Developing LIBS for Molten Salt Reactor Monitoring

Hunter Andrews is an R&D Staff Scientist in the Isotope Applications Research Group within the Radioisotopes Science and Technology Division, where his work focuses on developing in-situ, online monitoring tools for complex environments. His primary expertise is in optical spectroscopy, particularly laser-induced breakdown spectroscopy (LIBS), a rapid elemental analysis technique applicable to a wide range of sample types (1). His broader research interests span analytical chemistry, electrochemistry and spectroelectrochemistry, neutron imaging, molten salt systems, inorganic mass spectrometry, chemometrics, and machine learning (1).

Dr. Andrews earned his PhD in Mechanical and Nuclear Engineering from Virginia Commonwealth University in 2020, with graduate research centered on near-real-time material detection using integrated electrochemistry and LIBS for molten salt applications (1). He joined Oak Ridge National Laboratory as a postdoctoral researcher in 2020 and became a staff scientist in 2021 (1).

As a preview to the upcoming Winter Conference on Plasma Spectrochemistry set to take place next week (2), Spectroscopy sat down with Andrews to ask him about his upcoming talk at the 2026 Winter Conference on Plasma Spectrochemistry.

Spectroscopy: Can you provide a brief overview of your talk at the Winter Conference and what you will be discussing?

Hunter Andrews: At the Winter Conference, I'm giving an invited presentation on our work developing LIBS for molten salt reactor monitoring, mainly related to off-gas systems. So, for molten salt reactors, which are an advanced reactor concept, your liquid fuel is dissolved into a molten salt, and this circulates around the main coolant loop.

Since your fuel is a liquid as it undergoes fission, your fission products will be within this liquid. And some of those fission products are gasses like xenon and krypton. Some of them are volatile species like iodine. Those things are going to evolve out of the liquid phase into the gas phase, and then the headspace will be recirculated with an inert gas to keep the salt free of oxygen and hydrogen and other atmospheric impurities. So that headspace above the reactor gets swept and taken to what we call the off gas, and that's where basically all of those things that are evolving into the gas phase get cleaned out before that gas is recirculated back to the core. We're looking at filters to take out xenon, krypton, noble gasses, volatiles, and things like tritium that have negative consequences to either the reactor or public safety.

As you can imagine, with the nuclear reactor, you have radiation fields and stuff like that. As a result, a lot of traditional analytical techniques aren't really well suited for this application. Fortunately, optical spectroscopy is really well suited for it. You can do optical spectroscopies like LIBS or Raman or even absorbance spectroscopy all through fibers or through propagated laser light and be able to do those measurements remotely. It also allows you to keep your computer, your operator, and your spectrometers located at a distance in a shielded facility, so that they don't have to worry about the dose. And so, that's really what we're kind of talking about. We've been developing it for the last five years or so, we've made some really great progress here recently, so I'm excited to give an update on it.

This video clip is the first part of our conversation with Andrews. To stay up to date on our coverage of the Winter Conference, click here.

References

1. Oak Ridge National Laboratory, Hunter B. Andrews. ORNL.gov. Available at: https://www.ornl.gov/staff-profile/hunter-b-andrews (accessed 2026-01-05).
2. IASA, Winter Conference on Plasma Spectrochemistry. IASA. Available at: https://iasa.world/winter-plasma-conference (accessed 2026-01-05).