Showing papers in "Journal of Radioanalytical and Nuclear Chemistry in 1982"

Teabags: Computer programs for instrumental neutron activation analysis

Abstract: Described is a series of INAA data reduction programs collectively known as TEABAGS (Trace Element Analysis By Automated Gamma-ray Spectrometry). The programs are written in FORTRAN and run on a Nuclear Data ND-6620 computer system, but should be adaptable to any medium-sized minicomputer. They are designed to monitor the status of all spectra obtained from samples and comparison standards irradiated together and to do all pending calculations without operator intervention. Major emphasis is placed on finding all peaks in the spectrum, properly identifying all nuclides present and all contributors to each peak, determining accurate estimates of the background continua under peaks, and producing realistic uncertainties on peak areas and final abundances.

Real-time correction of counting losses in nuclear pulse spectroscopy

Abstract: Reviewing the current status of real-time correction of counting losses in nuclear pulse spectroscopy, the pileup problem is identified as the last question not resolved satisfactorily up to now. Correction of pileup losses in provided, at least in principle, by the classical pulse generator method, however, severe limitations in test frequency prohibit its application to real-time correction of counting losses. A solution is offered by the novel principle of the virtual pulse generator which obviates the shortcomings of the classical method simply by not introducing pulses into the spectroscopy system. Instead, the probability for pileup-free pulse processing is determined by suitable tests of the system status at arbitrarily high test frequencies. After a discussion of the principles of the new method and its application to a real-time correction system experimental evidence is provided for the complete correction of counting losses of more than 98% under conditions of stationary as well as variable counting rates up to the limit of stable operation of the underlying spectroscopy system which is 800 000 c/s for an experimental high-rate gamma spectrometer.

An anion exchange method for the determination of241Am and plutonium in environmental and biological samples

Abstract: An accurate and reliable method has been developed for the sequential determination of241Am and plutonium in miscellaneous environmental and biological samples. In the course of the analysis,244Cm and236Pu tracers were used for the determination of chemical recoveries. After suitable pretreatment procedures, plutonium and americium were separated by means of anion exchange and the separate nuclides were electroplated onto stainless steel discs and determined by alpha sepectrometry. The final recovery ranged from 70.7 to 99.4% for plutonium and from 75.4 to 91.9% for americium and curium with 50 g of soil samples. No interference of210Po was detected.

Application of neutron activation analysis to the study of element concentration and exchange in fossil bones

Abstract: It has long been known that a variety of elements are introduced into voids in the structure of bone during fossilization. Visual examination of the cross-section of many bones in the early stages of fossilization reveal a staining which is most intense near the outer surface. This suggests that concentration gradients must exist for elements entering the bone. To investigate this possibility quantitatively, we have determined elemental concentrations in such bones as a function of depth below the outer surface. Using a SLOWPOKE reactor, we have analysed a number of samples of bone taken from secondary deposits of river sediments in the Old Crow region of the Yukon Territory, Canada. Our preliminary work indicates the decrease in concentration with depth into the cortex for previously recognized post-mortal elements such as U, F, Ba, Mn and Fe. Our measurements show that V, Sc, and Co also vary in this way and can be included in this group. As the hollow central shafts of bones are approached, concentrations increase again. Bones found in the Old Crow region display a variety of surface staining ranging from almost white through red to brown and black. There is a strong correlation between Fe and less positive relations between F and Ba, and staining. Highest Mn concentrations occur at the surfaces of light-coloured bones in which the staining is restricted to the outer 1 mm. Because of the wide range of concentrations which exist amont post-mortal elements in these bones, correlations among these elements can be studied. Manganese and barium, for example, are correlated within each bone, but the correlation patterns differ from bone to bone. These relationships must reflect the nature of the chemical processes associated with the deposition of the elements within the bones. A comparison of these patterns show that some of the bones have been exposed to more than one set of environmental conditions. This data thus provides a way of studying these processes in bones in which the introduction of elements from the environment has not completely and uniformly filled all the available voids.

Calculation of the absolute peak efficiency of Ge and Ge(Li) detectors for different counting geometries

Abstract: A new method is presented to calculate with improved accuracy the absolute peak efficiency of cylindrical Ge and Ge(Li) detectors for point, disk and cylinder sources, positioned at any source-detector distance. Moreover attention was paid to true-coincidence effects. The method is extensively tested and applied for the analysis of reference materials. The accuracy turned out to be 3% or better.

Ultratrace determination of platinum in biological materials via neutron activation and radiochemical separation

Abstract: A neutron activation analysis scheme based upon a radiochemical separation of the activation products has been developed. The method utilizes the inherent sensitivity of the activation reaction198Pt(n, γ)199Pt and counting of the daughter nuclide199Au. This nuclide is radiochemically separated from interfering activities by homogeneous precipitation as elemental gold. The remaining interference of the secondary reaction197Au(n,γ)198 Au(n,γ)199Au from gold in the samples is quantitatively assessed and corrected. During this process accurate gold concentrations in the samples are obtained at ultratrace levels. The analysis scheme is applied to gold and platinum determinations in biological Standard Reference Materials and human liver specimens. Gold and platinum are determined at concentrations of 5·10−11 g/g, and at higher levels.

An automated activation analysis system

Abstract: An automated delayed neutron counting and instrumental neutron activation analysis system has been developed at Los Alamos National Laboratory's Omega West Reactor (OWR) to analyze samples for uranium and 31 additional elements with a maximum throughput of 400 samples per day. The system and its mode of operation for a large reconnaissance survey will be described.

Evaluation of a system for routine instrumental neutron activation analysis

Abstract: The system for routine instrumental neutron activation analysis, in use for several years at the IRI at Delft, has been evaluated. Basis of this evaluation are: quality of the results, costs per analysis, capacity and ease of operation. A comprehensive description of the analysis system and associated hardware and software is included.

Precise trace rare earth analysis by radiochemical neutron activation

Abstract: A rare earth group separation scheme followed by normal Ge(Li), low energy photon detector (LEPD), and Ge(Li)−NaI(Tl) coincidence-noncoincidence spectrometry significantly enhances the detection sensitivity of individual rare earth elements (REE) at or below the ppb level. Based on the selected γ-ray energies, normal Ge(Li) counting is favored for140La,170Tb and169Yb; LEPD is favored for low γ-ray energies of147Nd,153Sm,166Ho and169Yb; and noncoincidence counting is favored for141Ce,143Ce,142Pr,153Sm,171Er and175Yb. The detection of radionuclides152mEu,159Gd and177Lu is equally sensitive by normal Ge(Li) and noncoincidence counting;152Eu is equally sensitive by LEPD and normal Ge(Li); and153Gd and170Tm is equally favored by all the counting modes. Overall, noncoincidence counting is favored for most of the REE. Precise measurements of the REE were made in geological and biological standards.

Trace element concentration in head hair of the inhabitans of the Rawalpindi-Islamabad area

Abstract: Instrumental neutron activation analysis technique has been used to determine the concentration levels of 12 trace elements in human head hair samples collected from 105 individuals living in various areas of Rawalpindi-Islamabad. The data show that the average concentrations of Mn, Co, Ag and Au are higher in the female group as compared to the male group. Four individuals were found to have elevated levels of Se due to the use of anti-dandruff shampoos, whereas two individials had elevated levels of Hg.

Interlaboratory study of trace and other elements in the iaea powdered human hair reference material, HH-1

Abstract: A powdered intercomparison material for trace element studies was prepared from human scalp hair and distributed to more than 100 laboratories of which 66 reported results for altogether more than 40 elements. By statistical evaluation of these data certified concentration values were derived for 20 elements, namely As, Au, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, Mg, Mn, Na, Pb, S, Sb, Se, Sr and Zn. The data also made it possible to compare different methods of analysis and to judge the value of different levels of experience on the part of the analyst concerned; these comparisons are presented here with special reference to the elements As, Cd, Hg, Pb and Sb.

Epithermal neutron activation analysis of short-lived nuclides in geological material

Abstract: The cadmium ratios of 52 short-lived nuclides have been measured. Epithermal neutron irradiation reduces the activities of20F,27Mg,28Al,38Cl,49Ca,46mSc,51Ti,56Mn and66Cu by factors of 20–30. The calculated improvements in detection limits for Ga, Br, Rb, Y, Mo, Rh, Pd, Ag, In, Sn, Sb, I, Ba, Nd, Sm, Gd, Dy, Er, Yb, Hf, W, Re, Pt, Au, Th and U are in the range 1–6. Hafnium was measured in USGS rocks: AGV-1 (4.9 μg g−1), G-2 (7.5 μg g−1) and GSP-1 (14.7 μg g−1) and IAEA standards: SOIL-5 (6.3 μg g−1 and SL-1 (4.6 μg g−1). CCRMP reference concentrates PTC and PTM were analysed for rhodium (1.1 and 0.75 μg g−1, respectively) and silver (69 and 5.8 μg g−1, respectively).

Arsenic pollution in the Yellowknife Area from gold smelter activities

Abstract: Gold has been mined on a large scale at Yellowknife located in the sub-arctic North West Territories of Canada since 1938. The gold is associated with arsenopyrite ores, with necessitates the oxidation of the arsenic and sulphur by roasting at two Yellowknife smelters. Other metals are also present in the ore, notably antimony. As2O3 and SO2 are emitted into the atmosphere. Large quantities of arsenic were liberated in the past and despite improvements in emission control, significant emission still occur. In order to assess the amount and extent of arsenic contamination in the local environment and the potential exposures and sources to man, soil samples and samples of the native vegetation were collected in and around the town of Yellowknife and the two smelters. Arsenic and antimony analyses were done by instrumental neutron activation analysis using the SLOWPOKE facility at University of toronto. Air-dried plant samples were bombarded at a neutron flux of 1·1012n cm2s and soil samples at 2.5·1011n cm2s for 6 minute periods. The122Sb and76As-ray emissions at 559 keV were analysed after decay periods of 24–48 hours and compared with standard solutions and NBS standards. Zinc, copper, lead and cadmium analyses were done by atomic absorption spectrophotometry.

Determination of free acidity in uranyl nitrate solutions

Abstract: Two modifications of the existing method of determining free acidity in highly concentrated uranyl nitrate solutions by alkalimetric titrations in neutral potassium oxalate medium have been carried out to improve the reliability of the method. Free acidities of several synthetic solutions containing uranium and nitric acid in a wide range of concentration ratios were determined by all the three methods and compared with the results obtained by a more accurate ion exchange method. Interference from other hydrolyzable ions and the precision and accuracy were studied and compared.

A Facility for Multielemental Analysis by PIXE and the F19(p,αγ)O16 Reaction

Abstract: Specific advantages with Particle Induced X-Ray Emission are: its (1) multielemental capability, especially when combined with nuclear techniques for lighter elements, (2) speed, (3) low detection limits for small samples and (4) accuracy. To make full use of these advantages, analytical parameters have to be chosen optimally and the facility to be carefully designed. This paper describes an experimental facility constructed to permit continuous development work to optimize the analytical conditions and to allow the gradual implementation of automatic control. Emphasis is also put on the simultaneous use of proton induced gamma rays from fluorine. The features and the performance of the set-up including its accuracy, precision and experimental detection limits are reported.

14.8 MeV neutron activation cross-sections for (n, p) and (n, α) reactions of some rare earth nuclides

Abstract: The activation cross-sections for sixteen (n, p) and (n, α) reactions on rare earth nuclides were measured at 14.8 MeV neutron energy. A Ge(Li) detector was used for the radioactivity measurements. The measured cross-sections are compared with the semi-empirical predictions of LEVKOVSKII3 and BAYHURST and PRESTWOOD.16

Synthesis of11C propranolol

Abstract: A method is described by which 60 mCi11C propranolol may be obtained from about 1 Ci11CO2 in 30 min without irradiation risk for personnel. The product is chromatographically pure, sterile and apyrogenic with a specific activity between 500 mCi and 2 Ci/μmole at the time of use. The synthesis involves the preparation of11C acetone followed by fixation of the isopropyl group on the precursor [1-amino-3-(1-naphtyloxy)-2-propanol] by formation of an imine, then reduction of the latter by sodium cyanoboro hydride. The influence of certain parameters (reagents, precursor, impurities) on the final product is discussed.

Status and recent developments in the k0-standardization method

Abstract: After critical evaluation of a number of existing standardization methods a new approach introducing generalized k0-factors was suggested in 1975 for use in (n, γ) reactor neutron activation analysis (RNAA). In order that the new method could soon be applied competitively in actual analytical work a cooperation between the Activation Analytical Laboratories of the Central Research Institute for Physics (KFKI), Budapest and the Institute for Nuclear Sciences (INW), Gent was established to determine the k0 and other related nuclear data (Q0, T1/2, Ēr, etc.) with a high accuracy, to develop procedures for monitoring essential irradiation and measuring parameters (Φs/Φe, α, ∈p, $$\bar \Omega $$ , etc.) as well as to share experiences when applying the method. This paper summarizes the main results of this cooperative work obtained in the last five years. The current status and recent developments in the k0-method are reviewed and a “Status and Request List” compiled from more than a thousand surveyed nuclear data on about 150 analitically important (n, γ) reactions in being prepared to suggest new or refined measurements and to prevent the use of unreliable data.

Trace impurities in Canadian oil-sands, coals and petroleum products and their fate during extraction, up-grading and combustion

Abstract: National energy programs for the next two decades entail increased total consumption of fossil fuels in general and, in particular of portable fuels extracted from oil sands and shales and from lower quality coals. Improved fuel-upgrading and combustion technologies are recognized to be vital for minimizing environmental degradation caused by continental and global acid-rain precipitation from fossil-fuel impurities. A further consideration, however, is the fate of those trace-element co-contaminants of acid-rain such as heavy metals, which are present at lower concentrations (10−4–10−7) but may also be of environmental significance when 107 to 109 tons·y−1 are utilized on several continents. In this laboratory, INAA procedures have been adapted for the determination of 25–30 trace impurities in a variety of fuels and extracts including: S, V and Al, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Dy, Eu, Fe, Hf, K, La, Mn, Na, Rb, Sb, Sc, Sm, Th, Ti, U. Samples were obtained of typical Canadian pumped crudes, and from several Canadian oil-sands and coal deposits (mostly bituminous and subbituminous) both in their natural states and after stages of extraction and upgrading. Also analyzed were fuels derived from them and the residues resulting from their refining and combustion. InAA of all fossil fuel extracts including light oils, viscous bitumen and such organic fluids could be performed under the same conditions as the parent substances: crude oils, oil-sands and coals, without any special sample preparation. Although no standard samples are routinely required because of the 1–2% long-term flux stability of the reactor, accuracy checks were performed periodically by reference to NBS-1632A standard coal and atomic absorption standard dilute solutions. Results obtained for the NBS coal SRM and the BAM flyash sample (1978) are also given. A wide range of trace impurities determined in the Canadian fossil fuels included some of those which are of particular significance in Canadian coals and their ashes (a STM standard ashing method). The ‘inorganic’ traces can also be grouped according to their fate during static combustion at 750°C.

Study on the solid solubility of transition metals in high-purity silicon by instrumental neutron activation analysis and anticompton-spectrometry

Abstract: The solid solubility of the 3d metals Cr, Mn, Fe, Co and Ni in high-purity silicon was studied by INAA and electron paramagnetic resonance techniques in the temperature range of ≊600°C–1250°C The solubility increases with atomic number from Cr to Mn and more distinctly from Co to Ni For Mn, Fe and Co the solubilities are nearly the same within the experimental errors An enthalpy of formation (ΔH) of about 28 eV was determined for Cr, Mn, Fe and Co, whereas for Ni 17 eV was derived Relatively large diffusion coefficients were estimated from the rather short times, in which saturation of the solid solution was reached From these observations and from the results of the EPR measurements it is concluded that the 3d metals occupy predominantly interstitial sites in the silicon lattice in thermal equilibrium

The effect of the epithermal neutron flux distribution on the accuracy of absolute and comparator standardization methods in (n, γ) activation analysis

Abstract: A description is given of the systematic errors which can be introduced when applying absolute or comparator standardization techniques to RNAA or ENAA at irradiation sites with a deviating 1/E1+α epithermal neutron flux distribution. A simple correction formula for a≠0 is presented and a survey is given of the present state-of-the-art for experimentala-monitoring and for the calculation or experimental determination of the effective resonance energy Ēr. Extensive error calculation leads to the conclusion that, with careful selection ofa monitors and of the nuclear data involved, the rather large errors (∼10% or more) are reduced, after correction fora, to uncertainties of about 2%.

Determination of platinum in urine and serum after the administration of cisplatin by neutron activation analysis

Abstract: A simple neutron activation method is described for platinum determination in urine and serum of dogs when studying the pharmacokinetics of cisplatin, an antitumour drug. The procedure is based on the nuclear reaction198Pt(n, ψ, β−)199Au, a radiochemical separation of gold, and gamma-spectrometry of the radionuclide199Au. Gold is separated as metal by coprecipitation with selenium after the addition of ascorbic acid in a highly acidic medium. The interference contribution of199Au originating from stable gold is evaluated, too.

Multielement analysis of Nigerian chewing sticks by instrumental neutron activation analysis

Abstract: In Nigeria, various parts of various species of native plants have long been used for dental hygiene, with reportedly considerable effectiveness. These materials are known as “chewing sticks”. This study was an effort to ascertain whether any unusual trace element concentrations might be present in Nigerian chewing sticks. Results are presented for 17 elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Mn, Fe, Co, Zn, Br, Cs, La, Sm, Au) detected and measured in 12 species of such plants, via instrumental thermal-neutron activation analysis.

Performance of the updated inaa advance prediction computer program

Abstract: This paper describes further development and experimental testing of the INAA Advance Prediction Computer Program (APCP). Copies of the APCP written in BASIC-PLUS are finally ready for distribution. Experimental tests with four reference materials are described. The program is extremely useful as a quide to optimum conditions, sample sizes, elements detectable, and INAA lower limits, of detection for any sample matrix of only approximately known major and minor elemental composition. Additional developments in progress are mentioned.

Simultaneous determination of twelve trace elements in estuarine and sea water using pre-irradiation chromatography

Abstract: A procedure is described for the preconcentration of 100 ml of estuarine and seawater into a solid sample using Chelex-100 resin. This solid sample weighs less than half a gram and contains the transition metals and many other elements of interest, but is essentially free from the alkali metals, the alkaline earth metals, and the halogens. The concentrations of Co, Cr, Cu, Fe, Mn, Mo, Ni, Sc, Th, U, V and Zn have been determined in seawater when this procedure was coupled to neutron activation analysis.

Rapid incorporation of radiobromine via the reaction of labeled sodium bromide with organoboranes

Abstract: Organoboranes react with82Br labeled sodium bromide in the presence of chloramine-T to yield the corresponding82Br labeled alkyl and aryl bromides. The reaction is rapid, proceeds under mild conditions, and tolerates a variety of functional groups.

Advanced system for separation of rare-earth fission products

Abstract: A microprocessor-controlled radiochemical separation system, which has been developed at the INEL, has been further advanced to separate individual rare-earth elements from mixed fission products in times of a few minutes. The system was composed of an automated chemistry system fed by two ∼300μg252Cf sources coupled directly by a He-jet to transport the fission products. Chemical separations were performed using two high performance liquid chromatography columns coupled in series. The first column separated the rare-earth group by extraction chromatography using dihexyldiethylcarbamoylmethylphosphonate (DHDECMP) adsorbed on Vydac C8 resin. The second column isolated the individual rare-earth elements by cation exchange chromatography using Aminex A-9 resin with α-hydroxyisobutyric acid (α-HIBA) as the eluent. Significant results, which have been obtained to date with this advanced system, are the identification of several new neutron-rich rare-earth isotopes including155Pm (T=48±4 s) and163Gd (T=68±3 s). In addition a half-life of 41±4 s is reported for160Eu.

A study of mesoamerican obsidian sources using activation analysis

Abstract: An extensive study of Mesoamerican obsidian source samples from 37 sites has been begun to better differentiate and define the trace element content at known Mesoamerican obsidian quarries, with particular emphasis on those in Mexico. This paper reports on the first results in that study as well as studies of sample contamination by grinding and results for the new National Bureau of Standards No. 278 Obsidian SRM.

Estimates of iodine in biological materials by epithermal neutron activation analysis

Abstract: Iodine abundances in NBS biological SRMs and various organs of rats were evaluated by epithermal neutron activation analysis with a boron carbide filter. Detectability of iodine in different biological materials by this method is discussed.