Page 151 - Fundamentals of Magnetic Thermonuclear Reactor Design

Superconducting Magnet Systems Chapter | 5 133

FIGURE 5.10 Cross-section of the first-generation superconducting cables [1].

FIGURE 5.11 Cross-section of the second-generation superconducting cables for fusion
applications [5].

NbTi in terms of mechanical performance, but can stand strong magnetic
fields, is the preferred choice for the TFCs and the CS. For example, OTR,
the Russian hybrid (fusion–fission) reactor, uses the NbTi and Nb Sn SCs
3
for its 7-T and 12-T coils, respectively. The operating current in the coils is
40 kA.
The conductors in Fig. 5.10 use a massive copper matrix. In present-
day tokamaks, including ITER, the rate of the magnetic field change is
1–2 T/s. Under such conditions currents induced in the copper matrix may
cause a strong heat release within the coil winding producing additional
load on the cryogenic system and opening up the potential for normal zone
development.
This limitation does not apply for forced-flow cooled cable-in-conduit con-
ductors (CICCs). CICCs are multistage twisted cables made of superconducting
strands, housed in a stainless-steel tube or jacket (Fig. 5.11) with one-phase
supercritical or two-phase helium circulated through the cooling channels. The
helium-tight jacket acts as a mechanical structure and protects the cable against