Coil winding pack FE-analysis for a HELIAS reactor

Abstract

At the Max-Planck-Institut fuer Plasmaphysik (IPP) a reference design is being created of an upgraded fiveperiodic HELIAS type stellarator reactor which evolves from Wendelstein 7-X (W7-X) by scaling of the coil centre line geometries by a factor of four. This reactor type was extensively investigated at IPP with regard to physical characteristics and to some extent also to engineering issues. The upgrade concerns an increase of the induction at the plasma axis and correspondingly at the superconductor.The aim is to develop the reactor concept to a stage and such detail that major engineering problems are unveiled, and relevant comparisons with other concepts, including tokamaks, can be drawn in view of upcoming decisions concerning a DEMO reactor. Even though progress in plasma physics, and in particular future results of W7-X and other machines -particularly of ITER -will probably lead to somewhat different coil shapes, no principal changes of the reference design are expected.In this paper the option of a roll-formed square coil cable jacket is investigated. Detailed structural FE analysis of the coil winding pack demonstrates the feasibility of such a conductor which appears to be the most economical option. It also allows sufficient space for a cable current density very similar to that of the ITER TF coil with a similar overall winding pack cross section of ≈0.5 m². Already existing Nb 3 Sn conductors could thus be safely applied in such a HELIAS reactor. Obvious progress of superconductor technology, particularly concerning Nb 3 Al, will be beneficial concerning savings of conductor material, ease of manufacture, higher operation temperature, etc.

Structural analysis of W7-X: From design to assembly and operation

“…In addition, the obtained experience is a basis for stellarator reactor studies in IPP [24,25]. Original block before cut Modified block Fig.…”

Wendelstein 7-X Program—Demonstration of a Stellarator Option for Fusion Energy

“…However, to ease the requirements for the support structure and to save costs, lower values are desirable. The size of the coils and the magnetic field are similar to the ITER values, enabling the use of the ITER coil technology [38] including the superconductor material and the magnetic field values. Bolted panels between the coils form the coil support structure [39].…”

System Code Analysis of HELIAS-Type Fusion Reactor and Economic Comparison With Tokamaks

“…In order to have enough space between the plasma and the coils to accommodate the specified blanket a higher aspect ratio of A = 12.2 has been chosen compared to the aspect ratio of A = 10.5 in W7-X [15]. The modular coil design and its cross-section are based on [16] where Nb 3 Sn is used as superconducting material reflecting the experience gained from ITER.…”

“…An upper bound on the stored magnetic energy of W mag = 160GJ was selected in accordance with [5] in order to keep the stress to components moderate, i.e. to stay below the typical stress limit for steel of 750MPa [16]. The average neutron wall load in this analysis is not a limiting factor.…”