Experimental observations on electrorefining spent nuclear fuel in molten LiCl-KCl/liquid cadmium system

Argonne National Laboratory (ANL) has developed and demonstrated an electro metallurgical process for the Department of Energy (DOE) which processes sp ent nuclear fuel from the Experimental Breeder Reactor (EBR-II). One of the key steps in this demonstration was electrorefining of the spent fuel in a molten LiCl-KCl/liquid cadmium system using a pilot scale electrorefiner ( Mk-IV ER). This article summarizes experimental observations and engineerin g aspects for electrorefining spent fuel in the molten LiCl-KCl/liquid cadm ium system. It was found that the liquid cadmium pool acted as an intermedi ate electrode during the electrorefining process in the ER. The cadmium lev el was gradually decreased due to its high vapor pressure and vaporization rate at the ER operational temperature. The low cadmium level caused the an ode assembly momentarily to touch the ER vessel hardware, which generated a periodic current change at the salt/cathode interface and improved uranium recovery efficiency for the process. The primary current distributions cal culated by numerical simulations were used in interpreting the experimental results.