Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Der Rothschönberger Stolln leitet den Hauptteil der Grubenwässer des stillgelegten Freiberger Bergbaureviers in die Triebisch, einem Nebenfluß der Elbe. Das Ziel unserer Untersuchungen waren Aussagen über den kolloidalen bzw. kolloidgebundenen Anteil der wichtigsten toxischen Elemente am Mundloch des Stollens.

Es wurden Wasserproben in den Monaten Februar, April, August, Oktober sowie Dezember 1998 genommen. Nach Vor-Ort-Analysen (T, pH, O2-Gehalt, Redox-Potential und Leitfähigkeit) wurden die Proben im Labor kolloidchemisch mit den folgenden Techniken untersucht: Filtration bzw. Ultrafiltration, Zentrifugation, Sedimentation, Photonenkorrelationsspektroskopie (PCS) und Rastereletronenmikroskopie (REM) mit energiedisperser Röntgenanalyse (EDX). Die chemischen Analysen erfolgten mittels induktiv gekoppelter Plasma-Massenspektroskopie (ICP-MS), Atomabsorptionsspektroskopie (AAS) sowie Ionenchromatographie (IC). Von der Arbeitsgruppe J. Thieme (Universität Göttingen, Einrichtung Röntgenphysik) wurden parallel röntgenmikroskopische Untersuchungen mittels Synchrotronstrahlung durchgeführt.

Die PCS-Messungen an den Wasserproben ergaben, daß im Wasser des Rothschönberger Stollns Kolloidpartikel im Bereich von 100 bis 300 nm mit einem Maximum bei ca. 200 nm anwesend sind. Ihre Konzentration beträgt etwa 1 mg/l. Auf REM-Aufnahmen an beladenen Kernspurfiltern sind diese Partikel zu erkennen. Die Abnahme der Streulichtintensität bei den PCS-Messungen und der chemischen Gehalte in den Zentrifugaten nach der Parallel-Zentrifugation mit zunehmender Zentrifugalbeschleunigung ergeben, daß es zwei Gruppen von chemischen Elementen gibt. Während die Elemente Fe, Al, Pb, As, La, Y und Cu mit wachsender Zentrifugalbeschleunigung und beim Filtrieren mit sinkender Porenweite zunehmend abgeschieden werden, lassen sich alle übrigen der 25 mit ICP-MS/AAS analysierten Elemente nicht abzentrifugieren bzw. passieren alle Filter und Ultrafilter bis zu einer Porenweite von 3kD (ca. 1, ...

Im Rahmen des Verbundprojektes wurden theoretische Untersuchungen zur Modellierung der aus periodischen Anordnungen von alternierenden Magneten und Elektroden entstehenden wandnahen Lorentzkräfte bei Körperumströmungen in schwach-leitfähigen Fluiden durchgeführt. Hierbei konnte die Beschreibung der Lorentzkräfte für die klassische Konfiguration aus rechteckigen Magneten und Elektroden entschieden verbessert werden. Diese Modellierung war notwendige Voraussetzung für die Durchführung numerischer Simulationen von Platten- und Tragflügelumströmungen, für welche im Rahmen des Verbundprojektes Umströmungsexperimente an der HSVA durchgeführt wurden. Existierende Codes zur Berechnung turbulenter Umströmungen enthalten stets aus der Turbulenztheorie abgeleitete Wandfunktionen für den wandnahen Bereich. Diese können hier nicht verwendet werden, da die elektromagnetische Kraft gerade im wandnahen Bereich ihre Wirkung entfaltet. Deshalb wurde bewußt eine direkte numerische Simulation der Umströmung gewählt, obwohl diese zunächst auf relativ niedrige Reynolds-Zahlen beschränkt ist. Hierbei fand ein moderner Code mit spektralen Elementen Anwendung. Die Simulationen belegen, daß mit Hilfe der Grenzschichtkontrolle durch wandparallele Lorentzkräfte die Strömungsablösung an der Saugseite eines angestellten Ruders wirksam verzögert bzw. unterdrückt werden kann und damit eine erhebliche Auftriebsverbesserung erreicht wird.

Im Rahmen des Verbundprojektes wurden Meßreihen zur Umströmung einer ebenen Platte und eines ruderförmigen Körpers durchgeführt. Die jeweils oberflächenparallele elektromagnetische Kraft entsteht durch die Kopplung äußerer elektrischer und magnetischer Felder, die von einer streifenartigen, wechselweisen Belegung der Körperoberflächen mit Permanentmagneten und Elektroden ausgehen. Aufgrund der Feldverteilungen ist die Kraftwirkung auf den Bereich der Strömungsgrenzschicht beschränkt. Es fanden Permanentmagnete mit einer Feldstärke im Bereich von 0.2 bis 0.4 Tesla Verwendung. Die Elektroden wurden mit Gleichstrom gespeist, bei maximalen mittleren Stromdichten von bis zu 0.5 A/cm2. Die Plattenexperimente zeigten eine deutliche Reduzierung des Strömungswiderstandes, die bei maximalem Elektrodenstrom bis zu 80% betrug. Dieses Ergebnis wird allerdings durch einen energetischen Aufwand erreicht, der die Einsparungen beim Reibungswiderstand überwiegt. Laser-Doppler Messungen der Grenzschichtprofile bestätigten das physikalische Konzept, durch die elektromagnetische Volumenkraft der Grenzschicht ein stabileres Profil aufzuprägen, welches bei höherem Elektrodenstrom in das eines Wandstrahles übergeht. Die Untersuchungen am Ruder waren vor allem auf die Unterdrückung der Strömungsablösung an der Saugseite des Profiles und die damit verbundene Auftriebserhöhung gerichtet. Dadurch konnte eine deutlich verbesserte Ruderwirkung erreicht werden. Experimentelle Weiterführungen des Konzeptes und Probleme infolge der auftretenden Elektrolyseblasen sowie Aspekte der Auswahl geeigneten Elektroden-materials werden diskutiert.

Das Ablösen von Wirbeln an umströmten Körpern bzw. das Verständnis der körpernahen Strömungsgrenzschicht sind ein altes Problem der Strömungsforschung von offensichtlich großer praktischer Bedeutung. Der hochgradig nichtlineare Charakter dieser Phänomene beschränkt heute und auf absehbare Zeit die Möglichkeit einer direkten numerischen Simulation auf relativ niedrige, für praktische Zwecke wenig relevante Reynolds-Zahlen.
Für den Fall, dass die strömende Flüssigkeit eine elektrische Leitfähigkeit wie die von Seewasser hat, wird im Verbundprojekt die Idee einer gezielten Grenzschichtkontrolle mittels geeigneter elektromagnetischer Felder untersucht. Durch wechselweise Anordnung von Permanentmagneten und Elektroden kann, entsprechende Stromzufuhr an den Elektroden voraussgesetzt, eine Volumenkraft erzeugt werden, die die Strömungsgrenzschicht vollständig kontrolliert. Experimentelle Ergebnisse von Umströmungsmessungen an einer ebenen Platte und einem Ruder, durchgeführt an der Hamburgischen Schiffbauversuchsanstalt, zeigen eindeutig die starke elektromagnetische Kontrollmöglichkeit, die sich u. a. in einem erheblich reduzierten Strömungswiderstand oder einer Unterdrückung der Wirbelablösung niederschlägt. Die ernergetische Bilanz wird analysiert. Das Anwendungspotential im Schiffbau dieser relativ universell einsetzbaren Möglichkeit zur Strömungskontrolle wird aufgezeigt. Weiterführende, bisher nicht realisierte Varianten wie die Optimierung der Stromzufuhr oder der geometrischen Anordnung von Magneten und Elektroden werden diskutiert.

The present paper deals with a shape of a sharp phase boundary under conductivity controlled quasisteady solidification in a long cylinder with a given surface temperature and growth velocity. An approximate analytical closed form solution is obtained linearizing the Stefan problem in a neighbourhood of the practically desirable planar interface. The relative error of the solution is evaluated numerically and shown below 15% for reasonable interface depths (1/2 of the crystal radius) and desreasing linearly (or more rapidly) as interface deformation decreases.

Stability of a solid sphere in both uniform and linear alternating magnetic fields is considered with respect to virtual rotations. When the frequency of the alternating magnetic field exceeds certain critical threshold despending on the configuration of the field, the sphere is found to spin up around a horizontal axis. The physical mechanism of this instability is the same as that of operation of a single-phase electromotor. Sufficiently small rotational disturbances can be completely suppressed by imposing an axial steady magnetic field of strength comparable to hat of the alternating field. Non-linear stability analysis shows that for sufficiently high frequencies spin-up can be caused by large disturbances even when all infinitesimal disturbances are stable.

This paper presents a linear-stability analysis of small-amplitude oscillations of a solid body suspended in an alternating magnetic field. An original theory is developed for an arbitrary configuration of the magnetic field. Stability of a solid sphere in an axisymmetric linear magnetic field is calculated analytically. Oscillations of the sphere are found to develop as the frequency of the field exceeds certain critical threshold relative to the characteristic diffusion time of the magnetic field in the sphere. The critical frequency for the onset of oscillations in linear magnetic field coincides with the critical frequency for the spin-up instability in uniform magnetic field. The growth rate of oscillations attains a maximum at some frequency above the threshold and tends to zero at high frequencies.

The flow around bodies (cylinder, plate) can be controlled by applying
electromagnetic forces originating from electrodes and permanent magnets
suitably placed on the surface of the body. There is a large variety for
applying those forces with respect to the geometrical arrangement and the
electrical current feeding the electrodes. The goals of this approach are
flow stabilization, drag reduction or manoeuvrability of the body in an
electrically low-conducting fluid like seawater.

Experimental and numerical results of our research programme will be
presented. Experiments were performed using a copper sulfate electrolytic
solution, a sodium hydroxide loop and large saltwater channels available at
a shipbuilding research center in Hamburg. A strong flow control has been
confirmed. The energetic limitations of the approach will be discussed

The synthesis and in vitro autoradiography of a novel Tc-99m ligand with subnanomolar affinity to the 5-HT_2A receptor is reported. The complex combines the 4-(4-fluoro)-benzoyl piperidine portion derived from the 5-HT_2A receptor antagonist ketanserin with a neutral oxotechnetium(V) chelate in form of a mixed ligand "3+1" unit containing the SNS/S donor set. The analogous rhenium compound has been synthesized as a surrogate for the Tc-99m complex for use in receptor binding assays and for complete structural characterization.
In competition experiments the Tc-99 complex as well as its Re analogue display subnanomolar affinity towards the 5-HT_2A receptor (K_i 0.44 nM for Tc, 0.25 nM for Re).
The subnanomolar 5-HT_2A receptor binding of the Re complex was confirmed by functional in vitro antagonism of contractile effects evoked by 5-HT in rat arterial tissue. Re 1 inhibited 5-HT-induced, 5-HT_2A receptor-mediated contractions of isolated rat tail artery in a competitive fashion and possessed nanomolar affinity (pA₂ = 9.08). Like ketanserin, Re 1 displayed moderate affinity for adrenergic alpha_1D (pA₂ = 8.23) and histamine H₁ receptors (pA₂ = 8.00), and was >600fold up to 10,700fold less active at several neurotransmitter receptor subtypes.
Autoradiographic studies clearly indicate the accumulation of the Tc-99m compound in 5-HT_2A receptor rich areas of the brain. This enrichment can be blocked by 5-HT_2A receptor antagonists such as mianserin and ketanserin and is therefore specific.

A novel technique has been developed to measure the local velocities in opaque liquid flows such as liquid metals. The measuring principle is based on the separation of a direct mechanical interaction between flow and sensor tip and the optical acquisition and processing of the signal. In principle, this fact allows the extension of the range of applicability to higher temperatures. Furthermore, the insensitivity of the system to electrical noise and external magnetic fields can be considered as an
important advantage. Until now, the sensor has been tested in metallic melts up to temperatures of about 350 °C. We present measurements of the local velocity obtained in an eutectic InGaSn melt driven by a rotating magnetic field.

The nodal expansion method HEXNEM presented here bases on the transverse integration in axial direction and over the hexagonal plane of the nodes. For that, the 3-dimensional problem is split into a 2-dimensional problem in the hexagonal plane and a 1-dimensional problem in the z-direction. The 2-dimensional hexagonal problem is solved by an expansion of the neutron flux using two-dimensional polynomials and exponential functions being the solutions of the homogeneous equation. The transversal leakage term and the fission and scattering sources are approximated by the polynomials. To improve the accuracy, the method is not only based on the side averaged fluxes and currents but also on the corner point values. An analogous flux expansion is used for the solution of the 1-dimensional equation in axial direction. An inner and outer iteration procedure is applied to the solution of the problem. This method leads to an improvement of the accuracy against the simpler method implemented in the code DYN3D. It is shown by comparing the results with reference solutions of 2- and 3-dimensional benchmark problems.

During a hypothetical break of a BWR feed water line, the feed water distributor (FWD) inside the RPV is subjected to a high pressure load for a short time (10 ms). Because of the sudden coolant release from the inner volume of the FWD there is a pressure difference between the inner and outer surface. It is conservatively assumed that the pressure difference nearly can reach the operating pressure for a few milliseconds. The distributor box and the ring line of the feed water distributor are modelled with shell and volume elements capable of being used for large strain analyses with elastic-plastic material behaviour. It is demonstrated by non-linear static calculations (without consideration of the inertia of the material) that a buckling instability occurs at about 60% and 80% of the maximum pressure load. The arc-length method is used for the numerical solution to overcome these points of instability. To evaluate the influence of the dynamics of the process a non-linear transient analysis is done showing that the maximum strain occurs with a time delay to the pressure peak. The maximum plastic strain differs only insignificantly between static and transient solution. Inspite of the large strains the mechanical integrity is maintained during the hypothetical event.

The master curve concept allows to determine limit curves of fracture toughness for defined failure probabilities and a reference temperatures based on it. Thus fracture mechanical values can be supplied for the stress analysis. This paper presents the application of the master curve concept for the determination of the reference temperature over the thickness of a plate of RPV steel. It was shown that the master curve concept is applicable for the fracture mechanical characterisation of material in different conditions using small test specimens. A special problem with the use small specimens is the definition of the test temperature, at which fracture toughness values can be determined within the validity limits. It became clear that the criteria for definition the test temperature and the minimum number of specimens indicated in the ASTM E1921-97 standard are applicable and sufficient respectively only for homogeneous materials.

The problem of velocity reconstruction in conducting fluids from measurements of induced magnetic fields and electric potentials is discussed in spherical geometry.
Under the special case that the externally applied magnetic field is uniform and homogeneous throughout the fluid, the non-uniqueness problem is treated in detail. Assuming kinetic energy minimization for the moving fluid it is shown that the velocity field can be reconstructed completely.

In der vorliegenden Arbeit wird der Einsatz von Positronenemittern zur Bestimmung der Dichte eines zweiphasigen Mediums beschrieben. Zur Messung wird die Dichteabhängigkeit der Positronenreichweite ausgenutzt. Die Realisierbarkeit des Verfahrens wird zunächst in einer Computersimulation geprüft. Danach werden Experimente an einem hochauflösenden PET-Scanner vorgestellt. Bei diesen Experimenten wird die Dichteabhängigkeit der Reichweite von Positronen anhand von Modellmedien aus festen Schaumstoffen untersucht. Dabei werden die in der Computersimulation erzielten Ergebnisse bestätigt. Aus den experimentellen Ergebnissen wird ein Modell zur Beschreibung der Abnahme der Koinzidenzrate in Abhängigkeit von der Entfernung des Detektors von der Positronenquelle und der Mediendichte entwikkelt. Auf der Basis des Modells erfolgt die Konzipierung einer für die Dichtemessung optimierten Detektoranordnung. Die Funktionsweise dieses Detektorsystems wird in Form technischer Unterlagen und experimenteller Ergebnisse beschrieben. Mit dem optimierten Detektorsystem werden die Untersuchungen an den Modellmedien nochmals durchgeführt, wobei die bisherigen Ergebnisse bestätigt werden.

Das beschriebene Meßverfahren dient der Bestimmung der mittleren Dichte in einem überwiegend gasförmigen Medium, wobei eine Mittelwertbildung über das Meßvolumen erfolgt. Das Verfahren kombiniert die Vorteile bekannter densitometrischer Meßmethoden auf der Basis einer Schwächung von Strahlung, indem die hohe Dichtesensitivität der Positronenstrahlung mit der relativ geringen Absorption der energiereichen Annihilationsquanten kombiniert wird.

Uranium can occur in reducing phosphate-containing environments as uranium(IV)-hadrogenphosphate, U(HPO4)2.4H2O. No thermodynamic complex formation constants are available for the uranium(IV)-phosphate complexes because of their low water solubility. For example, the solubility product /1/ of U(HPO4)2.4H2O limits the uranium(IV) concentration in 1 M perchloric acid to less than 1.2 x 10-4 M. We studied the formation of this complex at uranium concentrations between 2x10-6 M and 1x10-4M by Laser-Induced Photoacoustic Spectroscopy in acid media. To determine the complex formation constant we measured and analyzed the spectra from 610 nm to 690 nm. The spectra were corrected for the absorption of the solvent water. The solvated uranium(IV) shows a very intensive absorption band with a maximum at 649.8 nm and a smaller maximum at 671.9 nm. We found a shoulder at 630.0 nm by deconvoluting the absorption spectrum. The spectrum changes with increasing phosphate concentration. At a total phosphate concentration of 1.5x10-3M, we found maxima at 656.6 nm and 667.0 nm. Additionally a shoulder at 645.0 nm is found. Two isosbestic points were determined at 661.4 nm and 669.4 nm. Results will be presented for the determination of the formation equilibrium and the complex formation constant(s).

A large variety of bacteria was demonstrated to be present in soil and sediment samples of a uranium waste pile in Saxony, Germany. Anaerobic sulfate-reducing bacteria belonging to the genus Desulfovibrio were found among them. The study of these bacteria, which are also known to reduce U(VI), is of great importance for the development of bioremediation procedures for decontamination of the environments polluted with uranium. The indigenous for the waste Desulfovibrio isolates were classified by the use of Amplified Ribosomal DNA Restriction Endonucleases Analysis (ARDREA), Random Amplified Polymorphic DNA (RAPD), Repetitive Primer Amplified Polymorphic DNA (rep-APD), 16S rDNA Sequencing, and as well as with classical microbiological methods.
Using 16S- and IGS-ARDREA the pile isolates were phylogenetically affiliated to Desulfovibrio vulgaris (oxamicus). The RAPD and rep-APD analyses have demonstrated a close genomic relationship between the pile isolates, but D. vulgaris (oxamicus) 1925T was not closely related to them. These results are in agreement to the taxonomic characterization of the strains by comparison of the fatty acid spectra.

In natural bioleaching systems autochtonic microorganisms are involved in the solubilization of metals from solid minerals. The widest spreaded mesophilic group of bioleaching microorganisms are the chemolithoautotrophic bacteria Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans.
From the soil samples of different sites and depths of a former uranium mine in Saxony, Germany, several Thiobacillus strains were cultured. They were classified by the use of the amplified ribosomal DNA restriction enzyme analysis (ARDREA). The genomic organization of the strains was investigated using random amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE).
All strains were affiliated to the species T. ferrooxidans. Moreover, it was possible to distinguish members belonging to the two closely related phylogenetic groups of the species - one related to the reference strain T. ferrooxidans ATCC 33020 (recovered from a uranium mine) and a second one, related to the strain 21834 (recovered from a coal mine).
By the use of the RAPD and PFGE fingerprinting methods it was demonstrated that the strains recovered from different depths differ in their genomic organization.

Bacterial diversity in subsurface soil samples drawn from different depths of several uranium waste piles was studied using the 16S rDNA retrieval. Extremely high diversity was found in all samples investigated. In particular, the presence of several dominant 16S rDNA groups related to the genara $\I Thiobacillus, Bacillus, Pseudomonas, Desulfovibrio $$END was demonstrated. One of these 16S rDNA groups was affiliated to the species $\IT. ferrooxidans$$END. Interestingly, this group includes three 16S rDNA types which possess slightly different sequences. Strains of $\IT. ferrooxidans$$END corresponding to two of the mentioned three 16S rDNA types were recovered from two soil samples polluted in different extend with heavy metals. The two groups of isolates have different genomic organization. In addition, the members of the group recovered from the more polluted sample are tollerant to higher concentrations of uranyl ions which are lethal for the isolates of the second group. The expression of at least three genes of the U-tolerant strains is influenced by by the presence of uranyl ions in the nutrient medium. The capability of the U-mine isolates to interact with U(VI) was studied, and it was found that they accumulate significantly higher amounts of U(VI) in comparison to several reference $\IT. ferrooxidans$$END strains recovered from other environments. Using time-resolved laser fluorescence spectroscopy it was shown that the complexes build by one of the U-waste isolates with U(VI) are much stronger than those build by the reference strains. This is the first report which demonstrates a microdiversity in closely related natural isolates of $\IT. ferrooxidans$$END. We suggest that the microdiversity obsrved reflects the genetic adaptation of the strains studied to the different heavy metal concentrations in their natural environments.

A large variety of bacteria was demonstrated to be present in soil and sediment samples of a uranium waste pile in Saxony, Germany. Anaerobic sulfate-reducing bacteria belonging to the genus Desulfovibrio were found among them. The study of these bacteria, which are also known to reduce U(VI), is of great importance for the development of bioremediation procedures for decontamination of the environments polluted with uranium. The indigenous for the waste Desulfovibrio isolates were classified by the use of Amplified Ribosomal DNA Restriction Endonucleases Analysis (ARDREA), Random Amplified Polymorphic DNA (RAPD), Repetitive Primer Amplified Polymorphic DNA (rep-APD), and 16S rDNA Sequence.
The 16S and IGS rDNA retrieval allowed us to affiliate the natural Desulfovibrio isolates to the subspecies Desulfovibrio vulgaris (oxamicus). Using RAPD and rep-APD analyses, the natural isolates were grouped in particular cluster which was not very closely related to the type strain D. vulgaris (oxamicus) 1925T. Results demonstrating the capability of the uranium waste isolates to reduce U(VI) to U(IV) will be presented.

Bacterial diversity in soil samples drawn from different depths of several uranium waste piles was studied using 16S rDNA retrieval, RISA and rep-APD. Extremely high diversity was found in all samples investigated. Several dominant 16S rDNA groups related to the genera Thiobacillus, Bacillus, Pseudomonas, and Desulfovibrio were demonstrated. One of these groups was affiliated to the species T. ferrooxidans. This group includes three 16S rDNA types with slightly different sequences. Strains of T. ferrooxidans corresponding to two of the mentioned three 16S rDNA types were recovered from two samples of the waste polluted in different extend with heavy metals. The interactions of the natural T. ferrooxidans strains with U(VI) were group-specific. Microdiversity at the level of 16S- and IGS-rDNA was found also among the group of the uranium reducing Desulfovibrio waste isolates. The latter were affiliated to Desulfovibrio vulgaris subspecies oxamicus. These natural isolates are able to reduce more effectively higher amounts of U(VI) than the reference Desulfovibrio strains. In contrast to the reference strains, the waste isolates reduce U(VI) to U(IV) independently of the pH range of the medium. This is the first report demonstrating microdiversity of closely related natural isolates of T. ferrooxidans and D. vulgaris subsp. oxamicus. We suggest that the microdiversity observed reflects the genetic adaptation of the strains studied to the different heavy metal concentrations in their natural environments.

In the natural bioleaching systems autochtonic microorganisms are involved in the solubilization of metals from solid minerals. The widest spreaded mesophilic group of bioleaching microorganisms are the chemolithoautotrophic bacteria Thiobacillus ferrooxidans, Thiobacillus thiooxidans, and Leptospirillum ferrooxidans.
From soil samples drawn from two particular sites of a former uranium mine in Saxony, Germany, which were polluted in different extend with heavy metals, several Thiobacillus strains were cultured. Using ARDREA the strains were classified in two uranium-waste-site-specific 16S rDNA subgroups of the species Thiobacillus ferrooxidans. Moreover, RAPD and PFGE analyses have demonstrated that the natural T. ferrooxidans isolates possess also group-specific genomic organization. The strains from the more polluted sample were tolerant to higher concentrations of uranyl ions which were lethal for the isolates of the second group. In these strains the expression of at least three genes was influenced by the presence of uranyl ions. The uranium binding capability of the uranium mine isolates was strain-specific and higher than those of the reference T. ferrooxidans strains recovered from other environments.

About 160 uranium minerals are known. Although many of these minerals show fluorescence properties, detailed fluorescence spectra are not published in the literature. We studied the fluorescence properties of 120 uranium minerals in order to provide a data base of potential solids that may form in the flooding process of defunct uranium mines.

Humic acids influence the speciation and migration behavior of actinide ions in the environment. Due to their complex and heterogeneous nature, a thermodynamically based description of their complexation behavior with metal ions is difficult. Numerous uncertainties exist in the description of the complexation process, e.g., the kind and number of complexing functional groups is uncertain.
We are investigating the influence of different functional groups on the complexation behavior of humic acids to improve the understanding of the humic acid - metal ion interaction. Such information is very important for a more precise modeling of geochemical processes in the presence of humic acids.
We synthesized and characterized synthetic and natural humic acids with blocked phenolic hydroxyl groups. With these humic acids, we investigate the influence of phenolic hydroxyl groups on the complexation behavior of humic acids with UO22+ ions. The investigations were carried out by laser-induced fluorescence spectroscopy and FTIR spectroscopy.
For the first time, we compared the complexation behavior of a modified and non-modified synthetic humic acid with UO22+ ions at pH 4 by laser-induced fluorescence spectroscopy. The spectroscopic results show that the blocking of the phenolic hydroxyl groups changes the interaction behavior between the humic acid and the UO2 2+ ion.

Organic materials, such as humic and fulvic acids, that are present in natural aquifers interact with dissolved inorganic contaminants and affect their sorption behavior on geological materials and thus, their migration in aquifers. Consequently, a quantification of the influence of humic material on radionuclide sorption is necessary.
Phyllite was used as site-specific rock material because it is quite common in the Western ‘Erzgebirge' in Saxony, Germany, and is closely associated with uranium deposits of the uranium mining areas in East Germany. Site specific humic acid, isolated from the bog ‘Kleiner Kranichsee' and a 14C-labelled synthetic humic acid were used for the experiments.
The effect of humic acid was studied on the sorption behavior of uranium(VI) onto phyllite and its mineralogical components muscovite, albite and quartz in air-equilibrated batch experiments as a function of pH. The uranium sorption is strongly affected by both the pH and the presence of organic material. The kinetics and reversibility of the uranium and humic acid sorption were studied using the 14C-labelled humic acid. Furthermore, the influence of competing sulfate ions on the uranyl and humic acid sorption onto phyllite was determined, because seepage waters of the uranium mining areas in Saxony contain, among other anions, relatively high concentrations of sulfate (3 10-2 M).

Beim Schließen einer schnellwirkenden Absperrarmatur in einer Rohrleitung, in der eine Flüssigkeit strömt, kann es zu Kavitationsschlägen kommen. In vielen technischen Anwendungen ist ein möglichst rasches Absperren von Rohrleitungen erforderlich, insbesondere wenn es um die Beherrschung von Störungen geht. Es wird eine Methode zur Verhinderung des Kondensationsschlages vorgeschlagen. Sie besteht in der Einführung einer Hilfsarmatur, die sich hinter der eigentlichen Absperrarmatur befindet. Diese Hilfsarmatur wird zu dem Zeitpunkt geschlossen, an dem die Kavitationsblase ihre größte Ausdehnung in der Rohrleitung erreicht hat. Die Blase wird dadurch zwischen den beiden Armaturen eingeschlossen und so am Kollabieren gehindert. Im Vortrag werden die Meßergebnisse vorgestellt, die Rohrleitungs-Versuchsfeld von Fraunhofer UMSICHT mit Zweiphasen-Meßtechnik aus Rossendorf erhalten wurden. Die Auslegungskriterien für eine solche Anordnung werden diskutiert.

The first synthesis of 1-(1,2-dihydro-2-acenaphthylenyl)piperazine (5) – a new arylpiperazine is described. Preliminary binding studies on this new arylpiperazine reveal affinity for the 5-HT_1A and 5-HT_2A receptor subtypes. Incorporation of a dopamine pharmacophore onto this arylpiperazine provided compound (7) a potential antipsychotic with an atypical profile.

In a systematic experimental study of K$^{+}$ and K$^{-}$ production at energies close to and below the free nucleon-nucleon production threshold we have found several features indicating a change of kaon properties within the nuclear medium.

Plasma immersion ion implantation (PIII) on an industrial scale requires negative high voltage pulses in the kA range with voltages up to 200 kV. Hence, the equipment to produce suitable high voltage pulses is rather expensive and shares a considerable part of the total costs of PIII equipment. Reducing the costs of equipment is therefore still a challenge to promote the commercial use of PIII.
A new high voltage modulator is presented, which will meet the above requirements.
The basic idea of the new modulator is that in case of two floating electrodes, immersed into a plasma and connected to both plates of a charged capacitor, the anode potential will be close to the plasma potential, whereas the cathode potential will become negative compared to the plasma potential.
The new modulator works as a triode system, consisting of anode, cathode and grid, all located inside of the working chamber. The plasma is discharged between cathode and grid. As usual in PIII, the sample is immersed into the plasma and works as the cathode in the system. The grid is mounted between plasma and anode, in such a way that ions or electrons from the plasma can get to the anode by passing the grid plane only. Further a capacitor is connected to anode and cathode with both plates and the anode is additionally linked to a positive high voltage source. If the grid is negatively biased, the anode is isolated from the plasma, as electrons from the plasma are reflected by the grid bias, whereas the ions are reflected by the positive potential of the anode. As far as the grid is negatively biased the cathode is at plasma floating potential, and the capacitor may be charged by the positive high voltage source to the capacitor voltage. When the grid potential is switched to ground potential electrons from the plasma can reach the anode and will shift the anode potential to plasma potential. At the same time the cathode is switched to negative high voltage potential .
As the performance of the integrated modulator depends on the maximum of the electron current which can be extracted from the plasma by the anode, the basic considerations concerning the anode current and the revealing design parameters of the integrated modulator are given. The experimental results of modulating 20 kV at a maximum current of 4 A confirm the theory.

In Sachsen waren Ende 1998 Windenergieanlagen (WEA) mit einer installierten Leistung von etwa 140 MW in Betrieb. Als entscheidend für die sehr dynamische Entwicklung ist der in den letzten 10 Jahren erreichte technologische Stand der WEA anzusehen, der wesentlich durch die erreichte Leistungsgrößen (1,5 MW) und die Turmhöhen (60 m bis 80 m) sowie den Übergang zur Serienfertigung charakterisiert wird. Durch die damit verbundene Kostenreduktion steht die Windenergietechnik heute an der Schwelle zur Wirtschaftlichkeit.
Das auf der Basis eines mehrjährigen Meßprogramms ermittelte Windenergiepotential Sachsens liegt mit etwa 5 TWh bei 30 % des sächsischen Stromverbrauches. Bei einem Lastfaktor von 20 % entspricht dies einer installierten Leistung von etwa 3000 MW.
Die Auswertung der monatlichen Erträge von sächsischen WEA bestätigt den angegebenen Lastfaktor im Mittel. Die beobachteten Ertragsunterschiede zwischen einzelnen Standorten von mehr als dem Faktor 2 zeigen die Notwendigkeit, der Standortbewertung größere Aufmerksamkeit zu schenken. Hier besteht weiterer Forschungsbedarf.

The synthesis of the new and highly reactive ¹¹C-precursor triphenylarsonium [¹¹C]methylide 1 and its conversion into [2-¹¹C]indole 6 is described. [¹¹C]Methyltriphenylarsonium iodide 4 was prepared by quaternization of triphenylarsine 2 with [¹¹C]methyl iodide 3 in a THF/DMSO mixture or ethanol. Starting from 3 [¹¹C]methyltriphenylarsonium iodide 4 was obtained in a decay-corrected radiochemical yield of 55%-64% depending on the reaction solvent. The arsonium ylide 1 was prepared in situ by treatment of 4 with butyllithium. Conversion of 1 with o-aminobenzaldehyde 5 in THF/DMSO mixtures yielded [2-¹¹C]indole 6 in radiochemical yields of 23-27% (decay-corrected, in relation to 3). Preparation of 6 was completed after 15 – 20 min (starting from 3). The specific radioactivity of 6 was about 37 GBq/µmol (1 Ci/µmol, related to EOB).

Im Vortrag werden ausgewählte Ergebnisse des 1000-Dächer-Programms zusammengefaßt, die für den Entwurf und die Energieerträge künftiger netzgekoppelter Anlagen relevant sind. Eine kritische Auswertung der Ergebnisse im hier relevanten Leistungsbereich (1-5 kWp) führt relativ zwangsläufig zum Konzept der Einstrang-Anlage. Der DC-Trennschalter kann - ebenso wie die Überspannungsableiter - in das Netzeinspeisegerät integriert werden. Ein künftiges integriertes Netzeinspeisegerät sollte neben dem Wechselrichter noch eine Diagnose- sowie Anzeigeeinheit, die neben Strom-, Spannungs-und Leistungswerten mittels eines einfachen Solarimeters das Performance Ratio errechnet und anzeigt, enthalten. Neben dem Anlagenkonzept ist die Auswahl der Komponenten entscheidend für die erreichbaren Erträge. Bei Nutzung von Modulen mit garantierter STC-Leistung und von Wechselrichtern mit hohem Jahresnutzungsgrad kann ein jährlicher Ertrag von 800 bis 850 kWh pro installierte Generatorleistung von 1 kW erwartet werden. Eine Anlage mit einer Leistung von 5 kW kann demnach den Bedarf eines Durchschnittshaushaltes rechnerisch decken.

Estradiols are able to form two monosulphamates and one disulphamate. In the present work all the sulphamates of 17alpha-estradiol, 17beta-estradiol and 16alpha-fluoroestradiol were synthesized and characterized. For characterization NMR spectroscopy was used first of all. Because of its high sulphatase inhibitory efficiency and 16alpha-fluoroestradiol-3,17beta-disulphamate found a special interest among the new sulphamates. Just the binding between sulphamate and sulphatase favoured 16alpha-[¹⁸F]fluorestradiol-3,17beta-disulphamate to a new radiopharmaceutical which should be appropriate to image the active sites of sulphatase by positron emission tomography. The preparation of 16alpha[¹⁸F]fluoroestradiol-3,17beta-disulphamate requires a simple and rapid procedure. The conditions for such a procedure were also elaborated using non-radioactive substances.

2^nd Workshop on Kaon Production
During the fall of 1996 an internal mini-workshop on kaon production was organized at Rossendorf (cf. FZR-150 [September 19961). The aim of this first workshop was to give a survey on the experimental and theoretical Status of kaon production in elementary hadron reactions and in heavy-ion collisions. Since then the Department of Hadron Physics in the Institute of Nuclear and Hadron Physics of the FZR focused in its research activities on nearthreshold strangeness production in colliding hadron systems and on activities devoted to studies with electromagnetic probes.
Since 1996 a considerable Progress has been achieved in the field. New results from COSY (COSY-11, ToF, COSY-13 and first runs at ANKE) as well as SIS (KaoS and FOPI) allow to determine various elementary cross sections in hadron reactions and kaon yields from heavy-ion collisions. These new results led us to organize a second workshop bringing together the experts of these experiments and various theoreticians. An important purpose of the workshop was to enforce the mutual information and to demonstrate the close interrelation of COSY physics and the heavy-ion programme at SIS. Highlights in the field are (i) the consolidation of the need of strong in-medium modifications to describe the K^- production in heavy-ion reactions and (ii) refined measurements of various elementary strangeness channels near threshold. For the latter the role of final state interactions must be clarified ta arrive at a unique input to transport-model calculations for heavy-ion reactions. Many experimental aspects included in the programme have been proposed by P. Senger (GSI), whereas the composition of its theoretical part benefitted a lot from the support by J. Aichelin (Nantes).

Ausgehend von einer Untersuchung der Einbettung des Urans in die Sedimente, konnte für das Radium abgeleitet werden, daß es wesentlich durch Sorption gebunden in der Matrix vorliegt. Gestützt wird dies durch Freisetzungsuntersuchungen, die bei den vererzten Gesteinen und bei mit Ra beladenen Sedimenten eine Anbindung überwiegend durch Ionenaustausch an tonige Bestandteile ausweisen. In den gelaugten Sedimenten dagegen erfolgt eine Freisetzung von Ra- und Ba-Ionen durch Komplexbildner, was für deren gemeinsame sulfatische Ablagerung spricht.
Für die wäßrigen Phasen ist charakteristisch, daß in den Laugungs- und Flutungslösungen ein Sättigungszustand bezüglich des Bariumsulfats vorliegt, der Ursache für eine Radiumfreisetzung im Verlaufe des Flutungsprozesses ist.
Für die Radiumsorption an den Sedimenten wurden in mehreren Serien Verteilungsverhältnisse bestimmt, die die Grundlage sowohl für eine Abschätzung der Radium-entwicklung in der Flutungslösung (< 50 Bq/l bei Einstauende) als auch der Modellierung der Transportprozesse beim Aufstieg kontaminierter Wässer in den 3. Grundwasserleiter bildeten.
Migrationsuntersuchungen an kleinen Laborsäulen unter Anwendung der Drainagelösung ergaben beim Sandstein eine höhere Mobilität als aus den Batch-Untersuchungen zu erwarten war. Im Falle des Pläners und Tonsteins entsprach das Retardationsverhalten den Ergebnissen der Verteilungsuntersuchungen.
Eindimensionale Transportmodellierungen unter Anwendung der experimentell bestimmten Verteilungsverhältnisse ergab kurze Ausbreitungsstrecken im Grundwasserstauer unter den Bedingungen der Drainagelösung und einen Anstieg der Migrationsdistanzen im 3. Grundwasserleiter beim Übergang von der Drainagelösung zum Grundwasser, wobei eine maximale Transportstrecke von 1.5 km resultiert.

Mit Bezug auf die Stillegung und Sanierung der Uranbergwerke Schlema-Alberoda im Westerzgebirge und Königstein im Elbsandsteingebirge wurde (1) der Abbau des Grubenholzes im Kontakt mit dem Flutungswasser und (2) der Einfluß der gelösten
organischen Holzabbauprodukte auf den chemischen Zustand, die Sorption und das Ausbreitungsverhalten von U(VI), Th(IV), Pb(II) und Fe(III) grundlegend untersucht.

Fe/Al multilayers are prepared by crossed-beam pulsed laser deposition and investigated by Rutherford backscattering, conversion electron Mössbauer spectroscopy and transmission electron microscopy. The
results are compared with purely ballistic simulations of the deposition process using the TRIYDN4.0 code. It is found that the intermixing of adjacent layers must be decribed in terms of ballistic mixing followed
by chemical mixing. The phase build-up in the transition layer between adjacent layers follows the non-equilibrium behaviour of Fe/Al in analogy to investigations on mechanically alloyed and ion-beam mixed Fe/Al. In
Fe-rich areas a bcc-solid-solution is formed. In Al-rich environment an amorphous phase is observed.

Außerhalb und innerhalb eines Gefäßes wird Schall gemessen. Der Quotient aus den Fourier-Spektren beider Signale ist unabhängig von der Schallquelle. Dieser Quotient wird deshalb ausgenutzt, um den Füllstand im Gefäß zu klassifizieren.

Noise is measured inside and outside of a vessel. The quotient of the Fourier-spectra of both signals is independent of the source of noise. That's why the quotient is used to classify the content level in the vessel.

Vertical two-phase flow is normally classified into the four basic flow regimes bubble, slug, churn and annular flow. The transition between the different flow regimes does not occur suddenly and many extensions of this classification can be found in literature. For the prediction of flow patterns empirical and theoretical flow pattern maps have been developed.
A new criterion is presented for the transition between bubble and slug flow which is based on local instantaneous conductivity measurements with a wire mesh sensor (1 kHz that means 1000 frames per second, 242 measuring points in a tube cross section area). The high resolution allows the calculation of particle size distributions.

The transition from homogeneous bubble flow to heterogeneous bubble flow is indicated by the appearance of a bimodal bubble size distribution. If the equivalent bubble diameter exceeds the tube diameter the transition from bubble to slug flow occurs. The new criterion is compared with different empirical (Govier & Aziz, Weisman & Kang) and theoretical flow maps (Taitel, Bornea & Dukler, Ishii & Mishima) and shows a good agreement.

We have investigated the complexation behavior of natural humic acids (HA) with model substances. Our synthetic HA model substance, prepared from glutamic acid and xylose, shows operational properties comparable to those of natural HA in terms of water solubility at different pH and in the type and number of its functional groups. We investigated its complexation behavior with the UO₂ ²⁺ ion by time-resolved laser-induced fluorescence spectroscopy. For comparison, we used purified natural HA from Fluka and Aldrich. The experimental data were evaluated applying the metal ion charge neutralization model developed by Kim and Czerwinski. For our synthetic product, we determined a loading capacity of 23 ± 4 % and a complexation constant of log beta = 6.16 ± 0.22 (pH 3.90 ± 0.05; I: 0.1 M NaClO₄). The obtained values are comparable with experimental results determined for Fluka and Aldrich HA. These results lead to the conclusion that our synthetic product appropriately models the functionality of natural HA.

The report gives an overview on the scientific work of the Institute of Safety Research in 1997.

Dieser Bericht ist für mit den Grundlagen der Monte-Carlo Methode vertraute Leser bestimmt. Von Interesse für solche Leser könnten erfolgreiche Verallgemeinerungen und neue Ideen zur Verbesserung der statistischen Fehler sein. Andrerseits sollen die wichtigsten Grundlagen des Vielgruppen-Monte-Carlo Programms TRAMO dargestellt und das Programm einschließlich notwendiger Eingabe so weit beschrieben werden, daß man nach in jedem Fall notwendige Anpassung an die spezielle Rechentechnik eine wesentliche Grundlage für die Durchführung eigenständiger Rechnungen hat.
Für die meisten Probleme unumgängliches Hilfsmittel für TRAMO ist ein Programm, welches für die Anwendung der varianzreduzierenden "Weight Window Method" die notwendigen Gewichte berechnet (Monte-Carlo Programm TRAWEI), sowie Programme zur Erzeugung der Neutronenquerschnittsdaten und Gruppendaten.
Das Programm TRAMO berechnet bei gegebener Quellverteilung von Neutronen in Vielgruppennäherung Vielgruppenflüsse, integrierte Gruppenflüsse und Dosiswerte für vorgegebene Teilvolumina und Flächen. Es gibt weitere Programmversionen zur Berechnung von Neutronen- und Gammaflüssen sowie zur Kritikalität, welche jedoch nicht Gegenstand dieses Berichtes sind.
Das Vorläuferprogramm von TRAMO war das Programm SMO [1]. Eine fortgeschrittene Version, bereits unter dem Namen TRAMO, wurde in [2] dargestellt. Das hier beschriebene Programm ist wesentlich verallgemeinert und verbessert, umfangreich getestet und für eine große Zahl von Problemen angewendet worden, vor allem für Abschirmungsberechnungen und für Berechnungen von Neutronenfluenzen (siehe [3-5]).
Die oben erwähnten Voraussetzungen für die Nutzung des Programms sind die Bereitstellung von Gruppendaten (Nutzung des international gebräuchlichen Programms NJOY und eigenen Programmen, siehe Abschnitt 1 bzw. 6), die Berechnung von geeigneten Gewichtsfunktionen (Monte-Carlo Programm TRAWEI, siehe Abschnitt 3 bzw. Abschnitt 5) und die genaue Kenntnis der im Programm TRAMO gegebenen Möglichkeiten.
In Abschnitt 1 wird auf die Versorgung mit Neutronendaten eingegangen, Abschnitt 2 beschreibt die Möglichkeiten von TRAMO, in Abschnitt 3 werden die varianzreduzierenden Methoden beschrieben, vor allem wird hier auf die Grundlagen des Programms TRAWEI zur Berechnung der Gewichte ("Weight Window Method") Bezug genommen.
Abschnitt 4 gibt eine Eingabebeschreibung des Programms TRAMO, in Abschnitt 5 wird auf die Handhabung von TRAWEI eingegangen, und Abschnitt 6 befaßt sich mit Programmen zur Neutronengruppendatenerzeugung bzw. abgeleiteter Größen in einem für das Programm TRAMO geeigneten Format und in 7 wird auf das Hilfsprogramm SUMMA zur Zusammenfassung von Ergebnissen bei Anwendung von Parallelrechnung eingegangen.

Betrachtet werden Prozesse, in denen Teilprozesse voneinander abgrenzbar sind, die unabhängig voneinander zur Komplexität des Prozeßmodellfehlers beitragen. Auf der Grundlage von Dimensionsbetrachtungen wird versucht, die zu den Teilprozessen gehörenden Teilmodelle, d.h. die Elemente der Modellstruktur des Prozesses einzeln zu bestimmen. Ein Gesamtmodell des Prozesses soll auf diese Weise zielgerichteter als mit herkömmlichen Methoden gebildet werden können. Zur qualitativen Erfassung des Modellfehlers wird anhand von Ansätzen aus der Dimensionsanalyse, einem Bestandteil der Ähnlichkeitstheorie, ein Fehlermodell definiert. Zur quantitativen Erfassung der Komplexität des Modellfehlers werden dimensionsähnliche Kenngrößen eingeführt, die von einer Variante der fraktalen Dimension, der Zirkel- oder Liniendimension ausgehen.

Abstract.
The elastic backward proton-deuteron scattering is analyzed within a covariant approach based on the Bethe-Salpeter equation with realistic meson-exchange interaction. Contributions of the one-nucleon and one-pion exchange mechanisms to the cross section and polarization observables are investigated in explicit form. Results of numerical calculations for the cross section, tensor analyzing power and spin transfers are presented. The one-pion exchange contribution is essential for describing the spin averaged cross section, while in polarization observables it is found to be less important.

The genus Bacillus consists of more than 70 species of Gram-positive, aerobic or facultatively anaerobic spore-forming rod-shaped bacteria. Because of the high resistance of their spores, Bacilli were found in a large variety of natural habitats. For our accumulation studies with U(VI), we used vegetative cells and spores of three Bacillus isolates (JG-A 30, JG-A 12, JG-A 22, classified as Bacillus cereus, Bacillus sphaericus, Bacillus megaterium) from a uranium mining waste pile (Johanngeorgenstadt, Saxony) and their corresponding reference strains. Sorption studies at pH 5.0 have shown that in the concentration range examined (11 – 214 mg/L) Bacilli accumulate high amounts of uranium. Information on the binding strength and the reversibility were obtained from extraction studies with different extractants. With 0.01 M EDTA solution the uranium bound to the biomass was released almost quantitatively. The characterization of the bacterial-UO22+-complexes by time-resolved laser fluorescence spectroscopy (TRLFS) has proved the formation of inner-sphere complexes with the biomass. At pH 5 a ternary complex of uranyl with the biomass and hydroxide in solution was detected. After cell fractionation, we examined the spectroscopic properties of the U(VI)-complexes with the isolated cell walls and the isolated surface-layer protein fraction of the bacteria. Spectroscopic studies of these complexes have shown that with intact cells (vegetative cells or spores) the complexation of U(VI) is stronger than with isolated cell wall components. Therefore, the good complexation properties, the easy release of the bound uranium by EDTA-extraction, and the high resistance against harsh environmental conditions makes these bacteria applicable for bioremediation purposes.

Die zeitaufgelöste laserinduzierte Fluoreszenzspektroskopie (TRLFS) wird schon seit längerem als äußerst sensitive Methode zur Untersuchung der Komplexbildung von Radionukliden mit organischen und anorganischen Liganden eingesetzt. Hier sind insbesondere Untersuchungen an Uran(VI) und Cm(III) mit Huminsäuren zu nennen. Jedoch sind die bisher angewandte TRLFS-Techniken mit Anregungspulsen im Nanosekundenbereich nur auf Radionuklide mit Fluoreszenzeigenschaften beschränkt /1/. Die
Entwicklung und Anwendung einer TRLFS mit ultrakurzen Anregungspulsen, d.h. mit Pulsen im Pico- und emtosekundenbereich, eröffnet die Möglichkeit die Komplexbildung von nichtfluoreszierenden, umweltrelevanten Radionukliden, wie z. B. Neptunium, mit organischen Liganden über die Veränderung der Fluoreszenz-eigenschaften der Liganden zu untersuchen.
Ein erster Schritt für die Anwendung der TRLFS mit ultrakurzen Pulsen besteht im Aufbau eines solchen Lasersystem. Das neue Rossendorfer Lasersystem nutzt einen zweifach verstärkten Puls mit einer Pulsdauer von 130 fs eines mode-locked Ti:Sapphire Oszillators als Anregungspuls /2/. Die Auswahl der optimalen Anregungswellenlänge erfolgt über ein durchstimmbares estkörperlasersystem (OPA-System) zwischen 250 nm und 10 µm. Das Fluoreszenzlicht der Probe wird direkt in einen
Gitterspektrographen eingekoppelt, die Detektion des Fluoreszenzsignals erfolgt mit einer intensivierten CCD Kamera.
Zuerst wurden die Fluoreszenzeigenschaften (Fluoreszenzlebensdauer, Fluoreszenzintensität und -spektrum) von verschiedenen Huminsäuren untersucht. Dabei wurden die Probenparameter (pH-Wert, Konzentration,Ionenstärke) und verschiedene Systemparameter, wie z. B. Anregungswellenlänge, variiert. Das mit der bisherigen Lasertechnik sehr gut charakterisierte Komplexsystem Uran(VI) und Huminsäure /3/ wurde für eine Validierung des Femtosekunden-Lasersystems verwendet. Die
Ergebnisse der vergleichenden Messungen werden diskutiert.

A more detailed survey of modern methods for characterizing radionuclides and heavy metals in the environment and for elucidating the mechanisms of their interaction with biomolecules is given.
Laser-induced spectroscopies, including Time-Resolved Laser Fluorescence (TRLFS), Photoacustic (LIPAS), Thermal Lensing (LITLS) and Photothermal Deflection Spectroscopy (LIPDS) provide the identification of the chemical species of radionuclides and heavy metals in environmental media in concentrations down to the micro-molar range and even lower. This includes information on the oxidation state, the stöchiometry, and the structure of ions and dissolved complexes, including the discrimination between ionic and polynuclear or colloidal species that may preferentially be built with thorium, uranium and plutonium.
The complexes formed with the biomolecules as the result of the metal incorporation can be studied by X-ray absorption spectroscopies using synchrotron radiation, such as X-ray Absorption Near Edge Spectroscopy (XANES) and Extended X-ray Absorption Fine Structure. These methods give information on the valency and the coordination of the central ion as well as on the bond length to neighboring atoms, leading to an initial understanding of the spatial orientation and structure. This knowledge is essential to describe the interaction of radionuclides, such as U, Th, Ra, Np, Pu, Am, Cm, Zr, Sr, Cs and Tc with biomolecules and biomass. The selenium uptake by the soil bacterium Bacillus subtilis is cited as an example: from XANES spectra, the absorption process could be proved as an incorporation into the cell membrane under reduction of selenium(IV) to zerovalent selenium. From both the identified species and the characterized final complex, conclusions can be drawn regarding the overall absorption mechanism. These information are essential for selecting and optimizing biomolecular systems intended for environmental remediation purposes.

Mit Bezug auf die Flutung von Bergwerken im sächsischen Raum wurden die Redoxeigenschaften von natürlichen Polyelektrolyten, wie Holzabbauprodukten, Lignin und Huminsäuren und die Reduktion von Eisen(III) und Uran(VI) durch diese Polyelektrolyte untersucht. Außerdem wurde die Adsorption von Eisen(II,III) und Uran(IV,VI) aus Flutungswässern an grubentypischen Gesteinen und Sedimenten unter anaeroben Bedingungen bei Anwesenheit der organischen Substanzen untersucht. (Juni 1998)

Annual Report 1998
Institute of Radiochemistry

Der Rothschönberger Stolln ist der Hauptentwässerungsstollen des aufgelassenen Freiberger Bergbaureviers. An seinem Mundloch enthält sein Wasser etwa 1 mg/l an kolloidalen Partikeln des Größenbereichs 75 bis 300 nm. Die Partikel bestehen vor allem aus Eisen- und Aluminiumoxidhydroxid, tragen aber auch Spurenelemente (Pb, As, Cu, Y, La). Die Schadstoffe Pb und As z. B. sind im Rothschönberger Stolln nahezu vollständig an Kolloide gebunden. Das Uranium dagegen liegt in nichtkolloidaler Form (echt gelöst) vor; wahrscheinlich sind dafür Karbonatkomplexe des Uranylions verantwortlich. Nach Absenken des pH-Wertes auf etwa 5 (Zerstörung der Karbonatkomplexe) waren erhebliche Mengen des Uraniums an Kolloide gebunden. Letzteres besitzt Bedeutung für die Beurteilung des Verhaltens von Uranium in sauren Grubenwässern, wie z. B. in Wässern der Urangrube Königstein. Speziationsrechnungen mit Hilfe des thermodynamischen Geochemie-Rechenprogramms EQ6 stimmen zunächst schlecht mit den experimentellen Befunden überein. Die vom Experiment abweichenden Rechenergebnisse können jedoch leicht aus einer unzureichenden Berücksichtigung der Kinetik im chemischen Modell erklärt werden. Die Versuche zeigen Wege auf, wie Modellrechnungen mit EQ6 "praxisnäher" gemacht werden können.

The SWR1000 is a new innovative boiling water reactor concept, which is developed by Siemens AG. This concept is characterized in particular by passive safety systems (e.g. four emergency condensers, four building condensers, eight passive pressure pulse transmitters, six gravity-driven core flooding lines). In the framework of BWR Physics and Thermohydraulic Complementary Action (BWR-CA) to the EU BWR R&D Cluster emergency condenser tests were performed by Forschungszentrum Jülich at the NOKO test facility. In this paper post test calculations with ATHLET are presented, which aim at the determination of the removable power of the emergency condenser and its operation mode. The 1D thermal-hydraulic code ATHLET was extended by the module KONWAR for the calculation of the heat transfer coefficient during condensation in horizontal tubes. In addition, results of CFD-calculations using the code CFX-4 are presented, which investigate the natural convection during the heat up process at the secondary side of the NOKO test facility.

The condensation in horizontal tubes plays an important role e.g. for the determination of the operation mode of horizontal steam generators of VVER reactors or passive safety systems for the next generation of nuclear power plants. Two different approaches (HOTKON and KONWAR) for modeling this process have been undertaken by Forschungszentrum Jülich (FZJ) and University for Applied Sciences Zittau/Görlitz (HTWS) and implemented into the 1D-thermohydraulic code ATHLET, which is developed by the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH for the analysis of anticipated and abnormal transients in light water reactors.
Although the improvements of the condensation models are developed for different applications (VVER steam generators - emergency condenser of the SWR1000) with strongly different operation conditions (e.g. the temperature difference over the tube wall in HORUS is up to 30 K and in NOKO up to 250 K, the heat flux density in HORUS is up to 40 kW/m² and in NOKO up to 1 GW/m²) both models are now compared and assessed by Forschungszentrum Rossendorf FZR e.V. Therefore post test calculations of four selected HORUS experiments were performed with ATHLET/KONWAR. It can be seen that the calculations with the extension KONWAR as well as HOTKON improve significantly the agreement between computational and experimental data.

Abstract: The status of the ELBE FEL projects is reviewed. ü

The mass distributions of baryon resonances populated in near-central collisions of Au on Au and Ni on Ni are deduced by defolding the p_t spectra of charged pions by a method which does not depend on a specific resonance shape. In addition the mass distribution of resonances are obtained from the invariant masses of (p,π^±) pairs. With both methods the deduced mass distribution are shifted by an average value of -60 MeV/c² relative to the mass distribution of the free Δ(1232) resonance, the distribution descent almost exponentially towards mass values of 2000 MeV/c². The observed differences between (p,π^-) and (p,π⁺) pairs indicate a contribution of isospin I=1/2 resonances. The attempt to consistently describe the deduced mass distributions and the reconstructed kinetic energy spectra of the resonances leads to new insights about the freeze out conditions, i.e. to rather low temperatures and large expansion velocities.

For developing a dihydropyridine/pyridinium salt redox delivery system that could be useful for SPECT investigations by ^99mTc compounds the synthesis of a mixed-ligand complex of the long-lived isotope ⁹⁹Tc is described. The new compound bearing a pyridinium salt moiety was characterised by NMR-spectrometry and X-ray structure analysis. By reduction with sodium dithionite the corresponding 1,4-dihydropyridine complex was prepared and the stability in buffer, tissue homogenates, blood plasma and cerebrospinal fluid was investigated by UV-VIS spectrometry.

Die Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH entwickelt das Programmsystem ATHLET (Analyse der Thermohydraulik bei Lecks und Transienten) mit der Zielsetzung, das gesamte Spektrum von Kühlmittelverlust- und Transientenstörfällen in Leichtwasserreaktoren berechnen zu können. Voraussetzung hierzu ist jedoch, daß die in ATHLET enthaltenen Modelle in der Lage sind, die hierbei auftretenden Phänomene prinzipiell beschreiben zu können.
Speziell bei WWER-Reaktoren sowie dem SWR1000 treten konstruktive Besonderheiten auf (z. B. beim WWER die Leitungsführung der Hauptkühlmittelleitungen mit je einer Absenkung im heißen und kalten Strang, liegende Dampferzeuger, beim SWR1000 die horizontalen Notkondensatorbündel). Die im Rahmen des BMBF Projektes Nr. 150 0856 8 "Verifikation des Rechencodes ATHLET" [2] von der Hochschule Zittau/Görlitz (HTWS) durchgeführte unabhängige ATHLET-Verifikation und die "Berechnung des passiven Notkondensators eines mit Naturumlauf arbeitenden innovativen Siedewasserreaktors (SWR600) mit ATHLET" (BMBF Projek 15 NU 09485) der Forschungszentrum Jülich (FZJ) GmbH zeigen übereinstimmend, daß das in ATHLET enthaltene Kondensationsmodell für die Simulation der Kondensation innerhalb liegender Rohre ungünstig ist.
Daher wurden in beiden Organisationen umfangreiche Erweiterungen des Kondensationsmodells (HOTKON - HTWS, KONWAR - FZJ) vorgeschlagen, realisiert und anhand von HORUS- bzw. NOKO-Experimenten validiert. Die beiden Experimente unterscheiden sich jedoch hinsichtlich ihrer Betriebsparameter. Zielsetzung der dieser Veröffentlichung zugrunde liegenden Arbeiten ist, KONWAR anhand von HORUS-Experimenten zu validieren und die Rechenergebnisse mit der um KONWAR erweiterten ATHLET-Version mit den experimen-tellen Daten sowie den Rechenergebnissen der Original und um HOTKON erweiterten Version von ATHLET zu vergleichen.

Es wird ein neuerrichtetes Radionuklidlaboratorium zur Untersuchung bestrahlter Werkstoffproben vorgestellt und das Spektrum der gegebenen Untersuchungsmöglichkeiten vorgestellt.

no abstract

Der Einfluss von Kupfer, Phosphor und Nickel auf die Neutronenversprödung wird anhand von 8 Testlegierungen untersucht. Die Testlegierungen sind bis zu Neutronenfluenzen von 1x10¹⁹ und 8x10¹⁹ N/cm² [E>0.5 MeV] bei 270 °C in WWER-440-Reaktoren bestrahlt worden. Sowohl Ni als auch P und Cu erhöhen die Bestrahlungsempfindlichkeit. Eine überraschend hohe Bestrahlungsempfindlichkeit zeigt eine Fe-Mn-Si-Legierung hoher Reinheit.

Radionuclide concentrations have been determined by gamma-ray spectrometry in rock samples taken from a forty-years old uranium waste rock pile. With increasing depth, an increase of the Ra-226/U-238 activity ration was found. This can be explained by different migration rates of the individual nuclides.

Experiments were performed to investigate heating up processes of fluids in storage tanks under the in-fluence of an external heat source. As a con-se-quence of an external fire, the heat-up of the inventory may lead to the evaporation of the liquid and to release of significant quan-tities of dan-ge-rous gases into the envi-ron-ment. Several tests were performed both with heating from the bottom and with heating from the side walls. In recent tests in addition to thermocouples, the tank was equipped with needle probes for measuring of the local void fraction.
The paper presents experimental and numerical investigations of single and two phase heating up processes of tanks with side wall heating. The measurement of the temperature and of the void fraction makes interesting phenomena evident. which could be explained by an own 2D model. The gained experimental results may be used for the validation of boiling models in 3-D CFD codes.

A one-dimensional model for multiphase flow in a vessel was developed. The model bases on a new particle method and is free of numerical diffusion. This allows a consistent simulation of discontinuities such as the top level of the mixture without additional level tracking methods. The model distinguishes between continuous and dispersed phases. Levels mark the locations where the continuous phase change. This model for multiphase transport is the basic component of a new computer code. Flexible interfaces allow a convenient coupling of this model with constitutive laws for special phenomena. A special goal of the code is the transient simulation of emergency relief from chemical reactors with consideration of foam. For this reason the code was equiped with models for pressure calculation, conservation of energy, phase transfer, bubble generation, bubble growth, coalescence, drift of the phases, heat release from the vessel wall, discharge and homogeneous chemical reactions. A special interface, which enables the modelling of generation and decay of foam at the top level of the mixture, is included. Any of the phases can consist of several components. The code was validated for numerous depressurization experiments.

The process in the anode chamber of an alkaline chloride electrolysis cell was modelled by hydrogen peroxide decomposition at a platinum surface, which replaces the anode. Bubble size measurements and shutdown experiments have shown the ap-plicability of this model reaction. In the anode chamber regions of bubble flow, spherical foam and a transition to cell foam at the top were found. Gas fraction distributions were measured by the differential pressure method and gamma densitometry. LDA and PDPA were used to obtain velocity and bubble size distributions. For the bubble flow region, the correct consideration of the bubble size distribution was identified as determining factor to reproduce the volume flow rate of the gaseous phase from the measured gas fraction. Minor contributions to the gas flow rate are caused by bubbles of several millimetres magnitude generated in the ribs of the anode and by a liquid circulation driven by the lateral gas supply, which is characteristic for the design of membrane cells. In the foam region, large bubbles appearing as a result of coalescence carry a significant part of the gas flow rate.

In the framework of the external validation of the thermohydraulic code ATHLET Mod 1.1 Cycle D, which has been developed by the GRS, post test analyses of two experiments were done, which were performed at the french integral test facility BETHSY.
The BETHSY experiment 5.2c investigates the accident procedures in case of a total loss of feedwater at the steam generator secondary side, [3]. In such an accident the emergency cooling of the reactor core with primary bleed and feed, the behaviour of the steam generators in case of dry out and the long time behaviour of the test facility are special subjects of interest. During the experiment the high pressure injection system, the hydroaccumulators and the low pressure injection system were available.
The evaluation of the calculated results shows, that all main phenomena can be calculated in a good quality compared with the experiment. Resulting from various calculations it should be noticed that the quality of the results strongly depends on the modelling of the heat losses of the facility, which were partly compensated by the trace heating. This trace heating was changed several times in the experiment to compensate the changing heat losses. The exact modelling of the resulting heat losses has a strong influence on the course of the whole transient. In this test the unsufficient modelling of the resulting heat losses may be the reason for deviations of the calculated transient from the observed transient.
The results show, that the safety relevant statement of the experiment could be reproduced by the code ATHLET.

In the framework of the external validation of the thermalhydraulic code ATHLET MOD 1.1 CYCLE D, which is being developed by the GRS, post test analyses of two experiments were done, which were performed at the french integral test facility BETHSY. During test 9.3 the consequences of a steam generator U-tube rupture with failure of the high pressure injection and of the auxiliary feedwater supply were investigated. As accident management measures, the depressurization of the secondary sides, first of the two intact steam generators, then of the damaged steam generator and finally the primary depressurization by opening of the pressurizer valve were performed.
The results show, that the code ATHLET is able to describe the complex scenario in good accordance with the experiment. The safety relevant statement could be reproduced. Deviations, which did`nt impose the general results, occured concerning the break mass flow during the depressurization of the damaged steam generator and the description of the failure of the heat transfer to the damaged steam generator. Reasons are hardly to find, because these processes are highly complex.

Texture Analysis of EXAFS-Samples using the Rietveld Method

C. Hennig1, G. Nolze2
1Forschungszentrum Rossendorf e.V., ESRF- ROBL/CRG, B.P. 220, F-38043 Grenoble
2Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, D-12205 Berlin

Until now a lot of EXAFS measurements have been carried out on polycrystalline samples. It is known that powdered samples are characterized by a more or less strong texture, caused by an axial pressure during sample preparation. Owing to the polarized synchrotron radiation, this leads to an incorrect determination of the coordination number Nj, in particular for compounds with an anisotropic coordination center. Exemplarily, a strong polarization dependence can be detected in EXAFS spectra for oriented single crystals containing a uranyl coordination center [1]. The influence of preferred orientation on EXAFS measurements will be shown here for polycrystalline uranyl phosphate hydrate samples. The amplitude function of the EXAFS formula describes this polarization dependency with the term
Njeff = 1/2 Nj (1 + 3cos2*j), (1)
where *j is the angle between the polarization vector of the synchrotron radiation and the interatomic vector between the absorber and backscatterer. The exact calculation of the coordination number Nj is especially difficult because of its strong correlation to the Debye-Waller factor *j. A way to determine the preferred orientation is the use of X-ray diffraction measurements. The powder diffraction technique allows to determine the effective multiplicity of each Bragg reflection. One of the commonly used descriptions of a simple preferred orientation is this given by March and Dollase [2]. There, the preferred orientation is characterized by a single vector and the degree of preferred orientation:
Icorr = Istr (G2cos2 *k + G-1 sin2 *k )-2/3 (2)
For a given reflection hkl, this formula describes the relation between the corrected intensity Icorr and the integral intensity Istr resulting from well-known crystal structure data. Istr will be corrected by the preferred orientation in dependence of the orientation parameter G and the angles *k between the scattering vectors of all symmetry-equivalent lattice planes and the preferred orientation vector , assumed as lattice vector. In contrast, the orientation parameter G is valid for all reflection and must be fitted in a special refinement procedure. Most of Rietveld programs allows the use of the March-Dollase function. Both, the preferred orientation vector and the orientation parameter G should be introduced as additional amplitude correction terms for the calculation of polarization dependent EXAFS measurements on powder samples.

[1] C. Hennig, et al., Z. Krist. Suppl. 15, (1998) 156
[2] Dollase W.A., J. Appl. Cryst. 19 (1986) 267-272

Local Structure Analysis of Uranyl Phosphates and Arsenates using EXAFS Spectroscopy

C. Hennig, T. Reich, A. Roßberg, H. Funke, M. Rutsch,
G. Geipel, H. Nitsche, G. Bernhard

Forschungszentrum Rossendorf e.V., Institut für Radiochemie, P.F. 510119, D-01314 Dresden

First EXAFS measurements were taken on the new ROssendorf Beam Line (ROBL) [1]. This beamline is built by the Forschungszentrum Rossendorf as collaborating research group (CRG) at the ESRF in Grenoble. ROBL comprises a radiochemistry laboratory of type B and a materials research station. The radiochemistry station is designed for X-ray absorption spectroscopy whereas the materials research station uses X-ray diffraction techniques. The monochromator is equipped with a Si(111) and Si(311) water cooled double-crystal system of fixed-exit type which covers an energy range of 5keV-35keV. Higher harmonics are rejected by two Si/Pt coated mirrors.
Some saxonian granites contain uranium as hydrothermal crystallized uranyl phosphates and arsenates. Uranium and arsenic appear also in seepage waters of mine tailing piles from uranium mines and give stable complexes. Local structure analysis of these compounds is nessesary to understand the environmental weathering and mineralization processes.
The investigated samples are natural Cu[UO2PO4]2*nH2O, Ba[UO2PO4]2*nH2O, Ca[UO2PO4]2*nH2O, Cu[UO2AsO4]2*nH2O and synthetic H[UO2AsO4]*nH2O. The crystal structures are generally built up by stable layers of [UO2]2+ and [PO4]3-or [AsO4]3- units and the charge neutrality is achived by different interlayer cations.
U LIII-edge and As K-edge EXAFS spectra were collected in transmission, Cu K-edge EXAFS spectra were measured with a multichannel Ge fluorescence detector [2]. The measurements were carried out with a sample orientation of 0° and 45° to the beam direction in order to investigate the influence of polarization effects.
We have measured small but significant bond length differences within this structural isotypic group. Deviations in the coordination numbers are obtained as a result of polarization effects and moreover different Debye-Waller factors in connection with structural defects. In conclusion, the uranyl arsenate layer structure is nearly independent from the interlayer cation arrangement. Our investigation demonstrates the possibility for compensation the lost angle information in EXAFS spectroscopy by using the radial distribution functions at various absorption edges.

[1] ESRF Beamline Handbook 1997 pp.145
[2] Bucher, J.J., et al., Rev. Sci. Instrum. 67 (1996) 1

There is evidence from recent studies that the brain endothelium (of capillaries and/or larger vessels) may serve as a specific target for serotonin (5-HT). This neurotransmitter is expected to be involved in the regulation of the BBB permeability and/or of the cerebral blood flow via receptor-mediated mechanisms. Effective control of these processes depends on a speedy uptake and metabolism of released 5-HT molecules. To realise this, a similar mechanism of 5-HT uptake as in brain may exist at the BBB. In this study, we have demonstrated using reverse transcriptase-polymerase chain reaction (RT-PCR) that 5-HT transporter mRNA is present in the brain endothelium and that a saturable transport system for 5-HT is functionally expressed at immortalized rat brain endothelial cells (RBE4 cells). These cells take up [³H]5-HT by an active saturable process with a K _m-value of 397± 64 nmol/L and a transport capacity of 51.7 ± 3.5 pmol•g^-1•min^-1. The 5-HT uptake depends on Na⁺, as indicated by the replacement of NaCl by LiCl. The 5-HT uptake was sensitive to specific 5-HT transport inhibitors such as paroxetine, clomipramine, fluoxetine and citalopram, but not to inhibitors of the vesicular amine transporter such as reserpine or tetrabenazine. Our results demonstrate that cerebral endothelial cells are able to participate actively in the removal and metabolism of the released 5-HT, which supports the concept of direct serotonergic regulation of the BBB function.

Up-to-date methods of numerical modelling of random fields were applied to investigate some features of solute transport in saturated porous media with stochastic hydraulic conductivity. The paper describes numerical experiments which were performed and presents the first results.

New reactor designs comprise passive elements for decay heat removal. Computational-Fluid-Dynamics codes are an appropriate tool for the assessment of the efficiency of those components. Most of these codes are based either on the Finite-Volume or the Finite-Element method. Because of the importance for reactor safety these numerical tools have to be thoroughly validated using results from experimental setups.
The governing mechanism in passive components for decay heat removal is natural convection and heat transfer with internal heating. To assess the capability describing mixed convection flow, post test calculations of an IAHR benchmark exercise were performed (Kamide et. al, 1991). The commercial codes CFX-4® and ANSYS/FLOTRAN® were used, representing the Finite-Volume Method and the Finite-Element Method respectively.
This paper presents a discussion of the problems and capabilities of each code to calculate complex flow regimes and temperature fields.

A dedicated PET-system has been integrated into the heavy ion tumour facility at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt in order to monitor and control the applied dose distribution during the irradiation. The positron camera has strongly spatially-varying system behaviour due to its limited angle design and the presence of detector gaps. Furthermore, the expected counting statistics are limited by the doses applied per therapy fraction.
A three-dimensional Maximum-Likelihood Estimator algorithm has been adapted to this imaging situation. Corrections for activity outside of the field of view, parallax errors, randoms as well as normalization factors have been implemented. The algorithm has been validated using ²²Na reference sources. Resolution, edge detectability, geometrical fidelity of size and position have been chosen as figures of merit. Results of the performance studies as well as an example of the algorithm's application to patient data are presented.

Initiatoren des zweiten Workshops zum Thema „Meßtechnik für stationäre und transiente Mehrphasenströmungen" im Forschungszentrum Rossendorf (FZR) e.V. waren das Institut für Sicherheitsforschung des FZR und das Institut für Prozeßtechnik, Prozeßautomatisierung und Meßtechnik (IPM) an der Hochschule für Technik, Wirtschaft und Sozialwesen (HTWS) Zittau/Görlitz. Der Workshop wurde mit Unterstützung der Deutschen Gesellschaft für Chemisches Apparatewesen, Chemische Technik und Biotechnologie (Dechema) e.V. sowie der Kerntechnischen Gesellschaft (Fachgruppe Thermo- und Fluiddynamik) veranstaltet. In drei Haupt- sowie 13 Fachvorträgen wurden optische Meßverfahren, Impedanzverfahren und Sondergebiete zur Messung wichtiger Größen in einer Zwei- oder Mehrphasenströmung vorgestellt.