Chlorination of uranium and rare-earth oxides by use of ZrCl_4 in molten LiCl-KCl

摘要

A new chlorination method using ZrCl_4, which has a high reactivity with oxygen, has been investigated for pyrometallurgical reprocessing of nuclear fuels. After actinide oxides are chlorinated and dissolved in a molten chloride salt bath, actinide metals can be selectively collected using the electrorefining process. The behavior of ZrCl_4 in a LiCl-KCl eutectic melt was studied by cyclic voltammetry and the solubility of ZrCl_4 in the salt was measured. Then, the chlorination of rare-earth oxides (Y_2O_3, La_2O_3, CeO_2, and Nd_2O_3) and UO_2 with ZrCl_4 was examined in the salt bath at 773 K. As a result, the rare-earths and uranium were dissolved into the salt as trivalent ions and ZrO_2 was precipitated. When the oxides were in powder form, the reaction was observed to progress rapidly. The oxides were completely chlorinated by adding an excess of ZrCl_4. It was demonstrated that the ZrCl_4 chlorination method, free from corrosive gas such as chlorine, was very simple and useful.