TY - JOUR
T1 - Uranium Dioxides and Debris Fragments Released to the Environment with Cesium-Rich Microparticles from the Fukushima Daiichi Nuclear Power Plant
AU - Ochiai, Asumi
AU - Imoto, Junpei
AU - Suetake, Mizuki
AU - Komiya, Tatsuki
AU - Furuki, Genki
AU - Ikehara, Ryohei
AU - Yamasaki, Shinya
AU - Law, Gareth T.W.
AU - Ohnuki, Toshihiko
AU - Grambow, Bernd
AU - Ewing, Rodney C.
AU - Utsunomiya, Satoshi
N1 - Funding Information:
The authors are grateful to Dr. Watanabe for her assistance on SEM analyses at the Center of Advanced Instrumental Analysis, Kyushu University. This study is partially supported by JST Initiatives for Atomic Energy Basic and Generic Strategic Research and by a Grant-in-Aid for Scientific Research (KAKENHI) from the Japan Society for the Promotion of Science (16K12585, 16H04634, JP26257402). S.U. is also supported by The Mitsubishi Foundation/Research Grants in the Natural Sciences and by ESPEC Foundation for Global Environment Research and Technology (Charitable Trust) (ESPEC Prize for the Encouragement of Environmental Studies). G.L. acknowledges UK NERC funding (NE/ M014088/1). The findings and conclusions by the authors of this paper do not necessarily state or reflect those of the JST.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/3/6
Y1 - 2018/3/6
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.est.7b06309
DO - 10.1021/acs.est.7b06309
M3 - Article
C2 - 29378406
AN - SCOPUS:85043350891
VL - 52
SP - 2586
EP - 2594
JO - Environmental Science & Technology
JF - Environmental Science & Technology
SN - 0013-936X
IS - 5
ER -