Ammonium uranyl carbonate
) is known in the uranium
processing industry as AUC
and is also called uranyl ammonium carbonate
. This compound is important as a component in the conversion process of uranium hexafluoride
) to uranium dioxide
). The ammonium uranyl carbonate is combined with steam
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. This is separated from the solution, dried with methanol
and then calcinated with hydrogen directly to UO2
to obtain a sinterable grade powdwer. The ex-AUC uranium dioxide powder is free-flowing, relatively coarse (10 µ) and porous with specific surface area in the range of 5m2
/g and suitable for direct pelletisation, avoiding the granulation step. Conversion to UO2
is often performed as the first stage of nuclear fuel
The AUC process is followed in South Korea and Argentina. 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.
Ammonium uranyl carbonate is also one of the many forms called yellowcake in this case it is the product obtainded by the heap leach process.