Design progress of the VV sectors and ports towards the ITER construction

The ITER vacuum vessel (VV) is an all-welded torus-shaped double-wall structure with stiffening ribs between the shells. The VV main function is to provide the high-vacuum and primary confinement boundary. The vessel also supports in-vessel components such as the blanket modules and the divertor cassettes. Along with these components, the VV provides radiation shielding - the neutron heat is removed by water circulating between the shells. To satisfy the manufacture and assembly needs, the VV consists of nine sectors. To provide access inside the vessel for auxiliary plasma heating, diagnostics, vacuum pumping and other needs, the VV is equipped with upper, equatorial and lower ports. The upper and regular equatorial ports are occupied with the port plugs. In addition, there are three ports at the equatorial level dedicated for neutral beam (NB) injection. As the ITER construction phase approaches, the VV design has been improved and developed in more detail with the focus on improved manufacture and reduced cost. Based on achievements of manufacturing studies being performed in cooperation with industry, design improvement of the typical VV sector (1) has been nearly finalized. Design improvement of other sectors is in progress - in particular, of the VV sectors 2 and 3 which interface with the NB ports. For all sectors, the concept for the in-wall shielding has been improved and developed in more detail. The design progress of VV sectors 2-3 has been accompanied by progress in the NB port design (including the beam-facing components to handle the heat flux input of the neutral beams). Design of other port structures has also progressed. Thus, supporting and sealing components between the port plugs and the ports have been further developed with the focus on improved structural performance and maintenance. At the lower level, there are full-size ports, and the pipe feedthroughs and local small penetrations. Design of all port structures at this level has progressed towards completion. At this stage of the project, special attention is paid to the code related aspects of the machine. For the vacuum vessel, an addendum to the existing nuclear code is being developed to address the VV design/manufacture peculiarities and facilitate its acceptance by the licensing authorities. This work is being performed by the EU organizations in close cooperation with the ITER design team. Details of the current VV design and results of the related studies are reported in this paper. (orig.)