ITER DIAGNOSTIC PORT PLUG DESIGN

Many of the ITER diagnostic systems will be mounted in the equatorial and upper ports of the torus, supported by removable structures known as 'port plugs'. The port plugs support the diagnostics and provide functions of baking, cooling, and neutron shielding. They must operate reliably in the demanding ultra-high vacuum, high radiation environment of the ITER tokamak for many years. Recent work on the mechanical design of the equatorial port plugs is reported, including a proposal for a new conceptual design, which uses the lid of the port plug as a structural member. The design of a complex component like this is an iterative process considering the interaction of the features of the port plug structure, neutron shielding components and diagnostic components with the electromagnetic forces induced in the structure by plasma disruptions. These electromagnetic forces are recognised to dominate the requirements for the strength of the structure. Much work has been carried out on this topic by other people, but generally this has been based on models which make assumptions about the boundary conditions. An ANSYS electromagnetic model of a half-sector of ITER has now been developed by UKAEA, to study the induced forces in the equatorial port plugs.