Formation of intermetallics during the metallization of model nuclear fuel based on uranium dioxide containing oxides of rare earth metals and palladium

Abstract

The paper considers the reduction of rare earth metal (REM) oxides and uranium dioxide with lithium produced during the electrolysis of LiCl–Li₂O melt with the formation of intermetallics and palladium. At a cathode potential of 0.6–0.8 V relative to \(E_{{\mathrm{Li}^{+}}/{\mathrm{Li}^{0}}}\), intermetallic compounds of CePd₃, NdPd₃, and UPd₄ compositions are formed. The formation current for REM intermetallic compounds is significantly greater than that for uranium. Therefore, when they are co-present in samples, REM intermetallics are formed first, followed by intermetallic compounds of uranium in the presence of palladium unbound by REM alloys. This is due to the significantly greater solubility of neodymium and cerium oxides in the salt melt compared to uranium dioxide. At a cathode potential close to or equal to the potential of liquid lithium, intermetallics with palladium, lanthanides, and uranium Ln₃Pd₄, LnPd, UPd₃ are formed. In this case, an important role is played by the ability of lithium and palladium to form alloys that are liquid at 650 °C.