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Activation analysis of high-purity silicon
III. Multi-element activation analysis: Application of the triple comparator method
Abstract
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.
Abstract
Based on recently measured k0-factors and related nuclear data, an evaluation was performed, via the `activation method', of thermal (n,
) activation cross sections. It concerns 15 analytically-relevant cases with a short half-life and/or with a complex activation-decay scheme: 20F, 41Ar, 60mCo/60Co, 71Zn, 77mSe, 80mBr/80Br, 104mRh/104Rh, 109mPd/109Pd/109mAg, 110Ag, 122mSb/122Sb, 124m2Sb/ 124m1Sb/124Sb, 134mCs/134Cs, 179mHf, 199mPt/199Pt/199Au and 205Hg.
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.
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-g
1, 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.
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
limit.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.
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.
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.
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.
Abstract
The infinite dilution resonance integrals of fifteen (n,γ)reactions leading to the production of short-lived radioisotopes were determined. The irradiation parameters were checked by comparing the results of different methods and the measuring equipment was carefully controlled.
