Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33397 Publications

Transport of reacting solutes through the unsaturated zone

Kuechler, R.; Noack, K.
Unsaturated flows within subsurface regions control many large-scale hydrological
and environmental processes. This contribution presents and discusses the results of numerical calculations dealing with the flow of water, the chemical reaction at the water-mineral interface and the transport of chemical species caused by such flows. The reason for the water flow through the soil is solely the rainfall.
The water motion is calculated for two different soil classes and for a typical annual precipitation. The transport of chemical species is described by a set of partial differential equations, and the homogeneous chemical processes, under the assumption of equilibrium, are described by a set of nonlinear algebraic equations. The source terms of these partial differential equations are given by rate laws of chemical weathering. Rainfall and chemical weathering are therefore the reason of the transport of reactive multispecies in this model.
  • Transport in Porous Media 49 (2002) 361-375


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Publ.-Id: 3965

Prevention of impurity gettering in the RP/2 region of ion implanted silicon by defect engineering

Kögler, R.; Peeva, A.; Kaschny, J.; Skorupa, W.; Hutter, H.

Si+ ion implantation into Si under inclined incidence angle was applied to demonstrate that Cu gettering in the region around half of the projected ion range, RP/2, of ion-implanted Si is controlled by the same mechanism working for excess vacancy generation. The obtained results directly relate the appearance of the RP/2 gettering effect to radiation-induced excess vacancies. Excess vacancies were found to be origin for the dominating gettering sites of Cu at RP/2. Moreover, it was shown that the undesired impurity trapping at RP/2 can be prevented by means of additional Si+ implantation into the vacancy-rich region of ion-implanted Si to balance the excess of vacancies. The parameters were determined for the additional Si+ implantation to remove Cu gettering at RP/2. If the threshold fluence necessary to remove the Cu gettering at RP/2 is exceeded, the excess vacancies are overcompensated and new interstitial-type dislocation loops form.

Keywords: Ion implantation, defects, gettering, Si, Cu
  • Nuclear Instruments and Methods in Physics Research B 186 (2002) 298-302
  • Lecture (Conference)
    E-MRS Spring Meeting, Strasbourg, June 5-8, 2001


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Publ.-Id: 3964

Entwicklung einer Niederenergie-Implantationskammer mit einem neuartigen Bremslinsensystem

Teichert, J.; von Borany, J.
In diesem Report wird eine Niederenergie-Implantationskammer (NEI-Kammer) beschrieben, die im Forschungszentrum Rossendorf entwickelt und aufgebaut wurde. Die Kammer ermöglicht es, die Implantation von Ionen bei niedrigen Energien (< 30 keV) mit einer Implantationsanlage für mittlere Energien durchzuführen. In der Kammer werden der Ionenstrahl, den der Implanter liefert, auf die erwünschte niedrige Energie abgebremst. Dazu wird ein elektrostatisches Bremslinsensystem eingesetzt, das auf einem neuartigen Prinzip basiert. Das System besteht aus einer Sammellinse und einer Zerstreuungslinse, wobei die Öffnungsfehler beider Linsen entgegengesetzte Vorzeichen besitzen und sich gegenseitig kompensieren. Dadurch ist es möglich, Wafer gebräuchlicher Größe bei geringer Energie mit hoher Dosishomogenität zu implantieren. Die NEI-Kammer ist insbesondere für Forschungseinrichtungen eine vorteilhafte Lösung, da sie eine wesentlich kostengünstigere und flexiblere Alternative zur Anschaffung einer Niederenergie-Implantationsanlage darstellt.
Keywords: ion implantation, low-energy implantation, implanter, decel lens system, electrostatic lens, deceleration, dose uniformity
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-323 Mai 2001


Publ.-Id: 3963

P-type doping of SiC by high dose Al implantation - problems and progress

Heera, V.; Panknin, D.; Skorupa, W.
The development of optimized processes for p-type doping of SiC by ion implantation and subsequent annealing is a remaining challenge to SiC-device technology. Al is a promising acceptor in SiC. Compared to B it has a shallower acceptor level and a stronger tendency to occupy atomic sites in the Si sublattice which makes it more suitable for the production of heavily doped, low resistivity layers. However, also in the case of Al very high acceptor concentrations (>1019 cm-3) are necessary to obtain SiC layers with low resistivities (<1 cm). The physical consequences of such high impurity concentrations in SiC for the annealing of implantation damage and the electrical activation will be discussed. A survey of the results of several implantation and annealing schemes is presented.

Keywords: SiC, P-type doping, Al implantation, resistivity, annealing
  • Applied Surface Science 184 (2001) 307-316


Publ.-Id: 3962

Spreading resistance measurements on nanocrystalline SiC produced by ion beam induced crystallization

Madhusoodanan, K. N.; Heera, V.; Panknin, D.; Skorupa, W.
Ion beam induced crystallization (IBIC) of preamorphized surface layers on 6H-SiC has been stimulated by high dose Al implantation (0.3 - 3 E17 cm-2) at elevated temperatures (300 -500°C). Randomly oriented 3C-SiC nanocrystals withn diameters between 2 and 25 nm are formed depending on the implantation parameters as proved by XRD and XTEM. Spreading resistance measurements have been performed at bevelled as-implanted and annealed (1500°C, 10 min) samples in order to study the electrical behaviour of the Al acceptors in the nanocrystalline layer. Reference experiments have been carried out on single crystalline 6H- SiC crystals implanted at the similar conditions. It has been found that in the as-implanted state Al doped fine granular SiC has much lower spreading resistance than the corresponding single crystalline SiC. Only minor differences have been observed between the nano- and single crystalline samples after annealing.
Keywords: 6H-SiC, Ion implantation, amorphisation, recrystallisation, spreading resistance
  • Lecture (Conference)
    E-MRS 2001 SPRING MEETING, Strasbourg (France), June 5-8, 2001
  • Applied Surface Science 184 (2001) 209-213


Publ.-Id: 3960

Writing Cobalt FIB implantation into 6H:SiC

Bischoff, L.; Teichert, J.
Focused ion beam implantation of cobalt at 35 keV into 6H:SiC is used to investigate a possible ion beam synthesis of CoSi2 micro-structures. The pattern were studied using SEM and EDX measurements. The resistivity of the implanted test-structures was determined as a function of dose, implantation and annealing temperature. For room temperature irradiated samples after a 1150°C annealing resistivities of about 100 µScm could be achieved and a diode like behaviour influenced by parasitic resistors between structure and bulk was found.
Keywords: Focused ion beam, cobalt implantation, SiC, annealing, resistivity, diode
  • Lecture (Conference)
    E-MRS Spring Meeting, 5-8 June 2001, Strasbourg, France,
  • Applied Surface Science 184 (2001) 336 - 339


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Publ.-Id: 3959

Focused Ion Beam Sputtering Investigations on SiC

Bischoff, L.; Teichert, J.; Heera, V.
The focused ion beam is a very useful tool to sputter holes with well defined dimensions which can be easily analysed by surface profiling measurements. Applying this the sputte-ring yields of 6H:SiC were -measured for 35 and 70 keV Si, Co, Ge, Nd and Au ions from a mass separated focused ion beam. Additionally, the sputtering yield was determin-ed as a function of the angle of incidence and the target temperature for gold ions. The swelling due to ion implantation will be discussed.
Keywords: Focused ion beam, sputtering, SiC, swelling, millling rate
  • Lecture (Conference)
    E-MRS Spring Meeting, 5-8 June 2001, Strasbourg, France,
  • Applied Surface Science 184 (2001) 372 - 376


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Publ.-Id: 3958

Quantitative analysis of deuterium in a-C:D layers, a Round Robin experiment

Behrisch, R.; Mayer, M.; Jacob, W.; Assmann, W.; Dollinger, G.; Bergmayer, A.; Kreissig, U.; Friedrich, M.; Sun, G.-Y.; Hildebrandt, D.; Akbi, M.; Schneider, W.; Schleußner, D.; Knapp, W.; Edelmann, C.
The absolute amount of deuterium in amorphous deuterated carbon (a-C:D) layers has been measured by six laboratories with different techniques, such as MeV ion beam analysis, secondary ion mass spectrometry (SIMS), and thermal desorption spectrometry (TSD). The a-C:D layers have been deposited from a CD4 glow discharge plasma onto carbon and silicon substrates. The results for the absolute numbers obtained with the different analysing techniques show a scatter of up to about 35% around the average value. The deviations are larger than the errors stated by the experimentalists and indicate possible systematic uncertainties in some of the experiments.
Keywords: Mass spectrometry; Deuterium
  • Journal of Nuclear Materials 281 (2000) 42-56


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Publ.-Id: 3957

Accelerator mass spectrometry at the Rossendorf tandem accelerators

Friedrich, M.; Bürger, W.; Grötzschel, R.; Henke, D.; Sun, G.-Y.; Turuc, S.; Hebert, D.; Rothe, T.; Stolz, W.
A short description of the Rossendorf AMS system is given and first experimental results are presented. The planned applications are listed.
Keywords: Mass spectrometry; Radiodating; Electrostatic accelerators
  • Nuclear Instruments and Methods in Physics Research B 92 (1994) 58-60


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Publ.-Id: 3956

Status and research report at the Tritium Laboratory Karlsruhe

Penzhorn, R.-D.; Bekris, N.; Coad, P.; Dörr, L.; Friedrich, M.; Glugla, M.; Haigh, A.; Lässer, R.; Peacock, A.
The Tritium Laboratory Karlsruhe (TLK) has mainly designed for the conduction of technological experiments relevant to fusion under simulation of the conditions actually expected in the various tritium processing systems. Presently ongoing experimental and design work is almost exclusively oriented towards the needs of JET and ITER-H-FEAT. Basic research, while increasing in importance, plays predominatly a complementary role. This paper presents the most recent progress and developments related to the technological and applied experiments at the TLK.
Keywords: Tritium Laboratory Karlsruhe (TLK); Infrastructure systems; Calorimeters
  • Fusion Engineering and Design 49-50 (2000) 753-767


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Publ.-Id: 3950

Unterstützung der ukrainischen Aufsichtsbehörde beim Aufbau einer modernen KKW-Überwachung

Beyer, M.; Carl, H.
Das Mitte der 90er Jahre im KKW Saporoshje als Pilotprojekt für den 5. Block eingerichtete Fernüberwachungssystem wurde auf alle Blöcke der KKW Saporoshje und Rovno (Ukraine) erweitert und mittels moderner Kommunikationstechnik an das Informations- und Krisenzentrum der ukrainischen Aufsichtsbehörde in Kiew angeschlossen. Nach entsprechender Weiterentwicklung der Software für die Informationsverarbeitung, -übertragung und -bewertung können von diesen KKW-Blöcken sicherheitsrelevante betriebliche und radiologische Messwerte kontinuierlich erfasst, vor Ort in Form von Tabellen, Grafiken und Schemata online dargestellt sowie nach Kiew übertragen und dort visualisiert und bewertet werden.
Keywords: Kernkraftwerk, Ukraine, Fernüberwachung
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2001, Dresden, 15.-17. Mai 2001, Tagungsbericht, S. 463-466
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2001, Dresden, 15.-17. Mai 2001, Tagungsbericht, S. 463-466


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Publ.-Id: 3949

Aufbau und Funktionsweise eines Fernüberwachungssystems für technologische Parameter ukrainischer Kernkraftwerke (in Russisch)

in Russian
Beyer, M.; Carl, H.; Schumann, P.; Chernousov, V.
Es wird ein System zur Überwachung technologischer Parameter für Blöcke ukrainischer Kernkraftwerke beschrieben. Die Autoren erläutern die theoretischen Grundlagen der Fernüberwachung sowie Aufbau und Wirkungsweise des Systems. Nachfolgend wird seine Einordnung in die ukrainischen kerntechnischen Aufsichtsbehörden dargelegt. Die Bestandteile der speziell für diese Anwendung entwickelten Software werden anhand von Beispielen erklärt und die Implementierung auf die Hardware beschrieben. Erste Erprobungsergebnisse und Vorschläge zur Erweiterung des Systems beenden den Artikel.
Keywords: Kernkraftwerk, Fernueberwachung, Ukraine, Aufsichtsbehoerde
  • Kybernetische Systeme und Anlagen, Informationstechnologie


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Publ.-Id: 3948

Velocity measurements in liquid sodium by means of Ultrasound Doppler Velocimetry

Eckert, S.; Gerbeth, G.
A successful application of the Ultrasound Doppler Velocimetry (UDV) in liquid sodium flows is described.
To get sufficient Doppler signals different problems had to be solved: the transmission of the ultrasonic
beam through the channel wall made of stainless steel, the acousting coupling between transducer and
channel wall and the wetting of the inner surface of the wall by the liquid metal, respectively.
A sodium flow in a square duct exposed to a transverse magnetic field is investigated. According to the
existing knowledge about MHD channel flows we found the velocity profiles modified to a M-shape due to
the effect of an inhomogeneous magnetic field.
Keywords: flow measurement technique, ultrasound Doppler technique, fluid velocity, opaque fluids, liquid metal, MHD channel flow
  • Experiments in Fluids 32(2002)5, 542-546


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Publ.-Id: 3946

Self-Organization of Nanostructures With Ion Beams

Heinig, K.-H.; Schmidt, B.; von Borany, J.; Müller, T.; Bernas, H.
Self-organized nanostructures produced by far-from-equilibrium processing of semiconductor materials with ion beams can be applied in microelectronics (e.g. nanocluster memories), optoelectronics (luminescence from Si nanocrystals) and photonics (plasmonic devices using Au nanoclusters). Our recent experimental, theoretical and computer simulation work, which aimed at optimization and improved fundamental understanding of these processes, will be reviewed.
Two different regimes of self-organization will be distinguished: (i) Relaxation regime: Ion implantation of impurity atoms may produce extremely supersaturated solid solutions. During subsequent annealing this far-from-equilibrium state relaxes towards equilibrium by phase separation (nucleation, growth) and minimization of interface energy (Ostwald ripening, coalescence). Self-organization phenomena (e.g. pattern formation during spinodal decomposition, Rayleigh or pearling instability during interface minimization) are observed. (ii) Driven system: Interfaces or compounds like SiO2 can be driven into a steady state far from equilibrium by ion irradiation. The steady state is established by a competition between collisional mixing, diffusion and re-formation of the compound. The application of resulting effects like nanocluster d-layer formation and ''inverse'' Ostwald ripening for devices will be discussed.
Keywords: Ion beam synthesis, Ostwald ripening, nanocluster, far-from-equilibrium, inverse Ostwald ripening, Rayleigh instability
  • Lecture (Conference)
    E-MRS Spring Meeting, 5-8 June 2001, Strasbourg, France

Publ.-Id: 3944

Institute of Bioinorganic and Radiopharmaceutical Chemistry; Annual Report 2000

Johannsen, B.; Seifert, S.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-312 Januar 2001


Publ.-Id: 3933

Investigating interatomic solid state potentials using Crystal-GRID: a study of applicability; Dissertation

Hauschild, T.
Keywords: Crystal-GRID, interatomic solid state potentials, gamma spectroscopy, molecular dynamics, maximum likelihood estimation
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-321 Mai 2001


Publ.-Id: 3932

Das Sorptionsverhalten von U(VI) am Granit von Eibenstock (Erzgebirge) und seinen mineralogischen Komponenten

Krawczyk-Bärsch, E.; Arnold, T.; Bernhard, G.
Die Migration von Uranspezies durch geologische Formationen wird durch die mineralogische Zusam-mensetzung der Gesteine sowie durch die che-mischen Eigenschaften der wässrigen Lösung bestimmt. In Abhängigkeit von den chemisch-physikalischen Bedingungen wird Uran an den Mineralen sorbiert. Um diese Bedingungen näher einzugrenzen, wurden Batchexperimente im Labor durchgeführt, die die natürlichen Bedingungen simulieren. Als Gesteinsprobe wurde der Granit von Eibenstock ausgewählt, der als geologische Formation einen großen Bereich der ehemaligen Uranbergbauregion im westlichen Erzgebirge bestimmt. Die mineralogischen Bestandteile des Eibenstocker Granits sind Quarz (45 %), Orthoklas (35 %), Albit (7,5 %), Biotit (7,5 %) sowie Muskowit (4 %). Für die Batchexperimente wurden 0,5 g der Granitprobe (63-200 µm Körnung) sowie 0,5 g der einzelnen Mineralkomponenten des Granits mit jeweils 40 ml 0,1 M NaClO4-Lösung der Verwitterung über mehrere Wochen ausgesetzt. Im Anschluß an die Stabilisierung der eingestellten pH-Werte erfolgte die Zugabe einer 1.10-6 M UO2(ClO4)-Lösung. Nach einer Sorptionsdauer von 2,5 Tagen wurde der Urangehalt in den Lösungen massenspektrometrisch bestimmt.
Die Ergebnisse zeigen eine hohe Sorption von U(VI) am Granit in einem pH-Bereich von 5 bis 7 mit einer maximalen Sorption von 94,62 % bei einem pH von 6.57. Bei einem pH < 5 sowie > 7 nimmt die Sorption stark ab. Unterhalb pH 4, bzw. oberhalb pH 8.5 ist die Sorption < 1 %. Im Vergleich zu anderen Gesteinen des Erzgebirges ist die U(VI)-Sorption am Granit deutlich auf einen kleinen pH-Bereich beschränkt [1]. Die Sorption an den Mineralkomponenten des Granits zeigt eine ähnliche Tendenz, wobei die Schichtsilikate Muskowit und Biotit durch ihre im Vergleich zu den Feldspäten höhere Sorption dominieren [2].

[1] Krawczyk-Bärsch, E. (2000): Final Report DFG (Ni 210/5-1).
[2] Arnold, T. et al. (1998): Chemical Geology 151, 129-141.

  • Lecture (Conference)
    Vortrag / 79. Jahrestagung der Deutschen Mineralogischen Gesellschaft, Potsdam, 9.9.-13.9.2001

Publ.-Id: 3931

Implantation induced defects in silicon detected by Cu decoration technique

Kögler, R.; Peeva, A.; Eichhorn, F.; Kaschny, J.; Voelskow, M.; Skorupa, W.; Hutter, H.
Cu is especially suitable to decorate defects in silicon. The Cu decoration technique has been applied for the detection of point defect clusters in the RP/2 region of Si+ ion implanted silicon. The results of this technique are compared with the results obtained by other analysis techniques. Nanocavities at RP/2 could be observed only in cross section transmission electron microscopy specimen prepared by cleavage technique. These nanocavities are probably the dominant gettering centres for Cu at RP/2. Small interstitial clusters may exist there as well. The conditions for the formation and for the annealing of the gettering layer at RP/2 have been determined. Impurity gettering at RP/2 can be prevented by a sequence of additional Si+ implantations to balance implantation-induced excess vacancies which are the origin of the nanocavities.
Keywords: Ion implantation, defects, silicon, Cu, impurity gettering, Rp/2 defects, TEM specimen preparation
  • Journal of the Electrochemical Society 29 (2001) 133
  • Lecture (Conference)
    Symp. on Crystalline Defects and Contamination DECON 2001, Nürnberg Sept. 13-14, 2001

Publ.-Id: 3927

Energy resolution and energy-light response of CsI (Tl) scintillators for charged particle detection

Wagner, A.; Tan, W. P.; Chalut, K.; Charity, R. J.; Davin, B.; Larochelle, Y.; Lennek, M. D.; Lui, T. X.; Liu, X. D.; Lynch, W. G.; Ramos, A. M.; Shomin, R.; Sobotka, L. G.; de Souza, R. T.; Tsang, M. B.; Verde, G.; Xu, H. S.
This article describes the crystal selection and quality control utilized to develop and calibrate a high resolution array of CsI(TI) scintillator crystals for the detection of energetic charged particles. Alpha sources are used to test the light output variation due to thallium doping gradients. Selection of crystals with better than 1% non-uniformity in light output is accomplished using this method. Tests with 240 MeV alpha beam reveal that local light output variations within each of the tested CsI(TI) crystals limit the resolution to about 0.5%. Charge and mass dependences in the energy - light output relationship are determined by calibrating with energetic projectile fragmentation beams.
Keywords: crystal selection quality control CsI(TI) scintillator light output variation thallium doping gradient projectile fragmentation beam
  • Nucl.Instrum.Meth. A 456 (2001) 290-299


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Publ.-Id: 3924

The merits of particle induced X-ray emission in revealing painting techniques

Neelmeijer, C.; Mäder, M.
Particle Induced X-ray Emission (PIXE) at the external proton beam has proved ideal to study the individual techniques used for creating art objects. In particular, PIXE is tailored for examining paintings because of the low level of background produced by organic components like binders and paper backings. Thus, even traces of pigments as deposited by pens on cardboard can be identified by this method. The combination of PIXE with external Rutherford Backscattering Spectrometry (RBS) allows non-destructive gain of knowledge on near-surface and thin film arrangements of paint materials. Thicker but less complex layers of oil paintings can be identified by special procedures of depth resolved PIXE investigation. In this case, RBS provides additional information on organic coverings like madder lake or varnishes.
  • Nuclear Instruments and Methods in Physics Research B 189 (2002) 293


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Publ.-Id: 3923

Windenergie - heute und morgen

Rindelhardt, U.
Die Nutzung der seit Jahrhunderten bekannten Windkraft zur Erzeugung von
Strom hat im letzten Jahrzehnt eine dynamische Entwicklung erfahren. Basierend
vor allem auf den erreichten Fortschritten in der Technologie der Windenergie-
anlagen (WEA) und den damit verbundenen erheblichen Kostensenkungen steht
die Windenergienutzung heute an der Schwelle zur Wirtschaftlichkeit. Diese ent-
scheidende Voraussetzung hat besonders in Deutschland zur zunehmenden, in
einigen Gebieten sogar massenhaften Nutzung der Windenergie geführt. Die
wichtigsten technischen Entwicklungen der WEA im letzten Jahrzehnt werden
im Beitrag vorgestellt.
Gefördert wurde diese Entwicklung durch verschiedene größere Vorhaben des
Bundes und einzelner Länder. Hervorzuheben sind hier das 250-MW-Programm
sowie das Stromeinspeisegesetz. In den 90er Jahren bestanden somit stabile
Rahmenbedingungen für die Entwicklung der Windenergie. Die installierte WEA-
Leistung in Deutschland stieg von weniger als 30 MW im Jahr 1989 auf etwa
6000 MW zum Jahresende 2000. Im Jahr 2001 wird in Deutschland eine
Strommenge durch WEA erzeugt werden, die etwa 50% der aus Wasserkraft-
werken erzeugten Strommenge oder der Stromerzeugung des größten deutschen
Kernkraftwerkes entspricht.
Nach anfänglicher Zurückhaltung der meisten Energieversorgungsunternehmen
(EVU) erwägen derzeit auch diese ein Engagement in der Windkraftnutzung.
Dennoch werden sich die in den letzten Jahren erreichten Zuwachsraten mittel-
fristig nicht aufrechterhalten lassen. Ein absehbarer Leistungszuwachs bei den
Einzelanlagen auf bis zu 3 MW führt zwar zu einer Entlastung bei den benötigten
Standorten, die aus objektiven und subjektiven Gründen folgende Begrenzung
der nutzbaren Standorte limitiert jedoch insgesamt die Ausschöpfung der vor-
handenen Potenziale. Ein wesentliches begrenzendes Element ist bereits heute
der vermeintliche Widerspruch zwischen dem durch den Einsatz von WEA beför-
derten Umweltschutz (CO2-Problem) und dem Naturschutz in vielen Gebieten
(Landschaftsschutz), der auf der zuständigen kommunale Ebene kaum aufgelöst
werden kann.
Dennoch rechnet der Autor mit einer Verdoppelung der durch WEA erzeugten
Strommenge bis zum Jahr 2010 durch Neuinstallation bzw. Ersatz alter WEA auf
der Landfläche Deutschlands. Dies würde – bei unverändertem Stromverbrauch
– einem Anteil der Windkraft am Stromverbrauch von etwa 5 % entsprechen.
Etwa die gleiche Strommenge könnte um das Jahr 2015 durch offshore-WEA in
der Nord- und Ostsee erzeugt werden, so dass künftig mit einem „Windstroman-
teil“ von 10% in Deutschland gerechnet werden kann.

Keywords: Windenergie, WEA, Stromerzeugung
  • Lecture (Conference)
    6. Symposium "Energie und Energieversorgungssysteme der Zukunft", Lauta, 18. Mai 2001, Tagungsband Beitrag 12
  • Contribution to proceedings
    6. Symposium "Energie und Energieversorgungssysteme der Zukunft", Lauta, 18. Mai 2001, Tagungsband Beitrag 12

Publ.-Id: 3922

Effect of a superimposed DC magnetic field on the melt flow in an induction furnace experimental model

Bojarevics, A.; Gelfgat, Y.; Gerbeth, G.; Cramer, A.
The unsteady flow field has been studied experimentally in a cold metal
model of an existing 10 kHz induction furnace for the inter-metallic fibre
extraction process in presence of a DC magnetic field. It has been shown
that a vertical DC magnetic field normal to the free liquid metal surface
efficiently decreases turbulence in the melt volume and suppresses surface
deformations. Whereas the turbulence and free surface deformations were not
suppressed by a DC field parallel to the free surface.
  • Lecture (Conference)
    Lecture at: International Scientific Colloquium "Modelling for Saving Resources" Riga, May 17-18, 2001

Publ.-Id: 3921

In-beam PET measurements of beta+ radioactivity induced by proton beams

Parodi, K.; Enghardt, W.; Haberer, T.
Our first in-beam PET measurements of the beta+activation induced by proton irradiation are presented.
Monoenergetic proton beams in the energy and intensity range suited for the treatment of deep-seated tumours were delivered by the synchrotron of the Gesellschaft fuer Schwerionenforschung (GSI) at Darmstadt. They were stopped in PMMA blocks placed in the centre of the field of view of the positron camera that is installed in the heavy ion tumour treatment facility at GSI.
The beta+ activity signal was found to be three times larger than that produced by carbon ions at the same range and applied physical dose. The reconstructed spatial beta+ activity distributions were analysed and compared with the production of positron emitters predicted by a calculation based on experimental cross-sections and on the proton flux given by the FLUKA Monte Carlo code. The shape of the depth-activity-profiles was well reproduced by the model and the correlation with the proton
range and the depth-dose-distributions was carefully investigated. Despite the nontrivial range determination from the beta+ activity distribution in the proton case, our experimental investigation supports the feasibility of an in-situ proton therapy monitoring by means of in-beam PET, as already clinically implemented for the monitoring of carbon ion therapy at GSI Darmstadt.
  • Physics in Medicine and Biology 47 (2002) 21


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Publ.-Id: 3920

Investigations of Natural Circulation Instabilities in VVER-type Reactors at LOCA Conditions

Schäfer, F.
An important component of nuclear safety research is the analysis of abnormal transients and accident scenarios in nuclear power plants. In the presented work the ATHLET code was used for thermohydraulic calculations of small and intermediate break loss of coolant accident experiments, which were performed at the Hungarian test facility PMK-2. In the experiments different kinds of natural circulation instabilities could be observed. Such instabilities play an important role in the behaviour of the primary circuit, because the instabilities can disturb the heat removal from the reactor core. The aim of the presented calculations is to investigate whether the code is capable of modelling natural circulation phenomena in VVER-440-type reactors. It could be shown, that ATHLET can calculate the accident behaviour in good agreement with the experimental data. All significant phenomena, such as hot and cold leg loop seal clearing, stagnation of the natural circulation and especially the natural circulation instabilities are calculated very well. Calculations for a VVER-reactor show that the instabilities can also appear in a real plant.
Keywords: thermal-hydraulics, flow instabilities, code validation
  • Lecture (Conference)
    4th International Symposium on Safety and Reliability Systems of PWRs/VVER, 2001 May 14-17, Brno, Czech Republic, p. 94-100
  • Contribution to proceedings
    4th International Symposium on Safety and Reliability Systems of PWRs/VVER, 2001 May 14-17, Brno, Czech Republic, p. 94-100


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Publ.-Id: 3917

Kühlmittelvermischung in Druckwasserreaktoren

Höhne, T.
Die systematische Weiterentwicklung der gekoppelten neutronenkinetischen und thermohydraulischen Codes (DYN3D-ATHLET) erfordert den Einsatz von dreidimensionalen Vermischungsmodellen.

CFX-4-Nachrechnungen experimenteller Daten der Vermischungsanlage ROCOM ergeben im hochturblenten Bereich eine gute Übereinstimmung mit den Messdaten.

- Vierschleifenbetrieb:
- Sektorformation am Kerneintritt
- zeitliche Schwankungen der Konzentrationsprofile an den Sektorgrenzen

- Anlaufen der Kühlmittelzirkulation:
- Unterschiedliche Vermischungsbilder je nach Durchsatz und Anfahrvorgang
- Eintritt des Pfropfens in den Kern in den Randzonen der gegenüberliegenden Seite
Keywords: DWR, Borverdünnung, CFD
  • Poster
    Jahrestagung Kerntechnik 15.-17. Mai 2001, Dresden

Publ.-Id: 3916

Modellierung des Kernkraftwerks Stade Vorarbeiten für Rechnung mit dem Programm RALOC Mod4.0AG Teil2: Rekombinatoren, Eingabedatensatz, Rechnungen

Krüssenberg, A.-K.; Schaffrath, A.
In dem vorliegenden Bericht wird die Erstellung eines Containmenteingabedatensatzes für das Kernkraftwerk Stade (KKW Stade) für das von der Gesellschaft Anlagen- und Reaktorsicherheit (GRS) entwickelte Programmsystem RALOC (Radiolyse und lokalen Konzentrationen (der Gase, z.B. Wasserstoff) im Containment beschrieben und der Aufbau des Eingabedatensatzes, erste Rechnungen zum Nachweis der Lauffähigkeit, der Einbau der Rekombinatoren in den Datensatz sowie erste Testläufe dokumentiert. In einem ersten Bericht sind im Detail die verwendete Nodalisierung, d.h. die Unterteilung des Contaniments in Zonen, Verbindungen und Strukturen beschrieben
  • Other report
    FWS 01-2, Februar 2001

Publ.-Id: 3915

Erprobung passiver Komponenten für den SWR 1000 - Ergebnisse von Experimenten an den Versuchsanlagen PANDA und NOKO

Hicken, E. F.; Dreier, J.; Meseth, J.; Schaffrath, A.
Zur Validierung der thermohydraulischen Wirksamkeit der im SWR 1000 verwendeten passiven Sicherheitssysteme zur Nachwärmeabfuhr aus dem Reaktordruck-sowie dem Sicherheitsbehälter bei Störfällen wurden in den Versuchsanlagen PANDA (PSI / Schweiz) und NOKO (Forschungszentrum Jülich / Deutschland) umfangreiche Versuchsserien durchgeführt. Das Experimentalprogramm beinhaltete im Detail Versuche zum Notkondensator (zwei verschiedene Bündel), zum Passiven Flutsystem sowie dem Gebäudekondensator, der sowohl in NOKO (als Einzeleffektversuch) als auch in PANDA (als Systemversuch) getestet wurde. Zusätzlich wurden in NOKO noch mehrere Bauformen Passiver Impulsgeber erprobt. Allen Versuchen war gemein, dass die zu untersuchenden Systeme in Originalabmessungen sowie -materialien nachgebildet und unter adäquaten thermohydraulischen Randbedingungen getestet wurden. Die Versuchsergebnisse bestätigen ausnahmslos die Funktionalität und Effektivität der passiven Sicherheitssysteme.
Die Wärmeabfuhr in den Not- und Gebäudekondensatoren wurde mit den weltweit zur Sicherheitsanalyse von Reaktoren etablierten 1D-Thermohydraulikprogrammsystemen nachgerechnet. Die Ergebnisse der mit den unterschiedlichen Codes berechneten, integral durch Notkondensatoren abgeführten Energie stimmen sowohl untereinander als auch mit den Experimenten gut überein.
Bei den Gebäudekondensatoren konnten ebenfalls die globalen Werte mit den gebräuchlichen 1D-Containmentprogrammsystemen berechnet werden. Aufgrund der lokalen Anordnung der Gebäudekondensatoren stellen sich im Sicherheitsbehälter jedoch mit diesen 1D-Codes nicht beschreib- und somit modellierbare dreidimensionale Strömungs- und Temperaturfeldern (speziell Stratifizierungen) ein. Diese konnten zwar durch moderne Computational Fluid Dynamic (CFD) Codes punktuell wiedergegeben werden, zur Nachrechnung vollständiger Störfallsequenzen sind jedoch weitere Codeverbesserungen sowie schnellere Computer notwendig.

Keywords: NOKO, PANDA, SWR1000, Passive Komponenten
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2001, 15.-17. Mai 2001, Dresden, Berichtsheft der Fachsitzung "Grossversuche zur verbesserten Sicherheitsbewertung von LWR", S. 137-167
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2001, 15.-17. Mai 2001, Dresden, Berichtsheft der Fachsitzung "Grossversuche zur verbesserten Sicherheitsbewertung von LWR", S. 137-167

Publ.-Id: 3914

Comparison of the Irradiation Effects on Microstructure and Mechanical Properties of VVER-Type RPV Steels

Viehrig, H.-W.; Böhmert, J.; Ulbricht, A.
A German/Russian irradiation experiment has been performed at the pressurised water reactor VVER-70 of the Rheinsberg NPP (Germany). The programme aims at the evaluation of neutron embrittlement and annealing behaviour in dependence on the content of alloying elements and impurities. Charpy V-notch, SENB, tensile, and CT-type specimens have been irradiated.
Specimens have been subjected to instrumented Charpy V impact and fracture mechanical toughness testing according to the ASTM E 1921-97 standard for reference temperature, T0, de-termination. The results of Charpy-V testing were presented on the IAEA Specialist’s Meeting in Madrid 1999. This paper continues the presentation with reference temperature testing and results of microstructural investigations. The microstructure is analysed using SANS technique.
The Charpy-V transition temperature shifts due to neutron irradiation could be confirmed by the reference temperatures T0 shifts. Furthermore, the SANS experiments provide a clear evidence of irradiation-induced microstructural features. Between a microstructural and an embrittlement based radiation coefficient, there is a obvious correlation. The main parameters of influence are the neutron fluence and the nickel content.

Keywords: VVER-type reactor pressure vessel steel, irradiation, irradiation coefficients, Charpy-V parameter, fracture toughness, mechanisms, microstructure, small angle neutron scattering, defects, volume fraction
  • Lecture (Conference)
    Proceedings of the IAEA Specialists Meeting on Irradiation Embrittlement and Mitigation, Gloucester, England, 14-17 May 2001, p. 121-130
  • Contribution to proceedings
    Proceedings of the IAEA Specialists Meeting on Irradiation Embrittlement and Mitigation, Gloucester, England, 14-17 May 2001, p. 121-130

Publ.-Id: 3913

Magnetofluiddynamik - Beeinflussung metallischer Schmelzen mittels elektromagnetischer Felder

Gerbeth, G.
Es wird eine Übersicht über die Arbeiten zur Magnetofluiddynamik gegeben.
Die wesentlichen Effekte bestehen in der strömungsantreibenden Wirkung von
magnetischen Wechselfeldern und der dämpfenden Wirkung von Gleichfeldern.
Die Kombination beider Felder erlaubt meist die Entwicklung einer
Feldkonfiguration, die eine maßgeschneiderte Wirkung auf Strömung sowie
Wärme- und Stofftransport des jeweiligen Prozesses gestattet. Dafür werden
Beispiele aus Kristallzüchtung und Metallurgie angegeben.
  • Lecture (others)
    Einladungsvortrag im Kolloquium "Physik amorpher und flüssiger Legierungen", TU Chemnitz, 24.04.2001

Publ.-Id: 3912

The inverse approach to Magnetofluiddynamics

Gerbeth, G.
Today there are two developments for an inverse approach to liquid metal
magnetohydrodynamics. At first, the reconstruction of a three-dimensional
velocity field out of external magnetic field measurements. At second, the
design of tailored magnetic field actions specific for the heat- and mass
transfer needs of the corresponding process. Results for both methods are
presented. The application to the steel flow in the mould are discussed.
  • Lecture (others)
    Lecture at ABB Process Industries, Västeras, Sweden, 27.03.2001

Publ.-Id: 3911

Parametrische Bildgebung von [18F]OMFD Hirn-PET-Studien

Hinz, R.; Bredow, J.

Das Aminosäurederivat 3-O-methyl-6-[18F]fluoro-L-DOPA ([18F]OMFD) zeigt eine hohe Aufnahme in Hirntumoren im Gegensatz zum normalen Hirngewebe. Ziel dieser Arbeit war die Generierung parametrischer Datensätze des Tracer-Verteilungsraumes in der Positronen-Emissions-Tomographie (PET).
Nach vorangegangener Transmissionsmessung für die Schwächungs- und Streukorrektur wurden dynamische PET-Aufnahmen mit 34 Frames innerhalb von 90 Minuten auf einem hochauflösenden Scanner ECAT EXACT HR+ nach der intravenösen Gabe von 330 MBq [18F]OMFD akquiriert. Zur Reduktion des Rauschens wurden die Bilder nach der iterativen Rekonstruktion mit einem Savitzky-Golay-Filter geglättet. Die Angebotsfunktion wurde entweder extern aus gemessenen venösen Blutproben oder nichtinvasiv aus der A. carotis interna bestimmt. Eine Korrektur auf Metabolite ist bei
[18F]OMFD nicht erforderlich. Für die Erzeugung parametrischer Bilder wird das Eingewebs-Kompartimentmodell zur Beschreibung des kinetischen Verhaltens reversibler Tracer benutzt. Pixelweise werden die Einstromkonstante K1, die Eliminationskonstante k2 und das anteilige Blutvolumen fbv geschätzt. Das Verteilungsraumvolumen Vd des Tracers wird als Quotient von k1 und k2 bestimmt.
In den parametrischen Bildern des Verteilungsraumvolumens ist eine klarere Abgrenzung maligner Areale als in den Aktivitätsverteilungen möglich. Der Wert von Vd ist ein Indikator für die Aminosäuretransporteraktivität in den Zellen, von der angenommen wird, dass sie in Tumorzellen gegenüber Normalgewebe erhöht ist. Das Verhältnis der Vd-Werte von Tumor zu Nichttumor lag bei dem untersuchten Patientenkollektiv zwischen 2,2 : 1 und 3,2 : 1.
Die Berechnung der Verteilungsraumkoeffizienten Vd führt zu einer Quantifizierung onkologischer PET-Studien mit [18F]OMFD, mit der zahlenmäßige Aussagen bei Verlaufskontrollen und interindividuelle Vergleiche möglich werden.

Keywords: Positronen-Emissions-Tomographie Modellierung
  • Lecture (Conference)
    39. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin Hamburg 25.04. - 28.04.2001

Publ.-Id: 3910

Post Test CFD Calculations of Experiments at the ROCOM Mixing Test Facility related to Boron Dilution and Cold Water Transients

Höhne, T.; Rohde, U.; Prasser, H.-M.
The temperature and boron concentration fields established by the coolant mixing during nominal and transient flow conditions in the reactor pressure vessel of the PWR Konvoi were analyzed by numerical and experimental studies. The validation of the CFD results (CFD-code CFX-4) was carried out at the Rossendorf mixing test facility ROCOM. ROCOM is a 1:5 scaled Plexiglas model of the PWR Konvoi allowing velocity measurements by the LDA technique. Plugs of coolant with low boron acid concentration and/or different temperature are simulated by salt water injection. The CFD calculations were based on the assumption of incompressible turbulent flow. The turbulence was considered by an k--model. The perforated drum, as well as the reactor core with core internals, were represented by the model of a porous body. Calculations were performed for constant flow in the loops as well as for the scenario of an onset of the circulation. For transient CFD-calculation sensitivity studies were performed to check the numerical diffusion and the choice of different turbulence models.
Keywords: Boron Dilution, Coolant Mixing, CFD, PWR
  • Lecture (Conference)
    CFX Users Conference 2001,28-30 May 2001, Berchtesgaden
  • Contribution to proceedings
    CFX Users Conference 2001,28-30 May 2001, Berchtesgaden

Publ.-Id: 3909

Modellierung des Kernkraftwerks Stade Vorarbeiten für Rechnungen mit dem Programm RALOC Mod 4.0AG Teil 1: Zonen, Verbindungen, Strukturen

Krüssenberg, A.-K.; Schaffrath, A.
Grundlage für die Erstellung des Eingabedatensatzes ist die Nodalisierung, eine Unterteilung des Containments in Bilanzräume (sog. Zonen), die über definierte Strömungswege (sog. Junctions) miteinander verbunden sind. Für die Zonen werden während einer Rechnung Massen- und Energiebilanzen, für die Verbindungen hingegen Impulsbilanzen aufgestellt und gelöst. Zusätzlich können mit Hilfe von sog. wärmeleitenden Strukturen Wärmequellen und -senken definiert werden. Diese erlauben die Modellierung der Zufuhr von Wärme in bzw. die Abfuhr von Wärme aus einzelnen Zonen sowie die Berechnung von Temperaturprofilen in festen Materialien (z.B. Wänden, Einbauten, Armaturen, Leitungen, Komponenten) sowie des Wärmeübergangs an deren Oberflächen.
  • Other report
    FWS 01-1, April 2000

Publ.-Id: 3908

16Alpha-[18F]fluor-17Beta-Estradiol (FES) und [18F]FDG-PET zur präoperativen Diagnostik bei Mamma-Carcinom

Bredow, J.; Richter, B.; Beuthien-Baumann, B.; Römer, J.; Füchtner, F.; Distler, W.; Franke, W.-G.
Patientinnen (Pat.) mit hochgradigem V.a. Mamma-CA wurden präoperativ mit FES oder FDG untersucht. Ziel war die Beurteilung von Multizentrizität, axillärem Lymphknotenbefall und Estrogenrezeptorstatus (ER) bzw. metabolischen Aktivität mittels PET sowie der Vergleich mit den histologischen Befunden incl. Estrogenrezeptorstatus.

Die Pat. wurden radomisiert mit FDG oder FES im klinischen Stadium =pT2 an einem dedizierten PET-System (ECAT EXACT HR+, SIEMENS/CTI) untersucht. FES: Injektion von ca. 220 MBq i.v., 2 bed positions ab Axiallae bis Oberbauch in Bauchlage (Lagerungshilfe) ab 90 min p.i., anschließend ab prox. Oberschenkel bis Schädelbasis in Rückenlage, jeweils mit gemessener Transmissionskorrektur im 2D-Modus. FDG: Injektion von 290-370 MBq i.v., ab 60 min p.i. gleiche Aufnahmeparameter wie bei FES.

Es wurden bisher 5 Pat. mit FES und 4 Pat. mit FDG untersucht (Tabelle). Erste Daten zeigen für FES und FDG eine positive Carcinomdarstellung auch bei Multizentrizität. Bei einer Pat. fand sich mittels FES ein falsch-positiver bzw. ein falsch negativer Befund bezüglich der axillären LK und des Estrogenrezeptorstatus.

Lfd...Diagnose postoperativ....Präparat......PET:... .ER.. ..Vergleich PET - Histologie

1......pT4NxM1G3L1 (MZ)......FDG.............+/-........0.......RP......RP.......(FN).................2,0
4......pT2N1M0G3L1 (MZ)......FES..............+/+...>80......RP......RP........RP.......RP.......4,3
7......pT2N0M0 Dcis (MZ)......FDG..............+/-.......0.......RP......RN........RN..................1,8
8......pT2N1M0L1V1 (MZ)......FES..............+/-.......0.......RP......RP........FN.......FP.......1,6
9......pT4NxM1 (MZ).............FES..............+/+....>90......RP......RP.......(RP)......RP.......7,3

Erste mittels FES in Deutschland durchgeführte Untersuchungen weisen auf die Eignung zur präoperativen Diagnostik des Mamma-CA hin. Eine abschließende Beurteilung ist bei kleiner Fallzahl noch nicht möglich.
  • Poster
    39. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Hamburg, 25.-28.4.2001
  • Abstract in refereed journal
    Nuklearmedizin 40 (2001) A82

Publ.-Id: 3907

4. Workshop "Measurement techniques for stationary and transient multiphase flows", Rossendorf, November 16 - 17, 2000

Prasser, H.-M.; (Editor)
In November 2000, the 4th Workshop on Measurement Techniques for Stationary and Transient Multiphase Flows took place in Rossendorf. Three previous workshops of this series were national meetings; this time participants from different countries took part. The programme comprised 14 oral presentations, 9 of which are included in these proceedings in full length. A special highlight of the meeting was the main lecture "Ultrasonic doppler method for bubbly flow measurement" of Professor Masanori Aritomi, Dr. Hiroshige Kikura and Dr. Yumiko Suzuki, which was read by Dr. Hiroshige Kikura. The workshop again dealt with high-resolution phase distribution and phase velocity measurement techniques based on electrical conductivity, ultrasound, laser light and high-speed cinematography. A number of presentations were dedicated to the application of wire-mesh sensors developed by FZR for different applications used by the Technical Universities of Delft and Munich and the Tokyo Institute of Technology. The presentations were in particular:

M. Aritomi, H. Kikura, Y. Suzuki (Tokyo Institute of Technology): Ultrasonic doppler method for bubbly flow measurement

V. V. Kontelev, V. I. Melnikov (TU Nishny Novgorod): An ultrasonic mesh sensor for two-phase flow visualisation

A. V. Duncev (TU Nishny Novgorod): Waveguide ultrasonic liquid level transducers for power generating equipment

H.-M. Prasser, E. Krepper, D. Lucas, J. Zschau (FZR), D. Peters, G. Pietzsch, W. Taubert, M. Trepte (Teletronic Ingenieurbüro GmbH), Fast wire-mesh sensors for gas-liquid flows and decomposition of gas fraction profiles according to bubble size classes

D. Scholz, C. Zippe (FZR): Validation of bubble size measurements with wire-mesh sensors by high-speed video observation

A. Manera, H. Hartmann, W.J.M. de Kruijf, T.H.J.J. van der Hagen, R.F. Mudde, (TU Delft, IRI): Low-pressure dynamics of a natural-circulation two-phase flow loop

H. Schmidt, O. Herbst, W. Kastner, W. Köhler (Siemens AG KWU): Measuring methods for the investigation of the flow phenomena during external pressure vessel cooling of the boiling water reactor SWR1000

A. Traichel, W. Kästner, S. Schefter, V. Schneider, S. Fleischer, T. Gocht, R. Hampel (HTWS Zittau/Görlitz - IPM): Verification of simulation results of mixture level transients and evaporation processes in level measurement systems using needle-shaped probes

S. Richter, M. Aritomi (Tokyo Institute of Technology): Methods for studies on bubbly flow characteristics applying a new electrode-mesh tomograph

Keywords: multiphase flow, measurement instrumentation, workshop, transient flow
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-320 Mai 2001


Publ.-Id: 3906

Non-volatile memories based on Si+ - implanted Gate oxides

Gebel, T.; von Borany, J.; Thees, H.-J.; Wittmaack, M.; Stegemann, K.-H.; Skorupa, W.
Electrical properties of 20 ... 30 nm gate oxides implanted with Si+ ions are investigated using MOS capacitors and transistor structures. The observed programmming window can reach several volts and the structures exhibit good retention behavior. A first 256k - nvSRAM is demonstrated showing a programming window >1V for write pulses of 12V / 8 ms.
Keywords: nanocrystal, ion implantation, non-volatile memory
  • Microelectronic Engineering 59 (2001) 247-252
  • Lecture (Conference)
    INFOS Conference 2001, 20.-23.06.2001, Udine (Italy)


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Publ.-Id: 3904

Die Sorption des Uran(VI) und anderer radiotoxischer Schwermetalle an Kolloidpartikeln im Flutungswasser des Uranbergwerks Königstein

Zänker, H.; Richter, W.
Das untersuchte Flutungswasser (pH 5,5) enthält Fe(II), welches bei Sauerstoffzutritt Fe(III)-Oxyhydroxidpartikel bildet. Diese Partikel adsorbieren Radionuklide wie Po-210 und Pb-210. Im pH-Bereich von 4 bis 6 wird auch der größte Teil des Urans, welches in sechswertiger Form vorliegt, sorbiert. Radium dagegen ist kaum kolloidgetragen.

Keywords: colloids, particles, uranium, radium, polonium, iron oxyhydroxides, sorption
  • Lecture (others)
    Vortrag Universität Jena, Fachbereich Geologie der Universität Jena, 19. April 2001

Publ.-Id: 3903

TRIDYN_FZR User Manual

Möller, W.; Posselt, M.
The present report contains the User Manual of the FZR version of the dynamic binary-collision computer simulation code TRIDYN. The present version of the code is based on TRIDYN Vs. 4.0 by W.Möller and W.Eckstein, Department of Surface Physics, Max-Planck Institute of Plasma Physics, Boltzmannstraße 2, 85748 Garching, Germany (1989). Modifications, in particular for PC implementation, quasi-dynamic display and the input dialog have been performed at the Institute of Ion Beam Physics and Materials Research by V.Kharlamov, T.Schwieger, M.Posselt, and W.Möller (1995-2001).
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-317 April 2001


Publ.-Id: 3902

Pulsed Electron-Beam Melting of High-Speed Steel: Structural Phase Transformations and Wear Resistance

Ivanov, Y.; Matz, W.; Rotshtein, V.; Günzel, R.; Shevchenko, N.
The structural and phase transformations occurring in the near-surface layers of pre-quenched high-speed steel subjected to pulsed electron beam melting have been investigated. Melting was induced by a low-energy (20–30 keV), high-current electron beam with a pulse duration of 2.5 µs and an energy densities ranging from 3 to 18 J/cm2. Using electron microscopy and x-ray diffraction it has been revealed that with increasing beam energy density gradual liquid-phase dissolution of initial globular M6C carbide particles occurs in the near-surface layer of thickness up to ~1 µm. This process is accompanied by formation of martensite crystals (gamma-phase) and an increase of residual austenite (alpha-phase) content. When the carbide particles are completely dissolved, martensitic transformation is suppressed. In this case, a nonmisoriented structure is formed consisting predominantly of submicron cells of -phase separated by nanosized carbide interlayers. Irradiation of cutting tools (drills) in a mode corresponding to an abrupt decrease in the content of M6C particles due to their liquid-phase dissolution enhances the wear resistance of the drills by a factor of 1.7. This is associated with the fixation of undissolved particles in the matrix, the formation of residual compressive stresses and of dispersed M3C carbide particles as well as the high (~50 %) content of the metastable -phase in the surface layer.
Keywords: steel, electron beam melting, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, wear resistance
  • Surface & Coatings Technology 150 (2002) 188-198


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Publ.-Id: 3901

Infrarotspektroskopie von Halbleiter-Quantenstrukturen: vom Modellsystem zum Infrarot- und THz-Bauelement

Helm, M.
please contact the author
Keywords: Infrarotspektroskopie, Halbleiter
  • Lecture (others)
    Kolloquiumsvortrag am Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin (9.4.2001)

Publ.-Id: 3900

Energy dependence of quantum dot formation by ion sputtering

Facsko, S.; Kurz, H.; Dekorsy, T.
Ordered quantum dot patterns are generated on GaSb and InSb surfaces due to a
surface instability induced by Ar+ ion sputtering under normal incidence.
The characteristic length of the generated patterns scales with the square
root of the ion energy over the energy range of 75 - 1800 eV. This energy
dependence is compared to the solutions of the isotropic Kuramoto-Sivashinsky
equation and allows the determination of the lateral width of the energy
distribution deposited by the incident ions in the very low energy range. We
show that the observed energy dependence is in agreement with the linear
continuum theory under the assumption that the dominant smoothing process is
due to effective ion induced diffusion without mass transport on the surface.
Keywords: self-organization ion sputtering quantum dots surface roughening
  • Physical Review B 63 (2001) 165329 -1-5


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Publ.-Id: 3898

Institute of Ion Beam Physics and Materials Research; Annual Report 2000

von Borany, J.; Jäger, H.-U.; Helm, M.; Möller, W.; Wieser, E.
Summary of the Scientific Activities of the Institute in 2000
Keywords: Highlight Reports, Short Contributions, Statistics
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-314 März 2001


Publ.-Id: 3897

Synthesis of [1,2-14C]Trichloroacetic acid

Bubner, M.; Fuksora, K.; Matucha, M.; Heise, K.-H.; Bernhard, G.
Modern trends in investigating the phytotoxic effects of trichloroacetic acid (TCA) have initiated an actual interest in [1,2-14C]TCA with specific activities > 3.7 GBq/mmol. One-pot synthesis starting from potassium [1,2-14C]acetate yielding 80% of [1,2-14C]TCA is described. The specific activity of the product corresponds to that of the potassium or sodium [1,2-14C]acetate and the radiochemical purity is higher than 98%. The synthesis method is usable for the synthesis scale < 1 mmol.
Keywords: Key Words: [1,2-14C]trichloroacetic acid, one-pot synthesis
  • Labelled Comp. Radiopharm


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Publ.-Id: 3896

ROBL - A synchrotron radiation beamline for Radiochemistry and Materials Research

Matz, W.; Schell, N.; Eichhorn, F.; Prokert, F.; Reich, T.; Funke, H.; Berberich, F.
The Forschungszentrum Rossendorf has built a synchrotron radiation beamline at the ESRF, Grenoble, for radiochemistry and materials research. The radiochemistry set-up at ROBL is the only dedicated station in Europe for XAS experiments on actinides in solid or liquid samples. The materials end station is mainly for diffraction and reflectometry studies on thin films and has capabilities for in-situ experiments in film growth or temperature induced structural changes. The possibilities for materials research at ROBL are demonstrated by some experiments performed.
Keywords: synchrotron radiation, ROBL, EXAFS instrumentation, X-ray diffraction, thin films, reflectivity, in-situ experiments, ion implantation
  • Lecture (Conference)
    2nd International Workshop JINR Synchrotron Radiation Source (DELSY-2001), 02.-06.04.2001, Dubna, Russia

Publ.-Id: 3893

Studies of the development of texture in TiN films by use of in situ synchrotron x-ray scattering

Schell, N.; Matz, W.; Bottiger, J.; Chevallier, J.; Kringhoj, P.
During growth the micro-structural development of TiN films was studied – especially the change in texture with film thickness. The films were deposited by use of a magnetron sputtering source in a vacuum chamber equipped with two magnetron sources and mounted on a goniometer located at a synchrotron radiation beam line. X-ray diffraction and reflectivity measurements were carried out in situ to follow the microstructure as a function of film thickness. With the deposition parameters that were chosen, a crossover was observed: grains with a (002) plane parallel to the film surface dominate at small thickness, while, at larger thickness, (111) grains dominate. Recrystallization was identified as a mechanism that controls this texture development. The driving force for change of orientation of the individual grains arise from minimalization of the sum of the surface energy and the strain energy of the individual grains.
Keywords: thin film growth, sputter deposition, texture developments, TiN, in-situ experiments, synchrotron radiation
  • Journal of Applied Physics 91, No. 4, (2002) 2037-2044


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Publ.-Id: 3892

Influence of dose rate and temperature on ion-beam-induced defect evolution in Si investigated by channeling implantation at different doses

Posselt, M.; Bischoff, L.; Teichert, J.
A focused ion beam system is applied to study the dose dependence of the shape of Ge channeling implantation profiles at two very different dose rates (1018 and 1011 cm-2 s-1), and for implantation temperatures of 2500C and RT. A simple model for the buildup of radiation damage is developed to describe the dechanneling effect of defects formed during ion bombardment. The use of this model in atomistic computer simulations yields Ge depth profiles which agree well with measured data. The lifetime of ion-beam-induced defects at 2500C was estimated to be in the order of 100 s. At RT, some defect relaxation was found between 10 microseconds and 100 s after ion impact.
Keywords: ion implantation, radiation damage, channeling, computer simulation
  • Applied Physics Letters Vol. 79 , Nr. 10 (2001) 1444-1446


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Publ.-Id: 3891

Investigation of Si-nanocrystal memory structures obtained by r.f. sputtering

Schmidt, J. U.
Currently effects related to carrier confinement in nanometer sized silicon structures are extensively studied. So it has been shown that Si in spite of its indirect band
gap can efficiently emit photons due to carrier recombination provided that low dimensionality is achieved. Further a novel Si-nanocrystal floating gate MOSFET
memory structure has been proposed. In all these applications the formation of Si-quantum dots is a critical step being tackled using a variety of methods. Our
approach is rf magnetron sputtering, a popular thin film preparation technique compatible with conventional Si-technology and providing an elegant way to prepare
device quality SiO2 thin-films, but also SiO2/nanocrystalline (nc)-Si/SiO2 thin-film systems. SiO2 films were prepared by sputtering from an high purity quartz
target and characterized by TEM, FTIR, Current-Voltage and Capacitance-Voltage measurements. The electrical properties of the sputtered oxide films are
comparable to those of thermally grown oxides. By alternate sputtering from Si and SiO2-targets thin-film systems have been prepared. For the latter charge
storage in the nc-Si-floating gate has been demonstrated.
Keywords: silicon,nanocrystal,MOS,Capacitance-voltage measurements,sputtering,memory
  • Lecture (Conference)
    Tagung der Deutschen Physikalischen Gesellschaft, Hamburg 26. - 30. März 2001 Fachverband Dünne Schichten (DS 19.3)


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Publ.-Id: 3887

Step Edge Diffusion and Step Atom Detachment in Surface Evolution: Ion Erosion of Pt(111)

Michely, T.; Kalff, M.; Comsa, G.; Strobel, M.; Heinig, K.-H.
The temperature dependent morphological evolution of Pt(111) under 1 keV Xe normal
incidence ion bombardment has been investigated up to 600 monolayers removed.
Coarsening of the surface structures during erosion and a qualitative change in
roughness evolution between 650 and 700 K are found to be caused by different
atomic processes: the former by diffusion of atoms along steps, the latter by the
onset of step atom detachment.
Keywords: Ion Erosion, platinum, STM, kinetic Monte-Carlo simulation
  • Physical Review Letters 86 (2001) 2589


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Publ.-Id: 3886

Nanostructured Arrays Formed by Finely Focused Ion Beams

Zuhr, R. A.; Budai, J. D.; Datskos, P. G.; Meldrum, A.; Thomas, K. A.; Warmack, R. J.; White, C. W.; Feldman, L. C.; Strobel, M.; Heinig, K.-H.
Nanoparticles can be formed in a variety of substrates by ion implantation and
thermal annealing. These particles range from a few to several hundred nanometers
in diameter and may be metals or semiconductors containing either single or multiple elements. Particles formed in this way are not uniform in size and are randomly
distributed throughout the implant region. The purpose of this work is to make
uniformly spaced lattices of colloidal particles of more uniform size by using a finely
focused ion beam to implant ions only into a microscopic region at each point of
a two-dimensional array. Simulations using a kinetic
lattice Monte Carlo code indicate that such implants should form localized distributions of colloids that may Ostwald ripen into a single large colloid at each
lattice site. Such a composite would exhibit greatly improved optical characteristics. Initial work is being done with 30 keV Ga and As in Si. Particle formation
as a function of implant and annealing conditions will be discussed
Keywords: nanostructure, focused ion beam, ion beam synthesis
  • Lecture (Conference)
    American Physical Society, Centennial Meeting March 20-26, 1999, Atlanta, GA, USA

Publ.-Id: 3885

Strong electroluminescence of Sn-implanted silicon dioxide layers

Rebohle, L.; von Borany, J.; Fröb, H.; Gebel, T.; Skorupa, W.
The blue-violet electroluminescence (EL) of Sn-implanted SiO2 layers thermally grown on crystalline Si has been investigated at room temperature and compared with the corresponding photoluminescence (PL) spectra. It was shown that power efficiencies up to 2.5·10-4 can be achieved, and that the power efficiency slightly decreases for high injection currents. Because of the excellent correspondence between the EL and the PL spectra we interpreted the EL as due to a radiative triplet-singlet transition of a Sn-related oxygen deficiency center. Based on the electrical measurements, we assume that the luminescence centers will be excited either by impact excitation of hot electrons moving in the conduction band of SiO2 or by field ionization of luminescence centers in conjunction with hopping conduction.
Keywords: electroluminescence tin implanted silicon dioxide
  • Mat. Sci. Eng. C 19 (2001) 373

Publ.-Id: 3884

Nitrogen incorporation and loss during ion nitriding of Al

Telbizova, T.; Chevolleau, T.; Möller, W.
Ion nitriding of Al has been performed by a N2 reactive ion beam using a hot filament ion source. Quantitative determination of N incorporation and loss has been estimated at a beam energy of 1.6 keV with two ion current densities of 0.1 and 0.2 mA/cm2 and substrate temperature of 350°C. For this purpose, a characterisation of the ion beam has been carried out by an energy selective mass spectrometer. The analysis shows that the beam consists solely of N2+ and N+ ions with a composition of about 80 % and 20 %, respectively. The ion energy distribution of both N2+ and N+ consists of a single narrow peak with a full width at half maximum of about 10 eV and a mean ion energy corresponding to the applied beam potential. From the beam parameters, N loss due to sputtering and backscattering has been calculated using dynamic binary collision computer simulations. After an initial transient, the stationary partial sputtering yield of N is predicted to be 0.45, while the amount of backscattered N is about 5 % of the incident N fluence. The N loss obtained from the simulation is consistent with the incident fluence and the total amount of incorporated N measured by Nuclear Reaction Analysis (NRA).
Keywords: ion source, ion nitriding, sputtering yield, backscattering, Al, AlN
  • Nuclear Instruments and Methods in Physics Research B 184 (2001) p. 347


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Publ.-Id: 3881

Autoradiographische Untersuchungen zu 5-HT1A und 5-HT2A- Rezeptoren nach sozialer Isolation

Schiller, L.; Kretzschmar, M.; Brust, P.; Oehler, J.
Frühere Untersuchungen haben gezeigt, dass im Verlaufe sozialer Isolation - tierexperimentelles Modell gestörten Sozialkontaktes - serotonerge Alterationen Anteil an den neurobiologischen Veränderungen haben, die den auffälligen Verhaltensänderungen
zugrunde liegen. Die durch Bindungsassays nachgewiesenen Veränderungen von KD und Bmax Werten serotonerger Rezeptorpopulationen deuten an, dass eine Reihe lokaler quantitativer Veränderungen serotonerger Rezeptoren in verschiedenen Hirnregionen zu erwarten sind .
Mittels autoradiographischer Untersuchungen wurde die lokale Verteilung von spezifischen Rezeptorpopulationen, insbesondere von 5-HT1A und 5-HT2A Rezeptoren im Cortex, Hippocampus, Amygdala, Striatum und N. acccumbens verfolgt. Nach 28 Tagen zeigt sich eine massive Abnahme der 5-HT1A Rezeptordichte im Cortex, Hippocampus, Substantia nigra und in der Amygdala , die auch weitestgehend nach 12 Wochen Isolation noch nachweisbar ist. Die Dichte der 5-HT2A Rezeptoren ist ebenfalls nach 28 Tagen in den untersuchten Hirnregionen signifikant vermindert, während nach 12 Wochen kaum noch Veränderungen nachgewiesen werden können. In der Tendenz ist im Striatum und im N.accumbens sogar eine up-Regulation zu erkennen. Die Ergebnisse werden in Beziehung zu neurochemischen und Verhaltensveränderungen diskutiert.
  • Poster
    3. Mitteldeutsche Psychiatrie-Tage, Magdeburg, 15.-17.03.2001

Publ.-Id: 3879

Anwendung des Instrumentierten Kerbschlagbiegeversuch zur Ermittlung von Referenztemperaturen nach dem Master-Curve-Konzept

Viehrig, H.-W.; Böhmert, J.; Dzugan, J.
The instrumented impact test is suitable for the determination of fracture mechanical pa-rameters. In this paper the determination of the dynamic fracture toughness values in the lower ductile-to-brittle transition region is presented. The fracture toughness is determined at the onset of cleavage fracture and evaluated by the Master Curve (MC) concept. The MC concept allows to quantify the variation of fracture toughness with the temperature within the lower ductile-to-brittle transition region. Limit curves of fracture toughness for defined fail-ure probabilities and a reference temperatures can be determined using this method. This paper presents the application of the master curve concept to the reference temperature de-termination through the thickness of reactor pressure vessel (RPV) steel plate. The reference temperatures determined with dynamic fracture toughness values (T0dy) are compared with quasi-static reference temperatures (T0st) and Charpy-V transition temperatures (TT). The T0dy, T0st and TT increase from the surface to the middle of the RPV steel plate. Compared with T0st, the T0dy values are higher approximately 70 to 90 K.
Keywords: reactor pressure vessel steel, instrumented impact testing, J integral,fracture toughness, dynamic loading, Master Curve
  • Materialwissenschaft und Werkstofftechnik, Vol. 32, No. 6, June 2001, pp. 568-573

Publ.-Id: 3878

Simultaneous preparation of 16alpha-[18F]fluoroestradiol-sulphamates in an automated module. A high-yield procedure for 16alpha-[18F]fluoroestradiol-17beta-sulphamate

Römer, J.; Füchtner, F.; Steinbach, J.; Kasch, H.
After successful synthesizing 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate in an automatic procedure, we studied the conditions for obtaining 16alpha- [18F]fluoroestradiol-mono-sulphamates in a similar manner. The described procedure can simultaneously provide approximately 3 GBq of 16alpha-[18F]fluoroestradiol-3-sulphamate and 1 GBq of 16alpha-[18F]fluoroestradiol-17beta-sulphamate of high radiochemical purity. By treating 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate with Kryptofix 2.2.2 and potassium carbonate, 16alpha-[18F]fluoroestradiol-17beta-sulphamate also becomes available at high radioactivity.
Keywords: fluorine-18; nucleophilic fluorination; sulphamoylation; automated synthesis; PET tracer
  • Poster
    14th International Symposium on Radiopharmaceutical Chemistry, Interlaken/Schweiz, 10.-15.06.2001
  • Journal of Labelled Compounds and Radiopharmaceuticals 44 (2001) 689-700

Publ.-Id: 3877

Synthesis and host-guest properties of multi-crown-dendrimers towards sodium pertechnetate and mercury(II) chloride

Stephan, H.; Spies, H.; Johannsen, B.; Gloe, K.; Gorka, M.; Vögtle, F.
Multi-crown-dendrimers of four different generations have been synthesized by grafting 4, 8, 16 and 32 benzo[15]crown-5 units at the periphery of POPAM-dendrimers. The binding of sodium pertechnetate and mercury(II) chloride by the multi-crown-dendrimers has been studied by liquid-liquid extraction using the radioactive probes 22Na+, 99TcO4-, and 203Hg2+. The third- and fourth-generation dendrimers 3 and 4, in particular, are capable of extracting mercury(II) with high efficiency ( ca. 12 HgII ions per dendrimer molecule, even at low generation). It has been shown that the guest molecules investigated preferentially encapsulated inside the dendrimers.

Keywords: dendrimers; crown compounds; pertechnetate; mercury; solvent extraction
  • Eur. J. Inorg. Chem. (2001) 2957-2963


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Publ.-Id: 3876

Novel technetium(III) mixed-ligand chelates for the design of lipophilic complexes stable in vivo

Pietzsch, H.-J.; Seifert, S.; Drews, A.; Syhre, R.; Spies, H.; Leibnitz, P.; Tisato, F.; Refosco, F.
The most frequently used technetium compounds suitable for coupling the metal to biologically active molecules are square-pyramidal oxo complexes based on tetradentate N2S2 ligands (1). Properties and thus the in vivo behaviour of such complexes are strongly influenced by the presence of the quite polar [Tc=O]3+ unit. Whether such a polarity is beneficial or not is not obvious and depends on the requirements for specific radiotracers, e.g. for receptor-targeting agents or for metabolic tracers. Another crucial point in tracer design is the stability of the respective Tc chelate towards ligand exchange in vivo. Recently it was shown that the applicability of the "3+1" mixed-ligand Tc(V) chelates is limited because of their reaction with glutathione in vivo (2,3). So there is a considerable interest in alter-native chelate systems that combine lower polarity with enhanced in vivo stability. Such systems are based on oxo-free Tc cores at lower oxidation state.
Here we describe novel types of Tc(III) mixed-ligand complexes. Both chelate systems fulfil the requirements for a lipophilic, non-polar building block stable against ligand exchange reaction in vivo. They offer the advantage of high versatility in conjugating biomolecules as described for the "3+1"-series (4).

Keywords: Tc-99m, Tc(III) mixed-ligand complexes, thiolato ligands, isocyanides, phosphines
  • Lecture (Conference)
    14th International Symposium on Radiopharmaceutical Chemistry, Interlaken/Schweiz, 10.-15.06.2001
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 44 Suppl.1, (2001), S39-S41

Publ.-Id: 3875

Synthesis and autoradiographical evaluation of novel high-affinity Tc-99m ligands for the serotonin 5-HT1A receptor

Drews, A.; Heimbold, I.; Varnäs, K.; Hall, H.; Halldin, C.; Pietzsch, H.-J.; Syhre, R.; Seifert, S.; Brust, P.; Johannsen, B.
Despite tremendous effort in the development of Tc-99m complexes to image post-synaptic CNS receptors, various attempts failed so far (1). The combination of sufficient brain uptake and high affinity to the receptors (IC50 < 1 nM) seems to be crucial. Our studies are focused on complexes for serotonin 5-HT1A and 5-HT2A receptors. Recently we succeeded in synthesizing of complex I, which is a high affinity Tc-99m ligand for the 5-HT1A receptor derived from the well known serotonin 5-HT1A antagonist WAY 100635 and shows a subnanomolar affinity (0.13 nM) and a brain uptake of 0.20 % ID in rats, 5 min post injection (2). Figure 1 shows the structure of the complex I.

Here we report on the synthesis of new high-affinity Tc-99m ligands for the 5-HT1A receptor with improved brain uptakes. The complexes are evaluated in receptor binding assays, by in vitro autoradiography in post mortem human brain and by in vivo studies.

Keywords: serotonin 5-HT1A receptor, Tc-99m receptor ligand, receptor binding assay, in vitro autoradiography
  • Poster
    14th International Symposium on Radiopharmaceutical Chemistry, Interlaken/Schweiz, 10.-15.06.2001
  • Abstract in refereed journal
    J. Labelled Cpd. Radiopharm. 44, Suppl. 1 (2001), S544-S546

Publ.-Id: 3874

Synthese, physikalisch-chemische Charakterisierung und Bestimmung der Löslichkeit von Erdalkaliuranyltricarbonato-komplexen M2[UO2(CO3)3].xH2O; M = Mg, Ca, Sr, Ba

Amayri, S.; Geipel, G.; Reich, T.; Bernhard, G.
Uransekundärminerale sind in verschiedenen Uranerzbergbaugebieten (u.a. Schneeberg; Joachimstal, Adrinapole, Arizona) nachgewiesen worden. Aus der Kenntnis der Bildung von Erdalkaliuranylcarbonaten wie Bayleyit (M = Mg) und Liebigit (M = Ca) können wichtige Hinweise über den Transport und die Immobilisierung von Uran unter umweltrelevanten Bedingungen abgeleitet werden.
Ein Ziel der Arbeit war es, Syntheseverfahren für Ca-, Mg-, Sr- und Ba-Uranyltricarbonate zu erarbeiten bzw. zu optimieren und die Syntheseprodukte physikalisch-chemisch zu charakterisieren. Als Analysemethoden wurden Röntgendiffraktometrie, Elementaranalyse, ICP-MS, Thermoanalyse [1] durchgeführt. Desweiteren wurden die Produkte mit spektroskopischen Methoden wie IR, Raman, TRLFS und EXAFS untersucht.
Die Synthesen erfolgten in der Regel durch die Umsetzung von Uranylnitratlösung mit Erdalkalinitrat- oder -chloridlösung und Natriumcarbonat im pH-Bereich von 7 bis 8 [2]. Die charakterisierten Substanzen wurden für die Bestimmung ihrer Löslichkeit und für Speziationsuntersuchungen verwendet.
Hauptziel dieser Arbeit war die Bestimmung der Löslichkeit dieser Uranminerale, da bisher keine Daten bekannt sind. Die Löslichkeitsexperimente wurden bei 25°C im pH-Bereich von 7,0 bis 9,0 in 0,1 M NaClO4 - Lösung durchgeführt. Unter Gleichgewichtsbedingungen wurden die Festphasen mittels Röntgendiffraktometrie und die Lösungen mit TRLFS und EXAFS analysiert. Die Ergebnisse zeigten, daß bei pH 7,0 bis 9,0 die Minerale als Festphase vorliegen. Mittels TRLFS wurden in den Lösungen auch M2[UO2(CO3)3](aq)-Komplexe nachgewiesen.
Die Löslichkeit der Erdalkaliuranyltricarbonate vermindert sich in der Reihe von Magnesiumuranyltricarbonat (0.230 mol/l pH: 8,0) zum Bariumuranyltricarbonat (1.31x10-3 mol/l pH: 8,0) entscheidend [3]. Analoges Verhalten zeigt die Löslichkeit der entsprechenden Erdalkalicarbonate.


[1] J. Cejka; Reviews in Mineralogy (Uranium: Mineralogy, Geochemistry and the
Environment) volume 38,(1999) 521-622
[2] M. Bachelet , Cheylon E., Douis M.and Goulette G.; Bull. Soc. Chim. France 19 (3),
(1952) 565
[3] S. Amayri; Dissertation an der TU-Dresden in Vorbereitung (2001)
  • Lecture (Conference)
    GDCH-Tagung in Würzburg, 23.09.-29.09.2001

Publ.-Id: 3873

EXAFS investigations of erth alkaline metal uranyl tricarbonato complexes

Amayri, S.; Reich, T.; Bernhard, G.
Carbonate and bicarbonate are the common anions found in significant concentrations in many natural waters, and they are strong complexation agents for actinide ions. Seepage, flooding and mining waters from the uranium mining area in the southeast of Germany (Saxony and Thuringia), contain relatively high amounts of magnesium, calcium, carbonate and sulfate ions. In these waters the pH values range from 7.0 to 8.0 and the uranium content is about 0.02 mmol/L where magnesium, calcium and carbonate concentrations are 11.6 mmol/L, 6.9 mmol/L and 3.9 mmol/L, respectively /1/.
Recently we were able to confirm the existence of the natural complexes Ca2UO2(CO3)3(aq) and Mg2UO2(CO3)3(aq) by spectroscopic measurements /2/.
We performed Extended X-ray Absorption Fine Structure (EXAFS) measurements at the uranium LIII- edge to study the structures of these complexes. The obtained results by EXAFS of these complex solutions are compared with those from the corresponding EXAFS and XRD data related to the secondary minerals of uranium, liebigite, Ca2[UO2(CO3)3]×10H2O and bayleyite, Mg2[UO2(CO3)3]×10H2O and they are in good agreement.


/1/ Bernhard, G., G. Geipel, V. Brendler, H. Nitsche: Uranium speciation in waters of different
uranium mining areas, J. of Alloys and Compounds 201 (1998) 271-273.
/2/ Bernhard, G., G. Geipel, V. Brendler, H. Nitsche: Speciation of Uranium in Seepage Waters of a
Mine Tailing Pile Studied by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS),
Radiochim. Acta 74 (1996), 87-91.
  • Poster
    Eurokonferenz Actinide-XAS-2000, 10.09.-12.09. 2000, Grenoble

Publ.-Id: 3872

Retention of the potential energy of multiply charged argon ions incident on copper

Kentsch, U.; Tyrroff, H.; Zschornack, G.; Möller, W.

The retained fraction of the potential energy of argon ions incident on copper has been measured using stationary calorimetry at charge states up to 9+ and kinetic energies ranging from 75 eV and 240 eV per ionic charge. An average fraction of 30% to 40% is found with little dependence on the charge number and on the kinetic energy. The retention of the total energy ranges 60% to 75% and can mainly be accounted for by the retained fraction of the potential energy and the collisional energy lost by reflected ions and sputtered target atoms.

Keywords: PACS Nos. 61.80.Jh, 41.75.Ak, 79.20.Rf, 52.50.Gj
  • Physical Review Letters 87 (2001) 105504/1-4


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Publ.-Id: 3871

Growth of low stress cubic boron nitride films by simultaneous medium energy ion implantation

Fitz, C.; Kolitsch, A.; Fukarek, W.; Möller, W.
It is demonstrated that the intrinsic stress in cubic boron nitride films can be significantly relaxed during growth by simultaneous medium energy ion implantation. The stress in the growing film has been studied in-situ using cantilever curvature measurements and has been reduced to below 2 GPa by simultaneous Ar+ or N+ ion implantation with an energy of 70 keV and 35 keV, respectively. The resulting cubic boron nitride films show an increased long term stability. The results reveal that the stress in cBN is not reduced due to segregation of boron at grain boundaries.
Keywords: PACS Nos. 68.55.Jk, 68.55.Ln, 68.60.Bs, 81.15Jj, 61.80.Jh
  • Applied Physics Letters Vol. 80 Number 1 , 7 January 2002, 55-57


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Publ.-Id: 3870

Interactions of three eco-types of Acidithiobacillus ferrooxidans with U(VI)

Merroun, M.; Selenska-Pobell, S.
The interaction of uranium with cells of three recently described eco-types of Acidithiobacillus ferrooxidans recovered from uranium mining wastes was studied. The uranium sorption studies demonstrated that the strains from these types possess different capability to accumulate and tolerate uranium. The amount of uranium biosorbed by all A. ferrooxidans strains increased with increasing the concentration of uranium. We have found that the representatives of type II accumulate significantly higher amounts of uranium in comparison to the other A. ferrooxidans strains. The investigations of the tolerance to uranium showed that the types I and III are resistant to 8 and 9 mM of uranium respectively, whereas the type II does not tolerate more than 2 mM of uranium. The recovery of the accumulated uranium by desorption was investigated using various desorbing agents as sodium carbonate, sodium citrate and EDTA at different concentrations. Sodium carbonate was the most efficient desorbing agent, removing 97% of the uranium sorbed from the cells of A. ferrooxidans type III, and 88.33 and 88.50% from the cells of the types I and II, respectively.

  • Biometals 14 (2): 171-179 (2001)


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Publ.-Id: 3869

EXAFS investigations of uranium (VI) interaction with bacteria

Hennig, C.; Panak, P. J.; Reich, T.; Raff, J.; Selenska-Pobell, S.; Roßberg, A.; Funke, H.; Merroun, M. L.; Bernhard, G.
Mobilization of heavy metals in the environment due to industrial activities is of serious concern due to the toxicity of these metals in humans and other forms of life. Uranium is an example of these metals, and is considered one of the most seriously threatening heavy metals mainly because of its high toxicity, not so much radioactivity. Activities associated with the nuclear industry, mining and wastewater treatment have brought excessive amounts of uranium into the environment. In uranium deposits a number of acidophilic chemolithoautotrophic ( Acidithiobacillus ferrooxidans, for instance) bacteria have been identified which are able to oxidise sulphide minerals, elemental sulfur, ferrous iron. Sequence analysis of the 16S rRNA genes of several reference strains and uranium mining waste pile isolates of A. ferrooxidans revealed specific signatures which distinguish three types within the species. These types differ in their capability to accumulate and tolerate uranium /1/.
Uranium (VI) complexes formation at cell surfaces of A. ferrooxidans types was studied using uranium LIII-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. In all samples uranium is coordinated by two axial oxygen atoms (Oax) at distance of 1.77-1.78 Å. The average distance between uranium and the equatorial oxygen atoms (Oeq) is 2.35 Å. The coordination number for Oeq is 5-6.
Using U-C and U-P phase and amplitude functions, the third and the fourth peak in the FT of A. ferrooxidans give a distance of 2.91 and 3.58 ± 0.02Å, respectively. The latter is the same U-P bond distance as for the organic uranyl phosphate (U(VI)-ATP complex). But we do not exclude the possibility of implication of sulfur because these 2 elements (P and S) are close each other in the periodic system of elements and EXAFS can not distinguish between them. In addition, the P (or S) is bonded in a monodentate mode to the uranyl ion. A bidentate bounding would give a atomic distance of approximately 3.2 Å.
Moreover, no structural differences were observed between the uranium complexes formed by the 3 types of A. ferrooxidans. However, the EXAFS spectra are indicating a formation of uranium complexes which are different from those formed by Bacilli /2/.

/1/ M. Merroun et al., Interaction of three types of Acidithiobacillus ferrooxidans with uranium, Biometals (in preparation).
/2/ C. Hennig et al., EXAFS investigation of uranium(VI) complexes formed at Bacillus cereus and Bacillus sphaericus surfaces, Radiochim. Acta (in press).
  • Poster
    Second Euroconference and NEA Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, Grenoble, Frankreich, 10.-12.09.2000

Publ.-Id: 3868

Die Bedeutung von Kolloiden in der aquatischen Umwelt. Ein Beitrag der AG "Kooloide" aus der Wasserchemie.

Hofmann, T.; Baumann, T.; Bundschuh, T.; Kammer, F.; Leis, A.; Schmitt, D.; Schäfer, T.; Thieme, J.; Totschke, K.-U.; Zänker, H.
In den vergangenen Jahren wurde grundsätzlich akzeptiert, dass Kolloide unter bestimmten Randbedingungen einen erheblichen Beitrag zum Transport von Stoffen in aquatischen Systemen leisten können. Nach wie vor ist jedoch umstritten, welche Relevanz der kolloidale Transport bei einer Vielzahl von Fragestellungen hat.
  • Poster
    Jahrestagung Chemie 2001, Bad Wildungen 21.-23.5.

Publ.-Id: 3866

Plasma Diagnostic of a Plasma Immersion Ion Implantation Process for protecting TiAl Alloys against High Temperature Oxidation using Chlorine

Hornauer, U.; Günzel, R.; Richter, E.; Wieser, E.; Möller, W.; Dettenwanger, F.; Schütze, M.
Plasma immersion ion implantation (PIII) from a chlorine containing plasma has been used in order to improve the high temperature oxidation behavior of titanium aluminide alloys. This process is promising since the subsurface Cl concentration, which is needed for optimum protection against oxidation, can be quickly obtained (approx. fluence 1·1016 Cl/cm-2) in a PIII process.
A PIII system being resistant against the strongly etching Cl2 plasma is presented. Plasma diagnostics of the Cl2 plasma sustained by an ICP source using Langmuir probe measurements is discussed. For the electro-negative Cl plasma, the measurements are examined regarding the influence of negative ions. The implantation of Cl is correlated to the plasma parameters using AES depth profiling of the surface after implantation. The high temperature oxidation behavior is tested using thermogravimetrical analysis (TGA) in air at 900 °C and microstructural investigations of the oxide scale. PIII implantations of Cl2 with 30 kV HV pulses (effective energy 15 keV) show a strong reduction of the oxidation at 900 °C in air, which is comparable to conventional beam line im-plantations of Cl at 15 keV.

Keywords: plasma diagnostic, langmuir, chlorine, Plasma immersion, TiAl, oxidation
  • Lecture (Conference)
    Plasma-Based Ion Implantation (PBII) 2001, 26-28.6. Grenoble, France

Publ.-Id: 3865

Investigation for Safer Initiation of Grignard Reactions

Hessel, G.; Hulzer, G.; Kryk, H.; Schmitt, W.
Due to the spontaneous heat release during the initiation of the strongly exothermic Grignard reaction, these reactions dispose of considerable harzard potentials. Therefore, the knowledge of thermody-namic and thermokinetic parameters is one of the prerequisites for safe formation of Grignard rea-gents in production plants. To obtain more accurate results, these studies on the formation of Grignard reagents were carried out in a closed reaction calorimeter by dosing the pure bromobenzene deriva-tive for the first time. The molar reaction enthalpy per mole bromobenzene derivative was determined with a standard deviation of about 5%.
Keywords: Grignard reaction, Initiation, in-situ FTIR-specrometer
  • Lecture (Conference)
    Proceedings of the 3rd European Congress of Chemical Engineering, Nuremberg 26-28 June 2001, on ECCE-CD / Contents / 2. Sustainable Development, 2.2 Chemical Risk Management
  • Abstract in refereed journal
    Chemie Ingenieur Technik 73, 6 (2001) 611
  • Contribution to proceedings
    Proceedings of the 3rd European Congress of Chemical Engineering, Nuremberg 26-28 June 2001, on ECCE-CD / Contents / 2. Sustainable Development, 2.2 Chemical Risk Management

Publ.-Id: 3864

Mechanism for the generation of coherent longitudinal-optical phonons in GaAs/AlGaAs multiple quantum wells

Yee, K. J.; Lim, Y. S.; Dekorsy, T.; Kim, D. S.
We show that coherent optical phonons in GaAs multiple quantum wells are generated in a completely different way compared to bulk GaAs. Unlike in GaAs where the ultrafast screening of electric fields by photogenerated charge carriers is known to be dominant, three distinctive generation mechanisms contribute simoultaneously in multiple quantum wells.
Keywords: coherent phonons, multiple quantum wells, femtosecond spectroscopy
  • Physical Review Letters 86 (2001) 1630-1633


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Publ.-Id: 3862

Investigation of natural convection in large pools on the example of heating up the secondary side of an emergency condenser

Krepper, E.; Hicken, E. F.; Jaegers, H.
Natural convection is a basic principle for a lot of industrial processes. As an example for the investigation of natural convection phenomena, the paper describes investigations of a passive heat removal system in advanced designs of nuclear power plants. The SWR1000 concept of Siemens AG includes emergency condensers. In the Research Centre Jülich at the NOKO test facility experiments were performed, to investigate the heat transfer capability under different operation modes. In the last time the heating up phenomena on the secondary side were investigated in detail. The paper describes simulations performed in the Forschungszentrum Rossendorf using the CFD-code CFX-4 of AEA-Technology and comparisons to the experiments. Performing additional calculations, measures to avoid undesired temperature stratification were investigated.
Keywords: natural convection, large pools, heating up experiments, CFD calculations, comparison experiment - calculations, influence of geometry effects
  • Lecture (Conference)
    Int. Conf. on "Advances in computational heat transfer", Palm Cove, Australien Mai 2001, Proc. Vol. 2, pp. 835-842
  • International Journal of Heat and Fluid Flow Vol. 23 (2002) pp. 359-365
  • Contribution to external collection
    Int. Conf. on "Advances in computational heat transfer", Palm Cove, Australien Mai 2001, Proc. Vol. 2, pp. 835-842

Publ.-Id: 3861

Irradiation effects on toughness behaviour and microstructure of VVER-type Pressure Vessel Steels

Böhmert, J.; Viehrig, H.-W.; Ulbricht, A.
The irradiation sensibility and the annealing behaviour were studied on seven different heats from VVER 440 and VVER 1000-type reactor pressure vessel steels. The specimens were irradiated at the Rheinsberg prototype VVER 2 reactor to mean neutron fluences between 43 - 127.6A1018 n/cm² [E > 0.5 MeV] and afterwards toughness and strength properties were determined. In addition the microstructure was analysed using SANS technique. There is an obvious trend regarding the correlations between the irradiation-induced changes of transition temperature, hardness and volume fraction of microstructural features of the radius near of approx. 0 to 2 nm. The main parameters of influence are the neutron fluence and the nickel content. The nickel-containing VVER 1000-type pressure vessel steel is more sensible against irradiation than the VVER 440-type steel which has a low content of nickel. For the last one the sensibility against radiation embrittlement depends on content of copper and phosphorus. Annealing at 475 °C (100 h) reduces the irradiation effect but not completely in every case.
Keywords: Radiation embrittlement, reactor pressure vessel steel, small angle neutron scattering, microstructure
  • Journal of Nuclear Materials 297 (2001) 251-261


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Publ.-Id: 3860

Axial Distribution of DD-Neutron Yield in GDT under Skew Injection of Deuterium Neutral Beams

Ivanov, A. A.; Anikeev, A. V.; Bagryansky, P. A.; Karpushov, A. N.; Kornilov, V. N.; Maximov, V. V.; Noack, K.
Experiments with 3 MW deuterium injection have been carried out in the Gas Dynamic Trap (GDT) to simulate the axial profile of the fusion reaction intensity in the proposed neutron source based on the GDT. Quite narrow angular distribution function of the fast ions produced by an oblique neutral beam injection results in a peaked axial profile of the fusion yield. This strong peaking is essential to produce an intense neutron flux in the testing zones of the GDT-based neutron source.
The scintillation counters were installed in the central cell of the device to monitor the DD fusion reaction products: neutrons (2.45 MeV) and protons (3,02 MeV). They were closely located to the plasma column inside of the vacuum chamber in oreder to avoid contribution from the scattered neutrons and to improve the spatial resolution of the measurements. The axial profiles of the fusion neutrons and protons have been measured in the high-beta regime of the GDT operation.
In the paper the experimental data are compared with the results of numerical simulations. The conclusion may be drawn that the kinetics of the fast ion relaxation and scattering is determined by classical Coulomb collisions.
Keywords: fusion, 14 MeV neutrons, neutron source, gas dynamic trap, material irradiation, neutral beam injection, deuterium injection, DD fusion products, scintillation counters
  • Poster
    International Conference on Open Systems for Plasma Confinement, July 3-6, 2000, Tsukuba, Japan, Proc. in Transactions of Fusion Technology Vol. 39, p. 213 (2001)
  • Contribution to proceedings
    International Conference on Open Systems for Plasma Confinement, July 3-6, 2000, Tsukuba, Japan, Proc. in Transactions of Fusion Technology Vol. 39, p. 213 (2001)

Publ.-Id: 3857

Femtosecond-Laser-Induced Spectroscopy - A new tool to study interactions of actinides with organic ligands

Geipel, G.; Bernhard, G.; Rutsch, M.
Laser induced spectroscopic methods are an excellent tool for the study of complex formation of actinides with various ligands at relatively low concentrations. Laser-induced Photoacoustic spectroscopy and Time-resolved Laser-induced Fluorescence spectroscopy are well-known methods. These methods are inappropriate for metal ions which show no change in their spectroscopic properties with complexation. In the case of organic actinide complexes it is possible to use the dependence of fluorescence of the organic ligands on actinide concentration in order to determine complex formation constants. The fluorescence lifetimes of organic ligands in aqueous solution at room temperature are below 20 ns. To study fluorescence properties of theses organic substances laser systems with ultrashort pulses are inevitable. We, therefore, have installed a femtosecond-laser-induced fluorescence spectroscopy system in our laboratory.
The lasersystem provides femtosecond laserpulses in the wavelength range from 250 nm to 10 µm and a pulse duration of 130 fs. The repetition rate is 1 kHz. The emitted fluorescence signal is detected with an intensified CCD camera, with gate width between 80 ps and 6 ns. The delay for time resolved spectra can be adjusted between 0 and 20 ns after the laser pulse with stepwidth down to 25 ps.
We validated this time-resolved laser-induced fluorescence system by studying the fluorescence behavior of salicylic acid and 5-sulfosalicylic acid at pH 4.0 as function of the uranium(VI) concentration. Using a static quenching mechanism the complex formation constants are calculated to be log KI=0.1M= -1.12 ± 0.03 for salicylic acid and log KI=0.1M= -0.67 ± 0.08 for 5-sulfosalicylic acid, respectively, assuming a 1:1 complex formation. The data from the NIST database /1/ are log KI=0.1M= -1.0 and log KI=0.1M= -0.72, respectively. For the actinides neptunium and plutonium much less data are available. Complex formation constants of various substituted benzoic acids with these actinide elements are reported.

/1/ A.E. Martel, R.M. Smith and R.J. Motekaitis: NIST Critically Selected Stability Constants of Metal
Complexes Database Version 5.0; 1998

  • Lecture (Conference)
    Migration 2001, 16.-21.09.2001, Bregenz, Österreich

Publ.-Id: 3856

Protection of TiAl alloys against high temperature oxidation by Chlorine Plasma Immersion Ion Implantation

Hornauer, U.; Günzel, R.; Richter, E.; Wieser, E.; Möller, W.; Dettenwanger, F.; Schütze, M.
The effect of plasma immersion ion implantation of chlorine on the high temperature oxidation of titanium aluminides alloys was investigated. PIII implantations of Cl2 at 30 kV (effective energy 15 keV) show a strong reduction of the oxidation at 900°C in air, which is comparable to conventional beam line im-plantations of Cl at 15 keV. A specialized PI³ system for the strongly etching Cl2 plasma was set up. The chamber is coated inside with aluminum foil, in order to protect the chamber and to avoid contamination of the plasma except with Al. The pumping system is chemically resistant. First implantations and plasma diagnostic of an ICP source sustained Cl2 plasma are discussed. The effect on the high temperature oxidation behavior is tested using thermogravimetrical analysis and microstructural investigations
Keywords: plasmaimmersion ionimplantation oxidation TiAl
  • Lecture (Conference)
    SMMIB 2001, Marburg, Germany 9-14 September 2001

Publ.-Id: 3855

Local void measurements in integral-type experiments simulating nuclear power plant transients

Ezsöl, G.; Szabados, L.; Prasser, H.-M.
The Paks Nuclear Power Plant is equipped with VVER-440/V213-type pressurised water reactors. As known, these reactors have a number of special features, therefore the transient behaviour should be different from PWRs of usual design.
To study the transient behaviour of this type of NPPs an integral-type facility called PMK-2, a scaled-down model of the Paks NPP was designed and constructed in the middle of 1980s and several experiments of different types have been performed.
In the framework of a European Union financed Phare project an upgrading of PMK-2 was performed. Equipments installed are as follows: needle-shaped void-probes for local void measurements, full-flow turbines for velocity measurements, micro-turbines for two-phase flow measurements, three beam gamma densitometer to measure coolant density and to identify flow patterns, and in addition a new data acquisition system has been installed.
This paper deals with the application of void probes for the evaluation of the results of a loss of coolant accident.

Keywords: Nuclear reactor safety, thermal hydraulics, integral test facilities, small break loca, void fraction measurement
  • Lecture (Conference)
    5th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Thessalonoki, Greece, 24-28 September 2001, Vol. 2, pp. 1637 - 1641.
  • Contribution to proceedings
    5th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Thessalonoki, Greece, 24-28 September 2001, Vol. 2, pp. 1637 - 1641.

Publ.-Id: 3854

Prevention of Water Hammer in Pipelines in Case of Emergency Shut-Off by Fast Acting Valves

Prasser, H.-M.; Dudlik, A.; Schönfeld, S. B. H.; Fahlenkamp, H.; Schlüter, S.
The paper presents a method to prevent the water hammer by an adaptive control of the valve closing process. For this purpose, the valve is equipped with a brake system that acts onto the rotation axis of the valve flap. The brake cylinder of the applied hydraulic disk brake is connected to the pipeline just upstream the valve, so that the fluid pressure may activate the brake. By this means the closing is interrupted when the pressure of the fluid increases due to the water hammer. The pressure peak is limited to a maximum pressure given by the user.
The described system does not need any external energy source. Furthermore, it adapts to changes of the pipe system parameters, such as varying pipeline length (e.g. liquid supplied from tanks with a different distance from the valve), fluid velocity or physical properties of the fluid. These are major advantages compared to traditional damping systems, which delay valve closing in a fixed manner.

Keywords: Plant safety, pipelines, water hammer, passive safety systems
  • Poster
    ECCE-3, 3rd European Congress on Chemical Engineering, Nürnberg, 26.-28. Juni 2001, Proc. on CD-ROM, Poster P2 - 60.
  • Contribution to proceedings
    ECCE-3, 3rd European Congress on Chemical Engineering, Nürnberg, 26.-28. Juni 2001, Proc. on CD-ROM, Poster P2 - 60.

Publ.-Id: 3853

Fast Wire-Mesh Sensor for Two-Phase Flow Visualisation with 10 000 Frames per Second

Prasser, H.-M.; Zschau, J.; Peters, D.; Pietzsch, G.; Taubert, W.; Trepte, M.
The paper presents a new wire-mesh sensor for the fast visualisation of gas-liquid flows with a rate of 10 000 frames per second based on the measurement of the local instantaneous conductivity of the two-phase mixture. With this resolution it is now possible to visualise and quantify individual bubbles at mixture velocities of about 10 m/s. The sensor consists of two electrode grids with 16 electrodes each, placed at a small axial distance behind each other. The conductivity is measured at the crossing points of the wires of the two grids. The high measuring rate was achieved by applying an integrated digital signal processor for the control of the signal acquisition process. For the link to the data acquisition PC an ETHERNET interface is used. The internal memory is sufficient to store 170,000 frames, i.e. a continuous measurement over 17 s is possible. In the paper, results obtained in a vertical two-phase air-water flow are presented.
Keywords: Gas-liquid flow, void fraction measurement, wire-mesh sensor, bubble flow, annular flow
  • Poster
    ECCE-3, 3rd European Congress on Chemical Engineering, Nürnberg, 26.-28. Juni 2001, Proc. on CD-ROM, poster P16 - 1.
  • Contribution to proceedings
    ECCE-3, 3rd European Congress on Chemical Engineering, Nürnberg, 26.-28. Juni 2001, Proc. on CD-ROM, poster P16 - 1.

Publ.-Id: 3852

A comparison of void-fraction measurements during flashing-induced instabilities obtained with a wire-mesh sensor and a gamma-transmission set-up

Manera, A.; Prasser, H.-M.; van der Hagen, T. H. J. J.; Mudde, R. F.; de Kruijf, W. J. M.
The void fraction produced in an adiabatic section (riser) during flashing-induced instabilities in a natural-circulation steam/water loop is measured by means of a wire-mesh sensor and two gamma-transmission set-ups located just above and below the wire-mesh sensor respectively. In this paper a comparison between the two different measuring techniques is given. The wire-mesh sensor is capable of measuring the time-dependent two-dimensional void-fraction distribution on a grid of 16x16 points equally distributed over a cross section of the riser, while the gamma-transmission set-ups measure the chordal void fraction along a collimated beam through the riser at a certain height.
The high sampling rate of the wire-mesh sensor (up to 1200 Hz) allows to detect both the frequencies characteristic of the flashing process (between 2 and 4 Hz) and the frequencies characteristic of the flashing-induced flow oscillation (below 0.05 Hz). The former frequencies are less visible in the spectrum of the gamma-transmission signal due to the lower signal-to-noise ratio.
The effect of the wire-mesh sensor on the triggering of void production due to the provision of extra nucleation sites is also studied; no significant differences are observed in the main parameters of the instability if the wire-mesh sensor is removed from the experimental loop.

Keywords: boiling water reactor stability, two-phase flow, wire-mesh sensors, gamma densitometers, void fraction measurement
  • Lecture (Conference)
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001. Proc. CD-ROM, paper 436.
  • Contribution to proceedings
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001. Proc. CD-ROM, paper 436.

Publ.-Id: 3851

Stress relaxation and phase stability of cubic boron nitride films during annealing and ion implantation

Fitz, C.; Fukarek, W.; Möller, W.
The high intrinsic stresses in cBN films after deposition are reduced significantly employing thermal treatment and ion implantation. In-situ stress measurement and ex-situ polarized infrared reflection spectroscopy are utilized to study stress relaxation and the phase stability. Argon ion implantation into cBN films at room temperature and at 340°C reveals that the critical fluence for amorphization increases with increasing temperature. The fraction of cBN transformed into sp2 bonded BN by Ar ion implantation decreases with increasing substrate temperature for the same amount of stress release.
Keywords: cubic boron nitride, intrinsic stress, annealing, ion implantation, infrared spectroscopy
  • Thin Solid Films 408 (2002) 155


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Publ.-Id: 3850

Metallic impurity gettering to defects remaining in the Rp/2 region of MeV-ion-implanted and annealed silicon

Peeva, A.; Koegler, R.; Brauer, G.; Werner, P.; Skorupa, W.
Damage has been observed in MeV-ion-implanted Si away from the maximum of the nuclear energy deposition profile, mainly around the half of the projected ion range, Rp/2, after annealing at temperatures between 700°C ad 1000°C. This damage is primarily created by the implanted ions and consists of intrinsic defects remaining so small that they have not been observed by techniques sensitive to the lattice structure (RBS/C, TEM). The only way to detect this damage is to decorate it with metals and to measure the metal distribution. In this study the formation and disappearance of the Rp/2 damage has been investigated by Cu gettering in Si +-ion implanted Si versus temperature and time of the annealing cycle. The defects undergo a defect evolution during annealing which results in a decrease of the width of the damage layer with increasing temperature and prolonged time of the annealing. It is mostly believed that an excess of vacancies around Rp/2 getter metal impurities. Nevertheless, by means of positron annihilation spectroscopy no vacancy defects have been observed. In contrast in our XTEM investigation we found small (20-30nm) interstitial loops in the Rp/2 region. The creation of these loops is triggered by injected interstitials resulting from the ion milling procedure used during TEM specimen preparation. The ion bombardment of Si give rise to self-interstitials that diffuse extensively at room temperature and may modify the existing interstitial clusters to bigger agglomerates which can be observed by XTEM.
Keywords: ion implantation, gettering
  • Materials Science in Semiconductor Processing 3 (2000) 297-301

Publ.-Id: 3848

Transition strengths in magnetic dipole bands in 82Rb, 83Rb and 84Rb

Schwengner, R.; Rainovski, G.; Schnare, H.; Wagner, A.; Dönau, F.; Hausmann, M.; Iordanov, O.; Jungclaus, A.; Lieb, K. P.; Napoli, D. R.; de Angelis, G.; Axiotis, M.; Marginean, N.; Brandolini, F.; Alvarez, C. R. Keywords: Nuclear structure, in-beam gamma spectroscopy, magnetic rotation, tilted-axis cranking model.
  • Contribution to proceedings
    Proceedings der Konferenz NP2001, 5.3. - 8.3.2001, Göttingen, Deutschland

Publ.-Id: 3847

Structural relation between Si and SiC formed by carbon ion implantation

Eichhorn, F.; Schell, N.; Mücklich, A.; Metzger, H.; Matz, W.; Kögler, R.
The formation of crystalline SiC by implantation of C ions into silicon is not a single-step process. The implantation results in an elastic distortion of the Si matrix lattice and in a formation of crystalline SiC particles depending on ion fluence and thermal conditions at implantation and post-annealing.
The growth of the SiC particles in the Si matrix was studied with different x-ray scattering techniques and high-resolution transmission electron microscopy. Crystallites of the 3C-SiC polytype are formed in a buried layer. Three groups of crystallites with different orientation relation to the Si matrix are found: with a random orientation like a powder material, with a fibre texture axis parallel to the surface normal, and completely aligned to the Si matrix lattice due to a partially coherent growth of SiC in the Si matrix. The thermal treatment favours the growth of highly oriented material: a higher implantation temperature is more efficient than a post-implantation treatment even at higher temperatures.

Keywords: SiC, Si, ion beam synthesis, x-ray diffraction, texture study, reciprocal space map
  • Journal of Applied Physics 91 (2002) 1287 - 1292


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Publ.-Id: 3846

18F-Labeled Neurotensin(8-13) Analogues for Tumour Imaging in vivo

Bergmann, R.; Heichert, C.; Wittrisch, H.; Kretzschmar, M.; Rodig, H.; Scheunemann, M.; Tourwé, D.; Iterbeke, K.; Chavatte, K.; Zips, D.; Reubi, J. C.; Johannsen, B.
4-([18F]fluoro)benzoyl-neurotensin(8-13) (18FB-Arg8-Arg9-Pro10-Tyr11- Ile12-Leu13-OH, 1) and three analogues stabilized in one, two and three positions (18FB-Arg8Psi(CH2NH)Arg9-Pro10-Tyr11- Ile12-Leu13-OH, 2, 18FB-Arg8Psi(CH2NH)Arg9-Pro10-Tyr11-Tle12-Leu13-OH, 3, 18FB-Arg8Psi(CH2NH)Arg9-Pro10-DmTyr11-Tle12-Leu13-OH, 4) were synthesized in a radiochemical yield of 25 - 36% and a specific activity of 5 - 15 GBq/mmol. The peptides were evaluated in vitro and in vivo for their potential to image tumours, overexpressing neurotensin receptor 1 (NTR1) by positron emission tomography (PET). The analogues exhibited in vitro binding affinity in the low nanomolar range to NTR1-expressing human tumours, measured by quantitative receptor autoradiography (IC50: 1 0.42±0.05 nM, 2 0.91±0.20 nM, 3 4.1±0.60 nM) , HT-29 (IC50: 24.0±4.2 nM) and WiDr cells and to sections of tumours derived from these cell lines in mice. The radiotracers were internalised in the cells in vitro, and the fluorinated peptides were able to mobilize intracellular Ca2+ of WiDr cells. In in vivo studies in rats and in mice bearing HT-29 cell tumours, only a moderate uptake of the radioligands into the studied tumours was observed, presumingly due to degradation in vivo and fast elimination by the kidneys of rats and by the liver of mice. The pathway of the fast enzymatic degradation of the non-stabilized or not sufficiently stabilized 18F-labeled peptides was elucidated. The main catabolic product is the 18FB-Arg8Psi(CH2NH)Arg9-Pro10. In vivo, in comparison with the other analogues, the specific tumour uptake expressed as tumour-to-muscle relation was highest for the radioligands 3 and 4. The blood clearance of the analogues was reduced by co-injection of peptidase inhibitors.
The 4-[18F]fluorobenzoyl label on the N-terminal arginine, the introduction of one reduced peptide bond and two bulky amino acid residues (Tle, DmTyr), are tolerable for a high in vitro affinity to the neurotensin receptor 1 (NTR1) and the ability to be internalised in receptor-positive tumour cells. Only the double and threefold-stabilized (3, 4) exhibited a remarkable specific tumour uptake which was, however, not sufficient for tumour imaging in the abdomen. Additional efforts are required to improve molecule stabilization against enzymatic attack and to enable receptor-based tumour imaging.
This work was partially supported by the BIOMED grant BMH4-CT98-3198 of the EC.

  • Lecture (Conference)
    5. Deutsches Peptidsymposium, Bielefeld, Deutschland, 11.-14.3.2001

Publ.-Id: 3845

A scissors-like excitation on the quadrupole vibrational state in 88Sr

Käubler, L.; Schnare, H.; Schwengner, R.; Prade, H.; Dönau, F.; Grosse, E.; Schilling, K.-D.; Wagner, A.
Dipole excitations in the spherical nucleus 88Sr, observed in the energy region 4.5 MeV < E_x < 5.5 MeV,
are proposed to be scissors-like excitations on top of the dynamically deformed quadrupole vibrational state.
  • Contribution to proceedings
    Proceedings of the Int. Symposium on Nuclear Structure Physics, Göttingen, March 5 - 8, 2001: Ed. R. Casten et al.; World Scientific 2001, p. 363

Publ.-Id: 3844

PET imaging for quality assurance of heavy ion therapy and potential extension to proton therapy.

Parodi, K.; Enghardt, W.; Hinz, R.; Lauckner, K.; Pawelke, J.; Pönisch, F.; Crespo, P.; Kausch, C.
no abstract
  • Lecture (Conference)
    International Conference: Imaging Technologies in Biomedical Sciences (ITBS) "Detectors for PET, SPECT, Radiology and for in vitro Imaging", 20-24 May, 2001, Milos Island, Greece
    Book of Abstract (2001) 40-42
  • Contribution to proceedings
    International Conference: Imaging Technologies in Biomedical Sciences (ITBS) "Detectors for PET, SPECT, Radiology and for in vitro Imaging", 20-24 May, 2001, Milos Island, Greece
    Book of Abstract (2001) 40-42

Publ.-Id: 3843

Strukturaufklärung im Submikromolbereich : TRLFS-Untersuchungen zur Cm(III) Sorption an und zum Einbau in Calcit

Stumpf, T.; Fanghänel, T.
Die Wechselwirkung von Cm(III) (9E-8 mol/L) mit einer Calcit Suspension (1 g/L) wurde mit Hilfe der zeitaufgelösten Laserfluoreszenzspektroskopie untersucht. Dabei konnte ein Cm(III)/Calcit Oberflächenkomplex nachgewiesen und charakterisiert werden. Das Maximum der Fluoreszenzemission dieser Curium Spezies liegt bei 607.5 nm und entspricht damit dem des Tetracarbonatokomplexes Cm(CO3)45- in Lösung. Während das freie Cm-Aquoion von 9 Wassermolekülen umgeben ist, läßt die für den Oberflächenkomplex ermittelte Fluoreszenzlebensdauer von 314 ± 6 ms auf ein Wassermolekül in der ersten Koordinationssphäre des Curiums schließen. Mit zunehmender Cm(III)/Calcit Kontaktzeit nimmt die Stärke des Signals mit einem Emissionsmaximum bei 607.5 nm sukzessive ab und ein sehr weit rot verschobenes Signal wird sichtbar. Die gemessene extreme Verschiebung zu einem Wert von 619 nm ist bisher einmalig und deutet auf eine starke Veränderung des Cm-Ligandenfeldes hin. Für diese Spezies wurde eine Fluoreszenzlebensdauer von 1302 ± 75 ms gemessen. Das entspricht dem theoretisch bestimmten Wert für wasserfreies Curium. Die ermittelte Fluoreszenzlebensdauer und die starke Verschiebung des Cm-Spektrums mit der Dauer der Kontaktzeit ist der spektroskopische Beweis für den Einbau des Curiums in das Calcitgitter.

Lecture (Conference): GDCh Jahrestagung der Fachgruppe Nuklearchemie 2001 in Würzburg, Sept. 2001 (submitted)
  • Lecture (Conference)
    GDCh Jahrestagung der Fachgruppe Nuklearchemie, 24.-26.09.2001, Würzburg, Deutschland

Publ.-Id: 3842

Uran (VI) - Komplexierungen mit Modellverbindungen aus der Pflanzenchemie

Günther, A.; Geipel, G.; Koban, A.; Bernhard, G.
Radionuklidkontaminationen können über den Belastungspfad Boden-Pflanze-Nahrungskette deutlich zur Strahlenbelastung des Menschen beitragen. Für zuverlässige Abschätzungen der Radionuklidmigrationen in das geologische und biologische Umfeld ist ausgehend von der Verteilung der Nuklide die chemische Charakterisierung der Radionuklidspezies unbedingt erforderlich, um den summarischen Transferfaktor durch chemisch eindeutig identifizierte Parameter zu ersetzen. In verschiedenen Versuchsreihen wurde mit der Bestimmung der chemischen Speziation von U(VI) in Pflanzen begonnen. Durch Untersuchungen mittels zeitaufgelöster Laser-induzierten Fluoreszenzspektroskopie und Röntgenabsorptionsspektroskopie wurde deutlich, daß Uran in der Oxidationsstufe +6 in der Pflanze vorliegt und es Unterschiede zwischen der Angebotsspeziation im Porenwasser des Bodens bzw. in der Hydrokulturlösung und der Akkumulationsspeziation in der Pflanze gibt. Es zeigte sich, daß der chemische Zustand des Urans im Gleichgewicht in der Wurzel, Sproßachse und im Blatt identisch und unabhängig von der Art der Pflanze, den Wachstumsbedingungen und der Angebotsspeziation ist. Die bisherigen spektroskopischen Resultate deuten auf die Bildung von Uranyl-Phophato-Komplexe als Hauptspezies hin. Neben der Phosphatanbindung müssen aber auch carboxylische Bindungen zum Uran in den Pflanzenproben in Betracht gezogen werden.[1]
Ausgehend von diesen Ergebnissen, wurden Modellkomplexierungen von U(VI) mit ausgewählten organischen Liganden durchgeführt, die im Aufbau und Stoffwechsel der Pflanzen eine große Rolle spielen. In Anlehnung an das Verhalten von Schwermetallen im pflanzlichen System wurden Vertreter aus den Substanzklassen Carbonsäuren, Aminosäuren und Peptide, Kohlenhydrate, Lipoide und aus der Gruppe der freien und polymergebundenen Nukleobasen für die Modellkomplexierungen ausgewählt. Für die Untersuchungen des Reaktionsverhaltens von U(VI) gegenüber den ausgewählten Bioliganden werden neben der UV-Vis Spektroskopie insbesondere die zeitaufgelöste Laser-induzierte Fluoreszenzspektroskopie genutzt. Erste Ergebnisse werden hier vorgestellt. Ziel ist es, die erhaltenen spektroskopischen Datensätze mit Daten von kontaminierten Pflanzenproben zu vergleichen, um auf diese Weise U(VI)-Spezies in Pflanzen eindeutig zu charakterisieren.

[1] A. Günther, Zwischenbericht DFG-BE 2234/1-1
  • Lecture (Conference)
    GDCh Jahrestagung Chemie, 23.-29.09.2001, Würzburg, Deutschland

Publ.-Id: 3841

Die Anlagerung von radiotoxischen Schwermetallen an Kolloidpartikel im Flutungswasser einer stillgelegten Urangrube

Zänker, H.; Richter, W.; Schreyer, J.; Jenk, U.
Das Uranbergwerk Königstein (Sachsen) befindet sich zur Zeit in der Flutungsphase. Es wurde Flutungswasser kolloidchemisch untersucht (pH 5,6; Eh 450 mV; CCa 0,9 mM, CFe 0,3 mM, CU 0,05 mM, CSulfat 1,2 mM, CHydrogenkarbonat 1,0 mM). Nahezu 90% des Fe waren zweiwertig. Auf Grund des Eh-Wertes erwarten wir, daß das Uran sechswertig vorlag. Die Kolloidkonzentration betrug 2 bis 3 mg/l, die Partikelgröße war 100 bis 300 nm. Die Partikel bestanden vor allem aus Fe, Al, S und U.
Grubenwässer können kolloidchemisch zwischen zwei Extreme eingeordnet werden:
(a) Hochmineralisierte Porenwässer mit pH-Werten von 1 bis 3, die ultrafeine Fe(III)-
Partikel im g/l-Bereich enthalten (Partikelgröße <5 nm) und
(b) "Bulk"-Wässer mit pH-Werten um 7, die Fe(III)/Al-Submicronpartikel im Konzen-
trationsbereich von wenigen mg/l enthalten (Partikelgröße 100 bis 300 nm) [1].
Die pH-Abhängigkeit der Schwermetallsorption an Oxyhydroxysulfaten und Oxyhy-droxiden des Fe(III) und Al kann durch sigmoide Kurven mit einem steilen Anstieg bei mittleren pH-Werten ("Adsorption Edge") beschrieben werden. Bei Wässern des Typs (a) findet kaum Adsorption statt (Ausnahmen: 210Pb, Ra-Isotope). Bei Wässern des Typs (b) werden viele radiotoxische Schwermetalle stark sorbiert und sind somit fil-trierbar (210Po, 230Th, 227Ac, 210 Pb). Bemerkenswert ist das Verhalten von U(VI). In karbonatfreien Lösungen zeigt es an Fe(III)-Partikeln eine starke Adsorption bei pH-Werten >4 [2]. In realen "Bulk"-Wässern aus Bergwerken wird die U-Adsorption durch die Bildung von Uranylkarbonatokomplexen jedoch deutlich unterdrückt [1].
Flutungswässer repräsentieren den Übergang von Wässern des Typs (a) in Wässer des Typs (b). In unseren Proben waren stark adsorbierende Nuklide wie 210Po und 210Pb zum größten Teil an Kolloidpartikel gebundenen (filtrierbar). In-teressanterweise erwiesen sich aber auch 60 bis 90% des Urans als kolloidgetragen. Offensichtlich wird bei dem vorliegenden pH-Wert von 5,6 die Uranadsorption weder durch hohe Azidität noch durch Karbonatkomplexierung verhindert.
Der Zutritt von Sauerstoff löst eine Vielfalt von chemischen Reaktionen in den Proben aus. Durch die Oxidation des Fe2+ steigt der Gehalt an Fe(III)-Partikeln (Faktor 10). Trotz der höheren Trägerkolloidkonzentration sinkt der filtrierbare Uranylanteil zunächst. Grund ist der pH-Abfall (bis auf etwa 4,5), den die Fe-Oxidation verursacht. Mit einiger Verzögerung steigt der pH-Wert wieder weil die Ge-samtkarbonatkonzentration durch CO2-Entgasung sinkt; der Hydrogenkarbonatgehalt fällt bis auf <0,05 mMol/l. Beides bewirkt einen Anstieg des filtrierbaren Urananteils auf fast 100%. Alle diese Vorgänge (O2-Zutritt, pH-Variationen, CO2-Entgasung) spielen auch im Bergwerk eine Rolle.
Die oft getroffene Annahme einer ungehinderten Migration von Uranyl in gelö-ster Form ist für pH-Werte von 4 bis 6 "überkonservativ". Scavenging durch Fe(III)-Partikel und Kolloidkoagulation plus Sedimentation kann in diesem pH-Bereich das U(VI) in erheblichem Maße immobilisieren.

[1] Zänker, H. et al.; Radiochim. Acta 88, 619 (2000)
[2] Hsi, C.D. and Langmuir, D.; Geochim. Cosmochim. Acta 49, 1931 (1985)
  • Lecture (Conference)
    GDCh Jahrestagung Chemie Würzburg, Deutschland, 23.-29.09.2001

Publ.-Id: 3840

Energy-dependent anisotropic deformation of colloidal silica particles under MeV Au irradiation

van Dillen, T.; Polman, A.; Fukarek, W.; van Blaaderen, A.
Spherical silica colloids with a diameter of 1.0 µm, made by wet chemical synthesis, were irradiated with 2–16 MeV Au ions at fluences in the range (2–11)×1014 cm–2. The irradiation induces an anisotropic plastic deformation turning the spherical colloids into ellipsoidal oblates. After 16 MeV Au irradiation to a fluence of 11×1014 cm–2, a size aspect ratio of 5.0 was achieved. The size polydispersity (~3%) remains unaffected by the irradiation. The transverse diameter increases exponentially with ion fluence. By performing measurements as a function of ion energy at a fixed fluence, it is concluded that the transverse diameter increases linearly with the average electronic energy loss above a threshold value of ~0.6 keV/nm. Nonellipsoidal colloids are observed in the case where the projected ion range is smaller than the colloid diameter. The data provide strong support for the thermal spike model of anisotropic deformation.
  • Applied Physics Letters 7 (2001) 910-912


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Publ.-Id: 3839

Atomistische Computersimulation der Defektbildung und -evolution in Si bei Ionenimplantation

Posselt, M.
For further informations, please contact the author (
  • Lecture (Conference)
    39. Arbeitskreis Punktdefekte, Dresden, February 12 - 13, 2001

Publ.-Id: 3838

Understanding of ta-C Film Deposition by Means of Atomistic Simulations

Jäger, H.-U.
Ion beam deposition of carbon films was studied by molecular-dynamics simulations. Using a slightly modified version1 of the analytical hydrocarbon potential of Brenner, deposition of films with a thickness of up to 10 nm was computed for ion energies E = 10-80 eV, and for substrate temperatures ranging from 100 to 900 K.
The following properties of the calculated films were analysed: (i) sp3 content versus mass density in inner film regions, (ii) binding energies of 3- and 4-fold coordinated carbon atoms in films of different mass densities, (iii) probability distributions for the number of sp3 atoms generated (or annihilated) per deposited ion, and (iv) structure and width of the graphite-like surface regions. As a result, an atomistic picture is provided which shows how the formation of tetrahedral amorphous carbon (ta-C) films is affected by both ion energy and substrate temperature.

1 H.U. Jäger and K. Albe, J. Appl. Phys. 88, 1129 (2000).
  • Poster
    International Conference on Materials for Advanced Technologies (ICMAT 2001), Symp. F: Diamond, Diamond-like Carbon & Related Materials, 1 - 6 July 2001, Singapore

Publ.-Id: 3837

Schnelles Freimeßverfahren auf alpha-aktive Nuklide

Nebelung, C.; Henniger, J.
Bei der Freimessung von Bauschutt aus dem Abriß von Nuklearanlagen ist eine direkte Messung der alpha-aktiven Nuklide im stehenden Gebäude auf Grund ihrer geringen Reichweite und ihrer Absorption im Beton nicht möglich. Die im Rahmen von BMBF-Projekten entwickelte Methode der direkten Alpha-Spektrometrie von großflächigen dünnen Meßpräparaten nach nur mechanischer Präparation des Betons ermöglicht eine Bestimmung der Actinide bis zu 0,02Bq/g in Multielementspektren [1,2]. Durch die große Fläche wird eine hohe Impulsrate und durch die dünne Schicht eine geringe Selbstabsorption der Alpha-Strahlung und damit eine gute Auflösung der Spektren erreicht. In einem aus zwei Schritten bestehendem Zerkleinerungsprozeß wurden mittlere Partikeldurchmesser von 0,5µm erreicht. Die Grobzerkleinerung erfolgt mit einem Backenbrecher (reiner Beton) oder mit einer Tischfragmentierungsanlage (Trennung von Beton und Armierungseisen), die Feinzerkleinerung durch Naßmahlen mit Spezialmahlkugeln. Die Meßproben mit einem Durchmesser von 20cm und Schichtdicken zwischen 0,6 und 5µm entstanden durch Sprühen mit einer Zweistoffdüse aus der Betonsuspension auf Probenträger und anschließendes Trocknen. Die Suspensionsstabilität konnte durch verschiedene Peptisatoren erhöht werden. Die Alpha-Spektren der Meßproben wurden in einer Gitterionisationskammer aufgenommen. Durch die Verwendung von Standardbeton mit zugefügten Actiniden konnten die Selbstabsorption der Alpha-Strahlung und die Peakform in Abhängigkeit der Probendicke ermittelt werden. Somit konnten die Spektren unbekannter Betonproben gleicher Geometrie entfaltet werden. Das für diese Arbeit entwickelte Programm WINKRUM basiert auf einem geometrischen Modell für Partikelgröße, Partikelverteilung und Packungsdichte. Mit Strahlungstransportberechnungen [3] können Spektren simuliert werden, die ebenfalls eine Peakentfaltung von Mul-tielementspektren ermöglichen.

Das diesem Bericht zugrundeliegende Vorhaben wurde mit Mitteln des Bundesministeriums für Bildung und Forschung unter dem Förderkennzeichen 02 S 7768 gefördert. Die Verantwortung für den Inhalt liegt bei den Autoren.

[1] Nebelung, C.; Nitsche, H., Henniger, J.
"Stillegung und Rückbau: Direktmessung alpha-aktiver Nuklide in Bauschutt zur Freigabe-entscheidung Schlußbericht" BMBF 02S 7655 /02S7655A, 1999
[2] Nebelung, C.; Henniger, J.
Schlußbericht zum Fördervorhaben BMBF 02 S 7768 in Vorbereitung
[3] Henniger, J.
"AMOS - ein multivalent nutzbares Programmsystem zur Berechnung von Strahlungstrans-portproblemen", Strahlenschutz : Physik und Messtechnik, Band 1, 26. Jahrestagung des Fachverbandes für Strahlenschutz e.V., Karlsruhe, 24.-26. Mai 1994; Verlag TÜV Rhein-land.

Keywords: Freimessung, Bauschutt, Alpha-Spektrometrie
  • Poster
    GDCH- Tagung Würzburg, 23.9.-29.9.2001

Publ.-Id: 3834

Simulation of Scaled Core-Meltdown-Experiments and Investigation of a Possible Vessel Support against Failure

Willschütz, H.-G.; Altstadt, E.; Weiss, F.-P.; Sehgal, B. R.
At present the scaled core melt down experiments FOREVER are underway. These experiments are simulating the lower head of a reactor pressure vessel under the load of a melt pool with internal heat sources. Due to the multiaxial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments are an excellent possibility to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep model procedure. Additionally the material damage is evaluated considering the creep deformation as well as the prompt plasticity.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the experiments to come are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. Analysing the calculations it seems to be advantageous to introduce a vessel support which can disburden the vessel from a part of the mechanical load and therefore avoid the vessel failure or at least prolongate the failure time as a possible accident mitigation strategy. Additionally, it seems to be possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in case of a core melt down.
Keywords: FOREVER-Experiment, Coupling of Thermo-Fluid Dynamic and Structural Mechanical FE-Model, Advanced Creep Modelling, Vessel Support as Accident Mitigation Strategy
  • Lecture (Conference)
    16th International Conference on Structural Mechanics in Reactor Technology SMiRT16, Washington, DC, USA, August 12-17, 2001, Paper No. 1145
  • Contribution to proceedings
    16th International Conference on Structural Mechanics in Reactor Technology SMiRT16, Washington, DC, USA, August 12-17, 2001, Paper No. 1145


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Publ.-Id: 3832

Effect of temperature on the emission characteristics of liquid metal alloy ion sources

Bischoff, L.; Teichert, J.; Ganetsos, T.; Mair, G. L. R.
In spite of the fact that a great deal of research has been carried out on liquid metal ion sources, suprisingly few results exist on the temperature dependence of their emission characteristics. In this article we study two liquid metal alloy ion sources (LMAISs), namely Co36Nd64 and Au77Ge14Si9. While the results of the former source were as expected, the latter displayed an entirely different dependence of its emission characteristics on temperature. The unusual results of the Au77Ge14Si9 LMAIS are explained in terms of the abnormal behavior of the surface tension of the alloy with temperature.
Keywords: liquid metal alloy ion source, temperature dependence, emission behavior
  • Journal of Vacuum Science and Technology B19 (1) 2001 76 -78


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Publ.-Id: 3830

Investigation on multiphase and multicomponent flows - experiments and measurement devices

Schaffrath, A.; Krüssenberg, A.-K.
Vertical two-phase flow is normally classified into the four basic flow regimes bubble, slug, churn and annular flow. The transition between the different flow regimes does not occur suddenly and many extensions of this classification can be found in literature. For the prediction of flow patterns empirical and theoretical flow pattern maps have been developed.
  • Lecture (others)
    Politecnico di Milano, Dipartimento di Ingegneria Nucleare, 13.03.2000, Milano, Italy

Publ.-Id: 3823

A mineral-specific thermodynamic sorption database

Brendler, V.; Arnold, T.; Bernhard, G.; Fanghänel, T.
This paper presents a digitized version of a thermodynamic sorption database, implemented as a relational database under MS Access. The data are required for the parametrization of Surface Complexation Models (SCM). It is mineral-specific and can therefore also be used for additive models of more complex solid phases such as rocks or soils. An integrated user interface helps users to access selected mineral and sorption data, to convert parameter units, to extract internally consistent data sets for sorption modeling, and to export them into formats suitable for other modeling software. Data records comprise of mineral properties, specific surface area values, characteristics of surface binding sites and their protolysis, sorption ligand information, and surface complexation reactions. The following submodels are already implemented, extensions to other variants are straightforward: the Non-Electrostatic Model, the Diffuse Double Layer Model, the Constant Capacitance Model, the Triple Layer Model, and the Basic Stern Model. For every SCM type (where applicable), also the concept of strong and weak binding sites, and the 1-pK approach is included. Surface species composed from up to three different ligands can be incorporated.
An extensive bibliography is also included, providing links not only to the above listed data items, but also to background information concerning surface complexation model theories, related software for data processing and modeling, and sorption experiment techniques. Only very few of the abundant surface complexes proposed in the literature (mostly resulting just from best-fit considerations) are actually validated by spectroscopic evidence or supported by theoretical (quantum-chemical) calculations. If such information is available it is also stored in the database.
The database will help to substitute the at present in risk assessment studies most often applied simplistic distribution coefficients (Kd-values) by the more realistic description of sorption phenomena with SCM. It assists the identification of critical data gaps, the evaluation of existing parameter sets, consistency tests and the establishment of selected reference data sets. As to the knowledge of the authors, so far there is no such digital thermodynamic database for surface complexation equilibria existent world-wide, despite the vast amount of available data.

  • Lecture (Conference)
    Migration 2001, Bregenz, Österreich, 16.-21.09.2001

Publ.-Id: 3822

Structure parameter analysis of Cu(UO2Aso4)2 nH2 using EXAFS spectroscopy

Hennig, C.; Reich, T.; Funke, H.; Roßberg, A.; Rutsch, M.; Bernhard, G.
kein Abstract vorgesehen
  • Poster
    ESRF Meeting, Grenoble, Frankreich, 19.-21.02. 2001

Publ.-Id: 3821

The effect of secondary iron mineral and colloid formation on uranium sorption during the dissolution of chlorite

Krawczyk-Bärsch, E.; Arnold, T.; Hüttig, G.; Zänker, H.; Brandt, F.; Bernhard, G.
Chlorite is a common accessory mineral, commonly found in sedimentary and low grade metamorphic rocks like the phyllite in the former uranium mining area of Saxony (Germany). The cur-rent flooding of the mines leads to an interaction be-tween the uranium containing flooding water and the surfaces of the wall rock. During the weathering of phyllite a secondary mineral is formed, which in further investigations [1] was described as ferrihydrite. The source of this secondary mineral is the iron-rich chlo-rite of the phyllite.
Chlorite is a phyllosilicate with a trioctahedral structure, consisting of negatively charged 2:1 layers that alternate regularly with positively charged interlayer sheets [2]. During the weathering of chlorite the main constituents of the octahedral sheets, Mg2+, Fe2+, Fe3+ and Al3+, are released into the aqueous solu-tions. In laboratory experiments the dissolution of chlo-rite was studied with a continuous flow-through reactor and in batch experiments. In this study we will lay em-phasis on the released iron because of its ability to form secondary minerals and colloids.
Experiments: Batch experiments were carried out on an iron-rich chlorite from Flagstaff Hill, California, with a grain size of 63-200 µm. Half a gram of the samples were added to 40 ml deionized water, which was previously adjusted to an ionic strength of 0.1 M with NaClO4. The suspension was aged during 2 months without any pH adjustment. A pH value of 7 was found at the end of the experiment. The freshly formed iron hydroxide particles were separated from the large excess of the micron-size chlorite powder particles by well-defined centrifugations (2500 x g, 1h and 3500 x g, 1h). A defined volume of the centrifugate was filtered through a 50 nm and 15 nm Nuclepore filter in order to fix the ultrafine iron particles on a substrate. The filter membranes were prepared for scanning electron microscopy (SEM).
Results: In SEM investigations spherical particles are detected on the Nuclepore filter. The size of these colloids ranges from 30 to 80 nm. The colloids are mainly arranged as agglomerates, while individual colloids are rarely observed. On several large agglom-erates energy-dispersive X-ray analysis (EDS) were taken in order to get information about the chemistry of these colloids. With this method we were able to detect directly iron colloids of a chlorite suspension at pH 7. The process leading to the formation of colloids can be explained as a consequence of the iron release during the dissolution of chlorite. The dissolved iron oxidizes to ferric iron which subsequently hydrolyses, precipi-tates and forms secondary minerals and iron colloids. The detection of iron colloids was previously described in a suspension of ground phyllite [3], where a com-bined technique of centrifugation at varying centrifugal speed and ICP-MS and AAS of the centrifugates was used. The formation of iron colloids was prevented in the acid region of pH = 4 due to the higher solubility of Fe in this pH region. With decreasing solubility in the neutral and alkaline medium, the released Fe forms iron colloids or precipitates as secondary iron mineral coatings. The formation of iron colloids during the dissolu-tion of chlorite must be taken into consideration in the assessment of contaminant behavior in the nature. Though contributing only little to the mass balance of a water body, iron colloids can show significant adsorp-tion of trace elements because of their high specific surface area and their affinity to heavy metals.
The formation of secondary iron mineral coatings is also of importance for the behavior of contaminants in the nature since coatings significantly change the sur-face properties of the weathering chlorite. The most common secondary iron mineral is ferrihydrite, a poorly crystallized iron mineral with a chemical for-mula of 5Fe2O3 . 9H2O [4] and a large specific surface area. Sorption experiments which were carried out with ur...
  • Lecture (Conference)
    Goldschmidt Conference, Hot Springs, Virginia, USA , 19.5. - 24.5.2001

Publ.-Id: 3820

Complexation of Cm(III) and Eu(III) by glycolic acid: TRLFS studies

Stumpf, T.; Fanghänel, T.; Grenthe, I.; Kim, J. I.
Complexation processes of Cm(III) and Eu(III) by glycolic acid are studied by time-resolved laser fluorescence spectroscopy (TRLFS). The experiments with curium are performed in 0.1 M and 3.0 M NaClO4. The glycolic acid concentration is varied between 0.01 mol/L and 0.5 mol/L at pH 3. Cm(III) and Eu(III) fluorescence emission spectra are obtained at a fixed glycolic acid concentration of 0.5 mol/L, the pH is varied between 3 and 11. In addition to the Cm3+ aquo ion, two Cm(III)-glycolic acid species are observed by peak deconvolution: Cm(gly)2+ and Cm(gly)2+. Above pH 5 a chelate Cm-glycolate complex is formed. This curium-glycolate complex is characterised by its emission spectrum (peak maximum at 611.2 nm) and its fluorescence emission lifetime (172 ± 8 µs). The corresponding chelate europium-glycolate complex with 300 ± 10 µs lifetime is obtained above pH 6.83. In the pH range 6 to 8 the decay behaviour of the excited state is different in the Cm(III)- and Eu(III)-glycolate system. While a bi-exponential decay behaviour was observed for the Cm-system, indicating slow exchange kinetics in comparison to the fluorescence decay of the exited state, the corresponding Eu-system shows mono-exponential decay behaviour. More over the reversibility of Eu-chelating is much faster than in the case of the Cm(III) complex. The results show that the strength and kinetics of the chelating is different for Cm(III) and Eu(III).

  • Lecture (Conference)
    Actinides-2001, Hayama, Japan vom 4. - 9. November 2001.

Publ.-Id: 3818

The NOKO/TOPFLOW Facility for Natural Convection Flow

Hicken, E.-F.; Jaegers, H.; Schaffrath, A.; Weiß, F.-P.
For the study of the effectiveness of passive safety systems a high pressure (up to 7 MPa) and high power (up to 4 MW) test facility – named NOKO – has been constructed and operated at the Forschungszentrum Jülich. From 1996-1998 this facility was used for a project within the 4th FP of the EU "European BWR R&D Cluster for Innovative Passive Safety Systems". An overview and selected results are given for the tests with two bundles of the emergency condenser, with the building and plate condenser, with 4 different passive initiators, with a passive flooding system and with decay heat removal tests during shutdown.
It has been decided to decrease substantially the safety research at the Forschungszentrum Jülich; to maintain the experimental competence for two-phase flow the NOKO facility will be transferred to the Forschungszentrum Rossendorf by the end of the year 2000 up to the beginning of the year 2001. The facility will be named TOPFLOW; the main objectives of future tests will be oriented towards more generic research: investigation of steady state and transient two phase flow phenomena especially transient two phase flow patterns, the development of two-phase flow instrumentation, the generation of a data basis for Computational Fluid Dynamic (CFD)-Code validation and testing of heat exchangers and safety systems. An overview will be given about the modifications and improvements related to the test facility and the planned test.
  • Lecture (Conference)
    Technical Committee Meeting on Natural Circulation Data and Methods for Innovative Nuclear Power Plant Design, Session 3, International Atomic Energy Agency, Vienna (Austria), July 18-21, 2000
  • Contribution to proceedings
    Technical Committee Meeting on Natural Circulation Data and Methods for Innovative Nuclear Power Plant Design, Session 3, International Atomic Energy Agency, Vienna (Austria), July 18-21, 2000

Publ.-Id: 3807

Neutron Flux Uncertainty and Covariances for Spectrum Adjustment and Estimations of Pressure Vessel Fluences

Böhmer, B.; Manturov, G.
Results of estimations of covariance matrices of neutron spectra in VVER-1000 reactor pressure vessel and cavity positions are presented. Two-dimensional calculations with the discrete ordinates transport code DORT in r-theta and r-z-geometries are used to determine the neutron group spectrum covariances including cross-correlations between interesting positions. The new Russian ABBN-93 data set and the CONSYST code are used to supply the transport calculations with neutron group data. All possible sources of uncertainties, as neutron cross sections, fission sources, geometrical dimensions and material densities, were considered, whereas, the uncertainty of the calculation method was assumed to be negligible in view of the available precision of Monte Carlo simulation.
Keywords: fluence covariance, spectrum adjustment, uncertainty analysis, cross-correlation, reactor pressure vessel, reactor dosimetry
  • Lecture (Conference)
    Tenth Symposium of AER on Reactor Physics and Reactor Safety 2000, Moscow (Russia) 18 - 22 September 2000, Proceedings, Vol. I, pp. 345-351
  • Contribution to proceedings
    Tenth Symposium of AER on Reactor Physics and Reactor Safety 2000, Moscow (Russia) 18 - 22 September 2000, Proceedings, Vol. I, pp. 345-351

Publ.-Id: 3802

Technical description of the radiological safety system for X-ray absorption spectroscopy experiments on radioactive samples at the Rossendorf Beamline

Funke, H.; Bernhard, G.; Reich, T.; Matz, W.; Oehme, W.; Claußner, J.; Jansen, K.-H.; Röllig, D.; Nitsche, H.
The Rossendorf Beamline at the European Synchrotron Radiation Facility is equipped with a unique radiochemistry experimental station. This dedicated station has been designed to perform environmentally relevant experiments on radionuclides, in particular actinides, using synchrotron based X-ray absorption fine structure spectroscopy. The technical concepts and the layout of this experimental station, where radioactive solids and liquids with activities of up to 185 MBq can be studied, are presented. The radiological safety of experimenters, equipment, and of the environment are ensured by the specially developed radiochemistry safety system. The multibarrier concept, the ventilation and air monitoring systems, the radiological protection system, and special software components for recording and visualisation of the safety status are described in detail.

  • Kerntechnik 66(2001) 195-201

Publ.-Id: 3801

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