C. Bachmann

The physics and technology basis entering European system code studies for DEMO

A large scale program to develop a conceptual design for a demonstration fusion power plant (DEMO) has been initiated in Europe. Central elements are the baseline design points, which are developed by system codes. The assessment of the credibility of these design points is often hampered by missing information. The main physics and technology content of the central European system codes have been published (Kovari et al 2014 Fusion Eng. Des. 89 3054–69, 2016 Fusion Eng. Des. 104 9–20, Reux et al 2015 Nucl. Fusion 55 073011). In addition, this publication discusses key input parameters for the pulsed and conservative design option and provides justifications for the parameter choices. In this context several DEMO physics gaps are identified, which need to be addressed in the future to reduce the uncertainty in predicting the performance of the device. Also the sensitivities of net electric power and pulse duration to variations of the input parameters are investigated. The most extreme sensitivity is found for the elongation ( corresponds to ).

ITER vacuum vessel design and construction

Abstract According to recent design review results, the original reference vacuum vessel (VV) design was selected with a number of modifications including 3D shaping of the outboard inner shell. The VV load conditions were updated based on reviews of the plasma disruption and vertical displacement event (VDE) database. The lower port gussets have been reinforced based on structural analysis results, including non-linear buckling. Design of in-vessel coils for the mitigation of edge localized modes (ELM) and plasma vertical stabilization (VS) has progressed. Design of the in-wall-shielding (IWS) has progressed in details. The detailed layout of ferritic steel plates and borated steel plates is optimized based on the toroidal field ripple analysis. The procurement arrangements (PAs) for the VV including ports and IWS have been prepared or signed. Final design reviews were carried out to check readiness for the PA signature. The procedure for licensing the ITER VV according to the French Order on Nuclear Pressure Equipment (ESPN) has started and conformity assessment is being performed by an Agreed Notified Body (ANB). A VV design description document, VV load specification document, hazard and stress analysis reports and particular material appraisal were submitted according to the guideline and RCC-MR requirements.

Structural load specification for ITER tokamak components

The substantial mechanical loads which can develop in multiple components are a major technical challenge associated with the design of the ITER tokamak. The various loads acting on ITER can be grouped into several types: inertial loads, associated with gravity and seismic events; pressure loads, particularly significant for the ITER pressure equipment; electromagnetic loads, which affect all conducting structures as a consequence of transient events inducing rapid magnetic field changes and which possibly involve currents flowing between the plasma and in-vessel components; thermal loads, which are extremely severe in the plasma facing components; assembly loads, typically due to preloads imposed during assembly.

Dynamic response of the ITER vacuum vessel to electromagnetic loads during VDEs

During vertical displacement events (VDEs) plasma halo currents can flow partly through the passive structure. Additionally induced currents occur in the passive structure. Due to these electrical currents, major electromagnetic forces act on the passive structures and hence on the vacuum vessel (VV). As these forces change in time the vessel response is dynamic. This response determines important design drivers such as the reaction forces at the vessel supports, the vessel displacements and stress levels in the vessel structure, and it affects all components attached to the vessel. It is expected that the most severe dynamic response of the vessel occurs during asymmetric VDEs with slow current quench. Experiments on existing tokamak machines have shown that asymmetric loads can rotate around the vertical machine axis. This possible rotation is considered here. Using the finite element (FE) method the dynamic response of the vessel was analyzed in full transient dynamic analyses for the worst case VDEs according to the ITER VV load specification [2]. A 360° FE model of the VV is used since the loads are partly asymmetric. One major difficulty in this assessment was to predict how the sideways load is shared between three simultaneously acting support types. Attention was therefore given to the modeling of the VV supports including the coupling effect with the toroidal magnetic field.

Review of the Innovative H&CD Designs and the Impact of Their Configurations on the Performance of the EU DEMO Fusion Power Plant Reactor

Heating and current drive (H&CD) systems are being investigated for a demonstration fusion power plant DEMO to deliver net electricity for the grid around 2050. Compared to ITER, which has to show the generation of 500-MW thermal power, the target of DEMO is the successful production of 300 to 500 MW electrical power to the grid and to aim for a self-sufficient tritium fuel cycle. Three H&CD systems are under development for DEMO in Europe, the electron cyclotron (EC) system, the neutral beam injection (NBI) system, and the ion cyclotron system. Based on present studies for plasma ramp-up, ramp-down, and flat top phases, to be further validated in more detailed simulations, the assumed total launched power needed from the H&CD system in DEMO is in the range of 50–100 MW, to be provided for plasma heating and control. This paper describes the design and Research and Development status of selected H&CD systems, considered for their deployment in the EU DEMO. It was always considered that different H&CD configurations and design variants will have an impact on the performances for the whole fusion plant. It shall be noted that the basis for the H&CD integrated design and system development is the actual version of the European fusion electricity roadmap. The project also elaborates on H&CD efficiency improvements which will reduce the recirculating power fraction in the future fusion power plants. Different studies under investigation will be discussed such as for NBI the photoneutralization and for EC novel concepts for gyrotron multistage-depressed collector.