps; c is the leakage transmission coefficient of the heat transfer tubes, with the unit of h / (L×s).

3. The method for monitoring the leakage rate of the main steam pipeline at low power of the reactor according to claim 2, wherein: The leakage transmission coefficient c of the heat transfer tubes is calculated using formula (2): c = K×Av (2) Where: K is the N16 detection efficiency calculated by the MCNP program, with the unit of c×s -1 / (Bq×m -3 ); $A_v$ is the N-16 radioactivity at the monitoring point of the main steam pipeline when the heat transfer tube leaks, with the unit of Bq×m -3 / (l×h -1 ).

4. The monitoring method for the main steam pipeline leakage rate under low reactor power according to claim 3, characterized in that The N16 radioactivity Av at the monitoring point of the main steam pipeline when the heat transfer tubes leak is calculated using formula (3): Av = Ap×(ρP / 1000)×ρv×e -λt / (Q×3600) (3) Where: Ap: Specific activity of N-16 in the primary circuit, Bq·kg -1 ; ρP: The density of the coolant in the primary circuit, kg·m -3 ; ρv: Steam density at the outlet of the steam generator, kg·m -3 ; Q: Steam flow rate in the main steam pipeline, kg·s -1 ; λ: The γ decay constant of N-16, 0.0972 s -1 ; t: The transfer time, in s, from the leakage point of the heat transfer tubes to the monitoring point of the main steam pipeline for N-16.

5. The monitoring method for the main steam pipeline leakage rate under low power of the reactor according to any one of claims 1-4, characterized in that, The signal acquisition and processing unit includes a signal conversion module and a data processing module. The signal conversion module is electrically connected to the detector, and is used to receive the electrical signal and process it to obtain the pulse count value corresponding to the γ rays with an energy of 511 keV. The data processing module is electrically connected to the signal conversion module, and is used to calculate the leakage rate of the main steam pipeline corresponding to the pulse count value.

6. A monitoring device for the leakage rate of the main steam pipeline under low power of a reactor, characterized in that Including: A detector and a signal acquisition and processing unit. The detector is installed at the monitoring point of the secondary loop main steam pipeline. The detector is used to detect γ rays generated by the decay of N-16 at the leakage point of the heat transfer tubes of the primary loop steam generator and convert them into electrical signals for output. The signal acquisition and processing unit is electrically connected to the detector, and is used to receive the electrical signal and process it when the power of the reactor is lower than 20% to obtain the pulse count value corresponding to the γ rays with an energy of 511 keV, and calculate the leakage rate of the main steam pipeline corresponding to the pulse count value.

7. The monitoring device for the main steam pipeline leakage rate at low reactor power according to claim 6, characterized in that, The signal acquisition and processing unit includes a signal conversion module and a data processing module. The signal conversion module is electrically connected to the detector, and is used to receive the electrical signal and process it to obtain the pulse count value corresponding to the γ rays with an energy of 511 keV. The data processing module is electrically connected to the signal conversion module, and is used to calculate the leakage rate of the main steam pipeline corresponding to the pulse count value.

8. The device for monitoring the leakage rate of the main steam pipeline at low power of the reactor according to claim 7, wherein: The data processing module calculates the leakage rate of the main steam pipeline corresponding to the pulse count value according to formula (1) stored therein. q = n / c (1) Wherein: q is the leakage rate of the main steam pipeline, with the unit of L / h; n is the pulse count value corresponding to the γ-ray with an energy of 511 KeV entering the detector, with the unit of cps; c is the leakage transmission coefficient of the heat transfer tube, with the unit of h / (L×s).

9. The monitoring device for the leakage rate of the main steam pipeline under low reactor power according to claim 8, wherein the data processing module also calculates the leakage transmission coefficient c of the heat transfer tube according to formula (2) stored therein: c = K×Av (2) Wherein: K is the N16 detection efficiency calculated by the MCNP program, with the unit of c×s -1 / (Bq×m -3 ); Av is the N16 radioactivity at the monitoring point of the main steam pipeline when the heat transfer tube leaks, with the unit of Bq×m -3 / (l×h -1 ).

10. The monitoring device for the leakage rate of the main steam pipeline under low reactor power according to claim 9, wherein the data processing module also calculates the N16 radioactivity Av at the monitoring point of the main steam pipeline when the heat transfer tube leaks according to formula (3) stored therein: Av = Ap × (ρP / 1000) × ρv × e -λt / (Q × 3600) (3) Wherein: Ap: Specific activity of N-16 in the primary circuit, Bq·kg -1 ; ρP: The density of the coolant in the primary loop, kg·m -3 ; ρv: The steam density at the outlet of the steam generator, kg·m -3 ; Q: Steam flow rate in the main steam pipeline, kg·s -1 ; λ: The γ decay constant of N-16, 0.0972 s -1 ; t: the transfer time between the leakage point of the heat transfer tube and the monitoring point of the main steam pipeline for N-16, s.

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