CN107064987A - A kind of radioactive source alignment system and localization method - Google Patents

Abstract

The invention discloses a radioactive source positioning system and positioning method. The system includes: at least two nuclear radiation detectors, a blocking sheet, and an information processing center; the detectors are used to obtain the nuclear radiation count and energy of the radioactive source; the blocking sheet is located at Between the detectors, it is used to block part of the nuclear radiation counts received by at least one of the nuclear radiation detectors; the information processing center is used to read the signals of the detectors, and determine the azimuth information of the radioactive source according to the signals; and , looking for radioactive sources by driving a car, or a drone, or a submarine, or a handheld terminal. The radiation source positioning system and method of the present invention have low cost, good repeatability, and can work stably for a long time; the azimuth angle is determined, the positioning field of view is large, blind search is avoided, and the efficiency of radiation source search is improved; the positioning process is simple and fast, It can reduce the harm caused by long-term exposure to radiation sources.

Description

A radioactive source positioning system and positioning method

technical field

The invention belongs to the technical field of nuclear radiation detection, and in particular relates to a radiation source positioning system and a positioning method.

Background technique

Since the discovery of radioactivity, humans have been committed to applying radiation to various aspects such as industry, agriculture, medicine, resources, environment, and military affairs, such as non-destructive testing, radiation therapy, and radiation treatment. While the radiation sources that emit rays benefit mankind, they are also very dangerous. As far as the radioactive source itself is concerned, due to its high energy, it can cause ionizing radiation, cause cell lesions or destroy cell tissues, thus causing harm to the human body. Therefore, reasonable preservation of radioactive sources is very important. When a radioactive source is lost, leaked or stolen, it is necessary to find, locate and deal with the radioactive source.

In the prior art, the traditional work of searching for radioactive sources is to manually carry nuclear radiation detectors on foot to determine the nuclear contaminated area and search for lost radioactive sources. A large number of detections are required to determine the approximate location of radioactive sources; in order to accurately obtain the location of radioactive sources For specific locations, surveyors need to carry detectors into high-radiation areas for measurement and positioning. Because the detection process takes a long time, source search personnel are likely to be exposed to radiation from radioactive sources at close range, resulting in additional dose exposure.

On the other hand, the commonly used conventional nuclear radiation detectors do not have the ability to locate the direction and can only increase the dose value, thus making it difficult to find the radioactive source. In recent years, detectors with imaging capabilities, such as coded plate imaging detectors and Compton cameras, have also been developed and utilized, but these detectors are expensive and difficult to be widely used.

Contents of the invention

The technical problem to be solved by the embodiments of the present invention is to reduce the risk and cost of the radioactive source locating process. The present invention proposes a radioactive source locating system and locating method. The cost of locating the radioactive source is low. Quickly locate and reduce the physical injury to the source-finding staff during the source-finding process.

According to one aspect of the present invention, a radioactive source location system is provided, the system comprising: at least two nuclear radiation detectors, a blocking sheet and an information processing center; wherein,

The nuclear radiation detector is used to obtain the nuclear radiation count of the radioactive source;

The blocking sheet is located between the radiation detectors and is used to block part of the nuclear radiation counts received by at least one of the nuclear radiation detectors;

The information processing center is used to read and process the signal of the nuclear radiation detector, and determine the orientation information of the radioactive source according to the different counting ratios obtained from the different distances of the radioactive source incident at different angles and passing through the blocking plate.

In the above solution, the system further includes: a terminal for controlling the movement of the system, including a handheld terminal, a vehicle, a submersible or an unmanned aerial vehicle;

The information processing center is also used to send the orientation information to the mobile terminal of the control system;

The mobile terminal of the control system is used to receive the orientation information of the radioactive source sent by the information processing center, and control the forward direction to find the radioactive source.

In the above solution, the nuclear radiation detectors include: gas detectors, and/or liquid detectors, and/or solid detectors.

In the above solution, the material of the barrier sheet is one of tungsten, lead, iron, steel and aluminum.

In the above solution, the blocking sheet is a cuboid, the side area of the blocking sheet is larger than the side area of the nuclear radiation detector, and has a predetermined thickness.

In the above solution, the thickness or material of the blocking sheet can be manually or automatically switched according to the detected energy information of the radiation source.

According to another aspect of the present invention, a radioactive source location method is also provided, the method comprising:

The first nuclear radiation detector directly detects the count and energy of the radioactive source radiation without any blocking effect, which is recorded as the first signal;

The second nuclear radiation detector is blocked by the blocking sheet, and the count and energy of the received radioactive source radiation are different from those of the first radiation detector, which is recorded as the second signal;

Based on at least the first signal and the second signal, the position orientation angle of the radiation source is solved.

In the above scheme, the method also includes:

According to the position and direction angle, the radioactive source is searched by people, vehicles, boats, submersibles or unmanned aerial vehicles.

As can be seen from above technical scheme, advantage of the present invention has:

(1) The cost is low, the repeatability is good, and it can work stably for a long time.

(2) The azimuth angle is determined, so the positioning field of view is larger, and blind search is avoided.

(3) The positioning process is simple and fast, which can reduce the harm caused by long-term exposure to radiation sources.

Description of the drawings:

Fig. 1 is a schematic structural diagram of a radioactive source positioning system according to the first embodiment of the present invention;

Fig. 2 is a schematic diagram of the first positional relationship between the nuclear radiation detector and the blocking sheet according to the first embodiment of the present invention;

Fig. 3 is a schematic diagram of the second positional relationship between the nuclear radiation detector and the blocking sheet according to the first embodiment of the present invention;

4 is a schematic diagram of establishing coordinate axes for radiation devices based on radiation sources according to the first embodiment of the present invention;

Fig. 5 is the relationship between the angle between the radiation source and the sensor and the ratio of photon numbers corresponding to the angle according to the first embodiment of the present invention;

Fig. 6 is a schematic flowchart of a method for locating a radioactive source according to a second embodiment of the present invention.

Explanation of reference signs:

1-Nuclear radiation detector; 2-Blocker; 3-Information processing center; 4-Drive trolley.

detailed description

By referring to exemplary embodiments, the technical problems, technical solutions and advantages of the present invention are explained. However, the present invention is not limited to the exemplary embodiments disclosed below, and may be implemented in various forms. The essence of the description is only to help those skilled in the relevant art comprehensively understand the specific details of the present invention, and the embodiments described with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Examples of the described embodiments are shown in the drawings, wherein like or similar reference numerals designate like or similar elements or elements having the same or similar functions throughout.

An embodiment of the present invention provides a radiation source positioning system and positioning method, the positioning system includes: two nuclear radiation detectors, used to obtain nuclear radiation counts and energy; a high-density blocking sheet is sandwiched between the radiation detectors , and has a certain thickness and density; the information processing center reads out the signals from the two radiation detectors, and uses analytical calculation formulas or pre-stored ratio lookup tables to deduce the incident angle of rays in reverse, so as to determine the direction and position of the radioactive source, and combine The position coordinates, movement direction and the ratio and energy information of the above-mentioned detectors at each moment in the past period of time are jointly reconstructed to obtain the precise incident direction of the radioactive source at the current moment; the car is driven to receive the orientation information of the information processing center, and based on the location information Control the forward direction, so as to gradually approach the radioactive source.

The present invention will be described in further detail below through specific embodiments in conjunction with the accompanying drawings.

first embodiment

This embodiment provides a radiation source positioning system. Fig. 1 is a schematic structural diagram of the radioactive source positioning system described in this embodiment. As shown in FIG. 1 , the radioactive source locating system of this embodiment includes: at least two nuclear radiation detectors 1 , a blocking sheet 2 , and may also include: an information processing center 3 and a driving car 4 . Here, the information processing center 3 and the driving trolley 4 can constitute an independent intelligent sourcing subsystem.

Wherein, the nuclear radiation detector 1 is used to obtain nuclear radiation counts of radioactive sources. Nuclear radiation detectors include: gas detectors, and/or liquid detectors, and/or solid detectors

The blocking sheet 2 is located between the radiation detectors 1, the side area of the blocking sheet is larger than the side area of the nuclear radiation detector, and has a predetermined thickness and density. The blocking plate is made of one of tungsten, lead, iron, steel and aluminum. Preferably, the barrier sheet is a tungsten sheet.

Fig. 2 is a schematic diagram of the positions of the radiation detectors and the blocking sheet when there are two radiation detectors in this embodiment, and Fig. 3 is a schematic diagram of the positions of the radiation detectors and the blocking sheet when there are three radiation detectors in this embodiment. The setting of the thickness and density of the blocking sheet satisfies the requirement that the work between different radiation detectors 1 will not be affected. Figure 2 and Figure 3 show 2 and 3 spherical radiation detectors respectively, and 1 and 3 cuboid blocking sheets, and the detectors or blocking sheets in practical applications can be in any shape required . It should be noted that this is only an example, for the convenience of describing the embodiments of the present invention, and should not be construed as a limitation of the present invention.

The radioactive source positioning system shown in FIG. 2 is used for description as follows.

As shown in FIG. 2 , the radiation detector 1 is composed of a photodetection element and a scintillation crystal. The following photodetection element is a silicon photomultiplier tube as an example. In order to further illustrate the technical solution of this embodiment, here the two detectors are divided into a first radiation detector and a second radiation detector. The radiation source emits particle rays to the surroundings. When the particles hit the scintillation crystal, there is a probability that physical action will occur to deposit energy. The scintillation crystal de-excites to generate scintillation light. The scintillation light is detected by the silicon photomultiplier tube and output in the form of an electrical pulse signal. The blocking sheet 2 has a certain thickness and density, and has a radiation shielding effect. The following blocking sheet takes a tungsten plate as an example.

If it is assumed that the thickness of the tungsten plate is d, the distance between the radioactive point source and the detector is r, the activity of the radioactive source is A, the area of the detector receiving radiation is S, and the receiving efficiency of the detector is η, then when there is no tungsten plate blocking The general equation for the measured value is:

When the radiation source is far away from the detector, it can be considered that r>>d, at this time, the first radiation detector and the second radiation detector can be assumed to be at the same position relative to the radiation point source, which greatly simplifies the mathematical processing, and A relatively simple mathematical expression will be obtained. In this case, the two detectors are identical, and the only difference in the amount of radiation detected is whether they are blocked by the tungsten sheet. The attenuation of radioactive substances obeys the law of exponential decay. At this time, we can obtain the number of photons received by the first radiation detector and the second radiation detector per unit time (when the angle is between -90° and 0°):

Among them, θ takes the line connecting _C1 and _C2 as the horizontal axis, and the tungsten plate as the vertical axis to establish the coordinate axis. The angle between the line connecting the origin and the radiation point source and the y-axis is shown in Figure 4. λ is the attenuation coefficient, which is determined according to different radioactive sources and different media. Further, the relationship between the ratio of C ₁ /C ₂ and the direction of the radioactive source can be obtained as:

Figure 5 shows the relationship between the angle between the radiation source and the sensor and the ratio of the number of photons corresponding to the angle, assuming that the radiation source is on the left side directly in front of the detector, because the tungsten plate between the two sensors is very thin. Turn left and slowly align the radiation source. Before the radiation source is not aligned, the number of photons received by the left sensor remains unchanged, while the number of photons received by the right sensor is due to the distance that the ray needs to pass through the tungsten plate Longer and longer, and less and less, resulting in larger and larger ratios. When at a certain moment, the detector is aligned with the radioactive source, the ratio of the number of photons is equal to 1. Before that, the ratio of the left and right sensors is constantly increasing. When the detector is aligned with the radioactive source, the ratio will be greatly increased. mutation. Conversely, when the radiation source is on the right side of the detector, the detector turns right\left, and the ratio will become smaller and smaller. When the radiation source is aligned, the ratio becomes 1, and a sudden change will also occur here. Conversely, it can be seen that when the ratio curve shows a steep rise or fall, it indicates that the radioactive source is within a small range facing the detector.

Finally, the azimuth angle of the radioactive source can be obtained by Si: θ=arcsin(λd/lnS _{i )} .

The information processing center 3 is used to read the signal of the radiation detector 1, and then use an analytical calculation formula or a pre-stored ratio lookup table to reversely deduce the incident angle of the ray according to the acquired signal, so as to determine the direction and position of the radiation source, specifically Yes, the processing center determines the orientation information of the radioactive source according to the different counting ratios obtained from the different distances the radioactive source passes through the blocking plate when it is incident at different angles. The nuclear radiation source emits radiation. Due to the ray attenuation effect of the blocking sheet, the number of photons received by the two radiation detectors of the detection system is different. According to the number of photons received by the two radiation detectors, a comparison can be obtained The position orientation angle of the radiation source. This principle is explained in detail in the description of FIG. 2 .

Combining the position coordinates, movement direction and the ratio and energy information of the above-mentioned detectors at each moment in the past period of time to jointly reconstruct, obtain the precise incident direction and position of the radioactive source at the current moment; and send the finally calculated radioactive source orientation information Give the drive car 4.

The driving car 4 is used to receive the orientation information sent by the information processing center, control the forward direction based on the orientation information, and gradually approach the radioactive source.

The drive trolley in this embodiment can also be replaced in the following ways:

The first alternative way: a handheld terminal; the information processing center is also used to send the orientation information to the handheld terminal; the handheld terminal is used to display the radiation source orientation information sent by the information processing center.

The second alternative mode: submarine; the information processing center is also used to send the orientation information to the submarine; the submarine is used to receive the radiation source orientation information sent by the information processing center, and control Going forward, looking for radioactive sources.

The third alternative: unmanned aerial vehicle; the information processing center is also used to send the orientation information to the unmanned aerial vehicle; the unmanned aerial vehicle is used to receive the orientation of the radioactive source sent by the information processing center Information, and control the direction of travel, looking for radioactive sources.

The driving trolley and its replacement method in this embodiment can be a mobile terminal of the control system in a broader sense, and the mobile terminal of the control system is used to receive the radiation source orientation information sent by the information processing center, And control the direction of progress, search for radioactive sources, and are not limited by the above-mentioned specific schemes.

The radiation source locating system described in this embodiment has low cost, good repeatability, and can work stably for a long time; the azimuth is determined, so the positioning field of view is large, blind search is avoided, and the efficiency of radiation source search is improved; the positioning process is simple Fast, can reduce the harm caused by long-term exposure to radiation sources.

second embodiment

This embodiment provides a radiation source positioning method. Fig. 6 is a schematic flowchart of the method for locating the radioactive source described in this embodiment. As shown in Figure 6, the radioactive source locating system method in this embodiment includes the following process:

After entering the radiation range of the nuclear radiation source, the nuclear radiation source emits radiation rays;

The first radiation detector does not have any blocking effect, and directly detects the radiation rays;

Due to the ray attenuation effect of the blocking sheet, the count received by the second radiation detector is different from that of the first radiation detector;

Based on the counts received by the two radiation detectors combined with energy information, the position and direction angle of the radiation source can be obtained by calculating it.

Specifically, the radioactive source locating method of this embodiment can be realized through the following process through the radioactive source locating system of the first embodiment of the present invention.

Step S201, after entering the radiation range of the nuclear radiation source, the first nuclear radiation detector obtains the nuclear radiation count and energy information (E) of the radiation source. Denote as the first signal C ₁ .

Step S202, due to the blocking sheet between the first radiation detector and the second radiation detector, the radioactive rays obey the law of exponential decay with the blocking thickness, therefore, the number of photons of the radiation source received by the second radiation detector is the same as that of the first The radiation detector is different, denoted as the second signal C ₂ .

Step S203, the first signal and the second signal are transmitted to the information processing center at the same time.

Step S204, the information processing center processes the first signal and the second signal, and calculates the azimuth angle θ of the radiation source according to the ratio of C1 and C2, that is, obtains the direction of the radiation source.

Take the tungsten plate as an example for the barrier sheet. When a photon hits a tungsten plate, there are two situations: the photon flies out from the other side of the tungsten plate or the photon does not fly out from the other side of the tungsten plate. There are only two possibilities for this probability to belong to the binomial distribution. When a large number of photons strike the tungsten plate, the probability of photons passing through the tungsten plate can be regarded as the superposition of a large number of binomial distributions, which is approximately the probability of photons passing through the tungsten plate per unit time, which also conforms to the Poisson distribution.

If it is assumed that the thickness of the tungsten sheet is d, the distance between the radioactive point source and the detector is r, the activity of the radioactive source is A, the area of the detector receiving radiation is S, and the acceptance efficiency of the detector is η, then the general equation of the detection value is :

When the radiation source is far away from the detector, it can be considered that r>>d, at this time, the first radiation detector and the second radiation detector can be assumed to be at the same position relative to the radiation point source, which greatly simplifies the mathematical processing, and A relatively simple mathematical expression will be obtained. In this case, the two detectors are identical and the only difference in the amount of radiation detected is whether they are blocked by the tungsten plate. The attenuation of radioactive substances obeys the law of exponential decay. At this time, we can obtain the number of photons received by the first detector and the second detector respectively (when the angle is between -90° and 0°):

Among them, θ takes the line connecting _C1 and _C2 as the horizontal axis, the tungsten plate as the vertical axis to establish the coordinate axis, and the angle between the line connecting the origin and the radiation point source and the y-axis. λ is the attenuation coefficient, which is determined according to the energy of the radioactive source and the type of blocking sheet. Further, the relationship between the ratio of C ₁ /C ₂ and the direction of the radioactive source can be obtained as:

Figure 5 shows the relationship between the angle between the radiation source and the sensor and the ratio of the number of photons corresponding to the angle, assuming that the radiation source is on the left side directly in front of the detector, because the tungsten plate between the two sensors is very thin. Turn left and slowly align the radiation source. Before the radiation source is not aligned, the number of photons received by the left sensor remains unchanged, while the number of photons received by the right sensor is due to the distance that the ray needs to pass through the tungsten plate Longer and longer, and less and less, resulting in larger and larger ratios. When at a certain moment, the detector is aligned with the radioactive source, the ratio of the number of photons is equal to 1. Before that, the ratio of the left and right sensors is constantly increasing. When the detector is aligned with the radioactive source, the ratio will be greatly increased. mutation. Conversely, when the radiation source is on the right side of the detector, the detector turns right\left, and the ratio will become smaller and smaller. When the radiation source is aligned, the ratio becomes 1, and a sudden change will also occur here. Conversely, it can be seen that when the ratio curve shows a steep rise or fall, it indicates that the radioactive source is within a small range facing the detector.

Finally, the azimuth angle of the radioactive source can be obtained by Si: θ=arcsin(λd/lnS _{i )} .

Step S205, combined with the position coordinates, motion direction and the ratio and energy information of the above-mentioned detectors at each time in the past period of time for joint reconstruction, to obtain the precise incident direction and position of the radioactive source at the current time; and the finally calculated radioactive source The orientation information is sent to the driving car.

In step S206, the driving car receives the orientation information sent by the information processing center, and controls the forward direction based on the orientation information, thereby gradually approaching the radiation source, and finally accurately locating the radiation source.

The drive trolley in this embodiment can also be replaced in the following ways:

The first alternative way: a handheld terminal; the information processing center is also used to send the orientation information to the handheld terminal; the handheld terminal is used to display the radiation source orientation information sent by the information processing center.

The second alternative mode: submarine; the information processing center is also used to send the orientation information to the submarine; the submarine is used to receive the radiation source orientation information sent by the information processing center, and control Going forward, looking for radioactive sources.

The third alternative: unmanned aerial vehicle; the information processing center is also used to send the orientation information to the unmanned aerial vehicle; the unmanned aerial vehicle is used to receive the orientation of the radioactive source sent by the information processing center Information, and control the direction of travel, looking for radioactive sources.

The method for locating the radioactive source described in this embodiment quickly locates the radioactive source through the combination of the radiation detector, the blocking sheet and the information processing center, and uses the driving trolley to locate and find the radioactive source, which reduces the cost of the nuclear radiation source detector , improve the efficiency of radiation source search, and reduce the danger of source search staff.

In the description of this specification, descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific examples" or "some examples" mean that specific structures, features described in conjunction with this embodiment or examples , material or feature is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, for those skilled in the art, various modifications and changes can be made to the present application without departing from the principle and spirit of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of the claims of the present application.

The above description is a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, these improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (8)

1. A radioactive source location system, characterized in that the system comprises: at least two nuclear radiation detectors, blocking sheets and an information processing center; wherein, The nuclear radiation detector is used to obtain the nuclear radiation count of the radioactive source; The blocking sheet is located between the radiation detectors and is used to block part of the nuclear radiation counts received by at least one of the nuclear radiation detectors; The information processing center is used to read and process the signal of the nuclear radiation detector, and determine the orientation information of the radioactive source according to the different counting ratios obtained from the different distances of the radioactive source incident at different angles and passing through the blocking plate. 2. A radioactive source locating system according to claim 1, characterized in that, the system further comprises: a terminal for controlling the movement of the system, including a handheld terminal, a vehicle, a submersible vehicle or an unmanned aerial vehicle; The information processing center is also used to send the orientation information to the mobile terminal of the control system; The mobile terminal of the control system is used to receive the orientation information of the radioactive source sent by the information processing center, and control the forward direction to find the radioactive source. 3. The radioactive source locating system according to claim 1, wherein the nuclear radiation detector comprises: a gas detector, and/or a liquid detector, and/or a solid detector. 4 . The radioactive source locating system according to claim 1 , wherein the blocking sheet is made of one of tungsten, lead, iron, steel and aluminum. 5 . The radioactive source locating system according to claim 1 , wherein the blocking sheet is a cuboid, the side area of the blocking sheet is larger than the side area of the nuclear radiation detector, and has a predetermined thickness. 6 . The radioactive source locating system according to claim 1 , wherein the thickness or material of the blocking sheet can be manually or automatically switched according to the detected energy information of the radioactive source. 7 . 7. A radioactive source location method, characterized in that the method comprises: The first nuclear radiation detector directly detects the count and energy of the radioactive source radiation without any blocking effect, which is recorded as the first signal; The second nuclear radiation detector is blocked by the blocking sheet, and the count and energy of the received radioactive source radiation are different from those of the first radiation detector, which is recorded as the second signal; Based on at least the first signal and the second signal, the position orientation angle of the radiation source is solved. 8. The radioactive source location method according to claim 7, wherein the method further comprises: According to the position and direction angle, the radioactive source is searched by people, vehicles, boats, submersibles or unmanned aerial vehicles.