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. 2016 Feb 3:6:20548.
doi: 10.1038/srep20548.

Internal structure of cesium-bearing radioactive microparticles released from Fukushima nuclear power plant

Noriko Yamaguchi  1 , Masanori Mitome  2 , Akiyama-Hasegawa Kotone  2 , Maki Asano  1   3 , Kouji Adachi  4 , Toshihiro Kogure  5
Affiliations

Internal structure of cesium-bearing radioactive microparticles released from Fukushima nuclear power plant

Noriko Yamaguchi et al. Sci Rep. .

Abstract

Microparticles containing substantial amounts of radiocesium collected from the ground in Fukushima were investigated mainly by transmission electron microscopy (TEM) and X-ray microanalysis with scanning TEM (STEM). Particles of around 2 μm in diameter are basically silicate glass containing Fe and Zn as transition metals, Cs, Rb and K as alkali ions, and Sn as substantial elements. These elements are homogeneously distributed in the glass except Cs which has a concentration gradient, increasing from center to surface. Nano-sized crystallites such as copper- zinc- and molybdenum sulfide, and silver telluride were found inside the microparticles, which probably resulted from the segregation of the silicate and sulfide (telluride) during molten-stage. An alkali-depleted layer of ca. 0.2 μm thick exists at the outer side of the particle collected from cedar leaves 8 months after the nuclear accident, suggesting gradual leaching of radiocesium from the microparticles in the natural environment.

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Figures

Figure 1
Figure 1
(a) Bright-field (BF) image of NWC-1. The opaque material outside the microparticle is tungsten (W) and copper (Cu) deposited in the FIB process. (b) Electron diffraction (ED) pattern from the particle. (c,d) EDS spectrum acquired from almost the whole area of the particle for the energy range of (c) 0–11 keV and (d) 10–30 keV. (e) BF image of CB-8. The opaque material outside the sphere is W and the thin transparent material is Kapton tape. (f) ED pattern from the particle.
Figure 2
Figure 2
(a) Element maps of NWC-1 acquired by STEM-EDS with a STEM Dark-field (DF) image at the same area, and (top) TEM Bright-field image in which the rectangle indicates the area analyzed by STEM-EDS. The thin area around the top of the particle which was not observed in Fig. 1a was formed by a further thinning process by FIB. (b) Element maps and images of CB-8 with the same framing as in (a).
Figure 3
Figure 3
(a) Element maps and STEM bright-field (BF) image of the two nanoparticles inside NWC-1. The circular contrasts outside the nanoparticles in the BF image are radiation damage in glass formed by the electron probe for chemical analyses. (b) (Left) ED pattern from the left nanoparticle. (Right) Drawing of ED pattern for the high-temperature polymorph of digenite (Cu2−xS) along <121>.
See this image and copyright information in PMC

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