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Abstract  

A non-destructive method has been developed for the precise and accurate determination of Sn in cassiterite ores. Irradiation is performed by means of a 6.6 Ci227Ac−BE isotopic neutron source with a total neutron output of 108 n·sec−1. Samples are pellets pressed from a mixture of cassiterite powder and wax as a binding material. With a 4 hrs analysis time and a relative precision of 0.45%, the new method is faster and at least as precise as any existing destructive chemical method. The accuracy is proved to be better than that of the commonly used iodimetric titration method.

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Abstract  

The determination of boron in rocks by charged particle activation using the10B(d, n)11C reaction is studied. A sample holder that allows reproducible irradiation of powdered samples is developed.11C is separated as11CO2. For boron concentrations between 2.35 and 25.2 μg·g−1, the standard deviations ranges from 7.1 to 22.8%. The results for USGS reference silicate rocks and Moroccan phosphate rock are compared to those obtained by other techniques.

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Abstract  

A method has been developed to routinely analyse managanese ores and ferro-manganese, by neutron activation making use of a cylindrical 1 Ci226Ra−Be source. A description of the source, the moderator and the pneumatic irradiation facility is given. The irradiation position has been optimized for minimum flux gradients and maximum reproducibility. Samples and standards consist of pellets pressed from a mixture of powdered material and graphite weighing approximately 5 g. Samples and standards alternatively go through a sequence of 20 min irradiation, 20 min decay, and 20 min counting. Pyrolusites containing from 30 to 55% Mn and ferro-manganese containing approximately 80% Mn have been analysed with a precision of 0.1% absolute.

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Abstract  

The neutron flux distribution in the vicinity of 30, 20 and 10 mm diameter targets is measured by irradiating concentric ring-type iron monitors at different distances from the target and counting the induced56Mn activity. Considering the many uncertainties, satisfactory agreement was found between theory and experiment.

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Abstract  

The single comparator method has been extended to a triple comparator method, using60Co,114m In 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)114m In have been determined.

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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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Abstract  

Owing to the high ratio of resonance integral to thermal neutron activation cross-section of238U, a 5 min epithermal neutron irradiation under cadmium shielding, followed by measurement of the 74 keV photopeak of239U with a high resolution low-energy photon Ge(Li) detector, allows the fast determination of uranium in aerosols collected on a Whatman 41 cellulose filter. Uranium blanks of the cellulose filter paper require correction and limit the sensitivity. Simultaneously the concentrations of the elements cobalt, bromine, antimony and indium can be determined. In Belgium, the uranium concentrations of the aerosols were found to be constant and comparable to the uranium contents of rocks.

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Activation analysis of high-purity silicon

I. Determination of phosphorus

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

Abstract  

32P was separated from the irradiated silicon matrix as ammonium phosphomolybdate and the activity was measured with a GM tube or on a plastic scintillator. The second-order interference was taken into consideration.

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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  

A method is described for the determination of Au, Pt, Pd, Ag and Ir in two atmospheric aerosol samples, namely in Ghent and in the Milanese intercomparison sample. After neutron irradiation the samples are fused with Na2O2. Gold is extracted with ethylacetate, Pt precipitated as (NH4)2PtCl6 Pd as dimethylglyoximate, Ag as chloride and Ir separated by anion-exchange adsorption and batch extraction. Ge(Li) gamma-spectrometry is applied for all determinations. The concentrations in ng·g−1 in the samples are respectively: Au: 49 and 3000; Pt: below 100 for both samples; Pd: 7 and 28; Ag: 6000 and 14 000; Ir: 2.5 and 1.3.

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