共查询到20条相似文献,搜索用时 15 毫秒
1.
A. G. Elayi 《Journal of Radioanalytical and Nuclear Chemistry》1985,90(1):137-144
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. 相似文献
2.
R. Van Grieken A. Speecke J. Hoste 《Journal of Radioanalytical and Nuclear Chemistry》1973,13(1):225-233
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. 相似文献
3.
S. Taczanowski 《Journal of Radioanalytical and Nuclear Chemistry》1972,12(1):535-542
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. 相似文献
4.
A detailed theoretical treatment of cyclic activation analysis of thorium and uranium using a 14 MeV neutron generator and
delayed neutron counting is presented. Variations of the detector response with sample transfer and total experiment times
are examined in order to obtain the optimum cycle periods for the maximum detector response. Cycle optimization for 95% and
90% of the maximum detector response is investigated. Furthermore, elimination of the delayed neutrons produced by the reaction17O(n,p)17N is also considered in optimum cycle timing. Finally, calculations are carried out to estimate detection limits for thorium
and uranium. Experimental results will be reported in a subsequent paper. 相似文献
5.
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. 相似文献
6.
G. C. Meggitt 《Journal of Radioanalytical and Nuclear Chemistry》1979,48(1-2):105-116
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. 相似文献
7.
A. G. Elayi 《Journal of Radioanalytical and Nuclear Chemistry》1977,35(2):377-382
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. 相似文献
8.
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. 相似文献
9.
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. 相似文献
10.
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. 相似文献
11.
Z. Idiri M. Siad B. Kaddari L. Omari M. Seghir A. Zerrouki 《Journal of Radioanalytical and Nuclear Chemistry》1993,169(2):283-289
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. 相似文献
12.
The conventional method of measurement in 14 MeV activation analysis is to employ gamma-ray spectrometry. The method has the
advantage of good selectivity but this is at the expense of sensitivity. In order to improve sensitivity the authors have
employed Cerenkov counting techniques and by the careful use of absorbers in a specially designed cell together with double
decay procedures have still retained a considerable degree of selectivity. The method has been applied to neutron flux measurement
and to the majority of the elements in the periodic table. 相似文献
13.
M. Berrada M. A. Misdaq P. Thalouarn 《Journal of Radioanalytical and Nuclear Chemistry》1979,54(1-2):361-366
The applicability of 14 MeV neutron activation analysis for the determination of K in beet has been investigated by measuring
the 2.167 MeV gamma-line from the decay of38gK produced in the39K(n, 2n) reaction. Beet samples were treated in different solutions of KCl and HgCl2 to study the diffusion of K+ ions into the beet cells. The contribution of the gamma-line to the measured peak area from38Cl produced in the37Cl(n, γ) reaction was found to be 1%. Results obtained by fast neutron activation analysis and by flame spectrometry have
been compared, and good agreements were found. 相似文献
14.
The Si-contents of flue-dust and sedimented dust from Czechoslovak mines were determined by instrumental activation analysis
with 14 MeV neutrons using a flux of 107 cm−2·s−1. The amounts determined range from 3 to 30 mg. 相似文献
15.
A method has been developed for determining silicon in aluminium by fast neutron activation. It is based on the separation
of two gamma lines by a Ge(Li) detector: the 1.73 MeV line from the product of27Al(n, α)24Na and the 1.78 MeV line from the28Si(n, p)28Al reaction. In the case of aluminium-silicon alloys 100 μg silicon can be determined, with an error of 10% in an aluminium
sample of 1 g.
This work was supported in part by the International Atomic Energy Agency. 相似文献
16.
The method of simulation of gamma-spectra based on the experimental library spectra of particular radioisotopes is described.
The library spectra were obtained by activation of pure element sample with the use of a 14 MeV neutron generator, counting
them with a NaI(T1) scintillation spectrometer and decomposing of mixed spectra to spectra of separate radioisotopes. The
simulated and measured spectra of an artificial sample are compared. 相似文献
17.
L. S. Chuang D. A. Miller W. P. Lay W. Y. Chiu 《Journal of Radioanalytical and Nuclear Chemistry》1977,38(1-2):279-289
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. 相似文献
18.
A. G. Elayi 《Journal of Radioanalytical and Nuclear Chemistry》1983,76(1):203-213
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. 相似文献
19.
C. C. Hayward G. Oldham A. R. Ware 《Journal of Radioanalytical and Nuclear Chemistry》1971,7(2):341-346
The feasibility and advantages of fast neutron activation analysis in a non-aqueous flowing system, using economical irradiation
techniques are outlined. The application of the method to the determination in solution of elements producing isotopes with
half lives in the range 588—29.4 sec, the selection of the optimum flow rate to minimise interferences for each element, and
their limits of detection are also given. A method for the prediction of the optimum flow rate, on a given system, for the
determination of any element producing an isotope of known half life is also given. 相似文献
20.
V. N. Bhoraskar S. Y. Mahajan S. S. Jayanthakumar V. D. Gogate 《Journal of Radioanalytical and Nuclear Chemistry》1985,95(2):73-79
Ancient iron objects excavated from five different sites around Nagpur city in Maharashtra State /India/ were cut into small pieces and samples were prepared. Each sample was irradiated with 14 MeV neutrons for 8 min. From the recorded gamma ray spectrum for each sample, the presence of trace elements Cu, Si, Al, Mg and Mn were detected and their mutual ratios of activities were determined. The results show that all the iron objects obtained from five different sites are of the same origin. 相似文献