DEMO single null inner mid-plane limiter RM feasibility study

Abstract

DEMO is a key part of the EU fusion roadmap, where the programme is reaching the end of the pre-conceptual phase with a gate review in 2020. As part of the work to complete this phase, eight Key Design Integration Issues (KDIIs) have been identified as critical to the programme [1] (Bachmann, 2020). Within KDII#1 (Wall protection to withstand plasma transients) the feasibility of the Inner Mid-plane Limiter (IML) is assessed from a remote maintenance perspective.The IML is an actively cooled component attached to the inner ring of the tokamak torus, with access for removal and installation only possible from the plasma facing side. The IML service life is less than that of the Breeder Blankets (BBs), due to the foreseen transients and/or the CuCrZr cooling pipes that have limited irradiation lifetime. This drives the need to change the IML with the BB in position. When replacing the IML, the pipework is expected to be too highly irradiated to allow re-welding. This drives the need to change the pipework to the IML, a challenging task when the BB are in their installed position.This paper presents the preliminary development of a maintainable IML concept, including: the development of the IML fastening for remote maintenance; a proposal for a new IML cooling pipe chute; and the rationale for the options selected.