The purpose of this master’s thesis is to investigate the concept for mitigation of a potential loss of cooling accident, caused by a total loss of cooling in one of the primal components of the demonstrational fusion reactor DEMO. In this regard, the most critical components are the ones inside the tokamak, such as the Breeding Blanket. When the reactor is in operation, in-vessel components heat up significantly due to an exposure to high neutron fluxes. This accumulated heat can be removed with an active cooling system, which ensures that an appropriate temperature of the Breeding Blankets is maintained. In the case of the loss of active cooling, despite immediate shut down of a fusion reaction, the temperature of the affected components (e.g. Breeding Blankets) starts to rise due to the internal heat generation by decay heat. Thus the development of the conceptual DEMO design also addresses the mitigation concepts for potential accidents to effectively reduce the damage of the reactor and to shorten the outage time. The aim of this research was to calculate the diameter of cooling system nozzles. The diameter was determined using a 0D model, which was later checked by a 3D model in Ansys Fluent program. It was concluded that using a 0D model the results are accurate enough and require much less computation time.
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