Special Issue on Robotics and Mechatronics for Fusion Experimental Reactor (ITER)

Engineering design activities (EDA) demonstrating the science and technology for the International Thermonuclear Experimental Reactor (ITER), are being conducted based on the four-party international collaboration of Japan (JA), the U.S.A (US), Europe (EU), and Russia (RF). EDA basically concerns engineering design required for ITER construction and technical development confirming design feasibility. In engineering R&D design, the central role is being played by an International Joint Design Team (JCT) consisting of scientists and engineers from the four parties, conducting work on detailed component design, buildings and plant facilities design, safety analysis and evaluation, and comprehensive overall system design. In engineering R&D, whose final objective is to demonstrate engineering technology necessary for ITER construction, a wide variety of technical development ranging from data acquisition on material characteristics to verification of system performance is being conducted through equal participation of the four parties. Because of the importance of principal ITER components, such as superconducting coils, vacuum vessel, in-vessel components such as diverters and blankets, and remote maintenance equipment, a large-scale project has been set up for manufacturing prototypes, including full-scale models, and for demonstrating performance. In-vessel components such as blankets and divertors are exposed radioactivity of 14 MeV neutrons due to DT operation, and therefore must be maintained or replaced remotely. Plansbased on stage-by-stage ITER operation call for shielding blankets to be replaced by blankets for breeding tritium. Diverters require scheduled maintenance and replacement because they are subjected to severe plasma heat and particle loads. For in-vessel components that undergo scheduled maintenance, remote maintenance is an important technical issue that may affect the performance of ITER, so component structures and layout consistent with remote handling receive top priority and will be subjected to remote maintenance demonstration-testing of using full-scale models. Remote ITER maintenance focuses on technologies involving radiation-hard devices designed for a gamma radiation environment, remote operation and metrology and control for precisely handling heavy in-vessel payloads, and welding and cutting and inspection in narrow confines. Thus, use must be made of robot technologies in Japan and a design concept conceived that meets unique ITER needs. Because device handling precision, the working environment, and other factors surpass conventional technical levels, technical data on large-scale tokamaks, experience in handling heavy payloads in industry, and nuclear field environmental resistance must be studied and system development, including technical demonstrations, conducted on a full engineering scale. This is the backer of ITER device design and development. Good prospects exist for developing a large number of remote maintenance equipment satisfying ITER specifications through the development of a new remote maintenance concept that calls for the handling of heavy payloads with high precision, the acquisition of technical data confirming concept feasibility, the development of components having 2 to 3 times higher resistance to radiation than anything available previously, and the development of remote maintenance based tools that cut, weld, and inspect in narrow confines. In final development, steady progress is being made in fabricating, testing, and demonstrating full-scale remote maintenance. This Special Issue summarizes these achievements and provides an overview of the remote maintenance design on in-vessel components, introducing current status and plans on remote maintenance technology in which the Japan Home Teams is engaged in. Topics covered include the following: 1. Remote Maintenance Development for ITER 2. Blanket Remote Maintenance Development 3. Diverter Remote Maintenance Development 4. In-Vessel Metrology and Viewing Development 5. Pipe Welding and Cutting Tool Development 6. Pipe Inspection Tool Development 7. Thick-Plate Welding and Cutting Tool Development 8. Radiation-Hard Component Development 9. Standard Component Development 10. Data Acquisition and Control