The impact of oxide impurity on the structure of FLiNaK and FLiNaK–CeF3 melts: A simulation study

Abstract

Oxide impurities affect the performance of the molten mixtures applicable in molten salt reactors. To reveal the underlying reasons of changes in physicochemical properties, the in-depth investigations on microscopic structure of melts are demanded. In this study, the FLiNaK and FLiNaK–CeF3 molten mixtures with small addition of Li2O were simulated within the ab initio theory to obtain the local structure patterns. The emphasis is placed on oxygen-based groupings since these are expected to be the most stable. In order to estimate the stability, the calculation of ion pair lifetimes was performed. It is shown that the most probable ion groupings existing in the FLiNaK–Li2O melt are [OLi5K], [OLi5K2] and [OLi4NaK2], while the FLiNaK–Li2O–CeF3 melt contain [OCe2Li2], [OCe2Li2K], [OCe2Li3] and [OCe3Li] units predominantly. Within the groupings, the most stable ion pairs are O-Li or O-Ce, depending on the melt composition.