ITER divertor, design issues and research and development

Over the period of the ITER Engineering Design Activity (EDA) the results f rom physics experiments, modelling, engineering analyses and R&D, have been brought together to provide a design for an ITER divertor. The design sati sfies all necessary requirements for steady state and transient heat flux, nuclear shielding, pumping, tritium inventory, impurity control, armour lif etime, electromagnetic loads, diagnostics, and remote maintenance. The desi gn consists of 60 cassettes each comprising a cassette body onto which the plasma facing components (PFCs) are mounted. Each cassette is supported by toroidal rails which are attached to the vacuum vessel. For the PFCs the fi nal armour choice is carbon-fibre-composite (CfC) for the strike point regi ons and tungsten in all remaining areas. R&D has demonstrated that CfC mono blocks can routinely withstand heat loads up to 20 MW m(-2) and tungsten ar mour > 10 MW m(-2). Analysis and experiment show that a CfC armour thicknes s of similar to 20 mm will provide sufficient lifetime for at least 1000 fu ll power pulses. The thickness of the cassette body is sufficient to shield the Vacuum vessel, so that, if necessary, rewelding is possible, and also provides sufficient stiffness against electromagnetically generated loads. The cassette design provides efficient and proven remote maintenance which should allow exchange of a complete divertor within similar to 6 months. (C ) 1999 Elsevier Science S.A. All rights reserved.