A nuclear power plant primary coolant leakage quantitative monitoring device

Abstract

The present application belongs to the technical field of nuclear instruments and meters, and particularly relates to a nuclear power plant primary coolant leakage quantitative monitoring device. 13 The coincidence detection device is connected with the N sampling device, and the gas medium collected by the N sampling device is detected by the coincidence detection device 13 The N sampling device is connected with the refrigeration device, and the temperature in the N sampling device is maintained by the refrigeration device 13 The N sampling device is connected with the refrigeration device, and the temperature in the N sampling device is maintained by the refrigeration device 13 The temperature in the N sampling device is maintained within a normal working range; the digital coincidence measurement system is connected with the coincidence detection device, and the signal of the coincidence detection device is measured by the digital coincidence measurement system; the electrical junction box is connected with the digital coincidence measurement system and the refrigeration device, and the digital coincidence measurement system and the refrigeration device are powered by the electrical junction box; the upper computer is connected with the digital coincidence measurement system, and the transmission and reception of monitoring data and energy spectrum data are realized by the upper computer. The present application can realize quantitative monitoring of primary pressure boundary coolant leakage, and the lower limit of leakage rate measurement can reach 1L / h.

Description

Technical Field

[0001] This invention belongs to the field of nuclear instrumentation technology, specifically relating to a quantitative monitoring device for primary coolant leakage in nuclear power plants. Background Technology

[0002] The primary circuit pressure boundary of a nuclear power plant is a crucial barrier, containing high-temperature, high-pressure, and radioactive coolant. However, during long-term operation, due to fatigue and corrosion, weak points in the primary circuit pressure boundary, such as joints, flanges, and welds, may develop surface or internal defects, posing a risk of cracks or fissures. This can lead to coolant leakage at the primary circuit pressure boundary, releasing radioactive nuclides into the containment, causing environmental pollution within the containment, and potentially even resulting in a loss-of-coolant accident in the reactor core, severely threatening the safe operation of the nuclear power plant. As coolant leaks escalate, radioactive nuclides may pollute the atmosphere, causing serious social impacts and environmental hazards. Therefore, to ensure the immediate detection of coolant leaks at the primary circuit pressure boundary, a primary circuit pressure boundary leakage radiation monitoring system must be installed.

[0003] There are many methods for monitoring coolant leakage at the pressure boundary of a reactor's primary circuit, typically including basic physical quantity monitoring, acoustic emission monitoring, video monitoring, and radioactivity monitoring. Among these, radioactivity monitoring is currently the most commonly used and effective method both domestically and internationally. Commonly used radioactivity monitoring methods include radioactive aerosol, iodine, and inert gas monitoring (PING monitoring method). 13 N gas method and 18 F. Aerosol method.

[0004] The PING monitoring method monitors β-aerosols generated by coolant leaks. 131 I represents the gaseous radioactive iodine of the nuclide I. 41 Ar、 85 Kr、 133 Radioactive inert gases, such as Xe, are used to determine the leakage level at the primary circuit pressure boundary. Since the monitored objects are fission and corrosion products, only qualitative monitoring is possible.

[0005] 18 F-aerosol method is mainly used to monitor coolant leaks. 18 F, 18 F exists primarily in the form of aerosols. However, aerosols undergo deposition and aggregation during transport and diffusion within the sampling pipeline. If the sampling pipeline is poorly designed, the aerosol penetration rate will be extremely low, which will significantly affect the sampling efficiency. 18 Currently, there are no mature applications of the F-aerosol method in the engineering field. 18 F monitoring equipment.

[0006] 13 The nitrogen gas method uses the sampled gas... 13 Using nuclear density as a benchmark, and since nuclear density depends only on reactor nuclear power, the leakage rate can be quantitatively calculated, enabling quantitative measurement; furthermore, 13 Nitrogen (N) exists primarily as a gas in the reactor. Nitrogen is chemically inert and does not readily deposit in ventilation and sampling ducts. Therefore, the design of sampling ducts is relatively simpler. 13 The nitrogen gas method is currently the most widely used measurement method for primary loop pressure boundary leakage monitoring.

[0007] The patent "A Method, System and Monitor for Monitoring Pressure Boundary Leakage in the Primary Circuit of a Pressurized Water Reactor" (CN108877972A) discloses a method, system and monitor for monitoring the pressure boundary of the primary circuit of a pressurized water reactor. The method includes the following steps: obtaining sampled gas at a sampling point through a sampling pipeline; calculating the content of the sampled gas... 13 N and 18 The sampling concentration ratio of F; according to 13 N and 18 The initial concentration ratio of F at the leak point and 13 N and 18 Calculate the proportion of the sampling concentration of F at the sampling point. 13 N and 18 F represents the diffusion time from the leak point to the sampling point; comparing this diffusion time with a preset time threshold obtains the location information of the leak point at the primary circuit boundary of the pressurized water reactor, which helps improve the repair speed of personnel and reduce the radiation dose received by personnel during repairs. The above patent requires continuous calculation. 13 N and 18 The concentration ratio of F is a relatively complex process to calculate, and it is closely related to the process system. Inaccurate calculation will lead to large errors in the results. The above patent adopts the common measurement method of threshold comparison + counting in the field of radiation monitoring. The measurement accuracy is low, which leads to a high measurement lower limit of the monitoring equipment and is prone to false alarms. Summary of the Invention

[0008] The purpose of this invention is to provide a quantitative monitoring device for primary coolant leakage in nuclear power plants, which can realize quantitative monitoring of primary coolant leakage at the pressure boundary, and the lower limit of leakage rate measurement can reach 1L / h.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A quantitative monitoring device for primary coolant leakage in a nuclear power plant, comprising: 13 N sampling device, coincidence detection device, digital coincidence measurement system, cooling device, electrical junction box and host computer, coincidence detection device and 13N sampling device connected, detected by coincidence detection device 13 The gaseous medium collected by the N sampling device; the refrigeration device and 13 The N sampling device is connected and maintained by a cooling device. 13 The temperature inside the N sampling device is within the normal operating range; the digital coincidence measurement system is connected to the coincidence detection device, and the signal of the coincidence detection device is measured through the digital coincidence measurement system; the electrical junction box is connected to the digital coincidence measurement system and the cooling device respectively, and the power supply is provided to the digital coincidence measurement system and the cooling device through the electrical junction box; the host computer is connected to the digital coincidence measurement system, and the monitoring data and energy spectrum data are transmitted and received through the host computer.

[0011] 13 The N sampling device, coincidence detection device, digital coincidence measurement system, cooling device, electrical junction box, and host computer are assembled on the bracket.

[0012] 13 The N sampling device includes a three-way valve, an aerosol filter, a sampling pump, a sampling container, and a flow meter. Two manual valves are connected to the three-way valve at the sampling inlet and compressed air inlet, respectively. These manual valves control the sampling and compressed air flushing functions. The manual valves, aerosol filter, regulating valve, and flow meter are connected sequentially. The aerosol filter filters the aerosol in the sampling medium, retaining only the gaseous medium. The regulating valve controls the flow rate, which is displayed on the flow meter. The flow meter is connected to the sampling container, which collects the gaseous medium. The sampling container is connected to the manual valve and the sampling pump, which provides the sampling power.

[0013] Nine absorption plates are installed inside the sampling container, evenly distributed along the height direction.

[0014] The sampling pumps are set to dual redundancy, with only one pump operating at a time. The two pumps alternate within a certain working cycle. When a pump fails, both local and remote alarms are triggered. After receiving the alarm, the operator goes to the site to investigate and ensure that the sampling of the entire monitoring equipment is not interrupted.

[0015] The detection device consists of a detection module, a silicon photomultiplier tube (SMT) device, a temperature sensor, and a shielding module. The detection module is connected to the SMT device to realize the photoelectric conversion of the detection module signal. The detection module is connected to the temperature sensor to accurately determine the operating temperature of the detection module. The shielding module completely encloses the detection module, the SMT device, and the temperature sensor.

[0016] The detection module consists of two 5-inch BGO scintillator detectors, positioned face-to-face. 13 Both sides of the sampling container of the N sampling device are probed. 13 N is a radioactive gas.

[0017] The shielding module has an overall 4π structure.

[0018] The digital coincidence measurement system comprises an amplification unit, an energy measurement unit, a time measurement unit, and a data processing unit. It acquires the energy and time information of the detector waveforms in channels γ0 and γ1 using waveform digitization and time-to-digital conversion technologies. A coincidence event is considered to have occurred when the time interval between the measured waveform signals in channel γ0 and channel γ1 is less than τ (where τ is the coincidence resolution time of the measurement system), and the difference between the energy signals in channels γ0 and γ1 is less than an energy threshold. Conversely, if the time interval is greater than τ and the energy difference is greater than the threshold, no coincidence event is considered to have occurred. For positron annihilation events, precise measurement of the energy and time information of the waveform signals in the three channels (channel γ0, channel γ1, and the coincidence channel) is achieved. 13 Measurement of the activity of N radionuclides.

[0019] For time measurement, the high-precision ADC first identifies the rising and falling edges of the waveform signal, acquiring rising and falling edge flag signals. After obtaining the flag signals, time-to-digital conversion technology is used to obtain specific time information. When the flag signal is valid, a counter is started, using the FPGA master clock as the reference clock for pulse counting. The counting module starts counting when the flag signal is valid and stops counting when the flag signal ends. The carry chain within the FPGA is used as the basic delay unit, with each delay unit having a delay time ranging from tens to over one hundred picoseconds. A serial multi-bit adder is used to cascade the carry chain within the FPGA. The addend of the first-stage adder is connected to the start signal, while the addends of the remaining adders are connected to a low level. The augend of each adder is connected to a high level, and the carry ends are cascaded. When the start signal of the waveform signal arrives, the carry output of the first-stage adder... The low level then transitions to a high level and is transmitted to the carry chain input of the next cascaded adder. This process repeats, with the carry signal propagating down the carry chain. The outputs of each adder also transition from high to low levels. A set of D flip-flops below the carry chain latches the output of each adder after the rising edge of the clock. The position of the carry signal in the carry chain can be determined by confirming the 1→0 transition in the output. For the energy measurement circuit, the ADC is used to acquire detector waveform data and convert the detector's analog signal into a digital signal. It is also necessary to identify the rising and falling edges of the waveform. When a rising edge flag is detected, a baseline needs to be calculated to reduce waveform fluctuations in the initial stage of the ADC. Before energy summation, a portion of the data is averaged as the baseline value. To reduce the impact of baseline fluctuations on the measurement results, the baseline data needs to be calculated and evaluated, as shown in the formula. As shown, the baseline average value is obtained as a reference value when summing the integral area, where P i The value represents the waveform sampled at point i, Baseline represents the average baseline value, and k represents the number of sampling points used for baseline average calculation. After the baseline calculation phase is completed, energy summation begins, calculated as shown in the formula. As shown, after the summation begins, each ADC measurement value is subtracted from the baseline average value to obtain a normalized value. The summation of all normalized values ​​yields the energy value of the current waveform signal. For the multi-channel measurement circuit, used to acquire the radioactive gamma spectrum across the entire energy range of 0.2 MeV to 2.2 MeV, a high-speed ADC is used to digitize the detector waveform signal. Based on the energy measurement, the maximum value of the energy signal is obtained. For the data acquired within a certain effective range, each ADC measurement value is compared with the previous measurement value. If it is greater than the previous measurement value, the current value is buffered; otherwise, it is not buffered. This process continues until the maximum value of the current waveform signal is obtained. The amplitude of the waveform signal is classified and recorded to acquire the radioactive gamma spectrum within a certain energy range.

[0020] The beneficial effects achieved by this invention are as follows:

[0021] The present invention proposes based on 13 N's primary coolant leakage quantitative monitoring equipment will 13 N is used as a radioactive tracer, by 13 It consists of an N-sampling device, a coincidence detection device, a digital coincidence measurement system, a cooling device, an electrical junction box, and a host computer, etc., and obtains the N-sampling device, a coincidence detection device, a digital coincidence measurement system, a cooling device, an electrical junction box, and a host computer. 13 The radioactivity of N, and then with 13 The N-transmission coefficient is used for conversion to obtain the primary loop pressure boundary coolant leakage rate. This method employs digital coincidence measurement technology, which reduces the influence of background interference and external interfering nuclides to a certain extent, improves measurement accuracy, and obtains a lower detection limit.

[0022] Compared to traditional PING monitoring devices, this invention utilizes activated products. 13 N is used as a radioactive tracer, through calculation 13 The invention uses N radioactivity and the sampling system transfer coefficient to quantitatively calculate the primary loop pressure boundary coolant leakage; it employs a digital coincidence measurement method, fully utilizing... 13 The positron annihilation property of the N radionuclide minimizes the impact of environmental background interference and external interfering nuclides, significantly improving measurement accuracy and achieving a lower detection limit. This invention employs a cooling device to control the temperature of the coincidence detection system in real time, ensuring the detector operates within its effective temperature range and reducing the impact of temperature on detection accuracy. This invention also significantly optimizes the design of the external shielding module, featuring high integration, miniaturization, and lightweight design. Attached Figure Description

[0023] Figure 1 for 13 N monitoring equipment connection diagram;

[0024] Figure 2 for 13 Schematic diagram of N sampling device;

[0025] Figure 3 To conform to the schematic diagram of the detection device;

[0026] Figure 4 Schematic diagram of a digital coincidence measurement system;

[0027] Figure 5 This is a schematic diagram of the time measurement unit;

[0028] Figure 6 This is a schematic diagram of the energy measurement unit;

[0029] Figure 7 This is a multi-channel diagram. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] based on 13 N's primary coolant leakage quantitative monitoring equipment includes 13 The N-sampling device, coincidence detection device, digital coincidence measurement system, cooling device, electrical junction box, and host computer are all assembled together on a support frame. 13 N monitoring equipment. Technical specifications: Energy range: 0.511 MeV; 13 N Measurement range: 1L / h~3000L / h; Equipment power supply: 220VAC / 50Hz; Measurement error: ≤±20%; Alarm: Capable of generating various types of alarms, including fault alarms, level 1 alarms, and level 2 alarms, with alarm thresholds set by the user within the measurement range.

[0032] like Figure 1 As shown, based on 13 N's primary coolant leakage quantitative monitoring equipment includes 13 The N-sampling device, coincidence detection device, digital coincidence measurement system, cooling device, electrical junction box, and host computer are all assembled together on a support frame. 13 N monitoring equipment. Among them, the conformity detection device and 13 N sampling device connected, detected by coincidence detection device 13 The gaseous medium collected by the N sampling device; the refrigeration device and 13 The N sampling device is connected and maintained by a cooling device. 13 The temperature inside the N sampling device is within the normal operating range; the digital coincidence measurement system is connected to the coincidence detection device, and measures the signal of the coincidence detection device through the digital coincidence measurement system; the electrical junction box is connected to the digital coincidence measurement system and the cooling device respectively, and supplies power to the digital coincidence measurement system and the cooling device through the electrical junction box; the host computer is connected to the digital coincidence measurement system, and realizes the transmission and reception of monitoring data and energy spectrum data of the monitoring equipment through the host computer.

[0033] like Figure 2 As shown, 13 The N sampling device uses a sampling pump to sample the sample containing... 13The gas containing nitrogen is drawn into a sampling container for measurement by a coincidence detection device, which includes a manual valve, a three-way valve, an aerosol filter, a sampling pump, a sampling container, and a flow meter. At the sampling inlet and compressed air inlet, two manual valves are connected to a three-way valve. The manual valves control sampling and compressed air flushing. The manual valves, aerosol filter, regulating valve, and flow meter are connected sequentially. The aerosol filter filters aerosols from the sampling medium, retaining only the gaseous medium to prevent aerosols from affecting the overall measurement. The regulating valve controls the flow rate, which is displayed on the flow meter. The flow meter is connected to the sampling container, which collects the gaseous medium. Nine absorption plates are evenly distributed along the height of the sampling container to improve sampling efficiency. The sampling container is connected to the manual valve and sampling pump, which provides sampling power. The sampling pump is configured with dual-pump redundancy, with only one pump operating at a time, rotating between the two pumps within a certain working cycle. A pump failure triggers both local and remote alarms. Upon receiving the alarm, operators go to the site to investigate, ensuring uninterrupted sampling by the entire monitoring equipment.

[0034] like Figure 3 As shown, the detection device consists of a detection module, a silicon photomultiplier tube (SMT) device, a temperature sensor, and a shielding module. The detection module is connected to the SMT device to perform photoelectric conversion of the detection module's signal. The detection module consists of two 5-inch BGO scintillator detectors, positioned face-to-face. 13 Both sides of the sampling container of the N sampling device are probed. 13 N is a radioactive gas; the detection module is connected to a temperature sensor, which accurately determines the operating temperature of the detection module and provides parameters for equipment temperature compensation; the shielding module completely encloses the detection module, silicon photomultiplier tube device, and temperature sensor. The shielding module has an overall 4π structure to reduce the impact of the environmental background on the measurement and lower the detection limit.

[0035] like Figure 4 As shown, the digital coincidence measurement system is mainly used to achieve the measurement of... 13The coincidence measurement function for N radionuclide activity mainly includes an amplification unit, an energy measurement unit, a time measurement unit, and a data processing unit. By employing waveform digitization and time-to-digital conversion techniques, the energy and time information of the detector waveforms in channels γ0 and γ1 are acquired separately. A coincidence event is considered to have occurred when the time interval between the measured waveform signals in channel γ0 and channel γ1 is less than τ (where τ is the coincidence resolution time of the measurement system) and the difference between the energy signals in channels γ0 and γ1 is less than an energy threshold. Conversely, if the time interval is greater than τ and the energy difference is greater than the threshold, no coincidence event is considered to have occurred. For positron annihilation events, precise measurement of the energy and time information of the waveform signals in the three channels (channel γ0, channel γ1, and the coincidence channel) can achieve [the desired result]. 13 Measurement of the activity of N radionuclides.

[0036] like Figure 5 As shown, for time measurement, the high-precision ADC first identifies the rising and falling edges of the waveform signal to obtain rising and falling edge flag signals. After obtaining the flag signals, time-to-digital conversion technology is used to obtain specific time information. Specifically, a "coarse precision + fine precision" measurement method is adopted. The "coarse precision" measurement method is implemented using a multi-bit counter within the FPGA. When the flag signal is valid, the counter starts counting, using the FPGA master clock as the reference clock for pulse counting. When the flag signal is valid, the counting module starts counting; when the flag signal ends, the counting module stops counting. The "fine precision" measurement method is implemented using the carry chain within the FPGA, using the carry chain as the basic delay unit. The delay time of each delay unit ranges from tens of picoseconds to over one hundred picoseconds, which can significantly improve the resolution of time measurement. Serial multi-bit adders are used to cascade the dedicated carry chain within the FPGA. The addend terminal of the first-stage adder is connected to the start signal, the addend terminals of the remaining adders are connected to a low level, the augend terminals of each stage of the adder are all connected to a high level, and the carry terminals are all cascaded into a chain. When the start signal of the waveform arrives, the carry output of the first-stage adder changes from low to high and is transmitted to the carry input of the next cascaded adder. This process repeats, with the carry signal propagating down the carry chain, and the output of each adder changing from high to low. A set of D flip-flops below the carry chain latches the output of each adder after the rising edge of the clock. By checking the position of the 1→0 transition in the output, the position of the carry signal in the carry chain can be determined.

[0037] like Figure 6As shown, for the energy measurement circuit, the detector waveform data is acquired by driving the ADC, converting the detector's analog signal into a digital signal. Similarly, it is necessary to identify the rising and falling edges of the waveform. When a valid rising edge flag signal is detected, a baseline needs to be calculated to reduce waveform signal fluctuations in the initial stage of the ADC. Before energy summation, a subset of data is selected and averaged as the baseline value. To reduce the impact of baseline fluctuations on the measurement results, the baseline data needs to be calculated and evaluated, as shown in the following formula, to obtain the baseline average value as a reference value for summing the integral area.

[0038]

[0039] Where P i The waveform sample value at point i is represented by , Baseline represents the average baseline value, and k represents the number of sampling points used for baseline average calculation.

[0040] After the baseline calculation phase is completed, energy summation begins. As mentioned earlier, the peak area method is beneficial for improving the accuracy of energy measurement. The calculation method is shown in the following formula. After the summation begins, each ADC measurement value is subtracted from the baseline average value to obtain a normalized value. The energy value of the current waveform signal is obtained by summing all the normalized values.

[0041]

[0042] like Figure 7 As shown, the multichannel measurement circuit is mainly used to acquire the radioactive gamma spectrum in the entire energy range of 0.2MeV to 2.2MeV. By using a high-speed ADC to digitize the detector waveform signal, the maximum value of the energy signal is measured based on the energy measurement. Here, the "bubble method" is used. For the data collected in a certain effective range, each ADC measurement value is compared with the previous measurement value. If it is greater than the previous measurement value, the current value is buffered; otherwise, it is not buffered. This process continues until the maximum value of the current waveform signal is obtained. The amplitude of the waveform signal is classified and recorded, thereby obtaining the radioactive gamma spectrum within a certain energy range.

[0043] The cooling system employs an evaporative cooling system based on a micro-compressor to provide stable cooling air in high-temperature environments. This cooled air is then blown into the detector body through pipes to cool the coincidence detection device. The electrical junction box primarily functions to introduce external power to the digital coincidence measurement system and the pump; two switches on the front control the pump's start and stop. The host computer system is mainly used for transmitting and receiving monitoring data and energy spectrum data, facilitating the storage, review, and querying of historical and current measurement data.

[0044] This invention discloses a method based on 13N's primary coolant leakage quantitative monitoring equipment includes 13 The system consists of an N-sampling system, a coincidence detector system, a coincidence measurement system, and a host computer. Sampling is performed using dual redundant sampling pumps. 13 N gas enters 13 N-sampling system 13 The coincidence detector system near the N sampling system detects... 13 The gamma characteristic of N is converted into an electrical signal, and the dual electrical signals enter the coincidence measurement system for coincidence calculation. 13 N radioactivity, finally 13 The final quantitative measurement result, leakage rate, is obtained by converting the N radioactivity activity into the transmission coefficient.

[0045] This invention includes 13 The system comprises an N-sampling device, a coincidence detection device, a digital coincidence measurement system, a cooling unit, an electrical junction box, and a host computer. It employs an aerosol filter and a redundant dual-sampling pump system. The aerosol filter directly removes aerosols from the sampling medium, while the redundant dual-sampling pump system extracts the sampling medium. This design enhances the reliability of the entire monitoring equipment. It fully utilizes… 13 The positron annihilation property of N is investigated using two identical scintillator detectors. 13 Measuring the radioactive properties of N improves detection efficiency; fully utilizing... 13 The positron annihilation property of N was precisely captured using high-resolution time measurement and high-precision energy measurement techniques. 13 The valid matching instances generated by N effectively calculate 13 The radioactivity activity of nitrogen nuclide was measured, improving measurement accuracy. Precise time measurement was achieved based on a "coarse accuracy + fine accuracy" measurement method. The "coarse accuracy" method was implemented using a multi-bit counter within the FPGA. The "fine accuracy" method was implemented using a carry chain within the FPGA. Waveform amplitude signals were acquired using a high-speed ADC, and the peak area method was employed to improve energy measurement accuracy. The maximum value of the energy signal was measured using the "bubble method," enabling the acquisition of the radioactive gamma spectrum across the entire energy range of 0.2 MeV to 2.2 MeV. An evaporative cooling system based on a micro-compressor was used to cool the coincidence detection device. A power relay, a pump protection circuit breaker, and overheat relay terminals were used to supply power and control the pump's start and stop. Monitoring data and energy spectrum data were transmitted and received.

Claims

1. A quantitative monitoring device for primary coolant leakage in a nuclear power plant, characterized in that: include 13 N sampling device, coincidence detection device, digital coincidence measurement system, cooling device, electrical junction box and host computer, coincidence detection device and 13 N sampling device connected, detected by coincidence detection device 13 The gaseous medium collected by the N sampling device; the refrigeration device and 13 The N sampling device is connected and maintained by a cooling device. 13 The temperature inside the N sampling device is within the normal operating range; the digital coincidence measurement system is connected to the coincidence detection device, and the signal of the coincidence detection device is measured through the digital coincidence measurement system; the electrical junction box is connected to the digital coincidence measurement system and the cooling device respectively, and the power supply is provided to the digital coincidence measurement system and the cooling device through the electrical junction box; the host computer is connected to the digital coincidence measurement system, and the monitoring data and energy spectrum data are transmitted and received through the host computer.

2. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 1, characterized in that: 13 The N sampling device, coincidence detection device, digital coincidence measurement system, cooling device, electrical junction box, and host computer are assembled on the bracket.

3. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 1, characterized in that: 13 The N sampling device includes a three-way valve, an aerosol filter, a sampling pump, a sampling container, and a flow meter. Two manual valves are connected to the three-way valve at the sampling inlet and compressed air inlet, respectively. These manual valves control the sampling and compressed air flushing functions. The manual valves, aerosol filter, regulating valve, and flow meter are connected sequentially. The aerosol filter filters the aerosol in the sampling medium, retaining only the gaseous medium. The regulating valve controls the flow rate, which is displayed on the flow meter. The flow meter is connected to the sampling container, which collects the gaseous medium. The sampling container is connected to the manual valve and the sampling pump, which provides the sampling power.

4. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 3, characterized in that: Nine absorption plates are installed inside the sampling container, evenly distributed along the height direction.

5. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 3, characterized in that: The sampling pumps are set to dual redundancy, with only one pump operating at a time. The two pumps alternate within a certain working cycle. When a pump fails, both local and remote alarms are triggered. After receiving the alarm, the operator goes to the site to investigate and ensure that the sampling of the entire monitoring equipment is not interrupted.

6. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 1, characterized in that: The detection device consists of a detection module, a silicon photomultiplier tube (SMT) device, a temperature sensor, and a shielding module. The detection module is connected to the SMT device to realize the photoelectric conversion of the detection module signal. The detection module is connected to the temperature sensor to accurately determine the operating temperature of the detection module. The shielding module completely encloses the detection module, the SMT device, and the temperature sensor.

7. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 6, characterized in that: The detection module consists of two 5-inch BGO scintillator detectors, positioned face-to-face. 13 Both sides of the sampling container of the N sampling device are probed. 13 N is a radioactive gas.

8. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 6, characterized in that: The shielding module has an overall 4π structure.

9. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 1, characterized in that: The digital coincidence measurement system acquires the energy and time information of the detector waveforms in channels γ0 and γ1 using waveform digitization and time-to-digital conversion technologies. A coincidence event is considered to have occurred when the time interval between the measured waveform signals in channel γ0 and channel γ1 is less than τ (where τ is the coincidence resolution time of the measurement system) and the difference between the energy signals in channels γ0 and γ1 is less than an energy threshold. Conversely, if the time interval is greater than τ and the energy signal difference is greater than the threshold, no coincidence event is considered to have occurred. For positron annihilation events, precise measurement of the energy and time information of the waveform signals in the three channels (channel γ0, channel γ1, and the coincidence channel) is achieved. 13 Measurement of the activity of N radionuclides.

10. The quantitative monitoring device for primary coolant leakage in a nuclear power plant according to claim 9, characterized in that: For time measurement, the high-precision ADC first identifies the rising and falling edges of the waveform signal, acquiring rising and falling edge flag signals. After obtaining the flag signals, time-to-digital conversion technology is used to obtain specific time information. When the flag signal is valid, a counter is started, using the FPGA master clock as the reference clock for pulse counting. The counting module starts counting when the flag signal is valid and stops counting when the flag signal ends. The carry chain within the FPGA is used as the basic delay unit, with each delay unit having a delay time ranging from tens to over one hundred picoseconds. A serial multi-bit adder is used to cascade the carry chain within the FPGA. The addend of the first-stage adder is connected to the start signal, while the addends of the remaining adders are connected to a low level. The augend of each adder is connected to a high level, and the carry ends are cascaded. When the start signal of the waveform signal arrives, the carry output of the first-stage adder... The low level then transitions to a high level and is transmitted to the carry chain input of the next cascaded adder. This process repeats, with the carry signal propagating down the carry chain. The outputs of each adder also transition from high to low levels. A set of D flip-flops below the carry chain latches the output of each adder after the rising edge of the clock. The position of the carry signal in the carry chain can be determined by confirming the 1→0 transition in the output. For the energy measurement circuit, the ADC is used to acquire detector waveform data and convert the detector's analog signal into a digital signal. It is also necessary to identify the rising and falling edges of the waveform. When a rising edge flag is detected, a baseline needs to be calculated to reduce waveform fluctuations in the initial stage of the ADC. Before energy summation, a portion of the data is averaged as the baseline value. To reduce the impact of baseline fluctuations on the measurement results, the baseline data needs to be calculated and evaluated, as shown in the formula. As shown, the baseline average value is obtained as a reference value when summing the integral area, where P i The waveform sample value at point i is represented by , Baseline represents the average baseline value, and k represents the number of sampling points used for baseline average calculation. After the baseline calculation phase is completed, energy summation begins, calculated using the formula... As shown, after the summation begins, each ADC measurement value is subtracted from the baseline average value to obtain a normalized value. The summation of all normalized values ​​yields the energy value of the current waveform signal. For the multi-channel measurement circuit, used to acquire the radioactive gamma spectrum across the entire energy range of 0.2 MeV to 2.2 MeV, a high-speed ADC is used to digitize the detector waveform signal. Based on the energy measurement, the maximum value of the energy signal is obtained. For the data acquired within a certain effective range, each ADC measurement value is compared with the previous measurement value. If it is greater than the previous measurement value, the current value is buffered; otherwise, it is not buffered. This process continues until the maximum value of the current waveform signal is obtained. The amplitude of the waveform signal is classified and recorded to acquire the radioactive gamma spectrum within a certain energy range.

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