Progresses in the structural assessment of the central region of a HELIAS 5-B breeding blanket half sector

Within the framework of EUROfusion action, the HELIcal-axis Advanced Stellarator (HELIAS) is considered as a possible long-term alternative to a tokamak DEMOnstration power plant (DEMO). From the plasma physics point of view, the HELIAS 5-B is a very promising reactor concept. It consists in a large 5 field period stellarator reactor directly extrapolated from Wendelstein 7-X. Intense studies are currently ongoing at KIT in order to achieve a preliminary design of a breeding blanket (BB) for the HELIAS 5-B reactor which takes the outcomes from the preconceptual design of the tokamak DEMO BB into account. To this end, the Helium-Cooled Pebble Bed (HCPB) and the Water-Cooled Lithium Lead (WCLL) BB concepts have been considering, focusing on the investigation of the suitability of their main structural features to the stellarator geometry. In this regard, possible design constraints coming from the Remote Maintenance (RM) have to be fulfilled in order to better align the blanket segmentation. In the present work a more sophisticated structural assessment of the central region of a HELIAS 5-B BB half sector has been performed, paying attention to the predicted displacement field. The study has been aimed at the refinement of the numerical model so far adopted, investigating the impact of the major assumptions, such as Vacuum Vessel (VV) temperature and equivalent Young's Modulus, on the obtained results. The results are herewith presented and critically discussed, giving some hints for the follow-up of this activity.