The poloidal field coil (PFC) with a cooling pipe for nuclear fusion equipment is a very large scale coil with complex geometry. Confirmation of its reliability under operating loads must be made during the design process. The stress analysis of the coil conductor is carried out, including the following items:

  1. elastic-plastic behavior of the coil conductor
  2. large deformation that accompanies bending
  3. influence of cyclic electromagnetic forces followed by bending work of coil.
The PFC is confirmed to exhibit shakedown deformation when cyclic electromagnetic forces are applied. This analysis enables evaluation of the PFC fatigue strength where constant stress amplitude is applied under a constant mean stress. Regarding the cooling pipe joints, stress analysis is carried out to determine a reasonable structure for cooling pipe joints, given the limited space available. Experimental studies are also performed to evaluate the fatigue strength of pipe joints. As a result of these strength analyses, a bellows structure is selected as the most appropriate for the PFC cooling pipe joint.