Americium extraction

Figure 1. Stationary Extraction Furnace Assembly for Plutonium Reduction and Americium Extraction.

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). 

Figure 7. Distribution Coefficient for Americium Extraction vs MgC12 Concentration in the NaCl-KCl-MgCl2 and NaCl-CaCI2 MgC12 Salt Systems.

Figure 10. Yield Contours for Americium Extraction vs s/m Ratio for 1, 2, and 3-Stage Counter-Current Extraction. Salt Composition 30 m/o MgCl2, 35 m/o NaCl,...

Americium Extraction (more commonly referred to as Molten Salt Ex-or MSE). This process is specifically designed to reduce the americium content of the plutonium metal. (Am241 spontaneously grows into plutonium as a result of Pu241 decay.) When the impure metal contains more than 1000 ppm of americium, it is run through the MSE process. Otherwise, it bypasses the MSE step and proceeds directly to electrorefining. 

Molten Salt Extraction (MSE) - Salt Recovery. The salt residue from the americium extraction process is made up of NaCl, KC1, MgCl2, PuCl3, and AmCl3. A typical residue weighs approximately 2.0 kg and contains 200 g plutonium, 10-20 g americium, 50 g MgCl3 with the remaining equimolar NaCl-KCl. 

Stationary extraction furnace assembly for Pu reduction and americium extraction. 348/... 

The presence of acidic degradation products of both TBP and CMPO (HDBP, compounds (1) and (5)—strong extracting agents) was responsible for the dramatic elevation of DAm at low acidities. Specific studies have indicated that HDBP could increase americium extraction even for such small amounts as 5 x 10-2 mol L 1 (41), and that DAm depends on phosphinic acid (1) concentration to the power of three (40). The increase of DAm measured at low acidity under dynamic conditions compared to static radiolysis has been attributed to the formation of larger amounts of acidic degradation products, such as (1) and (2) (46). 

Americium extraction (a factor of 106 after only 20 kGy with Et-BTP in hexanol (241) and a decrease greater than 99% after an absorbed dose of 100 kGy with iPr-BTP in a mixture with DMDOHEMA in octanol (240)) ... 

It was necessary, because of economic restraints, to locate the americium extraction battery in the same canyon as the mainline PRF TBP extraction equipment. Compromises in americium extraction equipment design and hydraulics were mandated to accommodate the americium extraction system in this existing facility. In particular, all the columns had to be shortened from the optimum heights recommended by the pilot plant studies. The hydraulics of the installed system were such that the organic flowrate to the extraction column (WE-1 Column) was inadequate with the result that the extraction factor was too low to permit quantitative extraction of all the 21tlAm. Furthermore, the combination of a short extraction column and a 1-inch air pulse leg sometimes led to a hydraulic upset whereby the entire column contents were lost recovery from such hydraulic upsets required an hour or more. 

Co-location of the TBP and DBBP extraction processes in the same facility led inevitably to cross contamination of extractants. This problem was of greater consequence to the PRF system where small concentrations of DBBP in the TBP extractant interfered with plutonium stripping. No specific system malfunctions directly attributable to the presence of TBP in the DBBP solvent were identified. However, dilution of the DBBP extractant with TBP reduces its efficiency as an americium extractant. 

Limited laboratory tests to explore the feasibility of substituting T0P0 (trioctyl phosphine oxide) for DBBP were performed. Advantages cited by Bruns (lj>) for use of 0.15M T0P0-CC1 for DBBP in the americium extraction scheme would not eliminate the need for a difficult-to-control feed acidity adjustment step. Primarily for this latter reason, further consideration of T0P0 as an alternative americium extractant was not actively pursued. 

Americium Extraction (more commonly referred to as Molten Salt Ex-or MSE). This process is specifically designed to reduce the americium content of the plutonium metal. spontaneously... 

CMPO. As with tetravalent actinides, CMPO has the ability to strongly extract hexavalent actinides along with trivalent americium. Extractant dependency studies from hydrochloric and... 

All Ouadi, Benoit Gadenne, Peter Hesemann, et al. Task-specific ionic liquids bearing 2-hydroxybenzylamme units Synthesis and americium-extraction studies. Chem. Eur. J. 2006. 12, 3074-3081. 

The usual effect of increasing the acid concentration is reported to be an increase in the (due to increased amounts of the extractable MA3 in the aqueous phase) followed by a decrease in the (due to formation of the extractant-HNC adduct), resulting in a maximum extraction at an acid concentration between 2 and 6 M. However, one study has noted an increase in americium extraction at nitric acid concentrations from 12 to 16 M. These data are not consistent with the usual view of americium distribution dependence on nitric acid and nitrate concentration, and the authors hypothesize that a TBP HN03 adduct, which is a stronger extractant for americium than TBP alone, is formed above 8 M HNO3 and an organic-phase complex of Am(N03)3 (TBP mHNC ) is formed rather than Am(N03)3 nTBP (26). While one may not absolutely discount this possibility, additional factors such as the extraction of HAm(N03) and deviations from ideal activities in such concentrated acid solutions should definitely be considered. 

Americium extraction from nitric acid solutions by 0.1 M chloroform solution of reagent I... 

The emphasis of work by French researchers has been the use of soft-donor extractants and complexants to enhance actinide/lanthanide group separation (Vitorge 1985, Musikas et al. 1980, Musikas 1985). The relative stability constants for lanthanide and actinide azide complexes reported by Musikas etal. (1980) suggest that hydrazoic acid could function as a useful reagent for this separation. This is confirmed in a later report for Am/Eu separation (Musikas 1985) in which americium extraction is suppressed by complex formation with azide. The separation factors are not very different from those reported by Sekine (1965) using SCN as the complexant in TBP extraction. However, Choppin and Barber (1989) find that, while the trivalent actinide-azide stability constants are somewhat larger than those of the trivalent lanthanides, the complexation enthalpies calculated from the temperature coefficient of the / s do not support the existence of a covalent bonding contribution. 

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