Molecular Dynamics and Experimental Study of the Effect of CeF and NdF Additives on the Physical Properties of FLiNaK.

The paper presents the results, which are consistent within 2%, obtained both in the simulation of molecular dynamics and in the experiment on the study of the kinetic properties of molten FLiNaK with addition of lanthanide fluorides. The parameters of the Born-Huggins-Meier potential for the interaction of CeF or NdF with FLiNaK components are first calculated using the ab initio approach. The enthalpy of the system with dissolved CeF or NdF calculated in the model increases by ∼4.4% over the entire temperature range studied (800 ≤ ≤ 1020 K). The self-diffusion coefficients of the molten salt components are calculated from the Einstein relation and also estimated from the shear viscosity data. The temperature dependences of the shear viscosity of molten FLiNaK as well as FLiNaK with additions of 15 mol % CeF or NdF are determined experimentally and by calculation. In addition, the dependence of shear viscosity on the concentration of CeF and NdF in FLiNaK is measured and calculated. The linear growth of the shear viscosity with the CeF and NdF concentrations is obtained. Experimental dependence is in good agreement with the simulated results in the case of NdF, and there is the discrepancy while CeF addition. An analytical approximation of the temperature and concentration dependences for the viscosity of molten FliNaK and for the calculated self-diffusion coefficients of constituent elements is proposed. Linear approximation of temperature dependence of the self-diffusion coefficients of similar components in the corresponding extended systems is presented.