Rapid separations of corrosion and fission products

A separation scheme of a complex mixture of radiohygienically important radionuclides of corrosion and fission products has been worked out. Rapid separation by means of solvent extractions with metal (sodium, antimony, zinc) diethyldithiocarbamates has been achieved. Chloroform containing metal diethyldithiocarbamates has been used as the organic phase. The procedure permits to separate selectively the representative radionuclides. The selectivity of separation was verified by gamma spectrometry.     

Quantitative separation of carrier-free cerium from fission products

The extraction of Ce (IV) by di-(2-ethylhexyl)-phosphoric acid (HDEHP) has been studied as a function of nitric acid concentration. Using the distribution coefficient data, the optimum conditions for recovery of Ce (IV) from nitric acid medium were arrived at. Under the conditions employed for Ce(IV), a small percentage of Ru was also found to be extracted. Cerium could be selectively stripped from the organic phase with 8M HNO₃/30% H₂O₂ solution. This procedure led to the recovery of¹⁴⁴Ce free of¹⁰⁶Ru. Based on the solvent extraction data, an extraction-chromatographic procedure employing HDEHP (40% w/w) loaded on Amberlite XAD-7 as the stationary phase was developed for the isolation of pure, carrier-free¹⁴⁴Ce from the spent fuel solution.     

Advanced system for separation of rare-earth fission products

A microprocessor-controlled radiochemical separation system, which has been developed at the INEL, has been further advanced to separate individual rare-earth elements from mixed fission products in times of a few minutes. The system was composed of an automated chemistry system fed by two ∼300μg²⁵²Cf sources coupled directly by a He-jet to transport the fission products. Chemical separations were performed using two high performance liquid chromatography columns coupled in series. The first column separated the rare-earth group by extraction chromatography using dihexyldiethylcarbamoylmethylphosphonate (DHDECMP) adsorbed on Vydac C₈ resin. The second column isolated the individual rare-earth elements by cation exchange chromatography using Aminex A-9 resin with α-hydroxyisobutyric acid (α-HIBA) as the eluent. Significant results, which have been obtained to date with this advanced system, are the identification of several new neutron-rich rare-earth isotopes including¹⁵⁵Pm (T=48±4 s) and¹⁶³Gd (T=68±3 s). In addition a half-life of 41±4 s is reported for¹⁶⁰Eu. Work supported by the U.S. Department of Energy under DOE Contract No. De-ACO7-76IDO-1570.     

The separation of fission products by electrophoretic focussing of ions

Electrophoretic focussing of ions was applied to the separation of the long-lived fission products Zr, Nb, Ru, Y, Ce, Sr and Cs. With hydrochloric acid and nitrilotriacetic acid as the anodic and cathodic electrolytes respectively, a quantitative separation could be obtained, but Zr+Nb+Ru was left as one focus. Detection of the nuclides was by autoradiography or by γ- and β-counting.     

Liquid-liquid microbatch extraction system for rapid mutual separation of fission products

The liquid-liquid microbatch extraction system (LMES) was developed for rapid separation of short-lived metal ions. The equipment is composed of three simple extraction cells for phase mixing, phase separation, and collection of a solvent. Metal separation can be completed in a single operation, lasting only a minute, from solvent extraction to preparation for gamma-ray spectrometry. As a demonstration of the rapid operation of the LMES, fission products were each separated into several categories after three stages of operation. The extractability in the LMES was comparable to that of traditional methods, and the developed method was feasible for rapid separation.     

Extraction-chromatographic separation of uranium from long-lived fission products using tributyl phosphate

Extraction-chromatographic separation of uranium from fission products was performed using undiluted tributyl phosphate sorbed on Chromosorb W as a stationary phase, and nitric acid (1: 3) as a mobile phase. Most of the fission products that contributed greatly to the radiation level of the sample passed through the column; this effected considerable decontamination. Uranium retained on the column was quantitatively recovered by elution with water.     

Rapid activation product separations from fission products and soil matrixes

A rapid method for the separation and qualitative analysis of several neutron activation products (¹⁹⁸Au, ¹⁹²Ir, ⁷²Ga, ⁵¹Cr, ^191/195m/197Pt, ⁵⁴Mn, ⁵⁷Co, and ⁵⁹Fe) from fission products and soil matrixes has been developed. Analytes were isolated within 20 h using ion exchange chromatography. After separation, the activation products were characterized by γ-spectroscopy and inductively coupled plasma-optical emission spectroscopy. Validation experiments demonstrated versatility of the method, showing that the activation products could be isolated from fresh fission products and other contaminants associated with complex soil matrixes.

     

Rapid monitoring of gaseous fission products released from nuclear power stations

Rapid, in situ measurements were used for quantitative monitoring of gaseous fission products around the nuclear power stations in Taiwan. A portable high-resolution germanium detector with portable multichannel analyzer was used in the field monitoring work. The detecting unit was calibrated using activated Ar, Kr, and Xe isotopes dispersed in a large chamber to obtain absolute efficiency curve in terms of γ-counts per m³ versus gamma-ray energy. The calibrated detecting unit was brought to the nuclear power plants for in situ monitoring for both normal operation and nuclear accidental exercise. In a typical four-hour measurement, the detection limits for most Kr and Xe fission product isotopes were 0.0028%≈0.98% of the derived air concentration (DAC) imposed by the local authority. The dose rate caused by gaseous radioisotopes released from nuclear power stations and dispersed to the surroundings can be quantitatively monitored in a short period using this portable unit.     

Some aspects of the separation of nuclear fission products by liquid-liquid extraction

The technique for and methods of separation of products of nuclear fission play a major role in many stages of the nuclear fuel cycle. The extraction of these products from effluent solution after the processing of the burnt-up nuclear fuel is receiving considerable attention. Trivalent lanthanoides are usualy extracted together with Am(III) and their mutual separation is rather difficult.^1–4 The extraction of lanthanoides with tertiary amines or quaternary ammonium salts involving the benzyl group as one of substituents has been studied in order to find the influence of the alkyl chain length on the extraction selectivity and capacity.^3–5 Suitable extractants for the separation of Am(III) and Ln(III) from the acidic nitrate solutions were recommended. Using vapour phase osmometry and cryoscopy the association of these compounds was measured at 5.25 and 50°C allowing a rough estimation of medium association degree for the formation of the aggregates. The method of apparent molar volumes, supplemented by the spectrophotometric method, was used for identification of the chemical composition of the aqueous phase.     

Column separation of tetravalent cerium fission products from trivalent rare earth radio-isotopes

Journal of Radioanalytical and Nuclear Chemistry - Rapid and efficient isolation of individual rare earth element (REE) radioisotopes from complex mixtures is necessary to support the fields of...     

A new method for the radiochemical separation of copper from fission products

A new method for obtaining radiochemically pure⁶⁷Cu from highly active fission product solutions is described. The method is based on the solvent extraction of the Cu(II)-diethyldithiocarbamate complex in n-butyl acetate in the presence of hold-back carriers for Ni, Co, Mn, Mo, rare earths, Cd, Te and Sb, and subsequent purification steps involving scavengings for Ag, Ba, Sr and Fe followed by an anion-exchange purification step for decontamination from Te. Copper is finally extracted as the α-benzoin oxime complex in which form it is mounted and counted. The method has several advantages over other methods in that decontamination is very high and it is sufficiently fast considering the stringent radiochemical purity achieved. The⁶⁷Cu separated by this procedure from a one-day-old mixture of fission products arising from 10¹⁰ fissions was found to be completely free of any contamination.     

Rapid dissolution of large environmental samples for the determination of fission products

The dissolution of large environmental samples was investigated using a microwave autoclave, capable of digestion conditions of 300 °C and 200 bar, for the application of rapid determination of radionuclides. Six samples of up to 5 g plant material were digested, also eliminating predigestion steps such as ashing and grinding. Batches of forty 1 g samples of plant leaves were also completely digested in 75 minutes. Quantitative recovery of ⁹⁰Sr from 5 g soil samples by leaching with 8M HNO₃ at 200 °C was achieved, whereas ¹³⁷Cs was not completely recovered from the large soil samples using total digestion or leaching (HCl:HNO₃) techniques, but quantitative recovery was achieved using fusion and sinter procedures.     

The separation of fission products by electrophoretic focussing of ions. Part II

Electrophoretic focussing of ions was applied to the separation of the long-lived fission products Zr, Nb, Ru, Y, Ce, Sr and Cs. With hydrofluoric acid and nitrilotriacetic acid as the anodic and cathodic electrolytes respectively, a quantitative separation of Zr, Nb, Sr and Cs was obtained whereas Ru, Y and Ce did not focus sharply. The nuclides were detected by γ- and β-counting.     

Rapid separation of humic acid in fresh waters by coprecipitation and flotation

After removal of suspended matter in 1 liter of water by flotation with a cationic surfactant, humic acid at theg/l level is separated from fulvic acid by coprecipitation with milligram quantities of iron(III) hydroxide at pH 7 followed by flotation with anionic surfactants. The iron(III) hydroxide is dissolved in 2M hydrochloric acid, and the acid-insoluble humic acid is filtered off on an ultrafilter and then dissolved in 10 ml of 0.1M potassium hydroxide solution for measurements of absorption spectra, molecular weight distribution and complexing ability. The time required for the separation is ca. 1 h.     

Selective separation of99Mo from fission products in chloride media on activated alumina

The radioisotope⁹⁹Mo generated through the fission of neutron-irradiated uranium targets was separated in an extremely radiochemically pure state. The target dissolution mixture was run on a silica gel column whereby the⁹⁵Zr−⁹⁵Nb activity, the serious radiocontaminants of⁹⁹Mo, was adsorbed on the gel. The effluent from the gel column was processed and treated with sodium dihydrogen phosphate. The processed solution was run on an activated alumina column whereby⁹⁹Mo was adsorbed as phospho-molybdate complex ion, then desorbed from the column as the molybdate ion by eluting with 10% NaOH solution. By recycling the adsorption and desorption steps on alumnia,⁹⁹Mo was finally obtained totally free from all other radiocontaminants.     

The separation of99Tc from mixed fission products and its determination by neutron activation

Technetium is separated from the bulk of fission products and other elements in dissolved nuclear fuel by a ferric hydroxide precipitation followed by filtration and loading of the filtrate on an anion exchange resin. The technetium remains on the resin presumably as pertechnate ion. The resin is exposed to a neutron flux in a nuclear reactor activating⁹⁹Tc to¹⁰⁰Tc which decays with the emission of a 539keV gamma-ray with a 15.8 second half-life. This gamma-ray is conveniently counted with conventional solid state techniques.Work performed under contract to the U. S. Department of Energy under contract number DE-ACO7-76IDO1570.