Determination of thorium,uranium and plutonium isotopes in atmospheric samples

A new procedure for the radiochemical measurements of thorium, uranium and plutonium in atmospheric samples is described. Analysis involves coprecipitation of these actinides with iron hydroxide from a 40-to 50-dm³ sample of rainwater, followed by radiochemical separation and purification procedures by the use of ion exchange chromatography (Dowex AG1×8) and solvent extraction. The new procedure enables one to determine the isotopes of thorium, uranium and plutonium, which are found in rainwater at extremely low concentrations, with a chemical yield ranging from 60 to 80%.     

Precise coulometric determination of uranium,plutonium and americium-application to small samples

Summary Isotopic dilution followed by mass spectrometry is currently used for the determination of microquantities of actinides, but for this method it is necessary to prepare certified solutions of isotopic diluents. The isotopes used are very expensive and often available only in small quantities. New methods have been developed for the accurate and precise determination of small amounts of uranium, plutonium and americium. By using controlled-potential coulometry 0.5eq of uranium and plutonium can be determined with a precision of 0.1% (coefficient of variation). For americium a constant-current coulometric titration allows the determination of 1eq with a precision of 0.3%. The equipment, coulometric cells and procedures are described. The results obtained for standard materials and comparisons with results from other analytical methods are given.

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Genaue coulometrische Bestimmung von Uran, Plutonium and Americium; Anwendung auf kleine Proben

Zusammenfassung Isotopenverdünnung und nachfolgende Massenspektrometrie werden laufend für die Bestimmung kleiner Mengen von Actiniden verwendet; dazu ist es aber notwendig, genaue Lösungen von Isotopen zur Verdünnung herzustellen. Die dazu verwendeten Isotopen sind sehr teuer und oft nur in sehr kleinen Mengen zu haben. Für die genaue Bestimmung kleiner Mengen Uran, Plutonium und Americium wurden neue Methoden ausgearbeitet. Unter Verwendung der potential-kontrollierten Coulometrie lassen sich 0,5eq Uran und Plutonium mit einer Genauigkeit von 0,1% (Variations-Koeffizient) bestimmen. Gleichstromcoulometrische Titration ermöglicht die Bestimmung von 1eq Americium mit einer Genauigkeit von 0,3%. Einrichtung samt coulometrischer Zellen und Arbeitsweise wurden beschrieben. Die mit Standardproben erzielten Resultate wurden mit den Ergebnissen anderer Verfahren verglichen.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Simultaneous determination of trace uranium and vanadium in biological samples by radiochemical neutron activation analysis

Summary A radiochemical neutron activation analysis (RNAA) for simultaneous determination of uranium and vanadium in a single sample at trace levels is described. The method is based on post-irradiation wet-ashing and solvent extraction of vanadium with N-benzoyl-N-phenyl-hydroxylamine reagent. From the remaining aqueous phase, uranium is extracted into a toluene solution of tri-n-butyl phosphate. The chemical yields are determined spectrophotometrically for vanadium and by gamma-counting of the added natural uranium carrier for uranium. The method was evaluated by the analysis of reference materials and the results showed a good agreement with the certified values. The method was applied to the determination of vanadium and uranium in five military total diet samples in Slovenia.     

Simultaneous determination of trace uranium and thorium by radiochemical neutron activation analysis

A method for the simultaneous, radiochemical neutron activation analysis of uranium and thorium at trace levels in biological materials is described, based on a technique known as LICSIR, in which a double neutron irradiation is employed. In the first, long irradiation²³³Pa (27.0 d) is induced by neutron capture on²³²Th and then the sample is cooled for several weeks. A second short irradiation to induce²³⁹U (23.5 m) is followed by a rapid sequential radiochemical separation by solvent extraction of²³⁹U with TBP and²³³Pa with TOPO. Chemical yields of²³⁹U and²³³Pa were measured for each sample aliquot using added²³⁵U and²³¹Pa tracers from the -spectra of the separated fractions. The technique was validated by quality control analyses.     

Simultaneous radiochemical neutron activation analysis of iodine, uranium and mercury in biological and environmental samples

The determination of medium and long-lived nuclides can be combined with short-lived ones if a medium or long irradiation is made prior to the short irradiation and radiochemical processing. Thus, an RNAA method previously developed for determination of iodine based on the reaction¹²⁷I(n,)¹²⁸I (T _1/2=25 m) using oxygen flask ignition of the irradiated sample, followed by solvent extraction with an iodine-iodide redox cycle, was combined with an overnight preirradiation to induce the²³⁵U fission product¹³³I (T _1/2=20.8 h). By reactivating the sample, cooled 1–2 days after the first irradiation, for few minutes both¹²⁸I and¹³³I could be quantified in the separated iodine fraction. Non-combustible inorganic materials (e.g., sediment, soil, etc.) can be successfully ignited after mixing with excess cellulose powder. Chemical yields for iodine were determined spectrophotometrically in the organic phase, while homogeneously spiked Whatman cellulose powder was used as uranium standard. Mercury is also released on ignition and collected in the absorbing solution, from where it was separated by toluene extraction. Its chemical yield was determined for each aliquot using²⁰³Hg tracer and counting on an LEPD. Results for some suitable SRMs are presented, and the general features of the double irradiation technique discussed.     

Separation of radium,thorium, uranium and plutonium on OSTION anion exchanger in atmospheric precipitation samples

An anion exchanger OSTION AT 0807 of Czechoslovak production was tested for the separation of radium, thorium, uranium and plutonium. According to the results, the separation process is suitable for analysis of atmospheric precipitation samples. Separation efficiency can be increased by the repetition of the procedures.     

Simultaneous determination of plutonium and americium in biological and environmental samples

A radiochemical method is given to determine the specific activity of²³⁸Pu, and²⁴¹Am from the global fallout in environmental and biological samples. The radiochemical recovery was for human livers Pu: 60–70%, Am: 40–60%; Bran: Pu: 50–70%, Am: 30–40%; Soil: Pu: 50–80%, Am: 30–50%. The resolution of the alpha-spectrum was for soils 30–40 keV and for livers and brans 40–60 KeV. To facilitate the wet ashing of large amounts of bran (15 kg), which are necessary to determine the presently very small activity concentrations of the transuranic elements in these types of samples, a fermentation process was employed. The procedure was tested by using NBS standard reference material and subsequently applied for the determination of Pu and Am from the global fallout in livers, plant tissues (bran), and soils.     

Simultaneous radiochemical determination of237Np and239Np with235Np as a tracer,and application to environmental samples

Neptunium is sorbed, together with plutonium, uranium and iron on Bio Rad AG 1×4 anion exchange resin from 9 mol/1 HCl, eluted with 7 mol/l HNO₃ and 1.2 mol/l HCl, purified on a second, identical column and electrodeposited on stainless steel discs.²³⁷Np is determined by -spectrometry,²³⁹Np by -spectrometry with a Ge detector, or via its 14.3 keV LX-rays in a Si(Li) measurement. The neptunium yield is determined from the count rate of the 13.6 keV LX rays of the tracer²³⁵Np in a later Si(Li) measurement. The average chemical yield is 78±11%. The detection limit for²³⁷Np is 1 mBq. The procedure allows the sequential determination of neptunium, together with plutonium, strontium, uranium and iron from one sample. The method was applied to air and total deposition samples from Munich-Neuherberg and to sediment samples from the Irish sea.     

Problems of plutonium and uranium determination

The experience with the determination of plutonium and uranium in the samples of nuclear fuel obtained during a 10-years period of the activity of the Central Control Laboratory of the Nuclear Research Institute at e is evaluated. The paper describes the principles of the methods used and the reproducibilities and accuracies of the results obtained with the aid of the titrimetric methods used for the determination of plutonium and uranium.     

Combined procedure using radiochemical separation of plutonium,americium and uranium radionuclides for alpha-spectrometry

Radiochemical separation of Pu, Am and U was tested from synthetic solutions and evaporator concentrate samples from nuclear power plants for isolation of each of them for alpha-spectrometry analysis. The separation was performed by anion-exchange chromatography, extraction chromatography, using TRU resin, and precipitation techniques. The aim of the study was to develop a sensitive analytical procedure for the sequential determination of ²⁴²Pu^{, 238}Pu, ^239+240Pu, ²⁴¹Am and ^{235, 238}U in radioactive wastes. ²³⁸Pu, ²⁴²Pu, ²⁴³Am and ²³²U were used as tracers. The measurements of α emitting radionuclides were performed by semiconductor detector that is used especially when spectrometric information is needed. For synthetic solutions the chemical recovery was based on associated iron concentration and was about 93%.     

Processing of bone samples for the determination of ultra low-levels of uranium and plutonium

Summary We have developed cleanroom compatible techniques for processing bone samples for characterization of their uranium and plutonium content. The bone samples are dried and ashed in quartz crucibles placed inside cleanroom compatible thermal ashing furnaces. The bone ash is dissolved in ultra-pure acids prepared by sub-boiling distillation. The uranium and plutonium in the samples are isolated and purified by ion-exchange chromatography and measured by thermal ionization mass spectrometry. The technique is capable of detecting 74 picograms of ²³⁸U and 8 femtograms of ²³⁹Pu in 100 mg bone ash samples. If the ash contains larger amounts of uranium and plutonium, the technique can be used to isotopically fingerprint the material to identify potential origins.     

Simultaneous determination of uranium and plutonium isotopes in soils by means of single alpha-spectrometry

A simple, rapid and reliable method was developed for the simultaneous determination of uranium and plutonium isotopes by alpha-spectrometry using a single source. A new uranium tracer²³⁰U was applied as well as the²³⁶Pu tracer to determine overall yields of uranium and plutonium isotopes throughout the entire procedure employed. The analytical procedure consists of sample leaching with 8N HNO₃ solution, purification by solvent extraction, simultaneous electrodeposition of U and Pu, and subsequent alpha-spectrometry with a silicon detector. In the solvent extraction using TOA/xylene from 8N HNO₃ solution, the preferential extractability of Pu rather than U permits to purify simultaneously the trace amounts of Pu and the macro amounts of U, as in the case of ordinary soil samples, resulting in favourable peak heights for both isotopes. From a single alpha-spectrum, the determinations of²³⁸U,²³⁴U (and their ratio of²³⁴U/²³⁸U),^239+240Pu, and²³⁸Pu contents were conveniently carried out after correcting the overall yields obtained from²³⁰U and²³⁶Pu activities in the same spectrum. This analytical method was satisfactorily applied to the determination of U and Pu isotope contents in some soils.     

Efficient radiochemical separation for the determination of plutonium in environmental samples,using a supported,highly specific extractant

A radiochemical separation procedure has been developed for a very efficient isolation of plutonium from environmental samples. Essentially, the method involves the following steps: ashing of the sample and preparation of the load solution; separation of plutonium by a column containing a commercially available, highly specific, supported extractant; electrodeposition of Pu and subsequent -spectrometry. Detailed procedures are reported for liver samples and for soil. The modifications necessary for sample sizes above 5 g dry weight and up to 200 g are also given. Recoveries of added tracers are 60–70%. The precision of the method is <10% (RSD). The accuracy was examined by analyzing also certified standard reference materials. Due to the very efficient isolation of Pu, the resulting -spectrum is virtually free of interfering -emitters of Th and U.     

Simultaneous determination of iodine and selenium in biological samples by radiochemical neutron activation analysis

Summary Regarding the favourably sensitive nuclear characteristics of iodine and of selenium but the very different half lives of their induced nuclides ¹²⁸I and ⁷⁵Se, a radiochemical neutron activation analysis method for simultaneous determination of these elements in a single sample was developed. It is based on the double irradiation LICSIR technique — Long Irradiation for Se (40h), Cooling (a week or more), Short Irradiation for iodine (1–15 min) with following Radiochemistry. After the second short irradiation, the sample is ignited in an oxygen flask and iodine and selenium are sequentially and selectively extracted as elemental iodine and 5-nitro-2,1,3 benzoselena diazole chelate. With the described method biological samples were analysed and the reliability of the results was checked by the analyses of different standard reference materials. Good agreement with certified values and high radiochemical purity of the spectra show the applicability of the radiochemical separation developed.     

Simultaneous determination of arsenic and antimony in environmental samples by radiochemical neutron activation analysis

A radiochemical separation procedure using an inorganic exchanger, tin dioxide (TDO), for the separation of arsenic from antimony is reported here. This separation avoids the interference of 564 keV gamma-ray of¹²²Sb in the measurement of the 559 keV gamma-ray of⁷⁶As in neutron activation analysis. Environmental samples, after neutron irradiation and digestion, are taken up in 1M HCl–0.1M HF and passed through a TDO column which selectively retains arsenic. The effluent from the TDO column, after proper conditioning, is passed through an anion exchange column for quantitative retention of antimony. The procedure has been utilized for arsenic and antimony determination in NBS Orchard Leaves and NBS Albacore Tuna.     

X-Ray spectrometric methods for the determination of plutonium and uranium in their mixed oxide samples

An X-ray fluorescence binary ratio method to measure non-destructively the relative percentage of PuO₂ in (U, Pu)O₂ samples is described. Calibration lines for pellet and microsphere samples are established and evaluated. Independent X-ray measurement of the major component after dissolution leads to the determination of individual concentrations within ±0.5% rel. of the chemical values.     

Ion-exchange separation of uranium,thorium and plutonium isotopes from environmental samples

Radioisotopes of uranium, thorium and plutonium in water, soil and fertilizer samples, have been chemically separated and determined by alpha-spectrometry method. Radiochemical procedure involving ion-exchange, enabled to determine these isotopes in very low concentrations (under 50 Bq/g).²³²U,²²⁹Th and²³⁸Pu were used as a tracers for radiochemical yield recoveries (up to 90%). Thin layer sources have been obtained by electrodeposition.     

分光光度法同时测定硅石中的铁和铝

在邻二氮菲(Phen)、铬天青S(CAS)和十四烷基二甲基苄基氯化铵(TDMBA)的共同存在下,于pH 5～6的酸性介质中,铁、铝分别生成Fe-Phen和Al-CAS-TDMBA络合物,用同一份试液,在波长510 nm测定铁,在625 nm测定铝,两种络合物互不干扰。用该法可同时测定硅石中的铁和铝。