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| Titel |
Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of an atmospheric dispersion model with an improved deposition scheme and oceanic dispersion model |
| VerfasserIn |
G. Katata, M. Chino, T. Kobayashi, H. Terada, M. Ota, H. Nagai, M. Kajino, R. Draxler, M. C. Hort, A. Malo, T. Torii, Y. Sanada |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 2 ; Nr. 15, no. 2 (2015-01-30), S.1029-1070 |
| Datensatznummer |
250119353
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| Publikation (Nr.) |
 copernicus.org/acp-15-1029-2015.pdf |
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| Zusammenfassung |
| Temporal variations in the amount of radionuclides released into the
atmosphere during the Fukushima Daiichi Nuclear Power Station (FNPS1)
accident and their atmospheric and marine dispersion are essential to
evaluate the environmental impacts and resultant radiological doses to the
public. In this paper, we estimate the detailed atmospheric releases during
the accident using a reverse estimation method which calculates the release
rates of radionuclides by comparing measurements of air concentration of a
radionuclide or its dose rate in the environment with the ones calculated by
atmospheric and oceanic transport, dispersion and deposition models. The
atmospheric and oceanic models used are WSPEEDI-II (Worldwide version of
System for Prediction of Environmental Emergency Dose Information) and
SEA-GEARN-FDM (Finite difference oceanic dispersion model), both developed by the authors. A sophisticated deposition
scheme, which deals with dry and fog-water depositions, cloud condensation
nuclei (CCN) activation, and subsequent wet scavenging due to mixed-phase
cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2
and CH3I) and other particles (CsI, Cs, and Te), was incorporated into
WSPEEDI-II to improve the surface deposition calculations. The results
revealed that the major releases of radionuclides due to the FNPS1 accident
occurred in the following periods during March 2011: the afternoon of 12
March due to the wet venting and hydrogen explosion at Unit 1, midnight of
14 March when the SRV (safety relief valve) was opened three times at Unit
2, the morning and night of 15 March, and the morning of 16 March. According
to the simulation results, the highest radioactive contamination areas
around FNPS1 were created from 15 to 16 March by complicated interactions
among rainfall, plume movements, and the temporal variation of release
rates. The simulation by WSPEEDI-II using the new source term reproduced the
local and regional patterns of cumulative surface deposition of total
131I and 137Cs and air dose rate obtained by airborne surveys. The
new source term was also tested using three atmospheric dispersion models
(Modèle Lagrangien de Dispersion de Particules d'ordre zéro: MLDP0, Hybrid Single Particle
Lagrangian Integrated Trajectory Model: HYSPLIT, and Met Office's Numerical
Atmospheric-dispersion Modelling Environment: NAME) for regional and global calculations, and the
calculated results showed good agreement with observed air concentration
and surface deposition of 137Cs in eastern Japan. |
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