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Toshihiro Kogure, Toru Hara, Masanori Mitome, Noriko Yamaguchi, B11-P-05
Complete Elemental Analysis of Silicate Microparticles Released from Fukushima Nuclear Reactors Using Microcalorimeter EDS in TEM , Microscopy, Volume 64, Issue suppl_1, November 2015, Page i80, https://doi.org/10.1093/jmicro/dfv209Close - Share Icon Share
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Explosion of Fukushima Daiichi nuclear plant in 2011 released significant amounts of radionuclide, particularly radioactive cesium, and brought radiation contamination in the environments around Fukushima. Most of radioactive cesium was supposed to be released in a vapour form and deposited on the land with rain fall. Besides, solid microparticles of a few micrometers in diameter flown directly from the broken reactor, in which radioactive cesium was detected by X-ray microanalysis, were also found on the aerosol filter [ 1 ] and later on the land [ 2 ]. TEM examination with microsampling and thin-film preparation by FIB revealed that the microparticles are basically amorphous silicate glass with distinct elements including Cl, K, Rb, Cs, Fe, Zn and Sn, from TEM-EDS analysis [ 2 ]. However, complete elemental analysis was difficult due to its low energy-resolution of conventional Si-based EDS detectors. The accurate elemental identification is important to discuss the origin of the microparticles and actual melt-down process occurred in the reactor. Therefore, we adopted microcalorimeter type EDS detector equipped on a STEM to identify the elements hidden by the spread peaks in the conventional EDS. The equipment used in this study is a transition-edge sensor type X-ray detector [ 3 ] attached on a Hitachi HD-2700 STEM. The energy resolution of this detector is around 10eV, more than ten-fold higher than the conventional EDS detector. From the analysis, we could find several new elements including Ca and confirm the absence of Al, Na, Zr and Ti in the microparticles. As a conclusion, microcalorimetric EDS is the irreplaceable technique for such analysis.
