Establishing a Lab Scale Production for Lithium, Beryllium, and Thorium Fluoride Salts

Abstract

The work performed for this project demonstrated a method for producing purified LiF-BeF2-ThF4 salts using ammonium-bifluoride (NH4F2) as an alternative to pure anhydrous hydrofluoric acid (HF) gas. The objective was to produce purified material for use in molten salt experimental systems that are being developed at Texas A&M University’s Fuel Cycles and Materials Laboratory. Small salt samples (~6g) were generated and analyzed to evaluate the efficacy of the process. The purification process comprised: 1) preparing and mixing source materials, 2) melting the components at 600°C in a controlled atmosphere glovebox to facilitate the purification reaction, and 3) post-test evaluation and analyses. Salt samples were prepared with a base composition of 72LiF-8BeF2-20ThF4; this was the target composition for a subcritical molten salt experiment. This method was used to produce 35g of salt without ammonium-bifluoride purification and 50g of salt with purification. The products from these small-scale tests appeared satisfactory and the methods were scaled up in a large vacuum furnace to produce more than 60kg of purified salt. While the small-scale process produced satisfactory results, it was observed that the larger scale purification process was unsuccessful. Therefore ammonium-bifluoride was rejected for future process development.