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Uranium Enrichment, Nuclear Fuels, and Fuel Cycles
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
For the first step, raw uranium ore must first be crushed and ground to liberate the uranium from the other minerals. After being washed, it is then treated with sulfuric acid, and depending on the type of ore, it may also undergo several more processing steps. At the end of this process, what is left is a molecular compound called triuranium octoxide. The molecular formula for triuranium octoxide is U3O8, and it is also called uranium yellowcake for short. As the name suggests, yellowcake has a bright yellow color. It is also very heavy and has about the same consistency as premixed concrete. Its average density is about 2 g/cm3(or about twice the density of liquid water). Hence, a cubic meter of yellowcake would weigh about 2000 kg/m3. You can see a sample of refined uranium yellowcake in Figure 10.4. The yellowcake in this sample weighs about 25 kg (approximately 55 lb).
Direct Dissolution of Used Nuclear Fuel in PUREX Solvent: Review and Flowsheet Development
Published in Nuclear Technology, 2022
Disassembly and chopping of the UNF assemblies is followed by treating the fuel by standard voloxidation to drive tritium into the off-gas, which is filtered of fuel fines before the tritium is separated. Standard voloxidation exposes the uranium dioxide fuel to air at a temperature between 500°C and 600°C so that it is converted to a powder of triuranium octoxide. Various options are available for tritium separation from the voloxidation off-gas.8 The fuel powder (predominantly triuranium octoxide) generated by voloxidation is dissolved in hot concentrated nitric acid. Off-gas from acid dissolution is treated first through a condenser before iodine is separated. The off-gas is further treated to separate nitrogen oxides and oxygen before the separation of noble gases. Insoluble fission products, typically noble metal fission products, are separated from the dissolved fuel and stabilized with the fuel hulls into a metal waste form for disposal.