Projections for a Steady-State Tokamak Reactor Based on the International Thermonuclear Experimental Reactor

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Abstract
The extensions of the physics and engineering guidelines for the International Thermonuclear Experimental Reactor (ITER) device needed for acceptable operating points for a steady-state tokamak power reactor are examined. Noninductive current drive is provided in steady state by high-energy neutral beam injection in the plasma core, lower hybrid slow waves in the outer regions of the plasma, and bootstrap current. Three different levels of extension of the ITER physics/engineering guidelines, with differing assumptions on the possible plasma beta, elongation, and aspect ratio, are considered for power reactor applications. Plasma gain Q = fusion power/input power in excess of 20 and average neutron wall fluxes from 2.3 to 3.6 MW/m2 are predicted in devices with major radii varying from 7.0 to 6.0 m and aspect ratios from 2.9 to 4.3. Only modest enhancements over L-mode (Goldston) energy confinement are required. Peak divertor heat fluxes range up to 12.4 MW/m2, which is somewhat higher than the current ITER design limit of 10 MW/m2 with a magnetically swept divertor. These designs were selected on the basis of improvements in physics/engineering consistent with time scales for development of future reactors. The design reoptimization on the basis of cost of electricity (COE) was then examined using a reactor systems model. This analysis generally verified the original estimates for the required extensions of the ITER guidelines. The COE is projected to be <66 mill/kW(electric) · h in all of the configurations. The smallest reactor, which has the largest neutron wall flux and mass power density, yields the lowest COE, 56 mill/kW(electric)· h. While these costs are marginally competitive with fission power, these modest extensions of the ITER guidelines do produce a viable power reactor. With time for further improvements such as those pursued in the ARIES study, similar designs could present an even more competitive commercial product.