Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Nowadays, the majority of radiopharmaceuticals used in routine nuclear medicine imaging procedures are ^99mTc labelled compounds, and intensive research is in progress to design new ^99mTc radiopharmaceuticals. Investigation of Tc and Re carbonyl chemistry has led to an organometallic M(I) aqua ion, M(CO)₃(H₂O)₃]⁺
(M = Tc, Re), as a precursor for the preparation of complexes containing the small [M(CO)₃]⁺ moiety. Tc(I) and Re(I) tricarbonyl complexes represent a new and promising approach to low-valent, non-polar and inert compounds. Complexes with N-donor or S-donor chelating ligands coordinated to the M(I) tricarbonyl moiety with high stability in aqueous solution may serve in the design of radiopharmaceuticals [1, 2].

The aim of this work was to investigate the stability of a model Tc(I) dithioether-tricarbonyl complex, Tc1, in aqueous solution and to estimate structural
parameters for the dissolved compounds. Owing to the extremely small concentration of the radionuclide present in the radiopharmaceutical preparation (10^­6 ­ 10^­8 M), XAS studies as well as most other chemical investigations employ the long-lived isotope ⁹⁹Tc (K-edge at 21.044 keV). We found that the complex Tc1 is reversibly transformed into the complex Tc1a in aqueous solution (Figure 24).

Fig. 24: Reversible transformation of the complex Tc1 in aqueous solution.

Chemical investigations were performed both at the ⁹⁹Tc and ^99mTc levels. The change of charge of the complexes was determined by electrophoresis. Mass-spectrometric analyses and EXAFS measurements confirmed the composition of the compounds. EXAFS analyses were carried out at BM20 (Rossendorf CRG beamline, ROBL) [3]. ⁹⁹Tc solutions of Tc1 and Tc1a were prepared by dissolving solid Tc1 in water/methanol and adding chloride or Ag⁺, respectively. With an excess of sodium chloride the equilibrium (Figure 24) is on the side of the Tc1 complex. If chloride is removed from the equilibrium by precipitation as AgCl, Tc1a is the species in solution. To obtain a satisfactory evaluation of the EXAFS spectra and the Fourier transforms, single-scattering paths including the C, O and S/Cl coordination shells and multiple-scattering paths to model the oxygen atom of the carbonyl group were taken into account (Figure 25). The estimated atomic distances are 1.92 Å (Tc­C), 2.49 Å (Tc­S or Tc­Cl), 2.19 Å (Tc­O_aq) and 3.06 Å (Tc­O_CO). The coordination numbers agree with the molecular structure represented in Figure 24. EXAFS analysis of Tc1a shows the same structural parameters for the C, S/Cl and CO coordination shells as Tc1 except that the coordination number for the S/Cl coordination shell is lowered by approximately one. In addition, the detection of 1.2 ± 0.3 oxygen atoms at 2.19 Å proves the substitution of chlorine by water. This can be seen in Figure 25 as a reduction of the magnitude of the second peak in the Fourier transform since electron back-scattering from the oxygen atom is weaker than from the chlorine atom.

Fig. 25: Tc K-edge k3-weighted EXAFS spectra and the corresponding Fourier transforms of Tc1 and Tc1a (solid line: experimental data, dotted line: fit), transmission mode, sample concentration 3.5 x 10-2 M, sample thickness 1 cm, room temperature.

EXAFS analyses were successfully used to determine structural parameters of Tc(I) tricarbonyl complexes in solution. In connection with chromatographic,
electrophoretic and mass-spectrometric methods, it was found that Tc(I) tricarbonyl complexes containing a bidentate thioether ligand are able to react with water by
exchange of chlorine.

References
[1] R. Alberto et al., Coordination Chem. Rev., 190-192, 901 (1999).
[2] H.-J. Pietzsch et al., Bioconj. Chem., 11, 414 (2000).
[3] W. Matz et al., J. Synchrotron Rad., 6, 1076 (...

Die Erfindung betrifft Materialuntersuchungen mit Hilfe der Tomographie.
Der Erfindung liegt die Aufgabe zugrunde, auch dann eine quantitative Bildrekonstruktion durchführen zu können, wenn im zu untersuchenden Objekt kein Gebiet bekannter Absorption vorhanden ist.

Der Erfindung liegt die Aufgabe zugrunde, ein neues Schichtmaterial für optische Informationsträger und Lichtmasken sowie ähnlich gelagerte Anwendungen vorzuschlagen. Außerdem wird ein einfaches Verfahren zur lokalen Veränderung der optischen Absorption in diesem Schichtmaterial angegeben, mit dem Strukturgrößen erreichbar sind, wie sie die fortgeschrittene Halbleiterindustrie fordert.
Das Schichtmaterial besteht aus amorphem, hydroxierten Siliciumkarbid der Form a-SiC:H, die Schichtbereiche hoher optischer Absorption enthalten Metallatome, vorzugsweise Gallium oder Zinn.

Die Erfindung betrifft ein Biomaterial und ein Verfahren zu dessen Herstellung. Potentielle Anwendungen sind medizinische Implantologie, Gewebezüchtung, Biotechnologie und Pharmazeutik.
Der Erfindung liegt die Aufgabe zugrunde, ein Biomaterial für Anwendungen in medizinischer Implantologie, Gewebezüchtung, Biotechnologie und Pharmazeutik zu schaffen, das eine gute Strukturbildung und Haftfestigkeit aufweist sowie die zellbiologischen Aspekte berücksichtigt.
Der Erfindung obliegt auch die Aufgabe, ein einfaches und anwendungswirksames Verfahren zur Herstellung des genannten Biomaterials vorzuschlagen.

Aufgabe der Erfindung ist es Substanzen vorzuschlagen, die zur Diagnose und Therapie von Tumoren in der Nuklearmedizin geeignet sind und ein Verfahren zur Herstellung der Substanzen anzugeben.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Schaltungsanordnung vorzuschlagen, mit denen der Extremwert einer Größe, oft als Gütegröße bezeichnet, auch bei sehr kleinen Stellbewegungen zu finden und zu halten ist und bei denen der Suchverlust durch die Suchbewegungen konstant gehalten werden kann.

Die Erfindung betrifft ein Verfahren zur Behandlung heteroepitaktisch auf Siliziumsubstraten abgeschiedener Halbleiterschichten. Die Erfindung soll insbesondere für die Herstellung elektronischer Bauelemente eingesetzt werden.

Die Erfindung betrifft ein Verfahren zur Behandlung heteroepitaktisch auf SOI-Substraten abgeschiedener Halbleiterschichten. Die Erfindung soll insbesondere für die Herstellung elektronischer Bauelemente eingesetzt werden.

Der Erfindung liegt die Aufgabe zugrunde, dass bei Auftreten von Fluid-Gas-Gemischen (2-Phasen-Gemischen) für das Rekonstruktionsobjektbild die Fehler verringert oder vermieden werden.

Die Anwendung ist insbesondere als tomographische Anordnung zur Erzeugung von Schnittbildern von Objekten gegeben, deren Gestalt beziehungsweise Zusammensetzung schnellen Änderungen unterworfen ist, und zwar für den Fall, dass die Änderungen sich zeitlich periodisch wiederholen.
Aufgabe der Erfindung ist es, eine Anordnung vorzuschlagen, die auch bei Objekten, deren Gestalt beziehungsweise Zusammensetzung schnellen, sich periodisch wiederholenden Änderungen unterworfen sind, die Ermittlung von Projektionen gestattet, die einen Momentanzustand oder eine Abfolge von Momentanzuständen der periodisch veränderlichen Verteilung des Absorptionsverhaltens repräsentieren und aus denen sich die Verteilungen selbst rekonstruieren lassen und die dabei mit einer kontinuierlich Strahlung aussendenden Gammaquelle auskommt.

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The experimental investigations of the emergency condenser of the SWR1000 done at Forschungszentrum Jülich is described in detail. After the description of the emergency condenser operation mode and the NOKO Test facility the performance and the evaluation of several bundle tests are presented. From the bundle tests a thermal and a hydraulic condition are developed. Single tube test results are remarked at the end of the presentation.

In the presentation the modeling of condensation inside horizontal tubes is described. The differences between condensation in vertical tubes and in horizontal tubes is explained in detail. The development of the improvement KONWAR for the German thermohydraulic program system ATHLET is decribed in detail. Afterwards the validation of this improvement with the two different experiments NOKO (Forschungszentrum Jülich GmbH) and HORUS (Universität Zittau/Görlitz) is presented.

In the presentation a description of the investigations concerning flowmaps for vertical pipes done at the institute of safety research are given. That means, the test facility MTLOOP of the institute with its measurement techniques and the test matrix is described in detail. From these experiments a new criterium for the bubble to slug flow transition is presented. Afterwards, the comparison of this criterium to existing flow maps is done.

In the presentation a description of the new multipurpose thermohydraulic test facility TOPFLOW is given including the construction phase and the main working fields. Then, after the details about flow diagram and facility loayout as well as the building layout the chosen documentatin form via internet and intranet is presented. Ideas concerning possible CAREM system tests in TOPFLOW are summarized, too.

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We have studied the isotopes 82Rb45, 83Rb46, and 84Rb47 to search for magnetic rotation which is predicted in the tilted-axis cranking model for a certain mass region around A = 80. Excited states in these nuclei were populated via the reaction 11B + 76Ge with E = 50 MeV at the XTU tandem accelerator of the LNL Legnaro. Based on a -coincidence experiment using the spectrometer GASP we have found magnetic dipole bands in each studied nuclide. The regular M1 bands observed in the odd-odd nuclei 82Rb and 84Rb include B(M1)/B(E2) ratios decreasing smoothly with increasing spin in a range of 13^-≤J^π≤16^-. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type π(fp) πg_9/2 ² vg_9/2. This is the first evidence of magnetic rotation in the A ≈ 80 region. In contrast, the M1 sequences in the odd-even nucleus 83Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.

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We report the results of recent measurements of the spectroscopic quadrupole moments of high-spin isomers. For the K-pi = 35/2(-) five-quasiparticle isomer in W-179 we measured Q(B) =4.00 ((+0.83)(-1.06)) eb. It corresponds to a smaller deformation compaxed to the ground states of the W isotopes and is in disagreement with the current theoretical predictions. We also measuredthe quadrupole moment of the I-pi = 11(-) isomer in Pb-196, Q(s) = (-)3.41(66) eb. It has the same proton (s(1/2)(-2)h(9)/(2)i(13/2)) configuration as the one suggested for the 11 = 16(-) magneticbandhead which allows to deduce the quadrupole moment of the 16(-) state as Q(s) = -0.316(97) eb. This small value proves the near sphericity of the bandhead.

Tc(III) and Re(III) complexes [M(NS₃)(CNR)] (M = Re, ^99mTc, NS₃ = 2,2',2''-nitrilotris(ethanethiol), CNR = functionalized isocyanide bearing a derivative of WAY 100635) have been synthesized and characterized. Re was used as Tc surrogate for chemical characterization and in vitro receptor-binding studies. For two representatives subnanomolar affinities for the 5-HT_1A as well as for the alpha1-adrenergic receptor were reached. Biodistribution studies in rats of the ^99mTc complexes showed brain uptakes between 0.3 and 0.5 % ID/organ (5 min p.i.). In vitro autoradiography of one ^99mTc representative in sections of post mortem human brain indicate its accumulation in 5-HT_1A receptor-rich brain regions. However, addition of the specific 5-HT_1A receptor agonist 8-OH-DPAT as well as the alpha1-adrenoceptor antagonist prazosin could not substantially block this tracer accumulation. A preliminary SPET study in a monkey showed negligible brain uptake.

Ziel des Vorhabens war die analytische und numerische Simulation der Kühlmittelvermischung im Ringraum und unteren Plenum von Druckwasserreaktoren. Generell ist die Kühlmittelvermischung relevant für zwei große Störfallgruppen - Borsäureverdünnungsstörfälle und Kaltwassertransienten. Zur Untersuchung der Vermischungsphänomene aus diesen Störfallszenarien wurde die Rossendorfer Versuchsanlage ROCOM konzipiert, die ein 1:5 skaliertes Plexiglasmodell des DWR Konvoi darstellt, in dem auch Geschwindigkeitsmessungen mit Hilfe von LDA-Technik möglich sind. Konstruktion, Errichtung und meßtechnische Ausstattung von ROCOM erfolgten in einem 2. Teil des Vorhabens. Im Vorfeld der Errichtung des ROCOM-Versuchsstandes wurden mit Hilfe des dreidimensionalen Strömungsberechnungsprogrammes CFX-4 Skalierungseffekte untersucht. Die Vergleichsrechnungen belegten, daß eine 1:5 Skalierung ausreichend ist. Nach dem Aufbau des Versuchsstandes und der Inbetriebnahme im 2. Teil des Vorhabens wurden die Vorausberechnungen anhand von experimentellen Ergebnissen bestätigt. Es wurde weiterhin ein Verfahren zur vereinfachten analytischen 2D-Beschreibung des Strömungsfeldes im Ringraum von Druckwasserreaktoren aufgestellt. Es beruht auf der Potentialtheorie, wobei Quellen an den Kühlmitteleintrittspositionen und Wirbel unter Beachtung der Randbedingungen der typischen Ringspaltgeometrie von DWR überlagert wurden. Der Schwerpunkt des Projektes lag jedoch in der numerischen Simulation der Kühlmittelvermischung unterschiedlicher Reaktoranlagen mit CFX-4 und der Validierung des Rechenprogramms anhand von Vermischungsexperimenten. Dabei wurden sowohl stationäre Schleifendurchsätze bei Nominalbetrieb und Teilschleifenbetrieb bzw. transiente Strömungsbedingungen der Reaktortypen DWR Konvoi und WWER-440 untersucht. Die Ergebnisse der CFX-4 Rechnungen im Vergleich mit den Leitfähigkeits- bzw. LDA-Messungen sind im Abschlußbericht dokumentiert. Grundlage für diesen Abschlußbericht ist eine Promotionsarbeit von T. Höhne zum gleichnamigen Thema im Rahmen des Kompetenzerhaltungsprogrammes Kerntechnik.

A short review of our investigations devoted to the use of ion beam synthesized nanoclusters for silicon based light emission and nonvolatile memory effects is presented. Blue-violet light emission is demonstrated basing on Ge-implanted silicon dioxide layers thermally grown on silicon substrates. This version of silicon-based light emission relies on Ge-related defects in the amorphous -Si-O-Si- network. The photo (PL) - and electroluminescence (EL) is excited by a singlett S0-S1 transition of neutral oxygen vacancy and by electron injection from the silicon substrate into the silicon dioxide layer, respectively. Whereas the PL excitation is a well-known mechanism, for the case of electroluminescence an interpretation was performed for the first time in the course of our studies. It is found that the most probable way to excite luminescence centers is the impact excitation by hot electrons. Whereas the injection is explained by trap assisted tunneling of electrons from the substrate into the oxide, the electrons will be transported via traps or in the SiO2 conduction band. The application of the silicon-based light emitting devices for an optocoupler arrangement are described. Another application of nanoclusters is basing on the investigation of thin Si-implanted silicon dioxide layers for nonvolatile memory applications. First promising results demonstrated that the observed programming window can reach several volts and the devices exhibit excellent retention behavior. A 256k-nv-SRAM is demonstrated showing a programming window >1V for write pulses of 12V/8ms.

Der Stofftransport über Flüssig-Flüssig-Phasengrenzen führt sehr oft zu hydrodynamischen Instabilitäten und zur Bildung von dissipativen, d. h. konvektiven Strukturen. Zwei Mechanismen liegen diesen Instabilitäten zurunde. Der erste ist mit dem Wirken von Grenzflächenspannungsgradienten in Systemen mit flüssigen oder flüssig-gasförmigen Grenzflächen verbunden und wird als Marangoniinstabilität bezeichnet. Der zweite, als Rayleigh-Bénard-Instabilität bezeichnete Mechanismus wird durch Auftriebskräfte aufgrund lokaler Dichteunterschiede verursacht. In diesem Beitrag soll über experimentelle und numerische Untersuchungen berichtet werden, die an Systemen vorgenommen wurden, bei denen die übergehende Komponente eine chemischen Reaktion an der Grenzfläche eingeht und Auftriebskräfte bei der Ausbildung der Instabilität dominieren.

The proton-rich isotope 56Cu was produced at the GSI On-Line Mass Separator by means of the 28Si(32S, p3n)
fusion¯evaporation reaction. Its -decay properties were studied by detecting -delayed rays and protons. A half-life of
93±3 ms was determined for 56Cu. Compared to the previous work, six new rays and three new levels were assigned to the
daughter nucleus 56Ni. The measured Gamow¯Teller strength values for five 56Ni levels are compared to shell-model
predictions

Mass transfer across interfaces in liquid-liquid systems may give rise to hydrodynamic instability and the formation of various dissipative, i. e. convective, structures. There are two basic mechanisms leading to instability. The first one is related to the action of surface tension gradients in systems with free interfaces and is referred to as Marangoni effect while the second one is related to buoyancy forces and is referred to as Rayleigh-B'enard instability. Convection at the interface and in the bulk of the liquids greatly enhances mass transfer rates. This paper reports on experimental and numerical studies which have been carried out on systems where the transferred species undergoes a chemical reaction at the interface and buoyancy forces predominate.

Transient boiling is examined for conditions related to the hypothetical heating of liquids in a storage tank by an external fire, with the potential for evaporation of the liquids and the release of toxic gases into the environment. Temperature and void fraction distribution data were obtained from an experiment on water heated in a tank. Numerical simulations were also performed. These generally agreed reasonably well with measurements.

Bericht über Dienste und Weiterentwicklung der IT-Infrastruktur des FZR im Zeitraum 1999 bis 2000 in den Tätigkeitsbereichen Zentrale Server, Datennetz und Benutzerservice.

The most prominent back-reaction effects observed in the Riga dynamo experiment are presented and a preliminary interpretation of them is given.

Color centers have been generated on [100] surfaces of LiF crystals by irradiation with a focussed beam of 35 keV Ga+ ions at room temperature and at 240 K. The luminescence of two centers at 655 and 540 nm, ascribed to F2 and F3+ centers, respectively, has been detected and spatially resolved, with spatial resolution in the range of 1 µm, by imaging microscopy, as well as by laser scanning confocal microscopy. Diffusion and pinning of color centers have been observed directly in this way. Due to the high intensity in the focal spot of the confocal microscope nonlinear photophysical and photochemical processes are observed. For example an additional emission at 775 nm could be detected at high excitation density. The luminescence band is tentatively ascribed to radiative triplet-triplet emissions of F2 centers after recombination of F2+ centers with an electron.

The uptake of heavy metals into plants is commonly quantified by the soil-plant transfer factor. Up to now little is known about the chemical speciation of actinides in plants. To compare the obtained spectroscopic data of uranium complexes in plants with model compounds, we investigate the complexation of uranium with relevant bioligands of various functionalities. A very important class of ligands are phosphate esters, which serve as phosphate group and energy transmitters as well as energy storage mediums in biological systems. Heavy metal ions bound to the phosphate esters can be transported into living cells and than deposited.
Therefore, in our study we present the results of uranium complexation with glucose-6-phosphate (G6P), and fructose-6-phosphate (F6P) obtained by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The experiments were performed at a fixed uranyl concentration (10^-5 M) as a function of the ligand concentrations (10^-5 to 10^-3 M) in a pH range from 2 to 4.5.
For the glucose phosphate system we observed, using increasing ligand concentrations, a decreased fluorescence intensity and a small red shift of the emission bands. From this we conclude that the complexed uranyl glucose phosphate species either show only minor or no fluorescence properties. The TRLFS spectra of the glucose phosphate samples indicated the presence of only one species with fluorescence properties. This species has a lifetime of approximately 1.5µs and was identified as the free uranyl ion.
An opposite phenomenon was observed for the fructose phosphate system: There was no decrease of fluorescence intensity. However, a strong red shift of the spectra was observed illustrating the fluorescence properties of the uranyl fructose phosphate complex. The TRLFS spectra of the fructose phosphate system showed a second lifetime (<1µs) belonging to the complexed species.
The concentration of the free uranyl ion was determined on the basis of the measured fluorescence spectra. These data were used to calculate the corresponding concentrations of the uranyl sugar phosphate complexes and the non complexed ligands. The complex formation reaction is assumed to be:
x lig + UO₂ ²⁺ <==> UO₂(lig)_x ^(2-y)+ + y H⁺ (lig = sugar phosphate)
Applying the mass action law and transformation to the logarithmic scale, we obtain:
log {[UO₂(lig)_x ^(2-y)+] / [UO₂ ²⁺]} = x log[lig_nonkomplexed] - y log[H⁺] + logK

From this we conclude, that 1:1 uranyl sugar phosphate species UO₂(ROPO₃) (R is either glucose or fructose) has formed. Using these data complex formation constants for the complexes were calculated to be in the range of logK=3.7 for G6P and 3.2 for F6P.

Bei einer Vielzahl von natürlichen und technischen Strömungsvorgängen besteht das strömende Medium aus mehreren Phasen. Bei der Förderung derartiger Medien mit Kreiselpumpen führen bislang nicht genügend bekannte Vorgänge bei bestimmten Betriebsbedingungen zu einer starken Verringerung der Förderleistung und einem Anstieg des Leistungsbedarfs. Bei der Förderung von gasbeladenen Flüssigkeiten kann ein zu hoher Gasanteil zum vollständigen Zusammenbruch der Förderung führen. Zusätzlich führt die erosive Wirkung von Kavitation zu einer starken Minderung der Lebensdauer der Pumpe.

Diese Arbeit beschreibt ein neuartiges Verfahren, das es erstmals gestattet, die Methode der Gamma-Tomographie zur Bestimmung der örtlichen Phasenverteilung innerhalb von rotierenden Pumpenläufern und ähnlichen Bauteilen anzuwenden. Dabei wird eine Zeitauflösung von ca. 100 µs erreicht, mit der die Gasverteilung wesentlich genauer als bisher erfaßt werden kann. Mit dem Tomographen wurden die Vorgänge innerhalb des Läufers einer Axialpumpe bei Förderung eines Luft-Wasser-Gemischs visualisiert. Es wird gezeigt, wie sich die Änderung äußerer Strömungsparameter und die Variation des Arbeitspunktes auf die räumliche Phasenverteilung innerhalb des Läufers auswirkt.

The nuclei $^{91}$Sr and $^{92}$Sr were produced at high spin as fission fragments following the fusion reaction $^{36}$S + $^{159}$Tb at 165 MeV. Gamma rays were detected with the Gammasphere array. The level schemes of
$^{91}$Sr and $^{92}$Sr were extended up to $E \approx$ 6 MeV and $E \approx$ 8 MeV, respectively. Level structures in $^{91}$Sr and $^{92}$Sr were interpreted in terms of the shell model. The calculations were performed in the configuration space $(0f_{5/2}, 1p_{3/2}, 1p_{1/2}, 0g_{9/2})$ for the
protons and $(1p_{1/2}, 0g_{9/2}, 1d_{5/2})$ for the neutrons. Negative-parity states in the yrast sequences are described in these calculations by coupling $3^-$ proton excitations to the unpaired $1d_{5/2}$ neutrons. A possible reduction of the gap between the proton $1p_{3/2}$ and $1p_{1/2}$ orbitals in
$^{92}$Sr is discussed.

The Forschunszentrum Rossendorf (FZR) e.V. is constructing a new large-scale test facility, TOPFLOW, for thermalhydraulic single effect tests. The acronym stands for Transient Two Phase Flow Test Facility. It will mainly be used for the investigation of generic and applied steady state and transient two phase flow phenomena and the development and validation of models of Computational Fluid Dynamic (CFD) Codes.

The ATHLET code has been improved and validated for the safety analysis of high flux research reactors against experimental data of the Thermalhydraulic Test Loop of Oak Ridge National Laboratory (ORNL). Therefore, an extensive series of "stiff mode" experiments were recalculated. The comparison between experiments and ATHLET posttest calculations shows that the extended code simulates accurately the thermalhydraulic conditions and the flow instabilities in a wide range of inlet velocity, head and mass flux.

The 6th dynamic benchmark is a logical continuation of the work to validate systematically coupled neutron kinetics / thermohydraulics code systems for the estimation of the transient behaviour of VVER type nuclear power plant which was started in the 5th dynamic benchmark. This benchmark concerns a double ended break of one main steam line (asymmetrical MSLB) in a VVER-440 plant. The core is at the end of first cycle in full power conditions. The asymmetric leak causes a different depressurization of all steam generators. New features in comparison to the 5th dynamic benchmark were included: asymmetric operation of the feed water system, consideration of incomplete coolant mixing in the reactor vessel, and the definition of a fixed isothermal recriticality temperature for normalising the nuclear data.

The solution of this benchmark was obtained by means of coupled code system DYN3D/ATHLET. There, the whole core including neutron kinetics and thermohydraulics processes was calculated by three dimensional neutron kinetics core model DYN3D. The thermal hydraulics behaviour of primary and secondary circuit was modelled by the system code ATHLET.
For the purpose of realisation of the fixed isothermal recriticality temperature Trecrit = 210°C the cross section data of absorber were adapted.

During the transient calculation of MSLB scenario, the reactor scram was initiated with the assumption that two of the most reactive control rods in the sector of highest overcooling are stuck at their fully withdrawn position. Accordingly, the power is decreased due to reactor scram. Thereafter, the reactivity feedback caused by the decrease of coolant temperature entailed the increase of the reactor power. Based on an assumed delayed start of the high pressure safety injection, the recriticality of the shut-off reactor is achieved. The value of total power in the second maximum is about 80 MW.

In this paper the behaviour of the main thermohydraulic and neutron kinetic parameters is presented.

Seepage and mine waters of the abandoned uranium mining and milling sites in Saxony and Thuringia are contaminated by uranium and its decay products. Therefore, efficient water purification technologies are necessary.
The separation of uranium(VI) from aqueous solution by calixarenes by means of solvent extraction is described in the literature. Calixarenes are macrocyclic molecules formed by 4, 6 or 8 para-substituted phenolic units linked by methylene bridges ortho to the OH functions. Thus, molecules of different ring sizes are formed. Especially calix[6]arenes functionalized with carboxylic or hydroxamic groups on the lower rim are suitable to separate uranium from aqueous solution.
In the present work, the extraction efficiency of various carboxylate derivatives of calix[6]arene, e.g., carboxymethoxy-p-tert-octyl-calix[6]arene, including their selectivity towards uranium(VI) is studied in a two phases solvent extraction system in dependence on pH value and the amount of competing ions in aqueous solution as well as in dependence on ligand concentration and solvent. The complex formation between uranium(VI) and calix[6]arenes is further studied by means of time-resolved laser-induced fluorescence spectroscopy (TRLFS). Uranium species are identified, complex formation constants are determined, and reaction mechanisms are discussed. The suitability of the calix[6]arenes as efficient reagents for selective separation of uranium from aqueous solution, even in the acidic pH region, is shown.

In einem gemeinsamen Vorhaben mit dem Diagnosezentrum für russische Kernkraftwerke (DIAPROM Moskau) wurde ein Beitrag zur verbesserten Beurteilung der mechanischen Integrität von Reaktoren der russischen WWER-Baureihen, insbesondere zur empfindlichen Früherkennung und Lokalisation mechanischer Schädigungen an Reaktorkomponenten mit Hilfe schwingungsdiagnostischer Methoden geleistet. Zu diesem Zweck wurde für den WWER-440 und WWER-1000 das mechanische Schwingungsverhalten aller Primärkreiskomponenten mit finiten Elementen (FE) modelliert. Dafür wurde das Programmpaket ANSYS® genutzt.
Der Einfluss des strömenden Kühlmittels auf die schwingenden mechanischen Strukturen ist im Rahmen der Fluid-Struktur-Interaktion (FSI) berücksichtigt worden. Die Berechnungsmodelle wurden mit Ergebnissen experimenteller Schwingungsuntersuchungen justiert. Zum Teil konnte auf aktuelle Messungen zurückgegriffen werden. Die Modelle können als weitgehend verifiziert gelten. Diese wurden in der Hauptsache genutzt, um zu klären, wie sich unterstellte mechanische Defekte von Reaktoreinbauten auf die Schwingungen der Gesamtanlage auswirken. Diese Schadenssimulation ist besonders geeignet, empfindliche Messpositionen für die on-line Überwachung zu finden und physikalisch fundierte Grenzwerte zu definieren.
Die entwickelten Modelle sind grundsätzlich auch geeignet, um Lastabschätzung für die Reaktorkomponenten bei Einwirkung von außen (Explosion, Erdbeben) vorzunehmen.

Charge storage properties of 20-30 nm gate oxides implanted with Si+ ions are investigated using MOS capacitors, single transistor structures and a non-volatile memory. The observed programming window can reach several volts for programming with electric fields of about 4-7 MV/cm. The structures exhibit good retention (250°C, 280h) and the endurance (>106 w/e-cycles) considerably exceeds the typical values of present EEPROM technologies. The capability of Si implanted SiO2 films as gate dielectrics for a real non-volatile memory is demonstrated for the first time by a 256k - nvSRAM showing a programming window of larger than 1 volt.

no abstract

The wire-mesh sensor developed by the Forschungszentrum Rossendorf produces measuring sequences of instantaneous gas fraction distributions in a cross section at a rate of up to 10 000 frames per second and a spatial resolution of about 2-3 mm. This sensor was applied to an upwards air-liquid flow in a vertical channel. After a brief introduction of the functioning of the sensor, the paper presents results obtained at a rate of 1200 frames per second, which were used to study the evolution of bubble size distributions and radial gas fraction profiles along the pipe, starting at a relative distance of L/D=0.6 above the gas injection and ending at L/D=60. The developed bubble identification algorithm allows to select bubbles of a given range of the effective diameter and to calculate partial gas fraction profiles for this diameter range. In this way, the different behaviour of small and large bubbles in respect to the action of the lift force was observed in a mixture of small and large bubbles. Furthermore, the paper presents results of a flow visualisation at the rate of 10 000 frames per second, showing details of the flow structure in the region of transition to annular flow.

For studies on the characteristics of bubble flow in a rectangular channel (20x100mm) an electrode-mesh tomograph has been applied. The measuring principle is based on local conductivity measurement. The applied sensor scans the local void fraction distribution in 2 parallel planes, separated 1.5mm in flow direction, with a resolution of 6.1x2.2mm and an overall sampling rate of 1200Hz (all 256 points). Algorithms for the calculation of the local instantaneous void fraction distribution and the true gas velocity are presented. Based on these values the approximate shape of bubbles has been reconstructed and the gas volume flow through the sensor evaluated. The superficial gas velocity as well as the local distribution of the gas volume flux was
calculated. Finally, bubble diameter spectra have been obtained and the statistical behavior of the bubble rising velocity in its dependency from bubble diameter in a turbulent flow of high void fraction has been investigated. An extensive sensitivity study illustrating the applicability and accuracy is presented, based on experimental observations as well as theoretical considerations. The evaluated results are compared with high-speed video observations of the flow field as well as data comparing the reconstructed volume flow with measurements by a laminar flow meter. Good agreement can be stated.

We summarize the history and the results of the first successful hydromagnetic dynamo experiment which was prepared and run at the Institute of Physics in Riga, Latvia.

The electronic confinement in semiconductor quantum wells gives rise to the formation of electronic subbands within the conduction or valence band. Due to the same curvature of initial and final subband, intersubband optical transitions (within one band) exhibit a quasi-zero-dimensional joint density of states and therefore resemble atomic transitions in some way. The typical energy spacing from 10 to a few 100 meV corresponds to the far- and mid infrared spectral range. Thus, for the study of nonlinear or time resolved phenomena in these structures, IR free-electron lasers are among the most – or the only – suitable light sources.

As an example, I will review some experiments on the energy relaxation of electrons in wide GaAs/AlGaAs quantum wells, performed with FELIX.

Transitions between minibands in strongly coupled superlattices exhibit a one-dimensional joint density of states, and I will show how the dispersion along the growth axis can be employed to study the electron distribution function.

Finally I will present the status of the ELBE project at the Forschungszentrum Rossendorf near Dresden. This project comprises a superconducting electron accelerator, providing the electron beam for two undulators. The latter form the heart of the FELs, which are planned to operate from 5 to 25 microns and 20 to 100 (or 150) microns, respectively. First lasing is expected for early 2002.

First I will give a brief overview of my institution, the Research Center Rossendorf near Dresden. Though much smaller than LBNL, its activities also cover a wide range from Nuclear Physics over Materials Science to Radiochemistry and Biomedical Research. The Institute of Ion Beam Physics and Materials Research accommodates a large ion beam center (with ions from eV to MeV available), other local groups have been involved in the construction of the superconducting electron accelerator ELBE, which will, apart from other applications, be the basis of an infrared free-electron laser (FEL). This FEL, whose first lasing is expected in early 2002, will be used for semiconductor spectroscopy as well as for studies on biological samples.

In the second part of my talk I will stroll around two of the main playgrounds for infrared spectroscopy of semiconductor quantum structures: the physics of intersubband transitions in quantum wells, which have brought us novel infrared lasers and detectors, and the physics of Bloch oscillations in superlattices, which are supposed to bring us a tunable THz source at some point. Finally I will present some infrared experiments concerning the electron distribution function in superlattices, performed with a step-scan FTIR with sub-microsecond time resolution, and will be touching on the issue of appropriate narrow- and broad-band infrared and THz sources.

Structural and micromechanical properties of ion-beam mixed tungsten layers were studied. 45 nm thick W layers deposited on HSS substrates were Kr-ion-beam mixed at temperatures ranging from RT up to 450°C. The samples mixed at RT are amorphous. Increase of the process temperature results in the formation of crystalline layers. Amorphous layer are characterized by low friction coefficient and relatively low hardness. Crystallization of layers results in the increase of their hardness and friction coefficient. Wear rates of ion-beam mixed layers are always lower when compared with untreated steel substrates. The results are discussed in the frames of the model assuming the presence of thin, soft layer on hard substrate.

By use of nanoidentation, the hardness was measured in dc-magnetron sputterd Ag/Ni, Au/Ni and Cu/Ni multilayers as a function of the modulation period. In a limited modulation period range, the expression k*lambda**(-n) where k and n are fitting parameters and lambda is the modulation period, was fitted to the curves of hardness versus modulation period for the three types of multilayer. The exponent n of Ag/Ni was found to deviate by a factor of three from the n value of Au/Ni, which is surprising since no significant difference exists between the lattice parameters, shear moduli, morphologies and microstructures of the two systems. The results are discussed considering theoretical models and published experimental data.

The sixth dynamic AER benchmark is used for the continuation of a systematic validation of coupled 3D neutron kinetic/thermohydraulic system codes. In this benchmark, a hypothetical double ended break of one main steam line (asymmetric MSLB) at full power in a VVER-440 plant is investigated. The main thermohydraulic features are the consideration of incomplete coolant mixing inside the reactor pressure vessel and an asymmetric operation of the feed water system. For the tuning of the different nuclear cross section data used by the participants, an isothermal recriticality temperature was defined.

Solutions were received from VTT Energy Espoo (HEXTRAN/SMABRE), Kurchatov Institute Moscow (BIPR8/ATHLET), KFKI AEKI Budapest (KIKO3D/ATHLET), NRI Rez (RELAP-3D) and Forschungszentrum Rossendorf (DYN3D/ATHLET). This paper gives an overview on the behaviour of the main thermohydraulic and neutron kinetic parameters in the provided solutions. In all calculations, the overcooling after leak opening leads to a power rise and the activation of the reactor scram. The continuing overcooling after reactor scram results in a second power rise in all calculations. This power rise is eventually stopped by the injected highly-borated water from the high pressure injection system. Differences in the gradient of overcooling and different moderator temperature coefficients (MTC) in the used nuclear data are responsible for a spreading of the time of scram activation over several seconds in the various calculations. Differences in the thermohydraulic behaviour of the secondary side (modeling of the steamgenerator and the critical flow) together with the mentioned different MTC cause significant differences in the value of the second power peak.

In the Riga dynamo experiment, a helical flow with a velocity up to 15 m/s is produced by a motor driven propeller. This flow is free enough to be modified by the Lorentz forces in a non-trivial manner.
In addition to the increase of the necessary motor power due to the axial components of the Lorentz force, we observed a significant deformation of the magnetic field structure and a shift of the eigenvalue. Both observations can be explained by the downward accumulating brake effect of the azimuthal Lorentz force component.
The occurence of a triple frequency in the magnetic field spectrum gives indications for the action of the non-axisymmetric parts of the Lorentz forces on the flow.

An efficient semi-analytical model for the description of the coolant mixing during stationary and transient processes inside the reactor pressure vessel (RPV) of pressurised water reactors (PWR) has been developed. Both boron concentration and coolant temperature mixing are described by a dimensionless mixing scalar which is transported with the fluid and is subject of turbulent dispersion, but does not affect the flow field. This model is based on the technique of linear superposition of response functions on Dirac impulse shaped perturbations of the mixing scalar. In the model, the RPV is represented formally by a group of transfer systems (for each combination of inlet nozzle position and fuel element position one) with one input and one output each. These systems have different transfer properties which are determined by the flow field and turbulent mixing being strongly dependent on geometrical details of the flow domain. In this work, one way of obtaining the transfer properties is shown on the example of the German PWR KONVOI. The validation of the model against experimental data from the 1:5 scaled coolant mixing test facility ROCOM is presented.
The semi-analytical model for the description of coolant mixing has been used in combination with the 3D reactor dynamics code DYN3D for the analysis of a hypothetical boron dilution event after start-up of the first main coolant pump (MCP) in a generic four-loop PWR. The model provides realistic time-dependent boron concentration fields at the core inlet. By varying the initial plug volume it was found, that for the given core configuration plugs of less than 20 m3 did not lead to a re-criticality of the shut-off reactor.
Besides the modelling of the coolant mixing inside the RPV, a proper description of the boron transport in the reactor core in the considered case was absolutely necessary to calculate the neutron kinetic behaviour of the core correctly. Otherwise the numerical diffusion distorts the boron front and the reactivity insertion is smoothed artificially. In DYN3D, a particle-in-cell method is used to describe the boron transport without numerical diffusion.
The semi-analytical model is not restricted to one reactor type. The transfer properties used in the model can be explored also by means of computational fluid dynamics codes (CFD). The use of calculated response functions allows to apply the model for the description of coolant mixing in different geometry (i.e. RPV of VVER) and under various conditions without performing additional experiments.

Presently, no experimental benchmark data are available allowing to test calculations of gamma spectra in neutron-gamma reactor environments. As newer findings indicate a possible influence of gamma radiation on reactor pressure vessel embrittlement, a neutron-gamma experiment using NE213 scintillation spectrometry to measure gamma and neutron spectra in iron-water slabs has been started at the training reactors of the Technical University Dresden and the University of Applied Sciences Zittau/Goerlitz. The measured data will be used to test the accuracy of Monte Carlo Calculations of gamma and neutron spectra in environments typical for pressure vessel dosimetry applications. Particularly, the code Monte Carlo code TRAMO will be validated in connection with the nuclear data library ENDF/B-VI. After a description of the experimental facilities, the schedule of measurements and the applied measurement and calculation methods are described.

Discrepancies found between DORT and MCNP calculation results for neutron and gamma fluxes in the surveillance and PV regions of a PWR gave the impulse for this work. As nuclear data were suspected to be the reason for these discrepancies a simple 2-zone one-dimensional cylindrical model was defined, allowing to exclude modeling uncertainties and to calculate fluxes in outer zones made of pure materials, as H2O, Fe, Cr, Ni. Compared were the neutron flux integrals over energy regions E<0.414 eV, E >0.0, 0.1, 0.5, 1.0, 3.0 MeV and the gamma flux integrals over energy regions E>0.0, 1.0, 3.0 MeV calculated with DORT-3D-synthesis/BUGLE-96 and MCNP-4B/ENDF/-B-VI at 12-15 radial points in core and outer zones. The reasons of the found discrepancies are not simply to understand. One important difference is the group approximation in DORT/BUGLE and the different treatment of resonance effects. Another is the different treatment of cross sections in the thermal region.
As the used model is supposed to be of general interest for testing codes and data , a detailed specification of the model is given as appendix. It is proposed to be used as benchmark model for coupled neutron-gamma flux calculations, including comparisons with the presented calculation results.

Es werden die Grundlagen der Fehlerermittlung an technischen Anlagen und Prozessen mit Hilfe von neuronalen Netzen vorgestellt. Vor ihrer Anwendung als Fehlerklassifikator müssen neuronale Netze zunächst mit den Messdaten der normalen und gestörten Betriebszustände unter Zuhilfenahme von Expertenwissen trainiert werden, um das Anlagen- und Prozessverhalten bis hin zum Entscheidungsresultat zu implementieren. Nach diesem überwachten Lernprozess kann das trainierte Netz zur Fehlerermittlung genutzt werden.
Da diese Methode ohne die zeit- und kostenintensive analytische Modellierung des Anlagen- und Prozessverhaltens auskommt, können neuronale Netze vor allem bei komplexen, nichtlinearen Prozessen vorteilhaft zur Fehlerermittlung eingesetzt werden. Die Methodik und die Probleme bei der Anwendung in der industriellen Praxis werden am Beispiel dreischichtiger Perceptron-Netze ausführlich beschrieben.

no abstract delivered from author

Die zuverlässige Prognose der Langzeitsicherheit von ober- und untertägigen Einrichtungen des ehemaligen Uranerzbergbaus sowie von Endlagern für radioaktiven Abfall erfordert die detaillierte Untersuchung der Ausbreitung von radioaktiven und toxischen Metallionen in der Umwelt. Die Ausbreitung dieser Schadstoffe über den Wasserpfad wird durch eine Vielzahl von Prozessen beeinflußt, wobei die Wechselwirkung mit Huminstoffen dabei eine wesentliche Rolle spielt.
Huminstoffe sind ubiquitär in der Natur vorkommende organische, polyelektrolytische Makromoleküle, die beim Abbau von Biomasse gebildet werden. Aufgrund der Vielzahl an Ausgangsstoffen kann der natürliche Huminstoffbildungsprozess nicht durch einfache chemische und biochemische Reaktionen beschrieben werden. In Abhängigkeit von ihrer Herkunft zeigen Huminstoffe unterschiedliche strukturelle und funktionelle Eigenschaften. Huminstoffe können aufgrund ihrer Löslichkeit bei verschiedenen pH-Werten operationell in drei Fraktionen eingeteilt werden [1]. Humin repräsentiert die Fraktion, die bei allen pH-Werten unlöslich ist, wohingegen Huminsäuren bei pH-Werten > 3.5 und Fulvinsäuren bei allen pH-Werten löslich sind.
Innerhalb natürlicher Wechselwirkungsprozesse können Huminsäuren aufgrund ihrer guten Löslichkeit bei pH-Werten natürlicher Wässer eine entscheidende Rolle spielen. Huminsäuren sind in der Lage Metallionen, z. B. Actinidionen, zu komplexieren. Sie beeinflussen somit deren Speziation und auch deren Mobilisierung bzw. Immobilisierung in der Umwelt. Aufgrund der großen strukturellen und funktionellen Heterogenität von Huminsäuren ergeben sich zahlreiche Probleme bei der thermodynamischen Beschreibung ihres Wechselwirkungsverhaltens in natürlichen Systemen.
Die vorliegende Arbeit gibt einen Überblick zu Untersuchungen, die zur Erlangung detaillierter Kenntnisse zum Wechselwirkungsverhalten von Huminsäuren mit Uran(VI) unter natürlichen Bedingungen durchgeführt wurden [2]. Es werden Ergebnisse zum Komplexbildungsverhalten von Huminsäuren mit Uran(VI) sowie zum Einfluß von Huminstoffen auf das Migrationsverhalten von Uran vorgestellt.

[1] Choppin, G.R.: The Role of Natural Organics in Radionuclide Migration in Natural Aquifer Systems. Radiochim. Acta 58/59, 113 (1992).
[2] Pompe, S., Bubner, M., Schmeide, K., Heise, K.H., Bernhard, G., Nitsche, H.: Influence of Humic Acids on the Migration Behavior of Radioactive and Non-Radioactive Substances under Conditions Close to Nature. Wissenschaftlich-Technische Berichte, FZR-290, Rossendorf 2000.

In diesem Beitrag werden Tetradentate Tc-99m Liganden mit hoher Affinität zum 5-HT_1A Rezeptor vorgestellt. Die Verbindungen weisen sowohl eine moderate Selektivität gegenüber dem alpha1-adrenergen Rezeptor als auch eine verbesserte Hirnaufnahme auf. Sie leiten sich strukturell von den PET-Liganden WAY 100635 und DWAY ab. Als Chelatorensystem für Oxotechnetium(V) wird Bis(aminoethanthiol) (BAT) genutzt welches über Spacer unterschiedlicher Länge mit der Phenylpiperazineinheit verknüpft ist.
Der Beitrag behandelt die Ligandsynthese, die Markierung mit Technetium sowie die biologische Evaluierung der Komplexe (in vitro Rezeptorbindungsstudien, Bioverteilungen und Autoradiographische Untersuchungen).

Magnetron sputtered polycrystalline Ta and Ta(Si) barriers for copper metallization schemes were modified by nitrogen or oxygen high dose ion implantation to improve their thermo-mechanical stability. The ion bombardment changes the initially polycrystalline microstructure to amorphous-like. In contrast to pure Ta, Ta(Si) layers are already X-ray amorphous after deposition. Here the implantation enhances the recrystallization temperature by about 100 K. In order to demonstrate the improvement in the barrier properties of the implanted Ta films the intermixing of Ta and Cu at the interface of corresponding layer structures was measured by AES depth profiling as a function of the annealing temperature. The thermal stability of Ta and Ta(Si) barriers increases from 6000C/ 1h for the non-implanted layers up to 750° C/1h after implantation of nitrogen or oxygen.

Calciumphosphates are the main component of bone and as a coating they promise optimal bone integration of an implant. Titanium as a leading implant material does not support calciumphosphate precipitation on its surface. The aim is to modify the titanium surface for spontaneous deposition of calciumphosphate out of a solution and to demonstrate its biocompatibility. Non treated, Na implanted (3.2 x 1017 Na cm-2), or NaOH (10 mol/L) etched Ti samples were used. Bone forming SAOS-2 cells were seeded out on the surface. After 3, 14, and 28 days samples were investigated for cell count and morphology, biochemical markers and ratio of Ca and P as a hint for the type of calciumphosphate. For a second series calciumphosphate was precipitated by incubation in a simulated body fluid prior to cell culture. On Na implanted Ti without treatments in simulated body fluid, cells grow more oriented in comparison to pure or etched Ti and the cell count was higher, but the cells did not cover the whole surface. Characteristic markers for bone cell metabolism did not differ significantly between the samples. Apatite formation was low but increased in experiments after calciumphosphate precipitation out of solution. The cell morphology improved when the cells were grown on samples after treatment with simulated body fluid. Na implantation can enhance calciumphosphate precipitation on Ti and this way promote the growth of bone forming cells.

Poster
Kolloidchemische Untersuchungen an Umweltwässern unter anoxischen Bedingungen

At the Dresden Radiation Source ELBE an intense IR beam in 3 - 30 µm range will be produced in the undulator U27. It consists of two 34-pole sections, allowing to insert a magnetic chicane in between. The undulator structure has a period of 27.3 mm and consists of NdFeB permanent magnets and poles of decarborized iron, mounted on two carriages such that the distance between the two sections is adjustable for phase-matching. The gaps of both sections can be varied independently to eventually produce two IR-colours at the same electron energy. For high-gain lasing one can introduce a tapering of the field.

An intensity modulated focused ion beam (FIB) which is hitting the surface of a solid, leads to a small temperature variation in the near subsurface region which is sufficient for thermal elastic wave generation. The measurement of these waves can be used for analysis and imaging of surface as well as near subsurface structures in the material. The modified FIB equipment IMSA-100 working with 35 keV Ga+ and Au+ ions and a current of about 3 nA was employed to obtain acoustic images from structures on silicon, aluminum and glass targets. The acoustic signals were detected using a PZT transducer delivering an output voltage of 50 - 100 nV at modulation frequency of 100kHz. The frequency was varied in the range of 60kHz - 2MHz. The obtained lateral resolution of the ion acoustic images at 80 kHz was about 16 µm on silicon and about 7µm on glass and at 2 MHz it decreases to 5 µm and 3 µm, respectively.

Within a transport code of BUU type the production of phi mesons in the reactions Ni + Ni at 1.93 AGeV and Ru + Ru at 1.69 AGeV is studied. New elementary reaction channels rho N Delta to phi N and pi N(1520) to phi N are included. In spite of a substantial increase of the phi multiplicities by these channels the results stay below the tentative numbers extracted from experimental data.

Surface modification of austenitic stainless steel 316L due to incubation in growing cell cultures and cell culture media as control has been studied. The following treatments were applied: mouse fibrosarcoma cells L929 during 3 and 7 days, polymorphonuclear neutrophils 3 and 7 days and human osteosarcoma cells SAOS-2 in during 7 and 14 days. Cells were enzymatically removed in all cases. The modified surfaces were probed in comparison with untreated ones by means of spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS shows the appearance of the peak of bonded nitrogen at 400.5 eV characteristic for adsorbed proteins on the surface for each type of cells and for the cell-free medium. Migration of Ni in the adsorbed layer is observed in all cases for samples after the cell cultures. The protein layer thickness is ellipsometrically determined to be within 2.5-6.0 nm for all treated samples with parameterization of its optical constants in Cauchy approach. The study showed that for such biological treatments of the stainless steel the protein adsorption is the dominating process in the first two weeks, which could play a role in the process of corrosion by complex forming properties with metal ions.

With the invention of the liquid metal ion source (LMIS) in the sixties the focused ion beam (FIB) technique started an impressive development from the laboratory level to high performance industrial equipments. At present, the FIB is a very useful and versatile tool in microelectronics industry for mask and integrated circuit repair and modification, failure analysis or TEM specimen preparation, as well as in the material science for radiation damage and sputtering investigations, for grain size and distribution analysis in metals and alloys, for the formation of silicides or the fabrication of micro-tools. A modern FIB column which is operated with gallium liquid metal ion souces (LMIS) only reaches a spot size in the range of 10 nm and current densities of more than 10 A/cm2 .

For special purposes in the field of research and development, like writing ion implantation or ion mixing in the µm- or sub-µm range other ion species than Ga are needed. Therefore alloy LMIS are used. The energy distribution of the ions from an alloy LMIS is one of the determining factors for the performance of the source in the FIB equipment, in other words, the obtainable spot size. Different source materials like the alloys Au73Ge27 (Tm = 366°C), Au77Ge14Si9 (Tm = 365°C), Co36Nd64 (Tm = 566°C), Er69Ni31 (Tm = 765°C), and Er70Fe22Ni5Cr3 (Tm = 862°C) were investigated and compared with respect to the energy spread of the different ion species depending on the operation parameters emission current I, ion mass m and temperature T. For single charged ions the predicted dependence of the energy spread according to DE µ I2/3 m1/3 T1/2 found for Ga could be confirmed in reasonable agreement. Due to the ion mass, for doubly charged ions a weaker and for clusters a stronger slope was found. The temperature dependence of the source behaviour is strongly related to the surface tension coefficient of the used alloy.

The alloy LMIS`s discussed above have been used in the Rossendorf FIB system IMSA-100 especially for writing implantation to fabricate sub-µm pattern without any lithographic steps. So a Co-FIB was applied for the ion beam synthesis of CoSi2 micro-structures with a minimum feature size of 60 nm. Additionally, the possibility of varying the current density with the FIB by changing the pixel dwell-time was used for radiation damage investigations in Si and SiC at elevated implantation temperatures. Furthermore, a broad spectrum of ions was employed to study the sputtering process depending on temperature, angle of incidence and ion mass on a couple of target materials using the volume loss method. The effective erosion properties of the FIB were exploided in fabricating micro-tools with dimensions smaller than 40 µm from WC(Co) and HSS steel. The application of the FIB as a scanning ion microscope with high topographic resolution of the sample surface can be used to study the grain size and distribution of metals and alloys as well as micoelectronic structures on the surface and also, after sputtering, in deeper layers. The sputtered holes can also be imaged after polishing with the FIB and tilding as a cross section by SEM. All the examples underline the importance of a FIB in modern research.

The transport of L-carnitine (4-N-trimethylamino-3-hydoxybutyric acid), a compound known to be transported by the organic cation transporter / carnitine transporter OCTN2, was studied in immortalized rat brain endothelial cells (RBE4). The cells were found to take up L-carnitine by a sodium-dependent process. This uptake process was saturable with an apparent Michaelis-Menten constant for L-carnitine of 53.8 ± 9.8 µM and a maximal velocity of 214.5 ± 34.7 pmol/mg protein/h. Besides L-carnitine, the cells also took up acetyl-L-carnitine and propionyl-L-carnitine in a sodium-dependent manner and TEA in a sodium-independent manner. RT-PCR with primers specific for the rat OCTN2 transporter revealed the existence of OCTN2 mRNA in RBE4 cells. Screening of a cDNA library from RBE4 cells with rat OCTN2 cDNA as a probe identified a positive clone which showed, when expressed in HeLa cells, the functional characteristics of OCTN2. The HeLa cells expressing the RBE4 OCTN2 cDNA showed a six-fold increase in L-carnitine uptake and a four-fold increase in TEA uptake in a sodium-containing buffer. Typical inhibitors for organic cation transporters (e.g., MPP⁺ or TEA) showed an inhibitory effect on the transport of L-carnitine and TEA into the transfected cells. Similarly, unlabeled L-carnitine inhibited the transport of [³H]-L-carnitine and [¹⁴C]TEA in transfected HeLa cells. It is concluded that RBE4 cells, a widely used in vitro model of the blood-brain barrier (BBB), express the organic cation/carnitine transporter OCTN2.

The contribution will review recent results to the fabrication and investigation of semiconductor nanoclusters (Si, Ge, Sn) embedded in SiO2 films. Due to quantum confinement effects or the large surface/volume ratio of such clusters typical dimensions of only few nanometers exhibit remarkable properties which differ to that of the bulk values. Among different fabrication techniques the ion beam synthesis offers specific advantages to realize a large density of tiny (2-4 nm) nanoclusters and to fulfil the requirements of CMOS technology. The results of presented experiments clearly indicate that the size, density and distribution of clusters are strongly influenced by the implantation and annealing conditions. Taking these influences into account it is possible to realize desired nanocluster distributions in the SiO2 layer, e.g. the fabrication of wide regions with homogeneously distributed clusters or d-like nanocluster bands in thin SiO2 films.
The specific features of semiconductor nanoparticles in SiO2 films comprise an enormous potential for future opto- and microelectronics.
Optoelectronics
In general, group IV nanocluster containing SiO2 films can emit light in a wide wavelength region. The topic of light emission from ion beam synthesized nanoclusters is focused on recent success in extracting intensive violet/blue photo- and electroluminescence (EL) from Si-, Ge- or Sn implanted SiO2 layers which can be attributed to a specific defect formed after the IBS process. A power efficiency up to 0,5 % for EL has been established using MOS structures. Among possible applications the properties of a monolithically integrated optocoupler with ultra low power consumption will be discussed.
Microelectronics
Based on a FET structure with semiconductor nanocluster containing gate oxide, a new non-volatile memory cell has been designed which makes use from the charge storage ability of small quantum dots. The advantages of this memory are attributed to the features, that (i) the nanoclusters act as an ensemble of single storage elements, and (ii) the charge transfer during programming occurs preferably by direct tunnelling. Therefore, lower programming voltages and considerably increased endurance (1010 w/e-cycles) in comparison to the present (Flash)- EEPROM technique is expected. Routes towards the fabrication of a shallow band of nanoclusters in the gate oxide of a FET very close, but well separated to the Si/SiO2-interface will be discussed in detail. CV or IV measurements reveal the charge storage effect of cluster containing thin SiO2 films by a remarkable shift of the flatband or threshold voltage of MOS or FET-structures, respectively. Recently, Zentrum Mikroelektronik Dresden has been successfully realized the first 256 nv-SRAM based on ion beam modified gate oxides.

This is a comprehensive study of the characteristics of an AuGeSi and CoNd liquid metal alloy ion sources [Focused ion beams from liquid metal ion sources, 1991]. Such characteristics include current-voltage curves and ion beam mass-spectra. A careful investigation has been undertaken where the temperature is one of the main variable experimental parameters. Theoretical models support the experimental results.

Chemical vapor deposited (CVD) diamond films thermochemically polished on cylindrical steel plates are subjected to Rutherford Backscattering Spectrometry (RBS) and Scanning Electron Microscopy - Energy Diffractive X-ray Spectrometry (SEM-EDX). A diamond film polished for 25 hours at 950 °C is etched in chromic acid (K2Cr2O7 + H2SO4 + H2O) prior to RBS measurement while two other films also polished at 950 °C for 8 and 25 hours, respectively are analyzed as polished. The RBS spectra of as-polished diamond films contain peaks of iron contaminant while the surface of the etched film is devoid of iron. Moreover, the concentration/magnitude of the contaminant on the film polished for 25 hours is about 2-fold that of the film polished for 8 hours. SEM-EDX spectra taken from dark and bright spots manifest the presence of iron contaminant in as-polished films but its absence in the etched film regardless of the surface topology. Thus, the depth measured by the RBS is assumed to represent the characteristic thickness of the non-diamond carbon layer in which the iron contaminant originating from the polishing plate are embedded. The presence of silicon and oxygen bands in the SEM-EDX spectra of both as-polished and etched diamond films is attributed to their inclusion during film deposition.

Temperature and strain rate change tensile tests were performed at two VVER 1000-type reactor pressure vessel welds with different content of nickel in unirradiated and irradiated conditions in order to determine the activation parameter of the contribution of the thermally activated deformation. There are no differences in the activation parameters in the unirradiated and the irradiated condition as well as for the two different materials. This shows irradiation hardening preferentially results from a friction hardening mechanism by long-range obstacles.

In the Forschungszentrum Rossendorf (FZR), an infrared FEL at the radiation source ELBE is under construction. For the measurements of the electron beam position in the undulator, two systems will be used. The first one consists of seven insertable beryllium OTR (Optical Transition Radiation) view screens, which will also be used for the alignment of the FEL optical resonator. The second one will use a single moveable YAG (Yttrium Aluminium Garnet activated by Cerium) screen, which can travel within the undulator vacuum chamber such that the electron beam position can be measured at any place in the undulator.

Annual Report 2000
Institute of Radiochemistry

Für den 3. Block vom KKW Rovno - WWER-1000/W-320 - wurde in Analogie zu den 6 typengleichen Blöcken des KKW Saporoshje eine verbesserte betriebliche Überwachung eingerichtet. Dazu werden der Aufsichtsbehörde vor Ort und in Kiew einmal pro Minute 57 aktuelle sicherheitsrelevante Parameter zur Erfassung und Bewertung mittels moderner technischer Mittel on-line zur Verfügung gestellt. Die entwickelte Auswertesoftware gestattet die Darstellung der Bewertungsergebnisse in Form von Tabellen, Grafiken und Schemata, wobei durch einen Archivmodus auch Trendanalysen von allen Parametern möglich sind. Des Weiteren wurde die Leistungsfähigkeit und Zuverlässigkeit des gesamten Fernüberwachungssystem weiter erhöht, so dass derzeit mehr als 60 % der ukrainischen KKW-Kapazität unter einer deutlich verbesserten behördlichen Aufsicht stehen.

Die genaue Messung der Lamb-Verschiebung stark gebundener Elektronen in Zusammenhang mit Tests der Quantenelektrodynamik (QED) in starken Feldern in hochgeladenen Ionen ist eines der Hauptthemen der heutigen Atomphysik. Die gegenwärtig durchgeführten Hochpräzisionsmessungen erfordern eine hohe Genauigkeit in den theoretischen Berechnungen der Lamb-Verschiebung. Diese Genauigkeit impliziert eine Berücksichtigung aller QED-Korrekturen der Ordnung α und α², aber exakt in allen Ordnungen in Zα. In den zurückliegenden Jahren sind die meisten dieser QED-Korrekturen sowohl in 1. Ordnung als auch in 2. Ordnung Störungstheorie berechnet worden. Der Beitrag der Zwei-Photonen-Selbstenergie konnte jedoch bisher nicht ausgewertet werden und stellte somit die größte Ungenauigkeit in der Vorhersage der Lamb-Verschiebung für wasserstoffartige Systeme dar. In dieser Arbeit wird der Beitrag dieser Prozesse zur Lamb-Verschiebung untersucht. Darüber hinaus werden erstmals renormierte Ausdrücke der Zwei-Photonen-Vakuumpolarisation und der Selbstenergie-Vakuumpolarisation hergeleitet. Bisher konnten diese Beträge nur in Uehling-Näherung ausgewertet werden.

The Rossendorf electrostatic accelerator facility, consisting of three accelerators with rated voltages of 2 -5 MV, has been extended by a 100 kV tandem accelerator for tritium depth profiling by AMS and by concentration of two implanters at the same location. Two experimental chambers were installed, which give the possibility of dual beam experiments using the beams from the 3 MV tandetron and from the 500 kV implanter. At the 5 MV tandem the original inclined field acceleration tubes were exchanged by straight field tubes with spiraling magnetic field. First results of the accelerator modernisation and of the beam line extension are presented.

Recent findings indicate that gamma radiation can contribute to the embrittlement of reactor materials. On this background an experimental benchmark programme at two low power reactors was started to measure both, neutron and gamma spectral fluences behind and inside of transmission modules consisting of variable iron and water slabs using a NE213 scintillation spectrometer and partly a HPGe detector. The experimental results are used to validate Monte Carlo calculation methods in reactor dosimetry for coupled neutron/gamma problems. The experiment and results of a first series of measurements and comparisons to MCNP calculations for neutron and gamma energy spectra are presented. The investigations will be continued with an extension and validation of the Monte Carlo transport code TRAMO.

Within a transport code of BUU type the production of Φ mesons in the reactions Ni+Ni at 1.93 A GeV and Ru + Ru at 1.69 A GeV is studied.
New elementary reaction channels ρN(Δ) → ΦN and πN(1520)→ ρN are included.
In spite of a substantial increase of the Φ multiplicities by these channels the results stay below the tentative numbers extracted from experimental data.

Physical vapor deposition (PVD) processes are nowadays common in synthesis of hard coatings like cubic boron nitride (cBN). Precise knowledge of plasma characteristics (ion flux, ion energy distribution and plasma composition) is crucial for understanding and controlling cBN thin film growth. This work is devoted to the characterization of an unbalanced RF magnetron Ar/N2 discharge using a Langmuir probe and an energy selective mass spectrometer. RF power and total pressure were varied from 50 to 300 W and from 0.1 to 0.5 Pa respectively for different Ar/N2 mixtures. Main ionic species are found to be Ar+ and N2+ with a very low fraction of N+. The ion density increases with RF power, pressure and Ar content. The ion energy distribution consists of one single narrow peak with full width at half maximum of a few eV. The main neutral species are Ar and N2. Atomic nitrogen could not be detected by mass spectrometry, indicating a low fraction of this species in the discharge.

In der vorliegenden Arbeit wird die methodische Entwicklung eines Ultraschall-Einprobenverfahrens zur Erfassung duktilen Rissfortschritts im quasistatischen Dreipunktbiegeversuch auf der Grundlage eines Ultraschallverfahrens vorgestellt. Das Verfahren wird an Werkstoffen unterschiedlichen Zähigkeits-Festigkeitsverhältnisses erprobt.
Das Messverfahren beruht auf der wiederholten Messung der Laufzeit des von einem Sendewandler auf die Rissspitze gerichteten und dort in Richtung Empfangswandler gebeugten Ultraschallimpulses. Als Voraussetzung für die In-situ-Rissfortschrittsmessung auf der Grundlage der Signallaufzeitmessung wurde die Schallwellenausbreitung und Signalbildung mittels Schallfeldsimulationen anhand der Elastodynamischen Finiten Integrationstechnik modelliert und zusätzlich durch stroboskopische Messungen der Schallfeldausbreitung experimentell bestätigt. Zur Kalibrierung des Messverfahrens wurde ein analytischer Zusammenhang entwickelt, der die eindeutige Zuordnung der Signallaufzeit zum gesuchten Rissfortschritt gestattet und den Einfluss der während des Dreipunktbiegeversuches stattfindenden plastischen Verformungen berücksichtigt. Das Ultraschall-Laufzeit-Beugungsverfahren wurde für den Einsatz an bruchmechanischen Kleinproben (ISO-V-Geometrie) spezifiziert. Die in den Prüfvorschriften formulierte Genauigkeitsanforderung an ein Einprobenverfahren kann mit dem ULB-Verfahren erfüllt werden. Die erreichbare Messpunktdichte des Rissfortschritts ermöglicht eine nahezu kontinuierliche Darstellung resultierender J-Risswiderstandskurven.

The fast neutron induced embrittlement of the reactor pressure vessel (RPV) is the main cause limiting the lifetime of many types of nuclear reactors, especially of the VVER type, produc-ing most of the nuclear energy in Russia and seven other countries. Uncertainty estimations show that the largest contribution to the uncertainty of calculated fluences is the uncertainty of the neutron cross section data. In the present work, different aspects of uncertainties of neutron fluence determination connected with the neutron data for transport calculations, data preparation methods and activation dosimetry cross sections have been investigated by com-parison of calculations with data from different libraries and by comparison of calculated and measured activation rates. The main object of these investigations was the VVER-1000 type reactor Balakovo-3. The tested libraries were the ENDF/B-VI based 47n/20g-group library BUGLE-96, the Russian 299n/15g-group library ABBN-93 (v. 99.01) and two modifications of the ABBN library: ABBN/B-VI and ABBN/JEF-2.2. In these modifications the cross sec-tion data of Fe, Cr and Ni are replaced by data based on the evaluated nuclear data libraries ENDF/B-VI and JEF-2.2, respectively. This allows to investigate the influence of the data of the elements most critical for the RPV fluence. Although thermal neutrons contribute only negligible to the embrittlement they are a strong source of gamma irradiation, which is proba-bly contributing noticeable to RPV embrittlement, as newer results showed. Therefore, the influence of different treatment of neutron data in the thermal energy region was investigated by calculations with and without upscattering in the region below 5 eV, as well as with and without consideration of core heterogenity effects. The neutron transport calculations were performed by the discrete ordinate code DORT using a 3D synthesis of (r-*)-, (r-z)- and r-calculations. Results obtained with the Monte Carlo codes MCNP and TRAMO with ENDF/B-VI data, were used to validate the DORT-results. The results of calculations at ex-vessel positions were compared with reference data of the Interlaboratory Experiment at Balakovo-3. The best agreement between results of calculations (C) and experiments (E) was obtained for BUGLE-96 and ABBN/B-VI, and 3D TRAMO results for all used reactions: 237Np(n,f), 93Nb(n,n'), 238U(n,f), 58Ni(n,p), 54Fe(n,p), 46Ti(n,p) and 63Cu(n,a). Further, the in-fluence of using different dosimetry cross sections, from IRDF-90v2, JENDL/D-99, RRDF-98 and a new Russian evaluation for 237Np(n,f), was investigated. The systematic calcula-tional underestimation of 237Np(n,f) reaction rates in case of IRDF-90v2, observed also by other investigators, can be removed using JENDL/D-99 or the new Russian evaluation. A similar underestimation for 93Nb(n,n') is reduced largely if JENDL/D-99 data are used. To evaluate the influence of cross sections of individual elements and of water on neutron and gamma fluence calculations, a simple two-zone cylindrical model was defined. The inner zone simulates the reactor core, the outer consists of H2O or Fe or Cr or Ni. In addition to DORT calculations with different libraries MCNP calculations with ENDF/B-VI were per-formed, to test the influence of point-wise data representation. The found discrepancies should be investigated further.

Introduction

If a fluid is electrically conductive, its flow may be controlled using electromagnetic forces. Meanwhile, this technique is a recognized tool even on an industrial scale for handling highly conductive materials like liquid metals.
However, also fluids of low electrical conductivity as considered in the present study, like sea--water and other electrolytes, permit electromagnetic flow control. Experimental results on the prevention of flow separation by means of a streamwise, wall parallel Lorentz force acting on the suction side of inclined flat plates and hydrofoils will be presented.

Force Configuration
The stripwise arrangement of permanent magnets and electrodes of alternating magnetization direction and polarity shown in Fig. 1 was proposed by Gailitis and Lielausis (1961). It generates a wall parallel force with a maximum value directly at the wall, decaying exponentially with the wall distance. Due to the low electrical conductivity, both electric and magnetic fields have to be applied to generate a Lorentz force of adequate strength. The width of the electrodes is equal to that of the magnets and
determines the penetration of the force into the flow. The ratio of electromagnetic to inertial force can be characterized by the interaction parameter. In analogy to the terminology used in separation control by blowing, one may also define an electrohydrodynamic momentum coefficient.

Results and Discussion
A downstream directed force adds momentum to the flow and accelerates the fluid in the vicinity of the wall. This flow acceleration may be used to counteract the energy loss due to friction and adverse pressure gradients. Actually, a streamwise Lorentz force has already been successfully applied to control the flow around a circular cylinder in Weier et al. (1998). The two inserts in Fig. 2 show the flow around an inclined flat plate. In the lower left photograph, the unforced separated flow is visible, whereas the upper subfigure depicts the fully attached flow under the action of a suction side Lorentz force. The graph indicates that the interaction
parameter, necessary to completely suppress separation, decreases with increasing chord length Reynolds number. The effect of a suction side Lorentz force on lift and drag of NACA--0017--like hydrofoils has been quantified by means of force balance measurements. Depending on the inclination angle, two different effects are observed. At small angles of incidence, a moderate lift increase due to additional circulation is observed. Simultaneously, caused by the added momentum, the drag is decreased. At higher angles of attack, where the unforced hydrofoil would normally stall, a more pronounced lift increase occurs.
Fig. 3 shows the lift gained by the suction side Lorentz force at a fixed inclination angle of 17. Here delta CL is the difference of the lift coefficients of the forced and the unforced hydrofoil at the specified chord length Reynolds number. The shape of the curve as well as the total values of the lift gain and the momentum coefficient resemble the behavior found in separation control experiments with steady blowing. In the presentation, a complementary discussion on scaling issues based on experiments with a NACA 0015 hydrofoil will be given.

Monte Carlo simulations have been used to optimize the monochromator shielding of the polarized cold neutron triple axis spectrometer PANDA at the Munich high flux reactor FRM-II. By using the Monte Carlo program MCNP-4B the destiny of the total spectrum of incoming neutron and gamma radiation from the beam tube SR-2 have been determined during the 3-dimensional diffusion process in different types of heavy concrete and other absorbing material. Special attention has been paid to build a compact and highly efficient shielding, partially non-magnetic, with a total biological radiation dose of less than 10 µSv/h at its outsides. Specially considered was the construction of an albedo reducer, which serves to reduce the background in the experiment outside the shielding.

We present new experimental data obtained with the FOPI detector at SIS, for the Au+Au heavy-ion collisions at 400 AMeV incident energy. The sideward flow, determined from a method without reaction-plane reconstruction, and the nuclear stopping are studied as a function of the centrality of the collisions. In order to study the nuclear in-medium effects, which act on the NN cross sections and potential and hence on experimental observables like the nuclear-matter flow and stopping, these results are compared with the predictions of two different QMD versions. The first one offers a fully microscopic calculation of the cross sections and potential in the G-matrix formalism and naturally includes the in-medium effects (this version is for the first time confronted with experiment). The second one uses a standard Skyrme potential plus a momentum-dependent term in order to mimic the in-medium effects.

The ratio of the total charge bound in fragments with Z between 2 and 15 to the hydrogen yield has been measured, and the neutron-to-proton ratio n/p has been estimated from the data of central Au+Au reactions between 100 and 400 AMeV, measured with the phase I setup of the detector system FOPI at the GSI, Darmstadt, in the polar angle range between 7^o and 30^o. These two quantities were used to determine the entropy per nucleon S/A by comparing them with the predictions of the FREESCO code. The analysis allows the simultaneous extraction of the values of the baryonic entropy, temperature, and collective flow. The extracted values are in good agreement with the values obtained in earlier FOPI studies and, for the baryonic entropy, with recent hydrodynamic caculations.

Light-particle emission from Au+Au collisions has been studied in the bombarding-energy range 100-250 AMeV, using Delta-E-E_R telescopes in coincidence with the FOPI detector in its phase I configuration. Center-of-mass energy spectra have been measured for Z=1, 2 isotopes emitted in central colisions at CM polar angles between 60^o and 90^o. Evidence for a collective expansion is reported, on the basis of the mean kinetic energies of hydrogen isotopes. Comparison is presented with statistical calculations (WIX code). For CM kinetic energy spectra, fair agreement is found between data and a recently developed transport model.

Inorganic colloids are ubiquitous in mine waters. They are primarily produced by the formation of oxyhydroxides and oxyhydroxy sulfates of iron(III) and aluminum due to the oxidation of Fe2+ and the hydrolysis of Fe3+ and Al3+. Colloidal particles are able to adsorb heavy metals and to influence trace heavy metal transport as for instance the transport of uranium. However, colloid formation and heavy metal adsorption are strongly dependent on pH. From a colloid-chemical point of view it can be differentiated between two principal types of mine waters:

(i) Type "acidic pore water" [1]
These waters can be separated from the rock by centrifugation or can be collected in the mines as acid rock drainage (ARD) samples. The waters possess high salt concentrations and are very acidic (pH 3 to 1). Ultrafine particles of <5 nm in size are the main colloidal component (based on photon correlation spectroscopy and ultrafiltration). The colloid concentration reaches the g/L range. The particles consist mainly of hydronium jarosite and schwertmannite (based on EXAFS). As and Pb show a high tendency to adsorb onto these particles.

(ii) Type "bulk water" [2]
This type of waters mainly refers to the flowing mine waters like adit waters which possess a near-neutral pH. Typical colloid contents of such waters are about 1 mg/L, typical particle sizes are 100 to 300 nm (based on photon correlation spectroscopy and scanning electron microscopy). The particles consist of Fe(III) and Al oxyhydroxides (ferrihydrite, alumogel). Their electrostatic stabilization is weak (zeta potential only about -10 mV), i. e. they show a larger tendency to coagulate and aggregate than the colloids found in the type (i) waters. Contaminants such as As, Pb, Cu, Th, U(IV), Po, and in the absence of carbonate complexation also U(VI), are strongly bound onto these particles. Uranium(VI) adsorption is often suppressed due to the formation of dissolved uranyl carbonato complexes in mine waters [2].

Important colloid-chemical processes are observed during the transition of type (i) waters to type (ii) waters which occurs in the course of the flooding of abandoned ore mines (dilution of the type (i) waters). Huge amounts of iron(III) particles with a size of 100 to 300 nm are formed under such conditions due to O2 ingress and pH increase. The adsorption rises drastically when the pH reaches the near-neutral region (cf. [3]). The sorption behavior of U(VI) in flooding waters differs significantly from that of U(VI) in both typical "acidic pore waters" and typical steady-state "bulk waters". Typical pH values of the flooding waters are in the range between 4 and 6 after some flooding time. Uranyl adsorption to the iron(III) particles is neither suppressed by high acidity nor by uranyl carbonate complexation in this pH region and the assumption of an unretarded migration of uranyl is "over-conservative". Scavenging by Fe(III) particles and colloid coagulation plus sedimentation can significantly immobilize the U(VI) in waters of the transition type. This scavenging mechanism refers also to trace elements such as Cu, As, Mo, Sb, Y, and Ce. Also the radiotoxic heavy metals Po, Pb, Th and Ac are colloid-borne above pH 4. Ra is usually truly dissolved.

[1] Zänker, H.; Moll, H.; Richter, W.; Brendler, V.; Hennig, C.; Reich, T.; Kluge, A.; Hüttig, G. (2001)
The colloid chemistry of acid rock drainage solution from an abandoned Zn-Pb-Ag mine. Appl. Geochem. (accepted).

[2] Zänker, H.; Richter, W.; Brendler, V.; Nitsche, H. (2000)
Colloid-borne uranium and other heavy metals in the water of a mine drainage gallery. Radiochim. Acta 88, 619-624.

[3] Hsi, C.-K. D.; Langmuir, D. (1985)
Adsorption of uranyl onto ferric oxyhydroxides: Application of the surface complexation site-binding model. Geochim. Cosmochim. Acta 49, 1931-1941.

The entropy per nucleon (S/A) has been extracted for the Au (150-800 AMeV)+Au reaction by using the phase I setup of the 4pi facility at GSI, Darmstadt. The entropy has been obtained from the comparison of various observables characterizing the dM/dZ fragment multiplicity distribution, extending up to Z=15, with those calculated with the quantum statistical model. It is the first time that S/A values are determined by considering the full ensemble of charged products detected in the reaction. Consistent values of S/A are found from different methods. These entropy values are shown to be fairly independent of the volume of the "participant" region considered. They are somewhat lower than those extracted in earlier works but are in good agreement with hydrodynamic calculations and suggest a low viscosity for the hot and dense nuclear matter.

Charged particles have been observed in collisions of Au+Au at an incident energy of 150 AMeV using a high-granularity detector system covering approximately the forward hemisphere in the center-of-mass system. Highly central collisions have been studied using a double selection criterion which combines large charged-particle multiplicities with small transverse-momentum directivities. In this class of events about one-quarter of the total nuclear charge emerges as intermediate-mass fragments with nuclear chages Z>2. These fragments are centered at midrapidity and are produced with large transverse velocities.

At the SIS/ESR accelerator facility at GSI in Darmstadt the 4pi-detector system FOPI is under construction at present. It is designed for the investigation of central collisions of heavy ions in the energy range up to 2 AGeV. As phase I of this detector a forward wall has been built and used in various experiments. It comprizes a total number of 764 scintillators with an additional shell of 188 thin Delta-E-detectors in front of it and covers the full azimuth of the polar angles from 1 to 30 degrees. the velocity and the nuclear charge of the fragments are determined by a combined time-of-flight and Delta-E measurement.

Using the FOPI facility at GSI Darmstadt, complete data of Au+Au collisions at 150 AMeV were collected for charged products (Z=1-15) at laboratory angles from 1 to 30 degrees. Central collisions were selected by applying various criteria. The kinentic energy spectra of fragments from an isolated midrapidity source are investigated in detail for center-of-mass angles from 25 to 45 degrees. The heavy products (Z>=3) are used to determine the collective energy which is found to be at least 10 AMeV.

Complete distributions of the light and intermediate mass fragments (Z=1-6) produced within the polar angle range of 1 to 30 degrees in highly central collisions of 250 AMeV Au+Au are presented. The results of this measurement and a model analysis are used to study the expansion and clustering of the hot and compressed transient state formed in central collisions of such a heavy system. The influence of the initial conditions on the final observables is discussed.

Particles with strange quark content produced in the system 1.93 AGeV ⁵⁸Ni on ⁵⁸Ni have been investigated at GSI Darmstadt with the FOPI detector system. The correlation of these produced particles was analyzed with respect to the reaction plane. Lambda baryons exhibit a very pronounced sideward flow pattern which is qualitatively similar to the proton flow. However, the kaon (K⁺,K_s ⁰) flow patterns are significantly different from that of protons, and their form may be useful to restrict theoretical models on the form of the kaon potential in the nuclear medium.

Charged pion spectra measured in ⁵⁸Ni+⁵⁸Ni collisions at 1, 06, 1.45 and 1.93 AGeV are interpreted in terms of a thermal model including the decay of Delta resonances. The transverse momentum spectra of pions are well reproduced by adding the pions originating from the Delta-resonance decay to the component of thermal pions, deduced from the high transverse momentum part of the pion spectra. about 10 and 18% of the nucleons are excited to Delta states at freeze-out for beam energies of 1 and 2 AGeV, respectively

The Mössbauer spectra of single crystals of the iron silicides e-FeSi, ß-FeSi2 and a-FeSi2 are collected by conversion electron Mössbauer spectroscopy at room temperature. Measurements were performed at different angles between the propagation direction of the exciting g-radiation and the crystal axis of the single crystals.
The hyperfine parameters are determined with high accuracy. Moreover, the signs of the quadrupole splittings and the direction of the main axis of the electric field gradient in regard to the crystal orientation was determined for the disilicides. For the monosilicide, this was impossible because of the particular crystal symmetry.

Im Rahmen eines vom BMBF/BMWi geförderten WTZ-Vorhabens wurde dem Institute for Nuclear Research and Nuclear Energy (INRNE) in Sofia der Programmcode DYN3D sowie der gekoppelte Programmkomplex ATHLET-DYN3D verfügbar gemacht. Dabei stellt dieser Programmkomplex eine Anbindung des im FZR entwickelten 3D Kernmodells DYN3D an den thermohydraulischen Systemcode ATHLET der GRS dar.
Zur Validierung dieser Programmcodes wurde eine Messdatensammlung zu einem Inbetriebnahmeexperiment am Block 6 des KKW Kozloduj (WWER-1000/320) erstellt. Die Ergebnisse der durchgeführten Validierungsrechnungen wurden mit den Messwerten aus der Datensammlung verglichen.
In den Programmcode DYN3D wurde von den bulgarischen Experten ein vereinfachtes Modell zur Simulation von Querströmungen zwischen den Brennelementen integriert. Dieses Querströmungsmodell ermöglicht es, Prozesse mit asymmetrischen Randbedingungen realistischer zu betrachten. Eine erste Bewertung des implementierten Strömungsmodells erfolgt durch Vergleichsrechnungen zwischen dem modifizierten DYN3D Code und dem Unterkanalanalyse-Code COBRA-4I sowie auf der Grundlage von verfügbaren Messdaten aus dem KKW Kozloduj.

Two models of material damage occuring with viscoplasticity are presented:

1. accumulation model based on rupture strain
2. constitutive model based on the volume fraction of creep cavities

The creep model for porous material is developed by numerical simulation experiments with a FE model representing the simplified microstructure of a representative volume element.

The damage accumulation model is integrated into ANSYS via the user programmable features.

The efficiency as diffusion barrier of RF-Magnetron sputtered Ta-layer modified by ion implantation has been studied using Auger electron spectroscopy and X-ray diffraction. Two systems were prepared : 50nm-Ta/500nm-Cu/50nm-Ta/ on SiO2 and 200nm-Cu/50nm-Ta/ on SiO2. The samples were annealed at temperatures from 600 to 850°C in a vacuum of 2 x 10-4 Pa. The thermal stability was determined by interdiffusion of Cu into the diffusion barrier. The as-deposited Ta barriers are polycrystalline. After annealing at 600°C for 1 hour interdifusion of Cu is observed for the non-implanted barrier. Ion implantation of nitrogen into the Ta layer leads to a nanocrystalline or amorphous-like structure with an important improvement of the barrier effect. The nitrogen implanted 50 nm Ta-barrier on Cu is stable up to 750°C for 1h. A higher thermal stability reveals the Ta layers between the Cu and SiO2. Cu/Ta/SiO2 system shows beginning of copper diffusion and a strong interaction between Ta and SiO2 after annealing at 800°C without implantation. The implanted Ta-barriers in this system are still effective, after annealing with 850°C for 3h.

Acidic pore waters are the waters of most chemical importance in abandoned ore mines before the mines' flooding. These waters possess high concentrations of sulfuric acid and reach pH values of 3 to 1. In particular in the case of the Königstein uranium mine they contain high amounts of sulfuric acid because of the former ore extraction technology (acidic underground leaching with sulfuric acid). Typically, acidic pore waters have iron concentrations of the range of grams per liter. This iron is partly dissolved and partly colloidal (particle size < 5 nm, cf. [1]). Most of the heavy metals, including U(VI), are truly dissolved in acidic pore waters. Only As and Pb have been found in a colloid-borne form [1].

From a chemical point of view, the flooding of a mine is primarily the dilution of the pore waters by groundwaters. The following concomitant phenomena are accompanying this process in the Königstein mine: a decrease in heavy metal concentrations, a decrease in H2SO4 concentration (increase of the pH), an ingress of oxygen and an ingress of carbonate. This gives rise to chemical reactions such as the neutralization of sulfuric acid by carbonate, the degassing of carbonate as CO2, the oxidation of Fe2+ into Fe3+ and the hydrolysis of Fe3+, i.e. the formation of Fe(III) particles. We asked ourselves what the interactions of the radiotoxic heavy metals with these Fe(III) particles are and what the behavior and later fate of the particles (possibly carrying radiotoxic heavy metals) is.

According to the existing knowledge there should not be much interaction between the < 5 nm Fe(III) particles and the radiotoxic heavy metals in the acidic pore waters (exception: 210Pb). With increasing pH, elements such as Th, Po, Ac etc. begin to adsorb strongly onto the particles. Also the uranyl increasingly tends to sorb onto the particles with increasing pH. However, uranyl adsorption to the particles is counteracted by carbonate complexation in the solution the importance of which also increases with increasing pH. Therefore, uranyl is often assumed to be truly dissolved under the conditions of real mine waters, either due to high acidity (low pH region) or due to carbonate complexation (higher pH). It remains to be elucidated if there is a pH region where also the uranyl occurs colloid-borne in a mine.

We investigated flooding waters from the Königstein mine by light scattering, centrifugation, filtration, ultrafiltration, scanning electron microscopy, laser doppler electrophoresis, ICP-MS, AAS, ion chromatography and diverse radiometric methods. The waters had a pH of 5.6 and an Eh of 450 mV, the concentrations of important constituents were CCa 0.9 mM, CFe 0.3 mM, CU 0.05 mM, Csulfate 1.2 mM, Ccarbonate 1,0 mM and CO2 0.11mM. Almost 90 % of the iron was divalent. Because of the Eh value we assume that the uranium was hexavalent. Colloid concentrations in the range of 2 to 3 mg/L were found; they rose rapidly if the access of oxygen was allowed. The particle size was about 100 nm. We measured a zeta potential of only -7.5 mV, i.e. the electrostatic stabilization of the particles was weak. Therefore the particles showed a pronounced tendency to aggregate and sediment. Strongly-sorbing radionuclides such as 210Po and 210Pb, but also significant fractions of the uranyl (up to 100 %) were colloid-borne. The amount of the sorbed uranyl was very sensitive to pH changes of only few tenth of pH units. This senstivity is obviously attributable to the fact that the pH of the water was in the vicinity of the point of inflection of the uranyl - Fe oxyhydroxide "adsorption edge". The uranium and the other radiotoxic heavy metals studied, with the exception of radium, followed the tendency of the iron(III) particles to aggregate and sediment.

We conclude that there is a pH range where the U(VI) occurs colloid-borne in mine waters, even if carbonate is present. This range is pH 4 to 6 (see also [2]). The assumption of an unretarded m...