Liquid salts and metals can be effectively employed for separating fissile materials from fission products in reprocessing high burn-up nuclear fuels with short cooling time. Separation factor Θ depends on the electrode potentials (E*) of separating element in the salt phase and their activity coefficients (γ) in the metallic alloy. If the separating metals form the ions in the same oxidation state (like actinides and lanthanides), the separation factor can be expressed as lgΘMe1/Me2 = [n F / (2.303 R T)] (E*Me2 – E*Me1) + (lgγMe1 – lg γMe2). In the present study the effect of temperature, cationic composition of alkali chloride based melts, and composition of the liquid metal were considered and separation of uranium from neodymium was taken as an example. Gallium, indium, tin and their mixtures (Ga-In, Ga-Al, Ga-Sn) of various compositions were used. Thermodynamic and electrochemical properties of uranium and neodymium were determined between 573-1073 K thus allowing to model separation processes. Cationic composition of the salt phase has little effect on the separation factor whilst the effect of the metallic phase nature is substantially more pronounced. Decreasing temperature increases Θ value. Calculated Nd/U separation factors for various liquid metals and LiCl-KCl-CsCl eutectic melt are presented in the Fig. To confirm the results of calculations, experiments on separating Nd and U were performed. This work was supported by the Government of the Russian Federation (Act 211, contract 02.A03.21.0006).

Separation of 4f- and 5f-elements in a “fused salt – liquid metal” system

251st National Meeting (2016)

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