Conceptual design study of the moderate size superconducting spherical tokamak power plant

Keii Gi, Yasushi Ono, Makoto Nakamura, Youji Someya, Hiroyasu Utoh, Kenji Tobita, Masayuki Ono

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


A new conceptual design of the superconducting spherical tokamak (ST) power plant was proposed as an attractive choice for tokamak fusion reactors. We reassessed a possibility of the ST as a power plant using the conservative reactor engineering constraints often used for the conventional tokamak reactor design. An extensive parameters scan which covers all ranges of feasible superconducting ST reactors was completed, and five constraints which include already achieved plasma magnetohydrodynamic (MHD) and confinement parameters in ST experiments were established for the purpose of choosing the optimum operation point. Based on comparison with the estimated future energy costs of electricity (COEs) in Japan, cost-effective ST reactors can be designed if their COEs are smaller than 120 mills kW-1 h-1 ($2013). We selected the optimized design point: A = 2.0 and Rp = 5.4 m after considering the maintenance scheme and TF ripple. A self-consistent free-boundary MHD equilibrium and poloidal field coil configuration of the ST reactor were designed by modifying the neutral beam injection system and plasma profiles. The MHD stability of the equilibrium was analysed and a ramp-up scenario was considered for ensuring the new ST design. The optimized moderate-size ST power plant conceptual design realizes realistic plasma and fusion engineering parameters keeping its economic competitiveness against existing energy sources in Japan.

Original languageEnglish
Article number063036
JournalNuclear Fusion
Issue number6
Publication statusPublished - 2015 Jun 1
Externally publishedYes


  • plasma physics design
  • ramp-up scenario
  • reactor design
  • spherical tokamak
  • system design

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics


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