The impact on remote maintenance of varying the aspect ratio and number of TF coils for DEMO

As part of the conceptual design studies for a European DEMO, different tokamak geometries are being considered. As identified in the EFDA Roadmap to the realisation of Fusion Energy, 2013: “The integration of the Remote Maintenance system within the DEMO plant is an essential task within the DEMO CDA phase. This will involve establishing requirements, functions and interfaces with many other systems to ensure that plant availability and maintainability are considered from the outset.” In order to fulfil this integration requirement different geometries of DEMO have been assessed for their impact on remote maintenance (RM). The aspect ratio and number of TF coils have been identified as the pivotal variables, driving the tokamak geometry, with significant effects on remote maintenance both in terms of technical feasibility and speed of operation. Tokamak geometries with aspect ratios from 2.6 to 4.0 and 16 or 18 TF coils have been compared. The results of this evaluation show that higher aspect ratios and lower numbers of TF coils are beneficial to RM both in terms of technical feasibility and speed of operations. To deliver a maintainable DEMO, efforts must be made to maximize its aspect ratio and minimize the number of TF coils.