Distribution pattern of REE and other elements in the host rocks of the Gubrunde uranium occurrence,NE Nigeria

Prospecting for high grade uranium deposits in NE Nigeria has over the years among other reasons been handicapped by lack of adequate understanding of the elemental primary dispersion pattern associated with known occurrences in this region. Thirty six samples from a low grade uranium occurrence at Gubrunde consisting of disseminated ores and hostrocks were therefore analyzed for 38 elements by NAA, DNAA, EDXRF and flame AAS techniques. The analytical data were evaluated using multivariate statistical techniques. The results show three element groupings (associations). The first group consists of Pb, Ba, Ce, Sm (LREE), that are enriched with increasing uranium concentration in the mineralized zone and are therefore capable of serving as pathfinder elements for uranium. The second group comprising of MgO, K₂O, CaO, Na₂O and the HREE are depleted in the mineralized zone due to action of hydrothermal fluids and are indicative of altered/mineralized rocks. The third group consists of the rest bulk of elements which feature little or no significant enrichment with increasing uranium but associate with ferruginization (haematite) and possibly refractory minerals.     

Determination of uranium in ores using instrumental neutron activation analysis

An instrumental neutron activation analysis method based on the measurement of²³⁹Np has been developed for the determination of uranium in ores. The samples after 5 sec irradiation were cooled for 3 days and the gamma-ray spectra were measured with a 30 cm³ Ge(Li) detector. The precision and accuracy of the proposed method were determined by analysing IAEA Standard Uranium Ore samples.     

Flame-photometric determination of sodium in uranium ores

A flame-photometric method of determining sodium in uranium, phosphate, carbonate, and silicate rocks has been developed. The mutual enhancement of the alkali metals is overcome by the addition of a radiation buffer added to both the sample and to the standards. The method is rapid and suitable for routine analysis. Results obtained are within ± 2% of the sodium content.     

Simultaneous determination of thorium and uranium in ores and SRMs by instrumental neutron activation analysis

A procedure has been developed for the determination of thoirum and uranium in ores and geological materials. The technique is relatively simple, accurate and adaptable routinely. Gamma-ray peak interferences are discussed in detail and the usefulness of the multiple gamma-ray peak ratios in the determination of the purity of peaks has been explained. The precision and accuracy of the method have been determined by analysing IAEA and NBL Standard thorium/uranium ores.     

A contribution to the chemical aspects of precise mass spectrometric analysis or uranium

The chemical aspects of isotopic fractionation in a multiple filament thermal ionization source were investigated. Samples of uranium were loaded as nitrates, chlorides and sulphates. The dependence of measured isotopic ratios on the filament material and the chemical form of the loading solution was studied. The dependence of the formation of uranium and its oxide ions on various chemical and instrumental conditions were investigated using tungsten and rhenium filaments.     

Determination of rare earths in low grade uranium ores and SRM-rock by instrumental neutron activation analysis

An instrumental neutron activation analysis technique has been developed for simultaneous determination of 10 REE in low grade U/Zr ores and other geological materials. The samples were irradiated with reactor neutrons for 2 min to 8 hrs followed by a cooling of 30 min to 3 weeks. The γ-ray activity was measured with a semi-planar Ge(Li) detector. A precision of 5% has been obtained by the repeated analysis of NBS-SRM. The technique is relatively simple and adaptable on the routine basis.     

Simultaneous determination of uranium and thorium in high grade thorium ores

A routine procedure has been developed for the simultaneous determination of uranium and thorium in high concentration thorium ores. INAA is used to determine the uranium and thorium concentration. However, for very low concentrations of uranium a radiochemical procedure based on the use of NPy/benzene as an extractant has to be employed. The precision and accuracy of the method has been determined by analyzing IAEA and NBL standard thorium/uranium ores.     

Analysis of uranium ores by energy dispersive X-ray fluorescence

Summary The determination of uranium in ores by energy-dispersive X-ray fluorescence (XFA) is demonstrated for uranium ore samples of known content. For calibration silica gel standards are used. Matrix effects are corrected by measuring the Compton scattering peaks. The radionuclide ¹⁰⁹Cd as well as a X-ray tube in combination with Mo or Sn as secondary targets are suited as X-ray sources. The mean relative deviation of the values found from the given values is 5%

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Analyse von Uranerzen mit Hilfe der energiedispersiven Röntgenfluorescenz

Zusammenfassung Die Anwendbarkeit der energiedispersen Röntgenfluorescenzanalyse zur Bestimmung des Urangehaltes in Erzen wird am Beispiel von Uranerzproben bekannten Gehaltes demonstriert. Für die Eichung werden Kieselgel-Standards verwendet. Die Matrixeffekte werden mit Hilfe der ComptonStreupeaks korrigiert. Als Röntgenquellen eignen sich sowohl eine ¹⁰⁹Cd-Radionuklidquelle als auch eine Röntgenröhre mit Mo oder Sn als Sekundärtarget. Die mittlere relative Abweichung der Analysenwerte von den gegebenen Werten beträgt 5 %.

     

Isotopic analysis of uranium by neutron activation and high resolution gamma ray spectrometry

A method is described for the non-destructive and accurate determination of the isotopic composition of uranium by activation analysis. The high resolving power of Ge(Li) detectors permits easy identification on a single gamma spectrum of the gamma peaks of²³⁹Np formed from²³⁸U by activation and those of fission products formed from²³⁵U. The ratio of the peak intensities is proportional to the²³⁸U/²³⁵U ratio in the sample. A precision of ±0.6% has been obtained.     

Neutron activation analysis of microgram amounts of thorium in uranium ores and process liquors by means of thorium-233

A method is described for neutron activation analysis of thorium by employing thorium-233. Decontamination steps include anion exchange in 12.5 N HCL, precipitation of fluoride, extraction with mesityl oxide and thorium oxalate precipitation. The time spent is less than 1 h; spurious activities in counting samples amount only to 2% and can easily be corrected for. The sensitivity of the method is ca. 0.02 μg of thorium in a neutron flux of 10¹²n/cm²/sec with an irradiation time of 5 min.     

Rare earth elements,thorium and uranium in ores of the North-Latium (Italy)

In geochemistry, the distribution of the Rare Earth Elements (REEs) in earth crust and mantle allows to understand geochemical cycles and origin and age of igneous rocks. In this article REEs (Ce, Dy, Eu, La, Nd, Sm, Tb, and Yb), Th and U in ores of the North-Latium (Bracciano area, Ceriti Mt., Fate Mt., Sabatini Mt., Vulsini Mt., Acqua Rossa basin), have been investigated for evaluating the extraction feasibility for industrial applications. 107 samples were irradiated in the rotating rack of the TRIGA Mark II reactor of the R.C. Casaccia (ENEA) at neutron flux of 2.6 × 10¹² n × cm⁻² × s⁻¹ for 12 h together with primary and secondary standards. The gamma spectrometry measurements were performed after 8 h, 3 and 30 days of decay by means of HPGe detector (FWHM 1.75 keV at 1332.5 keV, peak/Compton ratio 55.1, relative efficiency of 22%) connected to a multi-channel analyzer. The total REE mean content is 105 μg g⁻¹, ranging widely between 2.23 and 410.5 μg g⁻¹ (average coefficient of variation 112%). A similar behavior is found for Th and U: their average levels are 13.5 and 6.0 μg g⁻¹, respectively. A quite good correlation between REEs and Th (and U) is found for Ceriti Mt. (r ² > 0.8) whereas for the other areas the correlation is <0.7. The results obtained evidence the low U content in the investigated locations.     

Simultaneous determination of hafnium and zirconium in low grade uranium ores using INAA

A non-destructive neutron activation analysis technique has been developed for the determination of hafnium and zirconium in low grade uranium ores. In order to calculate the fission contribution of²³⁵U, thermal neutron absorption cross-section /_a/ for⁹⁴Zr has been determined. The study shows that 1 g of uranium produces the same activity as from 10.03 g of zirconium. Based on this fact, the degree of interferences have been calculated for each sample and the necessary corrections have been applied. The values have been compared with the reported IAEA and NBS values.     

On the determination of226Ra in soils and uranium ores by direct gamma-ray spectrometry

The evaluation of the source term in facilities related to the first stages of nuclear fuel involves the determination of radium concentration, as well as those from other radionuclides members of the uranium series. These activities are often required within a short time period, making impossible the use of radiochemical methods or the gamma-ray spectrometry of radium daughters. In those situations it can be very convenient to determine the²²⁶Ra activity by means of its 186 keV gamma-ray line. For this purpose it is necessary to estimate the interference due to²³⁵U, also present in natural samples. This method has been applied successfully to several soil samples from an old uranium factory in Southern Spain.     

Development of methodologies for the analysis of uranium ores by k 0-instrumental neutron activation analysis and inductively coupled plasma atomic emission spectrometry

Journal of Radioanalytical and Nuclear Chemistry - Analytical methodologies were developed for the determination of elemental contents in four uranium ore samples (S-8, S-12, S-13 and S-17) from...     

A specific method for the determination of uranium in ores by cathode ray polarography

A method is presented for the specific determination of uranium in ores by cathode my polarography. The uranium is separated by a simple and rapid mercury-cathode electrolysis, then determined polarographically in a base electrolyte in which vanadium, titanium and tungsten do not interfere. Application of the method to the analysis of ten standard uranium ores is shown.     

Titrimetric determination of uranium in low-grade ores by the ferrous ion-phosphoric acid reduction method

The modification and extension of the U.S.A.E.C. ferrous ion-phosphoric acid reduction method for the determination of uranium in high-grade or relatively pure material to a method for the determination of uranium with a high accuracy and precision, in ores containing 0.004-7% U is described. It is simple, rapid and requires no prior separations from elements that, in other methods, frequently interfere. For sample materials having very high concentrations of interfering elements, a prior concentration step using extraction with tri-n-octylphosphine oxide is described, but it is shown that, for most low-grade ores, this step is unnecessary.     

Determination of hexavalent and tetravalent uranium in phosphate ores through hydrochloric acid selective leaching

The tetravalent and hexavalent uranium content of three Egyptian phosphate type ore samples namely; Sebayia, Abu Tartur and Qatrani have been studied through selective leaching by hydrochloric acid at normal, oxidized and reduced conditions at an amount of hydrochloric acid less than the stoichiometric value i.e. before phosphoric acid production. Oxidizing condition is attained by incorporating 2% of manganese dioxide in the leaching cycle, whereas reducing condition is attained by adding 2% iron powder. The achieved results show that the amount of tetravalent uranium varies between 5 and 95%. As soon as the achieved stoichiometric value of hydrochloric acid is sufficient to produce phosphoric acid both tetravalent and hexavalent uranium dissolve by virtue of phosphoric acid complexing power for uranium. The chemical form of uranium in the ore determines the type of solvent needed to recover it.