1 Forschungszentrum Karlsruhe, Association
FZK-Euratom,
(a) Institute for Materials Research I, (b) Institute for Reactor Safety,
2 Pfinzstraße 46, D-76689 Karlsdorf-Neuthard, Germany
3 FOM Institute for Plasma
Physics “Rijnhuizen”, Association EURATOM-FOM ,Nieuwegein, The Netherlands
roland.heidinger@imf.fzk.de
The upper port positions for the EC wave launching system on ITER are reserved to stabilise the Neoclassical Tearing Modes (NTM) at the q=3/2 and q=2/1 surfaces by inducing off-axis current drive. The actual mm-wave system design has defined a reference beam line based on the remote steering with focusing in the steering (poloidal) and orthogonal (toroidal) plane. The waveguide system has to be integrated into the frame of the plug (‘main structure’) and the blanket shield module that closes the gap in the blanket structure and has to provide effective neutron and thermal shielding. The boundary for in-vessel components in the port plug is set by a closure plate at which CVD diamond ‘torus’ windows form the primary tritium confinement to the mm-wave system.
The in-vessel components
including the corrugated waveguides are cooled by regular ITER blanket water
from the Primary First Wall/ Blanket heat transfer system operated at 3 MPa
with an inlet temperature of 100°C, which is increased to 4.4 MPa and 240°C under
baking conditions. For the torus window, structures that could withstand the baking
operation were analysed and found to introduce excessive tensile stresses in
the CVD diamond disk. However, for the cooling of ex-vessel components (such as
remote steering mirrors), a secondary cooling system is admissible, which can
be the base for cooling of the torus windows.
The cooling for the in-vessel
parts is designed to provide single inlet and outlet pipe connections with a
forced sequential flow through the walls of the main structure, the blanket
shield module and the internal shields. The integration of the cooling circuit
of waveguides needs additional studies, but an option is foreseen to have the
related lines branching off from cooling of the internal shield. The piping
includes dog legs for thermal expansion but no double containment even outside
the closure plate. Only three joints are foreseen for dismantling the structure
by remote handling in the hot cells. Thermal-hydraulic assessment shows good performance,
but requires refinement as the detailed data for volume heating by neutrons are
still under evaluation. The integrated cooling concept for the launcher with
details on thermal-hydraulic performance will be presented.
The CVD diamond window is exposed
to non-axially symmetric thermal loads, as there is an input steering range of
up +/- 12° projected at the corrugated waveguide. Accordingly the beam center
is shifted by up to 27 mm off the window axis. The window structure is formed
by copper cuffs which are brazed to the CVD diamond disk (aperture: 95 mm) and
connected to a stainless steel flange forming the outer housing.
Thermal-hydraulic and thermo-mechanical analysis was performed to show that
critical stress occurs in the OFHC copper structure. The stress levels
occurring for different steering angles are discussed with respect to their
tolerance in relation to available yield strength in soft copper grades.