In Situ Spectroscopic Monitoring of MSR Molten Salt and Off-Gas Systems
A significant challenge that must be overcome before commercialization of molten salt reactors is tracking special nuclear material (SNM) through the reactor and subsystems such as fuel chemical processing and off-gas systems. In recent years, several approaches have been explored to track SNM, fission products, and corrosion products in these different subsystems. One such approach is to employ laser and optical spectroscopy to measure the atomic and molecular signals of MSR salts. The advantages of these approaches are that they typically are non-intrusive and offer the capability of process monitoring while still providing low uncertainties. At the Idaho National Laboratory, spectroscopy approaches such as laser-induced breakdown spectroscopy (LIBS) and ultraviolet-visible (UV-Vis) spectroscopy have been utilized to investigate molten salts in an aerosol (LiCl, KCl, RbCl2, NdCl3, and PrCl3) and vapor phases (MgCl5, NdCl5, and ZrCl4) with success. Testing to date has yielded qualitative information on all the above species and quantitative data and analytical figures of merit for species in the vapor phases. These findings, including results from ongoing testing, as well as the experimental conditions and potential applications will be presented.