Quantifying Dense Multicomponent Slurries with In-Line ATR-FTIR and Raman Spectroscopies: A Hanford Case Study

Abstract

The multiphase nature of slurries can make them difficult to process and monitor in real time. For example, the nuclear waste slurries present at the Hanford site in Washington State are multicomponent, multiphase, and inhomogeneous. Current analytical techniques for analyzing radioactive waste at Hanford rely on laboratory results from an on-site analytical laboratory, which can delay processing speed and create exposure risks for workers. However, in-line probes can provide an alternative route to collect the necessary composition information. In the present work, Raman spectroscopy and attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy are tested on simulants of nuclear waste slurries containing up to 23.2 wt % solids. We observe ATR-FTIR spectroscopy to be effective in measuring the solution phase of the studied slurry systems (3.52% mean percent error), while Raman spectroscopy provides information about the suspended solids in the slurry system (18.21% mean percent error). In-line measurement of multicomponent solids typical of nuclear waste processing has been previously unreported. The composition of both the solution and solid phases is vital in ensuring stable glass formulation and effective disposal of nuclear waste at Hanford. Raman and ATR-FTIR spectroscopies can provide a safer and faster alternative for acquiring compositional information on nuclear waste slurries.

Iterative Regression of Corrective Baselines (IRCB): A New Model for Quantitative Spectroscopy

“…Lastly, in case study 3, IRCB was tested to predict the concentrations of five solids within a complex slurry using Raman spectroscopy. For case studies 2 and 3, the modeling results may be compared to the previously published benchmarks. , …”

“…The statistical metrics of the test set prediction are shown and compared with the previously reported PLS-R results in Table . The PLS-R model from the previously work utilized 10 principal components and the application of Savitzky–Golay filter …”

“…Raman and infrared spectroscopies have been applied for an increasing number of use cases. Among others, these applications of spectroscopy include food, − pharmaceuticals, − cosmetics, tobacco, and nuclear waste. , In 2004, the US Food and Drug Administration (FDA) and the International Council for Harmonization (ICH) established an initiative to apply process analytical technologies (PAT), including spectroscopic PAC, for manufacturing quality assurance. , Many studies have reported on the use of spectroscopic analyzers, such as infrared (IR) and Raman, to monitor various stages of pharmaceutical manufacturing. ,,− Spectroscopic PAT is useful both for real-time release and model predictive control. ,,, The linking of PAT to continuous manufacturing for real-time optimization and control using artificial intelligence was referred to by Price et. al as the “holy grail” …”

“…Next, IRCB is applied, and the statistical results are compared for two additional previously benchmarked case studies. Case study 2 is near-infrared (NIR) measurements of crude soil samples, and case study 3 is Raman spectroscopy quantification of solids in a slurry of simulated nuclear waste . The additional insights from the novel matrix transformation are also discussed.…”

“…Among others, these applications of spectroscopy include food, 4 − 6 pharmaceuticals, 7 − 10 cosmetics, 11 tobacco, 12 and nuclear waste. 13 , 14 In 2004, the US Food and Drug Administration (FDA) and the International Council for Harmonization (ICH) established an initiative to apply process analytical technologies (PAT), including spectroscopic PAC, for manufacturing quality assurance. 15 , 16 Many studies have reported on the use of spectroscopic analyzers, such as infrared (IR) and Raman, to monitor various stages of pharmaceutical manufacturing.…”