Development of steady-state fusion reactor by Helical Fusion

The Helical Fusion group (Helical Fusion Co., Ltd. in Japan and Helical Fusion USA, Inc.) is developing a 50 MWe-class steady-state helical fusion reactor, which is a kind of stellarator called heliotron composed of two continuous helical coils similar to the large helical device and is operated without plasma current. HESTIA plays the role of the fusion pilot plant. The first-of-a-kind fusion power plant that would follow HESTIA will be a 100 MWe-class steady-state helical fusion reactor. After more than one year of continuous operation, maintenance will be completed within 3 months, aiming for an availability larger than 80%. High-temperature superconducting magnet coils are adopted to generate 8 T of the magnetic field at the helical coil center. HESTIA is a deuterium-tritium fusion reactor, where tritium is self-produced using liquid metal blanket systems. The first wall of the liquid metal blanket including the divertor strike zone is covered and protected by liquid metal free-surface flow, and therefore, individual divertor systems are not required in HESTIA. Electron cyclotron heating is adopted for plasma heating. Since plasma current drive is not required, HESTIA can be operated at a low fusion gain of similar to 13, and steady-state operation is principally possible on the order of a year. After a few years of individual development phases, a prototype device is planned to be constructed and operated for the integrated demonstration before starting the construction of HESTIA.