Preconcentration and Analysis of Strontium-90 and Technetium-99 from Hanford Groundwater Using Solid Phase Extraction

Solid-phase extraction disks produced by 3M and Eichrom were evaluated for routine use in supporting the Hanford Groundwater Monitoring Project. Both disk formats contain Sr- or Tc-selective extractants, bound in a filter support, that act to preconcentrate and isolate the isotope of interest. The 3M Empore Sr Rad Disks and Tc Rad Disks were tested with respect to precision, accuracy, radiochemical yields, interferences, and volume-load variation. The Empore and Eichrom solid-phase extraction disks were applied to the ⁹⁰Sr and/or ⁹⁹Tc determination in representative Hanford groundwater samples with varying chemical and isotopic compositions. Results were compared to standard analytical methods. Both the Empore and Eichrom Tc extraction disks produced consistently higher radiochemical yields, lower detection limits, and greater accuracy than the standard analysis method. The Empore Sr extraction disks produced comparable radiochemical yields, detection limit, and accuracy relative to the standard method; however, total uncertainties were lower.     

Studies on the recovery of Pu(IV) from hydrochloric acid-oxalic acid solutions using an anion exchange method

Sorption of Pu(IV) from hydrochloric acid-oxalic acid solutions has been investigated using different anion exchangers, viz., Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) for the recovery of plutonium from plutonium oxalate solutions. Distribution ratios of Pu(IV) for its sorption on these anion exchangers have been determined. The sorption of Pu(IV) from hydrochloric acid solutions decreases drastically in the presence of oxalic acid. However, addition of aluminium chloride enhances the sorption of plutonium in the presence of oxalic acid, indicating the feasibility of recovery of plutonium. Pu(IV) breakthrough capacities have been determined with a 10 ml resin bed of each of these anion exchangers at a flow rate of 60 ml per hour using a solution of Pu(IV) with the composition: 6M HCl+0.05M HNO₃+0.1M H₂C₂O₄+0.5M AlCl₃+100 mg.l^–1 Pu(IV). The 10% Pu(IV) breakthrough capacities for Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) are 15.0, 8.9 and 6.2 g of Pu(IV) l^–1 of resin respectively.     

Plutonium removal by ion exchange chromatography

A study of Pu recovery at trace level from U solutions by ion exchange technique is presented. Plutonium retention >99.5% onto strong anionic resin, AG-X8, from nitric acid solutions and a 92% recovery using 0.4M HNO₃ at 60°C as eluent, were obtained. Uranium interference in Pu sorption from mixed U/Pu nitrate solutions with low U/Pu ratio (25) was not verified. However, for high U/Pu ratio solutions (10000), uranium interference in Pu retention on the resin, decreases to 59%. Selecting the loading conditions and using AG-X4 resin, 99% Pu retention was achieved. The Pu product is still contaminated with U and another purification cycle is recomended. A scheme for U/Pu first cycle separation is proposed.     

Characterization of SiO2-P2O5-ZrO2 Sol-Gel/NAFION™ Composite Membranes

Composite membranes were prepared by (a) infiltrating NAFION with SiO₂-P₂O₅-ZrO₂ sol, and (b) recasting a film using NAFION solution containing SiO₂-P₂O₅-ZrO₂ sol. The membranes were characterized by Differential Thermal Analysis and ac-impedance spectroscopy as a function of relative humidity. The influences of the heat treatment (80°C–150°C) and cleaning on the electrical properties were investigated. The incorporation of SiO₂-P₂O₅-ZrO₂ gels into NAFION lead to improvements in its thermal stability and proton conductivity.     

Determination of low-level99Tc in environmental samples by high resolution ICP-MS

An analytical method has been developed for the determination of low-level⁹⁹Tc in environmental samples by High Resolution ICP-MS. The method consists of leaching of⁹⁹Tc by HNO₃ and separation by three different solvent extractions with 30% TOA-xylene, MEK, and cyclohexanone. Finally, purification of⁹⁹Tc was made by using an anion exchange resin column to reduce dissolved solids content. The final solution was adjusted to 1M HNO₃ for introducing into the HR-ICP-MS. The accuracy and precision of the method was confirmed to be satisfactory by applying this technique to the determination of⁹⁹Tc in IAEA marine algae sample (AG-B-1). Measurements of⁹⁹Tc using 0.5–2.5 g of sediment samples from the Irish Sea, UK, were successfully performed by the present method.     

Solid Phase Extraction of Molybdenum on Modified Octadecyl Silica Sorbents in the Presence of Cationic Surfactants and on Silica-Based Anionic Exchanger and its Determination by Inductively Coupled Plasma Emission Spectrometry

Molybdenum was separated and preconcentrated as molybdate on microcolumns of octadecyl silica sorbents and silica-based strongly basic anion exchanger prior to its determination by ICP-AES. With octadecyl silica Separon SGX C18 and Separon SGX RPS, the retention of 0.01–0.4µg·mL^–1 Mo from 50–1000mL sample solutions was quantitative in the presence of the cationic surfactants carbethoxypentadecyltrimethylammonium bromide (Septonex^®), dodecylbenzyldimethylammonium bromide (Ajatin^®) or tetradecylbenzyldimethylammonium chloride (Zephyramine^®) at pH 6–8. 96% ethanol was the most suitable eluent of the molybdate/surfactant associate. For the strongly basic anion exchanger Separon SGX AX, the optimal conditions for sorption of 5–20µg Mo from 50–250mL sample solutions were at pH 2 in the presence of 0.05M ascorbic acid and ammonium citrate. 3M HNO₃ was a satisfactory eluent in this case. Organic solvents and excess of acids were removed by evaporation prior to the determination of Mo by ICP-AES in eluates. Both procedures can be used for the determination of ion-level molybdenum in waters.     

On-line preconcentration of arsenic from water samples with an anion-exchanger column coupled to a hydride generation ICP system

Summary An on-line anion-exchange preconcentration hydride generation ICP system for the determination of total inorganic arsenic in water is described. The column was packed with strongly basic anion-exchange resin (AG 1-X8). Experimental conditions including pH of the sample solution, eluent, flow rate of eluent, oxidation states of arsenic and competing anion ions were studied. Compared with the conventional continuous hydride generation ICP, a 9.2-fold improvement in sensitivity was obtained with RSD 1–2% at 100 ng/ml. The detection limit (3) was 0.08 ng/ml. The recoveries in water samples were satisfactory. The system provides complete automation of sample loading, eluting and regenerating of the resin.On leave from Shanghai Institute of Metallurgy, Chinese Academy of Sciences, Shanghai, China 200050     

Tail-end purification of americium from plutonium loading effluents using a mixture of octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide and tri-N-butyl phosphate

The tail-end purification of Am from Pu loading effluents in 7.5M HNO₃ containing 160 mg l^–1 Am and 1.2 mg l^–1 Pu has been carried out. With 0.2M CMPO+1.2M TBP in dodecane as the extractant and stripping by 0.04M HNO₃+0.05M NaNO₂, the Pu level is brought down to 31.2 g l^–1. When the acidity was reduced to 4.2M HNO₃, one contact with 20% TLA/dodecane and subsequent extraction by a mixture of CMPO and TBP and stripping with 0.04M HNO₃+0.05M NaNO₂ gave Am samples without any detectable amounts of Pu. The recovery of Am was 90% by the first procedure and 98% by the second one.     

Simultaneous Plutonium and Uranium Isotopic Analysis from a Single Resin Bead - A Simplified Chemical Technique for Assaying Spent Reactor Fuels

Abstract

The method uses basic anion resin to adsorb plutonium and uranium from 7–8 M HNO₃ solutions containing dissolved spent reactor fuels. After equilibrating the resin with the solution, a single bead is used to determine the isotopic composition of plutonium and uranium on sample sizes as small as 10^?9 to 10^?10 g of each element per bead. Isotopic measurements are essentially free of isobaric interferences and fission product contamination in the mass spectrometer is eliminated. A very small aliquot of dissolver solution containing 10^?6 g of U and 10^?8 g of Pu is sufficient sample for chemically preparing several resin beads. A single prepared bead is loaded onto a rhenium filament and analyzed in a two-stage mass spectrometer using pulse counting for ion detection to obtain the high sensitivity required. Total quantity of the elements, in addition to isotopic abundances, can be determined by isotope dilution. Other areas where the method may be useful are: in plutonium production, isotope separations, and for trace detection of contamination on reactor parts.     

Evaluation of a rapid technique for measuring actinide oxidation states in a ground water simulant

A system using an ion chromatograph coupled to a flow-cell scintillation detector for rapidly measuring the oxidation states of actinides at low concentrations (<10–6M) in aqueous solutions was evaluated. The key components of the system are a cation–anion separation column (Dionex, CS5) and a flow cell detector with scintillating cerium activated glass beads. The typical procedure was to introduce a 0.5 ml aliquot of sample spiked with actinides in the +III to +VI oxidation states into a 5 ml sample loop followed by 4 ml of synthetic groundwater simulant. Separation was achieved at a flow rate of 1 ml/min using an isocratic elution with oxalic, diglycolic, and nitric acids followed by distilled water. Tests were first conducted to determine elution times and recoveries for an acidic solution (pH 2) and a ground water simulant (pH 8) containing Am(III), Pu(IV), Th(IV), Pu(V), and U(VI). Then, an analysis was performed using a mixture of Pu(IV), Pu(V), and Pu(VI) in the ground water simulant and compared to results using the DBM extraction technique. Approximate elution times were the same for both the acidic solution and the ground water simulant. These were as follows: Pu(V) at 10 min, Am(III) at 15 min, Pu(IV) at 25 min, Th (IV) at 28 min and U(VI) at 36 min. Recoveries for the acidic solution were quantitative for U(VI) and Th(IV) and exceeded 80% for Am(III). Recoveries for the ground water simulant were quantitative for U(VI), but they were generally not quantitative for Th(IV), Pu(IV), and Am(III). For Th(IV) and Pu(IV), less than quantitative recoveries were attributed to the formation of neutral hydroxides and colloids; for Am(III) they were attributed to insoluble carbonates and/or hydroxycarbonates. When applied to the measurement of plutonium in the ground water simulant, the technique provided showed good agreement with the dibenzoylmethane (DBM) extraction technique, but it could not distinguish between Pu(V) and Pu(VI). This was likely due to the reduction of Pu(VI) to Pu(V) in the sample by the oxalic acid eluent. However, in spite of this limitation, the technique can be used to distinguish between Pu(IV) and Pu(V) in aqueous environmental samples within a pH range of 4 to 8 and an E _H range of -0.2 to 0.6 V, the predominance region for Pu(III), (IV), and (V). In addition, this technique can be used to corroborate oxidation state analysis from the dibenzoylmethane (DBM) extraction method for environmental samples.     

Determination of the plutonium concentration by isotope dilution mass spectrometry using239Pu as a spike

A method is described for the determination of plutonium concentration in the presence of a bulk of other impurities by isotope dilution mass spectrometry /IDMS/ using²³⁹Pu as a spike. The method involves the addition of²³⁹Pu spike / 90 atom%/ to samples with²³⁹Pu / 70 atom%/ and vice versa. After ensuring chemical exchange between the sample and the spike isotopes, plutonium is purified by conventional anion exchange procedure in 7M HNO₃ medium.²³⁹Pu/²⁴⁰Pu atom ratio in the purified spiked sample is determined with high precision /better than 0.1%/ using a thermal ionization mass spectrometer. Concentration of plutonium in the sample is calculated from the changes in²³⁹Pu/²⁴⁰Pu atom ratio in the spiked mixture. Results obtained on different plutonium samples using²³⁹Pu as a spike are compared with those obtained by the use of²⁴²Pu spike. Precision and accuracy comparable to those achieved by using²⁴²Pu are demonstrated. The method provides an alternative in the event of non-availability of enriched²⁴²Pu or²⁴⁴Pu required in IDMS of plutonium and at the same time, offers certain advantages over the use of²⁴²Pu or²⁴⁴Pu spike.     

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.     

Improved separation method for determining actinides in soil samples

Radionuclides have been identified as a significant source of contamination at many United States Department of Energy (DOE) sites. As a result, reliable and accurate methods to determine actinide content in environmental samples have become increasingly important. Therefore, an improved analytical scheme using a series of actinide-selective extraction chromatography (Tru-Spec, Teva-Spec) and ion-exchange (Diphonix) resins was designed to satisfy the requirements of both alpha spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). Alpha spectrometry required the sequential isolation of the actinides, whereas ICP-MS required only a group separation of the actinides. The separation schemes were designed to allow analysis of the actinides in soil, whether the soils were acid leached or totally dissolved through fusion. For those analytes present as contaminants (^239/240Pu,²⁴¹Am), the laboratory results agreed favorably with the accepted values for several reference soils. However, for the acid digestion procedure, the results for matrix constitutents (²³⁸U,²³⁴U,²³²Th) were quite low because the silicate matrix was not decomposed. The sodium hydroxide fusion technique described allowed accurate analysis of both matrix constituents and contaminants because a total dissolution was achieved.     

Adsorption of gadolinium on activated charcoal from electrolytic aqueous solution

Adsoprtion of gadolinium on activated charcoal has been studied as a function of shaking time, pH, concentration of adsorbate and temperature. Gadolinium adsorption obeys the Langmuir isotherm. H^o and S^o were calculated from the slope and intercept of the In K_D 1/T plot. The influence of different cations and anions on gadolinium adsorption has been examined. The adsorption of other metal ions on activated charcoal has been studied under optimum conditions to check the selectivity of gadolinium adsorption. Consequently, gadolinium was removed from Ni, V, Zn, Cu, Rb, Sr and Mn. More than 97% of the adsorbed gadolinium on activated charcoal can be recovered with 35 ml of 3M HNO₃ solution. Wavelength dispersive X-ray fluorescence spectrometer was used for measuring gadolinium concentration.     

Separation of Zr in the rubble waste generated at the Fukushima Daiichi Nuclear Power Station

Separation method of Zr using trans uranium resin (TRU resin) and tetra valent actinide resin (TEVA resin) was developed for the analysis of ⁹³Zr contained in the rubble waste. Zr, Nb, and U were quantitatively extracted on the TRU resin from 3 M HNO₃ and striped with 0.01 M HF, in addition, some part of Mo, Hg, Bi, and Th were also included in the stripping solution. The stripping solution was evaporated to eliminate HNO₃ and the residue was dissolved in 0.1 M HF. Finally, Zr was separated from Nb and Mo with the TEVA resin.     

210Pb and210Po in tobacco-with a special focus on estimating the doses of210Po to man

Studies have been carried out on the solubility of Pu(III) oxalate by precipitation of Pu(III) oxalate from varying concentrations of HNO₃/HCl (0.5–2.0M) solutions and also by equilibrating freshly prepared Pu(III) oxalate with solutions containing varying concentrations of HNO₃/HCl, oxalic acid and ascorbic acid. Pu(III) solutions in HNO₃ and HCl media were prepared by reduction of Pu(IV) with ascorbic acid. 0.01–0.10M ascorbic acid concentration in the aqueous solution was maintained as holding reductant. The solubility of Pu(III) oxalate was found to be a minimum in 0.5M–1M HNO₃/HCl solutions containing 0.05M ascorbic acid and 0.2M excess oxalic acid in the supernatant.     

Americium and plutonium separation by extraction chromatography for determination by accelerator mass spectrometry

A simple method was developed to separate Pu and Am using single column extraction chromatography employing N,N,N′,N′-tetra-n-octyldiglycolamide (DGA) resin. Isotope dilution measurements of Am and Pu were performed using accelerator mass spectrometry (AMS) and alpha spectrometry. For maximum adsorption Pu was stabilized in the tetra valent oxidation state in 8 M HNO₃ with 0.05 M NaNO₂ before loading the sample onto the resin. Am(III) was adsorbed also onto the resin from concentrated HNO₃, and desorbed with 0.1 M HCl while keeping the Pu adsorbed. The on-column reduction of Pu(IV) to Pu(III) with 0.02 M TiCl₃ facilitated the complete desorption of Pu. Interferences (e.g. Ca²⁺, Fe³⁺) were washed off from the resin bed with excess HNO₃. Using NdF_3, micro-precipitates of the separated isotopes were prepared for analysis by both AMS and alpha spectrometry. The recovery was 97.7 ± 5.3% and 95.5 ± 4.6% for ²⁴¹Am and ²⁴²Pu respectively in reagents without a matrix. The recoveries of the same isotopes were 99.1 ± 6.0 and 96.8 ± 5.3% respectively in garden soil. The robustness of the method was validated using certified reference materials (IAEA 384 and IAEA 385). The measurements agree with the certified values over a range of about 1–100 Bq kg⁻¹. The single column separation of Pu and Am saves reagents, separation time, and cost.     

Stability of selenium and its speciation analysis in water using automatic system separation and HR-ICP-MS measurement

A simple and convenient method has been developed for the pre-concentration and separation of inorganic selenium species from environmental water samples using anion exchange chromatographic column combined with high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) measurement. ⁷⁵Se(IV) and ⁷⁵Se(VI) were prepared and used as tracers during the experiments. The volatility of selenium during solution evaporation was investigated to establish a reliable water samples pretreatment procedure. The parameters which affect the uptake of Se(IV) and Se(VI) on Dowex1 × 8 resin was optimized and the procedure for Se(IV) and Se(VI) separation was proposed. Both Se(IV) and Se(VI) are retained on the column in natural or alkaline solution with high distribution coefficient. The successive gradient elution of pre-concentrated species of selenium with HNO₃ solution allows to differentiate between them. Se(IV) and Se(VI) finally were eluted with 0.05 mol/L HNO₃ and 5.0 mol/L HNO₃, respectively. The proposed method has been successfully verified using the certified reference materials (CRMs) of real water samples, and spiked recoveries for real samples were 98%-104% with 5% relative standard deviations (RSDs). The developed procedure is proved to be reliable and can be used for the rapid determination of selenium species in environmental water samples.     

Innovative characterization, monitoring and sensor technologies for environmental radioactivity at USDOE sites

The mission of the U. S. Department of Energy Office of EnvironmentalManagement (EM) is to clean up its contaminated sites from the past productionof nuclear weapons. Within EM, the Office of Science and Technology (OST)is responsible for providing a full range of science and technology resourcesneeded to support resolution of EM cleanup and long-term environmental stewardshipproblems. This responsibility includes implementation of a technology developmentpathway from basic research to development, demonstration, and deploymentof scientific and technological solutions needed by DOE sites. One OST Programis the Characterization, Monitoring, and Sensor Technology Crosscutting Program(CMST-CP), which aims to provide innovative technologies (i.e., faster, better,cheaper, and/or safer) for environmental characterization and monitoring.This paper describes several technologies that CMST-CP has supported for developmentwith significant benefits realized or projected over the baseline characterizationand monitoring practices. Examples of these technologies include mapping ofsubsurface radioactivity using Cone Penetrometer and drilling techniques;a Rapid Liquid Sampler for Sr, Ra, Tc, and Cs using 3M Empore Rad Disks;Long-Range Alpha Detectors; a Compact High Resolution Spectrometer; BetaScintfor determination of Sr in soil; Laser-Induced Fluorescence Imaging techniquesfor mapping U on surfaces; the Environmental Measurements While Drilling System;and the Expedited Site Characterization methodology.     

Rare earth impurities in high purity lanthanum oxide determined by neutron activation analysis

Individual rare earth impurities in high purity La₂O₃ (99.9%) have been determined by NAA after pre-separation of the matrix (La). The separation is carried out on an anion exchanger (Dowex 1×8) using different mixtures of methanol/nitric acid as eluants. The rare earth elements from Dy to Lu are eluted quantitatively using a 10% 1M HNO₃-90% methanol mixture, while the light rare earths from Ce to Gd are eluted quantitatively using a 10% 0.05M HNO₃-90% methanol mixture. La, which is retained on the column, is eluted using 0.1M HNO₃. The recoveries of the various rare earth elements have been checked using radiotracers and also by spiking the sample with known amount of elements, and the recoveries are found to be quantitative. Results obtained on a typical high purity lanthanum oxide are reported here.