Synthesis of U3+ with Cd2+ or Bi3+ was investigated in a LiCl-KCl eutectic melt at 500 degrees C by using cyclic voltammetry (CV) and ultraviolet-visible (UV-vis) spectroscopy. CV results showed that the equilibrium potentials of the species are larger in sequence of U0/3+< Cd0/2+ < U3+/4+ < Bi0+/3+. UV-vis spectroscopy results exhibited that U3+ was directly produced in the eutectic melt containing Cd2+. In BiCl3, U metal was oxidized to U4+ by Bi3+, and then U4+ was reduced to U3+ by additional U. From these results, the reaction mechanisms taking place during the synthesis are proposed. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3465303] All rights reserved.