Thermal-hydraulic performance evaluation and optimization of the T-tube divertor design using numerical simulations
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A key technology issue in magnetic fusion energy is plasma-materials interactions (PMI). Because our understanding of how materials change when exposed to burning plasmas over extended periods is limited, Oak Ridge National Laboratory (ORNL) has proposed a linear plasma simulator, the Material-Plasma Exposure eXperiment (MPEX), to test various fusion-relevant materials. Since this facility will expose various materials to conditions similar to those in a burning plasma (except for fusion-relevant neutrons) at steady state, effectively cooling the target plate which will be exposed to steady-state heat fluxes of several MW/m2 is a major challenge. The objective of this Master's thesis is to use numerical simulation to evaluate and improve the thermal-hydraulic performance of a helium-cooled divertor design adapted for cooling the target plate in a linear plasma simulator. The T-tube divertor design, originally developed by the Advanced Reactor Innovations and Evaluations Compact Stellarator Study (ARIES-CS), was used as the starting point for these simulations because it can withstand a uniform heat flux of 10 MW/m2 over an area of several cm2 when cooled by helium (He) at 10 MPa and 600 °C. The T-tube was adapted for cooling the proposed target plate design for the MPEX using He at 4 MPa and room temperature. Given the much lower coolant temperatures, the simulations considered a target plate consisting of a copper chromium zirconium (CuCrZr) alloy, vs. the tungsten alloy proposed for the original T-tube. The simulations considered two different He flow configurations; a number of modified geometries were evaluated in an attempt to improve the thermal-hydraulic performance of both configurations. The simulations also compared the performance of two different target plate materials, namely the original CuCrZr and a titanium zirconium molybdenum (TZM) alloy.