298 research outputs found

    High-Level Synthesis for Embedded Systems

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    Orbital debris research at NASA Johnson Space Center, 1986-1988

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    Research on orbital debris has intensified in recent years as the number of debris objects in orbit has grown. The population of small debris has now reached the level that orbital debris has become an important design factor for the Space Station. The most active center of research in this field has been the NASA Lyndon B. Johnson Space Center. Work is being done on the measurement of orbital debris, development of models of the debris population, and development of improved shielding against hypervelocity impacts. Significant advances have been made in these areas. The purpose of this document is to summarize these results and provide references for further study

    Advanced Reactor Physics Methods for Transient Analysis of Boiling Water Reactors

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    The safety assessment of nuclear power plants requires the consideration of the several physical phenomena taking place in the reactor core. Since the last decade, the simulations are performed using the so-called Best-Estimate (BE) thermal-hydraulic system codes coupled with 3D nodal diffusion reactor dynamics solvers. These numerical tools are well developed and validated for PWR but for BWR there are still improvements and developments to be done. In addition, homogenized cross sections libraries, depending on the individual thermal-hydraulic state parameters, e.g. fuel temperature, moderator density, etc., must be supplied to take into account the interdependencies of the involved physics. In this PhD a new coupled code system named TRADYN was developed that consists of the novel and innovative integration of the core simulator DYN3D into the code system TRACE/PARCS using compiler preprocessor directives. This has the advantage to preserve the original TRACE/PARCS system “untouch” and to facilitate the maintenance, modification and debugging. In order to manage the transfer information between TRACE and DYN3D, a General Interface and Specific Data Map routines in FORTRAN were developed. To properly describe the tightly-coupled neutronics and thermal-hydraulic phenomena within the core of a BWR, different physical models were extended and new ones implemented in DYN3D and PARCS. Another contribution of this doctoral thesis is the development of a new in-house methodology called GENSIM-XS for the generation of nodal cross sections for BWRs considering history effects of control rods and void. GENSIM-XS is able to greatly simplify the number of the neutronics regions present in the reactor core. This new methodology uses the AUDIT option of SIMULATE-3 (S3) to report the cross sections on the output file. Then, they are extracted and written in multi-group tabulated cross sections in NEMTAB format in an automatized manner using Python scripts. The validation of TRADYN is based on Boiling Water Reactor Turbine Trip (TT) benchmark data, where TRADYN has demonstrated its capability to predict the stationary plant conditions as well as the temporal evolution of the main plant parameters, showing a good agreement with the measurements e.g. core power and dome pressure. The static core of the cycle 4 of BWR Laguna Verde nuclear power plant was selected as second case for the validation not only of the GENSIM-XS methodology but also of TRADYN. The TRADYN results such as k-eff, axial power profile, axial void fraction exhibit an excellent agreement with the reference values. This underpins the capabilities of the new methodology to generate cross-sections for coupled thermal-hydraulic/neutronics calculations accounting also for history effects for BWR core analysis

    Nuclear Power

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    At the onset of the 21st century, we are searching for reliable and sustainable energy sources that have a potential to support growing economies developing at accelerated growth rates, technology advances improving quality of life and becoming available to larger and larger populations. The quest for robust sustainable energy supplies meeting the above constraints leads us to the nuclear power technology. Today's nuclear reactors are safe and highly efficient energy systems that offer electricity and a multitude of co-generation energy products ranging from potable water to heat for industrial applications. Catastrophic earthquake and tsunami events in Japan resulted in the nuclear accident that forced us to rethink our approach to nuclear safety, requirements and facilitated growing interests in designs, which can withstand natural disasters and avoid catastrophic consequences. This book is one in a series of books on nuclear power published by InTech. It consists of ten chapters on system simulations and operational aspects. Our book does not aim at a complete coverage or a broad range. Instead, the included chapters shine light at existing challenges, solutions and approaches. Authors hope to share ideas and findings so that new ideas and directions can potentially be developed focusing on operational characteristics of nuclear power plants. The consistent thread throughout all chapters is the "system-thinking" approach synthesizing provided information and ideas. The book targets everyone with interests in system simulations and nuclear power operational aspects as its potential readership groups - students, researchers and practitioners

    Table of Regulations [1993]

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    The Table of Regulations shows the regulations contained in Revised Regulations of Ontario, 1990 and those made after December 31, 1990 and before January 1, 1994. It also shows the amendments to those regulations. Most of the listings are in English only. Some regulations have an official French version. Bilingual regulations are indicated by a bilingual title. Occasionally numerical, typographical or other clerical errors are made in the publication of the text of regulations. Corrections are published in The Ontario Gazette. A schedule of the dates these corrections were published is included at the end of this Table. The dates on which regulations were published in The Ontario Gazette are set out in a table immediately following this Table

    Nuclear Power - System Simulations and Operation

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    At the onset of the 21st century, we are searching for reliable and sustainable energy sources that have a potential to support growing economies developing at accelerated growth rates, technology advances improving quality of life and becoming available to larger and larger populations. The quest for robust sustainable energy supplies meeting the above constraints leads us to the nuclear power technology. Today's nuclear reactors are safe and highly efficient energy systems that offer electricity and a multitude of co-generation energy products ranging from potable water to heat for industrial applications. Catastrophic earthquake and tsunami events in Japan resulted in the nuclear accident that forced us to rethink our approach to nuclear safety, requirements and facilitated growing interests in designs, which can withstand natural disasters and avoid catastrophic consequences. This book is one in a series of books on nuclear power published by InTech. It consists of ten chapters on system simulations and operational aspects. Our book does not aim at a complete coverage or a broad range. Instead, the included chapters shine light at existing challenges, solutions and approaches. Authors hope to share ideas and findings so that new ideas and directions can potentially be developed focusing on operational characteristics of nuclear power plants. The consistent thread throughout all chapters is the system-thinking approach synthesizing provided information and ideas. The book targets everyone with interests in system simulations and nuclear power operational aspects as its potential readership groups - students, researchers and practitioners

    The selection of biodiversity indicators for business landholdings

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    Businesses are seen as the next stage in delivering biodiversity improvements linked to local and UK Biodiversity Action Plans. Global discussion of biodiversity continues to grow, with the Millennium Ecosystem Assessment, updates to the Convention on Biological Diversity and The Economics of Ecosystems and Biodiversity being published during the time of this project. These publications and others detail the importance of biodiversity protection and also the lack of strategies to deliver this at an operational level. Pressure on UK landholding businesses is combined with significant business opportunities associated with biodiversity engagement. However, the measurement and reporting of biodiversity by business is currently limited by the complexity of the term and the lack of suitable procedures for the selection of metrics. Literature reviews identified confusion surrounding biodiversity as a term, limited academic literature regarding business and choice of biodiversity indicators. The aim of the project was to develop a methodology to enable companies to identify, quantify and monitor biodiversity. Research case studies interviews were undertaken with 10 collaborating organisations, selected to represent =best practice‘ examples and various situations. Information gained through case studies was combined with that from existing literature. This was used to develop a methodology for the selection of biodiversity indicators for company landholdings. The indicator selection methodology was discussed during a second stage of case study interviews with 4 collaborating companies. The information and opinions gained during this research was used to modify the methodology and provide the final biodiversity indicator selection methodology. The methodology was then tested through implementation at a mineral extraction site operated by a multi-national aggregates company. It was found that the methodology was a suitable process for implementation of global and national systems and conceptual frameworks at the practitioner scale. Further testing of robustness by independent parties is recommended to improve the system

    BS News March/April

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    Extension of the nodal code DYN3D to SFR applications

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    DYN3D is a well-established Light Water Reactor (LWR) simulation tool and is being extended for safety analyses of Sodium cooled Fast Reactors (SFRs) at the Helmholtz-Zentrum Dresden-Rossendorf. This thesis focuses on the first stage of the development process, that is, the extension and application of DYN3D for steady-state and transient SFR calculations on reactor core level. In contrast to LWRs, the SFR behavior is especially sensitive to thermal expansions of the reactor components. Therefore, a new thermal-mechanical module accounting for thermal expansions is implemented into DYN3D. At first step, this module is capable of treating two important thermal expansion effects occurring within the core, namely axial expansion of fuel rods and radial expansion of diagrid. In order to perform nodal calculations with DYN3D, pre-generated homogenized few-group cross sections (XS) are necessarily needed. Therefore, prior to the development of thermal expansion models, a general methodology for XS generation is established for SFR nodal calculations based on the use of the Monte Carlo code Serpent. The new methodological developments presented in this thesis are verified against the Monte Carlo solutions of Serpent. Two SFR cores are used for testing: the large oxide core of the OECD/NEA benchmark and a smaller core from the Phenix end-of-life tests. Finally, the extended DYN3D is validated against selected IAEA benchmark tests on the Phenix end-of-life experiments that contain both steady-state and transient calculations. The contribution to the SFR-related developments at the HZDR, as presented in this thesis, makes it possible of performing steady-state and transient calculations for SFRs on reactor core level by using DYN3D. With this study, the basis of the next stage of DYN3D developments is established, that is, the up-scale of SFR analysis to system level can continue by coupling with a sodium capable thermal-hydraulic system code

    Advanced Methodology to Simulate Boiling Water Reactor Transient Using Coupled Thermal-Hydraulic/Neutron-Kinetic Codes

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    Gekoppelte Thermohydraulik/Neutronenkinetik (TH/NK) Simulationen von Siedewasser-reaktor Transienten erfordern gut validierte und prĂ€zise Simulationswerkzeuge. Die Erzeugung der Wirkungsquerschnitte (XS), abhĂ€ngig von individuellen thermohydraulischen Zustandsparameter, ist von grĂ¶ĂŸter Bedeutung fĂŒr gekoppelte Simulationen. ProblemabhĂ€ngige XS-Sets fĂŒr 3D-Kern Simulationen werden hauptsĂ€chlich von gut validierten, schnell laufenden kommerziellen und benutzerfreundlich Zellcodes wie CASMO und HELIOS erzeugt. In dieser Arbeit soll eine Berechnungsmethode, basierend auf dem Zellcode SCALE6/TRITON, dem XS Interface GenPMAXS, dem „Best-Estimate“ (BE) Systemcode TRACE und dem Kernsimulator PARCS fĂŒr die Analyse von Siedewasserreaktor (SWR) Transienten vorgestellt werden. Die Rechenroutine ist durch eine weitere Unsicherheit und SensitivitĂ€tsanalyse, basierend auf Monte Carlo Zufallsvariablen und der Fortpflanzung der Unsicherheiten von Eingabeparametern bis zur Ausgabe (SUSA Code) ergĂ€nzt. Die Untersuchung mit PARCS von Abbrandrechnungen eines einzelnen Brennelementes mit von SCALE/TRITON erzeugten XS zeigt eine gute Übereinstimmung mit den Ergebnissen mit den XS von CASMO. Um jedoch Defizite des Interface Programms GenPMAXS zu kompensieren, wurden Python-Skripte entwickelt, um fehlende Daten zu integrieren, z.B. die Ausbeuten an Jod, Xenon und Promethium in die aus der SCALE/TRITON Ausgabe von GenPMAXS generierten XS DatensĂ€tze (PMAXS-Format). Die Ergebnisse der Abbrandrechnungen eines ganzen SWR-Kerns zeigen die Wichtigkeit von Abbrandhistorien, adĂ€quater Modellierung der Reflektorregionen und der KontrollstĂ€be, da die PARCS Simulationen fĂŒr abgebrannten Brennstoff und mit allen eingefĂŒhrten KontrollstĂ€ben an der Brennelementspitze und dem Brennelementende erheblich abweichen. Systematische Untersuchungen mit den gekoppelten Codes TRACE/PARCS wurden durchgefĂŒhrt, um das Kern Verhalten bei verschiedenen thermischen Bedingungen mit den von SCALE6/TRITON und CASMO erstellten XS-Sets zu analysieren. Dabei geben die gekoppelten Rechnungen mit TRACE/PARCS die Ergebnisse der einzelnen Brennelementabbrandrechnung und der PARCS Rechnungen wieder. Eine Turbinenschnellabschaltung (TUSA), welche in einem SWR Typ-72 auftrat, wurde unter Verwendung der Wirkungsquerschnittsbibliotheken von SCALE/TRITON und CASMO im Detail untersucht. Dabei ist die Entwicklung der integralen SWR-Parameter, welche durch die gekoppelten Codes mit den XS von SCALE/TRITON bestimmt wurden sehr nah an den globalen Trends berechnet mit den CASMO XS. Weiter wurde der reaktordynamische Code PARCS erweitert (Unsicherheitsmodul), um die BerĂŒcksichtigung der Unsicherheiten der neutronenkinetischen Parameter in gekoppelten TRACE/PARCS Simulationen zu erleichtern. FĂŒr einen postulierten Druckstoß wurden eine Unsicherheit und SensitivitĂ€tsanalyse mit TRACE/PARCS und SUSA durchgefĂŒhrt. Die erhaltenen Ergebnisse zeigen die FĂ€higkeit solcher Methoden, die sich noch in der Entwicklung befinden. Basierend auf diesen Analysen konnte das Unsicherheitsband fĂŒr SchlĂŒsselparameter, wie z.B. ReaktivitĂ€t, sowie die Bedeutung der neutronenkinetischen Parameter fĂŒr diese Unfallszenarien bestimmt und identifiziert werden
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