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  • Author or Editor: V. Krivan x
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Abstract  

This table enables a quick estimate of the primary reaction interferences which can occur in 14-MeV neutron activation analysis for all determinable elements throughout the periodic system. Published experimental cross-sections, and cross-sections estimated by semiempirical formulae and systematics were used to calculate the ratio of the radioactivity produced from the element to be determined via the principal reaction and of the radioactivity produced via the primary interference reaction for three energy intervals between 14 MeV and 15 MeV. Also listed are the used cross-section data and abundances of the appropriate isotopes for both the element to be determined and the interfering element, as well as the half-lives of the indicator radionuclides.

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Abstract  

Proton activation analysis has been applied to develop a procedure for the simultaneous determination of chromium, nickel and copper. The procedure involves the bombardment of the sample with protons to induce52Cr(p, n)52mMn,60Ni(p, n)60Cu and63Cu(p, n)63Zn reactions. These reactions have been studied for proton energies from 11 MeV to 15 MeV. Thick target yields for the production of the indicator radionuclides as well as the sensitivities of the determination have been measured in this energy region and are compared with results obtained for other charged particle induced reactions. Detailed data are given on nuclear and instrumental interferences. The trace elements have been determined nondestructively and simultaneously in cobalt with a relative precision of 8 to 15%.

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Abstract  

Instrumental and radiochemical neutron activation analysis has been applied to a comprehensive trace characterization of AlSiCu sputter targets. By instrumental neutron activation analysis via long-lived indicator radionuclides, up to 33 elements were assayed with detection limits between 0.01 and 200 ng·g–1. The high activity of64Cu and24Na produced from the matrix significantly limits the instrumental performance via short- and medium-lived indicator dionuclides. For this reason, a radiochemical separation was developed based on adsorption of24Na on hydrated antimony pentoxide and extraction of64Cu by diethylammonium diethyldithiocarbamate from HCl medium. By this radiochemical method, As, Ga, K, La, Mn, Mo, Re, Sb, U and W could be assayed via medium-lived radionuclides and the achievable limits of detection were between 0.1 and 25 ng·g–1. Further improvement of detection limits for U and Th was achieved by a selective radiochemical separation of239Np and233Pa on a Dowex 1×8 column in HF and HF/NH4F medium providing limits of detection for U and Th of 0.06 and 0.02 ng·g–1, respectively. These techniques were applied to the analysis of two AlSiCu sputter target materials. Results are compared with those of glow discharge mass spectrometry.

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Abstract  

A systematic study of activation analysis with cyclotron-produced neutrons for (n, 2n), (n, p) and (n, α) reactions is presented. The limits of detection for elements of atomic number from 6 to 80 are given. The possibilities of optimization of irradiation conditions by the choice of the most suitable neutron spectrum are discussed. The potential of this fast neutron activation analysis method is compared with that of 14 MeV neutron activation analysis.

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Abstract  

The behaviour of the elements As, Ba, Cr, Fe, Eu, Hf, La, Mo, Nb, Pa, Re, Sb, Sc, Sn, Ta, Tc, W, and Zr on Dowex-1X8 in 0.1 to 29.5M HF and mixed solutions of HF and NH4F of different concentration combinations varying for both reagents from 0.1 to 10M has been studied. The influence of the ionic form of Dowex-1 on the distribution of elements has also been examined. The distribution ratio for the mixed solutions are given in form of adsorption contour lines.

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Abstract  

Distribution ratios for As(V), Fe(III), Sb(V), Sc, Sn(IV), Mo, W, Tc(VII) and Re(VII) in the system Dowex-1X8 and 0.1–11.5M HCl, and Dowex-1X8 and the mixture of HF and HCl with HF concentrations varying from 0.1M to 20M and HCl concentrations from 0.1 to 10M have been measured. The distribution ratios for mixed solutions are presented in form of adsorption contour plots. The connection between the possible composition of the adsorbable complexes and the character of the respective contour plots is discussed.

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Abstract  

A radiochemical neutron activation technique for the detemination of 19 elements in high purity tungsten has been developed. It is based on extraction with diantipyrylmethane (for tantalum and antimony), substoichiometric extraction of molybdophosphate (for phosphorus) and anion-exchange chromatography (other elements) in hydrofluoric acid medium. The results obtained and achievable limits of detection are given. The effects of self-shielding and nuclear interfering reactions are discussed.

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Abstract  

Three different methods for pre-irradiation separation of the tantalum matrix combined with preconcentration of trace elements for NAA were developed. They involve selective extraction of tantalum with diantipyrylmethane, and anion- and cation-exchange from hydrofluoric acid medium. The role of the blank as the limiting factor for limits of detection and accuracy was one of the main aspects of this investigation. A conventional radiochemical NAA based on post-irradiation separation of the matrix radionuclides was also applied. The trace elements considered were Ag, Ba, Ce, Co, Cr, Cu, Eu, Hf, K, La, Mn, Mo, Na, Rb, Re, Sc, W, Y, Zn, Zr. The methods were used for the analysis of tantalum materials of different purity grades. The advantages and disadvantages of each technique are discussed and the achievable limits of detection are given.

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Abstract  

The sorption of niobium and tantalum on Dowex-1 and open-cell polyurethane foam polyether-type in HF–H2SO4 and HF–HCl medium has been investigated. The mechanism of the sorption as well as the composition of adsorbable complexes is discussed. A selective adsorption of tantalum was achieved from solutions, in which the concentration range of HF was 0.05–2M, of H2SO4 5M and of HCl4M. The most interesting separation possibilities have been tested under dynamic conditions.

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Abstract  

Anion-exchange data have been obtained for the elements As, Hf, Mo, Nb, Pa, Re, Sb, Sn, Ta, Tc, W, and Zr in 0.1 to 10M H2SO4 and in HF–H2SO4 mixtures of combination extending from 0.1 to 10M HF and from 0.1 to 10M H2SO4. The distribution ratios for mixed solutions are presented in form of adsorption contour lines.

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