Gamma-ray and beta-ray coupled measurement system for airborne radioactivity measurement and its working method

Abstract

The present application belongs to the field of nuclear radiation detection, and provides a gamma ray-beta ray coupling measurement system for airborne radioactivity measurement and a working method thereof. The system comprises an open gas detector, a spectrum measurement detector, a preamplifier, a signal processing device, etc. The open gas detector and the spectrum measurement detector are connected with the preamplifier through waterproof aviation connectors, high-temperature-resistant shielding cables, and the preamplifier is connected with the signal processing device through waterproof aviation connectors, high-temperature-resistant shielding cables, and the signal processing device is connected with the superior system through waterproof aviation connectors, high-temperature-resistant communication cables, and the system is connected with the power supply line and the commercial power supply. The system has small overall volume, small noise in the working process, low power consumption, does not need to use filter paper to enrich airborne radionuclides, does not need to use semiconductor detectors, can rely on the built-in battery of the signal processing device for power supply in the power-off state, and can work in the high-temperature, high-humidity and power-off conditions after the accident.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nuclear radiation detection, and particularly relates to a gamma ray-beta ray coupling measurement system for airborne radioactivity measurement and a working method thereof. BACKGROUND

[0002] Airborne radioactivity measurement plays an important role in the fields of nuclear safety, radiation protection, environmental protection, etc. of nuclear power plants and nuclear power devices. The traditional airborne radioactivity measurement method samples and enriches radioactive gas through an air pump, a sampling pipeline and filter paper, and then measures the rays generated by the decay of radionuclides by using a semiconductor detector and a plastic scintillator. The advantages of this measurement method are high sensitivity and low measurement lower limit, and the disadvantages are that the sampling pipeline is relatively complex, the air pump is relatively large in size, the sampling pipeline, the air pump, the detection device and the signal processing device need to be arranged integrally on a rack, resulting in a relatively large overall size of the system and difficulty in deployment; the air pump operation results in a relatively high overall power consumption and a relatively large noise of the system; the filter paper and the semiconductor detector cannot work in a high-temperature and high-humidity environment, and the air pump needs to be powered by commercial power, so the system cannot work in a high-temperature, high-humidity and power-off condition after an accident. As a supplement to the existing measurement method, a system with a small size, easy deployment, low power consumption and applicability to post-accident conditions is needed. SUMMARY

[0003] The present application is to overcome the problems of a large system size, high power consumption and inapplicability to post-accident conditions in the traditional airborne radioactivity measurement method, and provides a gamma ray-beta ray coupling measurement system for airborne radioactivity measurement and a working method thereof, which has the characteristics of a small system size, easy deployment, low power consumption and applicability to post-accident conditions.

[0004] To achieve the above object, the technical scheme adopted by the present application is as follows: a gamma ray-beta ray coupling measurement system for airborne radioactivity measurement, comprising an open gas detector, a spectrum measurement detector, a preamplifier, a signal processing device, a high-temperature-resistant shielding cable and a high-temperature-resistant communication cable.

[0005] The open gas detector and the spectrum measurement detector are connected through a waterproof aviation connector, a high-temperature-resistant shielding cable and the preamplifier. The preamplifier is connected through a waterproof aviation connector, a high-temperature-resistant shielding cable and the signal processing device. The signal processing device is connected through a waterproof aviation connector, a high-temperature-resistant communication cable and a superior system, and is connected through a power line and commercial power.

[0006] The open gas detector and the spectrum measurement detector reduce the response to gamma rays by adding a lead shielding body. The open gas detector, the spectrum measurement detector and the preamplifier reduce the influence of high temperature on the performance of the equipment by wrapping with thermal insulation materials.

[0007] The open gas detector, energy spectrum measurement detector, preamplifier, signal processing device, lead shielding body and the like are installed on a rack or other mounting part by a plurality of fastening bolts and elastic washers, flat washers and nuts, and the open gas detector and energy spectrum measurement detector are arranged nearby.

[0008] The open gas detector is composed of CaF2(Eu) crystal, crystal support, annular light guide glass, photomultiplier tube, rubber sleeve, voltage divider circuit board, voltage divider board support, waterproof connector socket, light shielding net and shell. The CaF2(Eu) crystal is arranged in a ring shape on the crystal support and is fixed by black silica gel; the crystal support is fixed on the shell and mechanical structure by a plurality of screws; the annular light guide glass is arranged outside the crystal support, and optical silica gel is applied between the CaF2(Eu) crystal and the photomultiplier tube; the photomultiplier tube is wrapped with a rubber sleeve; the voltage divider circuit board is welded on the pin of the photomultiplier tube and is connected by a circuit board connector, shielding wire and waterproof aviation connector socket; the annular light guide glass, photomultiplier tube and voltage divider board support are fixed in position by the shell; the waterproof aviation connector socket and light shielding net are fixed on the shell by a plurality of screws, elastic washers and flat washers.

[0009] The CaF2(Eu) crystal is in the form of a thin sheet with a thickness of not more than 2 mm, and the air contact surface is treated by double-layer coating. The first layer of coating is aluminum to achieve total reflection function; the second layer of coating is graphene to achieve light shielding function. The annular light guide glass is treated by total reflection film coating on all surfaces except the contact surface with the crystal and photomultiplier tube.

[0010] The energy spectrum measurement detector is composed of LaBr3 crystal, photomultiplier tube, rubber sleeve, voltage divider circuit board, voltage divider board support, waterproof connector socket, shell and mechanical structure. The LaBr3 crystal and photomultiplier tube are coated with optical silica gel, and the side surface of the photomultiplier tube is wrapped with a rubber sleeve; the voltage divider circuit board is welded on the pin of the photomultiplier tube and is connected by a circuit board connector, shielding wire and waterproof aviation connector socket; the LaBr3 crystal, photomultiplier tube and voltage divider board support are fixed in position by the shell; the waterproof aviation connector socket is fixed on the shell by a plurality of screws, elastic washers and flat washers.

[0011] The photomultiplier tubes are all high-temperature resistant photomultiplier tubes to enhance the high-temperature resistance of the equipment. The resistors used in the voltage divider circuit board should all be selected to have relatively large resistance values within a reasonable range to reduce the power consumption of the detector.

[0012] The preamplifier comprises a preamplification circuit board, a waterproof aviation connector, a shell and a mechanical structure. The preamplifier provides working voltage for two detectors. The preamplification board comprises two amplification circuits, both of which are charge-sensitive amplification circuits and are used for amplifying the output signals of the open gas detector and the energy spectrum measurement detector respectively. The preamplification board is connected with the waterproof aviation connector socket through a circuit board connector and a shielding wire.

[0013] The signal processing device is used for realizing functions such as two-way analog quantity sampling, count rate statistics, energy spectrum measurement, coupling measurement correction, information display, device control, over-threshold alarm and information uploading. The signal processing device is powered by a built-in battery or external power supply and provides working voltage for the preamplifier.

[0014] The application further provides a working method of the gamma ray-beta ray coupling measurement system for airborne radioactivity measurement.

[0015] (1) In the open gas detector, beta rays and gamma rays generate photons in the CaF2(Eu) crystal, the photons enter the annular light guide glass and are finally converted into electric signals on the photomultiplier tube;

[0016] (2) In the energy spectrum measurement detector, gamma rays generate photons in the LaBr3 crystal, and the photons are converted into electric signals on the photomultiplier tube;

[0017] (3) The preamplifier amplifies the electric signals generated by the open gas detector and the energy spectrum measurement detector respectively and transmits the signals to the signal processing device;

[0018] (4) The signal processing device counts the signals generated by the open gas detector into a count rate N0, unit: cps;

[0019] (5) The signal processing device counts the signals generated by the energy spectrum measurement detector into an energy spectrum, divides the energy spectrum into I energy regions, counts the count rate in the i-th energy region as n i , unit: cps; and obtains the corrected count rate N1 of the open gas detector as:

[0020]

[0021] wherein k i , unit: cps / (μGy / h), is the response value of the energy spectrum measurement detector to the gamma rays in the energy region and can be determined through experiments or simulation calculation; K i , unit: cps / (μGy / h), is the response value of the open gas detector to the gamma rays in the energy region and can be determined through experiments or simulation calculation;

[0022] (6) The airborne radioactivity concentration C can be obtained by calculation q , unit: Bq / L, is:

[0023] C q = N1 / R

[0024] Wherein R, unit: cps / (Bq / L), is the response value of the open gas detector to beta rays, which can be determined by test or simulation calculation method.

[0025] The gamma ray-beta ray coupling measurement system for airborne radioactivity measurement and the working method thereof have the following beneficial effects compared with the prior art:

[0026] 1. The complex sampling pipeline, the large-volume air pump and the like are cancelled, the overall volume of the system is small, the noise is small during the working process, and the power consumption is reduced.

[0027] 2. The filter paper is not needed to be used to enrich the airborne radionuclide, the semiconductor detector is not needed to be used, the signal processing device can be powered by the built-in battery in the power-off state, and the system can work in the high temperature, high humidity and power-off state after the accident. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a schematic diagram of the detection system composition of the application.

[0029] Figure 2 It is a structural schematic diagram of the open gas detector in the application.

[0030] Figure 3 It is a structural schematic diagram of the energy spectrum measurement detector in the application.

[0031] Figure 4 It is a working method flow chart of the coupling measurement system of the application.

[0032] Figure 5 It is a spectral partitioning schematic diagram.

[0033] Wherein: 1. Open gas detector, 2. Energy spectrum measurement detector, 3. Pre-amplifier, 4. Signal processing device, 5. High-temperature-resistant shielding cable, 6. High-temperature-resistant communication cable, 11. Shell, 12. Ring-shaped light guide glass, 13. CaF2(Eu) crystal, 14. Crystal support, 15. Light shielding net, 16. Rubber sleeve, 17. Photomultiplier tube, 18. Voltage dividing circuit board, 19. Voltage dividing plate support, 20. Waterproof connector socket, 21. LaBr3 crystal. DETAILED DESCRIPTION

[0034] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a number of different manners according to other specific embodiments, and similar improvements can be made by those skilled in the art without departing from the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0035] It should be noted that when an element is referred to as being "mounted on" another element, it can be directly on the other element or there can be an intervening element.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this description, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0037] As shown in Figure 1 The embodiment of the present application provides a gamma ray-beta ray coupling measurement system for airborne radioactivity measurement, which comprises an open gas detector 1, a spectrum measurement detector 2, a preamplifier 3, a signal processing device 4, a high-temperature-resistant shielding cable 5, a high-temperature-resistant communication cable 6 and the like.

[0038] As shown in Figure 2 The open gas detector 1 comprises a shell 11, an annular light guide glass 12, a CaF2(Eu) crystal 13, a crystal support 14, a light shielding net 15, a rubber sleeve 16, a photomultiplier tube 17, a voltage dividing circuit board 18, a voltage dividing board support 19, a waterproof connector socket 20 and the like.

[0039] As shown in Figure 3 The spectrum measurement detector 2 comprises a shell and a mechanical structure 11, a LaBr3 crystal 21, a rubber sleeve 16, a photomultiplier tube 17, a voltage dividing circuit board 18, a voltage dividing board support 19, a waterproof connector socket 20 and the like.

[0040] As shown in Figure 4 The embodiment also provides a working method of the gamma ray-beta ray coupling measurement system for airborne radioactivity measurement, which comprises the following steps:

[0041] (1) The open gas detector 1 is used to detect beta rays generated by the decay of airborne radionuclides, and the influence of gamma rays needs to be eliminated. The airborne radioactive material enters the central cavity of the open gas detector 1 through the light-shielding net 15, and the beta rays and gamma rays generated by its decay deposit energy in the CaF2(Eu) crystal 13, causing the latter to generate photons.

[0042] The CaF2(Eu) crystal 13 and its air contact surface are coated. The second coating material is graphene, which prevents photons from the environment from passing through the CaF2(Eu) crystal 13 into the annular light guide glass 12 and being further converted into electrical signals on the photomultiplier tube 17, thus avoiding noise interference. The first coating material is aluminum, which reflects all photons generated by the CaF2(Eu) crystal 13 into the light guide glass 12, where they are further converted into electrical signals on the photomultiplier tube 17. The CaF2(Eu) crystal 13 has a thickness of no more than 1 mm, which can reduce the response of the open gas detector 1 to gamma rays.

[0043] (2) The energy spectrum detector 2 is used for gamma-ray measurement, including gamma rays generated by the decay of gaseous radioactive nuclides and other gamma rays in the environment. The gamma rays deposit energy in the LaBr3 crystal 21, causing the latter to generate photons. The photons are converted into electrical signals on the photomultiplier tube 17.

[0044] (3) The preamplifier 3 amplifies the electrical signals generated by the open gas detector 1 and the energy spectrum measurement detector 2 respectively, and transmits them to the signal processing device 4.

[0045] (4) The signal processing device 4 counts the signal generated by the open gas detector 1 as the count rate N0 (unit: cps, i.e., counts per second).

[0046] (5) The signal processing device 4 statistically analyzes the signal generated by the energy spectrum measuring detector 2 into an energy spectrum. For example... Figure 5 As shown, the energy spectrum is divided into I energy regions, and the count rate in the i-th energy region is counted as n. i (Unit: cps). The corrected count rate N1 (unit: cps) for open gas detector 1 is then obtained as follows:

[0047]

[0048] Where k i (Unit: cps / (μGy / h)) represents the response value of energy spectrum detector 2 to γ-rays in this energy range, which can be determined experimentally or through simulation calculations; K i (Unit: cps / (μGy / h)) is the response value of open gas detector 1 to γ-rays in this energy range, which can be determined by experimental or simulation calculation.

[0049] (6) Calculate the airborne radioactivity concentration C q (Units: Bq / L) is:

[0050] C q = N1 / R

[0051] Wherein R (Units: cps / (Bq / L)) is the response value of open gas detector 1 to beta rays, which can be determined by experimental or simulation calculation method.

[0052] The above provides a kind of for airborne radioactivity measurement γ-ray-beta ray coupling measurement system and its working method are introduced in detail, the principle and implementation mode of the present application are described in this paper by applying specific examples, the above example is only for helping to understand the method of the present application and its core idea;For the general technical personnel in the art, according to the idea of the present application, the specific implementation mode and application range will be changed, as described above, the content of the specification is only the implementation mode of the present application, not therefore limit the patent range of the present application, any equivalent structure or equivalent process conversion using the content of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application. It should not be understood as the limitation of the present application.

[0053] The content not described in detail in the specification belongs to the prior art known to the professional technical personnel.

Claims

1. A gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements, characterized by: The application relates to a high-temperature-resistant cable, which comprises an open gas detector, a spectrum measurement detector, a preamplifier, a signal processing device, a high-temperature-resistant shielding cable and a high-temperature-resistant communication cable; the open gas detector and the spectrum measurement detector are connected with the preamplifier through waterproof aviation connectors and the high-temperature-resistant shielding cable; the preamplifier is connected with the signal processing device through waterproof aviation connectors and the high-temperature-resistant shielding cable; the signal processing device is connected with a superior system through waterproof aviation connectors, the high-temperature-resistant communication cable and the superior system; the signal processing device is powered by an internal battery or external commercial power supply and provides working voltage for the preamplifier; the open gas detector comprises a CaF2 (Eu) crystal and annular light guide glass, and optical silica gel is coated between the CaF2 (Eu) crystal and the annular light guide glass; in the open gas detector, beta rays and gamma rays generate photons in the CaF2 (Eu) crystal, and the photons enter the annular light guide glass; the spectrum measurement detector comprises a LaBr3 crystal, and in the spectrum measurement detector, gamma rays generate photons in the LaBr3 crystal; the signal processing device counts the signal generated by the open gas detector as a count rate N0 (unit: cps); the signal processing device counts the signal generated by the spectrum measurement detector as a spectrum; the spectrum is divided into I energy regions, and the count rate n in the i-th energy region is counted (unit: cps); and the corrected count rate N1 of the open gas detector is obtained as follows. i ​ wherein k i , units: cps / (μGy / h), is the response value of the energy spectrum measurement detector to the γ rays in the energy region, which can be determined by experimental or simulation calculation method; K i , units: cps / (μGy / h), is the response value of the open gas detector to the γ rays in the energy region, which can be determined by experimental or simulation calculation method.

2. The gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements according to claim 1, characterized in that: The open gas detector, the energy spectrum measurement detector, the preamplifier, the signal processing device and the lead shielding body are installed on a rack or other installation site by a plurality of sets of fastening bolts and elastic washers, flat washers and nuts, and the open gas detector and the energy spectrum measurement detector are arranged close to each other.

3. The gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements according to claim 1, characterized in that: The open gas detector further comprises a crystal support, a photomultiplier, a rubber sleeve, a voltage division circuit board, a voltage division board support, a waterproof aviation connector socket, a light shielding net and a shell, the CaF2(Eu) crystal is arranged in a ring shape on the crystal support and is fixed by black silica gel, the crystal support is fixed on the shell by a plurality of sets of screws, the annular light guide glass is arranged outside the crystal support, optical silica gel is applied between the CaF2(Eu) crystal, the photomultiplier and the annular light guide glass, and the photomultiplier is wrapped with the rubber sleeve, the voltage division circuit board is welded on the pin of the photomultiplier and is connected by a circuit board connector, a shielding wire and the waterproof aviation connector socket, and the waterproof aviation connector socket and the light shielding net are fixed on the shell by a plurality of sets of screws, elastic washers and flat washers.

4. The gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements according to claim 1, characterized in that: The CaF2(Eu) crystal is in a sheet shape, the thickness is not greater than 2 mm, and the contact surface with air is treated by double-layer coating, the first layer of coating material is aluminum to realize total reflection, and the second layer of coating material is graphene to realize light shielding.

5. The gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements according to claim 1, characterized in that: The annular light guide glass is treated by total reflection coating on the rest surfaces except the contact surfaces with the crystal and the photomultiplier.

6. The gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements according to claim 1, characterized in that: The energy spectrum measurement detector further comprises a photomultiplier, a rubber sleeve, a voltage division circuit board, a voltage division board support, a waterproof aviation connector socket and a shell, optical silica gel is applied between the LaBr3 crystal and the photomultiplier, the photomultiplier is wrapped with the rubber sleeve, the voltage division circuit board is welded on the pin of the photomultiplier and is connected by a circuit board connector, a shielding wire and the waterproof aviation connector socket, and the waterproof aviation connector socket is fixed on the shell by a plurality of sets of screws, elastic washers and flat washers.

7. The gamma-ray-beta-ray coupling measurement system for airborne radioactivity measurement according to claim 3 or 6, characterized in that: The photomultipliers are high-temperature-resistant photomultipliers to enhance the high-temperature resistance of the equipment, and the resistors of the voltage division circuit board should all be selected to have a large resistance value within a reasonable range to reduce the power consumption of the detector.

8. The gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements according to claim 1, characterized in that: The preamplifier comprises a preamplification circuit board, a waterproof aviation connector and a shell, provides working voltages for two detectors, contains two amplification circuits which are charge-sensitive amplification circuits and are respectively used for amplifying the output signals of the open gas detector and the energy spectrum measurement detector, and is connected with the waterproof aviation connector socket by a circuit board connector and a shielding wire.

9. The gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements according to claim 1, characterized in that: The signal processing device is used for realizing two-way analog sampling, count rate statistics, energy spectrum measurement, coupling measurement correction, information display, equipment control, over-threshold alarm and information uploading, is powered by a built-in battery or external power supply and provides working voltages for the preamplifier.

10. A method of operating a gamma-ray-beta-ray coupled measurement system for airborne radioactivity measurements as defined in claim 1, characterized in that The method comprises the following steps: (1) in the open gas detector, β rays and γ rays generate photons in the CaF2(Eu) crystal, the photons enter the annular light guide glass and are finally converted into electric signals on the photomultiplier. (2) In the energy spectrum measurement detector, the gamma rays generate photons in the LaBr3 crystal, and the photons are converted into electrical signals on the photomultiplier tube; (3) The preamplifier amplifies the electrical signals generated by the open gas detector and the energy spectrum measurement detector respectively, and transmits them to the signal processing device; (4) The signal processing device counts the signals generated by the open gas detector as the count rate N0, unit: cps. (5) The signal processing device counts the signal generated by the energy spectrum measurement probe as an energy spectrum, divides the energy spectrum into I energy regions, and counts the count rate in the i-th energy region as n i , unit: cps; then the corrected count rate N1 of the open gas detector is obtained as: wherein k i , units: cps / (μGy / h), is the response value of the energy spectrum measurement detector to the γ rays in the energy region, which can be determined by experimental or simulation calculation method; K i , units: cps / (μGy / h), is the response value of the open gas detector to the γ rays in the energy region, which can be determined by experimental or simulation calculation method; (6) The airborne radioactivity concentration C is obtained by calculation q in Bq / L is: C q = N1 / R Wherein R, unit: cps / (Bq / L), is the response value of the open gas detector to beta rays, which is determined by experimental or simulation calculation method.

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