Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

Optical spectroscopy of molten fluorides: Methods, electronic and vibrational data, structural interpretation, and relevance to radiative heat transfer

Journal Article · · Journal of Molecular Liquids
In this study, to help address the need for predicting radiative heat transfer (RHT) behavior of molten salts, we conducted a comprehensive review of methods and data from optical spectroscopic measurements on molten fluoride salts. Transmittance, reflectance, and trans-reflectance experimental methods are discussed, along with the corresponding data reduction methodology and the limitations of each technique. Optical spectroscopy is a convenient indirect probe for changes in structural parameters with temperature and composition. Electronic and vibrational absorption data for transition-metal, lanthanide, and actinide solutes and vibrational absorption data for alkali and alkaline earth fluoride solvents are compiled, and the corresponding structural interpretation is discussed and compared with other experimental and theoretical work. We find that solvent and solute vibrational absorption can be significant in the mid-infrared, resulting in near-infrared edges of significance to RHT. Extrapolation and averaging of existing edge data leads to estimated gray absorption coefficient values at 700 °C of 546 m—1 for FLiBe and 276 m—1 for FLiNaK, both within the range of 1 – 6000 m—1 identified to be of engineering relevance for radiative heat transfer analysis.
Research Organization:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Organization:
National Science Foundation (NSF); USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Nuclear Energy (NE), Nuclear Energy University Program (NEUP)
Grant/Contract Number:
AC07-05ID14517; NE0008985
OSTI ID:
2310922
Report Number(s):
INL/JOU-22-66522-Revision-0
Journal Information:
Journal of Molecular Liquids, Journal Name: Journal of Molecular Liquids Vol. 385; ISSN 0167-7322
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (109)

In situ high temperature Raman and DFT analysis of cerium fluoride and oxyfluoride structures in molten FLiNaK journal March 2021
Precision Measurements of Temperature‐Dependent and Nonequilibrium Thermal Emitters journal June 2020
Molten Salt Spectroscopy book January 1984
Vibrational Aspects of Molten Salts book January 1971
The infrared absorption coefficient of alkali halides journal March 1980
CVD diamond windows for infrared synchrotron applications journal April 1998
Containment of molten fluorides in silica; effect of temperature on the spectrum of U4+ in molten LiF-BeF2 mixtures journal August 1968
Absence of an effect of oxide on the solubility and the absorption spectra of PuF3 in molten LiFBeF2ThF4 and the instability of plutonium(III) oxyfluorides journal October 1971
Spectral studies of O2−, NO2− and CrO42− in molten LiF-NaF-KF and of O2− in liquid ammonia journal August 1972
Stability of BF3OH− ion in molten and solid NaBF4 and NaFNaBF4 eutectics journal September 1972
Equilibria of uranium carbides in the molten fluoride solutions of UF3 and UF4 contained in graphite at 850°K journal May 1973
Electrochemical generation and spectrophotometric study of solute species in molten fluoride media journal May 1973
The chemistry of tellurium in molten Li2BeF4 journal May 1974
Spectral studies of f−d and f−f transitions of Pa(IV) in molten LiFBeF2ThF4 journal November 1974
The hydrogen reduction of uranium tetrafluoride in molten fluoride solutions journal January 1977
A polymer model for BeF2 and SiO2 melts journal January 1970
Absorption coefficient of infrared laser window materials journal December 1973
Chemistry of vanadium chlorides in molten salts: An electronic absorption spectroscopy study journal March 2003
Corrosion of Cr in molten salts with different fluoroacidity in the presence of CrF3 journal June 2020
Dissolved valence state of iron fluorides and their effect on Ni-based alloy in FLiNaK salt journal November 2021
Preparation of high-purity molten FLiNaK salt by the hydrofluorination process journal May 2017
First-principles molecular dynamics modeling of the molten fluoride salt with Cr solute journal June 2014
Redox condition in molten salts and solute behavior: A first-principles molecular dynamics study journal October 2015
The structure of molten FLiNaK journal August 2020
Investigation on molecular structure of molten Li 2 BeF 4 (FLiBe) salt by infrared absorption spectra and density functional theory (DFT) journal September 2017
Investigation of ionic local structure in molten salt fast reactor LiF-ThF4-UF4 fuel by EXAFS experiments and molecular dynamics simulations journal June 2020
Ab-initio simulation studies of chromium solvation in molten fluoride salts journal August 2021
Raman spectroscopic and theoretical studies on the structure of Ta (V) fluoro and oxofluoro complexes in molten FLiNaK journal September 2021
Radiative heat transfer in FLiBe molten salt participating medium in a vertical heated tube under forced and mixed convection laminar flows journal November 2020
Optical constants of ethylene glycol over an extremely wide spectral range journal November 2014
Spectral optical constants of ethanol and isopropanol from ultraviolet to far infrared journal October 2016
The molten salt reactor (MSR) in generation IV: Overview and perspectives journal November 2014
Phenomenology, methods and experimental program for fluoride-salt-cooled, high-temperature reactors (FHRs) journal November 2014
Design and licensing strategies for the fluoride-salt-cooled, high-temperature reactor (FHR) technology journal November 2014
Beer's law derived from electromagnetic theory journal May 2019
Raman and density functional theory studies of lutecium fluoride and oxyfluoride structures in molten FLiNaK journal April 2021
Optical properties of high temperature molten salt mixtures for volumetrically absorbing solar thermal receiver applications journal September 2017
High-Temperature Cell Assembly for Spectrophotometric Studies of Molten Fluoride Salts journal November 1959
Absorption Spectra of Molten Fluoride Salts. Solutions of Several Metal Ions in Molten Lithium Fluoride-Sodium Fluoride-Potassium Fluoride journal June 1960
Windowless Spectrophotometric Cell for Use with Corrosive Liquids. journal February 1964
Diamond-windowed cell for spectrophotometry of molten fluoride salts journal April 1969
Vibrational spectra of niobium(V) fluoro and oxo fluoro complexes formed in alkali-metal fluoride melts journal February 1991
Alkali fluoride complexes of tetravalent protactinium journal March 1967
Spectra of uranium(IV) and uranium(III) in molten fluoride solvents journal August 1967
Absorption spectra of several 3d transition metal ions in molten fluoride solution journal April 1969
Ligand-field spectrum of niobium(IV) in fluoride melts journal January 1976
Telluride ion chemistry in molten salts journal August 1978
Infrared and Raman Spectroscopic Investigations of the Nb(V) Fluoro and Oxofluoro Complexes in the LiF−NaF−KF Eutectic Melt with Development of a Diamond IR Cell journal July 2000
Raman spectra of Be2F73- and higher polymers of beryllium fluorides in the crystalline and molten state journal January 1973
Temperature and solvent effects on the equilibrium of dilute uranium trifluoride solutions contained in graphite journal November 1973
Raman spectra of tetrafluoroberyllate ion in molten sodium fluoride and lithium fluoride to 686.deg. journal January 1972
Coordination effects on the spectrum of uranium(IV) in molten fluorides journal March 1971
Infrared Reflection Spectra of Molten Fluoride Solutions. Hydrolysis of Tantalum(V) in Potassium Fluoride—Lithium Fluoride journal December 1965
ABSORPTION SPECTRA OF URANIUM(III) AND URANIUM(IV) IN DClO 4 SOLUTION 1 journal December 1960
Simultaneous voltammetric generation of uranium(III) and spectrophotometric observation of the uranium(III)-uranium(IV) system in molten lithium fluoride-beryllum fluoride-zirconium fluoride journal February 1967
Spectral evidence for the existence of the superoxide ion in molten lithium fluoride-sodium fluoride-potassium fluoride journal November 1969
Radiant Transfer of Heat in Molten Inorganic Compounds at High Temperatures. journal April 1962
Chemla Effect in Molten LiCl/KCl and LiF/KF Mixtures journal May 2003
A First-Principles Description of Liquid BeF 2 and Its Mixtures with LiF:  2. Network Formation in LiF−BeF 2 journal June 2006
In Situ Experimental Evidence for a Nonmonotonous Structural Evolution with Composition in the Molten LiF−ZrF 4 System journal April 2010
Electronic Absorption Spectra of the Ce3+Ions in Halide Melts journal November 2003
Absorption spectroscopy for the quantitative prediction of lanthanide concentrations in the 3LiCl–2CsCl eutectic at 723 K journal January 2016
Examination of the short-range structure of molten salts: ThF 4 , UF 4 , and related alkali actinide fluoride systems journal January 2021
Vibrational modes and structure of rare earth halide–alkali halide binary melts YBr3–ABr (A=Li, K, Cs) and YF3–KF journal January 1997
Vibrational modes and structure of lanthanide fluoride–potassium fluoride binary melts LnF3–KF (Ln=La, Ce, Nd, Sm, Dy, Yb) journal January 1998
Vibrational modes and structures of lanthanide halide–alkali halide binary melts LnBr3–KBr (Ln=La, Nd, Gd) and NdCl3–ACl (A=Li, Na, K, Cs) journal January 1998
Isotropic and anisotropic Raman scattering from molten alkali-metal fluorides journal January 2000
Solubility and Raman spectra of Ta(V) in LiF–NaF–KF–Na2O melts
  • Vik, Aasmund Fahre; Dracopoulos, Vassilis; Papatheodorou, George N.
  • Journal of the Chemical Society, Dalton Transactions, Issue 14 https://doi.org/10.1039/b101528l
journal January 2001
High temperature NMR study of the local structure of molten LaF3–AF (A = Li, Na, K and Rb) mixtures journal January 2008
Diffusion coefficients and local structure in basic molten fluorides: in situ NMR measurements and molecular dynamics simulations journal January 2009
Studies of the local structures of molten metal halides journal January 2011
Fused-salt spectrophotometry journal January 1965
Diffraction pattern and structure of molten BeF 2 –LiF solutions journal November 1973
Vibrational Spectra of Inorganic Molecules. II. Infrared Reflection Spectra of Liquid Lithium, Sodium, Potassium, and Silver Nitrates journal September 1961
Coordination of Fluoride Ions About Nickel (II) Ions in the Molten LiF–NaF–KF Eutectic journal February 1964
Infrared-Reflection Spectra of Molten Fluoride Solutions: Tantalum (V) in Alkali Fluorides journal February 1966
Infrared Spectra of Molten Salts journal November 1963
Infrared Spectra of Highly Associated Liquids and the Question of Complex Ions in Fused Salts journal October 1963
Optical constants of sapphire (α‐Al 2 O 3 ) single crystals journal December 1994
Raman spectroscopic studies of yttrium (III) chloride–alkali metal chloride melts and of Cs 2 NaYCl 6 and YCl 3 solid compounds journal April 1977
Design and performance of high-temperature furnace and cell holder for in situ spectroscopic, electrochemical, and radiolytic investigations of molten salts journal August 2020
Ab-Initio Calculation of Spectral Absorption Coefficients in Molten Fluoride Salts with Metal Impurities journal June 2018
Fusion Blankets and Fluoride-Salt-Cooled High-Temperature Reactors with Flibe Salt Coolant: Common Challenges, Tritium Control, and Opportunities for Synergistic Development Strategies Between Fission, Fusion, and Solar Salt Technologies journal December 2019
Convective and Radiative Heat Transfer in Molten Salts journal July 2020
Advancing Radiative Heat Transfer Modeling in High-Temperature Liquid Salts journal March 2020
Measurement of Infrared Absorption Coefficients of Molten Glasses journal July 2001
The effect of melting on the multiphonon infrared absorption spectra of KBr, NaCl and LiF journal August 1972
Comparison of the optical and dielectric properties of crystalline and molten lithium fluoride journal January 1974
A compact, windowless reflectance furnace for infrared studies of corrosive melts journal March 1973
Intermediate range chemical ordering of cations in simple molten alkali halides journal July 2008
Temperature Dependence of Infrared Dispersion in Ionic Crystals LiF and MgO journal June 1966
Vacuum-ultraviolet characterization of sapphire, ALON, and spinel near the band gap journal January 1993
Electronic spectra of praseodymium trifluoride solutions in molten alkali metal fluorides journal November 2015
Optical Spectra of Gadolinium(III) Ions in Melts of Alkali Metal Fluorides journal June 2019
Spectral-analytical system for recording the electronic spectra of high-temperature melts and its technical frontier journal February 2014
On the Absorption Spectra of Complex Ions. I journal September 1954
On the Absorption Spectra of Complex Ions II journal September 1954
The Aircraft Reactor Experiment—Operation journal November 1957
Radiation Heat Transfer in the Molten Salt FLiNaK journal October 2016
Current Status of Knowledge of the Fluoride Salt (FLiNaK) Heat Transfer journal February 2009
Molten-Salt Reactor Chemistry journal February 1970
The Design and Performance Features of a Single-Fluid Molten-Salt Breeder Reactor journal February 1970
Experience with the Molten-Salt Reactor Experiment journal February 1970
The coordination chemistry of 3d transition metal ions in fused salt solutions journal January 1963
Evaluation of the One-Angle Reflection Technique for the Determination of Optical Constants journal September 1963
Correcting thermal-emission-induced detector saturation in infrared spectroscopy journal October 2022
Reinvestigation of Molten Fluoroaluminate Raman Spectra: The Question of the Existence of AlF 5 2− Ions journal February 1990
Status of tellurium--hastelloy N studies in molten fluoride salts report October 1977
Absorption Spectra of Red Uranium(III)Chloro Complexes in Strong Hydrochloric Acid. journal January 1956

Similar Records

Radiative Heat Transport and Optical Characterization of High Temperature Molten Salts
Other · Wed Dec 29 23:00:00 EST 2021 · OSTI ID:1838441

Versatile Cell Design for Molten Fluoride Salt Spectroscopy: Investigating Metal-Ion Speciation in Molten Fluoride Salts
Journal Article · Sun Jul 06 20:00:00 EDT 2025 · Journal of the American Chemical Society · OSTI ID:2584151

Electrochemical Behavior of Lanthanum in Molten LiF-NaF-KF 'Flinak' Eutectic Salt
Journal Article · Sat Jul 01 00:00:00 EDT 2017 · Transactions of the American Nuclear Society · OSTI ID:23047369