Isotopic signature and nano-texture of cesium-rich micro-particles: Release of uranium and fission products from the Fukushima Daiichi Nuclear Power Plant

Junpei Imoto, Asumi Ochiai, Genki Furuki, Mizuki Suetake, Ryohei Ikehara, Kenji Horie, Mami Takehara, Shinya Yamasaki, Kenji Nanba, Toshihiko Ohnuki, Gareth T.W. Law, Bernd Grambow, Rodney C. Ewing, Satoshi Utsunomiya

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Highly radioactive cesium-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) provide nano-scale chemical fingerprints of the 2011 tragedy. U, Cs, Ba, Rb, K, and Ca isotopic ratios were determined on three CsMPs (3.79-780 Bq) collected within ~10 km from the FDNPP to determine the CsMPs' origin and mechanism of formation. Apart from crystalline Fe-pollucite, CsFeSi2O6 · nH2O, CsMPs are comprised mainly of Zn-Fe-oxide nanoparticles in a SiO2 glass matrix (up to ~30 wt% of Cs and ~1 wt% of U mainly associated with Zn-Fe-oxide). The 235U/238U values in two CsMPs: 0.030 (±0.005) and 0.029 (±0.003), are consistent with that of enriched nuclear fuel. The values are higher than the average burnup estimated by the ORIGEN code and lower than non-irradiated fuel, suggesting non-uniform volatilization of U from melted fuels with different levels of burnup, followed by sorption onto Zn-Fe-oxides. The nano-scale texture and isotopic analyses provide a partial record of the chemical reactions that occurred in the fuel during meltdown. Also, the CsMPs were an important medium of transport for the released radionuclides in a respirable form.

    Original languageEnglish
    Article number5409
    JournalScientific Reports
    Volume7
    Issue number1
    Early online date14 Jul 2017
    DOIs
    Publication statusPublished - 2017

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