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Tanaka, Takuro*; Fukuoka, Masafumi*; Toda, Kanako*; Nakanishi, Takahiro; Terashima, Motoki; Fujiwara, Kenso; Niwano, Yuma*; Kato, Hiroaki*; Kobayashi, Natsuko*; Tanoi, Keitaro*; et al.
ACS ES&T Water (Internet), 4(8), p.3579 - 3586, 2024/08
Nemoto, Takahiro; Fujiwara, Yusuke; Arakawa, Ryoki; Choyama, Yuya; Nagasumi, Satoru; Hasegawa, Toshinari; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; et al.
JAEA-Technology 2024-003, 17 Pages, 2024/06
JAEA-Technology-2024-003.pdf:1.91MB
In order to investigate the cause of the increase in differential pressure in the primary helium circulator filter that occurred during the RS-14 cycle, a clogged filter was investigated. As a result of the investigation, deposits caused by silicone oil were confirmed on the surface of the filter element. These results revealed that the cause of filter clogging was silicone oil mixed into the primary system due to performance deterioration of the charcoal filter in the gas circulator of primary helium purification system. As a measure to prevent the recurrence of this event, in addition to the conventional management based on operating hours for replacing of charcoal filter in the gas circulator of primary helium purification system, we have established a new replacement plan for every three years.
Hasegawa, Toshinari; Nagasumi, Satoru; Nemoto, Takahiro; Nakajima, Kunihiro; Yokoyama, Keisuke; Fujiwara, Yusuke; Arakawa, Ryoki; Iigaki, Kazuhiko; Inoi, Hiroyuki; Kawamoto, Taiki
Proceedings of 2024 International Congress on Advanced in Nuclear Power Plants (ICAPP 2024) (Internet), 10 Pages, 2024/06
The filter element of the primary gas circulators (PGC) in High Temperature engineering Test Reactor (HTTR) and its deposits were investigated by Scanning Electron Microscope (SEM) observation and Energy Dispersive X-ray spectroscopy (EDX) analysis to find the cause of the increase of the filter differential pressure during the operation in 2021. SEM observation showed that the clumpy deposits and fibrous deposits smaller than the filtration pore size and the rod-shaped deposits larger than the pore size were present on the filter element. EDX analysis showed that the clumpy deposits and fibrous deposits could include silicone oil in the primary helium purification system (PHPS) gas circulators and that the rod-shaped deposits were thermal insulators inside of the co-axial double pipes in the primary cooling system. It is considered that silicone oil leaked from the PHPS gas circulators due to deterioration in the absorption performance of the activated charcoal filter. Next, it could be vaporized and reach PGC's filter element after passing through the reactor core. Since those deposits including silicone oil were present over the entire surface of the filter element, the filter differential pressure could be increased due to a reduction in the pore size and a rise in its flow resistance. The thermal insulator was unrelated to filter clogging because it was present mainly in the lower part of the filter element. Therefore, silicone oil could increase the filter differential pressure, and the graphite powder, which is the cause of the previous issue was unrelated.
Dohi, Terumi; Iijima, Kazuki; Machida, Masahiko; Suno, Hiroya*; Omura, Yoshihito*; Fujiwara, Kenso; Kimura, Shigeru*; Kanno, Futoshi*
Environmental Radiochemical Analysis VII, p.50 - 57, 2023/12
GeFujiwara, Hidenori*; Nakatani, Yasuhiro*; Aratani, Hidekazu*; Kanai-Nakata, Yuina*; Yamagami, Kohei*; Hamamoto, Satoru*; Kiss, Takayuki*; Sekiyama, Akira*; Tanaka, Arata*; Ebihara, Takao*; et al.
New Physics; Sae Mulli, 73(12), p.1062 - 1066, 2023/12
symmetry for anisotropic 
hybridization in the heavy-fermion superconductor CeNiGeFujiwara, Hidenori*; Nakatani, Yasuhiro*; Aratani, Hidekazu*; Kanai-Nakata, Yuina*; Yamagami, Kohei*; Hamamoto, Satoru*; Kiss, Takayuki*; Yamasaki, Atsushi*; Higashiya, Atsushi*; Imada, Shin*; et al.
Physical Review B, 108(16), p.165121_1 - 165121_10, 2023/10
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)
SnS-based shandite filmsLau, Y.-C.*; Ikeda, Junya*; Fujiwara, Kohei*; Ozawa, Akihiro*; Zheng, J.*; Seki, Takeshi*; Nomura, Kentaro*; Du, L.*; Wu, Q.*; Tsukazaki, Atsushi*; et al.
Physical Review B, 108(6), p.064429_1 - 064429_11, 2023/08
Times Cited Count：8 Percentile：74.51(Materials Science, Multidisciplinary)Di Palma, A.; Adamo, P.*; Dohi, Terumi; Fujiwara, Kenso; Hagiwara, Hiroki; Kitamura, Akihiro; Sakoda, Akihiro; Sato, Kazuhiko; Iijima, Kazuki
Chemosphere, 308, Part 1, p.136179_1 - 136179_13, 2022/12
Times Cited Count：2 Percentile：12.53(Environmental Sciences)The present study shows the use of mosses transplanted in bags, called as moss bags, as biosensors of airborne radioactive dusts in the environment of the evacuated zone of Fukushima. A standardized protocol was applied and three moss species were used. Background sites of Okayama Prefecture were used for comparison. In the Fukushima area, the moss bags were able to accumulate radiocaesium in all exposure sites and periods, with Sphagnum palustre moss acting as the most performant moss. The radiocaesium activity concentrations dectected in mosses were in strong agreement with the Cs deposition levels and decontamination status of each exposure site. The accumulation of soil-derived radiocaesium by moss bags was supported by autoradiography and electron microscopy analyses. The linear dependency of Cs accumulation with the exposure time allowed a radiocaesium quantitative assessment.
Urushidate, Tadayuki*; Yoda, Tomoyuki; Otani, Shuichi*; Yamaguchi, Toshio*; Kunii, Nobuaki*; Kuriki, Kazuki*; Fujiwara, Kenso; Niizato, Tadafumi; Kitamura, Akihiro; Iijima, Kazuki
JAEA-Review 2022-023, 8 Pages, 2022/09
JAEA-Review-2022-023.pdf:1.19MB
After the accident of the Fukushima Daiichi Nuclear Power Station, the Japan Atomic Energy Agency has newly set up a laboratory in Fukushima and started measuring radioactivity concentrations of environmental samples. In October 2015, Fukushima Radiation Measurement Group has been accredited the ISO/IEC 17025 standard by the Japan Accreditation Board (JAB) as a testing laboratory for radioactivity analysis (
Cs, 
Cs) based on Gamma-ray spectrometry with germanium semiconductor detectors. The laboratory has measured approximately 60,000 of various environmental samples at the end of March 2022. The laboratory quality control and measurement techniques have been accredited by regular surveillance of JAB. In September 2019, the laboratory renewed accreditation as a testing laboratory for radioactivity analysis.
Kuwata, Haruka*; Tazoe, Hirofumi*; Kranrod, C.*; Fujiwara, Kenso; Terashima, Motoki; Matsueda, Makoto; Hirao, Shigekazu*; Akata, Naofumi*
Radiation Protection Dosimetry, 198(13-15), p.1014 - 1018, 2022/09
Times Cited Count：0 Percentile：0.00(Environmental Sciences)Yamamura, Sota*; Fujiwara, Kota*; Honda, Kota*; Yoshida, Hiroyuki; Horiguchi, Naoki; Kaneko, Akiko*; Abe, Yutaka*
Physics of Fluids, 34(8), p.082110_1 - 082110_13, 2022/08
Times Cited Count：3 Percentile：30.82(Mechanics)Liquid spreading and atomization due to jet impingement in liquid-liquid systems are considered to be crucial for understanding the cooling behavior of high-temperature molten material in a shallow water pool. This phenomenon takes place when a liquid jet enters a pool filled with other immiscible liquid. The jet spreads radially after impinging on the floor while forming a thin liquid film and atomizing droplets. In this paper, we explain the result to quantify the unsteady three-dimensional behavior of the spreading jet by the employment of 3D-LIF measurements and 3-dimensional reconstruction. Under high flow velocity conditions, the phenomena of hydraulic jump and atomization of the liquid film occurred along with the spreading. To evaluate the spreading behavior, a comparison of the jump radius position of the liquid-liquid system as the representative value was made with the one calculated by the existing theory of a gas-liquid system. As the result, the spreading of the liquid film in the liquid-liquid system was suppressed compared with that in the gas-liquid system. Furthermore, the PTV method was successfully used to measure the velocity boundary layer and velocity profile in the liquid film, which are important factors that affect the spreading mechanism of the liquid film. These results revealed that in liquid-liquid systems, shear stress at the liquid-liquid interface causes a decrease in the flow velocity and suppressed the development of the velocity boundary layer. Also, to evaluate the atomization behavior, the number and diameter distribution of the droplets were measured from the acquired 3-dimensional shape data of the jet. As the result, the number of droplets increased with the flow velocity. Based on these results, we concluded that the spreading of the liquid film is affected by such atomization behavior.
microscale localisation observationDohi, Terumi; Iijima, Kazuki; Machida, Masahiko; Suno, Hiroya*; Omura, Yoshihito*; Fujiwara, Kenso; Kimura, Shigeru*; Kanno, Futoshi*
PLOS ONE (Internet), 17(7), p.e0271035_1 - e0271035_21, 2022/07
Times Cited Count：4 Percentile：27.80(Multidisciplinary Sciences)Kimura, Fumihito*; Yamamura, Sota*; Fujiwara, Kota*; Yoshida, Hiroyuki; Saito, Shimpei*; Kaneko, Akiko*; Abe, Yutaka*
Nuclear Engineering and Design, 389, p.111660_1 - 111660_11, 2022/04
Times Cited Count：4 Percentile：53.26(Nuclear Science & Technology)O
with electrochemical Li
intercalationMurase, Satoshi*; Yoshikawa, Yumi*; Fujiwara, Kosuke*; Fukada, Yukimasa*; Teranishi, Takashi*; Kano, Jun*; Fujii, Tatsuo*; Inada, Yasuhiro*; Katayama, Misaki*; Yoshii, Kenji; et al.
Journal of Physics and Chemistry of Solids, 162, p.110468_1 - 110468_6, 2022/03
Times Cited Count：0 Percentile：0.00(Chemistry, Multidisciplinary)We report a trial of the valence control for mixed valence iron triangular oxide YbFeO in order to develop an effective technique to control the frustration of charges in strongly correlated electron systems. The electro-chemical doping of Li into YbFeO was examined on the cell type sample similar to the Li-ion secondary battery cell. Systematic change of the lattice constant, Fe-Fe and Fe-Yb distance were observed with Li doping. Maximum value of the doping was over 300 mAh/g. An EXAFS experiment indicated that Li positioned between Yb octahedron layer (U-layer) and Fe-bipyramidal layer (W-layer). However, detailed change of iron valence state of YbFeO was not clearly observed because of the superimpose of the signal from iron metal nano particles in XANES observation. The results indicate that the electrochemical method might be one of the potential technique to control the frustration of charges in YbFeO.
Horiguchi, Naoki; Yoshida, Hiroyuki; Yamamura, Sota*; Fujiwara, Kota*; Kaneko, Akiko*; Abe, Yutaka*
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 14 Pages, 2022/03
spp. microalgae in a pond near the Fukushima Dai-ichi Nuclear Power PlantSasaki, Yoshito; Funaki, Hironori; Fujiwara, Kenso
Limnology, 23(1), p.1 - 7, 2022/01
Times Cited Count：1 Percentile：3.90(Limnology)We investigated the transfer behavior of radiocesium in living cells and remains of a bloom of microalgae ( sp.) in a pond located about 5 km from the Fukushima Dai-ichi Nuclear Power Plant. As a positive correlation was detected between the cell number of microalgae and the radiocesium concentration (Bq/L) in the 
0.45-
m fraction, microalgae were the controlling factor for the radiocesium concentration of the 0.45-m fraction. The transfer factor of water-to-algae [(Cs concentration Bq/kg 0.45-m fraction) 
(Cs concentration Bq/L water)
] was 1.6 10
. The radiocesium concentration of microalgae remains was the same as that in intact cells.
Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.
Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12
Times Cited Count：7 Percentile：39.36(Geosciences, Multidisciplinary)The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.
Ishii, Mamoru*; Shiota, Daiko*; Tao, Chihiro*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Ishii, Takako*; Ichimoto, Kiyoshi*; Kataoka, Ryuho*; Koga, Kiyokazu*; Kubo, Yuki*; et al.
Earth, Planets and Space (Internet), 73(1), p.108_1 - 108_20, 2021/12
Times Cited Count：10 Percentile：53.42(Geosciences, Multidisciplinary)We surveyed the relationship between the scale of space weather events and their occurrence rate in Japan and we discussed the social impact of these phenomena during the Project for Solar-Terrestrial Environment Prediction (PSTEP). The information was compiled for domestic users of space weather forecasts for appropriate preparedness against space weather disasters. This paper gives a comprehensive summary of the survey, focusing on the fields of electricity, satellite operations, communication and broadcasting, satellite positioning usage, aviation, human space activity, and daily life on the Earth's surface, using the cutting-edge knowledge of space weather. Quantitative estimations of the economic impact of space weather events on electricity and aviation are also given.
Sm M
ssbauer and Sm L
-edge X-ray absorption spectroscopiesTsutsui, Satoshi; Higashinaka, Ryuji*; Nakamura, Raito*; Fujiwara, Kosuke*; Nakamura, Jin*; Kobayashi, Yoshio*; Ito, Takashi; Yoda, Yoshitaka*; Kato, Kazuo*; Nitta, Kiyofumi*; et al.
Hyperfine Interactions, 242(1), p.32_1 - 32_10, 2021/12
Times Cited Count：1 Percentile：75.14(Physics, Atomic, Molecular & Chemical)Otsuka, Yusuke*; Kanazawa, Naoya*; Hirayama, Motoaki*; Matsui, Akira*; Nomoto, Takuya*; Arita, Ryotaro*; Nakajima, Taro*; Hanashima, Takayasu*; Ukleev, V.*; Aoki, Hiroyuki; et al.
Science Advances (Internet), 7(47), p.eabj0498_1 - eabj0498_9, 2021/11
Times Cited Count：15 Percentile：61.77(Multidisciplinary Sciences)