Application of synchrotron radiation and other techniques in analysis of radioactive microparticles emitted from the Fukushima Daiichi Nuclear Power Plant accident-A review

Highlights: • Radioactive microparticles (RMs) were released from the Fukushima accident. • Synchrotron radiation techniques were applied to characterize these RMs. • Characteristics of these RMs were reviewed. • Comparison of RMs from the Fukushima and Chernobyl accidents was made. • Prospects for further characterization of RMs were demonstrated. - Abstract: During the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, large amounts of radioactive materials were released into the environment. Among them, a large proportion of the radionuclides, such as Cs, entered into the environment as radioactive microparticles (RMs). In recent years, the characterization of RMs based on synchrotron radiation (SR) techniques has been reported, since their physical and chemical properties played an important role in evaluating the chemical reactions and physical changes that occurred when the nuclear material meltdowns took place. In this review, we summarize separation and measurement technologies used in studies of RMs, and we emphasize the application of SR-based techniques in the characterization of RMs. We report research progress, including information for elemental composition, isotopic distribution, radioactivity, and formation processes. Also, we compare the RMs from the FDNPP and the Chernobyl Nuclear Power Plant accidents. The SR-based technologies offer great improvement in the resolution and precision compared to conventional technologies, such as X-ray fluorescence and X-ray diffraction.