Rapid determination of 89,90Sr in wide range of activity concentration by combination of yttrium, strontium separation and Cherenkov counting

The methodology for the rapid determination of ^89,90Sr in wide range of activity concentration is given. Methodology is based on simultaneous separation of strontium and yttrium from samples by mixed solvent anion exchange chromatography, mutual separation of ^89,90Sr from ⁹⁰Y by hydroxide precipitation and quantitative ^89,90Sr determination by Cherenkov counting within 3 days. It is shown that Y and Sr can be efficiently separated from alkaline, alkaline earth and transition elements as well as from lanthanides and actinides on the column filed by strong base anion exchanger in nitrate form and 0.25 M HNO₃ in mixture of ethanol and methanol as eluent. Decontamination factor for Ba, La and other examined elements except calcium is low and can not affect quantitative determination in predictable circumstances. Methodology for quantitative determination by Cherenkov counting based on following the changes of sample activity over time is described and discussed. It has been shown that ^89,90Sr can be determined with acceptable accuracy when ⁸⁹Sr/⁹⁰Sr ratio is over 10:1 and that separation of Y enables reliable determination of ⁸⁹Sr and ⁹⁰Sr in wide range of ⁸⁹Sr/⁹⁰Sr ratios (60:1) and in some cases in presence of other yttrium and strontium isotopes. The methodology was tested by determination of ^89,90Sr in Analytics crosscheck samples (nuclear waste sample) and ERA proficiency testing samples (low level activity samples). Obtained results shows that by using of low level liquid scintillation counter it can be possible to determine ⁸⁹Sr and ⁹⁰Sr in wide range of concentration activity (1–1,000 Bq/L/kg) with uncertainty below 10% within 2–3 days. Results also show that accuracy of determination of ⁸⁹Sr (and ⁹⁰Sr) strongly depends on the determination of difference between separation and counting time when activity ratio of ⁸⁹Sr/⁹⁰Sr is high. Examination the influence of media and vial type on background radiation and counting efficiency has shown that lowest limit of determination can be obtained by using of HNO₃ in plastic vials as counting media, because in this combination figure of merit is maximized. For the recovery of 50% and 100 min of counting time estimated MDA is 55 Bq and 90 Bq for ⁹⁰Sr and ⁸⁹Sr, respectively. Analysis of combined uncertainty shows that it mainly depends on uncertainty of efficiency and recovery determination, uncertainty of activities determination for both isotopes and level of background radiation.     

Separation of 90Y from 90Sr using sequential multiple column extraction chromatography

The distribution coefficient measurements on Y(III) and Sr(II) were performed using ditertiarybutyl dicyclohexano 18-crown-6 (Sr-selective resin) and N,N,N′,N′-tetraoctyldiglycolamide (Y-selective resin) in HNO₃, HCl and HClO₄ media. Separation factors (⁹⁰Y/⁹⁰Sr) based on distribution coefficient data suggested that perchloric acid is distinctly better medium as compared to nitric acid/hydrochloric acid. The mechanism of extraction changes with the nature and concentration of acid and is responsible for the high selectivity in perchloric acid medium. Sequential column studies were carried out on tracers (radioactive/stable) employing Sr-selective/Y-selective extraction chromatographic resins as stationary phases. The final elution of ⁹⁰Y was done in 0.01 M EDTA at pH 4.0 which can be used for clinical applications after radiochemical processing.     

Monodisperse Mesocrystals of YF3 and Ce3+/Ln3+ (Ln=Tb,Eu) Co‐Activated YF3: Shape Control Synthesis,Luminescent Properties,and Biocompatibility

A family of monodisperse YF₃, YF₃:Ce³⁺ and YF₃:Ce³⁺/Ln³⁺ (Ln=Tb, Eu) mesocrystals with a morphology of a hollow spindle can be synthesized by a solvothermal process using yttrium nitrate and NH₄F as precursors. The effects of reaction time, fluorine source, solvents, and reaction temperature on the synthesis of these mesocrystals have been studied in detail. The results demonstrate that the formation of a hollow spindle‐like YF₃ can be ascribed to a nonclassical crystallization process by means of a particle‐based reaction route in ethanol. It has been shown that the fluorine sources selected have a remarkable effect on the morphologies and crystalline phases of the final products. Moreover, the luminescent properties of Ln³⁺‐doped and Ce³⁺/Ln³⁺‐co‐doped spindle‐like YF₃ mesocrystals were also investigated. It turns out that Ce³⁺ is an efficient sensitizer for Ln³⁺ in the spindle‐like YF₃ mesocrystals. Remarkable fluorescence enhancement was observed in Ce³⁺/Ln³⁺‐co‐doped YF₃ mesocrystals. The mechanism of the energy transfer and electronic transition between Ce³⁺ and Ln³⁺ in the host material of YF₃ mesocrystals was also explored. The cytotoxicity study revealed that these YF₃‐based nanocrystals are biocompatible for applications, such as cellular imaging.     

不同形貌YF_3微米晶的水热合成及YF_3:Eu~(3+)荧光性质(英文)

水热条件下,Y(NO3)3·6H2O分别与K2SiF6、KPF6反应得到了不同形貌的YF3(八面体及椭球形)。以X射线光电子能谱(XPS)检测了产物的化学组成,表明产物中只含有Y和F。X射线衍射(XRD)结果表明所得的产物均为正交晶系。扫描电子显微镜(SEM)和透射电子显微镜(TEM)对产物的表征结果指明八面体形YF3棱长为200nm,而椭球形YF3是由小的纳米块自组装而成。还研究了Eu3+掺杂后YF3的荧光性质,并提出了可能的形成机理。     

Radiochemical determination of 90Sr and 86Sr in soil

Summary A modified HCl-leach method for the radiochemical ⁹⁰Sr and ⁸⁹Sr determination in soil has been developed. The sample is leached by HCl in the presence of the Sr-carrier. Then bi- and trivalent ions are separated by a combination of complexation and ion exchange. The separation of strontium and calcium is performed by fuming nitric acid. After further purification, strontium carbonate is precipitated and the activity of ⁹⁰Sr and ⁸⁹Sr is measured. ⁹⁰Sr determined by the isolation of ⁹⁰Y and by measuring its activity. The ⁹⁰Sr and ⁸⁹Sr content in soil is calculated from the measured activities of yttrium oxide and strontium carbonate by considering the counting efficiencies for ⁹⁰Y, ⁹⁰Sr and ⁸⁹Sr beta rays, the chemical yields of strontium and yttrium and the time of ⁹⁰Y growth from ⁹⁰Sr.

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Radiochemische Bestimmung von ⁹⁰Sr und ⁸⁹Sr in Boden

Zusammenfassung Eine modifizierte Auslaugungsmethode für die radiochemische Bestimmung von ⁹⁰Sr und ⁸⁹Sr im Boden wurde entwickelt. Die Probe wird in HCl in Gegenwart des Sr-Trägers ausgelaugt und die zwei- und dreiwertigen Ionen dann durch eine Kombination von Komplexierung und Ionenaustausch getrennt. Die Strontiumtrennung von Calcium erfolgt mit rauchender Salpetersäure. Nach weiterer Reinigung wird SrCO₃ gefällt und die Aktivität von ⁹⁰Sr und ⁸⁹Sr bestimmt. ⁹⁰Sr wird durch Isolierung und Zählung von ⁹⁰Y ermittelt. Der ⁹⁰Sr- und ⁸⁹-Sr-Gehalt im Boden wird aus der Aktivität von Y₂O₃ und SrCO₃ unter Berücksichtigung der Zählausbeute für ⁹⁰Y-, ⁹⁰Sr- und ⁸⁹-Sr-beta-Strahlen, aus der gravimetrischen Bestimmung von Strontium und Yttrium und aus der Zeit der ⁹⁰Y-Entstehung aus ⁹⁰Sr bestimmt.

     

Rapid determination of 90Sr/90Y in water samples by liquid scintillation and Cherenkov counting

Strontium-90 (⁹⁰Sr) is a ubiquitous contaminant at nuclear facilities, found at high concentrations in spent nuclear fuel and radioactive waste. Due to its long half-life and ability to be transported in groundwater, an accurate method for measuring ⁹⁰Sr in water samples is critical to the monitoring program of any nuclear facility. To address this need, a rapid procedure for sequential separation of Sr/Y was developed and tested in groundwater samples collected from an area of riverbed affected by a ⁹⁰Sr groundwater plume. Sixteen samples, plus spike and water blanks, were analyzed. Five different measurements were performed to determine the ⁹⁰Sr and yttrium-90 (⁹⁰Y) activities in the samples: direct triple-to-double-coincidence ratio (TDCR) Cherenkov counting of ⁹⁰Y, liquid scintillation (LS) counting for ⁹⁰Sr following radiochemical separation, LS counting for ⁹⁰Y following radiochemical separation, Cherenkov counting for ⁹⁰Y following radiochemical separation and LS counting of the Sr samples for ⁹⁰Y in-growth. The counting was done using a low-level Hidex 300SL TDCR counter. Each measurement method was compared for accuracy, sensitivity and efficiency. The results following Cherenkov counting and radiochemical separation were in very good agreement with one another.     

Atmospheric depositional fluxes of cosmogenic <Superscript>32</Superscript>P, <Superscript>33</Superscript>P and <Superscript>7</Superscript>Be in the Sevastopol region

⁹⁰Y was separated from ⁹⁰Sr using an extraction chromatographic resin consisting of 4, 4′(5′)-bis-t-butylcyclohexano-18-crown-6 (DtBuCH₁₈C₆), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide (C₂mimNTf₂), and a polymer (Amberlite XAD-7). Ionic liquid was introduced into the column to improve the separation efficiency. The column showed an excellent performance for the separation of Y from Sr. After the separation, the ratio of ⁹⁰Sr/⁹⁰Y was <2.0 × 10^?5; the column was recycled for >18 times. This study provides preliminary results on columns to produce ⁹⁰Y with a high purity in radiopharmaceuticals.     

Modified 2-window approach for rapid determination of 90Sr and 90Y at low quench level using liquid scintillation counting

⁹⁰Sr is a product of nuclear fission, the radioactivity of which can be determined by liquid scintillation counting (LSC). Because the LSC spectra of ⁹⁰Sr and its daughter ⁹⁰Y overlap each other, the following methods are usually used: (1) measuring immediately after ⁹⁰Sr/⁹⁰Y separation; (2) waiting to reach radioactive equilibrium; (3) adopting the conventional 2-window approach; and (4) using the spectra deconvolution technique. The first one requires ⁹⁰Sr/⁹⁰Y separation and immediate measurement; the second one is time-consuming; the third one is valid only for samples with the same quench level as the calibration standard; the last one is somewhat complicated, and in some cases it is not convenient to export the experimental data to some deconvolution software. Therefore, we have developed a modified 2-window approach to rapidly determine ⁹⁰Sr and ⁹⁰Y in either equilibrium or disequilibrium at low quench level. The key modification of the approach is to provide an LSC spectrum of pure ⁹⁰Y with the same quench level as the sample to be determined. This modification eliminates the need to conduct ⁹⁰Sr/⁹⁰Y separation for the sample itself, to prepare the quench curves, and to fit the LSC spectra with some deconvolution software.     

Study of HDEHP-PAN solid extractants for the determination of <Superscript>90</Superscript>Sr

Solid extractants containing di-(2-ethylhexyl)phosphoric acid (HDEHP) in the support based on modified polyacrylonitrile (PAN) were studied for the determination of ⁹⁰Sr by means of measuring the activity of its separated ⁹⁰Y daughter. In this paper, ¹⁵²Eu and ¹³³Ba were used as chemical homologues of ⁹⁰Y and ⁹⁰Sr. For these radionuclides, dependences of mass distribution coefficients (D _g) on the nitric acid concentration were measured for several types of HDEHP-PAN solid extractants. The mechanism of the Eu³⁺ and Ba²⁺ ions extraction was confirmed to follow the theoretical two-phase equation for the chelating extractants. Further, the influences of the presence of nitrates, calcium and iron ions on the values of D _g(Ba, Eu) were determined concentrating on the possibility of masking the iron ions by the addition of the ascorbic acid. This method was tested on the solution simulating the leachate of ashed green plant sample. The results obtained make the application of solid extractants containing HDEHP in PAN support prospective for ⁹⁰Sr determination.     

The separation of daughter nuclides from90Sr−90Y and140La−140Ba systems by thin-layer chromatographic methods

The separation of daughter nuclides in the carrier-free state from⁹⁰Sr?⁹⁰Y and¹⁴⁰Ba?¹⁴⁰La aqueous solution systems was performed by thin-layer chromatographic methods. (1) When a silica gel adsorbent and a developer of 1N NaCl, KCl, NH₄Cl, CaCl₂, SrCl₂ or BaCl₂ solutions was employed,⁹⁰Y and¹⁴⁰La were retained at the origin, while⁹⁰Sr and¹⁴⁰Ba advanced with the developer front. Addition of gypsum as binder to the silica gel prevented the separation of the¹⁴⁰Ba?¹⁴⁰La system, retaining both components at the origin. (2) When the¹⁴⁰Ba?¹⁴⁰La system was developed with water on a silica gel adsorbent containing 5% of gypsum, which was treated with various concentrations of nitric acid, the Rf value of¹⁴⁰La increased with the concentration of nitric acid used, reaching a maximum of 0.98 at 0.1 N. The Rf value then decreased on the further increase of the concentration of nitric acid. When the same process was applied to the⁹⁰Sr?⁹⁰Y system, there was no separation. The radiochemical purities of⁹⁰Y and¹⁴⁰La obtained in the above two ways were more than 99%.     

Variations in the gross alpha and beta activity in surface waters at the Atomic Weapons Establishment Aldermaston (UK)

N,N,N′,N′-tetra-2-ethylhexyldiglycolamide (T2EHDGA) has been used for the preferential extraction of ⁹⁰Y from its mixture with ⁹⁰Sr from HNO₃ as well as HCl medium. The separation efficiencies have been found out under varying experimental conditions. The extracted species were determined from T2EHDGA concentration variation experiments carried out at 3 M nitric acid as well as HCl and were found out to be Y(X₃)₃·3(TEHDGA)_(o) for both the extraction systems, where X = NO₃ ⁻ and Cl⁻, respectively. Comparison of the T2EHDGA and TODGA based separation methods is also made. In order to avoid third phase formation, iso-decanol has been used as the modifier in all the studies. The modifier content was optimized to 30% for 4 M HCl and 20% for 6 M HNO₃ as the feed aqueous phases. Separation schemes were developed for the separation of carrier free ⁹⁰Y and the purity was checked by the half-life measurement method.     

Measurement of 90Sr in Marine Biological Samples

Strontium-90 (⁹⁰Sr) is one of the most hazardous radionuclides, and it contributes to radiation exposure by ingestion. The routine determination of ⁹⁰Sr in marine biological samples is highly desirable given the development of the nuclear power industry. A fast, simple, and low-detection-limit method was developed for the measurement of ⁹⁰Sr in marine biological samples based on determining ⁹⁰Y by means of coprecipitation and solvent extraction with bis-2-ethylhexyl-phosphoric acid (HDEHP) in n-heptane. The interfering ²¹⁰Bi is removed using Bi₂S₃ precipitation. The separation and purification of eight samples per day can be accomplished through this method. The detection limit of ⁹⁰Sr for this method is 0.10 Bq/kg (ash weight). The radiochemical procedure was validated by fitting the decay curve of the sample source and by the determination of ⁹⁰Sr standards.     

Facile Synthesis of Lanthanide (Ce,Eu, Tb,Ce/Tb,Yb/Er,Yb/Ho,and Yb/Tm)‐Doped LnF3 and LnOF Porous Sub‐Microspheres with Multicolor Emissions

Monodisperse YF₃ and YOF porous sub‐microspheres were synthesized by using a novel sacrificing template method with amorphous Y(OH)CO₃ ⋅ x H₂O as the precursors and the template. It was found that the size and shape were well maintained, and the condensed precursor was transformed into uniform porous structures after fluoridation. By fine‐tuning the feed of the fluorine source, the final product could be converted from YF₃ to YOF. A possible growth mechanism is proposed for the uniform porous YF₃ structure and the porous yolk–shell‐like YOF structure. The luminescence properties showed that the as‐synthesized YF₃:Ln³⁺ (Ln=Eu, Tb, Ce, Ce/Tb, Yb/Er, Yb/Ho, and Yb/Tm) products exhibited strong multicolor emissions, which included down‐/upconversion and energy‐transfer processes. Additionally, YOX (X=Cl and Br) could be obtained if a different halogen source was used during calcination. However, the spheres were almost completely destroyed. Our novel synthetic route can also be extended to other lanthanide fluorides (REF₃, RE=Gd, Lu), which may open a facile way to fabricate novel porous nanostructures.     

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.     

A Simple and Rapid Method for the Preparation of 87Y/87mSr Generator

A simple and efficient process for the preparation of ⁸⁷Y/^87mSr generator with adsorption chromatography on -Fe₂O₃ was developed. A 0.25 g pallet of natural SrCl₂ was employed as a solid target which was irradiated at INER TR30/15 cyclotron. After irradiation the target was dissolved into a saline solution and adjusted with HCl/NaOH to a pH of 6.3. This solution was then passed directly through the column (1 cm×4 cm), loaded with appropriate amounts of -Fe₂O₃, at a flowrate of 1.0 ml/min for adsorption of ⁸⁷Y. Nonradioactive Sr was unadsorbed and washed out from the column. Above 90% of the available ^87mSr with a ⁸⁷Y breakthrough less than 10^–3% could be obtained with 10 ml of 0.9% saline solution per elution from the generator system. The chemical contaminants of Fe and Sr in the eluates were found below 0.04 and 0.1 ppm, respectively.     

Possible overestimation of the external standard quench parameter on Wallac 1220 Quantulus™ with high energetic beta-emitters

The 1220 Quantulus is equipped with an ¹⁵²Eu external source used to determine an external standard quench parameter SQP(E). The relationship between ⁹⁰Sr/⁹⁰Y counting efficiency and SQP(E) was found linear in a defined range of SQP(E) values. This function was fixed after many counting experiences made with ⁹⁰Sr/⁹⁰Y standards. The sasme equation is used for the measurement of ⁹⁰Sr in environmental samples. The first goal of this paper is to objectify an overestimation of the SQP(E) when high energetic beta-emitters like ⁹⁰Y are present (1 to 4% in routine conditions). The second one is to show how this artefact could induce a bias in the calculation of ⁹⁰Sr activity in environmental samples. The median of this overestimation is estimated around 6%. Another approach using ⁸⁵Sr standard is suggested to avoid this overestimation. Provided the chemical composition — and thus the quenching — is similar for the two standards, the counting efficiency measured with the ⁹⁰Sr/⁹⁰Y standard could be related to the SQP(E) value of the ⁸⁵Sr standard. Indeed this one appears to be more robust regarding to the range of activity and to the counting time of the external source.     

Ein Beitrag zur Strukturchemie der Selten-Erd-Trifluoride

Some Aspects of the Structural Chemistry of the Rare Earth Trifluorides The preparation and characterization of the rare earth trifluorides crystallizing in the hexagonal LaF₃-type and the orthorhombic YF₃-type is described. The lattice parameters were derived from GUINIER powder data of high precision. These lattice parameters served to calculate the effective ionic radii of the tripositive rare earth ions for coordination numbers 8 and 9. It is shown that both structure types can be stabiblized by the formation of nonstoichiometric compounds of the general formula (Me, RE)F_x (Me ? Eu²⁺, Sr²⁺ and RE ? Eu³⁺, Gd³⁺) with x varying approximately from 2,77 to 2,94 for the hexagonal and from 2,94 to 3,00 for the orthorhombic nonstoichiometric phases. For the pure trifluorides and the nonstoichiometric phases a critical radius ratio of 0.830±0.008 was found for the changeover from the LaF₃- to the YF₃-structure.     

Rapid determination of radiostrontium in seawater samples

A new method for the determination of radiostrontium in seawater samples has been developed at the Savannah River National Laboratory (SRNL) that allows rapid pre-concentration and separation of strontium and yttrium isotopes in seawater samples for measurement. The new SRNL method employs a novel and effective pre-concentration step that utilizes a blend of calcium phosphate with iron hydroxide to collect both strontium and yttrium rapidly from the seawater matrix with enhanced chemical yields. The pre-concentration steps, in combination with rapid Sr Resin and DGA Resin cartridge separation options using vacuum box technology, allow seawater samples up to 10 L to be analyzed. The total ⁸⁹Sr + ⁹⁰Sr activity may be determined by gas flow proportional counting and recounted after ingrowth of ⁹⁰Y to differentiate ⁸⁹Sr from ⁹⁰Sr. Gas flow proportional counting provides a lower method detection limit than liquid scintillation or Cerenkov counting and allows simultaneous counting of samples. Simultaneous counting allows for longer count times and lower method detection limits without handling very large aliquots of seawater. Seawater samples up to 6 L may be analyzed using Sr Resin for ⁸⁹Sr and ⁹⁰Sr with a minimum detectable activity (MDA) of 1–10 mBq/L, depending on count times. Seawater samples up to 10 L may be analyzed for ⁹⁰Sr using a DGA Resin method via collection and purification of ⁹⁰Y only. If ⁸⁹Sr and other fission products are present, then ⁹¹Y (beta energy 1.55 MeV, 58.5 day half-life) is also likely to be present. ⁹¹Y interferes with attempts to collect ⁹⁰Y directly from the seawater sample without initial purification of Sr isotopes first and ⁹⁰Y ingrowth. The DGA Resin option can be used to determine ⁹⁰Sr, and if ⁹¹Y is also present, an ingrowth option with using DGA Resin again to collect ⁹⁰Y can be performed. An MDA for ⁹⁰Sr of <1 mBq/L for an 8 h count may be obtained using 10 L seawater sample aliquots.     

Preparation of 90Y by the 90Sr-90Y Generator for Medical Purpose

The production of ⁹⁰Y by ⁹⁰Sr-⁹⁰Y generator was studied. ⁹⁰Sr was adsorbed on a column with Aminex A-5 resin. The daughter radionuclide ⁹⁰Y was eluted with 0.7M -hydroxyisobutyrate (-HIB, pH 5.4). Radionuclidic, radiochemical and chemical purities were >98% and yield >85%. After converting into chloride form ⁹⁰YCl₃-solution (pH:1) was used for preparing injectable yttrium citrate and labeling some other radiopharmaceuticals. Furthermore, a fast ITLC-method for the determination of ⁹⁰Sr in ⁹⁰Y-eluate was developed.     

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.