The JET remote maintenance system

One of the main objectives of JET is to reach near ignition conditions in D-T phase during an operational period of two years, when remote maintenance will be needed due to neutron activation. The maintenance criterion has been to replace rather than repair faulty components. The machine is segmented so that in case of major failure an octant can be replaced. To achieve a high degree of reliability, established technology has been applied throughout and in particular to vaccum, fluid and electrical connections, which are defined and standardised in the remote handling manual. To cope with the complexity and unpredictability of the tasks likely to be required, a flexible system, consisting of general purpose handling devices positioned by large transporters and supplemented by special tools, has been adopted. For remote operations within the vacuum vessel the transporter is an articulated boom which can reach all around the torus through a horizontal port. It carries either a manipulator or end-effectors for handling heavy components. Outside the vessel a crane-mounted telescopic mast will position a manipulator all around the machine, working in combination with lifting facilities provided by the main hook of the crane or by an auxiliary jib crane mounted on the telescopic mast, and in areas not accessible from above, by a low-level transporter. Periodic inspections of the interior of the vessel have to be done to check for damage due to plasma disruptions. Our system scans the vessel under vacuum using four TV probes through small apertures in the top of the vessel and can work at operating temperature (300 deg. C). Remote handling specialists vet the design of all systems classified as requiring remote handling, and prepare procedures for the envisaged maintenance. Mock-up tests lead to the identification of special tools and computer-aided techniques which may be needed. Experience was gained in installing antennae and limiters during the last shutdown. (author). 10 figs, 1 tab