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| Titel |
Atmospheric Radionuclides from the FDNPP Accident-Four years' observations in Tsukuba, Japan and immediate resuspension |
| VerfasserIn |
Yasuhito Igarashi, Mizuo Kajino, Yuji Zaizen, Kouji Adachi, Masao Mikami |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108233
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| Publikation (Nr.) |
 EGU/EGU2015-7977.pdf |
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| Zusammenfassung |
| The accident of Fukushima Dai-Ichi Nuclear Power Plant (FDNPP) of the Tokyo Electric
Power Corporation arisen by the hit of great earthquake and tsunami in March 11, 2011,
emitted abundant fresh radioactive material to the atmospheric environment. With 4-years’
observation for the Fukushima radioactivity at the Meteorological Research Institute, Japan
(MRI) the persisting resuspension has been observed. The resuspension seems still in
difficulty to give forecast by computer modeling; the observations are indispensable bodies of
the research even in the future.
As a primary approach, immediate re-suspension factors were roughly estimated
with modeled deposition amounts by the first plume to the Kanto district and the
observed minimum activity concentration between two plume events, i.e. Mar 17
09JST to Mar. 20 09JST, by assuming mass closure between re-suspension from the
contaminated surface and outflow by horizontal advection and turbulence vertical mixing as
follows:
Diki δCi- δ2Ci-
δz = U δx + Kz δz2 ,
where i indicates radionuclides namely 137Cs and 131I, Diindicates modeled total
(gas+aerosol) cumulative deposition (Bq/m2) by Mar 17 09JST, ki is the re-suspension factor
(/s), U and Kz are modeled space- and time- averaged horizontal wind speed (m/s) and
vertical turbulent diffusivity (m2/s), respectively, Ci indicates time-averaged observed
concentration of radionuclides (9.75x10-4 and 3.14x10-1 Bq/m3 for 137Cs and 131I,
respectively), and δx and δz are horizontal and vertical length of space where the above
mass closure is obtained. In order to obtain the horizontal and vertical gradient terms on the
right hand of the equation, concentrations outside the space are assumed zero (no inflow to
the space).
The re-suspension factors for 137Cs and 131I are 7.0x10-6 and 5.3x10-4 (/s),
respectively, for the smallest volume of space (δx and δz are 3 km and 100 m, respectively).
Those for 137Cs and 131I varied 1.6x10-6–1.5x10-5 (6.1x10-6 on average) and
5.3x10-4–1.3x10-3 (4.6x10-4 on average), respectively, for the various spaces of
horizontally plus-minus zero, one, or two grids from the grid center (i.e. δx = 3, 9, or 15 km)
and vertically plus zero, one, or two grids from the bottom (δz = 100, 200 or 400
m).
In summary, the immediate re-suspension factors for 137Cs and 131I are estimated in the
order of 10-6–10-5 (/s) and 10-4–10-3 (/s) respectively and then that of 131I is
approximately two orders of magnitude larger than that of 137Cs. |
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