共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
T. Nozaki M. Ichikawa T. Sasuga M. Inarida 《Journal of Radioanalytical and Nuclear Chemistry》1970,6(1):33-40
Uranium in human bone, drinking water and daily diet has been determined by neutron activation analysis using the238U(n, γ)239U reaction. An improved scheme for the separation of the239U is proposed; with this scheme, after neutron irradiation in a 100 kW TRIGA reactor, a uranium content as low as 5·10−11 g can be determined reliably, rapidly and easily. A wide range of uranium concentrations, from about 0.1 ppb up to about
10 ppb has been found in the bones of normal Japanese. Water from several Japanese city water services, and the daily diet
taken in two Japanese cities, have been found to contain an average 9·10−9 g/l and 1.5 μg per person-day uranium, respectively. 相似文献
3.
J. H. Augustson J. W. Haynes T. W. Sanders 《Journal of Radioanalytical and Nuclear Chemistry》1980,60(2):373-383
A method for the determination of uranium based on235U thermal neutron fission, has been developed and employed on samples of ashed fish tissue and seaweed. The method involves
a post-irradiation ion exchange separation of iodine isotopes. The 884 keV photopeak of134I is used for measurement. Uranium detection limits in the samples concerned have been estimated to be 1·10−8g in terms of natural uranium. The precision achieved in analysing several series of 3–5 samples was 4–10 per cent. The accuracy
of the method was tested by employing an independent neutron activation procedure based on239U measurement. The accuracy of both methods was checked by analysing NBS SRM 1571 ‘Orchard Leaves’. 相似文献
4.
N. Megouda M. S. Hamlat H. Kadi H. Saibi A. Gherbi 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(1):75-79
Batch sorption experiments have been carried out to remove natural uranium (NORM) from water obtained together with crude
oil and natural gas, using Algerian bentonites. The effect of some important factors such as S/L ratio, pH, initial concentration, particle size was evaluated and a kinetic study performed. The value of the distribution
coefficient (K
d) at equilibrium for natural uranium varied from 30 to 600 cm3·g−1 and 50 to 1100 cm3·g−1 (∼10% margin error) using natural bentonite and drilling bentonite, respectively. The isotherms showed that the data are
consistent with both Freundlich and Langmuir models. 相似文献
5.
M. Alkhorayef E. Abuelhia K. Alzimami M. Marouli M. P. W. Chin N. M. Spyrou 《Journal of Radioanalytical and Nuclear Chemistry》2009,280(2):315-318
The yield of three photon positron annihilation is measured using semiconductor and scintillation detectors in a comparison
for applications in positron emission tomography, particularly in the exploitation of three photon positron annihilation imaging
where good energy resolution and good efficiency are required. In this experimental study four detectors, High-purity Germanium
(HPGe), Sodium Iodide (NaI(Tl)), Lanthanum Chloride (LaCl3:10%Ce3+) and Lanthanum Bromide (LaBr3:5%Ce3+) were used. The peak-to-peak method was used with a 22Na source to determine these yields. Aluminium was employed as a reference material as its high electron density reduces positronium
formation and lifetimes. Teflon was also used in order to enhance the formation of ortho-positronium, since quenching is low,
leading to increased three photon positron annihilation. The relative 3γ/2γ yields obtained were (3.04±0.11)·10−2, (2.17±0.11)·10−2, (3.26±0.10)·10−2 and (2.03±0.11)·10−2 for LaBr3:Ce, LaCl3:Ce, NaI(Tl) and HPGe detectors, respectively. Among these detectors LaBr3:Ce proved to be the detector of choice for three photon imaging applications as it has both good energy resolution and efficiency. 相似文献
6.
J. Cabicar A. Gosman J. Plicka K. Štamberg 《Journal of Radioanalytical and Nuclear Chemistry》1983,80(1-2):71-80
The kinetics of isotope exchange in the238U(VI)-233U(VI)-strongly acidic cation exchanger Ostion KS system was studied in the temperature range 275–307K and for total uranium
concentration 2.94·10−4–1.75·10−2 mol·l−1 in UO2(NO3)2 solution. The experimental results were evaluated by means of the “two-film mass-transfer model” and by the use of Fick's
diffusion equations which have been proved more suitable for the system studied than McKay's equation. The influence of the
temperature was evaluated using the Arrhenius equation. The diffusion character of the process follows also from the value
of the activation energy (15.12 kJ·mol−1). In comparison with the UO
2
2+
↔H+ ion exchange6 the isotope exchange studied is faster and less dependent on temperature (the activation energy is substantially lower). 相似文献
7.
R. K. Singhal J. Preetha Rupali Karpe P. Hema Ajay Kumar V. M. Joshi A. K. Ranade A. G. Hegde 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):301-306
During this work the determination of uranium in the range of μg·L−1 to tens of μg·L−1 was done by alpha-spectrometry after electroplating the aliquots of water sample using (NH4)2SO4 as an electrolyte. In general, the determination of uranium by alpha-spectrometry needs its separation from other transuranics
specially thorium. The process described here does not involve any sample digestion and radiochemical separation of uranium
from other transuranics. In this method an aliquot (1 to 3 mL) of the sample was dried and dissolve in (NH4)2SO4 and thereafter the sample was electroplated on a stainless steel (SS) planchet by using an electrochemical cell of special
design. The proposed techniques have a distinct advantage over the determination of uranium by adsorptive stripping voltammetry
(AdSV) in which uranium-chloranilic (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) acid complex was used for concentrating
the uranium from the solution. Since in the case of AdSv, the determination of uranium was not possible for samples having
dissolved organic carbon (DOC) more than 15 mg·L−1 and Cl− concentration is in the range of 40,000 μ·g−1. In the case of spike experiments with 232U the recovery was observed in the range of 90–95% in aqueous medium having higher concentration of Cl− and DOC as indicated above. 相似文献
8.
U(VI) was quantitatively extracted from 1·10−3M HNO3 using 5·10−3M Cyanex 302 in xylene and was stripped from organic phase with 5M HCl. The optimum extraction conditions have been evaluated
by studying parameters like acidity, effect of diluents, extractant concentration and period of equilibration. Based on this
data, the separations of uranium from binary and complex metal mixtures and its recovery from uranmicrolite tailings (leachate)
were successfully tested. Uranium can be determined with a relative standard deviation of 0.4%. 相似文献
9.
Ph. Cauchetier 《Journal of Radioanalytical and Nuclear Chemistry》1979,51(2):225-231
Neptunium is produced in significant amounts in the “light-water” reactors and must be controlled at different steps of fuel
reprocessing. For this purpose, we have developed a method of differential pulse polarography. A tight cell containing 10
ml solution is set up in a Faraday cage. Adjustment to the tetravalent state, Np(IV), is carried out electrochemically on
a mercury layer and the Np(IV) concentration is determined by differential pulse polarography, using a dropping mercury electrode.
In 0.5M sulfuric acid medium, the redox potential of the reversible couple Np(IV)/Np(III) is-0.3V/SCE. Concentrations as low
as 5·10−7M neptunium can be measured and detection at the 2·10−7 M level is still possible. (0.5μg in the polarographic cell). Precision is about 2% in the 10−5M and 10% in the 10−6M range. The method has been applied to aqueous and organic (TBP_dodecane) solutions. Neptunium can be determined without
separation in the presence of plutonium or uranium at M/Np ratios of 103 and 5·104, respectively. In the presence of fission products a separation is needed. 相似文献
10.
L. D. Akol'zina I. P. Alimarin G. N. Bilimovich N. N. Churkina 《Journal of Radioanalytical and Nuclear Chemistry》1980,57(2):279-285
The possibility of using coprecipitation on Cu(OH)2·nH2O and Fe2O3·nH2O precipitates to separate a part of zirconium unreacted with complexone in the presence of a 100-fold amount of impurities
has been examined. The reaction between ethylenedia-minetetraacetic acid (EDTA) and zirconium 10−3−10−5 M has been used as substoichiometric reaction. A zirconium determination in the concentration range of 10−4−10−6 g/ml in artificial mixtures and steel samples has been developed using the systems of EDTA-Zr−Cu(OH)2·nH2O and EDTA−Zr−Fe2O3·nH2O. 相似文献
11.
I. F. Yazikov N. N. Rodin M. A. Dembrovsky V. G. Lambrev 《Journal of Radioanalytical and Nuclear Chemistry》1969,3(1-2):11-16
A method is described for the radioanalytical determination of traces of chlorine in aqueous solutions without radiochemical
separation or purification. Using a gamma-spectrometer with monocrystal scintillator, the sensitivity of the analysis is about
1·10−8 g of chlorine/ml, the time of analysis being 15 minutes. For the selective determination of chlorine in aqueous solutions
containing a large amount of impurities, a bicrystal scintillation sum-coincidence spectrometer was employed with 120×100
mm NaI(Tl) crystals and thus the38Cl cascade radiation could be used. Application of the sum-coincidence spectrometer allowed a reliable determination of 1·10−7 g of Cl/ml against a background of 1·10−5 g of Na/ml. 相似文献
12.
I. P. Alimarin A. Z. Miklishanskii Yu. V. Yakovlev 《Journal of Radioanalytical and Nuclear Chemistry》1970,4(1):45-51
A method with a sensitivity of 2·10−7 to 1·10−10% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation.
The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by
passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the
resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·1013 n·cm−2·sec−1. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)3, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8
anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2
cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant. 相似文献
13.
The possibility to use the most intensive gamma-peak of239Np for INAA of uranium with epithermal neutrons and high resolution Ge(Li)-spectrometry is evaluated. A way for calculation
of the peak area of overlapping peaks of153Sm and239Np is proposed. This can be used in other similar cases in the practice of NAA. On this basis a scheme for NAA of uranium
in geological objects is proposed. Lower detection limit is 8·10−8 g U the precision 5–10% (relative standard deviation). The accuracy is demonstrated by the analysis of some geological standard
reference materials. 相似文献
14.
I. Pashalidis G. J. Kontoghiorghes 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(1):181-184
In an effort to develop new chelating agents for the decorporation of uranium and other actinides, the interaction of the
clinically used 1,2-dimethyl-3-hydroxypyrid-4-one (Deferiprone or L1) with hexavalent uranium was investigated by using UV-VIS
spectroscopy and solubility measurements. The complex stoichiometry estimation carried out by the Job plot method indicated
that under normal conditions up to pH 8.0 a 1[U(VI)]∶1[L1] complex is formed. The stability constant of the UO2L1+ complex was determined by spectroscopic and solubility experiments and found to be log β11=9.1±0.3. The molar extinction coefficient at pH 7.6 for the complex at 500 nm was estimated to be 650 l·mol−1·cm−1. At ligand concentrations higher than 6·10−4 mol·l−1 the formation of a precipitate was observed. The stoichiometry UO2(L1)2 was identified following FTIR measurements of the red precipitate and UV/VIS spectroscopy after dissolution. 相似文献
15.
Detection of small quantities of uranium in silicon wafers has been carried out by neutron activation followed by observation
of fission product140La. Irradiations of about one week were made at a flux of 6·1014n cm−2 s−1 and the activity of the 1596 keV line was determined. Counting rates of as low as 1 count per minute have been observed.
This indicates uranium concentrations of about 5·1010 atoms per cubic centimeter of silicon or about 0.01 mg/g, assuming activity from other fissionable nuclides to be negligible. 相似文献
16.
A method for the analysis of uranium in natural waters based on preconcentration of uranium on activated carbon, irradiation
with epithermal neutrons, and a high resolution gamma-spectrometry of239Np was developed. The chemical yield of uranium preconcentration is determined by treating a parallel sample to which a known
uranium quantity is added. The lower limit of determination amounts to 1.4·10−8 g uranium per liter. The possible interfering in gamma-spectrometry of neptunium-239 was discussed too. The applicability
of the proposed method is shown by the analysis of uranium in sea-, river-, geothermal-, drinking- and rain-water samples. 相似文献
17.
R. Sampatkumar A. Ramaswami P. C. Kalsi R. J. Singh S. B. Manohar 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(3):825-827
A simple technique based on the measurement of the ratio of alpha-decay constant to neutron induced fission cross section
for pure actinides using solid state nuclear track detectors (SSNTDs) is developed for the identification of the actinides
in trace levels in pure solutions. The alpha-decay constant to fission cross section ratios for depleted U,238Pu and240Pu have been measured for the epicadmium neutron induced fission of these actinides. The measured values are (6.19±0.34)·106, (6.95±0.26)·1012, (2.12±0.95)·109 and (2.18±1.58)·1011 sec−1·cm−2, respectively. These ratios can be used for the trace level identification of pure actinides. 相似文献
18.
T. Fujinaga Y. Kusaka M. Koyama H. Tsuji T. Mitsuji S. Imai J. Okuda T. Takamatsu T. Ozaki 《Journal of Radioanalytical and Nuclear Chemistry》1973,13(2):301-311
A method is described for the determination of trace metal ions, V, Al, Cu, Mo Zn, and U, in natural water samples by neutron
activation analysis, using organic coprecipitation as a preconcentration method. The preconcentration of trace elements was
accomplished by converting the dissolved trace metal ions into the oxine chelates atpH 5.2 and extraction of the chelates witho-phenylphenol which is a liquid above 56 °C and solidifies at room temperature. After cooling the extraction system, the fine
particles of the organic phase were collected on a millipore filter and the precipitate was air-dried in a clean environment.
The solid extract was wrapped up in a sheet of clean polyethylene and subjected to neutron irradiation in a reactor for less
than 10 min at a thermal flux of 2·1013 n·cm−2·sec−1. γ-Ray spectrometry by a coaxial Ge(Li) detector connected to a 1024-channel PHA was performed on the irradiated sample without
further chemical separation, and thus the ppb level concentration of the elements in natural water samples could be determined.
The fundamental study of the collection of the trace elements is also described. 相似文献
19.
The electrochemical behavior of the ofloxacin–copper complex, Cu(II)L2, at a mercury electrode, and the interaction of DNA with the complex have been investigated. The experiments indicate that
the electrode reaction of Cu(II)L2 is an irreversible surface electrochemical reaction and that the reactant is of adsorbed character. In the presence of DNA,
the formation of the electrochemically non-active complexes Cu(II)L2-DNA, results in the decrease of the peak current of Cu(II)L2. Based on the electrochemical behavior of the Cu(II)L2 with DNA, binding by electrostatic interaction is suggested and a new method for determining nucleic acid is proposed. Under
the optimum conditions, the decrease of the peak current is in proportional to the concentration of nucleic acids in the range
from 3 × 10−8 to 3 × 10−6 g · mL−1 for calf thymus DNA, from 1.6 × 10−8 to 9.0 × 10−7 g · mL−1 for fish sperm DNA, and from 3.3 × 10−8 to 5.5 × 10−7 g · mL−1 for yeast RNA. The detection limits are 3.3 × 10−9, 6.7 × 10−9 and 8.0 × 10−9 g · mL−1, respectively. The method exhibits good recovery and high sensitivity in synthetic samples and in real samples. 相似文献
20.
S. Guedes J. C. Hadler N P. J. Iunes S. R. Paulo A. Zuñiga 《Journal of Radioanalytical and Nuclear Chemistry》2000,245(2):441-442
This work reports the results of 5 measurements of the 238U decay constant for spontaneous fission, f carried out using solid state nuclear track detectors (SSNTD), resulting in a mean value of f = (8.35±0.24)· 10–17 y–1. The neutron fluence of the irradiations needed for these measurements were monitored with thin films of natural uranium. 相似文献