Trace characterization of high-purity nickel by instrumental and radiochemical neutron activation analysis

Summary The high activity of the radionuclides ⁶⁵Ni (t_1/2=2.52 h) and ⁵⁸Co (t_1/2=70.8 d) imposes severe limitations on the performance of direct instrumental neutron activation analysis of nickel. The extent of the interference of the ⁵⁸Co depends on the ratio of the fluxes of the fast and thermal neutrons. A method of selective removal of cobalt, based on extraction with -nitroso--naphthol has been developed for the purpose of radiochemical NAA. Separation yields have been determined for 36 elements. The detection limits obtainable with both the instrumental and the radiochemical method are <10^–4 g/g for the elements Au, Eu, Ir, La, Sc and Sm, between 10^–4 and 10^–3 g/g for Cr, Cs, Hf, Hg, Lu, Re, Sb, Ta, Th, Tm and Yb, between 10^–3 and 10^–2 g/g for As, Ag, Br, Ce, Ga, Na, Ru, Se, W and Zn, and in the range 0.01–1 g/g for Ba, Cd, Co, Fe, In, K, Mo, Nd, Pd, Rb, Sn, U and Zr.     

Determination of traces of rare earths in high-purity thorium dioxide by neutron activation analysis

The use of thorium dioxide as a nuclear fuel requires the determination of individual rare earth impurities at 0.08–1 mg kg^?1 levels. Neutron activation is sufficiently sensitive but separation from the matrix is essential. In the proposed method, thorium dioxide (5–20 g) is dissolved in concentrated nitric acid with a little hydrofluoric acid; after evaporation, thorium is complexed with ammonium carbonate and the solution is passed through a small column of Chelex-100 resin which retains the rare earths quantitatively without retaining thorium. The rare earth elements are eluted with dilute nitric acid, concentrated, and irradiated with standards; after irradiation the rare earth are collected on a lanthanum carrier and measured by γ-ray spectrometry. The recoveries of rare earths were checked with tracers and by standard addition to thorium dioxide matrices. The reproducibility for La, Eu and Dy was satisfactory at 0.01, 0.003 and 0.002 mg kg^?1, respectively; as was the reproducibility for all rare earths added to thorium dioxide (1–4 μg/5 g). Limits of detection are adequate for certification of nuclear-grade material.     

Multi-element analysis of soils by computerized instrumental neutron activation analysis

The applicability of instrumental neutron activation analysis (INAA) for soils is described and demonstrated and its restrictions mentioned.     

Multi-element analysis of blood for trace metals by neutron activation analysis

Fourteen elements can be rapidly determined in whole blood by the neutron activation analysis procedure described. Three of these (Ag, Cl, Se) are measured after a 10-s irradiation and eleven others (Al, Ba, Br, Ca, Cu, I, Mg, Mn, Mo, Rb, V) are determined by a 180-s irradiation of a 1-cm³ sample of whole blood after destruction of organic matter and removal of sodium by hydrated antimony pentoxide. A further 13 elements (As, Au, Co, Cr, Cs, Fe, Hg, K, Na, Ni, Sb, Sc, Zn) are determined after overnight irradiation in the SLOWPOKE reactor.     

Multi-element analysis of Ghanaian crude oils by instrumental neutron activation analysis

Instrumental neutron activation analysis based on thermal neutrons from the Ghana Research Reactor-1 facility was utilized to analyze 18 trace elements namely Al, As, Br, Ca, Cd, Cl, Co, Cu, Fe, K, Mg, Mn, Na, Ni, S, Si, V, and Zn in two different crude oil samples from the Saltpond and Jubilee field in the Saltpond, Central region and Cape Three Points, Western region of Ghana, respectively. The sulfur concentration for both samples were low and within globally accepted range of 0.1–0.5%wt for sweet crude oil. The results of the elemental analysis showed that the two samples are relatively low in trace element concentrations compared to crude oils of other countries. Higher Fe concentration in the Jubilee crude oil indicates younger oil. The V/Ni ratios obtained for crude oils from both locations imply a possible marine organic origin and also suggest the Saltpond crude oil is more matured than the Jubilee crude oil.     

Multi-element determination in sandstone rock by instrumental neutron activation analysis

Summary Instrumental neutron activation analysis (INAA) was used for the qualitative and quantitative analysis of sandstone samples of Aswan area, in South Egypt. The samples were properly prepared together with standards and simultaneously irradiated by a neutron flux of 7 ^. 10¹¹ n ^. cm^-2.s^-1. in the TRIGA research reactor facilities in Mainz. The gamma-spectra from a hyperpure germanium HPGe detector were analyzed. The present study provides the basic data of elemental concentrations of a sandstone rock. The following elements have been determined: Na, K, Fe, Sc, Cr, Co, Zr, Ce, La, Nd, Sm, Eu, Yb, Lu, Hf, Ta, Th and U. Energy dispersive X-ray fluorescence (EDXRF) was used for comparison and to detect elements which can be detected only by this method.     

Multi-element determination in silicate rocks by instrumental neutron activation analysis

Instrumental neutron activation analysis technique was applied for the determination of 20 elements in 54 silicate rock samples which belong to three sedimentary geological formations located in the western desert of Iraq. The samples along with USGS standards were irradiated in an IRT-5000 reactor at a neutron flux of 3.7·10¹³ n·cm^–2·s^–1 The following minor and trace element constituents have been determined: Na, K, Ca, Fe, Sc, Cr, Co, Zr, Ce, La, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Th and U.     

Determination of impurities in high-purity solvents by neutron activation analysis

The determination of impurities in high-purity solvents, (acetone, isopropanol, trichloroethylene and trichlorotrifluoroethane) used in the production of integrated circuits was carried out by reactor neutron activation analysis. A special vacuum evaporation technique was used for the preconcentration of the solvents. The results showed that sodium and iron are the main impurity components in the solvents and on the other hand the quality of the solvents satisfies the specifications required by high-technology standards. The suspended solid particles in solvents were counted by a Microscopic Image Analysis System (MIAS).     

Determination of copper in high-purity tin by reactor neutron activation analysis

For the determination of very low concentrations of copper in tin, an analytical method involving reactor neutron activation was developed whereby the copper activity was separated from the tin matrix by extraction of the Cu(I) cuproin complex in n-amyl alcohol. A new decontamination technique was sought in order to remove the copper contamination present on the tin surface. Pre-irradiation removal of the tin surface combined with post-irradiation etching appeared to be the most efficient.     

Overall instrumental thermal neutron activation analysis of high-purity materials

A more or less routine method for the determination of up to 55 trace elements down to the ppb range is described. To obtain this, irradiation in a high thermal neutron flux, followed by Ge(Li) γ-spectrometry with large detectors and off-line computerized evaluation of the spectra, is necessary. To cover the range of halflives of the nuclides formed, spectrum measurements are carried out about one hour, one day, one week and one month after irradiation. Only in the case of highly active and rather long-living matrices is chemical separation of the matrix from all impurities necessary. The computer program is written in ALGOL-60.     

Determination of impurities in titanium and titanium dioxide by neutron activation analysis : Simultaneous determination of 16 trace elements in titanium

The most important metallic impurities in titanium which give long-lived isotopes on neutron irradiation can be determined by a rapid anion-exchanged seperation of Ti, Sc, Cr, Na and Ag, after which the resin, containing most of the impurities, is counted on a high-resolution Ge(Li) γ-spectrometer. Cu, W, As, Ga, Au, Sn, Fe, Zn, Co, Ta, Mo and Ni can be determined in one measurement, while Na, Cr and Ag can be determined after an additional separation from the Sc isotopes, the major activities originating from the titanium on neutron irradiation. Three different samples were analysed five times, and the reproducibility of the results was good.     

Multi-element analysis of japanese tea leaves by neutron activation analysis and the single comparator method

The reliability of the single comparator method in neutron activation analysis has been studied by comparing the calculated and experimental k values and by determining the concentration of trace elements in iron. The method has been applied to the analysis of tea leaves for thirteen elements; their concentrations varied over five orders of magnitude.     

Determination of impurities in titanium and titanium oxide by radiochemical neutron activation analysis

A radiochemical neutron activation analysis has been applied to 2N–4N grade titanium metal and its oxide. Twenty two impurities were separated in a group from scandium by a radiochemical separation method using cation exchange resin with HBr and HCl. The contents of the elements were calculated by a single comparator method using two monitors. The analytical results agree well within 10% deviation with those obtained by instrumental method. Eighteen elements, Na, Fe, Co, As, Se, Sr, Mo, Sb, La, Eu, Tb, Yb, Lu, Hf, Ta, W, Th and U, are determined in titanium oxides and 17 elements, Na, Cr, Fe, Co, Se, As, Zr, Mo, Sb, Cs, Ce, Tb, Yb, Hf, Ta, W and Th, in titanium metals.     

Extraction-chromatographic system TBP-HBr in radiochemical neutron activation analysis of high-purity materials

The extraction and extraction-chromatographic behaviour of a variety of elements in the TBP-HBr system with concentrations from 0.1 to 7M HBr has been studied. The results allowed the development of simple procedures for radiochemical neutron activation determination of 22 impurity elements (Na, K, Sc, Cr, Mn, Fe, Co, Ni, Cu, Ga, As, Se, Rb, Sr, Zn, Mo, Ag, Sb, Te, Ba, La, Hf and W) in high-purity cadmium and indium samples with detection limits from 1 g g^–1 for Fe and Zr to 0.01 ng g^–1 for Na, Sc, Mn with relative standard deviations < 0.15. To increase the selectivity of the extraction-chromatographic separation, use was made of extraction suppression and co-extraction effects. The procedure for the extraction-chromatographic separation of scandium from a number of other elements is described as an example. The procedure can be used for simultaneous quantitative separation of impurity radionuclides from radiation produced long-life scandium radionuclides in the neutron activation analysis of titanium and vanadium.     

Elemental characterization of mineral supplements by neutron activation analysis

Instrumental neutron activation analysis (INAA) was applied to assess element concentrations in eleven samples of mineral supplements/multivitamins acquired in drugstores and pharmacies in São Paulo city, SP, Brazil. Concentrations of Ca, Co, Cr, Cu, Fe, K, Na, Se and Zn were determined. A comparison was made between the results obtained with the labels of the mineral supplents. Certified reference materials, NIST SRM1400 Bone Ash and NIST SRM 1633b Coal Fly Ash were analyzed for quality control of the analytical results.     

Chemical characterization of graphite by instrumental neutron activation analysis

Nuclear and commercial grade graphite samples were analysed by instrumental neutron activation analysis (INAA) using high flux reactor neutrons. Eleven elements (Na, K, As, Sc, Fe, Cr, Co, Zn, La, Ce, and Sm) were determined in eight samples of graphite (two nuclear grade and six commercial grade) by irradiating at a neutron flux of 3?×?10¹³ cm^?2 s^?1 in CIRUS reactor and assaying the activity by high-resolution gamma ray spectrometry using 40% relative efficiency HPGe detector coupled to an MCA. Concentrations of elements were determined by relative method of INAA. Results of both types of graphites as well as detection limits achieved by INAA method are discussed in the paper.     

Investigation of silicon dioxide films by neutron activation analysis and autoradiography

Investigations of insulating silicon dioxide films formed on silicon epitaxial layers are reported. Activation analysis and surface autoradiography were used to determine the concentration distribution and precipitation of contaminants in the internal part of the films and on the surfaces. The aim of this work was to study the origin of the contaminants by sampling each technological product following thermal oxidation, doped oxide deposition, heating and metallizing. Under the given conditions the following detection limits of impurities could be obtained in silicon dioxide films: Na=80 ppb, Sb=100 ppb, Cu=20 ppb and Au=5 ppb.     

Trace element determination in high-purity scandium by neutron activation analysis and pre-irradiation matrix separation

A pre-irradiation separation procedure has been developed for the determination of trace elements in high-purity scandium by neutron activation analysis. The sample is dissolved in high-purity concentrated hydrochloric acid and scandium is extracted with the same volume of a solution of 50 vol.% bis(2-ethyl hexyl)-orthophosphoric acid (HDEHP) in toluene. The scandium matrix is removed from the most important trace impurities and the residual amount of Sc is in the range of 0.001%. The separation is carried out in the vial to be used in irradiation to prevent sample contamination. Detection limits in the ppb range were achieved with a sample of 10 mg, a thermal neutron flux of 2 · 10¹³ n · cm^–2 · s^–1 and an irradiation time of 48 hours. Most of the elements sought in two samples of high-purity scandium were below the detection limits.