NEUTRON THERMALIZATION IN LIQUID FLIBE

摘要

The molten salt material Li_2BeF_4 (FLiBe) has been widely proposed as a moderator and coolant material in nuclear reactor applications. Its usage and impact on neutron thermalization in the system requires accurate generation of FLiBe thermal neutron scattering libraries. In this work, liquid FLiBe is modeled using the classical molecular dynamics code LAMMPS. Experimental bounds are of liquid FLiBe properties are determined from reported databases. Predicted properties of FLiBe from molecular dynamics simulations including as density, viscosity, and atomic species diffusivities are computed and compared to the experimental results. To initiate the calculation sof the thermal neutron scattering law, the velocity autocorrelation functions are calculated from molecular dynamic atomic trajectories and subjected to Fourier transformation to obtain the density of states. Bound modes and translational modes of the density of states are separated to calculate the corresponding dynamic structure factor S_b (α, β) and S_(diff)(α, β) respectively. ENDF/B Ⅶ. 1 (i.e., File 7) thermal neutron scattering cross section libraries of F, Li, Be in FLiBe are generated at 873 K, 923 K and 973 K.