Ammonium uranyl carbonate

Ammonium uranyl carbonate
Names

IUPAC name uranium(VI)dioxide tetra-ammonium tricarbonate
Other names uranyl ammonium carbonate AUC
Identifiers
CAS Number	18077-77-5
3D model (JSmol)	Interactive image
ChemSpider	32697822
ECHA InfoCard	100.038.156
PubChem CID	76961635
UNII	5F29TO8JCF
InChI InChI=1S/3CH2O3.4H3N.2O.U/c32-1(3)4;;;;;;;/h3(H2,2,3,4);41H3;;;/q;;;;;;;2-2;+6/p-2 Key: XHYJUAIOADBAKQ-UHFFFAOYSA-L
SMILES C(=O)([O-])[O-].C(=O)([O-])[O-].C(=O)([O-])[O-].[NH4+].[NH4+].[NH4+].[NH4+].[O-2]=[U+6]=[O-2]
Properties
Chemical formula	UO₂CO₃·2(NH₄)₂CO₃
Molar mass	522.199 g/mol
Appearance	lemon-yellow crystalline^[1]
Density	2.72^[1]
Melting point	Decomposes between 165 °C and 185 °C
Solubility in water	Insoluble
Structure^[1]
Crystal structure	monoclinic
Space group	C_2/c
Lattice constant	a = 10·68, b = 9·38, c = 12·85 α = 90°, β = 96.45°°, γ = 90°
Lattice volume (V)	1279
Formula units (Z)	4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references

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.

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.

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References

^ ^a ^b ^c Graziani, R.; Bombieri, G.; Forsellini, E. (1972). "Crystal structure of tetra-ammonium uranyl tricarbonate". Journal of the Chemical Society, Dalton Transactions (19): 2059. doi:10.1039/DT9720002059.
^ Mellah, A.; Chegrouche, S.; Barkat, M. (2007-03-01). "The precipitation of ammonium uranyl carbonate (AUC): Thermodynamic and kinetic investigations". Hydrometallurgy. 85 (2–4): 163–171. Bibcode:2007HydMe..85..163M. doi:10.1016/j.hydromet.2006.08.011. ISSN 0304-386X.
^ Krishnan, V. N.; Visweswaraih, M. S.; Shringarpure, P. D.; Koppiker, K. S.; Date, V. G. "Studies on the preparation and characterisation of ammonium uranyl carbonate (AUC)". {{cite journal}}: Cite journal requires |journal= (help)
^ Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.; Mausolf, Edward J.; Kim, Eunja; Weck, Philippe F.; Buck, Edgar C.; McNamara, Bruce K. (2015-05-22). Fountain, Augustus W (ed.). "Dehydration of uranyl nitrate hexahydrate to uranyl nitrate trihydrate under ambient conditions as observed via dynamic infrared reflectance spectroscopy". Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XVI. 9455: 945504. doi:10.1117/12.2179704. S2CID 121901323.
^ Glazoff, Michael; J. van Rooen, Isabella; D. Coryell, Benjamin; J. Parga, Clemente (2016-05-05). Comparison of Nuclear Fuels for TREAT: UO2 vs. U3O8.
^ Tae-Joon, Kim; Kyung-Chai, Jeong; Jin-Ho, Park; In-Soon, Chang; Cheong-Song, Choi (1994-05-01). "Crystallization characteristics of ammonium uranyl carbonate (AUC) in ammonium carbonate solutions". Journal of Nuclear Materials. 209 (3): 306–314. Bibcode:1994JNuM..209..306T. doi:10.1016/0022-3115(94)90268-2. ISSN 0022-3115.
^ Dominguez, C. A.; Leyva, A. G.; Marajofsky, A. "Conditions study of ammonium uranyl tricarbonate precipitation through ammonium carbonate" (in Spanish). {{cite journal}}: Cite journal requires |journal= (help)

Extra reading

Yi-Ming, Pan; Che-Bao, Ma; Nien-Nan, Hsu (September 1981). "The conversion of UO2 via ammonium uranyl carbonate: Study of precipitation, chemical variation and powder properties". Journal of Nuclear Materials. 99 (2–3): 135–147. Bibcode:1981JNuM...99..135Y. doi:10.1016/0022-3115(81)90182-3.
Kan-Sen, Chou; Ding-Yi, Lin; Mu-Chang, Shieh (May 1989). "Precipitation studies of ammonium uranyl carbonate from UO2F2 solutions". Journal of Nuclear Materials. 165 (2): 171–178. Bibcode:1989JNuM..165..171K. doi:10.1016/0022-3115(89)90246-8.
Mellah, A.; Chegrouche, S.; Barkat, M. (March 2007). "The precipitation of ammonium uranyl carbonate (AUC): Thermodynamic and kinetic investigations". Hydrometallurgy. 85 (2–4): 163–171. Bibcode:2007HydMe..85..163M. doi:10.1016/j.hydromet.2006.08.011.