Advanced design of a pulsed tokamak fusion reactor

The effect of advanced plasma physics on the design of an inductively operated, pulsed tokamak fusion reactor has been studied, and it is found that ultra long pulse operation of several hours or more is possible with a device of a major radius R of 7.5 m, and a flexible operation mode to adapt a large variation of electric power demand during one day is available. The plasma parameters employed here are: A = 4, k = 1.7, Bt = 7.32 T, fHe 10%; conventional engineering constraints, Bt,max = BOH,max = 13 T, are assumed. By reducing the plasma current to Ip = 10.6 MA, the poloidal beta value is increased in order to realize a plasma with a high bootstrap current fraction of 70-80%, while a confinement improvement factor H from ITER-89P scaling of 2.6 is required for sustaining an ignition plasma. The transformer flux of 600 Wb realizes a pulse length of 5-8 h, keeping the supply of a fusion power of 2.7 GW, which is provided for the electric power demand during daytime. The reactor is operated with a reduced fusion power of 1.5 GW for 10 h or more during the night by reducing the plasma current down to 7.9 MA, where further improvement of plasma confinement with H = 3.3 is required. Use of non-inductive current ramp-up is helpful in prolonging the pulse length. It is estimated that a lower hybrid wave power of 40 MW is sufficient to ramp up the plasma current within 100 s in the low density ( ∼ 1019 m-3) regime. This yields an extension of the pulse length by a factor of 1.4. Results of transport simulation support these advanced operation scenarios and predict a capability of producing a hollow current profile by the combination of ohmic and bootstrap currents only. (author). 6 refs, 2 figs