Reduction of U3O8 in a High Temperature Molten LiCl-Li2O Salt

Abstract

Molten salts are regarded as excellent media for the electrochemical processes of metal oxides. The advanced spent fuel conditioning process (ACP) which has been developed at the Korea Atomic Energy Research Institute (KAERI) adopted a LiCl based molten salt for an electrolytic reduction process in order to reduce spent oxide fuels. In this work, the reduction of U3O8 without an electric current was investigated to establish the behavior of U3O8 in a molten LiCl–Li2O salt. The uranium oxide was reduced to UO2 by way of a substoichiometric solid solution of U–O and a lithium uranate in the form of LiUO3 which is produced from reduced form of U3O8 and Li2O in a melt, and the reduction proceeded almost linearly with time until 42 h in the current system of LiCl–3 wt% Li2O at 650°C. However, the reduced UO2 still contained a small amount of excess oxygen even after 75 h of a reduction.