(FT/1-1) Critical Physics Issues for Tokamak Power Plants

D.J. Campbell1), F. De Marco2), G. Giruzzi3), G.T. Hoang3), L.D. Horton4), G. Janeschitz5), J. Johner3), K. Lackner4), D.C. McDonald6), D. Maisonnier1), G. Pereverzev4), B. Saoutic3), P. Sardain1), D. Stork6), E. Strumberger4), M.Q. Tran7), D.J. Ward6)
1) European Fusion Development Agreement, Close Support Unit, European Commission (EC), Garching, Germany
2) Association Euratom-ENEA Frascati, 00044 Frascati, Italy
3) Association Euratom-CEA, CEA Cadarache, F-13108 St. Paul-lez-Durance, France
4) Association Euratom-Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
5) Association Euratom-Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany
6) Euratom-UKAEA Fusion Association, Abingdon OX11 3EA, United Kingdom
7) Association Euratom-Confédération Suisse, PPB-EPFL, 1015 Lausanne, Switzerland

Abstract.  Analysis of tokamak fusion power plants such as the EU power plant conceptual study (PPCS) makes clear that, to ensure that tokamaks can be exploited to generate electricity at economically attractive rates, improvements beyond the ITER baseline performance levels are required. Recent studies within the EU which extend the results of the PPCS analysis have provided a more quantitative characterization of the physics of tokamak reactors which will follow ITER and have highlighted the key issues which must be resolved to establish a convincing physics basis for these devices. The power plants investigated typically have net electrical power in the range 1-1.5 GW in steady-state operation, and the aim of the studies has been to develop an improved characterization of physics performance in reactor-scale devices by validating the 0-D systems code analysis used previously against 1-D and 2-D modelling of the plasma core and edge transport and 2-D mhd stability analysis. The PPCS study showed that high beta and high density appear explicitly in the derived scaling for the cost of electricity (CoE). The need for high plasma beta is well established, while high density - typical cases studied have a Greenwald fraction above unity - is required to allow efficient use of the plasma beta and efficient radiation of exhaust power to the reactor walls. Additional critical factors include the ability to handle the power exhausted from the plasma while maintaining high energy confinement quality, high beta and acceptable plasma contamination, achievement of sufficiently high current drive efficiencies to maintain steady-state operation, and the exploitation of auxiliary heating and current drive systems to maintain the current profiles required for high confinement and mhd stability. Steady-state operation is considered to be the preferred operating scenario for fusion reactors following ITER and has formed the focus of these studies, but the development of the “hybrid” scenario, with enhanced plasma confinement and mhd stability characteristics, offers a fall-back approach to power plant operation. Our analysis indicates that trade-offs among the principal power plant parameters could allow steady-state operation in the hybrid regime. The paper will present the results of the latest modelling analysis and discuss the implications for tokamak physics R&D.

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