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Cs discharge in rivers from immediately after the Fukushima accident until 2017Sakuma, Kazuyuki; Nakanishi, Takahiro; Yoshimura, Kazuya; Kurikami, Hiroshi; Namba, Kenji*; Zheleznyak, M.*
Journal of Environmental Radioactivity, 208-209, p.106041_1 - 106041_12, 2019/11
Times Cited Count：22 Percentile：65.32(Environmental Sciences)We developed a simple model to evaluate and predict Cs discharge from catchment using tank model and L-Q equation. Using this model, Cs discharge and discharge ratio from Abukuma River and 13 other rivers in Fukushima coastal region were estimated from immediately after Fukushima accident to 2017. Cesium-137 discharge ratio to the deposition amount in catchment through Abukuma River and 13 other rivers in Fukushima coastal region during about initial six months were estimated to be 18 TBq (3.1%) and 11 TBq (0.8%), respectively. These values were 1-2 orders of magnitude larger than the previous study observed after June 2011, indicating that initial Cs discharge from catchment through rivers was a significant. However it was founded that an impact on the ocean derived from initial Cs discharge through river can be limited because Cs discharge from Abukuma River and 13 other rivers in Fukushima coastal region (29 TBq) was two orders of magnitude smaller than the direct release from FDNPP into the ocean (3.5 PBq) and from atmospheric deposition into the ocean (7.6 PBq).
Onuki, Toshihiko; Sakamoto, Fuminori; Kozai, Naofumi; Namba, Kenji*; Neda, Hitoshi*; Sasaki, Yoshito; Niizato, Tadafumi; Watanabe, Naoko*; Kozaki, Tamotsu*
Environmental Science; Processes & Impacts, 21(7), p.1164 - 1173, 2019/07
Times Cited Count：10 Percentile：44.69(Chemistry, Analytical)The fate of radioactive Cs deposited after the Fukushima nuclear power plant accident and its associated radiological impacts are largely dependent on its mobility from surface soils to forest ecosystems. We measured the accumulation of radioactive Cs in the fruit bodies of wild fungi in the forest at Iidate, Fukushima, Japan. The transfer factors (TFs) of radioactive Cs from soil to the fruit bodies of wild fungi were between 10 
to 10
, a range similar to those reported for the fruit bodies collected in Europe after the Chernobyl accident and in parts of Japan contaminated by nuclear bomb test fallout. Comparison of the TFs of the wild mushroom and that of the fungal hyphae of 704 stock strains grown on agar medium containing nutrients and radioactive Cs showed that the TFs of wild mushroom were lower. TF was less than 0.1 after addition of the minerals zeolite, vermiculite, phlogopite, smectite, or illite of 1% weight to the agar medium. These results indicate that the presence of minerals decrease Cs uptake by fungi grown in the agar medium.
Yamasaki, Shinya*; Imoto, Jumpei*; Furuki, Genki*; Ochiai, Asumi*; Onuki, Toshihiko; Sueki, Keisuke*; Namba, Kenji*; Ewing, R. C.*; Utsunomiya, Satoshi*
Science of the Total Environment, 551-552, p.155 - 162, 2016/05
Times Cited Count：32 Percentile：70.18(Environmental Sciences)Cesium-137 (Cs) of estuary sediment impacted by the FDNPP was measured. Increasing radioactivity was observed from surface to bottom. 90% of the Cs was strongly bound to clay minerals in the estuary sediments. These results suggest that Cs is being transported from contaminated paddy fields to the estuary.
Cs and Mn accumulator plant, 
, increase Cs and Mn desorption in the soilYamaji, Keiko*; Nagata, Satoshi*; Haruma, Toshikatsu*; Onuki, Toshihiko; Kozaki, Tamotsu*; Watanabe, Naoko*; Namba, Kenji*
Journal of Environmental Radioactivity, 153, p.112 - 119, 2016/03
Times Cited Count：20 Percentile：54.68(Environmental Sciences)Of the 463 strains that we isolated, 107 (23.1%) produced the siderophores. We found Cs and Mn desorption concomitant with Al and Fe desorption. These results suggest that root endophytes of Cs accumulator plant produce siderophores, resulting in the desorption of Cs from the contaminated soil collected at Fukushima, Japan.
Konoplev, A.*; Golosov, V.*; Laptev, G.*; Namba, Kenji*; Onda, Yuichi*; Takase, Tsugiko*; Wakiyama, Yoshifumi*; Yoshimura, Kazuya
Journal of Environmental Radioactivity, 151(Part 3), p.568 - 578, 2016/01
Times Cited Count：78 Percentile：92.19(Environmental Sciences)Kaneko, Makoto*; Iwata, Hajime; Shiotsu, Hiroyuki; Masaki, Shota*; Kawamoto, Yuji*; Yamasaki, Shinya*; Nakamatsu, Yuki*; Imoto, Jumpei*; Furuki, Genki*; Ochiai, Asumi*; et al.
Frontiers in Energy Research (Internet), 3, p.37_1 - 37_10, 2015/09
The mobility of the aggregates of submicron-sized sheet aluminosilicate in the surface environment is a key factor controlling the current Cs migration in Fukushima.
Sakamoto, Fuminori; Onuki, Toshihiko; Kozai, Naofumi; Yamasaki, Shinya; Yoshida, Zenko*; Namba, Kenji*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 12(4), p.257 - 266, 2013/12
no abstracts in English
Kawachi, Tetsuya; Kado, Masataka; Tanaka, Momoko; Hasegawa, Noboru; Nagashima, Keisuke; Sukegawa, Kota*; Lu, P.; Takahashi, Kenjiro; Namba, Shinichi; Koike, Masato; et al.
Applied Optics, 42(12), p.2198 - 2205, 2003/04
Times Cited Count：27 Percentile：72.26(Optics)no abstracts in English
Kawachi, Tetsuya; Kado, Masataka; Tanaka, Momoko; Sasaki, Akira; Hasegawa, Noboru; Kilpio, A.*; Namba, Shinichi; Nagashima, Keisuke; Lu, P.; Takahashi, Kenjiro; et al.
Physical Review A, 66(3), p.033815_1 - 033815_7, 2002/09
Times Cited Count：85 Percentile：93.03(Optics)A silver and tin slab targets were irradiated by a line-focused CPA glass laser light. In this experiment, the laser pulses consisted of two pulses with 4 ps duration, separated by 1.2 ns. Strong amplification in the nickel-like silver and tin x-ray lasers at the wavelengths of 13.9nm and 12.0nm was demonstrated with a pumping energy of 12 J and 14 J, respectively, and gain-saturation behaviors could be seen. A hydro-dynamics simulation coupled with a collisional-radiative model was performed under the present experimental condition, and the calculated result was compared with the experimental results.
Kado, Masataka; Kawachi, Tetsuya; Tanaka, Momoko; Hasegawa, Noboru; Takahashi, Kenjiro; Namba, Shinichi; Sukegawa, Kota*; Sasaki, Akira; Lu, P.; Tang, H.; et al.
Soft X-Ray Lasers and Applications IV (Proceedings of SPIE Vol.4505), p.54 - 61, 2001/12
Times Cited Count：4 Percentile：79.48(Optics)no abstracts in English
Miyasaka, Iku*; Fukunaga, Sakae*; Kanno, Takeshi*; Tochigi, Yoshikatsu; Namba, Kenji*
no journal, ,
no abstracts in English
Onuki, Toshihiko; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya; Yoshida, Zenko*; Namba, Kenji*
no journal, ,
Local area distribution and relocation of radiocesium in trees has been studied by measuring its spatial distribution on/in trees using autoradiography analysis. Our results indicate that distribution of radiocesium deposited on/in the trees has been gradually changed with time in the scale of the year.
Onuki, Toshihiko; Namba, Kenji*
no journal, ,
The migration behavior of radiocesium in plants and soil collected in Fukushima, Japan have been studied by the analyses of contaminated plants and soil using autoradiography, sequential desorption, size fractionation, XRD, and SEM analysis. Our results clearly showed that plants and soil act as retardation barrier in the migration of radiocesium.
Iijima, Kazuki; Dohi, Terumi; Niizato, Tadafumi; Fujiwara, Kenso; Koma, Yoshikazu; Suzuki, Shinichi; Oda, Yoshihiro; Omura, Yoshihito*; Sasaki, Takayuki*; Namba, Kenji*
no journal, ,
For the purpose of estimation of radionuclides inventory in the various radioactive solid wastes, such as soils, trees, generated from decommissioning of Fukushima Daiichi Nuclear Power Station (FDNPS), the methodology of estimation of on-site radionuclides inventories is being developed based on the dependency on distance and direction from the FDNPS of their off-site distribution.
Niizato, Tadafumi; Sasaki, Yoshito; Namba, Kenji*; Tsukada, Hirofumi*; Vasyl, Y.*
no journal, ,
We determined the Cs aggregated transfer coefficients for trees from the Cs activities of tree organs and soil layers collected in the off-site localities on the path of the radioactive plumes (southern and southwestern plume), and assessed the contamination status of each tree type. As a result, it was revealed that although the Japanese red pine has no distinct difference, but the Japanese cedar has a large change in aggregated transfer coefficients due to the plume.
Cs discharge from river catchments during initial period after Fukushima accident using a tank modelSakuma, Kazuyuki; Zheleznyak, M.*; Namba, Kenji*
no journal, ,
We developed a simple model that is composed of tank model, relationships between water discharge and suspended solids load, and two-component exponential model for Cs concentration in river water to estimate Cs discharge from river catchments. We applied this model to Abukuma River and several rivers in coastal region in Fukushima to estimate Cs discharge from these catchments through rivers during initial period after Fukushima accident.
Cs discharge from river catchments using a tank modelSakuma, Kazuyuki; Zheleznyak, M.*; Namba, Kenji*
no journal, ,
To understand how much radiocesium discharge to a reservoir and the ocean through rivers from catchments is important for residents and municipal officials from immediately after Fukushima accident to the present. It is not easy to estimate Cs discharge from catchments based on observations because there are many processes such as continuous monitoring of water level and turbidity and Cs concentrations in river water to estimate Cs discharge fluxes. Therefore we developed a user-friendly model that is composed of tank model, which can predict water discharge easily, relationships between water discharge and suspended solids load, and two-component exponential models for Cs concentration in river water. Using developed model we estimated Cs discharge to the ocean from Abukuma River catchment and several rivers in coastal region from immediately after Fukushima accident to 2017.
Zheleznyak, M.*; Pylypenko, O.*; Kivva, S.*; Sakuma, Kazuyuki; Igarashi, Yasunori*; Wakiyama, Yoshifumi*; Konoplev, A.*; Namba, Kenji*
no journal, ,
We developed physically-based watershed models based on the distributed hydrological-sediment transport model. The model implementation for the experimental plots in Fukushima prefecture was conducted for particulate Cs transport. Also, we developed model that combines the watershed empirical models based on the washing-out coefficient approach and GIS data. The model was tested on the basis of the measurements of Cs concentration in Abukuma river and validated also on the basis of the data sets of radionuclide transport in the Pripyat and Dnieper rivers.
