Process for dissolving the plutonium or plutonium alloy

The invention concerns a method for dissolving plutonium or a plutonium alloy by contacting with an aqueous dissolving mixture, wherein said dissolving mixture comprises nitric acid, a carboxylic acid with complex-forming properties with respect to plutonium, and a compound comprising at least a NH2 radical such as urea. The invention also concerns a method for converting plutonium or a plutonium alloy into plutonium oxide, and for making nuclear fuel from said oxide. The invention is particularly useful for dismantling plutonium contained in nuclear weapons so as to use it in civil nuclear reactors, in particular in the form of MOX fuel.