A sustainable plasma-facing material design based on advanced W fusion materials will require four primary design elements: 1) high-heat flux handling including enhanced recrystallization properties balanced with gas impurity radiative protection to handle off-normal exposures, 2) management of helium exhaust and hydrogen retention, 3) enhanced thermo-mechanical properties addressing creep strength and fatigue, and 4) management of erosion and re-deposition properties to maintain sustainable material lifetime. Novel complex W-based alloys address most of these design criteria, however the effect of chemically-reactive processes on their performance is relatively unknown. Each of these design elements have in common their susceptibility to the intrinsic chemical reactivity in the expected ambient of a fusion reactor chamber and high-duty cycle operation that includes surface temperatures between 800-1000 C, and incident energy and fluxes that vary in tokamak fusion device location. The He fluxes are expected to be about 10% of the fuel particle flux. In detached plasma operation, using radiative cooling strategies to protect the PFM surface, N or Ne-based gases can be used and they would consist of about 1- 5% of the incident particle flux. To manage high-Z impurity intrinsic to the erosion and re-deposition processes in a nuclear fusion reactor, low-Z wall conditioning may be necessary using B, Li or the use of a low-Z wall material (e.g. Be). With this in mind, the proposed work has three primary objectives:

1. Decipher chemically-driven mechanisms for W-based alloys from intrinsic oxygen and interactions impacting fuel retention;

2. Investigate the chemically-driven mechanisms for W-based alloys from extrinsic reactive impurities (B and N) impacting fuel retention and He exhaust properties;

3. Validation of computational tools from #1 and #2 elucidating extrinsic and intrinsic impurity effects on plasma material interaction properties of W-based materials.

To achieve these objectives, we combine atomistic MD codes based on bond-order ReaxFF potentials and QCMD with BCA-based DYNAMIX surface-response codes built in a formalism known as “ExASIM” (Expanded Atomistic Simulations of Irradiated Materials) to provide input to kinetic MC codes for mesoscale treatise of reactive plasma material interactions and their impact on fuel retention and He exhaust in specific problems such as: the impact of oxygen at the interface of W and carbide dispersoid boundaries, ion-driven mixing of reactive impurities (e.g. B, N), and synergistic D and He interactions in a chemically-reactive surface.