Characteristics of Oxidation Reaction of Rare-earth Chlorides for Precipitation in LiCl-KCl Molten Salt by Oxygen Sparging

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The precipitation reaction of some rare earth chlorides (La/Ce/Nd/GdCl3) in a LiCl-KCl molten salt has been carried out by using the oxygen sparging method. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for LaCl3, NdCl3 and GdCl3, and an oxide (REO2) for CeCl3 are formed as a precipitate. The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value at 1,023 K of the molten salt temperature condition. The conversion ratios of LaCl3, NdCl3 and GdCl3 were increased with the molten salt temperature, however, even though the conversion ratio was increased from 0.660 to 0.995 with increasing molten salt temperature from 823 to 923 K at 60 min of a sparging time, the values of the conversion ratio of CeCl3 were nearly constant (over 0.999) with the molten salt temperature. As a result of the thermogravimetric analysis of the precipitates (oxychlorides), about 11–13% of a weight loss happened in the case of LaOCl, NdOCl and GdOCl, and all the oxychlorides were converted to their oxides i.e. La2O3, Nd2O3 and Gd2O3 at a high temperature and oxygen atmosphere.
社団法人日本原子力学会の論文
2006-10-25