Design, modelling and testing of high heat flux components for fusion devices
<p>The commercial feasibility of fusion energy requires advanced technological research, needed for withstanding more extreme conditions than fission or aerospace applications. One of the areas needing viable solution is the handling of high heat fluxes experienced by the wall surrounding the...
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
2023
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| Subjects: |
| _version_ | 1811139568040148992 |
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| author | Richiusa, ML |
| author2 | Ireland, P |
| author_facet | Ireland, P Richiusa, ML |
| author_sort | Richiusa, ML |
| collection | OXFORD |
| description | <p>The commercial feasibility of fusion energy requires advanced technological research, needed for withstanding more extreme conditions than fission or aerospace applications. One of the areas needing viable solution is the handling of high heat fluxes experienced by the wall surrounding the plasma, especially during off–normal transients. In such cases, the plasma can touch the wall, releasing up to GigaJoules of energy in milliseconds, which leads to surface degradation due to melting and vaporization. The wall protection strategy adopted for the EU–DEMO tokamak relies on sacrificial protruding panels, called limiters, devoted to deal with plasma–wall contact events following both normal and accidental transients. Limiters can be damaged, provided that their active cooling system preserves its integrity under any circumstances. Therefore, the limiter design requires any armour phase change to be considered, since it affects the cooling system design and integrity.</p>
<p>This research encompasses the limiter integrated design workflow under high heat flux and strong electro–magnetic loads due to disruptive events, with specific focus on tackling the heat transfer in solid components undergoing phase change through the development of an engineering methodology. The main steps of the research are here highlighted. Given the initial assessment of plasma magnetic configurations during off–normal events, the limiter’s plasma facing surface is designed and shaped accordingly, with the aim of spreading the energy deposited over as large a surface area as possible, avoiding edge–localized hot spots. The shaping is then verified and adapted to the different plasma magnetic configuration of the longest normal operation under heat load estimates by means of field line tracing codes.</p>
<p>Efforts towards heat transfer modelling in presence of phase change bring the author to the development of 3D–TARTIFL&TTE (Thermal Analysis foR Tracking InterFaces under meLting&vaporizaTion–induced plasma Transient Events), implemented through COMSOL Multiphysics. It is an engineering model tracking the solid–to–liquid moving boundary within one single domain, while gas kinetics governs the amount of material removed by vaporization. The vapour domain is not modelled. The material removal due to the evaporative mass flux is modelled by means of moving mesh frames which push the recessive liquid interface backwards according to gas kinetics–driven boundary conditions. The melt pool is not removed during the transient. Mass balance considerations drive the liquid–to–vapour interface velocity. The approach is benchmarked against Quasi–Stationary Plasma Accelerator (QSPA kh-50, Kharkov, Ukraine) data, and dedicated melting experiments run in Garching LArge DIvertor Sample test facility (GLADIS, Garching, Germany). In either cases, the code shows the capability to predicting surface temperature, absorbed energy, and melt layer thickness, paving the way for its use within the engineering design workflow of metallic plasma–facing components.</p>
<p>The application of 3D–TARTIFL&TTE to a tungsten monoblock armour leads to a preferred chosen thickness of 20 mm, as a conservative preliminary value to be checked under pressure and temperature values calculated at the cooling system outlet.</p>
<p>The first concept of the integrated design of the upper limiter is also presented. It is equipped with a sliced structural box which breaks down the eddy current paths and, hence, reduces the electro–mechanical loads acting on it. Built on static–structural and energy balance hand calculations based on, respectively, preliminary electro–magnetic and neutronic loads, the performance of the integrated design will be verified in a future work against electro–magnetic, neutronic, thermal–hydraulic load combination. The outcome is expected to be used as reference for future limiter engineering designs.</p> |
| first_indexed | 2024-09-25T04:08:09Z |
| format | Thesis |
| id | oxford-uuid:eae3f2e4-e64e-4dc9-b2f8-d6b7ff09f973 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:08:09Z |
| publishDate | 2023 |
| record_format | dspace |
| spelling | oxford-uuid:eae3f2e4-e64e-4dc9-b2f8-d6b7ff09f9732024-06-04T10:17:15ZDesign, modelling and testing of high heat flux components for fusion devicesThesishttp://purl.org/coar/resource_type/c_db06uuid:eae3f2e4-e64e-4dc9-b2f8-d6b7ff09f973Nuclear fusionMechanical engineeringThermal analysisEnglishHyrax Deposit2023Richiusa, MLIreland, PVizvary, Z<p>The commercial feasibility of fusion energy requires advanced technological research, needed for withstanding more extreme conditions than fission or aerospace applications. One of the areas needing viable solution is the handling of high heat fluxes experienced by the wall surrounding the plasma, especially during off–normal transients. In such cases, the plasma can touch the wall, releasing up to GigaJoules of energy in milliseconds, which leads to surface degradation due to melting and vaporization. The wall protection strategy adopted for the EU–DEMO tokamak relies on sacrificial protruding panels, called limiters, devoted to deal with plasma–wall contact events following both normal and accidental transients. Limiters can be damaged, provided that their active cooling system preserves its integrity under any circumstances. Therefore, the limiter design requires any armour phase change to be considered, since it affects the cooling system design and integrity.</p> <p>This research encompasses the limiter integrated design workflow under high heat flux and strong electro–magnetic loads due to disruptive events, with specific focus on tackling the heat transfer in solid components undergoing phase change through the development of an engineering methodology. The main steps of the research are here highlighted. Given the initial assessment of plasma magnetic configurations during off–normal events, the limiter’s plasma facing surface is designed and shaped accordingly, with the aim of spreading the energy deposited over as large a surface area as possible, avoiding edge–localized hot spots. The shaping is then verified and adapted to the different plasma magnetic configuration of the longest normal operation under heat load estimates by means of field line tracing codes.</p> <p>Efforts towards heat transfer modelling in presence of phase change bring the author to the development of 3D–TARTIFL&TTE (Thermal Analysis foR Tracking InterFaces under meLting&vaporizaTion–induced plasma Transient Events), implemented through COMSOL Multiphysics. It is an engineering model tracking the solid–to–liquid moving boundary within one single domain, while gas kinetics governs the amount of material removed by vaporization. The vapour domain is not modelled. The material removal due to the evaporative mass flux is modelled by means of moving mesh frames which push the recessive liquid interface backwards according to gas kinetics–driven boundary conditions. The melt pool is not removed during the transient. Mass balance considerations drive the liquid–to–vapour interface velocity. The approach is benchmarked against Quasi–Stationary Plasma Accelerator (QSPA kh-50, Kharkov, Ukraine) data, and dedicated melting experiments run in Garching LArge DIvertor Sample test facility (GLADIS, Garching, Germany). In either cases, the code shows the capability to predicting surface temperature, absorbed energy, and melt layer thickness, paving the way for its use within the engineering design workflow of metallic plasma–facing components.</p> <p>The application of 3D–TARTIFL&TTE to a tungsten monoblock armour leads to a preferred chosen thickness of 20 mm, as a conservative preliminary value to be checked under pressure and temperature values calculated at the cooling system outlet.</p> <p>The first concept of the integrated design of the upper limiter is also presented. It is equipped with a sliced structural box which breaks down the eddy current paths and, hence, reduces the electro–mechanical loads acting on it. Built on static–structural and energy balance hand calculations based on, respectively, preliminary electro–magnetic and neutronic loads, the performance of the integrated design will be verified in a future work against electro–magnetic, neutronic, thermal–hydraulic load combination. The outcome is expected to be used as reference for future limiter engineering designs.</p> |
| spellingShingle | Nuclear fusion Mechanical engineering Thermal analysis Richiusa, ML Design, modelling and testing of high heat flux components for fusion devices |
| title | Design, modelling and testing of high heat flux components for fusion devices |
| title_full | Design, modelling and testing of high heat flux components for fusion devices |
| title_fullStr | Design, modelling and testing of high heat flux components for fusion devices |
| title_full_unstemmed | Design, modelling and testing of high heat flux components for fusion devices |
| title_short | Design, modelling and testing of high heat flux components for fusion devices |
| title_sort | design modelling and testing of high heat flux components for fusion devices |
| topic | Nuclear fusion Mechanical engineering Thermal analysis |
| work_keys_str_mv | AT richiusaml designmodellingandtestingofhighheatfluxcomponentsforfusiondevices |