Americium separation

Europium/americium separation factors for a series of acidic extractants (Sekine and Dyrssen 1964). 

The many possible oxidation states of the actinides up to americium make the chemistry of their compounds rather extensive and complicated. Taking plutonium as an example, it exhibits oxidation states of -E 3, -E 4, +5 and -E 6, four being the most stable oxidation state. These states are all known in solution, for example Pu" as Pu ", and Pu as PuOj. PuOl" is analogous to UO , which is the stable uranium ion in solution. Each oxidation state is characterised by a different colour, for example PuOj is pink, but change of oxidation state and disproportionation can occur very readily between the various states. The chemistry in solution is also complicated by the ease of complex formation. However, plutonium can also form compounds such as oxides, carbides, nitrides and anhydrous halides which do not involve reactions in solution. Hence for example, it forms a violet fluoride, PuFj. and a brown fluoride. Pup4 a monoxide, PuO (probably an interstitial compound), and a stable dioxide, PUO2. The dioxide was the first compound of an artificial element to be separated in a weighable amount and the first to be identified by X-ray diffraction methods. 

Kilogram quantities of americium as Am can be obtained by the processing of reactor-produced plutonium. Much of this material contains an appreciable proportion of Pu, which is the parent of Am. Separation of the americium is effected by precipitation, ion exchange, or solvent extraction. 

EXTRACTANT CONCENTRATION GRADIENT IN THE AMERICIUM(III) / CURIUM(III) SEPARATION BY COUNTERCURRENT CHROMATOGRAPHY... 

Early experimental work in electrorefining at Los Alamos by Mullins et-all ) demonstrated that americium could be partitioned between molten plutonium and a molten NaCl-KCl salt containing Pu+3 ions, and Knighton et-al(8), working at ANL on molten salt separation processes for fuel reprocessing, demonstrated that americium could be extracted from Mg-Zn-Pu-Am alloys with immiscible molten magnesium chloride salts. Work... 

Americium metal has been obtained by heating americium oxide, Am203, with lanthanum at 1,200 °C americium, which is more volatile than other actinides, volatilizes and can readily be separated from other actinides. Am02 can be obtained by igniting most trivalent americium compounds (Budavari 1996 Cotton and Wilkinson 1980 UIC 1997). 

Guogang J, Testa C, Desideri D, et al. 1998. Sequential separation and determination of plutonium, americium-241 and strontium-90 in soils and sediments. J Radioanal Nucl Chem 230(l-2) 21-27. 

Sekine K, Imai T, Kasai A. 1987. Liquid-liquid extraction separation and sequential determination of plutonium and americium in environmental samples by alpha-spectrometry. Talanta 34(6) 567-570. 

Pressly, R. S. Separation of Americium and Promethium. Report ORNL-... 

Schell et al. [ 57] have described a sorption technique for sampling plutonium and americium, from up to 4000 litres of water in 3 h. Battelle large-volume water samples consisting of 0.3 xm Millipore filters and sorption beds of aluminium oxide were used. Particulate, soluble, and presumed colloidal fractions are collected and analysed separately. The technique has been used in fresh and saline waters, and has proved to be reliable and comparatively simple. 

Street, K., and G. T. Seaborg Separation of Americium and Curium from... 

Dr. Glenn T. Seaborg proposed the term actinide for the new heavy elements that were predicted to follow the lanthanide series (Z-57 to Z-71). Dr. Seaborg believed that the actinides would be difficult to discover, and he proposed they would be trivalent homo-logues to the elements in the lanthanide series in which the 4f orbitals would be filled. His team at the Lawrence Berkeley National Laboratory (LBNL), located at the University of California s Berkeley campus, separated Z-95 (americium) and Z-96 (curium) as trivalent homologues of two of the elements in the lanthanide series located just above them in the periodic table. 

The Pu-242 obtained in the nuclear reaction is separated by chemical extraction. Americium metal can be prepared from its dioxide by reducing with lanthanum metal at high temperature in a vacuum. 

Americium may be separated from other elements, particularly from the lanthanides or other actinide elements, by techniques involving oxidation, ion exchange and solvent extraction. One oxidation method involves precipitation of the metal in its trivalent state as oxalate (controlled precipitation). Alternatively, it may be separated by precipitating out lanthanide elements as fluorosilicates leaving americium in the solution. Americium may also he oxidized from trivalent to pentavalent state by hypochlorite in potassium carbonate solution. The product potassium americium (V) carbonate precipitates out. Curium and rare earth metals remain in the solution. An alternative approach is to oxidize Am3+ to Am022+ in dilute acid using peroxydisulfate. Am02 is soluble in fluoride solution, while trivalent curium and lanthanides are insoluble. 

Americium and other actinide elements may be separated from lanthanides by solvent extraction. Lithium chloride solution and an eight to nine carbon tertiary amine are used in the process. Americium is then separated from curium by the above methods. 

Albright, D. Barbour, L. 1999. Separated neptunium and americium. In Albright, D. O Neil K. (eds) The Challenges of Fissile Material Control. ISIS, Washington, DC, 85-96. 

Actinides were determined at the ultratrace level in moss samples collected from the eastern Italian Alps (1500 m a.s.l.). The frozen samples were cut into 1-2 cm sections and analyzed separately to obtain the distribution curves of the vertical concentrations. For plutonium and americium isotope analysis, 1-2 g of the samples were ashed, leached, separated with respect to analytes and analyzed by alpha spectrometry and LA-ICP-MS after the plutonium or americium had been electroplated on a stainless steel disk.23 Estimated limits of quantification of LA-ICP-MS for actinide radionuclides deposited on stainless steel plates after chemical separation are summarized in Table 9.45. For most of the long-lived radionuclides in moss samples, lower limits of determination were found at the 10 15gg 1 concentration level compared to those of a - spectrometry 23... 

Litvina, M.N., Chmutova, M.K., Myasoedov, B.F., Kabachnik, M.1.1996. Extraction and separation factors of lanthanides and americium in aqueous nitric acid- diaryl(dialkyl)-(dialkylcarbamoyl-methyl)phosphine oxide systems. Radiochemistry 38 (6) 494 -99. 

Zhu, Y. 1995. The separation of americium from light lanthanides by Cyanex 301 extraction. Radiochim. Acta 68 (1) 95-98. 

Chen, J., Tian, G., Jiao, R., Zhu, Y. 2001. A hot test for separating americium from fission product lanthanides by purified Cyanex 301 extraction in centrifugal contactors. Actinides 2001, Hayama, Japan, November 4—9. 

Bhattacharyya, A., Mohapatra, P.K., Manchanda, V.K. 2006. Separation of americium(in) and europium(IB) from nitrate medium using a binary mixture of Cyanex-301 with N-donor ligands. Solvent Extr. Ion Exch. 24 (1) 1-17. 

Alyapyshev, M.Yu., Babain, V.A., Smirnov, I.V., Shadrin, A.Yu. 2006. Separation of americium and europium from solutions of nitric and perchloric acid using dipicolinic acid diamides. Czech. J. Phys. 56, Suppl. D D469-D475. 

Weaver, B.S., Kappelmann, F.A. 1964. Talspeak A new method of separating americium and curium from lanthanides by extraction from an aqueous solution of aminopo-lyacetic acid complex with a monoacidic phosphate or phosphonate. ORNL-3559. 

Rais, J.,Tachimori, S. 1994. Extraction separation of tervalent americium and lanthanides in the presence of some soft and hard donors and dicarbollide. Sep. Sci. Technol. 29 (10) 1347-1365. 

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