Development of an EDS-Based Grain Segmentation Method for MIMAS-MOX Nuclear Fuels

Area of Science:

• Materials Science
• Nuclear Engineering
• Analytical Chemistry

Background:

• Mixed oxide (MOX) nuclear fuels manufactured via the MIMAS process exhibit complex microstructures with varying plutonium content.
• Understanding the phase-dependent microstructure is crucial for fuel performance and safety.

Purpose of the Study:

• To develop and validate a scanning electron microscopy (SEM) method for detailed microstructural and chemical analysis of MIMAS-type MOX fuels.
• To enable phase-dependent grain size analysis within different plutonium-rich and uranium-rich agglomerates.

Main Methods:

• Simultaneous acquisition of energy dispersive X-ray spectroscopy (EDS) and electron backscattered diffraction (EBSD) maps using SEM.
• Post-treatment of EDS/EBSD data to generate maps of plutonium-rich agglomerates, grain boundaries, and porosities.
• Development and validation of a criterion for attributing grains to specific agglomerate types, compared against electron probe microanalyzer (EPMA) data.

Main Results:

• The developed EDS/EBSD method successfully maps microstructural features and chemical compositions in MOX fuels.
• A criterion was established to differentiate between plutonium-rich and uranium-rich grains.
• The method provides insights into the relationship between microstructural features and chemical composition, allowing for accurate grain size measurements in different phases.

Conclusions:

• The presented EDS/EBSD method offers a simple and convenient approach for analyzing the microstructure of MIMAS-type MOX fuels.
• This technique facilitates the study of microstructural and chemical heterogeneities, crucial for optimizing nuclear fuel design and performance.
• The method validates the interdependence of microstructural and chemical characteristics in MOX fuels.