[en] The wetting of irradiated ceramics by liquid metals has been examined to provide guidance about the possible differences between the surface energy, γsub(S)sub(V), of used and unused uranium dioxide fuel. The invariant contact angles measured for copper drops at 1100⁰C in argon, resting on UO₂ fuel samples with burn-up levels of up to 1,2%, suggests that little change in γsub(S)sub(V) had occurred during irradiation. Analysis of the evidence from this work and the wetting behaviour of low neutron-irradiated Al₂O₃ and MgO suggests that several processes occur: for example, defect damage and stoichiometric changes during irradiation which tend to increase the surface energy and fission product contamination and recovery of defect damage which tend to decrease it. (orig.)