Ammonium uranyl carbonate

{{chembox

| Watchedfields = changed

| verifiedrevid = 419771945

| ImageFile =

| ImageFile1 = Uranyl-ammonium-carbonate-3D-vdW.png

| ImageSize1 = 300px

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| Name = Ammonium uranyl carbonate

| IUPACName = uranium(VI)dioxide tetra-ammonium tricarbonate

| OtherNames = uranyl ammonium carbonate
AUC

| SystematicName =

| Section1 = {{Chembox Identifiers

| CASNo = 18077-77-5

| ChemSpiderID = 32697822

| PubChem = 76961635

| UNII = 5F29TO8JCF

| SMILES = C(=O)([O-])[O-].C(=O)([O-])[O-].C(=O)([O-])[O-].[NH4+].[NH4+].[NH4+].[NH4+].[O-2]=[U+6]=[O-2]

| StdInChI=1S/3CH2O3.4H3N.2O.U/c3*2-1(3)4;;;;;;;/h3*(H2,2,3,4);4*1H3;;;/q;;;;;;;2*-2;+6/p-2

| StdInChIKey = XHYJUAIOADBAKQ-UHFFFAOYSA-L

}}

| Section2 = {{Chembox Properties

| Formula = UO₂CO₃·2(NH₄)₂CO₃

| MolarMass = 522.199 g/mol

| Density = 2.72

| Solubility = Insoluble

| MeltingPt = Decomposes between 165 °C and 185 °C

| Appearance = lemon-yellow crystalline

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| Section3 = {{Chembox Structure

| Structure_ref ={{cite journal|last1=Graziani|first1=R.|last2=Bombieri|first2=G.|last3=Forsellini|first3=E.|title=Crystal structure of tetra-ammonium uranyl tricarbonate|journal=Journal of the Chemical Society, Dalton Transactions|date=1972|issue=19|pages=2059|doi=10.1039/DT9720002059}}

| CrystalStruct = monoclinic

| SpaceGroup = C_2/c

| PointGroup =

| LattConst_a = 10·68

| LattConst_b = 9·38

| LattConst_c = 12·85

| LattConst_alpha =

| LattConst_beta = 96.45°

| LattConst_gamma =

| LattConst_ref =

| LattConst_Comment =

| UnitCellVolume = 1279

| UnitCellFormulas = 4

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Ammonium uranyl carbonate (UO₂CO₃·2(NH₄)₂CO₃) is known in the uranium processing industry as AUC{{Cite journal|date=2007-03-01|title=The precipitation of ammonium uranyl carbonate (AUC): Thermodynamic and kinetic investigations|journal=Hydrometallurgy|language=en|volume=85|issue=2–4|pages=163–171|doi=10.1016/j.hydromet.2006.08.011|issn=0304-386X|last1=Mellah|first1=A.|last2=Chegrouche|first2=S.|last3=Barkat|first3=M.|bibcode=2007HydMe..85..163M }} 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).{{Cite journal|last1=Krishnan|first1=V. N.|last2=Visweswaraih|first2=M. S.|last3=Shringarpure|first3=P. D.|last4=Koppiker|first4=K. S.|last5=Date|first5=V. G.|title=Studies on the preparation and characterisation of ammonium uranyl carbonate (AUC)|url=http://inis.iaea.org/Search/search.aspx?orig_q=RN:24000267|language=English}} 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.{{Cite journal|last1=Johnson|first1=Timothy J.|last2=Sweet|first2=Lucas E.|last3=Meier|first3=David E.|last4=Mausolf|first4=Edward J.|last5=Kim|first5=Eunja|last6=Weck|first6=Philippe F.|last7=Buck|first7=Edgar C.|last8=McNamara|first8=Bruce K.|editor1-first=Augustus W|editor1-last=Fountain|date=2015-05-22|title=Dehydration of uranyl nitrate hexahydrate to uranyl nitrate trihydrate under ambient conditions as observed via dynamic infrared reflectance spectroscopy|journal=Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XVI|volume=9455|pages=945504|doi=10.1117/12.2179704|s2cid=121901323}} 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.{{Cite book|url=https://www.researchgate.net/publication/305398098|title=Comparison of Nuclear Fuels for TREAT: UO2 vs. U3O8|last1=Glazoff|first1=Michael|last2=J. van Rooen|first2=Isabella|last3=D. Coryell|first3=Benjamin|last4=J. Parga|first4=Clemente|date=2016-05-05}}

The AUC process is followed in South Korea{{Cite journal|date=1994-05-01|title=Crystallization characteristics of ammonium uranyl carbonate (AUC) in ammonium carbonate solutions|journal=Journal of Nuclear Materials|language=en|volume=209|issue=3|pages=306–314|doi=10.1016/0022-3115(94)90268-2|issn=0022-3115|last1=Tae-Joon|first1=Kim|last2=Kyung-Chai|first2=Jeong|last3=Jin-Ho|first3=Park|last4=In-Soon|first4=Chang|last5=Cheong-Song|first5=Choi|bibcode=1994JNuM..209..306T}} and Argentina.{{Cite journal|last1=Dominguez|first1=C. A.|last2=Leyva|first2=A. G.|last3=Marajofsky|first3=A.|title=Conditions study of ammonium uranyl tricarbonate precipitation through ammonium carbonate|url=http://inis.iaea.org/Search/search.aspx?orig_q=RN:24046621|language=Spanish}} 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.{{cn|date=January 2025}}

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.{{cn|date=January 2025}}

Ammonium uranyl carbonate

References

Further reading