Ammonium uranyl carbonate

Ammonium uranyl carbonate
Names
IUPAC name
uranium(VI)dioxide tetra-ammonium tricarbonate
Other names
uranyl ammonium carbonate
AUC
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.038.156 Edit this at Wikidata
UNII
  • InChI=1S/3CH2O3.4H3N.2O.U/c3*2-1(3)4;;;;;;;/h3*(H2,2,3,4);4*1H3;;;/q;;;;;;;2*-2;+6/p-2
    Key: XHYJUAIOADBAKQ-UHFFFAOYSA-L
  • C(=O)([O-])[O-].C(=O)([O-])[O-].C(=O)([O-])[O-].[NH4+].[NH4+].[NH4+].[NH4+].[O-2]=[U+6]=[O-2]
Properties
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
Insoluble
Structure[1]
monoclinic
C2/c
a = 10·68, b = 9·38, c = 12·85
α = 90°, β = 96.45°°, γ = 90°
1279
4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.[citation needed]

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.[citation needed]

References

  1. ^ 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.
  2. ^ 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.
  3. ^ 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)
  4. ^ 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.
  5. ^ Glazoff, Michael; J. van Rooen, Isabella; D. Coryell, Benjamin; J. Parga, Clemente (2016-05-05). Comparison of Nuclear Fuels for TREAT: UO2 vs. U3O8.
  6. ^ 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.
  7. ^ 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)

Further reading