CN115638926A - FBG (fiber Bragg Grating) monitoring system and method for leakage of pipeline valve of nuclear power station - Google Patents
FBG (fiber Bragg Grating) monitoring system and method for leakage of pipeline valve of nuclear power station Download PDFInfo
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- CN115638926A CN115638926A CN202211325687.7A CN202211325687A CN115638926A CN 115638926 A CN115638926 A CN 115638926A CN 202211325687 A CN202211325687 A CN 202211325687A CN 115638926 A CN115638926 A CN 115638926A
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Abstract
A distributed FBG sensor array is arranged at specific positions of a valve, an upstream pipeline and a downstream pipeline, a temperature value is monitored in real time, when leakage occurs, alarm is triggered, meanwhile leakage amount estimation is carried out through a temperature characteristic value of a cross section, and real-time monitoring of valve leakage in the whole pipeline system is achieved. According to the invention, the real-time monitoring of the wall temperature of the pipeline is used as alarm triggering, and the leakage amount is predicted through the temperature monitoring value during leakage, so that the real-time monitoring of the valve leakage is realized, the measurement is accurate, the response is fast, the occurrence of serious accidents is prevented in time, and the safety is ensured.
Description
Technical Field
The invention relates to a technology in the field of nuclear power station safety control, in particular to a system and a method for monitoring the leakage of a nuclear power station valve Fiber Bragg Grating (FBG).
Background
Thermal stratification is common in nuclear grade pipelines and is typically caused by turbulent infiltration of the reactor coolant system into branch lines or by leakage within valves in the branch lines, affecting the safe operation of the nuclear power industry. It has been found that when a valve leaks, thermal stratification occurs in the downstream region of the valve. By arranging the outer wall surface temperature monitoring points in front of and behind the valve and establishing the relational expressions between the thermal stratification characteristic temperature parameters of the monitoring points and the leakage amount, the flow rate and the temperature of the main pipeline fluid, the temperature of the leaked fluid and other factors, the leakage amount of the valve can be effectively predicted. The existing technology can not meet the requirements of real-time monitoring and measurement of leakage, including timely reflecting the temperature fluctuation of the wall surface of a pipeline and accurately measuring the leakage amount.
Disclosure of Invention
The invention provides an FBG (fiber Bragg Grating) leakage monitoring system and method of a pipeline valve of a nuclear power station, aiming at the problem that the pipeline valve of the existing nuclear power station does not monitor leakage in real time.
The invention is realized by the following technical scheme:
the invention relates to a FBG real-time leakage monitoring method for a thermal pipeline valve of a nuclear power station, which is characterized in that a distributed FBG sensor array is arranged at a specific position of the valve and upstream and downstream pipelines to monitor a temperature value in real time, and when leakage occurs, an alarm is triggered and leakage amount estimation is carried out through a temperature characteristic value of a cross section, so that the valve leakage in the whole pipeline system is monitored in real time.
The specific position comprises: at the top of the pipe upstream L1 of the valve, at the side of the valve body, at the top and bottom of the pipe downstream L2 of the valve, at the top and bottom of the pipe downstream L3 of the valve.
Preferably, L1= L2=0.5m, l3=1m.
The distributed FBG sensor array specifically comprises: six FBG sensor probes through optic fibre series connection, wherein: sensors disposed upstream and downstream of the valve are used to measure temperature, and sensors disposed on the valve body measure temperature and vibration simultaneously.
The real-time monitoring temperature value is as follows: the distributed FBG sensor array outputs the output modulation signal to an FBG demodulation analyzer through an optical fiber after modulating an input light source, the drift amount of the FBG center wavelength is obtained through demodulation, and the temperature characteristic value is obtained through calculation by utilizing the properties of different FBG sensors, and the method specifically comprises the following steps: when the ambient temperature T changes to Δ T, the period change of the FBG grating due to the thermal expansion effect is:
the effective refractive index change due to the thermo-optic effect is:
obtaining the center wavelength lambda of the FBG B Drift amount delta lambda B And the temperature change Δ T are:
wherein:
is the coefficient of thermal expansion of the optical fiber;
is the thermo-optic coefficient of the fiber; lambda is FBG period, T is temperature value, n is effective refractive index, and Lambda B Is the FBG center wavelength value. The corresponding temperature value is calculated by measuring the drift amount of the central wavelength of the FBG, when the valve leaks, the temperature gradient of the cross section changes, and the temperature of the monitoring point rapidly rises.
The input light source comprises: the device comprises a dynamic scanning narrow-band semiconductor laser, a low-power-consumption embedded processor and an online calibration wavelength reference module, wherein the output progress of the input light source in a working temperature range is +/-1 pm.
The leakage amount estimation refers to: when leakage occurs, calculating a corresponding temperature characteristic value according to a measured value of the temperature, and predicting the leakage amount by establishing an empirical relation between the temperature characteristic value and the leakage amount of the valve, wherein the method specifically comprises the following steps: when leakage occurs, the magnitude of leakage Q Leakage net And the temperature T of the fluid Leakage net The temperature distribution of the pipe wall is influenced, i.e. T = F (Q) Leakage net ，T Leakage net ). Establishing a temperature characteristic value at a moment t according to a temperature monitoring value of the wall surface of the pipeline: t is a unit of A ＝f(T 1 ，T 2 ，T 3 ，T 4 ，T 5 ，T 6 ) Section temperature difference value: Δ T = T top -T Bottom Wherein: t is 1 As upstream temperature measurement, T 2 As measured value of valve body temperature, T 3 Is the temperature value at the top of the pipeline at the downstream L2, T 4 Is the temperature value of the bottom of the pipeline at the downstream L2, T 5 Is the temperature value at the top of the pipeline at the downstream L3, T 6 Is the temperature value of the bottom of the pipeline at the downstream L3. Since the leak temperature is known and the wall temperature is measured, the amount of leak can be estimated from the known data, i.e.
In the specific measurement, the coefficient of the function relation can be determined through calibration, so that the leakage amount can be calculated according to the measured temperature value.
The invention relates to a FBG real-time leakage monitoring system for a nuclear power station valve, which realizes the method and comprises the following steps: six in proper order concatenate and set up in valve and upstream and downstream pipeline specific position's FBG sensor probe, FBG demodulation analysis appearance and the control module that links to each other in proper order with it through output fiber, wherein: the FBG demodulation analyzer outputs the collected FBG central wavelength drift amount to the control module, the FBG central wavelength drift amount is converted into a temperature value through the control module, and the temperature value is input into the leakage analysis model, so that the real-time valve leakage monitoring, the leakage amount analysis and the safety alarm are realized.
The FBG sensor probe comprises: protective sleeve, capillary steel pipe, adhesive layer and bare fiber grating that set gradually by outer to interior, wherein: the two ends of the bare fiber grating are respectively connected with the transmission optical fiber, the bare fiber grating is positioned in the center of the capillary steel pipe, the adhesive layer is used for fixing the position of the bare fiber grating, and the protective sleeve is sleeved outside the transmission optical fiber and fixedly connected with the outer surface of the capillary steel pipe to realize packaging.
Technical effects
The invention adopts FBG as a sensor to monitor and measure the temperature and vibration of the valve and the characteristic positions of the upstream pipeline and the downstream pipeline in real time, and establishes an analysis model to realize the monitoring of the leakage flow according to the dependency relationship between the dynamic characteristic of thermal stratification generated by the leakage of the valve and the leakage amount and the temperature of the leakage fluid. Compared with the current situation that most valves lack real-time leakage monitoring in a nuclear power station system, the valves need to be dismantled for leakage detection in the overhaul process, and the workload is huge, the method can realize real-time leakage monitoring of the valves of the nuclear power station, and has the function of timely eliminating potential safety hazards on one hand; on the other hand, through leakage monitoring and leakage amount measurement, the method has a good guiding effect on maintenance work, large-scale disassembly and assembly inspection of the valve is not needed, and time and labor are saved.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a schematic diagram of an FBG sensor structure;
in the figure: the system comprises a pipeline valve 1, six FBG sensors 2-7, an output optical fiber 8, an FBG demodulation analyzer 9, a cable 10, a control module 11, a display 12, an alarm 13, a transmission optical fiber 14, a capillary steel pipe 15, an adhesive 16, a protective sleeve 17 and a bare fiber grating 18.
Detailed Description
This embodiment exemplifies a safety injection system (RIS) line and a heat pipe section that is a reactor coolant system (RCP) loop. The inner diameter phi of the pipeline pipe is 736mm, the wall thickness is 67mm, the length is 4900mm, and the pipeline pipe is horizontally placed; the safety injection pipe with the outer diameter phi of 168mm and the SCH160 (the inner diameter phi of 132 mm) is connected with the hot section of the main pipeline by a nozzle and the horizontal plane of 30 degrees, and a valve is arranged on the safety injection pipe. The outer walls of the main pipeline and the safety injection pipeline are not provided with heat insulation layers.
As shown in fig. 1, for the present embodiment, a method for monitoring FBG real-time leakage of a nuclear power plant safety injection pipeline is provided, in which an array composed of six FBG sensor probes 2 to 7 is serially arranged at the top of a pipeline 0.5m upstream of a safety injection pipeline check valve 1, the side surface of a valve body of the safety injection pipeline check valve 1, the top of a pipeline 0.5m downstream of the safety injection pipeline check valve 1, the top of a pipeline 1m downstream of the safety injection pipeline check valve 1, the bottom of a pipeline 1m downstream of the safety injection pipeline check valve 1, and the bottom of a pipeline 0.5m downstream of the safety injection pipeline check valve 1, wherein: the sensor at the upstream and the downstream of the safety injection pipeline check valve is used for measuring temperature, the sensor (FBG bare fiber probe) on the valve body is used for simultaneously measuring temperature and vibration, the optical fiber where each FBG sensor is located is connected with an FBG demodulation analyzer 9 through an output optical fiber 8, the FBG demodulation analyzer is connected with a control module 11 through a cable 10, the FBG central wavelength drift amount obtained by the FBG demodulation analyzer is transmitted to the control module 11, the FBG central wavelength drift amount is converted into a temperature value through the control module, a display 12 and an alarm 13 are connected with the control module 11 through the cable 10 and are used for monitoring positioning and sending an alarm signal in real time and monitoring the real-time leakage amount of the safety injection pipeline check valve.
The control module comprises: signal receiving unit, signal preprocessing unit, signal processing unit and signal output unit, wherein: the signal receiving unit is connected with the FBG demodulation analyzer to receive optical signal information in the FBG, the signal preprocessing unit is connected with the signal receiving unit to receive optical signals and digitize the signals and extract data points required by the signal processing unit, the signal processing unit is connected with the signal preprocessing unit to receive the digitized optical signals and process the signals by using a data acquisition program to obtain a wavelength value and spectrogram information, and the signal output unit is connected with the signal processing unit to receive the wavelength value and the spectrogram information and output corresponding temperature signals to be finally output on the display.
As shown in fig. 2, the FBG sensor probe comprises: protective sleeve 17, capillary steel pipe 15, adhesive layer 16 and bare fiber grating 18 that set gradually from outside to inside, wherein: two ends of the bare fiber grating 18 are respectively connected with the transmission fiber 14, the bare fiber grating 18 is located at the center of the capillary steel tube 15, the adhesive layer 16 is used for fixing the position of the bare fiber grating 18, and the protective sleeve 17 is sleeved outside the transmission fiber 14 and fixedly connected with the outer surface of the capillary steel tube 15 to realize packaging.
The technical parameters of the FBG fiber grating adopted in this embodiment are: the grating of the temperature sensor, namely the bare fiber grating 18, is written by the femtosecond laser writing method in the external writing method, and the FBG sensor manufactured by the method can bear higher temperature and can keep better linear relation with the temperature at high temperature.
The packaging adopts special adhesive, thereby reducing the cross sensitivity of temperature-strain.
The present embodiment is based on the above system, and displays the measured value condition of each measuring point in real time by outputting the output value via signal to the display. Once leakage occurs, the temperature sensor reflects the fluctuation value of the temperature to the display, the alarm system is triggered to give an alarm, and the corresponding leakage amount is obtained by analyzing the leakage model, so that a basis is provided for the next operation of a worker.
Compared with the prior art, the wall surface temperature of the safety injection pipeline of the nuclear power station is measured in real time through the distributed FBG fiber bragg grating sensor, the reaction is rapid, and the measurement result is accurate; according to the leakage prediction model, the leakage is estimated by utilizing the temperature monitoring value, the required measured value is less, and the labor cost can be saved.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (7)
1. A FBG real-time leakage monitoring method for a thermal pipeline valve of a nuclear power station is characterized in that a distributed FBG sensor array is arranged at a specific position of the valve and upstream and downstream pipelines to monitor a temperature value in real time, and when leakage occurs, alarm is triggered and leakage amount estimation is carried out through a temperature characteristic value of a cross section, so that real-time monitoring of valve leakage in the whole pipeline system is realized;
the specific position comprises: a top of the pipe upstream of the valve, a side of the valve body, a top and a bottom of the pipe downstream of the valve;
the real-time monitoring temperature value is as follows: the distributed FBG sensor array modulates an input light source and then outputs an output modulation signal to the FBG demodulation analyzer through an optical fiber, the drift amount of the FBG center wavelength is obtained through demodulation, and the temperature characteristic value is obtained through calculation by utilizing the properties of different FBG sensors.
2. The FBG real-time leakage monitoring method for the thermal pipeline valve of the nuclear power plant as claimed in claim 1, wherein the distributed FBG sensor array is specifically: six FBG sensor probes through optic fibre series connection, wherein: the sensors arranged at the upstream and the downstream of the valve are used for measuring temperature, and the sensors arranged on the valve body simultaneously measure temperature and vibration.
3. The FBG real-time leakage monitoring method for the thermal pipeline valve of the nuclear power plant as claimed in claim 1, wherein the real-time monitoring temperature value is specifically as follows: when the ambient temperature T changes to Δ T, the period of the FBG grating due to the thermal expansion effect changes to:
the effective refractive index change due to the thermo-optic effect is:
obtaining the center wavelength λ of the FBG B Drift amount delta lambda B And the temperature change Δ T are:
wherein:
is the coefficient of thermal expansion of the optical fiber;
is the thermo-optic coefficient of the fiber; lambda is FBG period, T is temperature value, n is effective refractive index, and Lambda B And calculating a corresponding temperature value for the central wavelength value of the FBG by measuring the drift amount of the central wavelength of the FBG, wherein when the valve leaks, the temperature gradient of the cross section changes, and the temperature of a monitoring point rapidly rises.
4. The method for monitoring real-time FBG leakage of the thermal pipeline valve of the nuclear power plant as claimed in claim 1, wherein the input light source comprises: the device comprises a dynamic scanning narrow-band semiconductor laser, a low-power-consumption embedded processor and an online calibration wavelength reference module, wherein the output progress of the input light source in a working temperature range is +/-1 pm.
5. A method for monitoring real-time FBG leakage of a thermal pipeline valve in a nuclear power plant as claimed in claim 1, wherein the leakage estimation is: when leakage occurs, calculating a corresponding temperature characteristic value according to a measured value of the temperature, and predicting the leakage amount by establishing an empirical relation between the temperature characteristic value and the leakage amount of the valve, wherein the method specifically comprises the following steps: when leakage occurs, the magnitude of leakage Q Leakage net And the temperature T of the fluid Leakage net The temperature distribution of the pipe wall is influenced, i.e. T = F (Q) Leakage net ，T Leakage net ) And establishing a temperature characteristic value at the moment t according to the temperature monitoring value of the wall surface of the pipeline: t is A ＝f(T 1 ，T 2 ，T 3 ，T 4 ，T 5 ，T 6 ) And section temperature difference value: Δ T = T top -T Bottom Wherein: t is a unit of 1 As upstream temperature measurements, T 2 As measured value of valve body temperature, T 3 Is the downstream L2 pipeline top temperature value, T 4 Is the downstream L2 pipeline bottom temperature value, T 5 Is the temperature value at the top of the pipeline at the downstream L3, T 6 Is the temperature value of the bottom of the pipeline at the downstream L3.
6. A system for realizing the FBG real-time leakage monitoring method of the thermal pipeline valve of the nuclear power plant as claimed in any one of claims 1 to 5, which is characterized by comprising the following steps: six are connected in series in proper order and set up in the FBG sensor probe of valve and upstream and downstream pipeline specific location, FBG demodulation analysis appearance and the control module who links to each other in proper order with it through output fiber, wherein: the FBG demodulation analyzer outputs the collected FBG center wavelength drift amount to the control module, the control module converts the FBG center wavelength drift amount into a temperature value, and the temperature value is input into the leakage analysis model, so that real-time valve leakage monitoring, leakage amount analysis and safety alarm are realized.
7. The system as claimed in claim 6, wherein the FBG sensor probe comprises: protective sleeve, capillary steel pipe, adhesive layer and bare fiber grating that set gradually by outer to interior, wherein: the two ends of the bare fiber grating are respectively connected with the transmission optical fiber, the bare fiber grating is positioned in the center of the capillary steel pipe, the adhesive layer is used for fixing the position of the bare fiber grating, and the protective sleeve is sleeved outside the transmission optical fiber and fixedly connected with the outer surface of the capillary steel pipe to realize packaging.
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