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A Computational Study of Isotope Exchange as a Tritium Removal Tool in Tungsten

Show simple item record 2020-12-11T13:19:56Z 2020-12-11T13:19:56Z 2020-12-11
dc.title A Computational Study of Isotope Exchange as a Tritium Removal Tool in Tungsten en
ethesis.discipline none und
ethesis.department none und
ethesis.faculty Matemaattis-luonnontieteellinen tiedekunta fi
ethesis.faculty Faculty of Science en
ethesis.faculty Matematisk-naturvetenskapliga fakulteten sv
ethesis.faculty.URI Helsingin yliopisto fi University of Helsinki en Helsingfors universitet sv
dct.creator Lindblom, Otto
dct.issued 2020
dct.language.ISO639-2 eng
dct.abstract Due to its exceptional thermal properties and irradiation resistance, tungsten is the material of choice for critical plasma-facing components in many leading thermonuclear fusion projects. Owing to the natural retention of hydrogen isotopes in materials such as tungsten, the safety of a fusion device depends heavily on the inventory of radioactive tritium in its plasma-facing components. The proposed methods of tritium removal typically include thermal treatment of massive metal structures for prolonged timescales. A novel way to either shorten the treatment times or lower the required temperatures is based performing the removal under an H-2 atmosphere, effectively exchanging the trapped tritium for non-radioactive protium. In this thesis, we employ molecular dynamics simulations to study the mechanism of hydrogen isotope exchange in vacancy, dislocation and grain boundary type defects in tungsten. By comparing the results to simulations of purely diffusion-based tritium removal methods, we establish that hydrogen isotope exchange indeed facilitates faster removal of tritium for all studied defect types at temperatures of 500 K and above. The fastest removal, when normalising based on the initial occupation of the defect, is shown to occur in vacancies and the slowest in grain boundaries. Through an atom level study of the mechanism, we are able to verify that tritium removal using isotope exchange depends on keeping the defect saturated with hydrogen. This study also works to show that molecular dynamics indeed is a valid tool for studying tritium removal and isotope exchange in general. Using small system sizes and spatially-parallelised simulation tools, we have managed to model isotope exchange for timescales extending from hundreds of nanoseconds up to several microseconds. en
dct.subject hydrogen
dct.subject tritium
dct.subject isotope exchange
dct.subject molecular dynamics
dct.subject tungsten
dct.language en
ethesis.isPublicationLicenseAccepted true
ethesis.language.URI und
ethesis.language englanti fi
ethesis.language English en
ethesis.language engelska sv
ethesis.thesistype pro gradu -tutkielmat fi
ethesis.thesistype master's thesis en
ethesis.thesistype pro gradu-avhandlingar sv
dct.identifier.ethesis E-thesisID:3bc24161-712e-43c3-9ebc-403075faed98
dct.identifier.urn URN:NBN:fi:hulib-202012114996
dc.type.dcmitype Text
ethesis.facultystudyline Laskennallinen materiaalifysiikka fi
ethesis.facultystudyline Computational Material Physics en
ethesis.facultystudyline Beräkningsmaterialfysik sv
ethesis.facultystudyline.URI und
ethesis.mastersdegreeprogram Materiaalitutkimuksen maisteriohjelma fi
ethesis.mastersdegreeprogram Master's Programme in Materials Research en
ethesis.mastersdegreeprogram Magisterprogrammet i materialforskning sv
ethesis.mastersdegreeprogram.URI und

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