The enhanced dissolution of uranium oxides by the application of ultrasound in supercritical fluid carbon dioxide containing dissolved 4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and tributyl phosphate is demonstrated. Under conditions of 60 degreesC and 150 atm. the steady state dissolution of UO3 with sonification is increased by approximately 100%. Furthermore, the effect of adding hydrogen peroxide to the supercritical system above enables the lower oxides of uranium, UO2 and U3O8, to be extracted.