The single comparator method has been extended to a triple comparator method, using60Co,114mIn and198Au. In this technique, thek-ratios of the elements to be analyzed, now determined against the three comparators, are corrected for each new ratio of
thermal to epithermal reactor neutron flux. These flux ratios are calculated from the absolute activities of the three comparators.
The thermal neutron activation cross-section and the resonance integral for the reaction113In(n,γ)114mIn have been determined.
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.
The triple comparator method is used for the analysis of impurities of high purity silicon by neutron activation. The ratios
of the specific photopeak activities of the isotopes investigated to the specific photopeak activities of the gold, indium
and cobalt comparators were determined. The triple comparator method avoids some tedious problems in the multi-element activation
analysis and it is very well suited for the determination of ‘non-expected’ elements.
Authors:F. De Corte, A. Simonits, A. De Wispelaere, and J. Hoste
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.
Authors:A. Simonists, F. De Corte, A. De Wispelaere, and J. Hoste
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
. 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.
Authors:B. Smodiš, F. De Corte, and A. De Wispelaere
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.
Authors:F. De Corte, A. Simonits, and A. De Wispelaere
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.
Authors:F. de Corte, A. Simonits, A. de Wispelaere, and A. Elek
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.
Authors:F. De Corte, E. Steinnes, P. de Neve, and A. Simonits
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,)]141Ce, and164Dy[(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.
Authors:A. Simonits, F. De Corte, L. Moens, and J. Hoste
Isotopic abundance values for50Cr,58Fe and109Ag and the absolute gamma-intensities for51Cr,59Fe and110mAg were evaluated. These evaluated data, together with experimental k0-determinations (i.e. from the