Thermodynamic assessment of the LiF-NiF 2 , NaF-NiF 2 and KF-NiF 2 systems

Using the modified quasi-chemical model in the quadruplet approximation, three new thermodynamic assessments of binary systems useful for the detailed operational design of the Molten Salt Reactor are presented: AF-NiF2 (A = Li, Na, K). These systems are particularly relevant for the study of the molten salt-structural materials interaction, as the salt containment is made of a Ni-based alloy. Using powder X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC), new experimental data were gathered for two of these systems, LiF-NiF2 and KF-NiF2, and compared to previous experimental assessments. Our data have confirmed the formation of a (Li1-2xNix)F solid solution. The three thermodynamic models show a very good agreement with the experimental data. The melting point of NiF2 was measured for the first time to be T = (1629 ± 5) K, and the thermal expansion coefficient for Li2NiF4 was found to be α=27.6·10-6K-1 in the temperature range T = (298–773) K.

[1]  Heinz Gamsjäger,et al.  Chemical Thermodynamics of Nickel , 2005 .

[2]  O. Beneš,et al.  Excess heat capacity in liquid binary alkali-fluoride mixtures. , 2013, Inorganic chemistry.

[3]  O. Beneš,et al.  A DSC study of the NaNO3–KNO3 system using an innovative encapsulation technique , 2010 .

[4]  J. Kloosterman,et al.  The Molten Salt Reactor in Generation IV: Overview and Perspectives , 2014 .

[5]  J. C. Taylor.  A comparison of profile decomposition and Rietveld methods for structural refinement with powder diffraction data , 1987 .

[6]  O. J. Kleppa,et al.  Enthalpies of mixing of binary liquid mixtures of cadmium chloride with cesium and lithium chlorides , 1971 .

[7]  H. Sakaebe,et al.  Synthesis and characterization of the crystal structure, the magnetic and the electrochemical properties of the new fluorophosphate LiNaFe[PO4]F. , 2012, Dalton transactions.

[8]  F. L. Carter.  On the existence of two forms of NaNiF3 , 1969 .

[9]  O. J. Kleppa,et al.  Enthalpies of mixing in the liquid mixtures of the alkali chlorides with MnCl2, FeCl2 and CoCl2 , 1971 .

[10]  D. Babel,et al.  Untersuchungen an ternären Fluoriden. I. Struktur, Magnetismus und Reflexionsspektren von Alkali‐, Ammonium‐ und Thallium‐Nickel(II)‐fluoriden , 1962 .

[11]  P. Svoboda,et al.  Application of Neumann–Kopp rule for the estimation of heat capacity of mixed oxides , 2010 .

[12]  B. N. Wani,et al.  Fluorination of oxides of uranium and thorium by ammonium hydrogenfluoride , 1989 .

[13]  D. Gruen,et al.  Tetrahedral NiCl4− Ion in Crystals and in Fused Salts. Spectrophotometric Study of Chloro Complexes of Ni(II) in Fused Salts , 1959 .

[14]  O. Beneš,et al.  Thermodynamic investigation of the LiF–ThF4 system , 2013 .

[15]  C. R. Boston,et al.  Electronic Spectra and Coordination Geometry in Molten Mixtures of CsCl and NiCl2 Containing up to 60 Mole% NiCl2 , 1966 .

[16]  O. J. Kleppa,et al.  Enthalpies of mixing of liquid nickel(II) chloride-alkali chloride mixtures at 810°C , 1970 .

[17]  H. D. Merchant,et al.  Thermal expansion of alkali halides above 300°K , 1973 .

[18]  Marie-Aline Van Ende,et al.  FactSage thermochemical software and databases, 2010–2016 , 2016 .

[19]  Gunnar Eriksson,et al.  The modified quasichemical model I—Binary solutions , 2000 .

[20]  M. Allibert,et al.  Reactor physic and reprocessing scheme for innovative molten salt reactor system , 2009 .

[21]  V. Ignatiev,et al.  Alloys compatibility in molten salt fluorides: Kurchatov Institute related experience , 2013 .