This paper describes an empirically demonstrated mechanism of UO2-ZrO2 cathode deposit formation during the (NaCl-KCl)(equim).-UO2-Cl-2-ZrCl4 melts electrolysis. The first layer of the cathode product was formed through UO22+ ion reduction to uranium dioxide followed by an exchange reaction with Zr4+ ions, which are present in the electrolyte. The subsequent reactions proceeded through simultaneous reduction and exchange reactions at the cathode. (C) 2013 Elsevier Ltd. All rights reserved.