Fundamental Studies on Uranium Oxides. II : Equilibria among UO_2, U_4O_9 and U_3O_8 at 500〜1, 200℃
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概要
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Oxidation and reduction equilibria among UO_2, U_4O_9 and U_3O_8 were measured up to 1, 200℃ with a flow method. It was found that the knowledge about relationship among pO_2, O/U ratio and temperature in the first report could be extended to higher temperatures, and a new phase diagram of the UO_2-U_3O_8 System was proposed. In this temperature and composition range, there are three stoichiometric oxides, namely, UO_2, U_4O_9 and U_3O_8. UO_2 increases its oxygen solubility with rising temperature above 580℃ and below this temperature, the solubility increases with lowering temperature. The oxygen rich side of this region is heterogeneous and expressed as UO_<2+x>+U_4O_9. Its upper limit was found to be 1, 073℃. The temperature dependence of oxygen potential was given by the following equations : 2U_4O_9 =8UO_2 (saturated with O) + O_2, log PO_2=-53, 158/T+17.059 log T-0.02713T+17.715. Above 800℃ it may be simplified as follows : logPO_2 =-21, 884/T+11.265. In the composition range of U_4O_9-U_3O_8, it was found to be homogeneous solid solution up to 1, 200℃.
- 東北大学の論文
著者
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KIGOSHI Akiichi
The Research Institute of Mineral Dressing and Metallurgy
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SUDO Kingo
The Research Institute of Mineral Dressing and Metallurgy
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