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1.
A detailed theoretical treatment of cyclic activation analysis of thorium and uranium using a 14 MeV neutron generator and
delayed neutron counting is presented. Variations of the detector response with sample transfer and total experiment times
are examined in order to obtain the optimum cycle periods for the maximum detector response. Cycle optimization for 95% and
90% of the maximum detector response is investigated. Furthermore, elimination of the delayed neutrons produced by the reaction17O(n,p)17N is also considered in optimum cycle timing. Finally, calculations are carried out to estimate detection limits for thorium
and uranium. Experimental results will be reported in a subsequent paper. 相似文献
2.
Concentrations of uranium and thorium in some West Malaysian limestones have been determined using neutron activation and delayed neutron analyses. These limestones are mainly calcium carbonates and contain uranium and thorium in concentrations of about a few parts per million. 相似文献
3.
R. J. Rosenberg V. Pitkänen A. Sorsa 《Journal of Radioanalytical and Nuclear Chemistry》1977,37(1):169-179
An automated device for the analysis of uranium is described. The analyser comprises a sample transfer system, a neutron counter,
a microprocessor and a teletype. A set of 100 samples, 14 ml of maximum volume, is analysed without manual intervention. The
capacity is 45 samples per hour. Using a 10 g sample the detection limit is 0.06 ppm and uranium concentrations of 1 ppm can
be determined with a precision of better than ±5%. The only source of systematic error is thorium the sensitivity of thorium
being 2.3% of that of uranium. Results for USGS standard rocks are reported and the cost of the analysis is discussed. 相似文献
4.
5.
E. S. Gladney D. R. Perrin W. K. Hensley 《Journal of Radioanalytical and Nuclear Chemistry》1980,59(1):249-251
Uranium was measured in eight biological standards at the part-per-billion level. Matrix effects encountered in the use of
liquid standards are discussed.
This work performed under auspices of the U.S. Department of Energy 相似文献
6.
R. J. Rosenberg 《Journal of Radioanalytical and Nuclear Chemistry》1981,62(1-2):145-149
A simple method for the determination of uranium and thorium by delayed neutron counting is described. One portion of the
sample is irradiated in a reactor and the delayed neutrons are counted. Another portion of the sample is mixed with B4 C powder absorbing the thermal neutrons, and irradiated in the same position. From those data, both uranium and thorium can
be calculated when a quantitative calibration has been made beforehand. The detection limits for the pure elements are 0.07
ppm for uranium and 2 ppm for thorium with the minimum analyzing time being 2 min. The accuracy of the method is investigated
by comparing results obtained by the method described here with results obtained by epithermal activation analysis. 相似文献
7.
Three analytical methods for uranium by neutron activation are described. The methods are based on the substoichiometric separation of barium or lanthanum, which are the fission products of uranium-235 by neutron irradiation. Uranium contents in high purity materials were determined by the methods, which were found to be useful for the determination of a trace amounts of uranium. 相似文献
8.
N. C. Silva J. F. Macacini H. T. Fukuma E. A. N. Fenandes 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(2):211-213
Phosphoric acid is generally obtained from an aqueous process starting with the reaction between phosphate rock and sulphuric
acid. Due to their chemical similarity, uranium is usually associated with phosphate rock which during chemical processing
is partitioned to phosphoric acid. Uranium determination in this matrix is a very important task because of its ingestion
it could lead to radiological impact on the population. Therefore, a procedure was developed using an initial precipitation
with calcium hydroxide and evaporation, followed by instrumental neutron activation analysis (INAA). The procedure was applied
to analyse fourteen uranium enriched phosphoric acid samples. 相似文献
9.
M. S. Chaudhry M. I. Qureshi I. H. Qureshi 《Journal of Radioanalytical and Nuclear Chemistry》1978,42(2):427-434
An instrumental neutron activation analysis method based on the measurement of239Np has been developed for the determination of uranium in ores. The samples after 5 sec irradiation were cooled for 3 days
and the gamma-ray spectra were measured with a 30 cm3 Ge(Li) detector. The precision and accuracy of the proposed method were determined by analysing IAEA Standard Uranium Ore
samples. 相似文献
10.
P. Schlechte 《Journal of Radioanalytical and Nuclear Chemistry》1981,61(1-2):55-61
A fast, sensitive and routine methode for quantitative analysis of uranium and thorium in natural samples is described. The
identification is done by counting the delayed neutrons of mainly the short living fission products after sample-irradiation
with and without cadmium shielding. The rabbit system used is installed at the Forschungsreaktor Neuherberg, type TRIGA Mark
III. The limits of detection (relative to 2 g of sample weight) were specified to be 20 ppb (U) and 3 ppm (Th) using puls
irradiations, 150 ppb (U) and 15 ppm (Th) using 1 MW steady state reactor power. A single determination is done within less
than 60 s. The methods were proved by about 3000 measurements also including comparison experiments. 相似文献
11.
N. K. Mumba L. Vas Cs. M. Buczkó 《Journal of Radioanalytical and Nuclear Chemistry》1985,95(5):311-322
Applicability of a small neutron generator and a dual rectangular tube sample transfer system for analyses of U and Th using delayed fission neutron technique has been investigated. A way of optimizing the timing parameters is reported. At a fast neutron flux of 108 n.cm–2s–1, 0.02 w% U can be determined. For thorium determination this method is less sensitive. The Cd difference technique can be used for the simultaneous determination of U and Th but it has lower sensitivity.This work was supported in part by the IAEA. 相似文献
12.
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
13.
A method for the continuous on-stream determination of trace concentrations of uranium and thorium in flowing streams is developed.
The 14 MeV neutron generator was used for irradiation and the delayed neutron counting technique was employed in counting
the induced neutron activity. The dependence of the minimum detectable concentration on the irradiation, decay and counting
times, liquid flow-rate and the background was studied. At optimal conditions, uranium and thorium concentrations were determined
down to 20 and 100 ppm, respectively. The interference of the neutron emitting nuclide17m
O was reduced to an insignificant level by optimizing the decay time. 相似文献
14.
A new type of extractant, sym-dibenzo-16-crown-5-oxyhydroxamic acid (HL) is introduced. The extractions of UO22+, Na+, K+, Sr2+, Ba2+ and Br- were studied with HL in chloroform. The results obtained show that UO22+ can be quantitatively extracted at pH values above 5, whereas the extractions of K+, Na+, Sr2+, Ba2+ and Br- are negligible in the pH range of 2 - 7. The dependence of the distribution ratio of U(VI) on both the concentration of the HL and pH are linear, and they have the same slope of 2. This suggests that U(VI) appears to form a 1:2 complex with ligand. Uranium(VI) can be selectively separated and concentrated from interfering elements such as Na, K, Sr and Br by solvent extraction with HL under specific conditions. The recovery of uranium is nearly 100% and the radionudear purity of uranium is greater than 99.99%. Therefore, neutron activation analysis has greatly improved the sensitivity and accuracy for the detection of trace uranium from seawater. 相似文献
15.
Xiao Caijin Yao Yonggang Jin Xiangchun Hua Long Wang Pingsheng Ni Bangfa 《Journal of Radioanalytical and Nuclear Chemistry》2017,312(3):711-715
Journal of Radioanalytical and Nuclear Chemistry - Delayed neutron counting (DNC) was applied in quantitative determination of 235U/238U, quantitative determination of 235U and 239Pu in... 相似文献
16.
R. Kapsimalis D. Glasgow B. Anderson S. Landsberger 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(3):1721-1726
Delayed neutron activation analysis (DNAA) remains one of the most sensitive methods of nondestructively determining fissile materials in a variety of sample matrices, provided that the samples contain only a single fissile component. This has historically been the limiting factor in many applications of DNAA, and often chemically destructive methods of analysis have needed to be utilized for many real-world samples. This work seeks to develop a method that will allow for DNAA to be utilized on samples containing multiple fissile components. Initial efforts, presented here, show that using a multivariate linear regression model to describe the delayed neutron emission profile of an irradiated sample allows for the concurrent determination of fissile nuclides in samples containing both 235U and 239Pu, without chemical separations and using only a single counting step. 相似文献
17.
M. Kadri J. J. Schleiffer J. P. Adloff 《Journal of Radioanalytical and Nuclear Chemistry》1992,158(2):353-366
The chemical state of239Np formed in the -decay of239U produced by thermal neutron capture in239U, has been determined in simple uranium compounds as well as in macrocyclic complexes of this element. It is shown that the behavior of neptunium depends on such factors as the nature of the target, the counter-ion of the complex, the dissolution medium and the pH. The change of the oxidation state of239Np with time and the effect of the presence of macroscopic amounts of238UO
2
2+
and of238U(IV) in the solution have also been investigated. The results are discussed in terms of the hot atom behavior of239U and of the genuine effects of -decay. 相似文献
18.
N. M. Spyrou J. M. Sharaf S. Rajeswaran E. Mesbahi 《Journal of Radioanalytical and Nuclear Chemistry》1997,217(2):237-241
The factors that affect accurate, quantitative results to be obtained by neutron induced gamma-ray emission tomography are stated. The technique, which is a combination of neutron activation analysis with computerised gamma-ray emission tomography, would be enhanced by the use of multiple detector assemblies, in geometrical configurations, which simultaneously record the gamma-rays emitted and improve detection efficiency. Developments in the past few years in positron emission tomography (PET) where scanners made of single scintillation block detectors, cut into smaller segments, to form individual crystal detector elements and packed in ring around the radioactive object, are discussed. The coincident detection efficiency for annihilation photons and cascade gamma-rays for such systems are considered and the possibilities of carrying out NIGET with coincident gamma-ray tomography are explored whilst indicating some of the limitations. This is an area which requires further, intense investigation and has an impact on a wide range of applications, particularly in the biomedical field. 相似文献
19.
Zeinab F. Akl 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(1):21-28
This article reports the utilization of cloud point extraction as a preconcentration strategy prior to U(VI) determination by inductively coupled plasma-optical emission spectrometry. Complexes of U(VI) with Cyanex-301 were preconcentrated into mixed-micellar medium using Triton X-100 and Cetylpyridinium bromide at ambient temperature. Optimal values of parameters impacting the extraction efficiency were determined. The proposed technique has linearity range of 5–200 ng mL?1 with r = 0.99 and detection and quantification limits of 0.57 and 0.85 ng mL?1, respectively. The method has good selectivity for U(VI) over various cations and was successfully applied to U(VI) determination in water samples with satisfactory results. 相似文献
20.
Mohammad Ejaz 《Mikrochimica acta》1976,66(3-4):265-270
Summary Radiochemical cerium has been separated from young fission products by extraction of uranium and fission product nuclides using tri-n-octylamine oxide and an anion exchange column for preconcentration followed by extraction of cerium(IV) with 0.25M xylene solution of 4-(5-nonyl) pyridine oxide from 0.1M nitric acid. Cerium is then back extracted by reduction with HCl-H2O2 mixture.
Zusammenfassung Zur Abtrennung radioaktiven Cers werden Uran und Spaltproduktnuklide mittels Tri-n-oktylaminoxid extrahiert. Mit Hilfe einer Anionen-austauschersäule und nachfolgender Einengung des Effluenten wird angereichert, der Rückstand wird in 0,1-m Salpetersäure aufgenommen und das Cer(IV) daraus mit einer 0,25-m Lösung von 4-(5-Nonyl)pyridinoxid in Xylol extrahiert. Aus der organischen Phase wird das Cer mittels salzsaurem Wasserstoffperoxid rückextrahiert.相似文献