Determination of Gd concentration profile in UO2-Gd2O3 fuel pellets
  A transversal mapping of the Gd concentration was measured in UO2-Gd2O3 nuclear fuel pellets by electron paramagnetic resonance spectroscopy (EPR). The quantification was made from the comparison with a Gd2O3 reference sample. The nominal concentration in the pellets is UO2: 7.5 % Gd2O3. A concentration gradient was found, which indicates that the Gd2O3 amount diminishes towards the edges of the pellets. The concentration varies from (9.3 +/- 0.5)% in the center to (5.8 +/- 0.3)% in one of the edges. The method was found to be particularly suitable for the precise mapping of the distribution of Gd3+ ions in the UO2 matrix. 
D. Tobia, E. L. Winkler, J. Milano, A. Butera, R. Kempf, L. Bianchi,   F. Kaufmann
nucl-ex cond-mat.mtrl-sci