Study of steam, helium and supercritical CO2 turbine power generations in prototype fusion power reactor

Power generation systems such as steam turbine cycle, helium turbine cycle and supercritical CO2 (S-CO2) turbine cycle are examined for the prototype nuclear fusion reactor. Their achievable cycle thermal efficiencies are revealed to be 40%, 34% and 42% levels for the heat source outlet coolant temperature of 480 °C, respectively, if no other restriction is imposed. In the current technology, however, low temperature divertor heat source is included. In this actual case, the steam turbine system and the S-CO2 turbine system were compared in the light of cycle efficiency and plant cost. The values of cycle efficiency were 37.7% and 36.4% for the steam cycle and S-CO2 cycle, respectively. The construction cost was estimated by means of component volume. The volume became 16,590 m3 and 7240 m3 for the steam turbine system and S-CO2 turbine system, respectively. In addition, separation of permeated tritium from the coolant is much easier in S-CO2 than in H2O. Therefore, the S-CO2 turbine system is recommended to the fusion reactor system than the steam turbine system.