1. magnetic confinement - ENEA - Fusione

66
3. FUSION TECHNOLOGY
3.2 First Wall and Divertor
600°C leaves the mechanical properties at acceptable values, although better results
can be expected from a manufacturing process that starts from an as-received
condition, with the temperature kept below or equal to 650°C.
3.2.2 Manufacturing of small-scale W monoblock mockups by hot
radial pressing (ITER EFDA R&D Tasks)
The aim of this activity is to develop an alternative technique for manufacturing the
ITER PFCs, which have a monoblock geometry (i.e. the vertical target).
The basic idea is to perform radial diffusion bonding between the cooling tube and
the tungsten tile, with the process parameters such that degradation of the thermalmechanical
properties remains limited.
The feasibility of joining Cu//Cu and Cu//W by diffusion bonding was studied,
and some small-scale W monoblock mockups were successfully manufactured by
placing them inside a special stainless steel container that does not deform during
HIP, and tested for thermal fatigue (20 MW/m 2 for 1000 cycles).
Following the good results obtained in the tests, a canister was then designed to
perform hot radial pressing (HRP) in a standard furnace in which only a section of
the canister (fig. 3.1) is heated and just the internal tube is pressurised up to the
bonding pressure. The main advantage of this technique compared to HIP is that
neither a high temperature/pressure furnace nor machining of the sheath is
required.
A dummy component was first tested using the following process parameters:
temperature 600°C and pressure 700 bar applied for 3 h. The tests confirmed the
capability of the canister to withstand the load conditions required by HRP.
3.2.3 Runaway electrons on ITER PFCs (EFDA Contract /00-520)
In 2001, the assessment of the thermal effects of runaway electrons (RAEs) on the
ITER-FEAT plasma-facing components was concluded [3.1, 3.2].
The integrated, versatile, multi-particle Monte Carlo code FLUKA was used to get
the energy deposited inside the PFCs by a 10- or 15-MeV RAE impinging on the firstwall
structures with an incidence angle of 1°. The geometrical model is a 3-D layered
structure divided into 24 unit regions centred on the cooling tubes. Starting from the
plasma, the model consists of armour, heatsink, cooling tube and coolant. Constant
conditions were assumed in the poloidal direction. Five different geometries were
investigated: 1) primary first wall armoured with Be (with and w/o protecting
carbon fibre composite (CFC) poloidal limiters); 2) two port limiter first-wall options;
3) Be flat tile; 4) CFC monoblock; 5) divertor baffle first wall armoured with W. The
deposited energy density, normalised to one electron, for the Be-armoured first wall,
and a 10-MeV RAE is shown in figure 3.2.
∅54
∅26
[3.1] G. Maddaluno, S.
Rollet, G. Maruccia,
Thermal effects of
runaway electrons on
ITER plasma facing
components, EFDA
Contract 00-520 - Final
Report - September 2001
[3.2] G. Maddaluno et al.,
Energy deposition and
thermal effects of
runaway electrons in
ITER-FEAT plasma
facing components, in
preparation
115
150
Fig. 3.1 - Cross section of
the canister.