CN119535521A - Radiation source positioning system and positioning method - Google Patents
Radiation source positioning system and positioning method Download PDFInfo
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Abstract
The invention discloses a radioactive source positioning system and a positioning method, wherein the positioning method comprises the steps of preparing a radiation detector and a shielding detector with a shielding block sleeved on a detection end; the thickness of the shielding block is uniformly increased, the outer end face is spiral, the shielding block reaches a suspected radiation field area, a radiation source radiation intensity counting rate N 0 and a radiation source shielding radiation intensity counting rate N of a current area are detected at the same position by adopting a radiation detector and a shielding detector, the incidence thickness and incidence angle of a radiation passing through the shielding block are judged according to a radiation attenuation formula, the direction of the radiation source is determined, radiation source direction information is obtained, meanwhile, the distance between the radiation source and the radiation detector is calculated according to the measured radiation intensity of the radiation source, and the radiation source is positioned according to the direction information of the radiation source and the distance between the radiation source and the radiation detector.
Description
Technical Field
The invention relates to the field of nuclear radiation detection, in particular to a radioactive source positioning system and a radioactive source positioning method.
Background
With the continuous development of the nuclear industry, the application of the radioactive source is more and more extensive, and the radioactive source is frequently leaked and stolen, so that the physical health and life safety of people are seriously threatened, and the rapid searching and removal of scattered radioactive pollution sources has great practical significance. Currently, the radiation source is searched for a target area by a worker who engages in nuclear technology professionals, carries a radiation detector, and is performed by self experience, or by a vehicle loading detector. These approaches are inefficient and, in severe cases, may jeopardize the safety of the operator.
The China patent with the application number 2024103808269 discloses a radioactive source positioning method and device, wherein a detection device is used for collecting radiation intensity information of surrounding environment, first position information of the detection device is obtained, horizontal rotation and pitching deflection of the detection device are controlled, the first radiation intensity information of the surrounding environment is collected, a first radiation intensity image is generated according to the first radiation intensity information, a first azimuth angle of a radioactive source relative to the detection device is determined according to the first radiation intensity image, second position information of the detection device when the detection device is at a second position is obtained, second radiation intensity information of the surrounding environment is collected, a second radiation intensity image is generated according to the second radiation intensity information, a second azimuth angle of the radioactive source relative to the detection device is determined according to the second radiation intensity image, and position information of the radioactive source is determined according to the first azimuth angle, the second azimuth angle and the distance between the first position and the second position. The detection method adopts a detection device to acquire different radiation intensities at different positions, and then determines the position information of the radioactive source by the distance between the radiation intensities detected twice and the position information. Although the radiation source position is acquired through the integration of the two azimuth angles, the method of determining the azimuth angle by detecting the primary radiation intensity through one detector is not accurate in both the acquisition of the azimuth angles.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a radioactive source positioning system and a radioactive source positioning method, which solve the problem that the acquisition mode of the azimuth angle of the radioactive source is inaccurate, so that the later positioning result is inaccurate in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme:
A radioactive source positioning system comprises a detection module, a power supply module and a main control module, wherein the detection module is electrically connected with the power supply module 1 and comprises a radiation detector and a shielding detector, the radiation detector is used for detecting the radiation intensity counting rate of a radioactive source in the current environment and transmitting the detected radiation intensity to the main control module, a shielding block with the thickness being uniformly increased is sleeved on a detection end of the shielding detector and is used for detecting the shielding radiation intensity counting rate of the radioactive source in the same position and the detection environment of the radiation detector and transmitting the shielding radiation intensity counting rate of the radioactive source to the main control module, the main control module is electrically connected with the power supply module and comprises a data processing module, the data processing module is used for receiving the radiation intensity counting rate of the radioactive source sent by the radiation detector and the shielding radiation intensity counting rate of the radioactive source sent by the shielding detector, calculating the distance of the radioactive source relative to the detection module according to a radiation attenuation formula, meanwhile, judging the incidence thickness and incidence angle of the radiation source passing through the shielding block, determining the azimuth of the radioactive source and finally determining the position information of the radioactive source relative to the position of the radioactive source or the cloud end of the radioactive source. Therefore, the adopted radioactive source positioning system is provided with the radiation detector and the shielding detector, can test the radiation intensity of the suspected lost area of the radioactive source at the same position, and obtain the shielded radiation intensity and the unshielded radiation intensity, so that the incident thickness of rays emitted by the radioactive source can be judged according to the proportional relation between the two, and the azimuth of the radioactive source is further determined. The method comprises the steps of comparing the shielding radiation intensity with the current radiation intensity, determining the shielding thickness, and determining the position of the radioactive source according to the position of the shielding thickness corresponding to the shielding block, so that the position acquisition is more accurate. The thickness of the shielding block is balanced and increased, and the installation orientation is fixed, so that after the radioactive rays are injected into different orientations, the intensity counting rate of the radioactive sources detected after shielding is different, and the orientations are more accurate. On the premise that the radiation source position is more accurate, the radiation source positioning obtained by combining the radiation source position and the distance between the radiation source and the radiation detector is more accurate. The adopted system has less parts and less calculation amount, and can be widely popularized.
Further, the ray attenuation formula is as follows, wherein N=N 0e-ud, N 0 is radiation intensity counting rate of the radioactive source, N is shielding radiation intensity counting rate of the radioactive source, u is attenuation coefficient of gamma rays in the shielding block, d is shielding thickness of the shielding block at the incidence position, and the ray attenuation formula is transformed to obtain the following formula: The position of the shielding thickness d corresponding to the thickness position interval on the shielding block is the incident angle of the ray, and the incident angle indication azimuth is the azimuth of the radioactive source. Thus, after the formula is adopted, specific numerical values detected by the radiation detector and the shielding detector are substituted into the formula, so that the shielding thickness of the incident rays can be rapidly obtained, and the incident angle and the direction can be determined.
The wireless remote control system further comprises a display alarm module, wherein the display alarm module is electrically connected with the power supply module and is in communication connection with the main control module, the wireless remote control system comprises a display module and an alarm module, the display module is used for displaying the positioning information of the radioactive source sent by the main control module, the main control module is further used for sending alarm information to the alarm module after receiving the radiation intensity exceeding an alarm threshold value, and the alarm module is used for receiving the alarm information sent by the main control module and giving an alarm through voice or lamplight. Therefore, after the display alarm module is adopted, the corresponding operation of operators can be conveniently carried out.
The radiation detector and the shielding detector are respectively assembled in a protective cover or in a protective shell, and the detection ends are adjacently arranged. Thus, in application, the radiation detector and the shielded detector may be mounted as desired.
A radioactive source positioning method includes the steps of S1, preparing two detectors, wherein one of the two detectors is a radiation detector 21, the other one of the two detectors is a shielding detector with a shielding block sleeved on a detection end, the thickness of the shielding block is uniformly increased, the outer end face of the shielding block is spiral, S2, reaching a suspected radiation field area, detecting a radioactive source radiation intensity counting rate N 0 and a radioactive source shielding radiation intensity counting rate N of a current area at the same position by the aid of the radiation detector and the shielding detector, S3, calculating the incidence thickness and the incidence angle of a radiation passing through the shielding block according to a radiation attenuation formula through a controller, determining the position of the radioactive source, obtaining radioactive source position information, meanwhile, calculating the distance between the radioactive source and the radiation detector according to the measured radioactive source radiation intensity, and determining the position of the radioactive source according to the position information of the radioactive source and the distance of the radioactive source relative to the radiation detector, and positioning the radioactive source. Therefore, when the radioactive source is positioned, the azimuth of the radioactive source is determined according to different radiation intensity counting rates detected by the two detectors, and then the distance between the detectors and the radioactive source is calculated by combining the radiation intensity dosage rates of the radioactive source detected by the detectors, so that the accurate position of the radioactive source can be determined under the double indication of the azimuth and the distance. When the direction of the radioactive source is determined, the shielding thickness of the radioactive rays is calculated according to the ratio of the radiation intensity counting rate of the unshielded radioactive source to the radiation intensity counting rate of the shielded radioactive source, and the direction of the radioactive source is determined according to the direction corresponding to the shielding thickness in the shielding block, so that the direction is acquired more accurately. The thickness of the shielding block is balanced and increased, and the installation orientation is fixed, so that after the radioactive rays are injected into different orientations, the intensity counting rate of the radioactive sources detected after shielding is different, and the orientations are more accurate.
Further, in order to reduce errors during positioning of the radioactive source, two radioactive source positioning steps are performed successively, wherein the testing position in the second radioactive source positioning step is to replace a new position after the first testing step is finished and then to perform radioactive source radiation intensity testing, the two radioactive source positioning steps are as described in S2-S4, a radioactive source positioning section 1 is obtained after the first radioactive source positioning step, a radioactive source positioning section 2 is obtained after the second radioactive source positioning step, whether overlapping exists between the two radioactive source positioning sections or not is determined after the radioactive source positioning section 1 and the radioactive source positioning section 2 are obtained, if the radioactive source is not considered to be shielded, multiple testing steps are required to be performed, and accuracy is improved, and if the overlapping sections exist, the overlapping sections are integrated and then are used as the radioactive source positioning sections. In this way, after the radiation source positioning section is determined a plurality of times, the manner in which the overlapping portions of the positioning sections are set as the radiation source positioning sections is more accurate than the one-time determination.
Further, in order to adapt the method for rapid positioning of the radiation source to a plurality of nuclides, appropriate expansion is required. For the formula n=n 0e-ud, N and N 0 are detector measurement data, which can be directly read, e is a constant, u is a shielding coefficient of a shielding body to a certain nuclide, u is a constant when the nuclide is determined, d is a thickness of the shielding body corresponding to the direction of the radioactive source, and is the only required variable. For a specific nuclide, the shielding coefficient u can be found, the thickness d can be calculated only by substituting measured N and N 0, the direction of the radioactive source can be determined, the nuclide type can be determined by using a detector with nuclide identification capability, different u values are called according to the nuclide type, and the quick positioning of a plurality of nuclides is realized.
Further, in S2, when detecting the radiation intensity counting rate N 0 of the radiation source and the shielding radiation intensity counting rate N of the radiation source, the radiation detector and the shielding detector are installed in the same protective cover to synchronously detect, and when installing, the detection end of the radiation detector and the shielding detector are arranged up and down, and the two detection ends are adjacent. In the specific implementation, when the radiation intensity counting rate N 0 of the radioactive source and the shielding radiation intensity counting rate N of the radioactive source are detected, the radiation detector and the shielding detector can be respectively assembled in a protective shell and tested at the same test position in sequence. Therefore, in the application process, synchronous measurement and sequential measurement can be realized, so that the existing detector can be modified according to actual conditions, and the radiation intensity counting rate N 0 of the radioactive source and the shielding radiation intensity counting rate N of the radioactive source can be measured in two modes. The two detectors are arranged together and then are synchronously detected, so that the method is more convenient and faster.
Drawings
FIG. 1 is a block diagram of a radiation source positioning system according to an embodiment;
FIG. 2 is a schematic diagram of a split structure of a shielding detector and a shielding block in an embodiment;
FIG. 3 is a schematic diagram illustrating a state that a radiation beam is incident on a shielding block according to an embodiment;
FIG. 4 is a flowchart of a method for positioning a radiation source according to an embodiment;
FIG. 5 is a schematic view of the ray angle between the detector and the radiation source according to an embodiment;
FIG. 6 is a schematic diagram showing azimuth angles under multiple measurements in the embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that like reference numerals and letters refer to like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. In the description of the present invention, it should be noted that, directions or positional relationships indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., are directions or positional relationships based on those shown in the drawings, or are directions or positional relationships conventionally put in use of the inventive product, are merely for convenience of describing the present invention and simplifying the description, and are not indicative or implying that the apparatus or element to be referred to must have a specific direction, be constructed and operated in a specific direction, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance. Furthermore, the terms "horizontal," "vertical," and the like do not denote a requirement that the component be absolutely horizontal or overhang, but rather may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined. In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, integrally connected, mechanically connected, electrically connected, directly connected, indirectly connected through an intermediary, or in communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
This example investigated how to quickly locate a lost source, generally known as a gamma source, which has a strong penetration. In radiation source positioning, the radiation source can be regarded approximately as a point source, the gamma ray source constantly emits gamma photons to the surrounding space, the gamma photons emitted by the source to the surrounding space are isotropic, and the counting rate n of the detector at the distance r obeys the following formula:
Where ε is the detection efficiency of the detector, A is the activity of the radiation source, and r is the distance between the detector and the radiation source. From the above equation, it can be derived that the detector count rate n is inversely proportional to the square of its distance from the source, and that determining the position of the radiation source by detecting a change in the radiation light count rate is one of the most basic methods. In addition, the gamma rays generated by the radioactive source propagate along a straight line and have directivity, the intensity of the gamma rays is weakened when the gamma rays pass through the shielding substance, the attenuation formula is obeyed by N=N 0e-ud,
Wherein N 0 and N respectively represent the photon numbers before and after passing through the material layer, d is the thickness of the material layer, u is the line weakening coefficient of gamma rays in the material, and the direction detector sensitive to the gamma rays can be researched by the property so as to achieve the purpose of positioning the radioactive source.
As shown in fig. 1 and 2, the radiation source positioning system provided in this embodiment includes a detection module 2, a power supply module 1 and a main control module 3, where the detection module 2 is electrically connected with the power supply module 1, and includes a radiation detector 21 and a shielding detector 22, where the radiation detector 21 is configured to detect the radiation intensity counting rate of the radiation source in the current environment and send the detected radiation intensity to the main control module 3, a shielding block 23 with a uniformly increasing thickness is sleeved on the detection end of the shielding detector 22, and is configured to detect the radiation intensity counting rate of the radiation source in the same position and in the detection environment of the radiation detector 21 and send the radiation intensity counting rate of the radiation source to the main control module 3, and the main control module 3 is electrically connected with the power supply module 1, and includes a data processing module 31 configured to receive the radiation intensity counting rate of the radiation source emitted by the radiation detector 21 and control the starting and stopping of the first detection module and the shielding detector 22, and calculate the radiation intensity counting rate of the radiation source according to the radiation intensity counting rate p of the radiation source, and simultaneously determine the radiation intensity counting rate of the radiation source passing through the radiation source and the radiation intensity counting rate of the radiation source and the radiation source according to the position of the radiation source position and the radiation intensity counting angle of the radiation source and the radiation source position of the radiation source. The power supply module 1 is provided with electric energy by a power supply source and is also provided with a charging circuit for charging the power supply source by an external power supply. Thus, the adopted radioactive source positioning system is provided with the radiation detector 21 and the shielding detector 22, can test the radiation intensity of the suspected lost area of the radioactive source at the same position, and obtain the shielded radiation intensity and the unshielded radiation intensity, so that the incident thickness of rays emitted by the radioactive source can be judged according to the proportional relation between the two, and the azimuth of the radioactive source is further determined. The method of comparing the shielding radiation intensity with the current radiation intensity, determining the shielding thickness, and determining the position of the radioactive source according to the position of the shielding thickness corresponding to the shielding block 23 is more accurate in position acquisition. The thickness of the shielding block 23 is balanced and increased, and the mounting orientation is fixed, so that after the radiation is injected into different orientations, the counting rate of the intensity of the radiation source detected after shielding is different, and the orientation is more accurate. The radiation source positioning obtained by combining the radiation source position and the distance of the radiation source from the radiation detector 21 is more accurate on the premise that the radiation source position is more accurate. The adopted system has less parts and less calculation amount, and can be widely popularized.
Further, the ray attenuation formula is as follows, n=n 0e-ud, where N 0 is the radiation intensity counting rate of the radioactive source, N is the shielding radiation intensity counting rate of the radioactive source, u is the line attenuation coefficient of gamma rays in the shielding block 23, d is the shielding thickness of the shielding block 23 at the incidence position, and the ray attenuation formula is transformed to obtain: The position of the shielding thickness d corresponding to the thickness position interval on the shielding block 23 is the incident angle of the ray, and the direction indicated by the incident angle is the direction of the radioactive source. Thus, after the above formula is adopted, specific values detected by the radiation detector 21 and the shielding detector 22 are substituted into the formula, so that the shielding thickness of the incident ray can be rapidly obtained, and the incident angle and the direction can be determined.
The intelligent power supply system further comprises a display alarm module 4, wherein the display alarm module 4 is electrically connected with the power supply module 1 and is in communication connection with the main control module 3, the intelligent power supply system comprises a display module 41 and an alarm module 42, the display module 41 is used for displaying radioactive source positioning information sent by the main control module 3, the main control module 3 is also used for sending alarm information to the alarm module 42 after receiving radiation intensity exceeding an alarm threshold, and the alarm module 42 is used for receiving the alarm information sent by the main control module 3 and giving an alarm through voice or lamplight. Thus, after the display alarm module 4 is adopted, the operator can conveniently perform corresponding operation. After the alarm module 42 alarms, the main control module 3 can control the shielding detector 22 to be turned on to perform radiation measurement. The shielding detector 22 and the radiation detector 21 in this embodiment are LaBr3 detectors. The main control module 3 further comprises a storage module and a communication module, the storage module is used for storing the detection data sent by the detection module 2, and the communication module is used for transmitting information.
Further, the shielding block 23 is a lead shielding block 23 or a tungsten shielding block, the radiation detector 21 and the shielding detector 22 are respectively assembled in a protective cover or a protective shell, and the detection ends are adjacently arranged. Thus, in application, the radiation detector 21 and the shielded detector 22 may be mounted as desired.
As shown in fig. 2-6, the present embodiment further provides a method for positioning a radiation source, including the steps of S1, preparing two detectors, one of which is a radiation detector 21 and the other is a shielding detector 22 having a shielding block 23 sleeved on a detection end; the thickness of the shielding block 23 is uniformly increased, the outer end face is spiral, S2, the suspected radiation field area is reached, the radiation intensity counting rate N 0 and the radiation source shielding radiation intensity counting rate N of the current area are detected at the same position by adopting the radiation detector 21 and the shielding detector 22, S3, the incidence thickness and incidence angle of the radiation passing through the shielding block 23 are judged according to a radiation attenuation formula, the position of the radiation source is determined according to the incidence thickness and incidence angle of the radiation source, so as to obtain radiation source position information, meanwhile, the distance between the radiation source and the radiation detector 21 is calculated according to the measured radiation intensity of the radiation source, S4, the position of the radiation source is determined according to the position information of the radiation source and the distance between the radiation source and the radiation detector 21, the first positioning of the radiation source is completed, the radiation source positioning interval 1 is obtained, S5, the second positioning of the radiation source is completed by repeating S2-S4, the radiation source positioning interval 2 is obtained, S6 is determined, whether the two radiation source positioning intervals are coincident or not is carried out, if the two radiation source positioning intervals are coincident, and if the two radiation positioning intervals are coincident, and the two radiation positioning intervals are integrated, and the two overlapping intervals are taken as the radiation positioning intervals after the coincidence intervals are carried out. Therefore, when the radioactive source is positioned, the azimuth of the radioactive source is determined according to different radiation intensity counting rates detected by the two detectors, and then the distance between the detectors and the radioactive source is calculated by combining the radiation intensity dosage rates of the radioactive source detected by the detectors, so that the accurate position of the radioactive source can be determined under the double indication of the azimuth and the distance. When the position of the radioactive source is determined, the shielding thickness of the radioactive source is calculated according to the ratio of the radiation intensity counting rate of the unshielded radioactive source to the radiation intensity counting rate of the shielded radioactive source, and the position of the radioactive source is determined according to the position corresponding to the shielding thickness in the shielding block 23, so that the position acquisition is more accurate. The thickness of the shielding block 23 is balanced and increased, and the mounting orientation is fixed, so that after the radiation is injected into different orientations, the counting rate of the intensity of the radiation source detected after shielding is different, and the orientation is more accurate. After the radioactive source positioning interval is judged for a plurality of times, the mode of taking the superposition part of each positioning interval as the radioactive source positioning interval is more accurate compared with the one-time judgment.
Further, in order to adapt the method for rapid positioning of the radiation source to a plurality of nuclides, appropriate expansion is required. For the formula n=n 0e-ud, N and N 0 are detector measurement data, which can be directly read, e is a constant, u is a shielding coefficient of a shielding body to a certain nuclide, u is a constant when the nuclide is determined, d is a thickness of the shielding body corresponding to the direction of the radioactive source, and is the only required variable. For specific nuclides, the shielding coefficient u can be found, the thickness d can be calculated by substituting measured N and N 0, the direction of the radioactive source is determined, the nuclide type can be determined by using a detector with nuclide identification capability, different u values are called according to the nuclide type, and the rapid positioning of multiple nuclides is realized. In order to further improve the positioning accuracy, the specific values of N and N 0 when a specific radioactive source is positioned in the directions of different thicknesses d of the shielding body can be measured through an actual measurement experiment, a fitting formula for expressing the thickness d by using N and N 0 is obtained, a main control program of the system is directly written, and the system can automatically judge the azimuth of the radioactive source according to the measured values of N and N 0. The fitting formula is not greatly different from the theoretical formula obtained by inquiring the u value, and the fitting formula can be directly used if the conditions are limited. In order to verify the accuracy of the fitting formula, the error analysis can be carried out on the results of multiple actual measurement experiments, the formula is finely adjusted in the process, and the obtained shielding angle calculation formula is more accurate.
Further, in S2, when the radiation intensity counting rate N 0 of the radiation source and the shielding radiation intensity counting rate N of the radiation source are detected, the radiation detector 21 and the shielding detector 22 are installed in the same protective cover to synchronously detect, and when the radiation detector is installed, the detection end of the radiation detector 21 and the shielding detector 22 are arranged up and down, and the two detection ends are adjacent. In the specific implementation, when the radiation intensity counting rate N 0 of the radioactive source and the shielding radiation intensity counting rate N of the radioactive source are detected, the radiation detector 21 and the shielding detector 22 can also be respectively assembled in a protective shell and tested at the same test position in sequence. Therefore, in the application process, synchronous measurement and sequential measurement can be realized, so that the existing detector can be modified according to actual conditions, and the radiation intensity counting rate N 0 of the radioactive source and the shielding radiation intensity counting rate N of the radioactive source can be measured in two modes. The two detectors are arranged together and then are synchronously detected, so that the method is more convenient and faster.
During field measurement, a tripod can be optionally matched to adapt to uneven terrain. A level gauge is arranged above the tripod, so that the level gauge can be placed horizontally during measurement.
The shielding block 23 adopted in the embodiment is a lead shielding block 23, the minimum thickness is 2mm, the maximum thickness is 20mm, the thickness is uniformly increased along the clockwise direction, a mounting hole is formed in the middle of the shielding block 23, and the shielding block 23 is sleeved and fixed with the detection end of the shielding detector 22 through the mounting hole. The radiation source azimuth measuring device has the working principle that the device is provided with two independent detection ends for measuring the radiation intensity of a measured environment, one detector is unshielded and can directly measure the radiation intensity of the position, the detection end of the other detector is sleeved with a lead shielding block 23, the measured radiation intensity is that rays pass through the lead shielding block 23 and are attenuated, the attenuation coefficient of the rays passing through a substance is related to the type and the thickness of the substance according to a ray attenuation formula, the thickness of shielding lead is uniformly increased, the thickness of lead in each direction is different, therefore, for gamma rays injected in different directions, the measured values of the lead shielding detectors 22 are different, the proportional relation is calculated by comparing the measured results of the two detectors, the incidence angle of the gamma rays can be judged, and the azimuth of the radiation source is determined.
Taking the experimental data of one 137Cs azimuth measurement as an example, the count n0= 105438 of the actually measured unshielded detector 22, and the change of the count N of the lead shielded detector 22 along with the angle are as follows (the measurement time is uniformly 30 s):
substituting N0, N and β, calculating an angle fitting formula of β=183.705×ln (N/N0) -45.468, substituting the angle fitting formula into the actual measurement result, and calculating an angle measurement error as follows:
| Actual beta | 0 | 15 | 30 | 45 | 60 | 75 |
| Error value | -0.86 | 0.85 | 0.74 | -0.29 | -0.12 | 0.33 |
| Actual beta | 90 | 105 | 120 | 135 | 150 | 165 |
| Error value | -0.49 | -0.69 | 0.50 | 0.61 | -0.59 | -0.65 |
| Actual beta | 180 | 195 | 210 | 225 | 240 | 255 |
| Error value | -0.53 | -0.10 | -0.39 | 0.51 | -0.90 | -0.32 |
| Actual beta | 270 | 285 | 300 | 315 | 330 | 345 |
| Error value | -0.80 | -0.71 | -0.78 | -0.37 | -0.69 | 0.63 |
The fitting equation was verified with another 137Cs source, n=298389, N 0 and the angle error are as follows (30 s for measurement time unification):
| Angle beta | 0 | 15 | 30 | 45 | 60 | 75 |
| Count N | 233862 | 213891 | 197211 | 182409 | 168165 | 154280 |
| Error value | -0.70 | 0.69 | 0.60 | -0.05 | -0.12 | 0.70 |
| Actual beta | 90 | 105 | 120 | 135 | 150 | 165 |
| Count N | 143116 | 131832 | 120892 | 111239 | 102985 | 94548 |
| Error value | -0.49 | -0.40 | 0.50 | 0.79 | -0.03 | 0.66 |
| Actual beta | 180 | 195 | 210 | 225 | 240 | 255 |
| Count N | 87504 | 80636 | 74311 | 68257 | 63294 | 58236 |
| Error value | -0.11 | -0.09 | -0.09 | 0.51 | -0.61 | -0.31 |
| Actual beta | 270 | 285 | 300 | 315 | 330 | 345 |
| Count N | 53612 | 49568 | 45651 | 42020 | 38756 | 35494 |
| Error value | -0.11 | -0.70 | -0.58 | -0.36 | -0.50 | 0.64 |
The two measurement results are similar, the error is controllable, and the situation is unchanged in a plurality of experiments, so that the fitting formula is suitable for the azimuth detection of the 137Cs radioactive source by the device. The maximum thickness of the lead shielding block 23 in this embodiment is 20mm, the angle of the radial line of this thickness is positioned 0 °, and so on. On this basis, the radiation source shielding azimuth angle beta and the thickness d of the lead shielding block 23 are related by beta=20 (d-2).
In the specific implementation, the shielding blocks 23 are made of different materials, and under the condition that the shielding thickness is set to be different, the calculation formulas of the shielding angles are also different.
After the above-described position determination is completed, the position direction will be opposite the radiation source, while the indicated dose rate P is the dose rate of the radiation field generated by the radiation source at the device. According to the dose rate formula of a certain point in the radiation field:
Wherein P is the air kerma rate, namely the dosage rate, the unit is Gy/h, A is the activity of the point source, the unit is Ci or Bq, L is the distance between the measuring point and the point source, the unit is m, and Γ K is the air kerma rate constant.
When the type of the lost radioactive source is known, the distance between the radioactive source and the equipment can be directly calculated, and the position of the radioactive source can be deduced by combining the current azimuth direction. In practical situations, the measured dose rate value may have an error, the azimuth measurement value may have an error, and the positioning result may be inaccurate, so that data processing is required. The azimuth measurement angle error may cause the radioactive source to be positioned at an angle offset from the direction of indication, the angle being the maximum value of the angle error of the measuring instrument, and the radioactive source is positioned between two clip angles. Thus, to reduce errors, the source position is quickly determined, in this embodiment two source positions are performed one after the other. After multiple measurements, the radiation source position interval is gradually narrowed, the actual position of the radiation source is in the intersection of all test results, and the positioning is completed at this time, so that the radiation source can be recovered. If the area of the contaminated area is large or the site topography is complex, the increase of measurement points can be considered to improve the positioning accuracy.
When the radioactive source is shielded, the measurement result in a certain direction can generate larger deviation, the positioning interval formed by measurement is greatly different from other measurement results, the point position test result is ignored during positioning, and the shielded obstacle is bypassed for detection again.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the technical solution, and those skilled in the art should understand that modifications and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the present invention, and all such modifications and equivalents are included in the scope of the claims.
Claims (9)
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