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Journal Articles

Detection of Simulated Fukushima Daiichi Fuel Debris Using a Remotely Operated Vehicle at the Naraha Test Facility

Nancekievill, M.*; Espinosa, J.*; Watson, S.*; Lennox, B.*; Jones, A.*; Joyce, M. J.*; Katakura, Junichi*; Okumura, Keisuke; Kamada, So*; Kato, Michio*; et al.

Sensors (Internet), 19(20), p.4602_1 - 4602_16, 2019/10

 Times Cited Count:1 Percentile:70.51(Chemistry, Analytical)

In order to contribute to fuel debris search at the Fukushima Daiichi Nuclear Power Station, we developed a system to search for submerged fuel debris by mounting a sonar on the remotely operated vehicle (ROV). The system can obtain 3D images of submerged fuel debris in real time by using the positioning system, depth sensor, and collected sonar data. As a demonstration test, a simulated fuel debris was installed at the bottom of the water tank facility at the Naraha Center for Remote Control Technology Development, and a 3D image was successfully obtained.

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:99 Percentile:0.17(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Development of ROV system to explore fuel debris in the Fukushima Daiichi Nuclear Power Plant

Kamada, So*; Kato, Michio*; Nishimura, Kazuya*; Nancekievill, M.*; Watson, S.*; Lennox, B.*; Jones, A.*; Joyce, M. J.*; Okumura, Keisuke; Katakura, Junichi*

Progress in Nuclear Science and Technology (Internet), 6, p.199 - 202, 2019/01

As a technology development to investigate the distribution of submerged fuel debris in the primary containment vessel (PCV) of the Fukushima Daiichi Nuclear Power Station, we are conducting development experiments of sonar system to be mounted in a compact ROV. The experiments were conducted in two types of water tanks with different depths, simulating the PCV, using sonar with different sizes, ultrasonic frequencies, and beam scanning method, and simulated fuel debris. As a result, we characterized the shape discrimination performance of the simulated debris, and the noise due to multi-path in narrow closed space.

Journal Articles

Development of a radiological characterization submersible ROV for use at Fukushima Daiichi

Nancekievill, M.*; Jones, A. R.*; Joyce, M. J.*; Lennox, B.*; Watson, S.*; Katakura, Junichi*; Okumura, Keisuke; Kamada, So*; Kato, Michio*; Nishimura, Kazuya*

IEEE Transactions on Nuclear Science, 65(9), p.2565 - 2572, 2018/09

 Times Cited Count:6 Percentile:17.69(Engineering, Electrical & Electronic)

In order to contribute to the development of technology to search fuel debris submerged in water inside the primary containment vessel of the Fukushima Daiichi Nuclear Power Station, we are developing a remotely operated vehicle (ROV) system equipped with a compact radiation detector and sonar. A cerium bromide (CeBr$$_{3}$$) scintillator detector for dose rate monitoring and $$gamma$$ ray spectroscopy was integrated into ROV and experimentally validated with a $$^{137}$$Cs source, both in the conditions of laboratory and submerged. In addition, the ROV combined with the IMAGENEX 831L sonar could characterize the shape and size of a simulated fuel debris at the bottom of the water pool facility.

Journal Articles

NIRS3; The Near Infrared Spectrometer on Hayabusa2

Iwata, Takahiro*; Kitazato, Kohei*; Abe, Masanao*; Otake, Makiko*; Arai, Takehiko*; Arai, Tomoko*; Hirata, Naru*; Hiroi, Takahiro*; Honda, Chikatoshi*; Imae, Naoya*; et al.

Space Science Reviews, 208(1-4), p.317 - 337, 2017/07

 Times Cited Count:24 Percentile:33.41(Astronomy & Astrophysics)

NIRS3: The Near Infrared Spectrometer is installed on the Hayabusa2 spacecraft to observe the target C-type asteroid 162173 Ryugu at near infrared wavelengths of 1.8 to 3.2 micrometer. It aims to obtain reflectance spectra in order to detect absorption bands of hydrated and hydroxide minerals in the 3 micrometer-band. We adopted a linear-image sensor with indium arsenide (InAs) photo diodes and a cooling system with a passive radiator to achieve an optics temperature of 188 K, which enables to retaining sufficient sensitivity and noise level in the 3 micrometer wavelength region. We conducted ground performance tests for the NIRS3 flight model (FM) to confirm its baseline specifications. The results imply that the properties such as the signal-to-noise ratio (SNR) conform to scientific requirements to determine the degree of aqueous alteration, such as CM or CI chondrite, and the stage of thermal metamorphism on the asteroid surface.

Journal Articles

A Remote-operated system to map radiation dose in the Fukushima Daiichi primary containment vessel

Nancekievill, M.*; Jones, A. R.*; Joyce, M. J.*; Lennox, B.*; Watson, S.*; Katakura, Junichi*; Okumura, Keisuke; Kamada, So*; Kato, Michio*; Nishimura, Kazuya*

Proceedings of 5th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications (ANIMMA 2017) (USB Flash Drive), 6 Pages, 2017/06

We are developping a submersible ROV system, coupled with radiation detectors aimed at mapping the interior of the reactors at the Fukushima Daiichi Nuclear Power Station. To map the $$gamma$$-ray intensity environment a cerium bromide (CeBr$$_{3}$$) inorganic scintillator detector sensitive to $$gamma$$-rays has been incorporated into the ROV to measure $$gamma$$-ray intensity and identify radioactive isotopes. The ROV is a cylindrical shape with a diameter of about 150 mm, and it have two end caps of five pumps each allowing control of the ROV in 5 degree of freedom. It is possible to directly replace the CeBr$$_{3}$$ detector with a single crystal chemical vapour deposition (CVD) neutron detector with a $$^{6}$$Li convertor foil that is capable of mapping the thermal neutron flux.

Journal Articles

Development of multi-colored neutron talbot-lau interferometer with absorption grating fabricated by imprinting method of metallic glass

Seki, Yoshichika; Shinohara, Takenao; Parker, J. D.*; Yashiro, Wataru*; Momose, Atsushi*; Kato, Kosuke*; Kato, Hidemi*; Sadeghilaridjani, M.*; Otake, Yoshie*; Kiyanagi, Yoshiaki*

Journal of the Physical Society of Japan, 86(4), p.044001_1 - 044001_5, 2017/03

 Times Cited Count:13 Percentile:19.82(Physics, Multidisciplinary)

For the effective phase imaging at pulsed neutron sources, we have designed and developed the multi-colored Talbot-Lau interferometer which works at several wavelengths. At the Energy Resolved Neutron Imaging System RADEN in J-PARC, we demonstrated its operation by observing the visibilities of moire fringes derived from different wavelengths (0.25, 0.50, and 0.75 nm). We also investigated the variation of moire fringes dependent on the wavelength resolution from 18% to 50% and showed the advantage of pulsed beams. At the central wavelength of 0.5 nm, we have succeeded in interferometric imaging for the samples of metal rods made of aluminum, lead, and copper. An absorption grating as an analyzer was fabricated by imprinting of metallic glass for the first time, and showed a clear moire fringe with the high visibility of 68% and a well-controlled shape in comparison with previous ones fabricated by oblique evaporation of gadolinium.

Journal Articles

Electrical conductivity through a single atomic step measured with the proximity-induced superconducting pair correlation

Kim, H.*; Lin, S.-Z.*; Graf, M.*; Miyata, Yoshinori*; Nagai, Yuki; Kato, Takeo*; Hasegawa, Yukio*

Physical Review Letters, 117(11), p.116802_1 - 116802_5, 2016/09

 Times Cited Count:12 Percentile:26.43(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Ion induced modifications of Mn-doped ZnO films

Matsunami, Noriaki*; Ito, M.*; Kato, M.*; Okayasu, Satoru; Sataka, Masao*; Kakiuchida, Hiroshi*

Nuclear Instruments and Methods in Physics Research B, 365(Part A), p.191 - 195, 2015/12

 Times Cited Count:4 Percentile:55.12(Instruments & Instrumentation)

We have studied ion impact effects on atomic structure in terms of X-ray diffraction (XRD), optical absorption and electrical resistivity of Mn (6%)-doped ZnO films under 100 MeV Xe ion impact at room temperature. We find the monotonic reduction of the XRD intensity to 1/50 of that of unirradiated film at 5 $$times$$10$$^{14}$$ cm$$^{-2}$$, little bandgap change ($$<$$0.02 eV) and decrease of the resistivity by 4 order of magnitude. The resistivity modification has been compared with that by irradiations of low energy ions such as 100 keV Ne and N, which show more effective decrease of resistivity. We also find that temperature (T) dependence of the magnetic susceptibility ($$chi$$) of Mn-doped ZnO follows the Curie law: $$chi$$ = $$chi$$$$_{o}$$ + C/T (i.e., paramagnetic) and the Curie constant C decreases to a half of that before irradiation (C$$_{O}$$ = 0.012 emu cm$$^{-3}$$ K) at 100 MeV Xe ion fluence of 10$$^{12}$$ cm$$^{-2}$$.

Journal Articles

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; Koga, J. K.; Mori, Michiaki; Kawase, Keigo*; et al.

RAL-TR-2015-025, P. 22, 2015/00

Journal Articles

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; et al.

New Journal of Physics (Internet), 16(9), p.093003_1 - 093003_30, 2014/09

 Times Cited Count:24 Percentile:17.43(Physics, Multidisciplinary)

Journal Articles

Characterization and storage of radioactive zeolite waste

Yamagishi, Isao; Nagaishi, Ryuji; Kato, Chiaki; Morita, Keisuke; Terada, Atsuhiko; Kamiji, Yu; Hino, Ryutaro; Sato, Hiroyuki; Nishihara, Kenji; Tsubata, Yasuhiro; et al.

Journal of Nuclear Science and Technology, 51(7-8), p.1044 - 1053, 2014/07

 Times Cited Count:8 Percentile:40.08(Nuclear Science & Technology)

For safe storage of zeolite wastes generated by treatment of radioactive saline water at the Fukushima Daiichi Nuclear Power Station, properties of the Herschelite adsorbent were studied and its adsorption vessel was evaluated for hydrogen production and corrosion. Hydrogen production depends on its water level and dissolved species because hydrogen is oxidized by radicals in water. It is possible to evaluate hydrogen production rate in Herschelite submerged in seawater or pure water by taking into account of the depth effect of the water. The reference vessel of decay heat 504 W with or without residual pure water was evaluated for the hydrogen concentration by thermal hydraulic analysis using obtained fundamental properties. Maximum hydrogen concentration was below the lower explosive limit (4 %). The steady-state corrosion potential of a stainless steel 316L increased with absorbed dose rate but its increase was repressed by the presence of Herschelite. At 750 Gy/h and $$<$$60$$^{circ}$$C which were values evaluated at the bottom of the vessel of 504 W, the localized corrosion of SUS316L contacted with Herschelite would not immediately occur under 20,000 ppm of Cl$$^{-}$$ concentration.

Journal Articles

Safe storage of zeolite adsorbents used for treatment of accident-generated water at Fukushima Daiichi Power Station

Yamagishi, Isao; Nagaishi, Ryuji; Terada, Atsuhiko; Kamiji, Yu; Kato, Chiaki; Morita, Keisuke; Nishihara, Kenji; Tsubata, Yasuhiro; Ji, W.*; Fukushima, Hisashi*; et al.

IAEA-CN-211 (Internet), 5 Pages, 2013/01

Since the accident at Fukushima Daiichi Nuclear Power Station, a large amount of radioactive contaminated water has been generated to cool damaged reactor cores. Adsorption of cesium with zeolite-like media was employed for treatment of this contaminated saline water. As spent zeolite media are highly radioactive, their safe storage is a pressing issue. Japan Atomic Energy Agency has extensively conducted R&D on the management of secondary wastes produced by the operation of the treatment system. Subjects on the safe storage of spent zeolites include the analysis of their characteristics and the evaluation of effectiveness of the present safety measures in consideration of decay heat emission and hydrogen generation by water radiolysis as well as durability of vessels exposed to saline. Preliminary results obtained are described in the present paper.

Journal Articles

Relativistic high harmonic generation in gas jet targets

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

AIP Conference Proceedings 1465, p.167 - 171, 2012/07

 Times Cited Count:1 Percentile:49.15

Journal Articles

The Spectra of the multicharged argon hollow ions; Observation, modeling and using for diagnostics of the early stage of the heating of clusters by a supper high contrast femtosecond laser pulses

Pikuz, T.; Faenov, A.*; Skobelev, I.*; Fortov, V. E.*; Boldarev, A.*; Gasilov, V.*; Chen, L. M.*; Zhang, L.*; Yan, W.*; Yuan, D.*; et al.

AIP Conference Proceedings 1465, p.181 - 201, 2012/07

 Times Cited Count:0 Percentile:100

Journal Articles

High-order harmonics from bow wave caustics driven by a high-intensity laser

Esirkepov, T. Z.; Pirozhkov, A. S.; Kando, Masaki; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

AIP Conference Proceedings 1465, p.172 - 180, 2012/07

 Times Cited Count:0 Percentile:100

The bow wave induced mechanism of high-order harmonics generation was discovered using simulations and catastrophe theory. This mechanism feasibility was successfully demonstrated in 3D and 2D PIC simulations. The mechanism and the simulations explained high-order harmonics in the XUV spectral region seen in recent experiments with terawatt lasers. Development of new XUV light and X-ray source based on the high-order harmonics generation mechanism is proposed.

Journal Articles

X-ray emission from relativistically moving electron density cusps

Kando, Masaki; Pirozhkov, A. S.; Nakamura, Tatsufumi; Hayashi, Yukio; Kotaki, Hideyuki; Kawase, Keigo*; Esirkepov, T. Z.; Fukuda, Yuji; Kiriyama, Hiromitsu; Okada, Hajime; et al.

AIP Conference Proceedings 1465, p.159 - 166, 2012/07

 Times Cited Count:0 Percentile:100

Journal Articles

Substrate recognition mechanism of a glycosyltrehalose trehalohydrolase from ${it sulfolobus solfataricus}$ KM1

Okazaki, Nobuo; Tamada, Taro; Feese, M. D.*; Kato, Masaru*; Miura, Yutaka*; Komeda, Toshihiro*; Kobayashi, Kazuo*; Kondo, Keiji*; Blaber, M.*; Kuroki, Ryota

Protein Science, 21(4), p.539 - 552, 2012/04

 Times Cited Count:3 Percentile:91.51(Biochemistry & Molecular Biology)

Journal Articles

Soft-X-ray harmonic comb from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

Physical Review Letters, 108(13), p.135004_1 - 135004_5, 2012/03

 Times Cited Count:62 Percentile:7.92(Physics, Multidisciplinary)

We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multi-terawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving $$mu$$J/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations.

Journal Articles

Coherent X-ray generation in relativistic laser - gas jet interactions

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Koga, J. K.; Kiriyama, Hiromitsu; et al.

Proceedings of SPIE, Vol.8140, p.81400A_1 - 81400A_16, 2011/10

88 (Records 1-20 displayed on this page)