Physical Properties of Salt Fluoride Melts in the Presence of Tritium: Ab Initio Modeling

Understanding the structure and electronic properties of the eutectic FLiNaK melt (LiF‐NaF‐KF) with dissolved tritium and uranium fluorides is crucial for molten salt reactors (MSRs) to close the nuclear fuel cycle. These data inform corrosion resistance, tritium management, fuel behavior, and thermal‐hydraulic design. In this study, first‐principles molecular dynamics calculations are used to study the structural changes of the molten LiF–NaF–KF system upon the addition of uranium trifluoride and tetrafluoride and/or tritium in the temperature range from 750 to 1050 K. Isobaric heat capacity and partial cation‐anion radial distribution functions are calculated. A statistical geometry method based on the construction of Voronoi polyhedra is used to describe the tritium environment in the model in detail. The relationship between the volumes of space potentially available for the motion of a tritium atom in the melt and the trajectories of this atom is examined. Partial spectrum of the electron density of states is determined for the molten salt FLiNaK, including that containing 3 H. The obtained results expand the database on the physical properties of LiF–NaF–KF molten salt systems containing uranium and tritium fluorides and can serve to develop and expand their applications.