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1.
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
2.
Photonuclear activation and high resolution gamma spectrometry have been used to determine nondestructively 28 trace elements
in coal. The samples and synthetic multielement standards were simultaneously irradiated in the bremsstrahlung beam at 18
and 30 MeV maximum energies. Taking into account the contribution of the main possible interferences, limits of detection
between 0.2 and 125 μg·g−1 were obtained.
Stagiaire Etranger au C. E. A. 相似文献
Stagiaire Etranger au C. E. A. 相似文献
3.
W. J. Naudé M. Peisach R. Pretorius P. J. Strebel 《Journal of Radioanalytical and Nuclear Chemistry》1968,1(3):231-241
Carbon, nitrogen and oxygen were determined in gases by time-of-flight spectrometry of prompt neutrons from the respective
reactions12C(d, n)13N,14N(d, n)15O and16O(d, n)17F, produced by a pulsed beam of deuterons of 2 MeV (for nitrogen) or 3 MeV. The analysis is non-destructive and requires about
15 min. per sample. The relative standard deviation for all three elements was about ±3%. Detection limits, using a total
irradiation current of 20 millicoulombs, for carbon, nitrogen and oxygen, respectively, were 6·10−8 g, 2·10−7 g and 1.7·10−7 g per cm2 cross-sectional area of irradiating beam. 相似文献
4.
A rapid, nondestructive method has been developed for determination of fluorine by activation with fast neutrons from a241Am-242Cm-Be source and counting the 6–7 MeV γ rays of the product nitrogen-16. The total neutron output of the source is 4.8·109 unmoderated neutrons per second and the flux is 1.4·108 fast n·cm−2· sec−1. The γ-ray detectors consist of two opposing, matched cylindrical NaI(Tl) crystals 10 cm long and 10 cm in diameter. The
sample is irradiated for 30 seconds, cooled for 4 seconds, and then counted for 30 seconds. The sensitivity is 4.8·104 counts nitrogen-16 per gram fluorine, and the limit of detection is 0.4 mg fluorine in a 10-gram sample. A reproducibility
of 0.24% is achieved. The relative standard deviation of the specific count rate of nitrogen-16 for 11 fluorine compounds
is 1.31%. 相似文献
5.
An INAA technique employing beta spectrometry was developed for the determination of phosphorus in polymers. The (n,γ) reaction
on phosphorus produces32P, half-life 14.3 days, a pure beta emitter with end-point energy 1.71 MeV. Polymer samples in the form of powders, films
and pellets are irradiated and then counted with a plastic scintillator. The beta spectrum is corrected for interferences
(especially Sb, Zn and Br which are quantified by gamma spectrometry) and for energy loss in the thick sample. Samples must
also be analyzed for S and Cl which cause nuclear interferences. With an irradiation time of 4 hours at a neutron flux of
5·1011 n·cm−2
s
−1, decay time 10 days and counting time 10 minutes, the sensitivity is 520 counts/μg phosphorus and the detection limit is
typically 2μg/g. 相似文献
6.
The use of 2.8 MeV neutrons produced by the D(d, n)3He reaction should be taken into consideration in some applications of radioactivation analysis. The low number of elements
activable by these neutrons makes possible to minimize the matrix interference and the background below the characteristic
photopeaks. The very low dead-time of the spectrometric measurements permits the use of the maximum neutron flux available
now and in the future. The purpose of this paper is to define experimentally the sensitivity of determination for the 16 main
elements activable with a 400 keV Van de Graaff accelerator at a 2.8 MeV neutron flux of 2·106 n·cm−2·sec−1 on the sample. 相似文献
7.
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
8.
P. Ghorbani D. Sardari E. Bayat V. Doostmohammadi 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(3):839-842
Material analysis with prompt gamma neutron activation analysis (PGNAA) requires a proper geometrical arrangement for equipments
in laboratory. Application of PGNAA in analysis of biological samples, due to small size of sample, needs attention to the
dimension of neutron beam. In our work, neutron source has been made of 241Am–Be type. Activity of 241Am was 20 Ci which lead to neutron source strength of 4.4 × 107 neutrons per second. Water has been considered as the basic shielding material for the neutron source. The effect of various
concentration of boric acid in the reduction of intensity of fast and thermal components of the neutron beam and gamma ray
has been investigated. Gamma ray is produced by (α, n) reaction in Am–Be source (4.483 MeV), neutron capture by hydrogen (2.224 MeV), and neutron capture by boron (0.483 MeV).
Various types of neutron and gamma ray dosimeters have been employed including BF3 and NE-213 detectors to detect fast and thermal neutrons. BGO scintillation detector has been used for gamma ray spectroscopy.
It is shown that the gamma and neutron radiation dose due to direct beam is of the same magnitude as the dose due to radiation
scattered in the laboratory ambient. It is concluded that 14 kg boric acid dissolved in 1,000 kg water is the optimum solution
to surround the neutron source. The experimental results have been compared with Monte Carlo simulation. 相似文献
9.
A procedure for the determination of chromium in blood has been developed with a sensitivity of 5×10−3 μg Cr. Dried blood was irradiated with a neutron flux of 1012 n·cm−2·sec−1 in the VVRS reactor for 4 weeks, then the sample was mineralized and the chromium isolated by extraction as perchromic acid.
The determination of the chromium content was accomplished by measuring the 0.32 MeV gamma energy of51Cr. In order to make correction for the interfering reaction54Fe(n,α)51Cr, the formation of chromium from high-purity iron was investigated. The chromium content of the blood samples was between
1.03×10−2 and 5.2×10−2 ppm Cr. 相似文献
10.
E. W. Haas R. Hofmann F. Richter 《Journal of Radioanalytical and Nuclear Chemistry》1982,69(1-2):219-233
The recoil energies of up to several MeV developed during nuclear reactions involving particle emission lead to the radionuclides
used in the analysis being redistributed between adjacent materials. In aluminum irradiated by reactor neutrons,24Na losses were observed up to a depth of 8·10−6 m; in the adjacent silicon, a24Na penetration depth was observed up to 4·10−6 m. Similar results were obtained from reaction products deriving from irradiation of Ti, Ni, N, S and Cl. This means that
the results of activation analysis investigations performed for the purpose of evaluating this type of reaction might contain
significant errors if thin layers, boundary zones of very small sample volumes are examined. In the analysis of surface layers
on silicon devices, completely erroneous results have been obtained in some cases due to the recoil phenomena described. 相似文献
11.
C. Friedli M. Rousseau P. Lerch 《Journal of Radioanalytical and Nuclear Chemistry》1981,64(1-2):239-247
In order to determine traces of boron, silicon and sulfur, B(18O, x)27Mg, Si(18O, x)43Sc and S(18O, x)47V reactions have been investigated between 15 and 44MeV. At 34 MeV, only a few of the systematically identified nuclear interferences
produce27Mg and the detection limit is 30ng boron for a 10 minute irradiation with a 0.3μA·cm−2 oxygen-18 beam. Silicon analysis has shown nuclear interferences from Al, P and K; interference-free detection limit is 80
ng silicon for an hour irradiation with a 0.4 μA·cm−2 beam at 39 MeV. There is no nuclear interference for the sulfur determination and the detection limit is 5 ng sulfur for
a 30 minutes irradiation with a 0.5 μA·cm−2 beam at 39 MeV. Thus a selective and sensitive sulfur determination can be achieved. 相似文献
12.
G. M. Brahmanandhan J. Malathi D. Khanna S. Selvasekarapandian N. Nidhya R. Usharani M. T. Jose V. Meenakshisundaram 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(2):373-377
Samples of natural and manufactured building materials used by the people of Gobichettipalayam town have been analyzed for
226Ra, 232Th and 40K using gamma-ray spectrometry. Radium equivalent activity of the materials has been measured using the formula given by OECD
and the geometric mean value of sand, clay and cements are found to be 53.53 Bq·kg−1, 89.09 Bq·kg−1 and 72.25 Bq·kg−1, respectively. The radium equivalent activities obtained in the building materials are all well below the acceptable limit.
The indoor gamma-dose has been measured using thermoluminescence dosimeters and it was found in the range of 1051.2–3946.0
μGy/year. The annual effective indoor gamma radiation dose to the people of Gobichettipalayam town has been found to be 0.8
mSv/y. 相似文献
13.
Photonuclear activation with 18 and 35 MeV bremsstrahlung beams and gamma ray spectrometry has been used to determine the
concentrations of 14 elements in human hair. A careful study of interferences made possible a nondestructive analysis with
practical limits of detection between 0.1 and 100 μg·g.
相似文献
14.
P. Holmberg M. Hyvönen M. Tarvainen 《Journal of Radioanalytical and Nuclear Chemistry》1978,42(1):169-175
Samples of compact bone, bone marrow and spongiosa of cow femur have been irradiated in vitro with 14 MeV neutrons. The Ca/P
ratio for compact bone was found to be 2.16±0.24. The suitability of using 14 MeV neutrons and the31P(n, α)28Al reaction for studying the bone mineral composition in vitro is discussed. 相似文献
15.
The technique of gamma-ray analysis of light elements (GRALE) is extended to measure the concentration of carbon, nitrogen,
oxygen, sulfur and silicon in coal samples. The composition of the sample is determined by analyzing the spectrum of gamma
rays emitted following inelastic scattering of protons bombarding the target. A large volume lithium drifted germanium detector
is used as a gamma-ray detector in this work. Coal samples are irradiated with 9.5 MeV protons in a helium atmosphere for
1000 sec. Results with standard coal samples indicate that the method has an accuracy of ∼5% of the concentration of each
element and a precision of ∼4% for elements constituting at least 1% of the coal by weight. 相似文献
16.
A. Godelitsas M. Kokkoris P. Misaelides 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(2):339-344
To enhance the applicability of the nuclear analytical technique in the field of industry and the environment, the inorganic
elemental content of the bottom ash from a municipal solid waste incinerator was determined by instrumental neutron activation
analysis. Bottom ash samples were monthly collected from an incinerator located at a metropolitan city in Korea, strained
through a 5 mm sieve, dried by an oven and pulverized by an agate mortar. The samples were irradiated at the NAA #1 irradiation
hole (thermal neutron flux: 2.92·1013 n·cm−2·s−1) in the HANARO research reactor of the Korea Atomic Energy Research Institute and the irradiated samples were measured by
a HP Ge gamma-ray spectrometer. Thirty-three elements including As, Cr, Cu, Fe, Mn, Sb and Zn were analyzed by an absolute
method. The quality control was conducted by a simultaneous analysis with NIST standard reference materials. The average concentrations
of the major elements such as Ca, Fe, Al, Na, Mg, K and Ti measured in the sample were 19.9%, 4.85%, 3.79%, 2.11%, 1.84%,
1.22% and 1.02%, respectively. In addition, the concentrations of the hazardous metals like Zn, Cu, Cr, Sb and As were 0.77%,
0.31%, 729 mg·kg−1, 116 mg·kg−1 and 22.2 mg·kg−1, respectively. 相似文献
17.
D. Gihwala I. S. Giles C. Olivier M. Peisach 《Journal of Radioanalytical and Nuclear Chemistry》1978,46(2):333-341
The prompt gamma-ray of 871 keV emitted during the bombardment of steels by 5 MeV alpha particles were used to determine nitrogen
by means of the reaction14N(α, pγ)17O. The method is non-destructive, rapid and experimentally simple. It has a sensitivity of about 7 μg·g−1. In the nitrogen concentration range of 101–102 μg·g−1 the relative precision of the method is about 3%. The accuracy of the method compares with that of other nuclear methods.
Presented at the 5th Symposium on Recent Developments in Activation Analysis, Oxford, 17–21 July, 1978. 相似文献
18.
Azzam A. M. El-Atrash A. M. Ghattas N. K. 《Journal of Radioanalytical and Nuclear Chemistry》1974,22(1-2):63-74
The analysis of less than 10−9 g of the isotope204Pb in lunar samples was carried out by an (n, 2n) activation using high energy (>8. 8 MeV) neutrons. A procedure of using
the neutrons produced by bombardment of a specially designed Be sample holder with deuterons in a cyclotron was developed
and compared to irradiation carried out in the core of a nuclear reactor, Radiochemical separations and X ray-γ ray coincidence
counting techniques are necessary to achieve the required sensitivity. Although the flux of neutrons of sufficient energy
from the cyclotron procedure is somewhat lower can be obtained in the best reactor irradiations, the high radioactivity due
to other elements produced by the (n, γ) reactions in the reactor is eliminated. Radiochemical procedures for the analysis
of Bi, Tl, Zn in the same samples are also described. 相似文献
19.
H. -U. Fanger R. Pepelnik W. Michaelis 《Journal of Radioanalytical and Nuclear Chemistry》1981,61(1-2):147-163
At the GKSS Research Center Geesthacht, a new 14 MeV activation facility—a 5·1012 n/s neutron generator combined with a fast rabbit system (KORONA)—is being installed. Homogeneous neutron flux at a level
of 5·1010 n·cm−2·s−1 and sample transfer times of 140 ms to a 16m distant detector station are characteristic features of the facility described
in the paper. With special consideration of short-lived nuclides and including cyclic activation, the analytical prospects
with the intense neutron source are discussed, and sensitivities for 78 elements are presented. 相似文献
20.
M. S. Abdelmonem A. A. Naqvi Hanan Al-Ghamdi Ghada Al-Misned 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):131-137
Performance of a 241Am-Be neutron source-based and 2.8 MeV neutrons-based moisture measurement setups have been compared using Monte Carlo simulation.
In the setup fast neutrons transmitted through the sample were detected by a fast neutron detector, which was placed behind
a massive long double truncated collimator. The setup geometry was optimized to detect maximum effect of 1–7 wt.% moisture
on the neutron intensity transmitted through the sample. The yield of neutrons transmitted through concrete, coal, wood and
soil samples containing 1–7 wt.% moisture was calculated for 2.8 MeV neutrons and neutrons from an 241Am-Be source. The slopes of the fast neutron intensities transmitted through the samples vs. their moisture contents are very
sensitive to the neutron energy and the sample composition. Higher slopes have been observed for the samples with larger bulk
density. The slopes of fast neutron yield show dependence on the incident neutron energy. Larger slopes have been observed
for neutrons with samller energy. Due to the overall large slopes of the transmitted intensity data of the samples for 2.8
MeV neutrons, it is expected to achieve better sensitivity in moisture measurements for a 2.8 MeV neutrons based moisture
setup. 相似文献