Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32227 Publications
A fast screening method for surface layers on Gram-positive bacteria
Wahl, R.; Raff, J.; Selenska-Pobell, S.; Mertig, M.; Pompe, W.;
A two-step screening method is described to identify regularly arranged surface layers (S layers) on Gram-positive bacterial strains. A non-destructive release of S-layer sheets is achieved by enzymatic hydrolysis of the underlying peptidoglycan using lysozyme. The existence of regular S layers is then directly confirmed by scanning force microscopy or transmission electron microscopy. This method requires a minimal amount of bacterial cells and may be used as a 'quick test' for demonstrating the presence of S layers.
Keywords: Bacillaceae, bacterial surface layer (S layer), lysozyme, microscopy, screening
  • Biotechnology letters 23, 1485-1490 (2001)

Publ.-Id: 4363 - Permalink


Electron-beam induced formation of highly ordered palladium and platinum nanoparticle arrays on the S-layer of Bacillus sphaericus NCTC 9602
Wahl, R.; Mertig, M.; Raff, J.; Selenska-Pobell, S.; Pompe, W.;
  • Advanced Materials 2001, 13, No. 10, May 17, p. 736-740

Publ.-Id: 4362 - Permalink


Complexation of U(VI) with cells of Thiobacillus ferrooxidans and Thiomonas cuprina of different geological origin
Panak, P.; Selenska-Pobell, S.; Kutschke, S.; Geipel, G.; Bernhard, G.; Nitsche, H.;
  • Radiochimica Acta 84, 183-190 (1999)

Publ.-Id: 4361 - Permalink


FT-Raman and FT-IR spectra of crosslinked polyurethaneurea films synthesised from solutions
Romanova, V.; Begishev, V.; Karmanov, V.; Kondyurin, A.; Maitz, M. F.;
The crosslinked polyurethaneurea films based on polyoxitetramethylenglycol and polyoxipropyleneglycol with toluenediisocyanate and 3,3'-dichlor,4,4'-diaminediphenylmethane were synthesised in a solution where the solvent evaporates during the polymerisation. FT-Raman and FTIR spectra were analysed and intermo-lecular force constants of hydrogen bonds were calculated. On the base of intensity of the Raman and IR line of spectra which reflects hydrogen bond formation, the optimal structure of hydrogen bonds and the conformations of macromolecules of polyure-thaneurea were observed for the solvent ethylacetate.
Keywords: Polyurethane Spectroscopy
  • Journal of Raman Spectroscopy 33(10): 769-777 (2002).

Publ.-Id: 4360 - Permalink


Substrate bias effects in Plasma Immersion Ion Implantation Assisted Deposition from a TiAl cathodic arc
Mukherjee, S.; Reuther, H.; Prokert, F.; Richter, E.; Möller, W.;
TixAl1-x thin films were deposited on stainless steel substrates using plasma immersion ion implantation and deposition (PIIIAD). A cathodic arc was employed as a source of metallic ions from Ti0.5Al0.5 targets and the arc plasma was guided by a curved magnetic field filter. The resultant thin films were analysed using Auger electron spectroscopy (AES) and X-ray diffraction techniques. A dynamic profile simulation code, TRIDYN, based on binary collision approximation was applied to understand the Ti and Al profiles in the deposited thin film. The results indicate that the film composition and phase formation depends on the applied bias, duty cycle and off time energy of the bombarding ions. The results also indicate that in PIIIAD conditions, the assumption of time averaged dc bias is improper to describe pulsed biasing, with deposition, resputtering and ion implantation all occuring simultaneously.
Keywords: PIIIAD, TRIDYN, pulsed biasing
  • Surface and Coatings Technology 160 (202) 93-98

Publ.-Id: 4359 - Permalink


Biological sol-gel ceramics with specific metal binding capacity
Raff, J.; Soltmann, U.; Matys, S.; Schnorrpfeil, M.; Boettcher, H.; Pompe, W.; Selenska-Pobell, S.;
Bacteria in polluted environments are adapted to the toxic compounds present there
and often possess effective detoxification strategies. For this reason they are
very prospective for development of in situ bioremediation processes. In former
experiments a selective binding by cells and spores of Bacillus sphaericus
JG-A12 of U, Cu, Pb, Al and Cd from drain waters of uranium mining wastes was
demonstrated. The strain JG-A12 was recovered from the uranium mining waste pile
"Haberland" near the town of Johanngeorgenstadt. B. sphaericus JG-A12 possesses
a surface layer (S-layer). The latter differs significantly at its N-terminal
domain from all other S-layers studied up to date. Cells, spores and purified
S-layer protein fraction of this strain were used for construction of biological
sol-gel ceramics (biocers). Metal-binding kinetics of cells, spores, purified
S-layer fraction and the corresponding biological ceramics were measured. The
biosorption of uranium and copper by the corresponding biocomposites was strongly
influenced by the way of the biocer preparation The highest metal binding capacity
possess biocers with embedded vegetative cells. Larger amounts of uranium and
copper were accumulated by biocers which were prepared by freeze drying or using
penetration reagents like sorbit. Desorption of the bound metals and regeneration
of the biological ceramics was achieved using aqueous citric acid.


  • Lecture (Conference)
    VAAM-Jahrestagung 2002 in Göttingen (24.03.-27.03.2002)

Publ.-Id: 4358 - Permalink


Biosorption of heavy metals by Bacillus sphaericus JG-A12 cells, spores and S-layer protein embedded in sol-gel ceramics
Raff, J.; Soltmann, U.; Mathys, S.; Boettcher, H.; Pompe, W.; Selenska-Pobell, S.;
Bacillus sphaericus strain JG-A12 was isolated from the uranium mining waste
pile "Haberland" near the town of Johanngeorgenstadt. Vegetative cells and spores
of this strain accumulate selectively large amounts of U, Cu, Pb, Al and Cd from the
highly polluted drain waters of this uranium waste. Interestingly, the strain
JG-A12 possess a surface layer protein (S-layer) with a novel structure. The ability
of B. sphaericus to interact with heavy metals and its geographic origin make
it a good candidate for preparation of bacteria-based ceramics (biocers) for in
situ bioremediation of uranium mining waste pile waters. Biocers were prepared by
dispersing vegetative cells, spores and purified S-layer protein fraction of B.
sphaericus JG-A12 in aqueous silica nano-sols, gelling and drying. Different types
of ceramics were prepared by using air or freeze drying and adding water soluble
compounds as sorbit. Variations in porosity and structure of the biocers were
examined using scanning electron microscopy. The sorption and desorption of uranium
and copper by these biocomposites were investigated and visualised by EDX analysis.
Highest binding capacity demonstrate biocers with embedded Bacillus cells. For
reusing the biocers sorbed uranium and copper can be completely removed from them
by washing with aqueous citric acid.
  • Poster
    VAAM-Jahrestagung 2002 in Göttingen (24.03.-27.03.2002)

Publ.-Id: 4357 - Permalink


Microbial bioremediation of uranium mining waste waters using sol-gel ceramics
Raff, J.; Soltmann, U.; Matys, S.; Schnorrpfeil, M.; Boettcher, H.; Pompe, W.; Selenska-Pobell, S.;
During the long period of uranium mining and production in Saxony, large amounts of ores were treated and leached. Waste piles and waste waters from those procedures with high concentrations of heavy metals and radionuclides still remain in this part of Germany. For further use of the mentioned areas, they have to be cleaned. For this purpose, bacteria recovered from the contaminated sites are very prospective, because developing detoxification strategies as binding or reduction of heavy metals and radionuclides, they are well adapted to the complex and toxic conditions in the wastes. Bacillus sphaericus JG-A12 was recovered form the uranium mining waste pile "Haberland" near the town of Johanngeorgenstadt. Vegetative cells and spores of this strain accumulate selectively and reversible large amounts of U, Cu, Pb, Cd and Al. Interestingly, B. sphaericus JG-A12 possesses a paracrystalline surface layer protein (S-layer) as outermost component of its cell wall. Compared to the known S-layers of the other B. sphaericus strains, the N-terminal domain of B. sphaericus JG-A12 S-layer possesses a novel primary structure. Cells, spores and stabilized S-layer sheets were embedded by sol-gel techniques in xerogels. The sorption and desorption of uranium and copper by the free biocomponents and the biocomposite material were investigated using EDX analysis.
  • Lecture (Conference)
    Uranium Mining and Hydrogeology (UMH III) in Freiberg (15.09.-21.09.2002)
  • Lecture (Conference)
    Konferenz UMH III Freiberg 15.-21.9.2002

Publ.-Id: 4356 - Permalink


Reversible accumulation of uranium by bacteria-based sol-gel ceramics
Raff, J.; Soltmann, U.; Matys, S.; Böttcher, H.; Pompe, W.; Schnorrpfeil, M.; Selenska-Pobell, S.;
Bacillus sphaericus JG-A12 was isolated from the uranium mining waste pile "Haberland" near the town of Johanngeorgenstadt, Saxony, Germany. The drain water and the soil at this site are highly contaminated with heavy metals and radionuclides. Sorption experiments with vegetative cells and spores of B. sphaericus JG-A12 demonstrate specific and reversible accumulation of U, Cu, Pb, Al and Cd from the drain water of the waste. The latter makes this bacteria an interesting candidate for the development of in situ bioremediation processes based on biological ceramics (biocers). In addition, B. sphaericus JG-A12 possesses a surface layer (S-layer) which differs at its N-terminal domain (220 amino acid residues) significantly from all other S-layers studied up to date. In this study vegetative cells, spores and stabilized S-layer sheets were immobilized in the SiO2 matrix by dispersing in aqueous silica nanosols, gelling and drying. Variations in the porosity and structure of the biocers were achieved by different drying methods or adding water soluble compounds as sorbitol. The time dependence of the uranium sorption and desorption by the free biocomponents and biocomposites was investigated. Localization of the bound metals and a characterization of the metal complexes formed at the biocer were carried out using scanning electron microscopy and EDX.

  • Poster
    Uranium Mining and Hydrogeology Conference Freiberg 2002, 15.09.-21.09.

Publ.-Id: 4355 - Permalink


Low resistivity, p-type SiC layers produced by Al implantation and ion beam induced crystallization
Heera, V.; Madhusoosanan, K. N.; Mücklich, A.; Panknin, D.; Skorupa, W.;
Low resistivity ( < 0.1 Ohm cm), p-type SiC layers can be produced by the combination of high dose Al ion beam doping and ion beam induced crystallization. The implanted SiC layers have a nanocrystalline structure consisting of randomly oriented grains of mainly 3C-SiC. The electrical properties of the doped layers were investigated by sheet resistance and Hall measurements in dependence on temperature. In comparison with the standard doping process the hole concentration is enhanced by more than one order of magnitude.
Keywords: SiC, p-type doping, Al implantation, ion beam induced crystallization, nanocrystalline semiconductor, sheet resistance, Hall measurements
  • Applied Physics Letters 81 (2002) 70-72

Downloads:

Publ.-Id: 4354 - Permalink


Simulation of scaled vessel failure experiments and investigation of a possible vessel support against failure
Willschütz, H.-G.;
Scaled coupled melt pool convection and vessel creep failure experiments are being performed in the FOREVER program at the Royal Institute of Technology, Stockholm. These experiments are simulating the lower head of a pressurized reactor vessel under the thermal load of a melt pool with internal heat sources. Due to the multi axial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments offer an excellent opportunity to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module, the melt pool convection is simulated and the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep modeling procedure. Additionally, the material damage is evaluated considering the creep deformation as well as the prompt plasticity.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. After analyzing the calculations, it seems to be advantageous to introduce a vessel support, which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.

Keywords: severe accident, molten corium pool, RPV lower head behavior, finite element creep modeling, accident management, vessel support, passive control device for flooding
  • Nuclear Engineering and Design, 228(2004)1-3, 401-414

Publ.-Id: 4353 - Permalink


Evidence for irradiation-induced metallic precipitates in neutron-irradiated model alloys and pressure vessel weld steel, using Doppler-broadening positron spectroscopy
Cumblidge, S. E.; Motta, A. T.; Catchen, G. L.; Brauer, G.; Böhmert, J.;
Positron Doppler-broadening spectoscopy was used to examine a series of neutron-irradiated model alloys and 73W-weld steel. The composition of the model alloys was systematically varied in the amounts of copper, nickel and phosphorus. The 73W-weld steel contains 0.31 % copper and 0.60 % nickel. The samples were examined in the non-irradiated and neutron-irradiated states, as well as after successive isochronal anneals at temperatures ranging from 200 °C to 600 °C.
By comparing the Doppler-broadening spectroscopy W-parameters measured in pure metals with those measured in the materials in this study, we were able to draw inferences as to the nature of the irradiation-induced defects that cause hardening and embrittlement. The results indicate that the damage is a combination of irradiation-induced metallic precipitates and vacancy-type defect clusters.
Keywords: positron annihilations spectroscopy, reactor pressure vessel, radiation defects
  • Journal of Nuclear Materials, Volume 320, No. 3, August, 2003, p. 245-257

Publ.-Id: 4352 - Permalink


Untersuchungen der Sorption von Uran(VI) an das Gestein Phyllit zur Bestimmung von Oberflächenkomplexbildungskonstanten
Zorn, T.;
kein Abstract
  • Other report
    Dissertation / Technische Universität Dresden, Februar 2000

Publ.-Id: 4350 - Permalink


Localization and characterization of uranium (VI) complexes formed by three eco-types of Acidithiobacillus ferrooxidans
Merroun, M.; Hennig, C.; Rossberg, A.; Geipel, G.; Reich, T.; Nicolai, R.; Heise, K.-H.;
Microorganisms have a potential to affect the mobility and overall environmental behaviour of uranium through solubility and speciation changes, biosorption, bioaccumulation or other transformations. Recently, three eco-types of A. ferrooxidans were recovered from different sites and depths of two uranium mining waste piles. These natural A. ferrooxidans isolates interact with uranium and tolerate this radionuclide in a type-specific way. In this study, we used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Infrared Spectroscopy (IRS), Time-resolved Laser-Induced Fluorescence Spectroscopy (TRLFS), Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray (EDX) analysis to conduct atomic and molecular scale studies on U(VI) interaction with the three eco-types of A. ferrooxidans. On the basis of the combined information from the above mentioned methods we conclude that the uranium is bound by A. ferrooxidans cells mainly in a form of organic uranyl phosphate complexes. Moreover, the largest part of the uranium accumulated by A. ferrooxidans cells is located within the extracellular polysaccharides. Additionally, some part of the uranium was found on the cell walls. A limited amount of the metal enters the cells and is than detoxified through sequestration by intracellular polyphosphate bodies.


  • Poster
    VAAM Jahrestagung 2002, 24.03.-27.03.2002, Göttingen, Deutschland

Publ.-Id: 4349 - Permalink


Characterization of uranium (VI) complexes formed by different bacteria recovered from uranium mining waste piles
Merroun, M.; Hennig, C.; Rossberg, A.; Geipel, G.; Reich, T.; Selenska-Pobell, S.;
Uranium and other actinides may be present initially as soluble or insoluble forms in nature and, after disposal, they may be converted from one to the other form by microorganisms. Under appropriate conditions, actinides can be mobilized or immobilized by direct (enzymatic) or indirect (nonenzymatic) microbial actions. These include: (i) oxidation-reduction reactions, (ii) changes in pH and Eh, (iii) chelation, or production of specific sequestering agents, (iv) formation of stable minerals, (v) biodegradation of actinides-organic complexes, and (vi) biosorption by microbial biomass and biopolymers. In this work, we investigated uranium sorption efficiency of different bacterial strains isolated from uranium mining wastes such as Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans Pseudomonas stutzeri and Pseudomonas migulae, and also of some reference strains under various conditions (pH, amount of biomass, temperature). In addition, from desorption studies we obtained information about the kind of interaction (sorption, surface complexation, or uptake) and the binding strength. In order to conduct atomic and molecular scale studies on U(VI) interaction with these bacteria, we used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Infrared Spectroscopy (IRS), Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS) analysis. Transmission electron microscope (TEM) was used for imaging the location of uranium accumulated by the bacterial cells, and for determining the active binding sites of the examined different types of biomass, and consequently to elucidate the possible mechanism of uranium accumulation. Electron-dispersive X-ray (EDX) analysis allowed to perform an elemental analysis of the uranium accumulates.




  • Lecture (Conference)
    UMH III, Freiberg, Sept. 15-21, 2002

Publ.-Id: 4348 - Permalink


Plasma immersion Ion implantation of TiAl using Chlorine containing plasma
Hornauer, U.; Richter, E.; Wieser, E.; Möller, W.; Donchev, A.; Schütze, M.;
In order to apply the protective effect of Cl doping on the high temperature oxidation resistance of TiAl alloys for complicated shaped parts, plasma immersion ion implantation (PI3) of chlorine into technical TiAl alloys was investigated. A specialized PI3 apparatus was optimized for the strongly etching electronegative Cl plasma. Plasma diagnostics was performed using a Langmuir probe. In order to sustain a sufficient dense plasma, different RF- antenna configurations are discussed and the resulting densities are compared. The influence of plasma pulsing on the surface interaction of Cl during the process is evaluated.
Different commercial alloys were implanted and tested. The resulting depth profiles of the modified surface layer are investigated using depth profiling with Auger electron spec-troscopy (AES). After implantation, the Cl is located close to the surface. Oxidation tests at 900°C in air for 100 h showed a strong reduction of the oxidation, which is comparable to conventional beam line im-plantations of Cl. The effect is rather independent of the alloy composition and therefore interesting for application.
ing depth profiles of Cl are investigated using depth profiling with Auger electron spectroscopy (AES). After treatment, the Cl is located close to the surface. The retained dose depends mainly on the temperature during implantation, which is controlled by the repetition rate of the pulses. Oxidation tests at 900°C in air for 100 h showed a strong reduction of the oxidation, which are comparable to conventional beam line im-plantations of Cl. The effect is rather independent of the alloy composition and therefore interesting for ap-plication.

Keywords: PIII, Chlorine, Oxidation, TiAl
  • Lecture (Conference)
    Plasma Surface Engineering, PSE2002, Garmisch-Partenkirchen, Germany, 9.-13. Sept. 2002
  • Surface and Coatings Technology 173-174 (2003) 1182-1186
  • Contribution to external collection
    Plasma Surface Engineering, PSE2002, Garmisch-Partenkirchen, Germany, 9.-13. Sept. 2002

Publ.-Id: 4347 - Permalink


Complexation of uranium (VI) by different bacteria recovered from uranium mining waste piles
Merroun, M.; Hennig, C.; Rossberg, A.; Geipel, G.; Reich, T.; Selenska-Pobell, S.;
Radioactive wastes are classified as high-level wastes (spent fuel etc.), transuranic wastes (wastes from spent fuel reprocessing, nuclear weapons), and low- and intermediate-level wastes which are generated from a variety of activities, for instance, uranium mining. The presence of uranium in these wastes, is a major concern because of its potential to migrate from the waste repositories and piles and to long-term contaminate the environment. Therefore, it is becoming increasingly clear that such polluted sites will require a long-term stewardship in addition to remediation. Effective remediation and stewardship will require a better understanding of the environmental chemistry of uranium. Results of experimental investigations of uranium accumulation and studies of microbial ecology in uranium-rich environments strongly imply that microorganisms play significant role in uranium mobilization and immobilization. Biological processes for uranium immobilization in particular, include biosorption, bioaccumulation, precipitation, and biomineralization. In this work, we investigated the uranium sorption efficiency of different bacterial strains isolated from uranium mining wastes such as Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Pseudomonas stutzeri, Pseudomonas migulae and the corresponding reference strains under various conditions (pH, amount of biomass, temperature). The ability of the above mentioned microorganisms to tolerate uranium and some other heavy metals was studied as well.



  • Poster
    UMH III Freiberg, Sept. 15-21, 2002

Publ.-Id: 4346 - Permalink


Molecular and atomic analysis of the uranium complexes formed by the three eco-types of Acidithiobacillus ferrooxidans
Merroun, M.; Hennig, C.; Rossberg, A.; Geipel, G.; Reich, T.; Selenska-Pobell, S.;
Over 40 years, the intensive uranium mining and milling in the Southeast of Germany (Saxony and Thuringia) has caused environmental pollution in this region. Therefore, it is becoming increasingly clear that such contaminated sites will require a long-term stewardship in addition to remediation. Effective remediation and stewardship will require a better understanding of uranium environmental chemistry. Microbial cells are known to reduce, oxidize, biosorb, bioaccumulate, and bioprecipitate uranium and other actinides. Recently, three different eco-types of A. ferrooxidans were recovered from different sites and depths of two uranium mining wastes. The strains of these three types possess different capability to accumulate and tolerate uranium. In this study, we used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Time-resolved Laser-Induced Fluorescence Spectroscopy (TRLFS), Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray (EDX) analysis to conduct atomic and molecular scale studies on U(VI) interactions with the three eco-types of A. ferrooxidans. On the basis of the combined information obtained by the above mentioned methods we conclude that the uranium is bound by the cells of the three A. ferrooxidans types in a form of organic uranyl phosphate complexes, which differ in their strength.
  • Lecture (Conference)
    Biometals, 13. April 2002, London, UK

Publ.-Id: 4345 - Permalink


Ion beam synthesis of SiC in Si: Real structure analysis at ROBL
Eichhorn, F.; Keywords: Ion beam synthesis, 3C-SiC, Si(001), x-ray diffraction, synchrotron x-rays
  • Lecture (others)
    ESRF Monday Seminar, April 23, 2001

Publ.-Id: 4344 - Permalink


Ionenstrahlsynthese von SiC in Si: Strukturelle Untersuchungen
Eichhorn, F.;
Die Synthese von SiC-Kristalliten durch Implantation von Kohlenstoff in Silizium ist kein einstufiger Prozess. Die Implantation bewirkt eine elastische Deformation der Si-Matrix und die Bildung von SiC-Partikeln in Abhängigkeit von der Ionenfluenz und den thermischen Bedingungen während der Implantation und des Anlassprozesses.
Das Wachstum der SiC-Kristallte in der Si-Matrix wurde mit unterschiedlichen Röntgentechniken wie Diffraktometrie zur Phasenidentifizierung, hochauflösender Diffraktometrie, Texturmessungen, grazing incidence diffraction, reciprocal space map an der Rossendorfer Beamline (ROBL) und hochauflösender Elektronenmikroskopie untersucht.
Es wurde gefunden, dass in einer vergrabenen Schicht 3C-SiC Kristallite gebildet werden. Nach ihrer Orientierung zur Si-Matrix können diese in drei Gruppen eingeteilt werden: mit (i) regelloser Orientierung wie in einem Pulvermaterial, (ii) Fasertextur mit der Oberflächennormale als Faserachse und (iii) perfekter kristallographischer Ausrichtung der kubischen Kristallachsen SiC<100> || Si<100>.
Eine thermische Behandlung begünstigt das Wachstum von hochorientiertem Material: dabei ist eine höhere Implantationstemperatur effektiver als ein nachfolgender Anlassprozess selbst bei höherer Temperatur.

Keywords: Ion beam synthesis, 3C-SiC, Si(001), x-ray diffraction, synchrotron x-rays
  • Lecture (others)
    Gemeinsames Seminar, Friedrich-Schiller-Universität Jena, April 6, 2001

Publ.-Id: 4343 - Permalink


RBS and ion channeling study of YBCO/STO and YBCO/LSMO/STO structures. Oxygen content estimated by X-ray diffraction.
Grigorov, K.; Tsaneva, V.; Spasov, A.; Matz, W.; Grötzschel, R.; Reuther, H.;
The structure and the elemental depth distributions of Y1Ba2Cu3O7-d (YBCO) and La0.7Sr0.3MnO3 (LSMO) were examined by q-2q XRD, and by 1.7 MeV 4He+ Rutherford Backscattering Spectrometry (RBS) in random and channeling geometry. The YBCO layers were magnetron sputtered, with the varying parameters oxygen pressure and annealing time. The layers have high crystalline quality and an almost sharp interface with the substrate as revealed by the analysis. It is shown that the oxygen content influences considerably not only the superconducting behavior, but also the lattice parameters and the cmin parameter (the minimum yield which is the ratio of aligned to random Rutherford backscattering spectra). We have found by high-precision RBS simulation, that independent on the film quality, a disordered interface region of 20 to 30 nm is present in all structures. As a complementary study we have performed also AES depth profiling.
Keywords: Y1Ba2Cu3O7-d layers, superconducting behavior, X-ray diffraction, Rutherford Backscattering Spectrometry, Auger Electron Spectroscopy
  • Poster
    12th Int. School VEIT´01, Varna, Bulgaria, Sept. 17-21, 2001
  • Contribution to external collection
    12th Int. School VEIT´01, Varna, Bulgaria, Sept. 17-21, 2001

Publ.-Id: 4341 - Permalink


AlN films obtained by broad energy nitrogen ion implantation and Rapid Thermal Annealing Process
Grigorov, K.; Beshkov, G.; Maciel, H. S.; Djouadi, A.; Matz, W.; Anguelov, C.; Velchev, N.;
The paper deals with structural, morphological and electrical investigations of thin AlN films obtained by two techniques. The first one consists in rapid thermal annealing of aluminium evaporated onto Si (100) at 600, 800 and 1000oC in NH3 atmosphere for times in the range of 15-180 sec. The other part of the structures was obtained by broad energy range ion bombardment (BERIB) of aluminium by doses ranging from 1.5x1017 cm-2 to 6x1017 cm-2. This technique, to our knowledge was not previously described in the literature. The ion implantation was carried out with two species - nitrogen atoms with energies from 50, 30, and 20 keV and nitrogen ions with energies from 50 and 30 keV. These energy spectra were chosen in order to ensure continued and wide nitride layer of thickness at least of 150 nm. The simulations of the implanted constituent distributions were estimated by the code SRIM. The both implanted series were consequently annealed at 800 and 1000oC for times ranging from 30 to 90 sec. Four-point electrical measurements, scanning electron microscopy, SEM, X-ray diffraction and Rutherford Backscattering Spectrometry (RBS) have been used to characterize the layers.
Keywords: Aluminium Nitrides, RTA, Ion Implantation, and Characterization
  • Poster
    Int. Conf. Diamond 2001, Budapest, Sept. 1-4, 2001
  • Journal of Optoelectronics and Advanced Materials 7(2005)1, 381-384

Publ.-Id: 4340 - Permalink


Ion beam synthesized based formation of Ge - rich thermally grown silicon dioxide layers: a promising approach for a silicon based light emitter
Gebel, T.; Rebohle, L.; Zhao, J.; Borchert, D.; Fröb, H.; von Borany, J.; Skorupa, W.;
The development of novel devices for optical communication and integrated sensor applications is mainly focused on their possible integration into dedicated integrated circuits. The main problem concerning integrated optical systems in silicon technology has always been the formation of an highly efficient silicon-based light emitter which is a key feature to make a real step into the world of integrated optoelectronics.
One of the most promising approaches to form such a silicon based light emitter is ion beam synthesis. In this paper we will report our recent progress in extracting blue-violet (~400 nm) electroluminescence (EL) from an ion beam synthesized Ge-rich silicon dioxide layer. The power efficiency of the EL was as high as 0.5 % which is one of the best values ever reported for Si - based light emission. The lifetime of the EL-device can reach several hours without special precautions of stabilizing the EL-active layer against ion or other contamination. Moreover, results are reported dedicated to the investigation of the excitation mechanism of this strong EL.

Keywords: ion implantation, electroluminescence, Si-based light emisison
  • Contribution to external collection
    Mat. Res. Soc. Symp. Proc. 638, F18.1 (invited) (2001)
  • Lecture (Conference)
    MRS Fall Meeting, Boston (USA), Nov. 27 - Dec. 1, 2000

Publ.-Id: 4339 - Permalink


Transient behaviour of the strong violet electroluminescence of Ge-implanted SiO2 layers
Rebohle, L.; Gebel, T.; von Borany, J.; Skorupa, W.; Helm, M.; Pacifici, D.; Franzo, G.; Priolo, F.;
Si-based light emitters will be a key element of future optoelectronics. One of the most promising approaches is Ge-implantation into thin SiO2 films on crystalline Si. This system exhibits a strong violet electroluminescence with a power efficiency up to 0.5 % [L. Rebohle et al., J. Electrochem. Soc.: Electrochem. and Solid State Lett. 7 G57 (2001)], but the mechanism of electrical excitation is not yet fully understood. In this paper the electrical excitation of the luminescence centers is investigated by means of electrical and electroluminescence transient measurements. It is found that the most probable way to excite luminescence centers is the impact excitation by hot electrons. Whereas the injection is explained by trap assisted tunneling of electrons from the substrate into the oxide, the electrons will be transported via traps or in the SiO2 conduction band. Furthermore, the electroluminescence rise and decay time is estimated to be of the order of 100 microsec.
Keywords: Electroluminescence, Photoluminescence, Ion implantation of Ge, Nanocrystalline materials-optical properties
  • Appl. Phys. B 74 (2002), 53-56

Publ.-Id: 4338 - Permalink


Flash lamp annealing with millisecond pulses for ultra-shallow boron profiles in silicon
Gebel, T.; Voelskow, M.; Skorupa, W.; Mannino, G.; Privitera, V.; Priolo, F.; Napolitani, E.; Carnera, A.;
In this paper we report on recent results obtained from flash lamp annealing (FLA) for the formation of ultra-shallow junctions. Si (100) wafers were implanted at ultra-low energy (500eV) with boron to a fluence of 1015 ions/cm2. FLA was carried out at temperatures of 1100 and 1200°C with a soak time of 20ms. For comparison conventional rapid thermal annealing (RTA) was performed at 1100°C and 1200°C. The boron diffusion and the dopant activation were investigated by secondary ion mass spectroscopy (SIMS) and spreading resistance profiling (SRP). The activated doses after FLA were as high as 20% of the implanted dose and confined in a layer of 60 nm. The sheet resistances were comparable to those after RTA treatment.


Keywords: shallow junctions, flash lamp annealing (FLA), rapid thermal annealing (RTA), spike anneal
  • Nuclear Instruments and Methods B 186 (2002) 287-290
  • Lecture (Conference)
    E-MRS Spring Meeting 2001, 04.-08.06.2001, Strasbourg (France)

Publ.-Id: 4337 - Permalink


Antimony implanted in silicon-a thin layer reference material for surface analysis
Ecker, K. H.; Berger, A.; Grötzschel, R.; Persson, L.; Wätjen, U.;
A reference material has been produced which can be used for the calibration of surface - and near-surface analytical methods.
Keywords: Certified reference material; RBS; Instrumental neutron activation analysis
  • Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Volumes 175-177 (2001)797

Publ.-Id: 4336 - Permalink


Determination of parameters for channeling of protons in SiC polytypes in the backscattering geometry
Kokkoris, M.; Kossionides, S.; Vlastou, R.; Aslanoglou, X. A.; Grötzschel, R.; Nsouli, B.; Kuznetsov, A.; Petrovic, S.; Paradellis, T.;
Energy spectra of protons channeling along the (0001) axis of several SiC polytype crystals, (namely 4H, 6H, 15R, 21R) in the energy region Ep=1.7-2.5 MeV, in the backscattering geometry, were taken and analyzed. Computer simulations based on the assumption that the dechanneling of protons follows an exponential law are in very good agreement with the measured spectra. The obtained results for the two crucial channeling parameters, ?, the mean channeling distance, and, a, the ratio of the stopping powers in the aligned and random mode are compared for the different structures and an attempt is made to explain the occuring similarities as well as the differences, in order to evaluate the use of SiC polytypes as substrates in implantations and thin film depositions. An attempt is also made to correlate the results from the present work to the ones obtained in the past for simpler crystallographic structures, namely Si <100> and Si <111>, as well as more complex ones, such as SiO2 (c-axis).


Keywords: Backscattering; Channeling; Nuclear resonance; SiC crystal; Protons; Polytype
  • Nuclear Instruments and Methodes in Physics Research B 184 (2001) 319-326

Publ.-Id: 4335 - Permalink


Phase transformations in nitrogen-implanted iron layers
Jagielski, J.; Kopcewicz, M.; Matz, W.; Grötzschel, R.; Thomé, L.;
Phase transformations in implanted iron may strongly depend on the sample thickness. The effect essentially relies on lower impurity concentration required for given phase transformation in thin films when compared with thick layers or bulk samples.
Keywords: Ion implantation; Phase formation; thin films
  • Nuclear Instruments and Methodes in Physics Research B 175-177 (2001) 448-452

Publ.-Id: 4334 - Permalink


RBS and HIRBS Studies of Nanostructured AgSiO2 Sol-Gel Thin Coatings
Kokkoris, M.; Trapalis, C. C.; Kossionides, S.; Vlastou, R.; Nsouli, B.; Grötzschel, R.; Spartalis, S.; Kordas, G.; Paradellis, T.;
In the present work, composite AgSiO2 thin coatings, containing metal nanoparticles, were prepared on glass substrates by the sol-gel route. The coatings were thermally treated in oxidative and reductive conditions up to 500oC for metal nanoparticle formation. The coating structure and the nanoparticle formation were studied by Atomic Force Microscopy (AFM) and Rutherford Backscattering Spectroscopy (RBS) techniques. In the case of RBS, 1.4 MeV 4He+ ions were used for all samples, and low energy 16O and 12C ions in selected ones (Heavy Ion RBS), in order to improve the depth resolution for the profiling of the metal component. The antibacterial activity against Escherichia Coli is examined by antibacterial-drop test. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the metal concentration and was reduced with the increase of the particle size of the metal nanoparticles. The possible correlation between the layer interdiffusion after the thermal treatment and the antibacterial activity is examined and analyzed. Although further studies are required, RBS and HIRBS seem to be excellent tools for the quality control in the production of sol-gel thin coatings.

Keywords: RBS; HIRBS; Sol-Gel; Antibacterial; XRD; Thin coatings
  • Lecture (Conference)
    ECAART-7 Conference, 21st - 25th August 2001, Guildford, UK

Publ.-Id: 4333 - Permalink


Post Test Calculation with CFX-4 of the OECD/CSNI International Standard Problem Nr. 43
Höhne, T.;
The need of the experimental support for validation of the computational tools to be applied to analyze the mixing of diluted slugs has been recognized in various countries. The test series for the International Standard Problem ISP-43 provides a platform for experiences to be applied to the simulation of a well-defined test series. Test A of the UM2x4 loop test facility was calculated with the CFD Code CFX-4.3. The results show qualitatively good agreement with the experimental data. The structure of the flow field and the form of the propagating temperature perturbation front are well modeled by the CFD code. However, deviations occur at local positions. Comparative calculations with and without taking into account buoyancy have shown, that buoyancy effects are noticeable, but the mixing is mainly momentum controlled.
Keywords: Boron Dilution, Pressurized Water Reactor
  • Lecture (Conference)
    ICONE 10-22722, Tenth International Conference on Nuclear Engineering Hyatt Regency Crystal City, Arlington, Virginia, USA, April 14-18, 2002, CD-ROM
  • Contribution to proceedings
    ICONE 10-22722, Tenth International Conference on Nuclear Engineering Hyatt Regency Crystal City, Arlington, Virginia, USA, April 14-18, 2002, CD-ROM

Publ.-Id: 4332 - Permalink


Die Mehrzweck-Thermohydraulikversuchsanlage TOPFLOW des Forschungszentrums Rossendorf e.V. - Aufbau, Ziele und Perspektiven
Schaffrath, A.; Krüssenberg, A.-K.; Weiß, F.-P.; Prasser, H.-M.;
Am Institut fuer Sicherheitsforschung des Forschungszentrums Rossendorf e.V. wird die Mehrzweck-Thermohydraulikversuchsanlage TOPFLOW zur Untersuchung stationaerer und transienter Phaenomene in Zweiphasenstroemungen sowie zur Entwicklung und Validierung der in Computational Fluid-Dynamic Codes enthaltenen Modelle aufgebaut. Im Detail sind Experimente zu den Themen
- transiente zweiphasige Stroemungen in vertikalen, horizontalen und beliebig geneigten Rohrleitungen sowie in reaktortypischen Geometrien,
- Sieden in grossen Behaeltern und Wasserpools,
- Erprobung passiver Komponenten und Sicherheitssysteme
sowie
- Kondensation in horizontalen Rohren in Ab- und Anwesenheit von nichtkondensierbaren Gasen.
  • Atomwirtschaft-Atomtechnik 47 (2002), Nr. 6, S. 383-388

Publ.-Id: 4331 - Permalink


Synthesis of nano-sized SiC precipitates in Si by simultaneous dual beam implantation of C+ and Si+ ions
Kögler, R.; Eichhorn, F.; Kaschny, J.; Mücklich, A.; Reuther, H.; Skorupa, W.; Serre, C.; Perez-Rodriguez, A.;
Nanometer-sized SiC precipitates were in-situ synthesized in Si by simultaneous implantation of two ion beams, of C+ and Si+ ions. The results of simultaneous dual beam implantation were compared with those of sequential dual beam ion implantation and of single beam C+ ion implantation. Remarkable differences were observed regarding the content and the crystal perfection of SiC precipitates as well as the defect structure of the Si substrate. The SiC precipitation during dual beam synthesis was found to depend on the ion energy of the second beam and on the implantation mode, simultaneous or sequential. For suitable implantation conditions the simultaneous dual beam synthesis can improve the in-situ SiC formation in comparison to the single beam synthesis. A higher density of the SiC precipitates with better crystal perfection was observed whereas their size was not changed. The second ion beam enables to shift the dynamic equilibrium of constructive and destructive processes for the SiC formation.
A model is proposed assuming that SiC precipitation preferentially proceeds in regions with vacancy defects. The implantation process itself creates vacancy-dominated and also interstitial-dominated regions. The balance of the local point defect composition is shifted under the second ion beam. In this way the conditions for SiC precipitation can be modified.


Keywords: Ion implantation, material synthesis, nanocluster, Si, SiC
  • Applied Physics A 76 (2003) 827-835

Publ.-Id: 4330 - Permalink


Structure and magnetic phase transformation in metastable Fe-Cr alloys induced by ion irradiation
Wieser, E.; Reuther, H.; Prokert, F.; Gorbunov, A.; Tselev, A.; Pompe, W.; Levin, A. A.; Meyer, D. C.; Paufler, P.;
Unusual metastable paramagnetic phases have been observed in Fe-Cr thin films fabricated by pulsed laser deposition. In the present paper, X-ray diffraction and Mössbauer spectroscopy have been applied to follow the structural and magnetic phase transformation in these alloys induced by ion irradiation. The projected range of the chosen implantation energies of 40 keV for Cr and 25 keV for Ne lies in the center of the about 40 nm thick films. It has been found that the critical dose for the transformation to the more stable body-centered cubic (b.c.c.) structure depends on the initial phase of the film and the ion mass. The initial body-centered tetragonal phase which forms in the alloys with low Cr content (~30 at.%) can be completely transformed in the b.c.c. phase already by a dose of 5x1015 Cr/cm2 whereas the primitive orthorombic phase at roughly equiatomic Fe-Cr alloys is about 4 times more resistant against ion bombardment. One needs to apply a five times higher Ne-ion dose to induce the same transformation as by the Cr bombardment. The observed effects are discussed comparing the radiation damage caused by the different ions and the grade of affinity of the initial phase to the b.c.c. one.
Keywords: Fe-Cr alloys, ion irradiation, crystallographic phase transformation, magnetic phase transformation
  • Journal Applied Physics 92 (2002) 572-577

Publ.-Id: 4326 - Permalink


Structural investigation and wear resistance of submicron TiN coatings obtained by a hybride plasma immersion ion implantation process
Günzel, R.; Shevshenko, N.; Matz, W.; Mücklich, A.; Celis, J. P.;
The ever increasing demands for high precision machining and increased cutting performance, in terms of cutting speed and lifetime, require wear resistant tools of large dimensional accuracy that have very sharp cutting edges. All these requirements can not be fulfilled by the classic PVD and CVD technologies because they result in rather thick overlay coatings.
In this report, first experiments are presented on a hybride plasma immersed ion implantation process (PIII) for depositing thin TiN coatings on hardened and annealed high speed steel or cemented carbides. The layers were produced using a dc-cathodic arc source with a titanium cathode and a nitrogen feed gas. As the cathodic arc generates additional to the metal plasma, a large amount of liquid metal droplets, the plasma was guided to the samples through a 900 magnetic bending field avoiding the deposition of droplets on the samples. The obtained layer thickness was below 1 µm for deposition times of 2 min.
To improve the adhesion of the deposited layers on the substrate materials, sputter cleaning by energetic ions was used during the initial phase of the process. Negative high voltage pulses in the range from zero to 5 kV have been applied to the samples during the deposition. The effect of the energy of these ions on the coating structure was also investigated by SEM, TEM and XRD. Mechanical and functional properties were investigated by hardness measurements and fretting wear tests respectively. Finally cutting performance tests of PIII-treated drills were performed, revealing that a 0.8µm thick TiN PIII-coating increased the lifetime of the drills by a factor of 2.5.

Keywords: cutting tools, coatings, ion implantation, PIII, TiN
  • Surf. Coat. Techn. 142-144 (2001) 978-983

Publ.-Id: 4323 - Permalink


Tiefenselektive Phasenanalyse der a-FeSi2-Bildung nach Beschuß von ß-FeSi2 mittels DCEMS, XPS und AES
Walterfang, M.; Keune, W.; Reiche, R.; Oswald, S.; Dobler, M.; Reuther, H.;
Tiefenselektive Phasenanalyse der a-FeSi2-Bildung nach Beschuß von ß-FeSi2 mittels DCEMS, XPS und AES
  • Lecture (Conference)
    65. Physikertagung, Hamburg, 26.-30.3.2001

Publ.-Id: 4322 - Permalink


Improvement of Tribological Properties of Ti6Al4V by Nitrogen Plasma Immersion Ion Implantation
Ueda, M.; Silva, M. M.; Otani, C.; Reuther, H.; Yatsuzuka, M.; Lepienski, C. M.; Berni, L. A.;
Improvement of Tribological Properties of Ti6Al4V by Nitrogen Plasma Immersion Ion Implantation
  • Lecture (Conference)
    International conference on Frontiers of Surface Engineering 2001, Nagoya, Japan, 28. October to 1. November 2001

Publ.-Id: 4321 - Permalink


Nitrogen Plasma Ion Implantation of Al5052 Alloy
Ueda, M.; Reuther, H.; Dias, F. G.; Rangel, E. C.; Cruz, N. C.;
Nitrogen Plasma Ion Implantation of Al5052 Alloy
  • Lecture (Conference)
    International conference on Frontiers of Surface Engineering 2001, Nagoya, Japan, 28. October to 1. November 2001

Publ.-Id: 4319 - Permalink


Determination of the hyperfine parameters of iron silicides by angle dependent conversion electron Mössbauer spectroscopy on single crystals
Reuther, H.; Behr, G.;
Iron silicides are of growing interest because of their interesting properties in reference to potential applications in thermoelectrics, photovoltaics and optoelectronics. For phase analysis by Mössbauer spectroscopy on bulk material or on thin layers, the knowledge of their hyperfine parameters is necessary.
In the present study, the Mössbauer spectra of single crystals of various silicides e-FeSi, ß-FeSi2 and a-FeSi2 are collected by conversion electron Mössbauer spectroscopy at room temperature. Measurements were performed at different angles between the propagation direction of the exciting g-radiation and the crystal axis of the single crystals.
The Mössbauer spectrum of the monosilicide consists of two lines while those of the disilicides consist of four lines. In the latter two cases, an unambiguous assignment of the lines to two quadrupole doublets could be performed. The hyperfine parameters including the signs of the quadrupole splittings are determined with high accuracy. Moreover, the direction of the main axis of the electric field gradient in regard to the crystal orientation was determined.
The results are compared with those obtained at powder or thin layer samples in the past. Differences and coincidences are discussed.

  • Lecture (Conference)
    International Conference on the Applications of the Mössbauer Effect, Oxford, England, 2.-7. Sept. 2001

Publ.-Id: 4314 - Permalink


Spin-density enhancement in the presurface zone of chromium
Dubiel, S. M.; Cieslak, J.; Zukrowski, J.; Reuther, H.;
Spin-density enhancement in the presurface zone of chromium
  • Lecture (Conference)
    International Conference on the Applications of the Mössbauer Effect, Oxford, England, 2.-7. Sept. 2001

Publ.-Id: 4313 - Permalink


Depth analysis of buried iron disilicide formation by Fe ion implantation into Si
Walterfang, M.; Kruijer, S.; Keune, W.; Dobler, M.; Reuther, H.;
Depth analysis of buried iron disilicide formation by Fe ion implantation into Si was performed by DCEMS.
  • Poster
    International Conference on the Applications of the Mössbauer Effect, Oxford, England, 2.-7. Sept. 2001

Publ.-Id: 4312 - Permalink


The effect of chlorite dissolution on the sorption behavior of U(VI)
Krawczyk-Bärsch, E.; Arnold, T.; Brandt, F.; Bosbach, D.; Bernhard, G.;
In the Western Erzgebirge in Germany the abandoned uranium mines are mostly related to the rock phyllite. Currently, many of these mines are being flooded. The flood water is contaminated with uranium and penetrates the phyllite through cracks and fissures. The contact of the flood water with the rock leads to dissolution processes. One of the major components in this phyllite is an iron-rich chlorite. Chlorites are 2:1 sheet silicates, with an octahedral sheet sandwiched between two tetrahedral sheets. In contact with water chlorites tend to dissolve leading to a loss of octahedral layer cations, i.e. Al3+ with Mg2+, Fe2+ and Fe3+ substitutions. During the dissolution the chlorites are progressively degenerating to vermiculite and secondary iron minerals. In previous studies these secondary iron minerals have been determined as a poorly-crystalline iron oxide hydroxide, like ferrihydrite, which has a significant influence on the uranium migration behavior.
In flow-through experiments the kinetics of the U(VI) uptake on chlorite were studied to show the sorption behavior of U(VI) during the dissolution of chlorite within the phyllite of the abandoned uranium mines. These flow-through experiments were carried out under oxic conditions and at room temperature, using a NaClO4-solution with an ionic strength of 0.1 M and a pH of 7. An UO2(ClO4)2 solution was added to reach an initial U(VI) concentration of 1*10-6 M. The dissolution rates calculated for Al, Mg and Si are decreasing during the first hours of the experiment. Due to the precipitation of iron oxide hydroxides in a pH-range > 5 the released Fe cations have not been determined in the reacted solution. The dissolution rate of Fe is for this reason remaining low during the experiment. The formed secondary iron minerals are responsible for the remarkable high uptake of U(VI) on chlorite. In the first 24 h period of the experiment 72 % of the totally uranium was sorbed. In the following hours the relative amount of the sorbed uranium decreases, since most of available sorption sites of the chlorite and of the secondarily formed iron oxide hydroxides were already occupied. Additional sorption of U(VI) out of solution on the solid chlorite during the flow-through experiment is therefore decreasing. Conclusively, the chlorite within the phyllite is retarding under oxic conditions most of the U(VI) during the flooding, due to the dissolution of chlorite and the subsequent precipitation of iron oxide hydroxides.
  • Lecture (Conference)
    Uranium Mining and Hydrology UMH III, Freiberg 2002, 15.-21.9. Uranium in the Aquatic Environment, 425-430, Springer Verlag, 2002

Publ.-Id: 4311 - Permalink


Investigation of gypsum dissolution under saturated and unsaturated water conditions
Kuechler, R.; Noack, K.; Zorn, T.;
Batch and column experiments were carried out to study the dissolution of gypsum by water under saturated and unsaturated conditions. The experimental results were verified by calculations. Comparing the dissolution in batch and column experiments, which were performed with a water flow velocity of 0.015 cm/h, one has to conclude that under unsaturated conditions only the
very small portion of 2.2 percent of the grain surface is chemically reactive. Experiments and calculation show that the gypsum release in the column is mainly determined by the flow velocity.
Keywords: Pollutant transport, Unsaturated soil, Gypsum dissolution, Transport modelling
  • Ecological Modelling 176(2004), 1-14

Publ.-Id: 4310 - Permalink


Infiltration water dating from tritium measurements in mining dumps: methodic specifics and case study
Mibus, J.; Szymczak, P.; Hebert, D.;
Mine waste dumps and industrial tailings often emit toxic substances like sulfuric acid, heavy metals, or radionuclides over seepage discharge. An important parameter to characterize these transfer processes is the mean residence time tm of the infiltration water usually determined from tritium measurements. Conventional models assume a constant reservoir size (aquifer thickness) and to a great extent stationary hydraulics.
Emerging dumps, in contrast, exhibit a more or less continuously increasing thickness during deposition. The infiltration water is partly or even completely consumed to build up a static reservoir of adhesive water in the initial dry pores. The water percolation begins not until the field capacity is reached. This deceleration depends on deposit rates, recharge rates and cap-illary capacity and increases the portion of older components in the effluent waters compared to model assumptions.
In a case study a time series of effluent waters from a mining dump of Kupferschiefer mining in the south-eastern Harz-foreland was analyzed for ³H. The interpretation using the linear model revealed contradictions between residence time of infiltration waters and life span of the dump.
For the case of the linear model a proposal is made to modify the residence time distribution function. The
  • Poster
    Uranium Mining and Hydrogeology, Freiberg 2002, 15.-21.9.
  • Contribution to external collection
    Uranium Mining and Hydrogeology, Freiberg 2002, 15.-21.9.

Publ.-Id: 4308 - Permalink


From KD to Surface Complexation Models: Present State of Actinide Data Supply
Brendler, V.; Arnold, T.; Richter, A.; Bernhard, G.; Fanghänel, T.;
Almost all risk assessment studies related to uranium mining and milling legacies rely on the wide-spread but simplistic KD concept of distribution coefficients, which subsumes all relevant physico-chemical phenomena into only one parameter. To overcome the resulting limitations, more realistic chemical speciation patterns are needed, including complex formation, heterogeneous phase equilibria and surface complexation. Following this strategy, the paper presents a digitized version of a thermodynamic sorption database as required for the parametrization of Surface Complexation Models (SCM). It is mineral-specific and hence also suitable for additive models of more complex solid phases such as rocks or soils. All major electrostatic variants of SCM are integrated. Also the concept of strong and weak binding sites, and the 1-pK approach is applicable. Surface species include ternary ones.
Data records comprise of mineral properties, specific surface areas, surface binding site concentrations and protolysis constants, sorption ligand information, and surface complexation reactions, all coupled to an extensive bibliography. Based on them, a detailed picture about the distribution of actinide SCM data amongst minerals, SCM subtypes and ligands is presented. Derived from that and focused on uranium, critical data gaps are identified, existing parameter sets are evaluated, and consistency tests are performed. Final goal is the establishment of recommended reference data sets.
Only few of the surface complexes proposed in the literature (mostly resulting just from best-fit considerations) are actually validated by spectroscopic evidence. If such information is available it is stored in the database and used for data evaluation.
Originally implemented as a stand-alone relational database under MS Access on a PC, the database RES³T (Rossendorf Expert System for Surface and Sorption Thermodynamics) is now connected to the WWW and accessible through common web browser interfaces.
  • Lecture (Conference)
    Uranium Mining and Hydrogeology III, Freiberg 2002, 15.-21.9.

Publ.-Id: 4307 - Permalink


Uranium speciation in plants
Günther, A.; Bernhard, G.; Geipel, G.; Rossberg, A.; Reich, T.;
The chemical characterization of the radionuclide species is essential for a reliable assessment of the migration of radionuclides and heavy metals into the geological and biological environment on the load pathway soil - plant - animal - human. Only a few is known about the speciation of uranium in plants. Therefore we investigate the change of speciation during the transfer of uranium from initial solution into plant.
Various plants (lupins, dandelion e.g.) were grown in an agricultural test field and in the laboratory on contaminated soils (up to concentration of 1g U/kg soil) and as hydroponics in the uranium containing solutions (uranium concentration: 10-5 M - 10-2 M, pH: 3 - 8). For the study of the chemical speciation in the initial solution (pore water and hydroponic solution) and in plant samples we use the Time-Resolved Laser-Induced Fluorescence Spectroscopy, the X-Ray-Absorption Spectroscopy and the Scanning Electron Microscopy. Differences between the uranium speciation in the initial solutions and the speciation in the plant could be detected spectroscopically. The chemical speciation of the uranium seems to be identical in the roots, shoot axes and leaves. It is independent of the growing conditions (soil culture or hydroponic) and the type of the plant. Spectroscopic results show the formation of uranyl phosphato complexes as the main species in plants.

  • Lecture (Conference)
    Uranium Mining and Hydrogeologie UMH II, 15.9.-21.9.02, Freiberg Proceedings, Uranium in the Aquatic Environment, Springer Verlag 2002, p 513-520

Publ.-Id: 4306 - Permalink


Formation of secondary Fe-oxyhydroxide phases during the dissolution of chlorite effect on uranium sorption
Krawczyk-Bärsch, E.; Arnold, T.; Reuther, H.; Brandt, F.; Bosbach, D.; Bernhard, G.;
The formation of Fe-colloids resulting from the chemical weathering of chlorite (Mg5.5Al2.48Fe2+3.02Fe3+0.94)[(Si5.33Al2.66)O20](OH)16) was studied in batch experiments. The chemistry of the detected colloids was determined by SEM/EDS measurements on separated agglomerated colloids fixed on filter membranes. The results show that the Fe-colloids exist as aqueous colloids as well as sorbed colloids forming iron coatings on the chlorite platelets. It was also observed that the newly-formed Fe-colloids are preferentially attached to the {hk0} edge surfaces and only to a minor extent as isolated Fe-colloids to the {001} basal plane surfaces. The average surface coverage of sorbed Fe-colloids on the {hk0} edge surfaces was found to be 0,276 žm2 of sorbed Fe-colloids per 1 žm2 of {hk0} chlorite surface, i.e. 27,6 % of the {hk0} surfaces is covered with adsorbed Fe-colloids. This value is significantly higher than the surface coverage found on the {001} basal plane surfaces. Here, the average surface coverage of Fe-colloids on the {001} basal plane surfaces was determined to be 0,030 žm2 of sorbed Fe-colloids per 1 žm2 of {001} chlorite surface, i.e. 3,0 % of the {001} surface area is covered with sorbed Fe-colloids. This shows that there are nine times more Fe-colloids adsorbed onto the edge surfaces than on the basal plane surfaces.
The detected colloids were, based on their chemistry, their spherical character and small particles sizes, identified as ferrihydrite. In addition, Mössbauer spectroscopy measurements were used to quantify the increase of ferric iron which formed during the batch experiment. This detected increase in ferric iron in the chlorite from 14.0 to 15.3 % š 1% was attributed to the formation of ferrihydrite.
The assumption that the edge surfaces of sheet silicates show a much higher affinity for adsorption reactions was so far not conclusively proven. However, the results of this study clearly show that colloid adsorption on the sheet silicate chlorite preferentially takes place on the {hk0} edge surfaces indicating that the edge surfaces of sheet silicates are by far more reactive in regard to sorption reactions than the distinctively less reactive {001} basal plane surfaces. In addition, the influence of Fe-phases as weathering products on sorption processes in nature is discussed.
Keywords: chlorite, colloids, ferrihydrite, chemical weathering, coating
  • Applied Geochemistry, 19(2004)9, 1403-1412, DOI:10.1016/j.apgeochem.2004.01.017

Publ.-Id: 4305 - Permalink


Der NOKO-Versuchsstand der Forschungszentrum Jülich (FZR) GmbH - Rückblick auf 7 Jahre experimentelle Untersuchungen zur Erhöhung der Sicherheit von Leichtwasserreaktoren
Hicken, E. F.; Schaffrath, A.; Fethke, M.; Jaegers, H.;
Es ist ein Zeichen einer guten Sicherheitskultur, wenn Hersteller, Betreiber und Gutachter gleichermassen das Sicherheitsniveau von Kernkraftwerken stetig anheben wollen. Derzeit bietet sich die Gelegenheit, ueber fruehere, aktuelle und zukuenftige Konzepte nachzudenken. Ziel ist es, zukuenftige Anlagen zu optimieren, durch Systemvereinfachungen die Uebersichtlichkeit zu erhoehen und somit ihre Zuverlaessigkeit zu verbessern. Ferner sollen Effektivitaet und Wirtschaftlichkeit gesteigert werden. Hierzu wird seit Mitte der 90er Jahre an verschiedenen Stellen weltweit die Effektivitaet und das Betriebsverhalten passiver Sicherheitssysteme untersucht.
Im Beitrag wird auf die Geschichte des NOKO-Versuchsstandes zurueckgeblickt. Ferner werden ausgewaehlte Hoehpunkte der experimentellen Untersuchungen (u.a. der experimentelle Nachweis der thermohydraulischen Wirksamkeit des Notkondensators, des Gebaeudekondensators sowie des passiven Impulsgebers) beschrieben.
Keywords: NOKO-Versuchsstand, Notkondensator, Gebaeudekondensator, Passiver Impulsgeber
  • Atomwirtschaft-Atomtechnik 47 (2002), Nr. 5, S. 343-348

Publ.-Id: 4304 - Permalink


Sorption of Uranium(VI) onto Schwertmannite - EXAFS Investigations
Walter, M.; Arnold, T.; Funke, H.; Reich, T.; Bernhard, G.;
The ferric oxide schwertmannite is commonly formed in acid mine drainage waters (pH-range from 2.8 to 4.5) in the presence of high sulfate concentrations. Because of its large specific surface area its may influence the migration of uranium(VI) by sorption processes. The aim of this study were structural informations for uranium(VI) surface complexes given by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. We include Goethite in our investigations as a reference to compare and interpret the schwertmannite data.

Samples for EXAFS analysis were prepared under N2 atmosphere using 200 mg of schwertmannite or goethite with initial uranium(VI) concentrations of 1x10-5 (pH 6.5) to 5x10-5 M (pH 4.2). The ionic strength was adjusted using 0.01 M Na2SO4 or NaClO4 respectively. EXAFS spectra were recorded at room temperature in fluorescence mode at the Rossendorf beamline (ROBL) at the ESRF in Grenoble. The measured EXAFS oscillations were fitted using EXAFSPAK procedure. The theoretical phase shifts and backscattering amplitudes were calculated with FEFF8.

All distances of the equatorial oxygens are about 2.37 Å. These are significantly shorter than typical values of 2.41 Å for the aquatic UO22+ ion, which indicates strong interactions. An iron backscatterer is clearly found for uranium(VI) sorbed onto goethite at pH 4.2 and 6.5 in sulfate-rich solution as well as for schwertmannite at pH 4.2 in perchloric solution. Such a uranium - iron distance indicates a bidentate inner sphere complexation. In contrast, the EXAFS of uranium(VI) sorbed onto schwertmannite at pH 4.2 in sulfate-rich solutions shows only a sulfur backscatterer at a distance of 3.66 Å, indicating the formation of a ternary surface complex.
  • Lecture (Conference)
    Uranium Mining and Hydrogeology UMH III, Freiberg , 15.9.-21.9. 2002, Proceedings: Uranium in the Aquatic Environment, 395-398, Springer Verlag, 2002
  • Contribution to external collection
    Uranium Mining and Hydrogeology UMH III, Freiberg , 15.9.-21.9. 2002, Proceedings: Uranium in the Aquatic Environment, 395-398, Springer Verlag, 2002

Publ.-Id: 4303 - Permalink


Atomic scale simulation of the stress relief in tetrahedral amorphous carbon
Belov, A.;
Tetrahedral amorphous carbon (ta-C) is an amorphous form of carbon with a high content of sp3 bonded atoms, which can be deposited as thin films by energetic carbon ions or neutral atoms. As-grown ta-C films possess a high level of intrinsic compressive stresses (~10 GPa) inhibiting the use of this very promising material. The stress is due to a specific growth mechanism (subplantation), resulting from a competition between the densification of subsurface layers by incoming ions and the thermally activated diffusion of subplanted atoms to the surface. In agreement with experiment, we demonstrate using atomic scale simulation that low-temperature annealing can induce a considerable stress reduction in as-grown ta-C with minor
changes in its atomic structure and density. Simulating annealing by means of empirical molecular-dynamics with the interatomic Brenner potential for carbon and realistic boundary conditions, the dependence of the residual stress on the annealing temperature was investigated. It is found that a complete stress relief in ta-C is not accompanied by a change in the short-range order. The average atomic coordination remains nearly constant up to 1400 K. The stress relaxation mechanism discussed involves only structural optimization within the sp3 bonded constituent of ta-C and does not require clustering of sp2 bonded atoms.
Keywords: tetrahedral amorhous carbon, intrinsic stress, simulated annealing, molecular-dynamics
  • Poster
    E-MRS 2002 Spring Meeting, June 18-21, 2002, Strasbourg (France), Symposium A: Atomic Scale Materials Design

Publ.-Id: 4288 - Permalink


Complex Formation of Uranium(VI) with Glucose-1-Phosphate
Koban, A.; Geipel, G.; Bernhard, G.; Fanghänel, T.;
The uptake of heavy metals into plants is commonly quantified by the soil-plant transfer factor. Up to now little is known about the chemical speciation of actinides in plants. To compare the obtained spectroscopic data of uranium complexes in plants with model compounds, we investigate the complexation of uranium with relevant bioligands of various functionalities. A very important class of ligands are phosphate esters, which serve as phosphate group and energy transmitters as well as energy storage mediums in biological systems.
Therefore, in our study we present the results of uranium complexation with glucose-1-phosphate (G1P) obtained by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and potentiometric titration. The TRLFS-experiments were performed at a fixed uranyl concentration (10-5 M) as a function of the ligand concentrations (10-5 to 10-3 M) in a pH range from 2 to 4.5. The potentiometric titrations were performed at fixed uranyl (10-4 M) and ligand (10-3 M) concentrations in a pH range from 3 to 10.
The TRLFS-measurements show a decrease in the fluorescence intensities with increasing ligand concentrations, and no shift of the emission bands. The TRLFS spectra indicate the presence of only one species with fluorescence properties. This species has a lifetime of 1.50 µs and was identified as the free uranyl ion. Therefore we conclude that the complexed uranyl glucose phosphate species shows no fluorescence.
From quantitative evaluation of the TRLFS spectra we conclude, that 1:1 uranyl glucose phosphate species UO2(G1P) has formed. The complex formation constant was calculated to be log beta=5.60.
The results of the potentiometric titration show the same type of complex with a stability constant of log beta=5.37.
  • Poster
    Uranium Mining and Hydrogeology Conference Freiberg UMH III 15.09.-21.09.2002. Uranium in the Aquatic Environment (Proceedings of the UMH III), 537-540, Springer Verlag 2002.
  • Contribution to proceedings
    Uranium Mining and Hydrogeology Conference Freiberg UMH III 15.09.-21.09.2002. Uranium in the Aquatic Environment (Proceedings of the UMH III), 537-540, Springer Verlag 2002.

Publ.-Id: 4287 - Permalink


Atomistic study of ion beam deposition conditions for hard amorphous carbon
Belov, A.; Jäger, H.-U.;
The influence of deposition conditions on the sp3 content, intrinsic stress, and elastic modulus in hard amorphous carbon (a-C) films was studied at the atomic scale. Simulation of ion beam deposition of carbon films was performed by the molecular-dynamics method with a modified analytical hydrocarbon potential of Brenner. Deposition of films with a thickness of up to 10 nm was computed for ion energies E = 10-80 eV, and for substrate temperatures ranging from 100 to 900 K. The dependence of the sp3 content and the intrinsic stress on substrate temperature was found to be in qualitative agreement with experiment. At low substrate temperatures and low ion energies, the sp3 fraction increases with ion energy, giving at E > 30 eV a highly sp3 bonded tetrahedral amorphous carbon (ta-C) with a high level of intrinsic compressive stress. This trend also remains at room emperature, however with lower values of sp3 content, whereas at T > 200 °C a transition to graphite-like a-C with dominating sp2 bonding was found.
Keywords: tetrahedral amorphous carbon, hard amorphous carbon fims, intrinsic stress, ion beam deposition, computer simulation, molecular-dynamics
  • Poster
    E-MRS 2002 Spring Meeting, June 18-21, 2002, Strasbourg (France), Symposium A: Atomic Scale Materials Design

Publ.-Id: 4286 - Permalink


A model of the thermochemical polishing of CVD diamond films on transition metals with emphasis on steel
Weima, J. A.; Fahrner, W. R.; von Borany, J.; Job, R.;
A model of thermochemical polishing, namely the conversion of diamond into non-diamond carbon at elevated temperatures and the subsequent dissolution of the non-diamond carbon into a transition metal polishing plate is investigated. Equations of the conversion rate k1, the dissolution rate k2, the diffusion constant of carbon in steel D, and the concentration profile of carbon in steel N(x,t)are derived. The rate constants are calculated for four diamond films polished at varying temperatures. Elastic recoil detection analysis (ERDA) measured carbon depth profiles in steel agree well with theoretical calculations. However, the calculated value of D = 1,16 x 10-14 cm2/s is far below the value of D = 1,19 x 10-7 cm2/s for gamma-iron. The discrepancy between the two values is related to oxygen-enhanced segregation of carbon in the near surface region of steel and to the incorporation of elements which act as trap centers of carbon in steel.
  • Journal of the Electrochemical Society

Publ.-Id: 4285 - Permalink


Thermochromatographic oxidation studies of plutonium dioxide
Hübener, S.; Fanghänel, T.;
The volatility of plutonium oxides in the O2-H2O(g)/SiO2(s) system has been studied by thermochromatography in the temperature range 1475 to 600 K. Oxides of uranium and neptunium have been studied for comparison. Oxide samples containing 1015 - 1016 actinide atoms were heated in the starting position of the thermochromatographic silica columns. Mixtures of helium, oxygen and water vapor were applied as reactive mobile gas phase. Resulting from thermochromatography the volatile actinide species are deposited in the column downstream, thus creating inner chromatograms along a temperature gradient. At the end of each experiment the actinide chromatograms were measured by alpha spectrometry.
Plutonium was found to be volatile in humid oxygen at temperatures above 1250 K. The Pu volatility is lower than that of uranium, but higher as one would expect for stable Pu(IV) which is nonvolatile under the applied experimental conditions. The Pu volatility is assigned to PuO2(OH)2(g). The experimental results give further evidence that water can oxidize plutonium dioxide.

Keywords: actinides, oxides, plutonium, oxidation state
  • Lecture (Conference)
    Rare Earth Research Conference, Davis, California, July 13-18, 2002, Abstracts

Publ.-Id: 4284 - Permalink


A novel technetium-99m radioligand for the 5-HT1A receptor derived from desmethyl-WAY-100635 (DWAY)
Heimbold, I.; Drews, A.; Syhre, R.; Kretzschmar, M.; Pietzsch, H.-J.; Johannsen, B.;
This paper reports the synthesis, biological evaluation and in vitro autoradiography of a new technetium-99m radioligand with high affinity for the 5-HT1A receptor. The neutral complex combines an N2S2 diamine dithiol (DADT) ligand as complexing moiety for oxotechnetium(V) and a 2-(1-piperazino)phenol via a 6-carbon alkyl chain, derived from desmethyl-WAY-100635 (DWAY). The complex displays an IC50 value for the 5-HT1A receptor of 1.29 nM against the selective 5-HT1A agonist [3H]8-OH-DPAT, a moderate selectivity towards the alpha1-adrenergic receptor (IC50 of 8.1 nM against [3H]prazosin) and a good selectivity for the D2 receptor (IC50 of 192 nM against [3H]spiperone) and the 5-HT2A receptor (IC50 of 922 nM against [3H]ketanserin). Biodistribution studies in rats show an initial brain uptake of 0.65%±0.07% ID 2.5 min p.i. In vitro autoradiographic studies of the 99mTc complex in rat brains indicate a strong specific accumulation of the radioactivity in 5-HT1A receptor-rich brain regions.
Keywords: 5-HT1A receptor; technetium-99m; 99mTc receptor ligand; DWAY analogue; radioligand
  • European Journal of Nuclear Medicine 29 (2002) 82-87

Publ.-Id: 4283 - Permalink


Separation of Uranium from Aqueous Solution by Textile Bound Calixarenes
Schmeide, K.; Geipel, G.; Keil, D.; Jansen, K.; Praschak, D.; Heise, K.-H.; Bernhard, G.;
The remediation of former uranium mining and milling sites of Saxony and Thuringia requires the purification of uranium contaminated seepage and mine waters. The separation of uranium(VI) from aqueous solution by calixarenes by means of solvent extraction is described in the literature (e.g., [1,2]). Calixarenes are macrocyclic molecules formed by 4, 6 or 8 parasubstituted phenolic units linked by methylene bridges ortho to the OH functions. Thus, molecules of various ring sizes are formed. The substitution of calix[6]arenes on the hydroxyl group by carboxylic and hydroxamic groups, respectively, leads to ligands that are able to bind uranium(VI) selectively.
The present work represents an innovative method for the separation of uranium(VI) from aqueous solution using uranophile calix[6]arenes that are fixed on textile substrates such as polyester fabric. For this, the calix[6]arenes are statistically functionalized by spacer groups (n-alkyl groups) that enable their fixation onto polyester fabric.
The complex formation of the textile bound calixarenes, e.g., carboxymethoxy-p-mono-nonyl-penta-tert-butyl-calix[6]arene, and their selectivity towards uranium(VI) ions is studied as a function of pH value, ionic strength and competing ions by means of batch experiments. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) is used to determine complex formation constants. The reaction mechanisms are discussed. As competing ions, Na+, Ca2+, Mg2+ and Fe3+ as well as SO42- are studied, that occur typically in mine waters. Furthermore, the reversibility of the uranium binding is evaluated. The results are compared with those obtained for the corresponding non-fixed calixarenes [3].
The new technique for the remediation of uranium contaminated waters is also applicable for lower contamination levels ([UO22+] < 1x10-6 M) and is especially suitable for smaller remediation objects. The applicability of this separation principle to further actinides is expected.

[1] Shinkai, S., Koreishi, H., Ueda, K., Arimura, T., Manabe, O.: Molecular Design of Calixarene-Based Uranophiles which Exhibit Remarkably High Stability and Selectivity. J. Am. Chem. Soc. 109, 6371 (1987).
[2] Nagasaki, T., Shinkai, S.: Synthesis and Solvent Extraction Studies of Novel Calixarene-based Uranophiles Bearing Hydroxamic Groups. J. Chem. Soc., Perkin Trans. 2 (7), 1063 (1991).
[3] Schmeide, K., Barz, B., Heise, K.H., Bernhard, G., Gloe, K.: Solvent Extraction of Uranium(VI) by Calix[6]arene. In: FZR-318, Annual Report 2000 (Th. Fanghänel, ed.). Forschungszentrum Rossendorf, Institute of Radiochemistry, Rossendorf 2001, p. 17.
Keywords: Uranium, calixaren, textile bound calixaren, extraction, remediation, complex formation, TRLFS
  • Lecture (Conference)
    International Conference Uranium Mining and Hydrogeology III and the International Mine Water Association Symposium, Freiberg, 15.-21.09.2002

Publ.-Id: 4282 - Permalink


Entwicklung und Relaxation mechanischer Spannungen in Bornitrid-Schichten
Fitz, C.;
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-337 Januar 2002

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Publ.-Id: 4281 - Permalink


Colloid-borne Uranium in Mine Waters
Zänker, H.; Richter, W.; Hüttig, G.; Moll, H.;
There is ample evidence from groundwaters, river waters, lakes or seawater that colloids influence the transport behavior of contaminants such as As, Pb, Cu, Zn, actinides, fission products, hydrophobic organics etc. Little efforts have been made to elucidate the role of colloids in mine waters. We studied mine waters of very different nature for their colloid-chemistry.
Very stable Fe(III) oxyhydroxy sulfate colloids were found in acid rock drainage (oxic acidic pore waters, pH < 3). The particle size was < 5 nm, the colloid concentration reached the g/l range. Mineralogically, the particles were a mixture of hydronium jarosite and schwertmannite. As and Pb showed a high tendency to adsorb onto these particles. Quite a different type of colloids was found in the oxic "bulk waters" of mines as for instance in tunnel waters (near-neutral pH). The particles were composed of oxyhydroxides of Fe(III) and Al, the particle size was 100 to 300 nm, the particle concentration was about 1 mg/l, the colloids were unstable, i.e. they tended to aggregate. Important colloid-borne contaminants were As, Cu, Zn, Pb, Po. Uranium(VI) adsorption is normally supressed due to the formation of uranyl carbonato complexes in such "bulk waters". The flooding of mines can be regarded as the dilution of acidic pore waters to form "bulk waters". Huge amounts of iron(III) particles with a size of 100 to 300 nm are formed under such conditions. The adsorption of trace elements rises drastically when the pH reaches the near-neutral region. Uranyl adsorption to the iron(III) particles is neither supressed by acidity nor by uranyl carbonate complexation in the pH region 4 to 6. Therefore most of the uranium(VI) is colloid-borne in waters of the transition type; scavenging, colloid aggregation and sedimentation can result in the immobilization of uranium in such waters ("natural attenuation").

Keywords: Uranium, colloids, oxyhydroxides, oxyhydroxy sulfates, iron, aluminum
  • Lecture (Conference)
    International Conference on Uranium Mining and Hydrology (UMH III). Freiberg, 15.09.-21.09.2002

Publ.-Id: 4280 - Permalink


Scavenging and immobilization of trace contaminants by colloids in the waters of abandoned ore mines
Zänker, H.; Richter, W.; Hüttig, G.;
Inorganic colloids in mine waters are able to influence trace heavy metal transport. In oxic waters they mainly result from the formation of oxyhydroxides and oxyhydroxy sulfates of Fe(III) and Al due to the oxidation of Fe2+ and the hydrolysis of Fe3+ and Al3+. However, the colloid inventories and the colloid properties depend on the mine wa-ter type. Acidic pore waters (pH < 3) contain large amounts (g/l range) of relatively stable ultrafine (< 5 nm) iron(III) oxyhydroxy sulfate particles which most probably consist of a mixture of hydronium jaro-site (HFe3(SO4)2(OH)6) and schwertmannite (Fe8O8(OH)6SO4). Arse-nic and lead tend to be adsorbed onto these colloids. Waters of higher pH (pH > 4) contain smaller amounts (mg/l range) of Fe- and Al-rich colloids of 100 to 300 nm that are unstable. They carry elements such as As, Pb, Zn, Cu, Po, Th, Ac. These trace heavy metals can be scavenged by the colloids and can be immobilized due to colloid coagulation and sedimentation ("natural attenuation"). In the pH range from 4 to 6 (flooding waters) also U(VI) is adsorbed onto the colloidal particles since their adsorption is neither prevented by high acidity nor by the formation of uranyl carbonato complexes. Also U(VI) can be scavenged and immobilized in this pH range. However, in "bulk wa-ters" of pH > 6 such as tunnel waters the adsorption of U(VI) to the colloids is normally prevented by carbonate complexation
Keywords: Colloids, mine waters, iron, aluminum, uranium
  • European Materials Research Society (E-MRS) 2002 Spring Meeting, Symposium C: Colloid 2002. Strasbourg (France), June 18 - 21, 2002.
  • Colloids and Surfaces A: Physicochemical and Engineering Aspects 217 (2003) 21-31

Publ.-Id: 4279 - Permalink


Analyses of the OECD Main Steam Line Break Benchmark with the Codes DYN3D and ATHLET
Grundmann, U.; Kliem, S.;
The OECD Main Steam Line Break (MSLB) Benchmark was defined to validate the thermal-hydraulic system codes coupled with three-dimensional neutron kinetic codes. The reference problem is a MSLB in a pressurized water reactor (PWR) at end of cycle (EOC). The analyses were performed with the three-dimensional core model DYN3D, the thermal-hydraulic system code ATHLET and the coupled code DYN3D/ATHLET. The results of the DYN3D and ATHLET simulations based on the specification are compared with the results of other participants in the final OECD reports. The effect of the thermal-hydraulic nodalisation of the core, i.e. the number of coolant channels, and the influence of the coolant mixing inside the pressure vessel are studied in the paper. Calculations with a reduced number of coolant channels are performed often in coupled calculations for saving
computational time. Results of a 25-channel model were compared with the 177-channel calculation (1 channel/assembly). The results for global parameters like nuclear power show only small differences for the two models, however the prediction of local parameters such as maximum fuel temperatures requires a detailed thermal-hydraulic modeling. The effect of different coolant mixing within the reactor pressure vessel is investigated. It is shown that the influence of coolant mixing mitigates the accident
consequences when three-dimensional neutron kinetics is applied. In case of point kinetics, coolant mixing leads to an opposite effect. To profit from the three-dimensional core model, a realistic description of the coolant mixing in the coupled codes is a topic of further investigations.
Keywords: coupled neutron kinetics/thermal-hydraulics codes main steam line break analyses coolant mixing
  • Nuclear Technology 142(2003) 146-153

Publ.-Id: 4278 - Permalink


Balakovo-3 Ex-vessel Exercise: Analysis of Calculation Results Intercomparison and Comparison with Reference Data
Borodkin, G.; Böhmer, B.; Konheiser, J.; Manturov, G.; Polke, E.; Brodkin, E.; Jegorov, A.; Zaritsky, S.;
Ex-vessel neutron dosimetry at NPP with VVER was used for validation of 3D absolute neutron fluence calculations. As second step of the VVER-1000 Balakovo-3 Ex-vessel Exercise, an analysis of calculational results has been performed. The reference experimental data - End-Of-Irradiation activities AEOI - were used as criteria of validation. The purpose of the research was to perform an intercomparison of independent calculational results and comparison with reference data of the full-scale VVER-1000 ex-vessel experiment. New and improved results of calculations analysed in the paper were run with codes and applied libraries DORT/BUGLE-96, DORT/EURLIB-6, DORT/ABBN-93 (and ABBN-93 modifications), TRAMO/ENDF/B-VI, MCNP/ENDF/B-VI. Calculated pure 3D or 3D synthesis multigroup neutron fluence rates in positions of experimental capsules provided by every calculator were used as basic calculational information. As first step of their comparative analysis a study was done of the used calculation input data prepared on the base of the same reactor information. For example, a difference of neutron source model details may be a reason of some discrepancy of results obtained by similar calculational procedures. Aspects of the influence of different dosimetry cross sections and local power history on the calculation of AEOI from calculated spectra were investigated. The analysed dosimetry cross section libraries were IRDF-90v2, JENDL-D99, RRDF-98 and ENDF/B-VI based BUGLE-96 responses. Final C/E values were based on AEOI. The C/E values for threshold dosimetry reactions 237Np(n,f), 93Nb(n,n'), 238U(n,f), 58Ni(n,p), 54Fe(n,p), 46Ti(n,p) and 63Cu(n,a), which are widely used in reactor pressure vessel dosimetry for fast neutron fluence evaluation, showed on the whole the expected agreement (better 20 %). It was found that the C/E data for the Balakovo-3 exercise in application to the 237Np(n,f) and 93Nb(n,n') reactions may be improved in case of using JENDL-D99 library. Another new aspect of the Balakovo-3 research is an analysis and intercomparison of calculational and experimental results for (n,g) dosimetry reactions. Different type (n,g) detectors were irradiated in cadmium. The obtained reaction rates characterize the distribution of epithermal neutrons. A comparison of the reaction rates, for example, for reactions 93Nb(n,g), 69Co(n,g) and 103Ag(n,g) in case of DORT/BUGLE-96 calculations has shown a coincidence of experiment and calculation data within ± 11 %. For one ex-vessel position where bare (n,g) detectors were irradiated thermal neutron parameters were evaluated and compared.
  • Lecture (Conference)
    11th International Symposium on Reactor Dosimetry, August 18-23, 2002 in Brussels, Belgium, Proceedings by World Scientific Publ., ISBN 981-238-448-0, p. 665-673
  • Contribution to proceedings
    11th International Symposium on Reactor Dosimetry, August 18-23, 2002 in Brussels, Belgium, Proceedings by World Scientific Publ., ISBN 981-238-448-0, p. 665-673

Publ.-Id: 4277 - Permalink


Complexation of uranium (VI) by three eco-types of Acidithiobacillus ferrooxidans studied using time-resolved laser-induced fluorescence spectroscopy and infrared spectroscopy
Merroun, M.; Geipel, G.; Nicolai, R.; Heise, K.-H.; Selenska-Pobell, S.;
Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used to study the properties of uranium complexes (emission spectra and fluorescence lifetimes) formed by the cells of the three recently described eco-types of Acidithiobacillus ferrooxidans. The results demonstrated that these complexes have different lifetimes which increase in the same order as the capability of the strains to accumulate uranium. The complexes built by the cells of the eco-type II were the strongest, whereas, those of the eco-types I and III were significantly weaker. The emission spectra of all A. ferrooxidans complexes were almost identical to those of the uranyl organic phosphate compounds. The latter funding was confirmed by infrared spectroscopic analysis.
Keywords: TRLFS, IRS, uranium, Acidithiobacillus ferrooxidans eco-types
  • Biometals 16, 331-339 (2003)

Publ.-Id: 4275 - Permalink


Column experiments with heap material of Kupferschiefer mining and thermodynamic interpretation
Mibus, J.;
Material of a mine waste dump of Kupferschiefer mining was investigated in column and equilibrium experiments in closed vessels over 64 days and 90 days, respectively. The de-ployed solids are composed of silicate phases, calcite, dolomite, gypsum, and a few percent of residual sulfides, already indicating a depletion of the karstifyable material and in particular a dedolomitization. The development of the solution composition at the columns outflow is characterized by a steady increase of alkalinity with a striking transient maximum, succeed-ing draw back and equilibration. In connection with an increasing mole fraction of magnesium in solution this phenomenon is interpreted as consequence of dedolomitization and depicted in abinary solubility diagram according to Lippmann (1980). In calcium rich pore waters (due to gypsum dissolution) dolomite dissolves incongruently precipitating calcite. Such compli-cated reaction paths are usually not identified by "crude" batch experiments. Moreover it could be shown that the formation of preferred flow paths may even affect the solution com-position in particular cases. In these experiments an estimation of transport parameters was not yet carried out, but is planned for the future to apply reactive transport codes for model-ing these processes.
  • FZKA scientific report 6721, 55-60
  • Poster
    Workshop on Modelling of Coupled Transport Reaction Processes TrePro 2002, 20.-21.03.2002, Karlsruhe, Deutschland

Publ.-Id: 4274 - Permalink


ANISN-DORT-ROZ-MCNP-TRAMO Neutron-Gamma Flux Intercomparison Exercise for a Simple Testing Model
Böhmer, B.; Borodkin, G.; Brodkin, E.; Egorov, A.; Konheiser, J.; Kozhevnikov, S.; Manturov, G.; Voloschenko, A.; Zaritsky, S.;
The ability of transport codes ANISN, DORT, ROZ-6, MCNP and TRAMO, as well as nuclear data libraries BUGLE-96, ABBN-93, VITAMIN-B6 and ENDF/B-6 to deliver consistent gamma and neutron flux results was tested in calculation of an one-dimensional cylindrical model consisting of a homogeneous core and an outer zone with a single material. Model variants with H2O, Fe, Cr and Ni in the outer zones were investigated. The results are compared with MCNP-ENDF/B-6 results. Discrepancies are discussed. The specified test model is proposed as a computational benchmark for testing calculation codes and data libraries.
Keywords: Coupled neutron-gamma transport calculations, neutron data libraries, Monte Carlo Codes, discrete ordinate codes, calculational benchmark
  • Poster
    11th International Symposium on Reactor Dosimetry, 18 -23 August 2002 in Brussels, Belgium, Proceedings by World Scientific Publ., ISBN 981-238-448-0, p. 572-579
  • Lecture (Conference)
    13th Seminar on Algorithms and Codes for Neutronics Calculations of Nuclear Reactors, 26-29 October 2002, Obninsk, Rußland
  • Contribution to proceedings
    11th International Symposium on Reactor Dosimetry, 18 -23 August 2002 in Brussels, Belgium, Proceedings by World Scientific Publ., ISBN 981-238-448-0, p. 572-579

Publ.-Id: 4273 - Permalink


Neutron and Gamma Fluence and Radiation Damage Parameters of Ex-core Components of Russian and German Light Water Reactors
Böhmer, B.; Borodkin, G.; Konheiser, J.; Noack, K.; Polke, E.; Rogov, A.; Vladimirov, P.;
Radiation embrittlement of pressure vessel steel in mixed neutron-gamma fields is mostly determined by neutrons, but in some cases also by gamma-radiation. Depending on the reactor type, gamma radiation can influence evaluations of lead factors of surveillance specimens, effect the interpretation of results of irradiation experiments and finally, it can result in changed pressure vessel lifetime evaluations. This work aims to facilitate for some reactor types the evaluation of the importance of gamma radiation for embrittlement studies. Absolute neutron and gamma fluence spectra had been calculated for two core loading variants of the Russian PWR type VVER-1000, for a German PWR of Konvoi-Type and for a German BWR. Based on the calculated spectra several fluence integrals and radiation damage parameters were derived for the region of the midplane azimuthal flux maximum for different radial positions between the core and the biological shield, particularly, the inner and outer PV walls, the ¼ PV thickness and the surveillance positions. The relative contributions of gamma radiation to the sums of gamma and neutron contributions are of special interest. As damage parameters the displacements per atom of iron are given separately for neutrons and gammas as well as some rough estimations of the numbers of freely migrating defects. To get some notion about the uncertainty of the obtained dpa, the calculations were performed using different dpa cross section evaluations. Additionally, gamma produced dpa were calculated by means of the Monte Carlo code EGS.
Another parameter of practical interest for pressure vessel dosimetry, the contribution of photofission to the total number fissions, was calculated for the detector reactions 237Np(n,f) and 238U(n,f).
Most of the calculations were performed using a 3D synthesis of 2D/1D-flux distributions obtained by the DORT code with the BUGLE-96 library. To increase the reliability of the evaluations some of the calculations were repeated by different laboratories. For two reactors the influence of the group approximation on the calculation results was investigated by parallel calculations with the continuous energy Monte Carlo code MCNP using nuclear data from the library ENDF/B-VI.
The results were compared and the reasons of found discrepancies were discussed.
  • Lecture (Conference)
    11th International Symposium on Reactor Dosimetry, 18 -23 August 2002 in Brussels, Belgium, Proceedings by World Scientific Publ., ISBN 981-238-448-0, p. 286-294
  • Contribution to proceedings
    11th International Symposium on Reactor Dosimetry, 18 -23 August 2002 in Brussels, Belgium, Proceedings by World Scientific Publ., ISBN 981-238-448-0, p. 286-294

Publ.-Id: 4272 - Permalink


TOPFLOW - A new multipurpose thermalhydraulic test facility for the investigation of steady state and transient two phase flow phenomena
Schaffrath, A.; Weiß, F.-P.;
The Forschungszentrum Rossendorf (FZR) e.V. is building a new large-scale test facility for thermal hydraulic single effect tests, named TOPFLOW. The acronym stands for Transient Two Phase Flow Test Facility. It will mainly be used for the investigation of generic and applied steady state and transient two phase flow phenomena in power- and process industries. Main research activities are the investigation of:
· transient flow regimes in horizontal, vertical and inclined tubes,
· the dynamic behaviour of interphase areas in gas-liquid flows,
· critical mass flows and oscillations during depressurization of chemical reactors,
· natural convection in large pools with local heating,
· natural convection in parallel channels and feed pipes and
· condensation phenomena (e.g. in emergency and isolation condensers, WWER steam generators).
It is FZR strategy to use TOPFLOW as a central experimental basis for the nuclear competence centre, rejoining FZR, the Technical University of Dresden (TUD) and the University of Applied Sciences Zittau-Görlitz (HTW) and to offer it to working groups throughout Europe. They will be invited to come to Rossendorf with their ideas and to perform their experiments here making use of the parameters (power, water and steam mass flow, pressure range, measuring instrumentation) and the multipurpose character of the test facility.

Keywords: TOPFLOW, two-phase flow, test facility
  • Lecture (Conference)
    NUSIM 2002 (11. Meeting of Nuclear Specialists from Slovakia, Czech and Germany), 13.-15.03.2002, Dresden

Publ.-Id: 4270 - Permalink


A small and compact AMS facility for tritium depth profiling
Friedrich, M.; Pilz, W.; Glugla, M.; Bekris, N.; Kiisk, M.; Liechtenstein, V.;
Depth profiling measurements of tritium at carbon samples have been performed during the past seven years at the AMS facility installed at the Rossendorf 3 MV tandetron. The samples have been cut from the inner wall of the fusion experiments ASDEX-upgrade/Garching and JET/Culham. The increasing amounts of tritium inside the samples from JET have been required a dedicated AMS facility to prevent any contamination of the versatile 3 MV tandetron. On base of an air-insulated 100 kV tandem accelerator equipped with a gas stripper a small dedicated AMS facility for tritium depth profiling was installed, tested and used for routinely measurements. After successful tests of diamond-like carbon (DLC) stripper foils at this accelerator a small and compact SF6-insulated 100 kV tandem accelerator with a DLC-stripper has been installed at the AMS facility. Results measured with the different tandem accelerators are presented.
Keywords: Tritium, Fusion, Mass Spectrometry, Electrostatic Accelerators
  • Contribution to proceedings
    PRAMANA-journal of physics, Vol. 59, No. 6 (2002) 1053. Proccedings of the 9th International Conference on Heavy Ion Accelerator Technology, New Delhi, India, January 14-18, 2002.

Publ.-Id: 4269 - Permalink


Kinetische Modellierung von PET-Studien des Neurokinin1-Rezeptors im menschlichen Hirn
Hinz, R.;
(kein Abstrakt)
  • Lecture (others)
    Universität Leipzig Klinik und Poliklinik für Nuklearmedizin Institut für Interdisziplinäre Isotopenforschung 20. Dezember 2001

Publ.-Id: 4268 - Permalink


Kinetic Modelling of Neurokinin-1 Receptor Studies in Human Brain
Hinz, R.;
(no abstract available)
  • Lecture (others)
    PET Methodology Seminar, Imaging Research Solutions Limited, London, UK 14 December 2001

Publ.-Id: 4267 - Permalink


Kinetic Modelling of NK1 Receptor Studies in Human Brain
Hinz, R.;
(no abstract available)
  • Lecture (others)
    National Institutes of Health, Positron Emission Tomography Department Bethesda, Maryland, USA, November 2, 2001

Publ.-Id: 4266 - Permalink


Gamma and Neutron Spectra Investigations in Iron-Water Benchmark Configurations for the Verification of Monte Carlo Calculations in Reactor Material Dosimetry
Böhmer, B.; Grantz, M.; Hansen, W.; Hinke, D.; Konheiser, J.; Mehner, H.-C.; Noack, K.; Schneider, R.; Stephan, I.; Unholzer, S.;
In order to validate Monte Carlo calculations for coupled neutron/gamma problems in reactor dosimetry an experimental benchmark programme at two low power reactors was started to measure both, neutron and gamma flux spectra behind and inside of transmission modules consisting of variable iron and water slabs. The comparison of the first series of experiments with MCNP calculations is presented.
Keywords: reactor dosimetry, neutron spectrometry, gamma spectrometry, reactor pressure vessel, steel embrittlemen, coupled neutron, gamma fluence calculations, benchmark
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Stuttgart, 14.-16. Mai 2002, Proceedings pp. 511-514
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Stuttgart, 14.-16. Mai 2002, Proceedings pp. 511-514

Publ.-Id: 4265 - Permalink


Detection and Characterization of ultrafine Fe-As-Pb colloids in acid rock drainage solution from an ore mine
Zänker, H.; Moll, H.; Richter, W.; Brendler, V.; Hennig, C.; Reich, T.; Kluge, A.; Hüttig, G.;
The processes of sulfide oxidation, water acidification and water mineralization in abandoned ore mines is closely associated with the existence of gangue fissures in the host rock that contain clay minerals and finely-divided sulfide ores. These fis-sures release highly mineralized, red-colored acid rock drainage (ARD) solutions which can easily be collected from pools in front of the fissures. ARD solution from an abandoned Zn-Pb-Ag mine at Freiberg, Germany, (pH 2.7, sulfate concentration 411 mmol/l, Fe concentration 93,5 mmol/l) was investigated by photon correlation spec-troscopy, centrifugation, filtration, ultrafiltration, scanning electron microscopy, ICP-MS, AAS, ion chromatography, TOC analysis, and X-ray absorption fine structure (EXAFS) spectroscopy. The question was if this ARD solution contains colloidal par-ticles of the lower nanometer range or if it is particle-free after the common filtration through a 450-nm filter. We found that the solution contains a small amount (about 20 mg/l) of submicron particles of about 100 nm in size. However, the major colloidal component was shown to be a population of ultrafine particles of less than 5 nm. The concentration of these particles is about 1 g/l. They consist of Fe, As and Pb com-pounds. According to EXAFS spectroscopy, the most probable mineralogical compo-sition of these particles is a mixture of hydronium jarosite (HFe3(SO4)2(OH)6) and schwertmannite (ideally Fe8O8(OH)6SO4). We also observed the formation of a rela-tively coarse precipitate of a similar mineralogy in the colloidal solution over a time span of months. The ultrafine colloids are obviously an intermediate in the formation process of the long-term precipitate. The arsenic is probably bound onto the ultrafine colloidal particles as a bidentate binuclear arsenate surface complex (inner-sphere complex). However, the transformation of the colloids to the more aggregated long-term precipitate leads to the incorporation of the arsenic into the interior of the iron hydroxy sulfate structures. The mechanism of this incorporation could be the substi-tution of arsenate for sulfate in the jarosite structure and/or the formation of very small scorodite clusters as occlusions within the oxyhydroxysulfate structures. The lead might occur as anglesite (PbSO4).
Keywords: colloids, ultrafiltration, EXAFS, acid rock drainage, jarosite, schwertmannite, arsenate
  • Lecture (Conference)
    XXVII General Assembly of the European Geophysical Society. Nice, France, 21 - 26 April 2002

Publ.-Id: 4260 - Permalink


Synthesis and structural characterization of two cis-dioxorhenium(V) ReO2[SN][P] mixed-ligand complexes
Bouziotis, P.; Papagiannopoulou, D.; Pirmettis, I.; Pelecanou, M.; Raptopoulou, C. P.; Stassinopoulou, C. I.; Terzis, A.; Friebe, M.; Spies, H.; Papadopoulos, M.; Chiotellis, E.;
Two novel five-coordinate cis-dioxorhenium(V) complexes of the general formula ReO2[R2NCH2CH2S][PPh3] (R2N=Et2N, complex 1 and R2N=(o-CH3O-C6H4N(CH2CH2)2N, complex 2) have been synthesized by reacting ReOCl3(PPh3)2 with the respective bidentate ligands R2NCH2CH2SH. The complexes have been characterized by elemental analysis, IR, NMR spectroscopies and X-ray crystallography. X-ray crystallographic studies showed that the coordination geometry around rhenium is distorted trigonal bipyramidal. the basal plane is defined by the two doubly bonded oxygen atoms and the sulfur of the bidentate ligand, while the nitrogen of the ligand and the phosphorus occupy the apical positions.
Keywords: Crystal structures; Rhenium complexes; Dioxo complexes
  • Inorganica Chimica Acta 320 (2001) 174-177

Publ.-Id: 4259 - Permalink


Simulation of two surge line break experiments at the PMK-2 Test Facility using the code ATHLET
Schäfer, F.; Krepper, E.; Prasser, H.-M.; Szabados, L.; Ezsöl, G.;
Results of two surge line break experiments, which were conducted at the PMK-2 test facility, are presented. The thermo-hydraulic computer code ATHLET, which was developed by GRS (Gesellschaft für Anlagen- und Reaktorsicherheit) mbH, was used for post-test calculations. The experiments simulate a break of the pressurizer surge line in the hot leg of a VVER-440-type reactor with different injection modes from the ECC systems. The main phenomena of the experiments are discussed and in case of selected events a more detailed interpretation with help of the measured void fraction, obtained with a special measurement device, is given. The results of the experiments and the ATHLET calculations are compared. In both experiments natural circulation instabilities could be observed. The physical mechanisms of the instabilities are discussed and it could be shown, that ATHLET can calculate the instabilities in good agreement with the experimental data.
Keywords: Thermo-hydraulics, Simulations, Instabilities, ATHLET
  • Lecture (Conference)
    Annual Meeting on Nuclear Technology, May 14-16, 2002, Stuttgart, Germany
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology, May 14-16, 2002, Stuttgart, Germany

Publ.-Id: 4258 - Permalink


Experimental analysis of crossflow in the reactor core geometry.
Kliem, M.;
A new method for the thermal-hydraulic calculations in the reactor core using a porous media approach is presented in this paper.
The Core Crossflow Experimental Facility (CCEF) was built for the validation of this method.
The comparison of the calculations using this method with the experimental data from CCEF are also presented.
Keywords: reactor core, crossflow, CCEF
  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2002, Stuttgart, Germany, May 14-16, 2002 Proceedings pp. 55-58
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2002, Stuttgart, Germany, May 14-16, 2002 Proceedings pp. 55-58

Publ.-Id: 4257 - Permalink


High-spin structure of the spherical nucleus 90Y
Rainovski, G.; Schwengner, R.; Schilling, K. D.; Wagner, A.; Jungclaus, A.; Galindo, E.; Thelen, O.; Napoli, D. R.; Ur, C.; de Angelis, G.; Axiotis, M.; Gadea, A.; Marginean, N.; Martinez, T.; Kröll, T.;
High-spin states in 90Y were populated in the 82Se(11B,3n)
reaction at a beam energy of 37 MeV. Gamma rays were detected with the spectrometer GASP. The level scheme of 90Y was extended up to J^\pi = (18^+) at 9.6 MeV. Mean lifetimes of four levels were determined using the Doppler-shift-attenuation method. The structure of 90Y was
interpreted in terms of the shell model. The calculations were performed in the model space \pi(0f_{5/2},1p_{3/2},1p_{1/2},0g_{9/2})
\nu(1p_{1/2},0g_{9/2},1d_{5/2}) and in an extended space including the \nu(0g_{7/2})$ orbital as well. The calculations in the extended model space reveal a correspondence between states in ^{90}Y and ^{89}Y. Moreover, a combination of the predicted states with J^\pi \geq 14^(+) can be found
that reproduces the large B(M1) values of up to about 1 W.u.
Keywords: Nuclear structure. In-beam gamma-ray spectroscopy. Shell model.
  • Physical Review C, Vol. 65, 044327

Publ.-Id: 4256 - Permalink


Synthetic Humic Acids A Useful Tool to Study the Interaction of Humic Acids with Actinides in the Environment
Sachs, S.; Schmeide, K.; Heise, K.-H.; Bernhard, G.;
The present work gives a detailed overview about our motivation for the synthesis of humic acid model substances. Exemplary for one synthetic humic acid (type M42), which is synthesized from xylose, glutamic acid and water [1], the synthesis, 14C-labeling ([14C]M42) and modification (M42-PB) of humic acids are described. We will discuss the characterization of these synthetic humic acids in comparison to natural humic acids from the literature as well as to natural humic acid Kranichsee [2]. This humic acid was isolated from surface water of the mountain bog "Kleiner Kranichsee" (Johanngeorgenstadt, Western Saxony, Germany) applying standard isolation techniques for humic acids.
The application of synthetic humic acid model substances will be presented with two examples. First, we will demonstrate the use of humic acid type M42 and humic acid type M42 with blocked phenolic and other blocked acidic OH groups (M42-PB) as model substances for the investigation of the neptunium(V) complexation by humic acids.
Secondly, we will discuss the application of 14C-labeled synthetic humic acid type M42 in batch and column experiments. The intend of these investigations is to improve the knowledge about the influence of humic acids on the mobilization or immobilization of actinides under natural conditions.
In addition to humic acid-like melanoidins, we synthesize humic acid model substances with distinct redox functionalities. Applying these model substances, detailed investigations with regard to the redox behavior of humic acids as well as to the redox stability of actinide humate complexes can be performed. In the present work we will give an brief overview about the synthesis, characterization and application of humic acids with pronounced redox functionalities.

[1] S. Pompe (Sachs), M. Bubner, K. Schmeide, K.H. Heise, G. Bernhard, H. Nitsche, 'Influence of Humic Acids on the Migration Behavior of Radioactive and Non-radioactive Substances under Conditions Close to Nature. Synthesis, Radiometric Determination of Functional Groups, Complexation', Report FZR-290, Rossendorf, 2000.
[2] K. Schmeide, H. Zänker, K.H. Heise, H. Nitsche, in Report FZKA 6124, G. Buckau (ed.), Karlsruhe, 1998, p. 161.
Keywords: Humic Acid, Synthesis, Modification, Labeling, Characterization, Complexation, Actinides, Neptunium, Migration
  • Lecture (Conference)
    20th Anniversary Conference of the International Humic Substances Society, July 21-26, 2002, Northeastern University Boston, Massachusetts, USA

Publ.-Id: 4255 - Permalink


Studies on interactions of actinides with organic ligands using femtosecond-laser-induced spectroscopy
Geipel, G.; Bernhard, G.; Fanghänel, T.;
Polyelectrolytic organic macromolecules, like humic substances, are important complexing agents towards actinide metal ions. Due to these properties humic substances are possible carriers for the migration of actinides in the environment. The study of the high molecular compounds is very complex. Therefore the investigation of simple model ligands would give a more detailed description of the binding behavior of humic substances. Especially the different bonding of carboxylic and phenolic group and the discrimination between them is of interest to get more detailed information about the complex formation. The various hydroxy benzoic acids allow the investigation of these differences.
To study the complex formation of actinides with such organic ligands we used the new, recently developed tool of femtosecond laser-induced time-resolved fluorescence spectroscopy. The method uses the fluorescence properties of organic ligands with p-electron systems and their change by interaction with metal ions to study the complex formation of these systems.
The method was validated by study of the deprotonation of 2,3 dihydroxybenzoic acid. Within the error limits a very good agreement of the third protonation constant was found.
The studies of the complex formation of uranium(VI) with 2,3 dihydroxybenzoic acid in the pH range from 3.0 to 4.5 showed an one to one complex. The dependence of the complex formation on pH leads to the conclusion that besides the carboxylic group one of the two phenolic OH-groups contributes to the complex formation. The formation constant was determined to be log K(I=0.1M) = - 3.02 ± 0.09.
Studies of the complex formation in the system neptunium(V)-2,3 dihydroxybenzoic acid showed a completely different behavior. At low pH values also an one to one complex formation was found. This complex formation was not dependent on pH. That means complexes with the deprotonated carboxylic group were formed.
The formation constant was determined to be log K(I=0.1M) = 0.11 ± 0.04. With increasing pH the complex reaction changes. An intermediate complex can be observed by its own fluorescence properties. At pH values higher then six an one to two complex will be formed. The complex formation constants and the stoichiometry of the complex reaction will presented.
  • Lecture (Conference)
    14th Radiochemical Conference, Marianzke Lazne, 14-19. April 2002

Publ.-Id: 4254 - Permalink


Inner-sphere, outer-sphere and ternary surface complexes: a TRLFS study of the sorption process of Eu(III) onto smectite and kaolinite
Stumpf, T.; Bauer, A.; Coppin, F.; Fanghänel, T.; Kim, I.;
Summary. The surface sorption process of Eu(III) onto smectite and kaolinite was investigated by time-resolved laser fluorescence spectroscopy (TRLFS) in the trace concentration range. The experiments were performed in 0.025 M and 0.45 M NaClO4. The sorption process of Eu(III) onto smectite was obtained by TRLFS under atmospheric conditions and in absence of CO2. The pH was varied between 3.5 and 9 at a fixed metal ion concentration of 3.3x10-6 mol/L Eu(III). At low pH (< 4) the metal ion keeps its complete hydration sphere indicating outer-sphere complexation. With increasing pH the formation of an inner-sphere Eu(III) surface complex was observed. The differences in the spectra and the fluorescence emission lifetimes of the surface sorbed Eu(III) in presence and absence of carbonate indicate the formation of ternary clay/Eu(III)/carbonate complexes. The different europium/clay surface complexes were characterized by their fluorescence emission spectra (5D0®7F1/5D0®7F2 intensity ratio) and their fluorescence emission lifetime.


  • Radiochimica Acta

Publ.-Id: 4253 - Permalink


Analyse der Schädigung eines Druckbehälters in Simulationsexperimenten von nuklearen Kernschmelzunfällen
Böhmert, J.; Müller, G.; Willschütz, H.-G.; Sehgal, B. R.;
Das Verhalten eines Reaktordruckbehälters bei Kernschmelzunfällen ist von hoher sicherheitstechnischer Bedeutung für die Beherrschung derartiger Störfälle. An der Königlich-Technischen Hochschule Stockholm werden in einem umfangreichen Programm (FOREVER - Failure Of REactor VEssel Retention) die Verformung und das Versagenverhalten des Druckbehälters unter der thermischen Belastung einer oxidischen Schmelze untersucht. Die Experimente werden begleitet durch Finite-Element-Modell-Vorausrechnungen und durch metallografische Nachuntersuchungen. Die Gefügeänderungen geben Hinweise auf die aufgetretenen Maximaltemperaturen und Temperaturgradienten, auf die Wechselwirkungen mit der Schmelze und der umgebenden Atmosphäre sowie auf den Versagensmechanismus. Am Beispiel eines FOREVER-Experimentes werden die Ergebnisse der Nachtestuntersuchungen mit den FE-Modellrechnungen verglichen. Die metallografischen Befunde bestätigen die FEM-Vorausrechnungen.
  • Lecture (Conference)
    DGM-Tagung Werkstoffprüfung 2001, Bad Nauheim, 6. - 7. 12. 2001

Publ.-Id: 4252 - Permalink


Separation Control On A NACA 0015 Hydrofoil Using Lorentz Forces
Weier, T.; Gerbeth, G.; Mutschke, G.; Lielausis, O.; Lammers, G.;
The use of electromagnetic forces to control the flow of electrically
conducting fluids is mostly associated with highly conducting liquids
like liquid metals and semiconductor melts. Only recently,
Electro-magnetic Flow Control for fluids of low electrical
conductivity like seawater has gained increasing interest. Most of the
published experimental and numerical work in this emerging field is
dedicated to skin friction reduction in turbulent boundary layers.

The present paper is focused on utilizing the accelerating effect of a
streamwise Lorentz force to prevent flow separation at the suction
side of a NACA 0015 hydrofoil. While the basic effects of
separation suppression and circulation enhancement have been
shown in [1], we will concentrate on the comparison of the
experimental results with such of separation control by steady
blowing. For this purpose, the Lorentz force strength will be given in
terms of an electromagnetic momentum coefficient C_EMHD, describing
the ratio of the total electromagnetic force imposed on the flow to
the product of dynamic pressure and wing area. Force measurements in
the Reynolds number range 2.9 10E4 < Re < 3.7 10E5, obtained with 3
different hydrofoils will be used to give a first approximation of the
maximum lift gain in dependence upon Reynolds number and Lorentz
force. Again, the electromagnetic momentum coefficient seems to be an
acceptable correlation factor to describe the control effect of the
Lorentz force in different flow configurations.
  • Lecture (Conference)
    12th European Drag Reduction Meeting, 18-20 April 2002, Herning, Denmark

Publ.-Id: 4251 - Permalink


Die kolloidalen Bestandteile von Lettenwasser (Acid Rock Drainage) aus der Himmelfahrt Fundgrube in Freiberg/Sa.
Zänker, H.; Moll, H.; Richter, W.; Brendler, V.; Hennig, C.; Reich, T.; Kluge, A.; Hüttig, G.;
Es wurde gezeigt, daß das Lettenwasser eine kleine Menge (ca. 20 mg/l) an Submicronpartiklen von etwa 100 nm Größe enthält. Die kolloidale Hauptkomponente sind jedoch ultrafeine Partikel einer Größe von weniger als 5 nm. Sie weisen eine Konzentration von ca. 1 g/l auf. Diese Partikel bestehen wahrscheinlich aus einem Gemisch von H-Jarosit und Schwertmannit und sind ein Zwischenprodukt bei der Ausscheidung gröberkristalliner Präzipitate. Außerdem tragen sie Arsen und Blei. Das As ist offensichtlich als Arsenat-Oberflächenkomplex an die ultrafeinen Partikel gebunden. Bei der Ausscheidung von gröberkristallinen Fe-Oxyhydroxisulfatpräzipitaten scheint dann auch Arsenateinbau in das Innere der Oxyhydroxisulfatstrukturen eine Rolle zu spielen.
Keywords: Acid Rock Drainage, Kolloide, Eisenoxyhydroxysulfate, Arsenat
  • Lecture (Conference)
    Jahrestagung der Wasserchemischen Gesellschaft, Eichstätt/Altmühltal, 6.-8. Mai 2002

Publ.-Id: 4245 - Permalink


Acceptance and count rate estimates for experiments on subthreshold Phi meson production in central collisions of C + C at 2 AGeV
Kotte, R.; Kämpfer, B.;
Monte-Carlo estimates of the subthreshold Phi meson production are performed for the reaction 12C + 12C at 2 AGeV assuming the Phi's to be emitted isotropically and distributed thermally in the center-of-mass system of the colliding nuclei. Different scenarios involving the detector installations FOPI and HADES at SIS/GSI are considered to determine the expected yields of Phi(1020) mesons identified via the K+K- and e+e- decay channels.

Keywords: PACS. 25.75.-q; 25.75.Dw
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-339 Januar 2002

Downloads:

Publ.-Id: 4244 - Permalink


phi puzzle in heavy-ion collisions at 2 AGeV: how many K^- from phi decays?
Kämpfer, B.; Kotte, R.; Hartnack, C.; Aichelin, J.;
The preliminary experimental data on phi production in the reaction Ni(1.93 AGeV) + Ni point to a puzzling high phi yield which can not be reproduced with present transport codes. We survey the experimental situation and present prospects for dedicated measurements of the phi multiplicities with the $K^+ K^-$ and $e^+ e^-$ channels at HADES and FOPI.
Keywords: Haevy-ion collisions, kaon production, phi mesons
  • J.Phys.G28:2035-2040,2002 arXiv: nucl-th/0112040

Publ.-Id: 4243 - Permalink


Ion Induced Formation of Regular Nanostructures on Amorphous GaSb Surfaces
Facsko, S.; Bobek, T.; Kurz, H.; Dekorsy, T.; Kyrsta, R.; Cremer, R.;
Crystalline and amorphous GaSb surfaces are compared concerning their response
to sputter erosion with low-energy Ar$^+$-ions under normal incidence. We show
that the formation of regular nanostructures on GaSb is basically independent
on whether the initial material is crystalline or amorphous. The similarity in
the temporal and spatial evolution demonstrates that the dynamics of the
morphology evolution is entirely controlled by a thin amorphous
nonstoichiometric surface layer.
Keywords: self organization, ion induced surface modification, quantum dots, nanotechnology
  • Applied Physics Letters 80 (2002) 130-132

Publ.-Id: 4242 - Permalink


Two crossovers in the pseudogap regime of YBa$_2$Cu$_3$O$_{7-x}$ superconductors observed by ultrafast spectroscopy
Misochko, O. V.; Georgiev, N.; Dekorsy, T.; Helm, M.;
We have investigated the temperature dependence of the optical reflectivity on
a femtosecond scale in a near-optimally doped YBa$_2$Cu$_3$O$_{7-x}$
superconductor. The combined study of the lattice and carrier dynamics at
temperatures above T$_c$ allows us to identify two crossover temperatures in
the normal state giving evidence for an inhomogeneity of the pseudogap regime.
These crossovers exhibit a clear hysteresis behavior depending on the direction
of temperature change. The carrier and lattice dynamics within the crossover
regimes show distinct differences from and similarities to the superconducting
state, which may help in choosing between the competing theories for the
pseudogap state.
Keywords: HTSC, coherent phonons, pseudogap, femtosecond spectroscopy
  • Physical Review Letters 89 (2002) 067002-067005

Publ.-Id: 4241 - Permalink


Prophylaxis of restenosis with 186Re-labeled stents in a rabbit model
Tepe, G.; Dinkelborg, L. M.; Brehme, U.; Muschick, P.; Noll, B.; Dietrich, T.; Greschniok, A.; Baumbach, A.; Claussen, C. D.; Duda, S. H.;
Background:
Intraluminal beta-irradiation has been shown to decrease neointimal proliferation after angioplasty in experimental models. The purpose of this study was to test the technical feasibility and biological effects of 186Re-labeled stents.

Methods and results:
Thirty-four New Zealand White rabbits were fed a 0.5% cholesterol diet before balloon angioplasty and insertion of Palmaz stents in the infrarenal aorta. The animals were killed 7 weeks after stent implantation. Two of 34 animals died prematurely (aortic leak, pneumonia). Control stents (n=7) were compared with 186Re stents (2.6 MBq [n=6], 8.1 MBq [n=5], 16 MBq [n=6], and 25.3 MBq [n=8]). Stent application was successful in all cases. No thrombus occlusion was observed. After 7 weeks, neointima formation was 2.2±0.2 mm2 in the control group. In the treatment groups, a dose-dependent neointima reduction was detectable (0.5±0.5 mm2 [2.6 MBq], 0.4±0.4 mm2 [8.1 MBq], and 0 mm2 [16.0 MBq, 25.3 MBq]). No induction of neointimal formation was observed at the edges of the stents. Radiation resulted in delayed reendothelialization.

Conclusions:
186Re stents were capable of reducing neointima formation in a dose-dependent fashion. 186Re stents did not cause late thrombosis or neointimal induction at the stent margins in the observation period of 7 weeks.


Keywords: atherosclerosis, angioplasty, hypertension, restenosis, radioisotopes, stents
  • Circulation 104 (2001) 480-485

Publ.-Id: 4240 - Permalink


Magnetic and collective rotation in 79Br
Schwengner, R.; Dönau, F.; Servene, T.; Schnare, H.; Reif, J.; Winter, G.; Käubler, L.; Prade, H.; Skoda, S.; Eberth, J.; Thomas, H. G.; Becker, F.; Fiedler, B.; Freund, S.; Kasemann, S.; Steinhardt, T.; Thelen, O.; Härtlein, T.; Ender, C.; Köck, F.; Reiter, P.; Schwalm, D.;
Excited states of the nucleus 79Br were investigated via the reaction
76Ge(7Li,4n) at 35 MeV. Coincidence data of emitted gamma rays
were measured with an arrangement of six EUROBALL CLUSTER detectors.
The E2 bands built on the 9/2+ and 3/2- states were extended up to
J = 37/2 at E \approx 8.8 MeV. The M1 band starting with a 15/2-
state at 2.6 MeV was extended to J = (29/2) at E = 6.4 MeV. Cross-over
E2 transitions within this band were observed for the first time. Mean
lifetimes of 17 levels were deduced using the Doppler-shift-attenuation method.
The M1 band can be described within theTilted-Axis-Cranking model on the
basis of the tilted three-quasiparticle configuration
pi(g9/2) nu (g9/2) nu (fp) which has a triaxial shape. This band
appears as a mixed case including contributions of both, magnetic and
collective rotation.
Keywords: Nuclear spectroscopy. Cluster detectors. Magnetic and collective rotation. Tilted-axis cranking model.
  • Physical Review C, Vol. 65, 044326

Publ.-Id: 4239 - Permalink


On parabolic potential profile in ion sheaths
Mukherjee, S.;
Parabolic potential profiles are commonly used in ion sheaths as it simplifies the mathematical formulation and is observed in limited experimental observations, where measurement uncertainties justify it. However, before using the parabolic potential profile assumption in all cases, there are other factors that needs to be concerned. The article highlights these factors for collisionless and collisional ion sheaths.
Keywords: parabolic potential profile, ion sheath, ion matrix
  • PHYS SCRIPTA 66 (2): 165-167 AUG 2002

Publ.-Id: 4238 - Permalink


Fluid-Structure Interaction Experiments at the Cold Water Hammer Test Facility (CWHTF) of the FZ-Rossendorf
Altstadt, E.; Carl, H.; Weiß, R.;
In existing NPPs water hammers can occur in case of an inflow of sub-cooled water into pipes or other parts of the equipment, which are filled with steam or steam-water mixture. They also may appear as the consequence of valve closing or opening actions or of breaks in pipelines, with single phase or two-phase flow. The influence of the fluid-structure interaction on the magnitude of the loads on pipe walls and support structures is not yet completely understood. The lack of experimental data obtained at well defined geometric boundary conditions is a significant obstacle for the validation of codes which consider fluid-structure interaction. Furthermore, up to now the feedback from structural deformations to the fluid mechanics is not fully implemented in existing calculation software codes. Therefore, at FZR a cold water hammer test facility (CWHTF) was designed and built up.
Keywords: fluid-structure interaction waterhammer
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Stuttgart, Tagungsband S. 59-64, May 14-16, 2002
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Stuttgart, Tagungsband S. 59-64, May 14-16, 2002

Publ.-Id: 4237 - Permalink


The influence of the N=50 neutron-core on dipole excitations in 87Rb
Käubler, L.; Schilling, K. D.; Schwengner, R.; Dönau, F.; Grosse, E.; Belic, D.; von Brentano, P.; Bubner, M.; Fransen, C.; Grinberg, M.; Kneissl, U.; Kohstall, C.; Linnemann, A.; Matschinsky, P.; Nord, A.; Pietralla, N.; Pitz, H. H.; Scheck, M.; Stedile, F.; Werner, V.;
Dipole excitations in the semimagic N=50 nucleus ^{87}Rb were investigated at the Stuttgart Dynamitron
facility using bremsstrahlung with an endpoint energy of 4.0 MeV. The widths Gamma or the reduced excitation probabilities B(Pi 1)uparrow of 19 states were determined for the first time. The magnetic dipole excitations
are well reproduced in the framework of the shell model, however, these calculations cannot describe the observed electric dipole excitations.The 1/2^+ state at 3060 keV is proposedto be the weak coupling of an f_{5/2} proton hole to the 3^- octupole vibrational state in the N=50 core ^{88}Sr. The relatively strong E1 transition from that state to the ground state is explained as mainly the neutron h_{11/2} \rightarrow g_{9/2} transition. The breakup of the N=50 core and neutron excitations into the h_{11/2} shell are essential to describe electric dipole excitations, but neutron-core excitations do not play an important role for the structure of magnetic dipole excitations.
  • Physical Review C, Vol. 65, 054315

Publ.-Id: 4233 - Permalink


Analysis and insights about FE-Calculations of the EC-Forever-Experiments
Willschütz, H.-G.; Altstadt, E.; Weiß, F.-P.; Sehgal, B. R.;
To get an improved understanding and knowledge of the melt pool convection and the vessel creep and possible failure processes and modes occurring during the late phase of a core melt down accident the FOREVER-experiments are currently underway at the Division of Nuclear Power Safety of the Royal Institute of Technology Stockholm. These experiments are simulating the behaviour of the lower head of the RPV under the thermal loads of a convecting melt pool with decay heating, and under the pressure loads that the vessel experiences in a depressurization scenario.
Due to the multi axial creep deformation of the vessel with a non-uniform temperature field these experiments are on the one hand an excellent source of data to validate numerical creep models which are developed on the basis of uniaxial creep tests. On the other hand the results of pre-test calculations can be used to optimize the experimental procedure and can help to make on-site decisions during the experiment.
Therefore a Finite Element model is developed based on a multi-purpose code. After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Additionally metallographic post test investigations of the experiments are conducted to improve the numerical damage model and to adjust the correlation between the metallographic observations and the calculated damage. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios.
After analysing the calculations, it seems to be advantageous to introduce a vessel support which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.
Keywords: Scaled Core Melt Down Experiments, FEM Calculations, Advanced Creep Modelling, Metallographic Investigations, Vessel Support as Accident Mitigation Measure
  • Lecture (Conference)
    10th International Conference on Nuclear Engineering, Arlington, VA, USA, April 14-18, 2002, Proceedings on CD-ROM, Paper No. 22262
  • Contribution to proceedings
    10th International Conference on Nuclear Engineering, Arlington, VA, USA, April 14-18, 2002, Proceedings on CD-ROM, Paper No. 22262

Publ.-Id: 4232 - Permalink


Scaled vessel failure experiment analysis and investigation of a possible vessel support
Willschütz, H.-G.; Altstadt, E.; Weiß, F.-P.; Sehgal, B. R.;
Scaled coupled melt pool convection and vessel creep failure experiments are being performed in the FOREVER program at the Royal Institute of Technology, Stockholm. These experiments are simulating the lower head of a pressurized reactor vessel under the thermal load of a melt pool with internal heat sources [1]. Due to the multi axial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments offer an excellent opportunity to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module, the melt pool convection is simulated and the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep modeling procedure. Additionally, the material damage is evaluated considering the creep deformation as well as the prompt plasticity [2, 3].
Pre- and post-test calculations of at least 4 FOREVER experiments have been performed successfully [4]. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios.
After analyzing the calculations, it seems to be advantageous to introduce a vessel support which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.
Keywords: LWR scaled vessel failure experiments, FE-simulation, vessel support as accident mitigation strategy
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Stuttgart, May 14-16, 2002, Tagungsband S. 173-178
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Stuttgart, May 14-16, 2002, Tagungsband S. 173-178

Publ.-Id: 4231 - Permalink


First measurement of beta-decay properties of the proton drip-line nucleus 60Ga
Mazzocchi, C.; Janas, Z.; Döring, J.; Axiotis, M.; Batist, L.; Borcea, R.; Cano-Ott, D.; Caurier, E.; de Angelis, G.; Farnea, E.; Fassbender, A.; Gadea, A.; Grawe, H.; Jungclaus, A.; Kapica, M.; Kirchner, R.; Kurcewicz, J.; Lenzi, S.; Mart'Inez, T.; Mukha, I.; N'Acher, E.; Napoli, D. R.; Roeckl, E.; Rubio, B.; Schwengner, R.; Tain, J. L.; Ur, C. A.;
By using the fusion-evaporation reaction 28Si(36Ar,p3n) and spectroscopy of beta-delayed gamma rays and charged particles on mass-separated sources, beta-decay properties of the neutron-deficient isotope 60Ga were studied for the first time. The half-life of 60Ga was determined to be 70(15) ms, and, based on gamma-gamma coincidences, the isobaric-analogue state in 60Zn was identified at 4851.9(7) keV. A semiempirical proton separation energy value of 40(70) keV was deduced for 60Ga. The experimental results on half-life, mass excess, proton separation energy, and structure of the 60Zn daughter states are discussed in comparison with various model predictions, including large scale shell model calculations.
Keywords: Properties of nuclei; nuclear energy levels; Beta decay; 21. Shell model
  • European Physical Journal A 12, 269-277 (2001)

Publ.-Id: 4230 - Permalink


Vacancy-type defects in 6H-SiC caused by N+ and Al+ high fluence co-implantation
Anwand, W.; Brauer, G.; Skorupa, W.;
6H-SiC n-type wafers were implanted with Al+ and N+ ions in two steps: first N+ double implantation (65 keV, 5x1016 cm-2 , 120 keV, 1.3x1017 cm-2 ) followed by Al+ double implantation (100 keV, 5x1016 cm-2 and 160 keV, 1.3x1017 cm-2 ). The implantation was carried out at a substrate temperature of 800 0C in order to avoid amorphisation. In this way a buried SiC1-x(AlN)x layer could be created. Variable-energy positron Doppler broadening measurements were performed at room temperature using a magnetic transport beam system in order to characterize the vacancy-type defects created by ion implantation. Depth profiles could be evaluated from the measured Doppler broadening profiles. The defect distribution and the defect size after the complete co-implantation are discussed and the contribution of the different implantation steps to the evolution of this defect structure is shown.
Keywords: 6H-SiC, N+ and Al+ co-implantation, vacancy-type defects, slow positron spectroscopy
  • Applied Surface Science 194 (2002) 131-135
  • Poster
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces, Dresden, Germany, September 16-22, 2001

Publ.-Id: 4229 - Permalink


The influence of substrate temperature on the evolution of ion implantation induced defects in epitaxial 6H-SiC
Anwand, W.; Brauer, G.; Wirth, H.; Skorupa, W.; Coleman, P. G.;
An epitaxial n-type 6H-SiC layer has been fourfold implanted with Al+ ions at temperatures ranging from room temperature to 1200 oC in order to create a buried p-doped layer from 200 nm to 600 nm below the surface. The defects induced by the ion implantation at different temperatures have been investigated by Slow Positron Implantation Spectroscopy. Higher substrate temperatures were found to lead to a significant reduction in the depth of the damage. However, this is accompanied by the formation of vacancy clusters of sizes up to seven Si-C divacancies. Only at 1200 ºC does the vacancy agglomeration disappear in the implanted region, and larger agglomerates are formed immediately below the surface. Furnace annealing at 1650 ºC was found to be insufficient to remove all damage.
Keywords: epitaxial 6H-SiC, Al implantation, vacancy-type defects, slow positron spectroscopy
  • Applied Surface Science 194 (2002) 127-130
  • Poster
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces, Dresden, Germany, September 16-22, 2001

Publ.-Id: 4228 - Permalink


Investigation of ion implantation induced damage in the carbon and silicon sublattices of 6H-SiC
Zolnai, Z.; Khánh, N. Q.; Szilágyi, E.; Kótai, E.; Ster, A.; Posselt, M.; Lohner, T.; Gyulai, J.;
Single crystal 6H-SiC samples were irradiated at room temperature with 200 keV Al+ ions at fluences ranging from 3.5x1013 to 2.8x1014 ion/cm2. Depth profiles of crystal defects both in the C and Si sublattices were measured by Backscattering Spectrometry combined with channeling technique (BS/C) at 3550 keV 4He+ ion beam energy along the <0001> axial channeling direction. Damage in the carbon sublattice was found to be higher than in the silicon one. Moreover, C/Si damage ratio decreased with increasing fluence. The crystal defect profiles can be well simulated both by full-cascade SRIM and Crystal-TRIM programs. Effective displacement energies for carbon and silicon sublattices in the applied fluence range of Al implantation were determined by comparing SRIM simulations to BS/C results.
Keywords: Silicon carbide, Ion implantation, Backscattering Spectrometry, Defects
  • Lecture (Conference)
    12th European Conf. on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide, September 2-7, 2001, Budapest, Hungary
  • Diamond and Related Materials 11 (2002) 1239-1242

Publ.-Id: 4227 - Permalink


Einfluss von Wasserstoff auf die Zähigkeit von Reaktordruckbehälterstählen
Uhlemann, M.; Böhmert, J.; Müller, G.;
Niedriglegierte ferritische Stähle gelten ebenso wie die hochlegierten austentischen Stähle als anfällig gegen Wasserstoffversprödung. Im Kernreaktor können Korrosion oder Radiolyse zur Bildung von atomaren Wasserstoff an der inneren Oberfläche des Reaktordruckbehälters und folglich zur Wasserstoffaufnahme während des Reaktorbetriebes führen. Der Beitrag stellt Ergebnisse zum Wasserstoffdiffusionsverhalten, zur Wasserstofflöslichkeit und zum Einfluss des Wasserstoffs auf die mechanischen Eigenschaften vor. Sie wurden an unbestrahlten Druckbehälterstählen unterschiedlicher Art gewonnen und beziehen sich auf solche Bedingungen, die denen im DWR nahe kommen.
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Tagungsbericht, 14.-16.05.2002, Stuttgart, S. 609
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Tagungsbericht, 14.-16.05.2002, Stuttgart, S. 609

Publ.-Id: 4226 - Permalink


ROCOM experiments on the influence of density differences on the coolant mixing inside the reactor pressure vessel of a PWR
Kliem, S.; Prasser, H.-M.; Grunwald, G.; Rohde, U.; Höhne, T.; Weiß, F.-P.;
During emergency core cooling (ECC) injection into the cold leg of a PWR an incomplete mixing of the injected water with the natural circulation flow in the loop takes place. Due to the higher density of the ECC water a streak of cold water is flowing downwards the downcomer. This causes thermal loads on the reactor pressure vessel wall. Furthermore, the core behaviour is determined by the resulting parameter distributions at the core inlet.
An experimental study was carried out at the ROCOM test facility, a fluid dynamic model of a German type PWR (KONVOI 1300 MWe) in the scale of 1:5. Natural circulation conditions in one loop were approximated by running the corresponding pump at low rotation speed by means of a frequency transformer system. The higher density of the injected water was simulated by adding sugar. The evolution of the spatial distribution of the ECC water was measured by tracering with sodium chloride. Conductivity distributions reflecting the share of ECC water present at given time and location were measured by electrode mesh sensors, one close to the reactor inlet nozzle (16 x 16 measuring points), two sensors in the upper and lower part of the downcomer (2D grids of 4 radial and 64 angular measuring positions) and one sensor at the core entrance (inlets of each of 193 fuel elements).
The paper presents visualisations of the streak effect in the downcomer. The transition from momentum driven flow in the downcomer to a density driven regime was identified (critical Froude number). In the experiments the relative density difference was varied between 0 and 10 % and the loop flow rate between 0 and 15 % of the nominal. The streak effect is more pronounced at higher density differences.
  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2002, Stuttgart, Germany, May 14-16, 2002 Proceedings pp. 65-69
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2002, Stuttgart, Germany, May 14-16, 2002 Proceedings pp. 65-69

Publ.-Id: 4225 - Permalink


Syntheses and first crystal structures of rhenium complexes derived from omega-functionalized fatty acids as model compounds of technetium tracers for myocardial metabolism imaging
Jung, C. M.; Kraus, W.; Leibnitz, P.; Pietzsch, H.-J.; Kropp, J.; Spies, H.;
In an attempt to develop new technetium-based radiopharmaceuticals for the non-invasive diagnosis of myocardial metabolism, we have synthesized three examples of novel metal-containing fatty acid derivatives according to the '3+1' mixed-ligand and the Schiff Base/tricarbonyl design. The chelates contain the metal core in the oxidation states +5 and +1 respectively, and were attached to the ending position of a fatty acid chain. The complex formation was accomplished by ligand exchange reactions using three different rhenium precursors, whereas the inactive rhenium metal was utilized as surrogate of the technetium radionuclide. The molecular structures of the fatty acid complexes 7, 10 and 14 were determined by single-crystal X-ray diffraction analyses and show impressively a general problem in technetium tracer research, namely the significant structural alterations of bioactive molecules by coordination even to small-sized metal chelates.
Keywords: rhenium; technetium; fatty acid; drug research, radiopharmaceuticals
  • European Journal of Inorganic Chemistry (2002) 1219-1225

Publ.-Id: 4224 - Permalink


Linear three-dimensional instability of a magnetically driven flow
Grants, I.; Gerbeth, G.;
The instability of a rotating magnetic field driven liquid metal flow in a finite cylinder with respect to infinitesimal azimuthally periodic
perturbations is studied numerically. This instability is observed to set in prior to its axisymmetric counterpart with relatively low frequency at diameter-to-height ratios between 0.5 and 2. The both, axisymmetric and three-dimensional instabilities have similar characteristic features. The instability originates in the cross-section of the horizontal and vertical rotating boundary layers and excites inertial waves in the inviscid core.
  • Journal of Fluid Mechanics (2002), vol. 463, pp. 229-239

Publ.-Id: 4223 - Permalink


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