Neutron activation analysis of uranium via239Np

A method is described for the analysis of uranium by neutron activation. The sample is brought into solution and the neptunium present is reduced to oxidation state (IV); quantitative extraction of²³⁹Np in the acidified aqueous phase (0.4<pH<1) is performed with a solution of HTTA (0.2M) in benzene. The use of a low-power reactor (100 kW_thermal) enables determination of uranium at a lower concentration limit of 33 ng for periods of irradiation. cooling and measurement of 3 hours, 24 hours and 900 seconds, respectively.     

Neutron activation analysis of rare earth impurities in metallic uranium

A method with a sensitivity of 2·10⁻⁷ to 1·10⁻¹⁰% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation. The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)₃, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8 anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant.     

Imaging uranium distributions in fossil bones by fission track etching

In the course of our work within the framework of an interdisciplinary project dealing with the absolute dating of fossil bones from Austrian caves by means of the U-series method we became interested in possible U-concentration gradients in the bone samples. A successful attempt is reported to make the U-distribution in bones directly visible by irradiating the samples with thermal neutrons and detecting the emitted fission products of²³⁵U in a plastic foil using the track etch method. This turns out to be possible also for relatively small U-concentrations of the order of 1 ppm. The uranium seems to concentrate near the surfaces which is in qualitative agreement with earlier results from the literature obtained by means of neutron activation analysis.     

Neutron activation analysis of pure uranium: Preconcentration of impurity elements

We have developed a radiochemical neutron activation analysis technique (RNAA) of pure uranium with using extraction chromatographic separation of ²³⁹Np from impurity elements in TBP-6M HNO₃ media. The estimation of influence of fission products of ²³⁵U on the results by radiochemical neutron activation analysis has been carried out. For it we have performed NAA with preconcentration of impurity elements. Experiments show that in this case the apparent concentration of Y, Zr, Mo, Cs, La, Ce, Pr, Nd exceeds the true concentration by 2500–3000 times. Therefore, determination of these elements is not possible by RNAA. This technique allowed to use the determination of 26 impurity elements with detection limit 10⁻⁵–10⁻⁹% by mass. This developed technique may be used for the determination of impurities in uranium and its compounds.     

Neutron activation analysis for ultra low contents of uranium and thorium in aluminium and silica

Highly sensitive neutron activation analysis of uranium and thorium in high quality silica and aluminium has been investigated using the Japan Materials Testing Reactor (JMTR), having a thermal neutron flux higher than 10¹⁴ n/cm²/s. In order to determine ultra-low contents of uranium and thorium,²³⁹Np and²³³Pa as activation products were separated by using anion exchange and LaF₃ coprecipitation methods. As a result, a number of interfering radioactive isotopes containing double neutron capture product such as¹⁸³Ta were removed completely from the isolated²³⁹Np and²³³Pa fraction and the detection limits for uranium and thorium were found to be 2·10^–12 g and 4·10^–13 g, respectively.     

Neutron activation analysis of uranium in human bone,drinking water and daily diet

Uranium in human bone, drinking water and daily diet has been determined by neutron activation analysis using the²³⁸U(n, γ)²³⁹U reaction. An improved scheme for the separation of the²³⁹U is proposed; with this scheme, after neutron irradiation in a 100 kW TRIGA reactor, a uranium content as low as 5·10⁻¹¹ g can be determined reliably, rapidly and easily. A wide range of uranium concentrations, from about 0.1 ppb up to about 10 ppb has been found in the bones of normal Japanese. Water from several Japanese city water services, and the daily diet taken in two Japanese cities, have been found to contain an average 9·10⁻⁹ g/l and 1.5 μg per person-day uranium, respectively.     

Progress in neutron activation analysis for uranium

A new type of extractant, sym-dibenzo-16-crown-5-oxyhydroxamic acid (HL) is introduced. The extractions of UO22+, Na+, K+, Sr2+, Ba2+ and Br- were studied with HL in chloroform. The results obtained show that UO22+ can be quantitatively extracted at pH values above 5, whereas the extractions of K+, Na+, Sr2+, Ba2+ and Br- are negligible in the pH range of 2 - 7. The dependence of the distribution ratio of U(VI) on both the concentration of the HL and pH are linear, and they have the same slope of 2. This suggests that U(VI) appears to form a 1:2 complex with ligand. Uranium(VI) can be selectively separated and concentrated from interfering elements such as Na, K, Sr and Br by solvent extraction with HL under specific conditions. The recovery of uranium is nearly 100% and the radionudear purity of uranium is greater than 99.99%. Therefore, neutron activation analysis has greatly improved the sensitivity and accuracy for the detection of trace uranium from seawater.     

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

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.     

Neutron activation analysis for aluminum in animal tissue

A method for the neutron activation analysis of aluminum in animal tissue has been developed which through pre-irradiation chemistry eliminates otherwise interfering nuclear reactions. The procedure gives a precision of ±0.1 ppm in samples of a few hundred milligrams dry tissue containing about 1 ppm Al.Bowen’s standard kale has been analysed instrumentally and a value of 45±4 ppm Al was found. Difficulties specifically related to the aluminum analysis of this material are discussed.     

Neutron activation analysis for trace elements in foods

Food samples reflecting average food consumption by an adult in the southeastern, northeastern, central, and western parts of the United States were collected and prepared as if for consumption. The prepared foods were divided into twelve different food categories and analyzed by instrumental neutron activation analysis. The concentration of Ca, Mn, Mg, Al, Na, K, Cu, Cl, Sb, Hg, Se, Fe, Zn and Co is reported for these food samples.     

Neutron activation analysis for sodium traces in magnesium

When sodium traces are determined in magnesium matrices by neutron activation analysis, the reaction ²⁴Mg(n,p)²⁴Na interferes by simulating spurious sodium concentrations (about 400–500 p.p.m. for usual irradiation positions in the RS 1 water-pool reactor). A preliminary separation of the sodium traces from the bulk of the matrix by electrudeposition on a mercury cathode and recovery in water by amalgam decomposition, prevented the fast-neutron effects. Electrolysis for 4 h gave almost quantitative recovery of sodium (93±5%) and satisfactory decontamination factors for magnesium (1.5 to 5. 10³). The method is limited by the blank correction (14 μg Na with a glass electrolysis cell). Some results for magnesium samples with both destructive and non-destructive techniques are reported.     

Simplified evaluation of214Bi/238U activity ratios in fossil bones using non-destructive activation analysis

A simple and reliable method has been developed for the evaluation of radioactive disequilibrium state in fossil bones. The fossil bone samples were irradiated with an extremely low neutron fluence, together with a standard pitchblende prevailing the secular equilibrium among the uranium series. The²³⁹Np activity induced from²³⁸U in both samples were adjusted to be gamma-ray spectrometrically nearly equivalent to the naturally occurring radioactivities by controlling the neutron flux and cooling time. Using single gamma-ray spectrometry of the irradiated samples, the determination of²¹⁴Bi/²³⁸U in a fossil bone was carried out by comparing the photopeak ratios of²¹⁴Bi /609 keV/ and²³⁹Np /278 keV/ instead of²³⁸U with the same ratios from the pitchblende standard sample.     

Neutron activation analysis of indium

The extraction and extraction-chromatographic behavior of many elements in the tributylphosphate — HBr solution system has been studied. The investigation performed has made it possible to develop a simple technique for neutron activation determination of 22 impurity elements in high purity indium samples with detection limits from 0.1 ppm for Fe and Zr to 0.01 ppb for Na, Sc, Cu, As, La and W.     

Neutron activation analysis of radiopharmaceuticals

In order to understand the chemical form of soluble technetium in paddy soil and its availability to a rice plant, soil incubation and uptake experiments have been carried out using^95mTc as a tracer. The chemical form of the soluble Tc was observed by gel chromatography and found not to be pertechnetate, but rather to be associated with soluble organic matter. An uptake experiment with rice seedlings using nutrient solution showed that this Tc-organic matter complex was less available than pertechnetate.     

Neutron activation analysis of soils

Résumé On décrit l'analyse de sols par activation neutronique au moyen de détecteur Ge(Li) à haute résolution pour la recherche de 31 éléments. Les éléments déterminés comprennent des métaux alcalins, des terres rares et des éléments de transition, la plupart d'entre eux sont utilisés, comme indices de différenciation géochimique et d'autres sont utilisés en tant que facteur de nutrition dans la physiologie des plantes. Quelques éléments comprenant Na, K, Rb, Cs, Ba, La, Ce, Sm, Eu, Th, Zr, Hf, Ta, Mn, Co, Fe, Sc, Cr, Sb, Ca, V, Al, Ti, Br et U ont été déterminés par spectrométrie gamma non-destructive, et d'autres Mo, W, Sr, Cu, Zn et Ga après une simple séparation radio chimique basée sur un échange d'ions et une extraction par solvant. On a employé l'activation dans les neutrons épithermique pour la recherche de l'U, utilisant des neutrons de réacteur. Les risques d'interférence dans les réactions et dans les spectres gamma, l'autoabsorption et les autres causes possibles d'erreur sont analysées et évaluées quand c'est possible. Les résultats sont donnés en temps que moyenne de plusieurs dosages. Dans tous les cas, on est parvenu à une grande précision.      

Neutron activation analysis of scandium

A neutron activation method is proposed for the determination of trace quantities of scandium, down to submicrogram level, in rocks, ores and meteorites. The sample and standard are irradiated intermittently for a total of 30 h, at a neutron flux of 5·10¹¹ n/cm²/sec; the radiochemical separation consists essentially of a one-step anion exchange. The induced γ-activity of ⁴⁰Sc, 85 days, isolated from the sample is measured and compared with that of a standard. The chemical yield averages 85% and there is a considerable saving of time in the radiochemical work. Results are quoted for the scandium contents of 2 standard rocks, cassiterite and several stony meteorites. Details of conflicting nuclear reactions are also given.     

Neutron activation analysis for osmium and ruthenium in platinum

A sensitive procedure for the simultaneous determination of trace levels of osmium and ruthenium in platinum, by thermal neutron activation analysis utilizing γ-ray spectrometry, was developed. The radiochemical separation method utilized perchloric acid for a selective oxidation of osmium and ruthenium to the volatile tetroxides. The distillation of the tetroxides greatly reduced the radiation hazard presented by the bulk of the activities in the matrix. Activities of 15-day¹⁹¹Os and 40-day¹⁰⁴Ru were measured by accumulation of pulses from a 3″ diameter NaI(Tl) crystal detector. Analyses of γ-ray spectra were achieved using digital computer techniques. The procedure provided analyses for a high purity platinum stock of 0.032±0.007 ppm Os and 0.044±0.005 ppm Ru. Work was performed at the Ames Laboratory of the U. S. Atomic Energy Commission, Contribution No. 3073.