Chemical measurements with optical fibers for process control

Area of Science:

• Analytical Chemistry
• Process Chemistry
• Spectroscopy

Background:

• Chemical process control requires accurate in-situ measurements.
• Traditional methods may struggle with complex, automated, or hazardous environments.
• Optical fiber-based spectrophotometry offers a remote sensing solution.

Purpose of the Study:

• To explore remote in-situ spectrophotometric measurements using optical fibers for chemical process control.
• To assess the technique's applicability for measuring specific oxidation states and managing complex solutions.
• To evaluate limitations and potential applications in nuclear fuel reprocessing.

Main Methods:

• In-situ spectrophotometric measurements via optical fibers.
• Discrete wavelength measurements to extend dynamic range.
• Full spectral scans with real-time processing for complex kinetics.
• Utilizing photodiode array spectrophotometers.
• pH measurements in acidic and basic media.

Main Results:

• Successful sequential measurement of plutonium(VI) under automated conditions.
• Extended dynamic range achieved by measuring at wavelengths adjacent to absorption peaks.
• Demonstrated application in uranium isotopic separation (Chemex process).
• Identified Rayleigh scattering as a limitation for UV monitoring in optical fibers.
• Successful pH measurements in both acidic and basic ranges.

Conclusions:

• Remote spectrophotometry with optical fibers is a viable technique for chemical process control, particularly in automated and hazardous settings.
• The method allows for selective and sequential measurement of specific chemical species.
• Advanced spectral analysis and modeling are crucial for managing complex chemical systems and determining kinetics.
• While effective, UV monitoring via optical fibers has limitations that need consideration.