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Watanabe, Tsuyoshi; Asamori, Koichi
no journal, ,
no abstracts in English
Kawamura, Hideyuki; Kamidaira, Yuki; Kobayashi, Takuya
no journal, ,
The Japan Atomic Energy Agency developed a Short-Term Emergency Assessment system of the Marine Environmental Radioactivity (STEAMER). STEAMER is in daily test operation to predict the oceanic dispersion of radionuclides that are released into the ocean from nuclear facilities. The predictability of oceanic dispersion simulations is validated in this study. Oceanic dispersion simulations are performed for a hypothetical release of Cs-137 from the Fukushima Daiichi Nuclear Power Plant using oceanographic forecast and reanalysis data. Comparison between forecast and reanalysis simulations enables us to estimate the predictability quantitatively. Ensemble forecast simulations are also performed to improve the predictability. Moreover, a Regional Ocean Modeling System is applied to simulate ocean circulations accurately in the coastal and offshore areas. As a result, submesoscale eddies and tidal currents affect the oceanic dispersion of Cs-137.
Kadowaki, Masanao; Terada, Hiroaki
no journal, ,
A long-lived radioactive iodine (
I) has been released into the atmosphere throughout human nuclear activities since the 1940s. Airborne I compounds behave as gaseous and particulate forms, and the air concentrations of I compounds are determined by transport, deposition, atmospheric chemistry and sources. However, the global cycle has never been fully understood. In present study we newly introduced 2 gas-phase chemical reactions, 6 photolytic reactions and 6 heterogeneous reactions into our I transport model GEARN-FDM, and quantitively evaluated global emission and deposition fluxes for I during the 2000s. From the simulation result, the oceanic emission flux was estimated to be 7.4 GBq/y. In particular, the English Channel was the largest marine source of I (58% of the marine emission totals). In addition, we estimated the I emission flux totals from terrestrial: rice paddy, biomass burning, and wood fuel to be 0.6 GBq/y, in which the largest emission was from rice paddy (0.3 GBq/y). This result shows that the impact of terrestrial emission on I global budget is small in comparison with oceanic sources. However, those natural emission flux totals is much lower than the current I emission flux from major nuclear fuel reprocessing facilities at La Hague, Sellafield, and Mayak (34.2 GBq/y), showing that the anthropogenic release from ongoing facilities dominates to the current source of I. The airborne I emitted from anthropogenic sources was mainly deposited nearby the facilities due to dry deposition, and the deposition amount totals was estimated to be 41.0 GBq/y. The current I emission flux from the deposition areas throughout volatilization was approximated to be 1.4 GBq/y, which is larger than the emission flux from the other terrestrial sources. This suggests that the I emission nearby the facilities would currently dominate the terrestrial natural source.
Amano, Yuki; Beppu, Hikari*; Endo, Takashi*; Nemoto, Kazuaki*; Sato, Tomofumi*; Thomas, B. C.*; Banfield, J. F.*
no journal, ,
release from volcanic ash soils in a Japanese temperate forestNagano, Hirohiko; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
no abstracts in English
Aoki, Kazuhiro; Tanaka, Yukumo; Yoshida, Takumi; Seshimo, Kazuyoshi; Guglielmi, Y.*; Cook, P.*; Soom, F.*
no journal, ,
Shimo, Michito*; Niwa, Masakazu; Amano, Kenji; Tokunaga, Tomochika*; Tonokura, Kenichi*; Matsuoka, Toshifumi*; Biraud, S.*
no journal, ,
To investigate the possibility of cavity ring-down spectroscopy technology to the gas release detection from the active fault to the atmosphere, we conducted field measurements at the Atera fault area in Gifu prefecture, Japan. Based on the results, we expect that the real-time high precision gas measurement can be one of the promising approaches to locate the active faults creating paths for the deepseated fluids.
Takemi, Tetsuya*; Yoshida, Toshiya; Duan, G.*
no journal, ,
An intense tropical cyclone, Typhoon Jebi (2018) landed on the central part of Japan in September, caused severe damages due to strong winds in Osaka City. Buildings in urban areas are known to affect significantly the magnitude of wind gustiness. Thus, it is important to understand the underlying risks of wind damages derived from urban buildings. We investigate the influences of densely built urban environments on the occurrence of wind gusts in urban districts of Osaka City during the landfall of Typhoon Jebi by merging mesoscale meteorological and building-resolving Large Eddy Simulation (LES). The maximum wind gust in the analysis area is estimated as 60-70 m/s, which is comparable to the wind speed at the height of about 300 m. Instantaneous wind gusts are further examined in terms of building density and are found to become the strongest where the building density has a moderate value.
Horikawa, Shigeo*; Sasaki, Takeshi*; Koshigai, Masaru*; Fukushima, Shigeru; Ohara, Yoshiyuki
no journal, ,