EDITH experimental in-torus maintenance system for fusion reactors

With respect to the special environmental conditions - elevated γ-radiation and temperature - in the plasma chamber of a fusion reactor like NET/ITER, maintenance and replacement tasks can be performed only by means of remote handling systems. EDITH (Experimental Device for In-Torus Handling) is the prototype of such a system. It is based on an articulated boom transporter which can be equipped with different end-effectors and tools, respectively, depending on the different tasks to be carried out. EDITH is the central component of a testbed constructed in full scale to investigate experimentally remote handling operations in the simulated section of a plasma chamber. As typical tasks the replacement of protective tiles and divertor plates have been performed. In order to allow the operators a fast and reliable performance of the tasks an advanced guidance and control system has been developed. The guidance system forms a remote handling workstation which, together with the servo-manipulator, represents the man/machine interface for the control and surveillance of all devices. The workstation supports the operators at all operations to be manually controlled, at the planning, simulation and programming of automatically performed subtasks. It serves also as a permanently available documentation system and information source. The driving factors for the conceptual design of the control system were the dynamic behaviour, the operational reliability and the cooperation with the guidance system. Qualification tests and first practical experience confirm that this type of remote handling techniques permits to perform in-vessel maintenance tasks safely, reliably and in appropriate time. (orig.)