Design-point determination for the commercial spherical tokamak, ARIES-ST

Abstract

Motivations and constraints regarding the identification of DT-fueled, 1,000-We-class commercial powerplant embodiments of the (low-aspect-ratio) spherical tokamak (ST) are summarized in the context of ongoing ARIES studies. Key design drivers are identified and the prospects of this approach to magnetic fusion energy are considered.

Tokamak reactor designs as a function of aspect ratio

“…With the density profile factor of α n = 0.634 and the temperature profile factor of α T = 0.702, we can see that our projection fits the DIII-D high equivalent D-T yield results [4] very well. When compared to the ARIES-RS [5] (SC, A=4) and ARIES-ST [6] (NC, A=1.6) physics projections, our results are more conservative. For the following calculations, in addition to the projected physics performance we also assumed a bootstrap fraction of 90%.…”

“…2, the key difference between the SC and NC design is the standoff distance of the inboard design. Similar to the ARIES designs [5,6], we selected a standoff distance of 1.3 m for the SC design for superconducting magnet protection, and 0.25 m for the NC design. The latter choice is to minimize the amount of induced radioactive in order to maintain the Cu-alloy to be accepted as class-C waste at the end of reactor life.…”

“…To minimize the recirculating power of the NC coils, a tapering factor of 2.5 is used for the central column design, with the narrowest radius located at the mid-plane. Similar to the ARIES-ST [6] design, the 0.5 m thick outboard TF-coil leg is also used as the vacuum vessel. To minimize the temperature of the central column, the water coolant is operated at low temperatures of T in =30°C and T out =50°C.…”

“…For both NC and SC designs, similar to the ARIES-RS [5] and ARIES-ST [6] designs, the outboard coil thickness is assumed to be 0.5 m. The volume of the toroidal and poloidal coil set as dictated by the selected geometry is then used for the costing estimate for both designs.…”