Spherical tokamak power plant design issues

The very high beta potential of the spherical tokamak has been demonstrated in the START experiment. Systems code studies show the cost of electricity from spherical tokamak power plants, operating at high beta in second ball ooning mode stable regime, is comparable with fossil fuels and fission. Out line engineering designs are presented based on two concepts for the centra l rod of the toroidal field (TF) circuit - a room temperature water cooled copper rod or a helium cooled cryogenic aluminium rod. For the copper rod c ase the TF return limbs are supported by the vacuum vessel, while for the a luminium rod the TF coils form an independent structure. In both cases ther mohydraulic and stress calculations indicate the viability of the design. T wo-dimensional neutronics calculations show the feasibility of tritium self -sufficiency without an inboard blanket. The spherical tokamak has unique m aintenance possibilities based on lowering major component structures into a hot cell beneath the device and these are discussed. (C) 2000 Elsevier Sc ience S.A. All rights reserved.