Massive parametric study for prospective design space of a compact tokamak fusion reactor

Abstract

Using a novel computational algorithm that integrates tokamak systems analysis with neutron transport calculations, the minimum major radius (R0) and resulting maximum magnetic field at the plasma center (BT) can be determined uniquely for a given plasma performance. Plasma performance was varied extensively using a supercomputer (KAIROS) and scanning over a wide range of physics, technology, and system parameters to derive the optimal design space for a compact tokamak fusion reactor. Given the design goals of fusion gain Q > 20.0, net electric power > 100 MW, neutron wall loading < 2.0 MW/m2, indicator of divertor power handling PSOL/R0 < 25 MW/m, direct capital cost < $4.0 billion, and steady-state operation, a prospective design space was determined depending on the levels of physics and technology. Advanced engineering features, such as maximum allowable magnetic field at the toroidal field coil (Bmax = 23 T), were implemented by adopting high-temperature superconducting magnet technology, using an advanced shield material such as tungsten carbide (WC), and a plug-bucked magnet support structure. It was found that by exceeding the energy confinement scaling laws of IPB98y2, a design space of R0 < 4.0 m could be accessed under the following conditions for a conventional tokamak: confinement enhancement factor H > 1.7, bootstrap current fraction fBS > 0.55, magnetic field at the magnetic axis BT > 4.0 T, fusion power Pfusion > 600 MW, and thermodynamic efficiency ηth > 0.33. For a spherical tokamak, these conditions were H > 1.3, fBS > 0.6, BT 〈 6.0 T, and Pfusion 〉 500 MW. Sensitivity studies on the energy confinement scaling laws showed that stricter conditions on the physics parameters were required with the ITPA20 scaling law, whereas the conditions were mitigated with the β-independent scaling law.