Attachment system for DEMO in-vessel conponents: blanket, manifold and hot ring shield

On the way to the first commercial nuclear fusion reactor (DEMO) new conceptual studies tackling the design of the in-vessel components and their integration into the reactor have been initiated. The main in-vessel components are the breeding blankets, the helium supply unit, namely the manifold, and the hot ring shield. For enabling the handling of these large components the in-vessel reactor components have to be segmented. With regards to this a new so called Multi-Module-Segment (MMS) concept has been developed, whereas blanket and manifold constitute vertical non-permanent segments to be installed and dismantled with remote handling tools through the upper port of the reactor. Each MMS consists of a number of blankets connected to a manifold block containing the helium cooling channels. The blankets which have to sustain the fuel cycle by breeding tritium and are also used to extract the produced heat are exposed to high thermal and mechanical as well as pressure loads. Therefore, the attachment system between blanket and manifold needs to be flexible to compensate different thermal expansion, but also needs to be stiff enough to withstand the loads during normal as well as non-normal operation, e.g. disruptions. The MMS itself are attached to the permanent hot ring shield (HRS) structure. Since between the hot ring shield and the vacuum vessel also temperature differences are existent the attachment system between MMS and HRS needs to be capable of compensating different thermal expansions. Additionally it needs to support the weight of the components and disruption loads, whereas remote handling is required for maintenance operations from inside the vacuum vessel. The development of such an attachment system is a major engineering challenge, requiring reliability under harsh environmental and loading conditions. In this report requirements and proposals for possible solutions for the attachments between vacuum vessel and hot ring shield, between hot ring shield and MMS and between the manifold and blankets will be presented. (orig.)