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Sample records for isotopic uranium composition

  1. Semiempirical method to determine the uranium isotopic compositions

    International Nuclear Information System (INIS)

    Tegas Sutondo

    2008-01-01

    In a nuclear reactor design calculation, some variations of U 235 enrichment are commonly needed. This will affect the isotopic compositions of the 3 main uranium isotopes i.e. U 234 , U 235 and U 238 for the respective enrichment. Due to the limited compositions data available, it is urgent to make an approximate way that can be used to determine the compositions of the 3 isotopes, for the desired enrichments. This paper presents the theoretical background used for constructing a semi empirical formula to estimate the composition of the 3 uranium isotopes as a function of U 235 enrichment, obtained based on the measurement data available. Based on the available data, and the lack of compositions data within the enrichment range between 3.5 % and around 12 %, it is concluded that 2 separate linear equations i.e. for ≤ 3.5 % and ≥ 3.5 % might be needed for U 235 isotope. For the U 234 isotope, a polynomial equation of 4 th order is well suited to be used for the whole range of enrichment between 0.711 % and 20 %, whilst for higher enrichment (> 20 %), a power function seems to give a better approach. The composition of U 238 can then be determined from the U 235 and U 234 composition at the desired enrichment of U 235 . (author)

  2. Uranium isotopic composition and uranium concentration in special reference material SRM A (uranium in KCl/LiCl salt matrix)

    International Nuclear Information System (INIS)

    Graczyk, D.G.; Essling, A.M.; Sabau, C.S.; Smith, F.P.; Bowers, D.L.; Ackerman, J.P.

    1997-07-01

    To help assure that analysis data of known quality will be produced in support of demonstration programs at the Fuel Conditioning Facility at Argonne National Laboratory-West (Idaho Falls, ID), a special reference material has been prepared and characterized. Designated SRM A, the material consists of individual units of LiCl/KCl eutectic salt containing a nominal concentration of 2.5 wt. % enriched uranium. Analyses were performed at Argonne National Laboratory-East (Argonne, IL) to determine the uniformity of the material and to establish reference values for the uranium concentration and uranium isotopic composition. Ten units from a batch of approximately 190 units were analyzed by the mass spectrometric isotope dilution technique to determine their uranium concentration. These measurements provided a mean value of 2.5058 ± 0.0052 wt. % U, where the uncertainty includes estimated limits to both random and systematic errors that might have affected the measurements. Evidence was found of a small, apparently random, non-uniformity in uranium content of the individual SRM A units, which exhibits a standard deviation of 0.078% of the mean uranium concentration. Isotopic analysis of the uranium from three units, by means of thermal ionization mass spectrometry with a special, internal-standard procedure, indicated that the uranium isotopy is uniform among the pellets with a composition corresponding to 0.1115 ± 0.0006 wt. % 234 U, 19.8336 ± 0.0059 wt. % 235 U, 0.1337 ± 0.0006 wt. % 236 U, and 79.9171 ± 0.0057 wt. % 238 U

  3. Uranium in open ocean: concentration and isotopic composition

    International Nuclear Information System (INIS)

    Ku, T.L.; Knauss, K.G.; Mathieu, G.G.

    1977-01-01

    Uranium concentrations and 234 U/ 238 U activity ratios have been determined in 63 seawater samples (nine vertical profiles) from the Atlantic, and Pacific, and Arctic, and the Antarctic oceans, using the alpha-spectrometric method for their determinations. Correlation between uranium and salinity is well manifested by the data from the Arctic and the Antarctic oceans, but such a relation cannot be clearly defined with the +-(1 to 2)% precision of uranium measurements for the Atlantic and Pacific data. At the 95% confidence level: (1) the uranium/salinity ratio is (9.34 + - 0.56) x 10 -8 g/g for the seawater analyzed with salinity ranging from 30.3 to 36.2 per thousand; the uranium concentration of seawater of 35 per thousand salinity is 3.3 5 + - 0.2 μ g l -1 ; (2) the 234 U/ 238 U activity ratio is 1.14 +- 0.03. Uranium isotopes in interstitial waters of the Pacific surface sediments analyzed do not show large concentration differences across the sediment-water interface as suggested by previous measurements. Current estimations of the average world river uranium concentration (0.3 to 0.6 μ g l -1 ) and 234 U/ 238 U ratio (1.2 to 1.3) and of the diffusional 234 U influx from sediments 0.3 dpm cm -2 10 -3 yr -1 ) are essentially consistent with a model which depicts a steady state distribution of uranium in the ocean. However, the 0.3 to 0.6 μ g l -1 value for river uranium may be an upper limit estimate. (author)

  4. Determination of isotopic composition of uranium in microparticles by secondary ion mass spectrometry

    International Nuclear Information System (INIS)

    Veniaminov, N.N.; Kolesnikov, O.N.; Stebel'kov, V.A.

    1992-01-01

    Aerosol particles including uranium in their composition are specific atmospheric polutants. Uranium is used as nuclear fuel in atomic power stations and in spacecraft power units, and also as a component of nuclear warheads. In order to monitor the discharge of uranium-containing aerosol particles to the atmosphere, they must first be identified. As an example, one may cite an investigation of the elemental composition and radioactivity of particles formed in the accident at the Chernobyl atomic power station. One of the most informative indicators of the origin of uranium-containing aerosol particles is the isotopic composition of the uranium. Secondary ion mass spectrometry (SIMS) offers unique possibilities for the measurement of isotope ratios in individual microscopic objects. At the same time, a measurement of isotope ratios of sulfur in microsection of galenite PbS 2 has shown that the application of SIMS for these purposes is seriously limited by the difference in yield of secondary ions for isotopes with different masses. These discrimination effects, in the case of light elements such as boron, may result in distortion of the isotope ratios by several percent. In the case of heavy elements, however, the effect is less significant, amounting to about 0.5% for lead isotopes. 13 refs., 3 figs., 1 tab

  5. Influence of uncertainties of isotopic composition of the reprocessed uranium on effectiveness of its enrichment in gas centrifuge cascades

    Science.gov (United States)

    Smirnov, A. Yu; Mustafin, A. R.; Nevinitsa, V. A.; Sulaberidze, G. A.; Dudnikov, A. A.; Gusev, V. E.

    2017-01-01

    The effect of the uncertainties of the isotopic composition of the reprocessed uranium on its enrichment process in gas centrifuge cascades while diluting it by adding low-enriched uranium (LEU) and waste uranium. It is shown that changing the content of 232U and 236U isotopes in the initial reprocessed uranium within 15% (rel.) can significantly change natural uranium consumption and separative work (up to 2-3%). However, even in case of increase of these parameters is possible to find the ratio of diluents, where the cascade with three feed flows (depleted uranium, LEU and reprocessed uranium) will be more effective than ordinary separation cascade with one feed point for producing LEU from natural uranium.

  6. Isotopic composition and radiological properties of uranium in selected fuel cycles

    International Nuclear Information System (INIS)

    Fleischman, R.M.; Liikala, R.C.

    1975-04-01

    Three major topic areas are discussed: First, the properties of the uranium isotopes are defined relative to their respective roles in the nuclear fuel cycle. Secondly, the most predominant fuel cycles expected in the U. S. are described. These are the Light Water Reactor (LWR), High Temperature Gas Cooled Reactor (HTGR), and Liquid Metal Fast Breeder Reactor (LMFBR) fuel cycles. The isotopic compositions of uranium and plutonium fuels expected for these fuel cycles are given in some detail. Finally the various waste streams from these fuel cycles are discussed in terms of their relative toxicity. Emphasis is given to the high level waste streams from reprocessing of spent fuel. Wastes from the various fuel cycles are compared based on projected growth patterns for nuclear power and its various components. (U.S.)

  7. Uranium isotope composition of a laterite profile during extreme weathering of basalt in Guangdong, South China

    Science.gov (United States)

    Huang, J.; Zhou, Z.; Gong, Y.; Lundstrom, C.; Huang, F.

    2015-12-01

    Rock weathering and soil formation in the critical zone are important for material cycle from the solid Earth to superficial system. Laterite is a major type of soil in South China forming at hot-humid climate, which has strong effect on the global uranium cycle. Uranium is closely related to the environmental redox condition because U is stable at U(Ⅳ) in anoxic condition and U(Ⅵ) as soluble uranyl ion (UO22+) under oxic circumstance. In order to understand the behavior of U isotopes during crust weathering, here we report uranium isotopic compositions of soil and base rock samples from a laterite profile originated from extreme weathering of basalt in Guangdong, South China. The uranium isotopic data were measured on a Nu Plasma MC-ICP-MS at the University of Illinois at Urbana-Champaign using the double spike method. The δ238U of BCR-1 is -0.29±0.03‰ (relative to the international standard CRM-112A), corresponding to a 238U/235U ratio of 137.911±0.004. Our result of BCR-1 agrees with previous analyses (e.g., -0.28‰ in Weyer et al. 2008) [1]. U contents of the laterite profile decrease from 1.9 ppm to 0.9 ppm with depth, and peak at 160 - 170 cm (2.3 ppm), much higher than the U content of base rocks (~0.5 ppm). In contrary, U/Th of laterites is lower than that of base rock (0.27) except the peak at the depth of 160-170 cm (0.38), indicating significant U loss during weathering. Notably, U isotope compositions of soils show a small variation from -0.38 to -0.28‰, consistent with the base rock within analytical error (0.05‰ to 0.08‰, 2sd). Such small variation can be explained by a "rind effect" (Wang et al., 2015) [2], by which U(Ⅳ) can be completely oxidized to U(VI) layer by layer during basalt weathering by dissolved oxygen. Therefore, our study indicates that U loss during basalt weathering at the hot-humid climate does not change U isotope composition of superficial water system. [1] Weyer S. et al. (2008) Natural fractionation of 238U/235

  8. Development of a portable mass spectrometric system for determination of isotopic composition of solid uranium samples using fluorine volatilization

    Science.gov (United States)

    Loge, G.

    1994-09-01

    Using hardware and materials supplied by LANL, a prototype quadrupole mass spectrometer system designed for portable field analysis of isotopic composition of solid uranium samples was assembled and tested. The system contained the capability for fluorine volatilization of solid uranium samples with gas introduction, which was successfully tested and demonstrated using 100 mg samples of U3O8. Determination of precision and accuracy for measuring isotopic composition was performed using isotopic standards. Use with soil samples containing uranium were also attempted. Silicates in the soil forming SiF4 were found to be a kinetic bottleneck to the formation of UF6. This could be avoided by performing some sort of chemical separation as a pre-treatment step, which was demonstrated using nitric acid.

  9. Separation of uranium isotopes

    International Nuclear Information System (INIS)

    Porter, J.T.

    1980-01-01

    Methods and apparatus are disclosed for separation of uranium isotopes by selective isotopic excitation of photochemically reactive uranyl salt source material at cryogenic temperatures, followed by chemical separation of selectively photochemically reduced U+4 thereby produced from remaining uranyl source material

  10. IDMS analysis of blank swipe samples for uranium quantity and isotopic composition

    International Nuclear Information System (INIS)

    Ryjinski, M.; Donohue, D.

    2001-01-01

    Since 1996 the IAEA has started routine implementation of environmental sampling. During the last 5 years more than 1700 swipe samples were collected and analyzed in the Network of Analytical Laboratories (NWAL). One sensitive point of analyzing environmental samples is evidence of the presence of enriched U. The U content on swipes is extremely low and therefore there is a relatively high probability of a false positive, e.g. small contamination or a measurement bias. In order to avoid and/or control this the IAEA systematically sends to the laboratories blind blank QC samples. In particular more than 50 blank samples were analyzed during the last two years. A preliminary analysis of blank swipes showed the swipe material itself contains up to 10 ng of NU per swipe. However, about 50% of blind blank swipes analyzed show the presence of enriched uranium. A source of this bias has to be clarified and excluded. This paper presents the results of modeling of IDMS analysis for quantity and isotopic composition of uranium in order to identify the possible contribution of different factors to the final measurement uncertainty. This modeling was carried out based on the IAEA Clean Laboratory measurement data and simulation technique

  11. Uranium isotopic compositions of the crust and ocean: Age corrections, U budget and global extent of modern anoxia

    Science.gov (United States)

    Tissot, François L. H.; Dauphas, Nicolas

    2015-10-01

    The 238U/235U isotopic composition of uranium in seawater can provide important insights into the modern U budget of the oceans. Using the double spike technique and a new data reduction method, we analyzed an array of seawater samples and 41 geostandards covering a broad range of geological settings relevant to low and high temperature geochemistry. Analyses of 18 seawater samples from geographically diverse sites from the Atlantic and Pacific oceans, Mediterranean Sea, Gulf of Mexico, Persian Gulf, and English Channel, together with literature data (n = 17), yield a δ238U value for modern seawater of -0.392 ± 0.005‰ relative to CRM-112a. Measurements of the uranium isotopic compositions of river water, lake water, evaporites, modern coral, shales, and various igneous rocks (n = 64), together with compilations of literature data (n = 380), allow us to estimate the uranium isotopic compositions of the various reservoirs involved in the modern oceanic uranium budget, as well as the fractionation factors associated with U incorporation into those reservoirs. Because the incorporation of U into anoxic/euxinic sediments is accompanied by large isotopic fractionation (ΔAnoxic/Euxinic-SW = +0.6‰), the size of the anoxic/euxinic sink strongly influences the δ238U value of seawater. Keeping all other fluxes constant, the flux of uranium in the anoxic/euxinic sink is constrained to be 7.0 ± 3.1 Mmol/yr (or 14 ± 3% of the total flux out of the ocean). This translates into an areal extent of anoxia into the modern ocean of 0.21 ± 0.09% of the total seafloor. This agrees with independent estimates and rules out a recent uranium budget estimate by Henderson and Anderson (2003). Using the mass fractions and isotopic compositions of various rock types in Earth's crust, we further calculate an average δ238U isotopic composition for the continental crust of -0.29 ± 0.03‰ corresponding to a 238U/235U isotopic ratio of 137.797 ± 0.005. We discuss the implications of

  12. Determination of the isotopic composition of natural and slightly enriched uranium by alpha-spectrometry

    DEFF Research Database (Denmark)

    Kunzendorf, Helmar

    1968-01-01

    Determinations of the isotope contents of 238U, 235U and 234U in five uranium samples containing 0–5 at% 235U were carried out on the basis of a least-squares fit of the α-spectra from the samples, measured with a semiconductor detector, to the theoretically expected α-spectra. With a simple source...

  13. Isotope composition and uranium content in the rivers Naryn and Mailuu-Suu

    International Nuclear Information System (INIS)

    Vasiliev, I. A.; Alekhina, V. M.; Orozobakov, T.; Mamatibraimov, S.

    2002-01-01

    To solve the atomic problem, including the creation of an atomic weapon, one must embark on an intensive exploration and mining of radioactive raw materials, first among which uranium, together with other materials and metals. The acquisition of all these materials has thus been accompanied by the creation of a great deal of production and storage wastes and other refuse from plants, leading to many problems of protecting the environment from radioactive and other hazardous metals and materials. And so, as a result of the extensive mining and processing of radioactive and other raw materials that had been necessary for the atomic industry, in locations like Kara-Balty, Mailuu-Suu, Kavak, Kadamzhay and other places, a series of radioactive and hazardous tailings and dumps has been generated in the Kyrgyz Republic. The toxic ingredients from the dumps migrate and mix together with the ground waters that leach the tailings. However, how these waters migrate both in space and time have not been sufficiently studied; and, so, in general, we cannot forecast the propagation of these hazards. In the usual estimation of the scale of migration from uranium plants, only the total uranium content in the ground water is used. But this does not show natural or technogenic components; and it is obvious that the danger from the plants need only be characterized by the technogenic components. To solve this problem, one can employ the phenomenon where there is a natural separation in the fraction of 234 U and 238 U present in nature and as a result of technological processes. The essence of this understanding is that, as uranium transitions from solid form into a liquid, such as its dissolution in ground water, it undergoes isotope enrichment, i.e. hydrogenic uranium is enriched with 234 U compared to 238 U.The essence of this understanding is that, as uranium transitions from solid form into a liquid, such as its dissolution in ground water, it undergoes isotope enrichment, i

  14. Conceptual model: possible changes of the seawater uranium isotopic composition through time

    Energy Technology Data Exchange (ETDEWEB)

    Nowitzki, Hannah; Frank, Norbert; Fohlmeister, Jens [Universitaet Heidelberg (Germany)

    2015-07-01

    U behaves in seawater like a conservative element. More than 99% of the oceanic U content is {sup 238}U, whereas {sup 234}U is only present in trace amounts. As the residence time of U is significantly longer than the mixing time of the ocean, the ocean is well mixed with respect to U and its isotopic composition (Dunk 2002). Moreover, living corals incorporate U without isotopic fractionation. Therefore, the past seawater isotopic evolution of ({sup 234}U/{sup 238}U) can be accessed via U/Th age-dating of corals and the subsequent calculation of the initial ({sup 234}U/{sup 238}U) value. The isotopic ({sup 234}U/{sup 238}U) composition of seawater during the last 360 ka scatters around the modern seawater value (δ{sup 234}U ∼ (145±15) %, Henderson 2002). As these variations in the δ{sup 234}U value are rather small, a 'constant seawater isotopic composition hypothesis' is often used to validate U/Th ages of fossil corals. However, some authors find that the variability of the isotopic composition exceeds the expected range and suggest that it provides valuable information on variations in continental weathering and global run-off fluctuations or sea-level changes. This work will attempt to compare literature data of the seawater U isotopic composition to the results of a conceptual box-model of the oceanic U budget.

  15. Influence of size and surface structure of microparticles on accuracy of measurements of its uranium isotopic composition

    International Nuclear Information System (INIS)

    Stebelkov, V.; Kolesnikov, O.; Moulenko, D.; Sokolov, A.; Pavlov, A.; Simakin, S.

    2002-01-01

    Full text: One of the elements of the scheme for complex analysis of environmental samples, collected in the regions of location of nuclear facilities, is mass-spectrometry of microparticles of nuclear materials implemented for determination of isotopic composition of these materials. Widely used technique of mass-spectrometry of particles is secondary ion mass-spectrometry. This technique is characterized by successive acquisition of ions from different isotopes under gradual sputtering of microparticle during analysis. The purpose of this work was investigation of kinetic of size changing and changing of measured values of uranium-235 concentration as well as investigation of influence of size and surface structure of microparticle on measurement results. Method of investigation had been comprised to several sequential measurements of uranium isotopes content in the same particle and photography of this particle before every sequential measurement by using electron microscope. Analysis of each particle was finished when this particle was fully sputtered. There were investigated 33 particles of irregular shape and initial sizes from 0.5 μm to 3.5 μm. These particles had different types of surface structure and different isotopic composition. Besides there were investigated 22 spherical particles of UO 2 with 3.7% uranium-235 abundance with sizes from 0.7 μm to 2.4 μm. Thirteen particles of irregular shape were sputtered fully during first measurement of isotopic composition. Two sequential measurements were implemented for 12 particles, three sequential measurements were implemented for 7 particles. For 2 particles of sizes 3.5 μm x 2 μm and 1.2 μm there were implemented four sequential measurements of isotopic composition. During these investigations it was determined that the number of sequential measurements depends not only on size but also on surface structure of particle. With rare exception the sequential values of concentrations of uranium-235

  16. The U-Pu inspector, a new instrument to determine the isotopic compositions of uranium and plutonium

    International Nuclear Information System (INIS)

    Verplancke, J.; Van Dyck, R.; Tench, O.; Sielaff, B.

    1994-01-01

    The U/Pu-InSpector is a new integrated, portable instrument that can measure the isotopic composition of samples containing uranium and/or plutonium without prior calibration and without the need for skilled operators. It consists of a Low Energy Germanium detector in a Multi-attitude Cryostat (MAC). A shield and collimator are built-in, directly around the detector element, reducing the weight of this detector and shield to approximately 8 kg with a full dewar. The dewar can quickly and easily be filled with a self-pressurizing funnel. The detector is connected to a small portable battery operated analyzer and a Notebook computer. The spectra are automatically stored and analyzed with the help of the MGA codes for plutonium and/or for uranium. 5 refs., 1 fig

  17. Laser separation of uranium isotopes

    International Nuclear Information System (INIS)

    Porter, J.T.

    1981-01-01

    Method and apparatus for separating uranium isotopes are claimed. The method comprises the steps of irradiating a uranyl source material at a wavelength selective to a desired isotope and at an effective temperature for isotope spectral line splitting below about 77 deg.K., further irradiating the source material within the fluorescent lifetime of the source material to selectively photochemically reduce the excited isotopic species, and chemically separating the reduced isotope species from the remaining uranyl salt compound

  18. An IBM-1620 code for calculaton of isotopic composition of irradiated uranium (ISOCOM-1)

    International Nuclear Information System (INIS)

    Soliman, R.H.; Karchava, G.; Hamouda, I.

    1974-01-01

    The present work gives a description of an IBM-1620 code to calculate the isotopic composition during the irradiation of a nuclear fuel, which initially consists of 235 U and 238 U. The numerical results of test calculations as well as the ET-RR-1 reactor calculations are presented. The code is in operation since 1968

  19. Separation of uranium isotopes by accelerated isotope exchange reactions

    International Nuclear Information System (INIS)

    Seko, M.; Miyake, T.; Inada, K.; Ochi, K.; Sakamoto, T.

    1977-01-01

    A novel catalyst for isotope exchange reaction between uranium(IV) and uranium(VI) compounds enables acceleration of the reaction rate as much as 3000 times to make industrial separation of uranium isotopes economically possible

  20. Development of a portable mass spectrometric system for determination of isotopic composition of solid uranium samples using fluorine volatilization. Final report

    International Nuclear Information System (INIS)

    Loge, G.

    1994-01-01

    Using hardware and materials supplied by LANL, a prototype quadrupole mass spectrometer system designed for portable field analysis of isotopic composition of solid uranium samples was assembled and tested. The system contained the capability for fluorine volatilization of solid uranium samples with gas introduction, which was successfully tested and demonstrated using 100 mg samples of U 3 O 8 . Determination of precision and accuracy for measuring isotopic composition was performed using isotopic standards. Use with soil samples containing uranium were also attempted. Silicates in the soil forming SiF 4 were found to be a kinetic bottleneck to the formation of UF 6 . This could be avoided by performing some sort of chemical separation as a pre-treatment step, which was demonstrated using nitric acid

  1. Evolution of Uranium Isotopic Compositions of the Groundwater and Rock in a Sandy-Clayey Aquifer

    Directory of Open Access Journals (Sweden)

    Alexander I. Malov

    2017-11-01

    Full Text Available Uranium isotopes have been used as mechanistic or time scale tracers of natural processes. This paper describes the occurrence and redistribution of U in the Vendian aquifer of a paleo-valley in NW Russia. Forty-four rock samples were collected from nine boreholes with depths up to 160 m, and 25 groundwater samples were collected from 23 boreholes with depths up to 300 m. The U, Fe concentration, and 234U/238U activity ratio were determined in the samples. Estimations were made of the 14C and 234U-238U residence time of groundwater in the aquifer. It has been established that the processes of chemical weathering of Vendian deposits led to the formation of a strong oxidation zone, developed above 250 m.b.s.l. The inverse correlation between the concentrations of uranium and iron is a result of removal of U from paleo-valley slopes in oxidizing conditions, accumulation of U at the bottom of the paleo-valley in reducing conditions, and accumulation of Fe on the slopes and removal from the bottom of the paleo-valley. Almost all U on the slopes has been replaced by a newly formed hydrogenic U with a higher 234U/238U activity ratio. After, dissolution and desorption of hydrogenic U occurred from the slopes during periods with no glaciations and marine transgressions. Elevated concentrations of U are preserved in reduced lenses at the paleo-valley bottom. In these areas, the most dangerous aspect is the flow of groundwater from the underlying horizons, since during the operation of water supply wells it can lead to the creation of local zones of oxidizing conditions in the perforated screens zone and the transition of uranium into solution. For groundwater under oxidizing conditions, an increase in the concentration of uranium is characteristic of an increase in the residence time (age of water in the aquifer. Also, the 234U/238U activity ratio increases with increasing radioactivity of groundwater. Therefore, the most rational approach is to use

  2. Investigation of the isotopic composition of lead and of trace elements concentrations in natural uranium materials as a signature in nuclear forensics

    Energy Technology Data Exchange (ETDEWEB)

    Svedkauskaite-LeGore, J. [European Commission, Joint Research Centre, Karlsruhe (Germany). Inst. for Transuranium Elements; Institute of Physics, Vilnius (Lithuania); Mayer, K.; Millet, S.; Nicholl, A.; Rasmussen, G. [European Commission, Joint Research Centre, Karlsruhe (Germany). Inst. for Transuranium Elements; Baltrunas, D. [Institute of Physics, Vilnius (Lithuania)

    2007-07-01

    Lead is contained as trace element in uranium ores and propagates throughout the production process to intermediate products like yellow cake or uranium oxide. The lead isotopes in such material originate from two sources: natural lead and radiogenic lead. The variability of the isotopic composition of lead in ores and yellow cakes was studied and the applicability of this parameter for nuclear forensic investigations was investigated. Furthermore, the chemical impurities contained in these materials were measured in order to identify characteristic differences between materials from different mines. For the samples investigated, it could be shown, that the lead isotopic composition varies largely from mine to mine and it may be used as one of the parameters to distinguish between materials of different origins. Some of the chemical impurities show a similar pattern and support the conclusions drawn from the lead isotope data. (orig.)

  3. Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP-MS with multiple ion counters

    International Nuclear Information System (INIS)

    Boulyga, Sergei F.; Prohaska, Thomas

    2008-01-01

    This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) - a Nu Plasma HR - equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the 235 U/ 238 U, 236 U/ 238 U, 145 Nd/ 143 Nd, 146 Nd/ 143 Nd, 101 Ru/( 99 Ru+ 99 Tc) and 102 Ru/( 99 Ru+ 99 Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred μm to about 1 mm and with surface alpha activities of 3-38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA-MC-ICP-MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15-20 min (excluding MC-ICP-MS optimization and calibration). The 101 Ru/( 99 Ru+ 99 Tc) and 102 Ru/( 99 Ru+ 99 Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in 146 Nd of about 3-5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The 235 U/ 238 U and 236 U/ 238 U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus

  4. Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP-MS with multiple ion counters.

    Science.gov (United States)

    Boulyga, Sergei F; Prohaska, Thomas

    2008-01-01

    This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS)--a Nu Plasma HR--equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the 235U/238U, 236U/238U, 145Nd/143Nd, 146Nd/143Nd, 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred mum to about 1 mm and with surface alpha activities of 3-38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA-MC-ICP-MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15-20 min (excluding MC-ICP-MS optimization and calibration). The 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in 146Nd of about 3-5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The 235U/238U and 236U/238U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus, the 235U/238U ratios measured in ten

  5. Separation of uranium isotopes

    International Nuclear Information System (INIS)

    Ehrfeld, W.; Ehrfeld, U.

    1977-01-01

    In the nuclear fuel cycle, uranium enrichment is not a principal problem of technological feasibility. Several processes exist for producing LWR fuel and the enrichment method can be selected in consideration of economical, environmental, and political aspects. To date, the gaseous diffusion process constitutes the major part of enrichment capacity. This process has been well demonstrated for over 30 years and, as a matter of fact, no major technological and economical progress is to be expected in the future. Because of their comparatively high development potential, the centrifuge and the separation nozzle method may become increasingly favorable in economics. The development of the centrifuge process which is superior by its low specific energy consumption aims at technological improvements. In the separation nozzle process which offers the advantage of a comparatively simple technology a further reduction of the specific energy consumption is to be expected because of the thermodynamically favorable separation mechanism of this process. Laser isotope separation methods are still on the laboratory scale, although large financial funds have been spent. (orig.) [de

  6. Late quaternary history and uranium isotopic compositions of ground water discharge deposits, Crater Flat, Nevada

    International Nuclear Information System (INIS)

    Paces, J.B.; Taylor, E.M.; Bush, C.

    1993-01-01

    Three carbonate-rich spring deposits are present near the southern end of Crater Flat, NV, approximately 18 km southwest of the potential high-level waste repository at Yucca Mountain. We have analyzed five samples of carbonate-rich material from two of the deposits for U and Th isotopic compositions. Resulting U-series disequilibrium ages indicate that springs were active at 18 ± 1, 30 ± 3, 45 ± 4 and >70 ka. These ages are consistent with a crude internal stratigraphy at one site. Identical ages for two samples at two separate sites suggest that springs were contemporaneous, at least in part, and were most likely part of the same hydrodynamic system. In addition, initial U isotopic compositions range from 2.8 to 3.8 and strongly suggest that ground water from the regional Tertiary-volcanic aquifer provided the source for these hydrogenic deposits. This interpretation, along with water level data from near-by wells suggest that the water table rose approximately 80 to 115 m above present levels during the late Quaternary and may have fluctuated repeatedly. Current data are insufficient to allow reconstruction of a detailed depositional history, however geochronological data are in a good agreement with other paleoclimatic proxy records preserved throughout the region. Since these deposits are down gradient from the potential repository site, the possibility of higher ground water levels in the future dramatically shortens both vertical and lateral ground water pathways and reduces travel times of transported radionuclides to potential discharge sites

  7. Late quaternary history and uranium isotopic compositions of ground water discharge deposits, Crater Flat, Nevada

    Science.gov (United States)

    Paces, James B.; Taylor, Emily M.; Bush, Charles

    1993-01-01

    Three carbonate-rich spring deposits are present near the southern end of Crater Flat, NV, approximately 18 km southwest of the potential high-level waste repository at Yucca Mountain. We have analyzed five samples of carbonate-rich material from two of the deposits for U and Th isotopic compositions. Resulting U-series disequilibrium ages indicate that springs were active at 18 ?? 1, 30 ?? 3, 45 ?? 4 and >70 ka. These ages are consistent with a crude internal stratigraphy at one site. Identical ages for two samples at two separate sites suggest that springs were contemporaneous, at least in part, and were most likely part of the same hydrodynamic system. In addition, initial U isotopic compositions range from 2.8 to 3.8 and strongly suggest that ground water from the regional Tertiary-volcanic aquifer provided the source for these hydrogenic deposits. This interpretation, along with water level data from near-by wells suggest that the water table rose approximately 80 to 115 m above present levels during the late Quaternary and may have fluctuated repeatedly. Current data are insufficient to allow reconstruction of a detailed depositional history, however geochronological data are in good agreement with other paleoclimatic proxy records preserved throughout the region. Since these deposits are down gradient from the potential repository site, the possibility of higher ground water levels in the future dramatically shortens both vertical and lateral ground water pathways and reduces travel times of transported radionuclides to potential discharge sites.

  8. Determination of uranium isotopic composition and 236U content of soil samples and hot particles using inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Boulyga, S F; Becker, J S

    2001-07-01

    As a result of the accident at the Chernobyl nuclear power plant (NPP) the environment was contaminated with spent nuclear fuel. The 236U isotope was used in this study to monitor the spent uranium from nuclear fallout in soil samples collected in the vicinity of the Chernobyl NPP. Nuclear track radiography was applied for the identification and extraction of hot radioactive particles from soil samples. A rapid and sensitive analytical procedure was developed for uranium isotopic ratio measurement in environmental samples based on double-focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) with a MicroMist nebulizer and a direct injection high-efficiency nebulizer (DIHEN). The performance of the DF-ICP-MS with a quartz DIHEN and plasma shielded torch was studied. Overall detection efficiencies of 4 x 10(-4) and 10(-3) counts per atom were achieved for 238U in DF-ICP-QMS with the MicroMist nebulizer and DIHEN, respectively. The rate of formation of uranium hydride ions UH+/U+ was 1.2 x 10(-4) and 1.4 x 10(-4), respectively. The precision of short-term measurements of uranium isotopic ratios (n = 5) in 1 microg L(-1) NBS U-020 standard solution was 0.11% (238U/235U) and 1.4% (236U/238U) using a MicroMist nebulizer and 0.25% (235U/238U) and 1.9% (236U/P38U) using a DIHEN. The isotopic composition of all investigated Chernobyl soil samples differed from those of natural uranium; i.e. in these samples the 236U/238U ratio ranged from 10(-5) to 10(-3). Results obtained with ICP-MS, alpha- and gamma-spectrometry showed differences in the migration properties of spent uranium, plutonium, and americium. The isotopic ratio of uranium was also measured in hot particles extracted from soil samples.

  9. Determination of uranium isotopic composition and 236U content of soil samples and hot particles using inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Boulyga, S.F.; Becker, J.S.

    2001-01-01

    As a result of the accident at the Chernobyl nuclear power plant (NPP) the environment was contaminated with spent nuclear fuel. The 236 U isotope was used in this study to monitor the spent uranium from nuclear fallout in soil samples collected in the vicinity of the Chernobyl NPP. Nuclear track radiography was applied for the identification and extraction of hot radioactive particles from soil samples. A rapid and sensitive analytical procedure was developed for uranium isotopic ratio measurement in environmental samples based on double-focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) with a MicroMist nebulizer and a direct injection high-efficiency nebulizer (DIHEN). The performance of the DF-ICP-MS with a quartz DIHEN and plasma shielded torch was studied. Overall detection efficiencies of 4 x 10 -4 and 10 -3 counts per atom were achieved for 238 U in DF-ICP-QMS with the MicroMist nebulizer and DIHEN, respectively. The rate of formation of uranium hydride ions UH + /U + was 1.2 x 10 -4 and 1.4 x 10 -4 , respectively. The precision of short-term measurements of uranium isotopic ratios (n = 5) in 1 μg L -1 NBS U-020 standard solution was 0.11% ( 238 U/ 235 U) and 1.4% ( 236 U/ 238 U) using a MicroMist nebulizer and 0.25% ( 235 U/ 238 U) and 1.9% ( 236 U/ 238 U) using a DIHEN. The isotopic composition of all investigated Chernobyl soil samples differed from those of natural uranium; i.e. in these samples the 236 U/ 238 U ratio ranged from 10 -5 to 10 -3 . Results obtained with ICP-MS, α- and γ-spectrometry showed differences in the migration properties of spent uranium, plutonium, and americium. The isotopic ratio of uranium was also measured in hot particles extracted from soil samples. (orig.)

  10. Standard test method for analysis of isotopic composition of uranium in nuclear-grade fuel material by quadrupole inductively coupled plasma-mass spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This test method is applicable to the determination of the isotopic composition of uranium (U) in nuclear-grade fuel material. The following isotopic weight percentages are determined using a quadrupole inductively coupled plasma-mass spectrometer (Q-ICP-MS): 233U, 234U, 235U, 236U, and 238U. The analysis can be performed on various material matrices after acid dissolution and sample dilution into water or dilute nitric (HNO3) acid. These materials include: fuel product, uranium oxide, uranium oxide alloys, uranyl nitrate (UNH) crystals, and solutions. The sample preparation discussed in this test method focuses on fuel product material but may be used for uranium oxide or a uranium oxide alloy. Other preparation techniques may be used and some references are given. Purification of the uranium by anion-exchange extraction is not required for this test method, as it is required by other test methods such as radiochemistry and thermal ionization mass spectroscopy (TIMS). This test method is also described i...

  11. Method and apparatus for separating uranium isotopes

    International Nuclear Information System (INIS)

    Bernstein, E.R.

    1977-01-01

    A uranium compound in the solid phase (uranium borohydride four) is subjected to radiation of a first predetermined frequency that excites the uranium-235 isotope-bearing molecules but not the uranium-238 isotope-bearing molecules. The compound is simultaneously subjected to radiation of a second predetermined frequency which causes the excited uranium-235 isotope-bearing molecules to chemically decompose but which does not affect the uranium-238 isotope-bearing molecules. Sufficient heat is then applied to the irradiated compound in the solid phase to vaporize the non-decomposed uranium-238 isotope-bearing molecules but not the decomposed uranium-235 isotope-bearing molecules, thereby physically separating the uranium-235 isotope-bearing molecules from the uranium-238 isotope-bearing molecules. The uranium compound sample in the solid phase is deposited or grown in an elongated tube supported within a dewar vessel having a clear optical path tail section surrounded by a coolant. Two sources of radiation are focused on the uranium compound sample. A heating element is attached to the elongated tube to vaporize the irradiated compound

  12. Determination of uranium, thorium and radium isotope ratio

    International Nuclear Information System (INIS)

    Sokolova, Z.A.

    1983-01-01

    The problems connected with the study of isotope composition of natural radioactive elements in natural objects are considered. It is pointed out that for minerals, ores and rocks the following ratios are usually determined: 234 U/ 238 U, 230 Th/ 238 U, 226 Ra/ 238 U, 228 Th/ 230 Th, 228 Th/ 232 Th and lead isotopes; for natural waters, besides the enumerated - 226 Ra/ 228 Ra. General content of uranium and thorium in the course of isotope investigations is determined from separate samples, most frequently by the X-ray spectral method, radium content - by usual radiochemical method, uranium and radium content in waters -respectively by calorimetric and emanation methods. Radiochemical preparation of geologic powder and aqueous samples for isotope analysis is described in detail. The technique of measuring and calculating isotope ratios (α-spectrometry for determining isotope composition of uranium and thorium and emanation method for determining 226 Ra/ 228 Ra) is presented

  13. Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP-MS with multiple ion counters

    Energy Technology Data Exchange (ETDEWEB)

    Boulyga, Sergei F.; Prohaska, Thomas [University of Natural Resources and Applied Life Sciences, Department of Chemistry, Division of Analytical Chemistry-VIRIS Laboratory, Vienna (Austria)

    2008-01-15

    This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) - a Nu Plasma HR - equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the {sup 235}U/{sup 238}U, {sup 236}U/{sup 238}U, {sup 145}Nd/{sup 143}Nd, {sup 146}Nd/{sup 143}Nd, {sup 101}Ru/({sup 99}Ru+{sup 99}Tc) and {sup 102}Ru/({sup 99}Ru+{sup 99}Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred {mu}m to about 1 mm and with surface alpha activities of 3-38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA-MC-ICP-MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15-20 min (excluding MC-ICP-MS optimization and calibration). The {sup 101}Ru/({sup 99}Ru+{sup 99}Tc) and {sup 102}Ru/({sup 99}Ru+{sup 99}Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in {sup 146}Nd of about 3-5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The {sup 235}U/{sup 238}U and {sup 236}U/{sup 238}U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously

  14. The isotopic enrichment of uranium in 1979

    International Nuclear Information System (INIS)

    Baron, M.

    1979-01-01

    The Eurodif uranium enrichment plant built on the Tricastin site is described. The uranium isotope separation plants in service abroad are presented. The main characteristics of the international enrichment market are defined [fr

  15. Extermination Of Uranium Isotopes Composition Using A Micro Computer With An IEEE-488 Interface For Mass Spectrometer Analysis

    International Nuclear Information System (INIS)

    Prajitno; Taftazani, Agus; Yusuf

    1996-01-01

    A mass spectrometry method can be used to make qualitative or quantitative analysis. For qualitative analysis, identification of unknown materials by a Mass Spectrometer requires definite assignment of mass number to peak on chart. In quantitative analysis, a mass spectrometer is used to determine isotope composition material in the sample. Analysis system of a Mass Spectrometer possession of PPNY-BATAN based on comparison ion current intensity which enter the collector, and have been used to analyse isotope composition. Calculation of isotope composition have been manually done. To increase the performance and to avoid manual data processing, a micro computer and IEEE-488 interface have been installed, also software packaged has been made. So that the determination of the isotope composition of material in the sample will be faster and more efficient. Tile accuracy of analysis using this program on sample standard U 3 O 8 NBS 010 is between 93,87% - 99,98%

  16. Determination of uranium isotopic composition and {sup 236}U content of soil samples and hot particles using inductively coupled plasma mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Boulyga, S.F. [Radiation Physics and Chemistry Problems Inst., Minsk (Belarus); Becker, J.S. [Central Department for Analytical Chemistry, Research Centre Juelich (Germany)

    2001-07-01

    As a result of the accident at the Chernobyl nuclear power plant (NPP) the environment was contaminated with spent nuclear fuel. The {sup 236}U isotope was used in this study to monitor the spent uranium from nuclear fallout in soil samples collected in the vicinity of the Chernobyl NPP. Nuclear track radiography was applied for the identification and extraction of hot radioactive particles from soil samples. A rapid and sensitive analytical procedure was developed for uranium isotopic ratio measurement in environmental samples based on double-focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) with a MicroMist nebulizer and a direct injection high-efficiency nebulizer (DIHEN). The performance of the DF-ICP-MS with a quartz DIHEN and plasma shielded torch was studied. Overall detection efficiencies of 4 x 10{sup -4} and 10{sup -3} counts per atom were achieved for {sup 238}U in DF-ICP-QMS with the MicroMist nebulizer and DIHEN, respectively. The rate of formation of uranium hydride ions UH{sup +}/U{sup +} was 1.2 x 10{sup -4} and 1.4 x 10{sup -4}, respectively. The precision of short-term measurements of uranium isotopic ratios (n = 5) in 1 {mu}g L{sup -1} NBS U-020 standard solution was 0.11% ({sup 238}U/{sup 235}U) and 1.4% ({sup 236}U/{sup 238}U) using a MicroMist nebulizer and 0.25% ({sup 235}U/{sup 238}U) and 1.9% ({sup 236}U/{sup 238}U) using a DIHEN. The isotopic composition of all investigated Chernobyl soil samples differed from those of natural uranium; i.e. in these samples the {sup 236}U/{sup 238}U ratio ranged from 10{sup -5} to 10{sup -3}. Results obtained with ICP-MS, {alpha}- and {gamma}-spectrometry showed differences in the migration properties of spent uranium, plutonium, and americium. The isotopic ratio of uranium was also measured in hot particles extracted from soil samples. (orig.)

  17. Oxygen isotope fractionation in uranium oxides

    International Nuclear Information System (INIS)

    Zheng Yongfei

    1995-01-01

    Thermodynamic oxygen isotope factors for uranium oxides have been calculated by means of the modified increment method. The sequence of 18 O-enrichment in the uranium oxides with respect to the common rock-forming minerals is predicted as follows: spinel 3 < illite. Two sets of self-consistent fractionation factors between the uranium oxides and water and between the uranium oxides and the other minerals have been obtained for 0∼1200 degree C. The theoretical results are applicable to the isotopic geothermometry of uranium ores when pairing with other gangue minerals in hydrothermal uranium deposits

  18. Determination of elemental impurities and U and O isotopic compositions with a view to identify the geographical and industrial origins of uranium ore concentrates

    Science.gov (United States)

    Salaun, A.; Hubert, A.; Pointurier, F.; Aupiais, J.; Pili, E.; Richon, P.; Fauré, A.; Diallo, S.

    2012-12-01

    First events of illicit trafficking of nuclear and radiological materials occurred 50 years ago. Nuclear forensics expertise are aiming at determining the use of seized material, its industrial history and provenance (geographical area, place of production or processing), at assisting in the identification and dismantling of illicit trafficking networks. This information is also valuable in the context of inspections of declared facilities to verify the consistency of operator's declaration. Several characteristics can be used to determine the origin of uranium ore concentrates such as trace elemental impurity patterns (Keegan et al., 2008 ; Varga et al., 2010a, 2010b) or uranium, oxygen and lead isotopic compositions (Tamborini et al., 2002a, 2002b ; Wallenius et al., 2006; Varga et al., 2009). We developed analytical procedures for measuring the isotopic compositions of uranium (234U/238U and 235U/238U) and oxygen (18O/16O) and levels of elemental impurities (e.g. REE, Th) from very small amounts of uranium ore concentrates (or yellow cakes). Micrometer particles and few milligrams of material are used for oxygen isotope measurements and REE determination, respectively. Reference materials were analyzed by mass spectrometry (TIMS, SF-ICP-MS and SIMS) to validate testing protocols. Finally, materials of unknown origin were analyzed to highlight significant differences and determine whether these differences allow identifying the origin of these ore concentrates. References: Keegan, E., et al. (2008). Applied Geochemistry 23, 765-777. Tamborini, G., et al. (2002a). Analytical Chemistry 74, 6098-6101. Tamborini, G., et al. (2002b). Microchimica Acta 139, 185-188. Varga, Z., et al. (2009). Analytical Chemistry 81, 8327-8334. Varga, Z., et al. (2010a). Talanta 80, 1744-1749. Varga, Z., et al. (2010b). Radiochimica Acta 98, 771-778 Wallenius, M., et al. (2006). Forensic Science International 156, 55-62.

  19. Standard test method for determination of uranium or plutonium isotopic composition or concentration by the total evaporation method using a thermal ionization mass spectrometer

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This method describes the determination of the isotopic composition and/or the concentration of uranium and plutonium as nitrate solutions by the thermal ionization mass spectrometric (TIMS) total evaporation method. Purified uranium or plutonium nitrate solutions are loaded onto a degassed metal filament and placed in the mass spectrometer. Under computer control, ion currents are generated by heating of the filament(s). The ion beams are continually measured until the sample is exhausted. The measured ion currents are integrated over the course of the run, and normalized to a reference isotope ion current to yield isotopic ratios. 1.2 In principle, the total evaporation method should yield isotopic ratios that do not require mass bias correction. In practice, some samples may require this bias correction. When compared to the conventional TIMS method, the total evaporation method is approximately two times faster, improves precision from two to four fold, and utilizes smaller sample sizes. 1.3 The tot...

  20. Ultratrace Uranium Fingerprinting with Isotope Selective Laser Ionization Spectrometry

    International Nuclear Information System (INIS)

    Ziegler, Summer L.; Bushaw, Bruce A.

    2008-01-01

    Uranium isotope ratios can provide source information for tracking uranium contamination in a variety of fields, ranging from occupational bioassay to monitoring aftereffects of nuclear accidents. We describe the development of Isotope Selective Laser Ionization Spectrometry (ISLIS) for ultratrace measurement of the minor isotopes 234U, 235U, and 236U with respect to 238U. Optical isotopic selectivity in three-step excitation with single-mode continuous wave lasers is capable of measuring the minor isotopes at relative abundances below 1 ppm, and is not limited by isobaric interferences such as 235UH+ during measurement of 236U. This relative abundance limit approaches the threshold for measurement of uranium minor isotopes with conventional mass spectrometry, typically 10-7, but without mass spectrometric analysis of the laser-created ions. Uranyl nitrate standards from an international blind comparison were used to test analytical performance for different isotopic compositions and with quantities ranging from 11 ng to 10 (micro)g total uranium. Isotopic ratio determination was demonstrated over a linear dynamic range of 7 orders of magnitude with a few percent relative precision and detection limits below 500 fg for the minor isotopes

  1. Uranium isotope separation using styrene cation exchangers

    International Nuclear Information System (INIS)

    Kahovec, J.

    1980-01-01

    The separation of 235 U and 238 U isotopes is carried out either by simple isotope exchange in the system uranium-cation exchanger (sulphonated styrene divinylbenzene resin), or by combination of isotope exchange in a uranium-cation exchanger (Dowex 50, Amberlite IR-120) system and a chemical reaction. A review is presented of elution agents used, the degree of cation exchanger cross-linking, columns length, and 235 U enrichment. The results are described of the isotope effect study in a U(IV)-U(VI)-cation exchanger system conducted by Japanese and Romanian authors (isotope exchange kinetics, frontal analysis, reverse (indirect) frontal analysis). (H.S.)

  2. Isotopic composition of uranium in U3O8 by neutron induced reactions utilizing thermal neutrons from critical facility and high resolution gamma-ray spectrometry

    International Nuclear Information System (INIS)

    Acharya, R.; Pujari, P.K.; Goel, Lokesh

    2015-01-01

    Uranium in oxide and metal forms is used as fuel material in nuclear power reactors. For chemical quality control, it is necessary to know the isotopic composition (IC) of uranium i.e., 235 U to 238 U atom ratio as well as 235 U atom % in addition to its total concentration. Uranium samples can be directly assayed by passive gamma ray spectrometry for obtaining IC by utilizing 185 keV (γ-ray abundance 57.2%) of 235 U and 1001 keV (γ-ray abundance 0.837%) of 234m Pa (decay product of 238 U). However, due to low abundance of 1001 keV, often it is not practiced to obtain IC by this method as it gives higher uncertainty even if higher mass of sample and counting time are used. IC of uranium can be determined using activity ratio of neutron induced fission product of 235 U to activation product of 238 U ( 239 Np). In the present work, authors have demonstrated methodologies for determination of IC of U as well as 235 U atom% in natural ( 235 U 0.715%) and low enriched uranium (LEU, 3-20 atom % of 235 U) samples of uranium oxide (U 3 O 8 ) by utilizing ratio of counts at 185 keV γ-ray or γ-rays of fission products with respect to 277 keV of 239 Np. Natural and enriched samples (about 25 mg) were neutron irradiated for 4 hours in graphite reflector position of AHWR Critical Facility (CF) using highly thermalized (>99.9% thermal component) neutron flux (∼10 7 cm -2 s -1 )

  3. Isotopic ratio method for determining uranium contamination

    International Nuclear Information System (INIS)

    Miles, R.E.; Sieben, A.K.

    1994-01-01

    The presence of high concentrations of uranium in the subsurface can be attributed either to contamination from uranium processing activities or to naturally occurring uranium. A mathematical method has been employed to evaluate the isotope ratios from subsurface soils at the Rocky Flats Nuclear Weapons Plant (RFP) and demonstrates conclusively that the soil contains uranium from a natural source and has not been contaminated with enriched uranium resulting from RFP releases. This paper describes the method used in this determination which has widespread application in site characterizations and can be adapted to other radioisotopes used in manufacturing industries. The determination of radioisotope source can lead to a reduction of the remediation effort

  4. Stable isotope compositions of quartz pebbles and their fluid inclusions as tracers of sediment provenance: Implications for gold- and uranium-bearing quartz pebble conglomerates

    Energy Technology Data Exchange (ETDEWEB)

    Vennemann, T.W.; Kesler, S.E.; O' Neil, J.R. (Univ. of Michigan, Ann Arbor (United States))

    1992-09-01

    Oxygen isotope compositions of pebbles from late Archean to paleo-Proterozoic gold- and/or uranium-bearing oligomictic quartz pebble conglomerates of the Witwatersrand district, South Africa, and Huronian Supergroup, Canada, were determined in an attempt to define the nature of the source terrain. The [delta][sup 18]O values of quartz pebbles within any one sample typically vary by [approximately] 4[per thousand] or more, but occasionally by as much as 8[per thousand], even for adjacent pebbles within the same hand specimen. In addition, adjacent quartz pebbles of widely contrasting [delta][sup 18]O values also preserve distinct isotopic signatures of their fluid inclusions. This overall heterogeneity suggests that the pebbles did not undergo significant oxygen isotope exchange after incorporation in the conglomerates. Therefore, oxygen isotope analyses of such quartz pebbles, in combination with a detailed investigation of their mineral and fluid inclusions, can provide a useful method for characterizing pebble populations and hence dominant sediment source modes. Comparison of values found in this study with [delta][sup 18]O values of quartz from Archean granites, pegmatites, and mesothermal greenstone gold veins, i.e., [delta][sup 18]O values of sources commonly proposed for the conglomerate ores, suggests that uranium is derived from a granitic source, whereas gold has a mesothermal greenstone gold source. Low [delta][sup 18]O values of chert pebbles (9[per thousand] to 11.5[per thousand]) relative to those expected for Archean and Proterozoic marine cherts (commonly [ge] 17[per thousand]) effectively exclude marine cherts, and therefore, auriferous iron formations and exhalatives, as likely sources of gold.

  5. Stable isotope compositions of quartz pebbles and their fluid inclusions as tracers of sediment provenance: Implications for gold- and uranium-bearing quartz pebble conglomerates

    International Nuclear Information System (INIS)

    Vennemann, T.W.; Kesler, S.E.; O'Neil, J.R.

    1992-01-01

    Oxygen isotope compositions of pebbles from late Archean to paleo-Proterozoic gold- and/or uranium-bearing oligomictic quartz pebble conglomerates of the Witwatersrand district, South Africa, and Huronian Supergroup, Canada, were determined in an attempt to define the nature of the source terrain. The δ 18 O values of quartz pebbles within any one sample typically vary by ∼ 4 per-thousand or more, but occasionally by as much as 8 per-thousand, even for adjacent pebbles within the same hand specimen. In addition, adjacent quartz pebbles of widely contrasting δ 18 O values also preserve distinct isotopic signatures of their fluid inclusions. This overall heterogeneity suggests that the pebbles did not undergo significant oxygen isotope exchange after incorporation in the conglomerates. Therefore, oxygen isotope analyses of such quartz pebbles, in combination with a detailed investigation of their mineral and fluid inclusions, can provide a useful method for characterizing pebble populations and hence dominant sediment source modes. Comparison of values found in this study with δ 18 O values of quartz from Archean granites, pegmatites, and mesothermal greenstone gold veins, i.e., δ 18 O values of sources commonly proposed for the conglomerate ores, suggests that uranium is derived from a granitic source, whereas gold has a mesothermal greenstone gold source. Low δ 18 O values of chert pebbles (9 per-thousand to 11.5 per-thousand) relative to those expected for Archean and Proterozoic marine cherts (commonly ≥ 17 per-thousand) effectively exclude marine cherts, and therefore, auriferous iron formations and exhalatives, as likely sources of gold

  6. Isotopic anomalies in high Z elements: Uranium?

    International Nuclear Information System (INIS)

    Jovanovic, S.; Reed, G.W. Jr.; Essling, A.M.; Rauh, E.G.; Graczyk, D.G.

    1989-03-01

    Uranium in terrestrial volcanic ejecta from mantle-related sources has been analyzed mass spectrometrically. The objective was to seek supporting evidence for or refutation isotopic variations reported by Fried et al. (1985) for some such samples. The possibility that terrestrial U is not of constant isotopic composition is extraordinary. If true, mechanisms for creating the variation must be sought and the lack of homogenization within the earth addressed. Samples of 100 grams or more were processed in order to minimize reagent and environmental (laboratory) blank interference and to permit isolation of large amounts (several to tens of μg) of U for the mass spectrometer (MS) measurements, which utilizes aliquots of /approximately/1 μg. Aliquants from four volcanic samples gave data which indicate enrichments of 235 U ranging from 0.2% to 5.9% in the 235/238 ratio relative normal uranium ratios. These relative enrichments are consistent with, and in some cases, higher than the 0.18% enrichment reported by Fried et al. (1985) for two volcanic lava samples. However, we were not able to reproduce their results on the Kilauea lava for which they report 0.18% 235 U enrichment. The relative error in our MS ratios is 0.05% -- 0.07%. 1 tab

  7. A method of uranium isotopes concentration analysis

    International Nuclear Information System (INIS)

    Lin Yuangen; Jiang Meng; Wu Changli; Duan Zhanyuan; Guo Chunying

    2010-01-01

    A basic method of uranium isotopes concentration is described in this paper. The iteration method is used to calculate the relative efficiency curve, by analyzing the characteristic γ energy spectrum of 235 U, 232 U and the daughter nuclide of 238 U, then the relative activity can be calculated, at last the uranium isotopes concentration can be worked out, and the result is validated by the experimentation. (authors)

  8. Uranium isotopic signatures measured in samples of dirt collected at two former uranium facilities

    International Nuclear Information System (INIS)

    Meyers, L.A.; Stalcup, A.M.; LaMont, S.P.; Spitz, H.B.

    2014-01-01

    Nuclear forensics is a multidisciplinary science that uses a variety of analytical methods and tools to explore the physical, chemical, and isotopic characteristics of nuclear and radiological materials. These characteristics, when evaluated alone or in combination, become signatures that may reveal how and when the material was fabricated. The signatures contained in samples of dirt collected at two different uranium metal processing facilities in the United States were evaluated to determine uranium isotopic composition and compare results with processes that were conducted at these sites. One site refined uranium and fabricated uranium metal ingots for fuel and targets and the other site rolled hot forged uranium and other metals into dimensional rods. Unique signatures were found that are consistent with the activities and processes conducted at each facility and establish confidence in using these characteristics to reveal the provenance of other materials that exhibit similar signatures. (author)

  9. Isotope exchange between gaseous hydrogen and uranium hydride powder

    International Nuclear Information System (INIS)

    Shugard, Andrew D.; Buffleben, George M.; Johnson, Terry A.; Robinson, David B.

    2014-01-01

    Highlights: • Isotope exchange between hydrogen gas and uranium hydride powder can be rapid and reversible. • Gas–solid exchange rate is controlled by transport within ∼0.7 μm hydride particles. • Gas chromatographic separation of hydrogen isotopes using uranium hydride is feasible. - Abstract: Isotope exchange between gaseous hydrogen and solid uranium hydride has been studied by flowing hydrogen (deuterium) gas through packed powder beds of uranium deuteride (hydride). We used a residual gas analyzer system to perform real-time analysis of the effluent gas composition. We also developed an exchange and transport model and, by fitting it to the experimental data, extracted kinetic parameters for the isotope exchange reaction. Our results suggest that, from approximately 70 to 700 kPa and 25 to 400 °C, the gas-to-solid exchange rate is controlled by hydrogen and deuterium transport within the ∼0.7 μm diameter uranium hydride particles. We use our kinetic parameters to show that gas chromatographic separation of hydrogen and deuterium using uranium hydride could be feasible

  10. Lead isotopes as seepage indicators around a uranium tailings dam

    International Nuclear Information System (INIS)

    Gulson, B.L.; Mizon, K.J.; Korsch, M.J.; Noller, B.N.

    1989-01-01

    Lead isotope ratios and lead concentrations have been measured in water from 26 bores around the Ranger uranium tailings dam, Northern Territory, Australia, and from the dam itself to determine possible migration of lead derived from the radioactive decay of uranium. Lead isotope compositions have also been measured for the particulates retained on selected filters. The concentration of lead in the bore waters is extremely low (usually 206 Pb/ 204 Pb ratio measured in the bore waters differs by more than a factor of 100 from that in the tailings dam and shows no evidence of lead derived from a significant uranium accumulation. It may be possible to distinguish between lead from the tailings dam and that derived from a nearby uranium ore body

  11. Origin of uranium isotope variations in early solar nebula condensates.

    Science.gov (United States)

    Tissot, François L H; Dauphas, Nicolas; Grossman, Lawrence

    2016-03-01

    High-temperature condensates found in meteorites display uranium isotopic variations ((235)U/(238)U), which complicate dating the solar system's formation and whose origin remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide (247)Cm (t 1/2 = 15.6 My) into (235)U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of (235)U reaching ~+6% relative to average solar system composition, which can only be due to the decay of (247)Cm. This allows us to constrain the (247)Cm/(235)U ratio at solar system formation to (1.1 ± 0.3) × 10(-4). This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture.

  12. Uranium Isotopic Analysis with the FRAM Isotopic Analysis Code

    International Nuclear Information System (INIS)

    Vo, D.T.; Sampson, T.E.

    1999-01-01

    FRAM is the acronym for Fixed-Energy Response-Function Analysis with Multiple efficiency. This software was developed at Los Alamos National Laboratory originally for plutonium isotopic analysis. Later, it was adapted for uranium isotopic analysis in addition to plutonium. It is a code based on a self-calibration using several gamma-ray peaks for determining the isotopic ratios. The versatile-parameter database structure governs all facets of the data analysis. User editing of the parameter sets allows great flexibility in handling data with different isotopic distributions, interfering isotopes, and different acquisition parameters such as energy calibration and detector type

  13. New processes for uranium isotope separation

    International Nuclear Information System (INIS)

    Vanstrum, P.R.; Levin, S.A.

    1977-01-01

    An overview of the status and prospects for processes other than gaseous diffusion, gas centrifuge, and separation nozzle for uranium isotope separation is presented. The incentive for the development of these processes is the increasing requirements for enriched uranium as fuel for nuclear power plants and the potential for reducing the high costs of enrichment. The latest nuclear power projections are converted to uranium enrichment requirements. The size and timing of the market for new enrichment processes are then determined by subtracting the existing and planned uranium enrichment capacities. It is estimated that to supply this market would require the construction of a large new enrichment plant of 9,000,000 SWU per year capacity, costing about $3 billion each (in 1976 dollars) about every year till the year 2000. A very comprehensive review of uranium isotope separation processes was made in 1971 by the Uranium Isotope Separation Review Ad Hoc Committee of the USAEC. Many of the processes discussed in that review are of little current interest. However, because of new approaches or remaining uncertainties about potential, there is considerable effort or continuing interest in a number of alternative processes. The status and prospects for attaining the requirements for competitive economics are presented for these processes, which include laser, chemical exchange, aerodynamic other than separation nozzle, and plasma processes. A qualitative summary comparison of these processes is made with the gaseous diffusion, gas centrifuge, and separation nozzle processes. In order to complete the overview of new processes for uranium isotope separation, a generic program schedule of typical steps beyond the basic process determination which are required, such as subsystem, module, pilot plant, and finally plant construction, before large-scale production can be attained is presented. Also the present value savings through the year 2000 is shown for various

  14. Determination of uranium isotopes in urine

    International Nuclear Information System (INIS)

    Lellis, I.R.; Silva, D.V.F.M. Rey; Taddei, M.H.T.

    2017-01-01

    Variable concentrations of uranium occur naturally in waters, plant products and soils. Small amounts of this element are routinely incorporated by man. Occupationally exposed individuals (IOEs) are subject to the incorporation of higher amounts of uranium into their work routines. The effects on human health resulting from the incorporation of uranium in environmental doses are not very well established and are currently recognized as of little relevance. The incorporation resulting from occupational activities, where higher doses can be found, represents a health risk resulting from chemical damages to the kidneys. Considering that uranium is eliminated from the human body through urine and feces, and that the concentration in the urine can be obtained by means of radiochemical analyzes, this can be considered an efficient indirect method to verify the incorporation of this element. In the work the isotopes of 234 U, 235 U and 238 U were analyzed in urine samples of IOEs and the rate of uranium present in them was verified

  15. Uranium isotopic disequilibrium in ground water as an indicator of anomalies

    International Nuclear Information System (INIS)

    Osmond, J.K.; Cowart, J.B.; Ivanovich, M.

    1983-01-01

    Because of the unique elemental and isotopic properties of uranium, ground water surveys are a most appropriate approach to prospecting for surficial and secondary uranium deposits. Uranium4+ is generally immobile, but in oxidising and carbonate bearing waters U 6 + is mobile and conservative. Uranium 234 is the radiogenic daughter of 238 U. The intervening α-decay event causes recoil displacements and radioactive disequilibrium between the two isotopes in open systems such as surficial aquifers. Extreme variations in dissolved uranium composition of ground waters combined with significant variations in the ratio 234 U/ 238 U are indicative of the proximity and stage of evolution of secondary deposits. (author)

  16. Separation unit for uranium isotopes etc

    International Nuclear Information System (INIS)

    1975-01-01

    The task of the invention - improving the efficiency of a uranium isotope separation unit with a rotor as separation chamber by improving its flow characteristics - is solved by a central-axial gas conduction system with radial branches which leads the media into the separation chambers or out of these. (UWI) [de

  17. Uranium isotopic determination by alpha spectroscopy

    International Nuclear Information System (INIS)

    Acena, M.; Garcoa-Torano, E.

    1979-01-01

    A method for alpha-spectrometry determinations of uranium isotopes, using surface barrier detectors, is described. This method is based in the shape similarity of the most intense line groups for the nuclides 234 U, 235 U, 236 U and 238 U. The method yields analytical results sufficiently accurate in samples with 235 U contents lower than 25% in atoms. (author)

  18. LIQUID METAL COMPOSITIONS CONTAINING URANIUM

    Science.gov (United States)

    Teitel, R.J.

    1959-04-21

    Liquid metal compositions containing a solid uranium compound dispersed therein is described. Uranium combines with tin to form the intermetallic compound USn/sub 3/. It has been found that this compound may be incorporated into a liquid bath containing bismuth and lead-bismuth components, if a relatively small percentage of tin is also included in the bath. The composition has a low thermal neutron cross section which makes it suitable for use in a liquid metal fueled nuclear reactor.

  19. Characterizing uranium oxide reference particles for isotopic abundances and uranium mass by single particle isotope dilution mass spectrometry

    International Nuclear Information System (INIS)

    Kraiem, M.; Richter, S.; Erdmann, N.; Kühn, H.; Hedberg, M.; Aregbe, Y.

    2012-01-01

    Highlights: ► A method to quantify the U mass in single micron particles by ID-TIMS was developed. ► Well-characterized monodisperse U-oxide particles produced by an aerosol generator were used. ► A linear correlation between the mass of U and the volume of particle(s) was found. ► The method developed is suitable for determining the amount of U in a particulate reference material. - Abstract: Uranium and plutonium particulate test materials are becoming increasingly important as the reliability of measurement results has to be demonstrated to regulatory bodies responsible for maintaining effective nuclear safeguards. In order to address this issue, the Institute for Reference Materials and Measurements (IRMM) in collaboration with the Institute for Transuranium Elements (ITU) has initiated a study to investigate the feasibility of preparing and characterizing a uranium particle reference material for nuclear safeguards, which is finally certified for isotopic abundances and for the uranium mass per particle. Such control particles are specifically required to evaluate responses of instruments based on mass spectrometric detection (e.g. SIMS, TIMS, LA-ICPMS) and to help ensuring the reliability and comparability of measurement results worldwide. In this paper, a methodology is described which allows quantifying the uranium mass in single micron particles by isotope dilution thermal ionization mass spectrometry (ID-TIMS). This methodology is characterized by substantial improvements recently achieved at IRMM in terms of sensitivity and measurement accuracy in the field of uranium particle analysis by TIMS. The use of monodisperse uranium oxide particles prepared using an aerosol generation technique developed at ITU, which is capable of producing particles of well-characterized size and isotopic composition was exploited. The evidence of a straightforward correlation between the particle volume and the mass of uranium was demonstrated in this study

  20. Lasers and uranium isotope separation

    Energy Technology Data Exchange (ETDEWEB)

    Gilles, L

    1987-12-01

    The use of lasers by the electronuclear industry to enrich uranium is discussed, particularly economic aspects. The SILMO and SILVA processes (chosen by France for industrial development) are presented. Criteria which lead to the choice of lasers and to their set-up (architecture of the chain) are described. For electricity - consumption linked to the use of lasers of 40 kWh/STU, a laser uranium enrichment plant with 10 STU/yr capacity requires 50kW of light from copper vapor lasers, i.e., 500 units each having 100W capacity, compared with the 40W units currently marketed.

  1. Laser and uranium isotope separation

    International Nuclear Information System (INIS)

    Gilles, L.

    1987-07-01

    Industrial processes for uranium enrichment, economical context and market are briefly reviewed. Then physical principles of the two lasers processes: SILMO (molecular process) and SILVA (atomic process) are presented insisting on criteria for choosing lasers used in the SILVA process which will be developed in France [fr

  2. Isotopic exchange of nitrogen and ammonia synthesis on uranium nitride

    International Nuclear Information System (INIS)

    Panov, G.I.; Boreskov, G.K.; Kharitonov, A.S.; Moroz, Eh.M.; Sobolev, V.I.

    1984-01-01

    The catalytic properties of uranium nitride samples of different chemical composition: α - U 2 N 3 and UNsub(1, 70) are compared. The isotopic exchange at 553-623 K in both cases is realized by reversible dissociative nitrogen adsorption. Despite the proximity of structural and thermodynamic phase characteristics, the nitrogen adsorption heat differs by 120 kJ/mol which leads to strong differences in catalytic sample properties. It is shown that the isotopic exchange serves a reliable characteristic of activation of molecular nitrogen and its ability to react with the ammonia synthesis

  3. Uranium isotopes in El hamraween harbour sediments

    International Nuclear Information System (INIS)

    Salahel Din, K.

    2009-01-01

    Isotopes of uranium in marine sediments collected from El Hamraween harbour and Ras El-Bhar areas on the Egyptian coast of the Red Sea have been studied using radiochemical separation procedures and alpha-particle spectrometry. Activity concentrations of 238 U, 235 U, 234 U were calculated. The activities observed indicating the enhancement of radioactivity level in El Hamraween harbor area due to the activities of phosphate shipment operation. Secular equilibrium between 234 U and 238 U was found in the analyzed samples. The average activity ratio of 235 U/ 238 U was close to the value 0.046 for uranium in nature

  4. Natural fractionation of uranium isotopes

    International Nuclear Information System (INIS)

    Noordmann, Janine

    2015-01-01

    The topic of this thesis was the investigation of U (n( 238 U) / n( 235 U)) isotope variations in nature with a focus on samples (1) that represent the continental crust and its weathering products (i.e. granites, shales and river water) (2) that represent products of hydrothermal alteration on mid-ocean ridges (i.e. altered basalts, carbonate veins and hydrothermal water) and (3) from restricted euxinic basins (i.e. from the water column and respective sediments). The overall goal was to explore the environmental conditions and unravel the mechanisms that fractionate the two most abundant U isotopes, n( 238 U) and n( 235 U), on Earth.

  5. Uranium isotope ratio measurements in field settings

    International Nuclear Information System (INIS)

    Shaw, R.W.; Barshick, C.M.; Young, J.P.; Ramsey, J.M.

    1997-01-01

    The authors have developed a technique for uranium isotope ratio measurements of powder samples in field settings. Such a method will be invaluable for environmental studies, radioactive waste operations, and decommissioning and decontamination operations. Immediate field data can help guide an ongoing sampling campaign. The measurement encompasses glow discharge sputtering from pressed sample hollow cathodes, high resolution laser spectroscopy using conveniently tunable diode lasers, and optogalvanic detection. At 10% 235 U enrichment and above, the measurement precision for 235 U/( 235 U+ 238 U) isotope ratios was ±3%; it declined to ±15% for 0.3% (i.e., depleted) samples. A prototype instrument was constructed and is described

  6. Natural fractionation of uranium isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Noordmann, Janine

    2015-01-24

    The topic of this thesis was the investigation of U (n({sup 238}U) / n({sup 235}U)) isotope variations in nature with a focus on samples (1) that represent the continental crust and its weathering products (i.e. granites, shales and river water) (2) that represent products of hydrothermal alteration on mid-ocean ridges (i.e. altered basalts, carbonate veins and hydrothermal water) and (3) from restricted euxinic basins (i.e. from the water column and respective sediments). The overall goal was to explore the environmental conditions and unravel the mechanisms that fractionate the two most abundant U isotopes, n({sup 238}U) and n({sup 235}U), on Earth.

  7. Separation of uranium isotopes by gas centrifugation

    International Nuclear Information System (INIS)

    Jordan, I.

    1980-05-01

    The uranium isotope enrichment is studied by means of the countercurrent gas centrifuge driven by thermal convection. A description is given of (a) the transfer and purification of the uranium hexafluoride used as process gas in the present investigation; (b) the countercurrent centrifuge ZG3; (c) the system designed for the introduction and extraction of the process gas from the centrifuge; (d) the measurement of the process gas flow rate through the centrifuge; (e) the determination of the uranium isotopic abundance by mass spectrometry; (f) the operation and mechanical behavior of the centrifuge and (g) the isotope separation experiments, performed, respectively, at total reflux and with production of enriched material. The results from the separation experiments at total reflux are discussed in terms of the enrichment factor variation with the magnitude and flow profile of the countercurrent given by the temperature difference between the rotor covers. As far as the separation experiments with production are concerned, the discussion of their results is presented through the variation of the enrichment factor as a function of the flow rate, the observed asymmetry of the process and the calculated separative power of the centrifuge. (Author) [pt

  8. Uranium determination in different compositions

    International Nuclear Information System (INIS)

    Bulyanitsa, L.S.; Ivanova, K.S.; Ryzhinskij, M.V.; Alekseeva, N.A.; Solntseva, L.F.; Shereshevskaya, I.I.

    1978-01-01

    For clarifying the suitability of two different methods of analysis for determining uranium without its previous purification, the analysis of uranium carbides (UC, UC 2 , UC - ZrC) and alloys (U - Al, U - Zr - Nb, U- Ti) has been carried out. Dissolution of the compositions examined was carried out either after previous calcining (UC, UC 2 ) or fusion with KHSO 4 (UC - ZrC), or in phosphoric acid (alloys). The first method, a variant of potentiometric titration, has been modified for small amounts of uranium. Titration was carried out on a semiautomatic titrating unit. The uranium amount per titration is about 4 to 5 mg. The second method of analysis is the coulombmetric titration at a constant current intensity. The quantity of uranium per titration was equal to 1 - 3 mg. The statistical processing of the results obtained was carried out by a dispersion analysis that allowed to reveal the influence of separate factors, such as method of analysis, type of composition, the non-uniformity of a sample, the enumerated factors influencing the dispersion of the analysis results. It has been shown that the both methods are equally suitable for analysis of the uranium compounds examined

  9. Uranium isotopic effect studies on cation and anion exchange resins

    International Nuclear Information System (INIS)

    Sarpal, S.K.; Gupta, A.R.

    1975-01-01

    Uranium isotope effects in exchange reactions involving hexavalent and tetravalent uranium, on ion exchange resins, have been re-examined. The earlier work on uranium isotope effects in electron exchange reactions involving hexavalent and tetravalent uranium, has been critically reviewed. New experimental data on these systems in hydrochloric acid medium, has been obtained, using break-through technique on anion-exchange columns. The isotope effects in these break-through experiments have been reinterpreted in a way which is consistent with the anion exchange behaviour of the various uranium species in these systems. (author)

  10. Evaluating the reliability of uranium concentration and isotope ratio measurements via an interlaboratory comparison program

    International Nuclear Information System (INIS)

    Oliveira Junior, Olivio Pereira de; Oliveira, Inez Cristina de; Pereira, Marcia Regina; Tanabe, Eduardo

    2009-01-01

    The nuclear fuel cycle is a strategic area for the Brazilian development because it is associated with the generation of electricity needed to boost the country economy. Uranium is one the chemical elements in this cycle and its concentration and isotope composition must be accurately known. In this present work, the reliability of the uranium concentration and isotope ratio measurements carried out at the CTMSP analytical laboratories is evaluated by the results obtained in an international interlaboratory comparison program. (author)

  11. Mobilization of uranium isotopes in Brazilian aquifers

    International Nuclear Information System (INIS)

    Bonotto, Daniel Marcos

    1994-01-01

    The uranium isotopes 234 U and 238 U have been extensively used to study geochemical problems, mainly related to the hydrological medium. Active dissolution of these isotopes is occurring in groundwaters from several aquifers at southeastern region of Brazil. The dissolved uranium concentration showed variability related to the rainwater infiltration with the U content of groundwaters increasing during wet periods. The amount of uranium mobilized during rainwater infiltration showed an inverse correlation with the thickness of unsaturated silty clay at Morro do Ferro area. The experimental data favour the possibility of formation of soluble complexes of U and dissolved organic compounds at Morro do Ferro area, and also some absorption of U by clays during rainwater infiltration. Enhanced 234 U/ 238 U activity ratios for dissolved uranium have been found and explained in terms of combined chemical etch and leach processes for groundwaters of the Pocos de Caldas alkaline complex. These processes are considered responsible for the bulk dissolution of rock matrix rather then alpha-recoil effects. Several direct correlations have been found for groundwaters of Agua da Prata, which supported the effectiveness of etch/lead mechanisms, for example, between 234 U/ 238 U activity ratio and dissolved solids, ionic strength, C O 2 partial pressure, 'traditional' index of base exchange and 'new' index of base exchange (involving the anion fluoride). A higher 234 U/ 238 U activity ratio was found to be directly related to a higher value of dissolution rate and a higher value of 222 Rn content was found to be related with a higher value of specific surface area. These relationships explained a good inverse logarithmic correlation between 234 U/ 238 U activity ratio and 222 Rn content of the spring waters of Aguas da Prata. (author)

  12. The lead isotopic composition of dust in the vicinity of a uranium mine in northern Australia and its use for radiation dose assessment

    International Nuclear Information System (INIS)

    Bollhoefer, Andreas; Honeybun, Russell; Rosman, Kevin; Martin, Paul

    2006-01-01

    Airborne lead isotope ratios were measured via Thermal Ionisation Mass Spectrometry in samples from the vicinity of Ranger uranium mine in northern Australia. Dust deposited on leaves of Acacia spp. was washed off and analysed to gain a geographical snapshot of lead isotope ratios in the region. Aerosols were also collected on Teflon filters that were changed monthly over one seasonal cycle using a low volume diaphragm pump. Lead isotope ratios in dust deposited on leaves overestimate the relative amount of mine origin airborne lead, most likely due to a difference of the size distribution of particles collected on leaves and true aerosol size distribution. Seasonal measurements show that the annual average mine contribution to airborne lead concentrations in Jabiru East, approximately 2.5 km northwest of the mine, amounted to 13%, with distinct differences between the wet and dry season. The relative contribution of mine origin lead deposited on leaves in the dry season drops to less than 1% at a distance of 12.5 km from the mine along the major wind direction. An approach is outlined, in which lead isotope ratios are used to estimate the effective radiation dose received from the inhalation of mine origin radioactivity trapped in or on dust. Using the data from our study, this dose has been calculated to be approximately 2 μSv year -1 for people living and working in the area

  13. Uranium isotopes in groundwater: their use in prospecting for sandstone-type uranium deposits

    International Nuclear Information System (INIS)

    Cowart, J.B.; Osmond, J.K.

    1977-01-01

    The relative abundances of dissolved 238 U and its daughter 234 U appear to be greatly affected as the uranium is transported downdip in sandstone aquifers. In an actively forming uranium accumulation at a reducing barrier, an input of 234 U occurs in proximity to the isotopically non-selective precipitation of uranium from the water. The result is a downdip water much lower in uranium concentration but relatively enriched in 234 U. The measurement of isotopic as well as concentration changes may increase the effectiveness of hydrogeochemical exploration of uranium. The investigation includes the uranium isotopic patterns in aquifers associated with known uranium orebodies in the Powder River and Shirley Basins, Wyoming, and Karnes County, Texas, USA. In addition, the Carrizo sandstone aquifer of Texas was studied in detail and the presence of an uranium accumulation inferred

  14. Relative probabilities of the uranium isotopes for thorium x-ray emission and fluorescence of uranium x-rays

    International Nuclear Information System (INIS)

    Parker, J.L.

    1991-01-01

    Both thorium x-rays from decaying uranium isotopes and self-fluoresced uranium x-rays are prominent in high-resolution gamma-ray spectra of uranium-bearing materials. Useful application of the information carried by those x-rays has been curtailed because the probabilities of the uranium isotopes for thorium x-ray emission and for uranium x-ray fluorescence have not been known. By analyzing enrichment-meter geometry spectra from uranium oxide standards whose enrichments ranged from 0.7% to 91%, relative values, primarily, have been obtained for the probabilities of both processes. Thorium x-ray emission is very heavily dominated by 235 U. In all ordinarily occurring uranium isotopic distributions, thorium x-rays may be used as a valid 235 U signature. The probability for a thorium K α1 x-ray to be emitted in the decay of a 235 U atom is 0.048 ±0.002. In infinitely thick uranium oxide materials, the relative ratios of effectiveness for self-fluorescence, on a per unit mass basis, are approximately 234 U : 235 U : 236 U : 238 U = 1.13 : 1.00 : 0.52 : 0.028. on a per decay basis, the approximate ratios are 0.00039 : 1.00 : 0.017 : 0.18. These results imply that, contrary to what has often been stated, gamma rays are far more important than alpha particles in the self-fluorescence of uranium. Because of the importance of gamma-ray self-fluorescence, the uranium x-ray yield will be somewhat influenced by the size, shape, and composition of the materials. 4 refs., 1 fig

  15. Innovative lasers for uranium isotope separation

    International Nuclear Information System (INIS)

    Brake, M.L.; Gilgenbach, R.M.

    1993-07-01

    Copper vapor laser have important applications to uranium atomic vapor laser isotope separation (AVLIS). We have investigated two innovative methods of exciting/pumping copper vapor lasers which have the potential to improve the efficiency and scaling of large laser systems used in uranium isotope separation. Experimental research has focused on the laser discharge kinetics of (1) microwave, and (2) electron beam excitation/pumping of large-volume copper vapor lasers. Microwave resonant cavity produced copper vapor plasmas at 2.45 GHz, have been investigated in three separate experimental configurations. The first examined the application of CW (0-500W) power and was found to be an excellent method for producing an atomic copper vapor from copper chloride. The second used a pulsed (5kW, 0.5--5 kHz) signal superimposed on the CW signal to attempt to produce vaporization, dissociation and excitation to the laser states. Enhanced emission of the optical radiation was observed but power densities were found to be too low to achieve lasing. In a third experiment we attempted to increase the applied power by using a high power magnetron to produce 100 kW of pulsed power. Unfortunately, difficulties with the magnetron power supply were encountered leaving inconclusive results. Detailed modeling of the electromagnetics of the system were found to match the diagnostics results well. An electron beam pumped copper vapor system (350 kV, 1.0 kA, 300 ns) was investigated in three separate copper chloride heating systems, external chamber, externally heated chamber and an internally heated chamber. Since atomic copper spectral lines were not observed, it is assumed that a single pulse accelerator is not capable of both dissociating the copper chloride and exciting atomic copper and a repetitively pulsed electron beam generator is needed

  16. An improved FT-TIMS method of measuring uranium isotope ratios in the uranium-bearing particles

    International Nuclear Information System (INIS)

    Chen, Yan; Wang, Fan; Zhao, Yong-Gang; Li, Li-Li; Zhang, Yan; Shen, Yan; Chang, Zhi-Yuan; Guo, Shi-Lun; Wang, Xiao-Ming; Cui, Jian-Yong; Liu, Yu-Ang

    2015-01-01

    An improved method of Fission Track technique combined with Thermal Ionization Mass Spectrometry (FT-TIMS) was established in order to determine isotope ratio of uranium-bearing particle. Working standard of uranium oxide particles with a defined diameter and isotopic composition were prepared and used to review the method. Results showed an excellent agreement with certified values. The developed method was used to analyze isotope ratio of single uranium-bearing particle in swipe samples successfully. The analysis results of uranium-bearing particles in swipe samples accorded with the operation history of the origin. - Highlights: • The developed method was successfully applied in the analysis of real swipe sample. • Uranium-bearing particles were confined in the middle of track detector. • The fission tracks of collodion film and PC film could be confirmed each other. • The thickness of collodion film should be no more than about 60 μm. • The method could avoid losing uranium-bearing particles in the etching step.

  17. Process for producing uranium oxide rich compositions from uranium hexafluoride

    International Nuclear Information System (INIS)

    DeHollander, W.R.; Fenimore, C.P.

    1978-01-01

    Conversion of gaseous uranium hexafluoride to a uranium dioxide rich composition in the presence of an active flame in a reactor defining a reaction zone is achieved by separately introducing a first gaseous reactant comprising a mixture of uranium hexafluoride and a reducing carrier gas, and a second gaseous reactant comprising an oxygen-containing gas. The reactants are separated by a shielding gas as they are introduced to the reaction zone. The shielding gas temporarily separates the gaseous reactants and temporarily prevents substantial mixing and reacting of the gaseous reactants. The flame occurring in the reaction zone is maintained away from contact with the inlet introducing the mixture to the reaction zone. After suitable treatment, the uranium dioxide rich composition is capable of being fabricated into bodies of desired configuration for loading into nuclear fuel rods. Alternatively, an oxygen-containing gas as a third gaseous reactant is introduced when the uranium hexafluoride conversion to the uranium dioxide rich composition is substantially complete. This results in oxidizing the uranium dioxide rich composition to a higher oxide of uranium with conversion of any residual reducing gas to its oxidized form

  18. Uranium, RADON and radon isotopes in selected brines of Poland

    International Nuclear Information System (INIS)

    Kozlowska, B.; Walencik, A.; Zipper, W.; Dorda, J.; Przylibski, T.A.

    2010-01-01

    Natural radioactive isotopes were studied in nine different types of brines from four locations in Poland. Investigated brines are exploited from various geological structures composed of the rocks of different chemical and mineral composition as well as different age and depth. All investigated brines are used in balneotherapy (i.e. baths, inhalations, showers). The main goal of this study was to obtain some basic knowledge on the activity range of natural elements such as uranium, RADON and radon in different brine types in Poland and their variability depending on their location in certain geological structures. Activities of 234,238 U, 226,228 Ra and 222 Rn isotopes were measured with the use of two nuclear spectrometry techniques: liquid scintillation and alpha spectrometry. The activity concentrations of 222 Rn vary from below 1 to 76.1±3.7 Bq/l, for the 226 Ra isotope from 0.19±0.01 to 85.5±0.4 Bq/l and for 228 Ra from below 0.03 to 2.17±0.09 Bq/l. For uranium isotopes, the concentrations are in the range from below 0.5 to 5.1±0.4 mBq/l for 238 U and from 1.6±0.4 to 45.6±2.0 mBq/l for 2 34U . The obtained results indicate high RADON activity concentrations corresponding to high mineralization of waters. (authors)

  19. The determination of minor isotope abundances in naturally occurring uranium materials. The tracing power of isotopic signatures for uranium

    Energy Technology Data Exchange (ETDEWEB)

    Ovaskainen, R

    1999-11-01

    The mass spectrometric determination of minor abundant isotopes, {sup 234}U and {sup 236}U in naturally occurring uranium materials requires instruments of high abundance sensitivity and the use of highly sensitive detection systems. In this study the thermal ionisation mass spectrometer Finnigan MAT 262RPQ was used. It was equipped with 6 Faraday cups and a Secondary Electron Multiplier (SEM), which was operated in pulse counting mode for the detection of extremely low ion currents. The dynamic measurement range was increased considerably combining these two different detectors. The instrument calibration was performed carefully. The linearity of each detector, the deadtime of the ion counting detector, the detector normalisation factor, the baseline of each detector and the mass discrimination in the ion source were checked and optimised. A measurement technique based on the combination of a Gas Source Mass Spectrometry (GSMS) and a Thermal Ionisation Mass Spectrometry (TIMS) was developed for the accurate determination of isotopic composition in naturally occurring uranium materials. Because the expected ratio of n({sup 234}U)/n({sup 238}U) exceeded the dynamic measurement range of the Faraday detectors of the TIMS instrument, an experimental design using a combination of two detectors was developed. The n({sup 234}U)/n({sup 235}U) and n({sup 236}U)/n({sup 235}U) ratios were determined using ion counting in combination with the decelerating device. The n({sup 235}U)/n({sup 238}U) ratio was determined by the Faraday detector. This experimental design allowed the detector cross calibration to be circumvented. Precisions of less than 1 percent for the n({sup 234}U)/n({sup 235}U) ratios and 5-25 percent for the n({sup 236}U)/n({sup 235}U) ratios were achieved. The purpose of the study was to establish a register of isotopic signatures for natural uranium materials. The amount ratio, and isotopic composition of 18 ore concentrates, collected by the International

  20. The determination of minor isotope abundances in naturally occurring uranium materials. The tracing power of isotopic signatures for uranium

    International Nuclear Information System (INIS)

    Ovaskainen, R.

    1999-01-01

    The mass spectrometric determination of minor abundant isotopes, 234 U and 236 U in naturally occurring uranium materials requires instruments of high abundance sensitivity and the use of highly sensitive detection systems. In this study the thermal ionisation mass spectrometer Finnigan MAT 262RPQ was used. It was equipped with 6 Faraday cups and a Secondary Electron Multiplier (SEM), which was operated in pulse counting mode for the detection of extremely low ion currents. The dynamic measurement range was increased considerably combining these two different detectors. The instrument calibration was performed carefully. The linearity of each detector, the deadtime of the ion counting detector, the detector normalisation factor, the baseline of each detector and the mass discrimination in the ion source were checked and optimised. A measurement technique based on the combination of a Gas Source Mass Spectrometry (GSMS) and a Thermal Ionisation Mass Spectrometry (TIMS) was developed for the accurate determination of isotopic composition in naturally occurring uranium materials. Because the expected ratio of n( 234 U)/n( 238 U) exceeded the dynamic measurement range of the Faraday detectors of the TIMS instrument, an experimental design using a combination of two detectors was developed. The n( 234 U)/n( 235 U) and n( 236 U)/n( 235 U) ratios were determined using ion counting in combination with the decelerating device. The n( 235 U)/n( 238 U) ratio was determined by the Faraday detector. This experimental design allowed the detector cross calibration to be circumvented. Precisions of less than 1 percent for the n( 234 U)/n( 235 U) ratios and 5-25 percent for the n( 236 U)/n( 235 U) ratios were achieved. The purpose of the study was to establish a register of isotopic signatures for natural uranium materials. The amount ratio, and isotopic composition of 18 ore concentrates, collected by the International Atomic Energy Agency (IAEA) from uranium milling and mining

  1. Determination of isotopic uranium in food and water

    International Nuclear Information System (INIS)

    Baratta, E.J.; Mackill, P.

    2001-01-01

    The U.S. Food and Drug Administration (FDA) conducts surveys of foods both domestic and imported for the presence of radioactivity. It does not routinely analyze for the actinides, specifically uranium, as it has been shown by previously by studies as reported by WELFORD and others that the concentration in food is very low. This was the result of a 'Tri-City' study. However, at specific sites, the FDA has been requested to analyze for uranium. The concern is that either 'enriched' or 'depleted' uranium has been introduced into the environment and possibly contaminated the food supply. In addition some concern has been raised that water from wells or other sources used for processing food may contain uranium, both natural, depleted or enriched. Methodology for the determination of isotopic uranium, specifically for uranium-238 (depleted) and/or uranium-235 (enriched) in the analyses of food and water samples and the results of these surveys are discussed. (author)

  2. Bibliographical study on photochemical separation of uranium isotopes

    International Nuclear Information System (INIS)

    Bougon, Roland

    1975-01-01

    The objective of this report is to propose an overview of knowledge and current works on isotopic separation of uranium by means of selective excitation where this excitation is obtained by a light source with a wave length corresponding to a selective or preferential absorption by a molecule or by the atom itself of one of the isotopes. After a brief overview of principles and requirements of isotopic separation by selective excitation, the author reviews compounds which can be used for this process. These compounds are mainly considered in terms of spectroscopy, and the study focuses on the most volatile among them, the uranium hexafluoride, its spectra, and possible processes for extraction. Some much less volatile uranium compounds are also mentioned with, when available, their spectroscopic properties. The uranium vapour excitation process is described, and some orientations for further researches are proposed [fr

  3. Characterization of uranium isotopic abundances in depleted uranium metal assay standard 115

    International Nuclear Information System (INIS)

    Mathew, K.J.; Singleton, G.L.; Essex, R.M.; Hasozbek, A.; Orlowicz, G.; Soriano, M.

    2013-01-01

    Certified reference material (CRM) 115, Uranium (Depleted) Metal (Uranium Assay Standard), was analyzed using a TRITON Thermal Ionization Mass Spectrometer to characterize the uranium isotope-amount ratios. The certified 235 U/ 238 U 'major' isotope-amount ratio of 0.0020337 (12) in CRM 115 was determined using the total evaporation (TE) and the modified total evaporation (MTE) analytical techniques. In the MTE method, the total evaporation process is interrupted on a regular basis to allow correction of background from peak tailing, internal calibration of the secondary electron multiplier detector versus the Faraday cups, peak-centering, and ion source re-focusing. For the 'minor' 234 U/ 238 U and 236 U/ 238 U isotope-amount ratio measurements using MTE, precision and accuracy comparable to conventional analyses are achieved, without compromising the quality of the 235 U/ 238 U isotope-amount ratios. Characterized values of the 234 U/ 238 U and 236 U/ 238 U isotope-amount ratios in CRM 115 are 0.000007545 (10) and 0.000032213 (84), respectively. The 233 U/ 238 U isotope-amount ratio in CRM 115 is estimated to be -9 . The homogeneity of the CRM 115 materials is established through the absence of any statistically significant unit-to-unit variation in the uranium isotope-amount ratios. The measurements leading to the certification of uranium isotope-amount ratios are discussed. (author)

  4. Development of empirical relation for isotope of uranium in enriched uranium matrix

    International Nuclear Information System (INIS)

    Srivastava, S.K.; Vidyasagar, D.; Jha, S.K.; Tripathi, R.M.

    2018-01-01

    Uranium enriched in 235 U is required in commercial light water reactors to produce a controlled nuclear reaction. Enrichment allows the 235 U isotopes to be increased from 0.71% to a range between 2% to 5% depending upon requirement. The enriched uranium in the form of sintered UO 2 pellet is used for any commercially operating boiling light water reactors. The enriched uranium fuel bundle surface swipes sample is being analysed to assess the tramp uranium as a quality control parameter. It is known that the 234 U isotope also enriched along with 235 U isotope in conventional gaseous diffusion enrichment process. The information about enrichment percentage of 234 U helps to characterize isotopic properties of enriched uranium. A few reports provide the empirical equation and graphs for finding out the specific activity, activity percentage, activity ratio of 234 U isotopes for enriched uranium. Most of them have not provided the reference for the data used and their source. An attempt has been made to model the relationship between 234 U and 235 U as a function of uranium enrichment at low level

  5. Uranium isotopes in ground water as a prospecting technique

    International Nuclear Information System (INIS)

    Cowart, J.B.; Osmond, J.K.

    1980-02-01

    The isotopic concentrations of dissolved uranium were determined for 300 ground water samples near eight known uranium accumulations to see if new approaches to prospecting could be developed. It is concluded that a plot of 234 U/ 238 U activity ratio (A.R.) versus uranium concentration (C) can be used to identify redox fronts, to locate uranium accumulations, and to determine whether such accumulations are being augmented or depleted by contemporary aquifer/ground water conditions. In aquifers exhibiting flow-through hydrologic systems, up-dip ground water samples are characterized by high uranium concentration values (> 1 to 4 ppB) and down-dip samples by low uranium concentration values (less than 1 ppB). The boundary between these two regimes can usually be identified as a redox front on the basis of regional water chemistry and known uranium accumulations. Close proximity to uranium accumulations is usually indicated either by very high uranium concentrations in the ground water or by a combination of high concentration and high activity ratio values. Ground waters down-dip from such accumulations often exhibit low uranium concentration values but retain their high A.R. values. This serves as a regional indicator of possible uranium accumulations where conditions favor the continued augmentation of the deposit by precipitation from ground water. Where the accumulation is being dispersed and depleted by the ground water system, low A.R. values are observed. Results from the Gulf Coast District of Texas and the Wyoming districts are presented

  6. Isotopic composition of fission gases in LWR fuel

    International Nuclear Information System (INIS)

    Jonsson, T.

    2000-01-01

    Many fuel rods from power reactors and test reactors have been punctured during past years for determination of fission gas release. In many cases the released gas was also analysed by mass spectrometry. The isotopic composition shows systematic variations between different rods, which are much larger than the uncertainties in the analysis. This paper discusses some possibilities and problems with use of the isotopic composition to decide from which part of the fuel the gas was released. In high burnup fuel from thermal reactors loaded with uranium fuel a significant part of the fissions occur in plutonium isotopes. The ratio Xe/Kr generated in the fuel is strongly dependent on the fissioning species. In addition, the isotopic composition of Kr and Xe shows a well detectable difference between fissions in different fissile nuclides. (author)

  7. Aerodynamic isotope separation processes for uranium enrichment: process requirements

    International Nuclear Information System (INIS)

    Malling, G.F.; Von Halle, E.

    1976-01-01

    The pressing need for enriched uranium to fuel nuclear power reactors, requiring that as many as ten large uranium isotope separation plants be built during the next twenty years, has inspired an increase of interest in isotope separation processes for uranium enrichment. Aerodynamic isotope separation processes have been prominently mentioned along with the gas centrifuge process and the laser isotope separation methods as alternatives to the gaseous diffusion process, currently in use, for these future plants. Commonly included in the category of aerodynamic isotope separation processes are: (a) the separation nozzle process; (b) opposed gas jets; (c) the gas vortex; (d) the separation probes; (e) interacting molecular beams; (f) jet penetration processes; and (g) time of flight separation processes. A number of these aerodynamic isotope separation processes depend, as does the gas centrifuge process, on pressure diffusion associated with curved streamlines for the basic separation effect. Much can be deduced about the process characteristics and the economic potential of such processes from a simple and elementary process model. In particular, the benefit to be gained from a light carrier gas added to the uranium feed is clearly demonstrated. The model also illustrates the importance of transient effects in this class of processes

  8. A Convenient Method for Estimation of the Isotopic Abundance in Uranium Bearing Samples

    International Nuclear Information System (INIS)

    AI -Saleh, F.S.; AI-Mukren, Alj.H.; Farouk, M.A.

    2008-01-01

    A convenient and simple method for estimation of the isotopic abundance in some uranium bearing samples using gamma-ray spectrometry is developed using a hyper pure germanium spectrometer and a standard uranium sample with known isotopic abundance

  9. Development of a code for the isotopic analysis of Uranium

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J. H.; Kang, M. Y.; Kim, Jinhyeong; Choi, H. D. [Seoul National Univ., Seoul (Korea, Republic of)

    2013-05-15

    To strengthen the national nuclear nonproliferation regime by an establishment of nuclear forensic system, the techniques for nuclear material analysis and the categorization of important domestic nuclear materials are being developed. MGAU and FRAM are commercial software for the isotopic analysis of Uranium by using γ-spectroscopy, but the diversity of detection geometry and some effects - self attenuation, coincidence summing, etc. - suggest an analysis tool under continual improvement and modification. Hence, developing another code for HPGe γ- and x-ray spectrum analysis is started in this study. The analysis of the 87-101 keV region of Uranium spectrum is attempted based on the isotopic responses similar to those developed in MGAU. The code for isotopic analysis of Uranium is started from a fitting.

  10. The physics of uranium isotope separation by laser

    International Nuclear Information System (INIS)

    Clerc, M.; Rigny, P.

    1985-01-01

    SILMO is the isotopic separation process using a laser and the uranium hexafluoride molecule. SILVA is the laser process whereby the enriched medium is formed by the atomic vapour from uranium. The scientific bases of the two processes are described using very simple parameters such as photoionisation selectivity and useful availability of photons and atoms. It is shown that SILVA can have a specific energy consumption lower than 100 KWh/UTS. A separator module could be made up, for instance, of a dihedron of uranium vapour several metres long in which the laser beams would have to be bent within a multi-duct cell to cover about 180 to 200 meters. This separator module would use overall laser light power of some 10 KW and could supply 3.5% enriched uranium in a single phase from natural uranium by rejecting 0.20% impoverished U. 27 refs [fr

  11. Timescales of magma ascent and degassing and the role of crustal assimilation at Merapi volcano (2006-2010), Indonesia: Constraints from uranium-series and radiogenic isotopic compositions

    Science.gov (United States)

    Handley, H. K.; Reagan, M.; Gertisser, R.; Preece, K.; Berlo, K.; McGee, L. E.; Barclay, J.; Herd, R.

    2018-02-01

    We present new 238U-230Th-226Ra-210Pb-210Po, 87Sr/86Sr and 143Nd/144Nd isotopic data of whole-rock samples and plagioclase separates from volcanic deposits of the 2006 and 2010 eruptions at Merapi volcano, Java, Indonesia. These data are combined with available eruption monitoring, petrographic, mineralogical and Pb isotopic data to assess current theories on the cause of a recent transition from effusive dome-building (2006) to explosive (2010) activity at the volcano, as well as to further investigate the petrogenetic components involved in magma genesis and evolution. Despite the significant difference in eruption style, the 2006 and 2010 volcanic rocks show no significant difference in (238U/232Th), (230Th/232Th) and (226Ra/230Th) activity ratios, with all samples displaying U and Ra excesses. The 226Ra and 210Pb excesses observed in plagioclase separates from the 2006 and 2010 eruptions indicate that a proportion of the plagioclase grew within the decades preceding eruption. The 2006 and 2010 samples were depleted in 210Po relative to 210Pb ((210Po/210Pb)i monitoring parameters, 210Po ingrowth calculations suggest that initial intrusion into the shallow magma plumbing system occurred several weeks to a few months prior to the initial 2010 eruption. The 2006 and 2010 samples show a wide range in (210Pb/226Ra) activity ratio within a single eruption at Merapi and are largely characterised by 210Pb deficits ((210Pb/226Ra) monitoring data, previous petrological studies (mineral, microlite and melt inclusion work) and maximum calculated timescale estimates using Fe-Mg compositional gradients in clinopyroxene, that also suggest more rapid movement of relatively undegassed magma in 2010 relative to 2006.

  12. Isotopic analysis of uranium by thermoionic mass spectrometry

    International Nuclear Information System (INIS)

    Moraes, N.M.P. de.

    1979-01-01

    Uranium isotopic ratio measurements by thermoionic spectrometry are presented. Emphasis is given upon the investigation of the parameters that directly affect the precision and accuracy of the results. Optimized procedures, namely, chemical processing, sample loading on the filaments, vaporization, ionization and measurements of ionic currents, are established. Adequate statistical analysis of the data for the calculation of the internal and external variances and mean standard deviation are presented. These procedures are applied to natural and NBS isotopic standard uranium samples. The results obtained agree with the certified values within specified limits. 235 U/ 238 U isotopic ratios values determined for NBS-U500, and a series of standard samples with variable isotopic compositon, are used to calculate mass discrimination factor [pt

  13. Research on evolutionary laws of Sr, Nd, Pb isotopes of uranium metallization and volcanic rocks in south china

    International Nuclear Information System (INIS)

    Ying Junlong

    1998-01-01

    According to research on evolutionary tracer of Sr, Nd, Pb isotopes, the author proposes that isotopic evolution of Mesozoic volcanics in south China is controlled by regionally metamorphic rocks of ancient land basement, early reformed derivates and recycled continental crust. Isotopic composition of uranium metallization shows the characteristics of crust sources, and Yanshanian accretion of continental margin caused the crust movement such as magmatic activity in lower crust within continent, extension-down-faulting, etc., promoting the migration, enrichment and ore formation of uranium

  14. Fission decay properties of ultra neutron-rich uranium isotopes

    Indian Academy of Sciences (India)

    in the chain of neutron-rich uranium isotopes is examined here. The neutron ... mean field theory, this nucleus is shown to undergo exotic decay mode of thermal neu- .... For 250U with a fission barrier of 4.3 MeV [5], we obtain the value of.

  15. Uranium isotopes in carbonate aquifers of arid region setting

    DEFF Research Database (Denmark)

    Alshamsi, Dalal M.; Murad, Ahmed A.; Aldahan, Ala

    2013-01-01

    in the southern Arabian peninsula, namely at two locations within the United Arab Emirates (UAE) and two locations in Oman are discussed. The analyses of the uranium isotopes were performed using ICP-MS and the results indicated a range of concentrations for 235U and 238 U at 3–39 ng L-1 (average: 18 ng L-1...

  16. Relativistic Hartree-Bogoliubov description of thorium and uranium isotopes

    International Nuclear Information System (INIS)

    Naz, Tabassum; Ahmad, Shakeb

    2016-01-01

    The relativistic Hartree-Bogoliubov (RHB) theory is a relativistic extension of the Hartree-Fock- Bogoliubov theory. It is a unified description of mean-field and pairing correlations and successfully describe the various phenomenon of nuclear structure. In the present work, RHB is applied to study the thorium and uranium isotopes

  17. Uranium isotopes in groundwaters from Tubarao Group, Parana Basin, Brazil

    International Nuclear Information System (INIS)

    Bonotto, D.M.; Caprioglio, L.

    1999-01-01

    The purpose of this work is to characterize the uranium isotopes 238-U and 234-U in some important deep tubular wells drilled at Tubarao Group, with the aim of verifying if the dissolution processes that are taking place within the aquifer can generate enhanced 234-U/238-U activity ratios like those found at the Botucatu-Piramboia aquifer. (author)

  18. The jet nozzle process for uranium 235 isotopic enrichment

    International Nuclear Information System (INIS)

    Jordan, I.; Umeda, K.; Brown, A.E.P.

    1979-01-01

    A general survey of the isotopic enrichment of Uranium - 235, principally by jet nozzle process, is made. Theoretical treatment of a single stage and cascade of separation stages of the above process with its development in Germany until 1976 is presented [pt

  19. Pulsed CO laser for isotope separation of uranium

    Energy Technology Data Exchange (ETDEWEB)

    Baranov, Igor Y.; Koptev, Andrey V. [Rocket-Space Technics Department, Baltic State Technical University, 1, 1st Krasnoarmeyskaya st.,St. Petersburg, 190005 (Russian Federation)

    2012-07-30

    This article proposes a technical solution for using a CO laser facility for the industrial separation of uranium used in the production of fuel for nuclear power plants, employing a method of laser isotope separation of uranium with condensation repression in a free jet. The laser operation with nanosecond pulse irradiation can provide an acceptable efficiency in the separating unit and a high efficiency of the laser with the wavelength of 5.3 {mu}m. In the present work we also introduce a calculation model and define the parameters of a mode-locked CO laser with a RF discharge in the supersonic stream. The average pulsed CO laser power of 3 kW is sufficient for efficient industrial isotope separation of uranium in one stage.

  20. On the migration of uranium isotopes in sandstone aquifers

    International Nuclear Information System (INIS)

    Froehlich, K.; Gellermann, R.

    1982-01-01

    Measurements of natural 238 U and 234 U activity in groundwater of sandstone aquifers have been used to study the migration of these uranium isotopes. Regarding the uranium exchange between liquid phase and rock surface during migration, two different models were applied for evaluating the experimental results. Values of corresponding parameters (retardation factor K, removal rate R) reflecting different behaviour concerning this exchange were determined. For example, the values obtained for 238 U in a Triassic sandstone aquifer of the GDR are K = 8.6 x 10 6 and R = 1.3 x 10 -3 a -1 , respectively. It was found that, under the conditions of the sandstone aquifer concerned, the removal rate model is better suited for calculating uranium-isotope migration in groundwater. (author)

  1. Uniform deposition of uranium hexafluoride (UF6): Standardized mass deposits and controlled isotopic ratios using a thermal fluorination method

    Energy Technology Data Exchange (ETDEWEB)

    McNamara, Bruce K.; O’Hara, Matthew J.; Casella, Andrew M.; Carter, Jennifer C.; Addleman, R. Shane; MacFarlan, Paul J.

    2016-07-01

    Abstract: We report a convenient method for the generation of volatile uranium hexafluoride (UF6) from solid uranium oxides and other uranium compounds, followed by uniform deposition of low levels of UF6 onto sampling coupons. Under laminar flow conditions, UF6 is shown to interact with surfaces within the chamber to a highly predictable degree. We demonstrate the preparation of uranium deposits that range between ~0.01 and 470±34 ng∙cm-2. The data suggest the method can be extended to creating depositions at the sub-picogram∙cm-2 level. Additionally, the isotopic composition of the deposits can be customized by selection of the uranium source materials. We demonstrate a layering technique whereby two uranium solids, each with a different isotopic composition, are employed to form successive layers of UF6 on a surface. The result is an ultra-thin deposit of UF6 that bears an isotopic signature that is a composite of the two uranium sources. The reported deposition method has direct application to the development of unique analytical standards for nuclear safeguards and forensics.

  2. Uranium isotope separation from 1941 to the present

    International Nuclear Information System (INIS)

    Maier-Komor, Peter

    2010-01-01

    Uranium isotope separation was the key development for the preparation of highly enriched isotopes in general and thus became the seed for target development and preparation for nuclear and applied physics. In 1941 (year of birth of the author) large-scale development for uranium isotope separation was started after the US authorities were warned that NAZI Germany had started its program for enrichment of uranium and might have confiscated all uranium and uranium mines in their sphere of influence. Within the framework of the Manhattan Projects the first electromagnetic mass separators (Calutrons) were installed and further developed for high throughput. The military aim of the Navy Department was to develop nuclear propulsion for submarines with practically unlimited range. Parallel to this the army worked on the development of the atomic bomb. Also in 1941 plutonium was discovered and the production of 239 Pu was included into the atomic bomb program. 235 U enrichment starting with natural uranium was performed in two steps with different techniques of mass separation in Oak Ridge. The first step was gas diffusion which was limited to low enrichment. The second step for high enrichment was performed with electromagnetic mass spectrometers (Calutrons). The theory for the much more effective enrichment with centrifugal separation was developed also during the Second World War, but technical problems e.g. development of high speed ball and needle bearings could not be solved before the end of the war. Spying accelerated the development of uranium separation in the Soviet Union, but also later in China, India, Pakistan, Iran and Iraq. In this paper, the physical and chemical procedures are outlined which lead to the success of the project. Some security aspects and Non-Proliferation measures are discussed.

  3. Uranium isotope separation from 1941 to the present

    Energy Technology Data Exchange (ETDEWEB)

    Maier-Komor, Peter, E-mail: Peter@Maier-Komor.d [Retired from Physik-Department E12, Technische Universitaet Muenchen, D-85747 Garching (Germany)

    2010-02-11

    Uranium isotope separation was the key development for the preparation of highly enriched isotopes in general and thus became the seed for target development and preparation for nuclear and applied physics. In 1941 (year of birth of the author) large-scale development for uranium isotope separation was started after the US authorities were warned that NAZI Germany had started its program for enrichment of uranium and might have confiscated all uranium and uranium mines in their sphere of influence. Within the framework of the Manhattan Projects the first electromagnetic mass separators (Calutrons) were installed and further developed for high throughput. The military aim of the Navy Department was to develop nuclear propulsion for submarines with practically unlimited range. Parallel to this the army worked on the development of the atomic bomb. Also in 1941 plutonium was discovered and the production of {sup 239}Pu was included into the atomic bomb program. {sup 235}U enrichment starting with natural uranium was performed in two steps with different techniques of mass separation in Oak Ridge. The first step was gas diffusion which was limited to low enrichment. The second step for high enrichment was performed with electromagnetic mass spectrometers (Calutrons). The theory for the much more effective enrichment with centrifugal separation was developed also during the Second World War, but technical problems e.g. development of high speed ball and needle bearings could not be solved before the end of the war. Spying accelerated the development of uranium separation in the Soviet Union, but also later in China, India, Pakistan, Iran and Iraq. In this paper, the physical and chemical procedures are outlined which lead to the success of the project. Some security aspects and Non-Proliferation measures are discussed.

  4. Uranium isotope separation from 1941 to the present

    Science.gov (United States)

    Maier-Komor, Peter

    2010-02-01

    Uranium isotope separation was the key development for the preparation of highly enriched isotopes in general and thus became the seed for target development and preparation for nuclear and applied physics. In 1941 (year of birth of the author) large-scale development for uranium isotope separation was started after the US authorities were warned that NAZI Germany had started its program for enrichment of uranium and might have confiscated all uranium and uranium mines in their sphere of influence. Within the framework of the Manhattan Projects the first electromagnetic mass separators (Calutrons) were installed and further developed for high throughput. The military aim of the Navy Department was to develop nuclear propulsion for submarines with practically unlimited range. Parallel to this the army worked on the development of the atomic bomb. Also in 1941 plutonium was discovered and the production of 239Pu was included into the atomic bomb program. 235U enrichment starting with natural uranium was performed in two steps with different techniques of mass separation in Oak Ridge. The first step was gas diffusion which was limited to low enrichment. The second step for high enrichment was performed with electromagnetic mass spectrometers (Calutrons). The theory for the much more effective enrichment with centrifugal separation was developed also during the Second World War, but technical problems e.g. development of high speed ball and needle bearings could not be solved before the end of the war. Spying accelerated the development of uranium separation in the Soviet Union, but also later in China, India, Pakistan, Iran and Iraq. In this paper, the physical and chemical procedures are outlined which lead to the success of the project. Some security aspects and Non-Proliferation measures are discussed.

  5. Determination of uranium and its isotopic ratios in environmental samples

    International Nuclear Information System (INIS)

    Flues Szeles, M.S.M.

    1990-01-01

    A method for the determination of uranium and its isotopic ratios ( sup(235)U/ sup(238)U and sup(234U/ sup(238)U) is established in the present work. The method can be applied in environmental monitoring programs of uranium enrichment facilities. The proposed method is based on the alpha spectrometry technique which is applied after a purification of the sample by using an ionic exchange resin. The total yield achieved was (91 + 5)% with a precision of 5%, an accuracy of 8% and a lower limit of detection of 7,9 x 10 sup(-4)Bq. The uranium determination in samples containing high concentration of iron, which is an interfering element present in environmental samples, particularly in soil and sediment, was also studied. The results obtained by using artificial samples containing iron and uranium in the ratio 1000:1, were considered satisfactory. (author)

  6. Uranium isotopes in carbonate aquifers of arid region setting

    International Nuclear Information System (INIS)

    Alshamsi, D.M.; Murad, A.A.

    2013-01-01

    Groundwater in arid and semiarid regions is vital resource for many uses and therefore information about concentrations of uranium isotopes among other chemical parameters are necessary. In the study presented here, distribution of 238 U and 235 U in groundwater of four selected locations in the southern Arabian peninsula, namely at two locations within the United Arab Emirates (UAE) and two locations in Oman are discussed. The analyses of the uranium isotopes were performed using ICP-MS and the results indicated a range of concentrations for 235 U and 238 U at 3-39 ng L -1 (average: 18 ng L -1 ) and 429-5,293 ng L -1 (average: 2,508 ng L -1 ) respectively. These uranium concentrations are below the higher permissible WHO limit for drinking water and also comparable to averages found in groundwater from similar aquifers in Florida and Tunisia. Negative correlation between rainfall and uranium concentrations suggests that in lithologically comparable aquifers, climate may influence the concentration of uranium in subtropical to arid regions. (author)

  7. Charge exchange effect on laser isotope separation of atomic uranium

    International Nuclear Information System (INIS)

    Niki, Hideaki; Izawa, Yasukazu; Otani, Hiroyasu; Yamanaka, Chiyoe

    1982-01-01

    Uranium isotope separating experiment was performed using the two-step photoionization technique with dye laser and nitrogen laser by heating uranium metal with electron beam and producing atomic beam using generated vapour. The experimental results are described after explaining the two-step photoionization by laser, experimental apparatus, the selection of exciting wavelength and others. Enrichment factor depends largely on the spectrum purity of dye laser which is the exciting source. A large enrichment factor of 48.3 times was obtained for spectrum width 0.03A. To put the uranium isotope separation with laser into practice, the increase of uranium atomic density is considered to be necessary for improving the yield. Experimental investigation was first carried out on the charge exchange effect that seems most likely to affect the decrease of enrichment factor, and the charge exchange cross-section was determined. The charge exchange cross-section depends on the relative kinetic energy between ions and atoms. The experimental result showed that the cross-section was about 5 x 10 -13 cm 2 at 1 eV and 10 -13 cm 2 at 90 eV. These values are roughly ten times as great as those calculated in Lawrence Livermore Laboratory, and it is expected that they become the greatest factor for giving the upper limit of uranium atomic density in a process of practical application. (Wakatsuki, Y.)

  8. Isotopic measurement of uranium using NP-type chelate resin beads

    International Nuclear Information System (INIS)

    Wu Lanbi; Chen Wenpo; Wang Shijun

    1994-08-01

    NP-type chelate resin beads is used as a carrier of samples in the isotopic measurements of uranium by mass spectrometry. The results show that its absorption efficiency for uranium can be greater than 50%. It is one order magnitude higher than that strong basic anion resin, however, the ionization efficiencies of both are almost the same. Therefore, the amount of uranium required for isotopic analysis can be reduced one order of magnitude. This method has been used for isotopic analysis of uranium in NP-type chelate resin beads contained 10 -9 ∼ 10 -7 g uranium. For standard sample UTB-500, the external precision of measurements are within +-0.2%, for natural uranium samples are within +- 0.5%. The application of NP-type chelate resin beads in the isotopic measurement of uranium is a new creative achievement. It has been used in the depletion test of uranium-atomic vapor laser isotope separation

  9. A study of U-Pb isotopic evolutionary system in Chanziping uranium deposit

    International Nuclear Information System (INIS)

    Xu Weichang; Huang Shijie; Xia Yuliang.

    1988-01-01

    Chanziping uranium deposit occurred in the black siliceous slate of Lower cambrian. The uranium mineralization was controlled by both interstratified fault belt and the ore-bearing beds. Based on the study of the U-Pb isotopic system of the various rocks, ores and minerals in the ore-bearing beds, the authors find out the obvious disequilibrium of U-Pb isotopic composition in most rock samples which indicates the loss of uranium form the ore-bearing beds and surrounding granite. Its counting loss ranges from 30 to 80%. The age of rich ores of the U-Pb concordance diagram and the U-Pb three stage model are t 1 = 523 ± 19M. Y. , t 2 = 22 ± 2 M.Y.. The isochronal ages for pitchblend are 75 ± 4 M.Y., 43 ± 7 M.Y., and for rock is 416 M.y.. These data shows that the uranium in ore-bearing beds was mainly derived from the ore-bearing beds itself and partly from the surrounding granite. The ore deposit can be considered to be of stratabound uranium deposit of sedimentation and late transformation type

  10. Measurement system analysis (MSA) of the isotopic ratio for uranium isotope enrichment process control

    Energy Technology Data Exchange (ETDEWEB)

    Medeiros, Josue C. de; Barbosa, Rodrigo A.; Carnaval, Joao Paulo R., E-mail: josue@inb.gov.br, E-mail: rodrigobarbosa@inb.gov.br, E-mail: joaocarnaval@inb.gov.br [Industrias Nucleares do Brasil (INB), Rezende, RJ (Brazil)

    2013-07-01

    Currently, one of the stages in nuclear fuel cycle development is the process of uranium isotope enrichment, which will provide the amount of low enriched uranium for the nuclear fuel production to supply 100% Angra 1 and 20% Angra 2 demands. Determination of isotopic ration n({sup 235}U)/n({sup 238}U) in uranium hexafluoride (UF{sub 6} - used as process gas) is essential in order to control of enrichment process of isotopic separation by gaseous centrifugation cascades. The uranium hexafluoride process is performed by gas continuous feeding in separation unit which uses the centrifuge force principle, establishing a density gradient in a gas containing components of different molecular weights. The elemental separation effect occurs in a single ultracentrifuge that results in a partial separation of the feed in two fractions: an enriched on (product) and another depleted (waste) in the desired isotope ({sup 235}UF{sub 6}). Industrias Nucleares do Brasil (INB) has used quadrupole mass spectrometry (QMS) by electron impact (EI) to perform isotopic ratio n({sup 235}U)/n({sup 238}U) analysis in the process. The decision of adjustments and change te input variables are based on the results presented in these analysis. A study of stability, bias and linearity determination has been performed in order to evaluate the applied method, variations and systematic errors in the measurement system. The software used to analyze the techniques above was the Minitab 15. (author)

  11. The present state of laser isotope separation of uranium

    International Nuclear Information System (INIS)

    Tashiro, Hideo; Nemoto, Koshichi.

    1994-01-01

    As the methods of uranium enrichment, gas diffusion method and centrifugal separation method in which power consumption is less and the cost is low have been carried out. On the other hand, as the future technology, the research and development of laser isotope separation technology have been carried out. There are the atomic laser separation process in which the laser beam of visible light is irradiated to atomic state uranium and the molecular laser separation process in which far infrared laser beam is irradiated to uranium hexafluoride molecules. The atomic process is divided into three steps, that is, the processes of uranium evaporation, the reaction of uranium with laser beam and the recovery of enriched uranium. The principle of the laser separation is explained. The state of development of laser equipment and separation equipment is reported. The principle and the present state of development of the molecular separation process which consists of the cooling of UF 6 gas, the generation of high power 16 μm laser pulses and the collection of the reaction product are explained. The present state of both processes in foreign countries is reported. (K.I.)

  12. New aspects of uranium isotope separation

    International Nuclear Information System (INIS)

    Leonhardt, W.; Mueller, G.

    1979-01-01

    The need of 235 U enrichment capacity is discussed on the basis of the requirements for nuclear power in the next 10 ... 20 years. In this connection, the performance of gas diffusion, of the gas centrifuge and of the separation nozzle method are compared with each other, and an evaluation of the optical methods of isotope separation is given. (author)

  13. Performance of alpha spectrometry in the analysis of uranium isotopes in environmental and nuclear materials

    International Nuclear Information System (INIS)

    Carvalho, F.P.; Oliveira, J.M.

    2009-01-01

    The accuracy of alpha spectrometry in the determination of uranium isotopes at various concentrations levels and with various isotope ratios was tested in a round robin international intercomparison exercise. Results of isotope activity/mass and isotope mass ratios obtained by alpha spectrometry were accurate in a wide range of uranium masses and in isotopic ratios typical of depleted, natural, and low enriched uranium samples. Determinations by alpha spectrometry compared very satisfactorily in accuracy with those by mass spectrometry. For example, determination of U isotopes in natural uranium by alpha spectrometry agreed with mass spectrometry determinations at within ±1%. However, the 236 U isotope, particularly if present in activities much lower than 235 U, might not be determined accurately due to overlap in the alpha particle energies of these two uranium isotopes. (author)

  14. Development laser light facility for uranium isotope separation

    International Nuclear Information System (INIS)

    Dickinson, G.J.

    1992-01-01

    A laser light facility has been built and successfully commissioned as part of a programme to explore the economic potential of Laser Isotope Separation of Uranium. The laser systems are comprised of tunable dye lasers pumped by copper vapour lasers. The requirements for optical beam stability, alignment of lasers in chains, and protection of optical coatings have made challenging demands on the engineering design and operation of the facility. (Author)

  15. Optimization and Validation of the Developed Uranium Isotopic Analysis Code

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J. H.; Kang, M. Y.; Kim, Jinhyeong; Choi, H. D. [Seoul National Univ., Seoul (Korea, Republic of)

    2014-10-15

    γ-ray spectroscopy is a representative non-destructive assay for nuclear material, and less time-consuming and less expensive than the destructive analysis method. The destructive technique is more precise than NDA technique, however, there is some correction algorithm which can improve the performance of γ-spectroscopy. For this reason, an analysis code for uranium isotopic analysis is developed by Applied Nuclear Physics Group in Seoul National University. Overlapped γ- and x-ray peaks in the 89-101 keV X{sub α}-region are fitted with Gaussian and Lorentzian distribution peak functions, tail and background functions. In this study, optimizations for the full-energy peak efficiency calibration and fitting parameters of peak tail and background are performed, and validated with 24 hour acquisition of CRM uranium samples. The optimization of peak tail and background parameters are performed with the validation by using CRM uranium samples. The analysis performance is improved in HEU samples, but more optimization of fitting parameters is required in LEU sample analysis. In the future, the optimization research about the fitting parameters with various type of uranium samples will be performed. {sup 234}U isotopic analysis algorithms and correction algorithms (coincidence effect, self-attenuation effect) will be developed.

  16. Application of ion exchange to isotope separation. 2. Isotope separation of uranium

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Makoto; Fujii, Yasuhiko; Aida, Masao; Nomura, Masao; Aoyama, Taku

    1985-10-01

    Research work on the uranium isotope separation by ion exchange chromatography done by the ahthors was reviewed and summarized in the present paper. Specifically described are the determination of separation coefficients of uranium isotopes in various chemical systems involving uranium ions and complexes. The chemical systems are classifield into three main categories; (1) uranyl, U (VI), complex formation system, (2) uranous, U (IV), complex formation system and (3) U (IV) - U (VI) redox system. The redox system showed the largest separation coefficient of approx. 7 x 10/sup -4/, while the uranyl and uranous complex systems showed the separation coefficients of -- 2 x 10/sup -4/ and approx. 6 x 10/sup -5/, respectively.

  17. Experimental substantiation of separation techniques of lead and uranium microamounts using isotopic dilution method as control method

    International Nuclear Information System (INIS)

    Agapova, A.A.; Shcherbinina, N.K.

    1983-01-01

    Methods,ensuring at low levels of contamination a high degree of lead and uranium microamount separation from solutions of geological samples, have been selected and subjected to the detailed testing. The method of isotope dilution, , combining high accuracy and sensitivity of determinations, is used as the main control methods, is used as the main control method. Using the method, processe es of uranium extpaction are traced, special attention is paid to the detailed description of lead extraction at all the stages of the methods selected. Opera ations of ion exchange for lead and uranium in microcolumns with the Bio-Rad r sin are considered, as well as operations of lead electrolytic separation. The chemical procedures suggested permit to solve one of the main methodical tasks f sample preparation, containing microgram amounts of lead and uranium, for high h-prcision measurement of their isotope composition using mass-spectrometric method

  18. Uranium isotopes in groundwater occurring at Amazonas State, Brazil

    International Nuclear Information System (INIS)

    Luiz da Silva, Márcio; Bonotto, Daniel Marcos

    2015-01-01

    This paper reports the behavior of the dissolved U-isotopes 238 U and 234 U in groundwater providing from 15 cities in Amazonas State, Brazil. The isotope dilution technique accompanied by alpha spectrometry were utilized for acquiring the U content and 234 U/ 238 U activity ratio (AR) data, 0.01–1.4 µg L −1 and 1.0–3.5, respectively. These results suggest that the water is circulating in a reducing environment and leaching strata containing minerals with low uranium concentration. A tendency to increasing ARs values following the groundwater flow direction is identified in Manaus city. The AR also increases according to the SW–NE directions: Uarini→Tefé; Manacapuru→Manaus; Presidente Figueiredo→São Sebastião do Uatumã; and Boa Vista do Ramos→Parintins. Such trends are possibly related to several factors, among them the increasing acid character of the waters. The waters analyzed are used for human consumption and the highest dissolved U content is much lower than the maximum established by the World Health Organization. Therefore, in view of this radiological parameter they can be used for drinking purposes. - Highlights: • U-isotopes data in important aquifer systems in Amazon area. • Application of the U-isotopes data to investigate the groundwater flow direction. • Evaluation of the drinking-water quality in terms of dissolved uranium

  19. Use of lead isotopic composition in sulfides for the mineral-formation geochronology

    International Nuclear Information System (INIS)

    Ordynets, G.E.

    1977-01-01

    A study of the isotopic composition of lead in pyrites and galenites of a hydrothermal uranium deposit makes it possible to determine the time of ore formation. A few types of lead ores are distinguished. Each type corresponds to a definite period of mineralization and is characterized by a specific isotopic composition. The Cimmerian age of carbonate-sulphide veins has been established, the deposit being formed over a period of 150-200 million years

  20. Isotopic Tracking of Hanford 300 Area Derived Uranium in the Columbia River

    Energy Technology Data Exchange (ETDEWEB)

    Christensen, John N.; Dresel, P. Evan; Conrad, Mark E.; Patton, Gregory W.; DePaolo, Donald J.

    2010-10-31

    Our objectives in this study are to quantify the discharge rate of uranium (U) to the Columbia River from the Hanford Site's 300 Area, and to follow that U down river to constrain its fate. Uranium from the Hanford Site has variable isotopic composition due to nuclear industrial processes carried out at the site. This characteristic makes it possible to use high-precision isotopic measurements of U in environmental samples to identify even trace levels of contaminant U, determine its sources, and estimate discharge rates. Our data on river water samples indicate that as much as 3.2 kg/day can enter the Columbia River from the 300 Area, which is only a small fraction of the total load of dissolved natural background U carried by the Columbia River. This very low-level of Hanford derived U can be discerned, despite dilution to < 1 percent of natural background U, 350 km downstream from the Hanford Site. These results indicate that isotopic methods can allow the amounts of U from the 300 Area of the Hanford Site entering the Columbia River to be measured accurately to ascertain whether they are an environmental concern, or are insignificant relative to natural uranium background in the Columbia River.

  1. Use of minor uranium isotope measurements as an aid in safeguarding a uranium enrichment cascade

    International Nuclear Information System (INIS)

    Levin, S.A.; Blumkin, S.; Von Halle, E.

    1979-01-01

    Surveillance and containment, which are indispensable supporting measures for material accountability, do not provide those charged with safeguarding an installation with the assurance beyond the shadow of a doubt that all the input and output uranium will in fact be measured. Those who are concerned with developing non-intrusive techniques for safeguarding uranium enrichment plants under the Nuclear Non-Proliferation Treaty have perceived the possibility that data on the minor uranium isotope concentrations in an enrichment cascade withdrawal and feed streams may provide a means either to corroborate or to contradict the material accountability results. A basic theoretical study has been conducted to determine whether complete isotopic measurements on enrichment cascade streams may be useful for safeguards purposes. The results of the calculations made to determine the behaviour of the minor uranium isotopes ( 234 U and 236 U) in separation cascades, and the results of three plant tests made to substantiate the validity of the calculations, are reviewed briefly. Based on the fact that the 234 U and 236 U concentrations relative to that of 235 U in cascade withdrawal streams reflect the cascade flow-sheet, the authors conclude that the use of the minor isotope concentration measurements (MIST) in cascade withdrawal streams is a potentially valuable adjunct to material accounting for safeguarding a 235 U enrichment cascade. A characteristic of MIST, which qualifies it particularly for safeguards application under the NPT, is the fact that its use is entirely non-intrusive with regard to process technology and proprietary information. The usefulness of MIST and how it may be applied are discussed briefly. (author)

  2. Separation of uranium isotopes by selective photoionization

    International Nuclear Information System (INIS)

    Snavely, B.B.; Solarz, R.W.; Tuccio, S.A.

    1975-01-01

    Recent results of experiments on the laser photoseparation of U isotopes are reported. In the first series of experiments a two-step ionization process using a Xe laser to excite the atoms below the ionization level and then a Kr laser to ionize the atoms was described. Under the geometric conditions of the experiment and power of the Kr laser, enrichments between 2.5 and 3 percent were obtained in runs lasting 2 hrs. Calculations to describe the ion trajectories in the collector system reflected the two-band pattern observed on the Be collector plate. A system to study the photoionization process was assembled in which the U beam is excited to a desired energy level with a CW dye laser and an ultraviolet beam intercepts the excited U beam. An analysis of a photoionization spectrum obtained at a resolution of 8 A indicates that the peak cross section for transitions to autoionization states from the 7 M 7 level is large enough to be used in large-scale U separation systems. An ionization value of 6.15 +- 0.2 eV was deduced for the ionization potential of the U atom. (U.S.)

  3. Uranium isotope separation in the solid state. Final report for period ending September 30, 1978

    International Nuclear Information System (INIS)

    Bernstein, E.R.

    1978-09-01

    The final results of an investigation on the isotope separation of uranium in the solid state are presented in this report. The feasibility of separating uranium isotopes using the proposed system based on uranium borohydride (borodeuteride) in a low temperature mixed crystal has been determined. The first section of the report summarizes the background material relating to this work which includes: a calculation of isotope shifts (borodeuteride), details on the two-step, two-photon spectroscopic isotope separation technique, and a brief overview of the method and equipment used for separating uranium isotopes in the solid state. The second section concerns the experimental details of the present work performed in the laboratory. Representative spectroscopic data obtained in this investigation are presented and discussed in the third section. Finally, the report is concluded with recommendations for further investigations on the uranium borohydride (borodeuteride) system for isotope separation

  4. Candidate processes for diluting the 235U isotope in weapons-capable highly enriched uranium

    International Nuclear Information System (INIS)

    Snider, J.D.

    1996-02-01

    The United States Department of Energy (DOE) is evaluating options for rendering its surplus inventories of highly enriched uranium (HEU) incapable of being used to produce nuclear weapons. Weapons-capable HEU was earlier produced by enriching uranium in the fissile 235 U isotope from its natural occurring 0.71 percent isotopic concentration to at least 20 percent isotopic concentration. Now, by diluting its concentration of the fissile 235 U isotope in a uranium blending process, the weapons capability of HEU can be eliminated in a manner that is reversible only through isotope enrichment, and therefore, highly resistant to proliferation. To the extent that can be economically and technically justified, the down-blended uranium product will be made suitable for use as commercial reactor fuel. Such down-blended uranium product can also be disposed of as waste if chemical or isotopic impurities preclude its use as reactor fuel

  5. Magnesium isotopic composition of the mantle

    Science.gov (United States)

    Teng, F.; Li, W.; Ke, S.; Marty, B.; Huang, S.; Dauphas, N.; Wu, F.; Helz, R. L.

    2009-12-01

    Studies of Mg isotopic composition of the Earth not only are important for understanding its geochemistry but also can shed light on the accretion history of the Earth as well as the evolution of the Earth-Moon system. However, to date, the Mg isotopic composition of the Earth is still poorly constrained and highly debated. There is uncertainty in the magnitude of Mg isotope fractionation at mantle temperatures and whether the Earth has a chondritic Mg isotopic composition or not. To constrain further the Mg isotopic composition of the mantle and investigate the behavior of Mg isotopes during igneous differentiation, we report >200 high-precision (δ26Mg French Polynesian volcanoes (Society island and Cook Austral chain); 3) olivine grains from Hawaiian volcanoes (Kilauea, Koolau and Loihi) and 4) peridotite xenoliths from Australia, China, France, Tanzania and USA. Global oceanic basalts and peridotite xenoliths have a limited (<0.2 ‰) variation in Mg isotopic composition, with an average δ26Mg = -0.25 relative to DSM3. Olivines from Hawaiian lavas have δ26Mg ranging from -0.43 to +0.03, with most having compositions identical to basalts and peridotites. Therefore, the mantle’s δ26Mg value is estimated to be ~ -0.25 ± 0.1 (2SD), different from that reported by Wiechert and Halliday (2007; δ26Mg = ~ 0) but similar to more recent studies (δ26Mg = -0.27 to -0.33) (Teng et al. 2007; Handler et al. 2009; Yang et al., 2009). Moreover, we suggest the Earth, as represented by the mantle, has a Mg isotopic composition similar to chondrites (δ26Mg = ~-0.33). The need for a model such as that of Wiechert and Halliday (2007) that involves sorting of chondrules and calcium-aluminum-rich inclusions in the proto planetary disc is thus not required to explain the Mg isotopic composition of the Earth.

  6. First spatial isotopic separation of relativistic uranium projectile fragments

    International Nuclear Information System (INIS)

    Magel, A.; Voss, B.; Armbruster, P.; Aumann, T.; Clerc, H.G.; Czajkowski, S.; Folger, H.; Grewe, A.; Hanelt, E.; Heinz, A.; Irnich, H.; Jong, M. de; Junghans, A.; Nickel, F.; Pfuetzner, M.; Roehl, C.; Scheidenberger, C.; Schmidt, K.H.; Schwab, W.; Steinhaeuser, S.; Suemmerer, K.; Trinder, W.; Wollnik, H.

    1994-07-01

    Spatial isotopic separation of relativistic uranium projectile fragments has been achieved for the first time. The fragments were produced in peripheral nuclear collisions and spatially separated in-flight with the fragment separator FRS at GSI. A two-fold magnetic-rigidity analysis was applied exploiting the atomic energy loss in specially shaped matter placed in the dispersive central focal plane. Systematic investigations with relativistic projectiles ranging from oxygen up to uranium demonstrate that the FRS is a universal and powerful facility for the production and in-flight separation of monoisotopic, exotic secondary beams of all elements up to Z=92. This achievement has opened a new area in heavy-ion research and applications. (orig.)

  7. Experimental and Theoretical Understanding of Neutron Capture on Uranium Isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Ullmann, John Leonard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-09-21

    Neutron capture cross sections on uranium isotopes are important quantities needed to model nuclear explosion performance, nuclear reactor design, nuclear test diagnostics, and nuclear forensics. It has been difficult to calculate capture accurately, and factors of 2 or more be- tween calculation and measurements are not uncommon, although normalization to measurements of the average capture width and nuclear level density can improve the result. The calculations of capture for 233,235,237,239U are further complicated by the need to accurately include the fission channel.

  8. Concentrations of uranium and thorium isotopes in uranium millers' and miners' tissues

    International Nuclear Information System (INIS)

    Wrenn, M.E.; Singh, N.P.; Paschoa, A.S.; Lloyd, R.D.; Saccomanno, G.

    1985-09-01

    The alpha-emitting isotopes of uranium and thorium were determined in the lungs of 14 former uranium miners and in soft tissues and bones of three miners and two millers. These radionuclides were also determined in soft tissues and bones of seven normal controls. The average concentrations in pCi/kg wet weight in 17 former miners' lungs are as follows: 238 U, 75; 234 U, 80; 230 Th, 79. Concentrations of each nuclide ranged from 2 to 325 pCi/kg. The average ratio of 238 U/ 234 U was 0.92, ranging from 0.64 to 1.06. The mean ratio of 230 Th/ 234 U was 1.04, ranging from 0.33 to 3.54. The near equilibrium between 230 Th and /sup 238,234/U indicates that the rate of elimination of uranium and thorium from lungs is the same in former uranium miners. The concentrations of 234 U and 238 U were highest in lung; however, the concentration of 230 Th in bones was either higher than or comparable to its concentration in lung. The concentration ratios of 230 Th/ 234 U in bone of uranium miners and millers measured in our laboratory have been compared with results predicted by ICRP-30 metabolic models. These results indicate that the ICRP metabolic models for thorium and uranium were only marginally successful in predicting the ratio of 230 Th/ 234 U in bones, and that effective release rate of uranium from skeleton may be more rapid than predicted by the ICRP model. 9 figs., 21 tabs

  9. Isotopic analysis of uranium hexafluoride highly enriched in U-235

    International Nuclear Information System (INIS)

    Chaussy, L.; Boyer, R.

    1968-01-01

    Isotopic analysis of uranium in the form of the hexafluoride by mass-spectrometry gives gross results which are not very accurate. Using a linear interpolation method applied to two standards it is possible to correct for this inaccuracy as long as the isotopic concentrations are less than about 10 per cent in U-235. Above this level, the interpolations formula overestimates the results, especially if the enrichment of the analyzed samples is higher than 1.3 with respect to the standards. A formula is proposed for correcting the interpolation equation and for the extending its field of application to high values of the enrichment (≅2) and of the concentration. It is shown that by using this correction the results obtained have an accuracy which depends practically only on that of the standards, taking into account the dispersion in the measurements. (authors) [fr

  10. Preparation, characterization and certification of uranium isotope reference materials

    International Nuclear Information System (INIS)

    Oliveira Junior, Olivio Pereira de

    2006-01-01

    This work describes the preparation, characterization and certification of a set of uranium isotope reference materials ranging from 0.5 to 20.0 % of 235 U in mass. The most important concepts of metrology in chemical measurements were applied so that the certified quantities in these materials could be directly traceable to the International System of Units (SI). As a consequence of this approach, these materials can be used in the instruments calibration, estimation of measurement uncertainty, method validation, assessment of performance of analysts, quality control routines and interlaboratory comparison programmes. The most advanced methods and techniques in mass spectrometry, that is, gas source mass spectrometry (GSMS), thermal ionisation mass spectrometry (TIMS) and inductively coupled plasma mass spectrometry (ICPMS) were investigated to identify which are the dominant components in the uncertainty and to quantify its contribution to the final value of the measurement uncertainty of the isotopic ratio. The results obtained were then compared to verify which are the methods and techniques associated to the lowest measurement uncertainty values. The isotope amount ratio n( 235 U)/n( 238 U) was certified in the materials produced to expanded uncertainties ranging from 0.02 to 0.10 % and the ratios n( 234 U)/n( 238 U) and n( 236 U)/n( 238 U), to uncertainties ranging from 0.03 to 2.20 %. These values fully comply to the requirements of the isotopic characterization of nuclear fuel as well as the analysis of environmental samples for nuclear safeguards. (author)

  11. Radium 226 and uranium isotopes simultaneously determination in water samples using liquid scintillation counter

    International Nuclear Information System (INIS)

    Al-Masri, M.S.; Al-Akel, B.; Saaid, S.; Nashawati, A.

    2007-04-01

    In this work a method has been developed to determine simultaneously Radium 226 and Uranium isotopes in water samples by low back ground Liquid Scintillation Counter. Radium 226 was determined by its progeny Polonium 214 after one month of sample storage in order to achieve the equilibrium between Radium 226 and Polonium 214. Uranium isotopes were determined by subtracting Radium 226 activity from total alpha activity. The method detection limits were 0.049 Bq/L and 0.176 Bq/L for Radium 226 and Uranium isotopes respectively. The repeatability limits were ± 0.32 Bq/L and ± 0.9 Bq/L for Radium 226 and Uranium isotopes respectively. While relative errors were % 9.5 and %18.2 for Radium 226 and Uranium isotopes respectively. On the other hand, the report presented the results of different standard and natural samples.(author)

  12. Uranium determination in sea water using the isotopic dilution technique and HR-ICPMS

    International Nuclear Information System (INIS)

    Pereira, Marcio Henrique da Costa; Sarkis, Jorge Eduardo de Souza; Hortellani, Marcos Antonio; Nascimento, Marcos R.L.

    2009-01-01

    In this work, the uranium total and the isotopic composition in seawater were calculated using the isotopic dilution applied to the mass spectrometry. The used tracer was a 233 U solution . Near 99 % of the present salts in the matrix were separated by evaporation up to the saturation point. The uranium present in aqueous phase was separated from the matrix through the ion exchange chromatography using the strong Dowex 1 x 8 200-400 mesh anionic resin in chloridric medium 12 M. The analyses were performed in a high resolution mass spectrometer with plasma inductively coupled source. The method validation was done using the seawater standard CASS-4 (Near shore Seawater Reference Material for Trace metals) produced by the NRC C. The procedure allowed to obtain the fractions exempt of salts, having as consequence a greater stability in the analytical signal, and a rise in the instrumental revenue for a great number of samples. The uranium found in the samples was present in levels considered naturals and were obtained with a precision near 2 %

  13. Isotope ratio measurements of uranium by LA-HR-ICP-MS

    Energy Technology Data Exchange (ETDEWEB)

    Marin, Rafael C.; Sarkis, Jorge E.S., E-mail: rafael.marin@usp.b, E-mail: jesarkis@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    This work describes the utilization of Laser Ablation High Resolution Inductively Mass Spectrometry (LA-HR-ICP-MS) technique for the determination of uranium isotope composition in a UO{sub 2} pellet (CRM -125A) supplied and certified by the New Brunswick Laboratory (NBL). To carry out the adjustments of the parameters was used a glass standard NIST 610, supplied and certified by National Institute of Standards and Technology (NIST). The precision of the measurements were improved by adjusting the following parameters: RF power, laser beam diameter, defocusing of laser beam, laser energy, laser energy-density, auxiliary gas and sample gas. The measurements were performed on a continuous ablation with low energy density and defocusing, which demonstrated to be the optimum to reach the best signal stability. Isotope ratios, {sup 234}U/{sup 238}U, {sup 235}U/{sup 238}U and {sup 236}U/{sup 238}U were measured, reaching relative standard deviations (RSD) from 1.55% to 7.60%. The parameters which caused the greatest impact in order to improve the signal stability were RF power, defocusing and laser beam diameter. The results presented by the measurements revealed that the Laser ablation ICP-MS technique offers a rapid and accurate way to perform uranium isotope ratios without any sample preparation, since it allows carrying out the measurements straight on the sample, besides to preserve the testimony that is very important for safeguards and nuclear forensics purposes. (author)

  14. Uranium Isotope Compositions of Mid-Proterozoic Organic-rich Mudrocks: Evidence for an Episode of Increased Ocean Oxygenation at ca. 1.36 Ga and Evaluation of the Effect of Post-Depositional Hydrothermal Fluid Flow

    Science.gov (United States)

    Kendall, B.; Yang, S.; Lu, X.; Zhang, F.; Zheng, W.

    2016-12-01

    The U isotope system represents a relatively new paleoredox proxy that can help trace the evolution of global ocean redox chemistry, but has rarely been applied to the Mid-Proterozoic. We report U isotope data for marine black shales of the early Mesoproterozoic Velkerri Formation (Roper Group) and late Paleoproterozoic Wollogorang Formation (Tawallah Group) from the McArthur Basin, Northern Australia. An average authigenic δ238U of 0.13 ± 0.04‰ (1SD; relative to standard CRM145) was obtained for six euxinic shales from a 1 m interval that previously yielded a precise Re-Os depositional age of 1361 ± 21 Ma. After correcting for a U isotope fractionation of 0.60-0.85‰ between seawater and open-ocean euxinic sediments, we infer that coeval global seawater had a δ238U of -0.47‰ to -0.72‰, which is 0.1-0.3‰ lighter than modern seawater (-0.40 ± 0.03‰). A U isotope mass-balance model suggests that anoxic marine environments accounted for 25-50% of the global oceanic U sink at 1.36 Ga, which is 3-7 times greater than today. The model suggests that a significant proportion, potentially even a majority, of the seafloor was not covered by anoxic waters. Hence, we infer that a significant extent of the ocean floor was covered by O2-bearing waters at 1.36 Ga. The O2 concentrations of those waters were not necessarily high, and a large expanse of weakly to mildly oxygenated deep waters is consistent with the U isotope data. Uranium isotope data from a 1 m interval in the lower Velkerri Formation, deposited at 1417 ± 29 Ma based on Re-Os geochronology, yield a greater estimate for the extent of ocean anoxia. Hence, the upper Velkerri Formation may capture a transient episode of increased ocean oxygenation. Previous Re-Os isotope data from black shales of the ca. 1.73 Ga Paleoproterozoic Wollogorang Formation yielded an erroneously young date of 1359 ± 150 Ma because hydrothermal fluids percolated through the Tawallah Group rocks at ca. 1640 Ma. Higher δ238U

  15. Isotopic composition of past precipitation

    International Nuclear Information System (INIS)

    Edwards, T.W.D.

    1998-01-01

    The distribution of stable isotopes in precipitation provides critical quantitative information about the global water cycle. The first PAGES/IAEA ISOMAP workshop was held at the IAEA headquarters in Vienna, 24-26 August 1998, which gathered 32 participants. The presentation and discussions demonstrated that a high level of sophistication already exists in the development of transfer functions between measured parameters and precipitation, as a result of the extensive use of water isotope tracers in paleo-environmental investigations, but a major challenge facing both producers and users of paleo-isotope data is the effective management of data and meta-data, to permit ready retrieval of raw and inferred data for comparison and reinterpretation. This will be in important goal of future ISOMAP activities. The critical need for more paleo-data from low latitudes was clearly recognized

  16. Spectral determination of thallium isotope composition

    International Nuclear Information System (INIS)

    Polyanskij, V.A.; Turkin, Yu.I.; Yakimova, N.M.

    1986-01-01

    The photoelectric non-standard method for determination of the thallium isotope composition is developed. The analysis is carried out by measuring the brightness of the Hfs components in the line Tl Iλ535.04 nm. The relative standard deviation of the results of the isotope analysis of thallium as metal is 0.02 and of thallium salts - 0.02-0.05

  17. Determination of uranium isotopes in environmental samples by anion exchange in sulfuric and hydrochloric acid media

    International Nuclear Information System (INIS)

    Popov, L.

    2016-01-01

    Method for determination of uranium isotopes in various environmental samples is presented. The major advantages of the method are the low cost of the analysis, high radiochemical yields and good decontamination factors from the matrix elements, natural and man-made radionuclides. The separation and purification of uranium is attained by adsorption with strong base anion exchange resin in sulfuric and hydrochloric acid media. Uranium is electrodeposited on a stainless steel disk and measured by alpha spectrometry. The analytical method has been applied for the determination of concentrations of uranium isotopes in mineral, spring and tap waters from Bulgaria. The analytical quality was checked by analyzing reference materials. - Highlights: • The method allows cost-effective determination of U isotopes. • High amounts of environmental samples can be analyzed. • High chemical yields, energy resolution and decontamination factors were achieved. • Uranium isotope concentrations in mineral waters from Bulgaria are presented.

  18. Determination of trace quantities of uranium in rocks mass spectrometric isotope dilution technique

    International Nuclear Information System (INIS)

    Kakazu, Mauricio Hiromitu

    1980-01-01

    A detailed experimental investigation on the thermionic emission of uranium deposited on a single flat type rhenium filament has been carried out. The study was aimed at determining the influence of various forms of deposition on the emission sensitivity and thermal stability of U + , UO + and UO 2 + ions. Based on these investigations, a technique, involving an addition of a small quantity of colloidal suspension of graphite on top of the uranyl nitrate sample deposited, was chosen because of its higher, emission sensitivity for uranium metal ions. The experimental parameters of the technique were optimised and the technique was employed in the determination of trace quantities of uranium in rock samples using mass spectrometric isotope dilution method. For the mass spectrometric isotope dilution analysis National Bureau of Standards uranium isotopic standard NBS-U 970 was employed as a tracer, where as the mass discrimination effect in the uranium isotope analysis was corrected using the uranium isotopic standard NBS-U500. Uranium was determined in each of the seven granite samples from Wyoming, USA and two USGS standard rocks. The precision of the analysis was found to be ±1% . The uranium values obtained on the rock samples were compared with the analyses of other investigators. Influence of the sample splitting on the uranium analysis was discussed in the light of the analytical results obtained.(author)

  19. The theory and uses of natural uranium isotopic variations in hydrology

    International Nuclear Information System (INIS)

    Osmond, J.K.; Cowart, J.B.

    1976-01-01

    The dissolved concentration of uranium and the relative abundance of two uranium isotopes, 234 U and 238 U, vary over a wide range of values in natural waters. The concentration is controlled mainly by the redox potential of the environment and by CO 2 . The mechanism of isotope fractionation is thought to be entrainment of 234 U in the aqueous phase either by selective leaching of the solid phase or by direct recoil of the daughter nuclide. Ion exchange techniques and alpha-spectrometry permit the measurement of uranium at concentrations as low as pp 10 11 and the isotopic ratio to a few per cent. In oxidizing conditions the uranium isotopes behave in a chemically stable conservative manner such that separate groundwater sources may have identifiably different characteristics and mixing volume calculations may be made. Other potential use of these isotopes include radiometric dating, tracing of hydrologic systems, ore prospecting and earthquake prediction. (author)

  20. Linking specific heterotrophic bacterial populations to bioreduction of uranium and nitrate using stable isotope probing in contaminated subsurface sediments

    International Nuclear Information System (INIS)

    Akob, Denise M.; Kerkhof, Lee; Kusel, Kirsten; Watson, David B.; Palumbo, Anthony Vito; Kostka, Joel

    2011-01-01

    Shifts in terminal electron-accepting processes during biostimulation of uranium-contaminated sediments were linked to the composition of stimulated microbial populations using DNA-based stable isotope probing. Nitrate reduction preceded U(VI) and Fe(III) reduction in [ 13 C]ethanol-amended microcosms. The predominant, active denitrifying microbial groups were identified as members of the Betaproteobacteria, whereas Actinobacteria dominated under metal-reducing conditions.

  1. Uranium isotope separation by gaseous diffusion and plant safety

    International Nuclear Information System (INIS)

    Simeon, Claude; Dumas, Maurice.

    1980-07-01

    This report constitutes a safety guide for operators of uranium isotope separation plants, and includes both aspects of safety and protection. Taking into account the complexity of safety problems raised at design and during operation of plants which require specialized guides, this report mainly considers both the protection of man, the environment and goods, and the principles of occupational safety. It does not claim to be comprehensive, but intends to state the general principles, the particular points related to the characteristics of the basic materials and processes, and to set forth a number of typical solutions suitable for various human and technical environments. It is based on the French experience gained during the last fifteen years [fr

  2. Isotope analysis of uranium by optical spectroscopy; Analyse isotopique de I'uranium par spectroscopie optique

    Energy Technology Data Exchange (ETDEWEB)

    Gerstenkorn, S [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    Isotope analysis of uranium is made by means of hollow cathode lamp and Fabry-Perot photoelectric spectrometer. When using the line U I 5027 A, this method allows to determine isotopic concentrations in {sup 235}U down to 0,1 per cent. The relative precision is about 2 per cent for amounts of {sup 235}U over 1 per cent. For weaker amounts this line would allow relative measurements of better precision when using standard mixtures. (author) [French] L'analyse isotopique de l'uranium est effectuee a l'aide d'une lampe a cathode creuse et du spectrometre Fabry-Perot photo-electrique. On utilise la raie U I 5027 A. Cette methode permet de doser des melanges isotopiques dont la teneur en {sup 235}U, peut descendre jusqu'a 0,1 pour cent. La precision relative est de l'ordre de 2 pour cent pour des teneurs en {sup 235}U superieures a 1 pour cent. Pour des teneurs plus faibles cette raie {lambda} = 5027 A permettrait des mesures relatives de meilleure precision, en utilisant des melanges prealablement doses. (auteur)

  3. Innovative lasers for uranium isotope separation. [Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Brake, M.L.; Gilgenbach, R.M.

    1991-06-01

    Copper vapor lasers have important applications to uranium atomic vapor laser isotope separation (AVLIS). The authors have spent the first two years of their project investigating two innovative methods of exciting/pumping copper vapor lasers which have the potential to improve the efficiency and scaling of large laser systems used in uranium isotope separation. Experimental research has focused on the laser discharge kinetics of (1) microwave, and (2) electron beam excitation/pumping of large-volume copper vapor lasers. During the first year, the experiments have been designed and constructed and initial data has been taken. During the second year these experiments have been diagnosed. Highlights of some of the second year results as well as plans for the future include the following: Microwave resonant cavity produced copper vapor plasmas at 2.45 GHz, have been investigated. A CW (0--500 W) signal heats and vaporizes the copper chloride to provide the atomic copper vapor. A pulsed (5 kW, 0.5--5kHz) signal is added to the incoming CW signal via a hybrid mixer to excite the copper states to the laser levels. An enhancement of the visible radiation has been observed during the pulsed pardon of the signal. Electrical probe measurements have been implemented on the system to verify the results of the electromagnetic model formulated last year. Laser gain measurements have been initiated with the use of a commercial copper vapor laser. Measurements of the spatial profile of the emission are also currently being made. The authors plan to increase the amount of pulsed microwave power to the system by implementing a high power magnetron. A laser cavity will be designed and added to this system.

  4. Calcium Isotopic Composition of Bulk Silicate Earth

    Science.gov (United States)

    Kang, J.; Ionov, D. A.; Liu, F.; Zhang, C.; Zhang, Z.; Huang, F.

    2016-12-01

    Ca isotopes are used to study the accretion history of the Earth and terrestrial planets, but, Ca isotopic composition of the Bulk Silicate Earth (BSE) remains poorly constrained [1]. To better understand the Ca isotopic composition of BSE, we analyzed 22 well studied peridotite xenoliths from Tariat (Mongolia), Vitim (southern Siberia) and Udachnaya (Siberian Craton). These samples include both fertile and highly depleted garnet and spinel peridotites that show no or only minor post-melting metasomatism or alteration. Ca isotope measurements were done on a Triton-TIMS using double spike method at the Guangzhou Institute of Geochemistry, CAS. The data are reported as δ44/40Ca (relative to NIST SRM 915a). Results for geostandards are consistent with those from other laboratories. 2 standard deviations of SRM 915a analyses are 0.13‰ (n=48). δ44/40Ca of both and fertile and refractory peridotites range from 0.79 to 1.07‰ producing an average of 0.93±0.12‰ (2SD). This value defines the Ca isotopic composition of the BSE, which is consistent with the average δ44/40Ca of oceanic basalts ( 0.90‰)[2,3]. [1] Huang et al (2010) EPSL 292; [2] Valdes et al (2014) EPSL 394; [3]DePaolo (2004) RMG 55.

  5. Analysis of high burnup pressurized water reactor fuel using uranium, plutonium, neodymium, and cesium isotope correlations with burnup

    International Nuclear Information System (INIS)

    Kim, Jung Suk; Jeon, Young Shin; Park, Soon Dal; Ha, Yeong Keong; Song, Kyu Seok

    2015-01-01

    The correlation of the isotopic composition of uranium, plutonium, neodymium, and cesium with the burnup for high burnup pressurized water reactor fuels irradiated in nuclear power reactors has been experimentally investigated. The total burnup was determined by Nd-148 and the fractional 235 U burnup was determined by U and Pu mass spectrometric methods. The isotopic compositions of U, Pu, Nd, and Cs after their separation from the irradiated fuel samples were measured using thermal ionization mass spectrometry. The contents of these elements in the irradiated fuel were determined through an isotope dilution mass spectrometric method using 233 U, 242 Pu, 150 Nd, and 133 Cs as spikes. The activity ratios of Cs isotopes in the fuel samples were determined using gamma-ray spectrometry. The content of each element and its isotopic compositions in the irradiated fuel were expressed by their correlation with the total and fractional burnup, burnup parameters, and the isotopic compositions of different elements. The results obtained from the experimental methods were compared with those calculated using the ORIGEN-S code

  6. Calcium isotopic composition of mantle peridotites

    Science.gov (United States)

    Huang, F.; Kang, J.; Zhang, Z.

    2015-12-01

    Ca isotopes are useful to decipher mantle evolution and the genetic relationship between the Earth and chondrites. It has been observed that Ca isotopes can be fractionated at high temperature [1-2]. However, Ca isotopic composition of the mantle peridotites and fractionation mechanism are still poorly constrained. Here, we report Ca isotope composition of 12 co-existing pyroxene pairs in 10 lherzolites, 1 harzburgite, and 1 wehrlite xenoliths collected from Hainan Island (South Eastern China). Ca isotope data were measured on a Triton-TIMS using the double spike method at the Guangzhou Institute of Geochemistry, CAS. The long-term external error is 0.12‰ (2SD) based on repeated analyses of NIST SRM 915a and geostandards. δ44Ca of clinopyroxenes except that from the wehrlite ranges from 0.85‰ to 1.14‰, while opx yields a wide range from 0.98‰ up to 2.16‰. Co-existing pyroxene pairs show large Δ44Caopx-cpx (defined as δ44Caopx-δ44Cacpx) ranging from 0 to 1.23‰, reflecting equilibrium fractionation controlled by variable Ca contents in the opx. Notably, clinopyroxene of wehrlite shows extremely high δ44Ca (3.22‰). δ44Ca of the bulk lherzolites and harzburgites range from 0.86‰ to 1.14‰. This can be explained by extracting melts with slightly light Ca isotopic compositions. Finally, the high δ44Ca of the wehrlite (3.22‰) may reflect metasomatism by melt which has preferentially lost light Ca isotopes due to chemical diffusion during upwelling through the melt channel. [1] Amini et al (2009) GGR 33; [2] Huang et al (2010) EPSL 292.

  7. The separation nozzle process for uranium isotope enrichment

    International Nuclear Information System (INIS)

    Becker, E.W.

    1977-01-01

    In the separation nozzle process, uranium isotope separation is brought about by the mass dependence of the centrifugal forces in a curved flow of a UF 6 /H 2 -mixture. Due to the large excess in hydrogen the high ration of UF 6 flow velocity to thermal velocity required for an effective isotope separation is obtained at relatively low expansion ratios and, accordingly, with relatively low gas-dynamic losses. As the optimum Reynolds number of the curved jet is comparatively low and a high absolute pressure is essential for economic reasons, the characteristic dimensions of the nozzle systems are made as small as possible. For commercial application in the near future systems involving mechanical jet deflection were developed. However, promising results were also obtained with separation nozzle systems generating a streamline curvature by the interaction of opposed jets. Most of the development work has been done at the Nuclear Research Center of Karlsruhe. Since 1970 the German company STEAG has been involved in the commercial implementation of the process. Two industrial-scale separative stages were tested successfully. This work constitutes the basis of planning of a separation nozzle demonstration plant to be built in Brazil

  8. Evolution of the hafnium isotopic composition in the RBMK reactor

    International Nuclear Information System (INIS)

    Jurkevicius, A.; Remeikis, V.

    2002-01-01

    The isotopic composition of hafnium in the radial neutron flux sensor of the RBMK-1500 reactor, the rates of the neutron absorption on Hf isotopes and the neutron spectrum in the sensor were numerically modeled. The sequence SAS2 (Shielding Analysis Sequence) program from the package SCALE 4.4A and the HELIOS code system were used for calculations. It has been obtained that the overall neutron absorption rates in hafnium for the sensors located in the 2.4 % and 2.6 % enrichment uranium-erbium nuclear fuel assemblies are by 16 % and 19 % lower than in the 2.0 % enrichment uranium nuclear fuel assemblies. The overall neutron absorption rate in hafnium decreases 2.70-2.75 times due to the sensor burnup to 5800 MW d. The sensitivity of the Hf sensors to the thermal neutron flux increases twice due to the nuclear fuel assembly burnup to 3000 MW d. The corrective factors ξ d (I) at the different integral current I of the sensors and ξ td (E) at the different burnup E of the nuclear fuel assemblies were calculated. The obtained dependence ξ d (I) calculated numerically was compared to the experimental one determined by comparing signals of the fresh sensor and the sensor with the integral current I and by processing repeated calibration results of Hf sensors in RBMK-1500 reactors. The relative relationship coefficients K T (T FA ) were found for all RBMK-1500 nuclear fuel types. (author)

  9. Hydrologic and environmental controls on uranium-series and strontium isotope ratios in a natural weathering environment

    Science.gov (United States)

    White, A. M.; Ma, L.; Moravec, B. G.; McIntosh, J. C.; Chorover, J.

    2017-12-01

    In a remote, volcanic headwater catchment of the Jemez River Basin Critical Zone Observatory (JRB-CZO) in NM, stable water isotopes and solute chemistry have shown that snowmelt infiltrates and is stored before later discharging into springs and streams via subsurface flowpaths that vary seasonally. Therefore, water-rock reactions are also expected to change with season as hydrologic flowpaths transport water, gases and solutes through different biogeochemical conditions, rock types and fracture networks. Uranium-series isotopes have been shown to be a novel tracer of water-rock reactions and source water contributions while strontium isotopes are frequently used as indicators of chemical weathering and bedrock geology. This study combines both isotopes to understand how U and Sr isotope signatures evolve through the Critical Zone (CZ). More specifically, this work examines the relationship between seasonality, water transit time (WTT), and U-series and Sr isotopes in stream and spring waters from three catchments within the JRB-CZO, as well as lithology, rock type and CZ structure in solid phase cores. Samples from ten springs with known WTTs were analyzed for U and Sr isotopes to determine the effect of WTT on the isotopic composition of natural waters. Results suggest that WTT alone cannot explain the variability of U and Sr isotopes in JRB-CZO springs. Stream samples were also collected across two water years to establish how seasonality controls surface water isotopic composition. U and Sr isotope values vary with season, consistent with a previous study from the La Jara catchment; however, this study revealed that these changes do not show a systematic pattern among the three catchments suggesting that differences in the mineralogy and structure of the deep CZ in individual catchments, and partitioning of water along deep vs surficial and fracture vs matrix flow paths, likely also control isotopic variability. The distribution of U-series and Sr isotopes in

  10. A 2000-2010 years outlook of isotopic uranium enrichment

    International Nuclear Information System (INIS)

    Vasaru, G.

    1998-01-01

    The increase of the installed power in nuclear plants implies the following steps to be achieved: - developing a parallel industry for the nuclear fuel cycle able to ensure a rhythmic supply of natural uranium, possibly an isotopic enrichment of 235 U of around 1.2 - 3.2%, depending on the reactor system; - manufacturing the fuel elements and the operation of cycle back-end, which may, possibly, include a temporary storage of the irradiated fuel; - reprocessing the spend fuel; - radioactive waste processing in view of final disposal, as well as the recovery of un-spent uranium and of plutonium formed. The heavy water reactors of CANDU-PHW does not imply any isotopic enrichment but provides a lower burnup of only 7,000 MW day/tone. An enrichment to 1.2% in 235 U for this type of reactors could increase the burnup up to 20,000 MW day/tone. An advanced method of enriching 235 U is based on the Atomic Vapor Laser Isotop Separation (AVLIS). This procedure called AVLIS has several advantages which are pointed out in this paper, among which: a very high selectivity; high separation factors; a low energy consumption due to the fact that in the conditions of a selective photo ionization, the energy necessary to the process is only 6.2 eV for the separated 235 U atom vs 0.3 MeV in case of inertial separators or 3 MeV in case of gaseous diffusion procedure. With the current laser yields an energy consumption of 100 kWh/SWU is estimated for AVLIS procedures as compared with 2,400 kWh/SWU in case of gaseous diffusion; an almost entire extraction of 235 U, what ensures a more efficient utilisation of nuclear fuel. Due to its modular character and to potential improvement in the equipment which could be achieved, this procedure will ensure a reduction in the investment costs in the construction stage what will make AVLIS a substitute of the classical separation procedures

  11. petrography, compositional characteristics and stable isotope ...

    African Journals Online (AJOL)

    PROF EKWUEME

    Subsurface samples of the predominantly carbonate Ewekoro Formation, obtained from Ibese core hole within the Dahomey basin were used in this study. Investigations entail petrographic, elemental composition as well as stable isotopes (carbon and oxygen) geochemistry in order to deduce the different microfacies and ...

  12. Separation of compounds differing in isotopic composition

    International Nuclear Information System (INIS)

    Sievers, R.E.; Brooks, J.J.

    1976-01-01

    Compounds differing in isotopic composition are separated by introducing a mixture of the compounds into a chromatographic column containing a lanthanide chelate as a stationary phase and eluting from the column a fraction which is at least enriched with one of the compounds of the mixture. 17 claims, no drawings

  13. Separation of compounds differing in isotopic composition

    International Nuclear Information System (INIS)

    Sievers, R.E.; Brooks, J.J.

    1975-01-01

    Compounds differing in isotopic composition are separated by introducing a mixture of the compounds into a chromatographic column containing a lanthanide chelate as a stationary phase and eluting from the column a fraction that is at least enriched with one of the compounds of the mixture. (U.S.)

  14. Valence-associated uranium isotope fractionation of uranium enriched phosphate in a shallow aquifer, Lee County, Florida

    International Nuclear Information System (INIS)

    Weinberg, J.M.; Levine, B.R.; Cowart, J.B.

    1993-01-01

    The source of anomalously high concentrations of uranium, characterized by U-234/U-238 activity ratios significantly less than unity, in shallow groundwaters of Lee County, Florida, was investigated. Uranium in cores samples was separated into U(IV) and U(VI) oxidation state fractions, and uranium analyses were conducted by alpha spectrometry. Uranium mobility was also studied in selected leaching experiments. Results indicate that mobilization of unusually soluble uranium, present in uranium enriched phosphate of the Pliocene age Tamiami Formation at determined concentrations of up to 729 ppm, is the source for high uranium concentrations in groundwater. In leaching experiments, approximately one-third of the uranium present in the uranium enriched phosphate was mobilized into the aqueous phase. Results of previous investigations suggest that U-234, produced in rock by U-238 decay, is selectively oxidized to U(VI). The uranium enriched phosphate studied in this investigation is characterized by selective reduction of U-234, with a pattern of increasing isotopic fractionation with core depth. As a consequence, U-234/U-238 activity ratios greater than 1.0 in the U(IV) fraction, and less than 1.0 in the U(VI) fraction have developed in the rock phase. In leaching experiments, the U(VI) fraction from the rock was preferentially mobilized into the aqueous phase, suggesting that U-234/U-238 activity ratios of leaching groundwaters are strongly influenced by the isotopic characteristics of the U(VI) fraction of rock. It is suggested that preferential leaching of U(VI), present in selectivity reduced uranium enriched phosphate, is the source for low activity ratio groundwaters in Lee County

  15. Determination of natural alpha-emitting isotopes of uranium and thorium in environmental and geological samples

    International Nuclear Information System (INIS)

    Crespo, M.T.

    1996-01-01

    It is described the complete radiochemical procedure used for the determination of uranium and thorium isotopes in environmental and geological samples by alpha spectrometry. Source preparation methods, alpha-counting and spectral analysis are also included

  16. Evaluation of parameters associated with monitoring in vivo of uranium isotopes in the lungs

    International Nuclear Information System (INIS)

    Juppa, Silvia P.; Lucena, Eder A.; Dantas, Bernardo M.; Dantas, Ana Leticia A.

    2013-01-01

    The objective of this study is to evaluate the parameters associated with the technique of monitoring individuals exposed to uranium isotopes, aiming to optimize the technique and reduced uncertainties associated

  17. Isotopic compositions of boron in sediments and their implications

    Digital Repository Service at National Institute of Oceanography (India)

    Shirodkar, P.V.; Yingkai, X.

    The abundance and isotopic compositions of boron in sediments from the salt lakes of Qaidam Basin, China have been determined by thermal ionization mass spectrometry of cesium borate. The results show large variations in the isotopic compositions...

  18. Uranium Isotopes as a Tracer of Groundwater Evolution in the Complexe Terminal Aquifer of Southern Tunisia

    Energy Technology Data Exchange (ETDEWEB)

    Hadj Ammar, F. [Laboratory of Radio-Analysis and Environment, National School of Engineering of Sfax, Sfax (Tunisia); Centre Europeen de Recherche et d' Enseignement de Geosciences de l' Environnement, Aix en Provence (France); Deschamps, P.; Hamelin, B. [Centre Europeen de Recherche et d' Enseignement de Geosciences de l' Environnement, Aix en Provence (France); Chkir, N.; Zouari, K. [Laboratory of Radio-Analysis and Environment, National School of Engineering of Sfax, Sfax (Tunisia)

    2013-07-15

    The Complexe Terminal (CT) aquifer system is the main water supply for remote areas of southern Tunisia. Its exploitation has resulted in significant draw-down of the water table. The CT aquifer is a multilayered aquifer lodged in Miocene sand deposits, Senonian limestones and Turonian carbonates. Little is known about the relationships and exchanges between the different layers. Here, uranium isotopic measurements carried out in groundwater samples from the CT aquifer are presented in order to constrain models for mixing of water masses, water-rock interaction and groundwater flow. Analyses were performed using a VG54 (TIMS) at the CEREGE. Results indicate a range in {sup 238}U concentration and {sup 234}U/{sup 238}U activity ratios of 1.5 to 8 ppb and 1.1 to 3.2 respectively. Together with major and trace analyses, uranium isotopic compositions provide important insights into the factors controlling the chemical evolution of groundwater and shows very distinct patterns between carbonate and sandstone layers. (author)

  19. The use of environmental uranium isotopes in the study of the hydrology of the Burdekin Delta

    International Nuclear Information System (INIS)

    Campbell, B.L.

    1977-03-01

    Analyses of bore water samples from the Burdekin Delta, Queensland, show considerable variation in both the uranium concentration and the 234 U/ 238 U activity ratio. In many cases, the uranium concentration was closely correlated with the bicarbonate concentration, but not for waters with a very low uranium concentration. Mechanisms by which uranium can be removed from solution are discussed. They provide a basis for explaining the low uranium concentrations and, in some areas, the apparent lack of response of the aquifer to the input of uranium by recharge. The 234 U/ 238 U activity ratio is interpreted as a reflection of the extent of local interaction of infiltrating ground water with soil constituents. Measurement of the isotope activity ratio has confirmed the location of an area with significant recharge from the river into the aquifer system. The isotopic and supporting chemical data illustrate the complexity of the aquifer system. (author)

  20. Studying of isotope structure of uranium by alpha-spectrometric method

    International Nuclear Information System (INIS)

    Sattarov, G.S.; Muzafarov, A.M.; Petukhov, O.F.; Petrenko, V.Z.

    2004-01-01

    Full text: The knowledge of isotope structure of uranium in waters, in minerals and in finished goods gives the helpful information on the radiation and nuclear-physical processes occurring in natural environments. Besides, customers put a question before uranium producing enterprises on the control of limiting concentration of an isotope 234 U in finished goods (uranium protoxide-oxide). For these reasons studying and development of techniques of definition of isotope structure of uranium is an actual task. In this connection for researches alpha - spectrometers 'PROGRESS-ALPHA' produced by R and D 'DOZE' Russia and firms 'Canberra' the USA were used. The isotope structure of uranium ( 234 U, 235 U, 238 U) was determined on a known ratio 234 U/ 238 U, which is equal to 53,41micrograms/gram. Identification of isotopes carried out by 4198 keV ( 235 U), 4395 keV ( 234 U) and 4773 keV ( 238 U). The technique of radiochemical preparation of samples to the analysis included: clearing of organic chemistry and preventing natural isotopes; drawing by a method electrolytic sedimentation on a metal substrate (d=24mm) an active stain, the area 4,5 cm 2 , with isotropy distribution of ions 234 U, 235 U, 238 U. As standards, the international and All-Russian standards with known contents 234 U were used. The isotope structure of uranium in uranium protoxide-oxide, chemical concentrates, technological solutions is determined. Infringements of isotope balance 234 U/ 238 U on separate sites of fulfilled uranium deposits and in technological products are found out

  1. Determination of natural uranium, thorium and radium isotopes in water and soil samples by alpha spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Le Cong; Tao, Chau Van; Thong, Luong Van; Linh, Duong Mong [University of Science Ho Chi Minh City (Viet Nam). Faculty of Physics and Engineering Physics; Dong, Nguyen Van [University of Science Ho Chi Minh City (Viet Nam). Faculty of Chemistry

    2011-08-15

    In this study, a simple procedure for the determination of natural uranium, thorium and radium isotopes in water and soil samples by alpha spectroscopy is described. This procedure allows a sequential extraction polonium, uranium, thorium and radium radionuclides from the same sample in two to three days. It was tested and validated with the analysis of certified reference materials from the IAEA. (orig.)

  2. Information derived from French studies and achievements in the field of uranium isotope separation

    International Nuclear Information System (INIS)

    Frejacques, C; Galley, R.

    1964-01-01

    The work carried out in the field of uranium isotope separation, by gaseous diffusion and by ultracentrifugation, is reviewed. An economic estimate of the various parameters involved in the cost is given, and it is shown that only very large gaseous diffusion plants, corresponding to a programme of enriched uranium reactors of at least 4000 MWe to be installed yearly, can give an economically acceptable enriched uranium production. (authors) [fr

  3. Evaluation of precision in measurements of uranium isotope ratio by thermionic mass spectrometry

    International Nuclear Information System (INIS)

    Moraes, N.M.P. de; Rodrigues, C.

    1977-01-01

    The parameters which affect the precision and accuracy of uranium isotopic ratios measurements by thermionic mass spectrometry are discussed. A statistical designed program for the analysis of the internal and external variances are presented. It was done an application of this statistical methods, in order to get mass discrimination factor, and its standard mean deviation, by using some results already published for 235 U/ 238 U ratio in NBS uranium samples, and natural uranium [pt

  4. Isotope Analysis of Uranium by Interferometry; Analyse isotopique de l'uranium par interferometrie

    Energy Technology Data Exchange (ETDEWEB)

    Leicknam, J P [Commissariat a l' Energie Atomique. Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

    1962-07-01

    Among the optical methods which may be used to make isotopic measurements of {sup 235}U interferometry gives promising results. An apparatus is described which has a photomultiplier as receiver; the source must therefore have characteristics (intensity, stability, fineness of emitted rays) which have led to the use of electrode-less discharge tubes whose methods of production and excitation are given. An example of calibration is given. (author) [French] Parmi les methodes optiques permettant le dosage isotopique de l'uranium 235, l'interferometrie est une technique qui donne des resultats prometteurs. On decrit ici un appareil ayant un photo-multiplicateur comme recepteur; la source doit donc avoir des caracteristiques (intensite, stabilite, finesse des raies emises) qui ont conduit a utiliser des tubes a decharge sans electrode dont on indique la fabrication et le mode d'excitation. Un exemple d'etalonnage est enfin donne. (auteur)

  5. The use of uranium isotopes and the U/Th ratio to evaluate the fingerprint of plants following uranium releases from fuel cycle settlements

    International Nuclear Information System (INIS)

    Pourcelot, L.; Boulet, B.; Cariou, N.

    2015-01-01

    This paper uses data from the environmental monitoring of fuel cycle settlements. It aims to evaluate uranium released into the terrestrial environment. Measurement of uranium isotopes in terrestrial plants allows illustrating the consequences of chronic and incidental releases of depleted uranium into the atmosphere. However, such an analytical approach reaches its limits when natural uranium is released. Indeed, distinguishing natural uranium from releases and uranium from the radiological background is difficult. For this reason, we propose normalizing uranium activity measured in plants taken in the surroundings of nuclear sites with respect to 232 Th, considering that the source of this latter is the background. (authors)

  6. Unconventional isotope systems applied to enhancing the petrogenesis of uranium deposits

    International Nuclear Information System (INIS)

    Voignot, A.; Chipley, D.; Kyser, K.; Uvarova, Y.

    2014-01-01

    Among the new techniques applied to the petrogenesis and evolution of uranium deposits from their formation to later alteration is isotope tracing. The isotope systems being used include Li, C, N, Fe, Mo, Tl, Pb and U, all of which reflect different, but overlapping, processes. Although Pb isotopes have been used to understand the temporal evolution and migration of radiogenic Pb from the deposits, Li, C, N, Mo, Tl and U isotope systems are new ways to analyze deposits and barren areas and to reveal their precise redox mechanisms. Geochemical technologies for exploration include "2"3"8U/"2"3"5U ratios of uranium minerals, which vary as a function of the type of uranium deposit and the efficiency of the redox processes. Lithium isotope ratios in muscovite and chlorite associated with mineralizing events are distinct from background ratios, with the lowest values reflecting the beginning of hydrothermal alteration systems and the highest values indicative of the terminal flow of hydrothermal fluids. Carbon and N reflect the influence of biospheric processes on the deposits and dispersion of elements that can be used for exploration. Iron, Mo and Tl are common elements in many uranium deposits and are among the most redox active elements. Their isotopes separate among phases having different oxidation potentials. They reflect the efficiency of the redox systems associated with fixing the uranium and the subsequent processes involved in mobilizing elements from the deposits. Isotopes add benefits to refining genetic models for uranium deposits, thereby enhancing our exploration models as well. An additional goal of applying isotope geochemistry to uranium deposits is to be able to use them to reflect a definitive process that occurs in the deposit and not in barren systems, and then to relate these to something that is easier to measure, namely elemental concentrations. (author)

  7. Isotopic investigation of the colloidal mobility of depleted uranium in a podsolic soil

    International Nuclear Information System (INIS)

    Harguindeguy, S.; Crancon, P.; Pointurier, F.; Potin-Gautier, M.; Lespes, G.

    2014-01-01

    The mobility and colloidal migration of uranium were investigated in a soil where limited amounts of anthropogenic uranium (depleted in the "2"3"5U isotope) were deposited, adding to the naturally occurring uranium. The colloidal fraction was assumed to correspond to the operational fraction between 10 kDa and 1.2 μm after (ultra)filtration. Experimental leaching tests indicate that approximately 8-15% of uranium is desorbed from the soil. Significant enrichment of the leachate in the depleted uranium (DU) content indicates that uranium from recent anthropogenic DU deposit is weakly bound to soil aggregates and more mobile than geologically occurring natural uranium (NU). Moreover, 80% of uranium in leachates was located in the colloidal fractions. Nevertheless, the percentage of DU in the colloidal and dissolved fractions suggests that NU is mainly associated with the non-mobile coarser fractions of the soil. A field investigation revealed that the calculated percentages of DU in soil and groundwater samples result in the enhanced mobility of uranium downstream from the deposit area. Colloidal uranium represents between 10% and 32% of uranium in surface water and between 68% and 90% of uranium in groundwater where physicochemical parameters are similar to those of the leachates. Finally, as observed in batch leaching tests, the colloidal fractions of groundwater contain slightly less DU than the dissolved fraction, indicating that DU is primarily associated with macromolecules in dissolved fraction. (authors)

  8. On the accuracy of gamma spectrometric isotope ratio measurements of uranium

    Energy Technology Data Exchange (ETDEWEB)

    Ramebäck, H., E-mail: henrik.ramebeck@foi.se [Swedish Defence Research Agency, FOI, CBRN Defence and Security, SE-901 82 Umeå (Sweden); Chalmers University of Technology, Department of Chemistry and Chemical Engineering, SE-412 96 Göteborg (Sweden); Lagerkvist, P.; Holmgren, S.; Jonsson, S.; Sandström, B.; Tovedal, A. [Swedish Defence Research Agency, FOI, CBRN Defence and Security, SE-901 82 Umeå (Sweden); Vesterlund, A. [Swedish Defence Research Agency, FOI, CBRN Defence and Security, SE-901 82 Umeå (Sweden); Chalmers University of Technology, Department of Chemistry and Chemical Engineering, SE-412 96 Göteborg (Sweden); Vidmar, T. [SCK-CEN, Belgian Nuclear Research Centre, Boeretang 200, 2400 Mol (Belgium); Kastlander, J. [Swedish Defence Research Agency, FOI, Defence and Security, Systems and Technology, SE-164 90 Stockholm (Sweden)

    2016-04-11

    The isotopic composition of uranium was measured using high resolution gamma spectrometry. Two acid solutions and two samples in the form of UO{sub 2} pellets were measured. The measurements were done in close geometries, i.e. directly on the endcap of the high purity germanium detector (HPGe). Applying no corrections for count losses due to true coincidence summing (TCS) resulted in up to about 40% deviation in the abundance of {sup 235}U from the results obtained with mass spectrometry. However, after correction for TCS, excellent agreement was achieved between the results obtained using two different measurement methods, or a certified value. Moreover, after corrections, the fitted relative response curves correlated excellently with simulated responses, for the different geometries, of the HPGe detector.

  9. MUICYCL and MUIFAP: models tracking minor uranium isotopes in the nuclear fuel cycle

    International Nuclear Information System (INIS)

    Blum, S.R.; McLaren, R.A.

    1979-10-01

    Two computer programs have been written to provide information on the buildup of minor uranium isotopes in the nuclear fuel cycle. The Minor Uranium Isotope Cycle Program, MUICYCL, tracks fuel through a multiyear campaign cycle of enrichment, reactor burnup, reprocessing, enrichment, etc. MUICYCL facilities include preproduction stockpiles, U 235 escalation, and calculation of losses. The Minor Uranium Isotope Flowsheet Analyzer Program, MUIFAP, analyzes one minor isotope in one year of an enrichment operation. The formulation of the enrichment cascade, reactors, and reprocessing facility is presented. Input and output descriptions and sample cases are presented. The programs themselves are documented by short descriptions of each routine, flowcharts, definitions of common blocks and variables, and internal documentation. The programs are written in FORTRAN for use in batch mode

  10. Uniform deposition of uranium hexafluoride (UF6): Standardized mass deposits and controlled isotopic ratios using a thermal fluorination method.

    Science.gov (United States)

    McNamara, Bruce K; O'Hara, Matthew J; Casella, Andrew M; Carter, Jennifer C; Addleman, R Shane; MacFarlan, Paul J

    2016-07-01

    We report a convenient method for the generation of volatile uranium hexafluoride (UF6) from solid uranium oxides and other U compounds, followed by uniform deposition of low levels of UF6 onto sampling coupons. Under laminar flow conditions, UF6 is shown to interact with surfaces within a fixed reactor geometry to a highly predictable degree. We demonstrate the preparation of U deposits that range between approximately 0.01 and 500ngcm(-2). The data suggest the method can be extended to creating depositions at the sub-picogramcm(-2) level. The isotopic composition of the deposits can be customized by selection of the U source materials and we demonstrate a layering technique whereby two U solids, each with a different isotopic composition, are employed to form successive layers of UF6 on a surface. The result is an ultra-thin deposit that bears an isotopic signature that is a composite of the two U sources. The reported deposition method has direct application to the development of unique analytical standards for nuclear safeguards and forensics. Further, the method allows access to very low atomic or molecular coverages of surfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Application of isotope techniques to groundwater pollution research for Xiangshan uranium ore field, China

    International Nuclear Information System (INIS)

    Liu Fulin; Liu Peilun; Zhu Chuande; Wu Xiaowei; Zeng Yinsheng

    1998-01-01

    The investigation of groundwater pollution due to uranium deposits focused on the most important uranium metallogenic area-Zhoujiashan district of Xiangshan uranium ore field, China. Groundwater collected from five completed exploration boreholes in the area is regarded as the pollution source and is traced and analysed by using isotope as well as radio-hydrochemical techniques. In addition, the pollution situation of a small uranium ore pile for heap-leaching and a big uranium ore open pit are monitored by the same techniques. It has been experimentally proven that the uranium concentration and the uranium isotope ratio 234 U/ 238 U in natural waters are two sensitive indicators of radioactive pollution in natural waters. It was concluded that under present conditions, exploration of uranium deposits may not cause serious groundwater pollution of radioactive elements (U, Ra, Rn and Th), however, it is difficult to avoid the serious surface water pollution coming from the exploitation of uranium ore by a big open pit. (author)

  12. Application of the mass spectrometry-isotope dilution technique for the determination of uranium contents in rocks

    International Nuclear Information System (INIS)

    Kakazu, M.H.; Iyer, S.S.

    1980-01-01

    Application of the spectrometric isotope dilution technique for the accurate determination of parts per million range of uranium in rock samples is described. The various aspects of the method like sample dissolution, ion exchange separation, mass spectrometric procedures are discussed. A single filament ionization source was employed for the isotope analysis. A carbon reduction method was used to reduce uranium oxide ions to uranium metal ions. The tracer solution for isotope dilution was prepared from National Bureau of Standards uranium isotopic Standard NBS U-970. Uranium contents are meassured for nine rock samples and the values obtained are compared with the uranium values measured by others workers. Errors caused in the uranium determination due to sample splitting problems as well as the incomplete acid digestion of the samples are discussed. (Author) [pt

  13. THE NITROGEN ISOTOPIC COMPOSITION OF METEORITIC HCN

    Energy Technology Data Exchange (ETDEWEB)

    Pizzarello, Sandra, E-mail: pizzar@asu.edu [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85018-1604 (United States)

    2014-12-01

    HCN is ubiquitous in extraterrestrial environments and is central to current theories on the origin of early solar system organic compounds such as amino acids. These compounds, observed in carbonaceous meteorites, were likely important in the origin and/or evolution of early life. As part of our attempts to understand the origin(s) of meteoritic CN{sup –}, we have analyzed the {sup 15}N/{sup 14}N isotopic composition of HCN gas released from water extracts of the Murchison meteorite and found its value to be near those of the terrestrial atmosphere. The findings, when evaluated viz-a-viz molecular abundances and isotopic data of meteoritic organic compounds, suggest that HCN formation could have occurred during the protracted water alteration processes known to have affected the mineralogy of many asteroidal bodies during their solar residence. This was an active synthetic stage, which likely involved simple gasses, organic molecules, their presolar precursors, as well as mineral catalysts and would have lead to the formation of molecules of differing isotopic composition, including some with solar values.

  14. OXYGEN ISOTOPIC COMPOSITIONS OF SOLAR CORUNDUM GRAINS

    International Nuclear Information System (INIS)

    Makide, Kentaro; Nagashima, Kazuhide; Huss, Gary R.; Krot, Alexander N.

    2009-01-01

    Oxygen is one of the major rock-forming elements in the solar system and the third most abundant element of the Sun. Oxygen isotopic composition of the Sun, however, is not known due to a poor resolution of astronomical spectroscopic measurements. Several Δ 17 O values have been proposed for the composition of the Sun based on (1) the oxygen isotopic measurements of the solar wind implanted into metallic particles in lunar soil ( 2 O 3 ) is thermodynamically the first condensate from a cooling gas of solar composition. Corundum-bearing CAIs, however, are exceptionally rare, suggesting either continuous reaction of the corundum condensates with a cooling nebular gas and their replacement by hibonite (CaAl 12 O 19 ) or their destruction by melting together with less refractory condensates during formation of igneous CAIs. In contrast to the corundum-bearing CAIs, isolated micrometer-sized corundum grains are common in the acid-resistant residues from unmetamorphosed chondrites. These grains could have avoided multistage reprocessing during CAI formation and, therefore, can potentially provide constraints on the initial oxygen isotopic composition of the solar nebula, and, hence, of the Sun. Here we report oxygen isotopic compositions of ∼60 micrometer-sized corundum grains in the acid-resistant residues from unequilibrated ordinary chondrites (Semarkona (LL3.0), Bishunpur (LL3.1), Roosevelt County 075 (H3.2)) and unmetamorphosed carbonaceous chondrites (Orgueil (CI1), Murray (CM2), and Alan Hills A77307 (CO3.0)) measured with a Cameca ims-1280 ion microprobe. All corundum grains, except two, are 16 O-rich (Δ 17 O = -22.7 per mille ± 8.5 per mille, 2σ), and compositionally similar to the mineralogically pristine CAIs from the CR carbonaceous chondrites (-23.3 per mille ± 1.9 per mille, 2σ), and solar wind returned by the Genesis spacecraft (-27 per mille ± 6 per mille, 2σ). One corundum grain is highly 17 O-enriched (δ 17 O ∼ +60 per mille, δ 18 O

  15. Metals other than uranium affected microbial community composition in a historical uranium-mining site.

    Science.gov (United States)

    Sitte, Jana; Löffler, Sylvia; Burkhardt, Eva-Maria; Goldfarb, Katherine C; Büchel, Georg; Hazen, Terry C; Küsel, Kirsten

    2015-12-01

    To understand the links between the long-term impact of uranium and other metals on microbial community composition, ground- and surface water-influenced soils varying greatly in uranium and metal concentrations were investigated at the former uranium-mining district in Ronneburg, Germany. A soil-based 16S PhyloChip approach revealed 2358 bacterial and 35 archaeal operational taxonomic units (OTU) within diverse phylogenetic groups with higher OTU numbers than at other uranium-contaminated sites, e.g., at Oak Ridge. Iron- and sulfate-reducing bacteria (FeRB and SRB), which have the potential to attenuate uranium and other metals by the enzymatic and/or abiotic reduction of metal ions, were found at all sites. Although soil concentrations of solid-phase uranium were high, ranging from 5 to 1569 μg·g (dry weight) soil(-1), redundancy analysis (RDA) and forward selection indicated that neither total nor bio-available uranium concentrations contributed significantly to the observed OTU distribution. Instead, microbial community composition appeared to be influenced more by redox potential. Bacterial communities were also influenced by bio-available manganese and total cobalt and cadmium concentrations. Bio-available cadmium impacted FeRB distribution while bio-available manganese and copper as well as solid-phase zinc concentrations in the soil affected SRB composition. Archaeal communities were influenced by the bio-available lead as well as total zinc and cobalt concentrations. These results suggest that (i) microbial richness was not impacted by heavy metals and radionuclides and that (ii) redox potential and secondary metal contaminants had the strongest effect on microbial community composition, as opposed to uranium, the primary source of contamination.

  16. Internal dosimetry and radiotoxicity of long-lived uranium isotopes

    International Nuclear Information System (INIS)

    Jacobi, W.

    1980-03-01

    The dose to relevant tissues and the effective dose equivalent by ingestion and inhalation of uranium compounds are evaluated on the basis of the new metabolic and dosimetric models recommended by ICRP. Applying these dose factors annual limits for intake of these compounds by workers are derived. Finally the natural uranium exposure of the population is described. From the measured natural U-content of body tissues dose factors for the dietary intake of uranium can be estimated. (orig.) [de

  17. Uranium isotopes determination in urine samples using alpha spectrometry and ICP-MS

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, Mychelle M.L.; Maihara, Vera A. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Tine, Fernanda D.; Santos, Sandra M.C.; Bonifacio, Rodrigo L.; Taddei, Maria HelenaT. [Comissao Nacional de Energia Nuclear (LAPOC/CNEN-MG), Pocos de Caldas, MG (Brazil). Laboratorio de Pocos de Caldas

    2015-07-01

    The action of determining the concentration of uranium isotopes in biological samples, 'in vitro' bioassay, is an indirect method for evaluating the incorporation and quantification of these radionuclides internally deposited. When incorporated, these radionuclides tend to be disposed through excretion, with urine being the main source of data because it can be easily collected and analyzed. The most widely used methods for determination of uranium isotopes ({sup 234}U, {sup 235}U and {sup 238}U) are Alpha Spectrometry and ICP-MS. This work presents a comparative study for the determination of uranium isotopes using these two methodologies in real samples from occupationally exposed workers. In order to validate the methodology, a sample of the intercomparison exercise organized by PROCORAD (Association pour la Promotion du Controle de Qualite des Analyses de Biologie Medicale em Radiotoxicologie) was used, and the results were statistically compared applying the Student's t-test. (author)

  18. Uranium isotopes determination in urine samples using alpha spectrometry and ICP-MS

    International Nuclear Information System (INIS)

    Rosa, Mychelle M.L.; Maihara, Vera A.; Tine, Fernanda D.; Santos, Sandra M.C.; Bonifacio, Rodrigo L.; Taddei, Maria HelenaT.

    2015-01-01

    The action of determining the concentration of uranium isotopes in biological samples, 'in vitro' bioassay, is an indirect method for evaluating the incorporation and quantification of these radionuclides internally deposited. When incorporated, these radionuclides tend to be disposed through excretion, with urine being the main source of data because it can be easily collected and analyzed. The most widely used methods for determination of uranium isotopes ( 234 U, 235 U and 238 U) are Alpha Spectrometry and ICP-MS. This work presents a comparative study for the determination of uranium isotopes using these two methodologies in real samples from occupationally exposed workers. In order to validate the methodology, a sample of the intercomparison exercise organized by PROCORAD (Association pour la Promotion du Controle de Qualite des Analyses de Biologie Medicale em Radiotoxicologie) was used, and the results were statistically compared applying the Student's t-test. (author)

  19. A Metal Stable Isotope Approach to Understanding Uranium Mobility Across Roll Front Redox Boundaries

    Science.gov (United States)

    Brown, S. T.; Basu, A.; Christensen, J. N.; DePaolo, D. J.; Heikoop, J. M.; Reimus, P. W.; Maher, K.; Weaver, K. L.

    2015-12-01

    Sedimentary roll-front uranium (U) ore deposits are the principal source of U for nuclear fuel in the USA and an important part of the current all-of-the-above energy strategy. Mining of roll-front U ore in the USA is primarily by in situ alkaline oxidative dissolution of U minerals. There are significant environmental benefits to in situ mining including no mine tailings or radioactive dust, however, the long-term immobilization of U in the aquifer after the completion of mining remains uncertain. We have utilized the metal stable isotopes U, Se and Mo in groundwater from roll-front mines in Texas and Wyoming to quantify the aquifer redox conditions and predict the onset of U reduction after post mining aquifer restoration. Supporting information from the geochemistry of groundwater and aquifer sediments are used to understand the transport of U prior to and after in situ mining. Groundwater was collected across 4 mining units at the Rosita mine in the Texas coastal plain and 2 mining units at the Smith Ranch mine in the Powder River Basin, Wyoming. In general, the sampled waters are moderately reducing and ore zone wells contain the highest aqueous U concentrations. The lowest U concentrations occur in monitoring wells downgradient of the ore zone. 238U/235U is lowest in downgradient wells and is correlated with aqueous U concentrations. Rayleigh distillation models of the 238U/235U are consistent with U isotope fractionation factors of 1.0004-1.001, similar to lab-based studies. Based on these results we conclude that redox reactions continue to affect U distribution in the ore zone and downgradient regions. We also measured aqueous selenium isotope (δ82Se) and molybdenum isotope (δ98Mo) compositions in the Rosita groundwater. Se(VI) primarily occurs in the upgradient wells and is absent in most ore zone and downgradient wells. Rayleigh distillation models suggest reduction of Se(VI) along the groundwater flow path and when superimposed on the U isotope data

  20. Radioactivity and the French uranium bearing minerals

    International Nuclear Information System (INIS)

    Guiollard, P.Ch.; Boisson, J.M.; Leydet, J.C.; Meisser, N.

    1998-01-01

    This special issue of Regne Mineral journal is entirely devoted to the French uranium mining industry. It comprises 4 parts dealing with: the uranium mining industry in France (history, uranium rush, deposits, geologic setting, prosperity and recession, situation in 1998, ore processing); radioactivity and the uranium and its descendants (discovery, first French uranium bearing ores, discovery of radioactivity, radium and other uranium descendants, radium mines, uranium mines, atoms, elements and isotopes, uranium genesis, uranium decay, isotopes in an uranium ore, spontaneous fission, selective migration of radionuclides, radon in mines and houses, radioactivity units, radioprotection standards, new standards and controversies, natural and artificial radioactivity, hazards linked with the handling and collecting of uranium ores, conformability with radioprotection standards, radioactivity of natural uranium minerals); the French uranium bearing minerals (composition, crystal structure, reference, etymology, fluorescence). (J.S.)

  1. An oxygen isotope study on hydrothermal sources of granite-type uranium deposits in South China

    International Nuclear Information System (INIS)

    Yongfei, Z.

    1987-01-01

    The usefulness of oxygen isotope measurements in solving problems of hydrothermal sources has been demonstrated in a number of detailed studies of the granite type uranium deposits in this paper. Remarkly the granite-type uranium deposits in Southr China have been shown to have formed from magmatic water, meteoric water, of mixtures of both the above, and origin of waters in the ore-forming fluid may be different for differing uranium deposits ore differing stages of the mineralization. Consequences obtained in this study for typical uranium deposits of different age and geologic sitting agree well with that obtained by other geologic-geochemical investigation. Furthermore, not only meteoric water is of importance to origin and evolution of the ore-forming fluid, but also mixing of waters from different sources is considered to be one of the most characteristic features of many hydrothermal uranium deposits related to granitoids or volcanics. (C.D.G.) [pt

  2. Diode laser based resonance ionization mass spectrometry for spectroscopy and trace analysis of uranium isotopes

    International Nuclear Information System (INIS)

    Hakimi, Amin

    2013-01-01

    In this doctoral thesis, the upgrade and optimization of a diode laser system for high-resolution resonance ionization mass spectrometry is described. A frequency-control system, based on a double-interferometric approach, allowing for absolute stabilization down to 1 MHz as well as frequency detunings of several GHz within a second for up to three lasers in parallel was optimized. This laser system was used for spectroscopic studies on uranium isotopes, yielding precise and unambiguous level energies, total angular momenta, hyperfine constants and isotope shifts. Furthermore, an efficient excitation scheme which can be operated with commercial diode lasers was developed. The performance of the complete laser mass spectrometer was optimized and characterized for the ultra-trace analysis of the uranium isotope 236 U, which serves as a neutron flux dosimeter and tracer for radioactive anthropogenic contaminations in the environment. Using synthetic samples, an isotope selectivity of ( 236 U)/( 238 U) = 4.5(1.5) . 10 -9 was demonstrated.

  3. Determination of the separation factor of uranium isotopes by gaseous diffusion; Determination des facteurs de separation des isotopes de l'uranium par diffusion gazeuse

    Energy Technology Data Exchange (ETDEWEB)

    Bilous, O; Counas, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    A 12-stage pilot separation cascade with a low output has been constructed to measure the separation factor of uranium isotopes by gaseous diffusion. The report describes some of the separation results obtained, and also provides information on the time necessary for equilibrium to be established and on the influence of various perturbations on the pressure profile in the cascade. (author) [French] Une cascade pilote de 12 etages de separation a faible debit a ete construite pour mesurer le facteur de separation des isotopes de l'uranium par diffusion gazeuse. Le rapport decrit certains des resultats de separation obtenus et fournit egalement des donnees sur les temps de mise en equilibre et l'influence de diverses perturbations sur le profil des pressions dans la cascade. (auteur)

  4. A study on hydrogen, oxygen, carbon, sulfur and lead isotopes in the rich uranium deposit No.201

    International Nuclear Information System (INIS)

    Li Yuexiang; Li Tiangang; Tong Hongshou; Feng Mingyue; Xu Zhan

    1995-01-01

    The uranium deposit No.201 located in Indonesian granite is one of the richest uranium deposits of granite type in China. An attempt is made to investigate the sources of ore-forming solutions and ore-forming materials, and to presume the environment of ore formation in the light of the study on composition of stable isotopes such as hydrogen, oxygen, carbon, sulfur and lead. The research results indicate that the ore-forming fluids in the deposit is mainly composed of meteoric water, the ore-forming materials principally came from pre-Yanshanian granite Massif and possibly, partly from the lower crust, and metallogenesis was undertaken under relatively stable physicochemical conditions

  5. A study on hydrogen, oxygen, carbon, sulfur and lead isotopes in the rich uranium deposit No.201

    Energy Technology Data Exchange (ETDEWEB)

    Yuexiang, Li; Tiangang, Li; Hongshou, Tong; Mingyue, Feng; Zhan, Xu [Beijing Research Inst. of Uranium Geology (China)

    1995-09-01

    The uranium deposit No.201 located in Indonesian granite is one of the richest uranium deposits of granite type in China. An attempt is made to investigate the sources of ore-forming solutions and ore-forming materials, and to presume the environment of ore formation in the light of the study on composition of stable isotopes such as hydrogen, oxygen, carbon, sulfur and lead. The research results indicate that the ore-forming fluids in the deposit is mainly composed of meteoric water, the ore-forming materials principally came from pre-Yanshanian granite Massif and possibly, partly from the lower crust, and metallogenesis was undertaken under relatively stable physicochemical conditions.

  6. Stable-isotope composition of the water of apple juice

    International Nuclear Information System (INIS)

    Bricout, Jacques; Merlivat, Liliane

    1973-01-01

    By deuterium and oxygen 18 analysis, it was shown that apples' water is enriched in heavier isotopes as compared to rain water. The isotopic composition of the water of reconstituted apple juice is closed to the isotopic content of the rain water used for dilution. Thus, deuterium and oxyden 18 analysis allows a good analytical distinction between natural apple juice and reconstituted juices [fr

  7. A simplified method for preparing micro-samples for the simultaneous isotopic analysis of uranium and plutonium

    International Nuclear Information System (INIS)

    Carter, J.A.; Walker, R.L.; Eby, R.E.; Pritchard, C.A.

    1976-01-01

    In this simplified technique a basic anion resin is employed to selectively adsorb plutonium and uranium from 8M HNO 3 solutions containing dissolved spent reactor fuels. After a few beads of the resin are equilibrated with solution, a single bead is used for establishing the isotopic composition of plutonium and uranium. The resin-bead separation essentially removes all possible isobaric interference from such elements as americium and curium and at the same time eliminates most fission-product contamination in the mass spectrometer. Small aliquots of dissolver solution that contain 10 -6 g U and 10 -8 g Pu are adequate for preparing about ten resin beads. By employing a single focusing tandem magnet-type mass spectrometer, equipped with pulse counting for ion detection, simultaneous plutonium and uranium assays are obtained. The quantity of each element per bead may be as low as 10 -9 to 10 -10 g. The carburized bead, which forms as the filament is heated, acts as a reducing point source and emits a predominance of metallic ions as compared with oxide ion emission from direct solution loadings. In addition to isotopic abundance, the technique of isotope dilution can ve coupled with the ion-exchange bead separation and used effectively for measuring the total quantity of U and Pu. The technique possesses many advantages such as reduced radiation hazards from the infinitely smaller samples, thus less shielding and transport cost for sample handling; greatly simplified chemical preparations that eliminate fission products and actinide isobaric interferences; and the minor isotopes are more precisely established. (author)

  8. Direct isotope ratio measurement of uranium metal by emission spectrometry on a laser-produced plasma

    International Nuclear Information System (INIS)

    Pietsch, W.; Petit, A.; Briand, A.

    1995-01-01

    The method of Optical Emission Spectrometry on a Laser-Produced Plasma (OES/LPP) at reduced pressure has been studied for the determination of the uranium isotope ratio ( 235 U/ 238 U). Spectral profiles of the investigated transition U-II 424.437 nm show the possibility to obtain an isotopic spectral resolution in a laser-produced plasma under exactly defined experimental conditions. Spectroscopic data and results are presented. (author)

  9. Graphite Isotope Ratio Method Development Report: Irradiation Test Demonstration of Uranium as a Low Fluence Indicator

    International Nuclear Information System (INIS)

    Reid, B.D.; Gerlach, D.C.; Love, E.F.; McNeece, J.P.; Livingston, J.V.; Greenwood, L.R.; Petersen, S.L.; Morgan, W.C.

    1999-01-01

    This report describes an irradiation test designed to investigate the suitability of uranium as a graphite isotope ratio method (GIRM) low fluence indicator. GIRM is a demonstrated concept that gives a graphite-moderated reactor's lifetime production based on measuring changes in the isotopic ratio of elements known to exist in trace quantities within reactor-grade graphite. Appendix I of this report provides a tutorial on the GIRM concept

  10. Standard test method for isotopic analysis of hydrolyzed uranium hexafluoride and uranyl nitrate solutions by thermal ionization mass spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This method applies to the determination of isotopic composition in hydrolyzed nuclear grade uranium hexafluoride. It covers isotopic abundance of 235U between 0.1 and 5.0 % mass fraction, abundance of 234U between 0.0055 and 0.05 % mass fraction, and abundance of 236U between 0.0003 and 0.5 % mass fraction. This test method may be applicable to other isotopic abundance providing that corresponding standards are available. 1.2 This test method can apply to uranyl nitrate solutions. This can be achieved either by transforming the uranyl nitrate solution to a uranyl fluoride solution prior to the deposition on the filaments or directly by depositing the uranyl nitrate solution on the filaments. In the latter case, a calibration with uranyl nitrate standards must be performed. 1.3 This test method can also apply to other nuclear grade matrices (for example, uranium oxides) by providing a chemical transformation to uranyl fluoride or uranyl nitrate solution. 1.4 This standard does not purport to address al...

  11. Isotopic composition of primary xenon and the fission of Pu-244

    Energy Technology Data Exchange (ETDEWEB)

    Levskii, L K

    1983-05-01

    The hypothesis that the origin of xenon on earth is due to the fission of uranium and/or transuranium elements is examined. The isotopic composition of primary xenon on earth is calculated using a model (Levskii, 1980) of the isotopic composition of rare gases which is based on the hypothesis of the heterogeneity of the isotopic composition of the elements of the solar system. The isotopic composition of fission-produced xenon in the atmosphere and solid earth is determined to correspond to the abundance of xenon isotopes as a result of the spontaneous fission of Pu-244 (half-life of 8.2 x 10 to the 7th years). The amount of fission-produced xenon in the atmosphere is shown to amount to about 30 percent (Xe-136). Under certain conditions, the degree of the degassing of the solid earth for xenon is 25 percent, which corresponds to a ratio of Kr-84/Xe-130 45 for the earth as a whole.

  12. Concentration of uranium on TiO-PAN and NaTiO-PAN composite absorbers

    International Nuclear Information System (INIS)

    Motl, Alois; Sebesta, Ferdinand; John, Jan; Spendlikova, Irena; Nemec, Mojmir

    2013-01-01

    Inorganic ion exchangers have been extensively tested for use in separation and concentration of uranium from Surface water. Except for separation of uranium from uranium -Contaminated waste water (e.g. waste water from mining and milling of uranium, Waste from nuclear fuel reprocessing) their main area of application has been foreseen to be their use for extraction of uranium from sea water which could partially cover future needs of uranium. Another perspective area of application is pre-concentration of uranium from natural waters followed by uranium determination via various specialized techniques such as TRLFS or AMS. Possibilities of uranium extraction from sea water have been subject of several international conferences (e.g. Topical meetings on the Recovery of Uranium from Seawater in 1980's, ACS National Meetings 2012 etc.) and are critically evaluated in a review by Bitte or recently by Kim. In the Czech Republic uranium-selective inorganic ion exchangers might be applied for treatment of various wastes from uranium industry, namely underground Water, uranium milling over-balance water, or acid waste water from underground uranium leaching and also like in other countries for determination of uranium isotopic composition focusing on anthropogenic and natural 236 U content. Among the best performing inorganic ion exchangers for the above listed purposes hydrated titanium dioxide (abbreviated as TiO) and sodium titanate (abbreviated as NaTiO) can be listed. Properties of TiO and NaTiO were reviewed by Lehto. From the point of view of ion-exchange, properties of hydrated titanium oxide and sodium titanate are very similar. The main disadvantage of these ion exchangers for industrial-scale application is their insufficient mechanical stability. To improve this property, the sorption materials can be embedded into a binding matrix. Modified polyacrylonitrile (PAN) has been proposed at the Czech Technical University in Prague as a universal binding matrix for

  13. Preparation of electrodeless discharge lamps for emission studies of uranium isotopes at trace level

    International Nuclear Information System (INIS)

    Bhowmick, G.K.; Verma, R.; Verma, M.K.; Raman, V.A.; Joshi, A.R.; Deo, M.N.; Gantayet, L.M.; Tiwari, A.K.; Ramakumar, K.L.; Kumar, Navin

    2010-01-01

    A simplified method for preparation of electrodeless discharge lamp for uranium isotopes with specific concerns for 232 U is described. Micro-gram quantities of solid uranium oxides and aqueous solution of uranium nitrate have been used as a starting material for in situ synthesis of uranium tetraiodide. High temperature iodination reaction is carried out in the presence of inert gas neon. By careful design, the preparation time and surface area of quartz reaction tubes have been reduced considerably. The latter decreases the level of contamination which has a direct bearing on the operational lifetime of the lamps. Incorporation of steps to purify the product from an unwanted material improved the stability of the lamps. The procedure provides a safe and convenient way of handling 232 U in particular but can be extended in general to any actinides having radioactivity similar to that of freshly separated 232 U. Characteristic emission of uranium isotopes have been recorded by Fourier Transform Spectrometer to show the satisfactory operation of the lamps as well as their usage for studying emission spectra of the specific isotope.

  14. Three-stage method for interpretation of uranium-lead isotopic data

    International Nuclear Information System (INIS)

    Nejmark, L.A.; Ovchinnikova, G.V.; Levchenkov, O.A.

    1982-01-01

    Three-dimensional approach for the iterpretation of uranium-lead isoto e ratios in pnatural systems, development of which corresponds to three stages, has been considered. In the framework of the three-stage model two cases, differing in the character of uranium-lead systems violation at the beginning of the third stage, are discussed. The first case corresponds to uranium addition or lead substraction, and the second one - to addition of lead of unknown isotopic content. Three-stage approach permits without amending the isotopic content of lead captured during crystallization to calculated the beginning of the second and third stages of uranium-lead systems development and to evaluate parameters of lead added to the system. Concrete examples of interpretation of uranium-lead isotopic ratios in minerals and rock samples as a whole both of the terrestrial and cosmic origin are considered. Possibilities and limitations of the three-stage approach are analyzed and directions of further development are outlined

  15. Isotopic composition of cellulose from aquatic organisms

    International Nuclear Information System (INIS)

    DeNiro, M.J.; Epstein, S.

    1981-01-01

    The stable isotopic ratios of oxygen, carbon and the non-exchangeable carbon-bound hydrogen of cellulose from marine plants and animals collected in their natural habitats and from freshwater vascular plants grown in the laboratory under controlled conditions were determined. The delta 18 O values of cellulose from all the plants and animals were 27 +- 3 parts per thousand more positive than the delta 18 O values of the waters in which the organisms grew. Temperature had little or no influence on this relationship for three species of freshwater vascular plants that were analyzed. The deltaD values of the non-exchangeable hydrogen of cellulose from different organisms that grew in the same environment differed by large amounts. This difference ranged up to 200 parts per thousand for different species of algae collected at a single site; the corresponding difference for different species of tunicates and vascular plants was 60 and 20 parts per thousand respectively. The deltaD values of cellulose nitrate from different species of freshwater vascular plants grown in water of constant temperature and isotopic composition differed by as much as 60 parts per thousand. The relationship between the deltaD values of the carbon-bound hydrogen of cellulose and the water used in its synthesis displayed a significant temperature dependence for four species of freshwater vascular plants that were analyzed. (author)

  16. Determination of low level of plutonium and uranium isotopes in safeguard swipe sample

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Myung Ho; Park, Jong Ho; Oh, Seong Yong; Lee, Chang Heon; Ahn, Hong Ju; Song, Kyu Seok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-10-15

    For the determination of radionuclides, the separation techniques based on the principles of anion exchange, liquid-liquid extraction or column extraction chromatography are frequently used in nuclear analytical applications. Recently, a novel extraction chromatographic resin has been developed by Horwitz and co-workers, which are capable of selective extraction of the actinides. General separation of plutonium and uranium with extraction chromatographic techniques are focused on the environmental or radioactive waste samples. Also, the chemical yields for Pu and U isotopes with extraction chromatographic method sometimes are variable. For effective extraction of Pu isotopes in the very level of plutonium sample with UTEVA resin, the valence adjustment of Pu isotopes in the sample solution requires due to unstability in the oxidation state of Pu isotopes during separation step. Therefore, it is necessary to develop a simple and robust radiochemical separation method for nano- or pico gram amounts of uranium and plutonium in safeguard swipe samples. Chemical yields of plutonium and uranium with extraction chromatographic method of Pu and U upgrades in this study were compared with several separation methods for Pu and U generally used in the radiochemistry field. Also, the redox reactions of hydrogen peroxide with plutonium in the nitric acid media were investigated by UV-Vis-NIR absorption spectroscopy. Based on general extraction chromatography method with UTEVA resin, the separation method of nano- and picogram amounts of uranium and plutonium in safeguard swipe samples was developed in this study

  17. The relationship of uranium isotopes to oxidation/reduction in the Edwards carbonate aquifer of Texas

    International Nuclear Information System (INIS)

    Cowart, J.B.

    1980-01-01

    The concentration of dissolved uranium and 234 U/ 238 U alpha activity ratio ( A.R. ) were determined in water samples from 23 locations in the Edwards carbonate aquifer of south central Texas by isotope dilution methods and alpha spectrometry. (orig./ME)

  18. Alpha low activity determination from limitter isotopes of uranium, thorium ands radium in natural waters

    International Nuclear Information System (INIS)

    Gascon, J.L.; Crespo, M.T.; Acena, M.L.

    1989-01-01

    A method to concentrate uranium, thorium and radium in natural waters has been developed. The method, based on the adsorbing propert-ies of manganes dioxide, has been applied to determine the alpha emitter isotopes of these elements in drinking water of Madrid. In this work we present the description of the method, the analytical procedu-res and the obtained results. (Author)

  19. Determination of the separation factor of uranium isotopes by gaseous diffusion

    International Nuclear Information System (INIS)

    Bilous, O.; Counas, G.

    1958-01-01

    A 12-stage pilot separation cascade with a low output has been constructed to measure the separation factor of uranium isotopes by gaseous diffusion. The report describes some of the separation results obtained, and also provides information on the time necessary for equilibrium to be established and on the influence of various perturbations on the pressure profile in the cascade. (author) [fr

  20. Determination of uranium and thorium isotopes by solid phase extraction and alpha spectrometry

    International Nuclear Information System (INIS)

    Kuruc, J.; Kovacova, M.; Strisovska, J.; Galanda, D.

    2013-01-01

    The aim of this work was to test the modified method suitable for the separation of isotopes of uranium and thorium samples of rocks, including gold ore and gold concentrate using of extraction chromatography method, after digestion of the sample, concentrating, separate the isotopes of uranium and thorium isotopes to prepare sources for the measurement of alpha spectra. Samples of rocks, gold ore and gold concentrate were digered in microwave decomposition in the environment of hydrogen peroxide and concentrated nitric acid. For the separation of uranium and thorium the vacuum box with cartridges DGA Resin and Resin(R) UTEVA (Triskem International, France) was used. Both sorbents allow separation of uranium from thorium. The results confirmed that the both sorbents give the same results within expanded uncertainty. The mass activity of monitored uranium and thorium radioisotopes was determined by alpha spectrometry method. The yields of separation were determined using uranium-232 as a tracer radionuclide; the activity of 232 U was 0.1438 Bq. Alpha spectra were measured on the Alpha spectrometer EG and G ORTEC 576A with the software MAESTRO, MCA Emulator and Gamma Vision-32 for Windows, USA. Mass activities of radionuclides were converted to mass concentration of isotopes 238 U, 234 U, 232 Th, 230 Th and 228 Th. The highest concentration of 238 U was sampled in granodiorite (Tunnel S-XIV-2, southwards, mining of Cu ore, not working there since 1990), where m( 238 U) = (0.81 ± 0.09) mg kg -1 (DGA Resin) and m( 238 U) = (0.90 ± 0.09) mg kg -1 (UTEVA(R) Resin), as well as m( 232 Th) = (18.8 ± 1.7) mg kg -1 (DGA Resin) and m( 232 Th) = (17.8 ± 1.5) mg kg -1 (UTEVA(R) Resin). In other samples of rocks, gold ore and gold concentrates have specific masses of isotopes of uranium and thorium two-to ten-folds lower. It can be concluded that the rocks, gold ores and concentrates of gold from the 'Rozalia' mine contain lower concentrations of uranium several times against

  1. Measurement of isotope shift of recycled uranium by laser induced fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Oba, Masaki; Wakaida, Ikuo; Akaoka, Katsuaki; Miyabe, Masabumi

    1999-07-01

    Isotope shift of the recycled uranium atoms including the 236 U was measured by laser induced fluorescence method. Eight even levels at 2 eV and three odd levels at 4 eV were measured with isotope shifts among 238 U, 236 U and 235 U obtained. As for the measurement of the 4 eV levels, the Doppler free two photon absorption method was used, and the hyperfine structure of the 235 U was analyzed simultaneously. The isotope shift of 234 U was also observed in the three transition. (J.P.N.)

  2. Molybdenum isotope fractionation during acid leaching of a granitic uranium ore

    Science.gov (United States)

    Migeon, Valérie; Bourdon, Bernard; Pili, Eric; Fitoussi, Caroline

    2018-06-01

    As an attempt to prevent illicit trafficking of nuclear materials, it is critical to identify the origin and transformation of uranium materials from the nuclear fuel cycle based on chemical and isotope tracers. The potential of molybdenum (Mo) isotopes as tracers is considered in this study. We focused on leaching, the first industrial process used to release uranium from ores, which is also known to extract Mo depending on chemical conditions. Batch experiments were performed in the laboratory with pH ranging from 0.3 to 5.5 in sulfuric acid. In order to span a large range in uranium and molybdenum yields, oxidizers such as nitric acid, hydrogen peroxide and manganese dioxide were also added. An enrichment in heavy Mo isotopes is produced in the solution during leaching of a granitic uranium ore, when Mo recovery is not quantitative. At least two Mo reservoirs were identified in the ore: ∼40% as Mo oxides soluble in water or sulfuric acid, and ∼40% of Mo hosted in sulfides soluble in nitric acid or hydrogen peroxide. At pH > 1.8, adsorption and/or precipitation processes induce a decrease in Mo yields with time correlated with large Mo isotope fractionations. Quantitative models were used to evaluate the relative importance of the processes involved in Mo isotope fractionation: dissolution, adsorption, desorption, precipitation, polymerization and depolymerization. Model best fits are obtained when combining the effects of dissolution/precipitation, and adsorption/desorption onto secondary minerals. These processes are inferred to produce an equilibrium isotope fractionation, with an enrichment in heavy Mo isotopes in the liquid phase and in light isotopes in the solid phase. Quantification of Mo isotope fractionation resulting from uranium leaching is thus a promising tool to trace the origin and transformation of nuclear materials. Our observations of Mo leaching are also consistent with observations of natural Mo isotope fractionation taking place during

  3. Isotopic characterization of uranium in soils of the Ipanema National Forest (FLONA-Ipanema)

    International Nuclear Information System (INIS)

    Silva, F.B.; Marques, F.H.; Enzweiler, J.; Ladeira, F.S.B.

    2015-01-01

    The National Forest of Ipanema (FLONA) is situated on a geological anomaly, known as 'Domo de Aracoiaba'. The soils of the area include Oxisols, Inceptsols and Alfisols. The amount of uranium and respective isotope activities in a soil depend on the parental rock and on the pedologic processes. The aim of this study was to investigate the activities for uranium isotopes ("2"3"8U, "2"3"4U, "2"3"5U) and the activity ratio (AR) "2"3"4U/ "2"3"8U or secular equilibrium for different soil types of the area collected at horizons A and B. The amount of uranium showed no significant differences for soils generated from alkaline intrusive rocks and sandstone, however, secular equilibrium was observed for Oxisol (RA = 1), while Inceptsol presented RA> 1 and the other soils, Alfisols, presented RA values <1. (author)

  4. Determination of thorium and uranium isotopes in the mining lixiviation liquor samples

    Energy Technology Data Exchange (ETDEWEB)

    Reis Júnior, Aluísio de Souza; Monteiro, Roberto Pellacani Guedes, E-mail: reisas@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-07-01

    The alpha spectrometric analysis refers to determination of thorium and uranium isotopes in the mining lixiviation liquor samples. The analytical procedure involves sample preparation steps for rare earth elements, thorium and uranium separation using selective etching with hydrofluoric acid and further radiochemical separation of these using TRU chromatographic resins (Eichrom Industries Inc. USA) besides electroplating of the isolated radionuclides. An isotopic tracer is used to determine the overall chemical yield and to ensure traceability to a national standard. The results are compared to results obtained for the same samples by Becquerel laboratory. We improved the method looking for reproducibility and isotopes isolation as required by alpha spectrometry and the method showing effective in analysis of mining liquor. (author)

  5. Determination of thorium and uranium isotopes in the mining lixiviation liquor samples

    International Nuclear Information System (INIS)

    Reis Júnior, Aluísio de Souza; Monteiro, Roberto Pellacani Guedes

    2017-01-01

    The alpha spectrometric analysis refers to determination of thorium and uranium isotopes in the mining lixiviation liquor samples. The analytical procedure involves sample preparation steps for rare earth elements, thorium and uranium separation using selective etching with hydrofluoric acid and further radiochemical separation of these using TRU chromatographic resins (Eichrom Industries Inc. USA) besides electroplating of the isolated radionuclides. An isotopic tracer is used to determine the overall chemical yield and to ensure traceability to a national standard. The results are compared to results obtained for the same samples by Becquerel laboratory. We improved the method looking for reproducibility and isotopes isolation as required by alpha spectrometry and the method showing effective in analysis of mining liquor. (author)

  6. Discrimination of source reactor type by multivariate statistical analysis of uranium and plutonium isotopic concentrations in unknown irradiated nuclear fuel material.

    Science.gov (United States)

    Robel, Martin; Kristo, Michael J

    2008-11-01

    The problem of identifying the provenance of unknown nuclear material in the environment by multivariate statistical analysis of its uranium and/or plutonium isotopic composition is considered. Such material can be introduced into the environment as a result of nuclear accidents, inadvertent processing losses, illegal dumping of waste, or deliberate trafficking in nuclear materials. Various combinations of reactor type and fuel composition were analyzed using Principal Components Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLSDA) of the concentrations of nine U and Pu isotopes in fuel as a function of burnup. Real-world variation in the concentrations of (234)U and (236)U in the fresh (unirradiated) fuel was incorporated. The U and Pu were also analyzed separately, with results that suggest that, even after reprocessing or environmental fractionation, Pu isotopes can be used to determine both the source reactor type and the initial fuel composition with good discrimination.

  7. Monitoring of uranium isotopes in seaweeds and seawater

    International Nuclear Information System (INIS)

    Meena, Balram; Mehendarge, S.T.; Baburajan, A.; Rao, D.D.

    2012-01-01

    The paper deals with the concentration of uranium in seawater and different types of seaweed found along the coast line of Tarapur marine environment. The seaweeds are the trend indicators of heavy metals and radionuclides present in the aquatic environment. Seaweeds also serve as a food to the marine organisms and thus can enter the human being through food chain. The higher concentration of uranium in seafood may have radiological impact on human health. The Tarapur Atomic Power Station is adjoined to the sea and has a rocky surface area, which act as a good dwelling for the growth and survival of marine biota. In present study, separation and measurements were made to determine the uranium concentration in seaweed seawater at Tarapur coastal environment

  8. A review of laser isotope separation of uranium hexafluoride

    International Nuclear Information System (INIS)

    Kelly, J.W.

    1983-04-01

    There is continuing world-wide interest in the possibility of enriching uranium by a laser process which uses uranium hexafluoride. Since no actual commercial plant exists at present, this review examines the key areas of related research. It concludes that such a process is feasible, that it must employ an adiabatic cooling system, with UF 6 the minor constituent in a predominantly monatomic or diatomic carrier gas, that the necessary infrared and/or ultraviolet-visible lasers are in a state of development bordering on the minimum required, and that the economics of such a process appear highly promising

  9. Status of Uranium Atomic Vapor Laser Isotope Separation Program

    International Nuclear Information System (INIS)

    Chen, Hao-Lin; Feinberg, R.M.

    1993-06-01

    This report discusses demonstrations of plant-scale hardware embodying AVLIS technology which were completed in 1992. These demonstrations, designed to provide key economic and technical bases for plant deployment, produced significant quantities of low enriched uranium which could be used for civilian power reactor fuel. We are working with industry to address the integration of AVLIS into the fuel cycle. To prepare for deployment, a conceptual design and cost estimate for a uranium enrichment plant were also completed. The U-AVLIS technology is ready for commercialization

  10. Uranium Elemental and Isotopic Constraints on Groundwater Flow Beneath the Nopal I Uranium Deposit, Pena Blanca, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    S.J. Goldstein; M.T. Murrell; A.M. Simmons

    2005-07-11

    The Nopal I uranium deposit in Chihuahua, Mexico, is an excellent analogue for evaluating the fate of spent fuel, associated actinides, and fission products over long time scales for the proposed Yucca Mountain high-level nuclear waste repository. In 2003, three groundwater wells were drilled directly adjacent to (PB-1) and 50 m on either side of the uranium deposit (PB-2 and PB-3) in order to evaluate uranium-series transport in three dimensions. After drilling, uranium concentrations were elevated in all of the three wells (0.1-18 ppm) due to drilling activities and subsequently decreased to {approx}5-20% of initial values over the next several months. The {sup 234}U/{sup 238}U activity ratios were similar for PB-1 and PB-2 (1.005 to 1.079) but distinct for PB-3 (1.36 to 1.83) over this time period, suggesting limited mixing between groundwater from these wells over these short time and length scales. Regional groundwater wells located up to several km from the deposit also have distinct uranium isotopic characteristics and constrain mixing over larger length and time scales. We model the decreasing uranium concentrations in the newly drilled wells with a simple one-dimensional advection-dispersion model, assuming uranium is introduced as a slug to each of the wells and transported as a conservative tracer. Using this model for our data, the relative uranium concentrations are dependent on both the longitudinal dispersion as well as the mean groundwater flow velocity. These parameters have been found to be correlated in both laboratory and field studies of groundwater velocity and dispersion (Klotz et al., 1980). Using typical relationships between velocity and dispersion for field and laboratory studies along with the relationship observed from our uranium data, both velocity (1-10 n/yr) and dispersion coefficient (1E-5 to 1E-2 cm{sup 2}/s) can be derived from the modeling. As discussed above, these relatively small flow velocities and dispersivities agree with

  11. Uranium Elemental and Isotopic Constraints on Groundwater Flow Beneath the Nopal I Uranium Deposit, Pena Blanca, Mexico

    International Nuclear Information System (INIS)

    S.J. Goldstein; M.T. Murrell; A.M. Simmons

    2005-01-01

    The Nopal I uranium deposit in Chihuahua, Mexico, is an excellent analogue for evaluating the fate of spent fuel, associated actinides, and fission products over long time scales for the proposed Yucca Mountain high-level nuclear waste repository. In 2003, three groundwater wells were drilled directly adjacent to (PB-1) and 50 m on either side of the uranium deposit (PB-2 and PB-3) in order to evaluate uranium-series transport in three dimensions. After drilling, uranium concentrations were elevated in all of the three wells (0.1-18 ppm) due to drilling activities and subsequently decreased to ∼5-20% of initial values over the next several months. The 234 U/ 238 U activity ratios were similar for PB-1 and PB-2 (1.005 to 1.079) but distinct for PB-3 (1.36 to 1.83) over this time period, suggesting limited mixing between groundwater from these wells over these short time and length scales. Regional groundwater wells located up to several km from the deposit also have distinct uranium isotopic characteristics and constrain mixing over larger length and time scales. We model the decreasing uranium concentrations in the newly drilled wells with a simple one-dimensional advection-dispersion model, assuming uranium is introduced as a slug to each of the wells and transported as a conservative tracer. Using this model for our data, the relative uranium concentrations are dependent on both the longitudinal dispersion as well as the mean groundwater flow velocity. These parameters have been found to be correlated in both laboratory and field studies of groundwater velocity and dispersion (Klotz et al., 1980). Using typical relationships between velocity and dispersion for field and laboratory studies along with the relationship observed from our uranium data, both velocity (1-10 n/yr) and dispersion coefficient (1E-5 to 1E-2 cm 2 /s) can be derived from the modeling. As discussed above, these relatively small flow velocities and dispersivities agree with mixing

  12. Carbon and Oxygen isotopic composition in paleoenvironmental determination

    International Nuclear Information System (INIS)

    Silva, J.R.M. da.

    1978-01-01

    This work reports that the carbon and oxygen isotopic composition separate the mollusks from marine environment of the mollusks from continental environment in two groups isotopically different, making the biological control outdone by environment control, in the isotopic fragmentation mechanisms. The patterns from the continental environment are more rich in O 16 than the patterns from marine environments. The C 12 is also more frequent in the mollusks from continental environments. The carbon isotopic composition in paterns from continental environments is situated betwen - 10.31 and - 4,05% and the oxygen isotopic composition is situated between - 6,95 and - 2,41%. To the marine environment patterns the carbon isotopic composition is between - 2,08 and + 2,65% and the oxigen isotopic composition is between - 2,08 and + 0,45%. Was also analysed fossil marine mollusks shells and their isotopic composition permit the formulation of hypothesis about the environment which they lived. (C.D.G.) [pt

  13. Isotope separation of uranium by laser: tuning and frequency instability

    International Nuclear Information System (INIS)

    Broglia, M.; Massimi, M.; Spoglia, U.; Zampetti, P.

    1983-01-01

    Intensity measurements of laser induced fluorescence in an uranium atomic beam are affected by the axial mode structure of the commercial pulsed dye laser used and by its strong frequency instability. Qualitative and quantitative evaluations on the possible causes of frequency instability are reported

  14. Rubidium-strontium and uranium-lead isotopic age studies

    International Nuclear Information System (INIS)

    Loveridge, W.D.

    1980-01-01

    Rubidium-strontium whole rock isochron ages and initial 87 Sr/ 86 Sr ratios and uranium-lead ages on zircon from suites of samples selected from localities across Canada are presented. Descriptions of the geological probelms and interpretations of the measured ages are included. Laboratory age determination methods and techniques are described or referenced. (auth)

  15. Magnesium isotopic composition of the Earth and chondrites

    Science.gov (United States)

    Teng, Fang-Zhen; Li, Wang-Ye; Ke, Shan; Marty, Bernard; Dauphas, Nicolas; Huang, Shichun; Wu, Fu-Yuan; Pourmand, Ali

    2010-07-01

    To constrain further the Mg isotopic composition of the Earth and chondrites, and investigate the behavior of Mg isotopes during planetary formation and magmatic processes, we report high-precision (±0.06‰ on δ 25Mg and ±0.07‰ on δ 26Mg, 2SD) analyses of Mg isotopes for (1) 47 mid-ocean ridge basalts covering global major ridge segments and spanning a broad range in latitudes, geochemical and radiogenic isotopic compositions; (2) 63 ocean island basalts from Hawaii (Kilauea, Koolau and Loihi) and French Polynesia (Society Island and Cook-Austral chain); (3) 29 peridotite xenoliths from Australia, China, France, Tanzania and USA; and (4) 38 carbonaceous, ordinary and enstatite chondrites including 9 chondrite groups (CI, CM, CO, CV, L, LL, H, EH and EL). Oceanic basalts and peridotite xenoliths have similar Mg isotopic compositions, with average values of δ 25Mg = -0.13 ± 0.05 (2SD) and δ 26Mg = -0.26 ± 0.07 (2SD) for global oceanic basalts ( n = 110) and δ 25Mg = -0.13 ± 0.03 (2SD) and δ 26Mg = -0.25 ± 0.04 (2SD) for global peridotite xenoliths ( n = 29). The identical Mg isotopic compositions in oceanic basalts and peridotites suggest that equilibrium Mg isotope fractionation during partial melting of peridotite mantle and magmatic differentiation of basaltic magma is negligible. Thirty-eight chondrites have indistinguishable Mg isotopic compositions, with δ 25Mg = -0.15 ± 0.04 (2SD) and δ 26Mg = -0.28 ± 0.06 (2SD). The constancy of Mg isotopic compositions in all major types of chondrites suggest that primary and secondary processes that affected the chemical and oxygen isotopic compositions of chondrites did not significantly fractionate Mg isotopes. Collectively, the Mg isotopic composition of the Earth's mantle, based on oceanic basalts and peridotites, is estimated to be -0.13 ± 0.04 for δ 25Mg and -0.25 ± 0.07 for δ 26Mg (2SD, n = 139). The Mg isotopic composition of the Earth, as represented by the mantle, is similar to chondrites

  16. Risk due assessment of the intake of uranium isotopes in mineral spring waters

    International Nuclear Information System (INIS)

    Camargo, Iara M.C.; Mazzilli, Barbara

    1998-01-01

    To complement the data of a previous research concerning the evaluation of the lifetime risk of radiation-induced cancer due to the injection of 226 Ra, 228 Ra and 222 Rn in mineral spring waters from a natural highly radioactive region of Brazil. The study was performed to evaluate the lifetime risk of radiation-induced cancer due to the ingestion of 238 U and 234 U in the same spring waters. It is assumed that the risk coefficient for natural U isotopes is the same as for the 226 Ra-induced bone sarcomas and that the equilibrium for skeletal content is 25 times the daily ingestion of 226 Ra, but 11 times the daily ingestion of long-lived uranium isotopes. Waters samples were collected seasonally over a period of one year at all the spring sites used by the local population of Aguas da Prata, Sao Paulo State, Brazil. Concentrations ranging from 2.0 to 28.4 mBq/L and from 4.7 to 143 mBq/L were observed for 238 U and 234 U, respectively. Based upon the measured concentrations the lifetime risk due to the ingestion of uranium isotopes was estimated. A total of 0.3 uranium-induced cancers for 10 6 exposed persons was predicted, suggesting that chronic ingestion of uranium at the levels observed at these springs will result in an incremental increase of fatal cancers of 0.1%. (author)

  17. Isotopic composition of cosmic ray nuclei

    International Nuclear Information System (INIS)

    Enge, W.

    1976-01-01

    A review will be given on the role of cosmic ray isotopes as tracers of the astrophysical nucleo-synthesis. The products of every nuclear burning chain are first of all isotopes and not elements. Thus, it is the study of the isotopes rather than that of the elements that responds to the questions on these nucleo-synthetic reactions. The problems concerning the solar system isotopic abundances and the cosmic ray isotopic abundances as well as a comparison between both will be presented. Furthermore the present stage of the experimental techniques and the latest results will be discussed. (orig.) [de

  18. The IDA-80 measurement evaluation programme on mass spectrometric isotope dilution analysis of uranium and plutonium. Vol. 1

    International Nuclear Information System (INIS)

    Beyrich, W.; Golly, W.; Spannagel, G.; Kernforschungszentrum Karlsruhe G.m.b.H.; Bievre, P. de; Wolters, W.

    1984-12-01

    The main objective was the acquisition of basic data on the uncertainties involved in the mass spectrometric isotope dilution analysis as applied to the determination of uranium and plutonium in active feed solutions of reprocessing plants. The element concentrations and isotopic compositions of all test materials used were determined by CBNM and NBS with high accuracy. The more than 60000 analytical data reported by the participating laboratories were evaluated by statistical methods applied mainly to the calculation of estimates of the variances for the different uncertainty components contributing to the total uncertainty of this analytical technique. Attention was given to such topics as sample ageing, influence of fission products, spike calibration, ion fractionation, Pu-241 decay correction, minor isotope measurement and errors in data transfer. Furthermore, the performance of the 'dried sample' technique and the 'in-situ' spiking method of undiluted samples of reprocessing fuel solution with U-235/Pu-242 metal alloy spikes, were tested successfully. Considerable improvement of isotope dilution analysis in this safeguards relevant application during the last decade is shown as compared to the results obtained in the IDA-72 interlaboratory experiment, organized by KfK in 1972 on the same subject. (orig./HP) [de

  19. Trace elements and Pb isotopes in soils and sediments impacted by uranium mining

    Energy Technology Data Exchange (ETDEWEB)

    Cuvier, A., E-mail: alicia.cuvier@hotmail.fr [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France); IRSN/PRP-ENV/SESURE/Laboratoire d' études radioécologiques en milieu continental et marin, BP 1, 13108 Saint Paul Lez Durance Cedex (France); Pourcelot, L. [IRSN/PRP-ENV/SESURE/Laboratoire d' études radioécologiques en milieu continental et marin, BP 1, 13108 Saint Paul Lez Durance Cedex (France); Probst, A. [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France); Prunier, J. [Observatoire Midi-Pyrénées, laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université Paul Sabatier, 14 avenue Edouard Belin, 31400 Toulouse (France); Le Roux, G., E-mail: gael.leroux@ensat.fr [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France)

    2016-10-01

    The purpose of this study is to evaluate the contamination in As, Ba, Co, Cu, Mn, Ni, Sr, V, Zn and REE, in a high uranium activity (up to 21,000 Bq ∙ kg{sup −1}) area, downstream of a former uranium mine. Different geochemical proxies like enrichment factor and fractions from a sequential extraction procedure are used to evaluate the level of contamination, the mobility and the availability of the potential contaminants. Pb isotope ratios are determined in the total samples and in the sequential leachates to identify the sources of the contaminants and to determine the mobility of radiogenic Pb in the context of uranium mining. In spite of the large uranium contamination measured in the soils and the sediments (EF ≫ 40), trace element contamination is low to moderate (2 < EF < 5), except for Ba (5 < EF < 15), due to the precipitation of barium sulfate resulting from mining activities. Most of the trace elements are associated with the most mobile fractions of the sediments/soils, implying an enhanced potential availability. Even if no Pb enrichment is highlighted, the Pb isotopic signature of the contaminated soils is strongly radiogenic. Measurements performed on the sequential leachates reveal inputs of radiogenic Pb in the most mobile fractions of the contaminated soil. Inputs of low-mobile radiogenic Pb from mining activities may also contribute to the Pb signature recorded in the residual phase of the contaminated samples. We demonstrate that Pb isotopes are efficient tools to trace the origin and the mobility of the contaminants in environments affected by uranium mining. - Highlights: • Contamination of soils is evidenced by a multiproxy approach. • Enrichment factors highlight a low contamination except for U, S and Ba. • Pb isotope ratios point out inputs of radiogenic Pb from the mine. • Radiogenic Pb is mainly in the acid-soluble and the reducible fractions.

  20. Information derived from French studies and achievements in the field of uranium isotope separation; Enseignements tires des etudes et realisations francaises relatives a la separation des isotopes de l'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Frejacques, C; Galley, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    The work carried out in the field of uranium isotope separation, by gaseous diffusion and by ultracentrifugation, is reviewed. An economic estimate of the various parameters involved in the cost is given, and it is shown that only very large gaseous diffusion plants, corresponding to a programme of enriched uranium reactors of at least 4000 MWe to be installed yearly, can give an economically acceptable enriched uranium production. (authors) [French] La communication passe en revue les realisations effectuees dans le domaine de la separation des isotopes de l'uranium, par diffusion gazeuse et par ultracentrifugation. Elle donne une estimation economique des differents parametres intervenant dans les couts et met en evidence que seules les tres grandes usines de diffusion gazeuse, correspondant a un programme d'installation de reacteurs a uranium enrichi d'au moins 4000 MWe nouveaux par an, peuvent conduire a des productions d'uranium enrichi economiquement acceptables. (auteurs)

  1. The composition and character of oxycarbide phase in uranium metal

    International Nuclear Information System (INIS)

    Liu Kezhao; Lai Xinchun; Yu Yong; Ni Ranfu

    1999-08-01

    The oxide layer of uranium metal formed by vacuum heating were examined with X-ray photoelectron spectroscopy (XPS) and Auger Electron Spectroscopy (AES). XPS results indicated that the air-exposed surface of the oxide layer were mainly consisted of UO 2 and free carbon. After the air-exposed surface were removed by low energy argon ion sputtering, C1s spectra shifted from 284.8 eV to 281.8 eV, indicating the existence of carbide phase. AES results of C(KVV) Auger transitions confirmed this result. Resolved and fitted using a combination of Gaussian and Lorentzian peak shape, U4f 7/2 spectra showed that three uranium chemical states existed in the layer, there were uranium dioxide, uranium carbide (or oxycarbide, UC x O 1-x ) and uranium metal phase. Calculated the AES data by relatively sensitive factor, the composition of oxycarbide was given as UC 0.41+-0.04 O 0.62+-0.01

  2. Uncertainties achievable for uranium isotope-amount ratios. Estimates based on the precision and accuracy of recent characterization measurements

    International Nuclear Information System (INIS)

    Mathew, K.J.; Essex, R.M.; Gradle, C.; Narayanan, U.

    2015-01-01

    Certified reference materials (CRMs) recently characterized by the NBL for isotope-amount ratios are: (i) CRM 112-A, Uranium (normal) Metal Assay and Isotopic Standard, (ii) CRM 115, Uranium (depleted) Metal Assay and Isotopic Standard, and (iii) CRM 116-A, Uranium (enriched) Metal Assay and Isotopic Standard. NBL also completed re-characterization of the isotope-amount ratios in CRM 125-A, Uranium (UO 2 ) Pellet Assay, Isotopic, and Radio-chronometric Standard. Three different TIMS analytical techniques were employed for the characterization analyses. The total evaporation technique was used for the major isotope-amount ratio measurement, the modified total evaporation technique was used for both the major and minor isotope-amount ratios, and minor isotope-amount ratios were also measured using a Conventional technique. Uncertainties for the characterization studies were calculated from the combined TIMS data sets following the ISO Guide to the expression of uncertainty in measurement. The uncertainty components for the isotope-amount ratio values are discussed. (author)

  3. The analysis of uranium in environmental sample by mass spectrometer combined with isotopic dilution

    International Nuclear Information System (INIS)

    Fu Zhonghua; Jia Baoting; Han Jun

    2003-01-01

    Uranium in the environmental sample was analyzed by mass spectrometer combined with isotopic dilution. Before mass spectrometer analysis, samples were dissolved in a concentrated acidic solution containing HNO 3 , HF and HClO 4 and chemically processed to suit the analysis requirement. Analysis results indicated that the uranium content was 0.08 μg/g in river water, 0.1 μg/g in evergreen foliage, and 5-11 μg/g in surface soil respectively. (authors)

  4. A combined chemical, isotopic and microstructural study of pyrite from roll-front uranium deposits, Lake Eyre Basin, South Australia

    Science.gov (United States)

    Ingham, Edwina S.; Cook, Nigel J.; Cliff, John; Ciobanu, Cristiana L.; Huddleston, Adam

    2014-01-01

    The common sulfide mineral pyrite is abundant throughout sedimentary uranium systems at Pepegoona, Pepegoona West and Pannikan, Lake Eyre Basin, South Australia. Combined chemical, isotopic and microstructural analysis of pyrite indicates variation in fluid composition, sulfur source and precipitation conditions during a protracted mineralization event. The results show the significant role played by pyrite as a metal scavenger and monitor of fluid changes in low-temperature hydrothermal systems. In-situ micrometer-scale sulfur isotope analyses of pyrite demonstrated broad-scale isotopic heterogeneity (δ34S = -43.9 to +32.4‰VCDT), indicative of complex, multi-faceted pyrite evolution, and sulfur derived from more than a single source. Preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation. Authigenic pyrite underwent prolonged evolution and recrystallization, evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra. Secondary hydrothermal pyrite commonly displays hyper-enrichment of several trace elements (Mn, Co, Ni, As, Se, Mo, Sb, W and Tl) in ore-bearing horizons. Hydrothermal fluids of magmatic and meteoric origins supplied metals to the system but the geochemical signature of pyrite suggests a dominantly granitic source and also the influence of mafic rock types. Irregular variation in δ34S, coupled with oscillatory trace element zonation in secondary pyrite, is interpreted in terms of continuous variations in fluid composition and cycles of diagenetic recrystallization. A late-stage oxidizing fluid may have mobilized selenium from pre-existing pyrite. Subsequent restoration of reduced conditions within the aquifer caused ongoing pyrite re-crystallization and precipitation of selenium as native selenium. These results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at Beverley North. Insights into

  5. Variation of uranium isotopes in some carbonate aquifers

    International Nuclear Information System (INIS)

    Cowart, J.B.

    1980-01-01

    The 234 U/ 238 U alpha activity ratio (AR) and uranium concentrations are reported for 83 springs that issue from carbonate aquifers in Florida, Texas, Nevada-California, and Israel. Data for each aquifer fall within more or less mutually exclusive fields. In general, the spring in a humid climate have AR's approaching secular equilibrium, whereas those in more arid climates have AR's differing greatly from equilibrium

  6. Stable isotopic composition of East African lake waters

    International Nuclear Information System (INIS)

    Odada, E.O.

    2001-01-01

    The investigation of stable isotopic composition of East African lake waters was conducted by scientists from the Department of Geology, University of Nairobi, as part of the International Decade for the East African Lakes (IDEAL) project and in close collaboration with the scientists from Large Lakes Observatory of the University of Minnesota and the Isotope Hydrology Laboratory of the IAEA in Vienna. The Research Contract was part of the IAEA Co-ordinated Research Programme on Isotope Techniques in Lake Dynamics Investigations, and was sponsored by the Agency. Water and grab sediment samples were obtained from East African Lakes during the month of January and February 1994 and July/August 1995. Water samples were analysed for oxygen and deuterium isotopic composition at the IAEA Laboratories in Vienna, Austria. In this final paper we report the results of the study of oxygen and deuterium isotopic composition from the East African lake waters. (author)

  7. Calculation of isotope selective excitation of uranium isotopes using spectral simulation method

    International Nuclear Information System (INIS)

    Al-Hassanieh, O.

    2009-06-01

    Isotope ratio enhancement factor and isotope selectivity of 235 U in five excitation schemes (I: 0→10069 cm - 1 →IP, II: 0 →10081 cm - 1 →IP, III: 0 →25349 cm - 1→ IP, IV: 0→28650 cm - 1 →IP, V: 0→16900 cm - 1 →34659 cm - 1 →IP), were computed by a spectral simulation approach. The effect of laser bandwidth and Doppler width on the isotope ratio enhancement factor and isotope selectivity of 235 U has been studied. The photoionization scheme V gives the highest isotope ratio enhancement factor. The main factors which effect the separation possibility are the isotope shift and the relative intensity of the transitions between hyperfine levels. The isotope ratio enhancement factor decreases exponentially by increasing the Doppler width and the laser bandwidth, where the effect of Doppler width is much greater than the effect of the laser bandwidth. (author)

  8. The isotopic composition of CO in vehicle exhaust

    NARCIS (Netherlands)

    Naus, S.; Röckmann, T.; Popa, M.E.

    2018-01-01

    We investigated the isotopic composition of CO in the exhaust of individual vehicles. Additionally, the CO 2 isotopes, and the CO:CO 2 , CH 4 :CO 2 and H 2 :CO gas ratios were measured. This was done under idling and revving conditions, and for three vehicles in a full driving cycle on a testbench.

  9. Rubidium-strontium and uranium-lead isotopic age studies

    International Nuclear Information System (INIS)

    Loveridge, W.D.

    1981-01-01

    The results of five Rb-Sr isotopic age studies predominantly on whole-rock samples, and six U-Pb studies on zircon monazite concentrates are presented. Descriptions of the geological problems and interpretations of the measured ages are included. Laboratory age determination methods and techniques are described or referenced

  10. Experimental study on isotope fractionation of evaporating water of different initial isotopic composition

    International Nuclear Information System (INIS)

    Pooja Devi; Jain, A.K.; Rao, M.S.; Kumar, B.

    2014-01-01

    The studies of evaporative isotopic fractionation in controlled conditions are of particular importance for understanding the mechanism of evaporation fractionation in natural conditions. We present the measurements of the average isotopic fractionation factors during the evaporation of water having different initial isotopic compositions at constant temperature. The results show that the isotopic composition of residual water become more enriched over the time and the initial isotopic composition of evaporating water has considerable effect on the average isotopic fractionation factors. The average isotopic fractionation factors in evaporation of Water A and Water B under the present experimental conditions were found to be 0.9817 ± 0.0044 and 0.9887 ± 0.0031 for oxygen and 0.9178 ± 0.0182 and 0.9437 ± 0.0169 for hydrogen, respectively. The findings of this work should lead to a better understanding and use of stable isotope techniques in isotope hydrology by using a simple technique of evaporation pan. (author)

  11. Uranium, radium and 40K isotopes in bottled mineral waters from Outer Carpathians, Poland

    International Nuclear Information System (INIS)

    Kozlowska, B.; Walencik, A.; Dorda, J.; Przylibski, T.A.

    2007-01-01

    Radioactivity content in commercially bottled mineral waters from Outer Carpathians was investigated on the basis of 28 samples. Activity concentration results for radium isotopes 226,228 Ra, uranium isotopes 234,238 U and isotopic ratios 234 U/ 238 U were determined. The correlations between investigated isotopes and calculated potassium 40 K ions dissolved in water were carried out. The results show a correlation between TDS (total dissolved solids) values and dissolved radionuclides. High correlation coefficients were observed between total radium content and 40 K. The isotopic ratio of 234 U/ 238 U varies in the range from 1.6 to 7 in all investigated waters which means that there is no radioactive equilibrium between the parent nuclide 238 U and its daughter 234 U. The effective radiation dose coming from studied radium and uranium radionuclides consumed with mineral water from the Outer Carpathians obtained by a statistical Pole is equal to 4.3μSv/year (58 l/year water consumption) and do not exceed the permissible limit equal to 100μSv/year. Assuming 0.5 l consumption per day, i.e. 182.5 l/year, the effective dose is equal to 13.4μSv/year, what is still below the unit

  12. Nuclear structure of Uranium isotopes in the frame work of two parameter formula

    International Nuclear Information System (INIS)

    Vidya Devi; Gupta, J.B.

    2017-01-01

    We studied the power law, ab formula and SRF which are applicable for both deformed and soft nuclei. The formula is particularly successful in soft rotor and deformed nuclei with 2:8≤ R 4/2 3:3. The power law gives good fit of the data for b and a derived either from 2 + , 4 + or 6 + , 8 + energy levels. This study help to understand the structure of isotopes of Uranium and useful to find some new energy level of these isotopes theoretically

  13. Isotopic composition of atmospheric moisture from pan water evaporation measurements.

    Science.gov (United States)

    Devi, Pooja; Jain, Ashok Kumar; Rao, M Someshwer; Kumar, Bhishm

    2015-01-01

    A continuous and reliable time series data of the stable isotopic composition of atmospheric moisture is an important requirement for the wider applicability of isotope mass balance methods in atmospheric and water balance studies. This requires routine sampling of atmospheric moisture by an appropriate technique and analysis of moisture for its isotopic composition. We have, therefore, used a much simpler method based on an isotope mass balance approach to derive the isotopic composition of atmospheric moisture using a class-A drying evaporation pan. We have carried out the study by collecting water samples from a class-A drying evaporation pan and also by collecting atmospheric moisture using the cryogenic trap method at the National Institute of Hydrology, Roorkee, India, during a pre-monsoon period. We compared the isotopic composition of atmospheric moisture obtained by using the class-A drying evaporation pan method with the cryogenic trap method. The results obtained from the evaporation pan water compare well with the cryogenic based method. Thus, the study establishes a cost-effective means of maintaining time series data of the isotopic composition of atmospheric moisture at meteorological observatories. The conclusions drawn in the present study are based on experiments conducted at Roorkee, India, and may be examined at other regions for its general applicability.

  14. Carbon isotopic composition of fossil leaves from the Early ...

    Indian Academy of Sciences (India)

    considerable variation in carbon isotopic composition. The Trambau ... One of the most significant changes in the ocean atmosphere .... cryogenic separation of water, CO2 was dynami- .... light condition, nutrients and temperature are low,.

  15. Characters of chlorine isotopic composition in ocean water

    Digital Repository Service at National Institute of Oceanography (India)

    Xiao, Y.; Zhou, Y.; Liu, W.G.; Hong, A.; Wang, Q.; Wang, Y.; Wei, H.; Shirodkar, P.V.

    The chlorine isotopic composition of ocean water was determined using thermal ionization mass spectrometry based on the measurement of Cs sub(2) Cl sup(+) ion. The results show that the sup(37) Cl/ sup(35) Cl ratios are basically homogeneous...

  16. Lead isotopes as indicators of environmental contamination from the uranium mining and milling industry in the Grants Mineral Belt, New Mexico

    International Nuclear Information System (INIS)

    Curtis, D.B.; Gancarz, A.J.

    1978-01-01

    The unique isotopic composition of lead from uranium ores can be useful in studying the impact of ore processing effluents on the environment. Common lead on the earth's surface is composed of 1.4% 204 Pb, 24.1% 206 Pb, 22.1% 207 Pb, and 52.4% 208 Pb. In contrast, lead associated with young uranium ores may contain as much as 95% 206 Pb. These extreme differences provide the means to quantitatively evaluate the amount of lead introduced into the environment from the mining and milling of uranium ores by measuring variations of the isotopic composition of lead in environmental samples. The use of Pb isotopes as diagnostic tools in studying the hydrologic transport of materials from U ore dressing plants in the Grants Mineral Belt, New Mexico, is discussed. Preliminary measurements on effluents intimately associated with processing wastes are consistent with a simple model in which radiogenic lead from the ores is mixed with common lead from the uncontaminated environments

  17. Isotopic feature and uranium dating of the volcanic rocks in the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Volcanic rocks from the northern and middle Okinawa Trough were dated by uranium-series dating method. Differential fractions using magnetic procedure were designed to separate samples. New report on the ages and isotopic data of rocks in the northern trough (especially black pumice) was discussed. Based on the uranium dates and Sr-Nd isotopic ratio, magmatic evolution process of the Okinawa Trough was noted. Firstly, there have been wide silicic volcanic activities in the Okinawa Trough from late Pleistocene to present, and the volcanic rocks can be divided into three subgroups. Secondly, magma generally came from PREMA source area under the Okinawa Trough. Magmatic evolution in the northern trough was similar to the middle, but different to the south. Finally, volcanic activities indicated that opening of the southern Okinawa Trough did not happen due to the collision between Luson Arc and Eurasian Plate until the early Pleistocene.

  18. Determination of total uranium by mass spectrometry utilizing the isotopic dilution technique

    International Nuclear Information System (INIS)

    Cretella, R.F.; Noutary, C.J.; Servant, R.E.

    1981-01-01

    The isotopic dilution associated to mass spectrometry is a high-sensitivity technique that allows to work with microquantities of the sample, making it possible to analize the content in highly radioactive solutions with excellent accuracy and minimum risk. The proposed technique is described and its results are discussed through the analysis of: 1) A synthetic sample that simulates dissolved spent fuel elements; 2) Uranium dioxide of nuclear purity and 3) Uranium concentrate. 233 U(ORNL) was employed as a tracer and a Nuclide 12-90-SU mass spectrometer of simple magnetic focus as measurement instrument. The accuracy reached in the analyses is better than 0.5% with a reliability of 95%. The analysis of the errors shows that their main contributing source are the errors in the measurement of the isotopic ratios. (M.E.L.) [es

  19. Spectroscopic and thermal properties of uranium relevant to atomic schemes for laser isotope separation

    International Nuclear Information System (INIS)

    Ahmad, S.A.; Pandey, P.L.

    1980-01-01

    Spectroscopic data on uranium atom and thermal properties of uranium relevant to atomic schemes for laser isotope separation have been presented in this report. All the relevant spectroscopic data reported in literature so far, as well as some other parameters like photo-absorption cross sections, branching ratios, effects of magnetic and electric fields, evaluated using the existing data, have been presented here. Among the thermal properties, parameters like vapour pressure and number densities for U/Liquid U, U/URe 2 and U/UP systems, partition function, percentage population distribution in energy levels, thermal ionisation and velocities of uranium atom have been presented at different temperatures. Different possible collision processes are mentioned and cross-sections of U-U + charge-exchange and U + + e radiative recombination processes have been also evaluated. (author)

  20. Characteristics of isotope geology of sandstone-type uranium deposit in Turpan-Hami Basin

    International Nuclear Information System (INIS)

    Liu Hanbin; Xia Yuliang; Lin Jinrong; Fan Guang

    2003-01-01

    This paper expounds the isotope characteristics of in-situ leachable sandstone-type uranium deposit of Shihongtan in the southwestern part of Turpan-Hami basin. The results suggest that uranium mineralization age of 48 ± 2 Ma and 28 ± 4 Ma are obtained. The ages of the porphyritic granite and gneissic granite from the southwestern area are 422 ± 5 Ma and 268 ± 23 Ma. The U-Pb age of clastic zircons from ore-bearing sandstone is 283 ± 67 Ma, which is corresponding to the age of gneissic granite of the provenance area indicating the material source of uraniferous sandstone.Based. The sources are uraniferous sandstone accumulated during the deposition and the uranium leached from provenance area rocks by weathering. (authors)

  1. Isotopic compositions of the elements 2013 (IUPAC Technical Report)

    Science.gov (United States)

    Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna; Loss, Robert D.; Walczyk, Thomas; Prohaska, Thomas

    2016-01-01

    The Commission on Isotopic Abundances and Atomic Weights (ciaaw.org) of the International Union of Pure and Applied Chemistry (iupac.org) has revised the Table of Isotopic Compositions of the Elements (TICE). The update involved a critical evaluation of the recent published literature. The new TICE 2013 includes evaluated data from the “best measurement” of the isotopic abundances in a single sample, along with a set of representative isotopic abundances and uncertainties that accommodate known variations in normal terrestrial materials.

  2. The importance of colloids and mires for the transport of uranium isotopes through the Kalix River watershed and Baltic Sea

    International Nuclear Information System (INIS)

    Porcelli, D.; Wasserburg, G.J.; Andersson, P.S.

    1997-01-01

    The importance of colloids and organic deposits for the transport of uranium isotopes from continental source regions and through the estuarine environment was investigated in the mire-rich Kalix River drainage basin in northern Sweden and the Baltic Sea. Ultrafiltration techniques were used to separate uranium and other elements associated with colloids > 10 kD and >3 kD from open-quotes soluteclose quotes uranium and provided consistent results and high recovery rates for uranium as well as for other elements from large volume samples. Uranium concentrations in 0.45 μm-filtered Kalix River water samples increased by a factor of 3 from near the headwaters in the Caledonides to the river mouth while major cation concentrations were relatively constant. 234 U 238 U ratios were high (δ 234 U = 770-1500) throughout the basin, without showing any simple pattern, and required a supply of 234 U-rich water. Throughout the Kalix River, a large fraction (30-90%) of the uranium is carried by >10 kD colloids, which is compatible with uranium complexation with humic acids. No isotopic differences were found between colloid-associated and solute uranium. Within the Baltic Sea, about half of the uranium is removed at low salinities. The proportion that is lost is equivalent to that of river-derived colloid-bound uranium, suggesting that while solute uranium behaves conservatively during estuarine mixing, colloid-bound uranium is lost due to rapid flocculation of colloidal material. The association of uranium with colloids therefore may be an important parameter in determining uranium estuarine behavior. Mire peats in the Kalix River highly concentrate uranium and are potentially a significant source of recoil 234 U to the mirewaters and river waters. However, mirewater data clearly demonstrate that only small 234 U/ 238 U shifts are generated relative to inflowing groundwater. 63 refs., 8 figs., 3 tabs. groundwater. 63 refs., 8 figs., 3 tabs

  3. Analysis and optimization of gas-centrifugal separation of uranium isotopes by neural networks

    Directory of Open Access Journals (Sweden)

    Migliavacca S.C.P.

    2002-01-01

    Full Text Available Neural networks are an attractive alternative for modeling complex problems with too many difficulties to be solved by a phenomenological model. A feed-forward neural network was used to model a gas-centrifugal separation of uranium isotopes. The prediction showed good agreement with the experimental data. An optimization study was carried out. The optimal operational condition was tested by a new experiment and a difference of less than 1% was found.

  4. Improved Technique for the Determination of Uranium Minor Isotopes Concentrations in Microparticles by Using Secondary Ion Mass-Spectrometer in Multicollection Mode

    International Nuclear Information System (INIS)

    Aleshin, M.; Elantyev, I.; Stebelkov, Y.

    2015-01-01

    Traditional method of the analysis implies simultaneous measuring of secondary ion currents of isotopes 234U + , 235U + , 238U + , ions with mass 236 amu (236U + and 235UH + ) and hydride ions 238UH + by using mass-spectrometer Cameca IMS1280 in multicollection mode. Calculating of uranium isotopic composition is performed using the results of 40 successive measurements of those currents (cycles). Duration of each measurement is 8 s. Small amounts of uranium minor isotopes are limitation for precise determination of their concentrations. To prevent the damage of the secondary ions detector the intensity of ion current should be no more than 5 x 10 5 s -1 . This limitation does not allow setting a higher primary ion current for the increasing of minor uranium isotopes ions emission because of the signal of ions 238U + gets too high. New technique is developed to improve the accuracy of determination of uranium minor isotopes concentrations. Process of measurement is divided on two steps. First step is a measurement of ion currents during 20 cycles by five detectors. The second step implies the elimination of ions 238U + hitting to the detector and 10 times increasing of primary ion current. The ratio 235U/238U is calculated from the first step results, so uncertainty of determination of this value is 1.4 times bigger than with duration of 40 cycles of the measurement. The ratios 234U/235U and 236U/235U are calculated during the second step. This technique allows to determine content of 234U and 236U with 3 and 5 times less uncertainties respectively, but with different degree of the sputtering particles. Moreover the duration of each cycle was set less (1 second) to use data more efficient. The technique accordingly with every second counting provides uncertainty of determination 236U concentration 4 times less than traditional method at the same degree of sputtering particles. (author)

  5. Device for the separation of isotopic uranium compounds

    International Nuclear Information System (INIS)

    Niemann, H.J.; Sprehe, J.

    1985-01-01

    The UF6-isotopes selectively converted by low radiation are contained in a beam. The boundary region of this gas beam hits a target which is oriented in vertical angle to the gas beam and exerts a compression shock on it. This peel border leads to diversion of the reaction products of light mass, whereas the heavy mass, products flow into a receiver. (orig./PW)

  6. Uranium Isotopes in Calcium Carbonate: A Possible Proxy for Paleo-pH and Carbonate Ion Concentration?

    Science.gov (United States)

    Chen, X.; Romaniello, S. J.; Herrmann, A. D.; Wasylenki, L. E.; Anbar, A. D.

    2015-12-01

    Natural variations of 238U/235U in marine carbonates are being explored as a paleoredox proxy. However, in order for this proxy to be robust, it is important to understand how pH and alkalinity affect the fractionation of 238U/235U during coprecipitation with calcite and aragonite. Recent work suggests that the U/Ca ratio of foraminiferal calcite may vary with seawater [CO32-] concentration due to changes in U speciation[1]. Here we explore analogous isotopic consequences in inorganic laboratory co-precipitation experiments. Uranium coprecipitation experiments with calcite and aragonite were performed at pH 8.5 ± 0.1 and 7.5 ± 0.1 using a constant addition method [2]. Dissolved U in the remaining solution was periodically collected throughout the experiments. Samples were purified with UTEVA resin and 238U/235U was determined using a 233U-236U double-spike and MC-ICP-MS, attaining a precision of ± 0.10 ‰ [3]. Small but resolvable U isotope fractionation was observed in aragonite experiments at pH ~8.5, preferentially enriching heavier U isotopes in the solid phase. 238U/235U of the dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00002 - 1.00009. In contrast, no resolvable U isotope fractionation was detected in an aragonite experiment at pH ~7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among dissolved U species is the most likely mechanism driving these isotope effects. Our quantitative model of this process assumes that charged U species are preferentially incorporated into CaCO3 relative to the neutral U species Ca2UO2(CO3)3(aq), which we hypothesize to have a lighter equilibrium U isotope composition than the charged U species. According to this model, the magnitude of U isotope fractionation should scale with the fraction of the neutral U species in the solution, in agreement with our experimental results. These findings suggest that U isotope variations in

  7. Research and development prospects for the atomic uranium laser isotope separation process. Research report 442

    International Nuclear Information System (INIS)

    Janes, G.S.; Forsen, H.K.; Levy, R.H.

    1977-06-01

    Research and development activities are being conducted on many aspects of the atomic uranium laser isotope separation process. Extensive laser spectroscopy studies have been made in order to identify attractive multi-step selective ionization schemes. Using low density (10 10 atoms/cm 3 ) apparatus, the excited state spectra of atomic uranium have been investigated via multiple step laser excitation and photoionization studies using two, three and four pulsed lasers. Observation of the spectra was accomplished by observing the yield of 235 U and 238 U ions as a function of the wavelength, intensities and delays of the various lasers. These data yielded information on the photoexcitation and photoionizatin cross sections, and on the location, J values, lifetimes, isotope shifts and hyperfine structure of the various atomic levels of uranium. Experiments on selective ionization of uranium vapor by multiple step laser excitation followed by ion extraction at 10 13 atoms/cm 3 density have produced 6% enriched 235 U. These indicate that this process is well adapted to produce light water reactor fuel but less suitable for highly enriched material. Application has been made for license for a 1979 experimental facility to provide data for a mid-1980 commercial plant

  8. Factors controlling stable isotope composition of European precipitation

    International Nuclear Information System (INIS)

    Rozanski, K.; Sonntag, C.; Muennich, K.O.

    1982-01-01

    The seasonal and spatial variations of stable isotope ratios in present day European precipitation are simulated with a simple multibox model of the mean west-east horizontal transport of the atmospheric water vapour across the European continent. Isotope fractionation during the formation of precipitation leads to an increasing depletion of heavy isotopes in the residual air moisture as it moves towards the centre of the continent. This isotopic depletion is partly compensated, particularly in summer, by evapotranspiration, which is assumed to transfer soil water into the atmosphere without isotope fractionation. The model estimates are based on horizontal water vapour flux data, varying seasonally between 88 and 130 kg m -1 s -1 for the Atlantic coast region, and on the monthly precipitation, evapotranspiration and surface air temperature data available for various locations in Europe. Both continental and seasonal temperature effects observed in the stable isotope composition of European precipitation are fairly well reproduced by the model. The calculations show that the isotopic composition of local precipitation is primarily controlled by regional scale processes, i.e. by the water vapour transport patterns into the continent, and by the average precipitation-evapotranspiration history of the air masses precipitating at a given place. Local parameters such as the surface and/or cloud base temperature or the amount of precipitation modify the isotope ratios only slightly. Implications of the model predictions for the interpretation of stable isotope ratios in earlier periods as they are preserved in ice cores and in groundwater are also discussed. (Auth.)

  9. Determination of uranium concentration and burn-up of irradiated reactor fuel in contaminated areas in Belarus using uranium isotopic ratios in soil samples

    International Nuclear Information System (INIS)

    Mironov, V.P.; Matusevich, J.L.; Kudrjashov, V.P.; Ananich, P.I.; Zhuravkov, V.V.; Boulyga, S.F.; Becker, J.S.

    2005-01-01

    An analytical method is described for the estimation of uranium concentrations, of 235 U/ 238 U and 236 U/ 238 U isotope ratios and burn-up of irradiated reactor uranium in contaminated soil samples by inductively coupled plasma mass spectrometry. Experimental results obtained at 12 sampling sites situated on northern and western radioactive fallout tails 4 to 53 km distant from Chernobyl nuclear power plant (NPP) are presented. Concentrations of irradiated uranium in the upper 0-10 cm soil layers at the investigated sampling sites varied from 2.1 x 10 -9 g/g to 2.0 x 10 -6 g/g depending mainly on the distance from Chernobyl NPP. A slight variation of the degree of burn-up of spent reactor uranium was revealed by analyzing 235 U/ 238 U and 236 U/ 238 U isotope ratios and the average value amounted to 9.4±0.3 MWd/(kg U). (orig.)

  10. Separation of uranium and plutonium isotopes for measurement by multi collector inductively coupled plasma mass spectroscopy

    International Nuclear Information System (INIS)

    Martinelli, R.E.; Hamilton, T.F.; Kehl, S.R.; Williams, R.W.

    2009-01-01

    Uranium (U) and plutonium (Pu) isotopes in coral soils, contaminated by nuclear weapons testing in the northern Marshall Islands, were isolated by ion-exchange chromatography and analyzed by mass spectrometry. The soil samples were spiked with 233 U and 242 Pu tracers, dissolved in minerals acids, and U and Pu isotopes isolated and purified on commercially available ion-exchange columns. The ion-exchange technique employed a TEVA R column coupled to a UTEVA R column. U and Pu isotope fractions were then further isolated using separate elution schemes, and the purified fractions containing U and Pu isotopes analyzed sequentially using multi-collector inductively coupled plasma mass spectrometer (MCICP-MS). High precision measurements of 234 U/ 235 U, 238 U/ 235 U, 236 U/ 235 U, and 240 Pu/ 239 Pu in soil samples were attained using the described methodology and instrumentation, and provide a basis for conducting more detailed assessments of the behavior and transfer of uranium and plutonium in the environment. (author)

  11. Uptake of uranium, thorium and radium isotopes by plants growing in dam impoundment Tasotkel and the Lower Shu region (Kazakhstan)

    Energy Technology Data Exchange (ETDEWEB)

    Matveyeva, Ilona; Burkitbayev, Mukhambetkali [al-Farabi Kazakh National University, Almaty (Kazakhstan). Faculty of Chemistry and Chemical Technology; Jacimovic, Radojko [Jozef Stefan Institute, Ljubljana (Slovenia). Dept. of Environmental Sciences; Planinsek, Petra; Smodis, Borut [Jozef Stefan Institute, Ljubljana (Slovenia). Dept. of Environmental Sciences; Jozef Stefan International Postgraduate School, Ljubljana (Slovenia)

    2016-04-01

    The activity concentrations of isotopes of uranium, thorium and radium-226 in dominant species of plants (Xantium strumarium, Phragmites communis, Artemisia nitrosa and Artemisia serotina) growing on the territories contaminated by uranium industry of Kazakhstan (close to dam impoundment Tasotkel and the Lower Shu region) are presented. The obtained data showed the significant variations of activity concentrations of isotopes of uranium, thorium and radium-226 in above ground parts. The concentrations of most of the investigated radionuclides in the root system are higher than in the aboveground parts; it can be explained by root barrier. It was found that the highest root barrier has Xantium strumarium, especially for uranium isotopes. The concentration ratios of radionuclides were calculated, and as the result it was found that the highest accumulation ability in the investigated region has Artemisia serotina.

  12. Uptake of uranium, thorium and radium isotopes by plants growing in dam impoundment Tasotkel and the Lower Shu region (Kazakhstan)

    International Nuclear Information System (INIS)

    Matveyeva, Ilona; Burkitbayev, Mukhambetkali

    2016-01-01

    The activity concentrations of isotopes of uranium, thorium and radium-226 in dominant species of plants (Xantium strumarium, Phragmites communis, Artemisia nitrosa and Artemisia serotina) growing on the territories contaminated by uranium industry of Kazakhstan (close to dam impoundment Tasotkel and the Lower Shu region) are presented. The obtained data showed the significant variations of activity concentrations of isotopes of uranium, thorium and radium-226 in above ground parts. The concentrations of most of the investigated radionuclides in the root system are higher than in the aboveground parts; it can be explained by root barrier. It was found that the highest root barrier has Xantium strumarium, especially for uranium isotopes. The concentration ratios of radionuclides were calculated, and as the result it was found that the highest accumulation ability in the investigated region has Artemisia serotina.

  13. Elemental and Isotopic Analysis of Uranium Oxide an NIST Glass Standards by FEMTOSECOND-LA-ICP-MIC-MS

    International Nuclear Information System (INIS)

    Ebert, Chris; Zamzow, Daniel S.; McBay, Eddie H.; Bostick, Debra A.; Bajic, Stanley J.; Baldwin, David P.; Houk, R.S.

    2009-01-01

    The objective of this work was to test and demonstrate the analytical figures of merit of a femtosecond-laser ablation (fs-LA) system coupled with an inductively coupled plasma-multi-ion collector-mass spectrometer (ICP-MIC-MS). The mobile fs-LA sampling system was designed and assembled at Ames Laboratory and shipped to Oak Ridge National Laboratory (ORNL), where it was integrated with an ICP-MIC-MS. The test period of the integrated systems was February 2-6, 2009. Spatially-resolved analysis of particulate samples is accomplished by 100-shot laser ablation using a fs-pulsewidth laser and monitoring selected isotopes in the resulting ICP-MS transient signal. The capability of performing high sensitivity, spatially resolved, isotopic analyses with high accuracy and precision and with virtually no sample preparation makes fs-LA-ICP-MIC-MS valuable for the measurement of actinide isotopes at low concentrations in very small samples for nonproliferation purposes. Femtosecond-LA has been shown to generate particles from the sample that are more representative of the bulk composition, thereby minimizing weaknesses encountered in previous work using nanosecond-LA (ns-LA). The improvement of fs- over ns-LA sampling arises from the different mechanisms for transfer of energy into the sample in these two laser pulse-length regimes. The shorter duration fs-LA pulses induce less heating and cause less damage to the sample than the longer ns pulses. This results in better stoichiometric sampling (i.e., a closer correlation between the composition of the ablated particles and that of the original solid sample), which improves accuracy for both intra- and inter-elemental analysis. The primary samples analyzed in this work are (a) solid uranium oxide powdered samples having different 235 U to 238 U concentration ratios, and (b) glass reference materials (NIST 610, 612, 614, and 616). Solid uranium oxide samples containing 235 U in depleted, natural, and enriched abundances were

  14. Adsorptivity of uranium by aluminium-activated carbon composite adsorbent

    International Nuclear Information System (INIS)

    Katoh, Shunsaku; Sugasaka, Kazuhiko; Fujii, Ayako; Takagi, Norio; Miyai, Yoshitaka

    1976-01-01

    To research the adsorption process of uranium from sea water by aluminium-activated carbon composite adsorbent (C-Al-OH), the authors examined the effects of temperature, pH and carbonate ion concentration of the solution upon the adsorption of uranium, using sodium chloride solution and natural sea water. The continued mixing of the solution for the duration of two to four hours was required to attain the apparent equilibrium of adsorption. The adsorption velocity at an early stage and the uptake of uranium at the final stage showed an increase in proportion to a rise in the adsorption temperature. In the experiment of adsorption for which sodium chloride solution was used, the linear relationship between the logarithm of the distribution coefficient (K sub(d)) and the pH of the solution was recognized. The uptake of the uranium from the solution at the pH of 12 increased as the carbonate ion concentration in the solution decreased. The uranyl ion in the natural sea water was assumed to be uranyl carbonate complex ion (UO 2 (CO 3 ) 3 4- ). As the result of the calculation conducted by using the formation constants for uranyl complexes in literature, it was found that uranyl hydroxo complex ion (UO 2 (OH) 3 - ) increased in line with a decrease of the carbonate ion concentration in the solution. The above results of the experiment suggested that the adsorption of uranium by the adsorbent (C-Al-OH) was cationic adsorption or hydrolysis adsorption being related with the active proton on the surface of the adsorbent. (auth.)

  15. What Affects the Isotopic Composition of Precipitation - A New Interpretation?

    Energy Technology Data Exchange (ETDEWEB)

    Dody, A. [Nuclear Research Center, Negev, Beer Sheva (Israel)

    2013-07-15

    Rainfall events were sampled in high resolution for stable isotope analyses during four rainy seasons in the central negev of Israel. Each sample is equivalent to 1-2 mm of rain. High variability in the isotopic composition was found in fractions of rain during storms. Two modes of isotopic distribution were found. The first is a wave shaped distribution, where isotopic compositions showed enriched to depleted graded changes and vice versa. The second mode is a step function where each rain cell displayed a constant {delta}{sup 18}O value, but varied greatly from the other rain cells. New interpretation suggests that during the transport of the air parcel system three processes can occur. The first process is a complete blending among the rain cells. The second is a partial isotopic mixing between the rain cells. Finally the third case is when each rain cell maintains its own isotopic values separate from the other rain cells. The third case of no mixing showed unexpected results due to the high air turbulence, vertically and horizontally. There was no evidence of complete mixing among the rain cells of identical air parcel systems. The processes in the air parcel trajectory itself suggested here is put forward as a new way to explain the changes in the isotopic composition during the rain. (author)

  16. Characterization of groundwater composition in Punjab state with special emphasis on uranium content, speciation and mobility

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ajay; Rout, Sabyasachi; Mishra, Manish K.; Ravi, P.M. [Bhabha Atomic Reseach Centre, Mumbai (India). Health Physics Div.; Tripathi, R.M. [Bhabha Atomic Reseach Centre, Mumbai (India). Environmental Assessment Div.; Ghosh, A.K. [Bhabha Atomic Reseach Centre, Mumbai (India). Health, Safety and Environmental Group

    2014-04-01

    Groundwaters (borewell and handpump) were sampled from two districts (Bathinda and Mansa) of Punjab state and analyzed for their major ionic concentrations and uranium isotope compositions in order to assess the possible origins of the waters and water-rock interactions that occurred in the deep aquifer system. The major ionic concentrations of waters were plotted on a Piper diagram and grouped into four dominant hydrochemical facies as (Na+K)-SO{sub 4}+Cl type (69%-73%), (Ca+Mg)-SO{sub 4}+Cl type (6% - 21%), (Ca+Mg)-HCO{sub 3} type (4% - 6%) and (Na+K)-HCO{sub 3} type (2% - 19%). It was observed that mobility of uranium in groundwater was very much influenced by TDS (total dissolved solids). To investigate the various mechanisms for deriving the elevated uranium concentrations in groundwater, {sup 234}U/{sup 238}U activity ratios (ARs) were calculated using the determined activity levels of {sup 234}U and {sup 238}U. The mean ARs was found to be near unity (i.e. secular equilibrium) in the study regions confirmed that uranium in groundwaters was mainly resulted from its host/parent rocks through weathering processes. The concentration of HCO{sub 3}{sup -} in ground water showed one order of magnitude higher than the total dissolved SiO{sub 2} indicates that carbonate weathering was the dominant process due to major water-rock interaction. The uranium speciation in groundwaters was investigated by an equilibrium model calculation using MEDUSA (make equilibrium diagrams using sophisticated algorithms) under the influence of redox conditions and complexant concentration. At the observed range of pH values, the predominant redox speciation of uranium was observed as hydroxo-carbonato complexes of (UO{sub 2}){sub 2}(CO{sub 3})(OH){sub 3}{sup -} and hydroxyl complexes of UO{sub 2}(OH){sub 3}{sup -} which might be caused for increasing the solubility of uranium. Due to very low concentration of phosphate in groundwater, its effects on U(VI)-aqueous speciation was

  17. Spatiotemporal variation of stable isotopic composition in precipitation

    DEFF Research Database (Denmark)

    Müller, Sascha; Stumpp, Christine; Sørensen, Jens Havskov

    2017-01-01

    influences the isotopic composition at the study site. A simple model of evaporation on falling rain was applied with the aim to reproduce observational data and show the potential influence of changing humidity conditions on precipitation compositions. The rather simple model approach did not fully explain...

  18. The ruthenium isotopic composition of the oceanic mantle

    Science.gov (United States)

    Bermingham, K. R.; Walker, R. J.

    2017-09-01

    The approximately chondritic relative, and comparatively high absolute mantle abundances of the highly siderophile elements (HSE), suggest that their concentrations in the bulk silicate Earth were primarily established during a final ∼0.5 to 1% of ;late accretion; to the mantle, following the cessation of core segregation. Consequently, the isotopic composition of the HSE Ru in the mantle reflects an amalgamation of the isotopic compositions of late accretionary contributions to the silicate portion of the Earth. Among cosmochemical materials, Ru is characterized by considerable mass-independent isotopic variability, making it a powerful genetic tracer of Earth's late accretionary building blocks. To define the Ru isotopic composition of the oceanic mantle, the largest portion of the accessible mantle, we report Ru isotopic data for materials from one Archean and seven Phanerozoic oceanic mantle domains. A sample from a continental lithospheric mantle domain is also examined. All samples have identical Ru isotopic compositions, within analytical uncertainties, indicating that Ru isotopes are well mixed in the oceanic mantle, defining a μ100Ru value of 1.2 ± 7.2 (2SD). The only known meteorites with the same Ru isotopic composition are enstatite chondrites and, when corrected for the effects of cosmic ray exposure, members of the Main Group and sLL subgroup of the IAB iron meteorite complex which have a collective CRE corrected μ100Ru value of 0.9 ± 3.0. This suggests that materials from the region(s) of the solar nebula sampled by these meteorites likely contributed the dominant portion of late accreted materials to Earth's mantle.

  19. Uranium isotopic separation by aerodynamic methods. Final report

    International Nuclear Information System (INIS)

    Davidovitz, P.; Anderson, J.B.; Brook, J.W.; Calia, V.S.; Greene, G.T.

    1979-06-01

    Two aerodynamic separation techniques for uranium enrichment were investigated for technical feasibility and economic viability. These techniques are known as the Jet Membrane and Velocity Slip Processes. Both analytical and laboratory studies were conducted to explore the technical feasibility of the subject processes. The Jet Membrane Process Studies demonstrated that the process was feasible and that a condensable gas carrier is available. The Velocity Slip Studies demonstrated the predicted effects and did not identify a suitable condensable gas carrier. Hence the Velocity Slip Process exhibited a larger power consumption than did the Jet Membrane Process. An independent contractor prepared detailed cost estimates of the process. The independent results indicated that, based on the same costing ground rules, the Velocity Slip process would require 16 times the fixed capital costs and 12 times the cost per separative work unit as compared to the Jet Membrane Process. The same cost structure indicated that the cost per separative work unit for the Jet Membrane process would be two to three times that for the Gas Centrifuge process. There are a number of uncertainties associated with these cost estimates, such that, in the extreme, the costs might be the same. Further, more detailed cost analysis would be required to resolve the uncertainties associated with the initial cost estimates. The conduct of new studies was not considered to be appropriate for EPRI because of the changes in enrichment program management and security philosophy discussed in the text

  20. Uranium, plutonium, and thorium isotopes in the atmosphere and the lithosphere

    International Nuclear Information System (INIS)

    Essien, I.O.

    1983-01-01

    Concentration of 238 U in rain and snow collected at Fayetteville (36 0 N, 94 0 W), Arkansas, showed a marked increase during the summer months of 1980, while Mount St. Helens remained active. This observed increase of 238 U can be explained as due to the fallout of natural uranium from the eruption of Mount St. Helens. Large increases in the concentration of thorium isotopes detected in rain and snow samples during the last months of 1982 and early months of 1983 probably originated from the eruption of El Chichon volcano, which occurred on 28 March 1982. About 450 Ci of 232 Th is estimated to have been injected into the atmosphere by this eruption. Isotopic anomalies were observed in atmospheric samples such as rain and snow. These anomalies can be attributed to various natural as well as man-made sources: nuclear weapon tests, nuclear accidents involving the burn-up of nuclear powered satellites, and volcanic eruptions. The variation of 234 U/ 238 U ratios in radioactive minerals when leached with nitric acid were also noticed and this variation, while 235 U/ 238 U remained fairly constant, can be explained in terms of the α-recoil effect and changes in oxidation state of uranium. Difference found in 239 Pu/ 238 U ratios in terrestrial samples and uranium minerals can be explained as due to fallout contamination

  1. Standard test method for radiochemical determination of uranium isotopes in soil by alpha spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 This test method covers the determination of alpha-emitting uranium isotopes in soil. This test method describes one acceptable approach to the determination of uranium isotopes in soil. 1.2 The test method is designed to analyze 10 g of soil; however, the sample size may be varied to 50 g depending on the activity level. This test method may not be able to completely dissolve all forms of uranium in the soil matrix. Studies have indicated that the use of hydrofluoric acid to dissolve soil has resulted in lower values than results using total dissolution by fusion. 1.3 The lower limit of detection is dependent on count time, sample size, detector, background, and tracer yield. The chemical yield averaged 78 % in a single laboratory evaluation, and 66 % in an interlaboratory collaborative study. 1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. 1.5 This standard does not purport to address all of the safety concerns, if any, ass...

  2. Investigations into Pb isotope signatures in groundwater and sediments in a uranium-mineralized area

    Energy Technology Data Exchange (ETDEWEB)

    Vecchia, Adriana Monica Dalla; Rodrigues, Paulo Cesar Horta; Rios, Francisco Javier; Ladeira, Ana Claudia Queiroz, E-mail: amdvc@cdtn.br, E-mail: acql@cdtn.br, E-mail: javier@cdtn.br, E-mail: pchr@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-01-15

    This work presents the investigation in an environment that contains uranium deposits by using Pb isotope signatures. The study area, southeast of Brazil, is characterized by the lack of surface water and, as a consequence, the groundwater plays an important role in the economy of the region, such as the supply to the uranium industry and, above all serving the needs of the local population. The objective of the present investigation is the determination of the signatures of Pb in groundwater and sediments as well as the identification of environments under influences of geogenic and/or anthropogenic sources. It was determined that the Pb in the majority of sediments was geogenic in origin. Although data from the literature, related to the environmental studies, consider {sup 206}Pb/{sup 207}Pb isotopic ratio values below or close to 1.2 as an indicative of anthropogenic Pb, the {sup 206}Pb/{sup 207}Pb determined for the majority of groundwater samples ranged from 1.14 to 1.19, and are similar to the data reported for rocks samples (1.09 to 1.96) from area with U mineralization. It was also determined that the anthropogenic influence of the uranium was restricted to a single sampling point within the mining area. (author)

  3. Investigations into Pb isotope signatures in groundwater and sediments in a uranium-mineralized area

    Directory of Open Access Journals (Sweden)

    Adriana Mônica Dalla Vecchia

    Full Text Available ABSTRACT: This work presents the investigation in an environment that contains uranium deposits by using Pb isotope signatures. The study area, southeast of Brazil, is characterized by the lack of surface water and, as a consequence, the groundwater plays an important role in the economy of the region, such as the supply to the uranium industry and, above all serving the needs of the local population. The objective of the present investigation is the determination of the signatures of Pb in groundwater and sediments as well as the identification of environments under influences of geogenic and/or anthropogenic sources. It was determined that the Pb in the majority of sediments was geogenic in origin. Although data from the literature, related to the environmental studies, consider 206Pb/207Pb isotopic ratio values below or close to 1.2 as an indicative of anthropogenic Pb, the 206Pb/ 207Pb determined for the majority of groundwater samples ranged from 1.14 to 1.19, and are similar to the data reported for rocks samples (1.09 to 1.96 from area with U mineralization. It was also determined that the anthropogenic influence of the uranium was restricted to a single sampling point within the mining area.

  4. Report on the NAT-9 quality control exercise on uranium isotopes in two soil samples

    International Nuclear Information System (INIS)

    Bleise, Andreas

    2001-04-01

    The International Atomic Energy Agency (IAEA) section of Nutritional and Health related Environmental Studies (NAHRES) organized a quality control study for laboratories analysing samples from the UNEP field mission to Kosovo. Quality control was the major responsibility of the IAEA in the UN field assessment team. The NAT-9 quality control study consists of two soil materials from the IAEA Laboratories in Seibersdorf. The scope of this exercise was to determine the content of the uranium isotopes U-234, U-235 and U-238. The IAEA did not provide specific instructions, the participants were encouraged to apply their established analytical procedures to the samples. Five laboratories were invited to participate, four laboratories submitted results. For each soil sample 10 laboratory mean values were reported, using ICP-MS (3 laboratories) and α-spectrometry (1 laboratory). The participating laboratories were capable to distinguish the different uranium isotopes. All laboratories obtained the natural uranium ratio between U-235 and U-238. However, the results highlight a particular analytical weak spot. Although the methods of measuring the analytical signals are highly dependable, the sample preparation steps, in particular the sample dissolution procedure, appears to be lacking total quality control and has contributed to the deviations from the reported target values. One laboratory has documented evidence that extensive and well-controlled digestion methods can yield measurement results close to the target values. (author)

  5. Uranium isotope evidence for an expansion of marine anoxia during the end-Triassic extinction

    Science.gov (United States)

    Jost, Adam B.; Bachan, Aviv; van de Schootbrugge, Bas; Lau, Kimberly V.; Weaver, Karrie L.; Maher, Kate; Payne, Jonathan L.

    2017-08-01

    The end-Triassic extinction coincided with an increase in marine black shale deposition and biomarkers for photic zone euxinia, suggesting that anoxia played a role in suppressing marine biodiversity. However, global changes in ocean anoxia are difficult to quantify using proxies for local anoxia. Uranium isotopes (δ238U) in CaCO3 sediments deposited under locally well-oxygenated bottom waters can passively track seawater δ238U, which is sensitive to the global areal extent of seafloor anoxia due to preferential reduction of 238U(VI) relative to 235U(VI) in anoxic marine sediments. We measured δ238U in shallow-marine limestones from two stratigraphic sections in the Lombardy Basin, northern Italy, spanning over 400 m. We observe a ˜0.7‰ negative excursion in δ238U beginning in the lowermost Jurassic, coeval with the onset of the initial negative δ13C excursion and persisting for the duration of subsequent high δ13C values in the lower-middle Hettangian stage. The δ238U excursion cannot be realistically explained by local mixing of uranium in primary marine carbonate and reduced authigenic uranium. Based on output from a forward model of the uranium cycle, the excursion is consistent with a 40-100-fold increase in the extent of anoxic deposition occurring worldwide. Additionally, relatively constant uranium concentrations point toward increased uranium delivery to the oceans from continental weathering, which is consistent with weathering-induced eutrophication following the rapid increase in pCO2 during emplacement of the Central Atlantic Magmatic Province. The relative timing and duration of the excursion in δ238U implies that anoxia could have delayed biotic recovery well into the Hettangian stage.

  6. Soil Carbon: Compositional and Isotopic Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Moran, James J.; Alexander, M. L.; Laskin, Alexander

    2016-11-01

    This is a short chapter to be included in the next edition of the Encyclopedia of Soil Science. The work here describes techniques being developed at PNNL for investigating organic carbon in soils. Techniques discussed include: laser ablation isotope ratio mass spectrometry, laser ablation aerosol mass spectrometry, and nanospray desorption electrospray ionization mass spectrometry.

  7. Characteristics of stable carbon isotopic composition of shale gas

    Directory of Open Access Journals (Sweden)

    Zhenya Qu

    2016-04-01

    Full Text Available A type Ⅱ kerogen with low thermal maturity was adopted to perform hydrocarbon generation pyrolysis experiments in a vacuum (Micro-Scale Sealed Vessel system at the heating rates of 2 °C/h and 20 °C/h. The stable carbon isotopic compositions of gas hydrocarbons were measured to investigate their evolving characteristics and the possible reasons for isotope reversal. The δ13C values of methane became more negative with the increasing pyrolysis temperatures until it reached the lightest point, after which they became more positive. Meanwhile, the δ13C values of ethane and propane showed a positive trend with elevating pyrolysis temperatures. The carbon isotopic compositions of shale gasses were mainly determined by the type of parent organic matter, thermal evolutionary extent, and gas migration in shale systems. Our experiments and study proved that the isotope reversal shouldn't occur in a pure thermogenic gas reservoir, it must be involved with some other geochemical process/es; although mechanisms responsible for the reversal are still vague. Carbon isotopic composition of the Fayetteville and Barnett shale gas demonstrated that the isotope reversal was likely involved with water–gas reaction and Fischer-Tropsch synthesis during its generation.

  8. A state-of-the-art mass spectrometer system for determination of uranium and plutonium isotopic distributions in process samples

    International Nuclear Information System (INIS)

    Polson, C.A.

    1984-01-01

    A Finnigan MAT 261 automated thermal ionization mass spectrometer system was purchased by the Savannah River Plant and recently installed by Finnigan factory representatives. This instrument is a refinement of the MAT 260 which has been used routinely for three years in the laboratory at SRP. The MAT 261 is a highly precise, fully automated instrument. Many features make this instrument the state-of-the-art technology in precision isotopic composition measurements. A unique feature of the MAT 261 is the ion detection system which permits measurement of the three uranium or plutonium masses simultaneously. All Faraday cup measuring channels are of the same design and each is equipped with a dedicated amplifier. Each amplifier is connected to a linear voltage/frequency measuring system for ion current integration. These outputs are fed into a Hewlett-Packard 9845T desktop computer. The computer, and the Finnigan developed software package, control filament heating cycles, sample reconditioning, ion beam focusing, carrousel rotation, mass selection, and data collection and reduction. Precision, accuracy, and linearity were determined under normal laboratory conditions using a NBS uranium suite of standards. These results along with other developments in setting up the instrument are presented

  9. State-of-the-art mass spectrometer system for determination of uranium and plutonium isotopic distributions in process samples

    International Nuclear Information System (INIS)

    Polson, C.A.

    1983-01-01

    A Finnigan MAT 261 automated thermal ionization mass spectrometer system was purchased by the Savannah River Plant. The MAT 261 is a highly precise, fully automated instrument. Many features make this instrument the state-of-the-art technology in precision isotopic composition measurements. A unique feature of the MAT 261 is the ion detection system which permits measurement of the three uranium or plutonium masses simultaneously. All Faraday cup measuring channels are of the same design and each is equipped with a dedicated amplifier. Each amplifier is connected to a linear voltage/frequency measuring system for ion current integration. These outputs are fed into a Hewlett-Packard 9845T desk-top computer. The computer, and the Finnigan developed software package, control filament heating cycles, sample preconditioning, ion beam focusing, carrousel rotation, mass selection, and data collection and reduction. Precision, accuracy, and linearity were determined under normal laboratory conditions using a NBS uranium suite of standards. These results along with other development in setting up the instrument are presented

  10. A committee report on the state-of-art of uranium isotope enrichment measurement techniques

    International Nuclear Information System (INIS)

    1982-06-01

    The activity of a sectional meeting (June, 1979 - February, 1982) for uranium enrichment measurement under the Committee on Analytical Chemistry of Nuclear Fuels and Reactor Materials is summarized. In the first part of this report, the object and present state of the measurement at the following organization are described; two development organizations (Power Reactor and Nuclear Fuel Development Corporation and Japan Nuclear Fuel Development), two nuclear fuel makers (Japan Nuclear Fuel and Mitsubishi Nuclear Fuel), one safeguards inspection organization (Nuclear Material Control Center) and one research organization (Japan Atomic Energy Research Institute). The second part contains the principle and technique of several measurement methods for uranium isotopic assay, such as mass spectrometry, passive and active assays and optical spectral method. Lastly, the concept of the reference materials and its practical information for mass spectrometry and non-destructive assay are described. (author)

  11. Comparison of uranium and radium isotopes activities in some wells and thermal springs samples in Morroco

    International Nuclear Information System (INIS)

    Hakam, O.K.; Choukri, A.; Reyss, J.L.; Lferde, M.

    2000-01-01

    Activities and activity ratios of uranium and radium isotopes ( 234 U, 238 U, 226 Ra, 228 Ra, 234 U/ 238 U, 226 Ra/ 238 U, 228 Ra/ 226 Ra) have been determined, for the first time in Morocco, for 15 well water samples and 12 spring water samples. The obtained results show that, unlike well waters, the thermal spring waters present relatively low 238 U activities and elevated 226 Ra activities and 234 U/ 238 U activity ratios. Uranium and radium activities are similar to those published for other non polluting regions of the world, they are inferior to the Maximum Contaminant Levels and don't present any risk for public health in Morocco. (author) [fr

  12. Thermodynamic isotope effects of D2 and T2 reaction with uranium

    International Nuclear Information System (INIS)

    Huang Gang; Long Xinggui; Liang Jianhua; Yang Benfu; Liu Wenke

    2010-01-01

    The p-c-T curves of deuterium and tritium absorption by uranium and p-t curves of desorption were measured. The balance pressure of absorption and desorption on different temperatures were got and then the thermodynamic parameters were determined according to the Van't Hoff equation. It shows that the balance pressure of deuterium absorption is lower than that of tritium absorption on the same temperature and atom ratio. It has the same phenomena for desorption but there are obvious hysteresis effect for reversible process of absorption and desorption. There are a little thermodynamic isotope effects when deuterium and tritium absorption and desorption by uranium estimating from enthalpy and entropy values. (authors)

  13. Quantifying Uranium Isotope Ratios Using Resonance Ionization Mass Spectrometry: The Influence of Laser Parameters on Relative Ionization Probability

    Energy Technology Data Exchange (ETDEWEB)

    Isselhardt, Brett H. [Univ. of California, Berkeley, CA (United States)

    2011-09-01

    Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure relative uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process to provide a distinction between uranium atoms and potential isobars without the aid of chemical purification and separation. We explore the laser parameters critical to the ionization process and their effects on the measured isotope ratio. Specifically, the use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of 235U/238U ratios to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser in a 3-color, 3-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from >10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation. A rate equation model for predicting the relative ionization probability has been developed to study the effect of variation in laser parameters on the measured isotope ratio. This work demonstrates that RIMS can be used for the robust measurement of uranium isotope ratios.

  14. Stable isotope composition of human fingernails from Slovakia

    International Nuclear Information System (INIS)

    Grolmusová, Zuzana; Rapčanová, Anna; Michalko, Juraj; Čech, Peter; Veis, Pavel

    2014-01-01

    Stable isotope composition of human fingernails has proven to be useful for documenting human dietary information and geographical patterns in archeological, forensic, anthropological and biological studies. Therefore, it is of interest to detect all factors influencing the stable isotopic composition in the certain regions in the world. Carbon and nitrogen isotope data of human fingernail keratin from 52 individuals from Slovakia were reported in this study. The online combustion and continuous flow isotope-ratio mass spectrometer Delta V Advantage was used for δ 13 C and δ 15 N analysis of fingernail keratin samples from 24 vegetarian and 28 omnivorous individuals. A group of people with frequent meat consumption showed enrichment in 13 C and 15 N isotopes in fingernails. A similar trend was observed with increasing seafood in an individual's diet. Moreover a significant difference was revealed between smokers and nonsmokers for both δ 13 C and δ 15 N values. These data were compared to previously published δ 13 C and δ 15 N fingernail values from across the globe. This study brings new information on the stable isotope signature of individuals from Slovakia and characterizes the Central European region for the first time. The stable isotope composition of fingernails is influenced by the frequency of meat and seafood consumption as well as smoking. - Highlights: • This study deals with stable isotope analyses of fingernails from Slovak volunteers. • δ 13 C and δ 15 N values of vegetarian and omnivore fingernails were compared. • Influence of sex, diet and smoking was studied

  15. Stable isotope composition of human fingernails from Slovakia

    Energy Technology Data Exchange (ETDEWEB)

    Grolmusová, Zuzana, E-mail: zuzana.grolmusova@geology.sk [Comenius University in Bratislava, Faculty of Mathematics, Physics and Informatics, Department of Experimental Physics, Mlynská dolina F2, 842 48 Bratislava (Slovakia); State Geological Institute of Dionýz Štúr, Laboratory of Isotope Geology, Mlynská dolina 1, 817 04 Bratislava (Slovakia); Rapčanová, Anna [Comenius University in Bratislava, Faculty of Mathematics, Physics and Informatics, Department of Experimental Physics, Mlynská dolina F2, 842 48 Bratislava (Slovakia); Michalko, Juraj; Čech, Peter [State Geological Institute of Dionýz Štúr, Laboratory of Isotope Geology, Mlynská dolina 1, 817 04 Bratislava (Slovakia); Veis, Pavel [Comenius University in Bratislava, Faculty of Mathematics, Physics and Informatics, Department of Experimental Physics, Mlynská dolina F2, 842 48 Bratislava (Slovakia); State Geological Institute of Dionýz Štúr, Laboratory of Isotope Geology, Mlynská dolina 1, 817 04 Bratislava (Slovakia)

    2014-10-15

    Stable isotope composition of human fingernails has proven to be useful for documenting human dietary information and geographical patterns in archeological, forensic, anthropological and biological studies. Therefore, it is of interest to detect all factors influencing the stable isotopic composition in the certain regions in the world. Carbon and nitrogen isotope data of human fingernail keratin from 52 individuals from Slovakia were reported in this study. The online combustion and continuous flow isotope-ratio mass spectrometer Delta V Advantage was used for δ{sup 13}C and δ{sup 15}N analysis of fingernail keratin samples from 24 vegetarian and 28 omnivorous individuals. A group of people with frequent meat consumption showed enrichment in {sup 13}C and {sup 15}N isotopes in fingernails. A similar trend was observed with increasing seafood in an individual's diet. Moreover a significant difference was revealed between smokers and nonsmokers for both δ{sup 13}C and δ{sup 15}N values. These data were compared to previously published δ{sup 13}C and δ{sup 15}N fingernail values from across the globe. This study brings new information on the stable isotope signature of individuals from Slovakia and characterizes the Central European region for the first time. The stable isotope composition of fingernails is influenced by the frequency of meat and seafood consumption as well as smoking. - Highlights: • This study deals with stable isotope analyses of fingernails from Slovak volunteers. • δ{sup 13}C and δ{sup 15}N values of vegetarian and omnivore fingernails were compared. • Influence of sex, diet and smoking was studied.

  16. Anomalous isotopic composition of cosmic rays

    International Nuclear Information System (INIS)

    Woosley, S.E.; Weaver, T.A.

    1980-01-01

    Recent measurements of nonsolar isotopic patterns for the elements neon and (perhaps) magnesium in cosmic rays are interpreted within current models of stellar nucleosynthesis. One possible explanation is that the stars currently responsible for cosmic-ray synthesis in the Galaxy are typically super-metal-rich by a factor of two to three. Other possibilities include the selective acceleration of certain zones or masses of supernovas or the enhancement of 22 Ne in the interstellar medium by mass loss from red giant stars and planetary nebulas. Measurements of critical isotopic ratios are suggested to aid in distinguishing among the various possibilities. Some of these explanations place significant constraints on the fraction of cosmic ray nuclei that must be fresh supernova debris and the masses of the supernovas involved. 1 figure, 3 tables

  17. Uranium

    International Nuclear Information System (INIS)

    Hamdoun, N.A.

    2007-01-01

    The article includes a historical preface about uranium, discovery of portability of sequential fission of uranium, uranium existence, basic raw materials, secondary raw materials, uranium's physical and chemical properties, uranium extraction, nuclear fuel cycle, logistics and estimation of the amount of uranium reserves, producing countries of concentrated uranium oxides and percentage of the world's total production, civilian and military uses of uranium. The use of depleted uranium in the Gulf War, the Balkans and Iraq has caused political and environmental effects which are complex, raising problems and questions about the effects that nuclear compounds left on human health and environment.

  18. Uranium isotope separation by magnetic field gradient and visible light acting in a liquid medium

    International Nuclear Information System (INIS)

    Borges, O.N.

    1985-01-01

    The literature shows that excited uranyl can assume the ''singlet'' and ''triplet'' states, with different magnetic properties. In an aqueous medium, without organic complexity (to hamper dismutation), the action of light reduces uranyl to U(V), which is a radical -ion that can assume the ''doublet'' and ''quartet'' states, also with different magnetic properties. Due to the different constants of velocity of uranium 235 and 238 in the reduction of excited uranyl and in the oxidation of U(V) to UO 2 2+ , there is the probability of forming an isotopic gradient, in the aqueous solution, subjected to a magnetic field gradient, with consequent appropriate extraction. 6 refs

  19. Uranium isotope separation in the solid state. Progress report, December 1, 1976--June 1, 1977

    International Nuclear Information System (INIS)

    Bernstein, E.R.

    1977-06-01

    Since we were actively able to work on this project, we have been engaged in three separate lines of research. Each of these has been related to laser-induced isotope separation of uranium in the solid state. The three areas are: (a) improved reaction chemistry for both host materials Zr(BH 4 ) 4 and Hf(BH 4 ) 4 and U(BH 4 ) 4 itself; (b) improved spectroscopic techniques in order to obtain sharper spectra; and (c) solid state photochemical investigations to study U(BH 4 ) 4 photodecomposition mechanism and yield as a function of wave length. These are all integral parts of the solid state isotope separation procedure and are discussed in terms of the overall process proposed

  20. Polarography applied to the determination of uranium oxide composition; Application de la polarographie a la determination de la composition d'oxydes d'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Nens, C; Canton, C; Molina, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires, Departement de Chimie, Services d' Etudes Chimiques et d' Analyse, Service d' Etudes Analytiques, Section de Chimie Analytique du Plutonium et d' Electroanalyse

    1967-03-01

    An analytical method based on conventional polarography has been developed, for the determination of the O/U ratio in uranium oxides. The dissolution of the samples is effected by means of molten ammonium bifluoride. After a transfer to aqueous solution, polarography is used to determine the oxide composition by measurement of both the hexavalent and the total uranium. (author) [French] Une methode d'analyse utilisamt la polarographie conventionnelle a ete mise au point pour la determination du rapport O/U dans les oxydes d'uranium. La mise en solution des echgantillons est realisee en milieu de bifluorure d'ammonium fondu. Apres passage en salution aqueuse, la polarographie permet d'atteindre la composition de l'oxyde par determination de l'uranium hexavalent et de l'uranium total. (auteur)

  1. Influence of chemical structure on carbon isotope composition of lignite

    Science.gov (United States)

    Erdenetsogt, Bat-Orshikh; Lee, Insung; Ko, Yoon-Joo; Mungunchimeg, Batsaikhan

    2017-04-01

    During the last two decades, a number of studies on carbon isotopes in terrestrial organic matter (OM) have been carried out and used to determine changes in paleoatmospheric δ13C value as well as assisting in paleoclimate analysis. Coal is abundant terrestrial OM. However, application of its δ13C value is very limited, because the understanding of changes in isotopic composition during coalification is relatively insufficient. The purpose of this study was to examine the influence of the chemical structure on the carbon isotope composition of lignite. Generally, lignite has more complex chemical structures than other higher rank coal because of the existence of various types of oxygen-containing functional groups that are eliminated at higher rank level. A total of sixteen Lower Cretaceous lignite samples from Baganuur mine (Mongolia) were studied by ultimate, stable carbon isotope and solid-state 13C CP/MAS NMR analyses. The carbon contents of the samples increase with increase in depth, whereas oxygen content decreases continuously. This is undoubtedly due to normal coalification process and also consistent with solid state NMR results. The δ13C values of the samples range from -23.54‰ to -21.34‰ and are enriched in 13C towards the lowermost samples. Based on the deconvolution of the NMR spectra, the ratios between carbons bonded to oxygen (60-90 ppm and 135-220 ppm) over carbons bonded to carbon and hydrogen (0-50 ppm and 90-135 ppm) were calculated for the samples. These correlate well with δ13C values (R2 0.88). The results indicate that the δ13C values of lignite are controlled by two mechanisms: (i) depletion in 13C as a result of loss of isotopically heavy oxygen-bounded carbons and (ii) enrichment in 13C caused by a loss of isotopically light methane from aliphatic and aromatic carbons. At the rank of lignite, coal is enriched in 13C because the amount of isotopically heavy CO2 and CO, released from coal as a result of changes in the chemical

  2. Isotopic composition and origin of the precipitation in Northern Chile

    International Nuclear Information System (INIS)

    Aravena, R.; Pena, H.; Grilli, A.; Pollastri, A.; Fuenzalida, H.

    1997-01-01

    Full text: A three years isotope data on precipitation collected in northern Chile show a very distinct pattern, with depleted δ 18 and -150/00 observed at high altitude stations, compared to δ 18 0 values ranging between - 10 and -6/00 measured at the lower altitude areas. The depleted δ 0 values observed in the high altitude area, the Altiplano, are related to different processes that affect the air masses as moved from the Atlantic, crossed the Amazon Basin (continental effect), ascend the Andes (altitude effect) and precipitated (convective effect) in the Altiplano. It is postulated that a second source of moisture, associated to air masses from the Pacific, explained the enriched isotopic values observed in the lower altitude areas. Similar isotopic pattern, documented in springs and groundwater, indicates that the rain data presented in this paper is an accurate representation of the long term behavior of the isotopic composition of the rain in northern Chile

  3. Stable isotope composition of cocoa beans of different geographical origin.

    Science.gov (United States)

    Perini, Matteo; Bontempo, Luana; Ziller, Luca; Barbero, Alice; Caligiani, Augusta; Camin, Federica

    2016-09-01

    The isotopic profile (δ(13) C, δ(15) N, δ(18) O, δ(2) H, δ(34) S) was used to characterise a wide selection of cocoa beans from different renowned production areas (Africa, Asia, Central and South America). The factors most influencing the isotopic signatures of cocoa beans were climate and altitude for δ(13) C and the isotopic composition of precipitation water for δ(18) O and δ(2) H, whereas δ(15) N and δ(34) S were primarily affected by geology and fertilisation practises. Multi-isotopic analysis was shown to be sufficiently effective in determining the geographical origin of cocoa beans, and combining it with Canonical Discriminant Analysis led to more than 80% of samples being correctly reclassified. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  4. What controls the isotopic composition of Greenland surface snow?

    Directory of Open Access Journals (Sweden)

    H. C. Steen-Larsen

    2014-02-01

    Full Text Available Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically enabled atmospheric models. However, post-depositional processes linked with snow metamorphism remain poorly documented. For this purpose, monitoring of the isotopic composition (δ18O, δD of near-surface water vapor, precipitation and samples of the top (0.5 cm snow surface has been conducted during two summers (2011–2012 at NEEM, NW Greenland. The samples also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between near-surface vapor δ18O and air temperature (0.85 ± 0.11‰ °C−1 (R = 0.76 for 2012. The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1–5-day periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and near-surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated using the CROCUS snow model that 6 to 20% of the surface snow mass is exchanged with the atmosphere. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or deposition. Comparisons with atmospheric models show that day-to-day variations in near-surface vapor isotopic composition are driven by synoptic variations and changes in air mass trajectories and distillation histories. We suggest that, in between precipitation events, changes in the surface snow isotopic composition are driven by these changes in near

  5. Measurement of Plutonium Isotopic Composition - MGA

    Energy Technology Data Exchange (ETDEWEB)

    Vo, Duc Ta [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-21

    In this module, we will use the Canberra InSpector-2000 Multichannel Analyzer with a high-purity germanium detector (HPGe) and the MGA isotopic anlysis software to assay a variety of plutonium samples. The module provides an understanding of the MGA method, its attributes and limitations. You will assess the system performance by measuring a range of materials similar to those you may assay in your work. During the final verification exercise, the results from MGA will be combined with the 240Pueff results from neutron coincidence or multiplicity counters so that measurements of the plutonium mass can be compared with the operator-declared (certified) values.

  6. Determination of uranium in urine - measurement of isotope ratios and quantification by use of inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Krystek, P.; Ritsema, R.

    2002-01-01

    For analysis of uranium in urine determination of the isotope ratio and quantification were investigated by high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS). The instrument used (ThermoFinniganMAT ELEMENT2) is a single-collector MS and, therefore, a stable sample-introduction system was chosen. The methodical set-up was optimized to achieve the best precision for both the isotope ratio and the total uranium concentration in the urine matrix.Three spiked urine samples from an European interlaboratory comparison were analyzed to determine the 235 U/ 238 U isotope ratio. The ratio was found to be in the range 0.002116 to 0.007222, the latter being the natural uranium isotope ratio. The first ratio indicates the abundance of depleted uranium.The effect of storage conditions and the stability for the matrix urine were investigated by using ''real-life'' urine samples from unexposed persons in the Netherlands. For samples stored under refrigeration and acidified the results (range 0.8 to 5.3 ng L -1 U) were in the normal fluctuation range whereas a decrease in uranium concentration was observed for samples stored at room temperature without acidification. (orig.)

  7. Oxygen Isotope Composition of Nitrate Produced by Freshwater Nitrification

    Science.gov (United States)

    Boshers, D.; Granger, J.; Bohlke, J. K.

    2016-12-01

    Measurements of the naturally occurring nitrogen and oxygen stable isotope ratios of nitrate (NO3-), δ15N and δ18O, can be used to determine the source, dispersal, and fate of natural and contaminant NO3- in aquatic environments. To this end, it is necessary to know the extent to which NO3- isotopologues are modified by biological reactions, as heavy and light isotopes have different reaction rates. The purpose of this study was to determine the influence of the δ18O of ambient water on the isotope composition of NO3- produced during nitrification, the biological oxidation of ammonium (NH4+) to nitrite (NO2-) and then NO3-, which is poorly constrained in freshwater systems. To determine the δ18O of NO3- produced by nitrification in freshwater, we collected water from a stream in New England, which we amended with NH4+ and with increments of 18O-enriched water, to monitor the isotope composition of NO3- produced by a natural consortium of nitrifiers. Added NH4+ was completely oxidized to NO3- over 26 days. The final δ18O of nitrified NO3- revealed sensitivity to the δ18O of water mediated by (a) isotopic equilibration between water and NO2- and (b) kinetic isotope fractionation during O-atom incorporation from water into NO2- and NO3-. Our results concur with nitrifying culture experiments that have demonstrated analogous sensitivity of the δ18O of nitrified NO3- to equilibrium and kinetic O isotope effects (Buchwald et al. 2012), as well as show that these dynamics need to be considered to interpret NO3- isotope distribution in freshwater environments.

  8. Chemical and isotopic composition of precipitations in Syria

    International Nuclear Information System (INIS)

    Abou Zakhem, B.; Hafez, R.

    2007-05-01

    The objective of this study is to determine isotopic characteristics of precipitation, the climatic and geographical conditions affecting isotopic composition in order to obtain the input function of groundwater to evaluate the water resources.13 meteoric stations were selected in Syria for cumulative monthly rainfall sampling during two hydrological cycles; 1991-1992 and 1992-1993. The chemical and isotopic compositions of monthly precipitation were studied. The winter and spring rainfall isotopic characteristics were determined, in addition to the Syrian meteoric line (SMWL) was estimated with a slope of 6.62 and that of both Syria and Jordan of 6.73. The effect of climatic factors as temperature and relative air humidity on oxygen-18, deuterium and d-excess were studied and it was found that the relationship between temperature and oxygen-18 and deuterium is a positive linear correlation; however, it is a negative correlation with d-excess. The mean seasonal variation amplitude of 18 O was about 6%, and the amount effect on isotopic content of precipitation was studied. The geographic factors and its affect on isotopic contents of precipitation such as altitude were considered, furthermore, the isotopic gradient with altitude was determined for both oxygen-18 and deuterium (-0.14 % and -0.84% /100m respectively). The spatial distribution of oxygen-18, deuterium, tritium and d-excess indicted the effect of mountain chains and gaps between mountains on the isotopic content, the continental effect on tritium build-up by about 33% per 100 Km from the coast. The increase of d-excess values towards the south west proves the eastern Mediterranean climate type over this region.(author)

  9. H-Isotopic Composition of Apatite in Northwest Africa 7034

    Science.gov (United States)

    McCubbin, F. M.; Barnes, J. J.; Santos, A. R.; Boyce, J. W.; Anand, M.; Franchi, I. A.; Agee, C. B.

    2016-01-01

    Northwest Africa (NWA) 7034 and its pairings comprise a regolith breccia with a basaltic bulk composition [1] that yields a better match than any other martian meteorite to estimates of Mars' bulk crust composition [1]. Given the similarities between NWA 7034 and the martian crust, NWA 7034 may represent an important sample for constraining the crustal composition of components that cannot be measured directly by remote sensing. In the present study, we seek to constrain the H isotopic composition of the martian crust using Cl-rich apatite in NWA 7034.

  10. Tin isotope fractionation during magmatic processes and the isotope composition of the bulk silicate Earth

    Science.gov (United States)

    Wang, Xueying; Amet, Quentin; Fitoussi, Caroline; Bourdon, Bernard

    2018-05-01

    Tin is a moderately volatile element whose isotope composition can be used to investigate Earth and planet differentiation and the early history of the Solar System. Although the Sn stable isotope composition of several geological and archaeological samples has been reported, there is currently scarce information about the effect of igneous processes on Sn isotopes. In this study, high-precision Sn isotope measurements of peridotites and basalts were obtained by MC-ICP-MS with a double-spike technique. The basalt samples display small variations in δ124/116Sn ranging from -0.01 ± 0.11 to 0.27 ± 0.11‰ (2 s.d.) relative to NIST SRM 3161a standard solution, while peridotites have more dispersed and more negative δ124Sn values ranging from -1.04 ± 0.11 to -0.07 ± 0.11‰ (2 s.d.). Overall, basalts are enriched in heavy Sn isotopes relative to peridotites. In addition, δ124Sn in peridotites become more negative with increasing degrees of melt depletion. These results can be explained by different partitioning behavior of Sn4+ and Sn2+ during partial melting. Sn4+ is overall more incompatible than Sn2+ during partial melting, resulting in Sn4+-rich silicate melt and Sn2+-rich residue. As Sn4+ has been shown experimentally to be enriched in heavy isotopes relative to Sn2+, the effect of melting is to enrich residual peridotites in relatively more compatible Sn2+, which results in isotopically lighter peridotites and isotopically heavier mantle-derived melts. This picture can be disturbed partly by the effect of refertilization. Similarly, the presence of enriched components such as recycled oceanic crust or sediments could explain part of the variations in Sn isotopes in oceanic basalts. The most primitive peridotite analyzed in this study was used for estimating the Sn isotope composition of the BSE, with δ124Sn = -0.08 ± 0.11‰ (2 s.d.) relative to the Sn NIST SRM 3161a standard solution. Altogether, this suggests that Sn isotopes may be a powerful probe of

  11. Steady State Sputtering Yields and Surface Compositions of Depleted Uranium and Uranium Carbide bombarded by 30 keV Gallium or 16 keV Cesium Ions.

    Energy Technology Data Exchange (ETDEWEB)

    Siekhaus, W. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Teslich, N. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Weber, P. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-10-23

    Depleted uranium that included carbide inclusions was sputtered with 30-keV gallium ions or 16-kev cesium ions to depths much greater than the ions’ range, i.e. using steady-state sputtering. The recession of both the uranium’s and uranium carbide’s surfaces and the ion corresponding fluences were used to determine the steady-state target sputtering yields of both uranium and uranium carbide, i.e. 6.3 atoms of uranium and 2.4 units of uranium carbide eroded per gallium ion, and 9.9 uranium atoms and 3.65 units of uranium carbide eroded by cesium ions. The steady state surface composition resulting from the simultaneous gallium or cesium implantation and sputter-erosion of uranium and uranium carbide were calculated to be U₈₆Ga₁₄, (UC)₇₀Ga₃₀ and U₈₁Cs₉, (UC)₇₉Cs₂₁, respectively.

  12. DESIGN STUDY FOR A LOW-ENRICHED URANIUM CORE FOR THE HIGH FLUX ISOTOPE REACTOR, ANNUAL REPORT FOR FY 2010

    Energy Technology Data Exchange (ETDEWEB)

    Cook, David Howard [ORNL; Freels, James D [ORNL; Ilas, Germina [ORNL; Jolly, Brian C [ORNL; Miller, James Henry [ORNL; Primm, Trent [ORNL; Renfro, David G [ORNL; Sease, John D [ORNL; Pinkston, Daniel [ORNL

    2011-02-01

    This report documents progress made during FY 2010 in studies of converting the High Flux Isotope Reactor (HFIR) from high enriched uranium (HEU) fuel to low enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum alloy. With axial and radial grading of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in performance to users from the current level. Studies are reported of support to a thermal hydraulic test loop design, the implementation of finite element, thermal hydraulic analysis capability, and infrastructure tasks at HFIR to upgrade the facility for operation at 100 MW. A discussion of difficulties with preparing a fuel specification for the uranium-molybdenum alloy is provided. Continuing development in the definition of the fuel fabrication process is described.

  13. Determination of hydrogen isotope composition in organic compounds

    International Nuclear Information System (INIS)

    Ordzhonikidze, K.G.; Parulava, L.P.; Vakhaniya, G.V.; Tarielashvili, V.O.

    1989-01-01

    method for determination of hydrogen isotope composition just in organic compounds using mass-spectrometer of the second class is suggested. The method enables to determine atomic fraction of hydrogen without multiplet separation. The accuracy of determination of deuterium atomic fraction in acetone in 1-99% range was equal to 3-0.2% respectively

  14. Stable isotope compositions of organic carbon and contents of ...

    African Journals Online (AJOL)

    The stable isotope compositions of organic carbon (OC), and contents of OC and nitrogen for four sediment cores recovered from lakes Makat (located in the Ngorongoro Crater), Ndutu and Masek (located in the Serengeti Plains) are used to document sources of organic matter (OM) and climatic changes in sub-arid ...

  15. The usage of electron beam to produce radio isotopes through the uranium fission by γ-rays and neutrons

    International Nuclear Information System (INIS)

    Bunatyan, G.G.; Nikolenko, V.G.; Popov, A.V.

    2010-01-01

    We treat the production of desirable radio isotopes due to the 238 U photo-fission by the bremsstrahlung induced in converter by an initial electron beam provided by a linear electron accelerator. We consider as well the radio isotope production through the 238 U fission by the neutrons that stem in the 238 U sample irradiated by that bremsstrahlung. The yield of the most applicable radio isotope 99 Mo is calculated. We correlate the findings acquired in the work presented with those obtained by treating the nuclear photo-neutron reaction. Menace of the plutonium contamination of an irradiated uranium sample because of the neutron capture by 238 U is considered. As we get convinced, the photo-neutron production of radio isotopes proves to be more practicable than the production by the uranium photo- and neutron-fission. Both methods are certain to be brought into action due to usage of the electron beam provided by modern linear accelerators

  16. Genesis of carbonate-siliceous-pelitic type uranium deposits in Baoyuan area

    International Nuclear Information System (INIS)

    Guo Baochi; Zhang Daishi; Li Shengxiang; Zhu Jiechen

    1995-01-01

    Based on systematic studies of the regional geology, the fundamental geological characteristics of uranium mineralizations, and according to the researches of uranium source, the REE characteristics, the H,O,C,S isotope compositions, as well as the chronology of uranium metallogenesis of the uranium deposits, the authors consider that the multistage accumulative metallogenesis (especially the hydrothermal superimposed and reworking metallogenesis) is the universal and important uranium metallogenesis in the formation of carbonate-siliceous-pelitic type uranium deposits in the area

  17. Isotope composition and volume of Earth's early oceans.

    Science.gov (United States)

    Pope, Emily C; Bird, Dennis K; Rosing, Minik T

    2012-03-20

    Oxygen and hydrogen isotope compositions of Earth's seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen's was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as δD relative to Vienna standard mean ocean water (VSMOW)] by at most 25 ± 5‰, but oxygen isotope ratios were comparable to modern oceans. Mass balance of the global hydrogen budget constrains the contribution of continental growth and planetary hydrogen loss to the secular evolution of hydrogen isotope ratios in Earth's oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH(4) and CO(2) concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth.

  18. Hydrogen-isotopic composition of some hydrous manganese minerals

    International Nuclear Information System (INIS)

    Hariya, Y.; Tsutsumi, M.

    1981-01-01

    Initial data on the hydrogen-isotopic compositions in hydrous Mn minerals from various occurrences fall in a wide range from -298 to -84per thousand, relative to SMOW. deltaD-values of todorokite and cryptomelane from Tertiary deposits show -89 and -150per thousand. 10 A-manganite and delta-MnO 2 from deep-sea nodules have relatively restricted deltaD-values ranging from -96 to -84per thousand. The deltaD-values for manganese bog ores from recent hot springs show almost -105per thousand. It is recognized that the isotopic values obtained for the deep-sea nodules and recent bog ores are slightly different ranged. Manganite and groutite are unique in their hydrogen-isotopic compositions, having the most depleted deltaD-values ranging from -298 to -236per thousand. MnO(OH) minerals are more deuterium-depleted hydrous minerals than any other hydrothermal minerals from various ore deposits. Hydrogen-isotope fractionation factors between manganite and water were experimentally determined to be 0.7894, 0.7958 and 0.8078 at 150 0 , 200 0 and 250 0 C respectively. The present experimental results indicate that if manganites were formed at temperatures below 250 0 C, under isotopic equilibrium conditions most of the manganite mineralization in the Tertiary manganese deposits must have precipitated from meteoric hydrothermal solutions. (Auth.)

  19. Biosynthetic effects on the stable carbon isotopic compositions of agal lipids: Implications for deciphering the carbon isotopic biomarker record

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Schouten, S.; Klein Breteler, W.C.M.; Blokker, P.; Schogt, N.; Rijpstra, W.I.C.; Grice, K.; Baas, M.

    1998-01-01

    Thirteen species of algae covering an extensive range of classes were cultured and stable carbon isotopic compositions of their lipids were analysed in order to assess carbon isotopic fractionation effects during their biosynthesis. The fatty acids were found to have similar stable carbon isotopic

  20. Chemical and isotopic composition of precipitations in Syria

    International Nuclear Information System (INIS)

    Abou Zakhem, B.; Hafez, R.

    2008-01-01

    13 meteoric stations were selected in syria for cumulative monthly rainfall sampling during two hydrological cycles; 1991-1992 and 1992-1993. The chemical and isotopic compositions of monthly precipitation were studied. The winter and spring rainfall isotopic characteristics were determined, in addition to the syrian or local meteoric line (SMWL) was estimated with a slope of 6.63 and that of both syria and Jordan of 6.73. The effect of climatic factors as temperature and relative air humidity on oxygen-18, deuterium and d-excess were studied and it was found that the relationship between temperature and oxygen-18 and deuterium is a positive linear correlation; however, it is a negative correlation with d-excess. The mean seasonal variation amplitude was determined by 6%, and the amount effect on isotopic content of precipitation was studied. The geographic factors and its affect on isotopic contents of precipitation such as altitude were considered, furthermore, the isotopic gradient with altitude was determined for both oxygen-18 and deuterium (-0.14% and - 0.84%/100 m elevation respectively). The spatial variability of oxygen-18, deuterium, tritium and d-excess indicted the effect of mountain chains and gaps between mountains on the isotopic content of precipitation, the continental effect on tritium build-up by about 33% per 100 Km from the coast. The increase of d-excess values towards the south west proves the eastern mediterranean climate type over this region. (author)

  1. Uranium Bio-accumulation and Cycling as revealed by Uranium Isotopes in Naturally Reduced Sediments from the Upper Colorado River Basin

    Science.gov (United States)

    Lefebvre, Pierre; Noël, Vincent; Jemison, Noah; Weaver, Karrie; Bargar, John; Maher, Kate

    2016-04-01

    Uranium (U) groundwater contamination following oxidized U(VI) releases from weathering of mine tailings is a major concern at numerous sites across the Upper Colorado River Basin (CRB), USA. Uranium(IV)-bearing solids accumulated within naturally reduced zones (NRZs) characterized by elevated organic carbon and iron sulfide compounds. Subsequent re-oxidation of U(IV)solid to U(VI)aqueous then controls the release to groundwater and surface water, resulting in plume persistence and raising public health concerns. Thus, understanding the extent of uranium oxidation and reduction within NRZs is critical for assessing the persistence of the groundwater contamination. In this study, we measured solid-phase uranium isotope fractionation (δ238/235U) of sedimentary core samples from four study sites (Shiprock, NM, Grand Junction, Rifle and Naturita, CO) using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). We observe a strong correlation between U accumulation and the extent of isotopic fractionation, with Δ238U up to +1.8 ‰ between uranium-enriched and low concentration zones. The enrichment in the heavy isotopes within the NRZs appears to be especially important in the vadose zone, which is subject to variations in water table depth. According to previous studies, this isotopic signature is consistent with biotic reduction processes associated with metal-reducing bacteria. Positive correlations between the amount of iron sulfides and the accumulation of reduced uranium underline the importance of sulfate-reducing conditions for U(IV) retention. Furthermore, the positive fractionation associated with U reduction observed across all sites despite some variations in magnitude due to site characteristics, shows a regional trend across the Colorado River Basin. The maximum extent of 238U enrichment observed in the NRZ proximal to the water table further suggests that the redox cycling of uranium, with net release of U(VI) to the groundwater by

  2. Tracing anthropogenic thallium in soil using stable isotope compositions.

    Science.gov (United States)

    Kersten, Michael; Xiao, Tangfu; Kreissig, Katharina; Brett, Alex; Coles, Barry J; Rehkämper, Mark

    2014-08-19

    Thallium stable isotope data are used in this study, for the first time, to apportion Tl contamination in soils. In the late 1970s, a cement plant near Lengerich, Germany, emitted cement kiln dust (CKD) with high Tl contents, due to cocombustion of Tl-enriched pyrite roasting waste. Locally contaminated soil profiles were obtained down to 1 m depth and the samples are in accord with a binary mixing relationship in a diagram of Tl isotope compositions (expressed as ε(205)Tl, the deviation of the (205)Tl/(203)Tl ratio of a sample from the NIST SRM 997 Tl isotope standard in parts per 10(4)) versus 1/[Tl]. The inferred mixing endmembers are the geogenic background, as defined by isotopically light soils at depth (ε(205)Tl ≈ -4), and the Tl emissions, which produce Tl-enriched topsoils with ε(205)Tl as high as ±0. The latter interpretation is supported by analyses of the CKD, which is also characterized by ε(205)Tl ≈ ± 0, and the same ε(205)Tl value was found for a pyrite from the deposit that produced the cocombusted pyrite roasting waste. Additional measurements for samples from a locality in China, with outcrops of Tl sulfide mineralization and associated high natural Tl backgrounds, reveal significant isotope fractionation between soils (ε(205)Tl ≈ +0.4) and locally grown green cabbage (ε(205)Tl between -2.5 and -5.4). This demonstrates that biological isotope fractionation cannot explain the isotopically heavy Tl in the Lengerich topsoils and the latter are therefore clearly due to anthropogenic Tl emissions from cement processing. Our results thus establish that isotopic data can reinforce receptor modeling for the toxic trace metal Tl.

  3. Uranium

    International Nuclear Information System (INIS)

    Cuney, M.; Pagel, M.; Leroy, J.

    1992-01-01

    First, this book presents the physico-chemical properties of Uranium and the consequences which can be deduced from the study of numerous geological process. The authors describe natural distribution of Uranium at different scales and on different supports, and main Uranium minerals. A great place in the book is assigned to description and classification of uranium deposits. The book gives also notions on prospection and exploitation of uranium deposits. Historical aspects of Uranium economical development (Uranium resources, production, supply and demand, operating costs) are given in the last chapter. 7 refs., 17 figs

  4. Isotopic composition of chemical elements in natural cycles

    International Nuclear Information System (INIS)

    Wetzel, K.

    1977-12-01

    Mathematical models developed for planning and evaluating tracer experiments have been applied in investigations of the isotopic composition of carbon in its natural cycle through various periods of the last billion years. The influence on the natural isotope ratio due to industrial combustion of fossil fuels is shown. In order to describe regional differences from the global behaviour of carbon a parameter has been introduced, which represents the time needed for one total exchange of the atmosphere in a certain region with the global atmosphere

  5. Isotopic composition of steam samples from Lanzarote, Canary Islands

    Energy Technology Data Exchange (ETDEWEB)

    Arana, V. (CSIC, Madrid); Panichi, C.

    1974-12-01

    The isotopic analysis of the steam samples collected in the geothermal area of Lanzarote show that the values of delta D are practically constant, and those of delta /sup 18/O range in a shift of 17 /sup 0///sub 00/ reaching a maximum of +14.7 /sup 0///sub 00/ versus SMOW, this last value being the highest found in steam samples. This composition can be explained as a consequence of the isotopic exchange at high temperature between limestones and a mixture of marine and local meteoric waters. This interpretation agrees with previous geological and geophysical studies which consider that a promising geothermal field could exist in Lanzarote. (auth)

  6. The Itataia phosphate-uranium deposit (Ceará, Brazil) new petrographic, geochemistry and isotope studies

    Science.gov (United States)

    Veríssimo, César Ulisses Vieira; Santos, Roberto Ventura; Parente, Clóvis Vaz; Oliveira, Claudinei Gouveia de; Cavalcanti, José Adilson Dias; Nogueira Neto, José de Araújo

    2016-10-01

    The Itataia phosphate-uranium deposit is located in Santa Quitéria, in central Ceará State, northeastern Brazil. Mineralization has occurred in different stages and involves quartz leaching (episyenitization), brecciation and microcrystalline phase formation of concretionary apatite. The last constitutes the main mineral of Itatiaia uranium ore, namely collophane. Collophanite ore occurs in massive bodies, lenses, breccia zones, veins or episyenite in marble layers, calc-silicate rocks and gneisses of the Itataia Group. There are two accepted theories on the origin of the earliest mineralization phase of Itataia ore: syngenetic (primary) - where the ore is derived from a continental source and then deposited in marine and coastal environments; and epigenetic (secondary) - whereby the fluids are of magmatic, metamorphic and meteoric origin. The characterization of pre- or post-deformational mineralization is controversial, since the features of the ore are interpreted as deformation. This investigation conducted isotopic studies and chemical analyses of minerals in marbles and calc-silicate rocks of the Alcantil and Barrigas Formations (Itataia Group), as well as petrographic and structural studies. Analysis of the thin sections shows at least three phosphate mineral phases associated with uranium mineralizaton: (1) A prismatic fluorapatite phase associated with chess-board albite, arfvedsonite and ferro-eckermannite; (2) a second fluorapatite phase with fibrous radial or colloform habits that replaces calcium carbonate in marble, especially along fractures, with minerals such as quartz, chlorite and zeolite also identified in calc-silicate rocks; and (3) an younger phosphate phase of botryoidal apatite (fluorapatite and hydroxyapatite) related with clay minerals and probably others calcium and aluminum phosphates. Detailed isotopic analysis carried out perpendicularly to the mineralized levels and veins in the marble revealed significant variation in isotopic

  7. Contribution to the future prospects of laser separation of uranium isotopes

    International Nuclear Information System (INIS)

    Becker, F.S.

    1981-04-01

    In the past several years, the selective absorption of laser light has been considered as an alternative to the large-scale technical uranium isotope separation schemes based on the mass-dependence of the diffusion velocity or the centrifugal force. An analysis of the published results appears to show that two-frequency multiphoton dissociation is especially attractive for a technical process. To clarify the prospects of such a scheme, studies of the isotope selectivity of the multiphoton dissociation of statically cooled UF 6 with two infrared frequencies, one of which is tunable in the region of the UF 6 ν(3) band at 16 μm, are proposed. The construction and testing of a high-power laser, tunable in the 16 μm region, based on the frequency conversion of 10 μm CO 2 radiation by means of stimulated rotational Raman scattering in para-hydrogen, is described. Pulse-widths of about 80 nsec and pulse energies of about one half J are obtained which ought to permit, in combination with a CO 2 laser, the multiphoton dissociation of UF 6 without focussing. By means of UV-light experiments it is shown that optical dissociation of UF 6 can be obtained even in the presence of high F-concentrations, thus permitting a high dissociation yield without a F-scavenger which could negatively affect the isotope selectivity. (orig./HP) [de

  8. Are Polyatomic Interferences, Cross Contamination, Mixing-Effect, etc., Obstacles for the Use of Laser Ablation-ICP-MS Coupling as an Operational Technique for Uranium Isotope Ratio Particle Analysis?

    International Nuclear Information System (INIS)

    Donard, A.; Pointurier, F.; Pecheyran, C.

    2015-01-01

    Analysis of ''environmental samples'', which consists in dust collected with cotton clothes wiped by inspectors on surfaces inside declared nuclear facilities, is a key tool for safeguards. Although two methods (fission tracks-TIMS and SIMS) are already used routinely to determine the isotopic composition of uranium particles, the laser ablationinductively coupled plasma mass spectrometry (LA-ICP-MS) coupling has been proven to be an interesting option thanks to its rapidity, high sensitivity and high signal/noise ratio. At CEA and UPPA, feasibility of particle analysis using a nanosecond LA device and a quadrupole ICP-MS has been demonstrated. However, despite the obvious potential of LA-ICP-MS for particle analysis, the effect of many phenomena which may bias isotope ratio measurements or lead to false detections must be investigated. Actually, environmental samples contain many types of non-uranium particles (organic debris, iron oxides, etc.) that can form molecular interferences and induce the risk of isotopic measurement bias, especially for minor isotopes (234U, 236U). The influence of these polyatomic interferences on the measurements will be discussed. Moreover, different uranium isotopic compositions can be found in the same sample. Therefore, risks of memory effect and of particle-toparticle cross-contamination by the deposition of ablation debris around the crater have also been investigated. This study has been conducted by using a femtosecond laser ablation device coupled to a high sensitivity sector field ICP-MS. Particles were fixed onto the discs with collodion and were located thanks to their fission tracks so that micrometric particles can be analyzed separately. All uranium isotope ratios were measured. Results are compared with the ones obtained with the fission tracks-TIMS technique on other deposition discs from the same sample. Performance of the method in terms of accuracy, precision, and detection limits are estimated

  9. Determination of uranium in urine - Measurement of isotope ratios and quantification by use of inductively coupled plasma mass spectrometry

    NARCIS (Netherlands)

    Krystek, Petra; Ritsema, R.

    2002-01-01

    For analysis of uranium in urine determination of the isotope ratio and quantification were investigated by high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS). The instrument used (ThermoFinniganMAT ELEMENT2) is a single-collector MS and, therefore, a stable sample-introduction

  10. Dolomite clumped isotope constraints on the oxygen isotope composition of the Phanerozoic Sea

    Science.gov (United States)

    Ryb, U.; Eiler, J. M.

    2017-12-01

    The δ18O value of the Phanerozoic Sea has been debated several decades, largely motivated by an 8‰ increase in δ18O of sedimentary carbonates between the Cambrian and the present. Some previous studies have interpreted this increase to be a primary depositional signal, resulting from an increase in the 18O content of ocean water over time, or from a decrease in ocean temperature increasing the oxygen isotope fractionation between seawater and carbonates. In contrast, other studies have interpreted lower δ18O compositions as the products of diagenetic alteration at elevated burial temperatures. Here, we show that the Phanerozoic dolomite δ18O record overlaps with that of well-preserved calcite fossils, and use carbonate clumped isotope measurements of Cambrian to Pleistocene dolomites to calculate their formation temperatures and the isotopic compositions of their parent-waters. The observed variation in dolomite δ18O is largely explained by dolomite formation at burial temperatures of up to 158°C. The δ18O values of dolomite parent-waters range -2 to +12‰ and are correlated with formation temperatures. Such correlation is consistent with the modification of seawater (0±2‰, VSMOW) toward isotopically heavier compositions through water-rock reactions at elevated burial temperatures. The similarity between the dolomite and calcite δ18O records, and published clumped isotope-based calculations of water compositions, suggests that like dolomite, temporal variations of the calcite δ18O record may also be largely driven by diagenetic alteration. Finally, the relationship we observe between temperature of dolomitization and d18O of dolomite suggests platform carbonates generally undergo dolomitization through reaction with modified marine waters, and that there is no evidence those waters were ever significantly lower in d18O than the modern ocean.

  11. Trace uranium analysis in geological sample by isotope dilution-alpha spectrometry and comparison with other techniques

    International Nuclear Information System (INIS)

    Shihomatsu, H.M.; Iyer, S.S.

    1988-12-01

    Establishment of uranium determination in geological samples by alpha spectrometric isotope dilution technique using 233 U tracer is described in the present work. The various steps involved in the method namely, preparation of the sample, electrodeposition, alpha spectrometry, isotope dilution, calculation of the concentration and error statistics are discussed in detail. The experimental parameters for the electrodeposition of uranium, like current density, pH concentration of the electrolyte solution, deposition time, electrode distance were all optimised based on the efficiency of the deposition. The total accuracy and precision of the IDAS using 233 U tracer in the determination of uranium in mineral and granite samples were of the order of 1 to 2% for the concentration range of 50-1500 ppm of U. Our results are compared with those obtained by others workers using similar and different techniques. (author) [pt

  12. Modeling the carbon isotope composition of bivalve shells (Invited)

    Science.gov (United States)

    Romanek, C.

    2010-12-01

    The stable carbon isotope composition of bivalve shells is a valuable archive of paleobiological and paleoenvironmental information. Previous work has shown that the carbon isotope composition of the shell is related to the carbon isotope composition of dissolved inorganic carbon (DIC) in the ambient water in which a bivalve lives, as well as metabolic carbon derived from bivalve respiration. The contribution of metabolic carbon varies among organisms, but it is generally thought to be relatively low (e.g., 90%) in the shells from terrestrial organisms. Because metabolic carbon contains significantly more C-12 than DIC, negative excursions from the expected environmental (DIC) signal are interpreted to reflect an increased contribution of metabolic carbon in the shell. This observation contrasts sharply with modeled carbon isotope compositions for shell layers deposited from the inner extrapallial fluid (EPF). Previous studies have shown that growth lines within the inner shell layer of bivalves are produced during periods of anaerobiosis when acidic metabolic byproducts (e.g., succinic acid) are neutralized (or buffered) by shell dissolution. This requires the pH of EPF to decrease below ambient levels (~7.5) until a state of undersaturation is achieved that promotes shell dissolution. This condition may occur when aquatic bivalves are subjected to external stressors originating from ecological (predation) or environmental (exposure to atm; low dissolved oxygen; contaminant release) pressures; normal physiological processes will restore the pH of EPF when the pressure is removed. As a consequence of this process, a temporal window should also exist in EPF at relatively low pH where shell carbonate is deposited at a reduced saturation state and precipitation rate. For example, EPF chemistry should remain slightly supersaturated with respect to aragonite given a drop of one pH unit (6.5), but under closed conditions, equilibrium carbon isotope fractionation

  13. Deuterium isotope composition of palaeoinfiltration water trapped in speleothems

    International Nuclear Information System (INIS)

    Rozanski, K.

    1987-05-01

    Analytical and methodological aspects of combined isotope investigations of carbonate cave deposits are thoroughly discussed in the report. Weight is put on isotope analyses of fluid inclusions (D and 18 O content) extracted from speleothems of known age. Dating was done by the 230 Th/ 234 U ratio method. Isotopic analyses of speleothems originating from European caves allowed some important conclusions to be formulated regarding past climatic and environmental conditions prevailing over the European continent during the last 300,000 yrs: a) δD values of fluid inclusions suggest a remarkable constancy of the heavy-isotope content of European palaeoinfiltration waters recharged during interglacial periods, b) a climate-induced, long-term changes in isotopic composition of precipitation and surface air temperature over Europe can be characterized by the deuterium gradient of ca.1 4 deg./oo/deg. C, c) an apparent constancy of the continental gradient in deuterium content of European palaeoinfiltration waters as judged from the fluid inclusion data suggests that atmospheric circulation over Europe did not undergo substantial changes for at least 300,000 years

  14. Efficient uranium capture by polysulfide/layered double hydroxide composites.

    Science.gov (United States)

    Ma, Shulan; Huang, Lu; Ma, Lijiao; Shim, Yurina; Islam, Saiful M; Wang, Pengli; Zhao, Li-Dong; Wang, Shichao; Sun, Genban; Yang, Xiaojing; Kanatzidis, Mercouri G

    2015-03-18

    There is a need to develop highly selective and efficient materials for capturing uranium (normally as UO2(2+)) from nuclear waste and from seawater. We demonstrate the promising adsorption performance of S(x)-LDH composites (LDH is Mg/Al layered double hydroxide, [S(x)](2-) is polysulfide with x = 2, 4) for uranyl ions from a variety of aqueous solutions including seawater. We report high removal capacities (q(m) = 330 mg/g), large K(d)(U) values (10(4)-10(6) mL/g at 1-300 ppm U concentration), and high % removals (>95% at 1-100 ppm, or ∼80% for ppb level seawater) for UO2(2+) species. The S(x)-LDHs are exceptionally efficient for selectively and rapidly capturing UO2(2+) both at high (ppm) and trace (ppb) quantities from the U-containing water including seawater. The maximum adsorption coeffcient value K(d)(U) of 3.4 × 10(6) mL/g (using a V/m ratio of 1000 mL/g) observed is among the highest reported for U adsorbents. In the presence of very high concentrations of competitive ions such as Ca(2+)/Na(+), S(x)-LDH exhibits superior selectivity for UO2(2+), over previously reported sorbents. Under low U concentrations, (S4)(2-) coordinates to UO2(2+) forming anionic complexes retaining in the LDH gallery. At high U concentrations, (S4)(2-) binds to UO2(2+) to generate neutral UO2S4 salts outside the gallery, with NO3(-) entering the interlayer to form NO3-LDH. In the presence of high Cl(-) concentration, Cl(-) preferentially replaces [S4](2-) and intercalates into LDH. Detailed comparison of U removal efficiency of S(x)-LDH with various known sorbents is reported. The excellent uranium adsorption ability along with the environmentally safe, low-cost constituents points to the high potential of S(x)-LDH materials for selective uranium capture.

  15. Determination of uranium concentration and burn-up of irradiated reactor fuel in contaminated areas in Belarus using uranium isotopic ratios in soil samples

    Energy Technology Data Exchange (ETDEWEB)

    Mironov, V.P.; Matusevich, J.L.; Kudrjashov, V.P.; Ananich, P.I.; Zhuravkov, V.V. [Inst. of Radiobiology, Minsk Univ. (Belarus); Boulyga, S.F. [Inst. of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-Univ. Mainz, Mainz (Germany); Becker, J.S. [Central Div. of Analytical Chemistry, Research Centre Juelich, Juelich (Germany)

    2005-07-01

    An analytical method is described for the estimation of uranium concentrations, of {sup 235}U/{sup 238}U and {sup 236}U/{sup 238}U isotope ratios and burn-up of irradiated reactor uranium in contaminated soil samples by inductively coupled plasma mass spectrometry. Experimental results obtained at 12 sampling sites situated on northern and western radioactive fallout tails 4 to 53 km distant from Chernobyl nuclear power plant (NPP) are presented. Concentrations of irradiated uranium in the upper 0-10 cm soil layers at the investigated sampling sites varied from 2.1 x 10{sup -9}g/g to 2.0 x 10{sup -6}g/g depending mainly on the distance from Chernobyl NPP. A slight variation of the degree of burn-up of spent reactor uranium was revealed by analyzing {sup 235}U/{sup 238}U and {sup 236}U/{sup 238}U isotope ratios and the average value amounted to 9.4{+-}0.3 MWd/(kg U). (orig.)

  16. Design Study for a Low-Enriched Uranium Core for the High Flux Isotope Reactor, Annual Report for FY 2008

    Energy Technology Data Exchange (ETDEWEB)

    Primm, Trent [ORNL; Chandler, David [ORNL; Ilas, Germina [ORNL; Miller, James Henry [ORNL; Sease, John D [ORNL; Jolly, Brian C [ORNL

    2009-03-01

    This report documents progress made during FY 2008 in studies of converting the High Flux Isotope Reactor (HFIR) from highly enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum alloy. With axial and radial grading of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in reactor performance from the current level. Results of selected benchmark studies imply that calculations of LEU performance are accurate. Scoping experiments with various manufacturing methods for forming the LEU alloy profile are presented.

  17. The Development of Low-Level Measurement Capabilities for Total and Isotopic Uranium in Environmental Samples at Brazilian and Argentine Laboratories by ABACC

    International Nuclear Information System (INIS)

    Guidicini, Olga M.; Olsen, Khris B.; Hembree, Doyle M.; Carter, Joel A.; Whitaker, Michael; Hayes, Susan M.

    2005-01-01

    accurately measuring both the quantity and isotopic composition of uranium at the levels expected in typical environmental samples (i.e., nanogram quantities).

  18. Uranium isotopes distinguish two geochemically distinct stages during the later Cambrian SPICE event

    DEFF Research Database (Denmark)

    Dahl, Tais Wittchen; Boyle, Richard A.; Canfield, Donald E.

    2014-01-01

    . Here we report high-precision uranium isotopic data in marine carbonates deposited during the Late Cambrian 'SPICE' event, at ca. 499 Ma, documenting a well-defined -0.18‰ negative δ238U excursion that occurs at the onset of the SPICE event's positive δ13C and δ34S excursions, but peaks (and tails off......) before them. Dynamic modelling shows that the different response of the U reservoir cannot be attributed solely to differences in residence times or reservoir sizes - suggesting that two chemically distinct ocean states occurred within the SPICE event. The first ocean stage involved a global expansion...... depletion in the oceans (Gill et al., 2011). We discuss scenarios for how an interval of elevated pyrite and organic carbon burial could have been sustained without widespread euxinia in the water column (both non-sulfidic anoxia and/or a more oxygenated ocean state are possibilities). Either way, the SPICE...

  19. Possibility of determination of the Galaxy age by the method of uranium - thorium isotopic relations

    International Nuclear Information System (INIS)

    Lyutostanskij, Yu.S.; Malevannyj, S.V.; Panov, I.V.; Chechetkin, V.M.

    1988-01-01

    Calculations concerning the formation of heavy elements in an astrophysical fast nuclear process characteristics of the Supernova explosions are carried out in the kinetic model of nucleosynthesis. The age of the Galaxy T G has been calculated making use of the method of uranium-thorium isotopic relations supplemented with the data on 244 Pu abundance in meteorites. T G is shown to be strongly dependent upon the calculation method applied to production of nuclei in r process, upon the data on neutron-rich nuclei and as well upon the external conditions, i.e. the density and temperature in the explosing star. The possibility of nucleosynthesis takes place due to close Supernova explosion, which enriched the chemical content of earth matter with heavy elements is analyzed. The range of allowed values of parameters of the theory of nucleosynthesis is studied

  20. Uranium

    International Nuclear Information System (INIS)

    Anon.

    1984-01-01

    The article briefly discusses the Australian government policy and the attitude of political party factions towards the mining and exporting of the uranium resources in Australia. Australia has a third of the Western World's low-cost uranium resources

  1. Measurements of the isotopic composition of galactic cosmic rays

    International Nuclear Information System (INIS)

    Herrstroem, N.Y.

    1985-01-01

    The galactic cosmic-ray boron and carbon isotopic composition has been measured. The boron measurement is the first ever made in nuclear emulsion. The carbon measurement has substantially improved the statistical assuracy in the determination of the 13 C abundance as compared to an earlier measurement using the same technique. Mass-spectra of cosmic-ray carbon and oxygen in different zenith angle intervals have been compared with calculated spectra. The method makes it possible to study experimentally the atmospheric influence on the primary cosmic-ray isotopic composition. Photometric measurements on fragments from oxygen-induced interactions in nuclear emulsion have been made. Accurate charge assignments have been made on all heavy fragments which has made it possible to study the interaction exclusively event-by-event. Measurements on the isotopic composition of primary cosmic-ray neom have been made. The data are from the Danish-French instrument on the HEAO-3 satellite. The rigidity dependent filtering of the cosmic rays by the Earth's magnetic field has been used. The energy dependence of the 22 Ne/ 20 Ne-ratio and its astrophysical implications are discussed. (Author)

  2. Measurements of flux and isotopic composition of soil carbon dioxide

    International Nuclear Information System (INIS)

    Gorczyca, Z.; Rozanski, K.; Kuc, T.

    2002-01-01

    The flux and isotope composition of soil CO 2 has been regularly measured at three sites located in the southern Poland, during the time period: January 1998 - October 2000. They represent typical ecosystems appearing in central Europe: (i) mixed forest; (ii) cultivated agricultural field; (iii) grassland. To monitor the flux and isotopic composition of soil CO 2 , a method based on the inverted cup principle was adopted. The flux of soil CO 2 reveals distinct seasonal fluctuations, with maximum values up to ca. 25 mmol/m 2 /h during sommer months and around ten times lower values during winter time. Also significant differences among the monitored sites were detected, the flux density of this gas being highest for the mixed forest site and ca. two times lower for the cultivated grassland. Carbon-13 content of the soil CO 2 reveals little seasonal variability, with δ 13 C values essentially reflecting the isotopic composition of the soil organic matter and the vegetation type. The carbon-14 content of soil CO 2 flux also reveals slight seasonality, with lower δ 14 C values recorded during winter time. Significantly lower δ 14 C values recorded during winter time. Significantly lower δ 14 C values were recorded at depth. (author)

  3. Alkali elemental and potassium isotopic compositions of Semarkona chondrules

    Science.gov (United States)

    Alexander, C.M. O'D.; Grossman, J.N.

    2005-01-01

    We report measurements of K isotope ratios in 28 Semarkona chondrules with a wide range of petrologic types and bulk compositions as well as the compositions of CPX-mesostasis pairs in 17 type I Semarkona chondrules, including two chondrules with radial alkali zonation and 19 type II chondrules. Despite the wide range in K/Al ratios, no systematic variations in K isotopic compositions were found. Semarkona chondrules do not record a simple history of Rayleigh-type loss of K. Experimentally determined evaporation rates suggest that considerable alkali evaporation would have occurred during chondrule formation. Nevertheless, based on Na CPX-mesostasis distribution coefficients, the alkali contents of the cores of most chondrules in Semarkona were probably established at the time of final crystallization. However, Na CPX-mesostasis distribution coefficients also show that alkali zonation in type I Semarkona chondrules was produced by entry of alkalis after solidification, probably during parent body alteration. This alkali metasomatism may have gone to completion in some chondrules. Our preferred explanation for the lack of systematic isotopic enrichments, even in alkali depleted type I chondrule cores, is that they exchanged with the ambient gas as they cooled. ?? The Meteoritical Society, 2005.

  4. Uranium

    International Nuclear Information System (INIS)

    Poty, B.; Cuney, M.; Bruneton, P.; Virlogeux, D.; Capus, G.

    2010-01-01

    With the worldwide revival of nuclear energy comes the question of uranium reserves. For more than 20 years, nuclear energy has been neglected and uranium prospecting has been practically abandoned. Therefore, present day production covers only 70% of needs and stocks are decreasing. Production is to double by 2030 which represents a huge industrial challenge. The FBR-type reactors technology, which allows to consume the whole uranium content of the fuel, is developing in several countries and will ensure the long-term development of nuclear fission. However, the implementation of these reactors (the generation 4) will be progressive during the second half of the 21. century. For this reason an active search for uranium ores will be necessary during the whole 21. century to ensure the fueling of light water reactors which are huge uranium consumers. This dossier covers all the aspects of natural uranium production: mineralogy, geochemistry, types of deposits, world distribution of deposits with a particular attention given to French deposits, the exploitation of which is abandoned today. Finally, exploitation, ore processing and the economical aspects are presented. Contents: 1 - the uranium element and its minerals: from uranium discovery to its industrial utilization, the main uranium minerals (minerals with tetravalent uranium, minerals with hexavalent uranium); 2 - uranium in the Earth's crust and its geochemical properties: distribution (in sedimentary rocks, in magmatic rocks, in metamorphic rocks, in soils and vegetation), geochemistry (uranium solubility and valence in magmas, uranium speciation in aqueous solution, solubility of the main uranium minerals in aqueous solution, uranium mobilization and precipitation); 3 - geology of the main types of uranium deposits: economical criteria for a deposit, structural diversity of deposits, classification, world distribution of deposits, distribution of deposits with time, superficial deposits, uranium

  5. On monitoring anthropogenic airborne uranium concentrations and 235U/238U isotopic ratio by Lichen - bio-indicator technique

    International Nuclear Information System (INIS)

    Golubev, A.V.; Golubeva, V.N.; Krylov, N.G.; Kuznetsova, V.F.; Mavrin, S.V.; Aleinikov, A.Yu.; Hoppes, W.G.; Surano, K.A.

    2005-01-01

    Lichens are widely used to assess the atmospheric pollution by heavy metals and radionuclides. However, few studies are available in publications on using lichens to qualitatively assess the atmospheric pollution levels. The paper presents research results applying epiphytic lichens as bio-monitors of quantitative atmospheric contamination with uranium. The observations were conducted during 2.5 years in the natural environment. Two experimental sites were used: one in the vicinity of a uranium contamination source, the other one - at a sufficient distance away to represent the background conditions. Air and lichens were sampled at both sites monthly. Epiphytic lichens Hypogimnia physodes were used as bio-indicators. Lichen samples were taken from various trees at about 1.5m from the ground. Air was sampled with filters at sampling stations. The uranium content in lichen and air samples as well as isotopic mass ratios 235 U/ 238 U were measured by mass-spectrometer technique after uranium pre-extraction. Measured content of uranium were 1.45mgkg -1 in lichen at 2.09E-04μgm -3 in air and 0.106mgkg -1 in lichen at 1.13E-05μgm -3 in air. The relationship of the uranium content in atmosphere and that in lichens was determined, C AIR =exp(1.1xC LICHEN -12). The possibility of separate identification of natural and man-made uranium in lichens was demonstrated in principle

  6. Investigations on isotopic composition of dusty mist of southern Tajikistan

    International Nuclear Information System (INIS)

    Abdullaev, S.F.; Abdurasulova, N.A.; Maslov, V.A.; Madvaliev, U.; Juraev, A.A.; Davlatshoev, T. S.U.

    2012-01-01

    Atmosphere physics laboratory under S.U. Umarov Physical and Technical Institute Academy of Sciences of the Republic of Tajikistan have carried out investigations on optical and micro physical properties of arid zone aerosols from 1982. Traces of man-made radioactive isotopes were revealed in sands and dust compositions taken in arid zone of Tajikistan during Soviet-American tests on investigation of arid aerosol. Produced result was the basis for further investigation of element composition for dusty haze distributed from south till central part of the country. We investigated samples of soil collected by natural sedimentation along dusty haze distribution and samples of dusty aerosol (in total 80 samples).

  7. Uranium

    International Nuclear Information System (INIS)

    Mackay, G.A.

    1978-01-01

    The author discusses the contribution made by various energy sources in the production of electricity. Estimates are made of the future nuclear contribution, the future demand for uranium and future sales of Australian uranium. Nuclear power growth in the United States, Japan and Western Europe is discussed. The present status of the six major Australian uranium deposits (Ranger, Jabiluka, Nabarlek, Koongarra, Yeelerrie and Beverley) is given. Australian legislation relevant to the uranium mining industry is also outlined

  8. Uranium

    International Nuclear Information System (INIS)

    1982-01-01

    The development, prospecting, research, processing and marketing of South Africa's uranium industry and the national policies surrounding this industry form the headlines of this work. The geology of South Africa's uranium occurences and their positions, the processes used in the extraction of South Africa's uranium and the utilisation of uranium for power production as represented by the Koeberg nuclear power station near Cape Town are included in this publication

  9. Determination of uranium and thorium isotopes in soil samples by coprecipitation

    International Nuclear Information System (INIS)

    Ngo Quang Huy; Trinh Thi Bich; Nguyen Van Suc

    2012-01-01

    The paper presents a procedure to prepare soil samples for U and Th isotope measurement by alpha-spectrometry after coprecipitation with LaF 3 . In this procedure the reduction of U(VI) to U(IV) was performed by Zn metal in 4M HCl solution. The recoveries of chemical separation equal to ε U-chemistry = 78±4% for uranium and ε Th-chemistry = 82±4% for thorium. Canberra alpha-spectrometer was used with PIPS detectors of A-1200-37-AM Model of 1200 mm 2 active area. The counting efficiency of the measuring system equals to ε counting = 18% and the total efficiencies were ε U = ε counting - ε U-chemistry = 14.0 ± 0.7% for uranium and ε Th = ε counting - ε Th-chemistry = 14.7 ± 0.7% for thorium. The recoveries of chemical separation were rather high (about 80%), that leads to the use of a small weight of soil sample (about 0.5 g). The efficiencies were also stable, that allows analyzing the soil sample without using radiotracers. They are advantages of the sample preparation procedure of this work. (author)

  10. Process control of a gaseous diffusion cascade for isotopic separation of uranium

    International Nuclear Information System (INIS)

    Bilous, Olegh; Doneddu, F.

    1986-01-01

    Various aspects of dynamics and process control of a gaseous diffusion cascade are described. The cascade enriches uranium hexafluoride gas (HEX) in the light isotope of uranium in a countercurrent flow. The linearized equations describing the equipment models are derived. One can then write the mass balances on the high and low pressure sides of a stage and the overall heat balance of a stage. These heat and mass balances are linear difference equations on the stage number with time derivatives which are then replaced by jω factors to examine the effects of cyclic perturbations. The mass balances are first treated for a cascade section of 12 stages with temperatures assumed constant. The effect of a perturbation of pressure on one of the stages is described first for ω=0 (that is for steady state). Then Nyquist diagrams are obtained. The effect of transport change is also studied. Then temperature is introduced, assuming pressures to be constant. The cases of a section of 12 stages and a cascade of 120 stages are examined. Again Nyquist diagrams of temperature frequency response to a perturbation on one stage are calculated. Process control of the heat exchangers is introduced. The method used to solve the difference equations may be applied to other types of perturbations and to the complete scheme of process control. (author)

  11. Monitoring of uranium isotopes in the environment of ABB ATOM, Vaesteraas

    International Nuclear Information System (INIS)

    Pettersson, H.; Holm, E.

    1991-01-01

    Detailed investigations of the aerial dispersion of radionuclides from a Swedish nuclear fuel fabrication facility have been carried out. Spatial distributions of uranium isotopes and their origin (fuel fabrication operations versus natural background radiation) have been studied. Air concentrations and combined dry/wet depositions of radionuclides were investigated during a one year period along a 6 km transect using high-volume air filter samplers and funnel collectors. Biological samples such as moss, grass, wheat and spruce needles were also occasionally investigated to study their potentiality as indicators of airborne radionuclides. The data demonstrate clearly enhanced activity ratios (AR) of 234 U/ 238 U (3-4) and 235 U/ 238 U (0.15-0.20) for both air (1 m above the ground) and ground level deposition close to the discharge point (100-300 m) and thereafter a monotonic decrease to natural activity ratios. Analysis of biological samples shows that wheat and spruce needles reproduce the activity ratio distributions and are excellent indicators of the airborne uranium release. Source-related concentrations of 234 U and 235 U exceed natural concentrations up to 3 km from the discharge point, but the dose contributions to members of the public compared to doses from the natural background radiation are small (less than 1%). (au)

  12. Uranium isotope evidence for two episodes of deoxygenation during Oceanic Anoxic Event 2

    Science.gov (United States)

    Clarkson, Matthew O.; Stirling, Claudine H.; Jenkyns, Hugh C.; Dickson, Alexander J.; Porcelli, Don; Moy, Christopher M.; Pogge von Strandmann, Philip A. E.; Cooke, Ilsa R.; Lenton, Timothy M.

    2018-03-01

    Oceanic Anoxic Event 2 (OAE 2), occurring ˜94 million years ago, was one of the most extreme carbon cycle and climatic perturbations of the Phanerozoic Eon. It was typified by a rapid rise in atmospheric CO2, global warming, and marine anoxia, leading to the widespread devastation of marine ecosystems. However, the precise timing and extent to which oceanic anoxic conditions expanded during OAE 2 remains unresolved. We present a record of global ocean redox changes during OAE 2 using a combined geochemical and carbon cycle modeling approach. We utilize a continuous, high-resolution record of uranium isotopes in pelagic and platform carbonate sediments to quantify the global extent of seafloor anoxia during OAE 2. This dataset is then compared with a dynamic model of the coupled global carbon, phosphorus, and uranium cycles to test hypotheses for OAE 2 initiation. This unique approach highlights an intra-OAE complexity that has previously been underconstrained, characterized by two expansions of anoxia separated by an episode of globally significant reoxygenation coincident with the “Plenus Cold Event.” Each anoxic expansion event was likely driven by rapid atmospheric CO2 injections from multiphase Large Igneous Province activity.

  13. On the Effect of Planetary Stable Isotope Compositions on Growth and Survival of Terrestrial Organisms.

    Directory of Open Access Journals (Sweden)

    Xueshu Xie

    Full Text Available Isotopic compositions of reactants affect the rates of chemical and biochemical reactions. Usually it is assumed that heavy stable isotope enrichment leads to progressively slower reactions. Yet the effect of stable isotopes may be nonlinear, as exemplified by the "isotopic resonance" phenomenon. Since the isotopic compositions of other planets of Solar system, including Mars and Venus, are markedly different from terrestrial (e.g., deuterium content is ≈5 and ≈100 times higher, respectively, it is far from certain that terrestrial life will thrive in these isotopic conditions. Here we found that Martian deuterium content negatively affected survival of shrimp in semi-closed biosphere on a year-long time scale. Moreover, the bacterium Escherichia coli grows slower at Martian isotopic compositions and even slower at Venus's compositions. Thus, the biological impact of varying stable isotope compositions needs to be taken into account when planning interplanetary missions.

  14. Uranium

    International Nuclear Information System (INIS)

    Stewart, E.D.J.

    1974-01-01

    A discussion is given of uranium as an energy source in The Australian economy. Figures and predictions are presented on the world supply-demand position and also figures are given on the added value that can be achieved by the processing of uranium. Conclusions are drawn about Australia's future policy with regard to uranium (R.L.)

  15. Uranium

    International Nuclear Information System (INIS)

    Toens, P.D.

    1981-03-01

    The geological setting of uranium resources in the world can be divided in two basic categories of resources and are defined as reasonably assured resources, estimated additional resources and speculative resources. Tables are given to illustrate these definitions. The increasing world production of uranium despite the cutback in the nuclear industry and the uranium requirements of the future concluded these lecture notes

  16. Uranium isotopic analysis of depleted uranium in presence of other radioactive materials by using nondestructive gamma-ray measurements in coaxial and planar Ge detectors

    International Nuclear Information System (INIS)

    Yucel, H.; Yeltepe, E.; Dikmen, H.; Turhan, Sh.; Vural, M.

    2006-01-01

    Full text: The isotopic abundance of depleted uranium samples in the presence of other radioactive materials, especially actinide isotopes such as Th 232, Np 237-Pa 233 and Am 241 can be determined from two gamma-ray spectrometric methods. One is the absolute method which employs non-destructive gamma-ray spectrometry for energies below 1001 keV using a coaxial Ge detector calibrated with a set of standards. The other is the multi-group analysis (MGA) method using the low energy region (< 300 keV) with a planar Ge detector intrinsically calibrated with gamma and X-rays of uranium without use of standards. At present absolute method, less intense but cleaner gamma peaks at 163.33 keV (5.08 percent) and 205 keV(5.01 percent) of U 235 are preferred over more intense peaks at 143.76 keV(10.76 percent), possible interference with 143.25 keV(0.44 percent) of Np 237 and 185.705 keV(57.2 percent), possible interference with 186.21 keV(3.51 percent) of Ra 226. In the high energy region the 1001.03 keV(0.837 percent) peak of Pa 234 m is used for the isotopic abundance analysis because the more intense 63.3 keV peak of Th 234 daughter of U 238 parent has a fully multiplet(62.86 keV+63.29 keV) and include the interferences of the 62.70 keV(1.5 percent) peak of Pa 234, the 63.81 keV(0.263 percent) peak of Th 232 and the 63.90 keV(0.011 percent) peak of Np 237. Although the MGA method is quicker and more practical, the more laborious absolute gamma spectrometric method can give more accurate results for the isotopic determination of depleted uranium samples. The relative uranium abundances obtained with the second method (i,e., MGA) are in general inconsistent with the declared values for the uranium samples in the presence of the above mentioned actinides. The reason for these erroneous results is proposed to be the interference of the gamma and X-rays of uranium in the 80-130 keV region used in MGA with those emissions from other radioactive materials present

  17. Uranium isotopes in tree bark as a spatial tracer of environmental contamination near former uranium processing facilities in southwest Ohio.

    Science.gov (United States)

    Conte, Elise; Widom, Elisabeth; Kuentz, David

    2017-11-01

    Inappropriate handling of radioactive waste at nuclear facilities can introduce non-natural uranium (U) into the environment via the air or groundwater, leading to anthropogenic increases in U concentrations. Uranium isotopic analyses of natural materials (e.g. soil, plants or water) provide a means to distinguish between natural and anthropogenic U in areas near sources of radionuclides to the environment. This study examines the utility of two different tree bark transects for resolving the areal extent of U atmospheric contamination using several locations in southwest Ohio that historically processed U. This study is the first to utilize tree bark sampling transects to assess environmental contamination emanating from a nuclear facility. The former Fernald Feed Materials Production Center (FFMPC; Ross, Ohio) produced U metal from natural U ores and recycled nuclear materials from 1951 to 1989. Alba Craft Laboratory (Oxford, Ohio) machined several hundred tons of natural U metal from the FFMPC between 1952 and 1957. The Herring-Hall-Marvin Safe Company (HHM; Hamilton, Ohio) intermittently fabricated slugs rolled from natural U metal stock for use in nuclear reactors from 1943 to 1951. We have measured U concentrations and isotope signatures in tree bark sampled along an ∼35 km SSE-NNW transect from the former FFMPC to the vicinity of the former Alba Craft laboratories (transect #1) and an ∼20 km SW- NE (prevailing local wind direction) transect from the FFMPC to the vicinity of the former HHM (transect #2), with a focus on old trees with thick, persistent bark that could potentially record a time-integrated signature of environmental releases of U related to anthropogenic activity. Our results demonstrate the presence of anthropogenic U contamination in tree bark from the entire study area in both transects, with U concentrations within 1 km of the FFMPC up to ∼400 times local background levels of 0.066 ppm. Tree bark samples from the Alba Craft and

  18. The effect of exposure to employees from mining and milling operations in a uranium mine on lead isotopes--a pilot study.

    Science.gov (United States)

    Gulson, Brian L; Mizon, Karen J; Dickson, Bruce L; Korsch, Michael J

    2005-03-01

    Potential exposure during mining and milling of uranium ore has resulted in the industry being highly regulated. Exposure can arise from inhalation of the daughter product radioactive gas radon (222Rn), inhalation of radioactive dust particles from mining and milling, direct irradiation from outside the body, and ingestion of radionuclides (e.g. uranium or radium) in food or water. Making use of the highly unusual lead isotopic signature for uranium ores (high 206Pb/204Pb from the high uranium content, low 208Pb/204Pb from the low Th/U ratio), we undertook a pilot study of nine male mine employees and three controls from the Ranger uranium mine in the Northern Territory Australia to determine if it was feasible to use lead isotopes in blood to identify exposure to uranium-derived materials. The lead isotopic data for the mine employees and controls plot in two distinct fields which are consistent with predicted isotopic patterns. Assuming retention of 10% of the ingested lead, then the increases seen in 206Pb represent intakes of between 0.9 and 15 mg, integrated over the years of exposure. The small amount of lead does not affect blood lead concentrations, but appears to be sufficient to be detectable with sensitive isotopic methods. Further studies, including those on urine, should be undertaken to confirm the veracity of the lead isotope method in monitoring exposure of uranium industry employees.

  19. The effect of exposure to employees from mining and milling operations in a uranium mine on lead isotopes. A pilot study

    International Nuclear Information System (INIS)

    Gulson, Brian L.; Mizon, Karen J.; Dickson, Bruce L.; Korsch, Michael J.

    2005-01-01

    Potential exposure during mining and milling of uranium ore has resulted in the industry being highly regulated. Exposure can arise from inhalation of the daughter product radioactive gas radon ( 222 Rn), inhalation of radioactive dust particles from mining and milling, direct irradiation from outside the body, and ingestion of radionuclides (e.g. uranium or radium) in food or water. Making use of the highly unusual lead isotopic signature for uranium ores (high 206 Pb/ 204 Pb from the high uranium content, low 208 Pb/ 204 Pb from the low Th/U ratio), we undertook a pilot study of nine male mine employees and three controls from the Ranger uranium mine in the Northern Territory Australia to determine if it was feasible to use lead isotopes in blood to identify exposure to uranium-derived materials. The lead isotopic data for the mine employees and controls plot in two distinct fields which are consistent with predicted isotopic patterns. Assuming retention of 10% of the ingested lead, then the increases seen in 206 Pb represent intakes of between 0.9 and 15 mg, integrated over the years of exposure. The small amount of lead does not affect blood lead concentrations, but appears to be sufficient to be detectable with sensitive isotopic methods. Further studies, including those on urine, should be undertaken to confirm the veracity of the lead isotope method in monitoring exposure of uranium industry employees

  20. Uranium isotopes in rivers, estuaries and adjacent coastal sediments of western India: their weathering, transport and oceanic budget

    International Nuclear Information System (INIS)

    Borole, D.V.; Krishnaswami, S.; Somayajulu, B.L.K.

    1982-01-01

    The two major river systems on the west coast of India, Narbada and Tapti, their estuaries and the coastal Arabian sea sediments have been extensively studied for their uranium concentrations and 234 U/ 238 U activity ratios. The 238 U concentrations in the aqueous phase of these river systems exhibit a strong positive correlation with the sum of the major cations, and with the HCO 3 - ion contents. The abundance ratio of dissolved U to the sum of the major cations in these waters is similar to their ratio in typical crustal rocks. In the estuaries, both 238 U and its great-grand daughter 234 U behave conservatively beyond chlorosities 0.14 g/l. A review of the uranium isotope measurements in river waters yield a discharge weighted-average 238 U concentration of 0.22 μg/l with a 234 U/ 238 U activity ratio of 1.20 +-0.06. The residence time of uranium isotopes in the oceans estimated from the 238 U concentration and the 234 U/ 238 U A.R. of the rivers yield conflicting results; the material balance of uranium isotopes in the marine environment still remains a paradox. If the disparity between the results is real, then an additional 234 U flux of about 0.25 dpm/cm 2 .10 3 yr into the oceans is necessitated. (author)

  1. Comparison of femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry for uranium isotopic measurements

    Energy Technology Data Exchange (ETDEWEB)

    Havrilla, George Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); McIntosh, Kathryn Gallagher [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Judge, Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dirmyer, Matthew R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Campbell, Keri [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gonzalez, Jhanis J. [Applied Spectra Inc., Fremont, CA (United States)

    2016-10-20

    Feasibility tests were conducted using femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry for rapid uranium isotopic measurements. The samples used in this study consisted of a range of pg quantities of known 235/238 U solutions as dried spot residues of 300 pL drops on silicon substrates. The samples spanned the following enrichments of 235U: 0.5, 1.5, 2, 3, and 15.1%. In this direct comparison using these particular samples both pulse durations demonstrated near equivalent data can be produced on either system with respect to accuracy and precision. There is no question that either LA-ICP-MS method offers the potential for rapid, accurate and precise isotopic measurements of U10Mo materials whether DU, LEU or HEU. The LA-ICP-MS equipment used for this work is commercially available. The program is in the process of validating this work for large samples using center samples strips from Y-12 MP-1 LEU-Mo Casting #1.

  2. Comparison of femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry for uranium isotopic measurements

    International Nuclear Information System (INIS)

    Havrilla, George Joseph; McIntosh, Kathryn Gallagher; Judge, Elizabeth; Dirmyer, Matthew R.; Campbell, Keri; Gonzalez, Jhanis J.

    2016-01-01

    Feasibility tests were conducted using femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry for rapid uranium isotopic measurements. The samples used in this study consisted of a range of pg quantities of known 235/238 U solutions as dried spot residues of 300 pL drops on silicon substrates. The samples spanned the following enrichments of 235 U: 0.5, 1.5, 2, 3, and 15.1%. In this direct comparison using these particular samples both pulse durations demonstrated near equivalent data can be produced on either system with respect to accuracy and precision. There is no question that either LA-ICP-MS method offers the potential for rapid, accurate and precise isotopic measurements of U10Mo materials whether DU, LEU or HEU. The LA-ICP-MS equipment used for this work is commercially available. The program is in the process of validating this work for large samples using center samples strips from Y-12 MP-1 LEU-Mo Casting #1.

  3. The hydrogen isotopic composition of kaolin minerals in Japan

    International Nuclear Information System (INIS)

    Marumo, Katsumi; Nagasawa, Keinosuke; Kuroda, Yoshimasu.

    1979-01-01

    Hydrogen isotopic composition (D/H ratio) was determined for kaolin minerals from geothermal areas and sedimentary and hydrothermal kaolin deposits in Japan. On the Ohnuma, Matsukawa, and Ohtake geothermal areas, the hydrogen isotopic fractionation factor between kaolin minerals and water was calculated to fall between 0.97 and 0.99 for the temperature range of 50 to 200 0 C, a fact which shows that the temperature of formation has no important effect on the D/H ratio of kaolin minerals. D/H ratio of kaolinites and dickites from many kaolin deposits shows local variation, and seems to correlate with isotopic variation of the present-day meteoric surface water. Exceptions are seen in some kaolin deposits such as Shokozan, Hiroshima Prefecture, where kaolinite and dickite have considerably high values of D/H ratio, and seem to have reacted with water rich in deuterium. D/H ratio of halloysite is not correlated with that of the present-day meteoric surface water. As Lawrence and Taylor (1971) pointed out, the original D/H ratio of constitutional water of halloysite is not preserved because of the isotopic exchange between the interlayer water and the constitutional water. (author)

  4. Clumped-isotope geochemistry of carbonates: A new tool for the reconstruction of temperature and oxygen isotope composition of seawater

    Energy Technology Data Exchange (ETDEWEB)

    Bernasconi, Stefano M., E-mail: Stefano.bernasconi@erdw.ethz.ch [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Schmid, Thomas W.; Grauel, Anna-Lena [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Mutterlose, Joerg [Institut fuer Geologie, Mineralogie und Geophysik, Ruhr Universitaet Bochum, Universitaetsstr. 150, 44801 Bochum (Germany)

    2011-06-15

    Highlights: > Clumped-isotope thermometry of carbonates is discussed. > Clumped isotopes of Belemnites show higher sea surface temperatures than commonly assumed for the lower Cretaceous. > The potential of clumped-isotope measurement on foraminifera is discussed. - Abstract: Clumped-isotope geochemistry deals with State of ordering of rare isotopes in molecules, in particular with their tendency to form bonds with other rare isotopes rather than with the most abundant ones. Among its possible applications, carbonate clumped-isotope thermometry is the one that has gained most attention because of the wide potential of applications in many disciplines of the earth sciences. In particular, it allows reconstructing the temperature of formation of carbonate minerals without knowledge of the isotopic composition of the water from which they were formed. In addition, the O isotope composition of the waters from which they were formed can be calculated using the {delta}{sup 18}O of the same carbonate sample. This feature offers new approaches in paleoclimatology for reconstructing past global geochemical cycles. In this contribution two applications of this method are presented. First the potential of a new analytical method of measurement of clumped isotopes on small samples of foraminifera, for high-resolution SST and seawater {delta}{sup 18}O reconstructions from marine sediments is shown. Furthermore the potential of clumped isotope analysis of belemnites, for reconstructing seawater {delta}{sup 18}O and temperatures in the Cretaceous is shown.

  5. U-Pb isotopic evidence pertaining to the age and genesis of uranium mineralisation in Karoo sediments

    International Nuclear Information System (INIS)

    Allsopp, H.L.; Welke, H.J.; Armstrong, R.A.; Clough, W.; Evans, I.B.

    1984-01-01

    Preliminary investigations have been carried out, using the uranium-lead isotopic method, on the uranium mineralisation that occurs within the Karoo sediments. Two occurences were studied, namely the lower Beaufort sediments (Adelaide Subgroup) in the Beaufort West area and the Molteno Formation sediments in the Ficksburg area. The objective were to determine the age of the mineralisation and to study the mode of formation of the ores. The pattern of U-Pb apparent ages for all the Karoo samples is 207 Pb/ 206 Pb age >> 207 Pb* 235 U age > 206 Pb* 238 U age

  6. Chemical composition of HAL, an isotopically-unusual Allende inclusion

    International Nuclear Information System (INIS)

    Davis, A.M.; Tanaka, T.; Grossman, L.; Lee, T.; Wasserburg, G.J.

    1982-01-01

    Thirty-seven major, minor and trace elements were determined by INAA and RNAA in samples of hibonite, black rim and portions of friable rim from an unusual Allende inclusion, HAL. The peculiar isotopic, mineralogical and textural properties of HAL are accompanied by very unusual trace element abundances. The most striking feature of the chemistry is the virtual absence of Ce from an inclusion otherwise highly enriched in REE compared to C1 chondrites. HAL is also depleted in Sr, Ba, U, V, Ru, Os and Ir, relative to other refractory elements. Of the lithophile elements determined which are normally considered to be refractory in a gas of solar composition, Sr, Ba, Ce, U and V are the most volatile in oxidizing gases. The distribution of REE between hibonite and rims seems to have been established when hibonite and other refractory minerals were removed at slightly different temperatures from a hot, oxidizing gas in which they previously coexisted as separate grains. On the basis of HAL's chemical and isotopic composition, possible locations for the chemical and mass dependent isotopic fractionation are discussed. (author)

  7. Evaluation of parameters associated with monitoring in vivo of uranium isotopes in the lungs; Avaliacao de parametros associados a monitoracao in vivo de isotopos de uranio nos pulmoes

    Energy Technology Data Exchange (ETDEWEB)

    Juppa, Silvia P.; Lucena, Eder A.; Dantas, Bernardo M.; Dantas, Ana Leticia A., E-mail: adantas@ird.gov.br [Instiluto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Laboratorio de Monitoracao In Vivo. Divisao de Dosimetria

    2013-11-01

    The objective of this study is to evaluate the parameters associated with the technique of monitoring individuals exposed to uranium isotopes, aiming to optimize the technique and reduced uncertainties associated.

  8. Concentrations and activity ratios of uranium isotopes in groundwater from Donana National Park, South of Spain

    International Nuclear Information System (INIS)

    Bolivar, J. P.; Olias, M.; Gonzalez-Garcia, F.; Garcia-Tenorio, R.

    2008-01-01

    The levels and distribution of natural radionuclides in groundwaters from the unconfined Almonte-Marismas aquifer, upon which Donana National Park is located, have been analysed. Most sampled points were multiple piezometers trying to study the vertical distribution of the hydrogeochemical characteristics in the aquifer. Temperature, pH, electrical conductivity, dissolved oxygen and redox potential were determined in the field. A large number of parameters, physico-chemical properties, major and minor ions, trace elements and natural radionuclides (U-isotopes, Th-isotopes, Ra-isotopes and 210 Po), were also analysed. In the southern zone, where aeolian sands crop out, water composition is of the sodium chloride type, and the lower U-isotopes concentrations have been obtained. As water circulates through the aquifer, bicarbonate and calcium concentrations increase slightly, and higher radionuclides concentrations were measured. Finally, we have demonstrated that 234 U/ 238 U activity ratios can be used as markers of the type of groundwater and bedrock, as it has been the case for old waters with marine origin confined by a marsh in the south-east part of aquifer

  9. Economic study of an installation for uranium isotope separation by gaseous diffusion; Etude economique d'une installation de separation des isotopes de l'uranium par diffusion gazeuse

    Energy Technology Data Exchange (ETDEWEB)

    Bilous, O [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    This report describes the major problems which arise in the choice of characteristics required in a gaseous diffusion installation for the separation of uranium isotopes. This choice depends largely on economic evaluations, and also on considerations of simplicity. The choice of working pressures and of the characteristics of the membrane are described, as are the possible alternatives regarding the structure of the stages and the problems of control. (author) [French] Ce rapport decrit les problemes majeurs qui se posent dans le choix des caracteristiques d'une installation de diffusion gazeuse destinee a la separation des isotopes de l'uranium. Ce choix depend en grande partie d'evaluations economiques et repose egalement sur des considerations de simplicite. On decrit ainsi le choix des pressions d'operation, celui des caracteristiques de la barriere, les alternatives possibles concernant la structure des etages et les problemes de regulation. (auteur)

  10. Measurement of plutonium isotopic composition by gamma-ray spectroscopy

    International Nuclear Information System (INIS)

    Kim, J. S.; Shin, J. S.; Ahn, J. S.

    1998-01-01

    The technology of the analysis of plutonium isotopic ratio is independent of the measurement geometry and applicable to samples of physical and chemical composition. Three standard plutonium samples were measured in the HPGe system. The results showed that CRM 136 and CRM 137 containing 238 Pu(0.223%) and 238 Pu(0.268%) were 18.4% and 14.2% error and CRM 138 of 238 Pu(0.01%) was 76% error. However the analysis represented less than 1.6% and 9% error in the three standard samples of highly involved 239 Pu and 240 Pu. Therefore, gamma-ray spectroscopy is very effective in the plutonium isotope analysis, having greater than 10% in content

  11. The Chemistry and Toxicology of Depleted Uranium

    Directory of Open Access Journals (Sweden)

    Sidney A. Katz

    2014-03-01

    Full Text Available Natural uranium is comprised of three radioactive isotopes: 238U, 235U, and 234U. Depleted uranium (DU is a byproduct of the processes for the enrichment of the naturally occurring 235U isotope. The world wide stock pile contains some 1½ million tons of depleted uranium. Some of it has been used to dilute weapons grade uranium (~90% 235U down to reactor grade uranium (~5% 235U, and some of it has been used for heavy tank armor and for the fabrication of armor-piercing bullets and missiles. Such weapons were used by the military in the Persian Gulf, the Balkans and elsewhere. The testing of depleted uranium weapons and their use in combat has resulted in environmental contamination and human exposure. Although the chemical and the toxicological behaviors of depleted uranium are essentially the same as those of natural uranium, the respective chemical forms and isotopic compositions in which they usually occur are different. The chemical and radiological toxicity of depleted uranium can injure biological systems. Normal functioning of the kidney, liver, lung, and heart can be adversely affected by depleted uranium intoxication. The focus of this review is on the chemical and toxicological properties of depleted and natural uranium and some of the possible consequences from long term, low dose exposure to depleted uranium in the environment.

  12. Chlorination of antimony and its volatilization treatment of waste antimony-uranium composite oxide catalyst

    International Nuclear Information System (INIS)

    Sawada, K.; Enokida, Y.

    2011-01-01

    For the waste antimony-uranium composite oxide catalyst, the chlorination of antimony and its volatilization treatment were proposed, and evaluated using hydrogen chloride gas at 873-1173 K. During the treatment, the weight loss of the composite oxide sample, which resulted from the volatilization of antimony, was confirmed. An X-ray diffraction analysis showed that uranium oxide, U 3 O 8 , was formed during the reaction. After the treatment at 1173 K for 1 h, almost all the uranium contained in the waste catalyst was dissolved by a 3 M nitric acid solution at 353 K within 10 min, although that of the non-treated catalyst was less than 0.1%. It was found that the chlorination and volatilization treatment was effective to separate antimony from the composite oxide catalyst and change uranium into its removable form. (orig.)

  13. Discussion of metallogenic substance source of Xiangshan uranium orefield

    International Nuclear Information System (INIS)

    Shao Fei; Tang Xiangsheng; Zou Maoqin; Hu Maomei; He Xiaomei; Chen Xiaoming; Xu Hengli

    2008-01-01

    Analysis of uranium source is a key problem for study on uranium deposit genesis. Based on analysis of general implication for determination of uranium source on distribution characteristics of regional uranium abundance, according to temporal and spatial evolution of regional metallogenic substances in process of geological history, and combining with indication for analysis of uranium source by Pb isotopic composition of ores and REE geochemistry of both rocks and ores in Xiangshan orefield, Lower Cambrian strata are determined as regional uranium source bed, Xiangshan volcanic basin is the accumulation area for regional metallogenic substances, magma and hydrothermal solution of post magmatism are media for uranium. Magmatism realizes uranium migration from 'source' to 'accumulation'. In process of magmatic evolution, uranium transformed into gas phase to provide substance base for uranium mineralization. Fluid-rock interaction of post magmatism also promoted some uranium from schist of the basement and rhyodacite into metallogenic solution. (authors)

  14. Osmium Isotope Compositions of Komatiite Sources Through Time

    Science.gov (United States)

    Walker, R. J.

    2001-12-01

    Extending Os isotopic measurements to ancient plume sources may help to constrain how and when the well-documented isotopic heterogeneities in modern systems were created. Komatiites and picrites associated with plume-related volcanism are valuable tracers of the Os isotopic composition of plumes because of their typically high Os concentrations and relatively low Re/Os. Re-Os data are now available for a variety of Phanerozoic, Proterozoic and Archean komatiites and picrites. As with modern plumes, the sources of Archean and Proterozoic komatiites exhibit a large range of initial 187Os/188Os ratios. Most komatiites are dominated by sources with chondritic Os isotopic compositions (e.g. Song La; Norseman-Wiluna; Pyke Hill; Alexo), though some (e.g. Gorgona) derive from heterogeneous sources. Of note, however, two ca. 2.7 Ga systems, Kostomuksha (Russia) and Belingwe (Zimbabwe), have initial ratios enriched by 2-3% relative to the contemporary convecting upper mantle. These results suggest that if the 187Os enrichment was due to the incorporation of minor amounts of recycled crust into the mantle source of the rocks, the crust formed very early in Earth history. Thus, the Os results could reflect derivation of melt from hybrid mantle whose composition was modified by the addition of mafic crustal material that would most likely have formed between 4.2 and 4.5 Ga. Alternately, the mantle sources of these komatiites may have derived a portion of their Os from the putative 187Os - and 186Os -enriched outer core. For this hypothesis to be applicable to Archean rocks, an inner core of sufficient mass would have to have crystallized sufficiently early in Earth history to generate an outer core with 187Os enriched by at least 3% relative to the chondritic average. Using the Pt-Re-Os partition coefficients espoused by our earlier work, and assuming linear growth of the inner core started at 4.5 Ga and continued to present, would yield an outer core at 2.7 Ga with a gamma Os

  15. Numerical simulation of bellows effect on flow and separation of uranium isotopes in a supercritical gas centrifuge

    International Nuclear Information System (INIS)

    Borisevich, V.D.; Morozov, O.E.; Godisov, O.N.

    2000-01-01

    Numerical solving of the Navier-Stokes and convection-diffusion equations by the finite difference technique has been applied to study the influence of bellows on the flow and separation of uranium isotopes in a single supercritical gas centrifuge. Dependence of the separative power of a gas centrifuge on geometric parameters and position of a bellows on a rotor wall as well as the effect of scoop drag and feed flow on isotope separation in a gas centrifuge with a bellows have been obtained in computing experiments. It was demonstrated that increase of the separative power with increase of the gas centrifuge length is less considerable than predicted by the Dirac's law

  16. The IDA-80 measurement evaluation programme on mass spectrometric isotope dilution analysis of uranium and plutonium. Vol. 3

    International Nuclear Information System (INIS)

    Beyrich, W.; Golly, W.; Spannagel, G.

    1985-04-01

    The evaluation data derived from the measurement results of the laboratories participating in the IDA-80 programme have been compiled in tables and graphs. They concern a total of more than 2000 determinations of isotope ratios, isotope abundances and concentrations for uranium and plutonium obtained on test materials of industrial origin which contained fission products, and on fission product free synthetic reference solutions. Comparisons are made with data certified by CBNM and NBS, and estimates are given which were calculated by variance analyses for within- and between laboratory variations. (orig.) [de

  17. Stable isotope composition of atmospheric carbon monoxide. A modelling study

    International Nuclear Information System (INIS)

    Gromov, Sergey S.

    2014-01-01

    This study aims at an improved understanding of the stable carbon and oxygen isotope composition of the carbon monoxide (CO) in the global atmosphere by means of numerical simulations. At first, a new kinetic chemistry tagging technique for the most complete parameterisation of isotope effects has been introduced into the Modular Earth Submodel System (MESSy) framework. Incorporated into the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model, an explicit treatment of the isotope effects on the global scale is now possible. The expanded model system has been applied to simulate the chemical system containing up to five isotopologues of all carbon- and oxygen-bearing species, which ultimately determine the δ 13 C, δ 18 O and Δ 17 O isotopic signatures of atmospheric CO. As model input, a new stable isotope-inclusive emission inventory for the relevant trace gases has been compiled. The uncertainties of the emission estimates and of the resulting simulated mixing and isotope ratios have been analysed. The simulated CO mixing and stable isotope ratios have been compared to in-situ measurements from ground-based observatories and from the civil-aircraft-mounted CARIBIC-1 measurement platform. The systematically underestimated 13 CO/ 12 CO ratios of earlier, simplified modelling studies can now be partly explained. The EMAC simulations do not support the inferences of those studies, which suggest for CO a reduced input of the highly depleted in 13 C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH 4 ) molecule is simulated in the troposphere, to a large extent due to the competition between the deposition and convective transport processes affecting the CH 4 to CO reaction chain intermediates. None of the other factors, assumed or disregarded in previous studies, however hypothesised to have the potential in enriching tropospheric CO in 13 C, were found significant when explicitly simulated. The

  18. Condition of granulating titanium-activated carbon composite adsorbent and its adsorption for uranium

    International Nuclear Information System (INIS)

    Miyai, Yoshitaka; Kitamura, Takao; Katoh, Shunsaku; Miyazaki, Hidetoshi

    1979-01-01

    The powdery titanium-activated carbon composite adsorbent was granulated, and the strength and uranium adsorptivity of the granulated adsorbent were studied in relation to its granulating condition. By use of polyvinylalcohol (PVA) with degree of polymerization above 2,000 as binder, the granular adsorbent with as much the same strength as commercial granular activated carbon was obtained. Addition of PVA did not affect the amount of adsorbed uranium in equilibrium, but decreased the adsorption rate. Effect of granule size between 2-5 mm on the uranium adsorption rate was that the uranium adsorption rate changed proportionally to surface area of assumed sphere. As a test for practical use, 5 times repetitions of adsorption and desorption were carried out on the same granular adsorbent. During this repetition the adsorbent containing formalized PVA revealed smaller weight loss than non-treated adsorbent. The amount of adsorbed uranium decreased with increasing repetition times, and reason of this was discussed. (author)

  19. Determination of radium and uranium isotopes in natural waters by sorption on hydrous manganese dioxide followed by alpha-spectrometry

    International Nuclear Information System (INIS)

    Bojanowski, R.; Radecki, Z.; Burns, K.

    2005-01-01

    Water samples, spiked with 133 Ba and 232 U radiotracers, are scavenged for radium and uranium isotopes using hydrous manganese dioxide which is produced in-situ, by reacting manganese (+2) and permanganate ions at pH 8-9. The precipitate is solubilized with ascorbic and acetic acids and the resulting solution filtered through a glass fibre filter GF/F to remove particulate matter. The radium is co-precipitated with barium ions by the addition of a saturated Na 2 SO 4 solution where a small amount of BaSO 4 suspension is introduced to initiate crystallization. The micro precipitate containing the radium is collected on a 0.1 membrane filter and the filtrate saved for follow-up uranium analysis. The 226 Ra on the filter is determined by alpha-spectrometry and its recovery is assessed by measuring the 133 Ba on the same filter using gamma-spectrometry. The filtrate containing uranium is passed through a Dowex AG 1 x 4 ion-exchange resin in the SO 4 2- form which retains uranium while other ions are eluted by dilute (0.25M) sulphuric acid. Uranium is eluted from the column by distilled water, electrodeposited on a silver disc and the uranium isotopes and their recovery are determined by alpha-spectrometry. The method was tested on a variety of natural and spiked water samples with known concentrations of 226 Ra and 238 U and was found to yield accurate results within ±10% RSD of the target values. (author)

  20. Isotopic composition and origin of the precipitation in Northern Chile

    International Nuclear Information System (INIS)

    Aravena, R.; Suzuki, O.; Pena, H.; Pollastri, A.; Fuenzalida, H.; Grilli, A.

    1999-01-01

    A 3 a data set of isotopes in precipitation from northern Chile show a very distinct pattern, with δ 18 O values ranging between -18 and -15per thousand at high altitude stations, compared to δ 18 O values between -10 and -6per thousand at the lower altitude areas. The 18 O-depleted values observed in the high altitude area, the Altiplano, are related to processes that affect the air masses that originated over the Atlantic, cross the Amazon Basin (continental effect), ascend the Andes (altitude effect) and precipitated (convective effect) in the Altiplano. It is postulated that a second source of moisture, associated with air masses from the Pacific, may contribute to the 18 O-enriched values observed in the lower altitude areas. Similar isotopic patterns are documented in springs and groundwater indicating that the data presented in this paper are an accurate representation of the long term behavior isotopic composition of rain in northern Chile. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  1. Isotopic composition and origin of the precipitation in Northern Chile

    Energy Technology Data Exchange (ETDEWEB)

    Aravena, R. [Department of Earth Sciences, University of Waterloo, Waterloo (Canada); Suzuki, O. [Exploracion y Desarrollo de Recursos Hidricos, Santiago (Chile); Pena, H. [Direccion General de Aguas, Ministerio de Obras Publicas, Santiago (Chile); Pollastri, A. [Comision Chilena de Energia Nuclear, Santiago (Chile); Fuenzalida, H. [Departamento de Geofisica, Universidad of Chile, Santiago (Chile); Grilli, A. [Empresa Metropolitana de Obras Sanitarias, Santiago (Chile)

    1999-06-01

    A 3 a data set of isotopes in precipitation from northern Chile show a very distinct pattern, with {delta}{sup 18}O values ranging between -18 and -15per thousand at high altitude stations, compared to {delta}{sup 18}O values between -10 and -6per thousand at the lower altitude areas. The {sup 18}O-depleted values observed in the high altitude area, the Altiplano, are related to processes that affect the air masses that originated over the Atlantic, cross the Amazon Basin (continental effect), ascend the Andes (altitude effect) and precipitated (convective effect) in the Altiplano. It is postulated that a second source of moisture, associated with air masses from the Pacific, may contribute to the {sup 18}O-enriched values observed in the lower altitude areas. Similar isotopic patterns are documented in springs and groundwater indicating that the data presented in this paper are an accurate representation of the long term behavior isotopic composition of rain in northern Chile. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  2. Analysis of Uranium and Plutonium by MC-ICPMS

    International Nuclear Information System (INIS)

    Williams, R W

    2005-01-01

    This procedure is written as general guidance for the measurement of elemental isotopic composition by plasma-source inorganic mass spectrometry. Analytical methods for uranium and plutonium are given as examples

  3. The application of scanning electron microscopy to the determination of elemental and isotopic composition in individual actinide particles

    International Nuclear Information System (INIS)

    Vatter, I.; Cattle, G.; Tushingham, J.

    2000-01-01

    Techniques for the determination of both elemental and isotopic composition of actinides within single particles are required by the IAEA in support of their environmental safeguards programme. SEM and SIMS are valuable techniques for the measurement of elemental and isotopic composition, respectively, on the particle scale. The potential for effective combination of SEM and SIMS has been investigated at Harwell Laboratory. In trials, copper finder grids have been successfully used to enable re-identification of particles between SEM and SIMS instruments. Use of the grids enables rapid relocation of particles pre-selected by SEM for SIMS measurement. The work has highlighted a possible matrix effect in plutonium measurement that results in variable sensitivity dependent on the presence of other elements (including uranium). This effect would limit the use of SIMS to obtain elemental ratios, and highlights the requirement to use both SEM and SIMS to gain full and accurate information. The possible use of autoradiography as an adjunct to SEM has been investigated. In principle, autoradiography could be used to identify higher enrichments of uranium and enable pre-selection of particles for SIMS measurement. During trials, practical problems have been encountered which have demonstrated this particular approach to be unsuitable. (author)

  4. Mercury emissions and stable isotopic compositions at Vulcano Island (Italy)

    Science.gov (United States)

    Zambardi, T.; Sonke, J. E.; Toutain, J. P.; Sortino, F.; Shinohara, H.

    2009-01-01

    Sampling and analyses methods for determining the stable isotopic compositions of Hg in an active volcanic system were tested and optimized at the volcanic complex of Vulcano (Aeolian Islands, Italy). Condensed gaseous fumarole Hg (fum)T, plume gaseous elemental Hg (g)0 and plume particulate Hg (p)II were obtained at fumaroles F0, F5, F11, and FA. The average total Hg emissions, based on Hg T/SO 2 in condensed fumarolic gases and plumes, range from 2.5 to 10.1 kg y - 1 , in agreement with published values [Ferrara, R., Mazzolai, B., Lanzillotta, E., Nucaro, E., Pirrone, N., 2000. Volcanoes as emission sources of atmospheric mercury in the Mediterranean Basin. Sci. Total Environ. 259(1-3), 115-121; Aiuppa, A., Bagnato, E., Witt, M.L.I., Mather, T.A., Parello, F., Pyle, D.M., Martin, R.S., 2007. Real-time simultaneous detection of volcanic Hg and SO 2 at La Fossa Crater, Vulcano (Aeolian Islands, Sicily). Geophys. Res. Lett. 34(L21307).]. Plume Hg (p)II increases with distance from the fumarole vent, at the expense of Hg (g)0 and indicates significant in-plume oxidation and condensation of fumarole Hg (fum)T. Relative to the NIST SRM 3133 Hg standard, the stable isotopic compositions of Hg are δ 202Hg (fum)T = - 0.74‰ ± 0.18 (2SD, n = 4) for condensed gaseous fumarole Hg (fum)T, δ 202Hg (g)0 = - 1.74‰ ± 0.36 (2SD, n = 1) for plume gaseous elemental Hg (g)0 at the F0 fumarole, and δ 202Hg (p)II = - 0.11‰ ± 0.18 (2SD, n = 4) for plume particulate Hg (p)II. The enrichment of Hg (p)II in the heavy isotopes and Hg (g)0 in the light isotopes relative to the total condensed fumarolic Hg (fum)T gas complements the speciation data and demonstrates a gas-particle fractionation occurring after the gas expulsion in ambient T° atmosphere. A first order Rayleigh equilibrium condensation isotope fractionation model yields a fractionation factor α cond-gas of 1.00135 ± 0.00058.

  5. Uranium

    International Nuclear Information System (INIS)

    Whillans, R.T.

    1981-01-01

    Events in the Canadian uranium industry during 1980 are reviewed. Mine and mill expansions and exploration activity are described, as well as changes in governmental policy. Although demand for uranium is weak at the moment, the industry feels optimistic about the future. (LL)

  6. V isotope composition in modern marine hydrothermal sediments

    Science.gov (United States)

    Wu, F.; Owens, J. D.; Nielsen, S.; German, C. R.; Rachel, M.

    2017-12-01

    Vanadium is multivalence transition metal with two isotopes (51V and 50V). Recent work has shown that large V isotope variations occur with oxygen variations in modern sediments (Wu et al., 2016 and 2017 Goldschmidt Abstracts), providing its potential as a promising proxy for determining low oxygen conditions. However, the development of V isotopes as a proxy to probe past redox conditions requires a comprehensive understanding of the modern oceanic isotopic mass balance. Therein, the scavenging of V from the hydrous iron oxides in hydrothermal fluid has been shown to be an important removal process from seawater (Rudnicki and Elderfield, 1993 GCA) but remains unquantified. In this study, we analyzed V isotopic compositions of metalliferous sediments around the active TAG hydrothermal mound from the mid-Atlantic Ridge (26° degrees North) and the Eastern Pacific Zonal Transect (GEOTRACES EPZT cruise GP16). The TAG sediments deposited as Fe oxyhydroxides from plume fall-out, and have δ51V values between -0.3 to 0‰. The good correlation between Fe and V for these metalliferous sediments indicate that the accumulation of V in these samples is directly related to the deposition of Fe oxyhydroxides, which also control their V isotope signature. The EPZT samples cover 8,000 km in the South Pacific Ocean with sedimentary areas that underlie the Peru upwelling region and the well-oxygenated deep South Pacific Ocean influenced by hydtorthermal plume material from southern East Pacific Rise (EPR). The sediments collected at the east of the EPR have δ51V values between -1.2 to -0.7‰, similar to previous δ51V of oxic sediments. In contrast, the sediments from the west of the EPR have δ51V values (-0.4 to 0‰) similar to hydrothermal sediments from the mid-Atlantic Ridge, indicating the long transportation (more than 4,000 km, Fitzsimmons et al., 2017 NG) of Fe and Mn from hydrothermal plume and their incorporation into sediments have a major impact on the cycle of V

  7. Stable carbon isotopic composition of gasolines determined by isotope ratio monitoring gas chromatography mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Smallwood, B.J.; Philp, R.P.; Allen, J.D. [University of Oklahoma, Norman, OK (United States). School of Geology and Geophysics

    2002-07-01

    A large number of underground gasoline storage facilities in the United States continuously leak gasoline into the subsurface, which makes gasoline a major groundwater contaminant. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) are used currently to characterize contaminated groundwater and soils. Correlations of contaminants with suspected source(s) are extremely difficult by these techniques because many gasolines have similar hydrocarbon distributions. The present study applied the technique of isotope ratio monitoring gas chromatography-mass spectrometry (irmGC-MS) to 19 gasoline samples from different areas of the USA. This allows a much better correlation of gasoline contaminants to source. Data obtained indicate a wide range of {sup {delta}}{sup 13}C values for 16 ubiquitous compounds in the gasolines. The majority of samples could be distinguished from each other on the basis of {sup {delta}}{sup 13}C hydrocarbon composition. The oxygenated additive methyl tertiary butyl ether (MTBE) was present in ten of the gasolines analyzed, and had a relatively narrow range of {sup {delta}}{sup 13}C values (-30.4 to -28.3 per mille). Preliminary investigations were also made to determine the extent of carbon isotopic fractionation after simple water washing and evaporation experiments. Results indicate that the majority of compounds did not undergo significant carbon isotopic fractionation as a result of these processes. (author)

  8. A method for reducing memory errors in the isotopic analyses of uranium hexafluoride by mass spectrometry; Methode de reduction des erreurs de memoire dans les analyses isotopiques de l'hexafluorure d'uranium par spectrometrie de masse

    Energy Technology Data Exchange (ETDEWEB)

    Bir, R [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1961-07-01

    One of the most serious causes of systematic error in isotopic analyses of uranium from UF{sub 6} is the tendency of this material to become fixed in various ways in the mass spectrometer. As a result the value indicated by the instrument is influenced by the isotopic composition of the substances previously analysed. The resulting error is called a memory error. Making use of an elementary mathematical theory, the various methods used to reduce memory errors are analysed and compared. A new method is then suggested, which reduces the memory errors to an extent where they become negligible over a wide range of {sup 235}U concentration. The method is given in full, together with examples of its application. (author) [French] Une des causes d'erreurs systematiques les plus graves dans les analyses isotopiques d'uranium a partir d'UF{sub 6} est l'aptitude de ce produit a se fixer de diverses manieres dans le spectrometre de masse. Il en resulte une influence de la composition isotopique des produits precedemment analyses sur la valeur indiquee par l'appareil. L'erreur resultante est appelee erreur de memoire. A partir d'une theorie mathematique elementaire, on analyse et on compare les differentes methodes utilisees pour reduire les erreurs de memoire. On suggere ensuite une nouvelle methode qui reduit les erreurs de memoire dans une proportion telle qu'elles deviennent negligeables dans un grand domaine de concentration en {sup 235}U. On donne le mode operatoire complet et des exemples d'application. (auteur)

  9. Introduction and optimization of methods for isotopic determination of thorium and uranium via α-spectroscopy and their applications in analysis of water from Morro do Ferro, Brazil

    International Nuclear Information System (INIS)

    Vale, M.G.R.

    1982-01-01

    Methods for isotopic determination of thorium and uranium via α-spectroscopy, using a surface barrier detector, are described. The methods were applied in surface waters, borehole water, sediments and minerals from Morro do Ferro (MG), Brazil. Results and analysis by different techniques are compared and some discussions concerning to Th-concentration levels and anomalous isotopic and nuclidic ratios are presented. (Author) [pt

  10. Stable-carbon isotopic composition of maple sap and foliage

    International Nuclear Information System (INIS)

    Leavitt, S.W.; Long, A.

    1985-01-01

    The 13 C/ 12 C ratios of Acer grandidentatum sap sugar collected during the dormant period are compared to those of buds, leaves, and wood developed over the following growing season. As the primary carbon source for cellulose manufacture at initiation of annual growth in deciduous trees, sap sucrose would be expected to have an isotopic composition similar to first-formed cellulose. Although constancy in concentration and 13 C/ 12 C ratios of the maple sap sugar suggests any gains or losses (e.g. to maintenance metabolism) do not appreciably alter composition, the 13 C/ 12 C ratios of cellulose of the enlarging buds in the spring are quite distinct from those of the sap sugar, seemingly precluding a simple direct biochemical pathway of sap sucrose→glucose→cellulose in favor of a more complex pathway with greater likelihood of isotopic fractionation. The 13 C/ 12 C ratios of the leaves and in the growth ring were initially similar to the sap sugar but decreased steadily over the growing season. (author)

  11. Determination of uranium in uranyl nitrate solutions of nuclear grade quality - Gravimetric method

    International Nuclear Information System (INIS)

    1990-01-01

    This international Standard specifies a precise and accurate gravimetric method for determining the uranium content in uranyl nitrate product solutions of nuclear grade quality at concentrations above 100 g/l of uranium. Non-volatile impurities influence the accuracy of the method. Uranyl nitrate is converted into uranium octoxide (U 3 O 8 ) by ignition in air to constant mass at 900 deg. C ± 10 deg. C. Calculation of the uranium content in the sample using a gravimetric conversion factor which depends on the isotopic composition of the uranium. The isotopic composition is determined by mass spectrometry

  12. Natural uranium and strontium isotope tracers of water sources and surface water-groundwater interactions in arid wetlands: Pahranagat Valley, Nevada, USA

    Science.gov (United States)

    Paces, James B.; Wurster, Frederic C.

    2014-01-01

    Near-surface physical and chemical process can strongly affect dissolved-ion concentrations and stable isotope compositions of water in wetland settings, especially under arid climate conditions. In contrast, heavy radiogenic isotopes of strontium (87Sr/86Sr) and uranium (234U/238U) remain largely unaffected and can be used to help identify unique signatures from different sources and quantify end-member mixing that would otherwise be difficult to determine. The utility of combined Sr and U isotopes are demonstrated in this study of wetland habitats on the Pahranagat National Wildlife Refuge, which depend on supply from large-volume springs north of the Refuge, and from small-volume springs and seeps within the Refuge. Water budgets from these sources have not been quantified previously. Evaporation, transpiration, seasonally variable surface flow, and water management practices complicate the use of conventional methods for determining source contributions and mixing relations. In contrast, 87Sr/86Sr and 234U/238U remain unfractionated under these conditions, and compositions at a given site remain constant. Differences in Sr- and U-isotopic signatures between individual sites can be related by simple two- or three-component mixing models. Results indicate that surface flow constituting the Refuge’s irrigation source consists of a 65:25:10 mixture of water from two distinct regionally sourced carbonate aquifer springs, and groundwater from locally sourced volcanic aquifers. Within the Refuge, contributions from the irrigation source and local groundwater are readily determined and depend on proximity to those sources as well as water management practices.

  13. Variability of Fe isotope compositions of hydrothermal sulfides and oxidation products at mid-ocean ridges

    Science.gov (United States)

    Li, Xiaohu; Wang, Jianqiang; Chu, Fengyou; Wang, Hao; Li, Zhenggang; Yu, Xing; Bi, Dongwei; He, Yongsheng

    2018-04-01

    Significant Fe isotopic fractionation occurs during the precipitation and oxidative weathering of modern seafloor hydrothermal sulfides, which has an important impact on the cycling of Fe isotopes in the ocean. This study reports the Fe-isotope compositions of whole-rock sulfides and single-mineral pyrite collected from hydrothermal fields at the South Mid-Atlantic Ridge (SMAR) and the East Pacific Rise (EPR) and discusses the impacts of precipitation and late-stage oxidative weathering of sulfide minerals on Fe isotopic fractionation. The results show large variation in the Fe-isotope compositions of the sulfides from the different hydrothermal fields on the mid-oceanic ridges, indicating that relatively significant isotope fractionation occurs during the sulfide precipitation and oxidative weathering processes. The Fe-isotope compositions of the sulfides from the study area at the SMAR vary across a relatively small range, with an average value of 0.01‰. This Fe-isotope composition is similar to the Fe-isotope composition of mid-oceanic ridge basalt, which suggests that Fe was mainly leached from basalt. In contrast, the Fe-isotope composition of the sulfides from the study area at the EPR are significantly enriched in light Fe isotopes (average value - 1.63‰), mainly due to the kinetic fractionation during the rapid precipitation process of hydrothermal sulfide. In addition, the pyrite from different hydrothermal fields is enriched in light Fe isotopes, which is consistent with the phenomenon in which light Fe isotopes are preferentially enriched during the precipitation of pyrite. The red oxides have the heaviest Fe-isotope compositions (up to 0.80‰), indicating that heavy Fe isotopes are preferentially enriched in the oxidation product during the late-stage oxidation process. The data obtained from this study and previous studies show a significant difference between the Fe-isotope compositions of the sulfides from the SMAR and EPR. The relatively heavy

  14. Efficient isotope ratio analysis of uranium particles in swipe samples by total-reflection x-ray fluorescence spectrometry and secondary ion mass spectrometry

    International Nuclear Information System (INIS)

    Esaka, Fumitaka; Watanabe, Kazuo; Fukuyama, Hiroyasu; Onodera, Takashi; Esaka, Konomi T.; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu

    2004-01-01

    A new particle recovery method and a sensitive screening method were developed for subsequent isotope ratio analysis of uranium particles in safeguards swipe samples. The particles in the swipe sample were recovered onto a carrier by means of vacuum suction-impact collection method. When grease coating was applied to the carrier, the recovery efficiency was improved to 48±9%, which is superior to that of conventionally-used ultrasoneration method. Prior to isotope ratio analysis with secondary ion mass spectrometry (SIMS), total reflection X-ray fluorescence spectrometry (TXRF) was applied to screen the sample for the presence of uranium particles. By the use of Si carriers in TXRF analysis, the detection limit of 22 pg was achieved for uranium. By combining these methods with SIMS, the isotope ratios of 235 U/ 238 U for individual uranium particles were efficiently determined. (author)

  15. Preparation and certification of a uranium isotope certified reference material JAERI-U5

    International Nuclear Information System (INIS)

    Tamura, Shuzo; Hashitani, Hiroshi

    1982-06-01

    The Committee on Analytical Chemistry of Nuclear Fuels and Reactor Materials, JAERI had planned to prepare a new reference material, JAERI-U5 for uranium isotopic measurement since 1978. The reference material is composed of 6 samples of different enrichment in the range of 0.2 to 4.5 wt. percents of 235 U. The preparation includes dissolution of raw materials, blending of solutions, precipitation of ammonium diuranate, drying and ignition to U 3 O 8 . A mass-spectrometric collaborative analysis was carried out by well-trained two laboratories in this country, JAERI and PNC. The certified values were decided from the result of the collaborative work. As the measurements were based on NBS SRM's, JAERI-U5 should be called tertiary standard. The materials are packed in bottles of low-potassium-content glass for a possible use in non-destructive gamma-rays spectrometry. The reference material has been distributing from JAERI with a price of yen 140,000 per set (6 samples of 2 g of each) since 1979. (author)

  16. The separation nozzle method for enrichment of the light uranium isotope

    International Nuclear Information System (INIS)

    Becker, E.W.

    1982-05-01

    The history of the development of the separation nozzle method for enrichment of the light uranium isotope is described as a contribution to a memorandum published by Deutsche Forschungsgemeinschaft. The work was triggered off by an effect which had been observed in fundamental studies on gas kinetics. Development up to the technical maturity covered a period of more than 25 years. The implementation of the project at the Karlsruhe Nuclear Research Center provided an adequate financial and technical framework, the employment of senior staff without limitations in time being of major importance for the continuity of work. The links established between the Institute and the University and the resulting opportunity of having doctoral theses written, on the other hand, gave rise to a permanent flow of young, highly qualified scientists and engineers. Thus the Institut's requirements for junior staff could be satisfied in an optimum way. Although the Center offered a variety of possibilities of internal technical cooperation, important developments were performed jointly with industrial firms experienced in related fields. By this, not only a steady flow of know-how had been accumulated but also the large-scale applicability was ensured at a later date of results jointly obtained. (orig.) [de

  17. Uranium-lead isotope systematics in a regionally metamorphosed tonalite from the Eastern Alps

    Energy Technology Data Exchange (ETDEWEB)

    Cliff, R A; Cohen, A [Leeds Univ. (UK). Dept. of Earth Sciences

    1980-10-01

    U-Pb isotopic analyses were made on sphene, three epidote fractions, apatite, K-feldspar and plagioclase from a 314-m.y.-old tonalite member of the Zentralgneis plutonic suite in the southeast Tauern Window. The tonalite reached temperatures in excess of 550/sup 0/C during the Tertiary Alpine metamorphism. Apatite, fine-grained clinozoisite and feldspars equilibrated during the metamorphism, and the apatite yields an age of 22 m.y. which is 6 m.y. older than the Rb-Sr age of coexisting biotite. Sphene and coarse-grained iron-rich epidote did not reach equilibrium during Alpine metamorphism and the sphene data indicate crystallisation before 215 m.y. These minerals contain a large proportion of the uranium and thorium in the rock and the data thus imply that the present distribution of heat-producing elements in the tonalite was established long before the Alpine metamorphism. The very high closure temperatures for sphene and epidote implied by the data suggest they may be of value in dating metamorphism.

  18. Electron exchange reaction in anion exchangers as observed in uranium isotope separation

    International Nuclear Information System (INIS)

    Obanawa, Heiichiro; Takeda, Kunihiko; Seko, Maomi

    1991-01-01

    The mechanism of electron exchange in an ion exchanger, as occurring between U 4+ and UO 2 2+ in uranium isotope separation, was investigated. The height of the separation unit (H q ) in the presence of metal ion catalysts, as obtained from the separation experiments, was found to be almost coincident with the theoretical value of H q as calculated on the basis of the intrasolution acceleration mechanism of the metal ion, suggesting that the electron exchange mechanism in the ion-exchanger is essentially the same as that in the solution when metal ion catalysts are present. Separation experiments with no metal ion catalyst, on the other hand, showed the electron exchange reaction in the ion exchanger to be substantially higher than that in the solution, suggesting an acceleration of the electron exchange reaction by the ion-exchanger which is due to the close existence of higher order Cl - complexes of UO 2 2+ and U 4+ in the vicinity of the ion-exchange group. (author)

  19. Determination of uranium and thorium isotopes and polonium in sediment profiles from Baixada Santista, SP

    International Nuclear Information System (INIS)

    Ramos, Guilherme da Franca

    2010-01-01

    The objective of the present work is to determine the activity concentration of uranium and thorium isotopes and polonium in estuarine sediments from Baixada Santista. The area comprehends nine cities in the Brazilian coast (Bertioga, Guaruja, Santos, Sao Vicente, Cubatao, Praia Grande, Mongagua, Itanhaem and Peruibe). It is one of the most important industrial areas in Brazil due to the large number of industries operating in Cubatao, such as steel, petrochemical and fertilizer industries. That, together with a large population, causes a negative impact on the marine biota. In the present work 10 profiles of sediment cores, with depth varying from 41 to 98 cm, were analyzed. The cores were obtained from Santos, Cubatao, Sao Vicente and Bertioga. The cores were sliced every 2 cm and were treated with both physical and chemical processes, including drying, grinding and sieving. The samples were dissolved by acid digestion, till total dissolution and destruction of organic matter. After the acid digestion, the samples were filtered and evaporated till dryness. The radiochemical techniques used to separate the radionuclides and to prepare the final source for alpha counting were ion exchange chromatography and spontaneous deposition for polonium and electrodeposition for U and Th. The final sources were counted in a surface barrier alpha spectrometer. Values obtained for the radionuclides analyzed were similar to the activity concentrations of sediments in non polluted areas, with the exception of a few samples that showed anthropic influence. (author)

  20. Organic matter and containment of uranium and fissiogenic isotopes at the Oklo natural reactors

    International Nuclear Information System (INIS)

    Nagy, B.; Rigali, M.J.; Davis, D.W.; Parnell, J.

    1991-01-01

    Some of the Precambrian natural fission reactors at Oklo in Gabon contain abundant organic matter, part of which was liquefied at the time of criticality and subsequently converted to a graphitic solid. The liquid organic matter helps to reduce U(VI) to U(IV) from aqueous solutions, resulting in the precipitation of uraninite. It is known that in the prevailing reactor environments, precipitated uraninite grains incorporated fission products. We report here observations which show that these uraninite crystals were held immobile within the re-solidified, graphitic bituminous organics at Oklo thus enhanced radionuclide containment. Uraninite encased in solid graphitic matter in the organic-rich reactor zones lost virtually no fissiogenic lanthanide isotopes. The first major episode of uranium and lead migration was caused by the intrusion of a swarm of adjacent dolerite dykes about 1,100 Myr after the reactors went critical. Our results from Oklo imply that the use of organic, hydrophobic solids such as graphitic bitumen as a means of immobilizing radionuclides in pre-treated nuclear waste warrants further investigation. (author)

  1. Uranium isotope exchange between gaseous UF6 and solid UF5

    International Nuclear Information System (INIS)

    Yato, Yumio; Kishimoto, Yoichiro; Sasao, Nobuyuki; Suto, Osamu; Funasaka, Hideyuki

    1996-01-01

    Based on a collision model, a new rate equation is derived for uranium isotope exchange between gaseous UF 6 and solid UF 5 by considering the number of UF 5 molecules on the solid surface to be dependent on time. The reaction parameters included in the equation are determined from the experimental data and compared with the previous ones. A remarkable agreement is found between the particle sizes of UF 5 estimated from the reaction parameter and from the direct observation with an electron microscope. The rate equation given in this work fully satisfies the related mass conservation and furthermore includes explicitly the terms related to the UF 6 density and the mean size of UF 5 particles, both of which are considered to cause an important effect on the reaction. This remarkable feature facilitates the simulation studies on this reaction under various conditions. The long term behavior of a simulated exchange reaction is studied under the condition considered to be close to that in a recovery zone of the MLIS process. The result indicates that the reaction is virtually limited to the solid surface under this conditions and thus the depletion of 235 UF 5 concentration averaged over the whole UF 5 particles is not significant even after 200 h of the exchange reaction

  2. Improvement of Particle Recovery Method for Uranium Isotope Analysis Using SIMS

    International Nuclear Information System (INIS)

    Kim, Taehee; Park, Jinkyu; Lee, Chi-Gyu; Lim, Sang Ho; Han, Sun-Ho

    2017-01-01

    In this study, we developed a new design of vacuum-suction impactor with wider inlet nozzle and outlet nozzle for guiding particles to disperse the particles on the surface of carbon planchet. We prepared simulated samples with lead dioxide and examined particle recovery yield and degree of dispersion using the conventional vacuum impactor and the newly designed ones with different inlet nozzle diameters. We tried to improve the inlet part of vacuum impactor, in order to increase the recovery yield and disperse the collected particle on carbon planchet. As the diameter of inlet nozzle became larger, the collected particles were better dispersed on planchet. In addition, when the inner diameter of the impactor was 3 mm or 5 mm, the recovery yield was higher than that of conventional impactor. Considering the degree of dispersion and recovery yield, we used the impactor with 5 mm exit diameter and recovered the mixed uranium standard materials for SIMS measurement. We were able to reduce the mixing effect and measure the isotopic ratio more accurately and precisely.

  3. Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau

    Directory of Open Access Journals (Sweden)

    M. Casado

    2016-07-01

    Full Text Available Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require one to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for 1 month in December 2014–January 2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying

  4. Spectroscopic metrology for isotope composition measurements and transfer standards

    Science.gov (United States)

    Anyangwe Nwaboh, Javis; Balslev-Harder, David; Kääriäinen, Teemu; Richmond, Craig; Manninen, Albert; Mohn, Joachim; Kiseleva, Maria; Petersen, Jan C.; Werhahn, Olav; Ebert, Volker

    2017-04-01

    The World Meteorological Organization (WMO) has identified greenhouse gases such as CO2, CH4 and N2O as critical for global climate monitoring. Other molecules such as CO that has an indirect effect of enhancing global warming are also monitored. WMO has stated compatibility goals for atmospheric concentration and isotope ratio measurements of these gases, e.g. 0.1 ppm for CO2 concentration measurements in the northern hemisphere and 0.01 ‰ for δ13C-CO2. For measurements of the concentration of greenhouse gases, gas analysers are typically calibrated with static gas standards e.g. traceable to the WMO scale or to the International System of Units (SI) through a national metrology institute. However, concentrations of target components, e.g. CO, in static gas standards have been observed to drift, and typically the gas matrix as well as the isotopic composition of the target component does not always reflect field gas composition, leading to deviations of the analyser response, even after calibration. The deviations are dependent on the measurement technique. To address this issue, part of the HIGHGAS (Metrology for high-impact greenhouse gases) project [1] focused on the development of optical transfer standards (OTSs) for greenhouse gases, e.g. CO2 and CO, potentially complementing gas standards. Isotope ratio mass spectrometry (IRMS) [2] is currently used to provide state-of-the-art high precision (in the 0.01 ‰ range) measurements for the isotopic composition of greenhouse gases. However, there is a need for field-deployable techniques such as optical isotope ratio spectroscopy (OIRS) that can be combined with metrological measurement methods. Within the HIGHGAS project, OIRS methods and procedures based on e.g. cavity enhanced spectroscopy (CES) and tunable diode laser absorption spectroscopy (TDLAS), matched to metrological principles have been established for the measurement of 13C/12C and 18O/16O ratios in CO2, 15N/14N ratios in N2O, and 13C/12C and 2H

  5. Seasonality of Leaf Carbon Isotopic Composition and Leaf Water Isotopic Enrichment in a Mixed Evergreen Forest in Southern California

    Science.gov (United States)

    Santiago, L. S.; Sickman, J. O.; Goulden, M.; DeVan, C.; Pasquini, S. C.; Pivovaroff, A. L.

    2011-12-01

    Leaf carbon isotopic composition and leaf water isotopic enrichment reflect physiological processes and are important for linking local and regional scale processes to global patterns. We investigated how seasonality affects the isotopic composition of bulk leaf carbon, leaf sugar carbon, and leaf water hydrogen under a Mediterranean climate. Leaf and stem samples were collected monthly from four tree species (Calocedrus decurrens, Pinus lambertiana, Pinus ponderosa, and Quercus chrysolepis) at the James San Jacinto Mountain Reserve in southern California. Mean monthly bulk leaf carbon isotopic composition varied from -34.5 % in P. ponderosa to -24.7 % in P. lambertiana and became more depleted in 13C from the spring to the summer. Mean monthly leaf sugar varied from -29.3 % in P. ponderosa to -21.8 % in P. lambertiana and was enriched in 13C during the winter, spring and autumn, but depleted during the mid-summer. Leaf water hydrogen isotopic composition was 28.4 to 68.8 % more enriched in deuterium than source water and this enrichment was greater as seasonal drought progressed. These data indicate that leaf carbon and leaf water hydrogen isotopic composition provide sensitive measures that connect plant physiological processes to short-term climatic variability.

  6. NUCLEAR ISOTOPIC DILUTION OF HIGHLY ENRICHED URANIUM BY DRY BLENDING VIA THE RM-2 MILL TECHNOLOGY

    International Nuclear Information System (INIS)

    Rajamani, Raj K.; Latchireddi, Sanjeeva; Devrani, Vikas; Sethi, Harappan; Henry, Roger; Chipman, Nate

    2003-01-01

    DOE has initiated numerous activities to focus on identifying material management strategies to disposition various excess fissile materials. In particular the INEEL has stored 1,700 Kg of offspec HEU at INTEC in CPP-651 vault facility. Currently, the proposed strategies for dispositioning are (a) aqueous dissolution and down blending to LEU via facilities at SRS followed by shipment of the liquid LEU to NFS for fabrication into LWR fuel for the TVA reactors and (b) dilution of the HEU to 0.9% for discard as a waste stream that would no longer have a criticality or proliferation risk without being processed through some type of enrichment system. Dispositioning this inventory as a waste stream via aqueous processing at SRS has been determined to be too costly. Thus, dry blending is the only proposed disposal process for the uranium oxide materials in the CPP-651 vault. Isotopic dilution of HEU to typically less than 20% by dry blending is the key to solving the dispositioning issue (i.e., proliferation) posed by HEU stored at INEEL. RM-2 mill is a technology developed and successfully tested for producing ultra-fine particles by dry grinding. Grinding action in RM-2 mill produces a two million-fold increase in the number of particles being blended in a centrifugal field. In a previous study, the concept of achieving complete and adequate blending and mixing (i.e., no methods were identified to easily separate and concentrate one titanium compound from the other) in remarkably short processing times was successfully tested with surrogate materials (titanium dioxide and titanium mono-oxide) with different particle sizes, hardness and densities. In the current project, the RM-2 milling technology was thoroughly tested with mixtures of natural uranium oxide (NU) and depleted uranium oxide (DU) stock to prove its performance. The effects of mill operating and design variables on the blending of NU/DU oxides were evaluated. First, NU and DU both made of the same oxide

  7. Uranium

    Energy Technology Data Exchange (ETDEWEB)

    Williams, R M

    1976-01-01

    Evidence of expanding markets, improved prices and the short supply of uranium became abundantly clear in 1975, providing the much needed impetus for widespread activity in all phases of uranium operations. Exploration activity that had been at low levels in recent years in Canada was evident in most provinces as well as the Northwest Territories. All producers were in the process of expanding their uranium-producing facilities. Canada's Atomic Energy Control Board (AECB) by year-end had authorized the export of over 73,000 tons of U/sub 3/0/sub 8/ all since September 1974, when the federal government announced its new uranium export guidelines. World production, which had been in the order of 25,000 tons of U/sub 3/0/sub 8/ annually, was expected to reach about 28,000 tons in 1975, principally from increased output in the United States.

  8. High-precision measurements of uranium and thorium isotopic ratios by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS)

    Science.gov (United States)

    Wang, Lisheng; Ma, Zhibang; Duan, Wuhui

    2015-04-01

    Isotopic compositions of U-Th and 230Th dating have been widely used in earth sciences, such as chronology, geochemistry, oceanography and hydrology. In this study, five ages of different carbonate samples were measured using 230Th dating technique with U-Th high-precision isotopic measurements by multi-collector inductively coupled plasma mass spectrometry, in Uranium-series Chronology Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences.In this study, the precision and accuracy of uranium isotopic composition were estimated by measuring the uranium ratios of NBS-CRM 112A, NBS-CRM U500 and HU-1. The mean measured ratios, 234U/238U = 52.86 (±0.04) × 10-6 and δ234U = -38.36 (±0.77) × 10-3 for NBS-CRM 112A, 234U/238U = 10.4184 (±0.0001) × 10-3, 236U/238U = 15.43 (±0.01) × 10-4 and 238U/235U = 1.00021 (±0.00002) for NBS-CRM U500, 234U/238U = 54.911 (±0.007) and δ234U = -1.04 (±0.13) × 10-3 for HU-1 (95% confidence levels). The U isotope data for standard reference materials are in excellent agreement with previous studies, further highlighting the reliability and analytical capabilities of our technique. We measured the thorium isotopic ratios of three different thorium standards by MC-ICPMS. The three standards (Th-1, Th-2 and Th-3) were mixed by HU-1 and NBS 232Th standard, with the 230Th/232Th ratios from 10-4 to 10-6. The mean measured atomic ratios, 230Th/232Th = 2.1227 (±0.0024) × 10-6, 2.7246 (±0.0026) × 10-5, and 2.8358 (±0.0007) × 10-4 for Th-1, Th-2 and Th-3 (95% confidence levels), respectively. Using this technique, the following standard samples were dated by MC-ICPMS. Sample RKM-4, collected from Babardos Kendal Hill terrace, was used during the first stage of the Uranium-Series Intercomparison Project (USIP-I). Samples 76001, RKM-5 and RKM-6 were studied during the second stage of the USIP program (USIP-II). Sample 76001 is a laminated flowstone, collected from Sumidero Terejapa, Chiapas, Mexico, and samples

  9. Pb isotopic composition of the atmosphere of the Sao Paulo city, Brazil, and isotopic characterization of some pollutant sources

    International Nuclear Information System (INIS)

    Aily, C.; Babinski, M.; Ruiz, I.R.; Sato, K

    2001-01-01

    Lead isotopes are known to be good tools for surveying lead origin in atmospheric samples (Chow et al., 1975). Lead has four naturally occurring stable isotopes: 206 Pb, 207 Pb, 208 Pb and 204 Pb. The first three isotopes are end products of radioactive decay chains from 238 U, 235 U and 232 Th, respectively, and the last one is non-radiogenic. Therefore, their abundance and the ratios among the four isotopes gradually change with time. Lead in the atmosphere comes from various sources, such as leaded gasoline, industrial emissions and coal combustion. Thus, lead isotope ratios different from those of the mother rock in the region are often observed in the atmosphere (Tatsumoto and Patterson, 1963). Lead is emitted to the atmosphere in fine particles, which can be transported within air masses for very long distances, e. g. from mid latitude regions to the Artic and Antarctica (Sturges and Barrie, 1989). Lead isotopes have been used to trace the pollutant sources in many cities of the world. However, a systematic study using this methodology has not been done in any Brazilian city. The main purpose of the present work is to characterize the Pb isotope composition in the atmosphere in Sao Paulo city, and suggest the possible pollutant sources. For our study lead isotopes were measured in different samples: aerosols and rainwater which would yield the Pb isotope composition of the atmosphere. Samples of gasoline and ethanol, gutter sweepings, soot from vehicle exhaust pipes, and filters containing particulate material from industrial emissions were also analyzed, since they were considered potential pollutant sources of the atmosphere. In order to obtain the local geogenic Pb isotopic composition we also analyzed rock and K-feldspar samples. Lead concentrations were only determined on aerosols and rainwater samples (au)

  10. Uranium-236 as an indicator of fuel-cycle uranium in ground water

    International Nuclear Information System (INIS)

    Jaquish, R.E.

    1989-08-01

    Environmental monitoring on and around the Hanford Site includes regular sampling of onsite monitoring wells and offsite farm wells. Uranium has been identified in the ground water onsite and also in water from farm wells located on the east side of the Columbia River, across from the Hanford Site. Information on the hydrology of the area indicates that the source of the offsite uranium is not the Hanford Site. This study evaluated the isotopic composition of the uranium in water from the various wells to differentiate the onsite uranium contamination from natural uranium offsite. 5 refs., 2 figs., 2 tabs

  11. Main results obtained in France in the development of the gaseous diffusion process for uranium isotope separation; Principaux resultats obtenus en France dans les etudes sur la separation des isotopes de l'uranium par diffusion gazeuse

    Energy Technology Data Exchange (ETDEWEB)

    Frejacques, C; Bilous, O; Dixmier, J; Massignon, D; Plurien, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    The main problems which occur in the study of uranium isotope separation by the gaseous diffusion process, concern the development of the porous barrier, the corrosive nature of uranium hexafluoride and also the chemical engineering problems related to process design and the choice of best plant and stage characteristics. Porous barriers may be obtained by chemical attack of non porous media or by agglomeration of very fine powders. Examples of these two types of barriers are given. A whole set of measurement techniques were developed for barrier structure studies, to provide control and guidance of barrier production methods. Uranium hexafluoride reactivity and corrosive properties are the source of many difficult technological problems. A high degree of plant leak tightness must be achieved. This necessity creates a special problem in compressor bearing design. Barrier lifetime is affected by the corrosive properties of the gas, which may lead to a change of barrier structure with time. Barrier hexafluoride permeability measurements have helped to make a systematic study of this point. Finally an example of a plant flowsheet, showing stage types and arrangements and based on a minimisation of enriched product costs is also given as an illustration of some of the chemical engineering problems present. (author) [French] Les principaux problemes qui se sont poses dans l'etude de la separation des isotopes de l'uranium par diffusion gazeuse, sont ceux relatifs a l'obtention de barrieres poreuses, ceux lies a l'utilisation de l'hexafluorure d'uranium, enfin les problemes de genie chimique relatifs au procede et a l'agencement optimum des etages et des cascades entre elles. On peut obtenir des barrieres poreuses soit par attaque de membranes pleines, soit par agglomeration de poudres de petites dimensions. Des exemples de ces deux types de barrieres seront donnes. L'etude des proprietes de texture des barrieres obtenues, necessaire pour orienter les recherches de

  12. Variations in Urine Calcium Isotope: Composition Reflect Changes in Bone Mineral Balance in Humans

    Science.gov (United States)

    Skulan, Joseph; Anbar, Ariel; Bullen, Thomas; Puzas, J. Edward; Shackelford, Linda; Smith, Scott M.

    2004-01-01

    Changes in bone mineral balance cause rapid and systematic changes in the calcium isotope composition of human urine. Urine from subjects in a 17 week bed rest study was analyzed for calcium isotopic composition. Comparison of isotopic data with measurements of bone mineral density and metabolic markers of bone metabolism indicates the calcium isotope composition of urine reflects changes in bone mineral balance. Urine calcium isotope composition probably is affected by both bone metabolism and renal processes. Calcium isotope. analysis of urine and other tissues may provide information on bone mineral balance that is in important respects better than that available from other techniques, and illustrates the usefulness of applying geochemical techniques to biomedical problems.

  13. Desorption of uranium from titanium-activated carbon composite adsorbent with acidic eluent, 2

    International Nuclear Information System (INIS)

    Hirotsu, Takahiro; Fujii, Ayako; Sakane, Kohji; Katoh, Shunsaku; Sugasaka, Kazuhiko

    1984-01-01

    The desorption of uranium from the granular titanium-activated carbon composite adsorbent (concentration of uranium: 25.5 mg/1-Ad), which adsorbed uranium from natural sea water, was examined by the column process with acidic eluent at room temperature. The column operation was able to be carried out without destruction of the granular adsorbent by the generation of the carbon dioxide, and free from disturbance of the eluent flow by precipitate of calcium sulfate dihydrate with sulfuric acid eluent. The amount of acid consumption by the adsorbent was 0.87 eq/1-Ad. The alkaline earth metals were eluted in the range of elution volume below 2 1/1-Ad, whereas uranium, iron, and titanium were eluted above 2 1/1-Ad. Therefore, uranium was separable from the alkaline earth metals which were adsorbed in the most quantity in the adsorbent. In the range of elution volume 2 to 12 1/1-Ad, the percentage of desorbed uranium and the concentration ratio of uranium were 80 %, 680 with 0.5 N sulfuric acid, and 59 %, 490 with 0.5 N hydrochloric acid, respectively. The percentage of dissolved titanium (DTI) was 0.3 % with 0.5 N sulfuric acid, 0.26 % with 0.5 N hydrochloric acid in the same range. (author)

  14. Composition and method for solution mining of uranium ores

    International Nuclear Information System (INIS)

    Lawes, B.C.; Watts, J.C.

    1981-01-01

    It has been found that, in the solution mining of uranium ores using ammonium carbonate solutions containing hydrogen peroxide or ozone as an oxidant, the tendency of the formation being treated to become less permeable during the leaching process can be overcome by including in the leaching solution a very small concentration of sodium silicate

  15. Determination of total and isotopic uranium by inductively coupled plasma-mass spectrometry at the Fernald Environmental Management Project

    International Nuclear Information System (INIS)

    Miller, F.L.; Bolin, R.N.; Feller, M.T.; Danahy, R.J.

    1995-01-01

    At the Fernald Environmental Management Project (FEMP) in southwestern Ohio, ICP-mass spectrometry (ICP-MS), with sample introduction by peristaltic pumping, is used to determine total and isotopic uranium (U-234, U-235, U-236 and U-238) in soil samples. These analyses are conducted in support of the environmental cleanup of the FEMP site. Various aspects of the sample preparation and instrumental analysis will be discussed. Initial sample preparation consists of oven drying to determine moisture content, and grinding and rolling to homogenize the sample. This is followed by a nitric/hydrofluoric acid digestion to bring the uranium in the sample into solution. Bismuth is added to the sample prior to digestion to monitor for losses. The total uranium (U-238) content of this solution and the U 235 /U 238 ratio are measured on the first pass through the ICP-MS. To determine the concentration of the less abundant U 234 and U 236 isotopes, the digestate is further concentrated by using Eichrom TRU-Spec extraction columns before the second pass through the ICP-MS. Quality controls for both the sample preparation and instrumental protocols will also be discussed. Finally, an explanation of the calculations used to report the data in either weight percent or activity units will be given

  16. Chemical composition of HAL, an isotopically-unusual Allende inclusion

    Science.gov (United States)

    Davis, A. M.; Tanaka, T.; Grossman, L.; Lee, T.; Wasserburg, G. J.

    1982-01-01

    Samples of hibonite, black rim, and portions of friable rim from an unusual Allende inclusion, named HAL, were analyzed by INAA and RNAA for 37 major, minor, and trace elements. An unusually low amount of Ce was found in HAL, although it otherwise was highly enriched in REE compared to C1 chondrites. HAL is also depleted in Sr, Ba, U, V, Ru, Os, and Ir relative to other refractory elements. It is concluded that the distribution of REE between hibonite and rims was established when hibonite and other refractory minerals were removed at slightly different temperatures from a hot, oxidizing gas in which they previously coexisted as separate grains. Possible locations for the chemical and mass dependent isotopic fractionation are considered to be in ejecta from the low temperature helium-burning zone of a supernova and in the locally oxidizing environment generated by evaporation of interstellar grains of near-chondritic chemical composition.

  17. Characterization of low concentration uranium glass working materials

    Energy Technology Data Exchange (ETDEWEB)

    Eppich, G. R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wimpenny, J. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Leever, M. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Knight, K. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hutcheon, I. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ryerson, F. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-03-22

    A series of uranium-doped silicate glasses were created at (Lawrence Livermore National Laboratory) LLNL, to be used as working reference material analogs for low uranium concentration research. Specifically, the aim of this effort was the generation of well-characterized glasses spanning a range of concentrations and compositions, and of sufficient homogeneity in uranium concentration and isotopic composition, for instrumentation research and development purposes. While the glasses produced here are not intended to replace or become standard materials for uranium concentration or uranium isotopic composition, it is hoped that they will help fill a current gap, providing low-level uranium glasses sufficient for methods development and method comparisons within the limitations of the produced glass suite. Glasses are available for research use by request.

  18. Assay of Uranium Isotopic Ratios 234U/238U, 235U/238U in Bottom Sediment Samples Using Destructive and Non Destructive Techniques (Nasser Lake)

    International Nuclear Information System (INIS)

    Agha, A.R.; El-Mongy, S.A.; Kandel, A.E.

    2011-01-01

    Nasser Lake is the greatest man-made lake in the World. It is considered as the main source of water where the Nile water is impounded behind the Aswan high dam.. Uranium has three naturally occurring isotopes 234 U, 235 U and 238 U with isotopic abundance 0.00548, 0.7200 and 99.2745 atom percent. Dissolved uranium in the lake is primary due to weathering process. Monitoring of the isotopic ratios of uranium is used as a good indicator to trace and evaluate the origin and activities associated with any variation of uranium in the lake environment. The main objective of the present study is to clarify any potential variation of natural uranium 234 U/ 238 U, 235 U/ 238 U ratios in sediment samples of Nasser Lake by using destructive alpha and non destructive gamma- techniques. The results show that the uranium isotopic activity ratios are very close to the natural values. This study can also be used for radiological protection and safety evaluation purposes.

  19. Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition

    International Nuclear Information System (INIS)

    Zielinski, M.; Zielinska, A.; Papiernik-Zielinska, H.; McKenzie, J.A.; Bernasconi, S.; Paul, H.

    1998-01-01

    Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition above and below its melting temperature have been studied and compared with the primary (PKIE) and secondary kinetic isotope effects (SKIE) of 13 C and 18 O, respectively, in the decarboxylation of other heterocyclic acids. The temperature dependence of the secondary oxygen-18 isotope effects is negative in the total 221-255 deg C temperature interval investigated initially. The 13 C KIE measured above melting point of N.A. (temperature interval 235-270 deg C) are located in the range 1.007-1.009. Below melting point of nicotinic acid the 13 C KIE are larger and reveal the negative temperature dependence ( 13 C KIE decreases with decreasing the reaction temperature from 1.013/at 230 deg C to 1.0114/at 221 deg C). A discussion of the above isotopic results is presented. (author)

  20. Comparison of mass-spectrometry and α-counting in analysis of uranium and plutonium isotopes in environmental samples

    International Nuclear Information System (INIS)

    Irleweck, K.; Pichlmayer, F.

    1980-01-01

    The determination of trace amounts of U and Pu isotopes is of interest in environmental and personal monitoring programmes. Commonly after preconcentration and separation of the radionuclides a proper sample is prepared electrolytically and the measurements are performed by alpha spectrometry. Some investigations on uranium isotopic abundances and on plutonium fallout deposition in soil have been carried out in this way. It is impossible to distinguish between the isotopes 239 Pu and 240 Pu by alpha spectrometry, however, because their α-energies are too close together. Such determinations can only be carried out by mass spectrometry. Specific Pu emissions, e.g. from nuclear production plants, can be discriminated from the global fallout level. Mass spectrometry is the more sensitive method for measuring long-lived nuclides compared with α-spectrometry. In the case of soil analysis, however, Pu detection is obstructed by the high natural uranium content, usually in the range 0.2 to 2.0 ppm which exceeds the trace amounts of plutonium by several orders of magnitude. This work describes a chemical procedure which separates U/Pu sufficiently for alpha spectrometry as well as for mass spectrometry, and compares results of environmental analysis applying both methods. (author)

  1. Elemental hydrochemistry and hydro geochemistry of the uranium isotopes in Alter do Chao formation, Manaus (Amazon - Brazil)

    International Nuclear Information System (INIS)

    Silva, Marcio Luiz da; Bonotto, Daniel Marcos

    2006-01-01

    The water exploitation at Manaus city, Amazonas State, Brazil, takes place from Negro River and tubular wells, being performed by a private company. This paper evaluates the hydrochemistry and geochemical behavior of uranium isotopes ( 238 U and 234 U) in groundwaters from Manaus city, with the aim to characterize the contaminants or pollutants that possibly are affecting the quality of the underground hydrological resources, as well as to evaluate the potential use of the natural U-isotopes as hydrological tracers in the aquifer studied. The U-isotopes analysis allowed to determine 234 U/ 238 U activity ratios of 1.2-4.4, and dissolved uranium concentration of 0.003-1.1 μg.L -1 (ppb). These results and those concerning the others parameters indicated that the waters are appropriate for human consumption, permitting to classify the hydrological system as acid-reducing, and to say that the waters leach minerals in strata containing low U content.(author)

  2. Use of radioanalytical methods for determination of uranium, neptunium, plutonium, americium and curium isotopes in radioactive wastes

    International Nuclear Information System (INIS)

    Geraldo, Bianca

    2012-01-01

    Activated charcoal is a common type of radioactive waste that contains high concentrations of fission and activation products. The management of this waste includes its characterization aiming the determination and quantification of the specific radionuclides including those known as Difficult-to-Measure Radionuclides (RDM). The analysis of the RDM's generally involves complex radiochemical analysis for purification and separation of the radionuclides, which are expensive and time-consuming. The objective of this work was to define a methodology for sequential analysis of the isotopes of uranium, neptunium, plutonium, americium and curium present in a type of radioactive waste, evaluating chemical yield, analysis of time spent, amount of secondary waste generated and cost. Three methodologies were compared and validated that employ ion exchange (TI + EC), extraction chromatography (EC) and extraction with polymers (ECP). The waste chosen was the activated charcoal from the purification system of primary circuit water cooling the reactor IEA-R1. The charcoal samples were dissolved by acid digestion followed by purification and separation of isotopes with ion exchange resins, extraction and chromatographic extraction polymers. Isotopes were analyzed on an alpha spectrometer, equipped with surface barrier detectors. The chemical yields were satisfactory for the methods TI + EC and EC. ECP method was comparable with those methods only for uranium. Statistical analysis as well the analysis of time spent, amount of secondary waste generated and cost revealed that EC method is the most effective for identifying and quantifying U, Np, Pu, Am and Cm present in charcoal. (author)

  3. The NNSA global threat reduction initiative's efforts to minimize the use of highly enriched uranium for medical isotope production

    International Nuclear Information System (INIS)

    Staples, Parrish

    2010-01-01

    The mission of the National Nuclear Security Administration's (NNSA) Office of Global Threat Reduction (GTRI) is to reduce and protect vulnerable nuclear and radiological materials located at civilian sites worldwide. GTRI is a key organization for supporting domestic and global efforts to minimize and, to the extent possible, eliminate the use of highly enriched uranium (HEU) in civilian nuclear applications. GTRI implements the following activities in order to achieve its threat reduction and HEU minimization objectives: Converting domestic and international civilian research reactors and isotope production facilities from the use of HEU to low enriched uranium (LEU); Demonstrating the viability of medical isotope production technologies that do not use HEU; Removing or disposing excess nuclear and radiological materials from civilian sites worldwide; and Protecting high-priority nuclear and radiological materials worldwide from theft and sabotage. This paper provides a brief overview on the recent developments and priorities for GTRI program activities in 2010, with a particular focus on GTRI's efforts to demonstrate the viability of non-HEU based medical isotope production technologies. (author)

  4. Standard test method for isotopic analysis of uranium hexafluoride by double standard single-collector gas mass spectrometer method

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This is a quantitative test method applicable to determining the mass percent of uranium isotopes in uranium hexafluoride (UF6) samples with 235U concentrations between 0.1 and 5.0 mass %. 1.2 This test method may be applicable for the entire range of 235U concentrations for which adequate standards are available. 1.3 This test method is for analysis by a gas magnetic sector mass spectrometer with a single collector using interpolation to determine the isotopic concentration of an unknown sample between two characterized UF6 standards. 1.4 This test method is to replace the existing test method currently published in Test Methods C761 and is used in the nuclear fuel cycle for UF6 isotopic analyses. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro...

  5. The isotopic composition of CO in vehicle exhaust

    Science.gov (United States)

    Naus, S.; Röckmann, T.; Popa, M. E.

    2018-03-01

    We investigated the isotopic composition of CO in the exhaust of individual vehicles. Additionally, the CO2 isotopes, and the CO:CO2, CH4:CO2 and H2:CO gas ratios were measured. This was done under idling and revving conditions, and for three vehicles in a full driving cycle on a testbench. The spread in the results, even for a single vehicle, was large: for δ13 C in CO ∼ -60 to 0‰, for δ18 O in CO ∼ +10 to +35‰, and for all gas ratios several orders of magnitude. The results show an increase in the spread of isotopic values for CO compared to previous studies, suggesting that increasing complexity of emission control in vehicles might be reflected in the isotopic composition. When including all samples, we find a weighted mean for the δ13 C and δ18 O in CO of -28.7 ± 0.5‰ and +24.8 ± 0.3‰ respectively. This result is dominated by cold petrol vehicles. Diesel vehicles behaved as a distinct group, with CO enriched in 13C and depleted in 18O, compared to petrol vehicles. For the H2:CO ratio of all vehicles, we found a value of 0.71 ± 0.31 ppb:ppb. The CO:CO2 ratio, with a mean of 19.4 ± 6.8 ppb:ppm, and the CH4:CO2 ratio, with a mean of 0.26 ± 0.05 ppb:ppm, are both higher than recent literature indicates. This is likely because our sampling distribution was biased towards cold vehicles, and therefore towards higher emission situations. The CH4:CO2 ratio was found to behave similarly to the CO:CO2 ratio, suggesting that the processes affecting CO and CH4 are similar. The δ13 C values in CO2 were close to the expected δ13 C in fuel, with no significant difference between petrol and diesel vehicles. The δ18 O values in CO2 for petrol vehicles covered a range of 20-35‰, similar to the δ18 O of CO. The δ18 O values in CO2 for diesel vehicles were close to the δ18 O in atmospheric oxygen. A set of polluted atmospheric samples, taken near a highway and inside parking garages, showed an isotopic signature of CO and a H2:CO ratio that were

  6. Low-Enriched Uranium Fuel Conversion Activities for the High Flux Isotope Reactor, Annual Report for FY 2011

    Energy Technology Data Exchange (ETDEWEB)

    Renfro, David G [ORNL; Cook, David Howard [ORNL; Freels, James D [ORNL; Griffin, Frederick P [ORNL; Ilas, Germina [ORNL; Sease, John D [ORNL; Chandler, David [ORNL

    2012-03-01

    This report describes progress made during FY11 in ORNL activities to support converting the High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum (UMo) alloy. With both radial and axial contouring of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in performance to users from the current levels achieved with HEU fuel. Studies are continuing to demonstrate that the fuel thermal safety margins can be preserved following conversion. Studies are also continuing to update other aspects of the reactor steady state operation and accident response for the effects of fuel conversion. Technical input has been provided to Oregon State University in support of their hydraulic testing program. The HFIR conversion schedule was revised and provided to the GTRI program. In addition to HFIR conversion activities, technical support was provided directly to the Fuel Fabrication Capability program manager.

  7. Low-Enriched Uranium Fuel Conversion Activities for the High Flux Isotope Reactor, Annual Report for FY 2011

    International Nuclear Information System (INIS)

    Renfro, David G.; Cook, David Howard; Freels, James D.; Griffin, Frederick P.; Ilas, Germina; Sease, John D.; Chandler, David

    2012-01-01

    This report describes progress made during FY11 in ORNL activities to support converting the High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum (UMo) alloy. With both radial and axial contouring of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in performance to users from the current levels achieved with HEU fuel. Studies are continuing to demonstrate that the fuel thermal safety margins can be preserved following conversion. Studies are also continuing to update other aspects of the reactor steady state operation and accident response for the effects of fuel conversion. Technical input has been provided to Oregon State University in support of their hydraulic testing program. The HFIR conversion schedule was revised and provided to the GTRI program. In addition to HFIR conversion activities, technical support was provided directly to the Fuel Fabrication Capability program manager.

  8. Groundwater isotopic variations in a uranium mining site: subsidies for contamination studies

    International Nuclear Information System (INIS)

    Araujo, V. P. de

    2017-01-01

    The Caetite Experimental Basin (CEB), located in the semi-arid region of Northeastern Brazil, faces not only the challenges associated with water scarcity but also the potential contamination processes due to mining activity. The only active uranium production center in Brazil (URA) is located in this watershed and the sustainability of mining and milling operations, as well as the survival of the local community, is highly dependent on the availability of groundwater resources. This paper analyzes the stable isotopes variation of Deuterium ("2H) and Oxygen-18 ("1"8O) in CEB's groundwater to investigate its dynamics and mixing of water sources as part of initial efforts to characterize the hydrogeology of this area for future contamination and recharge studies. Measurements of δ"2H, δ"1"8O, total dissolved solids (TDS), pH, and electrical conductivity (EC) were carried out in water samples from 27 wells. A total of 98 groundwater samples were analyzed during the dry and wet seasons from 2012 to 2014. All the groundwater samples plotted below the local meteoric line toward more enriched δ"1"8O values, an indicative of evaporation process. "2H and "1"8O data suggests that the main source of groundwater recharge is local precipitation and there is no mixing of infiltrating rainwater with older groundwater. These results provide evidence that the aquifer system in the CEB has a relatively fast turnover time, which contribute to the vulnerability of the aquifer to contamination. These findings are corroborated by the low TDS and EC values indicative of short time in water-rock interaction. (author)

  9. Groundwater isotopic variations in a uranium mining site: subsidies for contamination studies

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, V. P. de [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Divisao de Engenharia Nuclear; Sobrinho, G.A.N.; Freitas, L.D.; Franklin, M.R., E-mail: mariza@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2017-09-01

    The Caetite Experimental Basin (CEB), located in the semi-arid region of Northeastern Brazil, faces not only the challenges associated with water scarcity but also the potential contamination processes due to mining activity. The only active uranium production center in Brazil (URA) is located in this watershed and the sustainability of mining and milling operations, as well as the survival of the local community, is highly dependent on the availability of groundwater resources. This paper analyzes the stable isotopes variation of Deuterium ({sup 2}H) and Oxygen-18 ({sup 18}O) in CEB's groundwater to investigate its dynamics and mixing of water sources as part of initial efforts to characterize the hydrogeology of this area for future contamination and recharge studies. Measurements of δ{sup 2}H, δ{sup 18}O, total dissolved solids (TDS), pH, and electrical conductivity (EC) were carried out in water samples from 27 wells. A total of 98 groundwater samples were analyzed during the dry and wet seasons from 2012 to 2014. All the groundwater samples plotted below the local meteoric line toward more enriched δ{sup 18}O values, an indicative of evaporation process. {sup 2}H and {sup 18}O data suggests that the main source of groundwater recharge is local precipitation and there is no mixing of infiltrating rainwater with older groundwater. These results provide evidence that the aquifer system in the CEB has a relatively fast turnover time, which contribute to the vulnerability of the aquifer to contamination. These findings are corroborated by the low TDS and EC values indicative of short time in water-rock interaction. (author)

  10. Transport of uranium in water and soil: colloidal-isotopic combined approach

    International Nuclear Information System (INIS)

    Harguindeguy, Stephanie

    2013-01-01

    Mechanisms of interaction between uranium and colloids were studied by samples taken from a site of interest for the 'French Nuclear Agency' (CEA). The mobilization of uranium from soils was apprehended by static and dynamic leaching experiments. The transfer and transport have been studied by considering pond waters and drain waters. Results confirm that anthropogenic uranium is more mobile than natural uranium. However mechanisms of mobilization and distribution of uranium, does not differ depending on its origin. The colloidal fraction plays an important role on the migration in soil and the transfer into water by representing from 10 to 90 % uranium depending on samples. The colloidal fractions of uranium are in a continuum of size up to about 200 nm hydrodynamic diameter. They are mainly composed of organic material, iron and aluminum. Along the drain, from the upstream to the downstream of the site, rearrangement of colloidal associations between uranium and organic material occurs in disfavor of colloidal associations between uranium and iron, the proportion of colloidal uranium bound to aluminum remains unchanged. (author) [fr

  11. Uranium

    International Nuclear Information System (INIS)

    Perkin, D.J.

    1982-01-01

    Developments in the Australian uranium industry during 1980 are reviewed. Mine production increased markedly to 1841 t U 3 O 8 because of output from the new concentrator at Nabarlek and 1131 t of U 3 O 8 were exported at a nominal value of $37.19/lb. Several new contracts were signed for the sale of yellowcake from Ranger and Nabarlek Mines. Other developments include the decision by the joint venturers in the Olympic Dam Project to sink an exploration shaft and the release of an environmental impact statement for the Honeymoon deposit. Uranium exploration expenditure increased in 1980 and additions were made to Australia's demonstrated economic uranium resources. A world review is included

  12. Uranium

    International Nuclear Information System (INIS)

    Gabelman, J.W.; Chenoweth, W.L.; Ingerson, E.

    1981-01-01

    The uranium production industry is well into its third recession during the nuclear era (since 1945). Exploration is drastically curtailed, and many staffs are being reduced. Historical market price production trends are discussed. A total of 3.07 million acres of land was acquired for exploration; drastic decrease. Surface drilling footage was reduced sharply; an estimated 250 drill rigs were used by the uranium industry during 1980. Land acquisition costs increased 8%. The domestic reserve changes are detailed by cause: exploration, re-evaluation, or production. Two significant discoveries of deposits were made in Mohave County, Arizona. Uranium production during 1980 was 21,850 short tons U 3 O 8 ; an increase of 17% from 1979. Domestic and foreign exploration highlights were given. Major producing areas for the US are San Juan basin, Wyoming basins, Texas coastal plain, Paradox basin, northeastern Washington, Henry Mountains, Utah, central Colorado, and the McDermitt caldera in Nevada and Oregon. 3 figures, 8 tables

  13. Low-Enriched Uranium Fuel Design with Two-Dimensional Grading for the High Flux Isotope Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Ilas, Germina [ORNL; Primm, Trent [ORNL

    2011-05-01

    An engineering design study of the conversion of the High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) to low-enriched uranium (LEU) fuel is ongoing at Oak Ridge National Laboratory. The computational models developed during fiscal year 2010 to search for an LEU fuel design that would meet the requirements for the conversion and the results obtained with these models are documented and discussed in this report. Estimates of relevant reactor performance parameters for the LEU fuel core are presented and compared with the corresponding data for the currently operating HEU fuel core. The results obtained indicate that the LEU fuel design would maintain the current performance of the HFIR with respect to the neutron flux to the central target region, reflector, and beam tube locations under the assumption that the operating power for the reactor fueled with LEU can be increased from the current value of 85 MW to 100 MW.

  14. Investigating Uranium Mobility Using Stable Isotope Partitioning of 238U/235U and a Reactive Transport Model

    Science.gov (United States)

    Bizjack, M.; Johnson, T. M.; Druhan, J. L.; Shiel, A. E.

    2015-12-01

    We report a numerical reactive transport model which explicitly incorporates the effectively stable isotopes of uranium (U) and the factors that influence their partitioning in bioactive systems. The model reproduces trends observed in U isotope ratios and concentration measurements from a field experiment, thereby improving interpretations of U isotope ratios as a tracer for U reactive transport. A major factor contributing to U storage and transport is its redox state, which is commonly influenced by the availability of organic carbon to support metal-reducing microbial communities. Both laboratory and field experiments have demonstrated that biogenic reduction of U(VI) fractionates the stable isotope ratio 238U/235U, producing an isotopically heavy solid U(IV) product. It has also been shown that other common reactive transport processes involving U do not fractionate isotopes to a consistently measurable level, which suggests the capacity to quantify the extent of bioreduction occurring in groundwater containing U using 238U/235U ratios. A recent study of a U bioremediation experiment at the Rifle IFRC site (Colorado, USA) applied Rayleigh distillation models to quantify U stable isotope fractionation observed during acetate amendment. The application of these simplified models were fit to the observations only by invoking a "memory-effect," or a constant source of low-concentration, unfractionated U(VI). In order to more accurately interpret the measured U isotope ratios, we present a multi-component reactive transport model using the CrunchTope software. This approach is capable of quantifying the cycling and partitioning of individual U isotopes through a realistic network of transport and reaction pathways including reduction, oxidation, and microbial growth. The model incorporates physical heterogeneity of the aquifer sediments through zones of decreased permeability, which replicate the observed bromide tracer, major ion chemistry, U concentration, and U

  15. NGSI FY15 Final Report. Innovative Sample Preparation for in-Field Uranium Isotopic Determinations

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Thomas M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Meyers, Lisa [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-11-10

    Our FY14 Final Report included an introduction to the project, background, literature search of uranium dissolution methods, assessment of commercial off the shelf (COTS) automated sample preparation systems, as well as data and results for dissolution of bulk quantities of uranium oxides, and dissolution of uranium oxides from swipe filter materials using ammonium bifluoride (ABF). Also, discussed were reaction studies of solid ABF with uranium oxide that provided a basis for determining the ABF/uranium oxide dissolution mechanism. This report details the final experiments for optimizing dissolution of U3O8 and UO2 using ABF and steps leading to development of a Standard Operating Procedure (SOP) for dissolution of uranium oxides on swipe filters.

  16. Study of the dissolution of uranium nitrides in nitric acid by measuring the isotope ratios, 15N/14N, of the formed products

    International Nuclear Information System (INIS)

    Hadibi-Olschewski, Nathalie

    1991-01-01

    The aim of this study was to investigate the dissolution behavior of nitride fuels in nitric acid. The use of nitride fuels in nuclear reactor has many advantages compared with the oxide fuels. One problem in employing nitrides as fuels is the formation of radio-toxic 14 C upon irradiation of natural nitrogen ( 14 N:99.64 pc, 15 N:0.36 pc) in a nuclear reactor ( 14 N (n,p) 14 C reaction). The use of 15 N-enriched fuels avoids these drawbacks. This study was undertaken so as to better understand the mechanisms of the dissolution process and also to follow the distribution of the expensive nitrogen isotope 15 N from the point of view of its behaviour during the recycling process. This study is based on previous work, where the evolution of the nitrogen compounds formed during the dissolution was measured as a function of time for different dissolution parameters. Using 15 N-enriched uranium nitrides or 15 N-enriched nitric acid, two methods were developed to study the influence of the dissolution parameters, nitric acid temperature and concentration, on the 15 N/ 14 N ratios of the nitrogen, nitrogen oxides and ammonium ions utilising a coupled gas-chromatograph/mass spectrometer. The main results are: - similar isotopic composition for NH 4 + and UN; - mixed 14 N/ 15 N composition for N 2 and N 2 O; - similar isotopic composition for NO, NO 2 and HNO 3 ; - no influence of the dissolution parameters on the isotopic composition of the products; an exception maybe made for the N 2 case, which contains more 15 N with increasing acidity and temperature. This work confirms that the first dissolution step is the oxidation of UN with HNO 3 to form NH 4 + and HNO 2 and that HNO 2 has a catalytic role in the dissolution to form other products. And we can conclude that to recycle 15 N, the ammonium ions must be recycled, at least for the case where nitrides are dissolved directly in HNO 3 . (author) [fr

  17. Fluid inclusion and oxygen isotope studies of the Nabarlek and Jabiluka uranium deposits, Northern Territory, Australia

    International Nuclear Information System (INIS)

    Ypma, P.J.M.; Fuzikawa, K.

    1980-01-01

    We lack a basic understanding of the solutions producing the uranium deposits of the Alligator Rivers Uranium Field (ARUF). Several theories have been proposed ranging from syngenetic, epigenetic hydrothermal, epigenetic metamorphogenic, surficial origin (Ferguson et al., this volume), and mobilization by evaporite deposits. As for a precipitation mechanism, we do not seem to find much beyond the presence of graphite in some ore-bearing and intra-formational strata, and pre-uranium sulphides, none of which reducing factors are common throughout all ore bodies. This study was initiated with the aim of obtaining direct fluid inclusion evidence of the solution transport and precipitation of uranium

  18. High burn-up plutonium isotopic compositions recommended for use in shielding analysis

    International Nuclear Information System (INIS)

    Zimmerman, M.G.

    1977-06-01

    Isotopic compositions for plutonium generated and recycled in LWR's were estimated for use in shielding calculations. The values were obtained by averaging isotopic values from many sources in the literature. These isotopic values should provide the basis for a reasonable prediction of exposure rates from the range of LWR fuel expected in the future. The isotopic compositions given are meant to be used for shielding calculations, and the values are not necessarily applicable to other forms of analysis, such as inventory assessment or criticality safety. 11 tables, 2 figs

  19. Uranium

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    Recent decisions by the Australian Government will ensure a significant expansion of the uranium industry. Development at Roxby Downs may proceed and Ranger may fulfil two new contracts but the decision specifies that apart from Roxby Downs, no new mines should be approved. The ACTU maintains an anti-uranium policy but reaction to the decision from the trade union movement has been muted. The Australian Science and Technology Council (ASTEC) has been asked by the Government to conduct an inquiry into a number of issues relating to Australia's role in the nuclear fuel cycle. The inquiry will examine in particular Australia's nuclear safeguards arrangements and the adequacy of existing waste management technology. In two additional decisions the Government has dissociated itself from a study into the feasibility of establishing an enrichment operation and has abolished the Uranium Advisory Council. Although Australian reserves account for 20% of the total in the Western World, Australia accounts for a relatively minor proportion of the world's uranium production

  20. Uranium

    International Nuclear Information System (INIS)

    Anon.

    1981-01-01

    The French Government has decided to freeze a substantial part of its nuclear power programme. Work has been halted on 18 reactors. This power programme is discussed, as well as the effect it has on the supply of uranium by South Africa

  1. Standard test method for analysis of total and isotopic uranium and total thorium in soils by inductively coupled plasma-mass spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This test method covers the measurement of total uranium (U) and thorium (Th) concentrations in soils, as well as the determination of the isotopic weight percentages of 234U, 235U, 236U, and 238U, thereby allowing for the calculation of individual isotopic uranium activity or total uranium activity. This inductively coupled plasma-mass spectroscopy (ICP-MS) method is intended as an alternative analysis to methods such as alpha spectroscopy or thermal ionization mass spectroscopy (TIMS). Also, while this test method covers only those isotopes listed above, the instrumental technique may be expanded to cover other long-lived radioisotopes since the preparation technique includes the preconcentration of the actinide series of elements. The resultant sample volume can be further reduced for introduction into the ICP-MS via an electrothermal vaporization (ETV) unit or other sample introduction device, even though the standard peristaltic pump introduction is applied for this test method. The sample preparatio...

  2. Extraction of uranium from sea water with the granular composite adsorbent by using the fixed bed

    International Nuclear Information System (INIS)

    Katoh, Shunsaku; Sakane, Kohji; Hirotsu, Takahiro; Fujii, Ayako; Kitamura, Takao

    1981-01-01

    To clarify the technical problems existing in the extraction process of uranium from sea water, uranium was extracted from natural sea water, with the granulated C-Ti-OH composite adsorbent. The adsorption of uranium from sea water was carried out by using the fixed bed that had been designed in our laboratory. The uranium recovery from the sea water was 13.9% in the adsorption process of 56 d. The adsorbed uranium was eluted from the adsorbent with 0.5 N NaHCO 3 -0.5N Na 2 CO 3 soln. at 70 0 C. The elution recovery was 97.4% for 35 h. The uranium contained in the eluate was concentrated twenty times as much as in the anion exchange process, and then 100 times in the solvent extraction process with oxine-chloroform and TOA-kerosene. About 0.7 g of yellow cake was prepared from natural sea water, and it was identified to be pure 2UO 2 .NH 3 .3H 2 O by X-ray diffraction method and X-ray fluorometry. (author)

  3. Desorption of uranium from titanium-activated carbon composite adsorbent with acidic eluent, 1

    International Nuclear Information System (INIS)

    Hirotsu, Takahiro; Fujii, Ayako; Sakane, Kohji; Katoh, Shunsaku; Sugasaka, Kazuhiko

    1984-01-01

    An investigation was carried out on the desorption of uranium from titanium-activated carbon composite adsorbent with acidic eluent by the batch process. The rate of desorption of uranium with acidic eluent depended on temperature, showing an increase as the temperature was raised. But the rate of desorption with acidic eluent was less dependent on temperature than that obtained when mixed eluent of sodium carbonate-sodium hydrogencarbonate was used. The rate of desorption of uranium did not vary in the range of concentration from 0.3 to 0.5 N, and the rate of desorption with sulfuric acid was slightly higher than that obtained when hydrochloric acid was used. The amount of dissolved titanium decreased as the ratio of adsorbent to eluent (RAE) was increased. At RAE of 10 %, the percentage of dissolved titanium (DTI) was below 0.38 % with sulfuric acid, below 0.7 % with hydrochloric acid. These values were found to be higher than the ones with the carbonate eluent. The elements except uranium, which were adsorbed on the adsorbent, were eluted simultaneously with acidic eluent. The regeneration of the adsorbent after desorption, therefore, was found to be unnecessary. In a repeated test of adsorption-desorption treatment up to five times, the percentage of uranium adsorbed from natural sea water was approximately constant of 85 %. From these results, the application of column process to the desorption of uranium with acidic eluent at room temperature was proposed to be feasible. (author)

  4. Desorption of uranium from titanium-activated carbon composite adsorbent with acidic eluent, (1)

    International Nuclear Information System (INIS)

    Hirotsu, Takahiro; Fujii, Ayako; Sakane, Kohji; Katoh, Shunsaku; Sugasaka, Kazuhiko

    1983-01-01

    An investigation was carried out on the desorption of uranium from titanium-activated carbon composite adsorbent with acidic eluent by the batch process. The rate of desorption of uranium with acidic eluent depended on temperature, showing an increase as the temperature was raised. But the rate of desorption with acidic eluent was less dependent on temperature than that obtained when mixed eluent of sodium carbonate-sodium hydrogencarbonate was used. The difference of the rate of desorption of uranium in the range of concentration from 0.3 to 0.5N was not found, and the rate of desorption with sulfuric acid was slightly higher than that obtained when hydrochloric acid was used. The amount of dissolved titanium decreased as the ratio of adsorbent to eluent (RAE) was increased. At RAE of 10%, the percentage of dissolved titanium (DTI) was below 0.38% with sulfuric acid, below 0.7% with hydrochloric acid. These values were found to be higher than the ones with the carbonate eluent. The elements except uranium, which were adsorbed on the adsorbent, were eluted simultaneously with acidic eluent. The regeneration of the adsorbent after desorption, therefore, was found to be unnecessary. In a repeated test of adsorption-desorption treatment up to five times, the percentage of uranium adsorbed from natural sea water was approximately constant of 85%. From these results, the application of column process to the desorption of uranium with acidic eluent at room temperature was proposed to be feasible. (author)

  5. Nutritional assessment by isotope dilution analysis of body composition

    International Nuclear Information System (INIS)

    Szeluga, D.J.; Stuart, R.K.; Utermohlen, V.; Santos, G.W.

    1984-01-01

    The three components of body mass, body cell mass (BCM), extracellular fluid (ECF), and fat + extracellular solids (ECS: bone, tendon, etc) can be quantified using established isotope dilution techniques. With these techniques, total body water (TBW) and ECF are measured using 3H 2 O and 82 Bromine, respectively, as tracers. BCM is calculated from intracellular fluid (ICF) where ICF . TBW - ECF. Fat + ECS is estimated as: body weight - (BCM + ECF). TBW and ECF can be determined by either of two calculation methods, one requiring several timed plasma samples (extrapolation method) and one requiring a single plasma sample and a 4-h urine collection (urine-corrected method). The comparability of the two calculation methods was evaluated in 20 studies in 12 bone marrow transplant recipients. We found that for determination of TBW and ECF there was a very strong linear relationship (r2 greater than 0.98) between the calculation methods. Further comparisons (by t test, 2-sided) indicated that for the determination of ECF, the methods were not significantly (p greater than 0.90) different; however, TBW determined by the urine-corrected method was slightly (0.1 to 6%), but significantly (p less than 0.01) greater than that determined by the extrapolation method. Therefore, relative to the extrapolation method, the urine-corrected method ''over-estimates'' BCM and ''under-estimates'' fat + ECS since determination of these compartment sizes depends on measurement of TBW. We currently use serial isotope dilution studies to monitor the body composition changes of patients receiving therapeutic nutritional support

  6. Modelling and interpreting the isotopic composition of water vapour in convective updrafts

    Directory of Open Access Journals (Sweden)

    M. Bolot

    2013-08-01

    Full Text Available The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed-phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters, including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener–Bergeron–Findeisen process. As all of these processes are related to updraft strength, particle size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

  7. Modelling and interpreting the isotopic composition of water vapour in convective updrafts

    Science.gov (United States)

    Bolot, M.; Legras, B.; Moyer, E. J.

    2013-08-01

    The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed-phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters, including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener-Bergeron-Findeisen process). As all of these processes are related to updraft strength, particle size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

  8. Modelling and intepreting the isotopic composition of water vapour in convective updrafts

    Science.gov (United States)

    Bolot, M.; Legras, B.; Moyer, E. J.

    2012-08-01

    The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener-Bergeron-Findeisen process). As all of these processes are related to updraft strength, droplet size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

  9. Determination of the activity of the uranium isotopes U-234, U-235 and U-238 in environmental samples by alpha spectrometry

    International Nuclear Information System (INIS)

    Kromphorn, G.

    1996-02-01

    Different materials containing urandium are regularly investigated in the Laboratory for Environmental Radioactivity of the Physikalisch-Technische Bundesanstalt (PTB) with respect to the activity of the uranium isotopes ( 234 U, 235 U, and 238 U). Moreover for reasons of quality assurance, the PTB takes part in international comparisons where also uranium contents are to be determined in environmental samples and in the framework of which reference materials can be certified. Finally in national comparisons the PTB has the task to determine values of the specific activity for the different isotopes which can play the role of nominal (orientation) values. The single steps of uranium analyses are described after a compilation of the most important data of the uranium isotopes contained in natural uranium: The use of 232 U as tracer, the chemical separation analytics, the production of α-sources and the measuring methods. Analyses of a soil sample and a waste water sample with respect to their specific uranium activity have been chosen as examples of a practical application. (orig.) [de

  10. Recovery of uranium from phosphoric acid medium by polymeric composite beads encapsulating organophosphorus extractants

    Energy Technology Data Exchange (ETDEWEB)

    Singh, D.K.; Yadav, K.K.; Varshney, L.; Singh, H. [Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2013-07-01

    The present study deals with the preparation and evaluation of the poly-ethersulfone (PES) based composite beads encapsulating synergistic mixture of D2EHPA and Cyanex 923 (at 4:1 mole ratio) for the separation of uranium from phosphoric acid medium. SEM was used for the characterization of the composite materials. Addition of 1% PVA (polyvinyl alcohol) improved the internal morphology and porosity of the beads. Additionally, microscopic examination of the composite bead confirmed central coconut type cavity surrounded by porous polymer layer of the beads through which exchange of metal ions take place. Effect of various experimental variables including aqueous acidity, metal ion concentration in aqueous feed, concentration of organic extractant inside the beads, extractant to polymer ratio, liquid to solid (L/S) ratio and temperature on the extraction of uranium was studied. Increase in acidity (1-6 M), L/S ratio (1- 10), metal ion concentration (0.2-3 g/L U{sub 3}O{sub 8}) and polymer to extractant ratio (1:4 -1:10) led to decrease in extraction of uranium. At 5.5 M (comparable to wet process phosphoric acid concentration) the extraction of uranium was about 85% at L/S ratio 5. Increase in extractant concentration inside the bead resulted in enhanced extraction of metal ion. Increase in temperature in the range of 30 to 50 Celsius degrees increased the extraction, whereas further increase to 70 C degrees led to the decrease in extraction of uranium. Amongst various reagents tested, stripping of uranium was quantitative by 12% Na{sub 2}CO{sub 3} solution. Polymeric beads were found to be stable and reusable up-to 10 cycles of extraction/stripping. (authors)

  11. Technical Report on the Behavior of Trace Elements, Stable Isotopes, and Radiogenic Isotopes During the Processing of Uranium Ore to Uranium Ore Concentrate

    Energy Technology Data Exchange (ETDEWEB)

    Marks, N. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Borg, L. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Eppich, G. R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Gaffney, A. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Genneti, V. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hutcheon, I. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kristo, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lindvall, R. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ramon, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Robel, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Roberts, S. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schorzman, K. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sharp, M. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Singleton, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Williams, R. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-07-09

    The goals of this SP-1 effort were to understand how isotopic and elemental signatures behave during mining, milling, and concentration and to identify analytes that might preserve geologic signatures of the protolith ores. The impurities that are preserved through the concentration process could provide useful forensic signatures and perhaps prove diagnostic of sample origin.

  12. Controls on the stable isotope compositions of travertine from hyperalkaline springs in Oman: Insights from clumped isotope measurements

    Science.gov (United States)

    Falk, E. S.; Guo, W.; Paukert, A. N.; Matter, J. M.; Mervine, E. M.; Kelemen, P. B.

    2016-11-01

    Carbonate formation at hyperalkaline springs is typical of serpentinization in peridotite massifs worldwide. These travertines have long been known to exhibit large variations in their carbon and oxygen isotope compositions, extending from apparent equilibrium values to highly depleted values. However, the exact causes of these variations are not well constrained. We analyzed a suite of well-characterized fresh carbonate precipitates and travertines associated with hyperalkaline springs in the peridotite section of the Samail ophiolite, Sultanate of Oman, and found their clumped isotope compositions vary systematically with formation environments. Based on these findings, we identified four main processes controlling the stable isotope compositions of these carbonates. These include hydroxylation of CO2, partial isotope equilibration of dissolved inorganic carbon, mixing between isotopically distinct carbonate end-members, and post-depositional recrystallization. Most notably, in fresh crystalline films on the surface of hyperalkaline springs and in some fresh carbonate precipitates from the bottom of hyperalkaline pools, we observed large enrichments in Δ47 (up to ∼0.2‰ above expected equilibrium values) which accompany depletions in δ18O and δ13C, yielding about 0.01‰ increase in Δ47 and 1.1‰ decrease in δ13C for every 1‰ decrease in δ18O, relative to expected equilibrium values. This disequilibrium trend, also reflected in preserved travertines ranging in age from modern to ∼40,000 years old, is interpreted to arise mainly from the isotope effects associated with the hydroxylation of CO2 in high-pH fluids and agrees with our first-order theoretical estimation. In addition, in some fresh carbonate precipitates from the bottom of hyperalkaline pools and in subsamples of one preserved travertine terrace, we observed additional enrichments in Δ47 at intermediate δ13C and δ18O, consistent with mixing between isotopically distinct carbonate end

  13. Irradiation tests of 99Mo isotope production targets employing uranium metal foils

    International Nuclear Information System (INIS)

    Hofman, G.L.; Wiencek, T.C.; Wood, E.L.; Snelgrove, J.L.; Suripto, A.; Nasution, H.; Lufti-Amin, D.; Gogo, A.

    1996-01-01

    Most of the world's supply of 99 mTc for medical purposes is currently produced from the decay of 99 Mo derived from the fissioning of high-enriched uranium (HEU). Substitution of low-enriched uranium (LEU) metal foils for the HEU UO 2 used in current target designs will allow equivalent 99 Mo yields with little change in target geometries. Substitution of uranium metal for uranium alloy and aluminide in other target designs will also allow the conversion of HEU to LEU. Several uranium-metal-foil targets have been fabricated at ANL and irradiated to prototypic burnup in the Indonesian RSG-GAS reactor. Postirradiation examination of the initial test indicated that design modifications were required to allow the irradiated foil to be removed for chemical processing. The latest test has shown good irradiation behavior, satisfactory dismantling and foil removal when the U-foil is separated from its containment by metallic, fission-recoil absorbing barriers. (author)

  14. Uranium 234U and 238U isotopes in the southern Baltic environment

    International Nuclear Information System (INIS)

    Borylo, A.; Skwarzec, B.

    2002-01-01

    The concentration and distribution of uranium in water and sediment of selected basins of the southern Baltic Sea have been analysed. It was observed that the concentration of uranium in sediments increases with core depth. This is probably connected to diffusion processes from sediments to water through interstitial water where uranium concentration is much higher than in bottom water. The measurements of 234 U/ 238 U activity ratios indicate that sedimentation of terrigenic material and transport through Vistula river are the major sources of uranium in sediments of the southern Baltic Sea. Estimation of the 234 U/ 238 U ratios in reduction areas of the Baltic Deep and the Bornholm Deep suggest that the processes of reduction of U(VI) to U(IV) and of removal of authogenic uranium from seawater to sediments do not play major roles in the Gdansk Deep. (author)

  15. Irradiation tests of 99Mo isotope production targets employing uranium metal foils

    International Nuclear Information System (INIS)

    Hofman, G.L.; Wiencek, T.C.; Wood, E.L.; Snelgrove, J.L.; Suripto, A.; Nasution, H.; Lufti-Amin, D.; Gogo, A.

    1996-01-01

    Most of the world's supply of 99m Tc for medical purposes is currently produced form the decay of 99 Mo derived from the fissioning of high-enriched uranium (HEU). Substitution of low-enriched uranium (LEU) metal foils for the HEU UO 2 used in current target designs will allow equivalent 99 Mo yields with little change in target geometries. Substitution of uranium metal for uranium alloy and aluminide in other target designs will also allow the conversion of HEU to LEU. Several uranium-metal-foil targets have been fabricated at ANL and irradiated to prototypic burnup in the Indonesian RSG-GAS reactor. Postirradiation examination of the initial test indicated that design modifications were required to allow the irradiated foil to be removed for chemical processing. The latest test has shown good irradiation behavior, satisfactory dismantling and foil removal when the U-foil is separated from its containment by metallic, fission-recoil absorbing barriers

  16. Development of 99Mo isotope production targets employing uranium metal foils

    International Nuclear Information System (INIS)

    Hofman, G.L.; Wiencek, T.C.; Wood, E.L.; Snelgrove, J.L.

    1997-01-01

    The Reduced Enrichment Research and Test Reactor Program has continued its effort in the past 3 yr to develop use of low-enriched uranium (LEU) to produce the fission product 99 Mo. This work comprises both target and chemical processing development and demonstration. Two major target systems are now being used to produce 99 Mo with highly enriched uranium-one employing research reactor fuel technology (either uranium-aluminum alloy or uranium aluminide-aluminum dispersion) and the other using a thin deposit of UO 2 on the inside of a stainless steel (SST) tube. This paper summarizes progress in irradiation testing of targets based on LEU uranium metal foils. Several targets of this type have been irradiated in the Indonesian RSG-GAS reactor operating at 22.5 MW

  17. Isotopic analysis of uranium hexafluoride highly enriched in U-235; Analyse isotopique de l'hexafluorure d'uranium fortement enrichi en U 235

    Energy Technology Data Exchange (ETDEWEB)

    Chaussy, L; Boyer, R [Commissariat a l' Energie Atomique, Pierrelatte (France). Centre d' Etudes Nucleaires

    1968-07-01

    Isotopic analysis of uranium in the form of the hexafluoride by mass-spectrometry gives gross results which are not very accurate. Using a linear interpolation method applied to two standards it is possible to correct for this inaccuracy as long as the isotopic concentrations are less than about 10 per cent in U-235. Above this level, the interpolations formula overestimates the results, especially if the enrichment of the analyzed samples is higher than 1.3 with respect to the standards. A formula is proposed for correcting the interpolation equation and for the extending its field of application to high values of the enrichment ({approx_equal}2) and of the concentration. It is shown that by using this correction the results obtained have an accuracy which depends practically only on that of the standards, taking into account the dispersion in the measurements. (authors) [French] L'analyse isotopique de l'uranium sous forme d'hexafluorure, par spectrometrie de masse, fournit des resultats bruts entaches d'inexactitude. Une methode d'interpolation lineaire entre deux etalons permet de corriger cette inexactitude, tant que les concentrations isotopiques sont inferieures a 10 pour cent en U-235 environ. Au-dessus de cette valeur, la formule d'interpolation surestime les resultats, notamment si l'enrichissement des echantillons analyses par rapport aux etalons est superieur a 1,3. On propose une formule de correction de l'equation d'interpolation qui etend son domaine d'application jusqu'a des valeurs elevees d'enrichissement ({approx_equal}2) et de concentration. On montre experimentalement que par cette correction, les resultats atteignent, a la precision des mesures, une exactitude qui ne depend pratiquement plus que de celles des etalons. (auteurs)

  18. Reaction of Antimony-Uranium Composite Oxide in the Chlorination Treatment of Waste Catalyst - 13521

    International Nuclear Information System (INIS)

    Sawada, Kayo; Hirabayashi, Daisuke; Enokida, Youichi

    2013-01-01

    The effect of oxygen gas concentration on the chlorination treatment of antimony-uranium composite oxide catalyst waste was investigated by adding different concentrations of oxygen at 0-6 vol% to its chlorination agent of 0.6 or 6 vol% hydrogen chloride gas at 1173 K. The addition of oxygen tended to prevent the chlorination of antimony in the oxide. When 6 vol% hydrogen chloride gas was used, the addition of oxygen up to 0.1 vol% could convert the uranium contained in the catalyst to U 3 O 8 without any significant decrease in the reaction rate compared to that of the treatment without oxygen. (authors)

  19. First measurements on the core and edge isotope composition using the JET isotope separator neutral particle analyser

    International Nuclear Information System (INIS)

    Bettella, D; Murari, A; Stamp, M; Testa, D

    2003-01-01

    Direct measurements of tokamak plasmas isotope composition are in general quite difficult and have therefore been very seldom performed. On the other hand, the importance of this measurement is going to increase, as future experiments will be progressively focused on plasmas approaching reactor conditions. In this paper, we report for the first time encouraging experimental evidence supporting a new method to determine the radial profile of the density ratio n H /(n H + n D ), based on neutral particle analyser (NPA) measurements. The measurements have been performed in JET with the ISotope SEParator (ISEP), a NPA device specifically developed to measure the energy spectra of the three hydrogen isotopes with very high accuracy and low cross-talk. The data presented here have been collected in two different experimental conditions. In the first case, the density ratio has been kept constant during the discharge. The isotope ratio derived from the ISEP has been compared with the results of visible spectroscopy at the edge and with the isotope composition derived from an Alfven eigenmodes active diagnostic (AEAD) system at about half the minor radius for the discharges reported in this paper. A preliminary evaluation of the additional heating effects on the measurements has also been carried out. In the second set of experiments, the isotope composition of deuterium plasmas has been abruptly changed with suitable short blips of hydrogen, in order to assess the capability of the method to study the transport of the hydrogen isotope species. Future developments of the methodology and its applications to the evaluation of hydrogen transport coefficients are also briefly discussed. The results obtained so far motivate further development of the technique, which constitutes one of the few candidate diagnostic approaches viable for ITER

  20. Sediment residence times constrained by uranium-series isotopes: A critical appraisal of the comminution approach

    Science.gov (United States)

    Handley, Heather K.; Turner, Simon; Afonso, Juan C.; Dosseto, Anthony; Cohen, Tim

    2013-02-01

    Quantifying the rates of landscape evolution in response to climate change is inhibited by the difficulty of dating the formation of continental detrital sediments. We present uranium isotope data for Cooper Creek palaeochannel sediments from the Lake Eyre Basin in semi-arid South Australia in order to attempt to determine the formation ages and hence residence times of the sediments. To calculate the amount of recoil loss of 234U, a key input parameter used in the comminution approach, we use two suggested methods (weighted geometric and surface area measurement with an incorporated fractal correction) and typical assumed input parameter values found in the literature. The calculated recoil loss factors and comminution ages are highly dependent on the method of recoil loss factor determination used and the chosen assumptions. To appraise the ramifications of the assumptions inherent in the comminution age approach and determine individual and combined comminution age uncertainties associated to each variable, Monte Carlo simulations were conducted for a synthetic sediment sample. Using a reasonable associated uncertainty for each input factor and including variations in the source rock and measured (234U/238U) ratios, the total combined uncertainty on comminution age in our simulation (for both methods of recoil loss factor estimation) can amount to ±220-280 ka. The modelling shows that small changes in assumed input values translate into large effects on absolute comminution age. To improve the accuracy of the technique and provide meaningful absolute comminution ages, much tighter constraints are required on the assumptions for input factors such as the fraction of α-recoil lost 234Th and the initial (234U/238U) ratio of the source material. In order to be able to directly compare calculated comminution ages produced by different research groups, the standardisation of pre-treatment procedures, recoil loss factor estimation and assumed input parameter values

  1. Uranium isotopes and dissolved organic carbon in loess permafrost: Modeling the age of ancient ice

    Science.gov (United States)

    Ewing, Stephanie A.; Paces, James B.; O'Donnell, J.A.; Jorgenson, M.T.; Kanevskiy, M.Z.; Aiken, George R.; Shur, Y.; Harden, Jennifer W.; Striegl, Robert G.

    2015-01-01

    The residence time of ice in permafrost is an indicator of past climate history, and of the resilience and vulnerability of high-latitude ecosystems to global change. Development of geochemical indicators of ground-ice residence times in permafrost will advance understanding of the circumstances and evidence of permafrost formation, preservation, and thaw in response to climate warming and other disturbance. We used uranium isotopes to evaluate the residence time of segregated ground ice from ice-rich loess permafrost cores in central Alaska. Activity ratios of 234U vs. 238U (234U/238U) in water from thawed core sections ranged between 1.163 and 1.904 due to contact of ice and associated liquid water with mineral surfaces over time. Measured (234U/238U) values in ground ice showed an overall increase with depth in a series of five neighboring cores up to 21 m deep. This is consistent with increasing residence time of ice with depth as a result of accumulation of loess over time, as well as characteristic ice morphologies, high segregated ice content, and wedge ice, all of which support an interpretation of syngenetic permafrost formation associated with loess deposition. At the same time, stratigraphic evidence indicates some past sediment redistribution and possibly shallow thaw among cores, with local mixing of aged thaw waters. Using measures of surface area and a leaching experiment to determine U distribution, a geometric model of (234U/238U) evolution suggests mean ages of up to ∼200 ky BP in the deepest core, with estimated uncertainties of up to an order of magnitude. Evidence of secondary coatings on loess grains with elevated (234U/238U) values and U concentrations suggests that refinement of the geometric model to account for weathering processes is needed to reduce uncertainty. We suggest that in this area of deep ice-rich loess permafrost, ice bodies have been preserved from the last glacial period (10–100 ky BP), despite subsequent

  2. Uranium-series isotopes transport in surface, vadose and ground waters at San Marcos uranium bearing basin, Chihuahua, Mexico

    International Nuclear Information System (INIS)

    Burillo Montúfar, Juan Carlos; Reyes Cortés, Manuel; Reyes Cortés, Ignacio Alfonso; Espino Valdez, Ma. Socorro; Hinojosa de la Garza, Octavio Raúl; Nevárez Ronquillo, Diana Pamela; Herrera Peraza, Eduardo; Rentería Villalobos, Marusia; Montero Cabrera, María Elena

    2012-01-01

    In the U deposit area at San Marcos in Chihuahua, Mexico, hydrogeological and climatic conditions are very similar to the Nopal I, Peña Blanca U deposit, 50 km away. The physicochemical parameters and activity concentrations of several 238 U-series isotopes have been determined in surface, vadose and ground waters at San Marcos. The application of some published models to activity ratios of these isotopes has allowed assessing the order of magnitude of transport parameters in the area. Resulting retardation factors in San Marcos area are R f238 ≈ 250–14,000 for the unsaturated zone and ≈110–1100 for the saturated zone. The results confirm that the mobility of U in San Marcos is also similar to that of the Nopal I U deposit and this area can be considered as a natural analog of areas suitable for geologic repositories of high-level nuclear waste.

  3. Budgets and behaviors of uranium and thorium series isotopes in the Santa Monica Basin off the California Coast

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Lei.

    1991-12-16

    Samples from three time-series sediment traps deployed in the Santa Monica Basin off the California coast were analyzed to study the flux and scavenging of uranium and thorium series isotopes. Variations of uranium and thorium series isotopes fluxes in the water column were obtained by integrating these time-series deployment results. Mass and radionuclide fluxes measured from bottom sediment traps compare favorably with fluxed determined from sediment core data. This agreement suggests that the near-bottom sediment traps are capable of collecting settling particles representative of the surface sediment. The phase distributions of {sup 234}Th in the water column were calculated by an inverse method using sediment trap data, which help to study the variations of {sup 234}Th scavenging in the water column. Scavenging and radioactive decay of {sup 234}Th are the two principal processes for balancing {sup 234}Th budget in the water column. The residence times of dissolved and particulate {sup 234}Th were determined by a {sup 234}Th scavenging model.

  4. Budgets and behaviors of uranium and thorium series isotopes in the Santa Monica Basin off the California Coast

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Lei [Oregon State Univ., Corvallis, OR (United States)

    1991-12-16

    Samples from three time-series sediment traps deployed in the Santa Monica Basin off the California coast were analyzed to study the flux and scavenging of uranium and thorium series isotopes. Variations of uranium and thorium series isotopes fluxes in the water column were obtained by integrating these time-series deployment results. Mass and radionuclide fluxes measured from bottom sediment traps compare favorably with fluxed determined from sediment core data. This agreement suggests that the near-bottom sediment traps are capable of collecting settling particles representative of the surface sediment. The phase distributions of 234Th in the water column were calculated by an inverse method using sediment trap data, which help to study the variations of 234Th scavenging in the water column. Scavenging and radioactive decay of 234Th are the two principal processes for balancing 234Th budget in the water column. The residence times of dissolved and particulate 234Th were determined by a 234Th scavenging model.

  5. Near Surface CO2 Triple Oxygen Isotope Composition

    Directory of Open Access Journals (Sweden)

    Sasadhar Mahata

    2016-02-01

    Full Text Available The isotopic composition of carbon dioxide in the atmosphere is a powerful tool for constraining its sources and sinks. In particular, the 17O oxygen anomaly [Δ17O = 1000 × ln(1 + δ17O/1000 - 0.516 × 1000 × ln(1 + δ18O/1000], with a value > 0.5‰ produced in the middle atmosphere, provides an ideal tool for probing the exchange of carbon dioxide between the biosphere/hydrosphere and atmosphere. The biosphere/hydrosphere and anthropogenic emissions give values ≤ 0.3‰. Therefore, any anomaly in near surface CO2 would reflect the balance between stratospheric input and exchange with the aforementioned surface sources. We have analyzed Δ17O values of CO2 separated from air samples collected in Taipei, Taiwan, located in the western Pacific region. The obtained mean anomaly is 0.42 ± 0.14‰ (1-σ standard deviation, in good agreement with model prediction and a published decadal record. Apart from typically used δ13C and δ18O values, the Δ17O value could provide an additional tracer for constraining the carbon cycle.

  6. Main results obtained in France in the development of the gaseous diffusion process for uranium isotope separation

    International Nuclear Information System (INIS)

    Frejacques, C.; Bilous, O.; Dixmier, J.; Massignon, D.; Plurien, P.

    1958-01-01

    The main problems which occur in the study of uranium isotope separation by the gaseous diffusion process, concern the development of the porous barrier, the corrosive nature of uranium hexafluoride and also the chemical engineering problems related to process design and the choice of best plant and stage characteristics. Porous barriers may be obtained by chemical attack of non porous media or by agglomeration of very fine powders. Examples of these two types of barriers are given. A whole set of measurement techniques were developed for barrier structure studies, to provide control and guidance of barrier production methods. Uranium hexafluoride reactivity and corrosive properties are the source of many difficult technological problems. A high degree of plant leak tightness must be achieved. This necessity creates a special problem in compressor bearing design. Barrier lifetime is affected by the corrosive properties of the gas, which may lead to a change of barrier structure with time. Barrier hexafluoride permeability measurements have helped to make a systematic study of this point. Finally an example of a plant flowsheet, showing stage types and arrangements and based on a minimisation of enriched product costs is also given as an illustration of some of the chemical engineering problems present. (author) [fr

  7. Establishing a Cost Basis for Converting the High Flux Isotope Reactor from High Enriched to Low Enriched Uranium Fuel

    International Nuclear Information System (INIS)

    Primm, Trent; Guida, Tracey

    2010-01-01

    Under the auspices of the Global Threat Reduction Initiative Reduced Enrichment for Research and Test Reactors Program, the National Nuclear Security Administration/Department of Energy (NNSA/DOE) has, as a goal, to convert research reactors worldwide from weapons grade to non-weapons grade uranium. The High Flux Isotope Reactor (HFIR) at Oak Ridge National Lab (ORNL) is one of the candidates for conversion of fuel from high enriched uranium (HEU) to low enriched uranium (LEU). A well documented business model, including tasks, costs, and schedules was developed to plan the conversion of HFIR. Using Microsoft Project, a detailed outline of the conversion program was established and consists of LEU fuel design activities, a fresh fuel shipping cask, improvements to the HFIR reactor building, and spent fuel operations. Current-value costs total $76 million dollars, include over 100 subtasks, and will take over 10 years to complete. The model and schedule follows the path of the fuel from receipt from fuel fabricator to delivery to spent fuel storage and illustrates the duration, start, and completion dates of each subtask to be completed. Assumptions that form the basis of the cost estimate have significant impact on cost and schedule.

  8. Optimisation and application of ICP-MS and alpha-spectrometry for determination of isotopic ratios of depleted uranium and plutonium in samples collected in Kosovo

    OpenAIRE

    Boulyga, S. F.; Testa, C.; Desideri, D.; Becker, J. S.

    2001-01-01

    The determination of environmental contamination with natural and artificial actinide isotopes and evaluation of their source requires precise isotopic determination of actinides, above all uranium and plutonium. This can be achieved by alpha spectrometry or by inductively coupled plasma mass spectrometry (ICP-MS) after chemical separation of actinides. The performance of a sector-field ICP-MS (ICP-SFMS) coupled to a low-flow micronebulizer with a membrane desolvation unit, "Aridus'', was stu...

  9. Advanced Collimators for Verification of the Pu Isotopic Composition in Fresh Fuel by High Resolution Gamma Spectrometry

    International Nuclear Information System (INIS)

    Lebrun, Alain; Berlizov, Andriy

    2013-06-01

    IAEA verification of the nuclear material contained in fresh nuclear fuel assemblies is usually based on neutron coincidence counting (NCC). In the case of uranium fuel, active NCC provides the total content of uranium-235 per unit of length which, combined with active length verification, fully supports the verification. In the case of plutonium fuel, passive NCC provides the plutonium-240 equivalent content which needs to be associated with a measurement of the isotopic composition and active length measurement to complete the verification. Plutonium isotopic composition is verified by high resolution gamma spectrometry (HRGS) applied on fresh fuel assemblies assuming all fuel rods are fabricated from the same plutonium batch. For particular verifications when such an assumption cannot be reasonably made, there is a need to optimize the HRGS measurement so that contributions of internal rods to the recorded spectrum are maximized, thus providing equally strong verification of the internal fuel rods. This paper reports on simulation work carried out to design special collimators aimed at reducing the relative contribution of external fuel rods while enhancing the signal recorded from internal rods. Both cases of square lattices (e.g. 17x17 pressurized water reactor (PWR) fuel) and hexagonal compact lattices (e.g. BN800 fast neutron reactor (FNR) fuel) have been addressed. In the case of PWR lattices, the relatively large optical path to internal pins compensates for low plutonium concentrations and the large size of the fuel assemblies. A special collimator based on multiple, asymmetrical, vertical slots allows recording a spectrum from internal rods only when needed. In the FNR case, the triangular lattice is much more compact and the optical path to internal rods is very narrow. However, higher plutonium concentration and use of high energy ranges allow the verification of internal rods to be significantly strengthened. Encouraging results from the simulation

  10. Nucleosynthesis in Wolf-Rayet stars and galactic cosmic-ray isotopic composition

    International Nuclear Information System (INIS)

    Prantzos, N.

    1984-01-01

    An explanation of the isotopic composition of galactic cosmic rays could provide some clues to the mystery of their origin. It seems now that the strong stellar winds of Wolf-Rayet stars could account for most of the isotopic anomalies that have been observed in cosmic rays. Some results are presented, obtained by detailed nucleosynthesis computations. 25 references

  11. Effects of climatic seasonality on the isotopic composition of evaporating soil waters

    Directory of Open Access Journals (Sweden)

    P. Benettin

    2018-05-01

    Full Text Available Stable water isotopes are widely used in ecohydrology to trace the transport, storage, and mixing of water on its journey through landscapes and ecosystems. Evaporation leaves a characteristic signature on the isotopic composition of the water that is left behind, such that in dual-isotope space, evaporated waters plot below the local meteoric water line (LMWL that characterizes precipitation. Soil and xylem water samples can often plot below the LMWL as well, suggesting that they have also been influenced by evaporation. These soil and xylem water samples frequently plot along linear trends in dual-isotope space. These trend lines are often termed "evaporation lines" and their intersection with the LMWL is often interpreted as the isotopic composition of the precipitation source water. Here we use numerical experiments based on established isotope fractionation theory to show that these trend lines are often by-products of the seasonality in evaporative fractionation and in the isotopic composition of precipitation. Thus, they are often not true evaporation lines, and, if interpreted as such, can yield highly biased estimates of the isotopic composition of the source water.

  12. Bulk Oxygen Isotopic Composition of Ultracarbonaceous Antarctic Micrometeorites with the NanoSIMS

    Science.gov (United States)

    Kakazu, Y.; Engrand, C.; Duprat, J.; Briani, G.; Bardin, N.; Mostefaoui, S.; Duhamel, R.; Remusat, L.

    2014-09-01

    We analyzed the carbon and oxygen isotope ratios of two UCAMMs with the NanoSIMS in order to understand the origin and formation of UCAMMs. One UCAMM has 16O-rich composition and a highly heterogeneous oxygen isotopic distribution.

  13. Isotopic composition of rainfall and runoff in a small arid basin with implications for deep percolation

    International Nuclear Information System (INIS)

    Dody, A.

    1995-08-01

    The aim of this work was to characterize the isotopic composition of potential recharge in an arid rocky watershed. Unique field observations were obtained from an arid watershed in the Negev Highlands, Israel, through utilization of the dynamic variations in the isotopic composition of rainfall and runoff. The hydrological system's inputs are rainfall and its isotopic composition. Rainfall and runoff were sampled in eight storms. High variability in the isotopic composition of rainfall was observed during any single rainstorm. The isotopic distribution in the runoff at the outlet of the basin appeared often not to be correlated to the isotopic patterns of the associated rain storm. A new mathematical model was developed to describe these physical processes. The model called A Double-Component Kinematic Wave Flow and Transport Approach, was designated to assess the dynamic isotopic distribution in arid rain storms and runoff. This model simulates the transport of rainfall into overland flow and runoff in an arid rocky watershed with uniformly distributed shallow depression storage. A numerical solution for the problem was developed, to estimate the depression storage parameters. The model also reflects the isotopic memory effect due to the depression storage between sequential rain showers. A good agreement between the observed and computed hydrograph and the change of the δ 18O values in runoff in time confirms the validity of the model. (author) 138 figs., 125 refs

  14. Soil drying effects on the carbon isotope composition of soil respiration

    Science.gov (United States)

    Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies. Environmental factors that change over time, such as moisture, can create dynamic changes in the isotopic composition of C assimilated by plants, and offers a unique opp...

  15. Isotopic composition of rainfall and runoff in a small arid basin with implications for deep percolation

    Energy Technology Data Exchange (ETDEWEB)

    Dody, A [Ben-Gurion Univ. of the Negev, Beersheba (Israel)

    1995-08-01

    The aim of this work was to characterize the isotopic composition of potential recharge in an arid rocky watershed. Unique field observations were obtained from an arid watershed in the Negev Highlands, Israel, through utilization of the dynamic variations in the isotopic composition of rainfall and runoff. The hydrological system`s inputs are rainfall and its isotopic composition. Rainfall and runoff were sampled in eight storms. High variability in the isotopic composition of rainfall was observed during any single rainstorm. The isotopic distribution in the runoff at the outlet of the basin appeared often not to be correlated to the isotopic patterns of the associated rain storm. A new mathematical model was developed to describe these physical processes. The model called A Double-Component Kinematic Wave Flow and Transport Approach, was designated to assess the dynamic isotopic distribution in arid rain storms and runoff. This model simulates the transport of rainfall into overland flow and runoff in an arid rocky watershed with uniformly distributed shallow depression storage. A numerical solution for the problem was developed, to estimate the depression storage parameters. The model also reflects the isotopic memory effect due to the depression storage between sequential rain showers. A good agreement between the observed and computed hydrograph and the change of the {delta}{sup 18O} values in runoff in time confirms the validity of the model. (author) 138 figs., 125 refs.

  16. Introduction of a method for determining uranium isotope ratio by α-spectroscopy and application to study the migration of this element in uranium occurence

    International Nuclear Information System (INIS)

    Bastos, K.F.

    1981-01-01

    A method of U and Th isotope ratio determination by α-spectroscopy to analyse the migration process of these elements at an uranium bearing region in Goias, Brazil, is described. The method consists of simultaneous extraction of U and Th with TOPO/cyclohexane, reextraction of Th with H 2 SO 4 (0.3M) and further purification of both phases. The interferent coextracted ions are eliminated by scrubbing with EDTA/NaNO 3 , and pure U is extracted with (NH 4 ) 2 CO 3 . The counting sources are prepared via extraction with TTA or MIBK, and evaporation of suitable aliquots on stainless steel disks. The recovery of U about 98% is obtained. The energy resolutions of U 238 peak (E α =4.195 MeV) are 52 and 83 KeV. The counting efficiencies are between 11 and 21+. Th is separated from the stripping solution by direct coprecipitation with macro amounts of LaF 3 and subsequent extraction with TTA/benzene for source preparation. Alternatively coprecipitation is proposed with micro quantities of LaF 3 and posterior filtration with membrane filters, where LaF 3 layer was previously deposited. This method allows direct counting of the filters and is superior in relation to energy resolution and counting efficiency. The U 238 /U 234 and U 234 /Th 230 isotope ratios in geological standards and prospecting samples were determined. The U 234 /Th 230 isotope ratio was used for analysing the migration of these elements because the most of analysed samples presented values, for this ratio, greater than unity, indicating that the anomalous concentrations of U are due to secondary enrichment processes. Aditional results of non equilibrium of the radioactivity of samples by γ-spectroscopy, are presented. (author) [pt

  17. Usage of burnt fuel isotopic compositions from engineering codes in Monte-Carlo code calculations

    International Nuclear Information System (INIS)

    Aleshin, Sergey S.; Gorodkov, Sergey S.; Shcherenko, Anna I.

    2015-01-01

    A burn-up calculation of VVER's cores by Monte-Carlo code is complex process and requires large computational costs. This fact makes Monte-Carlo codes usage complicated for project and operating calculations. Previously prepared isotopic compositions are proposed to use for the Monte-Carlo code (MCU) calculations of different states of VVER's core with burnt fuel. Isotopic compositions are proposed to calculate by an approximation method. The approximation method is based on usage of a spectral functionality and reference isotopic compositions, that are calculated by engineering codes (TVS-M, PERMAK-A). The multiplication factors and power distributions of FA and VVER with infinite height are calculated in this work by the Monte-Carlo code MCU using earlier prepared isotopic compositions. The MCU calculation data were compared with the data which were obtained by engineering codes.

  18. Carbon-13 kinetic isotope effects in the decarbonylation of lactic acid of natural isotopic composition in phosphoric acid medium

    International Nuclear Information System (INIS)

    Zielinski, M.; Czarnota, G.; Papiernik-Zielinska, H.; Kasprzyk, G.; Gumolka, L.; Staedter, W.

    1993-01-01

    The 13 C kinetic isotope effect fractionation in the decarbonylation of lactic acid (LA) of natural isotopic composition by concentrated phosphoric acids (PA) and by 85% H 3 PO 4 has been studied in the temperature interval of 60-150 deg C. The values of the 13 C (1) isotope effects in the decarbonylation of lactic acid in 100% H 3 PO 4 , in pyrophosphoric acid and in more concentrated phosphoric acids are intermediate between the values calculated assuming that the C (1)- OH bond is broken in the rate-controlling step of dehydration and those calculated for rupture of the carbon-carbon bond in the transition state. In the temperature interval of 90-130 deg C the experimental 13 C fractionation factors determined in concentrated PA approach quite closely the 13 C fractionation corresponding to C (2)- C (1) bond scission. The 13 C (1) kinetic isotope effects in the decarbonylation of LA in 85% orthophosphoric acid in the temperature range of 110-150 deg C coincide with the 13 C isotope effects calculated assuming that the frequency corresponding to the C (1) -OH vibration is lost in the transition state of decarbonylation. A change of the mechanism of decarbonylation of LA in going from concentrated PA medium to 85% H 3 PO 4 has been suggested. A possible secondary 18 O and a primary 18 O kinetic isotope effect in decarbonylation of lactic acid in phosphoric acids media have been discussed, too. (author) 21 refs.; 3 tabs

  19. Isotopic composition of Pb and Th in interplinian volcanics from Somma-Vesuvius volcano, Italy

    International Nuclear Information System (INIS)

    Cortini, M.; De Vivo, B.; Somma, R.; Ayuso, R.A.; Holden, P.

    2004-01-01

    We present a detailed isotopic study of volcanic rocks emitted from Somma-Vesuvius volcano during three periods of interplinian activity: 'Protohistoric' (3550 y B.P. to 79 A.D.), 'Ancient Historic' (79 to 472 A.D.) and 'Medieval' (472 to 1631 A.D.). Pb isotopic compositions of two acid leached fractions and whole rock residues of 37 whole rock samples (determined by Somma et al., 2001) show that each of the three interplinian periods is distinguished by small, systematic, and unique uranogenic and thorogenic Pb isotopic trends. This key and novel feature is compatible with the notion that the Pb isotopic data reflect small-scale source heterogeneity operating over relatively short periods of time. From this representative group of samples, a selected set of nine whole rocks were analyzed for Th isotopes. 232 Th/ 238 U ratios in the source can be obtained independently from Pb and from Th isotopes. Those obtained from Pb isotopes represent source ratios, time-integrated over the whole age of the earth; they range from 3.9 to 4.1. 232 Th/ 238 U obtained from Th isotopes are those of the present source. They are lower, and cluster around 3.5; this difference probably indicates recent U enrichment of the present source. The behavior of Pb, as inferred by its isotopic ratios, is quite distinct from that of Sr and Nd isotopes: Pb isotope variations are not correlated to Sr or Nd isotope variations. The isotopic contrast is compatible with the idea that the isotopes were decoupled during magmatic production, evolution, and ascent through the crust. Thus, the Pb isotopes do not reflect the effects of the same processes as in the case of the Sr and Nd isotopes, or, as we also favor, they do not necessarily reflect the same source contributions into the magmas. Moreover, the Pb isotopic evolution of the interplinian rocks chiefly reflects mixing, driven by processes that are superimposed on, and independent of, other source contributions that determine the isotopic

  20. Improvements to SFCOMPO - a database on isotopic composition of spent nuclear fuel

    International Nuclear Information System (INIS)

    Suyama, Kenya; Nouri, Ali; Mochizuki, Hiroki; Nomura, Yasushi

    2003-01-01

    Isotopic composition is one of the most relevant data to be used in the calculation of burnup of irradiated nuclear fuel. Since autumn 2002, the Organisation for Economic Co-operation and Development/Nuclear Energy Agency (OECD/NEA) has operated a database of isotopic composition - SFCOMPO, initially developed in Japan Atomic Energy Research Institute. This paper describes the latest version of SFCOMPO and the future development plan in OECD/NEA. (author)

  1. The use of stable isotope compositions of selected elements in food origin control

    International Nuclear Information System (INIS)

    Wierzchnicki, R.

    2002-01-01

    Stable isotope ratios have been used widely for authentication of foodstuffs especially for detection of added water and sugar in fruit juices and wines. Hydrogen and oxygen composition are particularly interesting probes for geographical origin and authenticity identification. Carbon and nitrogen composition of fruits contains the finger-print of their metabolism and growing condition. Exemplary data are presented which demonstrated the usefulness of the Isotope Ratio Mass Spectrometry (IRMS) methods for authenticating wines and fruits (juice and pulp). (author)

  2. Estimation of uranium isotopes in soil affected by Fukushima nuclear power plant accident and its mobility based on distribution coefficient and soil properties

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, S.K. [National Institute of Radiological Sciences (Japan); Mishra, S. [Bhabha Atomic Research Centre (India); Sorimachi, A.; Hosoda, M.; Tokonami, S. [Hirosaki University (Japan); Kritsananuwat, R. [Tokyo Metropolitan University (Japan); Ishikawa, T. [Fukushima Medical University (Japan)

    2014-07-01

    An extraordinary earthquake of magnitude 9.0 followed by Tsunami on 11 March 2011 caused serious nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) about 250 km north to Tokyo, capital of Japan. This resulted in radioactive contamination due to deposition of long-lived radionuclides. Contaminated soil can cause an enhanced radiation exposure even after many years. Depending upon environmental conditions radionuclides can be mobilized to aquatic systems. Therefore, the fate and transfer of these radionuclides in the soil water system is very important for radiation protection and dose assessment. In the present study, emphasis has been given on isotope ratio measurement of uranium that may give some idea about its contamination during accident. Soil and water samples were collected from contaminated areas around FDNPP. Inductively coupled plasma mass spectrometry (ICPMS) is used for total uranium concentration and thermal ionization mass spectrometry (TIMS) has been used for uranium isotopes measurement. Extraction chromatography has been used for the separation of uranium. We have observed, isotope ratio {sup 235}U/{sup 238}U is of natural origin, however in a few soil samples {sup 236}U has been detected. For the migration behavior, its distribution coefficient (K{sub d}) has been determined using laboratory batch method. Depleted uranium is used as tracer for uranium K{sub d} estimation. Chemical characterization of soil with respect to different parameters has been carried out. The effect of these soil parameters on distribution coefficient of uranium has been studied in order to explain the radionuclide mobility in this particular area. The distribution coefficient values for uranium are found to vary from 30-35679 L/Kg. A large variation in the distribution coefficient values shows the retention or mobility of uranium is highly dependent on soil characteristics in the particular area. This variation is explained with respect to pH, Fe, Mn

  3. Isotopic compositions of potassium and calcium in magnetic spherulesfrom marine sediments

    International Nuclear Information System (INIS)

    Shimarura, T.; Yanagita, S.; Yamakoshi, K.; Nogami, K.; Arai, O.; Tazawa, Y.; Kobayashi, K.

    1979-01-01

    Isotopic compositions of potassium and calcium in individual magnetic spherules were determined. No significant anomaly was observed for potassium within twice the statistical error (2sigma), although for calcium isotopes enrichment of 46 Ca, 44 Ca and 42 Ca were observed in one spherule. The relative excess of 46 Ca, 44 Ca and 42 Ca in the spherule agrees with the relative yield of spallogenic calcium isotopes observed in iron meteorites. This fact indicates that the enrichment in the calcium isotopes was caused by cosmic ray irradiation of the spherule in outer space. (Auth.)

  4. Comparison of solvent extraction and extraction chromatography resin techniques for uranium isotopic characterization in high-level radioactive waste and barrier materials.

    Science.gov (United States)

    Hurtado-Bermúdez, Santiago; Villa-Alfageme, María; Mas, José Luis; Alba, María Dolores

    2018-07-01

    The development of Deep Geological Repositories (DGP) to the storage of high-level radioactive waste (HLRW) is mainly focused in systems of multiple barriers based on the use of clays, and particularly bentonites, as natural and engineered barriers in nuclear waste isolation due to their remarkable properties. Due to the fact that uranium is the major component of HLRW, it is required to go in depth in the analysis of the chemistry of the reaction of this element within bentonites. The determination of uranium under the conditions of HLRW, including the analysis of silicate matrices before and after the uranium-bentonite reaction, was investigated. The performances of a state-of-the-art and widespread radiochemical method based on chromatographic UTEVA resins, and a well-known and traditional method based on solvent extraction with tri-n-butyl phosphate (TBP), for the analysis of uranium and thorium isotopes in solid matrices with high concentrations of uranium were analysed in detail. In the development of this comparison, both radiochemical approaches have an overall excellent performance in order to analyse uranium concentration in HLRW samples. However, due to the high uranium concentration in the samples, the chromatographic resin is not able to avoid completely the uranium contamination in the thorium fraction. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. Chromatographic separation process with pellicular ion exchange resins that can be used for ion or isotope separation and resins used in this process

    International Nuclear Information System (INIS)

    Carles, M.; Neige, R.; Niemann, C.; Michel, A.; Bert, M.; Bodrero, S.; Guyot, A.

    1989-01-01

    For separation of uranium, boron or nitrogen isotopes, an isotopic exchange is carried out betwen an isotope fixed on an ion exchange resin and another isotope of the same element in the liquid phase contacting the resin. Pellicular resins are used comprising composite particulates with an inert polymeric core and a surface layer with ion exchange groups [fr

  6. Validation of methods to measure uranium isotopes using magnetic sector mass spectrometry with inductively coupled plasma source

    International Nuclear Information System (INIS)

    Hernandez M, H.; Rios L, M. J.; Romero G, E. T.

    2017-10-01

    The mass spectrometry technique with inductively coupled plasma source (Icp-Ms) has been widely used to measure isotopic ratios of elements toxic to human health. Reason for which, in this work several measurement methods for the analysis of uranium isotopes in different matrices were implemented using magnetic sector mass spectrometry with inductively coupled plasma source (Icp-SFMS). Groundwater, sediment, soil and urine were the matrices analyzed, which were supplied by intercomparison tests conducted by the IAEA and Association for the Promotion of Quality Control of Medical Biology Analysis in Radio-toxicology. The procedures used in the treatment of soil, sediment and water samples were based on US EPA methods. In the case of the urine sample, the preparation was rapid (1:20 dilution). The average of the results obtained in yield of each matrix was 94, 71, 72 and 78% for water, urine, soil and sediment respectively. In addition, the precision in terms of standard relative deviation was less than 5% and the accuracy was less than 4%. In conclusion, the Icp-SFMS is a very sensitive technique for measuring isotopes of U in different matrices. However, careful tuning is necessary, especially in the mass regions of interest 234, 235 and 238 if an external quantification is considered using natural U solutions. (Author)

  7. Isotopic composition of Danube water in the pre-delta section from the years 2009 - 2012

    Directory of Open Access Journals (Sweden)

    RANK Dieter

    2013-12-01

    Full Text Available The isotopic composition of river water in the Danube Basin is mainly governed by the isotopic composition of precipitation in the catchment area, evaporation effects play only a minor role. Short-term and long-term isotope signals from precipitation are thus transmitted through the whole catchment. The isotopic composition of Danube water in the Delta region so provides an integrated isotope signal for climatic/hydrological conditions and changes in the whole catchment. The aim of this investigation was to establish a representative isotope monitoring near the Danube Delta. The results showed that the Danube River is regarding isotope content fully mixed at the bifurcation of the Danube Delta arms. Therefore routine sampling at only one location in the pre-delta region should be sufficient to obtain a representative isotope record for the whole Danube Basin. The δ 18 O time series from November 2009 to May 2012 (sampling twice a month shows seasonal variations in the range of -9.8 ‰ ± 0.7 ‰ with a minimum in spring and a maximum in autumn. The tritium results exhibit the influence of short term contaminations due to human activities. The expected “environmental” tritium content of river water in Central Europe would be about 10 TU. During this investigation 3 H values up to 100 TU were observed in the pre-delta section. This indicates short terms releases of tritium from local sources such as nuclear power plants in the Danube river system.

  8. Isotopic characterization of uranium in soils of the Ipanema National Forest (FLONA-Ipanema); Caracterizacao isotopica de uranio em solos da Floresta Nacional de Ipanema (FLONA-Ipanema)

    Energy Technology Data Exchange (ETDEWEB)

    Silva, F.B.; Marques, F.H., E-mail: fernandobaliani@yahoo.com.br, E-mail: fernando_henrique06@hotmail.com [Laboratorio de Pocos de Caldas (LAPOC/CNEN-MG), Pocos de Caldas, MG (Brazil); Enzweiler, J.; Ladeira, F.S.B., E-mail: Jacinta@ige.unicamp.br, E-mail: fsbladeira@ige.unicamp.br [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Instituto de Geociencias

    2015-07-01

    The National Forest of Ipanema (FLONA) is situated on a geological anomaly, known as 'Domo de Aracoiaba'. The soils of the area include Oxisols, Inceptsols and Alfisols. The amount of uranium and respective isotope activities in a soil depend on the parental rock and on the pedologic processes. The aim of this study was to investigate the activities for uranium isotopes ({sup 238}U, {sup 234}U, {sup 235}U) and the activity ratio (AR) {sup 234}U/ {sup 238}U or secular equilibrium for different soil types of the area collected at horizons A and B. The amount of uranium showed no significant differences for soils generated from alkaline intrusive rocks and sandstone, however, secular equilibrium was observed for Oxisol (RA = 1), while Inceptsol presented RA> 1 and the other soils, Alfisols, presented RA values <1. (author)

  9. Elemental and iron isotopic composition of aerosols collected in a parking structure

    International Nuclear Information System (INIS)

    Majestic, Brian J.; Anbar, Ariel D.; Herckes, Pierre

    2009-01-01

    The trace metal contents and iron isotope composition of size-resolved aerosols were determined in a parking structure in Tempe, AZ, USA. Particulate matter (PM) 2.5 μm were collected. Several air toxics (e.g., arsenic, cadmium, and antimony) were enriched above the crustal average, implicating automobiles as an important source. Extremely high levels of fine copper (up to 1000 ng m -3 ) were also observed in the parking garage, likely from brake wear. The iron isotope composition of the aerosols were found to be + 0.15 ± 0.03 per mille and + 0.18 ± 0.03 per mille for the PM 2.5 μm fractions, respectively. The similarity of isotope composition indicates a common source for each size fraction. To better understand the source of iron in the parking garage, the elemental composition in four brake pads (two semi-metallic and two ceramic), two tire tread samples, and two waste oil samples were determined. Striking differences in the metallic and ceramic brake pads were observed. The ceramic brake pads contained 10-20% copper by mass, while the metallic brake pads contained about 70% iron, with very little copper. Both waste oil samples contained significant amounts of calcium, phosphorous, and zinc, consistent with the composition of some engine oil additives. Differences in iron isotope composition were observed between the source materials; most notably between the tire tread (average = + 0.02 per mille ) and the ceramic brake linings (average = + 0.65 per mille ). Differences in isotopic composition were also observed between the metallic (average = + 0.18 per mille ) and ceramic brake pads, implying that iron isotope composition may be used to resolve these sources. The iron isotope composition of the metallic brake pads was found to be identical to the aerosols, implying that brake dust is the dominant source of iron in a parking garage.

  10. A paired apatite and calcite clumped isotope thermometry approach to estimating Cambro-Ordovician seawater temperatures and isotopic composition

    Science.gov (United States)

    Bergmann, Kristin D.; Finnegan, Seth; Creel, Roger; Eiler, John M.; Hughes, Nigel C.; Popov, Leonid E.; Fischer, Woodward W.

    2018-03-01

    The secular increase in δ18O values of both calcitic and phosphatic marine fossils through early Phanerozoic time suggests either that (1) early Paleozoic surface temperatures were high, in excess of 40 °C (tropical MAT), (2) the δ18O value of seawater has increased by 7-8‰ VSMOW through Paleozoic time, or (3) diagenesis has altered secular trends in early Paleozoic samples. Carbonate clumped isotope analysis, in combination with petrographic and elemental analysis, can deconvolve fluid composition from temperature effects and therefore determine which of these hypotheses best explain the secular δ18O increase. Clumped isotope measurements of a suite of calcitic and phosphatic marine fossils from late Cambrian- to Middle-late Ordovician-aged strata-the first paired fossil study of its kind-document tropical sea surface temperatures near modern temperatures (26-38 °C) and seawater oxygen isotope ratios similar to today's ratios.

  11. Variations in isotopic compositions of chlorine in evaporation-controlled salt lake brines of Qaidam Basin, China

    Digital Repository Service at National Institute of Oceanography (India)

    Xiao, Ying-kai; Liu, Wei-guo; Zhou, Y.M.; Wang, Yun-hui; Shirodkar, P.V.

    The variations in the isotopic compositions of chlorine in evaporation-controlled saline lake brines were determined by using an improved procedure for precise measurement of chlorine isotopes based on Cs sub(2) Cl sup(+) ion by thermal ionization...

  12. Uranium

    International Nuclear Information System (INIS)

    Battey, G.C.; McKay, A.D.

    1988-01-01

    Production for 1986 was 4899 t U 3 O 8 (4154 t U), 30% greater than in 1985, mainly because of a 39% increase in production at Ranger. Exports for 1986 were 4166 t U 3 O 8 at an average f.o.b. unit value of $40.57/lb U 3 O 8 . Private exploration expenditure for uranium in Australia during the 1985-86 fiscal year was $50.2 million. Plans were announced to increase the nominal capacity of the processing plant at Ranger from 3000 t/year U 3 O 8 to 4500 t and later to 6000 t/year. Construction and initial mine development at Olympic Dam began in March. Production is planned for mid 1988 at an annual rate of 2000 t U 3 O 8 , 30 000 t Cu, and 90 000 oz (2800 kg) Au. The first long-term sales agreement was concluded in September 1986. At the Manyingee deposit, testing of the alkaline solution mining method was completed, and the treatment plant was dismantled. Spot market prices (in US$/lb U 3 O 8 ) quoted by Nuexco were generally stable. From January-October the exchange value fluctuated from US$17.00-US$17.25; for November and December it was US$16.75. Australia's Reasonably Assured Resources of uranium recoverable at less than US$80/kg U at December 1986 were estimated as 462 000 t U, 3000 t U less than in 1985. This represents 30% of the total low-cost RAR in the WOCA (World Outside the Centrally Planned Economy Areas) countries. Australia also has 257 000 t U in the low-cost Estimated Additional Resources Category I, 29% of the WOCA countries' total resources in this category

  13. Spatial patterns of throughfall isotopic composition at the event and seasonal timescales

    Science.gov (United States)

    Allen, Scott T.; Keim, Richard F.; McDonnell, Jeffrey J.

    2015-03-01

    Spatial variability of throughfall isotopic composition in forests is indicative of complex processes occurring in the canopy and remains insufficiently understood to properly characterize precipitation inputs to the catchment water balance. Here we investigate variability of throughfall isotopic composition with the objectives: (1) to quantify the spatial variability in event-scale samples, (2) to determine if there are persistent controls over the variability and how these affect variability of seasonally accumulated throughfall, and (3) to analyze the distribution of measured throughfall isotopic composition associated with varying sampling regimes. We measured throughfall over two, three-month periods in western Oregon, USA under a Douglas-fir canopy. The mean spatial range of δ18O for each event was 1.6‰ and 1.2‰ through Fall 2009 (11 events) and Spring 2010 (7 events), respectively. However, the spatial pattern of isotopic composition was not temporally stable causing season-total throughfall to be less variable than event throughfall (1.0‰; range of cumulative δ18O for Fall 2009). Isotopic composition was not spatially autocorrelated and not explained by location relative to tree stems. Sampling error analysis for both field measurements and Monte-Carlo simulated datasets representing different sampling schemes revealed the standard deviation of differences from the true mean as high as 0.45‰ (δ18O) and 1.29‰ (d-excess). The magnitude of this isotopic variation suggests that small sample sizes are a source of substantial experimental error.

  14. Isotopic composition of carbon of natural gases in the sedimentary basins of Kamchatka and Chukotka

    Energy Technology Data Exchange (ETDEWEB)

    Lobkov, V.A.; Kudriavtseva, E.I.

    1981-01-01

    A study was carried out on the chemical and isotopic compositions of carbon of natural gases, which are prospective for oil and gas structures. An isotopic composition of the carbon of gases, covered by wells in possible oil and gas bearing basins (Eastern Kamchatka Central Kamchatka, Western Kamchatka, Anadyrsk, and Khatyrsk), created by terrigenic rock of the cretaceous, paleogenic, and neogenic ages, with dimensions of three to six kilometers, is presented. Investigation is made of the isotopic carbon of methane, ethane, and propane in 36 gas specimens. The plan of the distribution of the tested structures is shown, and an analysis is given of the chemical and isotopic composition of carbon of the prospected areas of Kamchatka and Chukotka and the interconnection of the isotopic composition of the carbon of methane with ethane and propane. A supposition is made concerning the existence of a single equilibrious volumetric system of CH/sub 4/--C/sub 2/H/sub 6/--C/sub 3/H/sub 8/--CO/sub 2/, in which ethane and propane are by-products, and owing to this, equilibrium establish according to this more slowly. The study of the isotopic composition of carbon of methane shows, that at various areas of depth formation of hydrocarbon gases is different. A conclusion is made that the gases formed at high temperatures. This points to a significant distance in the vertical migration of gases in the given region.

  15. Preparation, characterization and certification of uranium isotope reference materials; Preparacao, Caracterizacao e certificacao de materiais de referencia isotopicos de uranio

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira Junior, Olivio Pereira de

    2006-07-01

    This work describes the preparation, characterization and certification of a set of uranium isotope reference materials ranging from 0.5 to 20.0 % of {sup 235}U in mass. The most important concepts of metrology in chemical measurements were applied so that the certified quantities in these materials could be directly traceable to the International System of Units (SI). As a consequence of this approach, these materials can be used in the instruments calibration, estimation of measurement uncertainty, method validation, assessment of performance of analysts, quality control routines and interlaboratory comparison programmes. The most advanced methods and techniques in mass spectrometry, that is, gas source mass spectrometry (GSMS), thermal ionisation mass spectrometry (TIMS) and inductively coupled plasma mass spectrometry (ICPMS) were investigated to identify which are the dominant components in the uncertainty and to quantify its contribution to the final value of the measurement uncertainty of the isotopic ratio. The results obtained were then compared to verify which are the methods and techniques associated to the lowest measurement uncertainty values. The isotope amount ratio n({sup 235}U)/n({sup 238}U) was certified in the materials produced to expanded uncertainties ranging from 0.02 to 0.10 % and the ratios n({sup 234}U)/n({sup 238}U) and n({sup 236}U)/n({sup 238}U), to uncertainties ranging from 0.03 to 2.20 %. These values fully comply to the requirements of the isotopic characterization of nuclear fuel as well as the analysis of environmental samples for nuclear safeguards. (author)

  16. Stable isotopic composition of perchlorate and nitrate accumulated in plants: Hydroponic experiments and field data.

    Science.gov (United States)

    Estrada, Nubia Luz; Böhlke, J K; Sturchio, Neil C; Gu, Baohua; Harvey, Greg; Burkey, Kent O; Grantz, David A; McGrath, Margaret T; Anderson, Todd A; Rao, Balaji; Sevanthi, Ritesh; Hatzinger, Paul B; Jackson, W Andrew

    2017-10-01

    Natural perchlorate (ClO 4 - ) in soil and groundwater exhibits a wide range in stable isotopic compositions (δ 37 Cl, δ 18 O, and Δ 17 O), indicating that ClO 4 - may be formed through more than one pathway and/or undergoes post-depositional isotopic alteration. Plants are known to accumulate ClO 4 - , but little is known about their ability to alter its isotopic composition. We examined the potential for plants to alter the isotopic composition of ClO 4 - in hydroponic and field experiments conducted with snap beans (Phaseolus vulgaris L.). In hydroponic studies, anion ratios indicated that ClO 4 - was transported from solutions into plants similarly to NO 3 - but preferentially to Cl - (4-fold). The ClO 4 - isotopic compositions of initial ClO 4 - reagents, final growth solutions, and aqueous extracts from plant tissues were essentially indistinguishable, indicating no significant isotope effects during ClO 4 - uptake or accumulation. The ClO 4 - isotopic composition of field-grown snap beans was also consistent with that of ClO 4 - in varying proportions from irrigation water and precipitation. NO 3 - uptake had little or no effect on NO 3 - isotopic compositions in hydroponic solutions. However, a large fractionation effect with an apparent ε ( 15 N/ 18 O) ratio of 1.05 was observed between NO 3 - in hydroponic solutions and leaf extracts, consistent with partial NO 3 - reduction during assimilation within plant tissue. We also explored the feasibility of evaluating sources of ClO 4 - in commercial produce, as illustrated by spinach, for which the ClO 4 - isotopic composition was similar to that of indigenous natural ClO 4 - . Our results indicate that some types of plants can accumulate and (presumably) release ClO 4 - to soil and groundwater without altering its isotopic characteristics. Concentrations and isotopic compositions of ClO 4 - and NO 3 - in plants may be useful for determining sources of fertilizers and sources of ClO 4 - in their growth

  17. Uranium sorption to natural substrates-insights provided by isotope exchange, selective extraction and surface complexation modelling approaches

    International Nuclear Information System (INIS)

    Waite, T.D.; Payne T.E.; Davis, J.A.

    1993-01-01

    An extensive experimental program has been conducted over the last three years into the interaction of U(VI) with both single oxides and clays and complex natural substrates from the weathered zone in the vicinity of a uranium ore body in northern Australia. While iron oxides have frequently been considered to account for much of the uptake on such natural substrates, the results of laboratory open-quotes pH edgeclose quotes studies and of isotope exchange and selective extraction studies suggest that other phases must also play a significant role in controlling the partitioning of U(VI) between solid and solution phases. Supporting studies on kaolinite, the dominant clay in this system, provide insight into the most appropriate method of modelling the interaction of U(VI) with these natural substrates. The problems still remaining in adequately describing sorption of radionuclides and trace elements to complex natural substrates are discussed

  18. Iron Isotopic Compositions of Troilite (FeS) Inclusions from Iron Meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Cook, David L.; Schönbächler, Maria, E-mail: david.cook@erdw.ethz.ch [Institut für Geochemie und Petrologie, ETH Zürich, Clausiusstrasse 25, 8092 Zürich (Switzerland)

    2017-10-01

    We report non-mass-dependent Fe isotopic data for troilite (FeS) inclusions from 10 iron meteorites, representing both non-magmatic (IAB) and magmatic groups (IIAB, IIIAB, IVA). No resolvable variations are present in the most neutron-rich isotope ({sup 58}Fe), but small deficits (≈−0.1 ε ) in {sup 56}Fe were observed in several inclusions. With the exception of several Ca–Al-rich inclusions in primitive meteorites, these are the first reported non-mass-dependent variations in Fe isotopes for material formed in the early solar system. Nucleosynthetic variations in Ni isotopes were previously reported in these same samples. The effects in Fe isotopes are not correlated with those in Ni, which suggests that the origins of the isotopic variations are decoupled from one another. The {sup 56}Fe deficits may represent incomplete mixing of the precursor dust in the protoplanetary disk. Alternatively, a parent body process (e.g., irradiation by galactic cosmic rays) may have modified the Fe isotopic compositions of some inclusions, which initially had homogeneous Fe isotopic compositions.

  19. Normal variations in the isotopic composition of metabolically relevant transition metals in human blood

    Science.gov (United States)

    Van Heghe, L.; Cloquet, C.; Vanhaecke, F.

    2012-04-01

    Cu, Fe and Zn are transition metals with great catalytic, structural and regulating importance in the human body. Hence, an aberrant metabolism of these elements can have serious implications on the health of a person. It is assumed that, due to differences in isotope fractionation, the isotopic composition of these elements in whole blood of patients can be different from that in blood of healthy subjects. Therefore, isotopic analysis of the element affected by the disease can be a promising approach for early diagnosis. A method for isotopic analysis of Cu, Fe and Zn in human whole blood was developed. The simultaneous chromatographic isolation of these elements and the conditions for isotope ratio measurement via multi-collector ICP - mass spectrometry (MC-ICP-MS) were optimized. So far, only whole blood of supposedly healthy volunteers (reference population) was analyzed. Results for Fe confirmed the known differences in isotopic composition between male and female blood. It is also shown that other parameters can have influence as well, e.g., the isotopic composition of Zn seems to be governed by the diet.

  20. Constraining the redox landscape of the mid-Proterozoic oceans: new insights from the carbonate uranium isotope record

    Science.gov (United States)

    Gilleaudeau, G. J.; Kaufman, A. J.; Luo, G.; Romaniello, S. J.; Zhang, F.; Kah, L. C.; Azmy, K.; Bartley, J. K.; Sahoo, S. K.; Knoll, A. H.; Anbar, A. D.

    2017-12-01

    The redox landscape of the global oceans during the prolonged period between the Great Oxidation Event (GOE) and the Neoproterozoic Oxygenation Event (NOE) is a topic of considerable debate. Data from local redox proxies such as iron speciation suggest largely ferruginous conditions in the subsurface oceans (with the exception of one report of oxic subsurface waters) and a variable degree of euxinia in shallow shelf and epeiric sea environments. There is general consensus that anoxia was more widespread than in the modern ocean, but quantifying the degree of seafloor anoxia is challenging given that most redox proxies are inherently local and/or based on the relatively sparse black shale record. Here, we present new uranium (U) isotope data from carbonate rocks than span the mid-Proterozoic Eon. U-isotopes operate as a proxy for seafloor anoxia because the δ238U value of seawater is largely controlled by the size of the anoxic/euxinic U sink, which preferentially removes isotopically heavy 238U, leaving the oceans enriched in 235U. Our compilation of data from mid-Proterozoic successions reveals δ238U values similar to modern seawater (-0.39 ± 0.19 ‰ [1 s.d.] for the Gaoyuzhuang, Angmaat, El Mreiti, Vazante, and Turukhansk successions spanning 1.5 to 0.9 Ga). Given the potential for an isotopic offset between carbonate minerals and seawater of up to 0.3 ‰, we suggest that mid-Proterozoic seawater had a δ238U value generally between -0.4 and -0.7 ‰, which is lower than modern seawater, but higher than has been inferred for intervals of expanded anoxia elsewhere in Earth history. These results are consistent with recently published U-isotope data from the 1.36 Ga Velkerri Formation, and suggest that large portions of the seafloor may have been covered by at least weakly oxygenated waters during the mid-Proterozoic Eon. Uncertainty remains, however, because the isotopic effects of the non-euxinic anoxic sink are poorly constrained. Nonetheless, our data

  1. The stable Cr isotopic compositions of chondrites and silicate planetary reservoirs

    Science.gov (United States)

    Schoenberg, Ronny; Merdian, Alexandra; Holmden, Chris; Kleinhanns, Ilka C.; Haßler, Kathrin; Wille, Martin; Reitter, Elmar

    2016-06-01

    The depletion of chromium in Earth's mantle (∼2700 ppm) in comparison to chondrites (∼4400 ppm) indicates significant incorporation of chromium into the core during our planet's metal-silicate differentiation, assuming that there was no significant escape of the moderately volatile element chromium during the accretionary phase of Earth. Stable Cr isotope compositions - expressed as the ‰-difference in 53Cr/52Cr from the terrestrial reference material SRM979 (δ53/52CrSRM979 values) - of planetary silicate reservoirs might thus yield information about the conditions of planetary metal segregation processes when compared to chondrites. The stable Cr isotopic compositions of 7 carbonaceous chondrites, 11 ordinary chondrites, 5 HED achondrites and 2 martian meteorites determined by a double spike MC-ICP-MS method are within uncertainties indistinguishable from each other and from the previously determined δ53/52CrSRM979 value of -0.124 ± 0.101‰ for the igneous silicate Earth. Extensive quality tests support the accuracy of the stable Cr isotope determinations of various meteorites and terrestrial silicates reported here. The uniformity in stable Cr isotope compositions of samples from planetary silicate mantles and undifferentiated meteorites indicates that metal-silicate differentiation of Earth, Mars and the HED parent body did not cause measurable stable Cr isotope fractionation between these two reservoirs. Our results also imply that the accretionary disc, at least in the inner solar system, was homogeneous in its stable Cr isotopic composition and that potential volatility loss of chromium during accretion of the terrestrial planets was not accompanied by measurable stable isotopic fractionation. Small but reproducible variations in δ53/52CrSRM979 values of terrestrial magmatic rocks point to natural stable Cr isotope variations within Earth's silicate reservoirs. Further and more detailed studies are required to investigate whether silicate

  2. The Supply of Medical Radioisotopes. Market impacts of converting to low-enriched uranium targets for medical isotope production

    International Nuclear Information System (INIS)

    Westmacott, Chad; Cameron, Ron

    2012-01-01

    The reliable supply of molybdenum-99 ( 99 Mo) and its decay product, technetium-99m ( 99m Tc), is a vital component of modern medical diagnostic practices. At present, most of the global production of 99 Mo is from highly enriched uranium (HEU) targets. However, all major 99 Mo-producing countries have recently agreed to convert to using low-enriched uranium (LEU) targets to advance important non-proliferation goals, a decision that will have implications for the global supply chain of 99 Mo/ 99m Tc and the long-term supply reliability of these medical isotopes. This study provides the findings and analysis from an extensive examination of the 99 Mo/ 99m Tc supply chain by the OECD/NEA High-level Group on the Security of Supply of Medical Radioisotopes (HLG-MR). It presents a comprehensive evaluation of the potential impacts of converting to the use of LEU targets for 99 Mo production on the global 99 Mo/ 99m Tc market in terms of costs and available production capacity, and the corresponding implications for long-term supply reliability. In this context, the study also briefly discusses the need for policy action by governments in their efforts to ensure a stable and secure long-term supply of 99 Mo/ 99m Tc

  3. Anomalous behaviour of uranium isotopes in backwater sediments of Zuari river

    Digital Repository Service at National Institute of Oceanography (India)

    Joshi, L.U; Zingde, M.D.; Abidi, S

    The surface leaching of the labile component of uranium has been carried out in estuarine sediments of Zuari River in Goa, India The measurements of alpha activities of sup(238) U, sup(235) U and sup(234) U in the leachates indicated a remarkable...

  4. Measurement of natural carbon isotopic composition of acetone in human urine.

    Science.gov (United States)

    Yamada, Keita; Ohishi, Kazuki; Gilbert, Alexis; Akasaka, Mai; Yoshida, Naohiro; Yoshimura, Ryoko

    2016-02-01

    The natural carbon isotopic composition of acetone in urine was measured in healthy subjects using gas chromatography-combustion-isotope ratio mass spectrometry combined with headspace solid-phase microextraction (HS-SPME-GC-C-IRMS). Before applying the technique to a urine sample, we optimized the measurement conditions of HS-SPME-GC-C-IRMS using aqueous solutions of commercial acetone reagents. The optimization enabled us to determine the carbon isotopic compositions within ±0.2 ‰ of precision and ±0.3‰ of error using 0.05 or 0.2 mL of aqueous solutions with acetone concentrations of 0.3-121 mg/L. For several days, we monitored the carbon isotopic compositions and concentrations of acetone in urine from three subjects who lived a daily life with no restrictions. We also monitored one subject for 3 days including a fasting period of 24 h. These results suggest that changes in the availability of glucose in the liver are reflected in changes in the carbon isotopic compositions of urine acetone. Results demonstrate that carbon isotopic measurement of metabolites in human biological samples at natural abundance levels has great potential as a tool for detecting metabolic changes caused by changes in physiological states and disease.

  5. Bio sorption process for uranium (VI) by using algae-yeast-silica gel composite adsorbent

    International Nuclear Information System (INIS)

    Turkozu, D. A.; Aytas, S.

    2006-01-01

    Many yeast, algae, bacteria and various aquatic flora are known to be capable of concentrating metal species from dilute aqueous solution. Many researcher have found that non-living biomaterials can be used to accumulate metal ions from environment. In recent studies, mainly two process are used in biosorption experiments. These are the use of free cells and the use of immobilized cells on a solid support. A variety of inert supports have been used to immobilize biomaterials either by adsorption or physical entrapment. This uptake is often considerable and frequently selective, and occurs via a variety of mechanisms including active transport, ion exchange or complexation, and adsorption or inorganic precipitation. Biosorbent may be used as an ion exchange material. Adsorption occurs through interaction of the metal ions with functional groups that are found in the cell wall biopolymers of either living or dead organisms. In this study, the algae-yeast-silica gel composite adsorbent was tested for its ability to recover U(VI) from diluted aqueous solutions. Macro marine algae (Jania rubens.), yeast (Saccharomyces cerevisiae) and silica gel were used to prepare composite adsorbent. The ability of the composite biosorbent to adsorb uranium (VI) from aqueous solution has been studied at different optimized conditions of pH, concentration of U(VI), temperature, contact time and matrix ion effect was also investigated. The adsorption patterns of uranium on the composite biosorbent were investigated by the Langmuir, Freundlich and Dubinin-Radushkhevic isotherms. The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated. The results suggested that the macro algae-yeast-silica gel composite sorbent is suitable as a new biosorbent material for removal of uranium ions from aqueous solutions

  6. Natural variations in calcium isotope composition as a monitor of bone mineral balance in humans.

    Science.gov (United States)

    Skulan, J.; Anbar, A.; Thomas, B.; Smith, S.

    2004-12-01

    The skeleton is the largest reservoir of calcium in the human body and is responsible for the short term control of blood levels of this element. Accurate measurement of changes in bone calcium balance is critical to understanding how calcium metabolism responds to physiological and environmental changes and, more specifically, to diagnosing and evaluating the effectiveness of treatments for osteoporosis and other serious calcium-related disorders. It is very difficult to measure bone calcium balance using current techniques, however, because these techniques rely either on separate estimates of bone resorption and formation that are not quantitatively comparable, or on complex and expensive studies of calcium kinetics using administered isotopic tracers. This difficulty is even more apparent and more severe for measurements of short-term changes in bone calcium balance that do not produce detectable changes in bone mineral density. Calcium isotopes may provide a novel means of addressing this problem. The foundation of this isotope application is the ca. 1.3 per mil fractionation of calcium during bone formation, favoring light calcium in the bone. This fractionation results in a steady-state isotopic offset between calcium in bone and calcium in soft tissues, blood and urine. Perturbations to this steady state due to changes in the net formation or resorption of bone should be reflected in changes in the isotopic composition of soft tissues and fluids. Here we present evidence that easily detectable shifts in the natural calcium isotope composition of human urine rapidly reflect changes in bone calcium balance. Urine from subjects in a 17-week bed rest study was analyzed for calcium isotopic composition. Bed rest promotes net resorption of bone, shifting calcium from bone to soft tissues, blood and urine. The calcium isotope composition of patients in this study shifted toward lighter values during bed rest, consistent with net resorption of isotopically

  7. Chromium isotope composition of reducing and anoxic sediments from the Peru Margin and Cariaco Basin

    Science.gov (United States)

    Gueguen, B.; Planavsky, N.; Wang, X.; Algeo, T. J.; Peterson, L. C.; Reinhard, C. T.

    2014-12-01

    Chromium isotope systematics in marine sediments are now being used as a new redox proxy of the modern and ancient Earth's surface. Chromium is primarily delivered to the oceans by riverine inputs through weathering of Cr(III)-rich minerals present in the continental crust and oxidation of insoluble Cr(III) to soluble Cr(VI) species. Since oxidation-reduction reactions fractionate Cr isotopes whereby oxidized Cr(VI) species are preferentially enriched in heavy Cr isotopes, the Cr isotope composition of marine sediments may be useful tracers of redox conditions at the Earth's surface through geological time. Chromium is quantitatively removed in organic-rich sediments where reducing conditions prevail and promote reduction of Cr(VI) to Cr(III), and thus, these sediments should capture the ambient seawater Cr isotope composition. However, the isotopic composition of modern organic-rich sediments is poorly documented so far, and this step is essential for further modeling the global oceanic Cr isotope mass balance and assessing the effects of sedimentation and post-depositional processes on the marine Cr isotopes archive. In this study, we have characterized modern marine organic-rich sediments for their Cr isotope composition (δ53/52Cr) from two different settings, the Peru margin upwelling zone and the anoxic Cariaco Basin (Venezuela). Chromium isotopes were measured on a MC-ICP-MS (Nu Plasma) using a double-spike correction method. The authigenic fraction of shallow samples from the Peru margin sedimentary sequence with a high Total Organic Carbon (TOC) content (>10 wt%) yield an average δ53/52Crauthigenic value of +0.67 ±0.05 ‰ (2sd). However, although this value is close to the seawater value (Atlantic Ocean) and to Cariaco basin sediments (~ +0.6 ‰), reducing sediments from the Peru margin are on average isotopically slightly heavier, especially in samples having a low authigenic fraction and a low TOC content (δ53/52Crauthigenic values up to +1.30

  8. Recovery of uranium from seawater by composite fiber adsorbent

    Intern