On-Line Monitoring of Solvent Extraction Streams by Laser-Induced Breakdown and Raman Spectroscopy

Area of Science:

• Nuclear Chemistry
• Analytical Chemistry
• Process Engineering

Background:

• Solvent extraction is crucial for nuclear fuel reprocessing, but requires efficient monitoring.
• Radiolysis and solvent degradation can compromise separation efficiency and phase stability.
• Real-time analysis of organic and aqueous phases is needed for safe and sustainable operations.

Purpose of the Study:

• To develop an integrated optical approach for simultaneous monitoring of extractant composition and raffinate elemental content.
• To assess the feasibility of combining Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) for in situ analysis.
• To provide a reagent-free method for controlling solvent extraction processes in nuclear fuel reprocessing.

Main Methods:

• Raman spectroscopy was used to monitor tributyl phosphate (TBP) concentration in the organic phase.
• Laser-induced breakdown spectroscopy (LIBS) was employed to determine fission-product surrogate concentrations in the aqueous phase.
• Internal standardization was applied to LIBS measurements to account for shot-to-shot fluctuations.

Main Results:

• Raman spectroscopy showed an excellent linear correlation (R² = 0.996) with TBP concentration, with a 1.0% median prediction error.
• LIBS achieved mean absolute percentage errors of 4-8% for fission-product surrogates (Zr, La, Ce, Sr) with detection limits in the g/L range.
• The combined Raman-LIBS scheme demonstrated effective in situ monitoring capabilities.

Conclusions:

• The integrated Raman-LIBS approach provides a robust and reagent-free method for monitoring solvent extraction.
• This technique enhances the safety and sustainability of nuclear fuel reprocessing by enabling real-time process control.
• The study highlights the potential of optical spectroscopy for advanced process analytical technology in the nuclear industry.