Detection of Uranium and Chemical State Analysis of Individual Radioactive Microparticles Emitted from the Fukushima Nuclear Accident Using Multiple Synchrotron Radiation X-ray Analyses

Abstract

Synchrotron radiation (SR) X-ray microbeam analyses revealed the detailed chemical nature of radioactive aerosol microparticles emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, resulting in better understanding of what occurred in the plant during the early stages of the accident. Three spherical microparticles (∼2 μm, diameter) containing radioactive Cs were found in aerosol samples collected on March 14th and 15th, 2011, in Tsukuba, 172 km southwest of the FDNPP. SR-μ-X-ray fluorescence analysis detected the following 10 heavy elements in all three particles: Fe, Zn, Rb, Zr, Mo, Sn, Sb, Te, Cs, and Ba. In addition, U was found for the first time in two of the particles, further confirmed by U L-edge X-ray absorption near-edge structure (XANES) spectra, implying that U fuel and its fission products were contained in these particles along with radioactive Cs. These results strongly suggest that the FDNPP was damaged sufficiently to emit U fuel and fission products outside the containment vessel as aerosol particles. SR-μ-XANES spectra of Fe, Zn, Mo, and Sn K-edges for the individual particles revealed that they were present at high oxidation states, i.e., Fe(3+), Zn(2+), Mo(6+), and Sn(4+) in the glass matrix, confirmed by SR-μ-X-ray diffraction analysis. These radioactive materials in a glassy state may remain in the environment longer than those emitted as water-soluble radioactive Cs aerosol particles.

The seasonal variations of atmospheric 134,137Cs activity and possible host particles for their resuspension in the contaminated areas of Tsushima and Yamakiya, Fukushima, Japan

“…Another type of primary radiocesium emission has been reported to consist of glassy, water-insoluble particles with diameters of approximately 2 μm (Adachi et al 2013;Abe et al 2014;Yamaguchi et al 2016) and with high specific activity . These particles are stable at least for a few years in the environment and have recently been found at the ground surface (Satou et al 2016).…”

Atmospheric radioactivity over Tsukuba, Japan: a summary of three years of observations after the FDNPP accident

“…Adachi et al (2013) addressed this sort of contrast in the characteristics of the two plumes' radioactive aerosols in detail, and Abe et al (2014) added more information. They documented the discovery of insoluble, glassy spherules containing radioCs and assumed that the major fraction came from the first event.…”

Analysis of External Surface Irregularities on Fukushima-Derived Fallout Particles

“…Studies report preferential Cs sorption onto the interlayers (edge sites) both mica and clay-type minerals (Kogure et al, 2012;Mukai et al, 2014;Saito et al, 2014), where it is difficult to disassociate, and is subsequently transported, carried by the host particulate material. Additional studies have also identified Cs within larger material, including 1-2 µm diameter spherical particles (Adachi et al, 2013;Abe et al, 2014;Kogure et al, 2016). Typically employing air-sampling apparatus (located 170 km south west of the facility) in addition to ground-sampled material (tens of kilometers from the plant), some of these studies have also located the existence of uranium species (Martin et al, 2016) within the cores of several of these ejecta fragments (Abe et al, 2014;Kogure et al, 2016).…”

“…Additional studies have also identified Cs within larger material, including 1-2 µm diameter spherical particles (Adachi et al, 2013;Abe et al, 2014;Kogure et al, 2016). Typically employing air-sampling apparatus (located 170 km south west of the facility) in addition to ground-sampled material (tens of kilometers from the plant), some of these studies have also located the existence of uranium species (Martin et al, 2016) within the cores of several of these ejecta fragments (Abe et al, 2014;Kogure et al, 2016). Whereas some of the material encountered contains actinide species, and others do not, in each instance, the major component of the material analyzed is silicon-constituting the bulk of the material alongside other light and transition elements including C, O, Na, Mg, Al, K, Ca, Fe, and Zn.…”

“…The external surfaces of the spherical material have been shown to be highly smooth and regular (Adachi et al, 2013;Abe et al, 2014), with the larger-sized particles exhibiting significantly greater angularity and number of surface morphological features (Satou, 2016). Several fragments of particulate on the same micron length-scale of the spherical material, collected at 20 km from the FDNPP, have recently been isolated and found to also exhibit marked angularity .…”