Numerical Simulations of Tungsten under Helium Irradiation

摘要: Author(s): Faney, Thibault | Advisor(s): Ahn, Joonhong Abstract: Magnetic confinement fusion is a promising technology for electricity production due to available fuel and low waste products. However, the construction of nuclear reactor remains scientific challenge. One main issues resistance plasma facing materials exposed very harsh operating conditions. Tungsten leading candidate divertor, crucial component. This dissertation focuses on modeling behavior tungsten under irradiation conditions relevant divertor operations using multi-scale approach. In particular, high fluxes helium ions at energy impact are responsible changes in microstructure such as formation blisters ''fuzz"-like structures which can ultimately lead erosion, degradation performance failure. A spatially dependent cluster dynamics model introduced order evolution irradiation. continuum based kinetic rate theory handles each material defect type independently. Under assumptions dilute limit no spatial correlation between defects, this leads large system non-linear reaction-diffusion equations. Hence, results addressed thesis consist determination parameters model, solver efficiently deals with partial differential equations, applicability conditions, variety The input defects' diffusion coefficients, binding energies capture radii. These be determined molecular density functional simulations well empirical data. challenge lies obtaining consistent set parameters. Therefore, method determine value coefficients small helium, interstitial vacancy defects various temperatures only presented. Binding also dynamics, when combined they form An efficient implementation parallel presented deal number stiff non linear reaction SDIRK scheme modified version SPIKE algorithm gives excellent parallelization suggests that would an extension two or three dimensions. Convergence schemes show convergence reduction numerical stiffness terms. comparison simulation experimental essential assess validity model. Comparison thermal desorption spectrometry experiments flux fluence shows agreement indicate captures key physical properties affecting microstructure. Further extremely provides insight expected limitations surface effects approximations breakdown applied Results bubbles temperature depth. sensitive both temperature. At temperatures, concentration forms first deep surface, ``plug" moves towards until eventually approximation breaks down, indicating sub-surfaces become interlinked. larger smaller close bubble bursting occur. found good similar analytical More work needed simulate past examine possibility taking into account effects.