Preliminary results and lessons learned from upgrading the Tore Supra actively cooled plasma facing components (CIEL project)

The design and fabrication of large areas of actively cooled plasma facing components (PFCs) is a major issue for the next generation of tokamaks. Tore Supra is currently the only large fusion device which has implemented actively cooled PFCs from the beginning of operation in 1988, while maintaining continuous development activities to improve their performances and reliability. High heat flux PFCs based on copper alloy heat sink structures have been developed in order to enable a large increase of power extraction capacity. The result is an actively cooled high heat flux ‘finger’ element (capable of removing up to 10 MW/m2 in normal steady state operation). It has been used first for the RF antennas edge limiters (200 fingers) and then for the toroidal pump limiter (TPL), which is the main part of the Tore Supra upgrade of in-vessel components (CIEL project). The active part of the TPL structure is made of ≈600 actively cooled elements. Problems appeared during series manufacturing of such a large number of high heat flux elements that finally led to the development of a tile attachment repair process in order to allow the achievement of the manufacturing. The whole limiter was installed inside the Tore Supra inner vessel at the beginning of 2002. Very promising first results have been recently obtained (600 MJ of injected and removed power during 3 min 30 s discharge). Monitoring and technical lessons for future realisations from these more-than-10-year developments, in particular for ITER, are discussed.