Structural integrity for DEMO: An opportunity to close the gap from materials science to engineering needs

It is clear that fusion demonstration devices offer unique challenges due to the myriad, interacting material degradation effects and the numerous, conflicting requirements that must be addressed in order for in-vessel components to deliver satisfactory performance over the required lifetime. The link between mechanical engineering and materials science is pivotal to assure the timely realisation and exploitation of successful fusion power. A key aspect of this link is the verification of structural integrity, achieved at the design stage via structural design criteria against which designs are judged to be sufficiently resilient (or not) to failure, for a given set of loading conditions and desired lifetime. As various demonstration power plant designs progress through their current conceptual design phases, this paper seeks to highlight key shortfalls in this vital link between engineering needs and materials science, offering a perspective on where future attention can be prioritised to maximise impact. Firstly, issues in applying existing structural design criteria to demonstration power plant designs are identified. Whilst fusion offers particular challenges, there are significant insights to be gained from attempts to address such issues for high performance, high integrity applications in other demanding environments. Therefore case studies from beyond fusion are discussed. These offer examples where similar shortfalls have been successfully addressed, via approaches at the design stage and through service lifetime in order to deliver significant insight for structural materials and improved design solutions for first-of-a-kind engineering endeavours where the consequences of failure were of similar concern. Finally, drawing inspiration from these case studies, the current state-of-the-art is explored to propose how both materials science and engineering should be aligned in order to address the issues we face in realizing effective fusion demonstration power plants. (C) 2016 EURATOM/CCFE Fusion Association. Published by Elsevier B.V. All rights reserved.