Radiation source exploration device, radiation source exploration system, radiation source exploration method, and program

Abstract

Provided is a radiation source exploration device capable of detecting the position of a radiation source of radiation even in an environment with many obstacles, such as inside a building. The radiation source exploration device is capable of estimating its own position and moving autonomously, and comprises a radiation sensor unit for detecting radiation arriving from a specific direction, and a control unit for acquiring the detection result of the radiation sensor unit and controlling the movement of the radiation source exploration device, wherein the control unit: estimates a radiation source direction of the radiation on the basis of the detection result of the radiation sensor unit; moves the radiation source exploration device in the estimated radiation source direction; stops the movement when a radiation count rate obtained by the radiation sensor unit exceeds a threshold; and acquires the count rate in the stopped state.

Description

Radiation source detection device, radiation source detection system, radiation source detection method, and program

[0001] The present invention relates to a radiation source detection device, a radiation source detection system, a radiation source detection method, and a program. This application claims priority to Japanese Patent Application No. 2024-050873, filed on March 27, 2024, the contents of which are incorporated herein by reference.

[0002] There are radiation source position detection methods that use multiple radiation detectors to detect the position of a radiation source. For example, in the radiation source position detection method described in Patent Document 1, three or more radiation detectors are arranged at different positions. A curved surface on which the radiation source exists is calculated based on the radiation incident on each radiation detector. Then, the position of the radiation source is detected by simultaneously solving equations for each curved surface.

[0003] Japanese Patent Application Publication No. 2003-337176

[0004] However, the radiation source position detection method described in Patent Document 1 has a problem in that it may not be possible to detect the position of the radiation source in an environment with many obstacles, such as inside a building.

[0005] The present invention has been made in consideration of the above circumstances, and provides a radiation source detection device, a radiation source detection system, a radiation source detection method, and a program that can detect the position of a radiation source even in an environment with many obstacles, such as inside a building.

[0006] The present invention has been made to solve the above-mentioned problems, and one aspect of the present invention is a radiation source tracking device that estimates its own position and is capable of moving autonomously, the radiation source tracking device comprising: a radiation sensor unit that detects radiation arriving from a specific direction; and a control unit that acquires the detection result of the radiation sensor unit and controls movement of the radiation source tracking device, the control unit estimating the direction of the radiation source based on the detection result of the radiation sensor unit, moving the radiation source tracking device in the estimated direction of the radiation source, and, when the count rate of the radiation detected by the radiation sensor unit exceeds a threshold, stopping the movement and acquiring the count rate in the stopped state.

[0007] Another aspect of the present invention is the above-mentioned radiation source detection device, wherein the control unit estimates the source direction of the radiation while changing the specific direction in which the radiation sensor unit detects the radiation.

[0008] Another aspect of the present invention is the above-mentioned radiation source detection device, wherein the radiation sensor unit includes a plurality of detection units that detect radiation arriving from different directions, and when the difference in count rates between two of the plurality of detection units is within a predetermined range and the count rates of the two detection units are greater than the count rates of the remaining two detection units, the control unit estimates the direction of the radiation source using the directions in which the two detection units detect the radiation.

[0009] Another aspect of the present invention is the radiation source detection device described above, wherein the radiation sensor unit includes a plurality of detection units that detect radiation arriving from different directions, and the control unit estimates, as the radiation source direction of the radiation, a direction opposite to a direction in which the detection unit with the lowest count rate among the plurality of detection units detects the radiation.

[0010] Another aspect of the present invention is the above-mentioned radiation source tracking device, which includes a communication unit capable of communicating with other radiation source tracking devices, and when the radiation sensor unit detects radiation, the control unit uses the communication unit to notify the other radiation source tracking device of the location of the radiation source tracking device.

[0011] Another aspect of the present invention is a radiation source tracking system including a plurality of radiation source tracking devices as described above, and a radiation source estimation device that collects count rates and radiation source directions from each of the plurality of radiation source tracking devices and estimates the position of the radiation source.

[0012] Another aspect of the present invention is a method for detecting a radiation source using a radiation source detection device that estimates its own position and is capable of moving autonomously, the method comprising the steps of: estimating the direction of the radiation source based on the detection result of a radiation sensor unit that detects radiation arriving from a specific direction; moving the radiation source detection device in the estimated direction of the radiation source; and, when the count rate of the radiation detected by the radiation sensor unit exceeds a threshold, stopping the movement and acquiring the count rate in the stopped state.

[0013] Another aspect of the present invention is a program for causing a computer of a radiation source tracking device that estimates its own position and is capable of moving autonomously to execute the following steps: estimating the direction of the radiation source based on the detection result of a radiation sensor unit that detects radiation arriving from a specific direction; moving the radiation source tracking device in the estimated direction of the radiation source; and, if the count rate of the radiation detected by the radiation sensor unit exceeds a threshold, stopping the movement and acquiring the count rate in the stopped state.

[0014] According to the present invention, the position of a radiation source can be detected even in an environment with many obstacles.

[0015] FIG. 1 is a schematic block diagram showing the configuration of a radiation source tracking system 10 according to an embodiment of the present invention. FIG. 2 is a schematic block diagram showing the configuration of a radiation source tracking device 100 in the same embodiment. FIG. 3 is a perspective view showing the appearance of a radiation detection unit 110 in the same embodiment. FIG. 4 is a flowchart explaining the operation of the radiation source tracking device 100 in the same embodiment. FIG. 5 is a schematic diagram showing an example of measurement by a plurality of radiation source tracking devices 100a to 100f in the same embodiment. FIG. 6 is a schematic diagram showing an example of measurement by a plurality of radiation source tracking devices 100g to 100k in the same embodiment.

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of a radiation source tracking system 10 according to an embodiment of the present invention. The radiation source tracking system 10 includes multiple radiation source tracking devices 100 and a radiation source estimation device 300. Each of the multiple radiation source tracking devices 100 is a robot equipped with a radiation sensor for detecting radiation, capable of estimating its own position, and capable of autonomous movement. Note that the radiation source tracking device 100 may move by other means, including three-dimensional movement, such as flying, navigating, or walking, rather than by running. Note that, "autonomously mobile" here means that the device can move without receiving instructions, and may move along a predetermined route or determine its own route. The radiation source estimation device 300 collects radiation detection results (counting rates) and radiation source directions from the multiple radiation source tracking devices 100, and estimates the position of the radiation source. The radiation source estimation device 300 may be implemented by one or more computers loading and executing a program. A method for estimating the position of a radiation source may, for example, be to perform inverse problem analysis based on the radiation detection results obtained by the radiation source tracking device 100, thereby estimating the position of the radiation source in three-dimensional space, but is not limited to this. When solving the inverse problem, unfolding calculations or deep learning may be used, for example. Furthermore, by integrating and analyzing the radiation detection results (counting rates) obtained by multiple radiation source tracking devices 100, it is possible to achieve more accurate estimation than when estimating based on the detection results obtained from a single radiation source tracking device 100.

[0017] The plurality of radiation source tracking devices 100 and the radiation source estimation device 300 are communicably connected to each other via a network 200. The network 200 may include a multi-hop network formed by the plurality of radiation source tracking devices 100.

[0018] 2 is a schematic block diagram showing the configuration of the radiation source tracking device 100 according to this embodiment. The radiation source tracking device 100 includes a radiation detection unit 110, a control unit 120, a navigation function unit 130, a position detection sensor unit 140, and a communication unit 150. The radiation detection unit 110 includes a first direction detection unit 111, a second direction detection unit 112, a third direction detection unit 113, and an omnidirectional detection unit 114.

[0019] Each of the first direction detector 111, the second direction detector 112, and the third direction detector 113 (radiation sensor units) detects radiation arriving from a different specific direction more strongly. The omnidirectional detector 114 detects radiation arriving from all directions. Each of the first direction detector 111, the second direction detector 112, the third direction detector 113, and the omnidirectional detector 114 may include a scintillator such as bismuth germanate and a photomultiplier tube, and may detect radiation by amplifying the light emitted by the scintillator in response to incident radiation using the photomultiplier tube. The first direction detector 111, the second direction detector 112, and the third direction detector 113 may shield radiation incident from directions other than the specific direction with a shield such as lead, thereby detecting radiation arriving from a specific direction more weakly, i.e., having more anisotropy in the detection direction. Note that the radiation detectors are not limited to those described in this embodiment as long as they are capable of detecting radiation anisotropically.

[0020] The control unit 120 acquires the detection results from the first direction detection unit 111, the second direction detection unit 112, the third direction detection unit 113, and the omnidirectional detection unit 114. The control unit 120 also controls the movement of the radiation source tracking device 100 based on the detection results. For example, the control unit 120 estimates the direction of the radiation source based on the detection result from the radiation detection unit 110, and moves the radiation source tracking device in the estimated direction of the radiation source. If the radiation count rate detected by the radiation detection unit 110 exceeds a threshold, the control unit 120 stops the movement and acquires the count rate in the stopped state. The control unit 120 also estimates the self-position of the radiation source tracking device 100 using the detection result from the position detection sensor unit 140. Any method for estimating the self-position may be used, but for example, if the position detection sensor unit 140 is an inertial measurement unit, a method for estimating the self-position may be used that estimates the self-position from acceleration, angular velocity, etc., or if the position detection sensor unit 140 is a LiDAR (Light Detection And Ranging or LIDAR (Laser Imaging Detection And Ranging)), a method for estimating the self-position may be used that compares the situation around the radiation source exploration device 100 with a stored map. In addition, it is of course possible to use a GPS (Global Positioning System) depending on the location of use, etc.

[0021] The traveling function unit 130 includes tracks or wheels for propelling the radiation source tracking device 100, a motor for driving the tracks or wheels, and the like. The traveling function unit 130 is not limited to these, and may be a flying device such as a drone, a navigation device, or a walking device such as a robot. The traveling function unit 130 changes the orientation and moves the radiation source tracking device 100 under the control of the control unit 120. The position detection sensor unit 140 is a sensor for the radiation source tracking device 100 to detect its own position. The position detection sensor unit 140 may, for example, detect the number of rotations of each wheel of the traveling function unit 130, or may be an inertial measurement unit that detects acceleration, angular velocity, angular acceleration, etc., or may be a sensor such as LiDAR that detects the surrounding conditions of the radiation source tracking device 100. Of course, GPS can also be used depending on the location of use, etc.

[0022] The communication unit 150 communicates with other radiation source identification devices 100 and radiation source estimation devices 300. The communication by the communication unit 150 may be performed using any method such as a wireless local area network (LAN) or Bluetooth (registered trademark).

[0023] 3 is a perspective view showing the appearance of the radiation detection unit 110 in this embodiment. Scintillators S1, S2, S3, and S4 are the scintillators of the first direction detection unit 111, the second direction detection unit 112, the third direction detection unit 113, and the omnidirectional detection unit 114, respectively. Lead shielding walls W1, W2, and W3 are disposed between the scintillators S1, S2, and S3, which are arranged at equal intervals on a disk-shaped base plate B1. Therefore, radiation mainly arrives at each of the scintillators S1, S2, and S3 from directions within 120° where no shielding walls are installed. Because scintillator S4 is installed above the shielding walls W1, W2, and W3, radiation arrives from all directions (360°).

[0024] FIG. 4 is a flowchart illustrating the operation of the radiation source tracking device 100 according to this embodiment. First, the radiation source tracking device 100 performs a random walk, which is a random movement (step Sa1). The movement range of the random walk may be set in advance. For example, when a multi-hop network is configured with multiple radiation source tracking devices 100, the movement range of each radiation source tracking device 100 may be set so that it can communicate with adjacent radiation source tracking devices 100. Alternatively, the radiation source tracking device 100 may travel along a planned route instead of a random walk. When a movement range is set, the radiation source tracking device 100 can detect the position of a radiation source within the movement range with higher accuracy, so it is preferable that the radiation source tracking device 100 travels thoroughly within the movement range, regardless of the method for setting the movement.

[0025] The control unit 120 of the radiation source tracking device 100 determines whether radiation has been detected (step Sa2). This determination may use the detection results from all of the first direction detection unit 111, second direction detection unit 112, third direction detection unit 113, and omnidirectional detection unit 114, or may use only the detection result from the omnidirectional detection unit 114 and prevent power from being supplied to the first direction detection unit 111, second direction detection unit 112, and third direction detection unit 113 during the random walk in step Sa1. Alternatively, whether radiation has been detected may be determined based on whether the count rate exceeds a preset threshold.

[0026] If it is determined in step Sa2 that radiation has been detected (step Sa2-Yes), the control unit 120 of the radiation source tracking device 100 notifies the other radiation source tracking devices 100 that radiation has been detected via the communication unit 150 (step Sa3). This notification may include information indicating the self-location estimated by the radiation source tracking device 100 and information indicating the radiation counting rate. The other radiation source tracking devices 100 to which this notification is sent may be multiple, but may only be those that satisfy any of the following conditions: those within a predetermined distance from the radiation source tracking device 100, those that can directly receive this notification, and those that have not detected radiation.

[0027] Next, the control unit 120 of the radiation source tracking device 100 estimates the direction of the radiation source (radiation source direction) (step Sa4). The radiation source direction may be estimated, for example, as follows. The radiation source tracking device 100 performs measurements while changing the specific direction in which each direction detector detects radiation, for example, by changing the orientation of the device itself or by rotating the radiation detection unit 110, and estimates the radiation source direction. For example, if the difference in count rates between two of the first direction detector 111, the second direction detector 112, and the third direction detector 113 is within a predetermined range and the count rate between the first direction detector 111, the second direction detector 112, and the third direction detector 113 is greater than the remaining count rate, the control unit 120 determines that the estimated radiation source direction is the center direction of the directions in which the two direction detectors detect radiation, or the opposite direction to the direction in which the remaining direction detector detects radiation. In addition, the control unit 120 may estimate, as the radiation source direction, the direction opposite to the direction in which the direction detection unit with the lowest count rate among the first direction detection unit 111, the second direction detection unit 112, and the third direction detection unit 113 detects radiation.

[0028] Note that "two count rate values ​​being sufficiently close" may mean that the difference between the two count rates is less than or equal to a predetermined threshold, or that the ratio between the two count rates is within a predetermined range. Furthermore, "the remaining count rate value being sufficiently smaller than two count rate values" may mean that the result of subtracting the remaining count rate value from the average of the two count rate values ​​is equal to or greater than a predetermined threshold, or that the result of dividing the average of the two count rate values ​​by the remaining count rate is equal to or greater than a predetermined threshold. The radiation source tracking device 100 may estimate the radiation source direction while moving or while stationary. In addition to the condition that the two count rate values ​​are sufficiently close and the remaining count rate value is sufficiently smaller than the two count rate values, a condition that the two count rate values ​​are sufficiently smaller than the count rate detected by the omnidirectional detection unit 114 may be added.

[0029] Next, the radiation source tracking device 100 moves in the direction of the radiation source estimated in step Sa4 (step Sa5). The radiation source tracking device 100 continues to detect radiation during the movement in step Sa5, and after a predetermined time has elapsed or after the device has traveled a predetermined distance, the control unit 120 determines whether the count rate is equal to or greater than a predetermined threshold (step Sa6). This determination in step Sa6 may be based on whether the count rate exceeds a predetermined threshold (for example, the threshold may be set to "average value + 2 × σ" or "average value + 3 × σ" using the average value and standard deviation σ of the count rates measured from step Sa1 to step Sa6). Alternatively, this count rate may be the count rate measured while the radiation source tracking device 100 is moving. Alternatively, this count rate may be measured after the device has stopped moving in step Sa5 and a predetermined time has elapsed or after the device has traveled a predetermined distance. Furthermore, this counting rate may be measured by one of the first direction detection unit 111, the second direction detection unit 112, and the third direction detection unit 113 that is facing the estimated radiation source direction, or it may be measured by the omnidirectional detection unit 114.

[0030] If it is determined in step Sa6 that the count rate is not equal to or greater than the threshold (step Sa6—No), the radiation source tracking device 100 returns to step Sa4 and estimates the radiation source direction. If it is determined in step Sa6 that the count rate is equal to or greater than the threshold (step Sa6—Yes), the radiation source tracking device 100 stops and measures the count rate (step Sa7). This measurement may be performed by one of the first direction detector 111, the second direction detector 112, and the third direction detector 113 that is facing the radiation source direction, or by the omnidirectional detector 114. Furthermore, when performing this measurement, the radiation source tracking device 100 may estimate the radiation source direction and change its orientation so that any one of the first direction detector 111, the second direction detector 112, and the third direction detector 113 faces the radiation source direction.

[0031] Next, the control unit 120 of the radiation source tracking device 100 transmits the count rate measured in step Sa7, the estimated radiation source direction, and its own position to the radiation source estimation device 300 via the communication unit 150 (step Sa8). By receiving this transmission from multiple radiation source tracking devices 100, the radiation source estimation device 300 can estimate the position, shape, etc. of the radiation source.

[0032] On the other hand, if it is determined in step Sa2 that radiation has not been detected (step Sa2-No), the control unit 120 of the radiation source tracking device 100 determines whether or not there has been a notification from another radiation source tracking device 100 via the communication unit 150 (step Sa9). Here, the notification from the other radiation source tracking device 100 is a notification indicating that the other radiation source tracking device 100 has detected radiation, which is the notification from step Sa3 of the other radiation source tracking device 100. If it is determined that there has been no notification from the other radiation source tracking device 100 (step Sa9-No), the radiation source tracking device 100 returns to step Sa1 and performs a random walk.

[0033] On the other hand, if it is determined in step Sa9 that a notification has been received from another radiation source tracking device 100 (step Sa9—Yes), the radiation source tracking device 100 moves in the direction of the other radiation source tracking device 100 based on the location of the other radiation source tracking device 100 included in the notification (step Sa10). The radiation source tracking device 100 continues to detect radiation while moving in step Sa10, and after a predetermined time has elapsed or after moving a predetermined distance, the control unit 120 determines whether the count rate is equal to or greater than a preset threshold (step Sa11). This determination is the same as in step Sa6. If it is determined in step Sa11 that the count rate is not equal to or greater than the threshold (step Sa11—No), the radiation source tracking device 100 returns to step Sa10 and moves in the direction of the other radiation source tracking device 100. If it is determined in step Sa11 that the count rate is equal to or greater than the threshold (step Sa11—Yes), the radiation source tracking device 100 proceeds to step Sa7, stops, and measures the count rate.

[0034] As described above, the radiation source tracking device 100 performs measurements autonomously by performing random walks or other measures, enabling it to perform measurements even when there are obstacles such as walls or leftover objects. Furthermore, the radiation source tracking device 100 stops measuring the count rate for transmission only after the count rate reaches or exceeds a threshold, thereby improving the accuracy of the count rate. Furthermore, when the radiation detection unit 110 (radiation sensor unit) detects radiation, the control unit 120 of the radiation source tracking device 100 notifies other radiation source tracking devices 100 of the location (self-location) of the radiation source tracking device 100 using the communication unit 150. The other radiation source tracking devices 100 then move and gather near the target radiation source and perform measurements from multiple positions toward the target radiation source. This allows for early detection of a radiation source and for multiple radiation source tracking devices 100 to measure the same radiation source in parallel, thereby enabling highly accurate estimation of the radiation source's location, etc. After the multiple radiation source tracking devices 100 have performed measurements on the same radiation source in this manner, the flow returns to the start of the flow shown in FIG. 4 , and the radiation source tracking device 100 starts a random walk. When setting a movement range for the radiation source tracking device 100, repeating the flow shown in FIG. 4 allows the radiation source tracking device 100 to travel thoroughly through the movement range and measure the positions of radiation sources present within the movement range with higher accuracy. The radiation source tracking device 100 can also be configured to move to a pre-set location after traveling and measuring the entire movement range. Alternatively, the radiation source tracking device 100 can also be configured to move to a pre-set location after traveling for a certain period of time. Note that even if the radiation source tracking device 100 has completed traveling and measuring the planned route or the entire movement range, if there is no radiation source with a certain intensity or higher, the count rate will not be greater than the threshold, and the flow chart of FIG. 4 will not end. In such cases, various changes can be made depending on the usage situation, such as ending the program after driving and measuring the planned route or after driving the entire area of ​​movement, or after driving for a certain period of time.

[0035] FIG. 5 is a schematic diagram showing an example of measurements performed by multiple radiation source tracking devices 100a-100f according to this embodiment. Each of the radiation source tracking devices 100a-100f is the radiation source tracking device 100 shown in FIGS. 1 and 2. The schematic diagram in FIG. 5 shows an example in which multiple radiation source tracking devices 100a-100f are measuring a radiation source R1 that is larger than the other radiation source tracking devices. When the radiation source R1 is large, the radiation source tracking devices 100a-100f gather around it to measure the counting rate and transmit the counting rate to the radiation source estimation device 300. Using at least the positions and counting rates of the radiation source tracking devices 100a-100f, the radiation source estimation device 300 can estimate the general shape of the radiation source R1, the intensity distribution of the radiation dose, and the like.

[0036] FIG. 6 is a schematic diagram showing an example of measurements performed by multiple radiation source tracking devices 100g to 100k according to this embodiment. Each of the radiation source tracking devices 100g to 100k is the radiation source tracking device 100 shown in FIGS. 1 and 2. The schematic diagram in FIG. 6 shows an example in which multiple radiation source tracking devices 100g to 100k perform measurements on two radiation sources R2 and R3. When multiple radiation sources R2 and R3 are present, the radiation source tracking devices 100g to 100k gather around each of the multiple radiation sources R2 and R3, measure the count rate, and transmit the measured count rate to the radiation source estimation device 300. This allows the radiation source estimation device 300 to estimate the position, etc., of each of the multiple radiation sources R2 and R3.

[0037] The present invention may be embodied as follows: (1) One embodiment of the present invention is a radiation source tracking device that estimates its own position and is capable of autonomous movement, the radiation source tracking device comprising: a radiation sensor unit that detects radiation arriving from a specific direction; and a control unit that acquires a detection result from the radiation sensor unit and controls movement of the radiation source tracking device, the control unit estimating a direction of the radiation source based on the detection result from the radiation sensor unit, moving the radiation source tracking device in the estimated direction of the radiation source, and, when a count rate of the radiation detected by the radiation sensor unit exceeds a threshold, stopping the movement and acquiring the count rate in the stopped state.

[0038] (2) Another embodiment of the present invention is a radiation source detection device as described in (1), wherein the control unit estimates the direction of the radiation source while changing the specific direction in which the radiation sensor unit detects the radiation.

[0039] (3) Another embodiment of the present invention is a radiation source detection device as described in (1) or (2), wherein the radiation sensor unit includes a plurality of detection units that detect radiation arriving from different directions, and the control unit estimates the direction of the radiation source using the directions in which the two detection units detect the radiation when the difference in count rates between two of the plurality of detection units is within a predetermined range and the count rates of the two detection units are greater than the count rates of the remaining units.

[0040] (4) Another embodiment of the present invention is a radiation source detection device according to any one of (1) to (3), wherein the radiation sensor unit includes a plurality of detection units that detect radiation arriving from different directions, and the control unit estimates, as the radiation source direction of the radiation, a direction opposite to the direction in which the detection unit with the lowest count rate among the plurality of detection units detects the radiation.

[0041] (5) Another embodiment of the present invention is a radiation source tracking device according to any one of (1) to (3), further comprising a communication unit capable of communicating with another radiation source tracking device, and when the radiation sensor unit detects radiation, the control unit uses the communication unit to notify the other radiation source tracking device of the location of the radiation source tracking device.

[0042] (6) Another embodiment of the present invention is a radiation source detection system including a plurality of radiation source detection devices according to any one of (1) to (5) above, and a radiation source estimation device that collects count rates and radiation source directions from each of the plurality of radiation source detection devices and estimates the position of the radiation source.

[0043] (7) Another embodiment of the present invention is a method for detecting a radiation source using a radiation source detection device that estimates its own position and is capable of moving autonomously, the method including the steps of: estimating the direction of the radiation source based on the detection result of a radiation sensor unit that detects radiation arriving from a specific direction; moving the radiation source detection device in the estimated direction of the radiation source; and, when the count rate of the radiation detected by the radiation sensor unit exceeds a threshold, stopping the movement and acquiring the count rate in the stopped state.

[0044] (8) Another embodiment of the present invention is a program for causing a computer of a radiation source tracking device that estimates its own position and is capable of moving autonomously to execute the following steps: estimating the direction of the radiation source based on the detection result of a radiation sensor unit that detects radiation arriving from a specific direction; moving the radiation source tracking device in the estimated direction of the radiation source; and, if the count rate of the radiation detected by the radiation sensor unit exceeds a threshold, stopping the movement and acquiring the count rate in the stopped state.

[0045] 1 and the control unit 120 in Fig. 2 may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to realize the radiation source estimation apparatus 300 and the control unit 120. Note that the term "computer system" here includes hardware such as an OS and peripheral devices.

[0046] "Computer-readable recording media" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording media" also includes devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs over networks like the Internet or communication lines like telephone lines, and devices that store programs for a fixed period of time, such as volatile memory within the computer systems that serve as servers or clients. The programs may also be programs that implement some of the aforementioned functions, or may be programs that can realize the aforementioned functions in combination with programs already stored in the computer system.

[0047] The above describes an embodiment of the present invention in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present invention.

[0048] 10 Radiation source detection system 100, 100a to 100k Radiation source detection device 110 Radiation detection unit 111 First direction detection unit 112 Second direction detection unit 113 Third direction detection unit 114 Omnidirectional detection unit 120 Control unit 130 Travel function unit 140 Position detection sensor unit 150 Communication unit

Claims

1. A radiation source tracking device that estimates its own position and is capable of moving autonomously, comprising: a radiation sensor unit that detects radiation arriving from a specific direction; and a control unit that acquires the detection results of the radiation sensor unit and controls movement of the radiation source tracking device, wherein the control unit estimates the direction of the radiation source based on the detection results of the radiation sensor unit, moves the radiation source tracking device in the estimated direction of the radiation source, and stops movement when the radiation count rate of the radiation sensor unit exceeds a threshold, and acquires the count rate in the stopped state.

2. The radiation source detection device according to claim 1, wherein the control unit estimates the direction of the radiation source while changing the specific direction in which the radiation sensor unit detects the radiation.

3. The radiation source detection device of claim 1, wherein the radiation sensor unit comprises a plurality of detection units that each detect radiation arriving from a different direction, and the control unit estimates the direction of the radiation source using the directions in which the two detection units detect the radiation when the difference in count rates between two of the plurality of detection units is within a predetermined range and the count rates between the two detection units are greater than the count rates between the remaining units.

4. A radiation source detection device as described in claim 1, wherein the radiation sensor unit includes a plurality of detection units that detect radiation arriving from different directions, and the control unit estimates, as the radiation source direction of the radiation, the direction opposite to the direction in which the detection unit with the lowest count rate among the plurality of detection units detects the radiation.

5. A radiation source tracking device as described in claim 1, further comprising a communication unit capable of communicating with other radiation source tracking devices, wherein when the radiation sensor unit detects radiation, the control unit uses the communication unit to notify the other radiation source tracking device of the position of the radiation source tracking device.

6. A radiation source detection system comprising: a plurality of radiation source detection devices according to any one of claims 1 to 5; and a radiation source estimation device that collects the count rate and radiation source direction from each of the plurality of radiation source detection devices and estimates the position of the radiation source.

7. A method for detecting a radiation source using a radiation source detection device that can estimate its own position and move autonomously, comprising the steps of: estimating the direction of the radiation source based on the detection result of a radiation sensor unit that detects radiation arriving from a specific direction; moving the radiation source detection device in the estimated direction of the radiation source; and, when the count rate of the radiation detected by the radiation sensor unit exceeds a threshold, stopping the movement and obtaining the count rate in the stopped state.

8. A program for causing a computer of a radiation source tracking device that can estimate its own position and move autonomously to execute the following steps: estimating the direction of the radiation source based on the detection results of a radiation sensor unit that detects radiation arriving from a specific direction; moving the radiation source tracking device in the estimated direction of the radiation source; and, if the count rate of the radiation detected by the radiation sensor unit exceeds a threshold, stopping the movement and obtaining the count rate in the stopped state.

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