(309e) In-Situ Raman and ATR-FTIR Spectroscopy for Monitoring of Molecular Species in Low-Activity Nuclear Waste

A significant portion of the nuclear waste stored at the Hanford site is low-activity waste, primarily made up of non-radioactive components such as sodium salts. The DOE has initiated the Direct Feed Low-Activity Waste (DFLAW) project to expedite the clean-up of low-activity waste. Under DFLAW, a portion of the liquid low-activity waste will be preprocessed to reduce cesium levels and solid content and directly sent for vitrification. The complexity of the waste and its hazardous nature make the analysis challenging, thus reliable measurements of the composition and solid content are needed to facilitate processing.

In our present research, we are exploring use of in-situ monitoring tools, such as ATR-FTIR and Raman spectroscopy, to collect high-dimensional measurements of the waste. The data is collected on simulated waste mixtures that represent different DFLAW locations at Hanford. Our approach includes collecting training sets for the simulated mixtures that are used to build regression models. Next, we use the models to predict the composition of unknown mixtures. Our goal is to use the experimental findings to compare the performance of Raman and ATR-FTIR probes and build a robust model that will generate the composition of the multicomponent waste system.

Our research has shown that using in-situ ATR-FTIR and Raman spectroscopy, coupled with data-driven models can be used to monitor key species in simulated nuclear waste mixtures. This approach has the potential to reduce or eliminate the need for offline sample collection, which will minimize employee exposure to hazardous waste, while improving sample turn-around times.