Caesium fallout in Tokyo on 15$^{th}$ March, 2011 is dominated by highly radioactive, caesium-rich microparticles

Abstract : In order to understand the chemical properties and environmental impacts of low-solubility Cs-rich microparticles (CsMPs) derived from the FDNPP, the CsMPs collected from Tokyo were investigated at the atomic scale using high-resolution transmission electron microscopy (HRTEM) and dissolution experiments were performed on the air filters. Remarkably, CsMPs 0.58-2.0 micrometer in size constituted 80%-89% of the total Cs radioactivity during the initial fallout events on 15th March, 2011. The CsMPs from Tokyo and Fukushima exhibit the same texture at the nanoscale: aggregates of Zn-Fe-oxide nanoparticles embedded in amorphous SiO2 glass. The Cs is associated with Zn-Fe-oxide nanoparticles or in the form of nanoscale inclusions of intrinsic Cs species,rather than dissolved in the SiO2 matrix. The Cs concentration in CsMPs from Tokyo (0.55-10.9 wt%) is generally less than that in particles from Fukushima (8.5-12.9 wt%).The radioactivity per unit mass of CsMPs from Tokyo is still as high as 1E11 Bq/g, which is extremely high for particles originating from nuclear accidents. Thus, inhalation of the low-solubility CsMPs would result in a high localized energy deposition by beta (0.51-12)*1E-3 Gy/h within the 100-micrometer-thick water layer on the CsMP surface) and may have longer-term effects compared with those predicted for soluble Cs-species.
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https://hal.archives-ouvertes.fr/hal-02266349
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Submitted on : Wednesday, August 14, 2019 - 8:13:39 AM
Last modification on : Wednesday, August 21, 2019 - 7:57:59 AM

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Satoshi Utsunomiya, Genki Furuki, Asumi Ochiai, Shinya Yamasaki, Kenji Nanba, et al.. Caesium fallout in Tokyo on 15$^{th}$ March, 2011 is dominated by highly radioactive, caesium-rich microparticles. 2019. ⟨hal-02266349⟩

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