Nondestructive testing device and method based on compact D-D neutron source and application

Abstract

The invention discloses a nondestructive testing device and method based on a compact D-D neutron source and application. According to the device, a compact D-D neutron source is used as exogenous neutrons, and 2.5 MeV D-D fast neutrons are moderated into thermal neutrons or epithermal neutrons through a neutron moderator located in front of a neutron generator. The moderated neutrons enter a horizontally-arranged conical neutron collimator, and the hole channel is small in front and large in rear. The collimated thermal neutron beam penetrates through an object to be detected, and thermal neutrons penetrating through the object are detected by a thermal neutron image detector system installed in front of the moderator and converted into a digital transmission image. The system obtains the two-dimensional spatial distribution of the thermal neutron transmission intensity and the material component content, so that the internal structure of the detected object and the spatial distribution characteristics of different materials are analyzed. The device has the advantages of portability, rapidness, accuracy, nondestructive testing and good spatial resolution, and is suitable for nondestructive testing of objects.

Description

Technical Field

[0001] The present invention belongs to the technical field of nondestructive testing of objects, and in particular relates to a nondestructive testing device, method and application based on a compact DD neutron source. Background Art

[0002] Neutron radiography is a nondestructive testing method based on neutron beams, mainly including neutron transmission imaging, neutron tomography imaging, neutron resonance imaging, neutron polarization imaging, neutron phase imaging, neutron holographic imaging, neutron small-angle scattering imaging and neutron coded imaging. Similar to common X-ray imaging, neutron radiography obtains the internal structure and defect information of the object being tested through the intensity change caused by the scattering or absorption effect when the neutron beam penetrates the object. Since the sensitivity of neutrons to different elemental substances is significantly different from that of X-rays, and the absorption coefficients of neutrons of different energies to various substances are different, neutron radiography has become an important supplement to X-ray imaging. In particular, low-energy neutron imaging can detect light elements and their defects wrapped by heavy elements, and can also distinguish isotopes and adjacent elements. PGNAA (Prompt Gamma Neutron Activation Analysis) is a non-destructive detection technology for elemental analysis. It determines the type and content of elements in the sample by measuring the prompt gamma rays released when neutrons interact with matter. This technology is widely used in environmental monitoring, material science, archaeology, medical diagnosis and other fields.

[0003] Since the discovery of neutrons, neutron photography technology has been widely developed and applied. The earliest neutron photography patents were independently proposed in Germany, France and the United States, and then scientists from various countries conducted in-depth research and improvements on the technology. British scientists successfully obtained neutron photography photos in the reactor for the first time, marking the practical application of neutron photography technology. Canada's NRAY company used reactor neutron sources to carry out thermal neutron photography, and provided technical support to Toyota, Rolls-Royce and other companies for engine imaging detection. The Phoenix Nuclear Physics Laboratory in the United States and its companies have developed a mobile thermal neutron photography system based on accelerator neutron sources, and provided technical support to the US military for non-destructive testing of pyrotechnics such as artillery shells. With the development of computer technology, images have gradually been stored digitally, allowing advanced imaging processing technology to be applied to quantitative analysis. The fast neutron photography research of the Model National Laboratory in the United States has achieved non-destructive testing of low atomic number materials wrapped by high atomic number materials. The Paul Scherrer Laboratory in Switzerland has developed standard samples for thermal neutron imaging and used them. 6Neutron radiography experiments were performed using a LiF-ZnS phosphor screen and a CCD camera detection system. The FRM-II reactor at the Technical University of Munich was used for a variety of neutron imaging methods, including transmission radiography and neutron tomography. AS Tremsin achieved high spatial resolution imaging using CERN's Medipix delay line readout technology, while the Paul Scherrer Laboratory in Switzerland further improved spatial resolution and neutron fluence rate by using a MICRO-CT detector system.

[0004] The problems with the existing technology are: the current neutron radiography system is mainly based on the reactor neutron source. Although it can provide a strong neutron field, this system has the defects of complex structure, high gamma background, large operating system, high cost, expensive operation and maintenance costs, and immobility. Therefore, the reactor-based neutron radiography system is difficult to meet the needs of convenient transmission detection in the fields of industrial manufacturing, aerospace, and shipbuilding. Secondly, the existing neutron radiography detectors usually use sealed neutron tubes. Although this vacuum-encapsulated miniature neutron generator has made certain progress in the 1950s and 1960s, it still has some problems. Although the neutron yield of the sealed neutron tube developed by France and the United States can reach 8×10 8 n / s, and a life span of more than 1000 hours. However, the neutron yield of sealed neutron tubes developed in China is relatively low, and the life span is only about 200-300 hours, which limits its application. The most successful application field of sealed neutron tubes is oil well logging, and in recent years they have also been used in the research of other neutron application technologies. However, due to the limitations of the neutron tube microstructure, the neutron yield is low and the life span is short, which cannot fully meet the high neutron yield requirements of neutron photography, neutron activation analysis, and nuclear fuel rod enrichment and uniformity detection. In addition, the existing neutron photography system has limited detection capabilities for the internal elemental composition and content of the sample, making it difficult to achieve efficient and accurate non-destructive testing, especially in multi-angle and multi-directional three-dimensional imaging and elemental analysis. There are obvious limitations. Summary of the invention

[0005] The purpose of the present application is to solve the problems raised in the above-mentioned background technology, and to provide a non-destructive testing device, method and application based on a compact DD neutron source.

[0006] In order to achieve the above objectives, this application adopts the following technical solutions:

[0007] A nondestructive testing device based on a compact DD neutron source, comprising a DD neutron generator, a neutron moderator, a collimating channel and a neutron imaging sample platform;

[0008] The DD neutron generator is placed inside the neutron moderator, the front end of the neutron moderator is connected to the collimating channel, and the three are arranged in sequence along the propagation direction of the neutron beam;

[0009] The neutron imaging sample platform includes a rotating sample stage, a γ spectrum detector system, 6 LiF fluorescence conversion screen, reflector, EMCCD camera, dark box and sample stage control cabinet, the rotating sample stage is arranged above the γ spectrum detector system, the 6 The LiF fluorescence conversion screen, the reflector and the EMCCD camera are arranged in the dark box, and the sample stage control cabinet is arranged on one side of the dark box.

[0010] In the above technical solution, the collimating channel is located 5 cm in front of the neutron source emission point of the DD neutron generator.

[0011] In the above technical solution, the collimation channel is in the shape of a truncated cone, consisting of two parallel circular bottom surfaces and a side surface connecting them, forming a cone-shaped structure, and the diameter of the circular bottom surface close to the DD neutron generator side is smaller than the diameter of the circular bottom surface close to the neutron imaging sample platform side.

[0012] In the above technical solution, the thickness of the neutron moderator is 50 cm, and it has three layers, the first layer is a graphite layer, the second layer is boron-containing polyethylene, and the third layer is polyethylene.

[0013] In the above technical solution, the 6 The LiF fluorescence conversion screen is located right in front of the collimating channel.

[0014] In the above technical solution, a roller for moving the neutron imaging sample platform is provided below the neutron imaging sample platform.

[0015] In the above technical solution, an optical lens is arranged on the CCD camera.

[0016] In the above technical solution, the adjustable range between the gamma energy spectrum detector system and the rotating sample stage is 10-20 cm.

[0017] In the above technical solution, the rotating sample stage is connected to a PLC motor control system for realizing remote control of the rotation angle and the platform lifting distance, and the PLC motor control system is arranged in the sample stage control cabinet.

[0018] In the above technical solution, the gamma detector used in the gamma spectrum detector system is one of high-purity germanium, CZT, sodium iodide, BGO, sodium bromide and other detectors.

[0019] A nondestructive testing method based on a compact DD neutron source is as follows: a compact DD neutron source is used as an external neutron source, and the output 2.5 MeV DD fast neutrons are slowed down into thermal neutrons or epithermal neutrons through a neutron moderator, and then the collimated thermal neutron beam is transmitted through a horizontally arranged tapered neutron collimation channel with a small front and a large rear, and a transmission image is detected by a thermal neutron image detector system, thereby obtaining the internal structure and material distribution of the object being detected. During use, a rotating sample stage and a gamma spectrum detector system can be controlled to photograph samples from multiple angles and analyze the element composition and content in the samples.

[0020] The present invention further provides the application of the above-mentioned nondestructive testing device and method based on a compact DD neutron source in nondestructive testing using the spatial intensity distribution of transmitted thermal neutrons.

[0021] Beneficial effects:

[0022] The present invention discloses a nondestructive testing device, method and application based on a compact DD neutron source. The present invention adopts a neutron radiography device based on a DD neutron generator. Compared with the traditional system based on a reactor neutron source, the device structure is greatly simplified and the operation and maintenance costs are significantly reduced. Through a compact neutron source and an optimized neutron collimation channel, the device can flexibly adapt to the needs of convenient transmission detection in the fields of industrial manufacturing, aerospace, etc., while providing high-resolution and fast imaging capabilities. The neutron yield of the accelerator is 2×10 10 n / s, the energy is 2.5MeV, and the neutron injection rate can reach 10 after passing through the moderator 4 n / (cm 2 s), and more than 90% of the neutrons measured by the multi-sphere spectrometer are thermal neutrons. The controllable sample platform and gamma spectrum detector system enable it to achieve multi-angle and multi-directional three-dimensional imaging and element analysis, thereby providing detailed internal structure and element composition data. These advantages effectively overcome the limitations of complex structure, high cost and restrictive application in existing technologies, and provide an important technical foundation and practical value for the further development and application of neutron radiography technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of a movable neutron radiography device based on a DD neutron generator provided in an embodiment of the present invention.

[0024] Figure 2 It is a schematic diagram of the structure of a neutron imaging sample platform provided in an embodiment of the present invention.

[0025] Figure 3 It is a flow chart of a movable neutron radiography method based on a DD neutron generator provided in an embodiment of the present invention.

[0026] Components and reference numerals: 1. DD neutron generator; 2. Neutron moderator; 3. Collimation channel; 4. Neutron imaging sample platform, 401, rotating sample stage, 402, γ spectrum detector system, 403, 6 LiF fluorescence conversion screen, 404, reflecting mirror, 405, EMCCD camera, 406, dark box, 407, sample stage control cabinet. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] Example

[0029] This embodiment provides a nondestructive testing method based on a compact DD neutron source. Figure 3 The system uses a DD neutron generator to generate external neutrons, and the DD neutron yield is greater than 10 10 n / s, and thermal neutrons account for more than 90%. The 2.5MeV DD fast neutrons are slowed down into thermal neutrons or epithermal neutrons by the neutron moderator located in front of the neutron generator. The moderated neutrons enter the horizontally arranged collimated channel, which is small in the front and large in the back. The collimated thermal neutron beam passes through the object to be detected. The thermal neutrons after passing through the object are detected by the thermal neutron image detector system installed in front of the neutron imaging sample platform and converted into a digital transmission image. The system includes a rotating sample stage, which can shoot samples from multiple angles to achieve three-dimensional reconstruction of the samples. In addition, the sample stage can be placed with a gamma energy spectrum detector system for non-destructive testing of the elements and their contents inside the object. Finally, the system obtains the two-dimensional spatial distribution of the thermal neutron transmission intensity, thereby analyzing the internal structure of the object to be detected and the spatial distribution characteristics of different materials.

[0030] The detection device used to implement the above detection method refers to Figure 1A nondestructive testing device based on a compact DD neutron source includes a DD neutron generator 1, a neutron moderator 2, a collimating channel 3, and a neutron imaging sample platform 4. The DD neutron generator 1 is placed in the neutron moderator 2, and can effectively slow down 2.5 MeV DD fast neutrons into thermal neutrons, with the thermal neutrons accounting for more than 90%. The neutron moderator 2 is composed of three layers of materials: the innermost layer is a graphite layer, the outer layer is wrapped with a boron-containing polyethylene layer, and the outermost layer is a common polyethylene layer. The combination of the graphite layer, the boron-containing polyethylene and the polyethylene layer is used to effectively slow down and absorb fast neutrons. A 50 cm long collimating channel 3 is provided at the front end of the moderator. The channel is a hollow structure, and the thickness of the channel can be adjusted by placing polyethylene blocks of different thicknesses in the channel, so as to obtain the required collimated parallel neutron beam. The neutron imaging sample platform 4 is located in front of the collimating channel 3, and the distance can be adjusted according to the required collimation ratio. The neutron imaging sample stage 4 achieves multi-angle imaging of the sample by placing the sample to be tested on the rotating sample stage 401. The gamma spectrum detector system 402 is located below the rotating sample stage, with an adjustable distance range of 10cm-20cm, and is used to detect the elemental composition in the sample.

[0031] During the detection process, the dark box 406 on one side accommodates the EMCCD camera 405, the reflector 404 and 6 LiF fluorescence conversion screen 403, these components together form a thermal neutron imaging detector. 6 LiF interacts and undergoes nuclear reaction 6 Li+n→ 3 H+ 4 He+4.78MeV generates charged particles t and α particles. Charged photons deposit energy in the ZnS crystal, stimulating atoms to emit fluorescence. The light signal is transmitted to the EMCCD camera 405 through the reflector 404, and the EMCCD camera obtains the transmission image information of the sample to be tested. The neutron imaging information of the sample at multiple angles is captured by the rotating sample stage 401, and finally a three-dimensional reconstruction of the sample is formed. Behind the dark box 406 is a sample stage control cabinet 407, which integrates various sample stage control systems and can be remotely controlled in conjunction with the PLC to prevent people from being harmed by neutron radiation.

[0032] The above-mentioned nondestructive testing device and method based on a compact DD neutron source can realize high-resolution neutron imaging by using transmitted thermal neutrons, and accurately analyze the elemental composition and content of the sample through a gamma energy spectrum detector system for nondestructive testing applications.

[0033] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A nondestructive testing device based on a compact DD neutron source, characterized in that: Including DD neutron generator, neutron moderator, collimation channel and neutron imaging sample platform; The DD neutron generator is placed inside the neutron moderator, the front end of the neutron moderator is connected to the collimating channel, and the three are arranged in sequence along the propagation direction of the neutron beam; The neutron imaging sample platform includes a rotating sample stage, a γ spectrum detector system, 6 LiF fluorescence conversion screen, reflector, EMCCD camera, dark box and sample stage control cabinet, the rotating sample stage is arranged above the γ spectrum detector system, the 6 The LiF fluorescence conversion screen, reflector and EMCCD camera are placed in a dark box. 6 The LiF fluorescence conversion screen is located right in front of the collimating channel, and the sample stage control cabinet is arranged on one side of the dark box.

2. A nondestructive testing device based on a compact DD neutron source according to claim 1, characterized in that: The collimating hole is located 5 cm in front of the neutron source emission point of the DD neutron generator.

3. A nondestructive testing device based on a compact DD neutron source according to claim 1, characterized in that: The collimating channel is in the shape of a truncated cone, consisting of two parallel circular bottom surfaces and a side surface connecting them, forming a cone-shaped structure, and the diameter of the circular bottom surface close to the DD neutron generator side is smaller than the diameter of the circular bottom surface close to the neutron imaging sample platform side.

4. A nondestructive testing device based on a compact DD neutron source according to claim 1, characterized in that: The neutron moderator has a thickness of 50 cm and has three layers, the first layer is a graphite layer, the second layer is boron-containing polyethylene, and the third layer is polyethylene.

5. The nondestructive testing device based on a compact DD neutron source according to claim 1, characterized in that: A roller for moving the neutron imaging sample platform is arranged below the neutron imaging sample platform.

6. A nondestructive testing device based on a compact DD neutron source according to claim 1, characterized in that: The adjustable range between the gamma energy spectrum detector system and the rotating sample stage is 10-20 cm.

7. The nondestructive testing device based on a compact DD neutron source according to claim 1, characterized in that: The rotating sample stage is connected to a PLC motor control system for remotely controlling the rotation angle and the platform lifting distance. The PLC motor control system is disposed in a control cabinet of the sample stage.

8. The nondestructive testing device based on a compact DD neutron source according to claim 1, characterized in that: The gamma detector used in the gamma energy spectrum detector system is one of high-purity germanium, CZT, sodium iodide, BGO or sodium bromide detectors.

9. A nondestructive testing method based on a compact DD neutron source, characterized in that: A compact DD neutron source is used as an external neutron source. The output 2.5MeV DD fast neutrons are slowed down into thermal neutrons or epithermal neutrons through a neutron moderator. The collimated thermal neutron beam is then transmitted through a horizontally arranged tapered neutron collimation channel with a small front and a large back. The thermal neutron image detector system detects the transmission image, and then the internal structure and material distribution of the object being inspected are obtained. During use, the rotating sample stage and the gamma spectrum detector system are controlled to shoot samples from multiple angles and analyze the element composition and content in the samples.

10. Application of the nondestructive testing device based on a compact DD neutron source as claimed in any one of claims 1 to 8 or the nondestructive testing method based on a compact DD neutron source as claimed in claim 9 in nondestructive testing using the spatial intensity distribution of transmitted thermal neutrons.

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