検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年
検索結果: 49 件中 1件目~20件目を表示

発表形式

Initialising ...

選択項目を絞り込む

掲載資料名

Initialising ...

発表会議名

Initialising ...

筆頭著者名

Initialising ...

キーワード

Initialising ...

使用言語

Initialising ...

発行年

Initialising ...

開催年

Initialising ...

選択した検索結果をダウンロード

論文

Image reconstruction of radioactive contamination due to the Fukushima-Daiichi Nuclear Power Station Accident using a compact Compton camera

佐藤 優樹; 寺阪 祐太; 宮村 浩子; 冠城 雅晃; 谷藤 祐太; 川端 邦明; 鳥居 建男

Reactor Dosimetry; 16th International Symposium on Reactor Dosimetry (ISRD-16) (ASTM STP 1608), p.428 - 436, 2018/11

We developed a lightweight compact Compton camera to measure the distribution of radioactive contamination inside the Fukushima Daiichi Nuclear Power Station. We conducted performance evaluation tests in the coastal area of Fukushima, Japan, using the camera, which employs a cerium (Ce)-doped GAGG (Gd$$_{3}$$Al$$_{2}$$Ga$$_{3}$$O$$_{12}$$) scintillator coupled with a multipixel photon counter. The camera can clearly visualize spreading of radioactivity along the ground surface. In addition, we performed three-dimensional image reconstruction of the distribution of radioactive contamination using the multi-angle data obtained with the Compton camera. We succeeded in obtaining a three-dimensional image of radioactive contamination in the outdoor area.

論文

Gamma-ray imaging system for Fukushima Daiichi Nuclear Power Plant using silicon strip detector

冠城 雅晃; 佐藤 優樹; 吉原 有里*; 島添 健次*; 高橋 浩之*; 鳥居 建男

Reactor Dosimetry; 16th International Symposium on Reactor Dosimetry (ISRD-16) (ASTM STP 1608), p.405 - 414, 2018/11

On March 11, 2011, a massive earthquake occurred in the Tohoku region of Japan, and a large tsunami hit the Fukushima Daiichi Nuclear Power Plant (1F), resulting in a nuclear accident. Despite the years that have passed since the accident, decommissioning remains a concern. Radiation measurement techniques are very important for accelerating the decommissioning and ensuring low radiation exposure to workers. Our gamma-ray imaging system is the detection device for determining the three dimensional radioactive distributions of nuclear fuel debris, measuring high-energy gamma rays (greater than 1 MeV). Silicon semiconductor detectors are among the candidate detectors for radiation measurements in our system because of their radiation-hardness and high counting rate capability. We have been developing a stacked amorphous-silicon (Si)/crystal-Si heterojunction Si strip detector, which has 1-mm-pitch striped electrodes (0.5 mm wide) and 1.2-mm-pitch stacked technology. The detector consists of an Si strip mounted on a thin printed circuit board, front-end readout electronics with a complementary metal oxide semiconductor application specific integrated circuit, and a field programmable gate array. The threshold level of energy deposition of each pulse signal in each channel can be set from the application-specific integrated circuit, and gamma-ray images with energy discrimination can be obtained. The energy threshold level for discrimination of $$^{60}$$Co gamma rays from $$^{137}$$Cs gamma rays was investigated experimentally and by means of simulation, and it was found to be about 500 keV. Therefore, our Si strip detector has the required position sensitivity and energy discrimination ability for identifying high-energy gamma-ray source distributions.

論文

Radiation imaging using a compact Compton camera inside the Fukushima Daiichi Nuclear Power Station building

佐藤 優樹; 谷藤 祐太; 寺阪 祐太; 宇佐美 博士; 冠城 雅晃; 川端 邦明; 宇津木 弥*; 菊地 弘幸*; 高平 史郎*; 鳥居 建男

Journal of Nuclear Science and Technology, 55(9), p.965 - 970, 2018/09

 被引用回数:2 パーセンタイル:16.17(Nuclear Science & Technology)

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown after the occurrence of a large tsunami caused by the Great East Japan Earthquake of March 11, 2011. The radiation distribution measurements inside the FDNPS buildings are indispensable to execute decommissioning tasks in the reactor buildings. We conducted the radiation imaging experiment inside the turbine building of Unit 3 of the FDNPS using a compact Compton camera, and succeeded in visualizing the high-dose contamination (up to 3.5 mSv/h). We also drew a three-dimensional radiation distribution map inside the turbine building by integrating the radiation image resulting from the Compton camera into the point cloud data of the experimental environment acquired using the scanning laser range finder. The radiation distribution map shows the position of these contaminations on the real space image of the turbine building. The radiation distribution map helps workers to easily recognize the radioactive contamination and to decrease the radiation exposure; the contamination cannot be observed with the naked eye, naturally.

論文

A 3D radiation image display on a simple virtual reality system created using a game development platform

佐藤 優樹; 寺阪 祐太; 小澤 慎吾*; 谷藤 祐太; 鳥居 建男

Journal of Instrumentation (Internet), 13(8), p.T08011_1 - T08011_10, 2018/08

 パーセンタイル:100(Instruments & Instrumentation)

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., suffered a meltdown after a large tsunami caused by the Great East Japan Earthquake on March 11, 2011. The measurement of radiation distribution inside FDNPS buildings is indispensable for executing appropriate decommissioning tasks in the reactor's buildings. In addition, it is extremely important to accurately predict the location of radioactive contamination beforehand because the working time is limited owing to radiation exposure to workers. In this paper, a simple virtual reality (VR) system that can detect radioactive substances in virtual space has been developed to simulate real working environments. A three-dimensional (3D) photo-based model of the real working environment, including an image of the radioactive substance, was imported into the virtual space of the VR system. The developed VR system can be accessed using a smartphone and a cardboard goggle. The VR system is expected to be useful for preliminary training of workers and for recognizing radioactive hotspots during decommissioning of the work environment.

論文

放射線分布の3次元イメージング技術

佐藤 優樹; 鳥居 建男

Isotope News, (757), p.44 - 47, 2018/06

東京電力ホールディングス福島第一原子力発電所(以下、福島第一原発という)の円滑な廃炉作業に向けて、日本原子力研究開発機構廃炉国際共同研究センターでは、放射線イメージングセンサーとして大きな遮蔽体の要らない小型コンプトンカメラを用い、放射性物質の立体的な分布を示そうと、福島第一原発の作業環境において放射線物質の3次元可視化技術の研究開発に取り組んでいる。本研究開発では、レーザー光を利用した測域センサー(LiDAR)で取得した建屋構造物の3次元モデルにコンプトンカメラで取得される汚染分布の情報を重ね合わせることにより、実空間における汚染分布の拡がりをより詳細に可視化する手法を検討している。本稿では、これらの技術と取り組みについて紹介する。

論文

A Three-dimensional radiation image display on a real space image created via photogrammetry

佐藤 優樹; 小澤 慎吾*; 谷藤 祐太; 鳥居 建男

Journal of Instrumentation (Internet), 13(3), p.P03001_1 - P03001_8, 2018/03

 被引用回数:2 パーセンタイル:32.06(Instruments & Instrumentation)

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown after the large tsunami caused by the Great East Japan Earthquake of March 11, 2011. Radiation distribution measurements inside FDNPS buildings are indispensable to execute decommissioning tasks in the reactor buildings. We have developed a method of three-dimensional (3-D) image reconstruction for radioactive substances using a compact Compton camera. We also succeeded in visually recognize the position of the radioactive substances on the real space by integration of the 3D radiation image and the 3D photo-model created by photogrammetry.

論文

Remote radiation imaging system using a compact $$gamma$$-ray imager mounted on a multicopter drone

佐藤 優樹; 小澤 慎吾*; 寺阪 祐太; 冠城 雅晃; 谷藤 祐太; 川端 邦明; 宮村 浩子; 和泉 良*; 鈴木 敏和*; 鳥居 建男

Journal of Nuclear Science and Technology, 55(1), p.90 - 96, 2018/01

 被引用回数:6 パーセンタイル:2.39(Nuclear Science & Technology)

A remote radiation imaging system comprising a lightweight Compton camera and a multicopter drone was developed to remotely and quickly measure radioactive contamination inside the buildings of the Fukushima Daiichi Nuclear Power Station (FDNPS). The drone system is used for measuring detailed radiation distributions in narrow areas, which have been difficult to gauge with conventional aircraft monitoring using helicopters. A measurement of radiation distributions in outdoor environments in the coastal areas of Fukushima, Japan, was performed. The drone system with the Compton camera succeeded in remote observations of dense hotspots from the sky over a contaminated area near the FDNPS. The time required for image reconstruction is approximately 550 s in the case of a 9-m flight altitude for the hotspots with a surface dose rate of several tens of $$mu$$Sv/h. This drone system will be used inside the buildings of the FDNPS for remote measurement of radioactive contamination.

論文

Development of compact Compton camera for 3D image reconstruction of radioactive contamination

佐藤 優樹; 寺阪 祐太; 小澤 慎吾*; 宮村 浩子; 冠城 雅晃; 谷藤 祐太; 川端 邦明; 鳥居 建男

Journal of Instrumentation (Internet), 12(11), p.C11007_1 - C11007_8, 2017/11

 被引用回数:3 パーセンタイル:47.79(Instruments & Instrumentation)

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown after the large tsunami caused by the Great East Japan Earthquake of March 11, 2011. Very large amounts of radionuclides were released from the damaged plant. Radiation distribution measurements inside the building of FDNPS are indispensable to execute the decommission tasks in the reactor buildings. We have developed a light-weight compact Compton camera to three-dimensionally measure the distribution of radioactive contamination inside FDNPS. The total weight of the Compton camera is lower than 1.0 kg. The $$gamma$$-ray sensor of the Compton camera employs the Ce-doped GAGG scintillators coupled with a multi-pixel photon counter (MPPC: Hamamatsu Photonics K.K.,). We performed the 3D image reconstruction of the $$^{137}$$Cs-radioactive sources as shown in Fig. 1; the 3D radiation image is reconstructed using the multi-angle data measured with the Compton camera. Here, we introduce the development status of the 3D radiation imaging system consisting of the Compton camera. Moreover, we present the results of a performance evaluation test for 3D image reconstruction of radioactive contaminations in details.

論文

Radiation imaging system using a compact $$gamma$$-ray imager mounted on a remotely operated machine

佐藤 優樹; 川端 邦明; 小澤 慎吾*; 和泉 良*; 冠城 雅晃; 谷藤 祐太; 寺阪 祐太; 宮村 浩子; 河村 拓馬; 鈴木 敏和*; et al.

IFAC-PapersOnLine, 50(1), p.1062 - 1066, 2017/07

The development of remote and quick radiation imaging methods in the high dose-rate environment is requested to accelerate implementation of decommissioning of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP). We developed the remote radiation imaging system consisting of a Compton camera and a multicopter drone to remotely measure the radioactive contamination on the several radioactive fields in the environment and inside the building of nuclear facilities such as the FDNPP. The drone system succeeded in the observation of several hotspots from the sky at the outdoor environments in coastal areas of Fukushima, Japan. In addition, we are now developing the SLAM technology for remotely operated machines such as the drone to complete the remote radiation imaging system, which can autonomous flight.

論文

Charge-collection efficiency of single-crystal CVD diamond detector for low-energy charged particles with energies ranging from 100 keV to 2 MeV

佐藤 優樹; 村上 浩之*; 嶋岡 毅紘*; 坪田 雅功*; 金子 純一*

Nuclear Instruments and Methods in Physics Research A, 834, p.218 - 222, 2016/10

 パーセンタイル:100(Instruments & Instrumentation)

The performance of a diamond detector created from a single-crystal diamond grown by chemical vapor deposition was studied for application in detecting charged particles having energies ranging from 100 keV to 2 MeV. Energy peaks of these low-energy ions were clearly observed. However, we observed that the pulse height for individual incident ions decreases with increasing atomic number of the ions. We estimated the charge collection efficiency of the generated charge carriers by the incident charged particles. While charge collection efficiency above 95% is achieved for helium (He$$^+$$) at energies above 1.5 MeV, over the same incident energy range, the efficiencies are lower for heavy-ions: $$sim$$70% for silicon (Si$$^+$$) and $$sim$$30% for gold (Au$$^{3+}$$). We also found that the charge collection efficiency decreases as the generated charge density inside the diamond crystal increases.

論文

Fano factor evaluation of diamond detectors for alpha particles

嶋岡 毅紘*; 金子 純一*; 佐藤 優樹; 坪田 雅功*; 新名 宏明*; 茶谷原 昭義*; 渡辺 幸志*; 梅沢 仁*; 杢野 由明*

Physica Status Solidi (A), 213(10), p.2629 - 2633, 2016/10

 被引用回数:1 パーセンタイル:88.02(Materials Science, Multidisciplinary)

This report is the first describing experimental evaluation of Fano factor for diamond detectors. High-quality self-standing chemical vapor deposited diamond samples were produced using lift-off method. Alpha-particle induced charge measurements were taken for three samples. A 13.1 eV $$pm$$ 0.07 eV of the average electron-hole pair creation energy and excellent energy resolution of approximately 0.3$$%$$ were found for 5.486 MeV alpha particles from an $$^{241}$$Am radioactive source. The best Fano factor for 5.486 MeV alpha particles calculated from experimentally obtained epsilon values and the detector intrinsic energy resolution was 0.382 $$pm$$ 0.007.

論文

Charge-collection efficiency and long-term stability of single-crystal CVD diamond detector under different carrier-drift conditions

佐藤 優樹; 村上 浩之*; 嶋岡 毅紘*; 坪田 雅功*; 金子 純一*

Japanese Journal of Applied Physics, 55(4), p.046401_1 - 046401_5, 2016/04

 被引用回数:1 パーセンタイル:88.37(Physics, Applied)

化学気相成長法(CVD)により育成した人工単結晶ダイヤモンドを用いて放射線検出器を製作し、検出器のエネルギー分解能、生成電荷キャリアの収集効率、及び長時間安定性の調査を行った。検出器固有のエネルギー分解能は半値幅で約0.4%であり、$$^{241}$$Amから放出される4つのエネルギー(5.389, 5.443, 5.486及び5.545MeV)の$$alpha$$粒子の観測ができた。電荷キャリアの収集効率は電子、正孔ともに98%を達成し、さらに、主として電子を検出器内でドリフトさせた場合、100時間以上の$$alpha$$粒子照射でもエネルギースペクトルや分解能の劣化は見られなかった。一方で、主として正孔を検出器内でドリフトさせた場合、照射時間と共にエネルギースペクトルが劣化するポーラリゼイション現象が観測された。

口頭

研究拠点機能向上のための遠隔技術開発,7; 放射線環境における超小型ポータブルコンプトンカメラの要素技術開発

佐藤 優樹; 岸本 彩*; 冠城 雅晃; 片岡 淳*; 鳥居 建男

no journal, , 

東京電力福島第一原子力発電所の廃止措置で生じる放射性廃棄物を取り扱う施設において、$$gamma$$線イメージャの開発は廃棄物に付着した放射性物質の分布を可視化するうえで重要な課題となっている。日本原子力研究開発機構は早稲田大学と共同で、従来の$$gamma$$線イメージャと比較して小型・軽量であり、放射線作業環境において作業員がメガネ感覚で装着可能、もしくは遠隔機器に搭載可能といった特徴を持つポータブルコンプトンカメラの開発に着手した。これまでの実験では、シリコン半導体をベースとしたマルチピクセル光子カウンティングデバイスと、$$gamma$$線に対して高い検出効率を有するCe:GAGGシンチレータを組み合わせて小型コンプトンカメラを試作し、これを用いて$$^{137}$$Cs線源の二次元イメージング画像を取得できることを示した。本講演では実験結果に加えて、小型コンプトンカメラ開発の今後の展望について紹介する。

口頭

Superior radiation hardness of a single crystal CVD diamond detector under proton beam bombardment

佐藤 優樹; 村上 浩之*; 嶋岡 毅紘*; 坪田 雅功*; 金子 純一*

no journal, , 

Diamond crystals have long been recognized as an attractive material for radiation detectors because of their unique properties. The high electrical resistivity and high band gap energy of diamond crystal, compared with silicon-based solid-state detectors, makes it possible to operate with low noise performance. Fast responses with superior timing resolution are possible because of high carrier saturation velocities under high breakdown electric fields. Additionally, because of their high displacement energy, it is expected that diamond detectors will show superior radiation hardness compared with detectors made of other materials such as silicon. We have fabricated a charged-particle detector using single crystal (sc) diamond grown by chemical vapor deposition (CVD) to investigate the radiation hardness of the diamond detector. The radiation dose dependence of the output pulse height from the diamond detector was measured using proton beams generated by a pelletron accelerator. The total kinetic energy of accelerated protons was 2.4 MeV and the incident side of the detector was Au electrode. During an operation of the diamond detector under the proton beam bombardment, the polarization effect was not observed. Additionally, the radiation hardness performance for light ions was compared with that of silicon surface barrier detectors, and the diamond detector showed radiation hardness superior that of the silicon detectors.

口頭

Single crystal CVD diamond detector for charged particle detection

佐藤 優樹

no journal, , 

化学気相成長法により育成した人工単結晶ダイヤモンドを用いて荷電粒子検出器を製作し、加速器から得られるイオンビームを検出器に入射してその検出器特性を調査した。調査した項目は、エネルギー分解能、高速応答性能(時間分解能)、放射線耐久性の3点である。検出器固有のエネルギー分解能は5.486MeV-$$alpha$$粒子に対して、約0.4$$%$$(FWHM)とSi表面障壁型検出器に匹敵する性能を示し、$$^{241}$$Amから放出される4つのエネルギー(5.389, 5.443, 5.486及び5.545MeV)の$$alpha$$粒子の観測ができた。また、重イオンビームに対して、約30psの高速な時間分解能を達成している。一方で、荷電粒子入射に対する耐久性に関しては、軽イオンに対しては従来のSi表面障壁型検出器と比較して優れた性能を示したが、Auイオンのような重イオン入射に対しては耐久性に顕著な差は見られなかった。これらの結果に加えて、検出器動作の長時間安定性に関する調査も実施しており、放射線入射によって結晶内に生成される正孔の挙動が長時間動作における性能劣化に大きく影響することも明らかとした。発表では、上記に示すようなダイヤモンド検出器の荷電粒子入射に対する基礎特性について報告する。

口頭

$$alpha$$線に対する単結晶CVDダイヤモンド放射線検出器のFano因子評価

嶋岡 毅紘*; 金子 純一*; 佐藤 優樹; 坪田 雅功*; 新名 宏明*; 茶谷原 昭義*; 渡辺 幸志*; 梅澤 仁*; 杢野 由明*

no journal, , 

ダイヤモンド放射線検出器は高温動作、低漏れ電流、耐放射線性等の優れた特長を持つ。われわれはこれらの特長を生かし過酷環境で動作可能な検出器実現に向け、生産性に優れたLift-off法による単結晶CVDダイヤモンド放射線検出器開発を行ってきた。これまでに電荷キャリア輸送特性改善の取り組みにより電荷収集効率: 正孔100.1%、電子99.8$$%$$($$varepsilon_{Si}$$ = 3.62 eV, $$varepsilon_{diamond}$$ = 13.1eVとして計算)、エネルギー分解能0.3%台を持つ検出器開発に成功している。本研究では$$^{241}$$Am 5.486MeV $$alpha$$線を用いたファノ因子評価について報告する。

口頭

Fano factor evaluation of diamond detectors for alpha particles

嶋岡 毅紘*; 金子 純一*; 佐藤 優樹; 坪田 雅功*; 新名 宏明*; 茶谷原 昭義*; 渡辺 幸志*; 梅沢 仁*; 杢野 由明*

no journal, , 

Diamond radiation detectors have promising properties i.e. high-temperature operation, low leakage current and radiation hardness. The authors have developed CVD diamond detector using lift-off method. We have successfully obtained high performance detectors which have 100.1% of charge collection efficiency for holes and 99.8% for electrons, provided that $$varepsilon_{diamond}$$ = 13.1 eV. The detector also achieved approximate 0.3$$%$$ of one of the best energy resolution. This study reports a Fano factor evaluation of diamond detectors for alpha particles.

口頭

R&Ds on remote technology and radiation measurements in JAEA towards the decommissioning of FDNPP

佐藤 優樹; 冠城 雅晃; 寺阪 祐太; 三枝 純; 川端 邦明; 若井田 育夫; 鳥居 建男

no journal, , 

The development of radiation measurement methods in the high dose-rate environment is requested to accelerate implementation of decommissioning of the FDNPP. We are now developing the technology which can measure the 3D distribution of the contamination level with radioactive substances inside the building of FDNPP. Light-weight portable gamma camera is to be developed, and is used for drones that can remotely measure the radiation distributions in the high radioactive fields where workers are not allowed to enter and remain there. Radiation hard sensors that can measure the shapes and nuclide distributions of residual debris inside the reactor pressure vessel (RPV) and primary containment vessel (PCV) are also to be developed. Multi-layer silicon strip detector (SSD) is one of the candidate sensor, which can measure the above information on the debris because SSD can measure the energies and incident directions of the $$gamma$$-rays emitted from the debris. Fast-decay scintillator which has the high density and superior radiation hardness are also developed for measurement of the $$gamma$$-rays emitted from the debris. We are now investigating the radiation hard optical fibers which can transmit the scintillation light under high dose-rate environment. We introduce our recent study about such radiation imaging technology and sensing technology of fuel debris.

口頭

原子力機構における福島第一原子力発電所の廃止措置に向けた遠隔放射線測定技術の開発

佐藤 優樹; 冠城 雅晃; 寺阪 祐太; 三枝 純; 川端 邦明; 若井田 育夫; 鳥居 建男

no journal, , 

廃炉国際共同研究センター遠隔技術ディビジョンでは、東京電力ホールディングス福島第一原子力発電所の廃止措置に向けて、ガンマカメラと遠隔機器の融合による遠隔放射線測定技術の開発を進めている。これまでに遠隔技術ディビジョンでは、飛散した放射性物質を可視化するための装置として小型・軽量なコンプトンカメラを製作し、その動作試験を実施してきた。本会議では、コンプトンカメラの仕様と性能評価試験の結果を部分的に紹介し、加えて、今後予定しているコンプトンカメラを遠隔機器に搭載する計画についても発表する。

口頭

小型・軽量コンプトンカメラを用いた遠隔放射線イメージング技術の開発,3; コンプトンカメラデータを用いた3次元線源分布再構成に関する検討

宮村 浩子; 冠城 雅晃; 佐藤 優樹; 河村 拓馬; 井戸村 泰宏; 鳥居 建男

no journal, , 

コンプトンカメラによって測定したデータセットから2つの再構成アルゴリズムを使って線源分布の3次元ボリュームデータを再構成する実験結果を報告する。福島第一原子力発電所事故によって放出された放射性物質の分布を把握するために、$$gamma$$線の詳細な計測が必要である。本発表では、予備実験として、理想的な環境下で計測したデータに対して、3次元バックプロジェクション法、3次元リストモードMLEM(maximum likelihood estimation method)法2つのアルゴリズムを使って3次元再構成を試み、線源分布を再構成できることを確認した。

49 件中 1件目~20件目を表示