Viscosity of molten lithium, thorium and beryllium fluorides mixtures

Considering development of Molten Salt Fast Reactor (MSFR) concept, following Molten Salt fluorides mixtures have been chosen as an object for viscosity studies in this work (in mol%): 78LiF–22ThF4; 71LiF–27ThF4–2BeF2 and 75LiF–20ThF4–5BeF2. Additionally, the effect of the 3 mol% CeF3 additives on viscosity of the molten 75LiF–20ThF4–5BeF2 (mol%) salt mixture has been investigated experimentally. The method of torsional oscillations of cylindrical crucible filled by molten fluorides mixture has been chosen for kinematic viscosity measurement at temperatures up to 800–850 °C. In temperature ranges, where melts behave as normal liquids, dependences on viscosity vs. temperature are received: ν = А exp [B/T(K)], where ν – kinematic viscosity, m2/s; T – temperature, K. The kinematic viscosity Rout mean squares (RMS) estimated in the assumption about dispersion homoscedasticity is (0.04–0.12) × 10−6 (m2/s). Discrepancies left in the data of viscosity for molten mixtures of LiF, BeF2 and ThF4 received by different researchers need further investigations in this area to be continued.

► We measure viscosity of molten Li.Be,Th/F salt mixtures. ► Temperature is changed from liquidus up to 800–850 °C. ► Method of torsional oscillations is used.