Characterization by electron probe microanalysis, Raman spectroscopy and transmission electron microscopy of a MOX fuel sintered from a freeze-granulated powder

The microstructure of a 98.7 % dense U0.856Pu0.144O1.993 sintered sample (average grain size around 1.5 mu m) has been characterized by electron probe microanalysis, Raman spectroscopy and transmission electron microscopy. Raman spectroscopy gives results comparable to electron probe microanalysis in terms of studying the spatial distribution of plutonium in a homogeneous sintered MOX fuel. The use of transmission electron microscopy allows additional characterizations of great interest for investigating the chemical homogeneity of sintered MOX fuels. At the scale of the elementary grains constituting the sintered polycrystal, a variation in the Pu/(U+Pu) content has been observed which can change typically from 0 to about 40 at% over a short distance (from 100 to 150 nm). Thereby, the thorough characterization of the microstructure of MOX fuels by transmission electron microscopy is a critical step to understand their genesis and to apprehend their dissolution properties with a view to their reprocessing.

Automated summary

The microstructure of a 98.7% dense U0.856Pu0.144O1.993 sintered sample has been characterized by electron probe microanalysis, Raman spectroscopy, and transmission electron microscopy. Results from Raman spectroscopy and electron probe microanalysis are comparable in studying the spatial distribution of plutonium in a homogeneous sintered MOX fuel. Transmission electron microscopy provides additional characterizations for investigating the chemical homogeneity of sintered MOX fuels, revealing variations in the Pu/(U+Pu) content at the scale of elementary grains.