Structural analysis for an upper port of the ITER vacuum vessel

The international thermonuclear experimental reactor (ITER) vacuum vessel (VV) upper port has a trapezoidal/rectangular cross-section and consists of a port stub, a stub extension and a port extension with a connecting duct. To investigate the structural integrity and to increase the structural reliability of the VV and ports, the structural analyses of the upper port structure have been performed. Two advanced designs from the ITER international team have been deeply analyzed. To verify the strength of the reinforcing ribs for the connecting duct and of the fastening/sealing units, the local analyses utilizing the sub-modeling technique have been performed. The upper port flange based on the original design could withstand design loads, but the flange surface could be detached under the design condition. The advanced design using large superbolts is highly acceptable in the structural design point of view. The deflection of the plug for the other advanced design with a removable flange is relatively large since the stiffness of a port and a plug is reduced by the nut groove and the removable flange