Molecular Dynamics Simulation of the Structure and Transport Properties of LiF-ThF4

Leslie Dewan, Massachusetts Institute of Technology

Molten salt reactors (MSRs) are an innovative Generation IV nuclear reactor concept with numerous benefits in terms of safety and actinide management. While conventional light-water reactors use a solid uranium oxide fuel and a water coolant, the fuel for an MSR is dissolved in a molten salt. The molten salt thereby acts as both fuel and coolant in the reactor.

The temperature and ionic composition of the salt has a large influence on its structure and transport properties, which in turn have significant effects on a nuclear reactor’s thermohydraulic behavior. Many structure and transport properties can be probed by experimental techniques, but the available data are currently sparse. Furthermore, it is difficult to measure some transport properties, such as diffusion coefficients, of these high-temperature, corrosive liquids in an experimental setting. Molecular dynamics (MD) simulations, however, are well-suited to evaluating a system’s structure and transport properties, and can therefore be used successfully to fill in the gaps in existing experimental data.

This research uses MD potentials of ab initio accuracy that incorporate polarization effects to simulate a molten LiF-ThF4 mixture at the eutectic composition (78mol%LiF-22mol%ThF4) at a range of temperatures. This research examines the self-diffusion coefficients, electrical conductivity, viscosity, and structural properties at a range of temperatures from 825 K to 1,100 K.

Abstract Author(s): Leslie Dewan (MIT), Linn Hobbs (MIT), Mathieu Salanne (UPMC, Paris, France)