bluuebunny/crossref_metadata_2025 huggingface dataset:
Doppler broadening as a probe of the chemical environment following oxygen-14 decay
Authors: Nickles R. J. , Jensen M. , Paans A.M.J. , Holm S. , Schueller M.J. , Vaalburg W.
Published: August 2006

A search for the Doppler broadening following the beta decay of oxygen-14 was conducted with high resolution gamma spectroscopy on the 2313 keV gamma ray. Such a broadening should signal the mass of the labeled molecule and the nature of the stopping medium. Oxygen-14 labeled H2O, O2 and CO2 trapped on solid soda lime were investigated. No broadening was observed beyond the 1.65 keV instrumental resolution of the Ge detector, monitored by the unbroadened 2319 keV isomeric transition in 90Nb decay.
Specific activity of [11C]CO2 generated in a N2 gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy
Authors: Suzuki K. , Yamazaki T. , Sasaki M. , Kubodera A.
Published: August 2006

Pure and O2-mixed nitrogen gases were irradiated by 18 MeV protons (14.2 MeV on target) and analyzed directly by a specially designed radio-GC system with a FID coupled to a methanyzer. Non-radioactive carbon, especially CO2 was observed to be generated in the target chamber by irradiation and to decrease gradually with repeated irradiation. The amount of carbon was increased by the use of new materials for the front foil, transport line, and so on. Higher irradiation dose also increased the carrier carbon, where beam current affected carbon generation more strongly than irradiation time. The addition of oxygen gas to nitrogen gas also increased the amount of carrier carbon, nearly all of which was observed to be generated in the chemical form of CO2. The ratio of [11C]CO2 to total C-11 was always low in a pure N2 gas target and increased with higher irradiation dose, addition of oxygen gas and by changing some part of the irradiation system. The ratios of [11C]CO2 were 22.4±1.5%, 77.8±7.1% and 94.0±4.0% in a pure N2 gas, 9.8 ppm O2-mixed N2 gas and 2000 ppm O2-mixed N2 gas, respectively. The specific activity of [11C]CO2 increased by the addition of O2 gas, but the effect of irradiation dose was not clear. Maximal specific activity of 610±150 GBq/μmol was obtained at the irradiation condition of 15 μA and 20 minutes in a 2000 ppm O2-mixed N2 gas. The effect of proton energy on the CO2 generation was also examined by degrading the proton energy with different thick energy absorbers. The amount of CO2 generated in the target depended on the proton energy, i.e., larger amount of CO2 generated with higher proton energy. Surprisingly, some amount of CO2 (1.5±0.3 nmol) was still observed in the target, even in the condition that all the protons stopped in the front foil and did not irradiate the target gas.
Synthesis of substituted [123I]imidazo[1,2-α]pyridines as potential probes for the study of the peripheral benzodiazepine receptors using SPECT
Authors: Katsifis Andrew , Mattner F. , Dikic B. , Papazian V.
Published: August 2006

The imidazo[1,2-α]pyridines [N,N´-dimethyl-6-chloro-(4´zf-iodophenyl)imidazo[1,2-α]pyridine-3-acetamide 1, [N,N´l-6-chloro-(4´-iodophenyl)imidazo[1,2-α]pyridine-3-acetamide 2, and [N-methyl-6-chloro-(4´-iodophenyl)imidazo[1,2-α]pyridine-3-acetamide 3, are high affinity and selective ligands for the Peripheral Benzodiazepine Receptors (PBR). The [123I]1-3 labelled analogues of these compounds were subsequently synthesised for the potential study of the PBR in vivo using SPECT. Radioiodination was achieved by iododestannylation reactions of the corresponding tributyl tin precursors with Na[123I] in the presence of peracetic acid, chloramine-T or Iodogen. Purification of the crude product was achieved by semipreparative C-18 RP HPLC to give the products in radiochemical yields of 40-85%. The products were obtained in >97% chemical and radiochemical purity and with specific activities >80 GBq/μmol.
Fluoride complexation of rutherfordium (Rf, element 104)
Authors: Strub E. , Kratz Jens Volker , Kronenberg A. , Nähler A. , Thörle P. , Zauner S. , Brüchle W. , Jäger E. , Schädel M. , Schausten B.
Published: August 2006

The fluoride complexation of the group-4 elements Zr, Hf and Rf, and of the pseudo-homolog Th, has been investigated in mixed HNO3/HF solutions by studying Kd values on both cation exchange resins (CIX) and anion exchange resins (AIX) using the automated rapid chemistry apparatus ARCA. On the CIX, the four elements are strongly retained as cations below 10-3M HF. For Zr and Hf, the decrease of the Kd values due to the formation of fluoride complexes occurs between 10-3M HF and 10-2M HF. For Rf and Th, this decrease is observed at one order of magnitude higher HF concentrations. On the AIX, for Zr and Hf, a rise of the Kd values due to the formation of anionic fluoride complexes is observed between 10-3M HF and 10-2M HF, i.e. in the same range of HF concentrations where the decrease of the Kd values on the CIX is observed, yielding a consistent picture. For Rf and Th, on the AIX, no rise of the Kd values is observed even if the HF concentration is increased up to 1 M. By varying the concentration of the counter ion NO3-which is competing for the binding sites on the AIX resin, it could be shown, nevertheless, that Rf does form anionic fluoride complexes. Apparently, there is a more specific competition of NO3-with respect to [RfFx](x-4)-than with [ZrFy](y-4)-and [HfFz](z-4)-.
Continuous on-line chromatography of short lived isotopes of tungsten as homolog of seaborgium (element 106)
Authors: Pfrepper G. , Pfrepper R. , Kronenberg A. , Kratz Jens Volker , Nähler A. , Brüchle W. , Schädel M.
Published: August 2006

We have studied the sorption of W on anion-exchange resins from HNO3/HF solutions under on-line conditions using continuous chromatography with the multi-column technique. Kd values and the charge of the W species were determined. In order to achieve an effective separation of mother (W) and daughter (Ta), also the sorption of Ta from HNO3/HF solutions on various anion exchange resins with different functional groups was studied. This investigation serves the purpose to select a suitable anion exchange resin for planned experiments with Sg.
The influence of dibutylphosphate on actinide extraction by 30% tributylphosphate
Authors: May I. , Taylor Robin J. , Wallwork A.L. , Hastings J.J. , Fedorov Yu.S. , Zilberman B.Ya. , Mishin E.N. , Arkhipov S.A. , Blazheva I.V. , Poverkova L.Ya. , Livens F.R. , Charnock J.M.
Published: August 2006

The careful control of actinide distribution between 30% tributylphosphate (TBP) in organic diluent and nitric acid is vital to the successful operation of nuclear fuel reprocessing plants. Uranium (VI) and tetravalent actinides are extracted into the organic phase as the nitrate complexes UO2(NO3)2(TBP)2and An(NO3)4(TBP)2respectively. The presence of dibutylphosphate (HDBP), a tributylphosphate decomposition product, affects this distribution due to the formation of strong, organic soluble, complexes between the phosphate and the actinide ions. This paper describes the investigation of U(VI), U(IV), Np(IV) and Pu(IV) complexation with HDBP in 30% TBP/organic diluent solutions. The distribution of U(VI) between nitric acid and 30% TBP/organic diluent solutions containing HDBP and subsequent analysis of the organic phases by31P nuclear magnetic resonance spectroscopy, absorption spectroscopy and extended X-ray absorption spectroscopy indicates that U(VI) can form a range of complexes with HDBP. At comparatively high HNO3loading in the organic phase, HDBP can displace TBP groups to form either UO2(NO3)2(HDBP)(TBP) or UO2(NO3)2(HDBP)2. At lower HNO3loadings HDBP can also deprotonate and act as a chelate ligand displacing nitrates to form either UO2(DBP)2(HDBP)xor UO2(NO3)(DBP)(HDBP)x (where x = 1 or 2). Distribution data and absorption spectroscopy also indicates that Np(IV) forms at least two complexes in which nitrate groups are displaced by the DBP- anion. In contrast, for U(IV), it is almost certain that TBP groups are displaced by HDBP at increased HDBP loading forming U(NO3)4(HDBP) (TBP). There is no evidence for the displacement of nitrates. Finally, Pu(IV) distribution data suggested that complex reactions were taking place in both phases ensuring that equilibrium extraction was difficult to ascertain. Nevertheless, HDBP does readily complex with Pu(IV) increasing extraction and displacing nitrates from the Pu(IV) species formed in the organic phase.
Uranium and thorium isotopes in some red sea sediments
Authors: Sam A. K. , Ahamed M.M.O. , El Khangi F.A. , El Nigumi Y.O.
Published: August 2006

Alpha-emitting isotopes of uranium and thorium in surface marine sediments collected from the harbours at Port Sudan and Sawakin on the Sudanese coast of the Red Sea have been studied using radiochemical separation procedures and alpha-particle spectrometry. Activity concentrations of 238U, 235U, 234U, 232Th, 230Th and 228Th were measured. The ranges of activities observed for 238U and 232Th were 2.71-13.42 Bq/kg and 3.62-18.73 Bq/kg from Port Sudan and 3.87-24.79 Bq/kg and 1.13-10.04 Bq/kg dry weight from Sawakin, respectively. The behaviour of these decay-series nuclides was examined using daughter/parent and non-isotopic specific activity ratios in sediments. Simple regression analysis showed insignificant correlation between uranium and thorium activities and the organic matter content in sediments. The results are compared with those from coastal waters of other oceans.
Synergistic extraction of uranium(VI) from nitric acid solution by a mixture of n-octyldecylsulfoxide (ODSO) and petroleum sulfoxides (PSO) in carbon tetrachloride
Authors: Yan-Zhao Y. , Yong-Hui Y. , Xiao-Shi C. , Si-Xiu S.
Published: August 2006

The synergistic extraction of uranium(VI) from nitric acid aqueous solution with a mixture of n-octyldecylsulfoxide (ODSO) and petroleum sulfoxides (PSO) in carbon tetrachloride was studied. It has been found that the maximum synergistic extraction effect occurs where the molar ratio of PSO to ODSO is three to five. The composition of the complex of synergistic extraction is UO2(NO3)2· ODSO · PSO. The formation constant of the complex KOP = 57.6±5.19. The effect of extractant concentration, nitric acid concentration, salting-out agent concentration, complex anion concentration and temperature on the extraction equilibrium of uranium(VI) was also studied.
Separation of187,188Pt and187,188Ir produced in11B4+irradiated tantalum target
Authors: Banerjee K. , Lahiri S. , Ramaswamy A. , Manohar S.B. , Das N. R.
Published: August 2006

Heavy ion irradiation on tantalum metal target with 57 MeV11B4+leads to the production of no-carrier-added radioisotopes of platinum,187,188Pt and iridium,187,188Ir in the matrix, which have been effectively separated from the bulk target and from each other with suitable anion exchangers employing liquid-liquid extraction (LLX). Also188,189Pt and188,189Ir radionuclides have been produced, from their short-lived precursors188,189Au, in12C6+irradiated tantalum matrix. Gamma-spectroscopy has been utilised to determine the production, extent of separation and purity of the radiotracers at different stages of the experiment.
Comment on "Behaviour of europium(III) and its hydroxo and carbonate complexes in a solvent extraction system with HDBM in 2 M NaCl at 303 K" by M. Jiménez-Reyes, M. Solache-Rios and A. Rojas-Hernández
Authors: Fanghänel Thomas , Neck Volker
Published: August 2006

In a recent paper [1] the hydrolysis and carbonate complexation of Eu(III) was studied by potentiometric titration of 2×10-4M Eu(III) solutions in the range pH = 7-13. Under the experimental conditions applied in this study, the Eu(III) concentration exceeds the solubility of Eu(OH)3(s) or EuOHCO3(s) by several orders of magnitude. The formation constants derived for numerous aqueous Eu(III) hydrolysis species and ternay hydroxo-carbonate complexes must be considered as erroneous. They are the result of misinterpretation of the formation of solid Eu(III) particles as hydrolysis or carbonate complexation in solution.
Dehydration of synthetic autunite hydrates
Authors: Sowder A.G. , Clark Sue B. , Fjeld R.A.
Published: August 2006

The dehydration of uranyl minerals can affect phase structure and stability. Synthetic autunite hydrates, Ca[(UO2)(PO4)]2· × H2O, were studied by X-ray powder diffractometry (XRD) and thermogravimetric analysis (TGA) to address ambiguous or contradictory reports in the literature. Structurally, XRD analysis supported the three well-defined phases commonly reported in the literature, i.e. autunite, metaautunite I, and metaautunite II. In addition, a fourth phase with a basal plane spacing between that of autunite and metaautunite I, designated metaautunite Ia, was identified as an apparent metastable intermediate. TGA analysis confirmed that water loss or accumulation is tolerated to different degrees among the autunite hydrates. Loss of low temperature water appears to initiate collapse of the interlayer spacing from 10 to 9 Å to form metaautunite I and/or Ia, while the lower hydrates accommodate minor water loss and accumulation without significant structural alteration. Our results support previous research indicating the reversibility of the autunite to metaautunite I conversion. The complex dehydration pattern of autunite is not observed in all the 1:1 uranyl phosphates, such as chernikovite (H[(UO2)(PO4)] · 4 H2O).
The speciation of Tc(IV) in chloride solutions
Authors: Ben Said K. , Fattahi Massoud , Musikas C. , Revel R. , Abbé J. Ch.
Published: August 2006

The speciation of tetravalent technetium has been studied in HCl solutions ranging from 1.0 to 6.0 M. Tc(IV) exists in 6.0 M HCl as the well characterized TcCl62-chloride complex. In 1.0 M HCl, the chloride ligands of TcCl62-are slowly substituted by other ligands such as H2O, OH-or O2-. So TcClmOn(OH)p(H2O)q(4-m-2n-p)+compounds may form with (m + n + p + q) = 6. Several speciation techniques such as UV-visible and Raman spectrometries, X-ray absorption spectroscopy and electrochemistry have enabled to get an insight into this problem. All the results have indicated two most likely species of Tc(IV) after aging for about ten days in 1.0 M HCl to be aquo-chlorocomplexes of technetium and not oxo-chorocomplexes: TcCl5· H2O-and TcCl4· 2 H2O.
Complex formation of Eu(III) with polyacrylic acid
Authors: Kubota Takumi , Tochiyama Osamu , Tanaka K. , Niibori Yuichi
Published: August 2006

For the quantitative description of the interaction of metal ions with humic substances, it is necessary to clarify the effects of both polyelectrolyte and heterogeneous nature of humic substances. To estimate the polyelectrolyte effect separately, polyacrylic acid (MW = 90000) has been selected as a representative of well-defined, homogeneous polymeric weak acids, and its interaction with Eu(III) has been investigated by a solvent extraction method using152Eu (~10-8M) with TTA and TBP in xylene. By defining the apparent complex formation constant as βα= [ML]/([M][R]), where [M] = [Eu3+], [ML] is the concentration of Eu(III) associated with polyacrylic acid and [R] = CRα (CRis a total concentration of proton exchanging sites and α is a degree of dissociation determined by potentiometric titration), the apparent constants have been obtained at several pcH and ionic strength (0.1 M and 1.0 M NaClO4). The constants increased with pcH and decreased with an increase of ionic strength, that is, the values of log βαvaried from 6.0 (at pcH = 4.7) to 7.6 (pcH = 5.5) at 0.1 M NaClO4and from 4.8 (pcH = 4.4) to 6.5 (pcH = 5.4) at 1.0 M. The plots of log βαversus log α revealed almost linear relationship both at 0.1 and 1.0 M NaClO4.
Determination of Co(II) and Ni(II)-humate stability constants at high ionic strength NaCl solutions
Authors: Kurk D.N. , Choppin Gregory R.
Published: August 2006

Complexation of Ni(II) and Co(II) by unfractionated humic acid (HA) was measured in 0.3 to 5.0 m NaCl solutions at pH 6 and 20 °C, using a solvent extraction technique. The dissociation constants and capacities of the humic acid were investigated in 0.1 to 5.0 m NaCl solutions at 25 °C using potentiometric titration methods.
Mixed Ca2+/UO2
2+/CO3
2- complex formation at different ionic strengths
Authors: Kalmykov S. N. , Choppin Gregory R.
Published: August 2006

Fluorescence spectroscopy was used to study the Ca2+/UO2
2+/CO3
2- solution system at different ionic strengths. Fluorescent titrations confirmed formation of Ca2UO2(CO3)3 complex for which the values of log β213 were measured at 0.1, 0.3, 0.7, 1.0 and 3.0 m (NaClO4) at pcH = 8.1. Specific Interaction Theory (SIT) was used to correlate the log β213 values as a function of ionic strength. The value obtained for log β0
213 (I = 0) was 29.8 ± 0.7, indicating that Ca2UO2(CO3)3 was the predominant specie at the pH 8 in calcium rich, oxic waters.
Humic colloid-borne Np migration: influence of the oxidation state
Authors: Artinger Robert , Marquardt Christian M. , Kim J. I. , Seibert A. , Trautmann N. , Kratz Jens Volker
Published: August 2006

The migration behavior of Np(IV/V) is investigated by column experiments using a sandy sediment with groundwater rich in humic substances. NIR spectroscopy, redox speciation by TTA extraction and ultrafiltration are used for the Np speciation in the groundwater prior to its introduction into the column and after elution. Np is found to be transported as humic colloid-bound species which are eluted slightly faster than the water flow velocity. The fraction of humic colloid-borne Np increases with the reduction progress of Np(V) to Np(IV), because the interaction of Np(IV) with humic substances is much stronger than Np(V). The results demonstrate the importance of the speciation of redox sensitive actinides in natural aquifers for the assessment of the humic colloid facilitated migration.
Colloid-borne uranium and other heavy metals in the water of a mine drainage gallery
Authors: Zänker H. , Richter W. , Brendler V. , Nitsche Heino
Published: August 2006

The water of a mine drainage gallery was investigated for its contents of colloid-borne heavy metals with emphasis on uranium. About 1 mg/L of colloid particles of 100 to 300 nm were found. They consist of a matrix of Fe and Al oxyhydroxides and are formed when anoxic slightly acidic shaft waters mix with oxic near-neutral gallery water. The colloid particles bear toxic trace elements such as As, Pb, and Cu. Almost 100% of the As and Pb and about 70% of the Cu contained in the water are colloid-borne. Carbonato complexes prevent the uranyl from being adsorbed on the colloids in the unaltered gallery water. Acidification destroys these complexes: up to 50% of the uranium is attached to the colloids in the slightly acidic pH region. Further acidification converts the uranyl again to a ‘non-colloidal’ form.
Speciation analysis on europium(III) using laser-induced breakdown spectroscopy
Authors: Hotokezaka H. , Tanaka S. , Suzuki A. , Nagasaki S.
Published: August 2006

The generation of Eu(III) precipitation and the Eu sorption on TiO2particles in aqueous solution were studied using laser-induced breakdown spectroscopy (LIBS). The plasma emission intensity vs. the Eu concentration plot showed a good linearity in the concentration range of 6.6 × 10-3M - 1.3 × 10-2M for Eu aqueous solution at pH 1.1 and 6.6 × 10-5M - 6.6 × 10-4M for Eu2O3suspension at pH 5.0. It was found that the generation of Eu precipitation was detected through a drastic increase of plasma emission intensity of Eu. The results suggested that LIBS is useful for analyzing the particles and the precipitation of Eu in aqueous solution, even if the Eu ion concentration is higher by orders of magnitude. Furthermore, we could measure the plasma emission of Eu ions sorbed on TiO2particles under the conditions where the plasma emission of Eu ions could not be detected in the absence of TiO2. Hence, LIBS technique is considered to be useful to study the colloid generation of Eu.
Uranium(VI) and neptunium(V) transport through fractured, hydrothermally altered concrete
Authors: Matzen S.L. , Beiriger J.M. , Torretto P.C. , Zhao P. , Viani B.E.
Published: August 2006

In a high level waste repository in which temperatures are elevated due to waste decay, concrete structures will be subjected to hydrothermal conditions that will alter their physical and chemical properties. Virtually no studies have examined the interaction of hydrothermally altered concrete with radionuclides. We present the results of experiments in which soluble and colloid-associated U and Np, were eluted into a fractured, hydrothermally altered concrete core. Although the fluid residence time in the fracture was estimated to be on the order of 1 minute, U and Np in the effluent from the core were below detection (10-9 - 10-8 M), for both soluble and colloid-associated species. Inorganic colloids and latex microspheres were similarly immobilized within the core. Post-test analysis of the core identified the immobilized U and Np at or near the fracture surface, with a spatial distribution similar to that of the latex microspheres. Because hydrothermal alteration followed fracturing, the growth of crystalline calcium silicate hydrate and clay mineral alteration products on, and possibly across the fracture, resulted in a highly reactive fracture that was effective at capturing both soluble and colloidal radionuclides. Comparison of results from batch experiments [1] with these experiments indicate that partitioning of U and Np to the solid phase, and equilibration of the incoming fluid with the concrete, occurs rapidly in the fractured system. Transport of U through the concrete may be solubility and/or sorption limited; transport of Np appears to be limited primarily by sorption.
Aqueous Pu(IV) sorption on brucite
Authors: Farr J.D. , Schulze R.K. , Honeyman Bruce D.
Published: August 2006

The sorption behavior of aqueous Pu(IV) on brucite (Mg(OH)2) in the presence and absence of citrate was investigated by a combination of wet chemical batch sorption experiments and X-ray photoelectron spectroscopy (XPS). Sorption occurs rapidly at near 100% levels from pH 8 to pH 13, and is not affected by the presence of citrate. XPS results indicate that Pu was incorporated in the subsurface in the cases studied.
Evaluation of radioactive nickel distribution coefficient by analyzing background stable nickel
Authors: Igarashi T. , Mahara Y. , Ashikawa N. , Okamura M.
Published: August 2006

A simple method of evaluating the distribution coefficient (Kd) of radioactive Ni was examined. The method is based on the measurement of the solid-liquid concentration distribution ratio (fd) of background stable Ni. To verify the method, the Kd´s of both the radioactive Ni and stable Ni were simultaneously measured by using three different samples through batch sorption experiments in which radioactive Ni with a constant concentration and stable Ni with various concentrations coexisted. The fd of background stable Ni was then measured by extraction with 0.1 N CH3COONH4 and 0.1 N HCl solutions to compare fd with Kd. The results showed that the Kd´s of radioactive Ni agreed with those of stable Ni, and that the fd corresponded to the Kd when the liquid-phase concentration of stable Ni approached the background level. This indicates that the method of evaluating Kd by using fd is applicable to Ni within the experiment.
Effects of humic acid on the sorption of Am(III) and Cm(III) on kaolinite
Authors: Samadfam M. , Jintoku T. , Sato S. , Ohashi H. , Mitsugashira Toshiaki , Hara Mitsuo , Suzuki Yoshimitsu
Published: August 2006

Sorption coefficients of Am(III) and Cm(III) on kaolinite were determined at pH from 3.5 to 10 and humic acid (HA) concentrations of 0 to 20 ppm at ionic strength of 0.1 M (NaClO4) at 298 K with N2bubbling. The sorption ratio of HA on kaolinite was also measured under the same experimental conditions. The sorption coefficients of Am(III) and Cm(III) in the absence of HA increased with pH over the whole pH range. The presence of HA enhanced sorption coefficients at pH values up to around 5, above which the sorption coefficients were lowered by introducing HA. The effects of HA on sorption coefficients were interpreted by the use of a linear additive model, modified for metal-humate complex formation in the aqueous phase. The model was found to be in fairly good agreement with the experimental data.
Fracture smectite as a long-term sink for natural radionuclides – indications from unusual U-series disequilibria
Authors: Marcos N. , Suksi J. , Ervanne H. , Rasilainen K.
Published: August 2006

Occurrence of natural U in fracture smectite (main mineral component of bentonite) was studied as an analogue to radionuclide behaviour in the near-field of spent nuclear fuel repository. Elevated U content (57 ppm) was observed in fracture smectite sampled from the surface of water-carrying fracture in granite pegmatite at a depth of 70 m. The current groundwater conditions are oxidising at the sampled point. The U-234/U-238 activity ratio (AR) measured in the bulk U and in its sequentially extracted phases, displays unusually low value (around 0.30). Low AR indicates preferential loss of the U-234 isotope from the system. Because the U-234 loss can also be seen in the Th-230/U-234 activity ratio (clearly over 1), the selective removal of the U-234 isotope must have taken place more recently than what is needed to equilibrate Th-230/U-234 pair (i.e. 350000 a). To explain the selective U-234 loss from the smectite we postulate that bulk U is in reduced +4 form and a considerable part of the U-234 isotope in easily leachable oxidised +6 form. This study suggests that the long-term chemical stability of the bulk U in the smectite is due to irreversible fixation of U in the reduced +4 form.
The potential of subterranean microbes in facilitating actinide migration at the Grimsel Test Site and Waste Isolation Pilot Plant
Authors: Gillow J. B. , Dunn M. , Francis Arokiasamy J. , Lucero D.A. , Papenguth H. W.
Published: August 2006

Microorganisms may affect the long-term stability and mobility of radionuclides disposed of in deep geological formations. Of particular concern is the association of radionuclides with subterranean microbial cells and their subsequent transport as biocolloids. We characterized the total microbial populations in two groundwater samples: one from the Culebra dolomite member of the Rustler Formation at the Waste Isolation Pilot Plant (WIPP), NM, and the other from the granitic formation at the Grimsel Test Site (GTS), Switzerland. Culebra groundwater (ionic strength 2.8 M, pH 7) contained 1.51 ± 1.08 × 105cells ml-1, with a mean cell length of 0.75 ± 0.04 μm and width of 0.58 ± 0.02 μm. In contrast, low ionic-strength GTS groundwater (0.001 M, pH 10) contained 3.97 ± 0.37 × 103cells ml-1, with a mean cell length of 1.50 ± 0.14 μm and width of 0.37 ± 0.01 μm. Adding appropriate electron donors and acceptors to the groundwaters facilitated the growth of aerobic, denitrifying, fermentative, and acetogenic microorganisms. Uranium biosorption was studied in two isolates from these groundwaters, as well as several pure cultures from saline and non-saline environments. Halophilic and non-halophilic bacteria exhibited differences in the amount of U associated with the cells. Plutonium uptake by Acetobacterium sp. isolated from GTS varied from 30 - 145 pg of Pu mg-1dry weight of cells.
Application of gel electrophoretic techniques to the investigation of actinide-humic interactions in soils
Authors: Graham M.C. , Vinogradoff S.I. , Abbott A. , Farmer J.G.
Published: August 2006

Humic material from several soils was fractionated using both gel chromatographic and gel electrophoretic techniques. The distribution of uranium amongst fractions obtained by both methods was determined using ICP-MS. Humic material isolated from electrophoretic fractions was characterised using FTIR and UV-vis spectroscopy, base titration, Sephadex G200 size fractionation and CHN elemental analysis. Both size and chemical separation occurred during electrophoretic fractionation with the smaller, more hydrophilic molecules being more electrophoretically mobile. The gel chromatographic and gel electrophoretic studies showed that the association of U in soils was skewed towards the larger humic molecules but that some association with certain smaller humic molecules warrants further work to characterise the behaviour of these complexes under varying environmental conditions.
Neptunium redox speciation
Authors: Antonio R. , Soderholm L. , Williams C.W. , Blaudeau J.-P. , Bursten B. E.
Published: August 2006

Insights about the redox speciation of neptunium in an aqueous mineral acid electrolyte were obtained through a combination of in situ EXAFS (extended X-ray absorption fine structure) spectroelectrochemistry, density functional theory (DFT), and simple geometric modeling. A single solution of neptunium in 1 M perchloric acid was used to extract metrical information about the Np coordination environment, in terms of hydration numbers (n) and Np-O interatomic distances. Four aquo ions - Np3+·nH2O, Np4+· n´H2O, [Np5+O2]+· n´´H2O, and [Np6+O2]2+· n´´´H2O - were electrolytically prepared and precisely maintained by use of constant potential bulk electrolysis (with coulometry) throughout the simultaneous EXAFS data acquisition. For the Np(III) and Np(IV) aquo ions, the experiments revealed a contraction of the average Np-O bond lengths from 2.48(2) to 2.37(2) Å, respectively. The data analyses suggest that there are 9 water molecules in the first or inner hydration sphere about Np3+in [Np(OH2)9]3+and Np4+in [Np(OH2)9]4+. The DFT calculations reveal 8-9 water molecules coordinated to Np(III), supporting the EXAFS results. Simple geometric modeling supports a coordination number of 8 for both trivalent and tetravalent Np. For the Np(V) and Np(VI) aquo ions, the EXAFS revealed bond length contractions. The average interatomic distances for the trans-dioxygen atoms in [NpO2]+and [NpO2]2+decreased from 1.80(2) Å for Np(V) to 1.73(2) Å for Np(VI). The average interatomic distances to the oxygen atoms of the coordinated H2O molecules decreased from 2.44(3) Å to 2.36(3) Å, respectively. The oxygen coordination numbers were identical, suggesting that 5 water molecules are bound to Np5+in [NpO2(OH2)5]+and to Np6+in [NpO2(OH2)5]2+.
Interactions of Np(V) and U(VI) with dipicolinic acid
Authors: Friese J. I. , Nash K. L. , Jensen M. P. , Sullivan C.
Published: August 2006

To complement earlier studies of the complexation kinetics of Np(V) and U(VI) by oxydiacetic acid and several diphosphonic acids, the rate of complexation of these metal ions by dipicolinic acid (pyridine-2,6-dicarboxylic acid, DPA) has been investigated by stopped-flow spectrophotometry. This ligand is distinguished from the previously studied species by the rigid planar arrangement of the ligand functional groups and the presence of a pyridine nitrogen donor atom. Reactions of DPA with UO22+at p[H] 1 and NpO2+at p[H] 1 and 3 adhere to the comparatively simple first-order approach to equilibrium kinetic model used to describe the earlier results. At p[H] 3, the UO22+reaction is characterized by consecutive pseudo-first order reactions. The first is an apparent approach to equilibrium while the second process demonstrates a saturation effect, indicating the existence of a stable intermediate complex. Relative rates and activation parameters are discussed in comparison with the previous results.
A comparison of the extraction of carrier-free176,177W and99Mo with that of U, Th, Am, Cm, La, Ce, Tm, Yb, Lu, and Hf into tri-n-octyl amine in toluene from nitric, phosphoric, and sulphuric acid media
Authors: Johansson M. , Alstad J. , Omtvedt J. P. , Skarnemark G.
Published: August 2006

The extraction of carrier-free tungsten and molybdenum from nitric, phosphoric and sulphuric acid with 0.05 M TOA (tri-n-octyl amine, R3N) in toluene and 2.5% by volume 1-dodecanol has been studied. Their extraction behaviour has also been compared to hafnium, some trivalent lanthanides (lanthanum, cerium, thulium, ytterbium and lutetium) and some actinides (thorium, uranium, americium and curium). The extraction of these metal ions decreases in the order M4+>MO22+>M3+from >1 M nitric acid solutions, if hafnium, which is on the form HfO2+, is disregarded. At low nitric acid concentrations tungsten and molybdenum are most likely extracted as tungstate or molybdate ions (R3NH)2·MO4, while at higher concentrations they are most likely extracted similar to uranium, i.e. on the form R3NH·MO2(NO3)3. Further, the extraction from phosphoric acid solutions decreases in the order M4+>MO22+>M3+, if the elements which are easily hydrolysed, hafnium, molybdenum and tungsten, are disregarded. The major extracted complex of tungsten contains one TOA and the minor two TOA. The extracted complex with one TOA is probably (R3NH)·WO2(H2PO4)3or R3N·WO2(H2PO4)2, while that with two TOA more likely is (R3N)2H·WO2(H2PO4)3or even the more hydrolysed species of tungsten (R3NH)2·WO4. For molybdenum, the extracted complexes seem reasonably similar. Disregarding HfO2+the extraction decreases in the order MO22+>M4+>M3+for the chosen range of sulphuric acid concentration.
EXAFS investigation of uranium(VI) complexes formed at Bacillus cereus and Bacillus sphaericus surfaces
Authors: Hennig C. , Panak Petra J. , Reich T. , Roßberg A. , Raff J. , Selenska-Pobell S. , Matz W. , Bucher J. J. , Bernhard G. , Nitsche Heino
Published: August 2006

Uranium(VI) complex formation at vegetative cells and spores of Bacillus cereus and Bacillus sphaericus was studied using uranium L
II-edge and L
III-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. A comparison of the measured equatorial U-O distances and other EXAFS structural parameters of uranyl species formed at the Bacillus strains with those of the uranyl structure family indicates that the uranium is predominantly bound as uranyl complexes with phosphoryl residues.
Migration of99Tc in unsaturated Chinese loess under artificial rainfall condition: anin situtest
Authors: Liu C. L. , Li S. S. , Wang X. Y. , Wang Z. M. , Xin C. T. , Wang H.F. , Li R. J. , Li B. , Tang L. T. , Jiang L.
Published: August 2006

The migration of99Tc in unsaturated Chinese loess under artificial rainfall condition was investigatedin situ. Water suckers were buried at different depths under the bottom of an experimental pit of 2 m × 2 m × 1 m (deep). Quartz containing3H and99Tc was introduced into the experimental pit to an area of 40 cm × 40 cm and the pit was backfilled to a thickness of 30 cm. An artificial rainfall of 5 mm/h was applied to the experimental pit 4 h a day for 3 months. Moisture water samples were sucked with the help of a vacuum pumping system and the activity of3H and99Tc in the samples was determined. Breakthrough curves of3H and99Tc indicated that99Tc was slightly retarded. The calculated average apparent distribution coefficient of99Tc in the medium was (1.98±0.42)×10-2ml/g.
Excitation energy division in 51V+197Au collisions 75 MeV above the barrier
Authors: Wirtz Ch. , Kratz Jens Volker , Brüchle W. , Schädel M. , Schausten B. , Wiehl N.
Published: August 2006

We have previously determined the excitation energy division in 51V+197Au collisions at a bombarding energy corresponding exactly to the Bass-model barrier, E
cm=B, and at E
cm=B+25 MeV. At the barrier, the average excitation energies as a function of Z showed an extreme acceptor-donor asymmetry ("sawtooth" phenomenon) suggesting that the excitation energy division depends on how the neck nucleons are shared at scission. At the 25 MeV higher bombarding energy, a rapid change toward equipartition of the excitation energy was observed. We report here on the determination of the excitation energy division in the same system, using the same experimental technique, at E
cm=B+75 MeV. At this bombarding energy, the average excitation energies indicate that a temperature equilibrium has been reached for most partitions except for the - on the average - incompletely damped events near the entrance channel charges, where some remnant of the "sawtooth" phenomenon is still visible.
Aqueous chemistry of transactinides
Authors: Schädel M.
Published: August 2006

The aqueous chemistry of the first three transactinide elements is briefly reviewed with special emphasis given to recent experimental results. Short introductory remarks are discussing the atom-at-a-time situation of transactinide chemistry as a result of low production cross-sections and short half-lives. In general, on-line experimental techniques and, more specifically, the Automated Rapid Chemistry Apparatus, ARCA, are presented. Present and future developments of experimental techniques and resulting perspectives are outlined at the end. The central part is mainly focussing on hydrolysis and complex formation aspects of the superheavy group 4, 5, and 6 transition metals with F-and Cl-anions. Experimental results are compared with the behaviour of lighter homologuous elements and with relativistic calculations. It will be shown that the chemical behaviour of the first superheavy elements is already strongly influenced by relativistic effects. While it is justified to place rutherfordium, dubnium and seaborgium in the Periodic Table of the Elements into group 4, 5 and 6, respectively, it is no more possible to deduce from this position in detail the chemical properties of these transactinide or superheavy elements.
Separation of actinide redox species with cation exchange chromatography and its application to the analysis of spent fuel leaching solutions
Authors: Röllin Stefan , Eklund U.-B. , Spahiu Kastriot
Published: August 2006

Separation methods on a Dionex CS10 cation exchange chromatography column have been investigated by on-line coupling of an ion chromatograph to an ICP-MS. In spent nuclear fuel, isobaric interferences of Am, Pu and U often hinder direct mass spectrometric measurements of these elements. Am and U could easily be separated as they exist in different oxidation states (Am3+and UO22+). In order to separate Pu, Pu has been oxidised to PuO22+with KMnO4. The oxidised Pu could so be eluted first, together with Np, well separated from the U and Am fraction. This separation method has been applied to the determination of the isotopic composition of Pu and to the estimation of the Am concentrations in leaching solutions. Furthermore, the separation method has been applied to perform a speciation between the reduced (Pu3+, Pu4+) and the oxidised ions (PuO2+, PuO22+) of Pu in a leaching solution. The change of the oxidation state composition could so be followed in a leaching solution in contact with air.
α-Crystalline polyantimonic acid - an adsorbent for radiostrontium, and a potential primary barrier in waste repositories
Authors: Bilewicz A. , Narbutt J.
Published: August 2006

Dynamic adsorption of radiostrontium was studied on α-crystalline polyantimonic acid grains from aqueous solutions containing common components of liquid radioactive wastes - salts and chelating agents at moderate concentrations. Effective decontamination of the neutral solutions has been achieved, in the amounts of a few thousand bed volumes, depending on the flow rate through the column. After encapsulation in the matrix of Portland cement, the loaded adsorbent can serve as an effective primary barrier in nuclear waste repositories.
Thermodynamic model for the solubility of PuO2(am) in the aqueous Na+-H+-OH--Cl--H2O-ethylenediaminetetraacetate system
Authors: Rai Dhanpat , Bolton H. , Moore Dean A. , Hess Nancy J. , Choppin Gregory R.
Published: August 2006

The solubility of PuO2(am) was determined in the aqueous Na+H+-OH--Cl--H2O-ethylenediaminetetraacetate (EDTA) system as a function of pH (1 to 13.5) and EDTA concentrations (0.00001 to 0.093 M) to determine PuEDTA complexes important in a wide range of pH values and EDTA concentrations. The solubility studies were carried out as a function of time and show, as expected, that steady-state/equilibrium in this system is reached rapidly (<7 days). The aqueous Pu oxidation states were determined by X-ray absorption near edge spectroscopy and solvent extraction. The aqueous Pu(IV) concentrations in equilibrium with PuO2(am) at fixed concentrations of EDTA (0.0001 or 0.001;M) as a function of pH, and at fixed pH (∼9), and as a function of EDTA were interpreted using the Pitzer ion-interaction model. The model was developed based on a subset of the experimental data and was validated against the remaining, more extensive data not used in model development. The log K0values for the formation of Pu(OH)xEDTAx-according to the generalized reaction (Pu4++ xOH+EDTA4-↔ Pu(OH)xEDTA-x) were determined to be 36.44±0.35, 44.78±0.35, and 49.80±0.35 for x=1, 2, and 3, respectively, when log;K0of -56.85 for (PuO2(am)+2H2O harr; Pu4++4OH-) is used.
Study of the interaction of Pu(IV) and Np(IV,V,VI) with Fe hydroxides to predict the behavior of actinides in environmental media
Authors: Grigoriev M. S. , Fedosseev A. M. , Gelis A.V. , Budantseva N.A. , Shilov V.P. , Perminov V.P. , Nikonov M.V. , Krot N. N.
Published: August 2006

A Mössbauer effect method was used to study the formation of mixed hydroxides in the alkaline coprecipitation of Pu(IV) or Np(IV) with Fe(III). The Mössbauer spectra of mixed 239Pu(IV)-Fe(III) and 237Np(IV)-Fe(III) hydroxide samples differ from that of pure α-FeO(OH) formed in aqueous basic solutions. Alkaline coprecipitation of Np(V) or Np(VI) with Fe(III) hydroxides does not produce the mixed hydroxides shown by Pu(IV) or Np(IV) with Fe(III). The general Mössbauer spectral parameters of the Np(V),(VI)-Fe(III) hydroxides are similar to those of pure α-FeO(OH).
Pentavalent rhenium-188 dimercaptosuccinic acid: a new kit formulation and its initial evaluation in mice
Authors: Pirmettis I. , Limouris G.S. , Bouziotis P. , Papadopoulos M. , Knapp Jr. F.F. , Chiotellis E.
Published: August 2006

Pentavalent rhenium-188 dimercaptosuccinic acid [188Re(V)DMSA] is a β-emitting radiopharmaceutical that has been proposed for the treatment of painful bone metastases, medullary thyroid carcinoma and other soft tissue tumours. In this study the development of a kit formulation for convenient, routine preparation of 188Re(V)DMSA is presented. The kit contains all the ingredients in a single vial and its reconstitution with 188Re perrhenate, up to 4;mL, produces 188Re(V)DMSA in high radiochemical purity, suitable for clinical application. 188Re(V)DMSA prepared by this kit method was evaluated in mice and resulted in a biodistribution pattern similar to that of 99mTc(V)DMSA.
Differential pulse voltammetric determination of U(VI)-Tc(VII) and U(VI)-Cr(VI) in alkaline solutions
Authors: Sladkov V.E. , Peretroukhine V. , Maslennikov A. , David F.
Published: August 2006

Differential pulse voltammetric (DPV) technique has been developed for the simultaneous determination of the elements in Tc(VII)-U(VI) and U(VI)-Cr(VI) mixtures in alkaline solutions. The method gave a precision of about 14% to 2% in the range of 1×10-7--1×10-4 for Cr(VI) and Tc(VII) and 1×10-6--1×10-4 for U(VI). The detection limits are 8×10-8 mol l-1 for Tc(VII) and 3×-7 mol l-1 for Cr(VI), and 8×10-7 for U(VI). It has been established that Tc(VII) could be determined in the presence of about 350 excess fold U(VI). The reduction of Tc(VII) with hydrazine has been suggested to eliminate the effect of Tc(VII) ions on the U(VI) determination. U(VI) has been determined in the presence of Cr(VI) up to molar concentration ratio U(VI)/Cr(VI)=1:1, while Cr(VI) could be determined in the presence of U(VI) in the solutions with up to molar concentration ratio Cr(VI)/U(VI)=1:15. The reliability of the determination of the elements of Tc(VII)-U(VI) and U(VI)-Cr(VI) mixtures in alkaline solution has been tested by a standard addition method.
Study of Ru released under accidental conditions by overheated nuclear fuel: the emission of Ru and U
Authors: Froment P. , Cara J. , Vanbegin J. , Ronneau C.
Published: August 2006

The emission of uranium and ruthenium oxides from overheated nuclear fuel is a complex phenomenon which depends on the fuel matrix, on temperature, on the oxygen potential of the amosphere in contact and on the emission sequence. All these factors influence the properties of particles before their dispersion in the reactor containment building and in the environment: these properties are, among others, surface composition, particle size, and, as a consequence, weathering rates in the environment. Emission in air increases the solubility of U-oxides mainly. This first paper describes the main physico-chemical characteristics of condensation particles released by overheated U and Ru oxides mixtures, in small-scale laboratory simulations.
Evaluation of the natural and man-made radioactivity levels around the Egyptian nuclear facilities
Authors: Diab H.M. , El-Tahawy M.S. , El-Mongy S.A.M.
Published: August 2006

The monitoring and evaluation of the radioactivity levels around the Egyptian nuclear facilities located at Inshas, near Cairo, namely, two research reactors, an R & D fuel fabrication laboratory and a fuel fabrication pilot plant, were carried out. Soil, water and plant samples were collected from locations near and around the facilities and analyzed by using gamma, laser and alpha spectrometry. A preoperational radiological map for the new reactor site was established. The results of the postoperational monitoring around the first reactor show that the 38year operation of this reactor did not increase the radioactivity level around the facility. The observed man-made 137Cs was found to be (0.3-9.2 Bq/kg) and 239+240Pu 0.096-0.158 Bq/kg. The observed tritium was found to be in the range 0.6-1.48 Bq/L. The absorbed dose rate and radium equivalent are calculated and presented.
Nuclear data for medical applications: an overview
Authors: Qaim Syed M.
Published: August 2006

A brief introduction to nuclear data in medicine is given. The choice of a radioisotope for medical application demands an accurate knowledge of radioactive decay data. Short-lived single photon and β+-emitters are preferred for diagnostic investigations, and longer-lived corpuscular radiation emitting radioisotopes for endoradiotherapy. The nuclear reaction cross section data, on the other hand, are needed for optimising the production routes. Besides radioactive isotopes, the use of ionising radiation in therapy is discussed. External radiation therapy has achieved an important place in medicine. The role of nuclear data is briefly discussed; they are needed for radiation dose calculations. The hitherto rather neglected activation products in proton therapy are considered. The methodology of development of a nuclear data file for medical applications is outlined
In vivo functional imaging with SPECT and PET
Authors: Herzog H.
Published: August 2006

Nuclear medicine methods permit the visualisation of a variety of metabolic and physiological processes all over the body. Although planar scintigraphy has been found useful for many questions, detailed spatial information about the diseased organ can only be obtained with tomographic methods. Dependent on the radionuclide involved, two different tomographic procedures are available: single photon emission computed tomography (SPECT) and positron emission tomography (PET). The first part of this paper describes shortly the historical development of these methods as well as their technical and methodological basics. To elucidate the large variety of possible applications, an overview of SPECT and PET procedures utilised in research as well as in clinical practice are presented. Furthermore, both methods are compared and their individual advantages are pointed out.
Fast neutron and proton therapy sources
Authors: Jones D.T.L.
Published: August 2006

Neutrons from the reactions of protons or deuterons of energies between 35 and 70 MeV on beryllium are most suitable for therapy because of the high yield and good penetration. Lower energy sources are used for limited applications. Proton therapy is conducted mainly in two energy ranges, viz. 60–75 MeV (exclusively for the treatment of eye lesions) and ≥200 MeV for general applications. Characterisation of both neutron and proton therapy beams in terms of spectral fluence is important for accurate determination of dosimetry parameters, for interpreting biological effects, for intercomparison purposes and to perform accurate radiation transport calculations.