Uranium Dioxides and Debris Fragments Released to the Environment with Cesium-Rich Microparticles from the Fukushima Daiichi Nuclear Power Plant 29 Jan 2018


Uranium Dioxides and Debris Fragments Released to the Environment with Cesium-Rich Microparticles from the Fukushima Daiichi Nuclear Power Plant
Asumi Ochiai†, Junpei Imoto†, Mizuki Suetake†, Tatsuki Komiya†, Genki Furuki†, Ryohei Ikehara†, Shinya Yamasaki‡, Gareth T. W. Law§ , Toshihiko Ohnuki∥, Bernd Grambow⊥, Rodney C. Ewing#, and Satoshi Utsunomiya*†
† Department of Chemistry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
‡ 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
§ Centre for Radiochemistry Research, School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
∥ Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
⊥ SUBATECH, IMT Atlantique, CNRS-IN2P3, University of Nantes, Nantes 44307, France
# Department of Geological Sciences and Center for International Security and Cooperation, Stanford University, Stanford, California 94305-2115, United States
Environ. Sci. Technol., Article ASAP
DOI: 10.1021/acs.est.7b06309
Publication Date (Web): January 29, 2018
Copyright © 2018 American Chemical Society
*E-mail: utsunomiya.satoshi.998@m.kyushu-u.ac.jp.


Trace U was released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) during the meltdowns, but the speciation of the released components of the nuclear fuel remains unknown. We report, for the first time, the atomic-scale characteristics of nanofragments of the nuclear fuels that were released from the FDNPP into the environment. Nanofragments of an intrinsic U-phase were discovered to be closely associated with radioactive cesium-rich microparticles (CsMPs) in paddy soils collected ∼4 km from the FDNPP. The nanoscale fuel fragments were either encapsulated by or attached to CsMPs and occurred in two different forms: (i) UO2+X nanocrystals of ∼70 nm size, which are embedded into magnetite associated with Tc and Mo on the surface and (ii) Isometric (U,Zr)O2+X nanocrystals of ∼200 nm size, with the U/(U+Zr) molar ratio ranging from 0.14 to 0.91, with intrinsic pores (∼6 nm), indicating the entrapment of vapors or fission-product gases during crystallization. These results document the heterogeneous physical and chemical properties of debris at the nanoscale, which is a mixture of melted fuel and reactor materials, reflecting the complex thermal processes within the FDNPP reactor during meltdown. Still CsMPs are an important medium for the transport of debris fragments into the environment in a respirable form.

Further information: https://www.kyushu-u.ac.jp/en/researches/view/88