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| Titel |
Detailed source term estimation of atmospheric release during the Fukushima Dai-ichi nuclear power plant accident by coupling atmospheric and oceanic dispersion models |
| VerfasserIn |
Genki Katata, Masamichi Chino, Hiroaki Terada, Takuya Kobayashi, Masakazu Ota, Haruyasu Nagai, Mizuo Kajino |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095802
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| Publikation (Nr.) |
 EGU/EGU2014-11276.pdf |
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| Zusammenfassung |
| Temporal variations of release amounts of radionuclides during the Fukushima Dai-ichi
Nuclear Power Plant (FNPP1) accident and their dispersion process are essential to evaluate
the environmental impacts and resultant radiological doses to the public. Here, we estimated
a detailed time trend of atmospheric releases during the accident by combining
environmental monitoring data and coupling atmospheric and oceanic dispersion simulations
by WSPEEDI-II (Worldwide version of System for Prediction of Environmental
Emergency Dose Information) and SEA-GEARN developed by the authors. New
schemes for wet, dry, and fog depositions of radioactive iodine gas (I2 and CH3I)
and other particles (I-131, Te-132, Cs-137, and Cs-134) were incorporated into
WSPEEDI-II. The deposition calculated by WSPEEDI-II was used as input data of ocean
dispersion calculations by SEA-GEARN. The reverse estimation method based on
the simulation by both models assuming unit release rate (1 Bq h-1) was adopted
to estimate the source term at the FNPP1 using air dose rate, and air sea surface
concentrations. The results suggested that the major release of radionuclides from the
FNPP1 occurred in the following periods during March 2011: afternoon on the 12th
when the venting and hydrogen explosion occurred at Unit 1, morning on the 13th
after the venting event at Unit 3, midnight on the 14th when several openings of
SRV (steam relief valve) were conducted at Unit 2, morning and night on the 15th,
and morning on the 16th. The modified WSPEEDI-II using the newly estimated
source term well reproduced local and regional patterns of air dose rate and surface
deposition of I-131 and Cs-137 obtained by airborne observations. Our dispersion
simulations also revealed that the highest radioactive contamination areas around
FNPP1 were created from 15th to 16th March by complicated interactions among
rainfall (wet deposition), plume movements, and phase properties (gas or particle) of
I-131 and release rates associated with reactor pressure variations in Units 2 and 3. |
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