Optimization of UCl3 and MgCl2 separation from molten LiCl-KCl eutectic salt via galvanic drawdown with sacrificial Gd anode

Improvements in the galvanic reduction of UCl3 from LiCl-KCl-UCl3 molten salts are reported. This process has potential application for drawdown operations for electrorefiner salt. Short circuiting a gadolinium rod to a stainless steel basket causes a galvanic reaction which results in simultaneous reduction of UCl3 to U(0) and oxidation of Gd(0) to GdCl3. Two galvanic cell configurations were tested: one with the gadolinium metal inserted into the stainless steel basket, and one with the gadolinium metal separated from the stainless steel basket. When using a rotating basket and a physically separated gadolinium metal rod, concentration of uranium decreased from 0.168 to <0.00004 mol % within 105 min, representing over 99.97% removal from salt. Electrochemical potential measurements were recorded for the galvanic couple, and it was found that the potential became more negative during reduction process and leveled off when all of the UCl3 was reduced. In experiments in which MgCl2 was added to the salt as a surrogate for PuCl3, it was observed to co-deposit with the UCl3. Other rare earth chlorides (LaCl3, NdCl3, and CeCl3) were not removed from the salt during the reduction process.