Preliminary studies on preparation of U-Al alloy by electro-reduction of UO₂-Al₂O₃ mixed oxide in LiCl-Li₂O melt

Uranium–aluminium alloys have widespread application in nuclear industry. The alloy has been used as nuclear fuel elements in nuclear research reactors and as target for preparation of medical radio-isotopes. KAMINI research reactor in IGCAR uses ²³³U (20%)–Al alloy plates with Al clad as the fuel. UAl₂ is also considered for rod type fuel elements because of its high thermal conductivity and high melting point. Generally these alloys are prepared by induction or arc melting or by solid state reactions all of which are multi-step processes and needs specialised equipment operating at very high temperature and vacuum. Herein, we report the feasibility of preparation of U-Al alloy in a single step employing Direct Oxide Electro Reduction (DOER) method. Initially, cyclic voltammetry studies were performed using metallic cavity electrode to find the reduction steps involved during electro-deoxidation. The cathodic peak at – 2.16 V (A,B) against Ni. NiO was assigned to the reduction of both UO₂ and Al₂O₃. The feasibility of preparation of U-Al alloy was attempted by electro-lithiothermic reduction of UO₂-Al₂O₃ composite in LiCl-Li₂O molten salt. The composition of UO₂ and Al₂O₃ used in this study corresponded to the metal molar ratio of 1:3 (U:Al). Constant current electrolysis was performed on a sintered composite pellet configured as the cathode using platinum anode in LiCl-0.5wt% Li₂O melt at 630°C. At this condition, UO₂-Al₂O₃ composite reacted with in-situ electro-generated lithium and converted into alloy