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Journal Articles

Watershed-geochemical model to simulate dissolved and particulate $$^{137}$$Cs discharge from a forested catchment

Sakuma, Kazuyuki; Hayashi, Seiji*; Yoshimura, Kazuya; Kurikami, Hiroshi; Malins, A.; Funaki, Hironori; Tsuji, Hideki*; Kobayashi, Takamaru*; Kitamura, Akihiro; Iijima, Kazuki

Water Resources Research, 58(8), p.e2021WR031181_1 - e2021WR031181_16, 2022/08

 Times Cited Count:1 Percentile:0.05(Environmental Sciences)

Journal Articles

Radiocesium-bearing microparticles cause a large variation in $$^{137}$$Cs activity concentration in the aquatic insect ${it Stenopsyche marmorata}$ (Tricoptera: Stenopsychidae) in the Ota River, Fukushima, Japan

Ishii, Yumiko*; Miura, Hikaru*; Jo, J.*; Tsuji, Hideki*; Saito, Rie; Koarai, Kazuma; Hagiwara, Hiroki; Urushidate, Tadayuki*; Nishikiori, Tatsuhiro*; Wada, Toshihiro*; et al.

PLOS ONE (Internet), 17(5), p.e0268629_1 - e0268629_17, 2022/05

We investigated the variability in $$^{137}$$Cs activity concentration in individual aquatic insects in detritivorous caddisfly (${it Stenopsyche marmorata}$) and carnivorous dobsonfly (${it Protohermes grandis}$) larvae from the Ota River, Fukushima. Caddisfly larvae showed sporadically higher radioactivity, whereas no such outliers were observed in dobsonfly larvae. Autoradiography and scanning electron microscopy analyses confirmed that these caddisfly larvae samples contained radiocesium-bearing microparticles (CsMPs), which are insoluble Cs-bearing silicate glass particles. CsMPs were also found in potential food sources of caddisfly larvae, such as periphyton and drifting particulate organic matter, indicating that larvae may ingest CsMPs along with food particles of similar size. Although CsMPs distribution and uptake by organisms in freshwater ecosystems is relatively unknown, our study demonstrates that CsMPs can be taken up by aquatic insects.

Journal Articles

Remobilisation of radiocaesium from bottom sediments to water column in reservoirs in Fukushima, Japan

Funaki, Hironori; Tsuji, Hideki*; Nakanishi, Takahiro; Yoshimura, Kazuya; Sakuma, Kazuyuki; Hayashi, Seiji*

Science of the Total Environment, 812, p.152534_1 - 152534_10, 2022/03

 Times Cited Count:5 Percentile:51.81(Environmental Sciences)

Reservoir sediments generally act as a sink for radionuclides derived from nuclear accidents, but under anaerobic conditions, several radionuclides remobilise in bioavailable form from sediment to water columns, which may contribute to a long-term contamination in aquatic products. This study systematically investigated the $$^{137}$$Cs activities between sediment and pore water, which is a direct evidence of the remobilisation of bioavailable $$^{137}$$Cs from sediments, in two highly contaminated reservoirs affected by the Fukushima Dai-ichi Nuclear Power Plant accident. Our results strongly indicate a competitive ion exchange process between $$^{137}$$Cs and NH$$_{4}$$ via a highly selective interaction with the frayed edges sites of phyllosilicate minerals to be the major reason for the variability of the Kd values between sediment and pore water, even in the Fukushima case.

Journal Articles

Dynamics of $$^{137}$$Cs in water and phyto- and zooplankton in a reservoir affected by the Fukushima Daiichi Nuclear Power Plant Accident

Tsuji, Hideki*; Nakagawa, Megumi*; Iijima, Kazuki; Funaki, Hironori; Yoshimura, Kazuya; Sakuma, Kazuyuki; Hayashi, Seiji*

Global Environmental Research (Internet), 24(2), p.115 - 127, 2021/06

Lake water, phytoplankton and zooplankton were sampled by a total of 12 quarterly surveys from August 2014 to May 2017 at a dam lake in the Fukushima nuclear disaster area, and variations of dissolved form of $$^{137}$$Cs and planktonic $$^{137}$$Cs were observed. Seasonal variations in dissolved $$^{137}$$Cs concentration with high in summer and low in winter were observed in the upstream, midstream and downstream areas of the lake, but no seasonal or site specific differences in planktonic $$^{137}$$Cs concentrations and dominant species were found. The amount of planktonic form of $$^{137}$$Cs in the water was less than 1.4% of the total $$^{137}$$Cs in the lake water, therefore the effect of plankton on the dynamics of $$^{137}$$Cs in the lake was minimal.

Journal Articles

Evaluation of bioavailable radiocesium in the sediment in forest river and dam reservoir

Takechi, Seiichi*; Tsuji, Hideki*; Koshikawa, Masami*; Ito, Shoko*; Funaki, Hironori; Hayashi, Seiji*

Rikusuigaku Zasshi, 82(1), p.1 - 16, 2021/02

Since the Fukushima Daiichi Nuclear Power Plant accident in 2011, soil minerals and organic matter including radiocesium have been deposited in the dam lakes near the nuclear power plant. There is concern that radiocesium will gradually leach from the lake bottom into the lake water, resulting in prolonged radioactive contamination of the freshwater ecosystems especially in downstream of the dams. In this study, we collected undisturbed sediment core samples at the center of the Yokokawa Dam lake in Fukushima Prefecture and suspended sediment in the inflowing river of the dam for 4 years and evaluated the amount of bioavailable form of radiocesium (exchanged, oxidized, and organic forms) in these samples by sequential extraction tests using the BCR method focusing on the temporal change.

Journal Articles

An Experimental setup for creating and imaging $$^{4}$$He$$_{2}$$$$^{ast}$$ excimer cluster tracers in superfluid helium-4 via neutron-$$^{3}$$He absorption reaction

Sonnenschein, V.*; Tsuji, Yoshiyuki*; Kokuryu, Shoma*; Kubo, Wataru*; Suzuki, So*; Tomita, Hideki*; Kiyanagi, Yoshiaki*; Iguchi, Tetsuo*; Matsushita, Taku*; Wada, Nobuo*; et al.

Review of Scientific Instruments, 91(3), p.033318_1 - 033318_12, 2020/03

 Times Cited Count:0 Percentile:0(Instruments & Instrumentation)

Journal Articles

Factors controlling dissolved $$^{137}$$Cs concentrations in east Japanese rivers

Tsuji, Hideki*; Ishii, Yumiko*; Shin, M.*; Taniguchi, Keisuke*; Arai, Hirotsugu*; Kurihara, Momo*; Yasutaka, Tetsuo*; Kuramoto, Takayuki*; Nakanishi, Takahiro; Lee, S*; et al.

Science of the Total Environment, 697, p.134093_1 - 134093_11, 2019/12

 Times Cited Count:15 Percentile:62.22(Environmental Sciences)

To investigate the main factors that control the dissolved radiocesium concentration in river water in the area affected by the Fukushima Daiichi Nuclear Power Plant accident, the correlations between the dissolved $$^{137}$$Cs concentrations at 66 sites normalized to the average $$^{137}$$Cs inventories for the watersheds with the land use, soil components, topography, and water quality factors were assessed. We found that the topographic wetness index is significantly and positively correlated with the normalized dissolved $$^{137}$$Cs concentration. Similar positive correlations have been found for European rivers because wetland areas with boggy organic soils that weakly retain $$^{137}$$Cs are mainly found on plains. However, for small Japanese river watersheds, the building area ratio in the watershed strongly affected the dissolved $$^{137}$$Cs concentration.

Journal Articles

Repeatability and reproducibility of measurements of low dissolved radiocesium concentrations in freshwater using different pre-concentration methods

Kurihara, Momo*; Yasutaka, Tetsuo*; Aono, Tatsuo*; Ashikawa, Nobuo*; Ebina, Hiroyuki*; Iijima, Takeshi*; Ishimaru, Kei*; Kanai, Ramon*; Karube, Jinichi*; Konnai, Yae*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 322(2), p.477 - 485, 2019/11

 Times Cited Count:2 Percentile:25.74(Chemistry, Analytical)

We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima. Twenty-one laboratories pre-concentrated three of 10 L samples by five different pre-concentration methods (prussian-blue-impregnated filter cartridges, coprecipitation with ammonium phosphomolybdate, evaporation, solid-phase extraction disks, and ion-exchange resin columns), and activity of radiocesium was measured. The z-scores for all of the $$^{137}$$Cs results were within $$pm$$2, indicating that the methods were accurate. The relative standard deviations (RSDs) indicating the variability in the results from different laboratories were larger than the RSDs indicating the variability in the results from each separate laboratory.

Journal Articles

Applicability of $$K_{d}$$ for modelling dissolved $$^{137}$$Cs concentrations in Fukushima river water; Case study of the upstream Ota River

Sakuma, Kazuyuki; Tsuji, Hideki*; Hayashi, Seiji*; Funaki, Hironori; Malins, A.; Yoshimura, Kazuya; Kurikami, Hiroshi; Kitamura, Akihiro; Iijima, Kazuki; Hosomi, Masaaki*

Journal of Environmental Radioactivity, 184-185, p.53 - 62, 2018/04

 Times Cited Count:1 Percentile:4.48(Environmental Sciences)

A study is presented on the applicability of the distribution coefficient ($$K_{d}$$) absorption/desorption model to simulate dissolved $$^{137}$$Cs concentrations in Fukushima river water. The simulation results were in good agreement with the observations on water and suspended sediment fluxes, and on particulate bound $$^{137}$$Cs concentrations under both ambient and high flow conditions. By contrast the measured concentrations of dissolved $$^{137}$$Cs in the river water were much harder to reproduce with the simulations. By tuning the $$K_{d}$$ values for large particles, it was possible to reproduce the mean dissolved $$^{137}$$Cs concentrations during base flow periods (observation: 0.32 Bq/L, simulation: 0.36 Bq/L). However neither the seasonal variability in the base flow dissolved $$^{137}$$Cs concentrations (0.14-0.53 Bq/L), nor the peaks in concentration that occurred during storms (0.18-0.88 Bq/L, mean: 0.55 Bq/L), could be reproduced with realistic simulation parameters.

JAEA Reports

Description of "Design guideline for gas entrainment prevention using CFD method" (Cooperative research)

Ohshima, Hiroyuki; Sakai, Takaaki; Kamide, Hideki; Kimura, Nobuyuki; Ezure, Toshiki; Uchibori, Akihiro; Ito, Kei; Kunugi, Tomoaki*; Okamoto, Koji*; Tanaka, Nobuatsu*; et al.

JAEA-Research 2008-049, 44 Pages, 2008/06


Japan Atomic Energy Agency has conducted a conceptional design study of a sodium-cooled fast reactor in a frame work of the FBR feasibility study. The plant system concept for a commercial step is intended to minimize a vessel diameter to achieve an economical competitiveness. Therefore, the coolant in the vessel has relatively higher velocity and gas entrainment (GE) prevention from a liquid surface in the reactor vessel becomes one of important issues for the thermal-hydraulic design. In order to establish a design criteria for the GE prevention, the GE from vortex dimples at the liquid surface was investigated by a working group. The 1st proposal of "Design Guideline for Gas Entrainment Prevention Using CFD Method" was established based on the knowledge gained from the working group activities. This report introduces each study in the working group to clarify the basis of the design guideline.

JAEA Reports

Experimental Study on Gas Entrainment from Free-surface Generation Mechanism of Dimple-Eddy

Tsuji, Yoshiyuki*; Kamide, Hideki

JNC TY9400 2005-017, 54 Pages, 2005/03


Compact reactor vessel is designed to reduce construction cost of a fast reactor. In a compact reactor vessel flow velocity will increase and it causes gas entrainment at free surface. Thus, gas entrainment is one of significant issue of the reactor design. In this study we carried out a water experiment on the gas entrainment, especially the onset condition of a dimple vortex, which causes the gas entrainment in order to establish a guide line in a deisgn.This study is planned to carry in three years from 2003 to 2005. The year of 2004 corresponds to the second term. In this year, water experiment was carried out using a flow channel, vertical suction pipe, and an obstacle in order to see influences of obstacles on the gas entrainment and dimple vortex. Onset conditions of the gas entrainment due to the dimple vortex were obtained with experimental parameters of flow velocity in the channel, water level, and free surface wave or disturbance. It was shown that the onset of gas entrainment needed vertical vortex, e.g. in a wake of an obstacle, and disturbance of free surface block the onset of the dimple vortex and the gas entrainment.

Journal Articles

Electron acceleration by a nonlinear wakefield generated by ultrashort (23-fs) high-peak-power laser pulses in plasma

Kando, Masaki; Masuda, Shinichi; Zhidkov, A.*; Yamazaki, Atsushi; Kotaki, Hideyuki; Kondo, Shuji; Homma, Takayuki*; Kanazawa, Shuhei; Nakajima, Kazuhisa; Hayashi, Yukio; et al.

Physical Review E, 71(1), p.015403_1 - 015403_4, 2005/01

 Times Cited Count:33 Percentile:78.1(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Relativistic laser plasma from micron-sized argon clusters as a debris-free X-ray source for pulse X-ray diffraction

Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; Ueda, Hideki; Nakai, Yoshiki*; Tsuji, Koichi*; Yamakawa, Koichi; Hironaka, Yoichiro*; Kishimura, Hiroaki*; et al.

Applied Physics Letters, 85(21), p.5099 - 5101, 2004/11

 Times Cited Count:11 Percentile:43.22(Physics, Applied)

We have demonstrated diffraction from Si(111) crystal using X-rays from highly ionized Ar ions produced by laser irradiation with an intensity of 6$$times$$10$$^{18}$$ W/cm$$^{2}$$ and a pulse duration of 30 fs acting upon micron-sized Ar clusters. The measured total photon flux and line width in the He$$_{alpha1}$$ line (3.14 keV) were 4$$times$$10$$^{7}$$ photons/shot/4$$pi$$sr and 3.7 eV (FWHM), respectively, which is sufficient to utilize as a debris-free light source for time-resolved X-ray diffraction studies.

JAEA Reports

Experimental Study on Gas-Entrainment from Free-surface; Generation Mechanism of Dimple-Eddy

Obata, Takanori*; Tsuji, Yoshiyuki*; Kimura, Nobuyuki; Kamide, Hideki

JNC TY9400 2004-017, 36 Pages, 2004/03


Gas entrainment at free surface is of importance due to higher flow velocity in a compact reactor vessel. Dimple-eddy is one of major reasons for gas entrainment in case of low flow velocity condition at free surface. Water experiment was carried out to see generation of dimple-eddy in this study. A round shape obstacle was set in an open channel. Eddies are generated in wake region behind the obstacle.Laser beam and photo acceptance unit of PSD were used to measure inclined angle of free surface and shape of dimple-eddy. The dimple depth is one of the key parameter of eddy development. Following findings were obtained from the experiment; 1) This laser-PSD system can measure the inclined angle of free surface and find the dimple-eddy, 2) Shape of the dimple-eddy can be estimated by statistics of the free surface angle-data.

Journal Articles

Program of in-pile IASCC testing under the simulated actual plant condition; Thermohydraulic design study of saturated temperature capsule for IASCC irradiation test

Ide, Hiroshi; Matsui, Yoshinori; Nagao, Yoshiharu; Komori, Yoshihiro; Itabashi, Yukio; Tsuji, Hirokazu; Tsukada, Takashi; Nagata, Nobuaki*; Dozaki, Koji*; Takiguchi, Hideki*

Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 7 Pages, 2003/04

The advanced water chemistry controlled irradiation research device has been developed in JAERI to perform irradiation tests for research on IASCC. The irradiation device consists of the SATCAP (Saturated Temperature Capsule) inserted into the JMTR core and the water control unit installed out-of-core. Regarding the SATCAP, thermohydraulic design of the SATCAP was performed aiming at controlling the specimen temperature with high accuracy and increasing water flow velocity on the specimen surface to improve the controllability of water chemistry. As a result of irradiation test using the new type SATCAP, each specimen temperature and water chemistry were able to be controlled as designed.

Journal Articles

Research and development on materials as base technology in nuclear applications

Kondo, Tatsuo; Hishinuma, Akimichi; Noda, Kenji; Eto, Motokuni; Tsuji, Hirokazu; Nakajima, Hajime; Kiuchi, Kiyoshi; Ono, Hideo; Ogawa, Toru; Omichi, Hideki; et al.

Genshiryoku Kogyo, 39(8), p.1 - 80, 1993/08

no abstracts in English

Oral presentation

Radiocesium behavior of water and plankton in Dam Lake in Fukushima Prefecture

Tsuji, Hideki*; Hayashi, Seiji*; Funaki, Hironori; Iijima, Kazuki

no journal, , 

no abstracts in English

Oral presentation

Characteristics of radiocesium elution from sediment in Yokokawa Dam Lake

Tsuji, Hideki*; Koshikawa, Masami*; Ito, Shoko*; Funaki, Hironori; Iijima, Kazuki; Yasutaka, Tetsuo*

no journal, , 

no abstracts in English

Oral presentation

Simulation of behavior of dissolved and particulate radiological material in forested stream water

Sakuma, Kazuyuki; Funaki, Hironori; Kitamura, Akihiro; Iijima, Kazuki; Tsuji, Hideki*; Hayashi, Seiji*

no journal, , 

no abstracts in English

Oral presentation

Behaviour of dissolved radiocesium within a Yokokawa dam reservoir basin (Research collaboration with JAEA and NIES)

Sakuma, Kazuyuki; Tsuji, Hideki*

no journal, , 

We focus on a behavior of dissolved radiocesium within Yokokawa dam reservoir in Fukushima prefecture. (1) Horizontal distribution of dissolved $$^{137}$$Cs concentration in reservoir water, (2) $$^{137}$$Cs concentration of a plankton, (3) Investigation for sources of dissolved $$^{137}$$Cs from an upstream catchment of the dam reservoir, (4) Simulation for dissolved $$^{137}$$Cs discharge from the upstream catchment of the dam reservoir were studied. These indicated that dissolved $$^{137}$$Cs concentration in water at dam inlet and outlet were decreasing and an organic matter is one of the dissolved $$^{137}$$Cs source in forested catchment. Additionally we developed a numerical model to simulate dissolved $$^{137}$$Cs concentration at the catchment outlet, which reasonably reproduced a observation data under base flow periods.

24 (Records 1-20 displayed on this page)