Improved tokamak concept focusing on easy maintenance

Maintainability improvement on tokamak fusion reactor may prove to be a critical path in order to launch the fusion energy into commercial use. The more the development of tokamak device progresses from an experimental reactor to a commercial reactor, the more important the maintenance issue becomes. The maintenance difficulty of tokamak system is due to its configuration complexity, enormous electromagnetic loads and material radioactivation. In order to mitigate the difficulty, a very low activation material of SiC/SiC composite and a torus configuration with high aspect ratio of eight are introduced. The torus system is radially divided into equal sectors and each sector forms an assembly unit. All the piping and feeder systems are extracted to the spacious torus central region. The new concept is called 'DREAM' tokamak reactor, which stands for DRastically EAsy Maintenance. The maximum toroidal field strength of 20 T and the plasma major and minor radii of 16 m and 2 m lead to high fusion power of 5.5 GW under the moderate physics constraints such as a 'non-reversed shear profile' with the MHD safety factor of 3, Troyon factor of 3 for the beta limit and the energy confinement time enhancement factor of 2. (C) 1998 Elsevier Science S.A. All rights reserved.