Nuclear fuel element detection device and method based on gamma ray imaging and neutron activation

Abstract

The invention discloses a nuclear fuel element detection device and method based on gamma ray imaging and neutron activation, and relates to the technical field of nuclear fuel element detection, the detection device comprises a mechanical structure, a shielding structure, a transmission structure and a measurement control structure; the mechanical structure comprises a support assembly. The shielding structure comprises a first lead chamber, a second lead chamber and a third lead chamber which are installed on the support assembly at intervals. The transmission structure comprises a span bridge installed on the support assembly, an objective table is installed on the span bridge, and the objective table moves on the span bridge through power provided by a traction structure. The span bridge is provided with a limiting sensor used for providing position information of the objective table. The measurement control structure comprises a PLC control system. According to the device and the method, the neutron activation technology and the gamma ray imaging technology are integrated, and the 235U uniformity and the enrichment degree of the fuel element can be accurately and rapidly detected.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear fuel element detection, and in particular to a nuclear fuel element detection device and method based on gamma ray imaging and neutron activation. Background Art

[0002] Nuclear fuel elements are the core components of the reactor. Under normal operating conditions, nuclear fuel elements need to withstand high temperatures, high pressures, strong radiation, etc. When serving under such extreme conditions, the pellets inside the fuel elements are prone to swelling. As the fuel consumption increases, the swelling increases, causing deformation and cracking, internal defects, and even cladding damage, posing a serious threat to the safe operation of the reactor. In addition, due to the differences in the enrichment of nuclear fuel elements used in different reactor types, nuclear fuel element factories must produce nuclear fuel pellets with different enrichments to meet demand. When loading nuclear fuel pellets, there is a high probability of mixing due to certain reasons, resulting in abnormal pellets in the nuclear fuel elements. Later, during the operation of the reactor, due to these abnormal pellets and 235 Hot spots caused by uneven U enrichment are likely to cause swelling or even rupture of fuel elements, contaminating the coolant and causing shutdown. 235 The uniformity test of U is a very important quality control link to ensure the safe and reliable operation of fuel elements in the reactor. 235 The uniformity of U is 100% inspected.

[0003] In many standards for fuel elements, there are provisions for gamma or neutron scanning inspections of their uniformity and enrichment. For example, in the EJ / T 495-1989 standard, it is necessary to test the enrichment of fuel rods; EJ / T 323-1998 clearly stipulates that the quality inspection of fuel assemblies requires gamma or neutron scanning of fuel rods; EJ / T 497-1989 stipulates that fuel rods need to be gamma scanned; EJ / T 781-1993 stipulates the uniformity test of plate materials. In 1999, the EJ / T 1084-1998 standard, which was compiled based on the US ANSI N15.36-94 "Measurement Control and Assurance of Nondestructive Analysis of Nuclear Materials", was promulgated as a guiding document for the establishment, maintenance and supervision of nondestructive analysis measurement and control of fuel elements.

[0004] Domestic and foreign scholars have developed a variety of methods to detect 235 The uniformity and enrichment of U can be mainly divided into several methods according to the principle: passive detection method, neutron activation method, neutron fission method and neutron imaging method.

[0005] Patent CN212460062U discloses a nuclear fuel rod based on a DD neutron source 235The U enrichment and uniformity detection device comprises a compact DD neutron source, a neutron moderator, a γ shielding body, a nuclear fuel rod transmission channel and a γ detector system. The compact DD neutron source is wrapped with a hydrogen-containing neutron moderator, and the neutron moderator is wrapped with a γ shielding body. A nuclear fuel rod transmission channel is arranged in the neutron moderator above the compact DD neutron source, and a γ detector system is installed at the end of the nuclear fuel rod transmission channel.

[0006] The main problems of current fuel detection devices are poor integration of the detection system, low detection efficiency, and the inability of nuclide detection to achieve deterministic quantitative analysis. Summary of the invention

[0007] Based on the current fuel detection device, it is difficult to realize the fuel element 235 The problem of rapid qualitative and quantitative detection of the uniformity and enrichment of U is solved. The purpose of the present invention is to provide a nuclear fuel element detection device and method based on gamma-ray imaging and neutron activation. The device and method combine neutron activation technology and gamma-ray imaging technology to achieve rapid qualitative and quantitative detection of the uniformity and enrichment of U. 235 Rapid qualitative and quantitative detection of U uniformity and enrichment.

[0008] The present invention is achieved through the following technical solutions:

[0009] In a first aspect, the present application provides a nuclear fuel element detection device based on gamma ray imaging (GTR) and neutron activation (NAA), including a mechanical structure, a shielding structure, a transmission structure and a measurement control structure;

[0010] The mechanical structure includes a bracket assembly;

[0011] The shielding structure comprises a first lead chamber, a second lead chamber and a third lead chamber installed on the bracket assembly at intervals;

[0012] The transmission structure includes a span bridge installed on the bracket assembly, a loading platform is installed on the span bridge, and the loading platform moves on the span bridge through the power provided by the traction structure; a limit sensor for providing position information of the loading platform is installed on the span bridge.

[0013] Furthermore, the upper portion of the bridge is configured to be in the shape of a groove, the loading platform is installed in the groove and moves in the groove, and the groove of the bridge serves as a moving guide rail for the loading platform.

[0014] Furthermore, a rectangular groove is provided on the stage, and the component to be tested is placed flat on the stage; and a traction hole for connecting a traction wire rope is respectively provided at both ends of the stage.

[0015] Furthermore, notches are provided at both ends and the middle of the loading platform.

[0016] Furthermore, the detector installed in the second lead chamber is a panel-type detector with two upper and lower pieces, and the detector is provided with a through hole for the component to be tested.

[0017] Furthermore, the first lead chamber is used to achieve shielding against neutrons; the second lead chamber is used to shield gamma rays in the environment to reduce background interference; and the third lead chamber is used to achieve shielding against gamma rays.

[0018] In a second aspect, the present application provides a method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation, comprising the following steps:

[0019] The fuel element to be tested is first moved by the conveying structure to the third lead chamber for gamma transmission imaging;

[0020] Then it moves to the first lead chamber for neutron activation, and after cooling, it moves to the second lead chamber for delayed gamma measurement;

[0021] The gamma transmission imaging results and delayed gamma measurement results are transmitted to the computer in real time. After being analyzed by the detection algorithm, the uniformity test results of the components to be tested are qualitatively and quantitatively analyzed.

[0022] Among them, the NAA analysis method needs to slow down the fast neutrons to the thermal neutron energy range, use the Monte Carlo MCNP simulation program to select the type of moderator material, and reasonably combine the moderator materials to increase the proportion of thermal neutron injection rate; select appropriate shielding materials and sizes through simulation calculations to reduce the background radiation around the detector and protect the dose safety of the staff.

[0023] Among them, GTR imaging detection requires the irradiation of a gamma radiation source. The key point of the gamma radiation source shielding structure lies in the collimation and shielding of gamma rays. The purpose of collimation is to make the fuel element to be inspected evenly irradiated. The shielding is to reduce the interference to the NAA detector and the dose exposure to the staff. The Monte Carlo MCNP simulation program is used to select the gamma source shielding material and shielding structure.

[0024] Furthermore, the uniformity detection method of the element to be tested includes characterizing the distribution of the material by measuring the transmission intensity I at each position in the imaging and forming a grayscale image, or characterizing the uniformity of uranium distribution by forming a thermal map of the uranium surface density distribution.

[0025] Furthermore, the specific algorithm for characterizing the distribution of the substance by measuring the transmission intensity I at each position and forming a grayscale image is:

[0026] When the incident intensity is I 0 When a gamma ray of irradiates an object with a thickness of x, the transmission intensity I of the gamma ray passing through the object has the following relationship:

[0027] I=I 0 ×e-σ nx (1);

[0028] Where σ is the cross-sectional area of ​​the atom, n is the number of atoms per unit volume, and x is the thickness of the object;

[0029] The number of atoms per unit volume n can be expressed as:

[0030]

[0031] N is Avogadro's constant, ρ is the density of the substance, and A is the molar mass of the atom;

[0032] From (1) and (2), we can get:

[0033]

[0034] Equation (3) gives the attenuation equation of γ rays;

[0035] The linear absorption coefficient μ of a substance for gamma rays can be expressed as:

[0036]

[0037] Substituting into formula (3), we get:

[0038] I=I 0 ×e -μx (5);

[0039] μ / ρ is the mass absorption coefficient of the substance, expressed as μ m Indicates that:

[0040]

[0041] Furthermore, the specific algorithm for forming a thermal map of uranium surface density distribution to characterize the uniformity of uranium distribution is:

[0042] When testing nuclear fuel elements, there is the following relationship between the uranium surface density and the radiation transmission intensity of the element:

[0043] D u =K·ln(I)+b;

[0044] Where: D u --Uranium surface density of fuel elements, g / cm2;

[0045] I--transmission intensity of gamma rays, counts / s;

[0046] K--slope;

[0047] b--intercept;

[0048] By measuring the equivalent standard plate with known uranium surface density and fitting with the least square method, K and b are obtained. The transmission intensity I of the fuel element under test to low-energy gamma rays is measured with a single-channel gamma spectrometer and the uranium surface density can be calculated by substituting it into the formula.

[0049] Furthermore, the image formed during the imaging process of the component to be measured is reconstructed to improve the clarity.

[0050] Furthermore, the specific method is: first scan the image, and then obtain the image coordinates.

[0051] Furthermore, the methods for scanning the image include the following two methods:

[0052] Scanning mode 1 is continuous scanning, during which the DUT and the detector move simultaneously, and one of the collimating holes forms a continuous motion track on the motion path of the DUT;

[0053] Among them, the scanning component moves at a constant speed, and the moving speed satisfies: v s ≤2mm / T;v s is the moving speed of the scanning component, T is the transmission time of one detector signal;

[0054] The component to be tested moves at a constant speed, and the moving speed satisfies: v r ≤2mm(0.2d / v s );v s is the moving speed of the component under test, d is the width of the component under test, v s is the scanning component movement speed;

[0055] Scanning mode 2 is line-by-line scanning. During a scan, the component to be tested pauses for a while, waits for the current scan to be completed, moves to a scan interval unit, and then performs the next scan.

[0056] The moving interval of the component to be tested is 2 mm.

[0057] Furthermore, for scanning mode 1, the coordinate position of the scan is determined by the following formula:

[0058] X=υ r t;

[0059] Where X is the horizontal coordinate of the measurement point, v r is the moving speed of the component under test, and t is the running time;

[0060]

[0061] Where Y is the ordinate of the measuring point, v s is the moving speed of the scanning component, where mod(t, T) means the remainder with respect to t, T is half the scanning period,

[0062] C1 is:

[0063]

[0064] floor(t. / T) is a floor rounding function, and C1 indicates that the current scanning component moves forward;

[0065] C2 is:

[0066]

[0067] C1 indicates the return movement of the current scanning component;

[0068] Therefore, the coordinates of the measurement point corresponding to collimation hole 1 are (X, Y); for the other four collimation holes, the coordinates at the same time are (X+Δ, Y), (X+2Δ, Y), (X+3Δ, Y), (X+4Δ, Y), where Δ is the spacing between the collimation holes.

[0069] Furthermore, for scanning mode 2, the coordinate position of the scan is determined by the following formula:

[0070] X = Δ·n;

[0071] Where X is the horizontal coordinate of the measurement point, Δ is the interval distance of each scan, and n is the nth scan;

[0072] Y=v s ·t n ;

[0073] Among them, Y is the ordinate of the measuring point, υ s is the scanning component moving speed, t n The movement time of the nth scan.

[0074] In a third aspect, the present application provides a computer-readable storage medium storing a computer program, which, when executed by a processor, enables the processor to perform the steps of the above-mentioned method.

[0075] In a fourth aspect, the present application provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the above method.

[0076] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0077] (1) The detection device and method of the present invention integrate neutron activation technology and gamma-ray imaging technology to achieve the detection of fuel elements. 235Rapid qualitative and quantitative detection of U uniformity and enrichment.

[0078] (2) The detection device and method of the present invention can integrate radiation measurement, servo motor control, parameter setting, remote display, data analysis report, alarm prompt, etc., reflecting the autonomy, reliability and advancement of the measurement function. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0080] Figure 1 It is a schematic structural diagram of a nuclear fuel element detection device based on gamma-ray imaging and neutron activation in the present invention;

[0081] Figure 2 for Figure 1 Right view of;

[0082] Figure 3 for Figure 1 A top view of

[0083] Figure 4 It is a structural schematic diagram of the middle span bridge of the present invention;

[0084] Figure 5 It is a schematic diagram of the structure of the stage in the present invention;

[0085] Figure 6 It is a structural schematic diagram of the traction structure in the present invention;

[0086] Figure 7 It is a system block diagram of the PLC control system in the present invention;

[0087] Figure 8 It is a schematic diagram of the structure of the detector in the present invention;

[0088] Fig. 9 This is a schematic diagram of gamma ray attenuation in the present invention;

[0089] Fig.10 is a schematic diagram of scanning method 1 in the present invention;

[0090] Fig.11 Schematic diagram of scanning method 2 in the present invention;

[0091] Fig.12 This is the overall architecture diagram of the NAA-GTR software system in the present invention;

[0092] Fig.13 This is the technical roadmap for NAA-GTR analysis in the present invention.

[0093] Reference numerals:

[0094] 1-the third lead chamber, 2-the bracket assembly, 3-the second lead chamber, 4-the first lead chamber, 5-the wheel assembly, 6-the roller preload assembly, 7-the roller assembly, 8-the third span bridge, 9-the first span bridge, 10-the second span bridge, 11-the fourth span bridge, 12-the loading platform, 13-the lead chamber protective cover, 14-the detector, 15-the notch, 16-the limit sensor, 17-the through hole of the component to be tested, 18-the rectangular groove, 19-the traction hole, 20-the wire rope, 21-the stepping motor. DETAILED DESCRIPTION

[0095] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0096] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details need not be employed to practice the present invention. In other embodiments, in order to avoid confusing the present invention, well-known materials or methods are not specifically described.

[0097] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0098] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0099] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0100] Example 1

[0101] like Figures 1 to 8 As shown, this embodiment provides a nuclear fuel element detection device based on gamma ray imaging (GTR) and neutron activation (NAA), including a mechanical structure, a shielding structure, a transmission structure and a measurement control structure;

[0102] The mechanical structure includes a bracket assembly 2, wherein the bottom of the bracket assembly 2 is connected to a wheel assembly 5, a roller preload assembly 6 and a roller assembly 7.

[0103] The shielding structure includes a first lead chamber 4, a second lead chamber 3 and a third lead chamber 1 installed at intervals on the bracket assembly 2; wherein the third span bridge 8 and the first span bridge 9 are installed on the left and right sides of the third lead chamber 1, respectively, the second span bridge 10 is installed on the right side of the first lead chamber 4, and the fourth span bridge 11 is installed on the right side of the second lead chamber 3. Lead chamber protective covers 13 are installed on the first span bridge 9, the second span bridge 10, the third span bridge 8 and the fourth span bridge 11.

[0104] Specifically, the first lead chamber 4 is mainly made of lead, polyethylene, graphite, etc., to achieve a shielding effect on neutrons.

[0105] ① Neutron source shielding storage room: for storing neutron sources;

[0106] ② Neutron source moderator: neutrons released by the moderated neutron source;

[0107] ③ Neutron source collimator: collimates neutrons;

[0108] ④ Neutron reflector: reflects neutrons, increases the degree of activation and reduces the probability of neutrons being released into the environment;

[0109] ⑤ Neutron absorber: absorbs neutrons, reduces the probability of neutrons leaking into the environment, and protects the safety of personnel.

[0110] The second lead chamber 3 is mainly made of lead and shields the delayed γ-ray measuring detector 14 to shield the γ-rays in the environment and reduce background interference.

[0111] The third lead chamber 1 realizes the shielding effect on gamma rays.

[0112] ①γ source shielding storage room: for storing γ source;

[0113] ②γ-ray collimation

[0114] ③ Detector 14 shielding: shielding the gamma rays in the environment and reducing background interference.

[0115] Specifically, the main functions of the first span 9, the second span 10, the third span 8 and the fourth span 11 are to provide support for the stage 12 and connect various main functional devices. The upper part of the span is designed in a groove shape, and the stage 12 can be tightly placed in the groove of the span. The stage 12 moves in the groove, and the groove of the span serves as a moving guide rail for the stage 12. A limit sensor 16 opening is designed in the groove on the back of the span, which is used to install the limit sensor 16 and provide the position information of the stage 12.

[0116] Specifically, the stage 12 is a rectangular groove 18, and the component to be tested is placed flat in the rectangular groove 18. There is a traction hole 19 at each end of the stage 12, which is used to connect the traction wire rope 20. Notches 15 are designed at both ends and the middle of the stage 12, and the notches 15 can provide operating space for the staff when loading and unloading components, which is convenient for loading and unloading components.

[0117] The transmission structure includes a span bridge mounted on the bracket assembly 2, a loading platform 12 is mounted on the span bridge, and the loading platform 12 moves on the span bridge through the power provided by the traction structure; a limit sensor 16 for providing position information of the loading platform 12 is mounted on the span bridge;

[0118] Among them, the transmission structure is used to realize the movement function of the fuel assembly, mainly including starting, pausing, stopping and emergency stopping, fuel assembly movement position detection and control of fuel assembly movement speed, etc.

[0119] The movement of the stage 12 is powered by the traction motor, which pulls the stage 12 back and forth in the groove of the bridge through the traction wire rope 20, so as to realize the function of moving the component under test between various functional devices. The traction motor can control the moving direction of the stage 12 by switching forward and reverse rotation, and then control the component under test to move back and forth between various functional devices. In conjunction with the limit sensor 16 on the bridge, the moving position and distance of the stage 12 can be accurately controlled to realize the displacement control of the component under test.

[0120] The traction stepper motor 21 is fixed on the motor base and connected to the winch of the wire rope 20 through a coupling to drive the winch to rotate, thereby achieving the purpose of traction of the loading platform 12.

[0121] Specifically, the detector 14 installed in the second lead chamber 3 is a panel-type detector 14 consisting of two upper and lower panels, and the detector 14 is provided with a through hole 17 for the device to be tested.

[0122] The intensity of the delayed gamma rays after the fuel element is activated is not very high. Therefore, in order to improve the detection efficiency of the measurement system, the present invention adopts two upper and lower panel-type detectors 14 to simultaneously measure a large area. When the activated element to be tested is carried by the stage 12 to the second lead chamber 3, the upper and lower detectors 14 simultaneously perform delayed gamma ray measurement. At the same time, lead material is used to shield the background interference of the environment to improve the signal-to-noise ratio, and the purpose of fuel element uniformity detection is achieved by using the electronic measurement system matched with the back end.

[0123] The measurement control structure includes a PLC control system. The system consists of an Omron PLC, a host computer, a driver, a stepper motor 21, a 24V power supply and a load. The PLC is the control core of the entire system. The PULS pulse command is sent to the stepper motor 21 driver through the PLC to realize the two running states of the motor, forward and reverse, and the load follows the stepper motor 21 to realize left / right movement. During the operation of the motor, the PLC and the host computer realize real-time communication through the RS485 interface, realizing the real-time display of the running state of the stepper motor 21 in the configuration interface. The configuration interface has two control modes for the motor operation mode, namely time control and angle control button, which can realize real-time control and dynamic display of the running state of the stepper motor 21.

[0124] When using this detection device for detection, during the process of gamma rays penetrating the fuel element, 235 The distribution of U will affect the intensity and distribution of the outgoing gamma rays, so it can be seen intuitively from the imaging results. 235 The uniformity of U distribution; the intensity of delayed gamma rays released by the fuel element after thermal neutron activation reflects the uniformity of U distribution in the element. 235 U content, so by measuring the delayed gamma rays, we can get 235 U distribution uniformity and quantitative results 235 U enrichment, the two measurement methods can complement and verify each other, and realize the 235 Detection of uniformity and enrichment of U.

[0125] Example 2

[0126] This embodiment provides a nuclear fuel element detection method based on gamma-ray imaging and neutron activation, and uses the detection device in Example 1 for detection. The software part applied to the detection device has the functions of integrated control, signal acquisition, data calculation, result analysis, communication transmission, etc. The designed comprehensive software interface integrates ray measurement, servo motor control, parameter setting, remote display, data analysis reports, alarm prompts, etc., reflecting the autonomy, reliability and advancement of the measurement function.

[0127] The NAA-GTR software system architecture is mainly divided into four levels of design: basic data layer, data service layer, application analysis layer and interface presentation layer. The interface presentation layer is the user interface of the system, which accepts user requests and reflects them in the correct form; the application analysis layer mainly reflects the analysis logic design of the system, mainly including data acquisition, control, analysis, processing, query and other functions; the data service layer mainly reflects the functional scope of the system, and the protocol uses CAN bus for communication; the basic data layer is the bottom layer of this system, which is the basic data source for the operation of this system, mainly including database, text data, image data, etc. From top to bottom, they are the system function layer, data access interface layer, and system database layer. The system architecture is rigorous and concise, providing a stable and complete measurement software system for NAA-GTR measurement.

[0128] The method comprises the following steps: the fuel element to be tested is first moved by the conveying structure to the third lead chamber for gamma transmission imaging;

[0129] Then it moves to the first lead chamber for neutron activation, and after cooling, it moves to the second lead chamber for delayed gamma measurement;

[0130] The gamma transmission imaging results and delayed gamma measurement results are transmitted to the computer in real time. After being analyzed by the detection algorithm, the uniformity test results of the components to be tested are qualitatively and quantitatively analyzed.

[0131] Among them, the NAA analysis method needs to slow down the fast neutrons to the thermal neutron energy range, use the Monte Carlo MCNP simulation program to select the type of moderator material, and reasonably combine the moderator materials to increase the proportion of thermal neutron injection rate; select appropriate shielding materials and sizes through simulation calculations to reduce the background radiation around the detector and protect the dose safety of the staff.

[0132] Among them, GTR imaging detection requires the irradiation of a gamma radiation source. The key point of the gamma radiation source shielding structure lies in the collimation and shielding of gamma rays. The purpose of collimation is to make the fuel element to be inspected evenly irradiated. The shielding is to reduce the interference to the NAA detector and the dose exposure to the staff. The Monte Carlo MCNP simulation program is used to select the gamma source shielding material and shielding structure.

[0133] Specifically, in imaging, the distribution of the substance is characterized by measuring the transmission intensity I at each position and forming a grayscale image. The specific implementation method and principle are as follows:

[0134] When the incident intensity is I 0 When a gamma ray of irradiates an object with a thickness of x, the transmission intensity I of the gamma ray passing through the object has the following relationship:

[0135] I=I 0 ×e -σnx (1);

[0136] Where σ is the cross-sectional area of ​​the atom, n is the number of atoms per unit volume, and x is the thickness of the object;

[0137] The number of atoms per unit volume n can be expressed as:

[0138]

[0139] N is Avogadro's constant, ρ is the density of the substance, and A is the molar mass of the atom;

[0140] From (1) and (2), we can get:

[0141]

[0142] Equation (3) gives the attenuation equation of γ rays;

[0143] The linear absorption coefficient μ of a substance for gamma rays can be expressed as:

[0144]

[0145] Substituting into formula (3), we get:

[0146] I=I 0 ×e -μx (5);

[0147] μ / ρ is the mass absorption coefficient of the substance, expressed as μ m Indicates that:

[0148]

[0149] The image formed above is scanned, and the specific method is as follows:

[0150] Continuous scanning is adopted: during the scanning process, the DUT and the detector move simultaneously, and one of the collimating holes forms a continuous motion track on the motion path of the DUT;

[0151] Among them, the scanning component moves at a constant speed, and the moving speed satisfies: v s ≤2mm / T;v s is the moving speed of the scanning component, T is the transmission time of one detector signal;

[0152] The component to be tested moves at a constant speed, and the moving speed satisfies: v r ≤2mm(0.2d / v s );v s is the moving speed of the component under test, d is the width of the component under test, v s is the scanning component movement speed.

[0153] The coordinate position of the scan is determined by the following formula:

[0154] X=v r t (6);

[0155] Where X is the horizontal coordinate of the measurement point, v r is the moving speed of the component under test, and t is the running time;

[0156]

[0157] Where Y is the ordinate of the measuring point, v s is the moving speed of the scanning component, where mod(t, T) means the remainder with respect to t, T is half the scanning period,

[0158] C1 is:

[0159]

[0160] floor(t. / T) is a floor rounding function, and C1 indicates that the current scanning component moves forward;

[0161] C2 is:

[0162]

[0163] C1 indicates the return movement of the current scanning component;

[0164] Therefore, the coordinates of the measurement point corresponding to collimation hole 1 are (X, Y); for the other four collimation holes, the coordinates at the same time are (X+△, Y), (X+2△, Y), (X+3△, Y), (X+4△, Y), where △ is the spacing between the collimation holes.

[0165] The above method can be used to obtain image coordinates and grayscale values, thereby performing image reconstruction to make the resulting effect image more accurate and clear.

[0166] Example 3

[0167] This embodiment provides a nuclear fuel element detection method based on gamma-ray imaging and neutron activation. Different from Embodiment 2, the detection method of this embodiment uses a uranium surface density distribution to form a thermal map to characterize the uniformity of uranium distribution.

[0168] The specific implementation methods and principles are as follows:

[0169] When testing nuclear fuel elements, there is the following relationship between the uranium surface density and the radiation transmission intensity of the element:

[0170] D u =K·ln(I)+b (11);

[0171] Where: D u --Uranium surface density of fuel elements, g / cm2;

[0172] I--transmission intensity of gamma rays, counts / s;

[0173] K--slope;

[0174] b--intercept;

[0175] By measuring the equivalent standard plate with known uranium surface density and fitting with the least square method, K and b are obtained. The transmission intensity I of the fuel element under test to low-energy gamma rays is measured with a single-channel gamma spectrometer and the uranium surface density can be calculated by substituting it into the formula.

[0176] The image formed above is scanned, and the specific method is as follows:

[0177] The line-by-line scanning method is adopted: during a scanning process, the component to be tested pauses at different times, waits for the current scan to be completed, moves to a scanning interval unit, and then performs the next scan;

[0178] The moving interval of the component to be tested is 2 mm.

[0179] The coordinate position of the scan is determined by the following formula:

[0180] X = Δ·n (12);

[0181] Where X is the horizontal coordinate of the measurement point, △ is the interval distance of each scan, and n is the nth scan;

[0182] Y=v s ·t n (13);

[0183] Where Y is the ordinate of the measuring point, v s is the scanning component moving speed, t n The movement time of the nth scan.

[0184] The image coordinates and surface density values ​​can be obtained by using the above method, so as to reconstruct the image and make the resulting effect image more accurate and clear.

[0185] Example 4

[0186] This embodiment provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the nuclear fuel element detection method based on v-ray imaging and neutron activation in the above-mentioned embodiment 2 or embodiment 3.

[0187] The computer device may be a desktop computer, a notebook, a PDA, a cloud server, etc. The computer device may interact with the user through a keyboard, a mouse, a remote control, a touch pad, or a voice control device.

[0188] The storage includes at least one type of readable storage medium, and the readable storage medium includes flash memory, hard disk, multimedia card, card-type memory (for example, SD or D interface display memory, etc.), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, disk, optical disk, etc. In some embodiments, the memory can be an internal storage unit of the computer device, for example, a hard disk or memory of the computer device. In other embodiments, the memory can also be an external storage device of the computer device, such as a plug-in hard disk equipped on the computer device, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (FlashCard), etc. Of course, the memory can also include both the internal storage unit of the computer device and an external storage device. In this embodiment, the memory is often used to store the operating system and various application software installed on the computer device, such as the program code for running the nuclear fuel element detection method based on gamma-ray imaging and neutron activation, etc. In addition, the memory may also be used to temporarily store various types of data that have been output or are to be output.

[0189] The processor may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip in some embodiments. The processor is generally used to control the overall operation of the computer device. In this embodiment, the processor is used to run the program code stored in the memory or process data, such as running the program code of the nuclear fuel element detection method based on gamma-ray imaging and neutron activation.

[0190] Example 5

[0191] This embodiment provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of the nuclear fuel element detection method based on gamma-ray imaging and neutron activation in the above-mentioned embodiment 2 or embodiment 3.

[0192] Among them, the computer-readable storage medium stores an interface display program, and the interface display program can be executed by at least one processor so that the at least one processor executes the steps of the nuclear fuel element detection method based on gamma-ray imaging and neutron activation in the above-mentioned embodiment 2 or embodiment 3.

[0193] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0194] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0195] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0196] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0197] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for a terminal device (which can be a mobile phone, computer, server or network device, etc.) to execute the methods described in each embodiment of the present application.

[0198] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0199] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only the specific embodiments of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention. For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or basic features of the present application. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present application is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present application.

Claims

1. A nuclear fuel element detection device based on gamma-ray imaging and neutron activation, characterized in that: Including mechanical structure, shielding structure, transmission structure and measurement control structure; The mechanical structure comprises a support assembly (2); The shielding structure comprises a first lead chamber (4), a second lead chamber (3) and a third lead chamber (1) which are installed on the bracket assembly (2) at intervals; The transmission structure comprises a bridge mounted on the support assembly (2), a loading platform (12) being mounted on the bridge, the loading platform (12) being moved on the bridge by power provided by a traction structure; a limit sensor (16) for providing position information of the loading platform (12) being mounted on the bridge.

2. The nuclear fuel element detection device based on gamma-ray imaging and neutron activation according to claim 1 is characterized in that: The upper portion of the bridge is arranged in a groove shape, the loading platform (12) is installed in the groove and moves in the groove, and the groove of the bridge serves as a moving guide rail for the loading platform (12).

3. The nuclear fuel element detection device based on gamma-ray imaging and neutron activation according to claim 1 is characterized in that: The stage (12) is provided with a rectangular groove (18), and the component to be tested is placed flat on the stage (12); and a traction hole (19) for connecting a traction wire rope (20) is provided at each of the two ends of the stage (12).

4. The nuclear fuel element detection device based on gamma-ray imaging and neutron activation according to claim 1, characterized in that: Notches (15) are provided at both ends and the middle of the object carrier (12).

5. The nuclear fuel element detection device based on gamma-ray imaging and neutron activation according to claim 1, characterized in that: The detector (14) installed in the second lead chamber (3) is a panel-type detector (14) consisting of two upper and lower panels, and a through hole (17) for a component to be tested is provided on the detector (14).

6. The nuclear fuel element detection device based on gamma-ray imaging and neutron activation according to claim 1, characterized in that: The first lead chamber (4) is used to achieve a shielding effect on neutrons; the second lead chamber (3) is used to shield gamma rays in the environment to reduce background interference; and the third lead chamber (1) is used to achieve a shielding effect on gamma rays.

7. A method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation, characterized in that: The following steps are involved: The fuel element to be tested is first moved by the conveying structure to the third lead chamber (1) for gamma transmission imaging; Then, it is moved to the first lead chamber (4) for neutron activation, and after cooling, it is moved to the second lead chamber (3) for delayed gamma measurement; The gamma transmission imaging results and delayed gamma measurement results are transmitted to the computer in real time. After being analyzed by the detection algorithm, the uniformity test results of the components to be tested are qualitatively and quantitatively analyzed.

8. A method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation according to claim 7, characterized in that: The uniformity detection method of the element to be tested includes characterizing the distribution of the material by measuring the transmission intensity I at each position in the imaging and forming a grayscale image, or characterizing the uniformity of uranium distribution by forming a thermal map of the uranium surface density distribution.

9. A method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation according to claim 8, characterized in that: The specific algorithm for characterizing the distribution of the material by measuring the transmission intensity I at each position and forming a grayscale image is: When a gamma ray with an incident intensity of I0 irradiates an object with a thickness of x, the transmission intensity I of the gamma ray passing through the object has the following relationship: I=I0×e -σnx (1); Where σ is the cross-sectional area of ​​the atom, n is the number of atoms per unit volume, and x is the thickness of the object; The number of atoms per unit volume n can be expressed as: N is Avogadro's constant, ρ is the density of the substance, and A is the molar mass of the atom; From (1) and (2), we can get: Equation (3) gives the attenuation equation of γ rays; The linear absorption coefficient μ of a substance for gamma rays can be expressed as: Substituting into formula (3), we get: I=I0×e -μx (5); μ / ρ is the mass absorption coefficient of the substance, expressed as μ m Indicates that:

10. A method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation according to claim 8, characterized in that: The specific algorithm for forming a heat map of uranium surface density distribution to characterize the uniformity of uranium distribution is: When testing nuclear fuel elements, there is the following relationship between the uranium surface density and the radiation transmission intensity of the element: D u =K·n(I)+b; Where: D u --Uranium surface density of fuel elements, g / cm2; I--transmission intensity of gamma rays, counts / s; K--slope; b--intercept; By measuring the equivalent standard plate with known uranium surface density and fitting with the least square method, K and b are obtained. The transmission intensity I of the fuel element under test to low-energy gamma rays is measured with a single-channel gamma spectrometer and the uranium surface density can be calculated by substituting it into the formula.

11. A method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation according to claim 7, characterized in that: The image formed during the imaging process of the component to be tested is reconstructed to improve the clarity.

12. A method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation according to claim 11, characterized in that: The specific method is: first scan the image, and then obtain the image coordinates.

13. A method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation according to claim 12, characterized in that: There are two ways to scan an image: Scanning mode 1 is continuous scanning, during which the DUT and the detector move simultaneously, and one of the collimating holes forms a continuous motion track on the motion path of the DUT; Among them, the scanning component moves at a constant speed, and the moving speed satisfies: s ≤2mm / T;υ s is the moving speed of the scanning component, T is the transmission time of one detector signal; The component to be tested moves at a constant speed, and the moving speed satisfies: r ≤2mm / (0.2d / υ s ); s is the moving speed of the component under test, d is the width of the component under test, υ s is the scanning component movement speed; Scanning mode 2 is line-by-line scanning. During a scan, the component to be tested pauses for a while, waits for the current scan to be completed, moves to a scan interval unit, and then performs the next scan. Among them, the single movement interval of the component to be tested is ≤2mm.

14. A method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation according to claim 13, characterized in that: For scanning mode 1, the coordinate position of the scan is determined by the following formula: X=υ r ·t; Where X is the horizontal coordinate of the measurement point, υ r is the moving speed of the component under test, and t is the running time; Among them, Y is the ordinate of the measuring point, υ s is the moving speed of the scanning component, where mod(t,T) means the remainder with respect to t, T is half the scanning period, C1 is: floor(t. / T) is a floor rounding function, and C1 indicates that the current scanning component moves forward; C2 is: C1 indicates the return movement of the current scanning component; Therefore, the coordinates of the measurement point corresponding to collimation hole 1 are (X, Y); for the other four collimation holes, the coordinates at the same time are (X+Δ, Y), (X+2Δ, Y), (X+3Δ, Y), (X+4Δ, Y), where Δ is the spacing between the collimation holes.

15. The method for detecting nuclear fuel elements based on gamma-ray imaging and neutron activation according to claim 13, characterized in that: For scanning mode 2, the coordinate position of the scan is determined by the following formula: X = Δ·n; Where X is the horizontal coordinate of the measurement point, Δ is the interval distance of each scan, and n is the nth scan; Y=υ s ·t n ; Among them, Y is the ordinate of the measuring point, υ s is the scanning component moving speed, t n The movement time of the nth scan.

16. A computer-readable storage medium, characterized in that: A computer program is stored, and when the computer program is executed by a processor, the processor is caused to execute the steps of the method according to any one of claims 7 to 15.

17. A computer device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method according to any one of claims 7 to 15.

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