bluuebunny/crossref_metadata_2025 huggingface dataset:
Cation-cation complexes of PuO2+and NpO2+with Th4+and UO22+
Authors: Stoyer N. J. , Hoffman D.C. , Silva R.J.
Published: August 2006

Cation-cation complexes of NpO2+and PuO2+with UO22+and Th4+were studied using laser-induced photoacoustic spectroscopy (LIPAS). An equilibrium constant of 2.4±0.2 M-1was measured at an ionic strength of 6.0 M for the NpO2+· UO22+complex which is in good agreement with previous measurements using conventional absorption spectroscopy and Raman spectroscopy. Equilibrium constants of 1.8±0.9 and 2.2±1.5 M-1were measured for NpO2+· Th4+and PuO2+· UO22+complexes at an ionic strength of 6.0 M, respectively. This is the first time that LIPAS has been used to study cation-cation complexes and the first time that the PuO2+· UO22+cation-cation complex has been reported.
A preliminary study of the reduction of Np(VI) by formohydroxamic acid using stopped-flow near-infrared spectrophotometry
Authors: Colston B. , Choppin Gregory R. , Taylor Robin J.
Published: August 2006

The kinetics of the reduction of NpO2
2+ to NpO2
+ in nitric acid aqueous solution by formohydroxamic acid (FHA) were studied to allow more accurate flow sheet modelling of neptunium separation from uranium and plutonium in an Advanced PUREX process. The rate of the reaction was monitored using stopped-flow spectrophotometry with near-infrared detection. The conditional reduction rate in 2 M nitric acid at 22°C could be described by the following equation:

-d [NpO2
2+]/dt = k [NpO2
2+][FHA](M/s)

with k = 1.17×103 M-1 s-1 at [H+] = 2.0 M. Comparison with other data available in the literature, indicates that formohydroxamic acid is an unusually strong reducing agent for NpO2
2+.
Removal of234,238U,226Ra,210Po and210Pb from drinking water by ion exchange
Authors: Vaaramaa K. , Lehto Jukka , Jaakkola T.
Published: August 2006

Six organic and five inorganic ion exchangers were studied for the removal of natural radionuclides from drinking water. In the first phase, distribution coefficients (KD) of uranium and radium were determined in three model solutions: a good quality water, an Fe-Mn-rich water and a saline water simulant. The exchangers showing highest KD´s for U and Ra were tested in column mode experiments for the removal of U,226Ra,210Po and210Pb from a real ground water. Considering the total 1800 processed bed volumes, the best decontamination factors (DF) for U, 20-120, were obtained with the strong base anion exchange resin. The most efficient exchangers for the removal of226Ra were the weak and strong cation resins and zeolite A. With use of long regeneration intervals, conventional organic resins are thus most suitable for the removal of radionuclides. When only a few hundred bed volumes were processed, with the corresponding regeneration interval about one week, the aminophosphonate resin was most effective for the removal of both uranium and radium.210Po and210Pb in ground water were mainly bound in particles and adsorbed on the surface of the anion resins. The use of the aminophosphonate resin to remove uranium and radium would therefore require an anion resin to take up polonium and lead.
Mixed-ligand chelate extraction of thorium(IV) and uranium(VI) with thenoyltrifluroacetone and various imidazoles
Authors: Reddy M.L.P. , Ramamohan T.R. , Sahu S.K. , Thakur P. , Chakravortty V.
Published: August 2006

The synergistic extraction of thorium(IV) and uranium(VI) has been studied using mixtures of thenoyltrifluoroacetone (Htta) and various imidazoles such as imidazole (Imz), 2-methylimidazole (2-Meimz), benzimidazole (Bimz) or 2-pyridylbenzimidazole (2-Pybimz). The extraction data have been analysed by both graphical and theoretical methods by taking into account chemical mass action principles. The results demonstrate that these metal ions are extracted into chloroform as Th(tta)4 and UO2(tta)2 with Htta alone and as Th(tta)4 · nS and UO2(tta)2 · nS in the presence of imidazoles (where n = 1 and 2 for thorium(IV) and n = 1 for uranium(VI); S represents imidazole). The equilibrium constants of the above extracted complexes have been deduced by non-linear regression analysis. The addition of an imidazole to the metal chelate system enhances the extraction efficiency of these metal ions. The complexation strength of these metal ions with various imidazoles follows the order: Imz > 2-Meimz > Bimz > 2-Pybimz.
The hydrolysis of dioxouranium(VI) investigated using EXAFS and17O-NMR
Authors: Moll H. , Reich T. , Szabó Z.
Published: August 2006

The structure of dioxouranium(VI) as a function of pH at different (CH3)4N-OH concentrations has been investigated with the aid of U LIII-edge EXAFS. Polynuclear hydroxo species were identified by an U-U interaction at 3.808Å at pH = 4.1. The precipitate formed at pH = 7 has a schoepite like structure. In solution at high pH [0.5 M (CH3)4N-OH], the EXAFS data are consistent with the formation of a monomeric four coordinated uranium(VI) hydroxide complex UO2(OH)42-of octahedral geometry. The first shell contains two O atoms with a U=O distance of 1.830Å, and four O atoms were identified at a U-O distance of 2.265Å.

In strong alkaline solutions [>1 M (CH3)4N)-OH],17O-NMR spectra indicate the presence of two species, presumably UO2(OH)42-and UO2(OH)53-, the latter in low concentration, which are in rapid equilibrium with one another at 268 K in aqueous solution.
Non-destructive and radiochemical determination of the neutron-induced production cross section of I-129 from Te and other neutron-induced cross sections on Te at 14.7 MeV
Authors: Schnabel C. , Leya I. , Michel R. , Csikai J. , Dezso Z. , Lopez-Gutierrez J.M. , Synal H.-A.
Published: August 2006

Cross sections of twelve neutron-induced reactions on tellurium at 14.7 MeV have been determined. Among them are the (n,2n) cross sections for the production of both 129Te isomers which were determined using gamma ray spectrometry. These reactions dominate the cosmogenic production of 129I in meteoroids and are therefore of special importance. In addition, the neutron-induced cross section on Te at 14.7 MeV for the production of 129I was also determined directly by accelerator mass spectrometry (AMS) after radiochemical separation. The results for the production cross section of 129I determined by the two methods agree within 5%.
Electrochemical deposition of carrier-free radionuclides
Authors: Eichler B. , Kratz Jens Volker
Published: August 2006

The potential associated with the electrochemical deposition of radionuclides in metallic form from solutions of extremely small concentration is strongly influenced by the choice of the electrode material. In a macroscopic model, the interaction between the microcomponent and the electrode material is described by the partial molar adsorption enthalpy and -entropy. By combination with the thermodynamic description of the electrode process, a potential is calculated that characterizes the process at 50% deposition. Model calculations for Ni-, Cu-, Pd-, Ag-, Pt-, and Au-electrodes and the microcomponents Hg, Tl, Pb, Bi, and Po confirm the decisive influence of the electrode material on the deposition potential. The present study prepares an application of the same model to the superheavy elements 112-116.
Complex formation of Np(V) with humic acid and polyacrylic acid
Authors: Tochiyama Osamu , Yoshino Hirofumi , Kubota Takumi , Sato M. , Tanaka K. , Niibori Yuichi , Mitsugashira T.
Published: August 2006

By using239Np and/or237Np, the complexation of Np(V) with Aldrich humic acid and polyacrylic acid has been studied at the concentration of Np(V) from ~10-13to ~10-4M by the solvent extraction method using TTA and 1,10-phenanthroline in isoamyl alcohol. By defining the apparent formation constant as βα=[ML]/([M]CRα), where CRis the total concentration of proton exchanging sites and α is the degree of dissociation, [M] and [ML] respectively denote the concentrations of free and bound NpO2+, log βαhave been obtained at pH 6-7 in 0.1 and 1.0 M NaClO4. For both humate and polyacrylate, log βαslightly increased with the degree of dissociation, and slightly decreased with ionic strength. While the variation of Np(V) concentration had no appreciable influence on the log βαof polyacrylate (ranging from 1.8 to 3.0 depending on pH and ionic strength), log βαof humate decreased from 4.7-5.3 (depending on pH and ionic strength) at [M] < 10-9M to 2.8-3.1 at [M] = 10-5M, indicating the coexistence of weak and strong binding sites in the humic acid.
Extended X-ray absorption fine structure and time differential perturbed angular correlation study of hafnium(IV) sorbed onto amorphous silica
Authors: Denecke Melissa A. , Geckeis Horst , Pohlmann C. , Rothe J. , Degering D.
Published: August 2006

Sorption of Hf(IV) onto amorphous silica at pH values between 1 and 7 is investigated by extended X-ray absorption fine structure (EXAFS) and time differential perturbed angular correlation (TDPAC) spectroscopies. Hafnium(IV) is studied as a chemical analogue for understanding the speciation of tetravalent actinides. In addition, 181Hf is a frequently investigated TDPAC probe nuclide. Spectra obtained from both techniques show that there is a change in Hf-species with sample preparation pH. Results from TDPAC measurements show that two similar surface binding sites exist for Hf(IV) on the silica surface at low pH values. At a pH above 3, a third, unspecific surface binding site for Hf(IV) begins to dominate. EXAFS investigations do not detect the presence of polynuclear surface species. Both TDPAC and Hf L3 edge EXAFS spectra of the sorption samples differ from that of a Hf(IV) solution or a Hf(IV) hydrolysis product. This indicates that the sorbed species are different from solution or simple hydrolysis species. Short Hf-O distances are obtained from theoretical fits to the EXAFS oscillations for all samples. This suggests that the primary interaction of Hf(IV) with the silica surface occurs via silanol groups. Differences in the electric field gradient surrounding sorbed Hf(IV) cations as a function of pH, observed in the TDPAC spectra, must result from changes in overall species geometry rather than a change in the primary Hf-silica surface interaction.
Surface spectroscopic studies of Cs+, and Ba2+sorption on chlorite-illite mixed clay
Authors: Shahwan T. , Sayan S. , Erten H.N. , Black L. , Hallam K.R. , Allen G.C.
Published: August 2006

The sorption behavior of Cs+, and Ba2+on natural clay was investigated using ToF-SIMS, XPS, and XRD. The natural clay was composed mainly of chlorite and illite in addition to quartz and calcite. Depth profiling up to 70 Å was performed at 10 Å steps utilizing ToF-SIMS to study the amount of sorbed Cs+and Ba2+as a function of depth in the clay matrix. The results suggest that Cs+and Ba2+ions were sorbed primarily by ion exchange coupled with hydrolytic sorption. According to ToF-SIMS and XPS results, the total sorbed amount of Ba2+was larger than that of Cs+. Quantitative determination of the primary cations within the analyzed clay before and after sorption indicated that for Ba2+sorption, Ca2+, Mg2+and for Cs+sorption Ca2+, K+were the major exchanging ions. The XRD spectra of Ba-sorbed clay contained new peaks that were identified as BaCO3.
Approaches to modelling uranium(VI) adsorption on natural mineral assemblages
Authors: Waite T.D. , Davis James A. , Fenton B.R. , Payne Timothy E.
Published: August 2006

Component additivity (CA) and generalised composite (GC) approaches to deriving a suitable surface complexation model for description of U(VI) adsorption to natural mineral assemblages are pursued in this paper with good success. A single, ferrihydrite-like component is found to reasonably describe uranyl uptake to a number of kaolinitic iron-rich natural substrates at pH > 4 in the CA approach with previously published information on nature of surface complexes, acid-base properties of surface sites and electrostatic effects used in the model. The GC approach, in which little pre-knowledge about generic surface sites is assumed, gives even better fits and would appear to be a method of particular strength for application in areas such as performance assessment provided the model is developed in a careful, stepwise manner with simplicity and goodness of fit as the major criteria for acceptance.
Application of electrokinetic data to test the adsorption models
Authors: Kosmulski M. , Eriksson P. , Gustafsson J. , Rosenholm J.B.
Published: August 2006

The effect of adsorption of Gd(III) on the electrokinetic potential of silica (Aerosil, 390 m2/g) was studied at various Gd(III) concentrations (ranging from 10-6to 10-2mol dm-3) and at four different solid to liquid ratios (ranging from 0.05 to 8% of silica by weight). Up to some critical concentration of trivalent cations, their effect on the electrokinetic potential of silica is negligible and the sign is negative over the entire studied pH range. This critical concentration increases when the solid to liquid ratio increases. When Gd(III) concentration exceeds the critical value, the magnitude of the negative electrokinetic potential of silica is reduced. This effect is substantial at pH 6 but it is rather insignificant when the pH is very high (pH > 8) or very low (pH < 4). When the Gd(III) concentration is even higher, the sign of the electrokinetic potential is reversed to positive over certain pH range, which depends on the solid to liquid ratio and Gd(III) concentration. The shape of experimental electrokinetic curves of silica in the presence of trivalent cations often shows maximums and double isoelectric points, thus, it is very complex in comparison with the shape of the percentage of uptake vs. pH curves. Therefore, a test of an adsorption model based on electrokinetic curves is much more demanding than a test based merely on uptake vs. pH curves. The parameters of surface complexation model (SCM) derived from analysis of a large set of uptake curves were used to predict the course of electrokinetic curves. The calculated and experimentally observed maximums and isoelectric points do not exactly match (a difference up to one pH unit), but the model curves qualitatively reflect the trends observed in electokinetic experiments.
Sorption equilibrium and kinetics of NpO2+on dispersed particles of Na-montmorillonite
Authors: Nagasaki S. , Tanaka S.
Published: August 2006

Sorption equilibrium and kinetics of NpO2+on dispersed particles of Na-montmorillonite were experimentally investigated by using a°batch technique and a°spectroscopic method, respectively. Considering the heterogeneity of sorption sites, we investigated the affinity spectra for the sorption of NpO2+. It was found that the spectrum for NpO2+was monomodal but asymmetrical and that the half-width at half-maximum of the spectrum was relatively broad, indicating that the sorption sites of surface of Na-montmorillonite are strongly heterogeneous. From the kinetic spectrum for NpO2+, two sorption processes could be distinguished. It was considered that the fast process is attributable to the sorption of NpO2+on the easily accessible outer surface of Na-montmorillonite particles and that the slower process is assigned to the sorption on the interlayer surface. Mean apparent activation enthalpies for the fast and the slow processes were evaluated as 19 ± 2 kJ/mol and 23 ± 3 kJ/mol, respectively.
Spectroscopic properties of uranium(VI) minerals studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS)
Authors: Geipel Gerhard , Bernhard G. , Rutsch M. , Brendler V. , Nitsche Heino
Published: August 2006

We studied the fluorescence properties of 120 uranium minerals in order to provide a data base of potential secondary solids that may form in the flooding process of defunct uranium mines. This data base may provide a link of the fluorescence spectra of the minerals to solution spectra containing so far unknown tertiary and quaternary solution complexes in environmental uranium(VI)-containing waters. In our initial effort to establish the data base, we are focusing on phosphate- and arsenate-containing uranium(VI) minerals. Except for chernikovite [(H3O)2(UO2)2(PO4)2 · 6H2O], these minerals show intensive fluorescence emissions bands with a bathochromic shift of up to 18 nm compared to the fluorescence of the uranyl ion in solution.

We found hypsochromic shifts of the fluorescence emission for the uranyl phosphates and bathochromic shifts for the uranyl arsenates. The band spacing of the fluorescence emissions from the 20502 cm-1 level are comparable to the vibrational frequency available from IR-data. Using these data we estimated the axial U-O bond lengths. The decrease of the vibration frequency from 813 cm-1 (saleiite, [Mg(UO2)2(PO4)2 · 10(H2O)]) to 794 cm-1 (uranocircite, [Ba(UO2)2(PO4)2 · 12(H2O)]) is related to a slight increase of the U-O bond length by 3 pm.

In both series, the fluorescence lifetime decreases with decreasing crystal water. This is different compared to solution spectra where the lifetime increases as water is displaced from the inner coordination shell.

Comparing the fluorescence data of the mineral troegerite [H2(UO2)2(AsO4)2 · 8(H2O)] with the fluorescence spectra of uranyl arsenate solutions, we identified one of the three uranyl arsenate complexes in solution as HUO2(AsO4)(aq.).
Quantitative assessment of radiocaesium bioavailability in forest soils
Authors: Konoplev A.V. , Avila R. , Bulgakov A.A. , Johanson K.-J. , Konopleva I.V. , Popov V.E.
Published: August 2006

A method for quantitative characterisation of the radiocaesium availability to plants in forest ecosystems has been developed. For this purpose an expression has been proposed to calculate the radiocaesium availability factor in soils, which is a combination of key soil characteristics: radiocaesium exchangeability, exchangeable calcium in soil and effective selectivity coefficient. The experimental dependencies of the radiocaesium soil to plant concentration factors for fern and bilberry, on the availability factor calculated by the above equation were satisfactory described by linear function. The advantage of this method to characterise bioavailability of radiocaesium and to estimate site-specific values of concentration factor is that the necessary soil characteristics may be taken from the reference literature, evaluated by experts or determined with a simple experimental procedure. The method can be used in development of a radioecological Geographic Information Systems.
Adsorption of Cs and U(VI) on soils of the Australian arid zone
Authors: Payne Timothy E. , Harries J.R.
Published: August 2006

Distribution coefficients (Kd values) for Cs and U(VI) on soils from an arid region of Australia were measured under a range of conditions. The Kd values for trace 137Cs in 0.02 M NaCl were typically around 104 mL/g, and were not affected by the pH. However, the Kd decreased with increasing ionic strength, and was strongly dependent on the total Cs concentration. Much lower Kd values (around 102 mL/g) were measured in systems containing total Cs of 1 mmol/L in a background electrolyte of 0.10 M NaCl. The main factor determining the sorption behaviour of U(VI) in systems equilibrated with air was the pH, with the Kd decreasing from above 103 mL/g at pH 7 to around 10 mL/g at pH 9.
Solubility and hydrolysis of tetravalent actinides
Authors: Neck Volker , Kim J. I.
Published: August 2006

The solubility and hydrolysis of Th(IV), U(IV), Np(IV), and Pu(IV) are critically reviewed and a comprehensive set of thermodynamic constants at I = 0 and 25°C is presented. The hydrolysis constants are selected preferentially from experimental studies at actinide trace concentrations, where the interference of colloid formation can be excluded. Unknown formation constants of mononuclear complexes An(OH)n4-nare estimated by applying a semi-empirical electrostatic model and an empirical correlation with the known constants of other actinide ions. Based on the known and estimated hydrolysis constants, the solubility products of An(OH)4(am) or AnO2× xH2O(am) are calculated from experimental solubility data available in the literature. The SIT is used for ionic strength corrections.

The solubilities of U(IV), Np(IV), and Pu(IV) hydroxides or hydrous oxides can be calculated by accounting only for mononuclear hydrolysis species. The considerably higher solubilities of amorphous Th(IV) precipitates at pH <5 include major contributions of polynuclear species. The solubility data in acidic solutions depend strongly on the preparation and crystallinity of the solid phase. In neutral and alkaline solutions, where An(OH)4(aq) are the predominant aqueous species, the solubilities of AnO2(cr) become equal to those of the amorphous solids. This indicates that the crystalline dioxides are covered by amorphous hydroxide layers.
Positron annihilation in hydrogen-doped alkali-metal fullerides
Authors: Murakami H. , Ohtsu Y. , Ichikawa K. , Sano M. , Jin C. , Yonehara Y. , Ichimura K.
Published: August 2006

Hydrogen-doped alkali-metal fullerides were studied by means of mass-analyzed thermal desorption and positron annihilation. The hydrogen desorption spectra reveal the inclusion of hydrogen in the fullerides as two types of components; one weakly adsorbed and the other strongly bound, probably as hydride ion. The positron lifetime spectra demonstrate that hydrogen-doping to alkali-metal fullerides increases a concentration of higher-order vacancy-type defects, through which more than 50% injected positrons decay with a lifetime of 0.42–0.71 ns.
Sequential separation of americium, curium, plutonium, neptunium and uranium in various matrices from the electrometallurgic treatment of spent-nuclear fuel
Authors: Huntley M. W.
Published: August 2006

The separation of americium-241, curium-242/244, plutonium-238/239, neptunium-237, and uranium-234/235/238, in the same sample aliquot of clear acidic solution resulting from the electrometallurgical treatment of spent nuclear fuel has been investigated. Using ion exchange techniques in 10 M HCl media, it was determined that good separation can be achieved to resolve each isotope via alpha spectroscopy. The resin used was AG 1-x8 chloride form supplied by BioRad® Laboratories. The retention and eluting conditions for each isotope were determined using tracer techniques and will be presented. Based on this work, an analytical procedure for the sequential separation of Am, Cm, Pu, Np, and U, in various sample matrices recovered from the demonstration project is presented.
Impact of the contributions of Glenn T. Seaborg on nuclear science
Authors: Hoffman D.C.
Published: August 2006

Glenn Theodore Seaborg (1912-1999) was a world-renowned nuclear chemist, a Nobel Laureate in chemistry in 1951, co-discoverer of plutonium and nine other transuranium elements, Chairman of the U.S. Atomic Energy Commission from 1961-1971, scientific advisor to ten U.S. presidents, active in national and international professional societies, an advocate for nuclear power as well as for a comprehensive nuclear test ban treaty, a prolific writer, an avid hiker, environmentalist, and sports enthusiast. He was known and esteemed not only by chemists and other scientists throughout the world, but also by lay people, politicians, statesmen, and students of all ages. This memorial includes a brief glimpse of Glenn Seaborg's early life and education, describes some of his major contributions to nuclear science over his long and fruitful career, and highlights the profound impact of his contributions on nuclear science, both in the U.S. and in the international community.
Thin target cross sections for proton-induced formation of radionuclides from lead for E
p≤71 MeV
Authors: Kuhnhenn J. , Herpers U. , Glasser W. , Michel R. , Kubik P. W. , Suter M.
Published: August 2006

Some new cross sections for proton-induced radionuclide formation from lead are presented. The results extend the previous measurements from about 70 MeV down to threshold energies. Emphasis was placed upon an improved method of γ-ray spectrum analysis which proved to be reliable and effective. The new results are compared with model calculations on the basis of an improved hybrid model of preequilibrium reactions which is able to reproduce the near target products very well. But for more than 6 emitted nucleons, experimental measurements are superior.
Surface exposure dating by in-situ produced cosmogenic nuclides: chemical mineral separation of purified quartz
Authors: Altmaier M. , Klas W. , Herpers U.
Published: August 2006

The interaction of cosmic radiation with terrestrial matter leads to the in-situ production of cosmogenic nuclides in the exposed surface material. Accelerator mass spectrometry (AMS) enables us to quantitatively measure trace concentrations of in-situ produced radionuclides like 10Be and 26Al. 21Ne can be determined by conventional noble gas mass spectrometry. This ultimately allows the determination of surface exposure ages, erosion rates and other processes of landscape evolution. The availability of a pure and well defined mineral sample is an important prerequisite for surface exposure dating. As the samples taken in the field usually do consist of many different mineral components, a quartz separation technique has to be employed. We present a chemical mineral separation that allows the isolation of a pure quartz fraction, which is quantitatively decontaminated from the atmospheric 10Be contamination lying on the sample.
Application of radiotracer techniques to a kinetic study of the interaction of Eu with humic acid
Authors: Mizera J. , Benes P. , Hvozdová I. , Jansová A.
Published: August 2006

Experimental methods based on the radiotracer technique have been designed to study kinetic aspects of the interaction of humic substances (HS) with metal ions. The rate of dissociation of Eu-HS complexes was observed via the rate of the isotope exchange in the system152Eu - stable Eu - humic acid (HA) determined by the diaphragm method. The rate of exchange was found to be enhanced by decreasing pH value, increasing ionic strength and increasing degree of loading of HA with Eu, and was described with a simple 1-component kinetic model (mono-exponential decay function). Additional information on the kinetics has been derived from the electrophoretic mobilities of Eu depending on metal loading of HA and pH, determined by the free liquid/moving boundary electrophoresis with radiometric and spectrophotometric detection of the electromigration of the Eu/Eu-HA complex.
Distribution of 212Pb, 214Pb and 210Pb with its daughter products on aerosol fractions from Vienna and Badgastein (Austria)
Authors: Wallner G.
Published: August 2006

Aerosols were collected with cascade impactor devices and the activity concentrations of 210Pb, 210Bi and 210Po were measured by liquid scintillation counting. In samples collected near to the laboratory also 212Pb and 214Pb could be determined. The activity concentrations, their particle size distributions and the calculated aerosol ages are discussed with regard to the prevailing weather conditions. Special emphasis is given to the fact, that excess 210Po occurs not only in urban, but also in rural environments and that it is mainly found on particles with very small diameters (0.15-0.30 µm).
Determination of uranium and thorium in complex matrices by two solvent extraction separation techniques and photon electron rejecting alpha liquid spectrometry
Authors: Ayranov Marin , Wacker K. , Krähenbühl Urs
Published: August 2006

The separation of uranium and thorium from complex matrixes such as marine sediments using solvent extraction and determination by means of Photon-Electron Rejecting Liquid Alpha Spectrometry (PERALS®) has successfully been performed. Two extraction schemes, using TOPO and HDEHP, respectively, were compared for the separation of uranium and thorium from the matrix components. The results show recoveries between 73 and 92% for 234U, 238U, 232Th, 230Th and 228Th with an accuracy of the methods ±12%. Minimum detectable activities for counting time up to 500000 seconds for 0.5 g sample material were between 0.34-1.15 Bq/kg for uranium and 0.31-1.66 Bq/kg for thorium.
Using13N as tracer in heterogeneous atmospheric chemistry experiments
Authors: Amman M.
Published: August 2006

Current techniques aiming to study heterogeneous atmospheric chemistry under realistic conditions are often subject to restrictions caused by the low amount of processed material, the complex composition of gas and condensed phases and interference issues. The use of the short-lived tracer13N enables laboratory experiments pertaining to the atmospheric chemistry of nitrogen oxides to be performed at extremely low concentrations, ambient humidity and pressure.13N was produced through16O(p,α)13N reaction in a gas target in continuous mode, and transported as13NO in a carrier gas to the chemistry laboratory through a 70 m long capillary. Several gas-phase and surface chemical routines allowed converting13NO into other forms of oxidized nitrogen. Chemical separation and detection was achieved through chemically specific absorption reactions on the coatings of denuders, which additionally allowed separating gas-phase species from their particulate counterparts. In a first application, the reversible adsorption of NO2on a solid NaCl surface was investigated, from which an adsorption enthalpy of 28 kJ/mol was derived. As an example of a reaction with aerosol particles in gas suspension, the reaction of13N-labelled HNO3with sea-salt particles was studied using an aerosol flow reactor.
Pion transfer processes of pionic atoms in the gas mixtures containing hydrogen at various pressures
Authors: Shinohara Atsushi , Miura T. , Yokoyama Akihiko , Takamiya K. , Kaneko T. , Muroyama T. , Saito T. , Hamajima Y. , Muramatsu H. , Kojima S. , Baba H. , Furukawa M.
Published: August 2006

The pion capture process in gas mixtures containing hydrogen was studied by measuring pionic X rays and π0 decays. A little difference in pion transfer process was found between the H2+D2 and H2O+D2O systems. Pressure-dependence of the transfer rates was also revealed in the CH4+Ar system by the measurements at several gas pressures. The mechanism of the pion transfer process was discussed based on a comparison between transfer parameters in the gas and liquid phases.
Simultaneous production of 28Mg and 47Ca by high-energy heavy-ion irradiation for applications in biology
Authors: Ambe Shizuko , Ozaki Takuo , Weginwar R.G. , Enomoto S. , Ambe Fumitoshi
Published: August 2006

With the aim of preparing carrier-free 28Mg and 47Ca simultaneously, Ti, V and Fe targets were examined by irradiating with high-energy ions of 12C, 14N and 16O accelerated by the RIKEN Ring Cyclotron. Among the targets, V gave the highest cross section for the formation of both 28Mg and 47Ca irrespective of the kind of beams. The cross section for the formation of 28Mg by the reactions of Ti, V and Fe targets with ion beams increased in the order of 12C < 16O<14N. On the other hand, the three beams exhibited almost the same cross sections for the formation of 47Ca by the reaction of a given target. Titanium and V were selected as prospective targets and 14N as a suitable beam for the production of 28Mg and 47Ca. Chemical separation procedures of the radiotracers in carrier- and salt-free states have been established by using cation exchange resins. The recovery yields of 28Mg and 47Ca from Ti target were 70 and 90%, respectively, and the decontamination factor was less than 10-5. The recovery yields of 28Mg and 47Ca from V target were 80% and the decontamination factor was less than 10-7.
A kinetic model for the oxidation of U(IV) to U(VI) with O2: Determination of stability constants via oxidation kinetic experiments
Authors: Landgren A. , Ramebäck H.
Published: August 2006

The oxidation of U(IV) to U(VI) with molecular oxygen in acidic aqueous NaClO4 (I=0.5 M) solutions at different temperatures was studied. It was found that the reaction kinetics is a combination of a first-order reaction and an autocatalytic reaction. The speciation of tetravalent uranium is important since it was found that the two first hydrolysed uranium(IV) species are the reactive species under the conditions studied. One problem in interpreting the results comes from the lack of thermodynamic data. However, oxidation kinetic experiments may be a method for determining stability constants for redox sensitive tetravalent actinides. The stability constants for the formation of the first two hydrolysed complexes of U(IV) are reported in this work, e.g. log *β1 (I = 0.5;M, T = 303.15;K)= 1.39±0.42, as compared to the literature value of -1.39±0.20.
Fluorescence spectroscopy of U(VI) in the presence of perchlorate ions
Authors: Rustenholz A. , Billard I. , Duplatre G. , Lützenkirchen K. , Sémon L.
Published: August 2006

Time-Resolved Laser-induced Fluorescence spectroscopy (TRLFS) is used to study the properties of excited UO22+ions (fluorescence lifetimes and emission spectra) in the presence of perchlorate ions (up to 5.5 M concentration). The experiments are performed at three perchloric acid concentrations (0.2, 1 and 2 M). Although ClO4-is known not to complex with UO22+, increasing amounts of ClO4-lead to a decrease of the lifetime for each [H+] series. The emission spectra do not show any spectral shift and the fluorescence intensity is well correlated with the lifetime variation. Three different models are discussed to interpret the data: (a) A model based on the assumption of a chemical equilibrium between UO22+and ClO4-, both in their ground states. (b) A model which additionally takes into account excited state reactions of UO22+. (c) A third model which is solely based on photochemical, excited state reactions of UO22+. It is the only one consistent with the present data and results of other studies of the uranium(VI)/perchlorate system. Hence, photochemical reactions, even in the presence of weakly or non-complexing ligands like perchlorate ions, need to be taken into account in TRLFS experiments.
Multitracer studies on the effects of model acid rain on the adsorption of trace elements on soils
Authors: Wang H.F. , Ambe Shizuko , Takematsu N. , Ambe Fumitoshi
Published: August 2006

Using a multitracer technique, the effects of acid rain pH on the adsorption of 15 trace elements on soil were studied. Kaolin, forest soil (original and with partially removed oxides), black soil (original and without organic matter)and Kureha soil (original, with partially removed oxides, and without organic matter) were employed as the adsorbents. Instead of H2SO4solution, HCl solution was selected as the model acid rain based on the results of adsorption experiments on kaolin. In general, the percentage adsorption of cationic elements on three original soils and kaolin increased with increasing pH. The adsorption of oxyanionic elements, As and Se, on three soils was high over the entire pH range studied, while that on kaolin was low and decreased with an increase in pH. The differences in the physical and chemical properties of soils were reflected on the adsorption. The organicmatter in soil had positive effects on the extent of adsorption of most elements studied, while the oxides apparently showed positive effects only for Fe and Se adsorption. The results indicate that acid rain decreases the retention of cations in soil and that it increases or does not change the adsorption of anions.
Ortho-positronium annihilation parameters in polyvinyl alcohol films with various degrees of polymerization, saponification and crystallinity
Authors: Muramatsu H. , Matsumoto K. , Minekawa S. , Yagi Y. , Sasai S.
Published: August 2006

Positron annihilation lifetime (PAL) spectroscopy has been applied to polyvinyl alcohol (PVA) films prepared with commercially available PVA or from polyvinyl acetate (PVAc). The variation of lifetimes of ortho-positronium (o-Ps) formed in the films was investigated as a function of the degrees of polymerization, saponification, or crystallinity. For the fully saponificated samples, no dependence was found to exist on the degrees of polymerization or of crystallinity. For the partially saponificated samples, however, the dependence of the o-Ps lifetime on the degree of saponification was clearly observed, and this is explained by both the formation of hydrogen bonds among the polymer chains and the existence of acetyl group strongly inhibiting the hydrogen-bond formation due to steric hindrance.
Isotope correlations for determining the isotopic composition of plutonium
Authors: Alamelu D. , Aggarwal S. K.
Published: August 2006

Improved correlations using the 238Pu/(239Pu + 240Pu) alpha activity ratios determined alpha spectrometrically and the different atom ratios viz. 240Pu/239Pu, 241Pu/239Pu and 242Pu/239Pu determined mass spectrometrically are presented for Pu produced in Pressurised Heavy Water Reactors (PHWRs). These correlations are useful to obtain the different atom ratios, with reasonable accuracy (1 to 10% depending upon the atom ratio), using only the 238Pu/(239Pu+240Pu) alpha activity ratio determined alpha spectrometrically from a plutonium sample purified from 241Am. Since the correlations involve the relative values and not the absolute values of the atom% abundance of any specific isotope, the accuracy of the data obtained using these correlations is much better. In addition, the change in the atom% abundance of 241Pu due to the relatively short half-life of 241Pu (14.4 yr) does not create any ambiguity in the ratio 242Pu/239Pu and hence the accuracy of data for 242Pu is not affected by the uncertainty in the data for 241Pu.
Chemical analysis of transuranium nuclides in the uranium solution of the JCO criticality accident
Authors: Shinohara N. , Kohno N. , Suyama K. , Inagawa J. , Nakahara Y. , Kurosawa S. , Watanabe K. , Usuda S. , Oshima M. , Katsuta H.
Published: August 2006

Atom numbers of 239Np and 239Pu, which had been produced by the neutron capture reaction of 238U in the uranium solution of the JCO criticality accident at Tokai-mura, Japan, were determined precisely by a radiochemical method. It was found that the measured atom ratio of 239Np/239Pu at termination of the criticality depends sensitively on the history of the neutron capture reaction during the accident (about 20-hours continuance). The history was evaluated by comparing the measured value and those calculated by a burnup calculation code. The percentage of the number of the neutron capture reaction at the initial stage of the criticality during 25 min against the total events was determined to be 24±6%.
Nuclear data relevant to the production and application of diagnostic radionuclide
Authors: Qaim Syed M.
Published: August 2006

The types of nuclear data and their quality required in the production and application of diagnostic radionuclides are outlined. The radioactive decay data determine the suitability of a radioisotope forin vivotracer studies, both from the imaging and internal radiation dose considerations. The nuclear reaction cross section data allow optimisation of production routes. Both reactors and cyclotrons are used for production purposes. The nuclear data needed in the two cases and their present status are discussed. Special attention is paid to radionuclides suitable for emission tomography (PET and SPECT). The controversy aboutreactorvscyclotronproduction of the widely used99Mo/99mTc generator system is discussed. Some special considerations in cyclotron production of radionuclides are outlined. The need of accurate data near reaction thresholds, the constraint of available particles and their energies at a small cyclotron, the influence of increasing incident particle energy, and the formation of isomeric impurities are discussed in detail. The role of nuclear model calculations in predicting unknown data is considered.
Excitation function of the18O(p,n)18F nuclear reaction from threshold up to 30 MeV
Authors: Hess E. , Takács S. , Scholten B. , Tárkányi F. , Coenen Heinz H. , Qaim Syed M.
Published: August 2006

The available experimental data on the most common route for the production of18F, viz.18O(p,n)18F reaction, obtained both via neutron spectral studies and activation measurements, were critically reviewed. In some energy regions the cross section database was found to be rather weak or discrepant. In order to fill the gaps and to clear some of the discrepancies, the excitation function was remeasured from threshold up to 30 MeV using different solid and gas targets containing highly enriched18O. For this purpose a van de Graaff machine (Ep<4 MeV) and several cyclotrons (Ep= 4-30 MeV) were utilized. The new experimental data help to prepare a recommended data set. AtEp= 14 MeV the integral yield of18F calculated from the new excitation curve is slightly higher than that from the hitherto accepted data set; atEp> 14 MeV the yields reported here are new.
Plutonium in soil from Dolon near the Semipalatinsk nuclear test site
Authors: Gastberger M. , Hubmer A. , Steinhäusler F. , Lettner H. , Spano M. , Stronati L. , Testa A.
Published: August 2006

The plutonium activities (238Pu and 239,240Pu) of soil samples from the village of Dolon, located close to the Semipalatinsk Nuclear Test Site in Kazakhstan, were measured and compared with the 90Sr and 137Cs activities. Depth profiles of 239,240Pu were determined for four of the nine sampling sites. The 239,240Pu areal deposition at the nine sites is in the range of 140 to 9700 Bq m-2. For all samples, the 239,240Pu yield after destruction of the soil matrix is significantly higher than after extracting with 8 M HNO3 indicating that 239,240Pu originates mainly from local fallout. The fraction of 239,240Pu not leached with 8 M HNO3 is assumed to be associated with fused silicates.
Crown ether as size selective synergist in the solvent extraction of thorium(IV) and uranium(VI) with 3-phenyl-4-(4-fluorobenzoyl)-5-isoxazolone
Authors: Reddy M.L.P. , Meera R.
Published: August 2006

The synergistic extraction of thorium(IV) and uranium(VI) from nitric acid solutions has been investigated using mixtures of 3-phenyl-4-(4-fluorobenzoyl)-5-isoxazolone (HFBPI) and dicyclohexano-18-crown-6 (DC18C6), dibenzo-18-crown-6 (DB18C6) or benzo-15-crown-5 (B15C5). The results demonstrate that these metal ions are extracted into chloroform as Th(FBPI)4and UO2(FBPI)2with HFBPI alone and as Th(FBPI)4·CE and UO2(FBPI)2·CE in the presence of crown ethers (CE). The equilibrium constants of the above extracted complexes have been deduced by non-linear regression analysis. The addition of a crown ether to the metal chelate system enhances the extraction efficiency and also improves the selectivities significantly between thorium (IV) and uranium(VI). The complexation strength of uranium(VI) with various crown ethers follows the order: DC18C6>B15C5>DB18C6, which can be explained on the basis of crown ether basicity sequence and steric effects. On the other hand, the complexation strength of Th-FBPI chelate with crown ether follows the order: B15C5>DC18C6>DB18C6. The high extraction of thorium(IV) with B15C5 can be explained on the basis of ‘size-fitting effect’. Solid complexes of these metals with 4-acyl-3-phenyl-5-isoxazolones and with mixtures of HFBPI and crown ether have been isolated and characterised by elemental analyses, IR and1HNMR spectroscopic techniques.
Determination of fictive binary data for uranium(IV) nitrate: preliminary results
Authors: Charrin N. , Moisy Philippe , Blanc P.
Published: August 2006

The concept of simple solutions is applied to a quaternary system of U(NO3)4, HNO3, N2H5NO3 and H2O in order to determine fictive binary data for U(NO3)4. Hydrazinium nitrate solutions were used at low concentrations relative to the nitric acid and uranium(IV) nitrate concentrations, allowing this system to be considered as a ternary (U(NO3)4, HNO3, H2O) system. The simple behavior of the system allowed fictive binary data (osmotic coefficient and density) to be calculated from water activity and density measurements. The results were then used to calculate the coefficients related to Pitzer´s model and to specific interaction theory, used to model the deviation of the concentrated solution from ideality. The results were also used to calculate the activity coefficient of uranium(IV) nitrate in the presence of uranyl(VI) nitrate and nitric acid. The binary data obtained for uranium(IV) nitrate were found to differ significantly from the data for plutonium(IV) nitrate.
Streifende-Inzidenz-Interferometrie mit diffraktiven Elementen für die Formmessung von Mantelflächen stabförmiger Objekte I: Messprinzip und Theorie (Grazing Incidence Interferometry using Diffractive Optical Elements for the Shape Measurement of the Mantle Surface of Rod-shaped Objects I: Measuring Principle and Theory)
Authors: Brinkmann S. , Dresel T. , Schreiner R. , Schwider J.
Published: August 2006

In einem zweiteiligen Artikel wird über streifende Inzidenz-Interferometrie mit Hilfe von diffraktiven Referenzelementen berichtet. Streifende Inzidenz-Interferometrie ermöglicht auch das interferometrische Vermessen der Oberflächengestaltabweichungen bei rauhen Oberflächen.

Dabei werden im Teil I das Prinzip, die zugrunde liegende Theorie, die Designprinzipien angepaßter diffraktiver Phasenmasken sowie die Lösung der Justierprobleme der technischen Testobjekte relativ zum Interferometer dargestellt.
Dynamische Messungen mit einem polarisationsoptischen Laserinterferometer (Dynamic Measurements using a Laserinterferometer working with Polarized Light)
Authors: Lemke K. , Plagwitz K.-U. , Henke S.
Published: August 2006

Es wird ein Messverfahren zur Bestimmung des Augeninnendrucks vorgeschlagen, bei dem der gesamte zeitliche Verlauf der Korneaverformung bei Einwirkung eines Druckimpulses und das Ausschwingen danach für die Messwertgewinnung genutzt wird. Bei Messungen mit Lasern am biologischen Objekt  insbesondere am Auge  ist zu beachten, dass nur geringe Strahlungsleistungen angewendet werden können, die Messflächen gekrümmt sind und geringes Reflexionsvermögen aufweisen. Dadurch wird eine hohe Detektionsempfindlichkeit erforderlich, die immer mit einer Einschränkung der Dynamik verbunden ist. Das dynamische Verhalten der Messanordnung wurde überprüft; bei Lichtintensitäten von <50 μW im Messarm des Interferometers konnten Messflächengeschwindigkeiten bis 35 cm/s sicher detektiert werden. Untersuchungen an verschiedenen Messobjekten zeigen die Anwendbarkeit des Messverfahrens.
Untersuchung von Phasensingularitäten in der Umgebung kleiner Strukturen mit einem Linnik-Interferenzmikroskop (Investigation of Phase Singularities in the Vicinity of Small Structures Using a Linnik Interference Microscope)
Authors: Dorn R. , Eberler M. , Piringer M. , Quabis S. , Leuchs G.
Published: August 2006

Wir präsentieren Untersuchungen zur Feldverteilung in der Umgebung von Sub-λ-Strukturen. Das Auftreten von Singularitäten in der Phasenverteilung des reflektierten Feldes wird theoretisch und experimentell in Hinsicht auf die Möglichkeit der lateralen Überauflösung untersucht. Ein theoretisches Modell für die Berechnungen des elektrischen Feldes, welches auf dem Greenfunktion-Formalismus basiert, wird diskutiert. Messungen an zweidimensionalen Objekten wurden mit Hilfe eines Linnik-Interferenz-Mikroskopes durchgeführt.
Piezoelektrische Sensoren für die Viskositätsmessung (Piezoelectric Sensors for the Measurement of Viscosity)
Authors: Eberl R. , Wilke J.
Published: August 2006

Die traditionellen Methoden der Viskosimetrie besitzen Nachteile, die die Suche nach Alternativen immer wieder angeregt hat. Einer der erfolgversprechendsten Ansätze beruht auf dem Umstand, dass das Schwingverhalten piezoelektrischer Sensoren von der Viskosität einer angrenzenden Flüssigkeit abhängt. Aufbau, Funktionsweise und typische Eigenschaften von Schwingquarz- und Oberflächenwellensensoren zur Viskositätsmessung werden vorgestellt und mit den Ergebnissen eigener Testmessungen ergänzt.
Untersuchungen zur thermischen Alterung von Beschichtungen (Investigations of the Thermal Aging of Coatings)
Authors: Holzhausen U. , Millow S. , Adler H.-J.P.
Published: August 2006

Der Zusammenhang zwischen der Abgabe niedermolekularer Stoffe aus Beschichtungen unter dem Einfluss erhöhter Temperatur und ihren Eigenschaften wurde ermittelt. Dazu wurden Beschichtungen unterschiedlicher Lösemittelbasis und Trocknungsmechanismen wärmegelagert und die Änderungen der Beschichtungseigenschaften sowie die Abgabe flüchtiger organischer Verbindungen in Zeitabhängigkeit durch Prüfungen und Analysen erfasst.