A radiation source positioning device and method

Abstract

The invention discloses a radioactive source positioning device and method. The radioactive source positioning device is based on the fact that gamma rays are absorbed by matter and follow the negative exponential decay law. The scintillation crystals of two scintillator detectors are arranged vertically and opposite to each other, and the positions of the two are close, so that the counting rates of the two are approximately equal when there is no shielding body. Then, a special-shaped lead shielding body is arranged outside a scintillation crystal, so that the equivalent thickness of the lead shielding body for the radioactive source with different incident angles is different. The thickness value of the lead shielding body in the radial direction of the scintillation crystal at the position where the radioactive source is located is obtained by calculation, and then the position of the radioactive source is determined according to the thickness value. The radioactive source positioning device can obtain a relatively accurate radioactive source position at one time, and personnel will not be exposed to the radiation environment for a long time due to repeated adjustment of the search direction. The technical problem that the current radioactive source positioning device is relatively time-consuming in searching for the radioactive source can be effectively solved, and the search efficiency is improved and the equipment cost is controllable.

Description

Technical Field

[0001] The present invention belongs to the technical field of radiation source positioning, and in particular relates to a radiation source positioning device and method. Background Art

[0002] With the progress and development of society, the application of radioactive sources is becoming more and more extensive. When using radioactive sources for production and manufacturing, radioactive sources may be lost. Lost radioactive sources may have a huge impact on the ecological environment and public health. Therefore, after the radioactive source is lost, it needs to be retrieved as soon as possible to minimize the time the outside world is exposed to radiation from the radioactive source.

[0003] Since radioactive sources are generally small in size, it is difficult to find them quickly with the naked eye after they are lost. The longer the search time, the greater the radiation damage to the personnel. Therefore, it is necessary to use radioactive source positioning equipment to find the lost radioactive source. At present, there are generally two types of radioactive source positioning equipment. One is a radioactive source positioning equipment that uses a single detector. The operator needs to hold the radioactive source positioning equipment in the environment for detection. According to the CPS (count rate) of the radioactive source positioning equipment, the operator continuously moves in the direction of increasing CPS until the operator reaches the vicinity of the radioactive source. Using this radioactive source positioning equipment, the approximate direction of the radioactive source can only be determined based on the change in the count rate. The entire search process may require multiple adjustments to the search direction. The operator is exposed to the radiation environment for a long time, which causes greater harm to the operator. The second is a radioactive source positioning equipment that uses a gamma camera, but gamma cameras are only suitable for environments with smaller scenes, and gamma cameras are relatively expensive.

[0004] Therefore, it is necessary to design a low-cost radiation source positioning device that can quickly determine the orientation of the radiation source. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a radiation source locating device and method to solve the technical problem that the current radiation source locating device is time-consuming to find the radiation source, thereby achieving the effect of improving the search efficiency and controlling the equipment cost.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A radiation source positioning device comprises a scintillator detector, the scintillator detector comprises a cylindrical scintillator crystal, there are two scintillator detectors, the scintillator crystals of the two scintillator detectors are both arranged vertically, and the two scintillator crystals are arranged vertically opposite and adjacent to each other;

[0008] Any scintillation crystal is covered with a ring-shaped lead shielding body of equal length to the scintillation crystal. The thickness of the lead shielding body in the radial direction of the scintillation crystal gradually decreases from a maximum thickness to a minimum thickness in the circumferential direction of the scintillation crystal. The position of the maximum thickness and the position of the minimum thickness are adjacent to each other in the circumferential direction of the scintillation crystal.

[0009] Furthermore, the radiation source positioning device also includes a calculation control module and a display module, and the calculation control module is electrically connected to the display module and the two scintillator detectors respectively.

[0010] Furthermore, the outer contour of the horizontal cross section of the lead shield is circular and concentric with the scintillation crystal, and the inner contour is a spiral line connected at both ends by a straight line extending radially along the scintillation crystal, and the first and last ends of the spiral line are respectively the positions of the maximum thickness and the minimum thickness.

[0011] Furthermore, the inner contour of the horizontal cross section of the lead shield is circular and concentric with the scintillation crystal, and the outer contour is a spiral line connected at both ends by a straight line extending radially along the scintillation crystal, and the first and last ends of the spiral line are respectively the positions where the minimum thickness is located and the positions where the maximum thickness is located.

[0012] The present invention also includes a method for locating a radiation source, using the radiation source locating device as described above, comprising the following steps:

[0013] 1) Calibrate the radiation source positioning equipment in an environment without radiation sources;

[0014] 2) placing the radiation source positioning device in an environment with a radiation source, and two scintillator detectors perform measurements and transmit the measurement data to a computing control module;

[0015] 3) The calculation control module calculates and confirms the location of the radiation source based on the two sets of measurement data.

[0016] Further, step 3) includes the following sub-steps:

[0017] 31) The calculation control module brings the two sets of measurement data into a preset thickness value formula to calculate the thickness value of the lead shielding body in the radial direction of the scintillation crystal at the location of the radiation source;

[0018] 32) The calculation control module brings the calculated thickness value into the preset thickness value and direction comparison table, determines the location of the radiation source and displays it externally through the display module.

[0019] Furthermore, in step 1), the radiation source positioning device is first placed in an environment without a radiation source, and two scintillator detectors measure the background to obtain baseline data, and the two scintillator detectors are calibrated according to the baseline data.

[0020] Further, in step 2), the measurement data includes count rate and energy spectrum data.

[0021] Further, in step 31), the thickness value formula is as follows:

[0022] CPS S2 =CPS S1 ×e -L×λ

[0023] Among them, CPS S2 Count rate of a scintillator detector with a lead shield over the scintillator crystal, CPS S1 is the count rate of another scintillator detector, e is a constant, L is the thickness of the lead shielding body in the radial direction of the scintillator crystal at the location of the radiation source, and λ is the lead shielding coefficient of the radiation source.

[0024] Furthermore, in step 31), the calculation control module first determines the type of nuclide of the radiation source according to the energy spectrum data of the scintillator detector without the lead shielding body, and then determines the value of λ.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The radiation source positioning device of the present invention is based on the fact that gamma rays are absorbed by matter and follow the negative exponential decay law. The scintillation crystals of two scintillator detectors are arranged vertically and opposite to each other, and the positions of the two are close, so that the counting rates of the two without a shielding body should be approximately equal. Then, a special-shaped lead shielding body is arranged outside a scintillation crystal, so that the equivalent thickness of the lead shielding body for the radiation source with different incident angles is different; thereby, the thickness value of the lead shielding body in the radial direction of the scintillation crystal at the position of the radiation source is obtained by calculation. Since a certain specific thickness value has a unique corresponding position in the circumferential direction of the lead shielding body, the position of the radiation source can be determined according to the thickness value; through the radiation source positioning device, a relatively accurate radiation source position can be obtained at one time, and the operator will not be exposed to the radiation environment for a long time due to repeated adjustment of the search direction, which can effectively solve the technical problem that the current radiation source positioning device is relatively time-consuming in finding the radiation source, improve the search efficiency, and the equipment cost is not much increased compared with the existing single-detector radiation source positioning device, and the cost is controllable.

[0027] 2. The radiation source locating device of the present invention is based on two scintillator detectors and adds a lead shield, a computing control module and a display module. It has low cost and is applicable to a wider range of scenarios. It can achieve more accurate positioning of lost radiation sources and effectively reduce the time personnel spend searching for radiation sources.

[0028] 3. The radiation source locating method of the present invention provides a thickness formula based on the negative exponential decay law followed by the absorption of gamma rays by matter. By using the radiation source locating device to obtain the counting rates of two scintillator detectors and the lead shielding coefficient of the lost radiation source, the thickness of the lead shielding body in the radial direction of the scintillator crystal at the location of the radiation source can be calculated, and then the location of the radiation source can be quickly determined based on the thickness value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the main structure of a radiation source positioning device according to an embodiment;

[0030] Figure 2 A schematic diagram of the positional relationship between the lead shield and the scintillation crystal in the embodiment;

[0031] Figure 3 A schematic diagram of the composition of a radiation source positioning device according to an embodiment;

[0032] Figure 4 is a schematic diagram of the equivalent thickness of the lead shielding body at different incident angles described in the embodiment;

[0033] Figure 5 A flow chart of a method for locating a radiation source according to an embodiment;

[0034] Among them, there are scintillation crystal 1, photomultiplier tube 2, and lead shielding body 3. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0036] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invention product is usually placed when used, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical", etc. do not mean that the components are absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] Example:

[0038] See also Figure 1 and Figure 2 , a radioactive source positioning device, including a scintillator detector, which uses the flashes generated by ionizing radiation in certain substances for detection, and the detection end of the scintillator detector uses a cylindrical scintillator crystal 1, one end of the scintillator crystal is connected to a photomultiplier tube 2, and the photomultiplier tube is used to convert the optical signal generated by the scintillator crystal into an electrical signal for subsequent processing;

[0039] There are two scintillator detectors in the radiation source positioning device, and the scintillator crystals of the two scintillator detectors are both arranged vertically, and the scintillator crystals of the two scintillator detectors are arranged vertically opposite and adjacent to each other; a scintillator crystal of one scintillator detector is provided with a ring-shaped lead shielding body 3 of the same length as the scintillator crystal, and the upper and lower surfaces of the lead shielding body are respectively flush with the upper and lower surfaces of the scintillator crystal provided, and the lead shielding body is a body of equal cross-section, that is, the horizontal cross-sections of the lead shielding body at various locations in the vertical direction are equal, and the thickness value of the lead shielding body in the radial direction of the scintillator crystal is uniformly reduced from a maximum thickness value to a minimum thickness value in the circumferential direction of the scintillator crystal, and the position where the maximum thickness value is located and the position where the minimum thickness value is located are adjacent to each other in the circumferential direction of the scintillator crystal.

[0040] During implementation, the lead shielding body may adopt the following two structural forms. The first is that the outer contour of the lead shielding body in the vertical cross section is circular and concentric with the scintillation crystal, and the inner contour of the lead shielding body in the vertical cross section is a circle of spiral lines connected at both ends by a straight line extending radially along the scintillation crystal, and the first and last ends of the spiral line are respectively the positions of the maximum thickness and the minimum thickness; the second is that the inner contour of the lead shielding body in the vertical cross section is circular and concentric with the scintillation crystal, and the outer contour of the lead shielding body in the vertical cross section is a circle of spiral lines connected at both ends by a straight line extending radially along the scintillation crystal, and the first and last ends of the spiral line are respectively the positions of the minimum thickness and the maximum thickness; Figure 2 As shown, in this embodiment, the lead shielding body adopts the first structural form, and the outer contour of the lead shielding body in the vertical cross section is circular, which makes it easier to install and position based on the outer contour.

[0041] The principle of the radiation source positioning device described in the present invention is as follows: the scintillation crystals of the two scintillator detectors are arranged vertically and facing each other, and the positions of the two are close, so it can be considered that the detection efficiency of the two for the radiation source is consistent, that is, the counting rates of the two when there is no shielding body should be approximately equal; during measurement, the radiation source is generally far away from the radiation source positioning device, and the radiation source shoots toward the scintillation crystal mainly on the outer circumferential surface of the scintillation crystal. After the scintillation crystal of one scintillator detector is blocked by the lead shielding body, since a part of the gamma ray of the radiation source is blocked by the lead shielding body, the gamma ray is absorbed by the material and follows the negative exponential decay law, so the counting rate of the scintillator detector is lower than that of the other scintillator detector, and since the lead shielding body has different radiation incident angles, the gamma ray of the radiation source is partially blocked by the lead shielding body, and the gamma ray is absorbed by the material and follows the negative exponential decay law, so the counting rate of the scintillator detector is lower than that of the other scintillator detector. The equivalent thickness of the source shielding effect is different, so the thickness value of the lead shielding body in the radial direction of the scintillation crystal at the location of the radiation source can be calculated. Since a specific thickness value has a unique corresponding position in the circumferential direction of the lead shielding body, the location of the radiation source can be determined according to the thickness value; the main body of the radiation source locating device is two scintillator detectors, which have a low cost. Through the radiation source locating device, a relatively accurate radiation source location can be obtained at one time, and the operator will not be exposed to the radiation environment for a long time due to repeated adjustment of the search direction. It can effectively solve the technical problem that the current radiation source locating device is more time-consuming to find the radiation source, improve the search efficiency, and the equipment cost is not much increased compared to the existing single-detector radiation source locating device, and the cost is controllable.

[0042] During measurement, the radiation source is generally far away from the radiation source positioning device, and the radiation source shoots toward the scintillation crystal mainly on the outer circumferential surface of the scintillation crystal. However, in order to improve the accuracy of the measurement, a sheet of lead shielding can be used to cover the free ends of the two scintillation crystals to prevent the radiation source from entering from the free ends of the scintillation crystals.

[0043] In addition, in this embodiment, the radiation source positioning device also includes a calculation control module and a display module. The calculation control module is electrically connected to the display module and the two scintillator detectors respectively. The calculation control module is used to control the scintillator detectors and to calculate the position of the radiation source according to the measurement data obtained by the two scintillator detectors. The display module is used to present the calculated position of the radiation source to the operator. In this embodiment, the scintillator detector in which the scintillator crystal is provided with a lead shielding body is called detector S2, and the other scintillator detector is called detector S1. The radiation source positioning device includes detector S1, detector S2, a shielding body (i.e., the lead shielding body), a main control (i.e., the calculation control module), a screen (i.e., the display module), a structure and a power supply system, such as Figure 3 shown.

[0044] The present invention also includes a method for locating a radiation source, using the radiation source locating device as described above, comprising the following steps:

[0045] 1) Calibrate the radiation source positioning device in an environment without radiation sources; specifically, first place the radiation source positioning device in an environment without radiation sources, measure the background with two scintillator detectors to obtain baseline data, and calibrate the two scintillator detectors according to the baseline data;

[0046] 2) The radiation source locating device is placed in an environment where the radiation source is lost, and two scintillator detectors perform measurements and transmit the measurement data to the computing control module; the measurement data includes count rate and energy spectrum data;

[0047] 3) The control calculation module brings the two sets of measurement data into a preset thickness value formula to calculate the thickness value of the lead shielding body in the radial direction of the scintillation crystal at the location of the radiation source;

[0048] The counting rates of the two scintillator detectors in the radiation source positioning device are approximately equal when there is no shielding body; the counting rate of one scintillator detector is lower than that of the other scintillator detector after the scintillation crystal is blocked by the lead shielding body, and the equivalent thickness of the lead shielding body for radiation sources with different incident angles is different. Figure 4 As shown in Figure 2, among the radiation sources A, B, and C, the equivalent thickness of the lead shielding body for the radiation emitted by the radiation source A is the largest, and the equivalent thickness of the lead shielding body for the radiation emitted by the radiation source C is the smallest; therefore, it can be assumed that CPS S2 is the count rate of detector S2, CPS S1 is the counting rate of detector S1, L is the thickness of the lead shield in the radial direction of the scintillation crystal at the location of the radiation source, λ is the lead shielding coefficient of the lost radiation source, and the thickness value formula is obtained based on the negative exponential attenuation law of gamma ray absorption by matter as follows:

[0049] CPS S2 =CPS S1 ×e -L×λ

[0050] Wherein, e is a numerical constant, which is the base of the natural logarithm function, e=2.71828182…; In this way, L can be calculated by the counting rate of the two scintillator detectors, and then the position of the radiation source can be determined according to L;

[0051] In addition, if the type of nuclide of the radioactive source to be found is unknown, the calculation control module first brings the energy spectrum data of the scintillator detector without the lead shielding body into the preset nuclide identification algorithm to determine the type of nuclide of the lost radioactive source, and then brings the nuclide type into the preset nuclide type and λ comparison table to determine the value of λ; the identification algorithm for determining the type of nuclide through energy spectrum data is a relatively mature technology, and the nuclide type and λ comparison table is a table in which multiple nuclide types correspond to the lead shielding coefficient of the radioactive source of the nuclide type. The lead shielding coefficient of the radioactive source of each common nuclide type can be obtained by referring to relevant materials; the radioactive source positioning method corresponds to the following Figure 5 shown.

[0052] 4) The control calculation module brings the calculated thickness value into the preset thickness value and direction comparison table, determines the location of the radiation source and displays it to the outside through the display module; the thickness value and direction comparison table is a table in which the thickness value of the lead shielding body in the radial direction of the scintillation crystal corresponds to the direction thereof.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A method for locating a radiation source, the method for locating a radiation source being performed based on a radiation source locating device, the radiation source locating device comprising a scintillator detector, the scintillator detector comprising a cylindrical scintillator crystal, characterized in that: There are two scintillator detectors, and the scintillator crystals of the two scintillator detectors are both arranged vertically, and the two scintillator crystals are arranged vertically opposite and adjacent to each other; Any scintillation crystal is provided with a ring-shaped lead shielding body of the same length as the scintillation crystal, the thickness of the lead shielding body in the radial direction of the scintillation crystal gradually decreases from a maximum thickness to a minimum thickness in the circumferential direction of the scintillation crystal, and the position of the maximum thickness and the position of the minimum thickness are adjacent in the circumferential direction of the scintillation crystal; The radiation source positioning device also includes a calculation control module and a display module, and the calculation control module is electrically connected to the display module and the two scintillator detectors respectively; The radiation source positioning method comprises the following steps: 1) Calibrate the radiation source positioning equipment in an environment without radiation sources; 2) placing the radiation source positioning device in an environment with a radiation source, and two scintillator detectors perform measurements and transmit the measurement data to a computing control module; 3) The calculation control module calculates and confirms the location of the radiation source based on the two sets of measurement data; Step 3) includes the following sub-steps: 31) The calculation control module brings the two sets of measurement data into a preset thickness value formula to calculate the thickness value of the lead shielding body in the radial direction of the scintillation crystal at the location of the radiation source; 32) The calculation control module brings the calculated thickness value into the preset thickness value and direction comparison table, determines the location of the radiation source and displays it externally through the display module.

2. A method for locating a radiation source according to claim 1, characterized in that: The outer contour of the horizontal cross section of the lead shield is circular and concentric with the scintillation crystal, and the inner contour is a spiral line connected at both ends by a straight line extending radially along the scintillation crystal, and the first and last ends of the spiral line are respectively at the positions of the maximum thickness and the minimum thickness.

3. A method for locating a radiation source according to claim 1, characterized in that: The inner contour of the horizontal cross section of the lead shield is circular and concentric with the scintillation crystal, and the outer contour is a spiral line connected at both ends by a straight line extending radially along the scintillation crystal, with the first and last ends of the spiral line respectively being the positions of the minimum thickness and the maximum thickness.

4. A method for locating a radiation source according to claim 1, characterized in that: In step 1), the radiation source positioning device is first placed in an environment without radiation sources, two scintillator detectors measure the background to obtain baseline data, and the two scintillator detectors are calibrated according to the baseline data.

5. A method for locating a radiation source according to claim 1, characterized in that: In step 2), the measured data include count rate and energy spectrum data.

6. A method for locating a radiation source according to claim 5, characterized in that: In step 31), the thickness value formula is as follows: CPS S2 =CPS S1 ×e -L×λ Among them, CPS S2 Count rate of a scintillator detector with a lead shield over the scintillator crystal, CPS S1 is the count rate of another scintillator detector, e is a constant, L is the thickness of the lead shielding body in the radial direction of the scintillator crystal at the location of the radiation source, and λ is the lead shielding coefficient of the radiation source.

7. A method for locating a radiation source according to claim 6, characterized in that: In step 31), the calculation control module first determines the type of nuclide of the radiation source according to the energy spectrum data of the scintillator detector without the lead shielding body, and then determines the value of λ.

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