Method for Removal of Heavy Metal from Molten Salt

Abstract

The pyrometallurgical process for recycling spent metal fuels from the Integral Fast Reactor (IFR) involves electrorefining spent fuel in a molten salt electrolyte (LiCl-KCl-U/PuCl3) at 500°C. At some point, the concentrations of alkali, alkaline earth, and rare earth fission products in the salt must be reduced to lower the amount of heat generated in the electrorefiner. The heavy metal concentration in the salt must be reduced before removing fission products from the salt. The operation uses a lithium-cadmium alloy anode that is solid at 500°C and a solid mandrel cathode. In tests conducted in an engineering-scale electrorefiner (10 kg uranium per cathode), good separation was achieved while removing uranium and rare earths from the salt. Only 13% of the rare earths was removed, while 99.9 % of the uranium in the salt was removed; subsequently, the rare earths were also reduced to low concentrations.