Gamma-ray-beta-ray coupling measurement system for airborne radioactive measurement and working method of gamma-ray-beta-ray coupling measurement system

Abstract

The invention belongs to the field of nuclear radiation detection, and provides a gamma-ray-beta-ray coupling measurement system for airborne radioactive measurement and a working method of the gamma-ray-beta-ray coupling measurement system. The system comprises an open type gas detector, an energy spectrum measurement detector, a preamplifier, a signal processing device and the like, and the open type gas detector and the energy spectrum measurement detector are connected with the preamplifier through a waterproof aviation connector and a high-temperature-resistant shielding cable; the preamplifier is connected with the signal processing device through the waterproof aviation connector and the high-temperature-resistant shielding cable, and the signal processing device is connected with a superior system through the waterproof aviation connector and the high-temperature-resistant communication cable and is connected with the mains supply through the power line. The system is small in overall size, low in noise and low in power consumption in the working process, airborne radionuclides do not need to be enriched through filter paper, a semiconductor detector does not need to be used, power can be supplied by means of a built-in battery of the signal processing device in the power-off state, and the system can work under the high-temperature, high-humidity and power-off conditions after accidents.

Description

Technical Field

[0001] The invention belongs to the field of nuclear radiation detection, and in particular relates to a gamma-ray-beta-ray coupling measurement system for airborne radioactivity measurement and a working method thereof. Background Art

[0002] Airborne radioactivity measurement plays an important role in nuclear safety, radiation protection, environmental protection and other fields of nuclear power plants and nuclear power plants. The traditional airborne radioactivity measurement method uses a vacuum pump, sampling pipeline, filter paper, etc. to sample and enrich the radioactive gas, and then uses semiconductor detectors, plastic scintillators, etc. to measure the radiation generated by the decay of radionuclides. The advantages of this measurement method are high sensitivity and low measurement limit. The disadvantages are that the sampling pipeline is complicated and the vacuum pump is large in size. The sampling pipeline, vacuum pump, detection device, and signal processing device need to be arranged on a stand as a whole, resulting in a large overall system volume and difficult deployment; the operation of the vacuum pump causes the overall power consumption and noise of the system to be high; filter paper, semiconductor detectors, etc. cannot work in high temperature and high humidity environments, and the vacuum pump needs to be powered by mains electricity. The system is difficult to work in high temperature, high humidity, and power outage conditions under post-accident conditions. As a supplement to the existing measurement methods, it is necessary to propose an airborne radioactivity measurement method with a small system volume, convenient deployment, low power consumption, and suitable for post-accident conditions. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of large system size, high power consumption and unsuitability for post-accident conditions in traditional airborne radioactivity measurement methods. A γ-ray-β-ray coupled measurement system for airborne radioactivity measurement and its working method are proposed, which has the characteristics of small system size, easy deployment, low power consumption and suitability for post-accident conditions.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a γ-ray-β-ray coupled measurement system for airborne radioactivity measurement, including an open gas detector, an energy spectrum measurement detector, a preamplifier, a signal processing device, a high-temperature resistant shielded cable, a high-temperature resistant communication cable, etc.

[0005] The open gas detector and the energy spectrum measurement detector are connected to the preamplifier through a waterproof aviation connector, a high temperature resistant shielded cable. The preamplifier is connected to the signal processing device through a waterproof aviation connector, a high temperature resistant shielded cable. The signal processing device is connected to the upper system through a waterproof aviation connector, a high temperature resistant communication cable, and is connected to the mains through a power cord.

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

[0007] The open gas detector, energy spectrum measurement detector, preamplifier, signal processing device, lead shielding body, etc. are installed on a bench or other installation positions through multiple sets of fastening bolts and spring 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 a CaF2 (Eu) crystal, a crystal bracket, an annular light-guiding glass, a photomultiplier tube, a rubber sleeve, a voltage-dividing circuit board, a voltage-dividing plate support, a waterproof connector socket, a shading net, a shell, etc. The CaF2 (Eu) crystal is arranged in a ring shape on the crystal bracket and fixed by black silicone; the crystal bracket is fixed to the shell and the mechanical structure by multiple sets of screws; the annular light-guiding glass is arranged on the outside of the crystal bracket, and optical silicone is applied between the CaF2 (Eu) crystal and the photomultiplier tube, and the side of the photomultiplier tube is wrapped with a rubber sleeve; the voltage-dividing circuit board is welded on the pin of the photomultiplier tube and connected by a circuit board connector, a shielded wire and a waterproof aviation connector socket; the annular light-guiding glass, the photomultiplier tube, and the voltage-dividing plate support are fixed in position by the shell; the waterproof aviation connector socket and the shading net are fixed to the shell by multiple sets of screws, spring washers, and flat washers.

[0009] The CaF2 (Eu) crystal is in the form of a thin sheet with a thickness of no more than 2 mm, and the surface in contact with the air is double-layer coated. The first layer of coating material is aluminum, which realizes the total reflection function; the second layer of coating material is graphene, which realizes the light shielding function. The annular light guide glass is coated with a total reflection film on all surfaces except the surface in contact with the crystal and the photomultiplier tube.

[0010] The energy spectrum measurement detector is composed of LaBr3 crystal, photomultiplier tube, rubber sleeve, voltage divider circuit board, voltage divider support, waterproof connector socket, shell, mechanical structure and mechanical structure. Optical silicone is applied between the LaBr3 crystal and the photomultiplier tube, and the side 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 connected through a circuit board connector, a shielded wire and a waterproof aviation connector socket; the LaBr3 crystal, the photomultiplier tube and the voltage divider support are fixed in position by the shell; the waterproof aviation connector socket is fixed to the shell by multiple sets of screws, spring washers and flat washers.

[0011] The photomultiplier tubes are all high temperature resistant photomultiplier tubes to enhance the high temperature resistance of the device. The resistors used in the voltage divider circuit board should be selected with larger resistance within a reasonable range to reduce the power consumption of the detector.

[0012] The preamplifier includes a preamplifier circuit board, a waterproof aviation connector, a housing and a mechanical structure. The preamplifier provides working voltage for two detectors. The preamplifier board contains two amplification circuits, both of which are charge-sensitive amplification circuits, which are used to amplify the output signals of the open gas detector and the energy spectrum measurement detector respectively. The preamplifier board is connected to the waterproof aviation connector socket through a circuit board connector and a shielded wire.

[0013] The signal processing device is used to realize functions such as two-way analog sampling, counting rate statistics, energy spectrum measurement, coupling measurement correction, information display, equipment control, over-threshold alarm, information upload, etc. The signal processing device is powered by a built-in battery or relies on external mains power supply, and provides working voltage for the preamplifier.

[0014] The present invention also provides a working method of the above-mentioned γ-ray-β-ray coupled measurement system for airborne radioactivity measurement, comprising the following steps:

[0015] (1) In an open gas detector, beta rays and gamma rays generate photons in the CaF2(Eu) crystal, which enter the annular light-guiding glass and are eventually converted into electrical signals on the photomultiplier tube.

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

[0017] (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;

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

[0019] (5) The signal processing device counts the signal generated by the energy spectrum measurement detector as an energy spectrum, divides the energy spectrum into I energy regions, and counts the counting 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:

[0020]

[0021] where k i , unit: cps / (μGy / h), is the response value of the energy spectrum measurement detector to the gamma rays in this energy range, which can be determined by experiments or simulation calculations; K i , unit: cps / (μGy / h), is the response value of the open gas detector to the gamma rays in this energy range, which can be determined by experiments or simulation calculations;

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

[0023] C q =N1 / R

[0024] Where R, unit: cps / (Bq / L), is the response value of the open gas detector to β rays, which can be determined by experiments or simulation calculations.

[0025] The present invention provides a γ-ray-β-ray coupling measurement system for airborne radioactivity measurement and a working method thereof, which has the following beneficial effects compared with the prior art:

[0026] 1. The complex sampling pipeline and large vacuum pump are eliminated, the overall system size is small, the noise is small during operation, and the power consumption is reduced.

[0027] 2. There is no need to use filter paper to enrich airborne radioactive nuclides, and there is no need to use semiconductor detectors. In the power-off state, the signal processing device can be powered by the built-in battery, and can work under high temperature, high humidity and power-off conditions under post-accident working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 2 It is a schematic diagram of the structure of the open gas detector in the present invention.

[0030] Figure 3 It is a schematic diagram of the structure of the energy spectrum measurement detector in the present invention.

[0031] Figure 4 This is a flow chart of the working method of the coupling measurement system of the present invention.

[0032] Figure 5 Schematic diagram of energy spectrum partitioning.

[0033] Among them: 1. Open gas detector, 2. Energy spectrum measurement detector, 3. Preamplifier, 4. Signal processing device, 5. High temperature resistant shielded cable, 6. High temperature resistant communication cable, 11. Housing, 12. Ring light guide glass, 13. CaF2 (Eu) crystal, 14. Crystal bracket, 15. Shading net, 16. Rubber sleeve, 17. Photomultiplier tube, 18. Voltage divider circuit board, 19. Voltage divider support, 20. Waterproof connector socket, 21. LaBr3 crystal. DETAILED DESCRIPTION

[0034] 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 in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0035] It should be noted that when an element is referred to as being “mounted on” another element, it may be directly on the other element or there may be an element in the middle.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0037] like Figure 1 As shown, an embodiment of the present invention provides a γ-ray-β-ray coupled measurement system for airborne radioactivity measurement, including an open gas detector 1, an energy spectrum measurement detector 2, a preamplifier 3, a signal processing device 4, a high temperature resistant shielded cable 5, a high temperature resistant communication cable 6, etc.

[0038] like Figure 2 As shown, the open gas detector 1 is composed of a housing 11, an annular light-guiding glass 12, a CaF2 (Eu) crystal 13, a crystal bracket 14, a shading net 15, a rubber sleeve 16, a photomultiplier tube 17, a voltage divider circuit board 18, a voltage divider board support 19, a waterproof connector socket 20, etc.

[0039] like Figure 3 As shown, the energy spectrum measurement detector 2 is composed of a housing and a mechanical structure and a mechanical structure 11, a LaBr3 crystal 21, a rubber sleeve 16, a photomultiplier tube 17, a voltage divider circuit board 18, a voltage divider board support 19, a waterproof connector socket 20, etc.

[0040] like Figure 4 As shown, this embodiment also provides a working method of the above-mentioned γ-ray-β-ray coupling measurement system for airborne radioactivity measurement, which (combined with the description of each functional module of the measurement system) includes the following steps:

[0041] (1) The open gas detector 1 is used for detecting the 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 the decay of the airborne radionuclides deposit energy in the CaF2 (Eu) crystal 13, causing the latter to generate photons.

[0042] The CaF2 (Eu) crystal 13 and the air contact surface are coated. The second coating material is graphene, which can prevent the photons in the environment from entering the annular light guide glass 12 through the CaF2 (Eu) crystal 13, and further converting them into electrical signals on the photomultiplier tube 17, thereby generating noise interference; the first coating material is aluminum, which can reflect all the photons generated by the CaF2 (Eu) crystal 13 into the light guide glass 12, and further convert them into electrical signals on the photomultiplier tube 17. The thickness of the CaF2 (Eu) crystal 13 is only no more than 1mm, which can reduce the response of the open gas detector 1 to gamma rays.

[0043] (2) Energy spectrum measurement The detector 2 is used for gamma ray measurement, including gamma rays generated by the decay of airborne radionuclides 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 a counting rate N0 (unit: cps, i.e., counts per second).

[0046] (5) The signal processing device 4 counts the signal generated by the energy spectrum measurement detector 2 as an energy spectrum. Figure 5 As shown, the energy spectrum is divided into I energy regions, and the counting rate in the i-th energy region is n i (Unit: cps). Then the corrected count rate N1 (unit: cps) of the open gas detector 1 is obtained as:

[0047]

[0048] where k i (unit: cps / (μGy / h)) is the response value of the energy spectrum measurement detector 2 to the gamma rays in this energy range, which can be determined by experiments or simulation calculations; K i (Unit: cps / (μGy / h)) is the response value of the open gas detector 1 to the gamma rays in this energy range, which can be determined by experiments or simulation calculations.

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

[0050] C q =N1 / R

[0051] Wherein R (unit: cps / (Bq / L)) is the response value of the open gas detector 1 to β rays, which can be determined by experiments or simulation calculations.

[0052] The above is a detailed introduction to a γ-ray-β-ray coupling measurement system for airborne radioactivity measurement and its working method provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of ​​the present invention; at the same time, for those skilled in the art, according to the idea of ​​this patent, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification is only the implementation method of the present invention, and it does not limit the patent scope of the present invention. All equivalent structures or equivalent process changes made by using the contents of the present invention specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present invention. It should not be understood as a limitation on this patent.

[0053] The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A γ-ray-β-ray coupled measurement system for airborne radioactivity measurement, characterized in that: It includes an open gas detector, an energy spectrum measurement detector, a preamplifier, a signal processing device, a high temperature resistant shielded cable, and a high temperature resistant communication cable; the open gas detector and the energy spectrum measurement detector are connected to the preamplifier through a waterproof aviation connector and a high temperature resistant shielded cable; the preamplifier is connected to the signal processing device through a waterproof aviation connector and a high temperature resistant shielded cable; the signal processing device is connected to the upper system through a waterproof aviation connector and a high temperature resistant communication cable, and is connected to the mains through a power cord.

2. The γ-ray-β-ray coupled measurement system for airborne radioactivity measurement according to claim 1, characterized in that: The open gas detector, energy spectrum measurement detector, preamplifier, signal processing device, and lead shield are installed on a bench or other installation locations through multiple sets of fastening bolts and spring washers, flat washers, and nuts, and the open gas detector and energy spectrum measurement detector are arranged nearby.

3. The γ-ray-β-ray coupled measurement system for airborne radioactivity measurement according to claim 1, characterized in that: The open gas detector includes a CaF2 (Eu) crystal, a crystal bracket, an annular light-guiding glass, a photomultiplier tube, a rubber sleeve, a voltage-divider circuit board, a voltage-divider board support, a waterproof connector socket, a shading net, and a shell. The CaF2 (Eu) crystal is arranged in a ring shape on the crystal bracket and fixed by black silicone; the crystal bracket is fixed to the shell by multiple sets of screws; the annular light-guiding glass is arranged on the outside of the crystal bracket, and optical silicone is applied between the CaF2 (Eu) crystal and the photomultiplier tube, and the side of the photomultiplier tube is wrapped with a rubber sleeve; the voltage-divider circuit board is welded on the photomultiplier tube pin and connected by a circuit board connector, a shielded wire and a waterproof aviation connector socket; the waterproof aviation connector socket and the shading net are fixed to the shell by multiple sets of screws, spring washers and flat washers.

4. The γ-ray-β-ray coupled measurement system for airborne radioactivity measurement according to claim 3, characterized in that: The CaF2 (Eu) crystal is in the form of a thin sheet with a thickness of no more than 2 mm, and is double-layer coated on the surface in contact with the air; the first layer of coating material is aluminum to achieve a total reflection function; the second layer of coating material is graphene to achieve a shading function.

5. The γ-ray-β-ray coupled measurement system for airborne radioactivity measurement according to claim 3, characterized in that: The annular light-guiding glass, except for the surface in contact with the crystal and the photomultiplier tube, has all other surfaces plated with a total reflection film.

6. The γ-ray-β-ray coupled measurement system for airborne radioactivity measurement according to claim 1, characterized in that: The energy spectrum measurement detector includes a LaBr3 crystal, a photomultiplier tube, a rubber sleeve, a voltage divider circuit board, a voltage divider board support, a waterproof connector socket, and a shell; optical silicone is applied between the LaBr3 crystal and the photomultiplier tube, and the side of the photomultiplier tube is wrapped with a rubber sleeve; the voltage divider circuit board is welded on the photomultiplier tube pin, and is connected through a circuit board connector, a shielded wire and a waterproof aviation connector socket; the waterproof aviation connector socket is fixed to the shell by multiple sets of screws, spring washers, and flat washers.

7. The γ-ray-β-ray coupled measurement system for airborne radioactivity measurement according to claim 3 or 6, characterized in that: The photomultiplier tube is a high temperature resistant photomultiplier tube to enhance the high temperature resistance of the device. The resistors used in the voltage divider circuit board should be selected with larger resistance within a reasonable range to reduce the power consumption of the detector.

8. The γ-ray-β-ray coupled measurement system for airborne radioactivity measurement according to claim 1, characterized in that: The preamplifier includes a preamplifier circuit board, a waterproof aviation connector, and a shell. The preamplifier provides working voltage for two detectors. The preamplifier board contains two amplification circuits, both of which are charge-sensitive amplification circuits, which are respectively used to amplify the output signals of the open gas detector and the energy spectrum measurement detector. The preamplifier board is connected to the waterproof aviation connector socket through a circuit board connector and a shielded wire.

9. The γ-ray-β-ray coupled measurement system for airborne radioactivity measurement according to claim 1, characterized in that: The signal processing device is used to realize two-way analog quantity sampling, count rate statistics, energy spectrum measurement, coupled measurement correction, information display, equipment control, over-threshold alarm, and information upload functions. The signal processing device is powered by a built-in battery or relies on external AC power supply, and provides working voltage for the preamplifier.

10. A method for operating a γ-ray-β-ray coupled measurement system for airborne radioactivity measurement as claimed in claim 1, characterized in that The following steps are involved: (1) In an open gas detector, beta rays and gamma rays generate photons in the CaF2(Eu) crystal, which enter the annular light-guiding glass and are eventually converted into electrical signals on the photomultiplier tube. (2) In the energy spectrum measurement detector, gamma rays generate photons in the LaBr3 crystal, which 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 signal generated by the open gas detector as a count rate N0, in cps; (5) The signal processing device counts the signal generated by the energy spectrum measurement detector as an energy spectrum, divides the energy spectrum into I energy regions, and counts the counting 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: where k i , unit: cps / (μGy / h), is the response value of the energy spectrum measurement detector to the gamma rays in this energy range, which can be determined by experiments or simulation calculations; K i , unit: cps / (μGy / h), is the response value of the open gas detector to the gamma rays in this energy range, which can be determined by experiments or simulation calculations; (6) The airborne radioactivity concentration C can be obtained by calculation q , unit: Bq / L, is: C q =N1 / R Where R, unit: cps / (Bq / L), is the response value of the open gas detector to β rays, which can be determined by experiments or simulation calculations.

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