共查询到20条相似文献,搜索用时 31 毫秒
1.
S. Pavelka M. Vobecký A. Babický 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(3):575-579
The study describes a mode of non-destructive simultaneous determination of bromine and iodine concentrations, by reactor
instrumental neutron activation analysis (INAA) in the regime of short-term activation. Under the conditions of 1-minute activation
in the neutron flux of 8.0·1013 n·cm−2·s−1, it was possible to determine reliably as little as 5·10−8 g bromine and about 10−7 g iodine in matrices of a given type and of the mass of about 5 mg dry weight. We applied this method for the determination
of Br and I concentrations in the whole rat thyroid gland as well as for the halogen speciation in fractions separated from
this organ. 相似文献
2.
J. H. Lee J. S. Kim K. H. Cho J. Ch. Woo M. S. Han Y. S. Chung 《Journal of Radioanalytical and Nuclear Chemistry》1998,234(1-2):77-83
Trace impurity elements in high purity copper metal (4 mine class) put on the market were analyzed by Instrumental Neutron
Activation Analysis (INAA) and the results compared with those from Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS)
and Inductively Coupled Plasma Atomic Emission Spectrophotometry (ICP-AES). The sample irradiation was done at the irradiation
facilities (thermal neutron flux, 5·1012 n·cm−2·s−1) of the TRIGA Mark-III research reactor in the Korea Atomic Energy Research Institute. Four unalloyed copper standards (NIST
SRM # 393, 394, 395 and 398) were used to identify the accuracy and precision of the analytical procedure. The homogeneity
of samples was assessed by means of the elements such as Ag, As, Co, Sb, Se and Zn. The analytical results of INAA, GFAAS
and ICP-AES were in good agreement within expected uncertainties each other and showed the possibility of using them for the
analytical quality control. 相似文献
3.
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
4.
D. A. Becker 《Journal of Radioanalytical and Nuclear Chemistry》1998,233(1-2):155-160
Recently a new rapid pneumatic tube facility was inserted into a long unused location in the NIST 20 MW nuclear reactor. This
facility was designed and constructed specifically for rapid INAA using short lived activation products. Included is a computer
controlled console which uses fast sensors to accurately measure the irradiation capsule flight time, and a loss-free counting
system connected to a 32% efficient PHGe detector with a transistor reset preamplifier. Measurement of travel, times from
end-of-irradiation to detector were 473±8 ms. Measurement of the thermal neutron fluence rate was 5.0·1013 n·cm−2·s−1. The other three pneumatic tubes in the NIST reactor have transfer times of 3 to 15 seconds, and no timing capability more
accurate than human response. This new facility substantially improves our ability to accurately determine activation products
with half-lives from 1 to 100 seconds. Characterization information reported on this new irradiation facility includes absolute
fluence measurements, fluence rate variations within the capsule and variations with time, and determination of analytical
sensitivities for fluorine-20 selenium-77m, and silver-110g. 相似文献
5.
A. Meghea H. H. Rehner I. Peleanu R. Mihalache 《Journal of Radioanalytical and Nuclear Chemistry》1998,238(1-2):105-110
An alternative method of approach has been developed for the measurement of thermal neutron flux. The method depends only
on the activity of the bare foil if the cadmium ratio at the irradiation position is known. The method has been tested on
the GHARR-1 facility at the Ghana Atomic Energy Commission using gold and indium foils for the measurement of the thermal
neutron flux in the flux range of 1010–1012 n·cm−2·s−1 and the results compare very well with those obtained using the conventional method (cadmium separation method). 相似文献
6.
P. K. Nayak B. Wierczinski S. Lahiri 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(1):179-184
Representative banded iron-formations (BIFs) from various locations of the eastern Indian geological belt were investigated
by instrumental neutron activation analysis (INAA). After pre-concentration, irradiation was carried out using a neutron flux
of 5.1·1016 m−2·s−1, 1.0·1015 m−2·s−1 and 3.7·1015 m−2s−1, with thermal, epi-thermal and fast neutrons, respectively. The activities in these samples were measured by a HPGe detector.
Ten rare-earth elements, such as La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu, have been qualitatively identified and quantitatively
estimated in these samples. The present investigation is an example of employing a pre-concentration method for high iron-containing
ores prior to neutron activation analysis. 相似文献
7.
An instrumental neutron activation analysis (INAA) method has been developed for multi-element determination in geological
samples. The INAA method consists of irradiation of samples for 90 sec at a flux of 1.0·1012 n·cm−2·sec−1 and determination of 12 elements by using their short-lived nuclides. Samples have been re-irradiated for 3 hrs for measuring
concentrations of another 10 elements. Precision and accuracy of the INAA method have been evaluated by analysing samples
and USGS standard reference materials. Precision and accuracy are within±15% and ±10%, respectively. 相似文献
8.
Le Van So N. Morcos M. Zaw P. Pellegrini I. Greguric 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(3):663-673
The conventional multi-column solid phase extraction (SPE) chromatography technique using di-(2-ethylhexyl)orthophosphoric
acid (HDEHP) impregnated OASIS-HLB sorbent based SPE resins (OASIS-HDEHP) was developed for the separation of no-carrier added
(n.c.a) 177Lu from the bulk quantity of ytterbium target. This technique exploited the large variation of lutetium metal ion distribution
coefficients in the varying acidity of the HCl solution-OASIS-HDEHP resin systems for the consecutive loading-eluting cycles
performed on different columns. The production batches of several hundred mCi n.c.a 177Lu radioisotope separated from 50 mg Yb target activated in a nuclear reactor of medium neutron flux (Φ = 5·1013 n·cm−2·s−1) were successfully performed using the above mentioned separation technique. With the target irradiation in a reactor of
thermal neutron flux Φ = 2·1014 n·cm−2·s−1 or the parallel run of several separation units, many Ci-s of n.c.a 177Lu can be profitably produced. The OASIS-HDEHP resin based multi-column SPE chromatography technique makes the separation
process simple and economic and offers an automation capability for operation in highly radioactive hazardous environments. 相似文献
9.
10.
A sensitive, simple and time-saving method has been developed for the neutron activation analysis of gallium at concentrations
around 10−4 ppm in biological tissues. After a 24-hour irradiation in a thermal neutron flux of 2.8·1013 n·cm−2·s−1 and a purification by ion-exchange chromatography to eliminate troublesome elements such as sodium, iron and copper, the72Ga activity is measured with enough accuracy for the method to be applicable in animal physiology and clinical toxicology. 相似文献
11.
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
12.
A. V. Gurevich Z. V. Vikhrova V. Ya Vyropayev V. I. Drynkin D. I. Leipunskaya I. Ya. Shirokova 《Journal of Radioanalytical and Nuclear Chemistry》1980,57(2):417-422
The distribution of the elemental composition was studied mainly for microelements in the diabases of the Pechenga suite subjected
to various changes. Investigations were conducted by a combination of instrumental neutron activation INAA and X-ray fluoresence
XRFA analyses. The INAA was conducted with sample weights of 20–100 mg exposed to irradiation in a nuclear reactor by a flux
of neutrons ≈1013 n·cm−2·s−1. Measurements were carried out by means of a semi-conductor gamma-spectrometer with a Ge(Li) detector. The determination
of Al, Mn, Mg, Ti, V, Ca was conducted by short-lived isotopes, while the determination of Na, Sc, Fe, Co, Cr, Hf, Th, La,
Ce, Sm, Eu, Yb, Lu by longlived ones. For XRFA samples weighing up to 2 g were irradiated by means of an109Cd isotope source and were measured by a spectrometer with a Si(Li) detector and beryllium window. By this method we determined
the Sr, Zr an Nb contents. Continuous distribution histograms were plotted for the concentration of 22 elements and some of
their ratios. Considerable variations in microelemental composition observed in a number of cases make it possible to assess
the character of past processes of diabasic change. 相似文献
13.
Certain elements which are not possible to detect with conventional neutron activation analysis can be measured using thermal
neutron-capture gamma-ray analysis. The use of a curved neutron guide at the High Flux Reactor, Grenoble, with a thermal neutron
flux of 1.5·1010n·cm−2·sec−1 and the advantage of a low-background counting system (Ge(Li) detector) far from the reactor core are described. Experimental
detection limits of a number of elements are given for the low-energy and the high-energy regions. Some applications of the
capture gamma-ray method in the whole energy range are studied and are briefly discussed. 相似文献
14.
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
15.
S. E. Jarman J. Pinchin J. M. Brushwood T. McCarthy M. Bray P. A. Beeley 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):47-53
The potential for using a small, sealed tube, DT neutron generator for neutron activation analysis has been well documented
but not well demonstrated, except for 14 MeV activation analysis. This paper describes the design, construction and characterization
of a neutron irradiation facility incorporating a small sealed tube DT neutron generator producing 14 MeV neutrons with fluence
rates of 2·108 s−1 in 4π (steady state) and 1011 s−1 in 4π (pulsed). Monte Carlo modeling using MCNP4c and McBend9 has been used to optimize the design of this facility, including
the location of a thermal irradiation facility for conventional neutron activation analysis. A significant factor in designing
the facility has been the requirement to conform with Ionising Radiation Regulations and the design has been optimized to
keep potential radiation doses to less that 1 μSv/h at the external walls of the facility. Activation of gold foils has been
used for flux characterization and the experimental results agree well with the modeling. 相似文献
16.
T. Goldbrunner R. v. Hentig G. Angloher F. v. Feilitzsch 《Journal of Radioanalytical and Nuclear Chemistry》1998,234(1-2):43-49
We present a NAA method to determine ultratraces of K, Th, U and other trace impurities in liquid organic scintillators, which
are known as ultrapure detector materials for neutrino or dark matter experiments. A combined optimization of relevant factors
for sensitive NAA has been realized, leading to a sensitivity for U down to 10−16g/g. Samples of 250 ml have been irradiated up to 120 h at a thermal neutron flux of 5–8·1012·n·cm−2·s−1. Acidic extraction, wet ashing and TBP-extraction are used for radiochemical separations. Finally, coincidence techniques
are applied for increased sensitivity. 相似文献
17.
D. I. Leipuskaya V. I. Drynkin D. M. Voinkov I. F. Brovchuk K. I. Ilyasova B. V. Belenki 《Journal of Radioanalytical and Nuclear Chemistry》1980,57(2):407-416
A method has been worked out of multi-elemental instrumental neutron-activation analysis INAA of small weights some mg of
monomineral fractions of sulfide minerals pyrites, galenites, chalcopyrites, arsenopyrites, bornites, chalcosines and quartzes.
The samples were irradiated in a nuclear reactor under a flux of 1.3·1013 n·cm−2·s−1. For measuring the gamma radiation of the exposed samples Ge(Li) gamma-spectrometers with semiconductor detectors were used.
Determined in sulfide monofractions were the elements: Co, Sc, Ag, Se, Sb, Cr, Fe, Zr; rare-earth elements: Ce, Sm, Eu and
others at content levels of 10−1−10−4%. In quartzes they were: Mn, Na, Sb, Cr, Sc, Fe, Co at content levels of 10−5−10−7% and Au to n×10−9%. A special method has been worked out for the determination of In in sulfides with the irradiation of samples in a cadmium
screen. An example is cited of using the method for studying some peculiar features of the genetics of copper pyrite deposits.
The data on the distribution of admixture elements in sulfide monofractions produced in this work made it possible to conclude
that the oreformation in the deposits has a stage-by-stage character. 相似文献
18.
With the advent of Ge(Li) spectrometry, a high standard of purity for neutron flux monitors no longer remains an imperative
“must” and becomes rather superfluous. From this standpoint, commercial grade Al was investigated for its suitability as a
reactor flux monitor and was found to have a much greater practical utility than most of the monitors reported. Three Al foils
and one wire were randomly selected from four different commercial sources, and analysed for their Fe, Ga, Mn and Na contents
by neutron activation and high-resolution gamma-spectrometry. While Na was found to have a very heterogeneous distribution,
Fe, Mn and Ga concentrations in different splits of each type of Al were consistently uniform within ±2–3%. Eight possible
monitor reactions on Al, Mn, Fe and Ga have been recommended as neutron flux integrators for all the 3 components of a reactor
spectrum, viz. thermal, epithermal and fast, covering a wide range of flux levels from 107 to 1014n·cm−2·sec−1. The advantages and versatility of commercial grade Al as a pile neutron dosimeter are discussed. 相似文献
19.
One of the missions of our Institute is the promotion of basic nuclear teaching for students as well as professional teaching
for workers in nuclear industry and research. For nuclear chemistry education, we present here a one day teaching course on
radioactive decay and nuclear reactions, and a two or three days course based on reactor irradiation of uranium oxide, instrumental
and radiochemical analysis of fission products. In the first experiment, the neutron capture is presented as an example of
nuclear reaction; the neutron activation of a silver coin with a Am-Be neutron source, followed by γ-ray spectrometry, is
used to identify three radionuclides of silver and to calculate their half-lives. In the second experiment, our teaching reactor
is used as a neutron source with a flux about 1010 n·cm−2·s−1 at a low thermal power (10 kW). This low flux allows us to irradiate a small uranium sample which is usable for spectrometry
after a short cooling time of about two hours. The first day is reserved for instrumental analysis of the fission products
and a second day for the radiochemical separation of a fission radionuclides. With these experimental results, the students
have to calculate the number of fissions in the irradiated sample. On optional third day for postgraduate students is devoted
to the presentation of NAA and some applications as uranium determination by the fission product spectrometry. 相似文献
20.
Z. Lamari S. Landsberger J. Braisted H. Neggache R. Larbi 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(1):95-99
Neutron activation analysis (INAA) has been applied to multielemental determination of eleven medicinal plants used to cure
the urinary tract diseases observed in Algeria. These plants include Androgena Citratus, Ceratonia Siliquata, Punica Granatum, Glyryrrhiza Glabra, Lausaunia Alba, Fragaria Vesca, Arbutus Unedol,
Hordeum Vulgaris, Papieteria Officinalis, Zea Mays L, and Davallia Seae. Concentrations of twenty elements Ba, Br, Ca, Cl, Co, Cu, Cr, Fe, I, Mn, Na, Mg, Rb, Sb, Se, Sc, Sr, Ti, V, and Zn have
been determined by short, and long irradiation times with a thermal and epithermal flux of 1.4·1012 n·cm−2·s−1 and 1.4·1011 n·cm−2·s−1, respectively. These analyses were performed in conjunction with Compton suppression. In almost herbs studied the Co, Cr,
Cu, Rb, Sb, Sc, Se and V are found to be present at trace levels, Br, Mn, and Zn at the minor level, and Ca, Cl, Fe, Mg and
Na are generally at the major level. The accuracy of the measurements has been evaluated by analyzing NIST-botanical references
materials. 相似文献