High Precision Broadband Optical Spectrometer for Molten Salt Reactors

There is a critical need to accurately monitor the buildup of various fluoride and chloride salts as well as critical states of uranium present in molten salt reactors to prevent corrosion that would not only reduce the efficiency of power generation but also endanger operation safety of the facility. Online monitoring is, thus, needed for key salt parameters and the level of dissolved alloy constituents to implement corrosion control technologies to ensure that the reactor is operating within safety limits. To overcome these technical challenges, we propose using a broadband dual frequency comb source to characterize fuel materials. To do this, a small sample of the fuel material will be ionized into a plasma by an intense laser pulse. The plasma is then probed by dual frequency comb (DFC) and laser-induced breakdown spectroscopy (LIBS) to provide the characteristic spectrum for different fuel materials at high resolution over a broad spectral range. Because this is an optical technique, where no sample handling is required since the plasma can be generated at a safe distance away by the laser, any radiation hazard, specifically from nuclear materials can be minimized. We have assembled a furnace capable of reaching 510 °C allowing us to perform LIBS experiments on molten salts where trace elements of 150 ppm (part-per-million) could be detected. DFC experiments were performed with cerium, a surrogate for uranium where we demonstrated the high resolving power of the DFC technology. Some molten salts studied in Phase I included sodium nitrate (NaNO3) and LKE (LiCl- KCl eutectic). The proposed technology using a broadband dual frequency comb source for high precision absorption spectroscopy can be used to identify, characterize and analyze various materials for elemental composition and isotopic analysis in real-time. This may an alternative to conventional mass spectrometry where sample handling and analysis can take up to a few weeks long. Our technology will also be much more compact than mass spectrometer, allowing our technology to be more suitable for field applications and in challenging environments.