Computer simulation of multi-elemental fusion reactor materials

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http://urn.fi/URN:ISBN:978-952-10-7065-5
Title: Computer simulation of multi-elemental fusion reactor materials
Author: Vörtler, Katharina
Contributor: University of Helsinki, Faculty of Science, Department of Physics, Division of Materials Physics
Thesis level: Doctoral dissertation (article-based)
Abstract: Thermonuclear fusion is a sustainable energy solution, in which energy is produced using similar processes as in the sun. In this technology hydrogen isotopes are fused to gain energy and consequently to produce electricity. In a fusion reactor hydrogen isotopes are confined by magnetic fields as ionized gas, the plasma. Since the core plasma is millions of degrees hot, there are special needs for the plasma-facing materials. Moreover, in the plasma the fusion of hydrogen isotopes leads to the production of high energetic neutrons which sets demanding abilities for the structural materials of the reactor. This thesis investigates the irradiation response of materials to be used in future fusion reactors. Interactions of the plasma with the reactor wall leads to the removal of surface atoms, migration of them, and formation of co-deposited layers such as tungsten carbide. Sputtering of tungsten carbide and deuterium trapping in tungsten carbide was investigated in this thesis. As the second topic the primary interaction of the neutrons in the structural material steel was examined. As model materials for steel iron chromium and iron nickel were used. This study was performed theoretically by the means of computer simulations on the atomic level. In contrast to previous studies in the field, in which simulations were limited to pure elements, in this work more complex materials were used, i.e. they were multi-elemental including two or more atom species. The results of this thesis are in the microscale. One of the results is a catalogue of atom species, which were removed from tungsten carbide by the plasma. Another result is e.g. the atomic distributions of defects in iron chromium caused by the energetic neutrons. These microscopic results are used in data bases for multiscale modelling of fusion reactor materials, which has the aim to explain the macroscopic degradation in the materials. This thesis is therefore a relevant contribution to investigate the connection of microscopic and macroscopic radiation effects, which is one objective in fusion reactor materials research.Lämpöydinfuusio on kestävä energiaratkaisu, joka käyttää samoja prosesseja kuin auringossa. Tässä tekniikassa energia saadaan yhdistämällä vedyn isotooppeja ja tuottamalla siten sähköä. Fuusioreaktorissa vedyn isotoopit keskittyvät magneettikentässä ionisoituna kaasuna, plasmana. Koska ydinplasma on miljoonia asteita kuumaa, plasman suuntaiseen seinämateriaaliin on erityisiä vaatimuksia. Lisäksi vedyn isotooppien fuusio plasmassa johtaa korkeaenergisien neutronien tuotantoon, jotka asettavat korkeita vaatimuksia rakennusmateriaaleihin. Tämä väitöskirja tutkii materiaalien säteilytysvastetta, jotta niitä voitaisiin käyttää tulevaisuuden fuusioreaktoreissa. Väitöskirjan tutkimus tehtiin teoreettisesti tietokonesimulaatioiden avulla atomitasolla. Toisin kuin aiemmissa tutkimuksissa, tässä työssä käytettiin monimutkaisempia materiaaleja. Volframikarbidin tutkittiin ensiseinämämateriaalina, ja teräsrakenteide tutkimuksessa käytettiin sekä rautanikkeliä että rautakromia mallimateriaalina. Tulokset ovat mikroskooppiskaalassa, ja niitä käytetään pohjana monimittakaavamallinnuksessa jolla pyritään määrittämään makroskooppinen säteilyvaste. Tavoitteena on selvittää mikroskooppisen ja makroskooppisen säteilyvaikutuksien yhteydet.
URI: URN:ISBN:978-952-10-7065-5
http://hdl.handle.net/10138/28112
Date: 2011-11-25
Subject: fysiikka
Rights: This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.


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