Composition characterization is needed for a broad range of molten salt studies relevant to molten salt (MSR) and salt-cooled (FHR) nuclear reactors. For example, corrosion studies and measurements of physico-chemical properties of molten salt necessitate a correct characterization of salt composition.<br/><br/>Inductively coupled plasma optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS) allow to investigate the elemental composition of samples and to measure ppm to ppb of elements in each sample. In these instruments, a liquid sample is introduced and transformed into an aerosol by a high-speed flow of gas. The fine aerosol enters then the plasma that is analyzed. Thus, solid samples need to be transferred into the plasma. One of the techniques to transfer solid samples, as the fluoride salts investigated in this work, into the plasma involves digestion. Solid salt samples, Be swipes and air filters are dissolved in a heated aqueous solution of one or more acids. A microwave digestion system is used to dissolve the solid samples.<br/><br/>In this study, three digestion procedures, and three different digestion instruments were used. Prior standard procedures and calibration procedures used for fluoride salt analysis have been reviewed and the procedures were considered for the analysis. The dissolution of the solid salt was different with each digestion system and procedure. The effect of acid solution selection on digestion efficiency of specific elements will be shown. A comparison between variability arising from the elemental measurement instrument, and variability arising from digestion will be presented. The aim of this work is to evaluate the applicability and performance of the selected digestion systems for reproducible and standardized elemental analysis of fluoride salts.

Salt digestion methods: sample preparation and elemental analysis of molten fluoride salts (FLiNaK and FLiBe) by ICP techniques

ACS Fall 2021

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