共查询到20条相似文献,搜索用时 31 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.
J. S. Brahmaji Rao E. Senthilvadivu N. P. Seshadreesan R. Acharya C. R. Venkatasubramani A. V. R. Reddy 《Journal of Radioanalytical and Nuclear Chemistry》2012,294(1):137-141
The pneumatic fast transfer system position at KAMINI reactor, Indira Gandhi Centre for Atomic Research, India was characterized by determining the epithermal neutron flux shape factor (α) and the sub-cadmium to epithermal neutron flux ratio (f) for k 0-based Neutron Activation Analysis (k 0-NAA). For determination of α value, bare, Cd-ratio and Cd-cover methods were employed using dual and multi monitors namely Au, Zr and Zn. For calculation of f, Au and Zr monitors were used in the case of bare method and Au monitor was used for cadmium ratio and cadmium cover methods. The determined α-value of PFTS indicated a hard epithermal neutron spectrum and the f value indicated about 96 % thermal neutron component. For validation of k 0-NAA method, reference materials namely NIST SRM 1646a (Estuarine Sediment) and BCS Nb-stabilized Stainless Steel (BCS/SS No.261/1) were analyzed. The percentage errors of the determined concentration values of elements were within ±5 % with respect to the certified values and the Z-score values at 95 % confidence level were within ±2 in most of the cases. 相似文献
3.
Mohamed Soliman Nader M. A. Mohamed M. A. Gaheen E. A. Saad S. K. Yousef M. A. Sohsah 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(2):629-634
The k
0-method of INAA standardization has been implemented using the irradiation facilities of the fast pneumatic rabbit and some
selected manually loaded irradiation positions, which designated for short and long irradiation, respectively, at Egypt second
research reactor. The neutron flux parameters (f and α) in each site have been determined using Zr–Au sets as neutron flux monitors. The reference materials coal NIST 1632c
and IAEA-Soil 7 were analyzed for data validation and good agreement between the experimental values and the certified values
was obtained. 相似文献
4.
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
5.
M. Siddique N. M. Butt M. Shafi T. Abbas -ul-Islam Misbah 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(3):525-529
The neutron spectra of one outer (#10) and two inner (#2 and #3) sites of the Dalhousie University SLOWPOKE-2 reactor (DUSR) have been calibrated for the k
0-based neutron activation analysis (k
0-NAA). The parameters determined include the cadmium ratio (R
Cd), epithermal neutron flux shape factor (), subcadmium-to-epithermal neutron flux ratio (f), thermal-to-fast neutron flux ratio (f
F), modified spectral index r()(Tn/T0)1/2, Westcott g
Lu(T
n)-factor, and absolute neutron temperature (T
n). The a-values of -0.0098±0.0045 and -0.0425±0.0047 and -0.0422±0.0053 and f-values of 57.1±2.2 and 18.8±0.4 and 18.9±0.4 were obtained for the sites #10, #2 and #3, respectively. The modified spectral index (MSI), g
Lu(T
n)-factor, and T
n have been determined for the handling of non 1/v (n,) reactions. The accuracy of the method was evaluated by analyzing reference materials. 相似文献
6.
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
7.
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
8.
John W. Bennett Peter Grave Attila Stopic 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(1):13-17
The k
0-method of standardisation for instrumental neutron activation analysis (INAA) has been used at the OPAL research reactor
to determine the elemental composition of three certified reference materials: coal fly ash (SRM 1633b), brick clay (SRM 679)
and Montana soil (SRM 2711). Of the 41 certified elements in the three materials, 88 percent were within five percent of the
certified values and all determinations were within 15 percent of the certified values. The average difference between the
measured and certified values was 0.1 percent, with a standard deviation of 4.1 percent. Since these reference materials are
widely used as standards in the analysis of archaeological ceramics by INAA, it has been concluded that the INAA facility
in Australia is particularly well-suited for nuclear archaeometry. 相似文献
9.
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
10.
The use of thek
0-standardization method in instrumental neutron activation analysis gives good accuracy and precision. The analysis time can
be reduced drastically by employing software for thek
0-standardization calculations. In this work samples were irradiated in a TRIGA reactor and the gamma spectrum was analysed
by Sampo 90 and thek
0-standardization by the KAYZERO/SOLCOI code (DSM Research). The efficiency measurement and the peak to total ratio at the
reference and other geometries were measured and tested for their accuracy by analysing some reference materials. Reference
materials such as SRM 1572 (Citrus leaves), SRM 1573 (Tomato leaves), SRM 1575 (Pine needles), IAEA Soil-7 (Soil) and SRM
1646 (Estuarine sediment) were analysed for the major, minor and trace element contents. The results were in good agreement
with the certified or literature values. The recently released IAEA 140 (Sea plant homogenates) was also analysed for 28 elements. 相似文献
11.
O. Díaz Rizo M. V. Manso Guevara E. Herrera Peraza I. Alvarez Pellón M. C. López Reyes 《Journal of Radioanalytical and Nuclear Chemistry》1997,221(1-2):241-244
Using the facilities of the Triga Mark III reactor at the NNRI, Mexico and the HAV-1 multipurpose monitor, the reactor power dependency for thek
0-standardization essential neutron flux parameters as: epithermal shape factor (), thermal to epithermal ratio (f) and neutron temperature (T
n
) were experimentally obtained. Evaluation of the obtained dependencies shows that it is unnecessary to analyze the possible introduction of correction factors in thek
0-INAA experimental results. A single experimental procedure to determine throughf is suggested. 相似文献
12.
Thomas JB Duewer DL Mugenya IO Phinney KW Sander LC Sharpless KE Sniegoski LT Tai SS Welch MJ Yen JH 《Analytical and bioanalytical chemistry》2012,402(2):749-762
Standard Reference Material 968e Fat-Soluble Vitamins, Carotenoids, and Cholesterol in Human Serum provides certified values
for total retinol, γ- and α-tocopherol, total lutein, total zeaxanthin, total β-cryptoxanthin, total β-carotene, 25-hydroxyvitamin
D3, and cholesterol. Reference and information values are also reported for nine additional compounds including total α-cryptoxanthin,
trans- and total lycopene, total α-carotene, trans-β-carotene, and coenzyme Q10. The certified values for the fat-soluble vitamins and carotenoids in SRM 968e were based on the agreement of results from
the means of two liquid chromatographic methods used at the National Institute of Standards and Technology (NIST) and from
the median of results of an interlaboratory comparison exercise among institutions that participate in the NIST Micronutrients
Measurement Quality Assurance Program. The assigned values for cholesterol and 25-hydroxyvitamin D3 in the SRM are the means of results obtained using the NIST reference method based upon gas chromatography-isotope dilution
mass spectrometry and liquid chromatography-isotope dilution tandem mass spectrometry, respectively. SRM 968e is currently
one of two available health-related NIST reference materials with concentration values assigned for selected fat-soluble vitamins,
carotenoids, and cholesterol in human serum matrix. This SRM is used extensively by laboratories worldwide primarily to validate
methods for determining these analytes in human serum and plasma and for assigning values to in-house control materials. The
value assignment of the analytes in this SRM will help support measurement accuracy and traceability for laboratories performing
health-related measurements in the clinical and nutritional communities. 相似文献
13.
R. Jaćimović B. Smodiš T. Bučar P. Stegnar 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(3):659-663
A suite of natural matrix reference materials (RMs) were used to assess the quality of analytical results obtained by k
0-instrumental neutron activation analysis (k
0-INAA) at the Joef Stefan Institute (IJS). Five certified reference materials (CRMs) from the Institute for Reference Materials and Measurements (IRMM), two standard reference materials (SRMs) from the National Institute of Standards and Technology (NIST), three RMs from the International Atomic Energy Agency (IAEA) and one RM from IJS were analyzed. Altogether, results for twenty-four elements in inorganic matrices and twenty-nine elements in organic matrices, obtained by k
0-INAA, were compared to certified values. Results obtained show good agreement with certified or assigned values except for Fe, La, Nd, Sm and U in inorganic matrices, and Ag, Al and Cr in organic matrices. 相似文献
14.
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
15.
Silver in selected, predominantly biological, reference materials (NIST SRM 1515, 1547, 1549, 1566a, 1571, 1577b, 2704, CTA-OTL-1,
and Bowen’s Kale) was determined using neutron activation analysis (NAA) in two different analytical modes: instrumental NAA
with epithermal neutrons (ENAA), and NAA with radiochemical separation (RNAA). The ENAA mode was based on long-time 5-hour
irradiation of samples in a special Cd lined box with counting after 8-month decay. The RNAA procedure consisted in 20-hour
irradiation of samples, their decomposition/dissolution by alkaline-oxidative fusion, and precipitation of AgCl including
several purification steps. Both methods provided Ag contents in the analyzed reference materials consistent with certified
and/or literature values down to the ng·g−1 level. 相似文献
16.
C. O. Mustra M. C. Freitas S. M. Almeida 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(3):539-543
The Portuguese Research Reactor (RPI) is a 1 MW swimming pool type reactor, operating since the early 1960s. The fuel is MTR type, with flat plates of U-Al alloy enriched to 93% in 235U. As the core configuration changed in April 2000, it became essential to characterise the neutron field in the most useful irradiation positions of RPI, in order to guarantee the accuracy in the application of k
0-neutron activation analysis (k
0-NAA). Experimental values of the thermal to epithermal neutron flux ratio (f) and of the deviation of the epithermal neutron spectrum from the 1/E shape (a) were determined using the Cd-ratio for multi-monitor method. The neutron temperature (T
n) was obtained from co-irradiation of Lu with 1/v monitors. The results for several irradiation positions are presented and discussed in this work. Some element concentrations are determined based on the parameters obtained in this work, and compared with the certified reference material concentrations. 相似文献
17.
E. H. R. Montoya I. M. Cohen P. Mendoza Hidalgo B. Torres Chamorro P. Bedregal Salas 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(2):475-479
The errors occurred when α, the parameter that accounts for the non-ideal behavior of the epithermal flux, are neglected,
have been evaluated for the determination of twenty elements in biological materials, using. gold and sodium comparators,
and zirconium to measure the thermal to epithermal flux ratio (f). Sodium allows the determination of 15 elements, and up to 18 elements can be determined in positions relatively well thermalized
by the simultaneous use of gold and sodium comparators, in all the cases with errors ≦2%, when α is not considered. Results
obtained for reference materials are presented. 相似文献
18.
T. Bereznai D. Bódizs G. Keömley 《Journal of Radioanalytical and Nuclear Chemistry》1977,36(2):509-524
The possible extension of the comparator technique of reactor neutron activation analysis into the field of epithermal neutron
activation has been investigated. Ruthenium was used for multi-isotopic comparator. Experiments show that conversion of the
so-called reference k-factors—determined by irradiation with reactor neutrons—into kepi-factors usable at activation under cadmium filter, can be evaluated with fair accuracy. Sources and extent of errors and
their contribution to the final error of analysis are discussed.
Based on the paper presented at the 2nd European Conference on Analytical Chemistry, 25–30 August, 1975, Budapest, Hungary. 相似文献
19.
I. O. Abugassa A. T. Bashir K. Doubali R. H. Etwir M. Abu-Enawel S. O. Abugassa 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(3):559-563
Medicinal herbs are often used as alternative medicines for healing and controlling some diseases in the world. This study
focuses on the content of heavy and trace elements of some widely consumed herbs in Libya. Nine most popular herbs were analyzed
by k
0-instrumental neutron activation analysis. All the samples, SRM and flux monitors were irradiated for 7 and 10 hours under
thermal neutron flux of 1.3·1013 cm−2·s−1 at Tajoura nuclear reactor. In total, 33 elements were analyzed in different herbs. The variations in the concentration of
the elements are attributed to soil composition and the climate in which the plant grows. The study showed that the toxic
elements found in the samples were below the levels prescribed by health regulations. The precision and the accuracy of the
results were evaluated by analyzing the reference materials Pine Needles SRM 1575 and Citrus Leaves SRM1572. 相似文献
20.
A series of reference materials intended for use as activation or fission monitors for neutron fluence rate measurements has been prepared by the Joint Research Centre of the European Commission. Certification has been carried out by expert European laboratories and distribution of the certified reference materials (CRMs) is through the BCR programme of the Commission. The list (18 CRMs) includes materials to cover the complete energy spectrum, and suitable for different irradiation times. Fission monitors are 238UO2 or 237NpO2 in the form of microspheres. Activation monitors are high purity metals (Ni, Cu, Al, Fe, Nb, Rh, or Ti), certified for interfering trace impurities, or dilute aluminium-based alloys, where aluminium is chosen as a suitable matrix for reducing the neutron self-shielding effect. Newly certified materials are IRMM-530R Al-0.1%Au, replacing the exhausted IRMM-530 material, used as comparator for k
0-standardization, and three new Al-Co alloys (0.01-1%Co). Two others, in the process of certification are Al-0.1%Ag and Al-2%Sc for thermal and epithermal fluence rate measurements. Other candidate reference materials currently being certified are two uranium-doped glass intended for dosimetry by the fission-track technique. 相似文献