Construction of structural design guidelines for vacuum vessels and other components

Since November 1990, systematic research has been carried out in preparation for a Japanese draft of structural design guidelines for an experimental fusion reactor. This paper summarizes the major results of the work and the status of these efforts. At first, failure modes to be prevented by design standards were extracted by considering the materials, configurations and operating conditions of International Thermonuclear Experimental Reactor (ITER) components. Applicability of the current design standard was discussed by considering failure modes in the second stage. Specific issues regarding the individual components were also discussed. Major difficulties in vacuum vessel were how to classify stress due to magnetic load, how to define evaluation cross-section in complex 3-dimensional structures and how to estimate fatigue life of weldments. In designing in-vessel components (IVCs) such as blankets and divertors, the significant reduction in uniform elongation capability caused by heavy neutron irradiation should be taken into account. The validity of the existing structural design method was also confirmed by comparing the elastic–plastic design limit for virgin material, the elastic design limit for irradiated material and the fracture mechanics design limit for irradiated material.