Separation of curium from americium using composite sorbents and complexing agent solutions: part 2

TODGA–PAN composite sorbent and (PhSO₃H)₂–BTPhen in nitric acid solution were employed as a system for separation of curium from americium. The influence of aqueous phase composition (complexing agent and nitric acid concentrations) on weight distribution coefficients and Cm/Am separation factor was studied in batch experiments with trace amounts of ²⁴¹Am and ²⁴⁴Cm. Based on the results obtained, column experiment was designed and conducted. The Cm/Am separation factor of 3.8 ± 0.1 found in batch experiments with TODGA–PAN could be reproduced also in column experiment resulting in good separation of Cm from Am. The efficiency of Cm separation from Am in the TODGA–PAN system was compared with the analogous system with DGA resin (Triskem International). After separation on a 0.5 mL column (φ4.7 × 29 mm) the Cm fraction containing 93% of Cm(III) contained only 3% of Am(III) in optimum conditions.

     

Separation of curium and americium from spent fuel reprocessing solutions via displacement complexing chromatography on sulfocationites

Journal of Radioanalytical and Nuclear Chemistry - The process of curium and americium separation from solutions after spent fuel reprocessing by displacement complexing chromatography on sulfonic...     

Spectrochemical analysis of curium and americium samples

Spectrochemical procedures have been developed to determine impurities in americium and curium samples. The simultaneous separation of many impurity elements from the base material (americium and curium) is carried out with extraction and extraction-chromatographic methods using di(2-ethyl hexyl phosphoric acid (D2EHPA).

It is shown that part of the elements (alkalis, alkaline earths, silicon, tungsten, tantalum and other elements) are separated with extraction or sorption of americium and curium; the other part (rare earths, titanium, zirconium, niobium, molybdenum) with the Talspeak process.

Two fractions in the extraction chromatography and three fractions in the extraction separation of americium and curium, containing impurities, are analyzed separately by a.c. or d.c. arc spectrography. To increase the sensitivity of the spectrographic analysis and accelerate the burn-up of impurities from the crater of the carbon electrode bismuth fluoride and sodium chloride were used as chemically active substances. The extraction of impurities from weighed quantities of americium and curium samples of 5–10 mg permits the lower limit of determined impurity concentrations to be extended to 1 × 10⁻⁴–5 × 10⁻³% m/m.     

Analytical separation of americium and curium using high performance liquid chromatography

Americium and curium are separated on a column of cation exchange resin (Aminex) using hydroxyisobutyric acid (α HIBA) as eluent, at a temperature of 80°C. Americium and curium were detected on-line, using their α-emission; the separation was performed in a shielded glove box whose setting-up is given. The time necessary for a separation was between 30 min and 1 hr. The purity of separated fractions was assayed by mass spectrometry. An application to the determination of the isotopic composition of americium and curium in fuels is described.     

Separation of yttrium from heavy lanthanide by CA-100 using the complexing agent

The selective extraction of yttrium from heavy lanthanide by liquid-liquid extraction using CA-100 in the presence of the complexing agent, such as EDTA, DTPA, and HEDTA was investigated. The extraction of heavy lanthanide in the present of the complexing agent was suppressed when compared to that of Y because of the masking effect, but the selective extraction of Y was enhanced. All complexing agents formed 1:1 complex with rare earth elements (RE), and only free rare earth ions could take part in the extraction. The condition for separation was obtained by exploring the effects of the complexing agent concentration, the extractant concentration, pH and the equilibration time on the extraction of the heavy rare earth elements.     

Use of alcoholic solutions for the isolation and purification of americium and curium with anion-exchangers

The sorption of transplutonium (TPE), rare-earth (RE) and other elements by anion-exchangers (Dowex 1 type) from aqueous alcoholic solutions of nitric acid and ammonium thiocyanate was investigated. This investigation allowed the development of simple and effective methods of americium—curium separation from frradiated plutonium. Plutonium, TPE (in a +3 oxidation state) and RE are firmly sorbed by the anion-exchanger from 1 M HNO₃ in 90% alcohol, Fe, Al and fission products Cs, Sr, Nb, Zr, and Ru pass through the column under these conditions. The RE separation from TPE is achieved by washing the column with 0.5M NH₄SCN in 80% alcohol. The column is then washed with 0.5 M HNO₃ in 85% alcohol, and americium—curium separation proceeds. Use of this method for recovery of an irradiated plutonium target containing 100 mg Pu, Am and Cm is described.     

Efficient ion-exchange separation of americium,curium and californium using α-hydroxyα-methylbutyrate

Efficient separation of Am and Cm was performed on a spheroid cation exchanger OSTION LG KS 0800 by elution with ammonium -hydroxy-methylbutyrate. Separation factors for pairs Am-Cm and Cf-Cm have the values of 1.8 and 8.     

Final purification and concentration of americium/curium separated from high-level reprocessing waste

A cation-exchange cycle has been developed for the recovery and concentration of the Am/Cm product from a DTPA/lactic acid solution used in an extraction process for the isolation and separation of the actinides from lanthanide fission products. The optimum pH region for the sorption of Am³⁺ from 0.05M DTPA/1M lactic acid solutions by strongly acidic cation-exchange resins is pH 0.9–1.0. Maximum usable capacities, heights of the exchange zone, and concentration factors for different resins, cross-linkages and temperatures have been determined. Decontamination factors are given for some fission products, as well as U, Np and Pu.     

Separation of cobalt from thiocyanate solutions by crown ether-based impregnated sorbents

A number of impregnated sorbents based on di-(tert-butyldibenzo)-18-crown-6 (DTBDB18C6) and di-(tert-butylcyclohexano)-18-crown-6 (DTBDCH18C6) was obtained using different diluents for the crown ether and the styrene–divinylbenzene support. Sorption characteristics of the sorbents in relation to cobalt ions and ⁶⁰Co radionuclide in thiocyanate solutions were determined within the range of pH of 1–7. It was found the DTBDB18C6-based sorbents were the most efficient for the sorption of cobalt macro quantities whereas the DTBDCH18C6-based ones for the sorption of ⁶⁰Co radionuclide, using nitrobenzene as a diluent. A possibility was shown of the complete cobalt desorption by hydrochloric and nitric acid solutions with the concentration of 0.1–1.0 mol L^–1.     

Simultaneous determination of neptunium,plutonium, americium and curium using coprecipitation with bismuth phosphate

Radiochemical studies of the coprecipitation behaviour of neptunium, plutonium, americium and curium with bismuth phosphate were carried out on the basis of the effect of the following variables: kinds of acid, acidity, and amounts of bismuth and coexisting other elements. Simultaneous determination of the actinide elements using the coprecipitation was accomplished by adding 1 mg of bismuth at 0.2M phosphoric acid and by direct measurement of alpha spectrum of the precipitates. The order of the coprecipitation yields of the elements was also discussed by the difference of both the oxidation states and sulfate complex formation.     

Determination of americium and curium by using ion-exchange in nitric acid-methanol medium for environmental analysis

A method is presented for the determination of americium and curium isotopes in environmental samples, an ion-exchange clean-up procedure being used.     

Determination of plutonium,americium and curium in environmental meterials

A sequential radiochemical scheme for the separation of Pu and Am (along with Cm) from environmental materials is given. Optimum conditions for coprecipitation of these elements on bismuth phosphate and the influence of Fe and Th content of the sample on the recovery of Am were studied. Internal tracers²⁴²Pu and²⁴³Am were used as tracers for Pu and Am, respectively, and estimates were made by alpha-spectrometry. Average recoveries obtained from sea water were 85% and 77% for Pu and Am, respectively. Lower recoveries (<50%) were obtained for Am in sediments. Work carried out as part of the International Atomic Energy Agency Research Contract 1954/RB/RI.     

Sequential separation of neptunium,plutonium, americium and curium using coprecipitation with bismuth phosphate

The reaction of neptunium, plutonium and americium with oxidizing or reducing agents in phosphoric acid solution has been studied to design a separation procedure of the actinide elements using coprecipitation with bismuth phosphate. In the presence of uranium, successive separation of neptunium, plutonium, americium and curium was accomplished by combining the coprecipitation and redox reaction of the elements. The coprecipitation behaviour of fission products during the course of sequential separation of the actinide elements on bismuth phosphate was also discussed.     

Separation of americium and curium by use of tertiary pyridine resin in nitric acid/methanol mixed solvent system

The separation of Am and Cm by using the tertiary pyridine resin embedded in silica beads was studied in nitric acid/methanol mixed solvent system. This separation system of Am and Cm is very simple and easy. The adsorption and separation behaviors of Am and Cm were investigated with changing the nitric acid and the methanol concentrations. It was confirmed that Am can be almost completely separated from Cm.     

A procedure for concentrating americium and curium combined with their separation from plutonium and fission products using a chelating resin

The effect of agitation time and resin quantity on the sorption of americium, curium and europium from mineral acid solutions, using a chelating resin based on aminopolystyrene and Arsenazo I was determined, and the behaviour of plutonium and fission products was investigated under optimum conditions with respect to the sorption of americium and curium. A procedure is proposed for concentrating americium and curium from dilute solutions, combined with their separation from iron, plutonium and fission products. The procedure consists of sorption on the chelating resin from 0.1–1N mineral acid solutions, washing of the resin with 0.5M oxalic acid and 11N sulfuric acid, and elution of americium and curium with 2M triammonium citrate.     

Potentiometric determination of free acidity and uranium in uranyl nitrate solutions using sulfate as complexing agent

In this paper free acid and uranium present together in the range of 0.05–3.0 meq and 20–250 mg, respectively, have been determined by potentiometric titration, using Na₂SO₄ and (NH₄)₂SO₄ complexants and NaOH and Na₂CO₃ as titrants. The results are presented as percentage recovery of free acidity and uranium over the range studied. It has been shown that percentage recovery of free acidity suggests a bias which varied from –5% to +74% at different free acidity and uranium concentrations for the Na₂SO₄–NaOH, Na₂SO₄–Na₂CO₃ and (NH₄)₂SO₄–NaOH complexant — titrant combinations. The percentage recovery of uranium always showed a positive bias which could be up to +8% for extreme free acidity — uranium ratios in the case of Na₂SO₄–Na₂CO₃ complexant — titrant combination. For the other Na₂SO₄–NaOH and (NH₄)₂SO₄–NaOH complexant — titrant combinations a positive bias of up to only +4% has been noticed.     

Determination of plutonium,americium and curium isotopes in radioactive metal wastes deriving from nuclear decommissioning

A radiochemical analytical method, coupling different measurements techniques (alpha spectrometry, liquid scintillation counting and mass-spectrometry) for quantifying the content of the most significant plutonium and americium/curium isotopes in metal waste samples, is presented. The method based on the sequential determination of all the analytes of interest has the great advantage to perform the sample pre-treatment only once, resulting fast and cheap while maintaining sufficient selectivity and sensitivity. The mean values of radiochemical yields and the minimum detectable activities have been evaluated. Significant activity ratios between transuranic isotopes have been revealed and used to investigate the origin of the waste samples.

     

A novel approach for extraction of plutonium and americium from aqueous complexing media

Journal of Radioanalytical and Nuclear Chemistry - A new approach for the extraction of plutonium and americium from aqueous media containing complexing ligands has been investigated using a new...     

Development of novel composite sorbents for the removal of actinides from environmental and analytical solutions

A novel approach to preparing granular sorbents for the separation of actinides has been developed, where the extractant is directly immobilized in an inert matrix. This allows substantially higher extractant loadings in the sorbent than for conventional extraction chromatography resins. This approach utilizes polyacrylonitrile (PAN) as the inert matrix material. The well-known actinide extractant octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) has been loaded into sorbent granules at extractant loadings from 20 to 33 wt.% CMPO. The porosity of the PAN matrix allows the active material to have rapid and complete access to the solution containing the impurities, resulting in improved kinetics and higher sorption capacities. Sorbents containing CMPO were prepared using PAN as a binding matrix, and tested against commercially available actinide extraction chromatography resins. Direct comparative batch contact tests performed with TRU-Resin^Ò and CMPO-PAN using an INEEL tank waste simulant, resulting in distribution coefficient (K _d) values for Am approximately 2-90 times higher for CMPO-PAN than for TRU-Resin. Batch distribution coefficient (K _d) values for Pu were approximately 60-150 times higher for CMPO-PAN than for the TRU-Resin. Acid dependency curves were generated for Am and Pu with CMPO-PAN over a concentration range of 1 mM to 5M HNO₃.