FED/INTOR critical issues assessment of toroidal field coil options

This report is an assessment of the TF-coil options generally regarded as appropriate for near-term tokamak reactors such as FED and INTOR, which require peak fields in the 10 to 10 T range, and which feature external equilibrium field coils. The basic TF-coil options reviewed are: forced flow cable-in-conduit; 4.2 K bath-cooled Nb3Sn/NbTi cable; superfluid (He II) bath-cooled NbTi cable. Two forced-flow conductor/coolant configurations are reviewed: Nb3Sn cable-in-conduit, 4 K outlet to produce 11 to 12 T (INTOR); NbTi cable-inconduit, 3 K outlet to produce 10 T (FED). Also, the 4 K bath-cooled Nb3Sn/NbTi monolithic conductor option for FED was reviewed. Toroidal field coil requirements for FED and INTOR are presented. A comparison of cooling, superconductor, and configuration alternatives is presented, independently of specific option configurations. Alternatives discussed are bath cooling vs forced flow; He I vs He II bath; NbTi vs Nb3Sn; monolithic vs cabled conductor; distributed vs case support of winding pack and out-of-plane load support. Reference and normalized option configurations are presented. Reference configurations for FED and INTOR are the manifestation of each concept as developed by its originator. (For example, the NbTi cable-in-conduit forced-flow configuration identified by the Design Center staff as the baseline design for FED 81.) In order to provide a mutually consistent basis for comparison of the option configurations, certain normalization adjustments were performed upon the reference FED concepts. The basic TF-coil/cooling/structure option configurations are evaluated as to their relative appropriateness for FED and INTOR. In order to present the assessment in coherent manner, the various aspects are grouped as follows: technology maturity; reactor compatibility; reliability; and cost