| As part of an effort to produce an LEU graphitic matrix based fuel compact for re-start and operation of the TREAT reactor at Idaho National Laboratory, Idaho State University was tasked with development of a method by which compact matrix material could be characterized for non-graphitic carbon phase identity and quantity present after manufacturing. The objective of this project to develop and test a method by which the identity and quantity of non-graphitic phases in fuel compacts can be determined.
To adequately characterize the fuel compact for the presence and quantity of graphitic and non-graphitic carbon structures, the following techniques were used: scanning electron microscopy (SEM) (for initial scoping analysis, allowing for identification of areas of interest, and possibly identification of graphitic structures within the amorphous carbon sugar/resin residue), Raman spectroscopy (for partial quantification based on sensitivity to types of carbon bonding and structures) and X-ray diffraction (XRD) (for determination of "degree of graphitization"). Transmission electron microscopy (TEM) (for detection of graphite "nucleation" or the beginning of graphitic stacking) and 3-D precession diffraction tomography (for 3-D reconstruction of the sample, including respective volumes of the graphitic and non-graphitic phases) will be conducted in the near term. The analyses were performed on multiple sectioned specimens of fuel compacts, primarily from batch 13102. Additionally, Raman and XRD were performed on one of the matrix precursor materials, the natural graphite powder.
Since the accuracy of any one method and data analysis is unclear, multiple characterization techniques that provide partially overlapping data sets were used, in hopes that a single error affecting multiple methods would be minimized. Also, the techniques selected are partially or wholly complementary, with several requiring similar or identical test configurations and sample preparation.
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