1. magnetic confinement - ENEA - Fusione

3. FUSION TECHNOLOGY 65
3.1.1 Introduction
3.1 Technology Programme
In 2001, ENEA contributed to the Next-Step and Long-Term Programmes, the Power
Plant Conceptual Studies and Underlying Technology, in the framework of the
European Fusion Technology Agreement (EFDA).
The activities covered almost all the R&D fields: vesssel in-vessel (blanket, first wall
and divertor, remote handling, fuel cycle); magnets (conductor development, coil
tests); safety (including site and socio-economic studies); physics integration
(neutron diagnostics); long-term activities (breeding materials; structural materials,
liquid metal technology, helium-cooled components, IFMIF).
Further to the fusion activities, some valuable applications were developed in the
field of nuclear detectors. Experimental campaigns were carried out on new
hydrogen energy and plasma-focus studies.
The technology activities were performed at the Frascati and Brasimone laboratories,
with valuable contributions from other ENEA laboratories. Significant industrial
collaborations were also established.
It is worth mentioning that the three patents granted in 2001 resulted from the R&D
activities.
3.2 First Wall and Divertor
3.2.1 Influence of manufacturing heat cycles on CuCrZr properties
(ITER Task DV4/04)
CuCrZr alloy is one of most suitable materials for heatsinks in the ITER plasmafacing
components (PFCs). The main problem of the alloy is that its thermal and
mechanical properties degrade as soon as 450°C is exceeded, e.g., during the
component manufacturing process or during operation in off-normal conditions.
A parametric study of the degradation was carried out to define the safe working
limits of CuCrZr and to choose the best thermal cycle for the component
manufacturing. The specific aim was to envisage the temperature and the influence
of the thermal treatment time on the mechanical and thermal properties of this ITER
grade alloy.
Hence, CuCrZr, in the solution annealing/water quench condition, was subjected to
different heat treatments at temperatures of 475, 500, 550, 600 and 700°C and hold
times of 5, 10, 20, 30, 40, 60, 120, 180, 240, 300 and 360 min. The reference ageing
treatment for CuCrZr is 3 h at 475°C, which corresponds to a hardness of 130 HV.
This is lower than the HV (159) of the as-received condition, due to the cold work
effect. Assuming a minimum acceptable value of 100 HV for the mechanical strength
of CuCrZr (which should guarantee a tensile strength in excess of 300 MPa at room
temperature), a hot isostatic pressing (HIP) temperature as high as 550°C would be
acceptable.
A previous study by the Joint Research Centre (JRC) Ispra, aimed at establishing the
minimum cooling rate required by the annealing temperature, had demonstrated
that successful ageing of CuCrZr can only be achieved if the cooling rate is at least 2
K/s from 970 to 870°C, and after that, faster than 1 K/s. Analysis of the results
showed that a HIP temperature of ~550ºC is probably the best compromise for a
reliable manufacturing process.
The results also confirmed that, starting from an ageing condition, a hold time of