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

Fabrication of ceramic UO2 fuel pellets using microwave radiation was studied. The UO2 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 m2 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 UO2 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 % H2 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.