A Compact Advanced Tokamak for a Steady State Fusion Pilot Plant

First of a kind physics based simulations project a compact 200MW net electric fusion pilot plant is possible at a modest ~4m radius scale, based on the advanced tokamak concept and a new integrated 1.5D core-edge modeling approach. Such a device would prove that fusion can make energy and could address nuclear science and tritium breeding missions in a phased research program to establish the basis for future commercial fusion power plants. These new simulations provide additional insights compared to previous “systems code” projections by self-consistently applying transport, pedestal and current drive physics models to converge fully non-inductive stationary solutions without any significant free parameters. Increasing plasma density, pressure and toroidal field are found to lower auxiliary heating and current drive demands leading to high (~90%) bootstrap current fraction solutions (Fig. 1 and 2). In these simulations, remaining current drive is provided by neutral beams and helicon ultra-high harmonic fast wave (Fig. 3), though other options exist. An important aspect is good current drive efficiency and confinement in reducing required fusion power and device scale. The low recirculating power needs lead to tolerable divertor and neutron wall loading, with radiative solutions maintaining good H mode access (Fig. 4). A bucking approach of the TF off the central solenoid combined with a central plug reduces mechanical stress. The concept would benefit from high temperature demountable superconductors. Thus the compact approach poses a research challenge to develop more advanced science, technology and engineering approaches but offers the prospect of a lower capital cost facility to more rapidly enable the leap to fusion energy. 1. Motivation The first fusion reactors to produce net electricity will not do so at low cost of electricity (coe). They will be first of a kind devices, exploring new techniques and engineering solutions. It is thus posited that to enable a subsequent low coe device, these first ‘pilot plants’ do not need to be at the low coe scale. Rather they must prove the principles and explore the technologies, not least long timescale nuclear operation and breeding, in order to learn lessons and establish confidence for successor power plants – retiring risks in order to encourage the private sector take the final leap. Further, it is clear that paths exist to improved scientific and technical solutions, and with the time needed to reach a pilot, it is wise to first invest in more modest cost programs to advance this science and technology, in order to enable !"/!&' Pe (MW)