Gamma-ray tables for neutron fast neutron and photon activation analysis

In the past several years, a number of gamma-ray tables have been published. All of the tables limit themselves to those nuclides formed in (n, γ) reactions or at most to a few of the more prominent (n, 2n) products. A number of investigators are developing activation analysis methods using fast neutrons or photons. These investigations have been hampered by the lack of tables of gamma-rays of those nuclides that can be formed by (n, 2n), (n, p), (n, α), (n, n′) and (n, d) reactions. Since (γ, n) yields the same product as (n, 2n) the table would also be useful to photon activation studies. The authors have compiled such a table. Section II: list of the gamma-rays for all isotopes in order of increasing energy will be published in the J. Radioanal. Chem., 25 (1975) No. 2.     

Interference in neutron activation analysis of rocks by uranium fission

Interferences by uranium fission for⁹⁵Zr,⁹⁹Mo,¹⁰³Ru,¹⁴⁰La,¹⁴¹Ce and¹⁴⁷Nd have been studied using a single comparator method with two monitors. The effect of the neutron energy spectrum on the interference factor was examined by using the effective activation cross section. All the activities of¹⁴⁰La produced during neutron irradiation of uranium were included in the calculation of the factor for lanthanum. The calculated and experimental interference factors are in good agreement within 10% deviation. The results have been applied for the analysis of several rock samples containing uranium in a wide concentration range.     

Recoil properties of radionuclides formed in the photonuclear reactions onnatCu at intermediate energies

The recoil properties of 26 radionuclides produced in the photonuclear reactions on Cu at bremsstrahlung end-point energies (E ₀) of 250 to 1000 MeV have been investigated using the thick-target thick-catcher method. Kinematic properties of the product nuclei were calculated by the two-step vector velocity model. The calculated mean kinetic energies,T, of product nuclei increase with increase of the mass difference between products and target, reflecting the resonance natures and absorption mechanisms. TheT atE ₀≥600 MeV were well reproduced by a calculation performed by PICA code byGabriel andAlsmiller atE ₀=400 MeV, except for (γ,xn) products by giant-resonance.     

Determination of uranium by neutron activation and radiochemical separation of the tellurium fission product

After irradiation and dissolution of the samples (minerals, rocks etc.), elemental tellurium is precipitated, redissolved, extracted for its diethyldithiocarbamate, and finally reduced again for measurement of the ¹³²Te 228-keV γ-peak. The chemical yield is 75% and the lower limit of determination is 2 × 10^-7 g U.     

Determination of uranium in water by neutron activation and a low energy photon spectrometer

Ground and drinking water samples were analyzed for uranium by neutron activation analysis and a low energy photon spectrometer. Two methods were used: direct irradiation of water and pre-concentration by evaporation. The concentrations varied from 0.1 to 21 μg/l. The lowest detection limit obtained by pre-concentration was 0.01 μg/l while for the direct irradiation of water it was 0.04 μg/l. With these methods, we were able to determine the U concentration in all samples which were submitted for analysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

The determination of uranium using short-lived fission products by cyclic and other modes of activation analysis

The determination of elemental concentration in biological and environmental samples through the detection of short-lived nuclides has been of considerable interest in the last few years. In this context the relative advantages and disadvantages of cyclic activation analysis (CAA) with respect to single conventional one-shot irradiation and counting sequence (for one sample or replicate samples) and what has been termed pseudo-cyclic activation have been discussed with conflicting interpretations. It is the objective of this study to demonstrate through the irradiation of uranium standards by measurement of short-lived fission products how each mode of activation is best utilised. Application of CAA to the problem, in order to enhance signal-to-noise ratio, must also take into account an increasing dead-time with each cycle and therefore mass fractionation of a given sample and standard are investigated for replicate and pseudo-cyclic activation conditions. The variation of timing parameters in the cyclic mode, as well as irradation in a mixed reactor flux and epi-cadmium neutron flux, produces a set of equations from which half-life can be determined to confirm fission product identification in these complex gamma-ray spectra.     

The application of photon activation analysis for the characterization of uranium minerals

Instrumental photon activation analysis can be used advantageously for the homogeneity control and the determination of uranium concentration in minerals and ores to be certified as uranium reference materials. The homogeneity control of high contents of uranium can also be performed by passive gamma-ray spectrometry with high energy resolution. Interferences of²³⁷U characteristic lines with gamma-rays from other radionuclides produced in the 44 MeV bremsstrahlung are evaluated.     

Correcting for uranium fission in instrumental neutron activation analysis of high-uranium rocks

Failure to correct for fission products of²³⁵U is shown to result in significant errors in the measured concentrations of La, Sm, Nd, Ba, Zr, and Mo by Instrumental Neutron Activation Analysis of high uranium rocks. Measured and calculated correction factors are presented as the ratio of the fission product to parts per million by weight of uranium in the rock. Potential errors in petrogenetic interpretations of uncorrected data are outlined.     

The determination of uranium in biological materials by neutron activation analysis using the fission product134I

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’.     

Instrumental neutron activation analysis in geochemistry: Emphasis on spectral and uranium fission product interferences

Summary The accuracy of the analytical results may suffer from unsolved interferences both spectral or due to U fission products despite progress performed in electronics and informatics in instrumental neutron activation analysis. This contribution deals with the correction of spectral and U fission product interferences using a multicomponent method based on the resolution of simultaneous equation method and using the Erdtmann isotope-related k_I-factors for the determination of the correction factors of interferences due to U fission products, respectively. These resolution methods were tested on typical phosphate and uraniferous ore samples.     

Determination of235U abundance in uranium by neutron activation on the basis of the molybdenum fission interference

The purpose of the present paper is to suggest a method for determining the²³⁵U abundance in uranium samples (compounds, metallic alloys or other uranium materials, where this element may be natural or not) through a particular application of neutron activation analysis, based on the fission interference by molybdenum. The method lies on an a priori calibration with natural uranium, thus it does not require²³⁵U certified standards.     

Determination of traces of uranium in tungsten and molybdenum by radiochemical neutron activation analysis via the fission product140Ba

A radiochemical separation procedure has been developed to determine traces of uranium in tungsten and molybdenum. In this procedure the fission product¹⁴⁰Ba, as indicator nuclide for uranium, is selectively separated from the matrix activities and from all other long-lived activation and fission products and obtained at high purity. The radionuclide in the final fraction is sufficiently pure so that it can be measured with high counting efficiency by -counting. The separation procedure consists of two steps: a cation-exchange separation to separate barium from the anionic matrix tungste or molybdate, and many other elements. In the second step the Ba-fraction is further purified by precipitation of barium as barium chloride in 8M hydrochloric acid. The precipitate is then dissolved in water for -counting via the Cerenkov effect. The chemical yield for barium is 94.6±2.6%. When samples of 0.1 g, a thermal neutron flux of 2·10¹³ n·cm^–2·s^–1, an irradiation time of 10 hours and a measuring time of 2 hours were applied, then the detection limit of uranium was 4 ng/g.Presented at the 3rd Intern. Conf. on Nuclear and Radiochemistry, Vienna, September 7–11, 1992.     

Determination of uranium in various matrices using EDXRF and excitation by different radionuclides

The synergistic extractions of uranium(VI) nitrate using HDEHP,^* PMBP^** and TBP^*** have been studied from benzene media. A new method is proposed to calculate the equilibrium constants for such kinds of ternary synergistic extraction systems. The extraction reactions and their equilibrium constants were found. Models for the extraction mechanism are also discussed.     

A compilation of precisely determined gamma-transition energies of radionuclides produced by reactor irradiation

The gamma ray energies of nearly all radionuclides formed by reactor neutron irradiation have been determined using high resolution Ge(Li) spectrometry. The re-producibility of the determinations is demonstrated and, to estimate the accuracy of the measurements, the results are compared with those of other investigators. In the energy range from 80 to about 1400 keV the accuracy for the most abundant gamma rays is better than 0.2 keV. The energies of gamma transitions above 1400 KeV may be less accurate. The data are compiled in an atomic number and in a photon energy sequence. A table of characteristic X-rays is also included. The tables are intended to be helpful in the identification of isotopes in neutron activation analysis. Reprints of this compilation can be ordered from the Co-ordinating Editor (price: 2 US $).     

Radiochemical determination of fission products of uranium

An analysis has been elaborated to determine the long-living γ-emitting fission products of uranium. It consists of a sodium bisulphate melt of the fission product solution or the U-fuel, followed by liquid-liquid extractions. Afterwards the isotopes are absolutely counted with a standardized 3″×3″ NaI crystal. The total γ-spectrum of the original fission product solution, taken with a NaI crystal or a Ge−Li detector, is also analyzed mathematically by mixed γ-spectrometry. From a short post-irradiation of the fission product solution the concentrations of both²³⁵U and²³⁸U are determined. The absolute amount of fission products related to the U-concentration allows the calculation of the percent atomic burn-up, the irradiation time, the cooling period, the flux of the reactor and the original degree of enrichment of the uranium. Research associate of the I. I. K. W.