Results 1 - 10 of 144
Results 1 - 10 of 144. Search took: 0.027 seconds
|Sort by: date | relevance|
[en] The Minimum Bias Trigger Scintillators (MBTS) are sub-detectors in ATLAS delivering the primary trigger for selecting events from low luminosity proton–proton, lead–lead and lead–proton collisions with the smallest possible bias. The MBTS have undergone a complete replacement before LHC Run-2 and several improvements have been implemented in the layout. Since 2014 the MBTS have been commissioned with cosmic rays and first LHC Run-2 beam splash events. We summarise the outcome of the commissioning.
[en] The future medium energy physics program at the electron stretcher accelerator ELSA of Bonn University mainly relies on experiments using polarized electrons in the energy range from 1 to 3.2 GeV. To prevent depolarization during acceleration in the circular accelerators several depolarizing resonances have to be corrected for. Intrinsic resonances are compensated using two pulsed betatron tune jump quadrupoles. The influence of imperfection resonances is successfully reduced applying a dynamic closed orbit correction in combination with an empirical harmonic correction on the energy ramp. Both types of resonances and the correction techniques have been studied in detail. The imperfection resonances were used to calibrate the energy of the stretcher ring with high accuracy. A new technique to extract the beam with horizontal oriented polarization was successfully installed. For all energies a polarized electron beam with more than 50% polarization can now be supplied to the experiments at ELSA, which is demonstrated by measurements using a Moeller polarimeter installed in the external beamline. (orig.)
[en] On-Line Monitoring evaluates instrument channel performance by assessing its consistency with other plant indications. Elimination or reduction of unnecessary field calibrations can reduce associated labour costs, reduce personnel radiation exposure, and reduce the potential for calibration errors. On-line calibration monitoring is an important technique to implement a state-based maintenance approach and reduce unnecessary field calibrations. In this report we will look at how the concept is currently applied in the industry and what the arising needs are as it becomes more commonplace. We will also look at the PEANO System, a tool developed by the Halden Project to perform signal validation and on-line calibration monitoring. Some issues will be identified that are being addressed in the further development of these tools to better serve the future needs of the industry in this area. An outline for how to improve these points and which aspects should be taken into account is described in detail. (Author)
[en] In the present work a meson theoretical model for the production of kaons in the pion-nucleon interaction is developed. The study is done in a coupled channel framework where the channels πN, KΛ, KΣ and KY*(1385) are taken into account. The interactions in the various channels and the transition interactions are based on single meson and baryon exchange diagrams. Coupling constants are taken from SU(3) symmetry relations. Form factor parameters are deduced from previous investigations of other hadronic reactions by the Bonn-Juelich group. For the interaction in the initial πN state a phenomenological separable model is employed. This is necessitated by the complexity of the dynamics in the energy range relevant for kaon production, making a microscopic description practically infeasible. Our model for kaon production gives the correct magnitude of the cross sections for the reactions π-p→K0Λ, π+p→K+Σ+, π-p→K-Σ+, and π-p→K0Σ0. It turned out however, that it is not possible to obtain a quantitative description of experimental data if only t- and u-channel (meson and baryon) exchange is taken into account for the transition potentials and the final state interaction. This indicates that the inclusion of resonance contributions (s-channel exchange) is necessary in order to achieve a better agreement with the experiments. (orig.)
[en] The 1st Technical Report was prepared for the research project ''Validation and Interpretation of the ATHLET-CD Model Basis'' funded by the Federal Ministry of Economics and Technology (BMWi1501385) and carried out at the Chair of Energy Systems and Energy Economics at Ruhr-Universitaet Bochum (RUB). This report provides results of the simulation of the Boiling Water Reactor (BWR) experiments CORA-17 and -28 with ATHLET-CD Mod. 2.2A. The system code ATHLET-CD (Analysis of Thermal-hydraulics of Leaks and Transients - Core Degradation) is developed by the German Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH. Code results are compared to measurements in order to assess and to analyze the capabilities of the current code version with regard to the modeling of BWR components. The CORA test series was carried out between the years 1987 and 1993 at the former Kernforschungszentrum Karlsruhe (KfK), now Karlsruhe Institute of Technology (KIT). The investigations provided experimental data regarding the material behavior during the early phase of core degradation in Light Water Reactors (LWR). The tests CORA17 and -28 represented a typical BWR arrangement of the fuel rod bundle and provided insights about the bundle behavior during the quenching process (CORA-17) and regarding the influence of a preoxidized bundle (CORA-28), respectively. The simulation results are analyzed and discussed in terms of the thermal bundle behavior, the zirconium oxidation in steam and the resulting hydrogen generation as well as the material relocation. In particular, the recently extended modeling capabilities of the code in terms of the relocation of BWR components like the absorber blade and the canister wall are assessed. The analysis shows that the code captures the thermal behavior in good agreement in both experiments. An even enhanced reproduction of the test CORA-28 is obtained in comparison to a calculation using the previous code version ATHLET-CD Mod. 2.1A. Hydrogen regeneration calculated for CORA-28 agrees well to the measurements, too. In contrast, the hydrogen production in CORA-17 is underestimated during the quenching phase. Possible reasons for these discrepancies are the underestimation of melt oxidation as well as the oxidation of the absorber material B4C since an adequate modeling of these phenomena is not yet implemented in the code. The simulated material relocation of the fuel rods as well as of the BWR components provides plausible results compared to the experiments.
[en] The principles of strength computation are described. The combination of creep together with alternating stress has only been taken into consideration since high-strength materials were introduced. A summarizing evaluation of creep fatigue is given in annex 1. Primary creep with transients is shown using a simplified numerical example. Another annex shows a critical view on the Oak Ridge model of inelastic analysis. (DG)
[de]Die Grundlagen der Festigkeitsberechnung werden beschrieben. Der Kombination Kriechen und Wechselbeanspruchung wird erst seit der Einfuehrung von Werkstoffen mit hoeherer Festigkeit Beachtung entgegengebracht. Eine zusammenfassende Darstellung der Bewertung der Kriechermuedung ist in einem ersten Anhang wiedergegeben. Das Primaerkriechen mit Transienten wird anhand einer vereinfachten zahlenmaessigen Rechnung eines Beispiels dargestellt. Ein zweiter Anhang gibt kritische Betrachtungen zum Oak Ridge Modell der inelastischen Analyse wieder. (DG)
[en] This report deals with issues of data level integration among the increasing number of digital equipment and systems that are penetrating the plant floor, the plant control, and the plant management. This penetration is particularly topical when considering the increasing number of modernisation and life-extension programs being planned and implemented. It is our conviction that integration issues have a cardinal role to play whenever the focus of these projects is directed towards cost-efficiency and effectiveness. The report makes a case for the standardisation of data level integration and focuses on the OPC specifications that are becoming a de-facto standard in many industries. Example applications of OPC at the HRP are described together with related and forthcoming technologies such as Fieldbus and Web Services. While the focus of this report is on data level standardised integration, other levels of integration, such as the operational level and the functional level, have been identified in at the HRP (see HWR-744) and will be the subject of later reports. (Author)
[en] Recent years have seen a steady stream of new condition monitoring and diagnostic (CMD) systems and techniques being designed for applications in the nuclear industry. The HRP has been particularly active in this respect with the development of systems such as PEANO for on-line sensor calibration monitoring and aladdin for early fault detection and diagnosis. The availability at the HRP of a wide range of other Computerized Operations Support Systems as well as the availability of the HAMMLAB experimental control room has also allowed for the investigation of the range of issues related to the integration of such systems into control room settings. After a brief description of the development and application of these CMD systems, the report identifies three different levels of integration that should be taken into consideration. These are the data level, the operational level, and the functional level. The data level includes all aspects of data communication between the CMD system, the plant instrumentation, and the other computerized support systems present at the plant. The operational level includes all those aspects of integration that influence the way in which the operator interacts with the CMD system, with a clear emphasis on Human System Interface (HSI) integration. The functional level includes those aspects of integration that deal with the functionality of the CMD system and how this can support or be combined with the functionality offered by other support systems with the aim of exploiting synergistic effects and achieving new functions. Additionally, the report identifies a set of guiding principles of integration that can be applied at all three levels of integration. Case studies taken from experiences gathered at the HRP are used throughout the report to exemplify the identified integration principles. (Author)
[en] This Final Report to the research project 'Validation and Interpretation of the ATHLET- CD mode basis' (BMWi 1501385) funded by the German Federal Ministry of Economic Affairs and Energy (BMWi) summarizes and highlights the outcomes of code validation and assessment carried out at the Chair of Energy Systems and Energy Economics (LEE) of Ruhr-Universitaet Bochum (RUB) as part of the external validation of the system code ATHLET-CD (Analysis of Thermal Hydraulics of Leaks and Transients - Core Degradation). This best-estimate code is being developed by Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH. In the frame of this research project, simulations with ATHLET-CD of the experiments PHEBUS FPT-1 through to -3, CORA-17 and -28, QUENCH-12 and -16 as well as PARAMETER SF3 are performed and analysed. In addition, participation to international code benchmarks as well as pre-test calculations for the planning of the experiment QUENCH-17 support code validation activities. Based an the comparisons to the experimental measurements, the current modelling capabilities regarding the simulation of fission product behaviour as well as the behaviour of degraded BWR- and VVER-bundles during quenching are assessed. Code capabilities for plant calculations are analysed and discussed against TMI-2 calculations and alternative accident scenarios. In general, the code captures the experimental observations and measurements well. Potentials for further code improvements are identified and recommended.