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Fujihara, Hiro*; Toda, Hiroyuki*; Ebihara, Kenichi; Kobayashi, Masakazu*; Mayama, Tsuyoshi*; Hirayama, Kyosuke*; Shimizu, Kazuyuki*; Takeuchi, Akihisa*; Uesugi, Masayuki*
International Journal of Plasticity, 174, p.103897_1 - 103897_22, 2024/03
Times Cited Count：0Hydrogen(H) embrittlement in high-strength aluminum(Al) alloys is a crucial problem. H accumulation at the interface of precipitates in Al alloy is considered to cause embrittlement. However, there is no quantitative knowledge regarding the interaction between H distribution and stress field near cracks. In this study, using a multi-modal three-dimensional image-based simulation combining the crystal plasticity finite element method and H diffusion analysis, we tried to capture the stress distribution near the crack, its influence on the H distribution, and the probability of crack initiation in the experimental condition. As a result, it was found that grain boundary cracks transition to quasi-cleavage cracks in the region where the cohesive energy of the semi-coherent interface of MgZn
precipitates decreases due to H accumulation near the tip. We believe the present simulation method successfully bridges nanoscale delamination and macroscale brittle fracture.
Kawahara, Rika*; Ochi, Kotaro; Yamaguchi, Katsuhiko*; Torii, Tatsuo*
Hoshasen (Internet), 48(2), p.43 - 48, 2023/04
The accident at the Fukushima Daiichi NPP resulted in a large amount of radioactive material being dispersed into the surrounding environment. It is important to understand the radiation distribution in the area, which is still located in the difficult-to-return zone. In this study, a Compton camera and an optical camera were combined to produce a three-dimensional distribution map of source locations and their intensities. Two locations in the difficult-to-return zone (Okuma town) were surveyed: a park parking lot and the area around a private house. The distribution of air dose rates was determined by measurements with a survey meter with a wand-type GPS (Gamma Plotter H manufactured by Nippon Radiation Engineering Co. Measurements were taken with a Compton camera (H420, H3D, USA) at several different positions and angles towards the hotspots. The software (Application Programming Interface Example) allowed real-time confirmation of the radiation incident information (incident time, energy, x, y, z) obtained by the Compton camera. By photographing hotspots in high-dose areas from different positions and angles, the location of the radiation sources and their spatial extent could be confirmed.
Takai, Shizuka; Namekawa, Masakazu*; Shimada, Taro; Takeda, Seiji
IEEE Transactions on Nuclear Science, 69(7), p.1789 - 1798, 2022/07
Times Cited Count：0 Percentile：0.01(Engineering, Electrical & Electronic)To reduce a large amount of contaminated concrete rubble stored in the Fukushima Daiichi Nuclear Power Station site, recycling low-radioactivity rubble within the site is a possible remedy. To promote recycling while ensuring safety, not only the average radioactivity but also the radioactivity distribution of concrete rubble should be efficiently evaluated because the details of rubble contamination caused by the accident remain unclear and likely include hotspots. However, evaluating inhomogeneous contamination of thick and/or dense materials is difficult using previous measurement systems, such as clearance monitors. This study experimentally confirmed the potential applicability of image reconstruction algorithms for radioactivity distribution evaluation in concrete rubble filled in a chamber. Radiation was measured using plastic scintillation fiber around the chamber (50 
50 40 cm
). Localized hotspots were simulated using standard sources of 
Cs, which is one of the main nuclides of contaminated rubble. The radioactivity distribution was calculated for 100 or 50 voxels (voxel size: (10 cm) or 10 10 20 cm) constituting the chamber. For 100 voxels, inner hotspots were undetected, whereas, for 50 voxels, both inner and surface hotspots were reconstructible. The distribution evaluated using the maximum likelihood expectation maximization algorithm was the most accurate; the average radioactivity was estimated within 70% accuracy in all seven cases.
Shimada, Koji; Goto, Akira; Niwa, Masakazu; Shimo, Michito*
Chishitsugaku Zasshi, 127(10), p.I - II, 2021/10
Continuous leaking point of high-temperature fluid (liquid/gas) from underground can be easily grasped by infrared images. We show images confirmed by a FLIR C5 camera that can simultaneously obtain an infrared image and a visible light image at the outcrops of Kawayu Onsen that naturally spring along the river. Outcrops and river surface temperature rise due to hot springs that leaking from riverbanks and riverbeds, rock temperature rise around cracks where gas containing high-concentration methane leaks with hot springs, abandoned fluid pathway due to construction of the bank and damming river for hot spring river bath in winter can be confirmed at a glance. Infrared images may be useful for quick identification of hot fluid leaking points from underground.
Kawabata, Kuniaki
Japanese Journal of Applied Physics, 59(5), p.050501_1 - 050501_9, 2020/05
Times Cited Count：13 Percentile：18.54(Physics, Applied)This paper describes the decommissioning work being undertaken at the Fukushima Daiichi Nuclear Power Station of the Tokyo Electric Power Company Holdings Inc.'s (FDNPS) using remote controlled robotic systems, as well as lessons learned from past remote task executions. We also summarize the issues to be considered in promoting safe, steady, and efficient decommissioning based on past experiences. In response to these issues, we are developing test methods for performance evaluation of the robots for nuclear decommissioning, robot simulator for operator proficiency training, and information generation methods to improve the operator's status awareness. The current status of technological development is also described.
Hanari, Toshihide; Kawabata, Kuniaki; Nakamura, Keita*; Naruse, Keitaro*
Proceedings of International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP 2020) (Internet), p.242 - 245, 2020/02
In this paper, we propose an image selection method to realize efficient three-dimensional (3D) reconstruction from image sequence collected by a remotely operated robot. The proposed method is to select adequate images for reconstruction computation based on optical flow measures. We confirmed that the proposed method can select adequate images for 3D reconstruction from the image sequence recorded by the remotely operated robot that is commanded stop-and-go motions. As a result, we demonstrated a 3D reconstruction could be performed efficiently with relatively few images that were selected by the proposed method.
Kuriyama, Yasutoshi*; Iwashita, Yoshihisa*; Hirota, Katsuya*; Hayano, Hitoshi*; Fuwa, Yasuhiro
Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.32 - 35, 2019/10
Research and development of gradient enhancement of superconducting RF accelerating cavity is carried out by accelerator research institute in the world, but defects on the cavity surface limit accelerating electric field. Therefore, development of "Inside inspection system for superconducting accelerated cavity" that optically visualizes the state of the inner surface of the superconducting cavity has been carried out, and results have been achieved. In this research, we apply image processing technology that has developed remarkably in recent years to the internal inspection system, and advanced the defect recognition method. Extraction of depth information and image synthesis were performed from images obtained with different focal positions with the camera for internal surface inspection. Also, by performing pattern recognition processing on the images, automatic detection of defects has become possible. By integrating these techniques into the cavity inner surface inspection system, it becomes possible to shorten the scan time for defect search and acquire the defect shape.
)Matsuda, Asahi*; Takahashi, Satoru*; Kawabata, Kuniaki; Oda, Shoji*; Kaneko, Shunichi*
Denki Gakkai Rombunshi, D, 139(4), p.424 - 432, 2019/04
Kimbara, Shinji*; Ekawa, Hiroyuki; Hayakawa, Shuhei; Yoshida, Junya; 12 of others*
Progress of Theoretical and Experimental Physics (Internet), 2019(1), p.011H01_1 - 011H01_9, 2019/01
Times Cited Count：4 Percentile：36.66(Physics, Multidisciplinary)A development has been achieved in the identification method of the charges 1 to 5 of nuclides from the decay of double hypernuclei to be uniquely recognized by their nuclear species. The method is basically the measurement of track volume by the widths, depths, and angles of tracks of exposed nuclei of 
H, 
He, 
Li, 
Be, and 
B in nuclear emulsion at Riken Projectile-fragment Separator of RIKEN Radioactive Isotope Beam Factory. After their calibration by 
particles, we obtained a quadric function to present a unified recognition of tracks with volume ratios of five nuclei to the particles. The function in the emulsion has been applied to a candidate event of a 
hypernucleus for identification of the production and decay processes. We succeeded in recognizing a daughter nuclear fragment of a single-
hypernucleus as 
He with a likelihood ratio of 0.9; the process was then uniquely identified as 
+ 
N 
Be + 
He + 
.
Otsuka, Noriaki; Takeuchi, Tomoaki; Tsuchiya, Kunihiko; Shibagaki, Taro*; Komanome, Hirohisa*
Proceedings of 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC 2017) (Internet), 3 Pages, 2018/11
no abstracts in English
(Al,Ga)
O
scintillator Compton camera mounted on an unmanned helicopterShikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.
Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12
Times Cited Count：37 Percentile：96.48(Nuclear Science & Technology)The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 44 to 88 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m 60 m and 65 m 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the 
-ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10
).
Chiba, Atsuya; Ishii, Yasuyuki; Tajima, Satoshi
JAERI-Review 2003-033, TIARA Annual Report 2002, p.327 - 329, 2003/11
no abstracts in English
Yasuda, Ryo; Nakata, Masahito; Matsubayashi, Masahito; Harada, Katsuya; Hatakeyama, Yuichi; Amano, Hidetoshi
Journal of Nuclear Materials, 320(3), p.223 - 230, 2003/08
Times Cited Count：15 Percentile：69.06(Materials Science, Multidisciplinary)Neutron radiography is one of effective tools to determine hydrided region in Zircaloy cladding tubes. In this work, the practicability of the neutron radiography for hydrogen analysis is further investigated by using standard samples with known hydrogen concentration. Local hydrogen concentration in hydrided Zircaloy tube is quantitatively estimated using the standard samples by neutron imaging plate (NIP) method. The local area is equivalent to a picture element in the image; e.g., 0.1mm0.1mm. In addition, contribution of an oxide film in the tubes to the images is investigated using oxidized samples with hydrides or no hydride. In NIP images of oxidized tube no oxide film was recognized. Numerical image analysis also shows no effect of the oxide film on the image. These results show that the influence of oxygen on image contrast can be neglected when hydrogen analysis is performed on the Zircaloy tube with oxide film and hydrides by NIP method.
Kureta, Masatoshi
Kashika Joho Gakkai-Shi, 23(89), p.21 - 26, 2003/04
no abstracts in English
Chiba, Atsuya; Ishii, Yasuyuki; Tajima, Satoshi
Dai-15-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.74 - 76, 2003/03
no abstracts in English
Ishii, Toshimitsu; Inagaki, Terumi*; Sakane, Taisuke*; Nakatani, Takahiko*; Ooka, Norikazu; Omi, Masao; Hoshiya, Taiji
Hihakai Kensa, 51(4), p.223 - 230, 2002/04
no abstracts in English
Mori, Koichi*; Sekine, Norio*; Sato, Hajime*; Shikano, Naoto*; Shimayu, Daisuke*; Shiwaku, Hideaki; Hyodo, Kazuyuki*; Oka, Hiroshi*
Japanese Journal of Medical Physics, 22(1), p.13 - 19, 2002/03
no abstracts in English
Katagiri, Masaki; Sakasai, Kaoru; Kishimoto, Maki; Nakamura, Tatsuya; To, Kentaro; Takahashi, Hiroyuki*; Nakazawa, Masaharu*
Nuclear Instruments and Methods in Physics Research A, 477(1-3), p.179 - 183, 2002/03
Times Cited Count：4 Percentile：29.4(Instruments & Instrumentation)no abstracts in English
Kamiya, Tomihiro; Yokota, Wataru; Kobayashi, Yasuhiko; Cholewa, M.*; Krochmal, M. S.*; Laken, G.*; Larsen, I. D.*; Fiddes, L.*; Parkhill, G.*; Dowsey, K.*
Nuclear Instruments and Methods in Physics Research B, 181(1-4), p.27 - 31, 2001/07
Times Cited Count：30 Percentile：87.82(Instruments & Instrumentation)no abstracts in English
Takahashi, Tsuneo*; Ishihara, Masahiro; Baba, Shinichi; Arai, Taketoshi; Hayashi, Kimio; Konishi, Takashi*
JAERI-Research 2001-005, 62 Pages, 2001/03
JAERI-Research-2001-005.pdf:6.8MB
no abstracts in English
