Zugl.: Stuttgart, Univ., Diss., 2008.

<p>The use of hydrogen is predicted to increase substantially in the future, both as chemical feedstock and also as energy carrier for transportation. The annual world production of hydrogen amounts to some 50 million tonnes and the majority is produced using fossil fuels like natural gas, coal and naphtha. High temperature nuclear reactors (HTRs) represent a novel way to produce hydrogen at large scale with high efficiency and less carbon footprint. The aim of this master thesis has been to evaluate the feasibility of HTRs for hydrogen production by analyzing both the reactor concept and its potential to be used in certain hydrogen niche markets. The work covers the production, storage, distribution and use of hydrogen as a fuel for vehicles and aviation and as chemical feedstock for the oil refining and ammonia production industry.</p><p>The study indicates that HTRs may be suitable for hydrogen production under certain conditions. However, the use of hydrogen as an energy carrier necessitates a widespread hydrogen infrastructure (e.g. pipe-lines, refuelling stations and large scale storage), which is associated with major energy losses. Both mentioned industries could benefit from nuclear-based hydrogen with less infrastructural changes, but the potential market is by far smaller than if hydrogen is used as an energy carrier. A maximum of about 60 HTRs of 600 MWth worldwide has been estimated for the ammonia production industry. The Swedish refineries are likely too small to utilize the HTR but in the larger refineries HTR might be applicable.</p>

The use of hydrogen is predicted to increase substantially in the future, both as chemical feedstock and also as energy carrier for transportation. The annual world production of hydrogen amounts to some 50 million tonnes and the majority is produced using fossil fuels like natural gas, coal and naphtha. High temperature nuclear reactors (HTRs) represent a novel way to produce hydrogen at large scale with high efficiency and less carbon footprint. The aim of this master thesis has been to evaluate the feasibility of HTRs for hydrogen production by analyzing both the reactor concept and its potential to be used in certain hydrogen niche markets. The work covers the production, storage, distribution and use of hydrogen as a fuel for vehicles and aviation and as chemical feedstock for the oil refining and ammonia production industry. The study indicates that HTRs may be suitable for hydrogen production under certain conditions. However, the use of hydrogen as an energy carrier necessitates a widespread hydrogen infrastructure (e.g. pipe-lines, refuelling stations and large scale storage), which is associated with major energy losses. Both mentioned industries could benefit from nuclear-based hydrogen with less infrastructural changes, but the potential market is by far smaller than if hydrogen is used as an energy carrier. A maximum of about 60 HTRs of 600 MWth worldwide has been estimated for the ammonia production industry. The Swedish refineries are likely too small to utilize the HTR but in the larger refineries HTR might be applicable.

The sensitivity of two operational output parameters, criticality and isotopic composition during burnup, to specific design and operational reactor parameters in a Sodium Cooled Fast Reactor, is investigated. The computational simulation tool Serpent is used. The parameters varied include Uranium enrichment, Plutonium content, rod thickness, fuel temperature, and sodium density. In burnup, the development of the fraction of fissile isotopes, isotopes used for measurements, the isotopic composition of Plutonium, and isotopes that complicate fuel reprocessing is displayed. A surrogate model, optimized for use in determining how criticality develops between data points, is used. The results are displayed as plots created in Matlab. The results are discussed, with a focus on how large an effect varying different parameters have on different outputs related to the reactor's operation. It is concluded that the Plutonium content has the largest effect on the isotopic composition and that, based on the performed simulations, MOX fuel is potentially safer than Zirconium alloy fuel in a practical setting.

An IGBT/diode model with more accurate characteristics than simple switchis required to serve for EMC issues from converter valve. The purpose of thismaster thesis is to develop an IGBT and diode model to achieve both accuratetransient behavior and fast simulation time during single pulse switchingtest circuit for the 4:5 kV and 2:0 kA StakPakTM IGBT module. A gate unitwhich resembles the ABB gate unit is implemented to obtain a good agreementbetween simulation and measurement. For demonstration and verication, theIGBT/diode model is applied in a simplied arm simulation of full scale ABBGeneration 4 HVDC-VSC converter station and capable of a half cell consistingof 8 series-connected IGBTs and their anti-paralleled diodes. The arm simulationresults are analyzed further for converter station EMC studies.Convergence issue is the most important problem in the whole process of modelimplementation and application. To guarantee the convergence in simulationsome characteristics such as the tail voltage at the end of turn-o is disregarded.But overall, the model is validated and adopted successfully. / En IGBT-/diodmodell med mer exakta egenskaper an en enkel switch kravs foratt hantera EMC-problem fran omvandlarventilen. Syftet med denna magisteruppsatsar att utveckla en IGBT- och diodmodell for att uppna bade noggrantovergaende beteende och snabb simuleringstid under enkelpulsomkopplingstestkretsfor 4,5 kV och 2,0 kA-StakPak IGBT-modulen. En grindenhetsom liknar ABB-grindenheten implementeras for att fa god overensstammelsemellan simulering och matning. For demonstration och veriering, tillampasIGBT-/diodmodellen i en forenklad armsimulering av en fullskalig ABB Generation4 HVDC-VSC-omvandlarstation och med kapacitet for en halvcell bestaendeav 8 seriekopplade IGBT och deras anti-parallellkopplade dioder. Resultatenfran armsimuleringen analyseras vidare for EMC-studier av omvandlarstationen.Konvergensfragan ar det viktigaste problemet i hela processen for modellimplementeringoch -tillampning. For att garantera konvergensen i simulering ignorerasvissa egenskaper sasom svansspanningen vid slutet av avstangning. Mentotalt sett, valideras och antas modellen framgangsrikt.