Phase State and Physical Properties of the Mo-Ru-Ph-Pd Alloys

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Phase State and Physical Properties of the Mo-Ru-Ph-Pd Alloys Tohru Sugahara1, Ken Kurosaki1, Aikebaier Yusufu1, Hiroaki Muta1, Yuji Ohishi1, Shinsuke Yamanaka1, 2, Satoshi Komamine3, Eiji Ochi3 1 Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan 2 Research Institute of Nuclear Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 9108507, Japan 3 Japan Nuclear Fuel Limited, 4-108 Okitsuke Obuchi, Rokkasho, Kamikita, Aomori 039-3212, Japan ABSTRACT Mo3Ru5MPd (M = Ru, Rh, Pd) as the simulated materials for the undissolved residue in the nuclear fuel reprocessing were prepared by arc melting method. The physical properties and oxidation behavior of the alloys were evaluated from viewpoint of the safety and economy in the reprocessing. The electrical resistivity, ȡ, of Mo3Ru5RhPd was shown to be 0.8 ȝȍm at room temperature. On the other hand, the ȡ values of samples without Rh were marked at 0.4 ȝȍm. The thermal properties of the each sample had the different thermal transfer characteristics. In particular, although the thermal conductivities of Mo3Ru5RhPd and Mo3Ru5Pd2 samples show almost the same value, the lattice thermal conductivities of both samples showed different values. Oxidation behavior was analyzed using the thermogravity(TG) and differential thermal analyses(DTA). The TG curve of each sample by oxidation showed different results. These results indicate that the simulated materials of the alloys without Rh: Mo-Ru-Pd were not appropriate to simulate the thermophysical characteristics of the typical simulated materials with undissolved residue Mo-Ru-Rh-Pd alloys. Therefore, in the spent nuclear fuel reprocessing, the mock test of reprocessing without to use Rh is difficult to carry out. INTRODUCTION In the spent nuclear fuel reprocessing, one of the most important subjects is to understand the chemical and physical behavior of fission products. In the reprocessing, dissolving in nitric acid to fission products, generate high-level waste containing fission products. Then these highlevel waste liquid is solved in glass melts. Recently, a lot of perovskite structural type oxides and MoTcRuRhPd alloys have been observed in the irradiated fuel1-6 as fission products. From the point of view to understand behavior on the nuclear fuel and reprocessing process, the thermochemical and thermophysical properties of oxides and alloys have been systematically studied7-19. It has been well known that the alloys containing Mo, Tc, Ru, Rh, and Pd are undissolved in the nitric acid of the high-level waste liquid under the reprocessing and exist as the undissolved residues. Additionally, it has been thought that several constituent elements of the undissolved residues are oxidized by a variety of conditions in the glass melter. However, the thermophysical properties and oxidation behavior of the undissolved residues were scarcely reported. In the spent nuclear fuel reprocessing process, the detail data of the physical properties and oxidation behavior in the glass melts of the undiss

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