Synergy of electronic and nuclear energy depositions on the kinetics of extended defects formation in UO2, based on in situ TEM observations of ion-irradiation-induced microstructure evolution

•Dislocation loop change under dual-beam irradiation was studied using in situ TEM.•With ion fluence increase, small dislocation loops nucleate and grow.•Similar evolution is studied regardless of the energy losses regime.•Electronic excitations lead to an acceleration of the extended defect formation kinetics.