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Abstract. The good confinement, high beta, high bootstrap currents and low
halo currents achieved in spherical tokamaks (STs) make them potentially
attractive commercial power plants. The plasma and engineering parameters of
a conceptual ST power plant have been iterated to give a consistent design
based on a highly elongated, double null configuration. Steady-state
operation is feasible with 50 MW of neutral beam injection
or by using RF schemes e.g. Electron Bernstein Wave. Exhaust power densities
are relatively high but can be handled using a continuously renewable target
comprising a cascade of 2-3 mm diameter SiC pebbles which is being developed.
A helium cooled, ceramic pebble bed blanket with beryllium multiplier
generates the required tritium and achieves
43% overall
thermal efficiency. The layout of the torus hall is constrained by the need
for maintenance access from below and for the TF coil power supplies to be
near the torus to reduce power losses. Routine maintenance is achieved by
lowering the simple, robust centre column into a hot cell beneath the load
assembly for replacement. This work shows the ST to be a strong candidate
for future economic power generation by fusion.
IAEA 2003