(FT/1-5) Advanced Qualification Methodology for Actively Cooled High Heat Flux Plasma Facing Components
1) Association Euratom-CEA, Cadarache, France
2) IPP Garching, Germany
3) ITER Team, Garching, Germany
Abstract. High heat flux plasma facing components (PFCs) in steady state fusion devices require high reliability. This can be only guaranteed by a very high level of qualification obtained with a rigorous acceptance inspection protocol. These components have to withstand heat fluxes from the plasma in the range of 10-20 MW/m2 involving a number of severe engineering constraints: (i) the armour materials must be refractory and compatible with plasma wall interaction requirements; (ii) the heat sink should have a high thermal conductivity, high mechanical resistance and sufficient weldability behaviour; (iii) the cooling system, which is generally based on a circulation of pressurized water in the PFCs heat sink, must offer a high thermal efficiency; (iv) the joint of the refractory armour material onto the metallic heat sink,. To meet the power exhaust needs of PFCs during plasma operation requires control of their thermal and mechanical integrity. The first step is to detect defects in the element, such as material discontinuities like cracks and debondings. These will cause hot spots on the armour materiel and may even lead to the destruction of the PFC e.g. critical flux event. As the heat exhaust capability and the PFCs lifetime during plasma operation will stem from the manufacturing quality, a set of qualification activities should be performed during the component development and subsequent manufacturing phases. The major progress brought by this methodology stems from the combination and the correlation of three techniques: thermomechanical modelling, high heat flux testing and advanced non-destructive techniques, such as active infrared thermography. The scheme is applied during all the qualification activities: research and development phase, prototype manufacture including damage study for high heat flux, first series fabrication to define acceptance criteria and commissioning of the series fabrication. The paper describes the qualification route, which has been followed in order to define an acceptance criterion for CFC based flat tile target elements for the TORE SUPRA series production and more recently for the W7-X component first series production. First investigations for the ITER Divertor elements, which are more challenging due to the thicker armour material and the more complex monoblock geometry, are also presented.
Full paper and slides available (PDF)