TF Inner Leg Space Allocation for Pilot Plant Design Studies+
Authors: Peter H. Titus and Ali Zolfaghari
Abstract:
A critical design feature of any tokamak is the space
taken up by the inner leg of the toroidal field (TF) coil.
The radial build needed for the TF inner leg, along with
shield thickness , size of the central solenoid and plasma
minor radius set the major radius of the machine. The
cost of the tokamak core roughly scales with the cube of
the major radius. Small reductions in the TF build can
have a big impact on the overall cost of the reactor.
The cross section of the TF inner leg must
structurally support the centering force and that portion
of the vertical separating force that is not supported by
the outer structures. In this paper, the TF inner leg
equatorial plane cross sections are considered. Out-of-
Plane (OOP) forces must also be supported, but these
are largest away from the equatorial plane, in the inner
upper and lower corners and outboard sections of the TF
coil. OOP forces are taken by structures that are not
closely coupled with the radial build of the central
column at the equatorial plane. The "Vertical Access AT
Pilot Plant" currently under consideration at PPPL is
used as a starting point for the structural, field and
current requirements. Other TF structural concepts are
considered. Most are drawn from existing designs such as
ITER's circular conduits in radial plates bearing on a
heavy nose section, and TPX's square conduits in a case,
Each of these concepts can rely on full wedging, or
partial wedging. Vaulted TF coils are considered as are
those with some component of bucking against a central
solenoid or bucking post. With the expectation that the
pilot plant will be a steady state machine, a static stress
criteria is used for all the concepts. The coils are assumed
to be superconducting, with the superconductor not
contributing to the structural strength. Limit analysis is
employed to assess the degree of conservatism in the
static criteria as it is applied to a linear elastic stress
analysis. TF concepts, and in particular the PPPL AT
PILOT plate concept are evaluated based on amount of
space needed for structure and the amount of space left
for superconductor.
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Submitted to: Nuclear Technology Magazine (August 2012) TOFE 2012 Conference, Nashville, TN (August 27-31, 2012)
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Download PPPL-4806 (pdf 2.16 MB 6 pp)
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