Development of a methodology for the analysis of a fuel composition based on lithium and beryllium fluorides by atomic emission arc spectrometry

Abstract

An atomic emission technique for the analysis of a fuel salt containing uranium and a coolant based on lithium and beryllium fluorides has been developed and tested. When developing the technique, the conditions accepted at Rosatom enterprises for the analysis of beryllium oxide and lithium carbonate were taken into account. The complexity of the structure of the arc spectrum of the matrix is noted. X-ray phase analysis of the sample residues in the electrodes revealed that the source of molecular bands in the spectra is lithium fluoroberillate. The analytical lines of Al, B, Ca, Cd, Cr, Cu, Fe, Mg, Ni, Pb, Si and Zn, free from overlap with the lines of the molecular spectrum and uranium were selected. A method of extreme experiment design is used to select optimal conditions for the arc excitation of the sample: the type and strength of the discharge current (alternating current 12 A), exposure time (20 sec), the shape of the electrode («glass») and the mass of the material (30 mg). Recommendations are given and implemented for the preparing samples for calibration using pure lithium fluoroberillate as a matrix material when introducing controlled elements in the form of certified reference materials of graphite (graphite collector of trace impurities). Calibration graphs in logarithmic coordinates are linear with angular coefficients close to unity. The metrological characteristics of the technique are evaluated in analysis of real samples: the repeatability, intermediate precision of the results and the limits of the element detection.