ABSTRACT
In concurrence with objectives of advanced high level nuclear waste(HLW) management, separation of chemically similar trivalent actinides and lanthanides is accomplished using TALSPEAK (Trivalent Actinide - Lanthanide Separation by Phosphorous reagent Extraction from Aqueous Komplexes) process on hollow fibre renewable liquid membrane (HFRLM). Permeability coefficient(Kf) of metal ions are determined under varying concentrations of diethylene triamine pentacaetic acid (DTPA) and H+ in the feed solution, containing 241Am with other metal impurities usually occurred in the HLW, and di(2-ethylhexyl) phosphoric acid (HDEHP) in liquid membrane and receiving emulsion phase. Optimized process conditions obtained are: 5 ± 0.25 L feed solution: containing 0.05 M DTPA, 1 M lactic acid and metal ions under the agitation of 400 ± 15 rpm, receiving phase: emulsion of 400 ± 15 mL 2 M HNO3 + 100 mL 0.2 M HDEHP/dodecane under stirring at 650 ± 25 rpm. The Kf of metal ions obtained under optimized process conditions are in the order: Am(III)<
ABSTRACT
Analysis of U in the samples containing a significant proportion of (232)U and high concentration of Th is of great concern. Transmutation of Th in the nuclear power reactor produces a notable quantity of (232)U (half life 68.9 years) along with fissile isotope (233)U. The decay series of (232)U is initiated with (228)Th (half life 1.9 year) and it is followed by several short lived α emitting progenies, (224)Ra, (220)Rn, (216)Po, (212)Bi and (212)Po. Even at the smallest contamination of (228)Th in the sample, a very high pulse rate of α emission is obtained, which is to be counted for the radiometric determination of [U]. A commercially available anionic type of extractant Alamine®336 is used to obtain the selective extraction of U from other alpha active elements and fission products present in the sample. Experimental conditions of liquid-liquid extraction (LLE) are optimized for obtaining maximum decontamination and recovery of U in the organic phase. The effect of some interfering ionic impurities in the sample on the process of separation is investigated. Depending on the level of the concentration of U in the samples, spectrophotometry or radiometry methods are adopted for its determination after separation by LLE. Under optimized experimental conditions, i.e. 5.5M HCl in the aqueous phase and 0.27M Alamin®336 in the organic phase, the recovery of U is about 100%, the decontamination factor with respect to Th is >2000 and the extraction of fission products like (90)Sr, (144)Ce and (134,137)Cs is negligible. The detection limit for [U] using α radiometry is 10mg/L, even in presence of >100g/L of Th in the sample. Accuracy and precision for the determination of U is also assessed. Reproducibility of results is within 5%. This method shows very good agreement with the results obtained by mass spectrometry.
ABSTRACT
A liquid surfactant membrane (LSMs) containing 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (H(2)A(2)) was tested for the extraction of americium(III) from aqueous nitrate solutions of different compositions. Span 80 a surface-active agent and 0.5M HNO(3) were used as emulsion stabilizer and internal phase respectively in the LSM system. Influence of some important experimental parameters such as pH of the exterior phase, ionic impurities in the exterior phase, concentration of H(2)A(2) and Span80 in liquid membrane phase on the LSM permeation process was systematically studied. The maximum efficiency of Am(III) extraction among group of experiments was 93+/-2% with modified permeability coefficient=1.21+/-0.02min(-1) and the corresponding concentration factor of Am(III) in the receiving phase was 10.5+/-0.2. Extraction of commonly associated fission product elements such as (137)Cs, (152,154)Eu, (90)Sr, (95)Zr, (144)Ce, (95)Nb and (103)Ru was also investigated from feed solution in the exterior phase adjusted at different pH. In a single batch of extraction, more than 90% removal and about 10 times concentration of Am(III) was obtained from uranium and plutonium depleted (process of Plutonium Uranium Recovery by Extraction) waste solution. A complete demulsification of metal loaded emulsion was obtained by chemical using 2-ethylhexanol and physical using freeze thaw method.
