A possible new mechanism for defect formation in irradiated UO2

A defect formation mechanism is proposed in order to explain recently observed Raman defect lines on He2+ irradiated UO2. These defects are formed by electronic stopping of He2+ even though their dE/dx is less than the threshold for track formation. Referring to literature of self-trapped excitons, this mechanism is divided in three steps: creation of electronic defects by electron stopping, stabilization of self-trapped excitons on uranium sublattice and, after accumulation of self-trapped excitons, formation of structural defect on the oxygen sublattice. This proposed mechanism still needs to be validated by more experimental evidence of the Magneli type defect proposed to be the self-trapped excitons on uranium lattice.