Chemical Behavior of Fission Products in the Pyrochemical Process

The chemical behavior of lanthanide oxides has been studied both for the electrolytic reduction process and the electrorefining process. At high concentration of Li₂O in LiCl, lanthanide oxides reacted with Li₂O to form mixed oxides, LiLnO₂ (Ln = lanthanides), which decomposed to the starting materials at relatively low Li₂O concentration. The chemical behavior of lanthanide oxides under the condition of electrorefining process was investigated by optical fiber spectrophotometry and X-ray diffraction. Lanthanide oxides reacted with U³⁺ to produce Ln³⁺ and UO₂. The solubility of lanthanide oxides was measured under the electrolytic reduction and the electrorefining condition. All of the lanthanide oxides except Eu₂O₃ had relatively low solubility values in LiCl-KCl eutectic mixture at 450°C. Electrochemical behavior of Br^-, I^-, and Se^2- in LiCl was also investigated by cyclic voltammetry and by X-ray diffraction. All of the anions reacted with platinum anode and gave platinum compounds.