Dual-mode intelligent helium leak detection system and method for nuclear power plant

Abstract

The present application relates to the field of nuclear power equipment nondestructive testing, and discloses a nuclear power plant dual-mode helium intelligent leak detection system and method, which comprises a pneumatic circuit, a dynamic shielding suction gun, a micro-environment perception, a high-sensitivity helium mass spectrum detection, a two-dimensional coordinate positioning and servo drive, an industrial computer and a dynamic compensation operation and safety interlocking protection unit. The dynamic shielding suction gun forms an airflow isolation area by dispersing constant pressure airflow, the perception unit collects environmental parameters, the industrial computer performs dynamic pressure feedforward adjustment of the flow field according to the environmental parameters, the dispersed asymmetric airflow offsets external crosswind interference, and the original leakage rate is combined with temperature and humidity, dynamic pressure and background coefficient to perform multiplication correction, and real leakage rate data is output. The system supports scanning and cumulative detection dual modes, and purifies and compresses the tail gas to be used as a gas source for recycling. The present application effectively eliminates the interference of multi-dimensional environmental factors, improves the measurement accuracy of small leaks, and reduces the operating cost.

Description

Technical Field

[0001] This invention relates to the field of non-destructive testing of nuclear power equipment, and in particular to a dual-mode intelligent helium leak detection system and method for nuclear power plants. Background Technology

[0002] The airtightness of pressure vessels and pipeline systems in nuclear power plants is directly related to the operational safety of the nuclear island. Currently, helium mass spectrometry is commonly used to detect minor leaks. However, existing helium leak detection systems still have the following technical shortcomings in practical applications:

[0003] First, when traditional suction gun equipment performs scanning sampling, the negative pressure adsorption area at the end face of the suction gun is easily interfered with by external crosswinds. In environments with ventilation systems or natural airflow fluctuations, such as nuclear power plants, leaked tracer gases are often dispersed or diluted by the external flow field before being sucked in, resulting in unstable suction gun sampling and making it difficult to guarantee the collection rate of leaked gases in complex external airflow environments.

[0004] Second, the accurate measurement of extremely small leak rates is highly sensitive to environmental parameters. Local temperature, humidity, and air pressure at nuclear power plant sites are often dynamically changing, and there are fluctuations in background helium concentration in the air. Existing detection systems typically rely solely on factory calibration or single-point benchmark calibration for conversion, lacking a real-time acquisition and comprehensive compensation mechanism for the physical parameters of the microenvironment at the detection site. This results in leak rate outputs from the system being easily affected by factors such as temperature, humidity, and dynamic pressure, leading to significant measurement errors.

[0005] Third, in scenarios involving large-scale inspections of nuclear power plant systems or long-term testing, large quantities of helium-nitrogen mixtures are required. Currently, leak detection equipment often directly releases the exhaust gas extracted by the suction gun and residual gas from the inspected system into the external environment after the inspection process is completed. Because high-purity helium is expensive, this direct venting method results in significant waste of detection gas and substantially increases the overall operating cost of leak detection. Summary of the Invention

[0006] To overcome the above shortcomings, this invention provides a dual-mode intelligent helium leak detection system and method for nuclear power plants, aiming to improve the existing helium leak detection systems, which are mainly susceptible to external airflow interference during suction gun sampling, lack of a real-time comprehensive compensation mechanism for multi-dimensional micro-environment parameters leading to large measurement errors, and high operating costs due to direct emission of detected exhaust gas.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a dual-mode intelligent helium leak detection system for nuclear power plants, used to perform leak detection on the tested system, the dual-mode intelligent helium leak detection system for nuclear power plants includes: a pneumatic circuit unit, a dynamic shielded suction gun and micro-environment sensing unit, a high-sensitivity helium mass spectrometry detection unit, a two-dimensional coordinate positioning and servo drive unit, an industrial control computer and dynamic compensation calculation unit, and a safety interlock protection unit. The pneumatic circuit unit is connected to the system under test via a pneumatic circuit, and is used to establish a vacuum negative pressure state inside the system under test and to fill the system under test with helium-nitrogen mixed gas to maintain a positive pressure. The dynamic shielding suction gun and micro-environment sensing unit includes a coaxial pneumatic shielding suction gun. A central negative pressure sampling channel is arranged at the center of the coaxial pneumatic shielding suction gun. Four independent fan-shaped positive pressure spray chambers are symmetrically distributed on the outer ring of the coaxial pneumatic shielding suction gun. The dynamic shielding suction gun and micro-environment sensing unit are used to collect environmental parameters of the outer area of ​​the end face of the coaxial pneumatic shielding suction gun. The high-sensitivity helium mass spectrometry detection unit is connected to the gas path of the central negative pressure sampling channel. The high-sensitivity helium mass spectrometry detection unit is used to detect the leaked mixed gas and output the leaked gas concentration data, and to operate in the state of no tracer gas filling to output the background helium ion flow fluctuation value. The two-dimensional coordinate positioning and servo drive unit is mechanically connected to the coaxial pneumatic shielding suction gun and is used to control the coaxial pneumatic shielding suction gun to move along the outer surface of the system under test according to a preset trajectory. The industrial control computer and dynamic compensation calculation unit establish communication connections with the pneumatic circuit unit, the dynamic shielding suction gun and micro-environment sensing unit, the high-sensitivity helium mass spectrometry detection unit, the two-dimensional coordinate positioning and servo drive unit, and the safety interlock protection unit, respectively. The industrial control computer and dynamic compensation calculation unit receive the environmental parameters and output leakage rate data compensated for the environmental parameters based on the calculation model. The safety interlock protection unit is electrically connected to the pneumatic circuit unit and the industrial control computer and dynamic compensation calculation unit, and is used to monitor the working parameters of the system under test and cut off the power supply of the pneumatic circuit unit when the parameters exceed the safety limit.

[0008] As a further description of the above technical solution: The pneumatic circuit unit includes a forepump, a molecular pump, a main proportional mixing valve, a pressure stabilizing buffer tank, a dryer filter, a recovery compressor, a gas storage cylinder, and a return pipeline. The inlet of the fore-pump is connected in series with the outlet of the molecular pump, and the inlet of the molecular pump is connected to the interior of the system under test through a pipeline; the inlet of the main proportional mixing valve is connected to the external tracer gas source for initial charging and the return pipeline, and the outlet of the main proportional mixing valve is connected to the pressure stabilizing buffer tank, and the outlet of the pressure stabilizing buffer tank is connected to the charging port of the system under test through a pipeline; The air inlet of the dryer filter is connected to the central negative pressure sampling channel and the exhaust port of the tested system via a pipeline, and the air outlet of the dryer filter is connected to the air inlet of the recovery compressor. The exhaust end of the recovery compressor is connected to the gas storage cylinder, and the exhaust end of the gas storage cylinder is connected to the inlet end of the main proportional mixing valve through the return pipeline to serve as a source of circulating recovery gas.

[0009] As a further description of the above technical solution: The coaxial pneumatic shielded suction gun has a tubular nested structure. The coaxial pneumatic shielded suction gun includes an inner tube and an outer tube sleeved outside the inner tube. The internal space of the inner tube is the central negative pressure sampling channel. An annular space is formed between the inner wall of the outer tube and the outer wall of the inner tube. A cross-shaped isolation partition is fixed inside the annular space, and the cross-shaped isolation partition divides the annular space into four independent fan-shaped positive pressure injection chambers. The dynamic shielding suction gun and micro-environment sensing unit also include a multi-channel micro proportional mixing valve. The air inlet of the multi-channel micro proportional mixing valve is connected to an external protective air source, and the exhaust end of the multi-channel micro proportional mixing valve is connected to the air inlet of the four independent fan-shaped positive pressure injection chambers, respectively, for independently adjusting the constant pressure airflow rate input to the four independent fan-shaped positive pressure injection chambers.

[0010] As a further description of the above technical solution: The bottom surfaces of the four independent fan-shaped positive pressure injection chambers are respectively provided with micro-laminar flow nozzles and sensor mounting slots, and the dissipated constant pressure airflow forms an airflow isolation area around the central negative pressure sampling channel; The dynamic shielding suction gun and micro-environment sensing unit also include a four-quadrant micro-environment sensor array, which is fixedly installed inside the sensor mounting slot. The four-quadrant micro-environment sensor array includes four miniature temperature and humidity meters and four micro-differential pressure sensors. The four miniature temperature and humidity meters are respectively fixed in the sensor mounting slots inside the four independent fan-shaped positive pressure jet chambers, and are used to collect temperature and humidity data inside the airflow isolation area and output micro-domain Celsius temperature and micro-area relative humidity. The four micro-differential pressure sensors are respectively fixed in the sensor mounting slots inside the four independent fan-shaped positive pressure jet chambers, and are used to collect local static pressure values ​​and integrate them with spatial quadrant orientation information to output static pressure difference vector data.

[0011] As a further description of the above technical solution: The industrial control computer and the dynamic compensation calculation unit map the spatial installation positions of the four micro differential pressure sensors to a Cartesian coordinate system containing a horizontal reference axis and a vertical reference axis. The industrial control computer and the dynamic compensation calculation unit extract the local static pressure values ​​from the static pressure difference vector data. Based on the four micro differential pressure sensors distributed on the mutually perpendicular horizontal reference axis and vertical reference axis as differential pressure sensing nodes, the industrial control computer and the dynamic compensation calculation unit calculate the horizontal differential pressure component data and the vertical differential pressure component data. The industrial control computer and the dynamic compensation calculation unit calculate the square root of the sum of the squares of the lateral pressure difference component data and the squares of the longitudinal pressure difference component data, outputting the crosswind intensity parameter, and calculate the arctangent function of the quotient of the longitudinal pressure difference component data divided by the lateral pressure difference component data, outputting the crosswind dynamic pressure direction angle data. The industrial control computer and dynamic compensation calculation unit determine the intrusion quadrant position of the external crosswind flow field based on the crosswind dynamic pressure direction angle data, and set the fan-shaped positive pressure injection chamber associated with the intrusion quadrant position as the windward side injection node, and set the fan-shaped positive pressure injection chamber associated with its diagonal direction as the leeward side injection node. The industrial control computer and dynamic compensation calculation unit calculate the opening adjustment value and generate feedforward adjustment command through the built-in intensity compensation mapping matrix. The multi-channel micro proportional mixing valve increases the internal flow cross-sectional area of ​​the fluid control channel corresponding to the windward side injection node and decreases the internal flow cross-sectional area of ​​the fluid control channel corresponding to the leeward side injection node according to the feedforward adjustment command, thereby dispersing the asymmetric airflow to offset the dynamic pressure interference of the external crosswind flow field.

[0012] As a further description of the above technical solution: The industrial control computer and the dynamic compensation calculation unit perform an average calculation on the local static pressure value to obtain the average static pressure value of the airflow isolation area, and calculate the servo dynamic pressure compensation value based on the sum of the flow cross-sectional area parameters inside the fluid control channel and the preset flow dynamic pressure conversion coefficient constant. The industrial control computer and the dynamic compensation calculation unit add the average static pressure value of the airflow isolation area to the servo dynamic pressure compensation value and output the pressure data during detection. They also calculate the quotient of the calibrated pressure data divided by the pressure data during detection and output the dynamic pressure compensation coefficient. The industrial control computer and dynamic compensation calculation unit add the micro-domain Celsius temperature to the calibration reference constant and output the micro-domain absolute temperature data, and calculate the quotient of the calibration reference constant divided by the micro-domain absolute temperature data and output the temperature compensation coefficient; the industrial control computer and dynamic compensation calculation unit substitute the micro-area relative humidity into the humidity calibration mapping table and output the humidity compensation coefficient, and convert the extracted background helium ion flow fluctuation value into the background compensation coefficient; The industrial control computer and the dynamic compensation calculation unit calculate the original leakage rate data based on the leaked gas concentration data and the calibrated leakage rate parameters. The original leakage rate data is then multiplied by the temperature compensation coefficient, the humidity compensation coefficient, the dynamic pressure compensation coefficient, and the background compensation coefficient to output the true leakage rate data after comprehensive environmental elimination, which serves as the leakage rate data after environmental parameter compensation.

[0013] As a further description of the above technical solution: The system also includes a sealed collection hood and a bypass sampling line. The sealed collection hood is used to enclose a portion of the system under test to form a sealed collection space. The high-sensitivity helium mass spectrometry detection unit includes a preprocessing module, an ion source, a magnetic field deflection analyzer, a collecting electrode, and a switching valve interface. One end of the bypass sampling line is connected to the sealed collection space, and the other end is connected to the switching valve interface of the high-sensitivity helium mass spectrometry detection unit to form a connected gas path. The leaked mixed gas drawn by the central negative pressure sampling channel or the bypass sampling line enters the ion source through the preprocessing module for ionization. The ion beam generated by ionization enters the magnetic field deflection analyzer for mass separation. The collecting electrode receives a helium ion beam with a specified mass-to-charge ratio and outputs a corresponding ion current signal.

[0014] As a further description of the above technical solution: The two-dimensional coordinate positioning and servo drive unit includes a servo drive module and a coordinate positioning mechanism. The servo drive module controls the coordinate positioning mechanism to move the coaxial pneumatic shielded suction gun on the external surface of the system under test. The industrial control computer and dynamic compensation calculation unit are internally preset with a preset leak rate alarm threshold. When the leak rate data after environmental parameter compensation exceeds the preset leak rate alarm threshold, the industrial control computer and dynamic compensation calculation unit send a deceleration verification command to the servo drive module to reduce the running speed of the coordinate positioning mechanism, and transmit the current two-dimensional plane coordinate data, timestamp data, the leak rate data after environmental parameter compensation, and micro-domain.

[0015] As a further description of the above technical solution: The safety interlock protection unit includes an overpressure and overtemperature sensor and a radiation monitoring interface. The overpressure and overtemperature sensor is fixedly installed on the pressure-bearing outer wall and the filling interface of the system under test. The industrial control computer and the dynamic compensation calculation unit combine the basic definition calculation model of leakage rate to calculate the product of the pre-acquired volume parameters of the system under test and the pressure change obtained by the overpressure and overtemperature sensor, and divide the product by the pressure drop test time to output the theoretical leakage rate as the benchmark calibration data.

[0016] As a further description of the above technical solution: A dual-mode intelligent helium leak detection method for nuclear power plants, applied to a dual-mode intelligent helium leak detection system for nuclear power plants, includes the following working stages: State calibration stage: The industrial control computer and dynamic compensation calculation unit control the high-sensitivity helium mass spectrometry detection unit to execute the mass spectrometry calibration program to lock the calibration reference constant, and extract the background helium ion flow fluctuation value in the state without mixed gas to establish the background compensation baseline; Fluid replacement stage: The pneumatic circuit unit is used to pump air to reduce the internal air pressure of the system under test to a preset vacuum threshold. Then, helium and nitrogen are mixed to form a mixed gas and injected into the system under test to maintain the positive pressure of the mixed gas for a preset stabilization time. Scanning or cumulative sensing stage: When the scanning mode is executed, the two-dimensional coordinate positioning and servo drive unit is used to drive the coaxial pneumatic shielded suction gun to move. The dynamic shielded suction gun and the micro-environment sensing unit disperse the constant pressure airflow to form an airflow isolation area and collect micro-environment parameters. Under the condition that a sealed collection hood is set in a part of the tested system to form a sealed collection space, the cumulative detection mode is executed. The bypass sampling pipeline is used to draw gas in the sealed collection space and monitor the cumulative change of concentration over time. Compensation calculation stage: In scanning mode, the industrial control computer and dynamic compensation calculation unit are used to adjust the flow field dynamic pressure feedforward, and the original leakage rate data is combined with temperature, humidity, dynamic pressure and background to perform coefficient multiplication correction, so as to output leakage rate data after environmental parameter compensation. In cumulative detection mode, the cumulative leakage rate data is calculated and output based on the product of concentration change data and the known volume parameters of the sealed collection space preset by the system, divided by the product of the filling helium concentration and the accumulation time. Gas recovery stage: After the detection is completed or the over-limit alarm is verified, the mixed gas filling is interrupted, and the pneumatic circuit unit is used to perform dehydration treatment and volume compression operation to store the sampled tail gas and mixed residual gas into the gas storage cylinder as a source of recycled gas.

[0017] The present invention has the following beneficial effects: 1. This invention possesses reliable anti-crosswind interference capability, ensuring the stability of the suction gun sampling. During system operation, the multi-channel micro proportional mixing valve adjusts and independently controls the constant pressure airflow entering the four fan-shaped positive pressure injection chambers by increasing the internal flow cross-sectional area of ​​the fluid control channel corresponding to the windward side and decreasing the internal flow cross-sectional area of ​​the fluid control channel corresponding to the leeward side. This maintains the physical symmetry of the flow field inside the airflow isolation area. As a result, the asymmetric static pressure flow field inside the airflow isolation area cancels out the dynamic pressure interference of the external crosswind flow field, and the airflow isolation area blocks the external crosswind flow field from intruding into the central negative pressure sampling channel, effectively avoiding the damage of the complex external airflow environment to the collection of leaked gas.

[0018] 2. This invention can effectively eliminate the influence of multidimensional environmental factors on detection accuracy and improve the measurement accuracy of small leak rates. In the compensation calculation stage, the industrial control computer and the dynamic compensation calculation unit multiply the original leak rate data with the temperature compensation coefficient, humidity compensation coefficient, dynamic pressure compensation coefficient and background compensation coefficient to output the true leak rate data after comprehensive environmental elimination. This processing method makes the true leak rate data the corrected output result after eliminating the interference of physical quantities of temperature and humidity inside the airflow isolation area and the interference of external crosswind dynamic pressure, thus avoiding the measurement error caused by temperature and humidity fluctuations and background helium concentration changes at the nuclear power plant site.

[0019] 3. This invention achieves environmentally friendly recycling and reuse of detection gases, reducing the operating costs of long-cycle detection. In the gas recovery stage, the sampling tail gas retained inside the central negative pressure sampling channel and the mixed residual gas discharged from the tested system are discharged and flow through the pipeline to the inlet of the dryer filter for purification and dehumidification. Subsequently, the high-pressure purified mixed gas stored inside the gas storage cylinder is used as the recycling gas source in the next sealing test process and input into the main proportional mixing valve to complete the closed-loop recycling of helium-nitrogen mixed gas, which greatly reduces the consumption of expensive tracer gases. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall architecture and gas path principle of the dual-mode helium intelligent leak detection system for nuclear power plants of the present invention; Figure 2 This is a flowchart illustrating the dynamic compensation operation logic for the actual leakage rate data in this invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Reference Figure 1 - Figure 2 This invention provides a dual-mode intelligent helium leak detection system for nuclear power plants, comprising a pneumatic circuit unit, a dynamic shielded suction gun and microenvironment sensing unit, a high-sensitivity helium mass spectrometry detection unit, a two-dimensional coordinate positioning and servo drive unit, an industrial control computer and dynamic compensation calculation unit, and a safety interlock protection unit. The dual-mode intelligent helium leak detection system is used to perform leak detection on the tested system. In some embodiments, the system further includes a sealed collection hood to enclose a portion of the tested system, the internal space of which constitutes a sealed collection space. Additionally, the system is equipped with a bypass sampling line for connecting the sealed collection space to the gas path of the high-sensitivity helium mass spectrometry detection unit in the cumulative detection mode.

[0023] The pneumatic circuit unit is connected to the system under test via a pneumatic path. The pneumatic circuit unit includes a forepump, a molecular pump, a main proportional mixing valve, a pressure regulating buffer tank, a dryer filter, a recovery compressor, a gas cylinder, and a return line. The inlet of the forepump is connected in series with the outlet of the molecular pump. The inlet of the molecular pump is connected to the interior of the system under test via a pipeline to establish a vacuum negative pressure state within the system. The inlet of the main proportional mixing valve is connected to the initial external tracer gas source and the return line. The outlet of the main proportional mixing valve is connected to the pressure regulating buffer tank. The outlet of the pressure regulating buffer tank is connected to a pipeline... The pipeline connects to the charging port of the system under test, used to charge and maintain the positive pressure of the helium-nitrogen mixture in the system under test. The inlet of the dryer filter is connected to the central negative pressure sampling channel inside the coaxial pneumatic shielded suction gun (described later) and the exhaust port of the system under test through a pipeline. The outlet of the dryer filter is connected to the inlet of the recovery compressor. The exhaust of the recovery compressor is connected to the gas storage cylinder, used to compress and store the residual gas in the pipeline and the system under test into the gas storage cylinder after the test process is completed. The exhaust of the gas storage cylinder is connected to the inlet of the main proportional mixing valve through a return pipeline, serving as a source of recycled gas.

[0024] The dynamic shielded suction gun and micro-environment sensing unit include a coaxial pneumatic shielded suction gun, a multi-channel miniature proportional mixing valve, and a four-quadrant micro-environment sensor array. A central negative pressure sampling channel is arranged at the center of the coaxial pneumatic shielded suction gun. Four independent fan-shaped positive pressure injection chambers are symmetrically distributed on the outer ring of the coaxial pneumatic shielded suction gun. The air inlet of the multi-channel miniature proportional mixing valve is connected to an external protective air source, and the exhaust end of the multi-channel miniature proportional mixing valve is connected to the air path of the four fan-shaped positive pressure injection chambers respectively, for independently adjusting the constant pressure airflow rate input to the four fan-shaped positive pressure injection chambers.

[0025] The four-quadrant micro-environment sensor array is fixedly installed on the end face of the coaxial pneumatic shielded suction gun. The four-quadrant micro-environment sensor array includes four miniature thermometers and hygrometers and four micro-differential pressure sensors distributed in four quadrant regions. The four-quadrant micro-environment sensor array is used to collect static pressure difference vector data, micro-domain temperature in Celsius and micro-region relative humidity in the outer region of the end face of the coaxial pneumatic shielded suction gun.

[0026] The high-sensitivity helium mass spectrometry detection unit is connected to the gas path of the central negative pressure sampling channel. The high-sensitivity helium mass spectrometry detection unit includes a pretreatment module, an ion source, a magnetic field deflection analyzer, a collecting electrode, and a switching valve interface for connecting the bypass sampling line. The leaked mixed gas drawn by the central negative pressure sampling channel (or bypass sampling line) enters the ion source for ionization through the pretreatment module. The ion beam generated by ionization enters the magnetic field deflection analyzer for mass separation. The collecting electrode receives the helium ion beam with a specified mass-to-charge ratio and outputs the corresponding ion current signal. When the high-sensitivity helium mass spectrometry detection unit is running in the state of no tracer gas filling, it outputs the background helium ion current fluctuation value.

[0027] The two-dimensional coordinate positioning and servo drive unit is mechanically connected to the coaxial pneumatic shielded suction gun. The two-dimensional coordinate positioning and servo drive unit includes a servo drive module and a coordinate positioning mechanism. The servo drive module controls the coordinate positioning mechanism to drive the coaxial pneumatic shielded suction gun to move along the outer surface of the system under inspection according to a preset trajectory.

[0028] The industrial control computer and dynamic compensation calculation unit establish communication connections with the pneumatic circuit unit, the dynamic shielding suction gun and micro-environment sensing unit, the high-sensitivity helium mass spectrometry detection unit, the two-dimensional coordinate positioning and servo drive unit, and the safety interlock protection unit, respectively. The industrial control computer and dynamic compensation calculation unit are internally equipped with a memory and a processor. The memory stores computer programs or instructions, and the processor executes these programs or instructions to implement various calculations and compensation logics of the system. The industrial control computer and dynamic compensation calculation unit receive background helium ion flow fluctuations, static pressure difference vector data, micro-domain Celsius temperature, and micro-area relative humidity. Based on the static pressure difference vector data, the industrial control computer and dynamic compensation calculation unit output feedforward adjustment commands to the multi-channel micro proportional mixing valve and output actual leakage rate data based on the calculation model. The industrial control computer and dynamic compensation calculation unit have a pre-set leakage rate basic definition calculation model, used to assist in system benchmark calibration during routine pressure drop testing. The leakage rate basic definition calculation model outputs the theoretical leakage rate based on the leakage rate basic definition formula, which is:

[0029] In the formula, Represents the theoretical leakage rate. This represents the pressure change collected by the safety interlock protection unit. Represents the volume of the system under test. This represents the pressure drop test time.

[0030] The safety interlock protection unit is electrically connected to the pneumatic circuit unit and the industrial control computer and dynamic compensation calculation unit respectively. The safety interlock protection unit includes an overpressure and overtemperature sensor and a radiation monitoring interface. The overpressure and overtemperature sensor is fixedly installed on the pressure-bearing outer wall and the filling interface of the system under test to monitor the working parameters of the system under test. When the working parameters exceed the safety limit, the safety interlock protection unit cuts off the power supply of the pneumatic circuit unit.

[0031] Based on the aforementioned dual-mode intelligent helium leak detection system for nuclear power plants, the workflow of the system for leak detection includes state calibration, fluid replacement, scanning sensing, compensation calculation, and gas recovery stages.

[0032] During the calibration phase, the industrial control computer and the dynamic compensation calculation unit control the high-sensitivity helium mass spectrometer detection unit to run and execute the mass spectrometer calibration program, lock the calibration reference constant (e.g., absolute temperature 273.15) and record the calibration pressure data. At the same time, the industrial control computer and the dynamic compensation calculation unit combine the above-mentioned basic definition calculation model of leakage rate and use the pressure drop method (obtaining pressure data through overpressure and overtemperature sensors) to measure the theoretical leakage rate as macroscopic reference calibration data to assist in the subsequent comparison and correction of microscopic leakage rates. When the pneumatic circuit unit does not charge the tested system with mixed gas, the dynamic shielded suction gun and the micro-environment sensing unit stop outputting airflow. The high-sensitivity helium mass spectrometer detection unit detects the gas in the outer region of the coaxial pneumatic shielded suction gun end face and outputs the background helium ion flow fluctuation value. The industrial control computer and the dynamic compensation calculation unit receive the background helium ion flow fluctuation value and establish a background compensation baseline.

[0033] The forepump and molecular pump inside the pneumatic circuit unit operate synchronously to evacuate the internal space of the system under test, reducing the internal pressure of the system under test to a preset vacuum threshold of no more than 5 Pa. When the preset vacuum threshold is reached, the industrial control computer and the dynamic compensation calculation unit send an opening control command to the main proportional mixing valve. The main proportional mixing valve mixes helium and nitrogen at a helium concentration ratio of 5% to 15% to form a mixed gas. The main proportional mixing valve delivers the mixed gas to the pressure stabilizing buffer tank. The pressure stabilizing buffer tank injects the mixed gas into the internal space of the system under test, maintaining the positive pressure parameter of the mixed gas inside the system under test to a preset stabilization time limit of 5 to 10 minutes.

[0034] The servo drive module in the two-dimensional coordinate positioning and servo drive unit controls the operation of the coordinate positioning mechanism. The coordinate positioning mechanism drives the coaxial pneumatic shielded suction gun to move on the outer surface of the system under test at a speed of no more than 5 mm / s according to the preset grid coordinate points. During the movement of the coaxial pneumatic shielded suction gun, the multi-channel micro proportional mixing valve inputs constant pressure airflow into the four independent fan-shaped positive pressure injection chambers respectively. The four fan-shaped positive pressure injection chambers discharge airflow to the outside, forming an airflow isolation area around the central negative pressure sampling channel.

[0035] The four-quadrant micro-environment sensor array contains four miniature thermo-hygrometers and four miniature differential pressure sensors distributed in the four quadrant regions. These sensors collect static pressure difference vector data, micro-domain Celsius temperature, and micro-region relative humidity within the airflow isolation area. The industrial control computer and dynamic compensation calculation unit receive and process the static pressure difference vector data, calculate the dynamic pressure direction data of external flow field interference, and output feedforward adjustment commands to the multi-channel miniature proportional mixing valve based on the dynamic pressure direction data. The multi-channel miniature proportional mixing valve adjusts the internal flow cross-sectional area leading to each sector positive pressure injection chamber according to the feedforward adjustment commands to regulate the airflow parameters.

[0036] The industrial control computer and dynamic compensation calculation unit extract the current real-time servo opening command data of the multi-channel micro proportional mixing valve. The high-sensitivity helium mass spectrometry detection unit detects the gas drawn in by the central negative pressure sampling channel and outputs the leakage gas concentration data. The industrial control computer and dynamic compensation calculation unit substitute the real-time servo opening command data, static pressure difference vector data, micro-domain Celsius temperature, micro-area relative humidity, and leakage gas concentration data into the internal calculation model. The industrial control computer and dynamic compensation calculation unit run the internal calculation model and output the actual leakage rate data.

[0037] The industrial control computer and dynamic compensation calculation unit perform numerical comparison calculations between the actual leak rate data and the preset leak rate alarm threshold. When the actual leak rate data exceeds the preset leak rate alarm threshold, the industrial control computer and dynamic compensation calculation unit send a deceleration operation command to the two-dimensional coordinate positioning and servo drive unit, and record the current two-dimensional coordinate data of the coordinate positioning mechanism and the corresponding actual leak rate data. When the coordinate positioning mechanism in the two-dimensional coordinate positioning and servo drive unit completes all preset grid coordinate point movement actions, the pneumatic circuit unit interrupts the charging of mixed gas into the tested system. The exhaust gas drawn by the central negative pressure sampling channel and the residual gas discharged from the tested system enter the drying filter for dehydration treatment. The dehydrated gas is sent to the recovery compressor, which compresses and stores the gas in the gas storage cylinder.

[0038] As shown in the figure, the above-mentioned dynamic shielding suction gun and micro-environment sensing unit includes a coaxial pneumatic shielding suction gun. The coaxial pneumatic shielding suction gun has a tubular nested structure. The coaxial pneumatic shielding suction gun includes an inner tube and an outer tube sleeved outside the inner tube. The inner tube and the outer tube are arranged coaxially along the longitudinal extension direction of the coaxial pneumatic shielding suction gun.

[0039] The internal space of the inner tube is a central negative pressure sampling channel. The inlet end face of the central negative pressure sampling channel is flush with the bottom end face of the inner tube, and the outlet end of the central negative pressure sampling channel extends to the top of the inner tube. The outlet end of the central negative pressure sampling channel is connected to the gas path of the high-sensitivity helium mass spectrometry detection unit. The central negative pressure sampling channel constitutes a single flow path for leaked gas.

[0040] An annular space is formed between the inner wall of the outer tube and the outer wall of the inner tube. A cross-shaped isolation partition is fixed inside the annular space. The cross-shaped isolation partition extends radially and axially along the coaxial pneumatic shielded suction gun. The cross-shaped isolation partition is fixedly connected to the inner wall of the outer tube and the outer wall of the inner tube, respectively. The cross-shaped isolation partition divides the annular space into four independent fan-shaped positive pressure injection chambers. The four fan-shaped positive pressure injection chambers are axially symmetrically distributed around the central negative pressure sampling channel.

[0041] The top end faces of the four sector-shaped positive pressure injection chambers are respectively provided with air inlets. The air inlets of the four sector-shaped positive pressure injection chambers are connected to the exhaust end of the multi-channel micro proportional mixing valve through pipelines. The constant pressure airflow output by the multi-channel micro proportional mixing valve enters the corresponding sector-shaped positive pressure injection chamber through the air inlet.

[0042] The bottom surfaces of the four fan-shaped positive pressure injection chambers are respectively provided with micro-laminar flow nozzles. The micro-laminar flow nozzles are distributed in a ring around the air inlet end face of the inner tube. The constant pressure airflow entering the fan-shaped positive pressure injection chamber is dispersed to the outer area of ​​the coaxial pneumatic shielded suction gun end face through the micro-laminar flow nozzles. The dispersed constant pressure airflow forms an airflow isolation area around the central negative pressure sampling channel.

[0043] Sensor mounting slots are provided on the bottom surfaces of the four fan-shaped positive pressure injection chambers. The sensor mounting slots are used to fix the four-quadrant micro-environment sensor array. The sensor mounting slots and micro-laminar flow nozzles are arranged at intervals on the bottom surfaces of the four fan-shaped positive pressure injection chambers. The four-quadrant micro-environment sensor array is fixedly installed inside the sensor mounting slots and includes four miniature temperature and humidity meters and four micro-differential pressure sensors.

[0044] Four miniature temperature and humidity meters are fixed in the sensor mounting slots inside the four fan-shaped positive pressure jet chambers, and four micro differential pressure sensors are fixed in the sensor mounting slots inside the four fan-shaped positive pressure jet chambers. The detection end faces of the four miniature temperature and humidity meters and the detection end faces of the four micro differential pressure sensors all face the bottom of the coaxial pneumatic shielded suction gun.

[0045] The constant pressure airflow discharged from the four fan-shaped positive pressure jet chambers forms an airflow isolation area around the central negative pressure sampling channel. The detection ends of the four miniature temperature and humidity meters and the detection ends of the four micro-differential pressure sensors are located inside the airflow isolation area. The four miniature temperature and humidity meters collect temperature and humidity data inside the airflow isolation area and output micro-area Celsius temperature and micro-area relative humidity.

[0046] Four micro differential pressure sensors collect local static pressure values ​​inside the airflow isolation area corresponding to the bottom of the four fan-shaped positive pressure injection chambers. The four micro differential pressure sensors combine the local static pressure values ​​with the spatial quadrant orientation information of the four fan-shaped positive pressure injection chambers and integrate them to output static pressure difference vector data. The static pressure difference vector data includes the pressure gradient values ​​at different orientations of the airflow isolation area.

[0047] The four-quadrant micro-environment sensor array is electrically connected to the industrial control computer and the dynamic compensation calculation unit. Four miniature temperature and humidity meters transmit the micro-domain temperature in Celsius and the micro-area relative humidity to the industrial control computer and the dynamic compensation calculation unit. Four micro-differential pressure sensors transmit the static pressure difference vector data to the industrial control computer and the dynamic compensation calculation unit. The industrial control computer and the dynamic compensation calculation unit receive the static pressure difference vector data, the micro-domain temperature in Celsius, and the micro-area relative humidity.

[0048] The industrial control computer and the dynamic compensation calculation unit are electrically connected to the pneumatic circuit unit and the multi-channel miniature proportional mixing valve, respectively. The pneumatic circuit unit is controlled by the industrial control computer and the dynamic compensation calculation unit, and has vacuum operation mode and positive pressure operation mode.

[0049] When the pneumatic circuit unit is in a vacuum operating state, the industrial control computer and the dynamic compensation calculation unit transmit start commands to the forepump and molecular pump. The forepump and molecular pump operate synchronously, drawing gas from inside the system under test through the connected pipeline to reduce the gas pressure inside the system under test and establish a vacuum negative pressure environment.

[0050] When the pneumatic circuit unit is in positive pressure operation, the main proportional mixing valve receives the mixing ratio command transmitted by the industrial control computer and the dynamic compensation calculation unit. According to the mixing ratio command, the main proportional mixing valve mixes the helium and nitrogen gas input from the external tracer gas source or return pipeline during the initial charge according to the preset concentration ratio. The main proportional mixing valve outputs the helium-nitrogen mixed gas to the pressure stabilizing buffer tank. After the pressure stabilizing buffer tank stabilizes the helium-nitrogen mixed gas, it delivers the helium-nitrogen mixed gas to the inside of the system under test.

[0051] The multi-channel miniature proportional mixing valve has four independent fluid control channels inside. The air inlet of the multi-channel miniature proportional mixing valve is connected to an external protective air source. The exhaust end of the multi-channel miniature proportional mixing valve includes four exhaust ports, which are connected to the air inlets of the four fan-shaped positive pressure injection chambers respectively. The external protective air source inputs constant pressure airflow into the multi-channel miniature proportional mixing valve.

[0052] The industrial control computer and the dynamic compensation calculation unit retrieve static pressure difference vector data for analytical calculation, and calculate the dynamic pressure direction and intensity parameters of the crosswind flow field outside the coaxial pneumatic shielded suction gun. Based on the dynamic pressure direction and intensity parameters, the industrial control computer and the dynamic compensation calculation unit output feedforward adjustment commands. The industrial control computer and the dynamic compensation calculation unit send the feedforward adjustment commands to the multi-channel micro proportional mixing valve. The multi-channel micro proportional mixing valve receives the feedforward adjustment commands and adjusts the internal flow cross-sectional area of ​​the four independent fluid control channels according to the feedforward adjustment commands. By increasing the internal flow cross-sectional area of ​​the fluid control channel on the windward side and decreasing the internal flow cross-sectional area of ​​the fluid control channel on the leeward side, the multi-channel micro proportional mixing valve adjusts and independently controls the constant pressure airflow rate entering the four fan-shaped positive pressure injection chambers, maintaining the physical symmetry of the flow field inside the airflow isolation area.

[0053] For the analytical calculation of the above static pressure difference vector data, the industrial control computer and the dynamic compensation calculation unit map the spatial installation positions of the four micro differential pressure sensors to a plane rectangular coordinate system. The plane rectangular coordinate system takes the central axis of the central negative pressure sampling channel as the origin and includes mutually perpendicular horizontal reference axes and vertical reference axes. The four micro differential pressure sensors are divided into two horizontal differential pressure sensing nodes distributed at the positive and negative ends of the horizontal reference axis, and two vertical differential pressure sensing nodes distributed at the positive and negative ends of the vertical reference axis.

[0054] The industrial control computer and the dynamic compensation calculation unit extract the local static pressure values ​​from the static pressure difference vector data. The industrial control computer and the dynamic compensation calculation unit subtract the local static pressure values ​​output by the lateral pressure difference sensing nodes at the negative end of the lateral reference axis from the local static pressure values ​​output by the lateral pressure difference sensing nodes at the positive end of the lateral reference axis, and output the lateral pressure difference component data corresponding to the lateral reference axis. The industrial control computer and the dynamic compensation calculation unit subtract the local static pressure values ​​output by the longitudinal pressure difference sensing nodes at the negative end of the longitudinal reference axis from the local static pressure values ​​output by the longitudinal pressure difference sensing nodes at the positive end of the longitudinal reference axis, and output the longitudinal pressure difference component data corresponding to the longitudinal reference axis.

[0055] The industrial control computer and the dynamic compensation calculation unit input the transverse pressure difference component data and the longitudinal pressure difference component data into the built-in vector synthesis model. The industrial control computer and the dynamic compensation calculation unit calculate the sum of the square values ​​of the transverse pressure difference component data and the square values ​​of the longitudinal pressure difference component data, and perform a square root operation on the sum to output the crosswind intensity parameter.

[0056] The formula for calculating the crosswind intensity parameter is:

[0057] In the formula, Represents crosswind intensity parameters. Represents the lateral pressure differential component data. This represents the longitudinal pressure differential component data.

[0058] The industrial control computer and dynamic compensation calculation unit calculate the quotient obtained by dividing the longitudinal pressure difference component data by the transverse pressure difference component data, and perform arctangent function calculation on the quotient to output the crosswind dynamic pressure direction angle data. The crosswind dynamic pressure direction angle data reflects the vector direction deflection angle of the crosswind flow field outside the coaxial aerodynamic shielded suction gun.

[0059] The formula for calculating the crosswind dynamic pressure direction angle data is:

[0060] In the formula, This represents the angle data of the crosswind dynamic pressure direction.

[0061] The industrial control computer and the dynamic compensation calculation unit establish a mapping relationship between crosswind intensity parameters, crosswind dynamic pressure direction angle data and the spatial orientation of the four-quadrant micro-environment sensor array. The crosswind intensity parameters and crosswind dynamic pressure direction angle data constitute the dynamic pressure direction and intensity parameters of the external crosswind flow field. The industrial control computer and the dynamic compensation calculation unit store the crosswind intensity parameters and crosswind dynamic pressure direction angle data, providing feedback control input variables for the feedforward adjustment logic of the multi-channel micro proportional mixing valve.

[0062] Furthermore, the industrial control computer and the dynamic compensation calculation unit extract crosswind intensity parameters and crosswind dynamic pressure direction angle data, and perform quadrant interval comparison calculations in the plane rectangular coordinate system based on the crosswind dynamic pressure direction angle data to determine the intrusion quadrant position of the crosswind flow field outside the coaxial aerodynamic shielded suction gun.

[0063] The industrial control computer and dynamic compensation calculation unit set the fan-shaped positive pressure injection chamber associated with the intrusion quadrant position as the windward injection node, and set the fan-shaped positive pressure injection chamber associated with the diagonal direction of the intrusion quadrant position as the leeward injection node. The industrial control computer and dynamic compensation calculation unit have a pre-set intensity compensation mapping matrix, which is obtained by fitting through a pre-implemented flow field interference measurement experiment. The intensity compensation mapping matrix records the linear proportional correspondence between the crosswind intensity parameter scalar and the change in the internal flow cross-sectional area of ​​the multi-channel micro proportional mixing valve. The industrial control computer and dynamic compensation calculation unit input the crosswind intensity parameter into the intensity compensation mapping matrix, calculate the positive opening adjustment value corresponding to the windward injection node, and calculate the negative opening adjustment value corresponding to the leeward injection node.

[0064] The industrial control computer and the dynamic compensation calculation unit integrate the positive and negative opening adjustment values ​​to generate a feedforward adjustment command, which is then sent to the multi-channel micro proportional mixing valve. The multi-channel micro proportional mixing valve receives the feedforward adjustment command and increases the internal flow cross-sectional area of ​​the fluid control channel corresponding to the windward side injection node according to the positive opening adjustment value, while decreasing the internal flow cross-sectional area of ​​the fluid control channel corresponding to the leeward side injection node according to the negative opening adjustment value.

[0065] A multi-channel micro proportional mixing valve inputs a constant-pressure airflow that increases the airflow rate to the windward injection node and a constant-pressure airflow that decreases the airflow rate to the leeward injection node. The four fan-shaped positive pressure injection chambers disperse the asymmetric airflow according to the input constant-pressure airflow. The four fan-shaped positive pressure injection chambers form an airflow isolation region with an asymmetric static pressure distribution around the central negative pressure sampling channel. The asymmetric static pressure flow field inside the airflow isolation region cancels out the dynamic pressure interference of the external crosswind flow field, and the airflow isolation region blocks the external crosswind flow field from intruding into the central negative pressure sampling channel.

[0066] The multi-channel miniature proportional mixing valve transmits the current internal flow cross-sectional area status values ​​of the four independent fluid control channels after adjustment to the industrial control computer and dynamic compensation calculation unit. The industrial control computer and dynamic compensation calculation unit receive the current internal flow cross-sectional area status values ​​and convert them into real-time servo opening command data. The industrial control computer and dynamic compensation calculation unit store the real-time servo opening command data to provide servo state variables for subsequent dynamic pressure coupling calculations.

[0067] During dynamic pressure coupling calculation, the industrial control computer and the dynamic compensation calculation unit receive four local static pressure values ​​output by four micro differential pressure sensors inside the four-quadrant micro-environment sensor array, and perform an arithmetic average calculation on the four local static pressure values ​​to output the average static pressure value of the airflow isolation area.

[0068] The industrial control computer and the dynamic compensation calculation unit extract real-time servo opening command data. The real-time servo opening command data includes the internal flow cross-sectional area parameters of the four independent fluid control channels inside the multi-channel miniature proportional mixing valve. The industrial control computer and the dynamic compensation calculation unit retrieve the internally preset flow-dynamic-pressure conversion coefficient constant and calculate the sum of the four internal flow cross-sectional area parameters. The industrial control computer and the dynamic compensation calculation unit multiply the sum by the flow-dynamic-pressure conversion coefficient constant to calculate the servo dynamic pressure compensation value generated by the asymmetric airflow output by the multi-channel miniature proportional mixing valve.

[0069] The industrial control computer and dynamic compensation calculation unit add the average static pressure value of the airflow isolation area to the servo dynamic pressure compensation value, and output the pressure data during detection. The calculation formula for the pressure data during detection is:

[0070] In the formula, This represents the pressure data during testing. This represents the average static pressure value in the airflow isolation zone. This represents the sum of the four internal flow cross-sectional area parameters. The flow-pressure conversion constant represents a physical quantity that converts area parameters into equivalent pressure variables. This represents the servo dynamic pressure compensation value.

[0071] The industrial control computer and dynamic compensation calculation unit retrieve the calibration pressure data recorded by the high-sensitivity helium mass spectrometer detection unit during the mass spectrometry calibration procedure, calculate the quotient of the calibration pressure data divided by the pressure data during detection, and output the dynamic pressure compensation coefficient.

[0072] The formula for calculating the dynamic pressure compensation coefficient is:

[0073] In the formula, This represents the dynamic pressure compensation coefficient. Represents the calibration pressure data. This represents the pressure data during the test.

[0074] The dynamic pressure compensation coefficient reflects the coupling influence of the micro-domain dynamic pressure variable generated by servo intervention and the environmental static pressure variable on the pressure physical field of the airflow isolation area. The industrial control computer and the dynamic compensation calculation unit store the dynamic pressure compensation coefficient, providing a pressure dimension correction variable for the global multi-dimensional environmental compensation leakage rate conversion algorithm.

[0075] Combining the aforementioned corrected variables, the industrial control computer and the dynamic compensation calculation unit extract the micro-domain Celsius temperature output by the four-quadrant micro-environment sensor array, add the micro-domain Celsius temperature to the calibration reference constant, and output the micro-domain absolute temperature data. The industrial control computer and the dynamic compensation calculation unit calculate the quotient value of the calibration reference constant 273.15 divided by the micro-domain absolute temperature data and output the temperature compensation coefficient.

[0076] The formula for calculating the temperature compensation coefficient is:

[0077] In the formula, Represents the temperature compensation coefficient. Represents the micro-domain Celsius temperature. This represents absolute temperature data in the micro-domain.

[0078] The industrial control computer and dynamic compensation calculation unit extract the micro-area relative humidity output by the four-quadrant micro-environment sensor array, and substitute the micro-area relative humidity into the internally preset humidity calibration mapping table to output the humidity compensation coefficient (set as symbol). This humidity calibration mapping table was obtained through offline experimental calibration and fitting under different humidity conditions using an external standard leak. It records the measured attenuation correction factor of the helium ion current signal absorbed by water molecules due to different relative humidities. The industrial control computer and dynamic compensation calculation unit extract the background helium ion current fluctuation value output by the high-sensitivity helium mass spectrometry detection unit, and convert the background helium ion current fluctuation value into a background background compensation coefficient (denoted as symbol) according to a preset background equivalent ratio. The background equivalent ratio is also derived from pre-calibration and is used to convert the environmental baseline helium concentration into a correction multiplier to eliminate baseline offset.

[0079] The industrial control computer and dynamic compensation calculation unit receive the leaked gas concentration data (denoted as symbol) directly output by the high-sensitivity helium mass spectrometry detection unit. ), and combined with preset calibration leakage rate parameters (set as symbol) ), which yields the raw leakage rate data without environmental factor correction.

[0080] The formula for calculating the raw leak rate data is:

[0081] In the formula, Represents the original leak rate data. Data representing the concentration of leaked gas. This represents the calibration leak rate parameter.

[0082] The industrial control computer and the dynamic compensation calculation unit extract the temperature compensation coefficient, humidity compensation coefficient, dynamic pressure compensation coefficient, and background compensation coefficient. The industrial control computer and the dynamic compensation calculation unit multiply the original leakage rate data with the temperature compensation coefficient, humidity compensation coefficient, dynamic pressure compensation coefficient, and background compensation coefficient to output the true leakage rate data after comprehensive environmental elimination.

[0083] The formula for calculating the true leakage rate is:

[0084] In the formula, Represents the true leakage rate data. Represents the original leak rate data. Represents the temperature compensation coefficient. Represents the humidity compensation coefficient. This represents the dynamic pressure compensation coefficient. This represents the background compensation coefficient.

[0085] The industrial control computer and dynamic compensation calculation unit store the actual leakage rate data. The actual leakage rate data serves as the corrected output result to eliminate the interference of physical quantities such as temperature and humidity inside the airflow isolation area and the interference of external crosswind dynamic pressure. It provides numerical basis for the subsequent over-limit alarm verification of leakage point coordinates. The industrial control computer and dynamic compensation calculation unit have preset leakage rate alarm thresholds and perform numerical comparison calculations between the actual leakage rate data and the preset leakage alarm thresholds.

[0086] When the actual leakage rate exceeds the preset leakage rate alarm threshold, the industrial control computer and the dynamic compensation calculation unit generate an over-limit alarm signal and a deceleration verification command. The deceleration verification command is then sent to the servo drive module inside the two-dimensional coordinate positioning and servo drive unit. The servo drive module receives the deceleration verification command and reduces the running speed of the coordinate positioning mechanism according to the command. The coordinate positioning mechanism drives the coaxial pneumatic shielding suction gun to perform a secondary scanning action on the external surface area of ​​the inspected system corresponding to the current position at a reduced operating speed. During the execution of the secondary scanning action, the coordinate positioning mechanism transmits the two-dimensional planar coordinate data of the current spatial position of the coaxial pneumatic shielding suction gun to the industrial control computer and the dynamic compensation calculation unit.

[0087] The industrial control computer and the dynamic compensation calculation unit receive two-dimensional plane coordinate data and extract the current time stamp data, the actual leak rate data corresponding to the current spatial location, the micro-domain absolute temperature data, and the pressure data during detection generated by the system clock module built into the industrial control computer and the dynamic compensation calculation unit. The industrial control computer and the dynamic compensation calculation unit perform data splicing processing on the two-dimensional plane coordinate data, timestamp data, actual leak rate data, micro-domain absolute temperature data, and pressure data during detection.

[0088] The industrial control computer and the dynamic compensation calculation unit generate a high-dimensional feature dataset of leak points through data splicing and processing. The high-dimensional feature dataset of leak points includes the spatial location attributes, leakage rate numerical attributes, and environmental physical field state parameters of the leak points. The industrial control computer and the dynamic compensation calculation unit write the high-dimensional feature dataset of leak points into the internal storage module and generate a leak point distribution chart containing the mapping relationship between spatial location attributes and leakage rate numerical attributes based on the high-dimensional feature dataset of leak points.

[0089] For specific confined spaces or ultra-micro leak scenarios requiring long-term static testing, the nuclear power plant's dual-mode intelligent helium leak detection system can switch to cumulative detection mode. In this mode, the aforementioned sealed collection hood is placed over the surface of the system under test. The high-sensitivity helium mass spectrometry detection unit draws gas from the sealed collection space through the aforementioned bypass sampling line. The industrial control computer and dynamic compensation calculation unit monitor the cumulative change in helium concentration over time within the sealed collection space formed by the sealed collection hood, and extract the concentration change data. (i.e., the high-sensitivity helium mass spectrometry detection unit in the cumulative time) (Difference between continuously measured leaked gas concentration data) and the volume of the sealed collection space (Known constants pre-set within the system), Helium concentration during charging (Obtained from the set ratio value of the main proportional mixing valve) and cumulative time It then substitutes the data into the built-in cumulative leakage rate formula to output the cumulative leakage rate data.

[0090] The cumulative leakage rate formula is:

[0091] In the formula, Represents cumulative leakage rate data. Represents the volume of the enclosed collection space. Data representing concentration changes, Represents cumulative time. This represents the helium concentration.

[0092] Under the condition that the coordinate positioning mechanism in the two-dimensional coordinate positioning and servo drive unit has completed all preset grid coordinate point movement actions or the cumulative detection mode has ended, the industrial control computer and the dynamic compensation calculation unit determine that the external surface scanning detection process of the inspected system has ended, and send an air circuit cut-off command to the main proportional mixing valve inside the pneumatic circuit unit.

[0093] The main proportional mixing valve receives the gas circuit cut-off command, interrupts the mixing of helium and nitrogen input from the external tracer gas source or return pipeline, and stops supplying helium-nitrogen mixed gas to the pressure stabilizing buffer tank and the internal space of the system under test. The industrial control computer and dynamic compensation calculation unit send a start command to the recovery compressor inside the pneumatic circuit unit. The recovery compressor enters the running state according to the start command, so that the pneumatic circuit unit switches from the positive pressure running state to the recovery running state.

[0094] Under the suction negative pressure generated by the recovery compressor, the sampling tail gas retained inside the central negative pressure sampling channel and the mixed residual gas discharged from the tested system are discharged and flow through the pipeline to the air inlet of the dryer filter. The dryer filter is equipped with dehumidifying adsorption material and filter screen. The dryer filter uses the filter screen to intercept solid particles carried by the sampling tail gas and mixed residual gas, and uses the dehumidifying adsorption material to absorb free water molecules inside the sampling tail gas and mixed residual gas, and outputs purified mixed gas.

[0095] The purified gas mixture flows from the outlet of the dryer filter to the inlet of the recovery compressor. The recovery compressor performs volume compression on the purified gas mixture, outputs high-pressure purified gas mixture, and forces the high-pressure purified gas mixture into the gas storage bottle inside the pneumatic circuit unit.

[0096] The gas storage cylinder is sealed and stores high-pressure purified mixed gas. The exhaust end of the gas storage cylinder is connected to the inlet end of the main proportional mixing valve through a return pipeline. The high-pressure purified mixed gas stored inside the gas storage cylinder is used as a circulating recovery gas source in the next sealing test process and input into the main proportional mixing valve to complete the closed-loop recycling of helium-nitrogen mixed gas.

[0097] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-mode intelligent helium leak detection system for nuclear power plants, used for leak testing of the tested system, characterized in that, The nuclear power plant dual-mode helium intelligent leak detection system includes: a pneumatic circuit unit, a dynamic shielded suction gun and micro-environment sensing unit, a high-sensitivity helium mass spectrometry detection unit, a two-dimensional coordinate positioning and servo drive unit, an industrial control computer and dynamic compensation calculation unit, and a safety interlock protection unit. The pneumatic circuit unit is connected to the system under test via a pneumatic circuit, and is used to establish a vacuum negative pressure state inside the system under test and to fill the system under test with helium-nitrogen mixed gas to maintain a positive pressure. The dynamic shielding suction gun and micro-environment sensing unit includes a coaxial pneumatic shielding suction gun. A central negative pressure sampling channel is arranged at the center of the coaxial pneumatic shielding suction gun. Four independent fan-shaped positive pressure spray chambers are symmetrically distributed on the outer ring of the coaxial pneumatic shielding suction gun. The dynamic shielding suction gun and micro-environment sensing unit are used to collect environmental parameters of the outer area of ​​the end face of the coaxial pneumatic shielding suction gun. The high-sensitivity helium mass spectrometry detection unit is connected to the gas path of the central negative pressure sampling channel. The high-sensitivity helium mass spectrometry detection unit is used to detect the leaked mixed gas and output the leaked gas concentration data, and to operate in the state of no tracer gas filling to output the background helium ion flow fluctuation value. The two-dimensional coordinate positioning and servo drive unit is mechanically connected to the coaxial pneumatic shielding suction gun and is used to control the coaxial pneumatic shielding suction gun to move along the outer surface of the system under test according to a preset trajectory. The industrial control computer and dynamic compensation calculation unit establish communication connections with the pneumatic circuit unit, the dynamic shielding suction gun and micro-environment sensing unit, the high-sensitivity helium mass spectrometry detection unit, the two-dimensional coordinate positioning and servo drive unit, and the safety interlock protection unit, respectively. The industrial control computer and dynamic compensation calculation unit receive the environmental parameters and output leakage rate data compensated for the environmental parameters based on the calculation model. The safety interlock protection unit is electrically connected to the pneumatic circuit unit and the industrial control computer and dynamic compensation calculation unit, and is used to monitor the working parameters of the system under test and cut off the power supply of the pneumatic circuit unit when the parameters exceed the safety limit.

2. The dual-mode intelligent helium leak detection system for nuclear power plants according to claim 1, characterized in that, The pneumatic circuit unit includes a forepump, a molecular pump, a main proportional mixing valve, a pressure stabilizing buffer tank, a dryer filter, a recovery compressor, a gas storage cylinder, and a return pipeline. The inlet of the fore-pump is connected in series with the outlet of the molecular pump, and the inlet of the molecular pump is connected to the interior of the system under test through a pipeline; the inlet of the main proportional mixing valve is connected to the external tracer gas source for initial charging and the return pipeline, and the outlet of the main proportional mixing valve is connected to the pressure stabilizing buffer tank, and the outlet of the pressure stabilizing buffer tank is connected to the charging port of the system under test through a pipeline; The air inlet of the dryer filter is connected to the central negative pressure sampling channel and the exhaust port of the tested system via a pipeline, and the air outlet of the dryer filter is connected to the air inlet of the recovery compressor. The exhaust end of the recovery compressor is connected to the gas storage cylinder, and the exhaust end of the gas storage cylinder is connected to the inlet end of the main proportional mixing valve through the return pipeline to serve as a source of circulating recovery gas.

3. The dual-mode intelligent helium leak detection system for nuclear power plants according to claim 1, characterized in that, The coaxial pneumatic shielded suction gun has a tubular nested structure. The coaxial pneumatic shielded suction gun includes an inner tube and an outer tube sleeved outside the inner tube. The internal space of the inner tube is the central negative pressure sampling channel. An annular space is formed between the inner wall of the outer tube and the outer wall of the inner tube. A cross-shaped isolation partition is fixed inside the annular space, and the cross-shaped isolation partition divides the annular space into four independent fan-shaped positive pressure injection chambers. The dynamic shielding suction gun and micro-environment sensing unit also include a multi-channel micro proportional mixing valve. The air inlet of the multi-channel micro proportional mixing valve is connected to an external protective air source, and the exhaust end of the multi-channel micro proportional mixing valve is connected to the air inlet of the four independent fan-shaped positive pressure injection chambers, respectively, for independently adjusting the constant pressure airflow rate input to the four independent fan-shaped positive pressure injection chambers.

4. The dual-mode intelligent helium leak detection system for nuclear power plants according to claim 3, characterized in that, The bottom surfaces of the four independent fan-shaped positive pressure injection chambers are respectively provided with micro-laminar flow nozzles and sensor mounting slots, and the dissipated constant pressure airflow forms an airflow isolation area around the central negative pressure sampling channel; The dynamic shielding suction gun and micro-environment sensing unit also include a four-quadrant micro-environment sensor array, which is fixedly installed inside the sensor mounting slot. The four-quadrant micro-environment sensor array includes four miniature temperature and humidity meters and four micro-differential pressure sensors. The four miniature temperature and humidity meters are respectively fixed in the sensor mounting slots inside the four independent fan-shaped positive pressure jet chambers, and are used to collect temperature and humidity data inside the airflow isolation area and output micro-domain Celsius temperature and micro-area relative humidity. The four micro-differential pressure sensors are respectively fixed in the sensor mounting slots inside the four independent fan-shaped positive pressure jet chambers, and are used to collect local static pressure values ​​and integrate them with spatial quadrant orientation information to output static pressure difference vector data.

5. The dual-mode intelligent helium leak detection system for nuclear power plants according to claim 4, characterized in that, The industrial control computer and the dynamic compensation calculation unit map the spatial installation positions of the four micro differential pressure sensors to a Cartesian coordinate system containing a horizontal reference axis and a vertical reference axis. The industrial control computer and the dynamic compensation calculation unit extract the local static pressure values ​​from the static pressure difference vector data. Based on the four micro differential pressure sensors distributed on the mutually perpendicular horizontal reference axis and vertical reference axis as differential pressure sensing nodes, the industrial control computer and the dynamic compensation calculation unit calculate the horizontal differential pressure component data and the vertical differential pressure component data. The industrial control computer and the dynamic compensation calculation unit calculate the square root of the sum of the squares of the lateral pressure difference component data and the squares of the longitudinal pressure difference component data, outputting the crosswind intensity parameter, and calculate the arctangent function of the quotient of the longitudinal pressure difference component data divided by the lateral pressure difference component data, outputting the crosswind dynamic pressure direction angle data. The industrial control computer and dynamic compensation calculation unit determine the intrusion quadrant position of the external crosswind flow field based on the crosswind dynamic pressure direction angle data, and set the fan-shaped positive pressure injection chamber associated with the intrusion quadrant position as the windward side injection node, and set the fan-shaped positive pressure injection chamber associated with its diagonal direction as the leeward side injection node. The industrial control computer and dynamic compensation calculation unit calculate the opening adjustment value and generate feedforward adjustment command through the built-in intensity compensation mapping matrix. The multi-channel micro proportional mixing valve increases the internal flow cross-sectional area of ​​the fluid control channel corresponding to the windward side injection node and decreases the internal flow cross-sectional area of ​​the fluid control channel corresponding to the leeward side injection node according to the feedforward adjustment command, thereby dispersing the asymmetric airflow to offset the dynamic pressure interference of the external crosswind flow field.

6. The dual-mode intelligent helium leak detection system for nuclear power plants according to claim 5, characterized in that, The industrial control computer and the dynamic compensation calculation unit perform an average calculation on the local static pressure value to obtain the average static pressure value of the airflow isolation area, and calculate the servo dynamic pressure compensation value based on the sum of the flow cross-sectional area parameters inside the fluid control channel and the preset flow dynamic pressure conversion coefficient constant. The industrial control computer and the dynamic compensation calculation unit add the average static pressure value of the airflow isolation area to the servo dynamic pressure compensation value and output the pressure data during detection. They also calculate the quotient of the calibrated pressure data divided by the pressure data during detection and output the dynamic pressure compensation coefficient. The industrial control computer and dynamic compensation calculation unit add the micro-domain Celsius temperature to the calibration reference constant and output the micro-domain absolute temperature data, and calculate the quotient of the calibration reference constant divided by the micro-domain absolute temperature data and output the temperature compensation coefficient; the industrial control computer and dynamic compensation calculation unit substitute the micro-area relative humidity into the humidity calibration mapping table and output the humidity compensation coefficient, and convert the extracted background helium ion flow fluctuation value into the background compensation coefficient; The industrial control computer and the dynamic compensation calculation unit calculate the original leakage rate data based on the leaked gas concentration data and the calibrated leakage rate parameters. The original leakage rate data is then multiplied by the temperature compensation coefficient, the humidity compensation coefficient, the dynamic pressure compensation coefficient, and the background compensation coefficient to output the true leakage rate data after comprehensive environmental elimination, which serves as the leakage rate data after environmental parameter compensation.

7. The dual-mode intelligent helium leak detection system for nuclear power plants according to claim 1, characterized in that, The system also includes a sealed collection hood and a bypass sampling line. The sealed collection hood is used to enclose a portion of the system under test to form a sealed collection space. The high-sensitivity helium mass spectrometry detection unit includes a preprocessing module, an ion source, a magnetic field deflection analyzer, a collecting electrode, and a switching valve interface. One end of the bypass sampling line is connected to the sealed collection space, and the other end is connected to the switching valve interface of the high-sensitivity helium mass spectrometry detection unit to form a connected gas path. The leaked mixed gas drawn by the central negative pressure sampling channel or the bypass sampling line enters the ion source through the preprocessing module for ionization. The ion beam generated by ionization enters the magnetic field deflection analyzer for mass separation. The collecting electrode receives a helium ion beam with a specified mass-to-charge ratio and outputs a corresponding ion current signal.

8. A dual-mode intelligent helium leak detection system for nuclear power plants according to claim 6, characterized in that, The two-dimensional coordinate positioning and servo drive unit includes a servo drive module and a coordinate positioning mechanism. The servo drive module controls the coordinate positioning mechanism to move the coaxial pneumatic shielded suction gun on the external surface of the system under test. The industrial control computer and dynamic compensation calculation unit are internally preset with a preset leak rate alarm threshold. When the leak rate data after environmental parameter compensation exceeds the preset leak rate alarm threshold, the industrial control computer and dynamic compensation calculation unit send a deceleration verification command to the servo drive module to reduce the running speed of the coordinate positioning mechanism, and transmit the current two-dimensional plane coordinate data, timestamp data, the leak rate data after environmental parameter compensation, and micro-domain.

9. The dual-mode intelligent helium leak detection system for nuclear power plants according to claim 1, characterized in that, The safety interlock protection unit includes an overpressure and overtemperature sensor and a radiation monitoring interface. The overpressure and overtemperature sensor is fixedly installed on the pressure-bearing outer wall and the filling interface of the system under test. The industrial control computer and the dynamic compensation calculation unit combine the basic definition calculation model of leakage rate to calculate the product of the pre-acquired volume parameters of the system under test and the pressure change obtained by the overpressure and overtemperature sensor, and divide the product by the pressure drop test time to output the theoretical leakage rate as the benchmark calibration data.

10. A dual-mode intelligent helium leak detection method for nuclear power plants, applied to the dual-mode intelligent helium leak detection system for nuclear power plants as described in any one of claims 1 to 9, characterized in that, The work includes the following stages: State calibration stage: The industrial control computer and dynamic compensation calculation unit control the high-sensitivity helium mass spectrometry detection unit to execute the mass spectrometry calibration program to lock the calibration reference constant, and extract the background helium ion flow fluctuation value in the state without mixed gas to establish the background compensation baseline; Fluid replacement stage: The pneumatic circuit unit is used to pump air to reduce the internal air pressure of the system under test to a preset vacuum threshold. Then, helium and nitrogen are mixed to form a mixed gas and injected into the system under test to maintain the positive pressure of the mixed gas for a preset stabilization time. Scanning or cumulative sensing stage: When the scanning mode is executed, the two-dimensional coordinate positioning and servo drive unit is used to drive the coaxial pneumatic shielded suction gun to move. The dynamic shielded suction gun and the micro-environment sensing unit disperse the constant pressure airflow to form an airflow isolation area and collect micro-environment parameters. Under the condition that a sealed collection hood is set in a part of the tested system to form a sealed collection space, the cumulative detection mode is executed. The bypass sampling pipeline is used to draw gas in the sealed collection space and monitor the cumulative change of concentration over time. Compensation calculation stage: In scanning mode, the industrial control computer and dynamic compensation calculation unit are used to adjust the flow field dynamic pressure feedforward, and the original leakage rate data is combined with temperature, humidity, dynamic pressure and background to perform coefficient multiplication correction, so as to output leakage rate data after environmental parameter compensation. In cumulative detection mode, the cumulative leakage rate data is calculated and output based on the product of concentration change data and the known volume parameters of the sealed collection space preset by the system, divided by the product of the filling helium concentration and the accumulation time. Gas recovery stage: After the detection is completed or the over-limit alarm is verified, the mixed gas filling is interrupted, and the pneumatic circuit unit is used to perform dehydration and volume compression operations to store the sampled tail gas and mixed residual gas into the gas storage cylinder as a source of recycled gas.

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