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| Titel |
An inverse modeling method to assess the source term of the Fukushima Nuclear Power Plant accident using gamma dose rate observations |
| VerfasserIn |
O. Saunier, A. Mathieu, D. Didier, M. Tombette, D. Quélo, V. Winiarek, M. Bocquet |
| 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 ; 13, no. 22 ; Nr. 13, no. 22 (2013-11-25), S.11403-11421 |
| Datensatznummer |
250085834
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| Publikation (Nr.) |
 copernicus.org/acp-13-11403-2013.pdf |
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| Zusammenfassung |
The Chernobyl nuclear accident, and more recently the Fukushima accident,
highlighted that the largest source of error on consequences assessment is
the source term, including the time evolution of the release rate and its
distribution between radioisotopes. Inverse modeling methods, which combine
environmental measurements and atmospheric dispersion models, have proven
efficient in assessing source term due to an accidental situation (Gudiksen,
1989; Krysta and Bocquet, 2007; Stohl et al., 2012a; Winiarek et al.,
2012). Most existing approaches are designed to use air sampling
measurements (Winiarek et al., 2012) and some of them also use deposition
measurements (Stohl et al., 2012a; Winiarek et al., 2014). Some studies
have been performed to use dose rate measurements (Duranova et al., 1999;
Astrup et al., 2004; Drews et al., 2004; Tsiouri et al., 2012) but none
of the developed methods were carried out to assess the complex source term
of a real accident situation like the Fukushima accident. However, dose rate
measurements are generated by the most widespread measurement system, and in
the event of a nuclear accident, these data constitute the main source of
measurements of the plume and radioactive fallout during releases. This
paper proposes a method to use dose rate measurements as part of an inverse
modeling approach to assess source terms.
The method is proven efficient and reliable when applied to the accident at
the Fukushima Daiichi Nuclear Power Plant (FD-NPP). The emissions for the
eight main isotopes 133Xe, 134Cs, 136Cs, 137Cs,
137mBa, 131I, 132I and 132Te have been assessed.
Accordingly, 105.9 PBq of 131I, 35.8 PBq of 132I, 15.5 PBq of
137Cs and 12 134 PBq of noble gases were released. The events
at FD-NPP (such as venting, explosions, etc.) known to have caused
atmospheric releases are well identified in the retrieved source term. The
estimated source term is validated by comparing simulations of atmospheric
dispersion and deposition with environmental observations. In total, it was
found that for 80% of the measurements, simulated and observed dose
rates agreed within a factor of 2. Changes in dose rates over time have been
overall properly reconstructed, especially in the most contaminated areas to
the northwest and south of the FD-NPP. A comparison with observed atmospheric
activity concentration and surface deposition shows that the emissions of
caesiums and 131I are realistic but that 132I and 132Te are
probably underestimated and noble gases are likely overestimated. Finally, an
important outcome of this study is that the method proved to be perfectly
suited to emergency management and could contribute to improve emergency
response in the event of a nuclear accident. |
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