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Journal Articles

A Model intercomparison of atmospheric $$^{137}$$Cs concentrations from the Fukushima Daiichi Nuclear Power Plant accident, phase III; Simulation with an identical source term and meteorological field at 1-km resolution

Sato, Yosuke*; Sekiyama, Tsuyoshi*; Fang, S.*; Kajino, Mizuo*; Qu$'e$rel, A.*; Qu$'e$lo, D.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.

Atmospheric Environment; X (Internet), 7, p.100086_1 - 100086_12, 2020/10

The third model intercomparison project for investigating the atmospheric behavior of $$^{137}$$Cs emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident (FDNPP-MIP) was conducted. A finer horizontal grid spacing (1 km) was used than in the previous FDNPP-MIP. Nine of the models used in the previous FDNPP-MIP were also used, and all models used identical source terms and meteorological fields. Our analyses indicated that most of the observed high atmospheric $$^{137}$$Cs concentrations were well simulated, and the good performance of some models improved the performance of the multi-model ensemble. The analyses also confirmed that the use of a finer grid resolution resulted in the meteorological field near FDNPP being better reproduced. The good representation of the wind field resulted in the reasonable simulation of the narrow distribution of high deposition amount to the northwest of FDNPP and the reduction of the overestimation over the area to the south of FDNPP. In contrast, the performance of the models in simulating plumes observed over the Nakadori area, the northern part of Gunma, and the Tokyo metropolitan area was slightly worse.

Journal Articles

Seven-year temporal variation of caesium-137 discharge inventory from the port of Fukushima Daiichi Nuclear Power Plant; Continuous monthly estimation of caesium-137 discharge in the period from April 2011 to June 2018

Machida, Masahiko; Yamada, Susumu; Iwata, Ayako; Otosaka, Shigeyoshi; Kobayashi, Takuya; Watanabe, Masahisa; Funasaka, Hideyuki; Morita, Takami*

Journal of Nuclear Science and Technology, 57(8), p.939 - 950, 2020/08

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

After direct discharges of highly contaminated water of the Fukushima Daiichi Nuclear Power Plant (1F) from April to May 2011, Kanda suggested that relatively small amounts of run-off of radionuclides from the 1F port into the Fukushima coastal region subsequently continued by his estimation method. However, the estimation period was limited to up to September 2012. Therefore, this paper estimates the discharge inventory up to June 2018. In the missing period, the Japanese government and Tokyo Electric Power Company Holdings have continued efforts to stop the discharge, and consequently, the radionuclide concentration in seawater inside the 1F port has gradually diminished. We show the monthly discharge inventory of $$^{137}$$Cs up to June 2018 by two methods, i.e., Kanda method partially improved by the authors and a more sophisticated method using Voronoi tessellation reflecting the increase in the number of monitoring points inside the 1 F port. The results show that the former always yields overestimated results compared with the latter, but the ratio of the former to the latter is less than one order of magnitude. Using these results, we evaluate the impact of the discharge inventory from the 1F port into the coastal area and radiation dose upon fish ingestion.

Journal Articles

Predictability of a short-term emergency assessment system of the marine environmental radioactivity

Kawamura, Hideyuki; Kamidaira, Yuki; Kobayashi, Takuya

Journal of Nuclear Science and Technology, 57(4), p.472 - 485, 2020/04

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The Japan Atomic Energy Agency developed a Short-Term Emergency Assessment system of the Marine Environmental Radioactivity (STEAMER) to predict the oceanic dispersion of radionuclides in the ocean around Japan. The purpose of this study is to validate the predictability of STEAMER using oceanographic forecast and reanalysis data, which were saved for past several years. Results of oceanic dispersion simulations that are driven by oceanographic reanalysis data are assumed to be true solutions. Oceanic dispersion simulations are conducted for Cs-137 released hypothetically from the Fukushima Daiichi Nuclear Power Plant. The predictability of STEAMER is quantitatively examined for the length of the forecast period. Ensemble forecast simulations are also conducted to successfully improve the predictability of STEAMER.

Journal Articles

Seven-year temporal variation of cesium-137 discharge inventory from the port of Fukushima Dai-ichi Nuclear Power Plant; Continuous monthly estimation of cesium-137 discharge in the period from April 2011 to June 2018

Machida, Masahiko; Yamada, Susumu; Iwata, Ayako; Otosaka, Shigeyoshi; Kobayashi, Takuya; Watanabe, Masahisa; Funasaka, Hideyuki; Morita, Takami*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 18(4), p.226 - 236, 2019/12

After direct discharges of highly-contaminated water from Unit 2 and 3 in Fukushima Daiichi Nuclear Power Plant (1F) in April to May 2011, Kanda suggested that relatively small run-off of radionuclides from 1F port into Fukushima coastal region has subsequently continued by using his estimation scheme. However, the estimation period was limited until September 2012, and there has been no report on the issue since the work. Therefore, this paper focuses on discharge inventory from 1F port until June 2018. In the missing period, the central government and Tokyo Electric Power Company Holdings have done continuous efforts to stop the discharge, and consequently sea water concentration inside 1F port has diminished gradually. We show monthly discharge inventory of Cs-137 until June 2018 by two schemes, i.e., Kanda's scheme partially improved by authors and more sophisticated one using Voronoi tessellation reflecting the increment of the number of monitoring points inside 1F port. The results show that the former always presents overestimated results compared to the latter but the ratio of former to latter is less than one order. Based on these results, we evaluate impact of discharge inventory from 1F port into the coastal area and radiation does via fish digestion.

Journal Articles

Atmospheric modeling of $$^{137}$$Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of Japan

Kitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07

 Times Cited Count:10 Percentile:23.43(Meteorology & Atmospheric Sciences)

We compared seven atmospheric transport model results for $$^{137}$$Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of $$^{137}$$Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for $$^{137}$$Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated $$^{137}$$Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated $$^{137}$$Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced $$^{137}$$Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.

Journal Articles

Oceanic dispersion of Fukushima-derived Cs-137 simulated by multiple oceanic general circulation models

Kawamura, Hideyuki; Furuno, Akiko; Kobayashi, Takuya; In, Teiji*; Nakayama, Tomoharu*; Ishikawa, Yoichi*; Miyazawa, Yasumasa*; Usui, Norihisa*

Journal of Environmental Radioactivity, 180, p.36 - 58, 2017/12

 Times Cited Count:8 Percentile:48.08(Environmental Sciences)

This study simulates the oceanic dispersion of Fukushima-derived Cs-137 by an oceanic dispersion model and multiple oceanic general circulation models. The models relatively well reproduced the observed Cs-137 concentrations in the coastal, offshore, and open oceans. Multiple simulations in the coastal, offshore, and open oceans consistently suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Quantification of the Cs-137 amounts suggested that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layers in the North Pacific.

Journal Articles

Removal of radioactive substances using inorganic compounds entangled by polymer chain grafted onto fiber

Saito, Kyoichi*; Kojima, Takashi*; Asai, Shiho

Bunseki Kagaku, 66(4), p.233 - 242, 2017/04

 Times Cited Count:1 Percentile:93.04(Chemistry, Analytical)

Insoluble cobalt ferrocyanide and sodium titanate specifically capture cesium and strontium ions, respectively, in water contaminated with radionuclides which is found in Fukushima Daiichi NPP. The inorganic compounds used in this study were formed as precipitates in the polymer chain grafted onto a commercially available 6-nylon fiber using radiation-induced graft polymerization. An impregnation structure with the precipitates entangled by the grafted polymer chain through an electrostatic interaction via multipoints was indicated. The resultant insoluble cobalt ferrocyanide- or sodium titanate-impregnated fiber exhibited a higher adsorption rate and adsorption capacity per gram of the inorganic compound for cesium or strontium ions in seawater than conventional granular adsorbents.

Journal Articles

Evaluation of DNA damage induced by Auger electrons from $$^{137}$$Cs

Watanabe, Ritsuko; Hattori, Yuya; Kai, Takeshi

International Journal of Radiation Biology, 92(11), p.660 - 664, 2016/11

 Times Cited Count:2 Percentile:83.2(Biology)

To understand the effect of internal exposure of $$^{137}$$Cs, we focus on estimation of microscopic energy deposition pattern and DNA damage induced by directly emitted electrons (beta-rays, internal conversion electrons, Auger electrons) from $$^{137}$$Cs. Monte Carlo track simulation method was used to calculate the microscopic energy deposition pattern. To simulate the energy deposition by directly emitted electrons, we considered the multiple ejections of electrons after internal conversion. Induction process of DNA strand breaks and base lesions was modeled and simulated using Monte Carlo methods for cell mimetic condition. The yield and spatial distribution of simple and complex DNA damage were calculated for the cases of $$gamma$$-rays and electrons from $$^{137}$$Cs. The simulation showed that significant difference of DNA damage spectrum was not caused by the difference between secondary electron spectrum by $$gamma$$-rays and directly ejected electron spectrum. The result support that the existing evaluation that internal exposure and external exposure are almost equivalent.

Journal Articles

Modeling dynamics of $$^{137}$$Cs in forest surface environments; Application to a contaminated forest site near Fukushima and assessment of potential impacts of soil organic matter interactions

Ota, Masakazu; Nagai, Haruyasu; Koarashi, Jun

Science of the Total Environment, 551-552, p.590 - 604, 2016/05

 Times Cited Count:21 Percentile:21.68(Environmental Sciences)

A model for $$^{137}$$Cs transfer in forest was developed to assess behavior of Fukushima-derived $$^{137}$$Cs. The model simulation well reproduced observed 3 year migration of $$^{137}$$Cs in organic layer and mineral soil. Long-term predictions indicated that more than 90% of the deposited $$^{137}$$Cs remains in the top 5 cm soil till 30 years, suggesting that forest acts as a long-term reservoir of $$^{137}$$Cs with limited loss via groundwater pathway. Impacts of soil organic matter (SOM) on $$^{137}$$Cs dynamics were investigated by modifying parameters of $$^{137}$$Cs turnover. The results showed that SOM-induced reduction of $$^{137}$$Cs adsorption, slower fixation of $$^{137}$$Cs by clay and enhanced mobilization of the fixed $$^{137}$$Cs elevate soil-to-plant transfer of $$^{137}$$Cs by increasing fraction of dissolved $$^{137}$$Cs. A substantial proportion (27% $$sim$$ 73%) of $$^{137}$$Cs in these soils was delivered to horizons deeper than 5 cm decades later. These results suggested that SOM significantly influences behavior of $$^{137}$$Cs over long-term.

Journal Articles

Radioactive Cs in the estuary sediments near Fukushima Daiichi Nuclear Power Plant

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:21 Percentile:21.68(Environmental Sciences)

Cesium-137 ($$^{137}$$Cs) of estuary sediment impacted by the FDNPP was measured. Increasing radioactivity was observed from surface to bottom. 90% of the $$^{137}$$Cs was strongly bound to clay minerals in the estuary sediments. These results suggest that $$^{137}$$Cs is being transported from contaminated paddy fields to the estuary.

Journal Articles

A New comparison of marine dispersion model performances for Fukushima Dai-ichi releases in the frame of IAEA MODARIA program

Peri$'a$$~n$ez, R.*; Brovchenko, I.*; Duffa, C.*; Jung, K.-T.*; Kobayashi, Takuya; Lamego, F.*; Maderich, V.*; Min, B.-I.*; Nies, H.*; Osvath, I.*; et al.

Journal of Environmental Radioactivity, 150, p.247 - 269, 2015/12

 Times Cited Count:21 Percentile:27.57(Environmental Sciences)

A detailed intercomparison of marine dispersion models applied to the releases from Fukushima Dai-ichi Nuclear Power Plant has been carried out in the frame of MODARIA program, of the IAEA. Models have been compared in such a way that the reasons of the discrepancies between them can be assessed. The overall idea is to harmonize models, making them run with the same forcing in a step-by-step procedure, in such a way that the main agent in producing discrepancy between models can be found. It has been found that the main reason of discrepancies between models is due to the description of the hydrodynamics. However, once this has been suppressed, some variability between model outputs remains due to intrinsic differences between models. The numerical experiments have been carried out for a perfectly conservative radionuclide and for $$^{137}$$Cs. Model outputs for this radionuclide have also been compared with measurements in water and sediments.

Journal Articles

Anthropogenic radionuclides in seawater of the Japan Sea; The Results of recent observations and the temporal change of concentrations

Ito, Toshimichi; Aramaki, Takafumi*; Otosaka, Shigeyoshi; Suzuki, Takashi; Togawa, Orihiko; Kobayashi, Takuya; Kawamura, Hideyuki; Amano, Hikaru; Senju, Tomoharu*; Chaykovskaya, E. L.*; et al.

Journal of Nuclear Science and Technology, 42(1), p.90 - 100, 2005/01

 Times Cited Count:13 Percentile:30.82(Nuclear Science & Technology)

During 1996-2002, a wide-area research project on anthropogenic radionuclides was done in the Japanese and Russian EEZ of the Japan Sea to investigate their migration. As the results of expeditions in 2001 and 2002, (1) the concentrations and distributions of radionuclides are similar to the results of previous, (2) inventories of these radionuclides indicate accumulation in the Japan Sea seawater compared to the amounts supplied by global fallout, (3) $$^{90}$$Sr and $$^{137}$$Cs concentrations in intermediate layer show temporal variations, and 4) the variations may reflect the water mass movement in upper part of the Japan Sea.

Journal Articles

Anthropogenic radionuclides in seawater of the Japan Sea; The Results of recent expeditions carried out in the Japanese and Russian EEZ

Ito, Toshimichi; Aramaki, Takafumi*; Otosaka, Shigeyoshi; Suzuki, Takashi; Togawa, Orihiko; Kobayashi, Takuya; Senju, Tomoharu*; Chaykovskaya, E. L.*; Lishavskaya, T. S.*; Karasev, E. V.*; et al.

Proceedings of International Symposium on Radioecology and Environmental Dosimetry, p.396 - 401, 2003/10

no abstracts in English

Journal Articles

Application of MOGRA for migration of contaminants through different land utilization areas

Amano, Hikaru; Takahashi, Tomoyuki*; Uchida, Shigeo*; Matsuoka, Shungo*; Ikeda, Hiroshi*; Hayashi, Hiroko*; Kurosawa, Naohiro*

JAERI-Conf 2003-010, p.112 - 121, 2003/09

The functionality of MOGRA is being verified by applying it in the analyses of the migration rates of radioactive substances from the atmosphere to soils and plants and flow rates into the rivers. This has been achieved by also taking their mode classifications into consideration. In this report, a hypothetical combination of land usage was supposed to check the function of MOGRA. The land usage was consisted from cultivated lands, forests, uncultivated lands, urban area, river, and lake. Each land usage has its own inside model which is basic module. Also supposed was homogeneous contamination of the surface land from atmospheric deposition of Cs-137 (1.0 Bq/m$$^{2}$$). The system can analyze the dynamic changes of Cs-137 concentrations in each compartment, fluxes from one compartment to another compartment.

Journal Articles

Construction of river transfer models for MOGRA

Hayashi, Hiroko*; Matsuoka, Shungo*; Takahashi, Tomoyuki*; Amano, Hikaru

JAERI-Conf 2003-010, p.122 - 130, 2003/09

Two dynamic compartment models were constructed as basic river models for MOGRA (Migration Of GRound Additions), an environmental-load effect predicting code. One is 1 component river model, in which radionuclides in particulate form and dissolved form are considered to be in equilibrium in the river water. Another one is 2 component river model, in which particulate form and dissolved form are considered to be different component and are separately compartmentalized. In each model the river sediment is set in a compartment, and the sedimentation of particulate form and resuspension of radionuclides in the river sediment are taken into account.To verify the analysis function of the constructed models, calculation conditions were set using data of Cs-137 concentration in the river water derived from Kuji river, Japan, and analysis was carried out. Comparing two models, almost no difference is seen when sedimentation velocity is low, while there is apparent difference when sedimentation velocity is high.

Journal Articles

Equipment of model template for a code predicting the migration of ground additions, MOGRA

Takahashi, Tomoyuki*; Amano, Hikaru; Uchida, Shigeo*; Ikeda, Hiroshi*; Matsuoka, Shungo*; Hayashi, Hiroko*; Kurosawa, Naohiro*

Kankyo Eisei Kogaku Kenkyu, 17(3), p.340 - 344, 2003/07

no abstracts in English

Journal Articles

Atmospheric deposition of $$^{7}$$Be, $$^{40}$$K, $$^{137}$$Cs and $$^{210}$$Pb during 1993-2001 at Tokai-mura, Japan

Ueno, Takashi; Nagao, Seiya; Yamazawa, Hiromi

Journal of Radioanalytical and Nuclear Chemistry, 255(2), p.335 - 339, 2003/02

 Times Cited Count:16 Percentile:25.97

To evaluate the migration of radionuclides to the ground surface, deposition was collected from 1993 to 2001 with basin set up at Japan Atomic Energy Research Institute at Tokai-mura. Monthly basin samples were evaporated to dryness to obtain residual samples.These samples were measured by a well type Ge detector for natural and fallout radionuclide. These monthly depositions showed a clear seasonal variation with peaks in the early spring from February to April, and also in May in some years. The depositions of $$^{40}$$K and $$^{137}$$Cs have good correlation with the dry weight of deposited material, the depositions of $$^{7}$$Be and $$^{210}$$Pb showed much lower correlation coefficients. This difference in the correlation coefficient between these two groups of radionuclides can be attributed to the difference in the originating processes. These features in the concentration are thought to be caused by the difference in mechanism and location of origination, which would result in difference in the contributing particle size, and hence by the difference in the transport and deposition processes.

Journal Articles

Depth profiles of long lived radionuclides in Chernobyl soils sampled around 10 years after the accident

Amano, Hikaru; Onuma, Yoshikazu*

Journal of Radioanalytical and Nuclear Chemistry, 255(1), p.217 - 222, 2003/01

 Times Cited Count:8 Percentile:47.46

no abstracts in English

Journal Articles

Accumulation and potential dissolution of Chernobyl-derived radionuclides in river bottom sediments

Sanada, Yukihisa*; Matsunaga, Takeshi; Yanase, Nobuyuki; Nagao, Seiya; Amano, Hikaru; Takada, Hideshige*; Tkachenko, Y.*

Applied Radiation and Isotopes, 56(5), p.751 - 760, 2002/04

 Times Cited Count:12 Percentile:36.19(Chemistry, Inorganic & Nuclear)

Areas contaminated with radionuclides from the Chernobyl nuclear accident have been identified in Pripyat River near the Chernobyl Nuclear Power Plant. The bottom sediments contained $$^{137}$$Cs (10$$^{5}$$ - 10$$^{6}$$ Bq/m$$^{2}$$) within 0-30 cm depth, which is comparable to the ground soil of in the vicinity of the nuclear power plant (the Exclusion Zone). The sediments also accumulated $$^{90}$$Sr (10$$^{5}$$ Bq/m$$^{2}$$ ), $$^{239,240}$$Pu (10$$^{4}$$ Bq/m$$^{2}$$ ), $$^{241}$$Am (10$$^{4}$$ Bq/m$$^{2}$$ ) derived from the accident.The comparison of these inventories with those of the released radionuclides at the accident and the experimental analysis using the selective sequential extraction of the radionuclides in the sediments suggest that the potential mobility of $$^{137}$$Cs and $$^{239,240}$$Pu is low compared with $$^{90}$$Sr in the bottom sediment, while the potential dissolution of $$^{90}$$Sr from the river bottom sediment should be taken into account with respect to the long-term radiological influence on the aquatic environment.

Journal Articles

Radioactive contamination in the aquatic environment as a result of the Chernobyl nuclear accident

Matsunaga, Takeshi; Nagao, Seiya*

Sui Kankyo Gakkai-Shi, 25(4), p.193 - 197, 2002/04

no abstracts in English

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