Plasma facing components for helical reactors

The conceptual design of blanket and divertor for a force free helical reactor (FFHR) is presented. The demo relevant FFHR is a heliotron type helical reactor having superconducting helical and poloidal coils based on the Large Helical Device (LHD) which is now under construction in NIFS. The main feature of FFHR is force free configuration of helical coils, which allow us to simplify the coil supporting structure and to use high magnetic field instead of high plasma beta. For the goal of a self-ignited D-T reactor of 3GW thermal output, the design parameters for FFHR are investigated under the LHD scaling for energy confinement and density limit. In particular, to satisfy the reactor lifetime of 30 years, the engineering issues in FFHR are discussed by focussing on selection of structural materials for 500dpa, optimization of tritium breeding system, cooling with molten-salt Flibe and operation temperature in the blanket, radiation shielding, and steady state helium ash removal. (author)