Determination of90Sr by thin layer radiochromatography

A simple method for the determination of⁹⁰Sr by using thin layer chromatography on silica gel or cellulose pretreated with calcium oxalate is proposed. In these conditions a complete separation between strontium and its daughter yttrium is obtained. Radioactivity of separated elements was measured by a linear multiscanner analyzer and the results were computer processed to obtain the activity of⁹⁰Sr. The method has been applied to samples of water and milk subjected to a very simple extraction procedure. Under the experimental conditions used, the detection limit is about 25 mBq of deposited radioactivity, which corresponds to about 6 Bq/l.     

Extraction chromatographic separation of carrier-free90Y from90Sr/90Y generator by crown ether coated silica gels

A remarkable extraction chromatographic method for the preparation of⁹⁰Y of high radiochemical purity has been developed. The generator consists of silica gel coated crown ether. It functions as a strong adsorber for⁹⁰Sr and in the meantime high purity of⁹⁰Y is eluted with a dilute solution of picric acid after a suitable period. The experiments indicated that DC18C6 coated silica gel is better than that of DB18C6 coated. The extraction capacity of strontium on 3.8% DC18C6 coated silica gel is 5.6 mg Sr/g silica gel. Yttrium is obtained with more than 95% milking yield with radionuclide purity greater than 99.9%. The extraction chromatographic generator does not change its characteristics even after 5 elutions.     

Estimation of 90Sr in reprocessed uranium oxide samples

Summary A method has been developed for the estimation of ⁹⁰Sr in reprocessed uranium oxide samples obtained from the Purex processing of natural uranium spent fuel discharged from the research reactor. The method employs a combination of precipitation and solvent extraction procedure to eliminate other beta-impurities prior to resorting to the estimation of ⁹⁰Sr by beta-counting. ¹⁰⁶Ru was eliminated by volatalizing with perchloric acid, uranium was removed by carrier precipitation with strontium as sulphate. The sulphate precipitate was converted to carbonate and dissolved in nitric acid. ²³⁴Th and ²³⁴Pa were eliminated by synergistic solvent extraction using tri-n-butyl phosphate and thenoyl trifluoroacetone extractant mixture in xylene. An iron scavenging step was included to remove any residual impurities. Finally, strontium is precipitated as SrC₂O₄^. H₂O. The separated ⁹⁰Sr activity was followed to check the equilibrium growth of ⁹⁰Y.     

New method for90Sr determination in liquid samples

A method has been developed for measuring⁹⁰Sr activity in liquid samples. After concentrating strontium from the sample by coprecipitation with calcium phosphate, the residue is dissolved in 8N HNO₃ and passed through an extraction chromatographic column (Sr.Spec) containing a new material that selectively retains strontium. This is eluted from the column with 0.05N HNO₃ and counted by liquid scintillation. Measurement is performed using a double window method, that allows a rapid and single determination of⁹⁰Sr.     

The simple radiochemical determination of 90Sr in environmental solid samples by solvent extraction

Determination of ⁹⁰Sr in environmental solid samples is a challenging task because of the presence of so many other radionuclides in samples of interest. This problem was dealt with by radiochemical separation of strontium followed by yttrium separation and Cerenkov counting of the high-energy ??-particle emissions of ⁹⁰Y in order to quantitate ⁹⁰Sr. In this work, an improved method is described for the determination of ⁹⁰Sr in soil samples, through the separation of the daughter ⁹⁰Y at equilibrium. The procedure is based on the HDEHP solvent extraction in combination with liquid scintillation spectrometry (LSS). A low background Quantulus has been optimized for low level counting of Cerenkov radiation emitted by the hard ??-emitter ⁹⁰Y. The analytical quality of the method has been checked by analyzing IAEA Soil-375 reference materials. The analytical method has also been successfully applied to the determination of ⁹⁰Sr for moss-soil samples in inter-laboratory exercises through IAEA??s ALMERA network. The chemical recovery for ⁹⁰Y extraction ranged from 80 to 85% and the counting efficiency was 73% in the window 25?C400 keV.     

Rapid method for the determination of radiostrontium in milk

A radiochemical procedure comprising ion chromatography for preconcentration, oxalate precipitation for alkali/alkaline earth separation, strontium specific extraction chromatography with a crown ether for calcium/strontium separation, carbonate precipitation for counting on a low background proportional counter, provides a simple, rapid (48 h) and effective method for radiostrontium determination in emergency situation in milk. The separation scheme gives a strontium recovery rate of 62% and an empiric relative standard deviation of 11%. The detection limit for 500 ml milk and 3600-second counting time is 0.090 Bq^.l^-1.     

Separation of microamounts of yttrium from strontium by using sodium dicarbollylcobaltate, Slovafol 909 and ethylenediamine - N, N, N', N'-tetraacetic acid in the water - nitrobenzene extraction system

Summary A rapid extraction separation of trace amounts of yttrium from strontium by a nitrobenzene solution of sodium dicarbollylcobaltate (NaDCC) in the presence of p-nonylphenylnonaethylene glycol (Slovafol 909) and tetrasodium salt of ethylenediamine - N,N,N',N' - tetraacetic acid (Na₄L) in the aqueous phase was developed. The separation factor a(Sr/Y) was substantially higher than 10⁵. This water-nitrobenzene extraction system can be applied for the efficient separation of carrier-free ⁹⁰Y from ⁹⁰Y/⁹⁰Sr generator.     

Strontium isolation from natural samples with Sr resin and subsequent determination of 90Sr</p> </p>

The reliability of an ⁹⁰Sr determination method was tested using an Sr extraction chromatographic resin for strontium isolation. The ⁹⁰Sr-content in samples of vegetables, soil and water (obtained from Environmental Measurement Laboratory, USA) were determined and the results were controlled by classical methods and by using an anion-exchanger and an alcohol solution of nitric acid for the strontium isolation. These methods were previously tested by determining ⁹⁰Sr in IAEA 326 and 327 samples of soil. It is shown that the isolation process with Sr resin is simpler and faster than the classical and mixed solvent anion-exchange methods. The efficiency of isolation on a Sr column depends on the resin quantity and separation conditions; and is the highest with a Sr column, compared to the classical and anion-exchange methods. Experimental data and theoretical models were used to calculate the parameters that enable the estimation of optimum dimensions of the column for isolation. A simple relation is proposed for the calculation of breakthrough volume, which defines the sample and eluent volumes for an optimal strontium isolation.</p> </p>     

Radiochemical analysis of90Sr in milk,soil and plants by solvent extraction

A universal and fast method of⁹⁰Sr determination in environmental matrices (raw and dried milk, plants, soils) has been elaborated. Solvent extraction method of daughter⁹⁰Y by tributyl phosphate was used. The method of strontium determination is compatible with determination of other transuranic elements (americium, plutonium) and there is no need to check the chemical yield of strontium.     

Seasonal variations of atmospheric210Pb and7Be concentrations at Kumamoto, Japan and their removal from the atmosphere as wet and dry depositions</p> </p>

Summary A relatively simple chemical separation procedure has been developed for the simultaneous determination of⁸⁹Sr and ⁹ 0Sractivities in water samples and on aerosol-filters of the Nuclear Power Plant (NPP) Paks origin. The procedure combines the cation-exchange chromatographic (Dowex 50 WX 8 resin) and solid phase extraction (EIChroM Sr.Spec?, DC18C6 crown ether) steps. The beta-radiation of radionuclides can be measured directly after the chemical separation by LSC. The activities of⁸⁹Sr,⁹⁰Sr and⁹⁰Y are calculated from an over determined set of equations using a method of constrained optimization technique. The equations are based on LSC measurements performed in three counting windows plus the⁹⁰Sr-⁹⁰Y decay law. The chemical yield of strontium is determined by ICP-AES. The lowest limits of detectable activity, for the measurement time of 600 minutes, are 30 mBq/sample and 18 mBq/sample for⁸⁹Sr and⁹⁰Sr, respectively.     

Characterization and application of SuperLig<Superscript>®</Superscript> 620 solid phase extraction resin for automated process monitoring of <Superscript>90</Superscript>Sr

Characterization of SuperLig^® 620 solid phase extraction resin was performed in order to develop an automated on-line process monitor for ⁹⁰Sr. The main focus was on strontium separation from barium, with the goal of developing an automated separation process for ⁹⁰Sr in high-level wastes. High-level waste contains significant ¹³⁷Cs activity, of which ^137mBa is of great concern as an interference to the quantification of strontium. In addition barium, yttrium and plutonium were studied as potential interferences to strontium uptake and detection. A number of complexants were studied in a series of batch K_d experiments, as SuperLig^® 620 was not previously known to elute strontium in typical mineral acids. The optimal separation was found using a 2 M nitric acid load solution with a strontium elution step of ~0.49 M ammonium citrate and a barium elution step of ~1.8 M ammonium citrate. ⁹⁰Sr quantification of Hanford high-level tank waste was performed on a sequential injection analysis microfluidics system coupled to a flow-cell detector. The results of the on-line procedure are compared to standard radiochemical techniques in this paper.     

Estimation of <Superscript>90</Superscript>Sr activity in reprocessed uranium from the PUREX process

⁹⁰Sr estimation in reprocessed uranium was carried out by a series of solvent extraction and carrier precipitation techniques using strontium and lanthanum carriers. Fuming with HClO₄ was used to remove ¹⁰⁶Ru as RuO₄. Three step solvent extraction with 50% tri-n-butyl phosphate in xylene in presence of small amounts of dibutyl phosphate and thenoyl trifluoro acetone was carried out to eliminate uranium, plutonium, thorium and protactinium impurities. Lanthanum oxalate precipitation in acid medium was employed to scavenge the remaining multivalent ions. Strontium was precipitated as strontium oxalate in alkaline pH and ¹³⁷ Cs was removed by washing the precipitate with water. A strontium recovery well above 70% was obtained. Final estimation was carried out by radiometry using end window GM counter after drying the precipitate under an infra red lamp. The same procedure was extended to the estimation of ⁹⁰Sr in a diluted sample of the actual spent fuel solution. An additional lanthanum oxalate precipitation step was required to remove the entire ¹⁴⁴Ce impurity from this sample. This modified procedure was employed in the determination of ⁹⁰Sr in a number of reprocessed uranium samples and the over all precision of the method was found to be well within ±10%. An additional barium chromate precipitation step was necessary for the analysis of reprocessed uranium samples from high bumup fuels to eliminate trace amounts of short lived ²²⁴Ra produced during the decay of ²³²U and its daughters as they interfere in the estimation of ⁹⁰Sr.     

Separation of microamounts of yttrium from strontium by using nitrobenzene solution of sodium dicarbollylcobaltate in the presence of 18-crown-6

A rapid extraction separation of trace amounts of yttrium from strontium with a nitrobenzene solution of sodium dicarbollylcobaltate (NaDCC) and 18-crown-6 in the presence of tetrasodium salt of ethylenediamine-N,N,N",N"- tetraacetic acid (Na₄L) in the aqueous phase was developed. The separation factor a(Sr/Y) was substantially higher than 10⁶. This water-nitrobenzene extraction system can be applied for efficient separation of carrier-free ⁹⁰Y from ⁹⁰Sr/⁹⁰Y generator.     

Separation of strontium from nuclear waste solutions by solvent extraction with crown ethers

The possibilities of strontium separation from medium activity waste (MAW) solutions have been investigated. MAW originates from the PUREX process and contains NaNO₃ and HNO₃ in a large excess. By solvent extraction with the crown ether dicyclohexano-18-crown-6 (DC-18-C-6) in 1,1,2,2-tetrachloroethane, separation is possible. The distribution ratio for Sr²⁺ depends on the concentration of HNO₃, NaNO₃ and Pb(NO₃)₂. The extraction system is employed in a continuous counter-current process. After use, the extraction agent can easily be regenerated by reextraction with pure water.     

Determination of 90Sr in soil, grass and cereals

⁹⁰Sr was measured in environmental samples in Upper Austria in the year 2005. After the nuclear weapon tests the average deposition of ⁹⁰Sr in Austria amounted to 3.3 kBq/m². In 1986 the average deposition was 0.9 kBq/m² [1]. To assess the actual condition in soil, grass and cereals ⁹⁰Sr was measured in these samples. For all samples oxalate precipitation was conducted and strontium specific columns (Eichrom Industries, Inc.) were used. The calcium concentration in these samples was determined to estimate the amount of resin needed for the preparation. For grass and cereal samples columns were packed with the 100–150 μm resin to gain a lower limit of detection LLD below 2 and below 0.1 Bq/kg_{dry matter} respectively. The prepacked 2 mL columns with particle size 100–150 μm were used for soil (LLD below 2 Bq/kg_{dry matter}). After digestion of soil samples, hydroxide precipitation was used as an additional separation step. The ⁹⁰Sr was measured by liquid scintillation counting. For quality control reasons, first the initial strontium concentration in the sample was determined then a strontium carrier solution was added and after the separation steps the chemical recovery was determined by ICP-MS. Thus, no radioactive tracer and just a small amount of the measuring solution were needed. The results are presented and discussed. These results will be used as reference for further ⁹⁰Sr analyses which will be conducted in a 5 year period to detect any radiological impact of the nuclear power plant Temelin on the environment of Austria.     

Determination of 90Sr in Portuguese foodstuffs

The Nuclear and Technological Institute (ITN) has the legal responsibility to carry out the environmental radiological monitoring at a national level. This survey was planned to provide relevant information on radioactivity levels in different components of the ecosystem. In what concerns the terrestrial environment the evaluation of the ⁹⁰Sr activity concentrations in foodstuffs has been performed using a method based on the separation of ⁹⁰Sr by extraction chromatography and beta determination by liquid scintillation counting (LSC) technique. The trials were carried out using 7 g of ash samples and 3 g of commercial Sr-resin (Eichrom). Validation trials were also performed using ⁹⁰Sr spiked samples. The chemical yields were determined by gravimetric method, after the addition of stable strontium to the foodstuffs. The ⁹⁰Sr activity concentrations in complete meals, meat and vegetables were determined after ⁹⁰Y ingrowths in the region 12–862 keV, using the Tri-Carb 3170 TR/SL scintillation counter in normal mode and a counting time of 120 min. The results obtained were low and of the same order of magnitude of those reported by other European countries.     

A new method for the carrier-free production of 90y from 90sr-90y mixture and 89sr from neutron-irradiated y2o3

The extraction of strontium(II) and yttrium(III) ions from aqueous solutions at various pH values into methyl isobutyl ketone containing I-phenyl-3-methyl-4-caprylpyrazolone-5 is described. Quantitative extraction of Sr and Y at pH 8.6–10 and pH 2.8–5.4 respectively is utilized for the carrier-free production of ⁹⁰Y from ⁹⁰Sr–⁹⁰Y mixtures and ⁸⁹Sr from neutron-irradiated yttrium oxide. A clean separation of these elements from each other and more than 95% calculated activities were recovered     

Separation of radioactive strontium from natural samples by means of mixed-solvent anion exchange

A new procedure for isolation and determination of⁹⁰Sr in real natural samples is presented. It consists of bringing natural samples in a soluble form suitable for separation on an ion-exchange column, separation of calcium from strontium by means of the anion exchanger Amberlite CG-400 and 0.25M HNO₃ in methanol as eluent for calcium, and the determination of⁹⁰Sr using a low level -counter after elution with H₂O, scavenging steps and SrCO₃ precipitation. The method was tested with IAEA standards of natural samples with known contents of⁹⁰Sr, and water samples, where the concentration of⁹⁰Sr was previously determined by the standard IAEA procedure. The results obtained show that it is possible to isolate and determine low levels of⁹⁰Sr in natural samples. The procedure is favorable because of the simple separation of radioaactive strontium without using fuming nitric acid.     

Validation of <Superscript>90</Superscript>Sr separation method using molecular recognition product AnaLig<Superscript>®</Superscript> Sr01 gel and extraction chromatography Sr<Superscript>®</Superscript> resin

Two separation techniques for strontium determination using AnaLig^® Sr01 molecular recognition technology and extraction chromatography Sr^®  resin were tested. The methods performance was investigated by analysis of NPL (High Alpha–Beta 2003) intercomparison sample. The results obtained for both procedures were compared in terms of activities and recoveries. Data analysis proved a good agreement with the reference values. The AnaLig^® Sr01 separation method for ⁹⁰Sr determination was successfully validated with the same performance as the Sr^® resin method.     

Determination of strontium radioisotopes in soils

Summary A method is proposed for determination of radiostrontium in soils which is based on selective strontium separation by liquid-liquid extraction with dicyclohexano-18-crown-6 in chloroform, loading of the extract on a thin-layer plate and TLC separation of strontium and yttrium radioisotopes using a circular procedure. The method allows the separate determination of ⁸⁹Sr and ⁹⁰Sr. The strontium chemical yield is more than 90%, the detection limit is about 0.5 Bk/g, RSD is equal to 2–5%.