Study of entrainment of Li2O in product from direct electrolytic reduction of UO2 in molten LiCl–Li2O. Part 1: Post-processing and analysis techniques

Abstract

This paper describes experimental and characterization methods for gram-scale uranium oxide electrolytic reduction tests in molten LiCl–Li2O. Post-test analysis of the cathodically reduced UO2 involves acid-base titration and thermogravimetric analysis under flowing air. The titration was used to measure Li2O entrained inside reduced UO2 particles. Centrifugal salt removal was demonstrated to eliminate Li2O from the basket, but the Li2O entrained in the reduced uranium particles remained and was reacted over a period of several days in an autotitrator. Measuring the mass increase by thermogravimetry while heating to 800 °C and flowing air was found to be an effective way to measure the reduction extent, which was verified with pure U metal. The error of this measurement was estimated to be 1.65%. In addition, a LECO oxygen compositional analyzer was used to independently verify the oxygen content in the product from the thermogravimetric analysis.