Helical reactor design FFHR-d1 and c1 for steady-state DEMO

• More than 10 years’ operation is feasible using the inboard WC shield, where the total TBR is 1.18 with 90% 6Li.
• The divertor targets can be efficiently shielded, expanding the range of material choice (e.g., Cu alloys).
• Flinabe blanket mixed with metal powder is proposed to increase hydrogen solubility and thermal efficiency.
• Helical coils by connecting segments of 100 kA-class YBCO high-temperature superconductors is proposed.
• A multi-path strategy on FFHR-d1 is introduced with sub-ignition options for “before demo, compact and component-test”.

NIFS launched the Fusion Engineering Research Project (FERP) in preparation for DEMO by starting the redesign of the LHD-type helical reactor FFHR-d1. In the first round, the main parameters were selected. The second round is preparing detailed three-dimensional (3D) design of the superconducting magnet support structures, and 3D neutronics analyses, where the diverter targets can be efficiently shielded from fast neutrons. A new Flinabe blanket mixed with metal powder was proposed. Fabrication of helical coils by connecting half-helical-pitch segments of 100 kA-class YBCO high-temperature superconductors is proposed as a promising method. Also in progress is improvement of the first round of the core plasma design, ignition start-up analyses, and fueling scenario. As a consequence, a multi-path strategy on FFHR-d1 has been introduced with versions of -d1A, -d1B, and -d1C, where design flexibility is expanded to include subignition with options FFHR-c1 for “before demo, compact, and component-test.”