Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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.

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.

For the analysis of boron dilution transients and main steam line break scenarios the modelling of the coolant mixing inside the reactor vessel is important. The reactivity insertion due to overcooling or deboration depends strongly on the coolant temperature and boron concentration. The three-dimensional flow distribution in the downcomer and the lower plenum of PWR's was calculated with a computational fluid dynamics (CFD) code (CFX-4). Calculations were performed for the PWR's of SIEMENS KWU, Westinghouse and VVER-440 / V-230 type. The following important factors were identified: exact representation of the cold leg inlet region (bend radii etc.), extension of the downcomer below the inlet region at the PWR Konvoi, obstruction of the flow by the outlet nozzles penetrating the downcomer, etc. The k- turbulence model was used. Construction elements like perforated plates in the lower plenum have large influence on the velocity field. It is impossible to model all the orifi!
ces in the perforated plates. A porous region model was used to simulate perforated plates and the core. The porous medium is added with additional body forces to simulate the pressure drop through perforated plates in the VVER-440. For the PWR Konvoi the whole core was modelled with porous media parameters. The velocity fields of the PWR Konvoi calculated for the case of operation of all four main circulation pumps show a good agreement with experimental results. The CFD-calculation especially confirms the back flow areas below the inlet nozzles. The downcomer flow of the Russian VVER-440 has no recirculation areas under normal operation conditions. By CFD calculations for the downcomer and the lower plenum an analytical mixing model used in the reactor dynamic code DYN3D was verified. The measurements, the analytical model and the CFD-calculations provided very well agreeing results particularly for the inlet region.
The difficulties of analytical solutions and the uncertainties of turbulence models for the numerical solutions require additional experiments. Therefore a 1:5 scaled plexiglas model is under construction at RC Rossendorf. The model can be used variably for PWR's of KONVOI- and EPR- types including the primary loops. The measurements of the mixing effects will be performed with modern wire mesh sensors based on conductivity differences and LDA is used to measure the flow conditions.

The second workshop on “Measuring Techniques for Steady State and Transient Multiphase Flows” took place at the Forschungszentrum Rossendorf (FZR) from 24 - 25 September 1998. This series of meetings was initiated by the Institute for Safety Research of the FZR and by the Institute of Process Technology, Process Automation and Measuring Techniques of the Hochschule für Technik, Wirtschaft und Sozialwesen (HTWS) Zittau/Görlitz. The workshop was supported by the Deutsche Gesellschaft für Chemisches Apparatewesen, Chemische Technik und Biotechnologie (DECHEMA) and the Section “Thermo and Fluiddynamics” of the Kerntechnische Gesellschaft. Three main lectures and 13 technical papers dealt with measuring techniques such as optical and radiometric methods, impedance measurements, hot film probes and model-based methods for the measurement of important quantities in two or multiphase flows, such as phase fractions, particle size, velocities, material exchange and concentration of components.

To assist in the development of technetium-based radiopharmaceuticals that are useful for the diagnostic imaging of steroid receptor-positive breast tumors, we have synthesized a series of small-sized metal chelates according to 'n+1' mixed ligand, thioether-carbonyl and organometallic designs. In these preliminary investigations, rhenium was used as a model for the radioactive technetium. The metal chelates contain the rhenium metal in several oxidation states, being +5, +3, and +1, and they were attached to 21-substituted progesterone derivatives. A competitive receptor-binding assay (rat uterine cytosol, 0°C) was used to determine the binding affinity of these conjugates for the progesterone receptor. The highest affinity of 9% (RU5020=100%) was obtained with a '3+1' mixed-ligand complex, containing a NMe group as the central donor atom in the tridentate ligand part. This value reflects a relative binding affinity of 75% compared with the parent steroid progesterone.

Analyzing the safety margins in transients and accidents of nuclear reactors 3-dimensional models of the core were used to avoid conservative assumptions needed for point kinetics or 1-dimensional models. Therefore the 3D code DYN3D has been developed for the analysis of reactivity initiated accidents (RIA) in thermal nuclear reactors. The power distributions are calculated with the help of nodal expansion methods (NEM) for hexagonal and Cartesian geometry. The fuel rod model and the thermohydraulic part provide fuel temperatures, coolant temperatures and densities as well as boron concentrations for the calculation of feedback effects on the basis of cross section libraries generated by cell codes.

DYN3D can analyze RIA initiated by moved control rods and/or perturbations of the coolant flow. Stationary and transient boundary conditions for the coolant flow, the core inlet temperatures and boron concentrations at the core inlet have to be given. For analyzing more complex transients the code DYN3D is coupled with the plant model ATHLET of the GRS. Exercises are presented of the extensive validation work for DYN3D. Some examples are shown of application of the code.

Ausgehend von Messungen der Redoxpotentiale in Abhängigkeit von der Wassertiefe im gefluteten Teil des Schlema/Alberodaer Uranbergwerks werden die Konsequenzen bezüglich des Valenzzustandes des Eisens und Urans betrachtet. Um zu zeigen, daß nicht nur die Pyritoxidation als sauerstoffzehrender Prozeß im Grubenwasser in Frage kommt, sondern auch organische Substanzen, wie das Grubenholz einen Beitrag zur Bildung reduktiver Bedingungen leisten, wurde die Redoxsituation im Hochmoor "Kranichsee" am Erzgebirgskamm untersucht.

Im Laborexperiment wurde das Redoxpotential von Fichtenholzlignin in Abhängigkeit vom pH-Wert mittels der direkten Potentialmessung und der Titration mit Hexacyanoferrat(III) bestimmt. Dadurch werden Voraussagen bezüglich der durch Lignin verursachten Metallreduktionen möglich. Es wurde die Eisen(III)-Reduktion hinsichtlich ihres Umsatzes und ihrer Kinetik sowohl spektrophotometrisch mit o-Phenanthrolin als auch elektroanalytisch durch Square-wave-Voltammetrie untersucht.

The influence of mine-wood leachates on the adsorption of U(VI), Th(IV), Fe(III) and Pb(II) (1) on typical rocks and minerals of the mining sites in the German Erzgebirge and (2) on sediments of the Königstein mine (Saxony) and its near field was studied under aerobic condition.

The wood was decomposed by reflux boiling of wood shavings with water. The leachates were analysed for DOC, phenolic and saccharic compounds, molecular weight distribution and content of carboxylic and phenolic hydroxyl groups. The adsorption experiments were carried out equilibrating the geomaterial with the aqueous phase in the presence of U(VI) and DOC for 4-6 weeks. The uranium concentration ranged from 3.2 10-6 to 3.2 10-5 mol/L (0.76-7.62 mg/L) and the DOC content was 8.3-166 mg/L. The distribution ratio (Rs [mL/g]) was determined by liquid scintillation counting of an added 234U tracer (10-40 Bq/sample) after distribution and a careful phase separation.

Uranium adsorption on rocks and minerals from the Erzgebirge: The adsorption from a DOC-free synthetic mine water takes mainly place on diabase and on calcite; about 80% of the uranium is bound on these minerals. The influence of the wood degradation products and pine wood lignin increases the adsorption to 90-95 %. Granite and basalt adsorb from DOC-free mine water 50-60% of the uranium. In the presence of the wood leachate and lignin, the adsorption increases to about 80%. The effect of the wood leachate and lignin is insignificant for gneiss. Very little uranium adsorbs on phyllite. From all solutions practically no uranium is bound ( 2%).

Uranium adsorption on Königstein sediments: It is evident that uranium is preferentially bound to sandstone (91-97%); especially with a high distribution ratio to the limonithe-rich turonian sandstone (142 mL/g). Even under the influence of the organic compounds the sorption ranges from 68 to 93%. Wood leachate and lignin (2-4%) decrease the sorption. The adsorption o ...

The interaction of radium with characteristic sediments of the upper Saxon Elbe river valley was investigated with the aim to provide key data for transport modelling within the frame of mining site restoration. Adsorption measurements, therefore, were carried out on site-specific sediments (different kinds of sandstone, claystone and lime marl) using (1) acidic mine water coming from sulfuric acid residues of the former in-situ leaching process, (2) groundwater that is inflowing into the mine and (3) mixtures of both which simulates certain stages of the mine flooding process. The distribution ratios (Rd) were determined by batch experiments using an 8 weeks' equilibration at aquifer temperature (14 °C). Radium adsorption from acidic mine water onto different kinds of sandstone is characterized by high distribution ratios (3 400 mL/g). When contacted with groundwater, the sorption is decreased more than 20-fold (60-180 mL/g). For claystone and lime marl the distribution ratios amount to 130 and 480 mL/g, respectively, and they are nearly constant in the mine flooding process. The main adsorption mechanisms on the leached sandstone and the clayey sediments were identified as coprecipitation and ion exchange, respectively.

The long-term migration behaviour in the aquifers of the south-east Saxon Elbe basin was calculated on the basis of Hadermanns' equation, considering retardation, dispersion and radioactive decay.

With the background of uranium mine restoration the adsorption of radium on different kinds of sandstone, claystone and lime marl was studied in dependence on such parameters as water composition, acidity, phase contact time and the concentration of radium, barium and sulfate by static batch experiments at the mine temperature of 14°C.

Mit Hilfe neuartiger Gittersensoren können Gasgehaltsverteilungen in einer Zweiphasenströmung im Strömungsquerschnitt mit einer Zeitauflösung von über 1000 Hz gemessen werden. Die Sensoren beruhen auf einer elektrischen Leitfähigkeitsmessung. Zwei hintereinander angeordnete Sensoren erlauben die Ermittlung von Geschwindigkeitsverteilungen der Gasphase. Hierzu werden die Zeitverläufe des Gasgehalts an den einzelnen Meßpunkten der beiden Sensoren individuell durch Berechnung von Kreuzkorrelationsfunktionen ausgewertet. Die erhaltenen Geschwindigkeitsverteilungen können mit den ebenfalls gemessenen Gasgehalten multipliziert und über dem Querschnitt integriert werden. Dadurch erhält man den Gesamtvolumenstrom der Gasphase. Tests an einer mit Wasser-Luft-Gemisch betriebenen Versuchsschleife zeigen die Funktionsfähigkeit dieses Verfahrens.

An overview of the two years of operation of the Rossendorf CYCLONE 18/9 facility is given. Datas of the radionuclide production are presented and improvements at the cyclotron and our experience in operation and maintenance of the CYCLONE 18/9 are described.

The NOKO-Test facility is a rig for the test of passive components of nuclear power plants and is operated at the research centre J'lich. The facility is used for the experimental investigation of the emergency condenser of the SWR 600/1000, which is a new boiling water reactor design, developed by Siemens. The paper describes the numerical investigation of the natural circulation processes at the secondary side of the NOKO facility. Results of CFX-4 calculations are presented. They show, that during the operation of the emergency condenser a stable temperature stratification is evolving. At the lower part of the secondary side of the NOKO test facility even a dead volume is established. The fluid of this volume does not take part in the fluid circulation. The phenomena observed in the calculations were also found in the experimental results. Different changes of the tank configuration were investigated to reduce the effect of the temperature stratification.

In December 1997 the treatment of patients suffering from head and neck tumours with beams of high-energy ¹²C ions started at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt. By the simultaneous application of positron emission tomography (PET) the treatments are verified in-situ during the irradiation. The PET-based quality assurance procedure is a chain of consecutive steps. The starting point is the three-dimensional treatment planning on the basis of X-ray computed tomograms (CT). During the heavy ion treatment the produced positron-emitter distribution is measured simultaneously. After that the expected temporal and spatial activity distribution is computed. Both images are reconstructed iteratively and filtered. For the analysis the PET and CT images are superimposed.

The fifth dynamic benchmark is the first benchmark for coupled thermohydraulic system/three-dimensional hexagonal neutron kinetic core models. In this benchmark the interaction between the components of a VVER-440 NPP with the reactor core has been investigated.

The initiating event is a symmetrical break of the main steam header at the end of the first fuel cycle and hot shutdown conditions with one control rod group stucking. This break causes an overcooling of the primary circuit. During this overcooling the scram reactivity is compensated and the scrammed reactor becomes recritical. The calculation was continued until the highly-borated water from the high pressure injection system terminated the power excursion.

Several aspects of this very complex and complicated benchmark problem are analyzed in detail. Sensitivity studies with different hydraulic parameters are made. The influence on the course of the transient and on the solution is discussed.

Die durchgeführten Untersuchungen an 50 netzgekoppelten PV-Anlagen (Leistungsbereich < 5 kWp) ermöglichten eine vergleichende Analyse der eingesetzten Hauptkomponenten sowie eine Beurteilung der gewählten Anlagenkonzepte. Danach steht bei den Modulen -neben dem Übergang zu Großmodulen- die Erhöhung der Qualität (STC-Leistung !) eindeutig im Vordergrund. Als brauchbarstes Wandlungskonzept in den Wechselrichtern hat sich die Pulsweiten-Modulation erwiesen. Neben hohen Jahresnutzungsgraden (94 %) sollten künftige Modelle durch einen hohen Eingangsspannungsbereich (bis 600 V) die Installation von Einstrang-Anlagen ermöglichen. Durch die Integration von Komponenten zur Anlagendiagnose (etwa PR-Überwachung) und Erhöhung der Zuverlässigkeit können weitere Ertragspotentiale erschlossen werden. Jahreserträge von deutlich über 800 kWh/kWp sind damit bei gut ausgerichteten Anlagen auch im hier untersuchten Leistungsbereich erreichbar.
Durch Auswertung von Einstrahlungsdaten konnten zudem einige energiewirtschaftlich wichtige Parameter der photovoltaischen Energieerzeugung ermittelt werden.

Seit 1993 wird im Institut für Sicherheitsforschung des FZR ein Photovoltaik-Experimentierfeld betrieben. Neben einer kleinen netzgekoppelten PV-Anlage besteht die Gesamtanlage aus einem Strahlungsmeßfeld und einem Modulmeßfeld. Durch kontinuierliche mehrjährige Kennlinienvermessung wurden die ertragsrelevanten Parameter von Modulen ermittelt. Die jährlichen Energieerträge unterschiedlich orientierter Module entsprechen den Berechnungen der jeweiligen Einstrahlungssummen nach dem PEREZ-Modell.
Die STC-Leistung verschiedener Module wurde nach einem Outdoor-Verfahren bestimmt. Dabei wurden Minderleistungen zwischen 15 und 25 % gegenüber Datenblattangaben gefunden. Das auf den DC-Ertrag bezogene Performance Ratio der einzelnen Module lag zwischen 89 und 94 %. Ein mittleres jährliches Leistungsspektrum -gültig für große Teile Deutschlands und kristalline Module- wurde ermittelt.