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Okura, Takehisa; Feistenauer, P.*; Meisenberg, O.*; Shinonaga, Taeko*; Tschiersch, J.*
no journal, ,
The atmospheric radioactivity monitoring at Nuclear Science Research Institute, following the Fukushima accident was reviewed in this study. Comparison with measurement result of the filters at Helmholz Zentrum Muenchen (Germay) was made in order to discuss how to make an estimate of background under contaminated circumstance soon after the accident. Values of each other for samples with important level to estimate internal exposure was consistent; this points to that the adopted method to estimate background was appropriate. But some of samples with relative lower level were incompatible with each other. Penetration of radiocesium aerosols through HE-40TA was discussed with size distribution of radiocesium aerosols and characteristics of HE-40TA. Size distributions of radiocesium aerosols were evaluated experimentally, separated from HE-40TA and collected into a cascade impactor. The penetration was estimated by about 1% - 5%.
Okura, Takehisa; Meisenberg, O.*; Feistenauer, P.*; Shinonaga, Taeko*; Tschiersch, J.*
no journal, ,
Atmospheric radioactivity monitoring was made at Nuclear Science Research Institute, JAEA, following the Fukushima accident. Aerosol-bound radiocesium (Cs) was collected on paper filter (HE-40TA). In this study, to evaluate size distribution of the Cs, radioactive aerosols collected on HE-40TA was removed into distilled water, and then radioactive aerosols were extracted from the solution with a nebulizer and collected into a cascade impactor. The size distribution soon after the accident has one peak which is found around 0.3 
m. Corresponded temporal decreasing Cs concentration, the second peak which has median of 1-2 m was developed besides ca. 0.3-m-median peak at sites around field. The size distribution collected at a site in woods has only one peak after also significant decreasing of Cs concentration. It is presumed that the coarser-median peak was attributed to resuspended radioactivity, considered on the basis of distribution of radioactive aerosols on the filters observed with autoradiography and reference articles.