Overview of EU DEMO design and R&D activities

Blanket/first wall challenges and required R&D on the pathway to DEMO

Demonstrating the production of net electricity and operating with a closed fuel-cycle remain unarguably the crucial steps towards the exploitation of fusion power. These are the aims of a demonstration fusion reactor (DEMO) proposed to be built after ITER. This paper briefly describes the DEMO design options that are being considered in Europe for the current conceptual design studies as part of the Roadmap to Fusion Electricity Horizon 2020. These are not intended to represent fixed and exclusive design choices but rather ‘proxies’ of possible plant design options to be used to identify generic design/material issues that need to be resolved in future fusion reactor systems. The materials nuclear design requirements and the effects of radiation damage are briefly analysed with emphasis on a pulsed ‘low extrapolation’ system, which is being used for the initial design integration studies, based as far as possible on mature technologies and reliable regimes of operation (to be extrapolated from the ITER experience), and on the use of materials suitable for the expected level of neutron fluence. The main technical issues arising from the plasma and nuclear loads and the effects of radiation damage particularly on the structural and heat sink materials of the vessel and in-vessel components are critically discussed. The need to establish realistic target performance and a development schedule for near-term electricity production tends to favour more conservative technology choices. The readiness of the technical (physics and technology) assumptions that are being made is expected to be an important factor for the selection of the technical features of the device.

https://iopscience.iop.org/article/10.1088/1741-4326/57/9/092002/pdf

European DEMO design strategy and consequences for materials

Plasma-facing materials and components in a fusion reactor are the interface between the 
plasma and the material part. The operational conditions in this environment are probably 
the most challenging parameters for any material: high power loads and large particle and 
neutron fluxes are simultaneously impinging at their surfaces. To realize fusion in a tokamak 
or stellarator reactor, given the proven geometries and technological solutions, requires an 
improvement of the thermo-mechanical capabilities of currently available materials. In its 
first part this article describes the requirements and needs for new, advanced materials for the 
plasma-facing components. Starting points are capabilities and limitations of tungsten-based 
alloys and structurally stabilized materials. Furthermore, material requirements from the 
fusion-specific loading scenarios of a divertor in a water-cooled configuration are described, 
defining directions for the material development. Finally, safety requirements for a fusion 
reactor with its specific accident scenarios and their potential environmental impact lead to 
the definition of inherently passive materials, avoiding release of radioactive material through 
intrinsic material properties. The second part of this article demonstrates current material 
development lines answering the fusion-specific requirements for high heat flux materials. 
New composite materials, in particular fiber-reinforced and laminated structures, as well 
as mechanically alloyed tungsten materials, allow the extension of the thermo-mechanical 
operation space towards regions of extreme steady-state and transient loads. Self-passivating

/pdf/development-of-advanced-high-heat-flux-and-plasma-facing-4cdcf31umx.pdf

Development of advanced high heat flux and plasma-facing materials

https://biblio.ugent.be/publication/8666994/file/8670344.pdf

DEMO design activity in Europe: Progress and updates

The European Fusion Roadmap [1] shows the DEMO concept design phase commencing in 2014. The early implementation of systems engineering principles within the EU DEMO programme is essential to provide a framework for achieving this long-term mission. The aim of the systems engineering approach is to clearly define and justify the research and development (R&D) necessary to deliver a credible EU DEMO concept design by 2020 that will meet the agreed DEMO system requirements. The approach will lead to increased efficiency in the deployment of limited R&D resources and will facilitate the necessary discussion and agreement amongst stakeholders. Furthermore, it will enable transparent prioritisation of the required R&D for the strategically important technologies for DEMO. A systems decision process (SDP) is presented that provides a systematic, objective and traceable method for evaluating DEMO technologies and designs according to their capability to meet the top-level system criteria for the overall DEMO plant. Two preliminary examples where this approach should be applied are discussed: (i) the choice of primary coolant and (ii) the extension of pulse duration through auxiliary current drive.

J. Harman

Papers

Overview of EU DEMO design and R&D activities

The application of systems engineering principles to the European DEMO design and R&D studies