ARIES-ST design point selection

The spherical tokamak (ST) regime of low-aspect-ratio (LAR) tokamak operation has provided an opportunity to consider a 1000-MWe(net) D–T power plant conceptual design, designated ARIES-ST. Physics attributes include high beta (∼50%) together with high bootstrap current contribution (∼95%). Neutral-beam current drive (∼28 MW) supports steady-state operation. The plasma aspect ratio was selected to be A≃1.6 leading to the choice of major plasma toroidal radius, RT=3.2 m and plasma half-width, a=2.0 m. The usual engineering considerations of providing an efficient thermal power cycle (gross efficiency ≃45%), while handling first-wall (∼1 MW/m2) and divertor-plate (∼5 MW/m2) surface heat fluxes, leads to 14-MeV neutron wall loads near 4.1 MW/m2 (average) and 5.6 MW/m2 (peak at outboard mid-plane) in a dual (PbLi and He) coolant system. The water-cooled toroidal-field-coil (TFC) centerpost is protected by a 20-cm (inboard) shield that does not breed tritium. Joule dissipation in the TFC system provides the major contribution to the plant recirculating power; specifically, Cu centerpost (222 MW), Al outboard shell (47 MW), Cu leads (27 MW), and power supplies (33 MW). The overall plant recirculating power fraction is an uncomfortable 34%. For a plant capacity factor ∼76%, consistent with earlier ARIES studies, the COE is projected to be ∼84 mill/kWe h (1992 constant $), using similar unit-cost assumptions and some passive-safety cost credits. Inclusion of additional credits for advanced, low-unit-cost manufacturing based on plasma spray and related techniques (as applied to the TFC centerpost and outboard TFC shell only) lowers this COE estimate to ∼79 mill/kWe h.