Facility power balance, thermodynamic cycle, and fuel cycle analysis for the Helios fusion power plant

This paper outlines a study of three system-level cycles that govern the “Helios” fusion power plant. By modeling and examining these three cycles, we study the systems that govern energy, working fluid, and fusion fuel transport throughout the plant. This gives confidence that the power generation and energy conversion efficiency of the plant design results in a healthy margin of net electricity, and that tritium fuel self-sufficiency is achievable. The facility power balance illustrates the distribution of power throughout the facility. During near-ignited operation, 1094 MW of thermal energy is generated in the plasma and blanket; 703 MW is lost as waste heat through auxiliary system and energy conversion inefficiencies. A portion of power is recycled within the plant, leaving 390 MW of net electric power. A simulation of the thermodynamic cycle analyzes the conversion of thermal energy from fusion via a working fluid to electric power generation. Thermal power is transported from the stellarator via lead-lithium and helium to generate steam in heat exchangers. A simulation of the steam Rankine cycle results in a net cycle power of 438 MW, and the electrical efficiency that accounts for all fluid pumping and heat recovery is 40.2%. The fuel cycle models the life cycle of the fuel using a residence-time method. This simulates the generation, transport, extraction, processing, and reuse of the rare isotope tritium to ensure that the plant is self-sufficient and minimizes radiological hazard. The model results in a minimum startup inventory between 1.69 and < 3.6 kg tritium, and a minimum required tritium breeding ratio (“TBR”) of < 1.11 to achieve a tritium doubling time of 2 years, which is viable for the baseline scenario.