Extraction Of Americium Research Articles

Radiation stability of benzyldibutylamine and benzyldimethyldodecylammonium nitrate in the extraction of lanthanides and americium

The radiation stability was investigated of organic phases containing tertiary benzyldialkylamines and quaternary benzyltrialkylammonium salts which are sultable for the separation of lanthanides and americium from irradiated nuclear fuel. Attention was paid to changes of the extraction properties in Eu(III) and Am(III) extraction. The influence of the individual components forming the organic phase (extractant, solvent, solubilizer and nitric acid) on the decrease of the extraction capacity of the organic phase after irradiation is discussed. The greatest changes in the distribution coefficients DEu and DAm after irradiation were shown for extraction in the presence of nitric acid. As regards the absorbed dose, these systems can be considered as stable in comparison with organophosphorus extractans.

A study of radiation effects on the extraction of americium(III) with acidic organophosphates

Radiation effects on the extraction of americium(III) with several dialkylphosphoric and monoalkylphosphoric acids have been studied comparatively. The extractants were exposed to60Co γ-rays in the absence and presence of diluent and HNO3. The Df of Am(III) was measured and the yield of radiolytic products was determined after γ-irradiation as a function of the absorbed dose. Di(hexoxyethyl)phosphoric acid was the most susceptible to radiation among the extractants studied and its extractability was weakened by radiation regardless of the presence or absence of diluent or HNO3. Diisodecylphosphoric acid itself showed an enhancement upon irradiation but incurred a depressant effect upon intimate contact with HNO3·Mono(2-ethylhexyl)phosphoric acid showed a decrease of the Df of Am(III), similarly to DIDPA in the presence of HNO3 during γ-irradiation. All the above extractants gave H3PO4 as the principal radiolytic product upon γ-irradiation upon intimate contact with HNO3 causing decreasing solely the extraction of Am(III). Di(2-ethylhexyl)phosphoric acid proved to be the most stable extractant to radiation among those studied.

Effect of gamma-radiation on the extraction of europium and americium by benzyldibutylamine

The effect of gamma irradiation on benzene solutions of benzyldibutylamine with cetyl alcohol used for the extraction of europium and americium from nitrate solutions was investigated. The dependence of the distribution coefficient on the dose absorbed either by the whole system or some efficient component was measured. Nitric acid present during irradiation significantly lowers the radiation stability, while benzyldibutylamine and cetyl alcohol appear to be radiostable components. Up to tens of kGy's—the doses expected in an extraction process from highly active solutions—the system seems to be quite stable.

Extraction of americium, lanthanides and some fission product elements by bidentate phosphonates

The extraction of Am, Eu, Ce(III), Zr(IV), and Sr from aqueous nitric acid— nitrate media by dibutyl N,N-diethylcarbamylphosphonate and dibutyl N,N-diethylcar-bamylmethylenephosphonate dissolved in carbon tetrachloride was studied. The trivalent actinide and lanthanide elements may be separated in certain aqueous phase acidity regions from Fe(III), Zr(IV), and Sr, whereas the separation of actinide elements from the lanthanide elements is poor. The extractant to metal ratio in the extracted complexes of Am, Eu, and Ce(III) is 3. The interferences in the extraction due to acidic impurities in the extracting agent are discussed.

Radiation effects on the extraction of americium(III) with di(2-ethylhexyl) phosphoric acid

Radiation effects on the extraction of Am(III) with di (2-ethylhexyl) phosphoric acid (DEHPA) was studied by exposing DEHPA to gamma rays under various conditions. Gamma irradiation of undiluted DEHPA causes an enhancement of extraction of Am(III) due to the formation of mono (2-ethylhexyl) phosphoric acid (MEHPA) similarly to that of Nd(III). The presence of diluent during irradiation brought about a slight difference from the results in the absence of a diluent. The marked change occurred in Df when the organic solvent was exposed to γ-ray while being mixed with nitric acid solution. An initial slight increase of Df for Am(III) and Nd(III) was followed by a subsequent decrease beyond an absorbed dose of approximately 200 Wh·1−1. This phenomenon was explained by the enhanced decomposition of DEHPA and the subsequent strong hydrolytic and radiolytic decomposition of MEHPA to H3PO4 in the aqueous phase, and the complex forming nature of H3PO4 with Am(III) and Nd(III).

Effect of gamma-radiation on the extraction of europium and americium by benzyldimethyldodecylammonium nitrate

Previously it was found that in the extraction separation on lanthanides and americium from acidic nitrate solutions of nuclear fission products, benzyldimethyldodecylammonium nitrate gives high values of separation coefficients. The change in the extraction capacity of this agent and its solutions in benzene in the extraction of Eu(III) and Am(III) was investigated as a function of the adsorbed dose of ionizing radiation. The slight reduction in the extraction of both metals is caused mainly by the radiolysis products of nitric acid in the organic phase that enter into secondary reactions with both the solvent and the extractant. Comparison of the radiation stability of benzyldimethyldodecylammonium nitrate systems with tertiary amines show that the changes in distribution coefficients in the range of investigated absorbed doses are significantly lower in the former case. The investigated system may be characterized as radiation stable up to about 100 kGy even in the presence of nitric acid.

Synergistic extraction of americium with MEHPA-DEHPA mixed solvent from nitric acid solution

The synergistic effect of the MEHPA-DEHPA mixed system was examined for the extraction of Am(III) from nitric acid solution. Addition of DEHPA or 2-ethylhexanol in MEHPA results in a deleterious effect at MEHPA concentrations lower than 2·10−2M but an enhancing effect at higher concentrations. At DEHPA to MEHPA mole ratios of 2 to 4 in moles, the mixed solvent shows a Df for Am which is 1000 times higher than that of DEHPA.

Extraction of americium with benzyldimethyllaurylammonium nitrate from aqueous nitrate solutions

The extraction of Am(III) with benzyldimethyllaurylammonium nitrate from acidic nitrate solutions was studied. The effects of the kind and concentration of the salting-out agent, of the organic solvents, and of the concentrations of the other components in the extraction system on the distribution ratio values and applicability of this extracting agent to the separation of americium from lanthanoids are discussed. From the analytical data on the organic phase and from the infrared spectra, the composition of the extractable associates and their extraction mechanism were established.

Extraction of americium with benzyldibutylamine from nitrate solutions

The extraction of Am(III) with benzyldibutylamine from nitrate medium was examined in dependence on the concentration of nitric acid, kind and concentration of the salting-out agent in the aqueous phase, and on the solvent. Am(III) is extracted into the organic phase in the form of {(R3NH+)α, Am(NO3)52-}. The IR spectra of the organic phase are discussed and confronted with the results of the chemical analysis of the organic phase. The extraction of Am(III) and of lanthanoids was found to be considerably higher than that of some products of corrosion and nuclear fission (Cs, Sr, Zr, Fe), which is documented by the high values of the separation factors.

Determination of americium and curium in biological samples by extraction and liquid scintillation counting.

An extraction system based on monoisooctyl phosphate appeared to be the most promising since the reagent, when present only as an impurity in a solution of di-2-ethylhexyl phosphate in isooctane, will extract americium from dilute nitric acid. Due to the commercial unavailability of monoisooctyl phosphate the studies reported involve the appraisal of a homologue mono-3, 5, 5-trimethylhexyl phosphate (nonylphosphate). The method described utilizes the direct extraction of americium and curium from an acidic solution of sample ash into a solution of nonyl phosphate and scintillants in toluene. Liquid scintillation counting is done with both phases present in the vial. (LK)

Separation of oxidised americium from trivalent transplutonium elements and lanthanides by solvent extraction

Trace amounts of americium, contained in 0·05 M nitric acid and preheated with 0·05 M ammonium persulphate, remained in the aqueous phase, presumably as the pentavalant species, AMO 2 +, when contacted with the solvent mixture, thenoyltrifluoroacetone (HTTA) and tri- n-octylphosphine oxide (TOPO) in cyclohexane. However, synergism occurred in the solvent extraction of the trivalent actinides and lanthanides with this mixture, the extraction coefficients for these elements approaching 10 2. Occasional spurious results occurred in the solvent extraction of oxidised americium caused by initial failure to oxidise americium solutions quantitatively to the higher valence state and/or partial reduction of the oxidised species back to Am(III). These inconsistencies were eliminated by suitable pretreatment of glassware and solvents and the use of the more stable potassium persulphate as oxidant. The small extraction of the oxidised americium showed little dependence on the diluent, the concentration of HTTA or TOPO, and the persulphate concentration. This contrasted with the marked dependence of the extraction of curium(III) on each of these parameters. The extraction coefficient of this metal ion decreased by a factor greater than 10 2 for various diluents from cyclohexane to chloroform. Tracer studies showed that the composition of the extracting species for curium is Cm(TTA) 2 x (TOPO) 2, where x is NO 3 − or HS 2O 8 −. It was not possible to obtain quantitative extraction of hexavalent americium by this solvent mixture or the organophosphoric reagent, di-(2-ethylhexyl) phosphoric acid in cyclohexane.

Phosphine oxide and quaternary ammonium extraction of americium(III) from concentrated chloride solutions

The extraction of Am(III) and Eu(III) by tri- n-octylphosphine oxide (TOPO) and methyl trialkyl(C 8C 10) ammonium chloride (Adogen 464) from HCl and slightly acidic LiCl solutions was investigated. Linear extraction isotherms showed that macro Eu(III) specoes exist with the same degree of assocition in both organic and aqueous phases suggesting the same behavior for the actinide analog Am(III). Reagent dependences indicated the extraction of primarily AmCl 3·TOPO and AmCl 3·3TOPO from 1 and 5 M LiCl, respectively, and the extraction of only R 4NAmCl 4 (where R 4N + is the quaternary ammonium cation of Adogen 464) from both 1 and 5 M LiCl. However, detailed studies of the TOPO-LiCl and Adogen 464-LiCl systems showed wide variations in lithium and water extraction as a function of aqueous LiCl molarity, so that these systems are not suitable for investigating the aqueous chloride complex equilibria.

Extraction of americium, curium, strontium, and the rare earth elements from aqueous waste solutions of the reprocessing of spent fuel cells of VV�R reactors

Extraction of americium, curium, strontium, and the rare earth elements from aqueous waste solutions of the reprocessing of spent fuel cells of VV�R reactors

Cyclotriphosphazotriene complexing with actinides

The dependence of uranium, plutonium and americium extraction by substituted cyclotriphosphazotriene is discussed.

The extraction of thorium, neptunium, plutonium and americium with sodium amalgam from aqueous solution

In acetic acid and/or hydrochloric acid solutions the extraction of Th, Np, Pu and Am with sodium amalgam was investigated by use of the same procedure as in the case of previous uranium extraction. The results indicate that Np, Pu and Am were extracted in high yields (⪆95 per cent) from acetic acid solutions and plutonium amalgam containing 50 mg/ml Hg was obtained. Thorium was not extracted from acetic acid solutions, but it was slightly extracted from hydrochloric acid solutions.

Solvent extraction of trivalent actinides and lanthanides from a mixture of carboxylic and aminopolyacetic acids

The purity of di(2-ethylhexyl)phosphoric acid (HDEHP) markedly influenced the separation of cerium from americium in a lactic acid solution containing diethylenetriaminepentaacetic acid (DTPA) but had little influence on separations involving the least extractable rare earths, europium and promethium. Synergism occurred in the solvent extraction of these elements by mixtures of thenoyltrifluoroacetone (HTTA) and neutral organophosphates (S) from the same aqueous medium. This effect decreased as S was changed from a phosphine oxide, through phosphonate, to the neutral alkyl phosphates. Tracer studies showed that the composition of each extracting species is given by the general formula M(TTA) 3S 2 where M is a trivalent actinide or lanthanide. These species were independent of the diluent used but the extraction coefficients of the metal ions decreased by a factor of 10 4 from cyclohexane to chloroform. At a constant pH the extraction of americium and cerium was inversely proportional to DTPA concentration in the region 10 −3 −10 −1M. At lower DTPA concentrations the cerium dependence decreased rapidly while the americium increased until at 10 −4M concentration of DTPA the extraction order was reversed. When the DTPA concentration was constant the separation of cerium from americium increased with increasing pH, reaching a constant maximum at pH 2·6 and above.

Evidence for errors in the published enthalpies of formation: Δ fHo(Am 3+,aq) and Δ fHo(AmCl 3,c). The molten salt extraction of americium from plutonium metal

Evidence for errors in the published enthalpies of formation: Δ fHo(Am 3+,aq) and Δ fHo(AmCl 3,c). The molten salt extraction of americium from plutonium metal

Synergic extraction of americium(III) and europium(III) by a quaternary amine and organophosphorous extractants from thiocyanate solutions

Extraction of Am(III) and Eu(III) from 1M NH 4SCN by mixtures of thiocyanate form of Aliquat-336-S and three neutral organophosphorous extractants TOPO, TBPO and TBP in xylene has been investigated. Moderate synergic effects have been obtained which are ascribed to the extraction of mixed metal complexes whose composition has been determined. Probable reasons for the observed synergic effects have been discussed.

Equilibrium constants for aqueous fluoro complexes of scandium, yttrium, americanium(III) and curium(III) by extraction into di-2-ethylhexyl phosphoric acid

From studies of the extraction of yttrium, americium(III) and curium(III) from aqueous fluoride, [F −], into di-2-ethylhexyl phosphoric acid, H 2D 2, it has been deduced that for [F −] = (0·1 − 4·0) × 10 −3 ml −1 and pH = 3·60 substances other than M(HD 2) 3 contribute appreciably to the metal, M, ion distribution. From known equilibrium constants for for aqueous fluoro metal complexes of yttrium it was concluded that, under the prevailing experimental conditions, a substance of the form YF 3. 3H x D x (where x is an unknown integer) also extracts. A method was thus evolved whereby distribution data alone were made to yield equilibrium constants for the stepwise formation of the first three complexes for americium(III) [ β 1 = 2·46 × 10 3, β 2 = 1·28 × 10 6, β 3 = 1·0 × 10 9] and curium-(III) [ β 1 = 2·21 × 10 3, β 2 = 1·50 × 10 6, β 3 = 1·2 × 10 9] at μ = 0·500 (NaClO 4). For [F − = (0·2 − 220) × 10 −5 ml −1 and pH 2·50 scandium extracts overwhelmingly as Sc(HD 2) 3 and β 1 – β 4 are obtained in good agreement with published values. Tests, which throw light on the nature and number of the principle metal species which extract, are described.

Extraction of americium(III) and europium(III) by dinonylnapthalene sulphonic acid and its salts

Equilibrium constants for the exchange of monovalent cations with hydrogen ions in HDNNS dissolved in n-hexane and chloroform have been determined at an ionic strength of unity. Extraction of Am(III) and Eu(III) from various acids and salt solutions containing the monovalent cations has been studied with reference to the selectivity of DNNS − for these ions.