Density Measurements of Molten Salts

Abstract

The present study focused on the development of a method to measure the density of molten salt. The method was validated by measuring densities of molten LiF−ThF 4 and LiF−ThF 4 −UF 4 salts and comparing them with ideal-mixture calculations and reference data. For LiF−ThF 4 , densities obtained in this study showed deviations less than 3% from the previously reported densities and the calculated values obtained using the ideal-mixture formula. For LiF−ThF 4 −UF 4 , deviations from idealmixture calculations were within 3%. Densities of a molten NaF−KF−UF 4 and a molten NaF−BeF 2 −UF 4 −ZrF 4 were also measured from 813 to 1173 and 838 to 1073 K, respectively. The measured values of these salts showed less than 2% deviations from the ideal-mixture values. In addition, the measured densities of the NaF−KF−UF 4 and NaF−BeF 2 −UF 4 −ZrF 4 salts showed similar trends to the density-temperature correlations of NaF−KF−UF 4 and NaF−BeF 2 −UF 4 salts, respectively, with similar compositions reported by previous studies.

Thermophysical Properties of FUNaK (NaF-KF-UF4) Eutectics

“…This comparison implies that the density was relatively well estimated at the beginning of the 20th century. The composition measured by Park [ 10 ] is likewise close to the FUNaK #1 and FUNaK #2 compositions, but its density is significantly higher than this study or Cohen and Jones’ results [ 16 ]. The reasons for the deviation of the results between these studies are not clear at this point.…”

“…The density results demonstrated reasonable agreement with previous data on the named similar compositions from Cohen and Jones [ 16 ], falling into the uncertainty range of their measurements of ±5%. Significant differences in density were found compared to the closely related composition of Park, NaF-KF-UF 4 (57.05-16.04-26.91 mol%) [ 10 ], and further comparable studies with the setup of this study and Park’s study, utilizing the same FUNaK composition, may be desirable. Finally, all properties determined by KEMS measurements, i.e., vapor pressure, boiling point, and the vaporization enthalpy of FUNaK, have not yet been investigated in the literature, making the presented results important, novel experimental data for reactor design.…”

“…The results are plotted in Figure 4 , while Table 5 summarizes the different density equations of the two FUNaK compositions measured in this study. Additionally, the experimental results were compared to the data on slightly different compositions measured by Park et al [ 10 ] and Cohen and Jones [ 16 ] and to the density of the ideal mixture from the molecular dynamics (MD) model [ 31 ]. Deviant values were obtained close to the melting point, i.e., at 540 °C for FUNaK #1 and at 540, 560, and 580 °C for FUNaK #2, and were omitted for the density correlation.…”

“…However, due to the elevated toxicity associated with beryllium, there is an escalating exploration of alternative salts and their properties [ 4 , 5 , 6 , 7 , 8 ]. One such candidate is NaF-KF-UF 4 , commonly denoted as FUNaK, and recent studies have delved into its properties [ 9 , 10 ]. The noteworthy characteristics of FUNaK include the accessibility of all its components, favorable neutronic properties, the absence of the typically required Li enrichment in FLiBe-based salts, and the lower toxicity of Na and K in comparison to Be salts, thereby simplifying research and development as well as waste handling [ 11 ].…”

“…Their findings revealed a deviation of 2% between the calculated and the experimental density for NaF-KF-UF 4 (46.5-26.0-27.5 mol%) and a maximum deviation of 6% for all of the studied fluoride salt compositions in [ 16 ]. In a more recent study, experimental density measurements for NaF-KF-UF 4 (57.05-16.04-26.91 mol%) were published, indicating a deviation of approximately 2% from the molar volume addition method [ 10 ].…”