Nakano, Masanao; Hosomi, Kenji; Nishimura, Shusaku; Matsubara, Natsumi; Okura, Takehisa; Kuramochi, Akihiko; Kawasaki, Masatsugu; Takeuchi, Erina; Fujii, Yutaka*; Jinno, Tsukasa*; et al.
Hoken Butsuri (Internet), 55(2), p.102 - 109, 2020/06
After the Fukushima-Daiichi Nuclear Power Station (1F) Accident in March 2011, the increase was significantly observed in a part of the result of the environmental radiation monitoring in Ibaraki prefecture. "The review meeting of the environmental effect from 1F accident" was established to discuss technically the fluctuation of monitoring data. The review meeting collected the monitoring data from the four nuclear operators, and discussed a fluctuating trend, Cs/Cs activity ratio, and so on. In this report, the results of the dose rate and Cs in fallout, surface soil, flatfish and seabed sediment are introduced. Also the problem solving in the review meeting is introduced.
Uechi, Schun*; Uechi, Hiroshi*; Nishimura, Akihiko
World Journal of Engineering and Technology, 7(4), p.559 - 571, 2019/11
A water drinking bird is discussed in terms of a thermomechanical model. A mathematical expression of motion derived from the thermomechanical model of a drinking bird and numerical solutions are explicitly shown, which is helpful in understanding physical meanings and fundamental difference between mechanical and thermomechanical periodic motion. The mathematical and physical differences between mechanical and thermomechanical periodic motion. The process of a drinking bird motion could be applied to energy harvesting technology by way of the current modeling.
Furusawa, Akinori; Takenaka, Yusuke; Nishimura, Akihiko
Applied Sciences (Internet), 9(17), p.3544_1 - 3544_12, 2019/09
Remote-controlled, non-destructive testing is necessary to detect corrosion of the reinforced concrete structures at the Fukushima Daiichi Nuclear Power Plant (NPP) de-commissioning site. This work aims to demonstrate that laser-induced ultrasonic guided wave technology can be applied to achieve this task. Hence, accelerated electrolytic corrosion is performed on a reinforced concrete specimen fabricated by embedding a steel rod into mortar. Waveforms of the laser-induced ultrasonic guided wave on the rod are measured with a previously employed piezoelectric transducer (PZT) probe, for each fixed corrosion time. Based on the results of Fourier and wavelet transforms of the waveforms, issues concerning the detection and extent of rebar corrosion are discussed. It is exhibited that the changes in bonding strength due to corrosion are distinguishable in the frequency domain of the ultrasonic signal.
Furusawa, Akinori; Nishimura, Akihiko; Takenaka, Yusuke; Muramatsu, Toshiharu
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
The aim of this work presented here is to demonstrate the potential of our method for remote controllable systematization, of testing reinforced concrete based on ultrasonic guided-wave on rebar. In order to investigate how the deteriorated phenomena has the effects on the ultrasonic guided-wave propagating on the rebar, following experiments are conducted. Test pieces used for the experiments are made of bare steel rod and cylindrically pored mortar to be representing the actual reinforced concrete. Irradiating the end face of the rod with nanosecond pulsed laser makes the ultrasonic guided-wave induced, at the other end face, the guided wave signal is measured with ultrasonic receiver. One test piece is with no damage and the other is deteriorated test piece. The deterioration is made by electrolytic corroded method. The guided-wave signal from the deteriorated test piece is measured with respect to each energization time, the change in the waveform is investigated. Analyzing the results from the experiments above, it is found that the deterioration of rebar has remarkable effects on the guided-wave signal. The signal from test piece with no damage has strong peak at both specific frequency and lower region, on the other hand, signals from deteriorated test piece has only at the specific frequency depending on the diameter of the steel rod. Finally, discussion concerning with the experimental results and future perspective for remote controllable systematization of our method is carried out.
Nishimura, Akihiko; Yoshida, Minoru*; Yamada, Tomonori; Arakawa, Ryoki
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 3 Pages, 2019/05
JAEA support the development of remote sensing robotic system in the Naraha Remote Technology Development Center. A water tank is used as a mockup facility of nuclear reactor vessel. A compact seismic vibrometer based on an optical fiber interferometer is applied. A specially designed robotic system is also tested for installing the sensor unit. The experiment is prepared to clarify the transfer function of the water tank, using vibration noise of ground motion.
Dai-62-Kai Koha Senshingu Gijutsu Kenkyukai Koen Rombunshu, p.79 - 86, 2018/12
Thermal Energy Storage (TES) is important to stabilize increasing large amount of fluctuating renewable energy. For safety operation of TES, remote sensing by Fiber Bragg Grating (FBG) sensors is expected. FGB sensors were fabricated using precisely focused picosecond laser pulses. For the best use of heat resistant characteristic, we demonstrated to embed the FBG sensors in metal mold using colloidal silver adhesive. The FBG sensors were tested using a sodium circulation loop in JAEA Tsuruga site. Sodium was circulated with temperature of 500 degree. During emergency cooling, sudden shrinking of the loop was recorded. The application of FBG sensors to advanced remote monitoring for next generation TES plant is proposed.
Nishimura, Akihiko; Furusawa, Akinori; Takenaka, Yusuke*
AIP Conference Proceedings 2033, p.080002_1 - 080002_5, 2018/11
We developed a cpmpact laser maintenance device in order to access a 23 mm diameter for heat exchanger tubes of nuclear power plants. A laser instrumentation device was desighned and assembled to measure the corrosion depth at the inlet of heat exchanger tubes. This device can be applied for heat exchanger tubes in CSP where erosion or cracking might be caused by repetitive thermal induced stress.
Nguyen, P. L.; Daido, Hiroyuki; Yamada, Tomonori; Nishimura, Akihiko; Hasegawa, Noboru*; Kawachi, Tetsuya*
Journal of Laser Applications, 29(4), p.041501_1 - 041501_11, 2017/11
no abstracts in English
Komatsu, Kazumi*; Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi*; Nishimura, Akihiko
Hozengaku, 16(3), p.89 - 95, 2017/10
no abstracts in English
Ebisuzaki, Toshikazu*; Wada, Satoshi*; Saito, Norihito*; Fujii, Takashi*; Nishimura, Akihiko
Reza Kenkyu, 45(10), p.664 - 665, 2017/10
no abstracts in English
Nishimura, Akihiko; Takenaka, Yusuke*; Furusawa, Akinori; Torimoto, Kazuhiro; Ueda, Masashi; Fukuda, Naoaki*; Hirao, Kazuyuki*
E-Journal of Advanced Maintenance (Internet), 9(2), p.52 - 59, 2017/08
no abstracts in English
Furusawa, Akinori; Nishimura, Akihiko; Takebe, Toshihiko*; Nakamura, Masaki*; Takenaka, Yusuke*; Saijo, Shingo*; Nakamoto, Hiroyuki*
E-Journal of Advanced Maintenance (Internet), 9(2), p.44 - 51, 2017/08
The aim of this work is to investigate the applicability of ultrasonic guided wave for evaluation of laser beam butt-welding quality. Ten in total test pipes having welding seam is prepared. Two piece of pipe are jointed and continuous laser beam is irradiated on the edges, varying laser irradiation power, welding side and surface profile of the adjacent edges of the pipe. Ultrasonic guided wave testing experiment is performed on the pipes. Torsional mode guided wave is excited by EMAT. The experimental results are analyzed and issues are discussed. The reflection wave bullet from the poor interface of the welding seam is clearly observed, whereas no reflection from fine welded line. From the aspect of laser irradiation power, welding side and surface profile of the adjacent edges, the relation between the interface condition and detection wave bullet are analyzed. It is found that the ultrasonic guided wave technologies have the potential for evaluating laser beam butt-welding seam.
Furusawa, Akinori; Takenaka, Yusuke*; Nishimura, Akihiko; Mizutani, Haruki; Muramatsu, Toshiharu
Nippon Hozen Gakkai Dai-14-Kai Gakujutsu Koenkai Yoshishu, p.479 - 480, 2017/08
Industry development activities on applied laser research held at Fukui branch of Japan Atomic Energy Agency are reported. Industry development is inevitable in long-term vision and strategy for developing maintenance technology and establishing decommissioning technology. Fukui branch of JAEA has organized public seminar offering businesses to promote these activities and technology exchange for years. Here some examples offered in the current seminar are introduced concerning with laser technology. Finally, our goal and important point of view are discussed.
Nishimura, Akihiko; Takenaka, Yusuke*
Sumato Purosesu Gakkai-Shi, 6(2), p.74 - 79, 2017/03
no abstracts in English
Furusawa, Akinori; Nishimura, Akihiko; Takenaka, Yusuke*; Nakamura, Kaori*
Proceedings of 54th Annual Meeting of Hot Laboratories and Remote Handling (HOTLAB 2017) (Internet), 6 Pages, 2017/00
Testing of concrete structures in NPPs is needed to guarantee hereafter workability. Recent work says Core Concrete Reaction advances erosion of the concrete structures of Fukushima NPPs and it's difficult to estimate the correct depth of CCR. In addition, it is clear that seawater intrusion makes the rebar in the concrete structures corroded, thus, advanced remote testing methods for the deterioration should be considered. Gap or decrease of the adhesiveness between rebar and outer concrete appears in its deterioration process. We had a sense of possibility introducing a new testing method based on that. The concept is to propagate laser-excited ultrasonic gathering the information about the deterioration inside and received at distance with LDV. In this work, we investigate and report how it has the effect on propagating ultrasonic along the rebar to decrease adhesiveness between the rebar and the concrete experimentally.
Wakai, Eiichi; Kikuchi, Takayuki; Kim, B.*; Kimura, Akihiko*; Nogami, Shuhei*; Hasegawa, Akira*; Nishimura, Arata*; Soldaini, M.*; Yamamoto, Michiyoshi*; Knaster, J.*
Fusion Engineering and Design, 98-99, p.2089 - 2093, 2015/10
Abe, Hiroshi; Shimomura, Takuya; Tokuhira, Shinnosuke*; Shimada, Yukihiro*; Takenaka, Yusuke*; Furuyama, Yuta*; Nishimura, Akihiko; Uchida, Hirohisa*; Daido, Hiroyuki; Oshima, Takeshi
Proceedings of 7th International Congress on Laser Advanced Materials Processing (LAMP 2015) (Internet), 4 Pages, 2015/08
A short pulse laser (the nanosecond and femtosecond) was applied to hydrogen absorbing alloys surface layer, and a surface modification experiment was put into effective to aim at improvement of hydrogen adsorption functionally. It was investigated about correlation between an initial hydrogen absorption reaction rate of hydrogen alloys and a laser irradiation in this research. The laser irradiation condition was done with pulse width 100 fsec and energy 0.2 - 3.4 mJ/pulse. It blazed down on hydrogen absorbing alloys (LaNiAl) and changed local order in the surface. As a result, the initial hydrogen absorption reaction rate was 1.5 - 3.0 times as fast as a irradiated sample, and the result and laser irradiated sample found out that a hydrogen absorption function improves. A laser irradiation can conclude to be effective in surface modification of the hydrogen storage materials.
Terada, Takaya; Nishimura, Akihiko; Oka, Kiyoshi; Moriyama, Taku*; Matsuda, Hiroyasu*
Hozengaku, 13(4), p.87 - 94, 2015/01
Nishimura, Akihiko; Takenaka, Yusuke*; Furuyama, Takehiro*; Shimomura, Takuya; Terada, Takaya; Daido, Hiroyuki
Journal of Laser Micro/Nanoengineering, 9(3), p.221 - 224, 2014/11
Heat resistant FBG sensors were developed by femtosecond laser processing to apply them to high temperature operated piping system of nuclear power plants. The FBG sensor was installed on the surface of a steel blade and a vibration test was conducted to detect the resonant vibration frequency of the vibrating blade. The FBG sensor had the heatproof performance at 600C. A frequency stabilized sensing system using a tunable laser was tested for structural health monitoring in daily operation of nuclear power plants. The FBG sensor was installed on the surface of a steel blade for vibration induced strain measurements. Welding, brazing, soldering and noble metal powder adhesive were discussed for molding the FBG sensors.
Ito, Chikara; Naito, Hiroyuki; Nishimura, Akihiko; Oba, Hironori; Wakaida, Ikuo; Sugiyama, Akira; Chiyatani, Keiji
Journal of Nuclear Science and Technology, 51(7-8), p.944 - 950, 2014/07
In the Fukushima Daiichi Nuclear Power Station, it is necessary to survey the locations and conditions of fuel debris inside reactor pressure vessels or primary containment vessels under water and radiation environment in preparation for removing fuel debris. An optical fiber is well known for features such as signal transmission, light weight, superior insulation performance, water resistance and electromagnetic noise resistance. These features allow the optical fiber to simplify the instrumentation systems for in-vessel inspection, as long as provide that the optical fiber can be used under high radiation dose environment. The radiation resistance of an optical fiber was improved by increasing the amount of hydroxyl up to 1000 ppm in pure silica fiber. The improved optical fibers were irradiated with -ray up to 1 10 Gy using a Co source. They indicated a large peak around 600 nm and a peak tail from ultraviolet region, but no large absorption in infrared region except a hydroxyl absorption peak of 945 nm. We have confirmed that the optical fiber containing 1000 ppm hydroxyl has enough radiation resistance for radiation induced transmission losses and the infrared imaging is effective for observation under high radiation doses.