MONTE CARLO MODEL FOR NEUTRON PRODUCTION BY THE INTERACTIONS OF LOW ENERGY DEUTERONS IN SOLID TARGETS Alberto Milocco
, 2012, doktorska disertacija
Opis: The construction of the nuclear fusion plant 'ITER' has started in 2009 at Cadarache, France. The ITER machine represents a milestone in the civil use of the nuclear fusion energy. The physics of ITER is based on the fusion reaction between deuteron and triton nuclei (d-t). The deuteron-deuteron reaction (d-d) is also interesting and is foreseen for the next generation of fusion reactors. The experimental activities carried out in the context of the ITER neutronics involve intense fields of neutrons produced with a linear accelerator for deuterons, a target containing tritium or deuterium and auxiliary structures, such as the detector system, cooling system, room walls, etc. Experimental data have been obtained from the FNG (Frascati Neutron Generator, Italy), FNS (Fast Neutron Source, Japan), OKTAVIAN (Osaka University, Japan) and IRMM (Institute for Reference Materials and Measurements, EU). An independent method was developed at FNG for the simulation of the d-t neutron spectra at different angles. The FNG source routine models the Monte Carlo deuteron transport in solid tritiated targets as done in the well known SRIM code. The neutrons are generated according to the tabulated probability of the d-t reactions as for the DROSG2000 code. The FNG source routine is implemented into the MCNP distributions. The user is asked to define into the MCNP input file the deuteron energy (up to 10 MeV), the beam width and the target dimensions and composition. This source routine has been chosen as starter for the present thesis. Improvements and extensions were introduced.
- The methodology, originally developed for the d-t neutron source, has been extended to d-d neutron sources.
- Assuming the the SRIM code constitutes the reference calculation for the deuteron transport in matter, its implementation in the source routine has been cross-checked by extracting from the latter the same quantities as provided by the original code.
- In the present version of the source routines, the cross sections are internally generated from built in table based on modern evaluated nuclear data files instead of tables obtained from the DROSG200 code.
- Since the model may be used up to 10 MeV deuteron energy, the relativistic kinematics has been implemented to avoid unnecessary approximations.
- Simulations of the bare neutron source spectra and angular yields measurements have been carried out to validate the model.
- New editions of the d-t and d-d source routine have been released for the latest versions of the MCNP codes and tested on LINUX and WINDOWS machines. The validation activities with the FNG and IRMM experimental data suggested a possible application of the source routine for the characterisation of neutron spectrometers in the MeV energy region.
The source routine has been adopted to simulate integral benchmark experiments at FNG, FNS and OKTAVIAN. Brand new MCNP benchmark models have been developed for inclusion of all the available experimental information. It is shown that the d-t source routine is an accurate tool for the generation of the source eutrons. It also demonstrates to be useful for the evaluation of the neutron source term and associated uncertainties. The accuracy of the analyses is pursued to the point that the quality of the nuclear data employed in the simulation can be assessed. To this extent, the case of a new evaluation of the neutron interaction nuclear data for Manganese-55 is tested. A set of integral benchmark experiments has been used in the validation phase of the nuclear data. The computational models rely on the source routine, the object of the thesis. In conclusion, the source routine claims the inclusion of the major features responsible for the experimental resolution associated with the source term. The doctoral thesis explores its usage in the context of the experimental activities for ITER. The future exploitation of the source routine for the simulation of worldwide experiments might become an occasion to compare it with the source models available in the other laboratories
Ključne besede: deuteron-triton reactions, low-energy deuterons, neutron source model, Monte Carlo method, solid tritium target, solid deuterium target, fusion neutronics, benchmark experiments, diamond detectors.
Objavljeno: 07.03.2012; Ogledov: 2985; Prenosov: 90
Celotno besedilo (8,50 MB)
Design of the optimal total site heat recovery system using SSSP approachAndreja Goršek
, Peter Glavič
, Miloš Bogataj
, 2006, izvirni znanstveni članek
Opis: Site expansions or changes in production capacities are usually related with changes of utilities demands andžor utility system design. Despite several available and well established techniques for process synthesis and integration, very often, changes in process designs are made on the basis of intuition and experiences of engineers. In this paper possibilities of rational energy consumption and energy integration in an existing site for production of specialty chemicals were studied. On the basis of real process parameters and computer simulation results energy integration was re-examined.Total site analysis using modified Site Sink Source Profiles, which gives a profound insight into the site utility system configuration, heating-cooling demands and cogeneration design was performed. The existing site was found to be very well designed. With only few modifications additional 9% of hot utilities and 5% of cold utilities savings are possible.
Ključne besede: chemical engineering, process design, optimization, heat integration, cogeneration, pinch method, energy retrofit
Objavljeno: 30.05.2012; Ogledov: 1781; Prenosov: 60
Povezava na celotno besedilo
H2 separation and use in fuel cells and CO2 separation and reuse as a reactant in the existing methanol processAnita Kovač Kralj
, Peter Glavič
, 2007, izvirni znanstveni članek
Opis: Fuel-cell efficiencies yield substantial reductions in the emissions of climate-change gases and promise an end to exclusive reliance on carbon fuels for energy. Fuel cells, CO2 reuse, process heat integration, and open gas turbine electricity cogeneration can be optimized simultaneously, using a nonlinear programming (NLP) algorithm. The simplified NLP model contains equations of structural and parametric optimization. This NLP model is used tooptimize complex and energy-intensive continuous processes. This procedure does not guarantee a global cost optimum, but it does lead to good, perhaps near-optimum, designs. The plant, which produces methanol, has a surplus of hydrogen (H2) and CO2 flow rates in purge gas. H2 is separated from the purge gas by an existing pressure swing adsorption (PSA) column. Pure H2 can be usedas fuel in fuel cells. CO2 can be separated from the outlet stream (purge gas) by a membrane or absorption system (absorber and regenerator) or an adsorption system and reused as a reactant in a reactor system. Therefore, theproduct yield can be increased and CO2 emissions can be reduced, simultaneously. CO2 emissions can then be reduced at the source. The retrofitted process can be operated within existing parameters. Using a methanol process as a case study, the CO2 emission flow rate can be reduced by4800 t/a. The additional electricity cogeneration in the gas turbine and in fuel cells and additional flow rates of the raw material could generate an additional profit of 2.54 MEUR/a.
Ključne besede: chemical processing, methanol production, optimization, nonlinear programming, CO2 reuse, fuel cells, heat integration, energy cogeneration
Objavljeno: 31.05.2012; Ogledov: 1580; Prenosov: 47
Povezava na celotno besedilo
Journal of energy technology
Opis: Journal of Energy Technology is a scientific and professional journal in the field of energy and energy technologies. The first issue of Journal of Energy Technology was launched in November 2008. The founder of the journal is University of Maribor, Faculty of Energy Technology.
The journal is intended for domestic and foreign scientific, technical and general public. With the aim of increasing the recognition of the journal, the articles in journal are mainly in English. The journal is issued quarterly in both printed and electronic form.
Ključne besede: scientific journals, energy technology
Objavljeno: 28.05.2012; Ogledov: 329; Prenosov: 8
Povezava na datoteko
Aerodynamic analysis of an oscillating airfoil in a power-extraction regime using the compressible Navier-Stokes equations with efficient and accurate low-speed preconditioningJernej Drofelnik
, 2012, diplomsko delo
Opis: A wing that is simultaneously heaving and pitching may extract energy from an oncoming air flow, thus acting as turbine. The purpose of this study was to analyse the relationship between the aerodynamics and the theoretical performance of this device by means of timedependent
laminar flow simulations performed with a research compressible finite volume Navier-Stokes solver COSA. In presented analyses, which confirm the findings of another
independent study, the efficiency of the power extraction of this device can be of the order of 35 %, and such an efficient operating condition is characterized due to the favourable effects of a strong dynamic stall.
This study is a part of a wider research programme of Dr. Campobasso’s group at University of Glasgow, aiming to develop a general-purpose computational framework for
unsteady aerodynamic and aeroacoustic wind energy engineering. In view of aeroacoustic applications, the developed flow solver uses the compressible formulation of the Navier-Stokes equations with carefully optimized low-speed preconditioning. To demonstrate the modeling capabilities, the accuracy and the high computational performance of the developed low-speed preconditioning technology, the unsteady aerodynamics of the energy-extracting device is simulated by using a computationally challenging freestream Mach number of 0.001. A mixed preconditioning strategy that maintains both the nominal accuracy and the computational efficiency of the solver also for time-dependent low-speed problems is presented. A fundamental element of novelty of this study is a thorough assessment of the proposed approach partly based on the challenging and realistic problem associated with the oscillating wing device.
Ključne besede: Low-speed preconditioning, compressible multigrid Navier-Stokes solver, energy-extracting oscillating wing, computational fluid dynamics.
Objavljeno: 06.07.2012; Ogledov: 1713; Prenosov: 84
Celotno besedilo (2,40 MB)
Stimulating integral refurbishment principles in social housing as a challenge for sustainable development : case studyMetka Sitar
, Vesna Žegarac Leskovar
, Vlasta Krmelj
, 2009, objavljeni znanstveni prispevek na konferenci
Opis: Circumstances of climate changes have raised the awareness of the role housingconstruction activity plays in being one of the major stimuli of socio-economic processes in Slovenia. Further encouragement came through corresponding EU-strategies focusing not only on new housing constructions butalso on refurbishment and renewal of the existing stock, which has been rather neglected. Firstly, information on the Slovenian housing system along with institutional and governance changes - having taken place since 1991 - will be presented, particularly in terms of tenure and housing ownership. In the middle of the 1990s, fragmented ownership was regulated by the formation of condominiums as the basis of housing management and maintenance. Further on, special attention will be paid to newly introduced policies concerning energy efficiency of building constructions at the national level. In addition, the paper will concentrate on endeavours to refurbish the existing multi-family housing stock which represents the most problematic financial issue in terms of a long term investment perspective. Slovenia has in fact notdeveloped any special policies regarding refurbishment of the existing housing stock, either at the national, or at the local level. The housing development sector of the Municipality of Maribor is one of the most significant cases in Slovenia, as far as transition consequences to be effected in the social housing sector are concerned. However, the transformation from an old industrial town into a sustainable community was characterized by extreme complexity. Relying upon its own development strategies the local building construction sector succeeded in remaining one of the most dynamic economic activities of the town and the region. As a recommendation, ideas of energy renewal strategies and measures, based on the local energy concept and supported by financial mechanisms of public private partnership, will be discussed.
Ključne besede: Slovenia, Maribor, housing, refurbishment, energy efficiency, local energy concept, public intermunicipal housing fund
Objavljeno: 31.05.2012; Ogledov: 1358; Prenosov: 43
Povezava na celotno besedilo