[MAG41-P01] Discovering U particle with Zr from CsMP emitted from Unit 1 of FDNPP using synchrotron radiation X-ray analyses
Keywords:FDNPP accident, Cesium-bearing microparticle, Synchrotron radiation X-ray analysis
Method: In this study, we collected Type-A and B particles from road dusts and non-woven fabric cloths from Fukushima by a wet separation method. After measurement of radioactivity with a high-purity germanium semiconductor detector, scanning electron microscope and energy dispersive X-ray spectroscopy analyses were performed to confirm that separated particles were Type-A or Type-B particles. X-ray fluorescence (XRF) mapping and X-ray adsorption near edge structure (XANES) measurement were performed at BL37XU (SPring-8, Hyogo). Bent Crystal Laue Analyzer (BCLA) was used to detect U peaks, because energy of U Lα emission is close to energies of rubidium Kα and strontium Kα emissions.
Results: We could detect U in Type-A and B particles using BCLA which decreased background contribution about one tenth. U-enriched area in the Type-B particle was about several microns, which is much bigger than U nano-particle in Type-A particle reported by Ochiai et al. (2018). This difference in size possibly suggested that U particle in Type-B particle was derived from melt in contrast to that in Type-A particle possibly produced from vapor. XANES measurement showed the presence of U(IV) in Type-B particle but also U(VI) in Type-A and B particles, which suggested U(VI)O2 fuel was oxidized possibly due to its exposure to air at the surface of the particles. In the spots of detecting U, we also detected Zr which is used for fuel cladding tube. It is needed to identify chemical-states of Zr and U as a future study.