Structural analysis of the back supporting structure of the DEMO WCLL outboard blanket

Abstract Within the framework of EUROfusion R&D activities an intense research campaign has been carried out at the University of Palermo, in close cooperation with ENEA Brasimone, in order to investigate the thermo-mechanical performances of the outboard segment Back-Supporting Structure (BSS) of the DEMO Water-Cooled Lithium Lead breeding blanket (WCLL). In particular, the configuration of the outboard segment BSS, purposely set-up by the WCLL project team during 2015 according to the blanket “multi-module system” concept, has been taken into account in order to study its steady state thermo-mechanical behaviour, paying attention to the simulation of both modules-BSS and BSS-vacuum vessel attachment strategies and concepts. The research campaign has been mainly intended to investigate the thermo-mechanical performances of the outboard segment BSS when subjected to both the thermo-mechanical and electro-magnetic loads it is foreseen to undergo under particularly critical steady state loading conditions. A theoretical-numerical approach, based on the Finite Element Method (FEM), has been followed and the qualified ABAQUS v. 6.14 commercial FEM code has been adopted. The thermo-mechanical behaviour of the BSS has been assessed in order to verify its compliance with the design criteria foreseen for the structural material. To this purpose, a stress linearization procedure has been performed along the most critical paths located within the highly stressed BSS regions, in order to check the fulfilment of the rules prescribed by the SDC-IC safety code. Results obtained are herewith presented and critically discussed, highlighting the open issues and suggesting the pertinent modifications to the BSS geometric design aimed to obtain the complete fulfilment of the prescribed safety criteria.