ORNL turns spectrometers on aerosolized molten salts to spot impurities
Researchers at Oak Ridge National Laboratory have demonstrated a new method to track chemical changes in molten salt, according to a March 17 announcement from the Department of Energy’s Office of Nuclear Energy.
Work recently published in the Journal of the American Chemical Society could help develop new monitoring technologies for molten salt reactors. Companies including Kairos Power, Natura Resources, TerraPower (in collaboration with Southern Nuclear), and Terrestrial Energy are developing reactors that use molten salt—either fluoride or chloride salt—together with fuel in solid form or dissolved into the coolant.
Like other coolants, molten salt comes with both benefits and drawbacks. The mechanisms and impacts of corrosion in a high-temperature molten salt environment is one subject of ongoing research. Molten salt chemistry must be monitored to assess the presence and distribution of nuclear material and impurities.
LIBS for salt: ORNL researchers decided to see if a laser-induced breakdown spectroscopy (LIBS) technique could be used on molten salt by using a laser pulse to create a microplasma in a molten salt aerosol stream and then detect impurities within that stream.
By using several spectrometers to measure and identify the elements in the plasma, the researchers identified isotopes present in the molten salt using nonradiometric methods for the first time, according to the DOE. The measurements also allowed researchers to determine how fast gases spread throughout the molten salt and how much gas the molten salt could hold.
From proof of concept to future plans: “We’ve performed several proof-of-concept experiments with LIBS to track aerosols and gases, finding it extremely insightful—providing an elemental fingerprint of the sample in less than a second,” said ORNL staff scientist Hunter Andrews. “By making the jump to real molten salts, we were able to demonstrate in a more realistic system how LIBS could monitor a reactor and also be used by researchers to better understand their experiments.”
Researchers developing LIBS models for real-time monitoring of off-gases from a molten salt reactor have a goal of “outfitting engineering-scale test systems in the coming years” and hope to “eventually incorporate a LIBS sensor into a molten salt reactor at commercial scale,” the DOE said in its news release.
