Thermal and Structural Analysis of Outboard Divertor Row 1&2 Tiles for NSTX-U

The National Spherical Torus eXperiment (NSTX) has recently undergone a major upgrade and recovery to NSTX-U at Princeton Plasma Physics Laboratory (PPPL). With the double toroidal field, plasma current, and longer pulse duration, the original outboard divertor row 1&2 (OBD12) tiles could not meet the higher thermal requirements of NSTX-U project. The OBD tiles are used to protect the OBDs from the plasma and also protect the plasma from impurities generated by that surface. The transient thermal models with different faceted fishscaling factors and static structural models with halo and eddy loads have been analyzed to check the design qualification of new OBD12 tiles. The simplified rod and key submodels have been developed to optimize design elements and to resolve the over-stress issues with the rod and key contact areas. The redesign of OBD12 tiles can meet the system requirements on the high-flux plasma-facing components (PFCs).