Research Progress in Lithium Thermal Reduction Technology for Oxide Spent Fuel

Abstract

As a reactor which can reusing low-abundance 235U resources, fast reactor construction is an important part of China’s three-step nuclear energy process. Due to high burnup and strong irradiation of the spent fuel oxides of fast reactor, the dry reprocessing method based on molten salt electrolytic refining has unique advantages such as the ability to handle the widest range of fuel types and higher stability of the reaction system. Before the electrolytic refining step, the oxide spent fuel needs to be reduced to metal through electrical or thermal reduction. Thermal reduction requires the use of calcium, lithium, and magnesium as reducing agents. Compared with other alkali metal reduction process, lithium reduction process at high temperature has the advantages of simple recovery process, moderate temperature and lower equipment requirements, it may become the future tendency of thermal reduction. In this paper, the research progress of lithium high-temperature chemical reduction of spent fuel in dry reprocessing and compared the characteristics of lithium thermal reduction processes in various countries was investigated. The mechanism of high-temperature reduction with lithium was deduced based on thermodynamic calculation, and the influencing factors of reaction were discussed from the perspective of kinetics. Finally, the relevant research on the electrolytic recovery of residual salt from thermal reduction was described. The different reaction routes and technological process of lithium thermal reduction were summarized. The shortcomings of existing research were summarized, and the trend of lithium thermal reduction in the future was prospected. It gave a reference for the research of the process flow in China’s dry reprocessing.

Keywords

• spent fuel
• dry reprocessing
• lithium thermal reduction
• molten salt system