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Journal Articles

A Modeling approach to estimate $$^{3}$$H discharge from rivers; Comparison of discharge from the Fukushima Dai-ichi and inventory in seawater in the Fukushima coastal region

Sakuma, Kazuyuki; Machida, Masahiko; Kurikami, Hiroshi; Iwata, Ayako; Yamada, Susumu; Iijima, Kazuki

Science of the Total Environment, 806(3), p.151344_1 - 151344_8, 2022/02

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018) (Translated document)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2020-007, 249 Pages, 2020/10

JAEA-Research-2020-007.pdf:15.83MB

The accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, Japan Atomic Energy Agency (JAEA) has been conducting "Long-term Assessment of Transport of Radioactive Contaminants in the Environment of Fukushima" concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2019-002, 235 Pages, 2019/08

JAEA-Research-2019-002.pdf:21.04MB

The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Journal Articles

Simultaneous measurements of superradiance at multiple wavelength from helium excited states, 2; Analysis

Ohae, Chiaki*; Harries, J.; Iwayama, Hiroshi*; Kawaguchi, Kentaro*; Kuma, Susumu*; Miyamoto, Yuki*; Nagasono, Mitsuru*; Nakajima, Kyo*; Nakano, Itsuo*; Shigemasa, Eiji*; et al.

Journal of the Physical Society of Japan, 85(3), p.034301_1 - 034301_10, 2016/03

 Times Cited Count:7 Percentile:56.08(Physics, Multidisciplinary)

Journal Articles

A Streak camera study of superfluorescence at multiple wavelengths from helium atoms excited using free electron laser pulses

Harries, J.; Iwayama, Hiroshi*; Nagasono, Mitsuru*; Togashi, Tadashi*; Yabashi, Makina*; Kuma, Susumu*; Nakajima, Kyo*; Miyamoto, Yuki*; Ohae, Chiaki*; Sasao, Noboru*; et al.

Journal of Physics B; Atomic, Molecular and Optical Physics, 48(10), p.105002_1 - 105002_9, 2015/05

 Times Cited Count:7 Percentile:45.32(Optics)

Journal Articles

Simultaneous measurements of super-radiance at multiple wavelengths from helium excited states, 1; Experiment

Nakajima, Kyo*; Harries, J.; Iwayama, Hiroshi*; Kuma, Susumu*; Miyamoto, Yuki*; Nagasono, Mitsuru*; Ohae, Chiaki*; Togashi, Tadashi*; Yabashi, Makina*; Shigemasa, Eiji*; et al.

Journal of the Physical Society of Japan, 84(5), p.054301_1 - 054301_7, 2015/05

 Times Cited Count:6 Percentile:50.68(Physics, Multidisciplinary)

Oral presentation

Superfluorescence from 1snp excited helium studied using a streak camera

Harries, J.; Iwayama, Hiroshi*; Nagasono, Mitsuru*; Togashi, Tadashi*; Kuma, Susumu*; Nakajima, Kyo*; Shigemasa, Eiji*

no journal, , 

Oral presentation

Cascade and competitive superfluorescence in He studied at the EUV free-electron laser SCSS using a streak camera

Harries, J.; Iwayama, Hiroshi*; Nagasono, Mitsuru*; Togashi, Tadashi*; Kuma, Susumu*; Nakajima, Kyo*; Shigemasa, Eiji*

no journal, , 

Oral presentation

Multiple-transition superradiance from EUV-FEL excited helium atoms, 1; Experiment

Nakajima, Kyo*; Harries, J.; Iwayama, Hiroshi*; Kuma, Susumu*; Miyamoto, Yuki*; Nagasono, Mitsuru*; Ohae, Chiaki*; Togashi, Tadashi*; Shigemasa, Eiji*; Sasao, Noboru*

no journal, , 

no abstracts in English

Oral presentation

Multiple-transition superradiance from EUV-FEL excited helium atoms, 2; Experiment

Ohae, Chiaki*; Harries, J.; Iwayama, Hiroshi*; Kuma, Susumu*; Miyamoto, Yuki*; Nagasono, Mitsuru*; Nakajima, Kyo*; Shigemasa, Eiji*; Wakabayashi, Tomonari*; Sasao, Noboru*

no journal, , 

no abstracts in English

Oral presentation

Mathematical modeling of radio-cesium migrations and air dose rate changes in eastern Fukushima Prefecture

Kitamura, Akihiro; Kurikami, Hiroshi; Sakuma, Kazuyuki; Malins, A.; Okumura, Masahiko; Itakura, Mitsuhiro; Yamada, Susumu; Machida, Masahiko

no journal, , 

Radioactive cesium that was deposited over Fukushima after the accident at the FDNPP is one of the major concerns regarding health physics. In order to predict the future distribution of radioactive cesium and resulting air dose rate at any location in Fukushima, we have integrated a number of mathematical models covering different time and scales. We present simulation results of sediment movement and radioactive cesium migration using semi empirical and physics based watershed models, and that of sediment and radioactive cesium behavior in a dam reservoir using one and two dimensional river simulation models. We also present a tool for calculating air dose rates from arbitrary radio cesium depth profiles and spatial distributions. The predicted dose rates were compared against dose rates measured in the field with handheld survey meters and good correlation was found between the two.

Oral presentation

Multiple-wavelength superfluorescence in helium following FEL excitation; Ultrafast experiments and simulations

Harries, J.; Ohae, Chiaki*; Iwayama, Hiroshi*; Kawaguchi, Kentaro*; Kuma, Susumu*; Miyamoto, Yuki*; Nagasono, Mitsuru*; Nakajima, Kyo*; Yabashi, Itsuo*; Shigemasa, Eiji*; et al.

no journal, , 

Oral presentation

Integrated watershed modeling for simulation of radio-cesium migration after flood events in the catchment near the Fukushima Dai-ichi Nuclear Power Plant

Sakuma, Kazuyuki; Kurikami, Hiroshi; Malins, A.; Yamada, Susumu; Funaki, Hironori; Niizato, Tadafumi; Machida, Masahiko; Kitamura, Akihiro

no journal, , 

The environments of Fukushima near the Fukushima Dai-ichi Nuclear Power Plant have been contaminated by the explosion accident of the plant caused by the Great East Japan Earthquake on 11 March 2011. The contamination level and air-dose rate behavior at present and in future are significant concern for the people used to live nearby. Most dominant radioactive material is $$^{137}$$Cs at present and its migration is considered to be driven by soil erosion and subsequent transport. To estimate the amount of soil sedimentation and the $$^{137}$$Cs migration, a three-dimensional hydrological model of the catchment was developed focused on the Ogi-no-sawa catchment, located 15 km southwest of the Fukushima Dai-ichi Nuclear Power Plant. Base on the developed hydrological model, top soil transport and resulting radio-cesium movement was simulated. For the modeling and simulation, physics based code the General-purpose terrestrial fluid-flow simulator GETFLOWS model, which is one of the tools for watershed modeling, was applied. The simulation results were compared with monitored data of the amount of water discharge and concentration of suspended solids for model testing. As a result of the study, the soil and $$^{137}$$Cs redistribution patterns at various scales of flood events could be predicted based on the results of modeling and simulation.

Oral presentation

Prediction of radioactive sediment transport near the Ukedo river mouth by numerical simulation

Yamada, Susumu; Kitamura, Akihiro; Nakanishi, Takahiro; Sakuma, Kazuyuki; Machida, Masahiko

no journal, , 

no abstracts in English

Oral presentation

Models on radiocesium migration in the surface water system in Fukushima Prefecture

Kurikami, Hiroshi; Yamada, Susumu; Sakuma, Kazuyuki; Kitamura, Akihiro

no journal, , 

A comprehensive scheme that involves several models for migration of radiocesium has been developed to assess various issues such as air dose rate prediction and accumulation of radiocesium onto lake bed sediment. This paper shows some examples of modeling studies including the evolution of radiocesium distribution in regional scale up to hundred years after the fallout.

Oral presentation

Applications of radiocesium migration models to Fukushima environmental issues, 1; Overview

Kurikami, Hiroshi; Sakuma, Kazuyuki; Malins, A.; Yamada, Susumu; Machida, Masahiko

no journal, , 

Over recent years after the accident at the Fukushima Dai-ichi Nuclear Power Plant, we have developed and applied several numerical models covering various time- and spatial-scales to tackle environmental issues in Fukushima. Each issue requires selection of a suitable model. The issues we have tackled thus far include medium- to long-term prediction of the redistribution of radiocesium and changes of radiation dose rates in the air, estimation of discharge amounts of radiocesium from land to the ocean, understanding the behavior of radiocesium in rivers and lakes during heavy rainfall events, and evaluation of the effect of radocesium migration in the environment on forestry and fishery products. In this presentation, we give an overview of our modeling studies on environmental issues in Fukushima.

Oral presentation

Estimation of particulate and dissolved $$^{137}$$Cs discharge from rivers to the ocean near the Fukushima Dai-ichi Nuclear Power Plant using a simple model

Sakuma, Kazuyuki; Aoyama, Michio*; Nakanishi, Takahiro; Kurikami, Hiroshi; Machida, Masahiko; Yamada, Susumu; Iwata, Ayako

no journal, , 

MERCURY is one of the models developed to simply predict $$^{137}$$Cs discharge from rivers to the ocean for understanding of $$^{137}$$Cs migration from seawater and sediment to the ecosystem and for estimating $$^{137}$$Cs discharge under heavy rainfall immediately. It is composed of a tank model, relationships between water discharge and suspended solids load, and two-component exponential models for river water $$^{137}$$Cs concentration. Using the MERCURY, $$^{137}$$Cs discharge to the ocean from five rivers near the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in 2018 and 2019 was estimated to be 0.23 and 0.81 TBq. $$^{137}$$Cs discharge in 2019 was larger than in 2018 due to the two huge typhoons in October 2019, Hagibis and Bualoi. Although the model has some limitations such as underestimating the $$^{137}$$Cs discharge during a heavy rainfall due to lack of modeling dependence of $$^{137}$$Cs concentration on sediment size, it can quickly evaluate the effect of $$^{137}$$Cs discharge from rivers to the coastal area near FDNPP.

Oral presentation

Investigation on distribution of radioactive substances in Fukushima, 16; Development of a watershed modeling for radionuclides

Sakuma, Kazuyuki; Machida, Masahiko; Yamada, Susumu; Kurikami, Hiroshi

no journal, , 

We developed a watershed modeling for radionuclides behavior in the environment based on the surface and subsurface water discharge and sediment transports. The results we applied the model to the upstream Ohta river reproduced the observed results about water, sediment, radiocesium discharge.

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