ITER TF Load Transfer and Precompression Assembly Process Development

In the ITER magnetic system 18 Toroidal Field coils (TF coils, or TFC) must be assembled so that the Current Center Line (CCL) of the TF magnets is correctly positioned within its tight tolerances. There are two major processes that cause large deformation of the TF coils: the load transfer toward the gravity support, occurring when the temporary inboard vertical support is removed, and the centripetal displacement due to the Pre-Compression Ring (PCR) tensioning. For those processes, specific procedures and tools are being developed, investigating at the same time the proper method to verify the procedures. Monitoring deformations and forces during the application of huge loads is the key for guaranteeing CCL quality, construction schedule, and health & safety matter. As results of the investigation, a part of the components and tools for TF PCR pre-tensioning has been changed from baseline plan: manual tightening multi-jackbolt tensioners (MJT) have been replaced with hydraulic tools and dedicated nuts. Current procedures including the tools design, the FE simulations, and the monitoring system plans are presented in this paper.