Activity coefficients of plutonium and cerium in liquid gallium at 1073 K: Application to a molten salt/solvent metal separation concept

Activity coefficients in liquid metal and salt phases are important parameters for predicting the separation efficiency of reductive extraction or electrochemical pyrochemical processes. The electrochemical properties of Ce and Pu in gallium metal and chlorides media – CaCl2 and equimolar NaCl–KCl – have been studied at 1073 K. Cyclic voltammetry and chronoamperometry show the thermodynamic feasibility of using gallium as solvent metal for pyrochemical processes involving Pu and Ce. The activity coefficient of Pu in liquid Ga (log(γPu,Ga) = −7.3 ± 0.5) is deduced from the results and is a basis of assessing the potential for using liquid metals in pyrochemical separation of actinides and lanthanides. Evaluation of literature data for Al, Bi and Cd suggests that Ga is most favorable for selective separation of Pu from Ce near 1073 K.