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読売新聞 10月27日(木)3時11分配信
東京電力福島第一原発事故の初期に放出された放射性物質セシウム137は約3万5000テラ・ベクレルに上り、日本政府の推計の2倍を超える可能性があるとの試算を、北欧の研究者らがまとめた。
英科学誌「ネイチャー」が25日の電子版で伝えた。世界の核実験監視網で観測した放射性物質のデータなどから放出量を逆算。太平洋上空に流れた量を多く見積もっている。
For 137Cs, the inversion results give a total emission of 35.8 (23.3–50.1) PBq, or about 42% of the estimated Chernobyl emission.
we estimate that 6.4 TBq of 137Cs, or 19% of the total fallout until 20 April, were deposited over Japanese land areas, while most of the rest fell over the North Pacific Ocean.
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mainau
放射性物質の放出総量について、小出助教など反原発派の研究者からは、早くからチェルノブイリ事故のレベルにどんどんと近づいていくのではないか、という危惧がなされていた。今回、科学雑誌ネイチャーに発表された放射性物質の試算の仮説は、これらの危惧には根拠があることを裏付けている。
この試算によると、セシウム 137については、すでにチェルノブイリ事故での放出量の 42%が放出されたことになる。このうち、四月二十日までにセシウム 137の全放出総量の 19% が日本の国土に降り積もり、残りの大部分は北太平洋上に落ちたとされている。この論部の概要は以下に掲載した。
なお、この論文には、リンク先に論文の全文 Discussion Paper が載っているので、これを各自がダウンロードして自分のコンピューターに保管することをすすめる。
各自が論文本文の長いほうにて、全放出量の試算の比較、役に立つ地図、汚染状況などを確認しておくのがよい。
三月十五日、十六日、および二十日、二十一日においては、セシウム137の放出による放射能物質が関東地方に広く拡散していることが、この論文からもはっきりと図にて示されている。これらの図にも注目。
論文の全文 http://www.atmos-chem-phys-discuss.net/11/28319/2011/acpd-11-28319-2011.pdf
各自がダウンロードして自分のコンピューターに保管しよう。
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ネイチャーに発表された論文の概要 Abstract
消されたら困るから、概要は英文のまま、この掲示板に掲載する。
copy from
http://www.atmos-chem-phys-discuss.net/11/28319/2011/acpd-11-28319-2011.html
Atmos. Chem. Phys. Discuss., 11, 28319-28394, 2011
www.atmos-chem-phys-discuss.net/11/28319/2011/
doi:10.5194/acpd-11-28319-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Xenon-133 and caesium-137 releases into the atmosphere from the Fukushima Dai-ichi nuclear power plant: determination of the source term, atmospheric dispersion, and deposition
A. Stohl1, P. Seibert2, G. Wotawa3, D. Arnold2,4, J. F. Burkhart1, S. Eckhardt1, C. Tapia5, A. Vargas4, and T. J. Yasunari6
1NILU – Norwegian Institute for Air Research, Kjeller, Norway
2Institute of Meteorology, University of Natural Resources and Life Sciences, Vienna, Austria
3Central Institute for Meteorology and Geodynamics, Vienna, Austria
4Institute of Energy Technologies (INTE), Technical University of Catalonia (UPC), Barcelona, Spain
5Department of Physics and Nucelar Engineering (FEN),Technical University of Catalonia (UPC), Barcelona, Spain
6Universities Space Research Association, Goddard Earth Sciences and Technology and Research, Columbia, MD 21044, USA
Abstract. On 11 March 2011, an earthquake occurred about 130 km off the Pacific coast of Japan's main island Honshu, followed by a large tsunami. The resulting loss of electric power at the Fukushima Dai-ichi nuclear power plant (FD-NPP) developed into a disaster causing massive release of radioactivity into the atmosphere. In this study, we determine the emissions of two isotopes, the noble gas xenon-133 (133Xe) and the aerosol-bound caesium-137 (137Cs), which have very different release characteristics as well as behavior in the atmosphere. To determine radionuclide emissions as a function of height and time until 20 April, we made a first guess of release rates based on fuel inventories and documented accident events at the site. This first guess was subsequently improved by inverse modeling, which combined the first guess with the results of an atmospheric transport model, FLEXPART, and measurement data from several dozen stations in Japan, North America and other regions. We used both atmospheric activity concentration measurements as well as, for 137Cs, measurements of bulk deposition. Regarding 133Xe, we find a total release of 16.7 (uncertainty range 13.4–20.0) EBq, which is the largest radioactive noble gas release in history not associated with nuclear bomb testing. There is strong evidence that the first strong 133Xe release started very early, possibly immediately after the earthquake and the emergency shutdown on 11 March at 06:00 UTC. The entire noble gas inventory of reactor units 1–3 was set free into the atmosphere between 11 and 15 March 2011. For 137Cs, the inversion results give a total emission of 35.8 (23.3–50.1) PBq, or about 42% of the estimated Chernobyl emission. Our results indicate that 137Cs emissions peaked on 14–15 March but were generally high from 12 until 19 March, when they suddenly dropped by orders of magnitude exactly when spraying of water on the spent-fuel pool of unit 4 started. This indicates that emissions were not only coming from the damaged reactor cores, but also from the spent-fuel pool of unit 4 and confirms that the spraying was an effective countermeasure. We also explore the main dispersion and deposition patterns of the radioactive cloud, both regionally for Japan as well as for the entire Northern Hemisphere. While at first sight it seemed fortunate that westerly winds prevailed most of the time during the accident, a different picture emerges from our detailed analysis. Exactly during and following the period of the strongest 137Cs emissions on 14 and 15 March as well as after another period with strong emissions on 19 March, the radioactive plume was advected over Eastern Honshu Island, where precipitation deposited a large fraction of 137Cs on land surfaces. The plume was also dispersed quickly over the entire Northern Hemisphere, first reaching North America on 15 March and Europe on 22 March. In general, simulated and observed concentrations of 133Xe and 137Cs both at Japanese as well as at remote sites were in good quantitative agreement with each other. Altogether, we estimate that 6.4 TBq of 137Cs, or 19% of the total fallout until 20 April, were deposited over Japanese land areas, while most of the rest fell over the North Pacific Ocean. Only 0.7 TBq, or 2% of the total fallout were deposited on land areas other than Japan.
Discussion Paper (PDF, 6457 KB) Supplement (13 KB) Interactive Discussion (Open, 1 Comment) Manuscript under review for ACP
Citation: Stohl, A., Seibert, P., Wotawa, G., Arnold, D., Burkhart, J. F., Eckhardt, S., Tapia, C., Vargas, A., and Yasunari, T. J.: Xenon-133 and caesium-137 releases into the atmosphere from the Fukushima Dai-ichi nuclear power plant: determination of the source term, atmospheric dispersion, and deposition, Atmos. Chem. Phys. Discuss., 11, 28319-28394, doi:10.5194/acpd-11-28319-2011, 2011.
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