Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

A focused beam of Co+ ions has been used to produce CoSi2 interconnects by means of ion beam synthesis. Investigations have been performed using polysilicon, amorphous and crystalline silicon substrates. The influence of implantation dose and annealing temperature on the resistivity has been studied. For room temperature implantation and annealing 600°C for 1h, a resistivity of about 60µ(*cm has been obtained independent of the subtrate type. The CoSi2 layers have been found to be stable up to 700°C. CoSi2 interconnects have been fabricated on the slope walls of 200µm deep anisotropically etched grooves using a dynamic focus control of the focused ion beam.

In the framework of the computer code assessment programme for the VVER-440 type Paks Nuclear Power Plant a 1% cold leg break experiment has been conducted on the PMK-2 integral type test facility. It was followed by calculations using RELAP 5Mod3.1 and ATHLET in order to assess code capabilities. This experiment was started from the nominal operational parameters and it was considered that only the high pressure injection system (HPIS) is available and there is no injection from the safety injection tanks (SIT). This experiment was the repetition of the test measured in 1990 with improved data aquisition system. The first part of this report includes a short description of the facility, the measurement description, the test results including the local void measurement and a short interpretation of the main phenomena. In the second part of the report the analysis performed by the RELAP 5Mod3.1 and ATHLET Mod1.1 Cycle A codes are given.

AG₂S embedded into a 100 nm thin film of SiO₂ was fabricated synthetically from ist constituents by ion implantation. The ion sensing characteristics of such film material for Ag⁺ were shown to be analogous to conventional bulk materials, giving sensitivities <=59 mV per concentration decade.

The well-known methods of the acoustic leak localization using the attenuation differences or propagation time differences (e.g. cross correlation analysis) are restricted to the linear geometry of pipe lines. At complicated three-dimensional topologies they fail because there are several modes of the structure-borne sound that have different propagation velocities and because numerous connecting branches generate multiple sound reflexion. Therefore, a new method for detecting and localizing the leaks at complicated geometrical structures was developed and experimentally proved at an original facility. This approach is based on the detection of the leak induced airborne sound or structure-borne sound as well as on the application of pattern recognition procedures. The efficiency both of Fuzzy Logic and neural networks for the acoustic leak localization could be experimentally proved. Though the method has been prototypically developed for Russian pressurized water reactors of VVER-440 type, it can also be used by the self-learning capability of the classifiers at other pressurized facilities.

The report gives an overview on the scientific work of the Institute of Safety Research in 1993.

Hadron production in proton-proton interactions is described in the framework of a collision model, which aims at describing simultaneously all reaction channels in a wide energy region. An empirical matrix element based on the present knowledge of the partonic structure of hadrons is combined with the concept of intermediate subsystems and the calculation of modified statistical weights of the various final states. It is demonstrated that the energy dependence of total cross sections between threshold and about 50 GeV incident energy can be satisfactorily reproduced. This is the basis for concidering theoretical and experimental problems of K^-, η and η´ production in more detail.

For a lithium liquid metal ion source (LMIS) an especially high angular intensity and a low energy broadening is expected because of the low mass of lithium. For a Li LMIS the axial angular intensity and the FWHM of the energy distributation have been measured. The results have been compared with the theoretial predictions and with experimental results for gallium, the metal most widly used in LMIS. A correlation between angular intensity and the energy broadening is found. The Li LMIS has a high angular intensity, especially at low currents, compared to the Ga LMIS. With increasing emission current the rise of the angular intensity as well as the ernergy broadening is smaller than than for the gallium source.

Es ist bekannt, daß die Magnus-Kraft in einer aufwärtsgerichteten Zweiphasenströmung bei erzwungener Flüssigkeitsströmung aufgrund des Geschwindigkeitsprofils der Flüssigkeit in Richtung der Kanalwand wirkt. In einem senkrechten Rohr müßten demnach Gasgehaltsprofile zu beobachten sein, die in der Nähe der Rohrwand ihr Maximum aufweisen. In der Realität sind solche Profile nur bei sehr kleinen Gasvolumenstromdichten existent. Meist liegen Profile vor, die ein Maximum des Gasanteils im Zentrum der Rohrleitung aufweisen. Es wird vermutet, daß in diesem Fall die Turbulenz den Einfluß der Magnus-Kraft überwiegt und für die Herausbildung des Maximums im Zentrum verantwortlich ist. Zur genaueren Untersuchung des Übergangs zwischen den beiden Strömungsformen wurden Messungen der radialen Verteilung des volumetrischen Gasanteils an einer drucklosen, mit Luft-Wasser-Gemisch betriebenen Testschleife durchgeführt. Die Anlage verfügt über einen senkrechten Testkanal (NW 50). Zur Messung des Gasgehaltes dienten nadelförmige Leitfähigkeitssonden. Insgesamt wurden 8 Sonden über den Radius des Rohrs verteilt und deren Signale synchron aufgezeichnet. Die Lufteinspeisung erfolgte gleichmäßig über dem Querschnitt der Rohrleitung. Die maximalen Volumenstromdichte des Wassers betrug 2.8 m/s, der eingeperlte Gasstrom wurde von 0 bis ca. 0.4 m/s variiert. Durch eine Einlauflänge von 40 Rohrdurchmessern traten am Sondenkamm trotz der gleichmäßigen Einperlung ausgeprägte Gasgehaltsprofile auf. Dabei wurden für entsprechend kleine Luftdurchsätze Verteilungen erhalten, die ein stark ausgeprägtes Maximum am Rand der Rohrleitung aufweisen. Bei Vergrößerung des Luftstromes findet in einem bestimmten Durchsatzbereich ein kontinuierlicher Rückgang des Randmaximums statt. Gleichzeitig tritt das für die turbulente Verteilung typische Maximum im Zentrum auf und es stellt sich ein parabelförmiges Profil ein. Z.B. für eine Volumenstromdichte des Wassers von 0.7 m/s findet dieser Übergang bei einer Volumenstromdichte von ca. 0.2 m/s statt. Der Bereich der stabilen, durch die Magnus-Kraft gesteuerten Gasgehaltsverteilung wurde aufgezeichnet. Der Übergang zur parabelförmigen Verteilung des Gasgehalts verschiebt sich bei wachsender Wassergeschwindigkeit hin zu höheren Werten des Luftvolumenstroms.

interne Projektstudie

This paper presents a solution of the AER benchmark problem specified for the 7th cycle of the Paks-2 VVER-440 reactor. The problem concerns control rod worth for both the beginning and the end of burnup cycle states. The burnup distribution of cycle 7 was calculated starting from the burnup values of the third cycle. The calculations were carried out by using the burnup option of the DNYN3D code and a MAGRU group data library. The results are compared with calculations published by other authors on AER meetings. Furthermore the influence on reactivity of some control rod properties typical for VVER-440 was studied.

Mathematical benchmark are widely used and accepted means of verifying the reliability of numerical simulations. The present benchmark is aimed at assessing the discrepancies between three-dimensional core models used for transient calculations in VVER-reactor cores.
The second AER benchmark problem was defined at the 3nd AER Symposium in Pieštany (1993). The problem and the complete set of input data for a control rod ejection accident in a VVER-440 was described. An asymmetric control rod with a worth approximately 2 ßeff was ejected at hot zero power (HZP). The Doppler effect being the main feedback effect for this type of transients is the only feedback taken into account by an adiabatic model of fuel temperature. Therefore it was possible to calculate this type of transient with codes which do not contain a complete thermo-hydraulic model.
Results of the four codes BIPR-8 (RRI Moskau), DYN3D/M2 (RCR Rossendorf), HEXTRAN (VVT Espoo) and KOKO3D (KFKI-AERI Budapest) were obtained and analyzed by comparisons. The agreement of the results is quite satisfactory, however there exist some discrepancies.

Das Pilotprojekt Freital zur Einspeisung von Solarwärme in ein Fernwärmenetz wird vorgestellt und diskutiert. An sonnenscheinreichen Tagen wird die Rücklauftemperatur des Fernwärmenetzes von 58 °C auf 75°C erhöht. Der Kollektorkreiswirkungsgrad liegt an solchen Tagen bei Werten von über 40 %.

Ein Gerät zur Messung der Kennlinien von Photovoltaik-Generatoren wurde entwickelt. Es handelt sich ein transportables, PC-gesteuertes Gerät zur Messung von Generatoren im Leistungsbereich zwischen 1 und 5 kWp. Als leistungsmodulierbares Bauelement wird erstmalig ein MOS-Transistor genutzt. Erste Meßergebnisse werden vorgestellt.

The Rossendorf focused ion beam IMSA-100 was contructed and used for writing implantation of cobalt to form CoSi2-submicron strutures on silicon by ion beam synthesis. Two types of cobalt containing liquid alloy ion source were developed with Co-Nd and Co-Ge alloys. The fabrication of CoSi2 structures by stoichiometric implantation of Co+ (E = 30-35 keV, Iion = 1.3 nA) and Co2+ ions (E = 60 keV, Iion = 0.6 nA) at doses between 0.3 and 5x1017 cm-2 and a subsequent two step annealing (600°C, 60 min; 1000°C, 30 min in N2) is demonstrated. The dose dependence as well as the influence of the substrate temperature between room temperature and 400°C during ion implantation on the ion beam synthesis process were studied. The quality of the silicide submicron structures was investigated by scanning electron microscopy, energy dispersive x-ray analysis, and electrical measurments. While the room temperature implantation and subsequent annealing generate an inhomogeneous CoSi2 film, 400°C substrate heating during implantation leads to a countinuous film with a resistivity below 20µ( cm, comparable with broad beam implantation.

Die zwei größten solarthermischen Anlagen Sachsens werden im Anlagenaufbau und hinsichtlich der bisher vorliegenden Betriebserfahrungen vorgestellt und verglichen. Dies ist zum einen eine Anlage in Freital mit 90 m² Absorberfläche zur Warmwassererzeugung und Fernwärmeeinspeisung. Zum zweiten handelt es sich um sieben Anlagen mit je 100 m² Absorberfläche zur Warmwasserbereitung in Wohnblöcken in Oederan. Beide Anlagen arbeiten störungsfrei. Die geplanten solaren Erträge konnten in der ersten Betriebsperiode nicht erreicht werden. In der Freitaler Anlage lag die Rücklauftemperatur des Fernwärmenetzes etwa 20 K über der Auslegungstemperatur, was zu schlechten Kollektorwirkungsgraden führte. In Oederan betrug der Warmwasserbedarf nur ca. 60 % des Auslegungswertes mit dem gleichen negativen energetischen Effekt.

The semi-magic nucleus ₃₉ ⁸⁹Y₅₀ has been
studied in the framework of the spherical shell model. Relative to a hypothetical
⁶⁶Ni core the expanded configuration space (0f_5/2,
1p_3/2, 1p_1/2, 0g_9/2) and (1p_1/2,
0g_9/2, 1d_5/2, 0g_7/2) for protons and neutrons,
respectively, has bveen considered. The results, both for the excitation
energies and electromagnetic transition probabilities, suggest for the
positive-parity states above 4.5 MeV with 17/2 <= I <=23/2 significant
admixtures of the neutron [(0g_9/2)^-1(1d_5/2)]
excitation coupled to the odd proton occupying the 0g_9/2 orbital.
The calculations predict that the experimentally observed states above
7.2 MeV with 23/2 <= I <=31/2 are generated by the additional excitation
of one proton to the 0g_9/2 orbital resulting in a parity alteration.
The strength of the electric dipole transitions connecting the levels of
the two proposed high-spin structures might be explained by small contributions
of the neutron 0h_11/2 excitation to the involved wave functions.

Existing thermal hydraulic best-estimate codes have to undergo a procedure of extended verification in respect to the special qualities of VVERs. Concerning then VVER-1000 the Russian test facility ISB-VVER only is available, which is located in Elekrtogorsk near Moscow. It was put into operation in October 1992 and was used as the source of experimental data for the first Russian Standard Problem, a 2.4 % small break KOCA test. The present paper deals with a series of tests dedicated ro an 11 % break at the upper plenum of the reactor vessel. ISB-VVER is a two-loop model of the VVER-1000. The elevations are kept 1:1, while the volume and power scales are 1:3000. The four loops of the original plant are modelled as one single loop with one and a triple loop with three parallel steam generators. During the experiments needle shaped conductivity probes of the Recearch Center Rossendorf were applied for void measurements. The tests have shown that in case of a leak in the upper plenum, the cooling capability of the high-pressure injection system strongly depends on the location of the injection. The most favourable condictions for the core cooling are achieved by the injection in both the cold and the hot leg simultaneousely. In this case, an 11 % break in the upper plenum can be safely ruled over without fuel rod overheating by operating the HPIS only. In some cases, oscillations of void fractions and water levels were found.

Im Beitrag werden erste Ergebnisse der Messungen (Zeitraum Juli-Dezember 1994) an der Solaranlage vorgestellt. Kollektorkreis, Pufferspeicherladekreis, Brauchwasserladekreis und Fernwärmeeinspeisung werden im Einzelnen analysiert. Die Betriebsergebnisse bestätigen die Auslegung, aufgrund erhöhter Rücklauftemperaturen des Fernwärmenetzes liegen die energetischen Ergebnisse der Solaranlage unter den projektierten Werten.

The tenser analyzing power T-20 and the polarization transfer kappa in the deuteron break-up reaction Dp --> pX are calculated within a relativistic approach based on the Bethe-Salpeter equation with a realistic meson-exchange potential. Our results on T-20, kappa and the cross section are compared with experimental data and non-relativistic calculations and with the outcome of a relativization procedure of the deuteron wave function.

In the framework of the computer code assessment programme for the VVER-440 type Paks Nuclear Power Plant a 1% cold leg break experiment has been executed on the PMK-2 integral type test facility. For the test it was considered that only high pressure injection system (HPIS) is available and there is no injection from the safety injection tanks (SIT). The experiment was the repetition of the test measured in 1990, with improved data aquisition system. In the report the results of the experiment were discussed and a description of the phenomena was given.

We formulate the asymptotic theory of thermocapillary instability in a planar fluid layer heated from below in the presence of a strong magnetic field corresponding to high Hartmann number. Explicit asymptotic expressions are derived for the velocity perturbation, temperature perturbation and electric current density. Their spatial structure is characterized in terms of Hartmann boundary layers - a concept which permits a physical understanding of more complicated situations involving surface deformation, buoyancy and thermoelectric effects. The physical nature of large scale instabilities in the case of a deformable surface is clarified.

Im Rahmen eines vom Sächsischen Staatsministeriums für Wissenschaft und Kunst geförderten Vorhabens wurden 1994 die Untersuchungen zu den Aufgaben, zu den zu erwartenden Kosten und zu den Realisierungschancen für ein internationales Zentrum für Information und Frühwarnung bei nuklearen Ereignissen in mittel- und osteuropäischen Kernkraftwerken planmäßig fortgesetzt und das laufende Projekt mit dem Abschlußbericht zum 31.12.1994 abgeschlossen.
Für die anstehenden Aufgaben, nämlich Abschätzung der Emissionen, Prognose der Radioaktivitätsausbreitung, Verfolgung der Lageentwicklung und Mitwirkung bei der Vorbereitung von Notfallschutzmaßnahmen sind im wesentlichen radiologische Meßwerte über die freigesetzten radioaktiven Stoffe und meteorologischen Kennwerte zur Beschreibung der Ausbreitungsbedingungen an das Zentrum zu übertragen. Betriebliche Informationen über den Anlagenzustand sind nur im Sinne von Hintergrundinformationen erforderlich, wozu 8 bis 10 ausgewählte sicherheitsrelevante Betriebsparameter ausreichend sind.

Obwohl der Sinn eines solchen Vorhabens außer Frage steht, sind die Realisierungschancen ohne eine umfassende Förderung durch die EG und andere internationale Organisationen - World Association of Nuclear Operators WANO, International Atomic Energy Agency IAEA - gering.

Bestrahlungsinduzierte Ausscheidungen gelten als die strukturelle Ursache der Neutronenversprödung von Reaktordruckbehälterstahl (RDB-Stahl). Am Beispiel des WWER-440 RDB-Stahls 15Cr2MFA wird die Korrelation zwischen dem Volumenanteil an bestrahlungsinduzierten Ausscheidungen und der Erhöhung der Sprödbruchübergangstemperatur diskutiert. Es wird eine bimodale Abhängigkeit dieser beiden Größen gefunden. Ursache des bimodalen Verhaltens sind möglicherweise unterschiedliche Arten von bestrahlungsinduzierten Ausscheidungen, die vom Gehalt an Verunreinigungselementen bestimmt sind.
Erste resonante Röntgenkleinwinkelstreuexperimente an Material mit niedrigem Cu-Gehalt zeigen, daß Vanadium ein wesentlicher Bestandteil der bestrahlungsinduzierten Ausscheidungen ist. Die Ergebnisse von Neutronenkleinwinkelstreuung und Positronenannihilationsspektroskopie unterstützen die Hypothese, daß es sich bei den Ausscheidungen im RDB-Stahl 15Cr2MFA um Vanadiumkarbide handelt.

The New Rossendorf Nuclear Microprobe¹⁾
F. Herrmann and D. Grambole

Recently a 3 MV tandetron accelerator was put into operation at the Research Center Rossendorf. At this accelerator we have installed a new nuclear microprobe. The object forming aperture can be changed continuously from 0 to 150 µm and in each direction independently. The magnetic quadrupole triplet delivered by Danfysik has an energy mass product of 45 MeV.amu. Magnetic coils placed behind it scan the beam over an area up to 1 x 1 mm². A manipulator with X-Y-Z-translation, 360° rotation, and tilt enables us together with the adequate detectors to apply ERDA, PIXE, RBS, and NRA. A PC based CAMAC system acquires data from four ADCs. Up to four elemental maps with up to 128 x 128 pixels can be displayed on-line. All events are stored together with their coordinates in list mode for further analysis.
A general problem for a quantitative analysis is the accuracy of charge measurement. Using the whole target chamber as a Faraday cup which would be the best method is impossible in our installation. A negatively biased electrode in front of the target for suppressing the secondary electrons cannot be used either. Therefore a precise current integrator was developed which can operate with a positive offset voltage of several hundred volts at the input. The principle of this integrator will be described as well as first experiences and comparisons to other charge measuring methods. Furthermore, a beam monitoring system based on this integrator was set up for an easy control of the beam.

¹⁾ The project was supported by Bundesminister für Forschung und Technologie under contract 03-GR3ROS

The report contains results of the analysis of the transients "Loop connection" and "SG tube rupture" for NPP with VVER-440 type reactors. To obtain detailled informations about NPP's dynamic characteristics, various variants of initial and boundary conditions are considered.
Calculation of these transients was performed with use of the code SiTAP developed at the Nuclear Safety Institute of Russian Research Centre "Kurchatov Institute". SiTAP is a multi-functional computer tool for fast analysis of transient and accidental processes of VVER type reactors for engineers working in the field of NPP dynamics.
SiTAP can be used for comparative analysis of several variants of accident scenarios to find out the conditions leading to the most severe consequences from safety point of view. For this cases, additional analyses using best-estimate codes should be carried out.
The results from SiTAP for faulty loop connection leading to a boron dilution accident are intended to be used as boundary conditions for a more detailled analysis by the help of the three-dimensional reactor core model DYN3D, developed in the Research Centre Rossendorf for the simulation of reactivity initiated accidents.

Explicit asymptotic expressions are derived for the first unstable mode of surface tension driven instability in an electrically conducting fluid subjected to a strong magnetic field. The spatial structure of the velocity, temperature, and electric current density is characterized in terms of Hartmann boundary layers - a concept that permits a physical explanation of the role of the magnetic field and an understanding of scaling laws derived in previous work.

In 1991 a special programme was initiated by the Saxonian Environmental Ministry to estimate the wind energy potential in Saxony and to identify sites for economic operation of wind energy converters.
In the frame of the programme 16 wind measuring stations were erected, more concentrated in orographically complicated regions. The wind speed was measured at two heights between 10 m and 36 m a. g. l. Ten-minutes-averaging-values of wind velocity and direction were registrated over a time of minimally one year.
The danish Wind-Atlas Program WASP was applied to calculate wind atlas librariers from the measured wind datas. The atlas library represents the regional wind climate of the measuring station. Because WASP was developed mainly for coast and lowland regions far from mountains, special efforts were necessary to estimate the region of representance in Saxony. It could be shown, that in lowland regions the area of representance regions in some cases was comparable with WASP results from coast regions. Especially in the mountain region of the "Erzgebirge" the representance regions was found to be very small. By means of atlas libraries the wind power density in the northern part of Saxony was calculated.

On the basis of these investigations the wind energy potential of Saxony could be estimated. Totally 500 usable sites were identified with an average number of 5 500-kW-wind turbines at each site. Using these capacity a yearly energy production of 2200 GWh seems to be possible.

Single bubble motion driven purely by thermocapillarity (i.e. a linear temperature gradient in the surrounding liquid) is analyzed theoretically with the following steps: A full numerical simulation up to Re of several hundreds depending on the Prandtl-number of the liquid, and a simple analytical treatment describing the asymptotic migration at high Re. Results of short-term microgravity experiments performed at drop Tower Bremen will be reported for 20 < Re < 160. The theoretical migration velocities are slightly higher than the experimental values which might be due to the short-time nature of the experiments. An unsteady theoretical analysis will be given explaining, at least in part, the remaining discrep-ancy between theory and experiment.

The standard cylinder wake is considered for the magnetohydrodynamic (MHD) case: The fluid is electrically conducting and exposed to an external uniform magnetic field of different directions. In general, the magnetic field stabilizes the flow, the vortex street can be suppressed for each Re. A numerical simulation of the time-dependent flow as well as a simple analytical stability analysis will be presented and compared with available and own experiments. The experimentally found tendency of an increasing level of low-frequency perturbations for an increasing magnetic field will be discussed and compared with the analytical stability analysis. Typical features of the MHD case will be presented: Drag increase, up- and downstream wakes, surface pressure redistribution, recirculation bubbles at high Re, etc.

Die Nutzung der Photovoltaik in den neuen Bundesländern wird am Beispiel Sachsens dargestellt. Der größte Impuls kam vom Bund-Länder-1000-Dächer-Photovoltaik-Programm, das die Installation von kleinen netzgekoppelten PV-Anlagen förderte. Weitere Anwendungen betreffen Nischenmärkte wie z. B. Parkscheinautomaten.

On the occasion of Georgius Agricola's 500th birthday in 1994 attention has been focused on the paint material found in an exemplar of his famous scientific book “De re metallica”. The very thin color coatings on the highly sensitive paper substrate represent a challenge to the power and the guaranteed non-destructiveness of IBA. The combined implementation of PIXE and RBS on the external proton beam set-up allows one to determine the chemical elements of the pigments used and to identify the presence of organic layers. Results from selected colors are given to emphasize the complementary character of on-air PIXE-RBS analysis.

The Rossendorf Focused Ion Beam IMSA-100 was used for writing Co-implantation over a topographical structure surface with a prtly controlled focus. After a subsequent annealing the resulting CoSi2 interconnection lines were analysed by SEM and electrical measurements. Also the influence of the depth of focus on the height of the surface contours as well as the resulting radial beam profiles were investigated.

Solarwärme - Einbindung ins Fernwärmenetz wird in Sachsen erprobt
Die im Juni 1994 in Betrieb genommene solarthermische Anlage mit 100 m2 Kollektorfläche ist ein sächsisches Modellvorhaben. Neben der üblichen solaren Trinkwarmwasserbereitung - hier für die Schule - steht die Einspeisung von Solarwärme in ein neugeschaffenes gasbeheiztes Fernwärmenetz im Mittelpunkt eines Langzeitmeß- und analyseprogramms des Forschungszentrums Rossendorf. Die Solaranlage arbeitet nach dem Low-Flow-Prinzip der Kollektordurchströmung in Verbindung mit einer selbstregelnden Speicherschichtbeladung. Regelung und Meßdatenerfassung werden durch eine DDC-Anlage realisiert.

Excited states of the nuclei ⁸³Br and ⁸⁵Rb were populated
in the reaction ⁸²Se(⁷Li,alpha2n) and ⁸²Se(⁷Li,4n),
respectively, using the ⁷Li beams of the FN tandem accelerator
in Cologne (E=32 MeV) and of the 120 cm cyclotron in Rossendorf (E=35 MeV).Gamma-gamma-particle
coincidences were measured with six Ge and fourteen Si detectors installed
at the detector array Cologne OSIRIS CUBE. This technique enabled a reaction
channel selection. Multipole orders of the gamma-rays were derived from
directional correlations of coincident gamma-rays and from angular distributions.
Mean lifetimes were deduced for seven levels in ⁸³Br and two
levels in ⁸⁵Rb using the Doppler-shift-attenuation method. The
level scheme of ⁸³Br has been extended up to (21⁺/2)
and 15^-/2 states. In ⁸⁵Rb a level sequence built
on the ground state has been established up to 15^(-)/2 and a
new cascade of fast M1 transitions starting with a 17^(-)/2 state
at 3198.2 keV has been found. Furthermore, several medium-spin states have
been newly introduced. The level sequences inboth nuclei have been interpreted
in terms of the shell model. The calculations performed in the model space
pi(0g_9/2, 1p_1/2, 1p_3/2, 0f_5/2)
v(0g_9/2, 1p_1/2) reproduce single-particle characteristics
as well as collective properties of the level sequences.

Shell-model calculations for the N=50 nucleus ⁸⁶Kr are presented
and compared toresults of recent in-beam experiments. Two model spaces
are considered: a pure proton configuration space containing the 0f_5/2,
1p_3/2, 1p_1/2, 0g_9/2 orbitals and a model
space including additionally the particlehole  excitation generated
by one neutron lifted from the 0g_9/2 orbital across the shell
gap to the 1d_5/2 orbital. The predictions of the shell-model
using various sets of residual interactions and based on pure proton excitations
are comparable with the experimental findings for the states of positive
parity below 4 MeV and for the negative-parity states with spins up to
7^-. The inclusion of neutron-core excitations causes an improved
agreement between experimental and calculated level energies for the positive-parity
yrast states with spins 7, 9 and 10. The interpretation of neutron-core
excited high-spin states is supported by the comparision of the level structure
of ₃₆ ⁸⁶Kr₅₀ to the experimental levels
of the valence-mirror nucleus ₂₈ ⁶⁴Ni₃₆.

The coupling of advanced thermohydraulic codes with 3-dimensional neutron kinetic codes corresponds to the effort to replace conservative estimations by best estimate calculations. ATHLET is an advanced thermohydraulic code, developed by the German Gesellschaft fr Anlagen- und Reaktorsicherheit (GRS). Up to now only point kinetics and 1-dimensional neutron kinetics have been included. The DYN3D code, developed in the Research Centre Rossendorf (RCR) for the improvement of the simulation of reactivity initiated accidents in nuclear reactors with hexagonal fuel elements comprises 3-dimensional neutron kinetics, models for the thermohydraulics of the core including heat transfer from the fuel to the coolant and a fuel rod behavior model.

The reactor core model DYN3D was coupled with the ATHLET code on two basically different ways. The first way of coupling uses only the neutron kinetics part of the DYN3D code (internal coupling). This coupling along the core is very close and demands an high effort of programming due to the high number of coupling parameters.

In the second way the whole core is cut out from the ATHLET plant model. The core is completly modeled by the DYN3D code (external coupling). In this case the interfaces are located at the bottom and at the top of the core. At this interfaces the pressures, mass flow rates, enthalpies and concentrations of boron acid have to be transferred. This way of coupling is easy to realize by interconnection of an interface routine. It is effectively supported by the General Control and Simulation Modul (GCSM) of the ATHLET code. Almost no changes of the single programs are necessary. Another advantage of this coupling is that the complete DYN3D model can be used.

The disadvantage of this method is the splitting of the thermohydraulics. A closed implicit time integration of the whole system of thermohydraulic equations like in the ATHLET code would demand strong changes of the single programs o ...

Thermocapillary convection in low-Prandtl-number fluids up to now remains insufficiently studied experimentally due to difficulties to realize free surface conditions on liquid metals. A novel technique has been developed to produce small sized easily transportable deep vacuum container filled with a thin layer of gallium under a transparent glass window. The first tests showed that the free surface of the liquid gallium did not deteriorate during a period of up to 45 days. The flow pattern on the free surface, while point heating the bottom of the container, has been demonstrated. The temperature gradient on the free surface of the liquid gallium caused surface relief deformations of an order up to 10 - 100 microns. Video recordings of the tracer particle motion on the free surface of liquid gallium due to thermal convection and surface relief deformations due to changes in heating conditions has been made. The presence of the thermocapillary convection has been demonstrated.

In der Arbeit werden unterschiedliche Konzepte der Einbindung großer Solaranlagen in konventionelle Wärmesysteme untersucht. Am Beispiel der Solaranlagen in Oederan und Freital wird die dezentrale Einbindung und die Einkopplung in Fernwärmenetze mit den entsprechenden Vor- und Nachteilen diskutiert. Als entscheidender Parameter für den zu erwartenden Ertrag erweist sich das Temperaturniveau des aufnehmenden Netzes.

Experiments on the thermocapillary bubble migration are presently carried out in the Drop Tower Bremen. After a heating period of about two hours, a sufficiently linear temperature gradient is established with paraffin liquids in a cavity. For the moment of drop of the capsule two bubbles with diameters of up to 2 mm are generated and the injection needles are retracted. During 4.74 s under strongly reduced gravity the speed of the bubble migration is observed with video camera, the temperature field by Pt 100 temperature gauges and the use of a differential interferometer. First experimental results with a liquid characterized by the Prandtl number Pr = 10 (n-decane) agree very well with theoretical data available both from literature as well as with numerical simulations. The correspoding Reynolds numbers are in the range between 20 < Re < 160. The experimental setup, the measuring technique and the evaluation method will be presented as well as comparison between experimental and theoretical results.

Ion-beam analysis for determining the elemental composition and to obtain depth information has been carried out with MeV protons in air by means of simultaneous external PIXE and RBS. Stainless steel products of extended size and a historic painting are analysed non-destructively. These objects include systems of layers with area densities up to some mg/cm². Depth information is obtained by PIXE using energy variation of the primary proton beam and in addition directly from RBS for the outermost near-surface region. Main and secondary elements as well as impurities can be determined together with area densities. Particularly, the knowledge on the depth distribution of the pigments in paintings provides information on paint techniques.

The simultaneous combination of PIXE, RBS and PIGE at the external proton beam is presented as a useful tool for non-destructive studies on a variety of art objects, i.e. oil paintings, book paintings and historical glasses.

Es wird eine Übersicht über die wesentlichsten Ergebnisse bisheriger Arbeiten zur Verifikation des dreidimensionalen Kernmodells DYN3D/M2 für Reaktoren mit hexagonalen Brennelementen gegeben. Verifikationsuntersuchungen für stationäre und instationäre Leistungsdichteberechnung, Thermohydraulik und Brennstabmodell sowie das Gesamtmodell werden beschrieben. Die Verifikation erfolgte durch Nachrechnung von Einzeleffekttests und Experimenten an WWER-spezifischen Versuchsanlagen, Vergleich mit anderen Codes und Benchmarklösungen sowie teilweise durch Vergleich berechneter Parameter mit Betriebsmeßdaten aus KKW mit WWER. Verifikationsbedarf besteht insbesondere noch für das Gesamtmodell und die Anwendung auf den WWER-1000.

To identify layer structures of oil paintings and to determine their elemental composition, external beam PIXE and in addition external beam RBS have been applied simultaneously. The beam energy is varied to obtain depth information by means of PIXE. To check the evidence of the idea a set of test paint layers is prepared. It is found that a combination of the two ion-beam analysis techniques delivers the information needed. The pigment components of the test layers are detected and attached to the layers and additionally the layer thickness is determinable. As an example measurements on the historical painting "14 Nothelfer" (L. Cranach the elder) are presented which are gained by means of external PIXE at various proton energies coupled with external beam RBS.

Im Zeitraum von 1984 - 1988 wurde am Rheinsberger Reaktor ein umfangreiches Bestrahlungsprogramm für Stahlproben aus verschiedenen Druckbehältermaterialien durchgeführt. Zielstellung des Vorhabens ist die Ermittlung der Veränderung der bruchmechanische Eigenschaften durch den Einfluß der Neutronenstrahlung.
Ein Teilaspekt für diese Zielstellung ist die Bestimmung der Parameter für die Neutronenbelastung. In diesem Bericht werden das methodische Vorgehen zur Gewinnung dieser Werte beschrieben, mögliche Fehlerquellen diskutiert sowie ein umfangreicher Überblick über die Ergebnisse gegeben.
Grundlage der transporttheoretischen Berechnungen bei gegebenen Spaltquellen war die Vielgruppen-Monte-Carlo-Methode mit speziellen Verfahren zur Minimierung der statistischen Fehler, so daß Ergebnisse mit kleinem statistischen Fehler für jede Einzelprobe, die im allgemeinen noch in vertikaler bzw. horizontaler Richtung unterteilt wurde, erzielt werden konnten.
Zur Berechnung der Spaltquelle wurde die für ein Zeitraster für jedes Kassettenelement gegebenen Abbranddaten zugrunde gelegt, auf deren Basis für jeder Reaktorbetriebsperiode die integralen Spaltquellverteilungen für verschiedene Spaltisotope berechnet wurden.
Dargestelt werden die für die Neutronenversprödung relevanten Ergebnisse, nämlich die kumulativen Neutronenflüsse im Energiebereich größer 0,5 und 1 MeV sowie eine dpa-Rate. Als allgemeines Resultat kann man die starke Abhängigkeit der Ergebnisse in radialer Richtung vom Reaktormittelpunkt anführen. Dagegen ergaben sich in azimulater und vertikaler Richtung nur relativ schwache Veränderungen.

The nature of the irradiation-induced precipitates in the VVER-440-type steel 15Kh2MFA has been investigated by the combination of small angle neutron scattering and anomalous small angle X-ray scattering. By the method of contrast variation information about the chemical composition of the irradiation-induced precipitates was obtained. ASAXS experiments with variation of the X-ray energy near to the energy of the vanadium K-absorption edge prove the content of vanadium within the irradiation-induced precipitates. The scattering density of the precipitates is lower than the scattering density of the iron matrix. The chemical shift of the vanadium-K -absorption-edge and the results of the variation of the contribution of the magnetic scattering in the SANS experiment show, that vanadium does not precipitate in an elementary state. By assuming the precipitates being vanadium carbide these results can be explained in the best way.