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(FT/P1-20) System Assessment of Helical Reactors in Comparison with Tokamaks

K. Yamazaki1), S. Imagawa1), T. Muroga1), A. Sagara1), S. Okamura1)
1) National Institute for Fusion Science, Toki, Japan

Abstract.  Economically acceptable fusion reactors are required with steady-state and good-confinement plasmas. The tokamak is now best with respect to plasma confinement, however, the current-drive (CD) re-circulation power and the plasma disruptions are worried. In contrast, the helical system is expected as a steady-state reactor, but becomes a rather big and expensive system. System assessments have been done for LHD (Large Helical Device)-type reactors and quasi-axisymmetric modular reactors in comparisons with ITER-like tokamak designs. High plasma temperature operation is required in tokamaks to increase CD efficiency and to reduce CD power. However, rather low temperature operation is feasible in helical system. The weight and cost of the LHD-type fusion island are two times higher than those of reference tokamak design with same beta value and same net electric power. However, no need of CD power and the less-frequent replacement of blanket/heating equipments within the permissible neutron wall load can contribute to the reduction in COE of helical reactors. The unique differences between helical and tokamak reactor assessments are clarified.

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IAEA 2003