Determination of Gd concentration profile in UO2–Gd2O3 fuel pellets

Abstract A transversal mapping of the Gd concentration was measured in UO 2 –Gd 2 O 3 nuclear fuel pellets by electron paramagnetic resonance spectroscopy (EPR). The quantification was made from the comparison with a Gd 2 O 3 reference sample. The nominal concentration in the pellets is UO 2 : 7.5% Gd 2 O 3 . A concentration gradient was found, which indicates that the Gd 2 O 3 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 Gd 3+ ions in the UO 2 matrix.