Concentration-data of elements in liquid fuel oils as obtained by neutron activation analysis

The selection of exciting source both from the point of view of excitation efficiency and elimination of matrix effects using incoherently scattered radiation from the analyzed sample is discussed. Samples of materials from the flotation process of copper ore have been used and copper, iron and lead were the elements sought. For the excitation of fluorescence X-rays, sealed radioisotopic sources of²³⁸Pu,²⁴¹Am,²⁴⁴Cm,¹⁰⁹Cd and a molybdenum X-ray tube were used. For X-ray analysis a Si(Li) spectrometer was applied. The processing of X-ray spectra based on the application of the Gaussian peak representation gives results equivalent to the total peak area method. From the intensities of fluorescence and scattered radiation, the contents of elements were calculated using empirical formulae and the results were compared with those of the Heinrich-Rasberry method. A statistical analysis of the results has been carried out and the criteria of optimal regression formula selection are given.     

Possibilities of ED-XRF with radionuclide sources for analysis of plants

A comparative evaluation of the applicability of different radionuclide sources for the determination of toxic elements in plants by ED-XRF is presented.²³⁸Pu or¹⁰⁹Cd are suggested as most suitable single excitation sources in ED-XRF for monitoring investigations. More elements are determined with a combination of⁵⁵F/¹⁰⁹Cd(²³⁸Pu)/²⁴¹Am. The results obtained by radionuclide ED-XRF analysis of different plants show that the method permits the reliable determination of Br, Ca, Fe, K, Mn, Rb, Sr and Zn in plant bioindicators. For toxic elements like As, Cd, Cu Cr, Hg, Ni, Se and Pb the detection limits of the method are not low enough.     

Determination of ZnSe(Te) stoichiometry and dopant content by X-ray analysis

Summary Light output and response duration of isovalently doped zinc selenide single crystals depend on their element composition as well as on the dopant content and its distribution. For monitoring of these parameters, X-ray analysis suits best of all and was developed here. The ratio of Kα line intensities of Se and Zn was derived for the determination of ZnSe(Te) stoichiometry by taking into account the contribution of secondary excitation. The linear dependence of the TeKα intensity on the Te content was used for determining the latter. An annular ¹⁰⁹Cd source was used for the excitation of Zn and Se Kα-lines and the Kα line of Te was excited by three ²⁴¹Am sources. The measurement error (Sr) of ZnSe elemental composition was 0.01. The measurement error of the Te content was 0.06-0.09 in the range of 0.01-0.5% Te.     

The provenance of archaeological obsidian artifacts from Northern Chile determined by source-induced X-ray fluorescence

A study of provenance of obsidian artifacts from "site 25-Las Estacas", Quebrada de Jorquera (Copiapó, Northern Chile) was carried out by means of X-ray fluorescence, using radioactive sources. Obsidian samples from different Chilean geological regions, located in South Central Chile (Laguna del Maule volcanic area, sources of La Coloradas and La Plata), "Radal Siete Tazas" and the North of Chile (Copiapó Volcano) were analyzed. The analysis was performed using ¹⁰⁹Cd and ²⁴¹Am annular excitation sources and X-ray fluorescence. This allowed the determination of Fe, Cu, Rb, Sr, Y, Zr, and Ba concentrations on samples of ground obsidian from the aforementioned sites. The measured Rb, Sr, and Zr concentrations were used to construct discriminant diagrams, which clearly showed clustering of the samples from the different sources, and the association of the archaeological obsidian sample to the Copiapó Volcano source, which is geographically close to the site.     

Determination of uranium in solutions and sorbents by soft gamma-ray absorptiometry

The determination of uranium in solutions and sorbents by measurement of absorption of soft gamma-rays is described. The use of 22 keV gamma-rays of¹⁰⁹Cd enbled us to improve the sensitivity of the determination for nearly an order of magnitude when compared to the measurements using²⁴¹Am source. The application to the continuous measurement of uranium concentration in pilot-plant streams and of concentration profiles of uranium sorbed on columns of ion exchangers is described.     

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.     

A gamma monitoring technique for estimating plutonium contamination around nuclear weapons facilities

The objectives of this study were to establish a ratio for²⁴¹Am to²³⁹Pu in soil at the Rocky Flats Plant and to compare²⁴¹Am concentrations obtained using in-situ and laboratory gamma spectroscopy measurements to concentrations determined with radiochemical analysis and alpha spectroscopy. Soil samples were collected for radiochemical and laboratory gamma spectroscopy analysis from vertical profiles in 3 cm layers to a depth of 21 cm at predetermined locations along transects oriented in the direction of prevailing winds. The origin for the transects was the center of the 903 Pad at the Rocky Flats Plant, which is believed to be the source for most of the²⁴¹Am and²³⁹Pu contamination. A 100 minute in-situ gamma spectroscopy measurement was made at each soil sample location with a portable HPGe detector. Soil samples were dried, passed through a 2 mm sieve, mixed, and split in two fractions. One fraction was analyzed radiochemically for²⁴¹Am and²³⁹Pu and the second was analyzed using laboratory gamma spectroscopy. The median ratio of²⁴¹Am to²³⁹Pu activities, which appears to be independent of soil depth and distance from suspected sources, was 0.17. There is a strong correlation between²⁴¹Am and²³⁹Pu concentrations determined using radiochemical analysis with alpha spectroscopy and concentrations determined with laboratory gamma spectroscopy. Results from in-situ gamma spectroscopy measurements were also correlated with the radiochemical analyses but exhibited greater variability than laboratory measurements. This on-going investigation has demonstrated that it is possible to indirectly measure²³⁹Pu concentrations in soil if the ratio of²⁴¹Am to²³⁹Pu can be established. The results indicate that judicious use of a combination of radiochemical analyses with laboratory and in-situ gamma spectroscopy measurements may provide a cost-effective approach for characterization of large sites where²⁴¹Am and²³⁹Pu contamination occur.     

Chemical shift and intensity ratio values of dyspersium, holmium and erbium L X-ray emission lines

A systematic study of L X-ray spectrum has been made on the elements Dy, Ho and Er in the pure form elements and compounds to look into the influence of chemical effect. The vacancies were created by 59.54 keV γ-rays from an ²⁴¹Am radioactive source. The L X-ray emission spectra of heavy elements taken with the currently available Si(Li) detectors show four or five distinct peaks. Corrections for sample absorption and spectrometer efficiency were applied to the measured relative intensities. The results show agreement with the theoretical predictions of Scofield (Scofield, 1974a).     

Reverse isotope dilution alpha spectrometry using plutionium-239 spike for determining plutonium concentration in high burn-up fuel samples without purification from americium-241 and a bulk of other impurities

A reverse isotope dilution alpha spectrometric /R-IDAS/ method using²³⁹Pu as a spike is described for the determination of plutonium concentration in high burn-up fuel samples wth²³⁸Pu/(²³⁹Pu+²⁴⁰Pu) alpha activity ratio >0.5, without resorting to any purification from²⁴¹Am and a bulk of other impurities. It involves the addition of a pre-clibrated spike solution to a known aliquot of the plutonium sample solution followed by source preparation using TEG as a spreading agent. The results obtained on a number of plutonium samples containing 20–80% of²⁴¹Am /alpha activity wise/ using this method are compared with those achieved by R-IDAS using purification with TTA, with respect to precision and accuracy. Precision and accuracy of 0.5% are demonstrated. This method eliminates the need of any separation and purification of plutonium from²⁴¹Am and a bulk of other impurities like uranium.     

Sensitivities and detection limits of X-ray fluorescence analysis with a 10 mCi241Am source

Sieben Spurenelemente im Bereich von Chrom bis Barium wurden auf Amberlite IR-120 Kationenaustauschpapier angereichert und durch energiedispersive Röntgenfluorescenzanalyse mit einer 10 mCi²⁴¹Am-Quelle bestimmt. Die Übereinstimmung der experimentell gemessenen mit den theoretisch berechneten Empfindlichkeiten wird geprüft. Die Nachweisgrenzen werden verglichen mit den in typischen Oberflächengewässern vorkommenden und den in Trinkwasser maximal erlaubten Elementkonzentrationen. Die Möglichkeit der Anwendung in der Umweltanalytik wird diskutiert.

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Empfindlichkeiten und Nachweisgrenzen der Röntgenfluorescenzanalyse mit einer 10 mCi²⁴¹Am-Quelle

Summary Seven trace elements ranging from chromium to barium were preconcentrated on Amberlite IR-120 cation exchange paper and determined in an energy dispersive X-ray fluorescence system using a 10 mCi²⁴¹Am source. Sensitivities were experimentally determined and checked with theoretically calculated values. The detection limits are compared with elemental levels present in typical surface waters and those allowed in drinking water. Appropriate conclusions as to feasibility of such a system for environmental monitoring are drawn.

     

Simultaneous liquid scintillation determination of239Pu and241Am in tissue

A liquid scintillation counting method for the simultaneous determination of Pu and Am, with a two-phase cocktail, has been applied to the analysis of a tissue sample from an accidental exposure incident. The sample contained²³⁹Pu,²⁴¹Pu, and²⁴¹Am. In addition to analysis by two liquid scintillation counting techniques, analysis of the sample was performed by -spectroscopy and ZnS scintillation techniques, and the results were compared. The presence of²⁴¹Pu interfered with the liquid scintillation determination of²⁴¹Am when the two-phase cocktail was used, but the results were in agreement sufficient to be useful in determining what course of treatment, if any, might be necessary for the patient.     

Kb/Ka X-ray intensity ratios in calcium and potassium compounds

Summary Kb/Ka X-ray intensity ratios of some K and Ca compounds were studied. The samples were excited with 59.5 keV g-rays emitted from 75 mCi ²⁴¹Am radioisotope source and characteristic K X-ray from the samples were counted by means of an Si(Li) detector which has a resolution 155 eV at 5.9 keV. We found that Kb/Ka X-ray intensity ratios are changed by chemical effect for different K and Ca compounds. The experimental values were compared with the calculated theoretical values for elemental K and Ca.     

Chemical effects on Kβ/Kα X-ray intensity ratios of Mo,Ag, Cd,Ba, La,Ce compounds and total mass attenuation coefficients of Fe and Cu

The Kβ/Kα intensity ratios for pure Mo, Ag, Cd, Ba, La and Ce elements and for some of their compounds were investigated. The vacancies in the K shell were created by 59.5-keV γ-rays from a heavily filtered ²⁴¹Am radioactive source. K X-rays were measured using a Si(Li) detector with a resolution of 155 eV at 5.9 keV. We observed chemical effects on Kβ/Kα intensity ratios of Mo, Ag, Cd, Ba, La and Ce compounds. Detailed interpretation of data obtained from X-ray transmission measurements usually depends on the assumption that the contribution of each element is additive. This assumption yields the mixture rule for X-ray attenuation coefficients which is valid if molecular and chemical effects are negligible. We measured the total mass attenuation coefficients of Fe and Cu in various compounds. Self-absorption corrections were carried out on data for ligands in the different compounds. Our values were compared with the theoretical values for pure elements.     

Determination of 241Am in Environmental Samples: A Review

The determination of ²⁴¹Am in the environment is of importance in monitoring its release and assessing its environmental impact and radiological risk. This paper aims to give an overview about the recent developments and the state-of-art analytical methods for ²⁴¹Am determination in environmental samples. Thorough discussions are given in this paper covering a wide range of aspects, including sample pre-treatment and pre-concentration methods, chemical separation techniques, source preparation, radiometric and mass spectrometric measurement techniques, speciation analyses, and tracer applications. The paper focuses on some hyphenated separation methods based on different chromatographic resins, which have been developed to achieve high analytical efficiency and sample throughput for the determination of ²⁴¹Am. The performances of different radiometric and mass spectrometric measurement techniques for ²⁴¹Am are evaluated and compared. Tracer applications of ²⁴¹Am in the environment, including speciation analyses of ²⁴¹Am, and applications in nuclear forensics are also discussed.     

The Formation of Analytical and Background Signals in Radioisotope X-ray Fluorescence Analysis Using a 241Am Radioactive Source and a Si(Li) Detector

Reasons for the appearance of a background signal in the relatively soft x-ray range (2–15 keV) upon fluorescence excitation with the ²⁴¹Am radioisotope are discussed. Mathematical models are proposed for the interaction of the radiation of the radioactive source with the sample and the Si(Li) detector, capable of describing the appearance of the analytical and background signals. It was shown that processes occurring in the Si(Li) detector should be taken into account to explain and calculate the background signal in this range. The results of calculations agree well with the experimental data obtained using an ²⁴¹Am radiation source for fluorescence excitation.     

Trace elements in PM2.5 in Gothenburg,Sweden

Ambient aerosol particles smaller than 2.5 µm (PM_2.5) are getting more and more attention worldwide. While legal focus is mainly on sample mass, the composition of the particles is an important research field gaining increased interest. The interest is not only connected to possible health effects of the elemental content of the particles, but the elemental determination can also add valuable information for source apportionment. Samples were collected during 20 days in November 2007 at the campus of the Chemistry Department, University of Gothenburg, Gothenburg, Sweden. The particles were collected using a cyclone that separates the PM_2.5 particles from the air stream and impacts them on polycarbonate filters. Filters were changed at early afternoon. The samples were analyzed for particulate mass, black carbon (BC) and the elements S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, As, Br, Cd and Pb. Several of the elements were above detection limit in only a few of the samples. Total reflection X-ray fluorescence (TXRF) spectrometer based on the Wobi TXRF module supplied by the International Atom Energy Agency (IAEA) has been used for the determination of most trace elements in the samples. A Graphite Furnace Atomic Absorption Spectrometer (GF-AAS) was used for complementary trace element analysis and a reflectometer was used to analyze black carbon. Before elemental analysis the filters were digested using a microwave digestion system with temperature and pressure control. The results showed a large variation in sample mass, BC and analyzed elemental concentrations. The variation of the different constituents did not show the same pattern. This added to the picture of different sources for different pollutants. The highest S concentration was noted on a day when the air masses were determined to come from the southeast, i.e. Poland and some other Eastern European countries. From the results it can be concluded that more work is needed on the TXRF spectrometer to optimize it for determination of the EU legally regulated elements As, Ni, Pb and Cd. Despite this the study shows that there is no problem in meeting the AAQS limits for Cd and Pb in Gothenburg.     

Determination of <Superscript>241</Superscript>Am/<Superscript>243</Superscript>Am ratios

Determination of ²⁴¹Am/²⁴³Am ratios is required for vanous purposes including assay of Am by isotope dilution techniques. Alpha-spectrometry on electrodeposited sources is a preferred technique for this determination. However, there is an inherent problem of tail contribution which necessitates the use of suitable algorithms to account for the same. Recently, in the frame of a Coordinated Research Program (CRP) of the International Atomic Energy Agency (IAEA), WinALPHA software has been developed which is a combination of an asymmetrical Gaussian for the main part of the peak and a low energy function. Therefore, it was of interest to compare the use of this algorithm with the routinely used method, in our laboratory, based on geometric progression (G. P.) decrease. Since, there are no reference materials available commercially for ²⁴¹Am/²⁴³Am ratios, synthetic mixtures covening a wide range (0.3 to 2.0) of ²⁴¹Am/²⁴³Am α-activity ratios were used and un-ignited electrodeposited sources were prepared for α-spectrometry. The α-spectra obtained using PIPS detector, were evaluated using the two algonthms The ²⁴¹Am/²⁴³Am α-activity ratios obtained were also compared with those determined by thermal ionization mass spectrometry (TIMS). An agreement of about 1% was obtained in the ²⁴¹Am/²⁴³Am ratios determined by the two methods and also by using the two algorithms for α-spectrum evaluation.     

Determination of rare earth elements by radioisotope induced X-ray emission spectroscopy

A ring-shaped, 10⁹ Bq²⁴¹Am radioisotope source was used for the excitation of K-shell X-rays from rare earth elements (56<Z<64), present in powdered geological material. In order to improve the efficiency of the measurement of these elements in the concentration range down to 10 ppm, the optimum geometry of the system was found. The results obtained are presented and discussed.     

Performance of CdTe detector in the 13–1333 keV energy range

The photopeak efficiency, peak to valley ratio and energy resolution of a 3×3×1 mm³ CdTe detector were determined experimentally for 13–1333 keV photon energy by using polyester coated radioisotopes ²⁴¹Am, ²²Na, ⁵⁴Mn, ⁵⁷Co, ⁶⁰Co, ¹⁰⁹Cd, ¹³⁷Cs and ¹³³Ba. The data were analyzed by using PX4 from Amptek. The experimental values were fitted to an analytical function of photon energy, and an agreement was observed for the entire range of the studied energies. The results have shown that the CdTe detector has a high performance due to both the improved charge collection efficiency comparable with that of SI GaAs detectors (Vittone et al., 1999), and the low leakage current. Also, CdTe detector is very attractive for field application as it works at room temperature.     

Measurement of K β /K α intensity ratios for elements in the range 51 ≤ Z ≤ 67 at 59.54 keV

K-shell X-ray intensity ratios for some elements Sb, Cs, La, Ce, Pr, Nd, Sm, Gd, Dy and Ho have been measured experimentally. The elements were excited by 59.5 keV γ-ray from 100 mCi ²⁴¹Am radioactive source. The characteristic K X-rays emitted by samples were detected by using a hyper pure germanium detector. The experimental results were compared with theoretical predictions reported by several authors.