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.     

Alpha spectrum evaluation method for the simultaneous determination of plutonium,americium and curium

A method based on the geometric progression decrease of the counts in the far tail of the alpha spectrum is described for the simultaneous determination of plutonium, americium and curium by alpha spectrometry. For evaluating the precision and accuracy, synthetic mixtures were prepared from solutions of enriched isotopes and sources were prepared by direct evaporation method using tetraethylene glycol /TEG/ as a spreading agent and electropolished stainless steel discs as the backing material. Precision and accuracy of about 1% is demonstrated in the determination of²⁴⁴Cm/²³⁹Pu,²⁴¹Am/²³⁹Pu,²⁴⁴Cm/²³³U,²⁴¹Am/²³³U and²³⁹Pu/²³³U alpha activity ratios using a 450 mm² silicon surface barrier detector.     

Precision and accuracy in the determination of plutionium-239 /uranium-233, americium-241/ uranium-233 and curium-244 /uranium-233 alpha activity ratios by alpha spectrometry

Determination of²³⁹Pu/²³³U,²⁴¹Am/²³³U and²⁴⁴Cm/²³³U alpha activity ratios is required when using²³³U as a tracer for the determination of plutonium, americium and curium by alpha spectrometry. Precision and accuracy in the determination of these alpha activity ratios was evaluated by preparing synthetic mixtures from solutions of enriched isotopes of²³⁹Pu,²⁴¹Am,²⁴⁴Cm and²³³U. Separate synthetic mixtures were prepared for each of the three alpha activity ratios. The sources from the synthetic mixtures were prepared by direct evaporation method using tetra ethylene glycol /TEG/ as a spreading agent, alpha spectra were recorded by employing solid state silicon surface barrier detectors coupled to a 4 K analyzer and the alpha spectra were evaluated by a method based on the geometric progression decrease for the far tail of the spectrum. Large area detector /i.e. 450 mm²/ was observed to reduce the effect of nonhomogeneous distribution, if any, of the two elements present in the source. Precision and accuracy of about 1% is demonstrated for the determination of²³⁹Pu/²³³U,²⁴¹Am/²³³U and²⁴⁴Cm/²³³U alpha activity ratios using large area silicon surface barrier detector.     

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.     

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.     

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.     

Non-destructive determination of spontaneously fissioning nuclides by neutron coincidence counting using multichannel time spectroscopy

A non-destructive method for determining the amount of actinoids has been developed. The method is based on thermal neutron coincidence counting and employs a selective detection of neutrons resulting from the spontaneous fission of actinoids. The detection system is described in detail and the measurement results of²⁴⁴Cm as an example are presented. The results show that the measured fission rate of²⁴⁴Cm is consistent with the fission rate calculated from ENDF/B-V data and that the amount of²⁴⁴Cm can be determined within about 5% accuracy even in the presence of a large amount of actinoids, for example, up to 2.6·10⁶, 3.6·10⁴, or 1.6·10³ times in the mass ratio of²³⁹Pu,²⁴¹Am, or²⁴⁰Pu to²⁴⁴Cm, respectively.     

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.     

Separation and recovery of Cm from Cm–Pu mixed oxide samples containing Am impurity

Curium was separated and recovered as an oxalate from a Cm–Pu mixed oxide which had been a ²⁴⁴Cm oxide sample prepared more than 40 years ago and the ratio of ²⁴⁴Cm to ²⁴⁰Pu was estimated to 0.2:0.8. Radiochemical analyses of the solution prepared by dissolving the Cm–Pu mixed oxide in nitric acid revealed that the oxide contained about 1 at% of ²⁴³Am impurity. To obtain high purity curium solution, plutonium and americium were removed from the solution by an anion exchange method and by chromatographic separation using tertiary pyridine resin embedded in silica beads with nitric acid/methanol mixed solution, respectively. Curium oxalate, a precursor compound of curium oxide, was prepared from the purified curium solution. 11.9 mg of Cm oxalate having some amounts of impurities, which are ²⁴³Am (5.4 at%) and ²⁴⁰Pu (0.3 at%) was obtained without Am removal procedure. Meanwhile, 12.0 mg of Cm oxalate (99.8 at% over actinides) was obtained with the procedure including Am removals. Both of the obtained Cm oxalate sample were supplied for the syntheses and measurements of the thermochemical properties of curium compounds.     

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     

Development of a complex method for the determination of actinoides

A combined radiochemical separation method has been developed that enables the simultaneous determination of ²³⁴U, ²³⁵U, ²³⁸U, ²³⁷Np, ^239,240Pu, ²³⁸Pu, ²⁴¹Am, ²⁴²Cm, and ²⁴⁴Cm in medium and low level liquid radioactive wastes. The main steps of the method are sample destruction, co-precipitation on iron(II)-hydroxide and calcium-oxalate, separation by extraction chromatography using supported dipentyl-pentyl phosphonate (UTEVA) and supported N,N-octylphenyl-di-i-butylcarbamoylmethyl phosphine oxide with tributyl phosphate (TRU), and α source preparation. The key parameter of the method is the adjustment of the oxidation states of the actinoides before adding the sample onto the UTEVA column. It has been determined that (NH₄)₂S₂O₈ can be used for oxidation state adjustment resulting sufficient chemical yields.     

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.     

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.     

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.     

Preparation of actinide targets for the synthesis of the heaviest elements

The heaviest elements are synthesized in heavy-ion induced hot fusion reactions with various actinide targets. Because the actinide material is often available only in very limited amounts, a deposition method with high yields (~90 %) is needed. We report on the production of ²⁴⁴Pu, ²⁴³Am, ²⁴⁸Cm, ²⁴⁹Bk, and ²⁴⁹Cf targets on thin Ti backings by molecular plating. Different chemical purification steps using ion chromatographic techniques were applied for the purification of ²⁴⁹Cf and ²⁴⁴Pu. The deposition procedure applied for the production of ~0.4–0.8 mg/cm² thick targets is described. The deposition yield was determined either by α-particle or γ-ray spectroscopy. Furthermore, neutron activation analysis has been applied in the case of ²⁴⁴Pu, ²⁴³Am, and ²⁴⁸Cm. Information about the spatial distribution and homogeneity of the target layer was obtained by radiographic imaging.     

Determination of femtogram quantities of 239Pu and 240Pu in bioassay samples by thermal ionization mass spectrometry

Summary A thermal ionization mass spectrometry (TIMS) method is described for the determination of ultra-trace levels of plutonium isotopes in human urine samples. The method has been validated through the analysis of artificial urine samples spiked with known amounts of ²³⁹Pu ranging from 2.5 fg to 50 fg (6-115mBq). A slight positive bias of 1.7%-2.7% was determined, with a relative precision of 2.2% at 50 fg, increasing to 2.7% for 5-25 fg ²³⁹Pu. The detection limit of the method was 0.53 fg (1.2mBq) ²³⁹Pu, and the instrumental detection limit was at least 0.1 fg. The determination of the isotopic signature of the sample with ²³⁹Pu, ²⁴⁰Pu, and ²⁴¹Pu amounts of several femtograms is possible, and was demonstrated with the determination of the 240 to 239 ratio in an inter-laboratory sample comparison. The method is relatively free from interferences, 95% of sample preparations were acceptable both in terms of chemical recovery and lack of isobaric interference. The isotopic abundance of the ²⁴²Pu SRM 4334E of the National Institute of Standards and Technology (NIST) was also determined by TIMS and was found to be 99.99967 atom% ²⁴²Pu.     

Determination of plutonium,americium and curium in environmental meterials

A sequential radiochemical scheme for the separation of Pu and Am (along with Cm) from environmental materials is given. Optimum conditions for coprecipitation of these elements on bismuth phosphate and the influence of Fe and Th content of the sample on the recovery of Am were studied. Internal tracers²⁴²Pu and²⁴³Am were used as tracers for Pu and Am, respectively, and estimates were made by alpha-spectrometry. Average recoveries obtained from sea water were 85% and 77% for Pu and Am, respectively. Lower recoveries (<50%) were obtained for Am in sediments. Work carried out as part of the International Atomic Energy Agency Research Contract 1954/RB/RI.     

Gamma-rays emitted in the alpha-decay of <Superscript>245</Superscript>Cm

It has been observed that the intensities of the gamma-rays emitted in the alpha-decay of ²⁴⁵Cm reported in the literature result in calculated concentrations that do not agree with those obtained via other methods. In this work, a ²⁴⁵Cm sample was chemically isolated from a sample of ²⁴⁹Cf, and the gamma-ray intensities were measured relative to the alpha-particle emission rate of the resulting source; there is a systematic bias relative to the literature intensities of approximately 8%. In addition, gamma-rays that have never before been observed in the decay of ²⁴⁵Cm are placed in the level scheme of the decay product, ²⁴¹Pu.     

Determination of fission-products and actinides in the Black Sea following the Cherynobyl accident

Radiochemical procedures are discussed for the isolation and determination of a suite of radionuclides in samples from the Black Sea following their input from the Chernobyl reactor accident. The samples analyzed include discrete water samples and both suspended and dissolved phases collected by in-situ chemisorption techniques. The radiochemical scheme permits the separation and analysis of¹³⁴Cs,¹³⁷Cs,⁹⁰Sr,¹⁴⁴Ce,¹⁴⁷Pm,¹⁰⁶Ru,²³⁹Pu,²⁴⁰Pu, and in some instances²⁴²Cm,²³⁸Pu, and²⁴¹Am. The detection techniques employed include various instrumental gamma spectrometric methods, low-level beta counting, alpha spectrometry, and mass spectrometry.The method's developments are described and data are presented on some representative samples from the Black Sea. The sensitivity of the analysis for the various nuclides and sample types is summarized and questions of radiochemical interferences are addressed.