CN112764080A - Nuclide detection device and nuclide detection method - Google Patents
Nuclide detection device and nuclide detection method Download PDFInfo
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- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
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Abstract
The invention discloses a nuclide detection device and a nuclide detection method, wherein the device comprises the following components: an inverse compton scattering gamma ray source for generating monochromatic, bi-color or polychromatic gamma rays; the first shielding body is provided with a first opening through which gamma rays pass; the second shielding body is provided with a second opening for allowing gamma rays to pass through, the detected sample is positioned between the first opening and the second opening, and the gamma rays irradiate the detected sample from one side of the first shielding body, which is far away from the detected sample, along the axis of the first opening through the first opening; the detection sheet is positioned on one side of the second shielding body far away from the detected sample so as to receive the gamma rays passing through the second opening; and the detector is positioned between the second shielding body and the detection piece and used for receiving the nuclear resonance fluorescence photons generated by the detection piece. By adopting the technical scheme of the invention, on one hand, direct contact with the detected sample is not needed, on the other hand, the detection efficiency is improved by utilizing bicolor or multicolor gamma rays, and the high-efficiency indirect nondestructive detection of the detected sample is realized.
Description
Technical Field
The invention relates to the technical field of material detection, in particular to a nuclide detection device and a nuclide detection method based on gamma rays.
Background
The detection of the composition and content of substances is an important and indispensable means for people to recognize the objective existence, and is widely applied to industry and daily life. For example, in the nuclear power industry, radioactive substances contained in the spent fuel need to be detected to ensure the subsequent proper treatment of the spent fuel; in the security inspection of airports, ports and stations, necessary detection of articles and cargos is required to ensure public security and the like.
In the industrial field, nuclear energy as a clean energy without carbon emission can replace fossil energy to meet the requirements of production and domestic electricity of the country and the society. However, the radioactivity of the spent fuel generated by the nuclear power station has a great damage effect on the nature, and the total amount of the spent fuel generated by various nuclear power stations in China per year reaches about 1200 tons only in 2019. Radioactive elements such as uranium-235 and plutonium-239 contained in the spent fuel need to be properly treated and monitored, otherwise, the environment and the production and the life of residents are seriously influenced. Therefore, the harmful radioactive substances contained in the spent fuel must be detected in terms of content and the like so as to ensure accurate and correct treatment and supervision.
A nuclide refers to an atom having a number of protons and a number of neutrons. Nuclei of the same isotope with different nuclear properties have the same proton number and different neutron number, and have different structural modes, thereby showing different nuclear properties. Therefore, in the case of radioactive materials, the detection of nuclides can be performed by directly acting on the radioactive materials themselves, bypassing the influence of isotopes, and the most accurate results can be obtained.
At present, there are two methods for detecting the nuclear element in the spent fuel. The first method is to sample the spent fuel by a radiochemical analysis method and prepare a solution, and then to chemically analyze the sample solution containing the elements of the spent fuel to obtain the contents of various nuclides. Although the method has high precision of the content of the obtained nuclide, the sampling operation is complicated and has safety problems due to the high radioactivity of the spent fuel, and the radioactive hazard caused by the loss of the sample and the like also exist in the process of sampling the spent fuel.
The second method is to measure the decay gamma line of cesium, strontium and other elements in fission products of the spent fuel to analyze the radionuclide content of the spent fuel. Although safer than the first method, the accuracy is low and no specific content of nuclides can be given.
In addition, in the daily life field of people, security inspection equipment commonly used in customs and airports generally performs transmission imaging on objects such as goods and sealed containers by using an X-ray attenuation imaging principle. The two-dimensional image of the detected object can be obtained by the transmission imaging method, security personnel can judge whether the detected object contains contraband articles such as smuggled articles or explosives and the like according to the two-dimensional image, but the transmission method cannot effectively detect the objects sealed in materials with strong attenuation such as lead elements and the like.
Therefore, how to effectively detect the substance, especially the nuclide, contained in the sample to be detected without damage is an urgent problem to be solved.
Disclosure of Invention
In view of the above, the present invention provides a nuclide detection apparatus and a nuclide detection method, so as to achieve effective nondestructive detection of nuclides contained in a detected sample, so as to ensure that harmful substances and substances that are restricted for transportation and use in the industrial field and the civil field can be accurately identified, thereby ensuring safe production and the safety of lives and properties of people.
The technical scheme of the invention is realized as follows:
a nuclide detection apparatus for detecting a nuclide contained in a sample to be detected, comprising:
an inverse-Compton scattering ICS gamma-ray source for generating gamma-rays;
the first shielding body is provided with a first opening through which gamma rays generated by the gamma ray source pass;
the second shielding body is provided with a second opening through which the gamma ray passes, the second opening and the first opening are coaxial, the sample to be detected is positioned between the first shielding body and the second shielding body, the axis of the first opening and the axis of the second opening pass through the sample to be detected, and the gamma ray for performing detection is irradiated on the sample to be detected from one side of the first shielding body, which is far away from the sample to be detected, along the axis of the first opening through the first opening;
the detection sheet is positioned on one side of the second shielding body far away from the detected sample so as to receive the gamma rays passing through the second opening;
a detector positioned between the second shield and the test strip to receive nuclear resonance fluorescence photons generated by the test strip.
Further, the number of the detectors is multiple, the detectors are distributed in a ring shape, the center of the ring shape is coaxial with the second opening, so that gamma rays passing through the second opening pass through the center of the ring shape to directly irradiate the detection sheet;
the detector is provided with a photon collection surface, the photon collection surface faces the detection piece, and an included angle of 30-90 degrees is formed between the photon collection surface and the axis of the second opening hole.
Further, on the axis of the second opening, the distance between the detector and the detection sheet is at least 1/(γ sin (α)) of the distance between the generation point of the gamma ray and the detector, where γ is the ratio of electron beam energy and electron rest energy used for generating the gamma ray in the ICS gamma ray source, and α is the included angle between the photon collection surface and the axis of the second opening.
Further, the material of the first shield and the second shield is a high-density attenuation material.
Further, the thickness of the first shield is: a thickness of the gamma ray at which an intensity of the gamma ray after passing through the first shield body in a thickness direction of the first shield body is attenuated by at least 99%;
the thickness of the second shielding body is as follows: the intensity of the gamma ray after passing through the second shield body in the thickness direction of the second shield body is attenuated by at least 99%.
Further, the size of the first aperture and the second aperture is 1/gamma of the distance from the first aperture to the gamma ray generating point, wherein gamma is the ratio of the electron beam energy of the inverse Compton scattering gamma ray source to the electron rest energy.
Further, the gamma ray is a monochromatic gamma ray, and the detection sheet contains at least one known nuclide.
Further, the gamma ray is a bicolor gamma ray, and the detection sheet contains at least one known nuclide; or,
the gamma ray is multicolor gamma ray, and the detection sheet contains at least one known nuclide.
A nuclide detection method using the nuclide detection apparatus as set forth in any one of the above, comprising:
placing a sample to be tested on the axis of the first and second openings between the first and second shields;
irradiating gamma rays to the detected sample from the side of the first shielding body far away from the detected sample through the first opening;
detecting nuclear resonance fluorescence photons generated by the detection sheet by using the detector;
and determining the species and the content of nuclides contained in the detected sample according to the characteristic peak intensity of the nuclear resonance fluorescence photon energy spectrum.
Further, the method further comprises:
moving the sample to be detected in a direction perpendicular to the axes of the first and second openings during detection of nuclear resonance fluorescence photons of the detection piece by the detector to record characteristic peak intensities of the nuclear resonance fluorescence photon energy spectrum at different positions of the sample to be detected;
and determining the position distribution of nuclides contained in the detected sample according to the characteristic peak intensities of the nuclear resonance fluorescence photon energy spectrum recorded at different positions of the detected sample.
According to the nuclide detection device and the nuclide detection method, the detected sample is directly placed between the first shielding body and the second shielding body without directly contacting the detected sample, the detected sample is not required to be cut or chemically refined, the detected sample is not damaged, the nondestructive detection of the detected sample is realized, the radioactive risk of the operator due to the direct operation of the detected sample is reduced for high-radioactivity harmful substances, and the safety production and the life and property safety of people are guaranteed. The nuclide detection device and the nuclide detection method provided by the invention are combined with the narrow-bandwidth gamma ray generated by the inverse Compton scattering gamma ray source, so that the species, the content and the spatial position distribution of the nuclide in the detected sample can be accurately identified, the nuclide identification precision is improved, the species, the content and the spatial position distribution of at least two nuclides can be accurately identified at one time by combining the bicolor or multicolor gamma ray, and the nuclide identification efficiency is improved.
Drawings
FIG. 1 is a schematic diagram of a nuclide detection apparatus according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view of a probe and second opening and test piece in an embodiment of the invention;
FIG. 3 is a flowchart illustrating a nuclide detection method according to an embodiment of the present invention.
In the drawings, the names of the components represented by the respective reference numerals are as follows:
1. ICS gamma ray source
2. First shield
21. First opening hole
3. Second shield
31. Second opening hole
4. Detection piece
5. Detector
51. Photon collection surface
6. Sample to be tested
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and examples.
The nuclear resonance fluorescence physical process is a process that atomic nuclei enter an excited state after absorbing an incident gamma photon through resonance, and the atomic nuclei in the excited state are demagnetized to a ground state through different nuclear energy level paths to generate one or more outgoing photons with specific energy. Because the nuclear energy level energy of different atomic nuclei is different, the resonance absorption and the photon energy generated in the nuclear resonance fluorescence process of different nuclear species are different, and therefore the nuclear resonance fluorescence photons can be identified as the characteristic information of the atomic nuclei. Therefore, the gamma ray is used for irradiating the detected sample to excite the nuclide in the detected sample to generate a nuclear resonance fluorescence physical process, and the number of resonance fluorescence photons generated in the nuclear resonance fluorescence physical process is measured, so that the specific content of the nuclide in the detected sample (such as spent fuel, goods and the like) can be analyzed. Compared with the existing method, the measurement method utilizing the nuclear resonance fluorescence physical process is safer and more reliable because the sampling process of the detected sample does not exist in the whole measurement process.
Gamma-ray sources commonly used for nuclear resonance fluorescence physics are bremsstrahlung sources. The bremsstrahlung source has the characteristics of high energy and wide energy spectrum range of generated photons, and has the defects of long detection time, poor signal-to-noise ratio and the like when measuring nuclear resonance fluorescence photons due to low brightness. The inverse Compton scattering source has the characteristics of high brightness, narrow bandwidth, small scattering angle, high collimation, high energy, controllable and adjustable polarization and the like. Therefore, the gamma photons generated by the inverse Compton scattering source can be used for irradiating the object to be detected (the sample to be detected), and the nuclide characteristic identification can be carried out by measuring the resonance fluorescence photons generated by the nuclein in the object to be detected.
In addition, the nuclear energy level of the atomic nucleus is high, and the energy of nuclear resonance fluorescence photons generated by excitation after being excited by high-energy gamma rays is also high. The attenuation coefficient of high-energy photons in a material is generally smaller than that of low-energy photons, so that only a small part of nuclear resonance fluorescence photons are attenuated when passing through a sealing material such as lead. Therefore, the object in the sealing material can be irradiated by gamma photons generated by the single-energy gamma ray source, and the distribution condition of nuclides in the object can be analyzed by using the detector to record the space distribution of the generated nuclear resonance fluorescence photons, so that the problem that the object sealed in materials with strong attenuation, such as lead element, and the like can not be effectively detected by a transmission method is solved.
Based on the above theory, the embodiment of the present invention provides a nuclide detection apparatus for detecting nuclides contained in a detected sample 6, as shown in fig. 1, the nuclide monitoring apparatus includes an ICS (Inverse Compton Scattering) gamma ray source 1, a first shield 2, a second shield 3, a detection sheet 4, and a detector 5. The ICS gamma ray source 1 is configured to generate gamma rays, where the gamma rays are monochromatic gamma rays generated by the ICS gamma ray source 1 and/or two-color gamma rays generated simultaneously and/or multi-color gamma rays generated simultaneously, that is, the gamma rays generated by the ICS gamma ray source 1 may be monochromatic gamma rays, two-color gamma rays, or multi-color gamma rays. The first shield 2 defines a first opening 21 for passing gamma rays. The second shielding body 3 is provided with a second opening 31 for passing gamma rays, the second opening 31 and the first opening 21 are coaxial, the detected sample 6 is located between the first shielding body 2 and the second shielding body 3, the axes of the first opening 21 and the second opening 31 pass through the detected sample 6, and gamma rays (indicated by dotted arrows in fig. 1) generated by the inverse compton scattering gamma ray source and used for detection are irradiated on the detected sample 6 (located on the right side of the first shielding body 2 in fig. 1) from one side (located on the left side of the first shielding body 2 in fig. 1) of the first shielding body 2, which is far away from the detected sample 6, along the axis of the first opening 21 through the first opening 21, to the detected sample 6 (located on the right side of the first shielding body 2 in fig. 1). The detection sheet 4 is located on a side of the second shield 3 away from the sample 6 to be detected (a right side of the second shield 3 in fig. 1) to receive the gamma rays passing through the second opening 31 (the sample 6 to be detected is located on a left side of the second shield 3 in fig. 1). The detector 5 is positioned between the second shield 3 and the detection plate to receive nuclear resonance fluorescence photons generated by the detection plate 4.
Referring to fig. 2 in combination with fig. 1, in an alternative embodiment, the number of the detectors 5 is multiple, and the plurality of detectors 5 are distributed in a ring shape, wherein the center of the ring shape is coaxial with the second opening 31, so that the gamma ray passing through the second opening 31 passes through the center of the ring shape to directly irradiate the detection sheet 4. Meanwhile, each detector 5 has a photon collection surface 51, the photon collection surface 51 faces the detection sheet 4, and a first included angle θ is formed between the photon collection surface 51 and the axis of the second opening 31, in an alternative example, the first included angle θ is 30 ° to 90 °, and in a preferred example, the first included angle θ is 60 °.
In an alternative embodiment, the distance between the detector 5 and the detection sheet 4 is determined according to the size of the detector 5 and the intensity of the nuclear resonance fluorescence received from the detection sheet 4, and in some embodiments, the distance between the detector 5 and the detection sheet 4 on the axis of the second opening 31 is at least 1/(γ sin (α)) of the distance between the generating point of the gamma ray and the detector, where γ is the ratio of the electron beam energy and the electron rest energy used for generating the gamma ray in the ICS gamma ray source, and α is the angle between the photon collecting surface 51 and the axis of the second opening 31, for example, in one embodiment, the distance between the detector 5 and the detection sheet 4 on the axis of the second opening 31 is 20 cm.
In the embodiment of the present invention, the first shielding body 2 and the second shielding body 3 are made of high-density attenuation materials, in an alternative embodiment, the first shielding body 2 and the second shielding body 3 are made of lead bricks, and the lead bricks with sufficient thickness can perform a good blocking and isolating function on gamma rays.
The thickness of the lead bricks of the first shield 2 and the second shield 3 is required to ensure that gamma rays cannot pass through, and in an alternative embodiment, the thickness of the first shield 2 and the second shield 3 is determined according to the intensity of the gamma rays. Wherein, the thickness of the first shield 2 is: the thickness of the gamma ray when the intensity of the gamma ray passing through the body of the first shield 2 in the thickness direction of the first shield 2 is attenuated by at least 99%, that is, the intensity of the gamma ray having an intensity of 100% passing through the body of the first shield 2 is reduced to 1% or less than 1%. The thickness of the second shield 3 is: the thickness of the gamma ray when the intensity of the gamma ray passing through the second shield 3 body in the thickness direction of the second shield 3 is attenuated by at least 99%, that is, the intensity of the gamma ray having an intensity of 100% passing through the second shield 3 body is reduced to 1% or less than 1%. In some embodiments, the first shield 2 and the second shield 3 are at least 11.5 cm thick when lead is used for gamma photons having an energy of 2 MeV.
According to the principle of inverse Compton scattering of electrons and photons in physics, the energy spectrum width of gamma rays passing through the first opening 21 and the second opening 12 is related to the aperture size of the openings, the smaller the aperture of the first opening 21 is, the narrower the energy spectrum width of gamma rays passing through the first opening 21 is, the smaller the aperture of the second opening 31 is, the narrower the energy spectrum width of gamma rays passes through the second opening 31 is, the range of excited nuclides is more concentrated, and the detected nuclides are more targeted, for example, the nuclide detection only aiming at uranium-235 and plutonium-239 can be realized, meanwhile, the detection precision can be improved by the gamma rays with narrow bandwidth, and the mutual influence between the fluorescence spectra of various nuclides in nuclear resonance fluorescence generated by the gamma rays with wide bandwidth simultaneously exciting multiple nuclides can be avoided. The aperture size of the first and second openings 21 and 31 is related to the distance between the generation point of the gamma ray (located in the gamma ray source) and the sample 6 to be tested, and in an alternative embodiment, the radius of the first and second openings 21 and 31 is 1/γ of the distance between the generation point of the gamma ray and the sample to be tested, wherein γ is the ratio of the electron beam energy to the electron rest energy of the inverse-compton scattering gamma ray source (i.e. the ratio between the electron beam energy and the electron rest energy of the inverse-compton scattering gamma ray source). The second opening 31 has an aperture corresponding to the first aperture.
In an alternative embodiment, the gamma rays generated by the gamma ray source (directly) irradiate the detection sheet 4, and a nuclear resonance fluorescence process is generated on the detection sheet 4.
By adopting the nuclide detection device based on gamma rays, disclosed by the embodiment of the invention, various purposes of nuclide detection can be realized by combining gamma rays in different forms.
In an alternative embodiment, where the gamma ray is a monochromatic gamma ray, the detection sheet 4 contains at least one known nuclear species.
In another alternative embodiment, the gamma rays are bi-color gamma rays and the detection patch 4 contains at least one known nuclear species. When the gamma rays are two-color gamma rays and the detection sheet 4 contains a known nuclide corresponding to a certain single-color gamma ray in the two-color gamma rays, the detection of the known nuclide can be realized; when the gamma ray is a dual-color gamma ray and the detection sheet 4 contains two or more known nuclides at the same time (two known nuclides correspond to the dual-color gamma ray), the detection of the two known nuclides can be realized.
In yet another alternative embodiment, the gamma rays are polychromatic gamma rays and the detection plate 4 contains at least one known nuclear species. When the gamma rays are multi-color gamma rays and the detection sheet 4 contains a known nuclide corresponding to a certain single-color gamma ray in the multi-color gamma rays, the detection of the known nuclide can be realized; when the gamma rays are multicolor gamma rays and the detection sheet 4 simultaneously contains two known nuclides (the two known nuclides correspond to two monochromatic gamma rays in the multicolor gamma rays), the detection of the two known nuclides can be realized; when the gamma ray is a polychromatic gamma ray and the detection sheet 4 contains three or more known nuclides (three known nuclides correspond to three monochromatic gamma rays in the polychromatic gamma ray), the detection of the three known nuclides can be realized.
In some alternative embodiments, the gamma ray source may be an inverse compton scattering source, a bremsstrahlung source, or the like. Currently, gamma ray sources used for nuclear resonance fluorescence physics processes include the inverse compton scattering source and the bremsstrahlung radiation source. The Inverse Compton Scattering (ICS) refers to a scattering process in which high-energy electrons collide with low-energy photons to make the low-energy photons obtain energy, and the inverse compton effect causes the photons to obtain energy to cause a wavelength to be shortened, so that the low-energy photons are changed into high-energy gamma rays. Bremsstrahlung refers to radiation generated by the sudden deceleration of high-speed electrons, and broadly refers to radiation emitted by charged particles during collisions, particularly coulomb scattering between them. The inverse compton scattering source has the advantages of narrow bandwidth and high brightness compared with the bremsstrahlung source. Because the nuclear energy level energy difference of different nuclides is large, generally, a single-energy gamma ray generated by the inverse-Compton scattering gamma ray source can only excite one nuclear energy level of one nuclide at the same time, however, the energy of different clusters of electron beams or laser beams interacting with each other can be adjusted to simultaneously generate a bicolor gamma ray and a multicolor gamma ray with different central energies, so that the generated bicolor gamma ray and the multicolor gamma ray can be used for simultaneously exciting different nuclides in an object to be detected, and the nuclide identification and detection efficiency can be improved. Therefore, in a preferred embodiment, the gamma ray source is an ICS gamma ray source to enable the generation of monochromatic gamma rays, bi-chromatic gamma rays, and polychromatic gamma rays.
On the basis of the nuclide detection apparatus in the foregoing embodiment, an embodiment of the present invention further provides a nuclide detection method, as shown in fig. 3, which mainly includes the following steps:
step 1, placing a sample to be detected on the axes of a first opening and a second opening between a first shielding body and a second shielding body;
and 4, determining the species and the content of the nuclide contained in the detected sample according to the characteristic peak intensity of the nuclear resonance fluorescence photon energy spectrum.
The species and the content of the nuclide contained in the detected sample can be obtained through the steps.
In a further alternative embodiment, the nuclide detection method described above further includes the following processes performed simultaneously in step 4:
in the process of detecting the nuclear resonance fluorescence photons of the detection piece by using the detector, moving the detected sample in the direction vertical to the axes of the first opening and the second opening so as to record the characteristic peak intensity of the nuclear resonance fluorescence photon energy spectrum at different positions of the detected sample;
and determining the position distribution of nuclides contained in the detected sample according to the characteristic peak intensity of the nuclear resonance fluorescence photon energy spectrum recorded at different positions of the detected sample.
Due to the possible non-uniformity of the distribution of the nuclide in the detected sample, when the detected sample moves to different positions, the characteristic peak intensities of the nuclear resonance fluorescence photon energy spectrum generated by the detection sheet recorded by the detector are different, and the position distribution of the nuclide contained in the detected sample can be determined according to the different characteristic peak intensities.
With the above alternative embodiment, in addition to the species and content of the nuclide contained in the test sample, the distribution of the nuclide in the test sample can be further obtained. By adopting the mode, dangerous nuclides (such as various heavy metal radioactive dangerous substances) can be timely found from various articles in important high-safety scenes such as customs, airports, hospitals and the like, even if the dangerous nuclides are coated in shielding materials such as lead and the like, as long as the gamma rays used for detection can penetrate through the shielding materials, the detection of the dangerous nuclides can be realized, meanwhile, the detection of at least two dangerous nuclides can also be realized by utilizing multicolor gamma rays, and the detection efficiency is improved.
The first embodiment is as follows: monochromatic gamma ray
The compact inverse Compton scattering gamma source is used for generating high-brightness gamma rays, the gamma rays pass through the first opening 21 of the first shielding body 2 and irradiate on the detected sample 6, and the gamma rays passing through the detected sample 6 pass through the second opening 31 of the second shielding body 3 and irradiate on the detection sheet 4. The detector 5 is used to detect various signal photons generated by the detector plate 4.
The spectral width of the gamma ray irradiated on the sample 6 to be detected is related to the aperture size of the first opening 21, and the smaller the diameter of the first opening 21, the narrower the spectral width of the gamma ray, thereby realizing a narrow bandwidth.
After the energy level of the nuclide in the detected sample 6 is subjected to resonance absorption, photons in the gamma ray within a specific energy range (about eV) can be absorbed, so that the intensity of the photons in the specific energy range after the gamma ray passes through the detected sample 6 can be reduced, and the intensity change of the photons and the mass fraction of the nuclide in the detected sample 6 are in an exponential decay relationship.
The gamma ray generated by the gamma ray source (directly) irradiates the detection sheet 4, and a nuclear resonance fluorescence process is generated on the detection sheet 4.
When the nuclide contained in the detection sheet 4 is the same as the nuclide to be detected in the detected sample 6, the gamma ray irradiated on the detection sheet 4 after passing through the detected sample 6 can generate a nuclear resonance fluorescence process of the same nuclide, and the detector 5 can record a gamma photon signal generated by the nuclear resonance fluorescence of the detection sheet 4. The intensity of the photons in the specific energy range in the gamma ray irradiated on the detection sheet 4 after being absorbed by the detected sample 6 is reduced, and the nuclear resonance fluorescence signal detected by the detector 5 is also reduced correspondingly. The magnitude of the nuclear resonance fluorescence signal recorded by the detector 5 is therefore related to the mass fraction content of the nuclear species in the sample 6 being examined. The gamma ray generated by the inverse Compton scattering gamma ray source irradiates on the detection sheet 4, a nuclear resonance fluorescence process is generated on the detection sheet 4, namely, the energy of the gamma ray generated by the inverse Compton scattering gamma ray source corresponds to the energy absorbed by the nuclear resonance fluorescence process of the nuclide in the detection sheet 4, therefore, if the nuclide contained in the detection sheet 4 is different from the nuclide to be detected in the detected sample 6, when the gamma ray passes through the detected sample 6, the detected sample 6 will not generate a nuclear resonance fluorescence process, when the gamma ray passes through the detected sample 6, the gamma ray will not generate a nuclear resonance fluorescence process, photons in a specific energy range in the gamma ray will not be absorbed by the detected sample 6 due to the nuclear resonance fluorescence process, further, the intensity of the gamma rays irradiated on the detection sheet 4 within a specific energy range is not changed, and the nuclear resonance fluorescence signal detected by the detector 5 is not reduced. Therefore, if the nuclear resonance fluorescence signal detected by the detector 5 does not decrease after the sample 6 is placed, it indicates that the nuclear species in the detection piece 4 is not present in the sample 6. When the detection sheet 4 and the gamma ray corresponding to the detection sheet are used for detecting whether a certain dangerous nuclear species exists in the detected sample 6, if the intensity of the characteristic peak in the nuclear resonance fluorescence photon energy spectrum generated by the detection sheet 4 recorded by the detector 5 is not changed, the existence of the nuclear species in the detected sample 6 is indicated.
The second shielding body 3 can shield scattered photons generated by the irradiation of gamma rays on the detected sample 6, and prevent the scattered photons generated by the detected sample 6 from irradiating on the detector 5.
The thickness of the detection sheet 4 is optimized after the relative position of the detector 5 and the detection sheet 4 is fixed. When the thickness of the detection sheet 4 changes, the number of nuclear resonance fluorescence photons recorded by the detector 5 also changes, and when the thickness of the detection sheet 4 approaches infinity, the number of nuclear resonance fluorescence photons recorded by the detector 5 is a theoretical maximum value (the theoretical maximum value can be obtained by calculation). The thickness D of the detection sheet 4 corresponding to a certain proportion of the number of nuclear resonance fluorescence photons recorded by the detector 5 to the theoretical maximum value is taken. The magnitude of D is generally related to the density of the species in the detection patch 4, the distance of the detection patch 4 from the detector 5, depending on the particular parameters. In a specific embodiment, the density of the test piece 4 is 19.5 g/cm3And when the distance from the detection sheet 4 to the detector 5 is 20 cm, the number of nuclear resonance fluorescence photons recorded by the detector 3 is 90% of the theoretical maximum value, and D can be 11 mm.
In the above, the theoretical maximum value means: the maximum number of nuclear resonance fluorescence photons obtained on the detector 5 when the thickness of the detection plate 4 tends to infinity.
In the above, the ratio of the nuclear resonance fluorescence photon maximum recorded by the detector 4 can be specified according to the specific use condition, and in the preferred embodiment of the present invention, the value is 90%.
After the thickness D of the test strip 4 is determined, the presence of an optimum thickness H of the test sample 6 enables the detector 5 to record a maximum nuclear resonance fluorescence signal.
Example two: bicolor or polychromatic gamma rays
After the detected sample 6 is irradiated by the bicolor or multicolor gamma rays generated by the inverse Compton scattering gamma ray source, different nuclides in the detected sample 6 are respectively excited to generate a nuclear resonance fluorescence physical process.
The bi-color or multi-color gamma ray generated by the gamma ray source (directly) irradiates the detection sheet 4, and a nuclear resonance fluorescence process is generated on the detection sheet 4.
When the nuclide to be detected in the detected sample 6 is the same as the nuclide contained in the detection sheet 4, the two-color or multi-color gamma ray passes through the detected sample 6, passes through the second opening 31 of the second shielding body 3, and then irradiates the detection sheet 4. In this situation, nuclear resonance of the nuclear species in the sample 6 absorbs a part of photons with specific energy of the bi-or multi-color gamma ray, so that the number of nuclear resonance fluorescence photons generated in the physical process of nuclear resonance fluorescence of the detection sheet 4 per unit time is reduced, which results in the number of nuclear resonance fluorescence photons recorded by the detector 5 being reduced. Therefore, the nuclear resonance fluorescence signal recorded by the detector 5 has a magnitude related to the content of the nuclide to be detected in the detected sample 6, i.e., the higher the content of the nuclide to be detected in the detected sample 6 is, the smaller the nuclear resonance fluorescence signal recorded by the detector 5 is. The narrow bandwidth bi-color or multi-color gamma rays can simultaneously excite two or more different nuclear species to generate nuclear resonance fluorescence processes, thereby generating nuclear resonance fluorescence photons with different energies. If the nuclide contained in the detection sheet 4 is different from the nuclide to be detected in the detected sample 6, when the two-color or multi-color gamma ray passes through the detected sample 6, the detected sample 6 does not generate a nuclear resonance fluorescence process, the two-color or multi-color gamma ray passes through the detected sample 6 without generating the nuclear resonance fluorescence process, photons in a specific energy range in the two-color or multi-color gamma ray are not absorbed by the detected sample 6, the intensity of the two-color or multi-color gamma ray irradiated on the detection sheet 4 is not weakened due to the nuclear resonance fluorescence process in the detected sample 6, and a nuclear resonance fluorescence signal detected by the detector 5 is not reduced. Therefore, if the nuclear resonance fluorescence signal detected by the detector 5 does not decrease after the sample 6 is placed, it indicates that the nuclear species in the detection sheet 4 does not exist in the sample 6, and if the detection sheet 4 and the gamma ray corresponding to the detection sheet 4 are used to detect whether there is any dangerous nuclear species in the sample 6, the intensity of the characteristic peak in the nuclear resonance fluorescence photon energy spectrum generated by the detection sheet 4 recorded by the detector 5 does not change, it indicates that there is no such nuclear species in the sample 6.
The nuclear resonance fluorescence photons with different energies are detected by the detector 5, and the specific species of the nuclide in the detected sample 6 can be deduced by analyzing the characteristic peak in the photon energy spectrum recorded by the detector 5, so that the species (determined by the characteristic peak of the energy spectrum), the content (determined by the intensity of the characteristic peak of the energy spectrum) and the spatial position distribution (obtained by moving the detected sample 6 in the direction perpendicular to the axes of the first opening 21 and the second opening 31 to obtain the nuclide distribution at different positions) of the object to be detected are measured by using the bicolor or multicolor gamma rays generated by the inverse compton scattering gamma ray source.
By adopting the nuclide detection device and the nuclide detection method provided by the embodiment of the invention, the detected sample is only required to be directly placed between the first shielding body and the second shielding body, the detected sample is not required to be directly contacted, the operations of cutting or chemical refining and the like are not required to be carried out on the detected sample, the detected sample is not damaged, the nondestructive detection on the detected sample is realized, the radioactive risk of directly operating the detected sample on an operator is reduced for harmful substances with high radioactivity, and the safety production and the life and property safety of people are guaranteed. The nuclide detection device and the nuclide detection method provided by the embodiment of the invention are combined with the narrow-bandwidth gamma ray generated by the inverse Compton scattering gamma ray source, can accurately identify the species, content and spatial position distribution of the nuclide in the detected sample, improve the nuclide identification precision, and can accurately identify the species, content and spatial position distribution of at least two nuclides at one time by combining the bicolor or multicolor gamma ray, thereby improving the nuclide identification efficiency.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A nuclide detection apparatus for detecting a nuclide contained in a sample to be detected, comprising:
an inverse-Compton scattering ICS gamma-ray source for generating gamma-rays;
the first shielding body is provided with a first opening through which the gamma ray passes;
the second shielding body is provided with a second opening through which the gamma ray passes, the second opening and the first opening are coaxial, the sample to be detected is positioned between the first shielding body and the second shielding body, the axis of the first opening and the axis of the second opening pass through the sample to be detected, and the gamma ray for performing detection is irradiated on the sample to be detected from one side of the first shielding body, which is far away from the sample to be detected, along the axis of the first opening through the first opening;
the detection sheet is positioned on one side of the second shielding body far away from the detected sample so as to receive the gamma rays passing through the second opening;
a detector positioned between the second shield and the test patch to receive nuclear resonance fluorescence photons generated by the test patch.
2. The nuclide detection apparatus according to claim 1, characterized in that:
the number of the detectors is multiple, the detectors are distributed in a ring shape, the center of the ring shape is coaxial with the second opening, so that gamma rays passing through the second opening pass through the center of the ring shape to directly irradiate the detection sheet;
the detector is provided with a photon collection surface, the photon collection surface faces the detection piece, and an included angle of 30-90 degrees is formed between the photon collection surface and the axis of the second opening hole.
3. The nuclide detection apparatus according to claim 2, characterized in that:
on the axis of the second opening, the distance between the detector and the detection sheet is at least 1/(γ sin (α)) of the distance between the generation point of the gamma ray and the detector, wherein γ is the ratio of electron beam energy and electron rest energy used for generating the gamma ray in the ICS gamma ray source, and α is the included angle between the photon collection surface and the axis of the second opening.
4. The nuclide detection apparatus according to claim 1, characterized in that:
the material of the first shield and the second shield is a high-density attenuation material.
5. The nuclide detection apparatus according to claim 4, characterized in that:
the thickness of the first shielding body is as follows: a thickness of the gamma ray at which an intensity of the gamma ray after passing through the first shield body in a thickness direction of the first shield body is attenuated by at least 99%;
the thickness of the second shielding body is as follows: the intensity of the gamma ray after passing through the second shield body in the thickness direction of the second shield body is attenuated by at least 99%.
6. The nuclide detection apparatus according to claim 1, characterized in that:
the radius of the first opening and the second opening is 1/gamma of the distance between the generation point of the gamma ray and the detected sample, wherein gamma is the ratio of the electron beam energy of the inverse Compton scattering gamma ray source to the electron rest energy.
7. The nuclide detection apparatus according to claim 1, characterized in that:
the gamma ray is a monochromatic gamma ray, and the detection sheet contains at least one known nuclide.
8. The nuclide detection apparatus according to claim 1, characterized in that:
the gamma ray is a bicolor gamma ray, and the detection sheet contains at least one known nuclide; or,
the gamma ray is multicolor gamma ray, and the detection sheet contains at least one known nuclide.
9. A nuclide detection method using the nuclide detection apparatus as set forth in any one of claims 1 to 8, comprising:
placing a sample to be tested on the axis of the first and second openings between the first and second shields;
irradiating gamma rays to the detected sample from the side of the first shielding body far away from the detected sample through the first opening;
detecting nuclear resonance fluorescence photons generated by the detection sheet by using the detector;
and determining the species and the content of nuclides contained in the detected sample according to the characteristic peak intensity of the nuclear resonance fluorescence photon energy spectrum.
10. A nuclide detection method as in claim 9, the method further comprising:
moving the sample to be detected in a direction perpendicular to the axes of the first and second openings during detection of nuclear resonance fluorescence photons of the detection piece by the detector to record characteristic peak intensities of the nuclear resonance fluorescence photon energy spectrum at different positions of the sample to be detected;
and determining the position distribution of nuclides contained in the detected sample according to the characteristic peak intensities of the nuclear resonance fluorescence photon energy spectrum recorded at different positions of the detected sample.
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