Atmospheric Fallout of ¹²⁹I in Japan before the Fukushima Accident: Regional and Global Contributions (1963–2005)

Atmospheric ¹²⁹I deposition was studied in different locations of Japan (Akita, Tsukuba, Tokyo, and Ishigaki Island) with samples collected between 1963 and 2005 in order to understand the distribution and sources of this nuclide and provide a reference deposition level prior to the Fukushima accident. Over this time period, the deposition pattern of ¹²⁹I in Tsukuba and Tokyo (on the Pacific side) differed from that of Akita (on the Japan Sea side). The primary source of deposition in Tsukuba and Tokyo is related to the ¹²⁹I discharge from domestic reprocessing in Tokai-mura. In contrast, the time-series pattern of deposition in Akita seems to have been influenced by ¹²⁹I discharges from reprocessing facilities in Europe and the transport of this radionuclide by westerly winds to coastlines of the Japan Sea. The ¹²⁹I deposition in Ishigaki (one of the southernmost islands in Japan) is influenced primarily by oceanic air masses (easterly winds), and deposition was 1 order of magnitude lower than that observed in Tsukuba and Tokyo. Cumulative ¹²⁹I deposition in Tokyo before the Fukushima accident was estimated at 13 mBq/m². The results of this study on deposition contribute to understanding the deposition levels of ¹²⁹I prior to the accident

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

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., Fe³⁺, Zn²⁺, Mo⁶⁺, and Sn⁴⁺ 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

Additional file 1 of Atmospheric resuspension of insoluble radioactive cesium-bearing particles found in the difficult-to-return area in Fukushima

Additional file 1. Supporting figures and tables

Technique for estimating the charge number of individual radioactive particles using Kelvin probe force microscopy

The Fukushima Daiichi Nuclear Power Plant accident in Japan resulted in the emission of many radioactive cesium (Cs)-containing particles that have charges on the surface due to self-charging. Charged aerosol particles are efficiently deposited inside human airways, leading to adverse health effects. To evaluate these effects, we developed a technique for estimating the charge number (np) of radioactive particles by measuring the surface potentials (Vp) of individual radioactive particles using Kelvin probe force microscopy. The Vp values of the individual CsCl particles were highly correlated with the surface np, indicating that Vp is a measure of the charged aerosol state. To further examine the Vp–np relationship, a simplified capacitance model was developed to estimate the ratio of Vp to np per unit area of particles. Although the calculated Vp was proportional to the np, consistent with our experiment, the calculated ratio was higher than those determined experimentally. The magnitude of this ratio may depend on the conductivity, microphysical properties and chemical composition of the particles. Despite these uncertainties, the experimentally determined Vp–np relationship of the CsCl particles was used to estimate the np of the radioactive and non-radioactive particles from the measurement of the Vp of these particles. It was demonstrated that the np of the radioactive particles was much higher than that of the non-radioactive particles, suggesting that radioactive particles are efficiently charged by self-charging. These charged radioactive particles may strongly cause adverse human health effects owing to their efficient deposition in human airways.</p