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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:42.13(Environmental Sciences)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
Times Cited Count:3 Percentile:45.99We investigated the variability in Cs activity concentration in individual aquatic insects in detritivorous caddisfly () and carnivorous dobsonfly () 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.
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:8 Percentile:58.13(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 Cs activities between sediment and pore water, which is a direct evidence of the remobilisation of bioavailable 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 Cs and NH 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.
Hashimoto, Shoji*; Tanaka, Taku*; Komatsu, Masabumi*; Gonze, M.-A.*; Sakashita, Wataru*; Kurikami, Hiroshi; Nishina, Kazuya*; Ota, Masakazu; Ohashi, Shinta*; Calmon, P.*; et al.
Journal of Environmental Radioactivity, 238-239, p.106721_1 - 106721_10, 2021/11
Times Cited Count:8 Percentile:58.13(Environmental Sciences)This study was aimed at analysing performance of models for radiocesium migration mainly in evergreen coniferous forest in Fukushima, by inter-comparison between models of several research teams. The exercise included two scenarios of countermeasures against the contamination, namely removal of soil surface litter and forest renewal, and a specific konara oak forest scenario in addition to the evergreen forest scenario. All the models reproduced trend of time evolution of radiocesium inventories and concentrations in each of the components in forest such as leaf and organic soil layer. However, the variations between models enlarged in long-term predictions over 50 years after the fallout, meaning continuous field monitoring and model verification/validation is necessary.
Ozaki, Hirokazu*; Yoshimura, Kazuya; Asaoka, Yoshihiro*; Hayashi, Seiji*
Environmental Monitoring and Assessment, 193(6), p.369_1 - 369_9, 2021/06
Times Cited Count:6 Percentile:42.99(Environmental Sciences)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 Cs and planktonic Cs were observed. Seasonal variations in dissolved 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 Cs concentrations and dominant species were found. The amount of planktonic form of Cs in the water was less than 1.4% of the total Cs in the lake water, therefore the effect of plankton on the dynamics of Cs in the lake was minimal.
Iijima, Kazuki; Hayashi, Seiji*; Tamaoki, Masanori*
Global Environmental Research (Internet), 24(2), p.85 - 93, 2021/06
Environmental radioactive contamination by the Fukushima Daiichi Nuclear Power Plant accident has clearly been declining during the passage of almost 10 years from the accident. However, the prolongation of radioactive contamination in natural ecosystems probably derived from forested area without decontamination is pointed out by many studies, so more detailed examination will be needed for environmental dynamics of bioavailable radiocesium and its transfer to ecosystems. Also for influence of radiation to organisms, effects of evacuation on wild organisms are more pronounced than direct effect from radiation, especially in Fukushima evacuation area.
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.
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:16 Percentile:60.05(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 Cs concentrations at 66 sites normalized to the average 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 Cs concentration. Similar positive correlations have been found for European rivers because wetland areas with boggy organic soils that weakly retain Cs are mainly found on plains. However, for small Japanese river watersheds, the building area ratio in the watershed strongly affected the dissolved Cs concentration.
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:21.95(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 Cs results were within 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.
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:2 Percentile:7.31(Environmental Sciences)A study is presented on the applicability of the distribution coefficient () absorption/desorption model to simulate dissolved 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 Cs concentrations under both ambient and high flow conditions. By contrast the measured concentrations of dissolved Cs in the river water were much harder to reproduce with the simulations. By tuning the values for large particles, it was possible to reproduce the mean dissolved 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 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.
Tsuruta, Tadahiko; Niizato, Tadafumi; Nakanishi, Takahiro; Dohi, Terumi; Nakama, Shigeo; Funaki, Hironori; Misono, Toshiharu; Oyama, Takuya; Kurikami, Hiroshi; Hayashi, Seiji*; et al.
JAEA-Review 2017-018, 86 Pages, 2017/10
Since the accidents at Fukushima Daiichi Nuclear Power Plant following the Tohoku Region Pacific Coast Earthquake on March 11th, 2011, Fukushima Environmental Safety Center has carried out research on natural mobilization of radionuclide (especially radiocesium) and future forecast from forest to water system and surrounding residential areas. The report summarizes the latest results that have been accumulated from each study field, of our agency together with the other related research organizations. The contents of the report is to be used as evidence-based information for the QA-styled pages in the website of JAEA Sector of Fukushima Research and Development at the time of next renewal.
Kitamura, Akihiro; Imaizumi, Yoshitaka*; Yamaguchi, Masaaki; Yui, Mikazu; Suzuki, Noriyuki*; Hayashi, Seiji*
Kankyo Hoshano Josen Gakkai-Shi, 2(3), p.185 - 192, 2014/09
Annual discharge rates of radioactive cesium through selected rivers due to the Fukushima Dai-ichi Nuclear Power Plant accident were simulated by two different watershed models. One is the Soil and Cesium Transport, SACT, model which was developed by Japan Atomic Energy Agency and the other one is the Grid-Catchment Integrated Modeling System, G-CIEMS, which was developed by National Institute of Environmental Studies. We choose the Abukuma, the Ukedo, and the Niida rivers for the present study. Comparative results showed that while components and assumptions adopted in two models differ, both methods predicted the same order of magnitude estimates.
Kajiyama, Tadashi; Numata, Kazuaki; Otani, Seiji; *; *; Goto, Tatsuro*; Takahashi, Hideki*
JNC TN8440 2000-010, 45 Pages, 2000/02
This report describes about procedure and consequence of the welding process of the cladding tube and the lower end plug, the process of the test and inspection and the process of shipment for the 6th refueling core fuel assembly (46 fuel assemblies) of the experimental fast reactor JOYO. These works were carried out on July, 1996 from January, 1993 in Tamatukuri inspection branch of quality assurance section, technical administration division, plutonium fuel center. The 6th refueling core fuel assemblies are two kinds of the fuel assembly (1) and (2). The material of the lower end plug and the cladding tube used for the fuel assembly (1) is the type 316 stainless steel grade (here in after referred to as SUS316 grade) and austenitic stainless steel of high nickel content (here in after referred to as PNC 1520). That material used for the fuel assembly (2) is all SUS316 grade. The result of welding and the inspection is shown in the following table.
Kajiyama, Tadashi; Numata, Kazuaki; Otani, Seiji; *; *; Goto, Tatsuro*; Takahashi, Hideki*
JNC TN8440 2000-008, 34 Pages, 2000/02
The procedure and result of lower endplug welding, Test and Inspection and Shipment of the 1 reload core fuel assembly (80 Fuel Assemblies) for the fast breeder reactor MONJU should be report, which had examined and inspected in Tamatsukuri Branch, Material Insurance office, Quality Assurance Section, Technical Administration Division, Plutonium Fuel Center (before: Inspection Section, Plutonium Fuel Division), from June 1994 to January 1996. The number of cladding tubes welded to the endplug were total to 13,804, 7,418 for Core - Inside of 43 fuel Assemblies and 6,386 for Core-Outside of 37 fuel Assemblies. 13,794 of them, 7,414 Core-Inside and 6,379 Core-Outside were approved by the test and sent to Plutonium Fuel Center. 10 of them weren't approved mainly because of default welding. Disapproval rating is 0.07%.
Ozu, Akira; Takase, Misao; Kurata, Noritaka; Kobayashi, Nozomi; Yoshino, Seiji; Kureta, Masatoshi; Nakamura, Tatsuya; Soyama, Kazuhiko; Nakamura, Hironobu; Seya, Michio; et al.
no journal, ,
no abstracts in English
Tsuji, Hideki*; Hayashi, Seiji*; Funaki, Hironori; Iijima, Kazuki
no journal, ,
no abstracts in English
Sakuma, Kazuyuki; Funaki, Hironori; Kitamura, Akihiro; Iijima, Kazuki; Tsuji, Hideki*; Hayashi, Seiji*
no journal, ,
no abstracts in English
Nomura, Naoki*; Arai, Hirotsugu*; Kuramoto, Takayuki*; Niizato, Tadafumi; Hayashi, Seiji*
no journal, ,
Wildfire in the mountainous forest of Fukushima, approximately 11 km west-north of the Fukushima Dai-ichi Nuclear Power Plant, burned 75 ha, which was occurred on 29th April and extinguished on 10th May 2017. In this study, we estimate the burning temperature and radiocesium elution characteristics of the residual carbides based on the thermal analysis and the dissolution test for the samples collected at the site of the wildfire to assess the impact of the wildfire on the radiocesium outflow.
Niizato, Tadafumi; Sasaki, Yoshito; Watanabe, Takayoshi; Mitachi, Katsuaki*; Ito, Satomi; Kuramoto, Takayuki*; Arai, Hirotsugu*; Nomura, Naoki*; Hayashi, Seiji*; Tamaoki, Masanori*
no journal, ,
Cs released from the TEPCO's Fukushima Dai-ichi Nuclear Power Plant accident has a long half-life of about 30 years, it is necessary to monitor the distribution and its radioecological impact over the long term. Mountainous forests, which accounts for about 70% of Fukushima prefecture, tend to be a sink of radiocesium contamination rather than a source for the contamination of other ecosystems. An understanding of the environmental dynamics of radiocesium in the forest floor of various conditions is important issue, while progressing to the resident return. In this paper, we report on the results of the field investigation into the Cs distribution and the Cs outflow in the mountainous forest of Fukushima, where the wildfire broke out in the spring of 2017.