PNNL

Abstract

Growing research interest in molten salt nuclear systems requires a fundamental understanding of the chemical environment and physico-chemical properties of fission products, which includes elements of the lanthanide (rare earth) series. In this paper, we characterize LnCl3 nH2O before and after melting, where Ln is Eu, Gd, Tb, and Dy, using experimental and theoretical methods. X-ray absorption spectroscopy and x-ray diffraction confirm the predominant formation of oxychlorides (LnOCl) after melting in aerobic conditions. X-ray absorption data were collected using a laboratory-scale X-ray absorption spectrometer and complemented with synchrotron measurements. The collected X-ray absorption near edge structure (XANES) spectra were further analyzed and interpreted with theoretically computed spectra based on TDDFT calculations. Fundamental analysis of these systems was supplemented with extended X-ray absorption fine structure (EXAFS) fits, which were found to be in good agreement with the synchrotron data. This study provides a baseline for future studies of molten lanthanide chlorides in either the laboratory or synchrotron environment.