A Study of the Flow Patterns of Expanding Impurity Aerosol Following a Disruption Event in a Fusion Reactor

The current study focuses on the adiabatic expansion of aerosol impurity in the post-disruption and thermal quench scenario inside the vacuum chamber of a fusion reactor. A pulsed electrothermal plasma (ET) capillary source has been used as a source term simulating the surface ablation of the divertor or other interior critical components of a tokamak fusion reactor under hard disruption-like conditions. The capillary source generates particulates from wall evaporation by depositing transient radiant high heat flux onto the inner liner of the capillary. The particulates form a plasma jet moving towards the capillary exit at high speed and high pressure. The first chapter discusses briefly the relevance of the study pertaining to the impurities in a fusion reactor based on the work available in the form of published literature. The second chapter discusses briefly the operating principle of a pulsed electrothermal plasma source (PEPS), the virtual integration of PEPS with 1-D electrothermal plasma flow solver ETFLOW and the use of capillary plasma sources in various industrial applications. The third chapter discusses about primitive computational work, backed by the data from actual electrothermal source experiments from the in-house facility "PIPE" (Plasma Interactions with Propellants Experiment), that shows the supersonic bulk flow patterns for the temperature, density, pressure, bulk velocity and the flow Mach number of the impurity particulates as they get ejected as a high-pressure, high-temperature and hyper-velocity jet from the simulated source term. It also shows the uniform steady-state subsonic expansion of bulk aerosol inside the expansion chamber. The fourth chapter discusses scaling laws in 1-D for the aforesaid bulk plasma parameters for ranges of axial length traversed by the flow, so that one can retrieve the flow parameters at some preferred locations. The fifth chapter discusses the effect of temperature and the non--linearity of the adiabatic compressibility index on the supersonic flow patterns for ablated polycarbonate plasma, where the study shows significant changes in flow parameter values in the extreme limits of suggested non-linearities. The sixth chapter discusses the temperature-dependent flow patterns for high-density metal vapor plasmas, and the study brings out finer aspects like agglomeration and recombination in the dense bulk plasma as it undergoes isentropic expansion. The last chapter presents analytical expressions for the 2-D steady-state spatial evolution of polycarbonate ablated plasma utilizing the 1-D scaling laws that were developed and discussed in the fourth chapter and the modeling is expected to enable us in predicting the spatial distribution of the debris from the plasma facing components (PFC) or the migrated dust in an efficient manner.