Overview of remote-maintenance scenarios for the ITER machine

Maintenance of the International Thermonuclear Experimental Reactor (ITER) will have to be carried out remotely. A preliminary study has been made of remote-handling scenarios of the main components, including blanket, divertor and coils. Frequent scheduled maintenance operations will be carried out without breaking the cryostat vacuum and by working from (shielded) containers connected to maintenance ports external to the cryostat. Exchange of the blanket is foreseen after the initial basic performance phase. This involves application of special welding and cutting techniques that will have to be developed and remotized, as well as handling of modules weighing up to 60 tonnes via complex trajectories inside the vessel and through narrow ports, whilst balancing forces will have to be applied to counteract the out-of-centre-of-gravity lifting. Maintenance scenarios are designed with radiation exposure and contamination control as an overriding requirement. This may require the use of shielded, very heavy containment casks. Following the detailed study of remote handling feasibility, equipment design will proceed up to the end of Engineering Design Activities and beyond. Development will be required for welding, cutting and inspection equipment, and for radiation-hard components, and tests will have to be undertaken to verify particularly difficult operations. (orig.)