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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
JAEA-Review-2017-018.pdf:17.58MB
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.
Iijima, Kazuki
Chikyu Kagaku, 49(4), p.203 - 215, 2015/09
The Fukushima Dai-ichi Nuclear Power Plant accident led to the release of various and huge amount of radionuclides into the environment, and contamination of wide area of eastern Japan, mainly Fukushima prefecture. More than 70% of radioactive cesium, which dominates the exposure dose, was deposited in forest far from our living sphere and is considered to be remobilized with time by water flow and strong wind caused by natural events such as typhoons. Numerous researches on the behavior of radionuclides in the environment have been performed not only by observation in the contaminated regions but also by model analysis so far. This paper overviewed results of understanding and modeling of transport behavior of radiocesium from forests through river systems.
Iijima, Kazuki; Funaki, Hironori; Hagiwara, Hiroki; Nakanishi, Takahiro; Tsuruta, Tadahiko
no journal, ,
JAEA has carried out the project on the Long-term Assessment of Transport of Radioactive Contaminant in the Environment of Fukushima (F-TRACE project) since the end of 2012. Radiocaesium has been distributed by the fallout from the Fukushima Dai-ichi Nuclear Power Plant accident mainly to the coastal area of Fukushima Prefecture. In this project, the transport behavior of radiocaesium through water systems located in coastal areas of Fukushima was investigated to establish predictive modeling tools for distribution of radiocaesium and to estimate future effective dose of the residents. One of the study rivers in the coastal area was Ukedo River which was selected due to the high contamination of radiocaesium in the catchment especially upstream in contrast with less contamination downstream. This paper provides an overview of the results of field observations on the distribution and evolution of radiocaesium activity concentration in the Ukedo River water system carried out in 2013 and 2014. It can be concluded that the dam has a significant ability to constrain transport of radiocaesium from upstream to downstream.
Iijima, Kazuki; Niizato, Tadafumi; Tsuruta, Tadahiko; Kitamura, Akihiro
no journal, ,
Transport behavior of radioactive cesium in the Ukedo river system was quantitatively evaluated by combining field investigation in forests, rivers and a dam lake with analytical results by means of soil loss and transport in the river simulations. It can be considered that most of the radioactive cesium was eroded from the lower land than the dam lake.
Iijima, Kazuki
no journal, ,
JAEA has carried out "the project on the Long-term Assessment of Transport of Radioactive Contaminant in the Environment of Fukushima (F-TRACE project)" since the end of 2012. Radiocaesium has been widely distributed by the fallout from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, mainly to the coastal area of Fukushima Prefecture. In this project, the transport behavior of radiocaesium through seven water systems located in coastal areas of Fukushima was investigated to establish predictive modeling tools for distribution of radiocaesium and to estimate future effective dose of the residents. This paper provides understanding of transport behavior of radiocaesium lead by comparison among focused rivers and quantitative evaluation of mass flow in the water system based on the results of field observations. Especially, behavior and factors defining the concentrations of particulate and dissolved radiocaesium in the water systems will be discussed.
Iijima, Kazuki; Kitamura, Akihiro; Miyahara, Kaname
no journal, ,
Understandings of transport behaviour of radiocesium in the environment were overviewed, and distribution of other radionuclides was compared to that of radiocesium. Annual discharge of radiocesium from forest with soil particles and fine litter were around 0.1% of those of initially deposited and independent to vegetation and slope if there was enough litter and small plants. In the stream water taken nearby the flowing out point showed higher concentration of dissolved radiocesium that that of groundwater, suggesting that dissolved radiocesium was generated due to the degradation of litter or the desorption from soil and dissolved. The concentration of dissolved radiocesium in river water was lower than 1 Bq/L in all river systems. Since the direction dependency on the off-site distribution of these radionuclides were similar to that of observed in the FDNPS site, the estimation of the on-site distribution based on the off-site one was considered to be available.
Hagiwara, Hiroki
no journal, ,
no abstracts in English
Iijima, Kazuki
no journal, ,
Behavior of radioactive cesium in the environment from the forest to the estuary was discussed by comparing the data obtained from observations and laboratory experiments with the analytical results for the eight river systems in coastal area of Fukushima Prefecture. Concentration of dissolved radioactive cesium in river water decreased with time, with seasonal variations that became higher in summer and lower in winter. The behavior was analyzed with a simulation tool based on the water circulation simulator GETFLOWS. The behavior of particulate radioactive cesium was well reproduced. On the other hand, in case of dissolved fraction, although the concentration level could be roughly reproduced, the seasonal variation and the temporary concentration increase at the beginning of heavy rain could not be reproduced. In the current simulation, only the desorption is considered as the dissolving process, so that the contribution of other processes was considered.
Iijima, Kazuki
no journal, ,
Behavior of radioactive cesium in the environment from the forest to the estuary was discussed by comparing the data obtained from observations and laboratory experiments with the analytical results for the eight river systems in coastal area of Fukushima Prefecture. Concentration of dissolved radioactive cesium in river water decreased with time, with seasonal variations that became higher in summer and lower in winter. The behavior was analyzed with a simulation tool based on the water circulation simulator GETFLOWS. The behavior of particulate radioactive cesium was well reproduced. On the other hand, in case of dissolved fraction, although the concentration level could be roughly reproduced, the seasonal variation and the temporary concentration increase at the beginning of heavy rain could not be reproduced. In the current simulation, only the desorption is considered as the dissolving process, so that the contribution of other processes was considered.
Niizato, Tadafumi; Sakuma, Kazuyuki; Iijima, Kazuki; Nakanishi, Takahiro
no journal, ,
no abstracts in English
Ochiai, Shinya*; Nagao, Seiya*; Nakanishi, Takahiro; Tsuruta, Tadahiko; Misono, Toshiharu; Watanabe, Shun*; Suzuki, Kyuma*; Tomihara, Seiichi*
no journal, ,
We investigated the controlling factors of radiocesium derived from the nuclear accident in each river systems in Fukushima Prefecture and the surrounding area. Dissolved 
Cs concentration / Cs deposition ratio tended to be higher in the Tone River and lower in the Natsui River than in the Abukuma River. Dissolved Cs concentration generally decreases exponentially, but the half-life is shorter in the Natsui River and longer in the Tone River than in the Abukuma River.
Hagiwara, Hiroki; Konishi, Hiromi*
no journal, ,
no abstracts in English
