Ammonium uranyl carbonate
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| Template:Longitem | UO2CO3·2(NH4)2CO3 |
| Molar mass | 522.199 g/mol |
| Appearance | lemon-yellow crystalline[1] |
| Density | 2.72[1] |
| Melting point | Template:Chembox CalcTemperatures |
| Template:Longitem | monoclinic |
| Template:Longitem | C2/c |
| Template:Longitem | a = 10·68, b = 9·38, c = 12·85 α = 90°, β = 96.45°°, γ = 90°
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Ammonium uranyl carbonate (UO2CO3·2(NH4)2CO3) is known in the uranium processing industry as AUC[2] and is also called uranyl ammonium carbonate. This compound is important as a component in the conversion process of uranium hexafluoride (UF6) to uranium dioxide (UO2).[3] The ammonium uranyl carbonate is combined with steam and hydrogen at 500–600 °C to yield UO2. In another process aqueous uranyl nitrate, known as uranyl nitrate liquor (UNL) is treated with ammonium bicarbonate to form ammonium uranyl carbonate as a solid precipitate.[4] This is separated from the solution, dried with methanol and then calcinated with hydrogen directly to UO2 to obtain a sinterable grade powder. The ex-AUC uranium dioxide powder is free-flowing, relatively coarse (10 μ) and porous with specific surface area in the range of 5 m2/g and suitable for direct pelletisation, avoiding the granulation step. Conversion to UO2 is often performed as the first stage of nuclear fuel fabrication.[5]
The AUC process is followed in South Korea[6] and Argentina.[7] In the AUC route, calcination, reduction and stabilization are simultaneously carried out in a vertical fluidized bed reactor. In most countries, sinterable grade UO2 powder for nuclear fuel is obtained by the ammonium diuranate (ADU) process, which requires several more steps.Script error: No such module "Unsubst".
Ammonium uranyl carbonate is also one of the many forms called yellowcake; in this case it is the product obtained by the heap leach process.Script error: No such module "Unsubst".
References
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Further reading
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