PChem Seminar – Byron Fisher

About the event

Speaker: Byron Fisher

Group: Dr. Xiaofeng Guo

Title: Computational Thermodynamics of Molten Salts

Abstract

Molten salts are corrosive, and the introduction of radiological materials such as Th, U, and Pu further complicates the chemistry through the multivalent states of both U and Pu and the production of fission products.

The chemistry present in molten salt reactors is quite complex; one has to take into consideration not just the thermodynamics of the component salts, but also the impurities that arise from fission products and partial dissolution of the containment vessel. Experimental measurements of high-entropy molten salts are difficult, so the ability to further evaluate their properties with sparse experimental data is desirable.

Computational thermodynamics enables elucidation of a system’s properties with limited experimental information. Atomic-scale properties can be determined using first-principles methods such as density functional theory (DFT) and molecular dynamics (MD) for macroscopic properties. The information obtained from computations can be combined with experimental measurements to further optimize parameters used for the CALculation of PHAse Diagrams (CALPHAD) method for thermodynamic modeling.

The phase diagrams and mixing enthalpies of several AlkaliCl-UCl3 binaries have been computed using the CALPHAD method with Pycalphad, an open-source software package for CALPHAD calculations. The mixing enthalpy of the LiCl-UCl3 binary was measured by drop-calorimetry, which can be used to improve the accuracy of the CALPHAD model. In addition, the properties of bulk Si and UO2 have been determined using classical and ab initio MD and benchmarked using heat capacity, density, and coefficients of thermal expansion.