共查询到20条相似文献,搜索用时 754 毫秒
1.
P. Vermaercke P. Robouch L. Sneyers F. De Corte 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(1):235-241
The thermal to epithermal neutron flux ratio (f) and the deviation of the epithermal neutron spectrum from the 1/E shape (α) are essential parameters for the correct application of k
0-standardized neutron activation analysis. Several methods are applied for the determination of f and α. They are based on Cd-covered multi-monitor or on bare-irradiations methods. The recently developed and characterized synthetic
multi-element standards (SMELS) were designed as a validation tool for the proper implementation of the k
0-NAA method in a laboratory. In particular, SMELS Type III contains Au and Zr, thus allowing the direct determination of f and α. It could, therefore, replace the traditional flux monitors. Furthermore, it could be used as a quality control material
to monitor the stability of the irradiation facility and the detector. This paper presents the accuracy of the f and α determination and the feasibility of quality control using SMELS for irradiation channel Y4 of the BR1 reactor. 相似文献
2.
M. J. J. Koster-Ammerlaan P. Bode A. J. M. Winkelman 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):569-572
The assumption that the shape of the epithermal neutron spectrum can be described, in any research reactor, by the 1/E
1+α function is a fundamental starting point of the k
0 standardization. This assumption may be questioned from a reactor physics viewpoint. The type of moderator, the existence
of neutron reflectors, the additional production of (γ, n) neutrons and resonance capture by construction materials may be different for each reactor, with consequences for the shape
of the neutron spectrum. This dependency may explain that various practitioners reported contradicting experiences with the
use of Zr–Au flux monitors for the determination of the α-parameter. An objective view on the influence of the design of the
reactor and irradiation facility on the shape of the neutron spectrum can be obtained by modeling. This has been applied in
the Reactor Institute Delft for reactor configurations in which the irradiation facilities face the fuel elements with the
presence of beryllium reflector elements. The Monte Carlo calculations indicate a distortion of the 1/E
1+α relationship at the higher energy edge of the epithermal neutron spectrum. This distortion is attributed to the formation
and thermalisation of both photoneutrons and (n, 2n) produced fast neutrons in the beryllium, and has a direct impact on the resonance activation of 95Zr, other than represented by the 1/E
1+α function. The obtained relationship between neutron flux and neutron energy was also used for estimating the f-value and compared with the value obtained by the Delft Cr–Mo–Au flux monitor. 相似文献
3.
De Corte F. Speecke A. Hoste J. 《Journal of Radioanalytical and Nuclear Chemistry》1969,3(3-4):205-215
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. 相似文献
4.
I. O. Abugassa Y. S. Khrbish S. O. Abugassa N. Ben Faid A. T. Bashir S. Sarmani 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):27-30
The paper focuses on the validation of the k
0-method of instrumental neutron activation analysis (k
0-INAA) in the Tajura Nuclear Research Center (TNRC) via the analysis of several certified reference materials. The selected
reference materials were: SRM 1572 Citrus Leaves, SRM 1575 Pine Needles, IAEA-A11 Milk Powder, IAEA-V-10 Hay Powder, RM IAEA-Soil-7
and RM IAEA-SL-1 Lake Sediment. The method is based on the PC version Kayzero/Solcoi software package issued by DSM. All the
samples, reference materials and monitors were irradiated in various positions of the Tajura reactor with different f and α. The parameters f and α (f — thermal/epithermal neutron flux ratio, α — parameter accounting for the non-ideality of the 1/E epithermal neutron fluence rate distribution) were determined using the bare triple monitor method. The results obtained
for all the reference materials are in good agreement with the certified values. 相似文献
5.
E. V. Polyakov I. V. Volkov V. T. Surikov L. A. Perelyaeva 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(3):707-711
The α-factor is a measure of the epithermal neutron flux deviation from the ideal distribution 1/E, where E is neutron energy. It defends on the position of the irradiation channel in reactor. A determination method of the α-factors
in irradiation channels of Dalat reactor is presented by fitting the epithermal neutron spectrum obtained from the calculation
using MCNP code. The fitting α-values were compared to those by experiment used the “Cd-ratio” method with monitors 197Au–94Zr and 197Au–64Zn. It shows that the α-values calculated from neutron spectra agree well with experimental ones. The difference between both
data is about 6%. 相似文献
6.
F. De Corte L. Moens K. Sordo-El Hammami A. Simonits J. Hoste 《Journal of Radioanalytical and Nuclear Chemistry》1979,52(2):305-317
Some methods described in the literature for the determination of α in the 1/E1+α epithermal neutron spectrum are critically reviewed with respect to their accuracy. The multi resonance—detector method with
Cd-covered irradiations, as used by SCHUMANN and ALBERT, is generalized by subtracting the epithermal 1/v-tail and by introducing
the effective resonance energy, as defined by RYVES. The two-detector method of RYVES is modified by using Cd-ratio measurements,
thus eliminating the introduction of systematic errors due to the inaccuracy of absolute nuclear data. The adapted methods
are applied in channel 15 of the Thetis reactor (Gent).
Research Associate of the “Nationaal Fonds voor Wetenschappelijk Onderzoek” 相似文献
7.
M. Wasim J. H. Zaidi M. Arif I. Fatima 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(3):525-529
The k
0 method has been introduced at the 30 kW miniaturized neutron source reactor (MNSR) at the Pakistan Institute of Nuclear Science
& Technology (PINSTECH). It involved the full energy peak efficiency calibration of the HPGe detector for different counting
geometries and the characterization of the neutron flux at four inner irradiation channels. The latter involved the determination
of the thermal to the epithermal flux ratio, epithermal flux shape factor, the modified spectral index, Westcott’s g-factor,
the Maxwellian neutron temperature and the fast flux. The method was validated by analyzing IAEA-SL1 (Lake Sediment) and NIST-SRM-1572
(Citrus Leaves) reference materials. All calculations were performed in Excel, including the optimization step. The results
revealed that most of the elements were estimated with less than 10% relative deviation from the certified value. 相似文献
8.
P. Vermaercke L. Sneyers M. Bruggeman A. De Wispelaere F. De Corte 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(3):631-636
Several methods are in use for the determination of the thermal to epithermal neutron fluence rate ratio (f) and the deviation of the epithermal neutron spectrum from the 1/E shape parameter (α). In our former work, it was proven that the recently developed and characterized Synthetic Multi-ELement Standard (SMELS)
can be used for the fast verification of the stability of the irradiation parameters using the Au-Zr bare monitor method.
However, this latter method using SMELS had a too low precision for an accurate determination of f and α. Therefore, the Cd-ratio for multi-monitor method using SMELS was investigated for two irradiation channels. As shown the
material can also be used as a monitor for the calibration of an irradiation facility. 相似文献
9.
INAA of geological materials using a combination of epithermal activation and Compton suppression: Prediction of possibilities 总被引:1,自引:0,他引:1
E. Steinnes 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(2):313-317
Nuclear data relevant to the determination of elements in geological materials by instrumental neutron activation analysis
using a combination of epithermal neutron activation and Compton suppression counting are presented. The feasibility of this
combination is discussed considering data for desired as well as interfering nuclides. Among elements determined after short
irradiation, the conditions for Sr, Zr, I, Cs, Eu and U should be improved. After long epithermal irradiation and appropriate
decay, Compton suppression should lead to improvement in determination of As, Rb, Sr, Mo, Sn, Sb, Ba, Gd, Ho, Tm, W, Au, Th,
and U. In the case of Ga, Se, Ag, In, Cs, Tb, Yb, Hf, Ta, and W, the use of Compton suppression in connection with epithermal
activation is not recommended because the radionuclides concerned decay with coincident γ-rays. In general, the use of Compton
suppression should improve the determination of trace elements in geological materials by epithermal neutron activation analysis,
but more work is needed to better quantify these improvements. 相似文献
10.
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.
Research associate of the N. F. W. O. 相似文献
11.
J. D. Brockman N. J. Peters J. D. Robertson 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(1):41-44
In January 2006 the beryllium reflector and graphite wedge that contained the k0 INAA irradiation position were replaced at the University of Missouri Research Reactor. Prior to replacement the average
values of the flux ratio, f, and the epithermal non-ideality factor, α, were 57.4 ± 4.5 and 0.039 ± 0.012. The values of f and α immediately after the beryllium and graphite wedge replacement were 39.4 ± 0.6 and 0.021 ± 0.002. Subsequent measurements
indicate that the neutron spectrum hardened with time, possibly due to the buildup of the 6Li atom density to saturation. 相似文献
12.
Lylia Hamidatou Houcine Benkharfia 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(3):971-975
The Algerian research reactor (Es-Salam) is a 15 MW heavy water reactor type, operating since 1992. It became essential to
characterize the neutron field in the most useful irradiation positions, in order to guarantee the accuracy in the application
of k
0-neutron activation analysis (k
0-NAA). Experimental value of the thermal to epithermal neutron flux ratio (f) and of the deviation of the epithermal neutron spectrum from 1/E shape (α) were determined using different methods. This work focuses the verification of Monte Carlo neutron flux calculation
in typical irradiation channel. Comparison of the results for parameter f obtained experimentally and by Monte Carlo simulations
shows good agreement in the irradiation channel studied. The difference between both results is about 2.08%. 相似文献
13.
A. O. Brunfelt I. Roelandts E. Steinnes 《Journal of Radioanalytical and Nuclear Chemistry》1977,38(1-2):451-459
Three procedures are outlined for the determination of rare-earth elements in geological materials. The irradiation of the
samples is carried out by either thermal or epithermal neutrons. Two of the methods, one of which is especially suitable for
ultramafic rocks are based on radiochemical separations, while in the third method non-destructive analysis is applied to
apatites. The γ-ray activity measurements are performed by means of coaxial Ge(Li)-detectors. 相似文献
14.
R. Radhamani P. L. Mahanta P. Murugesan G. Chakrapani 《Journal of Radioanalytical and Nuclear Chemistry》2010,285(2):287-292
A simple, rapid, effective and eco-friendly decomposition method is developed for the determination of uranium (U) by laser
induced fluorimetry (LIF). The salts of sodium di-hydrogen phosphate (NaH2PO4) and di-sodium hydrogen phosphate (Na2HPO4) were used in the ratio of 1:1 (phosphate flux) for the decomposition and dissolution of refractory, non silicate minerals
like ilmenite, rutile, columbite, tantalite, and xenotime. The effect of associated matrix elements (Ti, Fe, Nb, Ta, Mn and
Y present in the sample) on quenching of uranyl fluorescence was studied. The flux used for the sample decomposition has several
advantages. In the reported sample decomposition methods, α-hydroxy acids are used as complexing agents to prevent hydrolysis
and to get clear and stable solution. This solution can not be directly used for U determination by LIF as α-hydroxy acids
quench uranyl fluorescence, hence separation is required. In the present method no such separation is required. The flux itself
acts as fluorescence enhancing reagent and buffer (maintaining the optimum pH of 7.1 ± 0.1). The fused melt of the flux mixture,
when disintegrated in water, gives clear and stable solution and has high tolerance for most of inorganic quenchers compared
to reported phosphate buffers. Also just by dilution (due to high sensitivity of LIF), the concentration of quenchers could
be brought down well within the tolerance limit. The accuracy and precision of the method was evaluated by analyzing Certified
Reference Materials (IGS-33 and IGS-34 of Institute of Geological Sciences, UK) and Synthetic Minerals. The accuracy of the
data is further evaluated by comparing with standard decomposition methods. The results are well within the experimental error.
The RSD of the method is ±10% (n = 6) at 10 ppm level for Ilmenite and for other minerals the RSD of the method is ±5% (n = 6) at 50 ppm level. The method is being routinely applied to various refractory samples received from Rare Metal and Rare
Earth Investigations for determination of uranium by laser fluorimetry. 相似文献
15.
Mohammad A. Hannan Jesus Tanguma 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(3):745-751
Neutron Activation Analysis (NAA) was applied to determine trace and major elements in Mission–Progresso (Texas) soils. The
Rio Grande river runs along the USA—Mexico border. The soil samples were collected at Mission and Progresso areas of the Rio
Grande riverbank in the USA side. Soils were analyzed for the presence of toxic effluents due to human activities that might
affect agricultural products and health because one of the possible paths of intoxication is the agricultural product consumption.
Dried, sieved, and blended soil samples (~1.5 g) were irradiated at the UT Austin TRIGA reactor at a thermal neutron flux
of 1 × 1012 n cm−2s−1 and epithermal neutron flux of 1 × 1011 n cm−2s−1. Different irradiations, decay, and counting times were combined to determine concentration and detection limits of 21 elements
which represent four areas in Mission–Progresso (Texas) with the aim to achieve a consistent characterization. NIST certified
reference materials were used in relative analysis and also to determine the accuracy and reproducibility values. The neutron
flux was monitored using sulfur flux monitor wires. Normal and Compton suppression gamma ray spectrometers were used to detect
different gamma ray energy peaks and this Compton system greatly reduces the background. Concentrations are evaluated in per
cent and parts per million and errors are within acceptable levels and these values are compared with values reported in literatures
from other countries. The results do not show significant contaminations neither from the Rio Grande river nor from nearby
industries. 相似文献
16.
K. Masumoto K. Iijima A. Toyoda Q. Wang 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(2):297-303
The spatial distribution of neutrons was measured at the muon science laboratory of KEK by the activation detector method
using an imaging plate for the radioactivity measurement. It was confirmed that this method is highly sensitive to detect
the average neutron dose of 10 μSv/h. The distribution of thermal and epithermal neutrons was also measured in the experimental
room. The cadmium ratio inside the experimental room is one except for the neutron leakage point. The spatial distribution
of neutrons inside the concrete shield of KENS was measured by the same method. Aluminum and gold foils were used for the
measurement of fast and thermal neutrons, respectively. Two dimensional change of the reaction rate of the 27Al(n,α)24Na reaction shows a good agreement with the results calculated by the Monte Carlo simulation using MARS14 code. Thermal and
epithermal neutron flux ratio on the beam axis was measured by the cadmium ratio method. The flux ratios were about 30 and
almost constant for every slot except for the surface of the shield, because the cadmium ratio is 2. This method was very
useful to measure the activity of many pieces of detector simultaneously without any efficiency and decay correction. Wide
dynamic range and high sensitivity are also the merit of this method. 相似文献
17.
18.
A comparative study is presented on neutron activation analysis of rock and soil samples using whole reactor neutron spectrum
and epithermal neutrons with both relative and monostandard procedures. The latter procedure used with epithermal neutron
activation analysis of soil samples necessitated the use of the “effective resonance integrals” which were determined experimentally.
The incorporation of the β factor, representing deviation of reactor epithermal neutron flux from 1/E law, is developed in
the present work. The main criteria for the choice of one or more of the procedures studied for a given purpose are also indicated.
Analysis of 15 trace elements, Ca and Fe in the standard Japanese granite JC-1 using monostandard epithermal neutron activation
gave results in good agreement with the average literature values.
This paper is dedicated to the 80th birthday of Professor Dr. Robert Klement, University of Munich. 相似文献
19.
Siaka Yusuf Melinda Krahenbuhl Bryan Haskins Mike Hartman 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):23-26
To measure the gold content of a catalyst accurately, neutron activation analysis (NAA) is one of the methods of choice. NAA is preferred for such heterogeneous catalysts because: (1) it requires minimal sample preparation; (2) NAA provides consistent and accurate results; and (3) in most cases results are obtained much quicker than competing methods. NAA is also used as a referee for the other elemental techniques when results do not fall within expected statistical uncertainties. However, at very high gold concentrations, applying NAA to determine the gold in a heterogeneous catalyst is more challenging than a routine NAA procedure. On the one hand, the neutron absorption cross section for gold is very high, resulting in significant self-shielding related errors. On the other hand, gold exhibits low energy resonance neutron absorptions. In this application the self-shielding minimization effort was handled more rigorously than the classic suppression of neutron flux within a specimen. This non-routine approach was used because: (1) for most applications, high accuracy, <3 % relative, is desired, (2) the low energy resonances of gold make its neutron reaction rate complex and (3) the TRIGA reactor flux profile used in this study contains both thermal and significant epithermal neutron fluxes. Accuracy and precision, using this new approach, are expected to improve from 15 % to better than 3 % relative uncertainty. This has been accomplished through a rigorous assessment of the observed effects of low energy resonance on the neutron flux spectral shape within the sample and designing an experiment to minimize the effects. 相似文献
20.
I. P. Alimarin Yu. V. Jakovlev A. Z. Miklishansky N. N. Dogadkin O. V. Stepanets 《Journal of Radioanalytical and Nuclear Chemistry》1968,1(2):139-145
Radioactivation analysis is the only method which allows the determination of individual rare earth element impurities in
rare earth elements of high purity. The determination of dysprosium, europium, samarium and gadolinium in yttrium oxide is
complicated by the short half-life of165Dy (138 min.) and by the difficulty of separating traces of these elements from the matrix. A chromatographic method has been
developed, for the separation of traces of Dy, Eu, Sm and Gd from ytrium, on a column packed with anion exchangerAV-17, by means of elution with 0.1N and 0.3M solutions of EDTA-sodium salt, followed by the separation of the mixture of the rare earth impurities on a microcolumn of
cation exchangerKU-2, using a 0.17M solution of ammonium α-hydroxyisobutyrate as the eluent. The sensitivity of the determination of Dy, in the case of irradiating
10 mg of Y2O3 with a flux of 1.2·1013 n·cm−2·sec−1 for 5 min. was 1·10−7%; the corresponding values for Sm, Eu and Gd, when irradiating a 100 mg sample of Y2O3 for 20 hours with the same flux, were 2·10−7%, 1·10−8% and 5·10−6%, respectively. 相似文献