Abstract
The potential minimum cost of electricity (COE) for superconducting tokamak power reactors is estimated by increasing the physics (confinement, beta-limit, bootstrap current fraction) and technology (neutral beam energy, toroidal field, or TF, coil allowable stresses, divertor heat flux, superconducting coil critical field, critical temperature, and quench temperature rise) constraints far beyond those assumed for the ITER (International Thermonuclear Experimental Reactor) until the point of diminishing returns is reached. A version of the TETRA systems code that is calibrated with the ITER design and modified for power reactors is used for the analysis, limiting the study to reactors with the same basic device configuration and costing algorithms as the ITER. A minimum COE is reduced from >200 to about $80 million/kWh when the allowable design constraints are raised to 2 times those of ITER. At 4 times the ITER allowables, a minimum COE of about $60 million/kWh is obtained. The corresponding tokamak has a major radius of approximately 4 m, a plasma current close to 10 MA, an aspect ratio of 4, a confinement H-factor ⩽3, a beta limit of approximately 2 times the first stability regime, a divertor heat flux of about 20 MW/m2, a Bmax ⩽18 T, and a TF coil average current density about 3 times that of the ITER.