A new method for the determination of plutonium and americium using high pressure microwave digestion and alpha-spectrometry or ICP-SMS

Plutonium and americium are radionuclides particularly difficult to measure in environmental samples because they are α-emitters and therefore necessitate a careful separation before any measurement, either using radiometric methods or ICP-SMS. Recent developments in extraction chromatography resins such as Eichrom^® TRU and TEVA have resolved many of the analytical problems but drawbacks such as low recovery and spectral interferences still occasionally occur. Here, we report on the use of the new Eichrom^® DGA resin in association with TEVA resin and high pressure microwave acid leaching for the sequential determination of plutonium and americium in environmental samples. The method results in average recoveries of 83 ± 15% for plutonium and 73 ± 22% for americium (n = 60), and a less than 10% deviation from reference values of four IAEA reference materials and three samples from intercomparisons exercises. The method is also suitable for measuring ²³⁹Pu in water samples at the μBq/l level, if ICP-SMS is used for the measurement.     

Pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues by extraction chromatography

An extraction chromatographic method is described for the pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues. Tissues such as lung and liver are oven dried at 120°C, ashed at 450°C and the ashed sample is alternately wet (HNO₃/H₂O₂) and dry ashed, and then dissolved in 8M HCl. Because of the complex matrix and large sample samples (up to 1500 g), the actinides were preconcentrated from the tissue solution using the TRU^TM resin (EIChroM) prior to elemental separation by extraction chromatography and determination of americium, plutonium, uranium and thorium by alpha spectrometry. The actinides were eluted from the preconcentration column and each actinide was individually eluted on TEVA^TM and TRU^TM resin columns in a tandem configuration. Actinide activities were then determined by alpha spectrometry after electrodeposition from a sulfate medium. The method was validated by analyzing human tissue samples previously analyzed for americium, plutonium, uranium and thorium in the United States Transuranium and Uranium Registries (USTUR). Two National Institute of Standards and Technology (NIST) Standard Reference Materials, SRM 4351-Human Lung and SRM 4352-Human Liver were also analyzed. United States Transuranium and Uranium Registries, Washington State University, Pullman, WA, 99163, USA.     

Electrodeposition of americium on the stainless steel support for the purpose of radiochemical assay

The kinetics of uranium, plutonium and americium electrodeposition on steel targets from organic solutions of diphenyl-(N,N-dibutyl) carbamoylmethylphosphine oxide supplemented with the ionic liquid of trihexyltetradecylphosphonium hexafluorophosphate ([PH₄]⁺PF₆ ^?) in ethanol or N,N-dimethylformamide has been studied. When running a process in a dimethylformamide medium, and 0.05 M concentration of [PH₄]⁺PF₆ ^? americium deposition degree exceeds 95 % at the electrolysis time of 2 h. Alpha-spectra resolution of obtained target does not exceed 40 keV.     

Plutonium and americium in sediment samples along the Romanian sector of the Danube river and the Black Sea coast

The concentrations of²³⁸Pu,^239,240Pu and²⁴¹Am were determined in eight sediment samples, collected from the bed of the Romanian sector of the Danube river and the Black Sea coast during 1994 and 1995. Fusion with potassium carbonate was used to achieve complete dissolution of the samples. Tracers,²⁴²Pu and²⁴³Am, were added and the separation of plutonium from americium, uranium and thorium was performed by anion exchange. Americium was separated from uranium in two steps, using a conventional anion exchange resin and an extraction chromatographic resin for transuranics. After electrodeposition on stainless steel discs the nuclides were counted with -spectrometry with -PIPS detectors. The total plutonium concentrations obtained by this method were compared with the acid leachable plutonium concentrations reported for the same samples in a previous paper.     

Determination of plutonium isotopes in urine samples from radiation workers using <Superscript>236</Superscript>Pu tracer,anion exchange resin and alpha spectrometry

Bioassay technique is used for the estimation of actinides present in the body based on their excretion rate through body fluids. For occupational radiation workers urine assay is the preferred method for monitoring of chronic internal exposure. Determination of low concentrations of actinides such as plutonium, americium and uranium at low level of mBq in urine by alpha spectrometry requires pre-concentration of large volumes of urine. This paper deals with standardization of analytical method for the determination of Pu-isotopes in urine samples using anion exchange resin and ²³⁶Pu tracer for radiochemical recovery. The method involves oxidation of urine followed by co-precipitation of plutonium along with calcium phosphate. Separation of Pu was carried out by Amberlite, IRA-400, anion exchange resin. Pu-fraction was electrodeposited and activity estimated using tracer recovery by alpha spectrometer. Twenty routine urine samples of radiation workers were analyzed and consistent radiochemical tracer recovery was obtained in the range 74–96% with a mean and standard deviation of 85 and 6% respectively.     

Determination of uranium isotopes in urine samples from radiation workers using 232U tracer, anion-exchange resin and alpha-spectrometry

Bioassay technique is used for the estimation of actinides present in the body based on the excretion rate of body fluids. For occupational radiation workers urine assay is the preferred method for monitoring of chronic internal exposure. Determination of low concentrations of actinides such as plutonium, americium and uranium at low level of mBq in urine by alpha-spectrometry requires pre-concentration of large volumes of urine. This paper deals with standardization of analytical method for the determination of U-isotopes in urine samples using anion-exchange resin and ²³²U tracer for radiochemical recovery. The method involves oxidation of urine followed by co-precipitation of uranium along with calcium phosphate. Separation of U was carried out by Amberlite, IRA-400, anion-exchange resin. U-fraction was electrodeposited and activity estimated using tracer recovery by alpha-spectrometer. Eight routine urine samples of radiation workers were analyzed and consistent radiochemical tracer recovery was obtained in the range of 51% to 67% with a mean and standard deviation of 60% and 5.4%, respectively.     

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.     

Determination of ultratrace amounts of plutonium in high saline groundwater by inductively coupled plasma mass spectrometry

For determination of ultratrace amounts of plutonium in high saline groundwater, large-volume sampling and preconcentration are necessary. However, traditional co-precipitation methods, such as Fe(OH)₃, Ca(OH)₂–Mg(OH)₂ and hydroxide-carbonate co-precipitation, are unable to meet the requirements of preconcentration of the ultratrace plutonium in high saline groundwater. In this paper, the ultratrace plutonium in high saline groundwater was concentrated by sequential co-precipitation with MnO₂ and Fe(OH)₃, and purified by two-stage anion-exchange separation on Dowex1 × 4 resin column. Quadrupole ICP-MS was employed for the determination of ²³⁹Pu with ²⁴²Pu spiked. After co-precipitation and purification, the major matrix elements were significantly decreased to μg mL^?1 level and decontamination factor of uranium is better than 10⁶. The detection limit for ²³⁹Pu in 50 L high saline water is 2.1 × 10^?16 g L^?1. Three high saline fountain samples (total dissolved solids more than 20 g L^?1) from Dunhuang region of China were analyzed using this method. The concentrations of ²³⁹Pu in these samples were 0.48 ± 0.2 × 10^?15, 1.40 ± 0.10 × 10^?15 and 2.13 ± 0.21 × 10^?15 g L^?1 respectively. The recovery obtained for 7 pg of ²⁴²Pu spiked into real high saline-water samples was all above 70 %.     

Separation of neptunium, plutonium, americium and curium from uranium with di-(2-ethylhexyl)-phosphoric acid (HDEHP) for radiometric and ICP-MS analysis

The possibility of using di-(2-ethylhexyl)-phosphoric acid (HDEHP) in solvent extraction for the separation of neptunium, plutonium, americium and curium from large amounts of uranium was studied. Neptunium, plutonium, americium and curium (as well as uranium) were extracted from HNO₃, whereafter americium and curium were back-extracted with 5M HNO₃. Thereafter was neptunium back-extracted in 1M HNO₃ containing hydroxylamine hydronitrate. Finally, plutonium was back-extracted in 3M HCl containing Ti(III). The method separates²³⁸Pu from²⁴¹Am for α-spectroscopy. For ICP-MS analysis, the interferences from²³⁸U are eliminated: tailing from²³⁸U, for analysis of²³⁷Np, and the interference of²³⁸UH⁺ for analysis of²³⁹Pu. The method has been used for the analysis of actinides in samples from a spent nuclear fuel leaching and radionuclide transport experiment.     

Simultaneous recovery of plutonium and americium from assorted analytical waste solutions using extraction chromatography

A rapid extraction chromatography based methodology was developed for simultaneous recovery of plutonium and americium from various kinds of analytical waste obtained during chemical quality control of plutonium based nuclear materials using sulphonic acid based actinide? resin. Efforts were made to understand the effect of initial feed acidity, gamma radiation and the concentrations of Am³⁺ and Pu⁴⁺ on their k _d. values. Processing of assorted analytical waste solutions through this method revealed that more than 95 % of Am³⁺ and 90 % of Pu⁴⁺ were adsorbed on the resin while iso- propanol can be successfully employed for the quantitative recovery of both the actinides from the loaded resin phase.     

The effect of physicochemical parameters on the separation recovery of plutonium and uranium from aqueous solutions by cation exchange

The effect of physicochemical parameters such as pH, salinity (e.g. [NaCl]) and competitive cation (e.g. Ca²⁺ and Fe³⁺) concentration on the separation recovery of plutonium and uranium from aqueous solutions by cation exchange has been investigated. The investigation was performed to evaluate the applicability of cation exchange as separation and pre-concentration method prior to the radiometric analysis of uranium and plutonium isotopes in natural water samples. Application of the method to test solutions of constant radionuclide concentration and variable composition (0.1, 0.5 and 1 M NaCl; 0.1 and 0.5 M Ca(NO₃)₂; 0.1 and 1 mM FeCl₃; 10) has generally shown that: (1) the optimum pH is 4.5 for uranium and plutonium, (2) increasing salinity results in slightly lower for uranium and significantly higher chemical recovery plutonium and (3) the presence of Ca(II) cations doesn’t significantly affect the chemical recovery of both radionuclides. Contrary, the presence of Fe(III) cations ([Fe(III)] > 0.1 mM) results in significantly lower chemical recovery for both radionuclides (<50%). The later is attributed to the formation of Fe(III) colloids, which present increased chemical affinity for uranium and plutonium and hence compete with the radionuclide binding by the resin. Nevertheless, the results indicate that the method could be successfully applied to a wide range of natural waters.     

Separation and determination of <Superscript>241</Superscript>Am in urine samples from radiation workers using PC88-A and alpha spectrometry

Bioassay technique is used for the estimation of actinides present in the body based on their excretion rate through body fluids. For occupational radiation workers urine assay is the preferred method for monitoring of chronic internal exposure. Determination of low concentrations of actinides such as plutonium, americium and uranium at low level of mBq in urine by alpha spectrometry requires pre-concentration of large volumes of urine. This article deals with standardization of analytical method for the determination of ²⁴¹Am isotope in urine samples using Extraction Chromatography (EC) and ²⁴³Am tracer for radiochemical recovery. The method involves oxidation of urine followed by co-precipitation of americium along with calcium phosphate. This precipitate after treatment is further subjected to calcium oxalate co-precipitation. Separation of Am was carried out by EC column prepared by PC88-A (2-ethyl hexyl phosphonic acid 2-ethyl hexyl monoester) adsorbed on microporous resin XAD-7 (PC88A-XAD7). Am-fraction was electro-deposited and activity estimated using tracer recovery by alpha spectrometer. Ten routine urine samples of radiation workers were analyzed and consistent radiochemical recovery was obtained in the range 44–60% with a mean and standard deviation of 51 and 4.7% respectively.     

Rapid column extraction method for actinides and 89/90Sr in water samples

Summary The SRS Environmental Laboratory analyzes water samples for environmental monitoring, including river water and ground water samples. A new, faster actinide and ^89/90Sr separation method has been developed and implemented to improve productivity, reduce labor costs and add capacity to this laboratory.This method uses stacked TEVA Resin^ò, TRU Resin^òand Sr-Resin^òcartridges from Eichrom Technologies (Darien, IL, USA) that allows the rapid separation of plutonium, neptunium, uranium, americium, curium and thorium using a single multi-stage column combined with alpha-spectrometry. By using vacuum box cartridge technology with rapid flow rates, sample preparation time is minimized. The method can be used for routine analysis or as a rapid method for emergency preparedness. Thorium and curium are often analyzed separately due to the interference of the daughter of ²²⁹Th tracer, actinium (²²⁵Ac) on curium isotopes when measured by alpha-spectrometry. This new method also adds a separation step using DGA Resin^ò, (diglycolamide resin, Eichrom Technologies) to remove ²²⁵Ac and allow the separation and analysis of thorium isotopes and curium isotopes at the same time.     

Development of radiochemical analysis of uranium isotopes in highly contaminated soil samples

An accurate and reliable analytical technique of uranium isotopes in highly contaminated soil samples was developed and applied to the IAEA reference samples. The conventional TBP method of uranium isotopes is insufficient to completely purify uranium from actinides such as plutonium and americium isotopes in highly contaminated soil samples. For overcoming the demerits of the conventional TBP extraction method, sample materials were decomposed with HNO₃ and HF, and uranium isotopes were purified by TBP extraction and anion exchange columns and extraction chromatography. Among the purifying methods of uranium, with a TRU Spec resin column after TBP solvent extraction, uranium was completely separated from the radionuclides in a highly contaminated samples. With the modified TBP extraction method, it was found that the concentrations of uranium isotopes were consistent with the reference values reported by the IAEA.     

Separation of plutonium from uranium using reactive chemistry in a bandpass reaction cell of an inductively coupled plasma mass spectrometer

Oxygen and ammonia were evaluated as reaction gases for the chemical separation between uranium and plutonium in the bandpass reaction cell or dynamic reaction cell (DRC) of the ELAN DRC II mass spectrometer. Both uranium and plutonium demonstrated similar reactivity with oxygen giving rise to corresponding oxides. At the same time, remarkable selectivity in the reaction with ammonia was observed. While uranium was rapidly converted into UNH ₂⁺ and UN₂H ₄⁺ , plutonium remained unreactive in the DRC pressurized with ammonia. This difference in the reactivity allowed the determination of plutonium isotopes in urine and water samples containing excess uranium without preceding separation procedure. Detection limits of 0.245, 0.092, 0.270 and 0.237 ng L^–1 were obtained for ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu and ²⁴²Pu, respectively, in urine spiked with 10 g L^–1 of U.     

A method for estimation of Pu-isotopes in urine samples using TEVA resin and alpha spectrometry

The conventional method used for estimation of Pu-isotopes in urine samples involves anion exchange resin followed by alpha spectrometry, which takes nearly one working week for complete sample analysis. Since the results of the analysis form an important input for decision making by the plant authorities, it is always preferable to reduce overall analysis time for the estimation of Pu-isotopes in bioassay samples. This paper deals with standardization of a relatively faster method for estimation of Pu-isotopes in bioassay samples using TEVA resin and ²³⁶Pu tracer for radiochemical recovery. The method involves oxidation of urine followed by co-precipitation of plutonium along with calcium phosphate and separation of Pu was carried out using TEVA resin. Pu-fraction was electrodeposited and activity estimated using tracer recovery by alpha spectrometer. Routine urine samples of radiation workers were analyzed and consistent radiochemical tracer recovery was obtained in the range 65–87 % with a mean and SD of 75 and 7.4 %, respectively. The standardized chromatographic technique reduces the analysis time by about 1 day as compared to conventional method for estimation of Pu-isotopes in urine samples.     

New fecal method for plutonium and americium

A new fecal analysis method that dissolves plutonium oxide was developedat the Westinghouse Savannah River Site. Diphonix Resin . (Eichrom Technologies),is used to pre-concentrate the actinides from digested fecal samples. A rapidmicrowave digestion technique is used to remove the actinides from the DiphonixResin ., which effectively extracts plutonium and americium from acidic solutionscontaining hydrofluoric acid. After resin digestion, the plutonium and americiumare recovered in a small volume of nitric acid that is loaded onto small extractionchromatography columns, TEVA Resin and TRU Resin (Eichrom Technologies). Themethod enables complete dissolution of plutonium oxide and provides high recoveryof plutonium and americium with good removal of thorium isotopes such as ²²⁸Th.     

Analysis of nuclear materials by energy dispersive X-ray fluorescence and spectral effects of alpha decay

Energy dispersive X-ray fluorescence (EDXRF) spectra collected from alpha emitters are complicated by artifacts inherent to the alpha decay process, particularly when using portable instruments. For example, ²³⁹Pu EDXRF spectra exhibit a prominent uranium L X-ray emission peak series due to sample alpha decay rather than source-induced X-ray fluorescence. A portable EDXRF instrument was used to collect qualitative spectra from plutonium and americium, and metal alloy identification was performed on a Pu-contaminated steel sample. Significant alpha decay-induced X-ray fluorescence peaks were observed in spectra obtained from the plutonium and americium samples due to the ²³⁵U and ²³⁷Np daughters, respectively. The plutonium sample was also analyzed by wavelength dispersive XRF (WDXRF) to demonstrate that alpha decay-induced X-ray emission has a negligible effect on WDXRF spectra.     

Rapid determination of 226Ra in emergency urine samples

A new method has been developed at the Savannah River National Laboratory (SRNL) that can be used for the rapid determination of ²²⁶Ra in emergency urine samples following a radiological incident. If a radiological dispersive device event or a nuclear accident occurs, there will be an urgent need for rapid analyses of radionuclides in urine samples to ensure the safety of the public. Large numbers of urine samples will have to be analyzed very quickly. This new SRNL method was applied to 100 mL urine aliquots, however this method can be applied to smaller or larger sample aliquots as needed. The method was optimized for rapid turnaround times; urine samples may be prepared for counting in <3 h. A rapid calcium phosphate precipitation method was used to pre-concentrate ²²⁶Ra from the urine sample matrix, followed by removal of calcium by cation exchange separation. A stacked elution method using DGA Resin was used to purify the ²²⁶Ra during the cation exchange elution step. This approach combines the cation resin elution step with the simultaneous purification of ²²⁶Ra with DGA Resin, saving time. ¹³³Ba was used instead of ²²⁵Ra as tracer to allow immediate counting; however, ²²⁵Ra can still be used as an option. The rapid purification of ²²⁶Ra to remove interferences using DGA Resin was compared with a slightly longer Ln Resin approach. A final barium sulfate micro-precipitation step was used with isopropanol present to reduce solubility; producing alpha spectrometry sources with peaks typically <40 keV FWHM (full width half max). This new rapid method is fast, has very high tracer yield (>90 %), and removes interferences effectively. The sample preparation method can also be adapted to ICP-MS measurement of ²²⁶Ra, with rapid removal of isobaric interferences.     

Rapid determination of 237Np and Pu isotopes in water by inductively-coupled plasma mass spectrometry and alpha spectrometry

A new method that allows rapid preconcentration and separation of plutonium and neptunium in water samples was developed for the measurement of ²³⁷Np and Pu isotopes by inductively-coupled plasma mass spectrometry (ICP-MS) and alpha spectrometry. ²³⁸U can interfere with ²³⁹Pu measurement by ICP-MS as ²³⁸UH⁺ mass overlap and ²³⁷Np via peak tailing. The method provide enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then moving Pu to DGA resin for additional removal of uranium. The decontamination factor for uranium from Pu is almost 100,000 and the decontamination factor for U from Np is greater than 10,000. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration is performed using a streamlined calcium phosphate precipitation method. Purified solutions are split between ICP-MS and alpha spectrometry so that long and short-lived Pu isotopes can be measured successfully. The method allows for simultaneous extraction of 20 samples (including QC samples) in 4?C6 h, and can also be used for emergency response. ²³⁹Pu, ²⁴²Pu and ²³⁷Np were measured by ICP-MS, while ²³⁶Pu, ²³⁸Pu, and ²³⁹Pu were measured by alpha spectrometry.