Design of in-vessel components for ITER

Abstract

This paper reviews the present design status of the major in-vessel components of ITER: the blanket, the divertor and the vacuum vessel. Substantial emphasis in the design of all in-vessel systems is given to the maintenance concept. For the blanket, integrating the remote handling approach with a robust design capable of reacting all thermal and mechanical loads is particularly challenging. A modular approach to the blanket design has been selected and both welded and mechanical attachments of the modules to the toroidal backplate are being evaluated. Transient thermal behavior produces deformations and stresses which must be carefully taken into account in the module attachment, in addition to the disruption loads. The divertor design is also modular and consists of 60 cassettes on which the high-heat flux components are mounted. These components can be replaced in hot cells. Transport of the cassettes into and out of the machine is accomplished by rotating them on the mounting rails installed in the vessel and pulling or pushing them radially outwards through dedicated ports. A mix of plasma facing materials has been provisionally identified: CFCs for the high-heat-flux targets, tungsten for areas bombarded by high neutral fluxes and Be for the remainder of the machine. While the vacuum vessel is of conventional double-wall design, it forms the first confinement barrier and all load cases must be carefully considered in the structural analysis. In all cases examined, the stresses are within allowables permitted by the codes when the appropriate load classification is considered.