Americium hydroxide

Solubility of Americium Hydroxide. Solutions containing greater than 10-6 M americium were examined by spectrophotometry to verify whether or not polymers were present. The molar extinction coefficient measured for the 503 nm absorption band was found to remain constant at e = 390 5 for all investigated solutions at pH = 3 6. Spectra recorded up to 850 nm in this pH range show the typical absorption bands of the Am3+ ion, which are similar to those observed in a dilute HCIO4 solution, without broadening or displacement. The concentration of americium ions in equilibrium solutions, [Am]s, is, therefore, considered a composite of only monomer species ... 

Figure 5. Americium hydroxide slurry after standing 12 h...

Figure 6. Americium hydroxide in stainless steel filter boat...

Synthesis of crystalline americium hydroxide, Am(OH)j, and determination of its enthalpy of formation. Estimation of the solubility-product constants of actinide(lll) hydroxides. Radiochim. Acta, 66/67, 89-93. 

Rai et al. (1983), Edelstein et al. (1983) and Nitsche and Edelstein (1985) studied the solubility of amorphous americium hydroxide. GuUlaumont etal. (2003) reviewed these data and determined a solubility constant at zero ionic strength of... 

Morss and Wilhams (1994) also estimated the solubility constant data for Bk(OH)g(s) and Cf(OH)g(s) from thermodynamic data determined for americium hydroxide and the relative change across the solubility of the lanthanide hydroxide phases. The solubilities (log determined for the two phases were 13.5 2.0 and 13.0 2.0, respectively. These values are retained in the present study ... 

Alpha carbon atoms, 348 Alpha decay, 417, 443 Alpha particle, 417 scattering, 245 Aluminum boiling point, 365 compounds, 102 heat of vaporization, 365 hydration energy, 368 hydroxide, 371 ionization energies, 269, 374 metallic solid, 365 occurrence, 373 properties, 101 preparation, 238. 373 reducing agent, 367 Alums, 403 Americium... 

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... 

Taya A, Hotz G, Seidel A. 1986. Biochemical and electron microscopic studies on binding and transport of americium and plutonium hydroxide polymers in bovine alveolar macrophages and rat lungs. J Aerosol Sci 17(3) 370-375. 

In comparison to plutonium both americium and curium are taken up by plants quite readily. The concentration factors for both americium and curium are 10-4 to 10-2 (127). While plutonium has been the subject of considerable research into its environmental impact there have been few investigations into americium and curium. Bondi-etti et al (94) have concluded that plutonium hydroxide polymers would be resistant... 

Americium sorption was decreased significantly when HEDTA or EDTA were present. Complexation of americium by these strong chelating agents was responsible for this behavior. Sodium hydroxide increased americium sorption but, again, its effect on americium was probably a manifestation of its effect on the sediment minerals. 

In summary, the solubility and sorption reactions of cobalt, strontium, neptunium, plutonium, and americium were found to be dependent on HLW compositions. Evidence revealed the formation in HLW of organic complexes of cobalt, strontium, and americium, and of hydroxide complexes of neptunium(V) and plutonium(V). Sorption reactions were dependent on radioelement complex formation and suspected waste/sediment reactions. These data can aid in assessing effects of future HLW processing operations as well as in judging the feasibility of continued storage of HLW in existing tanks. 

In a separate experiment, the hydroxide precipitate of americium was produced directly in each experimental solution 10 mL solution of 0.1 M HCIO4 containing 1.3 x 10-3 M americium was mixed with 10 mL of 0.1 M NaC104 and made alkaline to produce the hydroxide precipitate by adjusting the pH with addition of NaOH. Solutions thus prepared were left under argon gas to attain the solubility equilibrium. 

After changing the medium (allowing the elimination of DTPA) on the TBP column, the americium containing small amounts of Cm(III) and Ln(III) (Eu, Gd, Ce) is precipitated as an hydroxide, and redissolved in the minimum of nitric acid. This solution is then placed in 3.5 M K CO medium and AmO2... 

Co-extraction of Np and Pu The waste from the uranium extraction battery is adjusted to 5 M LiNO and then passed through an IRA-400 column at a high flow rate (30 L/h). The americium is not sorbed. Neptunium and plutonium are stripped by a dilute nitric acid solution and precipitated as a hydroxide, and calcined to yield mixture of oxides. 

The flowsheet for the FFTF Pu02 production is shown in Figure 2. Briefly, the plutonium metal is converted to an impure oxide by burning the metal in air. This is followed by dissolution of the impure oxide in a 15.6 M HN03 - 0.5 M HF solution. The americium is separated from the plutonium by precipitation of the plutonium as the peroxide. Americium does not form an insoluble peroxide and stays in the filtrate with other cationic impurities. The active peroxide filtrate is slowly dripped into 9 M NaOH. The combination of strong alkali and heat destroys the peroxides and precipitates the americium as the hydroxide. Any residual plutonium in the filtrate, along with other cations, is precipitated also as the hydroxide. The flowsheet for the americium oxide production is shown in Figure 3. 

Proper adjustment of CAW acidity within this narrow range obviously requires careful control of in-line addition of concentrated NaOH to an unbuffered solution. Over-addition of NaOH precipitates hydroxide solids which scavenge actinides and interfere greatly with phase dispersion and separation. Insufficient addition of NaOH leaves, of course, excess HNO3 to compete with americium for DBBP extractant. 

By solid-state reactions of Am02 with AI2O3 at 1250°C. in H2 no compound formation could be observed. In order not to increase the reaction temperature, a 1 1 mixed hydroxide precipitation of americium and aluminium reacted in H2 for 2-8 hrs. at 1250°C. This resulted in the quantitative formation of rose-colored AmAlOa having the hexagonal distorted perovskite structure of the aluminates of La, Pr, Nd (JJ), and Pu (17,35). 

Hydroxide, aqua, and hydrates. From the similar absorption spectra of Am in aqueous solution, AmCls, and in Lads, and the linear relationship between the decay rate of the americium fluorescence and the number of inner-sphere water molecules, it has been concluded that Am " is coordinated by nine inner-sphere water molecules. Similarly, the hydration number for the Cm ion has been estimated to be nine on the basis of fluorescence lifetimes. EXAFS studies of aqueous Am and Cm, however, have suggested coordination numbers closer to 10. " EXAFS investigation of Cf " " in aqueous solution indicates a coordination number of 8.5 ( 1.5), with a Cf—O distances of 2.41 0.02 A. This coordination number was confirmed for Am in the solid state by isolation of single crystals of the triflate salt of nonaqua complex, which contains a tricapped, trigonal prismatic cation that is isostructural with the analogous Pu" compound. ... 

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