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

doi:10.1038/s41598-017-05910-z

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

Sci Rep. 2017 Jul 14;7(1):5409. doi: 10.1038/s41598-017-05910-z.

Authors

Junpei Imoto¹, Asumi Ochiai¹, Genki Furuki¹, Mizuki Suetake¹, Ryohei Ikehara¹, Kenji Horie^{2

3}, Mami Takehara², Shinya Yamasaki⁴, Kenji Nanba⁵, Toshihiko Ohnuki⁶, Gareth T W Law⁷, Bernd Grambow⁸, Rodney C Ewing⁹, Satoshi Utsunomiya¹⁰

Affiliations

¹ Department of Chemistry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka-shi, Fukuoka, 819-0395, Japan.
² National Institute of Polar Research, 10-3, Midori-cho, Tachikawa-shi, Tokyo, 190-8518, Japan.
³ Department of Polar Science, The Graduate University for Advanced Studies (SOKENDAI), Shonan Village, Hayama, Kanagawa, 240-0193, Japan.
⁴ Faculty of Pure and Applied Sciences and Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan.
⁵ Department of Environment System Management, Faculty of Symbiotic Systems Science, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan.
⁶ Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan.
⁷ Centre for Radiochemistry Research, School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
⁸ SUBATECH, IMT Atlantique, the University of Nantes CNRS/IN2P3, Nantes, 44307, France.
⁹ Department of Geological Sciences and Center for International Security and Cooperation, Stanford University, Stanford, CA, 94305-2115, USA.
¹⁰ Department of Chemistry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka-shi, Fukuoka, 819-0395, Japan. utsunomiya.satoshi.998@m.kyushu-u.ac.jp.

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.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cesium Radioisotopes / analysis*
Fukushima Nuclear Accident*
Geography
Glass / analysis
Japan
Nuclear Power Plants*
Radiation Monitoring / methods*
Radioactive Pollutants / analysis
Silicon Dioxide / analysis
Uranium / analysis*

Substances

Cesium Radioisotopes
Radioactive Pollutants
Uranium-238
Uranium
Uranium-235
Silicon Dioxide