h1

%0 Thesis
%A Rayaprolu, Rahul
%T Cyclotron irradiation on tungsten </td><td width="150">
%T amp; co-relation of thermo-mechanical properties to displacement and transmutation damage
%V 540
%I RWTH Aachen University
%V Dissertation
%C Jülich
%M RWTH-2021-06067
%@ 978-3-95806-552-9
%B Schriften des Forschungszentrums Jülich. Reihe Energie & Umwelt = Energy & environment
%P xiv, 211 Seiten : Illustrationen, Diagramme
%D 2021
%Z Druckausgabe: 2021. - Onlineausgabe: 2021. - Auch veröffentlicht auf dem Publikationsserver der RWTH Aachen University
%Z Dissertation, RWTH Aachen University, 2021
%X Neutron damage is a major deciding factor in the commercialisation of a fusion power plant. Neutron damage inflicted on the walls of the reactor during operation, leads to changes in the behaviour of materials and ultimately decides the life time of the component. Consequently, it is essential that fusion relevant materials are tested under fusion irradiation conditions in order to qualify them, prior to use. Tungsten is a key material for the plasma facing component in a fusion reactor, and is located directly in the path of high energy fusion neutrons. Currently, it is not possible to test the change in material behaviour under high energy neutrons as there exits no high flux fusion neutron source. Moreover, high flux fission reactors are unable to re produce the high energy neutron damage. However, this work demonstrates the use of 30 MeV protons to induce fusion relevant neutron damage on tungsten. This work involves the first irradiation of tungsten using high energy protons (30 MeV). A complete irradiation cycle, including irradiation planning, sample design and manufacturing, polishing, irradiation, the setting up of post irradiation devices and post irradiation investigation was carried out within the scope of this work. Optimal sample geometry for accelerator irradiations, which is also directly comparable and compatible with fission reactor irradiations, was manufactured. The sample holder was designed such that in-situ temperature measurements were possible for the first time. Additionally, hot cell and remote handling conforming, punch and indentation testing have been developed and demonstrated through the use of irradiated active samples. In order to understand proton damage, pure tungsten was irradiated using three different proton energies 3, 16 </td><td width="150">
%X  30 MeV. The 3 MeV proton irradiation produces pure displacement damage, while the 16 </td><td width="150">
%X  30 MeV induce a combination of displacement and transmutation damage. Moreover, instrumented indentation was performed on the irradiated samples in a radiation environment (controlled areas). For all proton energies, an irradiation hardening of  0.6 GPa was observed at low doses of 0.003 dpa for 30 MeV protons and 0.005 dpa for 3 MeV protons. Further experiments with 3 MeV protons displayed an initial further increase followed by saturation at 0.4 dpa. A similar behaviour has been reported with self ion irradiations on pure tungsten. The TEM observations of 3 MeV proton irradiated tungsten shows the development of dislocation loops, which grow in size but also achieve a saturation in loop density. This correlates well with the saturation in irradiation hardening. Irradiation modelling was performed using MCNP6.1 and FISPACT-II on both the sample and the sample holder to estimate the damage capability of 30 MeV protons. Post irradiation, gamma analysis showed good agreement with the modelling. Additionally, dose rate measurements were in-line to estimates from the simulations. This, by extension validates the transmutation capability of 30 MeV protons and their ability to simulate fusion neutron damage in W.
%F PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
%9 Dissertation / PhD ThesisBook
%R 10.18154/RWTH-2021-06067
%U https://publications.rwth-aachen.de/record/821170