Preparation of homogeneous LiF-BeF2-ZrF4 molten salt with low oxygen content

Molten salt reactor uses LiF-BeF2-ZrF4 (FLiBeZr) as the solvent, and UF4 is dissolved in homogeneous FLiBeZr to form liquid fuel salt (FLiBeZrU). However, a second phase ZrO2 precipitate usually forms during the preparation of FLiBeZr solvent. In this paper, the formation mechanism of ZrO2, its dissolution equilibrium in FLiBeZr and its effect on the physical properties of molten salts were studied. Then, anhydrous HF-H2 gas was introduced as a deoxidizer to react with the dissolved oxide and ZrO2. By optimizing the H2-HF tube bubbling at the bottom, even with the addition of UF4, a uniform FLiBeZr with a total oxygen content of 120 ppm can be prepared without the production of UO2.