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)
A Multi-criteria assessment of energy crops for biogas productionPeter Vindiš
, Bogomir Muršec
, Črtomir Rozman
, Franc Čuš
, 2010, izvirni znanstveni članek
Opis: This paper presents the system for the assessment of energy crops for biogas production. The system is based on simulation modelling and multi criteria decision analysis. The deterministic simulation system consists of deterministic production simulation models that enable different types of costs calculations for the production of energy crops, electrical and heat energy in biogas production. Simulation model results were further evaluated using a qualitative multi-attribute modelling methodology (supported by the software tool DEX-i) and quantitative analytical hierarchical process - APH (supported by software toll Expert Choice 2000). The Analysis showed that by using current model the most relevant alternative used for energy crop for biogas production is maize. The maize results in the best multicriteria evaluation EC=0.248 and DEX-i evaluation = appropriate. the best alternative for maize is sorghum with multicriteria evaluation of EC=0.201 and DEX-i evaluation = less appropriate.
Ključne besede: simulation model, Expert Choice, AHP, DEX-i, energy, crops, biogas
Objavljeno: 10.07.2015; Ogledov: 551; Prenosov: 18
Povezava na celotno besedilo
Hemicelluloses application for synthetic polymer surfaces functionalisationNena Dimitrušev
, 2016, doktorska disertacija
Opis: The main aim of this thesis was development of thin functional layers from hemicelluloses xylans on the polyethylene terephthalate (PET) surfaces. Hemicelluloses, xylans, as renewable polymers, were chemically modified in order to introduce anionic and cationic functional groups. Two types of chemical modifications were performed: carboxymethylation in order to increase anionic nature of xylans and improve their hydrophilic character and cationization for introducing of amino groups and antimicrobial characteristics. Both types of modifications were successful, which was proved by ATR FTIR and raman techniques, elemental analysis, total bound nitrogen determination, size exclusion chromatography and polyelectrolyte titrations. Polyelectrolyte titration results showed increased amounts of deprotonated carboxyl groups in carboxymethylated xylans as well as increased amounts of protonated groups in cationized xylans. Antimicrobial activity of xylans was investigated by the determination of minimal inhibitory concentration (MIC) against S. aureus, E. coli, and C. albicans and it was found out that the samples with higher amounts of active amino groups showed lower MIC. Cationised glucuronoxylan showed significantly higher antimicrobial activities against S. aureus in comparison to cationised arabinoxylan and nonmodified xylan samples. However, none of xylan samples was active against fungi. In order to analyze surface properties of solid surfaces, films from xylan (nonmodified and modified) water solution was formed by casting method. The surface chemical composition of films were investigated by x-ray photoelectron spectroscopy (XPS), and the results showed that films made from carboxymethylated xylans had significantly higher amounts of carbon fraction involved in O=C-O bonds, compared to nonmodified xylans. Such surface chemical structure caused higher surface free energy with higher electron-donor contribution and thus high hydrophilicity of these films. Films made by cationized xylans had higher amount of carbon involved in C-C and C-H bonds compared to nonmodified and lower surface free energy with increase of dispersive Lifshitz Van der Waals contribution. In order to thoroughly investigate the adsorption of xylans onto synthetic surfaces Quartz crystal microbalance with dissipation unit (QCM-D) was used. For these measurements model films were prepared from PET by spin coating technique. Adsorption studies were performed at different conditions, such as pH, concentration and ionic strength of xylan solutions. For all the chemically modified xylans the adsorption was improved at pH 5 and with increased ionic strength with divalent ions. The adsorption increased as well with increasing of xylan solution concentration. In order to improve binding of adsorbed xylans so-called anchoring polymers were applied. When anchoring polymers were applied, better adsorption and fixation of adsorbed layer was confirmed, thus the adsorbed masses of xylans after rinsing with water were significantly higher in comparison to the adsorption without immediate anchoring layer. On the basis of these results, real PET fabric surfaces were treated using chemically modified xylans. The xylan solutions were applied onto PET fabric samples using spray coating technique, which is the best approximate to the large-scale procedures. In the first step, PET fabric was activated by alkaline hydrolysis and after that, anchoring agents and carboxymethylated and/or cationized xylans were adsorbed. The success of these treatments was evaluated by the determination of negative and positive charge of the treated PET fabric samples by titration techniques, methylene blue and acid orange 7 adsorption methods, water contact angles and wettability determination. From the potentiometric titrations results it was clearly seen that each new adsorbed layer onto PET fabric totally screened the charge of the former one. FESEM images showed rather thick layers covering the
Ključne besede: hemicellulose, polyethylene terephthalate, glucuronoxylan, arabinoxylan, carboxymethylation, cationization, PET model films, quartz crystal microbalance, PET fabric, surface free energy, wettability, antimicrobial properties
Objavljeno: 11.03.2016; Ogledov: 855; Prenosov: 62
Celotno besedilo (4,53 MB)
Public support of solar electricity and its impact on households - prosumersJarmila Zimmermannová
, Adam Pawliczek
, Petr Čermák
, 2018, izvirni znanstveni članek
Opis: Background and Purpose: Currently, the idea of households - prosumers is broadly discussed in public governments, mainly in connection with both the energy security issues and the environmental issues. Therefore, the main goal of this paper is to present new agent model of household - prosumer and to compare two scenarios – “off grid household” and “on grid household”. The additional goal is to evaluate the impact of public support of solar electricity on the economic efficiency of household – prosumer projects (systems).
Design/Methodology/Approach: The model is structured as a micro-level agent model, representing one household – prosumer. The model has the following general characteristics: one household with own electricity generation (photovoltaic panels), battery and in case of “on grid household” also connection to the grid. The main goal of the agent is to cover electricity consumption in household with minimal costs. The agent model of prosumer is tested and validated, using the empirical data.
Results: The highest level of subsidy has significant impact on the economic indicators of selected scenarios. It causes lower investment costs at the beginning of the project and consequently shorter payback period (3-4 years earlier), positive cumulative cash flow, net present value and IRR in earlier period (approximately 5-10 years earlier, depending on the scenario).
Conclusion: We can recommend to the government to continue with current system of subsidies, since it contributes to better economic indicators of particular solar electricity projects. On the other hand, the level of subsidy should be at least the same as in current year 2017, for the purposes of representing the significant part of the investment costs. Low level of subsidy has negligible impact on the economic indicators of households – prosumers projects. The developed agent model is suitable for the evaluation of economic impact of public support on households – prosumers.
Ključne besede: renewable electricity, photovoltaics, prosumers, households, public support, agent model, energy model
Objavljeno: 07.05.2018; Ogledov: 413; Prenosov: 160
Celotno besedilo (2,04 MB)
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