Prime pagine RA2010FUS:Copia di Layout 1 - ENEA - Fusione

052
progress report
2010
allows a very uniform temperature distribution to be achieved by the pipes and gives the opportunity to have
a single manifold for each segment, thus minimizing the eddy current effects on the structure and easing the
system remote handling. The heat load impinging on the FW is, on average, 1 MW m –2 , with about
3MWm –2 peak. The First Wall is designed to be actively cooled down by pressurized water flowing with a
rate of 5 m s –1 , able to keep the temperature around 200°C in order to avoid any impurities adsorption. The
design will be compatible with a completely remote handling and maintenance.
Vacuum vessel design
The vacuum vessel (VV) provides for vertical (up, down), oblique (up, down) and equatorial access ports (90 in
total) for the plasma diagnostics, the vacuum, the auxiliary heating, the in–vessel remote handling (RH)
maintenance and all of overall the systems that get to the vacuum vessel [2.10]. Special machine ports were
designed to accommodate a 10 MW (45° inclined on the plasma cord) NNBI system (fig. 2.11) [2.13].
The equatorial ports are characterized by an aperture shape that is relatively high and rather narrow. Two
ports are one side enlarged to accommodate the NNBI beam. Since the beam are injected 45° on the magnetic
axis the port available space is reduced. This configuration has been chosen to assure the best compromise
between the narrow spaces and the designed 10 MW of power input to be supplied. Although at high density
practically no shine–through is predicted, in case of low density operation a dump plate protection must be
foreseen in the inner and outer first wall.
Neutral beam
Critical
points
NBI equatorial port
Calorimeter
Beam line vessel
Figure 2.11 – Horizontal section of the NNBI system
access port at FAST
Figure 2.12 – FAST toroidal module
The vacuum system has to reach a base pressure of
about 1×10 –7 Pa, in order to minimise the presence of
any possible residual impurities in the vacuum vessel
before the plasma discharge. By allowing for a specific
outgassing rate (after all cleaning procedures) of
6.7×10 –9 Pa m 3 s –1 m –2 , the needed effective pumping
speed is about S eff
=2.2 m 3 s –1 . The conductance
between a pump and the vacuum vessel is dominated
by the conductance of the vacuum line between the
pump and the port, the dimensions of the latter being
rather large. As a result the overall pumping speed
must be about 4.25 m 3 s –1 and therefore 4
turbomolecular pumps, with pumping speed of
1.5 m 3 s –1 will have to be used.
Toroidal field coil system
The toroidal field coils (TFC) system has a 20°
modular configuration (fig. 2.12), with a total of 18
coils. Each coil consists of 14 oxygen free copper plates
suitably worked to realize 3 turns in radial direction.
The turns of each coil are welded on the most external
region in order to obtain a continuous helix and the
plates are tapered at the innermost region to realise the
wedged shape. A conceptual design of the feeding bars
has been done, keeping in account the “return
currents” for each coil: the relevant preliminary 3D
electromagnetic analysis has not indicated any
noticeable perturbation introduced by the bars. In the
highest performances H–mode scenario, a field of
8.5 T is foreseen at the major radius R 0
=1.82 m; this
corresponds to a total of 76.5 MA–turn, i.e., to
101.1 kA per turn. The maximum radial inward force
acting on each TFC is 66.5 MN, while the vertical
force on half of the TFC system is 690 MN, for the
highest performance case. An appropriate structural