Influence of temperature and electronic stopping power of UO2 irradiated with swift ions on Mo migration

Molybdenum migration was studied in polycrystalline UO2 pellets under irradiation with swift ions. 95Mo isotope was introduced in the samples by ion implantation at a maximum concentration of 0.8 at.%. Irradiation conditions were chosen in order to understand, from a fundamental point of view, the behaviour of Mo in nuclear fuel during reactor operation. In this paper, the effect of three electronic stopping power values (7, 15 and 30 keV.nm−1) were investigated at different temperatures (room temperature, 600 °C and 1000 °C). The Mo concentration profiles before and after irradiation were measured by SIMS (Secondary Ion Mass Spectrometry). Raman spectroscopy was used to probe the defect creation or annealing in the UO2 microstructure. It was evidenced that Mo is very stable in the UO2 matrix as it migrates only for irradiation conditions combining a Se value of 15 or 30 keV.nm−1 and a temperature value of 1000 °C.