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Abstract  

In order to provide a tailored solution for the correction of the 235U interference in k0-NAA, fission k0-factors for the analytically relevant radionuclides/gamma-lines (versus gold as the comparator), are experimentally determined in four channels of the Gent THETIS reactor. A comparison is made with former data from the literature. The new evaluated results are to be implemented in the forthcoming upgrade of the DSMKayzero software package for k0-NAA.

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Abstract  

A critical evaluation of different comparator methods is given. The method based on experimentally-determined and convertible comparison factors (k) is considered to be the most suitable for general use. An alternative method is proposed, introducing generalized k0 factors which are independent of irradiation and measuring conditions. This approach combines the simplicity of the absolute methods with nearly the same accuracy attained by the relative ones. It is suggested that k0 factors be compiled in all cases when using single-comparator methods, to allow a continuous re-evaluation.

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Activation analysis of high-purity silicon

II. Multi-element analysis: Separation scheme for 21 elements

Journal of Radioanalytical and Nuclear Chemistry
Authors:
F. De Corte
,
A. Speecke
, and
J. Hoste

Abstract  

A method for the simultaneous determination of 21 elements in high purity silicon was developed by activation analysis. Extraction, ion exchange, distillation and precipitation techniques were used combined with NaI(Tl) and Ge(Li) γ-spectrometry. Attention was paid to the separation time, sensitivity and selectivity of the method.

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Abstract  

The present paper deals with the accuracy and applicability of the k0-standardization technique in NAA. Topics included are: user-oriented outline of the method, relevant nuclear data (k0, Q0, tc.), the non-1/E epithermal flux distribution, small detector separations and/or extended source geometries, (n, ) reactions with a Westcott-g1, primary interferences, subsequent (interrupted) irradiations, the non-constancy of the neutron flux during irradiation, and a final account of the accuracy. Although the paper is written in terms of the k0-methodology, a good deal of the considerations can be transferred to most types of single-comparator standardization.

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Abstract  

The determination of k0-factors has been continued covering now the relevant gamma-lines of 112 analytically interesting radionuclides. Experimental details are given, and an extended tabulation is presented of complex activation decay types and the associated expression for the parameters involved in the k0-method.

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Abstract  

An investigation is made of the importance of (n,,n, ) second-order reaction interferences in reactor neutron activation analysis (NAA), in addition to the commonly considered (n, , ; n, ) interferences. The algorithms for the calculation of the interference are derived from the Bateman-Rubinson equation, taking into account the formation of all m-and g-states involved bum-up effects, and the growth of the interfering radionuclide after irradiation due to a mother-daughter relationship. The following practical cases are examined in detail:138Ba 140La (detemination of La in presence of excess Ba),139La 141Ce (Ce in La),164Dy 166Ho (Ho in Dy),186W 188Re (Re in W) and192Os 194Ir (Ir in Os). A computer search was done for the nuclear data involved in the computation. For139La[(n,; n,; )+(n,; ; n,)]141Ce, and164Dy[(n,; n,; )+ (n,; ; n,)]166Ho experimental checks were performed in the Budapest Research Reactor, which confirmed the calculations showing that the (n,; n,; ) interference gives the largest contribution to the apparent concentration of Ce in La and of Ho in Dy, respectively.

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Abstract  

In order to establish more accurate nuclear data for the zirconium isotopes94Zr and96Zr, joint experimental work has been conducted in three different reactor types. After carefully calibrating the neutron spectra in the irradiation channels used, nuclear constants k0 and Q0 were remeasured and found to be The relevant effective resonance energies
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\bar E_r$$ \end{document}
have been recalculated using the latest BNL neutron resonance parameters yielding
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\bar E_r (^{94} Zr) = 6260 eV ( \pm 4\% ) and \bar E_r (^{96} Zr) = 338 eV ( \pm 2\% )$$ \end{document}
. The epithermal neutron shielding factor Ge has been experimentally determined as a function of foil thickness. The results gave Ge(94Zr)=0.983 (±0.3%) and Ge(96Zr)=0.973 (±0.4%) for the most frequently used 0.125 mm foil thickness. Finally the half life of the97Zr isotope has also been remeasured to give T1/2(97Zr)=16.744±0.011 h with 1 limit.
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Abstract  

In the present paper, a tabulation is given of recommended Q0-values [the ratio of the resonance integral (I0) to the 2200 m·s–1 cross-section ( 0)] for 107 (n, ) reactions of interest in NAA, including a revision and updating of formerly published results for 57 isotopes. The values were either critically evaluated from literature, or-in the majority of cases — experimentally determined according to the Cd-ratio method, with a correction for a non-ideal epithermal neutron flux distribution. These Q0-measurements were performed at INW, Gent, at KFKI, Budapest, and occasionally at Risø. A comparison is made with results obtained by other workers or with values derived from 0's and I0's quoted in recent compilations.

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Abstract  

Although k0-factors and related nuclear data for 122 radionuclides of interest in (n,) reactor neutron activation analysis have been tabulated, there are still some reactions attracting interest with respect to the accuracy of the literature data. The present paper deals with the reaction130Ba(n,)131Ba, for which a more accurate half-life is proposed, together with re-evaluated Q0 and k0 factors. The new values are 11.53 days for T, 21.3 for Q0, and for the k0's 3.90×10–5, 2.75×10–5, 1.92×10–5 and 6.48×10–5 for the -rays at 123.8 keV, 216.1 keV, 373.2 keV and 496.3 keV, respectively.

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Abstract  

By comparison of experimental k0-factors, determined in reactor positions with greatly different thermal-to-epithermal neutron flux ratios, and by comparison of experimentally determined and theoretically calculated k0-factors, it is possible in some cases to select best values from literature data for (n, γ) activation cross-sections and for absolute gamma intensities. This is demonstrated for97Zr,95Zr,56Mn and65Zn.

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