An attempt to explain the uranium 238 resonance integral discrepancy

International Nuclear Information System (INIS)

Tellier, H.; Grandotto, M.

1978-01-01

Studies on uranium 238 resonance integral discrepancy were carried out for light water reactor physics. It was shown that using recently published resonance parameters and substituting a multilevel formalism to the usual Breit and Wigner formula reduced the well known discrepancy between two values of the uranium 238 effective resonance integral: the value calculated with the nuclear data and the one deduced from critical experiments. Since the cross section computed with these assumptions agrees quite well with the Oak-Ridge transmission data, it was used to obtain the self-shielding effect and the capture rate in light water lattices. The multiplication factor calculated with this method is found very close to the experimental value. Preliminary results for a set of benchmarks relative to several types of thermal neutron reactors lead to very low discrepancies. The reactivity loss is only 130 x 10 -5 instead of 650 x 10 -5 in the case of the usual libraries and the single level formula

An attempt to explain the uranium 238 effective capture integral discrepancy

International Nuclear Information System (INIS)

Tellier, Henry; Grandotto-Biettoli, Marc; Vanuxeem, Jacqueline

1979-02-01

Up to now, there was a discrepancy between the computed value and the measured value of the uranium 238 effective capture integral. The former has been always greater than the latter. For this reason, the reactor physicists have used an adjustment of the computed value. Nowadays the accuracy of the cross sections knowledge is increased and the reactors computation codes are almost exact. Such an adjustment is no more justified. Recently several new measurements of the resonance parameters were carried out and the use of a multilevel formalism was suggested to compute the uranium 238 cross sections. It is shown in this work that the simultaneous use of recent parameters and Reich and Moore formalism explain the discrepancy. For the thermal neutron reactors, two thirds of this discrepancy are explained by the neutron data and the last third by the multilevel formalism [fr

National low-level waste management program radionuclide report series, Volume 15: Uranium-238

International Nuclear Information System (INIS)

Adams, J.P.

1995-09-01

This report, Volume 15 of the National Low-Level Waste Management Program Radionuclide Report Series, discusses the radiological and chemical characteristics of uranium-238 ( 238 U). The purpose of the National Low-Level Waste Management Program Radionuclide Report Series is to provide information to state representatives and developers of low-level radioactive waste disposal facilities about the radiological, chemical, and physical characteristics of selected radionuclides and their behavior in the waste disposal facility environment. This report also includes discussions about waste types and forms in which 238 U can be found, and 238 U behavior in the environment and in the human body

Measurements of 234U, 238U and 230Th in excreta of uranium-mill crushermen

International Nuclear Information System (INIS)

Fisher, D.R.; Jackson, P.O.; Brodacynski, G.G.; Scherpelz, R.I.

1982-07-01

Uranium and thorium levels in excreta of uranium mill crushermen who are routinely exposed to airborne uranium ore dust were measured. The purpose was to determine whether 230 Th was preferentially retained over either 234 U or 238 U in the body. Urine and fecal samples were obtained from fourteen active crushermen with long histories of exposure to uranium ore dust, plus four retired crushermen and three control individuals for comparison. Radiochemical procedures were used to separate out the uranium and thorium fractions, which were then electroplated on stainless steel discs and assayed by alpha spectrometry. Significantly greater activity levels of 234 U and 238 U were measured in both urine and fecal samples obtained from uranium mill crushermen, indicating that uranium in the inhaled ore dust was cleared from the body with a shorter biological half-time than the daughter product 230 Th. The measurements also indicated that uranium and thorium separate in vivo and have distinctly different metabolic pathways and transfer rates in the body. The appropriateness of current ICRP retention and clearance parameters for 230 Th in ore dust is questioned

Simple and selective method for determination of microgram quantities of uranium-238 in urine

International Nuclear Information System (INIS)

Pavlovskaya, N.A.; Martakova, P.I.

1977-01-01

A technique has been developed and described to determine microgram quantities of uranium-238 in urea. The subject of the technique is as follows: urea (50-500 ml) is acidified with hydrochloric acid, and uranium(6) is quantitatively isolated by its coprecipitation with methylviolet rhodanide; the precipitate is separated by centrifuging and mineralized in the presence of nitric and chloric acids; then uranium (6) is reduced into uranium(4) and its amount is determined photoelectrocolorimetrically using the ''arsenazo 3'' reagent. The limiting amount of uranium in a sample being determined is 10 -6 . For a sample volume of 500 ml sensitivity of the technique of uranium determination is 2x10 -9 g/ml. Titanium, thorium and niobium do not interfere with determination of uranium

238U, and its decay products, in grasses from an abandoned uranium mine

Science.gov (United States)

Childs, Edgar; Maskall, John; Millward, Geoffrey

2016-04-01

Bioaccumulation of radioactive contaminants by plants is of concern particularly where the sward is an essential part of the diet of ruminants. The abandoned South Terras uranium mine, south west England, had primary deposits of uraninite (UO2) and pitchblende (U3O8), which contained up to 30% uranium. When the mine was active uranium and radium were extracted but following closure it was abandoned without remediation. Waste rock and gangue, consisting of inefficiently processed minerals, were spread around the site, including a field where ruminants are grazed. Here we report the activity concentrations of 238U, 235U 214,210Pb, and the concentrations of selected metals in the soils, roots and leaves of grasses taken from the contaminated field. Soil samples were collected at the surface, and at 30 cm depth, using an auger along a 10-point transect in the field from the foot of a waste heap. Whole, individual grass plants were removed with a spade, ensuring that their roots were intact. The soils and roots and grass leaves were freeze-dried. Activity concentrations of the radionuclides were determined by gamma spectroscopy, following 30 days incubation for development of secular equilibrium. Dried soils, roots and grasses were also digested in aqua regia and the concentrations of elements determined by ICP techniques. Maximum activity concentrations of 238U, 235U, 214Pb and 210Pb surface soils were 63,300, 4,510, 23,300 and 49,400 Bq kg-1, respectively. The mean 238U:235U ratio was 11.8 ± 1.8, an order of magnitude lower than the natural value of 138, indicating disequilibrium within the decay chain due to mineral processing. Radionuclides in the roots had 5 times lower concentration and only grass leaves in the vicinity of the waste heap had measureable values. The mean soil to root transfer factor for 238U was 36%, the mean root to leaf was 3% and overall only 0.7% of 238U was transferred from the soil to the leaves. The roots contained 0.8% iron, possibly as

Application of the grey system theory for forecasting the content of 238U in soil near a uranium mine exhaust outlet

International Nuclear Information System (INIS)

Ye Yongjun; Ding Dexin; Li Xiangyang; Zhou Xinghuo; Liu Dong

2008-01-01

In order to forecast the content of 238 U in soil near a uranium mine exhaust outlet, a general GM(1,1) forecasting model was established based on grey system theory, analyzing association degree and residual error distinction. According to the measuring datum of the content of 238 U in soil near a uranium mine exhaust outlet from 2001 to 2006, used the model to forecast the content of 238 U in soil, The results show that the forecasting value agrees with the measuring results and the forecasting precision is higher; at the same time the content of 238 U in soil in 2007 is also forecasted based on the model, the relative error was 4.8%; which shows the GM(1,1) forecasting model has higher practical value, and is a effective method for forecasting the content of 238 U in soil near a uranium mine exhaust outlet. (authors)

Cross Sections for the Production of Residual Nuclides by Proton-Induced Reactions with Uranium at Medium Energies

International Nuclear Information System (INIS)

Issa, S.A.M.; Michel, R.; Uosif, M.A.M.; Issa, S.A.M.; Flamentc, J.L.; David, J.C.; Leray, S.

2009-01-01

The production of residual nuclides by proton-induced reactions on uranium is investigated using activated targets from irradiation experiments at Saturne II synchrocyclotron at the Laboratory National Saturne/Saclay. These investigations contribute to the European research project NUDATRA within the IP EUROTRANS in which the feasibility of accelerator-driven transmutation of nuclear waste is evaluated. Experimental cross sections are derived from gamma-spectrometric measurements. A total of 1894 cross-section was deter-mined covering 44 residual nuclides in the energy range from 211 MeV to 2530 MeV. The experimental data together with those of earlier work of our group are discussed in the context of theoretical excitation functions calculated by the newly developed INCL4 + ABLA and the TALYS codes

Recoil properties of antimony isotopes produced by the reaction of 570 MeV and 18.2 GeV protons with uranium

CERN Document Server

Hagebø, E

1969-01-01

Using the method of thick target and thick catchers, the ranges and other recoil properties of 13 (12) antimony isotopes between A = 115 and A = 131 (130) have been measured for the reaction of 570 MeV (18·2 GeV) protons with uranium. The kinetic energies T are almost independent of product mass number at 570 MeV but show a strong dependence at 18·2 GeV, the lightest isotopes having only about half the kinetic energy of the heavy ones. \\\\ \\\\The cascade deposition energies for production of antimony isotopes are almost equal at 570 MeV and 18·2 GeV and fit well to straight lines of the form E$^{∗}$ (A, Z) = E$^{∗}$ (A$_{0}$, Z) + b(A − A$_{0}$). Exceptions are the cascade deposition energies for $^{115}$Sb and $^{116}$Sb which seem to be somewhat too high at 18·2 GeV. By comparison with other work it seems that the slope $b$ of these lines is independent of product element, target and of proton irradiation energy above 450 MeV. \\\\ \\\\If we assume at 570 MeV, that the fissioning nucleus is a uranium ...

Bioaccumulation of uranium 234U and 238U in marine birds

International Nuclear Information System (INIS)

Borylo, A.; Skwarzec, B.

2010-01-01

In the paper was presented results of our study about uranium 234 U and 238 U radioactivity in the marine birds samples, collected in the Polish area of the southern Baltic Sea. We chose 11 species of sea birds: three species permanently residing at southern Baltic, four species of wintering birds and three species of migrating birds. The obtained results indicated that uranium is very irregularly distributed in organs and tissues of marine birds. The highest uranium content is characterized in liver, rest of viscera and feathers, the smallest in skin and muscles. The uranium concentration was higher for carnivorous species (long-tailed duck (C. hyemalis), common eider (S. mollissima), lower for species eating fish (great cormorant (P. carbo), common guillemot (U. aalge), red-throated diver (G. stellata) and razorbill (A. tarda)), but the biggest amounts for herbivorous species [tufted duck (A. fuligula) and eurasian coot (F. atra)]. About 63-67% of uranium, which was located in feathers of two species of marine birds: razorbill (A. tarda) and long-tailed duck (C. hymealis), was apparently adsorbed, which suggests that uranium adsorption on the feathers may be an important transfer from air to water. (author)

Determination of uranium in plutonium--238 metal and oxide by differential pulse polarography

International Nuclear Information System (INIS)

Fawcett, N.C.

1976-01-01

A differential pulse polarographic method was developed for the determination of total uranium in 238 Pu metal and oxides. A supporting electrolyte of 0.5 M ascorbic acid in 0.15 N H 2 SO 4 was found satisfactory for the determination of 500 ppM or more of uranium in 10 mg or less of plutonium. A relative standard deviation of 0.27 to 4.3 percent was obtained in the analysis of samples ranging in uranium content from 0.65 to 2.79 percent. The limit of detection was 0.18 μg ml -1 . Peak current was a linear function of uranium concentration up to at least 100 μg ml -1 . Amounts of neptunium equal to the uranium content were tolerated. The possible interference of a number of other cations and anions were investigated

TRIMOLECULAR REACTIONS OF URANIUM HEXAFLUORIDE WITH WATER

Energy Technology Data Exchange (ETDEWEB)

Westbrook, M.; Becnel, J.; Garrison, S.

2010-02-25

The hydrolysis reaction of uranium hexafluoride (UF{sub 6}) is a key step in the synthesis of uranium dioxide (UO{sub 2}) powder for nuclear fuels. Mechanisms for the hydrolysis reactions are studied here with density functional theory and the Stuttgart small-core scalar relativistic pseudopotential and associated basis set for uranium. The reaction of a single UF{sub 6} molecule with a water molecule in the gas phase has been previously predicted to proceed over a relatively sizeable barrier of 78.2 kJ {center_dot} mol{sup -1}, indicating this reaction is only feasible at elevated temperatures. Given the observed formation of a second morphology for the UO{sub 2} product coupled with the observations of rapid, spontaneous hydrolysis at ambient conditions, an alternate reaction pathway must exist. In the present work, two trimolecular hydrolysis mechanisms are studied with density functional theory: (1) the reaction between two UF{sub 6} molecules and one water molecule, and (2) the reaction of two water molecules with a single UF{sub 6} molecule. The predicted reaction of two UF{sub 6} molecules with one water molecule displays an interesting 'fluorine-shuttle' mechanism, a significant energy barrier of 69.0 kJ {center_dot} mol{sup -1} to the formation of UF{sub 5}OH, and an enthalpy of reaction ({Delta}H{sub 298}) of +17.9 kJ {center_dot} mol{sup -1}. The reaction of a single UF{sub 6} molecule with two water molecules displays a 'proton-shuttle' mechanism, and is more favorable, having a slightly lower computed energy barrier of 58.9 kJ {center_dot} mol{sup -1} and an exothermic enthalpy of reaction ({Delta}H{sub 298}) of -13.9 kJ {center_dot} mol{sup -1}. The exothermic nature of the overall UF{sub 6} + 2 {center_dot} H{sub 2}O trimolecular reaction and the lowering of the barrier height with respect to the bimolecular reaction are encouraging; however, the sizable energy barrier indicates further study of the UF{sub 6} hydrolysis reaction

Assessment of uranium exposure from total activity and 234U:238U activity ratios in urine

International Nuclear Information System (INIS)

Nicholas, T.; Bingham, D.

2011-01-01

Radiation workers at Atomic Weapons Establishment (AWE) are monitored for uranium exposure by routine bioassay sampling (primarily urine sampling). However, the interpretation of uranium in urine and faecal results in terms of occupational intakes is difficult because of the presence of uranium due to intakes from environmental (dietary) sources. For uranium in urine data obtained using current analytical techniques at AWE, the mean, median and standard deviation of excreted uranium concentrations were 0.006, 0.002 and 0.012 μg per g creatinine, respectively. These values are consistent with what might be expected from local dietary intakes and the knowledge that occupational exposures at AWE are likely to be very low. However, some samples do exceed derived investigation levels (DILs), which have been set up taking account of the likely contribution from environmental sources. We investigate how the activity and isotopic composition of uranium in the diet affects the sensitivity of uranium in urine monitoring for occupational exposures. We conclude that DILs based on both total uranium in urine activity and also 234 U: 238 U ratios are useful given the likely variation in dietary contribution for AWE workers. Assuming a background excretion rate and that the enrichment of the likely exposure is known, it is possible to assess exposures using 234 U: 238 U ratios and/or total uranium activity. The health implications of internalised uranium, enriched to 235 U, centre on its nephrotoxicity; the DILs for bioassay samples at AWE are an order of magnitude below the conservative recommendations made by the literature. (authors)

Fission cross sections of {sup 235,238}U and {sup 209}Bi at incident proton energies above 70 MeV

Energy Technology Data Exchange (ETDEWEB)

Obukhov, A I; Rimskij-Korsakov, A A; Eismont, V P [V.G. Khlopin Radium Inst., St. Petersburg (Russian Federation)

1997-06-01

The proton fission cross-section data of {sup 235,238}U and Bi were measured in the V.G. Khlopin Radium Institute over a wide proton energy range. The experimental and calculated data were also compared with experimental neutron values. The proton cross-section of {sup 235,238}U increased up to 60-70 MeV and then decreased. The bismuth proton fission cross-section increased in line with the rise in proton energy up to 1 GeV. (author). 21 refs, 6 figs.

Uranium concentrations and 234U/238U activity ratios in fault-associated groundwater as possible earthquake precursors

International Nuclear Information System (INIS)

Finkel, R.C.

1981-01-01

In order to assess the utility of uranium isotopes as fluid phase earthquake precursors, uranium concentrations and 234 U/ 238 U activity ratios have been monitored on a monthly or bimonthly basis in water from 24 wells and springs associated with Southern California fault zones. Uranium concentrations vary from 0.002 ppb at Indian Canyon Springs on the San Jacinto fault to 8.3 ppb at Lake Hughes well on the San Andreas fault in the Palmdale area. 234 U/ 238 U activity ratios vary from 0.88 at Agua Caliente Springs on the Elsinore fault to 5.4 at Niland Slab well on the San Andreas fault in the Imperial Valley. There was one large earthquake in the study area during 1979, the 15 October 1979 M = 6.6 Imperial Valley earthquake. Correlated with this event, uranium concentrations varied by a factor of more than 60 and activity ratios by a factor of 3 at the Niland Slab site, about 70 km from the epicenter. At the other sites monitored, uranium concentrations varied in time, but with no apparent pattern, while uranium activity ratios remained essentially constant throughout the monitoring period

Recovery and purification of uranium-234 from aged plutonium-238

International Nuclear Information System (INIS)

Keister, P.L.; Figgins, P.W.; Watrous, R.M.

1978-01-01

The current production methods used to recover and purify uranium-234 from aged plutonium-238 at Mound Laboratory are presented. The three chemical separation steps are described in detail. In the initial separation step, the bulk of the plutonium is precipitated as the oxalate. Successively lower levels of plutonium are achieved by anion exchange in nitrate media and by anion exchange in chloride media. The procedures used to characterize and analyze the final U 3 O 8 are given

Concentration of uranium-235 in mixtures with uranium-238 using ion exchange resins

International Nuclear Information System (INIS)

Seko, M.; Kakihana, H.

1976-01-01

A method is described of simultaneously obtaining separate enriched fractions of 235 U and 238 U from isotopic mixtures thereof with the use of an ion exchange column by passing a liquid body containing the isotopic mixture through the column. The uranium as it is passed through the column is presented as a U(IV) coordination compound with a ligand at different valent states and is followed by an eluant and forms a band which travels through the column, the front and rear portions of which are respectively enriched in one of the isotopes and depleted in the other. 16 claims

Evaluation of neutron-induced reactions in 48Ti and 238U

International Nuclear Information System (INIS)

Carlson, B.V.; Fiorentino, J.; Frederico, T.; Isidro Filho, M.P.; Mastroleo, R.C.; Rego, R.A.

1984-05-01

Preliminary results of the evaluation of neutron-induced reactions in 48 Ti and 238 U are presented. Calculated cross sections for the reactions (n,γ), (n,n'), (n, 2n) and (n,p) as well as for (n,f) in 238 U are given. Comparisons with available experimental data are made and possible changes in the parameters are discussed. (Author) [pt

Uranium contents and {sup 235}U/{sup 238}U atom ratios in soil and earthworms in western Kosovo after the 1999 war

Energy Technology Data Exchange (ETDEWEB)

Di Lella, L.A.; Nannoni, F.; Protano, G.; Riccobono, F. [Dipartimento di Scienze Ambientali ' G. Sarfatti' -Sezione di Geochimica Ambientale, University of Siena, Via del Laterino 8, I-53100, Siena (Italy)

2005-01-20

The uranium content and {sup 235}U/{sup 238}U atom ratio were determined in soils and earthworms of an area of Kosovo (Djakovica garrison), heavily shelled with depleted uranium (DU) ammunition during the 1999 war. The aim of the study was to reconstruct the small-scale distribution of uranium and assess the influence of the DU added to the surface environment. The total uranium concentration and the {sup 235}U/{sup 238}U ratio of topsoils showed great variability and were inversely correlated. The highest uranium levels (up to 31.47 mg kg{sup -1}) and lowest {sup 235}U/{sup 238}U ratios (minimum 0.002147) were measured in topsoils collected inside, or very close to, the clusters of DU penetrator holes. Regarding the fractionation of uranium in the surface soils, the uranium concentrations in the soluble and exchangeable fractions increased as the total uranium concentration of the topsoils increased. High and rather uniform percentage contents of uranium (24-36%) were associated with the poorly crystalline iron oxide phases of soils. In the U-enriched soils the elevated levels of the element were probably due to the presence of very small, unevenly distributed oxidized DU particles. The total uranium concentration in earthworms was in the range 0.142-0.656 mg kg{sup -1}, with the highest concentrations in Lumbricus terrestris. The juveniles of all three studied species seemed to accumulate uranium more than adults, probably due to age-related differences in metabolism. The {sup 235}U/{sup 238}U ratio in the earthworms was variable (0.005241-0.007266) and independent of both the total uranium contents in soils and the absolute uranium levels in the animals. Bioconcentration was greater at lower U concentrations in soil, probably due to an increasing rate of elimination of uranium by the earthworms as the soil contents of the element increase. The results of this study clearly indicate that DU was added to the soil of the study area. Nevertheless, the phenomenon was

Concentration of uranium-235 in mixtures with uranium-238 using ion exchange resins

International Nuclear Information System (INIS)

Seko, M.; Kakihana, H.

1976-01-01

A method is described for simultaneously obtaining separate enriched fractions of 235 U and 238 U from isotopic mixtures of these with the use of an ion exchange column by passing a liquid body containing the isotopic mixture through the column. The uranium as it is passed through the column is present as a U(IV) coordination compound with a ligand at different valent states and is followed by an eluant and forms a band which travels through the column, the front and rear portions of which are respectively enriched in one of the isotopes and depleted in the other. 16 claims, no drawings

Certification of a uranium-238 dioxide reference material for neutron dosimetry (EC nuclear reference material 501)

International Nuclear Information System (INIS)

Pauwels, J.; Lievens, F.; Ingelbrecht, C.

1989-01-01

Uranium-238 oxide of 99.999% isotopic and 99.98% chemical purity was transformed into dioxide spheres of nominal 0.5 and 1.0 mm diameter by gel precipitation and subsequent calcination under carbon dioxide and under argon containing 5% hydrogen at 1 125 K. The spheres were analysed by thermal ionization mass spectrometry, including isotope dilution, by gravimetry and by potentiometric titration. On the basis of these analyses, the uranium mass fraction was certified at 879.4 ± 2.8 g.kg -1 , and the 235 U/U - and 238 U/U abundances at 10.4 ± 0.5 mg.kg -1 and 999.9896 ± 0.0005 g.kg -1 , respectively. The material is intended to be used as a reference material in neutron metrology

Determination of the isotopic ratio {sup 234} U/{sup 238} U and {sup 235} U/{sup 238} U in uranium commercial reagents by alpha spectroscopy; Determinacion de la relacion isotopica {sup 234} U/{sup 238} U y {sup 235} U/{sup 238} U en reactivos comerciales de uranio por espectrometria alfa

Energy Technology Data Exchange (ETDEWEB)

Iturbe G, J L

1990-02-15

In this work the determination of the isotope ratio {sup 234} U/{sup 238} U and {sup 235} U/{sup 238} U obtained by means of the alpha spectroscopy technique in uranium reagents of commercial marks is presented. The analyzed uranium reagents were: UO{sub 2} (*) nuclear purity, UO{sub 3} (*) poly-science, metallic uranium, uranyl nitrate and uranyl acetate Merck, uranyl acetate and uranyl nitrate Baker, uranyl nitrate (*) of the Refinement and Conversion Department of the ININ, uranyl acetate (*) Medi-Lab Sigma of Mexico and uranyl nitrate Em Science. The obtained results show that the reagents that are suitable with asterisk (*) are in radioactive balance among the one {sup 234} U/{sup 238} U, since the obtained value went near to the unit. In the case of the isotope ratio {sup 235} U/{sup 238} U the near value was also obtained the one that marks the literature that is to say 0.04347, what indicates that these reagents contain the isotope of {sup 235} U in the percentage found in the nature of 0.71%. The other reagents are in radioactive imbalance among the {sup 234} U/{sup 238} U, the found values fluctuated between 0.4187 and 0.1677, and for the quotient of activities {sup 235} U/{sup 238} U its were of 0.0226, and the lowest of 0.01084. Also in these reagents it was at the {sup 236} U as impurity. The isotope of {sup 236} U is an isotope produced artificially, for what is supposed that the reagents that are in radioactive imbalance were synthesized starting from irradiated fuel. (Author)

Monte carlo simulations of Yttrium reaction rates in Quinta uranium target

Science.gov (United States)

Suchopár, M.; Wagner, V.; Svoboda, O.; Vrzalová, J.; Chudoba, P.; Tichý, P.; Kugler, A.; Adam, J.; Závorka, L.; Baldin, A.; Furman, W.; Kadykov, M.; Khushvaktov, J.; Solnyshkin, A.; Tsoupko-Sitnikov, V.; Tyutyunnikov, S.; Bielewicz, M.; Kilim, S.; Strugalska-Gola, E.; Szuta, M.

2017-03-01

The international collaboration Energy and Transmutation of Radioactive Waste (E&T RAW) performed intensive studies of several simple accelerator-driven system (ADS) setups consisting of lead, uranium and graphite which were irradiated by relativistic proton and deuteron beams in the past years at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The most recent setup called Quinta, consisting of natural uranium target-blanket and lead shielding, was irradiated by deuteron beams in the energy range between 1 and 8 GeV in three accelerator runs at JINR Nuclotron in 2011 and 2012 with yttrium samples among others inserted inside the setup to measure the neutron flux in various places. Suitable activation detectors serve as one of possible tools for monitoring of proton and deuteron beams and for measurements of neutron field distribution in ADS studies. Yttrium is one of such suitable materials for monitoring of high energy neutrons. Various threshold reactions can be observed in yttrium samples. The yields of isotopes produced in the samples were determined using the activation method. Monte Carlo simulations of the reaction rates leading to production of different isotopes were performed in the MCNPX transport code and compared with the experimental results obtained from the yttrium samples.

Monte carlo simulations of Yttrium reaction rates in Quinta uranium target

Directory of Open Access Journals (Sweden)

Suchopár M.

2017-01-01

Full Text Available The international collaboration Energy and Transmutation of Radioactive Waste (E&T RAW performed intensive studies of several simple accelerator-driven system (ADS setups consisting of lead, uranium and graphite which were irradiated by relativistic proton and deuteron beams in the past years at the Joint Institute for Nuclear Research (JINR in Dubna, Russia. The most recent setup called Quinta, consisting of natural uranium target-blanket and lead shielding, was irradiated by deuteron beams in the energy range between 1 and 8 GeV in three accelerator runs at JINR Nuclotron in 2011 and 2012 with yttrium samples among others inserted inside the setup to measure the neutron flux in various places. Suitable activation detectors serve as one of possible tools for monitoring of proton and deuteron beams and for measurements of neutron field distribution in ADS studies. Yttrium is one of such suitable materials for monitoring of high energy neutrons. Various threshold reactions can be observed in yttrium samples. The yields of isotopes produced in the samples were determined using the activation method. Monte Carlo simulations of the reaction rates leading to production of different isotopes were performed in the MCNPX transport code and compared with the experimental results obtained from the yttrium samples.

Bioaccumulation of polonium ({sup 210}Po) and uranium ({sup 234}U, {sup 238}U) in plants around phosphogypsum waste heap in Wislinka (northern Poland)

Energy Technology Data Exchange (ETDEWEB)

Borylo, A.; Skwarzec, B. [Gdansk Univ. (Poland). Faculty of Chemistry

2011-07-01

In the study the activities of polonium {sup 210}Po and uranium {sup 234}U, {sup 238}U in plants, collected near phosphogypsum waste heap in Wis'linka (northern Poland), were determined by using the alpha spectrometry. The obtained results revealed that the concentrations of {sup 210}Po, {sup 234}U, and {sup 238}U in the analyzed plants were differentiated. In the analyzed flora organisms the highest amounts of polonium and uranium were found in ruderal plant samples as well as willow samples (Salix viminalis) from protection zone of phosphogypsum waste heap. The concentrations of {sup 210}Po, {sup 234}U and {sup 238}U in the analyzed plants were higher in roots than in green parts of plants. The higher concentrations of {sup 210}Po and {sup 238}U radionuclides were estimated for hydrophyte (common sedge Carex nigra Reichard), the favourite habitat of which is particularly wet meadow and for plants collected in the vicinity of phosphogypsum waste heap. The major source of polonium and uranium in analyzed plants is root system. The values of {sup 234}U/ {sup 238}U activity ratio in all analyzed plants are closed to one, what indicated that source of uranium in analyzed plants is phosphogypsum. The highest uranium and polonium concentrations were characterized for plants, which are covered with tomentose. The comparability polonium and uranium contents were confirmed in edible plants, but higher accumulation was determined in ripe species than immature species of vegetables. The higher polonium and uranium concentrations were noticed in green parts of plant, the lower in roots. Polonium concentration in cultivated plants samples was not species diverse. Therefore, the significant source of polonium and uranium in analyzed plants is wet and dry atmospheric falls gathering the soil and air dust from phosphogypsum waste dump. The maximum {sup 210}Po and {sup 238}U radionuclides concentrations were found in green parts of red beet (Beta vulgaris esculenta), the

Disintegration constant of uranium-238 by spontaneous fission redetermined by glass track method

International Nuclear Information System (INIS)

Lima Medeiros, E. de.

1978-01-01

The disintegration constant of U 238 by spontaneous fission using glass as fission fragment detector was redetermined. A film of natural uranium (UO 3 ) prepared by chemical methods on the glass lamina was used in a long time experience of exposure (about 16 years). The good conditions of sample preparation and storage allow to observe, after chemical etching, fission fragment tracks. (M.C.K.) [pt

Distribution of uranium-238 in environmental samples from a residential area impacted by mining and milling activities

International Nuclear Information System (INIS)

McConnell, M.A.; Ramanujam, V.M.S.; Alcock, N.W.; Gabehart, G.J.; Au, W.W.

1998-01-01

The northern region of Karnes County, Texas, USA, has been the site of extensive mining/milling of uranium for over 30 years. A previous study in their laboratory indicates that residents living near these facilities have increased chromosomal aberrations and a reduced DNA repair capacity. In this study, the long-lived radionuclides uranium-238 ( 238 U) and thorium-232 ( 232 Th) were measured in order to evaluate the extent of contamination from mining/milling facilities. 232 Th was quantified simultaneously and served as a reference. Soil samples were collected from the yards of previously studied households and adjacent areas near former mining and mining/milling sites at the surface and 30 cm subsurface. Additionally, samples from drinking water wells were collected from selected households. Sites located over 14 km from the study area with no known history of mining/milling served as the control. In the control area, 238 U concentrations in soil were consistent between surface (0.13--0.26 mg/kg) and subsurface samples. Near mining/milling sites, 238 U in surface soil was found to be consistently and statistically higher than corresponding subsurface samples. Near mining-only areas, 238 U in surface soil, however, was not significantly increased over subsurface soil. As expected, 238 U was much higher overall in the mining/milling and mining-only areas compared to the control sites. No trends were detected in the distribution of 232 Th. The concentration of 238 U was up to six times higher in a drinking water well near a former mining/milling operation, indicating possible leaching into the groundwater, while 232 Th concentrations were low and uniform. Furthermore, lead isotope ratio analysis indicates contamination from the interstate shipping of ore by rail to and from a mining/milling facility. These data indicate contamination of the environment by the mining/milling activities in a residential area

The Oklo natural nuclear reactors: neutron parameters, age and duration of the reactions, uranium and fission products migrations

International Nuclear Information System (INIS)

Ruffenach, J.-C.

1979-09-01

Mass spectrometry and isotopic dilution technique are used in order to carry out, on various samples from the fossil nuclear reactors at Oklo, Gabon, isotopic and chemical analyses of some particular elements involved in the nuclear reactions: uranium, lead, bismuth, thorium, rare gases (krypton, xenon), rare earths (neodymium, samarium, europium, gadolinium, dysprosium), ruthenium and palladium. Interpretations of these analyses lead to the determination of many neutron parameters such as the neutron fluence received by the samples, the spectrum index, the conversion coefficient, and also the percentages of fissions due to uranium-238 and plutonium-239 and the total number of fissions relative to uranium. All these results make it possible to determine the age of the nuclear reactions by measuring the amounts of fission rare earths formed, i.e. 1.97 billion years. This study brings some informations to the general problem of radioactive wastes storage in deep geological formations, the storage of uranium, plutonium and many fission products having been carried out naturally, and for about two billion years [fr

Inclusive quasifree electrofission cross section for 238U

International Nuclear Information System (INIS)

Likhachev, V.P.; Carvalho, W.R. Jr.; Deppman, A.; Hussein, M.S.; Macedo, L.F.R.; Mesa, J.; Vaudeluci, M.S.; Arruda-Neto, J.D.T.; Evseev, I.G.; Pashchuk, S.A.; Schelin, H.R.; Garcia, F.; Rodriguez, O.; Margaryan, A.; Nesterenko, V.O.

2003-01-01

We present results from a joint theoretical and experimental study of inclusive quasifree electrofission of 238 U. The off-shell cross sections for the quasifree reaction stage have been calculated within the plane wave impulse approximation with distortion corrections included in the effective momentum approximation. Proton and neutron single-particle momentum distributions were calculated in the macroscopic-microscopic approach. The fissility for proton and neutron single hole excited states of the residual nuclei 237 Pa and 237,238 U was calculated within the compound nucleus model. Final state interaction corrections to residual nucleus excitation energy were calculated using the imaginary part of the optical potential. The total inclusive electrofission cross section was measured with high absolute precision, and all principal partial contributions are analyzed, in particular, the quasifree one

232Th/238U in a uranium mobility estimate in an agricultural area in the municipality of Pedra-Pernambuco - Brazil

International Nuclear Information System (INIS)

Santos Junior, Jose Araujo dos; Amaral, Romilton dos Santos; Bezerra, Jairo Dias; Damascena, Kennedy Francys Rodrigues; Oliveira, Jose Valdez Monterazo de; Bispo, Rodrigo Cesar Bezerra; Silva, Cleomacio Miguel da; Rocha, Edilson Accioly

2011-01-01

The mobility of the radionuclides in soil depends primarily on the physic-chemical parameters. The uranium is easily oxidized in aqueous environment, which allows its characterization with higher mobility. The Thorium is practically insoluble, mainly if the environment has organic matter and sulfates. The geochemical characteristics of the rocks, associated with the weather and metamorphism produce alterations in the concentration diagrams of the natural radionuclides in different types of soil. The ratio 232 Th/ 238 U has been used as an indicator of oxidizing and reducing conditions. Th/U less than 2 suggests that the uranium is in its concentrated form abundantly when compared to the thorium. In reducing conditions, the value Th/U higher than 7 indicates a removal of the uranium. In this work it was possible to analyze the agricultural soil in the municipality of Pedra, Pernambuco, Brazil where there are uranium anomaly and thorium in rocky outcrops. Sixty-two samples of the horizon C soil were collected, in an area of 2 km 2 , where the main uranium occurrences are located. The analyses were done by High-Resolution Gamma-Spectroscopy. In the analyses the secular equilibrium was assumed and the 238 U and the 232 Th specific activities were used to estimate the oxidizing and reducing conditions defining the uranium mobility in the soil. The obtained findings show that the ratio Th/U varied from 0.3 to 13.4, with average of 4.6. The biggest 238 U fraction was fix (80.3%), with low mobility; the smallest fraction concentrated (6.6%) and a lixiviated intermediate fraction (13.1%). (author)

Study of reactions between uranium-plutonium mixed oxide and uranium nitride and between uranium oxide and uranium nitride; Etude des reactions entre l`oxyde mixte d`uranium-plutonium et le nitrure d`uranium et entre l`oxyde d`uranium et le nitrure d`uranium

Energy Technology Data Exchange (ETDEWEB)

Lecraz, C

1993-06-11

A new type of combustible elements which is a mixture of uranium nitride and uranium-plutonium oxide could be used for Quick Neutrons Reactors. Three different studies have been made on the one hand on the reactions between uranium nitride (UN) and uranium-plutonium mixed oxide (U,Pu)O{sub 2}, on the other hand on these between UN and uranium oxide UO{sub 2}. They show a sizeable reaction between nitride and oxide for the studied temperatures range (1573 K to 1973 K). This reaction forms a oxynitride compound, MO{sub x} N{sub y} with M=U or M=(U,Pu), whose crystalline structure is similar to oxide`s. Solubility of nitride in both oxides is studied, as the reaction kinetics. (TEC). 32 refs., 48 figs., 22 tabs.

Study of some modern carbonated marine organisms, using U234/U238 activities and its uranium concentration

International Nuclear Information System (INIS)

Pregnolatto, Y.

1975-01-01

Several types of alive carbonated organisms of marine fluvial or mixed environment origin were analized in its concentrations of Uranium and about its activity ratio U 234 /U 238 . In the same way measurements were made from the water of these three types of environments. The results indicate that the mollusks shells show a very low concentration compared with corals. Its concentration varies from 0.04 to 0.33 ppm. Inside the limit of errors we can say that the several types of carbonated organisms show the same disequilibrium U 234 /U 238 which was found in associated waters. An analysis of a piece of wood from long time immersed in the sea water was made. The result indicates that there was a marked high in concentration of Uranium due to chelatation with organic matter. (C.D.G.) [pt

Using 238U/235U ratios to understand the formation and oxidation of reduced uranium solids in naturally reduced zones

Science.gov (United States)

Jemison, N.; Johnson, T. M.; Druhan, J. L.; Davis, J. A.

2016-12-01

Uranium occurs in groundwater primarily as soluble and mobile U(VI), which can be reduced to immobile U(IV), often observed in sediments as uraninite. Numerous U(VI)-contaminated sites, such as the DOE field site in Rifle, CO, contain naturally reduced zones (NRZ's) that have relatively high concentrations of organic matter. Reduction of heavy metals occurs within NRZ's, producing elevated concentrations of iron sulfides and U(IV). Slow, natural oxidation of U(IV) from NRZ's may prolong U(VI) contamination of groundwater. The reduction of U(VI) produces U(IV) with a higher 238U/235U ratio. Samples from two NRZ sediment cores recovered from the Rifle site revealed that the outer fringes of the NRZ contain U(IV) with a high 238U/235U ratio, while lower values are observed in the center . We suggest that as aqueous U(VI) was reduced in the NRZ, it was driven to lower 238U/235U values, such that U(IV) formed in the core of the NRZ reflects a lower 238U/235U. Two oxidation experiments were conducted by injecting groundwater containing between 14.9 and 21.2 mg/L dissolved O2 as an oxidant into the NRZ. The oxidation of U(IV) from this NRZ increased aqueous U(VI) concentrations and caused a shift to higher 238U/235U in groundwater as U(IV) was oxidized primarily on the outer fringes of the NRZ. In total these observations suggest that the stability of solid phase uranium is governed by coupled reaction and transport processes. To better understand various reactive transport scenarios we developed a model for the formation and oxidation of NRZ's utilizing the reactive transport software CrunchTope. These simulations suggest that the development of isotopically heterogeneous U(IV) within NRZ's is largely controlled by permeability of the NRZ and the U(VI) reduction rate. Oxidation of U(IV) from the NRZ's is constrained by the oxidation rate of U(IV) as well as iron sulfides, which can prevent oxidation of U(IV) by scavenging dissolved oxygen.

Studying Angular Distribution of Neutron for (p,n) Reaction from 0.5 GeV to 1.5 GeV on some Heavy Targets 238U, 206Pb, 197Au, 186W

International Nuclear Information System (INIS)

Nguyen Mong Giao; Tran Thanh Dung; Nguyen Thi Ai Thu; Huynh Thi Xuan Tham

2010-08-01

The angular distributions of neutron are calculated for a spallation reaction induced by proton energy from 0.5 GeV to 1.5 GeV on target nuclei 206 Pb, 197 Au, 238 U, 186 W. In this report, we use nuclear data of JENDL-HE with evaluated proton induced cross-sections up to 3 GeV. The obtained results have been discussed in detail. (author)

A dispersive optical model potential for nucleon induced reactions on 238U and 232Th nuclei with full coupling

Directory of Open Access Journals (Sweden)

Chiba Satoshi

2013-03-01

Full Text Available A dispersive coupled-channel optical model potential (DCCOMP that couples the ground-state rotational and low-lying vibrational bands of 238U and 232Th nuclei is studied. The derived DCCOMP couples almost all excited levels below 1 MeV of excitation energy of the corresponding even-even actinides. The ground state, octupole, beta, gamma, and non-axial bands are coupled. The first two isobar analogue states (IAS populated in the quasi-elastic (p,n reaction are also coupled in the proton induced calculation, making the potential approximately Lane consistent. The coupled-channel potential is based on a soft-rotor description of the target nucleus structure, where dynamic vibrations are considered as perturbations of the rigid rotor underlying structure. Matrix elements required to use the proposed structure model in Tamura coupled-channel scheme are derived. Calculated ratio R(U238/Th232 of the total cross-section difference to the averaged σT for 238U and 232Th nuclei is shown to be in excellent agreement with measured data.

Reaction of uranium and the fluorocarbon FC-75

Science.gov (United States)

Young, R. H.

1985-04-01

Because of criticality concerns with water cooling in enriched uranium upgrading, a fluorocarbon has been evaluated as a replacement coolant for internal module components in the Plasma Separation Process (PSP). The interaction of bulk uranium and of powdered uranium with FC-75 has been investigated at temperatures between 200 and 700 C. The gas pressure and the metal temperature were monitored as a function of time. Modest temperature changes of 50 to 100 C were observed for the bulk uranium/fluorocarbon reaction. Much larger changes (up to 1000 C) were noted for the reaction involving high surface area uranium powder. These temperature transients, particularly for the powdered uranium reaction, were short-lived ( 10 seconds) and indicative of the formation of a protective layer of reaction products. Analysis of residual gas products by infrared spectroscopy indicated that one potentially serious hazard, UF6, was not present; however, several small toxic fluorocarbons were produced by thermolysis and/or reaction. X-ray diffraction analysis of the residual solids indicated UF4 and UO2 were the major solid products.

800-MeV proton irradiation of thorium and depleted uranium targets

Energy Technology Data Exchange (ETDEWEB)

Russell, G.J.; Brun, T.O.; Pitcher, E.J. [Los Alamos National Laboratory, NM (United States)] [and others

1995-10-01

As part of the Los Alamos Fertile-to-Fissile-Conversion (FERFICON) program in the late 1980`s, thick targets of the fertile materials thorium and depleted uranium were bombarded by 800-MeV protons to produce the fissile materials {sup 233}U and {sup 239}Pu, respectively. The amount of {sup 233}U made was determined by measuring the {sup 233}Pa activity, and the yield of {sup 239}Pu was deduced by measuring the activity of {sup 239}Np. For the thorium target, 4 spallation products and 34 fission products were also measured. For the depleted uranium target, 3 spallation products and 16 fission products were also measured. The number of fissions in each target was deduced from fission product mass-yield curves. In actuality, axial distributions of the products were measured, and the distributions were then integrated over the target volume to obtain the total number of products for each reaction.

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

Uranium ((234)U, (235)U and (238)U) contamination of the environment surrounding phosphogypsum waste heap in Wiślinka (northern Poland).

Science.gov (United States)

Olszewski, Grzegorz; Boryło, Alicja; Skwarzec, Bogdan

2015-08-01

The aim of this work was to determine the uranium concentration ((234)U, (235)U and (238)U) and values of the activity ratio (234)U/(238)U in soil samples collected near phosphogypsum waste heap in Wiślinka (northern Poland). On the basis of the studies it was found that the values of the (234)U/(238)U activity ratio in the analyzed soils collected in the vicinity of phosphogypsum dump in Wiślinka are in most cases close to one and indicate the phosphogypsum origin of the analyzed nuclides. The obtained results of uranium concentrations are however much lower than in previous years before closing of the phosphogypsum stockpile. After this process and covering the phosphogypsum stockpile in Wiślinka with sewage sludge, phosphogypsum particles are successfully immobilized. In the light of the results the use of phosphate fertilizers seems to be a major problem. Prolonged and heavy rains can cause leaching accumulated uranium isotopes in the phosphogypsum stockpile, which will be washed into the Martwa Wisła and on the fields in the immediate vicinity of this storage. Copyright © 2015 Elsevier Ltd. All rights reserved.

IAEA CIELO Evaluation of Neutron-induced Reactions on 235U and 238U Targets

Science.gov (United States)

Capote, R.; Trkov, A.; Sin, M.; Pigni, M. T.; Pronyaev, V. G.; Balibrea, J.; Bernard, D.; Cano-Ott, D.; Danon, Y.; Daskalakis, A.; Goričanec, T.; Herman, M. W.; Kiedrowski, B.; Kopecky, S.; Mendoza, E.; Neudecker, D.; Leal, L.; Noguere, G.; Schillebeeckx, P.; Sirakov, I.; Soukhovitskii, E. S.; Stetcu, I.; Talou, P.

2018-02-01

Evaluations of nuclear reaction data for the major uranium isotopes 238U and 235U were performed within the scope of the CIELO Project on the initiative of the OECD/NEA Data Bank under Working Party on Evaluation Co-operation (WPEC) Subgroup 40 coordinated by the IAEA Nuclear Data Section. Both the mean values and covariances are evaluated from 10-5 eV up to 30 MeV. The resonance parameters of 238U and 235U were re-evaluated with the addition of newly available data to the existing experimental database. The evaluations in the fast neutron range are based on nuclear model calculations with the code EMPIRE-3.2 Malta above the resonance range up to 30 MeV. 235U(n,f), 238U(n,f), and 238U(n,γ) cross sections and 235U(nth,f) prompt fission neutron spectrum (PFNS) were evaluated within the Neutron Standards project and are representative of the experimental state-of-the-art measurements. The Standards cross sections were matched in model calculations as closely as possible to guarantee a good predictive power for cross sections of competing neutron scattering channels. 235U(n,γ) cross section includes fluctuations observed in recent experiments. 235U(n,f) PFNS for incident neutron energies from 500 keV to 20 MeV were measured at Los Alamos Chi-Nu facility and re-evaluated using all available experimental data. While respecting the measured differential data, several compensating errors in previous evaluations were identified and removed so that the performance in integral benchmarks was restored or improved. Covariance matrices for 235U and 238U cross sections, angular distributions, spectra and neutron multiplicities were evaluated using the GANDR system that combines experimental data with model uncertainties. Unrecognized systematic uncertainties were considered in the uncertainty quantification for fission and capture cross sections above the thermal range, and for neutron multiplicities. Evaluated files were extensively benchmarked to ensure good performance in

238U series isotopes and 232Th in carbonates and black shales from the Lesser Himalaya: implications to dissolved uranium abundances in Ganga-Indus source waters

International Nuclear Information System (INIS)

Singh, S.K.; Dalai, Tarun K.; Krishnaswami, S.

2003-01-01

238 U and 232 Th concentrations and the extent of 238 U- 234 U- 230 Th radioactive equilibrium have been measured in a suite of Precambrian carbonates and black shales from the Lesser Himalaya. These measurements were made to determine their abundances in these deposits, their contributions to dissolved uranium budget of the headwaters of the Ganga and the Indus in the Himalaya and to assess the impact of weathering on 238 U- 234 U- 230 Th radioactive equilibrium in them. 238 U concentrations in Precambrian carbonates range from 0.06 to 2.07 μg g -1 . The 'mean' U/Ca in these carbonates is 2.9 ng U mg -1 Ca. This ratio, coupled with the assumption that all Ca in the Ganga-Indus headwaters is of carbonate origin and that U and Ca behave conservatively in rivers after their release from carbonates, provides an upper limit on the U contribution from these carbonates, to be a few percent of dissolved uranium in rivers. There are, however, a few streams with low uranium concentrations, for which the carbonate contribution could be much higher. These results suggest that Precambrian carbonates make only minor contributions to the uranium budget of the Ganga-Indus headwaters in the Himalaya on a basin wide scale, however, they could be important for particular streams. Similar estimates of silicate contribution to uranium budget of these rivers using U/Na in silicates and Na* (Na corrected for cyclic and halite contributions) in river waters show that silicates can contribute significantly (∼40% on average) to their U balance. If, however, much of the uranium in these silicates is associated with weathering resistant minerals, then the estimated silicate uranium component would be upper limits. Uranium concentration in black shales averages about 37 μg g -1 . Based on this concentration, supply of U from at least ∼50 mg of black shales per liter of river water is needed to balance the average river water U concentration, 1.7 μg L -1 in the Ganga-Indus headwaters

Concentrations and biological availability of 238U and 230Th in the environs of a uranium milling operation

International Nuclear Information System (INIS)

Ibrahim, S.; Flot, S.; Whicker, F.W.

1982-01-01

This paper reports on a study whose objectives were to determine 238 U and 230 Th concentrations in soil and native plants from various sites around a conventional acid leach uranium milling operation in the Western US, and to estimate plant/soil concentration factors. Soil and vegetation samples were collected from exposed, weathered tailings; near the edge of a tailings pond; from a reclamation area; and at several native range background (control) locations. The results indicate that mean plant/soil concentration factors varied significantly among sites and between radionuclides, but no significant differences between plant groups were found. Concentration factors for 230 Th were greater than for 238 U for plants growing at the edge of the tailings pond. It is speculated that the lower concentration factors for uranium relative to thorium at this site may be due to the proportion of their contents in soil that is biologically available for plant uptake

Cross-section activation measurement for U-238 through protons and deuterons in energy interval 10-14 MeV

Energy Technology Data Exchange (ETDEWEB)

Guzhovskii, B.Y.; Abramovich, S.N.; Zvenigorodskii, A.G. [Russia Federal Nuclear Centre, Arzamas (Russian Federation)] [and others

1995-10-01

There were presented results of cross-section measurements for nuclear reactions {sup 238}U(p,n){sup 238}Np, {sup 238}U(d,2n){sup 238}Np, {sup 238}U(d,t){sup 237}U, {sup 238}U(d,p){sup 239}U, and {sup 238}U(d,n){sup 239}Np. Interval of projectile energy was 10-14 MeV. For measurements of cross-sections it was used the activatio methods. The registration of {beta}- and {gamma}-activity was made with using of plastic scintillation detector and Ge(Li)-detector.

Uranium ({sup 238}U)-induced ROS and cell cycle perturbations, antioxidant responses and erythrocyte nuclear abnormalities in the freshwater iridescent shark fish Pangasius sutchi

Energy Technology Data Exchange (ETDEWEB)

Annamalai, Sathesh Kumar; Arunachalam, Kantha Deivi, E-mail: kanthad.arunachalam@gmail.com

2017-05-15

Highlights: • Exposure to {sup 238}U deteriorated the antioxidant defenses like SOD, CAT and LPO. • Flow cytometric analysis revealed the increase in G2/M phase and S phase. • Micronucleus frequencies increased with Increased {sup 238}U exposure and time. • Exposure to waterborne {sup 238}U induces both chemical and radiotoxicity in P. sutchi. • ROS-mediated {sup 238}U toxic mechanism and the antioxidant responses has been proposed. - Abstract: The strategic plan of this study is to analyze any possible radiological impact on aquatic organisms from forthcoming uranium mining facilities around the Nagarjuna Sagar Dam in the future. The predominantly consumed and dominant fish species Pangasius sutchi, which is available year-round at Nagarjuna Sagar Dam, was selected for the study. To comprehend the outcome and to understand the mode of action of {sup 238}U, the fish species Pangasius sutchi was exposed to ¼ and ½ of the LC{sub 50} doses of waterborne {sup 238}U in a static system in duplicate for 21 days. Blood and organs, including the gills, liver, brain and muscles, were collected at different time periods—0 h, 24 h, 48 h, 72 h, 96 h, 7, days 14 days and 21 days—using ICP-MS to determine the toxic effects of uranium and the accumulation of {sup 238}U concentrations. The bioaccumulation of {sup 238}U in P. sutchi tissues was dependent on exposure time and concentration. The accumulation of uranium was, in order of magnitude, measured as gills > liver > brain > tissue, with the highest accumulation in the gills. It was observed that exposure to {sup 238}U significantly reduced antioxidant enzymes such as superoxide dismutase, catalase, and lipid peroxidase. The analysis of DNA fragmentation by comet assay and cell viability by flow cytometry was performed at different time intervals. DNA histograms by flow cytometry analysis revealed an increase in the G2/M phase and the S phase. The long-term {sup 238}U exposure studies in fish showed increasing

238U content in soils of Byelorussia

International Nuclear Information System (INIS)

Shagalova, Eh.D.

1986-01-01

Results of detection in Byelorussian soils of a heavy natural radionuclide 238 U and its content in humus horizons of the soils on map-schemes are presented. 238 U content is determined by complete decomposition of soils by acids, isolation from thorium using EhDEh-10 P anionite and subsequent solution colorimetry. It is shown that the content of uranium-238 in soils decreases from the North to the South. Its maximum amount (>2x10 -4 %) is detected in turfy-podsolic soils in lake-glacier loams; the minimum one ( -4 %)- in peatymarshy soils. The map-scheme of 238 U content is a background base. Using the background base it is possible to trace the change in uranium content in soils under conditions of technogenic effect and to substantiate the efficiency of environment protection measures

Reaction between uranium hexafluoride and trimethylsilylhalides

Energy Technology Data Exchange (ETDEWEB)

Brown, D; Berry, J A [UKAEA Atomic Energy Research Establishment, Harwell. Chemistry Div.; Holloway, J H; Staunton, G M [Leicester Univ. (UK). Dept. of Chemistry

1938-07-01

Reactions involving 1.1:1 molar ratios of uranium hexafluoride to either trimethylsilylchloride or trimethylsilylbromide in halocarbon solutions yield ..beta..-UF/sub 5/ at room temperature. With 2 mol equivalents of trimethylsilylchloride the product is UF/sub 4/. The reactions appear to proceed via the intermediate formation of unstable brown uranium(VI) chloride and bromide fluorides. Calculations show that UClF/sub 5/ and UCl/sub 2/F/sub 4/ are thermodynamically unstable with respect to the loss of chlorine at room temperature.

A study on possible use of Urtica dioica (common nettle) plants as uranium (234U, 238U) contamination bioindicator near phosphogypsum stockpile.

Science.gov (United States)

Olszewski, Grzegorz; Boryło, Alicja; Skwarzec, Bogdan

The aim of this study was to determine uranium concentrations in common nettle ( Urtica dioica ) plants and corresponding soils samples which were collected from the area of phosphogypsum stockpile in Wiślinka (northern Poland). The uranium concentrations in roots depended on its concentrations in soils. Calculated BCF and TF values showed that soils characteristics and air deposition affect uranium absorption and that different uranium species have different affinities to U . dioica plants. The values of 234 U/ 238 U activity ratio indicate natural origin of these radioisotopes in analyzed plants. Uranium concentration in plants roots is negatively weakly correlated with distance from phosphogypsum stockpile.

A study on possible use of Urtica dioica (common nettle) plants as uranium (234U, 238U) contamination bioindicator near phosphogypsum stockpile

International Nuclear Information System (INIS)

Olszewski, Grzegorz; Borylo, Alicja; Skwarzec, Bogdan

2016-01-01

The aim of this study was to determine uranium concentrations in common nettle (Urtica dioica) plants and corresponding soils samples which were collected from the area of phosphogypsum stockpile in Wislinka (northern Poland). The uranium concentrations in roots depended on its concentrations in soils. Calculated BCF and TF values showed that soils characteristics and air deposition affect uranium absorption and that different uranium species have different affinities to U. dioica plants. The values of 234 U/ 238 U activity ratio indicate natural origin of these radioisotopes in analyzed plants. Uranium concentration in plants roots is negatively weakly correlated with distance from phosphogypsum stockpile. (author)

Uranium ("2"3"8U)-induced ROS and cell cycle perturbations, antioxidant responses and erythrocyte nuclear abnormalities in the freshwater iridescent shark fish Pangasius sutchi

International Nuclear Information System (INIS)

Annamalai, Sathesh Kumar; Arunachalam, Kantha Deivi

2017-01-01

Highlights: • Exposure to "2"3"8U deteriorated the antioxidant defenses like SOD, CAT and LPO. • Flow cytometric analysis revealed the increase in G2/M phase and S phase. • Micronucleus frequencies increased with Increased "2"3"8U exposure and time. • Exposure to waterborne "2"3"8U induces both chemical and radiotoxicity in P. sutchi. • ROS-mediated "2"3"8U toxic mechanism and the antioxidant responses has been proposed. - Abstract: The strategic plan of this study is to analyze any possible radiological impact on aquatic organisms from forthcoming uranium mining facilities around the Nagarjuna Sagar Dam in the future. The predominantly consumed and dominant fish species Pangasius sutchi, which is available year-round at Nagarjuna Sagar Dam, was selected for the study. To comprehend the outcome and to understand the mode of action of "2"3"8U, the fish species Pangasius sutchi was exposed to ¼ and ½ of the LC_5_0 doses of waterborne "2"3"8U in a static system in duplicate for 21 days. Blood and organs, including the gills, liver, brain and muscles, were collected at different time periods—0 h, 24 h, 48 h, 72 h, 96 h, 7, days 14 days and 21 days—using ICP-MS to determine the toxic effects of uranium and the accumulation of "2"3"8U concentrations. The bioaccumulation of "2"3"8U in P. sutchi tissues was dependent on exposure time and concentration. The accumulation of uranium was, in order of magnitude, measured as gills > liver > brain > tissue, with the highest accumulation in the gills. It was observed that exposure to "2"3"8U significantly reduced antioxidant enzymes such as superoxide dismutase, catalase, and lipid peroxidase. The analysis of DNA fragmentation by comet assay and cell viability by flow cytometry was performed at different time intervals. DNA histograms by flow cytometry analysis revealed an increase in the G2/M phase and the S phase. The long-term "2"3"8U exposure studies in fish showed increasing micronucleus frequencies in

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)

Ternary fission of spontaneously fissile uranium isomers excited by neutrons

International Nuclear Information System (INIS)

Makarenko, V.E.; Molchanov, Y.D.; Otroshchenko, G.A.; Yan'kov, G.B.

1989-01-01

Spontaneously fissile isomers (SFI) of uranium were excited in the reactions 236,238 U(n,n') at an average neutron energy 4.5 MeV. A pulsed electrostatic accelerator and time analysis of the fission events were used. Fission fragments were detected by the scintillation method, and long-range particles from fission were detected by an ionization method. The relative probability of fission of nuclei through a spontaneously fissile isomeric state was measured: (1.30±0.01)·10 -4 ( 236 U) and (1.48±0.02)·10 -4 ( 238 U). Half-lives of the isomers were determined: 121±2 nsec (the SFI 236 U) and 267±13 nsec (the SFI 238 U). In study of the ternary fission of spontaneously fissile isotopes of uranium it was established that the probability of the process amounts to one ternary fission per 163±44 binary fissions of the SFI 236 U and one ternary fission per 49±14 binary fissions of the SFI 238 U. The substantial increase of the probability of ternary fission of SFI of uranium in comparison with the case of ternary fission of nuclei which are not in an isomeric state may be related to a special nucleon configuration of the fissile isomers of uranium

Measurement of radionuclide activities of uranium-238 series in soil samples by gamma spectrometry: case of Vinaninkarena

International Nuclear Information System (INIS)

Randrianantenaina, F.R.

2017-01-01

The aim of this work is to determine the activity level of radionuclides of uranium-238 series. Eight soil samples are collected at Rural Commune of Vinaninkarena. After obtaining secular equilibrium, these samples have been measured using gamma spectrometry system in the Nuclear Analyses and Techniques Department of INSTN-Madagascar, with HPGe detector (30 % relative efficiency) and a Genie 2000 software. Activities obtained vary from (78±2)Bq.kg -1 to (49 231 ± 415)Bq.kg -1 . Among these eight samples, three activity levels are shown. Low activity is an activity which has value lower or equal to (89±3)Bq.kg -1 . Average activity is an activity which has value between (186± 1)Bq.kg -1 and (1049 ±7)Bq.kg -1 . And high activity is an activity which has value higher or equal to (14501±209)Bq.kg -1 . According to UNSCEAR 2000, these value are all higher than the world average value which is 35 Bq.kg -1 .It is due to the localities of sampling points. The variation of the activity level depends on radionuclide concentration of uranium-238 series in the soil. [fr

Neutron scattering cross sections for 232Th and 238U inferred from proton scattering and charge exchange measurements

International Nuclear Information System (INIS)

Hansen, L.F.; Grimes, S.M.; Pohl, B.A.; Poppe, C.H.; Wong, C.

1980-01-01

Differential cross sections for the (p,n) reactions to the isobaric analog states (IAS) of 232 Th and 238 U targets were measured at 26 and 27 MeV. The analysis of the data was done in conjunction with the proton elastic and inelastic (2 + , 4 + , 6 + ) differential cross sections measured at 26 MeV. Because collective effects are important in this mass region, deformed coupled-channels calculations were carried out for the simultaneous analysis of the proton and neutron outgoing channels. The sensitivity of the calculations was studied with respect to the optical model parameters used in the calculations, the shape of the nuclear charge distribution, the type of coupling scheme assumed among the levels, the magnitude of the deformation parameters, and the magnitude of the isovector potentials, V 1 and W 1 . A Lane model-consistent analysis of the data was used to infer optical potential parameters for 6- to 7-MeV neutrons. The neutron elastic differential cross sections obtained from these calculations are compared with measurements available in the literature, and with results obtained using neutron parameters from global sets reported at these energies. 7 figures, 3 tables

Compact reaction cell for homogenizing and down-blending highly enriched uranium metal

Science.gov (United States)

McLean, W. II; Miller, P.E.; Horton, J.A.

1995-05-02

The invention is a specialized reaction cell for converting uranium metal to uranium oxide. In a preferred form, the reaction cell comprises a reaction chamber with increasing diameter along its length (e.g. a cylindrical chamber having a diameter of about 2 inches in a lower portion and having a diameter of from about 4 to about 12 inches in an upper portion). Such dimensions are important to achieve the necessary conversion while at the same time affording criticality control and transportability of the cell and product. The reaction chamber further comprises an upper port and a lower port, the lower port allowing for the entry of reactant gases into the reaction chamber, the upper port allowing for the exit of gases from the reaction chamber. A diffuser plate is attached to the lower port of the reaction chamber and serves to shape the flow of gas into the reaction chamber. The reaction cell further comprises means for introducing gases into the reaction chamber and a heating means capable of heating the contents of the reaction chamber. The present invention also relates to a method for converting uranium metal to uranium oxide in the reaction cell of the present invention. The invention is useful for down-blending highly enriched uranium metal by the simultaneous conversion of highly enriched uranium metal and natural or depleted uranium metal to uranium oxide within the reaction cell. 4 figs.

Compact reaction cell for homogenizing and down-blanding highly enriched uranium metal

Science.gov (United States)

McLean, II, William; Miller, Philip E.; Horton, James A.

1995-01-01

The invention is a specialized reaction cell for converting uranium metal to uranium oxide. In a preferred form, the reaction cell comprises a reaction chamber with increasing diameter along its length (e.g. a cylindrical chamber having a diameter of about 2 inches in a lower portion and having a diameter of from about 4 to about 12 inches in an upper portion). Such dimensions are important to achieve the necessary conversion while at the same time affording criticality control and transportability of the cell and product. The reaction chamber further comprises an upper port and a lower port, the lower port allowing for the entry of reactant gasses into the reaction chamber, the upper port allowing for the exit of gasses from the reaction chamber. A diffuser plate is attached to the lower port of the reaction chamber and serves to shape the flow of gas into the reaction chamber. The reaction cell further comprises means for introducing gasses into the reaction chamber and a heating means capable of heating the contents of the reaction chamber. The present invention also relates to a method for converting uranium metal to uranium oxide in the reaction cell of the present invention. The invention is useful for down-blending highly enriched uranium metal by the simultaneous conversion of highly enriched uranium metal and natural or depleted uranium metal to uranium oxide within the reaction cell.

Proton conduction based on intracrystalline chemical reaction

International Nuclear Information System (INIS)

Schuck, G.; Lechner, R.E.; Langer, K.

2002-01-01

Proton conductivity in M 3 H(SeO 4 ) 2 crystals (M=K, Rb, Cs) is shown to be due to a dynamic disorder in the form of an intracrystalline chemical equilibrium reaction: alternation between the association of the monomers [HSeO 4 ] 1- and [SeO 4 ] 2- resulting in the dimer [H(SeO 4 ) 2 ] 3- (H-bond formation) and the dissociation of the latter into the two monomers (H-bond breaking). By a combination of quasielastic neutron scattering and FTIR spectroscopy, reaction rates were obtained, as well as rates of proton exchange between selenate ions, leading to diffusion. The results demonstrate that this reaction plays a central role in the mechanism of proton transport in these solid-state protonic conductors. (orig.)

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

Study of reactions for the production of uranium titrafluoride and uranium hexafluoride

International Nuclear Information System (INIS)

Guzella, M.F.R.

1985-01-01

The main production processes of uranium hexafluoride in pilot plants and industrial facilities are described. The known reactions confirmed in laboratory experiments that lead to Uf 6 or other intermediate fluorides are discussed. For the purpose of determining a thermodinamically feasible reaction involving the sulfur hexafluoride as fluorinating agent, a mock-up facility was designed and constructed as a part of the R and D work planned at the CDTN (Nuclebras Center for Nuclear Technology Development). IN the uranium tatrafluoride synthesis employing U 3 O 8 and SF 6 several experimental parameters are studied. The reaction time, gasflow, temperature and stoechiometic relations among reagents are described in detail. (Author) [pt

Literature information applicable to the reaction of uranium oxides with chlorine to prepare uranium tetrachloride

International Nuclear Information System (INIS)

Haas, P.A.

1992-02-01

The reaction of uranium oxides and chlorine to prepare anhydrous uranium tetrachloride (UCl 4 ) are important to more economical preparation of uranium metal. The most practical reactions require carbon or carbon monoxide (CO) to give CO or carbon dioxide (CO 2 ) as waste gases. The chemistry of U-O-Cl compounds is very complex with valances of 3, 4, 5, and 6 and with stable oxychlorides. Literature was reviewed to collect thermochemical data, phase equilibrium information, and results of experimental studies. Calculations using thermodynamic data can identify the probable reactions, but the results are uncertain. All the U-O-Cl compounds have large free energies of formation and the calculations give uncertain small differences of large numbers. The phase diagram for UCl 4 -UO 2 shows a reaction to form uranium oxychloride (UOCl 2 ) that has a good solubility in molten UCl 4 . This appears more favorable to good rates of reaction than reaction of solids and gases. There is limited information on U-O-Cl salt properties. Information on the preparation of titanium, zirconium, silicon, and thorium tetrachlorides (TiCl 4 , ZrCl 4 , SiCl 4 , ThCl 4 ) by reaction of oxides with chlorine (Cl 2 ) and carbon has application to the preparation of UCl 4

From the HINDAS Project: Excitation Functions for Residual Nuclide Production by Proton-Induced Reactions

International Nuclear Information System (INIS)

Michel, R.; Gloris, M.; Protoschill, J.; Uosif, M.A.M.; Weug, M.; Herpers, U.; Kuhnhenn, J.; Kubik, P.-W.; Schumann, D.; Synal, H.-A.; Weinreich, R.; Leya, I.; David, J.C.; Leray, S.; Duijvestijn, M.; Koning, A.; Kelic, A.; Schmidt, K.H.; Cugnon, J.

2005-01-01

A survey is given about efforts undertaken during the HINDAS project to investigate the energy dependence of residual nuclide production by proton-induced reactions from thresholds up to 2.6 GeV. For proton-induced reactions, our experiments aimed to further develop and complete the cross-section database that was established by our collaboration in recent years. It was extended to the heavy-target elements Ta, W, Pb, and Bi for energies up to 2.6 GeV. In addition, new measurements for the target element iron were performed up to 2.6 GeV and for natural uranium for energies from 21 MeV to 69 MeV. For the target element lead, a comprehensive set of excitation functions published recently was completed by AMS-measurements of cross sections for the production of the long-lived radionuclides Be-10, Al-26, Cl-36, and I-129 and by mass spectrometric measurements for stable and radioactive rare gas isotopes of He, Ne, Ar, Kr, and Xe. Comprehensive tests of the nuclear-reaction codes TALYS and INCL4+ABLA, which were developed within the HINDAS project, were performed with the new experimental results over the entire energy range

Energy distribution of neutrons from the (n,2n) reaction in 238U

International Nuclear Information System (INIS)

Misulovin, A.

1978-12-01

Energy distribution of the first and second neutrons from (n,2n) scattering event in 238 U was evaluated according to the consistent compound nucleus model recently proposed by Segev. The law for deriving the energy distribution of secondary neutrons from a (n,2n) scattering event, depends on whether the reaction is considered as a simultaneous emission of two neutrons from one compound nucleus, or a successive emission of neutrons from different compound nuclei. Segev has presented a means of calculating the energy distribution assuming the latter model. The laws presented in the ENDF/B data files suggest the former model. The evaluation was based on inelastic level excitation and evaporation data for 238 U and 237 U. Data was retrieved from ENDF/B files. The evaporation data for 237 U was based on (γ,n) reaction 238 U. The inelastic level excitation data for 237 U was evaluated at the Soreq Nuclear Research Centre. It is concluded from the application of Segev's model to 238 U, that the energetic spectrum of secondary neutrons, is harder in the high range of energy than the one predicted by the use of the distribution law presented in ENDF/B data files. The spectrum of secondary (n,2n) neutrons, resulting from the interaction of 14 MeV neutrons in 238 U calculated with Segev's model, is compared with the corresponding spectrum of the LLL library, ENDF/B library and the recent evaluation of BNWL. It is found that the spectrum evaluated by LLL and BNWL is harder than that evaluated with Segev's model

Bioaccumulation of uranium and thorium from the solution containing both elements using various microorganisms

International Nuclear Information System (INIS)

Tsuruta, T.

2006-01-01

The effects of proton, thorium and uranium on the bioaccumulation of thorium and uranium from the solution (pH 3.5) containing uranium and thorium using Streptomyces levoris cells were examined. The amount of thorium accumulated using the cells decreased by the pre-contact between the cells and the solution (pH 3.5) containing no metals, whereas that of uranium was almost unaffected by the treatment. The amount of thorium was almost unaffected by the existence of uranium. On the other hand, the amount of uranium accumulated was strongly affected by the thorium, especially thorium addition after uranium accumulation. The decrease of uranium accumulated by the addition of thorium after the accumulation of uranium was higher than that from the solution containing both elements. Therefore, the contribution of uranium-thorium exchange reaction was higher than that of competition reaction. Accordingly, proton-uranium-thorium exchange reaction was occurred in the accumulation of thorium from the solution containing thorium and uranium. The gram-positive bacteria, such as Micrococcus luteus, Arthrobacter nicotianae, Bacillus subtilis and B. megaterium, has a much higher separation factor as thorium/uranium than that of actinomycetes. These gram-positive bacterial strains can be used for the accumulation of thorium from the solution containing uranium and thorium

Comparison of dynamical aspects of nonadiabatic electron, proton, and proton-coupled electron transfer reactions

International Nuclear Information System (INIS)

Hatcher, Elizabeth; Soudackov, Alexander; Hammes-Schiffer, Sharon

2005-01-01

The dynamical aspects of a model proton-coupled electron transfer (PCET) reaction in solution are analyzed with molecular dynamics simulations. The rate for nonadiabatic PCET is expressed in terms of a time-dependent probability flux correlation function. The impact of the proton donor-acceptor and solvent dynamics on the probability flux is examined. The dynamical behavior of the probability flux correlation function is dominated by a solvent damping term that depends on the energy gap correlation function. The proton donor-acceptor motion does not impact the dynamical behavior of the probability flux correlation function but does influence the magnitude of the rate. The approximations previously invoked for the calculation of PCET rates are tested. The effects of solvent damping on the proton donor-acceptor vibrational motion are found to be negligible, and the short-time solvent approximation, in which only equilibrium fluctuations of the solvent are considered, is determined to be valid for these types of reactions. The analysis of PCET reactions is compared to previous analyses of single electron and proton transfer reactions. The dynamical behavior is qualitatively similar for all three types of reactions, but the time scale of the decay of the probability flux correlation function is significantly longer for single proton transfer than for PCET and single electron transfer due to a smaller solvent reorganization energy for proton transfer

Literature information applicable to the reaction of uranium oxides with chlorine to prepare uranium tetrachloride

Energy Technology Data Exchange (ETDEWEB)

Haas, P.A.

1992-02-01

The reaction of uranium oxides and chlorine to prepare anhydrous uranium tetrachloride (UCl{sub 4}) are important to more economical preparation of uranium metal. The most practical reactions require carbon or carbon monoxide (CO) to give CO or carbon dioxide (CO{sub 2}) as waste gases. The chemistry of U-O-Cl compounds is very complex with valances of 3, 4, 5, and 6 and with stable oxychlorides. Literature was reviewed to collect thermochemical data, phase equilibrium information, and results of experimental studies. Calculations using thermodynamic data can identify the probable reactions, but the results are uncertain. All the U-O-Cl compounds have large free energies of formation and the calculations give uncertain small differences of large numbers. The phase diagram for UCl{sub 4}-UO{sub 2} shows a reaction to form uranium oxychloride (UOCl{sub 2}) that has a good solubility in molten UCl{sub 4}. This appears more favorable to good rates of reaction than reaction of solids and gases. There is limited information on U-O-Cl salt properties. Information on the preparation of titanium, zirconium, silicon, and thorium tetrachlorides (TiCl{sub 4}, ZrCl{sub 4}, SiCl{sub 4}, ThCl{sub 4}) by reaction of oxides with chlorine (Cl{sub 2}) and carbon has application to the preparation of UCl{sub 4}.

Temporal behavior of 222Radon, 226Radium and 238Uranium in deep water wells which provide Valle de Toluca with drinking water

International Nuclear Information System (INIS)

Pena, P.; Tamez, E.; Iturbe, J.L.; Acosta, A.; Segovia, N.; Carrillo, J.; Armienta, M.

1994-01-01

The presence of radionuclides in underground waters may be an indication of its origin and also the sign of the hydraulic properties of the aquifers layers where circulate. Additionally, the ingestion by human beings of water with radioactive elements (Radon 222, Radium 226, Uranium 238) can give as a result the accumulation of such elements in several organs of the body producing then health damages. In this work, the concentrations of Radon 222, Radium 226 and Uranium 238, in waters coming from deep wells which provide with drinking water the Toluca Valley, were determined. For this purpose, during a year (june 1991 to August 1992) ten wells were sampled with a tracking of the radionuclides concentration as well as the physical-chemical components of water; it was established the relationship presented by the analyzed waters with the local geology and the local and regional systems. (Author)

Uranium oxidation: characterization of oxides formed by reaction with water

International Nuclear Information System (INIS)

Fuller, E.L. Jr.; Smyrl, N.R.; Condon, J.B.; Eager, M.H.

1983-01-01

Three different uranium oxide samples have been characterized with respect to the different preparation techniques. Results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. 27 figures

Uranium/water vapor reactions in gaseous atmospheres

International Nuclear Information System (INIS)

Jackson, R.L.; Condon, J.B.; Steckel, L.M.

1977-07-01

Experiments have been performed to determine the effect of varying humidities, gaseous atmospheres, and temperatures on the uranium/water vapor reaction. A balance, which allowed continuous in-system weighings, was used to determine the rates of the uranium/water vapor reactions at water vapor pressures of 383, 1586, and 2853 Pa and at temperatures of 80, 100, and 150 0 C in atmospheres of hydrogen, argon, or argon/oxygen mixtures. Based on rate data, the reactions were characterized as hydriding or nonhydriding. Hydriding reactions were found to be preferred in moist hydrogen systems at the higher temperatures and the lower humidities. The presence of hydrogen in hydriding systems was found to initially inhibit the reaction, but causes an acceleration of the rate in the final stages. In general, reaction rates of hydriding systems approached the hydriding rates calculated and observed in dry hydrogen. Hydriding and nonhydriding reaction rates showed a positive correlation to temperature and water vapor pressure. Final reaction rates in moist argon/oxygen mixtures of 1.93, 4.57, and 9.08 mole percent oxygen were greater than the rates observed in moist hydrogen or argon. Final reaction rates were negatively correlated to the oxygen concentration

Proton-transfer reactions in ionized gases

International Nuclear Information System (INIS)

Stiller, W.; Schmidt, R.; Schuster, R.

1985-01-01

Ion-molecule reactions play an important role in various radiolytic processes, e.g. gas-pulse radiolysis, environmental research. For a discussion of mechanisms rate coefficients have to be assessed. Here gas-phase rate coefficients of ion-(polar) molecule reactions are calculated using the ideas of interaction potentials, reactive cross-sections and distribution functions of the translational energies of both the reactants (ions I, molecules M). The starting point of our approach, directed especially to gas-phase proton-transfer reactions, is the idea that the rate coefficient k can be calculated as an ion-molecule capture-rate coefficient multiplied by a 'steric factor' representing the probability for proton transfer. Mutual capture of the reaction partners within a possible reaction zone is caused by the physical interaction between an ion and a polar molecule. A model is discussed. Results are presented. (author)

Ground water contamination with (238)U, (234)U, (235)U, (226)Ra and (210)Pb from past uranium mining: cove wash, Arizona.

Science.gov (United States)

Dias da Cunha, Kenya Moore; Henderson, Helenes; Thomson, Bruce M; Hecht, Adam A

2014-06-01

The objectives of the study are to present a critical review of the (238)U, (234)U, (235)U, (226)Ra and (210)Pb levels in water samples from the EPA studies (U.S. EPA in Abandoned uranium mines and the Navajo Nation: Red Valley chapter screening assessment report. Region 9 Superfund Program, San Francisco, 2004, Abandoned uranium mines and the Navajo Nation: Northern aum region screening assessment report. Region 9 Superfund Program, San Francisco, 2006, Health and environmental impacts of uranium contamination, 5-year plan. Region 9 Superfund Program, San Franciso, 2008) and the dose assessment for the population due to ingestion of water containing (238)U and (234)U. The water quality data were taken from Sect. "Data analysis" of the published report, titled Abandoned Uranium Mines Project Arizona, New Mexico, Utah-Navajo Lands 1994-2000, Project Atlas. Total uranium concentration was above the maximum concentration level for drinking water (7.410-1 Bq/L) in 19 % of the water samples, while (238)U and (234)U concentrations were above in 14 and 17 % of the water samples, respectively. (226)Ra and (210)Pb concentrations in water samples were in the range of 3.7 × 10(-1) to 5.55 × 102 Bq/L and 1.11 to 4.33 × 102 Bq/L, respectively. For only two samples, the (226)Ra concentrations exceeded the MCL for total Ra for drinking water (0.185 Bq/L). However, the (210)Pb/(226)Ra ratios varied from 0.11 to 47.00, and ratios above 1.00 were observed in 71 % of the samples. Secular equilibrium of the natural uranium series was not observed in the data record for most of the water samples. Moreover, the (235)U/(total)U mass ratios ranged from 0.06 to 5.9 %, and the natural mass ratio of (235)U to (total)U (0.72 %) was observed in only 16 % of the water samples, ratios above or below the natural ratio could not be explained based on data reported by U.S. EPA. In addition, statistical evaluations showed no correlations among the distribution of the radionuclide concentrations

BetaScint{trademark} fiber-optic sensor for detecting strontium-90 and uranium-238 in soil. Innovative technology summary report

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-12-01

Accurate measurements of radioactivity in soils contaminated with Strontium-90 (Sr-90) or Uranium-238 (U-238) are essential for many DOE site remediation programs. These crucial measurements determine if excavation and soil removal is necessary, where remediation efforts should be focused, and/or if a site has reached closure. Measuring soil contamination by standard EPA laboratory methods typically takes a week (accelerated analytical test turnaround) or a month (standard analytical test turnaround). The time delay extends to operations involving heavy excavation equipment and associated personnel which are the main costs of remediation. This report describes an application of the BetaScint{trademark} fiber-optic sensor that measures Sr-90 or U-238 contamination in soil samples on site in about 20 minutes, at a much lower cost than time-consuming laboratory methods, to greatly facilitate remediation. This report describes the technology, its performance, its uses, cost, regulatory and policy issues, and lessons learned.

BetaScintTM fiber-optic sensor for detecting strontium-90 and uranium-238 in soil. Innovative technology summary report

International Nuclear Information System (INIS)

1998-12-01

Accurate measurements of radioactivity in soils contaminated with Strontium-90 (Sr-90) or Uranium-238 (U-238) are essential for many DOE site remediation programs. These crucial measurements determine if excavation and soil removal is necessary, where remediation efforts should be focused, and/or if a site has reached closure. Measuring soil contamination by standard EPA laboratory methods typically takes a week (accelerated analytical test turnaround) or a month (standard analytical test turnaround). The time delay extends to operations involving heavy excavation equipment and associated personnel which are the main costs of remediation. This report describes an application of the BetaScint trademark fiber-optic sensor that measures Sr-90 or U-238 contamination in soil samples on site in about 20 minutes, at a much lower cost than time-consuming laboratory methods, to greatly facilitate remediation. This report describes the technology, its performance, its uses, cost, regulatory and policy issues, and lessons learned

Search for surviving actinides and superheavy nuclei in damped collisions of 238U with 238U and 248Cm

International Nuclear Information System (INIS)

Kratz, J.V.

1980-03-01

In the present talk aspects of the reaction mechanism related to the survival probability of the heaviest fragments in 238 U + 238 U collisions are discussed first. This is followed by a description of the experiments that have been performed to search for surviving superheavy fragments in the 238 U + 238 U reaction and by a presentation of the results obtained so far. In a third section our recent first attempts with the 238 U + 248 Cm reaction are described and preliminary results are discussed. (orig.)

Determination of uranium in phosphorite by radiometric measurements and activation analysis

International Nuclear Information System (INIS)

Santos Amaral, R. dos.

1987-01-01

Uranium was determined by passive gamma ray counting in phosphate rocks in the range from 50 to 400 ppm U 3 O 8 . The measurements were carried out focusing on the 186 KeV gamma ray from the 235 U nuclide. The radioactive equilibrium of the 226 Ra in the uranium decay chain was investigated due its contribution in the 186 KeV compound 226 Ra 235 U photopeak. Therefore a simulataneous uranium determination through the 234 Th radionuclide demonstrate the equilibrium conditions. The results of the uranium analysis by the following methods: spectrophotometry, XRF and delayed neutrons from three independent laboratories were compared to evaluate the accuracy of the radioanalytical results. The uranium content was also determined by neutron activation analysis, followed by gamma measurement of the 239 Np formed by the 238 U (n,γ) 239 U reaction and 239 U beta decay and the fission products of 235 U. By the correlation of 239 Np, 99 Mo, 143 Ce, 131 I, and 133 I photopeak was measured the 238 U/ 235 U isotopic ratio. (author) [pt

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

Uranium fluoride chemistry. Part 1. The gas phase reaction of uranium hexafluoride with alcohols

International Nuclear Information System (INIS)

Schnautz, N.G.; Venter, P.J.

1992-01-01

The reaction between uranium hexafluoride (UF 6 ) and simple alcohols in the gas phase was observed to proceed by way of three possible reaction pathways involving dehydration, deoxygenative fluorination, and ether formation. These reactions can best be explained by assuming that alcohols first react with UF 6 to afford the alkoxy uranium pentafluoride intermediate ROUF 5 , which reacts further to give the dehydration, deoxygenative fluorination, and ether products. In each of the above three reaction pathways, UF 6 is transformed to UOF 4 , which being as reactive toward alcohols as UF 6 , reacts further with the alcohol in question to finally afford the unreactive uranyl fluoride (UO 2 F 2 ). 6 refs., 2 tabs

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

Neutron Induced Capture and Fission Processes on 238U

Directory of Open Access Journals (Sweden)

Oprea Cristiana

2016-01-01

Full Text Available Nuclear data on Uranium isotopes are of crucial interest for new generation of nuclear reactors. Processes of interest are the nuclear reactions induced by neutrons and in this work mainly the capture and the fission process on 238U will be analyzed in a wide energy interval. For slow and resonant neutrons the many levels Breit – Wigner formalism is necessary. In the case of fast and very fast neutrons up to 200 MeV the nuclear reaction mechanism implemented in Talys will be used. The present evaluations are necessary in order to obtain the field of neutrons in the design of nuclear reactors and they are compared with experimental data from literature obtained from capture and (n,xn processes.

Applying reaction condition index to predict sandstone type uranium deposit

International Nuclear Information System (INIS)

Chen Gongxin; Liu Jinhui; Cheng Hai

2002-01-01

On the basic of the explanation of reaction condition index, the deduction of reaction condition index calculation principle, the hydrogeological setting in Gongpoquan basin in Baishan, Gansu province and the study of reaction condition index of its water source point, the north Luotuoquan area in Gongpoquan basin seems to be a favourable place for sandstone type uranium deposit, and the prospect area for sandstone type uranium deposit is delimitated

Investigation of fission properties and evaporation residue measurement in the reactions using 238U target nucleus

Directory of Open Access Journals (Sweden)

Saro S.

2011-10-01

Full Text Available Fragment mass distributions for fission after full momentum transfer were measured in the reactions of 30Si,34,36 S,31P,40Ar + 238U at bombarding energies around the Coulomb barrier. Mass distributions change significantly as a function of incident beam energy. The asymmetric fission probability increases at sub-barrier energy. The phenomenon is interpreted as an enhanced quasifission probability owing to orientation effects on fusion and/or quasifission. The evaporation residue (ER cross sections were measured in the reactions of 30Si + 238U and 34S + 238U to obtain information on fusion. In the latter reaction, significant suppression of fusion was implied. This suggests that fission events different from compound nucleus are included in the masssymmetric fragments. The results are supported by a model calculation based on a dynamical calculation using Langevin equation, in which the mass distribution for fusion-fission and quasifission fragments are separately determined.

Origin and geochemical behavior of uranium in marine sediments. Utilization of the {sup 234}U/{sup 238}U ratio in marine geochemistry; Origine et comportement geochimique de l`uranium dans les sediments marins. Utilisation du rapport ({sup 234}U/{sup 238}U) en geochimie marine

Energy Technology Data Exchange (ETDEWEB)

Organo, Catherine [Paris-11 Univ., 91 - Orsay (France)

1997-01-20

The first part of this thesis presents the current situation of knowledge of uranium in marine environment. The second part describes the methods of analysis as well as the material support of the study, i.e., the sediments and marine deposits investigated. The third part is dedicated to the study of uranium mobility in marine sediments characterized by detrital terrigenous composition (pelagic clays). This approach allowed quantifying the entering and leaving flux of uranium after the sediment settling and, to discuss, on this basis, the consequences on the uranium oceanic balance. In the third part the origin and behavior of uranium in zones of high surface productivity is studied. The uranium enrichments observed in the hemi-pelagic sediments of the EUMELI (J.G.O.F.S.-France) programme will constitute a material of study adequate for measuring the variations in the {sup 234}U/2{sup 38U} ratio in solid phase, in response to the oxido-reducing characteristics of the sediment. Thus establishing the origin of the trapped uranium has been possible. Also, the nature of the sedimentary phases related to uranium in bio-genetic sediments in the Austral Ocean was determined. Thus a relationship between the variations in the {sup 234}U/{sup 238} and the diagenetic transformations was possible to establish. Finally in the fifth part a study of the behavior of uranium in a polymetallic shell characteristic for deposits of hydrogenized origin 146 refs., 57 figs., 23 tabs.

Plutonium-236 traces determination in plutonium-238 by α spectrometry

International Nuclear Information System (INIS)

Acena, M.L.; Pottier, R.; Berger, R.

1969-01-01

Two methods are described in this report for the determination of plutonium-236 traces in plutonium-238 by a spectrometry using semi-conductor detectors. The first method involves a direct comparison of the areas under the peaks of the α spectra of plutonium-236 and plutonium-238. The electrolytic preparation of the sources is carried out after preliminary purification of the plutonium. The second method makes it possible to determine the 236 Pu/ 238 Pu ratio by comparing the areas of the α peaks of uranium-232 and uranium-234, which are the decay products of the two plutonium isotopes respectively. The uranium in the source, also deposited by electrolysis, is separated from a 1 mg amount of plutonium either by a T.L.A. extraction, or by the use of ion-exchange resins. The report ends with a discussion of the results obtained with plutonium of two different origins. (authors) [fr

Experimental Observation of Nuclear Reactions in Palladium and Uranium - Possible Explanation by Hydrex Mode

International Nuclear Information System (INIS)

Dufour, J.; Murat, D.; Dufour, X.; Foos, J.

2001-01-01

Experiments with uranium are presented that show a highly exothermal reaction, which can only be of nuclear origin. One striking point of these results is that they clearly show that what is being observed is not some kind of fusion reaction of the deuterium present (only exceedingly small amounts of it are present). This is a strong indication that hydrogen can trigger nuclear reactions that seem to involve the nuclei of the lattice (which would yield a fission-like pattern of products). Confronted with a situation where some experiments in the field yield a fusion-like pattern of products (CF experiments) and others a fissionlike one (LENR experiments), one can reasonably wonder whether one is not observing two aspects of the same phenomenon. Thus, it is proposed to describe CF and LENR reactions as essentially the same phenomenon based on the possible existence of a still hypothetical proton/electron resonance, which would catalyze fissionlike reactions with a neutron sink. Finally, a series of experiments is proposed to assess this hypothesis

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

Reactive transport of uranium in a groundwater bioreduction study: Insights from high-temporal resolution 238U/235U data

Science.gov (United States)

Shiel, A. E.; Johnson, T. M.; Lundstrom, C. C.; Laubach, P. G.; Long, P. E.; Williams, K. H.

2016-08-01

We conducted a detailed investigation of U isotopes in conjunction with a broad geochemical investigation during field-scale biostimulation and desorption experiments. This investigation was carried out in the uranium-contaminated alluvial aquifer of the Rifle field research site. In this well-characterized setting, a more comprehensive understanding of U isotope geochemistry is possible. Our results indicate that U isotope fractionation is consistently observed across multiple experiments at the Rifle site. Microbially-mediated reduction is suggested to account for most or all of the observed fractionation as abiotic reduction has been demonstrated to impart much smaller, often near-zero, isotopic fractionation or isotopic fractionation in the opposite direction. Data from some time intervals are consistent with a simple model for transport and U(VI) reduction, where the fractionation factor (ε = +0.65‰ to +0.85‰) is consistent with experimental studies. However, during other time intervals the observed patterns in our data indicate the importance of other processes in governing U concentrations and 238U/235U ratios. For instance, we demonstrate that departures from Rayleigh behavior in groundwater systems arise from the presence of adsorbed species. We also show that isotope data are sensitive to the onset of oxidation after biostimulation ends, even in the case where reduction continues to remove contaminant uranium downstream. Our study and the described conceptual model support the use of 238U/235U ratios as a tool for evaluating the efficacy of biostimulation and potentially other remedial strategies employed at Rifle and other uranium-contaminated sites.

Origin and geochemical behavior of uranium in marine sediments. Utilization of the 234U/238U ratio in marine geochemistry

International Nuclear Information System (INIS)

Organo, Catherine

1997-01-01

The first part of this thesis presents the current situation of knowledge of uranium in marine environment. The second part describes the methods of analysis as well as the material support of the study, i.e., the sediments and marine deposits investigated. The third part is dedicated to the study of uranium mobility in marine sediments characterized by detrital terrigenous composition (pelagic clays). This approach allowed quantifying the entering and leaving flux of uranium after the sediment settling and, to discuss, on this basis, the consequences on the uranium oceanic balance. In the third part the origin and behavior of uranium in zones of high surface productivity is studied. The uranium enrichments observed in the hemi-pelagic sediments of the EUMELI (J.G.O.F.S.-France) programme will constitute a material of study adequate for measuring the variations in the 234 U/2 38U ratio in solid phase, in response to the oxido-reducing characteristics of the sediment. Thus establishing the origin of the trapped uranium has been possible. Also, the nature of the sedimentary phases related to uranium in bio-genetic sediments in the Austral Ocean was determined. Thus a relationship between the variations in the 234 U/ 238 and the diagenetic transformations was possible to establish. Finally in the fifth part a study of the behavior of uranium in a polymetallic shell characteristic for deposits of hydrogenized origin

The reaction of uranium with moist hydrogen

International Nuclear Information System (INIS)

Pearce, R.J.; Kay, P.

1987-10-01

The reaction of uranium in moist hydrogen at a total pressure of 101 kPa over the temperature range 105 0 -200 0 C and water vapour pressures in the range 5-100 kPa has been examined in a limited thermogravimetric study. It has been shown that initially there is a period during which only linear kinetics are observed with a rate similar to that exhibited in similarly moist argon, i.e. hydrogen has no apparent effect on the reaction. At water vapour pressures of and above 49 kPa, corresponding to hydrogen:water vapour pressure ratios in the range 1:1 to 1:100, over the exposure times studied (not > 20h) only such linear kinetics are observed. Below this water vapour pressure and after an initial period of linear kinetics a continuously increasing reaction rate was observed in some instances resulting from rapid attach on localised areas. The localised reaction rates were approximately 2-3 orders of magnitude faster than the original linear reaction kinetics and the interaction rates in either moist argon or moist air. Comparison with a single experiment carried out at 150 0 C indicated that breakaway rates were approaching that in dry hydrogen. During breakaway attack there was a significant increase in the relative amounts of uranium hydride formed. The duration of the linear kinetics phase was extended by pre-oxidation of the uranium surface, decreasing temperature at a constant water vapour pressure, or increasing water vapour pressure (or water vapour: hydrogen pressure ratio) at a constant temperature. (author)

Reaction of uranium oxides with chlorine and carbon or carbon monoxide to prepare uranium chlorides

Energy Technology Data Exchange (ETDEWEB)

Haas, P.A.; Lee, D.D.; Mailen, J.C.

1991-11-01

The preferred preparation concept of uranium metal for feed to an AVLIS uranium enrichment process requires preparation of uranium tetrachloride (UCI{sub 4}) by reacting uranium oxides (UO{sub 2}/UO{sub 3}) and chlorine (Cl{sub 2}) in a molten chloride salt medium. UO{sub 2} is a very stable metal oxide; thus, the chemical conversion requires both a chlorinating agent and a reducing agent that gives an oxide product which is much more stable than the corresponding chloride. Experimental studies in a quartz reactor of 4-cm ID have demonstrated the practically of some chemical flow sheets. Experimentation has illustrated a sequence of results concerning the chemical flow sheets. Tests with a graphite block at 850{degrees}C demonstrated rapid reactions of Cl{sub 2} and evolution of carbon dioxide (CO{sub 2}) as a product. Use of carbon monoxide (CO) as the reducing agent also gave rapid reactions of Cl{sub 2} and formation of CO{sub 2} at lower temperatures, but the reduction reactions were slower than the chlorinations. Carbon powder in the molten salt melt gave higher rates of reduction and better steady state utilization of Cl{sub 2}. Addition of UO{sub 2} feed while chlorination was in progress greatly improved the operation by avoiding the plugging effects from high UO{sub 2} concentrations and the poor Cl{sub 2} utilizations from low UO{sub 2} concentrations. An UO{sub 3} feed gave undesirable effects while a feed of UO{sub 2}-C spheres was excellent. The UO{sub 2}-C spheres also gave good rates of reaction as a fixed bed without any molten chloride salt. Results with a larger reactor and a bottom condenser for volatilized uranium show collection of condensed uranium chlorides as a loose powder and chlorine utilizations of 95--98% at high feed rates. 14 refs., 7 figs., 14 tabs.

Proton-proton reaction rates at extreme energies

International Nuclear Information System (INIS)

Nagano, Motohiko

1993-01-01

Results on proton-antiproton reaction rates (total cross-section) at collision energies of 1.8 TeV from experiments at Fermilab have suggested a lower rate of increase with energy compared to the extrapolation based on results previously obtained at CERN's proton-antiproton collider (CERN Courier, October 1991). Now an independent estimate of the values for the proton-proton total cross-section for collision energies from 5 to 30 TeV has been provided by the analysis of cosmic ray shower data collected over ten years at the Akeno Observatory operated by the Institute for Cosmic Ray Research of University of Tokyo. These results are based on the inelastic cross-section for collisions of cosmic ray protons with air nuclei at energies in the range10 16-18 eV. A new extensive air shower experiment was started at Akeno, 150 km west of Tokyo, in 1979 with a large array of detectors, both on the ground and under a 1-metre concrete absorber. This measured the total numbers of electrons and muons of energies above 1GeV for individual showers with much better accuracy than before. Data collection was almost continuous for ten years without any change in the triggering criteria for showers above10 16 eV. The mean free path for proton-air nuclei collisions has been determined from the zenith angle of the observed frequency of air showers which have the same effective path length for development in the atmosphere and the same primary energy

Calculations of neutron and proton induced reaction cross sections for actinides in the energy region from 10 MeV to 1 GeV

International Nuclear Information System (INIS)

Konshin, V.A.

1995-01-01

Several nuclear model codes were applied to calculations of nuclear data in the energy region from 10 MeV to 1 GeV. At energies up to 100 MeV the nuclear theory code GNASH was used for nuclear data calculation for incident neutrons for 238 U, 233-236 U, 238-242 Pu, 237 Np, 232 Th, 241-243 Am and 242-247 Cm. At energies from 100 MeV to 1 GeV the intranuclear cascade exciton model including the fission process was applied to calculations of protons and neutrons with 233 U, 235 U, 238 U, 232 Th, 232 Pa, 237 Np, 238 Np, 239 Pu, 241 Am, 242 Am and 242-248 Cm. Determination of parameter systematics was a major effort in the present work that was aimed at improving the predictive capability of the models used. An emphasis was made on a simultaneous analysis of data for a variety of reaction channels for the nucleus considered, as well as of data that are available for nearby nuclei or other incident particles. Comparison with experimental data available on multiple reaction cross sections, isotope yields, fission cross sections, particle multiplicities, secondary particle spectra, and double differential cross sections indicates that the calculations reproduce the trends, and often the details, of the experimental data. (author)

Calculations of neutron and proton induced reaction cross sections for actinides in the energy region from 10MeV to 1GeV

International Nuclear Information System (INIS)

Konshin, V.A.

1995-06-01

Several nuclear model codes were applied to calculations of nuclear data in the energy region from 10MeV to 1GeV. At energies up to 100MeV the nuclear theory code GNASH was used for nuclear data calculation for neutrons incident for on 238 U, 233-236 U, 238-242 Pu, 237 Np, 232 Th, 241-243 Am and 242-247 Cm. At energies from 100MeV to 1GeV the intranuclear cascade exciton model including the fission process was applied to calculations of protons and neutrons with 233 U, 235 U, 238 U, 232 Th, 232 Pa, 237 Np, 238 Np, 239 Pu, 241 Am, 242 Am and 242-248 Cm. Determination of parameter systematics was a major effort in the present work that was aimed at improving the predictive capability of the models used. An emphasis was placed upon a simultaneous analysis of data for a variety of reaction channels for the nuclei considered, as well as of data that are available for nearby nuclei or for other incident particles. Comparisons with experimental data available on multiple reaction cross sections, isotope yields, fission cross sections, particle multiplicities, secondary particle spectra, and double differential cross sections indicate that the calculations reproduce the trends, and often the details, of the measurements data. (author) 82 refs

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

Uranium geochemistry on the Amazon shelf: Evidence for uranium release from bottom sediments

International Nuclear Information System (INIS)

McKee, B.A.; DeMaster, D.J.; Nittrouer, C.A.

1987-01-01

In Amazon-shelf waters, as salinity increases to 36.5 x 10 -3 , dissolved uranium activities increase to a maximum of 4.60 dpm 1 -1 . This value is much higher than the open-ocean value (2.50 dpm 1 -1 ), indicating a source of dissolved uranium to shelf waters in addition to that supplied from open-ocean and riverine waters. Uranium activities are much lower for surface sediments in the Amazon-shelf sea bed (mean: 0.69 ± .09 dpm g -1 ) than for suspended sediments in the Amazon river (1.82 dpm g -1 ). Data suggest that the loss of particulate uranium from riverine sediments is probably the result of uranium desorption from the ferric-oxyhydroxide coatings on sediment particles, and/or uranium release by mobilization of the ferric oxyhydroxides. The total flux of dissolved 238 U from the Amazon shelf (about 1.2 x 10 15 dpm yr -1 ) constitutes about 15% of uranium input to the world ocean, commensurate to the Amazon River's contribution to world river-water discharge. Measurement of only the riverine flux of dissolved 238 U underestimates, by a factor of about 5, the flux of dissolved 238 U from the Amazon shelf to the open ocean

An alternative route for the preparation of the medical isotope 99Mo from the 238U(γ, f) and 100Mo(γ, n) reactions

International Nuclear Information System (INIS)

Naik, H.; Goswami, A.; Suryanarayana, S.V.; Jagadeesan, K.C.; Thakare, S.V.; Joshi, P.V.; Nimje, V.T.; Mittal, K.C.; Venugopal, V.; Kailas, S.

2013-01-01

The radionuclide 99 Mo, which has a half-life of 65.94 h was produced from 238 U(γ, f) and 100 Mo(γ, n) reactions using a 10 MeV electron linac at EBC, Kharghar Navi-Mumbai, India. This has been investigated since the daughter product 99m Tc is very important from a medical point of view and can be produced in a generator from the parent 99 Mo. The activity of 99 Mo was analyzed by a γ-ray spectrometric technique using a HPGe detector. From the detected γ-rays activity of 140.5 and 739.8 keV, the amount of 99 Mo produced was determined. For comparison, the amount of 99 Mo from 238 U(γ, f) and 100 Mo(γ, n) reactions was also estimated using the experimental photon flux from 197 Au(γ, n) 196 Au reaction. The amount of 99 Mo from the detected γ-lines is in agreement with the estimated value for 238 U(γ, f) and 100 Mo(γ, n) reactions. The production of 99 Mo activity from 238 U(γ, f) and 100 Mo(γ, n) reactions is a relevant and novel approach, which provides alternative routes to 235,238 U(n, f) and 98 Mo(n, γ) reactions, circumventing the need for a reactor. The viability and practicality of the 99 Mo production from the 238 U(γ, f) and 100 Mo(γ, n) reactions alternative to 235,238 U(n, f) and 98 Mo(n, γ) reactions has been emphasize. An estimate has been also arrived based on the experimental data of present work to fulfill the requirement of DOE. (author)

Nuclear reactions excited by recoil protons on a nuclear reactor

International Nuclear Information System (INIS)

Mukhammedov, S.; Khaydarov, A.; Barsukova, E.G.

2006-01-01

The nuclear reactions excited by recoil protons and of the detection possibility of the various chemical elements with the use of these secondary nucleus reactions were investigated. The recoil protons are produced on a nuclear reactor in the result of (n, p) inelastic and elastic scattering interaction of fast neutrons with nuclei of hydrogen. It is well known that the share of fast neutrons in energetic spectrum of reactor's neutrons in comparison with the share of thermal neutrons is small. . Consequently, the share of recoil protons produced in the result of fast neutron interaction with nuclei of light elements, capable to cause the nuclear reactions, is also small, des, due to Coulomb barrier of nuclei the recoil protons can cause the nuclear reactions only on nuclei of light and some middle elements. Our studies show that observable yields have radio nuclides excited in the result of nuclear reactions on Li, B, O, V and Cu. Our experimental results have demonstrated that the proton activation analysis based on the application of secondary nuclear reactions is useful technique to determine large contents of various light and medium chemical elements. Detection limits for studied chemical elements are estimated better than 10 ppm

The estuarine chemistry and isotope systematics of 234,238U in the Amazon and Fly Rivers

Science.gov (United States)

Swarzenski, P.; Campbell, P.; Porcelli, D.; McKee, B.

2004-01-01

Natural concentrations of 238U and ??234U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land-sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates. On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0-16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (???1 m) zones of Fe(III) - and, to a lesser degree, Mn(IV) - reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved 238U profile co-varied closely with Mn(II). Isotopic variations as evidenced in ??234U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the ??234U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched ??234U values represent a riverine surface complexation product that is actively involved in Mn-Fe diagenetic cycles and surface

The estuarine chemistry and isotope systematics of 234,238U in the Amazon and Fly Rivers

Science.gov (United States)

Swarzenski, Peter; Campbell, Pamela; Porcelli, Don; McKee, Brent

2004-12-01

Natural concentrations of 238U and δ234U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land-sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates. On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0-16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (˜1 m) zones of Fe(III)—and, to a lesser degree, Mn(IV)—reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved 238U profile co-varied closely with Mn(II). Isotopic variations as evidenced in δ234U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the δ234U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched δ234U values represent a riverine surface complexation product that is actively involved in Mn-Fe diagenetic cycles and surface

Quantitative determination of uranium by SIMS

International Nuclear Information System (INIS)

Kuruc, J.; Harvan, D.; Galanda, D.; Matel, L.; Aranyosiova, M.; Velic, D.

2008-01-01

The paper presents results of quantitative measurements of uranium-238 by secondary ion mass spectrometry (SIMS) with using alpha spectrometry as well as complementary technique. Samples with specific activity of uranium-238 were prepared by electrodeposition from aqueous solution of UO 2 (NO 3 ) 2 ·6H 2 O. We tried to apply SIMS to quantitative analysis and search for correlation between intensity obtained from SIMS and activity of uranium-238 in dependence on the surface's weight and possibility of using SIMS in quantitative analysis of environmental samples. The obtained results and correlations as well as results of two real samples measurements are presented in this paper. (authors)

The future plan for the applications of RI produced in the proton-induced spallation-reaction

Energy Technology Data Exchange (ETDEWEB)

Ikezoe, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1997-07-01

A plan of research facilities (transmutations of minor actinides and neutron scattering for material and life sciences) has been proposed in JAERI. This plan is based on a proton lineac with an energy of 1.5 GeV and a beam current of several mA. Among these facilities, we are planning to accelerate neutron-rich radioactive nuclei (RI) produced in the fission and spallation reactions of thorium or uranium bombarded by the intense high energy proton beams. The RI produced in an ion source are separated by a high resolution isotope separator and their charge states are changed to be negative to inject into the existing tandem-booster accelerator. Main purpose of this plan is to study the nuclear and chemical properties of neutron rich transactinium elements not yet synthesized and the nuclear structures of neutron rich nuclei far from the nuclear stability line. (author)

Kinetic study of the reaction of uranium with various carbon-containing gases; Etude cinetique de la reaction sur l'uranium de differents gaz carbones

Energy Technology Data Exchange (ETDEWEB)

Feron, G [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1963-09-15

The kinetic study of the reaction U + CO{sub 2} and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C The reaction with carbon monoxide leads to a mixture of dioxide UO{sub 2}, dicarbide UC{sub 2} and free carbon. The main reaction can be written. U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO{sub 2} and UC{sub 2} can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO{sub 2} and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author) [French] L'etude cinetique des reactions U sol + CO{sub 2} gaz et U sol + CO gaz a ete effectuee par thermogravirnetrie sur une poudre d'uranium a grains spheriques, les domaines de temperature etudies s'etendant respectivement de 460 a 690 deg. C et de 570 a 850 deg. C. L'action du dioxyde de carbone conduit au dioxyde d'uranium UO{sub 2}; il se produit en meme temps un depot de carbone. La reaction globale resulte des deux reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C Le mono-oxyde de carbone conduit a un melange de dioxyde UO{sub 2}, de dicarbure UC{sub 2} et de carbone libre. La reaction principale s'ecrit: U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} Le carbone libre provient de la dismutation du mono-oxyde de carbone. On observe une separation remarquable des deux phases UO{sub 2} et UC{sub 2}; un mecanisme rendant compte de ce phenomene a

Activation Doppler Measurements on U 238 and U 235 in Some Fast Reactor Spectra

Energy Technology Data Exchange (ETDEWEB)

Tiren, L I; Gustafsson, I

1968-03-15

Measurements of the Doppler effect in U-238 capture and U-235 fission have been made by means of the activation technique in three different neutron spectra in the fast critical assembly FR0. The experiments involved the irradiation of thin uranium metal foils or oxide disks, which were heated in a small oven located at the core centre. The measurements on U-238 were extended to 1780 deg K and on U-235 to 1470 deg K. A core region surrounding the oven was homogenized in order to facilitate the interpretation of results. The reaction rates in the uranium samples were detected by gamma counting. The experimental method was checked with regard to systematic errors by irradiations in a thermal spectrum. The data obtained for U-238 capture were corrected for the effect of neutron collisions in the oven wall, and were extrapolated to zero sample thickness. In the softest spectrum (core 5) a Doppler effect (relative increase in capture rate) of 0.260 {+-} 0.018 was obtained on heating from 343 to 1780 deg K, and in the hardest spectrum (core 3) the corresponding value was 0.030 {+-} 0.003. An appreciable Doppler effect in U-235 fission was obtained only in the softest spectrum, in which the measured increase in fission rate on heating from 320 to 1470 deg K was 0.007 {+-} 0.003.

Acute skin reactions observed in fractionated proton irradiation

International Nuclear Information System (INIS)

Arimoto, Takuro; Maruhashi, Noboru; Takada, Yoshihisa; Hayakawa, Yoshinori; Inada, Tetsuo; Kitagawa, Toshio

1989-01-01

Between May 1985 and July 1987, 49 skin reactions of 43 patients treated by proton irradiation were observed at the Particle Radiation Medical Science Center (PARMS), the University of Tsukuba. Taking the peak skin score as an endpoint, the radiobiological effects [relative biological effectiveness (RBE) and time-dose relationship] of the proton beam in multi-fractionated treatments were estimated. Factors influencing the skin dose, such as the prescribed tumor dose, tumor site, and number of applied fields, were also analyzed. The following conclusions regarding acute skin reactions to the clinical use of proton irradiation were obtained: 1) the physical skin-sparing effect of proton irradiation in single-field irradiation, especially in superficial regions, is not large compared with that of high-energy photon irradiation; 2) multidirectional proton irradiation significantly reduced the skin dose and severity of acute reasons; 3) the radiobiological effects of the proton beam, RBE and the time factor, estimated in human skin in multi-fractional treatment were slightly smaller than those of X-rays, i.e., 0.92 and -0.25±0.09, respectively. (author)

Neutron scattering cross sections of uranium-238

International Nuclear Information System (INIS)

Beghian, L.E.; Kegel, G.H.R.; Marcella, T.V.; Barnes, B.K.; Couchell, G.P.; Egan, J.J.; Mittler, A.; Pullen, D.J.; Schier, W.A.

1979-01-01

The University of Lowell high-resolution time-of-flight spectrometer was used to measure angular distributions and 90-deg excitation functions for neutrons scattered from 238 U in the energy range from 0.9 to 3.1 MeV. This study was limited to the elastic and the first two inelastic groups, corresponding to states of 238 U at 45 keV (2 + ) and 148 keV (4 + ). Angular distributions were measured at primary neutron energies of 1.1, 1.9, 2.5, and 3.1 MeV for the same three neutron groups. Whereas the elastic data are in fair agreement with the evaluation in the ENDF/B-IV file, there is substantial disagreement between the inelastic measurements and the evaluated cross sections. 12 figures

The inflow of 234U and 238U from the River Odra drainage basin to the Baltic Sea

Directory of Open Access Journals (Sweden)

Bogdan Skwarzec

2010-12-01

Full Text Available In this study the activity of uranium isotopes 234U and 238U in Odra river water samples, collected from October 2003 to July2004, was measured using alpha spectrometry. The uranium concentrations were different in each of the seasons analysed; the lowest values were recorded in summer. In all seasons, uranium concentrations were the highest in Bystrzyca river waters (from 27.81 ± 0.29Bq m-3 of 234U and 17.82 ± 0.23 Bq m-3 of 238U in spring to 194.76 ± 3.43 Bq m-3 of 234U and 134.88 ± 2.85 Bq m-3 of 238U in summer. The lowest concentrations were noted in the Mała Panew (from 1.33 ± 0.02 Bq m-3 of 234U and 1.06 ± 0.02 Bq m-3 of 238U in spring to 3.52 ± 0.05 Bq m-3 of 234U and 2.59± 0.04 Bq m-3 of 238U in autumn. The uranium radionuclides 234U and 238U in the water samples were not in radioactive equilibrium. The 234U / 238U activity ratios were the highest in Odra water samples collected at Głogów (1.84 in autumn, and the lowest in water from the Noteć (1.03 in winter and spring. The 234U / 238U activity ratio decreases along the main stream of the Odra, owing to changes in the salinity of the river's waters. Annually, 8.19 tons of uranium (126.29 G Bq of 234U and 100.80 G Bq of 238U flow into the Szczecin Lagoon with Odra river waters.

Single proton transfer reactions on odd-even nuclei

International Nuclear Information System (INIS)

Blasi, N.

1984-01-01

This thesis is devoted to the study of one proton transfer reactions, performed with the use of the magnetic spectrograph QMG/2 of the KVI, in two regions of the mass table. Stripping and pickup reactions on the odd-A target nuclei 193 Ir and 197 Au are described in the first part. The experimental spectroscopic factors obtained are used to test several collective models that are based on coupling between bosons (phonons) and fermions. In the second part, the proton stripping reactions on 113 In and 115 In are studied. Shell model calculations are performed and applied to the experimental results. (Auth.)

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.)

Reactions of plutonium and uranium with water: Kinetics and potential hazards

International Nuclear Information System (INIS)

Haschke, J.M.

1995-12-01

The chemistry and kinetics of reactions between water and the metals and hydrides of plutonium and uranium are described in an effort to consolidate information for assessing potential hazards associated with handling and storage. New experimental results and data from literature sources are presented. Kinetic dependencies on pH, salt concentration, temperature and other parameters are reviewed. Corrosion reactions of the metals in near-neutral solutions produce a fine hydridic powder plus hydrogen. The corrosion rate for plutonium in sea water is a thousand-fold faster than for the metal in distilled water and more than a thousand-fold faster than for uranium in sea water. Reaction rates for immersed hydrides of plutonium and uranium are comparable and slower than the corrosion rates for the respective metals. However, uranium trihydride is reported to react violently if a quantity greater than twenty-five grams is rapidly immersed in water. The possibility of a similar autothermic reaction for large quantities of plutonium hydride cannot be excluded. In addition to producing hydrogen, corrosion reactions convert the massive metals into material forms that are readily suspended in water and that are aerosolizable and potentially pyrophoric when dry. Potential hazards associated with criticality, environmental dispersal, spontaneous ignition and explosive gas mixtures are outlined

The reaction of sintered aluminium products with uranium dioxide and monocarbide

DEFF Research Database (Denmark)

Lauritzen, T.; Knudsen, Per

1965-01-01

The compatibility of SAP 930 with uranium dioxide and uranium monocarbide was investigated in the temperature range 450–600° C. The results indicate that a severe reaction occurs between SAP 930 and UO2 within 8000 hours at 600° C, a slight reaction at 600° C for 1000 hours and after 11 900 hours...... at 525° C, and no reaction in 14 300 hours at 450° C. Of the three grades of UC tested (hot pressed, arc cast, cold pressed and sintered) the slightly substoichiometric, hot-pressed UC is judged to be least compatible with SAP 930, reaction occurring after 7300 hours at 450° C. No reaction was observed...... between SAP 930 and the other carbides at this temperature. All SAP−UC combinations are incompatible at 600° C for as little as 100 hours of heat treatment. Tests designed to study the effect of a diffusion barrier on the SAP−UC reaction have shown that anodized SAP 930 and the three uranium carbides...

Two-proton correlation functions in nuclear reactions

International Nuclear Information System (INIS)

Verde, G.

2001-01-01

Full text: Proton-proton correlation functions can be used to study the space-time characteristics of nuclear reactions. For very short-lived sources, the maximum value of the correlation at 20 MeV/c, due to the attractive nature of the S-wave phase shift, provides a unique measure of the size of the emitting source. For long-lived sources, the height of this maximum depends, in addition, on the life time of the source. In this talk, we investigate the common reaction scenario involving both fast dynamical as well as slower emissions from evaporation and/or secondary decays of heavy fragments. We show that the maximum at 20 MeV/c depends both on the source dimension and on the fraction of coincident proton pairs produced in the early stage of the reaction, dominated by fast dynamical preequilibrium emission. The width of the peak at 20 MeV/c, on the other hand, is uniquely correlated to the size of the source. Hence, the size of the emitting source must be extracted from the width or, even better, from the entire shape of the correlation peak, and not from the height. By numerically inverting the measured correlation function, we show that existing data determine only the shape of the fast dynamical source and that its size changes little with proton momenta, contrary to previous analyses with Gaussian sources of zero-lifetime. We further show that the well documented dramatic decrease in the correlation maximum with decreasing total proton momentum reflects directly a corresponding decrease in the fraction of contributing proton pairs from preequilibrium emissions. This provides a powerful method to decompose the proton spectrum into a fraction that originates from fast dynamical emission and a complimentary fraction that originates from slower evaporative emission or secondary decays. We discuss also the comparison of such correlations to transport theories and the generalizations of these techniques to correlations between composite particles. Such studies can

Uranium Metal Reaction Behavior in Water, Sludge, and Grout Matrices

Energy Technology Data Exchange (ETDEWEB)

Delegard, Calvin H.; Schmidt, Andrew J.

2009-05-27

This report summarizes information and data on the reaction behavior of uranium metal in water, in water-saturated simulated and genuine K Basin sludge, and in grout matrices. This information and data are used to establish the technical basis for metallic uranium reaction behavior for the K Basin Sludge Treatment Project (STP). The specific objective of this report is to consolidate the various sources of information into a concise document to serve as a high-level reference and road map for customers, regulators, and interested parties outside the STP (e.g., external reviewers, other DOE sites) to clearly understand the current basis for the corrosion of uranium metal in water, sludge, and grout.

Uranium Metal Reaction Behavior in Water, Sludge, and Grout Matrices

Energy Technology Data Exchange (ETDEWEB)

Delegard, Calvin H.; Schmidt, Andrew J.

2008-09-25

This report summarizes information and data on the reaction behavior of uranium metal in water, in water-saturated simulated and genuine K Basin sludge, and in grout matrices. This information and data are used to establish the technical basis for metallic uranium reaction behavior for the K Basin Sludge Treatment Project (STP). The specific objective of this report is to consolidate the various sources of information into a concise document to serve as a high-level reference and road map for customers, regulators, and interested parties outside the STP (e.g., external reviewers, other DOE sites) to clearly understand the current basis for the corrosion of uranium metal in water, sludge, and grout.

Uranium-series constraints on radionuclide transport and groundwater flow at the Nopal I uranium deposit, Sierra Pena Blanca, Mexico.

Science.gov (United States)

Goldstein, Steven J; Abdel-Fattah, Amr I; Murrell, Michael T; Dobson, Patrick F; Norman, Deborah E; Amato, Ronald S; Nunn, Andrew J

2010-03-01

Uranium-series data for groundwater samples from the Nopal I uranium ore deposit were obtained to place constraints on radionuclide transport and hydrologic processes for a nuclear waste repository located in fractured, unsaturated volcanic tuff. Decreasing uranium concentrations for wells drilled in 2003 are consistent with a simple physical mixing model that indicates that groundwater velocities are low ( approximately 10 m/y). Uranium isotopic constraints, well productivities, and radon systematics also suggest limited groundwater mixing and slow flow in the saturated zone. Uranium isotopic systematics for seepage water collected in the mine adit show a spatial dependence which is consistent with longer water-rock interaction times and higher uranium dissolution inputs at the front adit where the deposit is located. Uranium-series disequilibria measurements for mostly unsaturated zone samples indicate that (230)Th/(238)U activity ratios range from 0.005 to 0.48 and (226)Ra/(238)U activity ratios range from 0.006 to 113. (239)Pu/(238)U mass ratios for the saturated zone are 1000 times lower than the U mobility. Saturated zone mobility decreases in the order (238)U approximately (226)Ra > (230)Th approximately (239)Pu. Radium and thorium appear to have higher mobility in the unsaturated zone based on U-series data from fractures and seepage water near the deposit.

Uranium-series constraints on radionuclide transport and groundwater flow at the Nopal I uranium deposit, Sierra Pena Blanca, Mexico

International Nuclear Information System (INIS)

Goldstein, S.J.; Abdel-Fattah, A.I.; Murrell, M.T.; Dobson, P.F.; Norman, D.E.; Amato, R.S.; Nunn, A.J.

2009-01-01

Uranium-series data for groundwater samples from the Nopal I uranium ore deposit were obtained to place constraints on radionuclide transport and hydrologic processes for a nuclear waste repository located in fractured, unsaturated volcanic tuff. Decreasing uranium concentrations for wells drilled in 2003 are consistent with a simple physical mixing model that indicates that groundwater velocities are low (∼10 m/y). Uranium isotopic constraints, well productivities, and radon systematics also suggest limited groundwater mixing and slow flow in the saturated zone. Uranium isotopic systematics for seepage water collected in the mine adit show a spatial dependence which is consistent with longer water-rock interaction times and higher uranium dissolution inputs at the front adit where the deposit is located. Uranium-series disequilibria measurements for mostly unsaturated zone samples indicate that 230 Th/ 238 U activity ratios range from 0.005-0.48 and 226 Ra/ 238 U activity ratios range from 0.006-113. 239 Pu/ 238 U mass ratios for the saturated zone are -14 , and Pu mobility in the saturated zone is >1000 times lower than the U mobility. Saturated zone mobility decreases in the order 238 U∼ 226 Ra > 230 Th∼ 239 Pu. Radium and thorium appear to have higher mobility in the unsaturated zone based on U-series data from fractures and seepage water near the deposit.

Neutron-induced reactions on U and Th - A new approach via AMS

International Nuclear Information System (INIS)

Wallner, A.; Capote, R.; Christl, M.; Fifield, L.K.; Srncik, M.; Tims, S.; Hotchkis, M.; Krasa, A.; Lachner, J.; Lippold, J.; Plompen, A.; Semkova, V.; Steier, P.; Winkler, S.

2014-01-01

Recent studies exhibit discrepancies at keV and MeV energies between major nuclear data libraries for 238 U(n,γ), 232 Th(n,γ) and also for (n,xn) reactions. We have extended our initial (n,γ) measurements on 235,238 U to higher neutron energies and to additional reaction channels. Neutron-induced reactions on 232 Th and 238 U were measured by a combination of the activation technique and atom counting of the reaction products using accelerator mass spectrometry (AMS). Natural thorium and uranium samples were activated with quasi-monoenergetic neutrons at IRMM. Neutron capture data were produced for neutron energies between 0.5 and 5 MeV. Fast neutron-induced reactions were studied in the energy range from 17 to 22 MeV. Preliminary data indicate a fair agreement with data libraries; however at the lower band of existing data. This approach represents a complementary method to on-line particle detection techniques and also to conventional decay counting. (authors)

Light particle production in spallation reactions induced by protons of 0.8-2.5 GeV incident kinetic energy

International Nuclear Information System (INIS)

Herbach, Claus-Michael; Enke, Michael; Boehm, Andreas

2002-01-01

Absolute production cross sections have been measured simultaneously for neutrons and light charged particles in 0.8-2.5 GeV proton induced spallation reactions for a series of target nuclei from aluminum up to uranium. The high detection efficiency both for neutral and charged evaporative particles provides an event-wise access to the amount of projectile energy dissipated into nuclear excitation. Various intra nuclear cascade plus evaporation models have been confronted with the experimental data showing large discrepancies for hydrogen and helium production. (author)

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

η production in proton-nucleus reactions

International Nuclear Information System (INIS)

Cassing, W.; Batko, G.; Vetter, T.; Wolf, G.

1991-01-01

The production of η-mesons in proton-nucleus reactions is analysed with respect to primary nucleon-nucleon (NN→NN η ) and secondary pion-nucleon (πN→ηN) production processes on the basis of Hartree-Fock groundstate momentum distributions and free on-shell production processes. The folding model adopted compares well for meson production with more involved simulations based on VUU transport equations. Similar to K + production in proton-nucleus reactions the η-mesons are primarily produced by the πN→ηN channel. However, η-mesons are absorbed in nuclei via excitation of the N * (1535) resonance which leads to strong distortions of the primordial spectra. On the other hand, the experimental mass dependence of the differential cross sections might yield information about the in-medium properties of this resonance. (orig.)

Performance evaluation of indigenous thermal ionization mass spectrometer for determination of 235U/238U atom ratios

International Nuclear Information System (INIS)

Alamelu, D.; Parab, A.R.; Sasi Bhushan, K.; Shah, Raju V.; Jagdish Kumar, S.; Rao, Radhika M.; Aggarwal, S.K.; Bhatia, R.K.; Yadav, V.K.; Sharma, Madhavi P.; Tulsyan, Puneet; Chavda, Pradip; Sriniwasan, P.

2014-07-01

A magnetic sector based Thermal Ionization Mass Spectrometer (TIMS) designed and developed at Technical Physics Division, B.A.R.C., was evaluated for its performance for the determination of 235 U/ 238 U atom ratios in uranium samples. This consisted of evaluating the precision and accuracy on the 235 U/ 238 U atom ratios in various isotopic reference materials as well as indigenously generated uranium samples. The results obtained by the indigenous TIMS were also compared with those obtained using a commercially available TIMS system. The internal and external precision were found to be around 0.1% for determining 235 U/ 238 U atom ratios close to those of natural uranium ( i.e. 0.00730). (author)

Uranium-series disequilibria as a means to study recent migration of uranium in a sandstone-hosted uranium deposit, NW China

International Nuclear Information System (INIS)

Min Maozhong; Peng Xinjian; Wang Jinping; Osmond, J.K.

2005-01-01

Uranium concentration and alpha specific activities of uranium decay series nuclides 234 U, 238 U, 230 Th, 232 Th and 226 Ra were measured for 16 oxidized host sandstone samples, 36 oxic-anoxic (mineralized) sandstone samples and three unaltered primary sandstone samples collected from the Shihongtan deposit. The results show that most of the ores and host sandstones have close to secular equilibrium alpha activity ratios for 234 U/ 238 U, 230 Th/ 238 U, 230 Th/ 234 U and 226 Ra/ 230 Th, indicating that intensive groundwater-rock/ore interaction and uranium migration have not taken place in the deposit during the last 1.0 Ma. However, some of the old uranium ore bodies have locally undergone leaching in the oxidizing environment during the past 300 ka to 1.0 Ma or to the present, and a number of new U ore bodies have grown in the oxic-anoxic transition (mineralized) subzone during the past 1.0 Ma. Locally, uranium leaching has taken place during the past 300 ka to 1.0 Ma, and perhaps is still going on now in some sandstones of the oxidizing subzone. However, uranium accumulation has locally occurred in some sandstones of the oxidizing environment during the past 1 ka to 1.0 Ma, which may be attributed to adsorption of U(VI) by clays contained in oxidized sandstones. A recent accumulation of uranium has locally taken place within the unaltered sandstones of the primary subzone close to the oxic-anoxic transition environment during the past 300 ka to 1.0 Ma. Results from the present study also indicate that uranium-series disequilibrium is an important tool to trace recent migration of uranium occurring in sandstone-hosted U deposits during the past 1.0 Ma and to distinguish the oxidation-reduction boundary

Reaction of uranium and plutonium carbides with nitrogen; Reaction avec l'azote des carbures d'uranium et de plutonium

Energy Technology Data Exchange (ETDEWEB)

Lorenzelli, R; Martin, A; Schickel, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1966-03-01

Uranium and plutonium carbides react with nitrogen during the grinding process preceding the final sintering. The reaction occurs even in argon atmospheres containing a few percent of residual nitrogen. The resulting contamination is responsible for the appearance of an equivalent quantity of higher carbide in the sintered products; nitrogen remains quantitatively in the monocarbide phase. UC can be transformed completely into nitride under a nitrogen pressure, at a temperature as low as 400 C. The reaction is more sluggish with PuC. The following reactions take places: UC + 0,8 N{sub 2} {yields}> UN{sub 1.60} + C and PuC + 0,5 N{sub 2} {yields} PuN + C. (authors) [French] Les carbures d'uranium et de plutonium reagissent avec l'azote au cours du broyage qui precede le frittage final. Cette reaction est sensible meme sous des atmospheres d'argon ne contenant que quelques pour cent d'azote. Cette contamination se traduit sur les produits frittes par l'apparition d'une quantite equivalente de carbure superieur, l'azote restant fixe quantitativement dans la phase monocarbure. On peut transformer entierement UC en nitrure par action de l'azote sous pression des 400 C. La reaction est plus difficile avec PuC. Les reactions sont les suivantes: UC + 0,8 N{sub 2} {yields} UN{sub 1.60} + C et PuC + 0,5 N{sub 2} {yields} PuN + C.

Uranium isotopic ratio measurements ({sup 235}U/{sup 238}U) by laser ablation high resolution inductively coupled plasma mass spectrometry for environmental radioactivity monitoring - {sup 235}U/{sup 238}U isotope ratio analysis by LA-ICP-MS-HR for environmental radioactivity monitoring

Energy Technology Data Exchange (ETDEWEB)

David, K.; Mokili, M.B.; Rousseau, G.; Deniau, I.; Landesman, C. [SUBATECH, Ecole des Mines de Nantes, Universite de Nantes, CNRS/IN2P3, 4 rue Alfred Kastler, 44307 Nantes cedex 3 (France)

2014-07-01

The protection of the aquatic and terrestrial environments from a broad range of contaminants spread by nuclear activities (nuclear plants, weapon tests or mining) require continuous monitoring of long-lives radionuclides that were released into the environment. The precise determination of uranium isotope ratios in both natural and potential contaminated samples is of primary concern for the nuclear safeguards and the control of environmental contamination. As an example, analysis of environmental samples around nuclear plants are carried out to detect the traces in the environment originating from nuclear technology activities. This study deals with the direct analysis of {sup 235}U/{sup 238}U isotope ratios in real environmental solid samples performed with laser ablation (LA)-HR-ICP-MS. A similar technique has already been reported for the analysis of biological samples or uranium oxide particles [1,2] but to our knowledge, this was never applied on real environmental samples. The high sensitivity, rapid acquisition time and low detection limits are the main advantages of high resolution ICP-MS for accurate and precise isotope ratio measurements of uranium at trace and ultra-trace levels. In addition, the use of laser ablation allows the analysis of solid samples with minimal preparation. A a consequence, this technique is very attractive for conducting rapid direct {sup 235}U/{sup 238}U isotope ratio analysis on a large set of various matrix samples likely to be encountered in environmental monitoring such as corals, soils, sands, sediments, terrestrial and marine bio-indicators. For the present study, LA-ICP-MS-HR analyses are performed using a New Wave UP213 nano-second Nd:YAG laser coupled to a Thermo Element-XR high resolution mass spectrometer. Powdered samples are compacted with an hydraulic press (5 tons) in order to obtain disk-shaped pellet (10-13 mm in diameter and 2 mm in thickness). The NIST612 reference glass is used for LA-ICP-MS-HR tuning and as

Uranium-series constraints on radionuclide transport and groundwater flow at the Nopal I uranium deposit, Sierra Pena Blanca, Mexico

Energy Technology Data Exchange (ETDEWEB)

Goldstein, S.J.; Abdel-Fattah, A.I.; Murrell, M.T.; Dobson, P.F.; Norman, D.E.; Amato, R.S.; Nunn, A. J.

2009-10-01

Uranium-series data for groundwater samples from the Nopal I uranium ore deposit were obtained to place constraints on radionuclide transport and hydrologic processes for a nuclear waste repository located in fractured, unsaturated volcanic tuff. Decreasing uranium concentrations for wells drilled in 2003 are consistent with a simple physical mixing model that indicates that groundwater velocities are low ({approx}10 m/y). Uranium isotopic constraints, well productivities, and radon systematics also suggest limited groundwater mixing and slow flow in the saturated zone. Uranium isotopic systematics for seepage water collected in the mine adit show a spatial dependence which is consistent with longer water-rock interaction times and higher uranium dissolution inputs at the front adit where the deposit is located. Uranium-series disequilibria measurements for mostly unsaturated zone samples indicate that {sup 230}Th/{sup 238}U activity ratios range from 0.005-0.48 and {sup 226}Ra/{sup 238}U activity ratios range from 0.006-113. {sup 239}Pu/{sup 238}U mass ratios for the saturated zone are <2 x 10{sup -14}, and Pu mobility in the saturated zone is >1000 times lower than the U mobility. Saturated zone mobility decreases in the order {sup 238}U{approx}{sup 226}Ra > {sup 230}Th{approx}{sup 239}Pu. Radium and thorium appear to have higher mobility in the unsaturated zone based on U-series data from fractures and seepage water near the deposit.

Determination of uranium concentrations and "2"3"4U/"2"3"8U activity ratio in some granitic rock samples by alpha spectrometry: application of a radiochemical procedure

International Nuclear Information System (INIS)

Khattab, Mahmoud R.

2016-01-01

The present study is an application of a radiochemical procedure using alpha spectrometry technique for determination of uranium isotopes "2"3"8U, "2"3"4U and "2"3"5U on 13 granitic samples. These samples were collected from Gabal Gattar area, Northeastern Desert, Egypt. The collected samples were digested using microwave technique with aqua regia and spiked with "2"3"2U for chemical yield and activity calculation. Separation of uranium isotopes from the samples was done by Dowex 1 x 4 (50-100 mesh) resin followed by source preparation using microprecipitation technique. The concentrations of "2"3"8U were ranged between 28.9±0.9 and 134.8±1.8 Bq/g, and the "2"3"4U concentrations were between 24±0.6 and 147.7±2.2 Bq/g. For the "2"3"5U, the activity concentrations were between 1.3±0.2 and 6.7±1.2 Bq/g. The activity ratio of "2"3"4U/"2"3"8U was calculated and varied from 0.80 to 1.30. (author)

Development of AN Active 238UF6 Gas Target

Science.gov (United States)

Eckardt, C.; Enders, J.; Freudenberger, M.; Göök, A.; von Neumann-Cosel, P.; Oberstedt, A.; Oberstedt, S.

2014-09-01

Detailed studies of the fission process, e.g., the search for parity nonconservation (PNC) effects, the energy dependence of fission modes or the population of fission isomers, depend on high quality data, therefore requiring high luminosities. An active gas target containing uranium may overcome the deterioration of energy and angular resolution caused by large solid target thicknesses. A single Frisch-grid ionization chamber has been built to test a mixture of standard counting gases (e.g., argon) with depleted uranium hexafluoride (238UF6), utilizing a triple alpha source to evaluate signal quality and drift velocity. For mass fractions of up to 4 percent of 238U the drift velocity increases with rising UF6 content, while a good signal quality and energy resolution is preserved.

Study on the surface reaction of uranium metal in hydrogen atmosphere with XPS

International Nuclear Information System (INIS)

Wang Xiaolin; Fu Yibei; Xie Renshou; Zuo Changming; Zhao Chunpei; Chen Hong

1998-01-01

The surface reactions of uranium metal in hydrogen atmosphere at 25 degree C and 200 degree C and effects of temperature and carbon monoxide to the hydriding reaction have been studied by X-ray photoelectron spectroscopy (XPS). The reaction between H 2 and uranium metal at 25 degree C leads to the further oxidation of surface layer of metal due to traces of water vapor. At 200 degree C, it may lead to the hydriding reaction of uranium and the hydriding increases with increasing exposure to H 2 in the initial stages. The U4f 7/2 binding energy of UH 3 has been found to be 378.6 eV. Investigation indicates carbon monoxide inhibits both the hydriding reaction and oxidation on the condition of H 2 -CO atmosphere

Photon and proton induced fission on heavy nuclei at intermediate energies

Directory of Open Access Journals (Sweden)

Andrade-II E.

2014-04-01

Full Text Available We present an analysis of fission induced by intermediate energy protons or photons on actinides. The 660 MeV proton induced reactions are on 241Am, 238U, and 237Np targets and the Bremmstrahlung-photons with end-point energies at 50 MeV and 3500 MeV are on 232Th and 238U targets. The study was performed by means of the Monte Carlo simulation code CRISP. A multimodal fission extension was added to the code within an approach which accounts for the contribution of symmetric and asymmetric fission. This procedure allowed the investigation of fission cross sections, fissility, number of evaporated nucleons and fission-fragment charge distributions. The comparison with experimental data show a good agreement between calculations and experiments.

Investigation of the fission fragment properties of the reaction 238U(N,F) at incident neutron energies up to 5.8 MeV

International Nuclear Information System (INIS)

Vives, F.

1998-01-01

The 238 U(n,f) reaction has been studied at various incident neutrons energies from 1,2 at 5,8 MeV. The author shows that the vibrational resonances presence in the cross section threshold area and the protons parity effect, lead to variations in the fission fragments properties. The mass, the total kinetic energy (TKE) and the fragments angular distribution have been obtained thanks a ionisation double chamber use. Mass function changes in the mass and kinetic energy distributions and their respectively contributions to the TKE variations, have also been studied. The two-dimension distributions adjustments mass-TKE have been compared to the theoretical calculus, compiled with the multi-modal random neck-rupture model: two solutions are possible. Meanwhile, only one leads to significant physical interpretation in terms of layers effects. (A.L.B.)

Kinetic study of the reaction of uranium with various carbon-containing gases

International Nuclear Information System (INIS)

Feron, G.

1963-09-01

The kinetic study of the reaction U + CO 2 and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO 2 → UO 2 + 2 CO U + CO 2 → UO 2 + C The reaction with carbon monoxide leads to a mixture of dioxide UO 2 , dicarbide UC 2 and free carbon. The main reaction can be written. U + CO → 1/2 UO 2 + 1/2 UC 2 The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO 2 and UC 2 can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO 2 and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author) [fr

Fixation and reduction of uranium by natural organic matter: reaction mechanisms and kinetics

International Nuclear Information System (INIS)

Nakashima, S.; Perruchot, A.; Trichet, J.; Disnar, J.R.

1987-01-01

The reactivity of lignite towards soluble uranyl species in an aqueous medium is experimentally investigated as a function of temperature (between 20 0 C and 400 0 C). The fixation process starts near 45 0 C, with reduction beginning around 120 0 C. The fixation process leads to the formation of chemically and thermally stable organo-uranyl species. The reduction of free uranyl species is accompanied by a stoichiometric (2:1) liberation of protons into the medium. These protons originate from the organic matter which thus undergoes dehydrogenation. The general evolution of the carbonaceous residue in the course of this reaction shows that alcoholic and aliphatic hydrocarbon groups are responsible for the reduction. This chemical dehydrogenation could explain the low hydrogen content of natural organic materials associated with uraniferous deposits. The kinetics of the reduction step have been studied at 180 0 C, 190 0 C and 200 0 C. The kinetic parameters determined over this temperature range, and the extrapolation made to 20 0 C, show that reduction can be a crucial process in the geochemical behaviour of uranium especially in the thermal conditions in which sedimentary basins evolve [fr

Investigation of (n, 2n) reaction and fission rates in iron-shielded uranium samples bombarded by 14.9 MeV neutrons

International Nuclear Information System (INIS)

Shani, G.

1976-01-01

The effect of the thickness of iron shielding on the (n, 2n) reaction rate in a fusion reactor (hybrid) blanket is investigated. The results are compared with the fission rate-dependence. Samples of natural uranium are irradiated with 14 MeV neutrons, with iron slabs of various thickness between the neutron generator target and the samples. Both reactions are threshold reactions but the fact that the 238 U (n, 2n) reaction threshold is at 6 MeV and that of fission is at 2 MeV makes the ratio between the two very much geometry-dependent. Two geometrical effects take place, the 1/r 2 and the build-up. While the build-up affects the (n, 2n) reaction rate, the fission rate is affected more by the 1/r 2 effect. The reason is that both elastic and inelastic scattering end up with neutrons with energy above fission threshold, while only elastic scattering brings high energy neutrons to the sample and causes (n, 2n) reaction. A comparison is made with calculated results where the geometrical effects do not exist. (author)

Sintering with a chemical reaction as applied to uranium monocarbide; Frittage-reaction dans le cas du monocarbure d'uranium

Energy Technology Data Exchange (ETDEWEB)

Accary, A; Caillat, R [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1960-07-01

The present paper provides a survey of different investigations whose aim was the preparation and fabrication of uranium monocarbide for nuclear use. If a chemical reaction takes place in the sample during the sintering operation, it may be expected that the atom rearrangements involved in this reaction should favour the sintering process and thereby lower the temperature needed to yield a body of a given density. With this hypothesis in mind, the following methods have been studied: - Sintering of U-C mixtures; - Sintering of UO{sub 2}-C mixtures; - Hot pressing of U-C mixtures; - Extrusion of U-C mixtures. To generalize our result, it could be said that a chemical reaction does not lead to high densification, if one depends on a simple contact between discrete particles. On the contrary, a chemical reaction can help sintering if, as our hot pressing experiments shows, the densification can be achieved prior to the reaction. (author) [French] Le present article resume les etudes faites pour le compte du Commissariat a l'Energie Atomique dans le but de preparer du monocarbure d'uranium pour usage nucleaire. Si, en meme temps que l'on fritte une poudre, celle-ci est le siege d'une reaction chimique, on peut s'attendre a ce que le rearrangement atomique d'une reaction chimique favorise le frittage et, ainsi abaisse la temperature de travail necessaire pour obtenir une densite donnee. Nous avons etudie les methodes suivantes: - frittage des melanges U-C; - frittage des melanges UO{sub 2}-C; - frittage sous charge des melanges U-C; - filage des melanges U-C. Nos resultats montrent qu'une reaction chimique en cours de frittage ne conduit pas a un produit de haute densite si on opere sur un melange de poudres. Par contre, elle permet d'atteindre de hautes densites si la densification peut etre obtenue avant la reaction chimique. (auteur)

Reactions of laser ablated uranium with nitrogen studied using matrix isolation spectroscopy

International Nuclear Information System (INIS)

Sankaran, K.; Sundararajan, K.; Viswanathan, K.S.

1999-01-01

Unusual reactions were found to occur when uranium was laser ablated in the presence of nitrogen. The reaction products were trapped in a rigid inert gas matrix and studied using infrared spectroscopy. The species formed were strongly dependent on the partial pressure of nitrogen in the matrix gas used during the ablation process; at low nitrogen partial pressures uranium dinitride (NUN) was the major reaction product, while at high partial pressures of nitrogen the mononitride, UN, was the predominant product. (author)

Uranium reactions with water vapor. Final progress report

International Nuclear Information System (INIS)

Condon, J.B.; Cristy, S.S.; Kirkpatrick, J.R.

1983-01-01

The reaction kinetics and ion microprobe mass analyzer (IMMA) depth-profile data for water-oxygen-uranium reaction is explained in terms of the perfusive-precipitation model. This model is reviewed extensively enough to deal with this interacting, 3-element reaction system. The model, based on simultaneous diffusion and product precipitation, can be applied to several systems in a parameterless fashion. It is applied to the uranium-water reaction in the absence and presence of the oxygen inhibitor. The results of the calculations of the model are compared to the experimental rates and the IMMA depth profiles obtained when 18 O-labeled water is used. The predictions are excellent for the pressure dependence of the rates, the activation energies for both the oxygen-poisoned and oxygen-free reactions, the absolute rates for the oxygen-poisoned case, and the IMMA depth profiles. The prediction of the absolute rate for the oxygen-free case is only within a factor of five due to the approximations made for the thermodynamics of the product layer that fixes the oxygen activity. Comparison of the model to experimental data for other metal-oxidation systems such as iron, silicon, copper, zirconium with oxygen, and thorium with water, is also presented to lend credibility to the modeling technique

Isotope effects for base-promoted, gas-phase proton transfer reactions

International Nuclear Information System (INIS)

Grabowski, J.J.; Cheng, Xueheng

1991-01-01

Proton transfer reactions are among the most basic, the most common and the most important of chemical transformations; despite their apparent simplicity, much is unknown about this most fundamental of all chemical processes. Active interest in understanding the underlying principles of organic proton transfer reactions continues because of efforts being made to develop the theory of elementary chemical processes, because of the resurgence of interest in mechanistic organic chemistry and because of the resurgence of interest in mechanistic organic chemistry processes, because of the resurgence of interest in mechanistic organic chemistry and because of the dynamic role played by proton transfers in biochemical transformations. As organic chemists, the authors have used the flowing afterglow technique to gain an appreciation of the fundamental issues involved in reaction mechanisms by examining such processes in a solvent-free environment under thermally-equilibrated (300 K) conditions. Recent characterization of the facile production of both acetate and the monoenolate anion from the interaction of hydroxide or fluoride with acetic acid reinforces the idea that much yet must be learned about proton transfers/proton abstractions in general. Earlier work by Riveros and co-workers on competitive H vs D abstraction from α-d 1 -toluenes and by Noest and Nibbering on competitive H vs D abstraction from α,α,α-d 3 -acetone, in combination with the acetic acid results, challenged the author's to assemble a comprehensive picture of the competitive nature of proton transfer reactions for anionic base-promoted processes

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

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.)

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.)

222Rn content and 234U/238U activity ratio in groundwaters

International Nuclear Information System (INIS)

Olguin, M.T.; Segovia, N.; Ordonez, E.; Iturbe, J.L.; Bulbulian, S.; Carrillo, J.

1990-01-01

Geochemical radioanalytical studies of ground water were perfomed in the valleys of Villa de Reyes and San Luis Potosi, Mexico. The experiments were designed to measure radon and uranium content and 234 U/ 238 U activity ratio in ground water samples taken from wells in these sites and at the Nuclear Center of Salazar, Mexico. 222 Rn content varied depending on the sample source, reaching a maximum value of 235 pCi/l; uranium concentration results were less than 1 μg/l and 234 U/ 238 U activity ratios were close to equilibrium. (author) 9 refs.; 1 fig.; 1 tab

Quasifree electrofission of 238U

International Nuclear Information System (INIS)

Likhachev, V.P.; Deppman, A.; Hussein, M.S.; Mesa, J.; Arruda-Neto, J.D.T.; Carlson, B.V.; Nesterenko, V.O.; Garcia, F.; Rodriguez, O.

2002-01-01

We present the result of a theoretical study of the quasifree electrofission of 238 U. The exclusive differential cross sections for the quasifree scattering reaction stage have been calculated in plane wave impulse approximation, using a macroscopic-microscopic approach for the description of the proton bound states. The nuclear shape was parametrized in terms of Cassinian ovoids. The equilibrium deformation parameters have been calculated by minimizing the total nuclear energy. In the calculation the axially deformed Woods-Saxon single-particle potential was used. The obtained single-particle momentum distributions were averaged over the nuclear symmetry axis direction. The occupation numbers were calculated in the BCS approach. The fissility for the single-hole excited states of the residual nucleus 237 Pa was calculated on the statistical theory grounds, both without taking into account the preequilibrium emission of the particle and with preequilibrium emission in the framework of the exciton model

New Oxime Ligand with Potential for Proton-Coupled Electron-Transfer Reactions

DEFF Research Database (Denmark)

Deville, Claire; Sundberg, Jonas; McKenzie, Christine Joy

Proton-coupled electron-transfer (PCET) is found in a range of oxidation-reduction reactions in biology.1 This mechanism is of interest for applications in energy conversion processes. The PCET reaction has been shown to be facilitated when the proton is transferred to an intramolecular basic sit...

Application of 234U/238U isotope ratio data for the study of geochemical problems associated with local water sources from Aguas da Prata (SP, Brazil)

International Nuclear Information System (INIS)

Bonotto, D.M.

1982-01-01

The uranium-238, uranium-234 and radon content of spring waters of Aguas da Prata (SP) - Platina, Paiol, Villela, Sao Bento, Prata-Radioativa, Prata-Nova, Boi, Vitoria and Prata-Antiga - was found; the activity ratio AR ( 234 U/ 238 U) was applied to the geochemistry of local water sources. The uranium analysis procedure consisted of the following steps: adition of 232 U- 228 Th spike to the samples, coprecipitation with iron, iron extraction with organic solvent, separation on anion-exchange resin, extraction with TTA, deposition on stainless steel disc and determination of uranium content by alpha spectrometry. The uranium-238 content changed from 0,10 to 11,56 ppb (average value = 2,3 ppb). The higher values were observed for the waters circulating through sandstones and the lower through volcanic rocks. The inverse correlation (r sub(s) =-0,76) between pH and uranium-238 content confirmed the contribution of this factor on its solubility. The significative correlation r sub(s) = 0,76 between dissolved oxygen and uranium-238 content also confirmed the higher uranium on the more oxidizing zones. The AR changed from 2,84 to 11,68 (average value = 6). These values defined the regional aquifer systems as mineralized in uranium. The higher AR were observed for the deep groundwaters and the lower for the shallow one. Because the 238 U→ 234 Th decay, the 234 Th ejection to the solution was confirmed as the most important factor responsible for the extreme observed isotopic fractionation. (Author) [pt

Hydro geochemistry of uranium in Aguas de Lindoia (Sao Paulo State)

International Nuclear Information System (INIS)

Silveira, E.G. da.

1992-01-01

A preliminary investigation concerning to the geochemical behaviour of uranium isotopes ( 233 U and 238 U) was performed on spring waters for Aguas de Lindoia city, Sao Paulo State. The reason for this study is because the natural radioactivity of these waters is poorly known, and no uranium content data have been published. Measurements of Uranium-238 contents and 234 U/ 238 U activity ratios in groundwaters were performed on the following springs issuing in the urban area from Aguas de Lindoia: Levissima I, Levissima II, Beleza, Sao Roque, Lindalia and Santa Izabel. (author)

Limitations on the precision of 238U/235U measurements and implications for environmental monitoring

International Nuclear Information System (INIS)

Russ III, G.P.

1997-01-01

The ability to determine the isotopic composition of uranium in environmental samples is an important component of the International Atomic Energy Agency's (IAEA) safeguards program, and variations in the isotopic ratio 238 U/ 235 U provide the most direct evidence of isotopic enrichment activities. The interpretation of observed variations in 238 U/ 235 U depends on the ability to distinguish enrichment from instrumental biases and any variations occurring in the environment but not related to enrichment activities. Instrumental biases that have historically limited the accuracy of 238 U/ 235 U determinations can be eliminated by the use of the 233 U/ 236 U double-spike technique. With this technique, it is possible to determine the 238 U/ 235 U in samples to an accuracy equal to the precision of the measurement, ca. 0.1% for a few 10's of nanograms of uranium. Given an accurate determination of 238 U/ 235 U, positive identification of enrichment activities depends on the observed value being outside the range of 238 U/ 235 U's expected as a result of natural or environmental variations. Analyses of a suite of soil samples showed no variation beyond 0.2% in 238 U/ 235 U

Photon and proton induced fission on heavy nuclei at intermediate energies

Energy Technology Data Exchange (ETDEWEB)

Andrade-II, E.; Karapetyan, G.S.; Deppman, A.; Guimaraes, V. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Fisica; Balabekyan, A.R. [Yerevan State University, Alex Manoogian 1, Yerevan (Armenia); Demekhina, N.A. [Yerevan Physics Institute, Alikhanyan Brothers 2, Yerevan (Armenia); Joint Institute for Nuclear Research (JINR), Flerov Laboratory of Nuclear Reactions (LNR), Moscow (Russian Federation)

2014-07-01

We present an analysis of fission induced by intermediate energy protons or photons on actinides. The 660 MeV proton induced reactions are on {sup 241}Am, {sup 238}U, and {sup 237}Np targets and the Bremsstrahlung-photons with end-point energies at 50 MeV and 3500 MeV are on {sup 232}Th and {sup 238}U targets. The study was performed by means of the Monte Carlo simulation code CRISP. A multimodal fission extension was added to the code within an approach which accounts for the contribution of symmetric and asymmetric fission. This procedure allowed the investigation of fission cross sections, fissility, number of evaporated nucleons and fission-fragment charge distributions. The comparison with experimental data show a good agreement between calculations and experiments. (author)

Gastrointestinal absorption of uranium in man

International Nuclear Information System (INIS)

Larsen, R.P.; Orlandini, K.A.

1984-01-01

A method has been established for determining the fractional absorption of uranium directly in man. Measurements are made of the urinary excretion rates of uranium for individuals whose drinking water has a high 234 U to 238 U activity ratio and is the primary source of 234 U in their diets. For two individuals, the values obtained for the fractional absorption of 234 U were 0.004 and 0.006. The values obtained for the fractional absorption of 238 U, using a literature value for the 238 U intake from food, were 0.008 and 0.015. The present ICRP value is 0.20. 7 references, 1 table

Experimental Cross Sections for Reactions of Heavy Ions and 208Pb, 209Bi, 238U, and 248Cm Targets

International Nuclear Information System (INIS)

Patin, Joshua B.

2002-01-01

The study of the reactions between heavy ions and 208 Pb, 209 Bi, 238 U, and 248 Cm targets was performed to look at the differences between the cross sections of hot and cold fusion reactions. Experimental cross sections were compared with predictions from statistical computer codes to evaluate the effectiveness of the computer code in predicting production cross sections. Hot fusion reactions were studied with the MG system, catcher foil techniques and the Berkeley Gas-filled Separator (BGS). 3n- and 4n-exit channel production cross sections were obtained for the 238 U( 18 O,xn) 256-x Fm, 238 U( 22 Ne,xn) 260-x No, and 248 Cm( 15 N,xn) 263-x Lr reactions and are similar to previous experimental results. The experimental cross sections were accurately modeled by the predictions of the HIVAP code using the Reisdorf and Schaedel parameters and are consistent with the existing systematics of 4n exit channel reaction products. Cold fusion reactions were examined using the BGS. The 208 Pb( 48 Ca,xn) 256-x No, 208 Pb( 50 Ti,xn) 258-x Rf, 208 Pb( 51 V,xn) 259-x Db, 209 Bi( 50 Ti,xn) 259-x Db, and 209 Bi( 51 V,xn) 260-x Sg reactions were studied. The experimental production cross sections are in agreement with the results observed in previous experiments. It was necessary to slightly alter the Reisdorf and Schaedel parameters for use in the HIVAP code in order to more accurately model the experimental data. The cold fusion experimental results are in agreement with current 1n- and 2n-exit channel systematics

Fluorination reaction uranium dioxide by fluorine

International Nuclear Information System (INIS)

Ogata, Shinji; Homma, Shunji; Koga, Jiro; Matsumoto, Shiro; Sasahira, Akira; Kawamura, Fumio

2004-01-01

Kinetics of the fluorination reaction of uranium dioxide is studied using un-reacted core model with shrinking particles. The model includes the film mass transfer of fluorine gas and its diffusion in the particle. The rate constants of the model are determined by fitting the experimental data for 370-450degC. The model successfully represents the fluorination in this temperature range. The rate control step is identified by examining the rate constants of the model for 300-1,800degC. For temperature range up to 900degC, the fluorination reaction is rate controlling. For over 900degC, both mechanisms of the mass transfer of fluorine and the fluorination reaction control the rate of the fluorination. With further increase of the temperature, however, the fluorination reaction becomes so fast that the mass transfer of fluorine eventually controls the rate of the fluorination. (author)

Uranium-238 and thorium-232 series concentrations in soil, radon-222 indoor and drinking water concentrations and dose assessment in the city of Alameda, Chihuahua, Mexico

Energy Technology Data Exchange (ETDEWEB)

Colmenero Sujo, L.; Montero Cabrera, M.E. E-mail: elena.montero@cimav.edu.mx; Villalba, L.; Renteria Villalobos, M.; Torres Moye, E.; Garcia Leon, M.; Garcia-Tenorio, R.; Mireles Garcia, F.; Herrera Peraza, E.F.; Sanchez Aroche, D

2004-07-01

High-resolution gamma spectrometry was used to determine the concentration of {sup 40}K, {sup 238}U and {sup 232}Th series in soil samples taken from areas surrounding the city of Aldama, in Chihuahua. Results of indoor air short-time sampling, with diffusion barrier charcoal detectors, revealed relatively high indoor radon levels, ranging from 29 to 422 Bq/m{sup 3}; the radon concentrations detected exceeded 148 Bq/m{sup 3} in 76% of the homes tested. Additionally, liquid scintillation counting showed concentrations of radon in drinking water ranging from 4.3 to 42 kBq/m{sup 3}. The high activity of {sup 238}U in soil found in some places may be a result of the uranium milling process performed 20 years ago in the area. High radon concentrations indoor and in water may be explained by assuming the presence of uranium-bearing rocks underneath of the city, similar to a felsic dike located near Aldama. The estimated annual effective dose of gamma radiation from the soil and radon inhalation was 3.83 mSv.

Uranium-238 and thorium-232 series concentrations in soil, radon-222 indoor and drinking water concentrations and dose assessment in the city of Aldama, Chihuahua, Mexico.

Science.gov (United States)

Colmenero Sujo, L; Montero Cabrera, M E; Villalba, L; Rentería Villalobos, M; Torres Moye, E; García León, M; García-Tenorio, R; Mireles García, F; Herrera Peraza, E F; Sánchez Aroche, D

2004-01-01

High-resolution gamma spectrometry was used to determine the concentration of 40K, 238U and 232Th series in soil samples taken from areas surrounding the city of Aldama, in Chihuahua. Results of indoor air short-time sampling, with diffusion barrier charcoal detectors, revealed relatively high indoor radon levels, ranging from 29 to 422 Bq/m3; the radon concentrations detected exceeded 148 Bq/m3 in 76% of the homes tested. Additionally, liquid scintillation counting showed concentrations of radon in drinking water ranging from 4.3 to 42 kBq/m3. The high activity of 238U in soil found in some places may be a result of the uranium milling process performed 20 years ago in the area. High radon concentrations indoor and in water may be explained by assuming the presence of uranium-bearing rocks underneath of the city, similar to a felsic dike located near Aldama. The estimated annual effective dose of gamma radiation from the soil and radon inhalation was 3.83 mSv.

Kinetics of gaseous uranium hexafluoride reaction with hydrogen chloride

International Nuclear Information System (INIS)

Ezubchenko, A.N.; Ilyukhin, A.I.; Merzlyakov, A.V.

1993-01-01

Kinetics of decrease of concentration of gaseous uranium hexafluoride in reaction with hydrogen chloride at temperatures close to room ones, was investigated by the method of IR spectroscopy. It was established that the process represented the first order reaction by both UF 6 and HCl. Activation energy of the reaction was determined: 7.6 ± 0.7 kcal/mol. Specific feature of reaction kinetics was noted: inversely proportional dependence of effective constant on UF 6 initial pressure. 5 refs., 3 figs

Compound Nucleus Reactions in LENR, Analogy to Uranium Fission

Science.gov (United States)

Hora, Heinrich; Miley, George; Philberth, Karl

2008-03-01

The discovery of nuclear fission by Hahn and Strassmann was based on a very rare microanalytical result that could not initially indicate the very complicated details of this most important process. A similarity is discussed for the low energy nuclear reactions (LENRs) with analogies to the yield structure found in measurements of uranium fission. The LENR product distribution measured earlier in a reproducible way in experiments with thin film electrodes and a high density deuteron concentration in palladium has several striking similarities with the uranium fission fragment yield curve.ootnotetextG.H. Miley and J.A. Patterson, J. New Energy 1, 11 (1996); G.H. Miley et al, Proc ICCF6, p. 629 (1997).This comparison is specifically focussed to the Maruhn-Greiner local maximum of the distribution within the large-scale minimum when the fission nuclei are excited. Implications for uranium fission are discussed in comparison with LENR relative to the identification of fission a hypothetical compound nuclear reaction via a element ^306X126 with double magic numbers.

Dynamics of Db isotopes formed in reactions induced by 238U, 248Cm, and 249Bk across the Coulomb barrier

Science.gov (United States)

Kaur, Gurjit; Sandhu, Kirandeep; Kaur, Amandeep; Sharma, Manoj K.

2018-05-01

The dynamical cluster decay model is employed to investigate the decay of *265Db and *267Db nuclei, formed in the 27Al+238U , 18O+249Bk , and 19F+248Cm hot fusion reactions at energies around the Coulomb barrier. First, the fission dynamics of the 27Al+238U reaction is explored by investigating the fragmentation and preformation yield of the reaction. The symmetric mass distribution of the fission fragments is observed for *265Db nucleus, when static β2 i deformations are used within hot optimum orientation approach. However, the mass split gets broaden for the use of β2 i-dynamical hot configuration of the fragments and becomes clearly asymmetric for the cold-static-deformed approach. Within the application of cold orientations of fragments, a new fission channel is observed at mass asymmetry η =0.29 . In addition to 238U-induced reaction, the work is carried out to address the fission and neutron evaporation cross sections of *267Db nucleus formed via 19F+248Cm and 18O+249Bk reactions, besides a comprehensive analysis of fusion and capture processes. Higher fusion cross sections and compound nucleus formation probabilities (PCN) are obtained for the 18O+249Bk reaction, as larger mass asymmetry in the entrance channel leads to reduced Coulomb factor. Finally, the role of sticking (IS) and nonsticking (INS) moments of inertia is analyzed for the 4 n and 5 n channels of *267Db nuclear system.

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

Statistical analysis of parameters of the uranium -238 resonances

International Nuclear Information System (INIS)

Nikolaev, M.N.; Abagyan, L.P.

1976-01-01

It has been shown that the distribution for 238 U p - levels can be in agreement with the theoretical one (Porter - Thomas distribution) only if the significant lack of p - levels in the experiments would be supposed. That means that density of 238 U levels with spin 1/2 is parity dependent, and therefore the whole number of p - resonances is 4.8 (instead of 3) times greater than the number of s - resonances in the same energy internal. With the assumption about spin dependence of strength function it is impossible to agree the experimental distribution with the theoretical one

Uranium and the use of depleted uranium in weaponry; L'uranium et les armes a l'uranium appauvri

Energy Technology Data Exchange (ETDEWEB)

Roussel, R

2000-07-01

In this brief report the author shows that the use of shells involving a load of depleted uranium might lead to lasting hazards to civil population and environment. These hazards come from the part of the shell that has been dispersed as contaminating radioactive dusts. The author describes some features of radioactivity and highlights the role of Uranium-238 as a provider of energy to the planet. (A.C.)

Protonation Reaction of Benzonitrile Radical Anion and Absorption of Product

DEFF Research Database (Denmark)

Holcman, Jerzy; Sehested, Knud

1975-01-01

The rate constant for the protonation of benzonitrile radical anions formed in pulse radiolysis of aqueous benzonitrile solutions is (3.5 ± 0.5)× 1010 dm3 mol–1 s–1. A new 270 nm absorption band is attributed to the protonated benzonitrile anion. The pK of the protonation reaction is determined t...

Uranium geochemistry and dating of Pacific island apatite

Energy Technology Data Exchange (ETDEWEB)

Roe, K K; Burnett, W C [Florida State Univ., Tallahassee (USA). Dept. of Oceanography

1985-07-01

Uranium-series disequilibrium dating of island phosphate deposits is evaluated in terms of known associated coral ages, uranium geochemistry, and stratigraphic sequences as well as the concordance between the geochronometers /sup 234/U//sup 238/U, /sup 230/Th//sup 234/U and /sup 226/Ra//sup 238/U. U(VI) is the predominant oxidation state of uranium in island phosphorites and by analogy to the youngest surficial deposits, most of the uranium initially bound is in the form of U(VI) sorbed by surfaces from seawater. Insular deposits contain more organic matter than even very young ocean floor samples and this leads to a greater probability of reduction of available recoil uranium than occurs in marine deposits. As a consequence, R(VI) <= R(T) <= R(VI), where R represents the /sup 234/U//sup 238/U activity ratio. This situation is completely opposite from that observed for marine-origin phosphorites. We determined that a fraction of U(VI) in ancient insular phosphorites is very labile and lost to alkaline carbonate solutions with a uranium activity ratio even more depleted in /sup 234/U than the bulk R(VI). The results are discussed.

Parallel proton transfer pathways in aqueous acid-base reactions

NARCIS (Netherlands)

Cox, M.J.; Bakker, H.J.

2008-01-01

We study the mechanism of proton transfer (PT) between the photoacid 8-hydroxy-1,3, 6-pyrenetrisulfonic acid (HPTS) and the base chloroacetate in aqueous solution. We investigate both proton and deuteron transfer reactions in solutions with base concentrations ranging from 0.25M to 4M. Using

Bimolecular reactions of carbenes: Proton transfer mechanism

Science.gov (United States)

Abu-Saleh, Abd Al-Aziz A.; Almatarneh, Mansour H.; Poirier, Raymond A.

2018-04-01

Here we report the bimolecular reaction of trifluoromethylhydroxycarbene conformers and the water-mediated mechanism of the 1,2-proton shift for the unimolecular trans-conformer by using quantum chemical calculations. The CCSD(T)/cc-pVTZ//MP2/cc-pVDZ potential-energy profile of the bimolecular reaction of cis- and trans-trifluoromethylhydroxycarbene, shows the lowest gas-phase barrier height of 13 kJ mol-1 compared to the recently reported value of 128 kJ mol-1 for the unimolecular reaction. We expect bimolecular reactions of carbene's stereoisomers will open a valuable field for new and useful synthetic strategies.

A kinetic study of the reaction of water vapor and carbon dioxide on uranium

International Nuclear Information System (INIS)

Santon, J.P.

1964-09-01

The kinetic study of the reaction of water vapour and carbon dioxide with uranium has been performed by thermogravimetric methods at temperatures between 160 and 410 deg G in the first case, 350 and 1050 deg C in the second: Three sorts of uranium specimens were used: uranium powder, thin evaporated films, and small spheres obtained from a plasma furnace. The experimental results led in the case of water vapour, to a linear rate of reaction controlled by diffusion at the lower temperatures, and by a surface reaction at the upper ones. In the case of carbon dioxide, a parabolic law has been found, controlled by diffusional processes. (author) [fr

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 )

Proton exchange in acid–base complexes induced by reaction coordinates with heavy atom motions

International Nuclear Information System (INIS)

Alavi, Saman; Taghikhani, Mahdi

2012-01-01

Highlights: ► Proton exchange in acid–base complexes is studied. ► The structures, binding energies, and normal mode vibrations are calculated. ► Transition state structures of proton exchange mechanism are determined. ► In the complexes studied, the reaction coordinate involves heavy atom rocking. ► The reaction coordinate is not simply localized in the proton movements. - Abstract: We extend previous work on nitric acid–ammonia and nitric acid–alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid–strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are −1 . This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm −1 . Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.

Advances in heterogeneous autocatalytic reactions applied to uranium dissolution - 5317

International Nuclear Information System (INIS)

Marc, P.; Magnaldo, A.; Godard, J.; Schaer, E.

2015-01-01

Dissolution and the solubilization of the chemical elements is a milestone of the head-end of hydrometallurgical processes. When dissolving spent nuclear fuels, additional constraints are added due to the permanent need to strictly control and limit the hold-up. Thus the need for kinetic modeling concerning the dissolution of spent nuclear fuels in nitric acid. This study aims at better understanding the chemical and physical-chemical phenomena of uranium dioxide dissolution reactions in nitric medium. It has been documented that the nitric acid attack of sintering-manufactured uranium dioxide solids occurs through preferential attack sites. This non uniform attack leads to the development of cracks in the solids. Optical microscopy observations show that in some cases, the development of these cracks can lead to the solid cleavage. In this case, we show that the dissolution of the detached fragments is much slower than the time required for the complete cleavage of the solid. These points motivated the measurements of dissolution kinetics using optical microscopy and image processing. A comparison of the measured kinetics with the diffusion kinetics by the mean of the external resistance fraction allows discriminating between measured kinetics corresponding to the chemical reaction or mass-transport limitation. This capability to measure, for the very first time, the 'true' chemical kinetics of the reaction has enabled the confirmation of the highly autocatalytic nature of the reaction, and first evaluation of the constants of the chemical reactions kinetic laws. These data are fundamental to set the kinetic parameters of the chemical reactions in a future model of the dissolution of uranium dioxide sintered pellets. (authors)

The distribution of depleted uranium contamination in Colonie, NY, USA

International Nuclear Information System (INIS)

Lloyd, N.S.; Chenery, S.R.N.; Parrish, R.R.

2009-01-01

Uranium oxide particles were dispersed into the environment from a factory in Colonie (NY, USA) by prevailing winds during the 1960s and '70s. Uranium concentrations and isotope ratios from bulk soil samples have been accurately measured using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) without the need for analyte separation chemistry. The natural range of uranium concentrations in the Colonie soils has been estimated as 0.7-2.1 μg g -1 , with a weighted geometric mean of 1.05 μg g -1 ; the contaminated soil samples comprise uranium up to 500 ± 40 μg g -1 . A plot of 236 U/ 238 U against 235 U/ 238 U isotope ratios describes a mixing line between natural uranium and depleted uranium (DU) in bulk soil samples; scatter from this line can be accounted for by heterogeneity in the DU particulate. The end-member of DU compositions aggregated in these bulk samples comprises (2.05 ± 0.06) x 10 -3235 U/ 238 U, (3.2 ± 0.1) x 10 -5236 U/ 238 U, and (7.1 ± 0.3) x 10 -6234 U/ 238 U. The analytical method is sensitive to as little as 50 ng g -1 DU mixed with the natural uranium occurring in these soils. The contamination footprint has been mapped northward from site, and at least one third of the uranium in a soil sample from the surface 5 cm, collected 5.1 km NNW of the site, is DU. The distribution of contamination within the surface soil horizon follows a trend of exponential decrease with depth, which can be approximated by a simple diffusion model. Bioturbation by earthworms can account for dispersal of contaminant from the soil surface, in the form of primary uranium oxide particulates, and uranyl species that are adsorbed to organic matter. Considering this distribution, the total mass of uranium contamination emitted from the factory is estimated to be c. 4.8 tonnes.

The distribution of depleted uranium contamination in Colonie, NY, USA

Energy Technology Data Exchange (ETDEWEB)

Lloyd, N.S., E-mail: nsl3@alumni.leicester.ac.uk [Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom); Chenery, S.R.N. [British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG (United Kingdom); Parrish, R.R. [Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom); NERC Isotope Geosciences Laboratory, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG (United Kingdom)

2009-12-20

Uranium oxide particles were dispersed into the environment from a factory in Colonie (NY, USA) by prevailing winds during the 1960s and '70s. Uranium concentrations and isotope ratios from bulk soil samples have been accurately measured using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) without the need for analyte separation chemistry. The natural range of uranium concentrations in the Colonie soils has been estimated as 0.7-2.1 {mu}g g{sup -1}, with a weighted geometric mean of 1.05 {mu}g g{sup -1}; the contaminated soil samples comprise uranium up to 500 {+-} 40 {mu}g g{sup -1}. A plot of {sup 236}U/{sup 238}U against {sup 235}U/{sup 238}U isotope ratios describes a mixing line between natural uranium and depleted uranium (DU) in bulk soil samples; scatter from this line can be accounted for by heterogeneity in the DU particulate. The end-member of DU compositions aggregated in these bulk samples comprises (2.05 {+-} 0.06) x 10{sup -3235}U/{sup 238}U, (3.2 {+-} 0.1) x 10{sup -5236}U/{sup 238}U, and (7.1 {+-} 0.3) x 10{sup -6234}U/{sup 238}U. The analytical method is sensitive to as little as 50 ng g{sup -1} DU mixed with the natural uranium occurring in these soils. The contamination footprint has been mapped northward from site, and at least one third of the uranium in a soil sample from the surface 5 cm, collected 5.1 km NNW of the site, is DU. The distribution of contamination within the surface soil horizon follows a trend of exponential decrease with depth, which can be approximated by a simple diffusion model. Bioturbation by earthworms can account for dispersal of contaminant from the soil surface, in the form of primary uranium oxide particulates, and uranyl species that are adsorbed to organic matter. Considering this distribution, the total mass of uranium contamination emitted from the factory is estimated to be c. 4.8 tonnes.

Precise 238U(n,2n)237U reaction cross-section measurements using the activation facility at TUNL

Science.gov (United States)

Krishichayan, Fnu; Bhike, M.; Tornow, W.

2014-09-01

Accurate neutron-induced 238U(n,2n)237U reaction data are required for many practical applications, especially in the field of nuclear energy, including advanced heavy water reactors, where 238U is used as the breeding material to regenerate the fissile material 239Pu. Precise (n,2n) cross-section measurements of 238U are underway at TUNL with mono-energetic neutrons in the 8.0 to 14.0 MeV energy range in steps of 0.25 MeV using the activation technique. After activation of the 0.5 inch diameter and 442 mg 238U foil, the activity of the 208 keV characteristic γ-line is tracked for 6 weeks with a high efficient HPGe clover detector to determine the initial activity needed for the cross-section determination. Results of the cross-section measurements, determined relative to 27Al and 197Au neutron activation monitor foils, and the comparison with theoretical models will be presented during the meeting.

Interest of uranium complexes for the mechanism study of the McMurry reaction; Interet des complexes de l`uranium pour l`etude du mecanisme de la reaction de McMurry

Energy Technology Data Exchange (ETDEWEB)

Maury, O

1997-07-04

The reducing coupling reactions of ketones in diols and olefins are generally carried out with titanium or samarium compounds. In this work uranium complexes have been used. They have allowed to study the chemical reaction mechanism. This thesis is divided into three parts: 1) the reduction mechanism of uranium tetrachloride by cyclic voltametry has been studied at first. It has been shown that this reduction is followed by a transfer reaction of chlorides between the reduced specie of the higher electronic density and UCl . 2) In the second part is described: the synthesis, the crystal structure, the reactivity of the chemical agents, the stereochemistry of diols and alkenes formation and the pinacolisation reaction catalysis. 3) In the last part, the limits of the McMurry reaction are given by the study of the aromatic ketones pinacolisation reaction by-products. The obtained results show that the complexes of the metals which present a high reducing and oxo-philic (Ti, Sm, U..) character react in a similar way with the carbonyl compounds. If the uranium compounds are less used than those of the titanium in the field of the organic synthesis applications, they are precious auxiliaries and excellent models for reactions mechanisms study and for the synthesis methods optimization. (O.M.). 284 refs.

Proton-induced fission of actinides at energies 26.5 and 62.9 MeV--Theoretical interpretation

International Nuclear Information System (INIS)

Demetriou, P.; Keutgen, Th.; Prieels, R.; El Masri, Y.

2011-01-01

Fission properties of proton-induced fission on 232 Th, 237 Np, 238 U, 239 Pu and 241 Am targets, measured at the Louvain-la-Neuve cyclotron facility at proton energies of 26.5 and 62.9 MeV, are compared with the predictions of the state-of-the-art nuclear reaction code TALYS. The sensitivity of the calculations to the input parameters of the code and possible improvements are discussed.

A review of the rates of reaction of unirradiated uranium in gaseous atmospheres

International Nuclear Information System (INIS)

Pearce, R.J.

1989-10-01

The review collates available quantitative rate data for the reaction of unirradiated uranium in dry and moist air, steam and carbon dioxide based atmospheres at temperatures ranging from room temperature to above the melting point of uranium. Reactions in nitrogen and carbon monoxide are also considered. The aim of the review is to provide a compilation of base data for the hazard analysis of fault conditions relating to Magnox fuel. (author)

Reaction of nickel with uranium mononitride; Reaction du nickel avec le nitrure d'uranium

Energy Technology Data Exchange (ETDEWEB)

Anselin, F; Calais, D; Lorenzelli, N; Passefort, J C [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1965-07-01

UN-Ni system has been investigated in solid phase by diffusion couples UN-Ni or by mixed powders pressed and sintered. Studies have been carried out by micrography, X-rays and microanalysis with a CASTAING microprobe. UN-Ni compatibility is quite good up to 600 C; beyond this temperature diffusion zones corresponding to UNi{sub 5} and U{sub 2}N{sub 3} appear in the couples either reaction : 3 U N + 5 Ni {yields} U{sub 2}N{sub 3} + UNi{sub 5}; UN + 5 Ni {yields} UNi{sub 5}+ 1/2 N{sub 2} takes place from 700 C according to nitrogen pressure involved. For temperatures between 800 and 1000 C nickel solubility in uranium nitride is 1500 {+-} 500 wt ppm. (authors) [French] Le systeme UN-Ni a ete etudie par diffusion en phase solide a partir de couples (UN-Ni) ou de melanges pulverulents presses et frittes. Les techniques utilisees sont la micrographie, les rayons X et l'analyse ponctuelle a la microsonde de CASTAING. La compatibilite UN-Ni est bonne jusqu'a 600 C; au-dela il apparait dans les couples de diffusion des zones correspondant a UNi{sub 5} et U{sub 2}N{sub 3}. L'une ou l'autre des deux reactions: 3UN + 5 Ni {yields} U{sub 2}N{sub 3} + UNi{sub 5}; UN + 5 Ni {yields} UNi{sub 5} + 1/2 N{sub 2} se produisant des 700 C suivant la pression d'azote exercee. La solubilite du nickel dans le nitrure d'uranium pour des temperatures comprises entre 800 et 1000 C est de 1500 {+-} 500 ppm en poids. (auteurs)

Fission properties of actinide nuclei from proton-induced fission at 26.5 and 62.9 MeV incident proton energies

International Nuclear Information System (INIS)

Demetriou, P.; Keutgen, Th.; Prieels, R.; El Masri, Y.

2010-01-01

Fission properties of proton-induced fission on 232 Th, 237 Np, 238 U, 239 Pu, and 241 Am targets, measured at the Louvain-la-Neuve cyclotron facility at proton energies of 26.5 and 62.9 MeV, are compared with the predictions of the state-of-the-art nuclear reaction code talys. The code couples the multimodal random neck-rupture model with the pre-equilibrium exciton and statistical models to predict fission fragment mass yields, pre- and post-scission neutron multiplicities, and total fission cross sections in a consistent approach. The sensitivity of the calculations to the input parameters of the code and possible improvements are discussed in detail.

The Determination of the Half-Life of U{sup 238} by Absolute Counting of {alpha} Particles in a 4 {pi}-Liquid Scintillation Counter; Determination de la periode de l'U{sup 238} au moyen du comptage absolu de particules {alpha} dans un comtpeur 4 {pi} a scintillateur liquide; Opredelenie perioda poluraspadda U{sup 238} posredstvom absolyutnogo scheta {alpha}-chastits v zhidkostnom stsintillyatsionnom schetchike 4 {pi}; Determinacion del periodo del U{sup 238} por recuento absoluto de las particulas {alpha} con un contador 4 {pi} de centelleador liquido

Energy Technology Data Exchange (ETDEWEB)

Steyn, J; Strelow, F W. E. [Council of Scientific and Industrial Research, Pretoria (South Africa)

1960-06-15

The specific activity of natural uranium was determined by liquid scintillation {alpha}-counting. Uranium was extracted from its decay products by methyl isobutyl ketone extraction and samples of this solution were added directly to the liquid scintillator. A quantitative investigation was made of the separation of uranium from thorium by the extraction method employed. Assuming that U{sup 238} and U{sup 234} were in equilibrium, and correcting for the presence of U{sup 235}, the specific activity and the half-life of the isotope U{sup 238} were calculated. (author) [French] L'activite specifique de l'uranium naturel est determinee au moyen d'un comptage a par scintillateur liquide. L'uranium est separe de ses produits de desintegration par une extraction a la methylisobutylceton e et des echantillons de cette solution sont ajoutes directement au scintillateur liquide. On fait une etude quantitative de la separation de l'uranium et du thorium par le procede d'extraction utilise. En admettant que U{sup 238} et U{sup 234} sont en equilibre et en faisant la correction voulue pour tenir compte de la presence de U{sup 235}, on calcule l'activite specifique et la periode de U{sup 238}. (author) [Spanish] La actividad especifica del uranio natural se determino con un contador {alpha} de centelleador liquido. El uranio se separo de productes de desintegracion por extraccion con metilisobutilcetona, y muestras de esta solucion se anadieron directamente al centelleador liquido. Se estudio cuantitativament e el grado de separacion uranio/torio alcanzado con el metodo de extraccion empleado. Introduciendo correcciones para tener en cuenta la presencia de U{sup 235}, se calculo la actividad especifica y el periodo de semidesintegracio n del U{sup 238} suponiendo que este isotopo se encontraba en equilibrio con el U{sup 234}. (author) [Russian] Spetsificheskaya aktivnost' estestvennogo urana byla opredelena s pomoshch'yu zhidkostnogo stsintillyatsionnog o schetchika {alpha

Distribution of nuclear charge in the proton-induced fission of Th-232

Energy Technology Data Exchange (ETDEWEB)

Pate, B D [Brookhaven National Laboratory, Upton, New York (United States); Foster, J S; Yaffe, L [McGill Univ., Montreal, Quebec (Canada)

1958-09-15

A great deal of work has been done on the distribution of nuclear mass in the fission process. About the nuclear charge distribution less is known. Data exist on the distribution from the fission of U-235 with thermal neutrons and with 14 Mev neutrons. Data also exist for the fission of uranium by 170 Mev protons, of bismuth by 190 Mev deuterons, and of uranium, thorium and bismuth by 480 Mev protons, and there is fragmentary information from other systems. The present work was undertaken to investigate the changes that occur in the charge distribution from proton-induced fission of Th-232 as the bombarding energy is raised from 8 to 90 Mev, the maximum proton energy of the McGill synchrocyclotron. This energy range is of interest in view of the substantial changes observed in the mass distribution. Also in this interval a change presumably begins in the nature of the initial step in nuclear reactions, from simple compound-nucleus formation, to a mechanism of direct interaction with individual nucleons. Thus at the lower energies studied, excitation of the nuclei at the end of the first step of the reaction will be essentially monochromatic whereas at the higher end of the bombarding-energy range, a broad spectrum of excitation energies will be produced, with corresponding complexity of the reaction products observed. (author)

Uranium and the use of depleted uranium in weaponry

International Nuclear Information System (INIS)

Roussel, R.

2000-01-01

In this brief report the author shows that the use of shells involving a load of depleted uranium might lead to lasting hazards to civil population and environment. These hazards come from the part of the shell that has been dispersed as contaminating radioactive dusts. The author describes some features of radioactivity and highlights the role of Uranium-238 as a provider of energy to the planet. (A.C.)

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

Chapter 1. General information about uranium. 1.10. Uranium application

International Nuclear Information System (INIS)

Khakimov, N.; Nazarov, Kh.M.; Mirsaidov, I.U.

2011-01-01

Full text: Metallic uranium or its compounds are used as nuclear fuel in nuclear reactors. A natural or low-enriched admixture of uranium isotopes is applied in stationery reactors of nuclear power plants, and products of a high enrichment degree are used in nuclear power plants or in reactors that operates with fast neutrons. 235 U is a source of nuclear energy in nuclear weapons. Depleted uranium is used as armour-piercing core in bombshells. 238 U serves as a source of secondary nuclear fuel - plutonium. (author)

Chapter 1. General information about uranium. 1.10. Uranium application

International Nuclear Information System (INIS)

Khakimov, N.; Nazarov, Kh.M.; Mirsaidov, I.U.

2012-01-01

Full text: Metallic uranium or its compounds are used as nuclear fuel in nuclear reactors. A natural or low-enriched admixture of uranium isotopes is applied in stationery reactors of nuclear power plants, and products of a high enrichment degree are used in nuclear power plants or in reactors that operates with fast neutrons. 235 U is a source of nuclear energy in nuclear weapons. Depleted uranium is used as armour-piercing core in bombshells. 238 U serves as a source of secondary nuclear fuel - plutonium.

A model for consecutive spallation and fragmentation reactions in inverse kinematics at relativistic energies

International Nuclear Information System (INIS)

Napolitani, P.; Tassan-Got, L.; Bernas, M.; Armbruster, P.

2003-04-01

Secondary reactions induced by relativistic beams in inverse kinematics in a thick target are relevant in several fields of experimental physics and technology, like secondary radioactive beams, production of exotic nuclei close to the proton drip line, and cross-section measurements for applications of spallation reactions for energy production and incineration of nuclear wastes. A general mathematical formulation is presented and successively applied as a tool to disentangle the primary reaction yields from the secondary production in the measurement of fission of a 238 U projectile impinging on a proton target at the energy of 1 A GeV. (orig.)

Interest of uranium complexes for the mechanism study of the McMurry reaction

International Nuclear Information System (INIS)

Maury, O.

1997-01-01

The reducing coupling reactions of ketones in diols and olefins are generally carried out with titanium or samarium compounds. In this work uranium complexes have been used. They have allowed to study the chemical reaction mechanism. This thesis is divided into three parts: 1) the reduction mechanism of uranium tetrachloride by cyclic voltametry has been studied at first. It has been shown that this reduction is followed by a transfer reaction of chlorides between the reduced specie of the higher electronic density and UCl . 2) In the second part is described: the synthesis, the crystal structure, the reactivity of the chemical agents, the stereochemistry of diols and alkenes formation and the pinacolisation reaction catalysis. 3) In the last part, the limits of the McMurry reaction are given by the study of the aromatic ketones pinacolisation reaction by-products. The obtained results show that the complexes of the metals which present a high reducing and oxo-philic (Ti, Sm, U..) character react in a similar way with the carbonyl compounds. If the uranium compounds are less used than those of the titanium in the field of the organic synthesis applications, they are precious auxiliaries and excellent models for reactions mechanisms study and for the synthesis methods optimization. (O.M.)

Quantification of 235U and 238U activity concentrations for undeclared nuclear materials by a digital gamma-gamma coincidence spectroscopy.

Science.gov (United States)

Zhang, Weihua; Yi, Jing; Mekarski, Pawel; Ungar, Kurt; Hauck, Barry; Kramer, Gary H

2011-06-01

The purpose of this study is to investigate the possibility of verifying depleted uranium (DU), natural uranium (NU), low enriched uranium (LEU) and high enriched uranium (HEU) by a developed digital gamma-gamma coincidence spectroscopy. The spectroscopy consists of two NaI(Tl) scintillators and XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The results demonstrate that the spectroscopy provides an effective method of (235)U and (238)U quantification based on the count rate of their gamma-gamma coincidence counting signatures. The main advantages of this approach over the conventional gamma spectrometry include the facts of low background continuum near coincident signatures of (235)U and (238)U, less interference from other radionuclides by the gamma-gamma coincidence counting, and region-of-interest (ROI) imagine analysis for uranium enrichment determination. Compared to conventional gamma spectrometry, the method offers additional advantage of requiring minimal calibrations for (235)U and (238)U quantification at different sample geometries. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Free energy for protonation reaction in lithium-ion battery cathode materials

International Nuclear Information System (INIS)

Benedek, R.; Thackeray, M. M.; van de Walle, A.

2008-01-01

Calculations are performed of free energies for proton-for-lithium-ion exchange reactions in lithium-ion battery cathode materials. First-principles calculations are employed for the solid phases and tabulated ionization potential and hydration energy data for aqueous ions. Layered structures, spinel LiMn 2 O 4 , and olivine LiFePO 4 are considered. Protonation is most favorable energetically in layered systems, such as Li 2 MnO 3 and LiCoO 2 . Less favorable are ion-exchange in spinel LiMn 2 O 4 and LiV 3 O 8 . Unfavorable is the substitution of protons for Li in olivine LiFePO 4 , because of the large distortion of the Fe and P coordination polyhedra. The reaction free energy scales roughly linearly with the volume change in the reaction

Uranium concentrations in sediments of the Suez Canal

International Nuclear Information System (INIS)

Ibrahiem, N.M.; Pimpl, M.

1994-01-01

Suez Canal bottom sediment samples have been analyzed by alpha-spectrometry for the measurement of uranium. This method is based on the extraction of uranium with trioctylphosphine oxide/cyclohexane (TOPO) followed by reextraction and separation on anion exchange resins, and finally electrodeposition. The α-activity of 238 U and 234 U were measured by surface barrier detectors, in Bq/kg dry weight. The obtained results were compared with concentrations determined by γ measurements. The results point to a state of disequilibrium between 238 U and RaeU (radium equivalent uranium) which is attributed to the escape of radon. (author)

Temporal behavior of {sup 222}Radon, {sup 226}Radium and {sup 238}Uranium in deep water wells which provide Valle de Toluca with drinking water; Comportamiento temporal de {sup 222}Radon, {sup 226}Radio y {sup 238}Uranio en pozos profundos que abastecen de agua potable al Valle de Toluca

Energy Technology Data Exchange (ETDEWEB)

Pena, P; Tamez, E; Iturbe, J L; Acosta, A; Segovia, N [Instituto Nacional de Investigaciones Nucleares, Mexico City (Mexico); Carrillo, J; Armienta, M [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Geofisica

1994-12-31

The presence of radionuclides in underground waters may be an indication of its origin and also the sign of the hydraulic properties of the aquifers layers where circulate. Additionally, the ingestion by human beings of water with radioactive elements (Radon 222, Radium 226, Uranium 238) can give as a result the accumulation of such elements in several organs of the body producing then health damages. In this work, the concentrations of Radon 222, Radium 226 and Uranium 238, in waters coming from deep wells which provide with drinking water the Toluca Valley, were determined. For this purpose, during a year (june 1991 to August 1992) ten wells were sampled with a tracking of the radionuclides concentration as well as the physical-chemical components of water; it was established the relationship presented by the analyzed waters with the local geology and the local and regional systems. (Author).

Comparison of the simulated diffusion of 238U and 234U isotopes with profile data from granite fractures

International Nuclear Information System (INIS)

Latham, A.G.

1991-01-01

The observed profiles of uranium content and 234 U/ 238 U activity ratios as they vary with distance into the rock at a granite fracture wall have been interpreted using a simple diffusion-sorption model. For simplicity, the model assumes a linear reversible isotherm. Using simple constraints, it has been possible to estimate long-term values appropriate for the distribution coefficient, K d for uranium in granite. A potential constraint on the uranium K d value is provided by the 234 U/ 238 U activity ratio variations. However, natural 234 U/ 238 U activity ratios seldom change monotonically with distance and it is suspected that they are the result, to some extent, of later uranium removal. To take this approach further, corresponding physical rock property data and closer sampling in the fracture profiles would be required. Estimates of K d are in the range 0.1 to 10 m 3 kg -1 , and are in agreement with the upper part of the range obtained from laboratory experiments. (author)

Influence of Proton Acceptors on the Proton-Coupled Electron Transfer Reaction Kinetics of a Ruthenium-Tyrosine Complex.

Science.gov (United States)

Lennox, J Christian; Dempsey, Jillian L

2017-11-22

A polypyridyl ruthenium complex with fluorinated bipyridine ligands and a covalently bound tyrosine moiety was synthesized, and its photo-induced proton-coupled electron transfer (PCET) reactivity in acetonitrile was investigated with transient absorption spectroscopy. Using flash-quench methodology with methyl viologen as an oxidative quencher, a Ru 3+ species is generated that is capable of initiating the intramolecular PCET oxidation of the tyrosine moiety. Using a series of substituted pyridine bases, the reaction kinetics were found to vary as a function of proton acceptor concentration and identity, with no significant H/D kinetic isotope effect. Through analysis of the kinetics traces and comparison to a control complex without the tyrosine moiety, PCET reactivity was found to proceed through an equilibrium electron transfer followed by proton transfer (ET-PT) pathway in which irreversible deprotonation of the tyrosine radical cation shifts the ET equilibrium, conferring a base dependence on the reaction. Comprehensive kinetics modeling allowed for deconvolution of complex kinetics and determination of rate constants for each elementary step. Across the five pyridine bases explored, spanning a range of 4.2 pK a units, a linear free-energy relationship was found for the proton transfer rate constant with a slope of 0.32. These findings highlight the influence that proton transfer driving force exerts on PCET reaction kinetics.

Two-proton transfer reactions on even Ni and Zn isotopes

International Nuclear Information System (INIS)

Boucenna, A.; Kraus, L.; Linck, I.; Tsan Ung Chan

1988-01-01

Two-proton transfer reactions induced by 112 MeV 12 C ions on even Ni and Zn isotopes are found to be less selective than the analogous two-neutron transfer reactions induced on the same targets in a similar incident energy range. The additional collective aspects observed in the proton transfer are examined in view of a semiphenomenological model of two quasi-particles coupled to a triaxial asymmetric rotor. Tentative spin and parity assignments emerge from this comparison, from crude shell model calculations and from systematic trends

Validation of the U-238 inelastic scattering neutron cross section through the EXCALIBUR dedicated experiment

Directory of Open Access Journals (Sweden)

Leconte Pierre

2017-01-01

Full Text Available EXCALIBUR is an integral transmission experiment based on the fast neutron source produced by the bare highly enriched fast burst reactor CALIBAN, located in CEA/DAM Valduc (France. Two experimental campaigns have been performed, one using a sphere of diameter 17 cm and one using two cylinders of 17 cm diameter 9 cm height, both made of metallic Uranium 238. A set of 15 different dosimeters with specific threshold energies have been employed to provide information on the neutron flux attenuation as a function of incident energy. Measurements uncertainties are typically in the range of 0.5–3% (1σ. The analysis of these experiments is performed with the TRIPOLI4 continuous energy Monte Carlo code. A calculation benchmark with validated simplifications is defined in order to improve the statistical convergence under 2%. Various 238U evaluations have been tested: JEFF-3.1.1, ENDF/B-VII.1 and the IB36 evaluation from IAEA. A sensitivity analysis is presented to identify the contribution of each reaction cross section to the integral transmission rate. This feedback may be of interest for the international effort on 238U, through the CIELO project.

Validation of the U-238 inelastic scattering neutron cross section through the EXCALIBUR dedicated experiment

Science.gov (United States)

Leconte, Pierre; Bernard, David

2017-09-01

EXCALIBUR is an integral transmission experiment based on the fast neutron source produced by the bare highly enriched fast burst reactor CALIBAN, located in CEA/DAM Valduc (France). Two experimental campaigns have been performed, one using a sphere of diameter 17 cm and one using two cylinders of 17 cm diameter 9 cm height, both made of metallic Uranium 238. A set of 15 different dosimeters with specific threshold energies have been employed to provide information on the neutron flux attenuation as a function of incident energy. Measurements uncertainties are typically in the range of 0.5-3% (1σ). The analysis of these experiments is performed with the TRIPOLI4 continuous energy Monte Carlo code. A calculation benchmark with validated simplifications is defined in order to improve the statistical convergence under 2%. Various 238U evaluations have been tested: JEFF-3.1.1, ENDF/B-VII.1 and the IB36 evaluation from IAEA. A sensitivity analysis is presented to identify the contribution of each reaction cross section to the integral transmission rate. This feedback may be of interest for the international effort on 238U, through the CIELO project.

Uranium and heavy metals in phosphate fertilizers

International Nuclear Information System (INIS)

Khater, A.E.M.

2008-01-01

Agricultural applications of chemical fertilizers are a worldwide practice. The specific activity of uranium-238 and heavy metals in phosphate fertilizers depends on the phosphate ore from which the fertilizer produced and on the chemical processing of the ore. Composite phosphate fertilizers samples where collected and the uranium-238 specific activity, in Bq/kg, and As, Cd, Cu, Pb, Se concentration, in ppm, were measured. The annual addition of these elements in soil due to fertilization were calculated and discussed. (author)(tk)

Uranium and heavy metals in phosphate fertilizers

International Nuclear Information System (INIS)

Khater, Ashraf E.M.; King Saud University, Riyadh

2008-01-01

Full text: Agricultural applications of chemical fertilizers are a worldwide practice. The specific activity of uranium-238 and heavy metals in phosphate fertilizers depends on the phosphate ore from which the fertilizer produced and on the chemical processing of the ore. Composite phosphate fertilizers samples were collected and the uranium-238 specific activity, in Bq/kg, and As, Cd, Cu, Pb, Se concentration were measured. The annual addition of these elements in soil due to soil fertilization were calculated and discussed. (author)

XPS study on the surface reaction of uranium metal in H2 and H2-CO atmospheres

International Nuclear Information System (INIS)

Wang Xiaolin; Fu Yibei; Xie Renshou

1996-04-01

The surface reactions of uranium metal in H 2 and H 2 -CO atmospheres and the effects of temperature and CO on the hydriding reaction have been studied by X-ray photoelectron spectroscopy (XPS). The reaction between commercial H 2 and uranium metal at 25 degree C leads mainly to the further oxidation of surface layer of metal due to traces of water vapour. At 200 degree C, it may lead to the hydriding reaction of uranium and the hydriding increases with increasing the exposure of H 2 . Investigation indicates CO inhibits both the hydriding reaction and oxidation on the condition of H 2 -CO atmospheres. (13 refs., 10 figs.)

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)

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)

Sunflower oil ozonation. Following of the reaction by proton Nuclear Magnetic Resonance

International Nuclear Information System (INIS)

Diaz Gomez, Maritza F.

2005-01-01

Previous studies have demonstrated that the technique of Proton Nuclear Magnetic Resonance can be used for the pursuit of the reaction between the ozone and the unsaturated fatty acids. It's carried out the sunflower oil ozonization to different applied dose of ozone and the index of peroxides and the concentration of aldehydes are determined. The main reaction products were identified by Proton Nuclear Magnetic Resonance Spectroscopy (NMR 1 H). The intensities of the signs were used to follow the advance of the reaction between the ozone and the sunflower oil. It is was carried out until obtaining an index of peroxides of 1 202 mmol-equiv/kg. The intensities of the signs of the olefinic protons diminish with a gradual increment in the dose of applied ozone, but without ending up disappearing completely. The ozonides of Criegee obtained to applied dose of ozone of 107,1 mg/g were approximately bigger 7,4 times that those obtained at the beginning from the reaction to applied dose of ozone of 15,3 mg/g. The aldehydes protons were observed as a sign of weak intensity in all the spectra. The signs belonging to the olenifics protons of the hydroperoxides in d = 5,55 ppm increases with the increment of the applied dose of ozone. You concludes that to higher applied dose of ozone, haggler is the advance of the ozonization reaction, what belongs together with a bigger formation of oxygenated compounds

Comparisons of theoretical and experimental neutron spectra, 115In(n,n') and fission rates, in the centre of three spherical natural uranium and iron shell configurations, located at BR1

International Nuclear Information System (INIS)

De Leeuw-Gierts, G.; De Leeuw, S.; Gilliam, D.M.

1984-01-01

Three spherical configurations of iron and uranium shells have been studied. The configurations were a 1-cm thick natural uranium shell, a 1-cm thick natural uranium shell with an inner 7-cm thick iron shell and a 1-cm thick natural uranium shell with an inner iron shell of 14-cm thickness. For the measurements, the shells were located at the centre of a hollow cavity, 100-cm in diameter, in the vertical graphite thermal column of the BR1 reactor. The central neutron spectra were calculated by means of the DTF-IV code, using the 208-group KEDAK-3 library, and by means of the ANISN code, using the 171-group VITAMIN-C library. Central neutron spectra, measured by the proton-recoil and 6 Li(n,α)t spectrometry techniques, are compared to the theory between ∼ 100 keV and 5 MeV. Mean fission cross-sections of 240 Pu, 237 Np, 234 U, 235 U, 236 U and 238 U were deduced from the calculations. Their ratios with respect to 238 U are compared to measurements made with NBS dual fission chambers. (Auth.)

Calculations of nuclear data for the reactions of neutrons and protons with heavy nuclei at energy from 1 MeV up to 2 GeV

International Nuclear Information System (INIS)

Konshin, V.A.

1995-01-01

Several nuclear model codes were applied to calculations of nuclear data in the energy region from 1 MeV to 2 GeV. At energies from 1 to 20 MeV the statistical model code STAPRE was used for calculations of the neutron cross-sections for fission, (n,2n) and (n,3n) reaction cross-sections for 71 actinide isotopes. In the energy region from 10 to 100 MeV the nuclear theory code GNASH was used to calculate the neutron fission and (n,xn) cross-sections for 238 U, 235 U, 239 Pu, 232 Th, 237 Np, 238 Pu, 241 Am, 243 Am, 245 Cm and 246 Cm. At energies from 100 MeV to 2 GeV the intranuclear cascade-exciton model including the fission process was applied to calculations of the interactions of protons and neutrons with actinides and the calculated results are compared with experimental data. (author)

Probing the role of Skyrme interactions on the fission dynamics of the {sup 6}Li + {sup 238}U reaction

Energy Technology Data Exchange (ETDEWEB)

Sharma, Ishita; Kumar, Raj; Sharma, Manoj K. [Thapar University, School of Physics and Materials Science, Patiala (India)

2017-06-15

The performance of selected five Skyrme forces (out of a set of 240), tested by Dutra et al., is analyzed in view of fusion-fission dynamics. These forces are assumed to perform better for neutron-rich systems, so the choice of the reaction is accordingly made by opting for a neutron-rich target in {sup 6}Li + {sup 238}U reaction. This reaction is diagnosed further in reference to fusion hindrance within the dynamical approach of the cluster-decay model (DCM). In order to reduce the computational time, three Skyrme forces are figured out with the criteria that these forces cover the barrier characteristics of the remaining two forces as well. The fission cross-sections are successfully addressed at low energies for the {sup 6}Li + {sup 238}U reaction. However, at relatively higher energies, the excitation functions show theoretical suppression with respect to experimental data, which may be associated with the possible existence of incomplete fusion (ICF). For ICF, we have considered that the {sup 6}Li broke into {sup 4}He + {sup 2}H, as mentioned in the experimental work. The calculations of ICF are carried out for the {sup 4}He + {sup 238}U reaction with the selected Skyrme forces at E{sub c.m.} = 26.20 and 27.51 MeV. These forces address the data nicely for the compound nucleus (CN) as well as ICF processes. Here, the NRAPR force seems to require lesser barrier modification as compared to the other forces, therefore it can be used as an alternate choice for calculating the interaction potential. Additionally, the prediction of cross-sections at lower energies has been done with DCM using the NRAPR force. The l-dependent % barrier modification of the Skyrme forces undertaken is also worked out in reference to fusion hindrance at below barrier energies. (orig.)

Uranium oxidation: Characterization of oxides formed by reaction with water by infrared and sorption analyses

Science.gov (United States)

Fuller, E. L.; Smyrl, N. R.; Condon, J. B.; Eager, M. H.

1984-04-01

Three different uranium oxide samples have been characterized with respect to the different preparation techniques. The results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. Inert gas sorption analyses and diffuse reflectance infrared studies combined with electron microscopy prove valuable in defining the chemistry and morphology of the oxidic products and hydrated intermediates.

Optimization of the binary breeder reactor. VIII annular core fueled with 233U - 238U and Pu-238U

International Nuclear Information System (INIS)

Nascimento, J.A. do; Ishiguro, Y.

1988-04-01

First cycle burnup characteristics of a 1200 MWe binary breeder reactor with annular core fueled with metallic 233 U- 238 U-Zr, Pu- 238 U-Zr and Th in the blankets have been analysed. The Doppler effect is small as expected in a metal fueled fast reactor. The sodium void reactivity is, in general, smaller than in metal fueled homogeneous fast reactors of 1 m core height. The estimates of the required and available control rod worths show a large shutdown margin throughout the operational cycle. There are flexibilities in the blanket fueling and well balanced breeding in the two cycles, uranium and thorium, with doubling times of about 20 years are possible. (author) [pt

Determination of uranium from nuclear fuel in environmental samples using inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

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

2000-01-01

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. A rapid and sensitive analytical procedure was developed for uranium isotopic ratio measurement in environmental samples based on inductively coupled plasma quadrupole mass spectrometry with a hexapole collision cell (HEX-ICP-QMS). The figures of merit of the HEX-ICP-QMS were studied with a plasma-shielded torch using different nebulizers (such as an ultrasonic nebulizer (USN) and Meinhard nebulizer) for solution introduction. A 238 U + ion intensity of up to 27000 MHz/ppm in HEX-ICP-QMS with USN was observed by introducing helium into the hexapole collision cell as the collision gas at a flow rate of 10 ml min -1 . The formation rate of uranium hydride ions UH + /U + of 2 x 10 -6 was obtained by using USN with a membrane desolvator. The limit of 236 U/ 238 U ratio determination in 10 μg 1 -1 uranium solution was 3 x 10 -7 corresponding to the detection limit for 236 U of 3 pg 1 -1 . The precision of uranium isotopic ratio measurements in 10 μg 1 -1 laboratory uranium isotopic standard solution was 0.13% ( 235 U/ 238 U) and 0.33% ( 236 U/ 238 U) using a Meinhard nebulizer and 0.45% ( 235 U/ 238 U) and 0.88% ( 236 U/ 238 U) using a USN. 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 . (orig.)

A kinetic study of the reaction of water vapor and carbon dioxide on uranium; Cinetique de la reaction de la vapeur d'eau et du dioxyde de carbone sur l'uranium

Energy Technology Data Exchange (ETDEWEB)

Santon, J P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1964-09-15

The kinetic study of the reaction of water vapour and carbon dioxide with uranium has been performed by thermogravimetric methods at temperatures between 160 and 410 deg G in the first case, 350 and 1050 deg C in the second: Three sorts of uranium specimens were used: uranium powder, thin evaporated films, and small spheres obtained from a plasma furnace. The experimental results led in the case of water vapour, to a linear rate of reaction controlled by diffusion at the lower temperatures, and by a surface reaction at the upper ones. In the case of carbon dioxide, a parabolic law has been found, controlled by diffusional processes. (author) [French] L'etude cinetique de la reaction de la vapeur d'eau et du dioxyde de carbone sur l'uranium a ete entreprise au moyen de methodes thermogravimetriques, dans te premier cas entre 160 et 410 deg C et dans le second entre 350 et 1050 deg C. Le materiau utilise se presentait sous trois formes: poudres, couches minces evaporees et billes obtenues par fusion en chalumeau a plasma. Les resultats experimentaux ont permis de mettre en evidence, dans le cas de la vapeur d'eau, une cinetique lineaire controlee par la diffusion a basse temperature et d'interface a haute temperature. Dans le cas du dioxyde de carbone par contre, on trouve une cinetique parabolique controlee par la diffusion. (auteur)

Fragment mass distribution of proton-induced spallation reaction with intermediate energy

International Nuclear Information System (INIS)

Fan Sheng; Ye Yanlin; Xu Chuncheng; Chen Tao; Sobolevsky, N.M.

2000-01-01

The test of part benchmark of SHIELD code is finished. The fragment cross section and mass distribution and excitation function of the residual nuclei from proton-induced spallation reaction on thin Pb target with intermediate energy have been calculated by SHIELD code. And the results are in good agreement with measured data. The fragment mass distribution of the residual nuclei from proton-induced spallation reaction on thick Pb target with incident energy 1.6 GeV have been simulated

The investigation of quasi-free scattering reactions with the two-proton-halo nucleus {sup 17}Ne

Energy Technology Data Exchange (ETDEWEB)

Lehr, Christopher; Aumann, Thomas; Marganiec, Justyna [TU Darmstadt (Germany); Wamers, Felix [GSI Helmholtzzentrum (Germany)

2016-07-01

{sup 17}Ne is a Borromean two-proton-halo nucleus located at the proton-dripline and therefore an interesting candidate for nuclear-structure studies. Reactions of the nucleus {sup 17}Ne have been measured in complete kinematics at the R3B/LAND setup at GSI in Darmstadt. It was studied in exclusive measurements of one-proton-removal reactions. Polyethylene (CH{sub 2}) and carbon (C) were used as targets. Thus it is possible to reconstruct the pure H contribution of the CH{sub 2} data by subtracting the carbon background. The resulting events are clean (p,2p) reactions showing the typical angular correlations known from p-p scattering. Thereby quasi-free (p,2p) and carbon-induced one-proton removal reactions are studied separately. Quasi-free scattering reactions are compared with carbon-induced one-proton removal reactions and shown to be a clean tool for nuclear-structure studies.

Utilisation of prompt fission neutron technology in Greenfields uranium exploration

International Nuclear Information System (INIS)

Mutz, P.R.

2007-01-01

Conventionally, gamma detection technology has been used in uranium exploration programs for the initial detection of uranium as well as for a determination of uranium concentration. Geophysical logging companies use wireline gamma probes to measure uranium within boreholes, and field technicians utilise hand held gamma meters to detect uranium in rock samples, drill cuttings and cores. Borehole geophysical logging equipment typically records the uranium concentration as %eU 3 O8, where e represents an equivalent determination of uranium concentration as opposed to a laboratory assay. This method of uranium determination is an indirect method, as it measures gamma radiation from uranium-238 (U-238) isotope decay chain progeny; principally the bismuth-214 (Bi-214) isotope. Consequently, the uranium determination can be inaccurate due to natural disequilibrium between the U-238 parent and the decay chain progeny. This is especially true in sedimentary hosted uranium deposits, where the uranium and daughter progeny may have been geochemically separated. The gamma detection method for uranium can also be rendered inaccurate by detecting the gamma signature from potassium in clays as well as from thorium; both of which can provide a false (enhanced) eU 3 O8 determination. Prompt Fission Neutron (PFN) technology is a geophysical wireline logging technology used in the same manner as conventional gamma logging. The difference is that PFN provides a direct determination of uranium within a borehole, irrespective of natural disequilibrium or the presence of other radioactive elements. This paper provides a brief description of natural uranium and radioactivity as a basis for explaining the conventional use of gamma radiation detectors for the detection and determination of uranium concentration in exploration boreholes, including the potential pitfalls of this technology. A detailed description of prompt fission neutron technology is also presented, along with a discussion

Detection of uranium mining activities

International Nuclear Information System (INIS)

Maiorov, V.; Ryjinski, M.; Bragin, V.

2001-01-01

In undisturbed natural uranium ore the 238 U decay chain isotopes appear in secular decay equilibrium with activity ratios equal to one. In the course of ore processing the bulk of the uranium decay products is separated from the uranium product and concentrated in the tails. Therefore the disturbed activity ratios of short-lived daughters to long-lived parents can be indicators of ore processing. Using 234 Th and 238 U activities (the short-lived daughter with T 1/2 =24.1 days and the long- lived parent respectively) one can roughly estimate how much time has elapsed since ore processing occurred. Equilibrium is reached in about three months after processing and the 234 Th and 238 U activity levels are approximately equal (taking into account the error of measurements). Higher or lower 234 Th activity levels, relative to 238 U, indicate the material has been recently processed. Assuming the product is depleted in Th and the tails are enriched, the activity of 234 Th in fresh product should be lower than 238 U and higher in fresh tails. The 234 Th/ 230 Th activity ratio can also be used for age estimations ( 230 Th is a long-lived nuclide). Five samples were taken from the Ranger Uranium Mine and Concentration Plant in Australia, and one sample was taken from the Jabiluka mine (10 km far from the Ranger Mine). The samples included non-processed ore, coarse ore from the stockpile, final crushed ore, fresh and old tails, and fresh product (U 3 O 8 ). All the samples were analyzed by HRGS to measure the activities of gamma emitting nuclides. XRF and IDMS were used to measure uranium content and isotopic composition. The 238 U activity was calculated from these measurement results. The 234 Th activity was measured by HRGS with a planar HPGe detector and a calibrated low activity 241 Am solution as an internal standard. The 234 Th/ 230 Th activity ratio was measured using the 60 keV energy region where both isotopes have gamma lines. Use of gamma lines with close

Proton transfers in the Strecker reaction revealed by DFT calculations

Directory of Open Access Journals (Sweden)

Shinichi Yamabe

2014-08-01

Full Text Available The Strecker reaction of acetaldehyde, NH3, and HCN to afford alanine was studied by DFT calculations for the first time, which involves two reaction stages. In the first reaction stage, the aminonitrile was formed. The rate-determining step is the deprotonation of the NH3+ group in MeCH(OH-NH3+ to form 1-aminoethanol, which occurs with an activation energy barrier (ΔE≠ of 9.6 kcal/mol. The stereochemistry (R or S of the aminonitrile product is determined at the NH3 addition step to the carbonyl carbon of the aldehyde. While the addition of CN− to the carbon atom of the protonated imine 7 appears to scramble the stereochemistry, the water cluster above the imine plane reinforces the CN− to attack the imine group below the plane. The enforcement hinders the scrambling. In the second stage, the aminonitrile transforms to alanine, where an amide Me-CH(NH2-C(=O-NH2 is the key intermediate. The rate-determining step is the hydrolysis of the cyano group of N(amino-protonated aminonitrile which occurs with an ΔE≠ value of 34.7 kcal/mol. In the Strecker reaction, the proton transfer along the hydrogen bonds plays a crucial role.

Isotopic production cross-sections and recoil velocities of spallation-fission fragments in the reaction 238U(1A GeV)+e

CERN Document Server

Pereira, J; Wlazlo, W; Benlliure, J; Casarejos, E; Armbruster, P; Bernas, M; Enqvist, T; Legrain, R; Leray, S; Rejmund, F; Mustapha, B; Schmidt, K.-H; Stéphan, C; Taïeb, J; Tassan-Got, L; Volant, C; Boudard, A; Czajkowski, S; 10.1103/PhysRevC.75.014602

2007-01-01

Fission fragments of 1A GeV 238U nuclei interacting with a deuterium target have been investigatedwith the Fragment Separator (FRS) at GSI (Darmstadt) by measuring their isotopicproduction cross-sections and recoil velocities. The results, along with those obtained recently forspallation-evaporation fragments, provide a comprehensive analysis of the spallation nuclear productionsin the reaction 238U(1A GeV)+d. Details about experiment performance, data reductionand results will be presented.

Accurate 238U(n , 2 n )237U reaction cross-section measurements from 6.5 to 14.8 MeV

Science.gov (United States)

Krishichayan, Bhike, M.; Tornow, W.; Tonchev, A. P.; Kawano, T.

2017-10-01

The cross section for the 238U(n ,2 n )237U reaction has been measured in the incident neutron energy range from 6.5 to 14.8 MeV in small energy steps using an activation technique. Monoenergetic neutron beams were produced via the 2H(d ,n )3He and 3H(d ,n )4He reactions. 238U targets were activated along with Au and Al monitor foils to determine the incident neutron flux. The activity of the reaction products was measured in TUNL's low-background counting facility using high-resolution γ -ray spectroscopy. The results are compared with previous measurements and latest data evaluations. Statistical-model calculations, based on the Hauser-Feshbach formalism, have been carried out using the CoH3 code and are compared with the experimental results. The present self-consistent and high-quality data are important for stockpile stewardship and nuclear forensic purposes as well as for the design and operation of fast reactors.

SIMS Analyses of Aerodynamic Fallout from a Uranium-Fueled Test

Energy Technology Data Exchange (ETDEWEB)

Lewis, L. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Berkeley, CA (United States); Knight, K. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Matzel, J. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Prussin, S. G. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ryerson, F. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kinman, W. S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Zimmer, M. M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hutcheon, I. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2014-09-09

Five silicate fallout glass spherules produced in a uranium-fueled, near-surface nuclear test were characterized by secondary ion mass spectrometry, electron probe microanalysis, autoradiography, scanning electron microscopy, and energy-dispersive x ray spectroscopy. Several samples display distinctive compositional heterogeneity suggestive of incomplete mixing, and exhibit heterogeneity in U isotopes with 0.02 < ²³⁵U/ ²³⁸U < 11.8 among all five samples and 0.02 < ²³⁵U/ ²³⁸U < 7.81 within a single sample. In two samples, the ²³⁵U/ ²³⁸U ratio is correlated with major element composition, consistent with the agglomeration of chemically and isotopically distinct molten precursors. Two samples are quasi-homogeneous with respect to composition and uranium isotopic composition, suggesting extensive mixing possibly due longer residence time in the fireball. Correlated variations between ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸U abundances point to mixing of end-members corresponding to uranium derived from the device and natural U ( ²³⁸U/ ²³⁵U = 0.00725) found in soil.

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.

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

Some Investigations of the Reaction of Activated Charcoal with Fluorine and Uranium Hexafluoride

Energy Technology Data Exchange (ETDEWEB)

Del Cul, G.D.; Fiedor, J.N.; Simmons, D.W.; Toth, L.M.; Trowbridge, L.D.; Williams

1998-09-01

The Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory has been shut down since 1969, when the fuel salt was drained from the core into two Hastelloy N drain tanks at the reactor site. Over time, fluorine (F{sub 2}) and uranium hexafluoride (UF{sub 6}) moved from the salt through the gas piping to a charcoal bed, where they reacted with the activated charcoal. Some of the immediate concerns related to the migration of F{sub 2} and UF{sub 6} to the charcoal bed were the possibility of explosive reactions between the charcoal and F{sub 2}, the existence of conditions that could induce a criticality accident, and the removal and recovery of the fissile uranium from the charcoal. This report addresses the reactions and reactivity of species produced by the reaction of fluorine and activated charcoal and between charcoal and F{sub 2}-UF{sub 6} gas mixtures in order to support remediation of the MSRE auxiliary charcoal bed (ACB) and the recovery of the fissile uranium. The chemical identity, stoichiometry, thermochemistry, and potential for explosive decomposition of the primary reaction product, fluorinated charcoal, was determined.

Some Investigations of the Reaction of Activated Charcoal with Fluorine and Uranium Hexafluoride

International Nuclear Information System (INIS)

Del Cul, G.D.; Fiedor, J.N.; Simmons, D.W.; Toth, L.M.; Trowbridge, L.D.; Williams

1998-01-01

The Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory has been shut down since 1969, when the fuel salt was drained from the core into two Hastelloy N drain tanks at the reactor site. Over time, fluorine (F 2 ) and uranium hexafluoride (UF 6 ) moved from the salt through the gas piping to a charcoal bed, where they reacted with the activated charcoal. Some of the immediate concerns related to the migration of F 2 and UF 6 to the charcoal bed were the possibility of explosive reactions between the charcoal and F 2 , the existence of conditions that could induce a criticality accident, and the removal and recovery of the fissile uranium from the charcoal. This report addresses the reactions and reactivity of species produced by the reaction of fluorine and activated charcoal and between charcoal and F 2 -UF 6 gas mixtures in order to support remediation of the MSRE auxiliary charcoal bed (ACB) and the recovery of the fissile uranium. The chemical identity, stoichiometry, thermochemistry, and potential for explosive decomposition of the primary reaction product, fluorinated charcoal, was determined

Test calculations of photoneutrons emission from surface of uranium sphere irradiated by 28 MeV electrons

International Nuclear Information System (INIS)

Blokhin, A.I.; Degtyarev, I.I.

2002-01-01

In this paper the results of physical verification for the BOFOD photonuclear data files are reported, available for the uranium isotopes U 235 , U 238 . These results were compared with calculated data by the parameterization driven model of photonuclear reaction and experimental data. Experimental data of photoneutron yields from surface of uranium sphere irradiated by 28 MeV electrons are used for a verification. Both calculations have been carried out with the RTS and T general purpose Monte Carlo code with detailed electron-photon-nucleon transport simulation using the ENDF/B-VI and EPDL evaluated data libraries

Reaction of water vapor with a clean liquid uranium surface

International Nuclear Information System (INIS)

Siekhaus, W.

1985-01-01

To study the reaction of water vapor with uranium, we have exposed clean liquid uranium surfaces to H 2 O under UHV conditions. We have measured the surface concentration of oxygen as a function of exposure, and determined the maximum attainable surface oxygen concentration X 0 /sup s/ as a function of temperature. We have used these measurements to estimate, close to the melting point, the solubility of oxygen (X 0 /sup b/, -4 ) and its surface segregation coefficient β/sup s/(> 10 3 ). 8 refs., 5 figs., 1 tab

Medium effects on spin observables of proton knockout reactions

International Nuclear Information System (INIS)

Krein, G.; Maris, T.A.J.; Rodrigues, B.B.; Veit, E.A.

1994-07-01

Medium modifications of the properties of bound nucleons and mesons are investigated by means of medium energy quasi free proton knockout reactions with polarized incident protons. The sensitivity of the spin observables of these reactions to modifications of the nucleon and meson properties is studied using the Bonn one-boson exchange model of the nucleon-nucleon interaction. A method proposed to extract the pp analysing power in medium from the (p, 2 p) asymmetries indicates a reduction of this quantity compared to its free space value. This reduction is linked to modifications of masses and coupling constants of the nucleons and mesons in the nucleus. The implications of these modifications for another spin observable to be measured in the future are discussed. (author). 39 refs, 9 figs

Medium effects on spin observables of proton knockout reactions

Energy Technology Data Exchange (ETDEWEB)

Krein, G [Instituto de Fisica Teorica (IFT), Sao Paulo, SP (Brazil); Maris, T A.J.; Rodrigues, B B; Veit, E A [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica

1994-07-01

Medium modifications of the properties of bound nucleons and mesons are investigated by means of medium energy quasi free proton knockout reactions with polarized incident protons. The sensitivity of the spin observables of these reactions to modifications of the nucleon and meson properties is studied using the Bonn one-boson exchange model of the nucleon-nucleon interaction. A method proposed to extract the pp analysing power in medium from the (p, 2 p) asymmetries indicates a reduction of this quantity compared to its free space value. This reduction is linked to modifications of masses and coupling constants of the nucleons and mesons in the nucleus. The implications of these modifications for another spin observable to be measured in the future are discussed. (author). 39 refs, 9 figs.

redox reactions of uranium in the presence of potassium 2-phospho-17-tungstate

International Nuclear Information System (INIS)

Maslov, L.P.; Rykov, A.G.; Sirotinkina, L.V.

1986-01-01

The redox reactions of uranium in the presence of potassium 2-phospho-17-tungstate (17W2P) - K 10 P 2 W 17 O 61 - were studied by the methods of spectrophotometry and potentiometry. It was established that in the presence of 17W2P the UO /SUP 2/2/ + ion is reduced by iron(II) to uranium(IV) as a result of the binding of U(IV) into a strong complex with composition (U(p 2 W 17 O 61 ) 2 ) 16- . The peculiarities of the coordination of uranium(IV) by voluminous 17W2P ligands are the cause of the different nature of its interaction with various types of oxidizing agents. It was established that under the action of oxidizing agents (K 2 Cr 2 O 7 , KMnO 4 ), the reduced form of which is a complex with 17W2P, there is a conversion of the complex of uranium(IV) to the corresponding complex of uranium(V), evidently with conservation of a structure analogous to that for uranium(IV). It was also shown that uranium(IV) in complex with 17W2P is practically not oxidized in the cold by persulfate ions which react according to a radical mechanism, whereas weaker oxidizing agents, for example, H 2 O 2 , oxidize it to the UO /SUP 2/2/ + ion. Hypotheses are advanced on the possible mechanisms of the occurrence of the corresponding reactions

Studies of projectile-like fragments in the 16O + 238U reaction at 20 MeV/u

International Nuclear Information System (INIS)

Dyer, P.; Awes, T.C.; Gelbke, C.K.; Back, B.B.; Mignerey, A.C.; Wolf, K.L.; Breuer, H.; Viola, V.E.; Meyer, W.G.

1979-01-01

Projectile residues were studied in coincidence with angle-correlated fission fragments resulting from reactions of 20-MeV/u 16 O ions on 238 U. Distributions of the missing parallel momentum are shown for different projectile residues, and the dependence of the average parallel recoil momentum on the average parallel momentum of the projectile residue is plotted. 2 figures

Production cross sections of proton-induced reactions on yttrium

Energy Technology Data Exchange (ETDEWEB)

Yang, Sung-Chul; Song, Tae-Yung; Lee, Young-Ouk [Nuclear Data Center, Korea Atomic Energy Research Institute, Daejeon 34057 (Korea, Republic of); Kim, Guinyun, E-mail: gnkim@knu.ac.kr [Department of Physics, Kyungpook National University, Daegu 41566 (Korea, Republic of)

2017-05-01

The production cross sections of residual radionuclides such as {sup 86,88,89g}Zr, {sup 86g,87m,87g,88}Y, {sup 83g,85g}Sr, and {sup 83,84g}Rb in the {sup 89}Y(p,x) reaction were measured using a stacked-foil activation and offline γ-ray spectrometric technique with proton energies of 57 MeV and 69 MeV at the 100 MeV proton linac in the Korea Multi-purpose Accelerator Complex (KOMAC), Gyeongju, Korea. The induced activities of the activated samples were measured using a high purity germanium (HPGe) detector, and the proton flux was determined using the {sup nat}Cu(p,x){sup 62}Zn reaction. The measured data was compared with other experimental data and the data from the TENLD-2015 library based on the TALYS code. The present results are generally lower than those in literature, but are found to be in agreement with the shape of the excitation functions. The integral yields for the thick target using the measured cross sections are given.

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)

Purification of free hydrogen or hydrogen combined in a gaseous mixture by chemical reactions with uranium

International Nuclear Information System (INIS)

Caron-Charles, M.; Gilot, B.

1989-01-01

Within the framework of the European fusion program, the authors are dealing with the tritium technology aspect. Hydrogen, free or under a combined form within a H 2 , N 2 , NH 3 , O 2 , gaseous mixture, can be purified by chemical reactions with uranium metal. The resulting reactions consist in absorbing the impurities without holding back H 2 . Working conditions have been defined according to two main goals: the formation of stable solid products, especially under hydrogenated atmosphere and the optimization of the material quantities to be used. Thermodynamical considerations have shown that the 950-1300 K temperature range should be suitable for this chemical process. Experiments performed with massive uranium set in a closed reactor at 973 K, have produced hydrogen according to the predicted reactions rates. But they have also pointed out the importance of interferences that might occur in the uranium-gas system, on the gases conversion rates. The comparison between the chemical kinetic ratings of the reactions of pure gases and the chemical kinetic ratings of the reactions of the same gases in mixture, has been set up. It proves that simultaneous reactions can modify the working conditions of the solid products formation, and particularly modify their structure. In this case, chemical kinetic ratings are increased up to their maximal value; that means surface phenomena are favoured as with uranium powder gases reactions. (orig.)

Proton-fission for the accelerator production of Mo-99

International Nuclear Information System (INIS)

Lagunas-Solar, M.C.; Jungerman, J.A.; Castaneda, C.M.

1993-01-01

The production of Mo-99 (66.0 h) via de U-238(p,f) Mo-99 fission reaction is proposed as a non-reactor source of this essential precursor of 6.6-h Tc-99m, an isotope of wide use of diagnostic nuclear medicine applications. Measurements of the total excitation function for the U-238(p,f) reaction indicated a maximum and fairly constant cross section of 1.4 barns at > 30 MeV. Combining the advances of high-current (mA) H-accelerators with dual beam (dual target) operation, and assuming a 5% fission yield, estimates of Mo-99 reaches 5 to 14 Ci/h at 1 mA. The proton fission production of Mo-99 appears to more advantageous than the reactor produced via evaporation neutron-induced fission. An accelerator method could allow securing ample supply of Mo-99 independently of the current scarce reactor operation, while also simplifying the associated waste management problems as well as some of the environmental concerns

Reaction of Tris(cyclopentadienyl)uranium compounds with amines, azides, and related ligands

International Nuclear Information System (INIS)

Rosen, R.K.

1989-12-01

The trivalent uranium compound, (MeC 5 H 4 ) 3 U(thf), serves as a one- or two-electron reducing agent towards azides, RN 3 . These reactions produce either the uranium(IV) azide, (MeC 5 H 4 ) 3 UN 3 , or uranium(V) imides, (MeC 5 H 4 ) 3 UNR. The role of steric and electronic effects upon this reaction has been investigated using several series of azides. For Me 3 XN 3 , the imides are produced when X = C or Si, both products are formed when X = Ge, and the azide is produced when X = Sn. For Ph 3 XN 3 , the azide is produced when X = C or Sn. For Ph 3-x CH 3 N 3 , the imide is produced when x = 2 and both compounds are produced when x = 1. For substituted phenylazides, RC 6 H 4 N 3 , only the imides are produced. The magnetic properties of uranium diimides, [(MeC 5 H 4 ) 3 U] 2 (μ-NRN), were investigated. Several uranium(III) amines, (MeC 5 H 4 ) 3 U(NH 2 R), were produced from (MeC 5 H 4 ) 3 U(thf) and RNH 2 , and NH 3 was found to be a better ligand towards (MeC 5 H 4 ) 3 U than is PMe 3

The Amster concept: a configuration generating its own uranium with a mixed thorium and uranium support

International Nuclear Information System (INIS)

Vergnes, J.; Garzenne, C.; Lecarpentier, D.; Mouney, H.; Delpech, M.

2001-01-01

AMSTER is a continuously reloaded, graphite-moderated molten salt critical reactor, using a 238 U or 232 Th fuel support, slightly enriched with 235 U if necessary. Using this concept, one can define a large number of configurations according to the products loaded and recycled. The choice of thorium fuel support leads to two configurations requiring no additional 235 U as fissile material: a configuration with one moderating zone, incinerating Transuranium elements (TRU); a configuration with 2 moderating zones self-consuming TRU and regenerating the fissile uranium ( 233 U). In this configuration, it is even possible to burn 238 U (from depleted uranium) by adding it to the thorium support. These configurations use a minimum amount of fuel (100 kg of 232 Th or 100 kg of a 232 Th- 238 U mix per TWh) and produce very little TRU (a few tens of grams per TWh). (author)

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

Natural radionuclides in the environment and problems of uranium mining

International Nuclear Information System (INIS)

Bowie, S.H.U.

1981-01-01

The subject is discussed under the headings: introduction (U-238, U-235, Th-232, K-40, and their decay products); distribution of radionuclides; α, β and γ radiation; uranium in rocks; uranium in soil and water; uranium mining (hazards of uranium and radon during mining and in tailings); assessment of risk. (U.K.)

The metrological activity determination of 238 U and 230 Th by gamma spectrometry to industrial fuel-cycle application

International Nuclear Information System (INIS)

Almeida M, M.C. de; Delgado, J.U.; Poledna, R.

2006-01-01

This work describes the difficulty for determining the activity of 238 U and 230 Th using gamma spectrometry due to the low gamma-ray emission probabilities of 92 and 67 keV, and, mainly, the associated high uncertainties about 13 and 11%, respectively. 230 Th is a 238 U daughter and it is product from uranium mills and refineries. 230 Th decays to 226 Ra and this decay has to be measured because these radionuclides are not in secular equilibrium with their daughter products, besides the gamma-energies have high uncertainties in the emission probabilities. These radionuclides, mostly 238 U, are important in the nuclear fuel-cycle, since the mining of uranium ore, where the nominal isotopic content of natural uranium is 99.27% of 238 U, until the irradiated fuel reprocessing, where this isotope, a fertile material, is recovered to be used again. The uranium and thorium are considered safeguarded nuclear materials and the metrology tries to calibrate and standardize these materials to improve the activity determination techniques applied in different fuel-cycle scopes. The essential characteristics of the safeguarded materials are low gamma energies (less than 100 keV) and emission probabilities but with high uncertainties. In this way, the metrology can contribute to homeland security defense against illicit nuclear trafficking with the identification and quantification of the safeguarded radionuclides such as uranium and thorium, using specific gamma window energy and high resolution planar or coaxial germanium detector. The efficiency curve is obtained from the reference source spectrum considering the photopeak areas corresponding the standard activities. This curve depends on radiation energy, sample geometry, photon attenuation (sample absorption and material absorption between sample-detector), dead time and sample-detector position. The metrological activity determinations of 238 U solid sources, and of 230 Th, in solution (5 ml flask), were performed using

Uranium in surficial deposits and waters at Palmottu

International Nuclear Information System (INIS)

Ahonen, L.; Blomqvist, R.; Ervanne, H.; Suksi, J.; Jaakkola, T.

1994-01-01

Occurrence of uranium in surficial formations in the vicinity of an underground U deposit was studied. Several water samples from the Lake Palmottu and nearby springs, three lake sediment cores and three peat cores were collected for the study. Uranium concentrations in the water samples varied from 1.4 to 6.9 mBq/l, reflecting the average concentration of near-surface waters in Finland. In some samples, however, the 234 U/ 238 U activity ratio and water chemistry suggest a partial mixing with deeper groundwaters. In the lake sediments, uranium concentrations increases from 53 Bq/kg in surface layer to five fold in the bottom layers deposited 9000 years ago. In peat cores large variations in uranium concentrations can be observed: from tens of Bq/kg to over 20 kBq/kg of peat ash. The large variation also in the 234 U/ 238 U activity ratio, from 0.79 to l.91, tends to indicate uranium migration to the peat from more than one uranium source. (orig.) (19 refs., 5 figs., 1 tab.)

Theoretical calculations of the reaction cross-sections for proton-induced reactions on natural copper using ALICE-IPPE code

International Nuclear Information System (INIS)

Alharbi, A.A.; Azzam, A.

2012-01-01

A theoretical study of the nuclear-reaction cross sections for proton-induced reactions on 63 Cu and 65 Cu was performed in the proton energy range from threshold values up to 50 MeV. The produced nuclei were different isotopes of Zn, Cu, Ni, Co and Mn, some of which have important applications. The reaction cross-section calculations were performed using the ALICE-IPPE code, which depends on the pre-equilibrium compound nucleus model. This code is suitable for the studied energy and isotopic mass ranges. Approximately 14 excitation functions for the different reactions have been constructed from the calculated cross-section values. The excitation function curves for the proton reactions with natural copper targets have been constructed from those for enriched targets using the natural abundance of the copper isotopes. Comparisons between the calculated excitation functions with those previously experimentally measured are given whenever the experimental values were available. Some statistical parameters were introduced to control the quality of the fitting between both the experimental and the theoretical calculated cross-section values. - Highlights: ► We performed reaction cross section calculations using ALICE-IPPE code. ► We constructed 14 excitation functions for nat Cu(p,xn)Zn,Cu,Ni,Co,Mn reactions. ► The available experimental data were fitted to the performed ALICE-IPPE calculations. ► Statistical parameters were introduced to control the quality of the fitting. ► The code failed to fit the experimental data for reactions with large nucleon emissions.

Proton capture reactions and nuclear structure

International Nuclear Information System (INIS)

Kikstra, S.W.

1989-01-01

Experimental studies are described of the structure of 40 Ca and 42 Sc with measurements at proton-capture of (p, gamma) reactions. Where possible, an attempt has been made to interpret the results of the measurements in termsof existing models. The 40 Ca and 42 Sc nuclides were excited by bombarding 39 K and 41 Ca targets, respectively with low energy protons (E p = 0.3-3.0 MeV), that were produced by the Utrecht 3MV van de Graaff accelerator. From the measured energy and intensity of the gamma-rays created in the subsequent decay of the cuclei, information was obtained on the existence and properties of their excited states. In addition properties of two T = 3/2 levels at high excitation energy of the 9 Be nucleus were investigated. These levels were excited by the resonant absorption of gamma-rays from the 11 B(p, gamma) 12 C reaction. The results of the measurements are interpreted by a comparison to the analoque β-decay of 9 Li and to shell model calculations. The total decay energy of the superallowed O + → O + transition between the ground states of 42 Sc and 42 Ca was determined by measurements in Utrecht of the proton separation energy S p of 42 Sc and in Oak Ridge of S n of 42 Sc and 42 Ca. The results were used for verification of the conserved vector current hypothesis, which implies that the ft values of all superallowed O + → O + β-decays are the same. An attempt was made to describe properties of odd-parity states of A = 37-41 nuclei with a variant of the Warburton, Becker, Millener and Brown (WBMB) interaction.Finally a new method for the assignment of nuclear spins by a simple statistical analysis of spectroscopic information is proposed. (author). 169 refs.; 22 figs.; 24 schemes; 29 tabs

Determination of uranium from nuclear fuel in environmental samples using inductively coupled plasma mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Boulyga, S.F. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen]|[Radiation Physics and Chemistry Problems Inst., Minsk (Belarus); Becker, J.S. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen

2000-11-01

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. A rapid and sensitive analytical procedure was developed for uranium isotopic ratio measurement in environmental samples based on inductively coupled plasma quadrupole mass spectrometry with a hexapole collision cell (HEX-ICP-QMS). The figures of merit of the HEX-ICP-QMS were studied with a plasma-shielded torch using different nebulizers (such as an ultrasonic nebulizer (USN) and Meinhard nebulizer) for solution introduction. A {sup 238}U{sup +} ion intensity of up to 27000 MHz/ppm in HEX-ICP-QMS with USN was observed by introducing helium into the hexapole collision cell as the collision gas at a flow rate of 10 ml min{sup -1}. The formation rate of uranium hydride ions UH{sup +}/U{sup +} of 2 x 10{sup -6} was obtained by using USN with a membrane desolvator. The limit of {sup 236}U/{sup 238}U ratio determination in 10 {mu}g 1{sup -1} uranium solution was 3 x 10{sup -7} corresponding to the detection limit for {sup 236}U of 3 pg 1{sup -1}. The precision of uranium isotopic ratio measurements in 10 {mu}g 1{sup -1} laboratory uranium isotopic standard solution was 0.13% ({sup 235}U/{sup 238}U) and 0.33% ({sup 236}U/{sup 238}U) using a Meinhard nebulizer and 0.45% ({sup 235}U/{sup 238}U) and 0.88% ({sup 236}U/{sup 238}U) using a USN. 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}. (orig.)

Mitigation of Hydrogen Gas Generation from the Reaction of Water with Uranium Metal in K Basins Sludge

International Nuclear Information System (INIS)

Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

2010-01-01

Means to decrease the rate of hydrogen gas generation from the chemical reaction of uranium metal with water were identified by surveying the technical literature. The underlying chemistry and potential side reactions were explored by conducting 61 principal experiments. Several methods achieved significant hydrogen gas generation rate mitigation. Gas-generating side reactions from interactions of organics or sludge constituents with mitigating agents were observed. Further testing is recommended to develop deeper knowledge of the underlying chemistry and to advance the technology aturation level. Uranium metal reacts with water in K Basin sludge to form uranium hydride (UH3), uranium dioxide or uraninite (UO2), and diatomic hydrogen (H2). Mechanistic studies show that hydrogen radicals (H·) and UH3 serve as intermediates in the reaction of uranium metal with water to produce H2 and UO2. Because H2 is flammable, its release into the gas phase above K Basin sludge during sludge storage, processing, immobilization, shipment, and disposal is a concern to the safety of those operations. Findings from the technical literature and from experimental investigations with simple chemical systems (including uranium metal in water), in the presence of individual sludge simulant components, with complete sludge simulants, and with actual K Basin sludge are presented in this report. Based on the literature review and intermediate lab test results, sodium nitrate, sodium nitrite, Nochar Acid Bond N960, disodium hydrogen phosphate, and hexavalent uranium [U(VI)] were tested for their effects in decreasing the rate of hydrogen generation from the reaction of uranium metal with water. Nitrate and nitrite each were effective, decreasing hydrogen generation rates in actual sludge by factors of about 100 to 1000 when used at 0.5 molar (M) concentrations. Higher attenuation factors were achieved in tests with aqueous solutions alone. Nochar N960, a water sorbent, decreased hydrogen

Mitigation of Hydrogen Gas Generation from the Reaction of Water with Uranium Metal in K Basins Sludge

Energy Technology Data Exchange (ETDEWEB)

Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

2010-01-29

Means to decrease the rate of hydrogen gas generation from the chemical reaction of uranium metal with water were identified by surveying the technical literature. The underlying chemistry and potential side reactions were explored by conducting 61 principal experiments. Several methods achieved significant hydrogen gas generation rate mitigation. Gas-generating side reactions from interactions of organics or sludge constituents with mitigating agents were observed. Further testing is recommended to develop deeper knowledge of the underlying chemistry and to advance the technology aturation level. Uranium metal reacts with water in K Basin sludge to form uranium hydride (UH3), uranium dioxide or uraninite (UO2), and diatomic hydrogen (H2). Mechanistic studies show that hydrogen radicals (H·) and UH3 serve as intermediates in the reaction of uranium metal with water to produce H2 and UO2. Because H2 is flammable, its release into the gas phase above K Basin sludge during sludge storage, processing, immobilization, shipment, and disposal is a concern to the safety of those operations. Findings from the technical literature and from experimental investigations with simple chemical systems (including uranium metal in water), in the presence of individual sludge simulant components, with complete sludge simulants, and with actual K Basin sludge are presented in this report. Based on the literature review and intermediate lab test results, sodium nitrate, sodium nitrite, Nochar Acid Bond N960, disodium hydrogen phosphate, and hexavalent uranium [U(VI)] were tested for their effects in decreasing the rate of hydrogen generation from the reaction of uranium metal with water. Nitrate and nitrite each were effective, decreasing hydrogen generation rates in actual sludge by factors of about 100 to 1000 when used at 0.5 molar (M) concentrations. Higher attenuation factors were achieved in tests with aqueous solutions alone. Nochar N960, a water sorbent, decreased hydrogen

238,234U contents on Lepomis Cyanellus from San Marcos dam located in a uraniferous area

Science.gov (United States)

Lares, Magaly Cabral; Luna-Porres, Mayra Y.; Montero-Cabrera, María E.; Renteria-Villalobos, Marusia

2014-07-01

Fish species are suitable biomonitors of radioisotopes in aquatic systems. In the present study, it was made the determination of uranium isotopic contents on fish fillet (Lepomis Cyanellus) from San Marcos dam which is located in uranium mineralized zone. Uranium activity concentrations (AC) in fish samples were obtained on wet weight (ww), using liquid scintillation. 238U and 234U AC in fish fillet ranged from 0.0004 to 0.0167 Bq kg-1, and from 0.0013 to 0.0394 Bq kg-1, respectively. The activity ratio (234U/overflow="scroll">238U) in fish fillet ranged from 2.2 to 8.8. Lepomis cyanellus from San Marcos dam shows bioaccumulation factor (FB) of 0.6 L kg-1. The results suggest that the Lepomis Cyanellus in environments with high U contents tends to have a greater bioaccumulation compared to others.

Long-term criticality control in radioactive waste disposal facilities using depleted uranium

International Nuclear Information System (INIS)

Forsberg, C.W.

1997-01-01

Plant photosynthesis has created a unique planetary-wide geochemistry - an oxidizing atmosphere with oxidizing surface waters on a planetary body with chemically reducing conditions near or at some distance below the surface. Uranium is four orders of magnitude more soluble under chemically oxidizing conditions than it is under chemically reducing conditions. Thus, uranium tends to leach from surface rock and disposal sites, move with groundwater, and concentrate where chemically reducing conditions appear. Earth's geochemistry concentrates uranium and can separate uranium from all other elements except oxygen, hydrogen (in water), and silicon (silicates, etc). Fissile isotopes include 235 U, 233 U, and many higher actinides that eventually decay to one of these two uranium isotopes. The potential for nuclear criticality exists if the precipitated uranium from disposal sites has a significant fissile enrichment, mass, and volume. The earth's geochemistry suggests that isotopic dilution of fissile materials in waste with 238 U is a preferred strategy to prevent long-term nuclear criticality in and beyond the boundaries of waste disposal facilities because the 238 U does not separate from the fissile uranium isotopes. Geological, laboratory, and theoretical data indicate that the potential for nuclear criticality can be minimized by diluting fissile materials with- 238 U to 1 wt % 235 U equivalent

Reaction rate constant for uranium in water and water vapor

Energy Technology Data Exchange (ETDEWEB)

TRIMBLE, D.J.

1998-11-09

The literature on uranium oxidation in water and oxygen free water vapor was reviewed. Arrhenius rate equations were developed from the review data. These data and equations will be used as a baseline from which to compare reaction rates measured for K Basin fuel.

Competing retention pathways of uranium upon reaction with Fe(II)

Science.gov (United States)

Massey, Michael S.; Lezama-Pacheco, Juan S.; Jones, Morris E.; Ilton, Eugene S.; Cerrato, José M.; Bargar, John R.; Fendorf, Scott

2014-10-01

Biogeochemical retention processes, including adsorption, reductive precipitation, and incorporation into host minerals, are important in contaminant transport, remediation, and geologic deposition of uranium. Recent work has shown that U can become incorporated into iron (hydr)oxide minerals, with a key pathway arising from Fe(II)-induced transformation of ferrihydrite, (Fe(OH)3·nH2O) to goethite (α-FeO(OH)); this is a possible U retention mechanism in soils and sediments. Several key questions, however, remain unanswered regarding U incorporation into iron (hydr)oxides and this pathway's contribution to U retention, including: (i) the competitiveness of U incorporation versus reduction to U(IV) and subsequent precipitation of UO2; (ii) the oxidation state of incorporated U; (iii) the effects of uranyl aqueous speciation on U incorporation; and, (iv) the mechanism of U incorporation. Here we use a series of batch reactions conducted at pH ∼7, [U(VI)] from 1 to 170 μM, [Fe(II)] from 0 to 3 mM, and [Ca] at 0 or 4 mM coupled with spectroscopic examination of reaction products of Fe(II)-induced ferrihydrite transformation to address these outstanding questions. Uranium retention pathways were identified and quantified using extended X-ray absorption fine structure (EXAFS) spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Analysis of EXAFS spectra showed that 14-89% of total U was incorporated into goethite, upon reaction with Fe(II) and ferrihydrite. Uranium incorporation was a particularly dominant retention pathway at U concentrations ⩽50 μM when either uranyl-carbonato or calcium-uranyl-carbonato complexes were dominant, accounting for 64-89% of total U. With increasing U(VI) and Fe(II) concentrations, U(VI) reduction to U(IV) became more prevalent, but U incorporation remained a functioning retention pathway. These findings highlight the potential importance of U(V) incorporation within iron

Experimental Cross Sections for Reactions of Heavy Ions and ²⁰⁸Pb, ²⁰⁹Bi, ²³⁸U, and ²⁴⁸Cm Targets

Energy Technology Data Exchange (ETDEWEB)

Patin, Joshua Barnes [Univ. of California, Berkeley, CA (United States)

2002-01-01

The study of the reactions between heavy ions and ²⁰⁸Pb, ²⁰⁹Bi, ²³⁸U, and ²⁴⁸Cm Cm targets was performed to look at the differences between the cross sections of hot and cold fusion reactions. Experimental cross sections were compared with predictions from statistical computer codes to evaluate the effectiveness of the computer code in predicting production cross sections. Hot fusion reactions were studied with the MG system, catcher foil techniques and the Berkeley Gas-filled Separator (BGS). 3n- and 4n-exit channel production cross sections were obtained for the ²³⁸U(¹⁸O,xn)^256-xFm, ²³⁸U(²²Ne,xn)^260-xNo, and ²⁴⁸Cm(¹⁵N,xn)^263-xLr reactions and are similar to previous experimental results. The experimental cross sections were accurately modeled by the predictions of the HIVAP code using the Reisdorf and Schaedel parameters and are consistent with the existing systematics of 4n exit channel reaction products. Cold fusion reactions were examined using the BGS. The ⁴⁸Pb(²³⁸Ca,xn)^256-xNo, ²⁰⁸Pb(⁵⁰Ti,xn)^258-xRf, ²⁰⁸Pb(⁵¹V,xn)^259-xDb, ⁵⁰Bi(²³⁸Ti,xn)^259-xDb, and ²⁰⁹Bi(⁵¹V,xn)^260-xSg reactions were studied. The experimental production cross sections are in agreement with the results observed in previous experiments. It was necessary to slightly alter the Reisdorf and Schaedel parameters for use in the HIVAP code in order to more accurately model the experimental data. The cold fusion experimental results are in agreement with current 1n- and 2n-exit channel systematics.

The Chemistry and Toxicology of Depleted Uranium

OpenAIRE

Sidney A. Katz

2014-01-01

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....

Analyses of uranium series nuclides by alpha spectrometer on the uranium deposit

International Nuclear Information System (INIS)

Wismawati, T.

2000-01-01

The research is one of the program which was planned by PNC (Power Reactor and Nuclear Fuel Development Corporation). In this research the analyses of the uranium series nuclide of rock samples from uranium Tono deposit, Japan have been carried out. The 17 samples were collected from Tsukiyoshi Fault, at Gallery X on Shaft 2 consist of granite, sedimentary rocks and fault area. The aim of the research is to determine the area of U accumulation, equilibrium and leaching. The samples were treated by chemical reagent, separated by ion exchange resin and extracted by organic compounds. The uranium and thorium were deposited on the stainless steel plate surface by the electrolysis process. The activity of uranium and thorium was determined by alpha spectrometer. From the analyses data have been obtained that shows that the maximum activity of 238 U is 3.6798±0.1873 Bq/g, activity 234 U is 3.5450±0.1805 Bq/g and activity 230 Th is 3.6720±0.1868 Bq/g. The ratio figure 234 U/ 238 U versus 2 34 U / 2 30 T h has been drawn. As the conclusion, 6 samples point (No.3, 5, 8, 11, 13 and 16) lied in or on the boundary of the uranium accumulation area, 7 samples (No. 4, 6, 9, 10, 12, 15 and 17) are very close to the equilibrium position, 4 points (No. 1, 2, 7, and 14) in the leaching process. (author)

Hematological responses after inhaling 238PuO2: An extrapolation from beagle dogs to humans

International Nuclear Information System (INIS)

Scott, B.R.; Muggenburg, B.A.; Welsh, C.A.; Angerstein, D.A.

1994-01-01

The alpha emitter plutonium-238 ( 238 Pu), which is produced in uranium-fueled, light-water reactors, is used as a thermoelectric power source for space applications. Inhalation of a mixed oxide form of Pu is the most likely mode of exposure of workers and the general public. Occupational exposures to 238 PuO 2 have occurred in association with the fabrication of radioisotope thermoelectric generators. Organs and tissue at risk for deterministic and stochastic effects of 238 Pu-alpha irradiation include the lung, liver, skeleton, and lymphatic tissue. Little has been reported about the effects of inhaled 238 PuO 2 on peripheral blood cell counts in humans. The purpose of this study was to investigate hematological responses after a single inhalation exposure of Beagle dogs to alpha-emitting 238 PuO 2 particles and to extrapolate results to humans

Analysis of photofission reactions of 235U, 238U, 232Th, 209Bi, natPb, 197Au, natPt, natW, 181Ta, and 27Al by photons of 69 MeV

International Nuclear Information System (INIS)

Paiva, Eduardo de

1997-04-01

Fission reactions induced in 235 U, 238 U, 232 Th, 209 Bi nat Pb, 197 Au, nat Pt, nat W, 181 Ta. and 27 Al nuclei by monochromatic photons of 69 MeV produced at the LADON facility of the Frascati National Laboratories (INFN-LNF, Frascati, Italy) have been analyzed on the basis of a simplified two-step model. In the first step of the reaction the incoming photon is considered to be absorbed by a neutron-proton pair ('quasi-deuteron') leading to excitation of the nucleus, followed, in the second step, by a mechanism of particle evaporation-fission competition for the excited residual nucleus. Estimates of nuclear fissility at 69 MeV show to be critically dependent on the parameter r (ratio of the level-density parameter at the fission saddle point to the level-density parameter of the residual nucleus after neutron evaporation), which can be determined in a semiempirical way from induced fission reaction data for various nuclei obtained at 60 - 80 MeV of excitation energy. Fissilities calculated by means of the simplified photofission reactions model are then compared with experimental data available in the literature. (author)

The combined measurement of uranium by alpha spectrometry and secondary ion mass spectrometry (SIMS)

International Nuclear Information System (INIS)

Harvan, D.

2009-01-01

The aim of thesis was to found the dependence between radiometric method - alpha spectrometry and surface sensitive method - Secondary Ion Mass Spectrometry (SIMS). Uranium or naturally occurring uranium isotopes were studied. Samples (high polished stainless steel discs) with uranium isotopes were prepared by electrodeposition. Samples were measured by alpha spectrometry after electrodeposition and treatment. It gives surface activities. Weights, as well as surface's weights of uranium isotopes were calculated from their activities, After alpha spectrometry samples were analyzed by TOF-SIMS IV instrument in International Laser Centre in Bratislava. By the SIMS analysis intensities of uranium-238 were obtained. The interpretation of SIMS intensities vs. surface activity, or surface's weights of uranium isotopes indicates the possibility to use SIMS in quantitative analysis of surface contamination by uranium isotopes, especially 238 U. (author)

Application of activation technique for mass and nuclear charge distributions studies of 3 Mev and 14 Mev neutrons induced 238-U(n,f) and 232-Th(n,f)

International Nuclear Information System (INIS)

Embarch, K.

1988-01-01

Fission product cumulative and independent yields were determined for 238-U(n,f) and 232-Th(n,f) reactions with essentially monoenergetic neutrons of 3 and 14 Mev. Fission product activities were measured by Ge(Li)γ-ray spectrometry of irradiated 238-U and 232-Th foils. These experiments allowed us to measure a great number of cumulative yields and to obtain the fission product mass distributions corresponding to the studied reactions mentioned above. The mass distributions were completely interpreted by nucleon shell effects and proton even-odd effects. The independent yield measurements are sometimes not possible using the activation technique because of the fission fragment decay data. The values which can not be measured were determined using the measured mass yields and a prediction systematic of fractional independent yield. The results allowed us to obtain the nuclear charge distributions and to estimate proton even-odd effect corresponding values. This effect decreases when the excitation energy of the fissioning nucleus increases, this shows the importance of this parameter in the viscosity study of the nuclear matter. In conclusion, the shell effects observed in the mass distributions show that the static aspect of the fission mechanism plays a great role during the fission process, and observed proton even-odd effects act for a weak nuclear viscosity. 54 refs., 27 figs., 25 tabs

Profileration-proof uranium/plutonium and thorium/uranium fuel cycles. Safeguards and non-profileration. 2. rev. ed.

Energy Technology Data Exchange (ETDEWEB)

Kessler, G.

2017-07-01

A brief outline of the historical development of the proliferation problem is followed by a description of the uranium-plutonium nuclear fuel cycle with uranium enrichment, fuel fabrication, the light-water reactors mainly in operation, and the breeder reactors still under development. The next item discussed is reprocessing of spent fuel with plutonium recycling and the future possibility to incinerate plutonium and the minor actinides: neptunium, americium, and curium. Much attention is devoted to the technical and scientific treatment of the IAEA surveillance concept of the uranium-plutonium fuel cycle. In this context, especially the physically possible accuracy of measuring U/Pu flow in the fuel cycle, and the criticism expressed of the accuracy in measuring the plutonium balance in large reprocessing plants of non-nuclear weapon states are analyzed. The second part of the book initially examines the assertion that reactor-grade plutonium could be used to build nuclear weapons whose explosive yield cannot be predicted accurately, but whose minimum explosive yield is still far above that of chemical explosive charges. Methods employed in reactor physics are used to show that such hypothetical nuclear explosive devices (HNEDs) would attain too high temperatures in the required implosion lenses as a result of the heat generated by the Pu-238 isotope always present in reactor plutonium of current light-water reactors. These lenses would either melt or tend to undergo chemical auto-explosion. Limits to the content of the Pu-238 isotope are determined above which such hypothetical nuclear weapons are not feasible on technical grounds. This situation is analyzed for various possibilities of the technical state of the art of making implosion lenses and various ways of cooling up to the use of liquid helium. The outcome is that, depending on the existing state of the art, reactor-grade plutonium from spent fuel elements of light-water reactors with a burnup of 35 to 58

SU-F-T-140: Assessment of the Proton Boron Fusion Reaction for Practical Radiation Therapy Applications Using MCNP6

Energy Technology Data Exchange (ETDEWEB)

Adam, D; Bednarz, B [University of Wisconsin, Madison, WI (United States)

2016-06-15

Purpose: The proton boron fusion reaction is a reaction that describes the creation of three alpha particles as the result of the interaction of a proton incident upon a 11B target. Theoretically, the proton boron fusion reaction is a desirable reaction for radiation therapy applications in that, with the appropriate boron delivery agent, it could potentially combine the localized dose delivery protons exhibit (Bragg peak) and the local deposition of high LET alpha particles in cancerous sites. Previous efforts have shown significant dose enhancement using the proton boron fusion reaction; the overarching purpose of this work is an attempt to validate previous Monte Carlo results of the proton boron fusion reaction. Methods: The proton boron fusion reaction, 11B(p, 3α), is investigated using MCNP6 to assess the viability for potential use in radiation therapy. Simple simulations of a proton pencil beam incident upon both a water phantom and a water phantom with an axial region containing 100ppm boron were modeled using MCNP6 in order to determine the extent of the impact boron had upon the calculated energy deposition. Results: The maximum dose increase calculated was 0.026% for the incident 250 MeV proton beam scenario. The MCNP simulations performed demonstrated that the proton boron fusion reaction rate at clinically relevant boron concentrations was too small in order to have any measurable impact on the absorbed dose. Conclusion: For all MCNP6 simulations conducted, the increase of absorbed dose of a simple water phantom due to the 11B(p, 3α) reaction was found to be inconsequential. In addition, it was determined that there are no good evaluations of the 11B(p, 3α) reaction for use in MCNPX/6 and further work should be conducted in cross section evaluations in order to definitively evaluate the feasibility of the proton boron fusion reaction for use in radiation therapy applications.

Uranium and radium-226 in the environment of the post-uranium mining areas in Poland

Energy Technology Data Exchange (ETDEWEB)

Kardas, M.; Suplinska, M.; Ciupek, K. [Central Laboratory for Radiological Protection (Poland)

2014-07-01

The work carried out under the project NCBiR - 'Technologies Supporting Development of Safe Nuclear Power Engineering'; Task 3: Meeting the Polish nuclear power engineering's demand for fuel - fundamental aspects. Depending on location, environmental components may have different concentration levels of radionuclides. Main source of uranium and radium in the natural environment is atmospheric precipitation of the material resulting weathering and erosion of older rocks, enhanced due to human activity by fertilizers used in agriculture and fossil fuel combustion. The waste heaps and dumps, especially derived from post-uranium mining and phosphate fertilizer industry are the another source of uranium and radium in the environment. Our studies include post-uranium mining areas (inactive mines and waste dumps) and those adjacent meadows and grassland at the area of the Giant Mountains (Karkonosze Mountains) in the south-west Poland. Samples of soil and mineral material from mine shafts, water samples from ponds, streams and small rivers and vegetation samples (grass, alfalfa, birch leaves) were analyzed. Also, similar samples from agricultural regions of Poland were examined as a reference level. Uranium isotopes were determined by radiochemical method (ion exchange and extraction) and activity measurement using alpha spectrometry. Concentration of {sup 226}Ra was determined radiochemically using emanation method. For the validation of the method, determinations of uranium isotopes and radium-226 in reference samples were performed. Depending on location, the different levels of activity concentration of analyzed radionuclides were detected. Samples from the mine shafts and dumps, both water and soil, were characterized by the activity concentrations of {sup 238}U and {sup 226}Ra even by several orders higher than outside of those areas. The concentrations of the radionuclides in the areas located in further distances from mine and dumps are similar to

Measurement of the 234U/238U activity ratios in the organs and internal tissues of a domestic goat kid (Capra aegagrus hircus)

International Nuclear Information System (INIS)

Francesco De Santis; Massimo Esposito

2015-01-01

In this paper, we compare the 234 U/ 238 U activity ratios (ARs) in various internal tissues and organs of a goat kid with the ingested 234 U/ 238 U AR to assess isotopic fractionation. The results obtained from soft tissues (i.e., the kidneys, liver, lung, and bladder) that undergo indirect assimilation of uranium from the feed through the bloodstream suggest an increase in the 234 U/ 238 U AR. In contrast, the intestine, bones and feces had the same AR values as the feed. Finally, we broadly assess uranium transfer from the feed to the animal based on the concentration ratio and the feed transfer coefficient. (author)

Fabrication of Cerium Oxide and Uranium Oxide Microspheres for Space Nuclear Power Applications

Energy Technology Data Exchange (ETDEWEB)

Jeffrey A. Katalenich; Michael R. Hartman; Robert C. O' Brien

2013-02-01

Cerium oxide and uranium oxide microspheres are being produced via an internal gelation sol-gel method to investigate alternative fabrication routes for space nuclear fuels. Depleted uranium and non-radioactive cerium are being utilized as surrogates for plutonium-238 (Pu-238) used in radioisotope thermoelectric generators and for enriched uranium required by nuclear thermal rockets. While current methods used to produce Pu-238 fuels at Los Alamos National Laboratory (LANL) involve the generation of fine powders that pose a respiratory hazard and have a propensity to contaminate glove boxes, the sol-gel route allows for the generation of oxide microsphere fuels through an aqueous route. The sol-gel method does not generate fine powders and may require fewer processing steps than the LANL method with less operator handling. High-quality cerium dioxide microspheres have been fabricated in the desired size range and equipment is being prepared to establish a uranium dioxide microsphere production capability.

Reaction of Tris(cyclopentadienyl)uranium compounds with amines, azides, and related ligands

Energy Technology Data Exchange (ETDEWEB)

Rosen, R.K.

1989-12-01

The trivalent uranium compound, (MeC{sub 5}H{sub 4}){sub 3}U(thf), serves as a one- or two-electron reducing agent towards azides, RN{sub 3}. These reactions produce either the uranium(IV) azide, (MeC{sub 5}H{sub 4}){sub 3}UN{sub 3}, or uranium(V) imides, (MeC{sub 5}H{sub 4}){sub 3}UNR. The role of steric and electronic effects upon this reaction has been investigated using several series of azides. For Me{sub 3}XN{sub 3}, the imides are produced when X = C or Si, both products are formed when X = Ge, and the azide is produced when X = Sn. For Ph{sub 3}XN{sub 3}, the azide is produced when X = C or Sn. For Ph{sub 3-x}CH{sub 3}N{sub 3}, the imide is produced when x = 2 and both compounds are produced when x = 1. For substituted phenylazides, RC{sub 6}H{sub 4}N{sub 3}, only the imides are produced. The magnetic properties of uranium diimides, ((MeC{sub 5}H{sub 4}){sub 3}U){sub 2}({mu}-NRN), were investigated. Several uranium(III) amines, (MeC{sub 5}H{sub 4}){sub 3}U(NH{sub 2}R), were produced from (MeC{sub 5}H{sub 4}){sub 3}U(thf) and RNH{sub 2}, and NH{sub 3} was found to be a better ligand towards (MeC{sub 5}H{sub 4}){sub 3}U than is PMe{sub 3}.

What's new in the proton transfer reaction from pyranine to water? A femtosecond study of the proton transfer dynamics

International Nuclear Information System (INIS)

Prayer, C.; Gustavsson, T.; Tran-Thi, T.-H.

1996-01-01

The proton transfer from excited pyranine to water is studied by the femtosecond fluorescence upconversion technique. It is shown for the first time that the proton transfer reaction in water proceeds by three successive steps: the solvent cage relaxation, the specific solute-solvent hydrogen-bond formation and finally the ion pair dissociation/diffusion

The metrological activity determination of {sup 238} U and {sup 230} Th by gamma spectrometry to industrial fuel-cycle application

Energy Technology Data Exchange (ETDEWEB)

Almeida M, M.C. de; Delgado, J.U.; Poledna, R. [Instituto de Radioprotecao e Dosimetria- IRD/SEMRA, CNEN, Av. Salvador Allende s/n, Recreio, CEP 22780-160, Rio de Janeiro (Brazil)]. e-mail: marcandida@yahoo.com.br

2006-07-01

This work describes the difficulty for determining the activity of {sup 238} U and {sup 230} Th using gamma spectrometry due to the low gamma-ray emission probabilities of 92 and 67 keV, and, mainly, the associated high uncertainties about 13 and 11%, respectively. {sup 230} Th is a {sup 238} U daughter and it is product from uranium mills and refineries. {sup 230} Th decays to {sup 226} Ra and this decay has to be measured because these radionuclides are not in secular equilibrium with their daughter products, besides the gamma-energies have high uncertainties in the emission probabilities. These radionuclides, mostly {sup 238} U, are important in the nuclear fuel-cycle, since the mining of uranium ore, where the nominal isotopic content of natural uranium is 99.27% of {sup 238} U, until the irradiated fuel reprocessing, where this isotope, a fertile material, is recovered to be used again. The uranium and thorium are considered safeguarded nuclear materials and the metrology tries to calibrate and standardize these materials to improve the activity determination techniques applied in different fuel-cycle scopes. The essential characteristics of the safeguarded materials are low gamma energies (less than 100 keV) and emission probabilities but with high uncertainties. In this way, the metrology can contribute to homeland security defense against illicit nuclear trafficking with the identification and quantification of the safeguarded radionuclides such as uranium and thorium, using specific gamma window energy and high resolution planar or coaxial germanium detector. The efficiency curve is obtained from the reference source spectrum considering the photopeak areas corresponding the standard activities. This curve depends on radiation energy, sample geometry, photon attenuation (sample absorption and material absorption between sample-detector), dead time and sample-detector position. The metrological activity determinations of {sup 238} U solid sources, and of

Uranium content in soils, vegetables, cereals and fruits

International Nuclear Information System (INIS)

Frindik, O.

1988-01-01

As compared to other vegetable samples, parsley leaves showed a much higher uranium content, presumably due to tightly adhering dust which could not be removed by washing. Uranium transfer factors from the soil to the plants were calculated; these factors always include the total uranium concentration and not only the 'soluble' uranium. As compared to U-238 the activity of U-234 is nearly always higher in vegetable samples, but lower in soil samples. (orig./HP) [de

Radioactively induced noise in gas-sampling uranium calorimeters

International Nuclear Information System (INIS)

Gordon, H.A.; Rehak, P.

1982-01-01

The signal induced by radioactivity of a U 238 absorber in a cell of a gas-sampling uranium calorimeter was studied. By means of Campbell's theorem, the levels of the radioactively induced noise in uranium gas-sampling calorimeters was calculated. It was shown that in order to obtain similar radioactive noise performance as U-liquid argon or U-scintillator combinations, the α-particles from the uranium must be stopped before entering the sensing volume of gas-uranium calorimeters

Measurement of the polarization of cumulative protons in γA → pX reaction

International Nuclear Information System (INIS)

Avakyan, R.O.; Avakyan, E.O.; Avetisyan, A.Eh.

1985-01-01

The polarization of cumulative protons in γA → px reaction is measured in the range of proton energy (190+270) MeV for C, Cu, Sn, Pb nuclei. The measured polarization is practically independent of the energy of protons and the atomic number of nuclei

Redox reactivity and coordination chemistry of uranium

International Nuclear Information System (INIS)

Nocton, G.

2009-09-01

The study and the understanding of actinides chemistry have important implications in the nuclear field both for the development of new actinides materials and the retreatment of the nuclear wastes. One of the major issues in that chemistry is that the actinides elements are known to undergo redox reaction and to form assemblies of different size and different topologies. In that context uranium can be a good model of the heavier radioelement because it is much less radioactive. So, this work concerns the synthesis and the study of the spectroscopy and the magnetic properties of several uranium based polymetallic assemblies synthesized by taking advantage of the redox properties and the coordination chemistry of uranium. The hydrolysis reactivity of trivalent uranium has been studied in absence of sterically hindered ligands and led to the synthesis of oxo/hydroxo uranium assemblies with different sizes by changing the starting complex or the reaction conditions. By following the same strategy, the controlled oxidation of trivalent uranium complexes led to an original azido/nitrido uranium complex. The coordination chemistry of the pentavalent uranyl polymer {[UO 2 py 5 ][KI 2 py 3 ]} n has also been studied with different ligand and in different conditions and led to several cation-cation complexes for which the stability is sufficient for studying there dismutation by proton NMR. By changing the ancillary ligands stable monomeric complexes of pentavalent uranyl complexes were also obtained. The magnetic properties of all the complexes, monomers and polymetallic complexes were studied and an antiferromagnetic coupling was observed for the cation-cation pentavalent uranyl dimer [UO 2 (dbm) 2 (K 18 C 6 )] 2 . (author)

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)

238U-234U-230Th chronometry of Fe-Mn crusts: Growth processes and recovery of thorium isotopic ratios of seawater

International Nuclear Information System (INIS)

Chabaux, F.; Cohen, A.S.; O'Nions, R.K.; Hein, J.R.

1995-01-01

Comparison of ( 234 U) excess /( 238 U) and ( 230 Th)/( 232 Th) activity ratios in oceanic Fe-Mn deposits provides a method for assessing the closed-system behaviour of 238 U- 234 U- 230 Th, as well as variations in the initial uranium and thorium isotopic ratios of the precipitated metal oxides. This approach is illustrated using a Fe-Mn crust from Lotab seamount (Marshall Islands, west equatorial Pacific). Here we report uranium and thorium isotopic compositions in five subsamples from the surface of one large 5 cm diameter botyroid of this crust, and from two depth profiles of the outermost rim of the same botyroid. The decrease of ( 234 U) excess /( 238 U) and ( 230 Th/ 232 Th) activity ratio with depth in the two profiles gives mean growth rates, for the last 150 ka, of 7.8 ± 2 mm/Ma and 6.6 ± 1 mm/Ma, respectively. All data points (surface and core samples) but one, define a linear correlation in the Ln ( 230 Th/ 232 Th) - Ln [( 234 U) excess ( 238 U)] diagram. This correlation indicates that for all points the U-Th system remained closed after the Fe-Mn layer precipitated, and that the different samples possessed the same initial Uranium and thorium isotope ratios. Furthermore, these results show that the preserved surface of this Fe-Mn crust may not be the present-day growth surface, and that the thorium and uranium isotopic ratios of seawater in west equatorial Pacific have not changed during the past 150 ka. The initial thorium activity ratio is estimated from the correlation obtained between Ln( 230 Th/ 232 Th) and Ln [( 234 U) excess /( 238 U)

Fission-residues produced in the spallation reaction 238U + p at 1 A GeV

International Nuclear Information System (INIS)

Bernas, M.; Armbruster, P.; Benlliure, J.; Boudard, A.; Casarejos, E.; Czajkowski, S.; Enqvist, T.; Legrain, R.; Leray, S.; Mustapha, B.; Napolitani, P.; Pereira, J.; Rejmund, F.; Ricciardi, M.V.; Schmidt, K.H.; Stephan, C.; Taieb, J.; Tassan-Got, L.; Volant, C.

2003-04-01

Fission fragments from 1 A GeV 238 U projectiles irradiating a hydrogen target were investigated by using the fragment separator FRS for magnetic selection of reaction products including ray-tracing and ΔE-ToF techniques. The momentum spectra of identified fragments were analysed to provide isotopic production cross sections, fission-fragment velocities and recoil momenta of the fissioning parent nuclei. Besides their general relevance, these quantities are also demanded for applications. Calculations and simulations with codes commonly used and recently developed or improved are compared to the data. (orig.)

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

Isotopic resolution of fission fragments from 238U + 12C transfer and fusion reactions

International Nuclear Information System (INIS)

Caamano, M.; Rejmund, F.; Derkx, X.; Schmidt, K. H.; Andouin, L.; Bacri, C. O.; Barreau, G.; Benlliure, J.; Casarejos, E.; Fernandez-Dominguez, B.; Gaudefroy, L.; Golabek, C.; Jurado, B.; Lemasson, A.; Navin, A.; Rejmund, M.; Roger, T.; Shrivastava, A.; Schmitt, C.; Taieb, J.

2010-01-01

Recent results from an experiment at GANIL, performed to investigate the main properties of fission-fragment yields and energy distributions in different fissioning nuclei as a function of the excitation energy, in a neutron-rich region of actinides, are presented. Transfer reactions in inverse kinematics between a 238 U beam and a 12 C target produced different actinides, within a range of excitation energy below 30 MeV. These fissioning nuclei are identified by detecting the target-like recoil, and their kinetic and excitation energy are determined from the reconstruction of the transfer reaction. The large-acceptance spectrometer VAMOS was used to identify the mass, atomic number and charge state of the fission fragments in flight. As a result, the characteristics of the fission-fragment isotopic distributions of a variety of neutron-rich actinides are observed for the first time over the complete range of fission fragments. (authors)

Activation cross-section measurements of some proton induced reactions on Ni, Co and Mo for proton activation analysis (PAA) purposes

International Nuclear Information System (INIS)

Alharbi, A.A.; Alzahrani, J.; Azzam, A.; Nuclear Research Center, Cairo

2011-01-01

The experimental proton induced reaction cross sections on some elements of the Havar alloy were measured using the activation method and the well established stacked-foil technique combined with high resolution gamma-ray spectroscopy. They included the reactions nat Ni(p,x) 57 Ni, nat Co(p,x) 58(m+g) Co and nat Mo(p,x) 94g,95g,96(m+g) Tc, the aim being to obtain reliable data in the proton energy range up to 26 MeV for some important reactions to be used in the proton activation analysis of steel or other alloys. Irradiations were performed using the CS-30 Cyclotron at KFSH and RC, Riyadh, Saudi Arabia. The activity measurements were carried out in PNU laboratories, Riyadh, Saudi Arabia. The experimental excitation functions for the investigated reactions were constructed and compared with the performed computed theoretical nuclear model calculations using two different codes: ALICE-IPPE and TALYS. A comparison between our measured cross-section values and the available published data is also presented, with a view to checking the consistency of the reported experimental work from various laboratories.

Estimation of uranium and cobalt-60 distribution coefficients and uranium-235 enrichment at the Combustion Engineering Company site in Windsor, Connecticut

International Nuclear Information System (INIS)

Wang, Y.; Orlandini, K.A.; Yu, C.

1996-05-01

Site-specific distribution coefficients for uranium isotopes and cobalt-60 (Co-60) and the fraction of uranium-235 (U-235) enrichment by mass were estimated for environmental samples collected from the Combustion Engineering Company site in Windsor, CT. This site has been identified for remedial action under the US Department of Energy's (DOE) Formerly Utilized Sites Remedial Action Program. The authority of DOE at the Combustion Engineering site is limited to (1) Building 3; (2) other activities or areas associated exclusively with Building 3 (such as sewer lines); or (3) contamination that is exclusively highly enriched uranium. In this study, 16 samples were collected from the Combustion Engineering site, including 8 soil, 4 sediment, 3 water, and 1 water plus sludge sample. These samples were analyzed for isotopic uranium by alpha spectrometry and for Co-60 by gamma spectrometry. The site-specific distribution coefficient for each isotope was estimated as the ratio of extractable radionuclide activity in the solid phase to the activity in the contact solution following a 19-day equilibration. The uranium activity measurements indicate that uranium-234 (U-234) and uranium-238 (U-238) were in secular equilibrium in two soil samples and that soil and sediment samples collected from other sampling locations had higher U-234 activity than U-238 activity in both the solid and solution phases. The site-specific distribution coefficient (Kd) ranged from 82 to 44,600 mL/g for U-238 and from 102 to 65,900 mL/g for U-234. Calculation of U-235 enrichment by mass indicated that four soil samples had values greater than 0.20; these values were 0.37, 0.38, 0.46, and 0.68. Cobalt-60 activity was detected in only three sediment samples. The measured Co-60 activity in the solid phase ranged from 0.15 to 0.45 pCi/g and that in the water phase of all three samples combined was 4 pCi/L. The Kd value for Co-60 in the site brook sediment was calculated to be 70 mL/g

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)

Reaction of nickel with uranium mononitride

International Nuclear Information System (INIS)

Anselin, F.; Calais, D.; Lorenzelli, N.; Passefort, J.C.

1965-01-01

UN-Ni system has been investigated in solid phase by diffusion couples UN-Ni or by mixed powders pressed and sintered. Studies have been carried out by micrography, X-rays and microanalysis with a CASTAING microprobe. UN-Ni compatibility is quite good up to 600 C; beyond this temperature diffusion zones corresponding to UNi 5 and U 2 N 3 appear in the couples either reaction : 3 U N + 5 Ni → U 2 N 3 + UNi 5 ; UN + 5 Ni → UNi 5 + 1/2 N 2 takes place from 700 C according to nitrogen pressure involved. For temperatures between 800 and 1000 C nickel solubility in uranium nitride is 1500 ± 500 wt ppm. (authors) [fr

Search for proton emission in {sup 54}Ni and multi-nucleon transfer reactions in the actinide region

Energy Technology Data Exchange (ETDEWEB)

Geibel, Kerstin

2012-06-15

The first part of the thesis presents the investigation of fusion-evaporation reactions in order to verify one-proton emission from the isomeric 10{sup +} state in the proton rich nucleus {sup 54}Ni. Between the years 2006 and 2009 a series of experimental studies were performed at the Tandem accelerator in the Institut fuer Kernphysik (IKP), University of Cologne. These experiments used fusion-evaporation reactions to populate {sup 54}Ni via the two-neutron-evaporation channel of the compound nucleus {sup 56}Ni. The cross section for the population of the ground state of {sup 54}Ni was predicted to be in orders of microbarn. This required special care with respect to the sensitivity of the experimental setup, which consisted of a double-sided silicon-strip detector (DSSSD), a neutron-detector array and HPGe detectors. In two experiments the excitation functions of the reactions ({sup 32}S+{sup 24}Mg) and ({sup 28}Si+{sup 28}Si) were determined to find the optimal experimental conditions for the population of {sup 54}Ni. A final experiment employed a {sup 28}Si beam at an energy of 70 MeV, impinging on a {sup 28}Si target. With a complex analysis it is possible to obtain a background-free energy spectrum of the DSSSD. An upper cross section limit for the population of the 10{sup +} state in {sup 54}Ni is established at σ({sup 54}Ni(10{sup +})) ≤ (13.9 ± 7.8) nbarn. In the second part of the thesis the population of actinide nuclei by multi-nucleon transfer reactions is investigated. Two experiments, performed in 2007 and 2008 at the CLARA-PRISMA setup at the Laboratori Nazionali di Legnaro, are analyzed with respect to the target-like reaction products. In both experiments {sup 238}U was used as target. A {sup 70}Zn beam with 460 MeV and a {sup 136}Xe beam with 926 MeV, respectively, impinged on the target, inducing transfer reactions. Kinematic correlations between the reaction partners are used to obtain information on the unobserved target-like reaction

Comparative studies for determining U-235/U-238 relation in solutions of natural and depleted uranium using gamma spectrometry and neutron activation analysis

International Nuclear Information System (INIS)

Cassorla F, V.; Valle M, L.; Pena V, L.

1988-01-01

Two experimental methods were developed for determining U-235/U-238 ratio in uranium solutions. The isotopic was measured by high resolution ratio gamma-ray spectrometry (G.S.) and neutron activation analysis (N.A.A.). The precision obtained was similar for both methods, but better sensitivity was obtained by N.A.A. The accuracy in both cases was stablished by comparison with samples previously analyzed by mass spectrometry, the results were satisfactory for both techniques. Studies involving the influence of the nitric acid concentration on the isotopic ratio measurement, also were done. In addition, computer programs for faster data reduction were developped, in the case of N.A.A. (author)

Application of activation methods on the Dubna experimental transmutation set-ups.

Science.gov (United States)

Stoulos, S; Fragopoulou, M; Adloff, J C; Debeauvais, M; Brandt, R; Westmeier, W; Krivopustov, M; Sosnin, A; Papastefanou, C; Zamani, M; Manolopoulou, M

2003-02-01

High spallation neutron fluxes were produced by irradiating massive heavy targets with proton beams in the GeV range. The experiments were performed at the Dubna High Energy Laboratory using the nuclotron accelerator. Two different experimental set-ups were used to produce neutron spectra convenient for transmutation of radioactive waste by (n,x) reactions. By a theoretical analysis neutron spectra can be reproduced from activation measurements. Thermal-epithermal and fast-super-fast neutron fluxes were estimated using the 197Au, 238U (n,gamma) and (n,2n) reactions, respectively. Depleted uranium transmutation rates were also studied in both experiments.

Detection limit of 238U by gamma spectrometry

International Nuclear Information System (INIS)

Tartaglione, A.; Blostein, J.; Mayer, R

2004-01-01

The detection limit of 238 U was determined by gamma spectra measurements of a depleted uranium sample using four NaI(Tl) scintillators in a compact arrangement.The sample was shielded with 5 and 10 cm of lead.Two different methods for data processing were used and compared.It was established that an appropriate array of 40 detectors could establish the presence of 220 g of this material in only 5 minutes [es

Low-Energy Nuclear Reactions of Protons in Host Metals at Picometre Distance

International Nuclear Information System (INIS)

Heinrich Hora; George H. Miley; Jak C. Kelly

2000-01-01

A review is given for the explanation of the measurements of Miley (et al.) of a fully reproducible generation of nuclei of the whole periodic table by protons in host metals during a several-weeks reaction. Similar low-energy nuclear reactions (LENR) were observed by other groups. The fact that the heavy nuclides are not due to pollution can be seen from the fact that such very rare elements as thulium and terbium were detected by unique K-shell X-ray spectra. The nuclear reaction energy goes into the heavy nuclei as measured from much bigger traces in CR39 than from alphas. The fact that any reaction of the protons results in stable daughter nuclei is confirmed by the fact that the highest energy gain is resulting with stable reaction products. This has been explained in Ref. 2, and the energy gain for the heavy element generation by a compound reaction was discussed. The explanation is based on the model of the authors from 1989 to assume free motion of the protons contrary to localized crystalline states. A relation of the reaction time U on distance d of the reacting nuclei by a power law with an exponent 34.8 was derived. Based on few reproducible D-D reactions, a reaction time near the range of megaseconds and a reaction distance of nanometers was concluded. A splendid confirmation of the picometre-megasecond reactions was achieved by Li (et al.) from his direct quantum mechanical calculations of the hot fusion D-T reactions based on a one-step selective resonance tunneling model. Li (et al.) were able for the first time to derive the cross sections of the hot fusion. Li's application to picometre distance showed megasecond reaction times with no neutron or gamma emission. Because of the imaginary part in the Schroedinger potential, the problem of the level width is reduced by damping

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

Quantitative analysis of skin reaction by reflectance spectrophotometer. Acute reaction following proton therapy

International Nuclear Information System (INIS)

Kawashima, Mitsuhiko; Okumura, Toshiyuki; Tatsuzaki, Hideo; Tsuji, Hiroshi; Tsujii, Hirohiko.

1994-01-01

Acute reactions induced by proton irradiation were measured using a reflectance spectrophotometer, which is commonly used in the printing and textile industries. In this method, the skin color was expressed by three parameters, lightness (L * ), chroma (C * ) and hue (h). At first, in order to evaluate the accuracy of this spectrophotometer, the skin color of a normal volunteer was measured 100 times. The values of the three parameters for normal skin were as follows (mean values and standard deviation), L * : 68.64±0.29, C * : 19.08±0.13, h: 69.41±0.76. The standard deviations with regard to L * and h, were considered to be sufficiently small when compared with the changes of these parameters (prefix: Δ) in the irradiated sites (ΔL * * and h values significantly decreased with time, and the L * values were highly correlated with elapsed treatment days. The h values had a relatively low linear correlation compared with L * . The C * values had no trends as the treatment period was extended. Among these parameters, the L * values were the most valuable for assessment of proton-induced skin reactions, and it was suggested that the L * values measured with this spectrophotometer were a useful index for showing biological effects induced by proton irradiation. Further experiments are needed to apply this method to quantify the biological effects induced by other forms of ionizing radiation. (author)

Influence of uranium hydride oxidation on uranium metal behaviour

International Nuclear Information System (INIS)

Patel, N.; Hambley, D.; Clarke, S.A.; Simpson, K.

2013-01-01

This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

Influence of uranium hydride oxidation on uranium metal behaviour

Energy Technology Data Exchange (ETDEWEB)

Patel, N.; Hambley, D. [National Nuclear Laboratory (United Kingdom); Clarke, S.A. [Sellafield Ltd (United Kingdom); Simpson, K.

2013-07-01

This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

Measurements of the effective range of fission fragments in UO2 and the disintegration constant for spontaneous fission of 238U

International Nuclear Information System (INIS)

Spaggiari, E.R.V.

1978-01-01

The results of measuments of the disintegration constant for spontaneous fission in 238 U are presented, with a discussion on the method used for the detection of fission tracks in muscovite mica. Samples of muscovite mica sandwiched between two natural uranium dioxide cylinders were irradiated with fragments of spontaneous fission and the etched tracks counted with projetion optical microscope. The effective thickness of the UO 2 layer which contributed to the observed tracks was measured through irradiation of mica samples, in contact with the UO 2 cylinder with 14,0 MeV neutrons from a (d,t) reaction. (Author) [pt

Uranium, thorium and potassium contents and radioactive equilibrium states of the uranium and thorium series nuclides in phosphate rocks and phosphate fertilizers

Energy Technology Data Exchange (ETDEWEB)

Komura, K; Yanagisawa, M; Sakurai, J; Sakanoue, M

1985-10-01

Uranium, thorium and potassium contents and radioactive equilibrium states of the uranium and thorium series nuclides have been studied for 2 phosphate rocks and 7 phosphate fertilizers. Uranium contents were found to be rather high (39-117 ppm) except for phosphate rock from Kola. The uranium series nuclides were found to be in various equilibration states, which can be grouped into following three categories. Almost in the equilibrium state, 238U approximately 230Th greater than 210Pb greater than 226Ra and 238U greater than 230Th greater than 210Pb greater than 226Ra. Thorium contents were found to be, in general, low and appreciable disequilibrium of the thorium series nuclides was not observed except one sample. Potassium contents were also very low (less than 0.3% K2O) except for complex fertilizers. Based on the present data, discussions were made for the radiation exposure due to phosphate fertilizers.

Estimates of the astrophysical S-factors for proton radiative capture by 10B and 24Mg nuclei using the ANCs from proton transfer reactions

International Nuclear Information System (INIS)

Artemov, S.V.; Igamov, S.B.; Karakhodzhaev, A.A.; Nie, G.K.; Yarmukhamedov, R.; Zaparov, E.A.; Burtebaev, N.; Rehm, K.E.

2010-01-01

The contribution of the direct radiative capture of protons by 10 B and 24 Mg nuclei at low energies to the astrophysical S-factors in the reactions 10 B(p,γ) 11 C and 24 Mg(p,γ) 25 Al have been calculated within the R-matrix formalism by using empirical proton asymptotical normalization coefficients (ANC). The ANCs for bound proton configurations { 10 B+p} and { 24 Mg+p} were obtained from the analysis of the reactions ( 3 He, d). The ANCs were also estimated from the values of the neutron ANCs in the mirror nucleus 25 Mg following the suggestion that the neutron and the proton in the mirror states have equivalent nuclear potentials. It has been found that the S-factor for the reaction 10 B(p,γ) 11 C extrapolated to zero energy contributes ~100 keV b to the radiative capture to the ground state of 11 C. For the reaction 24 Mg(p,γ) 25 Al the value S(0) gives 58 keV b with a direct capture contribution of 41 keV b. (author)

Spectrographic determination of boron and silicon in uranium tetrafluoride: Study of the chemical reactions in the electrode cavity when ZnO is used as a uranium excitation suppressor

International Nuclear Information System (INIS)

Alduan, F. A.; Capdevila, C.; Roca, M.

1973-01-01

A method has been developed for determining traces of boron and silicon in uranium tetrafluoride. Use is made of zinc oxide to decrease the volatilization of uranium and achieve high sensitivities. The thermochemical reactions which occur in the anode cavity during the arcing process have been investigated. UO 2 and a uranium, zinc and fluorine compound, both less volatile than uranium tetrafluoride, are formed. (Author)

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)

Isotope shift of 234U, 236U, 238U in U I

International Nuclear Information System (INIS)

Gagne, J.M.; Nguyen Van, S.; Saint-Dizier, J.P.; Pianarosa, P.

1976-01-01

New and very accurate data of isotope shifts and relative isotope shifts in 234 U, 236 U, 238 U are presented. The invariance of the relative isotope shift, for the transitions we have investigated, supports the hypothesis that the so called specific mass effect is negligible in uranium

Derivation of uranium residual radioactive material guidelines for the Shpack site

International Nuclear Information System (INIS)

Cheng, J.J.; Yu, C.; Monette, F.; Jones, L.

1991-08-01

Residual radioactive material guidelines for uranium were derived for the Shpack site in Norton, Massachusetts. This site has been identified for remedial action under the Formerly Utilized Sites Remedial Action Program (FUSRAP) of the US Department of Energy (DOE). The uranium guidelines were derived on the basis of the requirement that the 50-year committed effective dose equivalent to a hypothetical individual who lives or works in the immediate vicinity of the Shpack site should not exceed a dose of 100 mrem/yr following decontamination. The DOE residual radioactive material guideline computer code, RESRAD, which implements the methodology described in the DOE manual for implementing residual radioactive material guidelines, was used in this evaluation. Three potential scenarios were considered for the site; the scenarios vary with regard to time spent at the site, sources of water used, and sources of food consumed. The results of the evaluation indicate that the basic dose limit of 100 mrem/yr will not be exceeded for uranium (including uranium-234, uranium-235, and uranium-238) within 1000 years, provided that the soil concentration of combined uranium (uranium-234 and uranium-238) at the Shpack site does not exceed the following levels: 2500 pCi/g for Scenario A (recreationist: the expected scenario); 1100 pCi/g for Scenario B (industrial worker: a plausible scenario); and 53 pCi/g for Scenario C (resident farmer using a well water as the only water source: a possible but unlikely scenario). The uranium guidelines derived in this report apply to the combined activity concentration of uranium-234 and uranium-238 and were calculated on the basis of a dose of 100 mrem/yr. In setting the actual uranium guidelines for the Shpack site, DOE will apply the as low as reasonably achievable (ALARA) policy to the decision-making process, along with other factors, such as whether a particular scenario is reasonable and appropriate. 8 refs., 2 figs., 8 tabs

Radioactivity inventory of the test uranium target at TRIUMF

International Nuclear Information System (INIS)

Danas, Ridikas

2008-03-01

The main goal of this note is to characterize the radioactivity inventory for the licensing purposes of the low power uranium target at TRIUMF. The cylindrical target geometry was chosen in a rather simplistic way, where 56.71 g of uranium oxide (UO 2 : 50.0 g of 238 U and 6.71 g of 16 O with the theoretical density of 10.96 g/cm 3 ) was homogeneously distributed in the target active volume of 38.17 cm 3 . The target was irradiated with 500 MeV protons at the nominal beam intensity of 1 μA. In this work the Monte Carlo code MCNPX coupled to the material transmutation code CINDER-90, both being products of the LANL (Usa), were employed. This note is organized as follows: Appendix A gives a brief description of the modeling tools and Appendix B provides a number of benchmark examples in order to check the validity of model predictions. In the result section a summarized activation inventory history is provided as a function of different cooling time steps. A particular emphasis is given to the long-lived volatile fission products and heavy residual nuclei being alpha emitters

Reactive transport modeling of uranium 238 and radium 226 in groundwater of the Königstein uranium mine, Germany

Science.gov (United States)

Nitzsche, O.; Merkel, B.

Knowledge of the transport behavior of radionuclides in groundwater is needed for both groundwater protection and remediation of abandoned uranium mines and milling sites. Dispersion, diffusion, mixing, recharge to the aquifer, and chemical interactions, as well as radioactive decay, should be taken into account to obtain reliable predictions on transport of primordial nuclides in groundwater. This paper demonstrates the need for carrying out rehabilitation strategies before closure of the Königstein in-situ leaching uranium mine near Dresden, Germany. Column experiments on drilling cores with uranium-enriched tap water provided data about the exchange behavior of uranium. Uranium breakthrough was observed after more than 20 pore volumes. This strong retardation is due to the exchange of positively charged uranium ions. The code TReAC is a 1-D, 2-D, and 3-D reactive transport code that was modified to take into account the radioactive decay of uranium and the most important daughter nuclides, and to include double-porosity flow. TReAC satisfactorily simulated the breakthrough curves of the column experiments and provided a first approximation of exchange parameters. Groundwater flow in the region of the Königstein mine was simulated using the FLOWPATH code. Reactive transport behavior was simulated with TReAC in one dimension along a 6000-m path line. Results show that uranium migration is relatively slow, but that due to decay of uranium, the concentration of radium along the flow path increases. Results are highly sensitive to the influence of double-porosity flow. Résumé La protection des eaux souterraines et la restauration des sites miniers et de prétraitement d'uranium abandonnés nécessitent de connaître le comportement des radionucléides au cours de leur transport dans les eaux souterraines. La dispersion, la diffusion, le mélange, la recharge de l'aquifère et les interactions chimiques, de même que la décroissance radioactive, doivent être

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

Determination of average fission fraction produced by 14 MeV neutrons in assemblies with large volume of depleted uranium

International Nuclear Information System (INIS)

Wang Dalun; Li Benci; Wang Xiuchun; Li Yijun; Zhang Shaohua; He Yongwu

1991-07-01

The average fission fraction of 238 U caused by 14 MeV neutrons in assemblies with large volume depleted uranium has been determined. The measured value of p f 238U (R ∞ depleted ) 14 was 0.897 ± 0.036. Measurements were also completed for neutron flux distribution and average fission fraction of 235 U isotope in depleted uranium sphere. Values of p f 238U (R depleted ) have been obtained by using a series of uranium spheres. For a sphere with Φ 600 the p f 23 '8 U (R 300 depleted ) is 0.823 ± 0.041, the density of depleted uranium assembly is 18.8g/cm 3 and total weight of assembly is about 2.8t

p-process nucleosynthesis via proton-capture reactions in thermonuclear supernovae explosions

Directory of Open Access Journals (Sweden)

Endres Anne

2015-01-01

Full Text Available Model calculations within the framework of the so-called γ process show an underproduction of the p nucleus with the highest isotopic abundace 92Mo. This discrepancy can be narrowed by taking into account the alternative production site of a type Ia supernova explosion. Here, the nucleus 92Mo can be produced by a sequence of proton-capture reactions. The amount of 92Mo nuclei produced via this reaction chain is most sensitive to the reactions 90Zr(p,γ and 91Nb(p,γ. Both rates have to be investigated experimentally to study the impact of this nucleosynthesis aspect on the long-standing 92Mo-problem. We have already measured the proton-capture reaction on 90Zr using high-resolution in-beam γ-ray spectroscopy. In this contribution, we will present our preliminary results of the total cross sections as well as the partial cross sections. Furthermore, we plan to measure the 91Nb(p,γ reaction soon. Due to the radioactive target material, the 91Nb nuclei have to be produced prior to the experiment. The current status of this production will be presented in this contribution.

Multilevel effect in uranium-238 and thorium-232 effective neutron capture resonance integrals

International Nuclear Information System (INIS)

Tellier, H.

1981-01-01

Until now, there has been a discrepancy between the computed and the measured values of the /sup 238/U effective capture integral. Recently, several new measurements of the resonance parameters were carried out and the use of a multilevel formalism was suggested to compute the /sup 238/U cross sections. This paper shows that the simultaneous use of recent parameters and the Reich-Moore formalism explain the discrepancy. 31 refs

Practical issues in discriminating between environmental and occupational sources in a uranium urinalysis bioassay program

International Nuclear Information System (INIS)

Long, M.P.; Carbaugh, E.H.; Fairrow, N.L.

1994-11-01

Workers at two Department of Energy facilities, the Pantex Plant in Texas and the Hanford Site in Washington, are potentially exposed to class Y depleted or natural uranium. Since trace amounts of uranium are naturally present in urine excretion, site bioassay programs must be able to discern occupational exposure from naturally occurring uranium exposure. In 1985 Hanford established a 0.2-μg/d environmental screening level for elemental uranium in urine; the protocol was based on log-normal probability analysis of unexposed workers. A second study of background uranium levels commenced in 1990, and experiences in the field indicated that there seemed to be an excessive number of urine samples with uranium above the screening level and that the environmental screening level should be reviewed. Due to unforeseen problems, that second study was terminated before the complete data could be obtained. Natural uranium in rock (by weight, 99.27% 288 U, 0.72% 235 U, and 0.006% 234 U) has approximately equal activity concentrations of 238 U and 234 U. Earlier studies, summarized by the U.S. Environmental Protection Agency in 51 FR 32068, have indicated that 234 U (via 234 Th) has a greater environmental mobility than 238 U and may well have a higher concentration in ground water. By assuming that the 238 U-to 234 U ratio in the urine of nonoccupationally exposed persons should reflect the ratio of environmental levels, significant occupational exposure to depleted uranium would shift that ratio in favor of 238 U, allowing use of the ratio as a co-indicator of occupational exposure in addition to the isotope-specific screening levels. This approach has been adopted by Pantex. The Pacific Northwest Laboratory is studying the feasibility of applying this method to the natural and recycled uranium mixtures encountered at Hanford. The Hanford data included in this report represent work-in-progress

Investigation of spatial distribution of fission-rate of natural uranium nuclei in the blanket of electronuclear setup 'Energy plus Transmutation' at Dubna Nuclotron proton beam at energy 1.5 GeV

International Nuclear Information System (INIS)

Hashemi-Nezhad, S.R.; Zhuk, I.V.; Kievets, M.; Krivopustov, M.I.; Sosnin, A.N.; Westmeier, W.; Brandt, R.

2008-01-01

The 'Energy plus Transmutation' experimental setup of the Veksler and Baldin Laboratory of High Energy Physics within the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, is a lead target (with a diameter of 8.4 cm and length of 45.6 cm) surrounded by a uranium blanket (weight 206.4 kg of natural uranium). A polyethylene plus cadmium shield is placed around the target-blanket assembly to modify the spallation and fission neutron spectra in the system. The setup was irradiated by a proton beam of energy 1.5 GeV using the Nuclotron accelerator. The spatial distribution of natural uranium fission-rate in the assembly and fission-rate in the blanket was determined experimentally and compared with Monte Carlo predictions using the MCNPX 2.6C code. Besides neutron-induced fission the calculations include the Nat U(p,f), Nat U(π,f) as well as Nat U(γ,f) reactions. Good agreement between the experimental and calculation results was obtained. The possible sources of errors in the experiment and calculations are discussed in detail

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

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)

Uranium uptake history, open-system behaviour and uranium-series ages of fossil Tridacna gigas from Huon Peninsula, Papua New Guinea

Science.gov (United States)

Ayling, Bridget F.; Eggins, Stephen; McCulloch, Malcolm T.; Chappell, John; Grün, Rainer; Mortimer, Graham

2017-09-01

Molluscs incorporate negligible uranium into their skeleton while they are living, with any uranium uptake occurring post-mortem. As such, closed-system U-series dating of molluscs is unlikely to provide reliable age constraints for marine deposits. Even the application of open-system U-series modelling is challenging, because uranium uptake and loss histories can affect time-integrated uranium distributions and are difficult to constrain. We investigate the chemical and isotopic distribution of uranium in fossil Tridacna gigas (giant clams) from Marine Isotope Stage (MIS) 5e (128-116 ka) and MIS 11 (424-374 ka) reefs at Huon Peninsula in Papua New Guinea. The large size of the clams enables detailed chemical and isotopic mapping of uranium using LA-ICPMS and LA-MC-ICPMS techniques. Within each fossil Tridacna specimen, marked differences in uranium concentrations are observed across the three Tridacna growth zones (outer, inner, hinge), with the outer and hinge zones being relatively enriched. In MIS 5e and MIS 11 Tridacna, the outer and hinge zones contain approximately 1 ppm and 5 ppm uranium respectively. In addition to uptake of uranium, loss of uranium appears prevalent, especially in the MIS 11 specimens. The effect of uranium loss is to elevate measured [230Th/238U] values with little effect on [234U/238U] values. Closed-system age estimates are on average 50% too young for the MIS 5e Tridacna, and 25% too young for the MIS 11 Tridacna. A complex, multi-stage uptake and loss history is interpreted for the fossil Tridacna and we demonstrate that they cannot provide independent, reliable geochronological controls on the timing of past reef growth at Huon Peninsula.

The determination of trace quantities of thorium and uranium in thick ore samples by proton-induced x-ray emission

International Nuclear Information System (INIS)

Cohen, D.D.; Duerden, P.; Clayton, E.

1979-07-01

Proton-induced X-ray emission (PIXE) techniques have been used to estimate the concentrations of trace quantities of thorium and uranium in powdered rock and ore samples. Standards of known concentrations were prepared in a carbon matrix and the yields from these used to determine simultaneously the concentrations of thorium and uranium in the ore samples. The experimental detection limit of the technique was found to be 3 to 4 μg g -1 for a 100 μC irradiation. The appropriate matrix corrections for a carbon and ore matrix have been calculated for thick targets and taken into consideration

Secondary radiation yield from a surface of heavy targets, irradiated by protons of average energies (E sub p approx 1 GeV)

CERN Document Server

Krupnyj, G I; Yanovich, A A

2001-01-01

Experimental data on the nuclear reaction rates of threshold rhodium, indium, phosphorus, sulfur, aluminium, carbon, niobium and bismuth activated detectors are presented. The detectors were set up on the cylindrical surface of full absorption targets: tungsten, uranium and chloride with the molar ratios of the 70 % NaCl and 30 % PbCl sub 2 salts. The targets were irradiated by protons with the energies from 0.8 to 1.21 GeV. Growth of the reaction rate with increasing reaction of primary protons and raising atomic number of the targets, presence of the target profile, where the maximum reaction rate is observed, are noted

Measurement of {sup 238}Np fission cross-section by neutrons near thermal point (preliminary results)

Energy Technology Data Exchange (ETDEWEB)

Abramo; vich, S.N.; Andreev, M.F.; Bol`shakov, Y.M. [Institute of Experimental Physics, Arzamas (Russian Federation)] [and others

1995-10-01

Measurements have been carried out of {sup 238}Np fission cross-section by thermal neutrons. The isotope {sup 238}Np was built up through the reaction {sup 238}U(p,n) on an electrostatic accelerator. Extraction and cleaning of the sample were done by ion-exchange chromatography. Fast neutrons were generated on the electrostatic accelerator through the reaction {sup 9}Be(d,n); a polyethylene block was used to slow down neutrons. Registration of fission fragments was performed with dielectric track detectors. Suggesting that the behavior of {sup 238}Np and {sup 238}U. Westscott`s factors are indentical the fission cross-section of {sup 238}Np was obtained: {sigma}{sub fo}=2110 {plus_minus} 75 barn.

Determination of irradiated uranium in far-field contaminated areas of Belarus

International Nuclear Information System (INIS)

Mironov, V.; Pribylev, S.; Hotchkis, M.; Child, D.

2006-01-01

The possibility of using U 236 as an indicator for irradiated uranium is shown. The sensitivity of AMS is high enough for measurements of 236 U/ 238 U ratios down to 10 -9 on micrograms of uranium and therefore for the detection of Chernobyl originated uranium in the remote regions of radioactive fallout. (authors)

Ab initio study on the reaction between uranium and O2

International Nuclear Information System (INIS)

Shuai Maobing; Zhao Pengji; Tian Anmin

2000-08-01

Optimized geometries, total energies and electronic structures of some gaseous atoms and molecules of uranium-oxygen system are calculated with harmonic vibration analysis using ab initio method. The potential energy surfaces (PESs) of the uranium oxidation process are also constructed. The calculated optimized geometries, infrared vibrational frequencies and the first ionized potential energies are in well accordance with available experimental data. Although U6p, U7s and U6d valence orbital electrons take part in the formation of U - O bond, the U5f electrons play an dominant role in this process and because the energies of U5f, U6d, U7s and Uds atomic orbitals are close to each other, these orbitals may hybrid and interact with O2p orbital, simultaneously, to form molecular orbitals of uranium oxides. The PESs show that different reaction modes result in different product geometries

Intake of 210Po, 234U and 238U radionuclides with beer in Poland

International Nuclear Information System (INIS)

Skwarzec, B.; Struminska, D.I.; Borylo, A.; Falandysz, J.

2004-01-01

238 U, 234 U and 210 Po activity concentrations were determined in beer in Poland by alpha-spectrometry with low-level activity silicon detectors. The results revealed that the mean concentrations of 238 U, 234 U and 210 Po in the analyzed beer samples were 4.63, 4.11 and 4.94 mBq x dm -3 , respectively, the highest in Tyskie (5.71 for 210 Po, 5.06 for 234 U and 6.11 for 238 U) and the lowest in Lech (2.49 for 210 Po). The effective radiation dose due to uranium and polonium ingestions by beer was calculated and were compared to the effective radiation dose from drinking water. (author)

Reaction of uranium and plutonium carbides with austenitic steels; Reaction des carbures d'uranium et de plutonium avec des aciers austenitiques

Energy Technology Data Exchange (ETDEWEB)

Mouchnino, M [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1967-07-01

The reaction of uranium and plutonium carbides with austenitic steels has been studied between 650 and 1050 deg. C using UC, steel and (UPu)C, steel diffusion couples. The steels are of the type CN 18.10 with or without addition of molybdenum. The carbides used are hyper-stoichiometric. Tests were also carried out with UCTi, UCMo, UPuCTi and UPuCMo. Up to 800 deg. C no marked diffusion of carbon into stainless steel is observed. Between 800 and 900 deg. C the carbon produced by the decomposition of the higher carbides diffuses into the steel. Above 900 deg. C, decomposition of the monocarbide occurs according to a reaction which can be written schematically as: (U,PuC) + (Fe,Ni,Cr) {yields} (U,Pu) Fe{sub 2} + Cr{sub 23}C{sub 6}. Above 950 deg. C the behaviour of UPuCMo and that of the titanium (CN 18.12) and nickel (NC 38. 18) steels is observed to be very satisfactory. (author) [French] La reaction des carbures d'uranium et de plutonium avec des aciers austenitiques a ete etudiee entre 650 deg. C et 1050 deg. C a partir de couples de diffusion UC, acier et (UPu)C, acier. Les aciers sont du type CN 18.10 avec ou sans addition de molybdene. Les carbures utilises sont hyper-stoechiometriques. En outre on a fait des essais avec UCTi, UCMo, UPuCTi, UPuCMo. Jusqu'a 800 deg. C on ne detecte pas de diffusion sensible du carbone dans l'acier inoxydable. Entre 800 et 900 deg. C il y a diffusion dans l'acier du carbone provenant de la decomposition des carbures superieurs. A partir de 900 deg. C il y a decomposition du monocarbure selon une reaction que l'on ecrit schematiquement: (U,PuC) + (Fe, Ni, Cr) {yields} (U,Pu)Fe{sub 2} + Cr{sub 23}C{sub 6}. Nous notons a 950 deg. C le bon comportement de UPuCMo ainsi que celui des aciers au titane (CN 18. 12) et au nickel (NC 38.18). (auteur)

Review of inelastic proton-proton reactions

CERN Document Server

Morrison, Douglas Robert Ogston

1973-01-01

The most important new results on inelastic proton-proton scattering obtained with the new machines, I.S.R. and N.A.L., are: (1) The inelastic cross-section increases monotonically with energy from threshold to 1500 GeV/c. Above 6 GeV/c the energy variation has a s /sup +0.04/ behaviour. (2) Scaling is observed at I.S.R. energies in pion production. Confirmation is obtained of the hypothesis of limiting fragmentation. (3) The results are in general, consistent with the two-component model-one class of events being produced by diffraction dissociation and the other by a short-range-order process (e.g. the multiperipheral model). (4) There are indications that the protons have a granular structure; this from observation of secondaries of large transverse momenta. (33 refs).

New explanation for extreme u-234 u-238 disequilibria in a dolomitic aquifer

CSIR Research Space (South Africa)

Kronfeld, J

1994-05-01

Full Text Available High U-234/U-238 activity ratios are found in the shallow groundwater of the phreatic Transvaal Dolomite Aquifer. The aquifer is uranium poor, while the waters are oxygen rich and young. Tritium and C-14 are used to show that the disequilibrium...

Sorption study of 226Ra(II) et 238U(VI) on to peat organic matter, in mining environment

International Nuclear Information System (INIS)

Bordelet, Gabrielle

2014-01-01

The environmental footprint of former uranium mining sites is a major concern for society. In order to guarantee the protection of ecosystems and thus a minimal radiological impact on the biosphere, it is important to understand and to be able to model the phenomena controlling the migration of uranium and its decay products, specially radium ( 226 Ra) (AREVA's Envir-at-Mines project). In the environment, among solid phases which can retain 238 U(VI) and 226 Ra(II), peat is known to have relevant affinity for U(VI). Because peat is usually composed at 90% dry weight of organic matter, the aim of this study was to qualify and quantify peat organic matter affinity for 238 U(VI) and 226 Ra(II). Peat samples extracted from Les Sagnes (close to a former uranium mining site in Limousin area, France) was characterised and batch adsorption/desorption experiments were conducted. The results indicate that 226 Ra(II) adsorption onto that peat is higher than 97% for pH ≥ 4-6 (depending on the organic/mineral ratio in dry peat) corresponding to K d values about 4500 ± 500 mL/g and 238 U(VI) adsorption is higher than 80% at pH ≥ 3 with K d maximal values reaching 11000 mL/g around pH 4.5. Only a little desorption was measured after one month. An ion exchange modelling for radium adsorption onto one type of organic matter sorption site was enough to fit the experimental adsorption K d for the peat over the whole range of pH. However, uranium sorption on peat can be modelled on that organic sorption site only from pH 1 to 5. From pH 5 to 10, to explain the experimental uranium adsorption K d values (close to 1500 mL/g), uranium sorption onto mineral phases (such as smectite and iron oxide in this study) has to be considered. An operational data set is given for both 238 U(VI) and 226 Ra(II) sorption onto Les Sagnes peat. Unlike usual peat, peat from Les Sagnes contains more than 10% dry weight of mineral matter. That is why it is necessary to model sorption of those two

The shielded chemistry suite at BNL and its use in the study of the irradiated uranium-water reaction

International Nuclear Information System (INIS)

Bannister, G.H.; Tyfield, S.P.

1977-11-01

A versatile shielded facility for chemical studies is now in use at Berkeley Nuclear Laboratories. The suite was fully commissioned in 1976 and first utilised to study the aqueous corrosion of irradiated reactor grade uranium. The suite consists of three adjacent interconnected cells; a balance cell, a preparation cell and an experimental cell. The development, design and layout of the facilities are described, as are the details of the equipment installed to undertake a uranium corrosion study. The preparation cell is used for procedures that could results in high levels of contamination, such as cutting of uranium specimens. The uranium samples are corroded in sealed steel capsules installed in the experimental cell. The capsules are heated either isothermally or through a transient and the reaction monitored with a pressure transducer which records the rate of hydrogen evolution from the uranium-water reaction. The experimental results will be reported elsewhere. (author)

Analysis for the radionuclides of the natural uranium and thorium decay chains with special reference to uranium mine tailings

International Nuclear Information System (INIS)

Lowson, R.T.; Short, S.A.

1986-08-01

A detailed review is made of the experimental techniques that are available, or are in the process of development, for the determination of 238 U, 235 U, 234 U, 231 Pa, 232 Th, 230 Th, 228 Th, 228 Ra, 226 Ra, 223 Ra, 210 Po and 210 Pb. These products of the uranium and thorium decay chains are found in uranium mine tailings. Reference is also made to a procedure for the selective phase extraction of mineral phases from uranium mine tailings

A review of the behaviour of U-238 series radionuclides in soils and plants

International Nuclear Information System (INIS)

Mitchell, N; Pérez-Sánchez, D; Thorne, M C

2013-01-01

The U-238 series of radionuclides is of relevance in a variety of environmental contexts ranging from the remediation of former uranium mining and milling facilities to the deep geological disposal of solid radioactive wastes. Herein, we review what is known concerning the behaviour of radionuclides from the U-238 decay chain in soils and plants. This review is intended to provide a single comprehensive source of information to anyone involved in undertaking environmental impact assessment studies relating to this decay chain. Conclusions are drawn relating to values and ranges of distribution coefficients appropriate to uranium, thorium, radium, lead and polonium in different soil types and under various environmental conditions. Similarly, conclusions are drawn relating to plant:soil concentration ratios for these elements for different plant and soil types, and consideration is given to the distribution of these elements within plants following both root uptake and foliar application. (review)

Effects of the anion salt nature on the rate constants of the aqueous proton exchange reactions.

Science.gov (United States)

Paredes, Jose M; Garzon, Andres; Crovetto, Luis; Orte, Angel; Lopez, Sergio G; Alvarez-Pez, Jose M

2012-04-28

The proton-transfer ground-state rate constants of the xanthenic dye 9-[1-(2-methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II), recovered by Fluorescence Lifetime Correlation Spectroscopy (FLCS), have proven to be useful to quantitatively reflect specific cation effects in aqueous solutions (J. M. Paredes, L. Crovetto, A. Orte, J. M. Alvarez-Pez and E. M. Talavera, Phys. Chem. Chem. Phys., 2011, 13, 1685-1694). Since these phenomena are more sensitive to anions than to cations, in this paper we have accounted for the influence of salts with the sodium cation in common, and the anion classified according to the empirical Hofmeister series, on the proton transfer rate constants of TG-II. We demonstrate that the presence of ions accelerates the rate of the ground-state proton-exchange reaction in the same order than ions that affect ion solvation in water. The combination of FLCS with a fluorophore undergoing proton transfer reactions in the ground state, along with the desirable feature of a pseudo-dark state when the dye is protonated, allows one unique direct determination of kinetic rate constants of the proton exchange chemical reaction. This journal is © the Owner Societies 2012

Polonium (210Po) and uranium (234U, 238U) in water, phosphogypsum and their bioaccumulation in plants around phosphogypsum waste heap at Wislinka (nothern Poland)

International Nuclear Information System (INIS)

Skwarzec, B.; Borylo, A.; Kosinska, A.; Radzajewska, S.

2010-01-01

The principal sources of polonium and uranium radionuclides the Wislinka area waste dump are phosphorites and phosphogypsum produced by the Phosphoric Fertilizers Industry of Gdansk. The values of uranium and polonium concentration in water with immediate surroundings of waste heap are considerably higher than in the waters of the Martwa Wisla river. The activity ratio 234 U/ 238 U is approximately about one in the phosphogypsum (0.97±0.06 and 0.99±0.04) and in the water of a retention reservoir and a pumping station (0.92±0.01 and 0.99±0.04), while in the water from the Martwa Wisla river is slightly higher than one (1.00±0.07 and 1.06±0.02). The leaching process of uranium and polonium from the phosphogypsum waste heap is responsible for the maximum uranium concentration (1097±6 μg·dm -3 and 1177±6 μg·dm -3 ) and the high 210 Po concentration (131.4±0.9 mBq·dm -3 and 165.7±1.4 mBq·dm -3 ) in the retention reservoir. The major source of polonium and uranium in plants are wet and dry atmospheric falls gathering soil and air dust from the phosphogypsum waste dump and root system. The highest uranium and polonium concentrations were found in older part of grasses (yellow oatgrass, meadow foxtail, moneywort), exposed to atmospheric falls for a long time. The maximum concentrations of 210 Po were characterized for samples of plant root collected at the retention reservoir (150.50±4.97 and 108.55±3.95 Bq·kg -1 dry mass). Polonium and uranium concentrations in water samples of the Martwa Wisla river are relatively low in comparison with the value in the retention reservoir and pumping station near the phosphogypsum waste heap. This suggests that the radionuclides could be leached from the dumping site to the surrounding environment. (authors)

Influence of the cosmic-ray induced fission tracks on the fission track of extraterrestric minerals via the 238U spontaneous fission

International Nuclear Information System (INIS)

Damm, G.; Thiel, K.

1977-01-01

The age determined by counting fission tracks of lunar and meteorite materials is obviously falsified by additional fission track parts not to be accounted for by the spontaneous fission of uranium 238. For this p and n induced fissions of U, Th and other hreavy elements through the cosmic radiation come into consideration. In order to determine the possible part of such interference factors, a simulation experiment at the proton synchrocycloton (CERN, Geneva) has been carried out and independently of this, the production rates for the p and n induced U, Th, Bi, Pb and Au in the surface-near regolith layers of the moon were calculated. It could be seen that the irradiation age as well as the spacial distribution of the heavy metals in the samples to be dated must be considered. (RB) [de

Evaluation of the excitation function of the 238U(n,2n)237U reaction for neutron energies from threshold to 19 MeV

International Nuclear Information System (INIS)

Kornilov, N.V.; Vinogradov, V.N.; Gay, E.V.; Rabotnov, N.S.; Salnikov, O.A.; Raics, P.; Daroczy, S.; Nagy, S.; Csikai, J.

1983-01-01

Experimental results for the 238 U(n,2n) reaction were collected from the literature and evaluated. The normalisation of the measured cross sections was carried out using recent values for the cross sections of standard monitor reactions as well as new nuclear decay data. The evaluated excitation function was then obtained by the Pade-approximation. (Auth.)

Neutron induced fission cross sections for /sup 232/Th, /sup 235,238/U, /sup 237/Np and /sup 239/Pu from 1 to 400 MeV

Energy Technology Data Exchange (ETDEWEB)

Lisowski, P.W.; Ullmann, J.L.; Balestrini, S.J.; Carlson, A.D.; Wasson, O.A.; Hill, N.W.

1988-01-01

Neutron-induced fission cross section ratios for samples of /sup 232/Th, /sup 235,238/U, /sup 237/Np and /sup 239/Pu have been measured from 1 to 400 MeV. The fission reaction rate was determined for all samples simultaneously using a fast parallel plate ionization chamber at a 20-m flight path. A well characterized annular proton recoil telescope was used to measure the neutron fluence up to 30 MeV. These data provided the shape of the /sup 235/U(n,f) cross section relative to the hydrogen scattering cross section. That shape was then normalized to the very accurately known values were determined using the neutron fluence measured with a second proton recoil telescope. Cross section values for /sup 232/Th, /sup 238/U, /sup 237/Np, and /sup 239/Pu were computed from the ratio data using our values for /sup 235/U(n,f). In addition to providing new results at high neutron energies, these data resolve long standing discrepancies among different data sets. 1 ref., 1 fig.

Determination of sup 238 U in marine organisms by inductively coupled plasma mass spectrometry. Yudo ketsugo plasma shitsuryo bunsekiho ni yoru kaiyo seibutsuchu no sup 238 U no teiryo

Energy Technology Data Exchange (ETDEWEB)

Ishii, T.; Nakahara, M; Matsuda, M.; Ishikawa, M. (National Institute of Radiological Sciences, Ibaraki (Japan))

1991-05-25

Since the {sup 238} U concentration in seawater is about 3ng/ml at the element level and the activity concentration is 40 {mu} Bq/ml which are considerably higher that those of other {alpha} radioactive materials, it is necessary to study the concentration levels of many marine organisms. After confirming that the inductively coupled plasma mass spectrometry as a new high sensitive analysis for multi-elements is effective to analyze heavy elements such as rare earth elements or uranium, etc., this method was applied to determine {sup 238} U in 55 species of marine organism. The {sup 238} U concentration in soft tissues of marine animal ranged from 0.076 to 5000ng/g wet weight and large difference of concentration was observed depending on the kind of animal and the tissue. Especially, the branchial heart of cephalopod molluscs showed the specific accumulation of {sup 238} U. The concentration factor of branchial heart of Octopus vulgaris which showed the highest value was calculated to be about 10 {sup 3} by comparing it with the concentration of {sup 238} U in Japanese coastal waterseas. The concentration of {sup 238} U in 20 species of algae ranged from 10 to 3700ng/g dry weight. 11 refs., 2 figs., 9 tabs.

Aprotic solvent systems provide mechanistic windows for biomolecular reactions: nucleic acid proton exchange

International Nuclear Information System (INIS)

McConnell, B.; Tan, A.

1986-01-01

Detection of general acid-base catalysis of proton transfer reactions in aqueous cytidine (or adenosine) is completely obscured by the highly reactive endocyclic protonated species of the nucleobase, whose amino proton lifetime is much shorter than that of the neutral form. In aqueous solution, protonation of the nucleobase always accompanies protonation of the buffer catalyzing exchange. However, in DMSO/water mixtures this is not the case; aqueous protonated acetate or chloroacetate can be added to cytidine in DMSO solutions without further dissociation of the buffer or significant protonation of cytidine N-3. Under these conditions general acid catalysis is observed, which involves an H-bonded complex between cytidine (N-3) and the buffer acid. Increased amino proton exchange in response to H-bond donation to C(N-3) is further suggested by increased 1 H NMR saturation-recovery rates with the formation of G-C base-pairs in DMSO and by the inverse dependence of amino proton exchange on nucleoside concentration

Hematological responses after inhaling {sup 238}PuO{sub 2}: An extrapolation from beagle dogs to humans

Energy Technology Data Exchange (ETDEWEB)

Scott, B.R.; Muggenburg, B.A.; Welsh, C.A.; Angerstein, D.A.

1994-11-01

The alpha emitter plutonium-238 ({sup 238}Pu), which is produced in uranium-fueled, light-water reactors, is used as a thermoelectric power source for space applications. Inhalation of a mixed oxide form of Pu is the most likely mode of exposure of workers and the general public. Occupational exposures to {sup 238}PuO{sub 2} have occurred in association with the fabrication of radioisotope thermoelectric generators. Organs and tissue at risk for deterministic and stochastic effects of {sup 238}Pu-alpha irradiation include the lung, liver, skeleton, and lymphatic tissue. Little has been reported about the effects of inhaled {sup 238}PuO{sub 2} on peripheral blood cell counts in humans. The purpose of this study was to investigate hematological responses after a single inhalation exposure of Beagle dogs to alpha-emitting {sup 238}PuO{sub 2} particles and to extrapolate results to humans.

Reduction of uranium hexafluoride to uranium tetrafluoride

International Nuclear Information System (INIS)

Chang, I.S.; Do, J.B.; Choi, Y.D.; Park, M.H.; Yun, H.H.; Kim, E.H.; Kim, Y.W.

1982-01-01

The single step continuous reduction of uranium hexafluoride (UF 6 ) to uranium tetrafluoride (UF 4 ) has been investigated. Heat required to initiate and maintain the reaction in the reactor is supplied by the highly exothermic reaction of hydrogen with a small amount of elemental fluorine which is added to the uranium hexafluoride stream. When gases uranium hexafluoride and hydrogen react in a vertical monel pipe reactor, the green product, UF 4 has 2.5g/cc in bulk density and is partly contaminated by incomplete reduction products (UF 5 ,U 2 F 9 ) and the corrosion product, presumably, of monel pipe of the reactor itself, but its assay (93% of UF 4 ) is acceptable for the preparation of uranium metal with magnesium metal. Remaining problems are the handling of uranium hexafluoride, which is easily clogging the flowmeter and gas feeding lines because of extreme sensitivity toward moisture, and a development of gas nozzel for free flow of uranium hexafluoride gas. (Author)

Determination of extremely low 236U/238U isotope ratios in environmental samples by sector-field inductively coupled plasma mass spectrometry using high-efficiency sample introduction

International Nuclear Information System (INIS)

Boulyga, Sergei F.; Heumann, Klaus G.

2006-01-01

A method by inductively coupled plasma mass spectrometry (Icp-Ms) was developed which allows the measurement of 236 U at concentration ranges down to 3 x 10 -14 g g -1 and extremely low 236 U/ 238 U isotope ratios in soil samples of 10 -7 . By using the high-efficiency solution introduction system APEX in connection with a sector-field ICP-MS a sensitivity of more than 5000 counts fg -1 uranium was achieved. The use of an aerosol desolvating unit reduced the formation rate of uranium hydride ions UH + /U + down to a level of 10 -6 . An abundance sensitivity of 3 x 10 -7 was observed for 236 U/ 238 U isotope ratio measurements at mass resolution 4000. The detection limit for 236 U and the lowest detectable 236 U/ 238 U isotope ratio were improved by more than two orders of magnitude compared with corresponding values by alpha spectrometry. Determination of uranium in soil samples collected in the vicinity of Chernobyl nuclear power plant (NPP) resulted in that the 236 U/ 238 U isotope ratio is a much more sensitive and accurate marker for environmental contamination by spent uranium in comparison to the 235 U/ 238 U isotope ratio. The ICP-MS technique allowed for the first time detection of irradiated uranium in soil samples even at distances more than 200 km to the north of Chernobyl NPP (Mogilev region). The concentration of 236 U in the upper 0-10 cm soil layers varied from 2 x 10 -9 g g -1 within radioactive spots close to the Chernobyl NPP to 3 x 10 -13 g g -1 on a sampling site located by >200 km from Chernobyl

Determination of extremely low (236)U/(238)U isotope ratios in environmental samples by sector-field inductively coupled plasma mass spectrometry using high-efficiency sample introduction.

Science.gov (United States)

Boulyga, Sergei F; Heumann, Klaus G

2006-01-01

A method by inductively coupled plasma mass spectrometry (ICP-MS) was developed which allows the measurement of (236)U at concentration ranges down to 3 x 10(-14)g g(-1) and extremely low (236)U/(238)U isotope ratios in soil samples of 10(-7). By using the high-efficiency solution introduction system APEX in connection with a sector-field ICP-MS a sensitivity of more than 5,000 counts fg(-1) uranium was achieved. The use of an aerosol desolvating unit reduced the formation rate of uranium hydride ions UH(+)/U(+) down to a level of 10(-6). An abundance sensitivity of 3 x 10(-7) was observed for (236)U/(238)U isotope ratio measurements at mass resolution 4000. The detection limit for (236)U and the lowest detectable (236)U/(238)U isotope ratio were improved by more than two orders of magnitude compared with corresponding values by alpha spectrometry. Determination of uranium in soil samples collected in the vicinity of Chernobyl nuclear power plant (NPP) resulted in that the (236)U/(238)U isotope ratio is a much more sensitive and accurate marker for environmental contamination by spent uranium in comparison to the (235)U/(238)U isotope ratio. The ICP-MS technique allowed for the first time detection of irradiated uranium in soil samples even at distances more than 200 km to the north of Chernobyl NPP (Mogilev region). The concentration of (236)U in the upper 0-10 cm soil layers varied from 2 x 10(-9)g g(-1) within radioactive spots close to the Chernobyl NPP to 3 x 10(-13)g g(-1) on a sampling site located by >200 km from Chernobyl.

Sintering with a chemical reaction as applied to uranium monocarbide

International Nuclear Information System (INIS)

Accary, A.; Caillat, R.

1960-01-01

The present paper provides a survey of different investigations whose aim was the preparation and fabrication of uranium monocarbide for nuclear use. If a chemical reaction takes place in the sample during the sintering operation, it may be expected that the atom rearrangements involved in this reaction should favour the sintering process and thereby lower the temperature needed to yield a body of a given density. With this hypothesis in mind, the following methods have been studied: - Sintering of U-C mixtures; - Sintering of UO 2 -C mixtures; - Hot pressing of U-C mixtures; - Extrusion of U-C mixtures. To generalize our result, it could be said that a chemical reaction does not lead to high densification, if one depends on a simple contact between discrete particles. On the contrary, a chemical reaction can help sintering if, as our hot pressing experiments shows, the densification can be achieved prior to the reaction. (author) [fr

Determination of 234U and 238U activity concentrations in groundwaters from three deep wells drilled in Itu Intrusive Suite (SP)

International Nuclear Information System (INIS)

Souza, Francisca de

2006-01-01

Activity concentrations of ( 234 U) and ( 238 U) were determined in groundwaters drawn from three deep wells drilled in rocks from Itu Intrusive Suite (SP), two located in Salto town (S and SY wells) and the other one in Itu (I well). Sampling was done from September, 2004 to December, 2005, and twelve samples of each well were collected monthly. For those determinations alpha spectrometry technique was used, providing high precision results, as shown by the very good agreement of the data obtained in the analyses of 23 duplicates. The waters from the three wells presented a considerable enrichment of 234 U in relation to 238 U, indicating an important radioactive disequilibrium of these isotopes. In well I, the activity concentrations of ( 238 U) varied from (1,06 +- 0,03) to (2,1+- 0,2) mBq/L and those of ( 234 U) spanned from (3,1 +- 0,2) to (6,0 +- 0,4) mBq/L, whereas ( 234 U/ 238 U) activity ratios did not present significant variation, during the sampling time interval, presenting an average of 2,8 +- 0,1. The S waters showed the lowest uranium concentrations and the largest diversity of ( 238 U) and ( 234 U) activity concentrations, which varied from (0,26 +- 0,02) to (1,07+- 0,08) mBq/L and from (1,8 +- 0,1) to (7,0 +- 0,5) mBq/L, respectively, and also presented variable ( 234 U/ 238 U) activity ratios, spanning from (2,79 +- 0,07) to (8,1+- 0,3). In SY well, ( 238 U) activities varied between (0,8 +- 0,1) and (4,2 +- 0,3) mBq/L and those ones of ( 234 U) from (14 +- 1) to (53 +- 4) mBq/L, whereas ( 234 U/ 238 U) ratios fell in the interval from 12,6 +- 0,3 to 18,3 +- 0,4, with the highest activities of both radioisotopes registered during the dry season and the lowest ones in the rainy time period. The ( 234 U/ 238 U) activity ratios, which were invariable during sampling period of well I, indicated the contribution of rainfall to recharge the aquifer. The observed correlation between those ratios and uranium concentrations, for S and SY wells, showed

Some reactions of uranium chloride pentafluoride

International Nuclear Information System (INIS)

Downs, A.J.; Gardner, C.J.

1986-01-01

The molecule UF 5 Cl has been isolated, together with an excess of UF 6 , in a solid matrix of Ar, N 2 , or CO and characterised by its i.r. spectrum. Under these conditions it dissociates under the action of radiation having wavelengths close to 500 nm to give UF 5 ; OCCl and OCClF are also formed on photolysis in a solid CO matrix, whereas a species believed to be U 2 F 11 is formed on photolysis in a solid N 2 matrix. CCl 3 F solutions of fluoride-rich mixtures of uranium(VI) chloride fluorides have been shown to function as chlorinating, fluorinating, or chlorofluorinating reagents in their reactions with various unsaturated molecules at temperatures low enough to preclude thermal decomposition of the mixed halides ( 0 C). (author)

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.)

Violence of heavy-ion reactions from neutron multiplicity: 11 to 20A MeV /sup 20/Ne+ /sup 238/U

International Nuclear Information System (INIS)

Jahnke, U.; Ingold, G.; Hilscher, D.; Lehmann, M.; Schwinn, E.; Zank, P.

1986-01-01

The suitability of the neutron multiplicity as a gauge for the violence of medium-energy heavy-ion reactions is investigated for the first time. For this purpose the number of neutrons emitted from fission reactions induced by 220-, 290-, and 400-MeV /sup 20/Ne on /sup 238/U is registered event-by-event with a large 4π scintillator tank. It is shown that the neutron multiplicity is indeed closely related to the two quantities characterizing the violence: the induced total intrinsic excitation and the linear momentum transfer

Polarization of cumulative protons in the reaction. gamma. A r arrow pX

Energy Technology Data Exchange (ETDEWEB)

Avakyan, R.O.; Avetisyan, A.E.; Arestakesyan, G.A.; Bartikyan, M.V.; Garibyan, Y.A.; Grigoryan, A.E.; Eganov, V.S.; Karapetyan, A.P.; Karapetyan, M.P.; Keropyan, I.A.; and others

1989-02-01

The polarization of cumulative protons has been measured in the reaction {gamma}{ital A}{r arrow}{ital pX} in the proton-energy region 170--270 MeV for C and Sn nuclei in bremsstrahlung beams produced by 4.5- and 1.5-GeV electrons. The measured polarization value is close to zero.

Study of neutron-proton pairing in N=Z unstable nuclei through transfer reactions

International Nuclear Information System (INIS)

Le Crom, B.

2016-01-01

A nucleus is described as a set of independent neutrons and protons linked by a mean-field potential. However, in order to have a better description one needs to take into account some residual interactions such as pairing. Neutron-neutron and proton-proton pairings are well-studied but neutron-proton pairing is not well-known. np pairing can be isovector pairing such as nn and pp pairing or isoscalar which is yet unknown. Over-binding of N=Z nuclei could be a manifestation of np pairing. We have studied np pairing through transfer reactions. In this case, the cross-section of np pair transfer is expected to be enhanced in the presence of important np pairing. np pairing is expected to be important in N=Z nuclei with high J orbitals. Since the development of radioactive beam facilities, such beams are only available. The experiment was performed at GANIL with an efficient set-up so as to detect products from the (p, 3 He) transfer reaction. This reaction is affected by isovector and isoscalar np pairing. We used 56 Ni and 52 Fe beams so as to see the effect of the occupancy of 0f 7/2 shell on the np pairing. First, we analysed the data from the 56 Ni(p,d) 55 Ni reaction and we compared the results with the literature to validate analysis procedure. After analysing data from the 56 Ni(p, 3 He) 54 Co reaction and extracting the population of the various states of 54 Co, we obtained information about the relative intensity between isoscalar and isovector np pairing in 56 Ni showing the predominance of isovector np pairing in this nucleus. Moreover, in the framework of developing a new charged particle detector, research on the discrimination of light nuclei using pulse shape analysis was performed and is also presented. (author)

Recent research on nuclear reaction using high-energy proton and neutron

Energy Technology Data Exchange (ETDEWEB)

Shibata, Tokushi [Tokyo Univ., Tanashi (Japan). Inst. for Nuclear Study

1997-11-01

The presently available high-energy neutron beam facilities are introduced. Then some interesting research on nuclear reaction using high-energy protons are reported such as the intermediate mass fragments emission and neutron spectrum measurements on various targets. As the important research using high-energy neutron, the (p,n) reactions on Mn, Fe, and Ni, the elastic scattering of neutrons, and the shielding experiments are discussed. (author)

Analogue studies in the alligator rivers region. In-situ measurement of uranium series nuclides with SHRIMP

Energy Technology Data Exchange (ETDEWEB)

Nagano, Tetsushi; Yanase, Nobuyuki; Ohnuki, Toshihiko [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Sato, Tsutomu; Isobe, Hiroshi; Williams, I.S.; Zaw, M.; Payne, T.E.; Airey, P.L.

1999-03-01

The SHRIMP analyses have been conducted for rock samples from the Koongarra secondary ore deposit to obtain activity ratios of {sup 234}U/{sup 238}U and isotopic ratios of {sup 207}Pb/{sup 206}Pb and {sup 204}Pb/{sup 206}Pb. Target minerals for the analyses were iron minerals and kaolinite, which are the main weathering products in this area. The activity ratios of {sup 234}U/{sup 238}U were obtained based on counts at masses of uranium metal. The {sup 234}U/{sup 238}U activity ratios based on counts of uranium oxides were not appropriate, because count rates of {sup 234}U{sup 16}O were interfered by those of {sup 238}U{sup 12}C molecule. The activity ratios of {sup 234}U/{sup 238}U were approximately unity for crystalline iron nodules. This fact suggested that the mean residence time of uranium within the iron nodules was at least 1 million years. On the other hand, slightly higher values than unity were obtained for kaolinite. Lead isotopes were investigated and a positive relationship was recognized between {sup 207}Pb/{sup 206}Pb and {sup 204}Pb/{sup 206}Pb isotope ratios. (author)

Current status of uranium enrichment by way of chemical exchange reactions

International Nuclear Information System (INIS)

El Basyouny, A.; Bechthold, H.C.; Knoechel, A.; Vollmer, H.J.

1985-04-01

For this report, conference proceedings, patents and other types of literature have been collected to present an account of the current status of uranium enrichment by way of chemical exchange reactions. The report further presents a new concept along with the relevant process strategy developed by the authors. The principal process of the new concept is a chemical exchange process with crown ethers, complexed or free, playing an important part in the reactions. The authors also describe their experiments carried out for establishing suitable chemical systems. (orig./PW) [de

Alternative repository criticality-control strategies for fissile uranium wastes

International Nuclear Information System (INIS)

Forsberg, C.W.

1998-01-01

Methods to prevent long term, disposal site nuclear criticality from fissile uranium isotopes in wastes were investigated. Long term refers to the time period after waste package (WP) failure and the subsequent loss of geometry and chemistry control within the WP. The preferred method of control was found to be the addition of sufficient depleted uranium to each WP so that the uranium enrichment is reduced to 235 U and 233 U in 238 U

Measurement of proton capture reactions in the hot cycles: an evaluation of experimental methods

Energy Technology Data Exchange (ETDEWEB)

Leleux, P [Inst. de Physique Nucleaire, Univ. Catholique de Louvain, Louvain-la-Neuve (Belgium)

1998-06-01

In the hot cycles, most of the proton capture reactions involve radioactive nuclei in the entrance and exit channels. This paper evaluates the specific methods that were designed to measure such reactions. (orig.)

Uranium-Series Disequilibria in the Groundwater of the Shihongtan Sandstone-Hosted Uranium Deposit, NW China

Directory of Open Access Journals (Sweden)

Xinjian Peng

2015-12-01

Full Text Available Uranium (U concentration and the activities of 238U, 234U, and 230Th were determined for groundwaters, spring waters, and lake water collected from the Shihongtan sandstone-hosted U ore district and in the surrounding area, NW China. The results show that the groundwaters from the oxidizing aquifer with high dissolved oxygen concentration (O2 and oxidation-reduction potential (Eh are enriched in U. The high U concentration of groundwaters may be due to the interaction between these oxidizing groundwaters and U ore bodies, which would result in U that is not in secular equilibrium. Uranium is re-precipitated as uraninite on weathered surfaces and organic material, forming localized ore bodies in the sandstone-hosted aquifer. The 234U/238U, 230Th/234U, and 230Th/238U activity ratios (ARs for most water samples show obvious deviations from secular equilibrium (0.27–2.86, indicating the presence of water-rock/ore interactions during the last 1.7 Ma and probably longer. The 234U/238U AR generally increases with decreasing U concentrations in the groundwaters, suggesting that mixing of two water sources may occur in the aquifer. This is consistent with the fact that most of the U ore bodies in the deposit have a tabular shape originati from mixing between a relatively saline fluid and a more rapidly flowing U-bearing meteoric water.

Hyperon production in photonuclear reactions on protons and deuterons : The Kappa(0)Sigma(+) channel

NARCIS (Netherlands)

Lohner, H; Bacelar, J; Castelijns, R; Messchendorp, J; Shende, S; Maeda, K; Tamura, H; Nakamura, SN; Hashimoto, O

2004-01-01

With the combined setup of the Crystal Barrel and TAPS photonspectrometers at ELSA in Bonn we have studied photonuclear reactions on protons and deuterons. From the series of experiments on single and multiple neutral meson emission we concentrate here on the hyperon production off protons and

Kinetics and mechanism of the oxidation of uranium (IV) by hypochlorous acid in aqueous acidic perchlorate media

International Nuclear Information System (INIS)

Silverman, R.A.; Gordon, G.

1976-01-01

The oxidation of uranium(IV) by hypochlorous acid has been studied in aqueous sodium perchlorate--perchloric acid solutions. The reaction U 4 + + 2HOCl = UO 2 2 + + Cl 2 (aq) + 2H + proceeds appropriate to the rate law --d[U(IV)]/dt = k 0 . [U 4+ ][HOCl][H + ] -1 . At 25 0 and 3 M ionic strength, k 0 is 1.08 +- 0.07 sec -1 . Over the 1--25 0 temperature range, ΔH 2+ is 18.4 +- 0.1 kcal mole -1 , and ΔS 2+ is 3.1 +- 0.4 eu. The inverse hydrogen ion dependence of the rate law is explained by a rapid preequilibrium, in which a proton is lost from one of the reactants. A uranyl-like activated complex, [H 2 UO 2 Cl 3+ ] 2+ , is suggested, with one proton likely to be residing on each oxygen atom. Evidence is presented that the mechanism involves a two-electron transfer, with the intermediate chloride ion rapidly reacting with hypochlorous acid to form chlorine. The uranium(IV)-hypochlorous acid reaction plays an important role in the oxidation of uranium(IV) by aqueous chlorine solutions. The magnitude of this role was seriously underestimated by previous investigators

Thermodynamic analysis and experimental study on the chlorination of uranium oxide by gas-solid reaction

International Nuclear Information System (INIS)

Shin, Y.J.; Kim, I.S.; Shin, H.S.; Ro, S.G.; Park, H.S.

1998-01-01

In order to determine the operating condition of an uranium chlorination process with U 3 O 8 -C-Cl 2 system, the experimental conditions have been evaluated preliminarily by the thermochemical analysis and experimentally confirmed in this study. The dry-type chlorination of U 3 O 8 occurs as irreversible and exothermic reaction and produces many kinds of chloride compounds such as UCl 3 , UCl 4 , UCl 5 , and UCl 6 in the air and humidity controlled argon environment. Taking account of Gibbs free energy and vapor pressure for various chloride compounds, the proper temperature range of chlorination appears to be 863 to 953 K in aspects of increasing reaction rate and the yield of nonvolatile product. In the course of the experimental confirmation the powder of U 3 O 8 is perfectly converted into uranium chlorides within 4 hours above 863 K, and then the maximum fraction of uranium chloride remaining in the reactor is about 30% of total conversion mass. (author)

Reactions of uranium (III) and (IV) compounds with ketones, nitriles and acid chlorides. Towards a use of uranium complexes in organic synthesis

International Nuclear Information System (INIS)

Adam, Raymond

1993-01-01

In this research thesis, the author shows that various organic molecules can be interestingly transformed into uranium complexes with degrees of oxidation of +3 or +4. In a first part, the author describes reactions of carbonyl compounds with the UCl 4 -Na(Hg) reducing system. Then, he addresses reductions of ketones, nitriles and acid chlorides by a uranium (III) complex: Cp 3 U(THF). The third part reports a detailed study of the reduction of ketones by U(BH 4 ) 4 [fr

Methods for obtaining sorption data from uranium-series disequilibria

International Nuclear Information System (INIS)

Finnegan, D.L.; Bryant, E.A.

1987-12-01

Two possible methods have been identified for obtaining in situ retardation factors from measurements of uranium-series disequilibria at Yucca Mountain. The first method would make use of the enhanced 234 U/ 238 U ratio in groundwater to derive a signature for exchangeable uranium sorbed on the rock; the exchangeable uranium would be leached and assayed. The second method would use the ratio of 222 Rn to 234 U in solution, corrected for weathering, to infer the retardation factor for uranium. Similar methods could be applied to thorium and radium

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)

Determination of the effective range of fission fragments in UO2 and of the disintegration constant for the spontaneous fission of Uranium 238

International Nuclear Information System (INIS)

Spaggiari, E.R.V.

1980-01-01

Results are presented of measurements realized aiming to determine the disintegration constant of spontaneous fission of U-238, with a discussion of the method utilized in the detection of fission tracks in muscovite. Several blades of mica were placed between two cylinders of Uo 2 to be irradiated with the fragments of spontaneous fission of U-238, and the fission tracks duly enlarged after a convenient chemical action were observed with a projection optical microscope. The effective thickness of UO 2 contributing to the observed tracks was measured through the irradiation of mica samples juxtaposed to the UO 2 cylinder, with 14,0 MeV neutrons from the (d,t 2 ) reaction. The detection efficiency of fission tracks originated in that thickness is practically 100% [pt

Cross-sections of spallation residues produced in Proton –Induced reactions

International Nuclear Information System (INIS)

Al-Haydari, A.; Khan, A.A.; Abdul Ganai, A.; Hassan, G.S.

2013-01-01

The recent available GSI data for proton-induced spallation reactions by using inverse kinematics at different energies are analyzed for different reactions in terms of the percolation model together with the intranuclear cascade model (MCAS). The simulation results obtained for the cross sections of production of light ions and isotopes as a function of mass and charge number is calculated. Results of calculations are in good agreement with experiment

Proton transfer reaction time-of-flight mass spectrometry advancement in detection of hazardous substances

International Nuclear Information System (INIS)

Agarwal, B.

2012-01-01

Proton Transfer Reaction Mass Spectrometry (PTR-MS) is a mass spectrometric technique based on chemical ionization, which provides very rapid measurements (within seconds) of volatile organic compounds in air, usually without special sample preparation, and with a very low detection limit. The detection and study of product ion patterns of threat agents such as explosives and drugs and some major environmental pollutants (isocyanates and polychlorinated biphenyls (PCBs)) is explored in detail here using PTR-MS, specifically Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS). The proton transfer reaction (PTR) principle works on the detection of the compound in the vapor phase. For some compounds, which have extremely low vapor pressures, both sample and inlet line heating were needed. Generally, the protonated parent molecule (MH+) is found to be the dominant product ion, which therefore provides us with a higher level of confidence in the assignment of a trace compound. However, for several compounds, dissociative proton transfer can occur at various degrees resulting in other product ions. Analysis of other compounds, such as the presence of taggants and impurities were carried out, and in certain compounds unusual E/N anomalies were discovered (E/N is an instrumental set of parameters, where E is the electric field strength and N is the number density). Head space measurements above four different drinks (plain water, tea, red wine and white wine) spiked with four different 'date rape' drugs were also conducted. (author)

Maximum permissible concentrations of uranium in air

CERN Document Server

Adams, N

1973-01-01

The retention of uranium by bone and kidney has been re-evaluated taking account of recently published data for a man who had been occupationally exposed to natural uranium aerosols and for adults who had ingested uranium at the normal dietary levels. For life-time occupational exposure to uranium aerosols the new retention functions yield a greater retention in bone and a smaller retention in kidney than the earlier ones, which were based on acute intakes of uranium by terminal patients. Hence bone replaces kidney as the critical organ. The (MPC) sub a for uranium 238 on radiological considerations using the current (1959) ICRP lung model for the new retention functions is slightly smaller than for earlier functions but the (MPC) sub a determined by chemical toxicity remains the most restrictive.

Radioactive Contamination of Alluvial Soils in the Taiga Landscapes of Yakutia with 137Cs, 226Ra, and 238U

Science.gov (United States)

Chevychelov, A. P.; Sobakin, P. I.

2017-12-01

The concentrations and distribution of 137Cs in alluvial soils (Fluvisols) of the upper and middle reaches of the Markha River in the northwest of Yakutia and 226Ra and 238U in alluvial soils within the El'kon uranium ore deposit in the south of Yakutia have been studied. It is shown that the migration of radiocesium in the permafrost-affected soils of Yakutia owing to alluviation processes extends to more than 600 km from the source of the radioactive contamination. The migration of 137Cs with water flows is accompanied by its deposition in the buried horizons of alluvial soils during extremely high floods caused by ice jams. In the technogenic landscapes of southern Yakutia, active water migration of 238U and 226Ra from radioactive dump rocks. The leaching of 238U with surface waters from the rocks is more intense than the leaching of 226Ra. The vertical distribution patterns of 238U and 226Ra in the profiles of alluvial soils are complex. Uranium tends to accumulate in the surface humus horizon and in the buried soil horizons, whereas radium does not display any definite regularities of its distribution in the soil profiles. At present, the migration of 238U and 226Ra with river water and their accumulation in the alluvial soils extend to about 30 km from the source.

Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

Science.gov (United States)

Bediako, D. Kwabena; Solis, Brian H.; Dogutan, Dilek K.; Roubelakis, Manolis M.; Maher, Andrew G.; Lee, Chang Hoon; Chambers, Matthew B.; Hammes-Schiffer, Sharon; Nocera, Daniel G.

2014-01-01

The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring. PMID:25298534

Isotopic separation of 235U and 238U in an atomic beam with selective two-step photo-ionisation

International Nuclear Information System (INIS)

Boehm, H.D.V.

1977-01-01

The present work gives a report on investigations on isotope separation of 235 U and 238 U by means of selective two-stage photo-ionization on atomic uranium. An atomic beam of sufficient particle density was produced by dissociation of URe 2 in an electron beam heated tungsten furnace at a temperature of 2.500 k. A continuously operated rhodamin-69 dye laser with a maximum output of 120 mW and about 50 mHz band width in one-made operation was used for selective excitation from the ground state. From this state of excitation, ionization resulted achieving a light power of 1.8 W below 3030 A in the reaction volume. The measured separation factors show that the laser method enables the enrichment of uranium to the required valve of three or more percent 235 U for light water reactors in a single separation step. The hyperfine structure could be considerably better resolved compared to earlier investigations, so that it was possible for the first time to identify and measure hitherto unobserved weak components. (orig.) [de

Uranium half-lives: a critical review

International Nuclear Information System (INIS)

Holden, N.E.

1981-01-01

The experimental data are evaluated and values for the spontaneous fission half-life of 238 U and the total half-lives for 232 U, 233 U, 234 U, 235 U, 236 U, and 238 U are recommended. Also the variation of the isotopic abundance of 234 U in nature and the error involved in the assumption of secular equilibrium between 234 U and 238 U in the determination of the specific activity of natural uranium samples are discussed. The recommended half-life values and 95% confidence limits are: 238 U spontaneous fission: 8.09 +- 0.26 x 10 15 years; 232 U total: 69.8 +- 1.0 years; 233 U total: 1.592 +- 0.002 x 10 5 years; 234 U total: 2.454 +- 0.006 x 10 5 years; 235 U total: 7.037 +- 0.011 x 10 8 years; 236 U total: 2.342 +- 0.003 x 10 7 years 238 U total: 4.468 +- 0.005 x 10 9 years

Sequential fission process observed in the reaction (16.7 MeV/u) 238U + nat.Au using mica as dielectric track detector

International Nuclear Information System (INIS)

Shahzad, Muhammad Ikram; Qureshi, Imtinan Elahi; Manzoor, Shahid; Khan, Hameed Ahmed

1999-01-01

The evidence of sequential fission has been found in the heavy-ion reaction (16.7 MeV/u) 238 U + nat. Au, using muscovite mica as Dielectric Track Detector (DTD) placed in a 2π-geometry configuration. The reaction products originating from the interactions of 238 U ions with the atoms of gold were registered in the detector in the form of tracks and identified for performing a detailed kinematical analysis. For this purpose the spherical polar coordinates of the correlated tracks of the multipronged events have been analyzed on an event-by-event basis. Automatic, semi-automatic and manual measuring methods have been employed to collect and manipulate the track data. The known characteristics of binary and ternary events observed in the reaction have been used for the calibration of the detectors. The computed masses, Q-values and relative velocities of the reaction products determined in this analysis are compared with theoretical predictions based on sequential fission process. Agreement within one standard deviation with respect to the experimental values has been found for the majority of analyzed events. Therefore, it is concluded that three particles in the exit channel of the reaction are produced in two successive steps. In the first step of the reaction, two intermediate nuclei are formed as a result of an inelastic collision between projectile and target atoms while in the second step the fission of one of the intermediate nuclei of the previous step takes place. Furthermore no proximity effects have been observed

Comparative yields of alkali elements and thallium from uranium irradiated with GeV protons, $^{3}$He and $^{12}$C

CERN Document Server

Bjørnstad, T; Jonson, B; Jonsson, O C; Lindfors, V; Mattsson, S; Poskanzer, A M; Ravn, H L; Schardt, D

1981-01-01

Mass-separated ion beams of the alkali elements Na, K and Fr, and of the element Tl, are produced by bombarding a uranium target with 600 MeV protons, 890 MeV /sup 3/He/sup 2+/, and 936 MeV /sup 12/C/sup 4+/. Isotopic production yields are reported. In the case of the /sup 12/C beam, these are thick target yields. Absolute cross-sections for the proton beam data are deduced by normalizing the delay-time corrected yield curves to measured cross-sections. For products farthest away from stability, the /sup 3/He/sup 2+/ beam generally gives the highest yields. (17 refs).

Experimental determination of proton induced reaction cross sections on {sup nat}Ni near threshold energy

Energy Technology Data Exchange (ETDEWEB)

Uddin, Md. Shuza [Atomic Energy Research Establishment, Dhaka (Bangladesh). Tandem Accelerator Facilities; Forschungszentrum Juelich GmbH (Germany). Inst. fuer Neurowissenschaften und Medizin, INM-5: Nuklearchemie; Chakraborty, Animesh Kumer [Atomic Energy Research Establishment, Dhaka (Bangladesh). Tandem Accelerator Facilities; Chittagong University of Engineering and Technology (Bangladesh). Dept. of Physics; Spellerberg, Stefan; Spahn, Ingo; Qaim, Syed M. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Neurowissenschaften und Medizin, INM-5: Nuklearchemie; Shariff, Md. Asad; Das, Sopan [Atomic Energy Research Establishment, Dhaka (Bangladesh). Tandem Accelerator Facilities; Rashid, Md. Abdur [Chittagong University of Engineering and Technology (Bangladesh). Dept. of Physics

2016-08-01

A newly developed facility at the 3 MV Tandem Accelerator at Dhaka for measurement of proton induced reaction cross sections in the energy region below 5 MeV is outlined and tests for the beam characterization are described. The results were validated by comparison with the well-known excitation function of the {sup 64}Ni(p, n){sup 64}Cu reaction. Excitation functions of the reactions {sup nat}Ni(p, x){sup 60,61}Cu, {sup nat}Ni(p, x){sup 55,57,58m+g}Co and {sup nat}Ni(p, x){sup 57}Ni were also measured from threshold to 16 MeV using the stacked-foil technique, whereby irradiations were performed with 5 MeV protons available at the Tandem Accelerator and 16.7 MeV protons at the BC 1710 cyclotron at Juelich, Germany. The radioactivity was measured using HPGe γ-ray detectors. A few results are new, the others strengthen the database. In particular, the results of the reaction {sup nat}Ni(p, x){sup 61}Cu below 3 MeV could serve as beam monitor.

Analysis for mass distribution of proton-induced reactions in intermediate energy range

CERN Document Server

Xiao Yu Heng

2002-01-01

The mass and charge distribution of residual products produced in the spallation reactions needs to be studied, because it can provide useful information for the disposal of nuclear waste and residual radioactivity generated by the spallation neutron target system. In present work, the Many State Dynamical Model (MSDM) is based on the Cascade-Exciton Model (CEM). The authors use it to investigate the mass distribution of Nb, Au and Pb proton-induced reactions in energy range from 100 MeV to 3 GeV. The agreement between the MSDM simulations and the measured data is good in this energy range, and deviations mainly show up in the mass range of 90 - 150 for the high energy proton incident upon Au and Pb

Determination of extremely low {sup 236}U/{sup 238}U isotope ratios in environmental samples by sector-field inductively coupled plasma mass spectrometry using high-efficiency sample introduction

Energy Technology Data Exchange (ETDEWEB)

Boulyga, Sergei F. [Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10-14, 55099 Mainz (Germany)]. E-mail: sergei.boulyga@univie.ac.at; Heumann, Klaus G. [Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10-14, 55099 Mainz (Germany)

2006-07-01

A method by inductively coupled plasma mass spectrometry (Icp-Ms) was developed which allows the measurement of {sup 236}U at concentration ranges down to 3 x 10{sup -14} g g{sup -1} and extremely low {sup 236}U/{sup 238}U isotope ratios in soil samples of 10{sup -7}. By using the high-efficiency solution introduction system APEX in connection with a sector-field ICP-MS a sensitivity of more than 5000 counts fg{sup -1} uranium was achieved. The use of an aerosol desolvating unit reduced the formation rate of uranium hydride ions UH{sup +}/U{sup +} down to a level of 10{sup -6}. An abundance sensitivity of 3 x 10{sup -7} was observed for {sup 236}U/{sup 238}U isotope ratio measurements at mass resolution 4000. The detection limit for {sup 236}U and the lowest detectable {sup 236}U/{sup 238}U isotope ratio were improved by more than two orders of magnitude compared with corresponding values by alpha spectrometry. Determination of uranium in soil samples collected in the vicinity of Chernobyl nuclear power plant (NPP) resulted in that the {sup 236}U/{sup 238}U isotope ratio is a much more sensitive and accurate marker for environmental contamination by spent uranium in comparison to the {sup 235}U/{sup 238}U isotope ratio. The ICP-MS technique allowed for the first time detection of irradiated uranium in soil samples even at distances more than 200 km to the north of Chernobyl NPP (Mogilev region). The concentration of {sup 236}U in the upper 0-10 cm soil layers varied from 2 x 10{sup -9} g g{sup -1} within radioactive spots close to the Chernobyl NPP to 3 x 10{sup -13} g g{sup -1} on a sampling site located by >200 km from Chernobyl.

Evaluation of Uranium Measurements in Water by Various Methods - 13571

Energy Technology Data Exchange (ETDEWEB)

Tucker, Brian J. [Shaw Environmental and Infrastructure Group, 150 Royall Street, Canton, MA (United States); Workman, Stephen M. [ALS Laboratory Group, Environmental Division, 225 Commerce Drive, Fort Collins, CO 80524 (United States)

2013-07-01

In December 2000, EPA amended its drinking water regulations for radionuclides by adding a Maximum Contaminant Level (MCL) for uranium (so called MCL Rule)[1] of 30 micrograms per liter (μg/L). The MCL Rule also included MCL goals of zero for uranium and other radionuclides. Many radioactively contaminated sites must test uranium in wastewater and groundwater to comply with the MCL rule as well as local publicly owned treatment works discharge limitations. This paper addresses the relative sensitivity, accuracy, precision, cost and comparability of two EPA-approved methods for detection of total uranium: inductively plasma/mass spectrometry (ICP-MS) and alpha spectrometry. Both methods are capable of measuring the individual uranium isotopes U-234, U- 235, and U-238 and both methods have been deemed acceptable by EPA. However, the U-238 is by far the primary contributor to the mass-based ICP-MS measurement, especially for naturally-occurring uranium, which contains 99.2745% U-238. An evaluation shall be performed relative to the regulatory requirement promulgated by EPA in December 2000. Data will be garnered from various client sample results measured by ALS Laboratory in Fort Collins, CO. Data shall include method detection limits (MDL), minimum detectable activities (MDA), means and trends in laboratory control sample results, performance evaluation data for all methods, and replicate results. In addition, a comparison will be made of sample analyses results obtained from both alpha spectrometry and the screening method Kinetic Phosphorescence Analysis (KPA) performed at the U.S. Army Corps of Engineers (USACE) FUSRAP Maywood Laboratory (UFML). Many uranium measurements occur in laboratories that only perform radiological analysis. This work is important because it shows that uranium can be measured in radiological as well as stable chemistry laboratories and it provides several criteria as a basis for comparison of two uranium test methods. This data will

Evaluation of Uranium Measurements in Water by Various Methods - 13571

International Nuclear Information System (INIS)

Tucker, Brian J.; Workman, Stephen M.

2013-01-01

In December 2000, EPA amended its drinking water regulations for radionuclides by adding a Maximum Contaminant Level (MCL) for uranium (so called MCL Rule)[1] of 30 micrograms per liter (μg/L). The MCL Rule also included MCL goals of zero for uranium and other radionuclides. Many radioactively contaminated sites must test uranium in wastewater and groundwater to comply with the MCL rule as well as local publicly owned treatment works discharge limitations. This paper addresses the relative sensitivity, accuracy, precision, cost and comparability of two EPA-approved methods for detection of total uranium: inductively plasma/mass spectrometry (ICP-MS) and alpha spectrometry. Both methods are capable of measuring the individual uranium isotopes U-234, U- 235, and U-238 and both methods have been deemed acceptable by EPA. However, the U-238 is by far the primary contributor to the mass-based ICP-MS measurement, especially for naturally-occurring uranium, which contains 99.2745% U-238. An evaluation shall be performed relative to the regulatory requirement promulgated by EPA in December 2000. Data will be garnered from various client sample results measured by ALS Laboratory in Fort Collins, CO. Data shall include method detection limits (MDL), minimum detectable activities (MDA), means and trends in laboratory control sample results, performance evaluation data for all methods, and replicate results. In addition, a comparison will be made of sample analyses results obtained from both alpha spectrometry and the screening method Kinetic Phosphorescence Analysis (KPA) performed at the U.S. Army Corps of Engineers (USACE) FUSRAP Maywood Laboratory (UFML). Many uranium measurements occur in laboratories that only perform radiological analysis. This work is important because it shows that uranium can be measured in radiological as well as stable chemistry laboratories and it provides several criteria as a basis for comparison of two uranium test methods. This data will

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)

Study of proton-induced reactions and correlation with fast-neutron scattering

International Nuclear Information System (INIS)

Hansen, L.F.

1982-01-01

The generation of cross sections for fast neutron-nucleon interactions obtained from elastic and charge-exchange proton data is discussed in terms of the Lane model formalism. A general description of the interaction of nucleons with nuclei is presented in terms of the optical model and the extended (or coupled-channel) optical model, together with the relation of these models to microscopic calculations of the nucleon-nucleon interaction. Comparisons between neutron elastic data and calculations carried out with optical model potentials obtained from (p,p) and (p,n) data are presented for a large number of nuclei. The validity of the Lane model and the importance of coupled effects in the actinide region are shown in a detailed comparison of calculations for elastic and inelastic neutron differential cross sections and measurements for 232 Th and 238 U

Bioassay for uranium mill tailings

International Nuclear Information System (INIS)

Tschaeche, A.N.

1986-01-01

Uranium mill tailings are composed of fine sand that contains, among other things, some uranium (U/sup 238/ primarily), and all of the uranium daughters starting with /sup 230/Th that are left behind after the usable uranium is removed in the milling process. Millions of pounds of tailings are and continue to be generated at uranium mills around the United States. Discrete uranium mill tailings piles exist near the mills. In addition, the tailings materials were used in communities situated near mill sites for such purposes as building materials, foundations for buildings, pipe runs, sand boxes, gardens, etc. The Uranium Mill Tailings Remedial Action Project (UMTRAP) is a U.S. Department of Energy Program designed with the intention of removing or stabilizing the mill tailings piles and the tailings used to communities so that individuals are not exposed above the EPA limits established for such tailings materials. This paper discusses the bioassay programs that are established for workers who remove tailings from the communities in which they are placed

Dynamics of Anti-Proton -- Protons and Anti-Proton -- Nucleus Reactions

CERN Document Server

Galoyan, A; Uzhinsky, V

2016-01-01

A short review of simulation results of anti-proton-proton and anti-proton-nucleus interactions within the framework of Geant4 FTF (Fritiof) model is presented. The model uses the main assumptions of the Quark-Gluon-String Model or Dual Parton Model. The model assumes production and fragmentation of quark-anti-quark and diquark-anti-diquark strings in the mentioned interactions. Key ingredients of the model are cross sections of string creation processes and an usage of the LUND string fragmentation algorithm. They allow one to satisfactory describe a large set of experimental data, especially, a strange particle production, Lambda hyperons and K mesons.

Accumulations and sources of uranium, of its daughters and of metallic trace elements in wetlands located around old uranium mining sites

International Nuclear Information System (INIS)

Cuvier, Alicia

2015-01-01

Uranium mining and uranium ore processing increase the environmental activity of U and Th decay products and trace elements, in particular in case of releases to the adjacent rivers. Contaminants accumulate then preferentially in sedimentation areas (such as ponds or lakes) or in wetlands (peat lands, marshes or riverbanks) located downstream to the mine. Wetlands - generally located at the head of watershed - are particularly sensitive to environmental changes and anthropogenic pressure. This poses a risk of release of contaminants from these accumulation areas. The objective of the present study is to propose an easily reproducible methodology - in particular for the orphan mining sites - to identify and characterize accumulation areas. This study also aims to improve our understanding of the mechanisms of accumulation and release, in these areas. This study was performed around the former mining site of Bertholene (France). Standing and mobile in situ gamma spectrometry is used to accurately locate the accumulation areas. Soils, sediments, vegetation, water and peat are also sampled upstream and downstream of the mine, in order to (a) characterize the activities and the disequilibria of the U-Th decay chains and the associated trace elements according to the scale of observation, (b) understand the mechanisms of accumulation and release and (c) identify the potential sources using geochemical proxies and isotopic analyses. The results obtained show that radionuclides are mainly accumulated in a flooding area located downstream the mine. Strong U-238 activities (≥ 20000 Bq.kg"-"1) and strong Ra-226/U-238 and Th-230/Ra-226 activity ratios are recorded, involving preferential inputs of U-238 and Th-230 during flooding events. Trace element contamination is low, except for Mn, Ba and S. Such contaminations are potentially explained by the geochemical composition of the uranium ore and by the past and current processes of ore and water mine. Sequential extractions

Investigation of GeV proton-induced spallation reactions

International Nuclear Information System (INIS)

Hilscher, D.; Herbach, C.-M.; Jahnke, U.

2003-01-01

A reliable and precise modeling of GeV proton-induced spallation reactions is indispensable for the design of the spallation module and the target station of future accelerator driven hybrid reactors (ADS) or spallation neutron sources (ESS), in particular, to provide precise predictions for the neutron production, the radiation damage of materials (window), and the production of radioactivity ( 3 H, 7 Be etc.) in the target medium. Detailed experimental nuclear data are needed for sensitive validations and improvements of the models, whose predictive power is strongly dependent on the correct physical description of the three main stages of a spallation reaction: (i) the Intra-Nuclear-Cascade (INC) with the fast heating of the target nucleus, (ii) the de-excitation due to pre-equilibrium emission including the possibility of multi-fragmentation, and (iii) the statistical decay of thermally excited nuclei by evaporation of light particles and fission in the case of heavy nuclei. Key experimental data for this endeavour are absolute production cross sections and energy spectra for neutrons and light charged-particles (LCPs), emission of composite particles prior and post to the attainment of an equilibrated system, distribution of excitation energies deposited in the nuclei after the INC, and fission probabilities. The correlations of these quantities are particularly important to detect and identify possible deficiencies of the theoretical modeling of the various stages of a spallation reaction. Systematic measurements of such data are furthermore needed over large ranges of target nuclei and incident proton energies. Such data has been measured with the NESSI detector. An overview of new and previous results will be given. (authors)

The uranium behaviour during rock-water interaction in the granites from the Itu complex (Sao Paulo, Brazil): a laboratory study

Energy Technology Data Exchange (ETDEWEB)

Silva, Helen S.B. da; Marques, Leila S.; Kawauchi, Roberto K., E-mail: leila@iag.usp.br, E-mail: keiji@iag.usp.br [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas. Universidade de Sao Paulo (USP), SP (Brazil)

2011-07-01

In order to elucidate the mechanisms involved in the process of uranium leaching due to the rock-water interaction in the granitic rocks from Itu Complex (Sao Paulo, Brazil), an experimental arrangement was developed and built. About 2.5kg of crushed rock fragments from Cabreuva and Indaiatuba Intrusions were maintained at room temperature within a glass flask filled with circulating water. The percolating water was removed periodically (from 10 to 30 days) for uranium analysis and then replaced by an equal volume of fresh water. Alpha spectrometry was used to determine the activity concentrations of {sup 234}U and {sup 238}U, and {sup 234}U/{sup 238}U activity ratios, of the waters as well as of the granites. The results for both samples showed that most of the uranium is leached in the first days after the contact between rock and water. The {sup 234}U/{sup 238}U activity ratios were significantly greater than unity, indicating radioactive disequilibrium between those isotopes, probably due to alpha recoil. Although the uranium activity concentrations in the water samples diminished with the increasing of time, it was not observed considerable variations of the {sup 234}U/{sup 238}U activity ratios. It was also noticed that, the amount of leached uranium as well as the {sup 234}U/{sup 238}U activity ratios are characteristics of each sample submitted to leaching, reflecting the differences of the granite facies mineralogy.(author)

Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion.

Science.gov (United States)

Soudackov, Alexander V; Hammes-Schiffer, Sharon

2015-11-21

Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at high temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton

Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion

International Nuclear Information System (INIS)

Soudackov, Alexander V.; Hammes-Schiffer, Sharon

2015-01-01

Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at high temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton

Analysis of radon, uranium 238 and thorium 232 in potable waters: Dose to adult members of the Moroccan urban population

International Nuclear Information System (INIS)

Misdaq, M.A.; Ouabi, H.; Merzouki, A.

2007-01-01

Uranium ( 238 U) and thorium ( 232 Th) concentrations as well as radon ( 222 Rn) and thoron ( 220 Rn) alpha-activities per unit volume have been measured inside various potable water samples collected from nineteen cities in Morocco by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). Measured radon alpha-activities ranged from (0.37 ± 0.02) Bq l -1 to (13.6 ± 1.10) Bq l -1 for the potable water samples studied. Alpha-activities due to radon from the ingestion of the studied potable water samples were determined in different compartments of the gastrointestinal system by using the ICRP compartmental model for radon. Annual committed equivalent doses due to radon were evaluated in the gastrointestinal compartments from the ingestion of the potable water samples studied. The influence of the target tissue mass, radon intake and alpha-activity integral due to radon on the annual committed equivalent doses in the gastrointestinal compartments was investigated

Studies of the reactions of uranium pentabromide and hexabromouranate(V) in non-aqueous solvents

International Nuclear Information System (INIS)

Dehos, R.F.

1984-01-01

With the help of IR and electron spectra, the behaviour of uranium pentabromide and hexabromo uranate in non-aqueous nitromethane, nitroethane, bromine, dichlormethane, dibromomethane and acetonitrile was studied. By comparison of the spectra of the solutions in nitromethane with the solutions using other solvents on one side, and on the other side with the solids spectra of the end products, the redox reactions of the uranium V in nitromethane solutions could be more than clarified. Studies were also carried out on the time-dependency of the uranium IV and uranium V contents of the solutions at room temperature and at -20 0 C. The existence of the HUBr 6 which probably appears as an intermediate product was tested in another experiment. First evidence for the existence of UBr 6 as a disproportionation product of UBr 5 were achieved by tests in solutions of acetonitrile at -47 0 C. (RB) [de

Dissolution behaviour of 238U, 234U and 230Th deposited on filters from personal dosemeters

International Nuclear Information System (INIS)

Beckova, V.; Malatova, I.

2008-01-01

Kinetics of dissolution of 238 U, 234 U and 230 Th dust deposited on filters from personal alpha dosemeters was studied by means of a 26-d in vitro dissolution test with a serum ultra-filtrate simulant. Dosemeters had been used by miners at the uranium mine 'Dolni Rozinka' at Rozna, Czech Republic. The sampling flow-rate as declared by the producer is 4 l h -1 and the sampling period is typically 1 month. Studied filters contained 125 ± 6 mBq 238 U in equilibrium with 234 U and 230 Th; no 232 Th series nuclides were found. Half-time of rapid dissolution of 1.4 d for 238 U and 234 U and slow dissolution half-times of 173 and 116 d were found for 238 U and 234 U, respectively. No detectable dissolution of 230 Th was found. (authors)

The two-proton halo nucleus {sup 17}Ne studied in high-energy nuclear breakup reactions

Energy Technology Data Exchange (ETDEWEB)

Wamers, Felix [EMMI, GSI, Darmstadt (Germany); FIAS, Frankfurt (Germany); IKP, TU Darmstadt, Darmstadt (Germany); GSI, Darmstadt (Germany); Marganiec, Justyna [IKP, TU Darmstadt, Darmstadt (Germany); EMMI, GSI, Darmstadt (Germany); GSI, Darmstadt (Germany); Aumann, Thomas [IKP, TU Darmstadt, Darmstadt (Germany); GSI, Darmstadt (Germany); Bertulani, Carlos [Texas A and M University-Commerce, Commerce (United States); Chulkov, Leonid [GSI, Darmstadt (Germany); NRC Kurchatov Institute, Moscow (Russian Federation); Heil, Michael; Simon, Haik [GSI, Darmstadt (Germany); Plag, Ralf [GSI, Darmstadt (Germany); Goethe Universitaet, Frankfurt (Germany); Savran, Deniz [EMMI, GSI, Darmstadt (Germany); FIAS, Frankfurt (Germany); Collaboration: R3B-Collaboration

2014-07-01

We report on exclusive measurements of nuclear breakup reactions of highly-energetic (500 MeV) unstable {sup 17}Ne beams impinging on light targets in an experiment at the R{sup 3}B-LAND complete-kinematics reaction setup at GSI. Focusing on the properties of beam-like {sup 15}O-p (={sup 16}F) systems produced in one-proton-removal reactions, we are presenting a comprehensive analysis of the s-/d-wave configuration mixing of the {sup 17}Ne valence-proton pair that is used to quantify its halo-nature. The results include the {sup 15}O-p relative-energy spectrum, {sup 16}F momentum distributions, and their corresponding momentum profile.

Status of experimental data of proton-induced reactions for intermediate-energy nuclear data evaluation

Energy Technology Data Exchange (ETDEWEB)

Watanabe, Yukinobu; Kawano, Toshihiko [Kyushu Univ., Fukuoka (Japan); Yamano, Naoki; Fukahori, Tokio

1998-11-01

The present status of experimental data of proton-induced reactions is reviewed, with particular attention to total reaction cross section, elastic and inelastic scattering cross section, double-differential particle production cross section, isotope production cross section, and activation cross section. (author)

Cross sections and rate coefficients for charge exchange reactions of protons with hydrocarbon molecules

International Nuclear Information System (INIS)

Janev, R.K.; Kato, T.; Wang, J.G.

2001-05-01

The available experimental and theoretical cross section data on charge exchange processes in collisions of protons with hydrocarbon molecules have been collected and critically assessed. Using well established scaling relationships for the charge exchange cross sections at low and high collision energies, as well as the known rate coefficients for these reactions in the thermal energy region, a complete cross section database is constructed for proton-C x H y charge exchange reactions from thermal energies up to several hundreds keV for all C x H y molecules with x=1, 2, 3 and 1 ≤ y ≤ 2x + 2. Rate coefficients for these charge exchange reactions have also been calculated in the temperature range from 0.1 eV to 20 keV. (author)

Probing the structure of unstable nuclei through the recoiled proton tagged knockout reaction

International Nuclear Information System (INIS)

Ye, Y.; Cao, Z.; Jiang, D.

2010-01-01

Recoiled proton tagged knockout reaction experiments were carried-out for 8 He at 82,5 MeV/u in RIKEN and for 6 He at 65 MeV/u in Lanzhou. The very preliminary results for the distinguish of the reaction mechanism are presented and compared to the kinematics calculation. (authors)

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)

Protein expression of saccharomyces cerevisiae in response to uranium exposure

International Nuclear Information System (INIS)

Sakamoto, Fuminori; Nankawa, Takuya; Kozai, Naofumi; Ohnuki, Toshihiko; Fujii, Tsutomu; Iefuji, Haruyuki; Francis, A.J.

2007-01-01

Protein expression of Saccharomyces cerevisiae grown in the medium containing 238 U (VI) and 233 U (VI) was examined by two-dimensional gel electrophoresis. Saccharomyces cerevisiae of BY4743 was grown in yeast nitrogen base medium containing glucose and glycerol 2-phosphate and 238 U of 0, 2.0, and 5.0 x 10 -4 M or 233 U of 2.5 x 10 -6 M (radioactivity was higher by 350 times than 2.0 x 10 -4 M 238 U) and 5.0 x 10 -6 M for 112 h at 30 degC. The growth of Saccharomyces cerevisiae was monitored by measuring OD 600 at 112 h after the inoculation. Uranium concentrations in the media also were measured by radiometry using a liquid scintillation counter. The growths of the yeast grown in the above media were in the following order: control>2.5 x 10 -6 M 233 U>2.0 x 10 -4 M 238 U>5.0 x 10 -6 M 233 U>5.0 x 10 -4 M 238 U. This result indicated that not only radiological but also chemical effect of U reduced the growth of the yeast. The concentrations of U in the medium containing 238 U or 233 U decreased, suggesting U accumulation by the yeast cells. The 2-D gel electrophoresis analysis showed the appearance of several spots after exposure to 238 U or to 233 U but not in the control containing no uranium. These results show that the yeast cells exposed to U express several specific proteins. (author)

(238)U and total radioactivity in drinking waters in Van province, Turkey.

Science.gov (United States)

Selçuk Zorer, Özlem; Dağ, Beşir

2014-06-01

As part of the national survey to evaluate natural radioactivity in the environment, concentration levels of total radioactivity and natural uranium have been analysed in drinking water samples. A survey to study natural radioactivity in drinking waters was carried out in the Van province, East Turkey. Twenty-three samples of drinking water were collected in the Van province and analysed for total α, total β and (238)U activity. The total α and total β activities were counted by using the α/β counter of the multi-detector low background system (PIC MPC-9604), and the (238)U concentrations were determined by inductively coupled plasma-mass spectrometry (Thermo Scientific Element 2). The samples were categorised according to origin: tap, spring or mineral supply. The activity concentrations for total α were found to range from 0.002 to 0.030 Bq L(-1) and for total β from 0.023 to 1.351 Bq L(-1). Uranium concentrations ranging from 0.562 to 14.710 μg L(-1) were observed in drinking waters. Following the World Health Organisation rules, all investigated waters can be used as drinking water.

Reaction cross sections for 8He and 14B on proton target for the separation of proton and neutron density distributions

International Nuclear Information System (INIS)

Tanaka, Masaomi; Fukuda, Mitsunori; Nishimura, Daiki

2015-01-01

We utilized the proton-neutron asymmetry of nucleon–nucleon total cross sections in the intermediate energy region (σ pn ≠σ pp(nn) ) to obtain the information of proton and neutron distributions respectively. We have measured reaction cross sections (σ R ) for 14 B and 8 He on proton targets as isospin asymmetric targets in addition to symmetric ones. Proton and neutron density distributions were derived respectively through the χ 2 -fitting procedure with the modified Glauber calculation. The result suggests a necessity for 14 B of a long tail, and also a necessity for 8 He of a neutron tail. Root-mean-square proton, neutron and matter radii for 14 B and 8 He are also derived. Each radius is consistent with some of the other experimental values and also with some of the several theoretical values. (author)

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.

A simple functional form for proton-208Pb total reaction cross sections

International Nuclear Information System (INIS)

Majumdar, S.; Deb, P.K.; Amos, K.

2001-01-01

A simple functional form has been found that gives a good representation of the total reaction cross sections for the scattering from 208 Pb of protons with energies in the range 30 to 300 MeV. The ratios of the total reaction cross sections calculated under this approximations compared well (to within a few percent) to those determined from the microscopic optical model potentials

Uranium production in thorium/denatured uranium fueled PWRs

International Nuclear Information System (INIS)

Arthur, W.B.

1977-01-01

Uranium-232 buildup in a thorium/denatured uranium fueled pressurized water reactor, PWR(Th), was studied using a modified version of the spectrum-dependent zero dimensional depletion code, LEOPARD. The generic Combustion Engineering System 80 reactor design was selected as the reactor model for the calculations. Reactors fueled with either enriched natural uranium and self-generated recycled uranium or uranium from a thorium breeder and self-generated recycled uranium were considered. For enriched natural uranium, concentrations of 232 U varied from about 135 ppM ( 232 U/U weight basis) in the zeroth generation to about 260 ppM ( 232 U/U weight basis) at the end of the fifth generation. For the case in which thorium breeder fuel (with its relatively high 232 U concentration) was used as reactor makeup fuel, concentrations of 232 U varied from 441 ppM ( 232 U/U weight basis) at discharge from the first generation to about 512 ppM ( 232 U/U weight basis) at the end of the fifth generation. Concentrations in freshly fabricated fuel for this later case were 20 to 35% higher than the discharge concentration. These concentrations are low when compared to those of other thorium fueled reactor types (HTGR and MSBR) because of the relatively high 238 U concentration added to the fuel as a denaturant. Excellent agreement was found between calculated and existing experimental values. Nevertheless, caution is urged in the use of these values because experimental results are very limited, and the relevant nuclear data, especially for 231 Pa and 232 U, are not of high quality

Experimental Observation of Nuclear Reactions in Palladium and Uranium

International Nuclear Information System (INIS)

J. Dufour; D. Murat; X. Dufour; J. Foos

2001-01-01

By submitting various metals (Pd, U) containing hydrogen (from 2000 to 700 000 atoms of hydrogen for 1 000 000 atoms of the host metal) to the combined action of electrical currents and magnetic fields, we have observed a sizeable exothermal effect (from 0.1 to 8 W for 500 mg of metal used). This effect is beyond experimental errors, the energy output being typically 130 to 250% of the energy input and not of chemical origin (exothermal effect in the range of 7000 MJ/mol of metal in the case of palladium and of 60 MJ/mol in the case of uranium). New chemical species also appear in the processes metals. It has been shown by a QED calculation that resonances of long lifetime (s), nuclear dimensions (fm), and low energy of formation (eV) could exist. This concept seems to look like the 'shrunken hydrogen atoms' proposed by various authors. It is indeed very different in two ways (a) being a metastable state, it needs energy to be formed (a few eV) and reverts to normal hydrogen after a few seconds, liberating back its energy of formation (it is thus not the source of the energy observed); (b) its formation can be described as the electron spin/proton nuclear spin interaction becoming first order in the lattice environment (whereas it is third order in a normal hydrogen atom). Moreover, we consider that the hydrex cannot yield a neutron because this reaction is strongly endothermic. To explain our results, we put forward the following working hypothesis: In a metal lattice and under proper conditions, the formation of such resonances (metastable state) could be favored. We propose to call them HYDREX, and we assume that they are actually formed in cold fusion (CF) and low-energy nuclear reaction (LENR) experiments. Once formed, a number of HYDREX could gather around a nucleus of the lattice to form a cluster of nuclear size and of very long life time compared to nuclear time (10 -22 s). In this cluster, nuclear rearrangements could take place, yielding mainly 4 He

Production of He-, Ne-, Ar-, Kr-, and Xe-isotopes by proton-induced reactions on lead

International Nuclear Information System (INIS)

Leya, I.; Michel, R.

2003-01-01

We measured integral thin target cross sections for the proton-induced production of He-, Ne-, Ar-, Kr-, and Xe-isotopes from lead from the respective reaction thresholds up to 2.6 GeV. The production of noble gas isotopes in lead by proton-induced reactions is of special importance for design studies of accelerator driven systems and energy amplifiers. In order to minimise the influences of secondary particles on the production of residual nuclides a new Mini-Stack approach was used instead of the well-known stacked-foil techniques for all experiments with proton energies above 200 MeV. With some exceptions our database for the proton-induced production of noble gas isotopes from lead is consistent and nearly complete. In contradistinction to the production of He from Al and Fe, where the cross sections obtained by thin-target irradiation experiments are up to a factor of 2 higher than the NESSI data, both datasets agree for the He production from lead. (orig.)

Comparison of neutron activation analysis techniques for the determination of uranium concentrations in geological and environmental materials

International Nuclear Information System (INIS)

Landsberger, S.; Kapsimalis, R.

2013-01-01

We have described the determination of uranium in environmental, geological, and agricultural specimens by three different non-destructive nuclear methods. The effectiveness, as defined as the lower limits of detection in this work, of quantifying trace levels of bulk uranium in geological samples was evaluated for several common NAA techniques. These techniques include short-lived and medium-lived neutron activation analysis using thermal and epithermal neutrons; these results were compared with an assessment of Compton suppressed gamma-ray counting. A careful evaluation of three major (n,γ) reactions with chlorine, manganese and sodium that could impede determining low levels of uranium due to high Compton continuums was done. The evaluation of Compton suppressed passive gamma counting revealed that uranium concentrations below 50 mg kg −1 were not adequate to achieve good counting statistics using the 234m Pa the second daughter product of 238 U. -- Highlights: ► Determination of uranium concentrations in geological, environmental, and agricultural specimens. ► Use of several NAA and passive counting methods. ► Identified several key interferences. ► Use of Compton suppression to minimize effects of interferences

Uranium-thorium disequilibria and partitioning on melting of garnet peridotite

International Nuclear Information System (INIS)

Beattie, P.

1993-01-01

The abundances of isotopes in the 238 U decay series can be used as both tracers and chronometers of magmatic processes. In the subsolidus asthenosphere, the activity of each daughter isotope (defined as the product of its concentration and decay constant, and denoted by parentheses) is assumed to be equal to that of its parent. By contrast, ( 230 Th/ 238 U) is greater than unity in most recent mid-ocean-ridge and ocean-island basalts, implying that thorium is more incompatible (that is, it is partitioned into the melt phase more strongly) than uranium. Melting of spinel peridotite cannot produce the ( 230 Th) excesses, because measured partition coefficients for pyroxenes and olivine demonstrate that uranium is more incompatible than thorium for this rock. Here I report garnet-melt partitioning data which show that for this mineral-melt pair thorium does behave more incompatibility than uranium, thus supporting the suggestion that mid-ocean-ridge basalts (MORB) are produced by melting initiated at depths where garnet is stable. Using these data, I show that the observed ( 230 Th/ 238 U) ratios of MORB and most ocean-island basalts can be explained by slow, near-fractional melting initiated in the garnet stability field. (author)

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.)

Cross sections and rate coefficients for charge exchange reactions of protons with hydrocarbon molecules

Energy Technology Data Exchange (ETDEWEB)

Janev, R.K.; Kato, T. [National Inst. for Fusion Science, Toki, Gifu (Japan); Wang, J.G. [Department of Physics and Astronomy, University of Georgia, Athens (United States)

2001-05-01

The available experimental and theoretical cross section data on charge exchange processes in collisions of protons with hydrocarbon molecules have been collected and critically assessed. Using well established scaling relationships for the charge exchange cross sections at low and high collision energies, as well as the known rate coefficients for these reactions in the thermal energy region, a complete cross section database is constructed for proton-C{sub x}H{sub y} charge exchange reactions from thermal energies up to several hundreds keV for all C{sub x}H{sub y} molecules with x=1, 2, 3 and 1 {<=} y {<=} 2x + 2. Rate coefficients for these charge exchange reactions have also been calculated in the temperature range from 0.1 eV to 20 keV. (author)

Influence of soil structure on the "Fv approach" applied to 238U and 226Ra.

Science.gov (United States)

Blanco Rodríguez, P; Vera Tomé, F; Lozano, J C

2017-02-01

The soil-to-plant transfer factors were determined in a granitic area for the two long-lived uranium series radionuclides 238 U and 226 Ra. With the aim to identify a physical fraction of soil whose concentration correlates linearly with the plant concentration, the soil compartment was analyzed in various stages. An initial study identified the soil compartments as being either bulk soil or its labile fraction. The bulk soil was subsequently divided into three granulometric fractions consisting of: coarse sand, fine sand, and silt and clay. The soil-to-plant transfer of radionuclides for each of these three texture fractions was analyzed. Lastly, the labile fraction was extracted from each textural part, and the activity concentration of the radionuclides 238 U and 226 Ra was measured. In order to assess the influence of soil texture on the soil-to-plant transfer process, we sought to identify possible correlations between the activity concentration in the plant compartment and those found in the different fractions within each soil compartment. The results showed that the soil-to-plant transfer process for uranium and radium depends on soil grain size, where the results for uranium showed a linear relationship between the activity concentration of uranium in the plant and the fine soil fraction. In contrast, a linear relation between the activity concentration of radium in the plant and the soil coarse-sand fraction was observed. Additionally, the presence of phosphate and calcium in the soil of all of the compartments studied affected the soil-to-plant transfer of uranium and radium, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.