Use of Microwave Radiation for Denitration of Uranyl Nitrate Solution and Subsequent Sintering of Uranium Dioxide Fuel Pellets

Fabrication of ceramic UO 2 fuel pellets using microwave radiation was studied. The UO 2 powder was prepared by microwave denitration of a nitric acid solution containing 400 g L –1 uranium. The tapped density (2.39 g cm –3 ) and total specific surface area (2.70 m 2 g –1 ) of the powder obtained met the requirements to the powder for nuclear fuel fabrication (TU (Technical Specification) 95 414–2005: Uranium Dioxide Powder of Ceramic Grade with the Uranium-235 Isotope Content Lower than 5.0%). Pellets were pressed from the UO 2 powder under varied conditions including pressure, its application mode, pressing time, and presence of binder. The pressed pellets were sintered at 1650°С for 2 h in an Ar + 10 vol % H 2 atmosphere under the action of microwave radiation. The density of the samples obtained, 10.40 ± 0.02 g cm –3 , meets the requirements to ceramic fuel pellets used in thermal reactors.