scispace - formally typeset
Search or ask a question
Journal ArticleDOI

The use of k0-NAA for the determination of the n(235U)/n(238U) isotopic ratio in samples containing uranium

TL;DR: In this article, a reverse perspective of the problem, the observed 235 U-fission and 238 U activation products along with the k 0 -factors were used to obtain information about the n ( 235 U)/ n ( 238 U) 1 isotopic ratio in the samples.
Abstract: In the analysis of rare earth elements in samples containing uranium by k 0 -neutron activation analysis fission of 235 U was considered an undesired phenomenon until the “fission k 0 -factors” were introduced to account for natural-U fission interferences. In this work, by using a reverse perspective of the problem, the observed 235 U-fission and 238 U activation products (along with the k 0 -factors) were used to obtain information about the n ( 235 U)/ n ( 238 U) 1 isotopic ratio in the samples. The relevant formulae and data-filtering algorithm were implemented in a home-made computer software, allowing automated evaluation and selection of unbiased data. Two radioisotopes ( 131 I and 140 La) were demonstrated to be reliable candidates for n ( 235 U)/ n ( 238 U) determination in environmental samples. The accuracy of this method was determined using several isotopic standards varying from a depleted to a highly enriched 235 U content. An overall 2.31±0.03% overestimation of the isotopic ratio was observed (within 95% confidence level).
Citations
More filters
Journal ArticleDOI
07 Jun 2009
TL;DR: The feasibility of k-k-0-NAA as a screening technique for accurate and reliable screening method for the quantification of environmental samples up to several tens of ng is determined.
Abstract: Multi-elemental analysis of samples containing uranium by Instrumental Neutron Activation Analysis (INAA) has been generally known as a problematic task due to the numerous radioisotopes produced from the uranium fission when the sample is irradiated with thermal neutrons. In k 0 -standardised NAA (k 0 -NAA)it is possible to correct for this effect through the introduction of k 0 -fission factors. In this work the aim was to determine the feasibility of k 0 -NAA as a screening technique for accurate U and n(235U)/n(238U) isotopic ratio determination (we further refer to the technique as k 0 -UNAA) and where k 0 -UNAA could be positioned versus the other screening techniques. In k 0 -UNAA we use an adapted k 0 formalism to determine the n(235U)/n(238U)-ratio. Several swipe samples spiked with different isotopic ratio's U were analysed and demonstrate the feasibility of k 0 -UNAA as a accurate and reliable screening method for the quantification of environmental samples up to several tens of ng. At these levels the uranium concentration can be quantified with a reasonable uncertainty and reliable n(235U)/n(238U) isotopic ratio analysis could also be performed.

2 citations


Additional excerpts

  • ...[10], (1) can be used to obtain the isotopic ratio...

    [...]

Journal ArticleDOI
TL;DR: In this paper, delayed neuron counting combined with neutron activation analysis (NAA) and k0-NAA for the measurement of gamma rays emitted by 239U decay is suitable for fast determination of 235U/238U ratio.
Abstract: Delayed neutron counting (DNC) was applied in quantitative determination of 235U/238U, quantitative determination of 235U and 239Pu in 235U–239Pu co-existing samples at China Institute of Atomic Energy (CIAE). In this work, natural uranium, enriched uranium and their mixtures were used in the determinations of 235U/238U ratios. The results indicated that delayed neuron counting combined with neutron activation analysis(NAA) and k0-NAA for the measurement of gamma rays emitted by 239U decay is suitable for fast determination 235U/238U ratio. In addition, the contents of 235U and 239Pu in 235U–239Pu co-existing samples can also be determined respectively.

2 citations

Journal ArticleDOI
TL;DR: In this paper, the applicability of the current k€ 0 and k€ 1 fission factors for the determination of the n(235U)/n(238U) isotopic ratio in multi-elemental samples containing uranium was investigated.
Abstract: In 2010 we investigated the applicability of the current k 0 and k 0-fission factors for the determination of the n(235U)/n(238U) isotopic ratio in multi-elemental samples containing uranium. An overestimation 3–4 % was observed in our determinations when employing the recommended 2003 k 0-literature. After a recalibration of all our laboratory instruments, a 3 % overestimation was still observed in this work when employing this nuclear data. Therefore we aimed at the experimental re-determination of these composite nuclear constants in order to enhance the reliability of the isotopic ratio determination method and the accuracy of our data-filtering algorithms. New k 0-fission factors are given for 7 nuclides that are not currently present in the 2012 k 0-database. Several additional k 0 factors are introduced for some nuclides in this library. Our k 0 results are also compared with those recently reported by Blaauw et al.

Cites methods or result from "The use of k0-NAA for the determina..."

  • ...Two radioisotopes were selected as initial candidates for the iterative method: (131)I and (140)La [1]....

    [...]

  • ...In our previous work (2010) [1] we made use of the k0library in [2] (2003) for determining the (235)U enrichment or depletion levels in multi-elemental samples containing uranium....

    [...]

  • ...In this work we employed the same formulae and k0-concepts that are presented for instance in [1, 2, 5, 6]....

    [...]

  • ...similarly to what we found in our 2010 work [1] if we employ the current recommended k0-literature [8]....

    [...]

  • ...3 keV line of (103)Ru, although several of their k0 results were within a 3–4 % relative difference with the k0-literature (in a few cases even higher) and hence, in line with our observed overestimation [1]....

    [...]

References
More filters
Patent
06 Aug 1980
TL;DR: In this paper, high energy neutron irradiation of the sample, measurement of the thermal neutron flux in the sample and monitoring the gamma radiation from the sample at energies of (a) 1.78 MeV and (b) 0.844 MEV and/or 1.015 MeV.
Abstract: Neutron activation is used to analyse the silicon and aluminium content of samples of material, such as bauxite ore and coal. The analysis can be performed on bulk samples, on material on a moving conveyor belt, or on the walls of a borehole. The method involves high energy neutron irradiation of the sample, measurement of the thermal neutron flux in the sample, and monitoring the gamma radiation from the sample at energies of (a) 1.78 MeV and (b) 0.844 MeV and/or 1.015 MeV. Such gamma radiation is produced on decay of (a) 28 Al and (b) 27 Mg isotopes, produced by the reactions 28 Si(n,p) 28 Al and 27 Al(n,p) 27 Mg. A single gamma ray detector is used. The analysis preferably utilizes equations which include terms to compensate for (a) the production of radiation at 1.78 MeV as a result of the production of the isotope 28 Al from 27 Al by the thermal neutron reaction 27 Al(n,γ) 28 Al, and (b) the Compton scattering of 1.78 MeV gamma radiation and background.

512 citations

Journal ArticleDOI
TL;DR: In this article, the recommended values for the relevant gamma rays of 144 analytically interesting radionuclides are tabulated, together with evaluated values for their associated parameters such as resonance integral to thermal cross-section ratios and effective resonance energies.

249 citations

Journal ArticleDOI
TL;DR: An alternative method is proposed, introducing generalized k0 factors which are independent of irradiation and measuring conditions, which combines the simplicity of the absolute methods with nearly the same accuracy attained by the relative ones.
Abstract: A critical evaluation of different comparator methods is given. The method based on experimentally-determined and convertible comparison factors (k) is considered to be the most suitable for general use. An alternative method is proposed, introducing generalized k0 factors which are independent of irradiation and measuring conditions. This approach combines the simplicity of the absolute methods with nearly the same accuracy attained by the relative ones. It is suggested that k0 factors be compiled in all cases when using single-comparator methods, to allow a continuous re-evaluation.

246 citations

Journal ArticleDOI
TL;DR: The last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry was conducted by the Commission on Atomic Weights and Isotopic Abundances (CAWIA) as mentioned in this paper.
Abstract: The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the “best measurement” of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.

237 citations

Journal ArticleDOI
TL;DR: In this paper, 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.
Abstract: 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).

76 citations