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.     

Determination of Am and Cm in spent nuclear fuels by isotope dilution inductively coupled plasma mass spectrometry and isotope dilution thermal ionization mass spectrometry after separation by high-performance liquid chromatography

Elemental and isotopic determination of americium and curium in spent nuclear fuels is necessary to validate neutronic calculation codes and for nuclear waste disposal purposes. Prior to mass spectrometric analysis, it is mandatory to perform separations in order to eliminate isobaric interferences between U, Pu, Am and Cm. In the spent fuels samples analyzed, a separation of U and Pu has been first realized with an anion-exchange resin. Then a rapid Am/Cm separation has been developed by high-performance liquid chromatography (HPLC) with an on-line detection using the Am and Cm α-emission. The influence of the different parameters on the chromatographic separation are described and discussed. Inductively coupled plasma mass spectrometry (ICP-MS) and thermal-ionization mass spectrometry (TIMS) have been used to measure the isotopic composition of U, Am and Cm and to determine the ²⁴¹Am/²³⁸U and ²⁴⁴Cm/²³⁸U ratios with the double spike isotope dilution method. The measurement procedures and the accuracy and precision of the results obtained with a quadrupole ICP-MS on different spent fuels samples are discussed and compared with those obtained by TIMS, used as a reference technique. Received: 30 November 1998 / Revised: 8 January 1999 / Accepted: 12 January 1999     

Determination of Am and Cm in spent nuclear fuels by isotope dilution inductively coupled plasma mass spectrometry and isotope dilution thermal ionization mass spectrometry after separation by high-performance liquid chromatography

Elemental and isotopic determination of americium and curium in spent nuclear fuels is necessary to validate neutronic calculation codes and for nuclear waste disposal purposes. Prior to mass spectrometric analysis, it is mandatory to perform separations in order to eliminate isobaric interferences between U, Pu, Am and Cm. In the spent fuels samples analyzed, a separation of U and Pu has been first realized with an anion-exchange resin. Then a rapid Am/Cm separation has been developed by high-performance liquid chromatography (HPLC) with an on-line detection using the Am and Cm α-emission. The influence of the different parameters on the chromatographic separation are described and discussed. Inductively coupled plasma mass spectrometry (ICP-MS) and thermal-ionization mass spectrometry (TIMS) have been used to measure the isotopic composition of U, Am and Cm and to determine the ²⁴¹Am/²³⁸U and ²⁴⁴Cm/²³⁸U ratios with the double spike isotope dilution method. The measurement procedures and the accuracy and precision of the results obtained with a quadrupole ICP-MS on different spent fuels samples are discussed and compared with those obtained by TIMS, used as a reference technique. Received: 30 November 1998 / Revised: 8 January 1999 / Accepted: 12 January 1999     

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 actinides in urine by inductively coupled plasma mass spectrometry and alpha spectrometry: A hybrid approach

A new rapid separation method that allows separation and preconcentration of actinides in urine samples was developed for the measurement of longer lived actinides by inductively coupled plasma mass spectrometry (ICP-MS) and short-lived actinides by alpha spectrometry; a hybrid approach. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration, if required, is performed using a streamlined calcium phosphate precipitation. Similar technology has been applied to separate actinides prior to measurement by alpha spectrometry, but this new method has been developed with elution reagents now compatible with ICP-MS as well. Purified solutions are split between ICP-MS and alpha spectrometry so that long- and short-lived actinide isotopes can be measured successfully. The method allows for simultaneous extraction of 24 samples (including QC samples) in less than 3 h. Simultaneous sample preparation can offer significant time savings over sequential sample preparation. For example, sequential sample preparation of 24 samples taking just 15 min each requires 6 h to complete. The simplicity and speed of this new method makes it attractive for radiological emergency response. If preconcentration is applied, the method is applicable to larger sample aliquots for occupational exposures as well. The chemical recoveries are typically greater than 90%, in contrast to other reported methods using flow injection separation techniques for urine samples where plutonium yields were 70-80%. This method allows measurement of both long-lived and short-lived actinide isotopes. ²³⁹Pu, ²⁴²Pu, ²³⁷Np, ²⁴³Am, ²³⁴U, ²³⁵U and ²³⁸U were measured by ICP-MS, while ²³⁶Pu, ²³⁸Pu, ²³⁹Pu, ²⁴¹Am, ²⁴³Am and ²⁴⁴Cm were measured by alpha spectrometry. The method can also be adapted so that the separation of uranium isotopes for assay is not required, if uranium assay by direct dilution of the urine sample is preferred instead. Multiple vacuum box locations may be set-up to supply several ICP-MS units with purified sample fractions such that a high sample throughput may be achieved, while still allowing for rapid measurement of short-lived actinides by alpha spectrometry.     

Analysis of radioactive metal ions in environmental and liquid effluent samples

This paper describes the development and validation of analytical procedures for the separation and determination of⁹⁰Sr,⁹⁰Y,²³⁸Pu,^239/240Pu,²⁴¹Am,²⁴¹Cm and^243/244Cm in liquid effluents and environmental samples. The procedures use supported reagents for extraction chromatography (reversed phase partition chromatography) that enable the separation of the analytes from a large number of other radionuclides present.     

Age determination of plutonium using inductively coupled plasma mass spectrometry

The age of plutonium is defined as the time since the last separation of the plutonium isotopes from their daughter nuclides. In this paper, a method for age determination based on analysis of ²⁴¹Pu/²⁴¹Am and ²⁴⁰Pu/²³⁶Pu using ICP-SFMS is described. Separation of Pu and Am was performed using a solid phase extraction procedure including UTEVA, TEVA, TRU and Ln-resins. The procedure provided separation factors adequate for this purpose. Age determinations were performed on two plutonium reference solutions from the Institute for Reference Materials and Measurements, IRMM081 (²³⁹Pu) and IRMM083 (²⁴⁰Pu), on sediment from the Marshall Islands (reference material IAEA367) and on soil from the Trinity test site (Trinitite). The measured ages based on the ²⁴¹Am/²⁴¹Pu ratio corresponded well with the time since the last parent-daughter separations of all the materials. The ages derived from the ²³⁶U/²⁴⁰Pu ratio were in agreement for the IRMM materials, but for IAEA367 the determination of ²³⁶U was interfered by tailing from ²³⁸U, and for Trinitite the determined age was biased due to formation of ²³⁶U in the detonation of the “Gadget”.     

Determination of <Superscript>238</Superscript>Pu in plutonium bearing fuels by thermal ionization mass spectrometry

Determination of ²³⁸Pu in plutonium bearing fuels is required as a part of the chemical quality assurance of nuclear fuels. In addition, the determination of ²³⁸Pu is required in nuclear technology for many other applications, e.g., for developing isotope correlations and while using ²³⁸Pu as a spike (tracer) in isotope dilution α-spectrometry (IDAS). This determination usually involves the use of α-spectrometry on purified Pu sample. In view of the random errors associated with the counting statistics and the systematic errors due to (1) in-growth of ²⁴¹Am in purified Pu sample and (2) tail contribution correction methodology in α-spectrometry, the precision and accuracy obtainable by α-spectrometry are limited. Thermal ionization mass spectrometry (TIMS) is generally used for the determination of different Pu isotopes other than ²³⁸Pu. This is due to the ubiquitous isobaric interference from ²³⁸U at ²³⁸Pu in TIMS. Recently, we have carried out studies on the formation of atomic and oxide ions of U and Pu by TIMS and developed a novel approach using interfering element correction methodology to account for the isobaric interference of ²³⁸U at ²³⁸Pu in TIMS. This methodology is based on the addition of ²³⁵U (enrichment >90 atom%) to Pu sample followed by the determination of ²³⁸U/²³⁵U atom ratio using UO⁺ ion and determination of Pu isotope ratios using Pu⁺ ion, from the same filament loading. The TIMS methodology was used for the determination of ²³⁸Pu in different Pu samples in U based nuclear fuels from PHWRs with ²³⁸Pu content about 0.2 atom%. The ²³⁸Pu determination was also carried out using α-spectrometry. This paper reports the results obtained by the two methods and presents the ments and shortcomings of the two approaches.     

Simultaneous electrodeposition of actinides

A new system for simultaneous electrodeposition of U, Np, Pu, Am and Cm has been developed. The system consists of (NH₄)₂C₂O₄–H₂SO₄–HCl. The effects on recovery of pH, current density, interfering ions and the amount of added HCl have been studied. The optimum condition for simultaneous electrodeposition of actinides has been recommended. Under the recommended condition recoveries of U, Np, Pu, Am and Cm have been obtained by using²³²U,²³⁷Np,²⁴¹Am,²⁴²Pu and²⁴⁴Cm. The counting sources prepared are uniform, adherent and suitable for -spectrometry.     

Simultaneous determination of uranium and plutonium isotopes in soils by means of single alpha-spectrometry

A simple, rapid and reliable method was developed for the simultaneous determination of uranium and plutonium isotopes by alpha-spectrometry using a single source. A new uranium tracer²³⁰U was applied as well as the²³⁶Pu tracer to determine overall yields of uranium and plutonium isotopes throughout the entire procedure employed. The analytical procedure consists of sample leaching with 8N HNO₃ solution, purification by solvent extraction, simultaneous electrodeposition of U and Pu, and subsequent alpha-spectrometry with a silicon detector. In the solvent extraction using TOA/xylene from 8N HNO₃ solution, the preferential extractability of Pu rather than U permits to purify simultaneously the trace amounts of Pu and the macro amounts of U, as in the case of ordinary soil samples, resulting in favourable peak heights for both isotopes. From a single alpha-spectrum, the determinations of²³⁸U,²³⁴U (and their ratio of²³⁴U/²³⁸U),^239+240Pu, and²³⁸Pu contents were conveniently carried out after correcting the overall yields obtained from²³⁰U and²³⁶Pu activities in the same spectrum. This analytical method was satisfactorily applied to the determination of U and Pu isotope contents in some soils.     

Sequential determination of Am, Cm, Pu, Np and U by extraction chromatography

Environmental contamination by artificial radionuclides and the evaluation of their sources require precise isotopic analysis and accurate determination of actinide elements above all plutonium and americium. These can be achieved by alpha spectrometry or by inductively coupled plasma mass spectrometry (ICP-MS) after chemical separation. In the present work, a simple, rapid method has been developed for the sequential separation of actinide elements from aqueous solutions and their determination by alpha spectrometry. Extraction chromatography was applied to the separation of ²⁴¹Am, ²⁴⁴Cm, ^{239 + 240,238}Pu, ²³⁷Np and ^238,235,234U using microporous polyethylene supporting tri-n-octylamine as the stationary phase and hydrochloric acid with and without reducing agents as the mobile phase. Actinide in 9 M HCl solution is introduced into the anion exchange column; Pu (IV), Np (IV) and U(VI) are retained on the column while Am (III) and Cm passed through. Pu is eluted first, reductively, after which, Np and then U are eluted. The method can be applied to all aqueous solutions which do not contain strong complexing or precipitation agents for the elements considered.     

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.     

Radiolysis and corrosion of238Pu-doped UO2 pellets in chloride brine

Deaerated 5 M NaCl solution is irradiated in the presence of UO₂ pellets with α-radiation from²³⁸Pu. Experiments are conducted with²³⁸Pu doped pellets and others with²³⁸Pu dissolved in the brine. The radiolysis products and yields of mobilized U and Pu from the oxidative dissolution of UO₂ are determined. Results found for radiolysis products and for the oxidation/dissolution of pellets immersed in Pu containing brine are similar to results for Pu doped pellets, where the radiation chemical processes occur only in the liquid layer of some 10 σm thickness adjacent to the pellet. The yield of radiolysis products is comparable to earlier results, that of mobilized U from the pellets is < 1% of the total amount of oxidized species. Thus, the radiation chemical yield (G-value) for mobilized hexavalent U is < 0.01 ions/100 eV. In spite of the low radiation yield for the corrosion, the rate of UO₂dissolution is higher than expected for the concentrations of long-lived oxidizing radiolysis compounds found in the solutions.     

Determination of plutonium,americium and curium in airborne effluents of nuclear power plants

A radiochemical method has been developed for the determination of²³⁸Pu,^{239, 240}Pu,²⁴¹Am,²⁴²Cm and²⁴⁴Cm in airborne effluents of nuclear power plants. The method involves conversion of transuranium elements to acid-soluble forms, dissolution, purification, electrodeposition and alpha spectrometric determination. Final recovery ranged from 69.0 to 75.4% for plutonium and from 26.8 to 68.3% for americium and curium.     

Large volume preconcentration and purification for determining the240Pu/<Superscript>239</Superscript>Pu isotopic ratio and <Superscript>238</Superscript>Pu/<Superscript>239+240</Superscript>Pu alpha-activity ratio in seawater

Summary The present paper describes a new analytical method for determining the ²⁴⁰Pu/²³⁹Pu isotopic ratio and ²³⁸Pu/^239+240Pu α -activity ratio in seawater, both of which are important parameters for determining Pu sources in the ocean. Plutonium isotopes were preconcentrated from a large volume of seawater (4700-10800 liter) by solid phase extraction using MnO₂-impregnated fibers and eluted into 3M HCl. After the elution, the Pu species of all oxidation states were converted to Pu(IV) using NaNO₂, purified by solvent extraction using thenoyltrifluoroacetone (TTA)-benzene, and concentrated in 5 ml of 0.2M HNO₂. The ²⁴⁰Pu/²³⁹Pu and ²³⁸Pu/^239+240Pu ratios in the 5-ml final solution were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and α-spectrometry, respectively. A pg level of Pu, which was a sufficiently large amount for the determination, was obtained by the solid phase extraction. Through the redox conversion and solvent extraction, the Pu species, such as Pu(III), Pu(IV) and Pu(VI), were collected at a high recovery of 96±2% (n=3) despite the presence of large amounts of Mn, and interfering ²³⁸U (3.3 μg^. l^-1in seawater) was effectively removed with a decontamination factor of 1.7·10⁷. The accuracy of the method for the ²⁴⁰Pu/²³⁹Pu ratio was verified using reference materials of seawater and a terrestrial soil sample. The present technique was applied to the determination of the ²⁴⁰Pu/²³⁹Pu and ²³⁸Pu/^239+240Pu ratios in coastal and oceanic water.     

Measurements of actinide nuclides in water samples from the primary circuit of a nuclear power plant

Weekly, consecutive primary coolant samples from a boiling water reactor have been analyzed for^{239, 240}Pu,²³⁸Pu+²⁴¹Am,²⁴²Cm and²⁴⁴Cm for about two years, and for²³⁸Pu,²⁴¹Pu and²⁴¹Am for one year. Concentration ranges are reported. Samples were prepared for counting either directly by evaporation or by chemical separation on BioRad AG 1×4 resin and subsequent electrolysis, and were counted in 20 cm dia Frish grid ionization chambers. Procedures are described. For most actinide nuclides, activity ratios in primary coolant were found to be different from those in worldwide fallout, thus allowing an identification of origin in the case, that actinides should be detected in the vicinity of a nuclear power station.     

238U, 234U and 226Ra concentrations in mineral waters and their contribution to the annual committed effective dose in Turkey

Activity concentrations of ²³⁴U, ²³⁸U and ²²⁶Ra in mineral waters were determined on the basis of nine water bottling facilities using alpha particle spectrometry. The mineral water samples were collected from three geographic regions of Turkey. The radiochemical separation used in the uranium analysis is based on the isolation of uranium radioisotopes from other radionuclides such as Th, Am, Pu and Np using UTEVA resin. Alpha sources were prepared using electrodeposition method. The activity concentration of ²²⁶Ra was determined after deposition on a membrane using BaSO₄ co-precipitation method. The activity concentrations (mBq L^?1) of ²²⁶Ra, ²³⁸U and ²³⁴U ranged from <0.56 to 165, from <0.42 to 439 and from <0.42 to 464, respectively. The measured activity concentrations were used for the calculation of the average total annual effective ingestion doses for children and adults. The committed effective doses were calculated for three different scenarios according to mineral water consumption rate. In the most extreme scenario (for age group 12–17), all water samples except MW1 and MW2 cause annual committed effective doses below the reference level (0.1 mSv year^?1) recommended by World Health Organization (WHO).     

Determination of Pu in environmental soil using238Pu as a yield tracer

A procedure for determining Pu in environmental soil using²³⁸Pu as a yield tracer is described. The method involves radiochemical separation and electrodeposition onto a stainless steel disc followed by alpha-spectrometric measurement with a solid-state detector. In order to eliminate error in calculation caused by²³⁸Pu contained in original samples, a new calculating method is introduced in this paper. By using this method, the activity of²³⁸Pu contained in original samples can be substracted from the total activity of samples, to which the²³⁸Pu tracer is added. This procedure has been applied satisfactorily to the determination of Pu in a soil reference sample, which was supplied by the Institute of Metrological Science of China.     

Sequential separation of transuranic elements and fission products from uranium metal ingots in electrolytic reduction process of spent PWR fuels

A sequential separation procedure has been developed for the determination of transuranic elements and fission products in uranium metal ingot samples from an electrolytic reduction process for a metallization of uranium dioxide to uranium metal in a medium of LiCl-Li₂O molten salt at 650 °C. Pu, Np and U were separated using anion-exchange and tri-n-butylphosphate (TBP) extraction chromatography. Cs, Sr, Ba, Ce, Pr, Nd, Sm, Eu, Gd, Zr and Mo were separated in several groups from Am and Cm using TBP and di(2-ethylhexyl)phosphoric acid (HDEHP) extraction chromatography. Effect of Fe, Ni, Cr and Mg, which were corrosion products formed through the process, on the separation of the analytes was investigated in detail. The validity of the separation procedure was evaluated by measuring the recovery of the stable metals and ²³⁹Pu, ²³⁷Np, ²⁴¹Am and ²⁴⁴Cm added to a synthetic uranium metal ingot dissolved solution.     

Radiochemical determination of the yields of transuranium nuclides produced from natural uranium irradiated in a reactor

Transuranium nuclides were produced by irradiating a pellet of natural uranium sulfide in the Japan Material Testing Reactor (JMTR). After irradiation, a successive separation of uranium, plutonium, americium and curium was carried out. The fractional concentrations of the nuclides²³⁸Pu,²³⁹Pu,²⁴⁰Pu,²⁴¹Am,²⁴³Am,²⁴²Cm and²⁴⁴Cm were determined by α-ray spectrometry, and those of²⁴¹Pu and^242mAm were estimated from the build-up of α-emitting daughters,²⁴¹Am and²⁴²Cm, respectively. As the yield of²⁴²Pu was too slight to be detected by α-counting, the neutron activation analysis of the plutonium fraction based on the²⁴²Pu(n, γ)²⁴³Pu reaction was carried out by γ-ray spectrometry, and it was shown that a few pg of²⁴²Pu could be determined. A burn-up of²³⁵U was also estimated by neutron activation analysis. The experimental results are compared with the calculated ones.