Physics and technology maturity level required for the K-DEMO design points

The conceptual design study for the Korean fusion demonstration reactor (K-DEMO) has been conducted, placing an emphasis on the imperative to reduce the reactor's dimension as a means to cost minimization. The design space of K-DEMO was delineated based on maturity level of physics and technology. Advanced technology features such as a use of a tungsten carbide (WC) shield, a tritium breeding blanket concept of He cooled lithium lead (HCLL), the maximum allowable magnetic field at the TF coil, B-max = 16 T with a Nb3Sn superconducting material, etc. were adopted. With specified design criteria, including a net electric power >= 300 MW, a fusion gain, Q > 20.0, a neutron wall loading < 2.0 MW/m(2), an indicator of divertor power handling capability (ratio of power to divertor to major radius), P-div/R-0 < 25 MW/m, and the capability for steady-state operation, a design space of the K-DEMO was established based on the energy confinement scaling law of IPB98[y,2] under physics level of Greenwald density fraction, n(e)/n(G) < 1.2, normalized plasma beta (ratio of plasma pressure to magnetic pressure normalized by plasma current divided by the product of minor radius and toroidal magnetic field), beta(N) < 3.0, confinement enhancement factor, H < 1.3, and a direct cost <= 7.5 B$. After an exploration of system parameters, prospective design points for K-DEMO were identified, characterized by a major radius, R-0 similar to 6.8 m, an aspect ratio, A = 3.1, a toroidal magnetic field at plasma center, B-T >= 6.5 T, and a fusion power, P-fusion similar to 1,500 MW. When beta-independent energy confinement scaling law was applied, the design points were accessible with smaller n(e)/n(G), beta(N), H, P-fusion, and larger B-T. From a sensitivity analysis of the minimum major radius to the input parameters, strong sensitivities to Greenwald density fraction, n(e)/n(G), normalized plasma beta, beta(N), confinement enhancement factor, H, edge safety factor, q(edge), and elongation, kappa were found. Additionally, the operational envelope in physics and technology parameters was established with system parameters associated with the design points.