Radiochemical separation of Pu, U, Am and Sr isotopes in environmental samples using extraction chromatographic resins

This study presents a rapid and quantitative sequential radiochemical separation method for Pu, U, Am and Sr isotopes in environmental samples with extraction chromatographic resins. After radionuclides were leached from the samples with 6 M HNO₃, Pu and U isotopes were adsorbed onto the UTEVA column and Am isotopes were adsorbed onto the TRU column connected with the UTEVA column. Also, ⁹⁰Sr was adsorbed onto the Sr column connected with the TRU column. Pu and U isotopes were purified from other nuclides through the UTEVA column. In addition, Am isotopes were separated from other nuclides with the TRU column. Finally, ⁹⁰Sr was purified with the Sr resin. After α source preparation for the purified Pu, U and Am isotopes with micro-coprecipitation method, Pu, U and Am isotopes were measured using alpha spectrometry. On the other hand, ⁹⁰Sr was measured using a low level liquid scintillation counter. The radiochemical procedure for Pu, U, Am and Sr nuclides investigated in this study has been applied to environmental samples after validating the simulated samples.     

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.     

Preparation of animal tissue samples for the determination of90Sr and actinides

A unique procedure permitting the determination of⁹⁰Sr and actinides in the same protion of sample, with good chemical yields of all analytes, is presented. Animal tissue samples containing bone are ashed, spiked with^{2 3 2}U,^{2 4 2}Pu,^{2 4 3}Am and^{8 5}Sr and solubilized. The actinides and strontium are gathered and separated by a series of coprecipitations with, cerium hydroxide and cerium fluoride. Actinide separation and determination and purification and determination of⁹⁰Sr are accomplished by a combination of several well-known procedures. The laboratory method consistently results in high chemical yields of all the analytes and overcomes interferences from phosphates and calcium.     

Rapid column extraction method for actinides and strontium in fish and other animal tissue samples

The analysis of actinides and radiostrontium in animal tissue samples is very important for environmental monitoring. There is a need to measure actinide isotopes and strontium with very low detection limits in animal tissue samples, including fish, deer, hogs, beef and shellfish. A new, rapid separation method has been developed that allows the measurement of plutonium, neptunium, uranium, americium, curium and strontium isotopes in large animal tissue samples (100–200 g) with high chemical recoveries and effective removal of matrix interferences. This method uses stacked TEVA Resin®, TRU Resin® and DGA Resin® cartridges from Eichrom Technologies (Darien, IL, USA) that allows the rapid separation of plutonium (Pu), neptunium (Np), uranium (U), americium (Am), and curium (Cm) using a single multi-stage column combined with alphaspectrometry. Strontium is collected on Sr Resin® from Eichrom Technologies (Darien, IL, USA). After acid digestion and furnace heating of the animal tissue samples, the actinides and ^89/90Sr are separated using column extraction chromatography. This method has been shown to be effective over a wide range of animal tissue matrices. Vacuum box cartridge technology with rapid flow rates is used to minimize sample preparation time.     

Sequential separation and determination of plutonium, americium-241 and strontium-90 in soils and sediments

A sensitive and reliable metbod for the sequential separation and determination of plutonium,²⁴¹Am and⁹⁰Sr in soil samples was developed. Plutonium was separated by a Microthene-TNOA column. Then⁹⁰Y (for⁹⁰Sr determination) was separated from americium by a HDEHP column after elimination of large amounts of interfering stable or radioactive nuclides (iron,²¹⁰Bi and²¹⁰Po etc.) by an oxalate precipitation and a Microthene-TNOA column. Finally americium was purified by another HDEHP column and a PMBP-TOPO extraction. A special attention was paid to the decontamination of Pu and Am from²¹⁰Po and of⁹⁰Y from²¹⁰Bi; the relevant decontamination factors resulted greater than 10⁵, 10⁶ and 10⁴ respectively. The detection limits were 1.2 mBq/kg for Pu and 1.7 mBq/kg for²⁴¹Am and 0.32 Bq/kg for⁹⁰Sr. The procedure was checked by analyzing three certified samples supplied by IAEA. Some Italian soil samples were also analyzed giving average yields of 84.9±7.2% for Pu, 57.8±3.2%for Am and 96.7±1.6% for Y; the^239+240Pu,²³⁸Pu,²⁴¹Am and⁹⁰Sr contents (Bq/kg) ranged from 0.347 to 1.53, from 0.013 to 0.048, from 0.126 to 0.556 and from 2.89 to 11.6 respectively and the average ratios were 0.037±0.017 for²³⁸Pu/^239+240Pu, 0.357±0.040 for²⁴¹Am/^239+240Pu and 7.0±1.2 for⁹⁰Sr/^239+240Pu.     

Sequential isotopic determination of plutonium,thorium, americium and uranium in the air filter and drinking water samples around the WIPP site

The simultaneous determination of actinides in air filter and water samples around the WIPP site have been demonstrated. The analytical method is based on the selective separation and purification by anion exchange and Eichrome-TEVA, TRU and DGA-resin followed by determination of actinides by alpha spectrometry. Counting sources for alpha spectrometric measurements were prepared by microcoprecipitation on neodymium fluoride (NdF₃). Radiochemical yields were determined using ²⁴²Pu, ²²⁹Th, ²⁴³Am and ²³²U as tracers. The validation of the method is performed through the analysis of reference materials or participating in laboratory intercomparison programs. The plutonium concentrations in aerosols varied seasonally, being highest in spring and summer due to the spring-time enhanced wind-storm transportation of radioactive aerosols from the stratosphere to the troposphere. The ²³⁸Pu/^239+240Pu activity ratio in the aerosol samples is typically close to that of global fallout from historic above-ground nuclear weapons testing. The results presented here indicate that the source of plutonium in the WIPP environment results mainly from global nuclear fallout and there is no evidence of increases in radiological contaminants in the region that could be attributed to releases from the WIPP.     

Rapid analysis of emergency urine and water samples

There is a need for fast, reliable methods for the determination of actinides and ^89/90Sr analysis on environmental and bioassay samples in response to an emergency radiological incident. The Savannah River Site (SRS) Environmental Laboratory participated in the National Institute of Standards and Technology Radiochemistry Intercomparison Program (NRIP-06) and analyzed water and urine samples within 8 hours of receipt. The SRS Environmental Laboratory was the only lab that participated in the program that analyzed these samples for both actinides and ^89/90Sr within an eight hour turnaround time. A rapid actinide and ^89/90Sr separation method was used for both urine and water samples. This method uses stacked TEVA Resin®, TRU Resin® and Sr-Resin® cartridges from Eichrom Technologies (Darien, IL, USA) that allows the rapid separation of plutonium (Pu), neptunium (Np), uranium (U), and americium (Am), curium (Cm) and thorium (Th) using a single multi-stage column combined with alpha-spectrometry. Vacuum box cartridge technology with rapid flow rates was used to minimize sample preparation time. This paper discusses the technology and conditions employed for both water and urine samples and presents the SRS performance data on the NRIP-06 samples.     

Determination of radioactive strontium in seawater

This paper describes the procedures of isolating strontium and yttrium from seawater that enable the determination of ^89,90Sr. In one procedure, strontium is directly isolated from seawater on the column filled with Sr resin by binding of strontium to the resin from 3 M HNO₃ in a seawater, and successive elution with HNO₃. In others, strontium is precipitated from seawater with (NH₄)₂CO₃, followed by isolation on a Sr column or an anion exchange column. It is shown that strontium precipitation is optimal with concentration of 0.3 M (NH₄)₂CO₃ at pH = 11. In these conditions, 100% Y, 78% Sr, 80% Ca and 50% Mg are precipitated. Strontium is bound on to Sr column from 5 to 8 M HNO₃, separated from other elements by elution with 3 M HNO₃ and 0.05 M HNO₃. Strontium and yttrium are bound on to anion exchange column from alcoholic solutions of nitric acid. The optimum mixture of alcohols for sample binding is a mixture of ethanol and methanol with the volume ratio 1:3. Strontium and yttrium are separated from Mg, Ca, K, and other elements by elution with 0.25 M HNO₃ in the mixture of ethanol and methanol. After the separation, yttrium and strontium are eluted from the column with water or methanol.In the procedure of direct isolation from 1 l of the sample, the average recovery of 50% was obtained. In the remaining two procedures, the strontium recovery was about 60% for the Sr column and 65% for anion exchange column. Recovery of yttrium is about 70% for the anion exchange column. It turned out that the procedure with the Sr resin (direct isolation and isolation after precipitation) is simpler and faster in the phase of the isolation on the column in comparison with the procedure with the anion exchanger. The procedure with the anion exchanger, however, enables the simultaneous isolation of yttrium and strontium and rapid determination of ^89,90Sr. These procedures were tested by determination of ^89,90Sr on liquid scintillation counter and Cherenkov counting in 5 M HNO₃. Obtained results showed that activity of 50 mBq l⁻¹ of ^89,90Sr and higher can be simultaneously determined.     

Enzymatic degradation of large vegetation samples for the simultaneous determination of129I,actinides and strontium

A radiochemical procedure is given for the simultaneous determination of low levels of¹²⁹I, actinides (Pu, Am, Cm) and⁹⁰Sr in vegetation samples. It is shown that grass samples up to 5 kg fresh weight can be wet ashed conveniently by hydrogen peroxide under alkaline conditions, subsequent to an initial enzymatic disintegration. After purification of the iodine fraction,¹²⁹I is determined by neutron activation analysis. Using alpha spectrometry,²³⁸Pu and^239,240Pu are determined in the plutonium fraction, and²⁴¹Am,²⁴²Cm, and²⁴⁴Cm in the americium/curium fraction. The⁹⁰Sr is determined after separation by beta counting its decay product⁹⁰Y.     

Rapid separation of actinides and radiostrontium in vegetation samples

A new rapid method for the determination of actinides and radiostrontium in vegetation samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used in emergency response situations or for routine analysis. The actinides in vegetation method utilizes a rapid sodium hydroxide fusion method, a lanthanum fluoride matrix removal step, and a streamlined column separation process with stacked TEVA, TRU and DGA Resin cartridges. Lanthanum was separated rapidly and effectively from Am and Cm on DGA Resin. Alpha emitters are prepared using rare earth microprecipitation for counting by alpha spectrometry. The purified ⁹⁰Sr fractions are mounted directly on planchets and counted by gas flow proportional counting. The method showed high chemical recoveries and effective removal of interferences. The actinide and ⁹⁰Sr in vegetation sample analysis can be performed in less than 8 h with excellent quality for emergency samples. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory actinide particles or vegetation residue after furnace heating is effectively digested.     

Sequential determination of actinide isotopes and radiostrontium in swipe samples

Assays of alpha- and beta-emitting radionuclides in swipe samples are often required to monitor the presence of removable surface contamination for radiological protection and control in nuclear facilities. Swipe analysis has also proven to be a very sensitive analytical technique to detect nuclear signatures for safeguard verification purposes. A new sequential method for the determination of actinide isotopes and radiostrontium in swipe samples, which utilizes a streamlined column separation with stacked anion and extraction chromatography resins, has been developed. To validate the separation procedure, spike and blank samples were prepared and analyzed by inductively coupled mass spectrometry (ICP-MS), alpha spectrometry and liquid scintillation (LS) counting. Low detection limits have been achieved for isotopic analysis of Pu (²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu), U (²³⁴U, ²³⁵U, ²³⁸U), Am (²⁴¹Am), Cm (²⁴²Cm, ^243/244Cm) and Sr (⁹⁰Sr) at ultra-trace concentration levels in swipe samples.     

Combined procedure for the determination of90Sr,241Am and Pu radionuclides in soil samples

A combined procedure for sequential determination of low level activity concentrations of⁹⁰Sr,²⁴¹Am and Pu radionuclides is described. The analysis of -emitters is performed by isotope dilution -spectrometry using²⁴²Pu or²³⁶Pu and²⁴³Am tracers. Strontium-90 is analyzed by liquid scintillation counting using the double energetic windows method. The method combines the well established, procedure for Pu analysis based on anion exchange, the powerful and selective method for Sr isolation based on extraction chromatography using Sr-Spec resin and finally it includes the application of the TRU-Spec column for separation and purification of the Am fraction. The radiochemical procedure was tested using IAEA reference and intercomparison materials. Major parameters of the procedure as well as advantages and drawbacks are discussed in detail.     

Determination of activity concentrations and activity ratios of plutonium,americium and curium isotopes in radioactive waste samples

This paper presents a rapid and quantitative radiochemical separation method for the Pu, Am and Cm isotopes with an anion exchange resin and a TRU resin. After the Pu isotopes were purified with an anion exchange resin method and the Am and Cm isotopes were purified with the TRU resin method, micro-coprecipitation method was applied for an alpha-source preparation. The activity concentrations and activity ratios for the Pu, Am and Cm isotopes in a radioactive sample were measured by radiation counting methods such as an alpha-spectrometry and a liquid scintillation counting as well as by a mass spectroscopic method such as a thermal ionization mass spectrometry.     

137Cs, 40K, 90Sr, 238, 239+240Pu, 241Am and 243+244Cm in forest litter and their transfer to some species of insects and plants in boreal forests: Three case studies

Results for ¹³⁷Cs, ⁴⁰K, ⁹⁰Sr, ^238,239+240Pu, ²⁴¹Am and ^243+244Cm measurements in plant, insects and forest litter samples collected at three sites in Poland are presented. New results are compared with some existing data for locations examined during previous studies. Insect samples were introduced now for the first time. Relatively high activities of ⁹⁰Sr were noticed for spruce bark beetle (Ips typographus) and those for ¹³⁷Cs, plutonium and ²⁴¹Am for forest dung beetle (Anoplotrupes stercorosus). Faster than caused by physical decay decrease of radiocesium activity was noticed for the majority of plant and litter samples. The results for ^239+240Pu for litter were similar to previous results, but the activities of ²³⁸Pu were smaller. The activity ratio between ²⁴¹Am and ^239+240Pu was found lower than expected for known proportions between global and Chernobyl fallout. Thus a kind of dynamic behavior of Pu and Am in the forest ecosystem is concluded. Transfer factors and aggregation coefficients were estimated and discussed for both plants and insects as well as between insects and the part of plants (or litter) they feed on. Many of them were never presented before.The authors are thankful to the Polish State Committee for Scientific Research for financial support of this investigation, Grant No. PG04 07520.     

Rapid determination of actinides in seawater samples

A new rapid method for the determination of actinides in seawater samples has been developed at the Savannah River National Laboratory. The actinides can be measured by alpha spectrometry or inductively-coupled plasma mass spectrometry. The new method employs novel pre-concentration steps to collect the actinide isotopes quickly from 80 L or more of seawater. Actinides are co-precipitated using an iron hydroxide co-precipitation step enhanced with Ti⁺³ reductant, followed by lanthanum fluoride co-precipitation. Stacked TEVA Resin and TRU Resin cartridges are used to rapidly separate Pu, U, and Np isotopes from seawater samples. TEVA Resin and DGA Resin were used to separate and measure Pu, Am and Cm isotopes in seawater volumes up to 80 L. This robust method is ideal for emergency seawater samples following a radiological incident. It can also be used, however, for the routine analysis of seawater samples for oceanographic studies to enhance efficiency and productivity. In contrast, many current methods to determine actinides in seawater can take 1–2 weeks and provide chemical yields of ~30–60 %. This new sample preparation method can be performed in 4–8 h with tracer yields of ~85–95 %. By employing a rapid, robust sample preparation method with high chemical yields, less seawater is needed to achieve lower or comparable detection limits for actinide isotopes with less time and effort.     

Simultaneous determination of238Pu,239+240Pu,241Pu,241Am,242Cm,244Cm,89Sr,and90Sr in vegetation samples,and application to Chernobyl-fallout contaminated grass

A radiochemical procedure is described for the simultaneous determination of²³⁸Pu,^239+240Pu,²⁴¹Pu,²⁴¹Am,²⁴²Cm,²⁴⁴Cm,⁸⁹Sr, and⁹⁰Sr in vegetation samples. The method was applied for the determination of these, radionuclides in grass, collected near Munich after the fallout from the reactor accident at Chernobyl, USSR. The specific activities observed were (in Bq kg^–1 dry weight):²³⁸Pu, 0.077;^239+240Pu, 0.15;²⁴¹Pu, 3.9;²⁴¹Am, 0.031;²⁴²Cm, 3.0;²⁴⁴Cm, 0.008;⁸⁹Sr, 2000;⁹⁰Sr, 99.     

Soil and sediment sample analysis for the sequential determination of natural and anthropogenic radionuclides

A new sequential method for the determination of both natural (U, Th) and anthropogenic (Sr, Cs, Pu, Am) radionuclides has been developed for application to soil and sediment samples. The procedure was optimised using a reference sediment (IAEA-368) and reference soils (IAEA-375 and IAEA-326). Reference materials were first digested using acids (leaching), ‘total’ acids on hot plate, and acids in microwave in order to compare the different digestion technique. Then, the separation and purification were made by anion exchange resin and selective extraction chromatography: transuranic (TRU) and strontium (SR) resins. Natural and anthropogenic alpha radionuclides were separated by uranium and tetravalent actinide (UTEVA) resin, considering different acid elution medium. Finally, alpha and gamma semiconductor spectrometer and liquid scintillation spectrometer were used to measure radionuclide activities. The results obtained for strontium-90, cesium-137, thorium-232, uranium-238, plutonium-239+240 and americium-241 isotopes by the proposed method for the reference materials provided excellent agreement with the recommended values and good chemical recoveries. Plutonium isotopes in alpha spectrometry planchet deposits could be also analysed by ICPMS.     

An improved rapid method for the determination of actinides in water

A new rapid method has been developed for the determination of Th, Pu, Np, U, Am and Cm isotopes in water samples of about 1 L. Actinides are pre-concentrated by co-precipitation with Ca phosphate, sequentially separated on stacked TEVA and TK221 cartridges and measured by alpha spectrometry. The TK221 extraction chromatographic resin contains i.e. CMPO and DGA extractants. It has been characterized by measuring the weight distribution ratios (D_w) of actinides which are higher than 1000 for all actinides in 3 M HNO₃. The method has been optimized, applied for the analysis of tap and seawater samples and validated by participating in an IAEA proficiency test. Chemical recoveries for all actinides are better than 50%. The method can be performed within one day.

     

Determination of transuranic and thorium isotopes in ocean water: In solution and in filterable particles

A sensitive technique for the measurement of dissolved and particulate actinide concentrations and water column distributions is described. Pu, Am, and Th isotopes are collected using large-volume, wire-mounted electrical pumping systems. Particles were removed by filtration, and actinides by absorption on MnO₂-coated filters. The very large volumes processed (up to 4000 liters) result in very sensitive and precise concentration measurements after analyses of the samples by standard radiochemical and alpha spectrometric techniques.