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JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima; As a part of dissemination of evidence-based information

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.

Oral presentation

Transport behavior of radiocaesium through water system in the coastal area of Fukushima

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.

Oral presentation

Long-term assessment of transport of radioactive contaminant in the environment of Fukushima (F-TRACE Project), 7; Status of the project

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.

Oral presentation

Transport of radiocaesium from forests to ocean; What governs the concentration of radiocaesium?

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.

Oral presentation

Fate and transport of radiocesium in river systems of Fukushima

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.

Oral presentation

Mineralogical characteristics of sediments transporting radiocesium within river basin

Hagiwara, Hiroki

no journal, , 

no abstracts in English

Oral presentation

Behavior of radioactive caesium in the environment; Understanding based on observation and analysis

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.

Oral presentation

Behavior of radioactive caesium in the environment; Understanding based on observation and analysis

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.

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