Americium chlorides

Property Americium Americium dioxide Americium oxide Americium chloride... 

Americium Chloride. Report UCRL-1778 (AECD-3403). J. chem. Phys. 20, 1490 (1952). 

A multi-wall shipping container, holding 400 ml of a solution of americium chloride in a polythene bottle and sealed for over 3 months, exploded. The reason could have been a slow pressure build-up of radiolysis products. Venting and other precautions are recommended. 

Only a few compounds of americium exist. The most important is americium oxide (AmOj), whose main use is in the preparation of other compounds. Americium can also form compounds with the halogens, similar to other transuranic elements—for example, americium iodide (Aml ), americium fluoride, and americium chloride (AmF and ArnGl ). 

Many other trihalide adducts have been prepared. For example, americium chloride has been treated with a number of salts to yield AmCls MCl where MCI is LiCl, CsCl, (C4H9)4NC1, or (C2H5)4NC1. 

In general, the absorption bands of the actinide ions are some ten times more intense than those of the lanthanide ions. Fluorescence, for example, is observed in the trichlorides of uranium, neptunium, americium, and curium, diluted with lanthanum chloride (15). 

Figure 3 shows a flowsheet for plutonium processing at Rocky Flats. Impure plutonium metal is sent through a molten salt extraction (MSE) process to remove americium. The purified plutonium metal is sent to the foundry. Plutonium metal that does not meet foundry requirements is processed further, either through an aqueous or electrorefining process. The waste chloride salt from MSE is dissolved then the actinides are precipitated with carbonate and redissolved in 7f1 HN03 and finally, the plutonium is recovered by an anion exchange process. 

Molten salt extraction residues are processed to recover plutonium by an aqueous precipitation process. The residues are dissolved in dilute HC1, the actinides are precipitated with potassium carbonate, and the precipitate redissolved in nitric acid (7M) to convert from a chloride to a nitrate system. The plutonium is then recovered from the 7M HNO3 by anion exchange and the effluent sent to waste or americium recovery. We are studying actinide (III) carbonate chemistry and looking at new... 

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... 

A production process has evolved from this original work, and is presently used for extracting americium from kilogram amounts of plutonium metal. This process is based upon equilibrium partitioning (by oxidation-reduction reactions) of americium and plutonium between the molten chloride salt and the molten plutonium phase. The chemistry of this process is indicated by the following reactions ... 

Present production processes use two stage counter-current extraction to remove americium from molten plutonium with magnesium chloride based salts. Both 35 mole % NaCl - 35 mole % KC1 - 3D mole % MgCl2 and 50 mole % NaCl-26 mole % CaCl2 - 24 mole % Mg Cl 2 are used for americium extraction. Figures 4 and 5 show the ternary phase diagrams for these salt systemsU0). 

ICRP (1995) considers the experimental data on americium nitrate, chloride, citrate, and hydroxide to support classification of these compounds as either Type F or M. Americium oxides are classified as Type... 

Aluminium bromide, 0060 Aluminium chloride, 0062 Aluminium iodide, 0079 Americium trichloride, 0090... 

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. 

It can be seen that the (111) state is highly stable with respect to disproportionation in aqueous solution and is extremely difficult to oxidize or reduce. There is evidence for the existence of the (II) state since tracer amounts of amencium have been reduced by sodium amalgam and precipitated with barium chloride or europium sulfate as earner. The (IV) state is very unstable in solution the potential for americium(III)-ameridum(IV) was determined by thermal measurements involving solid Am02. Amencium can be oxidized to the (V) or (VI) state with strong oxidizing agents, and the potential for the americium(V)-americium(Vl) couple was determined potentiometrically. 

The process sequence currently used for waste salts (except those containing aluminum for which no process currently exists) is shown in Figure 1. The process includes (1) dilute hydrochloric acid dissolution of residues (2) cation exchange to convert from the chloride to the nitrate system and to remove gross amounts of monovalent impurities (3) anion exchange separation of plutonium (4) oxalate precipitation of americium and (5) calcination of the oxalate at 600°C to yield americium oxide. 

The chemical basis for americium-plutonium separation is the free energies of formation (AG) of the metal chlorides MgCl2, PuCl3, and AmCl3. 

Washing the column with 0.35N nitric acid first will not only remove the chloride ions, but also prevents the formation of hydrolytic or polymeric species of plutonium in comparison with the water wash formerly used. The second wash has been shown to effectively displace the impurity cations however, some bleeding of plutonium and americium may occur and cause higher... 

Additional work in progress includes optimization of parameters affecting the oxalate precipitation step this includes determination of the chloride concentration required to solubilize lead the oxalate ion concentration required for maximum americium recovery with minimum impurity precipitation precipitate aging and hydrogen ion concentrations that will minimize americium solubility yet maximize impurity solubilization. 

A general method for preparation of all An metals is by reduction of AnF3 or AnF4 with vapors of Li, Mg, Ca, or Ba at 1100 to 1400°C the chlorides or oxides are sometimes used. There are some special methods such as the preparation of Th or Pa from their tetraiodides by the van Arkel-de Boer process, or the following reaction for the relatively volatile americium ... 

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