Mineralogical characterization of radioactive particles from Fukushima soil using µ–XRD with synchrotron radiation

Radioactive particles of around 50 µm size were collected from highly contaminated soil in the Fukushima Prefecture, Japan, and characterized using micro X–ray diffraction with synchrotron radiation (SR–µ–XRD). Two–dimensional diffraction patterns from individual particles rotated during X–ray irradiation were recorded on a flat imaging plate and a one–dimensional diffraction profile, as a function of 2θ, was derived from the pattern. Weathered biotite (WB) particles with plate–like morphology showed a broad peak corresponding to a basal reflection with d = 10–14 Å, indicating various degrees of vermiculitization. Another peak of ∼ 7 Å was also detected in these WB particles, suggesting the parallel growth of kaolinite in the biotite particles. These characteristics were also found in the WB collected from an Abukuma granitic body, which is widespread in the eastern part of Fukushima. SR–µ–XRD of radioactive soil particles consisting of fine minerals or of those rich in organic matter indicated that these particles contain very fine 2:1 type clay minerals alongside detrital rock–forming minerals such as quartz and feldspar.