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論文

3D position and radioactivity estimation of radiation source by a simple directional radiation detector combined with structure from motion

佐藤 優樹; 峯本 浩二郎*; 根本 誠*

Radiation Measurements, 142, p.106557_1 - 106557_6, 2021/03

 被引用回数:0 パーセンタイル:0.01(Nuclear Science & Technology)

It is important to visualize radioactive substances' position and distribution and estimate their radioactivity levels to reduce the exposure dose of workers in radioactive areas (such as decommissioning worksites of nuclear power stations) and improve nuclear security functions. To visualize the radioactive substance's three-dimensional (3D) location, a directional radiation detector with a cylindrical shield on a simple single-pixel gamma-ray detector was applied to the structure from motion (SfM) technology using an ordinary digital camera. Verification was performed by a system that combines SfM with a CdTe sensor probe having narrow directivity. $$^{241}$$Am radiation source's position was visualized by drawing the radiation source's image acquired by the gamma-ray detector on the work area 3D model reconstructed through SfM. Furthermore, as SfM is a simultaneous localization and mapping technology, the system measures the gamma rays while measuring the gamma-ray detector's dynamic position and posture information. The measurements can be acquired while the gamma-ray detector is freely moving in the work area. These methods visualized the radiation source's position and quantitatively estimated the radiation source's radioactivity.

論文

Automatic data acquisition for visualizing radioactive substances by combining a gamma-ray imager and an autonomous mobile robot

佐藤 優樹; 峯本 浩二郎*; 根本 誠*; 鳥居 建男

Journal of Instrumentation (Internet), 16(1), p.P01020_1 - P01020_18, 2021/01

 被引用回数:0 パーセンタイル:0(Instruments & Instrumentation)

To reduce the exposure doses of workers and to establish decontamination plans, it is important to understand and visualize the distribution of radioactive substances at the Fukushima Daiichi Nuclear Power Station in Japan, where an accident occurred on the 11th of March, 2011. In this decommissioning work environment, radioactive substances adhered to various objects, such as rubble and equipment, and it was necessary to visualize the distribution of these contaminants in all three dimensions. The technology used to automatically and remotely acquire data to visualize the distribution of radioactive substances in three dimensions was useful for reducing the exposure dose of the workers and to shorten the survey time. We constructed an automatic data acquisition system that consisted of a Compton camera and a 3D-light detection and ranging sensor mounted on an autonomously moving robot. We also evaluated the system feasibility using radiation sources and succeeded in automatically acquiring the data required for visualizing the radiation sources. For this data acquisition, the operator did not need to operate the system after the measurements were started. The effects of the imaging parameters of the Compton camera and the accuracy of the self-position estimation of the system on the radiation-imaging accuracy are also discussed.

論文

Construction of virtual reality system for radiation working environment reproduced by gamma-ray imagers combined with SLAM technologies

佐藤 優樹; 峯本 浩二郎*; 根本 誠*; 鳥居 建男

Nuclear Instruments and Methods in Physics Research A, 976, p.164286_1 - 164286_6, 2020/10

 被引用回数:6 パーセンタイル:93.25(Instruments & Instrumentation)

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., experienced a meltdown as a result of a large tsunami caused by the Great East Japan Earthquake on March 11, 2011. At that time, it was necessary to understand the aspects of the decommissioning working environment inside the FDNPS, such as establishing how the radioactive substances were distributed across the site, for work to be done efficiently without exposure to large amounts of radiation. Therefore, virtual reality (VR) emerged as a solution. There have been previous reports done on a technique for visualizing the distribution of radioactive substances in three dimensions utilizing a freely moving gamma-ray imager combined with simultaneous localization and mapping (SLAM) technology. In this paper, we introduce imaging technologies for the acquisition of image data from radioactive substances and three-dimensional (3D) structural models of the working environment, using a freely moving gamma-ray imager combined with SLAM technology. For this research, we also constructed a VR system and displayed the 3D data in a VR space, which enables users to experience the actual working environment without radiation exposure. In creating the VR system, any user can implement this method by donning an inexpensive head-mounted display apparatus and using a free, or low-cost, application software.

論文

Remote detection of radioactive hotspot using a Compton camera mounted on a moving multi-copter drone above a contaminated area in Fukushima

佐藤 優樹; 小澤 慎吾*; 寺阪 祐太; 峯本 浩二郎*; 田村 智志*; 新宮 一駿*; 根本 誠*; 鳥居 建男

Journal of Nuclear Science and Technology, 57(6), p.734 - 744, 2020/06

 被引用回数:7 パーセンタイル:95.29(Nuclear Science & Technology)

The Fukushima Daiichi Nuclear Power Station, operated by Tokyo Electric Power Company Holdings, Inc., suffered a meltdown as a result of a large tsunami triggered by the Great East Japan Earthquake on March 11, 2011. To proceed with the environmental recovery by decontamination, drawing a radiation distribution map that can indicate the distribution of radioactive substances is extremely important to establish detailed decontamination plans. We developed a remote radiation imaging system consisting of a lightweight Compton camera and a multi-copter drone to remotely measure the distribution of the radioactive substances. This system can perform radiation imaging using a Compton camera while flying and moving. In addition, it is also possible to draw the distribution of radioactive substances three-dimensionally by projecting the radiation image measured with the Compton camera on a three-dimensional topography model separately acquired by a 3D-LiDAR. We conducted a survey of radioactive hotspots in difficult-to-return zone in the coastal area of Fukushima, Japan. The drone system succeeded in three-dimensional visualization of several hotspots deposited on the ground. Such remote technology would be useful not only for monitoring the difficult-to-return zone, but also for monitoring distribution of radioactive substances inside the site of the FDNPS where decommissioning work is ongoing.

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