Assessment of a cooperative maintenance scheme for ITER divertor cooling pipes

Divertor cassettes will require scheduled maintenance during the lifetime of ITER. Standard maintenance procedures for cassette removal include connection/disconnection operations of the cassette body from the reactor frame. Remote handling (R.H.) means are therefore required to remove the electrical connector and cut/weld the cassette cooling pipes. Evolutions of ITER design focused on a reduction of the divertor cooling pipes from the initial 6 in. straight pipes to 2.5 in. bent pipes. As a consequence of this new definition, the initial maintenance scheme where maintenance is completely performed from the inside of the pipe by one carrier becomes obsolete. A solution based on the cooperative work between a carrier sent into the pipe to perform part of the maintenance operations and an orbital tool positioned by a manipulator mounted on the Cassette Toroidal Mover (CTM) has been devised. A reference working area is defined and used to perform CAD simulations with a manipulator model. Work area accessibility is assessed using a virtual cutting/welding orbital tool