Pipeline inert gas radiation monitoring system

Abstract

The invention discloses a pipeline inert gas radiation monitoring system which comprises a detection unit which is provided with a main detector, an auxiliary detector and a signal processing board. The main detector and the auxiliary detector are sequentially provided with a photomultiplier, a quartz light guide and a plastic scintillator from top to bottom, the bottom of the plastic scintillator of the main detector is covered with a carbon fiber baffle, and the bottom of the plastic scintillator of the auxiliary detector is covered with a stainless steel baffle; the main detector is internally provided with a threshold discrimination circuit module, and the auxiliary detector is internally provided with a threshold discrimination circuit module and a current integration circuit module which are controlled to be switched through a relay. And the signal processing board is used for controlling the detection working condition according to the detection range so as to obtain the total beta and gamma activity concentration of the radioactive gas. The system can remove environment real-time gamma background, improves the accuracy of beta activity concentration detection results, and can realize gamma activity concentration measurement under a relatively high gas nuclear radiation level.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear radiation monitoring, in particular to a pipeline inert gas radiation monitoring system. Background Art

[0002] Nuclear radiation leakage from nuclear power plants can cause serious harm to human health and the environment. In order to prevent nuclear leakage from nuclear power plants from causing radioactive exposure of workers and the environment, nuclear power plants have deployed radiation monitoring systems to monitor the nuclear power plant process. The systems are used to continuously monitor the radioactivity of suspended matter in the air of nuclear power plants and the discharges from the production process of nuclear power plants.

[0003] The radiation monitoring system consists of a sampling system, detectors, and processing units, and includes multiple measurement channels. By monitoring the gamma and beta activity of media such as reactor cooling water, steam from steam generators, air and aerosols within the containment vessel, air and aerosols in the control room, ventilation ducts, and chimneys, gaseous and liquid outflows, and radioactive waste, the system determines whether the process is operating normally and whether there has been a radioactive leak. The exhaust radiation monitoring channel is used to monitor the activity concentrations of Kr-85 and Xe-133 in the exhaust ducts of industrial plants.

[0004] Currently, nuclear power plants primarily monitor Kr-85 and Xe-133 activity concentrations in exhaust duct gases using the BIM201 monitor from the French company MGP. The BIM201 monitor consists of a detector, an on-site radiation display unit, and a connecting cable connecting the two. The BIM201 monitor uses a Φ50mm×0.25mm thin plastic scintillator and a Φ50mm photomultiplier tube as measuring elements to measure the radioactivity concentration of beta radiation emitted by the inert gases in the exhaust duct. To ensure that the measurement results are closer to the true value, a fixed ambient background compensation is typically applied to the measurement. However, the radiation background in nuclear power plant exhaust ducts varies. If the compensated ambient background level is too high, the final measurement result will be over-compensated. If the level is too low, the final measurement result will be biased upward, distorting the real-time measurement results of the BIM201 monitor. Summary of the Invention

[0005] Based on this, it is necessary to provide a pipeline inert gas radiation monitoring system to address the above technical problems. It can remove the influence of environmental γ background radiation in real time when measuring the radiation level of radioactive inert gas in the pipeline, improve the accuracy of β activity concentration detection results, and realize the measurement of inert gas γ activity concentration under higher gas nuclear radiation levels.

[0006] The present invention provides a pipeline inert gas radiation monitoring system, comprising a detection unit, wherein the detection unit is provided with a main detector, an auxiliary detector and a signal processing board;

[0007] The main detector and auxiliary detector are equipped with a photomultiplier tube, a quartz light guide and a plastic scintillator from top to bottom. The bottom of the plastic scintillator of the main detector is covered with a carbon fiber baffle, and the bottom of the plastic scintillator of the auxiliary detector is covered with a stainless steel baffle.

[0008] The main detector is provided with a threshold discrimination circuit module, and the auxiliary detector is provided with a threshold discrimination circuit module and a current integration circuit module switched by relay control;

[0009] a signal processing board, configured to control the simultaneous turning on of the main detector and the auxiliary detector when the gas radiation level activity concentration is within a first detection range; the auxiliary detector is switched to the threshold discrimination circuit module via a relay; the auxiliary detector count rate is then deducted from the main detector count rate to obtain the total beta count rate of the noble gas after environmental background compensation; and the total beta activity concentration of the radioactive gas is calculated based on the total beta count rate of the noble gas;

[0010] It is also used to control the main detector to be powered off when the gas radiation level activity concentration is in the second detection range, and the auxiliary detector is switched to the current integration circuit module through the relay, and then the total gamma activity concentration of the radioactive gas is calculated according to the gamma counting rate of the auxiliary detector.

[0011] In one embodiment, the detection unit is further provided with a bracket, which is composed of a base for fixing and assembling with the exhaust duct and a cover for fixing the main detector and the auxiliary detector on the base;

[0012] The base is provided with a first mounting cavity and a second mounting cavity which pass through the base, the main detector is fixed in the first mounting cavity, and the auxiliary detector is fixed in the second mounting cavity;

[0013] The bottom of the first installation cavity and the bottom of the second installation cavity are both provided with an annular baffle, and the annular baffle is integrally connected to the bottom of the first installation cavity or the second installation cavity;

[0014] The cover plate is provided with a first through hole and a second through hole. The photomultiplier tube of the main detector is provided in the first through hole, and the photomultiplier tube of the auxiliary detector is provided in the second through hole.

[0015] In one embodiment, the first detection range is 3.70×10 3 Bq / m 4 ~3.70×10 9 Bq / m 3 , the second detection range is 3.70×10 9 Bq / m 3 ~3.70×10 15 Bq / m 3 .

[0016] In one embodiment, the signal processing board is fixedly connected to the top of the cover.

[0017] In one embodiment, the thickness of the carbon fiber baffle is 0.4 mm to 0.6 mm, and the thickness of the stainless steel baffle is 0.9 mm to 1.1 mm.

[0018] In one embodiment, an on-site radiation processing unit is further included for displaying the activity concentration measurement results uploaded by the signal processing board, judging and displaying faults and alarm events, and issuing a corresponding alarm signal when the measurement results exceed a predetermined threshold.

[0019] In one embodiment, a pad is provided between the cover plate and the main detector and the auxiliary detector, and the pad is horizontally sleeved on the outer sides of the photomultiplier tubes of the main detector and the auxiliary detector.

[0020] The beneficial effects of the present invention are:

[0021] (1) In the present invention, the bottom of the plastic scintillator of the main detector is covered with a carbon fiber baffle, and the bottom of the plastic scintillator of the auxiliary detector is covered with a stainless steel baffle. The stainless steel baffle can shield all beta rays. Therefore, the main detector can measure the beta and gamma rays emitted by the radioactive gas in the pipeline and the gamma rays of the environmental background, and the auxiliary detector can measure the gamma rays emitted by the radioactive gas in the pipeline and the gamma rays of the environmental background. When the gas radiation level activity concentration is within the first detection range, the signal processing board can calculate the total beta activity concentration of the radioactive gas based on the detector measurement results. The auxiliary detector is used to perform real-time environmental background compensation, which can improve the accuracy of the beta activity concentration detection results.

[0022] (2) In the present invention, when the gas radiation level activity concentration is in the second detection range, the main detector is controlled to be powered off, and the auxiliary detector is switched to the current integration circuit module through a relay. Since the current integration circuit has no dead time effect, the auxiliary detector can measure the total γ activity concentration in a higher detection range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a detection unit provided in an embodiment of the present invention;

[0024] Figure 2 for Figure 1 A structural diagram from another angle;

[0025] Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure along the AA plane;

[0026] Figure 4 for Figure 3 A schematic diagram of the enlarged structure at point B;

[0027] Figure 5 A schematic structural diagram of a bracket provided in an embodiment of the present invention.

[0028] Explanation of the accompanying drawings: 100, main detector; 200, auxiliary detector; 300, signal processing board; 400, photomultiplier tube; 500, quartz light guide; 600, plastic scintillator; 700, carbon fiber baffle; 800, stainless steel baffle; 900, bracket; 910, base; 920, cover; 930, first mounting cavity; 940, second mounting cavity; 950, annular baffle; 960, pad. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] It should be noted that in the description of the present invention, “upper”, “lower”, “top”, “bottom”, orientation or position relationship is based on the attached Figure 1 Regarding the orientation or positional relationship shown, it should be understood that these orientation terms are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0031] In one embodiment, Figure 1 、 Figure 2 、 Figure 3 and Figure 4 As shown, the pipeline inert gas radiation monitoring system of this embodiment includes a detection unit, which is provided with a main detector 100, an auxiliary detector 200 and a signal processing board 300.

[0032] The main detector 100 and the auxiliary detector 200 are provided with a photomultiplier tube 400, a quartz light guide 500 and a plastic scintillator 600 from top to bottom. The bottom of the plastic scintillator 600 of the main detector 100 is covered with a carbon fiber baffle 700, and the bottom of the plastic scintillator 600 of the auxiliary detector 200 is covered with a stainless steel baffle 800.

[0033] The pipeline inert gas radiation monitoring system of this embodiment is generally arranged in the auxiliary building of a nuclear power plant. The detector is installed at the opening of the air duct and connected to the air duct through a flange; the on-site radiation processing unit is installed in a wall-mounted manner.

[0034] Inert gases such as Kr-85 and Xe-133 emit both beta and gamma rays during their decay process. Kr-85 emits 0.67 MeV beta rays with a branching ratio of over 99% and 0.51 MeV gamma rays with a branching ratio of 0.4%. Xe-133 emits 0.346 MeV beta rays with a branching ratio of 99.1% and 80.1 keV gamma rays with a branching ratio of 36.1%. Inert gases in pipelines produce both beta and gamma rays.

[0035] The stainless steel baffle 800 blocks beta rays from any source and can only detect gamma rays, so the auxiliary detector 200 can only measure gamma rays emitted by radioactive gases and gamma rays from the real-time environmental background. In addition, the environmental background does not contain beta rays.

[0036] The thickness of the carbon fiber baffle 700 is 0.4 mm to 0.6 mm, and the thickness of the stainless steel baffle 800 is 0.9 mm to 1.1 mm. Specifically, in this embodiment, the length and height of the plastic scintillator 600 are 95 mm, 120 mm, and 1 mm, respectively. The thickness of the carbon fiber baffle 700 is 0.5 mm, and the thickness of the stainless steel baffle 800 is 1.0 mm.

[0037] The main detector 100 is equipped with a threshold discrimination circuit module, while the auxiliary detector 200 is equipped with a threshold discrimination circuit module and a current integration circuit module, which are switched via relay control. In addition, this embodiment also includes a blue LED with a light frequency of 1Hz to 100kHz for circuit inspection to ensure the stability and reliability of the detector.

[0038] The threshold discrimination circuit module uses a threshold discrimination method to process the signal output by the amplifier circuit, while the current integration circuit module uses a current integration method to amplify the signal output by the amplifier circuit. The current integration invention eliminates dead-time effects and can measure higher gas radiation activity concentrations. This embodiment of the pipeline inert gas radiation monitoring system has a wide range.

[0039] In this embodiment, the signal processing board 300 is used to control the main detector 100 and the auxiliary detector 200 to be turned on at the same time when the gas radiation level activity concentration is in the first detection range, and the auxiliary detector 200 is switched to the threshold discrimination circuit module through the relay, and then the total beta count rate of the inert gas after environmental background compensation is obtained by deducting the count rate of the auxiliary detector 200 from the count rate of the main detector 100, and then the total beta activity concentration of the radioactive gas is calculated based on the total beta count rate of the inert gas; and is used to control the main detector 100 to be powered off when the gas radiation level activity concentration is in the second detection range, and the auxiliary detector 200 is switched to the current integration circuit module through the relay, and then the total gamma activity concentration of the radioactive gas is calculated based on the gamma count rate of the auxiliary detector 200.

[0040] The signal processing board 300 deducts the counting rate of the auxiliary detector 200 from the counting rate of the main detector 100 to obtain the total beta counting rate of the noble gas after environmental background compensation. The environmental background compensation of the auxiliary detector 200 is detected in real time, which can improve the accuracy of the final calculated total beta activity concentration of the radioactive gas.

[0041] Specifically, in this embodiment, the first detection range is 3.70×10 3 Bq / m 3 ~3.70×10 9 Bq / m 3 , the second detection range is 3.70×10 9 Bq / m~3.70×10 15 Bq / m 3 .

[0042] It should be noted that the division of the first detection range and the second detection range is based on relevant standards. In this embodiment, the inert gas emissions are controlled within the first detection range. Exceeding the second detection range may indicate a nuclear power plant accident. Exceeding the second detection range indicates a major nuclear power plant reactor accident, which is generally unlikely. Therefore, in this embodiment, the detection range is divided into the first detection range and the second detection range.

[0043] In one embodiment, Figure 5 As shown, the detection unit is also provided with a bracket 900, which consists of a base 910 for fixed assembly with the exhaust duct and a cover 920 for fixing the main detector 100 and the auxiliary detector 200 on the base 910; the base 910 is provided with a first installation cavity 930 and a second installation cavity 940 that pass through the base 910, the main detector 100 is fixed to the first installation cavity 930, and the auxiliary detector 200 is fixed to the second installation cavity 940; the bottom of the first installation cavity 930 and the second installation cavity 940 are both provided with an annular baffle 950, and the annular baffle 950 is integrally connected to the bottom of the first installation cavity 930 or the second installation cavity 940.

[0044] The cover plate 920 is provided with a first through hole and a second through hole. The photomultiplier tube 400 of the main detector 100 is provided in the first through hole, and the photomultiplier tube 400 of the auxiliary detector 200 is provided in the second through hole. The signal processing board 300 is fixedly connected to the top of the cover plate 920.

[0045] Specifically, the bracket 900 of this embodiment is further provided with reinforcing ribs on the upper and lower sides thereof to increase the strength of the detection unit.

[0046] In one embodiment, an on-site radiation processing unit is further included for displaying the activity concentration measurement results uploaded by the signal processing board 300, judging and displaying faults and alarm events, and issuing a corresponding alarm signal when the measurement results exceed a predetermined threshold.

[0047] Specifically, the on-site radiation processing unit is a microprocessor-based controller that contains various electronic components required by the radiation monitor, mainly including the microprocessor and related cards, power supply, memory card, backup battery for memory, detector interface card, digital data link card, relay, on-site indication display, on-site control switch, analog input card and digital output card, etc.

[0048] The local radiation processing unit communicates with the signal processing board 300 through the RS485 interface, receives and processes the data sent by the signal processing board 300, displays the measurement data in the set format, and automatically switches the dimension; displays or issues corresponding status indications or sound and light alarm signals according to pre-set thresholds; and inputs corresponding information through the panel keyboard as required by the program.

[0049] In one embodiment, a backing plate 960 is disposed between the cover plate 920 and the primary and secondary detectors 100 and 200. The backing plate 960 is horizontally sleeved onto the outer sides of the photomultiplier tubes 400 of the primary and secondary detectors 100 and 200. The backing plate 960 can be made of a soft material and serves to secure the detectors and protect the quartz light guides 500 of the detectors.

[0050] The pipeline inert gas radiation monitoring system of this embodiment has high detection accuracy, a wide detection range, and can realize autonomous monitoring indication and alarm.

[0051] The above-described embodiments merely represent several implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A pipeline inert gas radiation monitoring system, characterized in that: The detection unit comprises a main detector (100), an auxiliary detector (200) and a signal processing board (300); The main detector (100) and the auxiliary detector (200) are sequentially provided with a photomultiplier tube (400), a quartz light guide (500) and a plastic scintillator (600) from top to bottom; the bottom of the plastic scintillator (600) of the main detector (100) is covered with a carbon fiber baffle (700), and the bottom of the plastic scintillator (600) of the auxiliary detector (200) is covered with a stainless steel baffle (800); The main detector (100) is internally provided with a threshold discrimination circuit module, and the auxiliary detector (200) is internally provided with a threshold discrimination circuit module and a current integration circuit module switched by relay control; The signal processing board (300) is used to control the main detector (100) and the auxiliary detector (200) to be turned on simultaneously when the gas radiation level activity concentration is within a first detection range, the auxiliary detector (200) is switched to the threshold discrimination circuit module through a relay, and then the counting rate of the auxiliary detector (200) is deducted from the counting rate of the main detector (100) to obtain the total beta counting rate of the inert gas after environmental background compensation, and then the total beta activity concentration of the radioactive gas is calculated based on the total beta counting rate of the inert gas; as well as The invention is used for controlling the main detector (100) to be powered off when the gas radiation level activity concentration is within a second detection range, the auxiliary detector (200) is switched to a current integration circuit module through a relay, and then the total gamma activity concentration of the radioactive gas is calculated according to the gamma counting rate of the auxiliary detector (200).

2. The pipeline inert gas radiation monitoring system according to claim 1, characterized in that: The detection unit is further provided with a bracket (900), and the bracket (900) is composed of a base (910) for fixing and assembling with the exhaust duct and a cover plate (920) for fixing the main detector (100) and the auxiliary detector (200) on the base (910); The base (910) is provided with a first mounting cavity (930) and a second mounting cavity (940) penetrating the base (910); the main detector (100) is fixed to the first mounting cavity (930), and the auxiliary detector (200) is fixed to the second mounting cavity (940); An annular baffle (950) is provided at the bottom of each of the first installation cavity (930) and the second installation cavity (940), and the annular baffle (950) is integrally connected to the bottom of the first installation cavity (930) or the second installation cavity (940); The cover plate (920) is provided with a first through hole and a second through hole, the photomultiplier tube (400) of the main detector (100) is provided in the first through hole, and the photomultiplier tube (400) of the auxiliary detector (200) is provided in the second through hole.

3. The pipeline inert gas radiation monitoring system according to claim 2, characterized in that: The first detection range is 3.70×10 3 Bq / m 3 ~3.70×10 9 Bq / m 3 , the second detection range is 3.70×10 9 Bq / m~3.70×10 15 Bq / m 3 .

4. The pipeline inert gas radiation monitoring system according to claim 3, characterized in that: The signal processing board (300) is fixedly connected to the top of the cover plate (920).

5. The pipeline inert gas radiation monitoring system according to claim 4, characterized in that: The thickness of the carbon fiber baffle (700) is 0.4 mm to 0.6 mm, and the thickness of the stainless steel baffle (800) is 0.9 mm to 1.1 mm.

6. The pipeline inert gas radiation monitoring system according to claim 5, characterized in that: It also includes an on-site radiation processing unit for displaying the activity concentration measurement results uploaded by the signal processing board (300), judging and displaying faults and alarm events, and issuing corresponding alarm signals when the measurement results exceed a predetermined threshold.

7. The pipeline inert gas radiation monitoring system according to claim 6, characterized in that: A pad (960) is further provided between the cover plate (920), the main detector (100) and the auxiliary detector (200), and the pad (960) is horizontally sleeved on the outer sides of the photomultiplier tubes (400) of the main detector (100) and the auxiliary detector (200).

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