Leveraging Multiple Raman Excitation Wavelength Systems for Process Monitoring of Nuclear Waste Streams

Abstract

Processing nuclear waste from sites such as Hanford is a significant environmental cleanup need while being a significant logistical challenge. Integration of process monitoring tools, which can provide in situ and real-time feedback about the process, can significantly alleviate needs to collect grab samples for process control and product characterization. Raman spectroscopy paired with chemometric analysis is one process monitoring tool that can provide chemical composition information on a large number of chemical targets in nuclear waste streams. However, methods to improve limits of detection as well as drop uncertainty in quantification are needed. Optimizing instrument specifications can achieve this; here, this is demonstrated by comparing limits of detection for key analytes when using Raman systems with 671, 532, and 405 nm excitation wavelengths. Generally, limits of detection decrease (allowing the measurement of lower salt concentrations) with decreasing wavelength. Similarly, data collection times and averaging were optimized. Finally, multiple chemometric modeling approaches were leveraged, including multiblock methods that combined data from all three Raman systems to simultaneously quantify targets with improved sensitivity.

Synthesis of Thorium Dioxide Nanocrystals via Molten Salt Thermal Decomposition for Nuclear Energy-Related Applications

“…The Raman spectra of the mixed powders of LiCl–KCl and Th­(NO 3 ) 4 ·4H 2 O at different temperatures are illustrated in Figure . The peak observed at 1050 cm –1 corresponds to the stretching vibration of N–O in NO 3 – and the peak located at 457 cm –1 corresponds to the T 2g mode of the Fm 3̅ m space group of the fluorite structure type of thorium oxide, which agree with the literature. − The stretching vibration peak of N–O in NO 3 – observed at 1050 cm –1 gradually weakens and completely disappears at 650 °C. At 500 °C, a peak corresponding to the stretching vibration of the Th–O bond appears at 457 cm –1 , and its intensity increases with increasing temperature.…”

In Situ Raman Methodology for Online Analysis of CO2 and H2O Loadings in a Water-Lean Solvent for CO2 Capture

“…While we have not developed models for other amine-based carbon-capture solvents, we are certain that would be possible and is currently planned. The techniques demonstrated in this manuscript are amenable to other systems, as have been amply demonstrated by our research group efforts in a variety of processes including online monitoring of nuclear waste streams, nuclear fuel reprocessing streams, ,,− and strong and weak acid solutions streams. ,,− …”

Practical Guide to Chemometric Analysis of Optical Spectroscopic Data

“…Frequently, based on learning from this modeling exercise and the treatment of the student’s own data, students participate during or after the expiration of the internship term in the adaptation of their modeled lab results to the inclusion of that material in peer reviewed publications. ,− The learning outcomes and corresponding methods of assessment, which were developed for this 10-week internship format, are shown in Table .…”