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Journal Articles

Development of field estimation technique and improvement of environmental tritium behavior model

Yokoyama, Sumi*; Takahashi, Tomoyuki*; Ota, Masakazu; Kakiuchi, Hideki*; Sugihara, Shinji*; Hirao, Shigekazu*; Momoshima, Noriyuki*; Tamari, Toshiya*; Shima, Nagayoshi*; Atarashi-Andoh, Mariko; et al.

Plasma and Fusion Research (Internet), 14(Sp.2), p.3405099_1 - 3405099_4, 2019/06

The Large Helical Device of the National Institute for Fusion Science started D-D experiments in 2017. To ensure the safety of the facility, it is important to develop evaluation methods for environmental tritium transfer. Tritiated water (HTO) in atmosphere and soil is transferred to plants, and organically bound tritium (OBT) is formed by photosynthesis. Prediction of OBT formation is important, because OBT accumulates in plants and causes dose through ingestion. The objective of this study is to estimate environmental tritium transfer using a simple compartment model and practical parameters. We proposed a simple compartment model consisting of air-soil-plant components, and tried to validate the model by comparison with a sophisticated model, SOLVEG. In this study, we plan to add wet deposition to the model and obtain parameters from measurements of soil permeability and tritium concentrations in air, soil and plants. We also establish rapid pretreatment methods for OBT analysis.

Journal Articles

Impacts of anthropogenic source from the nuclear fuel reprocessing plants on global atmospheric iodine-129 cycle; A Model analysis

Kadowaki, Masanao; Katata, Genki*; Terada, Hiroaki; Suzuki, Takashi; Hasegawa, Hidenao*; Akata, Naofumi*; Kakiuchi, Hideki*

Atmospheric Environment, 184, p.278 - 291, 2018/07

 Times Cited Count:1 Percentile:59.32(Environmental Sciences)

The long-lived radioactive iodine ($$^{129}$$I) is a useful geochemical tracer in the atmospheric environment. We recently observed clear seasonal trends in air concentration and deposition of $$^{129}$$I in Japan. Using these data, we developed a global atmospheric $$^{129}$$I transport model to reveal key processes for the global atmospheric $$^{129}$$I cycle. The model generally reproduced the observed seasonal change in air concentration and deposition of $$^{129}$$I in Japan, and the global distribution of $$^{129}$$I concentration in rain as presented in past literature. Numerical experiments changing the intensity of anthropogenic and natural sources were conducted to quantify the impact of anthropogenic sources on the global $$^{129}$$I cycle. The results indicated that the atmospheric $$^{129}$$I from the anthropogenic sources was deposited in winter and can be accumulated mainly in the northern part of Eurasia. In contrast, the atmospheric $$^{129}$$I from the natural sources dominated the deposition in summer. These results suggested that the re-emission process of $$^{129}$$I from the Earth's surface may be important as a secondary impact of $$^{129}$$I in the global-scaled environment. Furthermore, although wet deposition dominated the total deposition in the Northern hemisphere, dry deposition regionally and seasonally contributed to the total deposition over arctic and northern part of Eurasia in winter, suggesting that the dry deposition may play a key role in the seasonal change of $$^{129}$$I deposition in the Northern hemisphere high latitudes.

Journal Articles

Magnetic structure of divalent europium compound EuGa$$_{4}$$ studied by single-crystal time-of-flight neutron diffraction

Kawasaki, Takuro; Kaneko, Koji; Nakamura, Ai*; Aso, Naofumi*; Hedo, Masato*; Nakama, Takao*; Ohara, Takashi; Kiyanagi, Ryoji; Oikawa, Kenichi; Tamura, Itaru; et al.

Journal of the Physical Society of Japan, 85(11), p.114711_1 - 114711_5, 2016/11

 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Single crystal neutron diffraction study of high neutron absorbing compound EuGa$$_{4}$$

Kawasaki, Takuro; Kaneko, Koji; Aso, Naofumi*; Nakamura, Ai*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*; Ohara, Takashi; Kiyanagi, Ryoji; Oikawa, Kenichi; et al.

JPS Conference Proceedings (Internet), 1, p.014009_1 - 014009_4, 2014/03

Journal Articles

Field tests on migration of TRU-nuclide, 2; Migration test for engineered barrier materials in aerated soil

Maeda, Toshikatsu; Tanaka, Tadao; Mukai, Masayuki; Ogawa, Hiromichi; Yamaguchi, Tetsuji; Munakata, Masahiro; Matsumoto, Junko; Kozai, Naofumi; Bamba, Tsunetaka; Fan, Z.*; et al.

Nippon Genshiryoku Gakkai Wabun Rombunshi, 2(3), p.336 - 341, 2003/09

no abstracts in English

Oral presentation

Magnetic structure analysis of high neutron absorbing compound EuGa$$_{4}$$

Kawasaki, Takuro; Kaneko, Koji; Aso, Naofumi*; Nakamura, Ai*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*; Ohara, Takashi; Kiyanagi, Ryoji; Oikawa, Kenichi; et al.

no journal, , 

no abstracts in English

Oral presentation

Single crystal neutron diffraction study of high neutron absorbing compound EuX$$_{4}$$ (X = Al, Ga)

Kawasaki, Takuro; Kaneko, Koji; Aso, Naofumi*; Nakamura, Ai*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*; Moyoshi, Taketo*; Nakao, Akiko*; Hanashima, Takayasu*; et al.

no journal, , 

no abstracts in English

Oral presentation

Development of a global transport model for airborne iodine-129 including atmospheric photolysis and gas-particle conversion processes

Kadowaki, Masanao; Katata, Genki*; Terada, Hiroaki; Suzuki, Takashi; Hasegawa, Hidenao*; Akata, Naofumi*; Kakiuchi, Hideki*

no journal, , 

Iodine-129 ($$^{129}$$I) has been shown as a useful isotope for dating of water, tracing of marine sediments and investigating the geochemical cycle of iodine. Main sources of atmospheric $$^{129}$$I are volatilization from ocean and discharge from nuclear fuel reprocessing facilities. Although released $$^{129}$$I is globally transported in the atmosphere and deposited to the Earth's surface, spatial and temporal distributions of atmospheric $$^{129}$$I are still not well understood. In this study, we developed an atmospheric global transport model of $$^{129}$$I which includes the processes such as advection and turbulent diffusion, dry and wet deposition, discharge from nuclear fuel reprocessing facility, volatilization from ocean and atmospheric chemical reactions (atmospheric photolysis and gas-particle conversion). Input meteorological fields of three-dimensional components of wind, air temperature, atmospheric pressure, and turbulent diffusion coefficient were calculated using WRF (Weather Research and Forecasting) with ERA-Interim dataset. The simulation period was set to be from 1 Jan 2006 to 31 Dec 2010. For model validation, we used air concentration and deposition of gaseous and particulate forms of $$^{129}$$I measured at Rokkasho in Japan from 2006 to 2010 and past measurements of $$^{129}$$I concentration in rain water in Europe, Asia, and North America. The model successfully reproduced the seasonal variations of measured air concentration and deposition of $$^{129}$$I at Rokkasho as maximum and minimum values during the wintertime and summertime, respectively. Furthermore, spatial patterns of simulated $$^{129}$$I concentration in globe were similar to those of measurements. In the presentation, key factors in controlling the spatiotemporal distribution of airborne $$^{129}$$I and its cycle in the atmosphere suggested by model results will be discussed.

Oral presentation

Dose variation measurement at the high background radiation area in Indonesia

Sasaki, Michiya*; Yamada, Ryohei; Akata, Naofumi*; Tokonami, Shinji*; Hosoda, Masahiro*; Iwaoka, Kazuki*; Chanis, P.*; Kudo, Hiromi*; Sahoo, K.*; Iskandar, D.*; et al.

no journal, , 

Recently, Mamuju city in Sulawesi Island, Indonesia and its surrounding area is known as the high background radiation area, and is regarded as a possible area for an epidemiological study. In this study we have measured the hourly dose rates of individuals and the environment with the D-shuttle dosimeter, which has been developed by the Chiyoda Technol Corporation. With the aid of local residents living at Botteng village, which is located south of Mamuju city, short term and long term measurements were conducted for three days and nine months, respectively. Two volunteers have equipped the D-shuttle for the short term measurement, and seven families supported the short and long term measurements of the environmental dose rate, for both inside and outside the house. From our results, since some variation was observed regarding with day or night, correlation with radon concentration was suggested.

Oral presentation

Radiation dose estimation at the high background radiation area in Indonesia; Dose rate measurement at different height

Sasaki, Michiya*; Yamada, Ryohei; Nugraha, E.*; Akata, Naofumi*; Tokonami, Shinji*; Hosoda, Masahiro*; Iwaoka, Kazuki*; Pornnumpa, C.*; Kudo, Hiromi*; Sahoo, K.*; et al.

no journal, , 

The area around Mamuju city in West Sulawesi, Indonesia has high possibility of being a target of epidemiological research as a high natural radiation area. We would like to report the difference in radiation dose at different heights from the ground measured by the D-Shuttle.

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