Passive nuclear level gauge with anti-detection radiation interference multi-photomultiplier tube

Abstract

This application discloses a passive nuclear level gauge with multiple photomultiplier tubes to resist radiation interference from flaw detection, relating to the field of industrial measurement technology. It includes: a radiation detection component comprising at least one first scintillation crystal and at least one second scintillation crystal; at least two photomultiplier tubes, each first scintillation crystal and each second scintillation crystal being optically coupled to one photomultiplier tube; at least two electrical signal acquisition modules, the input terminal of each electrical signal acquisition module being electrically connected to the output terminal of one photomultiplier tube; a processing unit connected to each electrical signal acquisition module; and a spatial shielding structure. This application can suppress radiation interference from flaw detection, thereby enabling the measurement of material radiation even under flaw detection interference, and ensuring accurate measurement even under such conditions.

Description

Technical Field

[0001] This application relates to the field of industrial measurement technology, and in particular to a passive nuclear level gauge with multiple photomultiplier tubes that is resistant to radiation interference from flaw detection. Background Technology

[0002] Passive nuclear level gauges measure material level by measuring the nuclear radiation released by radioactive substances such as radium and uranium contained in the material itself. They have the advantages of being non-contact and having no radioactive source hazards, and are widely used in industries such as thermal power generation, steel, and metallurgy due to their suitability for special installation scenarios.

[0003] However, during industrial field flaw detection operations, the high-energy X-rays or strong radioactive sources such as cobalt used can cause strong interference to passive nuclear level gauges, even at a distance of hundreds of meters from the working position of the level gauge, which can lead to measurement errors or even complete failure to work.

[0004] Existing technologies employ specialized radiation sensors to measure changes in ambient radiation and provide background radiation correction for all passive nuclear level gauges on-site. Alternatively, a single radiation probe measuring the material and another measuring the environment are placed within a passive nuclear level gauge. Patents such as CN104390677B ("A Method and System for Background Radiation Correction Measurement of Passive Nuclear Level Gauges") utilize the process characteristics of containers like silos and pumps to identify and measure environmental changes. Patent CN205120206U ("A Measuring Device for Reducing the Influence of Ambient Radiation Changes on Passive Nuclear Level Gauges") utilize rotating radiation probes to measure material within the container and then ambient radiation. All these technologies identify and correct for normal environmental radiation changes (generally small in magnitude and slow in process). However, due to the extremely strong radioactivity and drastic changes in radiation interference during flaw detection, these existing technologies are completely ineffective when flaw detection actually occurs.

[0005] Existing technological attempts also hope to reduce the interference of flaw detection by increasing the thickness of existing conventional shielding components. However, due to the high intensity of the radiation source from the flaw detection, increasing the thickness of existing conventional shielding components can only reduce the interference slightly and cannot achieve effective shielding. Even if the intensity of nuclear radiation caused by flaw detection is reduced, the drastic changes in flaw detection radiation still cause the passive nuclear level gauge to fail to measure normally.

[0006] Existing technologies have also attempted to eliminate flaw detection interference by adjusting the pulse discrimination threshold in the electrical signal during flaw detection. However, since flaw detection interference basically overwhelms the usable discrimination range, simply adjusting the discrimination threshold has little effect.

[0007] Existing technologies have been exhausted, yet no effective solution has been found to address the problem of radiation interference during flaw detection. This forces users to either shut down level gauges during flaw detection operations or assume that all passive nuclear level gauge measurements are ineffective during this period. Current technologies lack effective solutions for addressing radiation interference during flaw detection in industrial settings, necessitating a technical solution capable of accurately measuring material levels even under flaw detection interference. Utility Model Content

[0008] The purpose of this application is to provide a passive nuclear level gauge with multiple photomultiplier tubes that resists radiation interference from flaw detection. It utilizes the characteristic that the radiation interference from flaw detection caused by the spatial shielding structure produces differences between at least one first scintillation crystal and at least one second scintillation crystal to identify and eliminate such interference. This enables the suppression of radiation interference, allowing for accurate measurement of material radiation even under flaw detection interference conditions. Furthermore, it can meet diverse needs for passive nuclear level gauges, including measuring weak signals and materials at greater distances, resisting interference other than flaw detection radiation interference, and providing precise analysis, through multiple operating modes.

[0009] To achieve the above objectives, this application provides a passive nuclear level gauge with multiple photomultiplier tubes to resist radiation interference from flaw detection, comprising: a radiation detection component including at least one first scintillation crystal and at least one second scintillation crystal, both of which are used to acquire nuclear radiation released from materials within a container; at least two photomultiplier tubes, each of the first and second scintillation crystals being optically coupled to one photomultiplier tube; at least two electrical signal acquisition modules, the input terminal of each electrical signal acquisition module being electrically connected to the output terminal of one photomultiplier tube, for acquiring and outputting corresponding electrical signals; a processing unit connected to each electrical signal acquisition module, for receiving electrical signals and calculating nuclear radiation data or level values; and a spatial shielding structure for at least partially blocking radiation from a preset flaw detection radiation interference source direction, so that when flaw detection radiation interference exists, the radiation characteristics characterized by the signals detected by the first and second scintillation crystals produce identifiable differences.

[0010] As described above, the spatial shielding structure includes: a first shielding component disposed between the first scintillation crystal and the second scintillation crystal; or, a second shielding component disposed on the circumferential side of the first scintillation crystal, wherein the second shielding component has a through-hole or opening on the side facing the container under test to allow nuclear radiation from the material inside the container under test to enter the first scintillation crystal; or, a third shielding component disposed on the circumferential side of the second scintillation crystal, wherein the third shielding component has a through-hole or opening on the side facing the container under test to allow nuclear radiation from the material inside the container under test to enter the second scintillation crystal; or, a first shielding component disposed between the first scintillation crystal and the second scintillation crystal, and a second shielding component disposed on the circumferential side of the first scintillation crystal, wherein the second shielding component faces the container under test. One side of the first scintillation crystal is provided with a through hole or opening that allows nuclear radiation from the material inside the container under test to enter the first scintillation crystal; or, a first shielding component is provided between the first scintillation crystal and the second scintillation crystal, and a third shielding component is provided on the circumferential side of the second scintillation crystal, with the third shielding component having a through hole or opening on the side facing the container under test that allows nuclear radiation from the material inside the container under test to enter the second scintillation crystal; or, a fourth shielding component is provided on the bottom surface of the first scintillation crystal away from the second scintillation crystal; or, a fifth shielding component is provided on the bottom surface of the second scintillation crystal away from the first scintillation crystal; or, a combination of the fourth shielding component and the first shielding component and / or the second shielding component; or, a combination of the fifth shielding component and the first shielding component and / or the third shielding component.

[0011] As described above, each first scintillation crystal is further provided with an independent first local shielding component. The first local shielding component is disposed on the circumferential side of the first scintillation crystal, and the side of the first local shielding component facing the container under test is provided with a through hole or opening that allows nuclear radiation of the material in the container under test to enter the first scintillation crystal. Each second scintillation crystal is further provided with an independent second local shielding component. The second local shielding component is disposed on the circumferential side of the second scintillation crystal, and the side of the second local shielding component facing the container under test is provided with a through hole or opening that allows nuclear radiation of the material in the container under test to enter the second scintillation crystal.

[0012] As described above, the adjacent first partial shielding component, second partial shielding component, first shielding component, second shielding component, third shielding component, fourth shielding component and / or fifth shielding component are integral structures; or, the adjacent first shielding component, second shielding component, third shielding component, fourth shielding component and / or fifth shielding component are integral structures.

[0013] As shown above, the first shielding component is a plate-shaped shielding component.

[0014] As shown above, the thickness of the plate-shaped shielding component ranges from 3mm to 200mm.

[0015] The beneficial effects achieved by this application are as follows: (1) The passive nuclear level gauge with multi-photomultiplier tubes that resists flaw detection interference in this application makes full use of the fact that flaw detection in industrial field is not carried out at the operating equipment but at the peripheral equipment. It utilizes the characteristic that the flaw detection radiation interference caused by the spatial shielding structure produces a difference in at least one first scintillation crystal and at least one second scintillation crystal to identify and eliminate flaw detection radiation interference, thereby obtaining the true nuclear radiation or accurate level value of the material in the container to be tested.

[0016] (2) The passive nuclear level gauge with multi-photomultiplier tubes that resists flaw detection interference in this application is equipped with an electrical signal synthesis module, a time coincidence module and / or an ADC sampling module, and a preset algorithm of the arithmetic processor. It can effectively eliminate or suppress flaw detection radiation interference. At the same time, the electrical signal synthesis module can be used to identify the weak nuclear radiation of the material, thereby making the passive nuclear level gauge measure farther. The time coincidence module or time radiation algorithm can be used to eliminate external interference generated by circuits, power supply and synchronization. The ADC sampling module can be used to achieve accurate analysis of the signal. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0018] Figure 1 A schematic diagram of the structure of Example 1 of a passive nuclear level gauge with multiple photomultiplier tubes to resist interference from flaw detection radiation; Figure 2 Schematic diagram of the structure of Example 2 of the passive nuclear level gauge with multiple photomultiplier tubes to resist interference from flaw detection radiation; Figure 3 Schematic diagram of the structure of Example 3 of a passive nuclear level gauge with multiple photomultiplier tubes to resist interference from flaw detection radiation; Figure 4 A schematic diagram of the structure of Example 4 of a passive nuclear level gauge with multiple photomultiplier tubes designed to resist interference from flaw detection radiation. Figure 5 A schematic diagram of the structure of Example 5 of a passive nuclear level gauge with multiple photomultiplier tubes designed to resist interference from flaw detection radiation. Figure 6 A schematic diagram of the structure of Example 6 of a passive nuclear level gauge with multiple photomultiplier tubes designed to resist interference from flaw detection radiation. Figure 7 A schematic diagram of the structure of Example 7 of a passive nuclear level gauge with multiple photomultiplier tubes designed to resist interference from flaw detection radiation. Figure 8This is an example of a passive nuclear level gauge with multiple photomultiplier tubes used in actual industrial field operation to resist interference from flaw detection radiation. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0020] During flaw detection operations in industrial settings, the high-energy X-rays or strong radioactive sources such as cobalt used can cause severe interference to passive nuclear level gauges. Even hundreds of meters away from the gauge's operating position, this can lead to measurement errors or even complete malfunction. Furthermore, because operators and equipment are constantly moving during actual flaw detection in industrial settings, the characteristics of the interference radiation are even more complex. Current technologies are essentially ineffective against flaw detection radiation interference.

[0021] like Figure 1 As shown, to solve the problem of radiation interference from industrial field flaw detection, this application provides a passive nuclear level gauge with multiple photomultiplier tubes to resist flaw detection radiation interference. The gauge includes: a radiation detection component, comprising at least one first scintillation crystal 1 and at least one second scintillation crystal 2, both used to acquire nuclear radiation released from materials within a container; at least two photomultiplier tubes 3, each first scintillation crystal 1 and each second scintillation crystal 2 being optically coupled to one photomultiplier tube 3; at least two electrical signal acquisition modules 4, each electrical signal acquisition module 4 having its input terminal electrically connected to the output terminal of one photomultiplier tube 3, used to acquire and output corresponding electrical signals; a processing unit 5, connected to each electrical signal acquisition module 4, used to receive electrical signals and calculate nuclear radiation data or level values; and a spatial shielding structure for at least partially blocking radiation from a preset flaw detection radiation interference source direction, so that when flaw detection radiation interference exists, the radiation characteristics characterized by the signals detected by the first scintillation crystal 1 and the second scintillation crystal 2 produce identifiable differences.

[0022] It should be noted that each electrical signal acquisition module 4 is connected to the processing processor 5, either directly or indirectly through the electrical signal synthesis module, timing module, or ADC sampling module described in this application. In other words, the electrical signals acquired by the electrical signal acquisition module 4 can be sent directly to the processing processor 5, or processed by other modules before being sent to the processing processor 5.

[0023] In practice, the path of electrical signal transmission acquired by the signal acquisition module can be changed by adding a signal switching component in order to achieve the goal of monitoring the signal.

[0024] Furthermore, the electrical signal acquisition module 4 in this application, as is common knowledge, can perform filtering, amplification, current or voltage signal discrimination, shaping, and other processing on the electrical signal, as is well known to those skilled in the art. When performing signal discrimination, one discrimination condition can be set, or multiple discrimination conditions can be set.

[0025] Specifically, both the first scintillation crystal 1 and the second scintillation crystal 2 are used to acquire nuclear radiation emitted by the material inside the container under test. In this application, the primary objective of both the first scintillation crystal 1 and the second scintillation crystal 2 is to measure the nuclear radiation emitted by the material inside the container, thereby achieving the measurement of the material level gauge within the container. Of course, in actual measurement, the first scintillation crystal 1 and the second scintillation crystal 2 will inevitably be affected to some extent by nuclear radiation emitted by the material inside the adjacent container or by cosmic environmental radiation. In practical applications, the specific number of the first scintillation crystal 1 and the second scintillation crystal 2 is set according to actual needs. It should be specifically noted that it is virtually impossible to eliminate interference from flaw detection radiation using only one scintillation crystal.

[0026] This application preferably uses a first scintillation crystal 1 and a second scintillation crystal 2 that are identical and arranged side-by-side in parallel. The scintillation crystal is a sensitive element for radiation detection, and its selection is crucial. The specific selection of the first scintillation crystal 1 and the second scintillation crystal 2 is determined according to actual needs. This application preferably uses a sodium iodide (thallium-doped) crystal, i.e., NaI(Tl) crystal. Sodium iodide (thallium-doped) has high gamma-ray blocking ability and excellent detection efficiency; it also has high luminous efficiency, capable of generating strong light signals; and the technology for obtaining sodium iodide (thallium-doped) is mature and the cost is relatively controllable. The dimensions of the first scintillation crystal 1 and the second scintillation crystal 2 are determined according to actual needs. This application preferably uses a diameter of 2 inches and a height of 2 inches. A larger scintillation crystal can capture more gamma photons, improving detection sensitivity, but it also increases cost and the overall size of the equipment. For the measurement of fly ash, the natural radioactivity of fly ash is usually sufficient to be effectively detected by a 2x2 inch NaI(Tl) crystal. Because NaI(Tl) crystals are highly hygroscopic, they must be sealed in a package. One end of the encapsulation shell has an optical glass window for optical coupling with the photomultiplier tube 3. The interior of the encapsulation shell is coated with a reflective layer (such as titanium dioxide) and an optically insulating layer to ensure that the scintillation photons generated by the scintillation are effectively guided to the photomultiplier tube 3. The shape of the encapsulation shell is determined according to actual needs; in this application, a cylindrical encapsulation shell is preferred. The material of the encapsulation shell is determined according to actual needs; in this application, an aluminum encapsulation shell or a stainless steel encapsulation shell is preferred.

[0027] A photomultiplier tube (PMT) is an extremely sensitive photoelectric conversion and signal amplification device. To ensure that scintillation photons can be efficiently transmitted from the scintillation crystal to the photocathode of the PMT, a high-transmittance silicone grease is coated between the optical glass window and the end face of the PMT. By filling the micron-sized air gaps with silicone grease, light loss caused by reflection can be avoided.

[0028] Furthermore, the spatial shielding structure includes: a first shielding component 6 disposed between the first scintillation crystal 1 and the second scintillation crystal 2, the positional relationship between the first shielding component 6 and the first scintillation crystal 1 and the second scintillation crystal 2 being as follows: Figure 1 As shown, it can also be as follows Figure 2 As shown, in both cases, the first scintillation crystal 1 and the second scintillation crystal 2 can effectively measure the nuclear radiation released from the material inside the container; or, the second shielding component 7, disposed on the circumferential side of the first scintillation crystal 1, such as... Figure 3 As shown, the second shielding component 7 has a through-hole or opening on the side facing the container under test, allowing nuclear radiation from the material inside the container to enter the first scintillation crystal 1; or, a third shielding component is disposed on the circumferential side of the second scintillation crystal 2, and the third shielding component has a through-hole or opening on the side facing the container under test, allowing nuclear radiation from the material inside the container to enter the second scintillation crystal 2; or, a first shielding component 6 is disposed between the first scintillation crystal 1 and the second scintillation crystal 2, and a second shielding component 7 is disposed on the circumferential side of the first scintillation crystal 1, as shown. Figure 4 As shown, the second shielding component 7 has a through-hole or opening on the side facing the container under test, allowing nuclear radiation from the material inside the container to enter the first scintillation crystal 1; or, the first shielding component 6 is disposed between the first scintillation crystal 1 and the second scintillation crystal 2, while a third shielding component is disposed on the circumferential side of the second scintillation crystal 2, and the third shielding component has a through-hole or opening on the side facing the container under test, allowing nuclear radiation from the material inside the container to enter the second scintillation crystal 2; or, a fourth shielding component 8 is disposed on the bottom surface of the first scintillation crystal 1 away from the second scintillation crystal 2, such as... Figure 5 As shown, in this spatial arrangement, the first scintillation crystal 1 and the second scintillation crystal 2 need to be positioned far apart; or, a fifth shielding component is positioned on the bottom surface of the second scintillation crystal 2, which is far apart from the first scintillation crystal 1; or, a combination of the fourth shielding component 8 with the first shielding component 6 and / or the second shielding component 7; or, a combination of the fifth shielding component with the first shielding component 6 and / or the third shielding component.

[0029] The specific materials of the first shielding component 6, the second shielding component 7, and the third shielding component are determined according to actual conditions; in this application, lead (Pb) is preferred. Lead (Pb) has a high atomic number (Z=82), a high density (11.34 g / cm³), a high linear attenuation coefficient for gamma rays, and is inexpensive and easy to process. The shielding performance of lead (Pb) follows the exponential attenuation law: I=I0*e^(-μx), where I is the intensity after penetration, I0 is the incident intensity, μ is the linear attenuation coefficient, x is the shielding thickness, and e is the base. For the 1.17 MeV and 1.33 MeV gamma rays emitted by cobalt-60, the μ values ​​of lead are 0.65 cm⁻¹ and 0.59 cm⁻¹, respectively. This means that a 50 mm thick lead plate can attenuate the intensity of 1.33 MeV gamma rays by approximately e^(-0.59*5)≈95%.

[0030] Furthermore, such as Figure 6 As shown, each first scintillation crystal 1 is further provided with an independent first local shielding component 10. The first local shielding component 10 is disposed on the circumferential side of the first scintillation crystal 1, and the side of the first local shielding component 10 facing the container under test is provided with a through hole or opening that allows the nuclear radiation of the material in the container under test to enter the first scintillation crystal 1. Each second scintillation crystal 2 is further provided with an independent second local shielding component 11. The second local shielding component 11 is disposed on the circumferential side of the second scintillation crystal 2, and the side of the second local shielding component 11 facing the container under test is provided with a through hole or opening that allows the nuclear radiation of the material in the container under test to enter the second scintillation crystal 2.

[0031] Specifically, the first partial shielding component 10 and the second partial shielding component 11 are used to shield against conventional environmental radiation, such as radiation from materials in adjacent containers or cosmic environment, except for interference from flaw detection radiation, when there is no flaw detection or during flaw detection. The function of the partial shielding components is the same as that of the shielding components in the passive nuclear level gauge in the prior art.

[0032] Furthermore, the specific shape of the first local shielding component 10 is set according to actual needs. In this application, it is preferred that the first local shielding component 10 is a lead plate component, disposed on the circumferential side of the first scintillation crystal 1 (except for the side facing the container under test), so that radiation from the direction of the container under test can enter the first scintillation crystal 1 without obstruction, while greatly attenuating radiation from other directions. The functions of the first local shielding component 10 include: 1. Reducing the environmental background: effectively shielding the natural background radiation from the surrounding environment (such as buildings, the ground, and other equipment), improving the signal-to-noise ratio; 2. Defending against multi-directional interference: able to resist flaw detection interference from almost all angles other than the direction of the container under test, greatly improving the robustness of the system; 3. Improving the energy spectrum response: by limiting the field of view of the detector, the contribution of Compton scattering events is reduced, which can improve the quality of the measured gamma energy spectrum to a certain extent.

[0033] Specifically, the second local shielding component 11 is used to shield against radiation from materials in adjacent containers or from the cosmic environment, except for radiation interference from the flaw detection process, when there is no flaw detection or during flaw detection.

[0034] Furthermore, the specific shape of the second local shielding component 11 is set according to actual needs. In this application, it is preferred that the second local shielding component 11 is a lead plate component, disposed on the circumferential side of the second scintillation crystal 2 (except for the side facing the container under test), so that radiation from the direction of the container under test can enter the second scintillation crystal 2 without obstruction, while greatly attenuating radiation from other directions. The functions of the second local shielding component 11 include: 1. Reducing the environmental background: effectively shielding the natural background radiation from the surrounding environment (such as buildings, the ground, and other equipment), improving the signal-to-noise ratio; 2. Defending against multi-directional interference: able to resist flaw detection interference from almost all angles other than the direction of the container under test, greatly improving the robustness of the system; 3. Improving the energy spectrum response: by limiting the field of view of the detector, reducing the contribution of Compton scattering events, the quality of the measured gamma energy spectrum can be improved to a certain extent.

[0035] Furthermore, the passive nuclear level gauge with photomultiplier tubes resistant to radiation interference from flaw detection also includes: a driving component 9, which is connected to a spatial shielding structure, a first local shielding component 10 and / or a second local shielding component 11. The processing unit 5 is configured to control the driving component 9 to drive the spatial shielding structure, the first local shielding component 10 and / or the second local shielding component 11 to move according to a preset trajectory, thereby adjusting their spatial position.

[0036] The drive component 9 can be a motor or a hydraulic probe, etc. Since the actual flaw detection process may occur randomly in any adjacent unit, the angle or path of the spatial shielding structure blocking the flaw detection radiation is also variable for the multi-probe passive nuclear level gauge with anti-flaw detection radiation interference of this application on the working unit. At some angles, the spatial shielding structure may block most of the radiation directed at the first scintillation crystal 1 or the second scintillation crystal 2, while at others it may only block a small portion. Clearly, during flaw detection, the more flaw detection radiation is blocked, the more significant the difference in effect on the first scintillation crystal 1 and the second scintillation crystal 2, and the more advantageous it is to identify this difference. Therefore, in practical use, the drive component 9 can be configured to maximize the blocking of flaw detection radiation interference by adjusting the spatial position of the spatial shielding structure. Figure 7 As shown, the driving component 9 can drive the second shielding component 7 to rotate along the side of the first scintillation crystal 1, thereby changing the spatial position of the second shielding component 7. In practice, if there are few adjacent units, several fixed angle positions can be preset. During flaw detection, the processing unit 5 controls the driving component 9 to adjust the spatial shielding mechanism to the preset fixed position. If there are many adjacent units on site, after the flaw detection working mode is activated, the processing unit 5 controls the driving component 9 to adjust to multiple positions, compare the actual shielding effect, and select the closest position from multiple positions. The optimal position is then searched again during the previous flaw detection.

[0037] Furthermore, adjacent first partial shielding component 10, second partial shielding component 11, first shielding component 6, second shielding component 7, third shielding component, fourth shielding component 8 and / or fifth shielding component are integral structures; or, adjacent first shielding component 6, second shielding component 7, third shielding component, fourth shielding component 8 and / or fifth shielding component are integral structures.

[0038] Specifically, the adjacent first partial shielding component 10, second partial shielding component 11, first shielding component 6, second shielding component 7, third shielding component, fourth shielding component 8 and / or fifth shielding component are integrated shielding bodies. The design and manufacturing process of the integrated shielding body, which designs the plate-shaped shielding component and the partial shielding component as a whole, has significant advantages: (1) Leak-free structure: It completely eliminates the assembly gap that may exist between the split shielding components; Gamma rays, especially high-energy rays, can penetrate tiny gaps, and the integrated shielding body can ensure the continuity of the shielding; (2) Excellent mechanical stability: The integrally cast or machined shielding body has a strong structure and is not easily deformed or displaced due to vibration, temperature changes or long-term use, which ensures the long-term stability of the detection geometry, which is crucial for the repeatability and accuracy of the measurement; (3) Thermodynamic properties: The integrated shielding body helps to evenly distribute and dissipate the heat generated in the shielding body due to radiation absorption.

[0039] Furthermore, integrated shielding bodies can be manufactured using casting, CNC machining, or welding processes.

[0040] Furthermore, the specific shape of the first shielding component 6 is set according to actual needs. In this application, it is preferred that the first shielding component 6 is a plate-shaped shielding component.

[0041] Furthermore, the specific dimensions of the plate-shaped shielding component are set according to actual needs. In this application, it is preferred that the thickness of the plate-shaped shielding component is 3mm to 200mm.

[0042] Specifically, when the thickness of the plate-shaped shielding component is 3mm-200mm, it covers various scenarios ranging from weak to extremely strong interference. A thickness of 3mm-20mm is suitable for low-energy flaw detection sources (such as selenium-75) or interference sources at very long distances, primarily providing basic asymmetry rather than absolute shielding. A thickness of 20mm-100mm is the most commonly used range; for example, 50mm of lead can generate a sufficiently significant differential signal for cobalt-60 flaw detection operations at a distance of 100 meters, while the equipment weight remains within acceptable limits. A thickness of 100mm-200mm is suitable for extreme cases, such as when the level gauge is installed very close to the flaw detection point, or when dealing with extremely high-activity radioactive sources. In these cases, the shielding component itself will be very heavy, requiring a special design for the installation structure. In practical implementation, a thickness of 50mm-100mm for the plate-shaped shielding component can handle the most flaw detection scenarios.

[0043] Furthermore, the passive nuclear level gauge with multiple photomultiplier tubes resistant to radiation interference from flaw detection also includes: an electrical signal synthesis module, wherein the electrical signal acquisition module 4 is connected to the processing processor 5 through the electrical signal synthesis module; multiple input terminals of the electrical signal synthesis module are respectively connected to the output terminals of at least two electrical signal acquisition modules 4 one-to-one, and the output terminal of the electrical signal synthesis module is connected to the processing processor 5; the electrical signal synthesis module is used to synthesize the electrical signals of at least two electrical signal acquisition modules 4 into one electrical signal and send it to the processing processor 5; and / or, the passive nuclear level gauge with multiple photomultiplier tubes resistant to radiation interference from flaw detection also includes: a time synchronization module, wherein the electrical signal acquisition module 4 is connected to the processing processor 5 through the time synchronization module; multiple input terminals of the time synchronization module are respectively connected to the output terminals of at least two electrical signal acquisition modules 4 one-to-one, and the output terminal of the time synchronization module is connected to the processing processor 5; the time synchronization module is used to discriminate the electrical signals of the electrical signal acquisition modules 4, based on the... At least two electrical signal acquisition modules 4 generate a single pulse signal from electrical signals with pulse times that match or are close to each other, and send it to the processing processor 5. Among these, electrical signals from at least two electrical signal acquisition modules 4 whose pulse times do not exceed a judgment threshold are considered to have pulse times that match or are close to each other. And / or, the anti-flaw detection radiation interference multi-photomultiplier tube passive nuclear level gauge also includes: an ADC sampling module, with the electrical signal acquisition modules 4 connected to the processing processor 5 via the ADC sampling module; the input terminal of the ADC sampling module is connected to the corresponding output terminal of each electrical signal acquisition module 4, and the output terminal of the ADC sampling module is connected to the processing processor 5; the ADC sampling module is used to analyze the pulse parameters of the electrical signals output by each electrical signal acquisition module 4, and sends the pulse parameters to the processing processor 5 via digital signals; wherein the pulse parameters include at least: time parameters, waveform characteristics, amplitude parameters, and noise-related parameters; the noise-related parameters are: signal-to-noise ratio and harmonic distortion.

[0044] Specifically, the passive nuclear level gauge with photomultiplier tubes that is resistant to radiation interference from flaw detection can add any one or two functional modules to the existing hardware, namely, an electrical signal synthesis module, a time synchronization module, and an ADC sampling module. Alternatively, it can add all three functional modules simultaneously.

[0045] Furthermore, the electrical signal synthesis module is an analog adder circuit, which includes: an operational amplifier, N independent input resistors, and a feedback resistor; the inverting input of the operational amplifier is connected one-to-one with the outputs of the N signal acquisition modules through the N independent input resistors, and the output of the operational amplifier is connected to the inverting input of the operational amplifier through the feedback resistor to form a negative feedback closed loop; the non-inverting input of the operational amplifier is connected to a reference voltage to achieve signal phase correction; the output of the operational amplifier is connected to the first electrical signal interface of the operational processor 5 to transmit the synthesized electrical signal to the operational processor 5.

[0046] Specifically, the electrical signal synthesis module can merge two or more pulse signals with similar timing into a single synthesized pulse signal. Since the first scintillation crystal 1 and the second scintillation crystal 2 respond identically to the same type of nuclear radiation, if the time interval between their detection of the same nuclear radiation is very short, a stronger pulse signal will be synthesized. For cases where the nuclear radiation source is a single source, differentiation can be achieved by examining the pulse's rising and falling edge characteristics, or by comparing the amplitudes of the corresponding pulse signals from the two scintillation crystals. Because signal synthesis creates a stronger pulse, the back-end processor will simultaneously include it in the counting cycle, classifying it more as a synthesized pulse and noise. The processing processor 5 can simultaneously process the electrical signals generated by the signal synthesis module and the individual first scintillation crystal 1 and second scintillation crystal 2. Because the first scintillation crystal 1 and the second scintillation crystal 2 respond identically to nuclear radiation, and the pulse amplitudes induced by the first scintillation crystal 1 and the second scintillation crystal 2 are the same, through experiments and statistics, pulses whose amplitudes in the synthesized pulse signal are a fixed ratio of the pulse amplitude of a single scintillation crystal (for example, the amplitude of two 1.5V pulse signals synthesized into a 3V pulse, which is twice the amplitude of a single scintillation crystal) can be considered as nuclear radiation data to be excluded. Signals with inconsistent nuclear radiation pulse amplitudes due to shielding interference from shielding components will not be counted because they do not conform to the synthesized pulse pattern. Therefore, situations where the first scintillation crystal 1 and the second scintillation crystal 2 respond inconsistently due to nuclear radiation interference can be identified, and nuclear radiation interference signals can be eliminated.

[0047] Furthermore, the timing matching module identifies the electrical signals from the selected electrical signal acquisition module 4: if at least two electrical signals have similar or identical pulse times, a composite pulse signal is generated and sent to the processing processor 5.

[0048] Specifically, the circuit architecture of the time synchronization module is as follows: Each input channel is first connected to a high-speed voltage comparator (such as the ADCOP60x series). This comparator compares the input analog pulse with a programmable discrimination threshold Vth. Pulses exceeding the discrimination threshold Vth are converted into a standard, fast-rising logic pulse (such as TTL or LVDS level). Since the arrival times of signals in different channels may have slight differences (due to cable length, circuit delay, etc.), one or more logic pulses need to be digitally delayed to align them in time. The aligned logic pulse is then fed into an AND gate circuit, which performs the judgment within a programmable time window (τ). This function is usually implemented by the logic unit inside the FPGA or CPLD. The time window setting needs to be greater than the system's timing jitter but much smaller than the random event acquisition module time, typically between 100ns and 1μs. The time synchronization module's immunity to radiation interference from flaw detection is achieved by forming a new pulse based on pulses with similar or identical times from the pulse signal acquisition modules of the two channels. Because the signal acquisition module has a certain pulse amplitude discrimination capability, it can send only pulses that meet the pulse statistical conditions to the time consistency module. However, due to the presence of the shielding component, the first scintillation crystal 1 and the second scintillation crystal 2 are affected by flaw detection radiation interference at different times, resulting in different flaw detection radiation pulse characteristics between the two among the pulses that meet the discrimination conditions. Furthermore, because the first scintillation crystal 1 and the second scintillation crystal 2 respond identically to the nuclear radiation pulses released from nuclear materials, their pulse timing characteristics are consistent among the pulses that meet the discrimination conditions. The time consistency module only counts pulses with similar or identical times, thereby accurately counting nuclear material radiation pulses and eliminating flaw detection radiation pulses, thus achieving the elimination or suppression of flaw detection radiation interference.

[0049] Furthermore, the ADC sampling module analyzes the pulse parameters of the electrical signals output by each electrical signal acquisition module 4, and sends the pulse parameters to the processing processor 5 via digital signals. The pulse parameters include: time parameters, waveform characteristics, amplitude parameters, and noise-related parameters (such as signal-to-noise ratio and harmonic distortion).

[0050] Specifically, the ADC sampling module, combined with Digital Pulse Shape Analysis (DPSA), forms the highest-level and most sophisticated anti-interference mode, elevating signal processing from the counting level to the waveform analysis level. Its system composition includes a high-speed ADC (the core being a high-speed ADC chip with at least two bits and a sampling rate of 14 bits or higher, such as the AD9245, responsible for real-time digitization of amplified and shaped analog pulses), a high-speed cache (such as a FIFO or DDR memory, used to temporarily store massive amounts of waveform data), and a powerful processing core (such as an FPGA, DSP, or high-performance ARM processor for real-time waveform data processing).

[0051] Furthermore, the arithmetic processor 5 has multiple preset operations, and the arithmetic processor 5 is configured to execute at least one of the multiple operations; the multiple operations include: a first operation, a second operation, a third operation, a fourth operation, and a fifth operation; the first operation is: the arithmetic processor 5 acquires pulse signals from each electrical signal acquisition module 4 to generate individual nuclear radiation data and / or total nuclear radiation data; the second operation is: the arithmetic processor 5 acquires pulse information from the electrical signal synthesis module to generate one nuclear radiation data; the third operation is: the arithmetic processor 5 acquires pulse information from the time matching module to generate one nuclear radiation data; the fourth operation is: after acquiring pulse signals from each electrical signal acquisition module 4, the arithmetic processor 5 filters out pulses with matching or similar times based on the recorded pulse times as nuclear radiation measurement data; electrical signals with time intervals between pulse times in each electrical signal acquisition module 4 that do not exceed a judgment threshold are considered pulses with matching or similar times; the fifth operation is: the arithmetic processor 5 filters and removes flaw detection interference pulses from the pulse data of the ADC sampling module to obtain total nuclear radiation data.

[0052] Furthermore, the processing processor 5 is configured to switch or select between multiple operating modes based on preset conditions or external commands. These operating modes include at least a normal operating mode and a flaw detection radiation interference operating mode. When the operating mode is normal operating mode, the processing processor 5 performs the first operation. When the operating mode is flaw detection radiation interference operating mode, the processing processor 5 performs the second, third, fourth, and / or fifth operations. Preset conditions include at least one of the following: the relationship or change between different nuclear radiation data sets meets preset requirements; the relationship or change between different total nuclear radiation data sets under different operations meets preset requirements; the environmental interference level meets preset requirements; the time condition meets preset requirements; or the processing processor 5 receives an external command signal. If any one of these conditions is met, flaw detection radiation interference is determined to exist on-site, and the processing processor 5 switches to the flaw detection radiation interference operating mode to perform nuclear radiation measurement. Users can also send external commands through the human-machine interface or buttons configured in this application, or through dedicated wired or wireless control devices, to initiate a specific operating mode.

[0053] The relationship or changes between the various nuclear radiation data meet preset requirements. Because the nuclear radiation released from the material has a consistent effect on each detector (the scintillation crystal, photomultiplier tube 3, and signal acquisition module connected in sequence), the nuclear radiation values ​​or changes in nuclear radiation values ​​of each detector are basically consistent in the first operating mode. If one detector's nuclear radiation value is greater than that of other detectors, it indicates that one detector may have abnormal noise interference, or if the change in nuclear radiation value measured by another detector is greater than that of other detectors, it indicates that that detector may have abnormal noise interference. For example, if the processing processor 5 is originally operating in the first operating mode, and if a detector value is 300 greater than that of other detectors, or the change is greater than that of other detectors by 20%, then the preset requirement is to activate the second operating mode to eliminate data distortion caused by abnormal detector noise or flaw detection interference.

[0054] In practical implementation, the processing processor 5 can simultaneously acquire the nuclear radiation data from each of the electrical signal acquisition modules 4 in the first operating mode, or the total nuclear radiation data generated based on the nuclear radiation data from each of the electrical signal acquisition modules 4 (this can be a direct sum of the nuclear radiation data from each signal, or the total nuclear radiation data can be generated by calculating the nuclear radiation data from each signal using other conventional methods). The total nuclear radiation data is the nuclear radiation data of the passive nuclear level gauge based on the material level it generates. In the second operating mode, the processor acquires the number of pulses from the electrical signal synthesis module that meet the time repetition requirements and the ADC sampling requirements, and generates the nuclear radiation data of the passive nuclear level gauge based on this number of pulses. However, whether to use the nuclear radiation data generated in the first operating mode or the nuclear radiation data generated in the second operating mode as the material nuclear radiation data or the basis data for generating the material level depends on the preset requirements after the preset conditions are met.

[0055] The relationship or change of total nuclear radiation data under each operation meets the preset requirements. Because the time matching scheme, electrical signal synthesis scheme, and ADC adoption scheme not only remove noise signals but also some material signals, the total nuclear radiation data of the passive nuclear level gauge is very small. If the total nuclear radiation data is too small, although the signal is clean, it no longer has the energy to identify material changes. Therefore, it can be preset in the second working mode that if the total nuclear radiation data of the passive nuclear level gauge is less than 300, the processing processor 5 starts the first working mode, or selects the nuclear radiation data generated in the first working mode as the passive nuclear level gauge data to generate the material level, thus better identifying material changes.

[0056] The environmental interference level has reached the preset requirements. Obviously, if the interference in the environment or the measurement environment reaches a certain level, such as when it is severe, the second operating mode will be activated to eliminate the noise caused by environmental interference. Environmental interference registration is usually provided by external sensor components responsible for monitoring the environment; for example, in the application of passive nuclear level gauges, a nuclear radiation detector is sometimes specifically configured to monitor environmental conditions. Classifying and labeling environmental interference is a common practice. When the environmental interference level is relatively low, or even nonexistent, the processing processor 5 can activate the first operating mode, or select the nuclear radiation data from the first operating mode as the nuclear radiation data for the passive nuclear level gauge to generate the material level.

[0057] The timing conditions meet the preset requirements. When noise or interference cannot be directly distinguished, the processor 5 can be preset to operate in a first working mode for a period of time, and then in a second working mode for a period of time, making it easier for users to distinguish the different data under the two working modes. Meanwhile, some interferences in industrial settings have temporal patterns; for example, flaw detection may occur at night, interfering with the operation of the passive nuclear level gauge. Therefore, the processor 5 can be preset to enter the second working mode at 8 PM and to switch to the first working mode at 6 AM when flaw detection work or the fan is turned off.

[0058] The comparison values ​​of nuclear radiation data in the two operating modes meet the preset requirements. The nuclear radiation data obtained in the first operating mode can be compared with the data in the second operating mode. For example, if the difference between the nuclear radiation data in the first operating mode and the second operating mode is greater than 600, it indicates that the interference is of a certain intensity. At this time, the second operating mode can be used, or the data in the second operating mode can be selected as the nuclear radiation data of the passive nuclear level gauge to generate material nuclear radiation or material level.

[0059] In actual implementation, a switching component can be used to change the electrical signal transmission path of each signal acquisition module, and the processing processor 5 can switch between various working modes.

[0060] like Figure 8 As shown, in actual industrial operations, flaw detection work is rarely performed on operating units. For example, it's impossible to perform flaw detection on the boiler of Unit 12 of a thermal power plant while it's running, but flaw detection is performed on the boiler of Unit 23 due to maintenance reasons. Figure 8As shown, due to the presence of the spatial shielding structure, namely the first shielding component 6, in the multi-probe passive nuclear level gauge of this application that resists radiation interference from the flaw detection, the flaw detection radiation from the thermal power plant boiler of Unit 2 13 directly radiates to the second scintillation crystal 2, while the first shielding component 6 blocks the flaw detection radiation from directly radiating to the first scintillation crystal 1. Obviously, the two scintillation crystals are significantly affected by the flaw detection radiation from the thermal power plant boiler of Unit 2 13. Such significant differences are eliminated by the passive nuclear level gauge's processing processor 5 and the configured functional modules, enabling the passive nuclear level gauge to achieve accurate measurement.

[0061] Obviously, since the primary function of the first scintillation crystal 1 and the second scintillation crystal 2 in this application is to measure the nuclear radiation released by the material, it is crucial that the nuclear radiation released by the material is not affected by the reception of the first scintillation crystal 1 and the second scintillation crystal 2. To achieve the claimed technical effect, the position of the passive nuclear level gauge relative to the material container 14 (i.e., the dust collector hopper of a thermal power plant) and other units (locations where potential interference from flaw detection radiation is foreseeable) is very important when using this application. When installing it on the container, it is essential to avoid the flaw detection radiation interference and the nuclear radiation from the material inside the container originating from the same direction.

[0062] Therefore, this application also provides a measurement method for a passive nuclear level gauge with multiple photomultiplier tubes resistant to radiation interference from flaw detection, comprising the following steps: S1: During installation and positioning, adjust the orientation of the aforementioned anti-flaw detection radiation interference multi-photomultiplier tube passive nuclear level gauge so that a portion of the spatial shielding structure can block the radiation propagation path between the preset flaw detection radiation interference source and the first scintillation crystal and / or the second scintillation crystal; the spatial shielding structure is: a first shielding component, or a second shielding component, or a third shielding component, or a first shielding component and a second shielding component, or a first shielding component and a third shielding component, or a fourth shielding component, or a fifth shielding component, or a combination of a fourth shielding component and a first shielding component and / or a second shielding component, or a combination of a fifth shielding component and a first shielding component and / or a third shielding component.

[0063] S2: Obtain the first detection signal through the photomultiplier tube of the first scintillation crystal; obtain the second detection signal through the photomultiplier tube of the second scintillation crystal.

[0064] S3: Based on the first and second detection signals, the difference in the radiation interference caused by the spatial shielding structure between the first and second detection signals is used to identify and eliminate the radiation interference, thereby obtaining the true nuclear radiation or accurate material level value of the material inside the container to be tested.

[0065] The beneficial effects achieved by this application are as follows: (1) The anti-flaw detection interference multi-photomultiplier tube passive nuclear level gauge and measurement method of this application fully utilizes the reality that flaw detection in industrial field is not carried out at the operating equipment but at the peripheral equipment. It utilizes the characteristic that the flaw detection radiation interference caused by the spatial shielding structure produces a difference in at least one first scintillation crystal and at least one second scintillation crystal to identify and eliminate flaw detection radiation interference, thereby obtaining the true nuclear radiation or accurate level value of the material in the container to be tested.

[0066] (2) The passive nuclear level gauge and measurement method of the multi-photomultiplier tube anti-flaw detection interference of this application, the configured electrical signal synthesis module, time coincidence module and / or ADC sampling module, and the preset algorithm of the computing processor can effectively eliminate or suppress flaw detection radiation interference. At the same time, the electrical signal synthesis module can be used to identify the weak nuclear radiation of the material, thereby making the passive nuclear level gauge measure farther. The time coincidence module or time radiation algorithm can be used to eliminate external interference generated by circuit, power supply and synchronization. The ADC sampling module can be used to achieve accurate analysis of the signal.

[0067] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the scope of protection of this application is intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application. Obviously, those skilled in the art can make various alterations and variations to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of protection of this application and its equivalents, this application also intends to include these modifications and variations.

Claims

1. A passive nuclear level gauge with multiple photomultiplier tubes resistant to radiation interference from flaw detection, characterized in that, include: The radiation detection assembly includes at least one first scintillation crystal and at least one second scintillation crystal, both of which are used to acquire nuclear radiation released from materials inside the container; At least two photomultiplier tubes, each of the first scintillation crystal and each of the second scintillation crystals being optically coupled to a photomultiplier tube; At least two electrical signal acquisition modules are provided, with the input terminal of each module electrically connected to the output terminal of a photomultiplier tube, for acquiring and outputting the corresponding electrical signals. The processing unit is connected to each electrical signal acquisition module and is used to receive electrical signals and calculate nuclear radiation data or material level values. A spatial shielding structure is used to at least partially block radiation from a preset flaw detection radiation interference source direction, so that when flaw detection radiation interference is present, the radiation characteristics characterized by the signals detected by the first scintillation crystal and the second scintillation crystal produce a identifiable difference.

2. The passive nuclear level gauge with multi-photomultiplier tube and anti-flaw detection radiation interference as described in claim 1, characterized in that, The spatial shielding structure includes: A first shielding component is disposed between the first scintillation crystal and the second scintillation crystal; Alternatively, a second shielding component is disposed on the circumferential side of the first scintillation crystal, and the second shielding component is provided with a through hole or opening on the side facing the container under test to allow nuclear radiation of the material in the container under test to enter the first scintillation crystal. Alternatively, a third shielding component is disposed on the circumferential side of the second scintillation crystal, and the third shielding component is provided with a through hole or opening on the side facing the container under test, allowing nuclear radiation of the material in the container under test to enter the second scintillation crystal. Alternatively, a first shielding component is disposed between the first scintillation crystal and the second scintillation crystal, and a second shielding component is disposed on the circumferential side of the first scintillation crystal, wherein the second shielding component is provided with a through hole or opening on the side facing the container under test, allowing nuclear radiation of the material in the container under test to enter the first scintillation crystal. Alternatively, a first shielding component is disposed between the first scintillation crystal and the second scintillation crystal, and a third shielding component is disposed on the circumferential side of the second scintillation crystal, wherein the third shielding component is provided with a through hole or opening on the side facing the container under test, allowing nuclear radiation of the material in the container under test to enter the second scintillation crystal. Alternatively, a fourth shielding component may be disposed on the bottom surface of the first scintillation crystal, away from the second scintillation crystal; Alternatively, a fifth shielding component may be disposed on the bottom surface of the second scintillation crystal, which is far from the first scintillation crystal; Alternatively, a combination of the fourth shielding component with the first shielding component and / or the second shielding component; Alternatively, a combination of the fifth shielding component with the first shielding component and / or the third shielding component.

3. The passive nuclear level gauge with multi-photomultiplier tube and anti-flaw detection radiation interference as described in claim 2, characterized in that, Each first scintillation crystal is further provided with an independent first local shielding component. The first local shielding component is disposed on the circumferential side of the first scintillation crystal, and the side of the first local shielding component facing the container under test is provided with a through hole or opening that allows nuclear radiation of the material in the container under test to enter the first scintillation crystal. Each second scintillation crystal is further provided with an independent second local shielding component. The second local shielding component is disposed on the circumferential side of the second scintillation crystal, and the side of the second local shielding component facing the container under test is provided with a through hole or opening that allows nuclear radiation of the material in the container under test to enter the second scintillation crystal.

4. The passive nuclear level gauge with multi-photomultiplier tube and anti-flaw detection radiation interference as described in claim 3, characterized in that, The adjacent first partial shielding component, second partial shielding component, first shielding component, second shielding component, third shielding component, fourth shielding component and / or fifth shielding component are an integral structure; Alternatively, the adjacent first shielding component, second shielding component, third shielding component, fourth shielding component and / or fifth shielding component may be an integral structure.

5. The passive nuclear level gauge with multi-photomultiplier tube and anti-flaw detection radiation interference as described in claim 1, characterized in that, The first shielding component is a plate-shaped shielding component.

6. The passive nuclear level gauge with multi-photomultiplier tube and anti-flaw detection radiation interference as described in claim 5, characterized in that, The thickness of the plate-shaped shielding component ranges from 3mm to 200mm.

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