Researchers at Oak Ridge National Laboratory (ORNL) have made significant strides in the real-time analysis of chemical changes in molten salt, a development that has the potential to boost the operational capabilities of next-generation molten salt reactors. This new method, described in detail in an article published by ORNL, employs laser-induced breakdown spectroscopy (LIBS) to measure and identify isotopic and elemental compositions within the salt.
Molten salt reactors, while not currently in operation within the United States, offer numerous advantages over traditional light-water reactors including greater efficiency and the ability to harvest radioisotopes on the fly; however, challenges such as the complex chemical environment of the reactor have hampered their widespread deployment, ORNL operated two experimental molten salt reactors in the 1950s and 1960s and the recent innovations at ORNL may address these prior technical hurdles. The LIBS technology allows scientists to focus a laser on the molten salt mixture, thereby creating a plasma that emits light, from which the chemical makeup can be deduced, enabling continuous monitoring without disrupting the reactor's operation.
The peer-reviewed findings, published in the Journal of the American Chemical Society, not only showcased LIBS's utility in analyzing static samples—such as those in plant biology, nuclear fuel, or geology—but also spotlighted its potential in dynamic, high-temperature systems like molten salt reactors. ORNL staff scientist Hunter Andrews, who contributed to the study, explained the significance of the breakthrough, "Here, we wanted to demonstrate the combined elemental and isotopic power of LIBS and harness its rapid measurement speed on the scale of milliseconds."
During their experiments, the ORNL team successfully tracked isotopes of hydrogen as they were introduced into a molten mixture of sodium nitrate and potassium nitrate, heated to 350 degrees Celsius the team used argon gas, which is inert, as a carrier for the isotopes and LIBS distinguished between hydrogen and water vapor by identifying oxygen presence concurrently. Such real-time data can substantially enhance our understanding of gas solubility and diffusion rates within molten salts, which are pivotal for the safe and efficient operation of these reactors.
The capability of the new LIBS spectroscopy method to perform uninterrupted measurements is particularly suited to the dynamic nature of molten salt reactors, where the molten salt itself acts as both coolant and fuel. This attribute enables the reactors to not only generate electricity more efficiently but also allows the possibility of extracting valuable isotopes during regular operation. As the primary funder, the DOE's Office of Science is eager to tackle ongoing scientific challenges with such innovative solutions, as reported by ORNL's coverage. UT-Battelle manages ORNL on behalf of the DOE’s Office of Science, which continues to champion basic research that underpins energy advancements like these.
