Proceedings of ITC/ISHW2007

Analysis of the ARIES-CS Compact Stellarator Power Plant
J. F. Lyon, L-P. Kua, L. El-Guebalyb, L. Brombergc, L. M. Waganerd, M. C. Zarnstorffa
and the ARIES TeamOak Ridge National Laboratory, PO Box 2008, MS-6169, Oak Ridge TN 37831-6169, USA
aPrinceton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543-0451, USAb
University of Wisconsin, 1500 Engineering Drive, Madison, WI 53706-1687, USAc
Massachusetts Inst. of Technology, 167 Albany St., Cambridge, MA 02139, USAdThe Boeing Company, PO Box 516, St. Louis, MO 63166, USA
lyonjf@ornl.gov

The US ARIES group has analyzed different magnetic configurations as potential fusion
power plants: different tokamaks, an ST, an RFP and a modular stellarator (SPPS). The latest
ARIES study examined compact stellarators, which combine the best features of high-current
tokamaks (moderate plasma aspect ratios, good confinement, and high plasma beta 〈β〉) withthose of large-aspect-ratio currentless stellarators (steady-state high-plasma-density operation
without external current drive or disruptions, stability without a close conducting wall or
active feedback systems, and low recirculating power in a fusion power plant).
A stellarator systems/optimization code was used to optimize the ARIES-CS power plantparameters for minimum cost of electricity (CoE) and beta subject to a large number ofvariable physics, engineering, and in-vessel component constraints. The most importantfactors determining the size and composition of the fusion power core were the allowable
neutron power flux to the wall, the distance needed between the edge of the plasma and themagnetic field coils for the intervening components and gaps, and adequate tritium breeding.
The magnetic field and coil parameters were determined by plasma performance and coil packconstraints. The previous ARIES costing approach and algorithms were updated with revisedmaterial and component costs.
An NCSX-based compact-stellarator plasma and coil configuration and a LiPb/FS/He blanket
and shield concept were used for the reference ARIES-CS power plant with R = 7.75 m, B =5.7 T, β = 6.4% and a projected CoE = 78 mills/kWhr (in 2004 $). A number of physics
assumptions (density and temperature profiles, impurity radiation levels, confinement
enhancement, β limits, alpha-particle energy losses, etc.) affected the plasma parameters, but
had little effect on the size and cost of the fusion power core. Other parameters (maximum
field at the coils, component cost penalties, different blanket and shield approaches,
alternative plasma and coil configurations, etc.) had a larger impact. In particular, the use ofan advanced LiPb/SiC blanket and shield concept like that adopted in the ARIES-AT tokamak
power plant study could reduce the CoE by approximately 17 mills/kWhr.
Optimization was not just a matter of low plasma aspect ratio. More important was having a
low plasma-coil-distance aspect ratio and a coil geometry that allowed a tapered
blanket/shield concept that can satisfy the breeding requirement. Although the MHH2 plasmaand coil configuration has a plasma aspect ratio 58% of the ARIES-CS configuration and asmaller plasma-coil-distance aspect ratio, the inability to use a tapered blanket/shield concept
drove the size and CoE for an MHH2 power plant higher than that for even an SNS-based
power plant where the plasma aspect ratio was a factor of 2.26 higher and theplasma-coil-distance aspect ratio was higher. Comparisons were also made with some earlier
ARIES power plant studies.