Plasma and Fusion Research

Volume 17, 1405103 (2022)

Regular Articles

Design Concept of Supercritical CO2 Gas Cooled Divertors in FFHR Series Fusion Reactors
Shintaro ISHIYAMA, Akio SAGARA1), Hirotaka CHIKARAISHI1) and Nagato YANAGI1)
School of Fundamental Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjyuku-ku, Tokyo 169-8555, Japan
National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
(Received 20 April 2022 / Accepted 16 September 2022 / Published 2 December 2022)


In the FFHR power reactor equipped with a supercritical CO2 gas turbine power generation system, an divertor cooling system is connected to this power generation system [S. Ishiyama et al., Prog. Nucl. Energy 50, No.12-6, 325 (2008) [1]]. In this paper, for the purpose of developing a diverter by supercritical CO2 gas cooling that can cope with a neutron heavy irradiation environment with a heat load of 15 MW/m2 or more, CFD heat transfer flow analysis was carried out for performance evaluation and its design optimization by a structural analysis models of a supercritical CO2 gas cooled divertors. As a result, in the supercritical CO2 gas cooled tungsten mono-block divertors (50 × 50 mm × 5 channel × 5,000 mL) with a flow path length of 5 m or less, the engineering designable range of these advanced diverters having the same cooling performance as the water cooling divertor was clarified, and its practicality is extremely high from the feature that the structural model has an extremely low risk during operation as compared with the water cooled divertor.


divertor, super critical CO2 gas turbine, Force Free Helical Reactor (FFHR), bypass control, axial-flow single-shaft design turbine, CFD, heat transfer flow analysis

DOI: 10.1585/pfr.17.1405103


  • [1] S. Ishiyama, Y. Muto, Y. Kato, S. Nishio, T. Hayashi and Y. Nomoto, Prog. Nucl. Energy 50, No.12-6, 325 (2008).
  • [2] A. Sagara, H. Tamura, T. Tanaka, N. Yanagi, J. Miyazawa, T. Goto, R. Sakamoto, J. Yagi, T. Watanabe, S. Takayama and the FFHR design group, Helical reactor design FFHRd1 and c1 for steady-state DEMO, Fusion Eng. Des. 89, 2114 (2014).
  • [3] A. Sagara, J. Miyazawa, H. Tamura, T. Tanaka, T. Goto, N. Yanagi, R. Sakamoto, S. Masuzaki, H. Ohtani and The FFHR Design Group, Two conceptual designs of helical fusion reactor FFHR-d1A based on ITER technologies and challenging ideas, Nucl. Fusion 57, 086046 (2017).
  • [4] A. Sagara, T. Tanaka, J. Yagi, M. Takahashi, K. Miura, T. Yokomine, S. Fukada and S. Ishiyama, Fusion Sci. Technol. 68, 303 (2015).
  • [5] S. Ishiyama, H. Chikaraishi and A. Sagara, Operating scenario of 3GWth class FFHR power plant with bypass controlled supercritical CO2 gas turbine power generation system, Fusion Eng. Des. 164, 112194 (2021).
  • [6] S. Ishiyama, T. Tanaka, A. Sagara and H. Chikaraishi, Fusion Sci. Technol., DOI: (2019).
  • [7] S. Ishiyama, H. Chikaraishi and A. Sagara, Up-grade Bypass controlled supercritical CO2 gas turbine for 0.6MWth FFHR series fusion reactors, Plasma Fusion Res. 17, 2405054 (2022).
  • [8]
  • [9] F.A. Garner and M.L. Hamilton, JNM 191-194, 386 (1992).
  • [10] D.J. Edwards et al., JNM 191-194, 416 (1992).
  • [11] M. Tokitani, S. Masuzaki, Y. Hiraoka et al., Potential of Copper Alloys using a Divertor Heat Sink in the Helical Reactor FFHR-d1 and their Brazing Properties with Tungsten Armor by using the Typical Candidate Filler Materials, Plasma Fusion Res. 10, 3405035 (2015).
  • [12] J. Reiser, M. Rieth, B. Dafferner and A. Hoffmann, Divertor from the technology perspective, 1st IAEA DEMO program workshop, 15-18 October 2012.
  • [13] A. Sagara, T. Goto, J. Miyazawa, N. Yanagi et al., Full report on the NIFS fusion engineering research project for the mid-tem of FY2010-2015, National Institute for Fusion Science.