Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31745 Publications
Die Stellung der Sekretärin nach dem BAT - eine moderne Form der Leibeigenschaften?
Joehnk, P.;
no abstract delivered from author
  • Lecture (others)
    Bundesverband Sekretariat und Büromanagement e. V., Dresden, 03.06.2002

Publ.-Id: 4475 - Permalink


Directed flow in Au+Au, Xe+CsI and Ni+Ni collisions and the nuclear equation of state
Andronic, A.; Reisdorf, W.; Herrmann, N.; Crochet, P.; Barret, V.; Basrak, Z.; Bastid, N.; Berek, G.; Caplar, R.; Devismes, A.; Dupieux, P.; Dzelalija, M.; Finck, C.; Fodor, Z.; Gobbi, A.; Grishkin, Y.; Hartmann, O. N.; Hildenbrand, K. D.; Hong, B.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Koczon, P.; Korolija, M.; Kotte, R.; Kress, T.; Lebedev, A.; Lee, K. S.; Leifels, Y.; Lopez, X.; Merschmeyer, M.; Neubert, W.; Pelte, D.; Petrovici, M.; Rami, F.; de Schauenburg, B.; Schuettauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Stockmeier, M.; Stoicea, G.; Tyminski, Z.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Yushmanov, I.; Zhilin, A.;
We present new experimental data on directed flow in collisions of Au+Au, Xe+CsI and Ni+Ni at incident energies from 90 to 400 A MeV. We study the centrality and system dependence of integral and differential directed flow for particles selected according to charge. All the features of the experimental data are compared with Isospin Quantum Molecular Dymnamics (IQMD) model calculations in an attempt to extract information about the nuclear matter equation of state (EoS). We show that the combination of rapidity and transverse momentum analysis of directed flow allows to disentangle various parametrizations in the model. At 400 A MeV, a soft EoS with momentum dependent interactions is best suited to explain the experimental data in Au+Au and Xe+CsI, but in case of Ni+Ni the model underpredicts flow for any EoS. At 90 A MeV beam energy, none of the IQMD parametrizations studied is able to consistently explain the experimental data.
  • Phys. Rev. C 67 (2003) 034907

Publ.-Id: 4474 - Permalink


Application of mass separated focused ion beams
Bischoff, L.;
With the invention of the liquid metal ion source (LMIS) in the sixties the focused ion beam (FIB) technique started an impressive development from the laboratory level to high performance industrial equipments. At present, the FIB is a very useful and versatile tool in microelectronics industry for mask and integrated circuit repair and modification, failure analysis or TEM specimen preparation, as well as in the material science for radiation damage and sputtering investigations, for grain size and distribution analysis in metals and alloys, for the formation of silicides or the fabrication of micro-tools. For special purposes in the field of research and development, like writing ion implantation or ion mixing in the µm- or sub-µm range different ion species are needed. Therefore alloy LMIS are used. The energy distribution of the ions from an alloy LMIS is one of the determining factors for the performance of the FIB equipment. Different source materials like Au73Ge27, Au77Ge14Si9, Co36Nd64, Er69Ni31, and Er70Fe22Ni5Cr3 were investigated with respect to the energy spread of the different ion species as a function of emission current I, ion mass m and temperature T. For single charged ions the predicted dependence of the energy spread according to DE µ I2/3 m1/3 T1/2 found for Ga could be confirmed. The alloy LMIS`s discussed above have been used in the Rossendorf FIB system IMSA-100 especially for writing implantation to fabricate sub-µm pattern without any lithographic steps. So a Co-FIB was applied for the ion beam synthesis of CoSi2 micro-structures. Additionally, the possibility of varying the current density with the FIB by changing the pixel dwell-time was used for radiation damage investigations in Si and SiC at elevated implantation temperatures. Furthermore, a broad spectrum of ions was employed to study the sputtering process depending on temperature, angle of incidence and ion mass on a couple of target materials using the volume loss method. All these examples underline the importance of a FIB in modern research and the new possibilities given by a mass separated system applying a broad spectrum of ion species.
Keywords: Focused ion beam, alloy liquid metal ion source, energy distribution, mass spectra, application
  • Lecture (Conference)
    IV-th International Scientific Symposium "Ion Implantation and Other Applications of Ions and Electrons ION 2002" Kazimierz Dolny, Poland, June 10 - 13, 2002

Publ.-Id: 4473 - Permalink


Development and application of a fast running model for the description of coolant mixing inside the pressure vessel of pressurized water reactors
Kliem, S.; Prasser, H.-M.; Höhne, T.; Rohde, U.;
An efficient semi-analytical model for the description of the coolant mixing during stationary and transient processes inside the reactor pressure vessel (RPV) of pressurised water reactors (PWR) has been developed. This model is based on the technique of linear superposition of response functions on Dirac impulse shaped perturbation functions. In the model, the RPV is represented formally by a group of transfer systems (for each combination of inlet nozzle position and fuel element position one) with one input and one output each. An experimental way of obtaining the transfer properties is shown on the example of the German PWR KONVOI. The validation of the model against experimental data from the 1:5 scaled coolant mixing test facility ROCOM is presented.
The semi-analytical model for the description of coolant mixing has been used in combination with the 3D reactor dynamics code DYN3D for the analysis of a hypothetical boron dilution event after start-up of the first main coolant pump in a generic four-loop PWR. The model provides realistic time-dependent boron concentration fields at the core inlet. By varying the initial slug volume it was found, that for the given core configuration slugs of less than 20 m3 do not lead to a re-criticality of the shut-off reactor. Calculations with the bounding slug volume of 36 m3 show, that the corresponding reactivity insertion does not lead the safety relevant consequences.
  • Lecture (Conference)
    Int. Conf. on the Physics of Reactors PHYSOR 2002,Seoul, Korea, 6.-10.10.2002, Proc. CD-ROM paper 5D-04
  • Contribution to external collection
    Int. Conf. on the Physics of Reactors PHYSOR 2002,Seoul, Korea, 6.-10.10.2002, Proc. CD-ROM paper 5D-04

Publ.-Id: 4472 - Permalink


The electron accelerator facility ELBE at Rossendorf/Dresden and its applications
Helm, M.;
At the Research Center Rossendorf near Dresden a superconducting electron accelerator is under construction and will start its operation in the course of this year. The electron beam with an energy of 20 (later up to 40) MeV is intended to provide the "source" for several types of secondary radiation: (1) gamma photons for nuclear spectroscopy, (2) X-rays for studies of cell damage, (3) neutrons for fusion-related research, (4) positrons for applications mostly in solid state physics, and finally (5) intense, coherent infrared radiation by means of two free-electron lasers, which will span the wavelength range between 5 and 150 microns. While giving a brief overview about all the above topics, I will concentrate on the free-electron lasers and the solid state spectroscopy we are planning to use them for. A focus will be time resolved studies of semiconductor quantum structures. It is intended to develop ELBE into a user facility, open to users worldwide, but of course in particular to researchers in central Europe.
Keywords: electron accelerator, free electron laser, ELBE, semiconductor quantum structures
  • Lecture (others)
    Vortrag an der Karls-Universität Prag, Tschechische Republik, 27.5.2002

Publ.-Id: 4471 - Permalink


Experimental high-resolution database for co-current air-water flow in a vertical pipe
Lucas, D.; Krepper, E.; Prasser, H.-M.;
Measurements were conducted in a vertical pipe with an inner diameter of 51.2 mm and a length of about 3 m for air/water bubble and slug flow. The use of a wire-mesh sensor allows a high resolution of the gas fraction data in space as well as in time. From these data time averaged values for the two-dimensional gas fraction profiles decomposed according to a large number of bubble size classes were calculated. This allows to extract data for the radial gas fraction profiles for a given range of bubble sizes as well as data for local bubble size distributions. The measurements were done for up to 10 different inlet lengths and for about 100 combinations of gas and liquid volume flow rates. Further experiments are planned. The data will be used for the development of models for the forces acting on a bubble in a shear field of the liquid flow and models for bubble coalescence and break-up.
Keywords: database, experiment, pipe flow, two-phase flow, bubble
  • Lecture (Conference)
    40th European Two-Phase Flow Group meeting, Stockholm, Sweden, June 10-13, 2002, Paper C4
  • Contribution to proceedings
    40th European Two-Phase Flow Group meeting, Stockholm, Sweden, June 10-13, 2002, Paper C4

Publ.-Id: 4470 - Permalink


Velocity measurements at high temperatures by ultrasound Doppler velocimetry using an acoustic wave guide
Eckert, S.; Gerbeth, G.; Melnikov, V. I.;
The ultrasound Doppler velocimetry (UDV) has been used to measure flow velocities at temperatures up to 620°C. To overcome the thermal restriction of the ultrasonic transducers an acoustic wave guide has been used. The acoustic wave guide and the piezoelectric element are combined in form of an integrated sensor. This approach allowed the first successful application of the ultrasound Doppler technique in liquid metals at temperatures above 200°C. The feasibility of this integrated sensor concept was demonstrated in experiments with metallic melts. Measurements were performed in a PbBi bubbly flow and in CuSn.
Keywords: flow measurement technique, ultrasound Doppler technique, fluid velocity, opaque fluids, liquid metal
  • Experiments in Fluids, Vol.35/5 (2003), 381-388

Publ.-Id: 4469 - Permalink


Analysis of the Boiling Water Reactor Turbine Trip Benchmark with the Code DYN3D
Grundmann, U.; Rohde, U.; (Editors)
Considering the phase 2 of the OECD/NRC BWR Turbine Trip Benchmark several analyses were performed with the help of the DYN3D code. Thermal-hydraulic boundary conditions of the core are given for this part of the benchmark. Concerning the modelling of the BWR in the DYN3D code several simplifications and their influence on the results were investigated. The standard calculations with DYN3D were performed with 764 coolant channels (1 channel per fuel assembly). It is shown that the power peak obtained for the given boundary conditions is close to the measured value. For numerical stability reasons, preliminary calculations were carried out neglecting the instationary mass balance equation. This approximation provided a stronger reduction of the core void that results in a higher power peak. The impact of the assembly discontinuity factors (ADF) was studied. It is shown that the influence on core-averaged values of the steady state and the transient is small. Considering local parameters the influence is not negligible. Several participants of the benchmark perform calculations with 33 thermal-hydraulic channels. The influence of the number of coolant channels has also a small effect on the core averaged values, but local parameters as axial power distribution in single fuel assemblies are affected. The phase slip model of MOLOCHNIKOV is the standard model of DYN3D for void fraction calculation. The ZUBER-FINDLAY model shows only small deviations from the standard case for both global and local values, however not in the direction of the measurement. Using the thermal-hydraulic boundary conditions the best agreement with the experiment was obtained for the standard model.
Keywords: nuclear reactors, transients, benchmarks, boiling water reactor, turbine trip, measurements, simulation, three-dimensional
  • Lecture (Conference)
    PHYSOR 2002 International Conference on the New Frontiers of Nuclear Technology: Reactor Physics, Safety and High-Performance Computing, October 7-10, 2002, Seoul, Korea
  • Contribution to proceedings
    PHYSOR 2002 International Conference on the New Frontiers of Nuclear Technology: Reactor Physics, Safety and High-Performance Computing, October 7-10, 2002, Seoul, Korea

Publ.-Id: 4468 - Permalink


Dynamic Master Curve Issues
Viehrig, H.-W.; Böhmert, J.; Dzugan, J.;
The paper links the Master Curve (MC) concept and the Charpy-V impact test to determine dynamic fracture mechanical parameters of ASTM A 533 B Cl. 1 nuclear pressure vessel steel. Pre-cracked and side-grooved Charpy size specimens were tested under impact loading using the instrumented impact pendulum test. J-integral based fracture toughness values, KJc, were determined at cleavage failure of the specimen. MC based reference temperatures, T0dy, were determined on the basis of measured KJc values.
The change in T0dy was determined in dependence on the thickness position of a steel plate and compared with the quasi-static reference temperature, T0st, and the Charpy-V transition temperature (TT). All three parameters increased from the surface towards the middle of the steel plate in the same course. However, in the middle section of the plate T0dy is in average approximately 26 K higher than TT41J and 72 K higher than T0st. Different T0 were found when tested at different temperatures, but the trend is ambiguous.
The results show that the MC based T0 is sensitive to reflect rather small microstructural differences by testing small Charpy size specimens and, thus it is applicable for the fracture mechanical characterisation of materials.
Keywords: instrumented impact testing, cleavage failure, fracture toughness, Master Curve, ductile-to brittle transition, reference temperature, reactor pressure vessel steel
  • Lecture (Conference)
    Proceedings, MASC 2002: Use and Applications of the Master Curve for Determining Fracture Toughness, June 12 - 14, 2002, Helsinki - Stockholm - Helsinki
  • Contribution to external collection
    Proceedings, MASC 2002: Use and Applications of the Master Curve for Determining Fracture Toughness, June 12 - 14, 2002, Helsinki - Stockholm - Helsinki

Publ.-Id: 4466 - Permalink


Scanning Force Microscopy of Spin-coated Humic Acid
Mertig, M.; Klemm, D.; Pompe, W.; Zänker, H.; Böttger, M.;
We report on investigations of spin-coated peat humic acid solutions by scanning force microscopy allowing, for the first
time, direct imaging of individual single humic acid molecules with a minimum diameter of 1.5-3.5 nm. The measured
height of the molecules deposited onto a mica substrate increases with decreasing pH value of the solution. This behaviour
can be explained by means of the random coil model if one takes the existence of charge carriers in organic macromolecules
into consideration. With increasing humic acid concentration the molecules arrange into a few monolayer-thick
agglomerates formed during the process of film deposition. In unfiltered solutions and in 1000 nm filtrates we find
additional particles well distinct from the above-mentioned molecules in size and properties. They possess an equivalent
spherical diameter of 70-160 nm and behave inert when the ambient conditions are changed.
Keywords: humic acid; random coil model; film formation; scanning force microscopy
  • Surface and Interface Analysis 27, 426-432 (1999)

Publ.-Id: 4465 - Permalink


Influence of dynamic annealing on the shape of channeling implantation profiles in Si and SiC
Posselt, M.; Bischoff, L.; Teichert, J.; Ster, A.;
The influence of dose rate and temperature on the dose dependence of the shape of Ge depth profiles obtained by channeling implantation into Si and SiC is investigated. A focused ion beam system is employed which enables the application of two widely different dose rates (1011 and 1018 cm-2 s-1). Implantations into Si are performed at room temperature (RT) and 250 0C. SiC is implanted at RT, 225, 450, and 580 0C. The Ge depth distributions are measured by secondary ion mass spectrometry. The shape of the channeling implantation profiles is affected by the formation and evolution of complex defects formed during ion bombardment, since these defects cause significant dechanneling of the implanted particles. The competing influence of dose rate and temperature on the shape of Ge depth profiles is explained in terms of intracascade defect relaxation. The time scale for the reduction of complex defects is estimated. At RT, in Si some defect relaxation occurs within the first 100 s after an ion impact. At temperatures of 225 and 250 0C, in SiC and Si, a considerable defect reduction is found within the first 10 ms as well as between 10 ms and 100 s after an ion impact. The complex defects in Si vanish entirely between 10 ms and 100 s, whereas in SiC some of them survive. At 450 and 580 0C, defects in SiC relax mainly within the first 10 ms after an ion impact. The defect reduction increases with growing implantation temperature. Different mechanisms which may be responsible for the dynamic annealing in Si and SiC are discussed. A phenomenological model is developed in order to treat the dose rate and temperature dependence of the defect-induced dechanneling within the framework of atomistic computer simulations of ion implantation. The simulated Ge depth profiles agree very well with the measured data.
Keywords: ion implantation into Si and SiC, radiation damage, channeling, computer simulation

Publ.-Id: 4464 - Permalink


Alternative Flüssigmetall-Ionenquellen
Bischoff, L.;
Als alternative Ionenquellen für Feinstrahlanlagen werden zur Ga-LMIS (liquid metal ion source) Flüssigmetall-Ionenquellen vorgestellt, die mit metallischen Legierungen arbeiten und so das Spektrum verfügbarer Ionen erweitern. Die Wirkungsweise sowie die Herstellungstechnologie werden diskutiert sowie vielfältige Anwendungen eines massenseparierten Ionenfeinstrahls (FIB = focused ion beam) dargestellt.
Keywords: Focused Ion Beam, Legierungs-Flüssigmetallionenquelle, Parameter, Massenspektrum, Wien-Filter, Applikationen
  • Lecture (others)
    LEO CrossBeam Workshop Dresden, 14.-16.05.2002

Publ.-Id: 4463 - Permalink


Transport of Reacting Solutes Through the Unsaturated Zone
Kuechler, R.; Noack, K.;
Unsaturated flows within subsurface regions control many large-scale hydrological and environmental processes. This contribution presents and discusses the results of numerical calculations dealing with the flow of water, the chemical reaction at the water-mineral interface and the transport of chemical species caused by such flows. The source of the water flow through the soil is solely the rainfall. The water motion is calculated for two different soil classes and for a typical annual precipitation. The codes which were used are based on the following model: The transport of chemical species is described by a set of partial differential equations, and the homogeneous chemical processes, under the assumption of equilibrium, are described by a set of nonlinear algebraic equations. The source terms of these partial differential equations are given by rate laws of the chemical weathering. Rainfall and chemical weathering are therefore the sources of the transport of reactive multispecies in this model.


Keywords: Rainfall, unsaturated zone, seepage water, weathering, geochemistry, aqueous solution, reactive solute transport
  • Transport In Porous Media 49 (2002) 361

Publ.-Id: 4462 - Permalink


Formation of Fe-oxyhydroxide particles during the dissolution of Fe-rich chlorite: Fate and behavior of heavy metals in the environment
Krawczyk-Bärsch, E.; Arnold, T.; Brandt, F.; Bosbach, D.; Bernhard, G.;
The rock phyllite is commonly encountered in uranium tailings associated with the former uranium mining activities in the Western Erzgebirge in Germany. Currently, many of these mines are being flooded. The flood water, which contains concen-tration of uranium penetrates through cracks and fissures of the phyllite and leads to a dissolution of several minerals. One of the major components in the phyllite is an iron-rich chlorite [1], which dominates the sorption behaviour for heavy metals.
During the dissolution of the chlorite a reaction causes the loss of octahedral layer cations, primarily Fe. Ferrous iron is released in the aqueous solution, where it is oxidized rapidly to ferric iron. Hydro-lysis of ferric iron leads to Fe-oxyhydroxide, which precipitates from the solution as due to the low solubility of iron in the pH region higher 4. By scanning electron microscopy, these precipitates of Fe-oxyhydroxide are detected as small spherical particles of ferrihydrite that are preferentially situated as immobile coatings on the most reactive edge surfaces of the chlorite crystals [2]. During the dissolution of chlorite a mobile component of ferrihydrite is formed, too. These are colloids, which are found under similar geochemical conditions. The mobile colloids are aqueous species that do not adsorb to rock surfaces. The adsorption of contaminants, for example uranium onto the colloidal particles of ferrihydrite influences and enhances the rate of contaminant transport. In previous investigations the uptake of uranium on ferrihydrite reaches almost 95-100 % in a pH range from 5.0 to 7.5 [1]. Conclusively, the formation of secondarily formed ferrihydrite as mobile colloids and as immobile coatings during the dissolution of chlorite in the rock phyllite is an important process which has to be considered in risk management.

References:
[1] Arnold, T. et al. (1998): Chemical Geology 151,
129-141.
[2] Krawczyk-Bärsch, E. et al. (2002): Chemical
Geology (submitted).





  • Lecture (Conference)
    80. Jahrestagung der Deutschen Mineralogischen Gesellschaft vom 8.9. - 12.9.02 in Hamburg
  • Beiheft zum European Journal of Mineralogy (2002)14, 92

Publ.-Id: 4460 - Permalink


Facility Management in Forschungseinrichtungen - unmöglich möglich?
Joehnk, P.;
  • Lecture (others)
    Workshop: "Technische Betriebsführung von A-Z", Heinrich Nickel GmbH, Bonn, 7.5.2002

Publ.-Id: 4459 - Permalink


Evaluation of QCD sum rules for light vector mesons at finite density and temperature
Zschocke, S.; Pavlenko, O. P.; Kämpfer, B.;
QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of mass parameters
for the lightest vector mesons ρ, ω and Φ in a strongly interacting medium. For conditions relevant for the starting experiments at HADES we find that the in-medium mass shifts of the ͦ and ω mesons are governed, within the Borel QCD sum rule approach, by the density and temperature dependence of the four-quark condensate. In particular, the variation of the strength of the density dependence of the four-quark condensate reflects directly the decreasing mass of the ρ meson and can lead to a change of the sign of the ω meson mass shift as a function of the density. In contrast, the in-medium mass of the Φ-meson is directly related to the chiral strange quark condensate which seems correspondingly accessible.
Keywords: QCD sum rules, vector meson properties

Publ.-Id: 4454 - Permalink


Chlorite dissolution relevant to environmental processes in Uranium tailings: influence on the Uranium(VI) migration
Krawczyk-Bärsch, E.; Arnold, T.; Walther, M.; Brandt, F.; Bosbach, D.; Bernhard, G.;
In flow-through reactor experiments the dissolution of a ripidolite chlorite (CCa-2) from Flagstaff Hill (El Dorado County, California, USA) was studied with the intention to approach mineral dissolution conditions occuring in the unsaturated zone of an uranium tailing. The experiments were conducted under atmospheric conditions, a temperature of 25 °C, an ionic strength of 0.1 M, and a pH of 7. In addition the experiments were conducted with and without 1.10-6 M uranium and also with and without a humic acid concentration of 5 mg/L.
During the first eight hours of the experiments high initial dissolution rates calculated from Mg, Si, Al and Fe concentrations were determined. These initial dissolution rates are attributed to reactive surface sites on the freshly crushed chlorite platelets /1/. High initial dissolution rates were obtained when using an aqueous solution with a humic acid or uranium concentration. The initial dissolution rates for Mg and Si are 250 times and 400 times greater than the initial dissolution rates determined in experiments with solutions free of humic acid. In uranium containing solutions an initial dissolution rate for Al was 50 times greater than in solutions free of uranium. It seems that humic acid as well as uranium ions initiate a fast dissolution of the chlorite mineral. A constant dissolution rate was obtained after 8 hours which is almost similar to experiments with solutions free of humic acid and uranium. Average dissolution rates of 3,18.10-12 and 1,86.10-11 mol.m-2.sec-1 were calculated for Mg and Si, respectively. The average dissolution rates for Fe and Al of 7,86.10-13 and 2,87.10-12 mol.m-2.sec-1 respectively seem to be very low. In fact they are primarily higher. But however, they are based on the concentration of Fe and Al in solution and do not consider precipitated Fe and Al phases. Due to the low solubility of Fe and Al in aqueous solutions with a pH > 5 Fe-oxyhydroxides and Al(OH)-phases are precipitating. Fe-oxyhydroxide particles have been detected on the {hk0}-faces of chlorite crystals and as well as immobile colloids in the surrounding solution /2/. Due to their very high specific surface area and their affinity to bind heavy metals the formation of secondary Fe-minerals may significantly influence as Fe-coatings and Fe-colloids the migration of uranium and other toxic heavy metals in uranium tailings. Additional EXAFS investigations of sorbed uranium on chlorite platelets were performed to find out if chlorite or the newly formed Fe-phases are responsible for the immobilization of uranium in the environment of uranium tailings.

/1/ Rochelle, C.A. et al., 1995. Mat. Res. Soc. Symp. Vol. 353, p. 149-156.
/2/ Krawczyk-Bärsch et al.: Formation of secondary iron oxyhydoxide phases during the
dissolution of chlorite - effect on uranium sorption. In: Chemical Geology (submitted).


  • Lecture (Conference)
    39th Annual Meeting of The Clay Minerals Society, June 8-13, 2002, Boulder, Colorado, USA

Publ.-Id: 4453 - Permalink


Füllstandswächter zur diversitären Grenzwertmeldung an Siedewasserreaktoren - Entwicklung und Erprobung
Prasser, H.-M.; Böttger, A.; Schütz, P.; Zschau, J.; Fleischer, S.; Gocht, T.; Hampel, R.;
Das Standardverfahren für die Füllstandsmessung von Flüssigkeiten in druckführenden Anlagenkomponenten von Kraftwerksanlagen basiert seit vielen Jahrzehnten auf einer Differenzdruckmessung. Am Siedewasserreaktor hat die Füllstandsmessung eine besonders hohe sicherheitstechnische Relevanz. Daher empfiehlt die Reaktorsicherheitskommission, eine diversitären Füllstandsmessung vorzusehen. Diversität bedeutet, dass das angewandte Verfahren nach einem andersartigen physikalischen Wirkprinzip funktionieren muss. Als diversitäres Messprinzip wurde die lokale Leitfähigkeitsmessung gewählt, mit der eine binär arbeitende Füllstandsdetektion zu realisieren war. Der Messwertgeber des vorgestellten Füllstandswächters ist für den Einbau in ein Standrohr vorgesehen. Der Nachweis der Flüssigphase geschieht durch Detektion deren elektrischer Leitfähigkeit. Der Füllstandswächter wurde entsprechend den Anforderungen an störfallfeste Instrumentierung für die Einbindung in den Reaktorsicherheitskreis entsprechend KTA 3505 ausgelegt. Weiterhin wurde er mit einem Selbsttest ausgestattet, die den Ausfall infolge Isolationsabfall oder Leitungsbruch signalisiert. Wesentliches Element des Messwertgebers ist eine isolierte Durchführung aus Aluminiumoxid-Sinterkeramik. Der Füllstandswächter wurde an einem Teststand der Hochschule Zittau/Görlitz unter Einsatznahen Bedingungen erprobt. Bei diesen und weiteren Tests wurde eine Standzeit von mindestens 5 Jahren bereits jetzt experimentell nachgewiesen. Die Qualifizierung des Füllstandswächters für den Einsatz im Kernkraftwerk ist im Gange. Sie umfasst hauptsächlich abschließende Entwicklungsschritte, die Durchführung der theoretischen und praktischen Prüfungen zur Bauartzulassung gem. KTA 3505 /3507 sowie die Untersuchung des Zusammenhangs von Füllstand im Standrohr und Füllstand im Reaktor zur Erarbeitung einer Konzeption zur Einbindung der Signale. Die Arbeiten zur Qualifizierung werden von Framatome ANP durchgeführt.
Keywords: coolant level, boilung water reactor, diversified level measurement system, conductivity probes
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Stuttgart, 14.-16. Mai 2002
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Stuttgart, 14.-16. Mai 2002

Publ.-Id: 4452 - Permalink


Charge trapping in light-emitting SiO2-layers implanted with Ge+ ions
Gebel, T.; Rebohle, L.; Skorupa, W.; Nazarov, A. N.; Osiyuk, I. N.; Lysenko, V. S.;
The trapping effects of negative and positive charges in Ge-enriched SiO2 layers during high-field electron injection from the Si-substrate of Al-SiO2-Si structures are studied. The capture cross-section and the concentration of negatively and positively charged traps are estimated and the location of the positively charged traps is determined. It is shown that increasing rapid thermal annealing (RTA) time from 6 s to 150 s at 1000°C leads to an enhanced diffusion of Ge towards the SiO2-Si interface and the increase of negatively and positively charged trap concentration. The mechanisms of the trap generation are discussed.
Keywords: silicon based light emission, charge trapping, nanocluster, electroluminescence
  • Applied Physics Letters 81 (2002) 1575

Publ.-Id: 4451 - Permalink


Observation of a hysteretic pseudogap behavior via coherent phonons in high temperature superconductors
Dekorsy, T.; Georgiev, N.; Helm, M.; Misochko, O. V.;
We investigate ultrafast reflectivity changes of a near-optimally doped YBa2Cu3O7-x (123) superconductor. The amplitude of coherently excited phonons show strong changes as a function of temperature above the superconducting transition temperature. These changes give evidence for two crossover temperatures within the pseudogap regime. In addition, these crossover temperatures exhibit a clear hysteretic behavior as a function of temperature.
Keywords: time-resolved spectroscopy, high temperature superconductivity, coherent phonons, quasi particle dynamics
  • Contribution to external collection
    Springer Series in Chemical Physics 71 (2003) 368-370

Publ.-Id: 4450 - Permalink


Structural studies of ion beam synthesized nanocrystals: diamond in SiC and SiC in diamond
Eichhorn, F.; Heera, V.; Weishart, H.; Schell, N.;
SiC and diamond are semiconductor materials with unique physical properties for very promising applications for high frequencies, high power and extreme environment (radiation, high temperature). However, the possibility of doping these materials are limited and complementary to each other. Only n-doped SiC and p-doped diamond can be produced in a reliable way [1]. It is found that p-n-junctions can be formed by ion beam synthesis of buried nanocrystallites, especially diamond in SiC [2] and SiC in diamond [3].
The materials studied were 6H-SiC(0001) implanted with 1x1018 cm-2 C+ (60 keV) at 900 °C and diamond(001) implanted with 5.3x1017 cm-2 Si+ (120 … 170 keV) at 900 °C. In this high temperature implantation processes nanocrystals of diamond are grown in 6H-SiC at a depth of (110 ± 30) nm below the surface and 3C-SiC nanocrystals in diamond at a depth of (90 … 130 ± 30) nm, respectively. At lower implantation temperatures it was not possible to grow diamond in 6H-SiC.
Various x-ray scattering techniques like coplanar diffraction, grazing incidence diffraction, texture studies, measurement of specular reflectivity, and reciprocal space mapping were used at laboratory and synchrotron (ROBL at ESRF) sources to study structural details of the material.
The nanocrystals of diamond have a diameter of 5 … 6 nm, and those of 3C-SiC a diameter of 7 … 8 nm. They are oriented completely heteroepitaxially according to
diamond < 1 1 1 > || substrate 6H-SiC < 0 0 0 1 >
diamond < 1 1 0 > || substrate 6H-SiC < 1 1 -2 0 >
3C-SiC < 0 0 1 > || substrate diamond < 0 0 1 >: all crystallographic directions of both cubic materials coincide.
The mosaicity (angular fluctuation of the alignment) is anisotropic to the surface and lies for diamond crystals in 6H-SiC in the range from 2° (220) to 6° (111) and for 3C-SiC crystallites in diamond in the range from 5° (111) to 12° (002), respectively.
The heteroepitactic growth is favoured by a partial coherence of the neighbouring crystal lattices: in both systems a 4:5 coherence between the crystal lattices of synthesized crystallites and substrate is observed:
5 x ddiamond(111) » 4 x d6H-SiC(0006) (1.027 nm » 1.004 nm)
5 x ddiamond(220) » 4 x d6H-SiC(11-20) (0.629 nm » 0.615 nm)
4 x a3C-SiC » 5 x adiamond (1.744 nm » 1.780 nm).
In all cases the strain does not exceed 2.3 %.
In conclusion it can be stated that well aligned nanocrystals can be grown by the ion beam synthesis at high temperatures in 6H-SiC as well as in diamond.


References
[1] - R. Kalish, Diamond and Related Materials 10, 1749 (2001)
[2] - V. Heera, W. Skorupa, B. Pécz and L. Dobos, Applied Physics Letters 76, 2847 (2000)
[3] - V. Heera, F. Fontaine, W. Skorupa, B. Pécz and A. Barna, Applied Physics Letters 77, 226 (2000)

Keywords: nanocrystals, x-ray diffraction, synchrotron x-rays, SiC, diamon
  • Poster
    X-TOP 2002 “6th Biennial Conference on High Resolution X-Ray Diffraction and Imaging” September 10–14, 2002 Grenoble-Aussois, France

Publ.-Id: 4449 - Permalink


AlN growth kinetics during ion nitriding of aluminum
Fitz, T.; Möller, W.;
To study the kinetics of Al ion nitriding, a series of experiments have been performed at an ion energy of 1.6 keV, an ion current density of 0.2 mA/cm2 and substrate temperatures varied from 250 °C to 400 °C. The nitride layers have been analyzed by nuclear reaction analysis (NRA) and scanning electron microscopy (SEM). Binary collision computer simulations have been performed to calculate the sputtering yields of N and Al. Depending on the experimental conditions, the nitriding kinetics is either controlled by the supply of N atoms from the ion beam or by the diffusion of Al atoms trough the growing nitride layer. Solutions of rate equations describing the growth of the nitride layer are fitted to the experimental data, from which diffusion and activation parameters are obtained for the transport of the Al atoms.
Keywords: Aluminium, nitriding, diffusion, AlN
  • J.Appl.Phys. Vol. 92, No. 11, (2002) p.6862-6867

Publ.-Id: 4448 - Permalink


An in-depth investigation of the energy distribution of doubly charged ions emitted from a liquid metal alloy ion source
Mair, G.; Bischoff, L.; Mair, A.; Aidinis, C.; Ganetsos, T.; Aleiev, C.;
We investigate the energy spread, dE½, vs emission current, i, of the doubly-charged ions emitted by a Au77Ge14Si9 Liquid Metal Alloy Ion Source (LMAIS). For the ionic species of main interest, namely Ge++, two modes were found with regard to the dependence of dE½ on i. In the first mode dE½ ~ i^ 0.3 and in the second dE½ ~ i . The difference is attributed to changes in the composition of the alloy during field-evaporation. Au++ an Si++ were also found to obey a dE½ ~ i^ 0.3 law; in the case of Si++ however, there is a deviation from this law at high currents.
Keywords: alloy liquid metal ion source, energy spread, doubly charged ions
  • Journal of Physics D: Applied Physics 35 (2002) L33 - L36

Publ.-Id: 4446 - Permalink


Electroproduction of Strangeness on Light Nuclei
Dohrmann, F.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Assamagan, K.; Avery, S.; Bailey, K.; Baker, O. K.; Beedoe, S.; Bitao, H.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Collins, G.; Cothran, C.; Crowder, J.; Cummings, W. J.; Danagoulian, S.; Duncan, F.; Dunne, J.; Dutta, D.; Eden, T.; Elaasar, M.; Ent, R.; Ewell, L.; Fenker, H.; Fortune, H. T.; Fujii, Y.; Gan, L.; Gao, H.; Garrow, K.; Geesaman, D. F.; Gueye, P.; Gustafsson, K.; Hafidi, K.; Hansen, J. O.; Hinton, W.; Jackson, H. E.; Juengst, H.; Keppel, C.; Klein, A.; Koltenuk, D.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Madey, R.; Markowitz, P.; Martoff, C. J.; Meekins, D.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mohring, R.; Mtingwa, S. K.; Mueller, B.; O'Neill, T. J.; Niculescu, G.; Niculescu, I.; Potterveld, D. H.; Price, J. W.; Raue, B. A.; Reimer, P. E.; Reinhold, J.; Roche, J.; Roos, P.; Sarsour, M.; Sato, Y.; Savage, G.; Sawafta, R.; Segel, R. E.; Semenov, A. Y.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Terburg, B.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan-1, C.; Yan-2, C.; Yuan, L.; Zeier, M.; Zeidman, B.; Zihlmann, B.;
The A(e,e'K+)YX reaction has been investigated in Hall C at Jefferson Laboratory for 6 different targets. Data were taken for Q2)approx 0.35 and 0.5 GeV2) at a beam energy of 3.245GeV for 1)H, 2)H, 3)He, 4)He, C and Al targets. The missing mass spectra are fitted with Monte Carlo simulations taking into account the production of Lambda and Sigma0) hyperon production off the proton, and Sigma-) off the neutron. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for Lambda-hypernuclear bound states is seen for 3,4)He targets.
Keywords: Electroproduction of strangeness, Nuclear targets, Spectral function
  • Lecture (Conference)
    B.A. Mecking and C.E. Carlson(eds.) Proceedings of the 9th International Conference on the Structure of Baryons, Baryons 2002, March 3-8 2002, Jefferson Lab, Newport News, VA, USA World Scientific, New Jersey, 2003 , 585-588
  • Contribution to proceedings
    B.A. Mecking and C.E. Carlson(eds.) Proceedings of the 9th International Conference on the Structure of Baryons, Baryons 2002, March 3-8 2002, Jefferson Lab, Newport News, VA, USA World Scientific, New Jersey, 2003 , 585-588

Publ.-Id: 4445 - Permalink


Transition from amorphous boron carbide to hexagonal boron carbon nitride thin films induced by nitrogen ion assistance
Gago, R.; Jiménez, I.; Agullo-Rueda, F.; Albella, J. M.; Czigány, Z.; Hultman, L.;
Boron carbon nitride films (BCN) were grown by B4C evaporation under concurrent N2 ion beam assistance (IBAD). The films were characterized by x-ray absorption near edge spectroscopy, IR and Raman spectroscopy and high-resolution transmission electron microscopy. The bonding structure and film composition correlate with the momentum transfer per incoming atom during deposition. As the momentum transfer is increased, the film structure evolves from an amorphous boron carbide network towards a hexagonal ternary compound (h-BCN) with standing basal planes. The growth of h-BCN takes place for momentum transfer in the window between 80 and 250 (eVxamu)1/2. The characteristic vibrational features of the h-BCN compounds have also been studied. Finally, the solubility limit of carbon in the hexagonal BN structure, under the working conditions of this report, is found to be ~15 at. %.
Keywords: Boron carbon nitride, IBAD, XANES, IR and Raman
  • Journal of Applied Physics 92 (2002) 5177-5182

Publ.-Id: 4444 - Permalink


N1-Methyl-9-[(4-[18F]fluoro-3-hydroxymethylbutyl]guanine [18F]MFHBG as new substrate of HSV-1-thymidine kinase to monitor gene expression?
Noll, B.; Grote, M.; Noll, S.; Bergmann, R.; Wolkersdorfer, G.; Johannsen, B.;
Aim
Gene therapy with the transfer of Herpes simplex virus type 1 thymidine kinase gene (HSV1-tk) has shown significant potential in treating several cancers. Many nucleoside analogues are known to localize selectively HSV1-tk transfected cells and show a high specificity for the viral enzyme, especially acyclic nucleosides such as ganciclovir or penciclovir. The penciclovir derivative [18F]FHBG is one of the proposed tracer for monitoring the gene expression by positron emission tomography. In order to improve the tracer properties, we modified the lipophilicity of [18F]FHBG by introduction of a methyl group into the N1-position to get N1-methyl-9-[(4-[18F]fluoro-3-hydroxymethylbutyl]guanine 3.

Materials and methods
The precursor 1 and the nonradioactive reference substance (MFHBG) were prepared by methylation of N1-Methyl-N2-(p-anisyldiphenylmethyl)-9-[(4-(p-toluene-sulphonyloxy))-3-(p-anisyldiphenylmethoxy)-methyl-butyl]guanine with methyl iodide in the N1 position. The precursor 1 reacts with a [18F]KF kryptofix complex to the intermediate 2 in a 65-75 % radiochemical yield. In a second step the protecting groups are removed from 2 by heating in methanolic HCl solution. The tracer is purified by RP HPLC separation. The identity of the tracer [18F]MFHBG with the nonradioactive reference compound was also proved by HPLC. The in vitro uptake of [18F]FHBG and [18F]MFHBG was evaluated into transduced and non-transduced human MC 38 cells.

Results
The labelling yield amounts to 70%, and the radiochemical purity of the tracer is greater than 98 %. Biodis-tribution data of [18F]MFHBG show a fast blood clearance without remarkable erythrocyte binding. An ini-tial high uptake of the tracer was found in the spleen, kindney and liver, which decreased rapidly in time. No metabolites were found. The rapid blood and organ clearance (faster than for [18F]FHBG) and the high in vivo stability of [18F]MFHBG are considered advantageous for in vivo monitoring of the gene transfer in tumours. The uptake of [18F]MFHBG is however lower than the uptake of [18F]FHBG in HSV1-tk trans-fected cell lines.

Conclusion
The novel tracer 9-[(4-[18F]fluoro-3-hydroxymethyl-butyl]-guanine ([18F]MFHBG) seems to be inferior to [18F]FHBG because of lower uptake in the target cells. It is assumed that the molecule position chosen for methylation is unsuitable for the anticipated improvement of the tracer.
  • Poster
    Annual Congress of the European Association of Nuclear Medicine, Vienna, 31.08.-04.09.2002

Publ.-Id: 4443 - Permalink


A new approach for a C-11-C bond formation: Synthesis and biodistribution studies of 17a-(3'-[11C]prop-1-ynyl)-3-methoxy-3,17b-estradiol
Wüst, F.; Zessin, J.; Bergmann, R.; Pawelke, B.;
AIMS: To expand the scope of 11C-labelled compounds, novel 11C-C bond forming reactions gain more and more attention. In this context, technically simple, high-yielding and functional group tolerating reactions are of particular interest. The Sonogashira copper-palladium catalysed coupling of terminal alkynes with aromatic and vinylic halides represents such a reaction. To the best of our knowledge, the Sonogashira-reaction has not yet been employed in 11C-chemistry. In this work we describe a modified Sonogashira-like reaction for labelling the terminal alkyne group of the potent contra-ceptive steroid mestranol with [11C]methyl iodide and biodistribution studies of the title compound.
METHODS: Pd2(dba)3/AsPh3/TBAF as catalyst/co-ligand/base combination was used to form the desired cross-coupling product in sufficient radiochemical yield. The labelling position was verified by the synthesis of the corresponding 13C-labelled compound using the same cross-coupling protocol. Biodistribution studies were performed with immature female Wistar rats. One group of animals was pre-treated with 1 mg/kg body weight 17a-ethynyl-estradiol 10 minutes before injecting the 11C-labelled compound. Radioactivity distribution in organs of interst was studies after 5 and 60 minutes after injection. Blood plasma samples were taken for metabolite analysis by means of radio-HPLC.
RESULTS: A new approach for a 11C-C bond formation via a Sonogashira-like cross-coupling reaction of terminal acetylenes with [11C]MeI was exemplified by the synthesis of 17a-(3'-[11C]prop-1-ynyl)-3-methoxy-3,17b-estradiol. Classical conditions of the Sonogashira reaction (Pd0, CuI and TEA or DIPA as the base) can not be employed for 11C-labelling with [11C]methyl iodide due to the rapid quaternization of the amine base. Using optimized alternative reaction conditions (Pd2(dba)3/AsPh3/TBAF/[11C]MeI/ steroid in THF, 5 minutes at 60°C) the title compound was obtained in decay-corrected radiochemical yields of 27-47% (n=8) based on [11C]MeI within 21-27 minutes after EOB. In a typical synthesis, 1-2 GBq of 17a-(3'-[11C]prop-1-ynyl)-3-methoxy-3,17b-estradiol could be synthesized in radiochemical purity >99%. The specific activity ranged between 10-19 GBq/µmol, and the labeling position was verified by the synthesis of the corresponding 13C-labeled compound. Biodistribution studies after 5 min. and 60 minutes exhibited no specific binding in target organs (uterus, ovaries). The highest uptake of radioactivity was observed in the fat (4.7% ID/g tissue nomalized to 100 g body weight at 60 minutes). The compound was fast metabolized and biliary eliminated.
CONCLUSION: We developed a new method for a 11C-C bond formation employing the cross-coupling of terminal alkynes with [11C]methyl iodide via a Sonogashira-like reaction in sufficient radiochemical yields. The biodistribution data of the title compound are consistent with the high lipophilicity of the compound.
  • Lecture (Conference)
    Turku PET Symposium, May 2002

Publ.-Id: 4442 - Permalink


Effect of hypoxia/hypercapnia on metabolism of 6-[18F]fluoro-L-DOPA in newborn piglets
Bauer, R.; Brust, P.; Walter, B.; Vorwieger, G.; Bergmann, R.; Elhalag, E.; Fritz, A.; Steinbach, J.; Füchtner, F.; Hinz, R.; Zwiener, U.; Johannsen, B.;
There is evidence that the dopaminergic system is sensitive to altered pO2 in the immature brain. However, the respective enzyme activities have not been measured in the living neonatal brain together with brain oxidative metabolism. Therefore 18F-labelled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) together with positron emission tomography (PET) was used to estimate the activity of the aromatic amino acid decarboxylase (AADC) in the brain of fifteen newborn piglets (2 - 5 days old). Two PET scans were performed in each piglet. Eleven animals underwent a period of normoxia and moderate hypoxia/hypercapnia (H/H). The remaining four animals were used as an untreated control group. Simultaneously, the brain tissue pO2 was recorded, the regional cerebral blood flow (CBF) was measured with colored microspheres and the cerebral metabolic rate of oxygen (CMRO2) was determined. In addition, in four untreated and six H/H treated piglets the relative amounts of fluorodopamine and the respective metabolites were determined in brain tissue samples using HPLC analysis. H/H conditions were induced by lowering the inspired fraction of oxygen from 0.35 to 0.10 and adding CO2 to the inspired gas resulting in an arterial pO2 between 74 and 79 mmHg. H/H elicited a more than 3-fold increase of the CBF(P < 0.05) so that CMRO2 remained unchanged throughout the H/H period. Despite this, the brain tissue pO2 was reduced from 19 ± 4 to 6 ± 3 mmHg /P < 0.05). The permeability-surface area product of FDOPA (PSFDOPA) was unchanged. However, the transfer rate of FDOPA (k3FDOPA of the nigrostriatal dopaminergic system and the relative amounts of fluorodopamine and the respective metabolites were significantly increased (P < 0.05). It is suggested that H/H induces an increase of AADC activity. However, an H/H-induced CBF increase maintains bulk O2 delivery and preserves CMRO2.
Keywords: FDOPA; Aromatic amino acid decarboxylase; Dopamine metabolism; Positron emission tomography; Colored microspheres; Newborn piglets
  • Brain Research 934 (2002) 22-33

Publ.-Id: 4441 - Permalink


Kombinierter Einsatz von FCKW und Tritium als Tracer
Mibus, J.; Szymczak, P.; Hebert, D.; Oster, H.;
Zur Bewertung der Grundwassergeschütztheit werden neben hydrogeologischen und hydrochemischen Untersuchungen auch die Altersdatierung der Grundwässer anhand der Konzentration des Tritiums (³H) herangezogen. Rückläufige Tritiumkonzentrationen im Niederschlag und eine im Modell-ansatz begründete, häufig auftretende Ambiguität der Ergebnisse schränken die Anwendbarkeit ein oder erfordern Zusatzinformationen. Eine Möglichkeit zum Informationsgewinn stellt die Messung von im low-level Konzentrationsbereich auftretenden FCKW dar. Die kombinierte Anwendung beider Umwelttracer wird in einem Gemeinschaftsprojekt bei der Untersuchung einer Trinkwasserfassung in der Jahna-Aue (Nordwest-Sachsen) gezeigt.
Aus dem Zusammenhang zwischen Tritium-Konzentration und dem aus FCKW-Gehalten berechneten Jungwasseranteil konnten Rückschlüsse über die Verweilzeit der Wässer in der Aerationszone gezogen werden. Damit war es möglich, das mehrdeutige Ergebnis der Simulation der Output-Funktion des Tritiums eindeutig zu interpretieren. Die Grundwässer weisen bei mittleren Verweilzeiten von ca. 50 Jahren eine gute Geschütztheit auf.
  • Contribution to external collection
    Isotopen und Tracer in der Wasserforschung, TU BA Freiberg, 21.6.2002

Publ.-Id: 4440 - Permalink


Validation of a creep and plasticity model for French and German RPV-steels
Willschütz, H.-G.; Altstadt, E.; Sehgal, B. R.; Weiß, F.-P.;
For pre- and post-test calculations of Lower Head Failure experiments like FOREVER or OLHF it is necessary to model creep and plasticity processes. Therefore a Finite Element Model is developed using a numerical approach which avoids the use of a single creep law employing constants derived from the data for a limited stress and temperature range. Instead of this a numerical creep data base (CDB) is developed where the creep strain rate is evaluated in dependence on the current total strain, temperature and equivalent stress. The CDB includes the primary, secondary and tertiary creep stage. A main task for this approach is the generation and validation of the CDB. The source for the CDB are uniaxial creep tests, like the REVISA-experiments.
For an evaluation of the failure times a damage model is necessary. The applied damage model accounts for the triaxiality of the mechanical stresses according to an approach of Lemaitre.
The validation of the numerical model is performed by the simulation of and comparison with experiments. This is done in 3 levels: starting with the simulation of single uniaxial creep tests, which is considered as a 1D-problem. In the next level so called “tube-failure-experiments” are modeled: the RUPTHER-14 and the “MPA-Meppen”-experiment. These experiments are considered as 2D-problems. The last level considers the application of the numerical model to scaled 3D-experiments, where the lower head of a PWR is represented in its hemispherical shape, like in the FOREVER-experiments.

Keywords: creep and plasticity, Finite Element Model, French and German RPV-steel
  • Lecture (Conference)
    OLHF Seminar 2002, Madrid, Spain, June 2002; OECD Nuclear Energy Agency Proceedings February 2003, NEA/CSNI/R(2003)1, pp 117-136
  • Contribution to proceedings
    OLHF Seminar 2002, Madrid, Spain, June 2002; OECD Nuclear Energy Agency Proceedings February 2003, NEA/CSNI/R(2003)1, pp 117-136

Publ.-Id: 4439 - Permalink


Cavitation behind a fast acting flap valve and prevention of water hammers
Prasser, H.-M.; Böttger, A.; Zschau, J.; Dudlik, A.; Schlüter, S.;
Fast shut-off experiments were carried out at a 200 m long experimental pipeline of the Fraunhofer Institute for Environmental, Safety, and Energy Technology (UMSICHT) in Oberhausen, Germany. The cavitation bubbles occurring at the fast acting valve were recorded by means of mesh sensors. Primarily these sensors record distributions of the electrical conductivity in the measuring cross section, which are converted into void fraction distributions, stored with a rate of 1024 frames per second. An excentrical butterfly valve was used to shut off the pipeline. The sensor was located at different positions up- and downstream the valve. In a pipe of 100 mm nominal diameter the cavitation bubble was recorded at distances of 0,15 m and 1,5 m downstream the valve. In the presentation, computer animations of the measured signals will be shown, in which the appearance and the collapse of the bubbles are visible in high temporal and spatial resolution. Furthermore, the influence of a pipe bridge located behind the valve as well as the damping effect of injected air to the amplitude of the pressure peaks will be discussed on the basis of such visualisations. Special cavitation patterns occurred during partial closing of the valve. In another experiment two sensors were directly flanged to a flap valve of 50 mm nominal diameter, located in the rear section of the pipeline. It was found that cavitation appeared also upstream the valve as well as at the edge of the flap of the valve. With the help of the obtained information it was possible to design measures for water hammer prevention. A back valve put at a certain distance downstream the shut-off valve closes in the moment of flow reverse. In this way, the cavitation bubble is captured and the cavitation collapse cannot occur. The closure of the back valve itself is not accompanied with a pressure peak. Water hammers upstream the main valve are prevented by a second measure: a disc brake acting at the shaft of the flap valve, which is interrupting the closing movement of the flap when the upstream pressure starts to grow. A combination of both methods allows to cut off the liquid flow without pressure peaks in the smallest possible time.
Keywords: water hammers, mesh sensors, void measurement, fast acting valve, cavitation
  • Lecture (Conference)
    XXXIV. Kraftwerkstechnisches Kolloquium, TU Dresden, 24.-26. September 2002, Vortrag VM8, Kurzfassung in Beitragsmanusskripte, S. 184.

Publ.-Id: 4438 - Permalink


Sorption of Uranium(VI) onto ferric oxides in sulfate-rich acid waters
Walter, M.; Arnold, T.; Reich, T.; Bernhard, G.;
The Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was used to study the sorption of uranium(VI) on schwertmannite and goethite. Samples for EXAFS analysis were prepared under N2 atmosphere with initial uranium(VI) concentrations of 1x10-5 (pH 6.5) to 5x10-5 M (pH 4.2). The ionic strength was adjusted to 0.02 N Na2SO4 or 0.01 N NaClO4, respectively. The results from EXAFS spectroscopy of uranium(VI) sorbed on goethite in sulfate-rich, acid and near-neutral solutions indicate that uranium(VI) is sorbed as an inner-sphere mononuclear bidentate surface complex which is coordinated to ferric iron at a distance of 3.44 Å. The uranium(VI) sorbed onto schwertmannite in acid and sulfate-rich solution is coordinated to one or two sulfate molecules at a distance of 3.66 Å. The EXAFS results indicate the formation of mononuclear-monodentate surface complexes and partly, of binuclear-bidentate surface complexes coordinated to the structural sulfate of schwertmannite. Considering the uncertainty in assigning the sulfate either to the bulk structure or to adsorption reactions, the formation of ternary uranium(VI)-sulfate surface complexes could not be excluded. Due to the release of sulfate from schwertmannite in perchlorate solution, the uranium(VI) adsorption occurs predominantly as a mononuclear bidentate complexation with the ferric iron.
Keywords: uranium, schwertmannite, goethite, EXAFS, acid mine drainage, sorption

Publ.-Id: 4437 - Permalink


Einfluss des Gefüges auf die Neutronenversprödung von Reaktordruckbehälterstählen
Böhmert, J.; Viehrig, H.-W.; Ulbricht, A.;
Neutronenstrahlen führen zu einer Degradation der mechanischen Eigenschaften niedriglegierter Stähle, die als Neutronenversprödung bezeichnet wird. Sie wirkt sich vorzugsweise als Erhöhung der Übergangstemperatur zwischen sprödem und duktilem Bruchverhalten und in einer Absenkung der Hochlagenbruchenergie aus. Die Größe des Effektes ist von der Neutronendosis abhängig, wird aber darüber hinaus vor allem mit dem Gehalt an bestimmten, versprödungsfördernden Elementen in Verbindung gebracht. Vergleichende Untersuchungen an Proben aus der Wand eines Druckbehälters, aus der Schweiße und der Wärmeeinflusszone oder an Proben aus unterschiedlichen Tiefenlagen eines Druckbehälters zeigen jedoch klar, dass die Gefügeausbildung einen dominierenden Einfluss ausübt. Es werden die Ergebnisse von mechanischen Prüfungen (Charpy-Versuche, Zugversuche, Bruchzähigkeitsbestimmung) nach Bestrahlungen bis 5 x 10 19 n/cm2 [E < 1 MeV] bei 255 °C vorgestellt. Die strahleninduzierten Strukturdefekte werden mit Hilfe der Neutronenkleinwinkelstreuung analysiert. Die erhaltenen Korrelationen zwischen den Änderungen der mechanischen Eigenschaften und den Strukturparametern werden unter dem Aspekt der unterschiedlichen Ausgangsgefüge klassifiziert und hinsichtlich ihrer Verträglichkeit mit bekannten Modellen zum Mechanismus der Neutronenversprödung bewertet.
  • Poster
    7. Tagung "Gefüge und Bruch", Tagungsband, Leoben (Österreich), April 2002, S. 129
  • Contribution to proceedings
    7. Tagung "Gefüge und Bruch", Tagungsband, Leoben (Österreich), April 2002, S. 129

Publ.-Id: 4436 - Permalink


Thermal Parameters in Heavy Ion Collisions at SPS and RHIC: Centrality Dependence
Kämpfer, B.; Cleymans, J.; Gallmeister, K.; Wheaton, S.;
The centrality dependence of thermal parameters describing hadron multiplicities and intermediate-mass dilepton spectra in heavy-ion collisions at SPS and RHIC is analyzed. From hadron multiplicities we deduce evidence for strangeness saturation at high energy and maximum centrality. The dilepton spectra can be parameterized by a centrality independent temperature.
Keywords: relativistic heavy-ion collisions, thermal models, hadron yields, dileptons
  • Acta Phys Hung NS-H 18(1):1-10 2003

Publ.-Id: 4435 - Permalink


Synthetische und modifizierte Huminsäuren zur Untersuchung des Wechselwirkungsverhaltens von Huminsäuren mit Metallionen
Sachs, S.; Heise, K.-H.; Bernhard, G.;
Huminstoffe sind aufgrund ihrer ausgeprägten Eigenschaft, Metallionen zu komplexieren, in der Lage, die Speziation von Metallionen in der Umwelt und somit auch deren Ausbreitungsverhalten zu beeinflussen. Bedingt durch ihre große strukturelle und funktionelle Heterogenität in Abhängigkeit von ihrer Herkunft ergeben sich Probleme bei der Beschreibung ihres Wechselwirkungsverhaltens mit Metallionen in natürlichen Systemen. Zur detaillierten Untersuchung des Wechselwirkungsverhaltens von Huminsäuren mit Metallionen wurden am Institut für Radiochemie des Forschungszentrums Rossendorf Huminsäuremodellverbindungen mit unterschiedlichen strukturellen und funktionellen Eigenschaften, basierend auf dem Melanoidinkonzept, entwickelt [1,2]. Darüber hinaus wurde ein Verfahren zur Synthese von chemisch modifizierten Huminsäuren, Huminsäuren mit blockierten phenolischen OH-Gruppen, erarbeitet [3]. Mit diesen Huminsäuren kann der Einfluß phenolischer OH-Gruppen auf das Wechselwirkungsverhalten von Huminsäuren mit Metallionen untersucht werden. Zur Untersuchung der Redoxeigenschaften von Huminsäuren sowie der Redoxstabilität von Metall-Humat-Komplexen werden Huminsäuremodellverbindungen mit ausgeprägter Redoxfunktionalität entwickelt.
Der Vortrag gibt einen Überblick zur Synthese und Anwendung von Huminsäuremodellverbindungen. Anhand der synthetischen Huminsäure vom Typ M1 [1] wird die Präparation von chemisch modifizierten Huminsäuren mit blockierten phenolischen OH-Gruppen erläutert. Ergebnisse NMR-spektroskopischer Untersuchungen, die den Verlauf des Modifzierungsprozesses bestätigen [4], werden diskutiert. Die Synthese von Huminsäuren mit ausgeprägt reduzierenden Eigenschaften wird vorgestellt und das Fe(III)-Reduktionsvermögen dieser Huminsäuremodellverbindungen mit dem natürlicher und anderer synthetischer Huminsäuren verglichen.

Literatur
[1] Pompe (Sachs), S. et al., Radiochim. Acta 74, 135 (1996).
[2] Pompe (Sachs), S. et al., Wissenschaftlich-Technische Berichte FZR-290, Rossendorf 2000.
[3] Pompe (Sachs), S. et. al., Radiochim. Acta 88, 553 (2000).
[4] Sachs, S. et al., Talanta, zur Publikation angenommen.

Keywords: Huminsäuren, Modellverbindungen, Modifizierung, Komplexierung, Redoxfunktionalität
  • Lecture (others)
    Symposium über Torfpräparate in der Medizin, Veterinärmedizin und Körperpflege, Bad Langensalza, 23.-24.Mai 2002
  • Contribution to external collection
    Sitzungsberichte der Mathematisch-Naturwissenschaftlichen Klasse der Akademie gemeinnütziger Wissenschaften zu Erfurt 2002. Sitzungsberichte der Mathematisch-Naturwissenschaftlichen Klasse 12 (2003) 125-137, ISBN 3-932295-62-5

Publ.-Id: 4434 - Permalink


Endangered glass objects identified by ion beam analysis
Neelmeijer, C.; Mäder, M.;
Art objects of glass are subjected to ageing processes even under air conditioning of museums. Glass surfaces are decomposed and sometimes their transparency is considerably reduced. This is the consequence of chemical processes which take place between the silicate network and the humidity of the ambient atmosphere. In particular, potassium-calcium-silica glasses are affected. Degradation takes place via ion exchange reactions where potassium and calcium are leached out and hydrogen-bearing species are incorporated into the silicate structure. Endangered glass objects of museums should be indicated by means of non-destructive composition analysis. Simultaneous use of the ion beam methods PIXE, PIGE and RBS at a non-vacuum facility proves ideal to determine both the corrosion state of the glass surface and the composition of the glass bulk. The results allow recommendations to museums regarding demands of special storage conditions. Art scientists may deduce details on the glass prove-nience or on special manufacturing technologies.
Keywords: glass corrosion, glass deterioration, glass disease, museum glass objects, non-destructive glass analysis, preventive ion beam analysis, PIXE, PIGE.
  • Lecture (Conference)
    Art2002, 7th Int. Conf. on Non-destructive Testing and Microanalysis for the Diagnostics and Conservation of the Cultural and Environmental Heritage, Antwerpen, Belgien, 2.-6. Juni 2002, Conference Proceedings
  • Contribution to external collection
    René Van Grieken, Koen Janssens, A.A. Balkema Publishers: Cultural Heritage Conservation and Environmental Impact Assessment by Non-Destructive Testing and Micro-Analysis, London: Taylor & Francis Group, 2005, 211-222

Publ.-Id: 4433 - Permalink


Strahlende Stützen - Radioaktiv markierte Stents verhindern die Re-Stenose von Blutgefäßen
Ottow, S.; Noll, B.;
Das Forschungszentrum Rossendorf (FZR) wurde am 1. Januar 1992 aus dem Zentralinstitut für Kernforschung der Akademie der Wissenschaften der DDR gegründet. Im neu gewonnenen Profil des FZR bilden nunmehr seit zehn Jahren Materialforschung, Biochemie-Medizin, Umwelt- und Sicherheitsforschung sowie Kernphysik die Schwerpunkte.
Durch seine Vergangenheit hat die Forschung rund um die Radioaktivität im FZR eine lange Tradition. Und genau dieser Tradition folgt der Beitrag "Strahlende Stützen". Er befasst sich mit dem Einsatz von Radioaktivität in der Medizin, die nicht nur zur Bekämpfung von Krebs ein unerlässliches Hilfsmittel ist. Mediziner setzen Radioaktivität zur Behandlung der unterschiedlichsten Krankheiten ein, so auch zur Behandlung von Arteriosklerose.
  • Leibniz 1 (2002) 13-14

Publ.-Id: 4432 - Permalink


Tc and Re chelates of 8alpha-amino-6-methyl-ergoline: synthesis and affinity to the dopamine D2 receptor
Spies, H.; Noll, B.; Noll, S.; Findeisen, M.; Brust, P.; Syhre, R.; Berger, R.;
The influence of structural changes at the 8alpha-amino position of 8alpha-amino-6-methyl-ergoline on the lipophilicity and affinity to the D2 receptor was studied.8alpha-amino- 6-methyl-ergoline (1) was converted into the derivatives (2a-f) by mercaptoacylation of the amino group to make it possible to prepare the rhenium and technetium complexes (3, 4a,b). Binding tests on cloned human dopamine D2 receptors show that the affinities of the coordination compounds (IC50 values between 50 and 240 nM) are less than those of the derivatives 2a-f (IC50= 3 to 50 nM) but more than those of the parent compound 1. Biodistribution studies of the Tc complexes 4a,b performed on Wistar rats show a slow blood clearance with substantial accumulation and retention in the liver and kidneys and low brain uptake.
  • Bioorganic and Medicinal Chemistry 10 (2002) 3523-3528

Publ.-Id: 4430 - Permalink


5HT1A- and 5HT2A-receptors during social isolation in mice
Oehler, J.; Schiller, L.; Kretzschmar, M.; Brust, P.;
Social isolation is an animal model for analysing behavioural and neurobiological processes caused by impairment of organism
environment relationships. In previous studies we found time dependent changes in behaviour and central transmitter metabolism
especially in the serotonergic and dopaminergic systems (Rilke et al. 1998a, Rilke et al. 1998b).
The aim of the study was to find out time-dependent effects of social isolation after 4 and 12 weeks at serotonin receptor 5HT1A- and
5HT2A-subtypes. Autoradiographic studies in distinct brain regions were carried out and the Bmax-values were determined.
After 4 weeks Bmax-values for both subtypes were diminished in all analysed brain regions. After 12 weeks of isolation weaker alterations were found. Only the Bmax-values for the 5HT1A-receptor in the hippocampus were significantly decreased. Furthermore up-regulations for both receptors were found in some regions.
The results we-re discussed in relation to biochemical and behavioural changes.
  • Poster
    7th World Congress of Biological Psychiatry, Berlin, 01.-06.07.2001
  • Abstract in refereed journal
    World J. Biol. Psychiatry 2 (2001) 221S

Publ.-Id: 4429 - Permalink


5HT1A- and 5HT2A-receptors during social isolation in mice
Schiller, L.; Kretzschmar, M.; Oehler, J.; Brust, P.;
Social isolation is an animal model for analysing behavioural and neurobiological processes caused by impairment of organism environment relationships. In previous studies we found time dependent changes in behaviour and central transmitter metabolism especially in the serotonergic and dopaminergic systems (Rilke et al. 1998a, Rilke et al. 1998b).
The aim of the study was to find out time-dependent effects of social isolation after 4 and 12 weeks at serotonin receptor 5HT1A- and 5HT2A-subtypes. Autoradiographic studies in distinct brain regions were carried out and the specific binding [fmol/mg protein] was determined. After 4 weeks specific binding for both receptor subtypes was diminished in all analysed brain regions of isolated mice in comparison to group housed animals. After 12 weeks of isolation, weaker alterations were found. Only the specific [3H]8-OH-DPAT binding for the 5HT1A-receptor in the hippocampus was significantly decreased. Furthermore up-regulations for both receptors were found in some regions. The results are discussed in relation to biochemical and behavioural changes.
  • Poster
    28th Göttingen Neurobiology Conference, Göttingen, 07.-10.06.2001
  • Contribution to proceedings
    Procceedings of the 4th Meeting of the German Neuroscience Society 2001, Volume II 28th Göttingen Neurobiology Conference (edited by Norbert Elsner and Georg W. Kreutzberg)

Publ.-Id: 4428 - Permalink


Untersuchung der Tumoraffinität, der Aufnahmekinetik und des Transportmechanismus von 3-O-methyl-6-[123I]iodo-L-DOPA (OMID) in HT-29 Zellen und Tumoren
Bergmann, R.; Wunderlich, G.; Füchtner, F.; Runge, R.; Steinbach, J.; Bredow, J.; Johannsen, B.;
Ziel:
Die deutliche Darstellung von Hirntumoren mit 3-O-methyl-6[18F]fluoro-L-DOPA (OMFD) in der PET lässt erwarten, dass auch der analoge, iodsubstituierte Radiotracer OMID von Tumoren mit erhöhtem Aminosäuretransport aufgenommen wird. Deshalb wurde die Aufnahmekinetik und der Transportmechanismus in Zellkulturen und die Bioverteilung von OMID in Nacktmäusen mit transplantierten Tumoren untersucht.

Methodik:
Ausgehend vom Precursor für das 3-O-methyl-6-[18F]fluoro-L-DOPA (OMFD) wurde das analoge 123I synthetisiert. Die Aufnahmekinetik von OMID in HT-29 Zellen wurde in Na+-haltigem und Na+-freiem Puffer und in Anwesenheit verschiedener Transportinhibitoren, wie 2-Aminobicyclo-[2,2,2]heptan-2-carbonsäure (BCH), L-Leucin, L-Phenylalanin und alpha-(Methylamino)-isobuttersäure (MeAIB) gemessen. Die Bioverteilung von OMID wurde an tumortragenden (HT-29) Nacktmäusen (5, 10, 30, 60, 120 min p.i.) untersucht.

Ergebnisse:
Die Aufnahme von OMID in HT-29-Zellen konnte durch Inhibitoren der L-Aminosäuretransporter gehemmt werden, von anderen Transportinhibitoren dagegen kaum. Der Influx des Tracers ist dabei unabhängig von Na-Ionen. Nach Inkubation (60 min) von OMID mit HT-29 Zellen und anschließender Proteinfällung konnte keine signifikante Aktivität in der Proteinfraktion gefunden werden. Die HPLC-Analyse der im Urin nach einer Stunde ausgeschiedenen Aktivität (39,5±4,9%ID) ergab einen Aktivitätspeak, der zur gleichen Zeit wie OMID eluiert wurde. Die Aktivität in der Schilddrüse war zu allen Zeiten kleiner 0,5%ID. 3,6±0,7%ID/g Gewebe wurden nach einer Stunde im Tumor gefunden. Dadurch ergaben sich Tumor zu Gewebsverhältnis (%ID/g Tumor/%ID/g Gewebe) von 3,5 (Blut), 2,9 (Hirn) und 1,9 (Muskel), die auch eine szintigraphische Darstellung der Tumore zuließen.

Schlussfolgerungen:
OMID wurde durch L-Aminosäuretransporter selektiv in Tumorzellen aufgenommen, in HT-29 Zellen nicht in Proteine eingebaut, in vivo kaum metabolisiert und hauptsächlich renal ausgeschieden. Diese Eigenschaften und die lange Retention im Tumorgewebe lassen OMID als SPECT-Tracer für die Tumordarstellung geeignet erscheinen, was in weiteren Untersuchungen geprüft wird.
  • Lecture (Conference)
    40. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Freiburg, 10.-13.04.2002
  • Abstract in refereed journal
    Nuklearmedizin 41 (2002) V204

Publ.-Id: 4427 - Permalink


Ti based coatings on stainless steel for bone integrated implants
Mukherjee, S.; Pham, M.-T.; Maitz, M. F.;
Various titanium based coatings have been produced by metal plasma immersion ion implantation assisted deposition (PIIIAD) technique on stainless steel. TiN coatings with some Al substitution for Ti exhibit good mechanical properties and their use for implant coating is considered. Therefore the adherence of rat bone marrow cells as osteoblast progenitor cells to these coatings was investigated in correlation with deposition parameters and surface morphology. For comparison of the above coating's performance with other coat-ings (Ti, TiAl), all these coatings were developed using PIIIAD technique on stainless steel with the bias voltages 0 kV, -1 kV, -2 kV. Apart from increasing the bonding strength between the coating and the stainless steel substrate, the bias can also be used to manipulate the surface roughness of the coatings (10 - 80 nm). Rat bone marrow cells at the first passage were seeded out on the samples in medium with or without serum, allowed to adhere for 6 hours, fixed with paraformaldehyde, fluorescent stained for the adhesion protein vinculin, the cytoskeleton protein actin, the nuclei were couterstained. No difference in cell behaviour in the different surfaces was seen in medium with serum, indicating that adsorbed serum pro-teins equalise differences between surfaces. In the serum free medium there was a general trend of a bet-ter adherence of the cells and better organisation of the cytoskeleton on coatings produced at 0 kV bias voltage compared to those with -1 kV or -2 kV bias voltage. There have been no signs of necrotic cell death but a high rate (5 to 25%) of pyknotic, fragmented nuclei has been found as hint for apoptotic cell death in serum free medium. This rate has been different for the different substrates, but there was no correlation to surface chemistry or surface roughness. As a reason an effect of the serum free medium, direct effect of the coating or inhibition of the adherence cells to the coating are discussed. For further research and possible applications gradient layers produced from -2 kV at the substrate to 0 kV at the top are suggested.
Keywords: Titanium Titanium Nitride Titanium Aluminum Nitride Cell culture biomaterial hard coating
  • Lecture (Conference)
    International Conference for Surface Engineering, Chengdu (China) 10.-13.10.2002 Z. Siwei, Z. Zhongrong, L. Liajun and Z. Minhao (Eds.), Contributions of Surface Engineering to Modern Manufacturing and Remanufacturing. Southwest Jiaotong Unive...
  • Contribution to proceedings
    International Conference for Surface Engineering, Chengdu (China) 10.-13.10.2002 Z. Siwei, Z. Zhongrong, L. Liajun and Z. Minhao (Eds.), Contributions of Surface Engineering to Modern Manufacturing and Remanufacturing. Southwest Jiaotong Unive...

Publ.-Id: 4426 - Permalink


3-O-methyl-6-[123I]iodo-L-DOPA (OMID) - ein Aminosäurederivat zur Tumordarstellung mit SPECT
Wunderlich, G.; Füchtner, F.; Bergmann, R.; Bredow, J.; Steinbach, J.; Johannsen, B.; Franke, W.-G.;
Ziel:
Seit der Einführung von PET in die klinische Anwendung werden 11C markierte Aminosäuren vor allem für die Hirndarstellung verwendet. Im Sinne breiterer Anwendbarkeit wurden Aminosäuren auch mit 18F und 123I markiert. Ausgehend vom Precursor für das 3-O-methyl-6-[18F]fluoro-L-DOPA (OMFD) synthetisierten wir das analoge Iodprodukt OMID, mit dem Ziel die guten Ergebnisse, die im PET erreicht wurden, zukünftig auf das breiter verfügbare SPECT zu übertragen.

Methodik:
Die stereoselektive Synthese basiert auf der elektrophilen Substitution des entsprechenden zinnorganischen Precursors. Die Markierung wird mit 1 mg Substanz in Acetonitril und N-chlorosuccinimid als Oxidationsmittel innerhalb von 10 min bei Raumtemperatur durchgeführt. Es schließt sich eine Hydrolyse der Schutzgruppen mit konzentrierter HCl bei 80°C und eine Reinigung mittels HPLC (PRP1 Säule, Laufmittel: Ethanol/Phosphatpuffer 70/30) an. Die Bioverteilung wurde nach Injektion von [123I]OMID und [18F]OMFD in Wistarratten verglichen.

Ergebnisse:
Der [123I]NaI Umsatz zu [123I]OMID erfolgt quantitativ. Nach abschließender Abspaltung der Schutzgruppen und Reinigung wird nach ca. 90 min eine Ausbeute von 50% bezogen auf das eingesetzte Iod erreicht. Das Endprodukt ist in vitro stabil markiert und auch nach Injektion in Wistarratten ist nur eine geringe Iodabspaltung (<5%) und -aufnahme in die Schilddrüse nachweisbar. Die Verteilungsbilder der Substanzen [123I]OMID und [18F]OMFD ähneln sich, wobei nach 1 h die Aufnahme von OMID in Hirn und Muskel geringer ist als die Aufnahme von OMFD. Erste Untersuchungen an tumortragenden (FaDu) Nacktmäusen zeigten eine brauchbare Darstellung der Tumore isb. 10-30 min p.i..

Schlussfolgerung:
Das Verfahren zur Herstellung von [123I]OMID ist einfach und ergibt in kurzer Zeit gute Ausbeuten. Die Verwendung von Iod an Stelle von Fluor führt zur Lipophilieerhöhung und zu Unterschieden in der Bioverteilung der markierten Substanzen. Weitere Untersuchungen zur Abschätzung der Potenzen von OMID bei der Tumordarstellung sind notwendig.
  • Poster
    40. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Freiburg, 10.-13.04.2002
  • Abstract in refereed journal
    Nuklearmedizin 41 (2002) P55

Publ.-Id: 4425 - Permalink


Autoradiografische Darstellung des Serotonin Transporters mit S- ([18F]Fluoromethyl)-(+)-McN5652 ([18F]FMe-McN) in verschiedenen Tierspecies
Kretzschmar, M.; Zessin, J.; Brust, P.; Cumming, P.; Bergmann, R.; Johannsen, B.;
Ziel:
Eine veränderte Serotonin-Transporter (SERT) Dichte im Hirn wird als Ursache zahlreicher neuropsychiatrischer Erkrankungen angesehen. Für Untersuchungen des Serotonin -Transporters mittels PET gilt derzeit (+)-[11C]McN5652 als Tracer der Wahl. Die kurze Halbwertszeit (HWZ) von 11C (20,4 min ) begrenzt jedoch seinen klinischen Einsatz. Es wurde deshalb S-([18F]Fluoromethyl)-(+)-McN5652 (HWZ 18F 109,8 min) synthetisiert und dessen regionale Hirnaufnahme in vitro an Hirnschnitten des Schweines und der Ratte sowie in vivo an Schnitten von Ratten und Mäusen bewertet. Zum Vergleich dienten dabei die SERT Liganden [3H]-Citalopram und (+)-[11C]McN5652.

Methodik:
Die regionale Hirnaufnahme der Radiotracer wurde mit quantitativer digitaler Autoradiographie (BAS 2000 Bildauswertesystem FUJI Co) in vitro nach Inkubation der Hirnschnitte und ex vivo 60 und 90 min nach Applikation der Verbindungen erfasst. Zur Bestimmung der Spezifität der Bindung an den SERT wurden die SERT-Inhibitoren Citalopram bzw. Fluoxetin eingesetzt.

Ergebnisse:
Das S-([18F]Fluoromethyl)-(+)-McN5652 wies eine ähnliche Affinität (Ki 2,3 nM) zum SERT wie (+)-McN5652 (Ki 0,72 nM) auf. Die regionale Hirnaufnahme von S-([18F]Fluoromethyl)-(+)-McN5652 im Hirn korrelierte gut mit der Aufnahme des hochaffinen SERT-Liganden [3H]-Citalopram, d.h. die höchste Aktivität zeigte sich in Amygdala ,Hypothalamus, einigen Nuklei des Thalamus, Substantia nigra und superfizieller Schicht der Colliculi superiores. Das Gewebe/Cerebellum Verhältnis in den SERT-reichen Hirnregionen lag in vitro und in vivo zwischen 3 und 5, welches dem Gewebe/Cerebellum Verhältnis nach in vivo Applikation von (+)-[11C]McN5652 entsprach, für [3H]-Citalopram wurden in vitro Werte von 8 bis 20 erreicht. Die Aufnahme war bei allen Verbindungen mit SERT Inhibitoren hemmbar. Der Blut/Hirnschranken Transfer des S-([18F]Fluoromethyl)-(+)-McN5652 war niedriger als der des (+)-[11C]McN5652.

Schlussfolgerungen:
In vitro und in vivo wurde S-([18F]Fluoromethyl)-(+)-McN5652 spezifisch in den Hirnregionen mit einer hohen SERT-Dichte bei verschiedenen Tierspecies angereichert. S-([18F]Fluoromethyl)-(+)-McN5652 erscheint somit als potentieller PET-Tracer für den SERT im Hirn geeignet.
  • Poster
    40. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Freiburg, 10.-13.4.2002
  • Abstract in refereed journal
    Nuklearmedizin 41 (2002) P23

Publ.-Id: 4424 - Permalink


Impaired glucose tolerance is not associated with lipid intolerance
Henkel, E.; Temelkova-Kurtschiev, T.; Köhler, C.; Pietzsch, J.; Leonhardt, W.; Hanefeld, M.;
Post-prandial (pp) hypertriglyceridaemia (HTG) plays an important role in the development of atherosclerosis in Type 2 diabetes. Impaired glucose tolerance (IGT) is associated with an increased risk of atherosclerosis and increased level of fasting triglycerides (TG). The aim of this study was to analyse pp HTG and the composition of TG-rich lipoproteins in carefully selected subjects with IGT in comparison to controls with normal glucose tolerance (NGT). Fifteen men with IGT and 27 men with NGT, aged 44 to 70 yr, were examined. All study participants were non-smokers and had fasting TG <4.6 mmol/l. The subjects underwent an oral glucose tolerance test (75 g glucose) and a lipid-glucose tolerance test (LGTT; 92 g fat, 126 g carbohydrate), that allowed the assessment of lipid and glucose tolerance in one test. HbA1c, plasma glucose and lipids were measured by routine methods. Lipoprotein subfraction analysis of VLDL (VLDL1: Sf 60-400 and VLDL2: Sf 20-60) was conducted in a fasting state, as well as 4 hr after the LGTT using a density gradient ultracentrifugation with a subsequent compositional analysis. No significant difference was found either for fasting or pp TG, nor for area under curve (AUC)-TG (12.21±4.27 mmol/l*6 hr vs 13.95±6.74 mmol/l*6 hr; p>0.05) between the IGT and NGT. A highly significant correlation was found between the fasting TG and the AUC-TG (r=0.925; p<0.01). To avoid bias by differences in fasting plasma TG known to affect lipid tolerance we investigated 11 matched pairs for fasting TG. Also, the matched-pairs evaluation pp TG course did not differ significantly from the IGT and NGT. No significant difference for fasting or pp levels of VLDL1 and VLDL2, or for the TG content of chylomicron, VLDL1 and VLDL2, and for the percentage of TG in VLDL1 and VLDL2 was found between the IGT and NGT group. In conclusion, IGT subjects with a similar level of fasting TG do not exhibit lipid intolerance. Our data suggest that glucose intolerance should precede lipid intolerance.
  • Diab Nutr Metab 15 (2002) 84-90

Publ.-Id: 4422 - Permalink


Institute of Bioinorganic and Radiopharmaceutical Chemistry; Annual Report 2001
Johannsen, B.; Seifert, S.; (Editors)
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-340 Januar 2002

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Publ.-Id: 4420 - Permalink


Synthese, Struktur, physikochemische und biologische Eigenschaften einiger schwefelhaltiger "3+1" Oxorhenium(V)-Komplexe
in Russian
Zablotskaya, A.; Segal, I.; Kemme, A.; Germane, S.; Popelis, J.; Lukevics, E.; Berger, R.; Spies, H.;
  • Chem. Heterocycl. Compds. 4 (2002) 543-555

Publ.-Id: 4418 - Permalink


Quadrupole Moment of the 11- Intruder Isomer in 196Pb and Its Implications for the 16- Shears Band Head
Vyvey, K.; Chmel, S.; Neyens, G.; Hübel, H.; Balabanski, D. L.; Borremans, D.; Coulier, N.; Coussement, R.; Georgiev, G.; Nenoff, N.; Pancholi, S.; Rossbach, D.; Schwengner, R.; Teughels, S.; Frauendorf, S.;
The quadrupole moment of the 11- isomer in 196Pb has been measured by the level mixing spectroscopy method.
This state has a pi (3s_1/2^-2 1h_9/2 1i_13/2)11- configuration which is involved in most of the shears band
heads in the Pb region. The first directly measured value of Qs(11-) = (-) 3.41(66) b, coupled to the previously known quadrupole moment of the nu (1i_13/2 )12+ isomer allows us to estimate the quadrupole moment of the 16- shears band head as Qs(16-) = -0.32(10) b. The experimental values are compared to tilted axis cranking calculations, giving insight into the validity of the additivity approach to couple quadrupole moments and on the amount of deformation in the shears bands.
Keywords: Quadrupole moment. LEMS technique. Shears bands. Tilted-Axis-Cranking Model.
  • Physical Review Letters 88 (2002) 102502

Publ.-Id: 4417 - Permalink


Erzeugung und Nutzung von Bibliotheken von Zwei-Gruppen-Diffusionsparametern zur Berechnung eines KWU-Konvoi-Reaktors mit dem Reaktordynamik-Programm DYN3D
Mittag, S.; Grundmann, U.; Koch, R.; Semmrich, J.;
Libraries of two-group neutron-diffusion parameters for a Siemens-KWU-Konvoi Pressurized Water Reactor have been generated at Forschungszentrum Rossendorf and TÜV Bau und Betrieb GmbH by using the codes HELIOS and CASMO, respectively. The libraries have been coupled to the reactor-dynamics code DYN3D. For a generic PWR core containing MOX fuel elements, DYN3D macro-burnup calculations and the calculation of different operation states have been carried out. The results will be used for the investigation of possible accident scenarios. Reactivity coefficients calculated by DYN3D are needed for accident analyses by the 1-D thermal-hydraulic code ATHLET. Using the cross section data, more detailed analyses can be carried out by applying the coupled-code system DYN3D-ATHLET, considering 3D neutron kinetics. The comparison of the results calculated by DYN3D with two different diffusion-parameter libraries can give an idea of how uncertainties in diffusion data influence the accuracy of reactor simulation.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-346 April 2002

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Publ.-Id: 4416 - Permalink


Institute of Ion Beam Physics and Materials Research: Annual Report 2001
von Borany, J.; Helm, M.; Jäger, H.-U.; Möller, W.; Wieser, E.; (Editors)
Summary of the scientific activities of the institute in 2001 including selected highlight reports, short research contributions and an extended statistics overview.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-338 März 2002

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Publ.-Id: 4412 - Permalink


Magnetic rotation in 82Rb and 84Rb
Schwengner, R.; Rainovski, G.; Schnare, H.; Wagner, A.; Dönau, F.; Jungclaus, A.; Hausmann, M.; Iordanov, O.; Lieb, K. P.; Napoli, D. R.; de Angelis, G.; Axiotis, M.; Marginean, N.; Brandolini, F.; Rossi Alvarez, C.;
High-spin states in 82Rb and 84Rb were populated in the reaction 11B + 76Ge at beam energies of 45 and 50 MeV. Gamma rays were detected with the spectrometer GASP. The level schemes of 82Rb and 84Rb were extended up to 6.0 and 7.4 MeV, respectively. Mean lifetimes of five levels in 82Rb and eleven levels in 84Rb were determined using the Doppler-shift-attenuation method. Regular magnetic dipole bands including strong M1 and weak E2 transitions observed in both nuclei show the characteristic features of magnetic rotation. These bands have been successfully described in the tilted-axis cranking model on the basis of the four-quasiparticle configuration pi(fp) pi(g_{9/2}^2) \nu(g_{9/2}). The calculations reproduce the band-like properties as well as absolute B(M1) and B(E2) transition strengths in both nuclei, which supports the concept of
magnetic rotation. Excited states in 84Rb were also interpreted in terms of the shell model using the model space
pi(0f_{5/2},1p_{3/2},1p_{1/2},0g_{9/2}) nu(1p_{1/2},0g_{9/2}).
These calculations reproduce the low-spin states. Moreover, calculated states with the main configuration
pi(0f_{5/2}^{-2}1p_{3/2}^{-1} 0g_{9/2}^2) nu(0g_{9/2}^{-3}) can be combined to M1 sequences that reproduce roughly
the experimental transition strengths, but do not describe the features of magnetic rotation, as regular level spacings and B(M1) values decreasing with increasing rotational frequency.
Keywords: Nuclear Structure, in-beam gamma-ray spectroscopy, magnetic rotation, tilted-axis cranking model, shell model.
  • Physical Review C 66, 024310, (2002)

Publ.-Id: 4411 - Permalink


Experimental and numerical investigation of one and two-phase natural convection
Krepper, E.; Prasser, H.-M.;
Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. Several tests were carried out both with heating from the bottom and with heating from the side walls. The test tank was equipped with thermocouples for measuring the temperature distribution and with needle probes for measuring of the local void fraction.
Calculations were performed using the CFD-code CFX-4. The simulation comprises two phase flow, subcooled boiling at the heated wall and steam release at the tank surface. The paper presents comparisons of measured and calculated temperatures and void fractions. CFX-4 simulations using the implemented boiling model reproduce and explain the observed physical phenomena. Convergence problems occurred with higher vapour volume fractions.
Keywords: Natural convection, heating up, boiling, experiments, CFD simulations
  • Lecture (Conference)
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 333-339
  • Contribution to proceedings
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 333-339

Publ.-Id: 4408 - Permalink


Annealing behavior of magnesium and aluminum implanted with iron ions
Reuther, H.;
Magnesium and aluminum were alloyed by implantation with iron ions. The implantation energy was 200 keV while the ion doses ranged over several decades from 1x1015 up to 9x1017 cm-2. In this way highly disordered alloyed layers with up to 90 at.% iron were obtained [1]. To study possible ordering, stabilization and redistribution processes samples were annealed in vacuum at subsequently increasing temperatures up to 600 °C for aluminum and up to 400 °C for magnesium. The annealing process was observed by conversion electron Mössbauer spectroscopy, Auger electron depth profiling, and X-ray diffraction. In the case of the Fe-Al system different iron aluminides are formed. In the case of the Fe-Mg system (insoluble with each other), a-iron is precipitated in small clusters in the final state.

  • Journal of Applied Physics 92 (2002) 7056-7061

Publ.-Id: 4407 - Permalink


Experimental Investigation of the Potential of In-Beam PET for the Monitoring of Proton Therapy
Parodi, K.; Enghardt, W.; Haberer, T.; Keywords: Proton Therapy, PET
  • Lecture (Conference)
    XXXVI PTCOG-Meeting, Catania, Italy, 29-31 May 2002
    Book of Abstract (2002) 12
  • Contribution to proceedings
    XXXVI PTCOG-Meeting, Catania, Italy, 29-31 May 2002
    Book of Abstract (2002) 12

Publ.-Id: 4406 - Permalink


Positron Emission Tomography for Quality Assurance of Carbon Ion Therapy
Enghardt, W.; Crespo, P.; Fiedler, F.; Parodi, K.; Pawelke, J.; Pönisch, F.; Haberer, T.; Kausch, C.; Krämer, M.; Schardt, D.; Keywords: Heavy-Ion-Therapy, PET
  • Lecture (Conference)
    XXXVI PTCOG-Meeting, Catania, Italy, 29-31 May 2002
    Book of Abstracts (2002) 12
  • Contribution to proceedings
    XXXVI PTCOG-Meeting, Catania, Italy, 29-31 May 2002
    Book of Abstracts (2002) 12

Publ.-Id: 4405 - Permalink


Evolution of flow patterns, gas fraction profiles and bubble size distributions in gas-liquid flows in vertical tubes
Lucas, D.; Krepper, E.; Prasser, H.-M.;
Air-water flow at ambient conditions in a vertical pipe with an inner diameter of 51.2mm is investigated. An electrode wire-mesh sensor enables the measurement of the phase distribution with a very high resolution in space and in time. Local bubble size distributions are calculated from the data. The measurements were done in different distances from the gas injection device. As a result the development of bubble size distributions as well as the development of the radial gas fraction profiles can be studied. It was found, that the bubble size distribution as well as local effects determine the transition from bubble flow to slug flow. The data are used for the development of a model, which predicts the development of the bubble size distribution and the transition from bubble flow to slug flow in case of stationary flow in a vertical pipe.
Keywords: Two-phase flow, Flow pattern transition, Bubble Flow, Slug flow
  • Lecture (Conference)
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 341 - 348
  • Transactions of the Institute of Fluid-Flow Machinery 112(2003)37-46
  • Contribution to proceedings
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 341 - 348

Publ.-Id: 4404 - Permalink


Application of Master Curve Approach for Rector Pressure Vessel Integrity Assessment
Viehrig, H.-W.; Langer, R.;
The state-of-the-art of structural integrity assessment of reactor pressure vessels (RPV) uses universal and experimentally verified reference fracture toughness curves. These curves are constructed as the lower boundary to an available plain strain fracture toughness, KIC, database.
Recent industry attention has been focussed on the direct use of measured fracture toughness properties in the RPV integrity assessment. The Master Curve Concept (MC)is a new methodology to characterise the fracture toughness in the transition region. The MC methodology provides a reference temperature, T0, that directly relates the reference toughness curve to the measured fracture toughness values.
The utilities and licensing authorities establish short and long-range objectives in implementing MC technology. The short range objective is to develop an alternative method of indexing the universal plain strain fracture toughness curves using measured fracture toughness T0 instead of the existing drop weight and Charpy-based methodology. The long range objective is to implement a statistically defined MC as an alternative fracture toughness curve in place of the KIC lower bound curves.
The paper introduces the state-of-the-art and future trend of the RPV integrity assessment in Germany. In the second part the MC approach is demonstrated for Russian WWER-type RPV steels.

Keywords: reactor pressure vessel, integrity assessment, reference temperature, fracture toughness, Master Curve
  • Lecture (Conference)
    Proceedings of the NATO Advanced Research Workshop On Scientific Fundamentals for the life Time Extension of Reactor Pressure Vessels, held in Kiev, Ukraine, from 22 to 25 April 2002.
  • Contribution to proceedings
    Proceedings of the NATO Advanced Research Workshop On Scientific Fundamentals for the life Time Extension of Reactor Pressure Vessels, held in Kiev, Ukraine, from 22 to 25 April 2002.

Publ.-Id: 4403 - Permalink


Approach towards spatial phase reconstruction in transient bubbly flow using a wire-mesh sensor
Richter, S.; Aritomi, M.; Prasser, H.-M.; Hampel, R.;
A wire-mesh sensor, which is based on local conductivity measurement, has been applied to studies on the characteristics of bubböe flow in a rectangular channel (20 x 100 mm²). Special design of the sensor allowed the measurement of the local instantaneous true gas velocity besides the measurement of the local instantaneous void fraction. A review of an already published method for true gas velocity measurement under consideration of the uncertainty caused by limitations in the sampling frequency is presented. A cluster-algorithm is proposed for the evaluation of bubble size distribution and volume flow reconstruction. The validity of this algorithm for spatial field reconstruction was benchmarked by theoretical considerations as well as comparison of the calculated with alternatively measured data. Good agreement was stated. The achieved information was used to obtain plots showing the bubble/slug velocity (up to the second statistical momentum) depending on the spherical-equivalent bubble diameter. This information was measured inside a transient bubble flow with void fraction of up to 20 %. Occurring phenomena are explained by presented Fourier spectra of the cross-sectional averaged void fraction and the gas volume flow.
Keywords: gas-liquid flow, two-phase flow, wire-mesh sensor, void fraction, gas velocity, bubble size
  • International Journal of Heat and Mass Transfer 45 (2002) 1063-1075.

Publ.-Id: 4402 - Permalink


Inverse Problems in MHD
Stefani, F.; Gerbeth, G.;
We consider inverse problems in MHD that are related to the reconstruction of velocity fields from external measurements of electromagnetic fields. Possible applications are contactless flow measurements in metallurgical and crystal growth facilities as well as velocity reconstructions for cosmic and laboratory hydromagnetic dynamos. In the case of small magnetic Reynolds numbers it is necessary to apply external magnetic field and to measure the flow induced electromagnetic fields. Analytical results concernig the uniqueness problem of velocity reconstruction and the need for regularization are discussed. First results for inverse dynamo theory, i.e. the region of high magnetic Reynolds number, are also presented.
  • Lecture (Conference)
    Jahrestagung der Gesellschaft für Angewandte Mathematik und Mechanik (GAMM) 2002, Universität Augsburg, 25.-28. März 2002

Publ.-Id: 4401 - Permalink


Surface structuring and phase formation in thin metallic layers deposited at various temperatures
Markwitz, A.; Matz, W.; Short, K.; Waldschmidt, M.;
Scanning electron microscopy, atomic force microscopy and XRD analyses were performed for the study of the influence of the substrate temperature during deposition on the surface structuring and phase formation on thin metallic double layers. Thin layers of Au, Cr, Al and Cr were deposited at 150 and 300 °C on 30-nm Cu layers evaporated on (100) wafer Si substrates. Possible applications of such layers are Raman active surfaces and model layers for diffusion experiments. The topographical investigation revealed an increase with temperature of surface structuring that is related to the formation of intermetallic and oxide phases. At 150 °C deposition temperature, the average roughness of the films was determined to 2 – 3 nm and the surfaces appeared smooth. In agreement with previous ion beam analysis measurements, a significant surface roughness occurred at 300 °C depending on the type of the metallic films. The lowest average surface roughness value was measured for the Al/Cu/Si system (Ra = 14.1 nm). About double the roughness was measured for the Au/Cu/Si and Cr/Cu/Si layer systems. In contrast, single Cu layers a high value of Ra = 93.0 nm was determined. The combined analyses showed that the formation of intermetallic phases, such as AlCu and CuAl2, reduces a surface roughening. However, the formation of oxide phases, such as CuO2, increase the average surface roughness.
Keywords: multilayers, metallic compounds, surface structuring, nanotechnology, diffusion, surface artefacts
  • Surface and Interface Analysis 33 (2002) 1-6

Publ.-Id: 4399 - Permalink


A Kinetic Study of Clusters Evolution under VVER-type Reactor Condition
Gokhman, A.; Böhmert, J.; Ulbricht, A.;
The evolution of copper rich clusters and vacancy clusters in the neutron irradiated VVEER steels is investigated beginning at the nucleation stage. For this, typical VVER-type reactor conditions are considered. Cluster dynamics approach is used for calculation of the size distribution function, mean radius, number density of copper precipitates and the concentration of free Cu-atoms in dependence on the irradiation time. The results for time of one year are compared with the results of small angle neutron experiments which were carried out at specimens irradiated at surveillance position of VVER reactors.
  • Lecture (Conference)
    Nucleation Theory and Applications, J. W. P. Schmelzer, G. Röpke, Y. B. Priezzhev (Eds.), Dubna, April 14-21, 2002, pp. 81-107
  • Contribution to external collection
    Nucleation Theory and Applications, J. W. P. Schmelzer, G. Röpke, Y. B. Priezzhev (Eds.), Dubna, April 14-21, 2002, pp. 81-107

Publ.-Id: 4398 - Permalink


Determination of velocity profiles in liquid metal flows by means of Ultrasound Doppler Velocimetry
Eckert, S.; Gerbeth, G.; Melnikov, V.;
The Ultrasound Doppler Velocimetry (UDV) is a non-intrusive technique to measure velocities of liquid flows. Because of the ability to work in opaque fluids and to deliver complete velocity profiles in real time it becomes very attractive for liquid metal applications. But, in case of hot metallic melts the user is confronted with a number of specific problems: First of all the application of the ultrasonic transducers is usually restricted to maximum temperatures of 150°C. The transmission of a sufficient amount of ultrasonic energy from the transducer to the fluid has to be guaranteed. Here, the acoustic coupling and the wetting conditions have to be considered as important issues. Moreover, the flow has to be seeded with reflecting particles to obtain Doppler signals from the fluid.
The feasibility of velocity profile measurements by UDV has already been demonstrated for low temperature liquid metals as mercury [1] and gallium [2]. Now, first successful measurements in liquid sodium at 150°C are published [3]. We will present mean profiles of a flow in a rectangular exposed to an external, transverse magnetic field. To demonstrate the capability of UDV the transformation of a well-known turbulent, piston-like profile to a M-shaped velocity profile with growing magnetic field strength was observed. The significance of artefacts such as caused the existence of reflecting interfaces in the measuring domain will be discussed.
An integrated ultrasonic sensor with acoustic wave guide has been developed to overcome the limitation of ultrasonic transducers to temperatures lower than 200°C. This sensor can be applied at maximum temperatures up to 400°C, but an extension up to 800°C can reasonably be expected.. In this presentation we show some experimental results obtained in a PbBi bubbly flow at 250...300°C. Ar bubbles were injected through a single orifice in a cylindrical container filled with stagnant PbBi. Velocity profiles were measured in the bubble plume. Mean values of the liquid as well as the bubble velocity were extracted from the data and will be presented as function of the gas flow rate.


[1] Y. Takeda: Measurement of velocity profile of mercury flow by ultrasound Doppler shift method. Nucl. Techn. 79 (1987), 120-124
[2] D. Brito, H.-C. Nataf, P. Cardin, J. Aubert, J.-P. Masson: Ultrasonic Doppler velocimetry in liquid gallium. Exp. Fluids 31 (2001) 6, 653-663
[3] S. Eckert, G.Gerbeth: Velocity measurements in liquid sodium by means of Ultrasound Doppler Velocimetry. accepted for publication in Exp. Fluids (2002)

Keywords: Ultrasonic Doppler Velocimetry, acoustic wave guide, liquid metals, flow velocity measurements, two-phase flow, bubbles
  • Lecture (Conference)
    5th International Conference on Fundamental and Applied MHD (PAMIR), September 16-20, 2002, Ramatuelle, France, Proceedings I 119-124
  • Contribution to proceedings
    5th International Conference on Fundamental and Applied MHD (PAMIR), September 16-20, 2002, Ramatuelle, France, Proceedings I 119-124

Publ.-Id: 4397 - Permalink


Application of Ultrasound Doppler Velocimetry to flows of hot metallic melts
Eckert, S.; Gerbeth, G.; Melnikov, V.; Lefhalm, C.-H.; Knebel, J.;
During the last decades the Ultrasound Doppler Velocimetry (UDV) became a very powerful tool to measure the velocity structure of liquid flows. Because of the ability to work in opaque fluids and to deliver complete velocity profiles in real time it becomes very attractive for liquid metal applications. But, in case of hot metallic melts the user is confronted with a number of specific problems: First of all, the application of the ultrasonic transducers is usually restricted to maximum temperatures of 150°C. The transmission of a sufficient amount of ultrasonic energy from the transducer to the fluid has to be guaranteed. Here, the acoustic coupling and the wetting conditions have to be considered as important issues. Moreover, the flow has to be seeded with reflecting particles to obtain Doppler signals from the fluid.
The feasibility of velocity profile measurements by UDV has already been demonstrated for low temperature liquid metals as mercury [1] and gallium [2]. Now, first successful measurements in liquid sodium at 150°C are published [3]. We will present mean profiles of a sodium flow in a rectangular duct exposed to an external, transverse magnetic field. To demonstrate the capability of UDV the transformation of a well-known turbulent, piston-like profile to a M-shaped velocity profile with growing magnetic field strength was observed. The significance of artefacts such as caused by the existence of reflecting interfaces in the measuring domain will be discussed.
An integrated ultrasonic sensor with acoustic wave guide has been developed to overcome the limitation of ultrasonic transducers to temperatures lower than 200°C. This sensor can presently be applied at maximum temperatures up to 400°C, but an extension up to 800°C can reasonably be expected. In this presentation we show some experimental results obtained in PbBi bubbly flows at temperatures up to 350°C. Ar bubbles were injected through a single orifice in a cylindrical container filled with stagnant PbBi. Velocity profiles were measured in the bubble plume. Mean values of the liquid as well as the bubble velocity were extracted from the data and will be presented as function of the gas flow rate.
Velocity profiles of a single-phase PbBi flow in a tube were successfully obtained at the KALLA laboratory of FZK. By means of the integrated sensor stable velocity signals could be received over a period of about 72 hours at temperatures between 180°C and 350°C.


[1] Y. Takeda: Measurement of velocity profile of mercury flow by ultrasound Doppler shift method. Nucl. Techn. 79 (1987), 120-124
[2] D. Brito, H.-C. Nataf, P. Cardin, J. Aubert, J.-P. Masson: Ultrasonic Doppler velocimetry in liquid gallium. Exp. Fluids 31 (2001) 6, 653-663
[3] S. Eckert, G.Gerbeth: Velocity measurements in liquid sodium by means of Ultrasound Doppler Velocimetry. accepted for publication in Exp. Fluids (2002)

Keywords: Ultrasonic Doppler Velocimetry, acoustic wave guide, liquid metals, flow velocity measurement, two-phase flow, bubbles
  • Lecture (Conference)
    3rd International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, September 9-11, 2002, Lausanne, Switzerland PSI-Proceedings 02-01, 77-82, ISSN 1019-6447
  • Contribution to proceedings
    3rd International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, September 9-11, 2002, Lausanne, Switzerland PSI-Proceedings 02-01, 77-82, ISSN 1019-6447

Publ.-Id: 4396 - Permalink


Dynamical moment of inertia and quadrupole vibrations in rotating nuclei
Nazmitdinov, R. G.; Almehed, D.; Dönau, F.;
The contribution of quantum shape fluctuations to inertial properties of rotating nuclei has been analysed within the self-consistent one-dimensional cranking oscillator model. It is numerically proven that for even-even nuclei the dynamical moment of inertia calculated in mean field approximation in the intrinsic frame is equivalent to the
Thouless-Valatin moment of inertia. If the contribution of the quantum fluctuations
to the total energy is taken into account, the dynamical moment of inertia differs from the Thouless-Valatin value.
Keywords: Cranking model, Random Phase Approximation, Moments of inertia
  • Physical Review C, Rapid Communication, Volume 65, 041307 (R), 2002

Publ.-Id: 4395 - Permalink


Numerical Simulation of ISP-43 Test A with CFX-4
Höhne, T.;
The test A of the test series performed at the UM2x4 loop test facility for the International Standard Problem ISP-43 was calculated with the CFD Code CFX-4.3. The results of the calculation show qualitatively good agreement with the experimental data. The structure of the flow field and the form of the propagating temperature perturbation front are well modeled by the CFD code. However, deviations occur at local positions. Comparative calculations with and without taking into account buoyancy have shown, that buoyancy effects are noticeable, but the mixing is mainly momentum controlled.
Keywords: Boron Dilution, Coolant Mixing
  • Lecture (Conference)
    ANS/ASME Student Conference, Penn State University, USA, April 10-13, 2002, CD-ROM
  • Contribution to proceedings
    ANS/ASME Student Conference, Penn State University, USA, April 10-13, 2002, CD-ROM

Publ.-Id: 4394 - Permalink


Berechnung des Strahlungsuntergrundes in der Umgebung der Strahlfänger an der Strahlungsquelle ELBE
Naumann, B.;
Beam dumps are installed at the experimental areas of the ELBE facility. Their purpose is to absorb the primary electron beam and the secondary radiation. The beam dump consists of a purified graphite core inside a water cooled stainless steel vessel. The radiation shield surrounding the beam dump will be designed individually for each experimental area. In this context, dose rate calculations were carried out to estimate the dose rate source term around the stainless steel vessel of the beam dump. Detailed Monte Carlo simulations were carried out using the code FLUKA. The energy dependent photon and neutron fluences and the equivalent dose rates were obtained near the surface of the cylindrical steel vessel for a beam current of 1 mA and energies of 20 MeV and 50 MeV.
Keywords: Beam dump, radiation protection, particle transport, code FLUKA, photon and neutron fluences
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-345 März 2002

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Publ.-Id: 4393 - Permalink


EXAFS Studies of the Am3+ AND Cm3+ AQUO IONS
Funke, H.; Stumpf, T.; Rossberg, A.; Hennig, C.; Reich, T.;
Besides plutonium, the long-lived isotopes of americium and curium play a crucial role for long-term performance assessment of nuclear waste repositories. In order to predict the mobilization and retardation of these nuclides, it is necessary to know the structures of the inorganic and organic actinide species that are involved in the process of migration. Thereby, the characterization of the Am3+ and Cm3+ aquo ions forms the base for further investigations.
In the literature only few measurements can be found of co-ordination numbers of trivalent actinides in aqueous solutions. By using UV/Vis spectroscopy, a co-ordination number of 9 was calculated for Am3+ aq [1]. The complexation behavior of curium is often investigated by time-resolved laser-induced fluorescence spectroscopy (TRLFS) [2,3]. In analogy to trivalent lanthanides, a co-ordination number of nine is assumed for Cm3+aq. An extended X-ray absorption fine structure (EXAFS) spectroscopy investigations of Am3+ and of Cm3+ in 0.25 M HCl obtained co-ordination numbers of 10.3(0.3) and 10.2(0.3), respectively [4].
In order to determine a reliable reference value for the co-ordination number of Cm3+ and Am3+ aquo ions, the samples used in our EXAFS measurements were prepared in non-complexing 1.0 M perchloric acid. High actinide concentrations (1 x 10-3 mol/L) were used in order to achieve low-noise EXAFS spectra, which enable a precise determination of bond lengths and co-ordination numbers of the Am3+ and Cm3+ aquo ions.
The experiments were performed at the Rossendorf beamline (ROBL) at the ESRF in Grenoble [5]. The radiochemistry experimental station at ROBL has been designed to perform X-ray absorption fine structure (XAFS) spectroscopy of solid and liquid non-sealed radioactive samples [6]. EXAFS spectra were collected in transmission mode at the americium LIII edge at 18504 eV (E0=18520 eV) and at the curium LIII-edge at 18970 eV (E0=18990 eV), respectively. Zr and Nb metal foils were measured and the first inflection point of the X-ray absorption spectra (Zr K edge at 17998 eV, Nb K edge at 18986 eV) were used for energy calibration. EXAFS data treatment and fit were done using the EXAFSPAK program package [7]. Parameters for the backscattering phase and amplitude, the mean free path, and the reduction factor were calculated using the FEFF8 code [8]. Since no suitable Am or Cm reference compound was available for the measurements, the EXAFS spectra were fitted with constant S02 equal to 0.9 and 1.0. Two different sets of atomic clusters were taken as the basis for the phase and amplitude calculations. On the one hand the solid state structure of the curium dioxides was used [9] with a co-ordination number of eight and on the other hand the structure of the tetraaquatrinitratoeuropium(III)-dihydrate [10]. This compound shows the curium-homologous lanthanide Eu3+ as central atom, which is surrounded by ten oxygen atoms. Both clusters lead to nearly the same results. Dirac-Fock potentials were used for the core of the central atoms in the FEFF calculations. The EXAFS spectra of the Am3+ and Cm3+ aquo ions using the Eu cluster [10] are shown in figure 1. One shell is uniquely defined in both cases. The corresponding EXAFS structural parameters are collocated in table 1.
Figure 1. Raw Am3+ (upper graph) and Cm3+ (lower graph) LIII-edge k3-weighted EXAFS spectra and corresponding Fourier transforms. (Solid line - experiment; dashed
line - theoretical fit.)

Table 1. EXAFS structural parameters for the Am3+ and Cm3+ aquo ions. The standard deviations as estimated by EXAFSPAK are given in parenthesis.
Sample Shell N (S02=0.9) N (S02=1.0) R [Å] s2·103 [Å2] ?E [eV]
Am3+ Am-O 10.4(0.3) 9.3(0.3) 2.47(0.02) 9.3(0.3) -12.6(0.3)
Cm3+ Cm-O 9.3(0.3) 8.4(0.3) 2.46(0.02) 7.5(0.4) -22.3(0.4)

The measured bond distances, R±0.02 Å, are the same for the Am3+ and Cm3+ aquo ions and agree with the results of [4]. The co-ordination number, N±1, is somewhat higher for ...
  • Lecture (Conference)
    32. Journées des Actinides, 2002, Ein-Gedi, Israel, 15.3.-23.3.2002

Publ.-Id: 4391 - Permalink


Vertical gradient freeze growth of GaAs with a rotating magnetic field
Pätzold, O.; Grants, I.; Wunderwald, U.; Jenkner, K.; Cröll, A.; Gerbeth, G.;
Results on the growth of GaAs by the vertical gradient freeze (VGF) technique with a rotating magnetic field (RMF) are presented. The experiments were aimed at influencing the heat flux at the liquid-solid interface in a predefined way to reduce its bending. Si doped crystals with a diameter of two inch were grown. Variation of the heat flux is directly evaluated from dopant striations artificially produced by means of pulses of the RMF itself. The results are compared with those obtained by global modelling of the furnace as well as by analytical and numerical treatment of the melt flow. The concave deflection of the interface is found to decrease considerably under forced convection and at certain aspect ratio a wavy shape is observed. The RMF induced redistribution of axial thermal gradients resulting in a temporary variation of the growth rate that becomes lower in the outer region of the melt and higher in the central part is measured directly. The experimental results agree well with the numerical
computations.
  • Journal of Crystal Growth 245 (2002) 237-246

Publ.-Id: 4390 - Permalink


Dose rate and temperature dependence of ion-beam-induced defect evolution in Si and SiC
Posselt, M.; Bischoff, L.; Teichert, J.; Ster, A.;
A focused ion beam system is applied to investigate the dose dependence of the shape of Ge channeling implantation profiles in Si and SiC at two very different dose rates (1011 and 1018 cm-2 s-1), and for implantation temperatures between room temperature and 580 0C. The competing influence of dose rate and temperature observed is explained in terms of intracascade defect relaxation. For the different implantation temperatures, the time scale for defect reduction is estimated. The results obtained for Si are compared with those for SiC.
Keywords: focused ion beam, channeling, ion-beam-induced defects, dose rate and temperature effects
  • Lecture (Conference)
    MRS 2002 Spring Meeting, San Francisco, USA, April 1 - 5, 2002
  • Contribution to external collection
    Mat. Res. Soc. Symp. Proc. Vol. 719 (2002), pp. F11.2-F11.8

Publ.-Id: 4389 - Permalink


Analytical Description of Brittle-to-Ductile Transition in bcc Metals. Nucleation of dislocation loop at the crack tip
Voskoboinikov, R. E.;
Nucleation of dislocation loop at the crack tip in a material subjected to uniaxial loading is investigated. Analytical expression for the total energy of rectangular dislocation loop at the crack tip is found. Depencence of the nucleation energy barrier on dislocation loop shape and stress intensity factor at the crack tip is determined. It is established that the energetic barrier for nucleation of dislocation loop strongly depends on the stress intensity factor. Nucleation of dislocation loop is very sensitive to stress field modifiers (forest dislocations, precipitates, clusters of point defects, etc.) in the crack tip vicinity.
Keywords: dislocation, crack, stress intensity factor, ductile-to-brittle transition, energetic barrier for nucleation
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-344 März 2002

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Publ.-Id: 4388 - Permalink


Characterization of the SiO2/Si interface by positron annihilation spectroscopy
Brauer, G.; Anwand, W.; Skorupa, W.; Revesz, A. G.; Kuriplach, J.;
The densification of SiO2 on silicon towards the interface, as already concluded in a recent work, is confirmed to exist in thinner oxides obtained by etching, and in a native oxide, too. Furthermore, an annihilation state is revealed in the thermally grown and etched, as well as a native, oxide which must resemble low quartz in its structure. A lower limit d = (2.2 +- 0.1) nm of the thickness of the interface layer resembling low quartz in its structure can be estimated. A variety of the state-of-the-art theoretical calculations to aid the experimental findings is summarized. It is discussed why the presented results corroborate the model of quasi-epitaxial oxide growth and pseudo-polymorphic relaxation of the grown oxide.
Keywords: positron annihilation spectroscopy, SiO2/Si structures
  • Phys.Rev.B66 (2002) 195331-1 - 195331-10

Publ.-Id: 4387 - Permalink


Simulation of Scaled Reactor Pressure Vessel Creep Failure Experiments
Willschütz, H.-G.; Altstadt, E.; Sehgal, B. R.; Weiß, F.-P.;
The hypothetical scenario of a severe accident with subsequent core meltdown and formation of a melt pool in the reactor pressure vessel (RPV) lower head of a Light Water Reactor (LWR) leads to the question about the behaviour of the RPV. One accident management strategy could be to stabilize the in-vessel debris configuration in the RPV as one major barrier against uncontrolled release of heat and radio nuclides.
Scaled coupled melt pool convection and vessel creep failure experiments are being performed in the FOREVER program at the Royal Institute of Technology, Stockholm. These experiments are simulating the lower head of a pressurized reactor vessel under the thermal load of a melt pool with internal heat sources. Due to the multi axial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments offer an excellent opportunity to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module, the melt pool convection is simulated and the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep modelling procedure. Additionally, the material damage is evaluated considering the creep deformation as well as the prompt plasticity.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. After analysing the calculations, it seems to be advantageous to introduce a vessel support which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.

Keywords: Severe nuclear power plant accident, core melt down, multi-axial creep deformation, Finite Element Simulation
  • Lecture (Conference)
    NUSIM 02, 11th annual Nuclear Societies Information Meeting, March 13 - March 15, 2002, Dresden
  • Contribution to proceedings
    NUSIM 02, 11th annual Nuclear Societies Information Meeting, March 13 - March 15, 2002, Dresden

Publ.-Id: 4381 - Permalink


Experimental and Numerical Investigations of Heating Up Processes of Fluids in Large Pools
Krepper, E.; Aszodi, A.; Weiß, F.-P.;
Heating up experiments at the secondary pools side of the NOKO test facility were performed, to investigate mixed convection phenomena. The NOKO test facility was designed to investigate the heat transfer capability of an emergency condenser and was operated in the Research Centre Jülich.
In the Forschungszentrum Rossendorf the heating up tests were analyzed by CFD-simulations using the AEA-Technology code CFX-4. Applying the Boussinesq approximation the simulation of the heating up process is possible, at least qualitatively. Using the laminar approach, temperature oscillations caused by plumes could be simulated.
A further test series performed at Forschungszentrum Rossendorf deals with the investigation of transient boiling. Heating up a 10 l water tank from the side walls, the temperatures and the void fractions at different locations in the tank were measured. CFX-4 simulations using the implemented boiling model reproduce and explain the observed phenomena. Convergence problems occurred with higher vapor volume fractions.
Keywords: Process safety, single and two phase mixed convection, boiling, heating up experiments, CFD simulations
  • Lecture (Conference)
    ASME Fluids Engineering Division Summer Meeting, Montreal July 2002, Conference-CD paper 31406
  • Contribution to proceedings
    ASME Fluids Engineering Division Summer Meeting, Montreal July 2002, Conference-CD paper 31406

Publ.-Id: 4380 - Permalink


Laboratory Experiments on Hydromagnetic Dynamos
Gailitis, A.; Lielausis, O.; Platacis, E.; Gerbeth, G.; Stefani, F.;
Cosmic magnetic fields, including the fields of planets, stars and galaxies, are believed to be caused by dynamo action in moving electrically conducting fluids. While theory and numerics of hydromagnetic dynamos have flourished during the last decades, an experimental validation of the effect was missing until recently. We sketch the long history towards a working laboratory dynamo. We report on the first successful experiments at the sodium facilities in Riga and Karlsruhe, and on other experiments which are carried out or planned at various places in the world.
  • Reviews of Modern Physics 74 (2002), 973-990

Publ.-Id: 4379 - Permalink


Monitoring-System mit adaptiven Wärmebilanzen für Batch-Reaktoren
Hessel, G.; Hilpert, R.; Kryk, H.; Roth, M.; Schmitt, W.; Seiler, T.;
Ein online Monitoring-System für die Prozessführung eines komplexen heterogenen Hydrierprozesses in einer Produktionsanlage der Degussa AG wird beschrieben. Es arbeitet mit gekoppelten Stoff- und Wärmebilanzen, die adaptive Modellkomponenten zur Anpassung an die jeweilige Zielanlage nutzen. Aus dem zeitlichen Verlauf der Bilanzen wird auf den aktuellen Prozesszustand geschlossen, der durch die Konzentrationsverteilung von Ausgangs-, Zwischen- und Endprodukten charakterisiert wird. Die Industrieerprobung des Monitoring-Systems erfolgte im Rahmen eines entwickelten Batch-Informations-Management-Systems, das in die vorhandene Prozessleittechnik einer Mehrzweckanlage eingebaut wurde. Ergebnisse der Prototyp-Erprobung während einer Hydrierungs-Produktionskampagne werden vorgestellt.
  • Poster
    GVC/DECHEMA-Jahrestagungen 2002, 11.-13. Juni 2002, Wiesbaden
  • Abstract in refereed journal
    Chemie Ingenieur Technik 74, 5 (2002) 596
  • Contribution to proceedings
    GVC/DECHEMA-Jahrestagungen 2002, 11.-13. Juni 2002, Wiesbaden

Publ.-Id: 4378 - Permalink


Calorimetric and FTIR Spectrometric Investigation of a Grignard Reaction
Hessel, G.; Hulzer, G.; Kryk, H.; Schmitt, W.;
Calorimetric and in situ Fourier Transform Infrared (FTIR) spectroscopic studies to monitor the unpredictable initiation of a strongly exothermic Grignard reaction and to determine their thermokinetic parameters are represented. Instead of operating under reflux conditions which are commonly used to control the Grignard formation, the calorimetric measurements were carried out in a closed jacketed stainless steel pressure reactor. This novel technique has some advantages. For example, a more accurate determination of the molar reaction enthalpy is possible, the increase of the reactor temperature and pressure can also be used to monitor the initiation process of the Grignard formation, and the dosage of the pure organic halide into a closed reactor vessel leads to a predictable and reproducible induction time. Thus, this technique might contribute to reduce the hazardous potentials of Grignard reactions.
  • Poster
    5th Workshop and Exhibition on Reaction Calorimetry, DECHEMA-House, Frankfurt am Main, 17. April 2002 (kein Pflichtexemplar)
  • Contribution to proceedings
    5th Workshop and Exhibition on Reaction Calorimetry, DECHEMA-House, Frankfurt am Main, 17. April 2002 (kein Pflichtexemplar)

Publ.-Id: 4377 - Permalink


Structure Investigations on Russian Reactor Pressure Vessel Steels by Small Angle Neutron Scattering
Ulbricht, A.; Böhmert, J.; Strunz, P.; Dewhurst, C.; Mathon, M. H.;
The effect of radiation embrittlement has high safety significance for Russian VVER reactor pressure vessel steels. Heats of base and weld metal of the as received state, irradiated state and post-irradiation annealed state were investigated by SANS to get insights about the microstructural features caused by neutron irradiation.
The SANS intensities increase in the momentum transfer range between 0.8 and 3 nm-1 for all material compositions in the irradiated states. The size distribution function of the irradiation-induced defects has a pronounced maximum at 1 nm in radius. Their volume content varies between 0.1 and 0.7 vol.% dependent on material composition and increase with the neutron fluence. The comparison of nuclear and magnetic scattering indicate that the defects differ in their composition. Thermal annealing reduces volume fraction of irradiation defects.
  • Poster
    International Conference on Neutron Scattering 2001, München, September 9-13, 2001

Publ.-Id: 4375 - Permalink


Elastic effect on the evolution of cluster ensembles in irradiated reactor pressure vessel steels
Gokhman, A.; Böhmert, J.; Ulbricht, A.;
Neutron irradiation leads to a number of phenomena that have been extensively studied. Stoller from Oak Ridge National Laboratory (USA) suggested to describe the real damage structure of VVER RPV steels by a composite model with point defect clusters and Cu-rich clusters. The kinetics theory has been applied in our investigations to clarify the relevance of this model for VVER reactor pressure vessel (RPV) steel. Kinetics theory has to take into account the nucleation, deterministic and coarsening stages. In accordance with experimental data the preferable attention is given to the vacancy clusters.
  • Lecture (Conference)
    V. Research Workshop Nucleation Theory and Applications, Dubna, April 2-28, 2001

Publ.-Id: 4374 - Permalink


Fast wire-mesh sensors for gas-liquid flows - visualisation with up to 10 000 frames per second
Prasser, H.-M.; Zschau, J.; Peters, D.; Pietzsch, G.; Taubert, W.; Trepte, M.;
A wire-mesh sensor developed by the Forschungszentrum Rossendorf produces sequences of instantaneous gas fraction distributions in a cross section at a rate of up to 10 000 frames per second and a spatial resolution of about 2-3 mm. This sensor was applied to an upwards air-liquid flow in a vertical pipe of 51.2 mm diameter. After a brief introduction of the functioning of the sensor, the paper presents results obtained in a at vertical pipe operated with an air-water mixture. Two wiremesh sensors with a measuring matrix of 24x24 points (resolution 2 mm) were placed in a small axial distance behind each other. They were used to study the flow structure in the transition region from bubble to slug flow at an imaging frequency of 2 500 Hz. The two available measuring planes allowed to obtain velocity profiles of the gaseous phase. A sensor with 16x16 points (resolution 3 mm) was applied to visualize the transition from bubbly via churn turbulent to annular flow with 10 000 frames per second. In the churn flow region, periodic plug-like structures were found. In the annular flow the sensor is able to resolve wispy structures.
Keywords: Gas-liquid flow, void fraction measurement, gas velocity measurement, wire-mesh sensor, bubble flow, slug flow, annular flow
  • Lecture (Conference)
    International Congress on Advanced Nuclear Power Plants (ICAPP), June 9-13, 2002 - Hollywood Florida, USA, Proc. CD-ROM, paper #1055.
  • Contribution to proceedings
    International Congress on Advanced Nuclear Power Plants (ICAPP), June 9-13, 2002 - Hollywood Florida, USA, Proc. CD-ROM, paper #1055.

Publ.-Id: 4373 - Permalink


Coolant mixing in a PWR - deboration transients, steam line breaks and emergency core cooling injection - experiments and analyses
Prasser, H.-M.; Grunwald, G.; Höhne, T.; Kliem, S.; Rohde, U.; Weiss, F.-P.;
The response of the reactor core to a reactivity perturbation caused by a decrease of the boron concentration or a decrease of temperature in one loop of the primary circuit strongly depends on the degree of mixing with the undisturbed loops. In case of an emergency core cooling (ECC) injection, the flow field can be additionally dominated by gravity effects, because the density difference between ECC water and coolant inventory is significant. The streak formation may cause thermal loads on the reactor pressure vessel wall (PTS).

In order to study coolant mixing inside the reactor pressure vessel in the flow path beginning from the inlet nozzles and ending at the core entrance the test facility ROCOM (Rossendorf Coolant Mixing Model) was built and operated during the last three years. The facility represents a German KONVOI type PWR (1300 MWel) in a scale of 1:5. ROCOM is equipped with four fully functioning loops. The circulation pumps are driven by motors with computer controlled frequency transformers. In this way, a wide variety of flow rate regimes, such as four-loop operation, operation with pumps off, simulated natural circulation modes and flow rate ramps can be realized.
In case of the experiments on ECC injection, the higher density of the injected water was simulated by adding sugar (glucose).
The evolution of the spatial distribution of the deborated coolant respectively the ECC water was measured by tracering with sodium chloride solution. Conductivity distributions were measured by electrode mesh sensors, one close to the reactor inlet nozzle (16x16 measuring points), two sensors in the upper and lower part of the downcomer (2D grids of 4 radial and 64 angular measuring positions) and one sensor at the core entrance (inlets of each of 193 fuel elements). The maximum measuring frequency is 200 Hz. The results allow the visualizations of the measured distributions at the sensor positions. In case of running main circulation pumps, the coolant from the affected loop arrives in a sector at the azimuthal position of the corresponding inlet nozzle. But on contrary to the extreme assumption of a sharp sector, the slopes of the sector are smooth and the maximum disturbance is about 70-80 % of the disturbance at the reactor inlet. Pump start-up scenarios as well as asymmetric natural circulation in one of the four loops are connected with a different picture. In this case, the water with a decreased boron concentration arrives at the core entrance at the side opposite to the azimuthal position of the inlet nozzle, in which the flow starts.
The injection of ECC water with a higher density is accompanied with the appearance of a streak of cold water streaming downwards in the downcomer. Experiments at ROCOM were carried out to identify the transition from momentum driven flow in the downcomer to a density driven regime (critical Froude number). The relative density difference was varied between 0 and 10 % and the loop flow rate between 0 and 15 % of the nominal. In case of momentum controlled flow (high Froude numbers) the ECC water reaches the core inlet first on the side opposite to the azimuthal position of the affected loop. If the density difference is large (low Froude numbers) the ECC water falls down almost in a straight line and reaches the core inlet at the azimuth of the inlet nozzle.
Parallel to the experimental work, CFD calculations were performed. Good results were achieved with the code CFX-4.2. Nozzle region, downcomer and lower plenum were discretized in a mesh of about 400 000 nodes. The calculations well reflect both shape and amplitude of the distributions at the core entrance, if a k-eps turbulence model is used. The code validation benefits from the detailed information delivered by the mesh sensors. Furthermore, a simplified mathematical model was developed to generalize experimental results using some linear properties of the transport equation for the temperature respectively the bo...
Keywords: pressurised water reactors, coolant mixing, deboration transients, main steam line breaks, emergency core cooling, experiments, computational fluid dynamics, pre-stressed thermal shock
  • Lecture (Conference)
    International Congress on Advanced Nuclear Power Plants (ICAPP), June 9-13, 2002 - Hollywood Florida, USA, Proc. CD-ROM, paper #1214.
  • Nuclear Technology 143 (2003) 37-56
  • Contribution to proceedings
    International Congress on Advanced Nuclear Power Plants (ICAPP), June 9-13, 2002 - Hollywood Florida, USA, Proc. CD-ROM, paper #1214.

Publ.-Id: 4372 - Permalink


High-speed measurement of the void fraction distribution in ducts by wire-mesh sensors
Prasser, H.-M.;
The paper presents a wire-mesh sensor for high-speed visualisation of transient gas fraction distributions in two-phase flows. It is based on the measurement of the local instantaneous conductivity of the two-phase mixture. The maximum time resolution of the device is 10 000 frames per second. The sensor consists of two electrode grids with 16 electrodes each. This results in 16 x 16 sensitive points, which are equally distributed over the cross section. The sensor was used to measure gas fraction and velocity profiles, bubble size distributions and their evolution along the flow path in a vertical upwards gas-liquid flow.
Keywords: Two-phase instrumentation, gas-liquid flow, wire-mesh sensor, void fraction
  • Lecture (Conference)
    International Meeting on Reactor Noise, Oct. 11-13, 2000, Athens, Greece, proc. on CD-ROM, paper_7_1.doc.
  • Contribution to proceedings
    International Meeting on Reactor Noise, Oct. 11-13, 2000, Athens, Greece, proc. on CD-ROM, paper_7_1.doc.

Publ.-Id: 4371 - Permalink


Centrality dependence of thermal parameters in heavy-ion collisions at SPS and RHIC
Kämpfer, B.; Cleymans, J.; Gallmeister, K.; Wheaton, S.;
We analyze the centrality dependence of thermal parameters describing hadron multiplicities, hadron spectra and dilepton
spectra in heavy-ion collisions at SPS and RHIC energies.
Keywords: relativistic heavy-ion collisions, hadron yields, dileptons
  • Contribution to proceedings
    Int. Workshop XXX on Gross Properties of Nuclei and Nucl. Excitations: Ultralrelativistic Heavy-Ion Collisions, Hirschegg, Jan. 13 - 19, 2002, p. 158

Publ.-Id: 4370 - Permalink


Evaluation of QCD sum rules for HADES
Zschocke, S.; Kämpfer, B.; Pavlenko, O.; Wolf, G.;
QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of pole mass parameters for the lightest vector mesons rho, omega and phi in a strongly interacting medium at conditions relevant for the starting experiments at HADES.
The role of the four-quark condensate is highlighted.
A few estimates (within a fire ball model and BUU calculations) of dilepton spectra in heavy-ion collisions at 1 AGeV are presented.

Keywords: HADES, QCD sum rules, dileptons
  • Contribution to proceedings
    Proc. XL Int. Winter Meeting on Nucl. Physics, Bormio, Jan. 20 - 26, 2002, p. 102, nucl-th/0202066

Publ.-Id: 4369 - Permalink


Prognostic value of positron emission tomography in the evaluation of post-treatment residual mass in patients with Hodgkin's disease and non-Hodgkin's lymphoma
Naumann, R.; Vaic, A.; Beuthien-Baumann, B.; Bredow, J.; Kropp, J.; Kittner, T.; Franke, W.-G.; Ehninger, G.;
The prognostic value of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in the assessment of post-treatment residual masses in patients with Hodgkin's disease (HD) or non-Hodgkin's lymphomas (NHL) was evaluated. We prospectively studies 58 patients with HD (n = 43) or NHL (n = 15) who had post-therapeutic complete remission with residual masses (CRu) indicated by computerized tomography. Analysis of 62 residual locations by FDG-PET was performed separately for HD and NHL. Patients with a PET-positive residual mass [standardized uptake value (SUV) > 3] had a recurrence rate of 62.5% (5/8 patients), whereas patients with PET-negative residual mass (SUV -< 3.0) showed a recurrence rate of 4% (2/50 patients, P = 0.004). A positive FDG-PET study correlated with a significantly poorer progression-free survival (P < 0.00001). No recurrence occurred in any of the 39 HD patients with negative PET scan (negative predictive value, 100%). Four out of four NHL patients with a positive PET study relapsed (positive predictive value, 100%).
In conclusion, FDG-PET is a suitable non-invasive method with a high degree of accuracy in the prediction of early recurrence in lymphoma patients with CRu.

Keywords: Hodgkin's disease, non-Hodgkin's lymphoma, 2-[F-18]fluoro-2-deoxy-D-glucose (FDG), PET, residual masses
  • British Journal of Haematology 115 (2001) 793-800

Publ.-Id: 4367 - Permalink


Effect of the Obstacles for Dislocation Motion on the Radiation Embrittlement of Fusion Reactor Materials
Voskoboinikov, R. E.; Böhmert, J.;
Embrittlement of nuclear reactor materials is regarded as one of the most important problems in radiation physics. One of the widespread approaches relates the embrittlement of bcc materials (ferritic/martensitic steels, vanadium alloys etc.) to impurities that can precipitate under irradiation. Fracture of iron as wll as modern structural materials occurs through crack nucleation and growth. Precipitation can affect crack growth directly via elastic interaction and indirectly through locking the dislocation motion. The primary topic of the research is the effect of obstacles for dislocation motion on the plastic zone formation, the crack blunting and shielding. Features of the plastic zone (size, dislocation density etc.) are investigated. Reduction of stress intensity factor vs. size, volume fraction and distribution of precipitates is evaluated. Dependence of embrittlement of structural reactor materials on the concentration of precipitates is established.
  • Poster
    10th International Conference on Fusion Reactor Materials, 14-19 October 2001, Baden-Baden, Germany

Publ.-Id: 4366 - Permalink


Analyse von Simulationsexperimenten zu nuklearen Kernschmelzunfällen - Beitrag der Metallographie -
Böhmert, J.; Müller, G.; Willschütz, H.-G.;
Das Verhalten des Reaktordruckbehälters bei Kernschmelzstörfällen ist von hoher sicherheitstechnischer Bedeutung für die Beherrschung derartiger Störfälle. An der Königlichen Technischen Hochschule Stockholm werden dazu EU-geförderte Simulationsexperimente (FOREVER) durchgeführt. Der untere Teil eines 1:10 skalierten Druckbehälters wird mit einer oxidischen, ca. 1200 °C heißen Schmelze und mit Innendruck belastet. Die dabei auftretenden Temperaturen und Dehnungen werden in Abhängigkeit von der Zeit während des Experimentes gemessen. Metallografische Untersuchungen nach Abschluss des Experimentes geben zusätzliche Informationen über die aufgetretenen Belastungen. In Abhängigkeit von der axialen und radialen Position lassen sich eine Reihe typischer Strukturen nachweisen, wie Oxidschichten, Reaktionszonen mit der Kernschmelze, Entkohlungszonen, bainitische Zonen oder Bereiche mit ferritisch-perlitischem Zeilengefüge. Von besonderem Aussagewert ist die räumliche Verteilung der Kriechporen. Glühexperimente an den Proben mit unbeeinflussten Ausgangsgefüge liefern eine Vergleichsgefügereihe. Auf diese Weise können die Maximaltemperaturen ebenso wie die axialen und radialen Temperaturgradienten abgeschätzt werden. Die metallografischen Befunde bestätigen die FEM-Vorausrechnungen der Experimente.
  • Poster
    Fortschritte in der Metallographie, Sonderbände der Praktischen Metallographie, G. Petzov (Hrsg.), Vortragstexte der 35. Metallographie-Tagung 2001, Neu-Ulm, 19.-21. September, S. 69
  • Contribution to proceedings
    Fortschritte in der Metallographie, Sonderbände der Praktischen Metallographie, G. Petzov (Hrsg.), Vortragstexte der 35. Metallographie-Tagung 2001, Neu-Ulm, 19.-21. September, S. 69

Publ.-Id: 4364 - Permalink


A fast screening method for surface layers on Gram-positive bacteria
Wahl, R.; Raff, J.; Selenska-Pobell, S.; Mertig, M.; Pompe, W.;
A two-step screening method is described to identify regularly arranged surface layers (S layers) on Gram-positive bacterial strains. A non-destructive release of S-layer sheets is achieved by enzymatic hydrolysis of the underlying peptidoglycan using lysozyme. The existence of regular S layers is then directly confirmed by scanning force microscopy or transmission electron microscopy. This method requires a minimal amount of bacterial cells and may be used as a 'quick test' for demonstrating the presence of S layers.
Keywords: Bacillaceae, bacterial surface layer (S layer), lysozyme, microscopy, screening
  • Biotechnology letters 23, 1485-1490 (2001)

Publ.-Id: 4363 - Permalink


Electron-beam induced formation of highly ordered palladium and platinum nanoparticle arrays on the S-layer of Bacillus sphaericus NCTC 9602
Wahl, R.; Mertig, M.; Raff, J.; Selenska-Pobell, S.; Pompe, W.;
  • Advanced Materials 2001, 13, No. 10, May 17, p. 736-740

Publ.-Id: 4362 - Permalink


Complexation of U(VI) with cells of Thiobacillus ferrooxidans and Thiomonas cuprina of different geological origin
Panak, P.; Selenska-Pobell, S.; Kutschke, S.; Geipel, G.; Bernhard, G.; Nitsche, H.;
  • Radiochimica Acta 84, 183-190 (1999)

Publ.-Id: 4361 - Permalink


FT-Raman and FT-IR spectra of crosslinked polyurethaneurea films synthesised from solutions
Romanova, V.; Begishev, V.; Karmanov, V.; Kondyurin, A.; Maitz, M. F.;
The crosslinked polyurethaneurea films based on polyoxitetramethylenglycol and polyoxipropyleneglycol with toluenediisocyanate and 3,3'-dichlor,4,4'-diaminediphenylmethane were synthesised in a solution where the solvent evaporates during the polymerisation. FT-Raman and FTIR spectra were analysed and intermo-lecular force constants of hydrogen bonds were calculated. On the base of intensity of the Raman and IR line of spectra which reflects hydrogen bond formation, the optimal structure of hydrogen bonds and the conformations of macromolecules of polyure-thaneurea were observed for the solvent ethylacetate.
Keywords: Polyurethane Spectroscopy
  • Journal of Raman Spectroscopy 33(10): 769-777 (2002).

Publ.-Id: 4360 - Permalink


Substrate bias effects in Plasma Immersion Ion Implantation Assisted Deposition from a TiAl cathodic arc
Mukherjee, S.; Reuther, H.; Prokert, F.; Richter, E.; Möller, W.;
TixAl1-x thin films were deposited on stainless steel substrates using plasma immersion ion implantation and deposition (PIIIAD). A cathodic arc was employed as a source of metallic ions from Ti0.5Al0.5 targets and the arc plasma was guided by a curved magnetic field filter. The resultant thin films were analysed using Auger electron spectroscopy (AES) and X-ray diffraction techniques. A dynamic profile simulation code, TRIDYN, based on binary collision approximation was applied to understand the Ti and Al profiles in the deposited thin film. The results indicate that the film composition and phase formation depends on the applied bias, duty cycle and off time energy of the bombarding ions. The results also indicate that in PIIIAD conditions, the assumption of time averaged dc bias is improper to describe pulsed biasing, with deposition, resputtering and ion implantation all occuring simultaneously.
Keywords: PIIIAD, TRIDYN, pulsed biasing
  • Surface and Coatings Technology 160 (202) 93-98

Publ.-Id: 4359 - Permalink


Biological sol-gel ceramics with specific metal binding capacity
Raff, J.; Soltmann, U.; Matys, S.; Schnorrpfeil, M.; Boettcher, H.; Pompe, W.; Selenska-Pobell, S.;
Bacteria in polluted environments are adapted to the toxic compounds present there
and often possess effective detoxification strategies. For this reason they are
very prospective for development of in situ bioremediation processes. In former
experiments a selective binding by cells and spores of Bacillus sphaericus
JG-A12 of U, Cu, Pb, Al and Cd from drain waters of uranium mining wastes was
demonstrated. The strain JG-A12 was recovered from the uranium mining waste pile
"Haberland" near the town of Johanngeorgenstadt. B. sphaericus JG-A12 possesses
a surface layer (S-layer). The latter differs significantly at its N-terminal
domain from all other S-layers studied up to date. Cells, spores and purified
S-layer protein fraction of this strain were used for construction of biological
sol-gel ceramics (biocers). Metal-binding kinetics of cells, spores, purified
S-layer fraction and the corresponding biological ceramics were measured. The
biosorption of uranium and copper by the corresponding biocomposites was strongly
influenced by the way of the biocer preparation The highest metal binding capacity
possess biocers with embedded vegetative cells. Larger amounts of uranium and
copper were accumulated by biocers which were prepared by freeze drying or using
penetration reagents like sorbit. Desorption of the bound metals and regeneration
of the biological ceramics was achieved using aqueous citric acid.


  • Lecture (Conference)
    VAAM-Jahrestagung 2002 in Göttingen (24.03.-27.03.2002)

Publ.-Id: 4358 - Permalink


Biosorption of heavy metals by Bacillus sphaericus JG-A12 cells, spores and S-layer protein embedded in sol-gel ceramics
Raff, J.; Soltmann, U.; Mathys, S.; Boettcher, H.; Pompe, W.; Selenska-Pobell, S.;
Bacillus sphaericus strain JG-A12 was isolated from the uranium mining waste
pile "Haberland" near the town of Johanngeorgenstadt. Vegetative cells and spores
of this strain accumulate selectively large amounts of U, Cu, Pb, Al and Cd from the
highly polluted drain waters of this uranium waste. Interestingly, the strain
JG-A12 possess a surface layer protein (S-layer) with a novel structure. The ability
of B. sphaericus to interact with heavy metals and its geographic origin make
it a good candidate for preparation of bacteria-based ceramics (biocers) for in
situ bioremediation of uranium mining waste pile waters. Biocers were prepared by
dispersing vegetative cells, spores and purified S-layer protein fraction of B.
sphaericus JG-A12 in aqueous silica nano-sols, gelling and drying. Different types
of ceramics were prepared by using air or freeze drying and adding water soluble
compounds as sorbit. Variations in porosity and structure of the biocers were
examined using scanning electron microscopy. The sorption and desorption of uranium
and copper by these biocomposites were investigated and visualised by EDX analysis.
Highest binding capacity demonstrate biocers with embedded Bacillus cells. For
reusing the biocers sorbed uranium and copper can be completely removed from them
by washing with aqueous citric acid.
  • Poster
    VAAM-Jahrestagung 2002 in Göttingen (24.03.-27.03.2002)

Publ.-Id: 4357 - Permalink


Microbial bioremediation of uranium mining waste waters using sol-gel ceramics
Raff, J.; Soltmann, U.; Matys, S.; Schnorrpfeil, M.; Boettcher, H.; Pompe, W.; Selenska-Pobell, S.;
During the long period of uranium mining and production in Saxony, large amounts of ores were treated and leached. Waste piles and waste waters from those procedures with high concentrations of heavy metals and radionuclides still remain in this part of Germany. For further use of the mentioned areas, they have to be cleaned. For this purpose, bacteria recovered from the contaminated sites are very prospective, because developing detoxification strategies as binding or reduction of heavy metals and radionuclides, they are well adapted to the complex and toxic conditions in the wastes. Bacillus sphaericus JG-A12 was recovered form the uranium mining waste pile "Haberland" near the town of Johanngeorgenstadt. Vegetative cells and spores of this strain accumulate selectively and reversible large amounts of U, Cu, Pb, Cd and Al. Interestingly, B. sphaericus JG-A12 possesses a paracrystalline surface layer protein (S-layer) as outermost component of its cell wall. Compared to the known S-layers of the other B. sphaericus strains, the N-terminal domain of B. sphaericus JG-A12 S-layer possesses a novel primary structure. Cells, spores and stabilized S-layer sheets were embedded by sol-gel techniques in xerogels. The sorption and desorption of uranium and copper by the free biocomponents and the biocomposite material were investigated using EDX analysis.
  • Lecture (Conference)
    Uranium Mining and Hydrogeology (UMH III) in Freiberg (15.09.-21.09.2002)
  • Lecture (Conference)
    Konferenz UMH III Freiberg 15.-21.9.2002

Publ.-Id: 4356 - Permalink


Reversible accumulation of uranium by bacteria-based sol-gel ceramics
Raff, J.; Soltmann, U.; Matys, S.; Böttcher, H.; Pompe, W.; Schnorrpfeil, M.; Selenska-Pobell, S.;
Bacillus sphaericus JG-A12 was isolated from the uranium mining waste pile "Haberland" near the town of Johanngeorgenstadt, Saxony, Germany. The drain water and the soil at this site are highly contaminated with heavy metals and radionuclides. Sorption experiments with vegetative cells and spores of B. sphaericus JG-A12 demonstrate specific and reversible accumulation of U, Cu, Pb, Al and Cd from the drain water of the waste. The latter makes this bacteria an interesting candidate for the development of in situ bioremediation processes based on biological ceramics (biocers). In addition, B. sphaericus JG-A12 possesses a surface layer (S-layer) which differs at its N-terminal domain (220 amino acid residues) significantly from all other S-layers studied up to date. In this study vegetative cells, spores and stabilized S-layer sheets were immobilized in the SiO2 matrix by dispersing in aqueous silica nanosols, gelling and drying. Variations in the porosity and structure of the biocers were achieved by different drying methods or adding water soluble compounds as sorbitol. The time dependence of the uranium sorption and desorption by the free biocomponents and biocomposites was investigated. Localization of the bound metals and a characterization of the metal complexes formed at the biocer were carried out using scanning electron microscopy and EDX.

  • Poster
    Uranium Mining and Hydrogeology Conference Freiberg 2002, 15.09.-21.09.

Publ.-Id: 4355 - Permalink


Low resistivity, p-type SiC layers produced by Al implantation and ion beam induced crystallization
Heera, V.; Madhusoosanan, K. N.; Mücklich, A.; Panknin, D.; Skorupa, W.;
Low resistivity ( < 0.1 Ohm cm), p-type SiC layers can be produced by the combination of high dose Al ion beam doping and ion beam induced crystallization. The implanted SiC layers have a nanocrystalline structure consisting of randomly oriented grains of mainly 3C-SiC. The electrical properties of the doped layers were investigated by sheet resistance and Hall measurements in dependence on temperature. In comparison with the standard doping process the hole concentration is enhanced by more than one order of magnitude.
Keywords: SiC, p-type doping, Al implantation, ion beam induced crystallization, nanocrystalline semiconductor, sheet resistance, Hall measurements
  • Applied Physics Letters 81 (2002) 70-72

Downloads:

Publ.-Id: 4354 - Permalink


Simulation of scaled vessel failure experiments and investigation of a possible vessel support against failure
Willschütz, H.-G.;
Scaled coupled melt pool convection and vessel creep failure experiments are being performed in the FOREVER program at the Royal Institute of Technology, Stockholm. These experiments are simulating the lower head of a pressurized reactor vessel under the thermal load of a melt pool with internal heat sources. Due to the multi axial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments offer an excellent opportunity to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module, the melt pool convection is simulated and the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep modeling procedure. Additionally, the material damage is evaluated considering the creep deformation as well as the prompt plasticity.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. After analyzing the calculations, it seems to be advantageous to introduce a vessel support, which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.

Keywords: severe accident, molten corium pool, RPV lower head behavior, finite element creep modeling, accident management, vessel support, passive control device for flooding
  • Nuclear Engineering and Design, 228(2004)1-3, 401-414

Publ.-Id: 4353 - Permalink


Evidence for irradiation-induced metallic precipitates in neutron-irradiated model alloys and pressure vessel weld steel, using Doppler-broadening positron spectroscopy
Cumblidge, S. E.; Motta, A. T.; Catchen, G. L.; Brauer, G.; Böhmert, J.;
Positron Doppler-broadening spectoscopy was used to examine a series of neutron-irradiated model alloys and 73W-weld steel. The composition of the model alloys was systematically varied in the amounts of copper, nickel and phosphorus. The 73W-weld steel contains 0.31 % copper and 0.60 % nickel. The samples were examined in the non-irradiated and neutron-irradiated states, as well as after successive isochronal anneals at temperatures ranging from 200 °C to 600 °C.
By comparing the Doppler-broadening spectroscopy W-parameters measured in pure metals with those measured in the materials in this study, we were able to draw inferences as to the nature of the irradiation-induced defects that cause hardening and embrittlement. The results indicate that the damage is a combination of irradiation-induced metallic precipitates and vacancy-type defect clusters.
Keywords: positron annihilations spectroscopy, reactor pressure vessel, radiation defects
  • Journal of Nuclear Materials, Volume 320, No. 3, August, 2003, p. 245-257

Publ.-Id: 4352 - Permalink


Untersuchungen der Sorption von Uran(VI) an das Gestein Phyllit zur Bestimmung von Oberflächenkomplexbildungskonstanten
Zorn, T.;
kein Abstract
  • Other report
    Dissertation / Technische Universität Dresden, Februar 2000

Publ.-Id: 4350 - Permalink


Localization and characterization of uranium (VI) complexes formed by three eco-types of Acidithiobacillus ferrooxidans
Merroun, M.; Hennig, C.; Rossberg, A.; Geipel, G.; Reich, T.; Nicolai, R.; Heise, K.-H.;
Microorganisms have a potential to affect the mobility and overall environmental behaviour of uranium through solubility and speciation changes, biosorption, bioaccumulation or other transformations. Recently, three eco-types of A. ferrooxidans were recovered from different sites and depths of two uranium mining waste piles. These natural A. ferrooxidans isolates interact with uranium and tolerate this radionuclide in a type-specific way. In this study, we used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Infrared Spectroscopy (IRS), Time-resolved Laser-Induced Fluorescence Spectroscopy (TRLFS), Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray (EDX) analysis to conduct atomic and molecular scale studies on U(VI) interaction with the three eco-types of A. ferrooxidans. On the basis of the combined information from the above mentioned methods we conclude that the uranium is bound by A. ferrooxidans cells mainly in a form of organic uranyl phosphate complexes. Moreover, the largest part of the uranium accumulated by A. ferrooxidans cells is located within the extracellular polysaccharides. Additionally, some part of the uranium was found on the cell walls. A limited amount of the metal enters the cells and is than detoxified through sequestration by intracellular polyphosphate bodies.


  • Poster
    VAAM Jahrestagung 2002, 24.03.-27.03.2002, Göttingen, Deutschland

Publ.-Id: 4349 - Permalink


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