In the next five to ten years, the use of plutonium-enriched fuels is expected to increase significantly. As is the case with irradiated uranium-only fuels, radiation levels within the reactor system can be expected to increase in the event of a severe fuel failure. The in-reactor dissolution of mixed-oxide UO2-PuO2 fuels has been reviewed with consideration of past experience and potentially useful decontamination solutions. The currently most suitable decontamination agent of mixed oxides is a solution of buffered oxalic acid/hydrogen peroxide/gluconic acid (OPG).