Generation of net electric power with a tokamak reactor under foreseeable physical and engineering conditions

This study reveals for the first time the plasma performance required for a tokamak reactor to generate net electric power under foreseeable engineering conditions. It was found that the reference plasma performance of the ITER inductive operation mode with β_N = 1.8, H H = 1.0, and f n _GW = 0.85 had sufficient potential to achieve the electric break-even condition (net electric power P_e^net = 0 MW) under the following engineering conditions: machine major radius 6.5 m ≤ R_p ≤ 8.5 m, the maximum magnetic field on TF coils B _tmax = 16 T, thermal efficiency η_e = 30%, and NBI system efficiency η_NBI = 50%. The key parameters used in demonstrating net electric power generation in tokamak reactors are β _N and f n_GW. βV ≤ 3.0 is required for P _e^net ∼ 600 MW with fusion power P_f ∼ 3000MW. On the other hand, fn_GW ≥ 1.0 is inevitable to demonstrate net electric power generation, if high temperatures, such as average temperatures of T_ave > 16 keV, cannot be selected for the reactor design. To apply these results to the design of a tokamak reactor for demonstrating net electric power generation, the plasma performance diagrams on the Q vs P_f (energy multiplication factor vs fusion power) space for several major radii (i.e. 6.5, 7.5, and 8.5 m) were depicted. From these figures, we see that a design with a major radius R_p ∼ 7.5 m seems preferable for demonstrating net electric power generation when one aims at early realization effusion energy.