Direct Electrochemical Preparation Of Ni-Zr Alloy And U Metal In LiCl Molten Salt

In order to realize the nuclear wastes recycling,the pyroprocess has a great many of characteristic advantages due to simple process and less environmental pollution.The closed cycle of advanced spent fuel was advocated to improve the use efficiency of nuclear fuel in our country.The key question for the nuclear wastes recycling is that how to turn the nuclear fuel oxides into their metallic form which was used in fast reactor.The FFC process provides a novel thinking for this transition between oxide and metal.In this paper,the two representative kinds of oxide,ZrO₂ and UO₂,were selected and explored the possibility of their electrochemical reduction in molten LiCl at 923 K.ZrO₂ is a very representative non-radioactive oxide,which is widely served in industry,aerospace and other fields.However,the electrochemical reduction of ZrO₂ remains difficult because its high affinity to oxygen and extremely high thermodynamic stability.NiO powder can promote the electrochemical reduction of ZrO₂ to form Ni-Zr alloy.In this way,some experimental experience of electrochemical reduce oxides was accumulated.A stable and long-life reference electrode is generally used to monitor electrode reactions for three-electrode cell system.However,the generally traditional reference electrode was difficult to adapt the high temperature condition of the electrochemical reduction of oxide.Thus,the Li-Bi alloy reference electrode was prepared to realize the transition between two-electrode system and three-electrode system.UO₂ is the main component of spent fuel,and the cycle of spent fuel is mainly for U recycling.Therefore,it is of great significance to research the electrochemical reduction of UO₂.Thus,this paper mainly studies the following three aspects:1.The possibility of electrochemical reduction of NiO,ZrO₂ and NiO-ZrO₂mixture oxide were verified by theoretical calculation and cyclic voltammetry in molten LiCl at 923 K.The influence of different loading form,mole ratio,the conditions of prepare pellet and LiCl-Li₂O system on electrochemical reduction products was studied,and the surface morphology and composition of productions have been characterized and analyzed by XRD and SEM-EDS.2.An BN housed Li-Bi reference electrode which was fit for LiCl molten salt was fabricated used in molten LiCl at 923 K,and its stability,reusability,parallelity,reversibility and corrosion situation of BN tube were evaluated,respectively.3.Theoretical analysis and CVs prove the feasibility of electrochemical reduction of UO₂.The potential-current curves of empty STS and STS-UO₂ were measured to decide the electrolytic current and the cutoff voltage of electrochemical reduce UO₂.The U metal was prepared by appropriate constant current to electrochemical reduce UO₂ and evaluated electrolytic efficiency.The product composition and morphology were also analyzed by XRD and SEM-EDS.