Utilization of characteristic X-rays in 14 MeV neutron activation analysis

The possibility of the use of characteristic X-rays, emitted after IT of EC type of radioactive decay, for analytical purposes in 14 MeV neutron activation analysis was investigated. Elements from Cr to U were theoretically considered and 24 of them experimentally examined. The results showed usefulness of the technique for several elements in spite of the troublesome selfabsorption effect. It is expected that the 0.1% determination limit can be achieved for the most suitable elements.     

Elimination of interelement effects in the determination of bromine by 14 MeV neutron activation analysis based on characteristic X-ray measurements

The problem of converting measured intensities into mass concentrations arises from the fact that the measured intensity of a characteristic X-ray line of an element or compound depends not only on the mass concentration of that element or compound but also on the nature and abundance of the other constituents of the specimen. In this work the empirical coefficient method which comprises both absorption and enhancement effects of each element on each other element by parameters independent of mass concentrations was used for correction of enhancement effects from antimony and praseodymium on bromine in two groups of samples. The results of analysis of bromine shows a relative error of not more than ±4%.     

Precision in 14 MeV neutron activation analysis

The errors of analysis due to the different parameters involved in 14 MeV neutron activation analysis method are studied. Formulae to calculate these erros have been developed when possible. Otherwise they have been evaluated for special experimental situations. Special cases where some parameters become critical, as far as precision is concerned, have been mentioned.     

Optimum sample shape for 14 MeV neutron activation analysis

Based on the criteria of the maximum induced activity, the problem of the optimum sample shape was analyzed for a given volume of sample. Its shape was assumed to be cylindrical and the optimum values for the height-to-diameter ratio (presented in the included tables) were calculated under various circumstances. Coaxial and perpendicular sample—target irradiation geometries were considered.     

Geometry errors in 14 MeV neutron activation analysis

The effects of inaccurate sample sizes and sample positioning on 14 MeV neutron activation analysis results are estimated for 30, 20 and 10 mm diameter targets. It appears that axial positioning is the most critical parameter and that using a larger tritium target will yield an overall improvement of the reproducibility. Aspirant of the N.F.W.O.     

14 MeV neutron activation analysis of gold jewellery

Samples of nominal 18 carat and 21 carat gold jewelleries from the local market were non-destructively bulk analyzed using neutron activation analysis. Neutrons of 14 MeV energy were used with a fast pneumatic sample transfer system. The actual gold contents, as well as the composition of the base metals in these samples were determined. The fast neutron activation was found to be an efficient, quick and accurate method of characterizing the precious metal objects routinely in bulk, with a large sample throughput. The results demonstrate the commercial availability of the technique for non-destructive bulk analysis of precious metal objects.     

14 MeV neutron activation analysis using short-lived products

Cyclic activation using pneumatic shuttling system and switch off and on the neutron source and detector are described in order to eliminate some uncertainties by the provision of more accurate timing, the measurement of the effective activating neutron flux and the correction for the detection system dead time.     

Enhancement effect in 14 MeV neutron activation based on X-ray spectrometry

The intensity of characteristic X-rays emitted from one element may be reduced by partial absorption by other elements in the matrix, or alternatively it is enhanced by their presence. In this work the enhancement effect of antimony on bromine, cadmium and selenium are given. The dependence of the specific activity of each element /Cd, Br and Se/ on the ratio of the weight of Sb to that of the element is given, when the concentration of Sb is not very low /-5%/.     

14 MeV neutron activation analysis of ternary copper ilver selenide by X-ray and gamma-ray spectrometry

14 MeV neutron activation of ternary copper silver selenide gives rise to a predominant activity from the 0.511 MeV annihilation peak from the three elements when -ray spectrometry is used. To overcome the interference problems, X-ray spectrometry was applied to the simultaneous nondestructive determination of silver and selenium, after which copper can be determined by -ray spectrometry. The results of analysis show a relative error not higher than ±5%, when the samples were diluted with H₃BO₃ /90%/ to minimize the interelement effects.     

Gamma ray spectra and sensitivities for 14 MeV neutron activation analysis

The purpose of this study was to define experimentally the sensitivity of determination for 63 different elements by 14 MeV neutron activation, with a 150 kV Cockroft-Walton accelerator at a neutron flux of 2·10⁸ n·cm⁻²·sec⁻¹ on the sample. The obtained gamma ray spectra are given, and the origin of the photopeaks observed are explained. A maximum irradiation time of five minutes was used as a convenient experimental limit to obtain the maximum sensitivity, considering, however, that the tritium target life is limited, and that the time to perform an analysis has to be reasonable. The practical use of 14 MeV neutron activation analysis is demonstrated by the detection limits obtained.     

Calculated screening effect in 14 MeV neutron activation analysis

The screening effect produced by a sample upon a standard located behind it is calculated. Curves for the secreening effect as a function of the sample material and of the sample depth are given.     

The 14 MeV neutron activation analysis of Chinese foodstuffs for protein content

A method for determining protein content in foodstuffs by 14 MeV neutron activation analysis for nitrogen is described. The procedure proves to be quite precise, and potentially quite accurate, while only requiring about 7 min per sample. The effect of interfering activities is discussed, and corrections for³⁰P and³⁸K are described. The protein determinations for over 40 Chinese foodstuffs are given.     

Determination of total oxygen in standard rocks by cyclic activation analysis using a 14 MeV neutron generator

Total oxygen, in fourteen rock standards and three ores, was determined with an experimental set up employing cyclic activation analysis using a 14 MeV neutron generator gamma-spectroscopy and NaI(T1) detectors.     

Precise timing in program-controlled data acquisition for 14 MeV neutron activation analysis

A solution for the automation of a fast pneumatic transport system and its application is given.     

14 MeV neutron activation analysis of chicken dung and dates

Simultaneous determination of N, Mg, Al, Si, P, Cl, K, Ca and Fe in chicken dung and dates was carried out using fast neutron activation analysis (FNAA) with a SAMES J25 neutron generator. The activities were measured with a 72 cm³ high purity germanium detector using the relative method. The accuracy was checked with the aid of a standard reference material of milk powder A11 supplied by the IAEA. For the nitrogen contents, the results were compared to those obtained by the classical KJELDAHL method.     

Sulfur determination in coal by 14 MeV neutron activation analysis

A procedure involving the irradiation of coal samples with 14 MeV neutrons and subsequent gamma-ray spectrometry of the irradiated sample for the estimation of solfur in coal, has been outlined. The samples were irradiated with 14MeV neutrons from a Cockroft-Walton type generator for one minute and then subjected to gamma-ray spectrometry for another minute using an automated transfer cyclic system. Ten such cycles were repeated for accumulating events under the 2130 keV gamma ray photopeak belonging to³⁴P (T=12.4 s) produced by the³⁴S(n, p)³⁴P reaction for assessing the lower level of detection, LLD, of Sulfur. Interferences due to the presence of other elements in coal were also determined. Sulfur can be determined at LLD of 0.25% in coal provided a 5 g sample of the coal is irradiated with a neutron flux of 5·10⁹ n·cm⁻²·sec⁻¹ assayed with a gamma ray spectrometer having a large hollow core Ge(Li) detector and an anti-Compton shield.     

Simultaneous determination of four components by X-ray spectrometry after 14 MeV neutron activation

14 MeV neutron activation followed by X-ray spectrometry was applied to the simultaneous nondestructive determination of cadmium, antimony and bromine, utilizing praseodymium as an internal standard. The results of analysis show a relative error not higher than ±5%, when the samples were diluted with H₃BO₃ -5% to minimize the interelement effects.     

Reactor neutron activation analysis followed by characteristic X-ray spectrometry

The possibility of applications of characteristic X-rays from radioactive products of reactor neutron activation was investigated with particular emphasis on (n, ), n, n), (n, 2n), (n, p) and (n, ) products with long half-lives. The sensitivity and detection limits of silver, cerium, gadolinium, selenium, cadmium and europium have been investigated. The elements were studied both in a pure and in a matrix form, in both cases the samples were diluted with graphite (90%) to minimize matrix effects (absorption and enhancement).     

Reactor neutron activation analysis based on characteristic X-ray spectrometry

The possibility of using characteristic X-ray from radioactive products of reactor activation was investigated with particular emphasis on /n,/, /n,n/, /n,2n/, /n,p/ and /n,/ products with long half lives. The characteristic X-rays emitted are a result of electron capture or internal conversion processes during isomeric transition. First of all the sensitivity and detection limits were investigated.     

Calculated gamma-ray and/or neutron attenuation coefficients in 14 MeV neutron activation analysis

A program of theoretical and experimental work was performed to develop a mathematical model which can represent all the parameters of the neutron activation analysis operation. However, we avoid absolute technique by using a sample containing the same element as the reference but having a different geometry and weight. In the present work we apply this model to determine the neutron, gamma-ray and neutron-and-gamma-ray self-shielding of the sample in relation with the number of counts in the total absorption peak. However the results obtained should be applied within the limitations of the method.