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佐藤 優樹; 寺阪 祐太
Journal of Nuclear Science and Technology, 59(6), p.677 - 687, 2022/06
被引用回数：17 パーセンタイル：95.64(Nuclear Science & Technology)The Fukushima Daiichi Nuclear Power Station (FDNPS) went into meltdown after being hit by a large tsunami caused by the Great East Japan Earthquake on March 11, 2011. Measuring and understanding the distribution of radioactive contamination inside the FDNPS is essential for decommissioning work, reducing exposure to workers, and ensuring decontamination. This paper reports the visualization tests of radioactive contamination in the Unit 1/2 exhaust stack of the FDNPS using a compact Compton camera. Fixed-point measurements were conducted using only a Compton camera and moving measurements using an integrated radiation imaging system (iRIS) that combines a Compton camera with a simultaneous localization and mapping device. For the moving measurements, an operator carrying the iRIS acquires data continuously while walking in a passage near the stack. With both types of measurements, high-intensity contamination was detected at the base of the stack, and detailed three-dimensional (3D) visualization of the contamination was obtained from the moving measurement. The fixed-point measurements estimated the source intensity of the contamination from the reconstructed contamination image acquired by the Compton camera. Furthermore, workers can experience the work environment before actual work by importing a 3D structure model into a virtual reality system displaying the contamination image.
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：1 パーセンタイル：9.32(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.
佐藤 優樹; 鳥居 建男
Nuclear Technology, 206(7), p.v - xvi, 2020/07
被引用回数：2 パーセンタイル：24.28(Nuclear Science & Technology)The Fukushima Daiichi Nuclear Power Station (FDNPS) suffered a meltdown as a result of a large tsunami triggered by the Great East Japan Earthquake on March 11, 2011. Understanding the distribution of radioactive substances inside the FDNPS is essential to execute appropriate decommissioning tasks. In this paper, we propose method for visualizing three-dimensional (3D) images of radioactive substances as a point cloud data (PCD) and integrating these data into 3D environment models. To demonstrate the usefulness of the proposed methods, a Compton camera was first employed to capture 3D images of radiation sources. The resulting PCD were then integrated into a 3D environment model of a measurement area acquired using the 3D light detection and ranging (LiDAR). This allowed in successful construction of a map to visually recognize the positions of radiation sources.
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：20 パーセンタイル：93.76(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.
谷藤 祐太; 川端 邦明
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
This paper describes about the development of an environment recognition method with point cloud data collected in a dark place like Fukushima Daiichi Nuclear Power Station (FDNPS). We reported the results of a feasibility study of the structure discriminations from LiDAR 3D point cloud data by a deep learning approach. Proposed method utilizes the image data of projected 3D point cloud as input for the classifier instead of coordinate data of 3D points directly. This idea realized to make shorten the learning time without large capacity of the memory for the computations. We selected five kinds of structures (Stairs, Pipe, Grating, Switchboard and Valve) commonly appeared in the general plant as a discrimination subjects for evaluating proposed method. As a result, the classifier showed an accuracy of 99.6% to five categories and we could confirm the validity of proposed method for the structure discrimination.
佐藤 優樹
no journal, ,
東京電力ホールディングス福島第一原子力発電所(以下、1F)事故に伴い、大量の放射性物質が1Fサイト内外に放出された。1Fの廃炉作業を円滑に進めるためには、飛散した放射性物質の分布状況を把握することが重要である。これを踏まえて日本原子力研究開発機構(以下、原子力機構)廃炉国際共同研究センターでは、飛散した放射性物質を可視化するための技術開発を進めている。具体的には、放射性物質可視化装置のひとつであるコンプトンカメラの開発に加えて、ドローンやクローラーロボットにコンプトンカメラを搭載し、遠隔で放射性物質分布を可視化する手法を開発している。さらには、レーザースキャナやフォトグラメトリによる測量技術を用いて建屋構造物の3次元モデルを構築し、これを放射性物質イメージと重ね合わせることによって、より視認しやすい放射性物質分布図の構築を目指している。これらの技術について、電気学会調査専門委員会「福島第一原子力発電所廃炉に関わる放射線計測技術調査専門委員会」にて報告する。
佐藤 優樹
no journal, ,
福島第一原子力発電所(1F)の高線量率環境や福島県帰還困難区域の屋外環境において、作業者の被ばく線量やケガのリスクを低減するために、これらの環境に3次元的に沈着した放射性物質を遠隔にて測定する技術が求められている。申請者は、放射性物質の2次元分布を測定する装置であるコンプトンカメラに、レーザ測域センサや写真立体復元による3次元環境モデリング技術を統合することで、放射性物質の分布を3次元的に可視化できるとの着想に基づき、さらにこれらをロボットと組み合わせることによって統合型放射線イメージングシステムiRIS(アイリス: integrated Radiation Imaging System)を開発した。実証試験では、レーザ測域センサ及び写真立体復元による取得データを用いてコンピュータ上に1F建屋内現場を再現し、周囲に比べて線量率の高いホットスポットの存在箇所を3次元的に可視化することに成功した。このような技術は、作業者の被ばく線量管理を含む廃炉や除染作業の工程管理に直接貢献するものである。また、技術的貢献だけでなく、放射性物質を可視化することによって作業者の皆様に安心を提供することを目指している。
