Described are method of treating a radioactive organic waste stream comprising: (a) mixing a radioactive organic waste stream comprising organic compounds and radionuclides with phosphoric acid to form a reaction mixture; (b) heating the reaction mixture to a desired temperature in the presence of an oxidant to oxidize organic compounds present in the waste stream, and removing oxidized organic compounds from the reaction mixture; (c) optionally, adding a reducing agent to the reaction mixture to form insoluble radioactive metal phosphate compounds comprising one or more of the radionuclides, and separating the insoluble radioactive metal phosphate compounds from the reaction mixture; (d) optionally, adding a fluorine compound to the reaction mixture to react with uranium that may be present in the reaction mixture to form uranium hexafluoride, and removing uranium hexafluoride from the reaction mixture; (e) adding ammonia to the reaction mixture to neutralize phosphoric acid and to form ammonium phosphate complexes comprising one or more of the radionuclides, and separating the ammonium phosphate complexes from the reaction mixture to yield an ammonium phosphate liquor, wherein the method includes performing at least one of steps (c) and (d).