Analysis of particles containing alpha emitters in stagnant water in Fukushima Daiichi Nuclear Power Station's Unit 3 reactor building.

Particles containing alpha (α) nuclides were identified from sediment in stagnant water in the Unit 3 reactor building of the Fukushima Daiichi Nuclear Power Station (FDiNPS). We analyzed different concentrations of α-nuclide samples collected at two sampling sites, the torus room and the main steam isolation valve (MSIV) room. The solids in the stagnant water samples were classified, and the uranium (U) and total alpha concentrations of each fraction were measured by dissolution followed by inductively coupled plasma mass spectrometry and α-spectrometry. Most of the α-nuclides in the stagnant water samples from the torus and MSIV rooms were in particle fractions larger than 10 µm. We detected uranium-bearing particles ranging from sub-µm to 10 µm in size by scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) observations. The chemical forms of U particles were determined in U-Zr oxides, oxidized UO2, and U3O8 with micro-Raman spectroscopy. Other short-lived α-nuclides (plutonium [Pu], americium [Am], and curium [Cm]) were detected by alpha track detection, and the particles with α-nuclides was characterized by SEM-EDX analysis. α-nuclide-containing particles with several tens to several 100 µm in size mainly comprised iron (Fe) oxyhydroxides. In addition, we detected adsorbed U onto Fe oxyhydroxide particles in the MSIV room sample, which indicated nuclear fuel dissolution and secondary U accumulation. This study clarifies the major characteristics of U and other α-nuclides in sediment in stagnant water in the FDiNPS Unit 3 reactor building, which significantly contribute to the consideration of removal methods for particles containing α-nuclides in the stagnant water.

Selective Pd Separation from Simulated Radioactive Liquid Waste by Precipitation Using Xenon Lamp Irradiation for a Simplified Procedure.

In this study, we developed a simple and one-step Pd separation technique based on photoreduction with Xe lamp irradiation for the determination of 107Pd in highly radioactive samples. A simulated high-level radioactive liquid wastes (HLLW) solution, consisting of 14 major elements in a 3 mol L-1 HNO3 solution, was used to evaluate the separation performance. The Pd precipitate was formed by Xe lamp irradiation, and recovered by centrifugation. The Pd recovery from the simulated HLLW solution reached up to 50%, while 99.5% of the other 13 elements was separated. These results indicate that the applicability of the proposed separation technique to HLLW samples.