Qucosa – Hemholtz-Zentrum Dresden-Rossendorf
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Nanocluster-rich SiO2 layers produced by ion beam synthesis: electrical and optoelectronic properties
Get PDFThe aim of this work was to find a correlation between the electrical, optical and microstructural properties of thin SiO2 layers containing group IV nanostructures produced by ion beam synthesis. The investigations were focused on two main topics: The electrical properties of Ge- and Si-rich oxide layers were studied in order to check their suitability for non-volatile memory applications. Secondly, photo- and electroluminescence (PL and EL) results of Ge-, Si/C- and Sn-rich SiO2 layers were compared to electrical properties to get a better understanding of the luminescence mechanism
Berechnung des Notkondensators des Integralreaktors CAREM
Get PDFCAREM is an Argentine project to achieve the development, design and construction of an innovative, simple and small Nuclear Power Plant (NPP). This NPP has an indirect cycle reactor with some distinctive and characteristic features (e.g. integrated primary cooling system by natural circulation, self-pressurized primary system and passive safety systems, etc.). In the frame of an IAEA forwarded HUMAN RESOURCES DEVELOPMENT - "Advice on CAREM passive emergency condenser" at the Centro Atómico in San Carlos de Bariloche (Argentina) German experimental as well analytical investigation of passive safety systems - mainly performed at the research centers Jülich and Rossendorf were presented. During this visit it was decided that FZR should determine the emergency condenser capacity by using the ATHLET code with and without the condensation module extension KONWAR (condensation inside horizontal tube). These results should be compared and assessed with existing RELAP calculations. The ATHLET and ATHLET/KONWAR calculations of the emergency condenser were used for minimizing the user influence performed with exactly the same nodalization scheme and the same initial and boundary conditions than the RELAP calculations. The comparison of all three computational results shows that the required condenser capacities were achieved. The magnitudes were in order of up to 12%. An additionally performed evaluation of local flow parameters show large deviations especially for the heat transfer coefficients at the inner and outer tube wall. Due to the good validation progress of KONWAR by an extensive module validation against NOKO and HORUS experiments, the focus of the further investigation were concentrated on the boiling heat transfer. A comparison of the ATHLET boiling model (according to Forster and Zuber in combination with the equation of Thom for the determination of temperature difference between wall and saturated fluid) with other models from literature (Borishansky, Fritz, Gormenflo, Stefan and Abdelsalam) shows a strong underestimation of heat transfer coefficients in low pressure conditions. Therefore the model of Forster and Zuber is replaced against the model of Stefan and Abdelsalam. The calculations with ATHELT/KONWAR were repeated and show now a better agreement (deviations less equal than 3 %) with the RELAP results
Versuchsanlage ROCOM zur Untersuchung der Kühlmittelvermischung in Druckwasserreaktoren - Ergebnisse quasistationärer Vermischungsexperimente
Get PDFThe test facility ROCOM (Rossendorf Coolant Mixing Model) has been built for the investigation of coolant mixing processes in the reactor pressure vessel of pressurised water reactors (PWR). ROCOM is a 1:5 model of the German PWR KONVOI and has been designed for a wide range of different mixing scenarios. ROCOM disposes of four loops with fully controllable coolant pumps. The test facility is operated with demineralised water. For the investigation of mixing, tracer solution (water labelled with salt) is injected into the facility. The transient distribution of the electrical conductivity is is measured at different positions of the flow path by means of wire-mesh sensor technique with high resolution in space and time. The measured conductivity is transformed into a dimensionless mixing scalar. The mixing at quasi-stationary conditions (constant loop mass flow rates) has been investigated in the presented experiments. That concerned nominal operation conditions, the operation with a reduced number of loops and the investigation of cold-water transients with running pumps and conditions of developed natural circulation. In special experimental series, the reproducibility of the results at identicla boundary conditions within the confidence intervalls has been shown. Further, the influence of various factors on the mixing has been investigated. This included the pressure losses at the core bottom plate, the global coolant flow level and the influence of the loop flow rate on the perturbed sector at the core inlet. An analysis of the measurement error of the used measurement technique completes the report
Bestimmung der Aktivitätsverteilung in Gebinden mit geringfügig radioaktivem, Material unter Verwendung großflächiger, unkollimierter, feststehender Gamma-Szintillationsdetektoren
Get PDFDie Verwendung von großflächigen Gamma-Detektoren zeichnet sich durch hohe Effektivität und damit geringe Messzeit aus. Dagegen sind mit ihnen keine hohen Ortsauflösungen bei der Rekonstruktion der Aktivitätsverteilung möglich. Zur Untersuchung der Rekonstruierbarkeit unbekannter Aktivitätsverteilungen werden zwei in der Tomographie gebräuchliche Verfahren verglichen, ein algebraisches (iterativ) und ein analytisches (gefilterte Rückprojektion). Beide Verfahren erbringen qualitativ ähnliche Ergebnisse. Reale Aktivitätsverteilungen werden nach beiden Verfahren zufriedenstellend rekonstruiert
Neutronendosimetrie im Bestrahlungsprogramm Rheinsberg II
Get PDFIn einem mehrjährigen umfangreichen Bestrahlungsprogramm wurden in den Bestrahlungskanälen des Reaktors WWER-2 des KKW Rheinsberg Druckbehälterstahlproben bestrahlt. Das Programm diente der Erweiterung der Datenbasis zur Bewertung der Strahlenversprödung von Reaktordruckbehälterstählen. Zur Ermittlung der Neutronenbelastung wurden die Bestrahlungskapseln mit Neutronenaktivierungsdetektoren bestückt. Der Bericht enthält die Beschreibung des Typs, des Aufbaues und der Zusammensetzung der Neutronenfluenzmonitore, ihre Anordnung im jeweiligen Experiment, die Auswerteprozedur nach der Bestrahlung und gibt eine zusammenfassende Übersicht über die gemessenen und spektrumsjustierten Neutronenfluenzen für alle 8 Einzelexperimente des Bestrahlungsprogrammes Rheinsberg II. Die Ergebnisse der neutronendosimetrischen Messungen sind konsistent mit den Ergebnissen der Neutronenfeldrechnungen und ergeben in Verbindung mit diesen zuverlässigen Daten über die Neutronenbelastung der in den Bestrahlungsexperimenten neutronen-exponierten Materialproben
Berechnung des Strahlungsuntergrundes in der Umgebung der Strahlfänger an der Strahlungsquelle ELBE
Get PDFBeam 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
Synthese, Charakterisierung und Löslichkeit von Erdalkaliuranylcarbonaten M2[UO2(CO3)3]·xH2O; M: Mg, Ca, Sr, Ba
Get PDFAcceptance and count rate estimates for experiments on subthreshold Phi meson production in central collisions of C + C at 2 AGeV
Get PDFMonte-Carlo estimates of the subthreshold Phi meson production are performed for the reaction 12C + 12C at 2 AGeV assuming the Phi's to be emitted isotropically and distributed thermally in the center-of-mass system of the colliding nuclei. Different scenarios involving the detector installations FOPI and HADES at SIS/GSI are considered to determine the expected yields of Phi(1020) mesons identified via the K+K- and e+e- decay channels