Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32228 Publications
Uranium(VI) sorption on montmorillonite and bentonite: Prediction and experiments
Nebelung, C.; Brendler, V.;
The sorption characteristics of U(VI) on bentonite and montmorillonite were investigated in batch experiments for understanding the near-field behaviour in geological nuclear repositories. Sorption parameters were determined in batch tests. The sorption on bentonite (KWK) was studied at different dry bulk densities of the clay (1.3, 1.6, 1.9 g/cm3) at pH 8 for the U(VI) concentration dependence (10-4 to 10-9 m). The sorption on the pure mineral montmorillonite (SWy-1) in 0.1 M NaClO4 was determined for the concentration dependence at pH 5.5, and pH dependence between pH 3 and 11). A scientifically founded description of sorption processes at the mineral-liquid surface is possible with the surface complexation models (SCM), the ion adsorption on surface sites as complexation reaction. We use the diffuse double layer model (DDL) to predict the sorption with the code MINTEQA2 (Version 4.03, US EPA May 2006), thermodynamic data of aqueous and solid species from the NEA-TDB [1], the mineral characterization and the respective protolysis data [2] and surface complex constants from [3].
The prediction of U(VI) sorption on montmorillonite at the pH dependence was very good. The modelling of the sorption on montmorillonite and bentonite versus U(VI) concentration shows a good agreement of measured and predicted values.

[1] Guillaumont, R. et al. (2003) “Update on the chemical thermodynamics of U, Np, Pu, Am, Tc. Chemical Thermo-dynamics”, Vol. 5 (OECD Nuclear Energy Agency, ed.), Elsevier, Amsterdam.
[4] Pabalan, R.T. et al. (1997) Aquat. Geochem. 2, 203-226.
[3] Pabalan, R.T. et al. (1998) in: Adsorption of metals by geomedia. Variables, mechanisms, and model applications; Jenne EA (Ed.), Academic Press; San Diego.

Funding by the European Commission (NF-PRO C2-ST-C-01) is gratefully acknowledged.
Keywords: sorption, uranium(VI), montmoroillonite, bentonite, pore water, surface complexation, MINTEQA2
  • Lecture (Conference)
    5th International Conference Uranium Mining and Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 525-526

Publ.-Id: 10928 - Permalink


Experiments on the counter-current flow limitation (CCFL) in a model of a pressurised water reactor hot leg
Lucas, D.; Vallée, C.; Beyer, M.; Prasser, H.-M.; Deendarlianto;
Experiments were done on co-current and counter-current flows of air-water and also steam-water for a flat geometry reflecting a hot leg and steam generator inlet chamber of a Pressurized Water Reactor. The focus of the experiments was on the phenomenon of Counter-Current Flow Limitation. For air-water flows the flooding curve was obtained for this special geometry. The main aim of the experiments is however to provide a detailed database for CFD code validation. For this reason a model of a part of the hot leg and the steam generator inlet chamber was equipped with large glass windows to enable high speed camera observations. To use this measuring technique also for steam-water flows a new technology, the so-called pressure tank technology was used for the first time. The test section itself is built-in into a large pressure tank which can be operated for pressures up to 5 MPa. A condenser at the end of the test section guarantees the pressure equilibrium between the inside of the test section and the tank atmosphere. This enables to manufacture the test section from thin materials and to use large glass windows. For the first time steam-water co-current and counter-current flows were observed by high speed video observations at a pressure of 1.5 MPa. Further experiments with pressure up to 5 MPa will follow.
Keywords: stratified flow, CCFL, experiment, high speed video observation, pressure tank
  • Contribution to proceedings
    HEAT 2008, The Fifth International Conference on Transport Phenomena In Multiphase Systems, 30.06.-03.07.2008, Bialystok, Poland
    Transport Phenomena In Multiphase Systems, Volume 1, Bialystok, 325-332
  • Poster
    HEAT 2008, The Fifth International Conference on Transport Phenomena In Multiphase Systems, 30.06.-03.07.2008, Bialystok, Poland

Publ.-Id: 10926 - Permalink


Experimental Evaluation of Functional Imaging for Radiotherapy
Zips, D.; Yaromina, A.; Schütze, C.; Wüllrich, K.; Krause, M.; Krause, M.; Hessel, F.; Eicheler, W.; Dörfler, A.; Brüchner, K.; Menegakis, A.; Zhou, X.; Bergmann, R.; van den Hoff, J.; Beuthien-Baumann, B.; Baumann, M.;
Functional imaging for radiotherapy is expected to provide diagnostic as well as prognostic information, to monitor treatment, to help stratification of patients for specific therapeutic interventions and to guide dose-painting. During the last years radiotracer-based functional imaging with positron emission tomography (PET), mainly using the glucose analogue [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG), has been widely implemented in radiotherapy for a more accurate staging and an improved target volume definition in a variety of tumor types [1, 2, 4]. While the technology for integration of functional imaging into clinical radiotherapy is increasingly available, the biological implications for radiation response are poorly understood [6]. Importantly, biomarker development needs to account for the specific parameters known to determine the results of curative radiotherapy. Clinical as well as preclinical studies are necessary to exploit the potential of functional imaging to improve outcome after radiotherapy. In the following sections recent findings from experimental studies using xenotransplanted tumors in nude mice carried out in our laboratories are briefly summarized.
Keywords: Functional imaging · Tumor xenografts · Radiotherapy · FDG-PET · Small animal PET · Hypoxia · Proliferation · Cancer stem cells · Local tumor control

Publ.-Id: 10925 - Permalink


CFD-modeling and experiments of insulation debris transport phenomena in water flow
Krepper, E.; Cartland-Glover, G.; Grahn, A.; Weiss, F.-P.; Alt, S.; Hampel, R.; Kästner, W.; Seeliger, A.;
The investigation of insulation debris generation, transport and sedimentation becomes more important with regard to reactor safety research for PWR and BWR, when considering the long-term behavior of emergency core coolant systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems.
Open questions of generic interest are for example the particle load on strainers and corresponding pressure drop, the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow. A joint research project on such questions is being performed in cooperation with the University of Applied Science Zittau/Görlitz. The project deals with the experimental investigation and the development of CFD models for the description of particle transport phenomena in coolant flow. While the experiments are performed at the University Zittau, the theoretical work is concentrated at Forschungszentrum Dresden-Rossendorf.
In the current paper the basic concepts for CFD modeling are described and feasibility studies including the conceptual design of the experiments are presented.
Keywords: CFD, two-fluid approach, fiber flows
  • Nuclear Technology 167(2009)1, 46-59

Publ.-Id: 10924 - Permalink


Spectroscopic study of the uranium(IV) complexation by organic model ligands in aqueous solution
Schmeide, K.; Bernhard, G.;
In the present study, the model ligands citric acid and glutaric acid as well as mandelic acid and glycolic acid were chosen for the uranium(IV) complexation. These ligands stand for a variety of organic ligands in aqueous systems. The complex formation constants for the uranium(IV) complexation were determined applying UV-Vis absorption spectroscopy. Thereby, the hydrogen ion concentration and the ionic strength were varied.
For instance, the complexation of uranium(IV) with citric acid has been investigated in dependence on hydrogen ion concentration (1 M, 0.5 M, 0.1 M and 0.05 M). Thereby, the formation of 1:1 and 1:2 complexes was detected in the citrate media. The stability constants for 1:1 and 1:2 uranium(IV) citrate complexes of the type MpHqLr were determined with log ß101 = 13.5 ± 0.2 and log ß102 = 25.1 ± 0.2. The obtained log ß fit well in the known series of log ß determined for the complexation of further tetravalent actinides (e.g., Pu(IV), Np(IV), Th(IV)) by citric acid.
Keywords: uranium, tetravalent, complexation, citric acid
  • Lecture (Conference)
    5th International Conference Uranium Mining Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 591-598

Publ.-Id: 10923 - Permalink


Application of the effective convectivity model to an PWR in-vessel retention scenario
Willschütz, H.-G.; Altstadt, E.; Abendroth, M.;
For the very improbable scenario of a severe accident with core meltdown and for-mation of a melt pool in the lower plenum of a Light Water Reactor (LWR) Pressure Vessel (RPV) computer codes are developed to assess the thermal and mechanical behaviour of the RPV wall. If the RPV wall fails within the lower head region, the melt is discharged into the reactor pit, which can result in severe thermal and mechanical loads for the containment. One accident management strategy could be to stabilize the in-vessel debris or melt pool configuration in the RPV via external flooding.
Based on the successful simulation and analysis work of the FOREVER-experiments (cf. Fig. 1 and [1]) coupled thermo-mechanical models have been developed further to simulate the prototypical scenario of an In-Vessel-Retention in large PWRs [2]. According to the recent publication “An Effective Convectivity Model (ECM) for Simulation of In-Vessel Core Melt Progression in a Boiling Water Reactor” by Tran and Dinh [3] the thermal part of the FE-model developed at FZD is now improved to be able to apply the new ECM approach.
Keywords: In-vessel melt retention, reactor pressure vessel, thermal analysis, effective heat generation
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    Proceedings of the Annual Meeting of Nuclear Technology 2008
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10922 - Permalink


Fracture mechanical analysis of a VVER-440 PTS scenario
Abendroth, M.; Altstadt, E.;
The paper describes the modelling and evaluation of a pressurized thermal shock (PTS) scenario in a VVER-440 reactor pressure vessel due to an emergency case. An axially oriented semi-elliptical crack is assumed to be located in the core welding seam. Two variants of fracture mechanical evaluation are performed: the analysis of a sub-cladding crack and of a surface crack. Three-dimensional finite element (FE) models are used to compute the global transient temperature and stress-strain fields. By using a three-dimensional submodel, which includes the crack, the local crack stress-strain field is obtained. Within the subsequent postprocessing using the j integral technique the stress intensity factors KI along the crack front are obtained. The FE results are compared to analytical calculations proposed in the VERLIFE code. The stress intensity factors are compared to the fracture toughness curve for the weld material.
Keywords: Fracture mechanics, pressurised thermal shock, reactor pressure vessel, finite elements
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    Proceedings of the Annual Meeting of Nuclear Technology, Sankt Augustin: dbcm GmbH
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29,05,2008, Hamburg, Germany

Publ.-Id: 10921 - Permalink


CFD simulation of polydispersed bubbly two phase flow around an obstacle
Krepper, E.; Ruyer, P.; Beyer, M.; Lucas, D.; Prasser, H.-M.; Seiler, N.;
This paper concerns the model of a polydispersed bubble population in the frame of an ensemble averaged two-phase flow formulation. The ability of the moment density approach to represent bubble population size distribution within a multi-dimensional CFD code based on the two-fluid model is studied. Two different methods describing the polydispersion are presented: (i) a moment density method, developed at IRSN, to model the bubble size distribution function and (ii) a population balance method considering several different velocity fields of the gaseous phase. The first method is implemented in the NEPTUNE_CFD code whereas the second method is implemented in the CFD code ANSYS/CFX. Both methods consider coalescence and break-up phenomena and momentum inter-phase transfers related to drag and lift forces.
Air-water bubbly flows in a vertical pipe with obstacle of the TOPFLOW experiments series performed at FZD are then used as simulations test cases. The numerical results, obtained with NEPTUNE_CFD and with ANSYS/CFX, allow attesting the validity of the approaches. Perspectives concerning the improvement of the models, their validation, as well as the extension of their applicability range are discussed.
Keywords: bubbly flow, CFD, population balance method, moment density method, non-drag forces, bubble breakup, bubble coalescence, model validation

Publ.-Id: 10920 - Permalink


Bremsstrahlung in PLUTO simulations
Wüstenfeld, J.;
The talk presents our parametrization of a theoretical calculation of nuceon - nucleon Bremsstrahlung, done by L. Kaptari and B. Kaempfer, that is to be implemented in the PLUTO somulation framework
Keywords: Bremsstrahlung, PLUTO
  • Lecture (Conference)
    HADES Collaboration Meeting XVIII, 30.10.-04.11.2007, Ayia Napa, Cyprus

Publ.-Id: 10919 - Permalink


R&D for RPC - news from ELBE
Wüstenfeld, J.;
The talk presents recent results from our investigations of new nanocomposite materials for the construction of resistive plate counters. This counters are forseen as timing detectors for the upcomming Compressed Baryonic Matter (CBM) experiment at FAIR. These tests where performed at the electron beam of ELBE.
Keywords: RPC, nano composite materials, ELBE
  • Lecture (Conference)
    10th CBM Collaboration Meeting, 25.-28.09.2007, Dresden, Germany

Publ.-Id: 10918 - Permalink


Dosiskontrolle mit PET bei der Schwerionen-Tumortherapie
Priegnitz, M.; Shakirin, G.; Enghardt, W.; Fiedler, F.; Möckel, D.; Pawelke, J.;
Übersicht über die Anwendung des in-beam PET bei der Schwerionentherapie.
  • Poster
    Strategie-Meeting des OncoRay, 07.-08.01.2008, Gröditz, Germany

Publ.-Id: 10917 - Permalink


In-beam PET an harten Photonenstrahlen
Möckel, D.; Kluge, T.; Pawelke, J.; Enghardt, W.;
Übersicht über die Anwendung von in-beam PET bei harten Photonen
  • Poster
    Strategie-Meeting des OncoRay, 08.-09.01.2008, Gröditz, Germany

Publ.-Id: 10916 - Permalink


In-beam PET-Monitoring der Kohlenstoff-Ionentherapie: 10 Jahre Erfahrung in der klinischen Anwendung
Priegnitz, M.; Fiedler, F.; Möckel, D.; Parodi, K.; Pawelke, J.; Shakirin, G.; Skowron, J.; Enghardt, W.;
Ionenstrahlen bieten aufgrund ihrer besonderen physikalischen und biologischen Eigenschaften die Möglichkeit einer präzisen Tumorbestrahlung mit geringer Belastung für das umliegende gesunde Gewebe. Dadurch können auch tief sitzende Tumoren in der Nähe von Risikoorganen bestrahlt werden, die mit konventioneller Strahlung nur eingeschränkt therapierbar sind.
Im Dezember 1997 begann die Behandlung von Krebspatienten mit Kohlenstoffionen an der Gesellschaft für Schwerionenforschung (GSI) in Darmstadt. An dieser europaweit ersten Schwerionentherapie-Pilotanlage sind bis heute ca. 400 Patienten mit Kopf- und Beckentumoren bestrahlt worden.
Da die durch die Ionenstrahlen deponierte Dosisverteilung äußerst empfindlich auf Veränderungen in der Ionen-Reichweite reagiert, ist eine Verifikation der Bestrahlungsfeldposition unabhängig von der Strahlapplikation wünschenswert. Hierzu wurde am Forschungszentrum Dresden-Rossendorf eine Methode entwickelt, die auf der Detektion von Annihilationsphotonen mit PET (Positronen-Emissions-Tomographie) und einem Vergleich der gemessenen, rekonstruierten Aktivität mit Vorhersagen aus der Bestrahlungsplanung beruht. Die Positronen emittierenden Nuklide entstehen während der Bestrahlung durch Kernreaktionen zwischen den Atomkernen des Gewebes und den Ionen des Therapiestrahls. Dieses so genannte in-beam PET-Verfahren ist die zurzeit einzige bekannte Methode zur in-situ und in-vivo Verifikation der Dosisapplikation bei der Bestrahlung mit Ionen. Das Verfahren kam bei nahezu allen an der GSI behandelten Patienten zum Einsatz und führte zu einer Verbesserung des verwendeten Strahlenmodells. Ferner werden sporadische Abweichungen zwischen geplanter und realisierter Teilchenreichweite nachgewiesen. Diese Abweichungen können ihre Ursachen z.B. in temporären anatomischen Veränderungen im durchstrahlten Volumen, in geringfügigen Bewegungen des Patienten während der Bestrahlung oder in Fehlern bei der Patientenpositionierung haben.
Die gewebeabhängige Kinetik des metabolisch verursachten Abtransportes der Aktivität aus dem bestrahlten Volumen ist bisher nur unzureichend bekannt und steht einer quantitativen Berechnung der Dosis aus der gemessenen Aktivitätsverteilung entgegen. Hier kommt ein interaktives Verfahren zur Anwendung, das die Identifikation der Ursachen von auftretenden Abweichungen ermöglicht.
  • Contribution to proceedings
    14. Jahrestagung der Deutschen Gesellschaft für Radioonkologie, 25. Jahrestagung der Österreichischen Gesellschaft für Radioonkologie, Radiobiologie und Medizinische Strahlenphysik, 01.-04.05.2008, Wien, Austria
    Strahlentherapie und Onkologie 184(2008)Suppl. 1, 9-10
  • Lecture (Conference)
    14. Jahrestagung der Deutschen Gesellschaft für Radioonkologie, 25. Jahrestagung der Österreichischen Gesellschaft für Radioonkologie, Radiobiologie und Medizinische Strahlenphysik, 01.-04.05.2008, Wien, Österreich

Publ.-Id: 10915 - Permalink


Synthesis and Application of [18F]FDG-maleimidehexyloxime ([18F]FDG-MHO): A [18F]FDG-based Prosthetic Group for the Chemoselective 18F-Labeling of Peptides and Proteins
Wüst, F.; Berndt, M.; Bergmann, R.; van den Hoff, J.; Pietzsch, J.;
2-[18F]Fluoro-2-deoxy-D-glucose ([18F]FDG) as the most important PET radiotracer is available in almost every PET center. However, there are only very few examples using [18F]FDG as a building block for the synthesis of 18F-labeled compounds. The present study describes the use of [18F]FDG as building block for the synthesis of 18F-labeled peptides and proteins. [18F]FDG was converted into [18F]FDG-maleimidehexyloxime ([18F]FDG-MHO), a novel [18F]FDG-based prosthetic group for the mild and thiol group-specific 18F labeling of peptides and proteins. The reaction was performed at 100°C for 15 min in a sealed vial containing [18F]FDG and N-(6-aminoxy-hexyl)maleimide in 80% ethanol. [18F]FDG-MHO was obtained in 45-69% radiochemical yield (based upon [18F]FDG) after HPLC purification in a total synthesis time of 45 min. Chemoselecetive conjugation of [18F]FDG-MHO to thiol groups was investigated by the reaction with the tripeptide glutathione (GSH) and the single cysteine containing protein annexin A5 (anxA5). Radiolabeled annexin A5 ([18F]FDG-MHO-anxA5) was obtained in 43-58% radiochemical yield (based upon [18F]FDG-MHO, n=6), and [18F]FDG-MHO-anxA5 was used for a pilot small animal PET study to assess in vivo biodistribution and kinetics in a HT-29 murine xenograft model.
  • Bioconjugate Chemistry 19(2008)6, 1202-1210

Publ.-Id: 10914 - Permalink


A new 34-membered N6O4-donor macrocycle: synthetic, X-ray and solvent extraction studies
Wenzel, M.; Gloe, K.; Gloe, K.; Bernhard, G.; Clegg, J. K.; Ji, X.-K.; Lindoy, L. F.;
The synthesis and crystal structure of a new 34-membered N6O4-donor macrocycle 2 is reported. Solvent extraction experiments (water/chloroform) indicated that 2 acts as an efficient extractant towards silver(I) and zinc(II) at pH values beyond 6 while the extraction of iodide and chromate occurs below this pH. A competitive metal extraction experiment at pH 7.2 in which the perchlorate salts of cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) were present together in the aqueous phase led to the following order of increasing extraction efficiency: cobalt(II) o nickel(II) o zinc(II) o copper(II) B cadmium(II). A substantial synergistic enhancement of zinc(II) salt extraction was observed for a dual-host extraction system using the macrocycle 2 as cation binder and the tripodal thiourea ligand 3 as anion receptor; in particular, a notable extraction of zinc(II) sulfate was obtained.

Publ.-Id: 10913 - Permalink


Two-photon photocurrent autocorrelation using intersubband transitions at nearly-resonant excitation
Schneider, H.; Maier, T.; Liu, H. C.; Walther, M.;
We investigate nonlinear mid-infrared detection via two-photon transitions involving two bound subbands and one continuum resonance in an n-type multiple quantum well. By varying the excitation energy, we have tuned the two-photon transition from resonant, yielding optimum resonant enhancement with a real intermediate state, to nearly-resonant, with a virtual but resonantly enhanced intermediate state. For autocorrelation purposes, the latter configuration improves time resolution whilst partially retaining a resonant enhancement of the two-photon transition strength.
Keywords: intersubband transition, multiple quantum well, two-photon excitation, mid-infrared detector, ultrafast spectroscopy
  • Open Access LogoOptics Express 16(2008)3, 1523-1528

Publ.-Id: 10912 - Permalink


Experimental investigation and CFD simulation of the behaviour of mineral wool in the reactor sump
Krepper, E.; Cartland-Glover, G.; Grahn, A.; Weiss, F.-P.; Alt, S.; Hampel, R.; Kästner, W.; Seeliger, A.;
The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behavior of emergency core cooling systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems.
Open questions of generic interest are the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow and the particle load on strainers and corresponding pressure drop. A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Görlitz, the theoretical modeling efforts are concentrated at Forschungszentrum Dresden-Rossendorf.
In the current paper the basic concepts for CFD modeling are described and feasibility studies including the conceptual design of the experiments are presented.
Keywords: CFD, two-fluid approach, fiber flows
  • Contribution to proceedings
    16th International Conference on Nuclear Engineering, ICONE-16, 11.-15.05.2008, Orlando, Florida, USA
  • Lecture (Conference)
    16th International Conference on Nuclear Engineering, ICONE-16, 11.-15.05.2008, Orlando, Florida, USA

Publ.-Id: 10911 - Permalink


Development of segmented straws for very high-rate capability coordinate detector
Davkov, K.; Davkov, V.; Geyer, R.; Gusakov, Y. V.; Kekelidze, G. D.; Myalkovskiy, V. V.; Naumann, L.; Peshekhonov, D. V.; Peshekhonov, V. D.; Savenkov, A. A.; Tikhomirov, V. O.; Viryasov, K. S.;
To reduce the occupancy of the large-size coordinate detectors, the high-granularity straw tracking chamber has been designed and tested. The main tasks were to improve the detector granularity and provide the best value of the detector radiation thickness. We have developed the techniques of the multiple anode production, assembling of the segmented straws and the low-mass readout by means of flat cable. Testing of the constructed prototypes has shown that these techniques can be applied to build the high-granularity straw detectors.
Keywords: Straw-drift chamber; Tracking detector; High granularity; Small occupancy

Publ.-Id: 10910 - Permalink


Review of available data for validation of nuresim two-phase CFD software applied to CHF investigations
Bestion, D.; Anglart, H.; Carraghiaur, D.; Péturaud, P.; Smith, B.; Andreani, M.; Niceno, B.; Krepper, E.; Lucas, D.; Moretti, F.; Galassi, M. C.; Macek, J.; Vyskocil, L.; Koncar, B.; Hazi, G.;
The NURESIM Integrated Project of the 6th European Framework Program was envisaged to initiate the development of the next-generation common European Standard Software Platform for simulating nuclear reactors. The overall objective of NURESIM Thermalhydraulic sub-project is to improve the understanding and the predictive capabilities of the simulation tools for key two-phase flow thermal-hydraulic processes such as the Critical Heat Flux (CHF). A multi-scale analysis of reactor thermalhydraulics is envisaged and two-phase CFD is developed to allow some zoom on local processes when the resolution of system codes is not sufficient.
Current industrial methods for CHF mainly use the sub-channel analysis and empirical CHF correlations based on large scale experiments having the real geometry of the reactor assembly. The NURESIM-TH activities regarding CHF aim at using two-phase CFD as a tool for understanding boiling flow processes, in order to subsequently help new fuel assembly design and to develop better CHF predictions in both PWR and BWR. A “Local Predictive Approach” may be envisaged for the long term where CHF empirical correlations would be based on local T/H parameters provided by CFD.
This paper presents a review of existing experimental data bases which can be used for validation of the two-phase CFD application to Critical Heat Flux (CHF) investigations with respect to nuclear reactors. The phenomenology of DNB and Dry-Out are detailed identifying all basic flow processes which require a specific modeling in CFD tool. The resulting program of work is given and the current state of the art of the modeling is presented.
Keywords: Critical heat flux, experimenbtal data, CFD simulation

Publ.-Id: 10909 - Permalink


An overview of the Pressurized Thermal Shock issue in the context of the NURESIM project
Lucas, D.; Bestion, D.; Bodèle, E.; Scheuerer, M.; D’Auria, F.; Mazzini, D.; Smith, B.; Tiselj, I.; Martin, A.; Lakehal, D.; Seynhaeve, J.-M.; Kyrki-Rajamäki, R.; Ilvonen, M.; Macek, J.; Coste, P.;
This paper reports activities regarding the simulation of Pressurized Thermal Shock (PTS) performed within the European Integrated Project NURESIM. Some Loss of Coolant Accident (LOCA) scenarios for Pressurized Water Reactors (PWR) may cause Emergency Core Coolant injection into the cold leg and thus lead to PTS situations. They imply the formation of temperature gradients in the thick vessel walls with consequent localized stresses and the potential for propagation of possible flaws present in the material. The present paper, in the area of fluid dynamics, focuses on the study of two-phase conditions that are potentially at the origin of PTS. It summarizes recent advances in the understanding of the two-phase phenomena occurring within the geometric region of the nuclear reactor, i.e. the cold leg and the downcomer, where the ‘PTS fluid-dynamics’ is relevant. Available experimental data for validation of two-phase CFD simulation tools are reviewed and the capabilities of such tools to capture each basic phenomenon are discussed. Key conclusions show that several two phase flow sub-phenomena are involved and can individually be simulated at least at a qualitative level, but the capability to simulate their interaction and the overall system performance is still limited. In the near term, one may envisage a simplified treatment of two-phase PTS transients by neglecting some effects which are not yet well controlled, leading to slightly conservative predictions.
Keywords: PTS, CFD, Nuclear reactor simulation

Publ.-Id: 10908 - Permalink


Simulations of DEBORA data with CFX
Krepper, E.;
In the DEBORA experiments subcooled boiling is investigated heating up Dichlorodifluoromethane (R12) in a side wall heated tube. Radial profiles for gas volume fraction, gas velocity, liquid temperatures and bubble sizes were measured at the end of the heated length. This enables the validation not only of the wall boiling model but also of the models for liquid/gas momentum, heat and mass transfers.
The report describes the model simulating the wall boiling preliminary implemented in CFX-11 which is also implemented in the NEPTUNE code. These approaches are based on the proposal of Kurul and Podowski (1990). Specific model developments concerning the near wall phenomena are described in the report. Furthermore the momentum exchange models used in the CFX simulations are described.
The same parameters for the model correlations adjusted for water/steam flow were applied simulating the fluid R12. To investigate the influence on the results, essential boiling model parameters were varied and the sensitivity of the results is shown. The need of further model development and of further experiments can be confirmed. The validation applying for the different models shows the state and the limits of the present modelling.
The simulations are intended for the comparison to other CFD models e.g. to the NURESIM-CFD platform.
Keywords: Two phase flow, CFD, subcooled boiling, drag forces, non drag forces, experimente, model validation
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2008
    NURESIM-SP2-TH-D2.2.3.2 (Jauary 2008)
    37 Seiten

Publ.-Id: 10907 - Permalink


Fracture Mechanics Characterisation of the WWER-440 Reactor Pressure Vessel Core Welding Seam
Viehrig, H.-W.; Schuhknecht, J.;
The Master Curve (MC) approach as standardised in the ASTM Standard Test Method E 1921-05 was applied on weld metal of the reactor pressure vessel (RPV) core welding seam of Greifswald Unit 8 RPV. Charpy size SE(B) specimens from 13 locations equally spaced over the thickness of the welding seam were tested. The specimens are TL and TS orientation.
The fracture toughness values measured on the SE(B) specimens with both orientations follow the course of the Master Curve. Nearly all values lie within the fracture toughness curves for 5% and 95% fracture probability. There is a strong variation of the reference temperature T0 though the thickness of the welding seam, which can be explained with structural differences. The scatter is more pronounced for the TS SE(B) specimens. It can be shown that specimens with TL and TS orientation in the welding seam have a differentiating and integrating behaviour, respectively.
Keywords: reactor pressure vessel, multilayer welding seam, specimen orientation, structure, fracture toughness, Master Curve approach, reference temperature, integrity assessment of base metal from the Greifswald Unit 8 RPV show large scatter

Publ.-Id: 10906 - Permalink


Fullerene-like alloyed carbon films
Abrasonis, G.;
The synthesis, structure and properties of fullerene-like alloyed carbon films are reviewed. The term fullerene-like describes extended structures consisting of curved basal planes, which are stacked perpendicular to the basal planes. Fullerene-like structures can be observed in layered materials like graphitic carbon, carbon nitride, hexagonal boron nitride or tungsten disulfide. They can be characterized by extension, curvature and cross-linking of basal planes. Their structure results in an exceptional combination of mechanical properties such as high hardness, high elastic recovery, high wear resistance and low coefficient of friction.

In carbon based fullerene-like structures, these properties result from stiff (sigma pi)-bonds within the basal graphitic planes, fullerene-like structure assuring the presence of their 3D network due to the curvature and cross-linking. The fullerene-like structure of pure carbon can be further stabilized by alloying with nitrogen. Different nitrogen incorporation routes result in different local carbon-nitrogen bonding arrangements which then determine the extension, curvature and cross-linking of basal planes. Since both elements – carbon and nitrogen – can form sp1, sp2 and sp3 bonds, the nanostructure is determined by the relative concentration of local chemical environments such as nitrile-like, pyridine-like or graphite-substitutional. The former two configurations are terminating, thus hindering the extension of basal planes The latter induces buckling in the planes due to stabilization of pentagon rings or due to the difference between C-N and C-C bonds which locally shrinks the network.

An alternative way to produce fullerene-like structures is carbon alloying with metallic elements. The metal atoms segregate into the nanoparticles which act as catalytic sites for the six-fold-ring clustering of carbon atoms. Different metal incorporation routes determine the shape of metal nanoparticles ranging from completely spherical to nanorod-like. This significantly affects the graphitization of carbon as the so-formed graphitic planes follow the boundaries of the metal nanoparticles resulting in partially wrapped metal nanocolumns or completely encapsulated metal nanoparticles. These fullerene-like nanostructures might be used for applications as low-friction, self-lubrication, wear resistant coatings, as 2D network of tunnel junctions, as nanocontainers for foreign materials, or for encapsulation of ferromagnetic nanoparticles in non-magnetic media.
  • Invited lecture (Conferences)
    Fifteenth International Summer School on Vacuum, Electron and Ion Technologies, 17.-21.09.2007, Sozopol, Bulgaria

Publ.-Id: 10905 - Permalink


CFD calculation of new TOPFLOW hot leg experiments
Höhne, T.;
Usually, the slug flow regime is characterized by an acceleration of the gaseous phase and by the transition of fast liquid slugs, which carry a significant amount of liquid with high kinetic energy. It is potentially hazardous to the structure of a system due to the strong oscillating pressure levels formed behind the liquid slugs as well as the mechanical momentum of the slugs. Because slug flow cannot be predicted with the required accuracy and spatial resolution by the one-dimensional system codes, the stratified flows are increasingly modelled with computational fluid dynamics (CFD) codes. In CFD, closure models are required that must be validated. The recent improvements of the multiphase flow modelling in the ANSYS CFX code make it now possible to simulate these mechanisms in detail. In order to validate existing and further developed multiphase flow models, high-resolution measurement data is needed in time and also in space.

Thanks to the optical access of the test channels built at Forschungszentrum Dresden-Rossendorf, it is possible to study detailed local stratified air/water flow phenomena. These experimental results give an important input for two-phase flow CFD model validation (i.e. interfacial momentum transfer, turbulent profiles of each phase). For the experimental investigation of co-current air/water flows, the HAWAC (Horizontal Air/Water Channel) was built (Fig. 1). Its inlet device provides defined inlet boundary conditions for code comparison. The channel allows in particular the study of air/water slug flow under atmospheric pressure. A flow pattern map (Fig. 2) was arranged constructed on the basis of a visual observation of the flow structure at different combinations of the gas and liquid superficial velocities. Parallel to the experiments, CFD calculations were carried out. A picture sequence recorded during slug flow was compared with the equivalent CFD simulation made (Figs. 3 and 4). The two-fluid model was applied with a special turbulence damping procedure at the free surface. An Algebraic Interfacial Area Density (AIAD) model on the basis of the implemented mixture model was introduced, which allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value.

The behaviour of slug generation and propagation at the experimental setup was qualitatively reproduced by the simulation, while local deviations require a continuation of the work. The creation of small instabilities due to pressure surge or an increase of interfacial momentum should be analysed in the future. Furthermore, experiments like pressure and velocity measurements are planned and will allow quantitative comparisons, also at other superficial velocities.
Keywords: hot leg, TOPFLOW, CFD
  • Lecture (others)
    13th Meeting, 23.-24.01.2008, Großhartpenning, Deutschland

Publ.-Id: 10903 - Permalink


Experimental and numerical modeling of transition matrix from momentum to buoyancy-driven flow in a pressurized water reactor
Höhne, T.; Kliem, S.; Vaibar, R.;
The influence of density differences on the mixing of the primary loop inventory and the Emergency Core Cooling (ECC) water in the cold leg and downcomer of a Pressurised Water Reactor (PWR) was analyzed at the ROssendorf COolant Mixing (ROCOM) test facility. This paper presents a matrix of ROCOM experiments in which water with the same or higher density was injected into a cold leg of the reactor model with already established natural circulation conditions at different low mass flow rates. Wire-mesh sensors measuring the concentration of a tracer in the injected water were installed in the cold leg, upper and lower part of the downcomer. A transition matrix from momentum to buoyancy-driven flow experiments was selected for validation of the CFD software ANSYS CFX. A mesh with 4 million control volumes was used for the calculations. The turbulence models usually applied in such cases assume that turbulence is isotropic, whilst buoyancy actually induces anisotropy. Thus, in this paper, higher order turbulence models have been developed which take into account for that anisotropy. Buoyancy generated source and dissipation terms were proposed and introduced into the balance equations for the turbulent kinetic energy. The results of the experiments and of the numerical calculations show that mixing strongly depends on buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this circumferential propagation with lower mass flow rates and/or higher density differences. The ECC water falls in an almost vertical path and reaches the lower downcomer sensor directly below the inlet nozzle. Therefore, density effects play an important role during natural convection with ECC injection in PWR and should be also considered in Pressurized Thermal Shock (PTS) scenarios. ANSYS CFX was able to predict the observed flow patterns and mixing phenomena quite well.
Keywords: CFD, ROCOM, BUOYANCY-DRIVEN FLOW, PWR
  • Contribution to proceedings
    16th International Conference on Nuclear Engineering ICONE16, 11.-15.05.2008, Orlando, USA
    CD_ROM, 48490
  • Lecture (Conference)
    16th International Conference on Nuclear Engineering ICONE16, 11.-15.05.2008, Orlando, USA
  • Journal of Engineering for Gas Turbines and Power - Transactions of the ASME 131(2009)1, 012906
    DOI: DOI: 10.1115/1.2983137

Publ.-Id: 10902 - Permalink


Analysis of safety valve characteristics using measurements and CFD simulations
Höhne, T.; Moncalvo, D.;
In order to study valve characteristics, experiments of the Institut für Strömungsmechanik at the Technical University Hamburg-Haburg (TUHH) were used to validate the CFD-code ANSYS CFX. Due to the constant improvement of the physical models and numerics of the code it is now possible to simulate very complex flows through valves. This includes phenomena like jets, flow around obstacles, flow separation effects, stagnant regions and partly zones with high mach numbers. The geometric details of the safety valve internals have a strong influence on the flow field. Therefore, an exact representation of the inlet region, the seat and disc region and the shape of the valve body were necessary. The computational grid contains one million nodes. For code validation purposes experiments were taken with different fluids and mixtures and the influence of the different hubs was studied. In all cases a good agreement between measurements and numerical results could be achieved with existing models of the CFD code.
Keywords: safety valve, CFD
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    CD_ROM, paper 0249
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10901 - Permalink


Modelling
van den Hoff, J.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    XX. Winterschule für Medizinische Physik, 25.-29.02.2008, Pichl, Austria

Publ.-Id: 10900 - Permalink


Quantitative Verfahren in der Positronen-Emissions-Tomographie
van den Hoff, J.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Bildgebung des Herzens - Workshop zur biomedizinischen Bildgebung, 18.02.2008, Würzburg, Germany

Publ.-Id: 10899 - Permalink


Visualization of branch points in PT-symmetric waveguides
Klaiman, S.; Günther, U.; Moiseyev, N.;
The visualization of an exceptional point in a PT-symmetric directional coupler (DC) is demonstrated. In such a system the exceptional point can be probed by varying only a single parameter. Using the Rayleigh-Schrödinger perturbation theory we prove that the spectrum is real as long as the radius of convergence has not been reached. We also show how one can use a PT-symmetric DC to measure the radius of convergence for non PT-symmetric structures. For such systems the physical meaning of the rather mathematical term `radius of convergence´ is exemplified.

Publ.-Id: 10897 - Permalink


Neuartige Lichtemitter und Nanosonden für zukünftige Optoelektronik und Nanotechnologie
Helm, M.;
Nach einem kurzen Überblick über die Forschung an meinem Institut möchte ich zwei Themengebiete näher diskutieren:
(1) Lichtemitter auf Basis von Silizium MOS Strukturen als möglicher Weg zu einer integrierten Silizium-Optoelektronik
(2) Infrarot-Nahfeldmikroskopie als Methode zur Untersuchung von oberflächennahen Nanostrukturen, hier demonstriert an ferroelektrischen Domänen in BaTiO3.
Keywords: Silizium Lichtemitter, Infrarot Nahfeldmikroskopie
  • Lecture (others)
    Seminarvortrag an der TU Wien, 05.12.2007, Wien, Austria

Publ.-Id: 10896 - Permalink


Quantitative Chemical Speciation in Environmental Systems: Statistical Approaches to EXAFS
Scheinost, A.;
- wird nachgereicht
  • Invited lecture (Conferences)
    School on Synchrotron X-ray and IR Methods Focusing on Environmental Sciences, 21.-23.01.2008, Karlsruhe, Deutschland

Publ.-Id: 10895 - Permalink


Short time thermal processing: From electronics via photonics to pipe organs of the 17th century
Skorupa, W.;
There is a clear and increasing interest in short time thermal processing far below one second, i.e. the lower limit of RTP (Rapid Thermal Processing) called spike annealing. It is the world of preocessing in the millisecond or nanosecond range. This was driven by the need of suppressing the so-called Transient Enhanced Diffusion in advanced boron-implanted shallow pn-junctions in the front-end silicon chip technology. Meanwhile the interest in flash lamp annealing (FLA) in the millisecond range spread out into other fields related to silicon technology and beyond. This paper reports shortly about the restart in flash lamp annealing of the Rossendorf group in collaboration with the Mattson group and further on recent experiments regarding shallow junction engineering in germanium, annealing of ITO layers on glass and plastic foil to form an conductive layer as well as investigations which we did during the last years in the field of wide band gap semiconductor materials (SiC, ZnO). Moreover recent achievements in the field of silicon-based light emission basing on Metal-Oxide-Semiconductor Light Emitting Devices will be reported. Finally it will be demonstrated that the basic principle of short time thermal processing, i.e. surface heating on a colder bulk, features also advantages regarding the casting of lead sheets to produce organ pipes in the spirit of the 17th century.
Keywords: millisecond processing, flash lamp annealing, silicon, germanium, indium tin oxide, silicon carbide, ziic oxide, photonics, light emission, electroluminescence, wafer stress.
  • Materials Science Forum 573-574(2008), 417-428
  • Invited lecture (Conferences)
    Mattson International Technology Seminar, 07.05.2008, Maritim Hotel Ulm, Deutschland
  • Invited lecture (Conferences)
    23. Nutzertreffen Kurzzeittemperung, 08.05.2008, Erlangen, Deutschland
  • Invited lecture (Conferences)
    VII-th International Conference on Ion Implantation and Other Applications of Ions and Electrons, 16.-19.06.2008, Kazimierz Dolny, Polen

Publ.-Id: 10894 - Permalink


Realistische Simulation von Reaktivitätsstörfällen mit gekoppelten neutronenkinetisch-thermohydraulischen Systemcodes - Abschlussbericht
Kliem, S.;
Der gekoppelte Programmkomplex DYN3D/ATHLET wurde im Rahmen der Arbeiten zum Projekt weiterentwickelt. Dabei wurde das in der externen Kopplung von DYN3D und ATHLET verfügbare Modell für die Beschreibung der Kühlmittelvermischung auf weitere Szenarien erweitert und in die anderen beiden Kopplungsoptionen implementiert. Des Weiteren wurde ein spezielles Modell zur Vermeidung der numerischen Diffusion beim Bortransport innerhalb des Reaktorkerns, das für DYN3D entwickelt worden war, in das Thermohydraulikprogramm ATHLET übertragen.
Für die Analyse von heterogenen Borverdünnungsstörfällen wurde eine Methodik bestehend aus stationären und transienten Rechnungen entwickelt. Durch die Implementierung des o.g. Modells zur realistischen Beschreibung der Kühlmittelvermischung in den gekoppelten Programmkomplex DYN3D/ATHLET war es möglich, eine neue Qualität in der Analyse von Borverdünnungsstörfällen zu erreichen. Die Methodik wurde auf zwei verschiedene Borverdünnungsstörfalle angewandt. Wesentliches Ergebnis ist, dass entsprechend den Rechenergebnissen selbst bei Vorgabe einer aus konservativen Abschätzungen stammenden maximalen Pfropfengröße für beide Szenarien die Integrität des Brennstoffs nicht gefährdet ist. Die entsprechenden Studien zeigten die großen Reserven, die beim konsequenten Abbau von Konservativitäten freigesetzt werden können. Der entscheidende Beitrag zu diesem Abbau ist dabei auf die realistische Modellierung der Vermischung der deborierten Pfropfen innerhalb des Reaktordruckbehälters zurückzuführen. Von Vorteil erwies sich hier der Einsatz der verschiedenen Kopplungsoptionen. Die damit verbundene Anwendung unterschiedlicher Thermohydraulikmodelle auf ein und dieselbe Störfalltransiente erhöht das Vertrauen in die erzielten Ergebnisse.
Die Untersuchungen zur Borverdünnung während des Nachkühlbetriebes wurden in einem gesonderten Bericht ausführlich dargestellt. Dieser Bericht wird derzeit im Rahmen eines Genehmigungsverfahrens eingesetzt.
Erstmals wurde das Programm DYN3D/ATHLET auf eine ATWS-Transiente angewandt. Am Beispiel der Transiente: „Ausfall der Hauptspeisewasserversorgung“ wurde der Einfluss verschiedener thermohydraulischer und neutronenkinetischer Randbedingungen auf die Ergebnisse untersucht. Der wichtigste Sicherheitsparameter bei der betrachteten Transiente ist der Druck im Primärkreislauf. Im Bereich der thermohydraulischen Variationen hat die Effektivität der Entlastungs- und Sicherheitsventile den größten Einfluss auf diesen Parameter. Der berechnete Maximaldruck hängt auch stark von der Kernbeladung ab. So wurde gezeigt, dass mit Erhöhung der Anzahl der MOX-Brennelemente das berechnete Druckmaximum deutlich niedriger ausfällt. Weiterhin wurden die Rückkopplungsparameter einer generischen Kernbeladung einer statistischen Unsicherheits- und Sensitivitätsanalyse unterzogen, in deren Verlauf 100 Variationsrechnungen durchgeführt wurden. Diese Analyse ergab, dass dabei bei identischer relativer Variationsbreite der Rückkopplungskoeffizient der Moderatordichte einen doppelt so großen Einfluss auf den berechneten Maximaldruck hat wie der Koeffizient der Brennstofftemperatur.
Mit dem Programmkomplex DYN3D/ATHLET steht ein anwendungsbereites Werkzeug mit einer breiten Validierungsbasis für die Analyse von Störfällen zur Verfügung, in denen die enge Kopplung von Neutronenkinetik und Thermohydraulik unter Berücksichtigung des Einflusses der Anlagenkomponenten von Bedeutung ist. Es kann für konkrete Nachweisrechnungen einschließlich der Quantifizierung von Unsicherheiten auf Basis deterministischer oder statistischer Ansätze eingesetzt werden.
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2007
    FZD\FWS\2007\11
    113 Seiten

Publ.-Id: 10893 - Permalink


Science at the new Dresden High Magnetic Field Laboratory
Wosnitza, J.;
hat nicht vorgelegen
  • Invited lecture (Conferences)
    International Conference on Magnetic Materials (ICMM-2007), 11.-16.12.2007, Kolkata, India

Publ.-Id: 10892 - Permalink


Die Jagd nach dem Feldrekord: Forschung in hohen Magnetfeldern
Wosnitza, J.;
hat nicht vorgelegen
  • Invited lecture (Conferences)
    Physikalisches Kolloquium der Universität Frankfurt, 05.12.2007, Frankfurt/ M., Germany

Publ.-Id: 10891 - Permalink


Comparison of the americium(III), neptunium(V) and uranium(VI) sorption onto kaolinite in the absence and presence of humic acid
Schmeide, K.; Krepelova, A.; Sachs, S.; Bernhard, G.;
We studied the sorption of Am(III), Np(V) and U(VI) onto kaolinite under aerobic and anaerobic conditions as a function of pH, ionic strength and actinide concentration in a series of batch equilibrium experiments. These actinides were selected as representatives of actinides in different oxidation states. Furthermore, we studied the influence of humic acid on the actinide sorption.
Keywords: americium, neptunium, uranium, sorption, humic acid, trivalent, pentavalent, hexavalent
  • Lecture (Conference)
    2nd International Nuclear Chemistry Congress, 13.-18.04.2008, Cancún, Mexico
  • Contribution to proceedings
    2nd International Nuclear Chemistry Congress, 13.-18.04.2008, Cancún, Mexico

Publ.-Id: 10890 - Permalink


Sorption of U(VI) onto an artificial humic substance-kaolinite-associate
Sachs, S.; Bernhard, G.;
An artificial humic substance-kaolinite-associate was synthesized as a model substance for natural clays containing organic matter in clay formations, soils, and sediments. The U(VI) sorption onto this model substance was studied in batch experiments as a function of pH and compared to the U(VI) sorption onto kaolinite in absence and presence of separately added humic acid (HA).
The humic substance-kaolinite-associate has a TOC content of 4.9 mg/g. It was found that the humic matter associated with kaolinite exhibits an immobilizing as well as an mobilizing effect on U(VI). Between pH 3 and 5, humic matter causes an increase in the U(VI) sorption onto kaolinite, whereas at pH above 5 the release of humic matter from the associate in the solution and the formation of dissolved uranyl humate complexes reduces the U(VI) sorption. The U(VI) sorption onto the synthetic humic substance-kaolinite-associate differs from that of U(VI) in the system U(VI)-HA-kaolinite with comparable amounts of separately added HA. Separately added HA causes a stronger mobilizing effect on U(VI) than humic matter present in the humic substance-kaolinite-associate. This can be attributed to structural and functional dissimilarities of the humic substances.
Keywords: Uranium, Sorption, Clay, Kaolinite, Humic matter

Publ.-Id: 10889 - Permalink


Determination of structural components, e.g. exopolymeric substances (EPS) within biofilms and their effect on the immobilisation of actinides (U) - Determination of pH, Eh, and dissolved oxygen and their influence on the actinide speciation
Krawczyk-Bärsch, E.; Arnold, T.; Großmann, K.;
Fluorescent uranium(V) and uranium(VI) particles were observed for the first time in vivo by a combined laser fluorescence spectroscopy and confocal laser scanning microscopy approach in a living multispecies biofilm grown on biotite plates. Anaysis of amplified 16S rRNA fragments and fluorescence in situ hybridization were used to characterize the biofilm communities. Laser fluorescence spectroscopy was used to identify these particles. The particles showed either a characteristic fluorescence spectrum in the wavelength range of 415-475 nm, indicative for uranium(V), or in the range of 480-560 nm, which is typical for uranium(VI). Particles of uranium(V) as well as uranium(VI) were simultaneously observed in the biofilms. These uranium particles were attributed for uranium(VI) to biologically mediated precipitation and for uranium(V) to redox processes taking place within the biofilms. Concentration profiles of oxygen versus biofilm depths were measured in the biofilms by electrochemical microsensors with a tip diameter of 10µm. A motor-driven micromanipulator was used for moving downwards through the biofilm in 20 or 50µm steps. The microsensor results clearly showed that the vertical profiles of the O2 concentration within the biofilms are affected by the presence as well as by the concentration of U(VI) in the culture media. In the absence of uranium the O2 concentration in the well aerated biofilm decreased slightly. In contrast, O2 concentrations in the biofilms, which were exposed to different concentrations of uranium, decreased with increasing uranium concentration.
Keywords: biofilm, uranium, oxygen microsensors
  • Lecture (Conference)
    3rd Semi-Annual RTDC-2 meeting of FUNMIG, 26.08.2007, München, Deutschland

Publ.-Id: 10888 - Permalink


WnSm-Clusters: Possible Building Blocks for New Nanomaterials?
Westhäuser, W.; Mangler, T.; Fischer, T.; Gemming, S.; Seifert, G.; Ganteför, G.;
Since bulk WS2 forms layered structures similar to bulk graphite, this material might also built up stable cage-like fullerene structures. Large graphite-like structures (multiwall fullerenes, nanotubes) have been found in TEM experiments, but so far no anorganic fullerenes have been detected in the size regime of C60. Thus, we started a search for WS2 fullerenes by combining gas phase and deposition experiments. In the gas phase, we identified a variety of different structures (nanowires, nanoplatelets) in the size regime up to 30 metal atoms [1-3]. To investigate the suitability as building blocks, in a first attempt small size-selected WnSm-clusters were soft-landed on Ag- and Si substrates at ultrahigh vacuum conditions. These samples were analysed via HREELS and XPS. The HREELS spectra are different for the different cluster sizes indicating that these clusters survived the soft landing on the substrate and do not coalesce to bulk-like structures.
[1] S. Gemming, J. Tamuliene, G. Seifert, N. Bertram, Y.D. Kim, and G. Ganteför, Appl. Phys. 82, 161 (2006)
[2] N. Bertram, Y.D. Kim, G. Ganteför, Q. Sun, P. Jena, J. Tamuliene, and G. Seifert, Chem. Phys. Lett. 396, 341 (2004)
[3] N. Bertram, J. Cordes, Y.D. Kim, G. Ganteför, S. Gemming, and G. Seifert, Chem. Phys. Lett. 418, 36 (2006)
Keywords: MoS2, WS2, sulfide, nanostructures, DFT, density-functional
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10885 - Permalink


Modelling a nanoscale ferroic OFET
Gemming, S.; Enyashin, A. N.; Seifert, G.; Eng, L. M.;
The present study describes an approach for the scale-bridging modelling of ferroic materials as functional elements in micro- and nanoelectronic devices. Ferroic materials are characterised by temperature-dependent complex ordering phenomena of the internal magnetic, electronic, and structural degrees of freedom with several involved length and time scales. Hence, the modelling of such compounds is not straighforward, but relies on a combination of electronic-structure-based methods like ab-initio and density-functional schemes with classical particle-based approaches given by Monte-Carlo simulations with Ising, lattice-gas, or Heisenberg Hamiltonians, which incorporate material-specific parameters both from theory and experiment. The interplay of those methods is demonstrated for device concepts based on electroceramic materials like ferroelectrics and multiferroics, whose functionality is closely related with their propensity towards structural and magnetic polymorphism. In the present case, such scale-bridging techniques are employed to aid the development of an organic field effect transistor on a ferroelectric substrate generated by the self-assembly of field-sensitive molecules on the surfaces of ferroic oxides.
Keywords: OFET, ferroic, multi-scale, DFT, density-functional, Monte-Carlo
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10884 - Permalink


Point defects in germanium - theory and experiment
Gemming, S.; Wündisch, C.; Posselt, M.;
The functionality of standard silicon-based semiconductor devices is achieved by careful point defect engineering, hence tremendous efforts have been made to arrive at a quantitative understanding of the underlying interactions. Germanium has distinct advantages over silicon, for instance the lower energy gap between occupied and empty electronic states and the resultant lower carrier injection barriers. However, point defect engineering in germanium has not yet reached a level of sophistication comparable with the one in silicon. Thus, both theoretical and experimental investigations were carried out to study the interaction of point defects in germanium.
Conductivity measurements of phosphorus-implanted germanium indicate that not all dopant atoms are electronically active. Therefore density-functional calculations were carried out to study the properties of Ge vacancies, substitutional phosphorus defects and their interaction. Stable defect clusters are obtained, and in the limit of high dopant concentration an electrically inactive form of the P dopant is predicted.
Keywords: germanium, doping, phosphorus, DFT, density-functional
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10883 - Permalink


A Hybrid Modelling Approach for the Structural Evolution of Surfaces
Gemming, S.; Kundin, J.; Radke De Cuba, M.; Yu, C.-J.; Emmerich, H.;
The Burton-Cabrera-Frank (BCF) model describes the structural evolution of vicinal surfaces in terms of an incoming particle flux and concentration-dependent desorption and surface diffusion terms. A continuum formulation of the BCF scheme given by a phase-field implementation for the moving-boundary problem yields the long-term evolution of the step structure during a step-flow growth mode. A particle-based Ising-type approach with a Metropolis-Monte-Carlo kinetics additionally provides nucleation processes in a temperature-controlled manner and on a shorter time and length scale. We have integrated both approaches in a hybrid algorithm, which describes adsorption, nucleation, and structure evolution processes at solid-liquid and solid-gas interfaces on both time and length scales. The short term nucleation is resolved by the Monte-Carlo generated dynamics of an anisotropic Ising model, whose interaction parameters stem from first-principles calculations. The long-term microstructure dynamics is calculated by the phase-field method. Several growth modes are distinguished: In addition to step-flow growth the nucleation processes on the terraces can lead to roughening or an epitaxial layer-by-layer growth controlled by temperature and by flux.
Keywords: Burton-Cabrera-Frank, Hybrid model, Monte-Carlo, phase-field, vicinal, nucleation
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10882 - Permalink


DFT for the Actinides
Tsushima, S.;
no abstract for this publication
Keywords: DFT, actinide
  • Lecture (others)
    internal ROBL seminar, 13.3.2007, Grenoble, France

Publ.-Id: 10881 - Permalink


Hydration of U(VI,V) and Np(VI) Ions Revisited
Tsushima, S.;
no abstract for this publication
Keywords: hydration, actinide, DFT
  • Poster
    17th ESRF User's Meeting, 05.-8.2.2007, Grenoble, France

Publ.-Id: 10880 - Permalink


Quantum Chemical Calculations of U(VI) Aquo and Sulfato complexes
Tsushima, S.;
no abstract for this publication
Keywords: quantum chemistry, EXAFS
  • Invited lecture (Conferences)
    GRK Symposium "Speciation of Radionuclides in the Environment", 21.09.2006, Mainz, Germany

Publ.-Id: 10879 - Permalink


Thermochromatographic Studies of Plutonium Oxides
Hübener, S.; Taut, S.; Vahle, A.; Bernhard, G.; Fanghänel, T.;
Trace amounts of oxidic plutonium species were studied by thermochromatography in silica glass columns in comparison to oxidic species of Th, Pa, U, Np, and Am. Humid oxygen was used as reactive admixture to the carrier gas helium. The thermochromatographic behavior of plutonium provides evidence for the oxidation of Pu(IV) to Pu(VI) with humid oxygen. The gas chromatographic transport of U, Np, and Pu is governed by the surface reaction
MO2(OH)2(g) = MO3(ads) + H2O(g)
with M = U, Np, and Pu in the hexavalent state and competitive reactions of the actinide oxides with silica to nonvolatile compounds or solid solutions. There is good agreement with earlier volatility studies and the reported oxidation of PuO2 with water. The oxidation to PuO4 as claimed by Domanov could not be confirmed.
Keywords: Plutonium oxides, thermochromatography, oxidation, volatility

Publ.-Id: 10878 - Permalink


Influence of uranium (VI) on the metabolic activity of stable multispecies biofilms studied by oxygen microsensors and fluorescence microscopy
Krawczyk-Bärsch, E.; Arnold, T.; Großmann, K.; Hofmann, S.; Wobus, A.;
The effect of uranium added in ecologically relevant concentrations (1×10-5 M and 1×10-6 M) to stable multispecies biofilms was studied by electrochemical oxygen microsensors with tip diameters of 10 µm and by confocal laser fluorescence microscopy (CLSM). The microsensor profile measurements in the stable multispecies biofilms exposed to uranium showed that the oxygen concentration decreased faster with increasing biofilm depth compared to the uranium free biofilms. In the uranium containing biofilms, the oxygen consumption, calculated from the steady-state microprofiles, showed high consumption rates of up to 68 nmol cm-3s-1 in the top layer (0 - 70 µm) and much lower consumption rates in the lower zone of the biofilms. Staining experiments with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and 4,6-diamidino-2-phenylindole (DAPI) confirmed the high respiratory activities of the bacteria in the upper layer. Analysis of the amplified 16S rRNA gene fragments showed that the addition of uranium in ecological relevant concentrations did not change the bacterial diversity in the stable multispecies biofilms and is therefore not responsible for the different oxygen profiles in the biofilms. The fast decrease in the oxygen concentrations in the biofilm profiles showed that the bacteria in the top region of the biofilms, i.e. the metabolically most active biofilms zone, battle the toxic effects of aqueous uranium with an increased respiratory activity. This increased respiratory activity results in O2 depleted zones closer to the biofilm air interface which triggers redox processes leading to a precipitation of uranium(IV) solids and consequently to a removal of uranium from the aqueous phase.

Publ.-Id: 10876 - Permalink


Bacteria-based nanoscaled materials
Selenska-Pobell, S.;
- wird nachgereicht
  • Invited lecture (Conferences)
    Institut für Neue Materialien GmbH, 23.02.2007, Saarbrücken, Germany

Publ.-Id: 10875 - Permalink


Novel S-layer supported Pd bionanocatalysts
Selenska-Pobell, S.;
- wird nachgereicht
  • Invited lecture (Conferences)
    Institute of Molecular Biology, 26.09.2007, Sofia, Bulgaria

Publ.-Id: 10874 - Permalink


Biogeochemical changes in uranium wastes induced by increased U(VI) and nitrate concentrations
Selenska-Pobell, S.;
- wird nachgereicht
  • Invited lecture (Conferences)
    Institute of Microbiology, 02.11.2007, Prague, Czech Republic

Publ.-Id: 10872 - Permalink


Boden-Pflanzen Transfer von U(VI) - Anwendung mikroskopischer und spektroskopischer Methoden zur Charakterisierung der chemischen Speziation
Günther, A.;
Darstellung von ausgewählten Methoden zur Bestimmung der chemischen Speziation von Uran(IV) im System Boden-Pflanze
  • Lecture (Conference)
    Workshop "Uran in Böden", 04.12.2007, Freiberg, Germany

Publ.-Id: 10871 - Permalink


Increased metabolic activity in biofilms caused by uranium: A microsensor study
Krawczyk-Bärsch, E.; Arnold, T.; Großmann, K.; Wobux, A.; Diessner, S.;
- wird nachgereicht
  • Poster
    ISEB 18 - International Symposia on Environmental Biogeochemistry, 11.-16.11.2007, Taupo, New Zealand

Publ.-Id: 10870 - Permalink


Curvature effects of nitrogen on graphitic sheets: Structures and energetics
Mandumpal, J.; Gemming, S.; Seifert, G.;
A correlation of the nitrogen concentration on graphitic sheets with structural deformations is presented using the density functional based tight binding method (DFTB). Graphite sheets of various sizes were doped by nitrogen at different sites; either a local deviation from planarity or negative curvature is obtained. In addition, we derive a formula for constructing two sets of isomer series namely methylene cyclopentadiene and benzene to study nitrogen's role in positive curvature formation. Comparing these structures, the exact energy difference to convert a fully hexagonal network to a pentagon centered hexagonal network can be predicted systematically for infinitely large structures. (c) 2007 Elsevier B.V. All rights reserved.
Keywords: CNX THIN-FILMS; CARBON-NITRIDE; FULLERENES; DEPOSITION; STABILITY
  • Chemical Physics Letters 447(2007)(1-3), 115-120

Publ.-Id: 10869 - Permalink


Intersubband relaxation dynamics in narrow InGaAs/AlAsSb quantum well structures studied by femtosecond pump-probe spectroscopy
Tribuzy, C. V.-B.; Ohser, S.; Winnerl, S.; Grenzer, J.; Schneider, H.; Helm, M.; Neuhaus, J.; Dekorsy, T.; Biermann, K.; Künzel, H.;
Intersubband transitions (ISBT) in semiconductor quantum wells have been attracting much attention for infrared optoelectronic device applications such as quantum cascade lasers and quantum well infrared detectors. There is also considerable interest to extend ISBT to short wavelengths (< 2 μm), for devices applications such as fast switching and modulators, due to ultrafast intersubband relaxation in the picosecond and subpicosecond regime. Therefore attentions were driven to heterosystem with large conduction band offsets (> 1 eV).
On the other hand, to achieve short wavelengths thin quantum wells (< 3 nm) are required, where the first excited state inside the QW may lie higher than some state related to indirect valleys. Examples for such material systems are strained InGaAs/AlAs or lattice matched InGaAs/AlAsSb, both grown on InP.
We have studied the intersubband relaxation dynamics in multi QWs of both material systems by femtosecond pump-probe measurements using an optical parametric oscillator. By the transient transmission as a function of the pump-probe delay we observe that some long living states are present in our systems, showing that more than two levels might be involved in the relaxation dynamics. This can be caused by transfer of electrons to X- or L-states in the QWs or the barriers. To investigate the origin of such long living states and the involved relaxation time constants, we have studied samples with different QW thicknesses, containing doping impurities localized either inside the QW or at the barriers. The experimental results are compared to simulations based on rate equations.
Keywords: Intersubband relaxation, InGaAs/AlAsSb quantum wells
  • Poster
    28th International Conference on the Physics of Semiconductors (ICPS-28), 24.-28.07.2006, Wien, Österreich
  • Contribution to proceedings
    28th International Conference on the Physics of Semiconductors (ICPS-28), 24.-28.07.2006, Wien, Österreich
    AIP Conf. Proc. 893, 473 (2007)

Publ.-Id: 10868 - Permalink


Liquid metal Taylor-Couette experiment on the magnetorotational instability
Gundrum, T.; Stefani, F.; Gerbeth, G.; Szklarski, J.; Ruediger, G.; Hollerbach, R.;
The magnetorotational instability (MRI) plays an essential role in the formation of stars and black holes. By destabilizing hydrodynamically stable Keplerian flows, the MRI triggers turbulence and enables outward transport of angular momentum in accretion discs which is necessary for the mass accumulation of central objects.
In order to examine the MRI we applied helical magnetic fields to a Taylor-Couette experiment with the liquid alloy GaInSn [1,2,3]. The low velocities of the liquid metal in the experiment are measured using an ultrasonic Doppler velocimeter.
The results show typical predicted features of MRI at Reynolds numbers of the order 1000 and Hartmann numbers of the order 10. Particular focus is laid on new results with an improved experiment in which split end caps are used to minimize the effect of Ekman pumping.
Keywords: MRI
  • Lecture (Conference)
    6th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 09.-11.09.2008, Praha, Czech Republic
  • Contribution to proceedings
    6th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 09.-11.09.2008, Praha, Czech Republic
    Proceedings of the 6th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Praque, Czech Republic: Czech Technical University in Praque, 978-80-87117-05-7, 65-68

Publ.-Id: 10867 - Permalink


Severe accident analysis for VVER-1000/V-320 for a station blackout accident scenario with ASTEC V1.3.0
Tusheva, P.; Reinke, N.; Hurtado, A.; Schäfer, F.;
This paper presents the results from a severe accident analysis performed with ASTEC V1.3.0 code for a nuclear power plant with a VVER-1000/V-320 reactor. The purpose of this analysis is to assess the ASTEC code behaviour in modelling of main severe accident phenomena in the primary and secondary circuit arising during a hypothetical severe accident. The performed analyses cover a station blackout (SBO) sequence with passive safety injection systems (hydro-accumulators), in order to investigate the capabilities of ASTEC to model the physical phenomena during the in-vessel phase of such a transient.

An investigation on a SBO scenario with primary side depressurization has been carried out. The code results show delayed RPV failure by depressurization of the primary side, as slowing the core damage would allow more time for systems to be recovered to mitigate or terminate the accident. This would give more time and different possibilities for operator interventions.
Keywords: astec, severe accident analysis, SBO, accident management measures
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10866 - Permalink


P0609-Erhöhung der Oxidationsbeständigkeit von TiAl-Legierungen durch die kombinierte Implantation von Fluor und Silizium
Schütze, M.; Donchev, A.; Yankov, R.; Richter, E.;
Die kombinierte Implantation von Fluor und Silizium in die Werkstoffoberfläche von TiAl-Legierungen kann deren Oxidationsbestähigkeit im Temperaturbereich von 750 bis 1100°C an Luft gegenüber unbehandelten TiAl-Legierungen deutlich erhöhen. Die Implantation kann durch verschiedene Verfahren, einmal die Beamline-Ionenimplantation (BLII) oder die Plasma-lmmersion-Ionenimplantation(PlII,PI3), erfolgen. Entgegen dem bisherigen Kenntnisstand, wo nur reine Halogene imlantiert wurden, lassen sich durch die Kombination von Fluor und Silizium bessere Ergebnisse als bei reiner Fluorimplantation erzielen.
  • Patent
    DE 10 2006 043 436 B3 - 29 Nov 2007

Publ.-Id: 10865 - Permalink


Hydrophilic oxybathophenanthroline ligands: Synthesis and copper(II) complexation
Stephan, H.; Juran, S.; Born, K.; Comba, P.; Geipel, G.; Hahn, U.; Werner, N.; Vögtle, F.;
Hydrophilic oxybathophenanthroline dendrons (generation 1 to 3) have been synthesized by treatment of 4,7-bis(4´-hydroxyphenyl)-1,10-phenanthroline with the corresponding bromo-functionalized etheraryl branching units containing triethylene glycol monomethyl end groups. Radiotracer experiments using 64Cu prove the rapid formation of stable copper(II) complexes in aqueous solution. These 64Cu complexes remain unchanged even upon addition of a high excess of glutathion as competing ligand, thus demonstrating the high stability of the formed copper(II) complexes. Electronic and EPR spectroscopy indicate the formation of [Cu(L)2(OH2)2]2+ (L = Ligand) complexes in aqueous solution, confirmed by time-resolved laser fluorescence spectroscopy and supported by molecular mechanics modeling.

Publ.-Id: 10864 - Permalink


Synthesis of modified pyrimidine bases and positive impact of the chemically reactive substituents on their in vitro antiproliferative activity
Noll, S.; Kralj, M.; Suman, L.; Stephan, H.; Piantanida, I.;
The antiproliferative activity screening on human tumor cell lines of a series of modified uracil and cytosine bases as well as some corresponding acyclonucleotides, and comparison of structure-activity relationship revealed the importance of chemical reactivity of the substituent attached to the C5-position of uracil for the activity of studied compounds. Namely, the results obtained for the most active compounds, 5-(chloroacetylamino)uracil (2) and its acyclic sugar analogue 18, suggest that formation of a covalent bond between reactive substituent and several possible targets within the thymidylate synthase mechanism (sulphur of the cysteine residue, basic part of the enzyme, N,N-methylene tetrahydrofolate or its reactive iminium forms) is the most probable mode of action. In addition, novel C5-substituted uracil derivative 6 (5-[bis-(2-p-methoxybenzylthioethyl)amine]-acetylaminouracil) exhibited high antiproliferative activity against HeLa and MiaPaCa-2 cell lines, by an as yet unknown mechanism.
  • European Journal of Medicinal Chemistry 44(2009), 1172-1179
    DOI: 10.1016/j.ejmech

Publ.-Id: 10862 - Permalink


Junction formation in Ge by ion implantation
Satta, A.; Simoen, E.; van Daele, B.; Clarysse, T.; Nicholas, G.; Vandervorst, W.; Anwand, W.; Skorupa, W.; Peaker, T.; Markevich, V.;
Ion implantation in Ge is studied at energies and doses relevant for application to advanced modern devices, such as CMOS transistors. Shallow donors like P typically have high diffusivity and low activity in view of the formation of shallow, low-resistance junctions. Similarly to the Si case, co-doping with non-dopant elements (N in this study) and advanced annealing techniques, such as FLA annealing, can provide a viable route to significantly improve the trade-off of n-type Ge junctions.
Residual implant-induced defectivity, which can be a source of enhanced diffusion and generation currents in Ge diodes, seems to remain up to temperatures (≥ 500 oC) important for activation of dopants in Ge.
However, once the thermal budget is optimized for implant damage removal, the Ge diode leakage may be dominated by surface generation currents, due to a high density of surface states, not efficiently reduced by current passivation schemes.
Keywords: ion implantation, shallow junctions, germanium, flash lamp annealing, rapid thermal annealingphosphorus, co-doping, nitrogen, electrical activation, diodes, leakage current
  • Contribution to proceedings
    International Workshop on INSIGHT in Semiconductor Device Fabrication, Metrology and Modeling (INSIGHT-2007), 06.-09.05.2007, Napa, USA
    Proceedings INSIGHT-2007 Workshop, 297-308
  • Invited lecture (Conferences)
    International Workshop on INSIGHT in Semiconductor Device Fabrication, Metrology and Modeling (INSIGHT-2007), 06.-09.05.2007, Napa, USA

Publ.-Id: 10860 - Permalink


Meyer-Neldel rule in ZnO
Schmidt, H.; Wiebe, M.; Dittes, B.; Grundmann, M.;
Seventy years ago Meyer and Neldel investigated four polycrystalline n-type conducting ZnO rods [W. Meyer and H. Neldel, Z. Tech. Phys. (Leipzig) 12, 588 (1937)]. The specific conductivity increased exponentially with temperature. A linear relationship between the thermal activation energy for the specific conductivity and the logarithm of the prefactor was observed. Since then thermally activated processes revealing this behavior are said to follow the Meyer-Neldel (MN) rule. We show that the emission of charge carriers from deep electron traps in ZnO follows the MN rule with the isokinetic temperature amounting to 226±4 K.

Publ.-Id: 10859 - Permalink


Short time thermal processing of materials - beyond electronics and photonics to pipe organ materials
Skorupa, W.;
There is a clear and increasing interest in short time thermal processing far below one second, i.e. the lower limit of RTP (Rapid Thermal Processing) called spike annealing. It is the world of preocessing in the millisecond or nanosecond range. This was recently driven by the need of suppressing the so-called Transient Enhanced Diffusion in advanced boron-implanted shallow pn-junctions in the front-end silicon chip technology. Meanwhile the interest in flash lamp annealing (FLA) in the millisecond range spread out into other fields related to silicon technology and beyond. This talk reports shortly about the restart in flash lamp annealing of the Rossendorf group in collaboration with other groups and further on recent experiments regarding shallow junction engineering in germanium, annealing of ITO layers on glass and plastic foil to form an conductive layer as well as investigations which we did during the last years in the field of wide band gap semiconductor materials (SiC, ZnO). Moreover recent achievements in the field of silicon-based light emission basing on Metal-Oxide-Semiconductor Light Emitting Devices will be reported. Finally it will be demonstrated that short time thermal processing features also advantages regarding the casting of lead sheets to produce organ pipes in the spirit of the 17th century - as a completely different world of materials processing!
Keywords: short time annealing, flash lamp annealing, transient enhanced diffusion, silicon-based light emission, shallow junction engineering, germanium, silicon, silicon carbide, zinc oxide, indium tin oxide, lead casting, pipe organ materials
  • Invited lecture (Conferences)
    Seminarvortrag am Max Planck Institut für Mikrostrukturphysik, 05.12.2007, Halle/Saale, Germany

Publ.-Id: 10858 - Permalink


Investigations of biochemical interactions of actinides with microorganisms and plants.
Reitz, T.; Geissler, A.; Merroun, M. L.; Selenska-Pobell, S.; et all;
This presentation show an overview about the research at the IRC, in particular about the investigations of the biochemical interactions of actinides with microorganisms and plants.
  • Lecture (others)
    2nd phD Seminar, 26.-28.09.2007, Rabenberg, Germany

Publ.-Id: 10857 - Permalink


Changes in archaeal community of a uranium mining waste pile induced by treatments with uranyl or sodium nitrate.
Reitz, T.; Geissler, A.; Merroun, M. L.; Selenska-Pobell, S.;
Changes in the archaeal community of a uranium mining waste pile, called Haberland caused by the addition of uranyl or sodium nitrate were investigated by using the 16S rRNA gene retrieval. The natural archaeal diversity in studied environment was limited to only a few lineages of mesophilic Crenarchaeota, predominantly of subgroup 1.1a. Addition of and subsequent incubation with uranyl nitrate for 4 weeks resulted in a significant shifting of the archaeal populations to the soil/sediment cluster 1.1b of Crenarchaeota. The proliferation of the latter populations occurred independently of the amount of the added uranium and the aeration conditions during the incubation. The same shifting of the archaeal populations was also observed in the parallel control samples which were supplemented with sodium nitrate.
Efforts to culture members of the 1.1b Crenarchaeota resulted in their enrichment together with representatives of Firmicutes, mainly of Clostridium spp. Clostridia can effectively interact with uranium and they can also fermentatively reduce nitrate to ammonium. Because an ammonia oxidizing activity was deduced on the basis of meta-genomic analyses of the closest relative to the stimulated in our case 1.1b populations, we speculate that the clostridia possibly supply the crenarchaeal members of the recovered synergetic consortium with ammonia.
  • Poster
    BAGECO 9 - 9th Symposium on Bacterial Genetics and Ecology, 23.-27.07.2007, Wernigerode, Germany

Publ.-Id: 10856 - Permalink


Crenarchaeota 1.1b and Firmicutes consortium recovered from a uranyl nitrate treated uranium waste sample and its possible role against the toxicity of uranium.
Reitz, T.; Geissler, A.; Merroun, M. L.; Selenska-Pobell, S.;
Supplementations of a sample collected from a depleted uranium mining waste pile with uranyl nitrate induced significant changes in microbial community structure during the first four weeks of incubation. At the latter stages of the treatment, however, the initial composition of the community, indigenous for the untreated samples and consisting mostly of uranium sensitive populations, started to set up. This indicates that the added uranium was no longer bio-available, possibly due to the interactions of the induced at the first stages of the treatment uranium resistant populations with the added radionuclide. Studies on archaeal diversity demonstrated a strong shifting from the subgroup 1.1a to the subgroup 1.1b of the mesophilic soil Crenarchaeota within the first four weeks of the incubations.
Our efforts to cultivate representatives of this crenarchaeal group on specific enrichment media from the sample treated with uranyl nitrate under anaerobic (corresponding to the natural) conditions, resulted in the recovery of a consortium consisting of the mentioned 1.1b Crenarchaeota mixed with populations of Firmicutes, mainly of Clostridium spp. Clostridia can effectively interact with uranium and they can also fermentatively reduce nitrate to ammonium. Because an ammonia oxidizing activity was deduced on the basis of meta-genomic analyses for the closest relative to the stimulated in our case 1.1b populations, we speculate that the clostridia possibly supply the crenarchaeal members of the recovered synergetic consortium with ammonia. In addition, a Paenibacillus sp. isolate was cultivated from this consortium and its interactions with uranium were studied by using TEM and EDX analyses.
  • Poster
    Jahrestagung der Vereinigung für Allgemeine und Angewandte Mikrobiologie (VAAM), 01.-04.04.2007, Osnabrück, Germany

Publ.-Id: 10855 - Permalink


Interactions of U(VI) with members of a microbial consortium recovered from a uranium mining waste pile.
Reitz, T.; Geissler, A.; Merroun, M. L.; Selenska-Pobell, S.;
Treatments of a soil sample from a uranium mining waste pile with uranyl nitrate led to a shifting in the crenarchaeal populations from subgroup 1.1a to 1.1b. Efforts to culture members of these Crenarchaeota resulted in an enrichment of a mixed microbial consortium consisting of representatives of 1.1b Crenarchaeota and Firmicutes.
In this study interactions of U(VI) with a pure culture of Paenibacillus sp. JG35+U4-B1 isolated from the mentioned consortium were studied by using a combination of wet chemistry and microscopic methods. Preliminary analyses on U sorption showed that the Paenibacillus strain studied accumulated up to 85 mg U/g dry biomass from a solution with an initial uranium concentration of 120 mg U/l. Live/Dead cell staining indicated that less than 10% of the U-treated cells were viable. Transmission electron microscope (TEM) analyses showed that the cells of the isolated strain accumulated uranium intracellularly as needle-like fibrils, and also at the cell surface. Energy dispersive X-ray (EDX) analysis of these U accumulates demonstrated the presence of U and P indicating that in both cases the phosphate groups are, probably, the main functional binding sites for U(VI).
Efforts to culture other strains from the mentioned consortium and especially of the yet to be cultured 1.1b-Crenarchaeota are in progress in our laboratory. Because our results indicated that these archaeal populations are strongly induced by the addition of U(VI) the study of these organisms is of importance for understanding the natural behavior of U in soils and also for remediation of contaminated sites.
  • Lecture (Conference)
    37ièmes Journées des Actinides, 27.03.2007, Sesimbra, Portugal

Publ.-Id: 10854 - Permalink


Experimental studies and CFD calculations for buoyancy driven mixing phenomena
Da Silva, M. J.; Thiele, S.; Höhne, T.; Vaibar, R.; Hampel, U.;
Buoyancy driven flow is found in many engineering application such as the mixing of fluids with different densities. In nuclear reactor safety the mixing of borated and deborated water is a critical issue that needs investigation, assessment and prediction. Recent progress in computer hardware and numerical techniques has made it viable to predict these mixing patterns using CFD codes. However, as CFD codes contain more or less empirical models it is necessary to validate the predicted results using experimental data. Therefore, a combined numerical and experimental study of buoyant mixing processes has been performed. A newly developed planar sensor was applied to experimentally investigate the mixing process. Validation experiments were performed in the VeMix test facility, which show typical vertical and horizontal flow pattern under different flow regimes. The data from the planar sensor of mixing behavior and velocity fields were used for the validation of the simulation results. Comparisons of the experimental results with the corresponding simulations show similar flow patterns and typical periodic behavior.
Keywords: CFD, validation, buoyancy-driven flow, planar array sensor, image processing
  • Contribution to proceedings
    XCFD4NRS, Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France, MIX-02
  • Lecture (Conference)
    XCFD4NRS, Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France

Publ.-Id: 10853 - Permalink


An 86Y-Labeled Mirror-Image Oligonucleotide: Influence of Y-DOTA Isomers on the Biodistribution in Rats
Schlesinger, J.; Közle, I.; Bergmann, R.; Tamburini, S.; Bolzati, C.; Tisato, F.; Noll, B.; Klussmann, S.; Vonhoff, S.; Wüst, F.; Pietzsch, H.-J.; Steinbach, J.;
A mirror-image oligonucleotide (L-RNA) was radiolabeled with the positron emitting radionuclide 86Y (t1/2 = 14.7 h) via the bifunctional chelator approach. DOTA-modification of the L-RNA (sequence: 5’-Aminohexyl UGA CUG ACU GAC-3’; MW 3975) was performed using (S)-p-SCN-bz-DOTA.

86Y radiolabeling of the DOTA-bz-L-RNA produced more than one species as evidenced by HPLC radiometric detection. For the identification of the 86Y-labeled L-RNA the structural analogue ‘cold’ precursor [Y((S)-p-NH2-bz-DOTA)]- was synthesized. Two coordination isomers were separated via HPLC adopting the square antiprismatic (SAP) and the twisted square antiprismatic (TSAP) geometry, respectively. Their stereochemical configuration in the solution state was assessed by NMR and circular
dichroism spectroscopy. Both [Y((S)-p-NH2-bz-DOTA)]- isomers were converted into isothiocyanate derivatives [Y((S)-p-SCN-bz-DOTA)]- and conjugated to the L-RNA. The identity of the [86Y-DOTA-bz]-L-RNA species was finally established by comparison of the radiometric (86Y) and UV-visible (‘cold’ Y) chromatographic profiles.

Biodistribution studies in Wistar rats showed minor changes in the biodistribution profile of the [86Y((S)-p-NH2-bz-DOTA)]- complex isomers, while no significant differences where observed for the [86Y-DOTA-bz]-L-RNA isomers. High renal excretions were found for the [86Y((S)-p-NH2-bz-DOTA)]- complex isomers as well as for the L-RNA isomers.
  • Bioconjugate Chemistry 19(2008), 928-939
    DOI: 10.1021/bc700453h
  • Lecture (Conference)
    Turku PET Symposium New Targets in Molecular Imaging, 24.-27.05.2008, Turku, Finland
  • Contribution to proceedings
    Turku PET Symposium New Targets in Molecular Imaging, 24.-27.05.2008, Turku, Finland
    Abstracts of the XI Turku PET Symposium, Kaarina, Finland: Painola, 978-951-29-3563-5, 11

Publ.-Id: 10851 - Permalink


Double-electron excitations in L3-edge X-ray absorption spectra of Actinides
Hennig, C.;
Multielectron excitations are well known in absorption spectra of noble gases. There, the absorption signal is not affected from neighbored atoms that cause the extended X-ray absorption fine structure (EXAFS). Although EXAFS oscillations often cover these features, they have been revealed also in the spectra of liquids and solids. For the first time, this effect has been observed for actinides.
Keywords: Actinides, EXAFS, 2p4f double electron excitation
  • Poster
    17th ESRF Users Meeting, 07.02.2007, Grenoble, France

Publ.-Id: 10850 - Permalink


Spectroscopic investigation of uranium solution species
Hennig, C.;
The concept of in situ measurements in a spectro-electrochemical cell for XAFS measurements is presented.
Keywords: EXAFS, UV-vis, U(IV), U(V), U(VI)
  • Invited lecture (Conferences)
    CEA, Laboratoire de Reconnaissance Ionique et Chimie de Coordination, 08.06.2007, Grenoble, France

Publ.-Id: 10849 - Permalink


Die Koordination von Uran-Spezies in Loesungen - Eine Analyse mit EXAFS Spektroskopie
Hennig, C.;
Der Vortrag gibt eine kurze Einfuehrung in die experimentellen Moeglichkeiten und Besonderheiten der EXAFS Spektroskopie. Im Weiteren werden umweltelevante Probleme der Urankontamination im ehemaligen Bergbaugebiet der Wismut anhand spektroskopischer Analysen von umweltrelevanten Modellsystemen diskutiert.
Keywords: EXAFS, ehemaliger Uranbergbau
  • Invited lecture (Conferences)
    Bundesanstalt fuer Materialforschung und -pruefung, 05.06.2007, Berlin, Germany

Publ.-Id: 10848 - Permalink


The structure of actinides in solution - An investigation with XAFS spectroscopy
Hennig, C.;
Outline of this poesentation
1. Motivation.
2. Theory.
3. Experimental conditions
4. Comparison between EXAFS and XRD.
5. Electronic transitions in EXAFS and UV-vis.
6. U(VI) and U(IV) in aq. and nonaq. cloride media.
7. Sulfate coordination of aq. Th(IV), U(IV), U(VI), Pa(V),Np(IV), Np(V), and Np(VI) media.
8. Conclusion
Keywords: EXAFS, XRD, UV-vis, Actinides, Coordination, Speciation
  • Invited lecture (Conferences)
    Workshop on Structural Chemistry of Actinide and Lanthanide Inorganic Compounds, 29.09.-01.10.2007, Tsarskoe Selo, St. Petersburg, Russia

Publ.-Id: 10847 - Permalink


Investigation of actinides in solution under controlled redox conditions
Hennig, C.; Ikeda, A.; Rossberg, A.; Funke, H.; Scheinost, H.;
The results from the research activities of the last 5 years have been presented. This concerns the development and application of a spectro-electrochemical cell for in situ investigations of speciation and coordination of actinides in solution.
Keywords: actinides, EXAFS, electrochemistry
  • Lecture (others)
    ESRF Beamline Review Panel Meeting, 06.-07.11.2007, Grenoble, France

Publ.-Id: 10846 - Permalink


Complex structure and species distribution of U(VI) cloride in aqueous and nonaqueous solutions
Hennig, C.;
New spectroscopic techniques by combining UVvis and EXAFS will be discussed applied to the samples mentioned in the title.
Keywords: UVvis EXAFS uranium
  • Lecture (others)
    Institute de Physique Nucleaire, Groupe de Radiochemie, 13.12.2007, Paris-Orsay, France

Publ.-Id: 10845 - Permalink


Dynamoeffekt und Magnetorotationsinstabilität: Kosmische Magnetfelder im Laborexperiment
Stefani, F.;
Im Vortrag wird herausgearbeitet, dass kosmische Magnetfelder einerseits durch den hydromagnetischen Dynamoeffekt erzeugt werden und andererseits vermittels der Magnetorotationsinstabilität eine fundamentale Rolle in der kosmischen Strukturbildung spielen. Die Laborexperimente zum Dynamoeffekt in Riga, Karlsruhe und Cadarache sowie das PROMISE-Experiment zur Magnetorotationsinstabilität werden detailliert behandelt.
  • Invited lecture (Conferences)
    Lehrstuhlseminar Magnetofluiddynamik, TU Dresden, 05.12.2007, Dresden, Germany

Publ.-Id: 10844 - Permalink


Crystallographically oriented Fe nanocrystals formed in Fe-implanted TiO2
Zhou, S.; Potzger, K.; Talut, G.; Shalimov, A.; Grenzer, J.; Skorupa, W.; Helm, M.; Fassbender, J.ORC; Cizmar, E.; Zvyagin, S. A.; Wosnitza, J.
A comprehensive characterization of the structural and magnetic properties of Fe-implanted rutile TiO2(110) is presented. Fe and FeTiO3 (Ilmenite) nanocrystals (NCs) are identified by synchrotron-radiation X-ray diffraction. The majority of Fe NCs are crystallographically oriented with respect to the matrix following the relation Fe(001)[010]kTiO2(110)[110]. Post-annealing induced the out-diffusion of Fe and the growth of FeTiO3 at the cost of Fe NCs. Mössbauer spectroscopy and SQUID magnetometry reveal the corresponding evolution of magnetic properties, i.e. magnetization, and superparamagnetic blocking temperature. We unambiguously identify Fe NCs as the origin of the ferromagnetism. These Fe NCs possess a uniaxial in-plane magnetic anisotropy, such that the two Fe[100] axes are inequivalent.
Keywords: TiO2, Ferromagnetism, Nanocrystals

Publ.-Id: 10843 - Permalink


Structural and magnetic properties of Tb implanted ZnO single crystals
Zhou, S.; Potzger, K.; Mücklich, A.; Eichhorn, F.; Helm, M.; Skorupa, W.; Fassbender, J.ORC
ZnO single crystals have been implanted with Tb ions. For an atomic concentration of 1.5 %, annealing at 823 K leads to an increase of the saturation magnetization per implanted Tb ion up to 1.8 mu_B at room temperature. Structural investigations revealed no secondary phase formation, but the out-diffusion of Tb. No significant evidence is found for Tb substituting Zn sites neither in the as-implanted nor annealed samples. However, indications for the existence of a small amount of Tb nanoclusters however have been found using magnetization vs. temperature measurements. The ferromagnetic properties disappear completely upon annealing at 1023 K. This behavior is related to the formation of oxide complexes or nanoparticles.
Keywords: ZnO, rare earth, diluted magnetic semiconductors

Publ.-Id: 10842 - Permalink


Complexation of Curium(III) with Hydroxamic Acids Investigated by Time-Resolved Laser-Induced Fluorescence Spectroscopy
Glorius, M.; Moll, H.; Bernhard, G.;
The unknown complex formation of Cm(III) with two hydroxamic acids, salicylhydroxamic (SHA) and benzohydroxamic acid (BHA) was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Hydroxamate containing chelating substances have the potential to enhance the solubility and mobility of metals and radionuclides by forming complexes. We explored the fluorescence properties, lifetimes and individual fluorescence emission spectra of the formed Cm(III) hydroxamate species. In both Cm(III)-hydroxamic acid systems a 1: 1 and a 1:2 complex of the type MpLqHr could be identified from the fluorescence emission spectra having peak maxima at 600 and 609 nm, respectively. An indirect excitation mechanism of the Cm(III) fluorescence was observed in the presence of the hydroxamic acids. Consistent stability constants were determined by using either indirect or direct excitation mode of the Cm(III) fluorescence. In the Cm(III)-SHA system, the stability constants are log β111 = 16.52 0.14 and log β121 = 24.09 0.62. The complex formation constants of the Cm(III)-BHA species results to log β110 = 6.52 0.19 and log β120 = 11.60 0.50. The stability constants were compared to those of natural pyoverdins.
Keywords: Cm(III); Complexation; TRLFS; Hydroxamic acids

Publ.-Id: 10841 - Permalink


Initial stages in the metal-dusting process on alloy 800
Röhnert, D.; Phillipp, F.; Reuther, H.; Weber, T.; Wessel, E.; Schütze, M.;
The initial stages of the metal-dusting process on Alloy 800 at 620 degrees C were investigated by light optical microscopy, RAMAN spectroscopy, atomic-force microscopy, Auger electron spectroscopy, transmission-electron microscopy and electron back-scatter diffraction. As it turned out the incubation period for metal-dusting is characterized by simultaneous formation of a heterogeneously growing oxide scale and deposition of carbon. The material surface shows different tarnish colors depending on the substrate-grain orientation with different susceptibility to the beginning of metal-dusting attack. "Low-index" grains were not attacked within the times investigated while the other grain orientations showed pitting. Carbon is evidently incorporated into the oxide scale from the very beginning of exposure with different intensities depending on the underlying substrate-grain orientation leading to differences in the tarnish colors. As a consequence carbides are formed even underneath "dense" oxide layers. Evidently metal-dusting attack starts at positions of the oxide scale where "higher carbon concentrations" are present.
  • Oxidation of Metals 68(2007), 271-293

Publ.-Id: 10840 - Permalink


Recent achievement on actinide chemistry at FZD: Short introduction about electrochemical and structural study of uranium and neptunium in solution.
Ikeda, A.;
Understanding the electrochemical and complexation behavior of actinides in solution is very fundamental for the assessment of environmental impact on the geological disposal of radioactive wastes, such as predicting the migration behavior of these nuclides in the geosphere. Especially, uranium(U) and neptunium(Np) are some of the important nuclides for this kind of research.Therefore, in order to investigate the electrochemical and complexation properties of U and Np, cyclic voltammetry (CV), electrolysis, and X-ray absorption measurements were carried out in various types of aqueous- and nonaqueous solutions. In this presentation, some remarkable results are introduced and discussed to draw a general conclusion about the electro- and complexation chemistry of U and Np in solution.
Keywords: uranium, neptunium, electrochemistry, complex, solution, cyclic voltammetry, electrolysis, XAFS
  • Invited lecture (Conferences)
    Internal seminar at the Synchrotron Radiation Research Center, Japan Atomic Energy Agency, 29.11.2007, SPring-8, Hyogo, Japan

Publ.-Id: 10839 - Permalink


Time-resolved semiconductor spectroscopy in the mid-infrared and Terahertz regimes
Schneider, H.;
This talk will focus on several research topics exploiting our free-electron (FEL) and modelocked Ti:Sapphire lasers to investigate semiconductor nanostructures. Pump-probe spectroscopy and two-photon detection is used for time-resolved investigations of intersubband transitions in quantum wells and for FEL pulse diagnostics. Terahertz emitters based on interdigitated metal stripe arrays will also be discussed.
  • Lecture (others)
    Seminarvortrag, 30.11.2007, Palaiseau, France

Publ.-Id: 10838 - Permalink


Positronen-Emissions-Tomographie (PET) - von der Chemie radioaktiv markierter Verbindungen bis zu deren Herstellung für die klinische Praxis
Knieß, T.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Reihe der hochschuloffenen Kolloquien des FB MachinenBau/Verfahrenstechnik, Studiengang Chemieingenieurwesen der HTW Dresden, 06.12.2007, Dresden, Germany

Publ.-Id: 10837 - Permalink


Projective Hilbert space structures at exceptional points and Krein space related boost deformations of Bloch spheres
Günther, U.; Rotter, I.; Samsonov, B.;
Simple non-Hermitian quantum mechanical matrix toy models are considered in the parameter space vicinity of Jordan-block structures of their Hamiltonians and corresponding exceptional points of their spectra. In the first part of the talk, the operator (matrix) perturbation schemes related to root-vector expansions and expansions in terms of eigenvectors for diagonal spectral decompositions are projectively unified and shown to live on different affine charts of a dimensionally extended projective Hilbert space. The monodromy properties (geometric or Berry phases) of the eigenvectors in the parameter space vicinities of spectral branch points (exceptional points) are briefly discussed.

In the second part of the talk, it is demonstrated that the recently proposed PT-symmetric quantum brachistochrone solution [C. Bender et al, Phys. Rev. Lett. {\bf 98}, (2007), 040403, quant-ph/0609032] has its origin in a mapping artifact of the PT-symmetric 2×2 matrix Hamiltonian in the vicinity of an exceptional point. Over the brachistochrone solution the mapping between the PT-symmetric Hamiltonian as self-adjoint operator in a Krein space and its associated Hermitian Hamiltonian as self-adjoint operator in a Hilbert space becomes singular and yields the physical artifact of a vanishing passage time between orthogonal states. The geometrical aspects of this mapping are clarified with the help of a related hyperbolic Möbius transformation (contraction/dilation boost) of the Bloch (Riemann) sphere of the qubit eigenstates of the 2×2 matrix model.
The controversial discussion on the physics of the brachistochrone solution is briefly commented and a possible resolution of the apparent inconsistencies is sketched.

partially based on:
J. Phys. A 40 (2007) 8815-8833; arXiv:0704.1291 [math-ph].
arXiv:0709.0483 [quant-ph].
Keywords: non-Hermitian Hamiltonian, PT-symmetric Quantum Mechanics, Jordan block, exceptional point, projective Hilbert space, geometric phase, quantum brachistochrone, Bloch sphere, Möbius transformation, hyperbolic dilation-contraction mapping
  • Invited lecture (Conferences)
    7th Workshop Operator Theory in Krein Spaces and Spectral Analysis, 13.-16.12.2007, Berlin, Germany

Publ.-Id: 10836 - Permalink


Flüssigmetallströmung unter dem Einfluß eines elektromagnetischen Wanderfeldes bei der Kristallzüchtung nach der VGF-Methode - Numerische Simulation und Modell-Experimente -
Galindo, V.; Grants, I.; Lantzsch, R.; Pätzold, O.; Gerbeth, G.; Zhang, C.;
Die Strömung einer Flüssigmetall-Legierung unter dem Einfluß eines externen elektromagnetischen Wanderfeldes wurde untersucht mit besonderen Augemerk auf die Abhängigkeit von der Feld-Frequenz.
Keywords: crystal growth, traveling magnetic fields
  • Lecture (Conference)
    Workshop Strömungssimulation, 30.11.2007, Dresden, Germany

Publ.-Id: 10834 - Permalink


Use of a traveling magnetic field in VGF growth: flow reversal and resulting dopant distribution
Grants, I.; Gerbeth, G.;
The melt flow in a model of a vertical gradient freeze facility under the action of a traveling magnetic field (TMF) is studied numerically. The radial temperature gradient over a concave solidification interface drives a radially converging flow which may cause an undesirable dopant concentration peak on the axis. We study the characteristics of such a flow for parameters beyond the previously reported linear regime. An upward directed TMF induces a body force which counteracts buoyancy. We report conditions under which the TMF reverses the flow direction for a wide parameter range. These conditions depend primarily on the product of the thermal gradient and the interface deflection. The simulation of the dopant transport demonstrates that the concentration peak disappears as soon as the flow direction changes.
  • Journal of Crystal Growth 310(2008), 3699-3705

Publ.-Id: 10831 - Permalink


Magnetohydrodynamic experiments on cosmic magnetic fields
Stefani, F.;
It is well known that cosmic magnetic fields, including the fields of planets, stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving electrically conducting fluids. It is less well known that cosmic magnetic fields play also an active role in cosmic structure formation by enabling outward transport of angular momentum in accretion disks via the magnetorotational instability (MRI). Considerable theoretical and computational progress has been made in understanding both processes. In addition to this, the last ten years have seen tremendous efforts in studying these effects in the laboratory. In 1999, magnetic field self-excitation was observed in the large scale liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also observed in the French "von Karman sodium" (VKS) experiment, although with the help of iron propellers which complicates the interpretation of the results. The magnetorotational instability was recently observed in the ''Potsdam Rossendorf Magnetic Instability Experiment'' (PROMISE). In the talk, the history of dynamo and MRI experiments is delineated, and some interesting directions of future work are discussed.
  • Invited lecture (Conferences)
    79th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2008), 31.03.-04.04.2008, Bremen, Germany

Publ.-Id: 10830 - Permalink


Homotopic deformations of the Arnold tongue patterns in the MHD α2-dynamo spectrum
Günther, U.; Kirillov, O.;
The spectrum of an MHD α2-dynamo has been studied under perturbations of the α-profile as well as under smooth changes of the boundary conditions (BCs). Basic ingredient was a set of analytically (exactly) calculable bi-orthogonal eigenfunctions for constant α-profiles α0=const. These eigenfunctions have been used as input for both perturbative and numerical Galerkin (weighted residual) analyses with BCs imposed on them as one-parameter homotopic family which smoothly interpolates between idealized (Dirichlet) BCs and physically realistic (Robin) BCs.

For constant α-profiles the spectrum is purely real and depending on the BCs it changes from a spectral mesh (living as line structure on the doubly ruled surface of a hyperbolic paraboloid) into a countably infinite set of parabolic branches. Under inhomogeneous perturbations of the α-profile the spectrum deforms in such a way that complex spectral sectors form from a subset of intersection points of the spectral mesh. With increasing perturbation strength these complex sectors widen and have the well known form of partially merging Arnold tongues. Explicit analytical approximations are derived for the Arnold tongues. Technically the approximations are based on the perturbation theory of multiple eigenvalues applied to the double eigenvalues (diabolical points) at the nodes of the spectral mesh. A detailed analysis is presented of the interplay of inhomogeneous α-perturbations and homotopic BC deformations with the formation of a wealth of Arnold tongues and partially invariant spectral branch patterns. A good correspondence between the numerical and the perturbative approaches is observed.
Keywords: MHD dynamo, non-selfadjoint operator, bi-orthogonal eigenfunctions, spectral analysis, perturbation theory, homotopic deformation family, Arnold tongue, spectral mesh, diabolical point, ruled surface
  • Lecture (Conference)
    79th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM-2008), 31.03.-04.04.2008, Bremen, Germany

Publ.-Id: 10829 - Permalink


Binding form of ingested uranium in human urine
Bernhard, G.; Geipel, G.; Steudtner, R.;
The dominant reasons for the increase in uranium emitted to the environment arise from the use of uranium as a fuel for the generation of nuclear energy and as a basic material for nuclear weapons production, which also includes the use of depleted uranium metal in armor piercing ammunition.
Keywords: urine, ingested uranium
  • Contribution to proceedings
    2nd International Nuclear Chemistry Congress, 13.-18.04.2008, Cancun, Mexico
  • Lecture (Conference)
    2nd International Nuclear Chemistry Congress, 13.-18.04.2008, Cancun, Mexico

Publ.-Id: 10828 - Permalink


Implementation of a pressure drop model for the CFD simulation of clogged containment sump strainers
Grahn, A.; Krepper, E.; Alt, S.; Kästner, W.; Weiß, F.-P.; Hampel, R.;
In the present article a combination of a semi-empirical flow equation and a material equation is proposed that allows to calculate the pressure drop in beds composed of compressible, fibrous media. The model has been successfully implemented as an extension to the general-purpose CFD code ANSYS-CFX. Its capability to simulate the transient pressure drop build-up at non-uniformly loaded strainers in arbitrary three-dimensional geometries is demonstrated using a step-like flow geometry with a horizontally embedded strainer plate. It will be shown that the increasing pressure drop at the strainer has a rectifying effect on the flow field. The model could as well be implemented into system codes for nuclear reactor and containment simulation. Thus, existing system codes might be enabled for use in the risk assessment of loss-of-coolant accidents.
Keywords: safetety analysis, containment sump, strainer clogging, loss-of-coolant accident, pressure drop, cfd
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    Implementation of a pressure drop model for the CFD simulation of clogged containment sump strainers
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10827 - Permalink


THEREDA – Ein Beitrag zur Langzeitsicherheit von Endlagern nuklearer und nichtnuklearer Abfälle
Altmaier, M.; Brendler, V.; Hagemann, S.; Herbert, H.-J.; Kienzler, B.; Marquardt, C. M.; Moog, H. C.; Neck, V.; Richter, A.; Voigt, W.; Wilhelm, S.;
Im Rahmen von Langzeitsicherheitsanalysen für deutsche Endlager radioaktiver bzw. Untertagedeponien chemotoxischer Abfälle sowie weiterer Einsatzfelder (Altlastensanierung) wird eine einheitliche und umfassende thermodynamische Referenzdatenbasis dringend benötigt. Der ehemalige „Arbeitskreis Thermodynamische Standarddatenbasis“ (ATS) hatte sich die Aufgabe gestellt eine solche Datenbasis zu realisieren. Die Aktivitäten des ATS werden seit Juli 2006 in dem Projektverbund "THEREDA" (Thermodynamische Referenzdatenbasis) von BMBF, BMWi und BfS zunächst für 3 Jahre gefördert. THEREDA setzt sich aktuell aus fünf Partnerinstitutionen zusammen, die im Wesentlichen die deutschen Forschungsinstitutionen auf dem Gebiet der Endlagersicherheitsforschung repräsentieren. THEREDA soll die Transparenz und Belastbarkeit der Sicherheitsanalysen in Deutschland entscheidend verbessern und stellt erstmalig eine konsistente thermodynamische Datensätze für alle in Deutschland diskutierten Endlageroptionen und Wirtsgesteine bereit. Für jede thermodynamische Größe werden anhand eindeutig definierter Evaluierungskriterien Qualitätsstufen angegeben, mit Hilfe derer Anwender Daten, entsprechend der jeweiligen spezifischen Problemstellungen, gezielt einbeziehen oder ausschließen können. Für fehlende thermodynamische Daten werden im Rahmen von THEREDA begründete Schätzwerte ermittelt, sodass Modellrechnungen zur Sicherheitsanalyse in Zukunft auf einer deutlich breiteren Datenbasis durchgeführt werden können. Die Datenbasis wird in einer Datenbank zentral verwaltet und Anwendern über das Internet frei und unentgeltlich verfügbar sein. Importformate, um THEREDA in die gängigsten Modellierungscodes (EQ3/6, PHREEQC, Geochemist’s Workbench, CHEMAPP, usw.) überführen zu können, werden ebenfalls unentgeltlich zur Verfügung gestellt.
  • atw - International Journal for Nuclear Power 53(2008)4, 249-253

Publ.-Id: 10825 - Permalink


Influence of the Time of Flight Information on the Reconstruction of In-Beam PET Data
Shakirin, G.; Crespo, P.; Braess, H.; Enghardt, W.;
At the heavy ion therapy facility at the Gesellschaft für Schwerionenforschung Darmstadt, Germany, an in-beam PET scanner is operated for quality assurance monitoring simultaneously to the therapeutic irradiation. The PET scanner, which is completely integrated into the treatment facility, registers the annihilation γ - rays following the decay of minor amounts of β+ radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and the atomic nuclei of the irradiated tissue. From a comparison of the reconstructed activity distributions with those predicted from the treatment plan, deviations between the prescribed and the applied dose distributions can be detected. We investigate how reconstruction of in-beam PET data can profit from the time of flight (TOF) information taking into account specific issues of in-beam PET system, namely, a very low counting statistics and the dual head geometry of the PET scanner which results in missing ray sums in certain directions. We simulated β+-activity distributions based on real treatment plans and generated events measured with a timing resolution 1.2 ns FWHM. We further reconstructed the data via list mode MLEM algorithm and via randomly filled subsets expectation maximization (RFS-EM) algorithm (a modification of OSEM adapted for in-beam PET). Two irradiation situations were evaluated: a relatively small field in the head and neck region (clivus chondrosarcoma) and a large field in the pelvic region (prostate carcinoma). Root mean square error is reduced by 20 % for head and neck field and by 36 % for pelvic field for TOF included reconstructions. Also a significant reduction of specific reconstruction artifacts (in particular, elongation of the images caused by the dual head geometry of the scanner) is observed in TOF included reconstructions versus non-TOF ones for both irradiation cases.
Keywords: in-beam PET, reconstruction, time-of-flight, TOF, MLEM, OSEM
  • Poster
    2007 Nuclear Science Symposium & Medical Imaging Conference, 27.10.-03.11.2007, Honolulu, Hawaii, USA
  • Contribution to proceedings
    2007 Nuclear Science Symposium & Medical Imaging Conference, 27.10.-03.11.2007, Honolulu, Hawaii, USA
    Conference Record. 2007 IEEE Nuclear Science Symposium & Medical Imaging Conference: IEEE, 1-4244-0923-3

Publ.-Id: 10824 - Permalink


Two mononuclear Tc complexes: [2,2′-(3-phenylpropylimino)- and [2,2′-(propylimino)-bis(ethanethiolato)](4-methoxybenzenethiolato)-oxidotechnetate(V)
Emmerling, F.; Kraus, W.; Noll, B.; Noll, S.; Pietzsch, H.-J.;
The molecular structures of the two mononuclear title complexes, namely (4-methoxybenzene-thiolato-κS)oxido-[2.2′-(3-phenylpropylimino)bis(ethanethiolato)-κ3S,N,S′]technetium(V), [Tc(C14H21NS2)(C7H7OS)O], (I), and (4-methoxybenzenethiolato- κS)oxido[2, 2′-(propylimino)-bis(ethanethiolato) -κ3S,N,S′]technetium(V) [Tc(C7H15NS2)(C7H7OS)O], (II), exhibit the same coordination environment for the central Tc atoms. The atoms are five-coordinated (TcNOS3) with a square-pyramidal geometry comprising a tridentate 2.2′-(3-phenylpropylimino)bis(ethanethiolate) or 2, 2′-(propylimino)-bis(ethanethiolate) ligand, a 4-methoxybenzenethiolate ligand and an additional oxide O atom. Intermolecular C–H …O and C–H...S hydrogen bonds between the monomeric units result in two-dimensional layers with a parallel arrangement.

Publ.-Id: 10823 - Permalink


Determination of charge state in Co- and Mn-doped ZnO films
Markó, D.; Potzger, K.; Küpper, K.; Xu, Q.; Zhou, S.; Schmidt, H.; Fassbender, J.ORC; Lorenz, M.; Arenholz, E.; Denlinger, J. D.
We have investigated Co- and Mn-alloyed ZnO films grown by pulsed laser deposition (PLD) on a-plane sapphire substrates. X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements have been performed at beamline 8.0.1 and beamline 6.3.1 at the Advanced Light Source in Berkeley, USA. From XAS spectra, recorded in both total electron yield and total fluorescence yield mode, the valence states of Mn and Co have been determined. No ferromagnetic properties have been observed by means of XMCD at 20 K at the L2,3-absorption edges of Mn and Co, respectively. This observation agrees with the purely paramagnetic response of those Co- and Mn-alloyed ZnO films from SQUID magnetometry and Hall effect measurements.
Keywords: ZnO, magnetic semiconductor, XAS, XMCD
  • Poster
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10822 - Permalink


Study of dielectron production in C+C collisions at 1 AGeV
Agakichiev, G.; Agodi, C.; Alvarez-Pol, H.; Balanda, A.; Bassini, R.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Bortolotti, A.; Boyard, J. L.; Braun-Munziger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kajetanowicz, M.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krasa, A.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, J.; Otwinowski, J.; Pachmayer, Y.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Perez Cavalcanti, T.; Pietraszko, J.; Pleskac, R.; Pospisil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schroeder, C.; Schwab, E.; Simon, R. S.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Taranenko, A.; Teilab, K.; Tlusty, P.; Toia, A.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Weber, M.; Wen, H.; Wisniovski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.;
The emission of e+e- pairs from C+C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the pi0-Dalitz to the rho/omega invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.

Publ.-Id: 10821 - Permalink


Elementary Collisions with HADES
Froehlich, I.; Pietraszko, J.; Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Boehmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kaempfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krizek, F.; Kruecken, R.; Kuehn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Muentz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palk! A, M.; Pechenov, V.; Pechenova, O.; Cavalcanti, T. P.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Simon, R.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Wen, H.; Wisniowski, M.; Wojcik, T.; Wuestenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zumbruch, P.;
The "High Acceptance DiElectron Spectrometer" (HADES) at GSI, Darmstadt, is investigating the production of e+e- pairs in A+A, p+A and N+N collisions. The latter programm allows for the reconstruction of individual sources. This strategy will be roughly outlined in this contribution and preliminary pp/pn data is shown.
  • Open Access LogoContribution to proceedings
    MENU2007 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon, 10.-14.09.2007, Jülich, Germany
    http://www.slac.stanford.edu/econf Proceedings of MENU 2007 - 11th International conference on Meson-Nucleon Physics and the Structure of the Nucleon, 105-110
  • European Physical Journal A (2007)
  • Contribution to WWW
    arXiv: 0712.1505 [nucl-ex]: http://arxiv.org/pdf/0712.1505.pdf

Publ.-Id: 10820 - Permalink


Polyhedral Surface Approximation of Non-Convex Voxel Sets through the Modification of Convex Hulls
Schulz, H.;
In this paper we want to introduce an algorithm for the creation of polyhedral approximations for objects represented as strongly connected sets of voxels in three-dimensional binary images. The algorithm generates the convex hull of a given object and modifies the hull afterwards by recursive repetitions of generating convex hulls of subsets of the given voxel set or subsets of the background voxels. The result of this method is a polyhedron which separates object voxels from background voxels. The objects processed by this algorithm and also the background voxel components inside the convex hull of the objects are restricted to have genus 0.
Keywords: Digital Geometry, Convex Hull, Surface Approximation, Abstract Polyhedron
  • Contribution to proceedings
    12th International Workshop on Combinatorial Image Analysis, 07.-09.04.2008, Buffalo, NY, USA
    Combinatorial Image Analysis

Publ.-Id: 10819 - Permalink


Autonomous planar conductivity array sensor for fast liquid distribution imaging in a fluid coupling
Da Silva, M. J.; Lu, Y.; Sühnel, T.; Schleicher, E.; Thiele, S.; Kernchen, R.; Diele, K.-H.; Hampel, U.;
In this paper, we introduce a new autonomous planar array sensor based on the measurements of electrical conductivity which has been applied to the visualization of fluid distributions inside a fluid coupling during normal operation. The sensor is composed of approximately 1000 interdigital sensing structures which are used to measure the two-dimensional electrical conductivity distribution at the sensors’s surface with a fast multiplexed probing-sensing scheme at up to 10 kHz frame rate. Two such sensors where used to measure dynamic two-phase flow patterns in a fluid coupling at full operation at 790 rpm rotational speed. Therefore, the sensors were mounted on the pressure-side and the suction-side walls of a blade channel inside a test coupling. The whole measurement system is supplied by a battery and controlled via wireless link, thus being fully autonomous, which enable sensor and electronics to rotate together with the coupling.
Keywords: planar sensor, interdigital electrodes, conductivity measurement, flow measurement, fluid coupling, turbo machinery

Publ.-Id: 10817 - Permalink


A fast way to measure phase fractions in multiphase flow
Ondrey, G. S.;
A new measuring technique for the fast measurement of phase fractions in multiphase flow is presented.
Keywords: wire-mesh sensor, capacitance, multiphase flow
  • Chemical Engineering 114(2007)12, 16

Publ.-Id: 10816 - Permalink


Betriebserfahrungen mit PV-Megawattanlagen in Mitteldeutschland
Rindelhardt, U.;
Im Vortrag werden Auslegung und Betriebsergebnisse von 7 PV-Megawatt-Anlagen in Mitteldeutschland beschrieben.Die Module der meisten Anlagen haben eine feste, nach Süden ausgerichtete Orientierung, während eine Anlage mit zwei-achsig nachgeführten Trackern ausgerüstet ist. In allen Anlagen wurden poly- oder monokristalline Solarzellen verwendet. Es kamen sowohl Zentralwechselrichter als auch String-Wechselrichter zum Einsatz. Bei vergleichbaren Einstrahlungsbedingungen wurden Erträge zwischen 950 und 1080 kWh/kW erreicht, die Anlage mit nachgeführten Modulen übertraf diese Erträge erheblich. Durch Detailanalysen der Anlagenerträge wurden vermeidbare Quellen von Mindererträgen identifiziert.
Keywords: Solar radiation, grid connected PV systems, performance
  • Invited lecture (Conferences)
    Institutsseminar, 26.02.2008, Hameln-Emmerthal, Germany

Publ.-Id: 10815 - Permalink


Perspektiven der Kernenergie - Herausforderungen und Möglichkeiten
Rindelhardt, U.;
Ausgehend von der bisherigen Entwicklung wird der derzeitige Stand der Kernenergienutzung auf der Basis der Kernspaltung vorgestellt. Vertieft wird auf die Brennstoffausnutzung in modernen Kernkraftwerken eingegangen. Die Hauptmerkmale der KKW der 3. Generation und der in Entwicklung befindlichen 4. Generation werden dargestellt.Ein besonderes Gewicht liegt auf der Darstellung der Rolle von schnellen Brutreaktoren. Abschließend wird das Problem der Endlagerung und aktueller Alternativen (Transmutation) erörtert.
Keywords: nuclear power, safety, nuclear fuel cycle
  • Lecture (others)
    Mitgliederversammlung VDE-Bezirksverein Chemnitz, 17.01.2008, Zwickau, Germany

Publ.-Id: 10814 - Permalink


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