Abstract
The amount of addition of flux CaCl2 gives a singificiant effect on the yield of Th metal by Ca-reduction of ThO2. In order to clarify the role of CaCl2 in the Ca-reduction process, the defference in reducing rates of ThO2 by molten Ca and by saturated Ca in CaCl2, solubilities of Th, ThO2 in CaCl2 and molten Ca at 950°∼1050°C, have been examined. Furthermore, the distribution of each component (Th, ThO2, Ca, CaCl2, CaO) in reduction cake has been observed and the effects of briquetting and of stir of charge on the yield of Th have been examined. The results obtained are as follows: (1) The solubility of Th in CaCl2 at 950°C is very small (about 35 ppm), and that of ThO2 is nearly nil. (2) The reduction of ThO2 by saturated Ca in CaCl2 is more dominant than that by molten Ca, possibly due to the difference in removing rates of the CaO layer by two reducers. (3) The reducing power of Ca dissolved in CaCl2 decreases rapidly with decreasing Ca content. (4) The solubility of Th in molten Ca at 950°C is about 400 ppm. (5) The reduction cake is very porous and the distributions of Th, ThO2, CaCl2 do not show clear regularity, possibly due to high viscosity of charge at reduction temperature. (6) The briquetting of charge is effective in improving the yield of Th, especially in the shortening of the reduction time at relatively low temperatures. (7) The stir of charge at the reduction temperature is not effective for improvement of the yield.
