In-SEM Raman microspectroscopy coupled with EDX--a case study of uranium reference particles

Area of Science:

• Nuclear Chemistry
• Materials Science
• Analytical Chemistry

Background:

• Molecular composition of airborne uranium particles is crucial for nuclear safeguards.
• Existing methods lack the ability to combine particle detection with molecular form analysis.
• High vacuum environments pose challenges for analyzing fragile uranium particles.

Purpose of the Study:

• To develop and validate a hybrid system for simultaneous detection and molecular analysis of uranium particles.
• To assess the molecular composition and oxidation states of uranium particles under high vacuum conditions.
• To evaluate the utility of this technique for nuclear safeguards applications.

Main Methods:

• Utilized a hybrid Scanning Electron Microscope-Confocal Raman Analyzer (SEM-SCA) system for in-situ analysis.
• Employed automatic scanning for uranium particle detection and X-ray microanalysis.
• Performed Raman microanalysis on detected particles within a high vacuum SEM chamber.

Main Results:

• The SEM-SCA system successfully detected and analyzed micrometer-sized uranium particles.
• Uranium particles exhibited significant fragility, leading to damage and changes in oxidation state during analysis.
• Reliable Raman measurements were achieved for uranyl fluoride particles down to 1000 nm on smooth substrates.

Conclusions:

• The hybrid SEM-SCA system is a viable tool for analyzing the molecular composition of uranium particles.
• The observed particle fragility and oxidation state changes provide critical data for nuclear safeguards.
• Further optimization may enable analysis of even smaller uranium-bearing particles.