Waste barrel radioactive characterization phantom and detection efficiency calibration method

Abstract

The invention provides a waste bin radioactive characterization phantom and a detection efficiency calibration method, and belongs to the technical field of radioactive measurement, and the waste bin radioactive characterization phantom comprises a support frame, a spacer and a plurality of bearing frames. A shaft body is arranged on the support frame; the multiple bearing frames are coaxially arranged on the shaft body in a sleeving mode. A plurality of positioning holes are formed in the bearing frame, are distributed around the shaft body in the radial direction and the circumferential direction at intervals and are used for fixing point source components; the shaft body is sleeved with the spacer, and the spacer is located between every two adjacent bearing frames. According to the phantom, the shaft body is sleeved with the bearing frames to form the phantom with the specified shape to be measured, and the body source radiation of different matrix materials under different densities is simulated by adjusting the spacing distance between the bearing frames and the number and the distribution density of the point source components fixed to the bearing frames.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactive measurement, and particularly relates to a radioactive characterization phantom for waste bins and a method for calibrating detection efficiency. Background Art

[0002] A radioactive calibration source is a key material for calibrating the detection efficiency of radioactive detection equipment, and is also a technical means to achieve the calibration of radioactive measurement sources to national standards. It can help the detection equipment achieve quantitative and accurate measurement of radioactive activity.

[0003] In the traditional field of radioactive measurement, the calibration of the detection efficiency of detection equipment for radioactive sources is usually divided into two types. One is to conduct experimental radioactive measurement on small-sized radioactive sources. This type of experimental radioactive detection efficiency calibration method has relatively high measurement accuracy. The metrology department usually provides radioactive calibration sources of different specifications and sizes. Such calibration sources often have small geometric sizes and small source masses, usually in the range of several hundred grams. The other is to measure large-area or large-volume radioactive pollution sources. For such measurements, corresponding calibration sources cannot be prepared, and the detection equipment mainly uses computational simulation methods to achieve the calibration of detection efficiency. For example, for the current measurement requirements for the disposal or clearance release measurement of radioactive waste, the material to be measured is generally filled into a material bin with a fixed geometric shape for radioactive activity measurement. It is difficult to directly purchase large-volume calibration sources from the metrology department for such measurements, so it is impossible to accurately calibrate the detection efficiency of the detection equipment through physical measurement.

[0004] Therefore, it is necessary to provide a radioactive characterization phantom for waste bins and a method for calibrating detection efficiency to solve the above technical problems. Summary of the Invention

[0005] In view of the problems existing in the above prior art, the present invention provides a radioactive characterization phantom for waste bins to improve the technical problem that large-volume radioactive calibration sources are not easily obtained in the prior art.

[0006] To achieve the above object and other related objects, the present invention provides a radioactive characterization phantom for waste bins, which includes a support frame, a spacer, and a plurality of carrier frames.

[0007] Wherein, a shaft body is provided on the support frame; a plurality of carrier frames are coaxially sleeved on the shaft body; the carrier frame has a plurality of positioning holes, and the plurality of positioning holes are spaced apart radially and circumferentially around the shaft body, and the positioning holes are used for fixing point source components; the spacer is sleeved on the shaft body, and the spacer is located between any two adjacent carrier frames among the plurality of carrier frames.

[0008] In an example of the present invention, the plurality of positioning holes on each carrier frame correspond one by one and are located on the same axis.

[0009] In an example of the present invention, a wire source component is assembled in the phantom, and a plurality of the point source components are included on the wire source component. The plurality of point source components are arranged at intervals in the same direction, and the wire source component is inserted into the plurality of positioning holes located on the same axis.

[0010] In an example of the present invention, the point source component includes a point source sealed box and a radioactive substance, and the radioactive substance is encapsulated in the point source sealed box.

[0011] In an example of the present invention, the phantom is divided into a plurality of lattice cells along the radial direction around the shaft body. The plurality of lattice cells have the same volume, and the same number of the point source components are arranged in each lattice cell. The plurality of point source components in each lattice cell are spaced apart along the axial direction and the circumferential direction.

[0012] In an example of the present invention, the dimensions of the plurality of lattice cells satisfy the relationships of formula (1) and formula (2), and the formula (1) and formula (2) are:

[0013]

[0014]

[0015] Wherein, n is the number of the point source components, r1 is the maximum radius of the lattice cell closest to the shaft body, r i is the maximum radius of the i-th layer of the lattice cell, and 1 ≤ i ≤ m, and m is the number of the lattice cells.

[0016] In an example of the present invention, the plurality of positioning holes on each carrier are symmetrically distributed around the shaft body in a central symmetry manner.

[0017] In an example of the present invention, the projection of the carrier in the axial direction of the shaft body is circular.

[0018] In an example of the present invention, the material of the carrier is metal, plastic, fabric or concrete.

[0019] The present invention also provides a method for calibrating the detection efficiency of a detection device. The method for calibrating the detection efficiency uses the phantom described in any of the above examples to perform detection efficiency calibration. The detection device to which the detection efficiency calibration is applied includes a cavity and a plurality of detectors. The cavity is used to accommodate the phantom, and the plurality of detectors are spaced apart along the cavity wall; the method for calibrating the detection efficiency includes:

[0020] Divide the phantom into multiple detection regions; for each of the detection regions in the phantom, set at least one of the point source components in the detection region, place the phantom into the detection device for detection, and obtain the detection efficiency of the multiple detectors for the detection region based on the detection results obtained from the detection and the radioactivity of the point source components.

[0021] For the radioactive characterization phantom of the present invention, a plurality of carrier racks are sleeved onto a shaft body to form a three-dimensional phantom with a specified shape to be measured, and by adjusting the distance between the carrier racks and the quantity and distribution density of the point source components fixed on the carrier racks, the volume source radiation of different matrix materials at different densities can be simulated, effectively solving the problem that in the existing application scenarios, the detection device cannot pre-complete the calibration of the detection efficiency for large-size radioactive materials because there is no suitable calibration volume source. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those of ordinary skill in the art, other embodiments can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic structural diagram of the radioactive characterization phantom of a waste bin in an embodiment of the present invention;

[0024] Figure 2 It is an overall sectional structural diagram of the radioactive characterization phantom of a waste bin in an embodiment of the present invention;

[0025] Figure 3 It is a top view structural diagram of the radioactive characterization phantom of a waste bin in an embodiment of the present invention;

[0026] Figure 4 It is a partial sectional structural diagram of the radioactive characterization phantom of a waste bin in an embodiment of the present invention;

[0027] Figure 5 It is a schematic structural diagram of a line source component in an embodiment of the present invention;

[0028] Figure 6 It is a schematic structural diagram of a point source component in an embodiment of the present invention;

[0029] Figure 7 It is a schematic flow diagram of a detection efficiency calibration method in an embodiment of the present invention.

[0030] Explanation of Element Numbers

[0031] 100, Phantom; 110, Support Frame; 111, Base; 112, Shaft; 120, Carrier Frame; 121, Positioning Hole; 130, Spacer; 200, Linear Source Component; 210, Spacer Rod; 300, Point Source Component; 310, Point Source Sealing Box; 311, Loading Tray; 312, Titration Hole; 313, Sealing Cover; 320, Radioactive Substance. Detailed Embodiment

[0032] The following uses specific specific examples to illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. It should also be understood that the terms used in the embodiments of the present invention are for describing specific specific implementation schemes, rather than limiting the protection scope of the present invention. The test methods without specific conditions noted in the following embodiments are usually in accordance with conventional conditions or in accordance with the conditions recommended by each manufacturer.

[0033] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of clear narration, rather than to limit the scope of implementation of the present invention. The change or adjustment of their relative relationship, without substantial change in technical content, should also be regarded as the scope of implementation of the present invention.

[0034] Please refer to Figure 1 , the present invention provides a radioactive characterization phantom for waste bins, which can simulate the volume source radiation of different matrix materials at different densities, thereby effectively solving the technical problem that it is difficult to obtain a large-volume radioactive calibration volume source.

[0035] As Figures 1 to 4 shown, the radioactive characterization phantom 100 for waste bins includes a support frame 110, a plurality of carrier frames 120 and a plurality of spacers 130. The support frame 110 includes a base 111 and a shaft 112. The shaft 112 is fixed on the base 111, and the shaft 112 extends along the height direction. The plurality of carrier frames 120 have the same shape, and the plurality of carrier frames 120 are coaxially sleeved on the shaft 112. The spacer 130 is arranged between any two adjacent carrier frames 120 among the plurality of carrier frames 120, so that two adjacent carrier frames 120 are spaced apart in the height direction. A plurality of positioning holes 121 are arranged on each carrier frame 120. The plurality of positioning holes 121 on each carrier frame 120 are spaced apart radially and circumferentially around the shaft 112. The positioning holes 121 are used to fix the point source component 300. For example, as Figure 3As shown, in one embodiment, the multiple positioning holes 121 on each carrier 120 are symmetrically distributed around the shaft body 112 in a central symmetry manner.

[0036] By adjusting the height of the spacer 130 and the number of carriers 120, the phantom 100 can simulate uniform materials with different shapes and different densities. By arranging the point source components 300 at intervals radially and circumferentially on the carriers 120 at different heights, the phantom 100 can realize the simulation of volume source radiation under uniform materials by using multiple point source components 300. The phantom 100 uses the method of filling the point source components 300 into the material matrix, enabling a set of point sources to be reused or used for different base materials, thus improving the utilization efficiency of the radioactive substance 320.

[0037] In the detection efficiency calibration experiment of the detection device, by rotating and measuring the phantom 100 with the point source components 300 locally assembled, the phantom 100 can complete the test calibration of the detection efficiency of the detection device at different circumferential positions of the volume source, which solves the limitation of using a rotating volume source to calibrate the detection efficiency of the detection device in the prior art.

[0038] Meanwhile, the phantom 100 can simulate the volume source radiation of uniform materials under different radioactive activity densities by adjusting the distribution position and density of the point source components 300. In addition, when the same number of point source components 300 are set in the phantom 100, by adjusting the measurement distance between the detector and the volume source, the radioactive activity density of the volume source radiation simulated by the phantom 100 can also be corrected.

[0039] It should be noted that the material type of the carrier 120 is not limited, and the material of the carrier 120 can be adaptively adjusted according to the material type of the material to be simulated. For example, in some embodiments, the material of the carrier 120 can be metal, plastic, fabric or concrete. Among them, when the material of the carrier 120 is a metal material (such as iron), the phantom 100 can simulate a radioactive volume source of a metal material; when the material of the carrier 120 is a plastic material (such as styrene), the phantom 100 can simulate a radioactive volume source of a resin material; when the material of the carrier 120 is a fabric (such as cellulose), the phantom 100 can simulate a radioactive volume source of a knitted fabric material.

[0040] Such as Figure 2 and Figure 4As shown, in some embodiments, the spacer 130 is provided as a circular ring, and the thickness of the spacer 130 is any value in the range of 0.5 to 1 cm. For example, the thickness of the spacer 130 can be 0.5 cm, 0.6 cm, 0.7 cm, 0.8 cm, 0.9 cm, or 1 cm. Among them, by placing different numbers of spacers 130 between two adjacent carrier frames 120, the density of the multiple carrier frames 120 in the phantom 100 can be adjusted, thereby achieving the effect of adjusting the simulated material density of the phantom 100.

[0041] As Figure 2 and Figure 5 As shown, in some embodiments, in the phantom 100, multiple line source components 200 are assembled to simulate volume source radiation. The line source component 200 includes a plurality of point source components 300 and spacer rods 210. The multiple point source components 300 are linearly distributed on the line source component 200 and are spaced apart by the spacer rods 210. To facilitate the axial assembly of the line source component 200 into the phantom 100, the multiple positioning holes 121 on each carrier frame 120 in the phantom 100 are in one-to-one correspondence and aligned in the same axial direction. The height of the line source component 200 is set to be greater than or equal to the height of the phantom 100 to facilitate complete insertion into the interior of the phantom 100. The line source component 200 is inserted into the multiple positioning holes 121 located on the same axis from the top of the phantom 100 and is assembled into the interior of the phantom 100 by being fixedly inserted through the multiple positioning holes 121. The line source component 200 assembled into the interior of the phantom 100 enables the point source components 300 thereon to be spaced apart in the axial direction. By assembling multiple line source components 200 around the shaft body 112 at intervals in the radial and circumferential directions into the phantom 100, the effect of simulating volume source radiation through multiple line source radiations in the phantom 100 can be achieved.

[0042] In addition, the shape of the carrier 120 can be adaptively adjusted according to the shape of the body source simulated by the phantom 100. In some embodiments, when the phantom 100 is used to simulate a waste bin, the projection of the carrier 120 in the axial direction of the shaft body 112 is circular. For example, the carrier 120 is a disc. For example, when simulating a radiation body source of a 200L standard waste bin, 20 disc carriers 120 are sleeved onto the shaft body 112 of the support frame 110. The size of each carrier 120 is 560 mm (diameter) × 43 mm (thickness). There are 36 positioning holes 121 provided on each carrier 120, and the 36 positioning holes 121 are evenly distributed along the radial and circumferential directions on the carrier 120. By setting different numbers of spacers 130 between any two adjacent carriers 120, the density of the carriers 120 in the phantom 100 is adjusted to be able to simulate a preset material density, where the thickness of the spacer 130 is 1 cm. Finally, the multiple positioning holes 121 on each carrier 120 in the phantom 100 are aligned one by one, and multiple line source components 200 are inserted into the phantom 100 from the top. The multiple line source components 200 are evenly distributed along the radial and circumferential directions in the phantom 100, thus completing the preparation of the body source.

[0043] As Figure 6 shown, in some embodiments, the point source component 300 includes a point source sealing box 310 and a radioactive substance 320. The radioactive substance 320 is encapsulated in the point source sealing box 310. The point source sealing box 310 includes a loading plate 311 and a sealing cover 313. The loading plate 311 is in the shape of a disc. There is a recessed titration hole 312 in the loading plate 311 for loading the radioactive substance 320. The sealing cover 313 is detachably installed on the loading plate 311. When the sealing cover 313 is assembled to the loading plate 311, it can seal the titration hole 312. Among them, the preparation method of the point source component 300 is as follows: in the open cover state, the radioactive substance 320 is titrated into the titration hole 312 of the loading plate 311. The loading plate 311 is placed under normal temperature or infrared radiation for heating. After the radioactive substance 320 in the titration hole 312 is dried, the sealing cover 313 is installed on the loading plate 311, and sealant is applied to seal the gap between the sealing cover 313 and the loading plate 311, completing the loading and sealing of the radioactive substance 320 by the point source sealing box 310. For example, the point source component 300 uses a point source sealing box 310 with a diameter of 1.5 cm and a thickness of 0.3 cm to encapsulate the radioactive substance 320, and the titration hole 312 in the loading plate 311 can hold 0.5 ml - 1 ml of the radioactive substance 320.

[0044] It should be noted that the type of the radioactive substance 320 loaded in the point source component 300 is not limited and can be adaptively adjusted according to the needs of experimental tests. For example, the radioactive substance 320 can use 137 Cs, 60 Co,40 K, 58 Co, 133 radionuclide substances such as Ba.

[0045] As Figure 3 shown, in some embodiments, a plurality of point source components 300 are arranged in a volume-uniform distribution manner in the phantom 100 to simulate the uniform volume source radiation of a uniform material. Among them, in the radial direction around the shaft body 112, the phantom 100 is divided into a plurality of grid elements with different radii, and the volumes of the divided grid elements are the same; and the same number of point source components 300 are arranged in each grid element, and the plurality of point source components 300 in each grid element are spaced apart along the axial and circumferential directions, so that the phantom 100 simulates the uniform large-size volume source radiation.

[0046] Specifically, the sizes of the plurality of grid elements into which the phantom 100 is divided according to the volume-uniform distribution manner satisfy the relationships of Equation (1) and Equation (2), and Equation (1) and Equation (2) are:

[0047]

[0048]

[0049] where n is the number of point source components 300 arranged in the phantom 100, r1 is the maximum radius of the grid element closest to the shaft body 112, and r i is the maximum radius of the i-th layer of grid element in the radial direction, and 1 ≤ i ≤ m, and m is the total number of grid elements. The above relationships are used to represent the distribution of each layer of grid elements in the radial direction. For example, the grid element closest to the shaft body 112 is a cylinder with the shaft body 112 as the central axis and a radius of r1, and the i-th layer of grid element in the radial direction is an annular body with the shaft body 112 as the central axis. The inner radius of the i-th layer of grid element is r i-1 and the inner radius of the i-th layer of grid element is r i .

[0050] As Figure 3 shown, in some embodiments, in the phantom 100 in which the point source components 300 are arranged in the volume-uniform distribution manner, the point source components 300 are equally angularly distributed in the circumferential direction. In one example, considering that the distance between the detector and the phantom 100 is greater than the maximum point source-point source spacing, the included angle between adjacent point source components 300 in the circumferential direction around the shaft body 112 is 30°.

[0051] The present invention also provides a method for calibrating the detection efficiency of a detection device. This detection efficiency calibration method uses the phantom described in any of the above embodiments to calibrate the detection efficiency of the detection device. The detection device applied includes a cavity and a plurality of detectors. The cavity is used to accommodate the phantom or the sample to be measured. The plurality of detectors are spaced apart along the cavity wall. For example, the plurality of detectors are distributed in a 4π space along the cavity wall, and the plurality of detectors form a 4π space three-dimensional structure for the phantom or the sample to be measured in the cavity.

[0052] As Figure 7 shown, the method for calibrating the detection efficiency of the above detection device includes the following steps:

[0053] S1. Divide the phantom into a plurality of detection regions;

[0054] In some embodiments, in step S1, the phantom is evenly divided into at least two detection regions along the height direction. For example, in one example, the phantom is divided into 5 layers along the height direction, and a phantom divided into 5 cylindrical detection regions is obtained.

[0055] To achieve more accurate calibration of the detection efficiency of each region of the phantom by the detection device, in some other embodiments, in step S1, the phantom is first evenly divided into at least two segment layers along the height direction; then for each segment layer, along the circumferential direction around the geometric center of the segment layer, the segment layer is evenly divided into at least two detection regions, and the detection regions can be fan-shaped regions. For example, in one example, the phantom is first evenly divided into 5 segment layers along the height direction, and then each segment layer is evenly divided into 4 fan-shaped detection regions, and a phantom divided into 5×4 fan-shaped detection regions is obtained.

[0056] S2. For each detection region in the phantom, perform the following steps to measure the detection efficiency of the detection device for each detection region, that is, the detection efficiency of the plurality of detectors in the detection device for each detection region.

[0057] Specifically, for each detection region in the phantom: set at least one point source component in the currently tested detection region; after assembling the point source component, place the phantom into the detection device, and perform a radioactive activity test on the phantom through the plurality of detectors in the detection device. Based on the radioactive activity of the point source component in the phantom and the detection results of the plurality of detectors, obtain the detection efficiency of the plurality of detectors for the currently tested detection region. It can be seen that this detection efficiency calibration method uses the detection device to perform layered or partitioned measurement and calibration on the phantom, effectively reducing the usage amount of the point source component in the phantom.

[0058] For example, in some embodiments, the detection efficiency ε jk of the jth detector in the detection device for the kth detection region is jk ε jk =(n jb) / A, where A is the radionuclide activity of the k-th detection area among multiple detection areas, and n jk is the radioactive counting rate obtained by the j-th detector among multiple detectors detecting the k-th detection area, and n jb is the background counting rate detected by the j-th detector.

[0059] In some embodiments, step S2 further includes summarizing the results of the detection device for each detection area to obtain the total detection efficiency of the detection device for the phantom-simulated radiation source.

[0060] Specifically, the total detection efficiency ε of the detection device for the phantom is expressed as:

[0061]

[0062] where A is the radionuclide activity in each detection area, and n jk is the radioactive counting rate obtained by the j-th detector detecting the k-th detection area, and n jb is the background counting rate detected by the j-th detector.

[0063] In summary, for the radioactive characterization phantom of the waste bin of the present invention, multiple carriers are sleeved on the shaft body to form a three-dimensional phantom with a specified shape to be measured, and by adjusting the spacing distance between the carriers and the quantity and distribution density of the point source components fixed on the carriers, the simulation of the volume source radiation of different matrix materials at different densities is realized, effectively solving the problem that in the existing application scenarios, the detection device cannot pre-scale the detection efficiency of large-size radioactive materials because there is no suitable calibration volume source.

[0064] The above embodiments merely illustrate the principles and effects of the present invention and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A waste barrel radioactivity characterization phantom, characterized in that: include: A support frame, on which a shaft body is arranged; A plurality of carrier frames, which are coaxially mounted on the shaft body; The carrier frame is provided with a plurality of positioning holes, the plurality of positioning holes are spaced around the shaft body in radial and circumferential directions, and the positioning holes are used to fix the point source components; A spacer is sleeved on the shaft body, and the spacer is located between two adjacent support frames.

2. The phantom according to claim 1, characterized in that The plurality of positioning holes on each of the supporting frames correspond to each other one by one and are located on the same axis.

3. The phantom according to claim 2, characterized in that The phantom is equipped with a line source component, which includes a plurality of point source components. The plurality of point source components are arranged at intervals in the same direction, and the line source components are installed in the plurality of positioning holes located on the same axis.

4. The phantom according to claim 1 or 3, characterized in that: The point source component comprises a point source sealed box and a radioactive substance, and the radioactive substance is packaged in the point source sealed box.

5. The phantom according to claim 1, characterized in that The phantom is divided into a plurality of grid cells along a radial direction around the shaft body, the plurality of grid cells have the same volume, the same number of the point source components are arranged in each of the grid cells, and the plurality of the point source components in each of the grid cells are spaced apart in the axial and circumferential directions.

6. The phantom according to claim 5, characterized in that The sizes of the plurality of grid cells satisfy the relationship of formula (1) and formula (2), and the formula (1) and formula (2) are: R 2 / n=r1 2 (1) Wherein, n is the number of the point source components, r1 is the maximum radius of the grid element closest to the axis, and r i is the maximum radius of the grid cell of the i-th layer, and 1≤i≤m, where m is the number of the grid cells.

7. The phantom according to claim 1, characterized in that The multiple positioning holes on each of the supporting frames are distributed symmetrically around the axis.

8. The phantom according to claim 1, characterized in that The projection of the support frame in the axial direction of the shaft body is circular.

9. The phantom according to claim 1, characterized in that The material of the supporting frame is metal, plastic, textile or concrete.

10. A method for calibrating detection efficiency of a detection device, characterized in that: Using the phantom described in any one of claims 1 to 9 to calibrate detection efficiency, the detection device comprises a cavity and a plurality of detectors, the cavity is used to accommodate the phantom, and the plurality of detectors are distributed at intervals along the wall of the cavity; The method comprises: Dividing the phantom into a plurality of detection areas; For each of the detection areas in the phantom, at least one point source component is set in the detection area, and the phantom is placed in the detection equipment for detection, and the detection efficiency of the multiple detectors for the detection area is obtained based on the detection results obtained and the radioactive activity of the point source component.

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