An economical viable tokamak fusion reactor based on the ITER experience.

This is my personal vision and outlook towards a fusion reactor based on my extensive experience from being part of the ITER design, and now construction, as well as leading the largest fusion technology program worldwide (KIT-Karlsruhe Institute of Technology) for 7 years. In particular, I want to discuss how a fusion reactor can be economically viable without employing too advanced physics and technology. It certainly will be a pulsed machine (approx. 20 000 s pulses) with thermal energy storage (turbine is steady state). I also want to discuss the optimum machine size and toroidal field for such a machine and why I think that high field and smaller plasmas may not necessarily make a fusion reactor more competitive. When one extrapolates from today's knowledge on ITER construction, even considering that ITER can be built much cheaper, it is clear that a fusion power plant will cost more than 10 or more likely more than 15 billion Euros/Dollars (the first of a kind even approx. 30 billion). Therefore, in order to have an economically attractive fusion reactor, it needs to produce a large amount of power (on the order of 2.5 GW electric). The possible size (R ∼ 10 m) and reasonably conservative physics basis of such a machine will be briefly described in the presentation. If we are successful in achieving advanced physics in a burning plasma, e.g. in ITER, then we can make the machine slightly smaller but the principal arguments for a large machine will not change significantly. Key technologies and their status will be discussed with particular emphasis on a realistic blanket and divertor design and the size and issues of a tritium-plant (T-plant) for such a machine as well as the challenges which have to be overcome beyond what is needed for ITER. Finally, a simple economic consideration will be discussed to show that a large machine could be economically viable, even in today's environment, in particular, in competition with renewables. This article is part of a discussion meeting issue 'Fusion energy using tokamaks: can development be accelerated?'.