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20110816_icc_talk_ghn_r1.pdf2011-08-21 19:42:14G. Neilson

Stellarators as Pilot Plants and Power Plants

Author: G. H. Neilson
Requested Type: Consider for Invited
Submitted: 2011-06-09 19:01:19

Co-authors: M.C.Zarnstorff

Contact Info:
Princeton Plasma Physics Laboratory
P.O. Box 451, MS-38
Princeton, NJ   08543
U.S.A.

Abstract Text:
With the “ITER era” now well under way, the world fusion community is considering the next major steps in magnetic fusion energy (MFE) R&D. In the U.S., there is interest in a class of facilities, called fusion nuclear science facilities (FNSF), with missions that include development of steady-state DT operating scenarios, first wall and blanket technology, and tritium self-sufficiency. A scoping study led by PPPL has been examining options for an MFE pilot plant, a device that would support those missions and in addition would generate net electricity and prototype the machine configuration and maintenance scenario of a power plant. Net electricity generation requires a level of overall plant efficiency that is challenging, given realistic assumptions about plasma current drive efficiency and the wall plug efficiency of heating sources, for the advanced tokamak (AT) or spherical tokamak (ST). This is because external current drive and/or profile control is required to sustain these magnetic configurations. Stellarators are found to have a large advantage in this regard, since they require no current drive. A stellarator pilot plant design based on a quasi-axisymmetric (QA) configuration with aspect ratio 4.5, major radius 4.75 m, and magnetic field on axis of 5.6 T has a Qeng (ratio of electricity produced to electricity consumed) of 2.7 and an average neutron wall load greater than 1 MW/m2. The QA design is comparable in size to an AT pilot plant design having similar neutron wall load but Qeng of only 1, and can rely extensively on the tokamak data base since it shares many confinement physics properties with tokamaks. Currently, the lack of a magnet design compatible with rapid changeout of internal components is a disadvantage for the QA stellarator but a two-year ICC-supported program identified several feasible strategies for improving the engineering characteristics of stellarator magnets. The absence of an experimental test of QA stellarator physics properties is also a disadvantage, but the existence of a practical experimental device design and research program to develop the basic information has been demonstrated. If there were a decision to move rapidly toward a net-electricity generating MFE system such as a power plant, the stellarator would be a logical candidate, and the R&D programs needed to resolve these issues would be readily justified.

Characterization: A1,A3

Comments:

University of Washington

Workshop on Innovation in Fusion Science (ICC2011) and
US-Japan Workshop on Compact Torus Plasma
August 16-19, 2011
Seattle, Washington

ICC 2011