How the energy flows through a fusion power plant — from fusion reactions through blanket heating, turbine conversion, and recirculating power back to plasma heating and magnets.
In a D-T fusion reactor, each fusion reaction produces 17.6 MeV of energy: 14.1 MeV carried by the neutron (80%) and 3.5 MeV by the alpha particle (20%). The alpha heats the plasma directly; the neutron passes through the first wall into the blanket, where its kinetic energy is converted to heat through nuclear collisions. This heat drives a power conversion system (steam turbine or gas turbine).[1]
Gross electrical power: Total electricity generated by the turbine. Net electrical power: Gross minus all plant electrical loads (the power actually delivered to the grid). Plant efficiency: Net electrical power divided by fusion power — typically 25–40%. Engineering Q (Qeng): Net electrical output divided by total electrical input. Qeng > 1 is the true breakeven for a power plant.[2]
The power balance strongly favours high fusion gain (Q > 20), high thermal conversion efficiency (high blanket outlet temperature), and low recirculating power (efficient heating systems, low cryogenic load). This is why compact high-field devices (with smaller cryogenic loads and lower NBI power) and high-temperature blankets (SiC/SiC at 1000°C vs steel at 500°C) are attractive.[3]