SUMMARY

The target plates of the divertor in magnetic fusion energy (MFE) tokamak reactors are exposed directly to the private region of the plasma, removing the helium (He) ash and other impurities directed by the magnetic field lines. Gas-cooled solid-tungsten (W) divertors use gas jets impinging on the backside of the W target to remove the thermal energy in this harsh environment with expected incident steady-state surface heat fluxes of at least 10 MW/m2. A number of studies have estimated the capability of different individual divertor modules to remove incident heat fluxes under (near-)prototypical reactor thermal conditions. However, there is comparatively little research on the thermal performance achievable by realistic divertor arrays comprised of a large number (~103-105) of modules. Moreover, recent work evaluating the helium-cooled modular divertor with multiple jets (HEMJ) using ITER structural design codes suggest that structural, vs. temperature limits, may determine the performance of modular divertors.
The objective of this thesis is to accurately evaluate the thermal-fluids/structural performance of an array of the He-cooled T-tube modules under realistic operating conditions. An optimized T-tube design has been developed with excellent simulated thermal-fluids performance. After rigorous thermal-structural evaluation of this design, this work will use commercial computational fluid dynamics (CFD) software to quantify the thermal efficiencies achievable in a model array of modular T-tubes and systematically evaluate the impact of realistic nonuniform heat loads and inefficiencies resulting from simulated flow distributions to ~103 T-tube units. High fidelity large-eddy simulations (LES) will both verify the CFD Reynolds averaged Navier-Stokes (RANS)-based simulations, and quantify the impact of different turbulence models on thermal structural performance and system thermal efficiency.