Design study of superconducting coil system for JA DEMO

• Published in: Fusion engineering and design Vol. 202; p. 114345
• Main Authors: Utoh, Hiroyasu, Sakamoto, Yoshiteru, Miura, Hideaki, Arakawa, Hitoshi, Echizenya, Daisuke, Matsuda, Takuya, Hasegawa, Mitsuru, Nomoto, Kazuhiro
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-05-2024
• Subjects: Fusion Demo reactor; Magnet design; Superconducting magnet; Magnet design; Fusion Demo reactor; Superconducting magnet
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2024.114345

•The design study of options for cost rationalization and the R&D required for larger coil sizes on JA DEMO is being carried out.•Using "Hybrid R-shape" conductors offers the prospect of reducing insulation stresses in rectangular conductor layer winding concepts on JA DEMO.•On the development of hi`gh-strength structural materials, the development target of yield strength > 1600 MPa and fracture toughness 120 MPa√m was confirmed, and the development policy (increasing the amount of N) was correct.
A fusion demonstration (DEMO) reactor requires toroidal field (TF) coils larger than those used in ITER and can withstand higher electromagnetic forces. This creates significant challenges regarding the manufacturability of the TF coils, the increased electromagnetic forces on the TF inner leg case, and increased fabrication costs. This means that new winding pack designs and superconducting conductors must be designed to meet these requirements, and high-strength cryogenic steel for the coil case must be developed to withstand electromagnetic forces. This paper describes these possible solutions based on the Japanese DEMO (JA DEMO) design. In the layered winding of rectangular conductors, it was found that a new conductor geometry called the hybrid R-shape conductor can significantly reduce the stress on the turn insulation while reducing the superconducting wire to less than half. In addition, a guideline for designing the conductor strand structure was provided for a superconducting conductor subjected to electromagnetic forces 1.5 times greater than those of ITER. Furthermore, the effect of composition on strength was evaluated using several prototype materials based on high-Cr austenitic steels, and the feasibility of increasing the strength of cryogenic steels was confirmed.